Cyclophilin C-associated protein and cyclophilin C mRNA are upregulated in penumbral neurons and microglia after focal cerebral ischemia.

Immunophilin ligands, such as cyclosporin A and FK506, have neuroprotective effects in experimental stroke models, although the precise mechanism is unclear. Cyclophilin C-associated protein (CyCAP) is a natural cellular ligand for the immunophilin, cyclophilin C, and has a protective effect against endotoxins by downmodulating the proinflammatory response. Expressions of CyCAP and cyclophilin C mRNA in a rat middle cerebral artery (MCA) occlusion ischemia model were investigated by Northern blotting and in situ hybridization. Both CyCAP and cyclophilin C mRNAs were ubiquitously distributed in the neurons of the normal brain. Expression increased in neurons of the periinfarct zone up to 7 days after MCA occlusion. The neuronal distribution was confirmed by counterimmunostaining of NeuN. Both mRNAs were predominantly expressed in microglia of the ischemic core at 7 days, confirmed by immunostaining with the microglial marker, ED1. The quantification of CyCAP and cyclophilin C mRNAs at 7 days by Northern blot analysis showed the 8.5-fold increase (P<0.005, n=6) and 6.8-fold increase (P<0.005, n=6), respectively, in ischemic core compared with control. The coincidence of CyCAP and cyclophilin C expression in neurons and microglia suggests distinct roles in each cellular population. In particular, the early increase in penumbral neurons might be related to protection in periinfarct neurons.