Visit our Expo - Redox and Inflammation signaling 2012

Session II : Receptor signaling and G proteins Poster II, 15
Thromboxane A2-induced inhibition of Kv currents via PKCzeta: Role of reactive
oxygen species and Kv1.5 channels
Angel Cogolludo, Laura Moreno, Giovanna Frazziano, Federica Lodi, Laura Cobeño,
Valeria Queirolo, Eduardo Villamor, Juan Tamargo and Francisco Perez-Vizcaino.
Department Pharmacology. School Medicine. Universidad Complutense de Madrid.
28040 Madrid. SPAIN. E-mail: acogolludo@ift.csic.es.
Voltage-gated potassium channels (Kv) and thromboxane A2 (TXA2) have been involved in
several forms of human and experimental pulmonary hypertension. We have reported that the
TXA2 analog U46619, via activation of TP receptors, inhibited Kv currents in rat pulmonary
artery smooth muscle cells (PASMC), increased cytosolic calcium and induced a contractile
response in isolated rat and piglet pulmonary arteries (PA). These effects were inhibited by
non selective PKC inhibitors and by the selective PKCzeta pseudosubstrate inhibitor. Herein,
we have analyzed the role of reactive oxygen species and Kv1.5 channels, a major channel
protein contributing to Kv currents in PASMC, in the signalling pathway. U46619 inhibited
Kv currents in native PASMC and these effects were strongly inhibited by addition of catalase
to the internal solution in the patch pipette. The membrane permeable hydroperoxide t-butyl
hydroperoxide also inhibited Kv currents. The contractile responses to U46619 in isolated
pulmonary arteries were inhibited by polyethylenglycol-catalase (PEG-catalase, a membrane
permeable form of catalase) and the NADPH oxidase inhibitors DPI and apocynin. U46619
increased dichlorofluorescein fluorescence, an indicator of intracellular hydrogen peroxide, in
pulmonary arteries and this effect was prevented PEG-catalase. U46619 also inhibited Kv
currents in Ltk(-) cells stably expressing hKv1.5 channels. These cells strongly expressed
PKCzeta as measured by Western blot. In conclusion, activation of NADPH oxidase and the
subsequent production of hydrogen peroxide are involved in the Kv channel inhibition and the
contractile response induced by the TXA2 analog U46619 in rat PA. Kv1.5 channels are
possible targets for the inhibitory effect of TXA2 in native pulmonary arteries.
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