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Selected Publication:
Koeltgen, C.
The role of NOX4 in SIRT4-driven worsening of pathological cardiac hypertrophy
Humanmedizin; [ Diplomarbeit ] Medizinische Universität Graz; 2024. pp. 102
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- Authors Med Uni Graz:
- Advisor:
- Bugger Heiko Matthias
- Byrne Nikole
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- Abstract:
- Pathological hypertrophy leads to systolic and diastolic dysfunction and ultimately to heart failure. Oxidative stress has been shown to contribute to hypertrophic remodeling of the heart. Mitochondrial NAPDH oxidase 4 (NOX4) can be directly linked to the increase in oxidative stress in cardiac muscle cells through its production of reactive oxygen species (ROS). Sirtuin 4 (SIRT4) is a mitochondrial deacetylase that has been involved in the regulation of ROS homeostasis and is known to accelerate hypertrophic growth of the heart. Preliminary data from our group show that overexpression of SIRT4 drives aggravation of pressure overload-induced cardiac hypertrophy by oxidative stress, potentially mediated by markedly increased NOX4 expression. To evaluate the potential of SIRT4 to mediate NOX4 expression in cardiac hypertrophy, this study investigated whether SIRT4 overexpression increases NOX4 expression in response to pro-hypertrophic signaling in a cell culture model. Rat cardiomyoblasts (H9c2) were transfected with a vector for human SIRT4 overexpression and then stimulated with angiotensin II (ANG II) or isoproterenol (ISO) to induce a hypertrophic response. Cell size was quantified using wheat germ agglutinine (WGA) fluorescence staining. mRNA and protein levels of brain natriuretic peptide (BNP) and NOX4 were analyzed by RT-qPCR and JESS-automated immunoblotting, respectively. Transfection of rat cardiomyoblasts resulted in successful expression of human SIRT4 mRNA, whereas human SIRT4 expression was not detectable in cells undergoing control transfection. Expression of rat SIRT4 mRNA was almost significantly decreased (p=0.05) in SIRT4 transfected cells, indicative of compensatory suppression of endogenous SIRT4 expression. While ANG II treatment did not increase cardiomyocyte size or Bnp mRNA levels, ISO treatment resulted in increased cardiomyocyte size and increased Bnp mRNA levels, indicative of successful induction of cardiomyocyte hypertrophy. While SIRT4 overexpression alone did increase BNP levels compared to control transfections, combining SIRT4 transfection and ISO treatment did not synergistically increase Bnp mRNA levels. NOX4 mRNA or protein expression was not altered by ISO treatment of control cells. In addition, Nox4 mRNA levels were not significantly increased in SIRT4 overexpressing cells, neither in the presence or absence of ISO. Thus, we conclude that a) increased expression of SIRT4 leads to hypertrophy in H9c2 cardiomyoblasts, and b) NOX4 expression in H9c2 cardiomyoblasts is not driven by SIRT4.