Heterologous Overexpression and Purification of Cytochromec‘ fromRhodobacter capsulatusand a Mutant (K42E) in the Dimerization Region. Mutation Does Not Alter Oligomerization but Impacts the Heme Iron Spin State and Nitric Oxide Binding Properties†

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:

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

Stroke ◽

10.1161/str.52.suppl_1.p726 ◽

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.

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Abstract 107: Cytochrome B5 Reductase 3 Sensitizes Soluble Guanylate Cyclase to Nitric Oxide in Vascular Smooth Muscle

Hypertension ◽

10.1161/hyp.66.suppl_1.107 ◽

2015 ◽

Vol 66 (suppl_1) ◽

Author(s):

Adam C Straub ◽

Anh T Nguyen ◽

Mizanur Rahaman ◽

Stephanie M Mutchler ◽

Megan Miller ◽

...

Keyword(s):

Nitric Oxide ◽

Blood Pressure ◽

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Guanylate Cyclase ◽

Soluble Guanylate Cyclase ◽

Cytochrome B5 ◽

Heme Iron ◽

Cytochrome B5 Reductase ◽

Arterial Blood

The inability nitric oxide (NO) to stimulate soluble guanylate cyclase (sGC) has been linked to numerous cardiovascular diseases (CVD) including hypertension. While several studies have defined the importance of sGC expression in the cardiovascular system, the basic mechanisms that regulate sGC activity remain incompletely understood. Here, we report for the first time that sGC heme iron redox state, which is essential for NO-induced sGC activation, is regulated by cytochrome B5 reductase 3 (CyB5R3). Genetic knockdown and pharmacological inhibition of CyB5R3 in primary rat vascular smooth muscle cells resulted in a 60% loss in cGMP production. Conversely, the sGC activator Bay 58-2667, which activates oxidized or heme free sGC, reversed these effects. Consistent with our cell culture work, purified protein studies demonstrate that CyB5R3 can directly reduce oxidized sGC heme iron and sensitize sGC to NO. To test the functional importance of Cyb5R3 activity, we cultured mouse thoracodorsal arteries with a pharmacological inhibitor of Cyb5R3 (ZINC 747) and performed vascular reactivity studies using pressure myography. Arteries treated with ZINC 747 showed decreased responsiveness the NO donor DETA-NONOate but increase sensitivity to Bay 58-2667. We then treated mice with 10mg/kg/day of ZINC 747 using osmotic mini pumps, which caused an increase in mean arterial blood pressure (107.5±3.4 vs 131±13.16) measured via radio telemetry. Lastly, translational studies reveal that the CyB5R3 T116S polymorphism with allele frequency 0.23 only in African Americans is unable to reduce sGC and correlates with increased blood pressure. Considering the defining role of sGC in NO signaling and the fact that the oxidation state of sGC may predict responses to NO therapies and new classes of sGC activator medications, we anticipate that these studies may significantly impact our understanding of biology, precision therapeutics (right drug for the right patient) and pharmacogenetics (T117S SNP based drug selection).

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Influence of Cd2+on the spin state of non-heme iron and on protein local motions in reactions centers from purple photosynthetic bacteriumRhodospirilium rubrum

Journal of Physics Conference Series ◽

10.1088/1742-6596/217/1/012021 ◽

2010 ◽

Vol 217 ◽

pp. 012021 ◽

Cited By ~ 1

Author(s):

M Lipińska ◽

A Orzechowska ◽

J Fiedor ◽

A I Chumakov ◽

T Ślȩzak ◽

...

Keyword(s):

Spin State ◽

Heme Iron ◽

Non Heme Iron

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The Role of Nitric Oxide in γ-Globin Induction by Hydroxyurea.

Blood ◽

10.1182/blood.v108.11.3794.3794 ◽

2006 ◽

Vol 108 (11) ◽

pp. 3794-3794

Author(s):

Tzu-Fang Lou ◽

Ashley Williams ◽

Wei Li ◽

Betty S. Pace

Keyword(s):

Nitric Oxide ◽

Sickle Cell ◽

Fetal Hemoglobin ◽

K562 Cells ◽

Fold Increase ◽

Heme Iron ◽

Guanosine Monophosphate ◽

Erythroid Progenitors ◽

Globin Mrna ◽

No Donor

Abstract Hydroxyurea (HU) has been shown to induce fetal hemoglobin (HbF) synthesis through activation of the soluble guanosine cyclase/cyclic guanosine monophosphate signaling pathway. The release of NO from HU by heme iron is thought to be involved in this mechanism of HbF induction. Studies completed in sickle cell patients confirmed increased serum NO levels after oral HU therapy but NO generation in red blood cells and the effect on γ-gene transcription have not been extensively investigated. Therefore, we performed studies to quantify NO generated by HU in K562 cells and normal erythroid progenitors as a mechanism for γ-globin activation. NO levels were measured after drug treatments using the Nitric Oxide Assay Kit (Calbiochem) and γ-globin mRNA was measured using quantitative PCR. HU (100μM) increased NO 1.4 to 1.8-fold at 24–72 hrs in K562 cells compared to a 2.0 to 2.5-fold increase in NO produced by the known NO donor, deta-nonoate (DE; 400μM). NO levels were also measured in erythroid progenitors grown in liquid cultures; a 1.6-fold increase in NO was produced by 30μM HU after 48 hrs with comparable increases produced by 200μM DE. To understand the effects of HU on normal NO synthesis from L-arginine through the action of NO synthase (NOS), we performed studies with the NOS inhibitor, NG-Monomethyl-L-arginine (L-NMMA). Interestingly, HU increased NO levels 2.5-fold at 24 hrs when combined L-NMMA compared a 1.4-fold increase produced by HU alone; this pattern persisted up to 72 hrs. Parallel with these findings γ-globin activation by HU was augmented approximately 25% by L-NMMA; DE combined with L-NMMA did not produce the same effect. These data suggest a novel mechanism for NOS regulation by HU compared to DE. Subsequent studies were completed to determine if HbF synthesis could be augmented by combining NO donors since they have different mechanisms of action. HbF levels in K562 cells were measured by ELISA (Bethyl Laboratories) and normalized by total hemoglobin and protein. Treatment with HU or DE increased HbF 3.6-fold and 4.6-fold respectively; when HU was combined with DE an additive 7.6-fold increase in HbF was produced. These data confirm that HU treatment lead to NO generation in K562 cells and normal erythroid progenitors which plays a role in its mechanism of γ-globin activation. HU combined with DE had an additive effect on HbF synthesis. These findings are relevant to current research efforts to develop novel HbF inducers for therapy in sickle cell patients.

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