Effect of intracerebroventricular injection of miRNA-22 on expression of P2X7 receptor and inflammatory factors in hippocampus of rats with epilepsy

Abstract

Objective To investigate the effect of microRNA-22 (miRNA-22) on the expression of P2X7 receptor and inflammatory factors in hippocampus of rats with epilepsy. Methods Healthy SD male rats were intraperitoneal injected with lithium chloride and pilocarpine to induce epilepsy. Three days later, 45 epileptic rats were randomly divided into three groups: epilepsy group(EP group), miRNA-22 agomir group (EF+ agomir group)and miRNA-22 agomir control group(EF+ agomir control group). Another 15 healthy rats were selected as control group(N group). The expression of P2X7 protein was detected by Western blot and the levels of miRNA-22, P2X7 mRNA, NF-κB mRNA , IL-1β mRNA were detected by qRT-PCR. Nissl staining was used to observe the damage of Nissl bodies. Results Western blot result showed that compared with the N group(0.91±0.10), the level of P2X7 protein in EP group (1.17±0.052) increased, and the difference was statistically significant (t=-4.11, P=0.02). Compared with the EP+ agomir control group(0.94±0.14), the expression of P2X7 protein in EP+ agomir group (0.66±0.06) decreased and the difference was significant (t=-3.10, P=0.04). And the qRT-PCR results showed that compared with N group, the levels of P2X7mRNA (9.08±0.94), NF-κB mRNA (20.10±2.15) and IL-1β mRNA (50.64±5.42) in EP group increased(t=-14.96, P<0.05; t=-15.38, P<0.05; t=-15.87, P<0.05). The expression of P2X7mRNA (1.31±0.64), NF-κB mRNA (2.28±1.10) and IL-1β mRNA (2.12±1.20) in EF+ agomir group decreased compared with EP group((9.08±0.94), (20.10±2.15), (50.64±5.42)) and EF+ agomir control group((7.03 ±1.90), (18.72±1.76), (47.39±6.16)), and the differences were statistically significant(F=29.77, P<0.01; F=98.99, P<0.05; F=96.29, P<0.01). Nissl staining results showed that a large number of morphologically abnormal and disintegrated Nissl bodies could be observed in the hippocampal CA1 and CA3 regions of EP group, which showed a smaller size, irregular morphology, chromatin pyknosis, boundary blur between nucleus and cytoplasm. Compared with the normal group, the difference was significant (P<0.05). While in miRNA-22 agomir group, the disintegration of Nissl bodies was improved and the number of Nissl bodies increased. Conclusion Intraventricular injection of miRNA-22 agomir can down-regulate the expression of P2X7 receptor and related inflammatory factors in hippocampus of epileptic rats, thus inhibiting seizures. Key words: miRNA-22; P2X7 receptor; Epileptogenic zone; Inflammatory factor; Neuroprotection