Cellular and Molecular Responses in Striped Bass (\u3cem\u3eMorone saxatilis\u3c/em\u3e) and Nile Tilapia (\u3cem\u3eOreochromis niloticus\u3c/em\u3e) Cardiomyocytes in Response to Hypoxia.

For a talk. Oxygen deprivation (hypoxia) is a common stressor affecting cardiomyocytes (heart cells) when blood flow is reduced or cut off from the heart. In response, cardiomyocytes have been shown to undergo apoptosis (programmed cell death) which is suggested to have a role in the pathogenesis of cardiovascular diseases, the leading cause of mortality in developed nations. Since many species of fish can survive low oxygen levels that would be fatal to mammals, fish are an ideal model system to study changes at the cellular and molecular level that prevent or repair hypoxia-induced damage in cardiomyocytes. The hypoxia-sensitive striped bass (Morone saxatilis) and the hypoxia-tolerant Nile tilapia (Oreochromis niloticus) were sampled at four key time points: 1) prior to hypoxia exposure (normoxic control), 2) after four hours at the species’ specific Pcrit (hypoxia), 3) immediately upon return to normoxia (reperfusion), and 4) after four hours at normoxia (recovery). Evidence of apoptosis at the cellular level will be determined by measuring caspase-3/7 activity and DNA fragmentation. To detect apoptosis at the molecular level, RT-qPCR will be used to quantify changes in the transcriptome of cardiomyocytes of pro-apoptotic (BAX and FASL), anti-apoptotic (BCL2 and FLIP) and repair (HSP70) genes. We hypothesize that tilapia will have lower cellular markers of apoptosis due to higher anti-apoptotic and repair gene expression in their cardiomyocytes when compared to the striped bass, which we hypothesize will have higher cellular markers of apoptosis and pro-apoptotic gene expression levels. Preliminary data suggests DNA fragmentation (a late stage marker of apoptosis) was not present in either striped bass or tilapia cardiomyocytes. This suggests both species of fish did not experience hypoxia long enough to result in the detection of the final stages of apoptosis. Data collection is on-going for caspase-3/7 activity and RT-qPCR results