scholarly journals Exercise training mitigates ER stress and UCP2 deficiency-associated coronary vascular dysfunction in atherosclerosis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Junyoung Hong ◽  
Eunkyung Park ◽  
Jonghae Lee ◽  
Yang Lee ◽  
Bridgette V. Rooney ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Exercise Training ◽  
Er Stress ◽  
Nlrp3 Inflammasome ◽  
Uncoupling Protein ◽  
No Production ◽  
Apoe Ko Mice ◽  
Apoe Ko ◽  
Coronary Arterioles

AbstractEndoplasmic reticulum (ER) stress and uncoupling protein-2 (UCP2) activation are opposing modulators of endothelial dysfunction in atherosclerosis. Exercise reduces atherosclerosis plaques and enhances endothelial function. Our aim was to understand how exercise affects ER stress and UCP2 activation, and how that relates to endothelial dysfunction in an atherosclerotic murine model. Wild type (C57BL/6, WT) and apolipoprotein-E-knockout (ApoEtm1Unc, ApoE KO) mice underwent treadmill exercise training (EX) or remained sedentary for 12 weeks. Acetylcholine (ACh)-induced endothelium-dependent vasodilation was determined in the presence of an eNOS inhibitor (L-NAME), UCP2 inhibitor (genipin), and ER stress inducer (tunicamycin). UCP2, ER stress markers and NLRP3 inflammasome signaling were quantified by western blotting. p67phox and superoxide were visualized using immunofluorescence and DHE staining. Nitric oxide (NO) was measured by nitrate/nitrite assay. ACh-induced vasodilation was attenuated in coronary arterioles of ApoE KO mice but improved in ApoE KO-EX mice. Treatment of coronary arterioles with L-NAME, tunicamycin, and genipin significantly attenuated ACh-induced vasodilation in all mice except for ApoE KO mice. Exercise reduced expression of ER stress proteins, TXNIP/NLRP3 inflammasome signaling cascades, and Bax expression in the heart of ApoE KO-EX mice. Further, exercise diminished superoxide production and NADPH oxidase p67phox expression in coronary arterioles while simultaneously increasing UCP2 expression and nitric oxide (NO) production in the heart of ApoE KO-EX mice. Routine exercise alleviates endothelial dysfunction in atherosclerotic coronary arterioles in an eNOS, UCP2, and ER stress signaling specific manner, and resulting in reduced TXNIP/NLRP3 inflammasome activity and oxidative stress.

Endothelial dysfunction and arterial pressure regulation during early diabetes in mice: roles for nitric oxide and endothelium-derived hyperpolarizing factor

2007 ◽  
Vol 293 (2) ◽  
pp. R707-R713 ◽  
Author(s):  
Sharyn M. Fitzgerald ◽  
Barbara K. Kemp-Harper ◽  
Helena C. Parkington ◽  
Geoffrey A. Head ◽  
Roger G. Evans
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Arterial Pressure ◽  
Early Stage ◽  
Mesenteric Arteries ◽  
No Production ◽  
Wild Type ◽  
Early Diabetes ◽  
Diabetes In Mice ◽  
Vehicle Treatment

We determined whether nitric oxide (NO) counters the development of hypertension at the onset of diabetes in mice, whether this is dependent on endothelial NO synthase (eNOS), and whether non-NO endothelium-dependent vasodilator mechanisms are altered in diabetes in mice. Male mice were instrumented for chronic measurement of mean arterial pressure (MAP). In wild-type mice, MAP was greater after 5 wk of Nω-nitro-l-arginine methyl ester (l-NAME; 100 mg·kg−1·day−1 in drinking water; 97 ± 3 mmHg) than after vehicle treatment (88 ± 3 mmHg). MAP was also elevated in eNOS null mice (113 ± 4 mmHg). Seven days after streptozotocin treatment (200 mg/kg iv) MAP was further increased in l-NAME-treated mice (108 ± 5 mmHg) but not in vehicle-treated mice (88 ± 3 mmHg) nor eNOS null mice (104 ± 3 mmHg). In wild-type mice, maximal vasorelaxation of mesenteric arteries to acetylcholine was not altered by chronic l-NAME or induction of diabetes but was reduced by 42 ± 6% in l-NAME-treated diabetic mice. Furthermore, the relative roles of NO and endothelium-derived hyperpolarizing factor (EDHF) in acetylcholine-induced vasorelaxation were altered; the EDHF component was enhanced by l-NAME and blunted by diabetes. These data suggest that NO protects against the development of hypertension during early-stage diabetes in mice, even in the absence of eNOS. Furthermore, in mesenteric arteries, diabetes is associated with reduced EDHF function, with an apparent compensatory increase in NO function. Thus, prior inhibition of NOS results in endothelial dysfunction in early diabetes, since the diabetes-induced reduction in EDHF function cannot be compensated by increases in NO production.

scholarly journals The reciprocal relationship between adiponectin and LOX-1 in the regulation of endothelial dysfunction in ApoE knockout mice

2010 ◽  
Vol 299 (3) ◽  
pp. H605-H612 ◽  
Author(s):  
Xiuping Chen ◽  
Hanrui Zhang ◽  
Steve McAfee ◽  
Cuihua Zhang
Keyword(s):  
Endothelial Cells ◽  
Endothelial Dysfunction ◽  
Sodium Nitroprusside ◽  
Oxidized Ldl ◽  
Reciprocal Relationship ◽  
Reciprocal Regulation ◽  
Tnf Α ◽  
Ldl Uptake ◽  
Apoe Ko Mice ◽  
Apoe Ko

We hypothesized that the reciprocal association between adiponectin and lectin-like oxidized LDL (ox-LDL) receptor (LOX)-1 contributes to the regulation of aortic endothelial dysfunction in atherosclerosis. To test this hypothesis, endothelium-dependent (ACh) and endothelium-independent (sodium nitroprusside) vasorelaxation of isolated aortic rings from control mice, apolipoprotein E (ApoE) knockout (KO) mice, and ApoE KO mice treated with either adiponectin (15 μg·day−1·mouse−1 sc for 8 days) or neutralizing antibody to LOX-1 (anti-LOX-1, 16 μg/ml, 0.1 ml/mouse ip for 7 days) were examined. Although vasorelaxation to sodium nitroprusside was not different between control and ApoE KO mice, relaxation to ACh was impaired in ApoE KO mice. Adiponectin and anti-LOX-1 restored nitric oxide-mediated endothelium-dependent vasorelaxation in ApoE KO mice. Aortic ROS formation and ox-LDL uptake were increased in ApoE KO mice. Both adiponectin and anti-LOX-1 treatment reduced ROS production and aortic ox-LDL uptake. In mouse coronary artery endothelial cells, TNF-α incubation increased endothelial LOX-1 expression. Adiponectin reduced TNF-α-induced LOX-1 expression. Consistently, in ApoE KO mice, adiponectin treatment reversed elevated LOX-1 expression in aortas. Immunofluorescence staining showed that adiponectin was mainly colocalized with endothelial cells. Although adiponectin expression was lower in ApoE KO versus control mice, anti-LOX-1 increased aortic adiponectin expression, suggesting a reciprocal regulation between adiponectin and LOX-1. Moreover, both adiponectin and anti-LOX-1 reduced NF-κB expression in ApoE KO mice. Thus, adiponectin and LOX-1 may converge on NF-κB signaling to regulate their function. In conclusion, our results indicate that the reciprocal regulation between adiponectin and LOX-1 amplifies oxidative stress and ox-LDL uptake, leading to endothelial dysfunction in atherosclerosis.

Tetrahydrobiopterin Slows the Progression of Atherosclerosis

Pteridines ◽  
2007 ◽  
Vol 18 (1) ◽  
pp. 115-121
Author(s):  
Suzuki Kunihiro ◽  
Yoshiyuki Hattori ◽  
Teruo Jojima ◽  
Atsuko Tomizawa ◽  
Toshie Okayasu ◽  
...  
Keyword(s):  
Drinking Water ◽  
Endothelial Dysfunction ◽  
Nadph Oxidase ◽  
Endothelial Function ◽  
Oral Administration ◽  
Mrna Expression ◽  
Inflammatory Factors ◽  
Apoe Ko Mice ◽  
Progression Of Atherosclerosis ◽  
Apoe Ko

Abstract We investigated whether oral tetrahydrobiopterin (BH4) treatment might slow the progression of atherosclerosis using hypercholesterolemic ApoE-knockout (KO) mice. We report that ingesting BH4 in drinking water is effective to inhibit atherogenesis in mice. Furthermore, we report that BH4 treatment improves endothelial dysfunction and attenuates increased mRNA expression of NADPH oxidase components, as well as a number of inflammatory factors, such as LOX-1 and MCP-1, in the aortas of ApoE-KO mice. Strategies such as oral administration of BH4 to ensure continuous BH4 availability may be effective in restoring NO-mediated endothelial function and limiting vascular disease and the progression of atherosclerosis.

scholarly journals Diospyrin Modulates Inflammation in Poly I:C-Induced Macrophages via ER Stress-Induced Calcium-CHOP Pathway

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1050
Author(s):  
Hyun-Ju Kim ◽  
Inamullah Khan ◽  
Adnan Shahidullah ◽  
Syed Muhammad Ashhad Halimi ◽  
Abdur Rauf ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Er Stress ◽  
Intracellular Calcium ◽  
P38 Mapk ◽  
Janus Kinase ◽  
Poly I:C ◽  
No Production ◽  
Raw 264.7 ◽  
Mrna Levels ◽  
Polycytidylic Acid

Diospyrin, plant-derived bisnaphthoquinonoid, is known to have anticancer activity. However, pharmacological activity of diospyrin on viral infection is not well known. We investigated effects of diospyrin on macrophages induced by polyinosinic-polycytidylic acid (poly I:C), a mimic of double-stranded viral RNA. Various cytokines, intracellular calcium, nitric oxide (NO), phosphorylated p38 MAPK, and phosphorylated ERK1/2 as well as mRNA expressions of transcription factors were evaluated. Diospyrin significantly reduced NO production, granulocyte-macrophage colony-stimulating factor production, and intracellular calcium release in poly I:C-induced RAW 264.7. The phosphorylation of p38 MAPK and ERK1/2 was also significantly suppressed. Additionally, diospyrin inhibited mRNA levels of nitric oxide synthase 2, C/EBP homologous protein (CHOP), calcium/calmodulin dependent protein kinase II alpha, signal transducers and activators of transcription 1 (STAT1), STAT3, STAT4, Janus kinase 2, first apoptosis signal receptor, c-Jun, and c-Fos in poly I:C-induced RAW 264.7. Taken together, this study represents that diospyrin might have the inhibitory activity against viral inflammation such as excessive production of inflammatory mediators in poly I:C-induced RAW 264.7 via ER stress-induced calcium-CHOP pathway.

Aerobic exercise training-induced irisin secretion is associated with the reduction of arterial stiffness via nitric oxide production in adults with obesity

2020 ◽  
Vol 45 (7) ◽  
pp. 715-722 ◽  
Author(s):  
Kenichiro Inoue ◽  
Shumpei Fujie ◽  
Natsuki Hasegawa ◽  
Naoki Horii ◽  
Masataka Uchida ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Protein Kinase ◽  
Exercise Training ◽  
Arterial Stiffness ◽  
Aerobic Exercise ◽  
Animal Study ◽  
Human Study ◽  
Aerobic Exercise Training ◽  
No Production ◽  
Circulating Levels

This study aimed to clarify whether muscle-derived irisin secretion induced by aerobic exercise training is involved in reduction of arterial stiffness via arterial nitric oxide (NO) productivity in obesity. In animal study, 16 Otsuka Long-Evans Tokushima Fatty (OLETF) rats with obesity were randomly divided into 2 groups: sedentary control (OLETF-CON) and 8-week aerobic treadmill training (OLETF-EX) groups. In human study, 15 subjects with obesity completed 8-week aerobic exercise training for 45 min at 60%–70% peak oxygen uptake intensity for 3 days/week. As a result of animal study, carotid-femoral pulse wave velocity (cfPWV) was decreased, and arterial phosphorylation levels of AMP-activated protein kinase (AMPK), protein kinase B (Akt), and endothelial NO synthase (eNOS), circulating levels of nitrite/nitrate (NOx) and irisin, and muscle messenger RNA expression of fibronectin type III domain containing 5 (Fndc5) were increased in the OLETF-EX group compared with OLETF-CON group. In a human study, regular aerobic exercise reduced cfPWV and elevated circulating levels of NOx and irisin. Furthermore, change in circulating irisin levels by regular exercise was positively correlated with circulating NOx levels and was negatively correlated with cfPWV. Thus, aerobic exercise training-induced increase in irisin secretion may be related to reduction of arterial stiffness achieved by NO production via activated arterial AMPK–Akt–eNOS signaling pathway in obesity. Novelty Aerobic exercise training promoted irisin secretion with upregulation of muscle Fndc5 gene expression in rats with obesity. Irisin affected the activation of arterial AMPK–Akt–eNOS signaling by aerobic exercise training. Increased serum irisin level by aerobic exercise training was associated with reduction of arterial stiffness in obese adults.

scholarly journals Salidroside Stimulates Mitochondrial Biogenesis and Protects against H2O2-Induced Endothelial Dysfunction

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Shasha Xing ◽  
Xiaoyan Yang ◽  
Wenjing Li ◽  
Fang Bian ◽  
Dan Wu ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cells ◽  
Transcription Factor ◽  
Endothelial Dysfunction ◽  
Mitochondrial Biogenesis ◽  
Umbilical Vein ◽  
Adenosine Monophosphate ◽  
No Production ◽  
Peroxisome Proliferator ◽  
Atp Production

Salidroside (SAL) is an active component ofRhodiola roseawith documented antioxidative properties. The purpose of this study is to explore the mechanism of the protective effect of SAL on hydrogen peroxide- (H2O2-) induced endothelial dysfunction. Pretreatment of the human umbilical vein endothelial cells (HUVECs) with SAL significantly reduced the cytotoxicity brought by H2O2. Functional studies on the rat aortas found that SAL rescued the endothelium-dependent relaxation and reduced superoxide anion (O2∙-) production induced by H2O2. Meanwhile, SAL pretreatment inhibited H2O2-induced nitric oxide (NO) production. The underlying mechanisms involve the inhibition of H2O2-induced activation of endothelial nitric oxide synthase (eNOS), adenosine monophosphate-activated protein kinase (AMPK), and Akt, as well as the redox sensitive transcription factor, NF-kappa B (NF-κB). SAL also increased mitochondrial mass and upregulated the mitochondrial biogenesis factors, peroxisome proliferator-activated receptor gamma-coactivator-1alpha (PGC-1α), and mitochondrial transcription factor A (TFAM) in the endothelial cells. H2O2-induced mitochondrial dysfunction, as demonstrated by reduced mitochondrial membrane potential (Δψm) and ATP production, was rescued by SAL pretreatment. Taken together, these findings implicate that SAL could protect endothelium against H2O2-induced injury via promoting mitochondrial biogenesis and function, thus preventing the overactivation of oxidative stress-related downstream signaling pathways.

Nitric oxide and asymmetric dimethylarginine (ADMA) in malignancy associated thrombosis and their modulation by anticoagulants

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 10573-10573
Author(s):  
J. Fareed ◽  
D. A. Hoppensteadt ◽  
M. Demir ◽  
O. Iqbal ◽  
W. Jeske ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Cancer Patients ◽  
Asymmetric Dimethylarginine ◽  
Oral Anticoagulants ◽  
Treated Group ◽  
Competitive Inhibitor ◽  
No Production ◽  
Open Label ◽  
Stage Renal Disease

10573 Background: Cancer associated thrombotic complications are primarily due to endothelial dysfunction and upregulation of inflammatory processes. Nitric oxide (NO) represents one of the major endothelial derived vasoactive mediators. Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of NO synthase which inhibits NO production at pathophysiologic levels. Plasma ADMA levels are upregulated in atherosclerosis, hypertension, end stage renal disease, chronic heart failure and microangiopathy. Methods: To test the hypothesis that endothelial dysfunction in cancer patients may result in increased ADMA levels, plasma samples were retrospectively analyzed from an open label, multidose, active comparator designed study in which all patients (n = 110) were initially treated with low molecular weight heparin, enoxaparin (E) at 1–1.5 mg/kg sc for 5 days and further subdivided into group E which continued to receive E and warfarin (W) group which was given oral anticoagulants for a period of up to 12 weeks. Baseline blood samples (BL), 5 days post E (IPE) and 4–6 week samples from the E and W were analyzed for ADMA and NO levels by ELISA methods. Results: Both the ADMA and NO levels were markedly elevated in cancer patients. The E treated group showed a marked decrease in the ADMA levels which persisted throughout the treatment period. However, in the W converted group the ADMA levels rebounded to an increased level indicating that E differentially regulated ADMA in these patients. The down regulation pattern of NO was similar for both E and W. Conclusions: These results suggest that patients with cancer and thrombosis exhibit simultaneous upregulation of ADMA and NO. While E and W show a differential regulation of ADMA both result in downregulation of NO. The fact that E regulates ADMA is highly suggestive of its role in iNOS regulation which may be involved in the inflammatory response in cancer patients. [Table: see text] No significant financial relationships to disclose.

Nitric oxide and asymmetric dimethylarginine and CD 40 ligand levels in malignancy associated thrombosis and their modulation by anticoagulants

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 17049-17049
Author(s):  
D. Hoppensteadt ◽  
D. Fareed ◽  
O. Iqbal ◽  
A. Lale ◽  
J. Fareed
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Cancer Patients ◽  
Asymmetric Dimethylarginine ◽  
Oral Anticoagulants ◽  
Treated Group ◽  
Competitive Inhibitor ◽  
No Production ◽  
Open Label ◽  
Vasoactive Mediators

17049 Background: Cancer associated thrombotic complications are primarily due to endothelial dysfunction and upregulation of inflammatory processes. Nitric oxide (NO) represents one of the major endothelial derived vasoactive mediators. Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of NO synthase which inhibits NO production at pathophysiologic levels. CD 40 ligand (CD 40L) is also upregulated in cancer. Methods: To test the hypothesis that endothelial dysfunction in cancer patients may result in increased ADMA levels, plasma samples were retrospectively analyzed from an open label, multidose, active comparator designed study in which all patients (n=110) were initially treated with low molecular weight heparin, enoxaparin (E) at 1–1.5 mg/kg sc for 5 days and further subdivided into group E which continued to receive E and warfarin (W) group which was given oral anticoagulants for a period of up to 12 weeks. Baseline blood samples (BL), 5 days post E (IPE) and 4–6 week samples from the E and W were analyzed for ADMA and CD 40L levels by ELISA methods. NO levels were measured using a chromogenic method. Results: The baseline levels of NO, ADMA and CD 40L levels were markedly elevated in cancer patients. The E treated group showed a marked decrease in the ADMA and CD 40L levels which persisted throughout the treatment period. However, in the W converted group the ADMA and CD 40L levels rebounded to an increased level indicating that E differentially regulated ADMA in these patients. The down regulation pattern of NO was similar for both E and W. Conclusions: These results suggest that patients with cancer and thrombosis exhibit simultaneous upregulation of ADMA, CD 40L and NO. While E and W show a differential regulation of ADMA and CD 40L, both result in a downregulation of NO. The fact that E regulates ADMA is highly suggestive of its role in iNOS regulation which may be involved in the inflammatory response in cancer patients. [Table: see text] No significant financial relationships to disclose.

Abstract 141: Histone Deacetylase 1 Regulates Nitric Oxide Production and Nitric Oxide Synthase-3 Acetylation in Endothelial Cells

Hypertension ◽  
2012 ◽  
Vol 60 (suppl_1) ◽  
Author(s):  
Kelly A Hyndman ◽  
Dao H Ho ◽  
Jennifer S Pollock
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cells ◽  
Endothelial Dysfunction ◽  
Histone Deacetylase ◽  
Life Stress ◽  
Trichostatin A ◽  
Early Life Stress ◽  
No Production ◽  
Histone Deacetylase 1 ◽  
Nitrite Production

Previous reports showed that NOS3 is regulated by acetylation through transcriptional mechanisms via histone acetylation or through direct lysine acetylation. Histone deacetylase (HDAC) enzymes and histone acetyltransferases (HATs) modulate acetylation processes. Recent work by our lab, demonstrated increased expression of aortic HDAC1 and HDAC6 while HATs were unchanged in a mouse model of early life stress with endothelial dysfunction. These data suggest a negative correlation between endothelial dysfunction and HDAC expression. The purpose of this study was to test the hypothesis that HDAC1 and 6 regulate endothelial NO production and/or NOS3 acetylation. Initial immunoprecipitation studies with anti-acetyl lysine and anti-NOS3 antibodies demonstrated that NOS3 is basally acetylated in primary bovine aortic endothelial cells (BAECs). Treatment with the HDAC inhibitor, trichostatin A (500 nM) for 1 hr, significantly increased NOS3 acetylation. BAECs were transfected with HDAC1, HDAC6, vector expression plasmids, or untransfected, with nitrite production determined by HPLC and NOS3 acetylation and expression probed by immunoprecipitation and Western blotting. Untransfected and vector transfected control BAECs had similar NO production (357 ± 10 and 344 ± 30 pmol/mg pr/h, respectively, N=6) as well as NOS3 acetylation (7.8 ± 1.6 and 6.8 ±0.3 AU, N=3). HDAC6 transfected BAECs had similar NO production to the control BAECs (272 ± 93 pmol/mg pr/h, N=3) with an increase in NOS3 acetylation (17.4 ± 1.7 AU, N=3). In contrast, HDAC1 overexpression significantly decreased NO production (89 ± 50 pmol/mg pr/h, P< 0.05, N=3) and reduced NOS3 acetylation (3.8 ± 0.5 A.U, N=3), P <0.05). Control transfections, HDAC6, and HDAC1 transfected BAECS all had similar NOS3 expression (10.14 ± 1.8; 9.8 ±1.6; 8.9 ± 1.5; 10.6 ± 1.0 AU, respectively, N=3). Thus, we conclude that HDAC1 regulates NO production via direct lysine deacetylation of NOS3.

Hemolysis in Sickle Cell Mice Causes Pulmonary Hypertension Due to Global Impairment in Nitric Oxide Bioavailability.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 785-785
Author(s):  
Lewis L. Hsu ◽  
Hunter C. Champion ◽  
Sally A. Campbell-Lee ◽  
Trinity J. Bivalacqua ◽  
Elizabeth A. Manci ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Animal Model ◽  
Pulmonary Hypertension ◽  
Endothelial Dysfunction ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
No Production ◽  
Cell Disease ◽  
Sickle Hemoglobin ◽  
Pulmonary Vasodilators

Abstract Pulmonary hypertension is a highly prevalent complication of sickle cell disease and is a strong risk factor for early mortality. However, the pathophysiological mechanisms by which sickle hemoglobin leads to pulmonary vasculopathy remain unclear. Transgenic mice provide opportunities for mechanistic studies of vascular pathophysiology in an animal model of severe sickle cell disease. Using micro-cardiac catheterization we found that all mice expressing exclusively human sickle hemoglobin develop pulmonary hypertension. Recognizing that the NO pathways can have complex abnormalities in other conditions of pulmonary hypertension, the NO axis in sickle mice was assessed by multiple methods. From a mechanistic standpoint the mice exhibit profound pulmonary and systemic endothelial dysfunction and vascular instability characterized by diminished responses to authentic nitric oxide (NO), NO donors and endothelium-dependent pulmonary vasodilators, and enhanced responses to vaso-constrictors. However, endothelium-independent vasodilation in the sickle mice was normal. Mechanisms of vasculopathy in sickle mice involve global dysregulation of the NO-axis: impaired constitutive nitric oxide synthase activity with loss of eNOS coupling (dimerization), increased NO scavenging by plasma hemoglobin and superoxide, increased arginase activity, and depleted intravascular nitrite reserves. Consistent with a functional rather than structural defect, light microscopy and computed tomography of the lungs revealed no plexogenic arterial remodeling, thrombi/emboli, or inflammation. Transplanting sickle marrow into wild-type mice conferred the same phenotype. Similar pathobiology was observed in a non-sickle mouse model of acute alloimmune hemolysis, supporting a major role of hemolysis as a mechanism for this dysregulation of NO and vasculopathy. In this study, alloimmune hemolytic mice were chosen for comparison in order to generalize beyond hemoglobinopathies. Future analogous studies with thalassemic mice may be useful to model pulmonary hypertension in human thalassemia intermedia. In conclusion, this animal model extends the evidence for global impairment in NO responsiveness and NO production in sickle cell disease, and suggests that hemolytic anemia is associated with endothelial dysfunction and pulmonary hypertension.

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