Objective To determine whether aquaporin-4 （AQP4） regulates acute lesions, delayed lesions, and the associated microglial activation after cryoinjury to the brain. Methods Brain cryoinjury was applied to AQP4 knockout （KO） and wild-type mice. At 24 h and on days 7 and 14 after cryoinjury, lesion volume, neuronal loss, and densities of microglia and astrocytes were determined, and their changes were compared between AQP4 KO and wild-type mice. Results Lesion volume and neuronal loss in AQP4 KO mice were milder at 24 h following cryoinjury, but worsened on days 7 and 14, compared to those in wild-type mice. Besides, microglial density increased more, and astrocyte proliferation and glial scar formation were attenuated on days 7 and 14 in AQP4 KO mice. Conclusion AQP4 deficiency ameliorates acute lesions, but worsens delayed lesions, perhaps due to the microgliosis in the late phase.
Wen-Zhen Shi Chun-Zhen Zhao Bing Zhao Xiao-Liang Zheng San-Hua Fang Yun-Bi Lu Wei-Ping Zhang Zhong Chen Er-Qing Wei
Objective Aquaporin-4 （AQP4）, the main water channel protein in the brain, plays a critical role in water homeostasis and brain edema. Here, we investigated its role in the inflammatory responses after focal cerebral ischemia. Methods In AQP4-knockout （KO） and wild-type mice, focal cerebral ischemia was induced by 30 rain of middle cerebral arterial occlusion （MCAO）. Ischemic neuronal injury and cellular inflammatory responses, as well as the expression and localization of cysteinyl leukotriene CysLT2 and CysLT~ receptors, were determined at 24 and 72 h after MCAO. Results AQP4-KO mice showed more neuronal loss, more severe microglial activation and neutrophil infiltration, but less astrocyte proliferation in the brain after MCAO than wild-type mice. In addition, the protein levels of both CysLT1 and CysLT2 receptors were up-regulated in the ischemic brain, and the up-regulation was more pronounced in AQP4-KO mice. The CysLT1 and CysLT2 receptors were primarily localized in neurons, microglia and neutrophils; those localized in microglia and neutrophils were enhanced in AQP4-KO mice. Conclusion AQP4 may play an inhibitory role in postischemic inflammation.
