The immunoresponsive gene 1 （IRG 1） protein has crucial functions in embryonic implantation and neurodegeneration. IRG1 promotes endotoxin tolerance by increasing A20 expression in macrophages through reactive oxyge...The immunoresponsive gene 1 （IRG 1） protein has crucial functions in embryonic implantation and neurodegeneration. IRG1 promotes endotoxin tolerance by increasing A20 expression in macrophages through reactive oxygen species （ROS）. The cytoprotective protein heme oxygenase-1 （HO-1）, which generates endogenous carbon monoxide （CO）, is expressed in the lung during Lipopolysaccharide （LPS） tolerance and cross tolerance. However, the detailed molecular mechanisms and functional links between IRG1 and HO-1 in the innate immune system remain unknown. In the present study, we found that the CO releasing molecule-2 （CORM-2） and chemical inducers of HO- 1 increased I RG 1 expression in a time- and dose-dependent fashion in RAW264.7 cells. Furthermore, inhibition of HO-1 activity by zinc protoporphyrin IX （ZnPP） and HO-1 siRNA significantly reduced expression of IRG1 under these conditions. In addition, treatment with CO and HO-1 induction significantly increased A20 expression, which was reversed by ZnPP and HO-1 siRNA. LPS-stimulated TNF-a was significantly decreased, whereas IRG1 and A20 were increased by CORM-2 application and HO-1 induction, which in turn were abrogated by ZnPP. Interestingly, siRNA against IRG1 and A20 reversed the effects of CO and HO-1 on LPS-stimulated TNF-a production. Additionally, CO and HO-1 inducers significantly increased IRG1 and A20 expression and downregulated TNF-a production in a LPS-stimulated sepsis mice model. Furthermore, the effects of CO and HO-1 on TNF-α production were significantly reversed when ZnPP was administered. In conclusion, CO and HO-1 induction regulates IRG1 and A20 expression, leading to inhibition of inflammation in vitroand in an in vivomice model.展开更多
Inflammatory bowel disease(IBD)is a chronic relapsing gastrointestinal disorder,while the treatment effect is not satisfactory.Immune responsive gene 1(IRG1)is a highly ex-pressed gene in macrophage in response to inf...Inflammatory bowel disease(IBD)is a chronic relapsing gastrointestinal disorder,while the treatment effect is not satisfactory.Immune responsive gene 1(IRG1)is a highly ex-pressed gene in macrophage in response to inflammatory response and catalyzes the production of itaconate.Studies have reported that IRG1/itaconate has a significant antioxidant effect.This study aimed to investigate the effect and mechanism of IRG1/itaconate on dextran sulfate so-dium(DSS)-induced colitis in vivo and in vitro.In vivo experiments,we found IRG1/itaconate ex-erted protective effects against acute colitis by increasing mice weight,the length of colon,reducing disease activity index and colonic inflammation.Meanwhile,IRG1 deletion aggravated the macrophages/CD4+/CD8+T-cell accumulation,and increased the release of interleukin(IL)-1b,tumor necrosis factor-a(TNF-a),IL-6,the activation of nuclear factor-kB(NF-kB)/mitogen-activated protein kinase(MAPK)signaling pathway,and gasdermin D(GSDMD)mediated pyrop-tosis.Four-octyl itaconate(4-OI),a derivative of itaconate,attenuated these changes,therefore relieved DSS-induced colitis.In vitro experiment,we found 4-OI inhibited the reactive oxygen species production,thereby inhibiting the activation of MAPK/NF-kB signaling pathway in RAW264.7 and murine bone-marrow-derived macrophages.Simultaneously,we found 4-OI inhib-ited caspase1/GSDMD-mediated pyroptosis to reduce the release of cytokines.Finally,we found anti-TNF-a agent reduced the severity of DSS-induced colitis and inhibited gasdermin E(GSDME)-mediated pyroptosis in vivo.Meanwhile,our study revealed that 4-OI inhibited caspase3/GSDME-mediated pyroptosis induced by TNF-a in vitro.Taken together,IRG1/itaconate exerted a pro-tective role in DSS-induced colitis by inhibiting inflammatory response and GSDMD/GSDME-medi-ated pyroptosis,which could be a promising candidate for IBD therapy.展开更多
文摘The immunoresponsive gene 1 （IRG 1） protein has crucial functions in embryonic implantation and neurodegeneration. IRG1 promotes endotoxin tolerance by increasing A20 expression in macrophages through reactive oxygen species （ROS）. The cytoprotective protein heme oxygenase-1 （HO-1）, which generates endogenous carbon monoxide （CO）, is expressed in the lung during Lipopolysaccharide （LPS） tolerance and cross tolerance. However, the detailed molecular mechanisms and functional links between IRG1 and HO-1 in the innate immune system remain unknown. In the present study, we found that the CO releasing molecule-2 （CORM-2） and chemical inducers of HO- 1 increased I RG 1 expression in a time- and dose-dependent fashion in RAW264.7 cells. Furthermore, inhibition of HO-1 activity by zinc protoporphyrin IX （ZnPP） and HO-1 siRNA significantly reduced expression of IRG1 under these conditions. In addition, treatment with CO and HO-1 induction significantly increased A20 expression, which was reversed by ZnPP and HO-1 siRNA. LPS-stimulated TNF-a was significantly decreased, whereas IRG1 and A20 were increased by CORM-2 application and HO-1 induction, which in turn were abrogated by ZnPP. Interestingly, siRNA against IRG1 and A20 reversed the effects of CO and HO-1 on LPS-stimulated TNF-a production. Additionally, CO and HO-1 inducers significantly increased IRG1 and A20 expression and downregulated TNF-a production in a LPS-stimulated sepsis mice model. Furthermore, the effects of CO and HO-1 on TNF-α production were significantly reversed when ZnPP was administered. In conclusion, CO and HO-1 induction regulates IRG1 and A20 expression, leading to inhibition of inflammation in vitroand in an in vivomice model.
基金supported by the National Natural Science Foundation of China(No.81701883,82072736,82172171)。
文摘Inflammatory bowel disease(IBD)is a chronic relapsing gastrointestinal disorder,while the treatment effect is not satisfactory.Immune responsive gene 1(IRG1)is a highly ex-pressed gene in macrophage in response to inflammatory response and catalyzes the production of itaconate.Studies have reported that IRG1/itaconate has a significant antioxidant effect.This study aimed to investigate the effect and mechanism of IRG1/itaconate on dextran sulfate so-dium(DSS)-induced colitis in vivo and in vitro.In vivo experiments,we found IRG1/itaconate ex-erted protective effects against acute colitis by increasing mice weight,the length of colon,reducing disease activity index and colonic inflammation.Meanwhile,IRG1 deletion aggravated the macrophages/CD4+/CD8+T-cell accumulation,and increased the release of interleukin(IL)-1b,tumor necrosis factor-a(TNF-a),IL-6,the activation of nuclear factor-kB(NF-kB)/mitogen-activated protein kinase(MAPK)signaling pathway,and gasdermin D(GSDMD)mediated pyrop-tosis.Four-octyl itaconate(4-OI),a derivative of itaconate,attenuated these changes,therefore relieved DSS-induced colitis.In vitro experiment,we found 4-OI inhibited the reactive oxygen species production,thereby inhibiting the activation of MAPK/NF-kB signaling pathway in RAW264.7 and murine bone-marrow-derived macrophages.Simultaneously,we found 4-OI inhib-ited caspase1/GSDMD-mediated pyroptosis to reduce the release of cytokines.Finally,we found anti-TNF-a agent reduced the severity of DSS-induced colitis and inhibited gasdermin E(GSDME)-mediated pyroptosis in vivo.Meanwhile,our study revealed that 4-OI inhibited caspase3/GSDME-mediated pyroptosis induced by TNF-a in vitro.Taken together,IRG1/itaconate exerted a pro-tective role in DSS-induced colitis by inhibiting inflammatory response and GSDMD/GSDME-medi-ated pyroptosis,which could be a promising candidate for IBD therapy.
