Effects of NF-κB1 (p50) targeted gene disruption on ionizing radiation-induced NF-κB activation and TNF , IL-1 , IL-1β and IL-6 mRNA expression in vivo

Purpose : To investigate the role of the NF- κB1 (p50) gene in ionizing radiation (IR)-induced NF- κB activation and TNF α, IL-1 α, IL-1 β and IL-6 mRNA expression in vivo. Materials and methods : NF- κB activation was analysed by the gel shift/supershift assay and the levels of TNF α, IL-1 α, IL-1 β and IL-6 mRNA were measured using RNase protection assay (RPA). Various tissues from BALB/c, B6,129P-Nfkb1 (NF- κB1 or p50 gene knockout, p50 -/-) and B6,129PF2 (wild-type, p50 +/+) mice were analysed before or after exposure to a lethal dose (8.5 Gy) of total-body γ-irradiation. Results : Exposure of BALB/c mice to total-body IR selectively activated NF- κB in the spleen, mesenteric lymph nodes (LN) and bone marrow (BM). Gel supershift assay using polyclonal antibodies against NF- κB p50, p65 or c-Rel protein revealed that the NF- κB p50 subunit is a critical component of the NF- κB complexes activated by IR in vivo. Discretely augmented TNF α, IL-1 α, IL-1 β and IL-6 mRNA expression was found in the spleen, LN and BM after BALB/c mice received IR. However, mice lacking the p50 gene (p50 -/-) showed a significant reduction in IR-induced activation of NF- κB and increases in TNF α, IL-1 α, IL-1 β and IL-6 mRNA expression, as compared with that of wild-type mice (p50 +/+) . Conclusions : The NF- κB p50 subunit is a critical component of the NF- κB complexes activated by IR and it plays an important role in mediating IR-induced TNF α, IL-1 α, IL-1 β and IL-6 mRNA expression in vivo.