Mitrochondrial NADH dehydrogenase in cystic fibrosis.

Abstract

We have shown that skin fibroblasts from patients with cystic fibrosis (CF) and from carriers for CF [heterozygotes (HZ)] consume more 02 than do their controls. When the mitochondrial electron transport inhibitor rotenone was added to the cells, the relative inhibition of 02 consumption was CF > HZ > controls (P < 0.005 in both comparisons). Because rotenone specifically inhibits NADH dehydrogenase, [NADH:(acceptor) oxidoreductase, EC 1.6.99.31, which is the enzyme of energy-conserving site 1 of the mitochondrial electron transport system, activity and kinetics of this enzyme system were studied in fibroblast homogenates. NADH dehydrogenase activity was equal in cells from the three genotypes. At pH 8.0, affinity of the enzyme for its substrate was CF < HZ = controls; at pH 8.6, affinity was CF> HZ = controls (P < 0.005 for the differences). pH optima for the genotypes were without exception 8.6 (CF), 8.3 (HZ), and 8.0 (control). HZ and control lines were distinguished unequivocally in a blind test on the basis of differences in pH optima. Purified mitochondrial preparations revealed pH optima identical to those found in whole cell homogenates. These data suggest that the mutant gene responsible for CF is expressed in the complex mitochondrial NADH dehydrogenase system.

Oxygen Consumption and Ouabain Binding Sites in Cystic Fibrosis Nasal Epithelium

“…Previous investigators have noted that mitochondria derived from CF fibroblasts consumed oxygen more rapidly than mitochondria derived from normal fibroblasts (25). This difference was associated with increased Ca++ uptake by CF fibroblast mitochondria (26) and an altered pH optimum of the mitochondria1 NADH dehydrogenase (25). We have not explored the relationship of these findings to our results.…”

“…These data are consistent with the existence of a greater metabolic capacity in CF cells. Previous investigators have noted that mitochondria derived from CF fibroblasts consumed oxygen more rapidly than mitochondria derived from normal fibroblasts (25). This difference was associated with increased Ca++ uptake by CF fibroblast mitochondria (26) and an altered pH optimum of the mitochondria1 NADH dehydrogenase (25).…”

Prolonged Oxygen Kinetics During Constant Workload Submaximal Exercise Is Associated With Disease Severity in Adult Subjects With Cystic Fibrosis

“…Possible explanatory mechanisms for low oxidative capacity and prolonged oxygen kinetics in subjects with CF are deconditioning, abnormalities at the mitochondrial level such as increased calcium concentration, 31 lower NADH dehydrogenase activity, 32 and higher pH optimum of NADH dehydrogenase. 33 Moreover, previous data 34 suggest a reduced efficiency of oxidative ATP synthesis in subjects with CF. In the literature, an association between the main CF gene mutation and raised energy expenditure in subjects with CF is reported.…”

A Review. Cystic Fibrosis at Forty—Quo Vadis?

“…Because this is an energy-dependent process, they studied fibroblast oxygen consumption and found that mitochondria from CF homozygotes consumed more O2 than controls, with heterozygous cells intermediate (23). The authors suggested that this organelle might be a suitable focus for further investigation and went on to demonstrate that the pH optimum for NADH dehydrogenase is different from enzymes derived from normal, CF, and CF heterozygote fibroblasts (53). Also, CF leucocytes accumulate more calcium than normal cells and calcium accumulation of normal cells can be increased to CF levels by exposure to CF serum (I), raising the question of an ionophore-like effect of CF serum, as had been suggested previously (10).…”