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.
Cardiovascular Medicine Section, Department of Medicine, and Myocardial and Vascular Biology Units, Boston University Medical Center, Boston, MA 02118, USA.
Gabriela M
GM
Kuster
Steve
S
Lancel
Jingmei
J
Zhang
Catherine
C
Communal
Mario P
MP
Trucillo
Chee C
CC
Lim
Otmar
O
Pfister
Ellen O
EO
Weinberg
Richard A
RA
Cohen
Ronglih
R
Liao
Deborah A
DA
Siwik
Wilson S
WS
Colucci
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