hepatocyte growth factor is a downstream effector that mediates the antifibrotic action of peroxisome proliferator-activated receptor-gamma agonists

Multifaceted TGF-β signaling, a master regulator: From bench-to-bedside, intricacies, and complexities

Physiological embryogenesis and adult tissue homeostasis are regulated by transforming growth factor-β (TGF-β), an evolutionarily conserved family of secreted polypeptide factors, acting in an autocrine and paracrine manner. The role of TGF-β in inflammation, fibrosis, and cancer is complex and sometimes even contradictory, exhibiting either inhibitory or promoting effects depending on the stage of the disease. Under pathological conditions, especially fibrosis and cancer, overexpressed TGF-β causes extracellular matrix deposition, epithelial-mesenchymal transition, cancer-associated fibroblast formation, and/or angiogenesis. In this review article, we have tried to dive deep into the mechanism of action of TGF-β in inflammation, fibrosis, and carcinogenesis. As TGF-β and its downstream signaling mechanism are implicated in fibrosis and carcinogenesis blocking this signaling mechanism appears to be a promising avenue. However, targeting TGF-β carries substantial risk as this pathway is implicated in multiple homeostatic processes and is also known to have tumor-suppressor functions. There is a need for careful dosing of TGF-β drugs for therapeutic use and patient selection.

Evidence for the Benefits of Melatonin in Cardiovascular Disease

The pineal gland is a neuroendocrine gland which produces melatonin, a neuroendocrine hormone with critical physiological roles in the circadian rhythm and sleep-wake cycle. Melatonin has been shown to possess anti-oxidant activity and neuroprotective properties. Numerous studies have shown that melatonin has significant functions in cardiovascular disease, and may have anti-aging properties. The ability of melatonin to decrease primary hypertension needs to be more extensively evaluated. Melatonin has shown significant benefits in reducing cardiac pathology, and preventing the death of cardiac muscle in response to ischemia-reperfusion in rodent species. Moreover, melatonin may also prevent the hypertrophy of the heart muscle under some circumstances, which in turn would lessen the development of heart failure. Several currently used conventional drugs show cardiotoxicity as an adverse effect. Recent rodent studies have shown that melatonin acts as an anti-oxidant and is effective in suppressing heart damage mediated by pharmacologic drugs. Therefore, melatonin has been shown to have cardioprotective activity in multiple animal and human studies. Herein, we summarize the most established benefits of melatonin in the cardiovascular system with a focus on the molecular mechanisms of action.

Adipocytes contribute to tumor progression and invasion of peritoneal metastasis by interacting with gastric cancer cells as cancer associated fibroblasts

BACKGROUND

Peritoneal metastasis (PM) is one of the most common causes of noncurative surgery and the most frequent recurrence pattern in gastric cancer (GC). During the process of PM, GC cells detached from primary tumor interact with human peritoneal mesothelial cells (HPMC) overlapped with adipose tissues such as the omentum or mesentery. Although the interaction with HPMC promotes the malignancy of GC, the role of adipose tissues remains unclear.

AIMS

We aimed to clarify how adipose tissue are affected by adjacent primary tumors during the expression of adipokines and to elucidate whether GC cells transform adipocytes into CAFs in vitro. In addition, we investigated whether GC cells are affected by adipocytes in their ability to infiltrate.

METHODS

We investigated the phenotypic conversion of adipocytes during the malignant process of GC cells in vivo and in vitro. We evaluated the expression levels of adiponectin in the omental adipose tissue of gastric cancer patients by western blotting. Following adipocytes/gastric cancer cells coculture, adipocyte markers, adiponectin receptors, and inflammatory cytokine markers were detected by real-time PCR and/or western blotting in the single-cultured and co-cultured adipocytes; cancer-associated fibroblast (CAF) markers were detected by immunofluorescence and western blotting in the single-cultured and co-cultured adipocytes; invasion assays were performed in single cultured and co-cultured MKN45 and OCUM.

RESULTS

In omental adipose tissues that are situated close to the primary tumors, the expression of adiponectin tended to decrease in patients with subserosal or serosal invasion. By co-culturing with GC cells, adipocytes were dedifferentiated and the expression levels of CAF marker FSP1 and inflammatory cytokines, PAI-1 and IL-6, significantly increased (p < 0.05). Furthermore, GC cells co-cultured with adipocytes showed enhanced invasion ability.

CONCLUSION

Our findings suggest that the phenotypic conversion of adipocytes may promote the malignancy of GC in the construction of the cancer microenvironment of PM.

The Effect of Cigarette Smoke Exposure on Efferocytosis in Chronic Obstructive Pulmonary Disease; Molecular Mechanisms and Treatment Opportunities

Cigarette smoking-related inflammation, cellular stresses, and tissue destruction play a key role in lung disease, such as chronic obstructive pulmonary disease (COPD). Notably, augmented apoptosis and impaired clearance of apoptotic cells, efferocytosis, contribute to the chronic inflammatory response and tissue destruction in patients with COPD. Of note, exposure to cigarette smoke can impair alveolar macrophages efferocytosis activity, which leads to secondary necrosis formation and tissue inflammation. A better understanding of the processes behind the effect of cigarette smoke on efferocytosis concerning lung disorders can help to design more efficient treatment approaches and also delay the development of lung disease, such as COPD. To this end, we aimed to seek mechanisms underlying the impairing effect of cigarette smoke on macrophages-mediated efferocytosis in COPD. Further, available therapeutic opportunities for restoring efferocytosis activity and ameliorating respiratory tract inflammation in smokers with COPD were also discussed.

Healing through the lens of immunothrombosis: Biology-inspired, evolution-tailored, and human-engineered biomimetic therapies

Evolution, from invertebrates to mammals, has yielded and shaped immunoclotting as a defense and repair response against trauma and infection. This mosaic of immediate and local wound-sealing and pathogen-killing mechanisms results in survival, restoration of homeostasis, and tissue repair. In mammals, immunoclotting has been complemented with the neuroendocrine system, platelets, and contact system among other embellishments, adding layers of complexity through interconnecting blood-born proteolytic cascades, blood cells, and the neuroendocrine system. In doing so, immunothrombosis endows humans with survival advantages, but entails vulnerabilities in the current unprecedented and increasingly challenging environment. Immunothrombosis and tissue repair appear to go hand in hand with common mechanisms mediating both processes, a fact that is underlined by recent advances that are deciphering the mechanisms of the repair process and of the biochemical pathways that underpins coagulation, hemostasis and thrombosis. This review is intended to frame both the universal aspects of tissue repair and the therapeutic use of autologous fibrin matrix as a biology-as-a-drug approach in the context of the evolutionary changes in coagulation and hemostasis. In addition, we will try to shed some light on the molecular mechanisms underlying the use of the autologous fibrin matrix as a biology-inspired, evolution-tailored, and human-engineered biomimetic therapy.

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.

Oral administration of curcumin ameliorates pulmonary fibrosis in mice through 15d-PGJ2-mediated induction of hepatocyte growth factor in the colon

Oral administration of curcumin has been shown to inhibit pulmonary fibrosis (PF) despite its extremely low bioavailability. In this study, we investigated the mechanisms underlying the anti-PF effect of curcumin in focus on intestinal endocrine. In bleomycin- and SiO₂-treated mice, curcumin (75, 150 mg· kg^-1 per day) exerted dose-dependent anti-PF effect when administered orally or rectally but not intravenously, implying an intestinal route was involved in the action of curcumin. We speculated that curcumin might promote the generation of gut-derived factors and the latter acted as a mediator subsequently entering the lungs to ameliorate fibrosis. We showed that oral administration of curcumin indeed significantly increased the expression of gut-derived hepatocyte growth factor (HGF) in colon tissues. Furthermore, in bleomycin-treated mice, the upregulated protein level of HGF in lungs by oral curcumin was highly correlated with its anti-PF effect, which was further confirmed by coadministration of c-Met inhibitor SU11274. Curcumin (5-40 μM) dose-dependently increased HGF expression in primary mouse fibroblasts, macrophages, CCD-18Co cells (fibroblast cell line), and RAW264.7 cells (monocyte-macrophage cell line), but not in primary colonic epithelial cells. In CCD-18Co cells and RAW264.7 cells, curcumin dose-dependently activated PPARγ and CREB, whereas PPARγ antagonist GW9662 (1 μM) or cAMP response element (CREB) inhibitor KG-501 (10 μM) significantly decreased the boosting effect of curcumin on HGF expression. Finally, we revealed that curcumin dose-dependently increased the production of 15-deoxy-Δ^{12, 14}-prostaglandin J2 (15d-PGJ2) in CCD-18Co cells and RAW264.7 cells, which was a common upstream of the two transcription factors. Moreover, both the in vitro and in vivo effects of curcumin were diminished by coadministration of HPGDS-inhibitor-1, an inhibitor of 15d-PGJ2 generation. Together, curcumin promotes the expression of HGF in colonic fibroblasts and macrophages by activating PPARγ and CREB via an induction of 15d-PGJ2, and the HGF enters the lungs giving rise to an anti-PF effect.

Diabetes and Its Complications: Therapies Available, Anticipated and Aspired

Worldwide, diabetes ranks among the ten leading causes of mortality. Prevalence of diabetes is growing rapidly in low and middle income countries. It is a progressive disease leading to serious co-morbidities, which results in increased cost of treatment and over-all health system of the country. Pathophysiological alterations in Type 2 Diabetes (T2D) progressed from a simple disturbance in the functioning of the pancreas to triumvirate to ominous octet to egregious eleven to dirty dozen model. Due to complex interplay of multiple hormones in T2D, there may be multifaceted approach in its management. The 'long-term secondary complications' in uncontrolled diabetes may affect almost every organ of the body, and finally may lead to multi-organ dysfunction. Available therapies are inconsistent in maintaining long term glycemic control and their long term use may be associated with adverse effects. There is need for newer drugs, not only for glycemic control but also for prevention or mitigation of secondary microvascular and macrovascular complications. Increased knowledge of the pathophysiology of diabetes has contributed to the development of novel treatments. Several new agents like Glucagon Like Peptide - 1 (GLP-1) agonists, Dipeptidyl Peptidase IV (DPP-4) inhibitors, amylin analogues, Sodium-Glucose transport -2 (SGLT- 2) inhibitors and dual Peroxisome Proliferator-Activated Receptor (PPAR) agonists are available or will be available soon, thus extending the range of therapy for T2D, thereby preventing its long term complications. The article discusses the pathophysiology of diabetes along with its comorbidities, with a focus on existing and novel upcoming antidiabetic drugs which are under investigation. It also dives deep to deliberate upon the novel therapies that are in various stages of development. Adding new options with new mechanisms of action to the treatment armamentarium of diabetes may eventually help improve outcomes and reduce its economic burden.

PPARγ and Its Agonists in Chronic Kidney Disease

Chronic kidney disease (CKD) has become a global healthcare issue. CKD can progress to irreversible end-stage renal diseases (ESRD) or renal failure. The major risk factors for CKD include obesity, diabetes, and cardiovascular diseases. Understanding the key process involved in the disease development may lead to novel interventive strategies, which is currently lagging behind. Peroxisome proliferator-activated receptor γ (PPARγ) is one of the ligand-activated transcription factor superfamily members and is globally expressed in human tissues. Its agonists such as thiazolidinediones (TZDs) have been applied as effective antidiabetic drugs as they control insulin sensitivity in multiple metabolic tissues. Besides, TZDs exert protective effects in multiple other CKD risk disease contexts. As PPARγ is abundantly expressed in major kidney cells, its physiological roles in those cells have been studied in both cell and animal models. The function of PPARγ in the kidney ranges from energy metabolism, cell proliferation to inflammatory suppression, although major renal side effects of existing agonists (including TZDs) have been reported, which limited their application in treating CKD. In the current review, we systemically assess the function of PPARγ in CKDs and the benefits and current limitations of its agonists in the clinical applications.

Rosiglitazone Suppresses Calcium Oxalate Crystal Binding and Oxalate-Induced Oxidative Stress in Renal Epithelial Cells by Promoting PPAR-γ Activation and Subsequent Regulation of TGF-β1 and HGF Expression

Peroxisome proliferator-activated receptor- (PPAR-) γ is a ligand-dependent transcription factor, and it has become evident that PPAR-γ agonists have renoprotective effects, but their influence and mechanism during the development of calcium oxalate (CaOx) nephrolithiasis remain unknown. Rosiglitazone (RSG) was used as a representative PPAR-γ agonist in our experiments. The expression of transforming growth factor-β1 (TGF-β1), hepatocyte growth factor (HGF), c-Met, p-Met, PPAR-γ, p-PPAR-γ (Ser112), Smad2, Smad3, pSmad2/3, and Smad7 was examined in oxalate-treated Madin-Darby canine kidney (MDCK) cells and a stone-forming rat model. A CCK-8 assay was used to evaluate the effects of RSG on cell viability. In addition, intracellular reactive oxygen species (ROS) levels were monitored, and lipid peroxidation in renal tissue was detected according to superoxide dismutase and malondialdehyde levels. Moreover, the location and extent of CaOx crystal deposition were evaluated by Pizzolato staining. Our results showed that, both in vitro and in vivo, oxalate impaired PPAR-γ expression and phosphorylation, and then accumulative ROS production was observed, accompanied by enhanced TGF-β1 and reduced HGF. These phenomena could be reversed by the addition of RSG. RSG also promoted cell viability and proliferation and decreased oxidative stress damage and CaOx crystal deposition. However, these protective effects of RSG were abrogated by the PPAR-γ-specific inhibitor GW9662. Our results revealed that the reduction of PPAR-γ activity played a critical role in oxalate-induced ROS damage and CaOx stone formation. RSG can regulate TGF-β1 and HGF/c-Met through PPAR-γ to exert antioxidant effects against hyperoxaluria and alleviate crystal deposition. Therefore, PPAR-γ agonists may be expected to be a novel therapy for nephrolithiasis, and this effect is related to PPAR-γ-dependent suppression of oxidative stress.

Computational identification of tissue-specific transcription factor cooperation in ten cattle tissues

Transcription factors (TFs) are a special class of DNA-binding proteins that orchestrate gene transcription by recruiting other TFs, co-activators or co-repressors. Their combinatorial interplay in higher organisms maintains homeostasis and governs cell identity by finely controlling and regulating tissue-specific gene expression. Despite the rich literature on the importance of cooperative TFs for deciphering the mechanisms of individual regulatory programs that control tissue specificity in several organisms such as human, mouse, or Drosophila melanogaster, to date, there is still need for a comprehensive study to detect specific TF cooperations in regulatory processes of cattle tissues. To address the needs of knowledge about specific combinatorial gene regulation in cattle tissues, we made use of three publicly available RNA-seq datasets and obtained tissue-specific gene (TSG) sets for ten tissues (heart, lung, liver, kidney, duodenum, muscle tissue, adipose tissue, colon, spleen and testis). By analyzing these TSG-sets, tissue-specific TF cooperations of each tissue have been identified. The results reveal that similar to the combinatorial regulatory events of model organisms, TFs change their partners depending on their biological functions in different tissues. Particularly with regard to preferential partner choice of the transcription factors STAT3 and NR2C2, this phenomenon has been highlighted with their five different specific cooperation partners in multiple tissues. The information about cooperative TFs could be promising: i) to understand the molecular mechanisms of regulating processes; and ii) to extend the existing knowledge on the importance of single TFs in cattle tissues.

Amelioration of Endoplasmic Reticulum Stress by Mesenchymal Stem Cells via Hepatocyte Growth Factor/c-Met Signaling in Obesity-Associated Kidney Injury

Recent advances in the understanding of lipid metabolism suggest a critical role of endoplasmic reticulum (ER) stress in obesity‐induced kidney injury. Hepatocyte growth factor (HGF) is a pleiotropic cytokine frequently featured in stem cell therapy with distinct renotropic benefits. This study aims to define the potential link between human induced pluripotent stem cell‐derived mesenchymal stem cells (iPS‐MSCs)/bone marrow‐derived MSCs (BM‐MSCs) and ER stress in lipotoxic kidney injury induced by palmitic acid (PA) in renal tubular cells and by high‐fat diet (HFD) in mice. iPS‐MSCs or BM‐MSCs alleviated ER stress (by preventing induction of Bip, chop, and unfolded protein response), inflammation (Il6, Cxcl1, and Cxcl2), and apoptosis (Bax/Bcl2 and terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end labeling‐positive cells) in renal cortex of animals exposed to HFD thus mitigating histologic damage and albuminuria, via activating HGF/c‐Met paracrine signaling that resulted in enhanced HGF secretion in the glomerular compartment and c‐Met expression in the tubules. Coculture experiments identified glomerular endothelial cells (GECs) to be the exclusive source of glomerular HGF when incubated with either iPS‐MSCs or BM‐MSCs in the presence of PA. Furthermore, both GEC‐derived HGF and exogenous recombinant HGF attenuated PA‐induced ER stress in cultured tubular cells, and this effect was abrogated by a neutralizing anti‐HGF antibody. Taken together, this study is the first to demonstrate that MSCs ameliorate lipotoxic kidney injury via a novel microenvironment‐dependent paracrine HGF/c‐Met signaling mechanism to suppress ER stress and its downstream pro‐inflammatory and pro‐apoptotic consequences. stem cells translational medicine2019;8:898&910

Fibroblast mTOR/PPARγ/HGF axis protects against tubular cell death and acute kidney injury

Kidney fibroblasts play a crucial role in dictating tubular cell fate and the outcome of acute kidney injury (AKI). The underlying mechanisms remain to be determined. Here, we found that mTOR signaling was activated in fibroblasts from mouse kidneys with ischemia/reperfusion injury (IRI). Ablation of fibroblast Rheb or Rictor promoted, while ablation of fibroblast Tsc1 protected against tubular cell death and IRI in mice. In tubular cells cultured with conditioned media (CM) from Rheb^-/- or Rictor^-/- fibroblasts, less hepatocyte growth factor (HGF) receptor c-met signaling activation or staurosporine-induced cell apoptosis was observed. While CM from Tsc1^-/- fibroblasts promoted tubular cell c-met signaling activation and inhibited staurosporine-induced cell apoptosis. In kidney fibroblasts, blocking mTOR signaling downregulated the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and HGF. Downregulating fibroblast HGF expression or blocking tubular cell c-met signaling facilitated tubular cell apoptosis. Notably, renal PPARγ and HGF expression was less in mice with fibroblast Rheb or Rictor ablation, but more in mice with fibroblast Tsc1 ablation than their littermate controls, respectively. Together, these data suggest that mTOR signaling activation in kidney fibroblasts protects against tubular cell death and dictates the outcome of AKI through stimulating PPARγ and HGF expression.

Autologous fibrin scaffolds: When platelet- and plasma-derived biomolecules meet fibrin

The healing of vascularized mammalian tissue injuries initiate with hemostasis and clotting as part of biological defense system leading to the formation of a fibrin clot in which activated platelets are trapped to quickly stop bleeding and destroy microbials. In order to harness the therapeutic potential of biomolecules secreted by platelets and stemmed from plasma, blood deconstruction has allowed to yield autologous platelet-and plasma-derived protein fibrin scaffold. The autologous growth factors and microparticles stemmed from platelets and plasma, interact with fibrin, extracellular matrix, and tissue cells in a combinatorial, synergistic, and multidirectional way on mechanisms governing tissue repair. This interplay will induce a wide range of cell specifications during inflammation and repair process including but not limited to fibrogenesis, angiogenesis, and immunomodulation. As biology-as-a-drug approach, autologous platelet-and plasma-derived protein fibrin scaffold is emerging as a safe and efficacious natural human-engineered growth factor delivery system to repair musculoskeletal tissues, and skin and corneal ulcers and burns. In doing so, it acts as therapeutic agent not perfect but close to biological precision. However, this autologous, biocompatible, biodegradable, and long in vivo lasting strategy faces several challenges, including its non-conventional single dose-response effect, the lack of standardization in its preparation and application, and the patient's biological features. In this review, we give an account of the main events of tissue repair. Then, we describe the procedure to prepare autologous platelet-and plasma-derived protein fibrin scaffolds, and the rationale behind these biomaterials, and finally, we highlight the significance of strategic accuracy in their application.

Apoptotic cells trigger the ABCA1/STAT6 pathway leading to PPAR-γ expression and activation in macrophages

The signal transducer and activator of transcription 6 (STAT6) transcription factor activates peroxisome proliferator-activated receptor gamma (PPAR-γ)-regulated gene expression in immune cells. We investigated proximal membrane signaling that was initiated in macrophages after exposure to apoptotic cells that led to enhanced PPAR-γ expression and activity, using specific siRNAs for ABCA1, STAT6, and PPAR-γ, or their antagonists. The interactions between mouse bone marrow-derived macrophages or RAW 264.7 cells and apoptotic Jurkat cells, but not viable cells, resulted in the induction of STAT6 phosphorylation as well as PPAR-γ expression and activation. Knockdown of ATP-binding cassette transporter A1 (ABCA1) after the transfection of macrophages with ABCA1-specific siRNAs reduced apoptotic cell-induced STAT6 phosphorylation as well as PPAR-γ mRNA and protein expression. ABCA1 knockdown also reduced apoptotic cell-induced liver X receptor α (LXR-α) mRNA and protein expression. Moreover, inhibition of STAT6 with specific siRNAs or the pharmacological inhibitor AS1517499AS reversed the induction of PPAR-γ, LXR-α, and ABCA1 by apoptotic Jurkat cells. PPAR-γ-specific siRNAs or the PPAR-γ antagonist GW9662 inhibited apoptotic cell-induced increases in LXR-α and ABCA1 mRNA and protein levels. Thus, these results indicate that apoptotic cells trigger the ABCA1/STAT6 pathway, leading to the activation of the PPAR-γ/LXR-α/ABCA1 pathway in macrophages.

Myokine mediated muscle-kidney crosstalk suppresses metabolic reprogramming and fibrosis in damaged kidneys

Kidney injury initiates metabolic reprogramming in tubule cells that contributes to the development of chronic kidney disease (CKD). Exercise has been associated with beneficial effects in patients with CKD. Here we show that the induction of a myokine, irisin, improves kidney energy metabolism and prevents kidney damage. In response to kidney injury, mice with muscle-specific PGC-1α overexpression (mPGC-1α) exhibit reduced kidney damage and fibrosis. Metabolomics analysis reveals increased ATP production and improved energy metabolism in injured kidneys from mPGC-1α mice. We identify irisin as a serum factor that mediates these metabolic effects during progressive kidney injury by inhibiting TGF-β type 1 receptor. Irisin depletion from serum blunts the induction of oxygen consumption rate observed in tubule cells treated with mPGC-1α serum. In mice, recombinant irisin administration attenuates kidney damage and fibrosis and improves kidney functions. We suggest that myokine-mediated muscle-kidney crosstalk can suppress metabolic reprograming and fibrogenesis during kidney disease.

Progressive tubule cell damage results in defects in mitochondrial metabolism and exercise seems to be beneficial during chronic kidney disease. Here Peng et al. show that irisin, an exercise-induced myokine, improves kidney energy metabolism by inhibiting TGF-β type 1 receptors and ameliorates fibrosis.

Interactions between TGF-β1, canonical WNT/β-catenin pathway and PPAR γ in radiation-induced fibrosis

Radiation therapy induces DNA damage and inflammation leading to fibrosis. Fibrosis can occur 4 to 12 months after radiation therapy. This process worsens with time and years. Radiation-induced fibrosis is characterized by fibroblasts proliferation, myofibroblast differentiation, and synthesis of collagen, proteoglycans and extracellular matrix. Myofibroblasts are non-muscle cells that can contract and relax. Myofibroblasts evolve towards irreversible retraction during fibrosis process. In this review, we discussed the interplays between transforming growth factor-β1 (TGF-β1), canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR γ) in regulating the molecular mechanisms underlying the radiation-induced fibrosis, and the potential role of PPAR γ agonists. Overexpression of TGF-β and canonical WNT/β-catenin pathway stimulate fibroblasts accumulation and myofibroblast differentiation whereas PPAR γ expression decreases due to the opposite interplay of canonical WNT/β-catenin pathway. Both TGF-β1 and canonical WNT/β-catenin pathway stimulate each other through the Smad pathway and non-Smad pathways such as phosphatidylinositol 3-kinase/serine/threonine kinase (PI3K/Akt) signaling. WNT/β-catenin pathway and PPAR γ interact in an opposite manner. PPAR γ agonists decrease β-catenin levels through activation of inhibitors of the WNT pathway such as Smad7, glycogen synthase kinase-3 (GSK-3 β) and dickkopf-related protein 1 (DKK1). PPAR γ agonists also stimulate phosphatase and tensin homolog (PTEN) expression, which decreases both TGF-β1 and PI3K/Akt pathways. PPAR γ agonists by activating Smad7 decrease Smads pathway and then TGF-β signaling leading to decrease radiation-induced fibrosis. TGF-β1 and canonical WNT/β-catenin pathway promote radiation-induced fibrosis whereas PPAR γ agonists can prevent radiation-induced fibrosis.

Hepatocyte Growth Factor Prevented High-Fat Diet-Induced Obesity and Improved Insulin Resistance in Mice

Obesity and its associated chronic inflammation in adipose tissue initiate insulin resistance, which is related to several pathologies including hypertension and atherosclerosis. Previous reports demonstrated that circulating hepatocyte growth factor (HGF) level was associated with obesity and type 2 diabetes. However, its precise role in obesity and related-pathology is unclear. In this experiment, cardiac-specific over-expression of human HGF in mice (HGF-Tg mice) which showed 4–5 times higher serum HGF levels than wild-type mice were used. While body weight in wild-type mice fed with high fat diet (HFD) for 14 weeks was significantly increased accompanied with insulin resistance, HGF-Tg mice prevented body weight gain and insulin resistance. The accumulation of macrophages and elevated levels of inflammatory mediators in adipose tissue were significantly inhibited in HGF-Tg mice as compared to wild-type mice. The HFD-induced obesity in wild-type mice treated with HGF-neutralizing antibody showed an exacerbated response to the glucose tolerance test. These gain-of-function and loss-of-function studies demonstrated that the elevated HGF level induced by HFD have protective role against obesity and insulin resistance.

Mesenchymal Stem/Stromal Cells in Liver Fibrosis: Recent Findings, Old/New Caveats and Future Perspectives

Mesenchymal stem/stromal cells (MSCs) are progenitors which share plastic-adherence capacity and cell surface markers but have different properties according to their cell and tissue sources and to culture conditions applied. Many recent publications suggest that MSCs can differentiate into hepatic-like cells, which can be a consequence of either a positive selection of rare in vivo pluripotent cells or of the original plasticity of some cells contributing to MSC cultures. A possible role of MSCs in hereditary transmission of obesity and/or diabetes as well as properties of MSCs regarding immunomodulation, cell fusion and exosome release capacities are discussed according to recent literature. Limitations in methods used to track MSCs in vivo especially in the context of liver cirrhosis are addressed as well as strategies explored to enhance their migratory, survival and proliferation properties, which are known to be relevant for their future clinical use. Current knowledge regarding mechanisms involved in liver cirrhosis amelioration mediated by naïve and genetically modified MSCs as well as the effects of applying preconditioning and combined strategies to improve their therapeutic effects are evaluated. Finally, first reports of GMP guidelines and biosafety issues in MSCs applications are discussed.

Madecassoside ameliorates bleomycin-induced pulmonary fibrosis in mice through promoting the generation of hepatocyte growth factor via PPAR-γ in colon

BACKGROUND AND PURPOSE

Madecassoside has potent anti-pulmonary fibrosis (PF) effects when administered p.o., despite having extremely low oral bioavailability. Herein, we explored the mechanism of this anti-PF effect with regard to gut hormones.

EXPERIMENTAL APPROACH

A PF model was established in mice by intratracheal instillation of bleomycin. Haematoxylin and eosin stain and Masson's trichrome stain were used to assess histological changes in the lung. Quantitative-PCR and Western blot detected mRNA and protein levels, respectively, and cytokines were measured by ELISA. Small interfering RNA was used for gene-silencing. EMSA was applied to detect DNA-binding activity.

KEY RESULTS

Administration of madecassoside, p.o., but not its main metabolite madecassic acid, exhibited a direct anti-PF effect in mice. However, i.p. madecassoside had no anti-PF effect. Madecassoside increased the expression of hepatocyte growth factor (HGF) in colon tissues, and HGF receptor antagonists attenuated its anti-PF effect. Madecassoside facilitated the secretion of HGF from colonic epithelial cells by activating the PPAR-γ pathway, as shown by an up-regulation of PPAR-γ mRNA expression, nuclear translocation and DNA-binding activity both in vitro and in vivo. Also GW9662, a selective PPAR-γ antagonist, almost completely prevented the madecassoside-induced increased expression of HGF and amelioration of PF.

CONCLUSIONS AND IMPLICATIONS

The potent anti-PF effects induced by p.o. madecassoside in mice are not mediated by its metabolites or itself after absorption into blood. Instead, madecassoside increases the activity of PPAR-γ, which subsequently increases HGF expression in colonic epithelial cells. HGF then enters into the circulation and lung tissue to exert an anti-PF effect.

Rapid Identification of Potential Drugs for Diabetic Nephropathy Using Whole-Genome Expression Profiles of Glomeruli

Objective. To investigate potential drugs for diabetic nephropathy (DN) using whole-genome expression profiles and the Connectivity Map (CMAP). Methodology. Eighteen Chinese Han DN patients and six normal controls were included in this study. Whole-genome expression profiles of microdissected glomeruli were measured using the Affymetrix human U133 plus 2.0 chip. Differentially expressed genes (DEGs) between late stage and early stage DN samples and the CMAP database were used to identify potential drugs for DN using bioinformatics methods. Results. (1) A total of 1065 DEGs (FDR < 0.05 and fold change > 1.5) were found in late stage DN patients compared with early stage DN patients. (2) Piperlongumine, 15d-PGJ2 (15-delta prostaglandin J2), vorinostat, and trichostatin A were predicted to be the most promising potential drugs for DN, acting as NF-κB inhibitors, histone deacetylase inhibitors (HDACIs), PI3K pathway inhibitors, or PPARγ agonists, respectively. Conclusion. Using whole-genome expression profiles and the CMAP database, we rapidly predicted potential DN drugs, and therapeutic potential was confirmed by previously published studies. Animal experiments and clinical trials are needed to confirm both the safety and efficacy of these drugs in the treatment of DN.

Transforming growth factor beta (TGF-β) isoforms in wound healing and fibrosis

Scar formation, with persistent alteration of the normal tissue structure, is an undesirable and significant result of both wound healing and fibrosing disorders. There are few strategies to prevent or to treat scarring. The transforming growth factor beta (TGF-β) superfamily is an important mediator of tissue repair. Each TGF-β isoform may exert a different effect on wound healing, which may be context-dependent. In particular, TGF-β1 may mediate fibrosis in adults' wounds, while TGF-β3 may promote scarless healing in the fetus and reduced scarring in adults. Thus, TGF-β3 may offer a scar-reducing therapy for acute and chronic wounds and fibrosing disorders.

Induction of Angiogenesis by a Type III Phosphodiesterase Inhibitor, Cilostazol, Through Activation of Peroxisome Proliferator-Activated Receptor-γ and cAMP Pathways in Vascular Cells

OBJECTIVE

Peripheral arterial disease is highly prevalent in the elderly and in the subjects with cardiovascular risk factors such as diabetes. Approximately 2% to 4% of those affected with peripheral arterial disease commonly complain of intermittent claudication. Cilostazol, a type III phosphodiesterase inhibitor, is the only Food and Drug Administration-approved drug for the treatment of intermittent claudication. Cilostazol has been shown to be beneficial for the improvement of pain-free walking distance in patients with intermittent claudication in a series of randomized clinical trials. However, the underlying mechanism how cilostazol improved intermittent claudication symptoms is still unclear.

APPROACH AND RESULTS

In this study, the effect of cilostazol on ischemic leg was investigated in mouse ischemic hindlimb model. Administration of cilostazol significantly increased the expression of hepatocyte growth factor (HGF), vascular endothelial growth factor, angiopoietin-1, and peroxisome proliferator-activated receptor-γ in vasculature. The capillary density in ischemic leg was also significantly increased in cilostazol treatment group when compared with control and aspirin treatment group. However, an increase in capillary density and the expression of growth factors was almost completely abolished by coadministration of HGF-neutralizing antibody, suggesting that cilostazol enhanced angiogenesis mainly through HGF. In vitro experiment revealed that cilostazol treatment increased HGF production in vascular smooth muscle cells via 2 major pathways: peroxisome proliferator-activated receptor-γ and cAMP pathways.

CONCLUSIONS

Our data suggest that the favorable effects of cilostazol on ischemic leg might be through the angiogenesis through the induction of HGF via peroxisome proliferator-activated receptor-γ and cAMP pathways.

PPARγ activation following apoptotic cell instillation promotes resolution of lung inflammation and fibrosis via regulation of efferocytosis and proresolving cytokines

Changes in macrophage phenotype have been implicated in apoptotic cell-mediated immune modulation via induction of peroxisome proliferator-activated receptor-γ (PPARγ). In this study, we characterized PPARγ induction by apoptotic cell instillation over the course of bleomycin-induced lung injury in C57BL/6 mice. Next, the role of PPARγ activation in resolving lung inflammation and fibrosis was investigated. Our data demonstrate that apoptotic cell instillation after bleomycin results in immediate and prolonged enhancement of PPARγ mRNA and protein in alveolar macrophages and lung. Moreover, PPARγ activity and expression of its target molecules, including CD36, macrophage mannose receptor, and arginase 1, were persistently enhanced following apoptotic cell instillation. Coadministration of the PPARγ antagonist, GW9662, reversed the enhanced efferocytosis, and the reduced proinflammatory cytokine expression, neutrophil recruitment, myeloperoxidase activity, hydroxyproline contents, and fibrosis markers, including type 1 collagen α2, fibronectin and α-smooth muscle actin (α-SMA), in the lung by apoptotic cell instillation. In addition, inhibition of PPARγ activity reversed the expression of transforming growth factor-β (TGF-β), interleukin (IL)-10, and hepatocyte growth factor (HGF). These findings indicate that one-time apoptotic cell instillation contributes to anti-inflammatory and antifibrotic responses via upregulation of PPARγ expression and subsequent activation, leading to regulation of efferocytosis and production of proresolving cytokines.

The Role of PPAR Gamma in Systemic Sclerosis

Fibrosis is recognized as an important feature of many chronic diseases, such as systemic sclerosis (SSc), an autoimmune disease of unknown etiology, characterized by immune dysregulation and vascular injury, followed by progressive fibrosis affecting the skin and multiple internal organs. SSc has a poor prognosis because no therapy has been shown to reverse or arrest the progression of fibrosis, representing a major unmet medical need. Recently, antifibrotic effects of PPARγ ligands have been studied in vitro and in vivo and some theories have emerged leading to new insights. Aberrant PPARγ function seems to be implicated in pathological fibrosis in the skin and lungs. This antifibrotic effect is mainly related to the inhibition of TGF-β/Smad signal transduction but other pathways can be involved. This review focused on recent studies that identified PPARγ as an important novel pathway with critical roles in regulating connective tissue homeostasis, with emphasis on skin and lung fibrosis and its role on systemic sclerosis.

Hepatocyte growth factor, a biomarker of macroangiopathy in diabetes mellitus

Atherosclerotic involvements are an essential causal element of prospect in diabetes mellitus (DM), with carotid atherosclerosis (CA) being a common risk-factor for prospective crisis of coronary artery diseases (CAD) and/or cerebral infarction (CI) in DM subjects. From another point of view, several reports have supplied augmenting proof that hepatocyte growth factor (HGF) has a physiopathological part in DM involvements. HGF has been a mesenchymal-derived polyphenic factor which modulates development, motion, and morphosis of diverse cells, and has been regarded as a humor intermediator of epithelial-mesenchymal interplays. The serum concentrations of HGF have been elevated in subjects with CAD and CI, especially during the acute phase of both disturbances. In our study with 89 type 2 DM patients, the association between serum concentrations of HGF and risk-factors for macrovascular complications inclusive of CA were examined. The average of serum HGF levels in the subjects was more elevated than the reference interval. The serum HGF concentrations associated positively with both intimal-media thickness (IMT) (r = 0.24, P = 0.0248) and plaque score (r = 0.27, P = 0.0126), indicating a relationship between the elevated HGF concentrations and advancement of CA involvements. Multivariate statistical analysis accentuated that serum concentrations of HGF would be associated independently with IMT (standardized = 0.28, P = 0.0499). The review indicates what is presently known regarding serum HGF might be a new and meaningful biomarker of macroangiopathy in DM subjects.

Neuroprotectin/protectin D1: endogenous biosynthesis and actions on diabetic macrophages in promoting wound healing and innervation impaired by diabetes

Dysfunction of macrophages (MΦs) in diabetic wounds impairs the healing. MΦs produce anti-inflammatory and pro-resolving neuroprotectin/protectin D1 (NPD1/PD1, 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid); however, little is known about endogenous NPD1 biosynthesis by MΦs and the actions of NPD1 on diabetic MΦ functions in diabetic wound healing. We used an excisional skin wound model of diabetic mice, MΦ depletion, MΦs isolated from diabetic mice, and mass spectrometry-based targeted lipidomics to study the time course progression of NPD1 levels in wounds, the roles of MΦs in NPD1 biosynthesis, and NPD1 action on diabetic MΦ inflammatory activities. We also investigated the healing, innervation, chronic inflammation, and oxidative stress in diabetic wounds treated with NPD1 or NPD1-modulated MΦs from diabetic mice. Injury induced endogenous NPD1 biosynthesis in wounds, but diabetes impeded NPD1 formation. NPD1 was mainly produced by MΦs. NPD1 enhanced wound healing and innervation in diabetic mice and promoted MΦs functions that accelerated these processes. The underlying mechanisms for these actions of NPD1 or NPD1-modulated MΦs involved 1) attenuating MΦ inflammatory activities and chronic inflammation and oxidative stress after acute inflammation in diabetic wound, and 2) increasing MΦ production of IL10 and hepatocyte growth factor. Taken together, NPD1 appears to be a MΦs-produced factor that accelerates diabetic wound healing and promotes MΦ pro-healing functions in diabetic wounds. Decreased NPD1 production in diabetic wound is associated with impaired healing. This study identifies a new molecular target that might be useful in development of more effective therapeutics based on NPD1 and syngeneic diabetic MΦs for treatment of diabetic wounds.

Impact of stepwise sodium and ultra filtration profiles and dialysis solution flow rate profile on dialysis adequacy

BACKGROUND

Inadequate dialysis is one of the main causes of mortality of the patients undergoing hemodialysis. The methods that lead to improvement of dialysis adequacy in these patients are of great importance due to them causing an improvement of quality of life. As numerous factors can play a role in improvement of dialysis adequacy, the present study aimed to investigate the level of impact of stepwise sodium and ultra filtration profiles and dialysis solution flow rate profile on dialysis adequacy.

MATERIALS AND METHODS

This is a cross-over clinical trial conducted on 32 patients selected from two hemodialysis centers in Isfahan in 2013. The patients were assigned to two identical groups through random allocation, and each patient in group 1 underwent hemodialysis for four routine dialysis sessions, four stepwise sodium and ultra filtration profile sessions, and four sessions by stepwise dialysis solution flow rate profile. The patients in group 2 underwent hemodialysis for four sessions of stepwise dialysate flow rate profile, four sessions of stepwise sodium and ultra filtration profiles, and four sessions of routine dialysis method. Dialysis adequacy was on line calculated by Kt/V ratio in each session, and was analyzed by repeated measure analysis of variance (ANOVA), least significant difference (LSD) post-hoc test, and independent t-test.

RESULTS

Means of dialysis adequacies were 1.239 (0.25) in the routine method, 1.407 (0.26) in stepwise sodium and ultra filtration profiles, and 1.414 (0.26) in dialysis solution flow rate profile. There was a significant difference between the routine method and the other two profiles (P < 0.05), but the difference in dialysis adequacy means in the two profile methods was not significant (P > 0.05). Mean scores of dialysis adequacy in the three treatment methods in the two groups showed that the sequence of methods had no effect on treatment outcome (P > 0.05).

CONCLUSIONS

Stepwise sodium and ultra filtration profiles and stepwise dialysis solution flow rate profile are suggested as they can increase dialysis adequacy compared to the routine method.

ID2 predicts poor prognosis in breast cancer, especially in triple-negative breast cancer, and inhibits E-cadherin expression

Background

Inhibitors of DNA-binding (ID) proteins are known as important modulators in the regulation of cell proliferation and differentiation. This study sought to investigate the prognostic value of ID proteins in breast cancer.

Methods

The prognostic role of ID proteins in human breast cancer was investigated in 250 breast cancers, via tissue microarrays. The messenger (m)RNA and protein levels of E-cadherin were examined by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blotting, in cells overexpressing IDs. Dual-luciferase report assay was used to investigate the potential mechanism, and a migration assay was performed to investigate the influence of IDs on cell migratory activity.

Results

The survival analysis with Kaplan–Meier and Cox regression showed that ID2 expression level, which correlated with estrogen receptor status and E-cadherin abundance, served as an independent prognostic factor for disease-free survival (DFS) (P=0.013). The prognostic value of ID2 for DFS was most significant in triple-negative breast cancer patients (P=0.009). We also found that ID2 was negatively correlated with E-cadherin expression by correlation analysis (P=0.020, Pearson’s R=−0.155). Subsequently, we explored the biological rationale and uncovered that the enforced expression of ID proteins could suppress E-cadherin expression significantly, thus increasing the migration ability of mammary epithelial cells. Then using a combination of ID2 and E-cadherin expression, the patients were classified into four subgroups with different DFS (P=0.023).

Conclusion

The overexpression of ID2 can be used as a prognostic marker in breast cancer patients, especially in triple-negative breast cancer patients. ID proteins were still, unexpectedly, revealed to inhibit E-cadherin abundance.

Pioglitazone, a PPARγ agonist, provides comparable protection to angiotensin converting enzyme inhibitor ramipril against adriamycin nephropathy in rat

Peroxisome proliferator-activated receptor γ (PPARγ) agonists have been shown to ameliorate diabetic nephropathy, but much less are known about their effects in non-diabetic nephropathies. In the present study, metabolic parameters, blood pressure, aortic endothelial function along with molecular and structural markers of glomerular and tubulointerstitial renal damage, were studied in a rat model of normotensive nephropathy induced by adriamycin and treated with PPARγ agonist pioglitazone (12mg/kg, po), angiotensin converting enzyme (ACE) inhibitor ramipril (1mg/kg, po) or their combination. Pioglitazone had no effect on systolic blood pressure, marginally reduced glycemia and improved aortic endothelium-dependent relaxation. In the kidney, pioglitazone prevented the development of proteinuria and focal glomerulosclerosis to the similar extent as blood-pressure lowering ramipril. Renoprotection provided by either treatment was associated with a reduction in the cortical expression of profibrotic plasminogen activator inhibitor-1 and microvascular damage-inducing endothelin-1, and a limitation of interstitial macrophage influx. Treatment with PPARγ agonist, as well as ACE inhibitor comparably affected renal expression of the renin-angiotensin system (RAS) components, normalizing increased renal expression of ACE and enhancing the expression of Mas receptor. Interestingly, combined pioglitazone and ramipril treatment did not provide any additional renoprotection. These results demonstrate that in a nondiabetic renal disease, such as adriamycin-induced nephropathy, PPARγ agonist pioglitazone provides renoprotection to a similar extent as an ACE inhibitor by interfering with the expression of local RAS components and attenuating related profibrotic and inflammatory mechanisms. The combination of the both agents, however, does not lead to any additional renal benefit.

New molecular medicine-based scar management strategies

Keloids and hypertrophic scars are prevalent disabling conditions with still suboptimal treatments. Basic science and molecular-based medicine research have contributed to unravel new bench-to-bedside scar therapies and to dissect the complex signalling pathways involved. Peptides such as the transforming growth factor beta (TGF-β) superfamily, with Smads, Ski, SnoN, Fussels, endoglin, DS-Sily, Cav-1p, AZX100, thymosin-β4 and other related molecules may emerge as targets to prevent and treat keloids and hypertrophic scars. The aim of this review is to describe the basic complexity of these new molecular scar management strategies and point out new fibrosis research lines.

Correlation between TSP-1, TGF-β and PPAR-γ expression levels and glioma microvascular density

Gliomas are the most common type of primary tumor in the central nervous system and are characterized by abundant capillary angiogenesis. It is important to study the underlying molecular mechanisms of angiogenesis in order to aid the identification of potential therapeutic targets. The aim of the current study was to investigate the expression levels of thrombospondin-1 (TSP-1), transforming growth factor-β (TGF-β) and peroxisome proliferator-activated receptor-γ (PPAR-γ) in gliomas, and determine their relationships with angiogenesis. Immunohistochemical methods were used to detect TSP-1, TGF-β and PPAR-γ expression levels and to assess microvascular density (MVD) in 99 glioma tissue samples of various grades. The total positive expression rates of TSP-1 and PPAR-γ were 78.4 and 94.1% in low-grade gliomas and 45.8 and 39.6% in high-grade gliomas. These values suggest that their expression negatively correlated with tumor grade. However, TGF-β expression positively correlated with tumor grade; the total positive expression rate of TGF-β in high-grade gliomas (93.8%) was significantly increased compared with that in low-grade gliomas (43.1%). The MVD in the low-grade group was 28±7.2 vessels/field, which was significantly lower than in the high-grade group (45±6.2 vessels/field). TSP-1 and PPAR-γ expression levels were negatively correlated with MVD (P<0.05), while the TGF-β expression level was positively correlated with MVD (P<0.05). These results indicate that the TSP-1, TGF-β and PPAR-γ expression levels in gliomas are correlated with MVD, which suggests that these proteins may be involved in the regulation of glioma angiogenesis.

Cardiac and renal protective effects of irbesartan via peroxisome proliferator-activated receptorγ-hepatocyte growth factor pathway independent of angiotensin II Type 1a receptor blockade in mouse model of salt-sensitive hypertension

BACKGROUND

"Aldosterone breakthrough" observed in patients receiving long-term treatment with angiotensin blockade is strongly associated with increased risk of left ventricular hypertrophy, poor exercise capacity, refractory proteinuria, and declining glomerular filtration rate through the profibrotic actions of aldosterone. To overcome aldosterone breakthrough, we examined the additional organ-protective actions of irbesartan, because irbesartan is an angiotensin II type 1 receptor (AT1R) blocker (ARB) with peroxisome proliferator-activated receptor (PPAR)γ agonistic effects, which mediate organ-protective effects independent of AT1R blockade. In this study, we examined the organ-protective effects of irbesartan in a salt-sensitive hypertension model using AT1aR knockout mice.

METHODS AND RESULTS

Aldosterone and 1% NaCl treatment resulted in a significant increase in severe cardiac and renal fibrosis. Irbesartan, but not losartan, significantly reduced renal fibrosis, glomerular injury through inhibition of macrophage infiltration, epithelial-mesenchymal transition, and oxidative stress. Similarly, cardiac fibrosis and myocyte hypertrophy were decreased by irbesartan, but not losartan, treatment, associated with a significant reduction in oxidative stress. Importantly, anti-hepatocyte growth factor (HGF) neutralizing antibody and a PPARγ antagonist (GW9662) attenuated these organ-protective effects of irbesartan. HGF protein level was increased by irbesartan, especially in the kidney and heart, while GW9662 treatment inhibited the increase in HGF level.

CONCLUSIONS

In this study, we showed that irbesartan, which has not only AT1aR-blocking effects, but also PPARγ agonistic effects accompanied by HGF expression, inhibited organ damage by aldosterone and salt treatment. Second-generation ARBs such as irbesartan, which has the dual actions of AT1R blockade and PPARγ activation, may have clinical value for the treatment of hypertensive patients with aldosterone breakthrough.

Recent advances in understanding the biochemical and molecular mechanism of diabetic nephropathy

Diabetic nephropathy (DN) is a chronic disease characterized by proteinuria, glomerular hypertrophy, decreased glomerular filtration and renal fibrosis with loss of renal function. DN is the leading cause of end-stage renal disease, accounting for millions of deaths worldwide. Hyperglycemia is the driving force for the development of diabetic nephropathy. The exact cause of diabetic nephropathy is unknown, but various postulated mechanisms are: hyperglycemia (causing hyperfiltration and renal injury), advanced glycosylation products, activation of cytokines. In this review article, we have discussed a number of diabetes-induced metabolites such as glucose, advanced glycation end products, protein kinase C and oxidative stress and other related factors that are implicated in the pathophysiology of the DN. An understanding of the biochemical and molecular changes especially early in the DN may lead to new and effective therapies towards prevention and amelioration of DN.

Mechanisms of diabetic complications

It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.

Racial differences between blacks and whites with systemic sclerosis

PURPOSE OF REVIEW

Racial disparities appear to exist in the susceptibility and severity of systemic sclerosis (SSc, scleroderma) and are responsible for a greater health burden in blacks as compared with whites. Disparities in socioeconomic status and access to healthcare do not sufficiently explain the observed differences in prevalence and mortality. It is important to determine whether there might be a biologic basis for the racial disparities observed in SSc.

RECENT FINDINGS

We present data to suggest that the increased susceptibility and severity of SSc in blacks may result in part from an imbalance of profibrotic and antifibrotic factors. Racial differences in the expression of transforming growth factor-β1 (TGF-β1) and caveolin-1, as well as differences in the expression of hepatocyte growth factor and PPAR-γ, have been demonstrated in blacks with SSc, as well as in normal black individuals. A genetic predisposition to fibrosis may account for much of the racial disparities between black and white patients with SSc.

SUMMARY

A better understanding of the biologic basis for the racial disparities observed in SSc may lead to improved therapies, along with the recognition that different therapies may need to be adapted for different groups of patients.

MiRNA-200b represses transforming growth factor-β1-induced EMT and fibronectin expression in kidney proximal tubular cells

MicroRNAs (miRNAs) comprise of a novel class of endogenous small noncoding RNAs that frequently downregulate the expression of target genes. Recent reports suggest that miRNA-200b prevents epithelial-to-mesenchymal transition (EMT) in cancer cells by targeting the E-box binding transcription factors Zinc finger E-box-binding homeobox 1 (ZEB1) and Zinc finger E-box-binding homeobox 2 (ZEB2). About 35% of active fibroblasts are derived from EMT which is central to the development of progressive renal fibrosis. Hence, this study was designed to assess the effect of miRNA-200b on transforming growth factor-β (TGF-β1)-induced fibrotic responses in renal tubular cells. Morphologically, human kidney-2 cells transfected with miRNA-200b retained their epithelial cell characteristics when exposed to TGF-β1. miRNA-200b significantly increased E-cadherin (P < 0.001) and reduced fibronectin mRNA and protein expression (both P < 0.01) independent of phospho-Smad2/3 and phospho-p38 and p42/44 signaling. Increased E-cadherin expression was associated with decreased expression of ZEB1 and ZEB2 and repression of fibronectin was mediated through direct targeting of the fibronectin mRNA, demonstrated using pMIR luciferase reporter assay and site-directed mutagenesis. These results suggest that miRNA-200b suppresses TGF-β1-induced EMT via inhibition of ZEB1 and ZEB2 and the extracellular matrix protein fibronectin by directing targeting of its 3'UTR mRNA, independent of pathways directly involved in TGF-β1 signaling.

Mouse hepatic oval cells require Met-dependent PI3K to impair TGF-β-induced oxidative stress and apoptosis

We have previously shown that oval cells harboring a genetically inactivated Met tyrosine kinase (Met^−/− oval cells) are more sensitive to TGF-β-induced apoptosis than cells expressing a functional Met (Met^flx/flx), demonstrating that the HGF/Met axis plays a pivotal role in oval cell survival. Here, we have examined the mechanism behind this effect and have found that TGF-β induced a mitochondria-dependent apoptotic cell death in Met^flx/flx and Met^−/− oval cells, associated with a marked increase in levels of the BH3-only proteins Bim and Bmf. Bmf plays a key role during TGF-β-mediated apoptosis since knocking down of BMF significantly diminished the apoptotic response in Met^−/− oval cells. TGF-β also induced oxidative stress accompanied by NADPH oxidase 4 (Nox4) mRNA up-regulation and decreased protein levels of antioxidant enzymes. Antioxidants inhibit both TGF-β-induced caspase 3 activity and Bmf up-regulation, revealing an oxidative stress-dependent Bmf regulation by TGF-β. Notably, oxidative stress-related events were strongly amplified in Met^−/− oval cells, emphasizing the critical role of Met in promoting survival. Pharmacological inhibition of PI3K did impair HGF-driven protection from TGF-β-induced apoptosis and increased sensitivity of Met^flx/flx oval cells to TGF-ß by enhancing oxidative stress, reaching apoptotic indices similar to those obtained in Met^−/− oval cells. Interestingly, both PI3K inhibition and/or knockdown itself resulted in caspase-3 activation and loss of viability in Met^flx/flx oval cells, whereas no effect was observed in Met^−/− oval cells. Altogether, results presented here provide solid evidences that both paracrine and autocrine HGF/Met signaling requires PI3K to promote mouse hepatic oval cell survival against TGF-β-induced oxidative stress and apoptosis.

Serum levels of alpha-smooth muscle actin and c-Met as biomarkers of the degree of severity of Henoch-Schonlein purpura nephritis

Approximately 40% of patients with Henoch-Schonlein purpura (HSP) develop Henoch-Schonlein purpura nephritis (HSPN) after 4 to 6 weeks of subcutaneous hemorrhaging. Immunoglobulin-A nephropathy (IgAN) and HSPN have numerous similarities, which can cause difficulty in correctly diagnosing the disorder during a differential diagnosis. The pathogenesis of the 2 diseases is not clear. We enrolled 137 patients with HSPN, 107 patients with IgAN, and 28 healthy (control) patients in our study. The levels of alpha-smooth muscle actin (α-SMA), c-Met, and Gal-deficient IgA1 (Gd-IgA1) in the 3 patient groups were determined and compared. The α-SMA, c-Met, and Gd-IgA1 levels and the clinical data from the patients with HSPN were analyzed for any correlations. The α-SMA and c-Met levels of the HSPN group were significantly higher than those of the IgAN and healthy control groups (P < 0.01). The Gd-IgA1 levels of the HSPN and IgAN groups were significantly different from the Gd-IgA1 level of the healthy control group (P < 0.01). The α-SMA levels of the HSPN group were positively correlated with blood urea nitrogen levels, serum creatinine levels, hematuria index, and proteinuria levels (P < 0.01). The c-Met levels of the HSPN group were positively correlated with the blood urea nitrogen and serum creatinine levels (P < 0.01). There were no significant differences among the α-SMA, c-Met, and Gd-IgA1 levels or the clinical data for the child and adult patients with HSPN. The serum levels of α-SMA and c-Met in patients with HSPN may be associated with the degree of disease severity. Gd-IgA1 is involved in the common immunologic pathogenesis of HSPN and IgAN.

Improvement of metabolic syndrome by irbesartan via the PPARγ/HGF pathway in apolipoprotein E knockout mice

Irbesartan, a partial agonist of peroxisome proliferators activated receptor-γ (PPARγ), has been reported to improve insulin resistance and lipid profile in patients with diabetes mellitus or metabolic syndrome (MS). However, the down effectors of PPARγ have yet to be elucidated. Thus, in this study, we focused on the role of the hepatocyte growth factor (HGF) in the anti-metabolic effects of irbesartan, using apolipoprotein E (ApoE) knockout (KO) mice. ApoE KO mice placed on a high-fat diet (HFD) for 12 weeks were divided into four groups: i) the control (HFD only), ii) the HFD + irbesartan (5 mg/kg/day), iii) the HFD + irbesartan + GW9662, a PPARγ antagonist (0.5 mg/kg/day) and iv) the HFD + irbesartan + anti-HGF neutralizing antibody (200 μg/week). The liver and epididymal adipose tissues were evaluated histologically. Serum adiponectin and HGF levels were also measured by ELISA. Fatty liver (as detected by oil-red O staining) and macrophage infiltration were markedly reduced by irbesartan. Irbesartan treatment also reduced macrophage infiltration into epididymal adipose tissue and hypertrophy of adipocytes. However, these effects of irbesartan were attenuated by GW9662 as well as by anti-HGF neutralizing antibody. Serum and hepatic HGF levels were also markedly increased by irbesartan, whereas GW9662 decreased the HGF level. In conclusion, irbesartan, an angiotensin (Ang) receptor blocker (ARB) and partial agonist of PPARγ (metabosartan), demonstrated a reduction in fatty liver and chronic inflammation, such as macrophage infiltration, beyond its blood pressure-lowering effect. These favorable characteristics of irbesartan might be due to local HGF activation through its partial PPARγ agonistic action, in addition to Ang II blockade. Upregulation of local HGF by irbesartan might provide a novel advantage in a strategy for the prevention and treatment of cardiovascular diseases (CVDs).

15-deoxy-Δ12,14 -prostaglandin J2 reduces recruitment of bone marrow-derived monocyte/macrophages in chronic liver injury in mice

15-Deoxy-Δ(12,14) -Prostaglandin J(2) (15d-PGJ(2) ), a natural peroxisome proliferator-activated receptor gamma (PPAR-γ) ligand, has been implicated as a new antiinflammatory compound with possible clinical applications. Based on this concept, this study was designed to evaluate the effects of 15d-PGJ(2) on bone marrow-derived monocyte/macrophage (BMM) migration, phagocytosis, and cytokine expression after liver injury using mouse models induced by cholestasis or carbon tetrachloride. Mice were lethally irradiated and received bone marrow transplants from enhanced green fluorescent protein transgenic mice. Our results showed that recruitment of BMM was significantly increased during chronic liver injury, and that 15d-PGJ(2) administration reduced BMM, but not neutrophil, dendritic, or T cell migration toward the damaged liver, involving reactive oxygen species generation and independently of PPAR-γ. Moreover, 15d-PGJ(2) inhibited the phagocytic activity of BMM and down-regulated inflammatory cytokine expression in vivo and in vitro. Accordingly, hepatic inflammation and fibrosis were strikingly ameliorated after 15d-PGJ(2) administration.

CONCLUSION

Our findings strongly suggest the antiinflammation and antifibrogenic potential of 15d-PGJ(2) in chronic liver diseases.

Regulation of Matrix Remodeling by Peroxisome Proliferator-Activated Receptor-γ: A Novel Link Between Metabolism and Fibrogenesis

The intractable process of fibrosis underlies the pathogenesis of systemic sclerosis (SSc) and other diseases, and in aggregate contributes to 45% of deaths worldwide. Because currently there is no effective anti-fibrotic therapy, a better understanding of the pathways and cellular differentiation programs underlying fibrosis are needed. Emerging evidence points to a fundamental role of the nuclear hormone receptor peroxisome proliferator activated receptor-γ (PPAR-γ) in modulating fibrogenesis. While PPAR-γ has long been known to be important in lipid metabolism and in glucose homeostasis, its role in regulating mesenchymal cell biology and its association with pathological fibrosis had not been appreciated until recently. This article highlights recent studies revealing a consistent association of fibrosis with aberrant PPAR-γ expression and activity in various forms of human fibrosis and in rodent models, and reviews studies linking genetic manipulation of the PPAR-γ pathway in rodents and fibrosis. We survey the broad range of anti-fibrotic activities associated with PPAR-γ and the underlying mechanisms. We also summarize the emerging data linking PPAR-γ dysfunction and pulmonary arterial hypertension (PAH), which together with fibrosis is responsible for the mortality in patients in SSc. Finally, we consider current and potential future strategies for targeting PPAR-γ activity or expression as a therapy for controlling fibrosis.

PAI-1 in tissue fibrosis

Fibrosis is defined as a fibroproliferative or abnormal fibroblast activation-related disease. Deregulation of wound healing leads to hyperactivation of fibroblasts and excessive accumulation of extracellular matrix (ECM) proteins in the wound area, the pathological manifestation of fibrosis. The accumulation of excessive levels of collagen in the ECM depends on two factors: an increased rate of collagen synthesis and or decreased rate of collagen degradation by cellular proteolytic activities. The urokinase/tissue type plasminogen activator (uPA/tPA) and plasmin play significant roles in the cellular proteolytic degradation of ECM proteins and the maintenance of tissue homeostasis. The activities of uPA/tPA/plasmin and plasmin-dependent MMPs rely mostly on the activity of a potent inhibitor of uPA/tPA, plasminogen activator inhibitor-1 (PAI-1). Under normal physiologic conditions, PAI-1 controls the activities of uPA/tPA/plasmin/MMP proteolytic activities and thus maintains the tissue homeostasis. During wound healing, elevated levels of PAI-1 inhibit uPA/tPA/plasmin and plasmin-dependent MMP activities, and, thus, help expedite wound healing. In contrast to this scenario, under pathologic conditions, excessive PAI-1 contributes to excessive accumulation of collagen and other ECM protein in the wound area, and thus preserves scarring. While the level of PAI-1 is significantly elevated in fibrotic tissues, lack of PAI-1 protects different organs from fibrosis in response to injury-related profibrotic signals. Thus, PAI-1 is implicated in the pathology of fibrosis in different organs including the heart, lung, kidney, liver, and skin. Paradoxically, PAI-1 deficiency promotes spontaneous cardiac-selective fibrosis. In this review, we discuss the significance of PAI-1 in the pathogenesis of fibrosis in multiple organs.

Telmisartan exerts renoprotective actions via peroxisome proliferator-activated receptor-γ/hepatocyte growth factor pathway independent of angiotensin II type 1 receptor blockade

Angiotensin (Ang) II type 1 receptor blockers have demonstrated beneficial effects beyond blood pressure control in the treatment of chronic kidney disease. There is clinical evidence that telmisartan is more effective than losartan in reducing proteinuria in hypertensive patients with diabetic nephropathy, because it is a partial agonist of peroxisome-proliferator activated receptor-γ (PPARγ), as well as an Ang II type 1 receptor blocker (AMADEO Study [A comparison of telMisartan versus losArtan in hypertensive type 2 DiabEtic patients with Overt nephropathy]). In this study, we examined the role of PPARγ activation in the renal protective actions of telmisartan using Ang II type 1 receptor-deficient mice. Renal injury was induced in Ang II type 1 receptor-deficient mice by producing unilateral ureteral obstruction, which exhibited severe renal interstitial fibrosis and inflammation. In these mice, telmisartan prevented hydronephrosis induced by unilateral ureteral obstruction more strongly than did losartan. Importantly, the prevention of renal atrophy and fibrosis by telmisartan was significantly attenuated by GW9662, a PPARγ antagonist. Interestingly, the downstream effector of PPARγ activation by telmisartan is hepatocyte growth factor (HGF), a well-known antifibrotic factor, because renal HGF expression was significantly increased by telmisartan, and a neutralizing antibody against HGF diminished the renal protective action of telmisartan. These beneficial changes by telmisartan were associated with a decrease in the expression of transforming growth factor-β1 and other proinflammatory and profibrotic cytokine genes through PPARγ/HGF activation. Our findings provide evidence of organ protective actions of telmisartan through the PPARγ/HGF pathway, independent of Ang II type 1 receptor blockade. Further development of the next generation of Ang II type 1 receptor blockers with added organ protective actions, such as PPARγ activation, might provide new beneficial drugs to treat renal and cardiovascular diseases.

Rosiglitazone inhibits transforming growth factor-β1 mediated fibrogenesis in ADPKD cyst-lining epithelial cells

Background

Interstitial fibrosis plays an important role in progressive renal dysfunction in autosomal dominant polycystic kidney disease (ADPKD). In our previous studies, we confirmed that PPAR-γ agonist, rosiglitazone could protect renal function and prolong the survival of a slowly progressive ADPKD animal model by reducing renal fibrosis. However, the mechanism remains unknown.

Methods

Primary culture epithelial cells pretreated with TGF-β1 were incubated with rosiglitazone. Extracellular matrix proteins were detected using real-time PCR and Western blotting. MAPK and Smad2 phosphorylation were measured with western blot. ERK1/2 pathway and P38 pathway were inhibited with the specific inhibitors PD98059 and SB203580. The Smad2 pathway was blocked with the siRNA. To address whether PPAR-γ agonist-mediated inhibition of TGF-β1–induced collagen type I expression was mediated through a PPAR-γ dependent mechanism, genetic and pharmaceutical approaches were used to block the activity of endogenous PPARγ.

Results

TGF-β1-stimulated collagen type I and fibronectin expression of ADPKD cyst-lining epithelia were inhibited by rosiglitazone in a dosage-dependent manner. Smad2, ERK1/2 and P38 pathways were activated in response to TGF-β1; however, TGF-β1 had little effect on JNK pathway. Rosiglitazone suppressed TGF-β1 induced Smad2 activation, while ERK1/2 and P38MAPK signals remained unaffected. Rosiglitazone could also attenuate TGF-β1-stimulated collagen type I and fibronectin expression in primary renal tubular epithelial cells, but had no effect on TGF-β1–induced activation of Smad2, ERK1/2 and P38 pathways. There was no crosstalk between the Smad2 and MAPK pathways in ADPKD cyst-lining epithelial cells. These inhibitory effects of rosiglitazone were reversed by the PPARγ specific antagonist GW9662 and PPARγ siRNA.

Conclusion

ADPKD cyst-lining epithelial cells participate in TGF-β1 mediated fibrogenesis. Rosiglitazone could suppress TGF-β1–induced collagen type I and fibronectin expression in ADPKD cyst-lining epithelia through modulation of the Smad2 pathway. Our study may provide therapeutic basis for clinical applications of rosiglitazone in retarding the progression of ADPKD.

Peroxisome proliferator-activated receptor-γ cross-regulation of signaling events implicated in liver fibrogenesis

Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear receptor with transcriptional activity controlling multiple physical and pathological processes. Recently, PPARγ has been implicated in the pathogenesis of liver fibrosis. Its depleted expression has strong associations with the activation and transdifferentiation of hepatic stellate cells, the central event in liver fibrogenesis. Studies over the past decade demonstrate that PPARγ cross-regulates a number of signaling pathways mediated by growth factors and adipokines, and cellular events including apoptosis and senescence. These signaling and cellular events and their molecular interactions with PPARγ system are profoundly involved in liver fibrogenesis. We critically summarize these mechanistic insights into the PPARγ regulation in liver fibrogenesis based on the updated findings in this area. We conclude with a discussion of the impacts of these discoveries on the interpretation of liver fibrogenesis and their potential therapeutic implications. PPARγ activation could be a promising strategy for antifibrotic therapy.