Open AccessEstrogen inhibits starvation‐induced apoptosis in osteocytes by a redox‐independent process involving association of JNK and glutathione S‐transferase P1‐1
Author(s) -
Domazetovic Vladana,
Fontani Filippo,
Marcucci Gemma,
Iantomasi Teresa,
Brandi Maria Luisa,
Vincenzini Maria Teresa
Publication year - 2017
Publication title -
febs open bio
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.718
H-Index - 31
ISSN - 2211-5463
DOI - 10.1002/2211-5463.12216
Subject(s) - osteocyte , chemistry , oxidative stress , rankl , sclerostin , apoptosis , glutathione , microbiology and biotechnology , endocrinology , caspase 3 , kinase , medicine , activator (genetics) , osteoblast , programmed cell death , signal transduction , receptor , biology , biochemistry , wnt signaling pathway , in vitro , enzyme
Estrogen deficiency causes bone loss as a result of microdamage, oxidative stress, and osteocyte apoptosis. A relationship between oxidative stress‐induced apoptosis, c‐Jun N‐terminal kinase ( JNK ) activation, and expression of factors involved in bone remodeling has been demonstrated in osteocytes. However, the molecular regulation of these events in osteocytes treated with 17β‐estradiol (17β‐E2) remains unexplored. The MLO ‐Y4 murine osteocyte‐like cell line was used as a model to study starvation‐induced apoptosis and ROS production during 17β‐E2 treatment. Expression of glutathione S‐transferase P1‐1 ( GSTP 1‐1), receptor activator kB ligand ( RANKL ), osteoprotegerin ( OPG ), sclerostin, and kinases activation were measured by western blot. In addition, the GSTP 1‐1/ JNK association was assessed by immunoprecipitation, and GSTP 1‐1 involvement in the osteocyte response to 17β‐E2 was detected by specific si RNA transfection. 17β‐E2 prevents starvation‐induced apoptosis ( DNA fragmentation and caspase activation), the increase in sclerostin expression and the RANKL / OPG ratio, which are all related to JNK activation due to oxidative stress in osteocytes. This occurs through GSTP 1‐1 overexpression, which can inhibit JNK activation by formation of a GSTP 1‐1/ JNK complex. No early antioxidant action of 17β‐E2 has been found but the estrogen effect is similar to N‐acetylcysteine which, by increasing the intracellular redox state, maintains JNK bound to GSTP 1‐1. Thus, the antiapoptotic and osteogenic effect of 17β‐E2 in MLO ‐Y4 occurs by a redox‐independent process involving GSTP 1‐1/ JNK association. This study clarifies at molecular level the effect of 17β‐E2 on osteocyte activity and identifies a possible role of GSTP 1‐1 and JNK activity in bone remodeling and repair mechanisms.