Abstract 104: Cytochrome B5 Reductase 3 Regulates The Erythropoietin Response To Ischemic Stroke In A Mouse Model Of Chronic Anemia And Oxidative Stress

Stroke, Volume 54, Issue Suppl_1, Page A104-A104, February 1, 2023. Introduction:Cytochrome b5 reductase 3 (Cyb5R3) is a heme iron reductase that reverses oxidized soluble guanylate cyclase (sGC) heme iron (Fe3+Fe2+) to preserve nitric oxide signaling. Under oxidative stress, such as occurs with sickle cell disease (SCD) and ischemic stroke, Cyb5R3 redox signaling provides resilience against tissue damage. A loss-of-function (roughly 50%) Cyb5R3 missense variant (T117S) occurs with high frequency (0.23 minor allele) in persons of African ancestry, who also suffer a greater burden of sickle cell anemia and ischemic stroke than other races. We hypothesized that Cyb5R3 regulates the erythropoietin response to ischemic stroke in a mouse model of SCD.Methods:Age-matched male SCD mice with wild-type Cyb5R3 (SSWT) or T117S Cyb5R3 (SST117S) underwent middle cerebral artery occlusion (55 min) and reperfusion (48 hr). Blood was sampled at baseline and 48h reperfusion for hematology measurements. Brains were stained with 2,3,5-triphenyltetrazolium chloride to quantify infarct volume. Erythropoietin (EPO), heme oxygenase 1 (HMOX1) and sGC were assayed by Western blot.Results:We found brain infarct volume to be greater in SST117Svs SSWT(63 vs 27 cm3, respectively; P=0.003). Red cells, hematocrit and hemoglobin decreased in SST117Spost-stroke, which was opposite to SSWT(red cells: -13% vs 13%, P=0.01; hematocrit: -20% vs 0%, P=0.03; hemoglobin: -18% vs 3%, P=0.02, respectively). In the absence of stroke (age-matched controls), SSWThad elevated HMOX1 protein compared to SST117S, which normalized in post-stroke SSWTbut was unchanged in post-stroke SST117S. Kidney and plasma EPO levels significantly increased in SSWTpost-stroke, but not in SST117S. In vitro studies using HEK293 cells showed EPO and HMOX1 decrease with Cyb5R3 knockdown by siRNA.Conclusion:Our findings suggest a modifying role for Cyb5R3 in brain-kidney crosstalk during ischemic stroke, wherein loss of T117S Cyb5R3 activity negatively impacts renal and plasma EPO levels and resilience against infarct of ischemic brain tissue. The Cyb5R3 axis on which the brain-kidney-blood response to stroke in SCD turns represents a novel target for precision medicine approaches to managing stroke risk and pathology in SCD carriers of the T117S variant.

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Febbraio 2023