Sulfation of chondroitin and bile acids converges to antagonize Wnt/ß-catenin signaling and inhibit APC deficiency-induced gut tumorigenesis.

Sulfation is a crucial and prevalent conjugation reaction involved in cellular processes and mammalian physiology. 3'-Phosphoadenosine 5'-phosphosulfate (PAPS) synthase 2 (PAPSS2) is the primary enzyme to generate the universal sulfonate donor PAPS. The involvement of PAPSS2-mediated sulfation in adenomatous polyposis coli (APC) mutation-promoted colonic carcinogenesis has not been reported. Here, we showed that the expression of PAPSS2 was decreased in human colon tumors along with cancer stages, and the lower expression of PAPSS2 was correlated with poor prognosis in advanced colon cancer. Gut epithelial-specific heterozygous Apc deficient and Papss2-knockout (ApcΔgut-HetPapss2Δgut) mice were created, and the phenotypes were compared to the spontaneous intestinal tumorigenesis of ApcΔgut-Het mice. ApcΔgut-HetPapss2Δgut mice were more sensitive to gut tumorigenesis, which was mechanistically accounted for by the activation of Wnt/ß-catenin signaling pathway due to the suppression of chondroitin sulfation and inhibition of the farnesoid X receptor (FXR)-transducin-like enhancer of split 3 (TLE3) gene regulatory axis. Chondroitin sulfate supplementation in ApcΔgut-HetPapss2Δgut mice alleviated intestinal tumorigenesis. In summary, we have uncovered the protective role of PAPSS2-mediated chondroitin sulfation and bile acids-FXR-TLE3 activation in the prevention of gut carcinogenesis via the antagonization of Wnt/ß-catenin signaling. Chondroitin sulfate may be explored as a therapeutic agent for Papss2 deficiency-associated colonic carcinogenesis.

Hepatocyte estrogen sulfotransferase inhibition protects female mice from concanavalin A-induced T cell-mediated hepatitis independent of estrogens.

Autoimmune hepatitis (AIH) is a typical T cell-mediated chronic liver disease with a higher incidence in females. However, the molecular mechanism for the female predisposition is poorly understood. Estrogen sulfotransferase (Est) is a conjugating enzyme best known for its function in sulfonating and deactivating estrogens. The goal of this study is to investigate whether and how Est plays a role in the higher incidence of AIH in females. Concanavalin A (ConA) was used to induce T cell-mediated hepatitis in female mice. We first showed that Est was highly induced in the liver of ConA-treated mice. Systemic or hepatocyte-specific ablation of Est, or pharmacological inhibition of Est, protected female mice from ConA-induced hepatitis regardless of ovariectomy, suggesting the effect of Est inhibition was estrogen independent. In contrast, we found that hepatocyte-specific transgenic reconstitution of Est in the whole-body Est knockout (EstKO) mice abolished the protective phenotype. Upon the ConA challenge, EstKO mice exhibited a more robust inflammatory response with elevated production of proinflammatory cytokines and changed liver infiltration of immune cells. Mechanistically, we determined that ablation of Est led to the hepatic induction of lipocalin 2 (Lcn2), whereas ablation of Lcn2 abolished the protective phenotype of EstKO females. Our findings demonstrate that hepatocyte Est is required for the sensitivity of female mice to ConA-induced and T cell-mediated hepatitis in an estrogen-independent manner. Est ablation may have protected female mice from ConA-induced hepatitis by upregulating Lcn2. Pharmacological inhibition of Est might be a potential strategy for the treatment of AIH.

Gestational Diabetes Sensitizes Mice to Future Metabolic Syndrome That Can Be Relieved by Activating CAR.

Diabetes and related metabolic syndrome are common metabolic disorders. Gestational diabetes mellitus (GDM) is rather prevalent in the clinic. Although most GDM resolves after therapeutic intervention and/or after delivery, the long-term health effect of GDM remains to be better understood. The constitutive androstane receptor (CAR), initially characterized as a xenobiotic receptor, was more recently proposed to be a therapeutic target for obesity and type 2 diabetes mellitus (T2DM). In this study, high-fat diet (HFD) feeding was used to induce GDM. Upon delivery, GDM mice were returned to chow diet until the metabolic parameters were normalized. Parous non-GDM control females or metabolically normalized GDM females were then subjected to HFD feeding to induce nongestational obesity and T2DM. Our results showed that GDM sensitized mice to metabolic abnormalities induced by a second hit of HFD. Treatment with the CAR agonist 1,4-bis [2-(3,5 dichloropyridyloxy)] benzene efficiently attenuated GDM-sensitized and HFD-induced obesity and T2DM, including decreased body weight, improved insulin sensitivity, inhibition of hyperglycemia and hepatic steatosis, increased oxygen consumption, and decreased adipocyte hypertrophy. In conclusion, our results have established GDM as a key risk factor for the future development of metabolic disease. We also propose that CAR is a therapeutic target for the management of metabolic disease sensitized by GDM.

Chronic Activation of LXRα Sensitizes Mice to Hepatocellular Carcinoma.

The oxysterol receptor liver X receptor (LXR) is a nuclear receptor best known for its function in the regulation of lipid and cholesterol metabolism. LXRs, both the α and ß isoforms, have been suggested as potential therapeutic targets for several cancer types. However, there was a lack of report on whether and how LXRα plays a role in the development of hepatocellular carcinoma (HCC). In the current study, we found that systemic activation of LXRα in the VP-LXRα knock-in (LXRαKI) mice or hepatocyte-specific activation of LXRα in the VP-LXRα transgenic mice sensitized mice to liver tumorigenesis induced by the combined treatment of diethylnitrosamine (DEN) and 3,3',5,5'-tetrachloro-1,4-bis (pyridyloxy) benzene (TCPOBOP). Mechanistically, the LXRα-responsive up-regulation of interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signaling pathway and the complement system, and down-regulation of bile acid metabolism, may have contributed to increased tumorigenesis. Accumulations of secondary bile acids and oxysterols were found in both the serum and liver tissue of LXRα activated mice. We also observed an induction of monocytic myeloid-derived suppressor cells accompanied by down-regulation of dendritic cells and cytotoxic T cells in DEN/TCPOBOP-induced liver tumors, indicating that chronic activation of LXRα may have led to the activation of innate immune suppression. The HCC sensitizing effect of LXRα activation was also observed in the c-MYC driven HCC model. Conclusion: Our results indicated that chronic activation of LXRα promotes HCC, at least in part, by promoting innate immune suppressor as a result of accumulation of oxysterols, as well as up-regulation of the IL-6/Janus kinase/STAT3 signaling and complement pathways.

Inhibition of p53 Sulfoconjugation Prevents Oxidative Hepatotoxicity and Acute Liver Failure.

BACKGROUND & AIMS: Sulfoconjugation of small molecules or protein peptides is a key mechanism to ensure biochemical and functional homeostasis in mammals. The PAPS synthase 2 (PAPSS2) is the primary enzyme to synthesize the universal sulfonate donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS). Acetaminophen (APAP) overdose is the leading cause of acute liver failure (ALF), in which oxidative stress is a key pathogenic event, whereas sulfation of APAP contributes to its detoxification. The goal of this study was to determine whether and how PAPSS2 plays a role in APAP-induced ALF. METHODS: Gene expression was analyzed in APAP-induced ALF in patients and mice. Liver-specific Papss2-knockout mice using Alb-Cre (Papss2ΔHC) or AAV8-TBG-Cre (Papss2iΔHC) were created and subjected to APAP-induced ALF. Primary human and mouse hepatocytes were used for in vitro mechanistic analysis. RESULTS: The hepatic expression of PAPSS2 was decreased in APAP-induced ALF in patients and mice. Surprisingly, Papss2ΔHC mice were protected from APAP-induced hepatotoxicity despite having a decreased APAP sulfation, which was accompanied by increased hepatic antioxidative capacity through the activation of the p53-p2-Nrf2 axis. Treatment with a sulfation inhibitor also ameliorated APAP-induced hepatotoxicity. Gene knockdown experiments showed that the hepatoprotective effect of Papss2ΔHC was Nrf2, p53, and p21 dependent. Mechanistically, we identified p53 as a novel substrate of sulfation. Papss2 ablation led to p53 protein accumulation by preventing p53 sulfation, which disrupts p53-MDM2 interaction and p53 ubiquitination and increases p53 protein stability. CONCLUSIONS: We have uncovered a previously unrecognized and p53-mediated role of PAPSS2 in controlling oxidative response. Inhibition of p53 sulfation may be explored for the clinical management of APAP overdose.

The anti-fibrotic drug pirfenidone inhibits liver fibrosis by targeting the small oxidoreductase glutaredoxin-1.

Activation of the hepatic stellate cells (HSCs) is a key pathogenic event in liver fibrosis. Protein S-glutathionylation (PSSG) of cysteine residues is a distinct form of oxidative response that modifies protein structures and functions. Glutaredoxin-1 (GLRX) reverses PSSG by liberating glutathione (GSH). In this study, we showed that pirfenidone (PFD), an anti-lung fibrosis drug, inhibited HSC activation and liver fibrosis in a GLRX-dependent manner. Glrx depletion exacerbated liver fibrosis, and decreased GLRX and increased PSSG were observed in fibrotic mouse and human livers. In contrast, overexpression of GLRX inhibited PSSG and liver fibrosis. Mechanistically, the inhibition of HSC activation by GLRX may have been accounted for by deglutathionylation of Smad3, which inhibits Smad3 phosphorylation, leading to the suppression of fibrogenic gene expression. Our results have established GLRX as the therapeutic target of PFD and uncovered an important role of PSSG in liver fibrosis. GLRX/PSSG can be both a biomarker and a therapeutic target for liver fibrosis.

Intestinal Sulfation Is Essential to Protect Against Colitis and Colonic Carcinogenesis.

BACKGROUND & AIMS: Sulfation is a conjugation reaction essential for numerous biochemical and cellular functions in mammals. The 3'-phosphoadenosine 5'-phosphosulfate (PAPS) synthase 2 (PAPSS2) is the key enzyme to generate PAPS, which is the universal sulfonate donor for all sulfation reactions. The goal of this study was to determine whether and how PAPSS2 plays a role in colitis and colonic carcinogenesis. METHODS: Tissue arrays of human colon cancer specimens, gene expression data, and clinical features of cancer patients were analyzed. Intestinal-specific Papss2 knockout mice (Papss2ΔIE) were created and subjected to dextran sodium sulfate-induced colitis and colonic carcinogenesis induced by a combined treatment of azoxymethane and dextran sodium sulfate or azoxymethane alone. RESULTS: The expression of PAPSS2 is decreased in the colon cancers of mice and humans. The lower expression of PAPSS2 in colon cancer patients is correlated with worse survival. Papss2ΔIE mice showed heightened sensitivity to colitis and colon cancer by damaging the intestinal mucosal barrier, increasing intestinal permeability and bacteria infiltration, and worsening the intestinal tumor microenvironment. Mechanistically, the Papss2ΔIE mice exhibited reduced intestinal sulfomucin content. Metabolomic analyses revealed the accumulation of bile acids, including the Farnesoid X receptor antagonist bile acid tauro-ß-muricholic acid, and deficiency in the formation of bile acid sulfates in the colon of Papss2ΔIE mice. CONCLUSIONS: We have uncovered an important role of PAPSS2-mediated sulfation in colitis and colonic carcinogenesis. Intestinal sulfation may represent a potential diagnostic marker and PAPSS2 may serve as a potential therapeutic target for inflammatory bowel disease and colon cancer.

Activation of Liver X Receptor α Sensitizes Mice to T-Cell Mediated Hepatitis.

Autoimmune hepatitis (AIH) is an inflammatory disease of the liver. Liver X receptors (LXRs), including the α and ß isoforms, are previously known for their anti-inflammatory activities. The goal of this study is to determine whether and how LXR plays a role in AIH. LXRα gain-of-function and loss-of-function mouse models were used, in conjunction with the concanavalin A (ConA) model of T-cell mediated hepatitis. We first showed that the hepatic expression of LXRα was decreased in the ConA model of hepatitis and in human patients with AIH. In the ConA model, we were surprised to find that activation of LXRα in the constitutively activated VP-LXRα whole-body knock-in (LXRα-KI) mice exacerbated ConA-induced AIH, whereas the LXRα-/- mice showed attenuated ConA-induced AIH. Interestingly, hepatocyte-specific activation of LXRα in the fatty acid binding protein-VP-LXRα transgenic mice did not exacerbate ConA-induced hepatitis. Mechanistically, the sensitizing effect of the LXRα-KI allele was invariant natural killer T (iNKT)-cell dependent, because the sensitizing effect was abolished when the LXRα-KI allele was bred into the NKT-deficient CD1d-/- background. In addition, LXRα-enhanced ConA-induced hepatitis was dependent on interferon gamma. In contrast, adoptive transfer of hepatic iNKT cells isolated from LXRα-KI mice was sufficient to sensitize CD1d-/- mice to ConA-induced AIH. Conclusion: Activation of LXRα sensitizes mice to ConA-induced AIH in iNKT and interferon gamma-dependent manner. Our results suggest that LXRα plays an important role in the development of AIH.

ERINA Is an Estrogen-Responsive LncRNA That Drives Breast Cancer through the E2F1/RB1 Pathway.

Resistance to therapeutic drugs is a major challenge in the treatment of cancers, including breast cancer. Long noncoding RNAs (lncRNA) are known to have diverse physiologic and pathophysiologic functions, including in cancer. In searching for lncRNA responsible for cancer drug resistance, we identified an intergenic lncRNA ERINA (estrogen inducible lncRNA) as a novel lncRNA highly expressed in multiple cancer types, especially in estrogen receptor-positive (ER+) breast cancers. Expression of ERINA was inversely correlated with survival of patients with ER+ breast cancer and sensitivity to CDK inhibitor in breast cancer cell lines. Functional characterization established ERINA as an oncogenic lncRNA, as knockdown of ERINA in breast cancer cells inhibited cell-cycle progression and tumor cell proliferation in vitro and xenograft tumor growth in vivo. In contrast, overexpression of ERINA promoted cell growth and cell-cycle progression. ERINA promoted cell-cycle progression by interacting with the E2F transcription factor 1 (E2F1), which prevents the binding of E2F1 to the tumor suppressor retinoblastoma protein 1 (RB1). ERINA also functioned as an estrogen and ER-responsive gene, and an intronic ER-binding site was identified as an enhancer that mediates the transactivation of ERINA. In summary, ERINA is an estrogen-responsive oncogenic lncRNA that may serve as a novel biomarker and potential therapeutic target in breast cancer. SIGNIFICANCE: These findings identify ERINA as an estrogen-responsive, oncogenic lncRNA, whose elevated expression may contribute to drug resistance and poor survival of patients with ER+ breast cancer.

Hepatic Estrogen Sulfotransferase Distantly Sensitizes Mice to Hemorrhagic Shock-Induced Acute Lung Injury.

Hemorrhagic shock (HS) is a potential life-threatening condition that may lead to injury to multiple organs, including the lung. The estrogen sulfotransferase (EST, or SULT1E1) is a conjugating enzyme that sulfonates and deactivates estrogens. In this report, we showed that the expression of Est was markedly induced in the liver but not in the lung of female mice subject to HS and resuscitation. Genetic ablation or pharmacological inhibition of Est effectively protected female mice from HS-induced acute lung injury (ALI), including interstitial edema, neutrophil mobilization and infiltration, and inflammation. The pulmonoprotective effect of Est ablation or inhibition was sex-specific, because the HS-induced ALI was not affected in male Est-/- mice. Mechanistically, the pulmonoprotective phenotype in female Est-/- mice was accompanied by increased lung and circulating levels of estrogens, attenuated pulmonary inflammation, and inhibition of neutrophil mobilization from the bone marrow and neutrophil infiltration to the lung, whereas the pulmonoprotective effect was abolished upon ovariectomy, suggesting that the protection was estrogen dependent. The pulmonoprotective effect of Est ablation was also tissue specific, as loss of Est had little effect on HS-induced liver injury. Moreover, transgenic reconstitution of human EST in the liver of global Est-/- mice abolished the pulmonoprotective effect, suggesting that it is the EST in the liver that sensitizes mice to HS-induced ALI. Taken together, our results revealed a sex- and tissue-specific role of EST in HS-induced ALI. Pharmacological inhibition of EST may represent an effective approach to manage HS-induced ALI.

Aryl Hydrocarbon Receptor Signaling Prevents Activation of Hepatic Stellate Cells and Liver Fibrogenesis in Mice.

BACKGROUND & AIMS: The role of aryl hydrocarbon receptor (AhR) in liver fibrosis is controversial because loss and gain of AhR activity both lead to liver fibrosis. The goal of this study was to investigate how the expression of AhR by different liver cell types, hepatic stellate cells (HSCs) in particular, affects liver fibrosis in mice. METHODS: We studied the effects of AhR on primary mouse and human HSCs, measuring their activation and stimulation of fibrogenesis using RNA-sequencing analysis. C57BL/6J mice were given the AhR agonists 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE); were given carbon tetrachloride (CCl4); or underwent bile duct ligation. We also performed studies in mice with disruption of Ahr specifically in HSCs, hepatocytes, or Kupffer cells. Liver tissues were collected from mice and analyzed by histology, immunohistochemistry, and immunoblotting. RESULTS: AhR was expressed at high levels in quiescent HSCs, but the expression decreased with HSC activation. Activation of HSCs from AhR-knockout mice was accelerated compared with HSCs from wild-type mice. In contrast, TCDD or ITE inhibited spontaneous and transforming growth factor ß-induced activation of HSCs. Mice with disruption of Ahr in HSCs, but not hepatocytes or Kupffer cells, developed more severe fibrosis after administration of CCl4 or bile duct ligation. C57BL/6J mice given ITE did not develop CCl4-induced liver fibrosis, whereas mice without HSC AhR given ITE did develop CCl4-induced liver fibrosis. In studies of mouse and human HSCs, we found that AhR prevents transforming growth factor ß-induced fibrogenesis by disrupting the interaction of Smad3 with ß-catenin, which prevents the expression of genes that mediate fibrogenesis. CONCLUSIONS: In studies of human and mouse HSCs, we found that AhR prevents HSC activation and expression of genes required for liver fibrogenesis. Development of nontoxic AhR agonists or strategies to activate AhR signaling in HSCs might be developed to prevent or treat liver fibrosis.

Activation of Pregnane X Receptor Sensitizes Mice to Hemorrhagic Shock-Induced Liver Injury.

Hemorrhagic shock (HS) is a life-threatening condition associated with tissue hypoperfusion and often leads to injury of multiple organs including the liver. Pregnane X receptor (PXR) is a species-specific xenobiotic receptor that regulates the expression of drug-metabolizing enzymes (DMEs) such as the cytochrome P450 (CYP) 3A. Many clinical drugs, including those often prescribed to trauma patients, are known to activate PXR and induce CYP3A. The goal of this study is to determine whether PXR plays a role in the regulation of DMEs in the setting of HS and whether activation of PXR is beneficial or detrimental to HS-induced hepatic injury. PXR transgenic, knockout, and humanized mice were subject to HS, and the liver injury was assessed histologically and biochemically. The expression and/or activity of PXR and CYP3A were manipulated genetically or pharmacologically in order to determine their effects on HS-induced liver injury. Our results showed that genetic or pharmacological activation of PXR sensitized wild-type and hPXR/CYP3A4 humanized mice to HS-induced hepatic injury, whereas knockout of PXR protected mice from HS-induced liver injury. Mechanistically, the sensitizing effect of PXR activation was accounted for by PXR-responsive induction of CYP3A and increased oxidative stress in the liver. The sensitizing effect of PXR was attenuated by ablation or pharmacological inhibition of CYP3A, treatment with the antioxidant N-acetylcysteine amide, or treatment with a PXR antagonist. Conclusion: We have uncovered a function of PXR in HS-induced hepatic injury. Our results suggest that the unavoidable use of PXR-activating drugs in trauma patients has the potential to exacerbate HS-induced hepatic injury, which can be mitigated by the coadministration of antioxidative agents, CYP3A inhibitors, or PXR antagonists.

An Unexpected Role of Cholesterol Sulfotransferase and its Regulation in Sensitizing Mice to Acetaminophen-Induced Liver Injury.

Overdose of acetaminophen (APAP) is the leading cause of acute liver failure (ALF) in the United States. The sulfotransferase-mediated sulfation of APAP is widely believed to be a protective mechanism to attenuate the hepatotoxicity of APAP. The cholesterol sulfotransferase SULT2B1b is best known for its activity in catalyzing the sulfoconjugation of cholesterol to synthesize cholesterol sulfate. SULT2B1b can be transcriptionally and positively regulated by the hepatic nuclear factor 4α (HNF4α). In this study, we uncovered an unexpected role for SULT2B1b in APAP toxicity. Hepatic overexpression of SULT2B1b sensitized mice to APAP-induced liver injury, whereas ablation of the Sult2B1b gene in mice conferred resistance to the APAP hepatotoxicity. Consistent with the notion that Sult2B1b is a transcriptional target of HNF4α, overexpression of HNF4α sensitized mice or primary hepatocytes to APAP-induced hepatotoxicity in a Sult2B1b-dependent manner. We conclude that the HNF4α-SULT2B1b axis has a unique role in APAP-induced acute liver injury, and SULT2B1b induction might be a risk factor for APAP hepatotoxicity.

Sex-Dimorphic and Sex Hormone-Dependent Role of Steroid Sulfatase in Adipose Inflammation and Energy Homeostasis.

Steroid sulfatase (STS), a desulfating enzyme that converts steroid sulfates to hormonally active steroids, plays an important role in the homeostasis of sex hormones. STS is expressed in the adipose tissue of both male and female mice, but the role of STS in the development and function of adipose tissue remains largely unknown. In this report, we show that the adipose expression of Sts was induced in the high-fat diet (HFD) and ob/ob models of obesity and type 2 diabetes. Transgenic overexpression of the human STS in the adipose tissue of male mice exacerbated the HFD-induced metabolic phenotypes, including increased body weight gain and fat mass, and worsened insulin sensitivity, glucose tolerance, and energy expenditure, which were accounted for by adipocyte hypertrophy, increased adipose inflammation, and dysregulation of adipogenesis. The metabolic harm of the STS transgene appeared to have resulted from increased androgen activity in the adipose tissue, and castration abolished most of the phenotypes. Interestingly, the transgenic effects were sex specific, because the HFD-fed female STS transgenic mice exhibited improved metabolic functions, which were associated with attenuated adipose inflammation. The metabolic benefit of the STS transgene in female mice was accounted for by increased estrogenic activity in the adipose tissue, whereas such benefit was abolished upon ovariectomy. Our results revealed an essential role of the adipose STS in energy homeostasis in sex- and sex hormone-dependent manner. The adipose STS may represent a therapeutic target for the management of obesity and type 2 diabetes.

Chronic Activation of Liver X Receptor Sensitizes Mice to High Cholesterol Diet-Induced Gut Toxicity.

Cholesterol is essential for numerous biologic functions and processes, but an excess of intracellular cholesterol can be toxic. Intestinal cholesterol absorption is a major determinant of plasma cholesterol level. The liver X receptor (LXR) is a nuclear receptor known for its activity in cholesterol efflux and reverse cholesterol transport. In this study, we uncovered a surprising function of LXR in intestinal cholesterol absorption and toxicity. Genetic or pharmacologic activation of LXRα-sensitized mice to a high-cholesterol diet (HCD) induced intestinal toxicity and tissue damage, including the disruption of enterocyte tight junctions, whereas the same HCD caused little toxicity in the absence of LXR activation. The gut toxicity in HCD-fed LXR-KI mice may have been accounted for by the increased intestinal cholesterol absorption and elevation of enterocyte and systemic levels of free cholesterol. The increased intestinal cholesterol absorption preceded the gut toxicity, suggesting that the increased absorption was not secondary to tissue damage. The heightened sensitivity to HCD in the HCD-fed LXRα-activated mice appeared to be intestine-specific because the liver was not affected despite activation of the same receptor in this tissue. Moreover, heightened sensitivity to HCD cannot be reversed by ezetimibe, a Niemann-Pick C1-like 1 inhibitor that inhibits intestinal cholesterol absorption, suggesting that the increased cholesterol absorption in LXR-activated intestine is mediated by a mechanism that has yet to be defined.

Activation of Constitutive Androstane Receptor Ameliorates Renal Ischemia-Reperfusion-Induced Kidney and Liver Injury.

Acute kidney injury (AKI) is associate with high mortality. Despite evidence of AKI-induced distant organ injury, a relationship between AKI and liver injury has not been clearly established. The goal of this study is to investigate whether renal ischemia-reperfusion (IR) can affect liver pathophysiology. We showed that renal IR in mice induced fatty liver and compromised liver function through the downregulation of constitutive androstane receptor (CAR; -90.4%) and inhibition of hepatic very-low-density lipoprotein triglyceride (VLDL-TG) secretion (-28.4%). Treatment of mice with the CAR agonist 1,4-bis[2-(3,5 dichloropyridyloxy)] benzene (TCPOBOP) prevented the development of AKI-induced fatty liver and liver injury, which was associated with the attenuation of AKI-induced inhibition of VLDL-TG secretion. The hepatoprotective effect of TCPOBOP was abolished in CAR-/- mice. Interestingly, alleviation of fatty liver by TCPOBOP also improved the kidney function, whereas CAR ablation sensitized mice to AKI-induced kidney injury and lethality. The serum concentrations of interleukin-6 (IL-6) were elevated by 27-fold after renal IR, but were normalized in TCPOBOP-treated AKI mice, suggesting that the increased release of IL-6 from the kidney may have mediated the AKI responsive liver injury. Taken together, our results revealed an interesting kidney-liver organ cross-talk in response to AKI. Given the importance of CAR in the pathogenesis of renal IR-induced fatty liver and impaired kidney function, fatty liver can be considered as an important risk factor for kidney injury, and a timely management of hepatic steatosis by CAR activation may help to restore kidney function in patients with AKI or kidney transplant.

Regulation of Cholesterol Sulfotransferase SULT2B1b by Hepatocyte Nuclear Factor 4α Constitutes a Negative Feedback Control of Hepatic Gluconeogenesis.

The cholesterol sulfotransferase SULT2B1b converts cholesterol to cholesterol sulfate (CS). We previously reported that SULT2B1b inhibits hepatic gluconeogenesis by antagonizing the gluconeogenic activity of hepatocyte nuclear factor 4α (HNF4α). In this study, we showed that the SULT2B1b gene is a transcriptional target of HNF4α, which led to our hypothesis that the induction of SULT2B1b by HNF4α represents a negative feedback to limit the gluconeogenic activity of HNF4α. Indeed, downregulation of Sult2B1b enhanced the gluconeogenic activity of HNF4α, which may have been accounted for by the increased acetylation of HNF4α as a result of decreased expression of the HNF4α deacetylase sirtuin 1 (Sirt1). The expression of Sult2B1b was also induced by HNF4α upon fasting, and the Sult2B1b null (Sult2B1b-/-) mice showed increased gluconeogenic gene expression and an elevated fasting glucose level, suggesting that SULT2B1b also plays a restrictive role in HNF4α-mediated fasting-responsive gluconeogenesis. We also developed thiocholesterol, a hydrolysis-resistant derivative of CS, which showed superior activity to that of the native CS in inhibiting gluconeogenesis and improving insulin sensitivity in high-fat-diet-induced diabetic mice. We conclude that the HNF4α-SULT2B1b-CS axis represents a key endogenous mechanism to prevent uncontrolled gluconeogenesis. Thiocholesterol may be used as a therapeutic agent to manage hyperglycemia.

Transgenic Overexpression of Steroid Sulfatase Alleviates Cholestasis.

BACKGROUND AND AIM: Sulfotransferase (SULT)-mediated sulfation and steroid sulfatase (STS)-mediated desulfation represent two critical mechanisms that regulate the chemical and functional homeostasis of endogenous and exogenous molecules. STS catalyzes the hydrolysis of steroid sulfates to form hydroxysteroids. Oxygenated cholesterol derivative oxysterols are known to be endogenous ligands of the liver X receptor (LXR), a nuclear receptor with anti-cholestasis activity, whereas the sulfated oxysterols antagonize LXR signaling. The conversion of sulfated oxysterols to their non-sulfated counterparts is catalyzed by STS. The aim of this study is to determine whether STS can alleviate cholestasis by increasing the activity of LXR. METHODS: Liver-specific STS transgenic mice were created and subject to the lithocholic acid (LCA)-induced model of cholestasis. RESULTS: Transgenic overexpression of STS in the liver promoted bile acid elimination and alleviated LCA-induced cholestasis. The protective effect of the STS transgene was associated with the activation of LXR and induction of LXR target genes, likely because of the increased conversion of the antagonistic oxysterol sulfates to the agonistic oxysterols. CONCLUSIONS: STS has a novel function in controlling the homeostasis of bile acids by regulating endogenous LXR ligands.

Hepatic Induction of Fatty Acid Binding Protein 4 Plays a Pathogenic Role in Sepsis in Mice.

Sepsis is defined as the host's deleterious systemic inflammatory response to microbial infections. Herein, we report an essential role of the fatty acid binding protein 4 (FABP4; alias adipocyte protein 2 or aP2), a lipid-binding chaperone, in sepsis response. Bioinformatic analysis of the Gene Expression Omnibus data sets showed the level of FABP4 was higher in the nonsurvival sepsis patients' whole blood compared to the survival cohorts. The expression of Fabp4 was induced in a liver-specific manner in cecal ligation and puncture (CLP) and lipopolysaccharide treatment models of sepsis. The induction of Fabp4 may have played a pathogenic role, because ectopic expression of Fabp4 in the liver sensitized mice to CLP-induced inflammatory response and worsened the animal's survival. In contrast, pharmacological inhibition of Fabp4 markedly alleviated the CLP responsive inflammation and tissue damage and improved survival. We conclude that FABP4 is an important mediator of the sepsis response. Early intervention by pharmacological inhibition of FABP4 may help to manage sepsis in the clinic.

Activation of Liver X Receptor Attenuates Oleic Acid-Induced Acute Respiratory Distress Syndrome.

Liver X receptors (LXRs) were identified as receptors that sense oxidized cholesterol derivatives. LXRs are best known for their hepatic functions in regulating cholesterol metabolism and triglyceride synthesis, but whether and how LXRs play a role in the lung diseases is less understood. To study the function of LXRs in acute respiratory distress syndrome (ARDS), we applied the oleic acid (OA) model of ARDS to mice whose LXR was genetically or pharmacologically activated. The VP-LXRα knock-in (LXR-KI) mice, in which a constitutively activated LXRα (VP-LXRα) was inserted into the mouse LXRα locus, were used as the genetic gain-of-function model. We showed that the OA-induced lung damages, including the cytokine levels and total cell numbers and neutrophil numbers in the bronchoalveolar lavage fluid, the wet/dry weight ratio, and morphological abnormalities were reduced in the LXR-KI mice and wild-type mice treated with the LXR agonist GW3965. The pulmonoprotective effect of GW3965 was abolished in the LXR-null mice. Consistent with the pulmonoprotective effect of LXR and the induction of antioxidant enzymes by LXR, the OA-induced suppression of superoxide dismutase and catalase was attenuated in LXR-KI mice and GW3965-treated wild-type mice. Taken together, our results demonstrate that activation of LXRs can alleviate OA-induced ARDS by attenuating the inflammatory response and enhancing antioxidant capacity.