• Liver-specific glucocorticoid action in alcoholic liver disease

      Lu, Hong; Wang, Yazheng (2021)
      The number of deaths due to alcoholic liver disease is increasing every year. Glucocorticoids (GCs) are the only first-line drugs for alcoholic hepatitis (AH) treatment but have limited efficacy. Long-term high-dose GC use can cause various side effects on extrahepatic tissues, such as immunosuppression and neuromuscular side effects, which may be a limiting factor for GC treatment of AH. Therefore, liver-specific GC-targeted therapy may have multiple advantages compared with systemic GC for AH. This research explored the role of liver-specific deficiency of glucocorticoid receptor (GR) in AH induced by a high-fat diet (HFD) plus ethanol binge. Females are less prone to AH induced by HFD plus acute binge drinking, likely due to sex differences in estrogen (E2) signaling. We found that hepatic GR deficiency worsened steatosis in both genders of AH mice but only aggravated the liver injury in male AH mice. Multiple signaling pathways were dysregulated in GR knockout AH mice. Interestingly, hepatic expression of estrogen receptor (ERα) was induced, and the E2-inactivating enzyme was markedly down-regulated in GR knockout AH mice, suggesting enhanced E2 signaling in these mice. Our data mining found marked dysregulation of many GR-target genes important for lipid catabolism, cytoprotection, and inflammation in patients with severe AH. These key GR-target genes were similarly induced or down-regulated by our liver-targeting GC prodrugs and the parent drug at 1μM in primary human hepatocytes. In contrast, GC prodrugs had much weaker inhibitory effects than the parent drug on LPS-induction of IL-1B in mouse macrophages, suggesting a good liver selectivity of our liver-targeting GC prodrugs. The ultimate goal of this study is to determine the mechanistic role of GR in alcoholic fatty liver disease and develop targeted drug therapies to treat alcoholic hepatitis.
    • Metabolic Control of Autoimmunity in the Liver

      Perl, Andras; Oaks, Zachary (2016)
      Autophagy,literally meaning “self-eating,” is an integral part of cellularturnover of damaged organelles and proteins.This process is inextricably linked to mitochondrial function and turnover. Mitochondria can be degraded viaautophagy, known as mitophagy, as well as donate lipid membraneto generate autophagosomes fordigestingother organelles and proteins. On a larger scale, autophagy is essential for organ homeostasis. In the liver, autophagy ensures the turnover of damaged mitochondria that may otherwise increase oxidative stress which modifies DNA, proteins, and lipids resulting in the production of autoantigens or neoplasia. We investigated the role of autophagy and mitochondrial dysfunction prior to disease onset in mouse models of systemic lupus erythematosus (SLE). Patients and mice with SLE exhibit overexpression of transaldolase (TAL) and show predisposition to anti-phospholipid antibody production and associated liver diseases, including hepatocellular carcinoma. Wediscovered deficient mitophagy in the liver of lupus-prone mice prior to disease onset. Furthermore, these mice had increased mitochondrial respirationwith concomitant inner membrane hyperpolarization. These changes were coupled to overexpression of Rab4A, which depletes Drp1and thus inhibitsmitophagy.In addition,activation of complex I of the mechanistic target of rapamycin (mTORC1)was noted along with enhanced production of autoantibodies against mitochondrial phospholipids in lupus-prone mice. These changes were reversed by blockade of mTORC1 by rapamycin treatment in vivo. We then examined the role of TAL, a key enzyme of the pentose phosphate pathway (PPP) in mitochondrial dysfunction and oxidative stress. TAL-deficientmice showedincreased mitochondrial electron transport chain (ETC) activity and mTORC1 activation andreduced autophagy.Since inactivation of TAL caused oxidative stress via depletion of NADPH, we tested the hypothesis that aldose reductase(AR), a NADPH dependent enzymecan correct this metabolic defect without reversing the accumulation of TAL-specific substrates, sedoheptulose 7-phosphate and erythrose 4-phosphate. Moreover, deletion of AR reversed mTORC1 activation without affecting enhanced mitochondrial ETC activity or diminished autophagy. On a more global scale, predisposition to neoplasia and acetaminophen-induced liver failurewere reversed, while anti-phospholipid autoantibody production and liver fibrosis persisted in TAL/AR double-knockout mice indicatingthat the PPPmay act as a metabolic rheostat of organ-specific disease pathogenesis.