Improvement effect of TSPO ligand YL-IPA08 on lipopolysaccharide-induced depressive and anxiety-like behavior in mice and its anti-inflammatory mechanism
Objective To investigate the improvement effect of 18kD translocator protein(TSPO)ligand YL-IPA08 on lipopolysaccharide(LPS)-induced depressive,anxiety-like behaviors and cognitive dysfunction in mice and the related anti-inflammatory mechanism.Methods(1)50 male C57BL/6J mice were randomly divided into control group,LPS model group,LPS+YL-IPA08(1.0 or 3.0 mg/kg)group and YL-IPA08(3.0 mg/kg)group,with 10 mice in each group.Mice in LPS model group were intraperitoneally injected with LPS(0.5 mg/kg)once on day 1 and day 8.Mice in LPS+YL-IPA08(1 or 3 mg/kg)and YL-IPA08(3.0 mg/kg)groups were intragastrically administered YL-IPA08(1.0 or 3.0 mg/kg)for 13 consecutive days,once a day.From the 9th to 12th day,the open field test,tail suspension test,forced swimming test,novel object recognition test and elevated-plus maze test were used to evaluate the depressive,anxiety-like behaviors and cognitive function of mice.Western blotting was used to detect the expression levels of postsynaptic density protein 95(PSD95)and brain-derived neurotrophic factor(BDNF)in the prefrontal cortex of mice.(2)BV2 mouse microglia cells were divided into control group(phosphate buffered saline incubation for 1 h),LPS model group(incubated with 1.0 mg/L LPS for 6 h),LPS+YL-IPA08(0.5 or 1.0 μmol/L)group(incubated with 0.5 or 1.0 μmol/L YL-IPA08 for 1 h and then incubated with 1 mg/L LPS for 6 h),and YL-IPA08 group(incubated with 1.0 μmol/L YL-IPA08 for 1 h).ELISA was used to detect the expression levels of inflammatory factors interleukin-1β(IL-1β),interferon-γ(IFN-γ),IL-4,IL-10 and transforming growth factor-β1(TGF-β1).Western blotting was used to detect the expression levels of the members of Smad protein family(Smad2,Smad3)mediating signal transduction of TGF-β.Results(1)The results of behavioral experiments showed that there was no significant difference in the total movement distance of mice in each group in the open field test(P>0.05).Compared with the control group,the number of entries and duration time in the central area of mice in LPS model group were significantly decreased(P<0.05);the immobility time in the tail suspension test and the forced swimming test was significantly prolonged(P<0.05);the recognition index in the novel object recognition test,the percentage of entries into the open arms and the percentage of duration time in the open arm in the elevated-plus maze test were significantly decreased(P<0.05),and the expression levels of PSD95 and BDNF in the prefrontal cortex were significantly decreased(P<0.05).Compared with LPS model group,above behavioral and expression changes in LPS+YL-IPA08(3.0 mg/kg)group were significantly reversed(P<0.05).(2)Compared with control group,the expression levels of pro-inflammatory factors IL-1β and IFN-γ in BV2 cells in LPS model group were significantly increased(P<0.05),and the expressions of anti-inflammatory factors IL-4,IL-10 and TGF-β1 were significantly decreased(P<0.05),and the expression levels of Smad2 and Smad3 were significantly decreased(P<0.05).Compared with LPS model group,the expression level of IFN-γ in BV2 cells in LPS+YL-IPA08(0.5 μmol/L)group was significantly decreased,and the expression levels of IL-4 and TGF-β1 were significantly increased(P<0.05);the above changes were significantly reversed in LPS+YL-IPA08(1.0 μmol/L)group(P<0.05).Conclusion YL-IPA08 can significantly attenuate LPS-induced depressive and anxiety-like behaviors in mice and alleviate the decline in cognitive dysfunction,which mechanism may be related to improving neuroinflammation and regulating the TGF-β/Smad pathway.
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