Background: Increased airway inflammation at night is thought to be one of the underlying mechanisms in nocturnal asthma. Vascular adhesion molecules may be important for the recruitment of inflammatory cells in the process of asthmatic airway inflammation.
Objective: To determine the possible role of vascular adhesion molecules in increased airway inflammation at night in subjects with nocturnal asthma.
Methods: Bronchial biopsies were obtained at 16.00 h and 04.00 h from 13 healthy controls, 15 asthmatic patients with PEF variation < or = 15% and 10 asthmatic patients with PEF variation > 15%. Biopsies were snap-frozen and double-immunostained for CD31 in combination with P-selectin, E-selectin, ICAM-1 or VCAM-1.
Results: No significant day-night differences in expression of adhesion molecules were found in any of the three groups. The percentage of VCAM-1 positive vessels in biopsies of asthmatic patients was higher than in biopsies of healthy controls: 5.8 vs 2.5% (P < 0.05) at 16.00h and 11 vs 0% (P<0.05) at 04.00 h. In asthma, VCAM-1 expression was correlated with the number of EG2 positive cells: at 16.00 h (rho = 0.57, P < 0.01) as well as at 04.00 h (rho = 0.64, P< 0.01). Moreover, VCAM-1 expression was correlated with the number of CD25 positive cells at 16.00 h (rho = 0.43, P < 0.05) and at 04.00 h (rho = 0.41, P < 0.05).
Conclusion: Increased nocturnal airway obstruction in asthma is not associated with an increased nocturnal expression of vascular E-selectin, P-selectin, ICAM-1 or VCAM-1. The relationship between vascular VCAM-1 expression and sub-mucosal EG2 and CD25 positive cells, both at 16.00 h and 04.00 h, suggests a role for VCAM-1 in the ongoing airway wall inflammation of asthma.