Acute stroke is the leading cause of adult disability. Diabetes, which affects 30% of the 800,000 annual stroke victims, is a rapidly rising threat, increasing occurrence AND poor recovery of stroke. Recent evidence for neural repair and recovery after stroke strongly suggests that enhancement of brain's endogenous repair potential may improve recovery and reduce the burden of disability. However, most prior attempts focusing on solely neural mechanisms of recovery not only limited our understanding of how the brain orchestrates restorative and regenerative processes within the different cellular networks but also stalled the development of new therapeutic strategies. The limited use of animal models of diabetes in preclinical stroke research has further deepened this gap. The specific objective of this competing renewal proposal is to address this gap by focusing on the vascular mechanisms that hinder brain plasticity and repair in diabetes. Our central hypothesis is that ?diabetes-mediated dysregulation of the neurotrophic/proangiogenic microenvironment amplifies endothelial regulated cell death (RCD) after stroke leading to impaired vasoneuronal restoration and functional recovery?. Our novel findings in the past funding period showed that 1) in contrast to reparative angiogenesis in control animals, there is cerebrovascular regression associated with poor recovery of motor and memory function after stroke in diabetes, and 2) vasoregression is associated with greater peroxynitrite (PN) generation and cell death. Our preliminary data suggest that 1) in addition to apoptosis, necroptosis and ferroptosis, newly described forms of RCD are activated in endothelial cells from diabetic animals after stroke, 2) these pathways are differentially activated in brain microvascular endothelial cells (BMVECs) from male and female animals, 3) nitration of p85 subunit of PI3K by PN leads to decreased phospho(p)Akt and endothelial cell survival, 4) mature brain derived neurotrophic factor (mBDNF) is decreased while proapoptotic proBDNF and its cognate receptor p75NTR are increased in the diabetic brain, and 5) MMP9, a key protease involved in matrix degradation and cleavage of BDNF receptor TrkB, is activated by nitration after stroke.
Aim 1 will test the hypothesis that multiple RCD pathways orchestrate vasoregression and poor recovery after stroke in diabetes.
Aim 2 will test the hypothesis that PN-dependent nitration inhibits prosurvival signals amplifying endothelial RCD after diabetic stroke. The outcomes of these studies will significantly impact stroke research, human health and VA mission because it will a) advance the existing concept of neurorestoration and demonstrate that vascular restoration is fundamental for neuronal repair and functional recovery after stroke, b) generate important data related to mechanisms of how endothelial and neural repair processes are attenuated after stroke in diabetes which occurs in more than ~10% of the US population and 20% of our veterans, c) identify PN and cell death pathways as new promising therapeutic targets in stroke recovery, and d) provide comparative information on endothelial cell death pathways in females who are rapidly increasing in our veteran population.
More than 7% of the US population and 20% of our veterans have diabetes. Diabetic patients suffer from stroke injury to a greater extent, especially bleeding into the brain, and also experience poor recovery after stroke. However, we do not know the underlying mechanisms that contribute to poor brain repair and functional recovery in diabetes. Female subjects have long been neglected in experimental models. This project will determine the mechanisms how diabetes impacts stroke revovery in both sexes. Since a high percentage of veterans suffer from diabetes and stroke and female veterans are rapidly increasing, this project is highly relevant to the mission of Veterans Administration.
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