Deficient Chaperone-Mediated Autophagy in Macrophage Aggravates Inflammation of Nonalcoholic Steatohepatitis by Targeting Nup85.

BACKGROUND & AIMS: Nonalcoholic steatohepatitis (NASH), a more severe subtype of non-alcoholic fatty liver disease, can cause cirrhosis and hepatocellular carcinoma. Macrophages play critical roles in initiating and maintaining NASH-induced liver inflammation and fibrosis. However, the underlying molecular mechanism of macrophage chaperone-mediated autophagy (CMA) in NASH remains unclear. We aimed to investigate the effects of macrophage-specific CMA on liver inflammation and identify a potential therapeutic target for NASH treatment.

METHODS: The CMA function of liver macrophages was detected using western blot, quantitative reverse transcription-polymerase chain reaction (RT-qPCR) and flow cytometry. By constructing myeloid-specific CMA deficiency mice, we evaluated the effects of deficient CMA of macrophages on monocyte recruitment, liver injury, steatosis and fibrosis in NASH mice. A label-free mass spectrometry was utilised to screen the substrates of CMA in macrophages and their mutual interactions. The association between CMA and its substrate was further examined by immunoprecipitation, western blot and RT-qPCR.

RESULTS: A typical hallmark in murine NASH models was impaired CMA function in hepatic macrophages. Monocyte-derived macrophages (MDM) were the dominant macrophage population in NASH, and CMA function was impaired in MDM. CMA dysfunction aggravated liver-targeted recruitment of monocyte and promoted steatosis, fibrosis. Mechanistically, Nup85 functions as a substrate for CMA and its degradation was inhibited in CMA-deficient macrophages. Inhibition of Nup85 attenuated the steatosis and monocyte recruitment caused by CMA deficiency in NASH mice.

CONCLUSIONS: We proposed that the impaired CMA-induced Nup85 degradation aggravated monocyte recruitment, promoting liver inflammation and disease progression of NASH.