Peroxisome proliferator activated receptor-gamma (PPAR-γ) ligand, pioglitazone, increases analgesic and anti-inflammatory effects of naproxen

The aim of this study was the investigation of analgesic and anti-inflammatory activity of naproxen and pioglitazone following intra-plantar injection of carrageenan and assessment of the PPAR-γ receptor involvement in these effects. Rats were intra-plantarly injected with carrageenan (1%, 100 μl) to induce thermal hyperalgesia and paw inflammation. Different groups of rats were pre-treated intraperitoneally with naproxen (1 and 10 mg/kg) or pioglitazone (3 and 10 mg/kg) or GW9662 (a selective PPAR-γ antagonist, 100 μl/paw). The volume of the paw was evaluated using a plethysmometer, and the hot plate test was employed to assess the pain threshold in the animals. Finally, TNF-α, IL-1ß, IL-6, and myeloperoxidase (MPO) activity status were evaluated in the hind paw tissue. Naproxen and pioglitazone demonstrated analgesic and anti-inflammatory activity. Concurrent injection of an ineffective dose of naproxen (1 mg/kg) with an ineffective dose of pioglitazone (3 mg/kg) caused augmented analgesic and anti-inflammatory activity, significantly (p≤0.001 and p≤0.01, respectively). Additionally, intra-plantar injection of GW-9662 before naproxen or pioglitazone significantly suppressed their analgesic (p≤0.001) and anti-inflammatory activity (p≤0.01). Also, naproxen and pioglitazone (10 mg/kg) significantly (p≤0.001) reduced carrageenan-induced MPO activity and TNF-α, IL-6, and IL-1ß releasing. Furthermore, PPAR-γ blockade significantly prevented suppressive effects of naproxen and pioglitazone on the MPO activity and inflammatory cytokines. Pioglitazone significantly increased analgesic and anti-inflammatory effects of naproxen. This study proposes that concurrent treatment with naproxen and pioglitazone may be a substitute for overcome pain and inflammation clinically, in the future, particularly in patients with cardiovascular disorders and diabetes.

Evaluation of the protective effect of losartan in acetaminophen-induced liver and kidney damage in mice

Acetaminophen is widely used among humans as an antipyretic and analgesic. In this study, the protective effect of losartan in hepatotoxicity and nephrotoxicity induced by acetaminophen in mice was investigated owing to its anti-inflammatory and antioxidant effects. An injection of a single dose of 500 mg/kg (i.p.) acetaminophen was administered to induce hepatotoxicity and nephrotoxicity in Groups VI-X. Losartan at doses of 1 mg/kg (Group VII), 3 mg/kg (Group VIII), and 10 mg/kg (Groups III, V, IX, and X) was injected intraperitoneally twice, at 1 and 12 h after the acetaminophen injection. Additionally, a 4 mg/kg dose of GW9662 (peroxisome proliferator-activated receptor gamma (PPAR-γ) antagonist) was injected intraperitoneally 30 min before the losartan injections in Groups V and X. At the end of 24 h, the mice were euthanized, and blood, liver, and kidney tissue samples were collected. Levels of AST, ALT, creatinine, and oxidative stress markers including TBARS, SOD, CAT, GPx, TAS, TOS, GSH, and GSSG, along with pro-inflammatory cytokines IL-1β, IL-6, IL-8, IL-10, IL-17, and TNF-α, were measured using ELISA kits. Additionally, a histological evaluation of the tissue samples was performed. Acetaminophen causes increases in the levels of AST, ALT, creatinine, TBARS, TOS, GSSG, IL-1β, IL-6, IL-8, IL-10, IL-17, and TNF-α in serum, liver, and kidney tissue. Meanwhile, it led to a decrease in the levels of SOD, CAT, GPx, TAS, and GSH. Losartan injection reversed oxidative and inflammatory damage induced by acetaminophen. Histopathological changes in liver and kidney tissue were alleviated by losartan. The substance GW9662 increased the protective effect of losartan. In light of all the data obtained from our study, it can be said that losartan has a protective effect on liver and kidney damage induced by acetaminophen due to its antioxidant and anti-inflammatory effects. In terms of the study, losartan was found to be an alternative substance that could protect people from the harmful effects of acetaminophen.

GW9662 ameliorates nonalcoholic steatohepatitis by inhibiting the PPARγ/CD36 pathway and altering the gut microbiota

BACKGROUND & AIMS

Peroxisome proliferator-activated receptors (PPARs) are currently among the most focused-on therapeutic targets for non-alcoholic steatohepatitis (NASH), although no clinical transformation has been achieved to date. In this study, we aimed to evaluate the effects of GW9662 on choline-deficient, L-amino acid-defined high-fat diet (CDAA-HFD)-induced NASH mice and reveal the mechanism underlying this effect.

METHODS

GW9662 (1 mg/kg) was administered in CDAA-HFD mouse model of NASH. The effect of GW9662 on hepatic lipid metabolism was investigated using liver RNA-seq and HepG2 cells induced by oleic acid and palmitic acid. In addition, 16S rRNA gene sequencing was performed to analyze the effects of GW9662 on the composition and function of the fecal microbiota.

RESULTS

GW9662 improved the CDAA-HFD caused elevation in the levels of ALT, AST, hepatic free fatty acids and triglycerides. The liver pathological analysis indicated that GW9662 alleviated the hepatic steatosis and fibrosis. The NAFLD activity score and RNA-Seq revealed that GW9662 mainly regulated the fatty acids transport and lipid synthesis by inhibiting PPARγ, CD36, FABP1, FASN, and SCD1, and through the up-regulation of PPARα. Moreover, GW9662 reduced the epididymal fat weight. GW9662 reversed the gut microbiota disorder by increasing the abundance of the beneficial bacteria Dubosiella and Lactobacillus and decreasing the abundance of harmful bacteria Lachnospiraceae_NK4A136_group, Helicobacteraceae, Desulfovibriaceae, and Rickenaceae.

CONCLUSIONS

GW9662 ameliorated lipid metabolism by inhibiting the PPARγ/CD36 pathway and altering the composition of the gut microbiota in NASH mice. Therefore, the PPARγ antagonist GW9662 deserves more attention as a potential therapeutic agent for NASH.

Metabolic regulation of the circadian clock in classically and alternatively activated macrophages

Macrophages exhibit a range of functional pro- and anti-inflammatory states that induce changes in their cellular metabolism. We aimed to elucidate whether these changes affect the molecular properties of their circadian clock focusing on their anti-inflammatory phenotype. Primary cell cultures of bone marrow-derived macrophages (non-polarized M0 BMDM) from PER2::LUC mice were polarized into the M1 (pro-inflammatory) or M2 (anti-inflammatory) phenotype, and PER2-driven bioluminescence was recorded in real-time at the cell-population and single-cell levels. Viability, clock gene expression profiles, polarization plasticity and PPARγ protein levels were analyzed. The effects of pharmacological activation/inhibition of PPARγ (Rosiglitazone/GW9662) and inhibition of fatty acid oxidation (FAO) by Etomoxir in M2 BMDM cell cultures were examined. The parameters of PER2-driven bioluminescence rhythms differed between M0, M1 and M2 BMDM cultures at cell population and single-cell levels. Compared with M0, polarization to M2 did not change the period but increased amplitude, mean bioluminescence level and rhythm persistence. Polarization to M1 shortened the period but had no effect on the amplitude of the rhythm. The same period changes were observed after a bidirectional switch between M1 and M2 polarized states in the same culture. Both PPARγ activation/inhibition and FAO inhibition modulated the clock in M2 BMDM, suggesting metabolic regulation of the M2 clock. Our results indicate that bidirectional changes in the properties of BMDM circadian clocks in response to their actual polarization are mediated via changes in their metabolic state. They provide new information on the interrelationship between the BMDM polarization, their circadian clock and cellular metabolism.

The Cardioprotective Effect of Corosolic Acid in the Diabetic Rats: A Possible Mechanism of the PPAR-γ Pathway

The study was conducted to determine whether corosolic acid could protect the myocardium of diabetic rats from damage caused by isoproterenol (ISO) and, if so, how peroxisome proliferator-activated receptor gamma (PPAR-γ) activation might contribute into this protection. Diabetes in the rats was induced by streptozotocin (STZ), and it was divided into four groups: the diabetic control group, diabetic rats treated with corosolic acid, diabetic rats treated with GW9662, and diabetic rats treated with corosolic acid plus GW9662. The study was carried out for 28 days. The diabetic control and ISO control groups showed a decrease in mean arterial pressure (MAP) and diastolic arterial pressure (DAP) and an increase in systolic arterial pressure (SAP). The rat myocardium was activated by corosolic acid treatment, which elevated PPAR-γ expression. A histopathological analysis showed a significant reduction in myocardial damage by reducing myonecrosis and edema. It was found that myocardial levels of CK-MB and LDH levels were significantly increased after treatment with corosolic acid. By decreasing lipid peroxidation and increasing endogenous antioxidant levels, corosolic acid therapy showed a significant improvement over the ISO diabetic group. In conclusion, our results prove that corosolic acid can ameliorate ISO-induced acute myocardial injury in rats. Based on these results, corosolic acid seems to be a viable new target for the treatment of cardiovascular diseases and other diseases of a similar nature.

Antiapoptotic and anti-inflammatory effects of Pparγ agonist, pioglitazone, reversed Dox-induced cardiotoxicity through mediating of miR-130a downregulation in C57BL/6 mice

Doxorubicin (Dox) is an antitumor agent widely used in cancer therapy, with notable side effects of cardiac toxicity. Peroxisome proliferator-activated receptor γ (PPARγ), is a transcriptional factor with antiapoptotic and anti-inflammatory properties. Recently we indicated that cardiac toxicity of Dox was due to upregulation of miR-130a and further suppressive effect on cardiac Pparγ in vitro. In this study, we extended our proposed hypothesis in vivo. To achieve this, pioglitazone (Pio) and GW9662 were used as the specific agonist and antagonist of Pparγ to treat Dox-injected mice. Heart function, apoptosis, and inflammation in heart tissue were studied. Pretreatment of Dox-injected mice with Pio resulted in elevated expression of Pparγ and suppression of miR-130a. However, GW9662 pretreatment was unable to increase miR-130a expression. Pio pretreatment led to partially cardiac toxicity limitation of Dox whereas GW9662 caused heart damage. Finally, our observation determined that activation of Pparγ was not adequate to reverse the Dox-induced toxicity completely.

Effects of Intra-BLA Administration of PPAR Antagonists on Formalin-Evoked Nociceptive Behaviour, Fear-Conditioned Analgesia, and Conditioned Fear in the Presence or Absence of Nociceptive Tone in Rats

There is evidence for the involvement of peroxisome proliferator-activated receptors (PPARs) in pain, cognition, and anxiety. However, their role in pain–fear interactions is unknown. The amygdala plays a key role in pain, conditioned fear, and fear-conditioned analgesia (FCA). We investigated the effects of intra-basolateral amygdala (BLA) administration of PPARα, PPARβ/δ, and PPARγ antagonists on nociceptive behaviour, FCA, and conditioned fear in the presence or absence of nociceptive tone. Male Sprague-Dawley (SD) rats received footshock (FC) or no footshock (NFC) in a conditioning arena. Twenty-three and a half hours later, rats received an intraplantar injection of formalin or saline and, 15 min later, intra-BLA microinjections of vehicle, PPARα (GW6471) PPARβ/δ (GSK0660), or PPARγ (GW9662) antagonists before arena re-exposure. Pain and fear-related behaviour were assessed, and neurotransmitters/endocannabinoids measured post-mortem. Intra-BLA administration of PPARα or PPARγ antagonists potentiated freezing in the presence of nociceptive tone. Blockade of all PPAR subtypes in the BLA increased freezing and BLA dopamine levels in NFC rats in the absence of nociceptive tone. Administration of intra-BLA PPARα and PPARγ antagonists increased levels of dopamine in the BLA compared with the vehicle-treated counterparts. In conclusion, PPARα and PPARγ in the BLA play a role in the expression or extinction of conditioned fear in the presence or absence of nociceptive tone.

Bupleurum falcatum L. alleviates nociceptive and neuropathic pain: Potential mechanisms of action

ETHNOPHARMACOLOGICAL RELEVANCE

In Iranian folkloric medicine, Bupleurum falcatum L. (Chinese Thoroughwax) has been used as a selective analgesic remedy for several centuries.

OBJECTIVE

The current research was conducted to explore the anti-nociceptive and anti-allodynic action of Bupleurum falcatum L. roots essential oil (BFEO) in Swiss mice.

MATERIALS AND METHODS

Formalin-induced paw licking (FIPL) model was applied for exploring of BFEO antinociceptive effects (neurogenic or inflammatory pain). The involvements of L-arginine-NO-cGMP-KATP channel pathway and several receptors such as opioid, peroxisome proliferator-activated (PPA), cannabinoid, transient receptor potential vanilloid, and adrenergic receptors were assesses to detect the anti-nociceptive activity of BFEO. Cervical spinal cord contusion (CSC) paradigm was employed for induction of neuropathic pain.

RESULTS

BFEO (100 mg/kg), in the FIPL model, produced significant antinociception compared to the control mice (p < 0.01). Furthermore, L-arginine, methylene blue, glibenclamide, naloxonazine, GW9662, and SR141716A pre-treatments restored the BFEO anti-nociceptive effects (p < 0.05) in the FIPL (second phase) test (p < 0.05). Intraperitoneal administration of saikosaponin A (one of the main constituents of BFEO) partially alleviated (p < 0.05) pain in FIPL test. Likewise, in CSC mice, the von Frey assay exhibited that BFEO could alter mechanical allodynia.

CONCLUSION

Finally, it seems that, in male mice, BFEO has both anti-allodynic and anti-nociceptive effects. The present data also suggest activating the L-arginine-NO-cGMP-KATP channel pathway as well as interaction of opioid, PPA, and cannabinoid receptors in the BFEO anti-nociceptive activities. These results also propose that BFEO could effectively attenuate allodynia in CSC mice.

Preclinical Investigation of Alpinetin in the Treatment of Cancer-Induced Cachexia via Activating PPARγ

The ongoing loss of skeletal muscle is a central event of cancer cachexia, and its consequences include adverse effects on patient’s quality of life and survival. Alpinetin (Alp), a natural plant-derived flavonoid obtained from Alpinia katsumadai Hayata, has been reported to possess potent anti-inflammatory and antitumor activities. This study aimed to explore the therapeutic effect and underlying mechanism of Alp in the prevention of cancer cachexia. We found that Alp (25–100 μM) dose-dependently attenuated Lewis lung carcinoma–conditioned medium-induced C2C12 myotube atrophy and reduced expression of the E3 ligases Atrogin-1 and MuRF1. Moreover, Alp administration markedly improved vital features of cancer cachexia in vivo with visible reduction of the loss of tumor-free body weight and wasting of multiple tissues, including skeletal muscle, epididymal fat, and decreased expression of Atrogin-1 and MuRF1 in cachectic muscle. Alp suppressed the elevated spleen weight and serum concentrations of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. Further, Alp treatment remained protective against cancer cachexia in the advanced stage of tumor growth. Molecular docking results suggested that Alp was docked into the active site of PPARγ with the docking score of –7.6 kcal/mol, forming a hydrogen bond interaction with PPARγ protein amino acid residue HIS449 with a bond length of 3.3 Å. Mechanism analysis revealed that Alp activated PPARγ, resulting in the downregulated phosphorylation of NF-κB and STAT3 in vitro and in vivo. PPARγ inhibition induced by GW9662 notably attenuated the improvement of Alp on the above cachexia phenomenon, indicating that PPARγ activation mediated the therapeutic effect of Alp. These findings suggested that Alp might be a potential therapeutic candidate against cancer cachexia.

Comparison of PPAR Ligands as Modulators of Resolution of Inflammation, via Their Influence on Cytokines and Oxylipins Release in Astrocytes

Neuroinflammation is a key process of many neurodegenerative diseases and other brain disturbances, and astrocytes play an essential role in neuroinflammation. Therefore, the regulation of astrocyte responses for inflammatory stimuli, using small molecules, is a potential therapeutic strategy. We investigated the potency of peroxisome proliferator-activated receptor (PPAR) ligands to modulate the stimulating effect of lipopolysaccharide (LPS) in the primary rat astrocytes on (1) polyunsaturated fatty acid (PUFAs) derivative (oxylipins) synthesis; (2) cytokines TNFα and interleukin-10 (IL-10) release; (3) p38, JNK, ERK mitogen-activated protein kinase (MAPKs) phosphorylation. Astrocytes were exposed to LPS alone or in combination with the PPAR ligands: PPARα (fenofibrate, GW6471); PPARβ (GW501516, GSK0660); PPARγ (rosiglitazone, GW9662). We detected 28 oxylipins with mass spectrometry (UPLC-MS/MS), classified according to their metabolic pathways: cyclooxygenase (COX), cytochrome P450 monooxygenases (CYP), lipoxygenase (LOX) and PUFAs: arachidonic (AA), docosahexaenoic (DHA), eicosapentaenoic (EPA). All tested PPAR ligands decrease COX-derived oxylipins; both PPARβ ligands possessed the strongest effect. The PPARβ agonist, GW501516 is a strong inducer of pro-resolution substances, derivatives of DHA: 4-HDoHE, 11-HDoHE, 17-HDoHE. All tested PPAR ligands decreased the release of the proinflammatory cytokine, TNFα. The PPARβ agonist GW501516 and the PPARγ agonist, rosiglitazone induced the IL-10 release of the anti-inflammatory cytokine, IL-10; the cytokine index, (IL-10/TNFα) was more for GW501516. The PPARβ ligands, GW501516 and GSK0660, are also the strongest inhibitors of LPS-induced phosphorylation of p38, JNK, ERK MAPKs. Overall, our data revealed that the PPARβ ligands are a potential pro-resolution and anti-inflammatory drug for targeting glia-mediated neuroinflammation.

Effect of rosiglitazone on developmental competence of mouse embryos treated with lipopolysaccharide

Lipopolysaccharide (LPS) significantly reduces pre- and post-implantation developmental competence of embryos. One of the reason of this effect could be a consequence of TLR4-mediated inflammation. In this study, we assessed the anti-inflammatory effect of peroxisome proliferator activated receptor γ (PPAR γ) agonist, rosiglitazone (RGZ), in LPS-treated mouse embryos. Initially, the optimal doses of LPS, RGZ and GW9662 (a potent and selective PPARγ antagonist) were determined by treating the mouse zygotes up to blastocyst stage and assessment of compaction and blastocyst rates. Quantitative PCR was used to assess the mRNA expression of inflammatory cytokines. Immunostaining was used to study the translocation of PPARγ in blastocysts. Finally, the blastocysts were transferred to surrogate mouse to determine the post-implantation developmental competence. 0.0625 mg/mL of LPS significantly reduced the developmental competency by around 50% compared to control group. 10 μM of RGZ significantly ameliorated the toxic effect of LPS, which was also significantly reversed by 1.25 μM GW9662. Through immunostaining, it was shown that LPS could prevent the translocation of PPARγ to nucleus; and translocation was facilitated by RGZ and this effect was reversed by GW9662. A similar effect was also observed for the mRNA expression of inflammatory cytokines (Il-1β and Il-6). LPS significantly increased the expression of these cytokines, while RGZ significantly reduced their expression, which was also significantly reversed by GW9662. It was also shown that embryos exposed to LPS had significantly reduced post implantation developmental competence which was considerably improved by treatment with RGZ. In conclusion, these data may have clinical implications for ameliorating the adverse effects of LPS in dairy farming and infertility treatment.

Chrysin rescues rat myocardium from ischemia-reperfusion injury via PPAR-γ/Nrf2 activation

Pharmacological strategies aimed at co-activating peroxisome proliferator-activated receptor-gamma (PPAR-γ)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway have shown promising results in alleviating myocardial injury. The aim of the study was to evaluate the role of chrysin, a PPAR-γ agonist, in ischemia-reperfusion (IR)-induced myocardial infarction (MI) in rats and to explore the molecular mechanism driving this activity. To evaluate this hypothesis, chrysin (60 mg/kg, orally), PPAR-γ antagonist (GW9662, 1 mg/kg, intraperitoneally), or both were administered to rats for 28 days. On the 29th day, one-stage ligation of left anterior descending coronary artery for 45 min followed by 60 min of reperfusion was performed. Chrysin significantly decreased infarct size and improved cardiac functions following IR-induced MI. This improvement was corroborated by augmented PPAR-γ/Nrf2 expression as confirmed by immunohistochemistry and western blotting analysis. Chrysin exhibited strong anti-oxidant property as demonstrated by increased GSH and CAT levels and decreased 8-OHdG and TBARS levels. Our findings also imply that chrysin significantly inhibited inflammatory response as validated by decreased NF-κB, IKK-β, CRP, TNF-α and MPO levels. In addition, chrysin decreased TUNEL/DAPI positivity, a marker of apoptotic response and normalized cardiac injury markers. The histopathological and ultrastructural analysis further supported the functional and biochemical outcomes, showing preserved myocardial architecture. Intriguingly, co-administration with GW9662 significantly diminished the cardioprotective effect of chrysin as demonstrated by depressed myocardial function, decreased PPAR-γ/Nrf2 expression and increased oxidative stress. In conclusion, the present study demonstrates that co-activation of PPAR-γ/Nrf2 by chrysin may be crucial for its cardioprotective effect.

Telmisartan Protects Auditory Hair Cells from Gentamicin-Induced Toxicity in vitro

BACKGROUND

Telmisartan is an angiotensin II receptor blocker that has pleiotropic effects and protective properties in different cell types. Moreover, telmisartan has also shown partial agonism on the peroxisome proliferator-activated receptor γ (PPAR-γ). Auditory hair cells (HCs) express PPAR-γ, and the protective role of PPAR-γ agonists on HCs has been shown.

OBJECTIVES

The objective of this study was to investigate the effects of telmisartan on gentamicin-induced ototoxicity in vitro.

METHODS

Cochlear explants were exposed to gentamicin with or without telmisartan, and/or GW9662, an irreversible PPAR-γ antagonist.

RESULTS

Telmisartan protected auditory HCs against gentamicin-induced ototoxicity. GW9662 completely blocked this protective effect, suggesting that it was mediated by PPAR-γ signaling. Exposure to GW9662 or telmisartan alone was not toxic to auditory HCs.

CONCLUSIONS

We found that telmisartan, via PPAR-γ signaling, protects auditory HCs from gentamicin-induced ototoxicity. Therefore, telmisartan could potentially be used in the future to prevent or treat sensorineural hearing loss.

Mechanistic investigation of PPARγ-facilitated anti-asthmatic effects of Galangin (Norizalpinin): Insights from in silico and in vivo analyses

Peroxisome proliferator-activated receptor gamma (PPARγ) is a multifaceted ligand-activated transcription factor that regulates inflammatory responses in asthma pathophysiology. The present study corroborates PPARγ-mediated anti-asthmatic action of the flavonoid, galangin (norizalpinin). In silico molecular interactions reveal that galangin formed three H-bonds (Glu291, Leu340 and Ser342) and a π-sigma bond (Arg288) with PPARγ, contributing to the binding affinity and stability of the complex. In vivo studies explore the role of galangin as a propitious PPARγ agonist in mitigating airway inflammation, thereby excluding ligand-independent action of PPARγ. Accordingly, oral administration of galangin significantly ameliorated airway hyperresponsiveness, inflammation and goblet cell hyperplasia by the suppression of IL-4, 5, 13, 17, TNF-α, NO, ROS, EPO, IgE and increase of IFN-γ in ovalbumin-induced allergic asthma model. PPARγ expression (mRNA and protein) studies were performed to elucidate a possible mechanism by which galangin modulates. Furthermore, to eliminate PPARγ-independent effects of galangin, a specific PPARγ antagonist (GW9662) was administered, which dramatically reversed the effects of galangin on PPARγ up-regulation, confirming the pleiotropic role of galangin as a PPARγ agonist in asthma therapeutics. Taken together, our findings communicate that PPARγ plays as a master regulator in the anti-asthmatic action of galangin.

Asiatic acid prevents renal fibrosis in UUO rats via promoting the production of 15d-PGJ2, an endogenous ligand of PPAR-γ

Renal fibrosis is an inevitable outcome of all kinds of progressive chronic kidney disease (CKD). Recently, asiatic acid (AA), a triterpenoid compound from Chinese medicine Centella asiatica, has been found to attenuate renal fibrosis. In the current study, we explored the mechanisms underlying antifibrotic effect of AA on UUO model. SD rats and ICR mice were subjected to unilateral ureteral occlusion (UUO) surgery. Prior the surgery, rats were administered AA (10 mg·kg^-1 per day, ig) for 7 days, whereas the mice received AA (15 mg·kg^-1 per day, ig) for 3 days. UUO group displayed significant degree of renal dysfunction, interstitial fibrosis, oxidative stress, and activation of the TGF-β/Smad and Wnt/β-catenin signaling pathway in the kidney, these pathological changes were greatly ameliorated by pretreatment with AA. In addition, we found that co-treatment with GW9662, a selective PPAR-γ antagonist (1 mg·kg^-1 per day, ip) for 7 days, abolished the protective effects of AA. We further revealed that AA pretreatment did not significantly change the expression levels of PPAR-γ in the kidney, but markedly increase the plasma levels of 15d-PGJ2, an endogenous ligand of PPAR-γ. In UUO mice, pretreatment with 15d-PGJ2 (24 μg·kg^-1 per day, ip, for 7 days) produced similar protective effect as AA. Moreover, AA pretreatment upregulated the expression levels of active, nuclear-localized SREBP-1 (nSREBP-1), whereas fatostatin, a specific inhibitor of SREBP-1, decreased the expression of nSREBP-1, as well as the level of 15d-PGJ2. These results provide new insight into the antifibrotic mechanism of AA and endogenous metabolites might become a new clue for investigation of drug mechanism.

PPARγ-Independent Side Effects of Thiazolidinediones on Mitochondrial Redox State in Rat Isolated Hearts

The effect of anti-diabetic thiazolidinediones (TZDs) on contributing to heart failure and cardiac ischemia/reperfusion (IR) injury is controversial. In this study we investigated the effect of select TZDs on myocardial and mitochondrial function in Brown Norway rat isolated hearts. In a first set of experiments, the TZD rosiglitazone was given acutely before global myocardial IR, and pre- and post-IR function and infarct size were assessed. In a second set of experiments, different concentrations of rosiglitazone and pioglitazone were administered in the presence or absence of the specific PPARγ antagonist GW9662, and their effects on the mitochondrial redox state were measured by online NADH and FAD autofluorescence. The administration of rosiglitazone did not significantly affect myocardial function except for transiently increasing coronary flow, but it increased IR injury compared to the control hearts. Both TZDs resulted in dose-dependent, reversible increases in mitochondrial oxidation which was not attenuated by GW9662. Taken together, these data suggest that TZDs cause excessive mitochondrial uncoupling by a PPARγ-independent mechanism. Acute rosiglitazone administration before IR was associated with enhanced cardiac injury. If translated clinically, susceptible patients on PPARγ agonists may experience enhanced myocardial IR injury by mitochondrial dysfunction.

Involvement of peroxisome proliferator-activated receptor γ in anticonvulsant activity of α-asaronol against pentylenetetrazole-induced seizures in zebrafish

In mammals, peroxisome proliferators activated receptors (PPARs), the nuclear hormone receptors, have been reported to be involved in seizure control. Selective agonists and antagonists of PPARs raise seizure thresholds and suppress seizures, respectively. In this study, we evaluated the anticonvulsant effects of α-asaronol, a metabolic product of α-asarone, on pentylenetetrazole (PTZ)-induced seizures in zebrafish and investigated the underlying mechanisms. As a result, α-asaronol ameliorated seizures with increase of seizure latency, as well as decrease of seizure-like behavior, c-fos expression, and abnormal neuronal discharge in a concentration dependent manner. By comparing gene expression profiles of zebrafish undergoing seizures and α-asaronol pretreated zebrafish, we found that α-asaronol attenuate seizures through increase of PPAR γ expression, while PPAR γ antagonist GW9662 inhibit the anti-seizures actions of α-asaronol. Moreover, molecular docking simulation implied the physical interaction between α-asaronol and PPAR γ. The overall results indicated that the anticonvulsant effects of α-asaronol are regulated through PPAR γ-mediated pathway, which shed light on development of α-asaronol as a potential antiepileptic drug. In addition, it is for first time to report that PPAR γ is associated with seizures in zebrafish, supporting previous evidence that zebrafish is a suitable alternative for studying seizures.

PPARγ inhibition regulates the cell cycle, proliferation and motility of bladder cancer cells

Peroxisome proliferator-activated receptor gamma (PPARγ) is a member of the nuclear receptor family of ligand-activated transcription factors and plays an important role in regulating cell proliferation, inflammation and lipid and glucose homeostasis. Our results revealed that PPARγ was up-regulated in human bladder cancer (BCa) tissues both at transcriptional and translational levels. Moreover, down-regulation of PPARγ mRNA or inhibition of PPARγ function (using GW9662, antagonist of PPARγ) could significantly suppress the proliferation of BCa cells. Furthermore, the cell cycle arrested in G0/G1 phase was also induced by the down-regulated PPARγ possibly through AKT-mediated up-regulation of p21/p27, whereas no significant transformation of apoptosis was observed. In addition, knockdown or inhibition of PPARγ might reduce the invasion and migration of BCa cells by affecting epithelial-mesenchymal transition-related proteins through AKT/GSK3β signalling pathway. Additionally, in vivo studies showed that BCa cell proliferation was significantly suppressed by GW9662. In conclusion, our results indicated that PPARγ might be crucial for BCa tumorigenesis by interfering with the motility and viability of BCa cells.

Angiotensin II type 1 receptor blockade by telmisartan prevents stress-induced impairment of memory via HPA axis deactivation and up-regulation of brain-derived neurotrophic factor gene expression

Physical and psychological aspects of chronic stress continue to be a persistent clinical problem for which new pharmacological treatment strategies are aggressively sought. By the results of our previous work it has been demonstrated that telmisartan (TLM), an angiotensin type 1 receptor (AT1) blocker (ARB) and partial agonist of peroxisome proliferator-activated receptor gamma (PPARγ), alleviates stress-induced cognitive decline. Understanding of mechanistic background of this phenomenon is hampered by both dual binding sites of TLM and limited data on the consequences of central AT1 blockade and PPARγ activation. Therefore, a critical need exists for progress in the characterization of this target for pro-cognitive drug discovery. An unusual ability of novel ARBs to exert various PPARγ binding activities is commonly being viewed as predominant over angiotensin blockade in terms of neuroprotection. Here we aimed to verify this hypothesis using an animal model of chronic psychological stress (Wistar rats restrained 2.5h daily for 21days) with simultaneous oral administration of TLM (1mg/kg), GW9662 - PPARγ receptor antagonist (0.5mg/kg), or both in combination, followed by a battery of behavioral tests (open field, elevated plus maze, inhibitory avoidance - IA, object recognition - OR), quantitative determination of serum corticosterone (CORT) and evaluation of brain-derived neurotrophic factor (BDNF) gene expression in the medial prefrontal cortex (mPFC) and hippocampus (HIP). Stressed animals displayed decreased recall of the IA behavior (p<0.001), decreased OR (p<0.001), substantial CORT increase (p<0.001) and significantly downregulated expression of BDNF in the mPFC (p<0.001), which were attenuated in rats receiving TLM and TLM+GW9662. These data indicate that procognitive effect of ARBs in stressed subjects do not result from PPAR-γ activation, but AT1 blockade and subsequent hypothalamus-pituitary-adrenal axis deactivation associated with changes in primarily cortical gene expression. This study confirms the dual activities of TLM that controls hypertension and cognition through AT1 blockade.

Chrysin, a PPAR-γ agonist improves myocardial injury in diabetic rats through inhibiting AGE-RAGE mediated oxidative stress and inflammation

AGE-RAGE interaction mediated oxidative stress and inflammation is the key mechanism involved in the pathogenesis of cardiovascular disease in diabetes. Inhibition of AGE-RAGE axis by several PPAR-γ agonists has shown positive results in ameliorating cardio-metabolic disease conditions. Chrysin, a natural flavonoid has shown to possess PPAR-γ agonist activity along with antioxidant and anti-inflammatory effect. Therefore, the present study was designed to evaluate the effect of chrysin in isoproterenol-induced myocardial injury in diabetic rats. In male albino Wistar rats, diabetes was induced by single injection of streptozotocin (70 mg/kg, i.p.). After confirmation of the diabetes, rats were treated with vehicle (1.5 mL/kg, p.o.), chrysin (60 mg/kg, p.o.) or PPAR-γ antagonist GW9662 (1 mg/kg, i.p.) for 28 days. Simultaneously, on 27th and 28th day myocardial injury was induced by isoproterenol (85 mg/kg, s.c.). Chrysin significantly ameliorated cardiac dysfunction as reflected by improved MAP, ±LVdP/dtmax and LVEDP in diabetic rats. This improvement was associated with increased PPAR-γ expression and reduced RAGE expression in diabetic rats. Chrysin significantly decreased inflammation through inhibiting NF-κBp65/IKK-β expression and TNF-α level. Additionally, chrysin significantly reduced apoptosis as indicated by augmented Bcl-2 expression and decreased Bax and caspase-3 expressions. Furthermore, chrysin inhibited nitro-oxidative stress by normalizing the alteration in 8-OHdG, GSH, TBARS, NO and CAT levels and Nox4, MnSOD, eNOS and NT expressions. Co-administration of GW9662 significantly blunted the chrysin mediated cardioprotective effect as there was increase in oxidative stress, inflammation and apoptosis markers. Chrysin significantly ameliorated isoproterenol-induced myocardial injury in diabetic rats via PPAR-γ activation and inhibition of AGE-RAGE mediated oxidative stress and inflammation.

PPAR Agonists: I. Role of Receptor Subunits in Alcohol Consumption in Male and Female Mice

BACKGROUND

Several peroxisome proliferator-activated receptor (PPAR) agonists reduce voluntary alcohol consumption in rodent models, and evidence suggests that PPARα and γ subunits play an important role in this effect. To define the subunit dependence of this action, we tested selective PPARα and α/γ agonists and antagonists in addition to null mutant mice lacking PPARα.

METHODS

The effects of fenofibrate (PPARα agonist) and tesaglitazar (PPARα/γ agonist) on continuous and intermittent 2-bottle choice drinking tests were examined in male and female wild-type mice and in male mice lacking PPARα. We compared the ability of MK886 (PPARα antagonist) and GW9662 (PPARγ antagonist) to inhibit the effects of fenofibrate and tesaglitazar in wild-type mice. The estrogen receptor antagonist, tamoxifen, can inhibit PPARγ-dependent transcription and was also studied in male and female mice.

RESULTS

Fenofibrate and tesaglitazar reduced ethanol (EtOH) consumption and preference in wild-type mice, but these effects were not observed in mice lacking PPARα. MK886 inhibited the action of fenofibrate, but not tesaglitazer, while GW9662 did not inhibit either agonist. The PPAR agonists were more effective in male mice compared to females, and drinking in the continuous 2-bottle choice test was more sensitive to fenofibrate and tesaglitazar compared to drinking in the intermittent access test. Tamoxifen also reduced EtOH consumption in male mice and this action was inhibited by GW9662, but not MK886, suggesting that it acts by activation of PPARγ.

CONCLUSIONS

Our study using selective PPAR agonists, antagonists, and null mutant mice indicates a key role for PPARα in mediating reduced EtOH consumption by fenofibrate and tesaglitazar.

Cardiac differentiation of mouse embryonic stem cells is influenced by a PPAR γ/PGC-1α-FNDC5 pathway during the stage of cardiac precursor cell formation

Peroxisome proliferator-activated receptor (PPAR) γ co-activator 1α (PGC-1α) up-regulation induces FNDC5 expression in muscle and consequently causes browning of white adipose tissue (WAT). In addition to skeletal muscle, FNDC5 is mainly expressed in heart and brain tissues. Here, we demonstrate that FNDC5 expression increased during the process of cardiac differentiation of mouse embryonic stem cells (mESCs) similar to PGC-1α and PPARα. To testify the correlation between PGC-1α and FNDC5 in cardiac cell differentiation of mESCs, we utilized specific PPARγ agonist and antagonist in two stages of cardiac differentiation, during and post-cardiac precursor cells (CPCs) formation. Our results indicated that a reduction in PGC-1α expression, via treatment with GW9662 during CPCs formation stage, down-regulated FNDC5 transcript levels as well as mitochondrial markers which negatively influenced on the whole process of cardiac differentiation efficiency. On the other hand, increase PGC-1α expression during CPCs formation stage via rosiglitazone treatment increase FNDC5 and mitochondrial markers transcript levels which enhanced cardiac differentiation efficiency. Importantly, such alteration in PGC-1α expression at post-CPCs formation stage did not affect overall cardiac differentiation rate as expression of FNDC5 and mitochondrial markers were not significantly changed. We concluded that PPARγ agonist and antagonist induced up and down-regulation of PGC-1α and subsequently modulated the process of CPCs formation through an alteration in FNDC5 and mitochondrial markers expression.

PPARγ-dependent anti-tumor and immunomodulatory actions of pioglitazone

Peroxisome proliferator-activated receptor-γ (PPARγ) has been reported to play important roles in carcinogenesis. The current study was carried out to assess the possible anti-tumor effects of pioglitazone (PIO), a PPARγ agonist, in a mouse mammary carcinoma model, i.e. a solid Ehrlich carcinoma (SEC). Effects of PIO on tumor-induced immune dysfunction, and the possibility that PIO may modulate the anti-tumor and immunomodulatory effects of doxorubicin (DOX) were also studied. The effects in tumor-bearing hosts of several doses of PIO (100 mg/kg, per os), with and without the added presence of DOX (2 mg/kg, IP), was investigated in vivo; end-points evaluated included assessment of tumor volume, splenic lymphocyte profiles/functionality, tumor necrosis factor (TNF)-α content, as well as apoptosis and expression of nuclear factor-κB (NF-κB) among the tumor cells. The data indicate that PIO induced significant anti-tumor activity against the SEC. PIO treatments also significantly mitigated both tumor- and doxorubicin-induced declines in immune parameters assessed here. Moreover, PIO led to decreased NF-κB nuclear expression, and, in doing so, appeared to chemo-sensitize these tumor cells to DOX-induced apoptosis. All pioglitazone-studied effects were antagonized by GW9662, a selective PPARγ antagonist.

Ethanol intake and ethanol-conditioned place preference are reduced in mice treated with the bioflavonoid agent naringin

Recently, PPAR-γ activation has emerged as a potential treatment for alcoholism. However, the adverse effects of synthetic PPAR-γ activators, despite being effective drugs, prompted the need for novel PPAR-γ agonists that retain efficacy and potency with a lower potential of side effects. Hence, naringin, a bioflavonoid isolated from citrus fruits and recently identified as a natural ligand of PPAR-γ, has begun to be evaluated for treatment of alcoholism. It is well known to possess several therapeutic benefits in addition to its anti-anxiety and antidepressant properties. In the present study, we assessed whether naringin treatment possesses anti-ethanol reward properties in C57BL/6 mice. We used the two-bottle choice drinking paradigm and ethanol-induced conditioned place preference (CPP) to examine the effect of naringin treatment on ethanol drinking. Results have shown that, compared with vehicle, naringin (10-100 mg/kg) significantly and dose-dependently decreased voluntary ethanol intake and preference in a two-bottle choice drinking paradigm [3-15% (v/v) escalating over 2 weeks], with no significant effect observed on saccharin [0.02-0.08% (w/v)] or on quinine [15-60 μM (w/v)] intake. In addition, there was no significant difference in blood ethanol concentration (BEC) between groups following naringin administration of 3 g of ethanol/kg body weight. Interestingly, when mice were treated with vehicle or naringin (30 mg/kg) before injection of ethanol (1.5 g/kg) during conditioning days, naringin inhibited the acquisition of ethanol-CPP. More importantly, these effects were significantly attenuated when mice were pre-injected with the peroxisome proliferator-activated receptor-γ (PPAR-γ) antagonist, GW9662. Taken together, the present findings are the first to implicate naringin and PPAR-γ receptors in the behavioral and reward-related effects of ethanol and raise the question of whether specific drugs that target PPAR-γ receptors could potentially reduce excessive ethanol consumption and preference.

The hypolipidemic effect of cilostazol can be mediated by regulation of hepatic low-density lipoprotein receptor-related protein 1 (LRP1) expression

OBJECTIVES

Cilostazol, a selective phosphodiesterase 3 (PDE3) inhibitor, is a vasodilator and an anti-thrombotic agent. The mechanism whereby cilostazol reduces plasma triglyceride is not completely understood. Here we investigated the effect of cilostazol on a remnant lipoprotein receptor, low-density lipoprotein receptor-related protein 1 (LRP1), which has been reported to play an essential role in clearance of circulating triglyceride in the liver.

MATERIALS/METHODS

Total cellular expression, and functional and transcriptional regulation of LRP1 were analyzed in human hepatocarcinoma cell lines incubated with cilostazol. Also, C57BL/6 mice were subjected to high-fat diet (60% kcal) and cilostazol (30 mg/kg) treatment for 10 weeks.

RESULTS

Cilostazol increased both mRNA and protein expression of LRP1 in HepG2 and Hep3B cells. In addition, enhanced transcriptional activity of the LRP1 promoter containing a peroxisome proliferator response element (PPRE) was observed after cilostazol exposure. Cilostazol treatment enhanced the uptake of lipidated apoE3, and this effect was abolished when LRP1 was silenced by siRNA knockdown. High-fat diet induced hyperglycemia with high level of plasma triglycerides, and reduced hepatic LRP1 expression in mice. Treatment with cilostazol for the same period of time, however, successfully prevented this down-regulation of LRP1 expression and reduced plasma triglycerides.

CONCLUSION

Taken together, our results demonstrated that cilostazol enhances LRP1 expression in liver by activating PPARγ through the PPRE in the LRP1 promoter. Increased hepatic LRP1 may be essential for the reduction of circulating triglycerides brought about by cilostazol.

Telmisartan counteracts TGF-β1 induced epithelial-to-mesenchymal transition via PPAR-γ in human proximal tubule epithelial cells

Chronic renal failure (CRF) mainly results from kidney fibrosis. Epithelial-to-mesenchymal transition (EMT) occurs in stressed tubular epithelial cells and contributes to renal fibrosis. Transforming growth factor-β1 (TGF-β1) has been shown to initiate and complete the whole EMT process. Peroxisome proliferators-activated receptor-γ (PPAR-γ) exerts anti-inflammatory, anti-fibrotic and vaculo-protective effects on different renal diseases. Telmisartan is a member of angiotensin II (Ang II) receptor blocker (ARB) family. Recent studies show that Telmisartan has a partial agonistic effect on PPAR-γ. Therefore, we tested the hypothesis that Telmisartan reverses the progression of induced EMT by TGF-β1 in cultured human renal proximal tubular epithelial (HK-2) cells. Cultured HK-2 cells were treated with TGF-β1 (3 ng/ml), a combination of TGF-β1 and Telmisartan (10-200 umol/L) and a combination of TGF-β1, Telmisartan and GW9662, a PPAR-γ antagonist for 48 hours. EMT was determined by quantitative real-time PCR analysis of E-cadherin (E-cad), Connective Tissue Growth Factor (CTGF) and PPAR-γ transcript expression and immunocytochemical analysis of E-cad, α-Smooth Muscle Actin (α-SMA) and PPAR-γ protein expression. TGF-β1 induced phenotypic EMT in cultured HK-2 cell line via significantly reduced E-cad expression and significantly increased CTGF, α-SMA expression in association with the loss of epithelial morphology. Telmisartan reversed all EMT markers in a dose-dependent manner which was inhibited by PPAR antagonist GW9662. In the present study, it was suggested that Telmisartan attenuated TGF-β1 induced EMT by agonistic activation of PPAR-γ.