Genistein inhibits pressure-induced expression of c-fos in isolated mesenteric arteries.
We have previously demonstrated that elevating intraluminal pressure from 90 to 140 mm Hg in isolated mesenteric arteries increases the expression of proto-oncogenes. These proto-oncogenes encode nuclear transcription factors that regulate the expression of target genes during various stages of the cell cycle. Thus, pressure-induced proto-oncogene expression may represent a mechanism by which pressure can induce growth and/or proliferation of vascular smooth muscle. The purpose of this study was to determine the intracellular signals that contribute to the pressure-induced increase in c-fos expression. Small mesenteric arteries were isolated from male Wistar rats and transferred to a dual-vessel chamber. The arteries were cannulated and slowly equilibrated to initial conditions (90 mm Hg, 37 degrees C) while being continuously superfused with a HEPES-bicarbonate-buffered Krebs' solution. After the equilibration period, the intraluminal pressure in 1 artery was increased to 140 mm Hg for 1 hour. In experiments designed to determine the intracellular signals involved in the pressure-induced increase in c-fos expression, specific inhibitors were introduced to the superfusate reservoir of both arteries before the pressure increase. The arteries were then fixed in phosphate-buffered formalin and embedded in paraffin blocks. Sections of paraffin-embedded arteries were fixed on slides, and the expression of c-fos was determined by in situ hybridization with the use of (35)S-labeled riboprobes. The pressure-induced expression of c-fos was not inhibited by nitrendipine (10 micromol/L), a calcium-free Krebs' solution containing EGTA (1 to 2 mmol/L), calphostin C (0.1 micromol/L), or cytochalasin D (0.4 micromol/L) but was inhibited by genistein (30 micromol/L). The results suggest that activation of a tyrosine kinase is required for pressure-induced c-fos expression, but the signaling pathway does not require extracellular calcium entry, intact actin filaments, or protein kinase C. As we have shown previously, the expression of c-fos correlated with wall stress.
Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA, USA.
V A
VA
Miriel
S P
SP
Allen
S D
SD
Schriver
R L
RL
Prewitt
D000199:Actins / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology*; D017403:In Situ Hybridization; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism*; D009568:Nitrendipine / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D016760:Proto-Oncogene Proteins c-fos / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology
D000199:Actins; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D004533:Egtazic Acid; D009568:Nitrendipine; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C