Protective Effect of Leuprorelin on Radiation-induced Intestinal Toxicity

Background/Aim: Patients with prostate cancer treated with neoadjuvant androgen ablation experience less radiation-induced intestinal toxicity, mostly due to a reduction of the volume of normal tissue exposed to high radiation doses. We aimed to evaluate if the anti-androgenic drug leuprorelin itself exerts a protective effect on irradiated bowel. Materials and Methods: Female, intact and castrated male C57BL/6J mice underwent 12-Gy total body irradiation, with or without a three-month leuprorelin (0.054 mg/kg/month i.p.) pre-treatment. After 24-72 h, mice were sacrificed and intestinal segments collected for histological, immunohistochemical and molecular analyses. Results: Leuprorelin markedly reduced radiation-induced jejunal and colonic histological alterations in mice, increased the number of regenerating crypts vs. irradiation, and reduced radiation-induced nitrotyrosine immunoreactivity. Leuprorelin significantly reduced radiation-induced matrix metallo-proteinase-2 (Mmp2) and -13, collagen 1 and -3, transforming growth factor-beta (Tgfb), p53, interleukin 6 (Il6), and B-cell lymphoma 2 (Bcl2)-associated X protein (Bax) gene expressions, and nuclear factor-kappa B (NF kappa B) and TGF beta protein expression, and hampered radiation-induced BCL2 protein down-regulation. Conclusion: Leuprorelin protects mice from radiation-induced intestinal injury, likely through a reduction of tissue oxidative stress. These findings give a biological interpretation to clinical observations of improved intestinal tolerance in patients undergoing androgen ablation before RT.