Inhibitory effect of antisense oligodeoxynucleotide to p44/p42 MAPK on angiotensin II-induced hypertrophic response in cultured neonatal rat cardiac myocyte.

AIM: To explore the inhibitory effect of antisense oligonucleotide (ODN) to mitogen activated protein kinase(MAPK) on cardiomyocyte hypertrophy induced by angiotensin II (Ang II).

METHODS: A 17-mer phosphorothioate-protected antisense ODN directed against the initiation of translation sites of the p42 and p44 MAPK isoforms by liposomal transfection was applied to inhibit the translation of p44/p42 MAPK mRNA. The sense and random ODNs to p44/p42MAPK were used as sequence controls. Neonatal cardiac myocytes were exposed to Ang II (10 nmol/L) for 5 min and then harvested in lysis buffer for the measurement of the activity and the phosphorylated protein content of p44/p42MAPK that were tested by P-81 phosphocellulose filter paper method and Western blotting, respectively. The rate of protein synthesis by [3H]leucine incorporation and the diameter of cell were measured after exposure to Ang II for 24 h and 72 h, respectively.

RESULTS: In cardiac myocyte Ang II increased p44/p42 MAPK activity and phosphorylated protein content by 140 % and 699 %, and also increased [3H]leucine incorporation and cell diameter by 40 % and 27 %. c-fos and c-myc mRNAs were induced significantly after exposure to Ang II. Antisense ODN to p44/p42MAPK (0.2 micromol/L) reduced Ang II-induced MAPK activity by 30 %, and phophorylated MAPK protein expression by 59 % in cardiac myocyte, and inhibited c-fos and c-myc mRNA expression induced by Ang II by 44 % and 43 %, respectively. The diameter and the rate of protein synthesis of cardiac myocyte induced by Ang II were decreased by 16 % and 22 % after pretreatment with antisense ODN to p44/p42MAPK.

CONCLUSION: Antisense ODN to p44/p42 MAPK inhibited the increase of rate of protein synthesis, and the augmentation of cell diameter and expression of c-fos and c-myc mRNA induced by Ang II in cultured cardiac myocytes. p44/p42 MAPK played a critical role in the hypertrophic response induced by Ang II in cultured neonatal rat cardiac myocytes.