O0040 Free Fatty Acids Promote Hepatic Lipotoxicity by Stimulating TNF-Alpha Expression via a Lysosomal Pathway

Cell Type–Dependent Pro- and Anti-Inflammatory Role of Signal Transducer and Activator of Transcription 3 in Alcoholic Liver Injury

“…41 However, in our model, ethanol-fed H-STAT3KO mice had more steatosis than WT mice, but the degree of liver injury was unexpectedly similar in these 2 groups, suggesting that steatosis and injury may be independent. This notion was also supported by several other recent studies.…”

The lysosomal-mitochondrial axis in free fatty acid–induced hepatic lipotoxicity

“…We previously demonstrated that incubation of primary mouse hepatocytes as well as HepG2 cells with long-chain FFAs results in rapid lysosomal permeabilization and release of cathepsin B, a lysosomal cysteine protease, into the cytosol. 21 We hypothesized that mitochondrial dysfunction and subsequent mitochondrial ROS production in NAFLD are downstream events from lysosomal permeabilization and cathepsin B activation. To test this hypothesis, HepG2 cells were initially incubated in the presence or absence of 0.2 mM FFA for up to 6 hours.…”

“…This hypothesis stems from the observation that cathepsin B is released in the cytosol in response to FFAs in vitro and that the redistribution of cathepsin B in the cytoplasm is present in human liver tissues from patients with NAFLD. 21 To ascertain whether cathepsin B inhibition may protect against FFA-induced mitochondriotoxicity, we suppressed cathepsin B activity using both genetic and pharmacological approaches. We first evaluated cytosolic cytochrome c localization in FFA-treated HepG2 cells in the presence or absence of 20 M of the selective pharmacological cathepsin B inhibitor CA07 for 6 hours by immunoblotting (Fig.…”

“…20 Previous studies from our laboratory showed that these cells are sensitive to FFA-induced lysosomal permeabilization in a dose-and time-dependent manner, with kinetics comparable to those observed in primary mouse hepatocytes. 21 Cultured cells were treated with various concentrations (0.05-0.5 mM) of long-chain free fatty acids with different degrees of saturation, including palmitate (saturated), oleate (1 double bond), and linoleic (2 double bonds), from Sigma (St. Louis, MO), in media containing 1% bovine serum albumin for as long as 24 hours (0.5, 1, 2, 4, 8, 16, and 24 hours). In selected experiments, cells were incubated with the fatty acid mixture in the presence or absence of the cathepsin B-selective inhibitors CA074 (20 M, SigmaAldrich) or E-64 (10 M, Roche Diagnostics).…”

Mitochondrial dysfunction and oxidative stress in the pathogenesis of alcohol- and obesity-induced fatty liver diseases

“…The molecular mechanism underlying how steatosis predisposes liver to transition from simple fatty liver to steatohepatitis is not clear; however, several studies point to the possibility that when hepatocytes accumulate fat the fatty acids themselves are toxic and initiate a pathological response called "lipotoxicity" [14]. Studies show that free fatty acids are toxic to hepatocytes via deregulation of lysosomal metabolism [15,16] and induction of endoplasmic reticulum stress [17,18] resulting in apoptosis. Similarly, palmitate induced lipid accumulation in hepatocytes stimulated production of the neutrophil chemoattractant interleukin-8, which could have the effect of initiating hepatic inflammation and injury [19].…”