VLDL Modulates the Cytokine Secretion Profile to a Proinflammatory Pattern M. Cecilia Sampedro,* Cristina Motra ´ n,† Adriana Gruppi,† and Silvia C. Kivatinitz* ,1 *Departamento de Quı ´mica Biolo ´gica, Centro de Investigaciones en Quı ´mica Biolo ´gica de Co ´rdoba (CIQUIBIC, UNC-CONICET), and †Departamento de Bioquı ´mica Clı´nica, Facultad de Ciencias Quı´micas, Universidad Nacional de Co ´rdoba, Ciudad Universitaria, Co ´rdoba, Argentina Received May 29, 2001 Human very-low-density lipoprotein (VLDL) inhib- its DNA synthesis in lymphocytes activated by the nonspecific mitogen concanavalin A (Con A). We stud- ied the effects of VLDL on lymphocyte activation (IL-2 receptor expression), cell cycle progression, and pro- duction of IL-2 and of IL-4 (a proinflammatory and an anti-inflammatory interleukin, respectively) to under- stand why an atherogenic lipoprotein inhibits cell pro- liferation. After 48 h of stimulation with the mitogen, VLDL decreased the population of cells bearing IL-2 receptor and the population of T-cells that progress through the cell cycle, increasing the population of T-cells in G 0 /G 1 . Cells cultured in the presence of Con A and VLDL produced higher levels of IL-2 and lower levels of IL-4 than cells cultured without VLDL. These results suggest that VLDL inhibits lymphocyte prolif- eration by reducing IL-2 receptor and enhancing the levels of IL-2. Probably, one atherogenic effect of VLDL is to modulate the cytokine secretion profile of lymphocytes to a predominantly proinflammatory response. © 2001 Academic Press Key Words: lipoprotein; T-cell proliferation; athero- sclerosis; VLDL; IL-2. Vascular areas with proliferating smooth muscle and mononuclear cells, as well as extracellular ma- trix components, foam cells and deposits of choles- terol characterize atherosclerosis. The earliest rec- ognizable lesion of atherosclerosis (the “fatty streak”) is an aggregation of T-lymphocytes and lipid-rich macrophages within the intima. In these early lesions, there is a clear preponderance of T-cells over macrophages and it has been shown that most of these cells are CD4 + and interleukin-2 re- ceptor (IL-2R + ), i.e., activated T-lymphocytes (1). The information showing the possibility of B-cell in- volvement in atherogenesis is abundant but circum- stantial (2, 3). Physiological concentrations of very-low-density lipoprotein (VLDL) inhibit DNA synthesis in phyto- hemagglutinin-stimulated human lymphocytes proba- bly through interactions with a membrane receptor. These results suggest that VLDL may maintain circu- lating blood lymphocytes in a non-proliferative state (4). At first sight, the anti-proliferative effect of VLDL on human lymphocytes seems contradictory with a proatherogenic role of this lipoprotein. On the contrary the main apoprotein component of VLDL, apolipopro- tein E has been shown to protect against vascular disease. (5). The differences observed in the physiolog- ical and pathological roles of VLDL and apolipoprotein E could be mediated through interactions with the different VLDL and apoE binding receptors (6 – 8). Yet, it must be taken into account that the nature of T-cell response in vivo is a consequence of several fac- tors, including the production of cytokines. Th1 cells secrete IL-2 (a proinflammatory cytokine) and inter- feron gamma; Th2 lymphocytes produce IL-4 and sev- eral other cytokines to assist antibody production. In atherosclerotic lesions, activated T-lymphocytes pro- duce IL-2 (9) that could enhance proliferation of cells forming the atheroma (10). Thus, defining if VLDL is a factor that influences T-cell activation and cytokine production is clearly of considerable importance. Due to the great variability of mitogenic responses observed with human lymphocytes compared with in- bred mice and taking advantage of the fact that human and mouse VLDL receptors are 94% identical (11, 12), we studied the ability of human VLDL to affect the capacity of murine spleen lymphocytes to activate, pro- liferate, and produce cytokines (characteristics of acti- vated T-cells) after mitogenic stimulation. 1 To whom correspondence and reprint requests should be ad- dressed at CIQUIBIC, Departamento de Quı ´mica Biolo ´gica, Fac- ultad de Ciencias Quı ´micas, Pabello ´n Argentina, Ciudad Universi- taria, 5000 Co ´rdoba, Argentina. Fax: 0054-351-4334074. E-mail: skivat@dqb.fcq.unc.edu.ar. Biochemical and Biophysical Research Communications 285, 393–399 (2001) doi:10.1006/bbrc.2001.5202, available online at http://www.idealibrary.com on 393 0006-291X/01 $35.00 Copyright © 2001 by Academic Press All rights of reproduction in any form reserved.