Davidson, Nicholas O.; and Chen, Anping, ,"Perilipin 5 and liver fatty acid binding protein function to restore quiescence in mouse hepatic stellate cells. This article is available online at http://www.jlr.org Supplementary key words lipid droplets • perilipins • fatty acid-binding proteins • lipid metabolism • stellate cell activation Nonalcoholic fatty liver disease encompasses a spectrum of pathology ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis, but the

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... mechanisms and mediators that regulate necroinflammation and disease progression are still poorly understood (1-3). NASHassociated hepatic fibrosis is currently the target of significant scientific and clinical interest, in particular, the mechanisms regulating activation of hepatic stellate cells (HSCs), which are the major fibrogenic effectors (1-3). Quiescent HSCs contain abundant complex lipids that are localized within lipid droplets (LDs) (1-3). Upon HSC activation and the induction of fibrogenesis, HSCs undergo loss of LDs along with enhanced proliferation, de novo expression of -smooth muscle actin (-SMA), and overproduction of extracellular matrix, including I(I) collagen. Among the most abundant proteins on LDs are members of the perilipin (Plin) family of lipid droplet proteins, some of which (e.g., Plin2) play important roles in the regulation of lipid metabolism in a variety of tissues including liver (4-7). Our previous observations demonstrated that Abstract Hepatic stellate cell (HSC) activation occurs along with decreased Perilipin5 (Plin5) and liver fatty acid-binding protein (L-Fabp) expression and coincident lipid droplet (LD) depletion. Conversely, the activated phenotype is reversible in WT HSCs upon forced expression of Plin5. Here, we asked if L-Fabp expression is required for Plin5-mediated rescue of the quiescent phenotype. Lentiviral Plin5 transduction of passaged L-Fabp / HSCs failed to reverse activation markers or restore lipogenic gene expression and LD formation. However, adenoviral L-Fabp infection of lentiviral Plin5 transduced L-Fabp / HSCs restored both the quiescent phenotype and LD formation, an effect also mediated by adenoviral intestine-Fabp or adipocyte-Fabp. Expression of exogenous Plin5 in activated WT HSCs induced a transcriptional program of lipogenic gene expression including endogenous L-Fabp, but none of the other FABPs. We further demonstrated that selective, small molecule inhibition of endogenous L-Fabp also eliminated the ability of exogenous Plin5 to rescue LD formation and reverse activation of WT HSCs. This functional coordination of L-Fabp with Plin5 was 5′-AMP-activated protein kinase (AMPK)-dependent and was eliminated by AMPK inhibition. Taken together, our results indicate that L-Fabp is required for Plin5 to activate a transcriptional program that restores LD formation and reverses HSC activationand liver fatty acid binding protein function to restore quiescence in mouse hepatic stellate cells. J. Lipid Res. 2018. 59: 416-428. Abbreviations: abhd5, abhydrolase domain containing 5; ACC, acetyl coA carboxylase; AMPK, AMP-activated protein kinase; 1, 8 ANS, 8-anilinonaphthalene-1-sulfonic acid; ATGL, adipose triglyceride lipase; Ad-L-Fabp, adenoviral liver Fabp; Ad-I-Fabp, adenoviral intestine-Fabp; Ad-A-Fabp, adenoviral adipocyte-Fabp; -SMA, -smooth muscle actin; HSC, hepatic stellate cell; LD, lipid droplet; LOX-1, lectin-like oxidized LDL receptor-1; L-Fabp, liver fatty acid-binding protein; LRAT, lecithinretinol acyltransferase; LV, lentiviral; LXR, liver X receptor; NSOP313, NSOP00313; NASH, nonalcoholic steatohepatitis; PKA, protein kinase A; Plin 5, perilipin 5; PPRE, peroxisome proliferator response element; TG, triglyceride; YFP, yellow fluorescent protein.