ADP-Induced Ca 2+ Signaling and Proliferation of Rat Ventricular Myofibroblasts Depend on Phospholipase C-Linked TRP Channels Activation Within Lipid Rafts.

Nucleotides released during heart injury affect myocardium electrophysiology and remodeling through P2 purinoceptors activation in cardiac myofibroblasts. ATP and UTP endorse [Ca2+ ]i accumulation and growth of DDR-2/α-SMA-expressing myofibroblasts from adult rat ventricles via P2Y4 and P2Y2 receptors activation, respectively. Ventricular myofibroblasts also express ADP-sensitive P2Y1 , P2Y12 , and P2Y13 receptors as demonstrated by immunofluorescence confocal microscopy and western blot analysis, but little information exists on ADP effects in these cells. ADP (0.003-3 mM) and its stable analogue, ADPßS (100 μM), caused fast [Ca2+ ]i transients originated from thapsigargin-sensitive internal stores, which partially declined to a plateau sustained by capacitative Ca2+ entry through transient receptor potential (TRP) channels inhibited by 2-APB (50 μM) and flufenamic acid (100 μM). Hydrophobic interactions between Gq/11 -coupled P2Y purinoceptors and TRP channels were suggested by prevention of the ADP-induced [Ca2+ ]i plateau following PIP2 depletion with LiCl (10 mM) and cholesterol removal from lipid rafts with methyl-ß-cyclodextrin (2 mM). ADP [Ca2+ ]i transients were insensitive to P2Y1 , P2Y12 , and P2Y13 receptor antagonists, MRS2179 (10μM), AR-C66096 (0.1 μM), and MRS2211 (10μM), respectively, but were attenuated by suramin and reactive blue-2 (100 μM) which also blocked P2Y4 receptors activation by UTP. Cardiac myofibroblasts growth and type I collagen production were favored upon activation of MRS2179-sensitive P2Y1 receptors with ADP or ADPßS (30 μM). In conclusion, ADP exerts a dual role on ventricular myofibroblasts: [Ca2+ ]i transients are mediated by fast-desensitizing P2Y4 receptors, whereas the pro-fibrotic effect of ADP involves the P2Y1 receptor activation. Data also show that ADP-induced capacitative Ca2+ influx depends on phospholipase C-linked TRP channels opening in lipid raft microdomains. J. Cell. Physiol. 232: 1511-1526, 2017. © 2016 Wiley Periodicals, Inc.