PPARγ Antagonist Research Articles

Luteolin ameliorates chronic stress-induced depressive-like behaviors in mice by promoting the Arginase-1+ microglial phenotype via a PPARγ-dependent mechanism.

Accumulating evidence shows that neuroinflammation substantially contributes to the pathology of depression, a severe psychiatric disease with an increasing prevalence worldwide. Although modulating microglial phenotypes is recognized as a promising therapeutic strategy, effective treatments are still lacking. Previous studies have shown that luteolin (LUT) has anti-inflammatory effects and confers benefits on chronic stress-induced depression. In this study, we investigated the molecular mechanisms by which LUT regulates the functional phenotypes of microglia in mice with depressive-like behaviors. Mice were exposed to chronic restraint stress (CRS) for 7 weeks, and were administered LUT (10, 30, 40 mg· kg-1 ·day-1, i.g.) in the last 4 weeks. We showed that LUT administration significantly ameliorated depressive-like behaviors and decreased hippocampal inflammation. LUT administration induced pro-inflammatory microglia to undergo anti-inflammatory arginase (Arg)-1+ phenotypic polarization, which was associated with its antidepressant effects. Furthermore, we showed that LUT concentration-dependently increased the expression of PPARγ in LPS + ATP-treated microglia and the hippocampus of CRS-exposed mice, promoting the subsequent inhibition of the NLRP3 inflammasome. Molecular dynamics (MD) simulation and microscale thermophoresis (MST) analysis confirmed a direct interaction between LUT and peroxisome proliferator-activated receptor gamma (PPARγ). By using the PPARγ antagonist GW9662, we demonstrated that LUT-driven protection, both in vivo and in vitro, resulted from targeting PPARγ. First, LUT-induced Arg-1+ microglia were no longer detected when PPARγ was blocked. Next, LUT-mediated inhibition of the NLRP3 inflammasome and downregulation of pro-inflammatory cytokine production were reversed by the inhibition of PPARγ. Finally, the protective effects of LUT, which attenuated the microglial engulfment of synapses and prevented apparent synapse loss in the hippocampus of CRS-exposed mice, were eliminated by blocking PPARγ. In conclusion, this study showed that LUT ameliorates CRS-induced depressive-like behaviors by promoting the Arg-1+ microglial phenotype through a PPARγ-dependent mechanism, thereby alleviating microglial pro-inflammatory responses and reversing microglial phagocytosis-mediated synapse loss.

FGF21 Alleviates Hypoxic-Ischemic White Matter Injury in Neonatal Mice by Mediating Inflammation and Oxidative Stress Through PPAR-γ Signaling Pathway.

White matter injury (WMI), the most common type of brain damage in infants born preterm, is characterized by failure in oligodendrocyte progenitor cell maturation and myelination, thereby contributing to long-term neurological impairments. Regrettably, effective therapies for promoting remyelination and improving function are currently lacking for this growing population affected by WMI. Recombinant human fibroblast growth factor (rhFGF) 21 modulated microglial activation and then ameliorated brain damage and improved neurological deficits in several central nervous system diseases. However, the effects of rhFGF21 treatment on WMI in preterm infants remain uncertain. In this study, we established an in vivo mouse model of cerebral hypoxia-ischemia (HI)-induced brain WMI and an in vitro model using oxygen-glucose deprivation (OGD)-treated HMC3 cells to investigate the neuroprotective effects of rhFGF21 against WMI and elucidated the potential mechanism. Our findings demonstrated that administration of rhFGF21 significantly ameliorated the retardation of oligodendrocyte differentiation, promoted myelination, and mitigated axonal deficits, synaptic loss, and GFAP scarring, thereby improving lifelong cognitive and neurobehavioral dysfunction associated with WMI. Moreover, rhFGF21 modulated microglial polarization, promoted a shift from the M1 to the M2 microglial phenotype, and suppressed microglial activation, thus ameliorating inflammatory response and oxidative stress. Additionally, rhFGF21 treatment significantly inhibited the HMGB1/NF-κB pathway linked to inflammation, and activated the NRF2 pathway associated with oxidative stress through the upregulation of PPAR-γ. Importantly, the beneficial effects of rhFGF21 on HI-induced WMI and microglial activation were dramatically inhibited by PPAR-γ antagonist and its siRNA. Our findings provide compelling evidence that rhFGF21 treatment mitigated the inflammatory response and oxidative stress through the modulation of microglial polarization via the PPAR-γ-mediated HMGB1/NF-κB pathway and the NRF2 pathway, respectively, contributes to neuroprotection and the amelioration of WMI in neonatal mice. Thus, rhFGF21 represents a promising therapeutic agent for the treatment of neonatal WMI.

Odoratin balances ROS/NO through EZH2/PPARγ signalling to improve myocardial fibrosis.

Myocardial fibrosis is a critical concern in clinical medicine. This study explores the potential of odoratin as a treatment for myocardial fibrosis and investigates its underlying mechanisms. In vitro experiments involved stimulating primary mouse cardiomyocytes with TGF-β1, followed by odoratin treatment, to assess levels of reactive oxygen species (ROS) and nitric oxide (NO). In vivo, a mouse model of myocardial fibrosis was established using abdominal aortic constriction (AAC) and treated with odoratin. ROS and NO levels in myocardial tissue were then evaluated. Immunofluorescence and Western blotting analysis showed that odoratin reduced excess ROS, enhanced NO production and decreased fibrosis-related protein expression in vitro. In vivo, odoratin significantly improved cardiac function, reduced ROS, increased NO levels and mitigated fibrosis in AAC-induced mice. Both in vitro and in vivo, odoratin inhibited the expression of NADPH oxidase 4 and EZH2, while promoting the expression of phosphorylated endothelial nitric oxide synthase (p-eNOS) and PPARγ. The anti-fibrotic effects of odoratin were reversed by PPARγ antagonism, and EZH2 overexpression diminished PPARγ activation by odoratin. These findings suggest that odoratin may combat myocardial fibrosis by balancing ROS and NO through PPARγ activation, with EZH2 inhibition likely playing a key regulatory role.

LncRNA Snhg3 aggravates hepatic steatosis via PPARγ signaling.

LncRNAs are involved in modulating the individual risk and the severity of progression in metabolic dysfunction-associated fatty liver disease (MASLD), but their precise roles remain largely unknown. This study aimed to investigate the role of lncRNA Snhg3 in the development and progression of MASLD, along with the underlying mechanisms. The result showed that Snhg3 was significantly downregulated in the liver of high-fat diet-induced obesity (DIO) mice. Notably, palmitic acid promoted the expression of Snhg3 and overexpression of Snhg3 increased lipid accumulation in primary hepatocytes. Furthermore, hepatocyte-specific Snhg3 deficiency decreased body and liver weight, alleviated hepatic steatosis and promoted hepatic fatty acid metabolism in DIO mice, whereas overexpression induced the opposite effect. Mechanistically, Snhg3 promoted the expression, stability and nuclear localization of SND1 protein via interacting with SND1, thereby inducing K63-linked ubiquitination modification of SND1. Moreover, Snhg3 decreased the H3K27me3 level and induced SND1-mediated chromatin loose remodeling, thus reducing H3K27me3 enrichment at the Pparg promoter and enhancing PPARγ expression. The administration of PPARγ antagonist T0070907 improved Snhg3-aggravated hepatic steatosis. Our study revealed a new signaling pathway, Snhg3/SND1/H3K27me3/PPARγ, responsible for mice MASLD and indicates that lncRNA-mediated epigenetic modification has a crucial role in the pathology of MASLD.

LncRNA Snhg3 aggravates hepatic steatosis via PPARγ signaling

LncRNAs are involved in modulating the individual risk and the severity of progression in metabolic dysfunction-associated fatty liver disease (MASLD), but their precise roles remain largely unknown. This study aimed to investigate the role of lncRNA Snhg3 in the development and progression of MASLD, along with the underlying mechanisms. The result showed that Snhg3 was significantly downregulated in the liver of high-fat diet-induced obesity (DIO) mice. Notably, palmitic acid promoted the expression of Snhg3 and overexpression of Snhg3 increased lipid accumulation in primary hepatocytes. Furthermore, hepatocyte-specific Snhg3 deficiency decreased body and liver weight, alleviated hepatic steatosis and promoted hepatic fatty acid metabolism in DIO mice, whereas overexpression induced the opposite effect. Mechanistically, Snhg3 promoted the expression, stability and nuclear localization of SND1 protein via interacting with SND1, thereby inducing K63-linked ubiquitination modification of SND1. Moreover, Snhg3 decreased the H3K27me3 level and induced SND1-mediated chromatin loose remodeling, thus reducing H3K27me3 enrichment at the Pparg promoter and enhancing PPARγ expression. The administration of PPARγ antagonist T0070907 improved Snhg3-aggravated hepatic steatosis. Our study revealed a new signaling pathway, Snhg3/SND1/H3K27me3/PPARγ, responsible for mice MASLD and indicates that lncRNA-mediated epigenetic modification has a crucial role in the pathology of MASLD.

13-cis Retinoic Acid-Mediated Modulation of Human Meibomian Gland Epithelial Cells Development: Implications for In Vitro Modeling of Meibomian Gland Dysfunction.

Purpose: This study aimed to investigate the effect of 13-cis retinoic acid (13-cis RA) on human meibomian gland epithelial cells (HMGECs) and explore the potential of using this experimental model as an in vitro approach for studying meibomian gland dysfunction (MGD). Methods: First, HMGECs were cultured with 13-cis RA at different doses and times, and cell viability and proliferation rates were assessed to determine the appropriate stimulation concentration and time. Subsequently, during the proliferation stage, the expression of proliferation, inflammation, and oxidative stress genes and their products were evaluated. The meibum synthesis capacity was determined during the differentiation stage. Additionally, the peroxisome proliferator-activated receptor gamma (PPARγ) antagonist GW9662 was used as a control to assess the impact of 13-cis RA on PPARγ. Results: 13-cis RA significantly inhibited cell viability and proliferation in a time-dose response manner. Under the stimulation of 2 and 5 μM for 48 h during the proliferation stage, a significant decrease was observed in the expression of cell proliferation markers Ki67, antioxidant SOD-2, and Nrf-2. However, the expression of the pro-inflammatory factors IL-1β, IL-8, MMP9, and oxidative stress markers NOX-4 and reactive oxygen species increased. During the differentiation stage, it suppressed meibum synthesis and the expression of meibocyte differentiation-related proteins adipose differentiation-associated protein 4 (ADFP4), elongation of very long chain fatty acid protein 4 (ELOVL4), sterol regulatory element-binding protein 2 (SREBP-2), and PPARγ. Conclusion: 13-cis RA inhibited cell viability, promoted inflammation and oxidative stress, and suppressed meibum synthesis through the PPARγ pathway. Our study shed light on the effect of 13-cis RA on HMGECs and provided a promising direction for studying MGD in vitro.

Key role of PPAR-γ-mediated suppression of the NFκB signaling pathway in rutin's antidepressant effect

BackgroundDepression is a chronic and recurrent disorder with an unknown etiology. Efficacious antidepressant treatments with minimal side effects are urgently needed. Neuroinflammation may contribute to depression, as anti-inflammatory drugs have been shown to alleviate depressive symptoms in clinical practice. Rutin, a naturally occurring flavonoid derived from plants, is abundant in many antidepressant herbs, including Hemerocallis citrina Baroni. Historical Chinese medical texts, including the renowned Compendium of Materia Medica, document H. citrina Baroni as possessing antidepressant properties. Rutin, one of its primary active constituents, is recognized for its anti-inflammatory effects. Despite this, little is known about its specific target and mechanism. MethodsIn the present study, molecular docking, and surface plasmon resonance imaging (SPRi) analysis were used to identify the special targets of rutin. Meanwhile, the potential antidepressant effects were evaluated in the chronic social defeat stress (CSDS) paradigm, an animal model of depression. Then, Western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), Co-immunoprecipitation (Co-IP) as well as antagonists of PPAR-γ were utilized to investigate the mechanism underlying the antidepressant effect of rutin. ResultsBoth molecular docking and SPRi analysis showed high docking scores and interactions between rutin and PPAR-γ. In vivo, rutin promoted the nuclear translocation of PPAR-γ in the hippocampus of mice, inhibited NFκB-mediated inflammatory pathways, and subsequently reduced the expression of pro-inflammatory factors (e.g., iNOS, IL-6), aligning with an antidepressant effect. However, this therapeutic effect was attenuated by GW9662, a specific antagonist of PPAR-γ. ConclusionAs a result of activating PPAR-γ and inhibiting NFκB pathway activation, rutin reduces neuroinflammation and exhibits an antidepressant effect. These findings shed light on the antidepressant mechanism of rutin and could be valuable for the development of new antidepressants.

Qin-Yu-Qing-Chang decoction reshapes colonic metabolism by activating PPAR-γ signaling to inhibit facultative anaerobes against DSS-induced colitis

BackgroundQin-Yu-Qing-Chang decoction (QYQC), an herbal formula from China, is extensively employed to manage ulcerative colitis (UC) and exhibits potential benefits for colonic function. Nevertheless, the fundamental molecular mechanisms of QYQC remain largely uncharted.MethodsThe primary constituents of QYQC were determined utilizing UHPLC-MS/MS analysis and the effectiveness of QYQC was assessed in a mouse model of colitis induced by dextran sulfate sodium. Evaluations of colon inflammatory responses and mucosal barrier function were thoroughly assessed. RNA sequencing, molecular docking, colonic energy metabolism, and 16S rRNA sequencing analysis were applied to uncover the complex mechanisms of QYQC in treating UC. Detect the signal transduction of the peroxisome proliferator-activated receptor-γ (PPAR-γ) both in the nucleus and cytoplasm. Furthermore, a PPAR-γ antagonist was strategically utilized to confirm the functional targets that QYQC exerts.ResultsUtilizing UHPLC-MS/MS, the principal constituents of the nine traditional Chinese medicinal herbs comprising QYQC were systematically identified. QYQC treatment substantially ameliorated colitis in mice, as evidenced by the improvement in symptoms and the reduction in colonic pathological injuries. Besides, QYQC treatment mitigated the inflammatory response and improved mucosal barrier function. Furthermore, QYQC enhanced the mitochondria citrate cycle (TCA cycle) by triggering PPAR-γ signaling and increasing the proportion of PPAR-γ entering the nucleus. This prevented the unconstrained expansion of facultative anaerobes, particularly pathogenic Escherichia coli (E. coli, family Enterobacteriaceae) and thus improved colitis. Results of molecular docking indicated that the representative chemical components of QYQC including Baicalin, Paeoniflorin, Mollugin, and Imperatorin bound well with PPAR-γ. The impact of QYQC on colitis was diminished in the presence of a PPAR-γ antagonist.ConclusionsIn summary, QYQC ameliorates UC by activating PPAR-γ signaling and increasing the proportion of PPAR-γ entering the nucleus, which enhances the energy metabolism of intestinal epithelial cells and thereby preventing the uncontrolled proliferation of facultative anaerobes.

Interplay between bone marrow adiposity and bone resorption in RANKL-mediated modelled osteoporosis.

Bone marrow adipose tissue (BMAT) accrues in osteoporosis, whereas its contribution to the progression of bone resorption remains insufficiently understood. To understand the mechanisms that promote BMAT expansion in osteoporosis, in the present study, we performed extensive analysis of the spatiotemporal pattern of BMAT expansion during the progression of bone resorption in TgRANKL transgenic mouse models of osteoporosis expressing human RANKL (receptor activator of nuclear factor-κB ligand). Our results showed that TgRANKL mice of both sexes developed dramatically increased BMAT expansion compared to wild-type (WT) littermates, that was analogous to the levels of RANKL expression and the severity of the bone loss phenotype. BMAT was formed at close proximity to areas undergoing active bone remodelling and bone resorption, whereas bone resorption preceded BMAT development. Expression analysis in bone fractions demonstrated that BMAT constitutes a major source for RANKL production. Ex vivo analysis of isolated bone marrow stromal cells from TgRANKL mice showed an increased adipogenic differentiation capacity compared to WT, while osteoclast supernatants further exaggerated adipogenesis, supporting a critical role of the osteoclast-derived secretome in the differentiation of bone marrow adipocytes. Furthermore, the effectiveness of an antiosteoporosis treatment in BMAT development was investigated upon treatment of TgRANKL models with the bisphosphonate alendronate. Notably, alendronate effectively improved bone mass and attenuated BMAT expansion, indicating a possible involvement of osteoclasts and bone resorption in BMAT development. On the contrary, inhibition of BMAT with PPARγ antagonists (GW9662 or BADGE) effectively ameliorated BMAT expansion but failed to reverse the osteoporotic phenotype of TgRANKL mice. Overall, our data demonstrate that TgRANKL mice constitute unique genetic mouse models for investigating the pathogenic mechanisms that regulate the development and expansion of BMAT in osteolytic diseases.

Erythropoietin regulates osteoclast formation via up-regulating PPARγ expression

Erythropoietin (EPO), expressed in red blood progenitor cells, primarily regulates erythropoiesis by binding to its receptor. Besides anemia, recent studies have identified new therapeutic indications for EPO that are not connected to red blood cell formation. Elevated EPO levels harm bone homeostasis in adult organisms and are associated with increased osteoclast; however, the underlying molecular mechanisms remain unclear. This study demonstrated that EPO enhanced osteoclast differentiation and bone resorption in vitro. We showed that EPO promoted osteoclast formation by up-regulating PPARγ expression through activating the Jak2/ERK signaling pathway. Consistently, PPARγ antagonists rescued the hyperactivation of osteoclasts due to EPO, while PPARγ agonists reversed the EMP9-mediated decrease in osteoclast differentiation. Further, exposing female mice to EPO for two months led to a decrease in bone mass and increased osteoclast numbers. The present results suggested that EPO promotes osteoclastogenesis by regulating the Jak2/ERK/ PPARγ signaling pathway. From a clinical perspective, the risk of compromised bone health should be considered when using EPO to treat anemia in post-operative patients with intertrochanteric fractures of the femur, as it could significantly impact the patient’s recovery and quality of life.

Discovery of Novel Neo-Clerodane Derivatives as Potent Dual-Functional Antiosteoporosis Agents through Targeting Peroxisome Proliferator-Activated Receptor-γ.

A library of 31 natural neo-clerodanes isolated from Ajuga decumbens was assayed for antiosteoporosis. This results in 18 neo-clerodane osteoclastogenesis inhibitors, and compound 3 prevents bone loss in vivo. Further mechanistic studies demonstrated that these compounds inhibit osteoporosis by antagonizing peroxisome proliferator-activated receptor-γ (PPARγ). We designed and synthesized 17 compounds by chemically modifying the natural neo-clerodane 19 (highly potent and the major composition of A. decumbens extract) by means of structure-based drug design techniques. Among these neo-clerodane derivatives, compound 34 is the most potent osteoporosis inhibitor with a 46-fold improvement in inhibiting osteoclastogenesis (IC50 = 0.042 vs 1.92 μM), 11-fold increased activity in PPARγ antagonism (EC50 = 0.75 vs 8.35 μM), 66-fold enhancement in receptor affinity (KD = 0.27 vs 17.7 μM), and enhanced osteogenic promotion compared to 19. This underscores the potential of neo-clerodane diterpenoids as promising leads for osteoporosis treatment by targeting PPARγ.

Decoration of GW9662 scaffold with a fragment-like hit via copper-catalyzed azide-alkyne cycloaddition reaction into peroxisome proliferator-activated receptor γ agonists

PPARγ is a member of nuclear receptor superfamily, which possesses a large Y-shaped cavity in the ligand-binding pocket. GW9662 is a well-known PPARγ antagonist which covalently reacts with the Cys285 residue via nucleophilic substitution. In contrast to its irreversibility, the ability of GW9662 to prevent other ligands from accessing the ligand-binding pocket is partly defective. By focusing on this incompleteness, we develop an integrated approach to create a new PPARγ agonist by using a structure of GW9662 as a scaffold for linking with a fragment compound. A screening of 1,040 compounds identified a partner ligand which synergistically activates PPARγ transcription in combination with GW9662. We introduced an azido or alkyne group to GW9662 or the identified fragment hit, respectively, and then connected the two structures via copper-catalyzed azide-alkyne cycloaddition. A coupling reaction provided a series of hybrid structure with triazole linker, among which the compounds with a bent configuration function as a partial PPARγ agonist. These results highlight a potential utility of GW9662 for the decoration with a fragment compound to develop a covalent agonist for PPARγ activation.

Pioglitazone alleviates lacrimal gland impairments induced by high-fat diet by suppressing M1 polarization

A high-fat diet (HFD) contributes to the pathogenesis of various inflammatory and metabolic diseases. Previous research confirms that under HFD conditions, the extraorbital lacrimal glands (ELGs) can be impaired, with significant infiltration of pro-inflammatory macrophages (Mps). However, the relationship between HFD and Mps polarization in the ELGs remains unexplored. We first identified and validated the differential expression of PPAR-γ in murine ELGs fed ND and HFD through RNA sequencing. Tear secretion was measured using the Schirmer test. Lipid droplet deposition within the ELGs was observed through Oil Red O staining and transmission electron microscopy. Mps phenotypes were determined through quantitative RT-PCR, immunofluorescence, and flow cytometric analysis. An in vitro high-fat culture system for Mps was established using palmitic acid (PA), with supernatants collected for co-culture with lacrimal gland acinar cells. Gene expression was determined through ELISA, immunofluorescence, immunohistochemistry, quantitative RT-PCR, and Western blot analysis. Pioglitazone reduced M1-predominant infiltration induced by HFD by increasing PPAR-γ levels in ELGs, thereby alleviating lipid deposition and enhancing tear secretion. In vitro tests indicated that PPAR-γ agonist shifted Mps from M1-predominant to M2-predominant phenotype in PA-induced Mps, reducing lipid synthesis in LGACs and promoting lipid catabolism, thus alleviating lipid metabolic disorders within ELGs. Conversely, the PPAR-γ antagonist induced opposite effects. In summary, the lacrimal gland is highly sensitive to high-fat and lipid metabolic disorders. Downregulation of PPAR-γ expression in ELGs induces Mps polarization toward predominantly M1 phenotype, leading to lipid metabolic disorder and inflammatory responses via the NF-κb/ERK/JNK/P38 pathway.

Upregulation of peroxisome proliferator-activated receptor γ with resorcinol alleviates reactive oxygen species generation and lipid accumulation in neuropathic lysosomal storage diseases

Neuropathic lysosomal storage diseases (NLSDs), including ceroid lipofuscinosis neuronal 3 (CLN3) disease and Gaucher disease type 2 (GD2), are typically present in adolescents; however, there are no approved therapies. CLN3 disease is the most common of the 13 types of neuronal ceroid lipofuscinosis, and Gaucher disease is the most common type of lysosomal storage disease. These NLSDs share oxidative stress and lysosomal dysfunction with Parkinson’s disease. In this study, we used patient-derived cells (PDCs) and resorcinol to develop a therapeutic agent based on peroxisome proliferator-activated receptor γ (PPARγ) activation. PPARγ is a major regulator of autophagy and reactive oxygen species (ROS). Resorcinol, a polyphenolic compound, has been reported to exhibit PPARγ agonistic potential. Protein levels were analyzed by immunoblotting and immunofluorescence microscopy. Changes in cellular metabolism, including ROS levels, lipid droplet content, and lysosomal activity, were measured by flow cytometry. Resorcinol reduced ROS levels by suppressing hypoxia-inducible factor 1α levels in CLN3-PDCs. Resorcinol upregulated autophagy and reduced lipid accumulation in CLN3-PDCs; however, these effects were abolished by autophagy inhibitors. Resorcinol increased nuclear PPARγ levels in CLN3-PDCs, and PPARγ antagonists abolished the therapeutic effects of resorcinol. Moreover, Resorcinol upregulated nuclear PPARγ levels and lysosomal activity in GD2-PDCs, and reduced lipid accumulation and ROS levels. In summary, resorcinol alleviated the shared pathogenesis of CLN3 disease and GD2 through PPARγ upregulation. These findings suggest that resorcinol is a potential therapeutic candidate for alleviating NLSD progression.

Triclosan affects steroidogenesis in mouse primary astrocytes in vitro with engagement of Sirtuin 1 and 3

Triclosan (TCS) is a widely used antimicrobial, antifungal, and antiviral agent. To date, it has been reported that TCS can enter the human body and disrupt hormonal homeostasis. Therefore, the aim of our paper was to evaluate the impact of TCS on astrocytes, i.e. a crucial population of cells responsible for steroid hormone production. Our data showed that, in mouse primary astrocyte cultures, TCS can act as an endocrine disrupting chemical through destabilization of the production or secretion of progesterone (P4), testosterone (T), and estradiol (E2). TCS affects the mRNA expression of enzymes involved in neurosteroidogenesis, such as Cyp17a1, 17β-Hsd, and Cyp19a1. Our data showed that a partial PPARγ agonist (honokiol) prevented changes in Cyp17a1 mRNA expression caused by TCS. Similarly, honokiol inhibited TCS-stimulated P4 release. However, rosiglitazone (classic PPARγ agonist) or GW9662 (PPARγ antagonist) had a much stronger effect. Therefore, we believe that the changes observed in the P4, T, and E2 levels are a result of dysregulation of the activity of the aforementioned enzymes, whose expression can be affected by TCS through a Pparγ-dependent pathway. TCS was found to decrease the aryl hydrocarbon receptor (AhR) and Sirtuin 3 protein levels, which may be the result of the activation of the these proteins. Since our study showed dysregulation of the production or secretion of neurosteroids in astrocytes, it can be concluded that TCS reaching the brain may contribute to the development of neurodegenerative diseases in which an abnormal amount of neurosteroids is observed.

PPARγ activation ameliorates PM2.5-induced renal tubular injury by inhibiting ferroptosis and epithelial–mesenchymal transition

Exposure to fine particulate matter (PM2.5) has been associated with the development and progression of renal disease. Peroxisome proliferator-activated receptor gamma (PPARγ), a key transcription factor involved in inflammation as well as lipid and glucose metabolism, helps maintain the integrity of tubular epithelial cells. However, the precise role of PPARγ in PM2.5-induced tubular injury remains unclear. In this study, we investigated the regulatory effects of PPARγ on PM2.5-induced ferroptotic stress and epithelial–mesenchymal transition (EMT) in tubular (HK-2) cells. We found that downregulation of PPARγ expression was correlated with EMT in PM2.5-exposed cells. Pretreatment with the PPARγ agonist 15d-PGJ2 protected the cells from EMT by reducing ferroptotic stress, whereas that with the PPARγ antagonist GW9662 promoted EMT. Furthermore, pretreatment with ferrostatin-1 (Fer-1) significantly prevented PM2.5-induced EMT and downregulation of PPARγ expression. Notably, overexpression of PPARγ blocked PM2.5-induced downregulation of E-cadherin and GPX4 expression and upregulation of α-SMA expression. This study highlights the complex associations of PPARγ with ferroptosis and EMT in PM2.5-exposed tubular cells. Our findings suggest that PPARγ activation confers protection against PM2.5-induced renal injury.

Anti-inflammatory effect of covalent PPARγ ligands that have a hybrid structure of GW9662 and a food-derived cinnamic acid derivative

ABSTRACT Peroxisome proliferator-activated receptor γ (PPARγ) belongs to the nuclear receptor superfamily and is involved in the inflammatory process. Previously, we synthesized the ligands of PPARγ that possess the hybrid structure of a food-derived cinnamic acid derivative (CA) and GW9662, an irreversible PPARγ antagonist. These ligands activate the transcription of PPARγ through the covalent bond formation with the Cys285 residue of PPARγ, whereas their anti-inflammatory effect has not been examined yet. Here, we show the anti-inflammatory effect of the covalent PPARγ ligands in RAW264 cells, murine macrophage-like cells. GW9662 suppressed the production of nitric oxide (NO) stimulated by lipopolysaccharide and exerted a synergistic effect in combination with CA. The compounds bearing their hybrid structure dramatically inhibited NO production and transcription of proinflammatory cytokines. A comparison study suggested that the 2-chloro-5-nitrobenzoyl group of the ligands is important for anti-inflammation. Furthermore, we synthesized an alkyne-tagged analogue that becomes an activity-based probe for future mechanistic study.

Maresin 1 alleviates neuroinflammation and cognitive decline in a mouse model of cecal ligation and puncture.

Inflammation in the central nervous system plays a crucial role in the occurrence and development of sepsis-associated encephalopathy. This study aims to explore the effects of maresin 1 (MaR1), an anti-inflammatory and pro-resolving lipid mediator, on sepsis-induced neuroinflammation and cognitive impairment. Mice were randomly assigned to 4 groups: A sham group (sham operation+vehicle), a cecal ligation and puncture (CLP) group (CLP operation+vehicle), a MaR1-LD group (CLP operation+1 ng MaR1), and a MaR1-HD group (CLP operation+10 ng MaR1). MaR1 or vehicle was intraperitoneally administered starting 1 h before CLP operation, then every other day for 7 days. Survival rates were monitored, and serum inflammatory cytokines [tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6] were measured 24 h after operation using enzyme-linked immunosorbent assay (ELISA). Cognitive function was assessed 7 days after operation using the Morris water maze (MWM) test and novel object recognition (NOR) task. The mRNA expression of TNF-α, IL-1β, IL-6, inducible nitric oxide synthase (iNOS), IL-4, IL-10, and arginase 1 (Arg1) in cortical and hippocampal tissues was determined by real-time reverse transcription PCR (RT-PCR). Western blotting was used to determine the protein expression of iNOS, Arg1, signal transducer and activator of transcription 6 (STAT6), peroxisome proliferator-activated receptor gamma (PPARγ), and phosphorylated STAT6 (p-STAT6) in hippocampal tissue. Microglia activation was visualized via immunofluorescence. Mice were also treated with the PPARγ antagonist GW9662 to confirm the involvement of this pathway in MaR1's effects. CLP increased serum levels of TNF-α, IL-1β, and IL-6, and reduced body weight and survival rates (all P<0.05). Both 1 ng and 10 ng doses of MaR1 significantly reduced serum TNF-α, IL-1β, and IL-6 levels, improved body weight, and increased survival rates (all P<0.05). No significant difference in efficacy was observed between the 2 doses (all P>0.05). MWM test and NOR task indicated that CLP impaired spatial learning, which MaR1 mitigated. However, GW9662 partially reversed MaR1's protective effects. Real-time RT-PCR results demonstrated that, compared to the sham group, mRNA expression of TNF-α, IL-1β, and iNOS significantly increased in hippocampal tissues following CLP (all P<0.05), while IL-4, IL-10, and Arg1 showed a slight decrease, though the differences were not statistically significant (all P>0.05). Compared to the CLP group, both 1 ng and 10 ng MaR1 decreased TNF-α, IL-1β, and iNOS mRNA expression in hippocampal tissues and increased IL-4, IL-10, and Arg1 mRNA expression (all P<0.05). Immunofluorescence results indicated a significant increase in Iba1-positive microglia in the hippocampus after CLP compared to the sham group (P<0.05). Administration of 1 ng and 10 ng MaR1 reduced the percentage area of Iba1-positive cells in the hippocampus compared to the CLP group (both P<0.05). Western blotting results showed that, compared to the CLP group, both 1 ng and 10 ng MaR1 down-regulated the iNOS expression, while up-regulated the expression of Arg1, PPARγ, and p-STAT6 (all P<0.05). However, the inclusion of GW9662 counteracted the MaR1-induced upregulation of Arg1 and PPARγ compared to the MaR1-LD group (all P<0.05). MaR1 inhibits the classical activation of hippocampal microglia, promotes alternative activation, reduces sepsis-induced neuroinflammation, and improves cognitive decline.

Cilostazol protects against gastric ulcers by regulating PPAR-γ, HO-1, PECAM-1, pErk-1, NF-κB, Bcl-2, and cleaved caspase-3 protein expression

Millions of individuals worldwide, across all age groups, suffer from the widespread health issue of gastric ulcers. In many experiments, cilostazol (Cls), a phosphodiesterase-3 inhibitor, was recently shown to have anti-ulcer activity. Notably, Cls increases the expression and transcriptional activity of PPAR-γ in vitro and in vivo. This study aimed to evaluate the protective effect of Cls against ethanol-induced gastric ulcers and clarify the possible underlying mechanisms with an emphasis on the role of PPAR-γ. Male albino rats were treated with ethanol to induce gastric ulcers, or they were pretreated with Cls, omeprazole (Omp), GW9662, or Cls + GW9662 for 14 consecutive days before receiving ethanol. Cls protects against ethanol-induced gastric ulcers. Cls treatment significantly reduced ethanol-induced upregulation of the pro-inflammatory markers (IL-1β, IL-6, TNF-α, and NF-κB), MDA (a marker of lipid peroxidation), and caspase-3 and cleaved caspase-3 (apoptotic markers). On the other hand, Cls treatment counteracted ethanol-induced downregulation of PPAR-γ, pErk-1, HO-1 and GSH (antioxidant markers), PECAM-1 and NO (healing markers), and Bcl-2 (antiapoptotic marker). However, when combined with GW9662, a potent antagonist of PPAR-γ, Cls loses its effects. In conclusion, these results suggest that PPAR-γ and pErk-1 are essential for Cls’s protective effects against ethanol-induced gastric ulcers.Graphical abstract

Anti-depressant effect of Naringenin-loaded hybridized nanoparticles in diabetic rats via PPARγ/NLRP3 pathway

Naringenin (NAR) has various biological activities but low bioavailability. The current study examines the effect of Naringenin-loaded hybridized nanoparticles (NAR-HNPs) and NAR on depression induced by streptozotocin (STZ) in rats. NAR-HNPs formula with the highest in vitro NAR released profile, lowest polydispersity index value (0.21 ± 0.02), highest entrapment efficiency (98.7 ± 2.01%), as well as an acceptable particle size and zeta potential of 415.2 ± 9.54 nm and 52.8 ± 1.04 mV, respectively, was considered the optimum formulation. It was characterized by differential scanning calorimetry, examined using a transmission electron microscope, and a stability study was conducted at different temperatures to monitor its stability efficiency showing that NAR-HNP formulation maintains stability at 4 °C. The selected formulation was subjected to an acute toxicological test, a pharmacokinetic analysis, and a Diabetes mellitus (DM) experimental model. STZ (50 mg/kg) given as a single i.p. rendered rats diabetic. Diabetic rat groups were allocated into 4 groups: one group received no treatment, while the remaining three received oral doses of unloaded HNPs, NAR (50 mg/kg), NAR-HNPs (50 mg/kg) and NAR (50 mg/kg) + peroxisome proliferator-activated receptor-γ (PPAR-γ) antagonist, GW9662 (1mg/kg, i.p.) for three weeks. Additional four non-diabetic rat groups received: distilled water (normal), free NAR, and NAR-HNPs, respectively for three weeks. NAR and NAR-HNPs reduced immobility time in forced swimming test and serum blood glucose while increasing serum insulin level. They also reduced cortical and hippocampal 5-hydroxyindoeacetic acid, 3,4-Dihydroxy-phenylacetic acid, malondialdehyde, NLR family pyrin domain containing-3 (NLRP3) and interleukin-1beta content while raised serotonin, nor-epinephrine, dopamine and glutathione level. PPAR-γ gene expression was elevated too. So, NAR and NAR-HNPs reduced DM-induced depression by influencing brain neurotransmitters and exhibiting anti-oxidant and anti-inflammatory effects through the activation PPAR-γ/ NLRP3 pathway. NAR-HNPs showed the best pharmacokinetic and therapeutic results.