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Card9 protects sepsis by regulating Ripk2-mediated activation of NLRP3 inflammasome in macrophages.

ABSTRACT: Sepsis is characterized by systemic inflammation, it's caused by primary infection of pathogenic microorganisms or secondary infection of damaged tissue. In this study, we focus on sepsis-induced intestine barrier functional disturbalice, presenting as increased permeability of intestinal epithelium. We observed that the phenotype of LPS-induced sepsis was exacerbated in Card9^-/- mice, especially displaying more serious intestinal inflammation and gut barrier dysfunction. Next, we found the hyperactivation of NLRP3 inflammasome in the intestinal macrophages of Card9^-/--sepsis mice. Moreover, Card9 over-expression decreased NLRP3 inflammasome activation in macrophages. Furthermore, we found that Card9 inhibited NLRP3 inflammasome activation by recruiting Ripk2. The competitive binding between Ripk2 with Caspase-1, instead of ASC with Caspase-1, inhibited the NLRP3 inflammasome activation. Over-expression of Ripk2 alleviated septic intestinal injury caused by Card9 deficiency. Taken together, we suggested Card9 acts as a negative regulation factor of NLRP3 inflammasome activation, which protects against intestinal damage during sepsis. Therefore, maintaining Card9-Ripk2 signaling homeostasis may provide a novel therapy of septic intestinal damage.

SUBMITTER: Xu Z

PROVIDER: S-EPMC9135688 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Card9 protects sepsis by regulating Ripk2-mediated activation of NLRP3 inflammasome in macrophages.

Xu Zhen Z Li Daoqian D Qu Wei W Yin Yuxin Y Qiao Shuping S Zhu Yanan Y Shen Sunan S Hou Yayi Y Yang Jie J Wang Tingting T

Cell death & disease 20220526 5

Sepsis is characterized by systemic inflammation, it's caused by primary infection of pathogenic microorganisms or secondary infection of damaged tissue. In this study, we focus on sepsis-induced intestine barrier functional disturbalice, presenting as increased permeability of intestinal epithelium. We observed that the phenotype of LPS-induced sepsis was exacerbated in Card9<sup>-/-</sup> mice, especially displaying more serious intestinal inflammation and gut barrier dysfunction. Next, we fou ...[more]

PMID: 35618701

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Project description:The NLRP3 inflammasome plays a critical role in mediating the innate immune defense against pathogenic infections, but aberrant activation of NLRP3 inflammasome has been linked to a variety of inflammatory diseases. Thus targeting the NLRP3 inflammasome represents a promising therapeutic for the treatment of such diseases. Scutellarin is a flavonoid isolated from Erigeron breviscapus (Vant.) Hand.-Mazz. and has been reported to exhibit potent anti-inflammatory activities, but the underlying mechanism is only partly understood. In this study, we aimed to investigate whether scutellarin could affect the activation of NLRP3 inflammasome in macrophages. The results showed that scutellarin dose-dependently reduced caspase-1 activation and decreased mature interleukin-1β (IL-1β) release in lipopolysaccharide (LPS)-primed macrophages upon ATP or nigericin stimulation, indicating that scutellarin inhibited NLRP3 inflammasome activation in macrophages. Consistent with this, scutellarin also suppressed pyroptotic cell death in LPS-primed macrophages treated with ATP or nigericin. ATP or nigericin-induced ASC speck formation and its oligomerization were blocked by scutellarin pre-treatment. Intriguingly, scutellarin augmented PKA-specific phosphorylation of NLRP3 in LPS-primed macrophages, which was completely blocked by selective PKA inhibitor H89, suggesting that PKA signaling had been involved in the action of scutellarin to suppress NLRP3 inflammasome activation. Supporting this, the inhibitory effect of scutellarin on NLRP3 inflammasome activation was completely counteracted by H89 or adenyl cyclase inhibitor MDL12330A. As NLRP3-dependent release of IL-1β has a critical role in sepsis, the in vivo activity of scutellarin was assayed in a mouse model of bacterial sepsis, which was established by intraperitoneally injection of a lethal dose of viable Escherichia coli. Oral administration of scutellarin significantly improved the survival of mice with bacterial sepsis. In line with this, scutellarin treatment significantly reduced serum IL-1β levels and attenuated the infiltration of inflammatory cells in the liver of E. coli-infected mice. These data indicated that scutellarin suppressed NLRP3 inflammasome activation in macrophages by augmenting PKA signaling, highlighting its potential therapeutic application for treating NLRP3-related inflammatory diseases.

Project description:Macrophages are a type of innate immune cell that activates the NLRP3 inflammasome, causing the release of the cytokine IL-1β, which is a crucial mediator of the inflammatory response. NLRP3 activation that is dysregulated worsens a variety of inflammatory and autoimmune diseases, as well as neurodegenerative diseases. Oleamide is an endogenous fatty acid amide that was first determined as a sleep-inducing molecule and later shown to have wide-ranging beneficial effects on the central nervous system. How oleamide influences human macrophage polarization and NLRP3-inflammasome activation remains unclear. The effect of oleamide on macrophage polarization was explored using an in vitro culture of primary human monocyte-derived macrophages (MDMs) supplemented with human serum-containing media. Cellular and molecular mechanisms of oleamide-regulated MDMs polarization were also investigated. Results showed that oleamide promoted naïve macrophages (M0) toward the M1 phenotype by upregulating M1-associated genes (IL-1β, iNOS, CXCL10), along with downregulation of M2-associated genes (Arg-1, CD206, CCL22). Cell surface expression indicated that oleamide enhanced CD80 expression in M0 naïve macrophages and hider CD206 and CD163 expression in M2 macrophages. Higher production of IL-1β cytokine was observed but with no alteration in IL-6 and TNF-α levels by MDMs and differentiated THP-1 models. Whether oleamide functioned as a second signal that activated the NLRP3 inflammasome and mediated IL-1β production was further investigated using LPS-primed MDMs followed by oleamide treatment that induced activation of inflammasome-related proteins including NLRP3, ASC, cleaved casp-1, and cleaved IL-1β. These findings suggested that oleamide promoted M1 macrophage polarization and increased IL-1β production by activating the NLRP3 inflammasome in primary MDMs. This research reveals a new function for oleamide as well as prospective targets for treating NLRP3-related inflammatory disorders.

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Card9 protects sepsis by regulating Ripk2-mediated activation of NLRP3 inflammasome in macrophages.

Publications

Card9 protects sepsis by regulating Ripk2-mediated activation of NLRP3 inflammasome in macrophages.

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