Benzoxathiole derivative blocks lipopolysaccharide-induced nuclear factor-κB activation and nuclear factor-κB-regulated gene transcription through inactivating inhibitory κB kinase β

Benzoxathiole derivatives have been used in the treatment of acne and have shown cytostatic, antipsoriatic, and antibacterial properties. However, little is known about the molecular basis for these pharmacological properties, although nuclear factor NF)-kappa B activation is closely linked to inflammation and cell proliferation. Here, we demonstrate that the novel small-molecule benzoxathiole 6,6-dimethyl-2-( phenylimino)-6,7-dihydro-5H-benzo-[ 1,3] oxathiol-4-one ( BOT-64) inhibits NF-kappa B activation with an IC50 value of 1 mu M by blocking inhibitory kappa B (I kappa B) kinase beta (IKK beta), and suppresses NF-kappa B-regulated expression of inflammatory genes in lipopolysaccharide ( LPS)-activated RAW 264.7 macrophages. BOT-64 inhibits IKK beta-mediated I kappa B alpha phosphorylation in LPS-activated macrophages, resulting in sequential prevention of downstream events, including proteolytic degradation of I kappa B alpha, DNA binding ability, and transcriptional activity of NF-kappa B. BOT-64 inhibits LPS-inducible IKK beta activity in the cells and catalytic activity of highly purified IKK beta. Moreover, the effect of BOT-64 on cell-free IKK beta was abolished by substitution of Ser-177 and Ser-181 residues in the activation loop of IKK beta to glutamic acid residues, indicating a direct interaction site of benzoxathiole. BOT-64 attenuates NF-kappa B-regulated expression of inflammatory genes such as inducible nitric-oxide synthase, cyclooxygenase-2, tumor necrosis factor-alpha, interleukin (IL)-1 beta, and IL-6 in LPS-activated or expression vector IKK beta-transfected macrophages. Furthermore, BOT-64 dose-dependently increases the survival rates of endotoxin LPS-shocked mice.