ADP‐Induced Ca²⁺ 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 [Ca 2+ ] i accumulation and growth of DDR‐2/α‐SMA‐expressing myofibroblasts from adult rat ventricles via P2Y 4 and P2Y 2 receptors activation, respectively. Ventricular myofibroblasts also express ADP‐sensitive P2Y 1 , P2Y 12 , and P2Y 13 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 [Ca 2+ ] i transients originated from thapsigargin‐sensitive internal stores, which partially declined to a plateau sustained by capacitative Ca 2+ entry through transient receptor potential (TRP) channels inhibited by 2‐APB (50 μM) and flufenamic acid (100 μM). Hydrophobic interactions between G q/11 ‐coupled P2Y purinoceptors and TRP channels were suggested by prevention of the ADP‐induced [Ca 2+ ] i plateau following PIP 2 depletion with LiCl (10 mM) and cholesterol removal from lipid rafts with methyl‐ß‐cyclodextrin (2 mM). ADP [Ca 2+ ] i transients were insensitive to P2Y 1 , P2Y 12 , and P2Y 13 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 P2Y 4 receptors activation by UTP. Cardiac myofibroblasts growth and type I collagen production were favored upon activation of MRS2179‐sensitive P2Y 1 receptors with ADP or ADPßS (30 μM). In conclusion, ADP exerts a dual role on ventricular myofibroblasts: [Ca 2+ ] i transients are mediated by fast‐desensitizing P2Y 4 receptors, whereas the pro‐fibrotic effect of ADP involves the P2Y 1 receptor activation. Data also show that ADP‐induced capacitative Ca 2+ influx depends on phospholipase C‐linked TRP channels opening in lipid raft microdomains. J. Cell. Physiol. 232: 1511–1526, 2017.