Protein expression profiling in the hippocampus after focal cerebral ischemia injury in rats

The aim in this study was to explore protein expression profiles in the rat hippocampus after induction of focal ischemia injury. Forty male Sprague Dawley rats were randomly divided into four equal groups after ischemia injury surgery: Control, Day 3, Day 7, and Day 14. Focal cortical ischemia was induced in thirty rats by photothrombosis of cortical microvessels. After surgery, the induction of ischemia was confirmed by infarct size measurement using staining by 2, 3, 5-triphenyltetrazolium chloride. To identify the differential expression of proteins between the diseased and control sides of the hippocampus, a comparative proteome analysis was performed using isobaric tags for relative or absolute quantitation coupled with 2D liquid chromatographytandem mass spectrometry analysis. 4,081 proteins were identified, 260 of which were non-redundant and showed differential expression between the three surgery groups and the control. Hierarchical cluster analysis indicated that the three surgical groups had markedly different expression patterns of these 260 proteins, including 160 upregulated and 80 downregulated proteins. A gene ontology analysis revealed 4,944 terms, among which myelin sheath and cell junction were the two most enriched items. In KEGG database pathway analysis, ribosome was the most abundant item. A Venn diagram showing the overlap of 25 of the differentially expressed proteins quantified from the four groups and results from the KEGG pathway analysis suggested that Epstein-Barr virus infection was the most abundant item. From the protein-protein interaction network, a total of 223 interactive proteins were predicted and used to construct a network. In conclusion, myelin sheath, cell junction, and Epstein–Barr virus infection were implicated in focal ischemia injury. Vimentin and albumin may be important proteins involved in focal ischemia injury.