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Prostaglandin E 2 stimulates insulin‐like growth factor binding protein‐4 expression and synthesis in cultured human articular chondrocytes: Possible mediation by Ca ++ ‐calmodulin regulated processes
Author(s) -
Di Battista J.A.,
Doré S.,
Morin N.,
He Y.,
Pelletier J.P.,
MartelPelletier J.
Publication year - 1997
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(19970601)65:3<408::aid-jcb10>3.0.co;2-b
Subject(s) - ionomycin , medicine , endocrinology , protein kinase c , autocrine signalling , growth factor , chemistry , protein kinase a , prostaglandin e2 , chondrocyte , forskolin , biology , microbiology and biotechnology , signal transduction , receptor , kinase , biochemistry , stimulation , in vitro
Insulin‐like growth factor‐1, IGF‐1, is believed to be an important anabolic modulator of cartilage metabolism whose action is mediated by high affinity cell surface receptors and bioactivity and bioavailability regulated, in part, by IGF‐1 binding proteins (IGFBPs). Prostaglandin E 2 (PGE 2 ) stimulates collagen and proteoglycan synthesis in cartilage via an autocrine feedback loop involving IGF‐1. We determined whether the eicosanoid could regulate IGFBP‐4, a major form expressed by chondrocytes and, as such, act as a modifier of IGF‐1 action at another level. Using human articular chondrocytes in high‐density primary culture, Western and Western ligand blotting to measure secreted IGFBP‐4 protein, and Northern analysis to monitor IGFBP‐4 mRNA levels, we demonstrated that PGE 2 provoked a 2.7 ± 0.3‐ and 3.8 ± 0.5‐ (n = 3) fold increase in IGFBP‐4 mRNA and protein, respectively. This effect was reversed by the Ca ++ channel blocker, verapamil, and the Ca ++ /calmodulin inhibitor, W‐7. The Ca ++ ionophore, ionomycin, mimicked the effects of PGE 2 . The phorbol ester, PMA, which activated phospholipid‐dependent protein kinase C (PKC) in chondrocytes, had no effect on IGFBP‐4 production. Cyclic AMP mimetics and PKA activators, IBMX, and Sp‐cAMP, inhibited the expression of the binding protein as did the PGE 2 secretagogue, interleukin‐1β (IL‐β). The inhibitory effect of the latter cytokine was mediated by a erbstatin/genistein (tyrosine) sensitive kinase. Dexamethasone, an inhibitor of cyclooxygenase (COX‐2) expression and PGE 2 synthesis, down‐regulated control, constitute levels of IGFBP‐4 mRNA and protein, eliminating the previously demonstrated possibility of cross‐talk between glucocorticoid receptor (GR) and PGE 2 ‐receptor signalling pathways. The results suggest that extracellular signals control IGFBP‐4 production by a number of different transducing networks with changes in Ca ++ and calmodulin activity exerting a strong positive influence, possibly maintaining the constitutivity of IGFBP‐4 synthesis under basal conditions. PGE 2 activation of the IGF‐1/IGFBP axis may play a pivotal role in the metabolism of cartilage and possibly connective tissues in general. Eicosanoid biosynthesis may be a rate‐limiting step in cartilage repair processes. J. Cell. Biochem. 65:408–419. © 1997 Wiley‐Liss, Inc.