Rosiglitazone Pretreatment Research Articles

Microdialysis combined blood sampling technique for the determination of rosiglitazone and glucose in brain and blood of gerbils subjected to cerebral ischemia

Rosiglitazone is a potent synthetic peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist which improves glucose control in the plasma and reduces ischemic brain injury. However, the pharmacokinetics of rosiglitazone in the brain is still unclear. In this study, a method using liquid chromatography–mass spectrometry coupled with microdialysis and an auto-blood sampling system was developed to determine rosiglitazone and glucose concentration in the brain and blood of gerbils subjected to treatment with rosiglitazone (3.0mgkg−1, i.p.). The results showed the limit of detection was 0.04μgL−1 and the correlation coefficient was 0.9997 for the determination of rosiglitazone in the brain. The mean parameters, maximum drug concentration (Cmax) and the area under the concentration–time curve from time zero to time infinity (AUCinf), following rosiglitazone administration were 1.06±0.28μgL−1 and 296.82±44.67μgminL−1, respectively. The time to peak concentration (Cmax or Tmax) of rosiglitazone occurred at 105±17.10min, and the mean elimination half-life (t1/2) from brain was 190.81±85.18min after administration of rosiglitazone. The brain glucose levels decreased to 71% of the basal levels in the rosiglitazone-treated group when compared with those in the control (p<0.01). Treatment with rosiglitazone decreased blood glucose levels to 80% at 1h after pretreatment of rosiglitazone (p<0.05). In addition, pretreatment with rosiglitazone significantly reduced the cerebral infarct volume compared with that of the control group. These findings suggest that this method may be useful for simultaneous and continuous determination of rosiglitazone and glucose concentrations in brain and plasma. Rosiglitazone was effective at penetrating the blood–brain barrier as evidenced by the rapid appearance of rosiglitazone in the brain, and rosiglitazone may contribute to a reduction in the extent of injuries related to cerebral ischemic stroke via its hypoglycemic effect.

Rosiglitazone enhances the radiosensitivity of p53-mutant HT-29 human colorectal cancer cells

Combined-modality treatment has improved the outcome in cases of various solid tumors, and radiosensitizers are used to enhance the radiotherapeutic efficiency. Rosiglitazone, a synthetic ligand of peroxisome proliferator-activated receptors γ used in the treatment of type-2 diabetes, has been shown to reduce tumor growth and metastasis in human cancer cells, and may have the potential to be used as a radiosensitizer in radiotherapy for human colorectal cancer cells. In this study, rosiglitazone treatment significantly reduced the cell viability of p53-wild type HCT116 cells but not p53-mutant HT-29 cells. Interestingly, rosiglitazone pretreatment enhanced radiosensitivity in p53-mutant HT-29 cells but not HCT116 cells, and prolonged radiation-induced G 2/M arrest and enhanced radiation-induced cell growth inhibition in HT-29 cells. Pretreatment with rosiglitazone also suppressed radiation-induced H2AX phosphorylation in response to DNA damage and AKT activation for cell survival; on the contrary, rosiglitazone pretreatment enhanced radiation-induced caspase-8, -9, and -3 activation and PARP cleavage in HT-29 cells. In addition, pretreatment with a pan-caspase inhibitor, zVAD-fmk, attenuated the levels of caspase-3 activation and PARP cleavage in radiation-exposed cancer cells in combination with rosiglitazone pretreatment. Our results provide proof for the first time that rosiglitazone suppresses radiation-induced survival signals and DNA damage response, and enhances the radiation-induced apoptosis signaling cascade. These findings can assist in the development of rosiglitazone as a novel radiosensitizer.

Rosiglitazone‐induced myocardial protection against ischaemia–reperfusion injury is mediated via a phosphatidylinositol 3‐kinase/Akt‐dependent pathway

1. Rosiglitazone is widely used in the treatment of Type 2 diabetes. However, in recent years it has become evident that the therapeutic effects of peroxisome proliferator-activated receptor gamma ligands reach far beyond their use as insulin sensitizers. Recently, the ability of rosiglitazone pretreatment to induce cardioprotection following ischaemia-reperfusion (I/R) has been well documented; however, the protective mechanisms have not been elucidated. In the present study, examined the role of the phosphatidylinositol 3-kinase (PI3-K)/Akt signalling pathway in rosiglitazone cardioprotection following I/R injury. 2. Mice were pretreated with 3 mg/kg per day rosiglitazone for 14 days before hearts were subjected to ischaemia (30 min) and reperfusion (2 h). Wortmannin (1.4 mg/kg, i.p.), an inhibitor of PI3-K, was administered 10 min prior to myocardial I/R. Then, activation of the PI3-K/Akt/glycogen synthase kinase (GSK)-3alpha signalling pathway was examined. The effects of PI3-K inhibition on rosiglitazone-induced cardioprotection were also evaluated. 3. Compared with control rats, the ratio of infarct size to ischaemic area (area at risk) and the occurrence of sustained ventricular fibrillation in rosiglitazone-pretreated rats was significantly reduced (P < 0.05). Rosiglitazone pretreatment attenuated cardiac apoptosis, as assessed by ELISA to determine cardiomyocyte DNA fragmentation. Rosiglitazone pretreatment significantly increased levels of phosphorylated (p-) Akt and p-GSK-3alpha in the rat myocardium. Pharmacological inhibition of PI3-K by wortmannin markedly abolished the cardioprotection induced by rosiglitazone. 4. These results indicate that rosiglitazone-induced cardioprotection in I/R injury is mediated via a PI3-K/Akt/GSK-3alpha-dependent pathway. The data also suggest that modulation of PI3-K/Akt/GSK-3alpha-dependent signalling pathways may be a viable strategy to reduce myocardial I/R injury.

IL-10 Mediates Rosiglitazone-Induced Kidney Protection in Cisplatin Nephrotoxicity

Cisplatin, a major anti-neoplastic drug, is known to be nephrotoxic and inflammation-inducing. A peroxisome proliferator-activated receptor gamma agonist, regulating lipid metabolism, has known to have anti-inflammatory effect, but the protection mechanisms in various kidney injuries are not fully understood. The purpose of this study was to examine the reno-protective effect of rosiglitazone on cisplatin nephrotoxicity in mice focusing on inflammation and apoptosis. Male BALB/c mice were pretreated with rosiglitazone (10 mg/kg) or vehicle through daily intraperitoneal injection for 3 days and then were given a single injection of cisplatin (20 mg/kg). Cisplatin induced a significant rise in blood urea nitrogen and creatinine levels, and tubular cell damage with marked tissue inflammation. Tissue cytokines and chemokines measured by a cytometric bead array showed increased TNF-α, IL-6, MCP-1, and IFN-γ levels, while IL-10, an anti-inflammatory cytokine, was significantly decreased by cisplatin treatment. However, rosiglitazone pretreatment substantially reversed the depressed IL-10 level with simultaneous suppression of proinflammatory cytokines and chemokines. This tissue cytokine and chemokine milieu was associated with marked attenuation of kidney injury elicited by cisplatin. These findings suggest that the rosiglitazone-mediated renoprotective effect in cisplatin nephrotoxicity of mice is partially mediated by upregulation of anti-inflammatory IL-10 production.

Effect of rosiglitazone on adhesion molecule expression of lung injury in rats with acute pancreatitis

Objective To investigate the effect of rosiglitazone, the peroxisome proliferator-ac-tivated receptor-)' ligand, on adhesion molecule expression of lung injury in rats with acute pancreati-tis. Methods Fifty-four male Wistar rats were randomized into sham operation group (SO group), severe acute pancreatitis group (SAP group) and rosiglitazone pretreatment group (ROSI group). A-cute pancreatitis model was induced by retrograde infusion of 5% sodium taurocholate into the bilio-pancreatic duct. Rosiglitazone (6 mg/kg) dissolved in 10% DMSO was injected through the femoral vein 30 minutes piror to the operation. The rats of SO group and SAP group were injected partes ae-quales 10% DMSO. Rats were killed at 3, 6 and 12 h after operation. The serum amylase level, lung myeloperoxidase (MPO) activity and wet/dry ratio were determined. Lung tissue samples were stained respectively with hematoxylin and eosin for histopathological evaluation. Reverse transcription-polymerase chain reaction was used to detect the expression of ICAM-1, P-selectin and E-selectin mR-NA in lung tissue. Results The levels of amylase, MPO activity, wet/dry ratio and lung pathologic score were increased significantly in SAP group than in SO group (P< 0.05). Compared with SO group, the expression of ICAM-1, P-selectin and E-selectin mRNA were also increased significantly in SAP group (P<0.05). Pretreatment with rosiglhazone reduced amylase level, MPO activity, wet/ dry ratio and pathologic score at 6h and 12 h (P<0. 05), decreased the expression of ICAM-1, P-se-lectin and E-selectin mRNA at 12 h (P<0.05). Conclusion Rosiglitazone exerts the protective effect on acute pancreatitis associated lung injury through down-regulating the expression of ICAM-1, P-se-lectin and E-selectin mRNA. Key words: Pancreatitis; Peroxisome proliferator-activated receptor; Lung injury; Adhe-sion molecule

Rosiglitazone synergizes anticancer activity of cisplatin and reduces its nephrotoxicity in 7, 12-dimethyl benz{a}anthracene (DMBA) induced breast cancer rats

BackgroundAntineoplastic drug cisplatin remains the drug of choice for various solid tumours including breast cancer. But dose dependent nephrotoxicity is the major drawback in majority of platinum based chemotherapy regimens. Recent reports have shown that inflammatory pathways are the main offender for cisplatin induced nephrotoxicity. The present study was undertaken to assess the effect of rosiglitazone, a PPARγ agonist and an anti-inflammatory agent, on cisplatin induced nephrotoxicity, and its anticancer activity in DMBA induced breast cancer rats.MethodsMammary tumours were induced in female Sprague-Dawley rats by feeding orally with dimethylbenz [a]anthracene (DMBA) (60 mg/kg). Cisplatin induced nephropathy was assessed by measurements of blood urea nitrogen, albumin and creatinine levels. Posttranslational modifications of histone H3, mitogen-activated protein (MAP) kinase p38 expression and PPAR-γ expression were examined by western blotting.ResultsOur data shows involvement of TNF-α in preventing cisplatin induced nephrotoxicity by rosiglitazone. Rosiglitazone pre-treatment to cisplatin increases the expression of p38, PPAR-γ in mammary tumours and shows maximum tumour reduction. Furthermore, cisplatin induced changes in histone acetylation, phosphorylation and methylation of histone H3 in mammary tumours was ameliorated by pre-treatment of rosiglitazone. Suggesting, PPAR-γ directly or indirectly alters aberrant gene expression in mammary tumours by changing histone modifications.ConclusionTo best of our knowledge this is the first report which shows that pre-treatment of rosiglitazone synergizes the anticancer activity of cisplatin and minimizes cisplatin induced nephrotoxicity in DMBA induced breast cancer.

Adiponectin Deficiency Promotes the Production of Inflammatory Mediators While Severely Exacerbating Hepatic Injury in Mice with Polymicrobial Sepsis

Adiponectin (APN), which is an adipose tissue-derived hormone, is known as an anti-inflammatory cytokine. The effects of APN on the production of inflammatory mediators and hepatic injury during polymicrobial sepsis were evaluated using APN-knockout (KO) mice that had undergone a cecal ligation and puncture (CLP) and rosiglitazone, a selective peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, which increases the plasma APN concentration. Wild type (WT) and APN-KO mice were underwent CLP. The plasma and hepatic levels of inflammatory mediators, including tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1), were measured before, at 24, and 48 h after CLP. A histological analysis of the liver and the plasma alanine aminotransferase (ALT) levels were examined to evaluate hepatic injury. The plasma levels of inflammatory mediators after CLP with pretreatment of rosiglitazone were compared with those without rosiglitazone. APN deficiency resulted in significant increases in the plasma levels of TNF-alpha, IL-6, and MCP-1 at 24 h after CLP. Hepatic MCP-1 and plasma AST levels in APN-KO mice were significantly higher than those in WT mice at 48 h after CLP. A steatosis change and MCP-1 expressions in hepatocytes were induced in APN-KO mice during sepsis. The administration of rosiglitazone significantly lowered the plasma levels of inflammatory mediators, including TNF-alpha, IL-6, and MCP-1, in WT mice but not in APN-KO mice during sepsis. These results suggest that an APN deficiency induces an excessive systemic inflammatory status and exacerbates hepatic injury during polymicrobial sepsis.

Rosiglitazone pretreatment reduces pancreatic damage in rats with severe acute pancreatitis

Rosiglitazone pretreatment reduces pancreatic damage in rats with severe acute pancreatitis

Rosiglitazone inhibits expression of acyl-coenzyme A: cholesterol acyltransferase-1 in THP-1 macrophages induced by advanced glycation end-products ⋆

Objective To investigate the effects of rosiglitazone, a synthetic ligand of peroxisome proliferators-activated receptor gamma (PPARγ), on the expression of acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1) in phorbol myristate acetate (PMA)-pretreated THP-1 cells after the inducement of advanced glycation end products (AGEs). Methods After THP-1 cells were cultured in the presence of 0.1 μmol/L PMA for 72 h to induce phagocytic differentiation, the obtained THP-1 macrophages were treated with rosiglitazone for 4 h at different concentrations (1, 5 or 10 μmol/L) and then exposed to AGEs-modified bovine serum albumin (AGEs-BSA) for 24 h at a concentration of 200 mg/L. Reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis were performed to detect the mRNA and protein expressions of ACAT-1 respectively. Results Administration of AGEs-BSA (200 mg/L) into the THP-1 macrophages resulted in up-regulation of ACAT-1 at mRNA and protein levels when compared with the expressions in macrophages incubated with serum-free RPMI1640. Pretreatment of rosiglitazone inhibited significantly the increased expression of ACAT-1 induced by AGEs-BSA in a concentration-dependent manner. Conclusion PPARγ activation by rosiglitazone down-regulates ACAT-1 expression induced by AGEs in THP-1 macrophages, which might provide a new way for treating atherogenesis in diabetic patients.

Differential ability of a thiazolidinedione PPARγ agonist to attenuate cytokine secretion in primary microglia and macrophage‐like cells

Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists are known to inhibit select pro-inflammatory changes in models of CNS and systemic inflammation. Recent reports suggest that these anti-inflammatory effects are due to mechanisms other than canonical nuclear receptor-mediated transcriptional alteration. Using primary microglia and the monocytic cell line, THP-1, we demonstrate that rosiglitazone, a PPARgamma-activating thiazolidinedione, decreases pro-inflammatory cytokine secretion as measured by ELISA. Cells were pre-treated with various thiazolidinediones, including rosiglitazone, prior to stimulation with lipopolysaccharide or phorbol 12-myristate 13-acetate (PMA) to stimulate cytokine production. Tumor necrosis factor alpha (TNFalpha) secretion was significantly inhibited in both primary microglia and THP-1 cells differentiated for 72 h in the presence of PMA to induce a macrophage-like phenotype. No reduction in TNFalpha secretion was observed in undifferentiated THP-1 cells with rosiglitazone pre-treatment. Electrophoretic mobility shift assay revealed no significant difference in PPARgamma activation between PMA-differentiated and undifferentiated THP-1 cells. When PMA-differentiated and undifferentiated THP-1 cells were treated with the irreversible PPARgamma antagonist, GW 9662, a significant, dose-dependent decrease in TNFalpha secretion was observed. These results suggest that the anti-inflammatory benefit of PPARgamma ligands occur independently of classical PPARgamma activation.

Depot-specific regulation of perilipin by rosiglitazone in a diabetic animal model

Treatment with rosiglitazone, a potent peroxisome proliferator–activated receptor (PPAR) γ agonist, results in lipid storage coupled with reduced release of free fatty acids into the circulation. Many studies have reported that PPAR- γ agonists increase subcutaneous adiposity but have no effect on visceral fat mass. Perilipin, a family of phosphoproteins that coat intracellular lipid droplets in adipocytes, is essential for enlargement of lipid droplets. Recently, a functional PPAR-responsive element was identified within the murine perilipin gene. We hypothesized that the depot-specific regulation of perilipin by rosiglitazone may be associated with the fat-redistribution and insulin-sensitizing effects of rosiglitazone. After 6 weeks of rosiglitazone treatment in Otusuka Long-Evans Tokushima Fatty rats, an animal model of type 2 diabetes mellitus, we measured changes in adiposity, triglyceride content in liver and muscle, morphology of the pancreas, and perilipin messenger RNA and protein expression in adipose tissue. Rosiglitazone increased subcutaneous adiposity, decreased triglyceride content of liver and muscle, decreased plasma free fatty acids (2107 ± 507 μmol/L in the placebo group vs 824 ± 148 μmol/L in the rosiglitazone group; P < .05), and improved insulin resistance. The islets of placebo-treated rats showed hypertrophy and destruction, whereas the islets of rosiglitazone-treated rats showed hypertrophy, but the islet architecture remained intact. Perilipin messenger RNA and protein expression increased in subcutaneous fat, but did not change in visceral fat, after rosiglitazone treatment. In 3T3-L1 cells, rosiglitazone pretreatment decreased lipolysis and increased perilipin protein. In conclusion, increased perilipin expression in subcutaneous fat after rosiglitazone treatment is likely to be a mediator of reduced lipolysis, resulting in lipid storage in subcutaneous fat, fat redistribution, and insulin sensitization.

Ghrelin and insulin gene expression changes in streptozotocin-induced diabetic rats after rosiglitazone pretreatment.

The aim of the study was to evaluate the effect of rosiglitazone treatment on islet ghrelin and insulin gene expressions in streptozotocin (STZ)-induced diabetic rats. Animals were divided into four groups. 1. Intact controls. 2. Rosiglitazone-treated controls. 3. STZ-induced diabetes. 4. Rosiglitazone-treated diabetes. Rosiglitazone was given for 7 days at a dose of 20 mg/kg body weight. Ghrelin and insulin gene expressions were investigated by immunohistochemistry and in situ hybridization. There was no statistically significant difference in body weight between STZ-induced diabetic rats and rosiglitazone-treated diabetic rats during the experimental period. Furthermore, there were no significant differences in blood glucose levels and insulin immunoreactive cell numbers between STZ-induced diabetic rats and rosiglitazone-treated diabetic rats. There was a tendency towards a reduction of ghrelin gene expression in diabetic animals compared with intact controls. We found, in addition, that ghrelin immunoreactive and ghrelin mRNA expressing cells were frequent in the epithelial lining of the ducts suggesting ductal epithelium might be the source of the regenerating islet ghrelin cells, as is known for other islet cells. The results show that short-term rosiglitazone pretreatment had no significant effect on ghrelin and insulin gene expressions.

Signal Transducer and Activator of Transcription 5b Promotes Mucosal Tolerance in Pediatric Crohn's Disease and Murine Colitis

Growth hormone (GH) regulates anabolic metabolism via activation of the STAT5b transcription factor and reduces mucosal inflammation in colitis. Peroxisome proliferator-activated receptor (PPAR) gamma suppresses mucosal inflammation and is regulated by GH through STAT5b. We hypothesized that the GH:STAT5b axis influences susceptibility to colitis via regulation of local PPARgamma abundance. Colon biopsies from children with newly diagnosed Crohn's disease (CD) and controls were exposed to GH in short-term organ culture. Trinitrobenzene sulfonic acid (TNBS) administration was used to induce colitis in STAT5b-deficient mice and wild-type controls, with and without rosiglitazone pretreatment. GH receptor, STAT5b, PPARgamma, and nuclear factor kappaB activation and expression were determined. Epithelial cell GH receptor expression and GH-dependent STAT5b activation and PPARgamma expression were reduced in CD colon. STAT5b-deficient mice exhibited reduced basal PPARgamma nuclear abundance and developed more severe proximal colitis after TNBS administration. This was associated with a significant increase in mucosal nuclear factor kappaB activation at baseline and after TNBS administration. Rosiglitazone ameliorated colitis in wild-type mice but not STAT5b-deficient mice. GH-dependent STAT5b activation is impaired in affected CD colon and contributes to chronic mucosal inflammation via down-regulation of local PPARgamma expression. Therapeutic activation of the GH:STAT5b axis therefore represents a novel target for restoring both normal anabolic metabolism and mucosal tolerance in CD.

Effect of rosiglitazone, an insulin sensitizer, on myelotoxicity caused by repeated doses of 5-fluorouracil

Haematopoietic colony-stimulating factors are used frequently to moderate myelotoxicity, but administration of granulocyte-colony-stimulating factor (G-CSF) prior to chemotherapy actually may worsen the toxic effects on bone marrow. This is important in the design of clinical cancer treatment protocols. Previously, we found that rosiglitazone may protect granulocyte-macrophage progenitor cells (CFU-GM) against damage caused by a single dose of 5-fluorouracil (5-FU). Our new studies are designed to evaluate whether rosiglitazone has similar beneficial effects on bone marrow preservation when administered concurrently with repeated, daily doses of 5-FU while restricting regeneration time. Myelotoxicity characterized by the decrease in cellularity, frequency of granulocyte-macrophage progenitor cells and CFU-GM content of femoral bone marrow in mice. Five-day oral rosiglitazone pre-treatment decreased the susceptibility of granulocyte-macrophage progenitors to 5-FU damage. Significantly, more CFU-GM cells survived after the single intraperitoneal dose of 5-FU (100 mg kg −1). The increased frequency of CFU-GM cells with their intensive proliferation allowed faster restoration of the damaged CFU-GM compartment than was seen in the case of repeated daily administration of the cytostatic drug (25 or 50 mg kg −1) together with rosiglitazone for 7 consecutive days. The expansion of the CFU-GM compartment was 3 times and 50 times greater in the combined-treated mice than in their counterparts treated with repeated doses of 5-FU alone, although differences in absolute neutrophil counts were not significant. In conclusion, our results indicated that rosiglitazone has protective effects on bone marrow progenitor cells even after daily 5-FU treatment but further studies are warranted to evaluate the optimal treatment schedules.

Rosiglitazone, an agonist of peroxisome proliferator-activated receptor γ, reduces pulmonary inflammatory response in a rat model of endotoxemia

The effect of rosiglitazone, a potent peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist, on pulmonary inflammation in endotoxemia was investigated. Male Wistar rats were given either lipopolysaccharide (LPS, 6 mg/kg i.v.) or saline, pretreated with rosiglitazone (0.3 mg/kg i.v.) or its vehicle (dimethyl sulphoxide) 30 min before LPS. The selective PPAR-gamma antagonist GW9662 (0.3 mg/kg i.v.) was given 20 min before rosiglitazone. Wet/dry weight (W/D) ratio, myeloperoxidase (MPO) activity, malondialdehyde (MDA) as well as TNF-alpha and CINC-1 concentrations were measured in lung tissues 4 h after LPS injection. Expression of ICAM-1, NF-kappaB p65 and PPAR-gamma were also determined by immunohistochemistry or Western blot analysis. Rosiglitazone pretreatment significantly attenuated the increases in W/D ratio, MPO activity and MDA levels, and reduced pulmonary overproduction of TNF-alpha and CINC-1 as well as expression of ICAM-1 following endotoxemia. Rosiglitazone also inhibited the nuclear localization of NF-kappaB and up-regulated the expression of PPAR-gamma protein. The specific PPAR-gamma antagonist GW9662 abolished the effect of rosiglitazone. These findings suggest that PPAR-gamma agonists might be used as therapeutic agents in the therapy of inflammatory lung injury related to endotoxemia.

Rosiglitazone, a peroxisome proliferator-activated receptor-γ agonist, reduces acute lung injury in endotoxemic rats*

Rosiglitazone, a potent agonist of peroxisome proliferator-activated receptor (PPAR)-gamma, exerts anti-inflammatory effects in vitro and in vivo. This study was designated to determine the effects of rosiglitazone on endotoxin-induced acute lung injury in rats. Prospective, experimental study. University research laboratory. Thirty-six male Wistar rats. All the animals were randomly assigned to one of six groups (n = 6 per group) and were given either lipopolysaccharide (6 mg/kg intravenously) or saline, pretreated with rosiglitazone (0.3 mg/kg intravenously) or vehicle (10% dimethyl sulphoxide) 30 mins before lipopolysaccharide. The selective PPAR-gamma antagonist GW9662 (0.3 mg/kg intravenously) or its vehicle (10% dimethyl sulphoxide) was given 20 mins before rosiglitazone. Endotoxemia for 4 hrs induced evident lung histologic injury and edema, both of which were significantly attenuated by rosiglitazone pretreatment. The protective effects of rosiglitazone were correlated with the reduction by 71% of the increase of myeloperoxidase activity and the reduction by 84% of the increase of malondialdehyde in the lung tissue. The pulmonary hyperproduction of nitric oxide was reduced by 82% of the increase related to lipopolysaccharide challenge. Pretreatment with rosiglitazone also markedly suppressed lipopolysaccharide-induced expression of inducible nitric oxide synthase messenger RNA and protein in the lung, as demonstrated by reverse transcription-polymerase chain reaction or Western blot analysis. Immunohistochemical analysis revealed that rosiglitazone inhibited the formation of nitrotyrosine, a marker for peroxynitrite reactivity, in the lung tissue. In addition, the specific PPAR-gamma antagonist GW9662 antagonized the effects of rosiglitazone. This study provides evidence, for the first time, that the PPAR-gamma agonist rosiglitazone significantly reduces endotoxin-induced acute lung injury in rats.

15-Deoxy-Δ12,14-prostaglandin J2 inhibits IL-1β-induced IKK enzymatic activity and IκBα degradation in rat chondrocytes through a PPARγ-independent pathway

Peroxisome proliferator-activated receptor γ (PPARγ) ligands have been shown to inhibit the effects of proinflammatory cytokines such as interleukin-1β (IL-1β). This cytokine plays a key role in articular pathophysiologies by inducing the production of inflammatory mediators such as nitric oxide (NO) and prostaglandin E2 (PGE2). We previously demonstrated that 15d-PGJ2 was more potent than troglitazone to counteract IL-1β effects on chondrocytes. Here, we studied the action of 15d-PGJ2 on intracellular targets in nuclear factor-κB (NF-κB) signalling pathway in IL-1β treated rat chondrocytes. We found that 15d-PGJ2 decreased inhibitor κBα (IκBα) degradation but not its phosphorylation by specifically inhibiting IκB kinase β (IKKβ), but not IKKα, enzymatic activity. We further evaluated the involvement of PPARγ in the anti-inflammatory action of its ligands. In chondrocytes overexpressing functional PPARγ protein, 15d-PGJ2 pre-treatment inhibited inducible NO synthase and COX-2 mRNA expression, nitrite and PGE2 production, p65 translocation and NF-κB activation. Troglitazone or rosiglitazone pre-treatment had no effect. 15d-PGJ2 exhibited the same effect in chondrocytes overexpressing mutated PPARγ protein. These results suggest that 15d-PGJ2 exerts its anti-inflammatory effect in rat chondrocytes by a PPARγ-independent mechanism, which can be conferred to a partial inhibition of IκBα degradation.

Rosiglitazone-induced protection against myelotoxicity produced by 5-fluorouracil

Insulin promotes survival of haemopoietic progenitors. We investigated if rosiglitazone, an insulin sensitizer, could confer protection against 5-fluorouracil (5-FU)-induced myelotoxicity in mice. The decrease in bone marrow cellularity, frequency and content of granulocyte–macrophage progenitors (CFU-GM) characterized myelotoxicity in mice, while insulin sensitivity was determined by hyperinsulinaemic euglycaemic glucose clamping. CFU-GM colony numbers increased in groups pre-treated with rosiglitazone (1.5–6 mg/kg, 5 days), compared to that in mice treated with 5-fluorouracil alone. Since rosiglitazone pre-treatment significantly promoted the clonal expansion of CFU-GM when given in the insulin sensitizing dose, we conclude that rosiglitazone had myeloprotective effects possibly by amplifying endogenous insulin action.