Targeting superoxide dismutase to renal proximal tubule cells inhibits nephrotoxicity of cisplatin and increases the survival of cancer-bearing mice

Bismuth Reduces Cisplatin-Induced Nephrotoxicity Via Enhancing Glutathione Conjugation and Vesicular Transport

Bismuth drugs have long been used against gastrointestinal diseases, especially the gastric infection of Helicobacter pylori. Cisplatin is a widely used anticancer drug that tends to accumulate at renal proximal tubules and causes severe nephrotoxicity. It was found that bismuth pretreatment reduces cisplatin-induced nephrotoxicity, but the mechanism of action remains unclear. To understand bismuth’s effect on renal tubules, we profiled the proteomic changes in human proximal tubular cells (HK-2) upon bismuth treatment. We found that bismuth induced massive glutathione biosynthesis, glutathione S-transferase activity, and vesicular transportation, which compartmentalizes bismuth to the vesicles and forms bismuth–sulfur nanoparticles. The timing of glutathione induction concurs that of bismuth-induced cisplatin toxicity mitigation in HK-2, and bismuth enhanced cisplatin sequestration to vesicles and incorporation into bismuth–sulfur nanoparticles. Finally, we found that bismuth mitigates the toxicity of general soft metal compounds but not hard metal compounds or oxidants. It suggests that instead of through oxidative stress reduction, bismuth reduces cisplatin-induced toxicity by direct sequestration.

Therapeutic Potential of Superoxide Dismutase Fused with Cell-Penetrating Peptides in Oxidative Stress-Related Diseases

Superoxide dismutase (SOD) is a well-known cellular antioxidant enzyme. However, exogenous SOD cannot be used to protect tissues from oxidative damage due to the low permeability of the cell membrane. Cell-penetrating peptides (CPPs) are a class of short peptides that can cross the cell membrane. Recombinant fusion protein that fuses SOD protein with CPP (CPP-SOD) can cross various tissues and organs as well as the blood-brain barrier. CPP-SODs can relieve severe oxidative damage in various tissues caused by radiation, ischemia, inflammation, and chemotherapy by clearing the reactive oxygen species, reducing the expression of inflammatory factors, and inhibiting NF-κB/MAPK signaling pathways. Therefore, the clinical application of CPP-SODs provide new therapeutic strategies for a variety of oxidative stress-related disorders, such as Parkinson's disease, diabetes, obesity, cardiac fibrosis, and premature aging.

Regression Modeling of the Antioxidant-to-Nephroprotective Relation Shows the Pivotal Role of Oxidative Stress in Cisplatin Nephrotoxicity

The clinical utility of the chemotherapeutic drug cisplatin is significantly limited by its nephrotoxicity, which is characterized by electrolytic disorders, glomerular filtration rate decline, and azotemia. These alterations are consequences of a primary tubulopathy causing injury to proximal and distal epithelial cells, and thus tubular dysfunction. Oxidative stress plays a role in cisplatin nephrotoxicity and cytotoxicity, but its relative contribution to overall toxicity remains unknown. We studied the relation between the degree of oxidative reduction (provided by antioxidant treatment) and the extent of nephrotoxicity amelioration (i.e., nephroprotection) by means of a regression analysis of studies in animal models. Our results indicate that a linear relation exists between these two parameters, and that this relation very nearly crosses the value of maximal nephroprotection at maximal antioxidant effect, suggesting that oxidative stress seems to be a pivotal and mandatory mechanism of cisplatin nephrotoxicity, and, hence, an interesting, rationale-based target for clinical use. Our model also serves to identify antioxidants with enhanced effectiveness by comparing their actual nephroprotective power with that predicted by their antioxidant effect. Among those, this study identified nanoceria, erythropoietin, and maltol as highly effective candidates affording more nephroprotection than expected from their antioxidant effect for prospective clinical development.

The Evaluation of the Effects of N-Acetylcysteine on Cisplatin-Induced Alterations in Exploratory Activity in Elevated Plus Maze Test in Rats

The aim of this study was to evaluate the potential beneficial effect of N-acetylcysteine (NAC) on cisplatin-induced alterations in anxiety levels in rats, by means of parameters of the exploratory activity obtained in the elevated plus maze (EPM) test. Animals were divided into four groups: control group, cisplatin group (7.5 mg/kg/weekly of cisplatin), N-acetylcysteine group (500 mg/kg/weekly of NAC), and cisplatin plus N-acetylcysteine group (7.5 mg/kg/weekly of cisplatin, and 500 mg/kg/weekly of NAC). After two weeks of treatment, exploratory activity (estimated by means of the number of rearings, head-dippings and the number of total exploratory activity episodes) was significantly reduced in cisplatin group comparing to control values. Although NAC induced no alterations in exploratory activity when applied alone, simultaneous administration with cisplatin resulted in significant attenuation of cisplatin-induced decline in exploratory activity. The exploratory activity gradually decreased in time-dependent manner during five minutes of EPM test in all groups. The results of this study confirmed clear beneficial effect of NAC supplementation against cisplatin- induced neurotoxicity in rats. Antioxidative properties of NAC were manifested through restoration of exploratory activity, confirming that NAC administration can attenuate anxiogenic effect of cisplatin therapy. Those results could recommend NAC supplementation as a potential protection against cisplatin-induced neurotoxicity.

Persistent increase in mitochondrial superoxide mediates cisplatin-induced chronic kidney disease

Severe and recurrent cisplatin-induced acute kidney injury (AKI) as part of standard cancer therapy is a known risk factor for development of chronic kidney disease (CKD). The specific role of superoxide (O₂^•-)-mediated disruption of mitochondrial oxidative metabolism in CKD after cisplatin treatment is unexplored. Cisplatin is typically administered in weekly or tri-weekly cycles as part of standard cancer therapy. To investigate the role of O₂^•- in predisposing patients to future renal injury and in CKD, mice were treated with cisplatin and a mitochondrial-specific, superoxide dismutase (SOD) mimetic, GC4419. Renal function, biomarkers of oxidative stress, mitochondrial oxidative metabolism, and kidney injury markers, as well as renal histology, were assessed to evaluate the cellular changes that occur one week and one month (CKD phase) after the cisplatin insult. Cisplatin treatment resulted in persistent upregulation of kidney injury markers, increased steady-state levels of O₂^•-, increased O₂^•--mediated renal tubules damage, and upregulation of mitochondrial electron transport chain (ETC) complex I activity both one week and one month following cisplatin treatment. Treatment with a novel, clinically relevant, small-molecule superoxide dismutase (SOD) mimetic, GC4419, restored mitochondrial ETC complex I activity to control levels without affecting complexes II–IV activity, as well as ameliorated cisplatin-induced kidney injury. These data support the hypothesis that increased mitochondrial O₂^•- following cisplatin administration, as a result of disruptions of mitochondrial metabolism, may be an important contributor to both AKI and CKD progression.

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Cisplatin-induced AKI and CKD have a negative impact in long-term renal function.

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Cisplatin-induced CKD disrupts mitochondrial metabolism and increases O₂^•- levels.

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SOD mimetic, GC4419 mitigates renal damage and mitochondrial metabolism disruptions.

Mitochondrial function and disturbances in the septic kidney

Per milligram of tissue, only the heart exceeds the kidney's abundance of mitochondria. Not surprisingly, renal mitochondria are most densely concentrated in the epithelium of the nephron, at sites where the chemical work of moving solutes against electrochemical gradients places large and constant demands for adenosine triphosphate. Derangements of renal epithelial mitochondria appear to be a hallmark for diverse forms of acute kidney injury (AKI). The pathogenesis of multiple-organ dysfunction syndrome in sepsis is complex, but a substantial body of experimental and observational human data supports the twin concepts that mitochondrial dysfunction contributes to impaired filtration and that recovery of mitochondrial structure and function is essential for recovery from sepsis-associated AKI. These insights have suggested novel methods to diagnose, stratify, prevent, or even treat this common and deadly complication of critical illness. This review will do the following: (1) describe the structure and functions of healthy mitochondria and how renal energy metabolism relates to solute transport; (2) provide an overview of the evidence linking mitochondrial pathology to renal disease; (3) summarize the mitochondrial lesions observed in septic AKI; (4) analyze the role of mitochondrial processes including fission/fusion, mitophagy, and biogenesis in the development of septic AKI and recovery from this disease; and (5) explore the potential for therapeutically targeting mitochondria to prevent or treat septic AKI.

Antigenotoxic properties of chlorophyll b against cisplatin-induced DNA damage and its relationship with distribution of platinum and magnesium in vivo

The chemotherapeutic agent cisplatin (cDDP) is widely used to treat a variety of solid and hematological tumors. However, cDDP exerts severe side effects, such as nephrotoxicity, neurotoxicity, and bone-marrow suppression. The use of some dietary compounds to protect organs that are not targets in association with chemotherapy has been encouraged. This study evaluated the protective effects of chlorophyll b (CLb) on DNA damage induced by cDDP by use of single-cell gel electrophoresis (SCGE) assays. Further, this investigation also determined platinum (Pt) and magnesium (Mg) bioaccumulation in mice tissues after treatment with CLb alone and/or in association of cDDP (simultaneous treatment) by inductively coupled plasma-mass spectroscopy (ICP-MS). All parameters were studied in peripheral blood cells (PBC), kidneys, and liver of mice after administration of CLb (0.2 or 0.5 mg/kg of body weight [b.w.]), cDDP (6 mg/kg b.w.), and the combination CLb 0.2 plus cDDP or CLb 0.5 plus cDDP. Pt accumulation in liver and kidneys was higher than that found in PBC, while DNA damage was higher in kidneys and liver than in PBC. Further, treatment with CLb alone did not induce DNA damage. Evidence indicates that genotoxic effects produced by cDDP may not be related to Pt accumulation and distribution. In combined treatments, CLb decreased DNA damage in tissues, but the PT contents did not change and these treatments also showed that CLb may be an important source of Mg. Thus, our results indicate that consumption of CLb-rich foods may diminish the adverse health effects induced by cDDP exposure.

Computational modeling of apoptotic signaling pathways induced by cisplatin

Background

Apoptosis is an essential property of all higher organisms that involves extremely complex signaling pathways. Mathematical modeling provides a rigorous integrative approach for analyzing and understanding such intricate biological systems.

Results

Here, we constructed a large-scale, literature-based model of apoptosis pathways responding to an external stimulus, cisplatin. Our model includes the key elements of three apoptotic pathways induced by cisplatin: death receptor-mediated, mitochondrial, and endoplasmic reticulum-stress pathways. We showed that cisplatin-induced apoptosis had dose- and time-dependent characteristics, and the level of apoptosis was saturated at higher concentrations of cisplatin. Simulated results demonstrated that the effect of the mitochondrial pathway on apoptosis was the strongest of the three pathways. The cross-talk effect among pathways accounted for approximately 25% of the total apoptosis level.

Conclusions

Using this model, we revealed a novel mechanism by which cisplatin induces dose-dependent cell death. Our finding that the level of apoptosis was affected by not only cisplatin concentration, but also by cross talk among pathways provides in silico evidence for a functional impact of system-level characteristics of signaling pathways on apoptosis.

Transcriptional up-regulation of SOD1 by CEBPD: a potential target for cisplatin resistant human urothelial carcinoma cells

Bladder cancer is the fourth most common type of cancer in men (ninth in women) in the United States. Cisplatin is an effective agent against the most common subtype, urothelial carcinoma. However, the development of chemotherapy resistance is a severe clinical problem for the successful treatment of this and other cancers. A better understanding of the cellular and molecular events in response to cisplatin treatment and the development of resistance are critical to improve the therapeutic options for patients. Here, we report that expression of the CCAAT/enhancer binding protein delta (CEBPD, C/EBPdelta, NF-IL6beta) is induced by cisplatin in the human bladder urothelial carcinoma NTUB1 cell line and is specifically elevated in a cisplatin resistant subline. Expression of CEBPD reduced cisplatin-induced reactive oxygen species (ROS) and apoptosis in NTUB1 cells by inducing the expression of Cu/Zn-superoxide dismutase (SOD1) via direct promoter transactivation. Several reports have implicated CEBPD as a tumor suppressor gene. This study reveals a novel role for CEBPD in conferring drug resistance, suggesting that it can also be pro-oncogenic. Furthermore, our data suggest that SOD inhibitors, which are already used as anti-angiogenic agents, may be suitable for combinatorial chemotherapy to prevent or treat cisplatin resistance in bladder and possibly other cancers.

Enhancement of aglycone, vitamin K2 and superoxide dismutase activity of black soybean through fermentation with Bacillus subtilis BCRC 14715 at different temperatures

In the present study, the change in the content and activity of some functional constituents including aglycone, the bioactive form of isoflavone, vitamin K2, and superoxide dismutase (SOD) of black soybeans during their solid fermentation with Bacillus subtilis BCRC 14715 at different temperatures (35, 40, 45, and 50 degrees C) for 18 h was investigated. It was generally found that fermentation resulted in an enhancement of these constituents, regardless of fermentation temperature, while varying the fermentation temperature of black soybeans produced variations in the enhancement. The 50 degrees C -fermented black soybean showed the most marked increase in the content of daidzein and genistein aglycone. On the other hand, the highest SOD activity and vitamin K2 content were found in the black soybeans fermented at 45 and 40-45 degrees C, respectively. Thus functional properties of black soybeans can be further improved through fermentation with B. subtilis BCRC 14715.

Renal protection by 3H-1,2-dithiole-3-thione against cisplatin through the Nrf2-antioxidant pathway

Cisplatin is commonly used for the treatment of several solid tumors. However, its clinical use is often limited by renal toxicity. The indirect antioxidant 3H-1,2-dithiole-3-thione (D3T) has been known to protect cells from oxidative damage by up-regulating the expression of antioxidative genes through the transcription factor NF-E2-related factor 2 (Nrf2) pathway. We hypothesized that D3T treatment may be protective against cisplatin-induced nephrotoxicity by enhancing the antioxidative capacity of renal cells. In cultured murine tubular epithelial cells, D3T facilitates the nuclear accumulation of Nrf2 and the subsequent expression of its target genes such as glutamate cysteine ligase (GCL). Increased GSH pool in D3T-treated renal cells appears to be associated with amelioration of cisplatin-mediated cell death. Protective effects of D3T were also observed in mice. Oral administration of D3T (0.25mmol/kg) increased the expression of GCL in mouse kidney, which resulted in suppression of cisplatin-mediated increases in blood urea nitrogen and serum creatinine. Histopathological changes representing cisplatin-induced acute renal failure were also effectively ameliorated by D3T treatment. Collectively, these results indicate that pharmacological activation of the Nrf2 pathway might have a beneficial effect on reducing chemotherapy-associated cytotoxic adverse effects.

The fungal nephrotoxin orellanine simultaneously increases oxidative stress and down-regulates cellular defenses

Confusion of various nephrotoxic Cortinarius species with edible mushrooms occurs every year throughout Europe and North America. The toxin, orellanine (OR), accumulates selectively in renal tubular epithelium with ensuing renal failure after several days as the only clinical manifestation. This study was performed to clarify the mechanisms behind the kidney damage. Sprague-Dawley rats, 100 g bw, received various doses of purified OR ip (0-5 mg/kg bw). One week later, renal function (GFR) was determined (51Cr-EDTA), ascorbyl radicals in venous blood were analyzed using electron spin resonance, and oxidative protein damage was evaluated immunohistochemically. One OR-treated group (3.5 mg/kg) simultaneously received superoxide dismutase (SOD) targeted to tubular epithelium (HC-SOD; 10 mg/kg ip daily for 5 days). RT-PCR was used for analysis of mRNA expression of genes related to oxidative stress. OR caused a dose-dependent decrease in GFR, paralleled by increased levels of ascorbyl radicals and oxidative protein damage. Antioxidant treatment with HC-SOD decreased renal function even more and also increased tissue damage and mortality. Renal mRNA levels for key components in the antioxidative defense were strongly decreased, whereas those for several cytokines were increased. The data strongly suggest that OR nephrotoxicity in vivo is mediated by oxidative stress, including a virtual shutdown of important antioxidative enzymes. We interpret the unexpected effect of HC-SOD in terms of unbalanced SOD and catalase levels in the presence of OR, leading to massive generation of *OH and cell death.

The ameliorative effect of cysteine prodrug L-2-oxothiazolidine-4-carboxylic acid on cisplatin-induced nephrotoxicity in rats

Pathogenesis of nephrotoxicity of the synthetic anticancer drug cisplatin (CP) involves generation of reactive oxygen species and free radicals in the kidney cortex, and cysteine prodrug l-2-oxothiazolidine-4-carboxylic acid (OTC) has been confirmed to have a strong antioxidant action. Therefore, in the present work, we aimed at testing the possible protective or palliative effect of OTC on CP nephrotoxicity in rats. OTC was given at an oral dose of 150 mg/kg/day for 7 days. On day 7, some of these rats were given a single intraperitoneal injection of CP (or vehicle) at a dose of 6 mg/kg. Rats were killed, blood and urine samples were collected, and the kidneys were removed 6 days after CP treatment. Nephrotoxicity was evaluated histopathologically by light microscopy, and biochemically by measuring the concentrations of creatinine and urea in serum, reduced glutathione (GSH) concentration and superoxide dismutase (SOD) activity in renal cortex, and by urinalyses. CP significantly increased the concentrations of urea and creatinine (P < 0.05) by about 128% and 170% respectively. CP treatment reduced cortical GSH concentration by about 34% (P < 0.05), and the activity of SOD by about 28% (P < 0.05). CP treatment significantly increased urine volume and N-acetyl-beta-D-glucosaminidase (NAG) activity, and significantly decreased osmolality and protein concentrations. OTC significantly mitigated all these effects. Sections from saline- and OTC-treated rats showed apparently normal proximal tubules. However, kidneys of CP-treated rats had a moderate degree of necrosis. This appeared to be lessened when CP was given simultaneously with OTC. The concentration of CP in the cortical tissues was not significantly altered by OTC treatment. The results suggested that OTC had ameliorated the histopathological and biochemical indices of nephrotoxicity in rats. Pending further pharmacological and toxicological studies, OTC may potentially be useful as a nephroprotective agent.

Combining cisplatin with cationized catalase decreases nephrotoxicity while improving antitumor activity

Cisplatin is frequently used to treat solid tumors; however, nephrotoxicity due to its reactive oxygen species-mediated effect limits its use. We tested the ability of cationized catalase, a catalase derivative, to inhibit nephrotoxicity in cisplatin-treated mice. Immunohistochemical analysis showed that the catalase derivative concentrated in the kidney more efficiently than native catalase. Repeated intravenous doses of cationized catalase significantly decreased cisplatin-induced changes in serum creatinine, blood urea nitrogen, nitrite/nitrate levels, lactic dehydrogenase activity, and renal total glutathione and malondialdehyde contents. In addition, cationized catalase effectively blunted cisplatin-induced proximal tubule necrosis but had no significant effect on the cisplatin-induced inhibition of subcutaneous tumor growth. Repeated doses of catalase, especially cationized catalase, significantly increased the survival of cisplatin-treated tumor-bearing mice preventing cisplatin-induced acute death. Our studies suggest that catalase and its derivatives inhibit cisplatin-induced nephrotoxicity, thus improving the efficiency of cisplatin to treat solid tumors.

The role of the mitochondria in mediating cytotoxicity of anti-cancer therapies

Optimal cytotoxic anticancer therapy, at the cellular level, requires effective and selective induction of cell death to achieve a net reduction of biomass of malignant tissues. Standard cytotoxic chemotherapeutics have been developed based on the observations that mitotically active cancer cells are more susceptible than quiescent normal cells to chromosomal, microtubular or metabolic poisons. More recent development of molecularly targeted drugs for cancer focuses on exploiting biological differentials between normal and transformed cells for selective eradication of cancers. The common thread of "standard" and "novel" cytotoxic drugs is their ability to activate the apoptosis-inducing machinery mediated by mitochondria, also known as the intrinsic death signaling cascade. The aim of this article is to provide an overview of the role of the mitochondria, an energy-generating organelle essential for life, in mediating death when properly activated by cytotoxic stresses.

Fermentative production of superoxide dismutase with Kluyveromyces marxianus

This work sought to develop a fermentative process for the microbial production of superoxide dismutase (SOD), to overcome extraction from animal tissues. Twenty-eight wild-type yeast strains were screened for SOD productivity. Kluyveromyces marxianus L3 showed the highest SOD activity (62 U mg(-1)) and was used for process development. Oxidative stress conditions and parameters affecting oxygen transfer rate were exploited to improve production. The effects of dilution rate (0.067 vs 0.2 h(-1)), aeration pressure (0.3 vs 1.2 bar) and H(2)O(2) (0 vs 50 mM) were studied during chemostat experiments. Low dilution rate, high pressure and H(2)O(2) resulted in an increase in CuZn-SOD up to 475 U mg(-1). When a regulation of oxygen saturation was applied during batch cultures, CuZn-SOD was progressively higher at 60, 80 and 90% dissolved oxygen tension (DOT) (250, 330 and 630 U mg(-1), respectively). Furthermore, the highest growth rate and biomass yield were achieved at 90% DOT, this being therefore the best DOT condition for high overall productivity. Growth and productivity on different carbon sources were compared. Specific activity was higher on glycerol than on lactose or glucose (496, 454 and 341 U mg(-1), respectively). The highest biomass yield was achieved on lactose. It may be therefore the best substrate for SOD production.

Protective role of l-2-oxothiazolidine-4-carboxylic acid in cisplatin-induced renal injury

BACKGROUND

Oxidative stress and inflammation are implicated in the pathogenesis of cisplatin-induced nephrotoxicity. l-2-oxothiazolidine-4-carboxylic acid (OTC) is a cysteine prodrug, and increases cellular glutathione (GSH). OTC is converted to cysteine by the intracellular enzyme, oxoprolinase. To date, the protective role of OTC on cisplatin-induced renal injury has not been investigated. The purpose of the present study was to examine the protective effect of OTC on cisplatin-induced renal injury and to examine the mechanism of its protection.

METHODS

Mice were treated with cisplatin with or without administration of OTC. The generation of reactive oxygen species (ROS), expression of intercellular adhesion molecule (ICAM)-1 and monocyte chemoattractant protein (MCP)-1 were determined in the kidney using 2',7'-dichlorofluorescein diacetate, immunostaining or western blot analysis. Nuclear factor (NF)-kappaB activity, infiltration of F4/80-positive cells and apoptosis were also investigated in addition to renal function and histology using electrophoretic mobility shift assay, immunostaining, western blot analysis, uridine triphosphate (dUTP) nick-end labelling or periodic acid-Schiff staining. The effect of OTC on superoxide dismutase activity and GSH level in cisplatin-treated normal adult human kidney (HK-2) cells were measured using assay kits.

RESULTS

The administration of OTC resulted in a significant reduction of cisplatin-induced ROS production, the p65 subunit of NF-kappaB translocation into nucleus, expression of ICAM-1, caspase 3 activity, expression of MCP-1 and the infiltration of macrophages into renal tissue. OTC markedly ameliorated renal damage induced by cisplatin through antioxidant and anti-inflammatory effect.

CONCLUSIONS

These results suggest that OTC can be a potential therapeutic agent in cisplatin-induced renal injury through decreasing the ROS levels and activation of NF-kappaB.

Cisplatin up-regulates the in vivo biosynthesis and degradation of renal polyamines and c-Myc expression

Time-dependent changes in polyamine metabolism and c-Myc expression are reported in kidney of mice treated with cisplatin, a widely used anticancer drug. We show that cisplatin significantly induces the expression of two enzymes critical to proper homeostasis of cellular polyamines, ornithine decarboxylase (ODC) and spermidine/spermine N1-acetyltransferase (SSAT). We also document the cross-talk between signalling pathway(s) induced by cisplatin injury to renal tubules and the testosterone/androgen receptor pathway. Their interaction results in a decrease in testosterone-induced ODC activity and ODC mRNA level, and in differential modulation of SSAT expression. Moreover, cisplatin and antifolate CB 3717, another nephrotoxic drug examined, severalfold up-regulate expression of c-Myc mRNA, albeit with different kinetics. However, cisplatin, contrary to CB 3717, does not induce renal hepatocyte growth factor (HGF)/c-Met expression being without effect on HGF mRNA level and significantly down-regulating c-Met transmembrane receptor message. In conclusion, these in vivo studies document significant cisplatin-induced modulation of polyamine biosynthesis/degradation and up-regulation of c-Myc expression, and suggest that c-Myc transcription factor is involved in the induction of ODC in kidney injured with antifolate, but not with cisplatin.

Inhibition of vancomycin-induced nephrotoxicity by targeting superoxide dismutase to renal proximal tubule cells in the rat

Vancomycin, a glycopeptide antibiotic, has a broad spectrum against methicillin-resistant Staphylococcus aureus (MRSA). Because vancomycin induces renal dysfunction, the dose and the duration of its administration are limited. The mechanism of vancomycin-induced renal dysfunction is not known. We recently synthesized a hexamethylenediamine-conjugated cationic superoxide dismutase (AH-SOD) which rapidly accumulates in renal proximal tubule cells and inhibits oxidative injury of the kidney. The present work reports the protective effects of AH-SOD against vancomycin-induced renal dysfunction. Male Wistar rats (200-210 g) were intraperitoneally administered with either 200 or 400 mg/kg of vancomycin twice a day for 7 days. Either 5 mg/kg/day AH-SOD or saline was subcutaneously injected 5 min before every vancomycin injection. Biochemical analysis revealed that plasma levels of blood urea nitrogen and creatinine increased significantly in vancomycin-treated group by an AH-SOD-inhibitable mechanism. Histological examination revealed that vancomycin also elicited a marked destruction of glomeruli and necrosis of proximal tubule by an AH-SOD inhibitable mechanism. These results suggest that oxidative stress underlies the pathogenesis of vancomycin-induced nephrotoxicity and that targeting SOD and/or related antioxidants to renal proximal tubule cells might permit the administration of higher doses of vancomycin sufficient for eradication of MRSA without causing renal injury.

Superoxide dismutase: the balance between prevention and induction of oxidative damage

Cu,Zn-superoxide dismutase (SOD1) has been shown to be effective in several free radical mediated diseases, although some studies have pointed toward SOD1 toxicity at a high concentrations. In the present study, the balance between prevention and induction of damage by SOD1 has been investigated both in vitro and in vivo. In vitro superoxide was generated using xanthine/xanthine oxidase. In vivo superoxide was generated using the redox cycling compound doxorubicin. Furthermore, we determined the pharmacokinetics of lecithinized SOD1 (PC-SOD) in order to compare the results obtained in vivo with those obtained in vitro. It was found that in vitro high concentrations of SOD1 induce hydroxylation of coumarin 3-carboxylic acid (3-CCA). This could be caused by a peroxidative action of SOD1 or formation of the highly reactive hydroxyl radicals. Any signs of toxicity are absent in vivo because these concentrations are not reached. It can be concluded that SOD1 possesses a large therapeutic window and application of SOD1 or its derivatives for strengthening the body's defenses against oxidative stress in a variety of pathologies seems safe.

Protection by a radical scavenger edaravone against cisplatin-induced nephrotoxicity in rats

Acute renal failure is a dose-limiting factor of cisplatin chemotherapy. Here, we show the protective effect of edaravone, a recently developed radical scavenger for clinical use, against cisplatin-induced renal dysfunction in rats. A marked increase in blood urea nitrogen and creatinine in serum, and histological changes including vacuolation, necrosis and protein casts were observed in proximal renal tubules at the fourth day after cisplatin injection (5-10 mg/kg). Repeated injection of edaravone (1-10 mg/kg, i.v. twice a day for 3 days) reversed the cisplatin-induced elevation of blood urea nitrogen and creatinine, and morphological changes in a dose-dependent manner. In particular, the protective effect of edaravone was almost complete at 10 mg/kg. Moreover, the compound was still fully effective, when it was administered only at the second day after cisplatin injection. On the other hand, the glutathione content in renal tissues lowered at the fourth day after cisplatin injection, which was reversed by the late treatment with edaravone. These findings suggest that the clinically available radical scavenger edaravone is potentially useful for the prevention of cisplatin-induced renal toxicity.

Amelioration of cisplatin toxicity by a fermented grain food product

The most noticeable hypothesis regarding the pathogenesis of cisplatin toxicity, seen mainly in kidney and intestine, is oxidative stress, an imbalance between free-radical generating cisplatin and radical scavenging systems. This paper describes the role of the antioxidant system in cisplatin-induced toxicity and the protective effect by a processed grain food (Antioxidant Biofactor: AOB), which has been shown to exhibit strong antioxidant activity. Male Fischer 344 rats were used. They were pre-fed either a basal diet (control, 15 g/day) or the diet supplemented with AOB to provide 6.5% or 20% of total diet throughout the experiment. Cisplatin (5 mg/kg, i.v.) was administered at the start of the experiment, and the animals were sacrificed 5 days later. Blood urea nitrogen (BUN) and plasma creatinine, NO2(-) and NO3(-) (NOx) were determined from the plasma. The levels of 4-hydroxy-2-nonenal (a lipid peroxidation product), 8-hydroxy-deoxyguanosine (8-OHdG, an oxidatively modified DNA adduct) and nitrotyrosine were histologically analyzed. The cisplatin administration resulted in a loss of body weight and elevations of BUN, serum creatinine and NOx levels, whereas AOB supplement reversed these effects. The severe morphological damages induced in the kidney and intestine by the cisplatin administration were markedly improved in the AOB group. The levels of lipid peroxidation, 8-OHdG, and nitrotyrosine all paralleled the morphological damage. The AOB effect was dose dependent. In conclusion, the present study suggests that certain food additives like AOB may be of benefit against the side effects of cisplatin.