Elastin and collagen degradation products in urine of patients with cystic fibrosis.

Elastin degradation has been reported to be increased in patients with cystic fibrosis (CF). In order to further explore evidence for elastin degradation in a group of 18 patients with CF with a wide range of disease severity, we used an isotope dilution method to measure urinary desmosine (DES) and isodesmosine (IDES), amino acids derived exclusively from cross-linked elastin, and hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), amino acids derived exclusively from cross-linked collagen. Urinary DES and IDES (mean +/- SD) were 23.9 +/- 30.7 and 18.5 +/- 22.4 micrograms/g creatinine, respectively, in the patients with CF versus 7.5 +/- 1.7 and 6.8 +/- 1.4 micrograms/g creatinine, respectively, in 10 healthy control subjects (p < 0.001); only two patients with CF had DES values within the control range. The values of urinary HP and LP in the CF group were 54.9 +/- 39.1 and 12.3 +/- 8.6 nmol/mmol creatinine, respectively, versus 24.5 +/- 5.8 and 5.1 +/- 2.7 nmol/mmol creatinine, respectively, in the controls (p < 0.005). Both HP and LP were highly correlated (r = 0.71, p < 0.0001). Patients with CF had active pulmonary inflammation; neutrophils were abundant in the bronchoalveolar lavage fluid of the CF group and correlated with elastase activity measured with methoxysuccinyl Ala-Ala-Pro-Val paranitroanilide (r = 0.61, p < 0.05). Airway neutrophils had decreased expression of the complement receptor CR1 (CR1/CR3 of 0.17 +/- 0.15 versus 1.0 for blood neutrophils), a change known to be caused by uninhibited neutrophil elastase. We conclude that lung elastin is the most likely source of the increased DES and IDES in CF.