| Hypoxia is a common pathological process of various types of diseases and is a vital initiative factor in myocardial dysfunction induced by shock after severe trauma. The mechanisms of apoptosis induced by hypoxia gradually come to be one of the highlights in life science. Loss of myocytes is a feature of the cardiomyopathic process that contributes to progressive decline in the ventricular dysfunction and heart failure induced by hypoxia. Recent studies have proposed that myocyte loss induced by hypoxia can occur by apoptosis without an attendant inflammatory response. Programmed cell death plays critical roles in a wide varity of physiological processes during fetal development and in adult tissues. In most cases, physiological cell death occurs by apoptosis as opposed to necrosis. Defects in apoptotic cell death regulation contribute to many diseases, including disorders where cell accumulation occurs (cancer, restenocis) or where cell loss ensues (stroke, heart failure, neurodegeneration, AIDS). In recent years, the molecular mechanism responsible for apoptosis has been elucidates, revealing a family of intracellular proteases, the Caspases, which are responsible directly or indirectly for the morphological and biochemical changes that characterize the phenomenon of apoptosis. Activation of Caspases, which cleave their substrates at aspartic acid residues, is a critical step in induction of apoptosis. Caspases are present as inactive zymogens in essentially all animal cells, but can be triggered to assume active states, generally involving their proteolytic processing at conserved aspartic acidresidues. These proteases can be divided into the upstream Caspases (initiators) and the downstream ones (effectors). The upstream Caspases include Caspases-1,2,4,5,8,9,10,11,12,13 and downstream effectors are Caspases-3, 6,7. Though many pathways for activating Caspases may exist, the pathway for hypoxia induced Caspases in cardiomyocytes has not been fully elucidated in detail.The present study was designed to explore the possible roles of Caspase-3 activation in hypoxia induced cardiomyocytes damage Expressions of Caspases-3, -9 mRNA, release of mitochondrial cytochrome c, Fragmentation of genomic DNA, and morphological feature of apoptosis were determined by using RT-PCR, Western blotting, laser confocal scanning respectively. Main results of the present study were describes as follows. 1. Apoptosis is the major way of cell death in hypoxia induced cardiomyocyte damage, which is characterized by the decline in cell viability, increase in apoptotic cell percentage, induction of genomic DNA fragmentation, and appearance of apoptotic morphological features.2. Hypoxia can induce mitochodrial Cyt c release into cytoplasm. Elevation of Cyt c in cytosol is concurrently in accordance with the decline in mitochondrial Cyt c content. Significant increase in Cyt c in cytoplasm appeared at 12 h post hypoxia and peaked at 24 h while Cyt c in mitochondrial could not be detected at 24 h post hypoxia. 3. Hypoxia up-regulates Caspases-3, -9 mRNA expressions beginning at 3 h post hypoxia. Up-regulation of Caspases-3, -9 mRNA expressions is maintained during 24 h hypoxic insult. In consistence with the overexpression of Caspase-3 mRNA, Caspase-3 activity is markedly elevated.4. Intracellular calcium overload occurs earlier than release of mitochondrial Cyt c and the activation of Caspase-3 during the hypoxic insult. This fact indicates that Intracellular calcium overload is an earlier molecularevent in hypoxia induced cardiomyocyte damage. Chelation of intracellular free calcium significantly antagonizes hypoxia induced DNA fragmentation and apoptosis. 5. Inhibition of Caspase-3 activation can provide protective effects against hypoxia-induced apoptosis, which characterized by the blockade of drop in cell viability and decrease in apoptotic cell percentage. Therefore, Antagonism of Caspase-3 activation may be an important approach to protect myocardial function in hypoxia. 6. Pretreatment...
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