ROLE OF NO IN SOFT PERIODONTAL TISSUES OF RATS DURING STRESS AND INFLAMMATION

Abstract

Aim. To evaluate the activity of NO-synthase isoforms, the concentration of peroxynitrites and nitrosothiols in the soft tissues of the periodontium of rats under the conditions of modeling chronic stress against the background of lipopolysaccharide-induced inflammation. Methods. Experimental studies were performed on 24 male Wistar rats weighing 190–240 g. The animals were divided into 4 groups: 1 — control, 2 — chronic stress (ChrStr group), animals were kept above water for 1 hour every day for 30 days, 3 — animals that were intraperitoneally injected with 0.4 μg/kg of bacterial LPS of S. typhi (pyrogenal) (LPS group); 4 — animals that were simultaneously simulated chronic stress as in group 2 and administered LPS as in group 3 (ChrStr+LPS). The activity of inducible NO-synthase (iNOS), constitutive NO-synthase (cNOS), the concentration of nitrosothiols (S-NO), and concentration of peroxynitrites of alkali and alkaline earth metals (ONOO) were studied in the homogenate of the periodontal soft tissues of rats. Results. The activity of NOS in the soft periodontal tissues of rats under chronic stress simulation conditions, LPS administration, combined exposure to chronic stress and LPS was increased compared to control group. The concentration of ONOO- in the soft periodontal tissues of rats under chronic stress simulation conditions, LPS administration, combined exposure to chronic stress and LPS was increased compared to the control group. The concentration of nitrosothiols in the soft periodontal tissues of rats under the conditions of chronic stress simulation, LPS administration, combined exposure to chronic stress and LPS was decreased compared to the control group. Conclusions. The combined effect of bacterial lipopolysaccharide and chronic stress leads to increased production of nitrogen monoxide from inducible NO-synthase and elevates concentration of reactive forms of nitrogen, which creates possibility for development of nitrosative stress in the soft periodontal tissues.