Cysteinyl-leukotrienes in the regulation of beta2-adrenoceptor function: an in vitro model of asthma.
BACKGROUND
The response to beta2-adrenoceptor agonists is reduced in asthmatic airways. This desensitization may be in part due to inflammatory mediators and may involve cysteinyl-leukotrienes (cysteinyl-LTs). Cysteinyl-LTs are pivotal inflammatory mediators that play important roles in the pathophysiology of asthma, allergic rhinitis, and other inflammatory conditions. We tested the hypothesis that leukotriene D4 (LTD4) and allergen challenge cause beta2-adrenoceptor desensitization through the activation of protein kinase C (PKC).


METHODS
The isoproterenol-induced cAMP accumulation was evaluated in human airway smooth muscle cell cultures challenged with exogenous LTD4 or the PKC activator phorbol-12-myristate-13-acetate with or without pretreatments with the PKC inhibitor GF109203X or the CysLT1R antagonist montelukast. The relaxant response to salbutamol was studied in passively sensitized human bronchial rings challenged with allergen in physiological salt solution (PSS) alone, or in the presence of either montelukast or GF109203X.


RESULTS
In cell cultures, both LTD4 and phorbol-12-myristate-13-acetate caused significant reductions of maximal isoproterenol-induced cAMP accumulation, which were fully prevented by montelukast and GF109203X, respectively. More importantly, GF109203X also prevented the attenuating effect of LTD4 on isoproterenol-induced cAMP accumulation. In bronchial rings, both montelukast and GF109203X prevented the rightward displacement of the concentration-response curves to salbutamol induced by allergen challenge.


CONCLUSIONS
LTD4 induces beta2-adrenoceptor desensitization in human airway smooth muscle cells, which is mediated through the activation of PKC. Allergen exposure of sensitized human bronchi may also cause a beta2-adrenoceptor desensitization through the involvement of the CysLT1R-PKC pathway.
Rovati
G Enrico
GE
Laboratory of Molecular Pharmacology, Section of Eicosanoid Pharmacology, Dept. of Pharmacological Sciences, University of Milan, Italy. Genrico.Rovati@unimi.it
Baroffio
Michele
M
Citro
Simona
S
Brichetto
Lorenzo
L
Ravasi
Saula
S
Milanese
Manlio
M
Crimi
Emanuele
E
Brusasco
Vito
V
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000420:Albuterol / Q000008:administration & dosage / Q000494:pharmacology; D000485:Allergens / Q000276:immunology; D001249:Asthma / Q000378:metabolism*; D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D017998:Leukotriene D4 / Q000494:pharmacology; D015289:Leukotrienes / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D000485:Allergens; D001993:Bronchodilator Agents; D015289:Leukotrienes; D018343:Receptors, Adrenergic, beta-2; C112381:cysteinyl-leukotriene; D017998:Leukotriene D4; D000242:Cyclic AMP; D011493:Protein Kinase C; D003545:Cysteine; D007545:Isoproterenol; D000420:Albuterol