Effect of lead exposure on neuroinflammation of hippocampus and cognitive impairment in diabetic rats / 中国职业医学

ABSTRACT

OBJECTIVE: To explore the effects of lead exposure on inflammatory damage of hippocampus and cognitive impairment in diabetic rats. METHODS: The specific pathogen free(SPF) male healthy Wistar rats were randomly divided into control group and lead-exposed group. The SPF male Goto-Kakisaki Wistar rats rats were randomly divided into diabetes group and diabetes lead-exposed group, with 10 rats in each group. Rats in lead-exposed group and diabetes lead-exposed group were continuously exposed to lead acetate water with a mass fraction of 0.025% for 9 weeks. Rats in control group and diabetes group were given distilled water. The body weight and blood glucose level of rats were measured before lead exposure and at 1, 3, 5, 7 and 9 weeks after exposure. After the exposure, Morris water maze test was used to evaluate the learning and memory ability of rats. The lead levels in whole blood and hippocampal tissues were detected by inductively coupled plasma mass spectrometry, and the expression of mRNA and protein expression of inflammatory factors in hippocampal tissues of rats were detected by real-time fluorescence quantitative polymerase chain reaction and enzyme-linked immunoadsorption, respectively. RESULTS: At the end of lead exposure, the difference of body mass of rats in the diabetes group and the diabetes lead-exposed group was not statistically significant compared with that in the same group before exposure(all P values were >0.05); but the body mass of rats in these two groups was lower than that of the control group and the lead-exposure group(all P values were <0.05). The blood glucose levels of rats were higher in the diabetic group and the diabetes lead-exposed group than that in the control group and the lead-exposed group, respectively(all P values were <0.05). Morris water maze test showed that the escape latency of rats in the 1 st, 2 nd and 3 rd day were longer in diabetes group and the diabetes lead-exposed group than that in the control group and the lead-exposed group(all P values were <0.05). The number of times of crossing platforms were less in the lead-exposed group and the diabetes group than that of the control group(all P values were <0.05). The number of times of crossing platforms was more in the diabetes lead-exposed group than that in the other 3 groups(all P values were <0.05). The levels of lead in blood and hippocampus of rats were higher in the lead-exposed group than those in the control group(all P values were <0.05), and those in the diabetes lead-exposed group were higher than that in the other 3 groups(all P values were <0.05). The relative expression of mRNA of interferon-γ(ifn-γ) and interleukin(il)-6 in hippocampal tissues of rats was higher in the lead-exposed group and the diabetes group than that of the control group(all P values were <0.05). The relative expression of mRNA of tumour necrosis factor-α(tnf-α) and il-1β in the hippocampal tissues of rats was higher in the diabetes group than that of the control group and the lead-exposed group, respectively(all P values were <0.05). The relative expression of mRNA of ifn-γ, tnf-α, il-1β and il-6 in hippocampal tissues of rats was higher in the diabetes lead-exposed group than that of the other 3 groups(all P values were <0.05). The relative protein expression of IFN-γ, TNF-α, IL-4 and IL-6 in hippocampal tissues of rats was higher in lead-exposed group than that of the control group(all P values were <0.05). The relative protein expression of IFN-γ, TNF-α, IL-1β and IL-6 in hippocampal tissues of rats was higher in diabetes group than that of the control group(all P values were <0.05). The relative protein expression of IFN-γ, IL-1β and IL-6 in hippocampal tissues of rats was higher in diabetes group than that of the other 3 groups(all P values were <0.05). CONCLUSION: Diabetes can promote the lead accumulation in the blood and hippocampus of rats. The combined effect of lead exposure and diabetes can up-regulate the expression of pro-inflammatory cytokines in the hippocampal tissues of rats, aggravate the inflammatory response, and have a synergistic effect on the cognitive impairment in rats.