The Role of PPAR Agonists in Inflammation and stroke

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Stroke is a devastating disease. We desparately need to understand mechanisms of injury and recovery following ischemic stroke in order to design treatments that will limit ischemic injury and promote recovery. Inflammation exacerbates ischemic injury and may play a role in remodeling and recovery following stroke. Our long term objective is to clarify the role of inflammation in cerebral ischemia both in the acute and chronic time frames. To accomplish this, we propose to use a new class of drugs, PPARgamma agonists, that have anti-inflammatory properties. Troglitazone, a PPARgamma agonist, reduces the expression of the proinflammatory cytokines and other inflammatory molecules. Preliminary data show that troglitazone reduces infarct size following focal ischemia in rats and that immunoreactivity against proinflammatory cytokines is reduced in the same animals. Furthermore, we show that PPARgamma expression is increased following cerebral ischemia. This increase is present within hours and persists for least one week. Experiments are designed to test the role of PPARgamma activation in neuroprotection using additional PPARgamma agonists and antagonists. The time period in which the activation must occur will be examined. We propose to use a combination of Western blotting, quantitative rt-PCR and immunocytochemistry to assay the contribution of inflammation to the observed neuroprotection. We will specifically examine the role played by proinflammatory cytokines by administering compounds that block the cytokines, interleukin-lbeta and tumor necrosis factor alpha along with troglitazone to animals undergoing middle cerebral artery occlusion. We propose to further examine the expression of PPARgamma in ischemic brain and explore the effects of PPARgamma agonists on this expression. Finally the ability of PPARgamma agonists to modulate functional outcome after the time when infarct volume has been determined is explored. Preliminary data that suggests that troglitazone may improve outcome when administered twenty-four hours and four days after focal stroke. When administered at this time, troglitazone does not reduce infarct size. These preliminary data will be confirmed with a larger number of rats and additional behavioral analysis. Western blotting, rt-PCR and immunocytochemistry will be used to assay the effects of troglitazone on proinflammatory cytokines and growth factors that are likely candidates for modulating recovery followng cerebral ischemia.