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

Impact of protocatechuic acid on alleviation of pulmonary damage induced by cyclophosphamide targeting peroxisome proliferator activator receptor, silent information regulator type-1, and fork head box protein in rats

Cyclophosphamide (CP) is a chemotherapeutic agent that causes pulmonary damage by generating free radicals and pro-inflammatory cytokines. Pulmonary damage has a high mortality rate due to the severe inflammation and edema occurred in lung. PPARγ/Sirt 1 signaling has been shown to be cytoprotective effect against cellular inflammatory stress and oxidative injury. Protocatechuic acid (PCA) is a potent Sirt1 activator and exhibits antioxidant as well as anti-inflammatory properties. The current study aims to investigate the therapeutic impacts of PCA against CP-induced pulmonary damage in rats. Rats were assigned randomly into 4 experimental groups. The control group was injected with a single i.p injection of saline. CP group was injected with a single i.p injection of CP (200 mg/kg). PCA groups were administered orally with PCA (50 and 100 mg/kg; p.o.) once daily for 10 consecutive days after CP injection. PCA treatment resulted in a significant decrease in the protein levels of MDA, a marker of lipid peroxidation, NO and MPO along with a significant increase in GSH and catalase protein levels. Moreover, PCA downregulated anti-inflammatory markers as IL-17, NF-κB, IKBKB, COX-2, TNF-α, and PKC and upregulated cytoprotective defenses as PPARγ, and SIRT1. In addition, PCA administration ameliorated FoxO-1 elevation, increased Nrf2 gene expression, and reduced air alveoli emphysema, bronchiolar epithelium hyperplasia and inflammatory cell infiltration induced by CP. PCA might represent a promising adjuvant to prevent pulmonary damage in patients receiving CP due to its antioxidant and anti-inflammatory effects with cytoprotective defenses.

Crocodile Oil Modulates Inflammation and Immune Responses in LPS-Stimulated RAW 264.7 Macrophages

Crocodile oil (CO) is generated from the fatty tissues of crocodiles as a by-product of commercial aquaculture. CO is extensively applied in the treatment of illnesses including asthma, emphysema, skin ulcers, and cancer, as well as wound healing. Whether CO has anti-inflammatory properties and encourages an immune response remains uncertain. The impact of CO on inflammatory conditions in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and the mechanisms behind it were examined in this work. Cells were treated with 0.125–2% CO dissolved in 0.5% propylene glycol with or without LPS. The production and expression of inflammatory cytokines and mediators were also examined in this research. CO reduced the synthesis and gene expression of interleukin-6 (IL-6). Consistently, CO inhibited the expression and synthesis of inflammatory markers including cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), nitric oxide (NO), and nuclear factor kappa B (NF-κB). Furthermore, CO reduced the effects of DNA damage. CO also increased the cell-cycle regulators, cyclins D2 and E2, which improved the immunological response. CO might thus be produced as a nutraceutical supplement to help avoid inflammatory diseases.

Cyclopentenone Prostaglandins: Biologically Active Lipid Mediators Targeting Inflammation

Cyclopentenone prostaglandins (cyPGs) are biologically active lipid mediators, including PGA2, PGA1, PGJ2, and its metabolites. cyPGs are essential regulators of inflammation, cell proliferation, apoptosis, angiogenesis, cell migration, and stem cell activity. cyPGs biologically act on multiple cellular targets, including transcription factors and signal transduction pathways. cyPGs regulate the inflammatory response by interfering with NF-κB, AP-1, MAPK, and JAK/STAT signaling pathways via both a group of nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-γ) dependent and PPAR-γ independent mechanisms. cyPGs promote the resolution of chronic inflammation associated with cancers and pathogen (bacterial, viral, and parasitic) infection. cyPGs exhibit potent effects on viral infections by repressing viral protein synthesis, altering viral protein glycosylation, inhibiting virus transmission, and reducing virus-induced inflammation. We summarize their anti-proliferative, pro-apoptotic, cytoprotective, antioxidant, anti-angiogenic, anti-inflammatory, pro-resolution, and anti-metastatic potential. These properties render them unique therapeutic value, especially in resolving inflammation and could be used in adjunct with other existing therapies. We also discuss other α, β -unsaturated carbonyl lipids and cyPGs like isoprostanes (IsoPs) compounds.

Mycolactone toxin induces an inflammatory response by targeting the IL-1β pathway: Mechanistic insight into Buruli ulcer pathophysiology

Mycolactone, a lipid-like toxin, is the major virulence factor of Mycobacterium ulcerans, the etiological agent of Buruli ulcer. Its involvement in lesion development has been widely described in early stages of the disease, through its cytotoxic and immunosuppressive activities, but less is known about later stages. Here, we revisit the role of mycolactone in disease outcome and provide the first demonstration of the pro-inflammatory potential of this toxin. We found that the mycolactone-containing mycobacterial extracellular vesicles produced by M. ulcerans induced the production of IL-1β, a potent pro-inflammatory cytokine, in a TLR2-dependent manner, targeting NLRP3/1 inflammasomes. We show our data to be relevant in a physiological context. The in vivo injection of these mycolactone-containing vesicles induced a strong local inflammatory response and tissue damage, which were prevented by corticosteroids. Finally, several soluble pro-inflammatory factors, including IL-1β, were detected in infected tissues from mice and Buruli ulcer patients. Our results revisit Buruli ulcer pathophysiology by providing new insight, thus paving the way for the development of new therapeutic strategies taking the pro-inflammatory potential of mycolactone into account.

Buruli ulcer is a neglected tropical disease occurring mainly in poor rural areas of West and Central Africa. This cutaneous disease is caused by Mycobacterium ulcerans, a bacterium belonging to the same family as M. tuberculosis and M. leprae. The skin lesions are caused by a cytotoxic toxin named mycolactone, also known to act as an immunosuppressor and an anti-inflammatory molecule. However, Buruli ulcer lesions are characterized by a chronic cutaneous inflammation with a recruitment of cellular immune cells trying to counteract M. ulcerans. Our work allows for a reconcilitation of previous observations. We found by in vitro experiment on macrophages that the mycolactone-containing mycobacterial extracellular vesicles produced by M. ulcerans induced the production of IL-1β, a potent pro-inflammatory molecule, while other pro-inflammatory soluble factors are inhibited. We also detected IL-1β protein in a mouse model of M. ulcerans infection as well as in biopsies of Buruli ulcer patients. The pro-inflammatory potential of mycolacone has to be taken into account to understand the full pathophysiology of Buruli ulcer.

Geniposide ameliorated sepsis-induced acute kidney injury by activating PPARγ

Acute kidney injury is one of the most common complications that occurs in septic shock. An effective therapeutic intervention is urgently needed. Geniposide has been reported to possess pleiotropic activities against different diseases. However, the effect of geniposide on sepsis-induced kidney injury is unexplored. Our study aims to illustrate the mitigative effects of geniposide on sepsis-induced kidney injury and its relevant mechanisms. Sepsis was induced in mice undergoing cecal ligation and puncture (CLP) surgery. Mice were intraperitoneally injected with geniposide (10, 20 and 40 mg/kg) for treatment. The results showed that geniposide ameliorated kidney injury and dysfunction in CLP-induced septic mice, accompanied by reduction of inflammatory response and oxidative stress. We also found that geniposide significantly reduced vascular permeability and cellular apoptosis of the kidney, with increase of Bcl-2 and decrease of Bax and cleaved caspase-3. Moreover, PPARγ was found to be upregulated with the increasing concentration of geniposide. The protection of geniposide against inflammation and apoptosis was recovered by inhibition of PPARγ. Collectively, these results indicate that geniposide could significantly ameliorate acute kidney injury in CLP-induced septic mice and LPS-stimulated HK-2 cells by activating PPARγ. Geniposide might be a potential drug candidate for sepsis-induced kidney injury.

PPAR-Mediated Toxicology and Applied Pharmacology

Peroxisome proliferator-activated receptors (PPARs), members of the nuclear hormone receptor family, attract wide attention as promising therapeutic targets for the treatment of multiple diseases, and their target selective ligands were also intensively developed for pharmacological agents such as the approved drugs fibrates and thiazolidinediones (TZDs). Despite their potent pharmacological activities, PPARs are reported to be involved in agent- and pollutant-induced multiple organ toxicity or protective effects against toxicity. A better understanding of the protective and the detrimental role of PPARs will help to preserve efficacy of the PPAR modulators but diminish adverse effects. The present review summarizes and critiques current findings related to PPAR-mediated types of toxicity and protective effects against toxicity for a systematic understanding of PPARs in toxicology and applied pharmacology.

Omega-9 Oleic Acid, the Main Compound of Olive Oil, Mitigates Inflammation during Experimental Sepsis

The Mediterranean diet, rich in olive oil, is beneficial, reducing the risk of cardiovascular diseases and cancer. Olive oil is mostly composed of the monounsaturated fatty acid omega-9. We showed omega-9 protects septic mice modulating lipid metabolism. Sepsis is initiated by the host response to infection with organ damage, increased plasma free fatty acids, high levels of cortisol, massive cytokine production, leukocyte activation, and endothelial dysfunction. We aimed to analyze the effect of omega-9 supplementation on corticosteroid unbalance, inflammation, bacterial elimination, and peroxisome proliferator-activated receptor (PPAR) gamma expression, an omega-9 receptor and inflammatory modulator. We treated mice for 14 days with omega-9 and induced sepsis by cecal ligation and puncture (CLP). We measured systemic corticosterone levels, cytokine production, leukocyte and bacterial counts in the peritoneum, and the expression of PPAR gamma in both liver and adipose tissues during experimental sepsis. We further studied omega-9 effects on leukocyte rolling in mouse cremaster muscle-inflamed postcapillary venules and in the cerebral microcirculation of septic mice. Here, we demonstrate that omega-9 treatment is associated with increased levels of the anti-inflammatory cytokine IL-10 and decreased levels of the proinflammatory cytokines TNF-α and IL-1β in peritoneal lavage fluid of mice with sepsis. Omega-9 treatment also decreased systemic corticosterone levels. Neutrophil migration from circulation to the peritoneal cavity and leukocyte rolling on the endothelium were decreased by omega-9 treatment. Omega-9 also decreased bacterial load in the peritoneal lavage and restored liver and adipose tissue PPAR gamma expression in septic animals. Our data suggest a beneficial anti-inflammatory role of omega-9 in sepsis, mitigating leukocyte rolling and leukocyte influx, balancing cytokine production, and controlling bacterial growth possibly through a PPAR gamma expression-dependent mechanism. The significant reduction of inflammation detected after omega-9 enteral injection can further contribute to the already known beneficial properties facilitated by unsaturated fatty acid-enriched diets.

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

High fat diet-induced obesity increases myocardial injury and alters cardiac STAT3 signaling in mice after polymicrobial sepsis

Little is known about how obesity affects the heart during sepsis and we sought to investigate the obesity-induced cardiac effects that occur during polymicrobial sepsis. Six-week old C57BL/6 mice were randomized to a high fat (HFD) (60% kcal fat) or normal diet (ND) (16% kcal fat). After 6weeks of feeding, mice were anesthetized with isoflurane and polymicrobial sepsis was induced by cecal ligation and puncture (CLP). Plasma and cardiac tissue were obtained for analysis. Echocardiography was performed on a separate cohort of mice at 0 and 18h after CLP. Following 6-weeks of dietary intervention, plasma cardiac troponin I was elevated in obese mice at baseline compared to non-obese mice but troponin increased only in non-obese septic mice. IL-17a expression was 27-fold higher in obese septic mice versus non-obese septic mice. Cardiac phosphorylation of STAT3 at Ser727 was increased at baseline in obese mice and increased further only in obese septic mice. Phosphorylation of STAT3 at Tyr705 was similar in both groups at baseline and increased after sepsis. SOCS3, a downstream protein and negative regulator of STAT3, was elevated in obese mice at baseline compared to non-obese mice. After sepsis non-obese mice had an increase in SOCS3 expression that was not observed in obese mice. Taken together, we show that obesity affects cardiac function and leads to cardiac injury. Furthermore, myocardial injury in obese mice during sepsis may occur through alteration of the STAT3 pathway.

15-Deoxy-Δ12,14-prostaglandin J2 Exerts Antioxidant Effects While Exacerbating Inflammation in Mice Subjected to Ureteral Obstruction

Urinary obstruction is associated with inflammation and oxidative stress, leading to renal dysfunction. Previous studies have shown that 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) has both antioxidant and anti-inflammatory effects. Using a unilateral ureteral obstruction (UUO) mouse model, we examined the effects of 15d-PGJ₂ on oxidative stress and inflammation in the kidney. Mice were subjected to UUO for 3 days and treated with 15d-PGJ₂. Protein and RNA expression were examined using immunoblotting and qPCR. 15d-PGJ₂ increased NF-E2-related nuclear factor erythroid-2 (Nrf2) protein expression in response to UUO, and heme oxygenase 1 (HO-1), a downstream target of Nrf2, was induced by 15d-PGJ₂. Additionally, 15d-PGJ₂ prevented protein carbonylation, a UUO-induced oxidative stress marker. Inflammation, measured by nuclear NF-κB, F4/80, and MCP-1, was increased in response to UUO and further increased by 15d-PGJ₂. Renal injury was aggravated by 15d-PGJ₂ treatment as measured by kidney injury molecule-1 (KIM-1) and cortical caspase 3 content. No effect of 15d-PGJ₂ was observed on renal function in mice subjected to UUO. This study illustrates differentiated functioning of 15d-PGJ₂ on inflammation and oxidative stress in response to obstructive nephropathy. High concentrations of 15d-PGJ₂ protects against oxidative stress during 3-day UUO in mice; however, it aggravates the associated inflammation.

A PPARγ AGONIST ENHANCES BACTERIAL CLEARANCE THROUGH NEUTROPHIL EXTRACELLULAR TRAP FORMATION AND IMPROVES SURVIVAL IN SEPSIS

Dysregulation of the inflammatory response against infection contributes to mortality in sepsis. Inflammation provides critical host defense, but it can cause tissue damage, multiple organ failure, and death. Because the nuclear transcription factor peroxisome proliferator-activated receptor γ (PPARγ) exhibits therapeutic potential, we characterized the role of PPARγ in sepsis. We analyzed severity of clinical signs, survival rates, cytokine production, leukocyte influx, and bacterial clearance in a cecal ligation and puncture (CLP) model of sepsis in Swiss mice. The PPARγ agonist rosiglitazone treatment improved clinical status and mortality, while increasing IL-10 production and decreasing TNF-α and IL-6 levels, and peritoneal neutrophil accumulation 24 h after CLP. We noted increased bacterial killing in rosiglitazone treated mice, correlated with increased generation of reactive oxygen species. Polymorphonuclear leukocytes (PMN) incubated with LPS or Escherichia coli and rosiglitazone increased peritoneal neutrophil extracellular trap (NET)-mediated bacterial killing, an effect reversed by the PPARγ antagonist (GW 9662) treatment. Rosiglitazone also enhanced the release of histones by PMN, a surrogate marker of NET formation, effect abolished by GW 9662. Rosiglitazone modulated the inflammatory response and increased bacterial clearance through PPARγ activation and NET formation, combining immunomodulatory and host-dependent anti-bacterial effects and, therefore, warrants further study as a potential therapeutic agent in sepsis.

A lard-rich high-fat diet increases hepatic peroxisome proliferator-activated receptors in endotoxemic rats

BACKGROUND

Diets high in saturated fatty acids activate chronic inflammation. We previously reported that, in even acute inflammation caused by lipopolysaccharide (LPS), liver injury was exacerbated in rats fed a lard-rich diet. Peroxisome proliferator-activated receptors (PPARs) are related to inflammation and are also key regulators of lipid metabolism. In this study, we examined effects of high-fat diet on liver injury and hepatic lipid metabolism during endotoxemia, measuring hepatic PPARs and other markers.

MATERIALS AND METHODS

Male Wistar rats were fed a high-fat diet (HFD, 60 kcal% fat) or control diet (CD, 10 kcal% fat) for 4 or 12 wk, injected with LPS and sacrificed at 0, 1.5, or 6 h. Analyses included plasma aspartate transaminase (AST) and alanine transaminase (ALT) levels, messenger RNA (mRNA) and protein levels of hepatic PPARα and PPARγ, and mRNA levels of enzymes related to fatty acid oxidation and synthesis.

RESULTS

Endotoxemic rats on HFD for 12 wk, but not 4 wk, had higher mRNA and protein levels for hepatic PPARs, than did those on CD (P < 0.01-0.05). Similarly, these rats had increased mRNA expression of hepatic fatty acid oxidation- and synthesis-related enzymes (P < 0.01-0.05). Rats injected with LPS had more severe liver injury, indicated by plasma AST/ALT, if on the HFD for 12 wk, compared with for 4 wk.

CONCLUSIONS

Consumption of a lard-rich diet for 12 wk worsened liver injury and increased hepatic PPARα and PPARγ expression in endotoxemic rats.

PPARγ in Bacterial Infections: A Friend or Foe?

Peroxisome proliferator-activated receptor γ (PPARγ) is now recognized as an important modulator of leukocyte inflammatory responses and function. Its immunoregulatory function has been studied in a variety of contexts, including bacterial infections of the lungs and central nervous system, sepsis, and conditions such as chronic granulomatous disease. Although it is generally believed that PPARγ activation is beneficial for the host during bacterial infections via its anti-inflammatory and antibacterial properties, PPARγ agonists have also been shown to dampen the host immune response and in some cases exacerbate infection by promoting leukocyte apoptosis and interfering with leukocyte migration and infiltration. In this review we discuss the role of PPARγ and its activation during bacterial infections, with focus on the potential of PPARγ agonists and perhaps antagonists as novel therapeutic modalities. We conclude that adjustment in the dosage and timing of PPARγ agonist administration, based on the competence of host antimicrobial defenses and the extent of inflammatory response and tissue injury, is critical for achieving the essential balance between pro- and anti-inflammatory effects on the immune system.

The role of endogenous opioid peptides in the antinociceptive effect of 15-deoxy(Δ12,14)-prostaglandin J2 in the temporomandibular joint

We have previously demonstrated that peripheral administration of 15d-PGJ2 in the Temporomandibular joint (TMJ) of rats can prevent nociceptor sensitization, mediated by peroxisome proliferator activated receptor-γ (PPAR-γ), and κ- and δ- opioid receptors. However, the mechanism that underlies the signaling of PPAR-γ (upon activation by 15d-PGJ2) to induce antinociception, and how the opioid receptors are activated via 15d-PGJ2 are not fully understood. This study demonstrates that peripheral antinociceptive effect of 15d-PGJ2 is mediated by PPAR-γ expressed in the inflammatory cells of TMJ tissues. Once activated by 15d-PGJ2, PPAR-γ induces the release of β-endorphin and dynorphin, which activates κ- and δ-opioid receptors in primary sensory neurons to induce the antinociceptive effect.

PPARγ signaling and emerging opportunities for improved therapeutics

Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated nuclear receptor that regulates glucose and lipid metabolism, endothelial function and inflammation. Rosiglitazone (RGZ) and other thiazolidinedione (TZD) synthetic ligands of PPARγ are insulin sensitizers that have been used for the treatment of type 2 diabetes. However, undesirable side effects including weight gain, fluid retention, bone loss, congestive heart failure, and a possible increased risk of myocardial infarction and bladder cancer, have limited the use of TZDs. Therefore, there is a need to better understand PPARγ signaling and to develop safer and more effective PPARγ-directed therapeutics. In addition to PPARγ itself, many PPARγ ligands including TZDs bind to and activate G protein-coupled receptor 40 (GPR40), also known as free fatty acid receptor 1. GPR40 signaling activates stress kinase pathways that ultimately regulate downstream PPARγ responses. Recent studies in human endothelial cells have demonstrated that RGZ activation of GPR40 is essential to the optimal propagation of PPARγ genomic signaling. RGZ/GPR40/p38 MAPK signaling induces and activates PPARγ co-activator-1α, and recruits E1A binding protein p300 to the promoters of target genes, markedly enhancing PPARγ-dependent transcription. Therefore in endothelium, GPR40 and PPARγ function as an integrated signaling pathway. However, GPR40 can also activate ERK1/2, a proinflammatory kinase that directly phosphorylates and inactivates PPARγ. Thus the role of GPR40 in PPARγ signaling may have important implications for drug development. Ligands that strongly activate PPARγ, but do not bind to or activate GPR40 may be safer than currently approved PPARγ agonists. Alternatively, biased GPR40 agonists might be sought that activate both p38 MAPK and PPARγ, but not ERK1/2, avoiding its harmful effects on PPARγ signaling, insulin resistance and inflammation. Such next generation drugs might be useful in treating not only type 2 diabetes, but also diverse chronic and acute forms of vascular inflammation such as atherosclerosis and septic shock.

Bone-marrow-derived mesenchymal stem cells inhibit gastric aspiration lung injury and inflammation in rats

Gastric aspiration lung injury is one of the most common clinical events. This study investigated the effects of bone‐marrow‐derived mesenchymal stem cells (BMSCs) on combined acid plus small non‐acidified particle (CASP)‐induced aspiration lung injury. Enhanced green fluorescent protein (EGFP⁺) or EGFP⁻BMSCs or 15d‐PGJ₂ were injected via the tail vein into rats immediately after CASP‐induced aspiration lung injury. Pathological changes in lung tissues, blood gas analysis, the wet/dry weight ratio (W/D) of the lung, levels of total proteins and number of total cells and neutrophils in bronchoalveolar lavage fluid (BALF) were determined. The cytokine levels were measured using ELISA. Protein expression was determined by Western blot. Bone‐marrow‐derived mesenchymal stem cells treatment significantly reduced alveolar oedema, exudation and lung inflammation; increased the arterial partial pressure of oxygen; and decreased the W/D of the lung, the levels of total proteins and the number of total cells and neutrophils in BALF in the rats with CASP‐induced lung injury. Bone‐marrow‐derived mesenchymal stem cells treatment decreased the levels of tumour necrosis factor‐α and Cytokine‐induced neutrophil chemoattractant (CINC)‐1 and the expression of p‐p65 and increased the levels of interleukin‐10 and 15d‐PGJ₂ and the expression of peroxisome proliferator‐activated receptor (PPAR)‐γ in the lung tissue in CASP‐induced rats. Tumour necrosis factor‐α stimulated BMSCs to secrete 15d‐PGJ₂. A tracking experiment showed that EGFP⁺BMSCs were able to migrate to local lung tissues. Treatment with 15d‐PGJ₂ also significantly inhibited CASP‐induced lung inflammation and the production of pro‐inflammatory cytokines. Our results show that BMSCs can protect lung tissues from gastric aspiration injury and inhibit lung inflammation in rats. A beneficial effect might be achieved through BMSC‐derived 15d‐PGJ₂ activation of the PPAR‐γ receptor, reducing the production of proinflammatory cytokines.

Dietary Apigenin Exerts Immune-Regulatory Activity in Vivo by Reducing NF-κB Activity, Halting Leukocyte Infiltration and Restoring Normal Metabolic Function

The increasing prevalence of inflammatory diseases and the adverse effects associated with the long-term use of current anti-inflammatory therapies prompt the identification of alternative approaches to reestablish immune balance. Apigenin, an abundant dietary flavonoid, is emerging as a potential regulator of inflammation. Here, we show that apigenin has immune-regulatory activity in vivo. Apigenin conferred survival to mice treated with a lethal dose of Lipopolysaccharide (LPS) restoring normal cardiac function and heart mitochondrial Complex I activity. Despite the adverse effects associated with high levels of splenocyte apoptosis in septic models, apigenin had no effect on reducing cell death. However, we found that apigenin decreased LPS-induced apoptosis in lungs, infiltration of inflammatory cells and chemotactic factors’ accumulation, re-establishing normal lung architecture. Using NF-κB luciferase transgenic mice, we found that apigenin effectively modulated NF-κB activity in the lungs, suggesting the ability of dietary compounds to exert immune-regulatory activity in an organ-specific manner. Collectively, these findings provide novel insights into the underlying immune-regulatory mechanisms of dietary nutraceuticals in vivo.

Combined zinc supplementation with proinsulin C-peptide treatment decreases the inflammatory response and mortality in murine polymicrobial sepsis

Zinc is a trace element vital for immune function during host response to infection. The proinsulin C-peptide has been shown to exert beneficial effects through activation of the anti-inflammatory peroxisome proliferator-activated receptor γ (PPARγ) in experimental endotoxemia. Some in vitro activities of C-peptide appear dependent on the presence of zinc. We investigated the effect of zinc supplementation before onset of sepsis on the anti-inflammatory properties of C-peptide. Male C57BL/6 mice were subjected to polymicrobial sepsis by cecal ligation and puncture (CLP). Mice received zinc gluconate (1.3 mg/kg) intraperitoneally (i.p.) for 3 days before CLP. One hour after CLP, animals received C-peptide (280 nmol/kg i.p.) or the antimicrobial agent imipenem (25 mg/kg i.p.). Cecal ligation and puncture was associated with an 11% survival rate, pulmonary leukosequestration, and liver injury. Molecular analysis in lungs of septic mice showed increased nuclear activation of the proinflammatory extracellular signal-regulated kinases 1 and 2 and nuclear factor κB, but decreased PPARγ expression, when compared with sham animals. Combination of zinc supplementation with C-peptide posttreatment significantly improved survival rate (61%) similarly to antibiotic treatment (60%), ameliorated lung architecture and liver function, reduced tissue neutrophil infiltration, and increased bacterial clearance when compared with vehicle, C-peptide, or zinc treatment alone. These beneficial effects were associated with restored lung nuclear expression of PPARγ and reduction of phosphorylated extracellular signal-regulated kinases 1 and 2 and nuclear factor κB activities in comparison to vehicle or single treatment protocols. Our data demonstrate that short-term zinc prophylaxis before the infectious insult is a requisite for the anti-inflammatory properties of C-peptide by facilitating modulation of inflammatory pathways.

Oxidative stress-induced expression of HSP70 contributes to the inhibitory effect of 15d-PGJ2 on inducible prostaglandin pathway in chondrocytes

The inhibitory effect of 15-deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2) on proinflammatory gene expression has been extensively documented and frequently ascribed to its ability to prevent NF-κB pathway activation. We and others have previously demonstrated that it was frequently independent of the peroxisome proliferator activated receptor (PPAR)γ activation. Here, we provide evidence that induction of intracellular heat shock protein (HSP)70 by oxidative stress is an additional regulatory loop supporting the anti-inflammatory effect of 15d-PGJ2 in chondrocytes. Using real-time quantitative PCR and Western blotting, we showed that 15d-PGJ2 stimulated HSP70, but not HSP27 expression while increasing oxidative stress as measured by spectrofluorimetry and confocal spectral imaging. Using N-acetylcysteine (NAC) as an antioxidant, we demonstrated further that oxidative stress was thoroughly responsible for the increased expression of HSP70. Finally, using an HSP70 antisense strategy, we showed that the inhibitory effect of 15d-PGJ2 on IL-1-induced activation of the NF-κB pathway, COX-2 and mPGES-1 expression, and PGE2 synthesis was partly supported by HSP70. These data provide a new anti-inflammatory mechanism to support the PPARγ-independent effect of 15d-PGJ2 in chondrocyte and suggest a possible feedback regulatory loop between oxidative stress and inflammation via intracellular HSP70 up-regulation. This cross talk is consistent with 15d-PGJ2 as a putative negative regulator of the inflammatory reaction.

Regulation of cigarette smoke-induced toll-like receptor 4 expression by peroxisome proliferator-activated receptor-gamma agonists in bronchial epithelial cells

BACKGROUND AND OBJECTIVE

This study was designed to determine the effects of peroxisome proliferator-activated receptor-gamma (PPARγ) on airway inflammatory response to cigarette smoke (CS) exposure.

METHODS

For the in vivo experiments, 50 male Wistar rats were randomly assigned to one of four groups and were exposed to CS and pretreatment with a PPARγ agonist, rosiglitazone or a vehicle (saline). PPARγ antagonist bisphenol A diglycidyl ether (BADGE) or saline was administered before rosiglitazone treatment. Leukotriene B4 (LTB4) and interleukin-8 (IL-8) were measured by enzyme-linked immunosorbent assay. PPARγ and toll-like receptor 4 (TLR4) expression levels were assessed by immunohistochemistry and real-time polymerase chain reaction. For the in vitro experiments, human bronchial epithelial cells were stimulated with CS or phosphate buffer saline, pretreated with PPARγ agonist rosiglitazone or 15-deoxy-(Δ12,14)-PG J2 before CS exposure. BADGE was administered prior to the agonist treatment. PPARγ, TLR4 and inhibitor of κB (IκBα) expression levels were assessed by Western bot.

RESULTS

CS exposure decreased PPARγ expression, as well as increased IL-8, LTB4 and TLR4 expression levels in bronchial epithelial cells in vivo and in vitro. Moreover, PPARγ ligands counteracted CS-induced airway inflammation by reducing IL-8 and LTB4 expression levels that are associated with TLR4 and nuclear factor-kappa B (NF-κB).

CONCLUSION

CS exposure increased the pro-inflammatory activity of bronchial epithelial cells by affecting PPARγ expression. Moreover, PPARγ may play a significant role as a modulator of the TLR4-dependent inflammatory pathway through NF-κB in bronchial epithelial cells.

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.

Dietary fish oil reduces systemic inflammation and ameliorates sepsis-induced liver injury by up-regulating the peroxisome proliferator-activated receptor gamma-mediated pathway in septic mice

This study investigated the effect of dietary fish oil on systemic inflammation and hepatic injury in mice with polymicrobial sepsis. Male ICR mice were assigned to a control group (C, n=30) and a fish oil group (FO, n=30). Mice in the C group were fed a semi-purified diet with 10% soybean oil, and those in the FO group were fed a fish oil diet (2.5% fish oil+7.5% soybean oil; w/w). Three weeks later, sepsis was induced by cecal ligation and puncture (CLP), and mice were sacrificed at 0, 6 and 24 h after CLP, respectively. Results showed that compared with C group, the FO group had lower plasma levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10, and nitrite at 6 and 24 h after CLP. Also, peritoneal lavage fluid concentrations of TNF-α and prostaglandin (PG) E2 were significantly lower at 24 h in the FO than in the C group. The FO group had lower myeloperoxidase activities at 6 h after CLP in various organs. Plasma aminotransferase and alanine aminotransferase activities revealed significantly decreased in the FO group. The DNA-binding activity of peroxisome proliferators-activated receptor gamma (PPARγ) and mRNA expression of I kappaB alpha (IκBα) were up-regulated while nuclear factor (NF)-κB p65 DNA-binding activity, inducible nitric oxide synthase protein expression and the concentration of nitrotyrosine were significantly decreased in the FO group in liver after CLP. These results indicate that dietary fish oil administration may attenuate systemic inflammation and up-regulate hepatic PPARγ DNA-binding activity, which may consequently have ameliorated liver injury in these septic mice.

Pioglitazone reduces inflammation through inhibition of NF-κB in polymicrobial sepsis

The insulin sensitizing thiazolidinedione drugs, rosiglitazone and pioglitazone are specific peroxisome proliferator-activated receptor-gamma agonists and reduce pro-inflammatory responses in patients with type 2 diabetes and coronary artery disease, and may be beneficial in sepsis. Sepsis was induced in 8-10-wk-old C57BL/6 mice by cecal ligation and puncture (CLP) with a 22 -g double puncture technique. Mice received an i.p. injection of vehicle (DMSO:PBS) or pioglitazone (20 mg/kg) at 1 h and 6 h after CLP, and were sacrificed at various time points. In sepsis, vehicle-treated mice had hypoglycemia, increased lung injury and increased lung neutrophil infiltration. Pro-inflammatory plasma cytokines were increased, but the plasma adipokine, adiponectin, was decreased in vehicle-treated septic mice. This corresponded with inhibitor κB (IκBα) protein degradation and an increase in NF-κB activity in lung. Pioglitazone treatment improved plasma Glc and adiponectin levels, and decreased pro-inflammatory cytokines. Lung IκBα protein expression increased and corresponded with a decrease in NF-κB activity in the lung from pioglitazone-treated mice. Pioglitazone reduces the inflammatory response in polymicrobial sepsis in part through inhibition of NF-κB and may be a novel therapy in sepsis.

Low-level laser therapy restores the oxidative stress balance in acute lung injury induced by gut ischemia and reperfusion

It remains unknown if the oxidative stress can be regulated by low-level laser therapy (LLLT) in lung inflammation induced by intestinal reperfusion (i-I/R). A study was developed in which rats were irradiated (660 nm, 30 mW, 5.4 J) on the skin over the bronchus and euthanized 2 h after the initial of intestinal reperfusion. Lung edema and bronchoalveolar lavage fluid neutrophils were measured by the Evans blue extravasation and myeloperoxidase (MPO) activity respectively. Lung histology was used for analyzing the injury score. Reactive oxygen species (ROS) was measured by fluorescence. Both expression intercellular adhesion molecule 1 (ICAM-1) and peroxisome proliferator-activated receptor-y (PPARy) were measured by RT-PCR. The lung immunohistochemical localization of ICAM-1 was visualized as a brown stain. Both lung HSP70 and glutathione protein were evaluated by ELISA. LLLT reduced neatly the edema, neutrophils influx, MPO activity and ICAM-1 mRNA expression. LLLT also reduced the ROS formation and oppositely increased GSH concentration in lung from i-I/R groups. Both HSP70 and PPARy expression also were elevated after laser irradiation. Results indicate that laser effect in attenuating the acute lung inflammation is driven to restore the balance between the pro- and antioxidants mediators rising of PPARy expression and consequently the HSP70 production.

Short-term high fat feeding increases organ injury and mortality after polymicrobial sepsis

The purpose of this study was to examine the effect of short-term high fat feeding on the inflammatory response in polymicrobial sepsis. Male C57BL/6 mice at 6 weeks of age were randomized to a high-fat diet (HFD) (60% kcal fat) or control diet (CD) (16% kcal fat) for 3 weeks. After 3 weeks of feeding, sepsis was induced by cecal ligation and puncture (CLP) and animals were monitored for survival. In a separate experiment, after 3 weeks of feeding mice underwent CLP and were sacrificed at various time points thereafter. Tissue was collected for biochemical studies. Mice fed a HFD gained more weight and had a greater fat mass compared to CD-fed mice. Mice on a HFD had a lower probability of survival and more severe lung injury compared with CD-fed mice following sepsis. Myeloperoxidase (MPO) activity, an indicator of neutrophil infiltration, was increased in the lung and liver after CLP in HFD-fed mice compared with CD (P < 0.05). The plasma cytokines tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were increased in both groups after CLP, however, TNF-α and IL-6 levels were lower in HFD mice at 3 h after CLP compared with CD and consistent with lung, but not liver, messenger RNA (mRNA) expression. Leptin levels were higher in HFD-fed mice at 18 h after sepsis compared to baseline levels (P < 0.05). Polymicrobial sepsis increased hepatic nuclear factor-κB (NF-κB) activation in HFD-fed mice after CLP vs. CD-fed mice. Short duration high fat feeding increases mortality and organ injury following polymicrobial sepsis. These effects correspond to changes in NF-κB.

PPARγ ligand treatment inhibits cardiac inflammatory mediators induced by infection with different lethality strains of Trypanosoma cruzi

Trypanosoma cruzi (T. cruzi), the etiological agent of Chagas' disease, causes cardiac alterations in the host. Although the main clinical manifestations arise during the chronic stage, the mechanisms leading to heart damage develop early during infection. In fact, an intense inflammatory response is observed from acute stage of infection. Recently, peroxisome proliferator-activated receptors (PPARs) have attracted research interest due to their participation in the modulation of inflammation. In this work we addressed the role of 15-Deoxy-∆(12,14) ProstaglandinJ2 (15dPGJ2), a PPARγ natural ligand in the regulation of inflammatory mediators, in acute and chronic experimental mouse models of Chagas' disease with the RA and K98 T. cruzi strains, respectively. This work demonstrates that 15dPGJ2 treatment inhibits the expression and activity of inducible nitric oxide synthase (NOS2) as well as TNF-α and IL-6 mRNA levels. Also, expression and activity of metalloproteinases 2 (MMP-2) and 9 (MMP9) were inhibited by 15dPGJ2. Moreover GW9662, a specific PPARγ antagonist, revealed the participation of other signaling pathways since, in GW9662 presence, 15dPJG2 had a partial effect on the inhibition of inflammatory parameters in the acute model of infection. Accordingly, NF-κB activation was demonstrated, assessing p65 nuclear translocation in the hearts of infected mice with both T. cruzi strains. Such effect was inhibited after 15dPGJ2 treatment. Our findings support the concept that in vivo PPARγ and NF-κB pathways are implicated in the inhibitory effects of 15dPGJ2 on inflammatory mediators at different times depending on whether the infection is caused by the lethal or non-lethal T. cruzi strain.

Glycogen synthase kinase-3β regulates anti-inflammatory property of fluoxetine

A selective serotonin reuptake inhibitor fluoxetine not only is widely used in the treatment of depression but also has an anti-inflammatory property. Glycogen synthase kinase-3beta (GSK-3β) is a vital factor in the inflammation process. How fluoxetine interferes with inflammation via a GSK-3β-dependent pathway remains unclear. The aim of this study is to investigate the effects of fluoxetine on lipopolysaccharide (LPS)-induced inflammation. Results showed that fluoxetine decreased mortality rate of the mice. It also inhibited LPS-induced release of nitric oxide (NO) and prostaglandin E2 (PGE2) in serum and RAW264.7 murine macrophages and expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Upon LPS stimulation, fluoxetine caused a delay but increased in the phosphorylated levels of GSK-3β (ser9), whereas it did not affect LPS-induced activation of mitogen-activated protein kinase (MAPK) and generation of reactive oxygen species (ROS). Fluoxetine in combination with phosphatidylinositol 3-kinases/Akt inhibitors (LY294002 and Wortmannin) did not have a synergistic inhibition on LPS-induced NO release and PGE2 production. In addition, peroxisome proliferator-activated receptor γ (PPARγ) antagonist GW9622 showed no reverse effects of this inhibition of fluoxetine. GSK-3β knockdown blocked the inhibitory effects of fluoxetine on LPS-induced iNOS/NO release and COX-2/PGE2 production. These results indicated that GSK-3β regulated anti-inflammatory property of fluoxetine. However, Akt activation, ROS generation, and altered PPARγ activity were not involved in this inhibition of fluoxetine.

15-Deoxy-Δ(12,14)-prostaglandin J(2) attenuates the biological activities of monocyte/macrophage cell lines

Monocytes/macrophages link the innate and adaptive immune systems, and in inflammatory disorders their activation leads to tissue damage. 15-Deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), a natural peroxisome proliferator-activated receptor gamma (PPARγ) ligand, has garnered much interest because it possesses anti-inflammatory properties in a number of experimental models. However, whether it regulates monocytes/macrophage pathophysiology is still unknown. This study was designed to examine the effects of 15d-PGJ(2) on the phagocytosis, proliferation and inflammatory cytokines generation in mouse monocyte/macrophage cell line RAW264.7 and J774A.1 cells upon lipopolysaccharide challenge. Our results showed that 15d-PGJ(2) inhibited the phagocytic activity and cell proliferation in a dose-dependent manner, and suppressed proinflammatory cytokines expression, such as tumor necrosis factor-α, transforming growth factor-β1, interleukin-6, and monocyte chemotactic protein-1. These effects were independent of PPARγ, because PPARγ agonist (troglitazone or ciglitazone) and PPARγ antagonist (GW9662) did not affect these activities mentioned above in cells. Treatment of 15d-PGJ(2) also did not modulate expression and distribution of PPARγ. However, these effects of 15d-PGJ(2) were abrogated by antioxidant N-acetylcysteine. Moreover, treatment of 15d-PGJ(2) induced a significant increase in reactive oxygen species production in RAW264.7 and J774A.1 cells. In conclusion, 15d-PGJ(2) attenuates the biological activities of mouse monocyte/macrophage cell line cells involving oxidative stress, independently of PPARγ. These data further underline the anti-inflammation potential of 15d-PGJ(2).

15d-PGJ2-loaded in nanocapsules enhance the antinociceptive properties into rat temporomandibular hypernociception

AIMS

To verify whether the nanoencapsulation of 15d-PGJ(2) in poly(D,L-lactide-co-glycolide) (PLGA) nanocapsules (15d-PGJ(2)-NC) might potentialize its antinociceptive activity into rats' temporomandibular joint (TMJ).

MAIN METHODS

Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used to evaluate the morphology and suspension of the PLGA nanocapsules. Rats were pretreated (15 min) with an intra-TMJ injection of unloaded 15d-PGJ(2) or 15d-PGJ(2)-NC at concentrations of 10, 100 or 1000 pg followed by an ipsilateral intra-TMJ injection of 1.5% formalin. The nociceptive behavioral response was observed during 45 min; animals were then sacrificed and the periarticular tissue was removed for IL-1β measurements.

KEY FINDING

TEM and AFM analyses showed that 15d-PGJ(2)-NC is spherical without any aggregates or adhesion confirming that this formulation is a good drug carrier system for 15d-PGJ(2). Pretreatment with 15d-PGJ(2)-NC (100 and 1000 pg/TMJ), but not unloaded 15d-PGJ(2), was found to significantly decrease the release of IL-1β cytokine and the animals' nociceptive behavioral response induced by intra-TMJ injection of formalin.

SIGNIFICANCE

The compound 15d-PGJ(2)-NC might be used as a potential antinociceptive and anti-inflammatory agent to treat temporomandibular disorders in clinical practice.

CRTH2 is a critical regulator of neutrophil migration and resistance to polymicrobial sepsis

Although arachidonic acid cascade has been shown to be involved in sepsis, little is known about the role of PGD(2) and its newly found receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), on the septic response. Severe sepsis is associated with the failure of neutrophil migration. To investigate whether CRTH2 influences neutrophil recruitment and the lethality during sepsis, sepsis was induced by cecal ligation and puncture (CLP) surgery in mice. CRTH2 knockout (CRTH2(-/-)) mice were highly resistant to CLP-induced sepsis, which was associated with lower bacterial load and lower production of TNF-α, IL-6, and CCL3. IL-10, an anti-inflammatory cytokine, was higher in CRTH2(-/-) mice, blunting CLP-induced lethality in CRTH2(-/-) mice. Neutrophil accumulation in the peritoneum was more pronounced after CLP in CRTH2(-/-) mice, which was associated with higher CXCR2 levels in circulating neutrophils. Furthermore, sepsis caused a decrease in the level of acetylation of histone H3, an activation mark, at the CXCR2 promoter in wild-type neutrophils, suggesting that CXCR2 expression levels are epigenetically regulated. Finally, both pharmacological depletion of neutrophils and inhibition of CXCR2 abrogated the survival benefit in CRTH2(-/-) mice. These results demonstrate that genetic ablation of CRTH2 improved impaired neutrophil migration and survival during severe sepsis, which was mechanistically associated with epigenetic-mediated CXCR2 expression. Thus, CRTH2 is a potential therapeutic target for polymicrobial sepsis.

New insights into the role of peroxisome proliferator-activated receptors in regulating the inflammatory response after tissue injury

Major trauma results in a strong inflammatory response in injured tissue. This posttraumatic hyperinflammation has been implied in the adverse events leading to a breakdown of host defense mechanisms and ultimately to delayed organ failure. Ligands to peroxisome proliferator-activated receptors (PPARs) have recently been identified as potent modulators of inflammation in various acute and chronic inflammatory conditions. The main mechanism of action mediated by ligand binding to PPARs is the inhibition of the nuclear transcription factor NF-κB, leading to downregulation of downstream gene transcription, such as for genes encoding proinflammatory cytokines. Pharmacological PPAR agonists exert strong anti-inflammatory properties in various animal models of tissue injury, including central nervous system trauma, ischemia/reperfusion injury, sepsis, and shock. In addition, PPAR agonists have been shown to induce wound healing process after tissue trauma. The present review was designed to provide an up-to-date overview on the current understanding of the role of PPARs in the pathophysiology of the inflammatory response after major trauma. Therapeutic options for using recombinant PPAR agonists as pharmacological agents in the management of posttraumatic inflammation will be discussed.

Thy-1 signals through PPARγ to promote lipofibroblast differentiation in the developing lung

Thy-1 is a glycosylphosphytidylinositol-linked cell-surface glycoprotein present on a subset of lung fibroblasts, which plays an important role in postnatal alveolarization. In the present study, we define the role of Thy-1 in pulmonary lipofibroblast differentiation and in the regulation of lipid homeostasis via peroxisome proliferator-activated receptor-γ (PPARγ). Thy-1 was associated with interstitial cells containing lipid droplets in vivo. The transfection of Thy-1 into Thy-1 (-) fibroblasts increased triglyceride content, fatty-acid uptake, and the expression of the lipofibroblast marker adipocyte differentiation-related protein. Thy-1 (+) fibroblasts exhibited 2.4-fold higher PPARγ activity, and the inhibition or activation of PPARγ reduced and increased triglyceride content, respectively. Thy-1 (-) fibroblasts were not responsive to either of the PPARγ agonists ciglitazone or prostaglandin J(2), supporting the importance of Thy-1 in signaling via PPARγ. Thy-1 (+) fibroblasts expressed significantly higher concentrations of fatty-acid transporter protein-3 mRNA, and demonstrated higher rates of fatty-acid uptake and increased triglyceride content. The inhibition of fatty-acid transporter protein function reduced Thy-1 (+) fibroblast lipid content. The expression of Thy-1 in C57BL/6 lung fibroblasts increased during the neonatal period, coinciding with the onset of alveolarization. Thy-1 promoted lipofibroblast differentiation via the expression of PPARγ, stimulated lipid accumulation via fatty-acid esterification, and enhanced the fatty-acid uptake mediated by fatty-acid transporter proteins. Thy-1 is important in the regulation of lipofibroblast differentiation in the developing lung.

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.

Effects of 15d-PGJ₂-loaded poly(D,L-lactide-co-glycolide) nanocapsules on inflammation

BACKGROUND AND PURPOSE

The PPAR-γ agonist 15d-PGJ₂ is a potent anti-inflammatory agent but only at high doses. To improve the efficiency of 15d-PGJ₂, we used poly(D,L-lactide-co-glycolide) nanocapsules to encapsulate it, and function as a drug carrier system. The effects of these loaded nanocapsules (15d-PGJ₂-NC) on inflammation induced by different stimuli were compared with those of free 15d-PGJ₂.

EXPERIMENTAL APPROACH

Mice were pretreated (s.c.) with either 15d-PGJ₂-NC or unloaded 15d-PGJ₂ (3, 10 or 30 µg·kg⁻¹), before induction of an inflammatory response by i.p. injection of either endotoxin (LPS), carrageenan (Cg) or mBSA (immune response).

KEY RESULTS

The 15d-PGJ₂-NC complex did not display changes in physico-chemical parameters or drug association efficiency over time, and was stable for up to 60 days of storage. Neutrophil migration induced by i.p. administration of LPS, Cg or mBSA was inhibited by 15d-PGJ₂-NC, but not by unloaded 15d-PGJ₂. In the Cg model, 15d-PGJ₂-NC markedly inhibited serum levels of the pro-inflammatory cytokines TNF-α, IL-1β and IL-12p70. Importantly, 15d-PGJ₂-NC released high amounts of 15d-PGJ₂, reaching a peak between 2 and 8 h after administration. 15d-PGJ ₂ was detected in mouse serum after 24 h, indicating sustained release from the carrier. When the same concentration of unloaded 15d-PGJ₂ was administered, only small amounts of 15d-PGJ₂ were found in the serum after a few hours.

CONCLUSIONS AND IMPLICATIONS

The present findings clearly indicate the potential of the novel anti-inflammatory 15d-PGJ₂ carrier formulation, administered systemically. The formulation enables the use of a much smaller drug dose, and is significantly more effective compared with unloaded 15d-PGJ₂.

Microglia and Astrocyte Activation by Toll-Like Receptor Ligands: Modulation by PPAR-gamma Agonists. PPAR Res. 2008;2008:453120. [PMID: 18584038 PMCID: PMC2435222 DOI: 10.1155/2008/453120]

Microglia and astrocytes express numerous members of the Toll-like receptor (TLR) family that are pivotal for recognizing conserved microbial motifs expressed by a wide array of pathogens. Despite the critical role for TLRs in pathogen recognition, when dysregulated these pathways can also exacerbate CNS tissue destruction. Therefore, a critical balance must be achieved to elicit sufficient immunity to combat CNS infectious insults and downregulate these responses to avoid pathological tissue damage. We performed a comprehensive survey on the efficacy of various PPAR-γ agonists to modulate proinflammatory mediator release from primary microglia and astrocytes in response to numerous TLR ligands relevant to CNS infectious diseases. The results demonstrated differential abilities of select PPAR-γ agonists to modulate glial activation. For example, 15d-PGJ₂ and pioglitazone were both effective at reducing IL-12 p40 release by TLR ligand-activated glia, whereas CXCL2 expression was either augmented or inhibited by 15d-PGJ₂, effects that were dependent on the TLR ligand examined. Pioglitazone and troglitazone demonstrated opposing actions on microglial CCL2 production that were TLR ligand-dependent. Collectively, this information may be exploited to modulate the host immune response during CNS infections to maximize host immunity while minimizing inappropriate bystander tissue damage that is often characteristic of such diseases.

PPARs in alveolar macrophage biology

PPARs, most notably PPAR-gamma, play a crucial role in regulating the activation of alveolar macrophages, which in turn occupy a pivotal place in the immune response to pathogens and particulates drawn in with inspired air. In this review, we describe the dual role of the alveolar macrophage as both a first-line defender through its phagocytotic activity and a regulator of the immune response. Depending on its state of activation, the alveolar macrophage may either enhance or suppress different aspects of immune function in the lung. We then review the role of PPAR-gamma and its ligands in deactivating alveolar macrophages-thus limiting the inflammatory response that, if unchecked, could threaten the essential respiratory function of the alveolus-while upregulating the cell's phagocytotic activity. Finally, we examine the role that inadequate or inappropriate PPAR-gamma responses play in specific lung diseases.

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.

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.

Nrf2-regulated PPAR{gamma} expression is critical to protection against acute lung injury in mice

RATIONALE

The NF-E2 related factor 2 (Nrf2)-antioxidant response element (ARE) pathway is essential for protection against oxidative injury and inflammation including hyperoxia-induced acute lung injury. Microarray expression profiling revealed that lung peroxisome proliferator activated receptor gamma (PPARgamma) induction is suppressed in hyperoxia-susceptible Nrf2-deficient (Nrf2(-/-)) mice compared with wild-type (Nrf2(+/+)) mice. PPARgamma has pleiotropic beneficial effects including antiinflammation in multiple tissues.

OBJECTIVES

We tested the hypothesis that PPARgamma is an important determinant of pulmonary responsivity to hyperoxia regulated by Nrf2.

METHODS

A computational bioinformatic method was applied to screen potential AREs in the Pparg promoter for Nrf2 binding. The functional role of a potential ARE was investigated by in vitro promoter analysis. A role for PPARgamma in hyperoxia-induced acute lung injury was determined by temporal silencing of PPARgamma via intranasal delivery of PPARgamma-specific interference RNA and by administration of a PPARgamma ligand 15-deoxy-Delta(12,14)-prostaglandin J(2) in mice.

MEASUREMENTS AND MAIN RESULTS

Deletion or site-directed mutagenesis of a potential ARE spanning -784/-764 sequence significantly attenuated hyperoxia-increased Pparg promoter activity in airway epithelial cells overexpressing Nrf2, indicating that the -784/-764 ARE is critical for Nrf2-regulated PPARgamma expression. Mice with decreased lung PPARgamma by specific interference RNA treatment had significantly augmented hyperoxia-induced pulmonary inflammation and injury. 15 Deoxy-Delta(12,14)-prostaglandin J(2) administration significantly reduced hyperoxia-induced lung inflammation and edema in Nrf2(+/+), but not in Nrf2(-/-) mice.

CONCLUSIONS

Results indicate for the first time that Nrf2-driven PPARgamma induction has an essential protective role in pulmonary oxidant injury. Our observations provide new insights into the therapeutic potential of PPARgamma in airway oxidative inflammatory disorders.

15-deoxy-delta 12,14-prostaglandin J2 prevents inflammatory response and endothelial cell damage in rats with acute obstructive cholangitis

Acute obstructive cholangitis is a common disease with a high mortality rate. Ligands for peroxisome proliferator-activated receptor-gamma (PPARgamma), such as 15-deoxy-Delta(12,14)-prostaglandin J(2) (15D-PGJ(2)), have been proposed as a new class of anti-inflammatory compounds. This study investigated the effect of 15D-PGJ(2) treatment on lipopolysaccharide (LPS)-induced acute obstructive cholangitis. The rats were randomly assigned to five groups: sham operation (Sham; simple laparotomy), sham operation with intraperitoneal saline infusion (Sham+Saline), sham operation with intraperitoneal LPS infusion (Sham+LPS), bile duct ligation (BDL) with saline infusion into the bile duct (BDL+Saline), and BDL with LPS infusion into the bile duct (BDL+LPS). Biochemical assays of blood samples, histology of the liver, portal venous pressure, hyaluronic acid clearance, and expression of inflammation-associated genes in the liver were evaluated. Furthermore, the Sham+LPS and the BDL+LPS group were divided into two groups (with and without 15D-PGJ(2) treatment), and their survival rates were compared. Biochemical assays of blood samples, portal venous pressure, hyaluronic acid clearance, and expression of inflammation-associated genes in the liver were all significantly higher in the BDL+LPS group compared with those in the BDL+Saline group, indicating the presence of increased liver damage in the first group. However, preoperative administration of 15D-PGJ(2) significantly improved these outcomes. Furthermore, the survival rate after establishment of cholangitis was significantly improved by the administration of 15D-PGJ(2) in the BDL+LPS group. These results clearly demonstrate that 15D-PGJ(2) inhibits the inflammatory response and endothelial cell damage seen in acute obstructive cholangitis and could contribute to improve the outcome of this pathology.