Effect of inhibition of inducible nitric oxide synthase (iNOS) on the murine splenic immune response induced by Aggregatibacter ( Actinobacillus ) actinomycetemcomitans lipopolysaccharide

Animal studies suggest that inducible nitric oxide synthase (iNOS) may be associated with destructive periodontal disease. l‐ N 6 ‐(1‐Iminoethyl)‐lysine ( l ‐NIL) has been shown to inhibit iNOS in a selective manner, and hence the aim of the present study was to test the hypothesis that treatment with l ‐NIL may induce a T‐cell helper 1 (Th1)‐like immune response by Aggregatibacter ( Actinobacillus ) actinomycetemcomitans lipopolysaccharide (LPS)‐stimulated murine spleen cells in vitro . BALB/c mice were either sham‐immunized or immunized with A. actinomycetemcomitans LPS. Spleen cells were stimulated with A. actinomycetemcomitans LPS in the presence or absence of l ‐NIL. Nitric oxide (NO), iNOS activity, specific IgG subclass antibodies, interferon‐ γ (IFN‐ γ ), and interleukin‐4 (IL‐4) levels and cell proliferation were determined. The results showed that treatment with l ‐NIL suppressed both NO production and iNOS activity but enhanced specific IgG2a, IFN‐ γ levels, and increased cell proliferation following stimulation with A. actinomycetemcomitans LPS‐stimulated cells. The results of the present study suggest that inhibition of iNOS activity by l ‐NIL may skew the A. actinomycetemcomitans LPS‐stimulated murine splenic immune response towards the Th1‐like immune profile in vitro .