Decreased expression of the glucocorticoid receptor-GILZ pathway in Kupffer cells promotes liver inflammation in obese mice.

BACKGROUND & AIMS: Kupffer cells (KC) play a key role in the onset of inflammation in non-alcoholic steatohepatitis (NASH). The glucocorticoid receptor (GR) induces glucocorticoid-induced leucine zipper (GILZ) expression in monocytes/macrophages and is involved in several inflammatory processes. We hypothesized that the GR-GILZ axis in KC may contribute to the pathophysiology of obesity-induced liver inflammation. METHODS: By using a combination of primary cell culture, pharmacological experiments, mice deficient for the Gr specifically in macrophages and transgenic mice overexpressing Gilz in macrophages, we explored the involvement of the Gr-Gilz axis in KC in the pathophysiology of obesity-induced liver inflammation. RESULTS: Obesity was associated with a downregulation of the Gr and Gilz, and an impairment of Gilz induction by lipopolysaccharide (LPS) and dexamethasone (DEX) in KC. Inhibition of Gilz expression in isolated KC transfected with Gilz siRNA demonstrated that Gilz downregulation was sufficient to sensitize KC to LPS. Conversely, liver inflammation was decreased in obese transgenic mice specifically overexpressing Gilz in macrophages. Pharmacological inhibition of the Gr showed that impairment of Gilz induction in KC by LPS and DEX in obesity was driven by a downregulation of the Gr. In mice specifically deficient for Gr in macrophages, Gilz expression was low, leading to an exacerbation of obesity-induced liver inflammation. CONCLUSIONS: Obesity is associated with a downregulation of the Gr-Gilz axis in KC, which promotes liver inflammation. The Gr-Gilz axis in KC is an important target for the regulation of liver inflammation in obesity.

CXCR4 dysfunction in non-alcoholic steatohepatitis in mice and patients.

Homing of inflammatory cells to the liver is key in the progression of non-alcoholic steatohepatitis (NASH). An abnormal response of CD4+ T-cells from obese mice to the chemotactic effect of CXCL12 has been reported but the mechanism involved in this process and relevance in patients are unknown. We aimed to explore the mechanism involved in the abnormal chemotaxis of CXC chemokine ligand 12 (CXCL12) in several mouse models of NASH and the relevance in the context of human non-alcoholic fatty liver disease (NAFLD). We assessed chemotactic responsiveness of CD4+ T-cells to CXCL12, the effect of AMD3100, a CXC chemokine receptor 4 (CXCR4) antagonist, in mice and lymphocytes from patients with NAFLD, and the affinity of CXCL12 for CXCR4. CXCL12-promoted migration of CD4+ T-cells from three different mouse models of NASH was increased and dependent of CXCR4. CD4+ T-cells from patients with NASH, but not from patients with pure steatosis, responded more strongly to the chemotactic effect of CXCL12, and this response was inhibited by AMD3100. Treatment with AMD3100 decreased the number of CD4+ T-cells to the liver in ob/ob mice. CXCL12 expression in the liver, CXCR4 and CXCR7 expression in CD4+ T-cells were not increased in three different mouse models of NASH. However, the affinity of CXCL12 for CXCR4 was increased in CD4+ T-cells of ob/ob mice. In conclusion, the CXCL12/CXCR4 pathway contributes in both mice and patients to the enhanced recruitment of CD4+ T-cells in NASH. An increased affinity of CXCL12 to CXCR4 rather than a higher expression of the chemokine or its receptors is involved in this process.

Alcohol withdrawal alleviates adipose tissue inflammation in patients with alcoholic liver disease.

BACKGROUND & AIMS: Patients with alcoholic liver disease (ALD) display inflammation of the subcutaneous adipose tissue (SAT) which correlates with liver lesions. We examined macrophage markers and polarization in the SAT of alcoholic patients and adipokine expression according to liver inflammation; we studied the consequences of alcohol withdrawal. PATIENTS AND METHODS: Forty-seven patients with ALD were prospectively included. SAT and blood samples were collected at inclusion and after 1 week of alcohol withdrawal. Pro-inflammatory cytokines/chemokines, inflammasome components and products, adipokine expression levels, macrophage markers and polarization in liver and SAT samples were assessed by RT-PCR arrays. RESULTS: mRNA expression level of chemokines (IL8, semaphorin 7A) correlated with hepatic steatosis in both liver and SAT. Liver expression of inflammasome components (IL1ß, IL18, caspase-1) and SAT IL6 and CCL2 correlated with liver damage. In patients with mild ALD, 1 week of alcohol withdrawal was sufficient to decrease expression level of total macrophage markers in the adipose tissue, to orient adipose tissue macrophages (ATM) towards an anti-inflammatory M2 phenotype and to decrease the mRNA expression of cytokines/chemokines (IL18, CCL2, osteopontin, semaphorin 7A). In patients with severe ALD, 1 week of abstinence was also associated with an increase in CCL18 expression. CONCLUSIONS: In alcoholic patients, upregulation of chemotactic factors in the liver and SAT is an early event that begins as early as the steatosis stage. The inflammasome pathway is upregulated in the liver of patients with ALD. One week of alcohol withdrawal alleviates macrophage infiltration in SAT and orients ATM towards a M2 anti-inflammatory phenotype; this implicates alcohol in adipose tissue inflammation (ClinicalTrials.gov NCT00388323).

Housekeeping gene variability in the liver of alcoholic patients.

BACKGROUND: Quantification of gene expression using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) requires normalization to an endogenous reference gene termed housekeeping gene (HKG). Many of the commonly used HKGs are regulated and vary under experimental conditions and disease stages. Alcoholic liver disease (ALD) is associated with several different liver histological lesions that may modulate HKG expression. We investigated the variability of commonly used HGKs (18S, ß-actin, glyceraldehyde-3-phosphate [GAPDH], and arginine/serine-rich splicing factor [SFRS4]) in the liver of patients with ALD. METHODS: Fifty consecutive patients at different stages of ALD underwent liver biopsy. The stability of HKG was assessed according to liver histological lesions. RESULTS: ß-actin had the highest coefficient of dispersion (COD) (23.9). ß-actin tended to decrease with steatosis and to increase with alcoholic hepatitis; ß-actin also increased in patients with both alcoholic hepatitis and cirrhosis. GAPDH and SFRS4 COD were 2.8 and 2.1, respectively. GAPDH was decreased with steatosis and increased with alcoholic hepatitis and fibrosis. 18S had the lowest COD (1.4). Both 18S and SFRS4 levels were not significantly modified with respect to all alcohol-induced liver histological lesions. CONCLUSIONS: In patients with ALD, the most constantly expressed HKGs are 18S and SFRS4. These genes are appropriate reference genes for normalization of RT-qPCR in the liver of patients with ALD. The use of other HKGs such as ß-actin or GAPDH would lead to misinterpretation of the results.

Harmful effect of adipose tissue on liver lesions in patients with alcoholic liver disease.

BACKGROUND & AIMS: Adipose tissue is an important source of cytokines. Excess weight is an independent risk factor for steatosis, acute alcoholic hepatitis (AAH), and cirrhosis in patients with alcoholic liver disease (ALD). In this study, we investigated the role of adipose tissue in human ALD. PATIENTS AND METHODS: Fifty patients with ALD underwent liver and abdominal subcutaneous adipose tissue biopsies and supplied blood samples for the investigation of cytokine gene expression and secretion, as well as liver histology. RESULTS: The levels of TNF-alpha and IL-10 in adipose tissue were higher in patients with AAH. IL-10 level in adipose tissue was also correlated with fibrosis score. TNF-alpha gene expression in adipose tissue was correlated with Maddrey score, blood C-reactive protein (CRP) concentration and liver IL-6 concentration. IL-6 production levels in the liver were higher in patients with AAH and correlated with AAH score, liver histological lesions, liver TNF-alpha concentration, Maddrey score, and blood CRP concentration. Plasma concentrations of soluble forms of TNF-receptor were correlated with inflammatory lesions in the liver, Maddrey score and fibrosis score. CONCLUSION: In patients with ALD, inflammation occurs not only in the liver, but also in the adipose tissue. Adipose tissue inflammation is correlated with the severity of pathological features in the liver. Our findings may account for the harmful interactions between body mass index, AAH, fibrosis, and cirrhosis in alcoholic patients.