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Purinergic activation of Ca2+-permeable TRPV4 channels is essential for mechano-sensitivity in the aldosterone-sensitive distal nephron Mamenko M; Zaika O; Jin M; O'Neil RG; Pochynyuk OPLoS One 2011[]; 6 (8): e22824Mechanical forces are known to induce increases of [Ca(2+)](i) in the aldosterone-sensitive distal nephron (ASDN) cells to regulate epithelial transport. At the same time, mechanical stress stimulates ATP release from ASDN cells. In this study, we combined ratiometric Fura-2 based monitoring of [Ca(2+)](i) in freshly isolated split-opened ASDN with targeted deletion of P2Y2 and TRPV4 in mice to probe a role for purinergic signaling in mediating mechano-sensitive responses in ASDN cells. ATP application causes a reproducible transient Ca(2+) peak followed by a sustained plateau. Individual cells of the cortical collecting duct (CCD) and the connecting tubule (CNT) respond to purinergic stimulation with comparative elevations of [Ca(2+)](i). Furthermore, ATP-induced Ca(2+)-responses are nearly identical in both principal (AQP2-positive) and intercalated (AQP2-negative) cells as was confirmed using immunohistochemistry in split-opened ASDN. UTP application produces elevations of [Ca(2+)](i) similar to that observed with ATP suggesting a dominant role of P2Y2-like receptors in generation of [Ca(2+)](i) response. Indeed, genetic deletion of P2Y2 receptors decreases the magnitude of ATP-induced and UTP-induced Ca(2+) responses by more than 70% and 90%, respectively. Both intracellular and extracellular sources of Ca(2+) appeared to contribute to the generation of ATP-induced Ca(2+) response in ASDN cells. Importantly, flow- and hypotonic-induced Ca(2+) elevations are markedly blunted in P2Y2 -/- mice. We further demonstrated that activation of mechano-sensitive TRPV4 channel plays a major role in the sustained [Ca(2+)](i) elevation during purinergic stimulation. Consistent with this, ATP-induced Ca(2+) plateau are dramatically attenuated in TRV4 -/- mice. Inhibition of TRPC channels with 10 microM BTP2 also decreased ATP-induced Ca(2+) plateau whilst to a lower degree than that observed with TRPV4 inhibition/genetic deletion. We conclude that stimulation of purinergic signaling by mechanical stimuli leads to activation of TRPV4 and, to a lesser extent, TRPCs channels, and this is an important component of mechano-sensitive response of the ASDN.|Adenosine Triphosphate/pharmacology[MESH]|Aldosterone/*metabolism[MESH]|Animals[MESH]|Calcium/*metabolism[MESH]|Immunohistochemistry[MESH]|In Vitro Techniques[MESH]|Male[MESH]|Mechanotransduction, Cellular/drug effects/genetics/*physiology[MESH]|Mice[MESH]|Mice, Inbred C57BL[MESH]|Models, Biological[MESH]|Nephrons/cytology/drug effects/*metabolism[MESH]|Receptors, Purinergic P2Y2/genetics/*metabolism[MESH]|TRPV Cation Channels/genetics/*metabolism[MESH]|Uridine Triphosphate/pharmacology[MESH] |
