Fig. 2.

Increased expression of p-JNK, p53 and p21 and inhibition of NF-κB activation by a BH₄ antagonist or an inhibitor of BH₄ synthesis

(A–C) Jurkat cells were treated with the BH₄ antagonist 4-ABH₄ (200 μM) for 48 h and (A) transcript levels of TP53, CDKN1A and JUN were measured by quantitative PCR. Results are expressed as fold induction relative to GAPDH. (B) Levels of p-JNK, p53 and p21 protein were determined by flow cytometry. A representative flow diagram shows background fluorescence (grey) and results obtained with untreated (solid line) or 4-ABH₄-treated (dashed line) Jurkat cells. (C) MTX-, 4-ABH₄- or DAHP-treated Jurkat cells were stimulated with TNF-α for 24 h prior to luciferase measurements. Results are expressed as percentage inhibition of TNF-α-stimulated NF-κB activity in relative light units. Values are mean (s.d.). *P < 0.05 vs untreated cells. NF-κB: nuclear factor κB; JNK: Jun-N-terminal kinase; DAHP: 2,4-diamino-6-hydroxypyrimidine; BH₄: tetrahydrobiopterin.