PURPOSE: To analyze the action mechanism of NF-kappaB, IkappaB-alpha and effect of the Dexamethasone (DEXA) in mediating this inflammation, after stimulating cultured herniated intervertebral disc cells with TNF-alpha. MATERIALS AND METHODS: After cultured human intervertebral disc cells passaged three times, they were divided into four groups: A control group (A), DEXA treatment group (B), TNF-alpha treated group (C), TNF-alpha and DEXA were treated at the same time (D). IL-6 and IL-1beta gene expression were measured with semi-quantitative RT-PCR. Western blot analysis was performed to measure protein expression of IkappaB-alpha in the above groups for 10 minutes, 1 hour, 2 hours. In addition, in order to explain the mechanism of NF-kappaB nuclear binding for each group, the nuclear amount of NF-kappaB binding in the nucleus is measured by EMSA. RESULTS: In RT-PCR, expression of IL-6 and IL-1beta was greatest in group C, followed by group D, group A. IkappaB-alpha expression of the group treated with DEXA was not detected in Western blot results within 10 minutes. However, if stimulated by TNF-alpha, the DEXA was not inhibited of IkappaB-alpha concentration. After 1 hour and 2 hours, IkappaB-alpha levels were expressed by cells autonomously (autoregulatory induction). EMSA results expression levels in nuclear protein was maintained in accordance with protein expression. CONCLUSIONS: Our study shows that DEXA inhibits the production of mediators such as inflammatory IL-6 and IL-1beta, however, may not inhibit the transcription of NF-kappaB stimulated by TNF-alpha.