褪黑素对LPS致大鼠海马炎性损伤的保护作用

本研究旨在探究褪黑素（MT）对脂多糖（LPS）致大鼠海马炎性损伤的保护作用。选取40只4周龄健康雄性SD大鼠，随机分为4组：空白组（CON组）、模型组（LPS组）、褪黑素干预组（LPS+MT组）及褪黑素组（MT组）。通过腹腔注射的方式给予大鼠10 mg·kg^-1MT和/或10 mg·kg^-1LPS，4 h后，采用旷场试验对各组大鼠进行行为学测试；试验结束称大鼠体重，解剖取海马称重并计算海马体系数；苏木精-伊红（HE）染色观察脑切片中海马区域病理变化；RT-PCR技术检测海马中小胶质细胞激活标记物Iba-1和CD11b mRNA表达；Western blot法检测海马中炎性因子IL-1β、TNF-α、IL-6、IL-10及TGF-β蛋白表达。结果表明，与CON组相比，LPS组大鼠自主探索行为减少、运动能力下降，海马组织神经细胞排列松散、细胞间隙增大、胞质固缩深染、胶质细胞浸润，小胶质细胞激活标志物Iba-1和CD11b mRNA表达极显著升高（P<0.01），促炎因子IL-1β、TNF-α及IL-6蛋白表达极显著升高（P<0.01），抗炎因子IL-10和TGF-β蛋白表达极显著降低（P<0.01）。而与LPS组相比，LPS+MT组大鼠自主探索行为增加、运动能力增强，海马组织神经细胞排列紧密，未见明显病变，小胶质细胞激活标记物Iba-1和CD11b mRNA表达极显著降低（P<0.01），促炎因子IL-1β、TNF-α及IL-6蛋白表达极显著降低（P<0.01），抗炎因子IL-10和TGF-β蛋白表达极显著增加（P<0.01）。此外，MT组与CON组相比，所有指标差异均不显著（P>0.05）。结果提示，MT可抑制小胶质细胞激活，减轻海马炎症反应，从而改善LPS造成的大鼠海马炎性损伤。

Protective Effects of Melatonin on LPS-induced Hippocampal Inflammatory Lesion in Rats

The purpose of this study was to explore the protective effect of melatonin (MT) on hippocampal inflammatory injury induced by lipopolysaccharide (LPS) in rats. Forty 4-week-old healthy male SD rats were randomly divided into 4 groups:control group (CON group), model group (LPS group), MT intervention group (LPS+MT group) and MT group. Four hours after intraperitoneal injection of 10 mg·kg^-1 MT and/or 10 mg·kg^-1 LPS, the behavior of rats was tested by open field test. The hippocampus was weighed and coefficient of hippocampus was calculated. The pathological changes of the hippocampal region of brain were observed by hematoxylin-eosin (HE) staining. The mRNA expressions of microglial activation markers Iba-1 and CD11b in hippocampus were detected by RT-PCR. The protein expressions of inflammatory cytokines IL-1β, TNF-α, IL-6, IL-10 and TGF-β in hippocampus were detected by Weston blot. The results showed that compared with CON group, the autonomous exploration behavior and motor ability of rats in LPS group were decreased; the arrangement of nerve cells in hippocampus was loose, and the intercellular space of hippocampus was enlarged, cytoplasmic pyknosis was deeply stained, glial cells were infiltrated; the expression of microglia activation markers Iba-1 and CD11b mRNA were significantly increased (P<0.01); the protein expressions of pro-inflammatory factors IL-1β, TNF-α and IL-6 were significantly increased in LPS group (P<0.01); the protein expression of anti-inflammatory factors IL-10 and TGF-β decreased significantly (P<0.01). Compared with LPS group, the autonomous exploration behavior and motor ability of rats in LPS+MT group were increased; the arrangement of nerve cells in hippocampus was compact, and there was no obvious pathological change; the mRNA expressions of microglia activation markers Iba-1 and CD11b were significantly decreased (P<0.01); the protein expressions of pro-inflammatory factors IL-1β, TNF-α and IL-6 were significantly decreased in LPS+MT group (P<0.01); the protein expression of anti-inflammatory factors IL-10 and TGF-β increased significantly (P<0.1). In addition, there was no significant difference in all indexes between MT group and CON group (P>0.05). The above results suggest that MT can inhibit the activation of microglia and reduce the inflammatory response of hippocampus, thus improving the inflammatory injury of hippocampus induced by LPS in rats.