The Oxidized Lipid and Lipoxygenase Product 12(S)-Hydroxyeicosatetraenoic Acid Induces Hypertrophy and Fibronectin Transcription in Vascular Smooth Muscle Cells via p38 MAPK and cAMP Response Element-binding Protein Activation

Abstract

Growth factor-and cytokine-induced vascular smooth muscle cell proliferation, migration, hypertrophy, and matrix production have been shown to play important roles in the development of vascular disorders such as atherosclerosis, hypertension, and restenosis. Growth factors such as angiotensin II (AngII) 1 and platelet-derived growth factor (PDGF) activate intracellular phospholipases, leading to the formation of arachidonic acid, which can be further metabolized by cyclooxygenases, cytochrome P-450 oxygenases, and lipoxygenases (1). Lipoxygenase (LO) action leads to the formation of oxidized lipids such as 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE). LOs and their products of arachidonic acid and linoleic acid metabolism have been shown to mediate growth factor effects in vascular smooth muscle cells (VSMCs) as well as responses to vascular injury. Lipoxygenases are classified as 5-, 8-, 12-, and 15-lipoxygenases based on their ability to insert molecular oxygen at the corresponding carbon atom of arachidonic acid. Three major isoforms of 12-LO have been cloned. They are platelet-type 12-LO, leukocyte-type 12-LO, and epidermis-type 12-LO. These proteins are products of distinct genes and vary in tissue distribution (2, 3).Leukocyte 12-LO has been cloned from porcine and mouse leukocytes (4, 5). The presence of leukocyte-type 12-LO (also termed 12/15-LO) has also been demonstrated in various cell types and tissues, including VSMCs, adrenal cells, rat brain, and kidney (6 -11). Studies from this and other laboratories (12-21) have implicated the leukocyte-type 12-LO pathway in the pathogenesis of atherosclerosis and restenosis. 12-LO expression was demonstrated in atherosclerotic lesions (12). In vascular and mononuclear cells, growth factors and cytokines as well as high glucose stimulate both the activity and expression of 12-LO (6, 13-15). Furthermore, expression of 12-LO protein and mRNA is markedly increased in neointima of balloon-injured rat carotid arteries, and pretreatment with LO inhibitors reduces the rate of neointimal thickening in this model (16,17). We have demonstrated that treatment with a chimeric DNA-RNA hammerhead ribozyme targeted to cleave rat leukocyte-type 12-LO mRNA significantly reduces neointimal thickening in balloon-injured rat arteries (18). We have

Reduced Growth Factor Responses in Vascular Smooth Muscle Cells Derived from 12/15-Lipoxygenase–Deficient Mice

“…25,26 Furthermore, p38 MAPK activity was augmented in rat VSMC and cardiac fibroblasts overexpressing 12-LO cells. 25,34 Hence, we hypothesized that p38 MAPK activation may be reciprocally attenuated in LOKO VSMC. MVSMC were stimulated with serum (10% FBS) and cell lysates immunoblotted with phosphospecific-p38 MAPK antibody.…”

“…22,24 Recently, we showed that 12-LO products directly stimulated VSMC hypertrophy, activation of p38 mitogen-activated protein kinase (p38 MAPK), transcription factors NF-kappa B (NF-B), and cAMP response element binding protein (CREB) and induced transcription from the fibronectin and VCAM-1 promoters. 25,26 Furthermore, stable 12/15-LO overexpression in VSMC increased MAPK activity and induced hypertrophy. 25 Thus, 12/15-LO activation in VSMC may play a key role in vascular growth and injury responses.…”

“…25,26 Furthermore, stable 12/15-LO overexpression in VSMC increased MAPK activity and induced hypertrophy. 25 Thus, 12/15-LO activation in VSMC may play a key role in vascular growth and injury responses. The aim of the current study was to determine the in vivo pathologic role of 12/15-LO in VSMC by comparing basal and GF-mediated responses of VSMC derived from 12/15-LO knockout mice (LOKO) 27 with those isolated from genetic control (WT) mice.…”

Increased 12/15-Lipoxygenase Enhances Cell Growth, Fibronectin Deposition, and Neointimal Formation in Response to Carotid Injury

“…Reddy et al 6 previously demonstrated that 12S-HETE induces fibronectin promoter activity in VSMCs. To determine whether 12/15LO increases fibronectin production in vivo, potentially contributing to increased NIF in 12/15LO-tg mice, we performed immunostaining for fibronectin on 28-day postinjury LCCA sections (8 animals in each group).…”

“…12/15LO products of arachidonic acid, such as 12S-hydroxyeicosatetrenoic acid (HETE), 15S-HETE, and 13S-hydroperoxyoctadecadienoic acid (HPODE), are produced in VSMCs and have hypertrophic effects. 5,6 In vitro, 12/15LO inhibition attenuates hypertrophic effects of angiotensin II in VSMCs, mitogenic effects of cytokines, and chemotactic effects of platelet-derived growth factor. 5,7,8 Compared with VSMCs from C57BL/6 (BL-6) mice, VSMCs from 12/15LO-overexpressing transgenic (12/15LO-tg) mice grow faster, and VSMCs from 12/15LO Ϫ/Ϫ mice grow slower and display decreased S-phase entry in culture.…”