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Abstract

NAFLD is a clinically progressive disease with steatosis, inflammation, endothelial dysfunction and fibrosis being the stages where clinical intervention becomes necessary. Lack of early biomarkers and absence of a FDA approved drug obstructs efforts for effective treatment. NAFLD progression is strongly linked to a balance between liver injury, tissue regeneration and the functioning of endogenous defense mechanisms. The failure of the defense pathways to resist the tissue damage arising from redox stress, one of the “multiple hits” in disease progression, give rise to heightened inflammation and occasional fibrosis. We introduce an endogenous defense mechanism in the liver that is mediated by TRPV4, a transient receptor potential calcium-permeable ion channel that responds to the cytotoxic liver environment and negatively regulates CYP2E1, a cytochrome p450 enzyme. Using Trpv4-/- mice and cultured primary cells, we show that TRPV4 is activated both by damage associated molecular pattern HMGB1 and collagen in diseased Kupffer cells that in turn activate the endothelial NOS (NOS3) to release nitric oxide (NO). The diffusible NO acts in a paracrine fashion in neighboring hepatocytes to deactivate the redox toxicity induced by CYP2E1. We also find that CYP2E1-mediated TRPV4 repression in late stages causes an unrestricted progression of disease. Thus, TRPV4 functions as a sensor of cell stress in the diseased fatty liver and constitutes an endogenous defense molecule, a novel concept with potential for therapeutic approaches against NAFLD, perhaps also against hepatic drug toxicity in general.

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... We and others have previously shown that oxidative stress is the key regulator in NASH via second hit/multiple hit theory [10,[20][21][22]. The redox stress generated by xenobiotic enzyme Cytochrome p450 2E1 (CYP2E1) via a free-radical mechanism generates reactive oxygen species (ROS) and reactive nitrative species (RNS) in the liver [23]. The oxidative stress resulted from reductive metabolism of CYP2E1, can accelerate metabolic disturbances, leptin release and trigger host innate immune response (ref). ...
... Western blot for serum leptin was performed by using the standard protocol as described by Seth et al. [23]. Briefly, 20 µg of denatured serum protein resolved on novex 4-12% bis-tris gradient gel. ...
... We have shown previously that NASH in an underlying condition of obesity causes an increase in hepatic CYP2E1 activity with concomitant free radical damage to lipids and proteins [23]. The adipokine, leptin is mainly produced by adipocytes in obesity and poses inflammatory response in the liver. ...
Article
High insulin and leptin resistance followed by underlying inflammation is often ascribed to the ectopic manifestations in non-alcoholic fatty liver disease (NAFLD) but the exact molecular pathways remain unclear. We have shown previously that CYP2E1-mediated oxidative stress and circulating leptin in NAFLD is associated with renal disease severity. Extending the studies, we hypothesized that high circulatory leptin in NAFLD causes renal mesangial cell activation and tubular inflammation via a NOX2 dependent pathway that upregulates proinflammatory miR21. High fat diet (60%kcal) was used to induce fatty liver phenotype with parallel insulin and leptin resistance in WT, Leptin knockout (ob/ob) and p47 phox knockout mice. Kidneys were collected after pathology showed NASH-like phenotype and accelerated oxidative stress in the liver. The kidneys were probed for mesangial cell activation and tubular inflammation. Results showed that NAFLD kidneys had significant increases in α-SMA, a marker of mesangial cell activation, miR21 levels, tyrosine nitration and renal inflammation while they were significantly decreased in leptin and p47 phox knockout mice. Micro RNA21 knockout mice showed decreased tubular immunotoxicity and proinflammatory mediator release. Mechanistically, use of apocynin or phenyl boronic acid (FBA) or DMPO or miR21 antagomir inhibited leptin primed-miR21-mediated mesangial cell activation in vitro suggesting a direct role of leptin-mediated NOX-2 in miR21-mediated mesangial cell activation. Finally JAK-STAT inhibitor completely abrogated the mesangial cell activation in leptin-primed cells suggesting that leptin signaling in the mesangial cells depended on the JAK-STAT pathway. Taken together the study reports a novel mechanistic pathway of leptin-mediated renal inflammation in NAFLD. Grant support R00ES019875 to SC
... We and others have previously shown that oxidative stress is the key regulator in NASH via second hit/multiple hit theory [10,[20][21][22]. The redox stress generated by xenobiotic enzyme Cytochrome p450 2E1 (CYP2E1) via a free-radical mechanism generates reactive oxygen species (ROS) and reactive nitrative species (RNS) in the liver [23]. The oxidative stress resulted from reductive metabolism of CYP2E1, can accelerate metabolic disturbances, leptin release and trigger host innate immune response (ref). ...
... Western blot for serum leptin was performed by using the standard protocol as described by Seth et al. [23]. Briefly, 20 µg of denatured serum protein resolved on novex 4-12% bis-tris gradient gel. ...
... We have shown previously that NASH in an underlying condition of obesity causes an increase in hepatic CYP2E1 activity with concomitant free radical damage to lipids and proteins [23]. The adipokine, leptin is mainly produced by adipocytes in obesity and poses inflammatory response in the liver. ...
Article
High circulatory insulin and leptin followed by underlying inflammation are often ascribed to the ectopic manifestations in non-alcoholic fatty liver disease (NAFLD) but the exact molecular pathways remain unclear. We have shown previously that CYP2E1-mediated oxidative stress and circulating leptin in NAFLD is associated with renal disease severity. Extending the studies, we hypothesized that high circulatory leptin in NAFLD causes renal mesangial cell activation and tubular inflammation via a NOX2 dependent pathway that upregulates proinflammatory miR21. High-fat diet (60% kcal) was used to induce fatty liver phenotype with parallel insulin and leptin resistance. The kidneys were probed for mesangial cell activation and tubular inflammation that showed accelerated NASH phenotype and oxidative stress in the liver. Results showed that NAFLD kidneys had significant increases in α-SMA, a marker of mesangial cell activation, miR21 levels, tyrosine nitration and renal inflammation while they were significantly decreased in leptin and p47 phox knockout mice. Micro RNA21 knockout mice showed decreased tubular immunotoxicity and proinflammatory mediator release. Mechanistically, use of NOX2 siRNA or apocynin,phenyl boronic acid (FBA), DMPO or miR21 antagomir inhibited leptin primed-miR21-mediated mesangial cell activation in vitro suggesting a direct role of leptin-mediated NOX-2 in miR21-mediated mesangial cell activation. Finally, JAK-STAT inhibitor completely abrogated the mesangial cell activation in leptin-primed cells suggesting that leptin signaling in the mesangial cells depended on the JAK-STAT pathway. Taken together the study reports a novel mechanistic pathway of leptin-mediated renal inflammation that is dependent on NOX-2-miR21 axis in ectopic manifestations underlying NAFLD-induced co-morbidities.
... Recent reports of other soluble molecular mediators of inflammation in NAFLD have emerged. These include several damage associated molecular patterns like HMGB1, uric acid, extracellular ATP and NAD and has been found to be prime causes of sterile inflammation in the liver and other peripheral organs [9][10][11][12][13][14][15][16][17]. ...
... HMGB1 circulatory levels have been predictors of outcome in neuroinflammation, ischemia reperfusion injury and sepsis [11,[21][22][23][24][25]. We and others have shown that HMGB1 circulatory levels are increased in NASH and are found to contribute in the pathology of liver lobule and tubular toxicity [11,15]. ...
... Fatty liver causes the release of damage associated molecular pattern HMGB1 [11,15]. To study the levels of HMGB1 in the liver following development of fatty liver, C57BL6/J mice were fed with high fat diet for 18 weeks. ...
Article
Recent clinical studies found a strong association of colonic inflammation with NAFLD) yet the mechanisms remain unknown. The present study identifies HMGB1 as a key mediator of intestinal inflammation in NAFLD and outlines a detailed redox signaling mechanism for such a pathway. NAFLD mice showed liver damage and release of higher HMGB1 in systemic circulation, increased intestinal tyrosine nitration that was dependent on NADPH oxidase. Intestines from NAFLD mice showed higher TLR4 activation and proinflammatory cytokine release, an outcome strongly dependent on the existence of NAFLD pathology and NADPH oxidase. In vitro experimentation using IE6 cells showed the HMGB1 activation of Toll like receptor (TLR-4) was both NADPH oxidase and peroxynitrite dependent with the latter being formed from the activation of NADPH oxidase. Proinflammatory cytokine production was significantly blocked by the specific peroxynitrite scavenger FBA, AKT inhibitor and NADPH oxidase inhibitor Apocynin suggesting NADPH oxidase-dependent peroxynitrite as a key mediator in TLR-4 activation and cytokine release via an AKT dependent pathway. Studies to ascertain the mechanism of HMGB1-mediatied NADPH oxidase activation showed a distinct role of RAGE as the use of inhibitors targeted against RAGE prevented NADPH oxidase activation, peroxynitrite formation, TLR4 activation and finally cytokine release. Thus in conclusion, the present study identifies a novel HMGB1mediated inflammatory pathway that is RAGE and redox signaling dependent and helps promote ectopic intestinal inflammation in NAFLD. 5P30GM103336-03 and 7R00ES019875-03 awarded to Dr. Saurabh Chatterjee.
... Recent reports of other soluble molecular mediators of inflammation in NAFLD have emerged. These include several damage associated molecular patterns like HMGB1, uric acid, extracellular ATP and NAD and has been found to be prime causes of sterile inflammation in the liver and other peripheral organs [9][10][11][12][13][14][15][16][17]. ...
... HMGB1 circulatory levels have been predictors of outcome in neuroinflammation, ischemia reperfusion injury and sepsis [11,[21][22][23][24][25]. We and others have shown that HMGB1 circulatory levels are increased in NASH and are found to contribute in the pathology of liver lobule and tubular toxicity [11,15]. ...
... Fatty liver causes the release of damage associated molecular pattern HMGB1 [11,15]. To study the levels of HMGB1 in the liver following development of fatty liver, C57BL6/J mice were fed with high fat diet for 18 weeks. ...
Article
Full-text available
Recent clinical studies found a strong association of colonic inflammation and Inflammatory bowel disease (IBD)-like phenotype with Non Alcoholic Fatty liver Disease (NAFLD) yet the mechanisms remain unknown. The present study identifies high mobility group box 1 (HMGB1) as a key mediator of intestinal inflammation in NAFLD and outlines a detailed redox signaling mechanism for such a pathway. NAFLD mice showed liver damage and release of elevated HMGB1 in systemic circulation and increased intestinal tyrosine nitration that was dependent on NADPH oxidase. Intestines from NAFLD mice showed higher Toll like receptor 4 (TLR4) activation and proinflammatory cytokine release, an outcome strongly dependent on the existence of NAFLD pathology and NADPH oxidase. Mechanistically intestinal epithelial cells showed the HMGB1 activation of TLR-4 was both NADPH oxidase and peroxynitrite dependent with the latter being formed by the activation of NADPH oxidase. Proinflammatory cytokine production was significantly blocked by the specific peroxynitrite scavenger phenyl boronic acid (FBA), AKT inhibition and NADPH oxidase inhibitor Apocynin suggesting NADPH oxidase-dependent peroxynitrite is a key mediator in TLR-4 activation and cytokine release via an AKT dependent pathway. Studies to ascertain the mechanism of HMGB1-mediatied NADPH oxidase activation showed a distinct role of Receptor for advanced glycation end products (RAGE) as the use of inhibitors targeted against RAGE or use of deformed HMGB1 protein prevented NADPH oxidase activation, peroxynitrite formation, TLR4 activation and finally cytokine release. Thus, in conclusion the present study identifies a novel role of HMGB1 mediated inflammatory pathway that is RAGE and redox signaling dependent and helps promote ectopic intestinal inflammation in NAFLD.
... Therefore, Ca 2+ channels may be used as a potential target for the diagnosis, prevention and treatment of NAFLD. The following is a summary of the mechanism of action and/or treatment strategies of several types of Ca 2+ channels in NAFLD (Table II) (43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62). ...
... CYP2E1 is a cytochrome P450 enzyme, which can lead to lipid peroxidation following its activation and serves a pro-inflammatory role in NAFLD and enhances the progression of NAFLD (46). In progressive NAFLD, the promoter region of the TRPV4 gene is methylated, which inhibits TRPV4 expression and therefore reduces the levels of channel proteins associated with the progression of NAFLD (47). In a previous study, the NAFLD model was established in TRPV4-knockout mice and the deterioration of NAFLD was observed 1 week following CYP2E1 activation. ...
... Furthermore, the mRNA and protein expression levels of the damage-related nuclear DNA binding protein, high mobility group box 1 (HMGB1), were also increased, which promoted the further development of NAFLD. This aforementioned study therefore concluded that TRPV4 serves a protective role in the liver (47). This protective effect of TRPV4 may block the role of CYP2E1 via the activation of Kupffer cell NOS3 and the release of NO via the paracrine system (47). ...
Article
Full-text available
Non‑alcoholic fatty liver disease (NAFLD) is a clinically progressive illness that can advance from simple fatty liver to non-alcoholic hepatitis and liver fibrosis. Cirrhosis and hepatocellular carcinoma are two of the most common diseases caused by NAFLD. As there are no early disease biomarkers and no US Food and Drug Administration‑approved medications, treatment for NAFLD is still focused on altering lifestyle and dietary habits, which makes it difficult to treat effectively. As a result, a novel treatment is urgently needed to prevent NAFLD progression. Calcium (Ca2+) channels regulate intracellular Ca2+ homeostasis via the mediation of Ca2+ flow. Previous studies have reported that Ca2+ channel expression varies throughout the development and progression of NAFLD, which results in the dysregulation of intracellular Ca2+ homeostasis, endoplasmic reticulum stress, mitochondrial dysfunction and autophagy suppression, all of which contribute to NAFLD progression. Several types of Ca2+ channels (including two‑pore segment channel 2, transient receptor potential, inositol triphosphate receptor, voltage‑dependent anion channel 1, store‑operated Ca2+ entry, purinergic receptor X7 and potassium Ca2+‑activated channel subfamily N member 4) have been identified as potential targets for preventing NAFLD development and controlling intracellular Ca2+ homeostasis. To achieve this, these channels can be blocked or activated, which exerts anti‑steatotic, anti‑inflammatory, anti‑fibrotic and other effects, which ultimately prevents the development of NAFLD. In the present review NAFLD therapeutics and the treatments that target Ca2+ channels that are currently being developed were examined.
... We and others have previously shown that oxidative stress is the key regulator in NASH via second hit/multiple hit theory [10,[20][21][22]. The redox stress generated by xenobiotic enzyme Cytochrome p450 2E1 (CYP2E1) via a free-radical mechanism generates reactive oxygen species (ROS) and reactive nitrative species (RNS) in the liver [23]. The oxidative stress resulted from reductive metabolism of CYP2E1, can accelerate metabolic disturbances, leptin release and trigger host innate immune response (ref). ...
... Western blot for serum leptin was performed by using the standard protocol as described by Seth et al. [23]. Briefly, 20 µg of denatured serum protein resolved on novex 4-12% bis-tris gradient gel. ...
... We have shown previously that NASH in an underlying condition of obesity causes an increase in hepatic CYP2E1 activity with concomitant free radical damage to lipids and proteins [23]. The adipokine, leptin is mainly produced by adipocytes in obesity and poses inflammatory response in the liver. ...
Article
Non-alcoholic fatty liver disease is an emerging global pandemic with 15% of the cases progressing to steatohepatitis or cirrhosis and eventually to hepatocellular carcinoma. Though significant progress has been made in unravelling the pathophysiology of the disease, the effect of environmental and genetic factors in an underlying NAFLD pathophysiology remains unclear. The present report tests the hypothesis that microcystin (MC), a principal component of harmful algal blooms activates Kupffer cells and hepatic stellate cells, crucial mediators in hepatic fibrogenesis via NOX2 dependent pathway in an underlying condition of NAFLD. Mice that had mild steatosis and showed signs of NAFLD were exposed to microcystin via an intraperitoneal route. Results showed that MC exposure led to exacerbation of NAFLD pathology with increased CD68 immunoreactivity, release of proinflammatory cytokines and stellate cell activation, a process that was attenuated in miR21 knockout mice and mice that lacked the p47 phox gene. Mechanistically, immortalized Kupffer cells treated with apocynin or nitrone spin trap DMPO had significantly decreased CD68, decreased miR21 and α-SMA levels signifying the role of NOX2-dedendent reactive oxygen species in miR21-induced Kupffer cell activation and stellate cell pathology. Further, NOX2 dependent peroxynitrite generation was primarily responsible for cellular events observed following MC exposure since incubation with phenyl boronic acid attenuated miR21 levels, Kuppfer cell activation and inflammatory cytokine release. Taken together, we show that MC exposure exacerbates NAFLD pathology via NOX2 dependent peroxynitrite generation by increasing miR21 levels.
... Birincisi, TRPV4'ün sistemik inhibisyonu, karaciğer fonksiyonu üzerindeki potansiyel etkiler nedeniyle sorunlu olabilir (Özellikle kritik hastalarda ilgili bir endişe) [185], ancak TRPV4 inhibisyonunun hepatoprotektif bir rolü de asetaminofen toksisitesinde ileri sürülmüştür [207]. Özellikle, seçici bir TRPV4 inhibitörü kullanan faz I klinik denemeleri, sağlıklı gönüllülerde veya konjestif kalp yetmezliği olan hastalarda karaciğer enzimlerinde artış tespit etmemiştir [77]. ...
... [123] Liu D. X. & Inglis S. C. Association of the infectious bronchitis virus 3c protein with the virion envelope. Virology, 185 (2), 911-917, (1991). ...
Article
Full-text available
Abstract. In mid-August 2021, WHO reported 456.225.677 (4.400.284 death) confirmed cases of coronavirus-19 in the world and 8.641.372 (53.891 death) cases in Turkey. Corona-virus 19 produces severe acute respiratory syndrome characterized by cytokine release. Possible treatments for cytokine-mediated hyperinflammation need to be urgently investigated to reduce rising death rates. Although vaccine applications have been made, information is not yet available about vaccine's potential long-term effects. Also, there are no definitely approved treatments for Corona-viruses. Numerous aromatic herbs and phytochemicals await therapeutic use against genetically and functionally diverse viruses, including coronaviruses. Turkey has a high potential for research on this subject with its rich ethnomedical experience and rich flora (34% endemic). Plants that have been used against influenza for centuries can offer effective alternatives. Key words: Coronavirus-19, cytokine, antiviral, TRP channels, NF-κβ, STAT
... CYP2E1 catalyzes the biotransformation of different xenobiotics (e.g. carbon tetrachloride, ethanol and acetaminophen) and endogenous derivatives such as acetone and some fatty acids (Aubert et al., 2011;Seth et al., 2017). Notably, CYP2E1 is an enzyme located not only within the ER but also within mitochondria (Hartman, Miller, & Meyer, 2017;. ...
... Numerous experimental and clinical studies have reported higher hepatic CYP2E1 expression and/or activity in NAFLD, and more broadly in obesity (Aubert et al., 2011;Gade et al., 2018;Massart et al., 2017;Sadler et al., 2018;van Rongen et al., 2016). Moreover, a role of higher CYP2E1 activity in the pathogenesis of NAFLD is supported by different experimental investigations (Abdelmegeed et al., 2017;Aubert et al., 2011;Seth et al., 2017). Interestingly, induction of CYP2E1 could not only favor oxidative stress but also lipid accumulation (Abdelmegeed et al., 2017;Chen, Zhang, Zhao, Xie, & Zeng, 2014), possibly via a ROS-mediated reduction of PPARα activity (Lu, Zhuge, Wang, Bai, & Cederbaum, 2008;Zeng, Zhang, Song, Zhao, & Xie, 2014). ...
Chapter
Obesity is commonly associated with nonalcoholic fatty liver (NAFL), a benign condition characterized by hepatic lipid accumulation. However, NAFL can progress in some patients to nonalcoholic steatohepatitis (NASH) and then to severe liver lesions including extensive fibrosis, cirrhosis and hepatocellular carcinoma. The entire spectrum of these hepatic lesions is referred to as nonalcoholic fatty liver disease (NAFLD). The transition of simple fatty liver to NASH seems to be favored by several genetic and environmental factors. Different experimental and clinical investigations showed or suggested that obesity and NAFLD are able to increase the risk of hepatotoxicity of different drugs. Some of these drugs may cause more severe and/or more frequent acute liver injury in obese individuals whereas others may trigger the transition of simple fatty liver to NASH or may worsen hepatic lipid accumulation, necroinflammation and fibrosis. This review presents the available information regarding drugs that may cause a specific risk in the context of obesity and NAFLD. These drugs, which belong to different pharmacological classes, include acetaminophen, halothane, methotrexate, rosiglitazone and tamoxifen. For some of these drugs, experimental investigations confirmed the clinical observations and unveiled different pathophysiological mechanisms which may explain why these pharmaceuticals are particularly hepatotoxic in obesity and NAFLD. Because obese people often take several drugs for the treatment of different obesity-related diseases, there is an urgent need to identify the main pharmaceuticals that may cause acute liver injury on a fatty liver background or that may enhance the risk of severe chronic liver disease.
... TRPV4 is a calcium-permeable nonselective cation channel of TRP family, which biologically involved in osmotic sensitivity and mechanosensitivity 17,18 . TRPV4 participates in many physiological processes, such as liver 19 , intestinal 20 , renal 21 and bladder 22 functions, growth and structural integrity of the skeleton 23 , together with systemic osmotic pressure induced by the brain 24 . Until now, TRPV4 has been reported functionally related to cell proliferation 25 , differentiation 26 , apoptosis 27 , migration 28 , and many other physiological processes. ...
Article
Full-text available
The transient receptor potential ion-channel superfamily consists of nonselective cation channels located mostly on the plasma membranes of numerous animal cell types, which are closely related to sensory information transmission (e.g., vision, pain, and temperature perception), as well as regulation of intracellular Ca2+ balance and physiological activities of growth and development. Transient receptor potential ion channel subfamily V (TRPV) is one of the largest and most diverse subfamilies, including TRPV1–TRPV6 involved in the regulation of a variety of cellular functions. TRPV4 can be activated by various physical and chemical stimuli, such as heat, mechanical force, and phorbol ester derivatives participating in the maintenance of normal cellular functions. In recent years, the roles of TRPV4 in cell proliferation, differentiation, apoptosis, and migration have been extensively studied. Its abnormal expression has also been closely related to the onset and progression of multiple tumors, so TRPV4 may be a target for cancer diagnosis and treatment. In this review, we focused on the latest studies concerning the role of TRPV4 in tumorigenesis and the therapeutic potential. As evidenced by the effects on cancerogenesis, TRPV4 is a potential target for anticancer therapy.
... Indeed, TRPV4 have been recently described as a sensor of cell stress in the diseased fatty liver. These data lend solid support to the emerging concept of TRPV4 protecting a key epithelial cell -hepatocytes -from oxidative injury 52 . ...
Article
Full-text available
Transient receptor potential vanilloid 4 (TRPV4) cation channels are functional in all renal vascular segments and mediate endothelium-dependent vasorelaxation. Moreover, they are expressed in distinct parts of the tubular system and activated by cell swelling. Ischaemia/reperfusion injury (IRI) is characterized by tubular injury and endothelial dysfunction. Therefore, we hypothesised a putative organ protective role of TRPV4 in acute renal IRI. IRI was induced in TRPV4 deficient (Trpv4 KO) and wild-type (WT) control mice by clipping the left renal pedicle after right-sided nephrectomy. Serum creatinine level was higher in Trpv4 KO mice 6 and 24 hours after ischaemia compared to WT mice. Detailed histological analysis revealed that IRI caused aggravated renal tubular damage in Trpv4 KO mice, especially in the renal cortex. Immunohistological and functional assessment confirmed TRPV4 expression in proximal tubular cells. Furthermore, the tubular damage could be attributed to enhanced necrosis rather than apoptosis. Surprisingly, the percentage of infiltrating granulocytes and macrophages were comparable in IRI-damaged kidneys of Trpv4 KO and WT mice. The present results suggest a renoprotective role of TRPV4 during acute renal IRI. Further studies using cell-specific TRPV4 deficient mice are needed to clarify cellular mechanisms of TRPV4 in IRI.
... It has been demonstrated that high-fructose feeding causes fat deposition in the liver and induces oxidative stress, essentially through the deterioration of the antioxidant defense system [32]. Moreover, elevated oxidative stress and subsequent lipid peroxidation have been reported to play a crucial role in the pathogenesis of MetS, and it is well known that they are essential in the progression from NAFLD to steatohepatitis [33][34][35][36]. ...
Article
Full-text available
Snacks combining different functional ingredients could represent a useful therapeutic strategy against NAFLD. The present study aimed to analyze the effect of two snack formulations based on carob and wakame flour in the treatment for NAFLD in rats. For this purpose, metabolic syndrome was induced in 50 adult rats by a high-fat high-fructose diet over eight weeks. After this period, rats were fed either normal calorie diets supplemented or not with snack A (1/50 wakame/carob pod) and snack B (1/5 wakame/carob pod) for four additional weeks. After sacrifice, liver composition and serum parameters were analyzed. Different pathways of triacylglycerol metabolism in liver were studied including fatty acid oxidation, fatty acid synthesis, triglyceride assembly and release, fatty acid uptake and glucose uptake. Oxidative stress was also measured. Snack treatment, and mainly B snack, reduced liver triacylglycerol levels by increasing fat oxidation. Moreover, this snack reduced oxidative stress. Therefore, this snack formulation could represent an interesting tool useful for fatty liver treatment.
... In view of the fact that TGF␤1-induced actin polymerization facilitates MRTF-A release from actin monomers, thereby allowing for MRTF-A nuclear translocation, which induces ␣-SMA transcription during lung myofibroblast differentiation (6,41), it will be interesting to determine if the mechanism by which TRPV4 potentiates TGF␤1-induced dermal myofibroblast differentiation is through actin polymerization-dependent nuclear translocation of MRTF-A. Recently, Seth et al. (42) revealed that TRPV4 activation protects against nonalcoholic fatty liver disease, thus alerting against the consequences of global blocking of TRPV4 that can promote hepatotoxicity. Therefore, a suitable balanced approach will be required to inhibit TRPV4 by systemic application of TRPV4 blockers to treat fibrotic or other disorders. ...
Article
Scleroderma is a multisystem fibroproliferative disease with no effective medical treatment. Myofibroblasts are critical to the fibrogenic tissue repair process in the skin and many internal organs. Emerging data support a role for both matrix stiffness, and transforming growth factor β1 (TGFβ1), in myofibroblast differentiation. Transient receptor potential vanilloid 4 (TRPV4) is a mechanosensitive ion channel activated by both mechanical and biochemical stimuli. The objective of this study was to determine the role of TRPV4 in TGFβ1- and matrix stiffness-induced differentiation of dermal fibroblasts. We found that TRPV4 channels are expressed and functional in both human (HDF) and mouse (MDF) dermal fibroblasts. TRPV4 activity (agonist-induced Ca(2+) influx) was induced by both matrix stiffness and TGFβ1 in dermal fibroblasts. TGFβ1 induced expression of TRPV4 proteins in a dose-dependent manner. Genetic ablation or pharmacologic antagonism of TRPV4 channel abrogated Ca(2+) influx and both TGFβ1-induced and matrix stiffness-induced myofibroblast differentiation as assessed by i) α-smooth muscle actin expression/incorporation into stress fibers, ii) generation of polymerized actin, and iii) expression of collagen-1. We found that TRPV4 inhibition abrogated TGFβ1-induced activation of AKT but not of Smad2/3, suggesting that the mechanism by which profibrotic TGFβ1 signaling in dermal fibroblasts is modified by TRPV4 may be through non-Smad pathways. Altogether, these data identify a novel reciprocal functional link between TRPV4 activation and TGFβ1 signals regulating dermal myofibroblast differentiation. These findings suggest that therapeutic inhibition of TRPV4 activity may provide a targeted approach to the treatment of scleroderma.
... The results for the early (5-week) liver fibrosis model were similar to those for the advanced model (Fig. 2). TRPV ion channel family is associated with multiple physiological and pathological processes, including calcium influx, intracellular environment stability, and maintenance of vascular function 10,13 . Abnormal expres-sion of TRPV and alteration of its channel activity are associated with many diseases 6 . ...
Article
Background: Transient receptor potential vanilloid 4 (TRPV4) is a member of the TRP channel family and is involved in diverse physiological and pathological processes. Accumulating evidence from in vitro studies indicates that TRPV4 has a potential role in liver fibrosis, but its precise role in the pathophysiological development of this condition is unclear. Exogenous interventions and endogenous reactions should be considered. Methods: This study used a mouse model of carbon tetrachloride (CCl4)-induced liver fibrosis to investigate the effects of intraperitoneal injection of the novel TRPV4 channel selective agonist GSK1016790A (GSK) and antagonist HC-067047 (HC). Results: As compared with the CCl4 group, collagen fiber deposition and alpha-smooth muscle actin (α-SMA) levels were markedly higher and hepatic lobule disorganization was worse in the CCl4+GSK group, while collagen fiber deposition was significantly lower and hepatic lobule disorganization was less severe in the CCl4+HC group. Conclusions: The present findings suggest that activation of TRPV4 channels worsens liver fibrosis and that inhibition of TRPV4 channels may alleviate liver fibrosis in vivo.
... We argue for rapid consideration of TRPV4 inhibitory therapy that can be implemented essentially NOW for effective protection of the alveolo-capillary barrier of Covid-19 patients. Despite its clear promise, some potential restrictions and caveats should not go unmentioned: First, systemic inhibition of TRPV4 could prove problematic due to potential effects on hepatic function, a concern that is particularly relevant in the critically ill (40), yet a hepato-protective role of TRPV4 inhibition has also been postulated in acetaminophen toxicity (41). Notably, phase-I clinical trials using a selective TRPV4 inhibitor did not detect increased liver enzymes in healthy volunteers or patients with congestive heart failure (30). ...
Article
Lethality of Covid-19 during the 2020 pandemic, currently in the exponentially-accelerating phase in most countries, is critically driven by disruption of the alveolo-capillary barrier of the lung, leading to lung edema as a direct consequence of SARS-CoV-2 infection. We argue for inhibition of the TRPV4 calcium-permeable ion channel as a strategy to address this issue, based on the rationale that TRPV4 inhibition is protective in various preclinical models of lung edema, and that TRPV4 hyperactivation potently damages the alveolo-capillary barrier, with lethal outcome. We believe that TRPV4 inhibition has a powerful prospect at protecting this vital barrier in Covid-19 patients, even to rescue a damaged barrier. A clinical trial using a selective TRPV4 inhibitor demonstrated a benign safety profile in healthy volunteers and in patients suffering from cardiogenic lung edema. We argue for expeditious clinical testing of this inhibitor in Covid-19 patients with respiratory malfunction and at risk for lung edema. We note that among the currently pursued therapeutic strategies against Covid-19, none is designed to directly protect the alveolo-capillary barrier. Successful protection of the alveolo-capillary barrier will not only reduce Covid-19 lethality but will pre-empt a catastrophic scenario in healthcare with insufficient capacity to provide ventilator-assisted respiration.
... Despite its clear promise, some potential restrictions and caveats should not go unmentioned. First, systemic inhibition of TRPV4 could prove problematic because of potential effects on hepatic function, a concern that is particularly relevant in the critically ill (38), yet a hepatoprotective role of TRPV4 inhibition has also been postulated in acetaminophen toxicity (12). Notably, phase I clinical trials using a selective TRPV4 inhibitor did not detect increased liver enzymes in healthy volunteers or patients with congestive heart failure (17). ...
Article
Lethality of Covid-19 during the 2020 pandemic, currently still in the exponentially-accelerating phase in most countries, is critically driven by disruption of the alveolo-capillary barrier of the lung, leading to lung edema as a direct consequence of SARS-CoV-2 infection. We argue for inhibition of the TRPV4 calcium-permeable ion channel as a strategy to address this issue, based on the rationale that TRPV4 inhibition is protective in various preclinical models of lung edema, and that TRPV4 hyperactivation potently damages the alveolo-capillary barrier, with lethal outcome. We believe that TRPV4 inhibition has a powerful prospect at protecting this vital barrier in Covid-19 patients, even to rescue a damaged barrier. A clinical trial using a selective TRPV4 inhibitor demonstrated a benign safety profile in healthy volunteers and in patients suffering from cardiogenic lung edema. We argue for expeditious clinical testing of this inhibitor in Covid-19 patients with respiratory malfunction and at risk for lung edema. Perplexingly, among the currently pursued therapeutic strategies against Covid-19, none is designed to directly protect the alveolo-capillary barrier. Successful protection of the alveolo-capillary barrier will not only reduce Covid-19 lethality but will pre-empt a distressing healthcare scenario with insufficient capacity to provide ventilator-assisted respiration.
... TRPV-3 and TRPV-4 channels are expressed in human keratinocytes and are presumed to detect warm temperature stimuli below temperatures of 35°C (Fujii et al., 2019;Schepers & Ringkamp, 2009). TRPV-4 and TRPV-3 channels have been shown to be activated by NO (Fujii et al., 2019;Yoshida et al., 2006) and to increase NO production (Miyamoto, Petrus, Dubin, & Patapoutian, 2011;Seth et al., 2017). Therefore, warm afferents via TRPV channels may contribute to initial mechanisms of cutaneous sensory nerve-mediated vasodilation and, as such, may be paramount in understanding discrepancies between racial groups. ...
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Relative to non-Hispanic Whites, non-Hispanic Blacks are disproportionately affected by elevated blood pressure (BP). It is unknown whether race or subclinical increases in BP affect the ability of cutaneous sensory nerves to induce cutaneous microvascular vasodilation. Sixteen participants who self-identified as non-Hispanic Black (n = 8) or non-Hispanic White (n = 8) were subgrouped as normotensive or prehypertensive. Participants were instrumented with three intradermal microdialysis fibers: (a) control, (b) 1 μM sodium nitroprusside (SNP), an exogenous nitric oxide (NO) donor, and (c) 20 mM NG -nitro-l-arginine methyl ester (L-NAME), a non-selective NO synthase inhibitor. A slow local heating protocol (33-40°C, 0.1°C/min) was used to assess the onset of cutaneous sensory nerve-mediated vasodilation (temperature threshold) and skin blood flow was measured using laser-Doppler flowmetry. At control sites, the temperature threshold occurred at a higher temperature in non-Hispanic Blacks (normotensive: 37.2 ± 0.6°C, prehypertensive: 38.9 ± 0.5°C) compared to non-Hispanic Whites (normotensive: 35.2 ± 0.8°C, prehypertensive: 35.2 ± 0.9°C). L-NAME shifted the temperature threshold higher in non-Hispanic Whites (normotensive: 37.8 ± 0.7°C, prehypertensive: 38.2 ± 0.8°C), but there was no observed effect in non-Hispanic Blacks. SNP did not affect temperature threshold in non-Hispanic Whites, but shifted the temperature threshold lower in non-Hispanic Blacks (normotensive: 34.6 ± 1.2°C, prehypertensive: 34.8 ± 1.1°C). SNP mitigated differences in temperature threshold across all groups. There was no effect found for BP status in either the non-Hispanic Black or non-Hispanic White groups. These data suggest that reduced NO bioavailability affects the ability of cutaneous sensory nerves to induce microvascular vasodilation in young, otherwise healthy non-Hispanic Blacks.
... Increased CYP2E1 activity in MAFLD might explain why some drugs such as acetaminophen and halothane induce more severe hepatic liver injury in obese patients, as discussed in previous reviews [40,46,47]. Besides its effect on drug-induced liver injury, higher CYP2E1 activity seems to play a significant role in the progression of fatty liver to NASH [43,[48][49][50]. Indeed, the induction of CYP2E1 could favor oxidative stress, because this enzyme produces significant amounts of superoxide anion during its catalytic cycle [43,48]. ...
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Background In this study, the network pharmacological methods were used to predict the target of active components of Chaihu Lizhong Tang (CHLZT) in the treatment of non-alcoholic fatty liver disease (NAFLD). Method The active components of "CHLZT", their targets, and NAFLD related targets were screened by multiple databases, and the potential targets of "CHLZT" in the treatment of NAFLD were predicted. The active component-target network of "CHLZT" was constructed by Cytoscape software. The potential target of "CHLZT" for the treatment of NAFLD constructed protein-protein interaction (PPI) network in the Search Tool for the Retrieval of Interacting Genes Database (STRING). The hub genes of “CHLZT” in the treatment of NAFLD were screened by network topological parameters, and the results were verified by molecular docking. "ClusterProfiler" in R was used for Gene Ontology (GO) analysis and KEGG pathway enrichment analysis. Results OB ≥ 30% and DL ≥ 0.18 were selected as the screening criteria of active components. A total of 83 active components and 456 targets were selected. Based on the evaluation of topological parameters of degree network, five hub genes for interaction with "CHLZT" therapy for NAFLD were screened, that is, AKT1, ALB, IL6, EGFR, and CASP3. The results of molecular docking showed that the active components in "CHLZT" had a good binding ability with the key targets. The enrichment analysis results showed that the treatment of NAFLD with "CHLZT" mainly involved in cofactor binding, protease binding, AGE-RAGE signaling pathway in diabetic complications, and IL-17 signaling pathway, which mediated the potential mechanism of "CHLZT" intervention in NAFLD. Conclusion The molecular mechanism of "CHLZT" in the treatment of NAFLD indicated the synergistic features of multi-component, multi-target, and multi-pathway of traditional Chinese medicine, which provided an important scientific basis for further elucidating the mechanism of "CHLZT" in the treatment of NAFLD.
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Sinusoidal endothelial dysfunction (SED) has been found to be an early event in nonalcoholic steatohepatitis (NASH) progression but the molecular mechanisms underlying its causation remains elusive. We hypothesized that adipokine leptin worsens sinusoidal injury by decreasing functionally active nitric oxide synthase 3 (NOS)3 via miR21. Using rodent models of NASH, and transgenic mice lacking leptin and leptin receptor, results showed that hyperleptinemia caused a 4–5 fold upregulation of hepatic miR21 as assessed by qRTPCR. The upregulation of miR21 led to a time-dependent repression of its target protein Grhl3 levels as shown by western blot analyses. NOS3-p/NOS3 ratio which is controlled by Grhl3 was significantly decreased in NASH models. SED markers ICAM-1, VEGFR-2, and E-selectin as assessed by immunofluorescence microscopy were significantly up regulated in the progressive phases of NASH. Lack of leptin or its receptor in vivo, reversed the upregulation of miR21 and restored the levels of Grhl3 and NOS3-p/NOS3 ratio coupled with decreased SED dysfunction markers. Interestingly, leptin supplementation in mice lacking leptin, significantly enhanced miR21 levels, decreased Grhl3 repression and NOS3 phosphorylation. Leptin supplementation in isolated primary endothelial cells, Kupffer cells and stellate cells showed increased mir21 expression in stellate cells while sinusoidal injury was significantly higher in all cell types. Finally miR21 KO mice showed increased NOS3-p/NOS3 ratio and reversed SED markers in the rodent models of NASH. The experimental results described here show a close association of leptin-induced miR21 in aiding sinusoidal injury in NASH.
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Activation of M1 macrophages in the nonalcoholic steatohepatitis (NASH) following several external or endogenous factors viz inflammatory stimuli, oxidative stress and cytokines are known. However, any direct role of oxidative stress in causing M1 polarization in NASH has been unclear. We hypothesized that CYP2E1-mediated oxidative stress causes M1 polarization in experimental NASH and NO donor administration inhibits CYP2E1 mediated inflammation with concomitant attenuation of M1 polarization. Since CYP2E1 takes center stage in these studies we use a toxin model of NASH which uses a ligand and a substrate of CYP2E1 for inducing NASH. Subsequently we use a methionine and choline deficient diet induced rodent NASH model where CYP2E1 role in disease progression has been shown. Results show that CYP2E1 causes M1 polarization bias that includes a significant increase in IL-1β and IL-12 in both models of NASH while CYP2E1 null mice or diallyl sulfide administration prevented it. Administration of GdCl3, a macrophage toxin attenuated both the initial M1 response and subsequent M2 response showing the observed increase in cytokine levels is primarily from macrophages. Based on the evidence of an adaptive NO increase, NO donor administration in vivo, that mechanistically inhibited CYP2E1 catalyzed oxidative stress during the entire study in NASH abrogated M1 polarization and NASH progression. The results obtained show the association of CYP2E1 in M1 polarization and that inhibition of CYP2E1 catalyzed oxidative stress by NO donor (DETA NONOate) can be a promising therapeutic strategy in NASH.
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Fatty liver disease is an emerging public health problem without effective therapies, and chronic hepatic inflammation is a key pathologic mediator in its progression. Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs), which have potent anti-inflammatory effects. Although promoting the effects of EETs elicits anti-inflammatory and protective effects in the cardiovascular system, the contribution of CYP-derived EETs to the regulation of fatty liver disease-associated inflammation and injury is unknown. Using the atherogenic diet model of non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD/NASH), our studies demonstrated that induction of fatty liver disease significantly and preferentially suppresses hepatic CYP epoxygenase expression and activity, and both hepatic and circulating levels of EETs in mice. Furthermore, mice with targeted disruption of Ephx2 (the gene encoding soluble epoxide hydrolase) exhibited restored hepatic and circulating EET levels and a significantly attenuated induction of hepatic inflammation and injury. Collectively, these data suggest that suppression of hepatic CYP-mediated EET biosynthesis is an important pathological consequence of fatty liver disease-associated inflammation, and that the CYP epoxygenase pathway is a central regulator of the hepatic inflammatory response in NAFLD/NASH. Future studies investigating the utility of therapeutic strategies that promote the effects of CYP-derived EETs in NAFLD/NASH are warranted.
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TRPV4, one of the TRP channels, is implicated in diverse physiological and pathological processes including cell proliferation. However, the role of TRPV4 in liver fibrosis is largely unknown. Here, we characterized the role of TRPV4 in regulating HSC-T6 cell proliferation. TRPV4 mRNA and protein were measured by RT-PCR and Western blot in patients and rat model of liver fibrosis in vivo and TGF-β1-activated HSC-T6 cells in vitro. Both mRNA and protein of TRPV4 were dramatically increased in liver fibrotic tissues of both patients and CCl4-treated rats. Stimulation of HSC-T6 cells with TGF-β1 resulted in increase of TRPV4 mRNA and protein. However, TGF-β1-induced HSC-T6 cell proliferation was inhibited by Ruthenium Red (Ru) or synthetic siRNA targeting TRPV4, and this was accompanied by downregulation of myofibroblast markers including α-SMA and Col1α1. Moreover, our study revealed that miR-203 was downregulated in liver fibrotic tissues and TGF-β1-treated HSC-T6 cell. Bioinformatics analyses predict that TRPV4 is the potential target of miR-203. In addition, overexpression of miR-203 in TGF-β1-induced HSC significantly reduced TRPV4 expression, indicating TRPV4, which was regulated by miR-203, may function as a novel regulator to modulate TGF-β1-induced HSC-T6 proliferation.
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Transient receptor potential vanilloid type 4 (TRPV4) is an endothelial Ca(2+) entry channel contributing to endothelium-mediated dilation in conduit and resistance arteries. We investigated the role of TRPV4 in the regulation of blood pressure and endothelial function under hypertensive conditions. TRPV4-deficient (TRPV4(-/-)) and wild-type (WT) control mice were given l-NAME (0.5 g/L) in drinking water for 7 days or subcutaneously infused with angiotensin (Ang) II (600 ng/kg per minute) for 14 days, and blood pressure measured by radiotelemetry. TRPV4(-/-) mice had a lower baseline mean arterial pressure (MAP) (12-h daytime MAP, 94 ± 2 vs. 99 ± 2 mmHg in WT controls). l-NAME treatment induced a slightly greater increase in MAP in TRPV4(-/-) mice (day 7, 13 ± 4%) compared to WT controls (6 ± 2%), but Ang II-induced increases in MAP were similar in TRPV4(-/-) and WT mice (day 14, 53 ± 6% and 37 ± 11%, respectively, P < 0.05). Chronic infusion of WT mice with Ang II reduced both acetylcholine (ACh)-induced dilation (dilation to 10(-5) mol/L ACh, 71 ± 5% vs. 92 ± 2% of controls) and the TRPV4 agonist GSK1016790A-induced dilation of small mesenteric arteries (10(-8) mol/L GSK1016790A, 14 ± 5% vs. 77 ± 7% of controls). However, Ang II treatment did not affect ACh dilation in TRPV4(-/-) mice. Mechanistically, Ang II did not significantly alter either TRPV4 total protein expression in mesenteric arteries or TRPV4 agonist-induced Ca(2+) response in mesenteric endothelial cells in situ. These results suggest that TRPV4 channels play a minor role in blood pressure regulation in l-NAME- but not Ang II-induced hypertension, but may be importantly involved in Ang II-induced endothelial dysfunction.
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Obesity is associated with strong risks of development of chronic inflammatory liver disease and metabolic syndrome following a second hit. The present study tests the hypothesis that free radical metabolism of low chronic exposure of bromodichloromethane (BDCM), a disinfection byproduct of drinking water causes nonalcoholic steatohepatitis (NASH), mediated by cytochrome P450 isoform CYP2E1 and adipokine leptin. Using diet induced obese mice (DIO), mice deficient in CYP2E1 and spontaneous knock out of the leptin gene, we show that BDCM caused increased lipid peroxidation and increased tyrosine nitration in DIO mice, events dependent on reductive metabolism by CYP2E1. DIO mice, exposed to BDCM exhibited increased hepatic leptin levels, higher proinflammatory gene expression and Kupffer cell activation. Obese mice exposed to BDCM also showed profound hepatic necrosis, Mallory body formation, collagen deposition, higher alpha smooth muscle actin expression, events that are hallmarks of NASH. The absence of CYP2E1 gene in mice that were fed with a high fat diet did not show NASH symptoms and were also protected from hepatic metabolic alterations in Glut-1, Glut-4, phosphofructokinase and phosphoenolpyruvate carboxykinase gene expressions (involved in carbohydrate metabolism) and UCP-1, PGC-1α, SREBP-1c and PPAR-γ genes (involved in hepatic fat metabolism). Mice lacking the leptin gene were significantly protected from both NASH and metabolic alterations following BDCM exposure, suggesting that higher levels of leptin induction by BDCM in the liver contribute to the development of NASH and metabolic alterations in obesity. These results provide novel insights into BDCM-induced NASH, hepatic metabolic reprograming and show the regulation of obesity-linked susceptibility to NASH by environmental factors, CYP2E1 and leptin.
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The ion channel transient receptor potential vanilloid (TRPV) 4 can be activated by hypo-osmolarity, heat, or certain lipid compounds. Here, we demonstrate expression of functional TRPV4 protein in the urothelium lining the renal pelvis, ureters, urinary bladder, and urethra. Exposure of cultured rat urothelial cells from the urinary bladder to the TRPV4-selective agonist 4alpha-phorbol 12,13-didecanoate (4alpha-PDD) promoted Ca2+ influx, evoked ATP release, and augmented the ATP release evoked by hypo-osmolarity. In awake rats during continuous infusion cystometrograms, intravesical administration of 4alpha-PDD (10-100 microM) increased maximal micturition pressure by 51%, specifically by augmenting the portion of each intravesical pressure wave that follows high-frequency urethral oscillations and voiding. This unusual pharmacological effect was prevented by intravesical pretreatment with the nonselective ATP receptor antagonist, pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (100 microM), systemic treatment with the selective P2X3 purinergic antagonist 5-([(3-phenoxybenzyl)[1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]carbonyl)-1,2,4-benzenetricarboxylic acid (A317491) (250 micromol/kg), or urethane anesthesia, but was unaffected by capsaicin pretreatment (100 mg/kg s.c.) or denervation of the urethral sphincter. 4Alpha-PDD (1-100 microM) did not alter the contractility to electrical stimulation of excised bladder strips. We conclude that activation of urothelial TRPV4 by 4alpha-PDD and release of mediators such as ATP trigger a novel neural mechanism that regulates the late phase of detrusor muscle contraction after micturition. These data raise the possibility that TRPV4 channels in the urothelium could contribute to abnormal bladder activity.
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Here we provide evidence for a critical role of the transient receptor potential cation channel, subfamily V, member 4 (TRPV4) in normal bladder function. Immunofluorescence demonstrated TRPV4 expression in mouse and rat urothelium and vascular endothelium, but not in other cell types of the bladder. Intracellular Ca2+ measurements on urothelial cells isolated from mice revealed a TRPV4-dependent response to the selective TRPV4 agonist 4alpha-phorbol 12,13-didecanoate and to hypotonic cell swelling. Behavioral studies demonstrated that TRPV4-/- mice manifest an incontinent phenotype but show normal exploratory activity and anxiety-related behavior. Cystometric experiments revealed that TRPV4-/- mice exhibit a lower frequency of voiding contractions as well as a higher frequency of nonvoiding contractions. Additionally, the amplitude of the spontaneous contractions in explanted bladder strips from TRPV4-/- mice was significantly reduced. Finally, a decreased intravesical stretch-evoked ATP release was found in isolated whole bladders from TRPV4-/- mice. These data demonstrate a previously unrecognized role for TRPV4 in voiding behavior, raising the possibility that TRPV4 plays a critical role in urothelium-mediated transduction of intravesical mechanical pressure.
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Objective: To identify the subtype of transient receptor potential (TRPs) channel involved in stretch-induced injury of human brain microvascular endothelial cells (HBMEC) and to explore the mechanism responsible for eNOS expression. Methods: TRPs expression was examined by Western blot and immunocytofluoresence in the cultured HBMEC. Mechanical stretch was performed by mini-type multi-functional bio-impact machine. The levels of free calcium ion in cells were examined by the flow cytometry. The eNOS expression was detected by Western blot. Results: The mRNA and protein expression of TRPV4 was detected in HBMEC by qRT-PCR, Western blot and immunocytofluoresence. The levels of free calcium ion in the stretch-treated HBMEC was significantly decreased in the presence of TRPV4 specific inhibitor (P<0.001), but there was no difference in calcium levels between the stretch and the control or unspecific inhibitor group (P=0.072 or 0.308). The levels of eNOS protein in the stretch-treated HBMEC were reduced in the presence of TRPV4 specific inhibitor or NOS inhibitor (P<0.05), but it was not changed compared with that in the control group (P>0.05). Conclusion: The eNOS expression is up-regulated under the condition of mechanic stretch, which is related to the activation of TRPV4, resulting in the influx of calcium.
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Hepatic stellate cell (HSC) activation is a significant event in the development of liver fibrosis. Promoting the activated HSCs apoptosis contributes to the reversal of liver fibrosis. Autophagy is considered to be critical for many cellular and pathological processes including liver fibrosis. Transient receptor potential vanilloid 4 (TRPV4), another member of the transient receptor potential (TRP) channel, is proved to be a vital modulator in regulating HSC proliferation during liver fibrosis. However, the precise mechanism of TRPV4 on HSC apoptosis is still unclear. Here, we explored the role of TRPV4 in regulating HSC-T6 cell apoptosis. Our study detected that the expressions of TRPV4 mRNA and protein were dramatically increased in HSC-T6 in response to TGF-β1 stimulation by qRT-PCR and Western blot. Moreover, the HSC-T6 transfected with si-TRPV4 increased apoptosis and inhibited autophagy. In addition, the HSC-T6 treated with 4α-phorbol 12,13-didecanoate results in suppression of apoptosis and increase of autophagy. Furthermore, we indicated that TRPV4 induces autophagy by regulating AKT signaling pathway. In addition, we found that blockade of autophagy by chemical antagonists chloroquine (CQ) leads to increased apoptosis. Furthermore, blocking autophagy by CQ did not lead to a distinct change with or without TRPV4 over-expression. These results indicated that TRPV4 could inhibit HSCs apoptosis partially by regulating autophagy-dependent AKT signaling pathway activation.
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Nitric oxide (NO) regulates renal function. Luminal flow stimulates NO production in the thick ascending limb (TAL). Transient Receptor Potential Vanilloid 4 (TRPV4) is a mechano-sensitive channel activated by luminal flow in different types of cells. We hypothesized that TRPV4 mediates flow-induced NO production in the rat TAL. We measured NO production in isolated, perfused rat TALs using the fluorescent dye DAF FM. Increasing luminal flow from 0 to 20 nL/min stimulated NO from 8±3 to 45±12 arbitrary units (AU)/min (n=5;p<0.05). The TRPV4 antagonists, ruthenium red (15 μmol/L) and RN 1734 (10 μmol/L), blocked flow-induced NO production. Also, luminal flow did not increase NO production in the absence of extracellular calcium. We also studied the effect of luminal flow on NO production in TALs transduced with a TRPV4shRNA. In non-transduced TALs luminal flow increased NO production by 47±17 AU/min (p<0.05;n=5). Similar to non-transduced TALs, luminal flow increased NO production by 39±11 AU/min (p<0.03,n=5) in TALs transduced with a control negative sequence-shRNA while in TRPV4shRNA-transduced TALs, luminal flow did not increase NO production (Δ10±15 AU/min;n=5). We then tested the effect of two different TRPV4 agonists on NO production in the absence of luminal flow. 4α-phorbol 12,13-didecanoate (1 μmol/L) enhanced NO production by 60±11 AU/min (p<0.002;n=7) and GSK1016790A (10 ηmol/L) increased NO production by 52±15 AU/min (p < 0.03;n=5). GSK1016790A (10 ηmol/L) did not stimulate NO production in TRPV4shRNA-transduced TALs. We conclude that activation of TRPV4 channels mediates flow-induced NO production in the rat TAL.
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Fibrosis is a highly conserved and co-ordinated protective response to tissue injury. The interaction of multiple pathways, molecules and systems determines whether fibrosis is self-limiting and homeostatic, or whether it is uncontrolled and excessive. Immune cells have been identified as key players in this fibrotic cascade, with the capacity to exert either injury-inducing or repair-promoting effects. A multi-organ approach was recently suggested to identify the core and regulatory pathways in fibrosis, with the aim of integrating the wealth of information emerging from basic fibrosis research. In this Review, we focus on recent advances in liver fibrosis research as a paradigm for wound healing in solid organs and the role of the immune system in regulating and balancing this response.
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Obesity is strongly associated with the prevalence of nonalcoholic fatty liver disease (NAFLD) in adult and pediatric populations. Nutrition, physical activity, and behavioral modifications are critical components of the treatment regimen for all obese patients with NAFLD. Bariatric surgeries that affect or restrict the flow of food through the gastrointestinal tract may improve liver histology in morbidly obese patients with nonalcoholic steatohepatitis (NASH), although randomized clinical trials and quasi-randomized clinical studies are lacking. Early detection of NASH and hepatic fibrosis using noninvasive biochemical and imaging markers that may replace liver biopsy is the current challenge.
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Environmental toxins induce a novel CYP2E1/leptin signaling axis in liver. This in turn activates a poorly characterized innate immune response that contributes to nonalcoholic steatohepatitis (NASH) progression. To identify the relevant subsets of T-lymphocytes in CYP2E1-dependent, environment-linked NASH, we utilized a model of diet induced obese (DIO) mice that are chronically exposed to bromodichloromethane. Mice deficient in CYP2E1, leptin (ob/ob mice), or both T and B cells (Pfp/Rag2 double knockout (KO) mice) were used to delineate the role of each of these factors in metabolic oxidative stress-induced T cell activation. Results revealed that elevated levels of lipid peroxidation, tyrosyl radical formation, mitochondrial tyrosine nitration and hepatic leptin as a consequence of metabolic oxidative stress caused increased levels of hepatic CD57, a marker of peripheral blood lymphocytes including NKT cells. CD8+CD57+ cytotoxic T cells but not CD4+CD57+ cells were significantly decreased in mice lacking CYP2E1 and leptin. There was a significant increase in the levels of T cell cytokines IL-2, IL-1β, IFN-γ in bromodichloromethane exposed DIO mice but not in mice that lacked CYP2E1, leptin or T and B cells. Apoptosis as evidenced by TUNEL assay and levels of cleaved caspase-3 was significantly lower in leptin and Pfp/Rag2 KO mice and highly correlated with protection from NASH. The results described above suggest that higher levels of oxidative stress-induced leptin mediated CD8+CD57+ T cells play an important role in the development of NASH. It also provides a novel insight of immune dysregulation and may be a key biomarker in NASH.
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The outcome of liver injury is determined by the success of repair. Liver repair involves replacement of damaged liver tissue with healthy liver epithelial cells (including both hepatocytes and cholangiocytes), and reconstruction of normal liver structure and function. Current dogma posits that replication of surviving mature hepatocytes and cholangiocytes drives the regeneration of liver epithelium after injury, while failure of liver repair commonly leads to fibrosis, a scaring condition in which hepatic stellate cells, the main liver-resident mesenchymal cells, play the major role. The current review discusses other mechanisms that might be responsible for the regeneration of new liver epithelial cells and outgrowth of matrix-producing mesenchymal cells during hepatic injury. This theory proposes that during liver injury, some epithelial cells undergo epithelial-to-mesenchymal transition (EMT), acquire myofibroblastic phenotypes/features and contribute to fibrogenesis, while certain mesenchymal cells (namely hepatic stellate cells and stellate cell-derived myofibroblasts) undergo mesenchymal-to-epithelial transition (MET), revert to epithelial cells, and ultimately differentiate into either hepatocytes or cholangiocytes. Although this theory is highly controversial, it suggests that the balance between EMT and MET modulates the outcome of liver injury. This review summarizes recent advances that support or refute the concept that certain types of liver cells are capable of phenotype transition (i.e. EMT and MET) during both culture conditions and chronic liver injury.
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Background & aims: Progression from steatosis to steatohepatitic lesions is hypothesized to require a second hit. These lesions have been associated with increased oxidative stress, often ascribed to high levels of leptin and other proinflammatory mediators. Here we have examined the role of leptin in inducing oxidative stress and Kupffer cell activation in CCl4-mediated steatohepatitic lesions of obese mice. Methods: Male C57BL/6 mice fed with a high-fat diet (60%kcal) at 16 weeks were administered CCl₄ to induce steatohepatitic lesions. Approaches included use of immuno-spin trapping for measuring free radical stress, gene-deficient mice for leptin, p47 phox, iNOS and adoptive transfer of leptin primed macrophages in vivo. Results: Diet-induced obese (DIO) mice, treated with CCl4 increased serum leptin levels. Oxidative stress was significantly elevated in the DIO mouse liver, but not in ob/ob mice, or in DIO mice treated with leptin antibody. In ob/ob mice, leptin supplementation restored markers of free radical generation. Markers of free radical formation were significantly decreased by the peroxynitrite decomposition catalyst FeTPPS, the iNOS inhibitor 1400W, the NADPH oxidase inhibitor apocynin, or in iNOS or p47 phox-deficient mice. These results correlated with the decreased expression of TNF-alpha and MCP-1. Kupffer cell depletion eliminated oxidative stress and inflammation, whereas in macrophage-depleted mice, the adoptive transfer of leptin-primed macrophages significantly restored inflammation. Conclusions: These results, for the first time, suggest that leptin action in macrophages of the steatotic liver, through induction of iNOS and NADPH oxidase, causes peroxynitrite-mediated oxidative stress thus activating Kupffer cells.
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Ethanol-inducible cytochrome P450 2E1 (CYP2E1) activity contributes to oxidative stress. However, CYP2E1 may have an important role in the pathogenesis of high-fat mediated non-alcoholic steatohepatitis (NASH). Thus, the role of CYP2E1 in high-fat mediated NASH development was evaluated. Male wild type (WT) and Cyp2e1-null mice were fed a low-fat diet (LFD, 10% energy-derived) or a high-fat diet (HFD, 60% energy-derived) for 10weeks. Liver histology and tissue homogenates were examined for various parameters of oxidative stress and inflammation. Liver histology showed that only WT mice fed a HFD developed NASH despite the presence of increased steatosis in both WT and Cyp2e1-null mice fed HFD. Markers of oxidative stress such as elevated CYP2E1 activity and protein amounts, lipid peroxidation, protein carbonylation, nitration, and glycation with increased phospho-JNK were all markedly elevated only in the livers of HFD-fed WT mice. Furthermore, while the levels of inflammation markers osteopontin and F4/80 were higher in HFD-fed WT mice, TNFα and MCP-1 levels were lower compared to the corresponding LFD-fed WT. Finally, only HFD-fed WT mice exhibited increased insulin resistance and impaired glucose tolerance. These data suggest that CYP2E1 is critically important in NASH development by promoting oxidative/nitrosative stress, protein modifications, inflammation, and insulin resistance.
Article
Nonalcoholic fatty liver disease (NAFLD), the most common form of chronic liver disease in developed countries, may progress to nonalcoholic steatohepatitis (NASH) in a minority of people. Those with NASH are at increased risk for cirrhosis and hepatocellular carcinoma. The potential risk and economic burden of utilizing liver biopsy to stage NAFLD in an overwhelmingly large at-risk population are enormous; thus, the discovery of sensitive, inexpensive, and reliable noninvasive diagnostic modalities is essential for population-based screening. Acoustic Radiation Force Impulse (ARFI) shear wave imaging, a noninvasive method of assessing tissue stiffness, was used to evaluate liver fibrosis in 172 patients diagnosed with NAFLD. Liver shear stiffness measures in three different imaging locations were reconstructed and compared to the histologic features of NAFLD and AST-to-platelet ratio indices (APRI). Reconstructed shear stiffnesses were not associated with ballooned hepatocytes (p=0.11), inflammation (p=0.69), nor imaging location (p=0.11). Using a predictive shear stiffness threshold of 4.24kPa, shear stiffness distinguished low (fibrosis stage 0-2) from high (fibrosis stage 3-4) fibrosis stages with a sensitivity of 90% and a specificity of 90% (AUC of 0.90). Shear stiffness had a mild correlation with APRI (R(2)=0.22). BMI>40kg/m(2) was not a limiting factor for ARFI imaging, and no correlation was noted between BMI and shear stiffness (R(2)=0.05). ARFI imaging is a promising imaging modality for assessing the presence or absence of advanced fibrosis in patients with obesity-related liver disease.
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Whereas in most cases a fatty liver remains free of inflammation, 10%-20% of patients who have fatty liver develop inflammation and fibrosis (nonalcoholic steatohepatitis [NASH]). Inflammation may precede steatosis in certain instances. Therefore, NASH could reflect a disease where inflammation is followed by steatosis. In contrast, NASH subsequent to simple steatosis may be the consequence of a failure of antilipotoxic protection. In both situations, many parallel hits derived from the gut and/or the adipose tissue may promote liver inflammation. Endoplasmic reticulum stress and related signaling networks, (adipo)cytokines, and innate immunity are emerging as central pathways that regulate key features of NASH.
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In polycystic liver diseases, cyst formation involves cholangiocyte hyperproliferation. In polycystic kidney (PCK) rats, an animal model of autosomal-recessive polycystic kidney disease (ARPKD), decreased intracellular calcium [Ca(2+)](i) in cholangiocytes is associated with hyperproliferation. We recently showed transient receptor potential vanilloid 4 (Trpv4), a calcium-entry channel, is expressed in normal cholangiocytes and its activation leads to [Ca(2+)](i) increase. Thus, we hypothesized that pharmacologic activation of Trpv4 might reverse the hyperproliferative phenotype of PCK cholangiocytes. Trpv4 expression was examined in liver of normal and PCK rats, normal human beings, and patients with autosomal-dominant polycystic kidney disease or ARPKD. Trpv4 activation effect on cell proliferation and cyst formation was assessed in cholangiocytes derived from normal and PCK rats. The in vivo effects of Trpv4 activation on kidney and liver cysts was analyzed in PCK rats. Trpv4 was overexpressed both at messenger RNA (8-fold) and protein (3-fold) levels in PCK cholangiocytes. Confocal and immunogold electron microscopy supported Trpv4 overexpression in the livers of PCK rats and ARPKD or autosomal-dominant polycystic kidney disease patients. Trpv4 activation in PCK cholangiocytes increased [Ca(2+)](i) by 30%, inhibiting cell proliferation by approximately 25%-50% and cyst growth in 3-dimensional culture (3-fold). Trpv4-small interfering RNA silencing blocked effects of Trpv4 activators by 70%. Trpv4 activation was associated with Akt phosphorylation and beta-Raf and Erk1/2 inhibition. In vivo, Trpv4 activation induced a significant decrease in renal cystic area and a nonsignificant decrease in liver cysts. Taken together, our in vitro and in vivo data suggest that increasing intracellular calcium by Trpv4 activation may represent a potential therapeutic approach in PKD.
Article
Obesity is associated with a spectrum of chronic liver disease. Because obesity increases the risk for advanced forms of liver disease (ie, cirrhosis and liver cancer), the obesity epidemic is emerging as a major factor underlying the burden of liver disease in the United States and many other countries. This article reviews mechanisms that mediate the pathogenesis of obesity-related liver disease, summarizes clinical evidence that demonstrates obesity-related liver disease can be life-threatening, and discusses whether or not treatments for obesity or related comorbidities impact liver disease outcomes.
Article
The Transient Receptor Potential Vanilloid 4 channel, TRPV4, is a Ca(2+) and Mg(2+) permeable non-selective cation channel involved in many different cellular functions. It is activated by a variety of physical and chemical stimuli, including heat, mechano-stimuli, endogenous substances such as arachidonic acid and its cytochrome P450-derived metabolites (epoxyeicosatrienoic acids), endocannabinoids (anandamide and 2-arachidonoylglycerol), as well as synthetic alpha-phorbol derivatives. Recently, TRPV4 has been characterized as an important player modulating osteoclast differentiation in bone remodelling and as a urothelial mechanosensor that controls normal voiding. Several TRPV4 gain-of-function mutations are shown to cause autosomal-dominant bone dysplasias such as brachyolmia and Koszlowski disease. In this review we comprehensively describe the structural, biophysical and (patho)physiological properties of the TRPV4 channel and we summarize the current knowledge about the role of TRPV4 in the pathogenesis of several diseases.
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Nonalcoholic fatty liver disease (NAFLD) has become the most common form of liver disease, affecting 20% to 30% of the US population. Its clinical manifestations are usually absent or subtle, and it usually comes to medical attention incidentally when aminotransferase levels are found to be elevated or a radiographic study reveals that the liver is fatty. Primary NAFLD is now considered the hepatic manifestation of the metabolic syndrome. The pathogenesis is thought to be a multiple-hit process involving insulin resistance, oxidative stress, apoptosis, and adipokines. In general, the prognosis for simple steatosis is very good; however, nonalcoholic steatohepatitis (NASH) can progress to cirrhosis and hepatocellular carcinoma in 10% to 15% of patients. There is no established treatment for NAFLD except for weight loss and treating each component of the metabolic syndrome.
Article
The pathology of the liver in alcoholic steatosis and alcoholic steatohepatitis (ASH) is remarkably similar to that of nonalcoholic fatty liver disease (NAFLD), including nonalcoholic steatohepatitis (NASH), suggesting some common pathogenic mechanism. Studies carried out over the last three decades of possible mechanisms involved revealed one common link, namely the induction of cytochrome P4502E1. Its substrates include fatty acids, ketones and ethanol. These substances, when present chronically in large amounts, induce the activity of the enzyme which thereby contributes to the disposition of these substrates. This reaction, however, is associated with the release of free radicals which can cause lipid peroxidation and liver injury, including mitochondrial damage. Mitochondrial damage in turn exacerbates the oxidative stress. CYP2E1 can also convert various xenobiotics to toxic metabolites. When unchecked, this toxicity eventually results in inflammation and fibrosis, culminating in cirrhosis. Prevention of this disorder is based on limiting the substrates that induce the system, such as excessive fatty acid associated with obesity and excessive alcohol consumption. No effective pharmacologic treatment is presently available but there is ongoing research on possible inhibitors of CYP2E1, innocuous enough to be suitable for chronic human consumption and sufficiently effective to attenuate the CYP2E1 induction to avoid the consequences of its excessive activity while maintaining its physiologic role.
Article
The role of insulin resistance in non-alcoholic fatty liver disease is suggested by laboratory data (hyperinsulinemia and decreased sensitivity to endogenous and exogenous insulin). The clinical association with features of the metabolic syndrome, particularly in the most aggressive stages of the disease, further confirms a causative role. Fat accumulation in the liver may stem either from genetic defects, primarily responsible for insulin resistance, or excessive calorie intake and visceral obesity, and is mediated by adipocytokines (leptin, adiponectin, tumour necrosis factor-alpha). Progression of fatty liver to steatohepatitis may be the result of an imbalance between pro-inflammatory and anti-inflammatory cytokines, triggering the formation of reactive oxygen species and intrahepatic lipid peroxidation. This process may also be promoted or accelerated by pro-oxidant xenobiotics or environmental factors. Insulin resistance provides a target for specific treatment of non-alcoholic fatty liver, and insulin-sensitising agents (metformin or thiazolidinediones) as well as lifestyle changes to reduce visceral adiposity are the most promising therapeutic options. Future trials need to be performed in order to test the long-term effectiveness of these treatments on the basis of clinically relevant histological outcomes.
Article
Transient receptor potential (TRP) ion channels have been identified as cellular sensors responding to diverse external and internal stimuli. This review will cover the TRPV subfamily that comprises vertebrate and invertebrate members. The six mammalian TRPV channels were demonstrated to function in thermosensation, mechanosensation, osmosensation and Ca(2+) uptake. Invertebrate TRPV channels, five in Caenorhabditis elegans and two in Drosophila, have been shown to play a role in mechanosensation, such as hearing and proprioception in Drosophila and nose touch in C. elegans, and in the response to osmotic and chemical stimuli in C. elegans. We will focus here on the role that TRPV ion channels play in mechanosensation and a related sensory (sub-)modality, osmosensation.
Article
Nonalcoholic steatohepatitis (NASH), the lynchpin between steatosis and cirrhosis in the spectrum of nonalcoholic fatty liver disorders (NAFLD), was barely recognized in 1981. NAFLD is now present in 17% to 33% of Americans, has a worldwide distribution, and parallels the frequency of central adiposity, obesity, insulin resistance, metabolic syndrome and type 2 diabetes. NASH could be present in one third of NAFLD cases. Age, activity of steatohepatitis, and established fibrosis predispose to cirrhosis, which has a 7- to 10-year liver-related mortality of 12% to 25%. Many cases of cryptogenic cirrhosis are likely endstage NASH. While endstage NAFLD currently accounts for 4% to 10% of liver transplants, this may soon rise. Pathogenic concepts for NAFLD/NASH must account for the strong links with overnutrition and underactivity, insulin resistance, and genetic factors. Lipotoxicity, oxidative stress, cytokines, and other proinflammatory mediators may each play a role in transition of steatosis to NASH. The present "gold standard" management of NASH is modest weight reduction, particularly correction of central obesity achieved by combining dietary measures with increased physical activity. Whether achieved by "lifestyle adjustment" or anti-obesity surgery, this improves insulin resistance and reverses steatosis, hepatocellular injury, inflammation, and fibrosis. The same potential for "unwinding" fibrotic NASH is indicated by studies of the peroxisome proliferation activator receptor (PPAR)-gamma agonist "glitazones," but these agents may improve liver disease at the expense of worsening obesity. Future challenges are to approach NAFLD as a preventive public health initiative and to motivate affected persons to adopt a healthier lifestyle.
Article
Polyunsaturated fatty acids such as arachidonic acid (AA) play an important role in alcohol-induced liver injury. AA promotes toxicity in rat hepatocytes with high levels of cytochrome P4502E1 and in HepG2 E47 cells which express CYP2E1. Nitric oxide (NO) participates in the regulation of various cell activities as well as in cytotoxic events. NO may act as a protectant against cytotoxic stress or may enhance cytotoxicity when produced at elevated concentrations. The goal of the current study was to evaluate the effect of endogenously or exogenously produced NO on AA toxicity in liver cells with high expression of CYP2E1 and assess possible mechanisms for its actions. Pyrazole-induced rat hepatocytes or HepG2 cells expressing CYP2E1 were treated with AA in the presence or absence of an inhibitor of nitric oxide synthase L-N(G)-Nitroarginine Methylester (L-NAME) or the NO donors S-nitroso-N-acetylpenicillamine (SNAP), and (Z)-1-[-(2-aminoethyl)-N-(2-aminoethyl)]diazen-1-ium-1,2-diolate (DETA-NONO). AA decreased cell viability from 100% to 48+/-6% after treatment for 48 h. In the presence of L-NAME, viability was further lowered to 23+/-5%, while, SNAP or DETA-NONO increased viability to 66+/-8 or 71+/-6%. The L-NAME potentiated toxicity was primarily necrotic in nature. L-NAME did not affect CYP2E1 activity or CYP2E1 content. SNAP significantly lowered CYP2E1 activity but not protein. AA treatment increased lipid peroxidation and lowered GSH levels. L-NAME potentiated while SNAP prevented these changes. Thus, L-NAME increased, while NO donors decreased AA-induced oxidative stress. Antioxidants prevented the L-NAME potentiation of AA toxicity. Damage to mitochondria by AA was shown by a decline in the mitochondrial membrane potential (MMP). L-NAME potentiated this decline in MMP in association with its increase in AA-induced oxidative stress and toxicity. NO donors decreased this decline in MMP in association with their decrease in AA-induced oxidative stress and toxicity. These results indicate that NO can be hepatoprotective against CYP2E1-dependent toxicity, preventing AA-induced oxidative stress.
Article
Disruption of the alveolar septal barrier leads to acute lung injury, patchy alveolar flooding, and hypoxemia. Although calcium entry into endothelial cells is critical for loss of barrier integrity, the cation channels involved in this process have not been identified. We hypothesized that activation of the vanilloid transient receptor potential channel TRPV4 disrupts the alveolar septal barrier. Expression of TRPV4 was confirmed via immunohistochemistry in the alveolar septal wall in human, rat, and mouse lung. In isolated rat lung, the TRPV4 activators 4alpha-phorbol-12,13-didecanoate and 5,6- or 14,15-epoxyeicosatrienoic acid, as well as thapsigargin, a known activator of calcium entry via store-operated channels, all increased lung endothelial permeability as assessed by measurement of the filtration coefficient, in a dose- and calcium-entry dependent manner. The TRPV antagonist ruthenium red blocked the permeability response to the TRPV4 agonists, but not to thapsigargin. Light and electron microscopy of rat and mouse lung revealed that TRPV4 agonists preferentially produced blebs or breaks in the endothelial and epithelial layers of the alveolar septal wall, whereas thapsigargin disrupted interendothelial junctions in extraalveolar vessels. The permeability response to 4alpha-phorbol-12,13-didecanoate was absent in TRPV4(-/-) mice, whereas the response to thapsigargin remained unchanged. Collectively, these findings implicate TRPV4 in disruption of the alveolar septal barrier and suggest its participation in the pathogenesis of acute lung injury.
Article
Nonalcoholic fatty liver disease (NAFLD) refers to a spectrum of liver damage ranging from simple steatosis to nonalcoholic steatohepatitis, advanced fibrosis, and rarely, progression to cirrhosis. The pathogenesis of NAFLD is thought to be related to insulin resistance and oxidant stress. Truncal obesity, dyslipidema, hypertension, and hyperglycemia are strongly associated with NAFLD; therefore, management of NAFLD entails identification and treatment of metabolic risk factors, improving insulin sensitivity, and increasing antioxidant defenses in the liver. This article briefly summarizes advances in our understanding of the relationship between NAFLD and the insulin resistance (metabolic) syndrome, its prevalence, natural history, and treatment.
Article
Osmotic homeostasis is one of the most aggressively defended physiological parameters in vertebrates. However, the molecular mechanisms underlying osmotic regulation are poorly understood. The transient receptor potential channel, vanilloid subfamily (TRPV4), is an osmotically activated ion channel that is expressed in circumventricular organs in the mammalian CNS, which is an important site of osmotic sensing. We have generated trpv4-null mice and observed abnormalities of their osmotic regulation. trpv4-/- mice drank less water and became more hyperosmolar than did wild-type littermates, a finding that was seen with and without administration of hypertonic saline. In addition, plasma levels of antidiuretic hormone were significantly lower in trpv4-/- mice than in wild-type littermates after a hyperosmotic challenge. Continuous s.c. infusion of the antidiuretic hormone analogue, dDAVP, resulted in systemic hypotonicity in trpv4-/- mice, despite the fact that their renal water reabsorption capacity was normal. Thus, the response to both hyper- and hypoosmolar stimuli is impaired in trpv4-/- mice. After a hyperosmolar challenge, there was markedly reduced expression of c-FOS in the circumventricular organ, the organum vasculosum of the lamina terminalis, of trpv4-/- mice compared with wild-type mice. This finding suggests that there is an impairment of osmotic sensing in the CNS of trpv4-/- mice. These data indicate that TRPV4 is necessary for the normal response to changes in osmotic pressure and functions as an osmotic sensor in the CNS.
Recent advances in nonalcoholic fatty liver disease Current opinion in gastroenterology PubMed PMID: 19396962. 30 Noninvasive evaluation of hepatic fibrosis using acoustic radiation force-based shear stiffness in patients with nonalcoholic fatty liver disease
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  • Aj Sanyal
  • Ml Palmeri
  • Mh Wang
  • Nc Rouze
  • Mf Abdelmalek
  • Cd Guy
  • B Moser
Cheung O, Sanyal AJ. Recent advances in nonalcoholic fatty liver disease. Current opinion in gastroenterology. 2009;25(3):230-7. Epub 2009/04/28. PubMed PMID: 19396962. 30. Palmeri ML, Wang MH, Rouze NC, Abdelmalek MF, Guy CD, Moser B, et al. Noninvasive evaluation of hepatic fibrosis using acoustic radiation force-based shear stiffness in patients with nonalcoholic fatty liver disease. J Hepatol. 2011;55(3):666-72. Epub 2011/01/25. doi: 10.1016/j.jhep.2010.12.019. PubMed PMID: 21256907; PubMed Central PMCID: PMCPMC3092839. 31.
PubMed PMID: 24157970; PubMed Central PMCID: PMCPMC3882441. 27 Metabolites of arachidonic acid and linoleic acid in early stages of non-alcoholic fatty liver disease-A pilot study The cytochrome P450 epoxygenase pathway regulates the hepatic inflammatory response in fatty liver disease
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American journal of physiology Gastrointestinal and liver physiology. 2013;305(12):G881-90. Epub 2013/10/26. doi: 10.1152/ajpgi.00289.2013. PubMed PMID: 24157970; PubMed Central PMCID: PMCPMC3882441. 27. Maciejewska D, Ossowski P, Drozd A, Ryterska K, Jamiol-Milc D, Banaszczak M, et al. Metabolites of arachidonic acid and linoleic acid in early stages of non-alcoholic fatty liver disease-A pilot study. Prostaglandins & other lipid mediators. 2015;121(Pt B):184-9. Epub 2015/09/27. doi: 10.1016/j.prostaglandins.2015.09.003. PubMed PMID: 26408952. 28. Schuck RN, Zha W, Edin ML, Gruzdev A, Vendrov KC, Miller TM, et al. The cytochrome P450 epoxygenase pathway regulates the hepatic inflammatory response in fatty liver disease. PloS one. 2014;9(10):e110162. Epub 2014/10/14. doi: 10.1371/journal.pone.0110162. PubMed PMID: 25310404; PubMed Central PMCID: PMCPMC4195706. 29.
M1 polarization bias and subsequent nonalcoholic steatohepatitis progression is attenuated by nitric oxide donor DETA NONOate via inhibition of CYP2E1-induced oxidative stress in obese mice
  • R K Seth
  • S Das
  • S Pourhoseini
  • D Dattaroy
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