Advanced oxidation protein products impair autophagic flux in macrophage by inducing lysosomal dysfunction via activation of PI3K-Akt-mTOR pathway in Crohn's disease.

Abstract Dysfunction in macrophages is involved in the pathogenesis of various diseases, including Crohn's disease (CD). Previously, we found that advanced oxidation protein products (AOPPs) were predominantly deposited in macrophages in the intestinal lamina propria of CD patients. However, whether AOPPs contributes to macrophage dysfunction in CD and the underlying mechanism remains unknown. This study aimed to investigate the effects of AOPPs on macrophages functions in CD. In the present study, we discovered increased AOPPs levels were positively correlated with impaired autophagy in macrophages of CD patients. AOPPs could impair autophagic flux by inducing lysosomal dysfunction in RAW264.7 cell line and macrophages in AOPPs-treated mice, evidenced by increased number of autophagosomes, blocked degradation of autophagy-related proteins (LC3B-II and SQSTM1/p62), and decreased activity of lysosomal proteolytic enzymes after AOPPs challenge. Besides, AOPPs could also promote M1 polarization in RAW264.7 cells and bone marrow derived macrophages (BMDMs) in AOPPs-treated mice. In addition, our study revealed that PI3K-AKT-mTOR-TFEB pathway was activated by AOPPs in macrophages. Inhibition of the PI3K pathway effectively alleviated AOPPs-induced autophagy impairment and M1 polarization both in vitro and in vivo, thus reducing intestinal inflammation in AOPPs-challenged mice. Together, this study demonstrates that AOPPs-induced autophagy impairment in macrophages is crucial for CD progression.