The role of CD36 in ischemic inflammation and injury

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Post-ischemic inflammation complicates the development of cerebral injury triggered by ischemic stroke. CD36 is a class B scavenger receptor that has a high affinity for oxidized low-density lipoprotein (oxLDL). CD36 functions in the uptake of oxLDL and subsequent foam cell formation in aorta and may also contribute to the pro-inflammatory milieu. On the basis of proatherogenic and proinflammtory property of CD36, we hypothesize that CD36 expressed in brain functions as a primary mediator for ischemia-induced inflammation associated with cerebral injury and that CD36 is thus a target for pharmacological intervention. To test these hypotheses, Aim 1will investigate the dependency of CD36 in eliciting ischemia-induced inflammatory responses and cerebral injury using two approaches: Genetically using CD36 knock-out (KO) mice and pharmacologically using hexarelin. Aim 2 will determine whether microglia/macrophage CD36 expression is a critical mediator for post-ischemic inflammation and cerebral injury by comparing inflammatory markers and functional outcomes in wild type (WT) and CD36 KO mice transplanted with either WT or CD36 KO hematopoietic stem cells. A role for microglia CD36 will be further studied by assessing inflammatory responses in the post-ischemic brain prior to blood brain barrier deterioration. Aim 3 will test the clinical relevance of a pro-inflammatory role of CD36 by examining the CD36-mediated effects in a model of hypercholesterolemia. Accordingly, CD36 expression and ligand availability will be assessed in the post- ischemic brain in stroke-prone ApoE KO mice fed a high fat Western diet. In addition, we will compare inflammatory markers and functional outcomes in ApoE KO and ApoE/CD36 double KO mice fed the Western diet and also in ApoE KO mice fed the Western diet with statins, lipid lowering drugs. This proposal, in its entirety, will develop novel strategies important to ameliorating post-ischemic inflammation and cerebral injury in stroke victims. (lay version)This study aims to investigate whether CD36, a multifunctional receptor, is involved in inflammation and brain injury after an ischemic stroke. Understanding contributing roles of CD36 on brain injury will lead to potential therapeutic strategies to treat stroke patients.