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D S Leake

Publications and source records attributed to D S Leake.

61 records · Page 4Linked to original sources
PubMed1982

Lipid accumulation in arterial smooth muscle cells in culture. Morphological and biochemical changes caused by low density lipoproteins and chloroquine.

Cultured smooth muscle cells from pig aortas were incubated with low density lipoproteins (LDL) and chloroquine for up to 5 days, as an in vitro model for lipid accumulation in atherosclerosis. Cells incubated with LDL alone had a normal morphology, except that some cells contained large lipid droplets. The activities of acid phosphatase, catalase and malate dehydrogenase were increased in homogenates prepared from these cells. Cells incubated with chloroquine alone developed large autophagic vacuoles. The activities of the three acid hydrolases, acid phosphatase, N-acetyl-beta-glucosaminidase and beta-glucuronidase, were decreased, as was the proteolytic activity of the cell homogenates at acid pH toward 125I-labelled LDL. There was, however, a transient increase in the activity of malate dehydrogenase. Chloroquine by itself was toxic to the cells, but LDL protected against this toxic effect. Cells incubated with LDL and chloroquine together developed both autophagic vacuoles and large lipid droplets. The cholesteryl ester content of the cells was increased many-fold and the non-esterified cholesterol content was increased to a lesser extent. The above four acid hydrolase activities were decreased, as was the activity of catalase, whereas the activities of lactate dehydrogenase and malate dehydrogenase were increased.

Animals↗
PubMed1981

Proteolytic degradation of low density lipoproteins by arterial smooth muscle cells: the role of individual cathepsins.

Low density lipoproteins have been implicated in the pathogenesis of atherosclerosis. A study has therefore been made of their proteolytic degradation by homogenates of cultured smooth muscle cells from the pig aorta. The pH optimum of proteolysis of 125I-labelled low density lipoproteins was 4.25, thus suggesting the involvement of lysosomal cathepsins. Proteolysis at acid pH started to become saturated at low density lipoprotein concentrations of approx. 20 microgram of protein/ml, but did not obey Michaelis-Menten kinetics. After a lag period of approx. 10 min, proteolytic degradation was linear with time up to at least 4 h incubation, but showed a sigmoidal relationship with homogenate concentration. When cathepsin D was inhibited by pepstatin, the proteolysis of 125I-labeled low density lipoproteins was inhibited by more than 90%, whereas when cathepsin B was inhibited by leupeptin, the rate of proteolysis decreased by approx. 50%. Antipain, which inhibits both cathepsins A and B, did not inhibit proteolysis any more than leupeptin, thus suggesting a minor role, if any, for cathepsin A. a combination of pepstatin and either leupeptin or antipain inhibited proteolysis completely. Cathepsins B and D acted synergistically in the degradation of 125I-labelled low density lipoproteins.

Animals↗