关键词: GPR84, 神经元, 脑缺血, 凋亡

Abstract: Objective To determine the expression and function of G protein-coupled receptor 84 (GPR84) in rat cerebral ischemia/reperfusion（I/R）. Methods The rat middle cerebral artery occlusion (MCAO) models were performed, and rats were then divided into sham group, cerebral ischemia for 2 h and reperfusion for 12 h group (I/R 12 h), 24 h group (I/R 24 h), 48 h group (I/R 48 h), 72 h group (I/R 72 h); rat primary cortical neurons were isolated and cultured in vitro, neurons were then divided into control group (Con), oxygen-glucose deprivation (OGD) for 1 h and recovery for 24 h group (OGD/R 1 h), OGD for 2 h and recovery for 24 h group (OGD/R 2 h); neurons were transfected with GPR84 small interfering RNA (siRNA), cells were divided into Con group, OGD/R 1 h group, neurons pretreated with negative control and exposed to OGD for 1 h and recovery for 24 h group (NC+OGD/R 1 h), neurons pretreated with GPR84 siRNA and exposed to OGD for 1 h and recovery for 24 h group (GPR84 siRNA+OGD/R 1 h). Western blot was used to determine the expression of GPR84 protein. Immunofluorescence assay was used to analyze the localization of the immunofluorescence signals of GPR84 in cerebral ischemic tissues after MCAO. Terminal dexynucleotidyltransferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay was used to detect the percentage of apoptotic neurons. Results Compared with the sham group, the expression of GPR84 protein was significantly up-regulated at each time point after cerebral I/R (P < 0.01). In addition, GPR84 was mainly localized in neurons and microglia, while little GPR84 was found in astrocytes. Neurons in the MCAO group exhibited higher levels of GPR84 expression than those in the sham group. GPR84 knockdown significantly inhibited the increase of GPR84 expression induced by OGD/R. Compared with the control group, neurons in the OGD/R 1 h group exhibited higher apoptotic cells percentage. Compared with the NC+OGD/R 1 h group, the percentage of apoptotic neurons in GPR84 siRNA +OGD/R 1 h group was significantly decreased. Conclusions These results suggest that the elevated GPR84 expression induced by cerebral I/R may play an important role in cerebral ischemia injury.

Key words: GPR84, neuron, cerebral ischemia, apoptosis