KCa3.1 Inhibition Decreases Size and Alters Composition of Atherosclerotic Lesions Induced by Low, Oscillatory Flow

Darla L Tharp,Douglas K Bowles

doi:10.2991/artres.k.210202.001

Abstract

Low, oscillatory flow/shear patterns are associated with atherosclerotic lesion development. Increased expression of KCa3.1 has been found in Vascular Smooth Muscle (VSM), macrophages and T-cells in lesions from humans and mice. Increased expression of KCa3.1, is also required for VSM cell proliferation and migration. Previously, we showed that the specific KCa3.1 inhibitor, TRAM-34, could inhibit coronary neointimal development following balloon injury in swine. Atherosclerosis develops in regions with a low, oscillatory (i.e. atheroprone) flow pattern. Therefore, we used the Partial Carotid Ligation (PCL) model in high-fat fed, Apoe-/- mice to determine the role of KCa3.1 in atherosclerotic lesion composition and development. PCL was performed on 8–10 week old male Apoe-/- mice and subsequently placed on a Western diet (TD.88137, Teklad) for 4 weeks. Mice received daily s.c. injections of TRAM-34 (120 mg/kg) or equal volumes of vehicle (peanut oil, PO). 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) treatment reduced lesion size ~50% (p < 0.05). In addition, lesions from TRAM-34 treated mice contained less collagen (6% ± 1% vs. 15% ± 2%; p < 0.05), fibronectin (14% ± 3% vs. 32% ± 3%; p < 0.05) and smooth muscle content (19% ± 2% vs. 29% ± 3%; p < 0.05). Conversely, TRAM-34 had no effect on total cholesterol (1455 vs. 1334 mg/dl, PO and TRAM, resp.) or body weight (29.1 vs. 28.8 g, PO and TRAM, resp.). Medial smooth muscle of atherosclerotic carotids showed diminished RE1-Silencing Transcription Factor (REST)/Neural Restrictive Silencing Factor (NRSF) expression, while REST overexpression in vitro inhibited smooth muscle migration. Together, these data support a downregulation of REST/NRSF and upregulation of KCa3.1 in determining smooth muscle and matrix content of atherosclerotic lesions.

Highlights

Despite lipid lowering and emerging anti-inflammatory agents, atherosclerosis remains the leading cause of death in both men and women in the United States [1,2]
Atherosclerotic lesions are known to develop predominantly in regions of disturbed flow characterized by low, oscillatory shear in humans and animal models of atherosclerosis [10,11]
Body weights for control and TRAM-34 treated mice were similar at the beginning (25.3 ± 0.6 g vs. 25.9 ± 0.4 g, resp.) and end

Summary

Introduction

Despite lipid lowering and emerging anti-inflammatory agents, atherosclerosis remains the leading cause of death in both men and women in the United States [1,2]. Atherosclerosis is an inflammatory, proliferative disease that develops over decades, and includes the involvement of numerous cell types including endothelial cells, smooth muscle cells, fibroblasts, macrophages, T-cells, and B-cells as well as platelets. The intermediate-conductance Ca2+-activated K+ channel (KCa3.1) is expressed in all of these cell types, and contributes to T-cell, B-cell, fibroblast, and vascular Smooth Muscle Cells (SMC) proliferation; as well as the migration of Vascular Smooth Muscle (VSM) and macrophages and platelet coagulation [3,4,5,6,7]. Increased expression of the KCa3.1 has been observed in smooth muscle, macrophages and T-cells in atherosclerotic lesions from humans and mice [6], while treatment of Apoe−/− mice with the KCa3.1 inhibitor, TRAM-34, produced smaller lesions in the aortic root [6]. KCa3.1 activation in VSM likely contributes to plaque formation

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Conclusion