In vivo lipid peroxidation and platelet activation in cystic fibrosis

F-2-isoprostanes are bioactive peroxidation products of arachidonic acid wh ose urinary excretion provides an index of lipid peroxidation in vivo. We t ested the hypothesis that formation of F-2-isoprostanes is altered in patie nts with cystic fibrosis and contributes to platelet activation and pulmona ry dysfunction in this set-ting. The urinary excretion of immunoreactive 8- iso-prostaglandin F-2 alpha (PGF(2 alpha)) was significantly (p = 0.0001) h igher in 36 patients with cystic fibrosis than in 36 age-matched healthy su bjects: 618 +/- 406 versus 168 +/- 48 pg/mg creatinine. The urinary excreti on of Immunoreactive 11-dehydro-thromboxane B-2 (TXB2), an index of in vivo platelet activation, was also significantly (p = 0.0001) higher in patient s than in control subjects: 2,440 +/- 1,453 versus 325 +/- 184 pg/mg creati nine. The excretion rate of 8-iso-PGF(2 alpha) was correlated with that of 11-dehydro-TXB2 (rho = 0.51; p = 0.0026) and inversely related to FEV1 (rho = -0.40; p = 0.0195). Urinary 8-iso-PGF(2 alpha) excretion was largely una ffected during cyclooxygenase inhibition with low-dose aspirin, nimesulide, or ibuprofen, consistent with a noncyclooxygenase mechanism of F-2-isopros tane formation in cystic fibrosis. Increased vitamin E supplementation (fro m 200 to 600 mg/d) was associated with statistically significant (p = 0.005 ) reductions in urinary 8-iso-PGF(2 alpha) and 11-dehydro-TXB2 excretion, b y 42% and 29%, respectively. We conclude that enhanced lipid peroxidation i s an important feature of cystic fibrosis and may contribute to persistent platelet activation and pulmonary dysfunction via generation of bioactive i soeicosanoids. Our results provide a rationale for reassessing the adequacy of vitamin E supplementation in this setting.