Peroxisome proliferator-activated receptor-γ agonist pioglitazone suppresses experimental autoimmune uveitis

Canagliflozin impairs T cell effector function via metabolic suppression in autoimmunity

Augmented T cell function leading to host damage in autoimmunity is supported by metabolic dysregulation, making targeting immunometabolism an attractive therapeutic avenue. Canagliflozin, a type 2 diabetes drug, is a sodium glucose co-transporter 2 (SGLT2) inhibitor with known off-target effects on glutamate dehydrogenase and complex I. However, the effects of SGLT2 inhibitors on human T cell function have not been extensively explored. Here, we show that canagliflozin-treated T cells are compromised in their ability to activate, proliferate, and initiate effector functions. Canagliflozin inhibits T cell receptor signaling, impacting on ERK and mTORC1 activity, concomitantly associated with reduced c-Myc. Compromised c-Myc levels were encapsulated by a failure to engage translational machinery resulting in impaired metabolic protein and solute carrier production among others. Importantly, canagliflozin-treated T cells derived from patients with autoimmune disorders impaired their effector function. Taken together, our work highlights a potential therapeutic avenue for repurposing canagliflozin as an intervention for T cell-mediated autoimmunity.

Stabilization by Nano Spray Dryer of Pioglitazone Polymeric Nanosystems: Development, In Vivo, Ex Vivo and Synchrotron Analysis

Pioglitazone-loaded PLGA-PEG nanoparticles (NPs) were stabilized by the spray drying technique as an alternative to the treatment of ocular inflammatory disorders. Pioglitazone-NPs were developed and characterized physiochemically. Interaction studies, biopharmaceutical behavior, ex vivo corneal and scleral permeation, and in vivo bioavailability evaluations were conducted. Fibrillar diameter and interfibrillar corneal spacing of collagen was analyzed by synchrotron X-ray scattering techniques and stability studies at 4 °C and was carried out before and after the spray drying process. NPs showed physicochemical characteristics suitable for ocular administration. The release was sustained up to 46 h after drying; ex vivo corneal and scleral permeation profiles of pioglitazone-NPs before and after drying demonstrated higher retention and permeation through cornea than sclera. These results were correlated with an in vivo bioavailability study. Small-angle X-ray scattering (SAXS) analysis did not show a significant difference in the organization of the corneal collagen after the treatment with pioglitazone-NPs before and after the drying process, regarding the negative control. The stabilization process by Nano Spray Dryer B-90 was shown to be useful in preserving the activity of pioglitazone inside the NPs, maintaining their physicochemical characteristics, in vivo bioavailability, and non-damage to corneal collagen function after SAXS analysis was observed.

CD47 Deficiency Ameliorates Ocular Autoimmune Inflammation

Autoimmune uveitis is a sight-threatening ocular inflammatory condition in which the retina and uveal tissues become a target of autoreactive immune cells. The CD47 is a ubiquitously expressed transmembrane protein which plays multiple roles in fundamental cellular functions including phagocytosis, proliferation, and adhesion. Signal regulatory protein alpha (SIRPα), one of the CD47 ligands, is predominantly expressed in myeloid lineage cells such as dendritic cells (DCs) or macrophages, and CD47-SIRPα signaling pathway is implicated in the development of autoimmune diseases. Our current study demonstrates how CD47 depletion is effective in the prevention of experimental autoimmune uveitis (EAU), an animal model of human autoimmune uveitis, in animals deficient of CD47 (CD47-/- ). Systemic suppression of SIRPα+ DCs in animals deficient in CD47 resulted in the inability of autoreactive CD4+ T cells to develop, which is crucial to induction of EAU. Of interest, retinal microglia, the resident immune cell of the retina, express SIRPα, however these cells were not operative in EAU suppression in response to CD47 depletion. These results identify CD47 as a significant regulator in the development of SIRPα+ DCs that is vital to disease induction in EAU.

Development and Validation of an HPLC-MS/MS Method for Pioglitazone from Nanocarriers Quantitation in Ex Vivo and In Vivo Ocular Tissues

Pioglitazone (PGZ) is an oral anti-hyperglycemic agent, belongs to the class of thiazolidinediones, and is used for the treatment of diabetes mellitus type 2. In recent years, its anti-inflammatory activity has also been demonstrated in the literature for different diseases, including ocular inflammatory processes. Additionally, this drug belongs to Class II of the Biopharmaceutical Classification System, i.e., slightly soluble and highly permeable. The main objective of this study was to validate a new analytical HPLC-MS/MS method to quantify free-PGZ and PGZ from polymeric NPs to conduct nanoparticle application studies loaded with this active ingredient to transport it within ocular tissues. An accurate, sensitive, selective, reproducible and high throughput HPLC-MS/MS method was validated to quantify PGZ in cornea, sclera, lens, aqueous humor, and vitreous humor. The chromatographic separation was achieved in 10 min on a Kinetex C18 column. Linear response of PGZ was observed over the range of 5-100 ng/mL. The recovery of free-PGZ or PGZ from NPs was in the range of 85-110% in all tissues and levels tested. The intra-day and inter-day precision were <5% and <10%, respectively. The extracts were shown to be stable in various experimental conditions in all matrices studied. The range of concentrations covered by this validation is 80-1600 µg/kg of PGZ in ocular tissues. It is concluded that this method can be applied to quantify PGZ for in vivo and ex vivo biodistribution studies related to the ocular administration of free-PGZ and PGZ from nanoparticles.

Optimization, Biopharmaceutical Profile and Therapeutic Efficacy of Pioglitazone-loaded PLGA-PEG Nanospheres as a Novel Strategy for Ocular Inflammatory Disorders

PURPOSE

The main goal of this study was to encapsulate Pioglitazone (PGZ), in biodegradable polymeric nanoparticles as a new strategy for the treatment of ocular inflammatory processes.

METHODS

To improve their biopharmaceutical profile for the treatment of ocular inflammatory disorders, nanospheres (NSs) of PGZ were formulated by factorial design with poly (lactic-co-glycolic acid) polyethylene glycol (PLGA-PEG). Interactions drug-polymer have been carried out by spectroscopic (X-ray spectroscopy, FTIR) and thermal methods (DSC). The PGZ-NSs were tested for their in vitro release profile, cytotoxicity, and ocular tolerance (HET-CAM® test); ex vivo corneal permeation, and in vivo inflammatory prevention and bioavailability.

RESULTS

The optimized system showed a negative surface charge of -13.9 mV, an average particle size (Z_av) of around 160 nm, a polydispersity index (PI) below 0.1, and a high encapsulation efficiency (EE) of around 92%. According to the DSC results, the drug was incorporated into the NSs polymeric matrix. The drug release was sustained for up to 14 h. PGZ-NSs up to 10 μg/ml exhibited no retinoblastoma cell toxicity. The ex vivo corneal and scleral permeation profiles of PGZ-NSs showed that retention and permeation through the sclera were higher than through the cornea. Ocular tolerance in vitro and in vivo demonstrated the non-irritant character of the formulation.

CONCLUSION

The in vivo anti-inflammatory efficacy of developed PGZ-NSs indicates this colloidal system could constitute a new approach to prevent ocular inflammation.

Recent Advances of Curcumin in the Prevention and Treatment of Renal Fibrosis

Curcumin, a polyphenol derived from the turmeric, has received attention as a potential treatment for renal fibrosis primarily because it is a relatively safe and inexpensive compound that contributes to kidney health. Here, we review the literatures on the applications of curcumin in resolving renal fibrosis in animal models and summarize the mechanisms of curcumin and its analogs (C66 and (1E,4E)-1,5-bis(2-bromophenyl) penta-1,4-dien-3-one(B06)) in preventing inflammatory molecules release and reducing the deposition of extracellular matrix at the priming and activation stage of renal fibrosis in animal models by consulting PubMed and Cnki databases over the past 15 years. Curcumin exerts antifibrotic effect through reducing inflammation related factors (MCP-1, NF-κB, TNF-α, IL-1β, COX-2, and cav-1) and inducing the expression of anti-inflammation factors (HO-1, M6PRBP1, and NEDD4) as well as targeting TGF-β/Smads, MAPK/ERK, and PPAR-γ pathways in animal models. As a food derived compound, curcumin is becoming a promising drug candidate for improving renal health.

Quantitative PPARγ expression affects the balance between tolerance and immunity

PPARγ modulates energy metabolism and inflammation. However, its specific functions in the balance of immunity in vivo have been explored incompletely. In this study, by the age of 14 mo, Pparg^C/− mice with PPARγ expression at 25% of the normal level exhibited high autoantibody levels and developed mesangial proliferative glomerulonephritis, which resembled systemic lupus erythematosus (SLE)-like autoimmune disease. These symptoms were preceded by splenomegaly at an early age, which was associated with increases in splenocyte accumulation and B-cell activation but not with relocation of hematopoiesis to the spleen. The mechanism of splenic lymphocyte accumulation involved reduced sphingosine-1-phosphate receptor 1 (S1P₁) expression and diminished migration toward S1P in the Pparg^C/− splenocytes, which impeded lymphocyte egression. Mechanistically, increased Th17 polarization and IL-17 signaling in the Pparg^C/− CD4⁺ T cells contributed to B-cell hyperactivation in the spleen. Finally, the activation of the remaining PPARγ in Pparg^C/− mice by pioglitazone increased S1P₁ levels, reduced the Th17 population in the spleen, and ameliorated splenomegaly. Taken together, our data demonstrated that reduction of Pparg expression in T-helper cells is critical for spontaneous SLE-like autoimmune disease development; we also revealed a novel function of PPARγ in lymphocyte trafficking and cross talk between Th17 and B cells.

Resveratrol Pretreatment Protected against Cerebral Ischemia/Reperfusion Injury in Rats via Expansion of T Regulatory Cells

BACKGROUND

It is well accepted that repetitive resveratrol (RV) pretreatment (PRC) exerts neuroprotective effect on ischemic stroke. RV was shown to be able to enhance the production of T regulatory cells (Tregs) in autoimmune diseases whereas Tregs are considered to be the cerebroprotective immunomodulator in ischemic stroke. Thus, we hypothesized whether Tregs contributed to PRC-induced neuroprotection against cerebral ischemia/reperfusion (I/R) injury.

METHODS

Cerebral I/R injury was induced by middle cerebral artery occlusion for 90 minutes in rats. Adult male Sprague-Dawley rats were randomly assigned to 2 groups: I/R and RV I/R. RV (50 mg/kg) was administrated intraperitoneally once a day for 7 days prior to ischemia onset.

RESULTS

PRC significantly ameliorated neurological defects and reduced cerebral infarct volume, accompanied by the significantly increased frequencies of Tregs in the spleens and ischemic hemisphere, the significantly increased levels of interleukin-10 (IL-10) in the plasma and ischemic hemisphere, and the significantly decreased levels of tumor necrosis factor-α and IL-6 in the plasma and ischemic hemisphere at 24 hours after ischemia onset. In addition, we also found that PRC significantly improved the frequency and suppressive function of Tregs in the spleens prior to ischemia onset.

CONCLUSIONS

Thus, PRC-induced neuroprotection was in part mediated by more Treg accumulation and activation in vivo prior to ischemia onset except for less inflammation response at 24 hours after ischemia onset.

Diminished levels of regulatory T cell subsets (CD8+Foxp3, CD4+Foxp3 and CD4+CD39+Foxp3) but increased Foxp3 expression in adipose tissue from overweight subjects

OBJECTIVES

The aim of this study was to identify regulatory T cell (Treg) subsets residing in adipose tissue, demonstrate their immunosuppressive functions, and assess the possible role of Sirt1 in their function in overweight subjects.

METHODS

Fat samples were obtained by lipoaspiration from healthy overweight (n = 15) and normoweight (n = 11) subjects. We obtained the stromal vascular fraction and then isolated the mononuclear cells by Ficoll-Hypaque sedimentation. The Treg subsets were analyzed by flow cytometry, the expression of Sirt1 and Foxp3 was detected by western blot, and peroxisome proliferator-activated receptor gamma (PPAR-γ) expression was evaluated by qPCR.

RESULTS

We detected low numbers of Treg cell subsets displaying the phenotypes CD4+CD25-Foxp3+, CD8+CD25-Foxp3+, and CD4+CD39+Foxp3+ associated with increased body mass index in overweight subjects. We found lower levels of mRNA SIRT1 expression in adipocytes from overweight subjects than in those from normoweight subjects. In contrast, increased amounts of the Sirt1 and Foxp3 proteins in adipose tissue mononuclear cells from overweight subjects were observed. The immunosuppressive function of CD4+CD25+ Treg cells is higher in cells from obese subject than in those from normoweight subject.

CONCLUSIONS

Low levels of Treg subsets in overweight subjects with a high percentage of inhibition of proliferation could be related to high levels of the Foxp3 protein. Likewise, the low expression of SIRT1 and PPAR-γ mRNA levels and increased concentration of Sirt1 proteins allows adipose tissue mononuclear cells to respond to stimuli dependent on adenosine receptors and sirtuin pathways.

Role of Peroxisome Proliferator-Activated Receptor γ in Ocular Diseases

Peroxisome proliferator-activated receptor γ (PPAR γ), a member of the nuclear receptor superfamily, is a ligand-activated transcription factor that plays an important role in the control of a variety of physiological processes. The last decade has witnessed an increasing interest for the role played by the agonists of PPAR γ in antiangiogenesis, antifibrosis, anti-inflammation effects and in controlling oxidative stress response in various organs. As the pathologic mechanisms of major blinding diseases, such as age-related macular degeneration (AMD), diabetic retinopathy (DR), keratitis, and optic neuropathy, often involve neoangiogenesis and inflammation- and oxidative stress-mediated cell death, evidences are accumulating on the potential benefits of PPAR γ to improve or prevent these vision threatening eye diseases. In this paper we describe what is known about the role of PPAR γ in the ocular pathophysiological processes and PPAR γ agonists as novel adjuvants in the treatment of eye diseases.

The potential signaling pathway between peroxisome proliferator-activated receptor gamma and retinoic acid receptor alpha in renal interstitial fibrosis disease

Peroxisome proliferator-activated receptorγ (PPARγ) can regulate the process of cell apoptosis and is related to the progression of renal disorders. Retinoic acid receptor alpha (RARα) is one of the nuclear receptors involved in a variety of kidney diseases. Renal interstitial fibrosis (RIF) is a common denominator of chronic kidney disease (CKD). This study investigated whether a potential signaling pathway existed between PPARγ and RARα in RIF rats with unilateral ureteral obstruction (UUO). The rats were randomly divided into four groups: a model group subjected to UUO (GU), and three other groups treated with rosiglitazone sodium (GRS), GW9662 and dimethyl sulfoxide (DMSO), n = 40, respectively. Renal tissues were collected two and four weeks after post-surgery. The relevant indicators were detected. In comparison with the GU group, the expressions of PPARγ and RARα (protein and mRNA) were increased in the GRS group, and decreased in the GW9662 group (all p < 0.01). The RIF index, mRNA and protein expression of transforming growth factor-β1 (TGF-β1), and the protein expressions of collagen-IV (Col-IV) and fibronectin (FN) in the GRS group were more markedly reduced than those in the GU group; their levels in the GW9662 group were elevated (all p < 0.01). PPARγ or RARα was negatively correlated to the RIF index, TGF-β1, Col-IV and FN. PPARγ was positively correlated with RARα (all p < 0.01). In conclusion, PPARγ agonist can elevate the expression of PPARγ or RARα in RIF rats. There might be a potential signaling pathway between PPARγ and RARα in RIF disease.

Negatively regulating TLR4/NF-κB signaling via PPARα in endotoxin-induced uveitis

Toll-like receptor (TLR) signaling plays a fundamental role in the induction and progression of autoimmune disease. In the present study, we showed that lipopolysaccharide (LPS), a TLR4 ligand, functions as an antagonist of peroxisome proliferator-activated receptor alpha (PPARα), a nuclear transcription factor. Using endotoxin induced uveitis (EIU) as a model, we found that TLR was negatively regulated by PPARα. Our data revealed that treatment with the PPARα agonist fenofibrate dramatically prevented LPS-induced uveitis and inhibited TLR/ Nuclear factor-kappaB (NF-κB) signaling during inflammation. Evaluation of the severity of anterior uveitis further showed that PPARα agonist treatment significantly decreased inflammatory cell infiltration, total protein concentration, vessel density, inflammatory cytokine production, and clinical scores in the anterior section of the eye during EIU. Moreover, fenofibrate administration recovered retinal function and decreased the production of inflammatory cytokines, retinal vascular leukostasis, and inflammatory cell infiltration into the posterior section of the eyes during EIU. In vitro studies further showed that down-regulation or deletion of PPARα led to increased TLR4 levels and the activation of NF-κB signaling in RPE cells and also blocked the anti-inflammatory effects of fenofibrate. Furthermore, activation or up-regulation of PPARα decreased TLR4 levels and inhibited the NF-κB signaling pathway induced by LPS in RPE cells. In TLR4-expressing reporter cells, activation or up-regulation of PPARα partially inhibited the activation of NF-κB and also decreased TLR4 transcriptional activity. In conclusion, the activation of PPARα represents a novel therapeutic strategy for human uveitis, as PPARα negatively regulates TLR4 activity and therefore exerts anti-inflammatory actions.

22(R)-hydroxycholesterol and pioglitazone synergistically decrease cholesterol ester via the PPARγ-LXRα-ABCA1 pathway in cholesterosis of the gallbladder

Cholesterosis is a disease of cholesterol metabolism characterized by the presence of excessive lipid droplets in the cytoplasm. These lipid droplets are mainly composed of cholesterol esters derived from free cholesterol. The removal of excess cholesterol from gallbladder epithelial cells (GBECs) is very important for the maintenance of intracellular cholesterol homeostasis and the preservation of gallbladder function. Several lines of evidence have indicated that the activation of either peroxisome proliferator-activated receptor gamma (PPARγ) or liver X receptor α (LXRα) relates to cholesterol efflux. While pioglitazone can regulate the activation of PPARγ, 22(R)-hydroxycholesterol can activate LXRα and is a metabolic intermediate in the biosynthesis of steroid hormones. However, the effect of 22(R)-hydroxycholesterol in combination with pioglitazone on cholesterosis of the gallbladder is unclear. GBECs were treated with pioglitazone, 22(R)-hydroxycholesterol or PPARγ siRNA followed by Western blot analysis for ATP-binding cassette transporter A1 (ABCA1), PPARγ and LXRα. Cholesterol efflux to apoA-I was determined, and Oil Red O staining was performed to monitor variations in lipid levels in treated GBECs. Our data showed that 22(R)-hydroxycholesterol can modestly up-regulate LXRα while simultaneously increasing ABCA1 by 56%. The combination of 22(R)-hydroxycholesterol and pioglitazone resulted in a 3.64-fold increase in ABCA1 expression and a high rate of cholesterol efflux. Oil Red O staining showed an obvious reduction in the lipid droplets associated with cholesterosis in GBECs. In conclusion, the present findings indicate that the anti-lipid deposition action of 22(R)-hydroxycholesterol combined with pioglitazone involves the activation of the PPARγ-LXRα-ABCA1 pathway, increased ABCA1 expression and the efflux of cholesterol from GBECs. Thus, 22(R)-hydroxycholesterol synergistically combined with pioglitazone to produce a remarkable effect on lipid deposition in cholesterosis GBECs.

Association of peroxisome proliferator-activated receptor γ Pro12Ala gene polymorphism with type 2 diabetic nephropathy risk in Caucasian population

Association of peroxisome proliferator-activated receptor gamma (PPARγ) Pro12Ala gene polymorphism with type 2 diabetic nephropathy (T2DN) risk in Caucasians is still not clear. This investigation was conducted to assess if there was an association between the PPARγ Pro12Ala gene polymorphism and T2DN risk in Caucasians using meta-analysis. The relevant literatures were identified from PubMed, and Cochrane Library on 10 October 2013, and eligible studies were included and synthesized. Six reports including eight studies were recruited into this meta-analysis for the association of the PPARγ Pro12Ala gene polymorphism with T2DN risk in Caucasians. The Pro/Pro genotype was shown to be associated with T2DN risk in Caucasians. However, the Ala/Ala genotype and Ala allele were not associated with T2DN risk in Caucasians. In the sensitivity analysis, according to the control source from hospital, the control source from population, the genotyping methods using PCR-RFLP, Taqman, sample size of case <100, the association of the PPARγ Pro12Ala gene polymorphism with T2DN risk was similar to those in non-sensitivity analysis. In conclusion, the PPARγ Pro/Pro genotype was associated with T2DN risk in Caucasians, but the Ala/Ala genotype and Ala allele not. However, additional studies are required to firmly establish a correlation between the PPARγ Pro12Ala gene polymorphism and T2DN risk in Caucasians.