The pharmacodynamic effects of sirolimus and sirolimus-calcineurin inhibitor combinations on macrophage scavenger and nuclear hormone receptors.

BACKGROUND: Sirolimus (SIR) alone or in combination with cyclosporine (CsA) or tacrolimus (TAC) are used in solid organ transplantation, but uncertainty remains regarding their respective atherogenic potentials. METHODS: THP-1 cells were cultured as macrophages and then treated with plasma trough and peak concentration doses of SIR, SIR/CsA or SIR/TAC to assess the time- and dose-dependent mRNA or protein expression of selected atherogenic genes. The selected atherogenic genes included: the macrophage scavenger receptors (MSRs) CD36, CD68, scavenger receptor (SR)-A, SR-BII, and LOX-1; the nuclear hormone receptors peroxisome proliferator activated receptor gamma (PPARgamma) and liver-X-receptor alpha (LXRalpha); and the cholesterol efflux transporter (ABCA-1). RESULTS: SIR-mediated changes in mRNA included the upregulation of ABCA1, downregulation of CD68, SR-A and SR-BII, and concentration- and/or time-dependent effects on CD36, LOX-1, PPARgamma, and LXRalpha that did not translate into significant protein changes. With SIR/CsA, the protein expressions of PPARgamma and ABCA-1 were downregulated at 8 h. In contrast, with SIR/TAC, PPARgamma, and ABCA-1 protein expressions were upregulated at 8 h. CONCLUSIONS: Combination results differed from findings with SIR alone, supporting the observed clinical phenotype with calcineurin inhibitors. These findings may provide a rationale for the development of novel drug delivery strategies to mitigate adverse pharmacodynamic responses.

Effect of tacrolimus on the expression of macrophage scavenger and nuclear hormone receptors in THP-1-derived human macrophages.

BACKGROUND: Data indicate that tacrolimus and cyclosporine A (CsA) differentially affect the risk of atherosclerosis. The results of our recent in vitro studies of clinically relevant CsA concentrations demonstrated the modulation of macrophage scavenger receptors (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 hormone receptors peroxisome proliferator-activated receptor (PPAR)gamma and liver-X-receptor-alpha, and the cholesterol 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-dependent (1, 2, 4, 8, and 24 hr) and dose-dependent (concentrations [micrograms/liter] corresponding to the trough [15], peak [30], and 4 x peak [120]) manner using reverse-transcriptase polymerase chain reactions. The gene expression levels of interest were normalized to GAPDH expression in each sample to provide semiquantitative reverse-transcriptase polymerase chain reaction results. Additional immunoblotting studies demonstrated protein expression of CD36, PPARgamma, 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-alpha, and PPARgamma were regulated in a dose-dependent manner. Protein expression of CD36 was down-regulated, and PPARgamma and ABCA1 were relatively unchanged. CONCLUSIONS: Tacrolimus seems to regulate MSRs, nuclear hormone receptors, and ABCA1 in THP-1 macrophages. These results differ from previous findings with CsA and may provide insight into the mechanisms of posttransplant atherosclerosis.