Melatonin prevents overproduction of reactive oxygen species and vascular dysfunction induced by cyclophosphamide.

Aims: Overproduction of reactive oxygen species (ROS) is a pathologic hallmark of cyclophosphamide toxicity. For this reason, antioxidant compounds emerge as promising tools for preventing tissue damage induced by cyclophosphamide. We hypothesized that melatonin would display cytoprotective action in the vasculature by preventing cyclophosphamide-induced oxidative stress.

Materials And Methods: Male C57BL/6 mice (22-25 g) were injected with a single dose of cyclophosphamide (300 mg/kg; i.p.). Mice were pretreated or not with melatonin (10 mg/kg/day, i.p.), given during 4 days before cyclophosphamide injection. Functional (vascular reactivity) and oxidative/inflammatory patterns were evaluated at 24 h in resistance arteries. The antioxidant action of melatonin was assessed in vitro in cultured vascular smooth muscle cells (VSMCs) of mesenteric arteries.

Key Findings: Cyclophosphamide induced ROS generation in both mesenteric arterial bed (MAB) and cultured VSMCs, and this was normalized by melatonin. Cyclophosphamide-induced ROS generation and lipoperoxidation in the bladder and kidney was also prevented by melatonin. Increased levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 were detected in the MAB of cyclophosphamide-treated mice, all of which were prevented by melatonin. Functional assays using second-order mesenteric arteries of cyclophosphamide-treated mice revealed a decrease in vascular contractility. Melatonin prevented vascular hypocontractility in the cyclophosphamide group. Melatonin partially prevented the decrease in myeloperoxidase (MPO) and N-acetyl-beta-D-glucosaminidase (NAG) activities in the MAB of the cyclophosphamide group.

Significance: Melatonin may constitute a novel and promising therapeutic approach for management of the toxic effects induced by cyclophosphamide in the vasculature.