Introduction:

After myocardial infarction, reperfusion therapy as soon as possible is the best treatment for inhibition of myocardial damage. Although this restores the blood flow and thereby oxygen levels, it has been shown that reperfusion itself can cause myocardial damage by different mechanisms which are still incompletely understood. Among others, one mechanism could be a maladaptive protein synthesis response through activation of the kinase “mechanistic target of rapamycin complex 1” (mTORC1) during the reperfusion phase. In previous studies it has be shown that inhibition mTORC1, which is a key complex in the regulation of mRNA translation and protein synthesis, improves cardiac function after ischemia/ reperfusion (I/R) damage in mice. However, the relative contribution of inhibiting mRNA translation and protein synthesis to the beneficial outcome after mTORC1 inhibition was unknown.

Hypothesis:

Transient inhibition of mRNA translation during reperfusion protects from reperfusion injury.

Methods and Results:

Male and female mice were subjected to ischemia reperfusion damage by ligation of the LAD for 60 min. mRNA translation was inhibited for 48 h with an eIF4E/eIF4G interaction inhibitor. Protein aggregates were measured after I/R with eIF4F inhibition in vivo. 4EGI-1 reduced protein aggregates in comparison to only vehicle treated mice. ATP concentrations were measured after simulated I/R in cardiomyocytes in vitro and as well after I/R with eIF4F inhibition in vivo. Treatment with 4EGI-1 did not affect ATP levels compared to vehicle treated mice. Myocardial inflammation was measured by FACS analysis and by qPCR two days after I/R in vivo. Proinflammatory cytokines, like IL-1 and TNFα, were quantified by qPCR and were highly elevated in the left ventricle after I/R and were less abundant after inhibition of translation. The same was true for CCL2 and its receptor CCR2 which are involved in recruiting inflammatory cells, especially monocytes, to the site of inflammation. FACS analysis confirmed less monocytes and macrophages in the infarcted tissue and in general less leukocytes migrated to the site of inflammation. Finally, inhibition of mRNA translation, improved long term cardiac function after myocardial infarction and reduced infarct size compared to vehicle treated mice.

Conclusion:

eIF4F inhibition after I/R targets multiple pathways which ameliorate cardiac function. Less misfolded proteins and a reduction of an overshooting inflammatory response are associated with this improvement. Specific targeting of eIF4F formation might bypasses off-target effects that have been previously described for direct mTOR inhibitors and therefore improve its clinical usability compared to classical mTOR inhibitors for the treatment of reperfusion injury.