Role of Ca2+ mobilization and Ca2+ sensitization in 8-iso-PGF 2 alpha-induced contraction in airway smooth muscle.
BACKGROUND
Isoprostanes are prostaglandin (PG)-like compounds synthesized by oxidative stress, not by cyclooxygenase, and increase in bronchoalveolar lavage fluid of patients with asthma. The airway inflammation implicated in this disease may be amplified by oxidants. Although isoprostanes are useful biomarkers for oxidative stress, the action of these agents on airways has not been fully elucidated.


OBJECTIVE
This study was designed to determine the intracellular mechanisms underlying the effects of oxidative stress on airway smooth muscle, focused on Ca(2+) signalling pathways involved in the effect of 8-iso-PGF(2 alpha).


METHODS
Using simultaneous recording of isometric tension and F(340)/F(380) (an indicator of intracellular concentrations of Ca(2+), [Ca(2+)]i, we examined the correlation between tension and [Ca(2+)]i in response to 8-iso-PGF(2 alpha) in the fura-2 loaded tracheal smooth muscle.


RESULTS
Augmented tension and F(340)/F(380) by 8-iso-PGF(2 alpha) were attenuated by ICI-192605, an antagonist of thromboxane A(2) receptors (TP receptors). Moreover, D609, an antagonist of phosphatidylcholine-specific phospholipase C, markedly reduced both the tension and F(340)/F(380) induced by 8-iso-PGF(2 alpha), whereas U73122, an antagonist of phosphatidylinositol-specific phospholipase C, modestly inhibited them by 8-iso-PGF(2 alpha). SKF96365, a non-selective antagonist of Ca(2+) channels, markedly reduced both tension and F(340)/F(380) by 8-iso-PGF(2 alpha). However, diltiazem and verapamil, voltage-dependent Ca(2+) channel inhibitors, modestly attenuated tension although their reduction of F(340)/F(380) was not different from that by SKF96365. Y-27632, an inhibitor of Rho-kinase, significantly attenuated contraction induced by 8-iso-PGF(2 alpha) without reducing F(340)/F(380), whereas GF109203X and Go6983, protein kinase C inhibitors, did not markedly antagonize them although reducing F(340)/F(380) with a potency similar to Y-27632.


CONCLUSIONS
8-iso-PGF(2 alpha) causes airway smooth muscle contraction via activation of TP receptors. Ca(2+) mobilization by SKF96365- and D609-sensitive Ca(2+) influx and Ca(2+) sensitization by Rho-kinase contribute to the intracellular mechanisms underlying the action of 8-iso-PGF(2 alpha). Rho-kinase may be a therapeutic target for the physiologic abnormalities induced by oxidative stress in airways.
Shiraki
A
A
Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya University, Nagoya, Japan.
Kume
H
H
Oguma
T
T
Makino
Y
Y
Ito
S
S
Shimokata
K
K
Honjo
H
H
Kamiya
K
K
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001952:Bridged-Ring Compounds / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004110:Diltiazem / Q000494:pharmacology; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009636:Norbornanes; D011725:Pyridines / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013859:Thiocarbamates; D013871:Thiones / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects* / Q000502:physiology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors
D000577:Amides; D001952:Bridged-Ring Compounds; D002121:Calcium Channel Blockers; D004146:Dioxanes; D004791:Enzyme Inhibitors; D004963:Estrenes; D007093:Imidazoles; D007211:Indoles; D008301:Maleimides; D009636:Norbornanes; D011725:Pyridines; D011760:Pyrrolidinones; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013859:Thiocarbamates; D013871:Thiones; D014662:Vasoconstrictor Agents; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C057498:ICI 192605; C108830:Y 27632; C075750:8-epi-prostaglandin F2alpha; C046498:tricyclodecane-9-yl-xanthogenate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D015237:Dinoprost; D014700:Verapamil; D054460:rho-Associated Kinases; D010738:Type C Phospholipases; D004110:Diltiazem; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C070515:bisindolylmaleimide I