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The cytoprotective peptide humanin is induced and neutralizes Bax after pro‐apoptotic stress in the rat testis
Author(s) -
Jia Y.,
Lue Y.H.,
Swerdloff R.,
Lee K.W.,
Cobb L. J.,
Cohen P.,
Wang C.
Publication year - 2013
Publication title -
andrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.947
H-Index - 43
eISSN - 2047-2927
pISSN - 2047-2919
DOI - 10.1111/j.2047-2927.2013.00091.x
Subject(s) - apoptosis , cytosol , endocrinology , endogeny , medicine , germ cell , mitochondrion , chemistry , p38 mitogen activated protein kinases , biology , phosphorylation , protein kinase a , microbiology and biotechnology , biochemistry , enzyme , gene
Summary We have previously demonstrated that the mitochondria‐derived cytoprotective peptide humanin ( HN ), when administered intratesticularly to rats, rescues germ cells from apoptosis secondary to testicular stress of hormonal deprivation induced by gonadotropin‐releasing hormone antagonist (Gn RH ‐A). To decipher the cellular mechanisms of HN action in the amelioration of Gn RH ‐A‐induced germ cell apoptosis, adult male rats received the following treatments for 5 days: (i) daily intratesticular ( IT ) injections with saline (control); (ii) a single subcutaneous injection of Gn RH ‐A on Day 1 and daily IT injection of saline; (iii) daily IT injection of synthetic HN ; and (iv) Gn RH ‐A injection on Day 1 and daily IT injection of HN (Gn RH ‐A+ HN ). HN alone had no effect on germ cell apoptosis. Gn RH ‐A increased germ cell apoptosis and BAX in the testicular mitochondrial fractions. Synthetic HN decreased germ cell apoptosis induced by Gn RH ‐A and BAX in the mitochondria. We deduced that the cytoprotective action of synthetic HN on Gn RH ‐A‐induced germ cell apoptosis was mediated by attenuating p38 mitogen‐activated protein kinase activity and increasing STAT 3 phosphorylation. The effect of synthetic HN on the expression of endogenous rat HN in the testis was studied using rat HN specific antibody. Gn RH ‐A treatment increased, but concomitant treatment with synthetic HN reduced endogenous rat HN expression in both cytosolic and mitochondrial fractions in testis. Co‐immunoprecipitation experiments demonstrated that the increased rat HN was physically associated with BAX in the cytosolic testicular fractions after Gn RH ‐A treatment. Double‐immunofluorescence staining confirmed the co‐localization of BAX and rat HN in the cytoplasm of Leydig cells and spermatocytes after Gn RH ‐A treatment. We conclude that the cytoprotective effect of exogenously administered synthetic HN is mediated by interactions of endogenous rat HN with BAX in the cytoplasm preventing the entry of BAX to the mitochondria to govern the fate of germ cell survival or death during pro‐apoptotic stress to the testis in rats.