Tanshinone IIA ameliorates cisplatin-induced toxicology and cisplatin resistance via regulating SLC7A11 expression

Cisplatin, a potent chemotherapy agent, is highly effective against various cancers but is hindered by resistance and toxicities. This study aims to investigate the roles of SLC7A11, a cystine/glutamate transporter, in cisplatin resistance, and explored Tanshinone IIA as a therapeutic option. Cisplatin reduced SLC7A11 in renal cells, worsening toxicity. Cisplatin-resistant gastric cancer cells show increased SLC7A11, driving resistance, while SLC7A11 knockdown curbed resistance. Tanshinone IIA showed promise in alleviating cisplatin toxicity by enhancing SLC7A11 expression and reducing associated adverse effects, while it effectively reversed cisplatin resistance in gastric cancer cells by suppressing SLC7A11. Additionally, Tanshinone IIA counteracted cisplatin resistance by inhibiting PIAS4-mediated SUMOylation of SLC7A11. Simultaneously, overexpressing miR-375, which has been shown to target SLC7A11, exacerbated cisplatin toxicity via SLC7A11 downregulation, which Tanshinone IIA attenuates. In summary, our study unveils complex SLC7A11 regulation in cisplatin resistance and toxicity. Tanshinone IIA emerges as a promising modulator of SLC7A11 through individual pathways, offering novel insights into overcoming cisplatin resistance and reducing toxicities in cancer therapy.

Exploring the role of urinary extracellular vesicles in kidney physiology, aging, and disease progression

Extracellular vesicles (EVs), membranous vesicles present in all body fluids, are considered important messengers, carrying their information over long distance and modulating the gene expression profile of recipient cells. EVs collected in urine (uEVs) are mainly originated from the apical part of urogenital tract, following the urine flow. Moreover, bacterial-derived EVs are present within urine and may reflect the composition of microbiota. Consolidated evidence has established the involvement of uEVs in renal physiology, being responsible for glomerular and tubular cross talk and among different tubular segments. uEVs may also be involved in other physiological functions such as modulation of innate immunity, coagulation, or metabolic activities. Furthermore, it has been recently remonstrated that age, sex, endurance excise, and lifestyle may influence uEV composition and release, modifying their cargo. On the other hand, uEVs appear modulators of different urogenital pathological conditions, triggering disease progression. uEVs sustain fibrosis and inflammation processes, both involved in acute and chronic kidney diseases, aging, and stone formation. The molecular signature of uEVs collected from diseased patients can be of interest for understanding kidney physiopathology and for identifying diagnostic and prognostic biomarkers.

STING1 deficiency ameliorates immune-mediated crescentic glomerulonephritis in mice

Rapidly progressive/crescentic glomerulonephritis (RPGN/CGN) involves the formation of glomerular crescents by maladaptive differentiation of parietal epithelial cells that leads to rapid loss of renal function. The molecular mechanisms of crescent formation are poorly understood. Therefore, new insights into molecular mechanisms could identify alternative therapeutic targets for RPGN/CGN. Analysis of kidney biopsies from patients with RPGN revealed increased interstitial, glomerular, and tubular expression of STING1, an accessory protein of the c-GAS-dependent DNA-sensing pathway, which was also observed in murine nephrotoxic nephritis induced by an anti-GBM antibody. STING1 was expressed by key cell types involved in RPGN and crescent formation such as glomerular parietal epithelial cells, and tubular cells as well as by inflammation accessory cells. In functional in vivo studies, Sting1-/- mice with nephrotoxic nephritis had lower kidney cytokine expression, milder kidney infiltration by innate and adaptive immune cells, and decreased disease severity. Pharmacological STING1 inhibition mirrored these findings. Direct STING1 agonism in parietal and tubular cells activated the NF-κB-dependent cytokine response and the interferon-induced genes (ISGs) program. These responses were also triggered in a STING1-dependent manner by the pro-inflammatory cytokine TWEAK. These results identify STING1 activation as a pathological mechanism in RPGN/CGN and TWEAK as an activator of STING1. Pharmacological strategies targeting STING1, or upstream regulators may therefore be potential alternatives to treat RPGN. © 2023 The Pathological Society of Great Britain and Ireland.

Pharmacological inhibition of the mixed lineage leukemia 1-menin interaction aggravates acute kidney injury induced by folic acid and ischemia-reperfusion in mice

Mixed lineage leukemia 1 (MLL1) is a methyltransferase that induces histone H3 lysine 4 trimethylation (H3K4me3) and partially exerts its untoward functional effects by interacting with multiple subunits including menin and WD repeat-containing protein 5 (WDR5). In this study, we investigated the role and mechanisms of MLL1 in murine models of acute kidney injury induced by folic acid (FA) and ischemia-reperfusion. Injury to the kidney elevated the expression of MLL1, menin, WDR5, and H3K4Me3, which was accompanied by increased serum creatinine and blood urea nitrogen, renal tubular injury, and apoptosis. Pharmacological inhibition of MLL1 activity with MI503 to disrupt the interaction between MLL1 with menin further increased serum creatinine and blood urea nitrogen levels, enhanced expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1, and induced more apoptosis in the kidney following FA and ischemia-reperfusion injury. In contrast, MI503 treatment decreased the expression of vimentin and proliferating cell nuclear antigens. Similarly, treatment with MM102 to disrupt the interaction between MLL1 and WDR5 also worsened renal dysfunction, aggravated tubular cell injury, increased apoptosis, and inhibited cellular dedifferentiation and proliferation in mice following FA injection. Moreover, MI503 inhibited FA-induced phosphorylation of epidermal growth factor receptor, signal transducer and activator of transcription 3, and extracellular signal-regulated kinase-1/2 in injured kidneys. Collectively, these data suggest that MLL1 contributes to renal protection and functional recovery and promotes renal regeneration through a mechanism associated with activation of the epidermal growth factor receptor signaling pathway.NEW & NOTEWORTHY Mixed lineage leukemia 1 (MLL1) is a methyltransferase that induces histone H3 lysine 4 trimethylation and exerts its functional roles by interacting with multiple subunits. In this study, we demonstrated that inhibition of MLL1 activity by MI503 or MM102 aggravated renal injury and apoptosis and suppressed renal tubular cell dedifferentiation and proliferation, suggesting that MLL1 activation during acute kidney injury acts as an intrinsic protective mechanism to mediate renal tubular cell survival and regeneration.

TP53RK Drives the Progression of Chronic Kidney Disease by Phosphorylating Birc5

Renal fibrosis is a common characteristic of various chronic kidney diseases (CKDs) driving the loss of renal function. During this pathological process, persistent injury to renal tubular epithelial cells and activation of fibroblasts chiefly determine the extent of renal fibrosis. In this study, the role of tumor protein 53 regulating kinase (TP53RK) in the pathogenesis of renal fibrosis and its underlying mechanisms is investigated. TP53RK is upregulated in fibrotic human and animal kidneys with a positive correlation to kidney dysfunction and fibrotic markers. Interestingly, specific deletion of TP53RK either in renal tubule or in fibroblasts in mice can mitigate renal fibrosis in CKD models. Mechanistic investigations reveal that TP53RK phosphorylates baculoviral IAP repeat containing 5 (Birc5) and facilitates its nuclear translocation; enhanced Birc5 displays a profibrotic effect possibly via activating PI3K/Akt and MAPK pathways. Moreover, pharmacologically inhibiting TP53RK and Birc5 using fusidic acid (an FDA-approved antibiotic) and YM-155(currently in clinical phase 2 trials) respectively both ameliorate kidney fibrosis. These findings demonstrate that activated TP53RK/Birc5 signaling in renal tubular cells and fibroblasts alters cellular phenotypes and drives CKD progression. A genetic or pharmacological blockade of this axis serves as a potential strategy for treating CKDs.

microRNA Expression of Renal Proximal Tubular Epithelial Cells and Their Extracellular Vesicles in an Inflammatory Microenvironment In Vitro

Renal proximal tubular epithelial cells (PTCs) are central players during renal inflammation. In response to inflammatory signals, PTCs not only self-express altered mRNAs, microRNAs (miRNAs), proteins, and lipids, but also release altered extracellular vesicles (EVs). These EVs also carry inflammation-specific cargo molecules and are key players in cell-cell-communication. Understanding the precise molecular and cellular mechanisms that lead to inflammation in the kidney is the most important way to identify early targets for the prevention or treatment of acute kidney injury. Therefore, highly purified human PTCs were used as an in vitro model to study the cellular response to an inflammatory microenvironment. A cytokine-induced inflammatory system was established to analyze different miRNA expression in cells and their EVs. In detail, we characterized the altered miR expression of PTCs and their released EVs during induced inflammation and showed that 12 miRNAs were significantly regulated in PTCs (6 upregulated and 6 downregulated) and 9 miRNAs in EVs (8 upregulated and 1 downregulated). We also showed that only three of the miRNAs were found to overlap between cells and EVs. As shown by the KEGG pathway analysis, these three miRNAs (miR-146a-5p, miR-147b, and miR-155-5p) are functionally involved in the regulation of the Toll-like receptor signaling pathway and significantly correlated with the inflammatory mediators IL6 and ICAM1 released by stimulated PTCs. Especially with regard to a possible clinical use of miRs as new biomarkers, an accurate characterization of the miR expression altered during inflammatory processes is of enormous importance.

Lemon-Derived Extracellular Vesicle-like Nanoparticles Block the Progression of Kidney Stones by Antagonizing Endoplasmic Reticulum Stress in Renal Tubular Cells

Kidney stones, represented by the calcium oxalate (CaOx) type, are highly prevalent and recrudescent. Cumulative evidence shows regular consumption of lemonade intervenes with stone development. However, the detailed mechanism remains obscure. Here, extracellular vesicle-like nanoparticles (LEVNs) isolated from lemonade are demonstrated to traffick from the gut to the kidney, primarily enriched in tubule cells. Oral administration of LEVNs significantly alleviates the progression of kidney stones in rats. Mechanistically, in addition to altering the crystallization of CaOx toward a less stable subtype, LEVNs suppress the CaOx-induced endoplasmic reticulum stress response of tubule cells, as indicated by homeostasis of specific signaling molecules and restoration of subcellular function, thus indirectly inhibiting stone formation. To exercise this regulation, endocytosed LEVNs traffick along the microtubules throughout the cytoplasm and are eventually recruited into lysosomes. In conclusion, this study reveals a LEVNs-mediated mechanism against renal calculi and provides positive evidence for consumption of lemonade preventing stone formation.

Gliflozins Have an Anti-Inflammatory Effect on Renal Proximal Tubular Epithelial Cells in a Diabetic and Inflammatory Microenvironment In Vitro

Inflammation is intimately involved in the pathogenesis of diabetic kidney disease. Inhibition of SGLT-2 by a specific class of drugs, gliflozins, has been shown to reduce inflammation and attenuate the progression of diabetic nephropathy, in addition to its main effect of inhibiting renal glucose reabsorption. We used highly purified human renal proximal tubular epithelial cells (PTCs) as an in vitro model to study the cellular response to a diabetic (high glucose) and inflammatory (cytokines) microenvironment and the effect of gliflozins. In this context, we investigated the influence of SGLT-2 inhibition by empa- and dapagliflozin (500 nM) on the expression of pro-inflammatory factors (IL-1β, IL-6, TNF-α, MCP-1, and ICAM-1). The results clearly indicate an anti-inflammatory effect of both gliflozins. Although induced expression of the four cytokines was only slightly attenuated, there was a clear effect on the expression of the adhesion molecule ICAM-1, a master regulator of cellular responses in inflammation and injury resolution. The induced expression of ICAM-1 mRNA was significantly reduced by approximately 13.5% by empagliflozin and also showed an inhibitory trend with dapagliflozin. However, induced ICAM-1 protein expression was significantly inhibited from 24.71 ± 1.0 ng/mL to 18.81 ± 3.9 (empagliflozin) and 19.62 ± 2.1 ng/mL (dapagliflozin). In conclusion, an additional anti-inflammatory effect of empa- and dapagliflozin in therapeutically observed concentrations was demonstrated in primary human PTCs in vitro.

1,3-Dichloro-2-propanol-Induced Renal Tubular Cell Necroptosis through the ROS/RIPK3/MLKL Pathway

1,3-Dichloro-2-propanol (1,3-DCP), as a food pollutant, exists in a variety of foods. Studies have shown that it has nephrotoxicity. In the study, we found that 1,3-DCP caused renal injury with necroptosis in C57BL/6J mice. The mechanism of 1,3-DCP-caused nephrotoxicity was further explored in NRK-52E cells in vitro. We found that 1,3-DCP caused cell necroptosis with the increase in lactate dehydrogenase (LDH) levels and the expressions of RIPK3 and MLKL. But pretreatment with a ROS inhibitor N-acetyl-l-cysteine (NAC), a RIPK3 inhibitor GSK'872, or RIPK3 gene silencing alleviated 1,3-DCP-induced cell necroptosis. The data indicated that 1,3-DCP induced necroptosis through the ROS/RIPK3/MLKL pathway in NRK-52E cells. In further mechanistic studies, we explored how 1,3-DCP induced ROS production. We found that 1,3-DCP inhibited the expressions of nuclear and cytoplasmic Nrf2. But pretreatment with an Nrf2 activator dimethyl fumarate (DMF) up-regulated the expressions of nuclear and cytoplasmic Nrf2 and down-regulated ROS levels and RIPK3 and MLKL expressions. We also examined the effects of mitophagy on 1,3-DCP-induced ROS. The data manifested that 1,3-DCP suppressed mitophagy in NRK-52E cells by decreasing LC3-II, Pink1, and Parkin levels, increasing p62 levels, and decreasing colocalization of LC3 and Mito-Tracker Red. Pretreatment with an autophagy activator rapamycin (Rapa) decreased 1,3-DCP-induced ROS. Taken together, our data identified that 1,3-DCP caused renal necroptosis through the ROS/RIPK3/MLKL pathway.

VNN1 contributes to the acute kidney injury-chronic kidney disease transition by promoting cellular senescence via affecting RB1 expression

The mechanisms underlying acute kidney injury (AKI) and chronic kidney disease (CKD) progression include interstitial inflammation, cellular senescence, and oxidative stress (OS). Although vanin-1 (VNN1) plays an important role in OS, its contribution to the AKI-CKD transition remains unknown. Here, we explored the roles and mechanisms of VNN1 in the progression of the AKI-CKD transition. We observed that VNN1 expression was upregulated after ischemia/reperfusion (I/R) injury and high VNN1 expression levels were associated with poor renal repair after I/R injury. In VNN1 knockout (KO) mice, recovery of serum creatinine and blood urea nitrogen levels after I/R injury was accelerated and renal fibrosis was inhibited after severe I/R injury. Furthermore, in VNN1 KO mice, senescence of renal tubular cells was inhibited after severe I/R injury, as assessed by P16 expression and SA-β-Gal assays. However, our results also revealed that VNN1 KO renal tubular cells did not resist senescence when OS was blocked. To elucidate the mechanism underlying VNN1-mediated regulation of senescence during the AKI-CKD transition, retinoblastoma 1 (RB1) was identified as a potential target. Our results suggest that the reduced senescence in VNN1 KO renal tubular cells was caused by suppressed RB1 expression and phosphorylation. Collectively, our results unveil a novel molecular mechanism by which VNN1 promotes AKI-CKD transition via inducing senescence of renal tubular cells by activating RB1 expression and phosphorylation after severe renal injury. The present study proposes a new strategy for designing therapies wherein VNN1 can be targeted to obstruct the AKI-CKD transition.

Class IIa histone deacetylase inhibition ameliorates acute kidney injury by suppressing renal tubular cell apoptosis and enhancing autophagy and proliferation

Expression and function of histone deacetylases (HDACs) vary with cell types and pathological conditions. Our recent studies showed that pharmacological targeting class IIa HDACs attenuated renal fibrosis, but the effect of class IIa HDAC inhibition on acute kidney injury (AKI) remains unknown. In this study, we found that four class IIa HDACs (4, 5, 7, 9) were highly expressed in the kidney of folic acid (FA) and ischemia/reperfusion (I/R)-induced AKI in mice. Administration of TMP269, a potent and selective class IIa HDAC inhibitor, improved renal function and reduced tubular cell injury and apoptosis, with concomitant suppression of HDAC4 and elevation of acetyl-histone H3. Mechanistical studies showed that TMP269 treatment inhibited FA and I/R-induced caspase-3 cleavage, Bax expression and p53 phosphorylation. Conversely, TMP269 administration preserved expression of E-cadherin, BMP7, Klotho and Bcl-2 in injured kidneys. Moreover, TMP269 was effective in promoting cellular autophagy as indicated by increased expression of Atg7, beclin-1, and LC3II, and promoted renal tubular cell proliferation as shown by increased number of proliferating cell nuclear antigen-positive cells and expression of cyclin E. Finally, blocking class IIa HDACs inhibited FA-and I/R-induced phosphorylation of extracellular signal-regulated kinases 1 and 2, and p38, two signaling pathways associated with the pathogenesis of AKI. Collectively, these results suggest that pharmacological inhibition of class IIa HDACs protects against AKI through ameliorating apoptosis, enhancing autophagy and promoting proliferation of renal tubular cells by targeting multiple signaling pathways.

Defective lysosomal storage in Fabry disease modifies mitochondrial structure, metabolism and turnover in renal epithelial cells

Fabry disease (FD) is an X-linked lysosomal storage disorder. Deficiency of the lysosomal enzyme alpha-galactosidase (GLA) leads to accumulation of potentially toxic globotriaosylceramide (Gb3) on a multisystem level. Cardiac and cerebrovascular abnormalities as well as progressive renal failure are severe, life-threatening long-term complications. The complete pathophysiology of chronic kidney disease (CKD) in FD and the role of tubular involvement for its progression are unclear. We established human renal tubular epithelial cell lines from the urine of male FD patients and male controls. The renal tubular system is rich in mitochondria and involved in transport processes at high-energy costs. Our studies revealed fragmented mitochondria with disrupted cristae structure in FD patient cells. Oxidative stress levels were elevated and oxidative phosphorylation was upregulated in FD pointing at enhanced energetic needs. Mitochondrial homeostasis and energy metabolism revealed major changes as evidenced by differences in mitochondrial number, energy production and fuel consumption. The changes were accompanied by activation of the autophagy machinery in FD. Sirtuin1, an important sensor of (renal) metabolic stress and modifier of different defense pathways, was highly expressed in FD. Our data show that lysosomal FD impairs mitochondrial function and results in severe disturbance of mitochondrial energy metabolism in renal cells. This insight on a tissue-specific level points to new therapeutic targets which might enhance treatment efficacy.

Effect of amphotericin B-deoxycholate (Fungizone) on the mitochondria of Wistar rats' renal proximal tubules cells

Amphotericin B-deoxycholate (Fungizone [FZ]) is a widely used potent antimycotic drug in spite of its nephrotoxic effect via different mechanisms. The effect of FZ on renal cell bioenergetics is not clear. The current study evaluated the effect of FZ on the bioenergetics of albino rats' isolated renal proximal tubule cells (PTCs). The cytotoxic effect of FZ on the isolated renal cells was assessed by MTT and lactate dehydrogenase (LDH) assays. The effect of FZ on the PTCs uptake (OAT1 and OCT2) and efflux (P-gp and MRP2) transporters was evaluated. Then, the effect of FZ on mitochondria was assessed by studying complexes I-IV activities, lactate assay, oxygen consumption rates (OCR), and western blotting for all mitochondrial complexes. Moreover, the effect of FZ on mitochondrial membrane fluidity (MMF) and fatty acids composition was evaluated. Additionally, the protective effect of coenzyme q10 was studied. Outcomes showed that FZ was cytotoxic to the PTCs in a concentration and time-dependent patterns. FZ significantly inhibited the studied uptake and efflux tubular transporters with inhibition of the mitochondrial complexes activities and parallel increase in lactate production and decrease in OCRs. Finally, FZ significantly reduced the expression of all mitochondrial complexes in addition to significant increase in MMF and MMFA concentration. Coenzyme Q10 was found to significantly decrease FZ-induced cytotoxicity and transporters impairment in the PTC. FZ significantly inhibits bioenergetics of PTC, which may stimulate the cascade of cell death and clinical nephrotoxicity.

Delayed blockage of prostaglandin EP4 receptors can reduce dedifferentiation, epithelial-to-mesenchymal transition and fibrosis following acute kidney injury

Dedifferentiation of tubular epithelial cells is involved in both regeneration and fibrosis following acute kidney injury (AKI). Prostaglandin E₂ receptor 4 (EP₄ ) antagonist can inhibit the dedifferentiation of renal tubular cells. The present study investigated whether the time of blockage of EP₄ receptors, using grapiprant, could affect the tubular regeneration or interstitial fibrosis in AKI. Cisplatin was used to induce AKI in 72 C57BL/6 adult female mice. Animals were assigned to four groups; control, cisplatin-treated, cisplatin-treated with early grapiprant intervention and cisplatin-treated with late grapiprant intervention. AKI was assessed by kidney function tests and histopathology. Fibrosis was evaluated by Masson's trichrome and alpha smooth muscle actin (α-SMA) expression. Markers of dedifferentiation, CD133, and epithelial to mesenchymal transition (EMT), vimentin were assessed. Early intervention with grapiprant significantly ameliorated AKI more efficiently than late intervention. However, even late intervention was useful in reducing the overall fibrosis as demonstrated by Masson's trichrome and α-SMA expression. In both grapiprant-treated groups, a parallel reduction of dedifferentiation (CD133) and EMT (vimentin) was evident. It seems that the progressive fibrotic changes that follow AKI could still be reduced possibly by targeting dedifferentiation and/or EMT.

FBXW7 mediates high glucose‑induced SREBP‑1 expression in renal tubular cells of diabetic nephropathy under PI3K/Akt pathway regulation

Diabetic nephropathy (DN) is a severe complication of diabetes mellitus and lipid metabolism abnormality serves a key role in the pathogenesis of DN. Sterol regulatory element-binding protein 1 (SREBP-1) overexpression mediates aberrant lipid accumulation in renal tubular cells of DN. However, the exact mechanism involved in increased SREBP-1 has not been fully elucidated. The aim of the present study was to explore the mechanism involved in SREBP-1 upregulation. Diabetic mice and high glucose-cultured HKC cells were chosen to detect the expression of FBXW7 and SREBP-1 using immunohistochemistry, western blotting and PCR. The present study demonstrated that F-box and WD repeat domain containing 7 (FBXW7) expression was decreased in renal tubular cells of diabetic mice. Moreover, the co-expression of FBXW7 and SREBP-1 was observed in renal tubular cells, but not in the glomeruli. High glucose-induced the downregulation of FBXW7 expression in in vitro cultured HKC cells, which was accompanied by SREBP-1 upregulation. In addition, overexpression of FBXW7 in HKC cells led to SREBP-1 downregulation. By contrast, knockdown of FBXW7 caused SREBP-1 upregulation in HKC cells. It was found that the PI3K/Akt signaling pathway was activated in high glucose-stimulated HKC cells, and inhibition of PI3K/Akt pathway using LY294002 increased FBXW7 expression and decreased SREBP-1 expression. Taken together, the present results suggested that FBXW7 mediated high glucose-induced SREBP-1 expression in renal tubular cells of DN, under the regulation of the PI3K/Akt signaling pathway.

Exenatide Attenuates Obesity-Induced Mitochondrial Dysfunction by Activating SIRT1 in Renal Tubular Cells

Saturated free fatty acid (FFA)-induced lipotoxicity plays an important role in obesity-induced kidney injury. Exenatide, a Glucagon-like peptide-1 receptor agonist(GLP-1RA), protects against high-fat diet (HFD)-induced kidney injury. The precise mechanism needs to be further explored. This study investigated whether exenatide protects against FFA-induced tubular epithelial cells (TECs) lipotoxicity and elucidated its underlying mechanisms. Here, we show that exenatide treatment reversed HFD induced TECs injuries, including TECs apoptosis and SIRT1 downregulation. The efficacy of exenatide was better than simvastatin. In palmitate (PA)-stimulated HK2 cells, exenatide treatment reversed the downregulation of SIRT1 and prevented an increase in reactive oxygen species (ROS) production, a decrease in mitochondrial membrane potential, and mitochondrial apoptosis. The renal-protective effects of exenatide on the generation of mitochondrial ROS and mitochondrial apoptosis were blocked by inhibiting SIRT1 activation. Collectively, these findings show that exenatide was superior to simvastatin in the treatment of obesity-TECs injuries, the mechanism is partially through SIRT1 restoration, which directly reverses mitochondrial dysfunction and apoptosis.

No Cytotoxic and Inflammatory Effects of Empagliflozin and Dapagliflozin on Primary Renal Proximal Tubular Epithelial Cells under Diabetic Conditions In Vitro

Gliflozins are inhibitors of the renal proximal tubular sodium-glucose co-transporter-2 (SGLT-2), that inhibit reabsorption of urinary glucose and they are able to reduce hyperglycemia in patients with type 2 diabetes. A renoprotective function of gliflozins has been proven in diabetic nephropathy, but harmful side effects on the kidney have also been described. In the current project, primary highly purified human renal proximal tubular epithelial cells (PTCs) have been shown to express functional SGLT-2, and were used as an in vitro model to study possible cellular damage induced by two therapeutically used gliflozins: empagliflozin and dapagliflozin. Cell viability, proliferation, and cytotoxicity assays revealed that neither empagliflozin nor dapagliflozin induce effects in PTCs cultured in a hyperglycemic environment, or in co-medication with ramipril or hydro-chloro-thiazide. Oxidative stress was significantly lowered by dapagliflozin but not by empagliflozin. No effect of either inhibitor could be detected on mRNA and protein expression of the pro-inflammatory cytokine interleukin-6 and the renal injury markers KIM-1 and NGAL. In conclusion, empa- and dapagliflozin in therapeutic concentrations were shown to induce no direct cell injury in cultured primary renal PTCs in hyperglycemic conditions.

lncRNA GAS5/miR-452-5p Reduces Oxidative Stress and Pyroptosis of High-Glucose-Stimulated Renal Tubular Cells

BACKGROUND

Diabetic nephropathy (DN) is the leading cause of end-stage renal failure worldwide. lncRNAs are demonstrated to improve the DN by changing the expression of miRNAs. This study was aimed to investigate the effect of lncRNA GAS5/miR-452-5p on the inflammation, oxidative stress and pyroptosis of high-glucose-induced renal tubular cells.

METHODS

HK-2 cells were induced by HG to simulate DN cells. RT-qPCR analysis confirmed the transfection effects and detected the expression of GAS5, NLRP3, caspase1, IL-1β, pro-caspase1, pro-IL-1β, GSDMD-N and miR-452-5p. Western blot analysis determined the protein expression of NLRP3, caspase1, IL-1β, pro-caspase1, pro-IL-1β and GSDMD-N. The expression of GSDMD-N was also verified by immunofluorescence. The levels of TNF-α, IL-6, MCP-1, ROS, MDA and SOD were measured by commercial assay kits, respectively. Dual-luciferase reporter assay indicated that GAS5 could combine with miR-452-5p.

RESULTS

GAS5 expression was decreased in HG-induced HK-2 cells. GAS5 overexpression could decrease the levels of TNF-α, IL-6, MCP-1, ROS and MDA and increase the levels of SOD. Moreover, GAS5 overexpression suppressed the expression of NLRP3, caspase1, IL-1β and GSDMD-N, and the results of immunofluorescence verified the above results. miR-452-5p interference could cause the same changes as GAS5 overexpression for HG-induced HK-2 cells, and GAS5 inhibition could reverse the effect of miR-452-5p interference.

CONCLUSION

GAS5 overexpression inhibited the inflammation, oxidative stress and pyroptosis of HG-induced renal tubular cells by downregulating the expression of miR-452-5p.

Uric acid induced epithelial-mesenchymal transition of renal tubular cells through PI3K/p-Akt signaling pathway

The phenotypic changes of tubular epithelial cell are hallmark features of renal diseases caused by abnormal uric acid levels. We hereby intend to investigate whether PI3K/p-Akt signaling plays a role in uric-acid induced epithelial-mesenchymal transition process. The normal rat kidney cell line (NRK-52E) was used as a proximal tubular cell model in this study. NRK-52E cells were exposed to different concentrations of uric acid, or PI3K inhibitor LY294002, or both, respectively. The effects of uric acid on cell morphology were examined by phase contrast microscopy, while molecular alternations were assessed by western blot analysis and immunofluorescence staining. We found that uric acid induced visible morphological alterations in NRK-52E cells accompanied by increased expression of α-smooth muscle actin and reduced expression of E-cadherin. Moreover, phosphorylation of Akt protein was obviously increased, whereas Akt level remained stable. Furthermore, the above effects were abolished when PI3K/p-Akt pathway was blocked by the PI3K inhibitor. These findings demonstrated that high uric acid could induce phenotypic transition of cultured renal tubular cells, which was probably via activating PI3K/p-Akt signaling pathway.

Long noncoding RNA: an emerging player in diabetes and diabetic kidney disease. Clin Sci (Lond). 2019;133:1321-1339. [PMID: 31221822 DOI: 10.1042/cs20190372]

Diabetic kidney disease (DKD) is among the most common complications of diabetes mellitus (DM), and remains the leading cause of end-stage renal diseases (ESRDs) in developed countries, with no definitive therapy yet available. It is imperative to decipher the exact mechanisms underlying DKD and identify novel therapeutic targets. Burgeoning evidence indicates that long non-coding RNAs (lncRNAs) are essential for diverse biological processes. However, their roles and the mechanisms of action remain to be defined in disease conditions like diabetes and DKD. The pathogenesis of DKD is twofold, so is the principle of treatments. As the underlying disease, diabetes per se is the root cause of DKD and thus a primary focus of therapy. Meanwhile, aberrant molecular signaling in kidney parenchymal cells and inflammatory cells may directly contribute to DKD. Evidence suggests that a number of lncRNAs are centrally involved in development and progression of DKD either via direct pathogenic roles or as indirect mediators of some nephropathic pathways, like TGF-β1, NF-κB, STAT3 and GSK-3β signaling. Some lncRNAs are thus likely to serve as biomarkers for early diagnosis or prognosis of DKD or as therapeutic targets for slowing progression or even inducing regression of established DKD. Here, we elaborated the latest evidence in support of lncRNAs as a key player in DKD. In an attempt to strengthen our understanding of the pathogenesis of DKD, and to envisage novel therapeutic strategies based on targeting lncRNAs, we also delineated the potential mechanisms of action as well as the efficacy of targeting lncRNA in preclinical models of DKD.

Mechanisms of Age-Dependent Loss of Dietary Restriction Protective Effects in Acute Kidney Injury

Dietary restriction (DR) is one of the most efficient approaches ameliorating the severity of different pathological conditions including aging. We investigated the protective potential of short-term DR in the model of acute kidney injury (AKI) in young and old rats. In kidney tissue, the levels of autophagy and mitophagy were examined, and proliferative properties of renal cells obtained from rats of different age were compared. DR afforded a significant nephroprotection to ischemic kidneys of young rats. However, in old rats, DR did not provide such beneficial effect. On the assessment of the autophagy marker, the LC3 II/LC3 I ratio, and after staining the tissue with LysoTracker Green, we concluded that in old rats activity of the autophagic-lysosomal system decreased. Mitophagy, as assessed by the levels of PINK-1, was also deteriorated in old animals. Renal cells from old rats showed impaired proliferative capacity, a worse rate of recovery after ischemic injury, increased levels of oxidative stress, accumulation of lipofuscin granules and lower mitochondria membrane potential. The results suggest that the loss of DR benefits in old animals could be due to deterioration in the autophagy/mitophagy flux.

Febuxostat attenuates ER stress mediated kidney injury in a rat model of hyperuricemic nephropathy

Hyperuricemia contributes to kidney tubular injury and kidney fibrosis. However, the underlying mechanism remains unclear. Here we examined the role of RTN1A, a novel endoplasmic reticulum (ER)-associated protein and ER stress in hyperuricemic nephropathy. We first found the expression of RTN1A and ER stress markers was significantly increased in kidney biopsies of hyperuricemia patients with kidney injury. In a rat model of hyperuricemic nephropathy (HN) established by oral administration of a mixture of adenine and potassium oxonate, increased expression of RTN1A and ER stress was shown in tubular and interstitial compartment of rat kidneys. Treatment of Febuxostat, a new selective inhibitor of xanthine oxidase (XO), not only attenuated renal tubular injury and tubulointerstitial fibrosis, but also reduced uric acid crystals deposition in HN rat kidneys. In vitro, Febuxostat also reduced ER stress and apoptosis in uric acid treated tubular epithelial cells. Our data suggest that RTN1A and ER stress mediate tubular cell injury and kidney fibrosis in HN. Urate-lowering therapy (ULT) with Febuxostat attenuates uric-acid induced ER stress in renal tubular cells and the progression of HN.

Effect of Protriptyline on [Ca²⁺]i and Viability in MDCK Renal Tubular Cells

Protriptyline has been used as an antidepressant. Clinically it has been prescribed in the auxiliary treatment of cancer patients. However, its effect on Ca²⁺ signaling and related physiology is unknown in renal cells. This study examined the effect of protriptyline on cytosolic free Ca²⁺ concentrations ([Ca²⁺]i) and viability in Madin-Darby canine kidney (MDCK) tubular cells. Protriptyline induced [Ca²⁺]i rises concentration-dependently. The response was reduced by 20% by removing extracellular Ca²⁺. Protriptyline-induced Ca²⁺ entry was not altered by protein kinase C (PKC) activity but was inhibited by 20% by three modulators of store-operated Ca²⁺ channels: nifedipine, econazole and SKF96365. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5- di-tert-butylhydroquinone (BHQ) or thapsigargin partially inhibited protriptyline-evoked [Ca²⁺]i rises. Conversely, treatment with protriptyline inhibited partially BHQ or thapsigargin-evoked [Ca²⁺]i rises. Inhibition of phospholipase C (PLC) with U73122 did not change protriptyline-induced [Ca²⁺]i rises. Protriptyline at 5-200 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid-acetoxymethyl ester (BAPTA/ AM). Together, in MDCK cells, protriptyline induced [Ca²⁺]i rises by evoking PLC-independent Ca²⁺ release from the endoplasmic reticulum and other unknown stores, and Ca²⁺ entry via PKCinsensitive store-operated Ca²⁺ entry. Protriptyline also caused Ca²⁺-independent cell death.

Mitochondrial reactive oxygen species-mediated NLRP3 inflammasome activation contributes to aldosterone-induced renal tubular cells injury

Aldosterone (Aldo) is an independent risk factor for chronic kidney disease (CKD), and although Aldo directly induces renal tubular cell injury, the underlying mechanisms remain unclear. NLRP3 inflammasome and mitochondrial reactive oxygen species (ROS) have recently been implicated in various kinds of CKD. The present study hypothesized that mitochondrial ROS and NLRP3 inflammasome mediated Aldo–induced tubular cell injury. The NLRP3 inflammasome is induced by Aldo in a dose- and time-dependent manner, as evidenced by increased NLRP3, ASC, caspase-1, and downstream cytokines, such as interleukin (IL)-1β and IL-18. The activation of the NLRP3 inflammasome was significantly prevented by the selective mineralocorticoid receptor (MR) antagonist eplerenone (EPL) (P < 0.01). Mice harboring genetic knock-out of NLRP3 (NLRP3^−/−) showed decreased maturation of renal IL-1β and IL-18, reduced renal tubular apoptosis, and improved renal epithelial cell phenotypic alternation, and attenuated renal function in response to Aldo-infusion. In addition, mitochondrial ROS was also increased in Aldo-stimulated HK-2 cells, as assessed by MitoSOX^TM red reagent. Mito-Tempo, the mitochondria-targeted antioxidant, significantly decreased HK-2 cell apoptosis, oxidative stress, and the activation of NLRP3 inflammasome. We conclude that Aldo induces renal tubular cell injury via MR dependent, mitochondrial ROS-mediated NLRP3 inflammasome activation.

Use of vimentin immunocytochemical staining for evaluation of atypical cells in voided urine samples

BACKGROUND

Cytomorphology of exfoliated atypical reactive/repair renal tubular cells (RRTC) can resemble atypical urothelial cells thus suggesting a differential diagnostic question of urothelial neoplasia in urinary cytology. Vimentin expression has been shown in RRTC and used for differentiation from atypical urothelial cells.

METHODS

The institutional computer database was searched for urinary cytology cases with vimentin immunocytochemical staining (2008-2012). Original cytopathological diagnoses based on cytomorphology and the results of vimentin immunostaining were compared to follow-up data, including histopathological diagnosis, subsequent urinary cytopathology reports, and clinical findings.

RESULTS

Of the 42 cases with vimentin immunocytochemical staining, 33 were positive and 9 negative. Consequently, significant renal disease was found in 9/33 (27%) of vimentin positive cases and nehrolithiasis in 4/33 (12%) of vimentin positive and 1/9 (11%) of vimentin negative cases. Erythrocyturia of undetermined origin was diagnosed in nine cases (seven vimentin positive and two negative). Urinary cytology follow-up was negative in three vimentin positive cases. Urothelial carcinoma was found in 3/9 (30%) of vimentin negative cases. Thirteen patients were lost to follow-up.

CONCLUSIONS

Vimentin immunocytochemical staining could be used as an ancillary method for evaluation of atypical cells in urinary specimens in selected cases with RRTC exhibiting cytological atypia. Unnecessary diagnostic procedures for evaluation of urothelial carcinoma could be avoided in vimentin positive cases and further diagnostic work-up for evaluation of a significant renal disease could be suggested in vimentin positive cases. Diagn. Cytopathol. 2017;45:85-90. © 2016 Wiley Periodicals, Inc.

Ex vivo hyperpolarized MR spectroscopy on isolated renal tubular cells: A novel technique for cell energy phenotyping

PURPOSE

It has been demonstrated that hyperpolarized ¹³ C MR is a useful tool to study cultured cells. However, cells in culture can alter phenotype, which raises concerns regarding the in vivo significance of such findings. Here we investigate if metabolic phenotyping using hyperpolarized ¹³ C MR is suitable for cells isolated from kidney tissue, without prior cell culture.

METHODS

Isolation of tubular cells from freshly excised kidney tissue and treatment with either ouabain or antimycin A was investigated with hyperpolarized MR spectroscopy on a 9.4 Tesla preclinical imaging system.

RESULTS

Isolation of tubular cells from less than 2 g of kidney tissue generally resulted in more than 10 million live tubular cells. This amount of cells was enough to yield robust signals from the conversion of ¹³ C-pyruvate to lactate, bicarbonate and alanine, demonstrating that metabolic flux by means of both anaerobic and aerobic pathways can be quantified using this technique.

CONCLUSION

Ex vivo metabolic phenotyping using hyperpolarized ¹³ C MR in a preclinical system is a useful technique to study energy metabolism in freshly isolated renal tubular cells. This technique has the potential to advance our understanding of both normal cell physiology as well as pathological processes contributing to kidney disease. Magn Reson Med 78:457-461, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Electronegative low density lipoprotein induces renal apoptosis and fibrosis: STRA6 signaling involved

Dyslipidemia has been proven to capably develop and aggravate chronic kidney disease. We also report that electronegative LDL (L5) is the most atherogenic LDL. On the other hand, retinoic acid (RA) and RA receptor (RAR) agonist are reported to be beneficial in some kidney diseases. “Stimulated by retinoic acid 6” (STRA6), one retinol-binding protein 4 receptor, was recently identified to regulate retinoid homeostasis. Here, we observed that L5 suppressed STRA6 cascades [STRA6, cellular retinol-binding protein 1 (CRBP1), RARs, retinoid X receptor α, and retinol, RA], but L5 simultaneously induced apoptosis and fibrosis (TGFβ₁, Smad2, collagen 1, hydroxyproline, and trichrome) in kidneys of L5-injected mice and L5-treated renal tubular cells. These L5-induced changes of STRA6 cascades, renal apoptosis, and fibrosis were reversed in kidneys of LOX1^−/− mice. LOX1 RNA silencing and inhibitor of c-Jun N-terminal kinase and p38MAPK rescued the suppression of STRA6 cascades and apoptosis and fibrosis in L5-treated renal tubular cells. Furthermore, crbp1 gene transfection reversed downregulation of STRA6 cascades, apoptosis, and fibrosis in L5-treated renal tubular cells. For mimicking STRA6 deficiency, efficient silencing of STRA6 RNA was performed and was found to repress STRA6 cascades and caused apoptosis and fibrosis in L1-treated renal tubular cells. In summary, this study reveals that electronegative L5 can cause kidney apoptosis and fibrosis via the suppression of STRA6 cascades, and implicates that STRA6 signaling may be involved in dyslipidemia-mediated kidney disease.

Knockdown of RTN1A attenuates ER stress and kidney injury in albumin overload-induced nephropathy

Our previous studies have suggested a critical role of reticulon (RTN)1A in mediating endoplasmic reticulum (ER) stress in kidney cells of animal models and humans with kidney diseases. A large body of evidence suggests that proteinuria itself can cause tubular cell injury leading to the progression of kidney disease. In the present study, we determined whether RTN1A mediates proteinuria-induced tubular cell injury through increased ER stress. We found that incubation of HK2 cells with human serum albumin induced the expression of RTN1A and ER stress markers, whereas knockdown of RTN1A expression attenuated human serum albumin-induced ER stress and tubular cell apoptosis in vitro. In vivo, we found that tubular cell-specific RTN1 knockdown resulted in a significant attenuation of tubular cell ER stress, apoptosis, and renal fibrosis in a model of albumin overload nephropathy. Based on these findings, we conclude that RTN1A is a key mediator for proteinuria-induced tubular cell toxicity and renal fibrosis.

Associations of Urinary Uromodulin with Clinical Characteristics and Markers of Tubular Function in the General Population

BACKGROUND AND OBJECTIVES

Allelic variants in UMOD, the gene coding for uromodulin, are associated with rare tubulointerstitial kidney disorders and risk of CKD and hypertension in the general population. The factors associated with uromodulin excretion in the normal population remain largely unknown, and were therefore explored in this study.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Urinary uromodulin excretion was measured using a validated ELISA in two population-based cohorts that included more than 6500 individuals. The Swiss Kidney Project on Genes in Hypertension study (SKIPOGH) included 817 adults (mean age±SD, 45±17 years) who underwent renal ultrasonography and performed a 24-hour urine collection. The Cohorte Lausannoise study included 5706 adults (mean age, 53±11 years) with fresh spot morning urine samples. We calculated eGFRs using the CKD-Epidemiology Collaboration formula and by 24-hour creatinine clearance.

RESULTS

In both studies, positive associations were found between uromodulin and urinary sodium, chloride, and potassium excretion and osmolality. In SKIPOGH, 24-hour uromodulin excretion (median, 41 [interquartile range, 29-57] mg/24 h) was positively associated with kidney length and volume and with creatinine excretion and urine volume. It was negatively associated with age and diabetes. Both spot uromodulin concentration and 24-hour uromodulin excretion were linearly and positively associated (multivariate analyses) with eGFR<90 ml/min per 1.73 m(2).

CONCLUSION

Age, creatinine excretion, diabetes, and urinary volume are independent clinical correlates of urinary uromodulin excretion. The associations of uromodulin excretion with markers of tubular functions and kidney dimensions suggest that it may reflect tubule activity in the general population.

Generation of induced pluripotent stem cells from renal tubular cells of a patient with Alport syndrome

Alport syndrome (AS) is a hereditary disease that leads to kidney failure and is caused by mutations in the COL4A3, COL4A4, and COL4A5 genes that lead to the absence of collagen α3α4α5 (IV) networks in the mature kidney glomerular basement membrane. Approximately 80% of AS is X-linked because of mutations in COL4A5, the gene encoding the alpha 5 chain of type IV collagen. To investigate the pathogenesis of AS at the genetic level, we generated induced pluripotent stem cells (iPSCs) from renal tubular cells of a patient with AS. The successful iPSC generation laid the foundation to master the repair of the COL4A5 gene and to evaluate the differentiation of iPSC into Sertoli cells and the accompanying epigenetic changes at each stage. The generation of iPSCs from AS patients not only confirms that iPSCs could be generated from renal tubular cells, but also provides a novel type of genetic therapy for AS patients. In this study, we generated iPSCs from renal tubular cells via ectopic expression of four transcription factors (Oct4, Sox2, c-myc, and Klf4). According to the human embryonic stem cell (hESC) charter, iPSC formation was confirmed by comparatively analyzing hESC markers via colony morphology, immunohistochemistry, qRT-PCR, flow cytometry, gene expression profiling of the three germ layers, and karyotyping. Our results demonstrated that iPSCs were similar to hESCs with regard to morphology, proliferation, hESC-specific surface marker expression, and differentiation into the cell types of the three germ layers. The efficient generation of iPSCs from the renal tubular cells of an AS patient would provide a novel model to investigate the mechanisms underlying AS and to develop new treatments for AS.

Effect of triptolide on expression of thrombospondin-1 and transforming growth factor-β1 in renal tubular cells

The objective of our study is to investigate the effect of triptolide on expression of thrombospondin-1 and transforming growth factor β1 in renal tubular cells. Human renal tubular epithelial cells were stimulated by different concentrations of triptolide (0.1, 1, and 10 μg/L) in the presence of angiotensin-II (10(-7)mol/L). Real Time PCR was used to detect the mRNA expression of thrombospondin-1 and transforming growth factor β1. Western blot analysis was used to detect the protein expression. ELISA was used to detect the level of total and active transforming growth factor β1. The mRNA expression of thrombospondin-1 (3.66 ± 0.48 vs. 1.33 ± 0.26, p < 0.05) and transforming growth factor β1 (3.58 ± 0.59 vs. 1.26 ± 0.28, p < 0.05) were up-regulated obviously when stimulated by angiotensin-II. And the protein expression of thrombospondin-1 (0.5126 ± 0.0936 vs. 0.1025 ± 0.0761, p < 0.01) and transforming growth factor β1 (0.5948 ± 0.0736 vs. 0.1318 ± 0.0614, p < 0.01) were also up-regulated simultaneously when stimulated by angiotensin-II. The expression of thrombospondin-1 and transforming growth factor β1 induced by angiotensin-II were down-regulated markedly with 1 μg/L and 10 μg/L of triptolide in mRNA and protein levels (p < 0.05, p <  0.01). And triptolide (1 and 10 μg/L) could reduce the expression of total and active transforming growth factor β1 (p < 0.05, p < 0.01). In conclusion, triptolide can inhibit the expression of thrombospondin-1 and transforming growth factor β1 in mRNA and protein levels and down-regulate the levels of total and active transforming growth factor β1.

P2X7 receptor inhibition protects against ischemic acute kidney injury in mice

Activation of the purinergic P2X7 receptor (P2X7R) has been associated with the development of experimental nephritis and diabetic and hypertensive nephropathy. However, its role in acute kidney injury (AKI) remains unknown. In this study, we examined the effects of P2X7R inhibition in a murine model of ischemia-reperfusion (I/R)-induced AKI using A438079, a selective inhibitor of P2X7R. At 24 h after I/R, mice developed renal dysfunction and renal tubular damage, which was accompanied by elevated expression of P2X7R. Early administration of A438079 immediately or 6 h after the onset of reperfusion protected against renal dysfunction and attenuated kidney damage whereas delayed administration of A438079 at 24 h after restoration of perfusion had no protective effects. The protective actions of A438079 were associated with inhibition of renal tubule injury and cell death and suppression of renal expression of monocyte chemotactic protein-1 and regulated upon expression normal T cell expressed and secreted (RANTES). Moreover, I/R injury led to an increase in phosphorylation (activation) of extracellular signal-regulated kinases 1/2 in the kidney; treatment with A438079 diminished this response. Collectively, these results indicate that early P2X7R inhibition is effective against renal tubule injury and proinflammatory response after I/R injury and suggest that targeting P2X7R may be a promising therapeutic strategy for treatment of AKI.

mTOR contributes to ER stress and associated apoptosis in renal tubular cells

ER stress has been implicated in the pathogenesis of both acute and chronic kidney diseases. However, the molecular regulation of ER stress in kidney cells and tissues remains poorly understood. In this study, we examined tunicamycin-induced ER stress in renal proximal tubular cells (RPTC). Tunicamycin induced the phosphorylation and activation of PERK and eIF2α within 2 h in RPTC, which was followed by the induction of GRP78 and CHOP. Consistently, tunicamycin also induced apoptosis in RPTC. Interestingly, mTOR was activated rapidly during tunicamycin treatment, as indicated by phosphorylation of both mTOR and p70S6K. Inhibition of mTOR with rapamycin partially suppressed the phosphorylation of PERK and eIF2a and the induction of CHOP and GRP78 induction during tunicamycin treatment. Rapamycin also inhibited apoptosis during tunicamycin treatment and increased cell survival. Collectively, the results suggest that mTOR plays a regulatory role in ER stress, and inhibition of mTOR may have potential therapeutic effects in ER stress-related renal diseases.

mTOR plays a critical role in p53-induced oxidative kidney cell injury in HIVAN

Oxidative stress has been implicated to contribute to HIV-induced kidney cell injury; however, the role of p53, a modulator of oxidative stress, has not been evaluated in the development of HIV-associated nephropathy (HIVAN). We hypothesized that mammalian target of rapamycin (mTOR) may be critical for the induction of p53-mediated oxidative kidney cell injury in HIVAN. To test our hypothesis, we evaluated the effect of an mTOR inhibitor, rapamycin, on kidney cell p53 expression, downstream signaling, and kidney cell injury in both in vivo and in vitro studies. Inhibition of the mTOR pathway resulted in downregulation of renal tissue p53 expression, associated downstream signaling, and decreased number of sclerosed glomeruli, tubular microcysts, and apoptosed and 8-hydroxy deoxyguanosine (8-OHdG)-positive (+ve) cells in Tg26 mice. mTOR inhibition not only attenuated kidney cell expression of p66ShcA and phospho-p66ShcA but also reactivated the redox-sensitive stress response program in the form of enhanced expression of manganese superoxide dismutase (MnSOD) and catalase. In in vitro studies, the mTOR inhibitor also provided protection against HIV-induced podocyte apoptosis. Moreover, mTOR inhibition downregulated HIV-induced podocyte (HP/HIV) p53 expression. Since HP/HIV silenced for mTOR displayed a lack of expression of p53 as well as attenuated podocyte apoptosis, this suggests that mTOR is critical for kidney cell p53 activation and associated oxidative kidney cell injury in the HIV milieu.