Gene expression in LPS stimulated IkappaB-beta knockout bone marrow derived macrophage (BMDM)

Inflammation is beneficial when it is part of the innate immune response, but harmful when it occurs in an unregulated, chronic manner. We now report that IkappaB-beta, a member of the classical IkappaB family, serves a dual role of both inhibiting and facilitating the inflammatory response. IkappaB-beta degradation releases NF-kappaB dimers which upregulate proinflammatory target genes such as TNF-alpha. Suprisingly absence of IkappaB-beta results in a dramatic reduction of TNF-alpha in response to LPS even though the activation of NF-kappaB is normal. The inhibition of TNF-alpha mRNA expression can be correlated to the absence of nuclear, hypophosphorylated-IkappaB-beta bound to p65:cRel heterodimers at a specific kappaB site on the TNF-alpha promoter. Therefore IkappaB-beta acts through p65:cRel dimers to maintain prolonged expression of TNF-alpha. As a result, IkappaB-beta knockout mice are resistant to LPS induced septic shock and collagen-induced arthritis, and therefore blocking IkappaB-beta might be a promising new strategy for selectively inhibiting the chronic phase of TNF-alpha producting during the inflammatory response.

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Rao P, Hayden MS, Long M, Scott ML, West AP, Zhang D, Oeckinghaus A, Lynch C, Hoffmann A, Baltimore D, Ghosh S