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Experimental Biology and Medicine 229:1046-1052 (2004)
© 2004 Society for Experimental Biology and Medicine

ORIGINAL RESEARCH ARTICLE

Low-Density Lipoprotein Inhibits Secretion of Phospholipid Transfer Protein in Human Trophoblastic BeWo Cells

An-Yue Tu1, Marian C. Cheung, Xiaodong Zhu, Robert H. Knopp and John J. Albers

Northwest Lipid Research Laboratories and Northwest Lipid Research Clinic, Division of Metabolism, Endocrinology, and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98103

To whom requests for reprints should be addressed at 1 Department of Medicine, Northwest Lipid Research Laboratories, University of Washington, 2121 N 35th Street, Seattle, WA 98103. E-mail: aytu{at}u.washington.edu

Human plasma phospholipid transfer protein (PLTP) plays an important role in lipoprotein metabolism. In this study, we investigated the effects of lipoproteins on the secretion of PLTP in cultured BeWo choriocarcinoma cells. Low-density lipoproteins (LDLs) decreased PLTP secretion in a dose- and time-dependent manner, whereas very low density lipoproteins and high-density lipoproteins (HDLs) had little effect. LDL suppression of PLTP secretion was not altered by the inhibition of both LDL receptor and LDL receptor–related protein with receptor-associated protein. Mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor, U0126, could abolish the LDL-mediated inhibition of PLTP secretion. Furthermore, LDL, but not HDL, could stimulate the expression of MAPK phosphatase-1 (MKP-1) in BeWo cells that resulted in the inactivation of p44/p42 extracellular signal-regulated kinase (ERK) 1 and 2, the family members of MAPKs. These results support the conclusion that LDL-mediated suppression of PLTP secretion in BeWo cells is through a LDL receptor-independent MAPK signaling pathway.

Key Words: phospholipid transfer protein • human trophoblastic cells • MAPK signaling pathway






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