cGMP-elevating agents suppress proliferation of vascular smooth muscle cells by inhibiting the activation of epidermal growth factor signaling pathway.
BACKGROUND
Abnormal proliferation of vascular smooth muscle cells (VSMC) is a key event in the pathogenesis of atherosclerosis and many vascular diseases. It is known that nitric oxide released from the endothelium participates in the regulation of VSMC proliferation via a cyclic 3',5'-guanosine monophosphate (cGMP)-mediated mechanism. In a series of experiments, sodium nitroprusside (SNP) and A02131-1 were evaluated for their antiproliferative effect and the mechanism of their cGMP-elevating action.


RESULTS
The effect of SNP and A02131-1 on epidermal growth factor (EGF)-stimulated proliferation of rat aortic smooth muscle cells (VSMC) was examined. Cell proliferation was measured in terms of [3H]thymidine incorporation, flow cytometry, and the cell number. Further, their effect on the EGF-activated signal transduction pathway was assessed by measuring mitogen-activated protein kinases (MAPK), MAPK kinase (MEK). Raf-1 activity, and the formation of active form of Ras. SNP and A02131-1 inhibited EGF-induced DNA synthesis and subsequent proliferation of VSMC. These two increased cGMP but only a little cAMP in VSMC. A similar antiproliferative effect was observed with 8-bromo-cGMP. The antiproliferative effect of the two was reversed by KT5823 but not by dideoxyadenosine nor Rp-cAMPS. SNP and A02131-1 blocked the EGF-inducible cell cycle progression at the G1/S phase. Further experiments indicated that the two cGMP-elevating agents primarily blocked the activation of Raf-1 by EGF-activated Ras.


CONCLUSIONS
These results demonstrate that cGMP-elevating agents inhibit [3H]thymidine incorporation and thus the growth of VSMC, and this inhibition appears to attenuate EGF-activated signal transduction pathway by preventing Ras-dependent activation of Raf-1.
Yu
S M
SM
Department of Pharmacology, Chang Gung College of Medicine and Technology, Kwei-San, Tao-Yuan, Taiwan, Republic of China.
Hung
L M
LM
Lin
C C
CC
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D001011:Aorta; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D007770:L-Lactate Dehydrogenase; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D009599:Nitroprusside / Q000494:pharmacology; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*; D013876:Thiophenes / Q000494:pharmacology; D013936:Thymidine / Q000096:biosynthesis; D018631:ras Proteins / Q000378:metabolism
C094836:A 02011-1; D000906:Antibodies; D010446:Peptide Fragments; D010726:Phosphodiesterase Inhibitors; D011518:Proto-Oncogene Proteins; D011720:Pyrazoles; D013876:Thiophenes; D006153:Guanosine Diphosphate; D009599:Nitroprusside; C016276:8-bromocyclic GMP; D004815:Epidermal Growth Factor; D006160:Guanosine Triphosphate; D004247:DNA; D000242:Cyclic AMP; D007770:L-Lactate Dehydrogenase; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D018631:ras Proteins; D006152:Cyclic GMP; D013936:Thymidine