Mechanisms of ANG II-induced mitogenic responses: role of 12-lipoxygenase and biphasic MAP kinase

• Published in: The American journal of physiology Vol. 271; no. 4 Pt 1; p. C1212
• Main Authors: Wen, Y, Nadler, J L, Gonzales, N, Scott, S, Clauser, E, Natarajan, R
• Format: Journal Article
• Language: English
• Published: United States 01.10.1996
• Subjects: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid - physiology; Angiotensin II - pharmacology; Animals; Arachidonate 12-Lipoxygenase - physiology; Calcium-Calmodulin-Dependent Protein Kinases - physiology; CHO Cells; Cricetinae; Cyclooxygenase Inhibitors - pharmacology; DNA - biosynthesis; Enzyme Activation; GTP-Binding Proteins - physiology; Ibuprofen - pharmacology; Meclofenamic Acid - pharmacology; Mitosis - drug effects; Pertussis Toxin; Time Factors; Transfection; Virulence Factors, Bordetella - pharmacology
• ISSN: 0002-9513
• DOI: 10.1152/ajpcell.1996.271.4.c1212

The potential mechanisms of angiotensin II (ANG II)-induced mitogenesis were studied in a Chinese hamster ovary fibroblast cell line overexpressing the rat vascular type 1a ANG II receptor (CHO-AT1a). ANG II had potent mitogenic effects in these CHO-AT1a cells, leading to a sustained increase in cell number as well as a dose-dependent increase in DNA synthesis. ANG II treatment also induced a biphasic elevation of mitogen-activated protein (MAP) kinase activity of both p42MAPK and p44MAPK with a rapid early peak at 5 min (2- to 6-fold) followed by a second sustained increase that reached a peak at 3 h (1.5- to 3-fold). We have previously shown that the 12-lipoxygenase (12-LO) pathway of arachidonate metabolism plays a key role in ANG II-induced growth of vascular smooth muscle and adrenal cells. In the present study, ANG II (10(-7) M) increased the formation of the 12-LO product, 12-hydroxyeicosatetraenoic acid (12-HETE). ANG II-induced DNA synthesis was inhibited by a specific LO inhibitor, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (CDC, 10 microM). In contrast, a cyclooxygenase blocker of arachidonate metabolism such as ibuprofen had no effect on ANG II-induced DNA synthesis. ANG II-induced DNA synthesis was also partially (32%) blocked by pertussis toxin (PTX). CDC and PTX also selectively blocked only the late (3 h) peak of ANG II-induced MAP kinase activity, suggesting that the late sustained peak of MAP kinase activity may be linked to the mitogenic effect of ANG II. Direct addition of 12-HETE (10(-7) M) led to a sustained increase in cell number similar to the effect of ANG II. 12-HETE also caused an increase in MAP kinase activity, and 12-HETE effects were blocked by PTX. These results suggest that ANG II-induced mitogenic response is associated with sustained MAP kinase activation and that LO activation may play a key role in this process.