Akademik Veri Yönetim Sistemi
Internationl conference on Trace Elements and Minerals, Aachen, Almanya, 5 - 10 Haziran 2022
Introduction: Zinc ion (Zn2+)
is a highly abundant cation in the heart, essential for cellular functions,
including transcription, enzymatic and contractile activities, and cell
signaling. We have previously showed that intracellular free Zn2+ content
([Zn2+]i) is increased in early onset of diabetes
mellitus (DM) characterized, in part, as hyperglycemia (HG) and that exposure
of Zn2+ to isolated cardiomyocytes caused depressed
contraction-relaxation function and impaired mitochondrial function. It is well
documented that cardiomyocyte [Zn2+]i is regulated and
controlled efficiently with various Zn2+-transporters. Alterations
in expression and/or function of any of them can modulate the cytosolic and
organellar [Zn2+].
Aim: In the current
study, we examined the role of ZnT6 on sarco/endoplasmic reticulum (SER) and
mitochondria (Mit) [Zn2+] (such as [Zn2+]SER
and [Zn2+]Mit) and its role on mitochondrial function in
hyperglycemic rat ventricular cell-line (H9c2 cells).
Methods: We performed overexpression
of ZnT6 protein in H9c2 cells to determine its role on distribution of subcellular
[Zn2+] as well as ATP level and reactive oxygen species (ROS) production,
and mitochondrial membrane potential (MMP) in hyperglycemic (25 mM; for 24-h
incubation) cardiomyocytes comparison to those of controls (5.5 mM) by using Zn2+-sensitive
fluorescent FRET sensors or specific dyes. To examine the localization and
protein expression level of ZnT6, and the levels of mitochondrial proteins, we
used immunofluorescence and Western-blot analysis, respectively.
Results: Experimental
studies demonstrated that the mRNA and protein expression levels of ZnT6 is
increased, while S(E)R-mitochondrial functioning is depressed, both [Zn2+]cyc
and [Zn2+]Mit are increased in HG H9c2 cells. To mimic
the HG condition in these cells, the overexpressed ZnT6 caused a significant
decrease in [Zn2+]cyc and increase in [Zn2+]Mit
without changing the [Zn2+]SER. Our immunofluorescent
experiments showed that the ZnT6 localized on mitochondria together with ZnT5.
We also found that a loss of intracellular Zn2+-homeostasis,
increased ROS, depolarized MMP and decreased ATP production in ZnT6
overexpressed H9c2 cells. Overexpression of ZnT6 which regulates the Zn2+-homeostasis
caused mitochondrial dynamic imbalance towards fusion as previously observed in
hyperglycemic and hyperinsulinemic rat cardiomyocytes.
Conclusion: Our findings
suggest that any change in the Zn2+-homeostasis with ZnT6
overexpression exacerbates the mitochondrial function, including dissipation of
the MMP and inhibition of mitochondrial energy processes, which may further contribute
to cardiomyocyte damage, enhanced mitochondrial autophagy and subsequent whole
cell damage (Supported by Tubitak SBAG-117S386).