Pro-inflammatory properties for thiazolidinediones

Troglitazone, a PPAR-γ agonist, decreases LTC4 concentration in mononuclear cells in patients with asthma

BACKGROUND

Asthma is an inflammatory disorder with multiple mediators involved in the inflammatory response. Despite several attempts, no new anti-inflammatory drugs have been registered for asthma treatment for several years. However, thiazolidinediones, peroxisome proliferator-activated receptor agonists, have demonstrated some anti-inflammatory properties in various experimental settings. The aim of this study was to assess the influence of troglitazone on LTC₄ and 15-HETE concentrations. It also evaluates TNF-induced eotaxin synthesis in peripheral blood mononuclear cells from 14 patients with mild asthma and 13 healthy controls.

METHODS

PBMCs were isolated from the whole blood of the asthmatics and healthy subjects and pretreated with 0.1, 1 or 10μM of Troglitazone. The cells were then exposed to 10^-6M calcium jonophore or 10ng/ml TNF. The production and release of LTC₄, 15-HETE and eotaxin were then assessed.

RESULTS

Troglitazone caused a dose-dependent inhibition in LTC₄ synthesis in both asthmatics and healthy subjects. Troglitazone did not influence 15-HETE or eotaxin production in either asthmatic patients or in healthy individuals.

CONCLUSION

Due to its inhibition of LTC₄ synthesis, troglitazone therapy is an interesting potential therapeutic approach in asthma and other LTC₄ related inflammatory disorders.

Training-induced anti-atherosclerotic effects are associated with increased vascular PPARgamma expression in apolipoprotein E-deficient mice

AIM

Physical exercise prevents cardiovascular risk and atherosclerosis lesions. However, the molecular aspects are still unknown. Vascular peroxisome proliferator-activated receptors (PPARs) exert anti-atherogenic effects. The aim of this study was to determine whether exercise-induced anti-atherosclerotic effect is associated with change in PPARs vascular expression in apolipoprotein E-deficient (ApoE(-/-) ) mice.

METHODS

Male ApoE(-/-) mice were fed with a high-fat diet and randomized into two groups: one trained group undergoing swimming training for 3 months and one sedentary group. Sedentary and trained C57BL/6J mice were used as control. mRNA of PPAR-α, PPAR-β/δ and PPAR-γ was measured in aorta by quantitative PCR. mRNA of pro- (TNF-α, IL-1β) and anti-inflammatory (IL-10, IL-1Ra) cytokines was also measured.

RESULTS

Atherosclerotic lesion size was significantly reduced in trained ApoE(-/-) mice compared to sedentary ones. In contrast, reduction of atherosclerotic lesion size was not observed in trained ApoE(-/-) mice supplied with BADGE, an antagonist of PPAR-γ. Exercise training significantly increased PPAR-γ expression in aorta. PPAR-γ expression was inversely correlated with the atherosclerotic plaque area. Aortic PPAR-α and PPAR-β/δ mRNA expressions were not changed in response to exercise training. Atherosclerosis increased the aortic mRNA expression of TNF-α, IL-1β, IL-10 and IL-1Ra. Exercise training decreased aortic IL-1β mRNA expression in ApoE(-/-) mice, but did not change expression of TNF-α, IL-10 and IL-1Ra. IL-1β mRNA expression was also significantly lower in atherosclerosis lesions from trained ApoE(-/-) compared with those from sedentary ones.

CONCLUSIONS

Exercise training increases vascular PPAR-γ expression in ApoE(-/-) mice that could potentially underlie training-related beneficial effects on atherosclerosis.

Methyl 2-((2Z,5Z)-4-oxo-3-phenyl-2-{2-[(1E)-1,2,3,4-tetra-hydro-naphthalen-1-yl-idene]hydrazin-1-yl-idene}-1,3-thia-zolidin-5-yl-idene)acetate

In the title compound, C22H19N3O3S, the six-membered ring of the 1,2,3,4-tetra-hydro-naphthalene ring system adopts an envelope conformation with the central CH2 C atom as the flap. The mol-ecular conformation is stabilized by an S⋯O contact, forming a pseudo-five-membered ring. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds into chains propagating along [102].

15-Hydroxyprostaglandin dehydrogenase as a novel molecular target for cancer chemoprevention and therapy

Cyclooxygenase-2 (COX-2), a rate-limiting enzyme in arachidonic acid cascade, plays a key role in the biosynthesis of prostaglandin E(2) (PGE(2)) upon inflammatory insults. Overproduction of PGE(2) stimulates proliferation of various cancer cells, confers resistance to apoptosis of cancerous or transformed cells, and accelerates metastasis and angiogenesis. Excess PGE(2) undergoes metabolic inactivation which is catalyzed by NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). In this context, 15-PGDH has been speculated as a physiological antagonist of COX-2 and a tumor suppressor. Thus, overexpression of 15-PGDH has been known to protect against experimentally induced carcinogenesis and renders the cancerous or transformed cells susceptible to apoptosis by counteracting oncogenic action of PGE(2). In contrast, silence of 15-PGDH is observed in some cancer cells, which is associated with epigenetic modification, such as DNA methylation and histone deacetylation, in the promoter region of 15-PGDH. A variety of compounds capable of inducing the expression of 15-PGDH have been reported, which include the histone deacetylase inhibitors, nonsteroidal anti-inflammatory drugs, and peroxisome proliferator-activated receptor-gamma agonists. Therefore, 15-PGDH may be considered as a novel molecular target for cancer chemoprevention and therapy. This review highlights the role of 15-PGDH in carcinogenesis and its regulation.

Peroxisome proliferator activated receptor ligands as regulators of airway inflammation and remodelling in chronic lung disease

Inflammation is a major component in the pathology of chronic lung diseases, including asthma. Anti-inflammatory treatment with corticosteroids is not effective in all patients. Thus, new therapeutic options are required to control diverse cellular functions that are currently not optimally targeted by these drugs in order to inhibit inflammation and its sequelae in lung disease. Peroxisome proliferator activated receptors (PPARs), originally characterised as regulators of lipid and glucose metabolism, offer marked potential in this respect. PPARs are expressed in both lung infiltrating and resident immune and inflammatory cells, as well as in resident and structural cells in the lungs, and play critical roles in the regulation of airway inflammation. In vitro, endogenous and synthetic ligands for PPARs regulate expression and release of proinflammatory cytokines and chemoattractants, and cell proliferation and survival. In murine models of allergen-induced inflammation, PPARα and PPARγ ligands reduce the influx of inflammatory cells, cytokine and mucus production, collagen deposition, and airways hyperresponsiveness. The activity profiles of PPAR ligands differ to corticosteroids, supporting the hypothesis that PPARs comprise additional therapeutic targets to mimimise the contribution of inflammation to airway remodelling and dysfunction.

Ribonucleic acid interference knockdown of interleukin 6 attenuates cold-induced hypertension

The purpose of this study was to determine the role of the proinflammatory cytokine interleukin (IL) 6 in cold-induced hypertension. Four groups of male Sprague-Dawley rats were used (6 rats per group). After blood pressure was stabilized, 3 groups received intravenous delivery of adenoassociated virus carrying IL-6 small hairpin RNA (shRNA), adenoassociated virus carrying scrambled shRNA, and PBS, respectively, before exposure to a cold environment (5 degrees C). The last group received PBS and was kept at room temperature (25 degrees C, warm) as a control. Adenoassociated virus delivery of IL-6 shRNA significantly attenuated cold-induced elevation of systolic blood pressure and kept it at the control level for < or =7 weeks (length of the study). Chronic exposure to cold upregulated IL-6 expression in aorta, heart, and kidneys and increased macrophage and T-cell infiltration in kidneys, suggesting that cold exposure increases inflammation. IL-6 shRNA delivery abolished the cold-induced upregulation of IL-6, indicating effective silence of IL-6. Interestingly, RNA interference knockdown of IL-6 prevented cold-induced inflammation, as evidenced by a complete inhibition of tumor necrosis factor-alpha expression and leukocyte infiltration by IL-6 shRNA. RNA interference knockdown of IL-6 significantly decreased the cold-induced increase in vascular superoxide production. It is noted that IL-6 shRNA abolished the cold-induced increase in collagen deposition in the heart, suggesting that inflammation is involved in cold-induced cardiac remodeling. Cold exposure caused glomerular collapses, which could be prevented by knockdown of IL-6, suggesting an important role of inflammation in cold-induced renal damage. In conclusion, cold exposure increased IL-6 expression and inflammation, which play critical roles in the pathogenesis of cold-induced hypertension and cardiac and renal damage.

Rosiglitazone is associated with mortality in chronic hemodialysis patients

Recent studies have associated rosiglitazone, a thiazolidinedione drug, with adverse cardiovascular outcomes in the general population with diabetes. Using data from the Dialysis Outcomes and Practice Patterns Study in the United States, we examined cardiovascular hospitalization and mortality associated with prescription of rosiglitazone, compared with other oral hypoglycemic agents, among 2393 long-term hemodialysis patients who were followed for a median of 1.1 yr. We assessed mortality risk using Cox models in patient-level and dialysis facility-level analyses that used the facility proportion of patients on rosiglitazone as the predictor (instrumental variable approach) and adjusted the models for demographics, comorbid conditions, laboratory values, and achieved dialysis dosage. Compared with patients prescribed other oral hypoglycemic agents, patients prescribed rosiglitazone had significantly higher all-cause (hazard ratio [HR] 1.38; 95% confidence interval [CI] 1.05 to 1.82) and cardiovascular (HR 1.59; 95% CI 1.14 to 2.22) mortality, and their adjusted HR for hospitalization with myocardial infarction was 3.5-fold higher (P = 0.02). We did not observe similar associations in a secondary analysis evaluating pioglitazone. By the instrumental variable approach, facilities with more than the median adjusted percentage (6.2%) of patients who had diabetes and were prescribed rosiglitazone had significantly higher all-cause mortality (HR 1.36; 95% CI 1.15 to 1.62) and cardiovascular mortality (HR 1.42; 95% CI 1.07 to 1.88) than facilities with less than the median expected percentage prescribed rosiglitazone. Our practice-based findings suggest significant associations of rosiglitazone use with higher cardiovascular and all-cause mortality among hemodialysis patients with diabetes.

Rosiglitazone increases matrix production and quenches inflammation: studies in human cells

BACKGROUND

Type 2 diabetes (T2D) is characterized by an accelerated atherogenesis, a process to which both proliferative and inflammatory responses contribute. Peroxisome proliferator-activated receptors-gamma (PPARgamma) agonists have both anti-proliferative and anti-inflammatory properties. We tested the effect of therapeutic doses of rosiglitazone on proliferative and inflammatory pathways in fibroblasts (HF) from five controls (C) and five T2D patients, and in aortic smooth muscle cells (hSMC).

METHODS

Transforming growth factor-beta (TGFbeta) and interleukin-6 (IL-6) expression, and IL-6, laminin and fibronectin release were measured. To identify the involved intracellular signalling, extracellular signal-regulated kinases (ERK)1/2 phosphorylation and p38 activation were evaluated.

RESULTS

Both phorbol 12-myristate 13-acetate (PMA) [a protein kinase C (PKC) activator] and rosiglitazone increased TGFbeta expression and fibronectin and laminin release in C and T2D patients. Rosiglitazone effect was reversed by its specific inhibitor Sr202. The combination PMA + rosiglitazone was additive in C, but not in T2D patients. IL-6 production was stimulated by PMA in both C and T2D patients; this effect was prevented by rosiglitazone in a Sr202-inhibitable manner. Experiments performed in hSMC yielded the same results. Rosiglitazone increased p38 activation more in C than in T2D patients; PMA-induced phosphorylation of ERK1/2 was similarly reduced in both cells.

CONCLUSIONS

In HF and hSMC, rosiglitazone stimulates the synthesis of matrix components via enhanced TGFbeta expression; when combined with PMA, the resulting PKC activation is mediated by enhanced p38 phosphorylation. On the other hand, rosiglitazone quenches inflammation in both cell types, by counteracting PMA-induced phosphorylation of ERK1/2.

A novel activity for substance P: stimulation of peroxisome proliferator-activated receptor-gamma protein expression in human monocytes and macrophages

BACKGROUND AND PURPOSE

Substance P (SP) and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) play important roles in different inflammatory conditions and are both expressed in human monocytes and macrophages. However, it is not known whether or not they interact. This study was undertaken to evaluate the effects of SP on PPAR-gamma protein expression in monocytes and macrophages (MDMs: monocyte-derived macrophages) from healthy smokers and non-smokers.

EXPERIMENTAL APPROACH

PPAR-gamma protein was detected by western blot and quantified by calculating the ratio between PPAR-gamma and beta-actin protein expression. Constitutive tachykinin NK(1) receptor expression in monocytes and MDMs from healthy smokers and non-smokers was evaluated by western blot. Cytokine release was evaluated by ELISA.

KEY RESULTS

In the concentration range 10(-10)-10(-6) M, SP stimulated PPAR-gamma protein expression in monocytes and MDMs, being more effective in cells from healthy smokers. Moreover, in these cells there was a constitutively increased expression of NK(1) receptors. SP-induced expression of the PPAR-gamma protein was receptor-mediated, as it was reproduced by the NK(1) selective agonist [Sar(9)Met(O(2))(11)]SP and reversed by the competitive NK(1) antagonist GR71251. SP-induced maximal effects were similar to those evoked by 15-deoxy-Delta(12,14)-prostaglandin J(2); an endogenous PPAR-gamma agonist, and were significantly reduced by a PPAR-gamma antagonist. NK(1) and PPAR-gamma agonists exerted opposite effects on TNF-alpha release from monocytes and MDMs.

CONCLUSIONS AND IMPLICATIONS

Enhancement of PPAR-gamma protein expression represents a novel activity for SP, which could contribute to a range of chronic inflammatory disorders.

Rosiglitazone inhibits metastasis development of a murine mammary tumor cell line LMM3

Background

Activation of peroxisome proliferator-activated receptors γ (PPARγ) induces diverse effects on cancer cells. The thiazolidinediones (TZDs), such as troglitazone and ciglitazone, are PPARγ agonists exhibiting antitumor activities; however, the underlying mechanism remains inconclusive. Rosiglitazone (RGZ), a synthetic ligand of PPARγ used in the treatment of Type 2 diabetes, inhibits growth of some tumor cells and is involved in other processes related to cancer progression. Opposing results have also been reported with different ligands on tumor cells. The purpose of this study was to determine if RGZ and 15d-PGJ₂ induce antitumor effects in vivo and in vitro on the murine mammary tumor cell line LMM3.

Methods

The effect on LMM3 cell viability and nitric oxide (NO) production of different doses of RGZ, 15-dPGJ₂, BADGE and GW9662 were determined using the MTS colorimetric assay and the Griess reaction respectively. In vivo effect of orally administration of RGZ on tumor progression was evaluated either on s.c. primary tumors as well as on experimental metastasis. Cell adhesion, migration (wound assay) and invasion in Transwells were performed. Metalloproteinase activity (MMP) was determined by zymography in conditioned media from RGZ treated tumor cells. PPARγ expression was detected by inmunohistochemistry in formalin fixed tumors and by western blot in tumor cell lysates.

Results

RGZ orally administered to tumor-bearing mice decreased the number of experimental lung metastases without affecting primary s.c. tumor growth. Tumor cell adhesion and migration, as well as metalloproteinase MMP-9 activity, decreased in the presence of 1 μM RGZ (non-cytotoxic dose). RGZ induced PPARγ protein expression in LMM3 tumors. Although metabolic activity -measured by MTS assay- diminished with 1–100 μM RGZ, 1 μM-treated cells recovered their proliferating capacity while 100 μM treated cells died. The PPARγ antagonist Biphenol A diglicydyl ether (BADGE) did not affect RGZ activity. On the contrary, the specific antagonist GW9662 completely abrogated RGZ-induced decrease in cell viability. A decrease in NO levels was detected in the presence of either 1 or 100 μM RGZ. The natural ligand 15d-PGJ₂ did not affect metabolic activity although it induced a significant decrease in NO production.

Conclusion

A significant decrease in the number of experimental LMM3 lung metastasis, but not on primary tumor growth, after oral RGZ administration was observed. In vitro, 100 μMRGZ also reduced cell viability and NO production, while no changes were observed in the presence of 15d-PGJ₂. BADGE did not reverse RGZ effect while the antagonist GW9662 completely abrogated it, suggesting a PPARγ- dependent mechanism. Inhibition of lung metastatic nodules by RGZ administered in vivo, might be associated with the observed decrease in MMP-9 expression, in cell adhesion, migration and invasion. RGZ augmented its expression. PPARγ was detected in cell lysates by western blot and by immunohistochemistry in tumors from RGZ-treated mice. In summary we can suggest that RGZ or any other TZDs might be possible future approaches in the treatment of metastasis of PPARγ-expressing cells.

Upregulation of tumor necrosis factor-alpha expression by trans10-cis12 conjugated linoleic acid enhances phagocytosis of RAW macrophages via a peroxisome proliferator-activated receptor gamma-dependent pathway

The aim of this study was to examine whether tumor necrosis factor (TNF)-alpha expression in the phagocytic activity of RAW macrophages by trans10-cis12 (10t-12c) conjugated linoleic acid (CLA) is associated with peroxisome proliferator-activated receptor gamma (PPARgamma) activation. 10t-12c CLA induced the TNF-alpha expression in RAW macrophages. Phagocytic activity of naive RAW macrophages was increased either by recombinant mouse (rm) TNF-alpha or by culture supernatant from 10t-12c CLA-treated RAW macrophages. This phagocytic activity was inhibited by addition of anti-rmTNF-alpha polyclonal antibody (pAb). 10t-12c CLA also increased the level of PPARgamma protein and mRNA in RAW macrophages. When naive RAW macrophages were incubated with the culture supernatant from RAW macrophages treated with 10t-12c CLA plus GW 9662, a PPARgamma antagonist, their phagocytic activity was significantly inhibited. In addition, GW 9662 antagonized the effect of 10t-12c CLA in stimulating TNF-alpha expression. These results suggest that 10t-12c CLA modulates the phagocytic activity of RAW macrophages by upregulating TNF-alpha expression via a PPARgamma-dependent pathway.

The molecular mechanisms underlying the proinflammatory actions of thiazolidinediones in human macrophages

It is hypothesized that the antiinflammatory actions of peroxisome proliferator-activated receptors (PPARs) may explain the protective effect of these receptors in diabetes, atherosclerosis, cancer, and other inflammatory diseases. However, emerging evidence for proinflammatory activities of activated PPARs is concerning in light of new studies that associate PPAR modulators with an increased incidence of both cardiovascular events in humans and the sporadic formation of tumors in rodents. In an attempt to define the role of each PPAR subtype in inflammation, we made the unexpected observation that human PPARdelta is a positive regulator of inflammatory responses in both monocytes and macrophages. Notably, TNFalpha-stimulated cells administered PPARdelta agonists express and secrete elevated levels of inflammatory cytokines. Most surprising, however, was the finding that thiazolidinediones (TZDs) and other known PPARgamma ligands display different degrees of proinflammatory activities in a PPARgamma- and PPARalpha-independent manner via their ability to augment PPARdelta signaling. A series of mechanistic studies revealed that TZDs, at clinically relevant concentrations, bind and activate the transcriptional activity of PPARdelta. Collectively, these studies suggest that the observed proinflammatory and potentially deleterious effects of PPARgamma ligands may be mediated through an off-target effect on PPARdelta. These studies highlight the need for PPAR modulators with increased receptor subtype specificity. Furthermore, they suggest that differences in systemic exposure and consequently in the activation of PPARgamma and PPARdelta may explain why TZDs can exhibit both inflammatory and antiinflammatory activities in humans.

Vascular inflammation in hypertension and diabetes: molecular mechanisms and therapeutic interventions

More than 80% of patients with type 2 diabetes mellitus develop hypertension, and approx. 20% of patients with hypertension develop diabetes. This combination of cardiovascular risk factors will account for a large proportion of cardiovascular morbidity and mortality. Lowering elevated blood pressure in diabetic hypertensive individuals decreases cardiovascular events. In patients with hypertension and diabetes, the pathophysiology of cardiovascular disease is multifactorial, but recent evidence points toward the presence of an important component dependent on a low-grade inflammatory process. Angiotensin II may be to a large degree responsible for triggering vascular inflammation by inducing oxidative stress, resulting in up-regulation of pro-inflammatory transcription factors such as NF-kappaB (nuclear factor kappaB). These, in turn, regulate the generation of inflammatory mediators that lead to endothelial dysfunction and vascular injury. Inflammatory markers (e.g. C-reactive protein, chemokines and adhesion molecules) are increased in patients with hypertension and metabolic disorders, and predict the development of cardiovascular disease. Lifestyle modification and pharmacological approaches (such as drugs that target the renin-angiotensin system) may reduce blood pressure and inflammation in patients with hypertension and metabolic disorders, which will reduce cardiovascular risk, development of diabetes and cardiovascular morbidity and mortality.

Thiazolidinediones: potential as therapeutics for psoriasis and perhaps other hyperproliferative skin disease

The thiazolidinediones constitute a family of synthetic compounds that act as high-affinity ligands for persoxisome proliferator-activated receptor-gamma (PPAR-gamma), a member of the nuclear hormone receptor family. Although originally developed to facilitate glucose control in patients with Type 2 diabetes, a number of studies showed that these agents effectively inhibited epithelial cell proliferation and tissue inflammation. Many of the initial cell growth inhibition studies were conducted with malignant epithelial cells from various sites; however, in addition to malignant epithelial cells, other studies showed that rapidly proliferating epidermal keratinoctyes in culture were also sensitive to the growth-inhibiting action of these moieties. Additional studies subsequently demonstrated that some patients with plaque psoriasis responded to treatment with one or another member of the thiazolidinedione family. Due to the potential therapeutic benefit of these compounds in diseases such as psoriasis, studies have been conducted to elucidate mechanisms by which growth inhibition is achieved. Interference with a number of growth-influencing signalling pathways has been demonstrated. Of interest, some of the growth-inhibiting effects are seen under conditions in which PPAR-gamma activation may not be responsible for the activity. Based on therapeutic potential, additional ongoing studies are aimed at developing novel thiazolidinediones that may have better efficacy than the currently available agents. Other studies are aimed at identifying optimal ways to use these agents in the treatment of hyperplastic skin diseases such as psoriasis.

Effect of insulin-sensitizing agents in combination with ezetimibe, and valsartan in rats with non-alcoholic fatty liver disease

AIM: To assess whether treatment with insulin-sensitizing agents (ISAs) in combination with ezetimibe and valsartan have greater effect on hepatic fat content and lipid peroxidation compared to monotherapy in the methionine choline-deficient diet (MCDD) rat model of non-alcoholic fatty liver disease (NAFLD).

METHODS: Rats (n = 6 per group) were treated with different drugs, including MCDD only, MCDD diet with either metformin (200 mg/kg), rosiglitazone (3 mg/kg), metformin plus rosiglitazone (M+R), ezetimibe (2 mg/kg), valsartan (2 mg/kg), or combination of all drugs for a total of 15 wk. Liver histology, lipids, parameters of oxidative stress and TNF-alpha were measured.

RESULTS: Fatty liver (FL) rats demonstrated severe hepatic fatty infiltration (> 91% fat), with an increase in hepatic TG (+1263%, P < 0.001), hepatic cholesterol (+245%, P < 0.03), hepatic MDA levels (+225%, P < 0.001), serum TNF-alpha (17.8 ± 10 vs 7.8 ± 0.0, P < 0.001), but a decrease in hepatic alpha tocopherol (-74%, P < 0.001) as compared to the control rats. Combination therapy with all drugs produced a significant decrease in liver steatosis (-54%), hepatic TG (-64%), hepatic cholesterol (-31%) and hepatic MDA (-70%), but increased hepatic alpha tocopherol (+443%) as compared to FL rats. Combination therapy with ISA alone produced a smaller decrease in liver steatosis (-32% vs -54%, P < 0.001) and in hepatic MDA levels (-55% vs -70%, P < 0.01), but a similar decrease in hepatic lipids when compared with the all drugs combination. TNF-alpha levels decreased significantly in all treatment groups except in ISA group.

CONCLUSION: Combination therapies have a greater effect on liver fat content as compared to monotherapy. Rosiglitazone appears to improve hepatic steatosis to a greater extent than metformin.

Peroxisome proliferator-activated receptor-gamma1 is dephosphorylated and degraded during BAY 11-7085-induced synovial fibroblast apoptosis

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) plays a central role in whole body metabolism by regulating adipocyte differentiation and energy storage. Recently, however, PPAR-gamma has also been demonstrated to affect proliferation, differentiation, and apoptosis of different cell types. As we have previously shown that BAY 11-7085-induced synovial fibroblast apoptosis is prevented by PPAR-gamma agonist 15d-PGJ2; the expression of PPAR-gamma in these cells was studied. Both PPAR-gamma1 and PPAR-gamma2 isoforms were cloned from synovial fibroblast RNA, but only PPAR-gamma1 was detected by Western blot, showing constitutive nuclear expression. Within minutes of BAY 11-7085 treatment, a PPAR-gamma1-specific band was shifted into a form of higher mobility, suggesting dephosphorylation, as confirmed by phosphatase treatment of cell extracts. Of interest, BAY 11-7085-induced PPAR-gamma1 dephosphorylation was followed by PARP and caspase-8 cleavage as well as by PPAR-gamma1 protein degradation. PPAR-gamma1 dephosphorylation was followed by the loss of PPAR-DNA binding activity ubiquitously present in synovial fibroblast nuclear extracts. Unlike the phosphorylated form, dephosphorylated PPAR-gamma1 was found in insoluble membrane cell fraction and was not ubiquitinated before degradation. PPAR-gamma1 dephosphorylation coincided with ERK1/2 phosphorylation that accompanies BAY 11-7085-induced synovial fibroblasts apoptosis. 15d-PGJ2, PGD2, and partially UO126, down-regulated ERK1/2 phosphorylation, protected cells from BAY 11-7085-induced apoptosis, and reversed both PPAR-gamma dephosphorylation and degradation. Furthermore, PPAR-gamma antagonist BADGE induced PPAR-gamma1 degradation, ERK1/2 phosphorylation, and synovial fibroblasts apoptosis. The results presented suggest an anti-apoptotic role for PPAR-gamma1 in synovial fibroblasts. Since apoptotic marker PARP is cleaved after PPAR-gamma1 dephosphorylation but before PPAR-gamma1 degradation, dephosphorylation event might be enough to mediate BAY 11-7085-induced apoptosis in synovial fibroblasts.

Rosiglitazone and 15-deoxy-Delta12,14-prostaglandin J2 cause potent neuroprotection after experimental stroke through noncompletely overlapping mechanisms

Stroke triggers an inflammatory cascade which contributes to a delayed cerebral damage, thus implying that antiinflammatory strategies might be useful in the treatment of acute ischaemic stroke. Since two unrelated peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists, the thiazolidinedione rosiglitazone (RSG) and the cyclopentenone prostaglandin 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2), have been shown to possess antiinflammatory properties, we have tested their neuroprotective effects in experimental stroke. Rosiglitazone or 15d-PGJ2 were administered to rats 10 mins or 2 h after permanent middle cerebral artery occlusion (MCAO). Stroke outcome was evaluated by determination of infarct volume and assessment of neurological scores. Brains were collected for protein expression, gene array analyses and gene shift assays. Our results show that both compounds decrease MCAO-induced infarct size and improve neurological scores. At late times, the two compounds converge in the inhibition of MCAO-induced brain expression of inducible NO synthase and the matrix metalloproteinase 9. Interestingly, at early times, complementary DNA microarrays and gene shift assays show that different mechanisms are recruited. Analysis of early nuclear p65 and late cytosolic IkappaBalpha protein levels shows that both compounds inhibit nuclear factor-kappaB signalling, although at different levels. All these results suggest both PPARgamma-dependent and independent pathways, and might be useful to design both therapeutic strategies and prognostic markers for stroke.

Inflammatory Markers and the Metabolic Syndrome

Inflammation in the vasculature might be an important pathogenic link between cardiovascular diseases and the metabolic syndrome. Inflammation can be reduced by a variety of approaches including diet, exercise, cardiovascular drugs, and insulin sensitizers. Importantly, these different measures improve vascular function and reduce inflammation by distinct mechanisms. Therefore, combination therapy including lifestyle modifications and multiple drugs from separate classes might produce additive beneficial outcomes. We review plausible mechanisms for effects of combination therapy to reduce inflammation, improve endothelial dysfunction, and decrease insulin resistance in atherosclerosis, coronary heart disease, and hypertension in the context of insulin-resistant states including diabetes, obesity, and the metabolic syndrome.