Pyroptosis in defense against intracellular bacteria

Pathogenic microbes invade the human body and trigger a host immune response to defend against the infection. In response, host-adapted pathogens employ numerous virulence strategies to overcome host defense mechanisms. As a result, the interaction between the host and pathogen is a dynamic process that shapes the evolution of the host's immune response. Among the immune responses against intracellular bacteria, pyroptosis, a lytic form of cell death, is a crucial mechanism that eliminates replicative niches for intracellular pathogens and modulates the immune system by releasing danger signals. This review focuses on the role of pyroptosis in combating intracellular bacterial infection. We examine the cell type specific roles of pyroptosis in neutrophils and intestinal epithelial cells. We discuss the regulatory mechanisms of pyroptosis, including its modulation by autophagy and interferon-inducible GTPases. Furthermore, we highlight that while host-adapted pathogens can often subvert pyroptosis, environmental microbes are effectively eliminated by pyroptosis.     

阴道毛滴虫巨噬细胞迁移抑制因子对THP⁃1巨噬细胞的作用

目的　探讨阴道毛滴虫分泌的巨噬细胞迁移抑制因子（TvMIF）对THP⁃1巨噬细胞的作用。方法　原核表达重组TvMIF蛋白并纯化，鉴定后去内毒素。采用不同浓度（0、1、5、10、50 ng/mL和100 ng/mL）重组TvMIF蛋白作用于THP⁃1巨噬细胞，用细胞计数试剂盒（cell counting kit，CCK）⁃8检测重组TvMIF蛋白对THP⁃1巨噬细胞的毒性，采用流式细胞术检测细胞凋亡和活性氧（reactive oxygen species，ROS）水平，采用实时荧光定量PCR技术（real⁃time fluorescence quantitative PCR，qPCR）检测核苷酸结合寡聚化结构域样受体蛋白（nucleotide⁃binding oligomerization domain⁃like receptor protein 3，NLRP3）、caspase⁃1、白细胞介素1β（interleukin⁃1β, IL⁃1β）、IL⁃18 mRNA表达水平变化，采用Western blotting技术检测THP⁃1巨噬细胞中caspase1、NLRP3、消化道皮肤素D（gasdermin D，GSDMD）及GSDMD蛋白氨基端裂解片段（gasdermin D N⁃terminal，GSDMD⁃NT）、pro⁃IL⁃1β蛋白表达水平变化。结果　成功表达并纯化获得分子量为15.5 kDa的重组TvMIF蛋白。内毒素检测结果显示，已去除重组TvMIF蛋白的内毒素（浓度< 0.1 EU/mL），可用于蛋白功能研究。流式细胞术检测结果显示，当重组TvMIF蛋白浓度≤ 10 ng/mL时可促进THP⁃1巨噬细胞凋亡，当TvMIF浓度为5 ng/mL时凋亡现象最为明显，当重组TvMIF蛋白浓度为50、100 ng/mL时可抑制THP⁃1巨噬细胞凋亡。当TvMIF蛋白浓度为1 ng/mL时，ROS含量明显升高。qPCR检测结果显示，1 ng/mL 重组TvMIF蛋白作用THP⁃1巨噬细胞8 h后，caspase⁃1、NLRP3、IL⁃18和IL⁃1β mRNA水平均显著上升。Western blotting检测结果显示，1 ng/mL 重组TvMIF蛋白刺激THP⁃1巨噬细胞后，caspase⁃1和NLRP3蛋白表达量显著上升，pro⁃IL⁃1β、GSDMD和GSDMD⁃NT蛋白表达量显著增加；用NLRP3炎症小体特异性抑制剂MCC950预处理后，GSDMD和GSDMD⁃NT蛋白表达水平显著下降。结论　高浓度重组TvMIF蛋白抑制THP⁃1巨噬细胞凋亡；低浓度重组TvMIF蛋白激活NLRP3炎症小体，促进THP⁃1巨噬细胞焦亡。     

Gasdermin D-mediated pyroptosis in myocardial ischemia and reperfusion injury: Cumulative evidence for future cardioprotective strategies

Cardiomyocyte death is one of the major mechanisms contributing to the development of myocardial infarction (MI) and myocardial ischemia/reperfusion (MI/R) injury. Due to the limited regenerative ability of cardiomyocytes, understanding the mechanisms of cardiomyocyte death is necessary. Pyroptosis, one of the regulated programmed cell death pathways, has recently been shown to play important roles in MI and MI/R injury. Pyroptosis is activated by damage-associated molecular patterns (DAMPs) that are released from damaged myocardial cells and activate the formation of an apoptosis-associated speck-like protein containing a CARD (ASC) interacting with NACHT, LRR, and PYD domains-containing protein 3 (NLRP3), resulting in caspase-1 cleavage which promotes the activation of Gasdermin D (GSDMD). This pathway is known as the canonical pathway. GSDMD has also been shown to be activated in a non-canonical pathway during MI and MI/R injury via caspase-4/5/11. Suppression of GSDMD has been shown to provide cardioprotection against MI and MI/R injury. Although the effects of MI or MI/R injury on pyroptosis have previously been discussed, knowledge concerning the roles of GSDMD in these settings remains limited. In this review, the evidence from in vitro, in vivo, and clinical studies focusing on cardiac GSDMD activation during MI and MI/R injury is comprehensively summarized and discussed. Implications from this review will help pave the way for a new therapeutic target in ischemic heart disease.     

Preliminary evidence for the presence of multiple forms of cell death in diabetes cardiomyopathy

Diabetic mellitus (DM) is a common degenerative chronic metabolic disease often accompanied by severe cardiovascular complications (DCCs) as major causes of death in diabetic patients with diabetic cardiomyopathy (DCM) as the most common DCC. The metabolic disturbance in DCM generates the conditions/substrates and inducers/triggers and activates the signaling molecules and death executioners leading to cardiomyocyte death which accelerates the development of DCM and the degeneration of DCM to heart failure. Various forms of programmed active cell death including apoptosis, pyroptosis, autophagic cell death, autosis, necroptosis, ferroptosis and entosis have been identified and characterized in many types of cardiac disease. Evidence has also been obtained for the presence of multiple forms of cell death in DCM. Most importantly, published animal experiments have demonstrated that suppression of cardiomyocyte death of any forms yields tremendous protective effects on DCM. Herein, we provide the most updated data on the subject of cell death in DCM, critical analysis of published results focusing on the pathophysiological roles of cell death, and pertinent perspectives of future studies.     

Targeting the mevalonate pathway suppresses ARID1A-inactivated cancers by promoting pyroptosis

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Effect of procalcitonin on lipopolysaccharide-induced expression of nucleotide-binding oligomerization domain-like receptor protein 3 and caspase-1 in human umbilical vein endothelial cells北大核心CSCD

Objective To study the effect of procalcitonin (PCT) on lipopolysaccharide (LPS)-induced expression of the pyroptosis-related proteins nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) and caspase-1 in human umbilical vein endothelial cells (HUVECs). Methods HUVECs were induced by LPS to establish a model of sepsis-induced inflammatory endothelial cell injury. The experiment was divided into two parts. In the first part, HUVECs were randomly divided into four groups: normal control, LPS (1 μg/mL), PCT (10 ng/mL), and LPS+PCT (n=3 each). In the second part, HUVECs were randomly grouped: normal control, LPS, and LPS+PCT of different concentrations (0.1, 1, 10, and 100 ng/mL) (n=3 each). Quantitative real-time PCR and Western blot were used to measure the mRNA and protein expression levels of NLRP3 and caspase-1 in each group. Results In the first experiment: compared with the normal control group, the PCT, LPS, and LPS+PCT groups had significantly upregulated mRNA and protein expression levels of NLRP3 and caspase-1 (P<0.05); compared with the LPS group, the LPS+PCT group had significantly downregulated mRNA and protein expression levels of NLRP3 and caspase-1 (P<0.05). In the second experiment: compared with those in the LPS group, the mRNA and protein expression levels of NLRP3 and caspase-1 in the LPS+PCT of different concentrations groups were significantly downregulated in a concentration-dependent manner (P<0.05). Conclusions LPS can promote the expression of the pyroptosis-related proteins NLRP3 and caspase-1 in HUVECs, while PCT can inhibit the LPS-induced expression of the pyroptosis-related proteins NLRP3 and caspase-1 in HUVECs in a concentration-dependent manner. © 2023 Xiangya Hospital of CSU. All rights reserved.