Depletion of Mitogen-Activated Protein Kinase Using an Antisense Oligodeoxynucleotide Approach Downregulates the Phenylephrine-Induced Hypertrophic Response in Rat Cardiac Myocytes

Abstract

An antisense oligodeoxynucleotide (ODN) approach was used to investigate whether mitogen-activated protein kinase (MAPK) is necessary for the hypertrophic response in cardiac myocytes. A phosphorothioate-protected 17-mer directed against the initiation of translation sites of the p42 and p44 MAPK isoform mRNAs was introduced into cultured cardiac myocytes by liposomal transfection. At an antisense ODN concentration of 0.2 mumol/L, p42 MAPK protein was reduced by 82% (immunoblot) after 48 hours, and p42 and p44 MAPK activities were reduced by 44% and 60%, respectively. The same concentration of anti-MAPK ODN inhibited development of the morphological features of hypertrophy (sarcomerogenesis, increased cell size) in myocytes exposed to phenylephrine. Phenylephrine-induced activation of the atrial natriuretic factor (ANF) promoter (measured by the activity of a transfected ANF promoter/luciferase reporter gene) and induction of ANF mRNA (measured by RNase protection assay) were also attenuated. We conclude that MAPK is important for the development of the hypertrophic phenotype in this model of hypertrophy.

Mechanical Strain Increases Expression of the Brain Natriuretic Peptide Gene in Rat Cardiac Myocytes

“…In this study, the functional activity of the various pharmacological antagonists closely paralleled their ability to inhibit MAPK activity in these cultures. By inference, this suggests that MAPK participates in the signaling cascade linking mechanical strain to acquisition of the hypertrophic phenotype, a hypothesis that draws support from the studies of others (31)(32)(33). The activity of the inhibitors did not correlate well with their ability to inhibit JNK/SAPK activity.…”

“…MAPK, for example, is known to be activated by both the biochemical agonists of hypertrophy as well as mechanical strain (23, 27, 30 -32), and dominant-negative mutants of MAPK and MAPK kinase (MEK), which lies immediately upstream from MAPK in the effector cascade (34), suppress phenylephrine induction of a transiently transfected rat ANP promoter (31). Moreover, antisense oligonucleotides directed against MAPK have been shown to reduce phenylephrine-dependent increments in ANP mRNA levels and ANP promoter activity while, at the same time, suppressing sarcomerogenesis and increments in cell size that typically accompany hypertrophy induced by this agent (33). However, Post et al (32) recently reported that activation of MAPK does not routinely parallel the development of hypertrophy in the cultured myocyte model, and in their hands, dominant-negative mutants of the MAPK pathway failed to suppress phenylephrine-mediated activation of a transfected ANP promoter.…”

Interference with ERK Thr188 phosphorylation impairs pathological but not physiological cardiac hypertrophy

“…1B and quantification of cell size in Fig. S1E) (16,17). Strikingly, ERK2 T188A did not enhance H 2 O 2 -induced apoptotic cell death, as determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) (Fig.…”

Neuropeptide Y (NPY) potentiates phenylephrine-induced mitogen-activated protein kinase activation in primary cardiomyocytes via NPY Y5 receptors

“…Indeed, the activation of MAPK by various trophic factors appears important in the intracellular-signaling pathways leading to hypertrophy (17)(18)(19). For instance, blocking ERK protein synthesis using antisense oligodeoxynucleotides reduces transcriptional and morphological responses to PE in rat cardiomyocytes (30). NPY has been shown to potentiate the effects of various vasoactive substances including ␣-receptor agonists (6,8).…”