Olgar 2017 MiP2017

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Yusuf Olgar
Impaired mitochondrial function seems to be contributing to aging-associated abnormal heart function via increased production of reactive oxygen species.

Link: MiP2017

Olgar Y, Durak A, Degirmenci S, Tuncay E, Turan B (2017)

Event: MiP2017

COST Action MITOEAGLE

Reactive oxygen species (ROS) and subsequent mitochondrial dysfunction prominently associated with onset of failing heart in senescent myocardium [1]. Alterations of redox homeostasis lead to major cellular consequences such as matrix swelling, a release of apoptotic signaling molecules, and irreversible injury to the mitochondria. It also appears to be causally linked to the Ca2+ and Zn2+ handling in aging myocytes [2]. However, the correlation between mitochondrial dysfunction and electrical and mechanical activity of the heart in aging individuals is still unclear. Therefore, we aimed to clarify whether impaired mitochondrial function contributes to electrical function of cardiomyocytes isolated from aged rat hearts.

Confocal florescence imaging examinations demonstrated that intracellular basal free levels of both Ca2+ ([Ca2+]i) and Zn2+ [Zn2+]i in cells from 24-month-old rats were about 5-fold higher than those of cells from 6-month-old rats. Furthermore, we measured markedly increased ROS levels in aging-heart cells as well as depolarized mitochondrial membrane potential (ΔΨmit). With electrophysiological measurement in cellular level, we measured depolarized resting membrane potential and markedly prolonged action potential (AP) duration. Our patch-clamp measurements demonstrated that the prolongation in AP are mostly due to alterations in K+-channel currents. Particularly, activated ATP-sensitive K+ channel currents (KATP) seem to act as a compansatory ionic-mechanism to protect the myocardium similar to ischemic damage [3]. Our results exert that both repolarizing voltage gated K+ channels and KATP channel density reduced remarkably in senescent myocytes.

Taken together, our present data suggest that elevated ROS production and impaired mitochondrial function can account for increases in both [Ca2+]i and [Zn2+]i, which can in turn contribute to mechanical dysfunction of the heart. Moreover, the reduced voltage-dependent K+ channel currents and prolonged action potential in aging-cardiomyocytes are other contributing factors to abnormal heart function in aging-individuals.


Bioblast editor: Kandolf G


Labels: MiParea: Respiration  Pathology: Aging;senescence, Cardiovascular 

Organism: Rat  Tissue;cell: Heart 


Regulation: Calcium 




Affiliations

Dept Biophysics, Faculty Med, Univ Ankara, Turkey. - yolgar@ankara.edu.tr


References

  1. Moris D, Spartalis M, Tzatzaki E, Spartalis E, Karachaliou GS, Triantafyllis AS, Karaolanis GI, Tsilimigras DI, Theocharis S (2017) The role of reactive oxygen species in myocardial redox signaling and regulation. Ann Transl Med 5:324.
  2. Sag CM1, Wagner S, Maier LS (2013) Role of oxidants on calcium and sodium movement in healthy and diseased cardiac myocytes. Free Radic Biol Med 63:338-49.
  3. Bao L1, Taskin E, Foster M, Ray B, Rosario R, Ananthakrishnan R, Howlett SE, Schmidt AM, Ramasamy R, Coetzee WA (2013) Alterations in ventricular K(ATP) channel properties during aging. Aging Cell 12:167-76.