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CD40 ligand reversal of dexamethasone‐induced osteoblast apoptosis as measured by a colorimetric caspase‐3 assay
Author(s) -
Jones Daniel R.,
Jones Amber L.,
Bainbridge Carolyn R.,
Hoffman Jolie A.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.774.8
Subject(s) - dexamethasone , apoptosis , osteoblast , glucocorticoid , chemistry , caspase 3 , ligand (biochemistry) , caspase , medicine , pharmacology , endocrinology , in vitro , biochemistry , programmed cell death , receptor
Long‐term glucocorticoid therapy is one of the leading causes of osteoporosis. Glucocorticoid‐induced osteoporosis (GIOP) is investigated by treating osteoblasts with dexamethasone, a synthetic glucocorticoid known to produce subsequent apoptosis in the MC3T3‐E1 bone cell model. It is also known that dexamethasone‐induced apoptosis in MC3T3‐E1 cells can be significantly reversed in the presence of CD40 ligand. The mechanisms of this reversal to apoptosis are presently unknown. In order to determine if activated caspase‐3, a key mediator of apoptosis, was affected by CD40 ligand, MC3T3‐E1 cells were assayed for caspase‐3 activity following treatment with either 10 −6 M dexamethasone or 10 −6 M dexamethasone subsequent to pre‐treatment with 1.25 micrograms/ml CD40 ligand. Caspase‐3 activity determinations in cell extracts were made by measurement of absorbance at 405 nm following cleavage of the colorimetric Ac‐DEVD‐pNA substrate. Results indicate a 2‐fold induction of caspase‐3 activity on dexamethasone treatment (p<0.05) with CD40 ligand reducing that activation by 50%. These findings validate our in vitro model for GIOP and allow us to further investigate the mechanism of CD40 ligand's protective role. This research was funded through an Indiana Academy of Science senior research grant and an Indiana Wesleyan University‐administered Lilly Faculty Scholarship Award.