Age-related changes in resistance of rat hearts to ischemia and effect of remote ischemic preconditioning: Study of potential molecular mechanisms
Lucia Griecsová 1
Veronika Farkašová 1
Ľubomír Lonek 1
Ivan Gáblovksý 1
Iveta Bernatova 2
Táňa Ravingerová 1
1 Centrum experimentálnej medicíny SAV, Ústav pre výskum srdca, Bratislava 4, Slovenská republika 2 Centrum experimentálnej medicíny SAV, Ústav normálnej a patologickej fyziológie, Bratislava 4, Slovenská republika
|Section:||Cellular metabolism, physiology, molecular biology and genetics|
Background: Aging affects tolerance to ischemia/reperfusion (IR) and adaptive mechanisms, as shown in elder human and animal hearts, however, the onset of this unfavorable phenotype and cellular mechanisms behind remain unknown. Aging may interfere with the mechanisms of innate cardioprotection and cause defects in protective cell signaling. Although some studies demonstrated cardioprotective effects of ischemic preconditioning (IPC) even in the elderly, the results are not unequivocal. In our previous study we found that cardiac response to IR injury and efficacy of IPC may become modified already during the process of maturation. Attenuated IPC protection correlated with gradual reduction of proteins involved in “pro-survival” pathways and a failure of IPC to upregulate them. Although remote ischemic preconditioning (RIPC) has been shown to protect young and aged human hearts from IR, little is known with respect to its age-dependency in animals.
Methods: We aimed to study myocardial function, changes in response to IR and in adaptation mechanisms related to RIPC in the hearts of younger adult (3 months) and mature adult (6 months) male Wistar rats, with regards to selected proteins of protective signaling. Langendorff-perfused hearts were exposed to 30-min I/120-min R with or without prior RIPC (3 cycles of 5-min I/5-min R) applied on the hind limb of anesthetized rats (pressure cuff inflation/deflation). We measured infarct size (IS), susceptibility to ventricular arrhythmias and recovery of contractile function (LVDP). In parallel groups, LV tissue was sampled for the detection of protein levels (WB) of Akt kinase, phosphorylated Akt (p-Akt), endothelial NO synthase (eNOS), protein kinase Cɛ (PKCɛ), GSK-3β and p-GSK-3β, as well as proteins of pro/antiapoptotic cascades.
Results: Maturation did not affect heart function, however, it impaired cardiac response to lethal IR injury (increased IS), promoted arrhythmogenesis, decreased levels of protective proteins and increased apoptotic changes (BAX/Bcl-2). RIPC markedly reduced IS by 59% and by 33% (in 3m and 6m groups, respectively), as well as decreased severity of arrhythmias and improved LVDP recovery in both age groups as compared with non-preconditioned controls. In addition, in both groups, cardioprotective effects of RIPC were associated with increased phosphorylation (activation) of Akt, phosphorylation (inhibition) of GSK-3β, upregulation of eNOS and PKCɛ, as well as with reduced BAX/Bcl-2 and caspase-3 activity.
Conclusions: Early maturation already starts to impair the resistance of rat hearts against IR injury. On the other hand, mechanisms of innate cardioprotection can be restored by RIPC that appears as an effective and easily performed clinically relevant protective intervention.