The Mechanism Of Piperine On Suppressing ATP-induced Pyroptosis And Bacterial Sepsis

Aim:Piperine is a phytochemical present in black pepper(Piper nigrum Linn),Piper longum Linn and other related herbs,which possesses a wide array of pharmacological activities,including anti-tumor,anti-depression,anti-epileptic activities.In recent years,researches have shown that piperine has therapeutic effects on bacterial sepsis in mice,but the underlying mechanism has not been fully elucidated.In this study,in order to investigate whether piperine suppresses inflammasome activation and pyroptosis,mouse bone marrow-derived macrophages(BMDMs)and J774 A.1 cells were primed with LPS,followed by ATP stimulation.Piperine was pretreated before LPS and ATP treatment in these in vitro cellular models.In vivo,mice were intraperitoneally infected with live Escherichia coli,and inflammasome activation was evaluated by release of active caspase-1p10,mature IL-1? and HMGB1.And piperine was given intragastrically to the mice to evaluate its anti-septic effects.Methods:The effects of piperine and metformin on ATP-induced pyroptosis in BMDMs and J774 A.1 cell line were evaluated by propidium iodide(PI)staining assay.Western blotting analysis was used to detect the levels of mature IL-1?,caspase-1p10 and HMGB1 in cell culture supernatants and cell lysates.Cytometric beads array(CBA)was used to evaluate the levels of IL-1? in cell culture supernatants.Mice were intraperitoneally infected with live Escherichia coli serving as sepsis models,and CBA was used to detect the levels of IL-1? in serum and peritoneal lavage fluids.Western blotting analysis was used to evaluate the expression of pro-IL-1? and IL-1? in colonic tissues.Results:Piperine could inhibit ATP-induced pyroptosis of BMDM and J774 A.1 cells in dose-dependent manners,as well as suppress IL-1? and caspase-1 release from these cells.Piperine could enhance the mTORC1 activity and suppress the AMPK activity induced by LPS and ATP treatment.Metformin counteracted the effect of piperine on suppressing ATP-induced pyroptosis.Piperine administration reduced systemic IL-1? release in mouse bacterial sepsis.Conclusions:Piperine could inhibit pyroptosis and IL-1? release both in vitro and in vivo,and protect macrophages from pyroptosis by suppressing ATP-induced AMPK activation.Piperine treatment may inhibit bacterial sepsis by suppressing the activation of NLRP3 inflammasome activation,thus suppressing the release of IL-1?.The anti-inflammatory effect of piperine may have connection with enhancing the activity of mTORC1 and suppressing the over activation of AMPK induced by inflammatory stimulation.