Increased vascular expression of iNOS at day but not at night in asthmatic subjects with increased nocturnal airway obstruction.

Nitric oxide production by endothelial cells may have important consequences for the development of airway inflammation as well as for airway obstruction. The present study investigated whether the expression of vascular inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) in human bronchi differs between asthmatic and healthy subjects, and whether it shows a circadian rhythm, especially in subjects with increased nocturnal airway obstruction. Bronchial biopsy samples were taken at 16:00 and 04:00 h from 13 healthy and 25 asthmatic subjects, 18-45 yrs. Biopsy samples were snap-frozen and double-immunostained for iNOS and eNOS in combination with a common vascular antigen (CD31). The degree of immunopositivity was expressed as a percentage of CD31-positive vessels encountered in complete biopsy sections. Asthmatic subjects showed greater iNOS expression than healthy controls: 23+/-15 versus 7+/-17% (mean+/-SD) at 16:00 h (p<0.001) and 19+/-15 versus 8+/-11% at 04:00 h (p<0.05). Asthmatic subjects with a fall in forced expiratory volume in one second of >10% of the predicted value between 16:00 and 04:00 h showed greater iNOS expression at 16:00 than at 04:00 h: 32+/-16 versus 20+/-13% (p<0.05). eNOS expression did not differ between healthy controls and asthmatic patients, nor did it differ between 16:00 and 04:00 h. It is suggested that asthmatic subjects with increased nocturnal airway obstruction demonstrate increased activation of inducible nitric oxide synthase during the day. The resulting nitric oxide production might protect against airway obstruction during the day. However, at night, nitric oxide production is probably insufficient to counterbalance the bronchoconstricting forces.

Vascular adhesion molecules in nocturnal asthma: a possible role for VCAM-1 in ongoing airway wall inflammation.

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.

Increased peak expiratory flow variation in asthma: severe persistent increase but not nocturnal worsening of airway inflammation.

Asthma at night is characterized by a nocturnal increase in airway obstruction. It has been hypothesized that nocturnal asthma results from an increase in airway wall inflammation at night. However, studies on inflammatory cells in bronchoalveolar lavage (BAL) fluid and bronchial biopsies have produced conflicting data. This study assessed inflammatory cell numbers at 16:00 h and 04:00 h in bronchial biopsies of 13 healthy controls, 15 asthmatic patients with peak expiratory flow (PEF) variation < or =15% and 10 asthmatic patients with PEF variation >15%. There was no significant increase at night in the number of CD3, CD4, CD8, CD25, AAI (tryptase) and EG2-immunopositive cells in the submucosa in both groups. Numbers of EG2-positive cells in the two asthmatic groups were significantly higher than in healthy controls, both at 16:00 h (p<0.05) and 04:00 h (p<0.01). The number of EG2, CD4 and CD25-positive cells at 04:00 and 16:00 h tended to be higher in asthmatics with a PEF variation >15% than in asthmatics with PEF variation < or =15%. At 04:00 h the median numbers of EG2-positive cells (per mm basement membrane) in subjects with PEF variation >15% and < or =15% were 6 and 3 cells, respectively, and at 16:00 h 4 and 25 cells respectively. Increased nocturnal airway obstruction is not associated with increased numbers of inflammatory cells in the bronchial submucosa at night. Apparently, asthmatic patients with a peak expiratory flow variation >15% suffer from a higher overall severity of bronchial inflammation at night and during the day.