Hypoxia-inducible factor-1α (HIF-1α) in naive and lipopolysaccharide prestimulated human monocytic cells (THP-1). A, THP-1 cells were kept in medium only (naive) or were prestimulated with lipopolysaccharide (0.05ng/ml) for 48h. Afterward the cells were incubated with lipopolysaccharide (+LPS) or without lipopolysaccharide (1 µg/ml for 6h). HIF-1α mRNA expression was analyzed by using real-time polymerase chain reaction and the Δct method, and results are depicted as n-fold induction (2^ΔΔct, means ± SD). Naive cells had significantly greater HIF-1α mRNA expression compared to lipopolysaccharide prestimulated cells (0.05ng/ml lipopolysaccharide for 48h) with and without additional lipopolysaccharide stimulation. B, THP-1 cells were kept in medium only (naive) or were prestimulated with lipopolysaccharide (0.05ng/ml) for 48h. Afterward the cells were incubated with lipopolysaccharide (+LPS) or without lipopolysaccharide (as indicated: 0.05ng/ml or 1 µg/ml for 6h). Additionally, dimethyloxalylglycine (10 µm) was added, as indicated for each lane. HIF-1α protein was assessed by Western blotting. In naive cells, lipopolysaccharide stimulation and/or incubation with dimethyloxalylglycine increased HIF-1α protein concentration, whereas in prestimulated cells additional lipopolysaccharide stimulation and/or incubation with dimethyloxalylglycine only had no effects on HIF-1α protein stabilization. DMOG = dimethyloxalylglycine; mRNA = messenger ribonucleic acid.