Transient Receptor Potential Canonical-3 Channel―Dependent Fibroblast Regulation in Atrial Fibrillation

• Published in: Circulation (New York, N.Y.) Vol. 126; no. 17; pp. 2051 - 2064
• Main Authors: HARADA, Masahide, XIAOBIN LUO, YANFEN SHI, KAMIYA, Kaichiro, MUROHARA, Toyoaki, KODAMA, Itsuo, TARDIF, Jean-Claude, SCHOTTEN, Ulrich, VAN WAGONER, David R, DOBREV, Dobromir, NATTEL, Stanley, XIAO YAN QI, TADEVOSYAN, Artavazd, MAGUY, Ange, ORDOG, Balazs, LEDOUX, Jonathan, KATO, Takeshi, NAUD, Patrice, VOIGT, Niels
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 23.10.2012
• Subjects: Animals; Atrial Fibrillation - genetics; Atrial Fibrillation - metabolism; Atrial Fibrillation - pathology; Atrial Function, Right - genetics; Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Cell Proliferation; Cells, Cultured; Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous; Dogs; Down-Regulation - genetics; Fibroblasts - metabolism; Fibroblasts - pathology; Gene Knockdown Techniques - methods; Goats; HEK293 Cells; Hormones. Endocrine system; Humans; Medical sciences; Pharmacology. Drug treatments; Rats; TRPC Cation Channels - genetics; TRPC Cation Channels - physiology; remodeling; Calcium; Arrhythmia; Heart disease; Atrial fibrillation; Cardiovascular disease; Inorganic element; Fibroblast; Excitability disorder; ion channels; fibrillation
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/circulationaha.112.121830

Fibroblast proliferation and differentiation are central in atrial fibrillation (AF)-promoting remodeling. Here, we investigated fibroblast regulation by Ca(2+)-permeable transient receptor potential canonical-3 (TRPC3) channels. Freshly isolated rat cardiac fibroblasts abundantly expressed TRPC3 and had appreciable nonselective cation currents (I(NSC)) sensitive to a selective TPRC3 channel blocker, pyrazole-3 (3 μmol/L). Pyrazole-3 suppressed angiotensin II-induced Ca(2+) influx, proliferation, and α-smooth muscle actin protein expression in fibroblasts. Ca(2+) removal and TRPC3 blockade suppressed extracellular signal-regulated kinase phosphorylation, and extracellular signal-regulated kinase phosphorylation inhibition reduced fibroblast proliferation. TRPC3 expression was upregulated in atria from AF patients, goats with electrically maintained AF, and dogs with tachypacing-induced heart failure. TRPC3 knockdown (based on short hairpin RNA [shRNA]) decreased canine atrial fibroblast proliferation. In left atrial fibroblasts freshly isolated from dogs kept in AF for 1 week by atrial tachypacing, TRPC3 protein expression, currents, extracellular signal-regulated kinase phosphorylation, and extracellular matrix gene expression were all significantly increased. In cultured left atrial fibroblasts from AF dogs, proliferation rates, α-smooth muscle actin expression, and extracellular signal-regulated kinase phosphorylation were increased and were suppressed by pyrazole-3. MicroRNA-26 was downregulated in canine AF atria; experimental microRNA-26 knockdown reproduced AF-induced TRPC3 upregulation and fibroblast activation. MicroRNA-26 has NFAT (nuclear factor of activated T cells) binding sites in the 5' promoter region. NFAT activation increased in AF fibroblasts, and NFAT negatively regulated microRNA-26 transcription. In vivo pyrazole-3 administration suppressed AF while decreasing fibroblast proliferation and extracellular matrix gene expression. TRPC3 channels regulate cardiac fibroblast proliferation and differentiation, likely by controlling the Ca(2+) influx that activates extracellular signal-regulated kinase signaling. AF increases TRPC3 channel expression by causing NFAT-mediated downregulation of microRNA-26 and causes TRPC3-dependent enhancement of fibroblast proliferation and differentiation. In vivo, TRPC3 blockade prevents AF substrate development in a dog model of electrically maintained AF. TRPC3 likely plays an important role in AF by promoting fibroblast pathophysiology and is a novel potential therapeutic target.