Dan E Berkowitz

Johns Hopkins Medicine, Baltimore, Maryland, United States

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Publications (116)570.3 Total impact

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    ABSTRACT: Rationale: Increased arginase activity contributes to endothelial dysfunction by competition for L-arginine substrate and reciprocal regulation of NOS. The rapid increase in arginase activity in human aortic endothelial cells (HAEC) exposed to oxidized LDL is consistent with post-translational modification or subcellular trafficking. Objective: To test the hypotheses that OxLDL triggers reverse translocation of mitochondrial Arginase 2 (Arg2) to cytosol and Arg2 activation, and that this process is dependent upon mitochondrial processing peptidase (MPP), LOX-1 receptor and ROCK. Methods and Results: OxLDL triggered translocation of Arg2 from mitochondria to cytosol in HAEC and in murine aortic intima with a concomitant rise in arginase activity. All of these changes were abolished by inhibition of MPP or by its siRNA-mediated knockdown. ROCK inhibition and the absence of the LOX-1 receptor in KO mice also ablated translocation. Amino-terminal sequencing of Arg2 revealed 2 candidate mitochondrial targeting sequences, and deletion of either of these confined Arg2 to the cytoplasm. Inhibitors of MPP or LOX-1 receptor KO attenuated OxLDL-mediated decrements in endothelial-specific NO production and increases in superoxide generation. Finally, Arg2(-/-) mice bred on an ApoE(-/-) background showed reduced plaque load, reduced ROS production, enhanced NO, and improved endothelial function as compared with ApoE(-/-) controls. Conclusions: These data demonstrate dual distribution of Arg2, a protein with an unambiguous MTS, in mammalian cells, and its reverse translocation to cytoplasm by alterations in the extracellular milieu. This novel molecular mechanism drives OxLDL-mediated arginase activation, eNOS uncoupling, endothelial dysfunction, and atherogenesis.
    Circulation Research 06/2014; · 11.86 Impact Factor
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    ABSTRACT: Arginase 2 (Arg2) is a critical target in atherosclerosis because it controls endothelial nitric oxide, proliferation, fibrosis, and inflammation. Regulators of Arg2 transcription in the endothelium have not been characterized. The goal of the current study is to determine the role of specific histone deacetylases (HDACs) in the regulation of endothelial Arg2 transcription and endothelial function. The HDAC inhibitor trichostatin A increased levels of Arg2 mRNA, protein, and activity in both human aortic endothelial cells and mouse aortic rings. These changes occurred in both time- and dose-dependent patterns and resulted in Arg2-dependent endothelial dysfunction. Trichostatin A and the atherogenic stimulus oxidized low-density lipoprotein enhanced the activity of common promoter regions of Arg2. HDAC inhibition with trichostatin A also decreased endothelial nitric oxide, and these effects were blunted by arginase inhibition. Nonselective class I HDAC inhibitors enhanced Arg2 expression, whereas the only selective inhibitor that increased Arg2 expression was mocetinostat, a selective inhibitor of HDACs 1 and 2. Additionally, mouse aortic rings preincubated with mocetinostat exhibited dysfunctional relaxation. Overexpression of HDAC2 (but not HDAC 1, 3, or 8) cDNA in human aortic endothelial cells suppressed Arg2 expression in a concentration-dependent manner, and siRNA knockdown of HDAC2 enhanced Arg2 expression. Chromatin immunoprecipitation indicated direct binding of HDAC2 to the Arg2 promoter, and HDAC2 overexpression in human aortic endothelial cells blocked oxidized low-density lipoprotein-mediated activation of the Arg2 promoter. Finally, overexpression of HDAC2 blocked oxidized low-density lipoprotein-mediated vascular dysfunction. HDAC2 is a critical regulator of Arg2 expression and thereby endothelial nitric oxide and endothelial function. Overexpression or activation of HDAC2 represents a novel therapy for endothelial dysfunction and atherosclerosis.
    Arteriosclerosis Thrombosis and Vascular Biology 05/2014; · 6.34 Impact Factor
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    ABSTRACT: Both cardiopulmonary bypass (CPB) and red blood cell (RBC) storage are associated with detrimental changes in RBC structure and function that may adversely affect tissue oxygen delivery. We tested the hypothesis that in cardiac surgery patients, RBC deformability and aggregation are minimally affected by CPB with autologous salvaged blood alone but are negatively affected by the addition of stored allogeneic blood. In this prospective cohort study, 32 patients undergoing cardiac surgery with CPB were divided into 3 groups by transfusion status: autologous salvaged RBCs alone (Auto; n = 12), autologous salvaged RBCs + minimal (<5 units) stored allogeneic RBCs (Auto+Allo min; n = 10), and autologous salvaged RBCs + moderate (≥5 units) stored allogeneic RBCs (Auto+Allo mod; n = 10). Ektacytometry was used to measure RBC elongation index (deformability) and critical shear stress (aggregation) before, during, and for 3 days after surgery. In the Auto group, RBC elongation index did not change significantly from the preoperative baseline. In the Auto+Allo min group, mean elongation index decreased from 32.31 ± 0.02 (baseline) to 30.47 ± 0.02 (nadir on postoperative day 1) (P = 0.003, representing a 6% change). In the Auto+Allo mod group, mean elongation index decreased from 32.7 ± 0.02 (baseline) to 28.14 ± 0.01 (nadir on postoperative day 1) (P = 0.0001, representing a 14% change). Deformability then dose-dependently recovered toward baseline over the first 3 postoperative days. Changes in aggregation were unrelated to transfusion (no difference among groups). For the 3 groups combined, mean critical shear stress decreased from 359 ± 174 mPa to 170 ± 141 mPa (P = 0.01, representing a 54% change), with the nadir at the end of surgery and returned to baseline by postoperative day 1. In cardiac surgery patients, transfusion with stored allogeneic RBCs, but not autologous salvaged RBCs, is associated with a decrease in RBC cell membrane deformability that is dose-dependent and may persist beyond 3 postoperative days. These findings suggest that autologous salvaged RBCs may be of higher quality than stored RBCs, since the latter are subject to the so-called storage lesions.
    Anesthesia and analgesia 05/2014; · 3.08 Impact Factor
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    ABSTRACT: Glycosphingolipids are integral components of the cell membrane and have been shown to serve as messengers, transducing growth factor initiated phenotypes. Here we have examined whether inhibition of glycosphingolipid synthesis could ameliorate atherosclerosis and arterial stiffness in transgenic mice and rabbits. Apolipoprotein E-/- mice (12 weeks of age, n = 6) were fed regular chow or a western diet (1.25% cholesterol, 2% fat). Mice were fed 5mg/kg (mpk) or 10mpk of an inhibitor of glycosphingolipid synthesis, D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), solubilized in vehicle (5% Tween-80 in PBS) and the placebo group received vehicle only. At 20 and 36 weeks of age, serial echocardiography was performed to measure aortic intima medial thickening (IMT). Aortic pulse wave velocity (PWV) measured vascular stiffness. Feeding mice a western diet markedly increased aortic PWV, IMT, oxidized LDL, Ca(2+) deposits, and glucosyl- and lactosylceramide synthase activity. These were dose-dependently decreased by feeding D-PDMP. In liver, D-PDMP decreased cholesterol and triglyceride levels by raising the expression of SREBP2, LDL-r, HMGCo-A reductase, and cholesterol efflux genes (e.g., ABCG5, ABCG8). D-PDMP affected VLDL catabolism by increasing the gene expression for LPL and VLDLr. Rabbits fed a western diet for 90 days had extensive atherosclerosis accompanied by a 17.5-fold increase in total cholesterol levels and a 3-fold increase in lactosylceramide levels. This was completely prevented by feeding D-PDMP. Inhibition of glycosphingolipid synthesis ameliorates atherosclerosis and arterial stiffness in ApoE-/- mice and rabbits. Thus, inhibition of glycosphingolipid synthesis may be a novel approach to ameliorate atherosclerosis and arterial stiffness.
    Circulation 04/2014; · 15.20 Impact Factor
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    ABSTRACT: Vascular aging is closely associated with increased vascular stiffness. It has recently been demonstrated that decreased nitric oxide (NO)-induced S-nitrosylation of tissue transglutaminase (TG2) contributes to age-related vascular stiffness. In the current study, we tested the hypothesis that exercise restores NO signaling and attenuates vascular stiffness by decreasing TG2 activity and cross-linking in an aging rat model. Rats were subjected to 12 weeks of moderate aerobic exercise. Aging was associated with diminished phosphorylated endothelial nitric oxide synthase and phosphorylated vasodilator-stimulated phosphoprotein abundance, suggesting reduced NO signaling. TG2 cross-linking activity was significantly increased in old animals, whereas TG2 abundance remained unchanged. These alterations were attenuated in the exercise cohort. Simultaneous measurement of blood pressure and pulse wave velocity (PWV) demonstrated increased aortic stiffness in old rats, compared to young, at all values of mean arterial pressure (MAP). The PWV-MAP correlation in the old sedentary and old exercise cohorts was similar. Tensile testing of the vessels showed increased stiffness of the aorta in the old phenotype with a modest restoration of mechanical properties toward the young phenotype with exercise. Increased vascular stiffness during aging is associated with decreased TG2 S-nitrosylation, increased TG2 cross-linking activity, and increased vascular stiffness likely the result of decreased NO bioavailability. In this study, a brief period of moderate aerobic exercise enhanced NO signaling, attenuated TG cross-linking activity, and reduced ex vivo tensile properties, but failed to reverse functional vascular stiffness in vivo, as measured by PWV.
    Journal of the American Heart Association. 01/2014; 3(2):e000599.
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    ABSTRACT: Sickle cell disease (SCD) is associated with increase in oxidative stress and irreversible membrane changes that originates from the instability and polymerization of deoxygenated hemoglobin S (HbS). The relationship between erythrocyte membrane changes as assessed by a decrease in deformability and oxidative stress as assessed by an increase in heme degradation was investigated. The erythrocyte deformability and heme degradation for 27 subjects with SCD and 7 with sickle trait were compared with normal healthy adults. Changes in both deformability and heme degradation increased in the order of control to trait to non-crisis SCD to crisis SCD resulting in a very significantly negative correlation between deformability and heme degradation. However, a quantitative analysis of the changes in deformability and heme degradation for these different groups of subjects indicated that sickle trait had a much smaller effect on deformability than on heme degradation, while crisis affects deformability to a greater extent than heme degradation. These findings provide insights into the relative contributions of erythrocyte oxidative stress and membrane damage during the progression of SCD providing a better understanding of the pathophysiology of SCD.
    Blood Cells Molecules and Diseases 11/2013; · 2.26 Impact Factor
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    ABSTRACT: Cigarette smoke increases the risk of several cardiovascular diseases and has synergistic detrimental effects when present with other risks that contribute to its pathogenesis. Oxidative injury to the endothelium via reactive oxygen species (ROS) and nitric oxide (NO) dysregulation is a common denominator of smoking-induced alterations in vascular function. However, the mechanisms underlying ROS and NO dysregulation due to smoking remain unclear. We tested if arginase (Arg) activation/upregulation contributes to this phenomenon by constraining nitric oxide synthase (NOS) activity. Arg2 knockout (Arg2(-/-)) and control C57BL/6J mice were either exposed to cigarette smoke, 6 h/day/2 weeks (Second Hand Smoking; SHS) or housed in normal environment (Non Smoking; NS). Arg activity, NO and ROS levels were determined by measuring urea production, fluorescent dye (DAF), and dihydroethedium (DHE) respectively in isolated mouse aorta. Arg activity and ROS levels were higher NO lower in SHS compared to NS mice. SHS failed to lower NO levels in Arg2(-/-) mice. Endothelial dependent vasodilation (EDV) was attenuated in SHS mice as compared to controls (78.80% ± 8 vs 46.58% ± 5). This impaired EDV was abolished in Arg2(-/-) mice (67.48% ± 7 in SHS vs. 78.80% ± 8 in NS). Vascular stiffness was increased in SHS mice as compared to NS controls but remained unchanged in Arg2(-/-) mice. Endothelial NOS is uncoupled by smoking exposure, leading to endothelial dysfunction and vascular stiffness, a process that is prevented by Arg2 deletion. Hence, we identify Arg2 upregulation as a critical pathogenic factor and target for therapy in oxidative injury following smoking exposure through reciprocal regulation of endothelial NOS.
    Atherosclerosis 11/2013; 231(1):91-94. · 3.71 Impact Factor
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    ABSTRACT: Nitric oxide (NO) can modulate arterial stiffness by causing regulating both functional and structural changes in the arterial wall. Tissue transglutaminase (TG2) has been shown to contribute to increased central aortic stiffness by catalyzing the crosslinking of matrix proteins. Nitric oxide (NO) S-nitrosylates and constrains TG2 to the cytosolic compartment and thereby holds its crosslinking function latent. In the present study, the role of eNOS derived NO in regulating TG2 function was studied using eNOS knockout mice. Matrix associated TG2 and TG2 cross-linking function were higher while TG2 S-nitrosylation was lower in the eNOS-/- compared to wild type (WT) mice. Pulse wave velocity (PWV) and mean arterial pressure (MAP) measured non-invasively were elevated in the eNOS-/- compared to WT mice. Intact aortas and decellularized aortic tissue scaffolds of eNOS-/- mice were significantly stiffer as determined by tensile testing. The carotid arteries of the eNOS-/- mice were also stiffer as determined by pressure-dimension analysis. Invasive methods to determine the PWV-MAP relationship showed that PWV in eNOS-/- and WT diverge at higher MAP. Thus, eNOS derived NO regulates TG2 localization and function and contributes to vascular stiffness.
    AJP Heart and Circulatory Physiology 07/2013; · 4.01 Impact Factor
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    ABSTRACT: BACKGROUND: Red blood cell (RBC) deformation is critical for microvascular perfusion and oxygen delivery to tissues. Abnormalities in RBC deformability have been observed in aging, sickle cell disease, diabetes, and preeclampsia. Although nitric oxide (NO) prevents decreases in RBC deformability, the underlying mechanism is unknown. STUDY DESIGN AND METHODS: As an experimental model, we used ionophore A23187-mediated calcium influx in RBCs to reduce their deformability and investigated the role of NO donor sodium nitroprusside (SNP) and KCa3.1 (Gardos) channel blockers on RBC deformability (measured as elongation index [EI] by microfluidic ektacytometry). RBC intracellular Ca(2+) and extracellular K(+) were measured by inductively coupled plasma mass spectrometry and potassium ion selective electrode, respectively. RESULTS: SNP treatment of RBCs blocked the Ca(2+) (approx. 10 μmol/L)-induced decrease in RBC deformability (EI 0.34 ± 0.02 vs. 0.09 ± 0.01, control vs. Ca(2+) loaded, p < 0.001; and EI 0.37 ± 0.02 vs. 0.30 ± 0.01, SNP vs. SNP plus Ca(2+) loaded) as well as Ca(2+) influx and K(+) efflux. The SNP effect was similar to that observed after pharmacologic blockade of the KCa3.1 channel (with charybdotoxin or extracellular medium containing isotonic K(+) concentration). In RBCs from KCa3.1(-/-) mice, 10 μmol/L Ca(2+) loading did not decrease cellular deformability. A preliminary attempt to address the molecular mechanism of SNP protection suggests the involvement of cell surface thiols. CONCLUSION: Our results suggest that nitroprusside treatment of RBCs may protect them from intracellular calcium increase-mediated stiffness, which may occur during microvascular perfusion in diseased states, as well as during RBC storage.
    Transfusion 06/2013; · 3.53 Impact Factor
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    ABSTRACT: To investigate the effect of sildenafil citrate (SC) on skeletal muscle ischemia-reperfusion (IR) injury in rats. Adult male Wistar rats were randomized into three groups: vehicle-treated control (CTG), sildenafil citrate-treated (SCG), and sham group (SG). CTG and SCG had femoral artery occluded for 6 hours. Saline or 1 mg/kg of SC was given 5.5 hours after occlusion. SG had a similar procedure without artery occlusion. Soleus muscle samples were acquired 4 or 24h after the reperfusion. Immunohistochemistry caspase-3 analysis was used to estimate apoptosis using the apoptotic ratio (computed as positive/negative cells). Wilcoxon rank-sum or Kruskal-Wallis tests were used to assess differences among groups. Eighteen animals were included in the 4h reperfusion groups and 21 animals in the 24h reperfusion groups. The mean apoptotic ratio was 0.18±0.1 for the total cohort; 0.14±0.06 for the 4h reperfusion groups and 0.19±0.08 for the 24h groups (p<0.05). The SCG had lower caspase-3 ratio compared to the control groups at the 24h reperfusion time point (p<0.05). Sildenafil citrate administration after the onset of the ischemic injury reduces IR-induced cellular damage in skeletal muscle in this rat hindlimb ischemia model.
    Acta cirurgica brasileira / Sociedade Brasileira para Desenvolvimento Pesquisa em Cirurgia 04/2013; 28(4):282-7. · 0.48 Impact Factor
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    ABSTRACT: BACKGROUND:Erythrocyte cell membranes undergo morphologic changes during storage, but it is unclear whether these changes are reversible. We assessed erythrocyte cell membrane deformability in patients before and after transfusion to determine the effects of storage duration and whether changes in deformability are reversible after transfusion.METHODS:Sixteen patients undergoing posterior spinal fusion surgery were studied. Erythrocyte deformability was compared between those who required moderate transfusion (≥5 units erythrocytes) and those who received minimal transfusion (0-4 units erythrocytes). Deformability was measured in samples drawn directly from the blood storage bags before transfusion and in samples drawn from patients before and after transfusion (over 3 postoperative days). In samples taken from the blood storage bags, we compared deformability of erythrocytes stored for a long duration (≥21 days), those stored for a shorter duration (<21 days), and cell-salvaged erythrocytes. Deformability was assessed quantitatively using the elongation index (EI) measured by ektacytometry, a method that determines the ability for the cell to elongate when exposed to shear stress.RESULTS:Erythrocyte deformability was significantly decreased from the preoperative baseline in patients after moderate transfusion (EI decreased by 12% ± 4% to 20% ± 6%; P = 0.03) but not after minimal transfusion (EI decreased by 3% ± 1% to 4% ± 1%; P = 0.68). These changes did not reverse over 3 postoperative days. Deformability was significantly less in erythrocytes stored for ≥21 days (EI = 0.28 ± 0.02) than in those stored for <21 days (EI = 0.33 ± 0.02; P = 0.001) or those drawn from patients preoperatively (EI = 0.33 ± 0.02; P = 0.001). Cell-salvaged erythrocytes had intermediate deformability (EI = 0.30 ± 0.03) that was greater than that of erythrocytes stored ≥21 days (P = 0.047), but less than that of erythrocytes stored <21 days (P = 0.03).CONCLUSIONS:The findings demonstrate that increased duration of erythrocyte storage is associated with decreased cell membrane deformability and that these changes are not readily reversible after transfusion.
    Anesthesia and analgesia 02/2013; · 3.08 Impact Factor
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    Deepesh Pandey, Lewis Romer, Dan E Berkowitz
    Journal of the American Heart Association. 01/2013; 2(4):e000392.
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    Jochen Steppan, Daniel Nyhan, Dan E Berkowitz
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    ABSTRACT: Endothelial dysfunction and resulting vascular pathology have been identified as an early hallmark of multiple diseases, including diabetes mellitus. One of the major contributors to endothelial dysfunction is a decrease in nitric oxide (NO) bioavailability, impaired NO signaling, and an increase in the amount of reactive oxygen species (ROS). In the endothelium NO is produced by endothelial nitric oxide synthase (eNOS), for which l-arginine is a substrate. Arginase, an enzyme critical in the urea cycle also metabolizes l-arginine, thereby directly competing with eNOS for their common substrate and constraining its bioavailability for eNOS, thereby compromising NO production. Arginase expression and activity is upregulated in many cardiovascular diseases including ischemia reperfusion injury, hypertension, atherosclerosis, and diabetes mellitus. More importantly, since the 1990s, specific arginase inhibitors such as N-hydroxy-guanidinium or N-hydroxy-nor-l-arginine, and boronic acid derivatives, such as, 2(S)-amino-6-boronohexanoic acid, and S-(2-boronoethyl)-l-cysteine, that can bridge the binuclear manganese cluster of arginase have been developed. These highly potent and specific inhibitors can now be used to probe arginase function and thereby modulate the redox milieu of the cell by changing the balance between NO and ROS. Inspired by this success, drug discovery programs have recently led to the identification of α-α-disubstituted amino acid based arginase inhibitors [such as (R)-2-amino-6-borono-2-(2-(piperidin-1-yl)ethyl)hexanoic acid], that are currently under early investigation as therapeutics. Finally, some investigators concentrate on identification of plant derived compounds with arginase inhibitory capability, such as piceatannol-3'-O-β-d-glucopyranoside (PG). All of these synthesized or naturally derived small molecules may represent novel therapeutics for vascular disease particularly that associated with diabetes.
    Frontiers in Immunology 01/2013; 4:278.
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    ABSTRACT: Sildenafil citrate revolutionized the practice of sexual medicine upon its federal regulatory agency approval approximately 15 years ago as the prototypical phosphodiesterase type 5 inhibitor indicated for the treatment of male erectile dysfunction. We now provide scientific support for its alternative use in the management of priapism, a clinical disorder of prolonged and uncontrolled penile erection. Sildenafil administered continuously to sickle cell mice, which show a priapism phenotype, reverses oxidative/nitrosative stress effects in the penis, mainly via reversion of uncoupled endothelial nitric oxide synthase to the functional coupled state of the enzyme, which in turn corrects aberrant signaling and function of the nitric oxide/cyclic GMP/protein kinase G/phosphodiesterase type 5 cascade. Priapism tendencies in these mice are reverted partially toward normal neurostimulated erection frequencies and durations after sildenafil treatment in association with normalized cyclic GMP concentration, protein kinase G activity and phosphodiesterase type 5 activity in the penis. Thus, sildenafil exerts pleiotropic effects in the penis that extend to diverse erection disorders.
    PLoS ONE 01/2013; 8(7):e68028. · 3.53 Impact Factor
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    ABSTRACT: BACKGROUND: Although ex vivo lung perfusion (EVLP) is increasingly being used to evaluate and manipulate potential donor lungs before lung transplantation (LTx), data on the biochemistry of lungs during EVLP are limited. In this study, we examined the physiology and biochemistry of human lungs on an EVLP circuit. METHODS: We recovered unallocated double lungs in standard fashion and split them into single lungs. All lungs received a nebulized arginase inhibitor, 2-S-amino-6-boronohexanoic acid (ABH), at either the onset (n = 6) or after 3 h (n = 8) of EVLP. Serial biochemical analysis included levels of arginase, endogenous nitric oxide synthase (eNOS), cyclic guanosine monophosphate, and reactive oxygen species. We considered lungs transplantable if they sustained a PaO(2):FiO(2) ≥ 350 in addition to stable pulmonary function during EVLP. RESULTS: We recovered a total of 14 single lungs. We deemed three single lungs from different donors to be transplantable after EVLP. These lungs had superior oxygenation, lower carbon dioxide, and more stable pulmonary artery pressures. Transplantable lungs had higher baseline levels of eNOS and higher final levels of cyclic guanosine monophosphate than non-transplantable lungs. Early ABH administration was associated with a transient increase in dynamic compliance. CONCLUSIONS: In this biochemical characterization of lungs deemed unsuitable for LTx, early levels of eNOS and late levels of cyclic guanosine monophosphate appear to be associated with improved allograft function during EVLP. In addition, nebulized ABH is associated with a significant increase in dynamic compliance. These data suggest that biochemical markers during EVLP may predict acceptable allograft function, and that this platform can be used to biochemically manipulate donor lungs before LTx.
    Journal of Surgical Research 11/2012; · 2.02 Impact Factor
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    ABSTRACT: Cardiovascular dysfunction is a primary independent predictor of age-related morbidity and mortality. Frailty is associated with activation of inflammatory pathways and fatigue that commonly presents and progresses with age. Interleukin 10 (IL-10), the cytokine synthesis inhibitory factor, is an anti-inflammatory cytokine produced by immune and non-immune cells. Homozygous deletion of IL-10 in mice yields a phenotype that is consistent with human frailty, including age-related increases in serum inflammatory mediators, muscular weakness, higher levels of IGF-1 at midlife, and early mortality. While emerging evidence suggests a role for IL-10 in vascular protection, a clear mechanism has not yet been elucidated. METHODS: In order to evaluate the role of IL-10 in maintenance of vascular function, force tension myography was utilized to access ex-vivo endothelium dependent vasorelaxation in vessels isolated from IL-10 knockout IL-10(tm/tm) and control mice. Pulse wave velocity ((PWV), index of stiffness) of vasculature was measured using ultrasound and blood pressure was measured using the tail cuff method. Echocardiography was used to elucidated structure and functional changes in the heart. RESULTS: Mean arterial pressures were significantly higher in IL-10(tm/tm) mice as compared to C57BL6/wild type (WT) controls. PWV was increased in IL-10(tm/tm) indicating stiffer vasculature. Endothelial intact aortic rings isolated from IL-10(tm/tm) mice demonstrated impaired vasodilation at low acetylcholine doses and vasoconstriction at higher doses whereas vasorelaxation responses were preserved in rings from WT mice. Cyclo-oxygenase (COX-2)/ThromboxaneA2 inhibitors improved endothelial dependent vasorelaxation and reversed vasoconstriction. Left ventricular end systolic diameter, left ventricular mass, isovolumic relaxation time, fractional shortening and ejection fraction were all significantly different in the aged IL-10(tm/tm) mice compared to WT mice. CONCLUSION: Aged IL-10(tm/tm) mice have stiffer vessels and decreased vascular relaxation due to an increase in eicosanoids, specifically COX-2 activity and resultant thromboxane A2 receptor activation. Our results also suggest that aging IL-10(tm/tm) mice have an increased heart size and impaired cardiac function compared to age-matched WT mice. While further studies will be necessary to determine if this age-related phenotype develops as a result of inflammatory pathway activation or lack of IL-10, it is essential for maintaining the vascular compliance and endothelial function during the aging process. Given that a similar cardiovascular phenotype is present in frail, older adults, these findings further support the utility of the IL-10(tm/tm) mouse as a model of frailty.
    Experimental gerontology 11/2012; · 3.34 Impact Factor
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    ABSTRACT: Background:Vasopressin is frequently used to treat catecholamine-resistant vasodilatory shock. It enhances the vasoconstrictor effects of catecholamines at concentrations of vasopressin that have none or only minimal intrinsic pressor effects. However, the vascular mechanisms underlying this combined pharmacological approach have not been fully elucidated.Methods:We used isometric tension measurements in vascular rings to investigate potential cellular mechanisms. Vascular rings (0.2 mm diameter) were harvested from the superior mesenteric artery of Wistar rats (2 to 4 months of age). Dose-response relationships were derived for vasopressin (VP) and norepinephrine (NE), in the absence and presence of a subpressor dose of VP (10(-9 )M). The contribution of tyrosine kinase (TK), the TK pathway proteins SRC and PYK2, as well as protein kinase C (PKC) were determined by measuring the modulating influence of specific inhibitors on the pressor response to NE (10(-5 )M) alone and the augmented pressor response to VP (10(-9 )M).Results:VP (10(-9 )M) had only minimal pressor effect alone (10% of maximal response), but significantly increased the E(max) response to NE (587.8 ± 40.7 vs 331.2 ± 10.4 mg). TK inhibition completely abolished the pressor response to NE (100% vs 1.0% ± 0.5%) and the augmented VP response alone (100% vs 2.0% ± 1.01%). Both responses were significantly, but equally, decreased by SRC inhibition (63% ± 4.0% and 69% ± 1.0%). In contrast, inhibition of the TK molecule PYK2 with salicylate had differential inhibitory effects on the vasoconstrictor responses. Salicylate caused a greater inhibition of VP-induced augmented NE response in comparison with NE alone (62.1% ± 7% and 15% ± 2%). Inhibition of either the μ or γ PKC isoform significantly decreased both responses, but the magnitude of the inhibition was significantly different for each isoform. Inhibition of the γ PKC isoform significantly decreased the vasoconstriction responses to both NE and VP plus NE (82.9 ± 3.9 vs 32.8 ± 3.8). Inhibition of the μ PKC isoform significantly decreased both responses and completely abolished the VP-augmented response to NE.Conclusion:These data are consistent with a central role for TK in mediating both the NE response and the VP-augmented response. Moreover, PYK2 and the μ and γ isoforms of PKC seem to play a preferential role in mediating the augmented VP response. The apparent divergent roles of these pathways in mediating NE- versus VP-augmented pressor responses could potentially lead to new targeted therapies in catecholamine-resistant shock.
    Anesthesia and analgesia 08/2012; · 3.08 Impact Factor
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    Woosung Shin, Dan E Berkowitz, Sungwoo Ryoo
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    ABSTRACT: The incidence of cardiovascular disease is predicted to increase as the population ages. There is accumulating evidence that arginase upregulation is associated with impaired endothelial function. Here, we demonstrate that arginase II (ArgII) is upregulated in aortic vessels of aged mice and contributes to decreased nitric oxide (NO) generation and increased reactive oxygen species (ROS) production via endothelial nitric oxide synthase (eNOS) uncoupling. Inhibiting ArgII with small interfering RNA technique restored eNOS coupling to that observed in young mice and increased NO generation and decreased ROS production. Furthermore, enhanced vasoconstrictor responses to U46619 and attenuated vasorelaxation responses to acetylcholine in aged vasculature were markedly improved following siRNA treatment against ArgII. These results might be associated with increased L-arginine bioavailability. Collectively, these results suggest that ArgII may be a valuable target in age-dependent vascular diseases.
    Experimental and Molecular Medicine 08/2012; · 2.57 Impact Factor
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    ABSTRACT: OBJECTIVES: Ischemia/reperfusion injury (IRI) is a common complication of lung transplantation (LTx). Hydrogen sulfide (H(2)S) is a novel agent previously shown to slow metabolism and scavenge reactive oxygen species, potentially mitigating IRI. We hypothesized that pretreatment with inhaled H(2)S would improve graft function in an ex vivo model of LTx. METHODS: Rabbits (n = 10) were ventilated for 2 h prior to heart-lung bloc procurement. The treatment group (n = 5) inhaled room air (21% O(2)) supplemented with 150 ppm H(2)S while the control group (n = 5) inhaled room air alone. Both groups were gradually cooled to 34°C. All heart-lung blocs were then recovered and cold-stored in low-potassium dextran solution for 18 h. Following storage, the blocs were reperfused with donor rabbit blood in an ex vivo apparatus. Serial clinical parameters were assessed and serial tissue biochemistry was examined. RESULTS: Prior to heart-lung bloc procurement, rabbits pretreated with H(2)S exhibited similar oxygenation (P = 0.1), ventilation (P = 0.7), and heart rate (P = 0.5); however, treated rabbits exhibited consistently higher mean arterial blood pressures (P = 0.01). During reperfusion, lungs pretreated with H(2)S had better oxygenation (P < 0.01) and ventilation (P = 0.02), as well as lower pulmonary artery pressures (P < 0.01). Reactive oxygen species levels were lower in treated lungs during reperfusion (P = 0.01). Additionally, prior to reperfusion, treated lungs demonstrated more preserved mitochondrial cytochrome c oxidase activity (P = 0.01). CONCLUSIONS: To our knowledge, this study represents the first reported therapeutic use of inhaled H(2)S in an experimental model of LTx. After prolonged ischemia, lungs pretreated with inhaled H(2)S exhibited improved graft function during reperfusion. Donor pretreatment with inhaled H(2)S represents a potentially novel adjunct to conventional preservation techniques and merits further exploration.
    Journal of Surgical Research 06/2012; · 2.02 Impact Factor
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    ABSTRACT: Since the introduction of the first Angiotensin-converting enzyme inhibitor (ACEI) captopril in 1981, ACE inhibitors have become a mainstay of anti-hypertensive therapy. In addition to lowering BP, there is overwhelming evidence that ACE inhibitors (and angiotensin-receptor blockers (ARB)) provide end organ protection independent of blood their pressure lowering properties in diseases such as CHF, post MI, diabetes, and renal insufficiency.(1) It is an unresolved issue, however, if ACE inhibitors have a protective or deleterious effect on perioperative outcomes(2).(SELECT FULL TEXT TO CONTINUE).
    Circulation 06/2012; 126(3):249-51. · 15.20 Impact Factor

Publication Stats

3k Citations
570.30 Total Impact Points


  • 1997–2014
    • Johns Hopkins Medicine
      • • Department of Biomedical Engineering
      • • Division of Cardiac Surgery
      • • Department of Anesthesiology and Critical Care Medicine
      • • Division of Cardiology
      Baltimore, Maryland, United States
  • 1998–2013
    • Johns Hopkins University
      • • Department of Anesthesiology and Critical Care Medicine
      • • Department of Biomedical Engineering
      • • Department of Medicine
      Baltimore, MD, United States
  • 2000
    • University of Vermont
      • Department of Neurological Sciences
      Burlington, VT, United States
  • 1994–1996
    • Duke University Medical Center
      • • Department of Anesthesiology
      • • Department of Surgery
      Durham, North Carolina, United States