Taken together, data suggest that Cx43 and Panx1 containing hemichannels have a predominant role on ATP release from human subcutaneous fibroblasts stimulated with bradykinin, thereby instigating the re generative propagation of intracellular Ca2 signals. Our findings agree with the observation that mechanically selleck kinase inhibitor stimulated cardiac fibroblasts release ATP in a CBX sensitive manner, an effect that the authors attributed to Cx43 hemichannels not excluding a possible involvement of Panx1 containing hemichannels. Regardless of whether channel mediated efflux or vesicle exocytosis comprises the predominant ATP release mech anism, Inhibitors,Modulators,Libraries most studies have identified elevation of cytosolic Ca2 as an important regulator of nucleotide export in different cell model systems.

The molecular mechanism by which bradykinin releases ATP through the opening of Cx43 and Panx1 hemichannels in human subcutaneous fibroblasts may be the generation of inositol trisphosphate Inhibitors,Modulators,Libraries by phospholipase C and the downstream i mobilization from internal stores. Our data, showing that intracellular Ca2 depletion with thapsigargin impaired quinacrine dye Inhibitors,Modulators,Libraries Inhibitors,Modulators,Libraries destaining induced by bradykinin is in favor with the hypothesis that Ca2 mobilization is necessary for ATP release in these cells. Further experiments are required to discard Inhibitors,Modulators,Libraries the ability of bradykinin, like certain Gq coupled receptors, to additionally stimulate Rho GTPase acting to strongly potentiate a Ca2 activated ATP release pathway.

Seminario Vidal and col, demonstrated that Ca2 and RhoARho kinase dependent ATP release from thrombin stimulated A549 lung epithelial cells occurs via connexin or pannexin hemichannels, the site a pathway that seems to be not competent for ATP release in human astrocytoma cells. Given the actions exerted by RhoRho kinase on cytoskeleton components, those authors speculated that Rho promoted membrane cytoskeletal rearrangements facilitate the insertion of hemichannel subunits within the plasma membrane. Bradykinin can increase glutamate release from mouse astrocytes through volume sensitive outwardly rectifying anion channels without cell swelling via a mechanism that is regulated by high intracellular Ca2 in nanodomains. Although we did not test directly whether this pathway plays a role in bradykinin induced i dependent ATP release from human subcutane ous fibroblasts, it appears that VSOR currents would ex hibit a slow activation kinetics requiring 15 20 min after bradykinin application to reach a sustained plateau. This activation pattern is entirely different from the rapid ATP releasing response to bradykinin observed in human fibroblasts, thus indi cating that slow activating but prolonged VSOR cur rents play a minor, if some, role in the release of ATP in our experimental time frame.