BACKGROUNDAcute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the first steps in the development of multiple organ failure induced by sepsis. A systemic excessive inflammatory reaction is currently the accepted mechanism of the pathogenesis of sepsis. Several studies have suggested a protective role of the peroxisome proliferator activated receptor-β/δ (PPAR-β/δ) in related inflammatory diseases. But the role of PPARβ/δ in ALI remains uncertain. The aim of this study was to investigate the role and possible mechanism of PPARβ/δ in ALI induced by sepsis.

METHODSCecal ligation and puncture (CLP) was used as a sepsis model. Rats were randomly divided into four groups, the control group (CON, n = 6), sham-operation group (SHAM, n = 12), cecal ligation and puncture group (CLP, n = 30), GW501516 group (CLP+GW, n = 25), which underwent CLP and were subcutaneously injected with the PPAR-β/δ agonist GW501516 (0.05 mg/100 g body weight). Survival was monitored to 24 hours after operation. Blood pressure, serum creatinine, blood urea nitrogen, aspartate aminotrasferase and alanine aminotrasferase were measured after CLP. Concentrations of tumor necrosis factor α (TNF-α) and interleukin (IL)-1β in serum were detected by enzyme linked immunosorbent assay (ELISA) kits. Lung tissue samples were stained with H&E and scored according to the degree of inflammation. Bacterial colonies were counted in the peritoneal fluid. Alveolar macrophages were cultured and incubated with GW501516 (0.15 µmol/L) and PPARβ/δ adenovirus and then treated with Lipopolysaccharide (2 µg/ml) for 2 hours. The TNF-α, IL-1β and IL-6 RNA in lung and alveolar macrophages were determined by real-time PCR. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) in lung and alveolar macrophages was detected by Western blotting.

RESULTSGW501516 significantly increased the survival of septic rats, decreased histological damage of the lungs, reduced inflammatory cytokines in serum and lung tissues of septic rats and did not increase counts of peritoneal bacteria. In vitro, GW501516 and over-expression of PPARβ/δ attenuated gene expression of TNF-α, IL-1β and IL-6 in alveolar macrophages. Both in vivo and in vitro, PPARβ/δ inhibited the phosphorylation of STAT3.

CONCLUSIONPPARβ/δ plays a protective role in sepsis induced ALI via suppressing excessive inflammation.

Acute Lung Injury ; drug therapy ; etiology ; Animals ; Cells, Cultured ; Male ; PPAR delta ; agonists ; metabolism ; PPAR-beta ; agonists ; metabolism ; Rats ; Rats, Sprague-Dawley ; Sepsis ; complications ; drug therapy ; Thiazoles ; therapeutic use

Although peroxisome proliferator receptor (PPAR)-alpha and PPAR-gamma agonist have been developed as chemical tools to uncover biological roles for the PPARs such as lipid and carbohydrate metabolism, PPAR-delta has not been fully investigated. In this study, we examined the effects of the PPAR-delta agonist GW0742 on fatty liver changes and inflammatory markers. We investigated the effects of PPAR-delta agonist GW0742 on fatty liver changes in OLETF rats. Intrahepatic triglyceride contents and expression of inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and monocyte chemo-attractant protein-1 (MCP-1) and also, PPAR-gamma coactivator (PGC)-1alpha gene were evaluated in liver tissues of OLETF rats and HepG2 cells after GW0742 treatment. The level of TNF-alpha and MCP-1 was also examined in supernatant of Raw264. 7 cell culture. To address the effects of GW0742 on insulin signaling, we performed in vitro study with AML12 mouse hepatocytes. Rats treated with GW0742 (10 mg/kg/day) from 26 to 36 weeks showed improvement in fatty infiltration of the liver. In liver tissues, mRNA expressions of TNF-alpha, MCP-1, and PGC-1alpha were significantly decreased in diabetic rats treated with GW0742 compared to diabetic control rats. We also observed that GW0742 had inhibitory effects on palmitic acid-induced fatty accumulation and inflammatory markers in HepG2 and Raw264.7 cells. The expression level of Akt and IRS-1 was significantly increased by treatment with GW0742. The PPAR-delta agonist may attenuate hepatic fat accumulation through anti-inflammatory mechanism, reducing hepatic PGC-1alpha gene expression, and improvement of insulin signaling.
Animals ; Anti-Inflammatory Agents/*pharmacology/therapeutic use ; Blood Glucose ; Cytokines/genetics/metabolism ; Diabetes Mellitus/blood/immunology/metabolism ; Fatty Liver/blood/*drug therapy/immunology ; Glucose Tolerance Test ; Hep G2 Cells ; Humans ; Insulin Resistance ; Liver/metabolism ; Male ; PPAR delta/*agonists/metabolism ; Rats ; Rats, Long-Evans ; Thiazoles/*pharmacology/therapeutic use ; Triglycerides/metabolism

To establish a new high-throughput screening model for the agonist of PPARdelta, PPARdelta gene was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR), and subcloned to pGEM-T Vector for sequencing, then the PPARdelta fragment was excised by restriction enzymes, and inserted into pTARGET Vector to construct expression vector pTARGET-ppARdelta. Insert three copies of PPRE into pGl3-promoter vector to construct expression vector pGl3-PPRE x 3-luc. The vector pTARGET-ppARdelta was transiently cotransfected with pGl3-PPRE x 3-luc into different cell lines to assay the expression levels of luciferase. The PPARdelta agonist screening model was established and optimized. Bezafibrate and linoleic acid can induce the expression of luciferase significantly and in a dose-dependent manner. This method can be used for high throughput screening for the agonist of PPARdelta, which might become lead compounds for new anti-atheroscleriosis or anti-adiposity drugs.
3T3 Cells ; Animals ; Bezafibrate ; pharmacology ; Cell Line ; Dose-Response Relationship, Drug ; Drug Evaluation, Preclinical ; methods ; Genetic Vectors ; chemistry ; genetics ; HeLa Cells ; Humans ; Linoleic Acid ; pharmacology ; Lipids ; chemistry ; Luciferases ; genetics ; metabolism ; Mice ; PPAR delta ; agonists ; genetics ; Recombinant Fusion Proteins ; genetics ; metabolism ; Transfection ; methods