We recently found that manganese superoxide dismutase (Mn-SOD) is up-regulated by TNF alpha at the transcription level in human endometrial stromal cells (ESC) and that TNF alpha-induced Mn-SOD expression is mediated by protein kinase C (PKC)-dependent phosphorylation. This study was undertaken to investigate whether nuclear factor-kappa B (NF-kappa B), a transcription factor, is involved in Mn-SOD induction by TNF alpha or PKC in human ESC. Electrophoretic mobility shift assay revealed that TNF alpha (1 ng/ml) and phorbol 12-myristate 13-acetate (TPA; 0.4 micro M), PKC activator, caused marked increases in nuclear NF-kappa B DNA binding activity. Secondly, ESC were incubated with MG132 (proteasome inhibitor) or SN50 (inhibitor of translocation of NF-kappa B into the nucleus) in the presence of TNF alpha or TPA. TNF alpha and TPA significantly increased Mn-SOD activities and Mn-SOD mRNA levels, and those effects were completely inhibited by MG132 and SN50. TNF alpha alone caused no effect on cell viability, but in the presence of MG132, TNF alpha significantly decreased cell viability. This inhibitory effect of MG132 was blocked by simultaneous addition of N-acetyl-L-cysteine, an antioxidant. In conclusion, the present study showed the involvement of NF-kappa B in Mn-SOD induction by TNF alpha or PKC in human ESC. This phenomenon could be a self-defense system of ESC against TNF alpha-mediated oxidative stress.