DIVERSE CARDIOPROTECTIVE SIGNALING MECHANISMS OF PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-γ LIGANDS, 15-DEOXY-Δ12,14-PROSTAGLANDIN J2 AND CIGLITAZONE, IN REPERFUSION INJURY

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a nuclear receptor that regulates diverse biological functions including inflammation. The PPARgamma ligands have been reported to exert cardioprotective effects and attenuate myocardial reperfusion injury. Here, we examined the molecular mechanisms of their anti-inflammatory effects. Male Wistar rats were subjected to myocardial ischemia and reperfusion and were treated with the PPAR-gamma ligands, 15-deoxy-Delta-prostaglandin J2 (15d-PGJ2) or ciglitazone, or with vehicle only, in the absence or presence of the selective PPAR-gamma antagonist GW-9662. In vehicle-treated rats, myocardial injury was associated with elevated tissue activity of myeloperoxidase, indicating infiltration of neutrophils, and elevated plasma levels of creatine kinase and tumor necrosis factor-alpha. These events were preceded by activation of the nuclear factor-kappaB pathway. The PPAR-gamma DNA binding was also increased in the heart after reperfusion. Treatment with ciglitazone or 15d-PGJ2 reduced myocardial damage and neutrophil infiltration and blunted creatine kinase levels and cytokine production. The beneficial effects of both ligands were associated with enhancement of PPAR-gamma DNA binding and reduction of nuclear factor-kappaB activation. Treatment with 15d-PGJ2, but not ciglitazone, enhanced DNA binding of heat shock factor 1 and upregulated the expression of the cardioprotective heat shock protein 70. Treatment with 15d-PGJ2, but not ciglitazone, also induced a significant increase in nuclear phosphorylation of the prosurvival kinase Akt. The cardioprotection afforded by ciglitazone was attenuated by the PPAR-gamma antagonist GW-9662. In contrast, GW-9662 did not affect the beneficial effects afforded by 15d-PGJ2. Thus, our data suggest that treatment with these chemically unrelated PPAR-gamma ligands results in diverse anti-inflammatory mechanisms.

Therapeutic effect of epigallocatechin-3-gallate in a mouse model of colitis

Epigallocatechin-3-gallate (EGCG), a green tea catechin, has been shown to inhibit signaling pathways involved in inflammation, including nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), which are important inducers of pro-inflammatory mediators. Aim of our study was to evaluate the therapeutic efficacy of EGCG in experimental colitis, which was induced by rectal administration of trinitrobenzenesulfonic acid (TNBS) in C57/BL6 mice. Mice were treated twice daily with vehicle or with EGCG (10 mg/kg) intraperitoneally, and sacrificed on days 1, 3, and 7 after TNBS administration. After induction of colitis, vehicle-treated mice experienced bloody diarrhea and loss of body weight. A remarkable colonic damage with hemorrhage, ulcers, and edema was observed and was associated with neutrophil infiltration as evaluated by myeloperoxidase (MPO) activity. Elevated plasma levels of tumor necrosis factor alpha, interleukin (IL)-6, IL-10 and keratinocyte-derived chemokine were also found. These events were paralleled by increased DNA binding of NF-kappaB and AP-1 in the colon of the vehicle-treated group. In contrast, the EGCG-treated mice experienced a very mild diarrhea and no weight loss. Damage of the colon was characterized by edema and hyperemia only. Tissue levels of MPO were also significantly reduced when compared to vehicle-treated mice. These beneficial effects of EGCG were associated with a significant reduction of NF-kappaB and AP-1 activation. However, treatment with EGCG did not reduce plasma cytokine levels. Our data demonstrate that EGCG may be beneficial in colitis through selective immunomodulatory effects, which may be mediated, at least in part, by inhibition of NF-kappaB and AP-1.

Synergistic effect of peroxisome proliferator activated receptor-gamma and liver X receptor-alpha in the regulation of inflammation in macrophages

Peroxisome proliferator-activated receptor-gamma (PPARgamma) and liver X receptor-alpha (LXRalpha) are nuclear ligand-activated transcription factors, which regulate lipid metabolism and inflammation. Murine J774.2 macrophages were stimulated with Escherichia coli lipopolysaccharide (concentration, 10 microg/mL) with or without the PPARgamma ligand, 15-deoxy-Delta prostaglandin J2 (15d-PGJ2), or the LXRalpha ligands, 22(R)-hydroxycholesterol and T0901317 (concentration range, 0.01-10 micromol/L), alone or in combination. Nitric oxide (NO) metabolites and tumor necrosis factor alpha production, inducible NO synthase expression, and mitochondrial respiration were measured. When added to the cells as single agents, 15d-PGJ2, 22(R)-hydroxycholesterol, or T0901317 reduced the lipopolysaccharide-induced NO and tumor necrosis factor alpha production and the inducible NO synthase expression, and partially maintained mitochondrial respiration in a concentration-dependent manner. When added to the cells in combination at suboptimal concentrations, 15d-PGJ2 with 22(R)-hydroxycholesterol, or 15d-PGJ2 with T0901317, exerted anti-inflammatory effects similar to much higher concentrations (10,000-fold to 100,000-fold) of each ligand alone. The anti-inflammatory effects of these ligands, alone or in combination, were associated with reduction of nuclear factor-kappaB activation and with enhancement of PPARgamma DNA binding. LXRalpha expression was upregulated in response to 15d-PGJ2 and to the LXRalpha ligands when added alone or in combination. Immunoprecipitation experiments revealed that PPARgamma interacted with LXRalpha. Our data demonstrate that the PPARgamma ligand, 15d-PGJ2, and the LXRalpha ligands, 22(R)-hydroxycholesterol and T0901317, although binding to different nuclear receptors (i.e., PPARgamma and LXRalpha, respectively), affect mediator production through common cell signaling events and exert a synergistic potentiation in a combined treatment at suboptimal concentrations. Thus, our data suggest that PPARgamma and LXRalpha may interact in controlling the inflammatory response in macrophages.

Epigallocatechin, a green tea polyphenol, attenuates myocardial ischemia reperfusion injury in rats

Epigallocatechin-3-gallate (EGCG) is the most prominent catechin in green tea. EGCG has been shown to modulate numerous molecular targets in the setting of inflammation and cancer. These molecular targets have also been demonstrated to be important participants in reperfusion injury, hence this study examines the effects of EGCG in myocardial reperfusion injury. Male Wistar rats were subjected to myocardial ischemia (30 min) and reperfusion (up to 2 h). Rats were treated with EGCG (10 mg/kg intravenously) or with vehicle at the end of the ischemia period followed by a continuous infusion (EGCG 10 mg/kg/h) during the reperfusion period. In vehicle-treated rats, extensive myocardial injury was associated with tissue neutrophil infiltration as evaluated by myeloperoxidase activity, and elevated levels of plasma creatine phosphokinase. Vehicle-treated rats also demonstrated increased plasma levels of interleukin-6. These events were associated with cytosol degradation of inhibitor kappaB-alpha, activation of IkappaB kinase, phosphorylation of c-Jun, and subsequent activation of nuclear factor-kappaB and activator protein-1 in the infarcted heart. In vivo treatment with EGCG reduced myocardial damage and myeloperoxidase activity. Plasma IL-6 and creatine phosphokinase levels were decreased after EGCG administration. This beneficial effect of EGCG was associated with reduction of nuclear factor-kB and activator protein-1 DNA binding. The results of this study suggest that EGCG is beneficial for the treatment of reperfusion-induced myocardial damage by inhibition of the NF-kappaB and AP-1 pathway.

15-DEOXY-??12,14-PROSTAGLANDIN J2 (15D-PGJ2), A PEROXISOME PROLIFERATOR ACTIVATED RECEPTOR ?? LIGAND, REDUCES TISSUE LEUKOSEQUESTRATION AND MORTALITY IN ENDOTOXIC SHOCK

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor that requires ligand activation for transcription. Experimental studies have shown that 15-deoxy-Delta-PGJ2 (15d-PGJ2) is a natural PPARgamma ligand which has potent anti-inflammatory properties. This study was designed to examine the effect and the molecular mechanisms of 15d-PGJ2 on tissue neutrophil infiltration and survival in endotoxic shock. Male Swiss albino mice were subjected to intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS, 25 mg/kg). Three hours after LPS mice received vehicle or 15d-PGJ2 (1 mg/kg) and continued treatment every 12 hours. Survival was monitored for 72 hours. In a separate experiment, mice were sacrificed 6 hours after LPS and tissue examined. In vehicle-treated mice, LPS injection resulted in a survival rate of 9%. Marked lung injury was characterized by hemorrhage, infiltration of inflammatory cells and reduction of alveolar space. Elevated levels of myeloperoxidase activity in lung and small intestine were indicative of infiltration of neutrophils. Increased expression of intercellular adhesion molecule-1, vascular cellular adhesion molecule-1 and E-selectin were observed in the lung and small intestine. These inflammatory events were associated with reduced expression of PPARgamma and with activation of nuclear factor-kappaB (NF-kappaB) in the lung. Treatment with 15d-PGJ2 improved survival rate to 55%, downregulated expression of adhesion molecules and reduced neutrophil infiltration in tissues. These beneficial effects were associated with reduced activation of NF-kappaB DNA binding, whereas expression and DNA binding of PPARgamma and expression of the cytoprotective heat shock protein (HSP) 70 were increased in the lung. Our data demonstrate that 15d-PGJ2 ameliorates endotoxic shock most likely through repressing the proinflammatory pathway of NF-kappaB and enhancement of the cytoprotective heat shock response.

Activator protein-1 signalling pathway and apoptosis are modulated by poly(ADP-ribose) polymerase-1 in experimental colitis

Poly(ADP-ribose) polymerase-1 (PARP-1) is activated in response to DNA injury in the nucleus of eukaryotic cells and has been implicated in intestinal barrier dysfunction during inflammatory bowel diseases. In this study we investigated whether PARP-1 may regulate the inflammatory response of experimental colitis at the level of signal transduction mechanisms. Mice genetically deficient of PARP-1 (PARP-1(-/-)) and wild-type littermates were subjected to rectal instillation of trinitrobenzene sulphonic acid (TNBS). Signs of inflammation were monitored for 14 days. In wild-type mice, TNBS treatment resulted in colonic ulceration and marked apoptosis, which was associated with decreased colon content of the antiapoptotic protein Bcl-2, whereas the proapoptotic Bax was unchanged. Elevated levels of plasma nitrate/nitrite, metabolites of nitric oxide (NO), were also found. These inflammatory events were associated with activation of c-Jun-NH(2) terminal kinase (JNK), phosphorylation of c-Jun and activation of the nuclear transcription factor activator protein-1 (AP-1) in the colon. In contrast, PARP-1(-/-) mice exhibited a significant reduction of colon damage and apoptosis, which was associated with increased colonic expression of Bcl-2 and lower levels of plasma nitrate/nitrite when compared to wild-type mice. Amelioration of colon damage was associated with a significant reduction of the activation of JNK and reduction of the DNA binding of AP-1. The data indicate that PARP-1 exerts a pathological role in colitis possibly by regulating the early stress-related transcriptional response through a positive modulation of the AP-1 and JNK pathways.

Light spread and scatter from some common adapting stimuli: computations based on the point-source light profile

A point source of light is not so imaged on the photoreceptor mosaic. The light is distributed over the retina by diffraction, imperfections in the optics of the eye, and scatter. The spatial distribution of light is specified quantitatively by the point-source light profile, which can be used in convolution to determine light spread from more complex visual stimuli. We use the Vos, Walraven and van Meeteren [Vision Res. 16, 215-219 (1976)] light profile to determine spread light in specific regions within the spared area of an illuminated surround, and within a thin spared ring in an otherwise uniformly illuminated circular field. Surrounds of different sizes and rings of various widths and diameters are evaluated.