Effect of L-N6-(1-iminoethyl)-lysine, an inducible nitric oxide synthase inhibitor, on murine immune response induced by Actinobacillus actinomycetemcomitans lipopolysaccharide.

BACKGROUND AND OBJECTIVES

Inducible nitric oxide synthase (iNOS) activity is known to regulate the immune response. The present study was carried out to determine the effect of L-N6-(1-iminoethyl)-lysine (L-NIL), an iNOS inhibitor, on the induction of immune response to Actinobacillus actinomycetemcomitans lipopolysaccharide in mice.

MATERIAL AND METHODS

BALB/c mice were sham-immunized (group I), immunized with A. actinomycetemcomitans lipopolysaccharide (group II) or treated with L-NIL and immunized with A. actinomycetemcomitans lipopolysaccharide (group III). All animals were then challenged with viable A. actinomycetemcomitans. The levels of serum nitric oxide (NO), specific immunoglobulin G (IgG) isotypes and both interferon-gamma and interleukin-4, as well as spleen cell-derived iNOS activity, before and after bacterial challenge, were assessed. The diameter of skin lesions was also determined. Serum and spleen cells from the above groups were adoptively transferred to the recipients that were then subsequently challenged with live bacteria.

RESULTS

Treatment with L-NIL suppressed serum NO and splenic iNOS activity, but enhanced serum-specific IgG2a antibody and interferon-gamma levels. The lesions in L-NIL-treated mice healed much more rapidly. Transfer with serum and cells from L-NIL-treated and A. actinomycetemcomitans lipopolysaccharide-immunized donors resulted in rapid healing of the lesions in the recipients.

CONCLUSION

It is suggested that treatment with L-NIL in mice immunized with A. actinomycetemcomitans lipopolysaccharide may shift the immune response towards a protective T helper 1-like immunity against A. actinomycetemcomitans-induced infection.