Effect of PPAR-γ activation on IFN-γ expression in NK cells. (A-B) Inhibition of IL-2-induced IFN-γ response by 15d-PGJ2 or ciglitazone in PPAR-γ-positive NKL cells. PPAR-γ-positive NKL cells were preincubated with either 15d-PGJ2, ciglitazone, or drug vehicle for 1 hour, and IL-2 (200 U/mL) was added to the cells for 6 hours. IFN-γ production in the supernatant was measured by ELISA (A). Results are shown as a representative experiment conducted in duplicate (mean ± SD). Total RNA was isolated from the corresponding samples that were treated for 2 hours, and IFN-γ mRNA was analyzed by RPA (B). (C) Reduction of IL-2-induced IFN-γ mRNA in NK92 cells upon ectopic expression of PPAR-γ. PPAR-γ-null NK92 cells were retrovirally infected with or without PPAR-γ (pBABE-PPAR or pBABE) as described in “Materials and methods” and then treated with IL-2 (200 U/mL) and 15d-PGJ2 (2 μM), respectively, for a period of time as indicated in the figure. The total RNA was isolated and subjected to RPA analysis. The PPAR-γ mRNA levels were presented as arbitrary units that were derived from normalization densitometry values of each PPAR-γ band by corresponding L32 band.
