Dan E Berkowitz

Johns Hopkins University, Baltimore, Maryland, United States

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Publications (138)742.52 Total impact

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    ABSTRACT: Hyperglycemia-induced reactive oxygen species (ROS) production plays a major role in the pathogenesis of diabetic vascular dysfunction. However, the underlying mechanisms remain unclear. Toll-like receptor 4 (TLR4), a key component of innate immunity, is known to be activated during diabetes. Therefore, we hypothesize that hyperglycemia activates TLR4 signaling in vascular smooth muscle cells (VSMCs) that triggers ROS production and causes vascular dysfunction. Rat mesenteric VSMCs exposed to high glucose (25 mmol/l) increased TLR4 expression and activated TLR4 signaling via upregulation of myeloid differentiation factor 88 (MyD88). TLR4 inhibitor CLI-095 significantly attenuated elevated levels of ROS and nuclear factor-kappa B (NF-κB) activity in VSMCs exposed to high glucose. Mesenteric arteries from streptozotocin-induced diabetic rats treated with CLI-095 (2 mg/kg/day) intraperitoneally for 2 weeks exhibited reduced ROS generation and attenuated noradrenaline-induced contraction. These results suggest that hyperglycemia-induced ROS generation and NF-κB activation in VSMCs are at least, in part, mediated by TLR4 signaling. Therefore, strategies to block TLR4 signaling pathways pose a promising avenue to alleviate diabetic-induced vascular complications. High glucose-induced TLR4 activation in vascular smooth muscle cells. Inhibition of TLR4 attenuated high glucose-induced ROS production and NF-κB activity in VSMC. Suppression of TLR4 signaling attenuated mesenteric contraction in diabetic rat.
    Journal of Molecular Medicine 07/2015; DOI:10.1007/s00109-015-1318-7 · 4.74 Impact Factor
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    ABSTRACT: Emerging evidence strongly supports a role for HDAC2 in the transcriptional regulation of endothelial genes and vascular function. We have recently demonstrated that HDAC2 reciprocally regulates the transcription of Arginase2, which is itself a critical modulator of endothelial function via eNOS. Moreover HDAC2 levels are decreased in response to the atherogenic stimulus OxLDL via a mechanism that is apparently dependent upon proteasomal degradation. NEDDylation is a post-translational protein modification that is tightly linked to ubiquitination and thereby protein degradation. We propose that changes in NEDDylation may modulate vascular endothelial function in part through alterations in the proteasomal degradation of HDAC2. In HAEC, OxLDL exposure augmented global protein NEDDylation. Pre-incubation of mouse aortic rings with the NEDDylation activating enzyme inhibitor, MLN4924, prevented OxLDL-induced endothelial dysfunction. In HAEC, MLN enhanced HDAC2 abundance, decreased expression and activity of Arginase2, and blocked OxLDL-mediated reduction of HDAC2. Additionally, HDAC2 was shown to be a substrate for NEDD8 conjugation and this interaction was potentiated by OxLDL. Further, HDAC2 levels were reciprocally regulated by ectopic expression of NEDD8 and the de-NEDDylating enzyme SENP8. Our findings indicate that the observed improvement in endothelial dysfunction with inhibition of NEDDylation activating enzyme is likely due to an HDAC2-dependent decrease in Arginase2. NEDDylation activating enzyme may therefore be a novel target in endothelial dysfunction and atherogenesis.
    Journal of Molecular and Cellular Cardiology 04/2015; 81. DOI:10.1016/j.yjmcc.2015.01.019 · 5.22 Impact Factor
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  • Journal of Sexual Medicine 01/2015; 12:1-2. · 3.15 Impact Factor
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    ABSTRACT: We present a protocol for measuring in vivo aortic stiffness in mice using high-resolution ultrasound imaging. Aortic diameter is measured by ultrasound and aortic blood pressure is measured invasively with a solid-state pressure catheter. Blood pressure is raised then lowered incrementally by intravenous infusion of vasoactive drugs phenylephrine and sodium nitroprusside. Aortic diameter is measured for each pressure step to characterize the pressure-diameter relationship of the ascending aorta. Stiffness indices derived from the pressure-diameter relationship can be calculated from the data collected. Calculation of arterial compliance is described in this protocol. This technique can be used to investigate mechanisms underlying increased aortic stiffness associated with cardiovascular disease and aging. The technique produces a physiologically relevant measure of stiffness compared to ex vivo approaches because physiological influences on aortic stiffness are incorporated in the measurement. The primary limitation of this technique is the measurement error introduced from the movement of the aorta during the cardiac cycle. This motion can be compensated by adjusting the location of the probe with the aortic movement as well as making multiple measurements of the aortic pressure-diameter relationship and expanding the experimental group size.
    Journal of Visualized Experiments 12/2014; DOI:10.3791/52200 · 1.33 Impact Factor
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    ABSTRACT: Nitroxyl (HNO), the reduced and protonated form of nitric oxide (NO(.)), confers unique physiological effects including vasorelaxation and enhanced cardiac contractility. These features have spawned current pharmaceutical development of HNO donors as heart failure therapeutics. HNO interacts with selective redox sensitive cysteines to effect signaling but is also proposed to activate soluble guanylate cyclase (sGC) in vitro to induce vasodilation and potentially enhance contractility. Here, we tested whether sGC stimulation is required for these HNO effects in vivo and if HNO also modifies a redox-sensitive cysteine (C42) in protein kinase G-1α to control vasorelaxation. Intact mice and isolated arteries lacking the sGC-β subunit (sGCKO, results in full sGC deficiency) or expressing solely a redox-dead C42S mutant protein kinase G-1α were exposed to the pure HNO donor, CXL-1020. CXL-1020 induced dose-dependent systemic vasodilation while increasing contractility in controls; however, vasodilator effects were absent in sGCKO mice whereas contractility response remained. The CXL-1020 dose reversing 50% of preconstricted force in aortic rings was ≈400-fold greater in sGCKO than controls. Cyclic-GMP and cAMP levels were unaltered in myocardium exposed to CXL-1020, despite its inotropic-vasodilator activity. In protein kinase G-1α(C42S) mice, CXL-1020 induced identical vasorelaxation in vivo and in isolated aortic and mesenteric vessels as in littermate controls. In both groups, dilation was near fully blocked by pharmacologically inhibiting sGC. Thus, sGC and cGMP-dependent signaling are necessary and sufficient for HNO-induced vasodilation in vivo but are not required for positive inotropic action. Redox modulation of protein kinase G-1α is not a mechanism for HNO-mediated vasodilation. © 2014 American Heart Association, Inc.
    Hypertension 12/2014; 65(2). DOI:10.1161/HYPERTENSIONAHA.114.04285 · 7.63 Impact Factor
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    ABSTRACT: Melanopsin (opsin4; Opn4), a non-image-forming opsin, has been linked to a number of behavioral responses to light, including circadian photo-entrainment, light suppression of activity in nocturnal animals, and alertness in diurnal animals. We report a physiological role for Opn4 in regulating blood vessel function, particularly in the context of photorelaxation. Using PCR, we demonstrate that Opn4 (a classic G protein-coupled receptor) is expressed in blood vessels. Force-tension myography demonstrates that vessels from Opn4(-/-) mice fail to display photorelaxation, which is also inhibited by an Opn4-specific small-molecule inhibitor. The vasorelaxation is wavelength-specific, with a maximal response at ∼430-460 nm. Photorelaxation does not involve endothelial-, nitric oxide-, carbon monoxide-, or cytochrome p450-derived vasoactive prostanoid signaling but is associated with vascular hyperpolarization, as shown by intracellular membrane potential measurements. Signaling is both soluble guanylyl cyclase- and phosphodiesterase 6-dependent but protein kinase G-independent. β-Adrenergic receptor kinase 1 (βARK 1 or GRK2) mediates desensitization of photorelaxation, which is greatly reduced by GRK2 inhibitors. Blue light (455 nM) regulates tail artery vasoreactivity ex vivo and tail blood blood flow in vivo, supporting a potential physiological role for this signaling system. This endogenous opsin-mediated, light-activated molecular switch for vasorelaxation might be harnessed for therapy in diseases in which altered vasoreactivity is a significant pathophysiologic contributor.
    Proceedings of the National Academy of Sciences 11/2014; 111(50). DOI:10.1073/pnas.1420258111 · 9.81 Impact Factor
  • Nitric Oxide 11/2014; 42C:101-102. DOI:10.1016/j.niox.2014.09.013 · 3.18 Impact Factor
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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; 115(4). DOI:10.1161/CIRCRESAHA.115.304262 · 11.09 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; 34(7). DOI:10.1161/ATVBAHA.114.303685 · 5.53 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; 118(6). DOI:10.1213/ANE.0000000000000227 · 3.42 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; 129(23). DOI:10.1161/CIRCULATIONAHA.113.007559 · 14.95 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 03/2014; 3(2):e000599. DOI:10.1161/JAHA.113.000599 · 2.88 Impact Factor
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    ABSTRACT: The effect of inhalational anesthetics on myocardial contraction and energetics in type 2 diabetes mellitus is unknown. We investigated the effect of isoflurane (ISO) on force and intracellular Ca2+ transient (iCa), myocardial oxygen consumption (MVo2), and energetics/redox behavior in trabecular muscles from Zucker Diabetic Fatty (ZDF) rats. At baseline, force and corresponding iCa were lower in ZDF trabeculae than in controls. ISO decreased force in both groups in a dose dependent manner. ISO did not affect iCa amplitude in controls, but ISO >1.5% significantly reduced iCa amplitude in ZDF trabeculae. ISO-induced force depression fully recovered as a result of increased iCa when external Ca2+ was raised in controls. However, both force and iCa remained low in ZDF muscle at elevated external Ca2+. In controls, force, iCa and MVo2 increased when stimulation frequency was increased from 0.5 to 1.5 Hz. ZDF muscles, however, exhibited blunted responses in force and iCa and decreased MVo2. Oxidative stress levels were unchanged in control muscles, but increased significantly in ZDF muscles after exposure to ISO. Finally, the depressive effect of ISO was prevented by 4-Hydroxy-2,2,6,6- tetramethylpiperidine-N-oxyl (Tempol) in ZDF muscles. These findings suggest that ISO dosedependently attenuates force in control and ZDF muscles with differential effect on iCa. The mechanism of force depression by ISO in controls is mainly decreased myofilament Ca2+ sensitivity, whereas in ZDF muscles, the ISO-induced decrease in contraction is due to worsening oxidative stress, which inhibits iCa and force development.
    Journal of Pharmacology and Experimental Therapeutics 01/2014; 349(1). DOI:10.1124/jpet.113.211144 · 3.86 Impact Factor
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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; 52(4). DOI:10.1016/j.bcmd.2013.10.004 · 2.33 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. DOI:10.1016/j.atherosclerosis.2013.08.026 · 3.97 Impact Factor
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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 09/2013; 4:278. DOI:10.3389/fimmu.2013.00278
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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; 305. DOI:10.1152/ajpheart.00103.2013 · 4.01 Impact Factor
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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 07/2013; 8(7):e68028. DOI:10.1371/journal.pone.0068028 · 3.23 Impact Factor

Publication Stats

4k Citations
742.52 Total Impact Points

Institutions

  • 1998–2015
    • Johns Hopkins University
      • • Department of Anesthesiology and Critical Care Medicine
      • • Department of Biomedical Engineering
      • • Department of Surgery
      Baltimore, Maryland, United States
  • 1997–2014
    • Johns Hopkins Medicine
      • • Department of Biomedical Engineering
      • • Department of Anesthesiology and Critical Care Medicine
      • • Department of Medicine
      Baltimore, Maryland, United States
  • 1994–1996
    • Duke University Medical Center
      • Department of Anesthesiology
      Durham, North Carolina, United States
    • Duke University
      • Department of Surgery
      Durham, North Carolina, United States