Project description:The heart of late pregnant (LP) rodents is more prone to ischemia/reperfusion (I/R) injury compared to non-pregnant rodents. We hypothesized that Intralipid (ITLD) protects the heart in LP rodents against I/R injury. We performed genome-wide expression profiling to identify the underlying mechanisms. Female LP rat hearts were subjected to ischemia followed by reperfusion with vehicle or ITLD (one bolus of 5mg/kg).
Project description:The heart of late pregnant (LP) rodents is more prone to ischemia/reperfusion (I/R) injury compared to non-pregnant rodents. We hypothesized that Intralipid (ITLD) protects the heart in LP rodents against I/R injury. We performed genome-wide expression profiling to identify the underlying mechanisms.
Project description:Heart disease remains the leading cause of death globally. Although reperfusion following myocardial ischemia can prevent death by restoring nutrient flow, ischemia/reperfusion injury can cause significant heart damage. The mechanisms that drive ischemia/reperfusion injury are not well understood; currently, few methods can predict the state of the cardiac muscle cell and its metabolic conditions during ischemia. Here, we explored the energetic sustainability of cardiomyocytes, using a model for cellular metabolism to predict the levels of ATP following hypoxia. We modeled glycolytic metabolism with a system of coupled ordinary differential equations describing the individual metabolic reactions within the cardiomyocyte over time. Reduced oxygen levels and ATP consumption rates were simulated to characterize metabolite responses to ischemia. By tracking biochemical species within the cell, our model enables prediction of the cell’s condition up to the moment of reperfusion. The simulations revealed a distinct transition between energetically sustainable and unsustainable ATP concentrations for various energetic demands. Our model illustrates how even low oxygen concentrations allow the cell to perform essential functions. We found that the oxygen level required for a sustainable level of ATP increases roughly linearly with the ATP consumption rate. An extracellular O2 concentration of ~0.007 mM could supply basic energy needs in non-beating cardiomyocytes, suggesting that increased collateral circulation may provide an important source of oxygen to sustain the cardiomyocyte during extended ischemia. Our model provides a time-dependent framework for studying various intervention strategies to change the outcome of reperfusion.
Project description:Under stress conditions, cells elicit integrated stress response (ISR) to cope with intracellular and extracellular disturbances. However, its role in ischemic heart disease remains to be elucidated. Here, we show that oxygen deprivation in cardiomyocytes triggers significant changes in protein translation. Importantly, ischemia and ischemia/reoxygenation leads to suppression of protein synthesis, which is caused by activation of the PERK/eIF2α axis of ISR. At the functional level, cardiac specific elimination of PERK exacerbates cardiac response to ischemia/reperfusion whereas selective activation of PERK in the heart confers cardioprotection against reperfusion injury. Mechanistically, PERK-mediated improvement in cardiomyocyte survival depends on suppression of protein synthesis and consequently relieves energetic demand on mitochondria. We went further to show that mitochondrial complex components are targeted by protein translation suppression, which significantly diminishes mitochondria-associated production of reactive oxygen species. Indeed, pharmacological activation of ISR protects the heart from ischemia/reperfusion damage, even after the release of occluded coronary artery, highlighting clinical significance for myocardial infarction. Taken together, these findings suggest that ISR improves cell survival through selectively suppressing mitochondrial protein synthesis and reducing oxidative stress in ischemic heart disease.