Article

Effects of the ACE2 inhibitor GL1001 on acute dextran sodium sulfate-induced colitis in mice

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Abstract

Angiotensin-converting enzyme 2 (ACE2) is expressed in gastrointestinal tissue. Previous studies of GL1001, a potent and selective ACE2 inhibitor, have revealed anti-inflammatory activity in the mouse digestive tract. We hypothesized that GL1001 might also produce beneficial effects in a mouse DSS model of inflammatory bowel disease. Female mice were used for study. Animals were treated for 5 days with 5% DSS in the drinking water to induce colitis. For the following 9 days, animals were treated twice daily with GL1001 (30, 100, 300 mg/kg, s.c.), sulfasalazine (150 mg/kg, p.o.), or vehicle. Throughout the experiment, body weight, rectal prolapse, stool consistency, and fecal occult blood were monitored. At termination, colon length, histopathology, and myeloperoxidase activity were assessed. High-dose GL1001 ameliorated DSS-induced disease activity, including rectal prolapse and intestinal bleeding. The most robust effect of GL1001 was observed 48-96 h post DSS treatment and was comparable in magnitude to that of sulfasalazine. Colon pathology and myeloperoxidase activity were also markedly attenuated by high-dose GL1001 treatment, with the most profound effects observed in the distal segment. The findings support the previously observed anti-inflammatory effects of ACE2 inhibition in gastrointestinal tissue and suggest that GL1001 may have therapeutic utility for inflammatory bowel disease.

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... Within ACE/ACE2 pathways, this is true for ACE as well as for ACE2, suggesting that MLN-4760 might be helpful not only for COVID-19 but also in targeted therapies for pathologies correlated with an excessive increase of ACE2 activity that may involve heart, lung, liver, colon or other tissues/organs expressing ACE2. For example, GL1001 (old name of MLN-4760) showed to produce an anti-inflammatory activity in a mouse model of colitis [72], highlighting the importance of the yin-yang balance of ACE/ACE2 pathways ("in medio stat virtus"). ...
... 2) No adverse effects were described upon its chronic administration neither alone nor in combination with ACE2 activators (while inhibiting their activating effects) nor after inducing functional impairment of ACE2 activity in rodent experiments in vivo [30] [72]. Subchronic doses of GL1001 indicate no adverse effects up to 1,000 mg/kg (see [72] [90]. ...
... 2) No adverse effects were described upon its chronic administration neither alone nor in combination with ACE2 activators (while inhibiting their activating effects) nor after inducing functional impairment of ACE2 activity in rodent experiments in vivo [30] [72]. Subchronic doses of GL1001 indicate no adverse effects up to 1,000 mg/kg (see [72] [90]. Interestingly, the report underscores the role plaid by local concentration of molecules (ACE2) in modulating lung inflammation and disease. ...
... involving Bradykinin metabolites or other ACE2 substrates). For example, NAAE demonstrated an antiviral activity [32] and GL1001 showed to produce an anti-inflammatory activity in a mouse model of colitis [33], highlighting the importance of the yinyang balance of ACE/ACE2 pathways ("in medio stat virtus"). ...
... In particular: a) Chronic administration (about 4 weeks) of C-16/DLM-4760 in combination with ACE2 activating treatments was performed by daily intraperitoneal injection at a dose of 25mg/kg in distilled water (as a solution of 42mg/ml) or 0.9% sterile saline (as a solution of 84 mg/ml using a 0.5-ml insulin syringe) freshly prepared [21][37] [38]. b) Alternatively, chronic administration (about 8 days) of GL1001/DLM-4760 disodium salt in combination with an ACE2 activating treatment was performed by subcutaneous injection (5ml/kg) containing up to a dose of 300 mg/kg, twice a day, formulated in a vehicle solution [15% 2-hydroxypropyl-betacyclodextrin (HPBDC)/85% H 2 O] [33]. Subchronic doses of GL1001 indicate no adverse effects up to 1,000 mg/kg (see [33] . ...
... b) Alternatively, chronic administration (about 8 days) of GL1001/DLM-4760 disodium salt in combination with an ACE2 activating treatment was performed by subcutaneous injection (5ml/kg) containing up to a dose of 300 mg/kg, twice a day, formulated in a vehicle solution [15% 2-hydroxypropyl-betacyclodextrin (HPBDC)/85% H 2 O] [33]. Subchronic doses of GL1001 indicate no adverse effects up to 1,000 mg/kg (see [33] . 300 mg (active drug) oral capsules were used in a Phase Ib/IIa clinical trial that was, however, abandoned (https://clinicaltrials.gov/ct2/show/NCT01039597). ...
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The article describes the rational for inhibition of the angiotensin-converting enzyme 2 (ACE2) pathways as specific targets in patients infected by SARS-CoV-2. Making use of a large quantity of published reports in which human/rodent ACE2 pathway inhibitors were administered in vivo, I have hypothesized a possible therapeutic pharmacological intervention through an inhibition strategy of ACE2 pathway for SARS-CoV-2 patients who are suffering from critical, advanced and untreatable stages of the disease.
... These results also support the assertion that ACE2iSB is nicotianamine. Recently, various peptide and synthetic ACE2 inhibitors have been developed (2,3,7,8). The ACE2 inhibitor N-(2-aminoethyl)-1-aziridine-ethanamine discovered by structure-based studies is effective in blocking the SARS coronavirus spike protein-mediated cell fusion (2). ...
... Recently, various peptide and synthetic ACE2 inhibitors have been developed (2,3,7,8). The ACE2 inhibitor N-(2-aminoethyl)-1-aziridine-ethanamine discovered by structure-based studies is effective in blocking the SARS coronavirus spike protein-mediated cell fusion (2). On the other hand, synthetic ACE2 inhibitor, GL1001 has anti-inflammatory activity in the mouse digestive tract (3). ...
Article
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Angiotensin-converting enzyme 2 (ACE2) is a carboxypeptidase which is highly homologous to angiotensin-converting enzyme (ACE). ACE2 produces vasodilator peptides angiotensin 1-7 from angiotensin II. In the present study, we synthesized various internally quenched fluorogenic (IQF) substrates (fluorophore-Xaa-Pro-quencher) based on the cleavage site of angiotensin II introducing N-terminal fluorophore N-methylanthranilic acid (Nma) and C-terminal quencher N(ε)-2,4- dinitrophenyl-lysine [Lys(Dnp)]. The synthesized mixed substrates "Nma-Xaa-Pro-Lys(Dnp)" were hydrolyzed by recombinant human (rh) ACE2. The amount of each product was determined by liquid chromatography mass spectrometry (LC-MS) with fluorescence detection and it was found that Nma-His-Pro-Lys(Dnp) is the most suitable substrate for rhACE2. The Km, kcat, and kcat/Km values of Nma-His-Pro-Lys(Dnp) on rhACE2 were determined to be 23.3 μM, 167 s(-1), and 7.17 μM(-1) s(-1), respectively. Using the rhACE2 and the newly developed IQF substrate, we found rhACE2 inhibitory activity in soybean and isolated the active compound soybean ACE2 inhibitor (ACE2iSB). The physicochemical data on the isolated ACE2iSB were identical to those of nicotianamine. ACE2iSB strongly inhibited rhACE2 activity with an IC50 value of 84 nM. This is the first demonstration of an ACE2 inhibitor from foodstuffs.
... Therefore, MLN-4760 might be helpful not only for COVID-19 but also in targeted therapies for pathologies correlated with an excessive increase of ACE2 activity that may involve heart, lung, liver, colon or other tissues/organs expressing ACE2 such as blood and endothelial cells. As an example, GL1001 (old name of MLN-4760) showed to produce an anti-inflammatory activity in a mouse model of colitis [122], highlighting the importance of the yin-yang balance of ACE/ACE2 pathways ("in medio stat virtus"). ...
... (2) No significant adverse effects were described upon its chronic administration neither alone nor in combination with ACE2 activators (while inhibiting their activating effects) nor after inducing functional impairment of ACE2 activity in rodent experiments in vivo [52,117,118,122,183,184] nor in a clinical Phase I trial in humans (http://oreholdings.com/wp-content/uploads/2013/06/09. 10.09-425.pdf); ...
Article
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The article describes the rationale for inhibition of the renin-angiotensin system (RAS) pathways as specific targets in patients infected by SARS-CoV-2 in order to prevent positive feedback-loop mechanisms. Based purely on experimental studies in which RAS pathway inhibitors were administered in vivo to humans/rodents, a reasonable hypothesis of using inhibitors that block both ACE and ACE2 zinc metalloproteases and their downstream pathways in COVID-19 patients will be proposed. In particular, metal (zinc) chelators and renin inhibitors may work alone or in combination to inhibit the positive feedback loops (initially triggered by SARS-CoV-2 and subsequently sustained by hypoxia independently on viral trigger) as both arms of renin-angiotensin system are upregulated, leading to critical, advanced and untreatable stages of the disease.
... Preclinical in vivo studies as well as translational data from subjects with IBD further support the role of angiotensin signaling in mucosal inflammation. Mouse and rat colitis models that are exposed to ACEI and ARB, as well as AT 1 R knockout mice, have reduced colonic inflammation compared to control mice as determined by weight, histologic bowel evaluation, and cytokine levels [7][8][9][10][11][12][13][14][15][16]. Furthermore, transgenic mice that overproduce renin are also more susceptible to develop colitis [17]. ...
... AT 1 R activation in vitro and in vivo stimulates inflammatory cytokines, pro-inflammatory transcription factors, and cellular adhesion molecules, which suggests a role for targeting the angiotensin pathway to reduce inflammation in patients with IBD [2,3]. Supporting this hypothesis are data from multiple murine colitis models in which blockade of angiotensin signaling with ACEI or ARB has consistently improved inflammation [4,[7][8][9][10][11][12][13][14][15][16]. The findings of the current study suggest that these preclinical findings may also be applicable to patients with IBD who receive medications that block angiotensin II signaling. ...
Article
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Background Preclinical data demonstrate that activation of the renin–angiotensin system (RAS) contributes to mucosal inflammation, and RAS inhibition by angiotensin-converting-enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) improves colitis in animal models. Less is known regarding the effects of RAS inhibition on clinical outcomes in inflammatory bowel disease (IBD) patients. Aim Evaluate the impact of ACEI and ARB on clinical outcomes in IBD. Methods Rates of IBD-related hospitalizations, operations, and corticosteroid use were evaluated retrospectively in two groups. First, 111 IBD patients taking an ACEI or ARB were compared to nonusers matched 1:1 based on sex, age, diagnosis, disease location, and hypertension diagnosis. Second, outcomes in a cohort of 130 IBD patients were compared prior to and during ACEI/ARB exposure. Results Compared to matched controls, all IBD patients together with ACEI/ARB exposure had fewer hospitalizations (OR 0.26, p < 0.01), operations (OR 0.08, p = 0.02), and corticosteroid prescriptions (OR 0.5, p = 0.01). Comparing outcomes before and during ACEI/ARB use, there were no differences in hospitalizations, operations, or corticosteroid use for all IBD patients together, but patients with UC had increased hospitalizations (0.08 pre- vs. 0.16 during ACEI/ARB exposure, p = 0.03) and decreased corticosteroid use (0.24 pre-ACEI/ARB vs. 0.12 during ACEI/ARB exposure, p < 0.01) during ACEI/ARB use. Conclusions IBD patients with ACEI/ARB exposure had fewer hospitalizations, operations, and corticosteroid use compared to matched controls. No differences in outcomes were observed in individuals on ACEI/ARB therapy when compared to a period of time prior to medication exposure.
... It has been reported that renin-angiotensin system [7] is involved in the pathophysiology of colonic inflammation [8,9]. An increased angiotensin II level in colonic mucosa is reported in Crohn's disease patient [10] and DSS-induced experimental colitis [8], and the degree of colitis is attenuated by angiotensin-converting enzyme inhibitor [9,11] and in angiotensinogen gene-deficient mice [12]. ...
... It has been reported that renin-angiotensin system [7] is involved in the pathophysiology of colonic inflammation [8,9]. An increased angiotensin II level in colonic mucosa is reported in Crohn's disease patient [10] and DSS-induced experimental colitis [8], and the degree of colitis is attenuated by angiotensin-converting enzyme inhibitor [9,11] and in angiotensinogen gene-deficient mice [12]. However, there are a few reports about modulation of natriuretic peptide system, an antagonistic system of reninangiotensin system, in pathological condition of gastrointestinal (GI) tracts. ...
Article
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Background Renin-angiotensin system is involved in the pathophysiology of colonic inflammation. However, there are a few reports about modulation of natriuretic peptide system. Aims This study investigates whether a local atrial natriuretic peptide (ANP) system exists in rat colon and whether ANP plays a role in the regulation of colonic motility in experimental colitis rat model. Methods Experimental colitis was induced by an intake of 5 % dextran sulfate sodium (DSS) dissolved in tap water for 7 days. After rats were killed, plasma hormone concentrations and mRNAs for natriuretic peptide system were measured. Functional analysis of colonic motility in response to ANP was performed using taenia coli. Results DSS-treated colon showed an increased necrosis with massive infiltration of inflammatory cells. The colonic natriuretic peptide receptor-A mRNA level and particulate guanylyl cyclase activity in response to ANP from colonic tissue membranes were higher, and the mRNA levels of ANP and natriuretic peptide receptor-B were lower in DSS-treated rats than in control rats. ANP decreased the frequency of basal motility in a dose-dependent manner but did not change the amplitude. The inhibitory responses of frequency of basal motility to ANP and 8-bromo-cGMP were enhanced in DSS-treated rat colon. Conclusion In conclusion, augmentation of inhibitory effect on basal motility by ANP in experimental colitis may be due an increased expression of colonic natriuretic peptide receptor-A mRNA. These data suggest that local natriuretic peptide system is partly involved in the pathophysiology of experimental colitis.
... Of relevance, however, the expression of ACE2 in the two tissues undergoes an opposite regulation in response to inflammation. Thus, while the ileal expression of ACE2 is reduced in patients with active Crohn's disease of the ileum, the colonic expression of the receptor is robustly induced in patients with ulcerative colitis or Crohn's disease showing a colon involvement [47]. Further on, a linear correlation has been detected linking the severity of colon inflammation, colon expression of expression of pro-inflammatory cytokines including IFN-γ, TNF-α, IL-1β, and IL-6 and the expression of ACE2 mRNA [12,13,48,49]. ...
... Two recent studies [53,54] have shown that SARS CoV2 virus might directly infect the human gut, and therefore the modulation of ACE2 expression in the gastrointestinal tract might have therapeutic relevance in reducing the virus load. The data we have gathered from the two mouse models of IBD strongly support the notion that upregulation of Ace2 in the colon is due to a state of inflammation marked by strong induction of pro-inflammatory cytokines [47,55]. Importantly, in contrast to Ace2 the expression of the Ang 1-7 receptor Mas, was markedly downregulated in both models (Figs. 3 and 5). ...
Article
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The severe acute respiratory syndrome (SARS)-CoV-2 is the pathogenetic agent of Corona Virus Induced Disease (COVID)19. The virus enters the human cells after binding to the angiotensin converting enzyme (ACE)2 receptor in target tissues. ACE2 expression is induced in response to inflammation. The colon expression of ACE2 is upregulated in patients with inflammatory bowel disease (IBD), highlighting a potential risk of intestinal inflammation in promoting viral entry in the human body. Because mechanisms that regulate ACE2 expression in the intestine are poorly understood and there is a need of anti-SARS-CoV-2 therapies, we have settled to investigate whether natural flavonoids might regulate the expression of Ace2 in intestinal models of inflammation. The results of these studies demonstrated that pelargonidin activates the Aryl hydrocarbon Receptor (AHR) in vitro and reverses intestinal inflammation caused by chronic exposure to high fat diet or to the intestinal braking-barrier agent TNBS in a AhR-dependent manner. In these two models, development of colon inflammation associated with upregulation of Ace2 mRNA expression. Colon levels of Ace2 mRNA were directly correlated with Tnf-α mRNA levels. Molecular docking studies suggested that pelargonidin binds a fatty acid binding pocket on the receptor binding domain of SARS-CoV-2 Spike protein. In vitro studies demonstrated that pelargonidin significantly reduces the binding of SARS-CoV-2 Spike protein to ACE2 and reduces the SARS-CoV-2 replication in a concentration-dependent manner. In summary, we have provided evidence that a natural flavonoid might hold potential in reducing intestinal inflammation and ACE2 Induction in the inflamed colon in a AhR-dependent manner.
... For experimental procedures, mice were given 2.5% DSS (MW 36,000-50,000, 17.1% sulfur substitution, no detectable free sulfate, pH 7.1, MP Biomedicals, LLC., Illkirch, France) in their drinking water for 24 (24 h-group) or 48 (48 h-group) hours to allow for the investigation of initial mucus barrier disruptions. In addition, DSS administration for 7 days with 2 consecutive days of tap water only (7 d-group) allowed the monitoring of effects with a completely disrupted barrier and assessment of clinical parameters in terms of fecal blood content [34], using the hemoCARE Guaiac testing method (CARE diagnostic, Voerde, Germany) and stool consistency [35]. All mice were anesthetized with isoflurane prior to euthanasia by cervical dislocation. ...
... After induction of acute DSS colitis, an increase in the colonic clostridia and bifidobacteria was observed which is consistent with previous findings, yet without significant differences between the genotypes [30]. The expected increased scores of fecal blood content and stool consistency, monitored as clinical parameters of colitis occurred independently of the genotype [34,35]. ...
Article
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The secreted, goblet cell-derived protein Clca1 (chloride channel regulator, calcium-activated-1) has been linked to diseases with mucus overproduction, including asthma and cystic fibrosis. In the intestine Clca1 is found in the mucus with an abundance and expression pattern similar to Muc2, the major structural mucus component. We hypothesized that Clca1 is required for the synthesis, structure or barrier function of intestinal mucus and therefore compared wild type and Clca1-deficient mice under naive and at various time points of DSS (dextran sodium sulfate)-challenged conditions. The mucus phenotype in Clca1-deficient compared to wild type mice was systematically characterized by assessment of the mucus protein composition using proteomics, immunofluorescence and expression analysis of selected mucin genes on mRNA level. Mucus barrier integrity was assessed in-vivo by analysis of bacterial penetration into the mucus and translocation into sentinel organs combined analysis of the fecal microbiota and ex-vivo by assessment of mucus penetrability using beads. All of these assays revealed no relevant differences between wild type and Clca1-deficient mice under steady state or DSS-challenged conditions in mouse colon. Clca1 is not required for mucus synthesis, structure and barrier function in the murine colon.
... However, the inhibition of Ang II metabolisation by ACE2 could lead to an increase of blood pressure, as a potential risk. Nevertheless, the data from chronic administration of MLN-4760 do not reveal significant adverse effects or mortality in several rodent experimental models in vivo (Byrnes et al., 2009;Evans et al., 2020;Kim et al., 2010;Shenoy et al., 2013;Tikellis et al., 2008;Trask et al., 2010) nor in a clinical Phase I trial in humans (http://oreholdings.com/wp-content/uploads/2013/06/09.10.09-425.pdf). Similarly, chronic administration of Dx600 inhibitor in mice suggests that its use is safe (Sodhi et al., 2018). ...
... Therefore, inhibition of ACE2 activity using MLN-4760 might be helpful not only for COVID-19 but also for other chronic pathologies associated with a persistent ACE2 hyperactivity, such as cardiovascular diseases, hypertension, metabolic syndrome, and inflammatory bowel disease (Anguiano et al., 2015;Epelman et al., 2009;Garg et al., 2015;Kornilov et al., 2020;Narula et al., 2020;Ortiz-Pérez et al., 2013;Ramchand et al., 2018;Sama et al., 2020;Soro-Paavonen et al., 2012;Úri et al., 2014Walters et al., 2017). As an example, inhibition of ACE2 by GL1001 (an old name of MLN-4760) surprisingly showed to produce anti-inflammatory activity in a colitis mouse model (Byrnes et al., 2009), further suggesting that the well-known anti-inflammatory and protective activity of ACE2 in an acute phase of disease may lead to deleterious health effects when ACE2 is chronically activated. Unfortunately, a Phase Ib/IIa clinical trial using oral capsules (300 mg of ORE1001, the "clinical" name of MLN-4760) was abandoned (https:// clinicaltrials.gov/ct2/show/NCT01039597). ...
Article
The article describes the possible pathophysiological origin of COVID-19 and the crucial role of renin-angiotensin system (RAS), providing several "converging" evidence in support of this hypothesis. SARS-CoV-2 has been shown to initially upregulate ACE2 systemic activity (early phase), which can subsequently induce compensatory responses leading to upregulation of both arms of the RAS (late phase) and consequently to critical, advanced and untreatable stages of COVID-19 disease. The main and initial actors of the process are ACE2 and ADAM17 zinc-metalloproteases, which, initially triggered by SARS-CoV-2 spike proteins, work together in increasing circulating Ang 1-7 and Ang 1-9 peptides and downstream (Mas and Angiotensin type 2 receptors) pathways with anti-inflammatory, hypotensive and antithrombotic activities. During the late phase of severe COVID-19, compensatory secretion of renin and ACE enzymes are subsequently upregulated, leading to inflammation, hypertension and thrombosis, which further sustain ACE2 and ADAM17 upregulation. Based on this hypothesis, COVID-19-phase-specific inhibition of different RAS enzymes is proposed as a pharmacological strategy against COVID-19 and vaccine-induced adverse effects. The aim is to prevent the establishment of positive feedback-loops, which can sustain hyperactivity of both arms of the RAS independently of viral trigger and, in some cases, may lead to Long-COVID syndrome.
... Currently strategies are aimed at upregulation of ACE2 expression and activity, technically more complex than enzyme inhibition. This does not rule out any potential application of ACE2 inhibitors which have recently been proposed as possible anti-inflammatories [12], having initially but unsuccessfully been tested as potential antiobesity drugs. The main tissue sites of expression of ACE2 were originally identified as testis, heart, and kidney [1], where it was shown to be localised on the apical membrane of polarised cells whereas ACE is equally distributed between apical and basolateral membranes [13]. ...
... Novel roles for ACE2 may yet remain to be discovered and a new twist to the ACE2 story has emerged with the discovery of autoantibodies targeting ACE2 in the sera of patients with connective tissue diseases [127]. This, coupled with results showing that administration of an ACE2 inhibitor improved the pathology of inflammatory bowel disease [12], suggests that inhibition of ACE2 may be beneficial in inflammatory diseases such as arthritis. ...
Article
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The renin-angiotensin system (RAS) is a critical regulator of hypertension, primarily through the actions of the vasoactive peptide Ang II, which is generated by the action of angiotensin-converting enzyme (ACE) mediating an increase in blood pressure. The discovery of ACE2, which primarily metabolises Ang II into the vasodilatory Ang-(1-7), has added a new dimension to the traditional RAS. As a result there has been huge interest in ACE2 over the past decade as a potential therapeutic for lowering blood pressure, especially elevation resulting from excess Ang II. Studies focusing on ACE2 have helped to reveal other actions of Ang-(1-7), outside vasodilation, such as antifibrotic and antiproliferative effects. Moreover, investigations focusing on ACE2 have revealed a variety of roles not just catalytic but also as a viral receptor and amino acid transporter. This paper focuses on what is known about ACE2 and its biological roles, paying particular attention to the regulation of ACE2 expression. In light of the entrance of human recombinant ACE2 into clinical trials, we discuss the potential use of ACE2 as a therapeutic and highlight some pertinent questions that still remain unanswered about ACE2.
... Thus, ACE2 appears to link amino acid malnutrition to intestinal microbial ecology and inflammation (Hashimoto et al. 2012;Izcue and Powrie 2012). Conflicting data, however, exists showing antiinflammation effects of an ACE2 inhibitor (Byrnes et al. 2009). ...
Article
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The angiotensin I converting enzyme 2 (ACE2) is a key factor in the maintenance of intestinal homeostasis. Dysregulation of homeostasis can lead to inflammation of the colon (colitis), which can cause life-threatening enfeeblement or even cancer. Animal models are valuable surrogates in deciphering the pathology behind such human conditions and for screening of putative therapeutic targets or treatment paradigms. However, development of disease models can be time-consuming and technical demanding, which might hamper their application-value. In this study, we genetically disrupted the mouse Ace2 gene by direct injection of in vitro transcribed mRNA coding for transcription activator-like effector nucleases (TALENs) into the cytoplasm of outbred Kunming mouse zygotes. Consequently, somatic mutations were induced with an efficiency of 57 %, of which 39 % were frameshift mutations. Moreover, all modifications were stably transferred during germline transmission. In Ace2-knockout male mice (Ace2 −/y ), we observed severe chemical induced colitis, characterized by considerable weight loss, diarrhea and a shortened colon length. Histologically, Ace2 mutations resulted in the infiltration of leukocytes and the overt damage of the intestinal mucosal barrier. In addition, we detected an increased expression of inflammatory cytokines in the colon tissue of Ace2 −/y mice. Collectively, the data indicate that high targeting efficiency and heritability can be achieved in an outbred mouse model by zygote injection of TALEN mRNA. Furthermore, the generated Ace2 −/y mice display phenotypic traits reminiscent of colitis and we anticipate that such mice can be of value in studies of the intestinal microbiome or fecal transplantation.
... In dextran sulfate sodium– induced colitis in mice, captopril significantly reduced epithelial cell apoptosis and mucosal expression of TNF-α. The histopathologic grade of colitis was also significantly lowered in ACE-I treated mice (Ariel et al., 2007) and rats (Byrnes et al., 2009). Amelioration of induced colitis in angiotensinogen gene knockout mice has been also demonstrated (Inokuchi et al., 2005). ...
... In vivo administration of the ACE inhibitor enalaprilate has been proven to reduce weight loss and histological damage in murine dextran sulfate sodium (DSS)-induced colitis [146]. ACE inhibitor treatment was also effective in spontaneous colitis of IL-10deficient mice [147] and this finding has been confirmed by other studies [148,149]. ...
Article
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Crohn's disease (CD) is a chronic remitting and relapsing disease. Fibrostenosing complications such as intestinal strictures, stenosis and ultimately obstruction are some of its most common long-term complications. Despite recent advances in the pathophysiological understanding of CD and a significant improvement of anti-inflammatory therapeutics, medical therapy for stricturing CD is still inadequate. No specific anti-fibrotic therapy exists and the incidence rate of strictures has essentially remained unchanged. Therefore, the current therapy of established fibrotic strictures comprises mainly endoscopic dilation as well as surgical approaches. However, these treatment options are associated with major complications as well as high recurrence rates. Thus, a specific anti-fibrotic therapy for CD is urgently needed. Importantly, there is now a growing body of evidence for prevention as well as effective medical treatment of fibrotic diseases of other organs such as the skin, lung, kidney and liver. In face of the similarity of molecular mechanisms of fibrogenesis across these organs, translation of therapeutic approaches from other fibrotic diseases to the intestine appears to be a promising treatment strategy. In particular transforming growth factor beta (TGF-beta) neutralization, selective tyrosine kinase inhibitors, blockade of components of the renin-angiotensin system, IL-13 inhibitors and mammalian target of rapamycin (mTOR) inhibitors have emerged as potential drug candidates for anti-fibrotic therapy and may retard progression or even reverse established intestinal fibrosis. However, major challenges have to be overcome in the translation of novel anti-fibrotics into intestinal fibrosis therapy, such as the development of appropriate biomarkers that predict the development and accurately monitor therapeutic responses. Future clinical studies are a prerequisite to evaluate the optimal timing for anti-fibrotic treatment approaches, to elucidate the best routes of application, and to evaluate the potential of drug candidates to reach the ultimate goal: the prevention or reversal of established fibrosis and strictures in CD patients.
... Although no studies have examined the direct correlation between ACE and constipation, several accumulated reports suggest that the inhibition of ACE2 can ameliorate inflammatory bowel disease including ulcerative colitis and Crohn's disease. The treatment of potent and selective AEC2 inhibitors, such as enalapril and GL1001, resulted in a markedly attenuated colon pathology and myeloperoxidase activity by down-regulating the NF-κB and TGF-β signaling pathway [44,45,46]. In the present study, an alteration of the regulation of ACE2 was similar to that of CYP2B2. ...
Article
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To characterize the changes in global gene expression in the distal colon of constipated SD rats in response to the laxative effects of aqueous extracts of Liriope platyphylla (AEtLP), including isoflavone, saponin, oligosaccharide, succinic acid and hydroxyproline, the total RNA extracted from the distal colon of AEtLP-treated constipation rats was hybridized to oligonucleotide microarrays. The AEtLP treated rats showed an increase in the number of stools, mucosa thickness, flat luminal surface thickness, mucin secretion, and crypt number. Overall, compared to the controls, 581 genes were up-regulated and 216 genes were down-regulated by the constipation induced by loperamide in the constipated rats. After the AEtLP treatment, 67 genes were up-regulated and 421 genes were down-regulated. Among the transcripts up-regulated by constipation, 89 were significantly down-regulated and 22 were recovered to the normal levels by the AEtLP treatment. The major genes in the down-regulated categories included Slc9a5, klk10, Fgf15, and Alpi, whereas the major genes in the recovered categories were Cyp2b2, Ace, G6pc, and Setbp1. On the other hand, after the AEtLP treatment, ten of these genes down-regulated by constipation were up-regulated significantly and five were recovered to the normal levels. The major genes in the up-regulated categories included Serpina3n, Lcn2 and Slc5a8, whereas the major genes in the recovered categories were Tmem45a, Rerg and Rgc32. These results indicate that several gene functional groups and individual genes as constipation biomarkers respond to an AEtLP treatment in constipated model rats.
... Furthermore, mice with macrophage-specific deletion of HSP90B1 (a target of miR-223-3p) are more resistant to DSS-induced colitis than are their wild-type counterparts 13 . In contrast, another target for miR-223-3p is angiotensin converting enzyme-2 (ACE2), which is required to express an amino acid transporter on the luminal surface of IECs; ACE2 appears to promote the development of gut inflammation because its deficiency decreases the severity of DSS-induced colitis 14 . Therefore, various putative targets for miR-223-3p that are down-regulated in inflamed small-IECs likely participate in either antagonizing (DUOXA2 or HSP90B1) or accelerating (ACE2) inflammatory responses. ...
Article
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Inflammatory bowel diseases (IBDs) accompany a critical loss of the frontline barrier function that is achieved primarily by intestinal epithelial cells (IECs). Although the gene-regulation pathways underlying these host-defense roles of IECs presumably are deranged during IBD pathogenesis, the quantitative and qualitative alterations of posttranscriptional regulators such as microRNAs (miRNAs) within the cells largely remain to be defined. We aimed to uncover the regulatory miRNA-target gene relationships that arise differentially in inflamed small-compared with large-IECs. Whereas IBD significantly increased the expression of only a few miRNA candidates in small-IECs, numerous miRNAs were upregulated in inflamed large-IECs. These marked alterations might explain why the large, as compared with small, intestine is more sensitive to colitis and shows more severe pathology in this experimental model of IBD. Our in-depth assessment of the miRNA-mRNA expression profiles and the resulting networks prompts us to suggest that miRNAs such as miR-1224, miR-3473a, and miR-5128 represent biomarkers that appear in large-IECs upon IBD development and co-operatively repress the expression of key anti-inflammatory factors. The current study provides insight into gene-regulatory networks in IECs through which dynamic rearrangement of the involved miRNAs modulates the gene expression-regulation machinery between maintaining and disrupting gastrointestinal homeostasis.
... In dextran sulfate sodium-induced colitis in mice, captopril significantly reduced epithelial cell apoptosis and mucosal expression of TNF-α. The histopathologic grade of colitis was also significantly lowered in ACE-I treated mice (Ariel et al., 2007) and rats (Byrnes et al., 2009). Amelioration of induced colitis in angiotensinogen gene knockout mice has been also demonstrated (Inokuchi et al., 2005). ...
Article
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Accumulating data suggest the involvement of renin angiotensin system (RAS) in the pathogenesis of inflammatory bowel disease. The aim of the present study was to evaluate the potential protective and therapeutic effects of captopril and valsartan on acetic acid induced-ulcerative colitis in rats. The results were assessed by macroscopic and microscopic examinations of colonic tissues as ell as by biochemical measurement of malondialdehyde (MDA), tumor necrosis factor alpha (TNF-α), transforming growth factor-beta1 (TGF-β β β β 1), angiotensin converting enzyme (ACE), reduced glutathione (GSH) and platelet activating factor (PAF) levels in colonic tissues. Oral treatment with captopril or valsartan in a dose of 30 mg kg -1 body weight, starting one day before induction of colitis and continuing for 1 week (prophylactic groups) or starting one week after induction of colitis and continuing for another one week (therapeutic groups), significantly reduced MDA, TNF-α, PAF, TGF-β β β β1 and significantly increased colonic GSH in colonic tissues as compared to acetic acid control groups. Captopril and valsartan attenuated the macroscopic and microscopic colonic damage induced by acetic acid. No significant difference between the effect of either drug could be detected other than the significant decrease in ACE activity in colonic tissue exerted by captopril and not by valsartan, These results suggest that either captopril or valsartan may be effective in prophylaxis as well as in treatment of ulcerative colitis through targeting RAS.
... Regarding the influence of the ACE2/Ang 1-7/MAS-1 R axis in modulating colitis severity, one report demonstrated that administration to mice of GL1001 (as a chemical inhibitor of ACE2) reduced colitis severity [48]. However, it should be noted that the specificity of this inhibitor is questionable, since ACE2 inhibition may increase the levels of other substrates such as Ang I/II, ghrelin, dynorphin, bradykinin, neurotensin and apelin [49]. ...
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Background: There is evidence to support a role for angiotensin (Ang) 1-7 in reducing the activity of inflammatory signaling molecules such as MAPK, PKC and SRC. Enhanced angiotensin converting enzyme 2 (ACE2) expression has been observed in patients with inflammatory bowel disease (IBD) suggesting a role in its pathogenesis, prompting this study. Methods: The colonic expression/activity profile of ACE2, Ang 1-7, MAS1-receptor (MAS1-R), MAPK family and Akt were determined by western blot and immunofluorescence. The effect of either exogenous administration of Ang 1-7 or pharmacological inhibition of its function (by A779 treatment) was determined using the mouse dextran sulfate sodium model. Results: Enhanced colonic expression of ACE2, Ang1-7 and MAS1-R was observed post-colitis induction. Daily Ang 1-7 treatment (0.01-0.06 mg/kg) resulted in significant amelioration of DSS-induced colitis. In contrast, daily administration of A779 significantly worsened features of colitis. Colitis-associated phosphorylation of p38, ERK1/2 and Akt was reduced by Ang 1-7 treatment. Conclusion: Our results indicate important anti-inflammatory actions of Ang 1-7 in the pathogenesis of IBD, which may provide a future therapeutic strategy to control the disease progression.
... Performing such an analysis on a drug-by-drug basis is impractical, time consuming and inappropriate for systematic screens. Nevertheless, such a re-screening approach, in which alternative single targets for existing drugs or drug candidates are sought by simple screening, has been attempted by Ore Pharmaceuticals [33]. Systems biology provides a complementary method to manual reductionist approaches, by taking an integrated view of cellular and molecular processes. ...
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Drug development is expensive and prone to failure. It is potentially much less risky and expensive to reuse a drug developed for one condition for treating a second disease, than it is to develop an entirely new compound. Systematic approaches to drug repositioning are needed to increase throughput and find candidates more reliably. Here we address this need with an integrated systems biology dataset, developed using the Ondex data integration platform, for the in silico discovery of new drug repositioning candidates. We demonstrate that the information in this dataset allows known repositioning examples to be discovered. We also propose a means of automating the search for new treatment indications of existing compounds.
... ACE and ACE2 have roles in regulating blood pressure [64] and cardiac function [65], respectively. A number of inhibitors have been designed for ACE [66], and a few have been also developed for ACE2 [45,67].Figure 5 (inset) shows the overall structural similarity between TbM32m and ACE2. We created a structural alignment of TbM32m and the crystal structure for ACE2 bound with inhibitor MLN-4760 (PDB code 1R4L) [63], which showed that a TbM32m arginine (R348) likely corresponds to ACE2 R273 (Figure 5). ...
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Author Summary Human African trypanosomiasis (HAT) is caused by the protozoan parasite Trypanosoma brucei. HAT is fatal unless treated, yet the current treatment itself can cause death. New treatments are urgently needed. Our study focuses on proteases, which are enzymes that break down proteins. Because of their roles in many centrally important biological processes, proteases are targets for drugs to treat a variety of diseases including parasite infection. The recent explosion of protein sequence and structure information in public databases has made surveys of proteins on a genomic scale possible. However, collecting specific data of interest from diverse databases and synthesizing them in a way that is easy to interpret can be difficult. We used T. brucei and human protease sequences, crystal structures, and models to create network views that show how proteases cluster by similarity. Such views are valuable not only for understanding the evolution of the protein repertoire in each species, but also can give important clues for drug design. Two T. brucei protease groups (“M32” and “C51”) that are very different in sequence from human proteases were examined in structural detail. Based on our analyses, a human ACE2 inhibitor was selected for experimental testing on one of these parasite proteases, TbM32, and was shown to inhibit it.
... Acute colitis manifested as diarrhea and bloody feces, in some cases rectal prolapsed, has occurred as a complication in colitis models using sodium dextran sulphate. 19 PBZ shortened the duration of diarrhea in one day, whereas it was lasted longer, approximately for 1-2 and 2-3 days, during treatment with probiotics. This is presumably, because of a species-specific efficacy of probiotics in the treatment of acute diarrhea, and L. rhamnosus included in the probiotics mixture is the effective one. ...
Article
Acute, inflammatory processes contribute to the fact that conventionally pathogenic and pathogenic microorganisms colonize the mucous membranes of the small intestine and form biofilms, can become a source of bacterial toxin, which, when the epithelial layer breaks, penetrates to the lymphatic and blood systems, contributing to the formation of sepsis. The barrier function of the epithelium is critical in the development of inflammatory bowel diseases, while normal functioning requires a constant balance between reactivity and tolerance to microorganisms of the intestinal lumen. Increased permeability of the intestinal mucosa is the main risk factor for the spread of bacteria. Epithelium, being an essential element of tissue barriers, provides selective transport for the movement of ions and macromolecules, and also creates an obstacle for their penetration into the underlying tissues. Control of the permeability of the epithelial layer is carried out by the apical intercellular complex - tight contacts, which comprise proteins of the claudine family. Intestinal flora affects the sensory, motor and immune functions of the intestine, and also interacts with higher nervous centers. Immunosuppressive processes are one of the main causes of destabilization of the barrier function intestine and brain.
... 53 Moreover, ACE2 expression was shown to be elevated in the colon during experimental DSS colitis as compared with controls. 50 A chemical inhibitor of ACE2 (GL1001) reduced DSS colitis severity 54 suggesting that ACE2 plays a pathogenic role in colitis. In contrast, ACE2 deficiency caused enhanced on April 17, 2020 by guest. ...
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The current coronavirus pandemic is an ongoing global health crisis due to covid-19, caused by severe acute respiratory syndrome coronavirus 2. Although covid-19 leads to little or mild flu-like symptoms in the majority of affected patients, the disease may cause severe, frequently lethal complications such as progressive pneumonia, acute respiratory distress syndrome and organ failure driven by hyperinflammation and a cytokine storm syndrome. This situation causes various major challenges for gastroenterology. In the context of IBD, several key questions arise. For instance, it is an important question to understand whether patients with IBD (eg, due to intestinal ACE2 expression) might be particularly susceptible to covid-19 and the cytokine release syndrome associated with lung injury and fatal outcomes. Another highly relevant question is how to deal with immunosuppression and immunomodulation during the current pandemic in patients with IBD and whether immunosuppression affects the progress of covid-19. Here, the current understanding of the pathophysiology of covid-19 is reviewed with special reference to immune cell activation. Moreover, the potential implications of these new insights for immunomodulation and biological therapy in IBD are discussed.
... has been reported that they help in peptide digestion because of their localization at the brush border of the intestinal epithelia [20]. In addition, it has been found that ACE-2 expression is increased in gastritis and inflammatory bowel diseases (IBDs) suggestive of the potential benefit of ACE-2 blockers in ameliorating IBDs [21]. ...
Article
Angiotensin converting enzymes (ACE) and more recently discovered ACE-2 are important proteins involved in the renin-angiotensin system. The balance between ACE and ACE-2 is important for the regulation of blood pressure and electrolyte homeostasis. Inflammatory diseases like rheumatoid arthritis are associated with increased risk for cardiovascular complications. We studied the effect of inflammation on the expression levels of ACE and ACE-2 in two groups (n = 4/group) of adjuvant arthritis (AA) and healthy (control) rats. The AA group received 0.2 ml of 50 mg ml(-1) of Mycobacterium butyricum suspended in squalene into the tail base. On day 12, rats were euthanized and their organs (hearts, liver, kidney, and intestine) were excised. The mRNA of ACE and ACE-2 were determined by real-time polymerase chain reaction. ACE and ACE-2 protein expression in rat heart was determined by Western blot. Inflammation resulted in 80% reduction of ACE-2 gene expression in rat heart. ACE-2/ACE expression ratio was significantly reduced from 0.7 ± 0.4 in control rats to 0.07 ± 0.09 in AA. Similarly, ACE-2/ACE protein expression ratio was also disrupted with a significant reduction in AA animals (6.7 ± 4.8 vs. 0.9 ± 05 in control and AA, respectively). ACE-2 has been found to provide negative feedback of renin-angiotensin system and protection of the heart and kidneys. Disruption of the balance between ACE and ACE-2 observed in inflammation may be, at least in part, involved in the cardiovascular complications seen in patients with inflammatory diseases.
... For example, ACE2 fusion proteins and TMPRSS2 inhibitors are recommended for rapid diagnosis or, treatment of COVID-19 (2). ACE2 inhibitors are also considered since GL1001 (selective ACE2 inhibitor) was demonstrated to reduce DSS-induced mucosal inflammation and distal colon pathology in inflammatory bowel disease (IBD) animal model (57). In addition, ACE2 inhibition is thought to elevate its substrate level which in turn would block over production of different pro-inflammatory cytokines (58). ...
Article
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Outbreak of the novel coronavirus disease (COVID-19) was first reported in Wuhan, Hubei province of China, in early December 2019 which was later declared as a pandemic by World Health Organization (WHO) in March 2020. The International Committee on Taxonomy of Viruses has termed this novel coronavirus as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). According to the report of WHO on 29th April, 2020, 3018681 confirmed cases along with 207973 deaths have been documented globally. COVID-19 was originally reported as a lethal lung disease with fever and cough as the most common symptoms; however, the increasing number of gastrointestinal symptoms, such as diarrhoea, vomiting and abdominal pain in patients have clearly suggested that gastrointestinal tract (GIT) may also serve as a potential route for SARS-CoV-2 infection. To identify the effective therapies on this pandemic is urgent. Keeping this in mind, we realize that melatonin is a potent antioxidant, anti-inflammatory and immunomodulatory molecule and it has been used in diverse diseases and pathophysiological conditions, including respiratory disease and viral infections. Importantly, melatonin specific receptors and its endogenously synthetic machinery are distributed throughout the mammalian gastrointestinal system. Therefore, the therapeutic potentiality of melatonin in SARS-CoV-2 associated digestive symptoms cannot be ignored. In this review, we focus on the clinical implications of melatonin on the digestive complications associated with SARS-CoV-2 infection.
... Moreover, Ang (1-7) treatment alleviates colitis progression, whereas the blockade of Mas aggravates the disease [61], indicating the protective role of the ACE2/Ang (1-7)/Mas axis. In contrast, treatment with the ACE2 inhibitor GL1001 reduces the severity of colitis [62], suggesting that ACE2 plays a pathogenic role in intestinal inflammation. During SARS-CoV-2 infection, the downregulation of ACE2 would potentially result in unopposed functions of Ang II and decreased levels of Ang (1-7), thereby shifting the balance towards the pro-inflammatory side, which would contribute to epithelial injury [63,64]. ...
Article
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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the global coronavirus disease 2019 (COVID-19) outbreak. Along with the respiratory tract, the gastrointestinal (GI) tract is one of the main extra-pulmonary targets of SARS-CoV-2 with respect to symptom occurrence and is a potential route for virus transmission, most likely due to the presence of angiotensin-converting enzyme 2. Therefore, understanding the mechanisms of GI injury is crucial for a harmonized therapeutic strategy against COVID-19. This review summarizes the current evidence for the clinical features of and possible pathogenic mechanisms leading to GI injury in COVID-19.
... One of the hypotheses is that the role of virus-induced ACE2 receptor downregulation is the key to understanding its pathogenesis. Before the COVID-19 outbreak, ACE2 was considered as a target mostly for treating ulcerative colitis [3], although with a low therapeutic value (due to possible severe side effects) [4]. It is known that SARS-CoV-2 enters a cell via the binding of the viral S-protein to the extracellular domains of the transmembrane ACE2, which leads to subsequent knockdown of surface ACE2 expression [5]. ...
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We elaborate new models for ACE and ACE2 receptors with an excellent prediction power compared to previous models. We propose promising workflows for working with huge compound collections, thereby enabling us to discover optimized protocols for virtual screening management. The efficacy of elaborated roadmaps is demonstrated through the cost-effective molecular docking of 1.4 billion compounds. Savings of up to 10-fold in CPU time are demonstrated. These developments allowed us to evaluate ACE2/ACE selectivity in silico, which is a crucial checkpoint for developing chemical probes for ACE2.
... Several molecules have been developed to specifically inhibit human ACE2, and some of them have been widely used in mouse/rat models [27]. Among them, MLN-4760 seems of particular interest, as it was not associated to any significant adverse effect in animal models [147][148][149][150][151][152], can be administer by several routes (including inhalation) and has shown to retain its inhibitory effects on soluble ACE2 bound to spike proteins [52], indicating that it is able to bind and inhibit ACE2 activity regardless ACE2 binding to SARS-CoV-2 particles (Figure 1). ...
Article
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Since the end of 2019, the medical-scientific community has been facing a terrible pandemic caused by a new airborne viral agent known as SARS-CoV2. Already in the early stages of the pandemic, following the discovery that the virus uses the ACE2 cell receptor as a molecular target to infect the cells of our body, it was hypothesized that the renin-angiotensin-aldosterone system was involved in the pathogenesis of the disease. Since then, numerous studies have been published on the subject, but the exact role of the renin-angiotensin-aldosterone system in the path-ogenesis of COVID19 is still a matter of debate. RAAS represents an important protagonist in the pathogenesis of COVID19, providing the virus with the receptor of entry into host cells and determining its organotropism. Furthermore, following infection, the virus is able to cause an increase in plasma ACE2 activity, compromising the normal function of the RAAS. This dysfunction could contribute to the establishment of the thrombo-inflammatory state characteristic of severe forms of COVID19. Drugs targeting RAAS represent promising therapeutic options for COVID19 sufferers.
... MLN-4760 binds to the ligand-binding pocket of ACE2 at the enzymatic active site of ACE2 and inhibits ACE2 carboxypeptidase activity in low nanomolar range with an IC 50 of 0.44 nmol/l. MLN-4760 is shown to significantly reduce the formation of angiotensin 1-7 in human cell culture as well as in the in vitro models of murine kidney, endothelial, hearth, bone marrow, and colon cells [33,43,[47][48][49][50][51][52][53][54][55]. ...
Article
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Background: Hypertension has been identified as the most common comorbidity in coronavirus disease 2019 (COVID-19) patients, and has been suggested as a risk factor for COVID-19 disease outcomes. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus enters host human cells via binding to host cell angiotensin-converting enzyme 2 (ACE2) receptors. Inhibition of ACE2 has been proposed as a potential therapeutic approach to block SARS-CoV-2 contagion. However, some experts suggest that ACE2 inhibition could worsen the infection. Here, we aimed to study the effect of ACE2 inhibition on the SARS-CoV-2 spike protein binding to ACE2. Method: Crystallographic structures of the SARS-CoV-2 spike protein, the spike receptor-binding domain, native ACE2, and the ACE2 complexed with MLN-4760 were used as the study model structures. The spike proteins were docked to the ACE2 structures and the dynamics of the complexes, ligand-protein, and protein-protein interactions were studied by molecular dynamics simulation for 100 ns. Results: Our result showed that inhibition of ACE2 by MLN-4760 increased the affinity of the SARS-CoV-2 spike protein binding to ACE2. Results also revealed that spike protein binding to the ACE2 inhibited by MLN-4760 restored the enzymatic active conformation of the ACE2 from closed/inactive to open/active conformation by removing MLN-4760 binding from the ligand-binding pocket of ACE2. Conclusion: We conclude that using ACE2 inhibitors can increase the risk of SARS-CoV-2 infection and worsen COVID-19 disease outcome. We also found that the SARS-CoV-2 can abrogate the function of ACE2 inhibitors and rescue the enzymatic activity of ACE2. Therefore, ACE2 inhibition is not a useful treatment against COVID-19 infection.
... The surface spike glycoprotein (S protein) of SARS-CoV-2 enters human cells via a specific surface receptor, angiotensin-converting enzyme 2 (ACE2) [14][15][16][17][18] . This monocarboxypeptidase regulates the cleavage of several peptides within the renin-angiotensin system and is involved in regulation of the intestinal amino acid transporter B0AT1, whose activity controls tryptophan homeostasis. ...
Article
The coronavirus disease 2019 (COVID-19) pandemic is an ongoing global health crisis causing major challenges for clinical care in patients with gastrointestinal diseases. Although triggering of anti-viral immune responses is essential for clearance of infection, some patients have severe lung inflammation and multiorgan failure due to marked immune cell dysregulation and cytokine storm syndrome. Importantly, the activation of cytotoxic follicular helper T cells and a reduction of regulatory T cells have a crucial, negative prognostic role. These findings lead to the question of whether immunosuppressive and biologic therapies for gastrointestinal diseases affect the incidence or prognosis of COVID-19 and, thus, whether they should be adjusted to prevent or affect the course of the disease. In this Review, data on the use of such therapies are discussed with a primary focus on inflammatory bowel disease, autoimmune hepatitis and liver transplantation. In particular, the roles of corticosteroids, classic immunosuppressive agents (such as thiopurines and mycophenolate mofetil), small molecules (such as Janus kinase (JAK) inhibitors), and biologic agents (such as tumour necrosis factor (TNF) blockers, vedolizumab and ustekinumab) are reviewed. Finally, the use of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines for the prevention of infection in patients with gastrointestinal diseases and concomitant immunosuppressive or biologic therapy will be discussed.
... Furthermore, in the same study, exogenous Ang 1-7 treatment was accompanied by reduced neutrophil infiltration to colonic mucosa. Somewhat controversially, ACE2 inhibitor GL1001 improved DSS colitis in BALB/cJ mice by reducing colonic bleeding and diarrhoea, histopathologic damage, and MPO activity 61 The patients were matched according to age, sex, diagnosis, and disease location, but also according to diagnosis of hypertension, to avoid confounding factor of cardiovascular health status of the patients. In the same study, hospitalizations, operations, and corticosteroid use was also compared before and during use of ACE inhibitors and ARBs in a subset of patients who filled both conditions for at least six months. ...
Article
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Inflammatory bowel diseases (IBD) are chronic disorders of the gastrointestinal tract, which manifest in recurring gastrointestinal inflammation. The current treatment options of IBD are not curative and are lacking in aspects like prevention of fibrosis. New treatment options are needed to fulfil the unmet needs and provide alternatives to drugs with resistances and side effects. Drugs targeting the renin-angiotensin system (RAS), besides being anti-hypertensive, also possess anti-inflammatory and anti-fibrotic properties, and could offer an inexpensive alternative to control inflammation and fibrosis in the gut. RAS inhibitors have been effective in preventing and alleviating colitis in preclinical studies, but available human data are still sparse. This review outlines the pathophysiological functions of RAS in the gut and summarises preclinical studies utilizing pharmacological RAS inhibitors in the treatment of experimental colitis. We discuss the alterations in intestinal RAS and the available evidence of the benefits of RAS inhibitors for IBD patients. Retrospective studies comparing IBD patients using ACE inhibitors or angiotensin II receptor blockers have provided optimistic results regarding a milder disease course, and fewer hospitalizations and corticosteroid use in patients using RAS inhibitors. Prospective studies are needed to evaluate the effectiveness of these promising medications in the treatment of IBD.
... It has been reported that ACE2-deficient mice suffer from more severe symptoms in a dextran sodium sulfate (DSS)-induced experimental colitis model, which occurs not through the reninangiotensin system (RAS) but through the regulation of intestinal amino acid homeostasis (Hashimoto et al., 2012). Another study came to the opposite conclusion that the ACE2 inhibitor GL1001 attenuated the severity of DSS-induced colitis (Byrnes et al., 2009), and these data indicated that ACE2 may exert a dual role in inflammatory bowel disease (IBD). It has been reported that ACE2-knockout mice exhibit more severe insulin resistance and glucose intolerance in response to a high-fat diet (Xuan et al., 2018). ...
Article
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Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells through interactions with its receptor, Angiotensin-converting enzyme 2 (ACE2), causing severe acute respiratory syndrome and death in a considerable proportion of people. Patients infected with SARS-CoV-2 experience digestive symptoms. However, the precise protein expression atlas of ACE2 in the gastrointestinal tract remains unclear. In this study, we aimed to explore the ACE2 protein expression pattern and the underlying function of ACE2 in the gastrointestinal tract, including the colon, stomach, liver, and pancreas. Methods: We measured the protein expression of ACE2 in the gastrointestinal tract using immunohistochemical (IHC) staining with an ACE2-specific antibody of paraffin-embedded colon, stomach, liver, and pancreatic tissues. The correlation between the protein expression of ACE2 and the prognosis of patients with gastrointestinal cancers was analyzed by the log-rank (Mantel–Cox) test. The influence of ACE2 on colon, stomach, liver, and pancreatic tumor cell line proliferation was tested using a Cell Counting Kit 8 (CCK-8) assay. Results: ACE2 presented heterogeneous expression patterns in the gastrointestinal tract, and it showed a punctate distribution in hepatic cells. Compared to that in parallel adjacent non-tumor tissues, the protein expression of ACE2 was significantly increased in colon cancer, stomach cancer, and pancreatic cancer tissues but dramatically decreased in liver cancer tissues. However, the expression level of the ACE2 protein was not correlated with the survival of patients with gastrointestinal cancers. Consistently, ACE2 did not affect the proliferation of gastrointestinal cancer cells in vitro. Conclusion: The ACE2 protein is widely expressed in the gastrointestinal tract, and its expression is significantly altered in gastrointestinal tumor tissues. ACE2 is not an independent prognostic marker of gastrointestinal cancers.
... The general cardioprotective role of ACE2 has limited the development of ACE2 inhibitors because they are unlikely to be of therapeutic benefit in cardiovascular disorders where the upregulation of ACE2 expression and activity is beneficial. Even so, a number of ACE2 selective inhibitors have been developed, including MLN-4760 (GL1001), DX-600, and 416F2 [131][132][133]. On the contrary, ACE2 activators, such as xanthenone, have been tested in a heart failure rat model [134]. ...
Article
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Angiotensin converting enzyme 2 (ACE2) is the recognized host cell receptor responsiblefor mediating infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). ACE2bound to tissue facilitates infectivity of SARS-CoV-2; thus, one could argue that decreasing ACE2tissue expression would be beneficial. However, ACE2 catalytic activity towards angiotensin I (AngI) and II (Ang II) mitigates deleterious effects associated with activation of the renin-angiotensinaldosteronesystem (RAAS) on several organs, including a pro-inflammatory status. At the tissuelevel, SARS-CoV-2 (a) binds to ACE2, leading to its internalization, and (b) favors ACE2 cleavage toform soluble ACE2: these actions result in decreased ACE2 tissue levels. Preserving tissue ACE2activity while preventing ACE2 shredding is expected to circumvent unrestrained inflammatoryresponse. Concerns have been raised around RAAS modulators and their effects on ACE2expression or catalytic activity. Various cellular and animal models report conflicting results invarious tissues. However, recent data from observational and meta-analysis studies in SARS-CoV-2-infected patients have concluded that RAAS modulators do not increase plasma ACE2 levels orsusceptibility to infection and are not associated with more severe diseases. This review presentsour current but evolving knowledge of the complex interplay between SARS-CoV-2 infection, ACE2levels, modulators of RAAS activity and the effects of RAAS modulators on ACE2 expression.
... However, there have been debates on the role of ACE2 in IBD. It is also reported that an ACE2 inhibitor may have an anti-inflammatory effect in DSS-induced colitis mice (40). Considering the dual role of ACE2 in the development of colitis, it warrants further study. ...
Article
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Background and Aims: Angiotensin-converting enzyme II (ACE2) is the key molecule for understanding the pathophysiology of COVID-19. The risk of COVID-19 and impact of immunosuppressive treatment on disease course in patients with inflammatory bowel disease (IBD) remain controversial. We aimed to determine the change of intestinal ACE2 expression before and after biologics treatment including anti-tumor necrosis factor α (anti-TNFα), anti-integrin, and anti-interleukin (IL)12/23 in IBD patients. Methods: We analyzed the ACE2 expression through the public database of paired intestinal biopsies from IBD patients before and after biologic therapy. Change of ACE2 RNA and protein expression were validated in two independent cohorts (Birmingham cohort and Guangzhou cohort). The correlation between ACE2 expression and disease activity was also analyzed. Results: Mining information from the GEO database showed that compared with healthy control, intestinal ACE2 expression was downregulated in ileum of CD patients, while upregulated in colon of both CD and UC patients. Colonic ACE2 RNA expression was decreased significantly in patients responding to anti-TNFα but not anti-integrin and anti-IL12/23, which was validated in the Birmingham cohort. Using the Guangzhou cohort including 53 patients matched by pre- and post-anti-TNFα therapy, colonic ACE2 protein expression was significantly downregulated after anti-TNFα treatment in responders (P < 0.001) rather than non-responders. Colonic ACE2 expression was significantly higher in patients with severe histologically active disease compared with those with moderate (P < 0.0001) and mild (P = 0.0002) histologically active disease. Conclusion: Intestinal inflammation influences the expression of intestinal ACE2 in IBD patients, with different alterations in the ileum and colon. Colonic ACE2 expression was downregulated after anti-TNFα therapy in IBD patients responding to treatment. This might provide new clues regarding the risk of SARS-CoV-2 infection and the potential benefit of sustaining anti-TNFα treatment in patients with IBD.
... ACE2 was also evidenced through the use of a chemical inhibitor of ACE2 (GL1001), that was able to reduce dextran sulfate sodium (DSS) colitis severity, in the mouse model, suggesting that ACE2 plays a pathogenic role in colitis. 35,38 Second, tumor necrosis factor (TNF) inhibitors might be effective in reducing organ damage. 39 This effect is achieved through the decreased shedding of the ACE2 ectodomain (mediated by TNF-α-converting enzyme) which is essential for the penetration of SARS-CoV-2 into the cell. ...
Article
Our knowledge on COVID-19 is changing and evolving rapidly, with novel insights and recommendations, almost on a daily basis. It behooves the medical community to provide updated information on a regular basis, on best practice to facilitate optimal care of infected patients and appropriate advice for the general population. This is particularly important in the case of patients with chronic conditions, such as Inflammatory Bowel Disease (IBD). In this paper, we compiled the existing evidence on the impact of COVID-19 in IBD patients and provide guidance and on the most appropriate care to adopt during the pandemic. Our review highlighted that IBD, per se, is not a risk factor for COVID-19. However, all IBD patients with symptoms should be tested for SARS-CoV-2 and the procedures for disease management shall be carefully adapted: i) in SARS-CoV-2 positive IBD patients, medical treatments should be re-evaluated (with particular focus on corticosteroids) always with the purpose of treating active disease and maintaining remission; ii) non-urgent surgeries and endoscopic procedures should be postponed for all patients; iii) online consultancy should be implemented; and iv) hospitalization and surgery should be limited to life threatening situations
... However, there has been a debate with respect to the role of ACE2 in the gut. Elevated ACE2 level is observed in the colon isolated from the IBD mouse model [20], and ACEI could markedly rescue the progression of DSS-induced experimental colitis [21]. Nevertheless, Hashimoto et al. reported that ace2 deficiency causes a high risk of colitis due to hampered immune cell trafficking as well as alterations of gut microbiota [19]. ...
Article
Background The whole world was hit hard by the coronavirus disease-19 (COVID-19). Given that angiotensin I converting enzyme 2 (ACE2) is the viral entry molecule, understanding ACE2 has become a major focus of current COVID-19 research. ACE2 is highly expressed in the gut, but its role has not been fully understood and thus COVID-19 treatments intending to downregulate ACE2 level may cause untoward side effects. Gaining insight into the functions of ACE2 in gut homeostasis therefore merits closer examination, and is beneficial to find potential therapeutic alternatives for COVID-19. Methods: We took advantage of Ace2 knockout out mice and isolated intestinal organoids to examine the role of ACE2 in intestinal stemness. Inflammatory bowel disease (IBD) mouse model was established by 4% dextran sodium sulfate. LGR5 and KI67 levels were quantitated to reflect the virtue of intestinal stem cells (ISCs). FITC-dextran 4 (FD-4) assay was used to assess intestinal barrier function. Results: Western blotting identified the expression of ACE2 in colon, which was consistent with the results of immunofluorescence and RT-PCR. Moreover, Ace2−/− organoids showed decreased LRG5 and KI67 levels, and elevated calcium concentration. Furthermore, the permeability of ace2−/− organoids was markedly increased compared with ace2+/+ organoids. Collectively, ace2−/− mice were more susceptible than ace2+/+ mice to IBD, including earlier bloody stool, undermined intestinal architecture and more pronounced weight loss. Conclusions: Our data reveal that ACE2 contributes to the proliferation of intestinal stem cells and hence orchestrates the mucosal homeostasis.
... In the DSS model of experimental colitis, pharmacological inhibition of ACE2 with (S,S)-2-(1-Carboxy-2-(3-(3,5-dichlorobenzyl)-3H-imidazol-4yl)-ethylamino)-4-methylpentanoic acid (GL1001) attenuated the severity of experimental colitis, improved the pathologic alterations, and decreased myeloperoxidase levels in a similar manner as sulfasalazine treatment. 26 Other substrates of ACE2 are also associated with IBD. Ghrelin has a protective anti-inflammatory role in experimental colitis, 27 and its levels are increased in patients with IBD with active disease, likely to control the TNF-αmediated inflammatory response. ...
Article
Angiotensin-converting enzyme 2 (ACE2) has been highlighted for its role as a receptor for SARS-CoV-2, responsible for the current COVID-19 pandemic. This review summarizes current knowledge about ACE2 as a multifunctional protein, focusing on its relevance in inflammatory bowel disease (IBD). As an enzyme, ACE2 may be protective in IBD because it favors the counter-regulatory arm of the renin-angiotensin system or deleterious because it metabolizes other anti-inflammatory/repairing elements. Meanwhile, as a receptor for SARS-CoV-2, the impact of ACE2 expression/activity on infection is still under debate because no direct evidence has been reported and, again, both protective and deleterious pathways are possible. Research has shown that ACE2 regulates the expression of the neutral amino acid transporter B0AT1, controlling tryptophan-associated intestinal inflammation and nutritional status. Finally, intact membrane-bound or shed soluble ACE2 can also trigger integrin signaling, modulating the response to anti-integrin biologic drugs used to treat IBD (such as vedolizumab) and fibrosis, a long-term complication of IBD. As such, future studies on ACE2 expression/activity in IBD can improve monitoring of the disease and explore an alternative pharmacological target.
Article
Intestinal fibrosis is considered an inevitable complication of Crohn's disease (CD) that results in symptoms of obstruction and stricture formation. Endoscopic or surgical treatment is required to treat the majority of patients. Progress in the management of stricturing CD is hampered by the lack of effective anti-fibrotic therapy; however, this situation is likely to change because of recent advances in other fibrotic diseases of the lung, liver and skin. In this review, we summarized data from randomized controlled trials (RCT) of anti-fibrotic therapies in these conditions. Multiple compounds have been tested for the anti-fibrotic effects in other organs. According to their mechanisms, they were categorized into growth factor modulators, inflammation modulators, 5-hydroxy-3-methylgultaryl-coenzyme A (HMG-CoA) reductase inhibitors, intracellular enzymes and kinases, renin-angiotensin system (RAS) modulators and others. From our review of the results from the clinical trials and discussion of their implications in the gastrointestinal tract, we have identified several molecular candidates that could serve as potential therapies for intestinal fibrosis in CD.
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The recent outbreak of COVID-19 infection started in Wuhan, China, and spread across China and beyond. Since the WHO declared COVID-19 a pandemic (March 11, 2020), three vaccines and only one antiviral drug (remdesivir) have been approved (Oct 22, 2020) by the FDA. The coronavirus enters human epithelial cells by the binding of the densely glycosylated fusion spike protein (S protein) to a receptor (angiotensin-converting enzyme 2, ACE2) on the host cell surface. Therefore, inhibiting the viral entry is a promising treatment pathway for preventing or ameliorating the effects of COVID-19 infection. In the current work, we have used all-atom molecular dynamics (MD) simulations to investigate the influence of the MLN-4760 inhibitor on the conformational properties of ACE2 and its interaction with the receptor-binding domain (RBD) of SARS-CoV-2. We have found that the presence of an inhibitor tends to completely/partially open the ACE2 receptor where the two subdomains (I and II) move away from each other, while the absence results in partial or complete closure. The current study increases our understanding of ACE inhibition by MLN-4760 and how it modulates the conformational properties of ACE2.
Article
Novel anti-inflammatory compounds were synthesised by derivatization of militarin, a compound isolated from Cordyceps militaris that is an ethnopharmacologically well-known herbal medicine with multiple benefits such as anti-cancer, anti-inflammatory, anti-obesity, and anti-diabetic properties. In this study, we explored the in vitro and in vivo anti-inflammatory potencies of these compounds during inflammatory responses, their inhibitory mechanisms, and acute toxicity profiles. To do this, we studied inflammatory conditions using in vitro lipopolysaccharide-treated macrophages and several in vivo inflammatory models such as dextran sodium sulphate (DSS)-induced colitis, EtOH/HCl-induced gastritis, and arachidonic acid-induced ear oedema. Methods used included real-time PCR, immunoblotting analysis, immunoprecipitation, reporter gene assays, and direct kinase assays. Of the tested compounds, compound III showed the highest nitric oxide (NO) inhibitory activity. This compound also inhibited the production of prostaglandin (PG)E(2) at the transcriptional level by suppression of Syk/NF-κB, IKKɛ/IRF-3, and p38/AP-1 pathways in lipopolysaccharide (LPS)-activated RAW264.7 cells and peritoneal macrophages. Consistent with these findings, compound III strongly ameliorated inflammatory symptoms in colitis, gastritis, and ear oedema models. In acute toxicity tests, there were no significant differences in body and organ weights, serum parameters, and stomach lesions between the untreated and compound III-treated mice. Therefore, this compound has the potential to be served as a lead chemical for developing a promising anti-inflammatory drug candidate with multiple kinase targets.
Chapter
Protein turnover is orchestrated by a large array of proteases, and the gastrointestinal tract is the organ the most exposed to proteases, whether they originate from the pancreas for digestive purpose, from resident cells, from infiltrated inflammatory cells, or from microorganisms present in the intestinal lumen. To maintain tissue homeostasis, the gastrointestinal tract has developed mechanisms that tightly regulate the proteolytic balance in the tissues. Those mechanisms range from physical barriers (mucus layer, tight control of intestinal epithelial cell para- and transcellular passages) to molecular control of proteolytic activity through endogenous protease inhibitors. In the setting of inflammation, gastrointestinal tissues are overflowed with massive proteolytic activity that contributes to the generation of inflammatory symptoms. The present chapter analyses the disruption of the protease–antiprotease balance in the context of inflammatory bowel disease. It proposes to review the type of proteases that are present in the gastrointestinal tract, their known effects on the generation and/or maintenance of inflammatory symptoms, and their mechanisms of action. Further, the role of endogenous protease inhibitors is discussed, as well as the potential use of protease inhibition, as new possible therapeutic approach to treat chronic inflammatory disorders of the gut. KeywordsAlarmins-Antiproteases-Colitis-Colon-Crohn’s disease-Gut-Inflammation-Inflammatory bowel disease-Intestinal mucosa-Intestine-Pain-Proteases-Serpins-Ulcerative colitis
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Angiotensin Converting Enzyme 2 (ACE2) is the human receptor that interacts with the Spike protein of coronaviruses, including the one that produced the 2020 coronavirus pandemic (COVID‐19). Thus, ACE2 is a potential target for drugs that disrupt the interaction of human cells with SARS‐CoV‐2 to abolish infection. There is also interest on drugs that inhibit or activate ACE2, i.e. for cardiovascular disorders or colitis. Compounds binding at alternative sites could allosterically affect the interaction with Spike protein. We here review biochemical, chemical biology and structural information on ACE2, including the recent cryoEM structures of full length ACE2. We conclude that ACE2 is very dynamic and that allosteric drugs may be developed to target ACE2. At the time of the 2020 pandemic, we suggest that available ACE2 inhibitors or activators in advanced development should be tested for their ability to allosterically displace the interaction between ACE2 and the Spike protein.
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Angiotensin-converting enzyme (ACE) and its effector peptide angiotensin (Ang) II have been implicated in the pathogenesis of pancreatitis. ACE2, degrades Ang II to Ang (1-7), and has been recently described to have an antagonistic effect on ACE signaling. However, the specific underlying role of ACE2 in the pathogenesis of severe acute pancreatitis (SAP) is unclear. In the current study, the local imbalance of ACE and ACE2 as well as Ang II and Ang (1-7) expression were compared in wild-type (WT) and ACE2 knock-out (KO) or ACE2 transgenic (TG) mice subjected to cerulein-induced SAP. Serum amylase, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, IL-10 levels and histologic morphometry were used to determine the severity of pancreatitis. In WT mice, pancreatic ACE, Ang II and serum Ang II expression increased (P < 0.05) while pancreatic ACE2, Ang (1-7) and serum Ang (1-7) levels were also significantly elevated (P < 0.05) from 2 to 72 h after the onset of SAP. However, the ratio of pancreatic ACE2 and ACE expression was significantly reduced (from 1.46±0.09 to 0.27±0.05, P < 0.001) and paralleled the severity of pancreatitis. ACE2 KO mice exhibited increased levels of TNF-α, IL-1β, IL-6, multifocal coagulative necrosis, inflammatory infiltrate, and lower levels for serum IL-10, pancreatic Ang (1-7) (4.70±2.13 vs. 10.87±2.51, P < 0.001) compared with cerulein-treated WT mice at the same time point. Conversely, ACE2 TG mice with normal ACE expression were more resistant to SAP challenge as evidenced by a decreased inflammatory response, attenuated pathological changes and increased survival rates. These data suggest that the ACE2 and ACE imbalance plays an important role in the pathogenesis of SAP, and that pancreatic ACE2 is an important factor in determining the severity of SAP.
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COVID-19 is an infectious disease caused by novel coronavirus SARS-CoV-2, a betacoronavirus comprised of single-stranded ribonucleic acid (RNA), the first time reported in December 2019 as pneumonia with unknown etiology in Wuhan City in China. It is a very important current problem for public health worldwide. A typical clinical course includes dyspnoea, dry cough and fever. In the presented paper we conducted the literature review and described the most important facts within the current state of knowledge about symptomatology and pathophysiology of gastrointestinal dysfunction in the course of COVID-19. Data about prevalence of gastrointestinal symptoms in the course of COVID-19 show wide divergence in the cited literature. Generally, the most common reported digestive symptoms were loss of appetite, nausea and vomiting. Liver injury in the course of COVID-19 is also an important and not well understood problem. The virus has high affinity to cells containing angiotensin- -converting enzyme 2 (ACE2) protein. Digestive symptoms of COVID-19 may be associated with ACE2 expression in epithelial cells in upper oesophagus, ileum and colon. Previous scientific reports have elucidated the role of ACE2 in modulating intestinal inflammation and diarrhoea.
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Here, neuromodulatory effects of selective ACE2 inhibitors were investigated. Two different types of small molecule ligands for ACE2 inhibition were selected using chemical genetic approach, they were synthesized using developed chemical method and tested using presynaptic rat brain nerve terminals (synaptosomes). EBC-36032 (1 µM) increased in a dose-dependent manner spontaneous and stimulated ROS generation in nerve terminals that was of non-mitochondrial origin. Another inhibitor EBC-36033 (MLN-4760) was inert regarding modulation of ROS generation. EBC-36032 and EBC-36033 (100 µM) did not modulate the exocytotic release of L-[¹⁴C]glutamate, whereas both inhibitors decreased the initial rate of uptake, but not accumulation (10 min) of L-[¹⁴C]glutamate by nerve terminals. EBC-36032 (100 µM) decreased the exocytotic release as well as the initial rate and accumulation of [³H]GABA by nerve terminals. EBC-36032 and EBC-36033 did not change the extracellular levels and transporter-mediated release of [³H]GABA and L-[¹⁴C]glutamate, and tonic leakage of [³H]GABA from nerve terminals. Therefore, synthesized selective ACE2 inhibitors decreased uptake of glutamate and GABA as well as exocytosis of GABA at the presynaptic level. The initial rate of glutamate uptake was the only parameter that was mitigated by both ACE2 inhibitors despite stereochemistry issues. In terms of ACE2-targeted antiviral/anti-SARS-CoV-2 and other therapies, novel ACE2 inhibitors should be checked on the subject of possible renin–angiotensin system (RAS)-independent neurological side effects.
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Angiotensin-converting enzyme 2 (ACE2) is a human homolog of ACE. As a key enzyme of renin-angiotensin system (RAS), ACE2 has attracted much more attentions of the researchers. Many studies have shown that ACE2 plays important roles in the pathophysiology of diabetic nephropathy, hypertension, and heart failure. However, its role in intestine has not been fully clarified. Studies showed that ACE2 was closely related to the intestinal inflammation, but its effect on intestine is still a controversial issue. This article reviewed the advances in study on ACE2 in intestine.
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A group of presumed drug-like molecules that possess high in silico affinity for angiotensin-converting enzyme 2 were computationally designed. This enzyme is a promising new target in both cardiorenal disease and some coronavirus infections. A set of substrate analogous molecules were optimized by means of the LeapFrog module of the SYBYL package. Later, Molinspiration and Molsoft were used for screening out the compounds with low oral bioavailability. Similarly, OSIRIS was used for screening out the compounds having serious side effects. At the end of several stages of screening, seven candidates to anti-viral drugs fulfiling all the evaluated criteria were obtained. They are amenable for future studies in vitro and in vivo. These designed ligands were finally evaluated by Quantitative Structure Activity Relationship studies. 21 molecules were used to carry out the qsar models. Fom these four molecules were taken as external sets yielding models with q2 = 0.652 and r2 = 0.962 values.
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The emergence of COVID-19 in late 2019 is challenging the global public health community to confront a novel pandemic that spread rapidly from its origins in the Chinese city of Wuhan until it has reached more than 200 other countries within a matter of months. Minimal information is available regarding whether pregnant women are at greater risk of complications related to COVID-19 compared to the general population. This article reviews the effects and pathophysiology of SARS-CoV-2 infection during pregnancy and breastfeeding based on the current knowledge.
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Introduction: Angiotensin-(1-7) is a key component of the Renin-Angiotensin System, which can counter-regulate several deleterious effects caused by angiotensin II. Due to the potential for therapeutic use, several of its actions are specifically described in patents. Areas covered: In this review, the authors describe a plethora of therapeutic uses for Angiotensin-(1-7), claimed and supported by experimental evidence in patent documents and applications. Expert opinion: The clinical potential of Angiotensin-(1-7) as a therapeutic agent to treat several pathologies is evidenced by the variety of patents and clinical trials involving this peptide. Cancer treatment is one of the most advanced therapeutic areas, but clinical studies are also available in several other areas, such as cardiovascular, hematological, transplantation, surgical and medical procedures.
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Rectal prolapse is a common clinical problem in laboratory mice. This condition may occur spontaneously, develop after genetic manipulations, result from infections with pathogens such as Citrobacter species, or arise secondary to experimental design such as colitis models. The current standard of care at our institution is limited to monitoring mice until tissue becomes ulcerated or necrotic; this strategy often leads to premature euthanasia of valuable animals prior to the study endpoint. Surgical correction of rectal prolapse is performed routinely and with minimal complications in larger species by using manual reduction with placement of a pursestring suture. In this report, we investigated whether the use of a pursestring suture was an effective treatment for mice with rectal prolapse. The procedure includes anesthetizing mice with isoflurane, manually reducing prolapsed tissue, and placing a pursestring suture of 4-0 polydioxanone. We have performed this procedure successfully in 12 mice. Complications included self-trauma, fecal impaction due to lack of defecation, and mutilation of the surgical site by cage mates. Singly housing mice for 7 d postoperatively, applying multimodal analgesia, and releasing the pursestring when indicated eliminated these complications. The surgical repair of rectal prolapses in mice is a minimally invasive procedure that resolves the clinical symptoms of affected animals and reduces the number of mice that are euthanized prematurely prior to the study endpoint.
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Angiotensin-converting enzyme-2 (ACE2) may be involved in the physiological metabolism of angiotensin II to angiotensin(1-7) .... .
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Purpose of review: Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) has resulted in a global pandemic, with people with other conditions at greater risk of severe infection with intensified symptoms across multiple organ systems. Patients with cancer are at greater risk, and it is likely that those receiving treatment will experience greater incidence and severity of gastrointestinal toxicities, such as gastrointestinal mucositis, due to SARS-CoV-2 binding to angiotensin-converting enzyme (ACE)2 in the intestine. Recent findings: Recent studies have shown that SARS-CoV-2 patients experience gastrointestinal toxicities, and SARS-CoV-2 has capacity to infect intestinal cells through binding to ACE2 expressed in the intestine. ACE2 has a key role in intestinal homeostasis, and as such there is a concern for the impact of SARS-CoV-2 binding to ACE2 in terms of the implications for cancer treatment-induced gastrointestinal toxicities. Summary: SARS-CoV-2 is a high-risk infection for cancer patients receiving treatment. It is important to understand the mechanisms of intestinal infection with SARS-CoV-2 to determine the effect of SARS-CoV-2 infections on gastrointestinal toxicities, such as mucositis.
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Apelin and its cognate G protein-coupled receptor APJ constitute a signaling pathway with a positive inotropic effect on cardiac function and a vasodepressor function in the systemic circulation. The apelin-APJ pathway appears to have opposing physiological roles to the renin-angiotensin system. Here we investigated whether the apelin-APJ pathway can directly antagonize vascular disease-related Ang II actions. In ApoE-KO mice, exogenous Ang II induced atherosclerosis and abdominal aortic aneurysm formation; we found that coinfusion of apelin abrogated these effects. Similarly, apelin treatment rescued Ang II-mediated increases in neointimal formation and vascular remodeling in a vein graft model. NO has previously been implicated in the vasodepressor function of apelin; we found that apelin treatment increased NO bioavailability in ApoE-KO mice. Furthermore, infusion of an NO synthase inhibitor blocked the apelin-mediated decrease in atherosclerosis and aneurysm formation. In rat primary aortic smooth muscle cells, apelin inhibited Ang II-mediated transcriptional regulation of multiple targets as measured by reporter assays. In addition, we demonstrated by coimmunoprecipitation and fluorescence resonance energy transfer analysis that the Ang II and apelin receptors interacted physically. Taken together, these findings indicate that apelin signaling can block Ang II actions in vascular disease by increasing NO production and inhibiting Ang II cellular signaling.
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Acute and chronic experimental ulcerative colitis models were produced in mice by providing them with drinking water containing synthetic dextran sulfate sodium. Mice that developed acute colitis showed signs of diarrhea, gross rectal bleeding, and weight loss within 6-10 days after ingesting 3%-10% dextran sulfate sodium. On postmortem examination, multiple erosions and inflammatory changes including crypt abscesses were found on the left side of the large intestine. Mice that developed chronic colitis showed signs of erosions, prominent regenerations of the colonic mucosa including dysplasia, shortening of the large intestine, and frequent formation of lymphoid follicles after 5 administration cycles, where each cycle was composed of 7 days' consumption of drinking water containing 5% dextran sulfate sodium followed by 10 days' consumption of distilled water. The population of intestinal microflora, Bacteroides distasonis and Clostridium spp., increased significantly in mice with acute and chronic ulcerative colitis. Further, morphological studies suggest that the administered dextran sulfate sodium was partially phagocytized by macrophages in the colonic mucosa.
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A novel human zinc metalloprotease that has considerable homology to human angiotensin-converting enzyme (ACE) (40% identity and 61% similarity) has been identified. This metalloprotease (angiotensin-converting enzyme homolog (ACEH)) contains a single HEXXH zinc-binding domain and conserves other critical residues typical of the ACE family. The predicted protein sequence consists of 805 amino acids, including a potential 17-amino acid N-terminal signal peptide sequence and a putative C-terminal membrane anchor. Expression in Chinese hamster ovary cells of a soluble, truncated form of ACEH, lacking the transmembrane and cytosolic domains, produces a glycoprotein of 120 kDa, which is able to cleave angiotensin I and angiotensin II but not bradykinin or Hip-His-Leu. In the hydrolysis of the angiotensins, ACEH functions exclusively as a carboxypeptidase. ACEH activity is inhibited by EDTA but not by classical ACE inhibitors such as captopril, lisinopril, or enalaprilat. Identification of the genomic sequence of ACEH has shown that the ACEH gene contains 18 exons, of which several have considerable size similarity with the first 17 exons of human ACE. The gene maps to chromosomal location Xp22. Northern blotting analysis has shown that the ACEH mRNA transcript is approximately 3. 4 kilobase pairs and is most highly expressed in testis, kidney, and heart. This is the first report of a mammalian homolog of ACE and has implications for our understanding of cardiovascular and renal function.
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Angiotensin II (Ang II) regulates water and sodium transport in renal tubules and gastrointestinal tract. Two types of Ang II receptors have been cloned, but their distributions have not been determined in human colon. In addition, tissue renin-angiotensin systems (RAS) are believed to exist and to regulate local actions in human colon. We studied by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) the presence and localization of Ang II receptors Type 1 (AT(1)), Type 2 (AT(2)), and RAS components [angiotensinogen, renin, and angiotensin-converting enzyme (ACE)] in normal human colon. AT(1) receptors were localized in vessel walls, myofibroblasts, macrophages, and surface epithelium. AT(2) receptors were found in mesenchymal cells and weakly in parts of surface epithelium. Renin and ACE were distributed in vessel walls, mesenchymal cells, and in parts of surface epithelium. Angiotensinogen was also detected by RT-PCR. These findings demonstrated that Ang II receptors and RAS components were present in human colon, suggesting the possibility of its local regulation.
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Human angiotensin-converting enzyme-related carboxypeptidase (ACE2) is a zinc metalloprotease whose closest homolog is angiotensin I-converting enzyme. To begin to elucidate the physiological role of ACE2, ACE2 was purified, and its catalytic activity was characterized. ACE2 proteolytic activity has a pH optimum of 6.5 and is enhanced by monovalent anions, which is consistent with the activity of ACE. ACE2 activity is increased approximately 10-fold by Cl(-) and F(-) but is unaffected by Br(-). ACE2 was screened for hydrolytic activity against a panel of 126 biological peptides, using liquid chromatography-mass spectrometry detection. Eleven of the peptides were hydrolyzed by ACE2, and in each case, the proteolytic activity resulted in removal of the C-terminal residue only. ACE2 hydrolyzes three of the peptides with high catalytic efficiency: angiotensin II () (k(cat)/K(m) = 1.9 x 10(6) m(-1) s(-1)), apelin-13 (k(cat)/K(m) = 2.1 x 10(6) m(-1) s(-1)), and dynorphin A 1-13 (k(cat)/K(m) = 3.1 x 10(6) m(-1) s(-1)). The ACE2 catalytic efficiency is 400-fold higher with angiotensin II () as a substrate than with angiotensin I (). ACE2 also efficiently hydrolyzes des-Arg(9)-bradykinin (k(cat)/K(m) = 1.3 x 10(5) m(-1) s(-1)), but it does not hydrolyze bradykinin. An alignment of the ACE2 peptide substrates reveals a consensus sequence of: Pro-X((1-3 residues))-Pro-Hydrophobic, where hydrolysis occurs between proline and the hydrophobic amino acid.
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Severe acute respiratory syndrome (SARS) is an acute infectious disease that spreads mainly via the respiratory route. A distinct coronavirus (SARS-CoV) has been identified as the aetiological agent of SARS. Recently, a metallopeptidase named angiotensin-converting enzyme 2 (ACE2) has been identified as the functional receptor for SARS-CoV. Although ACE2 mRNA is known to be present in virtually all organs, its protein expression is largely unknown. Since identifying the possible route of infection has major implications for understanding the pathogenesis and future treatment strategies for SARS, the present study investigated the localization of ACE2 protein in various human organs (oral and nasal mucosa, nasopharynx, lung, stomach, small intestine, colon, skin, lymph nodes, thymus, bone marrow, spleen, liver, kidney, and brain). The most remarkable finding was the surface expression of ACE2 protein on lung alveolar epithelial cells and enterocytes of the small intestine. Furthermore, ACE2 was present in arterial and venous endothelial cells and arterial smooth muscle cells in all organs studied. In conclusion, ACE2 is abundantly present in humans in the epithelia of the lung and small intestine, which might provide possible routes of entry for the SARS-CoV. This epithelial expression, together with the presence of ACE2 in vascular endothelium, also provides a first step in understanding the pathogenesis of the main SARS disease manifestations.
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Ghrelin, identified in the gastric mucosa has been involved in control of food intake and growth hormone (GH) release but little is known about its influence on gastric secretion and mucosal integrity. The effects of ghrelin on gastric secretion, plasma gastrin and gastric lesions induced in rats by 75% ethanol or 3.5 h of water immersion and restraint stress (WRS) were determined. Exogenous ghrelin (5, 10, 20, 40 and 80 microg/kg i.p.) increased gastric acid secretion and attenuated gastric lesions induced by ethanol and WRS and this was accompanied by the significant rise in plasma ghrelin level, gastric mucosal blood flow (GBF) and luminal NO concentrations. Ghrelin-induced protection was abolished by vagotomy and attenuated by suppression of COX, deactivation of afferent nerves with neurotoxic dose of capsaicin or CGRP(8-37) and by inhibition of NOS with L-NNA but not influenced by medullectomy and administration of 6-hydroxydopamine. We conclude that ghrelin exerts a potent protective action on the stomach of rats exposed to ethanol and WRS, and these effects depend upon vagal activity, sensory nerves and hyperemia mediated by NOS-NO and COX-PG systems.
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Chronic arthritis induces hypermetabolism and cachexia. Ghrelin is a gastrointestinal hormone that has been proposed as a treatment to prevent cachexia. The aim of this work was to examine the effect of administration of the ghrelin agonist growth hormone-releasing peptide-2 (GHRP-2) to arthritic rats. Male Wistar rats were injected with Freund's adjuvant, and 15 days later arthritic and control rats were daily injected with GHRP-2 (100 microg/kg) or with saline for 8 days. Arthritis induced an increase in serum ghrelin (P < 0.01) and a decrease in serum concentrations of leptin (P < 0.01), whereas GHRP-2 administration increased serum concentrations of leptin. GHRP-2 increased food intake in control rats but not in arthritic rats. However, in arthritic rats GHRP-2 administration ameliorated the external symptoms of arthritis, as it decreased the arthritis score (10.4 +/- 0.8 vs. 13.42 +/- 0.47, P < 0.01) and the paw volume. In addition, circulating IL-6 and nitrites/nitrates were increased by arthritis, and GHRP-2 treatment decreased the serum IL-6 levels (P < 0.01). To elucidate whether GHRP-2 is able to modulate IL-6 release directly on immune cells, peritoneal macrophage cultures were incubated with GHRP-2 or ghrelin, the endogenous ligand of the growth hormone (GH) secretagogue receptor. Both GHRP-2 (10(-7) M) and ghrelin (10(-7) M) prevented endotoxin-induced IL-6 and decreased nitrite/nitrate release from peritoneal macrophages in vitro. These data suggest that GHRP-2 administration has an anti-inflammatory effect in arthritic rats that seems to be mediated by ghrelin receptors directly on immune cells.
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Numerous studies have shown that angiotensin II causes vasoconstriction both by a direct action on smooth muscle cells (postjunctional effect) and indirectly through the facilitation of noradrenaline release from postganglionic sympathetic neurons (prejunctional effect). The receptors through which angiotensin II exerts its actions were first divided into AT1 and AT2 subtypes. A further subdivision of AT1 receptors into AT1A and AT1B subtypes was based on cloning and receptor binding studies: AT1A showed a high affinity for losartan, but low affinity for PD123319, while AT1B receptors showed nearly 100-fold lower affinity for losartan and 10,000-fold higher affinity for PD123319 relative to AT1 sites. The present review deals with functional evidence supporting the existence of AT1A and AT1B subtypes in the cardiovascular system. Taken together, all the functional results obtained in vivo and in vitro–in a wide variety of vascular tissues from different species–allow one to conclude that angiotensin II AT1 receptors are different pre- and postjunctionally and also that prejunctional and postjunctional angiotensin II receptors most probably belong to AT1B and AT1A subtypes, respectively.
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Ghrelin, the gut-brain peptide recently identified as the natural endogenous ligand for growth hormone secretagogue receptors, exerts various endocrine and non-endocrine effects, including control of food intake and energy homeostasis.1 It could also play a role in modulating immune responses and inflammatory processes.1 Indeed, ghrelin exerts potent anti-inflammatory effects in vitro and in vivo,1–5 and high circulating ghrelin levels have been found in rats with septic shock, cysteamine induced duodenal ulcers, and adjuvant induced arthritis.4–6 Also, we have recently demonstrated that in patients with newly diagnosed coeliac disease, circulating ghrelin levels are abnormally high, correlate positively with intestinal mucosal lesion severity, and normalise in successfully gluten free diet treated patients.7 However, normal or even decreased ghrelin levels have been found in other inflammatory diseases, including rheumatoid arthritis and Helicobacter pylori associated …
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Ulcerative colitis is characterized by elevated rates of epithelial cell apoptosis, and an up-regulation of pro-apoptotic cytokines including tumor necrosis factor alpha (TNF-alpha). Recently, angiotensin converting enzyme (ACE) has been shown to promote apoptosis. In addition, pharmacologic ACE inhibition (ACE-I) both prevents apoptosis and reduces TNF-alpha expression in vitro. We hypothesized that ACE-I, using enalaprilat, would decrease colonic epithelial cell apoptosis and reduce colitis severity in the dextran sulfate sodium (DSS)-induced colitis model in mice. We assessed the severity of colitis, and colonic epithelial cell apoptosis, after administration of DSS. Mice were given either daily ACE-I treatment or daily placebo. ACE-I treatment markedly improved clinical outcomes. In addition, ACE-I treatment significantly reduced the maximum histopathologic colitis grade. ACE-I also dramatically reduced the epithelial apoptotic rate. To investigate the mechanism by which ACE-I reduced apoptosis; we measured TNF-alpha, Bcl-2, and Bax expression. TNF-alpha mRNA was significantly lower with ACE-I treatment compared to placebo at every time point, as was the ratio of Bax to Bcl-2. We conclude that ACE-I reduces the severity of DSS-induced colitis and reduces epithelial cell apoptosis.
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Angiotensin II (Ang II) receptor blockers have been reported to contribute to cytoprotective effects in various organs. However, the role of renin-angiotensin system (RAS) in modulation of the inflammatory bowel disease (IBD) remains unclear. In this study we assessed the role of angiotensin II type 1a (AT1a) receptor on the outcome of dextran sulfate sodium (DSS)-induced acute colitis by employing AT1a receptor deficient mice. The acute colitis was induced in wild type (WT) and AT1a receptor deficient mice by giving orally 3% DSS in drinking water for 7 days. Induction of DSS colitis resulted in up-regulation of Ang II and AT1a receptor in the colonic mucosa of WT mice. In parallel, loss of body weight, an increase in disease activity index (DAI), and the shortening of colon were found in DSS-challenged WT mice. In addition, an increase in thiobarbituric acid (TBA)-reactive substances and myeloperoxidase (MPO) activity, along with the up-regulation of tumor necrosis factor (TNF)-alpha were detected in the colonic mucosa of DSS-challenged WT mice. The endpoints mentioned above were significantly ameliorated in DSS-challenged AT1a receptor deficient mice. RAS is involved in the pathophysiology of DSS-induced colitis and AT1a receptor may be a novel therapeutic target for the treatment of IBD.
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Ghrelin, an orexigenic 28-amino-acid peptide, has been studied primarily in relation to the control of appetite and fat metabolism. In addition to these well-known functions, ghrelin, and its target receptors, growth hormone secretagogue receptors (GHS-Rs), have been localized to neutrophils, lymphocytes, and macrophages, which suggests that ghrelin may be involved in immune modulation. To assess the therapeutic role of ghrelin in production of pro-inflammatory and anti-inflammatory cytokines, the effects of exogenous ghrelin administration on the regulation of cytokine release in lipopolysaccharide (LPS)-activated murine RAW 264.7 macrophages were analyzed. Ghrelin and GHS-Rs are expressed in murine macrophages. In addition, exogenous ghrelin inhibited the production of pro-inflammatory cytokines IL-1beta and TNF-alpha in LPS-stimulated murine macrophages in a dose dependent and time-dependent fashion. Exogenous ghrelin pretreatment resulted in a decrease in LPS-induced NFkappaB activation and was presumably the reason for this ghrelin-mediated effect. In contrast to these findings, exogenous ghrelin significantly augmented the release of the anti-inflammatory cytokine IL-10 in a dose-dependent and time-dependent fashion from LPS-stimulated murine macrophages. Ghrelin administration enhanced activation of p38 MAPK, which is known to control the release of IL-10 in macrophages independent of the NFkappaB pathway. These effects of ghrelin on both pro-inflammatory and anti-inflammatory cytokines were offset when a specific GHS-R receptor antagonist was added to the culture media. These data suggest that ghrelin has potent anti-inflammatory properties through modulation of secretion of both pro-inflammatory and anti-inflammatory cytokines from LPS-stimulated macrophages through distinct signaling cascades. Therapeutic utility of ghrelin to control, modulate, or treat pathologic inflammatory conditions like endotoxemic shock and ulcerative colitis requires additional investigation.
Article
Acute and chronic experimental ulcerative colitis models were produced in mice by providing them with drinking water containing synthetic dextran sulfate sodium. Mice that developed acute colitis showed signs of diarrhea, gross rectal bleeding, and weight loss within 6–10 days after ingesting 3%–10% dextran sulfate sodium. On postmortem examination, multiple erosions and inflammatory changes including crypt abscesses were found on the left side of the large intestine. Mice that developed chronic colitis showed signs of erosions, prominent regenerations of the colonic mucosa including dysplasia, shortening of the large intestine, and frequent formation of lymphoid follicles after 5 administration cycles, where each cycle was composed of 7 days' consumption of drinking water containing 5% dextran sulfate sodium followed by 10 days' consumption of distilled water. The population of intestinal microflora, Bacteroides distasonis and Clostridium spp., increased significantly in mice with acute and chronic ulcerative colitis. Further, morphological studies suggest that the administered dextran sulfate sodium was partially phagocytized by macrophages in the colonic mucosa.
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In the decades since the major forms of idiopathic inflammatory bowel disease were defined on the basis of clinical manifestations, investigators have been challenged to identify the fundamental pathophysiologic processes underlying these enigmatic disorders, and clinicians have struggled to provide effective therapy for the often dismaying clinical manifestations. Clinical experience has led to the generally accepted notion that Crohn's disease and ulcerative colitis are distinct, if not discrete, entities. However, whether these are fundamentally different diseases or part of a mechanistic continuum remains an unanswered question, with both conceptual and practical management implications.
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The renin–angiotensin–aldosterone system (RAAS) is a key regulator of systemic blood pressure and renal function and a key player in renal and cardiovascular disease. However, its (patho)physiological roles and its architecture are more complex than initially anticipated. Novel RAAS components that may add to our understanding have been discovered in recent years. In particular, the human homologue of ACE (ACE2) has added a higher level of complexity to the RAAS. In a short period of time, ACE2 has been cloned, purified, knocked-out, knocked-in; inhibitors have been developed; its 3D structure determined; and new functions have been identified. ACE2 is now implicated in cardiovascular and renal (patho)physiology, diabetes, pregnancy, lung disease and, remarkably, ACE2 serves as a receptor for SARS and NL63 coronaviruses. This review covers available information on the genetic, structural and functional properties of ACE2. Its role in a variety of (patho)physiological conditions and therapeutic options of modulation are discussed. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Chapter
Experience in IBD animal modeling has shown us that an ideal animal model cannot be achieved, as the human disease is chronic, unrelenting with multiple remissions and relapses. Despite this shortcoming, the number of animal models of inflammation that relatively mimic IBD either naturally, spontaneously or phenotypically through experimental physical, immunological or genetic manipulations has significantly increased. Many of these models have helped us dissect and substantially advance our understandings of the pathogenesis of IBD, at the same time as providing an unprecedented opportunity for identifying targets for therapeutic intervention and prevention strategies. Since so many experimental animal models are now available, investigators must take into consideration the species, strains, substrains, the microenvironment in which they live and the mediators involved in each of these models, for application to preclinical testing to manipulate the immune system or to develop vaccines or gene therapy.
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Apelin and its receptor, the APJ receptor, are expressed in the gastrointestinal tract. The aims of this study were to examine the effects of sodium dextran sulfate (DSS)-induced experimental colitis in rats and mice and inflammatory bowel disease (IBD) in humans on intestinal apelin production, and the influence of exogenous apelin on colonic epithelial cell proliferation in mice. In rodents with experimental colitis, colonic apelin mRNA levels were elevated during the inflammatory reaction as well as during the tissue repair phase that ensues after DSS withdrawal. Fluctuations in colonic apelin expression were paralleled by similar changes in apelin immunostaining. Apelin immunostaining was increased in the surface epithelium, in epithelial cells along the length of the tubular gland and in the stem cell region at the gland base. In ulcerative colitis (UC) and Crohn's disease patients, apelin immunostaining revealed a pattern of increased intestinal apelin content similar to that observed in rodents with experimental colitis. Administration of synthetic apelin to mice during the recovery phase of DSS-induced colitis stimulated colonic epithelial cell proliferation significantly. Our observations that colonic apelin production is increased during and after DSS exposure indicate that apelin plays multiple roles during the different stages of colitis. Additionally, the stimulatory action of exogenous apelin on colonic epithelial proliferation suggests that the increased apelin production during intestinal recovery stage may contribute to the repair of the intestinal epithelium in experimental rodent models of colitis and in IBD patients.
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New components and functions of the renin-angiotensin system (RAS) are still being unravelled. The classical RAS as it looked in the middle 1970s consisted of circulating renin, acting on angiotensinogen to produce angiotensin I, which in turn was converted into angiotensin II (Ang II) by angiotensin-converting enzyme (ACE). Ang II, still considered the main effector of RAS was believed to act only as a circulating hormone via angiotensin receptors, AT1 and AT2. Since then, an expanded view of RAS has gradually emerged. Local tissue RAS systems have been identified in most organs. Recently, evidence for an intracellular RAS has been reported. The new expanded view of RAS therefore covers both endocrine, paracrine and intracrine functions. Other peptides of RAS have been shown to have biological actions; angiotensin 2-8 heptapeptide (Ang III) has actions similar to those of Ang II. Further, the angiotensin 3-8 hexapeptide (Ang IV) exerts its actions via insulin-regulated amino peptidase receptors. Finally, angiotensin 1-7 (Ang 1-7) acts via mas receptors. The discovery of another ACE2 was an important complement to this picture. The recent discovery of renin receptors has made our view of RAS unexpectedly complex and multilayered. The importance of RAS in cardiovascular disease has been demonstrated by the clinical benefits of ACE inhibitors and AT1 receptor blockers. Great expectations are now generated by the introduction of renin inhibitors. Indeed, RAS regulates much more and diverse physiological functions than previously believed.
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Activity of myeloperoxidase (MPO) was determined in different tissues to detect granulocyte infiltration. MPO was measured in the mouse ear after injection of interleukin-1 beta, in the rat paw after carrageenan-induced edema and in the lung of sensitized guinea pigs after ovalbumin inhalation. Pretreatment of the animals with antiinflammatory drugs abolished the increase of MPO activity in tissues induced by this different stimuli.
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Cell locomotion and chemotaxis are usually assayed by the Boyden chamber technique, in which the response is measured by microscopical counting of the cells migrated into a micropore filter. We report a simplified Boyden chamber method which utilizes myeloperoxidase (MPO) specific to neutrophilic and monocytic leukocytes. The chamber is incubated for a period long enough for the neutrophils to migrate through the first of two superimposed filters. The cells entering the second filter are then lysed and the released MPO activity is quantitated. Random migration, chemokinesis, and chemotaxis measurements of neutrophils were compared by the enzymatic and the conventional cell count methods. There was good agreement between the two methods (0.84 less than r less than 0.98). The intraassay precision of the enzymatic and the cell count methods was equal; the coefficients of variation were 14 and 15%, respectively. The enzymatic method provides a more objective, reliable, and rapid modification of the Boyden chamber assay for analysis of neutrophil chemotaxis.
Article
To define a potential role for the angiotensin system in Crohn's colitis, the colonic mucosal levels of angiotensin I and II were measured in endoscopic biopsy samples from patients with active Crohn's colitis (n = 20), ulcerative colitis (n = 13), other forms of colitis (n = 3), and normal controls (n = 17). Colonic mucosal levels of angiotensin I and II were greater in patients with Crohn's colitis than in normal subjects (p less than 0.001 and p less than 0.001, respectively). Mucosal levels of angiotensin I and II were also higher in Crohn's colitis than in ulcerative colitis (p less than 0.001 and p less than 0.001, respectively), and levels of angiotensin II were higher in Crohn's than in other forms of colitis (p = 0.014). Mucosal levels of angiotensin I and II correlated well with the degree of macroscopic inflammation in Crohn's colitis (r = 0.86, p less than 0.001 and r = 0.68, p less than 0.001, respectively). Mucosal levels of angiotensin I correlated fairly well with the Crohn's Disease Activity Index (r = 0.46, p less than 0.05) while angiotensin II levels correlated poorly. These studies suggest that angiotensin I and II may have a role in the inflammation associated with Crohn's colitis.
Article
The purpose of this study was to map the distribution of angiotensin II (ANG II) receptors and ANG I-converting enzyme (ACE) in rat intestine. ANG II binding sites were visualized by in vitro autoradiography using iodinated [Sar1, Ile8]ANG II. The distribution of ACE was mapped using an iodinated derivative of lisinopril. Male Sprague-Dawley rats were killed and the interior of the whole intestine washed with ice-cold saline. Segments of duodenum, jejunum, ileum, and colon were quickly frozen in a mixture of isopentane and dry ice. Twenty-micron frozen sections were thaw-mounted onto gelatin-coated slides, incubated with either ligand, and exposed to X-ray film. After exposure and subsequent development, the films were quantitated by computerized densitometry. ANG II receptors were most dense in the colon, followed by the ileum, duodenum, and jejunum. Within each segment of intestine, specific ANG II binding sites were localized exclusively to the muscularis. In contrast, ACE was present in both the mucosa and the muscularis. The colocalization of ANG II receptors and ACE may suggest a role for locally generated ANG II in the control of intestinal function. The luminal orientation of ACE in the mucosa of the small intestine may suggest that at this site ACE serves primarily to hydrolyze dietary peptides.
Article
Animal models of inflammatory bowel disease are artificial and more or less representative of human disease. However, the dextran sulphate sodium (DSS) induced intestinal inflammation model has recently been shown to fulfil some pathological criteria for an adequate experimental model. To determine whether this form of experimental intestinal inflammation responds to established therapy used for human inflammatory bowel disease. DSS was used to induce intestinal inflammation in conventional Balb/c mice and athymic nu/nu CD-1(BR) mice, and the well-documented 5-aminosalicylic acid (5-ASA) based anticolitis drugs sulphasalazine (SASP) and olsalazine (OLZ) were used to study therapeutic effects. Parameters which have been shown to reflect DSS-induced intestinal inflammation (body weight, colon length, spleen weight, diarrhoea, and rectal bleeding) were measured in the Balb/c mice. Significant amelioration was seen on these parameters after different treatment protocols. Survival in nu/nu CD-1 mice was studied, and after 16 days a death rate of 50% was noted in the DSS group. SASP (100 mg/kg/day) and OLZ (50 mg/kg/day) significantly prolonged the survival to 29 and 38 days, respectively. SASP and OLZ showed a dose-dependent effect in the range between 10 and 100 mg/kg/day, doses closely corresponding to those used in humans. SASP and OLZ are able to ameliorate the DSS-induced intestinal inflammation. The dose-response patterns suggested that the active therapeutic moiety for the two drugs appears to be mainly the liberated 5-ASA molecule.
Article
ACE2, the first known human homologue of angiotensin-converting enzyme (ACE), was identified from 5' sequencing of a human heart failure ventricle cDNA library. ACE2 has an apparent signal peptide, a single metalloprotease active site, and a transmembrane domain. The metalloprotease catalytic domains of ACE2 and ACE are 42% identical, and comparison of the genomic structures indicates that the two genes arose through duplication. In contrast to the more ubiquitous ACE, ACE2 transcripts are found only in heart, kidney, and testis of 23 human tissues examined. Immunohistochemistry shows ACE2 protein predominantly in the endothelium of coronary and intrarenal vessels and in renal tubular epithelium. Active ACE2 enzyme is secreted from transfected cells by cleavage N-terminal to the transmembrane domain. Recombinant ACE2 hydrolyzes the carboxy terminal leucine from angiotensin I to generate angiotensin 1-9, which is converted to smaller angiotensin peptides by ACE in vitro and by cardiomyocytes in culture. ACE2 can also cleave des-Arg bradykinin and neurotensin but not bradykinin or 15 other vasoactive and hormonal peptides tested. ACE2 is not inhibited by lisinopril or captopril. The organ- and cell-specific expression of ACE2 and its unique cleavage of key vasoactive peptides suggest an essential role for ACE2 in the local renin-angiotensin system of the heart and kidney. The full text of this article is available at http://www. circresaha.org.
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Many experimental data have suggested that the renin-angiotensin system participates in immune and inflammatory responses. Angiotensin II is involved in several steps of the inflammatory process: mononuclear cells respond to angiotensin II stimulation (cell proliferation and chemotaxis); angiotensin II regulates the recruitment of proinflammatory cells into the site of injury (mediated by the expression of vascular permeability factors, adhesion molecules and chemokines by resident cells); inflammatory cells can produce angiotensin II, and might therefore contribute to the perpetuation of tissue damage. In this review, we summarize the proinflammatory properties of angiotensin II, to demonstrate the novel role of this vasoactive peptide as a true cytokine. We will show the information obtained as a result of the pharmacological blockade of the renin angiotensin system, which has demonstrated that this system is involved in immune and inflammatory diseases. In this aspect, we discuss the molecular mechanism of angiotensin II-induced tissue damage, as well as its contribution to the pathogenesis of several diseases, including atherosclerosis, hypertension and renal damage, showing that angiotensin II plays an active role in the inflammatory response of these diseases.