Abstract
1235
Objectives: β-adrenergic stimulation by isoproterenol (ISO) is widely used as a heart failure model, but it remains unclear how this treatment affects cardiomyocyte glucose metabolism, a major factor in heart failure progression. Here, we investigated how ISO suppresses glycolysis and 18F-FDG uptake of differentiated H9C2 cardiomyocytes at doses associated with only modest cytotoxic effects.
Methods: H9C2 rat cardiomyoblast cells underwent differentiation via 7-day incubation in media containing 1% FBS that was changed daily. Sulforhodamine B (SRB) cell survival assays, 18F-FDG uptake and lactate release measurements, mitochondrial ROS measurements, and Western blot analysis was performed.
Results: Treatment with 200 μM ISO caused a 28.4 ± 5.4% decrease of cellular 18F-FDG uptake and 19.4 ± 2.1% decrease of lactate release at 24 hours, when its cytotoxic effect was only mild. This was accompanied by dose-dependent increases of mitochondria-derived ROS. In ISO-treated cells, N-acetyl-L-cysteine (NAC) effectivey scavenged cellular ROS, and returned 18F-FDG uptake and lactate release that had been suppressed by ISO to baseline levels. In addition, NAC prevented ISO-induced death of H9C2 cardiomyocytes, Thus, suppression of both glycolytic metabolism and cell survival by ISO occured by stimulatig an increase of mitochondrial ROS production. Further investigation of sigaling pathways that mediate the response revealed that ISO treatment decreased extracellular-signal-regulated kinase (ERK) activation but markedly upregulated p53 expression. Both of these signaling responses were completely abrogated by NAC. Silencing of p53 expression with siRNA completely blocked the ability of ISO to stimulate mitochondrial ROS generation and suppress 18F-FDG uptake.
Conclusions: These findings demonstrate that ISO treatment decreases cardiomyocyte 18F-FDG uptake by downregulating glycolytic flux and further reveals that ROS-p53 signaling plays a critical role in this metabolic response.