Abstract P726: Cytochrome B5 Reductase 3 Modifies The Brain-Blood Axis Response To Ischemic Stroke In Mice With Sickle Cell Disease

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Katherine C Wood ◽  
Heidi M Schmidt ◽  
Scott Hahn ◽  
Mehdi Nouraie ◽  
Mara Carreno ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Ischemic Stroke ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
African Ancestry ◽  
Cytochrome B5 ◽  
Heme Iron ◽  
Wild Type ◽  
Cell Disease ◽  
Cytochrome B5 Reductase

Introduction: Stroke and silent infarcts are serious complications of sickle cell disease (SCD), occurring frequently in children. Decreased nitric oxide bioavailability and responsiveness contribute to neurovascular disease. Cytochrome b5 reductase 3 (Cyb5R3) is a heme iron reductase that reduces oxidized soluble guanylate cyclase heme iron (Fe 3+ --> Fe 2+ ) to preserve nitric oxide signaling. A loss-of-function Cyb5R3 missense variant (T117S) occurs with high frequency (0.23 minor allele) in persons of African ancestry. Hypothesis: We hypothesized that impaired reductase function of T117S Cyb5R3 exacerbates brain damage after ischemic stroke in SCD. Methods: Bone marrow transplant was used to create male SCD mice with wild type (SS/WT) or T117S (SS/T117S) Cyb5R3. Blood was sampled before and after middle cerebral artery occlusion (55 minutes occlusion, 48 hours reperfusion). Infarct volume (IV) was determined by 2,3,5-triphenyltetrazolium chloride. Intravascular hemolysis and correlation (Pearson’s R) of hematology changes with IV were determined. Baseline Walk-PHaSST (NCT00492531) data were analyzed for stroke occurrence. Results: Brain IV (63 vs 27 cm 3 , P=0.003) and mortality (3/6 vs 0/8) were greater in SS/T117S vs SS/WT. Red blood cells, hemoglobin and hematocrit declined as IV increased. Plasma oxyhemoglobin increased in parallel with IV (r = 0.74, P=0.09). There were different signatures to hematologic changes that occurred with IV in SCD. Relative to wild type, T117S contracted the erythroid compartment (red blood cell: -13% vs 13%, P=0.003; hematocrit: -20% vs 1%, P=0.008; hemoglobin: -18% vs 2%, P=0.007). Mean platelet volume correlated with IV in SS/T117S (r = 0.87, P=0.06), while the inverse occurred in SS/WT (r = -0.63, P=0.09) Monocytes increased in parallel with IV in SS/T117S (r = 0.73, P=0.16), but followed the opposite trajectory in SS/WT (r = -0.77, P=0.04). WalkPHaSST participants with T117S Cyb5R3 self-reported more ischemic stroke (7.4% vs 5.1%) relative to wild type. Conclusion: Cyb5R3 is an important modifier of the evolution and outcome of ischemic brain injury in SCD and its hematologic consequences. Our findings indicate a bidirectional relationship between stroke and anemia in SCD that may axially turn on Cyb5R3 activity.

scholarly journals The T117S Variant of Cytochrome b5 Reductase 3 Increases the Risk for Ischemic Stroke with Enhanced Anemia in Mice with Sickle Cell Disease

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 17-18
Author(s):  
Katherine C Wood ◽  
Heidi M Schmidt ◽  
Scott Hahn ◽  
Subramaniam Sanker ◽  
Samit Ghosh ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Infarct Volume ◽  
Cytochrome B5 ◽  
Heme Iron ◽  
Cerebral Infarct ◽  
Cell Disease ◽  
Brain Infarct ◽  
Cytochrome B5 Reductase

Introduction. Stroke and silent infarcts are serious complications of sickle cell disease (SCD), occurring frequently in children between 3 and 14 years old. A vast amount of clinical and experimental evidence has concluded that decreased nitric oxide (NO) bioavailability and/or NO responsiveness, as is seen in SCD, is a major contributing factor in the pathogenesis of neurovascular disease. NO responsiveness, which occurs via NO-induced activation of soluble guanylate cyclase (sGC), requires reduced heme iron (Fe2+) in the sGC active site. We recently identified cytochrome b5 reductase 3 (Cyb5R3) as an sGC heme iron reductase in vascular smooth muscle (VSM), where it reverses the oxidized heme iron of sGC (Fe3+ --> Fe2+) to preserve NO sensing/signaling under conditions of oxidative stress. In a mouse model of SCD we have shown that knockdown of Cyb5R3 in VSM accelerates the development of pulmonary hypertension and cardiac remodeling. A missense variant of Cyb5R3 (T117S) that results in loss-of-function methemoglobin reductase activity occurs at a high frequency in persons of African ancestry (0.23 minor allele frequency). Unpublished baseline data from the Walk-PHaSSt trial (NCT00492531) reveals that persons with SCD who carry the T117S variant are at increased risk of ischemic stroke; these individuals self-reported almost 50% more (74 vs 51 cases per 1000 individuals) ischemic stroke than those with wild-type (WT) Cyb5R3. Hypothesis. We hypothesized that impaired reductase function of Cyb5R3 T117S leads to sustained sGC heme oxidation, which drives cerebral vascular dysfunction and exacerbates brain damage after ischemic stroke in SCD. Methods. Bone marrow transplant was used to create SCD mice with global expression of WT or T117S Cyb5R3, hereafter referred to as SS/WT or SS/T117S, respectively. All mice were male, C57Bl/6 background, and >85% engrafted with SS Hb for 12 weeks. Ischemic stroke was induced using transient middle cerebral artery occlusion (MCAO: 55 min occlusion, 48 hr reperfusion), after which brains were stained with 2,3,5-triphenyltetrazolium chloride (TTC,1%) to determine infarct volume. Blood was sampled before and after MCAO to assess effects of brain infarct on hematological parameters. Student's t-test was used for analysis of 2 groups and Pearson's R used for correlation analyses of brain infarct volume with hematology changes [(post-pre/pre) * 100]. Results. Global expression of T117S Cyb5R3 in SCD caused increased cerebral infarct volume (62.9 vs 26.7 cm3, P=0.003) and mortality (3/6 vs 0/6) relative to WT Cyb5R3. WT and T117S Cyb5R3 mice with SCD were similar in that both showed declining red blood cells (RBC), hemoglobin (Hgb) and hematocrit (Hct) as infarct volumes increased. In the SS/T117S group, the anemia was more severe in keeping with larger infarct volumes. There were different signatures to the hematologic changes that occurred with cerebral infarct in SCD. When compared to WT Cyb5R3, T117S caused the erythroid compartment to contract (RBC: -12.97% vs 13.41%, P=0.01; Hct: -19.75% vs 0.31%, P=0.025; Hgb: -17.93% vs 2.78%, P=0.017). In SS/WT mice platelet numbers increased more relative to SS/T117S (17.5 vs 9.7 * 103 cells/uL); and MPV, a measure of platelet activation, inversely correlated with brain infarct volume (r = -0.94, P=0.006), the opposite of what was seen in SS/T117S (r = 0.87, P=0.056). Monocytes seem to play an important role in the volume of brain infarct in SS/T117S as their numbers increased in parallel with infarct volume (r = 0.73, P=0.16), but followed the opposite trajectory in SS/WT mice (r = -0.75, P=0.14). Conclusion. These results indicate that Cyb5R3 is an important modifying factor in the evolution and outcome of ischemic brain injury in SCD. Our findings also raise questions on just how cerebral infarct modifies the anemia of SCD, as well as the role played by Cyb5R3 in the dynamics of that relationship. To what extent is the sGC-cGMP-PKG pathway involved at the cerebrovascular and erythropoietic levels? Does Cyb5R3 contribute resilience to ischemic stroke in SCD? The development and application of targeted therapies for effectively preventing and treating cerebrovascular disease in SCD rely on finding the answers to these questions. Disclosures No relevant conflicts of interest to declare.

scholarly journals Early and prominent alterations in hemodynamics, signaling, and gene expression following renal ischemia in sickle cell disease

2010 ◽  
Vol 298 (4) ◽  
pp. F892-F899 ◽  
Author(s):  
Julio P. Juncos ◽  
Joseph P. Grande ◽  
Anthony J. Croatt ◽  
Robert P. Hebbel ◽  
Gregory M. Vercellotti ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Renal Hemodynamics ◽  
Acute Ischemia ◽  
Heme Oxygenase 1 ◽  
Wild Type ◽  
Cell Disease ◽  
Oxide Synthase

Acute ischemic insults to the kidney are recognized complications of human sickle cell disease (SCD). The present study analyzed in a transgenic SCD murine model the early renal response to acute ischemia. Renal hemodynamics were profoundly impaired following ischemia in sickle mice compared with wild-type mice: glomerular filtration rate, along with renal plasma flow and blood flow rates, were markedly reduced, while renal vascular resistances were increased more than threefold in sickle mice following ischemia. In addition to these changes in renal hemodynamics, there were profound disturbances in renal signaling processes: phosphorylation of members of the MAPK and Akt signaling proteins occurred in the kidney in wild-type mice after ischemia, whereas such phosphorylation did not occur in the kidney in sickle mice after ischemia. ATP content in the postischemic kidney in sickle mice was less than half that observed in wild-type mice. Examination of the expression of candidate genes uncovered changes that may predispose to increased sensitivity of the kidney in sickle mice to ischemia: increased expression of inducible nitric oxide synthase and decreased expression of endothelial nitric oxide synthase, and increased expression of TNF-α. Inducibility of anti-inflammatory, cytoprotective genes, such as heme oxygenase-1 and IL-10, was not impaired in sickle mice after ischemia. We conclude that the kidney in SCD is remarkably vulnerable to acute ischemic insults. We speculate that such sensitivity of the kidney to ischemia in SCD may underlie the occurrence of acute kidney injury in patients with SCD and may set the stage for the emergence of chronic kidney disease in SCD.

Apoliprotein A-I Mimetic Peptide and Sickle Vasculopathy: Mouse Model Study of Acute Administration.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1521-1521
Author(s):  
Lewis L. Hsu ◽  
Valeriani Bead ◽  
Lita A. Freeman ◽  
Gregory J. Kato ◽  
James G Taylor ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Bone Marrow ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Acute Administration ◽  
Wild Type ◽  
Cell Disease ◽  
Mimetic Peptide ◽  
Mimetic Peptides

Abstract Abstract 1521 Poster Board I-544 Epidemiologic observations associate low levels of Apolipoprotein A-1 (ApoA-I) and low high density lipoprotein (HDL) with greater prevalence of pulmonary hypertension in sickle cell patients. Sickle cell mice with knockout of apoliproteins have greater pulmonary hypertension and endothelial dysfunction than sickle cell mice with wild-type levels of ApoA-I, and they have further worsening of the global dysregulation of the nitric oxide axis (NO) seen in sickle vasculopathy. Ou et al. (Circulation 2003; 107(18):2337-41) showed that chronic administration (3-4 weeks) of the ApoA-I mimetic L-4F improves vasodilation in hypercholesterolemic and sickle mice. Remaley et al. (Circulation 2006;114:II_23) showed atheroprotective effects after a single (1mg/mouse) intravenous administration of the ApoA-I mimetic peptide 5A as a result of increased reverse cholesterol transfer. These preclinical data provide a mechanistic basis for the effects of ApoA-I in sickle cell disease and suggest that ApoA-I mimetics deserve further study as a potential therapy for sickle cell disease. However, it is unknown whether acute administration of an ApoA-I mimetic has any efficacy for sickle cell disease, and whether all ApoA-I mimetic peptides will be helpful. We hypothesized that acute administration of ApoA-I mimetic could improve endothelial dysfunction in sickle cell mouse models. Bone marrow harvested from Berkeley sickle cell mouse donors and hemizygote non-sickling control mice were used to generate three groups of mice after myeloablative irradiation of wild-type C57BL6 recipient mice. Three million cells whole marrow was injected per mouse. Mice were fully engrafted by 3 months. Hemoglobin analysis showed one group produced only sickle RBC, another group only hemizygote RBC, and a third group were mixed chimeras with 30% sickle RBC and 70% hemizygote RBC (intended to model a sickle cell patient on chronic transfusion). Pulse-wave velocities, a measure of arterial stiffness, showed no improvement after IV injection of the ApoA-I mimetic peptide, 5A-POPC (170 mcl of 8.6 mg/ml). Aortic rings prepared from mice of all three groups showed blunted relaxation response to acetylcholine and sodium nitroprusside, as expected for abnormal nitric oxide bioavailability - these vasorelaxation responses were not significantly different in the absence vs. presence of 5A-POPC incubation in vitro. These results agree with our previous observation that sickle bone marrow transplanted into transgenic mice overexpressing ApoA-I had no difference in vasculopathy from sickle bone marrow transplanted into wild-type mice We conclude that acute exposure to this ApoA-I mimetic, either in vivo or in vitro, is not sufficient to relieve the vasculopathy of sickle cell mouse models. Higher doses or long term therapy may be necessary for benefit. An alternative explanation is that ApoA-I mimetic peptides differ in their benefit for sickle cell vasculopathy, and that the key property is the high level of oxidant scavenging by L-4F rather than cholesterol removal by 5A-POPC. Future studies can determine whether the cardiovascular benefits of ApoA-I mimetics correlate with their antioxidant function. Disclosures No relevant conflicts of interest to declare.

Cytochrome b5 Reductase T116S Mutation and Hemolysis in Sickle Cell Disease.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 903-903 ◽  
Author(s):  
Mehdi Nouraie ◽  
Noel S. Reading ◽  
Andrew Campbell ◽  
Caterina Minniti ◽  
Sohail R Rana ◽  
...  
Keyword(s):  
African Americans ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Tricuspid Regurgitation ◽  
Cytochrome B5 ◽  
Type I ◽  
Systolic Pulmonary Artery Pressure ◽  
Cell Disease ◽  
Cytochrome B5 Reductase ◽  
Membrane Bound

Abstract Abstract 903 Abstract Background: Deficiency of NADH-cytochrome b5 reductase (cytb5r, EC 1.6.2.2) is responsible for congenital methemoglobinemia. This enzyme exists in soluble and membrane-bound forms. The soluble erythrocytic cytb5r isoenzyme is involved in cytochrome b5 reduction and in erythrocyte methemoglobin reduction; the membrane-bound microsomal enzyme participates in a fatty acid desaturation complex and in drug metabolism. The cytb5r isoforms are the product of a single gene locus, DIA1 (or CYB5R3), on chromosome 22. More then 40 mutations which cause methemoglobinemia have been reported to date; the majority are missense mutations and are associated with mild type I methemoglobinemia. The CYBR5 T116S mutation is the most common genetic polymorphism among African Americans known (gene frequency as high as 20%) and it has not yet been detected in other ethnic and racial groups. This polymorphism is not associated with methemoglobinemia and its functional significance is not yet known. We studied the relationship of CYBR5 T116S with the degree of hemolysis and the tricuspid regurgitation velocity (which correlates with systolic pulmonary artery pressure) in patients with sickle cell disease. Methods: Two hundred sixty one children and adolescents with hemoglobin SS were recruited at three tertiary medical centers and studied at steady state. Patients with other sickle genotypes were excluded from this analysis of CYBR5 T116S. Principal component analysis was used to develop a hemolytic component from reticulocyte count and concentrations of lactate dehydrogenase, aspartate aminotransferase and bilirubin. PCR was used to determine the presence of the CYBR5 T116S mutation. Multivariate models were employed to determine the independent effects of this genotype on degree of hemolysis and tricuspid regurgitation velocity. Results: Ninety-eight of the patients (38%) were CYBR5 T116S heterozygotes and 26 (10%) were homozygotes, consistent with Hardy-Weinberg equilibrium. Both heterozygosity (beta = -0.4) and homozygosity (beta = -0.5) were associated with reduction in the hemolytic component (N = 261; P for trend = 0.002) (Figure 1). This relationship persisted after adjusting for α-thalassemia, hemoglobin F percent and hydroxyurea treatment in a subset of 113 patients with all of this information available (P for trend = 0.037) and it also persisted in a subset of 87 patients with no α-globin gene deletion who were not being treated with hydroxyurea (P for trend = 0.029). In none of these analyses did G6PD-202/-376 have an effect on hemolysis. Both heterozygosity (beta = -0.04) and homozygosity (beta = -0.14) for the CYBR5 T116S mutation were also associated with lower tricuspid regurgitation velocity (P for trend = 0.024). Conclusions: CYBR5 T116S is a common polymorphism among patients with sickle cell disease that appears to be associated with less hemolysis and lower tricuspid regurgitation velocity. We speculate that this polymorphism may be related to a previously reported subpopulation of African Americans with increased cytochrome b5 reductase activity, and that increased anti-oxidant activity may explain the polymorphism's hemolysis-reducing effect. Functional studies to investigate this possibility are planned. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Increased adhesive properties of neutrophils in sickle cell disease may be reversed by pharmacological nitric oxide donation

Haematologica ◽  
2008 ◽  
Vol 93 (4) ◽  
pp. 605-609 ◽  
Author(s):  
A. A. Canalli ◽  
C. F. Franco-Penteado ◽  
S. T.O. Saad ◽  
N. Conran ◽  
F. F. Costa
Keyword(s):  
Nitric Oxide ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Cell Disease ◽  
Adhesive Properties

scholarly journals Ischemic Stroke in Children and Young Adults with Sickle Cell Disease (SCD) in the Post-STOP Era

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 68-68 ◽  
Author(s):  
Janet L. Kwiatkowski ◽  
Julie Kanter ◽  
Heather J. Fullerton ◽  
Jenifer Voeks ◽  
Ellen Debenham ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
High Risk ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Stroke Prevention ◽  
Cell Disease ◽  
Clinical Series ◽  
The Mean

Abstract Background: The Stroke Prevention Trial in Sickle Cell Anemia (STOP) and Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP 2) established routine transcranial Doppler ultrasound (TCD) screening with indefinite chronic red cell transfusions (CRCT) for children with abnormal TCD as standard of care. To identify children at high-risk of stroke, annual TCD screening is recommended from ages 2 to 16 years, with more frequent monitoring if the result is not normal. A reduction in stroke incidence in children with SCD has been reported in several clinical series and analyses utilizing large hospital databases when comparing rates before and after the publication of the STOP study in 1998. We sought to determine the rate of first ischemic stroke in a multicenter cohort of children who had previously participated in the STOP and/or STOP 2 trials and to determine whether these strokes were screening or treatment failures. Subjects and Methods: Between 1995 and 2005, STOP and STOP 2 (STOP/2) were conducted at 26 sites in the US and Canada. These studies included 3,835 children, ages 2 to 16 y with SCD type SS or S-beta-0-thalassemia. Participation in STOP/2 ranged from a single screening TCD to randomization. STOP 2 also had an observational arm for children on CRCT for abnormal TCD whose TCD had not reverted to normal. The Post-STOP study was designed to follow-up the outcomes of children who participated in one or both trials. 19 of the 26 original study sites participated in Post-STOP, contributing a total of 3,539 (92%) of the STOP/2 subjects. After exit from STOP/2, these children received TCD screening and treatment according to local practices. Data abstractors visited each clinical site and obtained retrospective data from STOP/2 study exit to 2012-2014 (depending on site) including follow-up TCD and brain imaging results, clinical information, and laboratory results. Two vascular neurologists, blinded to STOP/2 status and prior TCD and neuroimaging results, reviewed source records to confirm all ischemic strokes, defined as a symptomatic cerebral infarction; discordant opinions were resolved through discussion. For the first Post-STOP ischemic stroke, prior TCD result and treatment history subsequently were analyzed. Results: Of the 3,539 subjects, follow-up data were available for 2,850 (81%). Twelve children who had a stroke during STOP or STOP2 were excluded from these analyses resulting in data on 2,838 subjects. The mean age at the start of Post-STOP was 10.5 y and mean duration of follow-up after exiting STOP/2 was 9.1 y. A total of 69 first ischemic strokes occurred in the Post-STOP observation period (incidence 0.27 per 100 pt years). The mean age at time of stroke was 14.4±6.2 (median 13.8, range 3.5-28.9) y. Twenty-five of the 69 patients (36%) had documented abnormal TCD (STOP/2 or Post-STOP) prior to the stroke; 15 (60%) were receiving CRCT and 9 (36%) were not (treatment data not available for 1 subject). Among the 44 subjects without documented abnormal TCD, 29 (66%) had not had TCD re-screen in the Post-STOP period prior to the event; 7 of these 29 (24%) were 16 y or older at the start of Post-STOP, which is beyond the recommended screening age. Four of the 44 (9%) patients had inadequate TCD in Post-STOP (1 to 10.7 y prior to event). Six (14%) had normal TCD more than a year before the event (1.2 - 4 y); all but one of these children were younger than 16 y at the time of that TCD. Only 5 (11%) had a documented normal TCD less than 1 year prior to the event. Conclusions: In the Post-STOP era, the rate of first ischemic stroke was substantially lower than that reported in the Cooperative Study of Sickle Cell Disease, prior to implementation of TCD screening. Many (39%) of the Post-STOP ischemic strokes were associated with a failure to re-screen according to current guidelines, while only 11% occurred in children who had had recent low-risk TCD. Among those known to be at high risk prior to stroke, treatment refusal or inadequate treatment may have contributed. While TCD screening and treatment are effective at reducing ischemic stroke in clinical practice, significant gaps in screening and treatment, even at sites experienced in the STOP protocol, remain to be addressed. Closing these gaps should provide yet further reduction of ischemic stroke in SCD. Disclosures No relevant conflicts of interest to declare.

The metabolites of nitric oxide in sickle-cell disease

1995 ◽  
Vol 91 (4) ◽  
pp. 834-837 ◽  
Author(s):  
David C. Rees ◽  
Paul Cervi ◽  
David Grimwade ◽  
Aisling O'Driscoll ◽  
Malcolm Hamilton ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Cell Disease

Abstract 15696: Cytochrome B5 Reductase 3 Sensitizes Soluble Guanylate Cyclase to Nitric Oxide

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Anh T Nguyen ◽  
Mizanur M Rahaman ◽  
Stephanie M Mutchler ◽  
Megan Miller ◽  
Josef T Prchal ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Soluble Guanylate Cyclase ◽  
Cytochrome B5 ◽  
Heme Iron ◽  
Proximity Ligation Assay ◽  
Cytochrome B5 Reductase ◽  
Cgmp Production ◽  
Iron Reductase

Impaired soluble guanylyl cyclase (sGC)-dependent nitric oxide (NO) signaling has been linked to numerous cardiovascular diseases (CVD) such as hypertension, myocardial infarction and atherosclerosis. Despite emerging evidence indicating the importance of sGC function within the cardiovascular system, the basic mechanisms that regulate sGC activity remain incompletely understood. Herein, we provide in vitro and in vivo evidence that cytochrome b5 reductase 3 (Cyb5R3) is an sGC heme iron reductase and regulates downstream cGMP signaling. Of major significance, we also demonstrate that a Cyb5R3 T116S polymorphism with allele frequency of 0.23 in African Americans associates with increase blood pressure and is incapable of reducing sGC. Proximity ligation assay (PLA) experiments show that endogenous Cyb5R3 and oxidized sGC associate. Knockdown of Cyb5R3 results in reduced cGMP production and downstream signaling in rat aortic smooth muscle cells (SMC). Overexpression of Cyb5R3 not only rescues cGMP production but also increases baseline cGMP, whereas T116S mutant does not. Finally, inhibition of Cyb5R3 in mice significantly increases systemic blood pressure. Our studies are the first to identify an sGC heme iron reductase, provide evidence for Cyb5R3 as a key biological regulator of sGC activity and vascular tone in SMC, and link a human polymorphism of Cyb5R3 to increased blood pressure; all of which may lead to the development of novel therapeutics targeting Cyb5R3 for the treatment of CVD. Importantly, the co-expression of Cyb5R3 and sGC in multiple cells types suggests that this regulation of sGC activity may have broad applications for multiple physiological and pathophysiological processes. Results: Conclusions:

Sign in / Sign up

Export Citation Format

Share Document