Molecular Mechanisms of LPS Preconditioning In Stroke

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DESCRIPTION (provided by applicant): Brain ischemia is one of the leading causes of morbidity and mortality in the United States, and many cases of ischemia are secondary to cardiovascular surgery. Pretreatment or preconditioning with a Tol-like Receptor agonist, LPS, induces a protective response to ischemic injury referred to as ischemic tolerance. This competitive renewal application seeks to elucidate the molecular events that define ischemic tolerance induced by LPS preconditioning. Our previous research revealed a novel genomic fingerprint that implicates type I interferons (IFNs) as primary effectors of LPS induced tolerance to ischemic injury. We discovered that the IFN transcription factor, IRF3 is required for LPS preconditioning and our recent preliminary work suggests that the IFN transcription factor, IRF7 may also be required. In addition we have found that the IFN genomic fingerprint extends to ischemic protection of the brain induced by two other preconditioning stimuli: a TLR9 ligand, unmethylated CpG ODNs and low dose ischemia thus broadening its importance. The appearance of a novel IFN fingerprint in neuroprotection supports a new working model of preconditioning in which Toll-like receptors are the central feature. Elucidation of the function of the IFN response may provide insight into the mechanism of TLR induced prophylactic treatment for stroke and lead to the development of a new TLR induced pathway of acute neuroprotection that by-passes the need for prior preconditioning. These findings have led us to hypothesize that LPS preconditioning induces neuroprotection through IRF3/IRF7 driven expression of a core set of genes that result in complimentary pathways of neuroprotection. We shall test the precepts of this model and its therapeutic potential in three aims: Aim 1. Elucidate the function of transcription factors IRF3 and IRF7 in TLR-induced neuroprotection. Aim 2. To determine the mechanism by which the IFN fingerprint confers neuroprotection in response to ischemic injury. Aim 3. Test whether direct activation of IRF3/7 in the acute setting of stroke leads to ischemic neuroprotection.