Role of Reactive Oxygen Species in TGF-β1-Induced Mitogen-Activated Protein Kinase Activation and Epithelial-Mesenchymal Transition in Renal Tubular Epithelial Cells

Engineered Nanoparticles for Effective Redox Signaling During Angiogenic and Antiangiogenic Therapy

SIGNIFICANCE

Redox signaling plays a vital role in regulating various cellular signaling pathways and disease biology. Recently, nanomedicine (application of nanotechnology in biology and medicine) has been demonstrated to regulate angiogenesis through redox signaling. A complete understanding of redox signaling pathways influenced angiogenesis/antiangiogenesis triggered by therapeutic nanoparticles is extensively reviewed in this article. Recent Advances: In recent times, nanomedicines are regarded as the Trojan horses that could be employed for successful drug delivery, gene delivery, peptide delivery, disease diagnosis, and others, conquering barriers associated with conventional theranostic approaches.

CRITICAL ISSUES

Physiological angiogenesis is a tightly regulated process maintaining a balance between proangiogenic and antiangiogenic factors. The redox signaling is one of the main factors that contribute to this physiological balance. An aberrant redox signaling cascade can be caused by several exogenous and endogenous factors and leads to reduced or augmented angiogenesis that ultimately results in several disease conditions.

FUTURE DIRECTIONS

Redox signaling-based nanomedicine approach has emerged as a new platform for angiogenesis-related disease therapy, where nanoparticles promote angiogenesis via controlled reactive oxygen species (ROS) production and antiangiogenesis by triggering excessive ROS formation. Recently, investigators have identified different efficient nano-candidates, which modulate angiogenesis by controlling intracellular redox molecules. Considering the importance of angiogenesis in health care a thorough understanding of nanomedicine-regulated redox signaling would inspire researchers to design and develop more novel nanomaterials that could be used as an alternative strategy for the treatment of various diseases, where angiogenesis plays a vital role.

Oxalate induces type II epithelial to mesenchymal transition (EMT) in inner medullary collecting duct cells (IMCD) in vitro and stimulate the expression of osteogenic and fibrotic markers in kidney medulla in vivo

EMT occurs in response to a number of stresses conditions as mechanical stretch, cancer, hypoxia, oxidative stress (ROS), among others. EMT describes a phenotypical change induced in epithelial cells. It is characterized by increases in motility, extracellular matrix synthesis, proliferation, and invasiveness. The present study analyzed if oxalate ions (Ox) could induce EMT in IMCD cells. Ox (0.5 mM) and transforming growth factor beta (TGF-β1 20 ng/mL) exposition during 48 hours increased migration and invasiveness, increased mesenchymal marker expression (Vimentin, alpha-smooth muscle actin: α-SMA, TGF-β1) and decreased epithelial marker expression (E-cadherin). IMCD stimulated with Ox and TGF-β1 and then exposed to the osteogenic medium during 15 days significantly increased early osteogenic markers (RUNX-2 and Alkaline Phosphatase) expression. Hyperoxaluric mice fed with trans-4-hydroxy-L-proline (HPL) presented calcium oxalate crystal excretion, increased in TGF-β1 expression and collagen fibers deposition and increased early osteogenic markers (RUNX-2 and Alkaline Phosphatase) at 60 days. Our in vitro and in vivo results suggest that oxalate induces EMT in inner medulla collecting duct cells and it may be involved in fibrotic tissue development, osteogenic differentiation and calcium crystal production both implicated in nephrolithiasis.

Implication of oxidative stress in the pathogenesis of systemic sclerosis via inflammation, autoimmunity and fibrosis

Systemic sclerosis is an autoimmune disorder characterized by inflammation and a progressive fibrosis affecting the skin and visceral organs. Over the last two decades, it became clear that oxidative stress plays a key role in its pathogenesis. In this review, we highlighted the role of ROS in the various pathological components of systemic sclerosis, namely the inflammatory, the autoimmune and the fibrotic processes. We also discussed how these pathological processes can induce ROS overproduction, thus maintaining a vicious circle. Finally, we summarized the therapeutic approaches targeting oxidative stress tested in systemic sclerosis, in cells, animal models and patients.

Exosome-mediated amplification of endogenous brain repair mechanisms and brain and systemic organ interaction in modulating neurological outcome after stroke

Ischemic stroke is caused by a regional interruption of cerebral blood flow to the brain. Rigorous pre-clinical and clinical research has made landmark progress in stroke treatment using thrombolytics and endovascular thrombectomy. Although numerous successful neuroprotective therapeutic agents for ischemic stroke have been reported in pre-clinical studies, most of them failed in clinical testing. Persistent pre-clinical research has demonstrated that the ischemic brain is not only passively dying but is also actively recovering. Within the neurovascular niche in the peri-infarct tissue, repair mechanisms thrive on the interactions between the neural and vascular compartments. In this review, we discuss exogenous therapy using mesenchymal stromal cell-derived exosomes to amplify endogenous brain repair mechanisms and to induce neurorestorative effects after stroke. Emerging evidence indicates that multiple communication axes between the various organs such as the brain, heart, kidney and gut, and whole body immune response mediated by the spleen can also affect stroke outcome. Therefore, in this review, we summarize this evidence and initiate a discussion on the potential to improve stroke outcome by amplifying multiple brain repair mechanisms after stroke, and by targeting peripheral organs and downstream events to enhance recovery in the injured brain and promote over all well being.

The role of decorin in cardiovascular diseases: more than just a decoration

Decorin (DCN) is a proteoglycan constituent of the extracellular matrix (ECM) possessing powerful antifibrotic, anti-inflammation, antioxidant, and antiangiogenic properties. By attaching to receptors in the cell surface or to several ECM molecules, it regulates plenty of cellular functions, consequently influencing cell differentiation, proliferation, and apoptosis. These processes are dependent on cell types, biological contexts, and interfere with pathological processes such as cardiovascular diseases. In this review, we briefly discuss the potential of DCN targeting in addressing cardiovascular diseases (CVD). We dive into its interactome and discuss how its interaction with the proteins can affect disease progression, and how DCN can be a possible target for CVD therapeutics.

Transforming growth factor-β1 mediated CHST11 and CHSY1 mRNA expression is ROS dependent in vascular smooth muscle cells

Transforming growth factor (TGF)-β1 mediates glycosaminoglycan (GAG) chain hyperelongation on secreted proteoglycans and these modifications are associated with increased lipid binding in the vessel wall and the development of atherosclerosis. In vascular smooth muscle cells (VSMCs), TGF-β1 regulated GAG elongation via extracellular signal-regulated kinase (ERK) and p38 as well as Smad2 linker region phosphorylation. In this study, our aim was to identify the TGF-β1 mediated signalling pathway involving reactive oxygen species (ROS) and Smad2 linker region phosphorylation that regulate the mRNA expression of GAG synthesizing enzymes, chondroitin 4-O-sulfotransferase 1 (CHST11) and chondroitin sulfate synthase 1 (CHSY1) which are the rate limiting enzymes involved in GAG chain elongation. Signalling molecules were assessed by western blotting, quantitative real-time PCR was used for analysis of gene expression and intracellular ROS level was measured by a fluorescence based assay. TGF-β1 induced ROS production in VSMCs. Nicotinamide adenine dinucleotide phosphate oxidase (Nox) inhibitors, diphenyleneiodonium (DPI) and apocynin blocked TGF-β1 mediated Smad2 linker region phosphorylation. TGF-β1 treatment increased the mRNA levels of CHST11 and CHSY1. Pharmacological inhibition of Nox blocked TGF-β1 mediated mitogen activated protein kinases (MAPKs) phosphorylation and TGF-β1 stimulated CHST11 and CHSY1 mRNA expression. These findings demonstrated that TGF-β1 mediated expression of CHST11 and CHSY1 can occur via Nox-dependent pathways and Smad2 linker region phosphorylation.

miR-15a-5p suppresses inflammation and fibrosis of peritoneal mesothelial cells induced by peritoneal dialysis via targeting VEGFA

Long-term peritoneal dialysis (PD) often ends up with ultrafiltration failure (UFF) which is partially caused by persistent inflammation and fibrosis of peritoneal tissues. However, the mechanism is still unclear. In the current study, the peritoneum from UFF patients demonstrated inflammation and fibrosis which were positively related to the expression of vascular endothelial growth factor A (VEGFA). The in vitro model using human peritoneal mesothelial cells (HPMCs) stimulated by high glucose or advanced glycation end (AGE) product showed consistent changes of inflammation, fibrosis, and VEGFA. What's more, we showed that VEGFA was an instigator of inflammation and fibrosis. Several microRNAs (miRNAs) have been reported to regulate expression of VEGFA elsewhere. Five of them were selected to test the expression in the peritoneum of patients with PD. Results suggested that miR-15a-5p was the most significantly downregulated one. Also, in high glucose or AGE product-stimulated HPMCs, miR-15a-5p decreased. When miRNA mimic was used to restore the expression of miR-15a-5p, high glucose-induced VEGFA was repressed. The predicted binding site between these two molecules was confirmed by the dual-luciferase assay. Restoration of miR-15a-5p restrained inflammation and fibrosis of HPMCs. TGF-β1/Smad2 was shown to be the downstream signaling pathway and their activity was regulated by miR-15a-5p/VEGFA. In conclusion, our current study demonstrates that miR-15a-5p acts as a regulator of VEGFA mRNA and the following inflammation and fibrosis in peritoneal mesothelial cells. The miR-15a-5p/VEGFA pathway may be a potential target for preventing ultrafiltration failure in patients with PD.

miR-330-3p promotes lung cancer cells invasion, migration, and metastasis by directly targeting hSOD2b

Lung cancer is a serious threat to human health. Studies have revealed that human manganese superoxide dismutase (hSOD2) and miRNAs play an essential role in the metastasis process of lung cancer. However, the miRNAs that associated with hSOD2 and involved in metastasis, remain elusive. After databases analysis and dual luciferase reporter validation, we demonstrated that miR-330-3p expression inversely correlated with hSOD2b expression level, and that miR-330-3p directly targeted the 3'untranslated region (3'UTR) of hSOD2b. Furthermore, overexpression of miR-330-3p promoted whereas knockdown of miR-330-3p inhibited invasion/migration and the epithelial-mesenchymal transition (EMT) process of lung cancer cells in vitro. Knockdown of miR-330-3p inhibited metastasis of lung cancer cells in vivo. Moreover, miR-330-3p-mediated enhancement of invasion/migration in 95-D cells could be rescued by over-expression of hSOD2. In conclusion, we demonstrated that miR-330-3p promoted metastasis of lung cancer cells by suppressing hSOD2b expression and unveiled a new clinical application of miR-330-3p in the therapy of lung cancer.

Rapid differentiation of the human RPE cell line, ARPE-19, induced by nicotinamide

Human RPE cell lines, especially the ARPE-19 cell line, are widely-used in eye research, as well as general epithelial cell studies. In comparison with primary RPE cells, they offer relative convenience and consistency, but cultures derived from these lines are typically not well differentiated. We describe a simple, rapid method to establish cultures from ARPE-19 cells, with significantly improved epithelial cell morphology and cytoskeletal organization, and RPE-related functions. We identify the presence of nicotinamide, a member of the vitamin B family, as an essential factor in promoting the observed differentiation, indicating the importance of metabolism in RPE cell differentiation.

Immunomodulatory Effects of the Nutraceutical Garlic Derivative Allicin in the Progression of Diabetic Nephropathy

Diabetic nephropathy (DN) is presently the primary cause of chronic kidney disease and end-stage renal disease (ESRD). It has been suggested that inflammation and oxidative stress, in addition to or in concert with the metabolic changes, plays an important role in the maintenance and progression of the disease. Therefore, attenuating or blocking these mechanisms may be a therapeutic target to delay the progression of the disease. Diallyl thiosulfinate (allicin), a compound derived from garlic, inhibits free radical formation, increases glutathione synthesis and decreases the levels of proinflammatory molecules in vitro. This research aimed to assess the effect of allicin on oxidative stress and inflammation-induced diabetes. Animals were divided into control and diabetes (streptozotocin 50 mg/kg i.p.), and maintained for 30 days. After 30 days, the group of diabetic animals was subdivided into diabetes and allicin-treated diabetes (16 mg/kg/day oral gavage). The three experimental groups were maintained for another month. We analyzed the status of renal function, oxidative stress and proinflammatory cytokines. The untreated diabetic group showed hyperglycemia and increased diuresis, creatinine clearance, proteinuria, glycosuria and urinary excretion of N-acetyl-β-d-glucosaminidase (NAG), as well as increased oxidative stress and the expression of interleukin 1β (IL-1β), IL-6, nuclear factor kappa beta (NFκβ) and transforming growth factor-β1 (TGF-β1) in plasma and kidney. In contrast, the inhibitor of NFκβ (Iκβ) is decreased in the cortex. It has been demonstrated that the allicin treatment decreases hyperglycemia, polyuria, and NAG excretion. The oxidative stress and proinflammatory cytokines were also reduced by the allicin treatment. In conclusion, allicin delays the progression of diabetic nephropathy through antioxidant and anti-inflammatory mechanisms.

Knockdown of NLRP3 alleviates high glucose or TGFB1-induced EMT in human renal tubular cells

Tubular injury is one of the crucial determinants of progressive renal failure in diabetic nephropathy (DN), while epithelial-to-mesenchymal transition (EMT) of tubular cells contributes to the accumulation of matrix protein in the diabetic kidney. Activation of the nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome leads to the maturation of interleukin (IL)-1B and is involved in the pathogenic mechanisms of diabetes. In this study, we explored the role of NLRP3 inflammasome on high glucose (HG) or transforming growth factor-B1 (TGFB1)-induced EMT in HK-2 cells. We evaluated EMT through the expression of α-smooth muscle actin (α-SMA) and E-cadherin as well as the induction of a myofibroblastic phenotype. Reactive oxygen species (ROS) was observed using the confocal microscopy. HG was shown to induce EMT at 48 h, which was blocked by NLRP3 silencing or antioxidant N-acetyl-L-cysteine (NAC). We found that NLRP3 interference could inhibit HG-induced ROS. Knockdown of NLRP3 could prevent HG-induced EMT by inhibiting the phosphorylation of SMAD3, P38 MAPK and ERK1/2. In addition, P38 MAPK and ERK1/2 might be involved in HG-induced NLRP3 inflammasome activation. Besides, TGFB1 induced the activation of NLRP3 inflammasome and the generation of ROS, which were blocked by NLRP3 interference or NAC. Tubular cells exposed to TGFB1 also underwent EMT, and this could be inhibited by NLRP3 shRNA or NAC. These results indicated that knockdown of NLRP3 antagonized HG-induced EMT by inhibiting ROS production, phosphorylation of SMAD3, P38MAPK and ERK1/2, highlighting NLRP3 as a potential therapy target for diabetic nephropathy.

Cancer driver mutations in endometriosis: Variations on the major theme of fibrogenesis

BACKGROUND

One recent study reports cancer driver mutations in deep endometriosis, but its biological/clinical significance remains unclear. Since the natural history of endometriosis is essentially gradual progression toward fibrosis, it is thus hypothesized that the six driver genes reported to be mutated in endometriosis (the RP set) may play important roles in fibrogenesis but not necessarily malignant transformation.

METHODS

Extensive PubMed search to see whether RP and another set of driver genes not yet reported (NR) to be mutated in endometriosis have any roles in fibrogenesis. All studies reporting on the role of fibrogenesis of the genes in both RP and NR sets were retrieved and evaluated in this review.

RESULTS

All six RP genes were involved in various aspects of fibrogenesis as compared with only three NR genes. These nine genes can be anchored in networks linking with their upstream and downstream genes that are known to be aberrantly expressed in endometriosis, piecing together seemingly unrelated findings.

CONCLUSIONS

Given that somatic driver mutations can and do occur frequently in physiologically normal tissues, it is argued that these mutations in endometriosis are not necessarily synonymous with malignancy or premalignancy, but the result of enormous pressure for fibrogenesis.

A Potential Link Between Oxidative Stress and Endothelial-to-Mesenchymal Transition in Systemic Sclerosis

Systemic sclerosis (SSc), an autoimmune disease that is associated with a number of genetic and environmental risk factors, is characterized by progressive fibrosis and microvasculature damage in the skin, lungs, heart, digestive system, kidneys, muscles, joints, and nervous system. These abnormalities are associated with altered secretion of growth factor and profibrotic cytokines, such as transforming growth factor-beta (TGF-β), interleukin-4 (IL-4), platelet-derived growth factor (PDGF), and connective-tissue growth factor (CTGF). Among the cellular responses to this proinflammatory environment, the endothelial cells phenotypic conversion into activated myofibroblasts, a process known as endothelial to mesenchymal transition (EndMT), has been postulated. Reactive oxygen species (ROS) might play a key role in SSs-associated fibrosis and vascular damage by mediating and/or activating TGF-β-induced EndMT, a phenomenon that has been observed in other disease models. In this review, we identified and critically appraised published studies investigating associations ROS and EndMT and the presence of EndMT in SSc, highlighting a potential link between oxidative stress and EndMT in this condition.

The cigarette smoke components induced the cell proliferation and epithelial to mesenchymal transition via production of reactive oxygen species in endometrial adenocarcinoma cells

Cigarette smoke (CS) causes about 480,000 deaths each year worldwide and is well-known to have harmful effects on the human body, leading to heart disease, stroke, lung cancer, and cardiovascular problems. In the present study, the effects of acrylonitrile (AN), benzo(a)pyrene (B(a)P), formaldehyde (FOR), isoprene (ISO), nicotine-derived nitrosamine ketone (NNK), which are the main components of CS, on the proliferation, invasion, and the epithelial-mesenchymal transition (EMT) process of human Ishikawa endometrial adenocarcinoma cells were investigated. Treating Ishikawa cells with CS components resulted in increased cell growth and altered expression of cell cycle-related genes: the protein expression of cyclin D & E increased, while the levels of p21 & p27 were reduced following treatment of these five CS components. In addition, CS components increased the invasion capacity of Ishikawa cells. The expression of the epithelial markers, E-cadherin and occludin, were significantly decreased, while the expression of the mesenchymal marker, N-cadherin, was significantly increased by CS components. In dichloro-dihydro-fluorescein diacetate (H2DCF-DA) assay, ROS production increased by treatment of CS components. The CS components activated the ROS-p38 MAPK-EMT pathway by increasing the level of phosphorylated p38 MAPK and p44/42 (ERK1/2), and by up-regulating Snail and Slug, the transcription factors for EMT. Taken together, these results indicate that CS components can promote progression of endometrial adenocarcinoma via increasing cell proliferation and the ROS-mediated EMT process.

NADPH oxidase, oxidative stress and fibrosis in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by damage of small vessels, immune abnormalities and exaggerated production of extracellular matrix. The etiology of the disease is unknown and the pathogenesis ill defined. However, there is consistent evidence that oxidative stress contributes to the establishment and progression of the disease. This review examines the most relevant research regarding the involvement of free radicals and of nicotinamide adenine dinucleotide phosphate oxidases (NADPH oxidases; NOX) in the pathogenesis of systemic sclerosis.

Activation of renal profibrotic TGFβ controlled signaling cascades by calcineurin and mTOR inhibitors

The calcineurin inhibitors (CNI) cyclosporine A (CsA) and tacrolimus represent potent immunosuppressive agents frequently used for solid organ transplantation and treatment of autoimmune disorders. Despite of their immense therapeutic benefits, residual fibrosis mainly in the kidney represents a common side effect of long-term therapy with CNI. Regardless of the immunosuppressive action, an increasing body of evidence implicates that a drug-induced increase in TGFβ and subsequent activation of TGFβ-initiated signaling pathways is closely associated with the development and progression of CNI-induced nephropathy. Mechanistically, an increase in reactive oxygen species (ROS) generation due to drug-induced changes in the intracellular redox homeostasis functions as an important trigger of the profibrotic signaling cascades activated under therapy with CNI. Although, inhibitors of the mechanistic target of rapamycin (mTOR) kinase have firmly been established as alternative compounds with a lower nephrotoxic potential, an activation of fibrogenic signaling cascades has been reported for these drugs as well. This review will comprehensively summarize recent advances in the understanding of profibrotic signaling events modulated by these widely used compounds with a specific focus put on mechanisms occurring independent of their respective immunosuppressive action. Herein, the impact of redox modulation, the activation of canonical TGFβ and non-Smad pathways and modulation of autophagy by both classes of immunosuppressive drugs will be highlighted and discussed in a broader perspective. The comprehensive knowledge of profibrotic signaling events specifically accompanying the immunomodulatory activity of these widely used drugs is needed for a reliable benefit-risk assessment under therapeutic regimens.

Membrane rafts-redox signalling pathway contributes to renal fibrosis via modulation of the renal tubular epithelial-mesenchymal transition

KEY POINTS

Membrane rafts (MRs)-redox signalling pathway is activated in response to transforming growth factor-β1 (TGF-β1) stimulation in renal tubular cells. This pathway contributes to TGF-1β-induced epithelial-mesenchymal transition (EMT) in renal tubular cells. The the MRs-redox signalling pathway is activated in renal tubular cells isolated from angiotensin II (AngII)-induced hypertensive rats. Inhibition of this pathway attenuated renal inflammation and fibrosis in AngII-induced hypertension.

ABSTRACT

The membrane rafts (MRs)-redox pathway is characterized by NADPH oxidase subunit clustering and activation through lysosome fusion, V-type proton ATPase subunit E2 (encoded by the Atp6v1e2 gene) translocation and sphingomyelin phosphodiesterase 1 (SMPD1, encoded by the SMPD1 gene) activation. In the present study, we hypothesized that the MRs-redox-derived reactive oxygen species (ROS) are involved in renal inflammation and fibrosis by promoting renal tubular epithelial-mesenchymal transition (EMT). Results show that transforming growth factor-β1 (TGF-β1) acutely induced MR formation and ROS production in NRK-52E cells, a rat renal tubular cell line. In addition, transfection of Atp6v1e2 small hairpin RNAs (shRNA) and SMPD1 shRNA attenuated TGF-β1-induced changes in EMT markers, including E-cadherin, α-smooth muscle actin (α-SMA) and fibroblast-specific protein-1 (FSP-1) in NRK-52E cells. Moreover, Erk1/2 activation may be a downstream regulator of the MRs-redox-derived ROS, because both shRNAs significantly inhibited TGF-β1-induced Erk1/2 phosphorylation. Further in vivo study shows that the renal tubular the MRs-redox signalling pathway was activated in angiotensin II (AngII)-induced hypertension, as indicated by the increased NADPH oxidase subunit Nox4 fraction in the MR domain, SMPD1 activation and increased ROS content in isolated renal tubular cells. Finally, renal transfection of Atp6v1e2 shRNA and SMPD1 shRNA significantly prevented renal fibrosis and inflammation, as indicated by the decrease of α-SMA, fibronectin, collagen I, monocyte chemoattractant protein-1 (MCP-1), intercellular cell adhesion molecule-1 (ICAM-1) and tumour necrosis factor-α (TNF-α) in kidneys from AngII-infused rats. It was concluded that the the MRs-redox signalling pathway is involved in TGF-β1-induced renal tubular EMT and renal inflammation/fibrosis in AngII-induced hypertension.

Epithelial mesenchymal transition (EMT): a universal process in lung diseases with implications for cystic fibrosis pathophysiology

Cystic Fibrosis (CF) is a genetic disorder that arises due to mutations in the Cystic Fibrosis Transmembrane Conductance Regulator gene, which encodes for a protein responsible for ion transport out of epithelial cells. This leads to a disruption in transepithelial Cl-, Na + and HCO₃− ion transport and the subsequent dehydration of the airway epithelium, resulting in infection, inflammation and development of fibrotic tissue. Unlike in CF, fibrosis in other lung diseases including asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis has been well characterised. One of the driving forces behind fibrosis is Epithelial Mesenchymal Transition (EMT), a process where epithelial cells lose epithelial proteins including E-Cadherin, which is responsible for tight junctions. The cell moves to a more mesenchymal phenotype as it gains mesenchymal markers such as N-Cadherin (providing the cells with migration potential), Vimentin and Fibronectin (proteins excreted to help form the extracellular matrix), and the fibroblast proliferation transcription factors Snail, Slug and Twist. This review paper explores the EMT process in a range of lung diseases, details the common links that these have to cystic fibrosis, and explores how understanding EMT in cystic fibrosis may open up novel methods of treating patients with cystic fibrosis.

Oleanolic acid attenuates TGF-β1-induced epithelial-mesenchymal transition in NRK-52E cells

Background

Epithelial-to-mesenchymal transition (EMT) plays an important role in the progression of renal interstitial fibrosis, which finally leads to renal failure. Oleanolic acid (OA), an activator of NF-E2-related factor 2 (Nrf2), is reported to attenuate renal fibrosis in mice with unilateral ureteral obstruction. However, the role of OA in the regulation of EMT and the underlying mechanisms remain to be investigated. This study aimed to evaluate the effects of OA on EMT of renal proximal tubular epithelial cell line (NRK-52E) induced by TGF-β1, and to elucidate its underlying mechanism.

Methods

Cells were incubated with TGF-β1 in the presence or absence of OA. The epithelial marker E-cadherin, the mesenchymal markers, α-smooth muscle actin (α-SMA), fibronectin, Nrf2, klotho, the signal transducer (p-Smad2/3), EMT initiator (Snail), and ILK were assayed by western blotting.

Results

Our results showed that the NRK-52E cells incubated with TGF-β1 induced EMT with transition to the spindle-like morphology, down-regulated the expression of E-cadherin but up-regulated the expression of α-SMA and fibronectin. However, the treatment with OA reversed all EMT markers in a dose-dependent manner. OA also restored the expression of Nrf2 and klotho, decreased the phosphorylation of Smad2/3, ILK, and Snail in cells which was initiated by TGF-β1.

Conclusion

OA can attenuate TGF-β1 mediate EMT in renal tubular epithelial cells and may be a promising therapeutic agent in the treatment of renal fibrosis.

Reactive Oxygen Species and p38MAPK Have a Role in the Smad2 Linker Region Phosphorylation Induced by TGF-β

BACKGROUND

Transforming growth factor-β (TGF-β) in addition to the C-terminal region can phosphorylate receptor-regulated Smads (R-Smads) in their linker region. The aim of the present study was to evaluate the role of signaling mediators such as NAD(P)H oxidases (reactive oxygen species [ROS] generators), ROS, and ROS-sensitive p38 mitogen-activated protein kinase (p38MAPK) in this signaling pathway in cultured human vascular smooth muscle cells (VSMCs).

METHODS

The present in vitro study was performed on human VSMCs. Proteins were detected by western blotting utilizing an anti-phospho-Smad2 (Ser245/250/255) rabbit polyclonal antibody and a horseradish peroxidase-labeled secondary antibody. Glyceraldehyde-3-phosphate dehydrogenase was used as a loading control. The phospho-Smad2 linker region (pSmad2L) was detected in all the experimental groups: a control group (untreated group), a group treated with TGF-β (2 ng/mL), and a group treated with TGF-β plus different inhibitors. The data were normalized and presented as mean±SEM. The statistical analyses were performed using SPSS, version 16.0, and the nonparametric Kruskal-Wallis test. A P value smaller than 0.05 was considered statistically significant.

RESULTS

The VSMCs treated with TGF-β (2 ng/mL) showed a time-dependent increase in the pSmad2L level. The highest level was observed at 15 minutes (P=0.03). The inhibitors of NAD(P)H oxidases (diphenyleneiodonium and apocynin) (P=0.04), ROS scavenger (N-acetylcysteine) (P=0.04), and p38MAPK inhibitor (SB-202190) (P=0.04) were able to reduce the increased level of the pSmad2L by TGF-β.

CONCLUSION

Our results suggested that NAD(P)H oxidases played an important role in the Smad2L phosphorylation in the human VSMCs. Furthermore, our results confirmed that ROS and p38MAPK were involved in this signaling pathway. Thus, TGF-β via a ROS-dependent mechanism can transmit its signals to the pSmad2L.

Hyperglycemia activates the renin-angiotensin system and induces epithelial-mesenchymal transition in streptozotocin-induced diabetic kidneys

INTRODUCTION

The renin-angiotensin system and epithelial-mesenchymal transition play crucial roles in the development of kidney fibrosis. The connection between the renin-angiotensin system and transforming growth factor-β in epithelial-mesenchymal transition remains largely unknown.

MATERIALS AND METHODS

We assessed oxidative stress, cytokine levels, renal morphology, profibrotic growth factor and renin-angiotensin system component expression, and cell-specific E- and N-cadherin expression in the kidneys of gerbils with streptozotocin-induced diabetes mellitus.

RESULTS

Animals in the experimental group received an intraperitoneal injection of streptozotocin to induce diabetes. The diabetic gerbil kidneys presented kidney injury, which was manifested as distorted glomeruli, necrosis of tubular cells, dilated tubular lumen, and brush border loss. Additionally, the diabetic gerbil kidneys exhibited significantly higher expressions of 8-hydroxy-2'-deoxyguanosine, nuclear factor-kB, toll-like receptor 4, tumor necrosis factor-α, transforming growth factor-β, connective tissue growth factor, α-smooth muscle actin, and N-cadherin and higher collagen deposition than did the control gerbil kidneys. Compared with the control kidneys, the diabetic gerbil kidneys exhibited significantly lower E-cadherin expression. These epithelial-mesenchymal transition characteristics were associated with an increase in renin-angiotensin system expression in the diabetic gerbils.

CONCLUSIONS

We demonstrate that hyperglycemia activated the renin-angiotensin system, induced epithelial-mesenchymal transition, and contributed to kidney fibrosis in an experimental diabetes mellitus model.

Reactive oxygen species in cancer stem cells of head and neck squamous cancer

One of the greatest challenges in systemic treatment of head and neck squamous cell carcinoma (HNSCC) is a small tumor cell population, namely, cancer stem-like cells (CSC). CSC can regenerate and maintain a heterogenic tumor by their self-renewal capacity. Their potential ability to be more resistant to and survival after chemo- and radiation therapy was also identified. Further studies have shown that reactive oxygen species (ROS) contribute to this CSC-associated resistance. In this review, we focus on the current knowledge of HNSCC-CSC, with regard to ROS as a possible and novel therapeutic approach in targeting CSC.

Elevated transforming growth factor β signaling activation in β-actin-knockout mouse embryonic fibroblasts enhances myofibroblast features

Signaling by the transforming growth factor‐β (TGF‐β) is an essential pathway regulating a variety of cellular events. TGF‐β is produced as a latent protein complex and is required to be activated before activating the receptor. The mechanical force at the cell surface is believed to be a mechanism for latent TGF‐β activation. Using β‐actin null mouse embryonic fibroblasts as a model, in which actin cytoskeleton and cell‐surface biophysical features are dramatically altered, we reveal increased TGF‐β1 activation and the upregulation of TGF‐β target genes. In β‐actin null cells, we show evidence that the enhanced TGF‐β signaling relies on the active utilization of latent TGF‐β1 in the cell culture medium. TGF‐β signaling activation contributes to the elevated reactive oxygen species production, which is likely mediated by the upregulation of Nox4. The previously observed myofibroblast phenotype of β‐actin null cells is inhibited by TGF‐β signaling inhibition, while the expression of actin cytoskeleton genes and angiogenic phenotype are not affected. Together, our study shows a scenario that the alteration of the actin cytoskeleton and the consequent changes in cellular biophysical features lead to changes in cell signaling process such as TGF‐β activation, which in turn contributes to the enhanced myofibroblast phenotype.

Rapeseed protein-derived antioxidant peptide RAP alleviates renal fibrosis through MAPK/NF-κB signaling pathways in diabetic nephropathy

Introduction

Kidney fibrosis is the main pathologic change in diabetic nephropathy (DN), which is the major cause of end-stage renal disease. Current therapeutic strategies slow down but cannot reverse the progression of renal dysfunction in DN. Plant-derived bioactive peptides in foodstuffs are widely used in many fields because of their potential pharmaceutical and nutraceutical benefits. However, this type of peptide has not yet been studied in renal fibrosis of DN. Previous studies have indicated that the peptide YWDHNNPQIR (named RAP), a natural peptide derived from rapeseed protein, has an antioxidative stress effect. The oxidative stress is believed to be associated with DN. The aim of this study was to evaluate the pharmacologic effects of RAP against renal fibrosis of DN and high glucose (HG)-induced mesangial dysfunction.

Materials and methods

Diabetes was induced by streptozotocin and high-fat diet in C57BL/6 mice and these mice were treated by subcutaneous injection of different doses of RAP (0.1 mg/kg and 0.5 mg/kg, every other day) or PBS for 12 weeks. Later, functional and histopathologic analyses were performed. Parallel experiments verifying the molecular mechanism by which RAP alleviates DN were carried out in HG-induced mesangial cells (MCs).

Results

RAP improved the renal function indices, including 24-h albuminuria, triglyceride, serum creatinine, and blood urea nitrogen levels, but did not lower blood glucose levels in DN mice. RAP also simultaneously attenuated extracellular matrix accumulation in DN mice and HG-induced MCs. Furthermore, RAP reduced HG-induced cell proliferation, but it showed no toxicity in MCs. Additionally, RAP inhibited the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) signaling pathways.

Conclusion

RAP can attenuate fibrosis in vivo and in vitro by antagonizing the MAPK and NF-κB pathways.

Pirfenidone suppresses MAPK signalling pathway to reverse epithelial-mesenchymal transition and renal fibrosis

AIM

Recent studies indicate that pirfenidone (PFD) may have anti-fibrotic effects in many tissues, but the potential molecular mechanism remains unknown. The purpose of this study is to investigate the potential effects of PFD on epithelial-to-mesenchymal transition (EMT) and renal fibrosis in a unilateral ureteral obstruction (UUO) rat model and the involved molecular mechanism related to cultured human renal proximal tubular epithelial cells (HK-2).

METHODS

Sixty rats were randomly divided into three groups: sham-operated, vehicle-treated UUO, and PFD-treated UUO. Kidney specimens were collected at day 7 or 14 after UUO. PFD treatment was also performed for human HK-2. The tubulointerstitial injury, interstitial collagen deposition, and expression of type I and III collagen, α-SMA, S100A4, fibronection and E-cadherin were assessed. In addition, extracellular signal regulated kinase (ERK1/2), p38 MAPK (p38), and c-Jun N-terminal kinase/stress-activated protein kinase (JNK) were also detected.

RESULTS

In vitro, PFD significantly attenuated TGF-β1-induced EMT and extracellular matrix (ECM) synthesis, as determined by reducing expression of α-SMA, type I and III collagen, S100A4, fibronection, and increased expression of E-cadherin. PFD treatment attenuated TGF-β1-induced up-regulation of phosphorylation of ERK1/2, p38 and JNK. In vivo, PFD reduced the degree of tubulointerstitial injury and renal fibrosis, which was associated with reduced expression of TGF-β1, type III collagen, α-SMA, S100A4, fibronection, and increased expression of E-cadherin.

CONCLUSION

These results suggest that pirfenidone is able to attenuate EMT and fibrosis in vivo and in vitro through antagonizing the MAPK pathway, providing a potential treatment to alleviate renal tubulointerstitial fibrosis.

TAK1 mediates apoptosis via p38 involve in ischemia-induced renal fibrosis

Renal fibrosis is a common and characteristic symptom of chronic kidney disease (CKD). However, the molecular mechanisms of renal fibrosis remain elusive. Ischemia injury, as a major cause of AKI, deserves more attention in order to improve the knowledge of AKI-induced fibrosis. Transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) interacts directly with TGF-β, which play a critical role in the progression of fibrosis. Therefore, the present study aimed to investigate the role of TAK1 in the pathogenesis of ischemia-induced renal fibrosis. Compared with mice in the vehicle group, mice intraperitoneally injected with TAK1 inhibitor were found to have lower serum creatinine, less tubular damage and more mild fibrosis following ischemia-induced AKI. Furthermore, inhibition of TAK1 reduced p38 phosphorylation, decreased expression of Bax and caspase 3 and apoptosis cells in kidneys of mice treated with IR-induced AKI. Compared with vehicle-treated renal tubular epithelial cells, TAK1 overexpression cells were found to have a higher apoptosis and fibrosis index level and p38 phosphorylation following hypoxia/reoxygenation (H/R) treatment. Furthermore, the p38 inhibitor combined with TAK1 overexpression verified the role of TAK1/p38 signaling pathway in apoptosis and fibrosis index level of renal tubular epithelial cells treated with H/R. Thus, our results show that TAK1 plays an important role in the pathogenesis of ischemia-induced renal fibrosis and may mediate p38-regulated cell apoptosis.

Protective effects of quercetin treatment in a pristane-induced mouse model of lupus nephritis

INTRODUCTION

Lupus nephritis (LN) is one of the most severe complications of systemic lupus erythematosus. As murine models of LN are valuable tools to better understand its pathophysiology and to search for new effective treatments, we investigated the effects of the bioflavonoid quercetin on pristane-induced LN mice through histomorphological analyses.

METHODS

Immunofluorescence and biochemical assays were used to evaluate the expression of markers of inflammation (interleukin-6, IL-6; tumour necrosis factor-α, TNF-α), oxidative stress (catalase, CAT; superoxide dismutase 1, SOD1; thiobarbituric acid reactive substances, TBARS), apoptosis (Bax), and fibrosis (transforming growth factor-β1, TGF-β1). Glomerular and tubular ultrastructure was analysed, and tissue messenger RNA of podocin, podoplanin and α3β1-integrin were quantified using the real-time polymerase chain reaction.

RESULTS

Pristane-induced LN mice showed severe kidney injury, characterized by increased proteinuria, glomerular mesangial expansion and inflammation, high expression of the pro-fibrotic, apoptotic and prooxidant markers and reduction of antioxidants. In the kidney ultrastructure, foot process (FP) effacement, apoptotic mesangial cells and abnormal mitochondria with disrupted cristae were observed, along with suppressed tissue mRNA of podocin, podoplanin and α3β1-integrin. Treatment with quercetin in the pristane-induced LN mice model was nephroprotective, decreasing proteinuria levels and significantly lowering tissue expression of IL-6, TNF-α, TGF-β1, Bax and TBARS. Simultaneously, quercetin significantly increased CAT and SOD1 expressions in these mice. In addition, it was observed improvement of the kidney ultrastructure, and tissue mRNA of podocin, but not podoplanin and α3β1-integrin, was restored to the levels found in the control mice.

CONCLUSION

In conclusion, these findings provide experimental evidence of the renoprotective effects of quercetin in the pristane-induced LN mice model. We suggest that quercetin effectively ameliorates the kidney damage caused by pristane, a bioflavonoid to be further evaluated as a new therapeutic strategy in this disease.

TGF-β2-induced EMT is dampened by inhibition of autophagy and TNF-α treatment

Hepatocellular carcinoma (HCC) typically develops in a chronic inflammatory setting causal to release of a plethora of growth factors and cytokines. However, the molecular effect of these cytokines on HCC progression is poorly understood. In this study, we exposed HCC cells to TGF-β2 (Transforming Growth Factor-β2), which resulted in a significant elevation of EMT (Epithelial to Mesenchymal Transition) like features. Molecular analysis of EMT markers showed an increase at both RNA and protein levels upon TGF-β2 administration along with up-regulation of TGF-β-induced Smad signaling. Induction of EMT was associated with a simultaneous increase in reactive oxygen species (ROS) and cytostasis of TGF-β2-treated cells. Importantly, quenching of ROS resulted in a significant promotion of TGF-β2-induced EMT. Furthermore, cells treated with TGF-β2 also showed an enhanced autophagic flux. Interestingly, inhibition of autophagy by chloroquine-di-phosphate (CQDP) or siRNA-mediated ablation of ATG5 drastically inhibited TGF-β2-induced EMT. Autophagy inhibition significantly increased ROS levels promoting apoptosis. It was further observed that pro-inflammatory cytokine like, TNF-α (Tumor Necrosis Factor-α) can antagonize TGF-β2-induced response by down-regulating autophagy, increasing ROS levels and thus inhibiting EMT in HCC cells. This inhibitory effect of TNF-α is serum-independent. Transcriptomic analysis through RNA sequencing was further performed which validated that TGF-β2-induced autophagic genes are inhibited by TNF-α treatment suppressing EMT. Our study suggests that autophagy plays a pro-metastatic role facilitating EMT by regulating ROS levels in HCC cells and TNF-α can suppress EMT by inhibiting autophagy. We provide unique mechanistic insights into the role of TGF-β2 in HCC cells, along with appropriate cues to effectively control the disease.

Berberine activates Nrf2 nuclear translocation and inhibits apoptosis induced by high glucose in renal tubular epithelial cells through a phosphatidylinositol 3-kinase/Akt-dependent mechanism

Apoptosis of tubular epithelial cells is a major feature of diabetic kidney disease, and hyperglycemia triggers the generation of free radicals and oxidant stress in tubular cells. Berberine (BBR) is identified as a potential anti-diabetic herbal medicine due to its beneficial effects on insulin sensitivity, glucose metabolism and glycolysis. In this study, the underlying mechanisms involved in the protective effects of BBR on high glucose-induced apoptosis were explored using cultured renal tubular epithelial cells (NRK-52E cells) and human kidney proximal tubular cell line (HK-2 cells). We identified the pivotal role of phosphatidylinositol 3-kinase (PI3K)/Akt in BBR cellular defense mechanisms and revealed the novel effect of BBR on nuclear factor (erythroid-derived 2)-related factor-2 (Nrf2) and heme oxygenase (HO)-1 in NRK-52E and HK-2 cells. BBR attenuated reactive oxygen species production, antioxidant defense (GSH and SOD) and oxidant-sensitive proteins (Nrf2 and HO-1), which also were blocked by LY294002 (an inhibitor of PI3K) in HG-treated NRK-52E and HK-2 cells. Furthermore, BBR improved mitochondrial function by increasing mitochondrial membrane potential. BBR-induced anti-apoptotic function was demonstrated by decreasing apoptotic proteins (cytochrome c, Bax, caspase3 and caspase9). All these findings suggest that BBR exerts the anti-apoptosis effects through activation of PI3K/Akt signal pathways and leads to activation of Nrf2 and induction of Nrf2 target genes, and consequently protecting the renal tubular epithelial cells from HG-induced apoptosis.

SIRT3 prevents angiotensin II-induced renal tubular epithelial-mesenchymal transition by ameliorating oxidative stress and mitochondrial dysfunction

Silent mating type information regulation 2 homolog 3 (SIRT3) is a major protective mediator that ameliorates oxidative stress and mitochondrial dysfunction, which are associated with the pathogenesis of epithelial-mesenchymal transition (EMT). The present study was aimed to investigate the potential role of SIRT3 in renal tubular EMT both in vitro and in vivo. Firstly, we showed that the expression of SIRT3 was repressed in angiotensin II-induced EMT. SIRT3 deficiency triggered EMT response, while over-expression of SIRT3 attenuated EMT response. In addition, over-expression of SIRT3 repressed AngⅡ-induced excessive production of mitochondrial superoxide, as well as mitochondrial dysfunction evidenced by the maintenance of mitochondrial number and morphology, and the stabilization of mitochondrial membrane potential. In conclusion, these findings identify a protective role of SIRT3 against angiotensin II-induced EMT in the kidney, and suggest SIRT3 upregulation is a potential therapeutic strategy for the treatment of renal tubulointerstitial fibrosis.

Troxerutin down-regulates KIM-1, modulates p38 MAPK signaling, and enhances renal regenerative capacity in a rat model of gentamycin-induced acute kidney injury

Troxerutin enhances renal tissue regeneration, improves renal function, and decreases renal tissue injury in gentamycin-treated rats.

Clair DK, Kyprianou N. Profiles of Radioresistance Mechanisms in Prostate Cancer

Radiation therapy (RT) is commonly used for the treatment of localized prostate cancer (PCa). However, cancer cells often develop resistance to radiation through unknown mechanisms and pose an intractable challenge. Radiation resistance is highly unpredictable, rendering the treatment less effective in many patients and frequently causing metastasis and cancer recurrence. Understanding the molecular events that cause radioresistance in PCa will enable us to develop adjuvant treatments for enhancing the efficacy of RT. Radioresistant PCa depends on the elevated DNA repair system and the intracellular levels of reactive oxygen species (ROS) to proliferate, self-renew, and scavenge anti-cancer regimens, whereas the elevated heat shock protein 90 (HSP90) and the epithelial-mesenchymal transition (EMT) enable radioresistant PCa cells to metastasize after exposure to radiation. The up-regulation of the DNA repairing system, ROS, HSP90, and EMT effectors has been studied extensively, but not targeted by adjuvant therapy of radioresistant PCa. Here, we emphasize the effects of ionizing radiation and the mechanisms driving the emergence of radioresistant PCa. We also address the markers of radioresistance, the gene signatures for the predictive response to radiotherapy, and novel therapeutic platforms for targeting radioresistant PCa. This review provides significant insights into enhancing the current knowledge and the understanding toward optimization of these markers for the treatment of radioresistant PCa.

The concomitant apoptosis and EMT underlie the fundamental functions of TGF-β

TGF-β's multipotent cellular effects and their relations are critical for TGF-β's pathophysiological functions. However, these effects may appear to be paradoxical in understanding TGF-β's functions. Apoptosis and epithelial-mesenchymal transition (EMT) are two fundamental events that are deeply linked to various physiological and disease-related processes. These two major cellular fates are subtly regulated and can be potently stimulated by TGF-β, which profoundly contribute to the biological roles of TGF-β. Moreover, these two events are also indirectly and directly correlated with TGF-β-mediated growth inhibition and are relevant to the current understanding of the roles of TGF-β in tumorigenesis and cancer progression. Although TGF-β-induced apoptosis and EMT can be singly independent cellular events, they can also be mutually exclusive but interrelated concomitant events in various cases. Thus, the modulation of apoptosis and EMT is essential for the seemingly paradoxical functions of TGF-β. However, the concomitant effect of TGF-β on apoptosis and EMT, the balance and regulated alterations of them are still been ignored or underestimated. This review focuses on the TGF-β-induced concomitant apoptosis and EMT. We aim to provide an insight in understanding their significance, balance, and modulation in TGF-β-mediated biological functions.

miR302a-3p May Modulate Renal Epithelial-Mesenchymal Transition in Diabetic Kidney Disease by Targeting ZEB1

BACKGROUND

Recent study found that microRNA (miRNA) are involved in diabetic kidney disease (DKD). The objective of this study is to determine the role of miR302a-3p in the process of renal epithelial-mesenchymal transition (EMT) in DKD.

METHODS

The miRNA expression profiling of the cell line stimulated by high glucose was performed by a microarray analysis. Then real-time polymerase chain reaction (PCR) were used to determine the expression of one of the miRNAs significantly upregulated in cell line stimulated by high glucose, miR302a-3p. miR302a-3p mimics and inhibitor were transfected to HK-2 cells following exposure to high glucose and normal glucose, respectively. The expressions of E-cadherin, vimentin, and Zinc finger E-box-binding protein 1 (ZEB-1) were determined by real-time PCR and Western blot. Finally, the levels of miR302a-3p in the plasma of DKD patients were detected by real-time PCR, and then the relationship of miR302a-3p and urinary albumin excretion (UAE) or estimated glomerular filtration rate (eGFR) was analyzed.

RESULTS

The expression of miR-302a-3p, 513a-5p, 1291 and the other 17 miRNA were increased significantly in HK-2 cell line after high glucose stimulation; on the other hand, miRNA490-3p, 638, 3203 and the other 19 miRNA were decreased significantly. In vitro, miR-302a-3p expression in HG group increased at 6 h and ascended to the highest level at 12 and 24 h and then gradually decreased from 48 to 72 h. More interesting, ZEB1 protein expression had an opposite change, which gradually decreased from 6 to 24 h and then gradually increased from 48 to 72 h. Moreover, overexpression of miR-302a-3p suppressed expression of ZEB1 in the post-transcriptional level and reversed high glucose-mediated downregulation of E-cadherin and upregulation of vimentin. Meanwhile, loss of miR-302a-3p expression can lead to EMT of HK-2 cells just as high glucose stimulation. Further study demonstrated that the expression of circulating miR-302a-3p was significantly increased in the diabetes mellitus (DM) with normoalbuminuria (DM group, n = 22) compared with control (healthy persons, n = 30) and then decreased in DM with microalbuminuria (DNE group, n = 20). Furthermore, its expression in DM with macroalbuminuria (DNC group, n = 18) was decreased significantly compared with DM group. Circulating miR-302a-3p had negative relevance with UAE in DNE group (r = -0.649, p = 0.002) and DNC group (r = -0.681, p = 0.006). Circulating miR-302a-3p had positive relevance with eGFR in DNC group (r = 0.486, p = 0.041).

CONCLUSIONS

These findings suggest that miR-302a-3p may play a protective role by targeting ZEB1 in renal EMT in DKD. In view of these findings, it is conceivable that miR-302a-3p may serve as a potential novel target in pre-EMT states for the amelioration renal fibrosis seen in DKD.

Modulation of the TGF-β1-induced epithelial to mesenchymal transition (EMT) mediated by P1 and P2 purine receptors in MDCK cells

Epithelial to mesenchymal transition (EMT) occurs during embryogenesis or under pathological conditions such as hypoxia, injury, chronic inflammation, or tissue fibrosis. In renal tubular epithelial cells (MDCK), TGF-β1 induces EMT by reducing or increasing epithelial or mesenchymal marker expression, respectively. In this study, we confirmed that the cAMP analogues, 8-CPT-cAMP or N6-Ph-cAMP, inhibited the TGF-β1-driven overexpression of the mesenchymal markers ZEB-1, Slug, Fibronectin, and α-SMA. Furthermore, we showed that A1, A2A, P2Y1, P2Y11, and P2X7 purine receptor agonists modulated the TGF-β1-induced EMT through the involvement of PKA and/or MAPK/ERK signaling. The stimulation of A2A receptor reduced the overexpression of the EMT-related markers, mainly through the cAMP-dependent PKA pathway, as confirmed by cell pre-treatment with Myr-PKI. Both A1 and P2Y1 receptor stimulation exacerbated the TGF-β1-driven effects, which were reduced by cell pre-treatment with the MAPK inhibitor PD98059, according to the increased ERK1/2 phosphorylation upon receptor activation. The effects induced by P2Y11 receptor activation were oppositely modulated by PKA or MAPK inhibition, in line with the dual nature of the Gs- and Gq-coupled receptor. Differently, P2X7 receptor induced, per se, similar and not additive effects compared to TGF-β1, after prolonged cell exposure to BzATP. These results suggest a putative role of purine receptors as target for anti-fibrotic agents.

Reduced Expression of Glutathione S-Transferase 4 Promotes Vascular Neointimal Hyperplasia in CKD

Neointima formation is the leading cause of arteriovenous fistula (AVF) failure. We have shown that CKD accelerates this process by transforming the vascular smooth muscle cells (SMCs) lining the AVF from a contractile to the synthetic phenotype. However, the underlying mechanisms affecting this transformation are not clear. Previous studies have shown that the α-class glutathione transferase isozymes have an important role in regulating 4-hydroxynonenal (4-HNE)-mediated proliferative signaling of cells. Here, using both the loss- and gain-of-function approaches, we investigated the role of glutathione S-transferase α4 (GSTA4) in modulating cellular 4-HNE levels for the transformation and proliferation of SMCs. Compared with non-CKD controls, mice with CKD had downregulated expression of GSTA4 at the mRNA and protein levels, with concomitant increase in 4-HNE in arteries and veins. This effect was associated with upregulated phosphorylation of MAPK signaling pathway proteins in proliferating SMCs. Overexpressing GSTA4 blocked 4-HNE-induced SMC proliferation. Additionally, inhibitors of MAPK signaling inhibited the 4-HNE-induced responses. Compared with wild-type mice, mice lacking GSTA4 exhibited increased CKD-induced neointima formation in AVF. Transient expression of an activated form of GSTA4, achieved using a combined Tet-On/Cre induction system in mice, lowered levels of 4-HNE and reduced the proliferation of SMCs. Together, these results demonstrate the critical role of GSTA4 in blocking CKD-induced neointima formation and AVF failure.

Protective effects of probucol on Ox-LDL-induced epithelial-mesenchymal transition in human renal proximal tubular epithelial cells via LOX‑1/ROS/MAPK signaling

Oxidized low-density lipoprotein (Ox-LDL), as a strong oxidant, results in renal injury through multiple mechanisms. The aim of the present study was to determine the injury effects of Ox‑LDL and the potential protective effects of the antioxidant reagent probucol on epithelial‑mesenchymal transition (EMT) in human renal proximal tubular epithelial cells (HK‑2) and to further explore the role and interrelation of lectin‑like oxidized low‑density lipoprotein receptor‑1 (LOX‑1), reactive oxygen species (ROS) and mitogen‑activated protein kinase (MAPK) pathway. In the present study, concentrations of 0‑100 µg/ml Ox‑LDL were used to induce HK‑2 cell EMT. Then, probucol (20 µmol/l) and the LOX‑1 inhibitor, polyinosinic acid (250 µg/ml), were also used to pretreat HK‑2 cells. Intracellular ROS activity was evaluated using the specific probe 2',7'‑dichlorodihydrofluorescein diacetate (DCFH‑DA). Concentration of nitric oxide (NO) was determined using a biochemical colorimetric method. Expression of E‑cadherin, α‑smooth muscle actin (SMA), LOX‑1, NADPH oxidase 4 (NOX4), cytochrome b‑245 α chain (p22phox), extracellular signal‑regulated kinase (ERK), and p38 MAPK protein levels were examined by western blotting. The results revealed that Ox‑LDL induced the expression of LOX‑1 and α‑SMA and reduced the expression of E‑cadherin in a dose‑dependent manner, and these effects were inhibited by polyinosinic acid or probucol pretreatment. Stimulation with 50 µg/ml Ox‑LDL induced the expression of NOX4 and p22phox and increased intracellular ROS activity, but NO production in the cell supernatants was not affected. The Ox‑LDL‑mediated increases in Nox4 and p22phox expression and in ROS activity were inhibited by probucol pretreatment. Further investigations into the underlying molecular pathways demonstrated that ERK and p38 MAPK were activated by Ox‑LDL stimulation and then inhibited by probucol pretreatment. The findings of the present study therefore suggest that Ox‑LDL induced EMT in HK‑2 cells, the mechanism of which may be associated with LOX‑1‑related oxidative stress via the ERK and p38 MAPK pathways. Notably, pretreatment with probucol inhibited the Ox‑LDL‑induced oxidative stress by reducing the expression of LOX‑1, and blocked the progression of EMT.

Saxagliptin Attenuates Albuminuria by Inhibiting Podocyte Epithelial- to-Mesenchymal Transition via SDF-1α in Diabetic Nephropathy

The dipeptidyl peptidase-4 (DPP-4) inhibitor saxagliptin has been found to reduce progressive albuminuria, but the exact mechanism of inhibition is unclear. Podocyte epithelial-to-mesenchymal transition (EMT) has emerged as a potential pathway leading to proteinuria in diabetic nephropathy (DN). Stromal cell–derived factor-1α (SDF-1α), one of the substrates of DPP-4, can activate the protein kinase A pathway and subsequently inhibit its downstream effector, transforming growth factor-β1 (TGF-β1), which induces podocyte EMT. Thus, this study was designed to test the hypothesis that saxagliptin reduces progressive albuminuria by preventing podocyte EMT through inhibition of SDF-1α cleavage in DN. The results of a series of assays, including ELISA, western blotting, and immunochemistry/immunofluorescence, showed that saxagliptin treatment obviously ameliorated urinary microalbumin excretion and renal histological changes in high-fat diet/streptozotocin-induced diabetic rats. Furthermore, saxagliptin-treated diabetic rats presented with suppression of DPP-4 activity/protein expression accompanied by restoration of SDF-1α levels, which subsequently hindered NOX2 expression and podocyte EMT. In vitro, we consistently observed that saxagliptin significantly inhibited increased DPP-4 activity/expression, oxidative stress and podocyte EMT. Application of an SDF-1α receptor inhibitor (AMD3100) to cultured podocytes further confirmed the essential role of SDF-1α in podocyte EMT inhibition. In sum, we demonstrated for the first time that saxagliptin treatment plays an essential role in ameliorating progressive DN by preventing podocyte EMT through a SDF-1α-related pathway, suggesting that saxagliptin could offer renoprotection and that SDF-1α might be a potential therapeutic target for DN.

Trichostatin A inhibits radiation-induced epithelial-to-mesenchymal transition in the alveolar epithelial cells

Radiation-induced pneumonitis and fibrosis are major complications following thoracic radiotherapy. Epithelial-to-mesenchymal transition (EMT) plays an important role in tissue injury leading to organ fibrosis, including lung. Our previous studies have reported that radiation can induce EMT in the type II alveolar epithelial cells in both in vitro and in vivo. HDAC inhibitors are a new family of anti-cancer agents currently being used in several clinical trials. In addition to their intrinsic anti-tumor properties, HDAC inhibition is also important in other human diseases, including fibrosis and radiation-induced damage. In this study, we evaluated the effect of Trichostatin A (TSA), a HDAC inhibitor, on radiation-induced EMT in type II alveolar epithelial cells (RLE-6TN). Pre-treatment of RLE-6TN cells with TSA inhibited radiation-induced EMT-like morphological alterations including elevated protein level of α-SMA and Snail, reduction of E-cadherin expression, enhanced phosphorylation of GSK3β and ERK1/2, increased generation of ROS. Radiation enhanced the protein level of TGF-β1, which was blocked by N-acetylcysteine, an antioxidant. Treating cells with SB-431542, TGF-β1 type I receptor inhibitor, diminished radiation-induced alterations in the protein levels of p-GSK-3β, Snail-1 and α-SMA, suggesting a regulatory role of TGF-β1 in EMT. Pre-incubation of cells with TSA showed significant decrease in the level of TGF-β1 compared to radiation control. Collectively, these results demonstrate that i] radiation-induced EMT in RLE-6TN cells is mediated by ROS/MEK/ERK and ROS/TGF-β1 signaling pathways and ii] the inhibitory role of TSA in radiation-induced EMT appears to be due, at least in part, to its action of blocking ROS and TGF-β1 signaling.

Propyl Gallate Exerts an Antimigration Effect on Temozolomide-Treated Malignant Glioma Cells through Inhibition of ROS and the NF-κB Pathway

In this study, we demonstrated that temozolomide (TMZ) and propyl gallate (PG) combination enhanced the inhibition of migration in human U87MG glioma cells. PG inhibited the TMZ-induced reactive oxygen species (ROS) generation. The mitochondrial complex III and NADPH oxidase are two critical sites that can be considered to regulate antimigration in TMZ-treated U87MG cells. PG can enhance the antimigration effect of TMZ through suppression of metalloproteinase-2 and metalloproteinase-9 activities, ROS generation, and the NF-κB pathway and possibly provide a novel prospective strategy for treating malignant glioma.

Renal protective effect and action mechanism of Huangkui capsule and its main five flavonoids

ETHNOPHARMACOLOGICAL RELEVANCE

The flower of Abelmoschus manihot (Linn.) Medicus (A. manihot), as a traditional Chinese Herbal medicine, was used widely in China with efficacy of inducing diuresis for treating strangurtia, and subdhing swelling and detoxicating. It has been reported that Huangkui capsule, prepared by the extract of the flower of A. manihot, can reduce the content of urinary protein, serum creatinine and serum urea nitrogen in nephropathy rats and processes renoprotective activity, while the action mechanism need to illuminate deeply.

AIMS OF THE STUDY

In this study, we investigated the protection effect of Huangkui capsule on tubulointerstitial fibrosis in chronic renal failure (CRF) rats and its mechanism against high glucose-induced epithelial to mesenchymal transition (EMT) in renal tubular epithelial cells (HK-2) of its bioactive components.

MATERIALS AND METHODS

The animals were divided into normal group, CRF model group and Huangkui capsule-treated group. Hematoxylin eosin (HE) staining and Masson staining were applied to observe pathological changes in renal tissue of different groups. Biochemical indicators including serum urea nitrogen (BUN), urine protein (UP) and serum creatinine (Scr) were measured according to the manufacturer's instructions of kits. HK-2 cell damaged model was established to access the protection effect and action mechanism of five main flavonoids from Huangkui capsule. The experimental cells were divided into eight groups: control group, model group, positive drug group and five main flavonoids treated groups. The dichlorodihydrofluorescein diacetate (DCFH-DA) assay was used to determine the reactive oxygen species (ROS) in different groups. Western blot was applied to analyze the expression of pathogenesis-related proteins in different groups.

RESULTS

The results stated that Huangkui capsule significantly inhibited the elevation of Scr, BUN, UP, the expression of α-smooth muscle actin (α-SMA), phosphorylation-extracellular signal-regulated kinase (p-ERK1/2), NADPH Oxidase 1, NADPH Oxidase 2 and NADPH Oxidase 4 in adenine-induced CRF rats. The main bioactive components of quercetin (QT), hyperoside (HY), isoquercitrin (IQT), gossypetin-8-O-β-D-glucuronide (GG) and quercetin-3'-O-glucoside (QG) at the dosage of 100µM, like NADPH oxidase inhibitor diphenyleneiodonium, exhibited a significant effect on inhibiting the expression of α-SMA, p-ERK1/2, NADPH Oxidase 1, NADPH Oxidase 2 and NADPH Oxidase 4 in high glucose-induced HK-2 cells, especially GG.

CONCLUSIONS

These results demonstrated that Huangkui capsule and the flavonoids components prevent tubulointerstitial fibrosis in CRF rat involvement in the action mechanism of inhibiting NADPH oxidase/ROS/ERK pathway.

Intermedin attenuates renal fibrosis by induction of heme oxygenase-1 in rats with unilateral ureteral obstruction

BACKGROUND

Intermedin [IMD, adrenomedullin-2 (ADM-2)] attenuates renal fibrosis by inhibition of oxidative stress. However, the precise mechanisms remain unknown. Heme oxygenase-1 (HO-1), an antioxidant agent, is associated with antifibrogenic effects. ADM is known to induce HO-1. Whether IMD has any effect on HO-1 is unclear. Herein, we determined whether the antifibrotic properties of IMD are mediated by induction of HO-1.

METHODS

Renal fibrosis was induced by unilateral ureteral obstruction (UUO) performed on male Wistar rats. Rat proximal tubular epithelial cell line (NRK-52E) was exposed to rhTGF-β1 (10 ng/ml) to establish an in vitro model of epithelial-mesenchymal transition (EMT). IMD was over-expressed in vivo and in vitro using the vector pcDNA3.1-IMD. Zinc protoporphyrin (ZnPP) was used to block HO-1 enzymatic activity. IMD effects on HO-1 expression in the obstructed kidney of UUO rat and in TGF-β1-stimulated NRK-52E were analyzed by real-time RT-PCR, Western blotting or immunohistochemistry. HO activity in the obstructed kidney, contralateral kidney of UUO rat and NRK-52E was examined by measuring bilirubin production. Renal fibrosis was determined by Masson trichrome staining and collagen I expression. Macrophage infiltration and IL-6 expression were evaluated using immunohistochemical analysis. In vivo and in vitro EMT was assessed by measuring α-smooth muscle actin (α-SMA) and E-cadherin expression using Western blotting or immunofluorescence, respectively.

RESULTS

HO-1 expression and HO activity were increased in IMD-treated UUO kidneys or NRK-52E. The obstructed kidneys of UUO rats demonstrated significant interstitial fibrosis on day 7 after operation. In contrast, kidneys that were treated with IMD gene transfer exhibited minimal interstitial fibrosis. The obstructed kidneys of UUO rats also had greater macrophage infiltration and IL-6 expression. IMD restrained infiltration of macrophages and expression of IL-6 in UUO kidneys. The degree of EMT was extensive in obstructed kidneys of UUO rats as indicated by decreased expression of E-cadherin and increased expression of α-SMA. In vitro studies using NRK-52E confirmed these observations. EMT was suppressed by IMD gene delivery. However, all of the above beneficial effects of IMD were eliminated by ZnPP, an inhibitor of HO enzyme activity.

CONCLUSION

This study demonstrates that IMD attenuates renal fibrosis by induction of HO-1.

Arctigenin suppresses renal interstitial fibrosis in a rat model of obstructive nephropathy

BACKGROUND

Renal tubulointerstitial fibrosis (TIF) is commonly the final result of a variety of progressive injuries and leads to end-stage renal disease. There are few therapeutic agents currently available for retarding the development of renal TIF.

PURPOSE

The aim of the present study is to evaluate the role of arctigenin (ATG), a lignan component derived from dried burdock (Arctium lappa L.) fruits, in protecting the kidney against injury by unilateral ureteral obstruction (UUO) in rats.

METHODS

Rats were subjected to UUO and then administered with vehicle, ATG (1 and 3mg/kg/d), or losartan (20mg/kg/d) for 11 consecutive days. The renoprotective effects of ATG were evaluated by histological examination and multiple biochemical assays.

RESULTS

Our results suggest that ATG significantly protected the kidney from injury by reducing tubular dilatation, epithelial atrophy, collagen deposition, and tubulointerstitial compartment expansion. ATG administration dramatically decreased macrophage (CD68-positive cell) infiltration. Meanwhile, ATG down-regulated the mRNA levels of pro-inflammatory chemokine monocyte chemoattractant protein-1 (MCP-1) and cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interferon-γ (IFN-γ), in the obstructed kidneys. This was associated with decreased activation of nuclear factor κB (NF-κB). ATG attenuated UUO-induced oxidative stress by increasing the activity of renal manganese superoxide dismutase (SOD2), leading to reduced levels of lipid peroxidation. Furthermore, ATG inhibited the epithelial-mesenchymal transition (EMT) of renal tubules by reducing the abundance of transforming growth factor-β1 (TGF-β1) and its type I receptor, suppressing Smad2/3 phosphorylation and nuclear translocation, and up-regulating Smad7 expression. Notably, the efficacy of ATG in renal protection was comparable or even superior to losartan.

CONCLUSION

ATG could protect the kidney from UUO-induced injury and fibrogenesis by suppressing inflammation, oxidative stress, and tubular EMT, thus supporting the potential role of ATG in renal fibrosis treatment.

Advanced Oxidation Protein Products Induce Epithelial-Mesenchymal Transition of Intestinal Epithelial Cells via a PKC δ-Mediated, Redox-Dependent Signaling Pathway

AIMS

Epithelial-mesenchymal transition (EMT) has been considered a fundamental mechanism in complications of Crohn's disease (CD), especially intestinal fibrosis. However, the mechanism underlying EMT regulation in intestinal fibrosis remains unclear. This study aimed to investigate the role of advanced oxidation protein products (AOPPs) in the occurrence of intestinal EMT.

RESULTS

AOPPs accumulated in CD tissues and were associated with EMT marker expression in fibrotic lesions from CD patients. Challenge with AOPPs induced intestinal epithelial cell (IEC) phenotype transdifferentiation, fibroblast-like phenotype acquisition, and production of extracellular matrix, both in vitro and in vivo. The effect of AOPPs was mainly mediated by a protein kinase C (PKC) δ-mediated redox-dependent pathway, including phosphorylation of PKC δ, recruitment of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, production of reactive oxygen species, and NF-κB p65 activation. Inhibition of AOPP-redox signaling activation effectively blocked AOPP-induced EMT in vitro. Studies performed in normal rats showed that chronic administration of AOPPs triggered the occurrence of EMT in rat intestinal epithelia, accompanied by disruption of intestinal integrity, and by promotion of collagen deposition. These effects could be reversed by inhibition of NADPH oxidase. Innovation and Conclusion: This is the first study to demonstrate that AOPPs triggered the occurrence of EMT in IECs in vitro and in vivo through PKC δ-mediated redox-dependent signaling. Our study identifies the role of AOPPs and, in turn, EMT in intestinal fibrosis and provides novel potential targets for the treatment of intestinal fibrotic diseases. Antioxid. Redox Signal. 27, 37-56.

Transforming Growth Factor β1 Function in Airway Remodeling and Hyperresponsiveness. The Missing Link?

The pathogenesis of asthma includes a complex interplay among airway inflammation, hyperresponsiveness, and remodeling. Current evidence suggests that airway structural cells, including bronchial smooth muscle cells, myofibroblasts, fibroblasts, and epithelial cells, mediate all three aspects of asthma pathogenesis. Although studies show a connection between airway remodeling and changes in bronchomotor tone, the relationship between the two remains unclear. Transforming growth factor β1 (TGF-β1), a growth factor elevated in the airway of patients with asthma, plays a role in airway remodeling and in the shortening of various airway structural cells. However, the role of TGF-β1 in mediating airway hyperresponsiveness remains unclear. In this review, we summarize the literature addressing the role of TGF-β1 in airway remodeling and shortening. Through our review, we aim to further elucidate the role of TGF-β1 in asthma pathogenesis and the link between airway remodeling and airway hyperresponsiveness in asthma and to define TGF-β1 as a potential therapeutic target for reducing asthma morbidity and mortality.

Human Peritoneal Mesothelial Cell Death Induced by High-Glucose Hypertonic Solution Involves Ca2+ and Na+ Ions and Oxidative Stress with the Participation of PKC/NOX2 and PI3K/Akt Pathways

Chronic peritoneal dialysis (PD) therapy is equally efficient as hemodialysis while providing greater patient comfort and mobility. Therefore, PD is the treatment of choice for several types of renal patients. During PD, a high-glucose hyperosmotic (HGH) solution is administered into the peritoneal cavity to generate an osmotic gradient that promotes water and solutes transport from peritoneal blood to the dialysis solution. Unfortunately, PD has been associated with a loss of peritoneal viability and function through the generation of a severe inflammatory state that induces human peritoneal mesothelial cell (HPMC) death. Despite this deleterious effect, the precise molecular mechanism of HPMC death as induced by HGH solutions is far from being understood. Therefore, the aim of this study was to explore the pathways involved in HGH solution-induced HPMC death. HGH-induced HPMC death included influxes of intracellular Ca²⁺ and Na⁺. Furthermore, HGH-induced HPMC death was inhibited by antioxidant and reducing agents. In line with this, HPMC death was induced solely by increased oxidative stress. In addition to this, the cPKC/NOX2 and PI3K/Akt intracellular signaling pathways also participated in HGH-induced HPMC death. The participation of PI3K/Akt intracellular is in agreement with previously shown in rat PMC apoptosis. These findings contribute toward fully elucidating the underlying molecular mechanism mediating peritoneal mesothelial cell death induced by high-glucose solutions during peritoneal dialysis.

Attenuation of diabetic nephropathy by Sanziguben Granule inhibiting EMT through Nrf2-mediated anti-oxidative effects in streptozotocin (STZ)-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic nephropathy (DN) is an acute and serious diabetic complication characterized by renal hypertrophy and renal fibrosis with the expansion of extracellular matrices. Diabetic nephropathy has become a major cause of end-stage kidney disease. Sanziguben Granule (SZGB) is a compound prescription which has been widely applied in clinical medicine for the prevention and treatment of diabetic nephropathy as well as for acute and chronic kidney injuries. However, the mechanism of protective effects of SZGB in DN remains unclear.

MATERIALS AND METHODS

In this research, we investigated the effects of SZGB on renal interstitial fibrosis, antioxidant proficiency, and apoptosis in streptozotocin (STZ)-induced diabetic rats. Diabetic rats were prepared by performing a right uninephrectomy along with a single intraperitoneal injection of STZ. Rats were divided into six groups including sham, DN, SZGB-D, SZGB-Z, SZGB-G and fosinopril. SZGB and fosinopril were given to rats by gavage for 12 weeks. Samples from urine, blood and kidneys were collected for biochemical, histological, immunohistochemical and western blot analyses.

RESULTS

We found that rats treated with SZGB showed reduced 24-h urinary protein excretion along with reduced serum total cholesterol (TC) and triglyceride (TG) levels. SZGB was also shown to prevent the disruption of catalase activity and reduce serum urea, creatinine, and renal malondialdehyde while increasing glutathione levels. Moreover, SZGB administration markedly improved the expression levels of E-cadherin, 4-HNE, Nrf2, HO-1, and Bcl-2, while it decreased the expression levels of Vimentin, α-SMA and Cleaved caspase-3 in the kidneys of diabetic rats. The renoprotective effects of SZGB was believed to be mediated by its antioxidant capacity, and SZGB treatment attenuated renal fibrosis through stimulating the nuclear factor erythroid-2-related factor 2 (Nrf2) signaling pathway in the diabetic kidneys.

CONCLUSIONS

Therefore, it is suggested that SZGB can restrain epithelial-mesenchymal transition (EMT) through stimulating the Nrf2 pathway, which improves renal interstitial fibrosis in DN.