Cellular and functional evidence for a protective action of neurosteroids against vincristine chemotherapy-induced painful neuropathy.

Painful neuropathy is a major side-effect limiting cancer chemotherapy. Therefore, novel strategies are required to suppress the neuropathic effects of anticancer drugs without altering their chemotherapeutic effectiveness. By combining biochemical, neuroanatomical/neurochemical, electrophysiological and behavioral methods, we demonstrated that progesterone-derived neurosteroids including 5alpha-dihydroprogesterone and 3alpha,5alpha-tetrahydroprogesterone suppressed neuropathic symptoms evoked in naive rats by vincristine. Neurosteroids counteracted vincristine-induced alterations in peripheral nerves including 2',3'-cyclic nucleotide 3'-phosphodiesterase, neurofilament-200 kDa and intraepidermal nerve fiber repression, nerve conduction velocity, and pain transmission abnormalities (allodynia/hyperalgesia). In skin-tumor rats generated with carcinosarcoma-cells, vincristine, which suppressed the skin tumor and restored normal blood concentration of vascular endothelial growth factor (VEGF), reproduced neuropathic side-effects. Administered alone, neurosteroids did not affect the tumor and VEGF level. Combined with vincristine, neurosteroids preserved vincristine anti-tumor action but counteracted vincristine-induced neural side-effects. Together, these results provide valuable insight into the cellular and functional mechanisms underlying anticancer drug-induced neuropathy and suggest a neurosteroid-based strategy to eradicate painful neuropathy.