Joan Clària

The selective cyclooxygenase-2 inhibitor SC-236 reduces liver fibrosis by mechanisms involving non-parenchymal cell apoptosis and PPARγ activation

The importance of inflammation in initiating the sequence of events that lead to liver fibrosis is increasingly recognized. In this study, we tested the effects of SC‐236, a selective cyclooxygenase (COX)‐2 inhibitor, in rats with carbon tetrachloride (CCl4)‐induced liver fibrosis. Livers from CCl4‐treated rats showed increased COX‐2 expression and 15‐deoxy‐prostaglandin (PG)J2 (15d‐PGJ2) formation, as well as decreased peroxisome proliferator‐activated receptor (PPAR)γ expression. In these animals, SC‐236 reduced liver fibrosis as revealed by histological analysis and by a reduction in hepatic hydroxyproline levels, metalloproteinase‐2 activity, and α‐smooth muscle actin expression. Interestingly, SC‐236 normalized 15d‐PGJ2 levels and restored PPARγ expression in the liver of CCl4‐treated rats. In isolated hepatic stellate cells (HSCs)—the major player in liver fibrogenesis—and Kupffer cells—the cell type primarily responsible for increased hepatic COX‐2—SC‐236 exhibited remarkable pro‐apoptotic and growth inhibitory properties. Of interest, SC‐236 decreased HSC viability to a similar extent than the PPARγ ligand rosiglitazone. Moreover, SC‐236 significantly induced PPARγ expression in HSCs and acted as a potent PPARγ agonist in a luciferase‐reporter trans‐activation assay. These data indicate that, by mechanisms involving non‐parenchymal cell apoptosis and PPARγ activation, the selective COX‐2 inhibitor SC‐236 might have therapeutic potential for prevention of liver fibrosis.

Incidence, Predictive Factors, and Prognosis of the Hepatorenal Syndrome in Cirrhosis With Ascites

BACKGROUND The aim of the study was to investigate the incidenc, predictive factors, and prognosis of the hepatorenal syndrome in cirrhosis with ascites. METHODS The study is a follow-up investigation in 234 nonazotemic patients with cirrhosis and ascites. Thirty-nine variables obtained at inclusion were analyzed as possible predictors of hepatorenal syndrome occurrence (Kaplan-Meier method, Mantel-Cox test, and step-wise Cox regression procedure). RESULTS The probability of hepatorenal syndrome occurrence was 18% at 1 year and 39% at 5 years. Sixteen variables had predictive value for hepatorenal syndrome occurrence in the univariate analysis: history of ascites, hepatomegaly, nutritional status, blood urea nitrogen level, serum creatinine concentration, serum sodium and potassium concentration, serum and urine osmolality, urinary sodium excretion, free water clearance after a water load, glomerular filtration rate, arterial pressure, plasma renin activity, plasma norepinephrine concentration, and esophageal varices. Neither etiology (alcoholic vs. nonalcoholic) nor the Child-Pugh score had predictive value. A multivariate analysis disclosed only three independent predictors of hepatorenal syndrome occurrence: low serum sodium concentration, high plasma renin activity, and absence of hepatomegaly. CONCLUSIONS The hepatorenal syndrome is a relatively frequent complication in cirrhotic patients with ascites that is associated with an extremely short survival. Liver size, plasma renin activity, and serum sodium concentration are predictors of hepatorenal syndrome occurrence in these patients.

Obesity-induced insulin resistance and hepatic steatosis are alleviated by ω-3 fatty acids: a role for resolvins and protectins

Omega‐3‐polyunsaturated fatty acids (w‐3‐PUFAs) have well‐documented protective effects that are attributed not only to eicosanoid inhibition but also to the formation of novel biologically active lipid mediators (i.e., resolvins and protectins). In this study, we examined their effects on ob/ob mice, an obesity model of insulin resistance and fatty liver disease. Dietary intake ofw‐3‐PUFAs had insulin‐sensitizing actions in adipose tissue and liver and improved insulin tolerance in obese mice. Genes involved in insulin sensitivity (PPAR/γ), glucose transport (GLUT‐2/GLUT–4), and insulin receptor signaling (IRS‐1/IRS–2) were up‐regulated byw‐3‐PUFAs. Moreover,w‐3‐PUFAs increased adiponectin, an anti‐inflammatory and insulin‐sensitizing adipokine, and induced AMPK phosphorylation, a fuel‐sensing enzyme and a gatekeeper of the energy balance. Concomitantly, hepatic steatosis was alleviated byw‐3‐PUFAs. A lipidomic analysis with liquid chromatography/mass spectrome‐try/mass spectrometry revealed that w‐3‐PUFAs inhibited the formation of w‐6‐PUFA‐derived eicosanoids, while triggering the formation of w‐3‐PUFA‐derived resolvins and protectins. Moreover, representative members of these lipid mediators, namely resolvin E1 and protectin D1, mimicked the insulin‐sensitizing and antisteatotic effects of w‐3‐PUFAs and induced adiponectin expression to a similar extent that of rosigli‐tazone, a member of the thiazolidinedione family of antidiabetic drugs. Taken together, these findings uncover beneficial actions of w‐3‐PUFAs and their bioactive lipid autacoids in preventing obesity‐induced insulin resistance and hepatic steatosis.—Gonzalez‐Periz, A.,Horrillo, R., Ferre, N., Gronert, K., Dong, B., Moran‐Salvador, E.,Titos, E., Martinez‐Clemente, M.,Lopez‐Parra, M.,Arroyo, V., Claria, J. Obesity‐induced insulin resistance and hepatic steatosis are alleviated byw‐3 fatty acids: a role for resolvins and protectins. FASEB J. 23, 1946–1957 (2009)

Resolvin D1 and Its Precursor Docosahexaenoic Acid Promote Resolution of Adipose Tissue Inflammation by Eliciting Macrophage Polarization toward an M2-Like Phenotype

We recently demonstrated that ω-3-polyunsaturated fatty acids ameliorate obesity-induced adipose tissue inflammation and insulin resistance. In this study, we report novel mechanisms underlying ω-3-polyunsaturated fatty acid actions on adipose tissue, adipocytes, and stromal vascular cells (SVC). Inflamed adipose tissue from high-fat diet-induced obese mice showed increased F4/80 and CD11b double-positive macrophage staining and elevated IL-6 and MCP-1 levels. Docosahexaenoic acid (DHA; 4 μg/g) did not change the total number of macrophages but significantly reduced the percentage of high CD11b/high F4/80-expressing cells in parallel with the emergence of low-expressing CD11b/F4/80 macrophages in the adipose tissue. This effect was associated with downregulation of proinflammatory adipokines in parallel with increased expression of IL-10, CD206, arginase 1, resistin-like molecule α, and chitinase-3 like protein, indicating a phenotypic switch in macrophage polarization toward an M2-like phenotype. This shift was confined to the SVC fraction, in which secretion of Th1 cytokines (IL-6, MCP-1, and TNF-α) was blocked by DHA. Notably, resolvin D1, an anti-inflammatory and proresolving mediator biosynthesized from DHA, markedly attenuated IFN-γ/LPS-induced Th1 cytokines while upregulating arginase 1 expression in a concentration-dependent manner. Resolvin D1 also stimulated nonphlogistic phagocytosis in adipose SVC macrophages by increasing both the number of macrophages containing ingested particles and the number of phagocytosed particles and by reducing macrophage reactive oxygen species production. No changes in adipocyte area and the phosphorylation of hormone-sensitive lipase, a rate-limiting enzyme regulating adipocyte lipolysis, were observed. These findings illustrate novel mechanisms through which resolvin D1 and its precursor DHA confer anti-inflammatory and proresolving actions in inflamed adipose tissue.

Cyclooxygenase-2 and 5-lipoxygenase converging functions on cell proliferation and tumor angiogenesis: implications for cancer therapy

Cyclooxygenase (COX) and lipoxygenase (LO) metabolic pathways are emerging as key regulators of cell proliferation and neo‐angiogenesis. COX and LO inhibitors are being investigated as potential anticancer drugs and results from clinical trials seem to be encouraging. In this article we will review evidence of COX‐2 and 5‐LO involvement in cancer pathobiology, propose a model of integrated control of cell proliferation by these enzymes, and discuss the pharmacologic implications of this model.—Romano, M., Clària, J. Cyclooxygenase‐2 and 5‐lipoxygenase converging functions on cell proliferation and tumor angiogenesis: implications for cancer therapy. FASEB J. 17, 1986–1995 (2003)

Role for PPARγ in obesity-induced hepatic steatosis as determined by hepatocyte- and macrophage-specific conditional knockouts

Peroxisome proliferator‐activated receptor (PPAR) γ is a nuclear receptor central to glucose and lipid homeostasis. PPARγ role in nonalcoholic fatty liver disease is controversial because PPARγ over‐expression is a general property of steatotic livers, but its activation by thiazolidinediones reduces hepatic steatosis. Here, we investigated hepatic PPARγ function by using Cre‐loxP technology to generate hepatocyte (PPARγΔhep)‐ and macrophage (PPARγΔmac)‐specific PPARγ‐knockout mice. Targeted deletion of PPARγ in hepatocytes, and to a lesser extent in macrophages, protected mice against high‐fat diet‐induced hepatic steatosis. Down‐regulated expression of genes involved in lipogenesis (SCD1, SREBP‐1c, and ACC), lipid transport (CD36/FAT, L‐FABP, and MTP), and β‐oxidation (PPARα and ACO) was observed in PPARγΔhep mice. Moreover, PPARγΔhep mice showed improved glucose tolerance and reduced PEPCK expression without changes in Pcx, Fbp1, and G6Pc expression and CREB and JNK phosphorylation. In precision‐cut liver slices (PCLSs) and hepatocytes, rosiglitazone either alone or in combination with oleic acid increased triglyceride accumulation, an effect that was blocked by the PPARγ antagonist biphenol A diglycidyl ether (BADGE). PCLSs and hepatocytes from PPARγΔhep mice showed blunted responses to rosiglitazone and oleic acid, whereas the response to these compounds remained intact in PCLSs from PPARγΔmac mice. Collectively, these findings establish PPARγ expression in hepatocytes as a prosteatotic factor in fatty liver disease.—Morán‐Salvador, E., López‐Parra, M., García‐Alonso, V., Titos, E., Martínez‐Clemente, M., González‐Périz, A., López‐Vicario, C., Barak, Y., Arroyo, V., Clària, J. Role for PPARγ in obesity‐induced hepatic steatosis as determined by hepatocyte‐ and macrophage‐specific conditional knockouts. FASEB J. 25, 2538–2550 (2011). www.fasebj.org

Docosahexaenoic acid (DHA) blunts liver injury by conversion to protective lipid mediators: protectin D1 and 17S-hydroxy-DHA

Docosahexaenoic acid (DHA) is a ω‐3 essential fatty acid that reduces the incidence and severity of a number of diseases. Recently, a novel series of DHA‐derived lipid mediators with potent protective actions has been identified. In this study we demonstrate that dietary amplification of these DHA‐derived products protects the liver from necroinflammatory injury. In vitro, supplementation of hepatocytes with DHA significantly reduced hydrogen peroxide‐induced DNA damage, evaluated by the “comet assay,” and oxidative stress, determined by measurement of malondialdehyde levels. In vivo, dietary supplementation of mice with DHA ameliorated carbon tetrachloride‐induced necroinflammatory damage. In addition, hepatic cyclooxygenase‐2 expression and PGE2 levels were significantly reduced in mice fed DHA‐enriched diets. In these animals, increased hepatic formation of DHA‐derived lipid mediators (i.e., 17S‐hydroxy‐DHA (17S‐HDHA) and protectin D1) was detected by HPLC‐gas chromatography/mass spectrometry analysis. Consistent with these findings, synthetic 17‐HDHA abrogated genotoxic and oxidative damage in hepatocytes and decreased TNF‐α release and 5‐lipoxygenase expression in macrophages. In a transactivation assay, 17‐ HDHA acted in a concentration‐dependent manner as a PPARγ agonist. Taken together, these findings identify a potential role for DHA‐derived products, specifically 17S‐HDHA and protectin D1, in mediating the protective effects of dietary DHA in necroinflammatory liver injury.—González‐Périz, A., Planagumà, A., Gronert, K., Miquel, R., López‐Parra, M., Titos, E., Horrillo, R., Ferré, N., Deulofeu, R., Arroyo, V., Rodés, J., Clària, J. Docosahexaenoic acid (DHA) blunts liver injury by conversion to protective lipid mediators: protectin D1 and 17S‐hydroxy‐DHA. FASEB J. 20, E1844–E1855 (2006)

Circulating levels of endothelin in cirrhosis

BACKGROUND Current information concerning endothelin in cirrhosis is conflicting. Plasma endothelin concentration has been found to be increased in some studies and normal or reduced in others. The present study was aimed to investigate the plasma levels of endothelin in cirrhosis and to assess whether it is involved in the renal and hemodynamic disturbances and neurohumoral changes present in this condition. METHODS Renal function, plasma renin activity, and plasma concentration of aldosterone, norepinephrine, antidiuretic hormone, atrial natriuretic factor, and endothelin were measured in 9 healthy subjects, 7 compensated cirrhotics, and 25 cirrhotics with ascites (10 with functional renal failure). RESULTS Cirrhotics with ascites with and without functional renal failure showed higher endothelin levels (15.6 +/- 6.4 and 15.7 +/- 4.6 pg/mL, respectively; mean +/- SD) than compensated cirrhotics (6.4 +/- 1.8 pg/mL) and healthy subjects (3.4 +/- 1.0 pg/mL) (analysis of variance, F = 21.84; P < 0.001). These patients also showed higher plasma levels of renin, aldosterone, norepinephrine, antidiuretic hormone, and atrial natriuretic factor, although plasma endothelin levels only correlated significantly with plasma atrial natriuretic factor (r = 0.73, P < 0.001) and antidiuretic hormone concentrations (r = 0.59, P < 0.001). In 7 additional nonazotemic cirrhotics with ascites, plasma renin activity and the plasma concentration of aldosterone and endothelin were measured before and 24 hours after the intravenous administration of a saline solution of human serum albumin. Volume expansion markedly suppressed renin and aldosterone but not endothelin (21.03 +/- 7.34 vs. 23.97 +/- 14.29 pg/mL). CONCLUSIONS Circulating plasma levels of endothelin are elevated in cirrhosis with ascites and do not decrease following plasma volume expansion.

Resolvins, specialized proresolving lipid mediators, and their potential roles in metabolic diseases.

Inflammation is associated with the development of diseases characterized by altered nutrient metabolism. Although an acute inflammatory response is host-protective and normally self-limited, chronic low-grade inflammation associated with metabolic diseases is sustained and detrimental. The resolution of inflammation involves the termination of neutrophil recruitment, counterregulation of proinflammatory mediators, stimulation of macrophage-mediated clearance, and tissue remodeling. Specialized proresolving lipid mediators (SPMs)-resolvins, protectins, and maresins-are novel autacoids that resolve inflammation, protect organs, and stimulate tissue regeneration. Here, we review evidence that the failure of resolution programs contributes to metabolic diseases and that SPMs may play pivotal roles in their resolution.

Cyclooxygenase-2 biology.

In mammalian cells, eicosanoid biosynthesis is usually initiated by the activation of phospholipase A(2) and the release of arachidonic acid from membrane phospholipids in response to the interaction of a stimulus with a receptor on the cell surface. Arachidonic acid is subsequently transformed by the enzyme cyclooxygenase (COX) to prostaglandins (PGs) and thromboxane (TX). The COX pathway is of particular clinical relevance because it is the major target for non-steroidal anti-inflammatory drugs, which are commonly used for relieving inflammation, pain and fever. In 1991, it was disclosed that COX exists in two distinct isozymes (COX-1 and COX-2), one of which, COX-2, is primarily responsible for inflammation but apparently not for gastrointestinal integrity or platelet aggregation. For this reason, in recent years, novel compounds that are selective for this isozyme, the so-called selective COX-2 inhibitors or COXIBs, which retain anti-inflammatory activity but minimize the risk of gastrointestinal toxicity and bleeding, have been developed. This review article provides an overview and an update on the progress achieved in the area of COX-2 and PG biosynthesis and describes the role of COX-2 in health and disease. It also discusses some unresolved issues related to the use of selective COX-2 inhibitors as a safe and promising therapeutic option not only for the treatment of inflammatory states but also for cancer.