The effect of NCX1.1 inhibition in primary cardiac myofibroblast cellular motility, contraction, and proliferation

• Main Author: Raizman, Joshua E.
• Other Authors: Dixon, Ian M.C. (Physiology)
• Language: en_US
• Published: 2006
• Subjects: cardiac wound healing; fibroblast and myofibroblast function; cellular motility; NCX; calcium signaling; collagen gel deformation assays; NSCC; myofibroblast contraction
• Online Access: http://hdl.handle.net/1993/239

Cardiac myofibroblasts participate in post-myocardial infarct (MI) wound healing, infarct scar formation, and remodeling of the ventricle remote to the site of infarction. The role of intracellular calcium handling in cardiac myofibroblasts as a modulator of cellular motility, contractile responses, and proliferation is largely unexplored. We have investigated the role of sodium calcium exchange (Na Ca exchange or NCX1.1) and non-selective cation channels (NSCCs) in regulation of myofibroblast function using a pharmacological inhibitor approach in vitro. Primary myofibroblasts were stimulated with PDGF-BB and cellular chemotaxis, contraction and proliferative responses were characterized using standard bioassays (Costar Transwell apparatuses, pre-formed collagen type I gel deformation assays, and 3H-thymidine incorporation). Stimulated cellular responses were compared to those in the presence of AG1296 (PDGFβR inhibitor), KB-R7943 (NCX inhibitor), gadolinium, nifedipine or ML-7. Immunofluorescence was used to determine localized expression of αSMA, SMemb, NCX1.1, and Cav1.2a in cultured myofibroblasts. Motility of myofibroblasts in the presence of PDGF-BB was blocked with AG1296 treatment. Immunoblotting and immunocytochemical studies revealed expression of NCX1.1 in fibroblasts and myofibroblasts. Motility (in the presence of either PDGF-BB or CT-1), contraction (in the presence of either PDGF-BB or TGFβ1), and proliferation (in the presence of PDGF-BB) were sensitive to KB-R7943 treatment of cells (7.5 and 10 μM for motility, 5 and 10 μM for contractility, and 10 μM for proliferation). Proliferation (in the presence of PDGF-BB), and contractility (in the presence of either PDGF-BB or TGFβ1) but not motility (in the presence of PDGF-BB) are sensitive to nifedipine treatment, while gadolinium treatment was associated only with decreased motility of cells (in the presence of either PDGF-BB, CT-1, or LoFGF-2). We found that ML-7 treatment inhibited cellular chemotaxis, and contraction. Thus cellular chemotaxis, contractile, and proliferation responses were sensitive to different pharmacologic treatment. Regulation of transplasmalemmal calcium movements may be important in cytokine and growth factor receptor-mediated cardiac myofibroblast motility, contractility, and proliferation. Furthermore, our results support the hypothesis that activation of specific calcium transport proteins is an important determinant of physiologic responses.