Local Delivery of the K Ca 3.1 Blocker, TRAM-34, Prevents Acute Angioplasty-Induced Coronary Smooth Muscle Phenotypic Modulation and Limits Stenosis

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Abstract
Objective— We previously demonstrated that upregulation of intermediate-conductance Ca2+-activated K+ channels (KCa3.1) is necessary for mitogen-induced phenotypic modulation in isolated porcine coronary smooth muscle cells (SMCs). The objective of the present study was to determine the role of KCa3.1 in the regulation of coronary SMC phenotypic modulation in vivo using a swine model of postangioplasty restenosis. Methods and Results— Balloon angioplasty was performed on coronary arteries of swine using either noncoated or balloons coated with the specific KCa3.1 blocker TRAM-34. Expression of KCa3.1, c-jun, c-fos, repressor element-1 silencing transcription factor (REST), smooth muscle myosin heavy chain (SMMHC), and myocardin was measured using qRT-PCR in isolated medial cells 2 hours and 2 days postangioplasty. KCa3.1, c-jun, and c-fos mRNA levels were increased 2 hours postangioplasty, whereas REST expression decreased. SMMHC expression was unchanged at 2 hours, but decreased 2 days postangioplasty. Use of TRAM-34 coated balloons prevented KCa3.1 upregulation and REST downregulation at 2 hours, SMMHC and myocardin downregulation at 2 days, and attenuated subsequent restenosis 14 and 28 days postangioplasty. Immunohistochemical analysis demonstrated corresponding changes at the protein level. Conclusion— Blockade of KCa3.1 by delivery of TRAM-34 via balloon catheter prevented smooth muscle phenotypic modulation and limited subsequent restenosis. The objective of the present study was to determine the role of KCa3.1 in the regulation of coronary smooth muscle cell (SMC) phenotypic modulation in a swine model of postangioplasty restenosis. Blockade of KCa3.1 by delivery of TRAM-34 via balloon catheter prevented SMC phenotypic modulation and limited subsequent restenosis.