Expression and activation of STAT3 in chronic proliferative immune complex glomerulonephritis and the effect of fosinopril

Renoprotective Effect of Pitavastatin against TAA-Induced Renal Injury: Involvement of the miR-93/PTEN/AKT/mTOR Pathway

This research investigated if pitavastatin (Pita) might protect rats' kidneys against thioacetamide (TAA). By altering the PTEN/AKT/mTOR pathway, pitavastatin may boost kidney antioxidant capacity and minimize oxidative damage. Statins have several benefits, including antioxidant and anti-inflammatory characteristics. The principal hypothesis of this study was that Pita can regulate the miR-93/PTEN/AKT/mTOR pathways, which is thought to be responsible for its renoprotective effects. The experiment divided male rats into four groups. Group 1 included untreated rats as the control. Group 2 included rats which received TAA (100 mg/kg intraperitoneally thrice a week for two weeks) to destroy their kidneys. Groups 3 and 4 included rats which received Pita orally at 0.4 and 0.8 mg/kg for 14 days after TAA injections. Renal injury increased BUN, creatinine, and MDA levels and decreased glutathione (GSH) levels. Pitavastatin prevented these alterations. TAA decreased PTEN and increased miR-93, Akt, p-Akt, mTOR, and Stat3 in the kidneys. Pitavastatin also regulated the associated culprit pathway, miR-93/PTEN/Akt/mTOR. In addition, TAA induced adverse effects on the kidney tissue, which were significantly ameliorated by pitavastatin treatment. The findings suggest that pitavastatin can attenuate renal injury, likely by regulating the miR-93/PTEN/Akt/mTOR pathway. This modulation of the pathway appears to contribute to the protective effects of pitavastatin against TAA-induced renal injury, adding to the growing evidence of the pleiotropic benefits of statins in renal health.

Chitosan oligosaccharide alleviates renal fibrosis through reducing oxidative stress damage and regulating TGF-β1/Smads pathway

Renal fibrosis (RF) is the common pathway for a variety of chronic kidney diseases that progress to end-stage renal disease. Chitosan oligosaccharide (COS) has been identified as possessing many health functions. However, it is not clear whether COS can prevent RF. The purpose of this paper was to explore the action and mechanism of COS in alleviating RF. First, an acute unilateral ureteral obstruction operation (UUO) in male BALB/c mice was performed to induce RF, and COS or fosinopril (positive control drug) were administered for 7 consecutive days. Data from our experiments indicated that COS treatment can significantly alleviate kidney injury and decrease the levels of blood urea nitrogen (BUN) and serum creatinine (SCr) in the UUO mouse model. More importantly, our results show that COS can reduce collagen deposition and decrease the expression of fibrosis proteins, such as collagen IV, fibronectin, collagen I, α-smooth muscle actin (α-SMA) and E-cadherin, ameliorating experimental renal fibrosis in vivo. In addition, we also found that COS suppressed oxidative stress and inflammation in RF model mice. Further studies indicated that the mechanism by which COS alleviates renal fibrosis is closely related to the regulation of the TGF-β1/Smad pathway. COS has a therapeutic effect on ameliorating renal fibrosis similar to that of the positive control drug fosinopril. Taken together, COS can alleviate renal fibrosis induced by UUO by reducing oxidative stress damage and regulating the TGF-β1/Smad pathway.

Meprin β expression modulates the interleukin-6 mediated JAK2-STAT3 signaling pathway in ischemia/reperfusion-induced kidney injury

Meprin metalloproteinases have been implicated in the pathophysiology of ischemia/reperfusion (IR)-induced kidney injury. Previous in vitro data showed that meprin β proteolytically processes interleukin-6 (IL-6) resulting in its inactivation. Recently, meprin-β was also shown to cleave the IL-6 receptor. The goal of this study was to determine how meprin β expression impacts IL-6 and downstream modulators of the JAK2-STAT3-mediated signaling pathway in IR-induced kidney injury. IR was induced in 12-week-old male wild-type (WT) and meprin β knockout (βKO) mice and kidneys obtained at 24 h post-IR. Real-time PCR, western blot, and immunostaining/microscopy approaches were used to quantify mRNA and protein levels respectively, and immunofluorescence counterstaining with proximal tubule (PT) markers to determine protein localization. The mRNA levels for IL-6, CASP3 and BCL-2 increased significantly in both genotypes. Interestingly, western blot data showed increases in protein levels for IL-6, CASP3, and BCL-2 in the βKO but not in WT kidneys. However, immunohistochemical data showed increases in IL-6, CASP3, and BCL-2 proteins in select kidney tubules in both genotypes, shown to be PTs by immunofluorescence counterstaining. IR-induced increases in p-STAT-3 and p-JAK-2 in βKO at a global level but immunoflourescence counterstaining demonstrated p-JAK2 and p-STAT3 increases in select PT for both genotypes. BCL-2 increased only in the renal corpuscle of WT kidneys, suggesting a role for meprins expressed in leukocytes. Immunohistochemical analysis confirmed higher levels of leukocyte infiltration in WT kidneys when compared to βKO kidneys. The present data demonstrate that meprin β modulates IR-induced kidney injury in part via IL-6/JAK2/STAT3-mediated signaling.

Exploring the Impact of ACE Inhibition in Immunity and Disease

Angiotensin-converting enzyme (ACE) is a zinc-dependent dipeptidyl carboxypeptidase and is crucial in the renin-angiotensin-aldosterone system (RAAS) but also implicated in immune regulation. Intrinsic ACE has been detected in several immune cell populations, including macrophages and neutrophils, where its overexpression results in enhanced bactericidal and antitumour responses, independent of angiotensin II. With roles in antigen presentation and inflammation, the impact of ACE inhibitors must be explored to understand how ACE inhibition may impact our ability to clear infections or malignancy, particularly in the wake of the coronavirus (SARS-CoV2) pandemic and as antibiotic resistance grows. Patients using ACE inhibitors may be more at risk of postsurgical complications as ACE inhibition in human neutrophils results in decreased ROS and phagocytosis whilst angiotensin receptor blockers (ARBs) have no effect. In contrast, ACE is also elevated in certain autoimmune diseases such as rheumatoid arthritis and lupus, and its inhibition benefits patient outcome where inflammatory immune cells are overactive. Although the ACE autoimmune landscape is changing, some studies have conflicting results and require further input. This review seeks to highlight the need for further research covering ACE inhibitor therapeutics and their potential role in improving autoimmune conditions, cancer, or how they may contribute to immunocompromise during infection and neurodegenerative diseases. Understanding ACE inhibition in immune cells is a developing field that will alter how ACE inhibitors are designed in future and aid in developing therapeutic interventions.

Mechanism of action of Tripterygium wilfordii for treatment of idiopathic membranous nephropathy based on network pharmacology

Background

Although thunder god vine (Tripterygium wilfordii) has been widely used for treatment of idiopathic membranous nephropathy (IMN), the pharmacological mechanisms underlying its effects are still unclear. This study investigated potential therapeutic targets and the pharmacological mechanism of T. wilfordii for the treatment of IMN based on network pharmacology.

Methods

Active components of T. wilfordii were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform. IMN-associated target genes were collected from the GeneCards, DisGeNET, and OMIM databases. VENNY 2.1 was used to identify the overlapping genes between active compounds of T. wilfordii and IMN target genes. The STRING database and Cytoscape 3.7.2 software were used to analyze interactions among overlapping genes. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses of the targets were performed using Rx64 4.0.2 software, colorspace, stringi, DOSE, clusterProfiler, and enrichplot packages.

Results

A total of 153 compound-related genes and 1485 IMN-related genes were obtained, and 45 core genes that overlapped between both categories were identified. The protein–protein interaction network and MCODE results indicated that the targets TP53, MAPK8, MAPK14, STAT3, IFNG, ICAM1, IL4, TGFB1, PPARG, and MMP1 play important roles in the treatment of T. wilfordii on IMN. Enrichment analysis showed that the main pathways of targets were the AGE signaling pathway, IL-17 signaling pathway, TNF signaling pathway, and Toll-like receptor signaling pathway.

Conclusion

This study revealed potential multi-component and multi-target mechanisms of T. wilfordii for the treatment of IMN based on network pharmacological, and provided a scientific basis for further experimental studies.

The potential therapeutic use of renin-angiotensin system inhibitors in the treatment of inflammatory diseases

Inflammation is a normal part of the immune response to injury or infection but its dysregulation promotes the development of inflammatory diseases, which cause considerable human suffering. Nonsteroidal anti-inflammatory agents are the most commonly prescribed agents for the treatment of inflammatory diseases, but they are accompanied by a broad range of side effects, including gastrointestinal and cardiovascular events. The renin-angiotensin system (RAS) is traditionally known for its role in blood pressure regulation. However, there is increasing evidence that RAS signaling is also involved in the inflammatory response associated with several disease states. Angiotensin II increases blood pressure by binding to angiotensin type 1 (AT₁ ) receptor, and direct renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors and AT₁ receptor blockers (ARBs) are clinically used as antihypertensive agents. Recent data suggest that these drugs also have anti-inflammatory effects. Therefore, this review summarizes these recent findings for the efficacy of two of the most widely used antihypertensive drug classes, ACE inhibitors and ARBs, to reduce or treat inflammatory diseases such as atherosclerosis, arthritis, steatohepatitis, colitis, pancreatitis, and nephritis.

The pathogenesis of diclofenac induced immunoallergic hepatitis in a canine model of liver injury

Hypersensitivity to non-steroidal anti-inflammatory drugs is a common adverse drug reaction and may result in serious inflammatory reactions of the liver. To investigate mechanism of immunoallergic hepatitis beagle dogs were given 1 or 3 mg/kg/day (HD) oral diclofenac for 28 days. HD diclofenac treatment caused liver function test abnormalities, reduced haematocrit and haemoglobin but induced reticulocyte, WBC, platelet, neutrophil and eosinophil counts. Histopathology evidenced hepatic steatosis and glycogen depletion, apoptosis, acute lobular hepatitis, granulomas and mastocytosis. Whole genome scans revealed 663 significantly regulated genes of which 82, 47 and 25 code for stress, immune response and inflammation. Immunopathology confirmed strong induction of IgM, the complement factors C3&B, SAA, SERPING1 and others of the classical and alternate pathway. Alike, marked expression of CD205 and CD74 in Kupffer cells and lymphocytes facilitate antigen presentation and B-cell differentiation. The highly induced HIF1A and KLF6 protein expression in mast cells and macrophages sustain inflammation. Furthermore, immunogenomics discovered 24, 17, 6 and 11 significantly regulated marker genes to hallmark M1/M2 polarized macrophages, lymphocytic and granulocytic infiltrates; note, the latter was confirmed by CAE staining. Other highly regulated genes included alpha-2-macroglobulin, CRP, hepcidin, IL1R1, S100A8 and CCL20. Diclofenac treatment caused unprecedented induction of myeloperoxidase in macrophages and oxidative stress as shown by SOD1/SOD2 immunohistochemistry. Lastly, bioinformatics defined molecular circuits of inflammation and consisted of 161 regulated genes.

Altogether, the mechanism of diclofenac induced liver hypersensitivity reactions involved oxidative stress, macrophage polarization, mastocytosis, complement activation and an erroneous programming of the innate and adaptive immune system.

Reno-protective effect and mechanism study of Huang Lian Jie Du Decoction on lupus nephritis MRL/lpr mice

BACKGROUND

Huang Lian Jie Du Decoction (HLJDD), a very famous traditional Chinese medicinal prescription, has been used for heat dissipation and detoxification in China. This study was aimed to evaluate the reno-protective effects of HLJDD against lupus nephritis (LN) in vivo in MRL/lpr mice.

METHODS

Animals were administered orally every day for eight consecutive weeks except the mice of normal group and model group. Organ indexes, serum interleukin-6 (IL-6), interleukin-10 (IL-10), interferon-gamma (IFN-γ) and the anti-double stranded DNA (anti-dsDNA) antibody were tested, respectively. Creatinine (Cr), blood urea nitrogen (BUN) and urine protein were measured for renal function evaluation. The expression of phosphorylated signal transducer and activator of transcription 3 (p-STAT 3) in kidney tissue was observed by western blot (WB) and immunohistochemical (IHC) method. Meanwhile, histopathological changes in the renal were studied by hematoxylin-eosin (H&E) staining.

RESULTS

The mice of HLJDD-treated group exhibited a significant reduced mortality (p < 0.05), serum anti-dsDNA level (p < 0.05) and renal immune complex deposition (p < 0.05), compared with the untreated MRL/lpr mice. In addition, HLJDD treatment remarkably reduced the levels of BUN, Cr, proteinuria (p < 0.01) and the levels of inflammatory cytokines such as IL-6, IL-10 and IFN-γ (p < 0.01). Moreover, HLJDD significantly suppressed the phosphorylations of STAT 3 (p < 0.05) and the renal pathological changes.

CONCLUSIONS

The study implied that HLJDD may be a potential agent for the therapy of LN, and the down-regulated p-STAT 3 expression suggesting that it may be one of the LN therapy targets for HLJDD.

Stat1 Regulates Lupus-like Chronic Graft-versus-Host Disease Severity via Interactions with Stat3

Systemic lupus erythematosus (SLE) is a complex multisystem autoimmune disease, characterized by a spectrum of autoantibodies that target multiple cellular components. Glomerulonephritis is a major cause of morbidity in patients with SLE. Little is known about the pathogenesis of SLE renal damage and compromised renal function. Activation of both Stat1 and Stat3 has been reported in lupus and lupus nephritis. The reciprocal activation of these two transcription factors may have a major impact on renal inflammation. To study the role of Stat1 in a lupus model, we induced lupus-like chronic graft-versus-host disease (cGVHD) in Stat1-knockout (KO) and wild-type (WT) mice by i.p. injection of class II-disparate bm12 splenocytes. WT recipients of these alloreactive cells developed anti-dsDNA autoantibodies starting at week 2 as expected, with a decline after week 4. In contrast, Stat1-KO hosts exhibited a prolonged and significant increase of anti-dsDNA autoantibody responses compared with WT mice (week 4 to week 8). Increased autoantibody titers were accompanied by increased proteinuria and mortality in the cGVHD host mice lacking Stat1. Further analysis revealed expression and activation of Stat3 in the glomeruli of Stat1-KO host mice but not WT mice with cGVHD. Glomerular Stat3 activity in the Stat1-KO mice was associated with increased IL-6 and IFN-γ secretion and macrophage infiltration. Interactions between Stat1 and Stat3 thus appear to be crucial in determining the severity of lupus-like disease in the cGVHD model.

Midkine in nephrogenesis, hypertension and kidney diseases

Midkine (MK; K; gene abbreviation, Mdk: mus musculus, MDK: homo sapiens) is a multifunctional heparin-binding growth factor that regulates cell growth, survival and migration as well as anti-apoptotic activity in nephrogenesis and development. Proximal tubular epithelial cells are the main sites of MK expression in the kidneys. The pathophysiological roles of MK are diverse, ranging from the development of acute kidney injury (AKI) to the progression of chronic kidney disease, often accompanied by hypertension, renal ischaemia and diabetic nephropathy. The obvious hypertension that develops in Mdk(+/+) mouse models of renal ablation compared with Mdk(-/-) mice eventually leads to progressive renal failure, such as glomerular sclerosis and tubulointerstitial damage associated with elevated plasma angiotensin (Ang) II levels. MK is also induced in the lung endothelium by oxidative stress and subsequently up-regulated by ACE, which hydrolyzes Ang II to induce further oxidative stress, thus accelerating MK generation; this leads to a vicious cycle of positive feedback in the MK-Ang II pathway. Kidney-lung interactions involving positive feedback between the renin-angiotensin system and MK might partly account for the pathogenesis of hypertension and kidney damage. MK is also involved in the pathogenesis of AKI and diabetic nephropathy through the recruitment of inflammatory cells. In contrast, MK plays a protective role against crescentic glomerulonephritis, by down-regulating plasminogen activator inhibitor-1. These diverse actions of MK might open up new avenues for targeted approaches to treating hypertension and various renal diseases.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

IL-18 induces profibrotic renal tubular cell injury via STAT3 activation

IL-18 is an important mediator of obstruction-induced renal fibrosis and renal tubular epithelial cell (TEC) injury. IL-18's proinflammatory properties have been attributed, in part, to NF-κB activation and the stimulation of cytokine gene expression; however, STAT3 has increasingly been shown to mediate renal fibrotic injury. We therefore hypothesized that IL-18 mediates profibrotic TEC injury via STAT3 activation. Male C57BL6 wild-type mice and transgenic mice for human IL-18-binding protein were subjected to unilateral ureteral obstruction or sham operation. The kidneys were harvested 1 or 2 wk afterward and analyzed for active STAT3 (p-STAT3) expression (Western blotting, immunohistochemistry) and suppressor of cytokine signaling 3 (SOCS3) expression. In a separate arm, renal tubular cells (HK-2) were directly stimulated with IL-18 for 2 days with or without the STAT3 inhibitor S3I-201 (50 μM). Cell lysates were then analyzed for p-STAT3 and SOCS3 expression, profibrotic cellular changes (collagen and α-SMA expression), and tubular cell apoptosis. p-STAT3 and SOCS3 expression increased significantly in response to obstruction; however, a significant reduction in p-STAT3 and SOCS3 expression occurred following 1 wk, but not 2 wk, of obstruction in the presence of IL-18 neutralization. In vitro results similarly demonstrate increased p-STAT3, SOCS3, α-SMA, and collagen III expression, and increased collagen production and TEC apoptosis in response to IL-18 stimulation, but the response was significantly diminished in the presence of STAT3 inhibition. These results demonstrate that IL-18-induces profibrotic cellular changes and collagen production in TECs via STAT3 activation.

Podocyte-specific deletion of signal transducer and activator of transcription 3 attenuates nephrotoxic serum-induced glomerulonephritis

Activation of signal transducer and activator of transcription (STAT)3 correlates with proliferation of extra-capillary glomerular epithelial cells and the extent of renal injury in glomerulonephritis. To delineate the role of STAT3 in glomerular epithelial cell proliferation we examined the development of nephrotoxic serum-induced glomerulonephritis in mice with and without podocyte-restricted STAT3 deletion. Mice with STAT3 deletion in podocytes developed less crescents and loss of renal function compared to those without STAT3 deletion. Proliferation of glomerular cells, loss of podocyte markers, and recruitment of parietal epithelial cells were found in nephritic mice without STAT3 deletion, but mitigated in nephritic mice with podocyte STAT3 deletion. Glomerular expression of pro-inflammatory STAT3 target genes was significantly reduced in nephritic mice with, compared to those without, podocyte STAT3 deletion. However, the extent of glomerular immune complex deposition was not different. Podocytes with STAT3 deletion were resistant to interleukin-6-induced STAT3 phosphorylation and pro-inflammatory STAT3 target gene expression. Thus, podocyte STAT3 activation is critical for the development of crescentic glomerulonephritis.

The role of the Janus kinase family/signal transducer and activator of transcription signaling pathway in fibrotic renal disease

Over the past several years, a number of cytokines and growth factors including transforming growth factor β1, tumor necrosis factor α, and angiotensin II have been shown to play a crucial role in renal fibrosis. The Janus kinase family (JAK) and signal transducers and activators of transcription (STATs) constitute one of the primary signaling pathways that regulate cytokine expression, and the JAK/STAT signaling pathway has increasingly been implicated in the pathophysiology of renal disease. This review examines the role of the JAK/STAT signaling pathway in fibrotic renal disease. The JAK/STAT signaling pathway is activated in a variety of renal diseases and has been implicated in the pathophysiology of renal fibrosis. Experimental evidence suggests that inhibition of the JAK/STAT signaling pathway, in particular JAK2 and STAT3, may suppress renal fibrosis and protect renal function. However, it is incompletely understood which cells activate the JAK/STAT signaling pathway and which JAK/STAT signaling pathway is activated in each renal disease. Research regarding JAK/STAT signaling and its contribution to renal disease is still ongoing in humans. Future studies are required to elucidate the potential role of JAK/STAT signaling inhibition as a therapeutic strategy in the attenuation of renal fibrosis.

Growth factor Midkine is involved in the pathogenesis of renal injury induced by protein overload containing endotoxin

BACKGROUND

Growth factor Midkine (MK), which expresses on endothelial cells and renal proximal tubules, has been implicated in inflammation-related kidney diseases such as ischemic reperfusion-induced tubulointerstitial injury and diabetic nephropathy. The biological actions of MK are elicited through its chemotactic activity and chemokine-driven inflammatory pathway. Post-infectious glomerulonephritis is caused by the deposition of immune complexes into glomeruli by infiltrating a number of inflammatory cells. Therefore, we investigated whether MK might be involved in the pathogenesis of acute glomerulonephritis.

METHODS

We induced endocapillary proliferative glomerulonephritis in 129/SV mice using intraperitoneal injections of a large amount of protein.

RESULTS

In contrast to mice deficient in MK (Mdk (-/-)), Mdk (+/+) mice induced by protein overload demonstrated more diffuse cellular proliferation in the mesangial areas and capillary lumens, eventually leading to glomerular damage and tubulointerstitial injury. This pathological observation could be attributable to neutrophil infiltration through the chemotaxis and stimulation of the MK-macrophage inflammatory protein (MIP)-2 pathway, but appeared to be due to the MK-related immunoglobulin (Ig)G deposition and C3 activation. These findings are often seen in infectious-related glomerular injury. Furthermore, the profile of MK expression was strongly consistent with that of glomerular damage and tubulointersititial injury.

CONCLUSION

This study might provide a new insight into understanding the deleterious role of MK in endocapillary proliferative glomerulonephritis induced by protein overload.

Treatment of collagen-induced arthritis by Natura-alpha via regulation of Th-1/Th-17 responses

Cytokines and CD4(+) Th cells play a crucial role in the pathogenesis of rheumatoid arthritis. Among the Th populations, Th-1 and Th-17 have been described as pathogenic in collagen-induced arthritis (CIA) whereas Th-2 and Treg were found to have protective effects. The objective of this study was to examine the affect of Natura-alpha, a newly developed cytokine regulator, on CIA and on Th cell development. Natura-alpha treatment was administered before or during arthritis induction. Anti-type II collagen antibodies and cytokine expression were evaluated by ELISA. Emergence of CD4(+)CD25(+)Foxp3(+) T cells was assessed by flow cytometry. Th-17 differentiation of naive CD4 T cells was assessed in cultures with anti-CD3 and anti-CD28. We showed that Natura-alpha both prevented and treated CIA. We further demonstrated that in vivo treatment with Natura-alpha inhibited IL-17 production and anti-type II collagen IgG development. We showed in vitro, using an APC-free system, that Natura-alpha acted directly on differentiating T cells and inhibiting the formation of Th-1 and Th-17 cells but did not affect Th-2 cells. Since Natura-alpha inhibits a large spectrum of important pathogenic factors in CIA, it may provide a new and powerful approach to the treatment of rheumatoid arthritis and other inflammatory diseases.

Activation of signal transducer and activator of transcription 3 correlates with cell proliferation and renal injury in human glomerulonephritis

BACKGROUND

Signal transducer and activator of transcription (STAT) 3 plays an important role in the regulation of cell proliferation. However, the mechanism of STAT3 activation in human glomerulonephritis is unclear.

METHODS

STAT3 activation was determined using immunohistochemistry for phosphorylated STAT3 (p-STAT3) in normal human kidney and various types of glomerulonephritis. We also identified the cell exhibiting activated p-STAT3 expression in human glomerulonephritis and correlated STAT3 activation with renal function and histologic injury.

RESULTS

p-STAT3 staining was identified in glomeruli and some tubules in normal human kidney. p-STAT3 positive glomerular cells were significantly increased in lupus nephritis, IgA nephropathy and vasculitis compared with normal kidney. p-STAT3 positive tubulointerstitial cells were significantly increased in IgA nephropathy and vasculitis compared with normal kidney. Glomerular and tubulointerstitial p-STAT3 staining was significantly decreased after steroid therapy. There was a significant correlation between the number of p-STAT3 positive cells and the number of PCNA positive glomerular and tubulointerstitial cells in all cases of glomerulonephritis. Furthermore, renal function inversely correlated with the number of p-STAT3 positive glomerular and tubulointerstitial cells in all cases of glomerulonephritis.

CONCLUSIONS

The present study has identified STAT3 activation in normal human kidney and a marked increase in STAT3 activation in many forms of glomerulonephritis. The correlation of STAT3 activation with clinical and histologic parameters suggests that this pathway plays an important role in the pathogenesis of kidney disease. Furthermore, localization of STAT3 activation to individual cell types suggests that this pathway may play a pivotal role in promoting renal inflammation and fibrosis.

STAT3 inhibits apoptosis of human renal tubular epithelial cells induced by ATP depletion/recovery

BACKGROUND/AIMS

Apoptosis has been implicated in renal ischemic injury, the regulating mechanism of which is still unclear. Signal transducers and activators of transcription (STAT) participate in inflammation, apoptosis, and tumorigenesis. In the in vitro model of renal ischemic injury, we explored the role of the STAT3, a major component of the STAT family, in apoptosis of human proximal tubular epithelial cell (HKC) induced by ATP depletion/recovery.

METHODS

Apoptosis of HKC was induced in an in vitro model of acute renal failure. STAT3 activation was analyzed by Western blotting. RNA interference was used to knock down STAT3 expression. The effect of STAT3 knockdown or STAT3C overexpression on apoptosis was assessed by annexin V binding and propidium iodide uptake.

RESULTS

STAT3 was phosphorylated during the course of ATP depletion-induced HKC cell apoptosis. STAT3 knockdown suppressed STAT3 phosphorylation, and promoted apoptosis of HKC subjected to ATP depletion/recovery, while STAT3C overexpression conferred resistance of HKC to ATP depletion-induced apoptosis.

CONCLUSION

Our results demonstrated that STAT3 mediates resistance to ATP depletion-induced apoptosis of HKC, which may be a potential target in treatment of renal ischemic injury.