Submitted on July 18, 2008
Revised on January 12, 2009
Accepted on January 26, 2009
Restoration of contractility in hyperhomocysteinemia by cardiac-specific deletion of NMDA-R1
Karni S Moshal1, Munish Kumar2, Neetu Tyagi2, Paras K Mishra, Naira metreveli, Walter E Rodriguez2, and Suresh C. Tyagi3*
1 Harvard University
2 University of Louisville
3 University of Louisville Health Sciences Center
* To whom correspondence should be addressed. E-mail: suresh.tyagi{at}louisville.edu.
Homocysteine (HCY) activated mitochondrial matrix metalloproteinase-9 (mtMMP-9) and led to cardiomyocyte dysfunction, in part, by inducing mitochondrial permeability (MPT). Treatment with MK-801 (NMDA receptor antagonist) ameliorated HCY-induced decrease in myocyte contractility. However, the role of cardiomyocyte NMDA-R1 activation in HHCY leading to myocyte dysfunction was not well understood. We tested the hypothesis that the cardiac-specific deletion of NMDA-R1 mitigated HCY-induced decrease in myocyte contraction, in part, by decreasing nitric oxide (NO). Cardiomyocyte-specific knockout (KO) of NMDA-R1 was generated using cre/lox technology. NMDA-R1 expression was detected by Western blot and confocal microscopy. MPT was determined using spectrophotometer. Myocyte contractility and calcium transients were studied using IonOptix video-edge detection system and FURA-2AM loading. We observed that HHCY induced NO production by agonizing NMDA-R1. HHCY induced the MPT by agonizing NMDA-R1. HHCY caused a decrease in myocyte contractile performance, maximal rate of contraction and relaxation [± dL/dt], and prolonged the time to 90% PS (TPS) and 90% relaxation (TR) by agonizing NMDA-R1. HHCY decreased contraction amplitude with the increase in calcium concentration. The recovery of calcium transient was prolonged in HHCY mouse myocyte by agonizing NMDA-R1. It was suggested that HHCY increased mitochondrial NO levels and induced MPT leading to the decline in myocyte mechanical function by agonizing NMDA-R1.
