Journal Article

Involvement of Mitogen-Activated Protein Kinase Pathways in Expression of the Water Channel Protein Aquaporin-4 after Ischemia in Rat Cortical Astrocytes

Endo, Hidenori, Lee, Yong-Sun, Nito, Chikako, Narasimhan, Purnima, Chan, Pak H., Kamada, Hiroshi

2012

Overview

Brain edema after ischemic brain injury is a key determinant of morbidity and mortality. Aquaporin-4 (AQP4) plays an important role in water transport in the central nervous system and is highly expressed in brain astrocytes. However, the AQP4 regulatory mechanisms are poorly understood. In this study, we investigated whether mitogen-activated protein kinases (MAPKs), which are involved in changes in osmolality, might mediate AQP4 expression in models of rat cortical astrocytes after ischemia. Increased levels of AQP4 in primary cultured astrocytes subjected to oxygen-glucose deprivation (OGD) and 2 h of reoxygenation were observed, after which they immediately decreased at 0 h of reoxygenation. Astrocytes exposed to OGD injury had significantly increased phosphorylation of three kinds of MAPKs. Treatment with SB203580, a selective p38 MAPK inhibitor, or SP600125, a selective c-Jun N-terminal kinase inhibitor, significantly attenuated the return of AQP4 to its normal level, and SB203580, but not SP600125, significantly decreased cell death. In an in vivo study, AQP4 expression was upregulated 1–3 days after reperfusion, which was consistent with the time course of p38 phosphorylation and activation, and decreased by the p38 inhibition after transient middle cerebral artery occlusion (MCAO). These results suggest that p38 MAPK may regulate AQP4 expression in cortical astrocytes after ischemic injury.

• Publisher: SAGE Publications,Mary Ann Liebert, Inc
• Subject: Animals / Animals, Newborn / Aquaporin 4 - metabolism / Astrocytes - enzymology / Astrocytes - metabolism / Astrocytes - pathology / Brain damage / Cerebral Cortex - enzymology / Cerebral Cortex - metabolism / Cerebral Cortex - pathology / Hypoxia-Ischemia, Brain - enzymology / Hypoxia-Ischemia, Brain - metabolism / Hypoxia-Ischemia, Brain - pathology / Ischemia / Kinases / MAP Kinase Signaling System - physiology / Neurology / Original / p38 Mitogen-Activated Protein Kinases - antagonists & inhibitors / p38 Mitogen-Activated Protein Kinases - physiology / Primary Cell Culture / Proteins / Rats / Rats, Sprague-Dawley / Reperfusion Injury - enzymology / Reperfusion Injury - metabolism / Reperfusion Injury - pathology / Rodents