Figure 4. FK506 (tacrolimus) treatment increases FK506 binding protein 51 (FKBP51) and nuclear factor kappa-light-chain-enhancer of activated B (NF-kB) cell protein levels. A: Twenty-four hour FK506 treatments significantly increased protein levels of FKBP51 and NF-κB in the 661w neuronal cell cultures. The 661w neuronal cell cultures were treated for 24 h with a vehicle—100 nM FK506, 1 μM FK506, or 10 μM FK506. Cell lysate proteins (25 µg) were separated by sodium dodecyl sulfate PAGE (SDS–PAGE), transferred to membranes, and immunoblotted for FKBP51, NF-κB, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The quantification of band intensity is represented as a percentage of FKBP51 or NF-κB of its corresponding GAPDH control band on the same membrane. B: FK506 significantly increased FKBP51 protein levels at a concentration of 10 μM (p=0.03), while 0.1 μM and 1 μM caused an increased in FKBP51 protein levels; however, significance was not obtained (n=3). Error bars represent SEM C: Additionally, FK506 significantly increased NF-κB protein levels at a concentration of 0.1 μM (p=0.004), while 1 μM and 10 μM caused larger increases in protein levels; however, significance was not obtained (n=3 for each dose indicated).