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

EI24 alleviates renal interstitial fibrosis through inhibition of epithelial-mesenchymal transition and fibroblast activation

Etoposide-induced 2.4 (EI24) exerts tumor suppressor activity through participating in cell apoptosis, autophagy, and inflammation. However, its role in renal diseases has not been elucidated. This study showed that the EI24 level decreased gradually in the kidneys of mice with unilateral ureteral obstruction (UUO) and in another fibrosis model induced by diabetic kidney disease. The overexpression of EI24 was used to investigate the possible role both in vivo and in vitro. The overexpression 1 day after UUO through tail vein injection alleviated the progression of renal interstitial fibrosis (RIF). EI24 inhibited epithelial-mesenchymal transition, excessive deposition of the extracellular matrix, and activation of fibroblasts. Furthermore, administration of EI24-overexpressing plasmids restrained the phosphorylation of nuclear factor-κB (NF-κB) and c-Jun kinase (JNK) through regulating the proteasome-dependent degradation of TRAF2, and then, inhibited the expression of downstream inflammation-associated cytokines (interleukin-6, tumor necrosis factor-α, and monocyte chemotactic protein-1) and infiltration of macrophages and neutrophils in mouse kidney after UUO. In conclusion, the data indicated that EI24, a novel anti-fibrosis regulator, was important in the progression of RIF.

Extra- and Intracellular Monitoring of TGF-β Using Single Immunoplasmonic Nanoprobes

Transforming growth factor-β (TGF-β) is a well-known disease-related biomarker associated with fibrotic diseases, and initiation and progression of cancer in many organs. Therefore, quantitative and sensitive detection of TGF-β and similar biomarkers is crucial for patient treatment in the early stages of diagnosis. In many studies, the detection of TGF-β, an important profibrotic and cancer promoting cytokine, has been generally conducted by fluorescence or absorbance-based immunoassays. However, conventional methods for detecting TGF-β have problems including use of time-consuming sample pretreatment steps and multiple reagents for signal amplification and difficulty in real-time detection from living cells. Herein, we present a plasmon-based immunoassay for TGF-β using antibody-conjugated single gold nanoparticles that act as optically excellent intracellular and extracellular detection probes that do not require additional signal amplification. To detect TGF-β sensitively and selectively, we exploited the localized surface plasmon resonance (LSPR) property of antibody-conjugated plasmonic gold nanoparticles at a single particle level. By measuring the LSPR spectral shifts of the single plasmonic nanoprobes, TGF-β can be detected down to the picomolar level, which is comparable with the conventional methods but without significant interference from other proteins. The optimized plasmonic nanoprobes were applied to quantify and monitor the extracellular TGF-β level secreted from the cells under stress conditions, such as cancer, and exposure to toxic environments. Owing to the ease of cellular internalization of the nanoprobes, we directly image and detect increases in intracellular TGF-β levels in living cells under the given stress conditions without cell lysis. We envision that this strategy of using individual nanoparticles as sensors to monitor protein biomarkers in living cells could be applied for various biological assays and diagnosis.

Dissecting the Involvement of Ras GTPases in Kidney Fibrosis

Many different regulatory mechanisms of renal fibrosis are known to date, and those related to transforming growth factor-β1 (TGF-β1)-induced signaling have been studied in greater depth. However, in recent years, other signaling pathways have been identified, which contribute to the regulation of these pathological processes. Several studies by our team and others have revealed the involvement of small Ras GTPases in the regulation of the cellular processes that occur in renal fibrosis, such as the activation and proliferation of myofibroblasts or the accumulation of extracellular matrix (ECM) proteins. Intracellular signaling mediated by TGF-β1 and Ras GTPases are closely related, and this interaction also occurs during the development of renal fibrosis. In this review, we update the available in vitro and in vivo knowledge on the role of Ras and its main effectors, such as Erk and Akt, in the cellular mechanisms that occur during the regulation of kidney fibrosis (ECM synthesis, accumulation and activation of myofibroblasts, apoptosis and survival of tubular epithelial cells), as well as the therapeutic strategies for targeting the Ras pathway to intervene on the development of renal fibrosis.

Endothelial-to-Mesenchymal Transition in Pulmonary Arterial Hypertension

Endothelial-to-mesenchymal transition (EndMT) is a process that encompasses extensive transcriptional reprogramming of activated endothelial cells leading to a shift toward mesenchymal cellular phenotypes and functional responses. Initially observed in the context of embryonic development, in the last few decades EndMT is increasingly recognized as a process that contributes to a variety of pathologies in the adult organism. Within the settings of cardiovascular biology, EndMT plays a role in various diseases, including atherosclerosis, heart valvular disease, cardiac fibrosis, and myocardial infarction. EndMT is also being progressively implicated in development and progression of pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH). This review covers the current knowledge about EndMT in PH and PAH, and provides comprehensive overview of seminal discoveries. Topics covered include evidence linking EndMT to factors associated with PAH development, including hypoxia responses, inflammation, dysregulation of bone-morphogenetic protein receptor 2 (BMPR2), and redox signaling. This review amalgamates these discoveries into potential insights for the identification of underlying mechanisms driving EndMT in PH and PAH, and discusses future directions for EndMT-based therapeutic strategies in disease management.

General Control of Amino Acid Synthesis 5-Like 1-Mediated Acetylation of Manganese Superoxide Dismutase Regulates Oxidative Stress in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the major cause of end-stage renal disease (ESRD). In the past few decades, there has been a large amount of evidence to highlight the pivotal role of oxidative stress in the development and progression of DKD. However, the detailed molecular mechanisms are not fully elucidated. A new sight has been established that the mitochondrial acetyltransferase GCN5L1 participates in cellular redox homeostasis maintenance in DKD. Firstly, we found that the expression of GCN5L1 is significantly elevated both in human and mouse kidney tissues with DKD and in hyperglycemic renal tubular epithelial cells (TECs), while deletion of GCN5L1 could effectively ameliorate oxidative stress-induced renal injury in DKD. Furthermore, deletion of GCN5L1 could reduce MnSOD acetylation on lysine 68 and activate its activity, thereby scavenging excessive ROS and relieving oxidative stress-induced renal inflammation and fibrosis. In general, GCN5L1-mediated acetylation of MnSOD exacerbated oxidative stress-induced renal injury, suggesting that GCN5L1 might be a potential intervention target in DKD.

Characterization of ferroptosis in kidney tubular cell death under diabetic conditions

Kidney tubular cell death induced by transforming growth factor-β1 (TGF-β1) is known to contribute to diabetic nephropathy, a major complication of diabetes. Caspase-3-dependent apoptosis and caspase-1-dependent pyroptosis are also involved in tubular cell death under diabetic conditions. Recently, ferroptosis, an atypical form of iron-dependent cell death, was reported to cause kidney disease, including acute kidney injury. Ferroptosis is primed by lipid peroxide accumulation through the cystine/glutamate antiporter system Xc- (xCT) and glutathione peroxidase 4 (GPX4)-dependent mechanisms. The aim of this study was to evaluate the role of ferroptosis in diabetes-induced tubular injury. TGF-β1-stimulated proximal tubular epithelial cells and diabetic mice models were used for in vitro and in vivo experiments, respectively. xCT and GPX4 expression, cell viability, glutathione concentration, and lipid peroxidation were quantified to indicate ferroptosis. The effect of ferroptosis inhibition was also assessed. In kidney biopsy samples from diabetic patients, xCT and GPX4 mRNA expression was decreased compared to nondiabetic samples. In TGF-β1-stimulated tubular cells, intracellular glutathione concentration was reduced and lipid peroxidation was enhanced, both of which are related to ferroptosis-related cell death. Ferrostatin-1 (Fer-1), a ferroptosis inhibitor, alleviated TGF-β1-induced ferroptosis. In diabetic mice, kidney mRNA and protein expressions of xCT and GPX4 were reduced compared to control. Kidney glutathione concentration was decreased, while lipid peroxidation was increased in these mice, and these changes were alleviated by Fer-1 treatment. Ferroptosis is involved in kidney tubular cell death under diabetic conditions. Ferroptosis inhibition could be a therapeutic option for diabetic nephropathy.

Effects of Curcumin on High Glucose-Induced Epithelial-to-Mesenchymal Transition in Renal Tubular Epithelial Cells Through the TLR4-NF-κB Signaling Pathway

OBJECTIVE

Diabetic kidney disease (DKD) is a microvascular complication in diabetes mellitus, while tubuloepithelial to mesenchymal transition (EMT) of mature tubular epithelial cells is a key point in the early development and progression of renal interstitial fibrosis. The present study aimed to investigate the protective effects of Curcumin on EMT and fibrosis in cultured normal rat kidney tubular epithelial cell line (NRK-52E).

METHODS

By using immunofluorescence staining and Western blot protocols, in vitro experiments were designed to analyze EMT markers, including collagen I and E-cadherin in high glucose (HG) exposed NRK-52E cells and to detect the expression levels of phosphorylated-NF-κB, TLR4 and reactive oxygen species (ROS) after Curcumin pre-treatment. With co-treatment with TAK242, these molecules in the TLR4-NF-κB signaling pathway were further evaluated.

RESULTS

Curcumin decreased the HG-induced EMT levels and ROS production in NRK-52E cells. Furthermore, Curcumin was found to inhibit the TLR4-NF-κB signaling activation in HG-induced EMT of NRK-52E cells.

CONCLUSION

The present study provides evidence suggesting a novel mechanism that Curcumin exerts the anti-fibrosis effects via inhibiting activation of the TLR4-NF-κB signal pathway and consequently protecting the HG-induced EMT in renal tubular epithelial cells. Thereby, TLR4-NF-κB may be a useful target for therapeutic intervention in DKD.

Signaling pathways and proteins targeted by antidiabetic chalcones

Chalcones have shown a broad spectrum of biological activities with clinical potential against various diseases. The biological activities are mainly attributed to the presence of α, β-unsaturated carbonyl system, perceived as potential Michael acceptors. In this review, we discussed the antioxidant potential of chalcones and elucidated the mechanisms of pathways and proteins such as carbohydrate digestive enzymes (α-amylase and α-glucosidase), aldose reductase, SGLT-2, and Nrf2 that are targeted by antidiabetic chalcones. In addition to their insulin mimetic potential, we explore the major molecular targets of chalcones and discuss the biochemical and therapeutic implication of modulating these targets. Finally, we dwell on the opulence of the literature and envisage how RNA interference-mediated gene silencing technique and in silico molecular docking could be exploited in the search for novel and more efficacious antidiabetic chalcones.

The role of heat shock proteins in the regulation of fibrotic diseases

Heat shock proteins (HSPs) are key players to restore cell homeostasis and act as chaperones by assisting the folding and assembly of newly synthesized proteins and preventing protein aggregation. Recently, evidence has been accumulating that HSPs have been proven to have other functions except for the classical molecular chaperoning in that they play an important role in a wider range of fibrotic diseases via modulating cytokine induction and inflammation response, including lung fibrosis, liver fibrosis, and idiopathic pulmonary fibrosis. The recruitment of inflammatory cells, a large number of secretion of pro-fibrotic cytokines such as transforming growth factor-β1 (TGF-β1) and increased apoptosis, oxidative stress, and proteasomal system degradation are all events occurring during fibrogenesis, which might be associated with HSPs. However, their role on fibrotic process is not yet fully understood. In this review, we discuss new discoveries regarding the involvement of HSPs in the regulation of organ and tissue fibrosis, and note recent findings suggesting that HSPs may be a promising therapeutic target for improving the current frustrating outcome of fibrotic disorders.

Pathophysiological relationship between hypoxia associated oxidative stress, Epithelial-mesenchymal transition, stemness acquisition and alteration of Shh/ Gli-1 axis during oral sub-mucous fibrosis and oral squamous cell carcinoma

Oral sub-mucous fibrosis (OSF) is a pathophysiological state of oral cavity or oropharynx having a high chance of conversion to oral squamous cell carcinoma (OSCC). It involves fibrotic transformation of sub-epithelial matrix along with epithelial abnormalities. The present work aims to unveil the mechanistic domain regarding OSF to OSCC conversion exploring the scenario of hypoxia associated oxidative stress, epithelial-mesenchymal transition (EMT), metastasis and stemness acquisition. The study involves histopathological analysis of the diseased condition along with the exploration of oxidative stress status, assessment of mitochondrial condition, immunohistochemical analysis of HIF-1α, E-cadherin, vimentin, ERK, ALDH-1, CD133, Shh, Gli-1 and survivin expressions in the oral epithelial region together with the quantitative approach towards collagen deposition in the sub-epithelial matrix. Oxidative stress was found to be associated with type-II EMT in case of OSF attributing the development of sub-epithelial fibrosis and type-III EMT in case of OSCC favoring malignancy associated metastasis. Moreover, the acquisition of stemness during OSCC can also be correlated with EMT. Alteration of Shh and Gli-1 expression pattern revealed the mechanistic association of hypoxia with the phenotypic plasticity and disease manifestation in case of OSF as well as OSCC. Shh/ Gli-1 signaling can also be correlated with survivin mediated cytoprotective phenomenon under oxidative stress. Overall, the study established the correlative network of hypoxia associated oxidative stress, EMT and manifestation of oral pre-cancerous and cancerous condition in a holistic approach that may throw rays of hope in the therapeutic domain of the concerned diseases.

Emerging cellular and molecular determinants of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), the most common form of idiopathic interstitial pneumonia, is a progressive, irreversible, and typically lethal disease characterized by an abnormal fibrotic response involving vast areas of the lungs. Given the poor knowledge of the mechanisms underpinning IPF onset and progression, a better understanding of the cellular processes and molecular pathways involved is essential for the development of effective therapies, currently lacking. Besides a number of established IPF-associated risk factors, such as cigarette smoking, environmental factors, comorbidities, and viral infections, several other processes have been linked with this devastating disease. Apoptosis, senescence, epithelial-mesenchymal transition, endothelial-mesenchymal transition, and epithelial cell migration have been shown to play a key role in IPF-associated tissue remodeling. Moreover, molecules, such as chemokines, cytokines, growth factors, adenosine, glycosaminoglycans, non-coding RNAs, and cellular processes including oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, hypoxia, and alternative polyadenylation have been linked with IPF development. Importantly, strategies targeting these processes have been investigated to modulate abnormal cellular phenotypes and maintain tissue homeostasis in the lung. This review provides an update regarding the emerging cellular and molecular mechanisms involved in the onset and progression of IPF.

Identification of NLRP3 Inflammation-Related Gene Promoter Hypomethylation in Diabetic Retinopathy

Purpose

To identify and validate key genes that could provide a new perspective for genetic marker screening of diabetic retinopathy (DR).

Methods

The gene expression and DNA methylation profiles were obtained from the Gene Expression Omnibus. Differential expression analysis was conducted using the limma package, and then the functions of the differentially expressed genes (DEGs) were analyzed using the DAVID database, followed by protein–protein interaction (PPI) networks using Cytoscape software. We employed the Sequenom MassARRAY system to detect the promoter methylation levels of the candidate genes in peripheral blood mononuclear cells from 32 healthy individuals and 94 patients with type 2 diabetes mellitus (T2D; 64 with DR and 30 without DR) and in fibrovascular membranes (FVMs) from three proliferative DR patients and three controls with idiopathic epiretinal membranes. The mRNA levels of candidate genes were further confirmed via real-time polymerase chain reaction.

Results

A significant enrichment of 5906 DEGs was found in immune and inflammatory responses. TGFB1, CCL2, and TNFSF2 were identified as the top three core genes associated with NLRP3 inflammation in PPI networks. These genes have relatively low levels of promoter methylation, which have been validated in peripheral blood mononuclear cells and FVMs from DR patients, and the methylation levels were found to be negative correlated with the mRNA levels and HbA1c levels in T2D patients.

Conclusions

Overall, these data indicate that promoter hypomethylation of NLRP3, TGFB1, CCL2, and TNFSF2 may increase the risk of DR in the Chinese Han population, indicating that these genes might serve as potential targets for the detection and treatment of DR.

Transforming Growth Factor β1 Induces Epithelial–mesenchymal Transition by Activating the Jnk–SMAD3 Pathway in Rat Peritoneal Mesothelial Cells

⋄ Background

Peritoneal fibrosis is a serious complication in long-term peritoneal dialysis (PD) patients. Epithelial-mesenchymal transition (EMT) plays an important role in peritoneal fibrosis, and TGFβ1 is the crucial inducer of EMT. Phosphorylation of Smad proteins is required for TGFβ1-induced EMT. It was reported that C-Jun N-terminal kinase (JNK) was involved in the TGFβ1/Smad signaling pathway and might regulate the activation of Smad proteins. However, whether JNK is activated by TGFβ1 in rat peritoneal mesothelial cells (RPMCs) and the role taken by JNK signaling in EMT induced by TGFβ1 remains undetermined. In the present study, we investigated the role of JNK-Smad pathway in EMT induced by TGFβ1 in RPMCs.

⋄ Methods

We harvested RPMCs from the peritoneum of male Sprague-Dawley rats and then cultured the cells in Dulbecco modified Eagle medium / F12 medium with 15% (volume:volume) fetal bovine serum. The cells were pretreated with SP600125, a specific inhibitor of JNK, for 4 hours before incubation with TGFβ1. The protein expression levels of phosphorylated JNK, Smad2, and Smad3 were detected by Western blotting. The messenger RNA levels and protein expression of α-smooth muscle actin (α-SMA), E-cadherin, and collagen I were determined with reverse transcriptase polymerase chain reaction and Western blotting respectively.

⋄ Results

Expression of α-SMA and collagen I were significantly increased and expression of E-cadherin decreased with TGFβ1 in RPMCs. Transforming growth factor β1 can stimulate phosphorylated JNK expression from 5 minutes, with the peak at 10 minutes, and phosphorylated Smad2 and Smad3 expression from 10 minutes, with the peak at 30 minutes. The addition of SP600125, which blocked activation of JNK, effectively inhibited TGFβ1-induced phosphorylation of Smad3, but not Smad2. Also, our results showed that SP600125 effectively suppressed TGFβ1-induced high expression of α-SMA and collagen I, and prevented TGFβ1-induced downregulation of E-cadherin expression in RPMCs.

⋄ Conclusions

This study demonstrated that JNK signaling may play an important role in EMT induced by TGFβ1 in RPMCs through activation of Smad3, suggesting that JNK inhibitor may prove to be a novel therapeutic agent for peritoneal fibrosis.

Targeted DNA oxidation by LSD1-SMAD2/3 primes TGF-β1/ EMT genes for activation or repression

The epithelial-to-mesenchymal transition (EMT) is a complex transcriptional program induced by transforming growth factor β1 (TGF-β1). Histone lysine-specific demethylase 1 (LSD1) has been recognized as a key mediator of EMT in cancer cells, but the precise mechanism that underlies the activation and repression of EMT genes still remains elusive. Here, we characterized the early events induced by TGF-β1 during EMT initiation and establishment. TGF-β1 triggered, 30–90 min post-treatment, a nuclear oxidative wave throughout the genome, documented by confocal microscopy and mass spectrometry, mediated by LSD1. LSD1 was recruited with phosphorylated SMAD2/3 to the promoters of prototypic genes activated and repressed by TGF-β1. After 90 min, phospho-SMAD2/3 downregulation reduced the complex and LSD1 was then recruited with the newly synthesized SNAI1 and repressors, NCoR1 and HDAC3, to the promoters of TGF-β1-repressed genes such as the Wnt soluble inhibitor factor 1 gene (WIF1), a change that induced a late oxidative burst. However, TGF-β1 early (90 min) repression of transcription also required synchronous signaling by reactive oxygen species and the stress-activated kinase c-Jun N-terminal kinase. These data elucidate the early events elicited by TGF-β1 and the priming role of DNA oxidation that marks TGF-β1-induced and -repressed genes involved in the EMT.

Stearic acid attenuates profibrotic signalling in idiopathic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

Lipid metabolism dysregulation has been implicated in the pathogenesis of IPF; however, the roles of most lipid metabolites in lung fibrosis remain unexplored. Therefore, we aimed to identify changes in lipid metabolites in the lung tissues of IPF patients and determine their roles in pulmonary fibrosis.

METHODS

Free fatty acids in the lung tissues of IPF patients and controls were quantified using a metabolomic approach. The roles of free fatty acids in fibroblasts or epithelial cells treated with TGF-β1 were evaluated using fibrotic markers. The antifibrotic role of stearic acid was also assessed in a bleomycin-induced lung fibrosis mouse model. Protein levels in cell lysates or tissues were measured by western blotting.

RESULTS

The levels of stearic acid were lower in IPF lung tissues than in control lung tissues. Stearic acid significantly reduced TGF-β1-induced α-SMA and collagen type 1 expression in MRC-5 cells. Furthermore, stearic acid decreased the levels of p-Smad2/3 and ROS in MRC-5 cells treated with TGF-β1 and disrupted TGF-β1-induced EMT in Beas-2B cells. Stearic acid reduced the levels of bleomycin-induced hydroxyproline in a mouse model.

CONCLUSION

Changes in the free fatty acid profile, including low levels of stearic acid, were observed in IPF patients. Stearic acid may exert antifibrotic activity by regulating profibrotic signalling.

Kaempferol Protects Renal Fibrosis through Activating the BMP-7-Smad1/5 Signaling Pathway

Renal interstitial fibrosis (RIF) is a common pathological characteristic associated with end-stage renal disease. However, treatment strategies for RIF are still very limited. In this study, we reported that kaempferol, a classic flavonoid, exhibited strong and widely inhibitory effect on the expression of fibrosis related genes in transforming growth factor beta 1 (TGF-β1) treated NRK-52E cells. Further studies revealed that kaempferol inhibited TGF-β1 induced epithelial-mesenchymal transition (EMT) process of NRK-52E cells and improved renal function deterioration and RIF in unilateral ureteral obstruction (UUO) rats. After exploring the underlying mechanisms, we found that kaempferol was able to activate the BMP-7-Smad1/5 pathway, rather than the TGF-β1-Smad2/3 pathway. To further validate these results, DMH1 and BMP-7 knockdown were utilized at the cellular level and the results showed that both methods were able to antagonize the effects of kaempferol on the EMT process of NRK-52E cells induced by TGF-β1. In UUO rats, inhibition of BMP-7 signaling by DMH1 also reversed the effects of kaempferol on renal function decline and RIF. Taken together, our findings demonstrated that kaempferol could be a good candidate for renal fibrosis treatment.

Metabolic Potential of Cancer Cells in Context of the Metastatic Cascade

The metastatic cascade is a highly plastic and dynamic process dominated by cellular heterogeneity and varying metabolic requirements. During this cascade, the three major metabolic pillars, namely biosynthesis, RedOx balance, and bioenergetics, have variable importance. Biosynthesis has superior significance during the proliferation-dominated steps of primary tumour growth and secondary macrometastasis formation and only minor relevance during the growth-independent processes of invasion and dissemination. Consequently, RedOx homeostasis and bioenergetics emerge as conceivable metabolic key determinants in cancer cells that disseminate from the primary tumour. Within this review, we summarise our current understanding on how cancer cells adjust their metabolism in the context of different microenvironments along the metastatic cascade. With the example of one-carbon metabolism, we establish a conceptual view on how the same metabolic pathway can be exploited in different ways depending on the current cellular needs during metastatic progression.

The renal antioxidative effect of losartan involves heat shock protein 70 in proximal tubule cells

Angiotensin II exerts a cardinal role in the pathogenesis of hypertension and renal injury via action of angiotensin II type 1 (AT1) receptors. Local renin-angiotensin system (RAS) activity is essential for the mechanisms mediating pathophysiological functions. Proximal tubular angiotensinogen and tubular AT1 receptors are augmented by intrarenal angiotensin II. Caveolin 1 plays an important role as a regulatory molecule for the compartmentalization of redox signaling events through angiotensin II-induced NADPH oxidase activation in the kidney. A role for the renin-angiotensin system in the development and/or maintenance of hypertension has been demonstrated in spontaneously hypertensive rats (SHRs). Many effects of angiotensin II are dependent on the AT1 stimulation of reactive oxygen species (ROS) production by NADPH oxidase. Angiotensin II upregulation stimulates oxidative stress in proximal tubules from SHR. The NADPH oxidase 4 (Nox4) is abundantly expressed in kidney proximal tubule cells. Induction of the stress response includes synthesis of heat shock protein 70, a molecular chaperone that has a critical role in the recovery of cells from stress and in cytoprotection, guarding cells from subsequent insults. HSP70 chaperones function in part by driving the molecular triage decision, which determines whether proteins enter the productive folding pathway or result in client substrate ubiquitination and proteasomal degradation. This review examines regulation of losartan-mediated antioxidative stress responses by the chaperone HSP70 in proximal tubule cells of spontaneously hypertensive rats.

ROS systems are a new integrated network for sensing homeostasis and alarming stresses in organelle metabolic processes

Reactive oxygen species (ROS) are critical for the progression of cardiovascular diseases, inflammations and tumors. However, the mechanisms of how ROS sense metabolic stress, regulate metabolic pathways and initiate proliferation, inflammation and cell death responses remain poorly characterized. In this analytic review, we concluded that: 1) Based on different features and functions, eleven types of ROS can be classified into seven functional groups: metabolic stress-sensing, chemical connecting, organelle communication, stress branch-out, inflammasome-activating, dual functions and triple functions ROS. 2) Among the ROS generation systems, mitochondria consume the most amount of oxygen; and nine types of ROS are generated; thus, mitochondrial ROS systems serve as the central hub for connecting ROS with inflammasome activation, trained immunity and immunometabolic pathways. 3) Increased nuclear ROS production significantly promotes cell death in comparison to that in other organelles. Nuclear ROS systems serve as a convergent hub and decision-makers to connect unbearable and alarming metabolic stresses to inflammation and cell death. 4) Balanced ROS levels indicate physiological homeostasis of various metabolic processes in subcellular organelles and cytosol, while imbalanced ROS levels present alarms for pathological organelle stresses in metabolic processes. Based on these analyses, we propose a working model that ROS systems are a new integrated network for sensing homeostasis and alarming stress in metabolic processes in various subcellular organelles. Our model provides novel insights on the roles of the ROS systems in bridging metabolic stress to inflammation, cell death and tumorigenesis; and provide novel therapeutic targets for treating those diseases. (Word count: 246).

Therapeutic Targeting of Signaling Pathways Related to Cancer Stemness

The theory of cancer stem cells (CSCs) proposes that the different cells within a tumor, as well as metastasis deriving from it, are originated from a single subpopulation of cells with self-renewal and differentiation capacities. These cancer stem cells are supposed to be critical for tumor expansion and metastasis, tumor relapse and resistance to conventional therapies, such as chemo- and radiotherapy. The acquisition of these abilities has been attributed to the activation of alternative pathways, for instance, WNT, NOTCH, SHH, PI3K, Hippo, or NF-κB pathways, that regulate detoxification mechanisms; increase the metabolic rate; induce resistance to apoptotic, autophagic, and senescence pathways; promote the overexpression of drug transporter proteins; and activate specific stem cell transcription factors. The elimination of CSCs is an important goal in cancer therapeutic approaches because it could decrease relapses and metastatic dissemination, which are main causes of mortality in oncology patients. In this work, we discuss the role of these signaling pathways in CSCs along with their therapeutic potential.

Diesel particulate matter2.5 promotes epithelial-mesenchymal transition of human retinal pigment epithelial cells via generation of reactive oxygen species

Although several studies have linked PM_2.5 (particulate matter with a diameter less than 2.5 μm) to ocular surface diseases such as keratitis and conjunctivitis, very few studies have previously addressed its effect on the retina. Therefore, the aim of this study was to evaluate the effect of PM_2.5 on epithelial-mesenchymal transition (EMT), a process involved in disorders of the retinal pigment epithelial (RPE) on APRE-19 cells. PM_2.5 changed the phenotype of RPE cells from epithelial to fibroblast-like mesenchymal, and increased cell migration. Exposure to PM_2.5 markedly increased the expression of mesenchymal markers, but reduced the levels of epithelial markers. Moreover, PM_2.5 promoted the phosphorylation of MAPKs and the expression of transforming growth factor-β (TGF-β)-mediated nuclear transcriptional factors. However, these PM_2.5-mediated changes were completely reversed by LY2109761, a small molecule inhibitor of the TGF-β receptor type I/II kinases, and N-acetyl-L-cysteine (NAC), a reactive oxygen species (ROS) scavenger. Interestingly, NAC, but not LY2109761, effectively restored the PM_2.5-induced mitochondrial defects, including increased ROS, decreased mitochondrial activity, and mitochondrial membrane potential disruption. Collectively, our findings indicate that the TGF-β/Smad/ERK/p38 MAPK signaling pathway is activated downstream of cellular ROS during PM_2.5-induced EMT. The present study provides the first evidence that EMT of RPE may be one of the mechanisms of PM_2.5-induced retinal dysfunction.

Hsc70 is required for E-cadherin expression in epithelial-like NRK-52E cells

Heat-shock cognate protein 70 (Hsc70), a molecular chaperone, is involved in multiple cellular functions. We previously demonstrated that Hsc70 is required for TGF-β-induced Smad signaling in mesenchymal-like NRK-49F cells. In the present study, to compare the Hsc70 functions in TGF-β-related signaling between epithelial and mesenchymal cells, we examined the effect of Hsc70 downregulation on TGF-β-induced signaling in epithelial-like NRK-52E cells. TGF-β-induced Smad signaling was suppressed in cells treated with small interfering RNA (siRNA) for Hsc70. Interestingly, despite interference with TGF-β signaling, TGF-β-induced suppression of E-cadherin expression was not affected by Hsc70 knockdown. Instead, Hsc70 knockdown itself caused the suppression of E-cadherin expression at the transcription level in cells treated with Hsc70 siRNA. We also examined the effects of Hsc70 knockdown on the level of E-cadherin-gene repressors, such as Snail1, Slug, Zeb1, Zeb2, and Twist1, and found that transcription of the repressors was upregulated after 24- or 36-h treatment with Hsc70 siRNA. Collectively, these results indicate that, in addition to a supportive role in TGF-β-induced signaling, Hsc70 supports E-cadherin expression through downregulation of the E-cadherin-gene repressors in NRK-52E cells, suggesting that Hsc70 plays a functional role to maintain the epithelial cell phenotype.

TGFβ-induced metabolic reprogramming during epithelial-to-mesenchymal transition in cancer

Metastasis is the most frequent cause of death in cancer patients. Epithelial-to-mesenchymal transition (EMT) is the process in which cells lose epithelial integrity and become motile, a critical step for cancer cell invasion, drug resistance and immune evasion. The transforming growth factor-β (TGFβ) signaling pathway is a major driver of EMT. Increasing evidence demonstrates that metabolic reprogramming is a hallmark of cancer and extensive metabolic changes are observed during EMT. The aim of this review is to summarize and interconnect recent findings that illustrate how changes in glycolysis, mitochondrial, lipid and choline metabolism coincide and functionally contribute to TGFβ-induced EMT. We describe TGFβ signaling is involved in stimulating both glycolysis and mitochondrial respiration. Interestingly, the subsequent metabolic consequences for the redox state and lipid metabolism in cancer cells are found to be in favor of EMT as well. Combined we illustrate that a better understanding of the mechanistic links between TGFβ signaling, cancer metabolism and EMT holds promising strategies for cancer therapy, some of which are already actively being explored in the clinic.

Integrated molecular signaling involving mitochondrial dysfunction and alteration of cell metabolism induced by tyrosine kinase inhibitors in cancer

Cancer cells have unlimited replicative potential, insensitivity to growth-inhibitory signals, evasion of apoptosis, cellular stress, and sustained angiogenesis, invasiveness and metastatic potential. Cancer cells adequately adapt cell metabolism and integrate several intracellular and redox signaling to promote cell survival in an inflammatory and hypoxic microenvironment in order to maintain/expand tumor phenotype. The administration of tyrosine kinase inhibitor (TKI) constitutes the recommended therapeutic strategy in different malignancies at advanced stages.

There are important interrelationships between cell stress, redox status, mitochondrial function, metabolism and cellular signaling pathways leading to cell survival/death. The induction of apoptosis and cell cycle arrest widely related to the antitumoral properties of TKIs result from tightly controlled events involving different cellular compartments and signaling pathways. The aim of the present review is to update the most relevant studies dealing with the impact of TKI treatment on cell function. The induction of endoplasmic reticulum (ER) stress and Ca²⁺ disturbances, leading to alteration of mitochondrial function, redox status and phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways that involve cell metabolism reprogramming in cancer cells will be covered. Emphasis will be given to studies that identify key components of the integrated molecular pattern including receptor tyrosine kinase (RTK) downstream signaling, cell death and mitochondria-related events that appear to be involved in the resistance of cancer cells to TKI treatments.

Ganoderic acid hinders renal fibrosis via suppressing the TGF-β/Smad and MAPK signaling pathways

Renal fibrosis is considered as the pathway of almost all kinds of chronic kidney diseases (CKD) to the end stage of renal diseases (ESRD). Ganoderic acid (GA) is a group of lanostane triterpenes isolated from Ganoderma lucidum, which has shown a variety of pharmacological activities. In this study we investigated whether GA exerted antirenal fibrosis effect in a unilateral ureteral obstruction (UUO) mouse model. After UUO surgery, the mice were treated with GA (3.125, 12.5, and 50 mg· kg-1 ·d-1, ip) for 7 or 14 days. Then the mice were sacrificed for collecting blood and kidneys. We showed that GA treatment dose-dependently attenuated UUO-induced tubular injury and renal fibrosis; GA (50 mg· kg-1 ·d-1) significantly ameliorated renal disfunction during fibrosis progression. We further revealed that GA treatment inhibited the extracellular matrix (ECM) deposition in the kidney by suppressing the expression of fibronectin, mainly through hindering the over activation of TGF-β/Smad signaling. On the other hand, GA treatment significantly decreased the expression of mesenchymal cell markers alpha-smooth muscle actin (α-SMA) and vimentin, and upregulated E-cadherin expression in the kidney, suggesting the suppression of tubular epithelial-mesenchymal transition (EMT) partially via inhibiting both TGF-β/Smad and MAPK (ERK, JNK, p38) signaling pathways. The inhibitory effects of GA on TGF-β/Smad and MAPK signaling pathways were confirmed in TGF-β1-stimulated HK-2 cell model. GA-A, a GA monomer, was identified as a potent inhibitor on renal fibrosis in vitro. These data demonstrate that GA or GA-A might be developed as a potential therapeutic agent in the treatment of renal fibrosis.

Astragaloside IV acts through multi-scale mechanisms to effectively reduce diabetic nephropathy

Diabetic nephropathy (DN), a common complication of diabetes mellitus, is the main cause of end-stage nephropathy, and thus developing novel strategies for reversing DN remains urgent. Astragaloside IV (AS-IV), a glycoside extracted from the Astragalus membranaceus (Fisch.) Bunge, is a widely used Traditional Chinese Medicine (TCM) in China and presents diverse pharmacological properties including the protective effect on DN. However, the rudimentary mechanism of AS-IV in remedying DN remains indeterminate. Currently, we systematically explore the pharmacological mechanism of action of AS-IV for treating DN. Firstly, AS-IV was evaluated by ADME assessment, and 26 targets were screened out through target prediction. Then, we decipher the protein-protein interaction (PPI), Gene Ontology (GO) enrichment analysis, disease and pathway network analysis to obtain the specific molecular biological process and pharmacological activity of AS-IV in the treatment of DN. Meanwhile, both in vivo and in vitro experiments confirmed that AS-IV has anti-oxidative stress, anti-inflammatory, anti-epithelial-mesenchymal transition (EMT) effects, and can inhibit the Wnt/β-catenin signaling pathway, ultimately ameliorating the renal injury caused by high glucose. Additionally, we also applied molecular docking and molecular dynamics simulation to predict the specific binding sites and binding capacity of AS-IV and related targets. Overall, the comprehensive system pharmacology method and experiment validations provide an accurate explanation for the molecular mechanism of AS-IV in the treatment of DN. Moreover, it is expected to provide a brand new strategy for exploring the effective components of TCM.

Mitochondrial oxidative stress by Lon-PYCR1 maintains an immunosuppressive tumor microenvironment that promotes cancer progression and metastasis

Mitochondrial Lon is a chaperone protein whose upregulation increases the production of mitochondrial reactive oxygen species (ROS). However, there is a lack of information in detail on how mitochondrial Lon regulates cancer metastasis through ROS production in the tumor microenvironment (TME). Our results show that elevated Lon promotes epithelial-mesenchymal transition (EMT) via ROS-dependent p38 and NF-κB-signaling. We further identified pyrroline-5-carboxylate reductase 1 (PYCR1) as a client of chaperone Lon, which induces mitochondrial ROS and EMT by Lon. Mitochondrial Lon induces ROS-dependent production of inflammatory cytokines, such as TGF-β, IL-6, IL-13, and VEGF-A, which consequently activates EMT, angiogenesis, and M2 macrophage polarization. In addition, Lon expression is induced upon the activation and M2 polarization of macrophages, which further promotes M2 macrophages to enhance the immunosuppressive microenvironment and metastatic behaviors in the TME. This raises the possibility that manipulation of the mitochondrial redox balance in the TME may serve as a therapeutic strategy to improve T cell function in cancer immunotherapy.

Diverse Signaling by TGFβ Isoforms in Response to Focal Injury is Associated with Either Retinal Regeneration or Reactive Gliosis

Müller cells may have stem cell-like capability as they regenerate photoreceptor loss upon injury in some vertebrates, but not in mammals. Indeed, mammalian Müller cells undergo major cellular and molecular changes summarized as reactive gliosis. Transforming growth factor beta (TGFβ) isoforms are multifunctional cytokines that play a central role, both in wound healing and in tissue repair. Here, we studied the role of TGFβ isoforms and their signaling pathways in response to injury induction during tissue regeneration in zebrafish and scar formation in mouse. Our transcriptome analysis showed a different activation of canonical and non-canonical signaling pathways and how they shaped the injury response. In particular, TGFβ3 promotes retinal regeneration via Smad-dependent canonical pathway upon regulation of junb gene family and mycb in zebrafish Müller cells. However, in mice, TGFβ1 and TGFβ2 evoke the p38MAPK signaling pathway. The activation of this non-canonical pathway leads to retinal gliosis. Thus, the regenerative versus reparative effect of the TGFβ pathway observed may rely on the activation of different signaling cascades. This provides one explanation of the different injury response in zebrafish and mouse retina.

ROS and oncogenesis with special reference to EMT and stemness

Elevation of the level of intracellular reactive oxygen species (ROS) has immense implication in the biological system. On the one hand, ROS promote the signaling cascades for the maintenance of normal physiological functions, the phenomenon referred to as redox biology, and on the other hand increased ROS can cause damages to the cellular macromolecules as well as genetic material, the process known as oxidative stress. Oxidative stress acts as an etiological factor for wide varieties of pathologies, cancer being one of them. ROS is regarded as a "double-edged sword" with respect to oncogenesis. It can suppress as well as promote the malignant progression depending on the type of signaling pathway it uses. Moreover, the attribution of ROS in promoting phenotypic plasticity as well as acquisition of stemness during neoplasia has become a wide area of research. The current review discussed all the aspects of ROS in the perspective of tumor biology with special reference to epithelial-mesenchymal transition (EMT) and cancer stem cells.

Kidney allograft fibrosis: what we learned from latest translational research studies

To add new molecular and pathogenetic insights into the biological machinery associated to kidney allograft fibrosis is a major research target in nephrology and organ transplant translational medicine. Interstitial fibrosis associated to tubular atrophy (IF/TA) is, in fact, an inevitable and progressive process that occurs in almost every type of chronic allograft injury (particularly in grafts from expanded criteria donors) characterized by profound remodeling and excessive production/deposition of fibrillar extracellular matrix (ECM) with a great clinical impact. IF/TA is detectable in more than 50% of kidney allografts at 2 years. However, although well studied, the complete cellular/biological network associated with IF/TA is only partially evaluated. In the last few years, then, thanks to the introduction of new biomolecular technologies, inflammation in scarred/fibrotic parenchyma areas (recently acknowledged by the BANFF classification) has been recognized as a pivotal element able to accelerate the onset and development of the allograft chronic damage. Therefore, in this review, we focused on some new pathogenetic elements involved in graft fibrosis (including epithelial/endothelial to mesenchymal transition, oxidative stress, activation of Wnt and Hedgehog signaling pathways, fatty acids oxidation and cellular senescence) that, in our opinion, could become in future good candidates as potential biomarkers and therapeutic targets.

Cisplatin-induced programmed cell death ligand-2 expression is associated with metastasis ability in oral squamous cell carcinoma

Programmed cell death ligands (PD‐Ls) are expressed in tumor cells where they bind to programmed cell death‐1, an immunocyte co–receptor, resulting in tumor cell evasion from the immune system. Chemotherapeutic drugs have been recently reported to induce the expression of PD‐L, such as PD‐L1, in some cancer cells. However, little is known regarding PD‐L2 expression and its role in oral squamous cell carcinoma (OSCC). In this study, we examined the effect of cisplatin on the expression and regulation of PD‐L2 in OSCC cell lines and analyzed malignant behavior in PD‐L2‐expressing cells using colony, transwell and transformation assays. In addition, we examined PD‐L2 expression in the tumor tissues of OSCC patients using cytology and tissue microarray methods. In OSCC cell lines, cisplatin treatment upregulated PD‐L2 expression, along with that of the drug efflux transporter ABCG2, via signal transducers and activator of transcription (STAT) 1/3 activation. Moreover, PD‐L2‐positive or PD‐L2‐overexpressing cells demonstrated upregulation in both invasion and transformation ability but not in proliferation compared with PD‐L2‐negative or PD‐L2‐silencing cells. PD‐L2 expression was also observed in OSCC cells of cytology samples and tissue from OSCC patients. The intensity of PD‐L2 expression was correlated with more malignant morphological features in the histological appearance and an invasive pattern. Our findings indicate that cisplatin‐upregulated PD‐L2 expression in OSCC via STAT1/3 activation and the expression of PD‐L2 are likely to be associated with malignancy in OSCC. The PD‐L2 expression in cisplatin‐resistant OSCC cells may be a critical factor in prognosis of advanced OSCC patients.

Protective Effect of Low-Molecular-Weight Fucoidan on Radiation-Induced Fibrosis Through TGF-β1/Smad Pathway-Mediated Inhibition of Collagen I Accumulation

Radiation-induced fibrosis (RIF) occurs after radiation therapy in normal tissues due to excessive production and deposition of extracellular matrix proteins and collagen, possibly resulting in organ function impairment. This study investigates the effects of low-molecular-weight fucoidan (LMF) on irradiated NIH3T3 cells. Specifically, we quantified cellular metabolic activity, fibrosis-related mRNA expression, transforming growth factor beta-1 (TGF-β1), and collagen-1 protein expression, and fibroblast contractility in response to LMF. LMF pre + post-treatment could more effectively increase cellular metabolic activity compared with LMF post-treatment. LMF pre + post-treatment inhibited TGF-β1 expression, which mediates negative activation of phosphorylated Smad3 (pSmad3) and Smad4 complex formation and suppresses downstream collagen I accumulation. In addition, LMF pre + post-treatment significantly reduced actin-stress fibers in irradiated NIH3T3 cells. LMF, a natural substance obtained from brown seaweed, may be a candidate agent for preventing or inhibiting RIF.

Circulating human microRNA biomarkers of oxalic acid-induced acute kidney injury

Oxalic acid-induced nephrotoxicity and acute kidney injury result from formation of calcium oxalate crystals. Oxalic acid-induced acute kidney injury is a significant problem in many parts of the world. Circulating biomarkers that can accurately and reproducibly detect acute kidney injury are highly desirable. We used a high sensitivity discovery platform to identify signature microRNAs to distinguish healthy individuals never exposed to oxalic acid (n = 4) from those who were exposed to oxalic acid but had no injury (NOAKI; n = 4), moderate injury (AKIN2; n = 4) or severe injury (AKIN3; n = 4). Longitudinal analyses identified 4-8 h post-ingestion as the best time to detect AKIN2/3. We validated a signature of 53 microRNAs identified in the discovery, in a second cohort of individuals exposed to oxalic acid (NOAKI = 11, AKIN2 = 8 and AKIN3 = 18) and healthy controls (n = 19). Thirteen microRNAs were significantly downregulated in acute kidney injury patients compared to NOAKI within 8-h post-ingestion. Five microRNAs (miR-20a, miR-92a, miR-93, miR-195, miR-451) had a highly significant correlation with normalized urinary albumin, serum creatinine at 24 h and creatinine clearance. Logistic regression of these microRNAs had AUC-ROC of 0.85 predicting AKIN2/3 and discriminated patients from healthy controls (AUC-ROC = 0.93). mRNA targets of these microRNAs identified oxidative stress pathways of nephrotoxicity in proximal tubule and glomeruli nephrotoxicity. In conclusion, the downregulation of multiple circulating microRNAs in patients correlated with the severity of oxalic acid-induced acute kidney injury. A set of microRNAs (miR-20a, miR-92a, miR-93, miR-195, miR-451) could be promising biomarkers for early detection of oxalic acid-induced acute kidney injury.

Brain-kidney interaction: Renal dysfunction following ischemic stroke

Stroke is a leading cause of mortality and morbidity, with long-term debilitating effects. Accumulating evidence from experimental studies as well as observational studies in patients suggests a cross talk between the brain and kidney after stroke. Stroke may lead to kidney dysfunction which can adversely impact patient outcome. In this review article, we discuss the epidemiology and mechanisms of brain–kidney interaction following ischemic stroke. Specifically, we discuss the role of the central autonomic network, autoregulation, inflammatory and immune responses, the role of extracellular vesicles and their cargo microRNA, in mediating brain–kidney interaction following stroke. Understanding the bidirectional nature of interaction between the brain and kidney after cerebral injury would have clinical implications for the treatment of stroke and overall patient outcome.

Underlying Histopathology Determines Response to Oxidative Stress in Cultured Human Primary Proximal Tubular Epithelial Cells

Proximal tubular epithelial cells (PTEC) are key players in the progression of kidney diseases. PTEC studies to date have primarily used mouse models and transformed human PTEC lines. However, the translatability of these models to human kidney disease has been questioned. In this study, we investigated the phenotypic and functional response of human primary PTEC to oxidative stress, an established driver of kidney disease. Furthermore, we examined the functional contribution of the underlying histopathology of the cortical tissue used to generate our PTEC. We demonstrated that human primary PTEC from both histologically ‘normal’ and ‘diseased’ cortical tissue responded to H₂O₂-induced oxidative stress with significantly elevated mitochondrial superoxide levels, DNA damage, and significantly decreased proliferation. The functional response of ‘normal’ PTEC to oxidative stress mirrored the reported pathogenesis of human kidney disease, with significantly attenuated mitochondrial function and increased cell death. In contrast, ‘diseased’ PTEC were functionally resistant to oxidative stress, with maintenance of mitochondrial function and cell viability. This selective survival of ‘diseased’ PTEC under oxidizing conditions is reminiscent of the in vivo persistence of maladaptive PTEC following kidney injury. We are now exploring the impact that these differential PTEC responses have in the therapeutic targeting of oxidative stress pathways.

LRRC8/VRAC channels exhibit a noncanonical permeability to glutathione, which modulates epithelial-to-mesenchymal transition (EMT)

Volume-regulated anion channels (VRAC) are chloride channels activated in response to osmotic stress to regulate cellular volume and also participate in other cellular processes, including cell division and cell death. Recently, members of the LRRC8 family have been identified as the main contributors of VRAC conductance. LRRC8/VRAC is permeable to chloride ions but also exhibits significant permeability to various substrates that vary strongly in charge and size. In this study, we explored the intriguing ability of LRRC8/VRAC to transport glutathione (GSH), the major cellular reactive oxygen species (ROS) scavenger, and its involvement in epithelial-to-mesenchymal transition (EMT), a cellular process in which cellular oxidative status is a crucial step. First, in HEK293-WT cells, we showed that a hypotonic condition induced LRRC8/VRAC-dependent GSH conductance (P_GSH/P_Cl of ~0.1) and a marked decrease in intracellular GSH content. GSH currents and GSH intracellular decrease were both inhibited by DCPIB, an inhibitor of LRRC8/VRAC, and were not observed in HEK293-LRRC8A KO cells. Then, we induced EMT by exposing renal proximal tubule epithelial cells to the pleiotropic growth factor TGFβ1, and we measured the contribution of LRRC8/VRAC in this process by measuring (i) EMT marker expression (assessed both at the gene and protein levels), (ii) cell morphology and (iii) the increase in migration ability. Interestingly, pharmacologic targeting of LRRC8/VRAC (DCPIB) or RNA interference-mediated inhibition (LRRC8A siRNA) attenuated the TGFβ1-induced EMT response by controlling GSH and ROS levels. Interestingly, TGFβ1 exposure triggered DCPIB-sensitive chloride conductance. These results suggest that LRRC8/VRAC, due to its native permeability to GSH and thus its ability to modulate ROS levels, plays a critical role in EMT and might contribute to other physiological and pathophysiological processes associated with oxidative stress.

PM2.5, Fine Particulate Matter: A Novel Player in the Epithelial-Mesenchymal Transition?

Epithelial-mesenchymal transition (EMT) refers to the conversion of epithelial cells to mesenchymal phenotype, which endows the epithelial cells with enhanced migration, invasion, and extracellular matrix production abilities. These characteristics link EMT with the pathogenesis of organ fibrosis and cancer progression. Recent studies have preliminarily established that fine particulate matter with an aerodynamic diameter of less than 2.5 μm (PM_2.5) is correlated with EMT initiation. In this pathological process, PM_2.5 particles, excessive reactive oxygen species (ROS) derived from PM_2.5, and certain components in PM_2.5, such as ions and polyaromatic hydrocarbons (PAHs), have been implicated as potential EMT mediators that are linked to the activation of transforming growth factor β (TGF-β)/SMADs, NF-κB, growth factor (GF)/extracellular signal-regulated protein kinase (ERK), GF/phosphatidylinositol 3-kinase (PI3K)/Akt, wingless/integrated (Wnt)/β-catenin, Notch, Hedgehog, high mobility group box B1 (HMGB1)-receptor for advanced glycation end-products (RAGE), and aryl hydrocarbon receptor (AHR) signaling cascades and to cytoskeleton rearrangement. These pathways directly and indirectly transduce pro-EMT signals that regulate EMT-related gene expression in epithelial cells, finally inducing the characteristic alterations in morphology and functions of epithelia. In addition, novel associations between autophagy, ATP citrate lyase (ACLY), and exosomes with PM_2.5-induced EMT have also been summarized. However, some debates and paradoxes remain to be consolidated. This review discusses the potential molecular mechanisms underlying PM_2.5-induced EMT, which might account for the latent role of PM_2.5 in cancer progression and fibrogenesis.

BRD4 blockage alleviates pathological cardiac hypertrophy through the suppression of fibrosis and inflammation via reducing ROS generation

Hypertension is an essential regulator of cardiac injury and remodeling. However, the pathogenesis that contributes to cardiac hypertrophy remains to be fully explored. BRD4, as a bromodomain and extra-terminal (BET) family member, plays an important role in critical biological processes. In the study, our results showed that BRD4 expression was up-regulated in human and mouse hypertrophied hearts, and importantly these effects were modulated by reactive oxygen species (ROS) generation. In angiotensin II (Ang II)-treated cardiomyocytes, BRD4 decrease markedly blunted the prohypertrophic effect, which was further promoted by the combinational treatment of ROS scavenger (N-acetyl-cysteine, NAC). In addition, NAC pre-treatment markedly elevated the anti-fibrotic role of BRD4 suppression in Ang II-incubated cardiomyocytes by repressing transforming growth factor β1 (TGF-β1)/SMADs signaling pathway. NAC combined with BRD4 reduction further alleviated inflammation and oxidative stress in Ang II-exposed cardiomyocytes, which was partly through inhibiting nuclear factor-κB (NF-κB) signaling and improving nuclear erythroid factor 2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1) pathway, respectively. Furthermore, the in vivo results confirmed the protective effects of BRD4 suppression on mice against aortic banding (AB)-induced cardiac hypertrophy, as evidenced by the reduced cross sectional area and fibrotic area using H&E and Masson trichrome staining. What's more, the degree of cardiac hypertrophy (ANP and BNP), the expression of pro-fibrotic genes (TGF-β1, Collagen I, Collagen III and CTGF), the levels of inflammation and oxidative stress were all significantly attenuated by the blockage of BRD4 in AB-operated mice. Taken together, repressing BRD4 expression was found to confer a protective effect against experimental cardiac hypertrophy in mice, demonstrating its potential as an effective therapeutic target for pathological cardiac hypertrophy.

Neutrophils from severe asthmatic patients induce epithelial to mesenchymal transition in healthy bronchial epithelial cells

BACKGROUND

Asthma is a heterogenous disease characterized by chronic inflammation and airway remodeling. An increase in the severity of airway remodeling is associated with a more severe form of asthma. There is increasing interest in the epithelial to mesenchymal transition process and mechanisms involved in the differentiation and repair of the airway epithelium, especially as they apply to severe asthma. Growing evidence suggests that Epithelial-Mesenchymal transition (EMT) could contribute to airway remodeling and fibrosis in asthma. Severe asthmatic patients with remodeled airways have a neutrophil driven inflammation. Neutrophils are an important source of TGF-β1, which plays a role in recruitment and activation of inflammatory cells, extracellular matrix (ECM) production and fibrosis development, and is a potent inducer of EMT.

OBJECTIVE

As there is little data examining the contribution of neutrophils and/or their mediators to the induction of EMT in airway epithelial cells, the objective of this study was to better understand the potential role of neutrophils in severe asthma in regards to EMT.

METHODS

We used an in vitro system to investigate the neutrophil-epithelial cell interaction. We obtained peripheral blood neutrophils from severe asthmatic patients and control subjects and examined for their ability to induce EMT in primary airway epithelial cells.

RESULTS

Our data indicate that neutrophils from severe asthmatic patients induce changes in morphology and EMT marker expression in bronchial epithelial cells consistent with the EMT process when co-cultured. TGF-β1 levels in the culture medium of severe asthmatic patients were increased compared to that from co-cultures of non-asthmatic neutrophils and epithelial cells.

CONCLUSIONS AND CLINICAL RELEVANCE

As an inducer of EMT and an important source of TGF-β1, neutrophils may play a significant role in the development of airway remodeling and fibrosis in severe asthmatic airways.

Reactive Oxygen Species-Dependent Calpain Activation Contributes to Airway and Pulmonary Vascular Remodeling in Chronic Obstructive Pulmonary Disease

Aims: Airway and pulmonary vascular remodeling is an important pathological feature in the pathogenesis of chronic obstructive pulmonary disease (COPD). Tobacco smoke (TS) induces the production of large amounts of reactive oxygen species (ROS) in COPD lungs. We investigated how ROS lead to airway and pulmonary vascular remodeling in COPD. Results: We used in vitro bronchial and pulmonary artery smooth muscle cells (BSMCs and PASMCs), in vivo TS-induced COPD rodent models, and lung tissues of COPD patients. We found that H2O2 and TS extract (TSE) induced calpain activation in BSMCs and PASMCs. Calpain activation was elevated in smooth muscle of bronchi and pulmonary arterioles in COPD patients and TS-induced COPD rodent models. Calpain inhibition attenuated H2O2- and TSE-induced collagen synthesis and proliferation of BSMCs and PASMCs. Exposure to TS causes increases in airway resistance, right ventricular systolic pressure (RVSP), and thickening of bronchi and pulmonary arteries. Calpain inhibition by smooth muscle-specific knockout of calpain and the calpain inhibitor MDL28170 attenuated increases in airway resistance, RVSP, and thickening of bronchi and pulmonary arteries. Moreover, smooth muscle-specific knockout of calpain did not reduce TS-induced emphysema in the mouse model, but MDL28170 did reduce TS-induced emphysema in the rat model. Innovation: This study provides the first evidence that ROS-induced calpain activation contributes to airway and pulmonary vascular remodeling in TS-induced COPD. Calpain might be a novel therapeutic target for the treatment of COPD. Conclusion: These results indicate that ROS-induced calpain activation contributes to airway and pulmonary vascular remodeling and pulmonary hypertension in COPD.

Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding

Recent data suggested a causative role of uric acid (UA) in the development of renal disease, in which endothelial dysfunction is regarded as the key mechanism. Endothelial-to-mesenchymal transition (EndoMT) and shedding of the glycocalyx are early changes of endothelial dysfunction. We investigated whether UA induced EndoMT in HUVECs and an animal model of hyperuricemia fed with 2% oxonic acid for 4 wk. UA induced EndoMT in HUVECs with a generation of reactive oxygen species via the activation of membranous NADPH oxidase (from 15 min) and mitochondria (from 6 h) along with glycocalyx shedding (from 6 h), which were blocked by probenecid. GM6001, an inhibitor of matrix metalloproteinase, alleviated UA-induced glycocalyx shedding and EndoMT. Antioxidants including N-acetyl cysteine, apocynin, and mitotempo ameliorated EndoMT; however, they did not change glycocalyx shedding in HUVECs. In the kidney of hyperuricemic rats, endothelial staining in peritubular capillaries (PTCs) was substantially decreased with a de novo expression of α-smooth muscle actin in PTCs. Plasma level of syndecan-1 was increased in hyperuricemic rats, which was ameliorated by allopurinol. UA caused a phenotypic transition of endothelial cells via induction of oxidative stress with glycocalyx shedding, which could be one of the mechanisms of UA-induced endothelial dysfunction and kidney disease.-Ko, J., Kang, H.-J., Kim, D.-A., Kim, M.-J., Ryu, E.-S., Lee, S., Ryu, J.-H., Roncal, C., Johnson, R. J., Kang, D.-H. Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Hydrogen Sulfide: Recent Progression and Perspectives for the Treatment of Diabetic Nephropathy

Diabetic kidney disease develops in approximately 40% of diabetic patients and is a major cause of chronic kidney diseases (CKD) and end stage kidney disease (ESKD) worldwide. Hydrogen sulfide (H₂S), the third gasotransmitter after nitric oxide (NO) and carbon monoxide (CO), is synthesized in nearly all organs, including the kidney. Though studies on H₂S regulation of renal physiology and pathophysiology are still in its infancy, emerging evidence shows that H₂S production by renal cells is reduced under disease states and H₂S donors ameliorate kidney injury. Specifically, aberrant H₂S level is implicated in various renal pathological conditions including diabetic nephropathy. This review presents the roles of H₂S in diabetic renal disease and the underlying mechanisms for the protective effects of H₂S against diabetic renal damage. H₂S may serve as fundamental strategies to treat diabetic kidney disease. These H₂S treatment modalities include precursors for H₂S synthesis, H₂S donors, and natural plant-derived compounds. Despite accumulating evidence from experimental studies suggests the potential role of the H₂S signaling pathway in the treatment of diabetic nephropathy, these results need further clinical translation. Expanding understanding of H₂S in the kidney may be vital to translate H₂S to be a novel therapy for diabetic renal disease.

Mitochondrial-Targeted Antioxidants Attenuate TGF-β2 Signaling in Human Trabecular Meshwork Cells

Purpose

POAG is a progressive optic neuropathy that is currently the leading cause of irreversible blindness worldwide. While the underlying cause of POAG remains unclear, TGF-β2-dependent remodeling of the extracellular matrix (ECM) within the trabecular meshwork (TM) microenvironment is considered an early pathologic consequence associated with impaired aqueous humor (AH) outflow and elevated IOP. Early studies have also demonstrated markedly elevated levels of oxidative stress markers in AH from POAG patients along with altered expression of antioxidant defenses. Here, using cultured primary or transformed human TM cells, we investigated the role oxidative stress plays at regulating TGF-β2-mediated remodeling of the ECM.

Methods

Primary or transformed (GTM3) human TM cells conditioned in serum-free media were incubated in the absence or presence of TGF-β2 and relative changes in intracellular reactive oxygen species (ROS) were measured using oxidation-sensitive fluorogenic dyes CellROX green or 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate (carboxy-H2DCFDA). TGF-β2-mediated changes in the content of connective tissue growth factor (CTGF) and collagen types 1α1 (COL1A1) and 4α1 (COL4A1) mRNA or collagens I and IV isoform proteins were determined in the absence or presence of mitochondrial-targeted antioxidants (XJB-5-131 or MitoQ) and quantified by quantitative PCR or by immunoblot and immunocytochemistry. Smad-dependent canonic signaling was determined by immunoblot, whereas Smad-dependent transcriptional activity was quantified using a Smad2/3-responsive SBE-luciferase reporter assay.

Results

Primary or transformed human TM cells cultured in the presence of TGF-β2 (5 ng/mL; 2 hours) exhibited marked increases in CellROX or fluorescein fluorescence. Consistent with previous reports, challenging cultured human TM cells with TGF-β2 elicited measurable increases in regulated Smad2/3 signaling as well as increases in CTGF, COL1A1, and COL4A1 mRNA and collagen protein content. Pretreating human TM cells with mitochondrial-targeted antioxidants XJB-5-131 (10 μM) or MitoQ (10 nM) attenuated TGF-β2-mediated changes in Smad-dependent transcriptional activity.

Conclusions

The multifunctional profibrotic cytokine TGF-β2 elicits a marked increase in oxidative stress in human TM cells. Mitochondrial-targeted antioxidants attenuate TGF-β2-mediated changes in Smad-dependent transcriptional activity, including marked reductions in CTGF and collagen isoform gene and protein expression. These findings suggest that mitochondrial-targeted antioxidants, when delivered directly to the TM, exhibit potential as a novel strategy by which to slow the progression of TGF-β2-mediated remodeling of the ECM within the TM.

GPCR transactivation signalling in vascular smooth muscle cells: role of NADPH oxidases and reactive oxygen species

The discovery and extension of G-protein-coupled receptor (GPCR) transactivation-dependent signalling has enormously broadened the GPCR signalling paradigm. GPCRs can transactivate protein tyrosine kinase receptors (PTKRs) and serine/threonine kinase receptors (S/TKRs), notably the epidermal growth factor receptor (EGFR) and transforming growth factor-β type 1 receptor (TGFBR1), respectively. Initial comprehensive mechanistic studies suggest that these two transactivation pathways are distinct. Currently, there is a focus on GPCR inhibitors as drug targets, and they have proven to be efficacious in vascular diseases. With the broadening of GPCR transactivation signalling, it is therefore important from a therapeutic perspective to find a common transactivation pathway of EGFR and TGFBR1 that can be targeted to inhibit complex pathologies activated by the combined action of these receptors. Reactive oxygen species (ROS) are highly reactive molecules and they act as second messengers, thus modulating cellular signal transduction pathways. ROS are involved in different mechanisms of GPCR transactivation of EGFR. However, the role of ROS in GPCR transactivation of TGFBR1 has not yet been studied. In this review, we will discuss the involvement of ROS in GPCR transactivation-dependent signalling.

Anti-EMT properties of CoQ0 attributed to PI3K/AKT/NFKB/MMP-9 signaling pathway through ROS-mediated apoptosis

Background

Breast cancer is the most prevalent cancer among women. In triple-negative breast cancer (TNBC) cells, a novel quinone derivative, coenzyme Q₀ (CoQ₀), promotes apoptosis and cell-cycle arrest. This study explored the anti-epithelial–mesenchymal transition (EMT) and antimetastatic attributes of CoQ₀ in TNBC (MDA-MB-231).

Methods

Invasion, as well as MTT assays were conducted. Lipofectamine RNAiMAX was used to transfect cells with β-catenin siRNA. Through Western blotting and RT-PCR, the major signaling pathways’ protein expressions were examined, and the biopsied tumor tissues underwent immunohistochemical and hematoxylin and eosin staining as well as Western blotting.

Results

CoQ₀ (0.5–2 μM) hindered tumor migration, invasion, and progression. Additionally, it caused MMP-2/− 9, uPA, uPAR, and VEGF downregulation. Furthermore, in highly metastatic MDA-MB-231 cells, TIMP-1/2 expression was subsequently upregulated and MMP-9 expression was downregulated. In addition, CoQ₀ inhibited metastasis and EMT in TGF-β/TNF-α-stimulated non-tumorigenic MCF-10A cells. Bioluminescence imaging of MDA-MB-231 luciferase–injected live mice demonstrated that CoQ₀ significantly inhibited metastasis of the breast cancer to the lungs and inhibited the development of tumors in MDA-MB-231 xenografted nude mice. Silencing of β-catenin with siRNA stimulated CoQ₀-inhibited EMT. Western blotting as well as histological analysis established that CoQ0 reduced xenografted tumor development because apoptosis induction, cell-cycle inhibition, E-cadherin upregulation, β-catenin downregulation, and metastasis and EMT regulatory protein modulation were observed.

Conclusions

CoQ₀ inhibited the progression of metastasis as well as EMT (in vitro and in vivo). The described approach has potential in treating human breast cancer metastasis.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1196-x) contains supplementary material, which is available to authorized users.

p53-Mediated PI3K/AKT/mTOR Pathway Played a Role in PtoxDpt-Induced EMT Inhibition in Liver Cancer Cell Lines

Epithelial-mesenchymal transition (EMT) involves metastasis and drug resistance; thus, a new EMT reversing agent is required. It has shown that wild-type p53 can reverse EMT back to epithelial characteristics, and iron chelator acting as a p53 inducer has been demonstrated. Moreover, recent study revealed that etoposide could also inhibit EMT. Therefore, combination of etoposide with iron chelator might achieve better inhibition of EMT. To this end, we prepared di-2-pyridineketone hydrazone dithiocarbamate S-propionate podophyllotoxin ester (Ptox^Dpt) that combined the podophyllotoxin (Ptox) structural unit (etoposide) with the dithiocarbamate unit (iron chelator) through the hybridization strategy. The resulting Ptox^Dpt inherited characteristics from parent structural units, acting as both the p53 inducer and topoisomerase II inhibitor. In addition, the Ptox^Dpt exhibited significant inhibition in migration and invasion, which correlated with downregulation of matrix metalloproteinase (MMP). More importantly, Ptox^Dpt could inhibit EMT in the absence or presence of TGF-β1, concomitant to the ROS production, and the additional evidence revealed that Ptox^Dpt downregulated AKT/mTOR through upregulation of p53, indicating that Ptox^Dpt induced EMT inhibition through the p53/PI3K/AKT/mTOR pathway.

Abrogation of transforming growth factor-β-induced tissue fibrosis in mice with a global genetic deletion of Nox4

Excessive connective tissue deposition in skin and various internal organs is characteristic of systemic sclerosis (SSc). The profibrotic growth factor TGF-β plays a crucial role in SSc pathogenesis. The expression of NADPH oxidase 4 (NOX4), a critical mediator of oxidative stress, is potently stimulated by TGF-β. Here, we evaluated the effect of NOX4 on the development of TGF-β-induced tissue fibrosis. C57BL6/J control mice and Nox4 knockout mice were implanted subcutaneously with osmotic pumps containing either saline or 2.5 µg TGF-β1. After 28 days, skin and lung samples were isolated for histopathologic analysis, measurement of hydroxyproline content and gene expression analysis. Histopathology of skin and lungs from normal C57BL6/J mice treated with TGF-β1 showed profound dermal fibrosis and peribronchial and diffuse interstitial lung fibrosis. In contrast, TGF-β-treated Nox4 knockout mice showed normal skin and lung histology. Hydroxyproline levels in TGF-β-treated C57BL6/J mice skin and lungs demonstrated significant increases, however, hydroxyproline content of TGF-β-treated Nox4 knockout mice tissues was not changed. Expression of various profibrotic and fibrosis-associated genes was upregulated in skin and lungs of TGF-β1-treated C57BL6/J mice but was not significantly changed in TGF-β1-treated Nox4 knockout mice. The induction of skin and lung tissue fibrosis by TGF-β1 parenteral administration in mice was abrogated by the genetic deletion of Nox4 confirming that NOX4 is an essential mediator of the profibrotic effects of TGF-β. These results suggest Nox4 inhibition as a potential therapeutic target for SSc and other fibroproliferative disorders.

Inhibition of class I HDACs attenuates renal interstitial fibrosis in a murine model

Renal interstitial fibrosis is the most common of all the forms of chronic kidney disease (CKD). Research has shown that histone deacetylases (HDACs) participate in the process leading to renal fibrosis. However, the effects of class I HDAC inhibitors on the mechanisms of onset and progression of renal interstitial fibrosis are still unclear. Here, we present the effects and mechanisms of action of FK228 (a selective inhibitor of class I HDACs) in the murine model of unilateral ureteral obstruction (UUO) and in vitro models. We investigated the antifibrotic role of FK228 in a murine model of UUO. We used two key effector cell populations, rat renal interstitial fibroblasts and renal tubular epithelial cells exposed to recombinant transforming growth factor-beta 1 (TGF-β1), to explore the mechanistic pathways among in vitro models. The results indicated that FK228 significantly suppressed the production of extracellular matrix (ECM) in both in vivo and in vitro models. FK228 inhibited renal fibroblast activation and proliferation and increased the acetylation of histone H3. We found that FK228 also inhibited the small mothers against decapentaplegic (Smad) and non-Smad signaling pathways. So FK228 could significantly suppress renal interstitial fibrosis via Smad and non-Smad pathways. FK228 may be the basis for a new and effective medicine for alleviating renal fibrosis in the future.

Fenofibrate Improved Interstitial Fibrosis of Renal Allograft through Inhibited Epithelial-Mesenchymal Transition Induced by Oxidative Stress

The best treatment for end-stage renal disease is renal transplantation. However, it is often difficult to maintain a renal allograft healthy for a long time following transplantation. Interstitial fibrosis and tubular atrophy (IF/TA) are significant histopathologic characteristics of a compromised renal allograft. There is no effective therapy to improve renal allograft function once IF/TA sets in. Although there are many underlying factors that can induce IF/TA, the pathogenesis of IF/TA has not been fully elucidated. It has been found that epithelial-mesenchymal transition (EMT) significantly contributes to the development of IF/TA. Oxidative stress is one of the main causes that induce EMT in renal allografts. In this study, we have used H₂O₂ to induce oxidative stress in renal tubular epithelial cells (NRK-52e) of rats. We also pretreated NRK-52e cells with an antioxidant (N-acetyl L-cysteine (NAC)) 1 h prior to the treatment with H₂O₂. Furthermore, we used fenofibrate (a peroxisome proliferator-activated receptor α agonist) to treat NRK-52e cells and a renal transplant rat model. Our results reveal that oxidative stress induces EMT in NRK-52e cells, and pretreatment with NAC can suppress EMT in these cells. Moreover, fenofibrate suppresses fibrosis by ameliorating oxidative stress-induced EMT in a rat model. Thus, fenofibrate may effectively prevent the development of fibrosis in renal allograft and improve the outcome.