Rationale: Airway inflammation is common in severe asthma despite antiinflammatory therapy with corticosteroids. Lipoxin A 4 (LXA 4 ) is an arachidonic acid-derived mediator that serves as an agonist for resolution of inflammation. Objectives: Airway levels of LXA 4 , as well as the expression of lipoxin biosynthetic genes and receptors, in severe asthma. Methods: Samples of bronchoalveolar lavage fluid were obtained from subjects with asthma and levels of LXA 4 and related eicosanoids were measured. Expression of lipoxin biosynthetic genes was determined in whole blood, bronchoalveolar lavage cells, and endobronchial biopsies by quantitative polymerase chain reaction, and leukocyte LXA 4 receptors were monitored by flow cytometry. Measurements and Main Results: Individuals with severe asthma had significantly less LXA 4 in bronchoalveolar lavage fluids (11.2 6 2.1 pg/ml) than did subjects with nonsevere asthma (150.1 6 38.5 pg/ml; P , 0.05). In contrast, levels of cysteinyl leukotrienes were increased in both asthma cohorts compared with healthy individuals. In severe asthma, 15-lipoxygenase-1 mean expression was decreased fivefold in bronchoalveolar lavage cells. In contrast, 15-lipoxgenase-1 was increased threefold in endobronchial biopsies, but expression of both 5-lipoxygenase and 15-lipoxygenase-2 in these samples was decreased. Cyclooxygenase-2 expression was decreased in all anatomic compartments sampled in severe asthma. Moreover, LXA 4 receptor gene and protein expression were significantly decreased in severe asthma peripheral blood granulocytes. Conclusions: Mechanisms underlying pathological airway responses in severe asthma include lipoxin underproduction with decreased expression of lipoxin biosynthetic enzymes and receptors. Together, these results indicate that severe asthma is characterized, in part, by defective lipoxin counterregulatory signaling circuits.

Docosahexaenoic acid (DHA) is a omega-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-alpha release and 5-lipoxygenase expression in macrophages. In a transactivation assay, 17-HDHA acted in a concentration-dependent manner as a PPARgamma 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.

No abstract

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)gamma 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 alpha-smooth muscle actin expression. Interestingly, SC-236 normalized 15d-PGJ2 levels and restored PPARgamma 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 PPARgamma ligand rosiglitazone. Moreover, SC-236 significantly induced PPARgamma expression in HSCs and acted as a potent PPARgamma agonist in a luciferase-reporter trans-activation assay. These data indicate that, by mechanisms involving non-parenchymal cell apoptosis and PPARgamma activation, the selective COX-2 inhibitor SC-236 might have therapeutic potential for prevention of liver fibrosis.

The wide spread use of statins for hypercholesterolemia has uncovered pleiotropic anti-inflammatory properties that were unexpected based on the drugs’ original design, yet mechanisms for these protective actions remains uncertain. Here, lovastatin triggered biosynthesis of the anti-inflammatory and pro-resolving mediator 15-epi-lipoxin A4 (15-epi-LXA4). During interactions between human neutrophils and airway epithelial cells, the statin induced increase in 15-epi-LXA4 was associated with increased 14,15-epoxyeicosatrienoic acid (14,15-EET) generation. When added to activated neutrophils, 14,15-EET enhanced 15-epi-LXA4 biosynthesis. In a murine model of airway mucosal injury and inflammation, lovastatin increased 15-epi-LXA4 formation in vivo and markedly decreased acute lung inflammation. Administration of 15-epi-LXA4 also inhibited lung inflammation in an additive manner with lovastatin. Together, these results indicate that statin-triggered 15-epi-LXA4 generation during human leukocyte-airway epithelial cell interactions is an endogenous mechanism for statin-mediated tissue protection at mucosal surfaces that may also be relevant in statins’ ability to stimulate the resolution of inflammation.

Background The relationship between anti-inflammatory lipoxins and pro-inflammatory leukotrienes may be important in the pathobiology of asthma and its severity. Objective To investigate whether exhaled breath condensate (EBC) lipoxin and leukotriene measurements can non-invasively characterize the asthmatic diathesis and its severity. Methods We measured lipoxin A4 (LXA4) and leukotriene B4 (LTB4) levels in EBC collected from asthmatics of different severities and from healthy controls. Results EBC LXA4 and LTB4 levels are elevated in asthmatics as compared to healthy controls (LXA4 31.40 vs. 2.41 pg/ml EBC respectively, p < 0.001; LTB4 45.62 vs. 3.82 pg/ml EBC, p < 0.001). While both eicosanoids are elevated in asthmatics, the ratio LXA4 to LTB4 decreases with increasing asthma severity. It is 41% lower in severe versus moderate asthmatics (0.52 vs. 0.88, p = 0.034). EBC LXA4 levels correlate with the degree of airflow obstruction measured by FEV1 (r = 0.28, p = 0.018). A cut-off value of 7 pg LXA4/ml EBC provides 90% sensitivity and 92% specificity for the diagnosis of asthma (AUC 0.96, p < 0.001). A cut-off value of 11 pg LTB4/ml EBC provides 100% sensitivity and 100% specificity for the diagnosis of asthma (AUC 1, p < 0.001). Conclusions Pro-resolving and pro-inflammatory eicosanoids are generated in airways of all asthmatics. The proportion of pro-resolving compounds declines with asthma severity. These findings support the role for EBC eicosanoid measurements in the non-invasive diagnosis of asthma and suggest that pro-resolving eicosanoid pathways are dys-regulated in severe asthma.

Estradiol enhances COX-2 expression and prostaglandin biosynthesis in TSC2-deficient cells via a rapamycin-insensitive, mTORC2-dependent mechanism.

Clària J. Increased susceptibility to exacerbated liver injury in hypercholesterolemic ApoEdeficient mice: potential involvement of oxysterols. Am J Physiol Gastrointest Liver Physiol 296: G553-G562, 2009. First published January 8, 2009 doi:10.1152/ajpgi.00547.2007.-The contribution of metabolic factors to the severity of liver disease is not completely understood. In this study, apolipoprotein E-deficient (ApoE Ϫ/Ϫ ) mice were evaluated to define potential effects of hypercholesterolemia on the severity of carbon tetrachloride (CCl 4)-induced liver injury. Under baseline conditions, hypercholesterolemic ApoE Ϫ/Ϫ mice showed increased hepatic oxidative stress (SOD activity/4-hydroxy-2-nonenal immunostaining) and higher hepatic TGF-␤1, MCP-1, and TIMP-1 expression than wild-type control mice. After CCl4 challenge, ApoE Ϫ/Ϫ mice exhibited exacerbated steatosis (Oil Red O staining), necroinflammation (hematoxylin-eosin staining), macrophage infiltration (F4/80 immunohistochemistry), and fibrosis (Sirius red staining and ␣-smooth muscle actin immunohistochemistry) and more severe liver injury [alanine aminotransferase (ALT) and aspartate aminotransferase] than wild-type controls. Direct correlations were identified between serum cholesterol and hepatic steatosis, fibrosis, and ALT levels. These changes did not reflect the usual progression of the disease in ApoE Ϫ/Ϫ mice, since exacerbated liver injury was not present in untreated age-paired ApoE Ϫ/Ϫ mice. Moreover, hepatic cytochrome P-450 expression was unchanged in ApoE Ϫ/Ϫ mice. To explore potential mechanisms, cell types relevant to liver pathophysiology were exposed to selected cholesterol-oxidized products. Incubation of hepatocytes with a mixture of oxysterols representative of those detected by GC-MS in livers from ApoE Ϫ/Ϫ mice resulted in a concentration-dependent increase in total lipoperoxides and SOD activity. In hepatic stellate cells, oxysterols increased IL-8 secretion through a NF-B-independent mechanism and upregulated TIMP-1 expression. In macrophages, oxysterols increased TGF-␤1 secretion and MCP-1 expression in a concentration-dependent manner. Oxysterols did not compromise cell viability. Taken together, these findings demonstrate that hypercholesterolemic mice are sensitized to liver injury and that cholesterol-derived products (i.e., oxysterols) are able to induce proinflammatory and profibrogenic mechanisms in liver cells.