Bone Morphogenic Protein-7 Contributes to Cerebral Ischemic Preconditioning Induced-Ischemic Tolerance by Activating p38 Mitogen-Activated Protein Kinase Signaling Pathway

Cerebral ischemic preconditioning (IPC), which refers to a transient and noninjurious ischemia is able to induce tolerance against the subsequent lethal ischemia, including ischemic stroke. We have previously reported that bone morphogenic protein-7 (BMP-7) contributes to the neuroprotective effects of IPC-induced ischemic tolerance, and thus ameliorates the following ischemia/reperfusion (I/R) injury in rats. Consequently, in the present study, we continued to explore the underlying regulatory mechanisms involved in BMP-7-mediated cerebral IPC in the rat model of ischemic tolerance. Male Wistar rats were preconditioned by 15-min middle cerebral artery occlusion (MCAO). After 2-day reperfusion, these animals were subjected to prolonged MCAO for 2 h. Our results showed that the phosphorylated p38 mitogen-activated protein kinase (MAPK) paralleling to BMP-7 was up-regulated by IPC in rat brain. Inactivation of p38 MAPK by pretreatment of SB203580, a p38 MAPK-specific suppressor, weakened the protective effect of IPC on CA1 neurons. Moreover, the enhanced phosphorylation of p38 MAPK induced by IPC was attenuated when the endogenous BMP-7 was inhibited by BMP-7 antagonist noggin. Besides, blockade of p38 MAPK signal transduction pathway via SB203580 abrogated the protective effects of exogenous BMP-7 against cerebral infraction. These present findings suggest that BMP-7 contributes to cerebral IPC-induced ischemic tolerance via activating p38 MAPK signaling pathway.