Peroxisome Proliferator-activated Receptor Gamma Ligands Research Articles

Macrophage Phenotype Induced by Circulating Small Extracellular Vesicles from Women with Endometriosis.

Evidence suggests that immune system dysfunction and macrophages are involved in the disease establishment and progression of endometriosis. Among the factors involved in this alteration in macrophage activity, Small Extracellular Vesicles (sEVs) have been described to play a role favoring the switch to a specific phenotype with controversial results. This study aims to investigate the potential effect of circulating sEVs in the plasma of well-characterized patients with endometriosis on the polarization of macrophages. sEVs were isolated from the plasma of patients diagnosed with endometriosis confirmed by histopathological analysis. Two groups of patients were recruited: the endometriosis group consisted of patients diagnosed with endometriosis by imaging testing (gynecological ultrasonography and/or magnetic resonance imaging), confirmed by histopathologic study (n = 12), and the control group included patients who underwent laparoscopy for tubal sterilization without presurgical suspicion of endometriosis and without endometriosis or signs of any inflammatory pelvic condition during surgery (n = 12). Human THP1 monocytic cells were differentiated into macrophages, and the effect of sEVs on cell uptake and macrophage polarization was evaluated by fluorescent labeling and measurement of the IL1B, TNF, ARG1, and MRC1 expression, respectively. Although no changes in cell uptake were detected, sEVs from endometriosis induced a polarization of macrophages toward an M2 phenotype, characterized by lower IL1B and TNF expression and a tendency to increase MRC1 and ARG1 levels. When macrophages were stimulated with lipopolysaccharides, less activation was also detected after treatment with endometriosis sEVs. Finally, endometriosis sEVs also induced the expression of the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARG); however, treatment with rosiglitazone, a PPARG agonist, had no effect on the change in macrophage phenotype. We conclude that circulating sEVs in women with endometriosis have a certain capacity to shift the activation state of macrophages toward an M2 phenotype, but this does not modify the uptake level or the response to PPARG ligands.

Lobeglitazone inhibits LPS-induced NLRP3 inflammasome activation and inflammation in the liver.

Liver inflammation is a common feature of chronic liver disease and is often associated with increased exposure of the liver to lipopolysaccharide (LPS). Kupffer cells (KCs) are macrophages in the liver and produce various cytokines. Activation of KCs through the NLRP3 inflammasome pathway leads to release of proinflammatory cytokines and induces hepatocyte injury and hepatic stellate cell (HSC) activation. Lobeglitazone is a peroxisome proliferator-activated receptor gamma ligand and a type of thiazolidinedione that elicits anti-inflammatory effects. However, there is no clear evidence that it has direct anti-inflammatory effects in the liver. This study showed that lobeglitazone reduces LPS-induced NLPR3 inflammasome activation and production of proinflammatory cytokines in primary KCs and hepatocytes. Cytokines secreted by activated KCs increased hepatocyte inflammation and HSC activation, and lobeglitazone inhibited these responses. In addition, lobeglitazone suppressed liver fibrosis by inhibiting LPS-induced transforming growth factor (TGF)-β secretion and TGF-β-induced CTGF expression. The inhibitory effect of lobeglitazone on inflammasome activation was associated with suppression of liver fibrosis. These results suggest that lobeglitazone may be a treatment option for inflammation and fibrosis in the liver.

In vitro effects of PPAR gamma ligands on gene expression in corpus luteum explants in non-pregnant pigs - Transcriptome analysis

The corpus luteum (CL) is a temporary endocrine structure in the female ovaries that develops cyclically in mature females during luteinization. This study aimed to determine the in vitro effects of peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the transcriptomic profile of the porcine CL in the mid- and late-luteal phase of the estrous cycle using RNA-seq technology. The CL slices were incubated in the presence of PPARγ agonist – pioglitazone or antagonist – T0070907. We identified 40 differentially expressed genes after treatment with pioglitazone and 40 after treatment with T0070907 in the mid-luteal phase as well as 26 after pioglitazone and 29 after T0070907 treatment in the late-luteal phase of the estrous cycle. In addition, we detected differences in gene expression between the mid- and late-luteal phase without treatment (409 differentially expressed genes). This study revealed a number of novel candidate genes that may play a role in controlling the function of CL by regulating signaling pathways related to ovarian steroidogenesis, metabolic processes, cell differentiation, apoptosis, and immune responses. These findings become a basis for further studies to explain the mechanism of PPARγ action in the reproductive system.

Structural Biology Inspired Development of a Series of Human Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) Ligands: From Agonist to Antagonist.

Recent progress in the structural and molecular pharmacological understanding of the nuclear receptor, peroxisome proliferator-activated receptor gamma (hPPARγ)-a transcription factor with pleiotropic effects on biological responses-has enabled the investigation of various graded hPPARγ ligands (full agonist, partial agonist, and antagonist). Such ligands are useful tools to investigate the functions of hPPARγ in detail and are also candidate drugs for the treatment of hPPARγ-mediated diseases, such as metabolic syndrome and cancer. This review summarizes our medicinal chemistry research on the design, synthesis, and pharmacological evaluation of a covalent-binding and non-covalent-binding hPPARγ antagonist, both of which have been created based on our working hypothesis of the helix 12 (H12) holding induction/inhibition concept. X-ray crystallographic analyses of our representative antagonists complexed with an hPPARγ ligand binding domain (LBD) indicated the unique binding modes of hPPARγ LBD, which are quite different from the binding modes observed for hPPARγ agonists and partial agonists.

Alcohol-Induced Glycolytic Shift in Alveolar Macrophages Is Mediated by Hypoxia-Inducible Factor-1 Alpha.

Excessive alcohol use increases the risk of developing respiratory infections partially due to impaired alveolar macrophage (AM) phagocytic capacity. Previously, we showed that chronic ethanol (EtOH) exposure led to mitochondrial derangements and diminished oxidative phosphorylation in AM. Since oxidative phosphorylation is needed to meet the energy demands of phagocytosis, EtOH mediated decreases in oxidative phosphorylation likely contribute to impaired AM phagocytosis. Treatment with the peroxisome proliferator-activated receptor gamma (PPARγ) ligand, pioglitazone (PIO), improved EtOH-mediated decreases in oxidative phosphorylation. In other models, hypoxia-inducible factor-1 alpha (HIF-1α) has been shown to mediate the switch from oxidative phosphorylation to glycolysis; however, the role of HIF-1α in chronic EtOH mediated derangements in AM has not been explored. We hypothesize that AM undergo a metabolic shift from oxidative phosphorylation to a glycolytic phenotype in response to chronic EtOH exposure. Further, we speculate that HIF-1α is a critical mediator of this metabolic switch. To test these hypotheses, primary mouse AM (mAM) were isolated from a mouse model of chronic EtOH consumption and a mouse AM cell line (MH-S) were exposed to EtOH in vitro. Expression of HIF-1α, glucose transporters (Glut1 and 4), and components of the glycolytic pathway (Pfkfb3 and PKM2), were measured by qRT-PCR and western blot. Lactate levels (lactate assay), cell energy phenotype (extracellular flux analyzer), glycolysis stress tests (extracellular flux analyzer), and phagocytic function (fluorescent microscopy) were conducted. EtOH exposure increased expression of HIF-1α, Glut1, Glut4, Pfkfb3, and PKM2 and shifted AM to a glycolytic phenotype. Pharmacological stabilization of HIF-1α via cobalt chloride treatment in vitro mimicked EtOH-induced AM derangements (increased glycolysis and diminished phagocytic capacity). Further, PIO treatment diminished HIF-1α levels and reversed glycolytic shift following EtOH exposure. These studies support a critical role for HIF-1α in mediating the glycolytic shift in energy metabolism of AM during excessive alcohol use.

Peroxisome proliferator-activated receptor gamma ligands regulate the expression of inflammatory mediators in porcine endometrium during LPS-induced inflammation

Inflammation in the female reproductive system is one of the most common causes of reproductive dysfunction such as infertility, delay of the reproductive cycle and a reduction in reproductive efficiency. In this study, we aimed to investigate the effect of peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the expression of selected inflammatory mediators: nuclear factor kappa (NF-κB), interleukin (IL)-1β, IL-6, IL-4, IL-10, leukemia inhibitory factor (LIF) and toll-like receptor 4 (TLR4) in the porcine endometrium treated in vitro with lipopolysaccharide (LPS) on days 10–12 and 18–20 of the estrous cycle. In addition, two experimental protocols were applied to evaluate the role of PPARγ agonists in ongoing and developing inflammation. Endometrial slices were incubated in vitro in the presence of LPS (to induce inflammation) and PPARγ agonists, prostaglandin J2 or pioglitazone (natural or synthetic, respectively). The study showed that PPARγ agonists decreased the expression of pro-inflammatory (NF-κB, TLR4, IL-6) and increased the abundance of anti-inflammatory mediators (IL-10) in the inflamed endometrium of pigs. These findings indicate anti-inflammatory properties of the tested ligands.

PPAR\u03b3 regulates the expression of genes involved in the DNA damage response in an inflamed endometrium

Inflammation is a biological response of the immune system, which can be triggered by many factors, including pathogens. These factors may induce acute or chronic inflammation in various organs, including the reproductive system, leading to tissue damage or disease. In this study, the RNA-Seq technique was used to determine the in vitro effects of peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the expression of genes and long non-coding RNA, and alternative splicing events (ASEs) in LPS-induced inflammation of the porcine endometrium during the follicular phase of the estrous cycle. Endometrial slices were incubated in the presence of LPS and PPARγ agonists (PGJ2 or pioglitazone) and a PPARγ antagonist (T0070907). We identified 169, 200, 599 and 557 differentially expressed genes after LPS, PGJ2, pioglitazone or T0070907 treatment, respectively. Moreover, changes in differentially expressed long non-coding RNA and differential alternative splicing events were described after the treatments. The study revealed that PPARγ ligands influence the LPS-triggered expression of genes controlling the DNA damage response (GADD45β, CDK1, CCNA1, CCNG1, ATM). Pioglitazone treatment exerted a considerable effect on the expression of genes regulating the DNA damage response.

Troglitazone-Induced Autophagic Cytotoxicity in Lung Adenocarcinoma Cell Lines.

Lung cancer is the leading cause of cancer-related deaths worldwide. Troglitazone (TGZ), a peroxisome proliferator-activated receptor gamma (PPARγ) ligand, is a potential antitumor agent. However, the action mechanism of TGZ in lung adenocarcinoma cells has not been completely elucidated. To assess this mechanism and the anticancer effects of TGZ in human lung adenocarcinoma cell lines (A549 and H1975), we investigated the involvement of PPARγ, apoptosis, the mitogen-activated protein kinase (MAPK) pathway, protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway, and autophagy. Cell viability was measured using fluorescence-based assays. Apoptotic cells were detected by Hoechst 33342 and Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) double staining; protein expression was detected by Western blotting. TGZ inhibited cell proliferation in a dose-dependent manner in both cell lines, and the effect was not suppressed by a PPARγ inhibitor. Additionally, TGZ increased apoptotic cell number and upregulated p38 and c-Jun N-terminal kinase (JNK) phosphorylation; however, p38 and JNK inhibitors did not block TGZ-mediated inhibition of cell proliferation in either cell line. TGZ also upregulated extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, whereas an ERK1/2 inhibitor enhanced TGZ-mediated cytotoxicity in A549 cells. Additionally, TGZ increased LC3-II expression, and chloroquine (an autophagy inhibitor) attenuated TGZ-mediated inhibition of cell proliferation. These findings suggest that TGZ-induced inhibition of cell proliferation is PPARγ independent. TGZ-mediated inhibition of cell proliferation was accompanied by apoptosis and independent of the MAPK signaling pathway. These results suggest that TGZ inhibits cell proliferation through autophagy-induced cytotoxicity. This study demonstrated that chemotherapy using TGZ may be effective for lung adenocarcinoma.

A novel peroxisome proliferator-activated receptor gamma ligand improves insulin sensitivity and promotes browning of white adipose tissue in obese mice

ObjectiveNuclear receptor Peroxisome Proliferator-Activated Receptor γ (PPARγ) is a promising target for the treatment of type 2 diabetes. The antidiabetic drug thiazolidinediones (TZDs) are potent insulin sensitizers as full agonists of PPARγ, but cause unwanted side effects. Recent discoveries have shown that TZDs improve insulin sensitivity by blocking PPARγ phosphorylation at S273, which decouples the full agonism-associated side effects. PPARγ ligands that act through the blockage of PPARγ phosphorylation but lack the full agonist activity would be expected to improve insulin sensitivity without TZD-associated side effects, however, chemicals that carry such traits and bind to PPARγ with high-affinity are lacking. Moreover, TZDs are known to promote white-to-brown adipocyte conversion and energy expenditure and appear to require their full agonism on PPARγ for this activity. It is unknown whether a partial or non-TZD agonist of PPARγ is capable of promoting browning effect. In this study, we developed a novel non-TZD partial agonist of PPARγ and investigated its function on insulin sensitivity and white-to-brown conversion and energy expenditure in diet-induced obese mice. MethodsA novel indole-based chemical WO95E was designed via medicinal chemistry and tested for PPARγ binding and activity and for the effect on PPARγ phosphorylation. Diet-induced obese mice were administered with WO95E for 4 weeks. Insulin sensitivity, glucose tolerance, body weight, fat tissue weight, adipocyte size, morphology, energy expenditure, and expression levels of genes involved in PPARγ activity, thermogenesis/browning, and TZD-related side effects were evaluated. ResultsWO95E binds to PPARγ with high affinity and acts as a PPARγ partial agonist. WO95E inhibits PPARγ phosphorylation and regulates PPARγ phosphorylation-dependent genes. WO95E ameliorates insulin resistance and glucose tolerance in mice of diet-induced obesity, with minimal TZD use-associated side effects. We found that WO95E promotes white-to-brown adipocyte conversion and energy expenditure and hence protects against diet-induced obesity. WO95E decreases the size of adipocytes and suppresses adipose tissue inflammation. WO95E also suppresses obesity-associated liver steatosis. ConclusionsWO95E improves insulin sensitivity and glucose homeostasis and promotes browning and energy expenditure by acting as a novel PPARγ phosphorylation inhibitor/partial agonist. Our findings suggest the potential of this compound or its derivative for the therapeutic treatment of insulin resistance and obesity.

Differential Effects of Estrogen Receptor Alpha and Beta on Endogenous Ligands of Peroxisome Proliferator-Activated Receptor Gamma in Papillary Thyroid Cancer.

PurposeThe inhibition of estrogen receptor alpha (ERα) or the activation of ERβ can inhibit papillary thyroid cancer (PTC), but the precise mechanism is not known. We aimed to explore the role of ERα and ERβ on the production of endogenous peroxisome proliferator-activated receptor gamma (PPARγ) ligands in PTC.Methods2 PTC cell lines, 32 pairs of PTC tissues and matched normal thyroid tissues were used in this study. The levels of endogenous PPARγ ligands 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE), 13-S-hydroxyoctadecadienoic acid (13(S)-HODE), and15-deoxy-Δ12,14-prostaglandin J2 (PGJ2) were measured by ELISA.ResultsThe levels of PGJ2 and 15(S)-HETE were significantly reduced in PTC, but 13(S)-HODE was not changed. Activation of ERα or inhibition of ERβ significantly downregulated the production of PGJ2, 15(S)-HETE and 13(S)-HODE, whereas inhibition of ERα or activation of ERβ markedly upregulated the production of these three ligands. Application of endogenous PPARγ ligands inhibited growth, induced apoptosis of cancer cells, and promoted the efficacy of chemotherapy.ConclusionThe levels of endogenous PPARγ ligands PGJ2 and 15(S)-HETE are significantly decreased in PTC. The inhibition of ERα or activation of ERβ can inhibit PTC by stimulating the production of endogenous PPARγ ligands to induce apoptosis in cancer cells.

Lobeglitazone attenuates fibrosis in corneal fibroblasts by interrupting TGF-beta-mediated Smad signaling

Transforming growth factor beta 1 (TGF-β1) is an important cytokine released after ocular surface injury to promote wound healing. However, its persistence at the injury site triggers a fibrotic response that leads to corneal scarring and opacity. Thiazolidinediones (TZDs) are synthetic peroxisome proliferator-activated receptor gamma (PPAR-γ) ligands used to regulate glucose and lipid metabolism in the management of type 2 diabetes. Studies have also showed TZDs have antifibrotic effect. In this study, we investigated the antifibrotic effect of the TZD lobeglitazone on TGF-β1-induced fibrosis in corneal fibroblasts. Human primary corneal fibroblasts were cultivated and treated with TGF-β1 (5 ng/mL) to induce fibrosis, with or without pre-treatments with different concentrations of lobeglitazone. Myofibroblast differentiation and extracellular matrix (ECM) protein expression was evaluated by western blotting, immunofluorescence, real-time PCR, and collagen gel contraction assay. The effect of lobeglitazone on TGF-β1-induced reactive oxygen species (ROS) generation was evaluated by DCFDA-cellular ROS detection assay kit. Signaling proteins were evaluated by western blotting to determine the mechanism underlying the antifibrotic effect. Our results showed lobeglitazone attenuated TGF-β1-induced ECM synthesis and myofibroblast differentiation of corneal fibroblasts. This antifibrotic effect appeared to be independent of PPAR signaling and rather due to the inhibition of the TGF-β1-induced Smad signaling. Lobeglitazone also blocked TGF-β1-induced ROS generation and nicotinamide adenine dinucleotide phosphateoxidase (Nox) 4 transcription. These findings indicate that lobeglitazone may be a promising therapeutic agent for corneal scarring. KEY MESSAGES.

Alcohol induces mitochondrial derangements in alveolar macrophages by upregulating NADPH oxidase 4.

Excessive alcohol users have increased risk of developing respiratory infections in part due to oxidative stress-induced alveolar macrophage (AM) phagocytic dysfunction. Chronic ethanol exposure increases cellular oxidative stress in AMs via upregulation of NADPH oxidase (Nox) 4, and treatment with the peroxisome proliferator-activated receptor gamma (PPARγ) ligand, rosiglitazone, decreases ethanol-induced Nox4. However, the mechanism by which ethanol induces Nox4 expression and the PPARγ ligand reverses this defect has not been elucidated. Since microRNA (miR)-92a has been predicted to target Nox4 for destabilization, we hypothesized that ethanol exposure decreases miR-92a expression and leads to Nox4 upregulation. Previous studies have implicated mitochondrial-derived oxidative stress in AM dysfunction. We further hypothesized that ethanol increases mitochondrial-derived AM oxidative stress and dysfunction via miR-92a, and that treatment with the PPARγ ligand, pioglitazone, could reverse these derangements. To test these hypotheses, a mouse AM cell line, MH-S cells, was exposed to ethanol invitro, and primary AMs were isolated from a mouse model of chronic ethanol consumption to measure Nox4, mitochondrial target mRNA (qRT-PCR) and protein levels (confocal microscopy), mitochondria-derived reactive oxygen species (confocal immunofluorescence), mitochondrial fission (electron microscopy), and mitochondrial bioenergetics (extracellular flux analyzer). Ethanol exposure increased Nox4, enhanced mitochondria-derived oxidative stress, augmented mitochondrial fission, and impaired mitochondrial bioenergetics. Transfection with a miR-92a mimic invitro or pioglitazone treatment invivo diminished Nox4 levels, resulting in improvements in these ethanol-mediated derangements. These findings demonstrate that pioglitazone may provide a novel therapeutic approach to mitigate ethanol-induced AM mitochondrial derangements.

Transcriptome analysis of porcine endometrium after LPS-induced inflammation: effects of the PPAR-gamma ligands in vitro†.

Female fertility depends greatly on the capacity of the uterus to recognize and eliminate microbial infections, a major reason of inflammation in the endometrium in many species. This study aimed to determine the in vitro effect of peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the transcriptome genes expression and alternative splicing in the porcine endometrium in the mid-luteal phase of the estrous cycle during LPS-stimulated inflammation using RNA-seq technology. The endometrial slices were incubated in vitro in the presence of LPS and PPARγ agonists-PGJ2 or pioglitazone and antagonist-T0070907. We identified 222, 3, 4, and 62 differentially expressed genes after LPS, PGJ2, pioglitazone, or T0070907 treatment, respectively. In addition, we detected differentially alternative spliced events: after treatment with LPS-78, PGJ2-60, pioglitazone-52, or T0070907-134. These results should become a basis for further studies explaining the mechanism of PPARγ action in the reproductive system in pigs.

Application of generalized concentration addition to predict mixture effects of glucocorticoid receptor ligands

Environmental exposures often occur in complex mixtures and at low concentrations. Generalized concentration addition (GCA) is a method used to estimate the joint effect of receptor ligands that vary in efficacy. GCA models have been successfully applied to mixtures of aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor gamma (PPARγ) ligands, each of which can be modeled as a receptor with a single binding site. Here, we evaluated whether GCA could be applied to homodimer nuclear receptors, which have two binding sites, to predict the combined effect of full glucocorticoid receptor (GR) agonists with partial agonists. We measured transcriptional activation of GR using a cell-based bioassay. Individual concentration-response curves for dexamethasone (full agonist), prednisolone (full agonist), and medroxyprogesterone 17-acetate (partial agonist) were generated and applied in three additivity models, GCA, effect summation (ES), and relative potency factor (RPF), to generate response surfaces. GCA and RPF yielded adequate predictions of the experimental data for two full agonists. However, GCA fit experimental data significantly better than ES and RPF for all other binary mixtures. This work extends the application of GCA to homodimer nuclear receptors and improves prediction accuracy of mixture effects of GR agonists.

SYNTHESIS AND SAR STRATEGY OF THIAZOLIDINEDIONE: A NOVEL APPROACH FOR CANCER TREATMENT

In current review, authors aim to inspire the researcher through structure activity relationship strategy for the finding of safe and effective anticancer molecules. Nowadays cancer is measured as one of the major health problems in human beings in the world from decades. A classes of heterocyclic compounds have been recognized through molecular biology, empirical screening and rational drug development for the evaluation of anticancer molecules however regrettably, till now we could not find a medicine to be entirely active and nontoxic for the treatment of cancer patients. In pointed view, it might be measured that Thiazolidinedione (TZD) heterocyclic compounds are prodigious standing in the synthetic and pharmacological approach of medicinal chemistry. Thiazolidinedione (TZD) nucleus upon the substitution of various functional groups is provides a wide spectrum of biological activity by the use of different mechanism on different target sites. Recently, some of the substituted thiazolidinedione molecules are designed for the treatment of human cancers cell line through different molecular mechanism such as EGFR & Mushroom Tyrosine kinase inhibitor, COX enzyme inhibitors, Histone deacetylase inhibitors, Alpha glucosidase inhibitor, DNA intercalation and Protein tyrosine phosphatase 1B (PTP1B) inhibitor, basically in which PPAR gamma express are in high levels. Peroxisome proliferator-activated receptor (PPAR) gamma ligands effect on apoptosis, cell proliferation and cell differentiation on different types of cell. The most commonly cascades in human cancers cell are Raf/MEK/ERK, Wnt and PI3/Akt. This article highlights and embraces a concise overview of recent approaches for the synthesis of new thiazolidinedione molecules with its structure activity relationship strategy and effects on various signaling pathways, which is responsible for the expresses of cancer cell line activity.

Synthesis and Characterization of Telmisartan-Derived Cell Death Modulators to Circumvent Imatinib Resistance in Chronic Myeloid Leukemia.

New strategies to eradicate cancer stem cells in chronic myeloid leukemia (CML) include a combination of imatinib with peroxisome proliferator‐activated receptor gamma (PPARγ) ligands. Recently, we identified the partial PPARγ agonist telmisartan as effective sensitizer of resistant K562 CML cells to imatinib treatment. Here, the importance of the heterocyclic core on the cell death‐modulating effects of the telmisartan‐derived lead 4′‐((2‐propyl‐1H‐benzo[d]imidazol‐1‐yl)methyl)‐[1,1′‐biphenyl]‐2‐carboxylic acid (3 b) was investigated. Inspired by the pharmacodynamics of HYL‐6d and the selective PPARγ ligand VSP‐51, the benzimidazole was replaced by a carbazole or an indole core. The results indicate no correlation between PPARγ activation and sensitization of resistant CML cells to imatinib. The 2‐COOH derivatives of the carbazoles or indoles achieved low activity at PPARγ, while the benzimidazoles showed 60‐100 % activation. Among the 2‐CO2CH3 derivatives, only the ester of the lead (2 b) slightly activated PPARγ. Sensitizing effects were further observed for this non‐cytotoxic 2 b (80 % cell death), and to a lesser extent for the lead 3 b or the 5‐Br‐substituted ester of the benzimidazoles (5 b).

Effects of DHA-enriched fish oil on gene expression levels of p53 and NF-κB and PPAR-γ activity in PBMCs of patients with T2DM: A randomized, double-blind, clinical trial

Background and AimsOmega-3 polyunsaturated fatty acids (PUFAs) are natural peroxisome proliferator-activated receptor gamma (PPAR-γ) ligands. Activated PPAR-γ protects the cardiovascular system against atherosclerotic lesion formation and exerts its anti-inflammatory role by suppressing cytokines induced by nuclear factor kappa-B (NF-κB) in endothelial cells (ECs), and it is hypothesized that apoptosis and cell cycle arrest induced by PPAR-γ ligands may be mediated by the p53-dependent pathway. The aim of our study was to investigate the effects of docosahexaenoic acid (DHA)-enriched fish oil supplement on PPAR-γ activity and mRNA expression levels of p53 and NF-κB. Methods and ResultsFifty patients with type 2 diabetes mellitus (T2DM) aged 30–70 years were randomly assigned to receive either 2400 mg/d DHA-rich fish oil or placebo for 8 weeks. Metabolic parameters were assessed at baseline and at the end of the intervention. PPAR-γ activity in the peripheral blood mononuclear cells (PBMCs) was measured using ELISA-based PPAR-γ Transcription Factor Assay Kit, and the gene expression levels of p53 and NF-κB were assessed using real-time quantitative reverse transcription polymerase chain reaction (RT-PCR). On the basis of our finding, 8 weeks of treatment with DHA-rich fish oil increased PPAR-γ activity in PBMCs of subjects with T2DM (p < 0.01) compared to that in placebo (p = 0.4). Between-group comparisons of mean PPAR-γ activity changes showed significant differences (p = 0.03), whereas mRNA expression levels of the p53 and NF-κB genes did not show significant differences between studied groups (p = 0.2 and p = 0.5, respectively). ConclusionOur findings indicated that short-term DHA-rich fish oil supplementation may modulate PPAR-γ activity in PBMCs.

Overcoming imatinib resistance in chronic myelogenous leukemia cells using non-cytotoxic cell death modulators

Recent studies examined the possibility to overcome imatinib resistance in chronic myeloid leukemia (CML) patients by combination therapy with peroxisome proliferator-activated receptor gamma (PPARγ) ligands. Pioglitazone, a full PPARγ agonist, improved the survival of patients by the gradual elimination of the residual CML stem cell pool. To evaluate the importance of the pharmacological profile of PPARγ agonists on the ability to circumvent resistance, the partial PPARγ agonist 4‘-((2-propyl-1H-benzo[d]imidazol-1-yl)methyl)-[1,1’-biphenyl]-2-carboxylic acid, derived from telmisartan, and other related derivatives were investigated. The 4-substituted benzimidazole derivatives bearing a [1,1′-biphenyl]-2-carboxamide moiety sensitized K562-resistant cells to imatinib treatment. Especially the derivatives 18a-f, which did not activate PPARγ to more than 40% at 10 μM, retrieved the cytotoxicity of imatinib in these cells. The cell death modulating properties were higher than that of pioglitazone. It is of interest to note that all novel compounds were not cytotoxic neither on non-resistant nor on resistant cells. They exerted antitumor potency only in combination with imatinib.

Development of a novel class of peroxisome proliferator-activated receptor (PPAR) gamma ligands as an anticancer agent with a unique binding mode based on a non-thiazolidinedione scaffold

We previously identified dibenzooxepine derivative 1 as a potent PPARγ ligand with a unique binding mode owing to its non-thiazolidinedione scaffold. However, while 1 showed remarkably potent MKN-45 gastric cancer cell aggregation activity, an indicator of cancer differentiation-inducing activity induced by PPARγ activation, we recognized that 1 was metabolically unstable. In the present study, we identified a metabolically soft spot, and successfully discovered 3-fluoro dibenzooxepine derivative 9 with better metabolic stability. Further optimization provided imidazo[1,2-a]pyridine derivative 17, which showed potent MKN-45 gastric cancer cell aggregation activity and excellent PK profiles compared with 9. Compound 17 exerted a growth inhibitory effect on AsPC-1/AG1 pancreatic tumor in mice. Furthermore, the decrease in the hematocrit (an indicator of localized edema, a serious adverse effect of PPARγ ligands) was tolerable even with oral administration at 200 mg/kg in healthy mice.

Peroxisome Proliferator Activated Receptor Gamma Sensitizes Non-small Cell Lung Carcinoma to Gamma Irradiation Induced Apoptosis.

The nuclear receptors known as peroxisome proliferator activated receptor gamma (PPARG) are lipid-activated transcription factors that have emerged as key regulators of inflammation. PPARG ligands have been shown to have an anti-proliferative effect on a variety of cancers. These ligands can induce apoptosis via TP53 (Tumor protein p53) or ERK1/2 (Extracellular signal-regulated kinases 1/2) (EPHB2) pathways. However, the exact mechanism is not known. PPAR, a type II nuclear hormone receptor deserves attention as a selective target for radiotherapy. Our study examines the potential of selective agonism of PPARG for radiation therapy in non-small cell lung carcinoma (NSCLC). We found that the overexpression of PPARG protein as well as its induction using the agonist, rosiglitazone was able to stimulate radiation-induced cell death in otherwise radio resistant NSCLC A549 cell line. This cell death was apoptotic and was found to be BAX (BCL2 associated X) mediated. The treatment also inhibited radiation-induced AKT (Protein Kinase B) phosphorylation. Interestingly, the ionising radiation (IR) induced apoptosis was found to be inversely related to TP53 levels. A relatively significant increase in the levels of radiation induced apoptosis was observed in H1299 cells (TP53 null) under PPARG overexpression condition further supporting the inverse relationship between apoptosis and TP53 levels. The combination of PPARG agonist and radiation was able to induce apoptosis at a radiation dose at which A549 and H1299 are radioresistant, thus confirming the potential of the combinatorial strategy. Taken together, PPARG agonism was found to invigorate the radiosensitising effect and hence its use in combination with radiotherapy is expected to enhance sensitivity in otherwise resistant cancer types.