Figure 1

[³H]DPA-713 TSPO binding competition studies. (A) Displacement of [³H]DPA-713 TSPO binding by PK11195, DPA-713 and DPA-714 in human THP-1 cells. Cells were incubated with 10 nM [³H]DPA-713 in the presence of increasing concentrations of unlabelled PK11195, DPA-713 and DPA-714. Fifty percent displacement of [³H]DPA-713 was observed at 128 nM PK11195, 18.5 nM DPA-713, and 5.2 nM DPA-714. Results are presented as mean ± SEM of three separate experiments. (B) [³H]DPA-713 binding competition by unlabelled PK11195, DPA713 and DPA714 in CD14⁺ monocytes from healthy volunteers. Assay conditions were that 1 mL of 10⁶ CD14⁺ cells were incubated with 10 pmol [³H]DPA-713 in the absence or presence of 20 or 50 pmol unlabelled PK11195, DPA-713 or DPA-714. Residual binding of [³H]DPA-713 under these conditions is depicted. Addition of excess (2,000-fold molar excess) DPA-713 resulted in almost complete displacement of [³H]DPA-713 (that is, 0.3 ± 0.2% residual binding, results not shown). Mean [³H]DPA-713 binding capacity was 2.6 pmol/10⁶ CD14⁺ cells (range 1.3 to 5.1). Results are presented as mean ± SEM of three separate experiments. SEM, standard error of the mean; TSPO, translocator protein.