Hydrogen‐rich water alleviates cyclosporine A‐induced nephrotoxicity via the Keap1/Nrf2 signaling pathway

Oxidative stress induced by long‐term cyclosporine A (CsA) administration is a major cause of chronic nephrotoxicity, which is characterized by tubular atrophy, tubular cell apoptosis, and interstitial fibrosis in the progression of organ transplantation. Although hydrogen‐rich water (HRW) has been used to prevent various oxidative stress‐related diseases, its underlying mechanisms remain unclear. This study investigated the effects of HRW on CsA‐induced nephrotoxicity and its potential mechanisms. After administration of CsA (25 mg/kg/day), rats were treated with or without HRW (12 mL/kg) for 4 weeks. Renal function and vascular activity were investigated. Histological changes in kidney tissues were analyzed using Masson's trichrome and terminal deoxynucleotidyl transferase dUTP nick‐end labeling stains. Oxidative stress markers and the activation of the Kelch‐like ECH‐associated protein 1 (Keap1)/nuclear factor erythroid 2‐related factor 2 (Nrf2) signaling pathway were also measured. We found that CsA increased the levels of reactive oxygen species (ROS) and malonaldehyde (MDA), but it reduced glutathione (GSH) and superoxide dismutase (SOD) levels. Such alterations induced vascular dysfunction, tubular atrophy, interstitial fibrosis, and tubular apoptosis. This was evident secondary to an increase in urinary protein, serum creatinine, and blood urea nitrogen, ultimately leading to renal dysfunction. Conversely, HRW decreased levels of ROS and MDA while increasing the activity of GSH and SOD. This was accompanied by an improvement in vascular and renal function. Moreover, HRW significantly decreased the level of Keap1 and increased the expression of Nrf2, NADPH dehydrogenase quinone 1, and heme oxygenase 1. In conclusion, HRW restored the balance of redox status, suppressed oxidative stress damage, and improved kidney function induced by CsA via activation of the Keap1/Nrf2 signaling pathway.     

Decreasing initial telomere length in humans intergenerationally understates age‐associated telomere shortening

Telomere length shortens with aging, and short telomeres have been linked to a wide variety of pathologies. Previous studies suggested a discrepancy in age‐associated telomere shortening rate estimated by cross‐sectional studies versus the rate measured in longitudinal studies, indicating a potential bias in cross‐sectional estimates. Intergenerational changes in initial telomere length, such as that predicted by the previously described effect of a father's age at birth of his offspring (FAB), could explain the discrepancy in shortening rate measurements. We evaluated whether changes occur in initial telomere length over multiple generations in three large datasets and identified paternal birth year (PBY) as a variable that reconciles the difference between longitudinal and cross‐sectional measurements. We also clarify the association between FAB and offspring telomere length, demonstrating that this effect is substantially larger than reported in the past. These results indicate the presence of a downward secular trend in telomere length at birth over generational time with potential public health implications.     

Oxidative stress‐induced attenuation of thrombospondin‐1 expression in primary rat astrocytes

Astrocytes, the major glial population in the central nervous system (CNS), can secrete thrombospondin (TSP)‐1 that plays the role in synaptogenesis and axonal sprouting during CNS development and tissue repair. However, little is known about the regulation of TSP‐1 expression in astrocytes under oxidative stress condition. Here, a hypoxic mimetic reagent, cobalt chloride (CoCl₂), was used to initiate hypoxia‐induced oxidative stress in primary rat astrocytes. CoCl₂ at the concentration range of 0.1–0.5 mM was found to cause no significant cell death in primary rat astrocytes. However, CoCl₂ at 0.2–0.5 mM increased intracellular reactive oxygen species (ROS) levels and glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) gene expression that is known as a hallmark for oxidative damage. We further found that TSP‐1 mRNA expression in astrocytes was inhibited dose‐ and time‐dependently by CoCl₂. TSP‐1 mRNA levels were increased in CoCl₂‐exposed astrocytes in the presence of the inhibitors (U0126 and PD98059) of mitogen‐activated protein kinase/extracellular signal‐regulated kinases (MAPK/ERK), when compared to that detected in the culture only exposed to CoCl₂. Moreover, the inhibition in TSP‐1 mRNA expression by CoCl₂ was blocked by the addition of the potent antioxidant, N‐acetylcysteine (NAC). Thus, we conclude that CoCl₂ inhibits TSP‐1 mRNA expression in astrocytes via a ROS mechanism possibly involving MAPK/ERK. This inhibition may occur after CNS injury and impair the supportive function of astrocytes on neurite growth in the injured CNS tissues. J. Cell. Biochem. 112: 59–70, 2011. © 2010 Wiley‐Liss, Inc.     

Protective effect of proanthocyanidins against doxorubicin‐induced nephrotoxicity in rats

Doxorubicin (DOX) exerts toxic effects in several organs particularly kidney. The present study aimed to assess the protective effect of proanthocyanidins (PAs) against DOX‐induced nephrotoxicity in rats. A single dose of DOX (7.5 mg/kg, i.v.) significantly increased kidney weight, kidney/body weight ratio, serum urea, creatinine, tumor necrosis factor alpha levels, and kidney contents of malondialdehyde, nitric oxide, cyclooxygenase‐2, and caspase‐3 activity with significant reduction in final body weight, serum albumin, kidney contents of reduced glutathione (GSH), and superoxide dismutase activity as compared with control group. In contrast, pretreatment with PAs (200 mg/kg, p.o.) for 14 days before DOX and for 7 days after DOX ameliorated kidney function and oxidative stress parameters. Histopathological evidence confirmed the protective effects of PAs from the tissue damage induced by DOX. In conclusion, PAs have a multi‐nephroprotective effect that might be attributed to its antioxidant, anti‐inflammatory, and antiapoptoic activities.     

Telomerase abrogates aneuploidy‐induced telomere replication stress,senescence and cell depletion

The causal role of aneuploidy in cancer initiation remains under debate since mutations of euploidy‐controlling genes reduce cell fitness but aneuploidy strongly associates with human cancers. Telomerase activation allows immortal growth by stabilizing telomere length, but its role in aneuploidy survival has not been characterized. Here, we analyze the response of primary human cells and murine hematopoietic stem cells (HSCs) to aneuploidy induction and the role of telomeres and the telomerase in this process. The study shows that aneuploidy induces replication stress at telomeres leading to telomeric DNA damage and p53 activation. This results in p53/Rb‐dependent, premature senescence of human fibroblast, and in the depletion of hematopoietic cells in telomerase‐deficient mice. Endogenous telomerase expression in HSCs and enforced expression of telomerase in human fibroblasts are sufficient to abrogate aneuploidy‐induced replication stress at telomeres and the consequent induction of premature senescence and hematopoietic cell depletion. Together, these results identify telomerase as an aneuploidy survival factor in mammalian cells based on its capacity to alleviate telomere replication stress in response to aneuploidy induction.     

Mitochondria‐mediated mitigatory role of curcumin in cisplatin‐induced nephrotoxicity

Cisplatin (CP) is one of the most potent chemotherapeutic anti‐tumour drugs, and it has been implicated in renal toxicity. Oxidative stress has been proven to be involved in CP‐induced toxicity including nephrotoxicity. However, there is paucity of literature involving role of mitochondria in mediating CP‐induced renal toxicity, and its underlying mechanism remains unclear. Therefore, the present study was undertaken to examine the antioxidant potential of curcumin (CMN; a natural polyphenolic compound) against the mitochondrial toxicity of CP in kidneys of male rats. Acute toxicity was induced by a single intra‐peritoneal injection of CP (6 mg kg^?1). We studied the ameliorative effect of CMN pre‐treatment (200 mg kg^?1) on the toxicity of CP in rat kidney mitochondria. CP caused a significant elevation in the mitochondrial lipid peroxidation (LPO) levels and protein carbonyl (PC) content. Pre‐treatment of rat with CMN significantly replenished the mitochondrial LPO levels and PC content. It also restored the CP‐induced modulatory effects on altered enzymatic and non‐enzymatic antioxidants in kidney mitochondria. We hypothesize that the reno‐protective effects of CMN may be related to its predisposition to scavenge free radicals, and upregulate antioxidant machinery in kidney mitochondria. Copyright © 2013 John Wiley & Sons, Ltd.     

Ceftriaxone ameliorates cyclosporine A-induced oxidative nephrotoxicity in rat

A growing body of evidence now suggested that cyclosporine A (CycA)‐induced nephrotoxicity is a crucial clinical problem and oxidative stress is importantly responsible for its toxicity. Ceftriaxone induced antioxidant effect in brain and neuronal tissues against oxidative damage although its antioxidant potential effect on kidney has not been clarified. The aim of this study was to evaluate whether ceftriaxone protects CycA‐induced oxidative stress kidney injury in rats. Twenty‐four rats were equally divided into four groups. First group was used as control. Ceftriaxone (200 mg/kg) and CycA (15 mg/kg) were administrated to second and third groups for 10 days, respectively. The ceftriaxone and CycA combination was given to rats constituting the fourth group for 10 days. Lipid peroxidation (LP), urea nitrogen and lactate dehydrogenase (LDH) levels were higher in CycA group than in control and ceftriaxone groups although LP, urea nitrogen and LDH levels were lower in ceftriaxone + CycA group than in control and ceftriaxone groups. Glutathione peroxidase and catalase activities were lower in CycA group than in control whereas their activities were increased in control and ceftriaxone groups. Superoxide dismutase activity did not change by the treatments. Ceftriaxone administration recovered also CycA‐induced atrophy, vacuolization and exfoliations of tubular epithelium and glomerular collapse in histopathological evaluation of kidney. In conclusion, we observed that ceftriaxone is beneficial on CycA‐induced oxidative stress in kidney of rats by modulating oxidative and antioxidant system. Copyright © 2011 John Wiley & Sons, Ltd.     

Sua5p a single‐stranded telomeric DNA‐binding protein facilitates telomere replication

In budding yeast Saccharomyces cerevisiae, telomere length maintenance involves a complicated network as more than 280 telomere maintenance genes have been identified in the nonessential gene deletion mutant set. As a supplement, we identified additional 29 telomere maintenance genes, which were previously taken as essential genes. In this study, we report a novel function of Sua5p in telomere replication. Epistasis analysis and telomere sequencing show that sua5Δ cells display progressively shortened telomeres at early passages, and Sua5 functions downstream telomerase recruitment. Further, biochemical, structural and genetic studies show that Sua5p specifically binds single‐stranded telomeric (ssTG) DNA in vitro through a distinct DNA‐binding region on its surface, and the DNA‐binding ability is essential for its telomere function. Thus, Sua5p represents a novel ssTG DNA‐binding protein and positively regulates the telomere length in vivo.     

Oxidative stress‐induced structural changes in the microtubule‐associated flavoenzyme Irc15p from Saccharomyces cerevisiae

The genome of the yeast Saccharomyces cerevisiae encodes a canonical lipoamide dehydrogenase (Lpd1p) as part of the pyruvate dehydrogenase complex and a highly similar protein termed Irc15p (increased recombination centers 15). In contrast to Lpd1p, Irc15p lacks a pair of redox active cysteine residues required for the reduction of lipoamide and thus it is very unlikely that Irc15p performs a similar dithiol‐disulfide exchange reaction as reported for lipoamide dehydrogenases. We expressed IRC15 in Escherichia coli and purified the produced protein to conduct a detailed biochemical characterization. Here, we show that Irc15p is a dimeric protein with one FAD per protomer. Photoreduction of the protein generates the fully reduced hydroquinone without the occurrence of a flavin semiquinone radical. Similarly, reduction with NADH or NADPH yields the flavin hydroquinone without the occurrence of intermediates as observed for lipoamide dehydrogenase. The redox potential of Irc15p was ?313 ± 1 mV and is thus similar to lipoamide dehydrogenase. Reduced Irc15p is oxidized by several artificial electron acceptors such as potassium ferricyanide, 2,6‐dichlorophenol‐indophenol, 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide, and menadione. However, disulfides such as cystine, glutathione, and lipoamide were unable to react with reduced Irc15p. Limited proteolysis and SAXS‐measurements revealed that the NADH‐dependent formation of hydrogen peroxide caused a substantial structural change in the dimeric protein. Therefore, we hypothesize that Irc15p undergoes a conformational change in the presence of elevated levels of hydrogen peroxide, which is a putative biomarker of oxidative stress. This conformational change may in turn modulate the interaction of Irc15p with other key players involved in regulating microtubule dynamics.     

Melatonin attenuates methotrexate‐induced oxidative stress and renal damage in rats

Nephrotoxicity is an adverse side effect of methotrexate (MTX) chemotherapy. The present study verifies whether melatonin, an endogenous antioxidant prevents MTX‐induced renal damage. Adult rats were administered 7 mg/kg body weight MTX intraperitoneally for 3 days. In the melatonin pretreated rats, 40 mg/ kg body weight melatonin was administered daily intraperitoneally 1 h before the administration of MTX. The rats were killed 12 h after the final dose of MTX/vehicle. The kidneys were used for light microscopic and biochemical studies. The markers of oxidative stress were measured along with the activities of the antioxidant enzymes and myeloperoxidase activity in the kidney homogenates. Pretreatment with melatonin reduced MTX induced renal damage both histologically and biochemically as revealed by normal plasma creatinine levels. Melatonin pretreatment reduced MTX induced oxidative stress, alteration in the activity of antioxidant enzymes as well as elevation in myeloperoxidase activity. The results suggest that melatonin has the potential to reduce MTX induced oxidative stress, neutrophil infiltration as well as renal damage. As melatonin is an endogenous antioxidant and is non‐toxic even in high doses it is suggested that melatonin may be beneficial in minimizing MTX induced renal damage in humans. Copyright © 2010 John Wiley & Sons, Ltd.     

基于氧化应激与细胞凋亡探究双酚A慢性暴露致小鼠肾毒性作用机制

双酚A (bisphenol A, BPA)被广泛应用于生产环氧树脂和聚碳酸酯塑料等制品,在强酸、强碱或高温条件下,BPA被释放出来,然后渗入环境中。在大多数生物液体中都检测到了不同浓度的BPA,BPA的存在已被证明与许多慢性疾病密切相关,包括慢性肾病(chronic kidney disease,CKD)。然而,关于BPA的有害作用及其对CKD的不良影响知之甚少。为了探讨BPA对动物肾毒性的作用机制,本研究通过向饮水中加入0.01、0.1和1 mg/L的BPA,暴露于雌性小鼠4周后,交配和怀孕的雌性小鼠持续接触BPA,直到断奶;F1代3周龄雄性仔鼠继续口服相同剂量的BPA,持续10周。结果表明,0.1mg/L和1mg/LBPA处理组小鼠的肾脏损伤严重,血清中肾脏功能指标尿素氮(urea nitrogen,UN)、肌酐(creatinine,CR)和尿酸(uric acid,UA)的含量均发生显著升高(P<0.05);肾脏组织形态结构被损害;肾脏抗氧化相关基因在mRNA和蛋白水平上的表达显著降低(P<0.05),包括谷胱甘肽硫转移酶(glutathione-S-transf...     

Alpha lipoic acid prevents doxorubicin‐induced nephrotoxicity by mitigation of oxidative stress,inflammation, and apoptosis in rats

This study aimed to evaluate the protective effects of alpha lipoic acid (ALA) against doxorubicin (DOX)‐induced nephrotoxicity in rats. A single dose of DOX (7.5 mg/kg i.v.) induced nephrotoxicity evidenced by significant elevations in kidney weight, kidney/body weight ratio, serum urea, creatinine, tumor necrosis factor alpha, and renal contents of malondialdehyde, nitric oxide, cyclooxygenase‐2, and caspase‐3. Also, it causes significant reduction in final body weight, serum albumin, renal contents of reduced glutathione and superoxide dismutase activity. Histopathological changes in the kidney tissue confirmed the nephrotoxic effect. In contrast, pretreatment with ALA (50 mg/kg, orally) for 14 days before DOX and for 7 days after DOX administration mitigated renal toxicity evidenced by greater improvement in the examined oxidative stress, inflammation, and apoptosis parameters. In conclusion, ALA had promising protective effects against DOX‐induced nephrotoxicity that might be attributed to its antioxidant, anti‐inflammatory, and antiapoptoic activities.     

Ondansetron enhanced diclofenac‐induced nephrotoxicity in mice

This study was performed to investigate the effect of ondansetron, a serotonin receptor (5‐HT3) antagonist, in the alleviation of diclofenac‐induced kidney injuries. NMRI mice were randomly divided into six groups and treated with (A) untreated control group, (B) diclofenac (100 mg/kg), (C) ondansetron (1 mg/kg), (D to F) ondansetron (0.1, 0.5, and 1 mg/kg, respectively) and diclofenac (100 mg/kg) for last 3 days of experiment. The oxidative stress tests strongly demonstrated the negative synergistic effects of diclofenac and ondansetron, regarding the observation of dose‐dependent enhancement of malondialdehyde concentration, and reduction of glutathione content, and superoxide dismutase and catalase activity. Histopathological analyses revealed dose‐dependent tubular epithelial cells degeneration, outstanding mononuclear cells infiltration, clear necrosis at the papillary region of kidney, dilation, and vascular hyperemia in mice kidney tissues treated with ondansetron and diclofenac. Conclusively, these findings suggested the possible ondansetron‐diclofenac interaction through the induction of oxidative stress.     

Stn1 is critical for telomere maintenance and long‐term viability of somatic human cells

Disruption of telomere maintenance pathways leads to accelerated entry into cellular senescence, a stable proliferative arrest that promotes aging‐associated disorders in some mammals. The budding yeast CST complex, comprising Cdc13, Stn1, and Ctc1, is critical for telomere replication, length regulation, and end protection. Although mammalian homologues of CST have been identified recently, their role and function for telomere maintenance in normal somatic human cells are still incompletely understood. Here, we characterize the function of human Stn1 in cultured human fibroblasts and demonstrate its critical role in telomere replication, length regulation, and function. In the absence of high telomerase activity, shRNA‐mediated knockdown of hStn1 resulted in aberrant and fragile telomeric structures, stochastic telomere attrition, increased telomere erosion rates, telomere dysfunction, and consequently accelerated entry into cellular senescence. Oxidative stress augmented the defects caused by Stn1 knockdown leading to almost immediate cessation of cell proliferation. In contrast, overexpression of hTERT suppressed some of the defects caused by hStn1 knockdown suggesting that telomerase can partially compensate for hStn1 loss. Our findings reveal a critical role for human Stn1 in telomere length maintenance and function, supporting the model that efficient replication of telomeric repeats is critical for long‐term viability of normal somatic mammalian cells.     

Metformin and silymarin afford protection in cyclosporine A induced hepatorenal toxicity in rat by modulating redox status and inflammation

The use of cyclosporine A (CsA) as an immunosuppressive agent is often limited owing to its hepatotoxic and nephrotoxic properties. The present study was designed to evaluate the protective effect of metformin and silymarin in a rat model of CsA induced hepatorenal toxicity. The study included seven groups of Wistar albino rats (n = 6 per group): normal control, experimental control (CsA alone, 25 mg/kg), CsA + metformin (50 and 500 mg/kg), CsA + silymarin (50 and 200 mg/kg) and CsA + vitamin E (100 mg/kg). All the drugs were given daily for a period of 21 days by oral gavage and their effect was evaluated on serum levels of organ function markers (serum glutamate pyruvate transaminase, serum glutamate oxaloacetate transaminase, bilirubin, urea/blood urea nitrogen, creatinine), markers of oxidative stress (thiobarbituric acid reactive substances, glutathione, superoxide dismutase), inflammation (nitrite, myeloperoxidase, tumour necrosis factor‐alpha, prostaglandin E₂), apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labelling positivity) in addition to tissue histology, cyclooxygenase (COX)‐2 and inducible nitric oxide synthase (iNOS) immunoreactivity. Administration of metformin and silymarin along with CsA ameliorated functional damage to liver and kidneys in a dose‐dependent manner. Significant and comparable improvement in the tissue levels of oxidative stress, inflammation, apoptotic markers was also observed following treatment with both the test drugs. Normalization of histology scores, as well as COX‐2 and iNOS immunoreactivity scores, further strengthened these findings. The hepatoprotective and nephroprotective effects of metformin and silymarin were comparable and matched with that of reference drug, vitamin E. The findings of the present study suggest that both metformin and silymarin have a potential for clinical use in patients receiving long‐term CsA treatment to maintain their liver and kidney functions.