Even after anti-CD3/CD28 antibody stimulation, RXRα expression did not change much between 1.5 and 24 h. In contrast, PPARγ expression increased after antibody stimulation Selleck HSP inhibitor and reached a maximum after 3 h ( Fig. 2A). PPARg protein expression increased

steadily upto 24 h after antibody stimulation ( Fig. 2B). We confirmed these properties by flow cytometric analysis (data not shown). To examine the subcellular localization of RXRα and PPARγ proteins in HOZOT cells, we performed immunohistochemical analysis and Western blotting analysis using nuclear extracts. RXRα protein was detected in the cytoplasm under both anti-CD3/28 antibody stimulated and unstimulated conditions. On the other hand, PPARγ protein was weakly detected under unstimulated conditions, but upon Ab stimulation, it appeared in the cytoplasm at high levels. When treated with agonistic ligands for RXRα and PPARγ, NEt-3IP and TZD, respectively, both RXRα and PPARγ proteins were translocated to the nuclei (Fig. 3A). NEt-3IP is an agonist specific for RXRα/β but not RXRγ, whereas TZD is specific for PPARγ but not PPARα/β. Western blotting analysis confirmed the

localization of both NRs (Fig. 3B). To further investigate the functional relevance of RXRα and PPARγ proteins in HOZOT cells, we treated HOZOT cells with their agonistic ligands and observed the effects on cytokine productions. HOZOT cells produce high amounts of IFN-γ, RANTES, and IL-10. Among them, IFN-γ production was inhibited in a dose-dependent

RO4929097 nmr manner by either NEt-3IP or TZD treatment alone (Fig. 4). To examine antagonist effects, we next treated HOZOT cells with combinations of agonists and antagonists, namely RXRα agonist (NEt-3IP) plus antagonist (NS-4TF) or PPARγ agonist (TZD) plus antagonist (GW9662). Each antagonist abolished its corresponding agonist’s effects on IFN-γ production (Fig. 4). In contrast, no significant decrease or increase in RANTES and IL-10 production was observed by NEt-3IP and TZD treatment (Suppl. Fig. 2). Cell viability was maintained at high levels at concentrations upto 10 mM for both ligands (data not shown). These results indicated that both NRs were functionally involved in IFN-γ production in HOZOT cells. To explain the SPTLC1 mechanism of suppression of IFN-γ production by NEt-3IP and TZD in HOZOT cells, we hypothesized that RXRα and PPARγ could directly bind to the IFN-γ promoter region. We first performed a bioinformatics search for DR1 and PPRE sites, specific binding sequences for nuclear receptors, on the IFN-γ promoter region using web-based software, rVISTA. A DR1-type PPRE was found in the IFN-γ promoter region at 493 bp upstream of the IFN-γ transcription start site ( Fig. 5). We next performed a ChIP analysis with anti-RXRα antibody and anti-PPARγ antibody using HOZOT cells treated with NEt-3IP or TZD. As shown in Fig. 6, low amounts of RXRα and PPARγ proteins were bound to the IFN-γ promoter region, even in ligand-unstimulated HOZOT cells.