Basic calcium phosphate crystal induction of collagenase 1 and stromelysinexpression is dependent on a p42/44 mitogen-activated protein kinase signal transduction pathway
Ma. Brogley et al., Basic calcium phosphate crystal induction of collagenase 1 and stromelysinexpression is dependent on a p42/44 mitogen-activated protein kinase signal transduction pathway, J CELL PHYS, 180(2), 1999, pp. 215-224
Synovial fluid basic calcium phosphate (BCP) crystals are markers of severe
joint degeneration in osteoarthritis. These crystals are mitogenic and ind
uce protooncogene expression and matrix metalloproteinase (MMP) synthesis a
nd secretion in human fibroblasts, effects that are specifically blocked by
phosphocitrate (PC). We have recently determined that crystals transduce s
ignals to the nucleus via the activation of the p42 and p44 mitogen-activat
ed protein (MAP) kinases (Nair et at., 1997, J Biol Chem 272:18920-18925).
Treatment of human fibroblasts (HF) with BCP induces phosphorylation of p42
/44 MAPK, which is inhibited by PC in a dose-dependent manner. Blocking of
p42/44 MAPK signal transduction with an inhibitor (PD98059) of MEK1, an ups
tream activator of MAPKs, reduces crystal-induced p42/44 MAPK activation an
d significantly inhibits crystal-induced cell proliferation. Based on these
findings, we sought to determine the role of the p42/44 MAPK signal transd
uction pathway in crystal-induced expression of matrix MMPs. We demonstrate
suppression of crystal-induced MMPs via the utilization of two different M
EK inhibitors: PD98059 and the recently described U0126, a novel inhibitor
of MEK1 and MEK 2. Treatment of HF with PD98059 blocks the induction of cry
stal-stimulated collagenase 1 (MMP-1) and stromelysin (MMP-3) expression. P
D98059 and PC reduced the level of crystal-induced MMP-1 and MMP-3 mRNA exp
ression to that observed in nonstimulated cells. Likewise, PD98059 treatmen
t of HF blocked the epidermal growth factor (EGF)- and crystal-induced incr
eases in MMP-1 and MMP-3 protein expression and secretion as demonstrated b
y Western blotting and zymography. Treatment of HF with U0126 inhibits EGF-
induced phosphorylation of p42/44 MAPK as well as crystal- and EGF-induced
upregulation of MMP-1 mRNA. Additionally, we demonstrate that treatment of
HF with BCP, EGF, or PD98059 does not significantly alter levels of gelatin
ase A (MMP-2) mRNA and protein expression. (C) 1999 Wiley-Liss, Inc.