Rd. Rakhit et al., Mitochondria as targets for nitric oxide-induced protection during simulated ischemia and reoxygenation in isolated neonatal cardiomyocytes, CIRCULATION, 103(21), 2001, pp. 2617-2623
Citations number
35
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Background-As shown previously, exposure to NO donors initiates protective
mechanisms in cardiomyocytes that persist after removal of the donor, a for
m of pharmacological preconditioning. Because NO also affects mitochondrial
respiration, we studied the effect of NO on mitochondrial Ca2+ uptake.
Methods and Results-Neonatal rat ventricular myocytes in primary culture we
re exposed to 1 hour of simulated ischemia and 1 hour of reoxygenation (sI/
R). Pretreatment with the NO donor S-nitroso-N-acetyl-penicillamine (SNAP)
(1 mmol/L for 90 minutes), followed by washing and incubation for 10 to 30
minutes, reduced sI/R-induced cell death to 25.4% compared with control (pr
opidium iodide exclusion assay, P<0.001). Short (10-second) exposures to SN
AP reversibly suppressed mitochondrial respiration without a detectable cha
nge in mitochondrial potential. In contrast, treatment with SNAP for 90 min
utes caused a modest but sustained mitochondrial depolarization, as judged
by JC-1 fluorescence. SNAP pretreatment limited cellular Ca2+ overload duri
ng ischemia (fura-2 ratio rose to 226+/-40% versus 516+/-170% of baseline,
n=5, P<0.05) and prevented loss of cell membrane integrity during reoxygena
tion. SNAP pretreatment also significantly reduced the ability of mitochond
ria to accumulate Ca2+ in the face of a similar cytosolic Ca2+ load (peak r
hod-2 fluorescence 133+/-4% versus 166+/-7% of baseline at similar fluo-3 l
evels. P=0.0004, n=52 and 25, respectively).
Conclusions-Pretreatment with an NO donor induces a modest, sustained mitoc
hondrial depolarization and protects cardiomyocytes from sI/R injury. The d
emonstrated reduction in mitochondrial Ca2+ uptake possibly reduces cytosol
ic Ca2+ overload, providing a likely mechanism for NO-induced protection.