Molecular mechanisms regarding potassium bromate-induced cardiac hypertrophy without apoptosis in H9c2 cells

Cardiac hypertrophy is commonly involved in cardiac injury. Oxidative stress can induce cardiac hypertrophy with apoptosis. Potassium bromate (KBrO3) has been widely used as a food additive due to its oxidizing properties. In the present study, the rat-derived heart cell line H9c2 was used to investigate the effect of KBrO3 on cell size. KBrO3 increased cell size at concentrations <250 mu M, in a dose-dependent manner. Additionally, KBrO3 also promoted the gene expression of two biomarkers of cardiac hypertrophy, brain/B-type natriuretic peptides (BNP) and beta-Myosin Heavy Chain (beta-MHC). However, apoptosis remained unobserved in these cells. Moreover, mediation of free radicals was investigated using a fluorescence assay, and it was observed that superoxide and reactive oxygen species (ROS) levels increased with KBrO3. Effects of KBrO3 were significantly reduced by tiron at concentrations sufficient to produce antioxidant-like action. Additionally, signals involved in cardiac hypertrophy such as calcineurin and nuclear factor of activated T-cells (NFAT) were also determined using western blot analysis. KBrO3 increased the protein levels of both these molecules which were decreased by tiron in a dose-dependent manner. Additionally, cyclosporine A attenuated the cardiac hypertrophy induced by KBrO3 in H9c2 cells at concentrations effective to inhibit calcineurin, in addition to reducing mRNA levels of BNP or beta-MHC. Finally, apoptosis was also identified in H9c2 cells incubated with KBrO3 at concentrations >300 mu M. Collectively, these results provided a novel perspective that KBrO3 induces cardiac hypertrophy without apoptosis at a low dose through the generation of ROS, activating the calcineurin/NFAT signaling pathway in H9c2 cells. Therefore, at a dose <250 mu M, KBrO3 can be applied as an inducer of cardiac hypertrophy without apoptosis in H9c2 cells. KBrO3 can also be developed as a tool to induce cardiac hypertrophy in animals.