The inhibition of lipopolysaccharide-induced tumor necrosis factor-α and nitric oxide production by Clostridium perfringens α-toxin and its relation to α-toxin-induced intracellular ceramide generation

The effect of Clostridium perfringens α-toxin on production of tumor necrosis factor (TNF)-α and nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells was studied. The pretreatment of wild type α-toxin, but not the inactive mutant, significantly decreased LPS-induced TNF-α and NO production. α-Toxin inhibited the expression of TNF-α and an inducible type of NO synthase protein and mRNA. Furthermore, it inhibited the phosphorylation of IκB-α and p65 NF-κB subunit, and the NF-κB luciferase reporter gene activity in LPS-stimulated cells. The pretreatment of α-toxin increased the level of intracellular ceramide. Taken together, Clostridium perfringens α-toxin pretreatment was suggested to inhibit LPS-induced TNF-α and NO production through the inhibition of NF-κB activation. The relationship between α-toxin-induced intracellular ceramide generation and the NF-κB inhibition is discussed.