Cerebral ischemia induces transcription of inflammatory and extracellular-matrix-related genes in rat cerebral arteries

Cerebral ischemia results in a local inflammatory response that contributes to the size of the lesion, however, the involvement of the cerebral vasculature is unknown. We hypothesise that the expression of inflammatory genes (Il6, iNOS, cxcl2, TNF-α and Il-1β) and extracellular-matrix-related genes (MMP9, MMP13) is induced in cerebral arteries following cerebral ischemia via activation of mitogen activated kinases (MAPKs). This hypothesis was tested in vivo by experimental subarachnoid haemorrhage (SAH) and temporal middle cerebral artery occlusion (MCAO), and by organ culture of isolated cerebral arteries with quantitative real time PCR (mRNA expression) and immunohistochemistry (localization of protein expression). The gene promoters were investigated in silica with computer analysis. The mRNA analysis revealed that the ischemic models, SAH and MCAO, as well as organ culture of isolated cerebral arteries resulted in transcriptional upregulation of the abovementioned genes. The protein expression involved phosphorylation of three different MAPKs signalling pathways (p38, ERK 1/2 and SAPK/JNK) and the downstream transcription factors (ATF-2, Elk-1, c-Jun) shown by immunohistochemistry and quantified by image analysis. All three models revealed the same pattern of activation in the cerebrovascular smooth muscle cells. The in silica analysis demonstrated binding sites for said transcription factors. The results suggest that cerebral ischemia and organ culture induce activation of p38, ERK 1/2 and SAPK/JNK in cerebral arteries which in turn activate the transcription factors ATF-2, Elk-1 and c-Jun and the expression of inflammatory and extracellular-matrix-related genes in the wall of cerebral arteries.