Lactosylceramide promotes hypertrophy through ROS generation and activation of ERK1/2 in cardiomyocytes

Hypertrophy is central to several heart diseases, however, not much is known about the role of glycosphingolipids (GSLs) in this phenotype. Since GSLs have been accorded several physiological functions, we sought to determine whether these compounds affect cardiac hypertrophy. By using a rat cardiomyoblast cell line; H9c2 cells and cultured primary neonatal rat cardiomyocytes, we have determined the effects of GSLs on hypertrophy. Our study comprised of a) Measurement of [3H]-Leucine incorporation into protein, b) Measurement of cell size and morphology by immunofluorescence microscopy and c) Real time quantitative mRNA expression assay for atrial natriuretic protein (ANP) and brain natriuretic peptide (BNP). Phenylephrine (PE), a well-established agonist of cardiac hypertrophy served as positive control in these studies. Subsequently, mechanistic studies were performed to explore the involvement of various signaling transduction pathways which may contribute to hypertrophy in these cardiomyocytes. We observed that Lactosylceramide (LacCer) specifically exerted a concentration (50-100μ M) and time (48hrs) dependent increase in hypertrophy in cardiomyocytes but not a library of other structurally related GSLs. Further, in cardiomyocytes, LacCer generated reactive oxygen species (ROS) and stimulated the phosphorylation of p44 MAP kinase and protein kinase-C and c-jun and c-fos expressions, ultimately leading to hypertrophy. In sum, we report here that LacCer specifically induces hypertrophy in cardiomyocytes via an "oxygen sensitive signal transduction pathway".