Regulatory effects of lactic acid bacteria on the secretion of LPS-induced inflammatory cytokines in THP-1 cells

Objective:To explore the regulatory effects of lactic acid bacteria on the secretion of tumor necrosis factor(TNF)-α,interleukin(IL)-12 p40 and transforming growth factor(TGF)-β in THP-1 cells induced by lipopolysaccharide(LPS).Methods:THP-1 cells were firstly stimulated by phorbol 12-myristate 13-acetate(PMA) to differentiate into macrophage-like cells,and were secondly treated by LPS to induce inflammatory cytokines.Six groups were designed,including blank control group,LPS-treated group,L.para-treated alone group,L.para plus LPS-treated group,L.acid-treated alone group and L.acid plus LPS-treated group.The levels of TNF-α mRNA in THP-1 cells were determined by RT-PCR.TNF-α,IL-12 p40 and TGF-β in the supernatant of THP-1 cells were assayed by ELISA.The subcellular localization of NF-κB p65 was observed by immunofluorescence,while the quantitation of NF-κB(p65/p50) in THP-1 nucleus was detected by TransAMTM NF-κB kit.Results:① The secretions of TNF-α,IL-12 p40 and TGF-β in PMA-induced macrophage-like THP-1 cells were remarkably increased when treated by LPS,the same as L.para or L.acid treated alone respectively.However,TNF-α and IL-12 p40 in L.para-treated alone group were lower than those in LPS-treated group,whereas TNF-α and IL-12 p40 in L.acid-treated alone group were similar to the LPS-treated group.TGF-β induced by L.para or L.acid was strikingly higher than that of LPS.Interestingly,TNF-α and IL-12 p40 in PMA-induced macrophage-like THP-1 cells stimulated by LPS were notably inhibited when cells were treated with L.para plus LPS or L.acid plus LPS.TNF-α and IL-12 p40 in L.para plus LPS-treated group were much lower than in LPS-treated group.No inhibition of TGF-β were observed in PMA-induced macrophage-like THP-1 cells when treated with both lactobacilli.② Similar to result one,phosphorylation of IκB-α and nuclear NF-κB(p65/p50) in PMA-induced macrophage-like THP-1 cells increased in LPS-treated group,L.para-treated alone group and L.acid-treated alone group,while non-phosphorylation of IκB-α accordingly decreased.The regulatory effect of L.para was a little weaker than L.acid.Phosphorylation of IκB-α and nuclear translocation of NF-κB were significantly reduced in PMA-induced macrophage-like THP-1 cells when treated with L.para plus LPS or L.acid plus LPS.Conclusion:L.para and L.acid can inhibit the secretion of LPS-induced inflammatory cytokines TNF-α and IL-12 p40 when they interacted with LPS respectively.The negative regulation of lactic acid bacteria was related to inhibition of NF-κB signaling.Besides,the regulatory effects of lactic acid bacteria were evidently different among species.