bims-inflin 2023-08-20 papers

Cell Mol Immunol. 2023 Aug 17.

cFLIPS regulates alternative NLRP3 inflammasome activation in human monocytes.

Yuhui Gao, Shi Yu, Mengdan Chen, Xun Wang, Lei Pan, Bin Wei, Guangxun Meng.

The innate immune responses, including inflammasome activation, are paramount for host defense against pathogen infection. In contrast to canonical and noncanonical inflammasome activation, in this study, heat-killed gram-negative bacteria (HK bacteria) were identified as single-step stimulators of the NLRP3 inflammasome in human monocytes, and they caused a moderate amount of IL-1β to be released from cells. Time course experiments showed that this alternative inflammasome response was finished within a few hours. Further analysis showed that the intrinsically limited NLRP3 inflammasome activation response was due to the negative regulation of caspase-8 by the short isoform of cFLIP (cFLIPs), which was activated by NF-κB. In contrast, overexpressed cFLIPS, but not overexpressed cFLIPL, inhibited the activation of caspase-8 and the release of IL-1β in response to HK bacteria infection in human monocytes. Furthermore, we demonstrated that TAK1 activity mediated the expression of cFLIPs and was upstream and essential for the caspase-8 cleavage induced by HK bacteria in human monocytes. The functional specificity of cFLIPs and TAK1 revealed unique responses of human monocytes to a noninvasive pathogen, providing novel insights into an alternative regulatory pathway of NLRP3 inflammasome activation.

Keywords: NLRP3 inflammasome; cFLIPS; gram-negative bacteria; human monocyte

DOI: https://doi.org/10.1038/s41423-023-01077-y

EMBO J. 2023 Aug 14. e113481

MARCH5-dependent NLRP3 ubiquitination is required for mitochondrial NLRP3-NEK7 complex formation and NLRP3 inflammasome activation.

Yeon-Ji Park, Niranjan Dodantenna, Yonghyeon Kim, Tae-Hwan Kim, Ho-Soo Lee, Young-Suk Yoo, June Heo, Jae-Ho Lee, Myung-Hee Kwon, Ho Chul Kang, Jong-Soo Lee, Hyeseong Cho.

The NLRP3 inflammasome plays a key role in responding to pathogens, and endogenous damage and mitochondria are intensively involved in inflammasome activation. The NLRP3 inflammasome forms multiprotein complexes and its sequential assembly is important for its activation. Here, we show that NLRP3 is ubiquitinated by the mitochondria-associated E3 ligase, MARCH5. Myeloid cell-specific March5 conditional knockout (March5 cKO) mice failed to secrete IL-1β and IL-18 and exhibited an attenuated mortality rate upon LPS or Pseudomonas aeruginosa challenge. Macrophages derived from March5 cKO mice also did not produce IL-1β and IL-18 after microbial infection. Mechanistically, MARCH5 interacts with the NACHT domain of NLRP3 and promotes K27-linked polyubiquitination on K324 and K430 residues of NLRP3. Ubiquitination-defective NLRP3 mutants on K324 and K430 residues are not able to bind to NEK7, nor form NLRP3 oligomers leading to abortive ASC speck formation and diminished IL-1β production. Thus, MARCH5-dependent NLRP3 ubiquitination on the mitochondria is required for NLRP3-NEK7 complex formation and NLRP3 oligomerization. We propose that the E3 ligase MARCH5 is a regulator of NLRP3 inflammasome activation on the mitochondria.

Keywords: MARCH5; NEK7; NLRP3 inflammasome; mitochondria; ubiquitination

DOI: https://doi.org/10.15252/embj.2023113481

Parasit Vectors. 2023 Aug 14. 16(1): 280

Inhibition of GSDMD-mediated pyroptosis triggered by Trichinella spiralis intervention contributes to the alleviation of DSS-induced ulcerative colitis in mice.

Zhen-Rong Ma, Zhuo-Lin Li, Ni Zhang, Bin Lu, Xuan-Wu Li, Ye-Hong Huang, Dibo Nouhoum, Xian-Shu Liu, Ke-Chun Xiao, Li-Ting Cai, Shao-Rui Xu, Xue-Xian O Yang, Shuai-Qin Huang, Xiang Wu.

BACKGROUND: Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is increasing worldwide. Although there is currently no completely curative treatment, helminthic therapy shows certain therapeutic potential for UC. Many studies have found that Trichinella spiralis (T.s) has a protective effect on UC, but the specific mechanism is still unclear.
METHODS: Balb/c mice drank dextran sulfate sodium (DSS) to induce acute colitis and then were treated with T.s. In vitro experiments, the LPS combination with ATP was used to induce the pyroptosis model, followed by intervention with crude protein from T.s (T.s cp). Additionally, the pyroptosis agonist of NSC or the pyroptosis inhibitor vx-765 was added to intervene to explore the role of pyroptosis in DSS-induced acute colitis. The degree of pyroptosis was evaluated by western blot, qPCR and IHC, etc., in vivo and in vitro.
RESULTS: T.s intervention significantly inhibited NLRP3 inflammasome activation and GSDMD-mediated pyroptosis by downregulating the expression of pyroptosis-related signatures in vitro (cellular inflammatory model) and in vivo (DSS-induced UC mice model). Furthermore, blockade of GSDMD-mediated pyroptosis by the caspase-1 inhibitor vx-765 has a similar therapeutic effect on DSS-induced UC mice with T.s intervention, thus indicating that T.s intervention alleviated DSS-induced UC in mice by inhibiting GSDMD-mediated pyroptosis.
CONCLUSION: This study showed that T.s could alleviate the pathological severity UC via GSDMD-mediated pyroptosis, and it provides new insight into the mechanistic study and application of helminths in treating colitis.

Keywords: GSDMD-mediated pyroptosis; Inhibition; Protective effect; Trichinella spiralis; Ulcerative colitis

DOI: https://doi.org/10.1186/s13071-023-05857-3