Cortical expression of peroxisome proliferator-activated receptor-alpha after human brain contusion

Recent studies have demonstrated that peroxisome proliferator-activated receptor-alpha (PPAR-alpha) agonists can protect the brain against excessive oxidative stress and inflammation in traumatic brain injury (TBI) and stroke through endogenous PPAR-alpha. However, it has not been investigated whether, and to what degree, cerebral expression of PPAR-alpha changes after TBI, especially in the human brain. In this study, 12 contused brain samples were obtained from 11 patients undergoing surgery for TBI 6 - 98 h after trauma. PPAR-alpha binding activity was measured by electrophoretic mobility shift assay, and temporal and cellular expression of PPAR-alpha by immunohistochemistry. The results showed that a persistent upregulation of PPAR-alpha binding activity and protein expression occurred in injured cortex after TBI, which peaked 24 - 72 h post-injury. Expression of PPAR-alpha was mainly located in glial and vascular endothelial cells with a little expression in the neurons. It is concluded that TBI could greatly upregulate the binding activity and protein expression of PPAR-alpha in injured human brain, which might be important in brain pathophysiology after TBI.     

Activation of peroxisome proliferator-activated receptor-alpha by fenofibrate prevents myocardial dysfunction during endotoxemia in rats

OBJECTIVE: To investigate the effects of fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, on cardiac function in a rat endotoxemia model. DESIGN: Prospective, randomized, controlled study. SETTING: University research laboratory. SUBJECTS: Three-month-old male Wistar rats. INTERVENTIONS: Animals were fed with standard diet containing no drug or fenofibrate (0.2%) for 14 days. They were then injected intravenously with either 5 mg/kg lipopolysaccharide (LPS and fenofibrate + LPS groups) or saline (control and fenofibrate groups). MEASUREMENTS AND MAIN RESULTS: In the LPS group, body weight loss, metabolic acidosis, and thrombocytopenia confirmed presence of systemic endotoxemia. LPS administration resulted in an early peak in plasma tumor necrosis factor-alpha, decreased cardiac contractility (isolated and perfused heart), reduced myofilament Ca2+ sensitivity (Triton-skinned cardiac fibers), and increased left ventricular nitric oxide (NO) end-oxidation products (NO(x) and NO2), without evidence of myocardial oxidative stress (thiobarbituric acid-reactive substances and antioxidant enzyme activities). Fenofibrate pretreatment (fenofibrate + LPS group) did not alter signs of endotoxemia but prevented reductions in both cardiac contractility and myofilament Ca2+ sensitivity. The peak of plasma tumor necrosis factor-alpha was attenuated, whereas myocardial NO(x) and NO2 remained similar to the LPS group. Oxidative stress was suggested from moderate increase in cardiac thiobarbituric acid-reactive substances and reduced glutathione peroxidase activity. CONCLUSION: Fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, may prevent endotoxemia-induced cardiac dysfunction and reduction in myofilament Ca2+ sensitivity. Our data also suggest a mediating role for early peak plasma tumor necrosis factor-alpha, but not for myocardial NO production or oxidative stress.     

Effect of peroxisome proliferator-activated receptor-alpha agonist (bezafibrate) on gastric secretion and gastric cytoprotection in rats

The effect of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) on gastric secretion and gastric cytoprotection was evaluated using five different models of gastric ulcers: acetic acid-induced chronic gastric ulcers, pylorus ligation, ethanol-induced, indomethacin-induced and ischemia-reperfusion-induced gastric ulcers. Bezafibrate, a PPAR-alpha agonist was administered at two different doses of 10 and 100 mg/kg body weight intraperitoneanally. Both doses of bezafibrate showed significant antiulcer effect in ethanol-induced, indomethacin-induced and pylorus ligation-induced gastric ulcers. Bezafibrate increased healing of ulcer in acetic acid-induced chronic gastric ulcer model. Both doses were also effective in preventing gastric lesions induced by ischemia-reperfusion. It was concluded that PPAR-alpha activation increases healing of gastric ulcers and also prevents development of gastric ulcers in rats.     

Thalidomide treatment reduces the alteration of paracellular barrier function in mice ileum during experimental colitis

Small intestine permeability is frequently altered in inflammatory bowel diseases and may be caused by the translocation of intestinal toxins through leaky small intestine tight junctions (TJs) and adherence. Thus, the aim of the present study was to examine the effects of thalidomide treatment on the permeability and structure of small intestine TJs in an animal model of experimental colitis induced by dinitrobenzene sulfonic acid (DNBS). Four days after colitis induction with DNBS, the ileal TJs were studied by means of transmission electron microscopy using lanthanum nitrate and immunohistochemistry of occludin and zonula occludens 1. When compared with DNBS-treated mice, thalidomide-treated (200 mg/kg orally starting 30 min after the administration of DNBS) mice subjected to DNBS-induced colitis experienced a significantly reduced rate of the extent and severity of the histological signs of colon injury associated with a significant reduction of plasma and colon tumor necrosis factor alpha levels. After administration of DNBS to the mice induced a significant increase of ileal permeability was observed. Distal colitis in mice induced an increase of TJ permeability throughout the entire small intestine, and the extent of alterations correlates with colonic damage. In particular, we have observed that thalidomide treatment resulted in a significant reduction of the following: (1) the degree of colon injury, (2) the alteration of zonula occludens 1 and occludin localization (immunohistochemistry), and (3) intestinal permeability caused by DNBS in the colon. Taken together, our results clearly show that thalidomide treatment reduced small intestinal permeability in experimental colitis through the regulation of TJ protein.     

5-lipoxygenase modulates the alteration of paracellular barrier function in mice ileum during experimental colitis

Small intestine permeability is frequently altered in inflammatory bowel disease and may be caused by the translocation of intestinal toxins through leaky small intestine tight junctions (TJs) and adherence. Recently, it has been shown that 5-lipoxygenase (5-LO) plays an important role in the development of various inflammatory conditions like inflammatory bowel disease. In the present study, by comparing the responses in wild-type mice (5-LOWT) with those of mice lacking the 5-lipoxygenase (5-LOKO), we investigated the role played by this enzyme in the permeability and structure of small intestine TJs in an animal model of experimental colitis. To address this question, we used an experimental model of colitis, induced by dinitrobenzene sulfonic acid (DNBS). Four days after colitis induction by DNBS, the ileal TJs were studied by means of transmission electron microscopy using lanthanum nitrate and immunohistochemistry of occludin and ZO-1. When compared with DNBS-treated 5-LOWT mice, DNBS-treated 5-LOKO mice experienced a reduced rate of the extent and severity of the histological signs of colon injury. After administration of DNBS, 5-LOWT mice showed a significant increase of ileal permeability (88.3% +/- 1.2%) compared with sham (5.6% +/- 0.5%). In colitis, the percentage of "leaky" junctions in terminal ilea correlated positively with the macroscopic colon damage score. Distal colitis in 5-LOWT mice induces an increase of TJ permeability throughout the entire small intestine, and the extent of alterations correlates with colonic damage. On the contrary, a significant reduction of (1) the degree of colon injury, (2) the alteration of ZO-1 and occludin localization (immunohistochemistry), and (3) ileal permeability (8.1% +/- 0.7%) caused by DNBS in the colon was observed in 5-LOKO mice. Similarly, the treatment of 5-LOWT with zileuton (50 mg/kg per oral gavage twice a day), a 5-LO inhibitor, resulted in a significant reduction of all the previously described parameters. Taken together, our results clearly demonstrate that 5-LO modulates small intestinal permeability in experimental colitis through the regulation of TJ protein.     

Modulation of cytochrome P-450 gene expression in endotoxemic mice is tissue specific and peroxisome proliferator-activated receptor-alpha dependent.

Administration of the bacterial endotoxin lipopolysaccharide (LPS) causes induction of cytochrome P-450 (CYP) 4A mRNAs in rat liver and kidney. Because induction of the CYP4A subfamily by chemicals requires peroxisome proliferator-activated receptor-alpha (PPARalpha), we determined whether CYP4A induction by LPS also requires PPARalpha by comparing the responses of PPARalpha-null (-/-) and wild-type (+/+) mice. Renal expression of CYP4A10, CYP4A14, and acyl-CoA oxidase was induced by LPS treatment in (+/+) mice, and these effects were absent in the (-/-) mice. In contrast, hepatic expression of CYP4A10 was down-regulated in the (+/+) animals, and no significant induction of acyl-CoA oxidase or CYP4A14 was detected in liver. Expression of the peroxisomal bifunctional enzyme was not significantly affected by LPS treatment. These results indicate that PPARalpha is activated in mouse kidney after LPS treatment and that this leads to modulation of some PPARalpha-regulated genes. However, the species and tissue specificity of these effects suggest that inflammatory pathways may modulate the induction via PPARalpha. Mice pair fed with LPS-treated mice showed no induction of renal CYP4A10 or CYP4A14, indicating that renal CYP4A induction during endotoxemia is not due to hypophagia. Down-regulation of CYP2A5, CYP2C29, and CYP3A11 by LPS was attenuated or blocked in the (-/-) mice, suggesting a role for PPARalpha in CYP down-regulation as well. Finally, we found that clofibrate caused an acute induction of two hepatic acute-phase mRNAs that was only partially dependent on PPARalpha.     

Effect of zinc supplementation on intestinal permeability in experimental colitis

Increased small-intestine permeability has been documented in experimental colitis in the rat. Zinc supplementation improves mucosal repair in patients with diarrhea, as well as paracellular permeability in malnourished guinea pigs. In this study, we sought to evaluate the effect of zinc supplementation on small-and large-intestine tight junctions in rats with acute colitis. Rats were given zinc at a dosage of 2 or 30 mg/kg body wt or glucose by gavage starting 3 days before colitis was induced through the intrarectal administration of dinitro-benzene-sulfonic acid and for 7 days thereafter. We evaluated small-intestine permeability by the number of tight junctions showing extravasation of lanthanum under electron microscopy. Low-dose zinc affected none of the examined parameters of colitis severity. Rats given high-dose zinc showed colitis of similar macroscopic and biochemical severity. However, zinc-treated rats weighed more than unsupplemented ones. The number of perfused tight-junction complexes was significantly higher in animals with colitis than in controls and in the rats with colitis given high-dose zinc. Zinc may regulate tight-junction permeability, with possible implications for healing processes in inflammatory bowel diseases.     

Down-regulation of X-linked inhibitor of apoptosis synergistically enhanced peroxisome proliferator-activated receptor gamma ligand-induced growth inhibition in colon cancer

We found previously that X-linked inhibitor of apoptosis protein (XIAP), a potent endogenous inhibitor of apoptosis, is overexpressed in colon cancer. Ligand-induced activation of peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to exert proapoptotic and antiproliferative effects in many cancer cell types. However, neither XIAP down-regulation alone nor monotherapy using PPARgamma ligands is potent enough to control colon cancer. We explored whether XIAP inhibition and PPARgamma activation offer a synergistic anticancer effect in colon cancer. HCT116-XIAP(+/+) and HCT116-XIAP(-/-) cells were treated with troglitazone or 15-deoxy-Delta(12,14)-prostaglandin J(2) (15-PGJ(2)). Cell growth and apoptosis were measured. Nude mice were s.c. inoculated with HCT116 cells with or without oral troglitazone. Tumor growth, angiogenesis, and apoptosis were measured. Troglitazone- and 15-PGJ(2)-induced growth inhibition and apoptosis were more prominent in HCT116-XIAP(-/-) cells. Troglitazone- and 15-PGJ(2)-induced apoptosis correlated with enhanced cleavage of caspases and poly(ADP-ribose) polymerase, which were more profound in HCT116-XIAP(-/-) cells. Pretreatment of cells with XIAP inhibitor 1396-12 also sensitized HCT116-XIAP(+/+) cells to PPARgamma ligand-induced apoptosis. Troglitazone significantly retarded the growth of xenograft tumors, more significantly so in HCT116-XIAP(-/-) cell-derived tumors. Reduction of tumor size was associated with reduced expression of Ki-67, vascular endothelial growth factor, and CD31 as well as increased apoptosis. Loss of XIAP significantly sensitized colorectal cancer cells to PPARgamma ligand-induced apoptosis and inhibition of cell proliferation. Thus, simultaneous inhibition of XIAP and activation of PPARgamma may have a synergistic antitumor effect against colon cancer.     

Chronic activation of peroxisome proliferator-activated receptor-alpha with fenofibrate prevents alterations in cardiac metabolic phenotype without changing the onset of decompensation in pacing-induced heart failure

Severe heart failure (HF) is characterized by profound alterations in cardiac metabolic phenotype, with down-regulation of the free fatty acid (FFA) oxidative pathway and marked increase in glucose oxidation. We tested whether fenofibrate, a pharmacological agonist of peroxisome proliferator-activated receptor-alpha, the nuclear receptor that activates the expression of enzymes involved in FFA oxidation, can prevent metabolic alterations and modify the progression of HF. We administered 6.5 mg/kg/day p.o. fenofibrate to eight chronically instrumented dogs over the entire period of high-frequency left ventricular pacing (HF + Feno). Eight additional HF dogs were not treated, and eight normal dogs were used as a control. [3H]Oleate and [14C]Glucose were infused intravenously to measure the rate of substrate oxidation. At 21 days of pacing, left ventricular end-diastolic pressure was significantly lower in HF + Feno (14.1 +/- 1.6 mm Hg) compared with HF (18.7 +/- 1.3 mm Hg), but it increased up to 25 +/- 2 mm Hg, indicating end-stage failure, in both groups after 29 +/- 2 days of pacing. FFA oxidation was reduced by 40%, and glucose oxidation was increased by 150% in HF compared with control, changes that were prevented by fenofibrate. Consistently, the activity of myocardial medium chain acyl-CoA dehydrogenase, a marker enzyme of the FFA beta-oxidation pathway, was reduced in HF versus control (1.46 +/- 0.25 versus 2.42 +/- 0.24 micromol/min/gram wet weight (gww); p < 0.05) but not in HF + Feno (1.85 +/- 0.18 micromol/min/gww; N.S. versus control). Thus, preventing changes in myocardial substrate metabolism in the failing heart causes a modest improvement of cardiac function during the progression of the disease, with no effects on the onset of decompensation.     

Vanin-1 licenses inflammatory mediator production by gut epithelial cells and controls colitis by antagonizing peroxisome proliferator-activated receptor gamma activity

Colitis involves immune cell-mediated tissue injuries, but the contribution of epithelial cells remains largely unclear. Vanin-1 is an epithelial ectoenzyme with a pantetheinase activity that provides cysteamine/cystamine to tissue. Using the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-colitis model we show here that Vanin-1 deficiency protects from colitis. This protection is reversible by administration of cystamine or bisphenol A diglycidyl ether, a peroxisome proliferator-activated receptor (PPAR)gamma antagonist. We further demonstrate that Vanin-1, by antagonizing PPARgamma, licenses the production of inflammatory mediators by intestinal epithelial cells. We propose that Vanin-1 is an epithelial sensor of stress that exerts a dominant control over innate immune responses in tissue. Thus, the Vanin-1/pantetheinase activity might be a new target for therapeutic intervention in inflammatory bowel disease.     

The anti-inflammatory effect of curcumin in an experimental model of sepsis is mediated by up-regulation of peroxisome proliferator-activated receptor-gamma

OBJECTIVE: Although phytochemical curcumin has been shown to possess anti-inflammatory properties, it remains unknown whether this agent has any beneficial effects in sepsis. The purpose of this study was to demonstrate whether curcumin protects septic animals and, if so, whether activation of peroxisome proliferator-activated receptor (PPAR)-gamma, an anti-inflammatory nuclear receptor, plays any role. DESIGN: Prospective, controlled, and randomized animal study. SETTING: A research institute laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: A bolus injection of 0.2 micromol of curcumin was given intravenously to male adult rats, followed by continuous infusion of curcumin (0.24 micromol/day) for 3 days via a primed 2-mL mini-pump. The rats were then subjected to sepsis by cecal ligation and puncture (CLP). MEASUREMENTS AND MAIN RESULTS: Serum levels of liver enzymes (alanine aminotransferase and aspartate aminotransferase), lactate, albumin, and tumor necrosis factor (TNF)-alpha were measured at 20 hrs after CLP (i.e., late stage of sepsis). In addition, a 10-day survival curve was conducted following CLP and cecal excision with or without curcumin treatment. Furthermore, macrophages cell line RAW 264.7 cells were treated with curcumin followed by stimulation with endotoxin. TNF-alpha and PPAR-gamma expression were then measured. The results indicate that intravenous administration of curcumin before the onset of sepsis attenuated tissue injury, reduced mortality, and decreased the expression of TNF-alpha in septic animals. Similar results were also found when curcumin was administered after the onset of sepsis. Moreover, the down-regulated PPAR-gamma in the liver at 20 hrs after CLP was significantly improved by curcumin treatment. Concurrent administration of curcumin and GW9662, a specific PPAR-gamma antagonist, completely abolished the beneficial effects of curcumin under such conditions. In cultured RAW 264.7 cells, curcumin inhibited endotoxin-induced increases in TNF-alpha expression and markedly up-regulated PPAR-gamma expression without affecting cell viability. Curcumin also prevented morphologic alterations in macrophages induced by endotoxin. CONCLUSIONS: The protective effect of curcumin makes it or its analogues strong candidates as a novel therapy for sepsis. The beneficial effect of curcumin appears to be mediated by up-regulation of nuclear receptor PPAR-gamma.