The intermediate-conductance calcium-activated potassium channel KCa3.1 contributes to atherogenesis in mice and humans.
ABSTRACT Atherosclerosis remains a major cause of death in the developed world despite the success of therapies that lower cholesterol and BP. The intermediate-conductance calcium-activated potassium channel KCa3.1 is expressed in multiple cell types implicated in atherogenesis, and pharmacological blockade of this channel inhibits VSMC and lymphocyte activation in rats and mice. We found that coronary vessels from patients with coronary artery disease expressed elevated levels of KCa3.1. In Apoe(-/-) mice, a genetic model of atherosclerosis, KCa3.1 expression was elevated in the VSMCs, macrophages, and T lymphocytes that infiltrated atherosclerotic lesions. Selective pharmacological blockade and gene silencing of KCa3.1 suppressed proliferation, migration, and oxidative stress of human VSMCs. Furthermore, VSMC proliferation and macrophage activation were reduced in KCa3.1(-/-) mice. In vivo therapy with 2 KCa3.1 blockers, TRAM-34 and clotrimazole, significantly reduced the development of atherosclerosis in aortas of Apoe(-/-) mice by suppressing VSMC proliferation and migration into plaques, decreasing infiltration of plaques by macrophages and T lymphocytes, and reducing oxidative stress. Therapeutic concentrations of TRAM-34 in mice caused no discernible toxicity after repeated dosing and did not compromise the immune response to influenza virus. These data suggest that KCa3.1 blockers represent a promising therapeutic strategy for atherosclerosis.
Article: Vascular smooth muscle cell-directed overexpression of heme oxygenase-1 elevates blood pressure through attenuation of nitric oxide-induced vasodilation in mice.[show abstract] [hide abstract]
ABSTRACT: To elucidate pathophysiological roles of heme oxygenase (HO)-1 in regulation of vascular tone in vivo, we have developed and characterized transgenic (Tg) mice that overexpress HO-1 site specifically in vascular smooth muscle cells (VSMCs). The Tg mice were generated by use of human HO-1 cDNA under the control of SM22-alpha promoter. The HO-1 gene overexpression was demonstrated by Northern blot analysis and coincided with increases in the protein expression in VSMCs and total HO activities. Tg mice exhibited a significant increase in arterial pressure at various ages and displayed impaired nitrovasodilatory responses in isolated aortic segments versus nontransgenic littermates while enhancing their nitric oxide (NO) production. The pressure of Tg mice was unchanged by systemic administration of either N(omega)-nitro-L-arginine or SNP. Furthermore, the isolated aorta in these mice exhibited lesser extents of NO-elicited cGMP elevation via soluble guanylate cyclase (sGC), while exhibiting no notable downregulation of sGC expression. Such impairment of the NO-elicited cGMP increase was restored significantly by tin protoporphyrin IX, an HO inhibitor. On the other hand, 3-(5'-hydroxymethyl-2' furyl)-1-benzyl-indazol (YC-1), an NO-independent activator of sGC, increased cGMP and relaxed aortas from Tg mice to levels comparable with those from nontransgenic mice, which indicates that contents of functionally intact sGC are unlikely to differ between the two systems. These findings suggest that site-specific overexpression of HO-1 in VSMCs suppresses vasodilatory response to NO and thereby leads to an elevation of arterial pressure.Circulation Research 08/2001; 89(1):55-62. · 9.49 Impact Factor
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ABSTRACT: Atherosclerosis is a chronic inflammatory disease, and is the primary cause of heart disease and stroke in Western countries. Derivatives of cannabinoids such as delta-9-tetrahydrocannabinol (THC) modulate immune functions and therefore have potential for the treatment of inflammatory diseases. We investigated the effects of THC in a murine model of established atherosclerosis. Oral administration of THC (1 mg kg(-1) per day) resulted in significant inhibition of disease progression. This effective dose is lower than the dose usually associated with psychotropic effects of THC. Furthermore, we detected the CB2 receptor (the main cannabinoid receptor expressed on immune cells) in both human and mouse atherosclerotic plaques. Lymphoid cells isolated from THC-treated mice showed diminished proliferation capacity and decreased interferon-gamma secretion. Macrophage chemotaxis, which is a crucial step for the development of atherosclerosis, was also inhibited in vitro by THC. All these effects were completely blocked by a specific CB2 receptor antagonist. Our data demonstrate that oral treatment with a low dose of THC inhibits atherosclerosis progression in the apolipoprotein E knockout mouse model, through pleiotropic immunomodulatory effects on lymphoid and myeloid cells. Thus, THC or cannabinoids with activity at the CB2 receptor may be valuable targets for treating atherosclerosis.Nature 05/2005; 434(7034):782-6. · 36.28 Impact Factor
Article: Selective blockade of the intermediate-conductance Ca2+-activated K+ channel suppresses proliferation of microvascular and macrovascular endothelial cells and angiogenesis in vivo.[show abstract] [hide abstract]
ABSTRACT: Ca2+-activated K+ (K(Ca)) channels have been proposed to promote mitogenesis in several cell types. Here, we tested whether the intermediate-conductance K(Ca) channel (IKCa1) and the large-conductance K(Ca) channel (BK(Ca)) contribute to endothelial cell (EC) proliferation and angiogenesis. Function and expression of IKCa1 and BK(Ca)/Slo were investigated by patch-clamp analysis and real-time RT-PCR in human umbilical vein ECs (HUVECs) and in dermal human microvascular ECs 1 (HMEC-1). HMEC-1 expressed IKCa1 and BK(Ca)/Slo, whereas HUVECs expressed IKCa1. A 48-hour exposure to basic fibroblast growth factor (bFGF) augmented IKCa1 current amplitudes and induced a 3-fold increase in IKCa1 mRNA expression in HUVECs and HMEC-1. Vascular endothelial growth factor (VEGF) was also effective in upregulating IKCa1. BK(Ca)/Slo expression and current amplitudes in HMEC-1 were not altered by bFGF. bFGF- and VEGF-induced EC proliferation was suppressed by charybdotoxin, clotrimazole, or the selective IKCa1 blocker 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34), whereas inhibition of BK(Ca)/Slo by iberiotoxin was ineffective. In the Matrigel plug assay in mice, administration of TRAM-34 for 2 weeks significantly suppressed angiogenesis by approximately 85%. bFGF and VEGF upregulate expression of IKCa1 in human ECs. This upregulation of IKCa1 seems to be required for mitogen-induced EC proliferation and angiogenesis in vivo. Selective IKCa1 blocker might be of therapeutic value to prevent tumor angiogenesis.Arteriosclerosis Thrombosis and Vascular Biology 05/2005; 25(4):704-9. · 6.37 Impact Factor