Neuroendocrine mechanisms in oxaliplatin-induced hyperalgesic priming.

Stress plays a major role in the symptom burden of oncology patients and can exacerbate cancer chemotherapy-induced peripheral neuropathy (CIPN), a major adverse effect of many classes of chemotherapy. We explored the role of stress in the persistent phase of the pain induced by oxaliplatin. Oxaliplatin induced hyperalgesic priming, a model of the transition to chronic pain, as indicated by prolongation of hyperalgesia produced by prostaglandin E2 (PGE2), in male rats that was markedly attenuated in adrenalectomized rats. A neonatal handling protocol that induces stress-resilience in adult rats prevented oxaliplatin-induced hyperalgesic priming. To elucidate the role of the hypothalamic-pituitary adrenal and sympathoadrenal neuroendocrine stress axes in oxaliplatin CIPN, we used intrathecally administered antisense oligodeoxynucleotides (ODN) directed against mRNA for receptors mediating the effects of catecholamines and glucocorticoids, and their second messengers, to reduce their expression in nociceptors. While oxaliplatin-induced hyperalgesic priming was attenuated by intrathecal administration of β2-adrenergic and glucocorticoid receptor antisense ODNs, oxaliplatin-induced hyperalgesia was only attenuated by β2-adrenergic receptor antisense. Administration of pertussis toxin, a non-selective inhibitor of Gαi/o proteins, attenuated hyperalgesic priming. Antisense ODNs for Gαi1 and Gαo also attenuated hyperalgesic priming. Furthermore, antisense for protein kinase C epsilon, a second messenger involved in Type I hyperalgesic priming, also attenuated oxaliplatin-induced hyperalgesic priming. Inhibitors of second messengers involved in the maintenance of Type I (cordycepin) and Type II (SSU6656 and U0126) hyperalgesic priming both attenuated hyperalgesic priming. These experiments support a role for neuroendocrine stress axes in hyperalgesic priming, in male rats with oxaliplatin CIPN.