Inhibition of Matrix Metalloproteinases Prevents the Synthesis of Insulin-Like Growth Factor Binding Protein-1 during Decidualization in the Baboon

Abstract

During pregnancy in the primate, uterine stromal fibroblasts are transformed into decidual cells. Decidualization is associated with extensive remodeling of the extracellular matrix (ECM). Matrix metalloproteinases (MMPs) play a pivotal role in ECM degradation. We hypothesized that MMPs also contribute to regulation of IGF binding protein-1 (IGFBP-1), a biochemical marker of primate decidual cells. We reported that IL-1β (10 ng/ml) with steroid hormones [36 nM estradiol-17β, 1 μM medroxyprogesterone acetate (P), and 100 ng/ml relaxin] induces in vitro IGFBP-1 synthesis. This study demonstrates that IL-1β also induces stromelysin-1 (MMP-3) mRNA and synthesis of the latent form of MMP-3 (pro-MMP-3) protein in baboon stromal fibroblasts. In contrast, hormones (particularly P) negatively regulate MMP-3 because their addition decreases IL-1β-induced pro-MMP-3 protein. The ERK and p38 MAPK pathways induced by IL-1β regulate proMMP-3 because inhibitors PD98059 (20 μM) and SB203580 (1 μM) prevent its synthesis. The nuclear factor-κB inhibitory peptide, SN50 (50 μg/ml), or proteasome inhibitor, MG-132 (1 μM), did not inhibit pro-MMP-3 synthesis but appeared to enhance it. The role of MMPs in IGFBP-1 induction was investigated using a broad-spectrum MMP inhibitor, doxycycline, and specific MMP-3 inhibitor, N-Isobutyl-N-(4-methoxyphenylsulfonyl)-glycylhydroxamic acid (NNGH). Both inhibitors caused the dose-dependent decrease of IGFBP-1. α-Smooth muscle actin, which is down-regulated during decidualization, was partially up-regulated by doxycycline or N-Isobutyl-N-(4-methoxyphenylsulfonyl)- glycylhydroxamic acid. This suggests that α-smooth muscle actin is modulated by changes in ECM caused by the action of MMPs/MMP-3. Disruption of actin filaments enhances IGFBP-1 induction. Thus, our data imply that IL-1β-induced MMPs and particularly MMP-3 may up-regulate IGFBP-1 by disrupting the actin cytoskeleton as a result of ECM degradation.