Complement C3 activation regulates the production of tRNA-derived fragments Gly-tRFs and promotes alcohol-induced liver injury and steatosis

Abstract

Complement is known to play a role in alcoholic fatty liver disease (AFLD), but the underlying mechanisms are poorly understood, thereby constraining the development of a rational approach for therapeutic intervention in the complement system. C3 deficiency has been shown to impart protective effects against ethanol-induced hepatic steatosis and inflammation. Here we demonstrate a protection effect in wild-type mice by treatment with CR2-Crry, a specific inhibitor of C3 activation. The expression of glycine transfer (t) RNA-derived fragments (Gly-tRFs) is upregulated in ethanol-fed mice and inhibition of Gly-tRFs in vivo decreases chronic ethanol feeding-induced hepatosteatosis without affecting inflammation. The expression of Gly-tRF was downregulated in C3-deficient or CR2-Crry-treated mice, but not in C5-deficient mice; Gly-tRF expression was restored by the C3 activation products C3a or Asp (C3a-des-Arg) via the regulation of CYP2E1. Transcriptome profiling of hepatic tissues showed that Gly-tRF inhibitors upregulate the expression of sirtuin1 (Sirt1) and subsequently affect downstream lipogenesis and β-oxidation pathways. Mechanistically, Gly-tRF interacts with AGO3 to downregulate Sirt1 expression via sequence complementarity in the 3′ UTR. Notably, the expression levels of C3d, CYP2E1 and Gly-tRF are upregulated, whereas Sirt1 is decreased in AFLD patients compared to healthy controls. Collectively, our findings suggest that C3 activation products contribute to hepatosteatosis by regulating the expression of Gly-tRF. Complement inhibition at the C3 activation step and treatment with Gly-tRF inhibitors may be potential and precise therapeutic approaches for AFLD.

HFD-induced hepatic lipid accumulation and inflammation are decreased in Factor D deficient mouse

“…Liver samples were fixed overnight in 4% paraformaldehyde for cryosections, or 10% neutral buffered formalin for paraffin embedding. Endogenous biotin-blocked, 4-µm-thick paraffin sections were stained with haematoxylin, anti-C3d antibody (R&D Systems, Inc.) or anti-F4/80 antibody (Biolegend, Inc.) 37,38 . Six-µm-thick cryosections were stained with Oil Red O (Sigma-Aldrich) and Mayer's Hematoxylin Solution (Fujifilm Wako Pure Chemical Corporation) 39 .…”

Roles of the complement system in alcohol-induced liver disease

“…A recent study showed that suppression of C3 activation can protect against the injury of steatosis and inflammation in ALD. 32 Therefore, targeted complement inhibitors may become a potential drug to protect against both infiammatory response syndrome and hepatic steatosis for AFLD patients (Fig. 3).…”

“…3). 32 According to the specific structure of complement molecules, complement mutants and complement peptides can also be used to regulate complement activity. 58,59 Moreover, the crosstalk between the complement, coagulation, and fibrinolysis systems also plays an important role in complement regulation.…”

tRNA-derived RNA fragments in cancer: current status and future perspectives

“…tRFs participate in various molecular processes such as gene silencing, RNA processing, and protein translation and different physiological processes such as cell stress, cell growth, and cell differentiation [5,[12][13][14][15]. tRFs also play significant roles in various human diseases, including cancer [16,17], neurodegenerative disease [18,19], virus infection [20][21][22], metabolic disorder [23], and inflammation [24]. Here, we will review the biogenesis and discovery of tRFs and delineate some of the major biological functions of tRFs as well as recent reports on the roles of tRFs in different types of cancer.…”