Ischemic tolerance is a phenomenon whereby a sub-lethal ischemic injury, preconditioning, induces endogenous protective mechanisms that lessen the impact of a subsequent, more severe ischemic insult. We have used modeled ischemic tolerance in rat and mouse, both in vivo and in vitro, to describe multiple effectors of neuroprotection in these endogenous systems. Recently, we used DNA microarray to examine changes in gene expression in mouse brains subjected to preconditioning induced by a brief duration of ischemia, injurious ischemia, or a tolerant brain (preconditioned, then challenged with injurious ischemia). These experiments revealed that injurious ischemia up-regulated gene expression, while ischemic tolerance resulted in significant down-regulation of gene expression. Thus the signature of ischemic tolerance is that of suppressed gene expression. Elucidating the molecular mechanism(s) that underlie this focused transcriptional suppression is our goal. Eukaryotic gene expression is regulated by microRNAs, a newly identified class of small non-protein coding RNAs that regulate mRNA translation and chromatin activity in mammalian cells. Based on the signature of ischemic tolerance, a suppression of gene expression, we hypothesize that ischemic tolerance leads to regulated microRNA expression that in turn leads to the protected phenotype. In support of this hypothesis, our preliminary data show that distinct subsets of microRNAs are regulated in preconditioned, ischemic, and tolerant mouse brain. Thus to fully examine a role for microRNAs in ischemic tolerance, we propose the following specific aims: 1) establish the expression profile of microRNAs in preconditioned, ischemic, and tolerant mouse brain by microarray analysis, 2) confirm changes in, and examine the temporal expression of, microRNAs regulated in preconditioned, ischemic, and tolerant mouse brain, and 3) examine the effect of regulated microRNAs on target protein expression and cell survival. These studies are among the first to examine the regulated expression of miRNAs in response to modeled ischemia, and given the current development of short, interference RNAs as novel therapeutic agents for a number of diseases including macular degeneration, asthma, diabetes, cancer, Huntington's, and Hepatitis C infection, these studies may provide rationale for the development of similar strategies for the treatment or prevention of stroke and brain ischemia. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21NS054220-02
Application #
7273884
Study Section
Special Emphasis Panel (ZRG1-NDBG-A (09))
Program Officer
Jacobs, Tom P
Project Start
2006-08-02
Project End
2008-06-30
Budget Start
2007-07-01
Budget End
2008-06-30
Support Year
2
Fiscal Year
2007
Total Cost
$203,182
Indirect Cost
Name
Emanuel Hospital and Health Center
Department
Type
DUNS #
050973098
City
Portland
State
OR
Country
United States
Zip Code
97232
Saugstad, Julie A (2015) Non-Coding RNAs in Stroke and Neuroprotection. Front Neurol 6:50
Lusardi, Theresa A; Murphy, Stephanie J; Phillips, Jay I et al. (2014) MicroRNA responses to focal cerebral ischemia in male and female mouse brain. Front Mol Neurosci 7:11
Saugstad, Julie Anne (2013) MicroRNAs as effectors of brain function. Stroke 44:S17-9
Lusardi, Theresa A; Thompson, Simon J; MacDonald, Ian C et al. (2012) Effect of (S)-3,5-DHPG on microRNA expression in mouse brain. Exp Neurol 235:497-507
Ceman, Stephanie; Saugstad, Julie (2011) MicroRNAs: Meta-controllers of gene expression in synaptic activity emerge as genetic and diagnostic markers of human disease. Pharmacol Ther 130:26-37
Saugstad, Julie A (2010) MicroRNAs as effectors of brain function with roles in ischemia and injury, neuroprotection, and neurodegeneration. J Cereb Blood Flow Metab 30:1564-76
Lusardi, Theresa A; Farr, Carol D; Faulkner, Craig L et al. (2010) Ischemic preconditioning regulates expression of microRNAs and a predicted target, MeCP2, in mouse cortex. J Cereb Blood Flow Metab 30:744-56