Role of peroxisome proliferator-activated receptor-gamma in the protection afforded by 15-deoxydelta12,14 prostaglandin J2 against the multiple organ failure caused by endotoxin

Role of JAK-STAT and PPAR-Gamma Signalling Modulators in the Prevention of Autism and Neurological Dysfunctions

The Janus-kinase (JAK) and signal transducer activator of transcription (STAT) signalling pathways regulate gene expression and control various factors involved in normal physiological functions such as cell proliferation, neuronal development, and cell survival. JAK activation phosphorylates STAT3 in astrocytes and microglia, and this phosphorylation has been linked to mitochondrial damage, apoptosis, neuroinflammation, reactive astrogliosis, and genetic mutations. As a regulator, peroxisome proliferator-activated receptor gamma (PPAR-gamma), in relation to JAK-STAT signalling, prevents this phosphorylation and aids in the treatment of the above-mentioned neurocomplications. Changes in cellular signalling may also contribute to the onset and progression of autism. Thus, PPAR-gamma agonist upregulation may be associated with JAK-STAT signal transduction downregulation. It may also be responsible for attenuating neuropathological changes by stimulating SOCS3 or involving RXR or SMRT, thereby reducing transcription of the various cytokine proteins and genes involved in neuronal damage. Along with JAK-STAT inhibitors, PPAR-gamma agonists could be used as target therapeutic interventions for autism. This research-based review explores the potential involvement and mutual regulation of JAK-STAT and PPAR-gamma signalling in controlling multiple pathological factors associated with autism.

Pioglitazone Ameliorates Acute Endotoxemia-Induced Acute on Chronic Renal Dysfunction in Cirrhotic Ascitic Rats

Endotoxemia-activated tumor necrosis factor (TNFα)/nuclear factor kappa B (NFκB) signals result in acute on chronic inflammation-driven renal dysfunction in advanced cirrhosis. Systemic activation of peroxisome proliferator-activated receptor gamma (PPARγ) with pioglitazone can suppress inflammation-related splanchnic and pulmonary dysfunction in cirrhosis. This study explored the mechanism and effects of pioglitazone treatment on the abovementioned renal dysfunction in cirrhotic rats. Cirrhotic ascitic rats were induced with renal dysfunction by bile duct ligation (BDL). Then, 2 weeks of pioglitazone treatment (Pio, PPAR gamma agonist, 12 mg/kg/day, using the azert osmotic pump) was administered from the 6th week after BDL. Additionally, acute lipopolysaccharide (LPS, Escherichia coli 0111:B4; Sigma, 0.1 mg/kg b.w, i.p. dissolved in NaCl 0.9%) was used to induce acute renal dysfunction. Subsequently, various circulating, renal arterial and renal tissue pathogenic markers were measured. Cirrhotic BDL rats are characterized by decreased mean arterial pressure, increased cardiac output and portal venous pressure, reduced renal arterial blood flow (RABF), increased renal vascular resistance (RVR), increased relative renal weight/hydroxyproline, downregulated renal PPARγ expression, upregulated renal inflammatory markers (TNFα, NFκB, IL-6, MCP-1), increased adhesion molecules (VCAM-1 and ICAM-1), increased renal macrophages (M1, CD68), and progressive renal dysfunction (increasing serum and urinary levels of renal injury markers (lipocalin-2 and IL-18)). In particular, acute LPS administration induces acute on chronic renal dysfunction (increasing serum BUN/creatinine, increasing RVR and decreasing RABF) by increased TNFα-NFκB-mediated renal inflammatory markers as well as renal M1 macrophage infiltration. In comparison with the BDL+LPS group, chronic pioglitazone pre-treatment prevented LPS-induced renal pathogenic changes in the BDL-Pio+LPS group. Activation of systemic, renal vessel and renal tissue levels of PPARγ by chronic pioglitazone treatment has beneficial effects on the endotoxemia-related TNFα/NFκB-mediated acute and chronic renal inflammation in cirrhosis. This study revealed that normalization of renal and renal arterial levels of PPARγ effectively prevented LPS-induced acute and chronic renal dysfunction in cirrhotic ascitic rats.

Thymopentin improves the survival of septic mice by promoting the production of 15-deoxy-prostaglandin J2 and activating the PPARγ signaling pathway

Sepsis, a systemic inflammatory response syndrome (SIRS) caused by infection, is a major public health concern with limited therapeutic options. Infection disturbs the homeostasis of host, resulting in excessive inflammation and immune suppression. This has prompted the clinical use of immunomodulators to balance host response as an alternative therapeutic strategy. Here, we report that Thymopentin (TP5), a synthetic immunomodulator pentapeptide (Arg-Lys-Asp-Val-Tyr) with an excellent safety profile in the clinic, protects mice against cecal ligation and puncture (CLP)-induced sepsis, as shown by improved survival rate, decreased level of pro-inflammatory cytokines and reduced ratios of macrophages and neutrophils in spleen and peritoneum. Regarding mechanism, TP5 changed the characteristics of LPS-stimulated macrophages by increasing the production of 15-deoxy-Δ^12,14 -prostaglandin J2 (15-d-PGJ2). In addition, the improved effect of TP5 on survival rates was abolished by the peroxisome proliferator-activated receptor γ (PPARγ) antagonist GW9662. Our results uncover the mechanism of the TP5 protective effects on CLP-induced sepsis and shed light on the development of TP5 as a therapeutic strategy for lethal systemic inflammatory disorders.

Sesamol ameliorates hypotension by modulating cytokines and PPAR-gamma in systemic inflammatory response

Sepsis is one of the major causes of death reported in intensive care units. Acute kidney injury (AKI) and hypotension are important in the pathogenesis and mortality of systemic inflammatory response (SIR). Sesamol delays mortality in sepsis; however, its effects on AKI and hypotension and the role of peroxisome proliferator-activated receptor-ɣ (PPAR-γ) activation have not been established. We investigated the effect of sesamol on SIR in cecal ligation and puncture (CLP)-induced acute kidney injury and lipopolysaccharide (LPS)-induced hypotension in rats. Sesamol was subcutaneously injected 1 h after SIR. Renal function (BUN and CRE) and proinflammatory mediators interleukin (IL)-1β and IL-6 were increased after CLP. Tumor necrosis factor (TNF)-α, IL-1β, IL-10, and nitrite production were significantly increased 6 h after LPS-induced hypotension (mean arterial pressure was significantly decreased). Sesamol significantly inhibited BUN, CRE, IL-1β, IL-6, and nitrite after CLP-induced acute renal injury. In addition, sesamol increased mean arterial pressure and IL-10, inhibited TNF-α and IL-1β, but did not affect nitrite production in LPS-induced hypotension. Sesamol increased PPAR-γ in the leucocytes and peritoneal macrophages in LPS-induced SIR. We conclude that sesamol regulates leucocyte and macrophage PPAR-γ-associated systemic cytokines expression, thereby ameliorates acute kidney injury and hypotension in rats.

PPARs: Protectors or Opponents of Myocardial Function?

Over 5 million people in the United States suffer from the complications of heart failure (HF), which is a rapidly expanding health complication. Disorders that contribute to HF include ischemic cardiac disease, cardiomyopathies, and hypertension. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor family. There are three PPAR isoforms: PPARα, PPARγ, and PPARδ. They can be activated by endogenous ligands, such as fatty acids, as well as by pharmacologic agents. Activators of PPARs are used for treating several metabolic complications, such as diabetes and hyperlipidemia that are directly or indirectly associated with HF. However, some of these drugs have adverse effects that compromise cardiac function. This review article aims to summarize the current basic and clinical research findings of the beneficial or detrimental effects of PPAR biology on myocardial function.

PPARγ activation following apoptotic cell instillation promotes resolution of lung inflammation and fibrosis via regulation of efferocytosis and proresolving cytokines

Changes in macrophage phenotype have been implicated in apoptotic cell-mediated immune modulation via induction of peroxisome proliferator-activated receptor-γ (PPARγ). In this study, we characterized PPARγ induction by apoptotic cell instillation over the course of bleomycin-induced lung injury in C57BL/6 mice. Next, the role of PPARγ activation in resolving lung inflammation and fibrosis was investigated. Our data demonstrate that apoptotic cell instillation after bleomycin results in immediate and prolonged enhancement of PPARγ mRNA and protein in alveolar macrophages and lung. Moreover, PPARγ activity and expression of its target molecules, including CD36, macrophage mannose receptor, and arginase 1, were persistently enhanced following apoptotic cell instillation. Coadministration of the PPARγ antagonist, GW9662, reversed the enhanced efferocytosis, and the reduced proinflammatory cytokine expression, neutrophil recruitment, myeloperoxidase activity, hydroxyproline contents, and fibrosis markers, including type 1 collagen α2, fibronectin and α-smooth muscle actin (α-SMA), in the lung by apoptotic cell instillation. In addition, inhibition of PPARγ activity reversed the expression of transforming growth factor-β (TGF-β), interleukin (IL)-10, and hepatocyte growth factor (HGF). These findings indicate that one-time apoptotic cell instillation contributes to anti-inflammatory and antifibrotic responses via upregulation of PPARγ expression and subsequent activation, leading to regulation of efferocytosis and production of proresolving cytokines.

Statins, fibrates, thiazolidinediones and resveratrol as adjunctive therapies in sepsis: could mitochondria be a common target?

Through their pleiotropic actions, statins, fibrates, thiazolidinediones and resveratrol can target multiple mechanisms involved in sepsis. Their actions on mitochondrial function are of interest in a pathological state where bioenergetic failure may play a key role in the development of organ dysfunction. We review these four drug groups as potential adjunctive therapies in sepsis with a particular focus upon mitochondria. Systematic review of clinical and experimental trials was done with a literature search using the PubMed database. Search terms included statins, fibrates, thiazolidinediones, resveratrol, mitochondria, sepsis, peroxisome proliferator-activated receptors, inflammation, oxidative stress and organ dysfunction. With the exception of statins, most of the compelling evidence for the use of these agents in sepsis comes from the experimental literature. The agents all exert anti-inflammatory and anti-oxidant properties, plus protective effects against mitochondrial dysfunction and stimulation of mitochondrial biogenesis. Improved outcomes (organ dysfunction, survival) have been reported in a variety of sepsis models. Notably, positive outcome effects were more commonly seen when the agents were given as pre- rather than post-treatment of sepsis. Statins, fibrates, thiazolidinediones and resveratrol prevent sepsis-induced injury to organs and organelles with outcome improvements. Their effects on mitochondrial function may be integral in offering this protection. Definitive clinical trials are needed to evaluate their utility in septic patients or those at high risk of developing sepsis.

PPAR-γ/IL-10 axis inhibits MyD88 expression and ameliorates murine polymicrobial sepsis

Polymicrobial sepsis induces organ failure and is accompanied by overwhelming inflammatory response and impairment of microbial killing. Peroxisome proliferator-activated receptor (PPAR)-γ is a nuclear receptor with pleiotropic effects on lipid metabolism, inflammation, and cell proliferation. The insulin-sensitizing drugs thiazolidinediones (TZDs) are specific PPAR-γ agonists. TZDs exert anti-inflammatory actions in different disease models, including polymicrobial sepsis. The TZD pioglitazone, which has been approved by the U.S. Food and Drug Administration, improves sepsis outcome; however, the molecular programs that mediate its effect have not been determined. In a murine model of sepsis, we now show that pioglitazone treatment improves microbial clearance and enhances neutrophil recruitment to the site of infection. We also observed reduced proinflammatory cytokine production and high IL-10 levels in pioglitazone-treated mice. These effects were associated with a decrease in STAT-1-dependent expression of MyD88 in vivo and in vitro. IL-10R blockage abolished PPAR-γ-mediated inhibition of MyD88 expression. These data demonstrate that the primary mechanism by which pioglitazone protects against polymicrobial sepsis is through the impairment of MyD88 responses. This appears to represent a novel regulatory program. In this regard, pioglitazone provides advantages as a therapeutic tool, because it improves different aspects of host defense during sepsis, ultimately enhancing survival.

Nuclear control of the inflammatory response in mammals by peroxisome proliferator-activated receptors

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that play pivotal roles in the regulation of a very large number of biological processes including inflammation. Using specific examples, this paper focuses on the interplay between PPARs and innate immunity/inflammation and, when possible, compares it among species. We focus on recent discoveries establishing how inflammation and PPARs interact in the context of obesity-induced inflammation and type 2 diabetes, mostly in mouse and humans. We illustrate that PPAR γ ability to alleviate obesity-associated inflammation raises an interesting pharmacologic potential. In the light of recent findings, the protective role of PPAR α and PPAR β / δ against the hepatic inflammatory response is also addressed. While PPARs agonists are well-established agents that can treat numerous inflammatory issues in rodents and humans, surprisingly very little has been described in other species. We therefore also review the implication of PPARs in inflammatory bowel disease; acute-phase response; and central, cardiac, and endothelial inflammation and compare it along different species (mainly mouse, rat, human, and pig). In the light of the data available in the literature, there is no doubt that more studies concerning the impact of PPAR ligands in livestock should be undertaken because it may finally raise unconsidered health and sanitary benefits.

Decreased hepatic peroxisome proliferator-activated receptor-γ contributes to increased sensitivity to endotoxin in obstructive jaundice

AIM: To investigate the role of hepatic peroxisome proliferator-activated receptor-γ (PPAR-γ) in increased susceptibility to endotoxin-induced toxicity in rats with bile duct ligation during endotoxemia.

METHODS: Male Sprague-Dawley rats were subjected to bile duct ligation (BDL). Sham-operated animals served as controls. DNA binding were determined by polymerase chain reaction, Western blotting analysis, and electrophoretic mobility shift assay, respectively. BDL and sham-operated rats received a non-lethal dose of intraperitoneal lipopolysaccharide (LPS) injection (3 mg/kg, i.p.). Additionally, the potential beneficial effects of the PPAR-γ agonist rosiglitazone were determined in BDL and sham-operated rats treated with a non-lethal dose of LPS. Survival was assessed in BDL rats treated with a non-lethal dose of LPS and in sham-operated rats treated at a lethal dose of LPS (6 mg/kg, i.p.).

RESULTS: PPAR-γ activity in rats undergoing BDL was significantly lower than in the sham-controls. Hepatic PPAR-γ gene expression was downregulated at both the mRNA and protein levels. In a parallel group, serum levels of pro-inflammatory cytokines were nearly undetectable in the sham-operated rats. When challenged with a non-lethal dose of LPS (3 mg/kg), the BDL rats had approximately a 2.4-fold increase in serum IL-6, a 2.7 fold increase in serum TNF-α, 2.2-fold increase in serum IL-1 and 4.2-fold increase in serum ALT. The survival rate was significantly lower as compared with that in sham-operated group. Additionally, rosiglitazone significantly reduced the concentration of TNF-α, IL-1β, IL-6 and ALT in sham-operated rats, but not in BDL rats, in response to LPS (3 mg/kg). Also, the survival was improved by rosiglitazone in sham-operated rats challenged with a lethal dose of LPS, but not in BDL rats, even with a non-lethal dose of LPS (3 mg/kg).

CONCLUSION: Obstructive jaundice downregulates hepatic PPAR-γ expression, which in turn may contribute to hypersensitivity towards endotoxin.

Mechanism of the Anti-inflammatory Effect of Curcumin: PPAR-gamma Activation

Curcumin, the phytochemical component in turmeric, is used as a dietary spice and a topical ointment for the treatment of inflammation in India for centuries. Curcumin (diferuloylmethane) is relatively insoluble in water, but dissolves in acetone, dimethylsulphoxide, and ethanol. Commercial grade curcumin contains 10-20% curcuminoids, desmethoxycurcumin, and bisdesmethoxycurcumin and they are as effective as pure curcumin. Based on a number of clinical studies in carcinogenesis, a daily oral dose of 3.6 g curcumin has been efficacious for colorectal cancer and advocates its advancement into Phase II clinical studies. In addition to the anticancer effects, curcumin has been effective against a variety of disease conditions in both in vitro and in vivo preclinical studies. The present review highlights the importance of curcumin as an anti-inflammatory agent and suggests that the beneficial effect of curcumin is mediated by the upregulation of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activation.

Optimal study design for pioglitazone in septic pediatric patients

The objective was to demonstrate the methodology and process of optimal sparse sampling pharmacokinetics (PK). This utilized a single daily dose of pioglitazone for pediatric patients with severe sepsis and septic shock based upon adult and minimal adolescent data. Pioglitazone pharmacokinetics were modeled using non-compartment analysis WinNonlin Pro (version 5.1) and population kinetics using NONMEM (version 7.1) with first order conditional estimation method (FOCE) with interaction. The initial model was generated from single- and multiple-dose pioglitazone PK data (15 mg, 30 mg, and 45 mg) in 36 adolescents with diabetes. PK models were simulated and overlaid upon original data to provide a comparison best described by a single compartment, first order model. The optimal design was based on the simulated oral administration of pioglitazone to three groups of pediatric patients, age 3.8 (2-6 years), weight 14.4 (7-28 kg); age 9.6 (6.1-11.9 years), weight 36.5 (28.1-48 kg) and age 15.5 (12-17 years,) weight 61.6 (48.1-80 kg). PFIM (version 3.2) was used to evaluate sample study size. Datasets were compiled using simulation for each dose (15, 30 and 45 mg) for the potential age/weight groups. A target dose of 15 mg daily in the youngest and middle groups was considered appropriate with area under the curve exposure levels (AUC) comparable to studies in adolescents. The final optimal design suggested time points of 0.5, 2, 6 and 21 h for 24 h dosing. This methodology provides a robust method of utilizing adult and limited adolescent data to simulate allometrically scaled, pediatric data sets that allow the optimal design of a pediatric trial. The pharmacokinetics of pioglitazone were described adequately and simulated data estimates were comparable to literature values. The optimal design provided clinically attainable sample times and windows.

Telmisartan, a dual ARB/partial PPAR-γ agonist, protects myocardium from ischaemic reperfusion injury in experimental diabetes

AIM

Apart from its angiotensin receptor blocker (ARB) activity, telmisartan is also a partial agonist of peroxisome proliferator-activated receptor gamma (PPAR-γ). Therefore, we assessed whether telmisartan treatment attenuates myocardial ischaemia/reperfusion (I/R) injury in diabetic rats through PPAR-γ pathway.

METHODS

Diabetic rats were randomized to receive vehicle (sham and I/R), telmisartan (10 mg/kg/day, orally), PPAR-γ antagonist GW9662 (1 mg/kg/day, intraperitoneally) or both for 14 days. On 15th day, excluding sham group, left anterior descending coronary artery occlusion was performed for 45 min followed by 1 h of reperfusion. Haemodynamic, biochemical, histopathological, ultrastructural, immunohistochemical (Bax and Bcl-2 protein), TUNEL positivity, infarct size and western blot studies were performed.

RESULTS

Telmisartan treatment significantly improved cardiac function by normalizing mean arterial pressure, left ventricular pressure (±LVdP/dt(max) , a marker of myocardial contraction and relaxation), by decreasing left ventricular end-diastolic pressure (a marker of preload, 3.7 ± 0.41 vs. 7.3 ± 0.89, p < 0.001) and percent infarct area (37.52 ± 5.83 vs. 46.27 ± 3.20, p < 0.01) as compared to diabetic I/R group. Interestingly, GW9662 worsens the I/R injury (percent infarct area, 54.38 ± 6.48 vs. 46.27 ± 3.20, p < 0.01), whereas telmisartan with GW9662 (percent infarct area, 41.16 ± 8.23 vs. 46.27 ± 3.20, p < 0.05) showed lesser significant results as compared to telmisartan alone. Additionally, telmisartan significantly ameliorates activities of endogenous antioxidants, creatine kinase-MB isoenzyme, lactate dehydrogenase and prevented the increase of tumour necrosis factor-alpha and malondialdehyde in myocardium. Furthermore, telmisartan also decreased Bax expression (4.45 ± 1.24% vs. 10.25 ± 0.96%, p < 0.01), number of TUNEL-positive cells (6.2 ± 0.98% vs. 13.0 ± 1.6, p < 0.01), inflammation, myonecrosis and increased Bcl-2 expression (5.45 ± 0.15% vs. 1.24 ± 0.3%, p < 0.01). On the other hand, GW9662 treatment alone increased the Bax expression, TUNEL positivity and decreased Bcl-2 expression. Telmisartan protective effects were partially attenuated by a co-administration with GW9662. Western blot analysis showed that telmisartan treatment enhanced PPAR-γ expression, whereas GW9662 decreased it in myocardium.

CONCLUSIONS

In addition to the class effect of ARBs, telmisartan has a beneficial effect in I/R injury in diabetic rats in part because of activation of PPAR-γ.

Modulation of inflammatory response and parasitism by 15-Deoxy-Δ(12,14) prostaglandin J(2) in Trypanosoma cruzi-infected cardiomyocytes

Trypanosoma cruzi infection produces an intense inflammatory response in diverse tissues including the heart. The inflammatory reaction is critical for the control of the parasites' proliferation and evolution of Chagas disease. 15-Deoxy-Δ(12,14) prostaglandin J(2) (15dPGJ2) can repress the inflammatory response in many experimental models. However, the precise role of peroxisome proliferator-activated receptor γ (PPARγ) ligands in T. cruzi infection or in Chagas disease is poorly understood. This work reports the first evidence that 15dPGJ2 treatment increases the number of intracellular parasites as shown by fluorescence microscopy and it is also able to inhibit the expression and activity of different inflammatory enzymes such as inducible nitric oxide synthase (NOS-2), matrix metalloproteinases 2 and 9 (MMP-2, MMP-9), as well as pro-inflammatory cytokine (TNF-α and IL-6) mRNA expression in neonatal mouse cardiomyocytes after T. cruzi infection. Transfection of cardiomyocytes with small interfering RNA (siRNA) induces silencing of PPARγ and impairs the effects of 15dPGJ2 on the modulation of pro-inflammatory enzymes. Moreover, transfection restores the ability of these cells to control the intracellular growth of T. cruzi. We also found that PPARγ-independent pathways are involved, since 15dPGJ2 also exerts its effect through extracellular signal-regulated kinases-mitogen-activated protein kinase (Erk-MAPK) and nuclear factor-κB (NF-κB). The use of specific pharmacological inhibitors confirmed these findings. Our data point out that 15dPGJ2 is a potent modulator of the inflammatory process and regulator of parasites growth through PPARγ-dependent and independent (Erk-MAPK- and NF-κB) pathways in T. cruzi infected neonatal cardiac cells.

Role of PPARγ in the salutary effects of 17β-estradiol on Kupffer cell cytokine production following trauma-hemorrhage

Studies have shown that administration of 17β-estradiol prevents trauma-hemorrhage-induced increase in proinflammatory cytokine production by Kupffer cells and associated multiple organ injury. Since activation of peroxisome proliferator-activated receptor γ (PPARγ) following ischemic conditions has been shown to be protective, we examined if PPARγ plays any role in the salutary effects of 17β-estradiol on Kupffer cell cytokine production following trauma-hemorrhage. Male mice underwent trauma-hemorrhage (mean blood pressure 40 mmHg for 90 min, then resuscitation). 17β-estradiol (50 µg/kg) or vehicle with or without PPARγ antagonist GW9662 was injected subcutaneously at the middle of resuscitation. At 2 h after trauma-hemorrhage, plasma interleukin (IL)-6 and tumor necrosis factor (TNF)-α levels, Kupffer cell IL-6 and TNF-α production and mRNA expression, and PPARγ, nuclear factor (NF)-κB and activator protein (AP)-1 DNA binding activity were determined. Kupffer cell IL-6 and TNF-α production, as well as plasma IL-6 and TNF-α levels, increased following trauma-hemorrhage. Moreover, NF-κB and AP-1 DNA binding activity and IL-6 and TNF-α mRNA expression were also enhanced under such conditions. However, 17β-estradiol administration normalized all these parameters. Although PPARγ activity decreased after trauma-hemorrhage, administration of 17β-estradiol following trauma-hemorrhage elevated PPARγ activity above the normal level. Inhibition of PPARγ by co-administration of GW9662, however, abolished the salutary effects of 17β-estradiol on plasma cytokine and Kupffer cells. Thus, activation of PPARγ appears to play an important role in mediating the salutary effects of 17β-estradiol on plasma cytokine levels and Kupffer cell cytokine production after trauma-hemorrhage, which are likely mediated via NF-κB and AP-1.

15-deoxy-Delta12,14 prostaglandin GJ2 but not rosiglitazone regulates metalloproteinase 9, NOS-2, and cyclooxygenase 2 expression and functions by peroxisome proliferator-activated receptor gamma-dependent and -independent mechanisms in cardiac cells

Sepsis or endotoxemia produced by LPS followed by hypotension and multiorganic failure may lead to cardiac dysfunction contributing to mortality. Cardiac failure is usually associated to activation of nuclear factor kappaB (NF-kappaB) and mitogen-activated protein kinase (MAPK), which play an important role in proinflammatory enzymes expression. It has been shown that 15-deoxy-Delta12,14 prostaglandin J2 (15dPGJ2) can repress the inflammatory response by means of peroxisome proliferator-activated receptor gamma (PPARgamma)-dependent and -independent mechanisms. However, its precise role in heart is poorly understood. In the present study, mouse neonatal cardiomyocytes were isolated and stimulated with LPS to investigate the role of PPARgamma-specific ligands 15dPGJ2 and rosiglitazone on cardiac inflammatory response. Inducible NO synthase, cyclooxygenase 2, and metalloproteinase 9 mRNA levels, protein expression, and activity were inhibited with 15dPGJ2 but not by rosiglitazone. Peroxisome proliferator-activated receptor gamma antagonist, GW9662, prevented all these 15dPGJ2 actions. To go inside the mechanisms by which 15dPGJ2 exerts inhibitory effects, cells were preincubated with specific chemical inhibitors of NF-kappaB and p38 MAPK, and we found that these signaling cascades are implicated in 15dPGJ2 action as well as PPARgamma. These results suggest that only the natural PPARgamma ligand, 15dPGJ2, but not the synthetic one, rosiglitazone, regulates the inflammatory response by inhibition of inducible NO synthase, cyclooxygenase 2, and metalloproteinase 9 expression. Moreover, our results offer an additional 15dPGJ2 mechanism of action, despite PPARgamma, showing NF-kappaB and p38 MAPK participation.

Phosphorylation of extracellular signal-regulated kinase (ERK)-1/2 Is associated with the downregulation of peroxisome proliferator-activated receptor (PPAR)-γ during polymicrobial sepsis

Peroxisome proliferator-activated receptor (PPAR)-γ is a ligand-activated transcription factor and regulates inflammation. Posttranslational modifications regulate the function of PPARγ, potentially affecting inflammation. PPARγ contains a mitogen-activated protein kinase (MAPK) site, and phosphorylation by extracellular signal-regulated kinase (ERK)-1/2 leads to inhibition of PPARγ. This study investigated the kinetics of PPARγ expression and activation in parenchymal and immune cells in sepsis using the MAPK/ERK kinase (MEK)-1 inhibitor, an upstream kinase of ERK1/2. Adult male Sprague Dawley rats were subjected to polymicrobial sepsis by cecal ligation and puncture. Rats received intraperitoneal injection of vehicle or the MEK1 inhibitor PD98059 (5 mg/kg) 30 min before cecal ligation and puncture. Rats were euthanized at 0, 1, 3, 6 and 18 h after cecal ligation and puncture. Control animals used were animals at time 0 h. Lung, plasma and peripheral blood mononuclear cells (PBMCs) were collected for biochemical assays. In vehicle-treated rats, polymicrobial sepsis resulted in significant lung injury. In the lung and PBMCs, nuclear levels of PPARγ were decreased and associated with an increase in phosphorylated PPARγ and phosphorylated ERK1/2 levels. Treatment with the MEK1 inhibitor increased the antiinflammatory plasma adipokine adiponectin, restored PPARγ expression in PBMCs and lung, and decreased lung injury. The inflammatory effects of sepsis cause changes in PPARγ expression and activation, in part, because of phosphorylation of PPARγ by ERK1/2. This phosphorylation can be reversed by ERK1/2 inhibition, thereby improving lung injury.

Inflammatory effects of phthalates in neonatal neutrophils

Hospitalized infants are exposed to numerous devices containing the plasticizer di-(2-ethylhexyl) phthalate. Urinary levels of the phthalate metabolite, mono-(2-ethylhexyl) phthalate (MEHP), are markedly elevated in premature infants. Phthalates inactivate peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear transcription factor that mediates the resolution of inflammation, a process impaired in neonates. We speculate that this increases their susceptibility to MEHP, and this was analyzed. MEHP inhibited neutrophil apoptosis; neonatal cells were more sensitive than adult cells. In neonatal, but not in adult neutrophils, MEHP also inhibited chemotaxis, stimulated oxidative metabolism, and up-regulated expression of NADPH oxidase-1. In both adult and neonatal neutrophils, MEHP stimulated IL-1beta and VEGF production, whereas IL-8 production was stimulated only in adult cells. In contrast, MEHP-inhibited production of MIP-1beta by adult cells, and Regulated on Activation Normal T Cell Expressed and Secreted (RANTES) by neonatal neutrophils. The effects of MEHP on apoptosis and oxidative metabolism in neonatal cells were reversed by the PPAR-gamma agonist, troglitazone. Whereas troglitazone had no effect on MEHP-induced alterations in inflammatory protein or chemokine production, constitutive IL-8 and MIP-1beta production was reduced in adult neutrophils, and RANTES and MIP-1beta in neonatal cells. These findings suggest that neonatal neutrophils are more sensitive to phthalate-mediated inhibition of PPAR-gamma, which may be related to decreased anti-inflammatory signaling.

Agonism of Peroxisome Proliferator Receptor-Gamma may have Therapeutic Potential for Neuroinflammation and Parkinson's Disease

Evidence suggests inflammation, mitochondria dysfunction, and oxidative stress play major roles in Parkinson's disease (PD), where the primary pathology is the significant loss of dopaminergic neurons in the substantia nigra (SN). Current methods used to treat PD focus mainly on replacing dopamine in the nigrostriatal system. However, with time these methods fail and worsen the symptoms of the disease. This implies there is more to the treatment of PD than just restoring dopamine or the dopaminergic neurons, and that a broader spectrum of factors must be changed in order to restore environmental homeostasis. Pharmacological agents that can protect against progressive neuronal degeneration, increase the level of dopamine in the nigrostriatal system, or restore the dopaminergic system offer various avenues for the treatment of PD. Drugs that reduce inflammation, restore mitochondrial function, or scavenge free radicals have also been shown to offer neuroprotection in various animal models of PD. The activation of peroxisome proliferator receptor- gamma (PPAR-gamma ) has been associated with altering insulin sensitivity, increasing dopamine, inhibiting inflammation, altering mitochondrial bioenergetics, and reducing oxidative stress - a variety of factors that are altered in PD. Therefore, PPAR-gamma activation may offer a new clinically relevant treatment approach to neuroinflammation and PD related neurodegeneration. This review will summarize the current understanding of the role of PPAR-gamma agonists in neuroinflammation and discuss their potential for the treatment of PD.

The importance of immune dysfunction in determining outcome in acute liver failure

Acute liver failure (ALF) shares striking similarities with septic shock with regard to the features of systemic inflammation, progression to multiple organ dysfunction and functional immunoparesis. While the existence of opposing systemic pro- and anti-inflammatory profiles resulting in organ failure and immune dysfunction are well recognised in septic shock, characterization of these processes in ALF has only recently been described. This review explores the evolution of the systemic inflammation in acute liver failure, its relation to disease progression, exacerbation of liver injury and development of innate immune dysfunction and extra-hepatic organ failure as sequelae. Defects in innate immunity are described in hepatic and extra-hepatic compartments. Clinical studies measuring levels of pro- and anti-inflammatory cytokines and expression of the antigen presentation molecule HLA-DR on monocytes, in combination with ex-vivo experiments, demonstrate that the persistence of a compensatory anti-inflammatory response syndrome, leading to functional monocyte deactivation, is a central event in the evolution of systemic immune dysfunction. Accurate immune profiling in ALF may permit the development of immunomodulatory strategies in order to improve outcome in this condition.

Augmentation of endogenous cannabinoid tone modulates lipopolysaccharide-induced alterations in circulating cytokine levels in rats

The endogenous cannabinoid system plays an important role in regulating the immune system. Modulation of endogenous cannabinoids represents an attractive alternative for the treatment of inflammatory disorders. This study investigated the effects of URB597, a selective inhibitor of fatty acid amide hydrolase (FAAH), the enzyme catalysing degradation of the endogenous cannabinoid anandamide, and AM404, an inhibitor of anandamide transport, on lipopolysaccharide (LPS)-induced increases in plasma cytokine levels in rats. Both URB597 and AM404 potentiated the LPS-induced increase in plasma tumour necrosis factor-alpha (TNF-alpha) levels. The peroxisome proliferator-activated receptor gamma (PPARgamma) antagonist, GW9662, attenuated the AM404-induced augmentation of TNF-alpha levels. Furthermore, the selective cannabinoid CB1 and CB2 receptor antagonists, AM251 and AM630 respectively, and the transient receptor potential vanilloid receptor-1 (TRPV1) antagonist, SB366791, reduced LPS-induced TNF-alpha plasma levels both alone and in combination with AM404. In contrast, AM404 inhibited LPS-induced increases in circulating interleukin-1beta (IL-1beta) and IL-6. AM251 attenuated the immunosuppressive effect of AM404 on IL-1beta. None of the antagonists altered the effect of AM404 on LPS-induced IL-6. Moreover, AM251, AM630 and SB366791, administered alone, inhibited LPS-induced increases in plasma IL-1beta and IL-6 levels. In conclusion, inhibition of endocannabinoid degradation or transport in vivo potentiates LPS-induced increases in circulating TNF-alpha levels, an effect which may be mediated by PPARgamma and is also reduced by pharmacological blockade of CB1, CB2 and TRPV1. The immunosuppressive effect of AM404 on IL-1beta levels is mediated by the cannabinoid CB1 receptor. Improved understanding of endocannabinoid-mediated regulation of immune function has fundamental physiological and potential therapeutic significance.

Peroxisome proliferator activated receptor gamma is not necessary for the development of LPS-induced tolerance in macrophages

Peroxisome proliferator activated receptor-gamma (PPARgamma) has been reported to exert anti-inflammatory properties in endotoxic shock and sepsis. One phenomenon that alters the inflammatory response to endotoxin [lipopolysaccharide (LPS)] is endotoxin tolerance, which is caused by previous exposure to endotoxin. Here, we investigate whether changes in endogenous PPARgamma function regulate this phenomenon using three different models of LPS-induced tolerance in macrophages. In a first in vitro model, previous LPS exposure of murine J774.2 macrophages suppressed tumour necrosis factor-alpha (TNF-alpha) release in response to subsequent LPS challenge. Treatment of J774.2 cells with the PPARgamma inhibitor GW9662 did not alter tolerance induction because these cells were still hyporesponsive to the secondary LPS challenge. In a second ex vivo model, primary rat peritoneal macrophages from LPS-primed rats exhibited suppression of thromboxane B2 and TNF-alpha production, while maintaining nitrite production in response to in vitro LPS challenge. Pretreatment of rats with the PPARgamma inhibitor GW9662 in vivo failed to alter the tolerant phenotype of these primary macrophages. In a third ex vivo model, primary peritoneal macrophages with conditional deletion of PPARgamma were harvested from LPS-primed Cre-lox mice (Cre+/+ PPARgamma-/-) and exhibited significant suppression of TNF-alpha production in response to in vitro LPS challenge. Furthermore, both LPS-primed PPARgamma-deficient Cre+/+ PPARgamma-/- mice and wild-type Cre-/- PPARgamma+/+ mice exhibited reduced plasma TNF-alpha levels in response to a high dose of LPS in vivo. These data demonstrate that PPARgamma does not play a role in the LPS-induced tolerant phenotype in macrophages.

Proinsulin c-peptide exerts beneficial effects in endotoxic shock in mice

OBJECTIVE

Insulin connecting peptide (c-peptide) aids the folding of proinsulin and has been considered to have little biological activity. Recently, c-peptide has been shown to improve diabetic neuropathy and nephropathy as well as vascular inflammation. In vitro studies have reported that c-peptide may activate peroxisome proliferator-activated receptor-gamma, a nuclear transcription factor that plays a regulatory role in inflammation. This study was designed to investigate the biological effects of c-peptide during endotoxemia.

DESIGN

Prospective, randomized laboratory investigation that used an established murine model of endotoxic shock.

SETTING

University hospital laboratory.

SUBJECTS

Mice were subjected to endotoxic shock by intraperitoneal administration of Escherichia coli lipopolysaccharide.

INTERVENTIONS

Mice received vehicle or c-peptide (70-140 nmol/kg) intraperitoneally at 3 hrs and 6 hrs after lipopolysaccharide. Mortality was monitored for 96 hrs. In a separate experiment, mice were killed at 4, 7, and 18 hrs after lipopolysaccharide administration. Lungs and plasma were collected for biochemical assays.

MEASUREMENTS AND MAIN RESULTS

In vehicle-treated mice, endotoxic shock resulted in lung injury and was associated with a 41% survival rate and elevation in plasma tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, monocyte chemoattractant protein-1, and keratinocyte-derived chemokine levels. Lung nuclear levels of phosphorylated extracellular signal-regulated kinases 1 and 2 were significantly increased in vehicle-treated mice. On the other hand, lung nuclear expression and DNA binding of proliferator-activated receptor-gamma were decreased in comparison to control animals. Treatment with c-peptide (140 nmol/kg) improved survival rate (68%) and reduced plasma levels of tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1, but it did not exert hypoglycemic effects. Treatment with c-peptide also up-regulated lung nuclear expression and DNA binding of proliferator-activated receptor-gamma and reduced phosphorylation of extracellular signal-regulated kinases 1 and 2 in comparison to vehicle-treated mice.

CONCLUSIONS

Our data show that c-peptide has beneficial effects in endotoxic shock, and this therapeutic effect is associated with activation of proliferator-activated receptor-gamma.

LYSOPHOSPHATIDIC ACID REDUCES THE ORGAN INJURY CAUSED BY ENDOTOXEMIA-A ROLE FOR G-PROTEIN-COUPLED RECEPTORS AND PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-γ

Exogenous lysophosphatidic acid (LPA) has been shown to beneficial in renal ischemia/reperfusion injury, wound healing and colitis. LPA acts via specific G-protein-coupled receptors and also peroxisome proliferator-activated receptor-gamma (PPAR-gamma). However, activation of PPAR-gamma is dependent on the presence of an unsaturated acyl chain. Here we investigate the effects of saturated LPA (18:0) and unsaturated LPA (18:1) on the organ injury associated with endotoxemia and the receptors mediating LPA activity. Male Wistar rats received either lipopolysaccharide (LPS, 6 mg/kg i.v.) or vehicle. The PPAR-gamma antagonist GW9662 (1 mg/kg i.v.), the LPA receptor antagonist Ki16425 (0.5 mg/kg i.v.) or vehicle was administered 30 min after LPS. LPA 18:0 or LPA 18:1 (1 mg/kg i.v.) or vehicle was administered 1 h after injection of LPS. Endotoxemia for 6 h resulted in an increase in serum levels of aspartate aminotransferase, alanine aminotransferase and creatine kinase. Therapeutic administration of LPA 18:0 or 18:1 reduced the organ injury caused by LPS. LPA 18:0 also attenuated the increase in plasma IL-1beta caused by LPS. Ki16425, but not GW9662, attenuated the beneficial effects of LPA 18:0, however, Ki16425 and GW9662 attenuated the beneficial effects of 18:1. In conclusion, LPA reduces the organ injury caused by endotoxemia in the rat. Thus, LPA may be useful in the treatment of shock of various aetiologies. The mechanism of action is related to acyl chain saturation, with LPA 18:0 acting via G-protein-coupled receptors and LPA 18:1 acting via G-protein-coupled receptors and PPAR-gamma.

Anti-inflammatory effects of PPAR-gamma agonists directly correlate with PPAR-gamma expression during acute pancreatitis

Peroxisome proliferator-activated receptors (PPARs) are ligand-inducible transcription factors that regulate cellular energy and lipid metabolism. PPAR-gamma agonists also have potent anti-inflammatory properties through down-regulation of early inflammatory response genes. The role of PPAR-gamma in acute pancreatitis has not been adequately examined. In this study, we determined the effect of PPAR-gamma agonists on the severity of pancreatitis and sought to correlate PPAR-gamma expression in pancreatic acinar cells and the severity of acute pancreatitis in vivo. Acute pancreatitis was induced in mice by hyperstimulation with the cholecystokinin analog, cerulein. PPAR-gamma agonists were administered by intraperitoneal injection 15-30 minutes before induction of pancreatitis (pretreatment) or at various times after induction of pancreatitis (treatment). Pancreata and serum were harvested over the course of 24 hours. Serum amylase activity and glucose levels were measured. Pancreata were used for histological evaluation as well as protein and mRNA analysis. Pretreatment of mice with the PPAR-gamma agonists 15-deoxy-Delta12, 14-prostaglandin J(2), or troglitazone significantly reduced the severity of pancreatitis in a dose-dependent manner. This reduction was indicated by reduced serum amylase activity and histological damage (leukocyte infiltration, vacuolization, and necrosis). Although cerulein decreased PPAR-gamma expression in the pancreas, pretreatment with agonists maintained PPAR-gamma expression early in acute pancreatitis. The expression of PPAR-gamma inversely correlated with pancreatitis severity and expression of the proinflammatory cytokines, interleukin-6, and tumor necrosis factor-alpha. Treatment with troglitazone after the induction of pancreatitis reduced serum amylase activity. The results suggest that PPAR-gamma plays a direct role in the inflammatory cascade during the early events of acute pancreatitis. Our data are the first to demonstrate that PPAR-gamma agonists represent a promising therapeutic strategy for acute pancreatitis.

A role of PPAR-gamma in androstenediol-mediated salutary effects on cardiac function following trauma-hemorrhage

OBJECTIVE

To examine the mechanism by which androstenediol improves cardiac function following trauma-hemorrhage (T-H).

SUMMARY BACKGROUND DATA

Androstenediol administration improves cardiovascular function and attenuates proinflammatory cytokine production following T-H. Activation of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) has been shown to be protective following ischemic conditions. We hypothesized that PPAR-gamma activation plays a role in the androstenediol-mediated salutary effects on cardiac function following T-H.

METHODS

Male rats underwent laparotomy and hemorrhagic shock (40 mm Hg for 90 minutes), followed by resuscitation with 4 times the shed blood volume in the form of Ringer's lactate. Androstenediol (1 mg/kg body weight, i.v.) was administrated at the end of resuscitation. In a separate group of animals, a PPAR-gamma antagonist (GW9662) was administered simultaneously with androstenediol and animals were killed at 5 hours thereafter.

RESULTS

A decrease in cardiac function and an increase in IL-6 and iNOS gene expression were observed following T-H. Androstenediol treatment normalized cardiac function, increased PPAR-gamma DNA binding activity, attenuated IL-6 and iNOS gene expressions, and reduced plasma IL-6. Plasma 15-deoxy-Delta12, 14-prostaglandin J2 (PGJ2, an endogenous PPAR-gamma agonist) levels were also increased in androstenediol-treated T-H rats, but these levels were lower than those observed in shams. Coadministration of PPAR-gamma antagonist along with androstenediol, however, prevented the androstenediol-mediated reduction in cardiac iNOS and IL-6 expressions and abolished the improvements in cardiac function.

CONCLUSION

The androstenediol-mediated salutary effects on cardiac function following T-H appear to be mediated at least in part via PPAR-gamma activation, which down-regulates IL-6 and iNOS gene expression in the heart.

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.

Peroxisome proliferator-activated receptor-gamma antagonists GW9662 and T0070907 reduce the protective effects of lipopolysaccharide preconditioning against organ failure caused by endotoxemia

OBJECTIVE

There is evidence that a) ligands of the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-gamma and b) lipopolysaccharide preconditioning protect the organs against the multiple organ injury and dysfunction caused by endotoxemia. Here we investigate the hypothesis that the protective effects of lipopolysaccharide preconditioning are due to an enhanced formation of endogenous ligands of PPAR-gamma.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Ninety-nine anesthetized male Wistar rats.

INTERVENTIONS

Rats were pretreated with low-dose lipopolysaccharide (1 mg/kg intraperitoneally, 24 hrs before induction of endotoxemia) in the absence or presence of the selective PPAR-gamma antagonists GW9662 (1 mg/kg intraperitoneally) or T0070907 (1 mg/kg intraperitoneally) or the selective cyclooxygenase-2 inhibitor parecoxib (20 mg/kg intraperitoneally). At 24 hrs after preconditioning with low-dose lipopolysaccharide, the rats were subjected to acute severe endotoxemia (lipopolysaccharide 6 mg/kg intravenously).

MEASUREMENTS AND MAIN RESULTS

Lipopolysaccharide preconditioning significantly attenuated the development of renal dysfunction (serum creatinine), hepatocellular injury (serum alanine aminotransferase and aspartate aminotransferase), and circulatory failure (hypotension) as well as the increase in the plasma levels of interleukin-1beta caused by severe endotoxemia. All of these beneficial effects afforded by preconditioning with lipopolysaccharide were attenuated by the specific PPAR-gamma antagonists used. In contrast, the cyclooxygenase-2 inhibitor parecoxib did not affect the beneficial effects afforded by preconditioning with lipopolysaccharide.

CONCLUSIONS

We propose that endogenous ligands of PPAR-gamma contribute to the protection afforded by lipopolysaccharide preconditioning against the organ injury and dysfunction associated with severe endotoxemia in the rat.

Effects of 15-deoxy-Δ12,14-prostaglandin-J2 during hyperdynamic porcine endotoxemia

OBJECTIVE

To investigate the hemodynamic and metabolic effects of the peroxisome proliferator-activated receptor (PPAR)-gamma ligand and nuclear-factor (NF)-kappa B inhibitor 15-deoxy-Delta12,14-prostaglandin-J2 (15d-PGJ2) during long-term, hyperdynamic porcine endotoxemia.

DESIGN

Prospective, randomized, controlled experimental study with repeated measures.

SETTING

Investigational animal laboratory.

SUBJECTS

19 anesthetized, mechanically ventilated and instrumented pigs.

INTERVENTIONS

At 12 h of continuous intravenous endotoxin and hydroxyethylstarch to keep mean arterial pressure (MAP)>60 mmHg, swine randomly received vehicle (control group, n=10) or 15-deoxy-Delta12,14-prostaglandin-J2 (15d-PGJ2 group, n=9; 1 microg kg(-1) min(-1) loading dose during 1 h; thereafter,0.25 microg kg(-1) min(-1) for 11 h).

MEASUREMENTS AND RESULTS

Hemodynamic, metabolic and organ function parameters were assessed together with parameters of nitric oxide production and oxidative stress. 15d-PGJ2 prevented the endotoxin-induced progressive hypotension, due to a positive inotropic effect, which resulted in a significantly higher blood pressure during the treatment phase and prevented the rise in hepatic vein alanine-aminotransferase activity. It did not affect, however, any other parameter of organ function nor of nitric oxide production, proinflammatory cytokine release or lipid peroxidation (8-isoprostane).

CONCLUSIONS

15d-PGJ2 stabilized systemic hemodynamics, due to improved myocardial performance, and resulted in an only transient effect on alanine-aminotransferase activity, without further beneficial effect on endotoxin-induced metabolic and organ function derangements. Low tissue 15d-PGJ2 concentrations and/or the delayed drug administration may explain these findings.

Peroxisome proliferator-activated receptor-gamma is a new therapeutic target in sepsis and inflammation

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a member of the nuclear receptor superfamily and a ligand-activated transcription factor with pleiotropic effects on lipid metabolism, inflammation, and cell proliferation. PPARgamma forms a heterodimer with the retinoid X receptor and upon ligand-activation binds to the PPAR response element in the promoter of genes to allow transcription. The class of insulin-sensitizing drugs known as thiazolidinediones have been identified as specific PPARgamma agonists that have allowed the characterization of many genes regulated by PPARgamma. Thiazolidinediones include rosiglitazone, pioglitazone, troglitazone, and ciglitazone. In addition to these synthetic agonists, cyclopentenone prostaglandins of the J2 series have been identified as natural ligands for PPARgamma. Several in vitro and in vivo studies have demonstrated that pharmacological activation of PPARgamma by 15-deoxy-Delta(12,14)-PGJ2 (15d-PGJ2) or thiazolidinediones has anti-inflammatory effects. This article provides an overview of the role of PPARgamma in regulating the inflammatory response and emphasizes the potential efficacy of PPARgamma ligands as novel therapeutic approaches beyond diabetes in sepsis, inflammation, and reperfusion injury.

The selective PPARγ antagonist GW9662 reverses the protection of LPS in a model of renal ischemia-reperfusion

BACKGROUND

We have recently reported that pretreatment of rats with endotoxin (lipopolysaccharide, LPS) and selective agonists of the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) protect the kidney against ischemia/reperfusion (I/R) injury. Here we investigate the hypothesis that the renoprotective effects of LPS may be due to an enhanced formation of endogenous ligands of PPARgamma, rather than an up-regulation of PPARgamma expression.

METHODS

Rats were pretreated with LPS (1 mg/kg, IP, 24 hours prior to ischemia) in the absence (control) or presence of the selective PPARgamma antagonist GW9662 (1 mg/kg, IP, 24 and 12 hours prior to ischemia). Twenty-four hours after injection of LPS, rats were subjected to 60 minutes of bilateral renal ischemia, followed by 6 hours of reperfusion. Serum and urinary indicators of renal injury and dysfunction were measured, specifically serum creatinine, aspartate aminotransferase, and gamma-glutamyl-transferase, creatinine clearance, urine flow, and fractional excretion of sodium. Kidney PPARgamma1 mRNA levels were determined by reverse transcriptase-polymerase chain reaction.

RESULTS

Pretreatment with LPS significantly attenuated all markers of renal injury and dysfunction caused by I/R. Most notably, GW9662 abolished the protective effects of LPS. Additionally, I/R caused an up-regulation of kidney PPARgamma1 mRNA levels compared to sham animals, which were unchanged in rats pretreated with LPS.

CONCLUSION

We document here for the first time that endogenous ligands of PPARgamma may contribute to the protection against renal I/R injury afforded by LPS pretreatment in the rat.

A PPAR-gamma ligand, 15-deoxy-Delta12,14-prostaglandin J(2), inhibited gastric mucosal injury induced by ischemia-reperfusion in rats

INTRODUCTION

Recent studies have demonstrated the anti-inflammatory action of 15-deoxy-Delta12,14-prostaglandin J(2) (15d-PGJ(2)), a derivative of the PGD(2) metabolic pathway. Acute inflammation, including neutrophil activation, plays a critical role in the pathogenesis of ischemia-reperfusion (I/R). The aim of the present study was to determine the effect of 15d-PGJ(2) on I/R-induced gastric mucosal injury in rats.

METHODS

Gastric mucosal damage was induced in male Wistar rats by clamping the celiac artery for 30 min followed by reperfusion. 15d-PGJ(2) (0.01-1.0 mg/kg) was given to the rats intraperitoneally 1 h before the vascular clamping. The area of gastric mucosal erosions (erosion index) was measured. Thiobarbituric acid reactive substances (TBARS) and tissue-associated myeloperoxidase (MPO) activity were measured in the gastric mucosa as indices of lipid peroxidation and neutrophil infiltration. The expression of tumor necrosis factor-alpha (TNF-alpha) in gastric mucosa was measured by ELISA. In addition, to elucidate whether the protective effects of 15d-PGJ(2) are related to the activation of the PPAR-gamma receptor, we also investigated the effects of a PPAR-gamma antagonist, GW9662.

RESULTS

After 60 min of reperfusion, the area of gastric erosion index had significantly increased from the mean basal levels. The increase in the erosion index was significantly inhibited by pretreatment with 15d-PGJ(2) in a dose-dependent manner. On the other hand, GW9662 reversed the protective effect of 15d-PGJ(2). The concentration of TBARS and MPO activity in the gastric mucosa were both significantly increased after I/R, and pretreatment with 15d-PGJ(2) significantly reduced these increases. The TNF-alpha content was significantly higher in the I/R group than in the sham-operated group. However, the increase in TNF-alpha was significantly inhibited by pretreatment with 15d-PGJ(2).

CONCLUSIONS

15d-PGJ(2) significantly inhibited the severity of acute gastric mucosal injury induced by I/R in rats through PPAR-gamma-dependent mechanisms. This effect may be due, in part, to a reduction in the infiltration of neutrophils into the gastric mucosa, possibly via the inhibition of inflammatory cytokine.

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.

Future strategies in the treatment of acute renal failure: growth factors, stem cells, and other novel therapies

PURPOSE OF REVIEW

Acute renal failure remains a significant cause of morbidity and mortality in adults and children. Despite advances in understanding the pathophysiology of acute renal failure, little progress has been made in its treatment. This review assesses the recent data on current and promising new therapies for acute renal failure.

RECENT FINDINGS

The first section of the review describes the recent therapies that have been used in humans, all of whom have been adults. The second section evaluates the use of agents given in experimental animal models during or after the onset of acute renal failure. The third section describes the many animal studies using therapies before the onset of experimental renal failure. The final section discusses how the emerging field of stem cell research might be used to treat acute renal failure.

SUMMARY

Among the recent studies in humans, the most intriguing have been the use of atrial natriuretic peptide in patients with nonoliguric renal failure and isotonic sodium bicarbonate infusions to prevent radiocontrast medium-induced renal failure. Among the agents used in animal studies, those with the greatest potential were hepatocyte growth factor and ethyl pyruvate, because they seem to protect against or accelerate recovery from acute renal failure after the renal insult. Finally, stem cell therapy may someday offer the best option for recovery from acute renal failure.

The cyclopentenone prostaglandin 15-deoxyΔ12,14-prostaglandin J2 attenuates the development of zymosan-induced shock

OBJECTIVE

Multiple-organ failure (MOF) is defined as the progressive deterioration in function which occurs in several organs or systems in patients with septic shock, multiple trauma, severe burns, or pancreatitis. This study investigated the effect of 15-deoxy-delta(12,14)-PGJ2 (15d-PGJ2), a PPAR-gamma ligand, in a model of zymosan-induced nonseptic shock in mice.

MATERIALS AND METHODS

Mice were randomly assigned to one of four groups (n=10 each) and treated i.p. as follows: group 1, zymosan (500 mg/kg suspended in saline solution) and vehicle (10% DMSO); group 2, zymosan (500 mg/kg suspended in saline solution) plus 15d-PGJ2 (30 microg/kg, suspended in 10% DMSO) 1 h before and 6 h after zymosan administration; group 3, 15d-PGJ2 (30 microg/kg, suspended in 10% DMSO; group 4, vehicle for PGJ2 (10% DMSO) always 1 h before and 6 h after saline administration. After 18 h mice were killed and tissues and biological fluids used for biochemical, immunohistochemical, and histological analysis.

MEASUREMENTS AND RESULTS

15d-PGJ2 inhibited the inflammatory response and significantly reduced peritoneal mononuclear cell infiltration and histological injury in mice. A significant protection was demonstrated in kidney, liver, and pancreas injury by the reduction in amylase, lipase, creatinine, AST, ALT, bilirubin, and alkaline phosphatase levels. 15d-PGJ2 also reduced the appearance of nitrotyrosine in the inflamed intestinal tissues. Histological examination revealed a significant reduction in zymosan-induced intestinal damage in 15d-PGJ2 treated mice.

CONCLUSIONS

Our findings demonstrate that 15d-PGJ2 exerts potent anti-inflammatory effects on zymosan-induced shock.

Growth Stimulation of COX-2–Negative Pancreatic Cancer by a Selective COX-2 Inhibitor

Cyclooxygenase 2 (COX-2) inhibitors are promising antiangiogenic agents in several preclinical models. The aim of the present study was to evaluate the effect of selective COX-2 inhibitors on vascular endothelial growth factor (VEGF) production in vitro and angiogenesis and growth of pancreatic cancer in vivo, focusing on putative differences between COX-2–negative and COX-2–positive tumors. VEGF production and angiogenesis in vitro were determined by ELISA and endothelial cell migration assay. To determine whether the effect of COX-2 inhibitors was mediated by peroxisome proliferator–activated receptor γ (PPAR-γ), we used a dominant-negative PPAR-γ and a pharmacologic inhibitor. In vitro findings were validated in a pancreatic cancer animal model. Microvessel density was assessed by CD31 immunostaining. Intratumoral prostaglandin and VEGF levels were measured by mass spectroscopy and ELISA. Selective COX-2 inhibitors had a concentration-dependent effect on VEGF production in vitro. Higher concentrations increased VEGF levels and stimulated angiogenesis by activating PPAR-γ. In vivo, nimesulide increased VEGF production by cancer cells in COX-2–positive and COX-2–negative pancreatic tumors. In COX-2–negative pancreatic cancer, this effect was associated with an increase in angiogenesis and growth. In COX-2–positive pancreatic cancer, the nimesulide-induced increase of VEGF production by the cancer cells was offset by a decrease in VEGF production by the nonmalignant cell types leading to reduced tumor angiogenesis and growth. Selective COX-2 inhibitors had opposite effects on growth and angiogenesis in pancreatic cancer depending on COX-2 expression. These findings imply that assessing the COX-2 profile of the pancreatic tumor is mandatory before initiating therapy with a selective COX-2 inhibitor.

WY 14643, A POTENT EXOGENOUS PPAR-?? LIGAND, REDUCES INTESTINAL INJURY ASSOCIATED WITH SPLANCHNIC ARTERY OCCLUSION SHOCK

The peroxisome proliferator-activated receptor-alpha (PPAR-alpha) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors related to retinoid, steroid, and thyroid hormone receptors. WY 14643 is a potent PPAR-alpha ligand that modulates the transcription of target genes. The aim of this study was to investigate the effect of WY 14643 on the tissue injury caused by ischemia-reperfusion (I/R) of the gut. I/R injury of the intestine was caused by clamping both the superior mesenteric artery and the celiac trunk for 45 min, followed by release of the clamp, allowing reperfusion for 2 h or 4 h. This procedure results in splanchnic artery occlusion (SAO) shock. Rats subjected to SAO developed a significant fall in mean arterial blood pressure, and only 20% of the animals survived for the entire 4-h reperfusion period. Surviving animals were sacrificed for histological examination and biochemical studies. Rats subjected to SAO displayed a significant increase in tissue myeloperoxidase (MPO) activity, significant increases in plasma tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta levels, and marked injury to the distal ileum. Increased immunoreactivity to nitrotyrosine and polyadenosine diphosphate [ADP]-ribose (PAR) was observed in the ileum of rats subjected to SAO. Staining of sections of the ileum obtained from SAO rats with anti-intercellular adhesion molecule (ICAM-1) antibody or with anti-P-selectin antibody resulted in diffuse staining. Administration of WY 14643 (1 mg/kg i.v.) 30 min before the onset of gut ischemia significantly reduced the (a) fall in mean arterial blood pressure, (b) mortality rate, (c) infiltration of the reperfused intestine with polymorphonuclear neutrophils (MPO activity), (d) production of proinflammatory cytokines (TNF-alpha and IL-1beta), and (e) histological evidence of gut injury. Administration of WY 14643 also markedly reduced the nitrotyrosine formation, poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) activation, up-regulation of ICAM-1, and expression of P-selectin during reperfusion. These results demonstrate that the PPAR-alpha agonist WY 14643 significantly reduces I/R injury of the intestine.

Protein thiol modification by 15-deoxy-Delta12,14-prostaglandin J2 addition in mesangial cells: role in the inhibition of pro-inflammatory genes

The cyclopentenone prostaglandin and PPARgamma agonist 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) displays anti-inflammatory effects in several experimental models. Direct modification of protein thiols is arising as an important mechanism of cyclopentenone prostaglandin action. However, little is known about the extent or specificity of this process. Mesangial cells (MC) play a key role in glomerulonephritis. In this work, we have studied the selectivity of protein modification by 15d-PGJ(2) in MC, and the correlation with the modulation of several proinflammatory genes. MC incubation with biotinylated 15d-PGJ(2) results in the labeling of a distinct set of proteins as evidenced by two-dimensional electrophoresis. 15d-PGJ(2) binds to nuclear and cytosolic targets as detected by fluorescence microscopy and subcellular fractionation. The pattern of biotinylated 15d-PGJ(2)-modified polypeptides is readily distinguishable from that of total protein staining or labeling with biotinylated iodoacetamide. 15d-PGJ(2) addition requires the double bond in the cyclopentane ring. 9,10-Dihydro-15d-PGJ(2), a 15d-PGJ(2) analog that shows the same potency as peroxisome proliferator-activated receptor (PPAR) agonist in MC but lacks the cyclopentenone moiety, displays reduced ability to modify proteins and to block 15d-PGJ(2) binding. Micromolar concentrations of 15d-PGJ(2) inhibit cytokine-elicited levels of inducible nitricoxide synthase, cyclooxygenase-2, and intercellular adhesion molecule-1 in MC. In contrast, 9,10-dihydro-15d-PGJ(2) does not reproduce this inhibition. 15d-PGJ(2) effect is not blocked by the PPARgamma antagonist 2-chloro-5-nitro-N-phenylbenzamide (GW9662). Moreover, compounds possessing an alpha,beta-unsaturated carbonyl group, like 2-cyclopenten-1-one and 2-cyclohexen-1-one, reduce pro-inflammatory gene expression. These observations indicate that covalent modification of cellular thiols by 15d-PGJ(2) is a selective process that plays an important role in the inhibition of MC responses to pro-inflammatory stimuli.