Effect of IKKα and p38 MAPK overexpression on HNE-regulated IL-6 and PGE2 release in MG-63 osteoblast-like line cells. Transient transfection of MG-63 osteoblasts was performed with 1 μg of expression vectors of IKKα (a), WT, or DN p38 MAPK (b) as described in Materials and methods. Six hours after transfection, fresh 0.5% foetal bovine serum/Dulbecco's modified Eagle's medium was added in the absence or presence of 20 μM HNE, 1 ng/ml TNF-α, and 20 μM HNE + 1 ng/ml TNF-α for another 24 hours. After incubation, culture medium was collected and IL-6 and PGE2 levels were evaluated by commercial kits. Values are mean ± standard error of the mean of three experiments. Statistics: p values determined by Student unpaired t test. P values are versus autologous untreated cells or TNF-α-treated cells as indicated in the figure. **p < 0.01, ***p < 0.001. DN, dominant negative; HNE, 4-hydroxynonenal; IKKα, IkappaB kinase alpha; IL-6, interleukin-6; MAPK, mitogen-activated protein kinase; PGE2, prostaglandin E2; TNF-α, tumour necrosis factor-α; WT, wild-type.