Abstract 14074: Attenuation of Ischemia-Reperfusion Injury by Ultrasound-Targeted S100A6 Gene Therapy
Introduction: The EF-hand Ca2+-binding protein S100A6 decreases cardiomyocyte apoptosis in vitro, and may play a role in the response to myocardial ischemia-reperfusion (I/R) injury. We hypothesized that S100A6 gene delivery by ultrasound-targeted microbubble destruction (UTMD) would attenuate myocardial I/R injury.
Methods: Using UTMD, we delivered human-S100A6 plasmid or empty plasmid to the LV in Fischer-344 rats, 2 days prior to I/R surgery, with control animals receiving no UTMD. All animals (n=120) underwent I/R induced by a 30-minute ligation of the left anterior descending artery followed by reperfusion. Serial echocardiography was performed, and animals were sacrificed at day28. In vitro studies were performed on isolated rat neonatal cardiomyocytes transduced with either adenoviral packaged GFP-tagged human-S100A6 plasmid, empty plasmid or rat S100A6-shRNA. The spatiotemporal dynamics of intracellular calcium during excitation-contraction coupling were measured applying fluorescent indicator fluo-4 acetoxymethyl and laser scanning confocal microscopy.
Results: Pre-treatment with S100A6 gene therapy resulted in lower mortality rates after I/R compared to empty-plasmid and non-treated controls (32% vs 47% and 60% respectively, p<0.05). The circumferential extent of akinesis was lower, while fractional area change (FAC) and ejection fraction (EF) were significantly greater in S100A6-treated rats at day 28, compared to empty-plasmid and non-treated controls. In vitro, expression of S100A1 and S100B was not influenced by S100A6 overexpression or knockdown. Calcium Sparks recording during excitation-contraction coupling showed significantly higher calcium release amplitude in S100A6-overexpressed cardiomyocytes and significantly lower calcium release amplitude in S100A6-knockdown cells, when compared to controls.
Conclusion: S100A6 gene delivery by UTMD attenuates myocardial I/R, resulting in lower mortality and improved LV systolic function post I/R. Therapeutic effects of S100A6 overexpression on myocardial I/R may not only be due to its anti-apoptotic effects but also due to regulation of intracellular calcium cycling. Our results suggest that S100A6 is a potential therapeutic target for I/R injury.
- © 2013 by American Heart Association, Inc.