TSG-6-Mediated Extracellular Matrix Modifications Regulate Hypoxic-Ischemic Brain Injury.

Proteoglycans containing link domains modify the extracellular matrix (ECM) to regulate cellular homeostasis and can also sensitize tissues/organs to injury and stress. Hypoxic-ischemic (H-I) injury disrupts cellular homeostasis by activating inflammation and attenuating regeneration and repair pathways. In the brain, the main component of the ECM is the glycosaminoglycan hyaluronic acid (HA), but whether HA modifications of the ECM regulate cellular homeostasis and response to H-I injury is not known. In this report, employing both male and female mice, we demonstrate that link-domain-containing proteoglycan, TNFα-stimulated gene-6 (TSG-6), is active in the brain from birth onward and differentially modifies ECM HA during discrete neurodevelopmental windows. ECM HA modification by TSG-6 enables it to serve as a developmental switch to regulate the activity of the Hippo pathway effector protein, yes-associated protein 1 (YAP1), in the maturing brain and in response to H-I injury. Mice that lack TSG-6 expression display dysregulated expression of YAP1 targets, excitatory amino acid transporter 1 (EAAT1; glutamate-aspartate transporter) and 2 (EAAT2; glutamate transporter-1). Dysregulation of YAP1 activation in TSG-6-/- mice coincides with age- and sex-dependent sensitization of the brain to H-I injury such that 1-week-old neonates display an anti-inflammatory response in contrast to an enhanced proinflammatory injury reaction in 3-month-old adult males but not females. Our findings thus support that a key regulator of age- and sex-dependent H-I injury response in the mouse brain is modulation of the Hippo-YAP1 pathway by TSG-6-dependent ECM modifications.

Liver Tumor Enhancement at Hybrid Angio-CT and Comparison With Tumor and Hepatic Parenchymal Distribution of Yttrium-90 Microspheres by Positron Emission Tomography.

This single-center retrospective study evaluated patients who underwent treatment of a primary or secondary hepatic malignancy with injection of glass or resin yttrium-90 (90Y) microspheres with a corresponding hybrid angiography-computed tomography (angio-CT) and 90Y positron emission tomography (PET). Volumetric contours were defined by three independent observers and were used to calculate relative tumoral enhancement at angio-CT. This parameter was compared with the tumor-to-normal (T/N) activity ratio predicted by technetium-99m macro-aggregated albumin (99mTc-MAA) single photon emission computed tomography (SPECT) and microsphere activity distribution by 90Y PET. A similar correlation was observed for the enhancement ratio at angio-CT with observed microsphere distribution at 90Y PET (r=0.34) to that predicted by 99mTc-MAA SPECT (r=0.32). The enhancement ratio on angio-CT performed as well as 99mTc-MAA in the prediction of 90Y PET activity distribution. The technique could not be readily applied to tumors with large areas of hypoattenuation (necrosis) on angio-CT. With refinement and further study, this technique could be used as a quantitative adjunct to standard-of-care 99mTc-MAA SPECT for dosimetry calculations and prediction of microsphere distribution to maximize tumor response and minimize hepatotoxicity.

Repeated Transarterial Radioembolization Adverse Event and Hepatotoxicity Profile in Cirrhotic Patients With Hepatocellular Carcinoma: A Single-Center Experience.

Purpose The study aimed to evaluate the adverse event (AE) and hepatotoxicity profile, including radioembolization induced liver disease (REILD), following repeat radioembolization (RE) to the same or overlapping vascular territories in patients with hepatocellular carcinoma (HCC) and limited functional hepatic reserve/cirrhosis. Methods Nine patients (seven male and two female; median age, 66 years) with cirrhosis and HCC who underwent repeat RE (cycle 1 and cycle 2) between January 2012 and August 2019 were included. Patient demographics, clinical and treatment history, and pertinent laboratory values were recorded at baseline and post-treatment time points over a period of four months. Post-RE AE/hepatotoxicity was assessed, organized by type and frequency, and graded by severity according to the National Cancer Institute common terminology criteria for adverse events, version 5.0 (CTCAE v5.0). To assess rudimentary comparisons for post-RE hepatotoxicity vs. factors of interest, Spearman's rank correlation/rho was calculated, and all relevant plots were constructed. Kaplan-Meier analysis was performed along with associated median survival time. All statistical analyses were performed with Stata v16.1. Results Following cycle 1, 22 objective AE were identified according to CTCAE v.5 (17 grade I, four grade II, and one grade III), with grade I, II, and III AE experienced by 78%, 33%, and 11% of patients, respectively. Following cycle 2, 19 objective AE were identified according to CTCAE v.5 (11 grade I, seven grade II, and one grade III), with grade I, II, and III AE experienced by 89%, 56%, and 11% of patients, respectively. A single patient developed REILD after cycle 1, which progressed to fatal REILD following cycle 2. Following cycle 2, an additional patient advanced from less severe hepatotoxicity to REILD. Following cycle 2, positive correlations between the higher model for end-stage liver disease (MELD; rho=0.70) and Child-Pugh (rho=0.74) scores and degree of post-RE hepatotoxicity/REILD appear to emerge. Post-repeat RE median overall survival was 12.5 months. Conclusion Post-RE hepatotoxicity following repeat RE to the same or overlapping vascular territories in patients with limited functional hepatic reserve/cirrhosis is a common occurrence with variable severity ranging from transient laboratory derangement to fatal REILD. Lack of a consensus REILD definition and grading scale results in non-uniform reporting of incidence as well as clinical and laboratory features of the disease process. Strides aimed at improving clinical characterization, forming a more complete diagnostic definition, and establishing a uniform grading system with respect to REILD are of particular importance and would ultimately improve repeat RE patient selection and risk management.

p66shc-mediated toxicity of high-dose alfa-tocopherol in renal proximal tubule cells

α-Tocopherol (TOC) is a widely used supplement known for its role as an antioxidant. Previously, we have shown that TOC elicits adaptive responses by upregulating the ERK/CREB/HO-1 pathway, which depends on its concentration in cultured renal proximal tubule cells (RPTCs). This suggests that high-dose TOC (hTOC) may elicit adverse effects via inflicting oxidative stress. Since the pro-oxidant p66shc is a major mediator of oxidant injury in various models of renal toxicants, we tested the hypothesis that hTOC elicits renal toxicity through activation of p66shc and consequent oxidative stress. RPTCs (NRK52E) were treated with high-dose TOC (hTOC; 400 nM) in cells where expression or mitochondrial cytochrome c-binding of p66shc was manipulated by genetic means. Intracellular production of reactive oxygen species (ROS), mitochondrial depolarization, and cell viability was also determined. Additionally, activation of the pro-survival ERK/CREB/HO-1 signaling and the p66shc promoter was determined via reporter luciferase assays. hTOC decreased cell viability via increasing ROS-dependent mitochondrial depolarization and suppressing the pro-survival ERK/CREB/HO-1 pathway via transcriptional activation of p66shc. Conversely, either knockdown of p66shc, mutation of its mitochondrial cytochrome c-binding site, or overexpression of ERK or HO-1 ameliorated adverse effects of hTOC and restored the pro-survival signaling. The pro-oxidant p66shc plays dual role in toxicity of high-dose TOC: it provokes oxidative stress and suppresses adaptive responses (AU)

No disponible

p66shc-mediated toxicity of high-dose α-tocopherol in renal proximal tubule cells.

α-Tocopherol (TOC) is a widely used supplement known for its role as an antioxidant. Previously, we have shown that TOC elicits adaptive responses by upregulating the ERK/CREB/HO-1 pathway, which depends on its concentration in cultured renal proximal tubule cells (RPTCs). This suggests that high-dose TOC (hTOC) may elicit adverse effects via inflicting oxidative stress. Since the pro-oxidant p66shc is a major mediator of oxidant injury in various models of renal toxicants, we tested the hypothesis that hTOC elicits renal toxicity through activation of p66shc and consequent oxidative stress. RPTCs (NRK52E) were treated with high-dose TOC (hTOC; 400 nM) in cells where expression or mitochondrial cytochrome c-binding of p66shc was manipulated by genetic means. Intracellular production of reactive oxygen species (ROS), mitochondrial depolarization, and cell viability was also determined. Additionally, activation of the pro-survival ERK/CREB/HO-1 signaling and the p66shc promoter was determined via reporter luciferase assays. hTOC decreased cell viability via increasing ROS-dependent mitochondrial depolarization and suppressing the pro-survival ERK/CREB/HO-1 pathway via transcriptional activation of p66shc. Conversely, either knockdown of p66shc, mutation of its mitochondrial cytochrome c-binding site, or overexpression of ERK or HO-1 ameliorated adverse effects of hTOC and restored the pro-survival signaling. The pro-oxidant p66shc plays dual role in toxicity of high-dose TOC: it provokes oxidative stress and suppresses adaptive responses.

The pro-oxidant gene p66shc increases nicotine exposure-induced lipotoxic oxidative stress in renal proximal tubule cells.

Nicotine (NIC) exposure augments free fatty acid (FFA) deposition and oxidative stress, with a concomitant increase in the expression of the pro-oxidant p66shc. In addition, a decrease in the antioxidant manganese superoxide dismutase (MnSOD) has been observed in the kidneys of mice fed a high­fat diet. The present study aimed to determine whether the pro­oxidant p66shc mediates NIC­dependent increases in renal oxidative stress by augmenting the production of reactive oxygen species (ROS) and suppressing the FFA­induced antioxidant response in cultured NRK52E renal proximal tubule cells. Briefly, NRK52E renal proximal tubule cells were treated with 200 µM NIC, 100 µM oleic acid (OA), or a combination of NIC and OA. The expression levels of p66shc and MnSOD were modulated according to genetic methods. ROS production and cell injury, in the form of lactate dehydrogenase release, were subsequently detected. Promoter activity of p66shc and MnSOD, as well as forkhead box (FOXO)­dependent transcription, was investigated using reporter luciferase assays. The results demonstrated that NIC exacerbated OA­mediated intracellular ROS production and cell injury through the transcriptional activation of p66shc. NIC also suppressed OA­mediated induction of the antioxidant MnSOD promoter activity through p66shc­dependent inactivation of FOXO activity. Overexpression of p66shc and knockdown of MnSOD had the same effect as treatment with NIC on OA­mediated lipotoxicity. These data may be used to generate a therapeutic means to ameliorate renal lipotoxicity in obese smokers.

Nicotine Enhances High-Fat Diet-Induced Oxidative Stress in the Kidney.

INTRODUCTION: Life expectancy of an obese smoker is 13 years less than a normal weight smoker, which could be linked to the increased renal risk imposed by smoking. Both smoking-through nicotine (NIC)-and obesity-by free fatty acid overload-provoke oxidative stress in the kidney, which ultimately results in development of chronic kidney injury. Their combined renal risk, however, is virtually unknown. We tested the hypothesis that chronic NIC exposure worsens renal oxidative stress in mice on high-fat diet (HFD) by altering the balance between expression of pro-oxidant and antioxidant genes. METHODS: Nine-week-old male C57Bl/6J mice consumed normal diet (ND) or HFD and received either NIC (200 µg/ml) or vehicle (2% saccharine) in their drinking water. Body weight, plasma clinical parameters, renal lipid deposition, markers of renal oxidative stress and injury, as well as renal expression of the pro-oxidant p66shc and the antioxidant MnSOD were determined after 12 weeks. RESULTS: NIC significantly augmented levels of circulating free fatty acid, as well as lipid deposition, oxidative stress and sublethal injury in the kidneys of mice on HFD. In addition, NIC exposure suppressed HFD-mediated induction of MnSOD while increased expression of p66shc in the kidney. CONCLUSIONS: Tobacco smoking or the increasingly popular E-cigarettes-via NIC exposure-could worsen obesity-associated lipotoxicity in the kidney. Hence, our findings could help to develop strategies that mitigate adverse effects of NIC on the obese kidney. IMPLICATIONS: Life expectancy of an obese smoker is 13 years less than a normal weight smoker, which could be linked to the increased renal risk imposed by smoking. NIC-the main component of tobacco smoke, E-cigarettes and replacement therapies-links smoking to renal injury via oxidative stress, which could superimpose renal oxidative stress caused by obesity. Our results substantiate this scenario using a mouse model of diet induced obesity and NIC exposure and imply the augmented long-term renal risk in obese smokers. Also, our study may help to develop strategies that mitigate adverse effects of NIC on the obese kidney.

Alpha-Tocopherol protects renal cells from nicotine- or oleic acid-provoked oxidative stress via inducing heme oxygenase-1

Smoking and obesity increases renal oxidative stress via nicotine (NIC) or free fatty acid such as oleic acid (OA) but decreases levels of the vitamin E-derivative alpha-tocopherol (TOC), which has shown to stimulate the antioxidant system such as heme oxygenase-1 (HO-1). Hence, we hypothesized that supplementation of TOC may protect renal proximal tubules from NIC- or OA-mediated oxidative stress by upregulating the HO-1 gene. NIC- or OA-dependent production of reactive oxygen species (ROS) was determined in the presence or absence of various pharmacologic or genetic inhibitors that modulate HO-1 activation and enhancer elements in the HO-1 promoter such as the antioxidant response element (ARE) and the cAMP-response element (CRE) in renal proximal tubule cells (NRK52E). Activity of the HO-1 promoter, the ARE and the CRE was determined in luciferase assays. We found that pre- or posttreatment with TOC attenuated NIC- or OA-dependent ROS production that required HO-1 activation. TOC activated the HO-1 promoter via the CRE but not the ARE enhancer through the extracellular signal-regulated kinase (ERK) and protein kinase A (PKA). Consequently, inhibitors of ERK, PKA, or CRE activation mitigated beneficial effects of TOC on NIC- or OA-mediated ROS production. Hence, vitamin E supplementation-via induction of the cytoprotective HO-1-may help to reduce renal oxidative stress imposed by smoking or obesity

α-Tocopherol protects renal cells from nicotine- or oleic acid-provoked oxidative stress via inducing heme oxygenase-1.

Smoking and obesity increases renal oxidative stress via nicotine (NIC) or free fatty acid such as oleic acid (OA) but decreases levels of the vitamin E-derivative α-tocopherol (TOC), which has shown to stimulate the antioxidant system such as heme oxygenase-1 (HO-1). Hence, we hypothesized that supplementation of TOC may protect renal proximal tubules from NIC- or OA-mediated oxidative stress by upregulating the HO-1 gene. NIC- or OA-dependent production of reactive oxygen species (ROS) was determined in the presence or absence of various pharmacologic or genetic inhibitors that modulate HO-1 activation and enhancer elements in the HO-1 promoter such as the antioxidant response element (ARE) and the cAMP-response element (CRE) in renal proximal tubule cells (NRK52E). Activity of the HO-1 promoter, the ARE and the CRE was determined in luciferase assays. We found that pre- or posttreatment with TOC attenuated NIC- or OA-dependent ROS production that required HO-1 activation. TOC activated the HO-1 promoter via the CRE but not the ARE enhancer through the extracellular signal-regulated kinase (ERK) and protein kinase A (PKA). Consequently, inhibitors of ERK, PKA, or CRE activation mitigated beneficial effects of TOC on NIC- or OA-mediated ROS production. Hence, vitamin E supplementation-via induction of the cytoprotective HO-1-may help to reduce renal oxidative stress imposed by smoking or obesity.

Sex hormones differentially modulate STAT3-dependent antioxidant responses during oxidative stress in renal proximal tubule cells.

BACKGROUND/AIM: Gender-associated dimorphism in renal oxidative stress may be related to the protective effects of estrogens or the adverse effects of testosterone. Signal transducer and activator of transcription-3 (STAT3)-dependent transcription is vital in renal antioxidant responses, which may be differentially regulated by sex hormones. MATERIALS AND METHODS: Renal proximal tubule cells were treated with 400 µM H2O2 in the presence or absence of 100 nM dihydrotestosterone (DHT), 100 nM 17ß-estradiol (E2) or dominant-negative STAT3 (dnSTAT3). Production of reactive oxygen species (ROS), phosphorylation/transcriptional activation of STAT3 and promoter activity of the STAT3-regulated antioxidant gene (MnSOD) were determined. RESULTS: After treatment with H2O2, DHT decreased tyrosine phosphorylation/transcriptional activity of STAT3 and promoter activity of MnSOD while E2 increased them. Consequently, DHT augmented while E2 attenuated ROS production. Effects of dnSTAT3 were similar to DHT. CONCLUSION: Sex hormones may influence renal oxidative stress through differential regulation of STAT3-dependent antioxidant responses.

p66shc and gender-specific dimorphism in acute renal injury.

BACKGROUND/AIM: Acute renal injury (AKI) is more prevalent in males than in females perhaps due to adverse effects of testosterone. The oxidant sensor p66shc is regulated by testosterone, hence may be responsible for the aforementioned gender disparity. MATERIALS AND METHODS: Wild-type or p66shc-knockdown renal proximal tubule cells were treated with 400 µM H2O2 in the presence or absence of 100 nM dihydrotestosterone (DHT); the production of reactive oxygen species and cell injury were determined. The impact of DHT on p66shc expression and promoter activity as well as gender-dependent expression of p66shc in the mouse kidney was also determined. RESULTS: DHT increased H2O2-dependent oxidative stress and injury via p66shc and expression of p66shc via promoter activation. Renal expression of p66shc was higher in male compared to female kidneys. CONCLUSION: Higher sensitivity of the male kidney to AKI may be due to the testosterone-dependent increase in p66shc expression.

Role of p66shc in renal toxicity of oleic acid.

BACKGROUND/AIMS: Adult and childhood obesity is an independent risk factor in development of chronic kidney disease (CKD) and its progression to end-stage kidney disease. Pathologic consequences of obesity include non-esterified fatty acid-induced oxidative stress and consequent injury. Since the serine36-phosphorylated p66shc is a newly recognized mediator of oxidative stress and kidney injury, we studied its role in oleic acid (OA)-induced production of reactive oxygen species (ROS), mitochondrial depolarization and injury in cultured renal proximal tubule cells. METHODS: Renal proximal tubule cells were used and treated with OA: ROS production, mitochondrial depolarization as well as injury were determined. Transcriptional effects of OA on the p66shc gene were determined in a reporter luciferase assay. The role of p66shc in adverse effects of OA was determined using knockdown, p66shc serine36 phosphorylation and cytochrome c binding-deficient cells. RESULTS: We found that OA increased ROS production via the mitochondria - and to a less extent via the NADPH oxidase - resulting in ROS-dependent mitochondrial depolarization and consequent injury. Interestingly, OA also stimulated the promoter of p66shc. Hence, knockdown of p66shc, impairment its Ser36 phosphorylation (mutation of Ser36 residue to alanine) or cytochrome c binding (W134F mutation) significantly attenuated OA-dependent lipotoxicity. CONCLUSION: These results offer a novel mechanism by which obesity may lead to renal tubular injury and consequently development of CKD. Manipulation of this pathway may offer therapeutic means to ameliorate obesity-dependent renal lipotoxicity.

The role of p66shc in taxol- and dichloroacetic acid-dependent renal toxicity.

BACKGROUND/AIM: Taxol and dichloroacetic acid (DCA) are anticancer agents with potential renal toxicity. Previously, we have shown that the Ser36-phosphorylated p66shc adaptor protein mediates renal toxicity of selected anticancer modalities through increasing production of intracellular reactive oxygen species and consequent mitochondrial depolarization. Here, we analyzed whether p66shc plays a role in potential renal toxicity of Taxol and DCA. MATERIALS AND METHODS: Cultured renal proximal tubule cells (TKPTS) were used. ROS production, mitochondrial depolarization (JC-1), cell injury [lactate dehydrogenase (LDH) release] and Ser36 phosphorylation of p66shc were determined after treatment with Taxol and DCA. Involvement of p66shc in adverse effects of these drugs was determined in p66shc knockdown, Ser36 phosphorylation (S36A) and cytochrome c-binding (W134F)- deficient cells. RESULTS: Both Taxol and DCA increased ROS production, mitochondrial depolarization, injury and Ser36 phosphorylation of p66shc in TKPTS cells. We showed that ROS production is responsible for mitochondrial depolarization and consequent injury. Knockdown of p66shc, mutation of its Ser36 (S36A) or cytochrome c binding site (W134F) attenuated adverse effects of the two drugs. CONCLUSION: Taxol and DCA are potentially nephrotoxic owing their adverse effects on activation of p66shc. Manipulation of expression or activity of p66shc may provide a means of ameliorating nephrotoxicity of these agents.

Chronic nicotine exposure augments renal oxidative stress and injury through transcriptional activation of p66shc.

BACKGROUND: Chronic nicotine (Ch-NIC) exposure exacerbates ischemia/reperfusion (I/R)-induced oxidative stress and acute kidney injury (AKI), and mitochondrial production of reactive oxygen species (ROS) in cultured renal proximal tubule cells (RPTCs). Because Ser36-phosphorylated p66shc modulates mitochondrial ROS production and injury of RPTCs, we hypothesized that Ch-NIC exacerbates AKI by increasing stress-induced phosphorylation of p66shc. METHODS: We first tested whether Ch-NIC augments I/R-AKI-induced expression and phosphorylation of p66shc in vivo. We then examined whether knocking down p66shc, or impairing its Ser36 phosphorylation or binding to cytochrome c, alters the effects of Ch-NIC on oxidative stress (H2O2)-induced production of ROS, mitochondrial depolarization and injury in RPTCs in vitro. RESULTS: We found that Ch-NIC increased the expression of p66shc in the control and ischemic kidneys, but only increased its Ser36 phosphorylation after renal I/R. Knocking down p66shc or impairing phosphorylation of its Ser36 residue, via the S36A mutation (but not the phosphomimetic S36D mutation), blunted Ch-NIC + H2O2-dependent ROS production, mitochondrial depolarization and injury in RPTCs. Additionally, Ch-NIC + H2O2-dependent binding of p66shc to mitochondrial cytochrome c was attenuated by S36A mutation of p66shc, and impairing cytochrome c binding (via W134F mutation) abolished ROS production, mitochondrial depolarization and injury, while ectopic overexpression of p66shc (which mimics Ch-NIC treatment) augmented oxidant injury. We determined that Ch-NIC stimulates the p66shc promoter through p53- and epigenetic modification (promoter hypomethylation). CONCLUSIONS: Ch-NIC worsens oxidative stress-dependent acute renal injury by increasing expression and consequent oxidative stress-dependent Ser36 phosphorylation of p66shc. Thus, targeting this pathway may have therapeutic relevance in preventing/ameliorating tobacco-related kidney injury.

Cisplatin enhances interaction between p66Shc and HSP27: its role in reorganization of the actin cytoskeleton in renal proximal tubule cells.

BACKGROUND/AIM: Cisplatin nephrotoxicity includes early activation of the pro-apoptotic p66Shc and disorganization of the actin cytoskeleton, integrity which is regulated by heat-shock protein-27 (Hsp27). Here we determined the potential role of p66Shc in abrogating the Hsp27 function. MATERIALS AND METHODS: Effects of p66Shc knockdown and Hsp27 overexpression on F-actin stress fibers after cisplatin treatment were visualized by phalloidin staining. Binding of p66Shc to Hsp27 after cisplatin treatment was determined by immunoprecipitation in cell and tissue lysates. The role of p66Shc and its Ser36 phosphorylation in Hsp27 binding was assessed by overexpressing it or mutating its Ser36 residue. RESULTS: Knockdown of p66Shc and overexpression of Hsp27 ameliorated cisplatin-mediated collapse of the actin cytoskeleton. Further studies revealed that p66Shc binds Hsp27 after treatment with cisplatin that requires Ser36 phosphorylation of p66Shc. CONCLUSION: We propose a novel function of p66Shc that, through interacting with Hsp27, accelerates cisplatin-dependent disruption of the actin cytoskeleton.

A novel U-STAT3-dependent mechanism mediates the deleterious effects of chronic nicotine exposure on renal injury.

Previous data from our group have demonstrated (Arany I, Grifoni S, Clark JS, Csongradi, Maric C, Juncos LA. Am J Physiol Renal Physiol 301: F125-F133, 2011) that chronic nicotine (NIC) exposure exacerbates acute renal ischemic injury (AKI) in mice that could increase the risk for development and progression of chronic kidney disease (CKD). It has been shown that proximal tubules of the kidney can acquire characteristics that may compromise structural recovery and favor development of inflammation and fibrosis following injury. Chronic NIC exposure can amplify this epithelial process although the mechanism is not identified. Recently, the unphosphorylated form of signal transducer and activator of transcription-3 (U-STAT3) has emerged as a noncanonical mediator of inflammation and fibrosis that may be responsible for the effects of chronic NIC. We found that levels of transforming growth factor ß-1 (TGF-ß1), α-smooth muscle actin (α-SMA), fibronectin, monocyte chemotactic protein-1 (MCP-1), and expression of U-STAT3 were increased in the ischemic kidneys of NIC-exposed mice. Chronic NIC exposure also increased TGF-ß1-dependent F-actin reorganization, vimentin, fibronectin, and α-SMA expression as well as promoter activity of α-SMA and MCP-1 without significant loss of epithelial characteristics (E-cadherin) in cultured renal proximal tubule cells. Importantly, transduction of cells with a U-STAT3 mimetic (Y705F-STAT3) augmented stress fiber formation and also amplified NIC+TGF-ß1-induced expression of α-SMA, vimentin, fibronectin, as well as promoter activity of α-SMA and MCP-1. Our results reveal a novel, chronic NIC-exposure-related and U-STAT3-dependent mechanism as mediator of a sustained transcription of genes that are linked to remodeling and inflammation in the kidney during injury. This process may facilitate progression of AKI to CKD. The obtained data may lead to devising therapeutic methods to specifically enhance the protective and/or inhibit adverse effects of STAT3 in the kidney.