0041-1337/04/7708-1281/0 TRANSPLANTATION Vol. 77, 1281–1287, No. 8, April 27, 2004 Copyright © 2004 by Lippincott Williams & Wilkins, Inc. Printed in U.S.A. EFFECT OF TACROLIMUS ON THE EXPRESSION OF MACROPHAGE SCAVENGER AND NUCLEAR HORMONE RECEPTORS IN THP-1–DERIVED HUMAN MACROPHAGES SONG JIN, 1 A. SCOTT MATHIS, 2,3 KEVIN GIOIA, 1 TAMARA MINKO, 1 GARY S. FRIEDMAN, 4 JOSEPH ROSENBLATT, 1 FELICE PENG, 1 DAVID S. SERUR 5 AND GREGORY T. KNIPP 1,6 Background. Data indicate that tacrolimus and cy- closporine A (CsA) differentially affect the risk of ath- erosclerosis. The results of our recent in vitro studies of clinically relevant CsA concentrations demon- strated the modulation of macrophage scavenger re- ceptors (MSRs) involved in atherogenesis. This work evaluated the effects of clinically relevant tacrolimus concentrations on the expression of the MSR genes CD36 and CD68, SR-A and SR-BII, lectin-like oxidized low-density lipoprotein receptor-1, the nuclear hor- mone receptors peroxisome proliferator-activated re- ceptor (PPAR) and liver-X-receptor-, and the choles- terol efflux pump ABCA1 in the in vitro human THP-1 macrophage model. Methods. The cells were cultured and differentiated into macrophages. Macrophages were treated with the tacrolimus to assess gene expression in a time-depen- dent (1, 2, 4, 8, and 24 hr) and dose-dependent (concen- trations [micrograms/liter] corresponding to the trough [15], peak [30], and 4 peak [120]) manner us- ing reverse-transcriptase polymerase chain reactions. The gene expression levels of interest were normal- ized to GAPDH expression in each sample to provide semiquantitative reverse-transcriptase polymerase chain reaction results. Additional immunoblotting studies demonstrated protein expression of CD36, PPAR, and ABCA1. Results. The gene expression of CD36, SR-BII, and lectin-like oxidized low-density lipoprotein receptor-1 were down-regulated, and ABCA1 was up-regulated. CD68, SR-AI, liver-X-receptor-, and PPAR were reg- ulated in a dose-dependent manner. Protein expres- sion of CD36 was down-regulated, and PPAR and ABCA1 were relatively unchanged. Conclusions. Tacrolimus seems to regulate MSRs, nuclear hormone receptors, and ABCA1 in THP-1 mac- rophages. These results differ from previous findings with CsA and may provide insight into the mecha- nisms of posttransplant atherosclerosis. Recent evidence indirectly implicates immunosuppressive agents, particularly calcineurin inhibitors, in the develop- ment of cardiovascular disease after solid-organ transplan- tation. Additional evidence indicates a differential effect of cyclosporine A (CsA) and tacrolimus, agents that inhibit cal- cineurin by different mechanisms to provide immunosup- pression. It is currently uncertain what mechanisms contrib- ute to the observed cardiovascular profile (1–3). Macrophage scavenger receptors (MSRs), including the class B SR-CD36, also identified as fatty acid translocase, and the type I class A SR-AI are involved in lipid-laden macrophage formation (4–9). Up-regulation of CD36 has been documented to occur as cholesterol enters cells, and CD36 may account for up to 80% of oxidized low-density lipoprotein (LDL) uptake in macrophage foam cells (7). CD68 (macrosialin) and SR-AI have a similar, albeit lesser, role in enhancing the uptake of oxidized LDL (4, 9). CD36 regulation is modulated by peroxisome proliferator-activated receptor (PPAR) in one pathway and is also believed to be modulated by an all-trans retinoic acid-mediated pathway through the activation of a retinoic acid receptor and its dimerization with a retinoid-X receptor (10). PPAR is also involved with the stimulation of a prominent cholesterol efflux mechanism, called ABCA1, through induction of liver-X-receptor (LXR)- (11, 12). Scavenger receptor BII (SR-BII) was also investi- gated because it seems to play a role in cholesterol efflux and cellular cholesterol removal, albeit lesser than ABCA-1 (13). Using a THP-1–induced macrophage in vitro model, we previously established that CsA affected a number of these receptors at plasma concentrations relevant to those used in solid-organ transplantation (14). The results of that study suggested the possibility of a direct proatherogenic effect through the up-regulation of these genes. The present study determines the effects of tacrolimus on mRNA expression profiles of the MSRs CD36, SR-AI, CD68, lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), and SR-BII; the regulatory nuclear hormone receptors (NHRs) PPAR and LXR; and the cholesterol efflux transporter ABCA1 (11, 12, 15). Protein expression studies were also performed for CD36, PPAR, and ABCA1. The results of this study should provide insight into potential mechanisms for the develop- ment of atherosclerosis after transplantation and provide foundation for further evaluation of these mechanisms. Supported by International Regenerative Medicine and the De- partment of Pharmaceutics, Ernest Mario School of Pharmacy, and in part by a Grant-in-Aid from the Cell Transplantation Research Associates, Inc., School of Pharmacy and the Department of Phar- maceutics at Rutgers University. 1 Department of Pharmaceutics, Ernest Mario School of Phar- macy, Rutgers, The State University of New Jersey, Piscataway, New Jersey. 2 Department of Pharmacy Practice and Administration, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey. 3 Department of Pharmacy, Saint Barnabas Medical Center, Liv- ingston, New Jersey. 4 International Regenerative Medicine, Inc., West Orange, New Jersey. 5 Rogosin Institute, New York Presbyterian Medical Center, New York, New York. 6 Address correspondence to: Gregory T. Knipp, Ph.D., Depart- ment of Pharmaceutics, Rutgers, The State University of New Jer- sey, 160 Frelinghuysen Rd., Piscataway, NJ 08854 – 8020. E-mail: gknipp@cop.rutgers.edu. Received 10 September 2003. Revised 5 October 2003. Accepted 26 October 2003. 1281 DOI: 10.1097/01.TP.0000120950.16995.20