Adipocyte-specific Repression of PPAR-gamma by NCoR Contributes to Scleroderma Skin Fibrosis

MiR-4769-3p suppresses adipogenesis in systemic sclerosis by negatively regulating the USP18/VDAC2 pathway

Systemic sclerosis (SSc) is an autoimmune disease affecting multiple tissues. The underlying causes and mechanisms of subcutaneous adipose tissue (SAT) loss in SSc remain unclear. Recent studies have highlighted the role of microRNAs in adipogenesis. Our study found that miR-4769-3p was upregulated in SSc patients and its silencing promoted SAT recovery in bleomycin-induced SSc mice, suggesting that miR-4769-3p might affect adipogenesis in SSc. Manipulating miR-4769-3p expression in 3T3-L1 cells revealed that its inhibition enhanced adipogenesis, while its overexpression weakened it. Further investigations showed that miR-4769-3p bound to 3'UTR of ubiquitin-specific protease-18 (USP18), inhibiting its expression, while USP18 interacted with voltage-dependent anion channel-2 (VDAC2), both of which were reduced in SSc. Silencing either USP18 or VDAC2 attenuated adipogenesis. Notably, USP18 inhibited VDAC2 ubiquitination and degradation, whereas miR-4769-3p reversed the VDAC2-induced elevation of adipogenesis, suggesting that miR-4769-3p inhibited adipogenesis by negatively regulating the USP18/VDAC2 pathway, providing a potential therapeutic target for SSc.

Aging and homeostasis of the hypodermis in the age-related deterioration of skin function

Adipose tissues in the hypodermis, the crucial stem cell reservoir in the skin and the endocrine organ for the maintenance of skin homeostasis undergo significant changes during skin aging. Dermal white adipose tissue (dWAT) has recently been recognized as an important organ for both non-metabolic and metabolic health in skin regeneration and rejuvenation. Defective differentiation, adipogenesis, improper adipocytokine production, and immunological dissonance dysfunction in dWAT lead to age-associated clinical changes. Here, we review age-related alterations in dWAT across levels, emphasizing the mechanisms underlying the regulation of aging. We also discuss the pathogenic changes involved in age-related fat dysfunction and the unfavorable consequences of accelerated skin aging, such as chronic inflammaging, immunosenescence, delayed wound healing, and fibrosis. Research has shown that adipose aging is an early initiation event and a potential target for extending longevity. We believe that adipose tissues play an essential role in aging and form a potential therapeutic target for the treatment of age-related skin diseases. Further research is needed to improve our understanding of this phenomenon.

Enhanced detection of ligand-PPARγ binding based on surface plasmon resonance through complexation with SRC1- or NCOR2-related polypeptide

A previous study reported the use of a biosensing technique based on surface plasmon resonance (SPR) for the ligand binding detection of peroxisome proliferator activator receptor gamma (PPARγ). This detection was designed based on the structural properties of PPARγ. Because of cross-linked protein inactivation and the low molecular weight of conventional ligands, direct ligand binding detection based on SPR has low stability and repeatability. In this study, we report an indirect response methodology based on SPR technology in which anti-His CM5 chip binds fresh PPARγ every cycle, resulting in more stable detection. We developed a remarkable improvement in ligand-protein binding detectability in vitro by introducing two coregulator-related polypeptides into this system. In parallel, a systematic indirect response methodology can reflect the interaction relationship between ligands and proteins to some extent by detecting the changes in SA-SRC1 and GST-NCOR2 binding to PPARγ. Rosiglitazone, a PPARγ agonist with strong affinity, is a potent insulin-sensitizing agent. Some ligands may be competitively exerted at the same sites of PPARγ (binding rosiglitazone). We demonstrated using indirect response methodology that selective PPARγ modulator (SPPARM) candidates of PPARγ can be found by competing for the binding of the rosiglitazone site on PPARγ, although they may have no effect on polypeptides and PPARγ binding.

Challenges and opportunities in obesity: the role of adipocytes during tissue fibrosis

Obesity is a chronic disease that affects the energy balance of the whole body. In addition to increasing fat mass, tissue fibrosis occurred in white adipose tissue in obese condition. Fibrosis is the over-activation of fibroblasts leading to excessive accumulation of extracellular matrix, which could be caused by various factors, including the status of adipocytes. The morphology of adipocytes responds rapidly and dynamically to nutrient fluctuations. Adaptive hypertrophy of normal adipocytes protects peripheral organs from damage from lipotoxicity. However, the biological behavior of hypertrophic adipocytes in chronic obesity is abnormally altered. Adipocytes lead to fibrotic remodeling of the extracellular matrix by inducing unresolved chronic inflammation, persistent hypoxia, and increasing myofibroblast numbers. Moreover, adipocyte-induced fibrosis not only restricts the flexible expansion and contraction of adipose tissue but also initiates the development of various diseases through cellular autonomic and paracrine effects. Regarding anti-fibrotic therapy, dysregulated intracellular signaling and epigenetic changes represent potential candidate targets. Thus, modulation of adipocytes may provide potential therapeutic avenues for reversing pathological fibrosis in adipose tissue and achieving the anti-obesity purpose.

Celastrol Stabilizes Glycolipid Metabolism in Hepatic Steatosis by Binding and Regulating the Peroxisome Proliferator-Activated Receptor γ Signaling Pathway

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been increasing. Obesity, insulin resistance, and lipid metabolic dysfunction are always accompanied by NAFLD. Celastrol modulates the Peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer binding protein α (C/EBPα) signaling pathways, thereby promoting lipolysis in 3T3-L1 adipocytes. In the present study, oleic-acid-induced NAFLD and differentiated 3T3-L1 preadipocytes were used as models of NAFLD and obesity to investigate the protective effect of celastrol. We investigated the impact of celastrol on hepatic steatosis caused by oleic acid (OA), as well as the associated underlying molecular pathways. To address the aforementioned questions, we used a cellular approach to analyze the signaling effects of celastrol on various aspects. These factors include the improvement in fatty liver in HepG2 cells, the differentiation of 3T3-L1 preadipocytes, glucose uptake, and the modulation of key transcriptional pathways associated with PPARγ. The administration of celastrol effectively mitigated lipid accumulation caused by OA in HepG2 cells, thereby ameliorating fatty liver conditions. Furthermore, celastrol suppressed the impacts on adipocyte differentiation in 3T3-L1 adipocytes. Additionally, celastrol exhibited the ability to bind to PPARγ and modulate its transcriptional activity. Notably, the ameliorative effects of celastrol on hepatic steatosis were reversed by rosiglitazone. According to our preliminary findings from in vitro celastrol signaling studies, PPARγ is likely to be the direct target of celastrol in regulating hepatic steatosis in HepG2 cells and adipocyte differentiation in 3T3-L1 cells.

Brown adipose tissue transplantation improves skin fibrosis in localized scleroderma

Adipose tissue transplantation shows great therapeutic potential in reversing localized scleroderma-associated skin fibrosis. Brown adipose tissue (BAT) can specifically secrete various cytokines against fibrosis, but its therapeutic potential in improving skin fibrosis has not yet been demonstrated. In this study, we have demonstrated the superior therapeutic efficacy of BAT transplantation for sclerotic skin by transplanting two distinct types of adipose tissue. In comparison to the white adipose tissue (WAT) group, mice treated with BAT transplantation exhibited a significant reduction in dermal thickness. BAT transplantation effectively reverses skin sclerosis through mechanisms involving inflammation reduction, promotion of angiogenesis, inhibition of myofibroblast accumulation, and collagen deposition. This therapeutic effect can be attributed to its unique paracrine effects. Furthermore, transcriptome sequencing (RNA-Seq) revealed upregulation of pathways associated with lipogenesis and fatty acid metabolism in BAT while downregulating pathways are related to transforming growth factor β(TGF-β), epithelial-mesenchymal transition (EMT), and inflammatory response. These findings suggest that BAT transplantation holds great promise as a novel approach for localized scleroderma treatment.

The Pathogenesis of Systemic Sclerosis: The Origin of Fibrosis and Interlink with Vasculopathy and Autoimmunity

Systemic sclerosis (SSc) is an autoimmune disease associated with increased mortality and poor morbidity, impairing the quality of life in patients. Whilst we know that SSc affects multiple organs via vasculopathy, inflammation, and fibrosis, its exact pathophysiology remains elusive. Microvascular injury and vasculopathy are the initial pathological features of the disease. Clinically, the vasculopathy in SSc is manifested as Raynaud's phenomenon (reversible vasospasm in reaction to the cold or emotional stress) and digital ulcers due to ischemic injury. There are several reports that medications for vasculopathy, such as bosentan and soluble guanylate cyclase (sGC) modulators, improve not only vasculopathy but also dermal fibrosis, suggesting that vasculopathy is important in SSc. Although vasculopathy is an important initial step of the pathogenesis for SSc, it is still unclear how vasculopathy is related to inflammation and fibrosis. In this review, we focused on the clinical evidence for vasculopathy, the major cellular players for the pathogenesis, including pericytes, adipocytes, endothelial cells (ECs), and myofibroblasts, and their signaling pathway to elucidate the relationship among vasculopathy, inflammation, and fibrosis in SSc.

Crocin Ameliorates Diabetic Nephropathy through Regulating Metabolism, CYP4A11/PPARγ, and TGF-β/Smad Pathways in Mice

INTRODUCTION

Crocin is one of the main components of Crocus sativus L. and can alleviate oxidative stress and inflammation in diabetic nephropathy (DN). However, the specific mechanism by which crocin treats DN still needs to be further elucidated.

METHOD

In the present study, a mouse model of DN was first established to investigate the therapeutic effect of crocin on DN mice. Subsequently, non-targeted metabolomics techniques were used to analyze the mechanisms of action of crocin in the treatment of DN. The effects of crocin on CYP4A11/PPARγ and TGF-β/Smad pathway were also investigated.

RESULT

Results showed that crocin exhibited significant therapeutic and anti-inflammatory, and anti-oxidative effects on DN mice. In addition, the non-targeted metabolomics results indicated that crocin treatment affected several metabolites in kidney. These metabolites were mainly associated with biotin metabolism, riboflavin metabolism, and arachidonic acid metabolism. Furthermore, crocin treatment upregulated the decreased levels of CYP4A11 and phosphorylated PPARγ, and reduced the increased levels of TGF-β1 and phosphorylated Smad2/3 in the kidneys of DN mice.

CONCLUSION

In conclusion, our study validated the considerable therapeutic, anti-inflammatory, and antioxidative impacts of crocin on DN mice. The mechanism of crocin treatment may be related to the regulation of biotin riboflavin and arachidonic acid metabolism, the activation of CYP4A11/PPARγ pathway, and the inhibition of TGF-β/Smad pathway in the kidney.

PPARγ signaling in hepatocarcinogenesis: Mechanistic insights for cellular reprogramming and therapeutic implications

Liver cancer or hepatocellular carcinoma (HCC) is leading cause of cancer-related mortalities globally. The therapeutic approaches for chronic liver diseases-associated liver cancers aimed at modulating immune check-points and peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathway during multistep process of hepatocarcinogenesis that played a dispensable role in immunopathogenesis and outcomes of disease. Herein, the review highlights PPARγ-induced effects in balancing inflammatory (tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1) and anti-inflammatory cytokines (IL-10, transforming growth factor beta (TGF-β), and interplay of PPARγ, hepatic stellate cells and fibrogenic niche in cell-intrinsic and -extrinsic crosstalk of hepatocarcinogenesis. PPARγ-mediated effects in pre-malignant microenvironment promote growth arrest, cell senescence and cell clearance in liver cancer pathophysiology. Furthermore, PPARγ-immune cell axis of liver microenvironment exhibits an immunomodulation strategy of resident immune cells of the liver (macrophages, natural killer cells, and dendritic cells) in concomitance with current clinical guidelines of the European Association for Study of Liver Diseases (EASL) for several liver diseases. Thus, mechanistic insights of PPARγ-associated high value targets and canonical signaling suggest PPARγ as a possible therapeutic target in reprogramming of hepatocarcinogenesis to decrease burden of liver cancers, worldwide.

MiR-27a as a diagnostic biomarker and potential therapeutic target in systemic sclerosis

Systemic sclerosis (SSc) or scleroderma is a multiorgan rheumatoid disease characterized by skin tightening or organ dysfunction due to fibrosis, vascular damage, and autoimmunity. No specific cause has been discovered for this illness, and hence no effective treatment exists for it. On the other hand, due to the lack of diagnostic biomarkers capable of effectively and specifically differentiating the patients, early diagnosis has not been possible. Due to their potent regulatory roles in molecular pathways, microRNAs are among the novel candidates for the diagnosis and treatment of diseases like SSc. MiR-27a is a microRNA known for its role in the pathogenesis of fibrosis and cancer, both of which employ similar signaling pathways; hence we hypothesized that Mir-27a could be dysregulated in the blood of individuals affected by SSc and it might be useful in the diagnosis or treatment of this disease. Blood was collected from 60 SSc patients (30 limited and 30 diffuse) diagnosed by a rheumatologist according to ACR/AULAR criteria; following RNA isolation and cDNA synthesis; real-time qPCR was performed on the samples using Taq-Man probes and data were analyzed by the ΔΔCT method. Also, potential targets of miR-27a were evaluated using bioinformatics. It was revealed that miR-27a was significantly down-regulated in SSc patients in comparison to healthy individuals, but there was no difference in miR-27 expression between limited and diffused SSc patients. Besides, miR-27a was found to target several contributing factors to SSc. It seems that miR-27a has a protective role in SSc, and its downregulation could result in the disease's onset. Based on bioinformatics analyses, it is speculated that miR-27a likely targets factors contributing to the pathogenesis of SSc, which are elevated upon the downregulation of miR-27a; hence, miR-27a mimics could be considered as potential therapeutic agents for the treatment of SSc in future studies. Since no difference was observed between limited and diffuse patient groups, it is unlikely that this microRNA has a role in disease progression. According to ROC analysis of qPCR data, miR-27a could be employed as a valuable diagnostic biomarker for SSc.

Epoxyeicosatrienoic Acids Inhibit the Activation of Murine Fibroblasts by Blocking the TGF-β1-Smad2/3 Signaling in a PPARγ-Dependent Manner

Background

Epoxyeicosatrienoic acids (EETs), the metabolite of arachidonic acid by cytochrome P450 (CYP), reportedly serve as a vital endogenous protective factor in several chronic diseases. EETs are metabolized by soluble epoxide hydrolase (sEH). We have observed that prophylactic blocking sEH alleviates bleomycin- (BLM-) induced pulmonary fibrosis (PF) in mice. However, the underlying mechanism and therapeutic effects of EETs on PF remain elusive.

Objective

In this study, we investigated the effect of CYP2J2/EETs on the activation of murine fibroblasts and their mechanisms.

Results

we found that administration of the sEH inhibitor (TPPU) 7 days after the BLM injection also reversed the morphology changes and collagen deposition in the lungs of BLM-treated mice, attenuating PF. Fibroblast activation is regarded as a critical role of PF. Therefore, we investigated the effects of EETs on the proliferation and differentiation of murine fibroblasts. Results showed that the overexpression of CYP2J2 reduced the cell proliferation and the expressions of α-SMA and PCNA induced by transforming growth factor- (TGF-) β1 in murine fibroblasts. Then, we found that EETs inhibited the proliferation and differentiation of TGF-β1-treated-NIH3T3 cells and primary murine fibroblasts. Mechanistically, we found that 14,15-EET disrupted the phosphorylation of Smad2/3 murine fibroblasts by activating PPARγ, which was completely abolished by a PPARγ inhibitor GW9662.

Conclusion

our study shows that EETs inhibit the activation of murine fibroblasts by blocking the TGF-β1-Smad2/3 signaling in a PPARγ-dependent manner. Regulating CYP2J2-EET-sEH metabolic pathway may be a potential therapeutic option in PF.

Adiponectin Deregulation in Systemic Autoimmune Rheumatic Diseases

Deregulation of adiponectin is found in systemic autoimmune rheumatic diseases (SARDs). Its expression is downregulated by various inflammatory mediators, but paradoxically, elevated serum levels are present in SARDs with high inflammatory components, such as rheumatoid arthritis and systemic lupus erythematosus. Circulating adiponectin is positively associated with radiographic progression in rheumatoid arthritis as well as with cardiovascular risks and lupus nephritis in systemic lupus erythematosus. However, in SARDs with less prominent inflammation, such as systemic sclerosis, adiponectin levels are low and correlate negatively with disease activity. Regulators of adiponectin gene expression (PPAR-γ, Id3, ATF3, and SIRT1) and inflammatory cytokines (interleukin 6 and tumor necrosis factor α) are differentially expressed in SARDs and could therefore influence total adiponectin levels. In addition, anti-inflammatory therapy could also have an impact, as tocilizumab treatment is associated with increased serum adiponectin. However, anti-tumor necrosis factor α treatment does not seem to affect its levels. Our review provides an overview of studies on adiponectin levels in the bloodstream and other biological samples from SARD patients and presents some possible explanations why adiponectin is deregulated in the context of therapy and gene regulation.

An inflammatory triangle in Sarcoidosis: PPAR-γ, immune microenvironment, and inflammation

INTRODUCTION

Sarcoidosis is an inflammatory disorder characterized by granuloma formation in several organs. Sarcoidosis patients experience higher inflammatory responses resulting in pulmonary fibrosis. Although the precise mechanisms have not been well elucidated, the relationship between the immune system activation and inflammatory status is pivotal in the pathogenesis of sarcoidosis.

AREAS COVERED

Peroxisome proliferator-activated receptor (PPAR) includes the transcription factors involved in cell metabolism, proliferation, and immune response. In the alveolar macrophages of patients with sarcoidosis, the reduced activity and a decreased level of PPAR-γ have been shown. In this study, we discuss how reducing the level of PPAR-γ could lead to increased inflammation and immune responses in patients with sarcoidosis.

EXPERT OPINION

Lack of PPAR-γ may contribute to the development of a suitable milieu for the formation of immune-associated pulmonary granuloma. Reduced levels of PPAR-γ in sarcoidosis could result from over-activation of the immune system and elevated inflammatory responses, as well. Due to the anti-inflammatory function of PPAR-γ, identifying the relation between PPAR-γ, sarcoidosis development, and inflammatory state could be essential to identify the appropriate therapeutic targets. The synthesis of PPAR-γ agonists or PPAR-γ ligands may be an effective step toward the treatment of sarcoidosis patients in the future.

Pathological changes of frozen shoulder in rat model and the therapeutic effect of PPAR-γ agonist

Frozen shoulder is a common shoulder disorder characterized by a gradual increase of pain and a limited range of motion. However, its pathophysiologic mechanisms remain unclear and there is no consensus as to the most effective treatment. The purpose of the study was to investigate the effect of transforming growth factor-β (TGF-β) on fibrosis and inflammatory response of the shoulder joint of rat models and to explore the therapeutic effect of the peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist. In the study, the effect of PPAR-γ agonist CDDO-IM treatment on cell proliferation, migration, and extracellular matrix proteins synthesis (vimentin, α-smooth muscle actin, collagen I, and collagen III) were tested by cell proliferation test, scratches test, real-time quantitative polymerase chain reaction, and Western blot analysis. The frozen shoulder was also established on the rat model by injecting adenovirus-TGF-β1 into rats' shoulder capsule. Pathological changes of the frozen shoulder tissue of the experimental group and PPAR-γ agonist treatment group were evaluated. The stiffness of joints of the three groups was tested. Inflammatory mediators' expression including cyclooxygenase-1, interleukin-1β, and tumor necrosis factor-α of the shoulder was tested by enzyme-linked immunosorbent assay, and the expression of extracellular matrix proteins was evaluated by hematoxylin and eosin staining and immunohistochemistry. The results showed that pathological changes of the frozen shoulder in the rat model include an abnormal proliferation of fibroblasts, infiltration of inflammatory cells, and disorder of fibrous structure, while rosiglitazone reduced the severity of the frozen shoulder in the treatment group. Clinically, PPAR-γ agonists may be a promising target for the treatment of the frozen shoulder.

Adipose-derived stem cells: Pathophysiologic implications vs therapeutic potential in systemic sclerosis

Adipose-derived stem cells (ADSCs) residing in the stromal vascular fraction (SVF) of white adipose tissue are recently emerging as an alternative tool for stem cell-based therapy in systemic sclerosis (SSc), a complex connective tissue disorder affecting the skin and internal organs with fibrotic and vascular lesions. Several preclinical and clinical studies have reported promising therapeutic effects of fat grafting and autologous SVF/ADSC-based local treatment for facial and hand cutaneous manifestations of SSc patients. However, currently available data indicate that ADSCs may represent a double-edged sword in SSc, as they may exhibit a pro-fibrotic and anti-adipogenic phenotype, possibly behaving as an additional pathogenic source of pro-fibrotic myofibroblasts through the adipocyte-to-myofibroblast transition process. Thus, in the perspective of a larger employ of SSc-ADSCs for further therapeutic applications, it is important to definitely unravel whether these cells present a comparable phenotype and similar immunosuppressive, anti-inflammatory, anti-fibrotic and pro-angiogenic properties in respect to healthy ADSCs. In light of the dual role that ADSCs seem to play in SSc, this review will provide a summary of the most recent insights into the preclinical and clinical studies employing SVF and ADSCs for the treatment of the disease and, at the same time, will focus on the main findings highlighting the possible involvement of these stem cells in SSc-related fibrosis pathogenesis.

Adipocytes fail to maintain cellular identity during obesity due to reduced PPARγ activity and elevated TGFβ-SMAD signaling

Objective

Obesity due to overnutrition causes adipose tissue dysfunction, which is a critical pathological step on the road to type 2 diabetes (T2D) and other metabolic disorders. In this study, we conducted an unbiased investigation into the fundamental molecular mechanisms by which adipocytes transition to an unhealthy state during obesity.

Methods

We used nuclear tagging and translating ribosome affinity purification (NuTRAP) reporter mice crossed with Adipoq-Cre mice to determine adipocyte-specific 1) transcriptional profiles (RNA-seq), 2) promoter and enhancer activity (H3K27ac ChIP-seq), 3) and PPARγ cistrome (ChIP-seq) profiles in mice fed chow or a high-fat diet (HFD) for 10 weeks. We also assessed the impact of the PPARγ agonist rosiglitazone (Rosi) on gene expression and cellular state of adipocytes from the HFD-fed mice. We integrated these data to determine the transcription factors underlying adipocyte responses to HFD and conducted functional studies using shRNA-mediated loss-of-function approaches in 3T3-L1 adipocytes.

Results

Adipocytes from the HFD-fed mice exhibited reduced expression of adipocyte markers and metabolic genes and enhanced expression of myofibroblast marker genes involved in cytoskeletal organization, accompanied by the formation of actin filament structures within the cell. PPARγ binding was globally reduced in adipocytes after HFD feeding, and Rosi restored the molecular and cellular phenotypes of adipocytes associated with HFD feeding. We identified the TGFβ1 effector protein SMAD to be enriched at HFD-induced promoters and enhancers and associated with myofibroblast signature genes. TGFβ1 treatment of mature 3T3-L1 adipocytes induced gene expression and cellular changes similar to those seen after HFD in vivo, and knockdown of Smad3 blunted the effects of TGFβ1.

Conclusions

Our data demonstrate that adipocytes fail to maintain cellular identity after HFD feeding, acquiring characteristics of a myofibroblast-like cell type through reduced PPARγ activity and elevated TGFβ-SMAD signaling. This cellular identity crisis may be a fundamental mechanism that drives functional decline of adipose tissues during obesity.

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Adipocytes after HFD intake exhibit defects in cellular identity maintenance.

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Adipocytes develop actin filament networks in obesity.

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Altered PPARγ activity mediates defective adipocyte identity phenotypes.

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TGFβ-SMAD pathways promote HFD-induced aberrant phenotype of adipocytes.

The roles of PPARγ and its agonists in autoimmune diseases: A comprehensive review

Autoimmune diseases are common diseases of the immune system that are characterized by the loss of self-tolerance and the production of autoantibodies; the breakdown of immune tolerance and the prolonged inflammatory reaction are undisputedly core steps in the initiation and maintenance of autoimmunity. Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors that belong to the nuclear hormone receptor family and act as ligand-activated transcription factors. There are three different isotypes of PPARs: PPARα, PPARγ, and PPARβ/δ. PPARγ is an established regulator of glucose homeostasis and lipid metabolism. Recent studies have demonstrated that PPARγ exhibits anti-inflammatory and anti-fibrotic effects in multiple disease models. PPARγ can also modulate the activation and polarization of macrophages, regulate the function of dendritic cells and mediate T cell survival, activation, and differentiation. In this review, we summarize the signaling pathways and biological functions of PPARγ and focus on how PPARγ and its agonists play protective roles in autoimmune diseases, including autoimmune thyroid diseases, multiple sclerosis, rheumatoid arthritis, systemic sclerosis, systemic lupus erythematosus, primary Sjogren syndrome and primary biliary cirrhosis.

Inhibition of microRNA-27b-3p relieves osteoarthritis pain via regulation of KDM4B-dependent DLX5

Osteoarthritis (OA) represents a progressive degenerative disorder that predominantly affects the synovial membranes of joints. Recent studies have highlighted the significant role played by microRNAs (miRNAs) in OA development. The current study aimed to elucidate the underlying modulatory role of miR-27b-3p in the development of OA. The expression of miR-27b-3p in the OA patients and rat models post anterior cruciate ligament transection operation was measured using reverse transcription quantitative polymerase chain reaction, through which overexpressed miR-27b-3p was found in both of the samples. To further explore the miR-27b-3p functions in OA, western blot analysis, enzyme-linked immunosorbent assay, and β-galactosidase activity assay were conducted with the results showing that knockdown of miR-27b-3p promoted expression of the osteogenic differentiation markers while inhibiting expression of the adipogenic differentiation markers, inflammatory factors, and cellular senescence of bone marrow mesenchymal stem cells (BMSCs). After that, the interactions between miR-27b-3p, lysine Demethylase 4B (KDM4B), and Distal-Less Homeobox 5 (DLX5) identified using dual-luciferase reporter gene assay and ChIP assay revealed that miR-27b-3p inhibited KDM4B and further reduced expression of DLX5. Finally, the paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were assessed in rat models, and increased PWT and PWL were detected after miR-27b-3p silencing. In conclusion, suppression of miR-27b-3p could enhance KDM4B and DLX5 to alleviate OA pain, shedding light on a new potential therapeutic target for OA.

Metabolic Dysregulation in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fibroproliferative disorder limited to the lung. New findings, starting from our proteomics studies on IPF, suggest that systemic involvement with altered molecular mechanisms and metabolic disorder is an underlying cause of fibrosis. The role of metabolic dysregulation in the pathogenesis of IPF has not been extensively studied, despite a recent surge of interest. In particular, our studies on bronchoalveolar lavage fluid have shown that the renin–angiotensin–aldosterone system (RAAS), the hypoxia/oxidative stress response, and changes in iron and lipid metabolism are involved in onset of IPF. These processes appear to interact in an intricate manner and to be related to different fibrosing pathologies not directly linked to the lung environment. The disordered metabolism of carbohydrates, lipids, proteins and hormones has been documented in lung, liver, and kidney fibrosis. Correcting these metabolic alterations may offer a new strategy for treating fibrosis. This paper focuses on the role of metabolic dysregulation in the pathogenesis of IPF and is a continuation of our previous studies, investigating metabolic dysregulation as a new target for fibrosis therapy.

Pathogenic Roles of Autoantibodies and Aberrant Epigenetic Regulation of Immune and Connective Tissue Cells in the Tissue Fibrosis of Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is a multi-system autoimmune disease with tissue fibrosis prominent in the skin and lung. In this review, we briefly describe the autoimmune features (mainly autoantibody production and cytokine profiles) and the potential pathogenic contributors including genetic/epigenetic predisposition, and environmental factors. We look in detail at the cellular and molecular bases underlying tissue-fibrosis which include trans-differentiation of fibroblasts (FBs) to myofibroblasts (MFBs). We also state comprehensively the pro-inflammatory and pro-fibrotic cytokines relevant to MFB trans-differentiation, vasculopathy-associated autoantibodies, and fibrosis-regulating microRNAs in SSc. It is conceivable that tissue fibrosis is mainly mediated by an excessive production of TGF-β, the master regulator, from the skewed Th2 cells, macrophages, fibroblasts, myofibroblasts, and keratinocytes. After binding with TGF-β receptors on MFB, the downstream Wnt/β-catenin triggers canonical Smad 2/3 and non-canonical Smad 4 signaling pathways to transcribe collagen genes. Subsequently, excessive collagen fiber synthesis and accumulation as well as tissue fibrosis ensue. In the later part of this review, we discuss limited data relevant to the role of long non-coding RNAs (lncRNAs) in tissue-fibrosis in SSc. It is expected that these lncRNAs may become the useful biomarkers and therapeutic targets for SSc in the future. The prospective investigations in the development of novel epigenetic modifiers are also suggested.

TAZ Is a Negative Regulator of PPARγ Activity in Adipocytes and TAZ Deletion Improves Insulin Sensitivity and Glucose Tolerance

Insulin resistance is a major factor in obesity-linked type 2 diabetes. PPARγ is a master regulator of adipogenesis, and small molecule agonists, termed thiazolidinediones, are potent therapeutic insulin sensitizers. Here, we studied the role of transcriptional co-activator with PDZ-binding motif (TAZ) as a transcriptional co-repressor of PPARγ. We found that adipocyte-specific TAZ knockout (TAZ AKO) mice demonstrate a constitutively active PPARγ state. Obese TAZ AKO mice show improved glucose tolerance and insulin sensitivity compared to littermate controls. PPARγ response genes are upregulated in adipose tissue from TAZ AKO mice and adipose tissue inflammation was also decreased. In vitro and in vivo mechanistic studies revealed that the TAZ-PPARγ interaction is partially dependent on ERK-mediated Ser112 PPARγ phosphorylation. As adipocyte PPARγ Ser112 phosphorylation is increased in obesity, repression of PPARγ activity by TAZ could contribute to insulin resistance. These results identify TAZ as a new factor in the development of obesity-induced insulin resistance.

PPAR-γ signalling as a key mediator of human hair follicle physiology and pathology

Peroxisome proliferator-activated receptors (PPARs) are abundantly expressed in human skin, with PPAR-γ being the most intensively investigated isoform. In various ex vivo and in vivo models, PPAR-γ-mediated signalling has recently surfaced as an essential element of hair follicle (HF) development, growth and stem cell biology. Moreover, the availability of novel, topically applicable PPAR-γ modulators with a favourable toxicological profile has extended the range of potential applications in clinical dermatology. In this review, we synthesize where this field currently stands and sketch promising future research avenues, focussing on the role of PPAR-γ-mediated signalling in the biology and pathology of human scalp HFs, with special emphasis on scarring alopecias such as lichen planopilaris and frontal fibrosing alopecia as model human epithelial stem cell diseases. In particular, we discuss whether and how pharmacological modulation of PPAR-γ signalling may be employed for the management of hair growth disorders, for example, in scarring alopecia (by reducing HF inflammation as well as by promoting the survival and suppressing pathological epithelial-mesenchymal transition of keratin 15 + epithelial stem cells in the bulge) and in hirsutism/hypertrichosis (by promoting catagen development). Moreover, we explore the potential role of PPAR-γ in androgenetic alopecia, HF energy metabolism and HF ageing, and consider clinical perspectives that emanate from the limited data available on this so far. As this field of translational human hair research is still in its infancy, many open questions exist, for which we briefly delineate selected experimental approaches that promise to generate instructive answers in the near future.

Editor’s Pick: Systemic Sclerosis: The Role of YAP/TAZ in Disease Pathogenesis

Systemic sclerosis (SSc) is a systemic autoimmune condition of unknown cause. Yes-Associated Protein/Tafazzin (YAP/TAZ) are transcriptional coactivators previously demonstrated to be involved in cellular stretch biology, and form the principal effector molecules of the Hippo signalling pathway. The association between YAP/TAZ and stretch is contingent upon their cytoplasmic localisation (with nuclear translocation, the cell adopts a relaxed state). The author weighs the evidence for a central role for YAP/TAZ signalling in scleroderma spanning the major clinical features of the condition. Several of the features unique to SSc are mediated by cytoplasmic localisation of YAP/TAZ, including the stretch phenotype (through binding to NF-2), arterial lumenal obliteration (through their binding to angiomotin), the promotion of hypergammaglobulinaemia (via feedback to the upstream Hippo signalling molecule Mammalian Ste20-like Kinase 1), and the induction of B-Lymphocyte-Induced Maturation Protein-1 leading to the adoption of Th2 lineage, prominent in SSc. One observes that the induction of the fibrotic phenotype of scleroderma is mediated through GLI1/GLI2 (the effector molecules of the Hedgehog pathway). GLI1/GLI2 are induced to reciprocally enter the nucleus when YAP/TAZ is intracytoplasmic. The latter explains the characteristically increased connective tissue growth factor 2 and endothelin-1 expression. In this article, the author references some examples of the role of YAP/TAZ in the biophysically similar condition nephrogenic systemic fibrosis and suggests a role of YAP/TAZ cytoplasmic sequestration in programmed cell death protein 1-ligand antagonist-induced scleroderma.

Evolving insights into the cellular and molecular pathogenesis of fibrosis in systemic sclerosis

Systemic sclerosis (SSc, scleroderma) is a complex multisystem disease characterized by autoimmunity, vasculopathy, and most notably, fibrosis. Multiple lines of evidence demonstrate a variety of emerging cellular and molecular pathways which are relevant to fibrosis in SSc. The myofibroblast remains the key effector cell in SSc. Understanding the development, differentiation, and function of the myofibroblast is therefore crucial to understanding the fibrotic phenotype of SSc. Studies now show that (1) multiple cell types give rise to myofibroblasts, (2) fibroblasts and myofibroblasts are heterogeneous, and (3) that a large number of (primarily immune) cells have important influences on the transition of fibroblasts to an activated myofibroblasts. In SSc, this differentiation process involves multiple pathways, including well known signaling cascades such as TGF-β and Wnt/β-Catenin signaling, as well as epigenetic reprogramming and a number of more recently defined cellular pathways. After reviewing the major and emerging cellular and molecular mechanisms underlying SSc, this article looks to identify clinical applications where this new molecular knowledge may allow for targeted treatment and personalized medicine approaches.