Increased arginase activity underlies allergen-induced deficiency of cNOS-derived nitric oxide and airway hyperresponsiveness.
1. A deficiency of constitutive nitric oxide synthase (cNOS)-derived nitric oxide (NO), due to reduced availability of L-arginine, importantly contributes to allergen-induced airway hyperresponsiveness (AHR) after the early asthmatic reaction (EAR). Since cNOS and arginase use L-arginine as a common substrate, we hypothesized that increased arginase activity is involved in the allergen-induced NO deficiency and AHR. 2. Using a guinea-pig model of allergic asthma, we addressed this hypothesis by examining the effects of the specific arginase inhibitor N(omega)-hydroxy-nor-L-arginine (nor-NOHA) on the responsiveness to methacholine of isolated perfused tracheae from unchallenged control animals and from animals 6 h after ovalbumin challenge. Arginase activity in these preparations was investigated by measuring the conversion of L-[14C]arginine to [14C]urea. 3. Airways from allergen-challenged animals showed a 2 fold (P<0.001) increase in responsiveness to intraluminal (IL) administration of methacholine compared to controls. A similar hyperresponsiveness (1.8 fold, P<0.01) was observed in control airways incubated with the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 0.1 mM, IL), while L-NAME had no further effect on the airways from challenged animals. 4. Remarkably, 5 microM nor-NOHA (IL) normalized the hyperresponsiveness of challenged airways to basal control (P<0.001), and this effect was fully reversed again by 0.1 mM L-NAME (P<0.05). Moreover, arginase activity in homogenates of the hyperresponsive airways was 3.5 fold (P<0.001) enhanced compared to controls. 5. The results indicate that enhanced arginase activity contributes to allergen-induced deficiency of cNOS-derived NO and AHR after the EAR, presumably by competition with cNOS for the common substrate, L-arginine. This is the first demonstration that arginase is involved in the pathophysiology of asthma.
Meurs
Herman
H
Department of Molecular Pharmacology, University Centre for Pharmacy, Antonius Deusinglaan 1, Groningen, NL-9713 AV, The Netherlands. h.meurs@farm.rug.nl
McKay
Sue
S
Maarsingh
Harm
H
Hamer
Marco A M
MA
Macic
Lejla
L
Molendijk
Niek
N
Zaagsma
Johan
J
D000485:Allergens; D000818:Animals; D001119:Arginase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016535:Bronchial Hyperreactivity / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D016210:Methacholine Chloride / Q000494:pharmacology; D023421:Models, Animal; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000172:deficiency / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010047:Ovalbumin; D014132:Trachea / Q000503:physiopathology
D000485:Allergens; D016085:Bronchoconstrictor Agents; D004791:Enzyme Inhibitors; C404735:N(omega)-hydroxynorarginine; D016210:Methacholine Chloride; D009569:Nitric Oxide; D010047:Ovalbumin; D001120:Arginine; D019001:Nitric Oxide Synthase; D001119:Arginase; D019331:NG-Nitroarginine Methyl Ester