Catalytic Hydrolysis of VIP in Pregnant Women with Asthma

Abstract

Rationale: The neuropeptide vasoactive intestinal peptide (VIP) is one of the physiologic mediators of non-adrenergic, non-cholinergic smooth muscle relaxation of the airway and an important modulator of innate and adaptive immune responses. VIP catalytic autoantibodies are increased in asthma and serum VIP level is decreased during acute exacerbation of asthma. The effect of pregnancy on asthma is variable and depends in part on the severity of pre-existing asthma, along with other physiological and pathophysiological changes. We hypothesized that hydrolysis of VIP by circulating catalytic VIP antibodies will be increased in pregnancy in patients with asthma. Study objective: To determine the level of catalytic autoantibodies to VIP in pregnant asthmatics compared to non-pregnant asthmatics and control pregnant women without asthma. Methods: We prospectively enrolled eight pregnant asthmatics (age, 26.5 ± 2.6 years; mean ± SEM), nine pregnant women without asthma (32.0 ± 3.0 years), seven non-pregnant women with asthma (25.0 ±1.9 years), and seven non-pregnant women without asthma (34.4 ± 2 years) into the study. VIP hydrolysis was performed in all subjects. Results: Immunoglobulin G (IgG) autoantibodies that catalyze the hydrolysis of vasoactive intestinal peptide (VIP) were present at greater levels in the blood of pregnant women with asthma (7.6 ± 1.1 pM VIP/6 h) compared to pregnant women without asthma (4.0 ± 0.5; p < 0.001), non-pregnant asthmatics (4.9 ± 0.9; p < 0.05) or non-pregnant women without asthma (1.9 ± 0.7; p < 0.05). Conclusion: An increase in the VIP hydrolyzing activity of IgG is independently associated with asthma and pregnancy. The autoantibodies hold the potential of affecting the pathophysiology of the airways in pregnant asthmatics.