Importance of a novel oxidative mechanism for elimination of intracellular cholesterol in humans

E Lund, O Andersson, J Zhang, A Babiker… - … , and vascular biology, 1996 - Am Heart Assoc
E Lund, O Andersson, J Zhang, A Babiker, G Ahlborg, U Diczfalusy, K Einarsson, J Sjövall…
Arteriosclerosis, thrombosis, and vascular biology, 1996Am Heart Assoc
We have recently demonstrated that cultured human alveolar macrophages efficiently
convert cholesterol into excretable 27-oxygenated products. We show here that increasing
the intracellular concentration of cholesterol by a factor of 10 leads to about a twofold
increase in the excretion of 27-oxygenated products from cultured macrophages. Inhibition
of the sterol 27-hydroxylase caused a significant intracellular accumulation of cholesterol. A
direct comparison was made between flux of cholesterol and 27-oxygenated products from …
Abstract
We have recently demonstrated that cultured human alveolar macrophages efficiently convert cholesterol into excretable 27-oxygenated products. We show here that increasing the intracellular concentration of cholesterol by a factor of 10 leads to about a twofold increase in the excretion of 27-oxygenated products from cultured macrophages. Inhibition of the sterol 27-hydroxylase caused a significant intracellular accumulation of cholesterol. A direct comparison was made between flux of cholesterol and 27-oxygenated products from macrophages preloaded with [4-14C]cholesterol. Under the specific conditions employed with fetal calf serum in the culture medium, the flux of 27-oxygenated products was about 10% of that of cholesterol. Since the sterol 27-hydroxylase, which converts cholesterol to 27-oxygenated products, is present in many cell types, we suggest that 27-oxygenation is a general mechanism for removal of intracellular cholesterol. To evaluate this hypothesis, we measured the net uptake by the human liver of circulating 27-oxygenated products, which was found to be about 20 mg/24 h. This uptake corresponds to ≈4% of the bile acid production, assuming quantitative conversion into bile acids. It is concluded that the 27-hydroxylase pathway is of significance for elimination of extrahepatic cholesterol.
Am Heart Assoc