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Background The altered expressions of hippocampal N-methyl-D-aspartate (NMDA) receptors induced by benzo[ɑ]pyrene (BaP) causes short-term spatial learning and memory impairment in humans and animals, but whether BaP causes alterations of NMDA receptor subunits in other brain regions and the associated neurotoxic mechanism is still essentially unknown. Objective To observe the mRNA expressions of NR1, NR2A, and NR2B of NMDA receptor subunits in different brain regions in SD rat model with subchronic exposure to BaP, and to provide a basis for in-depth study of the mechanism of BaP-induced neurotoxicity. Methods Forty male SD rats were selected and randomly divided into a control group and 1.00, 2.50, and 6.25 mg·kg−1 BaP exposure groups with 10 rats in each group. The exposure rats received intraperitoneal injection of BaP every other day for 90 d.The average latency to platform, the average total distance, and the duration spent in previous quadrant were measured by the Morris Water Maze. Real-time fluorescence quantitative PCR was used to detect the mRNA expressions of NR1, NR2A, and NR2B in hippocampus, cortex, cerebellum, and striatum of rats. Results The average latency to platform and the average total distance in the 2.50 and 6.25 mg·kg−1 BaP groups were significantly prolonged compared with the control group (P<0.05), and the duration that rats spent in previous quadrant in the 6.25 mg·kg−1 BaP group was significantly shortened (P<0.05). Compared with the control group, the mRNA expressions of NR1 and NR2B in the hippocampus in the 2.50 and 6.25 mg·kg−1 BaP groups were significantly reduced (P<0.05), and the NR2A mRNA expression in the hippocampus in the 6.25 mg·kg−1 BaP group was significantly reduced (P<0.05); the mRNA expressions of NR1 and NR2B in the cortical tissue in the 6.25 mg·kg−1 BaP group were significantly reduced (P<0.05), and the mRNA expression of NR2A in the cortical tissue in the 1.00 mg·kg−1 BaP group was reduced; the mRNA expression of NR2B in the cerebellar tissue in the 6.25 mg·kg−1 BaP group was significantly reduced (P<0.05); there were no differences in the mRNA expressions of NMDA receptor subunits in the striatum tissue (P>0.05). Conclusion Subchronic BaP exposure can cause short-term spatial learning and memory impairment in rats, which may be related to the down-regulation of mRNA expressions of NR1, NR2A, and NR2B in hippocampus, changes of mRNA expressions of NR1, NR2A, and NR2B in cortical area, and the down-regulation of NR2B mRNA expression in cerebellum.
ABSTRACT
Objective:To investigate the effects and its mechanism of chronic unpredictable stress on intestine and liver injuries in rats, and explore the possibility of the existence of brain-gut-liver axis.Methods:Twenty male SD rats were randomly divided into control group and stress group (with 10 in each group). The rats in the stress group were stimulated by chronic unpredictable stress for 4 weeks to prepare the chronic stress model. The rats in the control group were fed normally without stress stimulation. After modeling, ten rats in the control group and seven rats in the stress group were included. The depressive behavior of the two groups was evaluated by sugar water preference experiment. Then the rats were sacrificed. The diversity of gut flora in intestinal feces was analyzed by 16S rRNA sequencing analysis. The pathological injuries of ileum and liver were detected by HE staining. The expressions of occludin in ileum and Toll-like receptor 4 (TLR4) in liver were detected by immunohistochemistry. The expression of TLR4 protein in liver tissue was detected by Western blot. The level of lipopolysaccharide (LPS) in rat portal vein serum was detected by AZO chromogenic limulus test and blood biochemical method was used to detect liver function.Statistical analysis was performed using SPSS 25.0 software, and t-test or Mann-Whitney U test was used for comparison between the two groups. Using STAMP software, Wilcoxon rank sum test was used to analyze the difference in bacterial abundance between the two groups. Results:The consumption of sugar water ((7.86±0.90)ml) and the preference rate of sugar water ((43.06±5.65)%) in the stress group were lower than those in the control group ((15.10±1.51)ml, (76.81±6.44)%), and the difference were statistically significant ( t=11.33, 11.16, both P<0.01). Chronic stress caused pathological damage to rat ileum tissue. Compared with the control group, the ileum villi of rats in the chronic stress group were longer ((448.93±12.71)μm, (497.12±16.72)μm, t=-5.88, P<0.01) and thicker ((81.99±16.54)μm, (133.93±6.78)μm, t=-7.12, P<0.01), and the expression of occludin was significantly down-regulated ((0.236±0.011), (0.130±0.026), t=9.12 , P<0.01), the LPS level increased significantly ((18.83±2.62)EU/L, (38.64±2.51)EU/L, t=-5.79, P<0.01). The Beta diversity of rat intestinal flora changed under chronic stress, and the abundance of WPS-2 phylum in intestinal tract of rats in stress group was higher than that in control group ( t=2.76, P<0.05). Chronic stress caused pathological damage to the liver tissue of rats. Compared with the control group, the expression of TLR4 protein in the liver tissue of the chronic stress group increased ((0.169±0.014), (0.475±0.034), Z=-2.37, P<0.05). Compared with the control group, the ALT ((39.7±6.2)U/L, (82.9±43.1)U/L, Z=-2.35, P<0.05) and AST((130.9±28.9)U/L, (472.7±263.3)U/L, Z=-2.64, P<0.05) levels of the chronic stress group increased, especially in AST. Conclusion:Chronic stress cause synchronous damage to the intestine and liver in rats. The mechanism may be related to the results caused by chronic stress such as the changes of the diversity of intestinal flora, the increasing of intestinal permeability, the action of LPS translocated through portal vein blood on TLR4 in liver.
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This study was aimed to investigate the effect of baicalin on the proportion of Th22 cells and the concentration of IL-22 bothin vivo andin vitro, in order to explore the immune mechanism of baicalin on inflammatory bowel disease mice model. The 3.5% dextran sodium sulfate (DSS) was used on C57BL/6 mice for the establishment of colitis mice model. Mice were randomly divided into the blank control group, model group, and baicalin group. Flow cytometry and ELISA were used in the detection of the proportion of Th22 cells and concentration of IL-22 in peripheral blood serum, respectively. The spleen lymphocytes of mice were isolated and cultured by baicalin medium (0, 10, 20, 40μM) for 48 h. Flow cytometry was used in the detection of the proportion of Th22 cells. The results showed that baicalin reduced the proportion of Th22 cells and the expression of IL-22 bothin vivo andin vitro experiments. It was concluded that baicalin can inhibit Th22 cell differentiation and expression of IL-22in vitro and DSS-induced colitis mice. It indicated that baicalin had a good treatment potential in Th22 cell-mediated inflammatory diseases.