Abstract 17087: A Unique Calcium Channel Blocker Attenuates Myocardial Fibrosis and Prevents Human Cardiac Myofibroblast Activation Independent of Hemodynamics
Introduction: Myocardial fibrosis is mediated by myofibroblasts that alter extracellular matrix (ECM). Tetrandrine (TTD) is a calcium channel blocker (CCB) with documented anti-fibrotic actions believed to be secondary to its effects on lowering blood pressure. In this study, for the first time, we identified that TTD can directly prevent in vitro human cardiac fibroblast activation and limit in vivo myocardial fibrosis independent of hemodynamic load.
Methods and Results: IN VITRO: Cardiac fibroblasts from human atrial biopsies (N=10) were seeded in 3D collagen matrices. Cell-collagen constructs were exposed to TGF-β1 (10 ng/mL), with or without TTD (5μM) for 48 hours. Collagen gel contraction, myofibroblast activation (α-SMA expression), expression of pro-fibrotic mRNAs and rate of collagen protein synthesis was compared. TTD decreased collagen gel contraction (79.7±1.3 vs 60.1±8.9%, P< 0.01). Cell viability was similar between groups (annexin positive cells: 1.7% vs 1.4%). TTD decreased α-SMA expression (flow cytometry), decreased collagen synthesis ([3H]-proline incorporation), and decreased collagen mRNA expression. TTD inhibited collagen gel contraction in the presence of T-type, L-type CCB, and calcium chelator BAPTA-AM (15μM) suggesting that the observed effects are not mediated by calcium channel blockade. IN VIVO: Dahl salt-sensitive rats (pressure-overload model) were treated with TTD (15mg/kg by IP injection over 4 weeks, N=12) and compared to untreated controls (N=12). Systemic blood pressure was monitored by tail cuff. LV compliance, wall thickness and myocardial fibrosis was assessed by passive pressure-volume analysis, echocardiography and PSR staining. Myocardial fibrosis was attenuated after 4 weeks of TTD treatment as compared to untreated controls (% collagen area: 9.4±7.3 vs 2.9±1.6, P<0.01). LV compliance was preserved and increased wall thickness was prevented by TTD. Observed changes were independent of hemodynamic load.
Conclusions: TTD prevents human cardiac myofibroblast activation and myocardial fibrosis independent of calcium channel blockade and hemodynamic load. Mechanisms mediating TTD anti-fibrotic activity should be further explored and leveraged for its therapeutic potential.
Author Disclosures: G. Teng: None. H.J. Duff: None. D.D. Belke: None. C.H. Meijndert: None. E. O’Brien: None. Y. Chen: None. J. Turnbull: None. P.W. Fedak: None.
- © 2014 by American Heart Association, Inc.