A Xanthine-Based Epithelium-Dependent Airway Relaxant KMUP-3 (7-[2-[4-(4-Nitrobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine) Increases Respiratory Performance and Protects against Tumor Necrosis Factor-alpha-lnduced Tracheal Contraction,Involving N

摘要

KMUP-3 (7-[2-[4-(4-nitrobenzene)piperazinyl]ethyl]-1,3-dimethyl-xanthine) was investigated in guinea pig tracheal smooth muscle.Intratracheal instillation of tumor necrosis factor (TNF)-alpha (0.01 mg/kg/300 mu l) induced bronchoconstriction,increases of lung resistance,and decreases of dynamic lung compliance.Instillation of KMUP-3 (0.5-2.0 mg/kg) reversed this situation.In isolated trachea precontracted with carbachol,KMUP-3 (10-100 mu M)-caused relaxations were attenuated by epithelium removal and by pretreatments with an inhibitor of K~+ channel,tetraethylammo-nium (10 mM); K_(ATP) channel,glibenclamide (1 mu M); voltage-dependent K~+ channel,4-aminopyridine (100 mu M); Ca~(2+)-dependent K~+ channel,charybdotoxin (0.1 mu M) or apamin (1 mu M); soluble guanylate cyclase (sGC),1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ,1 mu M); nitric-oxide (NO) synthase,N~(omega)-nitro-L-arginine methyl ester (L-NAME,100 mu M); and adenylate cyclase,SQ 22536 [9-(terahydro-2-furanyl)-9H-purin-6-amine] (100 mu M).KMUP-3 (0.01-100 mu M) induced increases of cGMP and cAMP in primary culture of tracheal smooth muscle cells (TSMCs).The increase in cGMP by KMUP-3 was reduced by ODQ and L-NAME; the increase in cAMP was reduced by SQ 22536.Western blot analysis indicated that KMUP-3 (1 mu M) induced expression of protein kinase A (PKA)_(RI) and protein kinase G (PKG)_(1alpha1beta) in TSMCs.SQ 22536 inhibited KMUP-3-induced expression of PKA_(RI).On the contrary,ODQ inhibited KMUP-3-induced expression of PKG_(1alpha1beta).In epithelium-intact trachea,KMUP-3 increased the NO release.Activation of sGC,NO release,and inhibition of phosphodiester-ases in TSMCs by KMUP-3 may result in increases of intracellular cGMP and cAMP,which subsequently activate PKG and PKA,efflux of K~+ ion,and associated reduction in Ca~(2+) influx in vitro,indicating the action mechanism to protect against TNF-alpha-in-duced airway dysfunction in vivo.