Glycated Proteins Stimulate Reactive Oxygen Species Production in Cardiac Myocytes

Abstract

Background— Nonenzymatic glycation that results in the production of early-glycation Amadori-modified proteins and advanced-glycation end products may be important in the pathogenesis of diabetic complications. However, the effects of early-glycated proteins, such as glycated serum albumin (Gly-BSA), are poorly defined. In this study, we investigated the effects of Gly-BSA on reactive oxygen species (ROS) production by cardiomyocytes. Methods and Results— Cultured neonatal rat cardiomyocytes were incubated with Gly-BSA or vehicle (bovine serum albumin [BSA]) for up to 48 hours. Gly-BSA dose-dependently increased in situ ROS production (whole-cell dichlorodihydrofluorescein fluorescence), with an optimum effect at 400 μg/mL after 24-hour incubation (152±10% versus BSA 100%; P <0.01). Treatment with the NADPH oxidase inhibitor apocynin, a Nox2 (gp91phox) antisense oligonucleotide (Nox2 AS), or the peptide gp91ds-tat significantly reduced Gly-BSA–induced ROS production at 24 hours (68.5±2.2%, 61.4±8.3%, and 53.2±5.4% reduction, respectively). NADPH-dependent activity in cell homogenates was also significantly increased by Gly-BSA at 24 hours (161±8% versus BSA) and was inhibited by diphenyleneiodonium, apocynin, NOX2AS, and the protein kinase C inhibitor bisindolylmaleimide I but not by a nitric oxide synthase inhibitor or mitochondrial inhibitors. Furthermore, bisindolylmaleimide I prevented Gly-BSA–stimulated Rac1 translocation, an essential step for NADPH oxidase activation. Gly-BSA–induced increases in ROS were associated with apocynin-inhibitable nuclear translocation of nuclear factor-κB and an increase in atrial natriuretic factor mRNA expression. Conclusions— Gly-BSA stimulates cardiomyocyte ROS production through a protein kinase C–dependent activation of a Nox2-containing NADPH oxidase, which results in nuclear factor-κB activation and upregulation of atrial natriuretic factor mRNA. These findings suggest that early-glycated Amadori products may play a role in the development of diabetic heart disease.