Redox-mediated reciprocal regulation of SERCA and Na+-Ca2+ exchanger contributes to sarcoplasmic reticulum Ca2+ depletion in cardiac myocytes.
Myocardial failure is associated with increased oxidative stress and abnormal excitation-contraction coupling characterized by depletion of sarcoplasmic reticulum (SR) Ca(2+) stores and a reduction in Ca(2+)-transient amplitude. Little is known about the mechanisms whereby oxidative stress affects Ca(2+) handling and contractile function; however, reactive thiols may be involved. We used an in vitro cardiomyocyte system to test the hypothesis that short-term oxidative stress induces SR Ca(2+) depletion via redox-mediated regulation of sarcoendoplasmic reticulum Ca(2+)-ATPase (SERCA) and the sodium-Ca(2+) exchanger (NCX) and that this is associated with thiol oxidation. Adult rat ventricular myocytes paced at 5 Hz were superfused with H(2)O(2) (100 microM, 15 min). H(2)O(2) caused a progressive decrease in cell shortening followed by diastolic arrest, which was associated with decreases in SR Ca(2+) content, systolic [Ca(2+)](i), and Ca(2+)-transient amplitude, but no change in diastolic [Ca(2+)](i). H(2)O(2) caused reciprocal effects on the activities of SERCA (decreased) and NCX (increased). Pretreatment with the NCX inhibitor KB-R7943 before H(2)O(2) increased diastolic [Ca(2+)](i) and mimicked the effect of SERCA inhibition with thapsigargin. These functional effects were associated with oxidative modification of thiols on both SERCA and NCX. In conclusion, redox-mediated SR Ca(2+) depletion involves reciprocal regulation of SERCA and NCX, possibly via direct oxidative modification of both proteins.
Kuster
Gabriela M
GM
Cardiovascular Medicine Section, Department of Medicine, and Myocardial and Vascular Biology Units, Boston University Medical Center, Boston, MA 02118, USA.
Lancel
Steve
S
Zhang
Jingmei
J
Communal
Catherine
C
Trucillo
Mario P
MP
Lim
Chee C
CC
Pfister
Otmar
O
Weinberg
Ellen O
EO
Cohen
Richard A
RA
Liao
Ronglih
R
Siwik
Deborah A
DA
Colucci
Wilson S
WS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*
D016877:Oxidants; D019831:Sodium-Calcium Exchanger; D006861:Hydrogen Peroxide; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium