Role of Ca2+ signaling in initiation of stretch-induced apoptosis in neonatal heart cells.
Abnormal mechanical load, as seen in hypertension, is found to induce heart cell apoptosis, yet the signaling link between cell stretch and apoptotic pathways is not known. Using an in vitro stretch model mimicking diastolic pressure stress, here we show that Ca(2+) signaling participates essentially in the early stage of stretch-induced apoptosis. In neonatal rat cardiomyocytes, the moderate 20% stretch resulted in tonic elevation of intracellular free Ca(2+) ([Ca(2+)](i)). Buffering [Ca(2+)](i) by EGTA-AM, suppressing ryanodine-sensitive Ca(2+) release, and blocking L-type Ca(2+) channels all prevented the stretch-induced apoptosis as assessed by phosphatidylserine exposure and nuclear fragmentation. Notably, Ca(2+) suppression also prevented known stretch-activated apoptotic events, including caspase-3/-9 activation, mitochondrial membrane potential corruption, and reactive oxygen species production, suggesting that Ca(2+) signaling is the upstream of these events. Since [Ca(2+)](i) did not change without activating mechanosensitive Ca(2+) entry, we conclude that stretch-induced Ca(2+) entry, via the Ca(2+)-induced Ca(2+) release mechanism, plays an important role in initiating apoptotic signaling during mechanical stress.
Liao
Xu Dong
XD
Cardiovascular Institute, Peking Union Medical College, Beijing 100037, China.
Tang
Ai Hui
AH
Chen
Quan
Q
Jin
Hai Jing
HJ
Wu
Cai Hong
CH
Chen
Lan-Ying
LY
Wang
Shi Qiang
SQ
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D006321:Heart / Q000254:growth & development; D017136:Ion Transport; D007700:Kinetics; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical
D002118:Calcium