Cellular cholesterol metabolism in mitogen-stimulated lymphocytes--requirement for de novo synthesis.
The relationship between cholesterol synthesis and uptake in proliferating lymphocytes has been examined. [14C]Acetate incorporation into lymphocytes cultured under lipoprotein-deficient conditions increased initially in response to mitogen, decreased after 24 h, and increased rapidly between 72 and 96 h. Addition of LDL (10 micrograms/ml) to the culture during the 'trough' period caused [14C]acetate incorporation to return rapidly to baseline, while at peak periods LDL suppression of cholesterol synthesis was minimal. Lymphocytes cultured in the presence of the HMG-CoA reductase inhibitor, mevinolin, exhibited a time-dependent increase in their capacity to incorporate [14C]acetate into cholesterol, evident when mevinolin was removed by washing prior to assay. PHA enhanced 125I-labelled LDL receptor-mediated binding by lymphocytes cultured in lipoprotein-deficient medium over a 4 day period and mevinolin augmented the effect. [3H]Thymidine incorporation into mitogen-stimulated lipoprotein-deficient cultures was inhibited up to 75% by mevinolin (1 mumol/l). LDL (2.5-10 micrograms/ml) substantially reversed this inhibition in 72 h cultures, but only partially overcame inhibition in cells cultured for 96 h. Results suggest that endogenous cholesterol synthesis may be obligatory for lymphocyte proliferation after the initial round of cell division.
Owens
D
D
Department of Biochemistry, Royal College of Surgeons in Ireland, Dublin.
Collins
P
P
Johnson
A
A
Tomkin
G
G
D000085:Acetates / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D002784:Cholesterol / Q000096:biosynthesis*; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism / Q000494:pharmacology; D008148:Lovastatin / Q000494:pharmacology; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008934:Mitogens / Q000494:pharmacology*; D011485:Protein Binding; D013997:Time Factors
D000085:Acetates; D008077:Lipoproteins, LDL; D008934:Mitogens; D002784:Cholesterol; D008148:Lovastatin