Abstract 786: Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) Mediates β-Adrenergic Receptor-Stimulated Matrix Metalloproteinase-2 Expression in Cardiac Myocytes
Background: We have shown that extracellular matrix metalloproteinase inducer (EMMPRIN) expression is increased by β-adrenergic receptor (βAR) stimulated JNK activity in cardiac myocytes. βAR stimulation also increases matrix metalloproteinase-2 (MMP2) expression in myocytes. Therefore, we tested the hypothesis that βAR-stimulated MMP2 expression is dependent on EMMPRIN in adult rat ventricular myocytes (ARVM) in vitro.
Methods/Results: A truncated secreted mutant of human EMMPRIN was created by removing the transmembrane domain and cytosolic region after valine(207) and placed in the Ad5(ΔE1ΔE3) vector (AdEΔ). A similar mutant has previously been shown to inhibit EMMPRIN-stimulated MMPs. ARVM were infected with AdEΔ or an empty adenovirus (AdV; 200 MOI; 36 hr) before βAR stimulation (10 μmol/L norepinephrine plus 100 nmol/L prazosin) for 24 hr. Conditioned media was collected and assessed for MMP2 expression (immunoblotting) and activity (zymography). EMMPRINΔ inhibited βAR-stimulated increases in MMP2 expression (p=0.044 vs. AdV/βAR; n=3) and activity (p=0.018 vs. AdV/βAR; n=6). We next tested the role of EMMPRIN in signaling βAR-stimulated MMP2 activation. βAR stimulation caused rapid (15 min) increases in JNK and p38 activity, but a delayed increase in ERK1/ERK2 activity (1 hr). βAR-stimulated JNK and p38 activities were not inhibited by EMMPRINΔ. On the other hand, βAR-stimulated ERK1/ERK2 activity was inhibited by EMMPRINΔ, and βAR-stimulated MMP2 activity was inhibited by the MEK1/MEK2 inhibitor U0126 (10 μM) (p=0.036; n=5). The p38 inhibitor SB203580 (3–10 μM) had no effect on βAR-stimulated MMP2 activity. Inhibition of JNK activity by adenovirally expressed dominant negative-JNK1 inhibited both βAR-stimulated EMMPRIN expression (p=0.049 vs lacZ/βAR) and MMP2 activity (p=0.022 vs lacZ/βAR).
Conclusion: In cardiac myocytes, βAR stimulation causes JNK-mediated activation of EMMPRIN, which then acts in an autocrine manner to activate ERK, thereby leading to expression of MMP2. EMMPRIN may play an important autocrine role in mediating the effects of βAR on myocardial remodeling.