Dataset Information

Caspase 6 promotes innate immune activation by functional crosstalk between RIPK1-IκBα axis in liver inflammation.

ABSTRACT:

Background

Caspase 6 is an essential regulator in innate immunity, inflammasome activation and host defense. We aimed to characterize the causal mechanism of Caspase 6 in liver sterile inflammatory injury.

Methods

Human liver tissues were harvested from patients undergoing ischemia-related hepatectomy to evaluate Caspase 6 expression. Subsequently, we created Caspase 6-knockout (Caspase 6^KO) mice to analyze roles and molecular mechanisms of macrophage Caspase 6 in murine models of liver ischemia/reperfusion (IR) injury.

Results

In human liver biopsies, Caspase 6 expression was positively correlated with more severe histopathological injury and higher serum ALT/AST level at one day postoperatively. Moreover, Caspase 6 was mainly elevated in macrophages but not hepatocytes in ischemic livers. Unlike in controls, the Caspase 6-deficient livers were protected against IR injury, as evidenced by inhibition of inflammation, oxidative stress and iron overload. Disruption of macrophage NF-κB essential modulator (NEMO) in Caspase 6-deficient livers deteriorated liver inflammation and ferroptosis. Mechanistically, Caspase 6 deficiency spurred NEMO-mediated IκBα phosphorylation in macrophage. Then phosphorylated-inhibitor of NF-κBα (p-IκBα) co-localized with receptor-interacting serine/ threonine-protein kinase 1 (RIPK1) in the cytoplasm to degradate RIPK1 under inflammatory conditions. The disruption of RIPK1-IκBα interaction preserved RIPK1 degradation, triggering downstream apoptosis signal-regulating kinase 1 (ASK1) phosphorylation and inciting NIMA-related kinase 7/NOD-like receptor family pyrin domain containing 3 (NEK7/NLRP3) activation in macrophages. Moreover, ablation of macrophage RIPK1 or ASK1 diminished NEK7/NLRP3-driven inflammatory response and dampened hepatocyte ferroptosis by reducing HMGB1 release from macrophages.

Conclusions

Our findings underscore a novel mechanism of Caspase 6 mediated RIPK1-IκBα interaction in regulating macrophage NEK7/NLRP3 function and hepatocytes ferroptosis, which provides therapeutic targets for clinical liver IR injury. Video Abstract.

SUBMITTER: Lin Y

PROVIDER: S-EPMC10568785 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature

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Caspase 6 promotes innate immune activation by functional crosstalk between RIPK1-IκBα axis in liver inflammation.

Lin Yuanbang Y Sheng Mingwei M Qin Hua H Zhang Peng P Wang Chunli C Fu Wei W Meng Xiangjun X Wang Duowei D Hou Yachao Y

Cell communication and signaling : CCS 20231012 1

<h4>Background</h4>Caspase 6 is an essential regulator in innate immunity, inflammasome activation and host defense. We aimed to characterize the causal mechanism of Caspase 6 in liver sterile inflammatory injury.<h4>Methods</h4>Human liver tissues were harvested from patients undergoing ischemia-related hepatectomy to evaluate Caspase 6 expression. Subsequently, we created Caspase 6-knockout (Caspase 6<sup>KO</sup>) mice to analyze roles and molecular mechanisms of macrophage Caspase 6 in murin ...[more]

PMID: 37828624

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Project description:Upregulation of protein neddylation occurs in numerous types of human cancer, including liver cancer. MLN4924, a potent neddylation‑inhibiting pharmacological agent, demonstrates anticancer ability in numerous cancers. However, the sensitivity of MLN4924 in liver cancer remains unsatisfactory due to factors causing resistance. RT‑qPCR and western blotting were utilized to assess the mRNA and protein levels of genes, respectively. Cell Counting Kit‑8 assay and colony formation assays were employed to assess cell viability and proliferation. The pathway of protein degradation and stability were determined by western blotting after treatment with MG132 and cycloheximide. An immunoprecipitation assay was utilized to detect the ubiquitination of protein. An in vitro ubiquitination assay was used to determine the ubiquitin linkage. To the best of our knowledge, the present study was the first to demonstrate that NF‑κB inhibitor α (IκBα) downregulation and subsequent inflammation in response to MLN4924 limited the antitumor potential of MLN4924. Ectopic expression of IκBα enhanced the antitumor potential of MLN4924 in liver cancer cells. Moreover, the results of the present study demonstrated that MLN4924 decreased IκBα via promoting the K48 linkage of ubiquitin to IκBα. Mechanistic studies demonstrated that MLN4924 enhanced the protein stability of β‑transducin repeat‑containing protein (β‑TrCP), promoting the ubiquitination of IκBα, which led to the ubiquitin‑mediated degradation of IκBα. In addition, the results of the present study also demonstrated that β‑TrCP knockdown markedly inhibited MLN4924 from suppressing the growth of liver cancer cells, via attenuating MLN4924‑mediated IκBα downregulation and inflammation. Collectively, these results indicated that the β‑TrCP/IκBα/inflammation pathway may act as a novel resistance factor of MLN4924, and targeting β‑TrCP may be beneficial for the treatment of liver cancer.

Project description:Background & aimsGlycogen synthase kinase 3β (Gsk3β [Gsk3b]) is a ubiquitously expressed kinase with distinctive functions in different types of cells. Although its roles in regulating innate immune activation and ischaemia and reperfusion injuries (IRIs) have been well documented, the underlying mechanisms remain ambiguous, in part because of the lack of cell-specific tools in vivo.MethodsWe created a myeloid-specific Gsk3b knockout (KO) strain to study the function of Gsk3β in macrophages in a murine liver partial warm ischaemia model.ResultsCompared with controls, myeloid Gsk3b KO mice were protected from IRI, with diminished proinflammatory but enhanced anti-inflammatory immune responses in livers. In bone marrow-derived macrophages, Gsk3β deficiency resulted in an early reduction of Tnf gene transcription but sustained increase of Il10 gene transcription on Toll-like receptor 4 stimulation in vitro. These effects were associated with enhanced AMP-activated protein kinase (AMPK) activation, which led to an accelerated and higher level of induction of the novel innate immune negative regulator small heterodimer partner (SHP [Nr0b2]). The regulatory function of Gsk3β on AMPK activation and SHP induction was confirmed in wild-type bone marrow-derived macrophages with a Gsk3 inhibitor. Furthermore, we found that this immune regulatory mechanism was independent of Gsk3β Ser9 phosphorylation and the phosphoinositide 3-kinase-Akt signalling pathway. In vivo, myeloid Gsk3β deficiency facilitated SHP upregulation by ischaemia-reperfusion in liver macrophages. Treatment of Gsk3b KO mice with either AMPK inhibitor or SHP small interfering RNA before the onset of liver ischaemia restored liver proinflammatory immune activation and IRI in these otherwise protected hosts. Additionally, pharmacological activation of AMPK protected wild-type mice from liver IRI, with reduced proinflammatory immune activation. Inhibition of the AMPK-SHP pathway by liver ischaemia was demonstrated in tumour resection patients.ConclusionsGsk3β promotes innate proinflammatory immune activation by restraining AMPK activation.Lay summaryGlycogen synthase kinase 3β promotes macrophage inflammatory activation by inhibiting the immune regulatory signalling of AMP-activated protein kinase and the induction of small heterodimer partner. Therefore, therapeutic targeting of glycogen synthase kinase 3β enhances innate immune regulation and protects liver from ischaemia and reperfusion injury.

Dataset Information

Caspase 6 promotes innate immune activation by functional crosstalk between RIPK1-IκBα axis in liver inflammation.

Background

Methods

Results

Conclusions

Publications

Caspase 6 promotes innate immune activation by functional crosstalk between RIPK1-IκBα axis in liver inflammation.

Similar Datasets

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