Exploring the role and mechanism of Congrong Shujing Granules in regulating microglial polarization and inhibiting neuroinflammation based on the NLRP3/Caspase-1 signaling pathway
Objective To investigate the effect and mechanism of Congrong Shujing Granules on promoting microglial polarization and inhibiting neuroinflammation through the nucleotide-binding oligomeric domain-like receptor protein 3(NLRP3)/Caspase-1 signaling pathway.Methods Twenty Sprague-Dawley rats were assigned to the blank serum and Congrong Shujing Granules containing serum groups using random number table method,with 10 rats in each group.Rats in the Congrong Shujing Granules containing serum group received intragastric administration of Congrong Shujing Granules(2.57 g/kg)and the rats in the blank serum group received intragastric administration of physiological saline of equal volume.Blank serum and Congrong Shujing Granules containing serum were prepared separately.Mouse microglia cells BV-2 were cultured in vitro,and the optimal concentration of 1-methyl-4-phenylpyridine(MPP+)and optimal volume fraction of Congrong Shujing Granules containing serum were selected by the CCK-8 assay and immunofluorescence staining.And the NLRP3 inhibitor MCC950 was used as a postive control.Cells were divided into the blank serum group(10%blank serum),model group(10%blank serum+500 μmol/L MPP+),Congrong Shujing Granules containing serum group(10%Congrong Shujing Granules containing serum+500 μmol/L MPP+),and MCC950 group(10%blank serum+10 μmol/L MCC950+500 μmol/L MPP+),and intervened separately.After 14 h of intervention,morphological changes in BV-2 cells were observed.The contents of interleukin(IL)-1β,tumor necrosis factor-α(TNF-α),IL-6,and IL-4 were detected by an enzyme-linked immunosorbent assay.The mRNA expressions of differentiation cluster 86(CD86),inducible nitric oxide synthase(iNOS),CD206,and arginase 1(Arg1)were detected by real-time fluorescence PCR.The expressions of CD86,Arg1,Ionized calcium binding adaptor molecule 1(Iba1),and NLRP3 were detected by immunofluorescence staining.The expression of iNOS,Arg1,TNF-α,IL-6,IL-4,NLRP3,pro-cysteinyl aspartate specific proteinase 1(pro-Caspase-1),and Caspase-1 proteins was detected by Western blotting.Results Iba1 activation and expression increased under the MPP+(12 h,500 μmol/L)intervention(P<0.05),and cell viability was not affected.There was no statistically significant effect on cell viability after treatment with 10%Congrong Shujing Granules containing serum alone or in combination with MPP+(P>0.05).Compared to the blank serum group,BV-2 cells in the model group showed multiple branches and protruded in the shape of an amoeba.The contents of IL-1β,TNF-α,and IL-6 increased,while the contents of IL-4 decreased.The mRNA expressions of CD86 and iNOS increased,while mRNA expressions of CD206 and Arg1 decreased.The mean fluorescence intensity of CD86,Iba1,and NLRP3 increased,while the mean fluorescence intensity of Arg1 decreased.The protein expressions of iNOS,TNF-α,IL-6,NLRP3,pro-Caspase-1,and Caspase-1 increased,while the protein expressions of Arg1,IL-4 decreased,P<0.05.Compared to the model group,the Congrong Shujing Granules containing serum group and MCC950 group showed a decrease in the branch of cell protrusions,reduced cell activation,decreased levels of IL-1β,TNF-α,and IL-6,increased levels of IL-4,decreased expression of CD86 and iNOS mRNA,increased expression of CD206 mRNA,the decreased mean fluorescence intensity of CD86,Iba1,and NLRP3,the increased mean fluorescence intensity of Arg1,decreased expression of iNOS,TNF-α,IL-6,NLRP3,pro-Caspase-1,and Caspase-1 proteins,and increased expression of Arg1 and IL-4 proteins,P<0.05.Conclusion Congrong Shujing Granules containing serum may alleviate the MPP+-induced neuroinflammatory response by inhibiting the NLRP3/Caspase-1 signaling pathway to regulate M1/M2 phenotype polarization of microglia.
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