Increased Δ5- and Δ6-desaturase, cyclooxygenase-2, and lipoxygenase-5 expression and activity are associated with fatty acid and eicosanoid changes in cystic fibrosis

Patients with cystic fibrosis consistently demonstrate selective abnormalities in essential fatty acid concentrations, including decreased linoleate (LA) and docosahexaenoate (DHA), with variably increased arachidonate (AA). These changes appear important for the pathophysiology of the disease. However, the mechanisms of these changes are not clearly understood. The current study demonstrates that metabolism of LA and alpha linolenate (LNA) to AA and eicosapentaenoate (EPA), respectively, are significantly increased in two different cell culture models of cystic fibrosis. These changes correlated with increased expression of fatty acid Δ5- and Δ6-desaturases, key enzymes in this metabolic pathway. In contrast, cystic fibrosis cells showed decreased metabolism of AA and EPA to docosapentaenoate (DPA) and docosahexaenoate (DHA), respectively, although metabolism of 22:5n-3 to DHA was relatively unchanged. In addition, the expression and activity of both cyclooxygenase-2 and lipoxygenase-5 was markedly increased in these cells. Taken together, these findings are consistent with the conclusion that the diminished LA and increased AA in cystic fibrosis result from increased metabolism of LA, while the observed decrease in DHA is at least partly due to decreased elongation and desaturation beyond EPA.