Melanocortin 4 receptor activation protects against testicular ischemia-reperfusion injury by triggering the cholinergicantiinflammatory pathway

Melanocortins (MC) trigger a vagus nerve-mediated cholinergic-antiinflammatory pathway projecting to the testis. We tested whether pharmacological activation of brain MC receptors might protect the testis from the damage induced by ischemia-reperfusion. Adult male rats were subjected to 1-h testicular ischemia, followed by 24-h reperfusion [testicular ischemia-reperfusion (TI/R)]. Before TI/R, groups of animals were subjected to bilateral cervical vagotomy, or pretreated with the nicotinic acetylcholine receptor antagonist chlorisondamine or the selective MC receptor antagonist HS024. Immediately after reperfusion, rats were ip treated with saline or the MC analog [Nle 4,D-Phe 7]alpha-melanocyte-stimulating hormone (NDP-alpha-MSH) (340 ug/kg). We evaluated testicular IL-6 and TNF-alpha by Western blot analysis and organ damage by light microscopy. Some experimental groups were prepared for neural efferent activity recording along the vagus nerve starting 30 min after treatment with ND Palpha-MSH or saline, and for a 30-min period. Additional groups of TI/R rats were treated for 30 d with saline, ND Palpha-MSH, chlorisondamine plus NDP-alpha-MSH, or HS024 plus NDP alpha-MSH to evaluate spermatogenesis, organ damage, and the apoptosis machinery. After a 24-h reperfusion, in TI/R saline-treated rats, there was an increase in IL-6 and TNFalpha expression and a marked damage in both testes. ND Palpha-MSH inhibited IL-6 and TNF-alpha expression, decreased histological damage, and increased neural efferent activity. Furthermore, NDPalpha-MSH administration for 30 d greatly improved spermatogenesis, reduced organ damage, and inhibited apoptosis. All positive NDPalphaMSH effects were abrogated by vagotomy, chlorisondamine, or HS024. Our data suggest that selective MC4 receptor agonists might be therapeutic candidates for the management of testicular torsion.