Effect of colchicine on inducible nitric oxide synthase activity and nitric oxide production of mice induced by Aggregatibacter actinomycetemcomitans

Objective:\ua0Colchicine induced a non-protective Th2-like immunity in\ua0Aggregatibacter actinomycetemcomitans-stimulated murine immune response. The aim of the present study was to determine whether colchicine affects inducible nitric oxide synthase (iNOS) activity and nitric oxide (NO) production in\ua0A. actinomycetemcomitans-immunized mice.\ua0Materials and Methods:\ua0BALB/c mice were sham-immunized (group I) or immunized with heat-killed\ua0A. actinomycetemcomitans\ua0(group II-VII). Colchicine was injected intraperitoneally before (group III), on the same day of (group IV), or after (group V) the primary immunization and on the same day of (group VI) or after (group VII) the secondary immunization. In vitro, spleen cells from either sham- or heat-killed\ua0A. actinomycetemcomitan-immunized animals were cultured and stimulated with heat-killed\ua0A. actinomycetemcomitans\ua0in the presence or absence of colchicine with or without addition of L-arginine, Db-cAMP, forskolin or interferon-γ\ua0(IFN-γ). The levels of splenic iNOS activity and both serum and culture supernatant NO levels were assessed.\ua0Results:\ua0The results showed that colchicine did inhibit both splenic iNOS activity and serum NO levels only when the drug was injected at the same time as the immunization (group IV and VI). Splenic iNOS activity and NO levels on antigen-stimulated spleen cell cultures were also suppressed by colchicine, even in the presence of L-arginine, Db-AMP or forskolin. IFN-γ\ua0only partially restored iNOS activity and NO levels in the antigen and colchicine-treated spleen cell cultures.\ua0Conclusion:\ua0This study suggests, therefore, that colchicine may suppress the iNOS activity and NO production in\ua0A. actinomycetemcomitans-immunized mice in vivo and in vitro