Global gene expression profiling of ischemic preconditioning in the rat retina

To obtain and analyze the gene expression changes after ischemic preconditioning (IPC) in the rat retina.

Ischemic damage to the inner retina can be prevented by a short, non-deleterious, ischemic insult of 5 min applied 24 h preceding a full ischemic insult of 60 min; a phenomenon termed tolerance or IPC. The time course of changes in gene expression after induction of IPC was assessed by 22K oligonucleotide microarrays, followed by real-time quantitative polymerase chain reaction (qPCR) validation. Functional pathways of interest were identified by Gene Ontology-term analysis.

Histology confirmed that IPC induction by 5 min of retinal ischemia results in a complete protection against the neurodegenerative effects of a 60 min ischemic period applied 24 or 48 h later. The microarray analysis revealed differential expression of 104 known genes at one or more time points between 1 h and 7 days after IPC. The group of altered genes contained a significant overrepresentation of genes involved in aminoacyl-tRNA synthetase activity (Iars, Lars, Cars, Yars, Gars, Tars), amino acid transport (Slc3a2, Slc6a6, Slc7a1, Slc38a2), regulation of transcription (including Egr1, Egr4, Nr4a1, Nr4a3, c-fos), and cell death (including Anxa1, Trib3). qPCR assays on cDNA of individual animals confirmed the microarray results.

Endogenous neuroprotection, provoked by ischemic preconditioning is associated with changes in transcript levels of several functionally-related groups of genes. During the time window of effective protection, transcript levels of genes encoding for aminoacyl-tRNA synthetases and for amino acid transport are reduced. These changes suggest that a reduction of translational activity may play a significant role in preconditioning-mediated neuroprotection.