5-Aminolevulinic acid combined with ferrous iron ameliorates scrotal heat stress-induced spermatogenic damage through inhibiting MAPK pathway and inducing CD4+Foxp3+ Treg generation by enhancing HO-1 expression

Abstract Objective to explore whether 5-Aminolevulinic acid combined with ferrous iron(5-ALA/Fe2+) could protect testicular tissues damage of mice subjected to heat stress (HS) and provide its underlying mechanisms. Methods 5-ALA/Fe2+ was administered intragastrically to mice for 10 days, then exposed to a scrotal heat stress at 43℃ for 20 minutes on third day. Testes were harvested for morphologic and histopathological examination, oxidative stress, apoptosis, heme oxygenase-1 (HO-1) and inflammation detection. The mitogen-activated protein kinases (MAPK) signaling pathway in testis and CD4+FoxP3+regulatory T(Treg) cells in spleen were also detected. Results Compared to control group, the testis weight decreased and histological damage severed in HS group. Besides, HS also increased the oxidative stress, apoptosis and inflammation in testis. However, these indicators were ameliorated after 5-ALA/Fe2+ treatment but deteriorated after receiving ZnPPIX. The expression of HO-1 was increased both in HS group and 5-ALA/Fe2+ group. The protein expression levels of MAPK proteins were activated by HS and inhibited by 5-ALA/Fe2+. The CD4+FoxP3+ Treg generation was reduced by HS and increased by 5-ALA/Fe2+. Conclusion In this study, we have demonstrated that 5-ALA/Fe2+ ameliorated the spermatogenic damage induced by scrotal heat stress via up-regulating the expression of HO-1 and inhibiting MAPK mediated oxidative stress and apoptosis and inducing CD4+Foxp3+ Tregs to inhibit the inflammation induced by HS in mice.