Roles of mast cell proteases in airways

Pharmacogenetic association between ALOX5 promoter genotype and the response to anti-asthma treatment

Clinically similar asthma patients may develop airway obstruction by different mechanisms. Asthma treatments that specifically interfere with the 5-lipoxygenase (ALOX5) pathway provide a method to identify those patients in whom the products of the ALOX5 pathway (that is, the leukotrienes) contribute to the expression of the asthma phenotype. Failure of an asthma patient to respond to treatment with ALOX5-pathway modifiers indicates that leukotrienes are not critical to the expression of the asthmatic phenotype in that patient. We previously defined a family of DNA sequence variants in the core promoter of the gene ALOX5 (on chromosome 10q11.2) associated with diminished promoter-reporter activity in tissue culture. Because expression of ALOX5 is in part transcriptionally regulated, we reasoned that patients with these sequence variants may have diminished gene transcription, and therefore decreased ALOX5 product production and a diminished clinical response to treatment with a drug targeting this pathway. Such an effect indicates an interaction between gene promoter sequence variants and drug-treatment responses, that is, a pharmacogenetic effect of a promoter sequence on treatment responses.

Effects of chronic airway inflammation on the activity and enzymatic inactivation of neuropeptides in guinea pig lungs

The effects of airway inflammation induced by chronic antigen exposure on substance P (SP)-induced increases and vasoactive intestinal peptide (VIP)-induced decreases in airway opening pressure (Pao), and the recovery of intact and hydrolyzed radiopeptide were studied in tracheally perfused guinea pig lungs. SP (10(-6) mol/kg) induced a significantly greater increase in Pao in lungs from antigen-exposed (30 +/- 5 cm H2O) than saline-exposed animals (15 +/- 1 cm H2O, P < 0.05). Significantly more intact 3H-SP and significantly less 3H-SP 1-7, a neutral endopeptidase (NEP) hydrolysis product, were recovered from the lung effluent of antigen-exposed than saline-exposed animals (P < 0.05). Injection of VIP (10(-9) mol/kg) induced significantly more pulmonary relaxation in saline-exposed compared with antigen-exposed lungs (62 +/- 4%, P < 0.001). In contrast to effluent from saline-exposed animals, lung effluent from antigen-exposed lungs contained less intact VIP, increased amounts of a tryptic hydrolysis product, and no products consistent with the degradation of VIP by NEP. These data indicate that inflamed lungs are more sensitive to the contractile effects of SP because it is less efficiently degraded by NEP and are less sensitive to the relaxant effects of VIP because it is more efficiently degraded by a tryptic enzyme. Changes in airway protease activity occur with allergic inflammation and may contribute to airway hyperresponsiveness.

Dysfunction of nonadrenergic noncholinergic inhibitory system after antigen inhalation in actively sensitized cat airways

We have investigated whether proteases released during antigen inhalation cause dysfunction of the nonadrenergic noncholinergic inhibitory nervous system (NANCIS). Frequency-response (F-R) studies of NANCIS were performed before and after Ascaris antigen (ASC) inhalation using actively sensitized cats. NANC dilatatory effects were obtained by stimulating bilateral cervical vagi under cholinergic and beta-adrenergic blockade and serotonin-induced bronchoconstriction, and assessed by maximal percent relaxation (rmax) and the frequency causing 50% of maximal relaxation (EF50). ASC inhalation caused a transient increase in pulmonary resistance in all animals. One hour after ASC inhalation, pulmonary resistance returned to the baseline value, but ASC inhalation significantly attenuated NANC inhibitory activities: rmax decreased from 82.2 +/- 4.7 (mean +/- SE) to 64.3 +/- 11.2% (p less than 0.05), and the geometric mean of EF50 increased from 1.7 to 4.3 Hz (p less than 0.05). Dilatatory effects of infused VIP, a possible neurotransmitter of NANCIS, was also attenuated after ASC inhalation. Pretreatment with leupeptin (3 mg/kg) abolished ASC-induced impairment of NANC inhibitory activities. By contrast, dilatatory effects of adrenergic nerve stimulation were not affected by ASC inhalation. These results suggest that NANC inhibitory activities can be impaired after ASC inhalation, and that this impairment of NANCIS may be due to effects of proteases released during allergic reaction.