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Background: Nephrotoxicity is one of the adverse side effects of methotrexate (MTX) chemotherapy. The mechanism of renotoxicity of MTX is not fully understood. It is essential to understand the mechanism of nephrotoxicity of MTX in order to diminish the side effects and hence maximize the benefits of chemotherapy. Objectives: The aim of the study was to verify whether oxidative stress and neutrophil infiltration play a role in MTX-induced renal damage using a rat model. Methods: Adult male rats were administered MTX at the dose of 7 mg/kg body weight intraperitoneally for 3 consecutive days and sacrificed 12 or 24 h after the last dose. Vehicle-treated rats served as controls. The kidneys were removed and used for light microscopic and biochemical studies. Myeloperoxidase activity, a marker of neutrophil infiltration was measured in kidney homogenates along with the markers of oxidative damage including protein carbonyl content, protein thiol and malondialdehyde. The activities of the antioxidant enzymes, namely glutathione peroxidase, glutathione S-transferase, superoxide dismutase and catalase, were also assayed. Results: MTX treatment induced damage to the glomeruli and tubules. Plasma creatinine levels in the MTX-treated rats were significantly elevated compared with controls. A significant increase in myeloperoxidase activity (p < 0.05) was observed in the kidneys of MTX-treated rats. Protein carbonyl content and malondialdehyde, sensitive and reliable markers of oxidative damage to proteins and lipids, respectively, were significantly elevated (p < 0.01) in the kidneys of MTX-treated rats compared with controls. The activities of the antioxidant enzymes, namely, superoxide dismutase and glutathione peroxidase, were significantly elevated (p < 0.01 and p < 0.05, respectively) in kidneys of rats following MTX treatment. Conclusion: The results of the present study provide evidence for the role of neutrophil infiltration and oxidative stress in MTX-induced renal damage. Administration of inhibitors of myeloperoxidase or scavenging hypochlorous acid, the product of myeloperoxidase, by supplementation with antioxidants as an adjuvant therapy may be promising in alleviating the renal side effect of MTX.

The efficacy of methotrexate (MTX), a widely used chemotherapeutic drug, is limited by its gastrointestinal toxicity and the mechanism of which is not clear. The present study investigates the possible role of mitochondrial damage in MTX-induced enteritis. Small intestinal injury was induced in Wistar rats by the administration of 7 mg kg−1 body wt. MTX intraperitoneally for 3 consecutive days. MTX administration resulted in severe small intestinal injury and extensive damage to enterocyte mitochondria. Respiratory control ratio, the single most useful and reliable test of mitochondrial function, and 3-(4,5-dimethylthiazol-2-yll)-2,5-diphenyltetrazolium bromide reduction, a measure of cell viability were significantly reduced in all the fractions of MTX-treated rat enterocytes. A massive decrease (nearly 70%) in the activities of complexes II and IV was also observed. The results of the present study suggest that MTX-induced damage to enterocyte mitochondria may play a critical role in enteritis. MTX-induced alteration in mitochondrial structure may cause its dysfunction and decreases the activities of the electron chain complexes. MTX-induced mitochondrial damage can result in reduced adenosine triphosphate synthesis, thereby interfering with nutrient absorption and enterocyte renewal. This derangement may contribute to malabsorption of nutrients, diarrhea, and weight loss seen in patients on MTX chemotherapy.

Cyclophosphamide (CP) is an antineoplastic agent that is used for the treatment of many neoplastic diseases. Hemorrhagic cystitis (HC) is a major dose limiting side effect of CP. Recent studies show that aminogaunidine, an inhibitor of inducible nitric oxide synthase is a potent antioxidant and prevents changes caused by oxidative stress such as depletion of antioxidant activity and tissue injury. The purpose of the study is to investigate the effect of aminoguanidine on parameters of oxidative stress, antioxidant enzymes and bladder injury caused by CP. Adult male rats were randomly divided into four groups. Control rats were administered saline; the AG control group received 200 mg/kg body wt of aminoguanidine; The CP group received a single injection of CP at the dose of 150 mg/kg body wt intraperitoneally. The CP þAG group received aminoguanidine (200 mg/kg body wt) intraperitoneally 1 h before the administration of CP. The rats were sacrificed 16 h after CP/saline administration. The bladder was used for light microscopic studies and biochemical studies. The markers of oxidative damage including protein carbonyl content, protein thiol, malondialdehyde and conjugated dienes were assayed in the homogenates along with the activities of the antioxidant enzymes, superoxide dismutase, glutathione peroxidase, catalase, and glutathione reductase and glutathione S transferase. In the bladders of CP treated rats edema of lamina propria with epithelial and sub-epithelial hemorrhage was seen. All the parameters of oxidative stress that were studied were significantly elevated in the bladders of CP treated rats. The activities of the antioxidant enzymes were significantly lowered in the bladders of CP treated rats. Aminoguanidine pretreatment prevented CP-induced oxidative stress, decrease in the activities of anti-oxidant enzymes and reduced bladder damage. The results of the present study suggest the antioxidant role for aminoguanidine in CP-induced bladder damage.

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