Matrix metalloproteinase expression and activity in isolated myocytes after neurohormonal stimulation

Changes in myocardial matrix metalloproteinase (MMP) activity and expressio n have been associated with left ventricular (LV) remodeling. A recent stud y demonstrated that LV myocytes synthesize and release MMPs, which suggests that LV myocytes may participate in myocardial remodeling. However, extrac ellular stimuli that may potentially influence LV myocyte MMP production re mains to be defined. In the present study MMP activity and expression were measured in porcine LV myocyte preparations (10(5) total cells; n = 6) foll owing incubation (6 h) with endothelin-1 (ET-1;50 pM), angiotensin II (ANG II; 1 muM), or the beta -receptor agonist isoproterenol (Iso; 10 nM). LV my ocyte-conditioned media were then subjected to gelatin zymography and an MM P-2 antibody capture assay. MMP zymographic gelatinase activity and MMP-2 c ontent were increased by over 40% in LV myocyte-conditioned media after inc ubation with ET-1 or ANG II (P < 0.05). Exposure to the phorbol ester phorb ol 12-myristate 13-acetate (PMA; 50 ng/ml) resulted in a 30% increase in zy mographic gelatinase activity and a 63% increase in MMP-2 content (P, 0.05) , suggesting that protein kinase C activation may be an intracellular mecha nism for MMP induction. With the use of a confocal microscopy, membrane typ e-1 MMP (MT1-MMP) was localized to porcine LV myocytes, and immunoblotting for MT1-MMP using LV myocyte extracts revealed that after exposure to Iso, ET-1, ANG II, or PMA (P, 0.05), MT1-MMP abundance increased over 50%. Thus stimulation of specific neurohormonal systems that are relevant to LV remod eling influences LV myocyte MMP synthesis and release.