Apoptosis and JNK activation are differentially regulated by Fas expression level in renal tubular epithelial cells.

BACKGROUND: In chronic renal disease, renal tubular epithelial cell (RTC) Fas expression is up-regulated, leading to apoptotic RTC deletion and tubular atrophy. In vitro, cytokine- or hypoxia-induced up-regulation of Fas expression is associated with RTC apoptosis. In contrast, constitutively expressed, low level RTC Fas does not mediate apoptosis, suggesting that Fas may be coupled to expression level-dependent RTC signaling pathways. Fas is known to signal through JNK in many systems, but the requirement of JNK activation for apoptosis remains controversial. METHODS: To determine if RTC Fas regulates JNK activity and apoptosis, human RTC were transfected with graded concentrations of a eukaryotic expression vector for murine Fas. Apoptosis was measured by annexin V, TUNEL and PARP cleavage assays. JNK activity was determined by immune complex kinase assay and/or immunoblots with phospho-specific JNK antibodies, in the presence or absence of co-expressed dominant negative JNK constructs. RESULTS: Fas antibody stimulation of RTC with high Fas expression levels (to model RTC phenotype in renal disease) caused a tenfold increase in apoptosis, while RTC with low level Fas expression (to model normal RTC phenotype) were apoptosis-resistant. Fas ligation activated JNK in RTC expressing low levels of Fas, but not in apoptosis-sensitive RTC with increased Fas expression. Dominant negative JNK co-expression failed to inhibit apoptosis in RTC expressing high levels of Fas, suggesting that JNK is neither necessary, nor sufficient, for Fas-dependent apoptosis. CONCLUSIONS: At high levels of expression, RTC Fas promotes apoptosis in a JNK-independent manner. At low basal expression, Fas induces JNK activation, but not apoptosis, consistent with novel roles for RTC Fas as a mediator of cell stress or chronic inflammation.     

Apoptosis and expression of cytotoxic T lymphocyte effector molecules in renal allografts.

Cytotoxic T lymphocyte (CTL) mediated apoptosis is thought to play a major role in the rejection of renal allografts following transplantation, however, the CTL effector mechanism that is primarily responsible for immunological rejection is unknown. The two major effector pathways of CTL killing which lead to apoptosis involve the Fas/Fas ligand (Fas L) lytic pathway, and the perforin/granzyme degranulation pathway. The expression of CTL effector molecules which influence these pathways include Fas, Fas L and TiA-1 (cytotoxic granule protein). This study has investigated apoptosis by in situ terminal deoxytransferase-catalysed DNA nick end labelling (TUNEL), and the expression of CTL effector molecules by immunohistochemistry, in renal allograft biopsies obtained from patients following kidney transplantation. Renal biopsies were classified into three histological groups; acute cellular rejection, chronic rejection, or no rejection. The extent of T-cell infiltration of renal tissues was assessed by immunohistochemical staining with an anti-CD3 monoclonal antibody. Numerous TUNEL positive cells were detected in all transplant biopsies examined; these consisted mainly of renal tubular cells and infiltrating cells, with some TUNEL positive cells also detected in the glomeruli. In the case of normal kidney tissue, renal cells also stained positive for TUNEL but there was no lymphocytic infiltration. There was significantly more T-cell infiltration observed in acute rejection biopsies compared to the no rejection biopsies. In the case of Fas L expression, there was little expression in all three biopsy groups, apart from one case of chronic rejection. Conversely, although there were no significant differences in TiA-1 expression between the three biopsy groups, TiA-1 expression was more prominent in acute rejection biopsies. Furthermore, Fas expression was significantly decreased in acute rejection biopsies when compared to those of chronic and no rejection in which Fas was predominantly localized in the renal tubular cells. These results indicate that the mechanism of CTL killing leading to the rejection of renal allografts may be different in acute and chronic rejection. Moreover, our data indicate the potential for cytotoxic granule-based CTL killing in acute renal allograft rejection but not in chronic rejection.     

Renal phenotype is exacerbated in Os and lpr double mutant mice

BACKGROUND: ROP-Os/+ mice are born with oligosyndactyly and oligonephronia and develop renal dysfunction, which includes renal tubular epithelial cell (RTC) Fas-dependent apoptosis and tubular atrophy. MRL/lpr mice harbor a Fas-inactivating mutation and develop glomerulonephritis, whereas mice expressing lpr on a C3H background demonstrate no renal phenotype. We hypothesized that crossing ROP-Os/+ with CH3-lpr/lpr mice would rescue the Os/+ renal phenotype by reducing Fas-dependent RTC apoptosis. METHODS: ROP-Os/+ mice were intercrossed with C3H-lpr/lpr mice and F(2) generation animals were phenotyped by kidney weight, serum creatinine, and albuminuria. Kidney sections were scored for histopathology and apoptosis. Univariate and multivariate analyses were used to examine additive effects of Os and lpr on renal phenotype. RESULTS: By 16 weeks, F(2)Os/+ lpr/lpr mice developed significantly more albuminuria, glomerulosclerosis, and interstitial inflammation compared to Os/++/+ mice. Glomerular cell apoptosis was increased in Os/+ lpr/lpr compared to Os/++/+ mice, with no significant difference in RTC apoptosis. A statistically significant Os-lpr effect on renal phenotype was demonstrated by multivariate analysis, which exceeded the combined independent effects if Os and lpr, indicating a biologic interaction exists between Os and lpr. CONCLUSION: Os/+ mice with a superimposed lpr mutation displayed a more severe renal phenotype, rather than phenotype rescue, suggesting that Fas pathway activation is necessary to delete cells resulting from Os-dependent injury. We further propose that an Os-lpr gene interaction and/or mixed ROP-C3H genetic background regulated the renal phenotype, consistent with the concept that chronic renal disease pathogenesis reflects effects of multiple nephropathy susceptibility alleles.     

Proapoptotic Fas ligand is expressed by normal kidney tubular epithelium and injured glomeruli

Fas ligand (FasL) is a cell membrane cytokine that can promote apoptosis through activation of Fas receptors. Fas receptor activation induces glomerular cell apoptosis in vivo and participates in tubular cell death during acute renal failure. However, there is little information on the expression of FasL in the kidney. This study reports that FasL mRNA and protein are present in normal mouse and rat kidney. In situ hybridization and immunohistochemistry showed that proximal tubular epithelium is the main site of FasL expression in the normal kidney. In addition, increased total kidney FasL mRNA and de novo FasL protein expression by glomerular cells were observed in two different models of glomerular injury : rat immune-complex proliferative glumerulonephritis and murine lupus nephritis. Both full-length and soluble FasL were increased in the kidneys of the mice with nephritis. Cultured murine proximal tubular epithelial MCT cells and primary cultures of murine tubular epithelial cells expressed FasL mRNA and protein. Tubular epithelium-derived FasL induced apoptosis in Fassensitive lymphoid cell lines but not in Fas-resistant lymphoid cell lines. By contrast, MCT cells grown in the presence of the survival factors of serum were resistant to FasL, and only became partially sensitive to apoptosis induced by high concentrations (100 ng/ml) of FasL upon serum deprivation. However, MCT cells stimulated with inflammatory mediators (tumor necrosis factor-alpha, interferon-gamma, and lipopolysaccharide) increased cell surface Fas expression and were sensitized to apoptosis induced by FasL (FasL 55 +/- 5% versus control 8.3 +/- 4.1% apoptotic cells at 24 h, P < 0.05). Cytokine-primed primary cultures of tubular epithelial cells also acquired sensitivity to FasL-induced apoptosis. These results suggest that FasL expression by intrinsic renal cells may play a role in cell homeostasis in the normal kidney and during renal injury.     

Role of ubiquitin-like protein FAT10 in epithelial apoptosis in renal disease

Dysregulated apoptosis of renal tubular epithelial cells (RTEC) is an important component of the pathogenesis of several renal diseases, including HIV-associated nephropathy (HIVAN), the most common cause of chronic kidney failure in HIV-infected patients. In HIVAN, RTEC become infected by HIV-1 in a focal distribution, and HIV-1 infection has been shown to induce apoptosis in vitro. In microarray studies that used a novel renal tubular epithelial cell line from a patient with HIVAN, it was found that the ubiquitin-like protein FAT10 is one of the most upregulated genes in HIV-infected cells. Previously, FAT10 was shown to induce apoptosis in murine fibroblasts. The expression of FAT10 in HIVAN and the ability of FAT10 to induce apoptosis in human RTEC therefore were studied. This study revealed that FAT10 expression is induced after infection of RTEC by HIV-1 and that expression of FAT10 induces apoptosis in RTEC in vitro. Moreover, it was found that inhibition of endogenous FAT10 expression abrogated HIV-induced apoptosis of RTEC. Immunohistochemical studies demonstrated increased FAT10 expression in a murine model of HIVAN, in HIVAN biopsy samples, and in autosomal dominant polycystic kidney disease, another renal disease that is characterized by cystic tubular enlargement and epithelial apoptosis. These results suggest a novel role for FAT10 in epithelial apoptosis, which is an important component of the pathogenesis of many renal diseases.     

Paracetamol-induced renal tubular injury: a role for ER stress

Paracetamol (also known as acetaminophen) causes acute and chronic renal failure. While the mechanisms leading to hepatic injury have been extensively studied, the molecular mechanisms of paracetamol-induced nephrotoxicity are poorly defined. Paracetamol induced cell death with features of apoptosis in murine proximal tubular epithelial cells. While paracetamol increased the expression of the death receptor Fas on the cell surface, the Fas pathway was not involved in the paracetamol-induced apoptosis of tubular cells. The mitochondrial pathway was not activated during paracetamol-induced apoptosis; there was no dissipation of mitochondrial potential or release of apoptogenic factors such as cytochrome c or Smac/DIABLO. However, paracetamol-induced apoptosis is a caspase-dependent process that involves activation of caspase-9 and caspase-3 in the absence of cytosolic cytochrome c or Smac/DIABLO. The authors also detected induction of endoplasmic reticulum (ER) stress, characterized by GADD153 upregulation and translocation to the nucleus, as well as caspase-12 cleavage. Interestingly, after treatment of murine tubular cells with paracetamol and calpain inhibitors, the caspase-12 cleavage product was still detectable, and calpain inhibitors were unable to protect tubular cells from paracetamol-induced apoptosis. The results suggest that induction of apoptosis may underlie the nephrotoxic potential of paracetamol and identify ER stress as a therapeutic target in nephrotoxicity.     

Fas/FasL表达和细胞凋亡在人类同种异体移植肾急性排斥中的作用

目的探讨移植肾急性排斥（ＡＲ）时细胞凋亡与Ｆａｓ和Ｆａｓ配体（ＦａｓＬ）表达的作用及其临床意义。方法分别用原位末端标记技术（ＴＵＮＥＬ法）和免疫组织化学方法检测２６例移植肾ＡＲ标本中细胞凋亡和Ｆａｓ／ＦａｓＬ表达情况。结果细胞凋亡和Ｆａｓ／ＦａｓＬ表达主要在ＡＲ移植肾小管上皮发生,且凋亡指数和Ｆａｓ／ＦａｓＬ表达与肾组织病理损伤程度平行,与正常肾对照组和移植肾功能稳定组比较差异显著（Ｐ＜０．０１）。结论肾小管上皮细胞凋亡在ＡＲ所致的移植肾损伤中起重要作用,Ｆａｓ／ＦａｓＬ系统可能参与移植肾ＡＲ,是造成肾小管上皮细胞凋亡的重要因素。ＴＵＮＥＬ法检测细胞凋亡可作为判断移植肾病理变化和预后的重要指标     

Inflammatory cytokines and lipopolysaccharide induce Fas-mediated apoptosis in renal tubular cells

BACKGROUND/AIMS: Increased susceptibility of the kidney to acute renal failure (ARF) in the setting of sepsis even in the absence of systemic hypotension is well known. In the hypothesis that the proinflammatory cytokines and lipopolysaccharide (LPS) in gram-negative sepsis can directly cause renal tubular cell apoptosis via Fas- and caspase-mediated pathways, we examined apoptosis and Fas, Fas ligand, FADD expression, as well as PARP cleavage in cultured human proximal tubular cells under the cytokine and LPS-stimulated conditions. METHODS: HK-2 cell, immortalized human proximal tubular cell lines, were treated with 5 and 30 ng/ml of tumor necrosis factor-alpha (TNF-alpha), 5 and 20 ng/ml of interleukin-1beta (IL-1beta) and 30 ng/ml LPS for 24 h. Fas expression was examined by RT-PCR and Fas ligand, Fas-associated protein with death domain (FADD) and poly ADP ribose polymerase (PARP) cleavage were examined by Western blot analysis. Apoptosis was assessed by flow cytometer using Annexin V-FITC and propidium iodide (PI) staining and also by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) methods. RESULTS: Fas mRNA expression (ratio of Fas/L-19) increased in the TNF-alpha 5, 30 ng/ml and LPS treated group (p < 0.01, p < 0.01, p = 0.02), but there was no difference between the low- and high-dose TNF-alpha groups. Fas ligand protein expression did not increase in the low-dose TNF-alpha treated group, but it increased significantly in the high-dose TNF-alpha treated group (p < 0.01), IL-1beta- and LPS-treated groups (p < 0.01, p = 0.01, p < 0.01, p = 0.02). The intracellular adaptor protein, FADD expression also increased significantly in the high-dose TNF-alpha- and IL-beta-treated groups (p = 0.04, p = 0.04), but in the low-dose TNF-alpha and IL-beta treated group, it did not show statistically significant differences. In the LPS group, FADD expression also showed an increased tendency, but it was not statistically significant (p = 0.09). Western blot for PARP, a DNA repair enzyme mainly cleaved by caspase 3, showed increased 89- and 24-kD PARP cleavage products in TNF-alpha, IL-1beta and LPS treated cells. The degree of apoptosis examined by DNA fragmentation and translocation of membrane phosphatidyl serine significantly increased in cytokines and LPS treated groups. CONCLUSION: These results suggest that Fas- and caspase-mediated apoptosis of tubular cells by inflammatory cytokines and LPS can be one of the possible mechanisms of renal dysfunction in endotoxemia.     

Lethal activity of FADD death domain in renal tubular epithelial cells

Fas-associated death domain (FADD) is an adaptor protein that is required for the transmission of the death signal from lethal receptors of the tumor necrosis factor superfamily. FADD contains a death domain (DD) and a death effector domain (DED). As death receptors contribute to renal tubular injury and tubular cell FADD increases in acute renal failure, we have studied the function of FADD in tubular epithelium. FADD expression was studied in kidney samples from mice. In order to study the contribution of FADD to renal tubular cell survival, FADD or FADD-DD were overexpressed in murine tubular epithelium. FADD is expressed in renal tubules of the healthy kidney. Both FADD and FADD-DD induce apoptosis in primary cultures of murine tubular epithelium and in the murine cortical tubular cell line. Death induced by FADD-DD has apoptotic morphology, but differs from death receptor-induced apoptosis in that it is not blocked by inhibitors of caspases. Neither an inhibitor of serine proteases nor overexpression of antiapoptotic BclxL prevented cell death. However, the combination of caspase and serine protease inhibition was protective. FADD and FADD-DD overexpression decreased nuclear factor kappa B activity. These data suggest that FADD has a death regulatory function in renal tubular cells that is independent of death receptors. FADD-DD is sufficient to induce apoptosis in these cells. This information is relevant to understanding the role of FADD in tubular injury.     

Testosterone promotes apoptotic damage in human renal tubular cells

BACKGROUND: Apoptosis is a mode of cell death that participates in the kidney physiologic remodeling processes and is thought to contribute to cell loss and kidney structural damage in chronic renal diseases. Gender is one factor which contributes to accelerated nephron loss, with progression more rapid in men than in women in diabetic and nondiabetic chronic renal diseases. Mechanisms by which androgens may cause higher rate of progression of chronic renal diseases in men are poorly explored. METHODS: In this study, to investigate the role of androgens on apoptotic damage and its associated mechanisms, we examined the effects of testosterone (T) (0.1 nmol/L to 1 micromol/L) on apoptosis, and apoptosis-related proteins in a proximal human tubule cell line (HK-2 cells). Additional experiments were performed in primary cultures of proximal tubular epithelial cells (PTECs). Cells were grown to subconfluence in normal growth medium, and apoptotic damage was induced by serum deprivation for 24 to 48 hours. Cycloheximide, flutamide (a T-receptor antagonist), 17-beta estradiol, or caspase inhibitors were added to cultures that were successively processed for terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick end-labeling (TUNEL) analysis, annexin V/propidium iodide staining, immunofluorescence, or immunoblots to identify effects and apoptotic pathways that could be modulating cell survival. RESULTS: Both morphologic analysis by annexin V/propidium iodide staining and TUNEL showed that physiologic T levels (1 to 10 nmol/L) induced a significant increase in apoptosis both in HK-2 cells and PTECs. In both types of cell lines pretreatment with the androgen receptor antagonist flutamide prevented the T-induced apoptosis. T-induced apoptosis was enhanced by treatment with cycloheximide and prevented by 17beta-estradiol. Fas, Fas ligand (FasL), and Fas-associating death domain containing protein (FADD) were clearly up-regulated within 48 hours of T treatment in HK-2 cells. Also, T significantly increased the expression of Bax protein (P < 0.01 vs. control) (an effect which was blocked by flutamide), and decreased the expression of Bcl-2. Western blot analysis showed that caspase-3 was activated. Moreover, cleavage into an 85-kD poly(ADP-ribose) polymerase-1 (PARP-1) terminal breakdown product was detectable. The changes in cellular morphology induced by T at 48 hours were no longer observed after the addition of caspase-8, caspase-9, and caspase-3 inhibitors to the culture medium. CONCLUSION: These results indicate that T increases the permissiveness of proximal tubule kidney cells to apoptotic effects by triggering an apoptotic pathway involving caspase activation, Fas up-regulation, and FasL expression, thus potentially interacting with mechanisms of cell loss which have been already shown to be activated in chronic renal diseases. This is consistent with a role for T in promoting renal injury in men.     

Increasing Resistance of Tubular Epithelial Cells to Apoptosis by shRNA Therapy Ameliorates Renal Ischemia-Reperfusion Injury

Renal tubular epithelial cells (TEC) die by apoptosis or necrosis in renal ischemia-reperfusion injury (IRI). Fas/Fas ligand-dependent fratricide is critical in TEC apoptosis, and Fas promotes renal IRI. Therefore, targeting Fas or caspase-8 may have therapeutic potential for renal injury in kidney transplant or failure. RNA silencing by short hairpin RNA (shRNA) is a novel strategy to down-regulate protein expression. Using this approach, silencing of Fas or caspase-8 by shRNA to prevent TEC apoptosis and IRI was evaluated. IRI was induced by renal artery clamping for 45 or 60 min at 32 degrees C in uninephrectomized C57BL/6 mice. Here, we showed that Fas or pro-caspase-8 expression was significantly knocked down in TEC by stable expression of shRNA, resulting in resistance to apoptosis induced by superoxide, IFN-gamma/TNF-alpha and anti-Fas antibody. Inferior vena cava delivery of pHEX-small interfering RNA targeting Fas or pro-caspase-8 resulted in protection of kidney from IRI, indicated by reduction of renal tubular injury (necrosis and apoptosis) and serum creatinine or blood urea nitrogen. Our data suggest that shRNA-based therapy targeting Fas and caspase-8 in renal cells can lead to protection of kidney from IRI. Attenuation of pro-apoptotic proteins using genetic manipulation strategies such as shRNA might represent a novel strategy to promote kidney allograft survival from rejection or failure.     

New kids in the block: the role of FasL and Fas in kidney damage.

Fas ligand (FasL) is a lethal cytokine that promotes apoptosis through cross-linking of the Fas receptor, although it also has other, less well understood functions. The FasL/Fas system regulates immune and inflammatory responses. Evidence that FasL and Fas participate in kidney damage can be summarized as follows: 1) FasL is expressed by renal cells and its expression increases during kidney damage; 2) activation of the Fas receptor promotes apoptosis of non-stimulated or cytokine-primed renal cells in culture; 3) Fas agonists kill mesangial cells and induce glomerular injury in vivo, but can also reduce kidney damage by limiting injurious immunological responses; 4) mice with disrupted FasL/Fas systems are protected from acute tubular cell injury, although they develop autoimmune glomerulonephritis if other genetic predisposing factors are present. These facts imply that the FasL/Fas system can be considered a new target for therapeutic intervention in kidney damage. However, any therapeutic approach must consider interference with Fas in other cell systems. The complexities of the FasL/Fas system in the kidney are still far from clear.     

Cyclosporine-induced renal injury induces toll-like receptor and maturation of dendritic cells

BACKGROUND: The toll-like receptor (TLR) is stimulated by not only pathogen-associated molecular patterns but also endogenous TLR ligands provided by injured cells. The influence of cyclosporine A (CsA)-induced renal injury on TLR expression and subsequent signaling pathway was evaluated. METHODS: Induction of chronic CsA nephropathy was made by administering CsA (15 mg/kg/day) for 28 days in rats. The TLR2 and TLR4 mRNA and protein expression, TLR-signaling pathway (MYD88, NF-kappaB and AP-1), putative TLR ligand (heat shock protein 70 [HSP70]), and maturation of dendritic cells were evaluated in CsA-treated rat kidneys. RESULTS: Long-term CsA treatment upregulated TLR2 and TLR4 mRNA and protein expression on renal tubular cells, and these were accompanied by increased MYD88, NF-kappaB and AP-1 expression. Putative TLR ligand (HSP70) was also significantly increased in CsA-treated rat kidney compared with vehicle-treated rat kidney. CsA-treatment increased expression of TNF-alpha mRNA, the number of dendritic cells, and expression of MHC class II antigen. Double-labeling of markers of dendritic cells and MHC class II antigen revealed that matured dendritic cells increased in CsA-treated rat kidney. CONCLUSIONS: CsA-induced renal injury stimulates components of innate immunity, and this finding suggests close association between CsA-induced renal injury and activation of innate immunity.     

Activation of mitochondrial apoptotic pathways in human renal allografts after ischemiareperfusion injury

BACKGROUND: Ischemia-reperfusion injury in cadaveric (CAD) kidney allografts is associated with tubular cell injury, delayed graft function, and an increased incidence of acute and chronic rejection. We tested the hypothesis that activation of specific apoptotic pathways represents a mechanism for tubular cell death after CAD kidney transplantation. METHODS: Serial tissue sections from paraffin-embedded needle biopsy specimens obtained at approximately 1 hr of reperfusion after transplantation of 13 CAD and 12 living-related donor (LRD) renal allografts were examined by using the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay to detect apoptosis and by immunohistochemistry for expression of key pro-apoptotic molecules (Bax, Bak, tumor necrosis factor receptor [TNFR]-1, Fas, and cytochrome c). RESULTS: Apoptosis was detected primarily in tubular cells, with a mean+/-standard deviation of 6.8+/-2.2 apoptotic cells per 100 cells examined in CAD renal allografts compared with 1.8+/-2.7 cells per 100 in LRD (P<0.001) renal allografts. There was a significant correlation between apoptosis rate and cold ischemia time in CAD (r=0.86, P<0.001) renal allografts. Bax was expressed in 100% of CAD versus 17% of LRD renal allografts (P<0.001), Bak in 92% of CAD versus 17% of LRD renal allografts (P<0.001), and TNFR-1 in 100% of CAD versus 58% of LRD renal allografts (P<0.05). Fas was expressed in only a small number of samples (23% of CAD and 17% of LRD renal allografts, P=not significant). Bax and Bak were expressed predominantly in apoptotic cells. Cytochrome c was detected as a mitochondrial pattern in LRD renal allografts, but in a diffuse cytosolic distribution in CAD renal allografts. CONCLUSIONS: Ischemia-reperfusion injury in CAD kidney transplants is associated with a duration-dependent increase in tubular cell apoptosis, mediated at least in part by activation of mitochondrial pathways.     

Curcumin counteracts cisplatin-induced nephrotoxicity by preventing renal tubular cell apoptosis

Curcumin has several biological functions particularly antioxidant and anti-inflammatory. The aims of this study are determination of the protective effects of curcumin on cisplatin-induced renal tubular cell apoptosis and related pathways in kidney. Eighteen male Wistar albino rats were randomly divided into three groups (n?=?6): the control, cisplatin (CP), and cisplatin?+?curcumin (CP?+?CUR). Acute renal damage was induced by single dose of cisplatin (7.5?mg/kg) injected by intraperitoneally (i.p). The animals of curcumin-treated group were received daily 200?mg/kg curcumin per os (po), starting from 2 days before the injection of cisplatin to the day of sacrifice. Forty-eight hours after cisplatin injection, samples of cardiac blood and kidneys were harvested from the animals. In this study, the major finding is that curcumin treatment ameliorates the following conditions associated with cisplatin-induced nephrotoxicity: (1) the development of kidney injury (histopathology), (2) inflammatory responses [myeloperoxidase (MPO) and tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, IL-10 levels], (3) the degree of lipid peroxidation [malondialdehyde (MDA) level], (4) renal tubular cell apoptosis (active caspase-3) and expression of related proteins [p53, Fas, and Fas ligand (Fas-L)] by immunohistochemistry, (5) renal dysfunction (serum urea and creatinine). In a conclusion, this study suggests that curcumin has antiapoptotic effect against cisplatin nephrotoxicity, in addition to anti-inflammatory and antioxidant properties.     

Hepatocyte growth factor suppresses interstitial fibrosis in a mouse model of obstructive nephropathy

BACKGROUND: As tubulointerstitial fibrosis (TIF) reflects the prognosis of patients with various chronic renal diseases, the pathogenesis of TIF has to be clarified. Transforming growth factor-beta (TGF-beta) is a key mediator for renal fibrosis. We reported that hepatocyte growth factor (HGF) prevents renal fibrosis in nephrotic mice. However, the function of HGF in chronic renal failure, except for nephrotic syndrome, remains to be determined. METHODS: Using mice subjected to unilateral ureter-ligated obstruction (UUO), we investigated the roles of HGF in TIF, as induced by obstructive nephropathy. Pathophysiological changes in the kidney after UUO treatment were analyzed focusing on expressions of renal HGF and TGF-beta, TIF, tubular proliferation, and apoptosis. Neutralizing antibody against rodent HGF, or recombinant human HGF (rhHGF), was administrated to the UUO mice, and pathophysiological changes after neutralization or supplements of HGF were analyzed. RESULTS: In this UUO model, TIF with tubular apoptosis became evident, and it was accompanied by a decrease in renal HGF expression and an increase in renal TGF-beta expression. Neutralization of endogenous HGF accelerated the progression of TIF, accompanied by increases in TGF-beta expression and tubular apoptosis as well as by decreases in tubular proliferation. In contrast, rhHGF attenuated TIF progression, and there were decreases in TGF-beta expression and tubular apoptosis, and an increase in tubular proliferation. CONCLUSIONS: Endogenous as well as exogenous HGF attenuated the progression of the fibrosis caused by obstructive nephropathy in these mice. Thus, local reduction in HGF levels may account for TIF in chronic renal diseases.     

Expression of Smac/Diablo in tubular epithelial cells and during acute renal failure

BACKGROUND: Apoptosis contributes to tubular cell loss in the course of renal injury. However, the mechanisms regulating tubular cell apoptosis are not well understood. Smac/Diablo is a mitochondrial protein that is released to the cytosol during apoptosis, where it blocks the antiapoptotic activity of inhibitor of apoptosis proteins (IAPs). METHODS: We have studied the regulation of Smac/Diablo mRNA and protein expression in murine toxic acute tubular necrosis, and in cultured tubular epithelial cells exposed to the lethal cytokine tumor necrosis factor (TNF). RESULTS: Folic acid-induced acute renal failure was associated with tubular cell apoptosis. Smac/Diablo mRNA and protein levels increased by 50% at 24 hours. TNF, a cytokine whose renal expression increases in folic acid nephropathy, induced apoptosis in cultured tubular epithelial cells in a time-dependent manner. In addition, TNF increased the mRNA and protein expression of Smac/Diablo. CONCLUSION: These findings support the concept that regulation of Smac/Diablo mRNA and protein expression is a mechanism by which lethal stimuli amplify their lethal potential in renal cells.