Inflammatory reactions in extraoral tissues in mice after intragingival injection of lipopolysaccharide

Intragingival (ig) injection into mice of lipopolysaccharide (LPS) from Pre votella intermedia or Escherichia coli elevated the activity of the histami ne-forming enzyme, histidine decarboxylase (HDC), in the mandible, liver, l ung, and spleen, with a time course similar to that seen with intravenous ( iv) injection. The effect of ig injection was less than that of iv injectio n but similar to that of intraperitoneal (ip) injection. The ig injection a lso increased hepatic serotonin, reflecting platelet accumulation. In galac tosamine-treated mice, the minimum ig dose of LPS needed to induce lethal h epatitis was very small (less than that needed by ip injection). These resu lts support the idea that the LPS produced in oral tissues may be transport ed easily to extraoral tissues and, in some cases, may cause inflammatory o r immune responses. It also may influence the pathogenesis of some systemic diseases.