Type 2 diabetes induced chronic inflammation on stroke outcome

Type 2 diabetes (T2DM) not only increases the risk of stroke, but also worsens the stroke outcome. Poor blood perfusion, hypercoagulability and chronic inflammation are known to be contributing factors. Complement activation products, especially C3 opsonins and the C3a/C5a anaphylaxis, have been implicated in promoting secondary injury following cerebral ischemic/reperfusion. The involvement of complement in the pathogenesis of insulin resistance and complications associated with type 2 diabetes is also well documented. However, how complement predisposes the brain to exacerbated ischemic injury and functional impairment is not well understood, let alone which cell types are involved in propagating complement- mediated inflammation. Via single cell transcriptomics we detected elevated expression of complement genes in the brain myeloid cells of mice with T2DM prior to the onset of stroke, including components of the classical pathway (c1qa-c), the anaphylatoxin receptors (C3ar and C5ar), and complement receptor 3 (CR3, itgam), as well as a number of chemotaxis-related molecules. Multiphoton imaging confirmed that T2DM mice exhibited poor collateral flow, accompanied by increased WBC-platelet aggregates in cerebral vessels together with increased leukocyte rolling, resulting in increased infiltration of neutrophils into brain parenchyma. We here propose to investigate the role of complement in promoting worse stroke outcomes in T2DM mice. Our first aim will determine the functional role of P-selectin and the anaphylatoxin receptors C3aR and C5aR in T2DM promoted transmigration of peripheral myeloid cells into brain after stroke. Aim 2 will determine the spatial and temporal expression of complement C3 in brains after stroke, and experiments will also delineate the functional effect of C3 from infiltrating versus brain resident glia cells on neuronal loss and stroke outcome. Aim 3 will investigate the role of microglia specific complement receptor 3 (CR3) in aberrant neuronal/synaptic loss and the functional role of this receptor in determining outcomes in T2DM and control mice. With comprehensive and effective approaches incorporating multidisciplinary techniques, this project will provide significant insight into the mechanisms underlying T2DM-mediated inflammation in the context of stroke.