Angiotensin II activation of insulin-like growth factor 1 receptor transcription is mediated by a tyrosine kinase-dependent redox-sensitive mechanism.
We have recently shown that angiotensin II activation of insulin-like growth factor 1 receptor (IGF-1R) transcription is a critical requirement for angiotensin-stimulated vascular smooth muscle cell growth; therefore, we examined the signaling pathway involved. In rat aortic smooth muscle cells, the antioxidants N-acetyl-L-cysteine (5 mmol/L) and pyrrolidine dithiocarbamate (100 micromol/L) completely inhibited angiotensin II-stimulated increases in IGF-1R mRNA and protein levels, suggesting the involvement of reactive oxygen species. Indeed, catalase abolished the Ang II-stimulated increase of IGF-1R protein expression, and accordingly, H(2)O(2) (0.2 mmol/L) or the oxidized products of linoleic acid, hydroperoxyoctadecadienoic acids (10 micromol/L), increased IGF-1R mRNA levels at 3 hours by 74+/-20% and 107+/-22% and increased receptor number at 24 hours by 51+/-6.7% and 55+/-7.4%, respectively. The protein tyrosine kinase inhibitors genistein and tyrphostin A25 also blocked angiotensin II increases in IGF-1R mRNA and protein levels and blocked the ability of hydroperoxyoctadecadienoic acids and H(2)O(2) to increase IGF-1R expression, suggesting that oxidative stress may be an early event in the angiotensin II signaling cascade. Furthermore, calcium chelation inhibited the angiotensin II effect. Transient transfection assays revealed that a (-2350)+640 IGF-1R promoter/luciferase construct was fully responsive to angiotensin II stimulation (127+/-20% increase). Ten millimoles per liter hydroperoxyoctadecadienoic acids and 0.2 mmol/L H(2)O(2) increased luciferase activity by 79+/-8.5% and 63+/-12%, respectively, and 5 mmol/L N-acetyl-L-cysteine blocked the angiotensin II-induced upregulation of luciferase activity by 70%. These data suggest that angiotensin II stimulates IGF-1R gene transcription via calcium-dependent activation of protein tyrosine kinase activity that lies downstream from an oxidant stimulus. These findings provide key insights into the signaling mechanisms whereby angiotensin II exerts its growth-promoting effects on the vasculature.
Du
J
J
Emory University, Atlanta, Ga, USA.
Peng
T
T
Scheidegger
K J
KJ
Delafontaine
P
P
D000111:Acetylcysteine / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D017930:Genes, Reporter / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008041:Linoleic Acids / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D010084:Oxidation-Reduction; D011505:Protein-Tyrosine Kinases / Q000378:metabolism* / Q000502:physiology; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000235:genetics*; D013859:Thiocarbamates / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology
D000975:Antioxidants; D008041:Linoleic Acids; D011759:Pyrrolidines; D013859:Thiocarbamates; D000804:Angiotensin II; C020972:pyrrolidine dithiocarbamic acid; D006861:Hydrogen Peroxide; D011505:Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1; D002118:Calcium; D000111:Acetylcysteine