Insights into cyclosporine A-induced atherosclerotic risk in transplant recipients: Macrophage scavenger receptor regulation
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Clinical monitoring of organ-transplant recipients suggests that administration of cyclosporine (CsA) may increase the risk of atherosclerosis when compared with the general population. The purpose of this work is to demonstrate the utility of the in vitro Tamm-Horsfall protein (THP)-1 human monocyte cell culture model for determining drug-related atherosclerotic potential in macrophages. The effect of CsA on the mRNA expression of macrophage scavenger receptor genes including CD36, CD68, scavenger receptor (SR)-A, SR-BII, and lectin-like oxidized low-density lipoprotein receptor (LOX-1); the nuclear hormone receptors, including peroxisome-proliferator activated receptor (PPAR)gamma and liver-X-receptor (LXR)alpha; and the cholesterol efflux pump ABCA1 were investigated as markers of atherosclerotic progression. The THP-1 cells were cultured and differentiated into macrophages. The macrophages were then treated with CsA to assess gene expression. Time- (1, 2, 4, 8, and 24 hours) and dose- (concentrations [mg/L] corresponding to the trough [0.5], peak [1.25] and 4x peak ) dependency of CsA was assessed. The treated macrophage mRNA gene expression of CD36, CD68, and PPARgamma were up-regulated in the presence of CsA. Interestingly, SR-A, SR-BII, LOX-1, and LXRalpha expression appeared to be slightly down-regulated, and ABCA1 was relatively unchanged. Immunoblotting studies demonstrated that the protein expression of CD36 was unchanged or increased, PPARgamma was unchanged, and ABCA1 was unchanged or decreased at 4 and 8 hours. The results document CsA-induced mRNA and protein changes in receptors relevant to lipid-laden foam cell formation and demonstrate the utility of THP-1 macrophages for screening of atherosclerotic risk potential.