Use of IL-1alpha to Promote Angiogenesis and Functional Recovery After Experimental Stroke

Treatments for stroke-induced cerebral ischemia (CI) have failed in part due to lack of efficacy against post-stroke neuroinflammation. However, while acute inflammation may contribute to worse patient outcomes, we hypothesize that chronic/delayed inflammation could promote brain repair, and may be an attractive therapeutic target. In particular, we have demonstrated a significant role for the inflammatory cytokine interleukin-1 (IL-1) in CI. Although the deleterious role of IL-1â (the main isoform of IL-1 released following CI) in CI is established, IL-1á is also critically important and, in contrast to IL-1â, may play a beneficial role. We have recently shown that IL-1á causes cultured cells of the neurovascular unit to generate laminin globular domain 3 (LG3), the neuroprotective and pro-angiogenic protein fragment of the extracellular matrix component perlecan. Importantly, LG3 is persistently (weeks) generated in the brain after stroke, but whether this is caused, even in part, by IL-1á, or is of any pathophysiologic or therapeutic benefit, is completely unknown. Our preliminary data now suggest that IL-1á activates brain endothelium, is pro-angiogenic in vitro, remains chronically elevated in stroked brains where it could persistently impact recovery, and when absent (IL-1á knockout mice (KO)) results in or contributes to diminished post-stroke angiogenesis. Therefore, we hypothesize that IL-1á is a key enhancer of angiogenesis (a brain repair mechanism) after stroke-induced CI via generation of LG3. To explore this hypothesis, we propose the following specific aims: 1) Determine the role of IL-1á in modulating angiogenesis in brain endothelium under normal conditions and after CI, 2) Determine the role of perlecan LG3 in IL-1á regulation of angiogenesis under normal conditions and after CI. We will use a number of in vitro angiogenesis assays and a transient middle cerebral artery occlusion model in wild-type and IL-1á KO mice to determine the angiogenic effects of IL-1á in vitro and in vivo. Functional/behavioral analysis will also be performed to correlate the extent of angiogenesis and infarct volume with functional recovery. The importance of LG3 to IL-1á angiogenesis effects in vitro and in vivo (after stroke) will be determined using a perlecan transgenic mouse that expresses 10% of normal total perlecan levels (pln -/-). Finally, we will employ various genetic and biochemical methods to determine how IL-1á increases LG3 generation in brain endothelial cells in vitro with a focus on key cellular proteases, and determine whether disruption of this impacts IL-1á angiomodulatory activity. Successful completion of this proposal will demonstrate a novel beneficial effect of inflammatory cytokines, specifically IL-1á, in brain recovery after stroke.