PHOSPHATIDYLCHOLINE HYDROLYSIS IS REQUIRED FOR PANCREATIC-CHOLESTEROL-ESTERASE-FACILITATED AND PHOSPHOLIPASE-A(2)-FACILITATED CHOLESTEROL UPTAKE INTO INTESTINAL CACO-2 CELLS

Pancreatic secretion is required for efficient cholesterol absorption by the intestine, but the factors responsible for this effect have not been clearly defined, To identify factors involved and to investigate their role in cholesterol uptake, we studied the effect of Viokase(R) , a porcine pancreatic extract, on cholesterol uptake into human intes tinal Caco-2 cells. Viokase is capable of facilitating cholesterol upt ake into these cells such that the level of uptake is B-fold higher in the presence of solubilized Viokase. This stimulation is time-depende nt and is dependent on the presence of bile salt. However, bile salt-s timulated pancreatic cholesterol esterase, which has been proposed to mediate cholesterol uptake, is not fully responsible, The major choles terol transport activity was purified and identified as pancreatic pho spholipase A(2). Anti-phospholipase A(2) antibodies abolished virtuall y all of the phospholipase A(2) and cholesterol transport activity of solubilized Viokase, We demonstrate that both phospholipase A(2) and c holesterol esterase increase cholesterol uptake by hydrolyzing the pho sphatidylcholine that is used to prepare the cholesterol-containing mi celles, In the absence of cholesterol esterase or phospholipase A(2), uptake of cholesterol from micelles containing phosphatidylcholine is not as efficient as uptake from micelles containing phospholipase A(2) -hydrolytic products, These results indicate that phospholipase A(2) m ay mediate cholesterol absorption by altering the physical-chemical st ate of cholesterol within the intestine.