Browsing by Author "Sithelo, Pamela"
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- ItemInvestigating the efficacy and underlying mechanism of cardioprotection afforded by rooibos (aspalathus linearis) in angiotensin-ii induced cardiac hypertrophy & apoptosis(Stellenbosch : Stellenbosch University, 2021-03) Sithelo, Pamela; Marais, Erna; Maarman, Gerald; Strijdom, Hans; Lopes, John; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Medical Physiology.Purpose:Rooibos (RB) has been reported to confer cardioprotection, but the underlying mechanisms are not fully elucidated. Furthermore, RB has never been tested againstcardiac hypertrophy and apoptosis. Therefore, this study investigated the efficacy and underlying mechanisms of RB-induced cardioprotection in a model of angiotensin-II (Ang-II) induced cardiomyocyte hypertrophy & apoptosis. Methods:Six groups of H9c2cardiomyoblasts were either exposed to 2% FBS supplemented DMEM (control), Ang-II (20μM), RB (100μg/ml), Losartan (10μM) and co-treatment with RB + Ang-II or Ang-II + Losartan for 48 hrs. Cell viability, ATP levels, and hypertrophy and apoptosis signalling were measured with Western blotting. Cell size and mitochondrial membrane potential were measured using JC-1. Mitochondrial oxidative stress was measured with aconitase assay. Results:Ang-II induced hypertrophy as well as apoptosis in H9c2 cardiomyoblasts by increasing cell size and upregulating growth signalling pathways, while decreasing cell viability, up-regulating of pro-apoptotic markers (Bax and cleaved caspase-3) and downregulating anti-apoptotic Bcl-2. In addition, Ang-II decreased mitochondrial membrane potential and ATP levels. RB co-treatment effectively antagonized Ang-II-induced hypertrophy and apoptosis of H9c2 cells. This was mediated by reducing cell size and dephosphorylating growth signalling pathways such as ERK 1/2, PKB, mTOR, Calcineurin and GSK-3ß. RB also increased cell viability by increasing Bcl-2, decreasing Bax and cleaved caspase-3and thereby, inhibiting apoptosis.The administration of RB prevented depolarization of mitochondrial membrane potential and increased ATP activity. RB also enhanced the expression of mitochondrial respiratory chain complex IV and V, probably through the enhancement of mitochondrial biogenesis and the electron transfer system. Conclusion:To our knowledge, the current study is the first to show that RB attenuates Ang-II induced cardiomyoblast hypertrophy and apoptosis by improving mitochondrial parameters and restoring GSK-3 beta and Bcl-2 signalling.