c-Jun N-Terminal Kinase Primes Endothelial Cells at Atheroprone Sites for Apoptosis

Abstract

Objective-Atherosclerosis is a focal disease that occurs predominantly at branches and bends of the arterial tree.Endothelial cells (EC) at atherosusceptible sites are prone to injury, which can contribute to lesion formation, whereas EC at atheroprotected sites are resistant. The c-Jun N-terminal kinase (JNK) is activated constitutively in EC at atherosusceptible sites but is inactivated at atheroprotected sites by mitogen-activated protein kinase phosphatase-1 (MKP-1). Here, we examined the effects of JNK activation on EC physiology at atherosusceptible sites. Methods and Results-We identified transcriptional programs regulated by JNK by applying a specific pharmacological inhibitor to cultured EC and assessing the transcriptome using microarrays. This approach and subsequent validation by gene silencing revealed that JNK positively regulates the expression of numerous proapoptotic molecules. Analysis of aortae of wild-type, JNK1Ϫ/Ϫ, and MKP-1 Ϫ/Ϫ mice revealed that EC at an atherosusceptible site express proapoptotic proteins and are primed for apoptosis and proliferation in response to lipopolysaccharide through a JNK1-dependent mechanism, whereas EC at a protected site expressed lower levels of proapoptotic molecules and were protected from injury by MKP-1. Key Words: apoptosis Ⅲ arterial endothelium Ⅲ atherosusceptibility Ⅲ c-Jun N-terminal kinase Ⅲ mitogen-activated protein kinase phosphatase-1 A therosclerosis is characterized by the accumulation of cells, lipids, and extracellular matrix in the wall of an artery, which can result in occlusion of the vessel lumen. It develops predominantly at branches and bends that are exposed to disturbed patterns of blood flow, whereas regions exposed to uniform flow are protected. [1][2][3][4] The molecular mechanism underlying the distinct spatial distribution of lesions is likely to involve apoptosis. Regions that are predisposed to atherosclerosis are characterized by relatively high rates of endothelial cell (EC) injury and turnover, [5][6][7] and apoptosis can be induced in cultured EC by the application of atheroprone flow patterns. 8,9 A causal relationship between apoptosis and atherosclerosis was established by enforcing expression of a proapoptotic molecule in arterial EC, which enhanced the accessibility of lipoproteins and leukocytes to arteries and initiated lesion formation in hypercholesterolemic mice. 10 In addition, focal endothelial apoptosis/injury in atherosclerotic lesions can, in turn, lead to endothelial denudation and exposure of a procoagulant vascular wall, a major cause of coronary thrombosis. 11,12 Several proatherogenic agents are known to induce EC apoptosis, including oxidized low-density lipoproteins, 13 reactive oxygen intermediaries (eg, H 2 O 2 14 ) and proinflammatory mediators (eg, lipopolysaccharide [LPS], 15 tumor necrosis factor [TNF]-␣ 16 ) by activating distinct signaling pathways that converge to cleave procaspase-3 into the active form of caspase-3. Cleaved caspase-3, in turn, executes apoptosis by activating numerous downs...

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“…JNK associates with stress fibers in ECs and plays a role in actin remodeling (43,44). Regions of the vasculature with disturbed flow have higher levels of active JNK (45,46). Similarly, p38 plays a role in actin remodeling (41,47,48) and facilitates actin remodeling in response to changes in shear stress (49).…”

Molecular Biology of Atherosclerosis

“…These include PKC (which has multiple targets), (GCK; or MAP4K2), and PAK1/2 (p21 activated kinase 1 and 2). Flow-induced PAK activation in endothelial cells apparently activates JNK through the MAP2K MKK4 (285,692,1353). JNK induces bone morphogenic protein 2 (BMP2), BMP4, and Toll-like receptor 4 (TLR4) and has numerous other proinflammatory and pro-apoptotic effects in endothelial cells (285) yet only JNK2 appeared to be atherogenic (see TABLE 1).…”

“…Conversely, stimulation of the ␣ 5 ␤ 1 and ␣ V ␤ 3 integrins by onset of flow over endothelial cells grown on fibronectin resulted in activation of PKC␣, NF-B, p38, and JNK which inhibited the anti-inflammatory signaling from integrin ␣ 2 ␤ 1 (568,692,1352,1353,1878). Resulting JNK expression primes endothelial cells for apoptosis in atherosclerosis-prone areas (285). Importantly, these inflammatory signals are largely mediated by G proteins Rac1 and Cdc42 and the tyrosine kinase PAK (1353).…”

“…In contrast, BMP2 is produced in response to inflammation (such as in response to TNF-␣) or high pressure (278). Both BMP2 and BMP4 were induced by JNK1 in mice at atheroprone sites (285). Also, incubation of human aortic endothelial cells in high glucose increased expression of both BMP4 and BMP2; their type I receptors ALK1, ALK2, ALK3, and ALK6; the type II BMP receptor BMPRII; and at least two extracellular inhibitors of BMP receptor binding, Noggin and MGP.…”

Ovarian cancer G protein-coupled receptor 1-dependent and -independent vascular actions to acidic pH in human aortic smooth muscle cells

“…PAI-1 levels are altered in vascular disorders, including atherosclerosis, and modulate SMC responses, leading to vascular remodeling (10). MKP-1 expression is induced by various stimuli and regulates vascular function (2,4,21,24,26,27,54).…”