[Inhibitory effects of antisense oligonucleotides targeting mitogen-activated protein kinase (MAPK) mRNA on neonatal rat cardiac fibroblast proliferation induced by Ang II and EGF].
In the present study, the antisense oligodeoxynucleotide (ODN) approach was used to investigate whether mitogen-activated protein kinase (MAPK) is necessary for the proliferation response in neonatal rat cardiac fibroblast (FB) induced by angiotensin II (AngII) or epidermal growth factor (EGF), the proximal cytosolic signal transduction pathways which are quite different processes. A phosphorothioate-protected 17-mer directed against the initiation of translation sites P42 MAPK mRNA was introduced into FB by liposomal transfection. The results showed that (1) after a 24 h treatment with AngII or EGF (all 10(-8) mol/L), the FB numbers were increased by 39% and 68%, while the rate of DNA synthesis increased by 60% and 102%, respectively. (2) Following 5 min or 10 min stimulation with AngII or EGF, MAPK activity ([gamma-32P] ATP incorporation) increased by 202% and 305%, and phospho-MAPK protein content increased by 545% and 646% correspondingly. (3) As compared with lipofectin + AngII/EGF control, after pretreatment with MAPK antisense ODN, the MAPK protein expression was inhibited significantly; the rate of DNA synthesis of FB induced by AngII or EGF was reduced by 53% and 46%, cell numbers by 38% and 44%, respectively. Meanwhile, MAPK activity was decreased by 74.2% and 65.9%, phospho-MAPK protein content by 85% and 90%. The sense or random ODN has not much effect on them. Consequently, it can be concluded that (1) MAPK activity is essential in the event of involving FB proliferation response reduced by AngII and EGF, and (2) FB proliferation response could be inhibited by the MAPK antisense ODN through depletion of MAPK.