Abstract WP325: X, but Not Y, Sex Chromosome Contributes to Stroke Sensitivity in Aged Mice

Abstract

Introduction: Stroke is a sexually dimorphic disease. Women are protected against ischemia compared to men before menopause due to estrogen’s neuroprotection; after menopause the elderly women become vulnerable to stroke attack. Our previous studies with four core genotype mice found a chromosomal effect (either X or Y) in stroke sensitivity. Recently, we found two X-linked genes ( Kdm6a and Kdm5c ) that escape from X chromosome inactivation (XCI) are higher expressed in aged female vs. male microglia after stroke. KDM6A and KDM5C are histone demethylases that modify gene expression of inflammatory mediators. By these early studies, we hypothesized that the second X chromosome contributes to stroke sensitivity in aged mice through immune responses mediated by KDM6A and KDM5C. Methods: XY* aged (18-22 months) mice (natural menopause cohort) that have four genotypes (XO, XX, XY, XXY) were subjected to middle cerebral artery occlusion (MCAO). Another cohort of gonadectomized XY* mice were also used as the “surgical menopause” cohort. Infarct volumes and behavior deficits were quantified 3 days after MCAO. KDM6A and KDM5C localization with microglial marker TMEM119 was examined by IHC. Plasma inflammatory cytokine (IL-1β, TNF-α, IL-6, IL-4, TL-10, etc.) levels were analyzed with MultiPlex. The contribution of the second X-chromosome to stroke sensitivity was determined by comparing XX vs. XO or XXY vs. XY mice, and the effect of the Y-chromosome was evaluated by a comparison between XY vs. XO and XXY vs. XX mice. Results: In both surgical and natural menopause cohorts, XX and XXY mice showed worse stroke outcomes compared to XO or XY mice respectively; however, no significant difference was found between XX vs. XXY or XO vs. XY mice. IHC results showed higher expression of KDM6A and KDM5C in TMEM119 positive cells in mice with two vs. one copy of X chromosome. XXY mice had significantly higher levels of circulating TNF-α and IL-6 than XY mice. Conclusion: The second X chromosome contributes to stroke sensitivity in mice. Kdm6a and Kdm5c may play important roles in mediating post-stroke inflammation. Future work will genetically manipulate the expression of Kdm6a and Kdm5c in microglia to examine the roles of the two XCI escapee gene in stroke.