Effects of S1PR5 on cognitive behavior and inflammatory response in li-popolysaccharide-induced mice and its anti-inflammatory mechanism
AIM:To explore the impact of sphingosine 1-phosphate receptor 5(S1PR5)on lipopolysaccha-ride(LPS)-induced neuroinflammation and cognitive-behavioral impairments in mice,alongside the anti-inflammatory im-pacts on BV2 cells and associated mechanisms.METHODS:(1)C57BL/6 wild-type(WT)mice and homozygous S1PR5 knockout(KO)mice were utilized and categorized into WT control,WT-LPS,S1PR5 KO control,and S1PR5 KO-LPS groups using the random number method.Neuroinflammatory models in mice were induced by a single intraperitoneal injection of 5 mg/kg LPS in the WT-LPS and S1PR5 KO-LPS groups,while an equivalent volume of saline was injected in-to the WT control and S1PR5 KO control groups.Following 7 days of modeling,the Morris water maze test was conducted,followed by the collection of brain tissues from each group of mice.Hippocampal tissue sections were stained with Nissl.The mRNA expression levels of tumor necrosis factor-α(TNF-α),interleukin-1β(IL-1β)and IL-6 in hippocampal tis-sues were determined using RT-qPCR.Western blot and tissue immunofluorescence techniques were employed to assess the expression of nucleotide-binding oligomerization domain-like receptor protein 3(NLRP3)in hippocampal tissues.(2)The BV2 cells underwent LPS stimulation to induce an inflammatory response and were treated with either the S1PR5 ago-nist A971432 or lentiviral overexpression of S1PR5.The effects of S1PR5 agonism or overexpression on S1PR5,IL-1β,IL-6,TNF-α,and CD206 were assessed using RT-qPCR.Additionally,CD206 expression was examined via cellular im-munofluorescence.Western blot was employed to analyze the protein levels of microglia polarization markers CD206,in-ducible nitric oxide synthase(iNOS),cyclooxygenase 2(COX2),and NLRP3,as well as p-NF-κB,cleaved caspase-1,and IκBα.RESULTS:(1)Findings from in vivo experiments indicated that S1PR5 KO notably exacerbated LPS-induced memory impairments in mice,alongside increased mRNA levels of IL-1β and IL-6,and increased protein levels of NLRP3 in the hippocampus.(2)The presence of S1PR5 in BV2 cells remained unaffected by variations in A971432 concentration and exposure duration.(3)Activation of S1PR5 or its overexpression significantly mitigated LPS-induced expression of IL-1β,IL-6,and TNF-α,while concurrently enhancing CD206 expression in BV2 cells at the mRNA level.At the protein level,it led to a noteworthy increase in CD206 expression,indicative of M2-type macrophages,and a reduction in the ex-pression of iNOS and COX2,markers of M1-type macrophages.Furthermore,it downregulated NLRP3,p-NF-κB,and cleaved caspase-1 expression,while upregulating IκBα expression.CONCLUSION:S1PR5 deficiency exacerbates cog-nitive deficits in mice by promoting neuroinflammatory responses induced by LPS.
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