Oral glutamine attenuates cyclophosphamide-induced oxidative stress in the bladder but does not prevent hemorrhagic cystitis in rats

Abstract

Cyclophosphamide (CP) is widely used in the treatment of cancer and non-malignant disease states such as rheumatoid arthritis. Hemorrhagic cystitis is a major dose-limiting side effect of CP. The incidence of this side effect is related to the dosage and can be as high as 75%. Elimination of the side effects of CP can lead to better tolerance of the drug, and a more efficient therapy can be achieved for patients in need of CP treatment. Several studies have demonstrated that oxidative stress and neutrophil infiltration play important roles in CP-induced bladder damage. Glutamine is utilized under clinical conditions for preventing chemotherapeutic drug-induced side effects, based on its ability to attenuate oxidative stress. The aim of the study is to verify whether glutamine prevents CP-induced oxidative stress and bladder damage using a rat model. Adult male rats were administered 150 mg/kg body weight of CP intraperitoneally. Glutamine pretreated rats were administered 1 g/kg body weight of glutamine orally 2 h before the administration of CP. Vehicle/glutamine-treated rats served as controls. All the rats were killed 16 h after the dose of CP/vehicle. The urinary bladders were removed and used for light microscopic and biochemical studies. The markers of oxidative stress including malondialdehyde content, protein carbonyl content, protein thiol, and myeloperoxidase activity, a marker of neutrophil infiltration, were measured in bladder homogenates. CP treatment induced hemorrhagic cystitis in the rats. Pretreatment with glutamine significantly reduced CP-induced lipid peroxidation (p < 0.01), protein oxidation (p < 0.01), and increase in myeloperoxidase activity (p < 0.05). However, it did not prevent CP-induced bladder damage. The results of the present study show that glutamine pretreatment does not attenuate CP-induced hemorrhagic cystitis, although it prevents CP-induced oxidative stress and neutrophil infiltration significantly. It is therefore necessary to clarify the utility of glutamine as a chemoprotective agent before it is recommended in the market as a nutrient supplement.

Fig. 1

Light microscopy of the bladders of control rats and experimental rats. Original magnification, ×100. a Saline control rats with normal morphology. Arrow points to folded mucosa, with epithelium showing tight packing of cells and dense connective tissue in lamina propria. Subepithelial crypts also seen. No hemorrhage found. b Glutamine-treated rats with normal epithelium and lamina propria. c Bladder from cyclophosphamide-treated rat showing edema of epithelium, and it appears that epithelium has been breached. Vascular changes in lamina propria are apparent. d Bladder from GLN + CP-treated rat showing degeneration of the epithelium, edema in the lamina propria, and erosion of the mucosa

Fig. 2

MDA levels in the bladders of control rats and experimental rats. Data represent mean ± SD of five to seven rats. *P < 0.01 vs control, GLN, ^#P < 0.01 vs CP

Fig. 3

Protein carbonyl content in the bladders of control rats and experimental rats. Data represent mean ± SD of five to seven rats. *P < 0.01 vs control, GLN, ^#P < 0.01 vs CP

Fig. 4

Protein thiol in the bladders of control rats and experimental rats. Data represent mean ± SD of 5–7 rats. *P < 0.01 vs control, ^$P < 0.01 vs GLN

Fig. 5

MPO activity in the bladders of control rats and experimental rats. Data represent mean ± SD of five to seven rats. *P < 0.01 vs control, GLN, ^#P < 0.05 vs CP