title: Multiple Ca2+ signaling pathways regulate intracellular Ca2+ activity in human cardiac fibroblasts.
abstract: Ca(2+) signaling pathways are well studied in cardiac myocytes, but not in cardiac fibroblasts. The aim of the present study is to characterize Ca(2+) signaling pathways in cultured human cardiac fibroblasts using confocal scanning microscope and RT-PCR techniques. It was found that spontaneous intracellular Ca(2+) (Ca(i) (2+)) oscillations were present in about 29% of human cardiac fibroblasts, and the number of cells with Ca(i) (2+) oscillations was increased to 57.3% by application of 3% fetal bovine serum. Ca(i) (2+) oscillations were dependent on Ca(2+) entry. Ca(i) (2+) oscillations were abolished by the store-operated Ca(2+) (SOC) entry channel blocker La(3+), the phospholipase C inhibitor U-73122, and the inositol trisphosphate receptors (IP3Rs) inhibitor 2-aminoethoxydiphenyl borate, but not by ryanodine. The IP3R agonist thimerosal enhanced Ca(i) (2+) oscillations. Inhibition of plasma membrane Ca(2+) pump (PMCA) and Na(+)-Ca(2+) exchanger (NCX) also suppressed Ca(i) (2+) oscillations. In addition, the frequency of Ca(i) (2+) oscillations was reduced by nifedipine, and increased by Bay K8644 in cells with spontaneous Ca(2+) oscillations. RT-PCR revealed that mRNAs for IP3R1-3, SERCA1-3, Ca(V)1.2, NCX3, PMCA1,3,4, TRPC1,3,4,6, STIM1, and Orai1-3, were readily detectable, but not RyRs. Our results demonstrate for the first time that spontaneous Ca(i) (2+) oscillations are present in cultured human cardiac fibroblasts and are regulated by multiple Ca(2+) pathways, which are not identical to those of the well-studied contractile cardiomyocytes. This study provides a base for future investigations into how Ca(2+) signals regulate biological activity in human cardiac fibroblasts and cardiac remodeling under pathological conditions.
authors.affiliation: Li Ka Shing Faculty of Medicine, Department of Medicine, Research Centre of Heart, Brain, Hormone and Healthy Aging, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
authors.forename: Jing-Bo
authors.initials: JB
authors.lastname: Chen
authors.forename: Rong
authors.initials: R
authors.lastname: Tao
authors.forename: Hai-Ying
authors.initials: HY
authors.lastname: Sun
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
authors.forename: Gui-Rong
authors.initials: GR
authors.lastname: Li
mesh_terms: D000328:Adult; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000187:drug effects / Q000378:metabolism; D018613:Microscopy, Confocal; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism; D013997:Time Factors; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D053496:Inositol 1,4,5-Trisphosphate Receptors; D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; D010738:Type C Phospholipases; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium