Thromboxane A2-induced inhibition of voltage-gated K+ channels and pulmonary vasoconstriction: role of protein kinase Czeta.
Voltage-gated K+ channels (KV) and thromboxane A2 (TXA2) play critical roles in controlling pulmonary arterial tone under physiological and pathological conditions. We hypothesized that TXA2 might inhibit KV channels, thereby establishing a link between these two major pathogenic pathways in pulmonary hypertension. The TXA2 analogue U46619 inhibited IK(V) (Emax=56.1+/-3.9%, EC50=0.054+/-0.019 micromol/L) and depolarized pulmonary artery smooth muscle cells via activation of TP receptors. In isolated pulmonary arteries, U46619 simultaneously increased intracellular Ca2+ concentration and contractile force, and these effects were inhibited by nifedipine or KCl (60 mmol/L). U46619-induced contractions were not altered by the inhibitors of tyrosine kinase genistein or Rho kinase Y-27632 but were prevented by the nonselective protein kinase C (PKC) inhibitors staurosporine and calphostin C. Furthermore, these responses were sensitive to Gö-6983 but insensitive to bisindolylmaleimide I and Gö-6976. Based on the specificity of these drugs, we suggested a role for an atypical PKC in U46619-induced effects. Thus, treatment with a PKCzeta pseudosubstrate inhibitor markedly prevented the vasoconstriction, the inhibition of IK(V), and the depolarization induced by U46619. Western blots showed a transient translocation of PKCzeta from the cytosolic to the particulate fraction on stimulation with U46619. These results indicate that TXA2 inhibits IK(V), leading to depolarization, activation of L-type Ca2+ channels, and vasoconstriction of rat pulmonary arteries. We propose PKCzeta as a link between TP receptor activation and KV channel inhibition.
Cogolludo
Angel
A
Department of Pharmacology, School of Medicine, Universidad Complutense, 28040 Madrid, Spain. acogolludo@ift.csic.es
Moreno
Laura
L
Bosca
Lisardo
L
Tamargo
Juan
J
Perez-Vizcaino
Francisco
F
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors* / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors; D013928:Thromboxane A2 / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D000099221:Protein Kinase C zeta
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002118:Calcium; D020746:Calcium Channels, L-Type; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D024642:Potassium Channels, Voltage-Gated; D011493:Protein Kinase C; D017482:Receptors, Thromboxane; D013928:Thromboxane A2; D014662:Vasoconstrictor Agents; D000099221:Protein Kinase C zeta; C045749:SQ 29548