RESUMO
Background:Faecalibacterium prausnitzii(Fp)is a commensal intestinal bacterium that exhibits anti-inflammatory and immunomodulatory capacity in vivo and in vitro. It has been reported that Fp in intestinal lumen was reduced in patients with colorectal cancer,which might be a factor associated with cancer development. Aims:To investigate the effect and immunological mechanism of Fp and its genomic DNA(fDNA)on the killing activity of peripheral blood mononuclear cells (PBMCs)against human colon cancer LoVo cells. Methods:PBMCs derived from healthy adults were co-cultured in vitro with Fp,fDNA,or the digested fDNA(d-fDNA),respectively. Killing activity of PBMCs against LoVo cells was measured by MTT assay;concentrations of interferon-gamma(INF-γ),a Th1-type cytokine and interleukin-4(IL-4),a Th2-type cytokine in culture supernatant of PBMCs were determined by ELISA;and expressions of T-bet and GATA3,the transcription factors specific for Th1 and Th2 cells,were measured by real-time PCR. Results:Compared with the PBMCs not treated,fDNA could significantly enhance the killing activity of PBMCs against LoVo cells(P < 0. 05);meanwhile,it promoted IFN-γ secretion,up-regulated T-bet mRNA expression and inhibited IL-4 secretion and GATA3 mRNA expression in PBMCs(P < 0. 05). Similar effects were not observed in PBMCs treated with Fp and d-fDNA. Conclusions:fDNA enhances the killing activity of PBMCs against human colon cancer cells by up-regulating Th1 immune response.
RESUMO
Background:NLRP3 inflammasome attracts widespread attention in study of inflammatory bowel disease. Faecalibacterium prausnitzii(Fp)is an anti-inflammatory commensal bacterium that has preventive and therapeutic effects on rat colitis. Aims:To explore the underlying mechanism of Fp in treating experimental colitis in rats. Methods:Fifty rats were randomly divided into two groups,10 in control group and 40 in model group. Rats in model group were administered intrarectally with 5% TNBS and dehydrated alcohol to induce experimental colitis. Twenty-four hours afterwards,the model rats were further divided into four groups and administered intragastrically with PBS,culture medium,live Fp and Fp supernatant 1 mL per day,respectively,for 7 days. On day 8,all the rats were sacrificed for evaluation of colonic inflammation. Expressions of the constituents of NLRP3 inflammasome(NLRP3,ASC,and caspase-1)were assessed by Western blotting and real-time PCR;levels of IL-1β and IL-18,the downstream effectors of NLRP3 inflammasome,in colon and plasma were measured by real-time PCR and ELISA,respectively. Results:Weight loss, reduced colon length and colonic inflammatory injury were observed in model rats. These manifestations were ameliorated in live Fp and Fp supernatant groups than those in PBS and culture medium groups. In PBS and culture medium groups, expressions of NLRP3,ASC,and caspase-1 protein and mRNA in colonic tissue were significantly higher than those in control group(P < 0. 05),the colonic and plasma levels of IL-1β were increased(P < 0. 05),and IL-18 levels were decreased(P < 0. 05). In live Fp and Fp supernatant groups,IL-18 level showed a further reduction as compared with PBS and culture medium groups( P < 0. 05),but the increasing trend for other parameters was reduced( P < 0. 05). Conclusions:NLRP3 inflammasome participates in the development of TNBS-induced colitis in rats. Fp might alleviate colonic inflammation by inhibiting NLRP3 inflammasome and its downstream effectors.