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, w e h y p o t h e s i z e t h a t chronic/delayed inflammation could promote brain repair, and may b e 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-1? (the main isoform of IL-1 released following CI) in CI is established, IL-1? is also critically important and, in contrast toIL-1?, may play a beneficial role. We have recently shown that IL-1? causes c u l t u r e d 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-1?, or is of any pathophysiologic or therapeutic benefit, is completely unknown. Our preliminary data now suggest that IL-1? activates brain endothelium, is pro-angiogenic in vitro, remains chronically elevated in stroked brains where it could persistently impact recovery, and when absent (IL-1? knockout mice (KO)) results in or contributes to diminished post-stroke angiogenesis. Therefore, we hypothesize that IL-1? 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-1? in modulating angiogenesis in brain endothelium under normal conditions and after CI, 2) Determine the role of perlecan LG3 in IL-1? 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-1? KO mice to determine the angiogenic effects of IL-1? 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-1? 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-1? increases LG3 generation in brain endothelial cells in vitro with a focus on key cellular proteases, and determine whether disruption of this impacts IL-1? angiomodulatory activity. Successful completion of this proposal will demonstrate a novel beneficial effect of inflammatory cytokines, specifically IL-1?, in brain recovery after stroke.
Cerebral ischemia (CI) caused by stroke is one of the leading causes of death and disability worldwide, and is critically regulated by inflammation. Although acute inflammation after stroke is detrimental to the brain and contributes to a poor outcome, components of chronic inflammation may promote recovery. Our goal is to understand how one such chronic inflammatory component, interleukin-1 alpha, promotes recovery, with the aim to develop new stroke therapies.
|Salmeron, Kathleen; Aihara, Takuma; Redondo-Castro, Elena et al. (2016) IL-1alpha induces angiogenesis in brain endothelial cells inÂ vitro: implications for brain angiogenesis after acute injury. J Neurochem 136:573-80|