The interaction of X chromosome and sex hormonal effects in stroke and neuroinflammation

About This Grant

Project Summary The incidence of stroke increases in women after their menopause, and stroke outcomes also become worse with aging in female stroke patients. It has been hypothesized that the exacerbated stroke phenotypes seen in elderly women are due to the loss of E2’s neuroprotection after menopause; however, the Women’s Health Initiative trial (WHI) has found E2 replacement therapy (ERT) had detrimental effects on stroke. Stroke scientists have argued that the women involved in the WHI trial were well passed their menopause when they received the ERT (late ERT or lERT), and have now shown ERT administered early after the menopause (early ERT or eERT) confers neuroprotection. Interestingly, for the past decade the increasing data have suggested that the second X chromosome (chromosomal effect) contributes to the worsened stroke outcomes in elderly women in addition to the decline of E2 levels (hormonal effect). Specifically, the X chromosome linked gene Kdm6a that escapes from X chromosome inactivation (XCI) in microglia has been found to up-regulate the histone H3K27me1 activational effect on the transcription of the pro-inflammatory IRF5 (interferon regulatory factor 5; responsible for microglial pro-inflammatory activation), leading to exacerbated stroke outcomes. In this proposal, we hypothesize that eERT in postmenopausal females inhibits Kdm6a gene escape from XCI, and suppresses the Kdm6a-H3K27-IRF5 signaling to ameliorate post-stroke inflammation and improve stroke outcomes. Aim 1 will use aged WT mice (in vivo) and in vitro assays (human induced pluripotent stem cells, hiPSCs), and test the hypothesis that the escape of Kdm6a from XCI and the Kdm6a-IRF5 signaling in aged females are repressed by eERT; whereas lERT will not have the same effects. Aim 2 will Test the hypothesis that eERT’s effect on post-stroke inflammation and outcomes is not Kdm6a allele dosage dependent but lERT's is. Microglial and astrocytic Kdm6a conditional knockout (CKO) female mouse models will be used to produce the knockout of one allele of Kdm6a in these cells. Kdm6a floxed females (two alleles of Kdm6a) will be included as a comparison. Aim 3 will examine if surgical menopause promotes Kdm6a escape from XCI in microglia. Ovariectomy will be performed in young and adult female mice to generate surgical menopause model. Kdm6a escape from XCI, Kdm6a-H3K27-IRF5 signaling, post-stroke inflammation and outcomes will be investigated in Aim 3. The goal of this project is to target XCI gene escape to suppress neuroinflammation after stroke.