Macrophage OTUD1‐CARD9 axis drives isoproterenol‐induced inflammatory heart remodelling.

Background: Chronic inflammation contributes to the progression of isoproterenol (ISO)‐induced heart failure (HF). Caspase‐associated recruitment domain (CARD) families are crucial proteins for initiation of inflammation in innate immunity. Nonetheless, the relevance of CARDs in ISO‐driven cardiac remodelling is little explored. Methods: This study utilized Card9−/− mice and reconstituted C57BL/6 mice with either Card9−/− or Otud1−/− marrow‐derived cells. Mechanistic studies were conducted in primary macrophages, cardiomyocytes, fibroblasts and HEK‐293T cells. Results: Here, we demonstrated that CARD9 was substantially upregulated in murine hearts infused with ISO. Either whole‐body CARD9 knockout or myeloid‐specific CARD9 deletion inhibited ISO‐driven murine cardiac inflammation, remodelling and dysfunction. CARD9 deficiency in macrophages prevented ISO‐induced inflammation and alleviated remodelling changes in cardiomyocytes and fibroblasts. Mechanistically, we found that ISO enhances the activity of CARD9 by upregulating ovarian tumour deubiquitinase 1 (OTUD1) in macrophages. We further demonstrated that OTUD1 directly binds to the CARD9 and then removes the K33‐linked ubiquitin from CARD9 to promote the assembly of the CARD9‐BCL10‐MALT1 (CBM) complex, without affecting CARD9 stability. The ISO‐activated CBM complex results in NF‐κB activation and macrophage‐based inflammatory gene overproduction, which then enhances cardiomyocyte hypertrophy and fibroblast fibrosis, respectively. Myeloid‐specific OTUD1 deletion also attenuated ISO‐induced murine cardiac inflammation and remodelling. Conclusions: These results suggested that the OTUD1‐CARD9 axis is a new pro‐inflammatory signal in ISO‐challenged macrophages and targeting this axis has a protective effect against ISO‐induced HF. Key points: Macrophage CARD9 was elevated in heart tissues of mice under chronic ISO administration.Either whole‐body CARD9 knockout or myeloid‐specific CARD9 deficiency protected mice from ISO‐induced inflammatory heart remodeling.ISO promoted the assembly of CBM complex and then activated NF‐κB signaling in macrophages through OTUD1‐mediated deubiquitinating modification.OTUD1 deletion in myeloid cells protected hearts from ISO‐induced injuries in mice. [ABSTRACT FROM AUTHOR]