Inducible nitric oxide synthase (iNOS) in gingival tissues of chronic periodontitis with and without diabetes: immunohistochemistry and RT-PCR study.

BACKGROUND: There is few data concerning the pathogenesis and contribution of inducible nitric oxide synthase (iNOS) in the inflammatory reactions of the periodontium in the course of diabetes. This study evaluated the expression of iNOS in the gingival biopsies of periodontitis patients with and without type 2 diabetes.
METHODS: 80 subjects were evaluated in four groups: patients with chronic periodontitis and diabetes, patients with chronic periodontitis, periodontally healthy patients with diabetes, and systemically and periodontally healthy control subjects. Gingival biopsies were subjected to immunohistochemistry as well as reverse transcription polymerase chain reaction (RT-PCR) for determination of iNOS.
RESULTS: All diseased gingival tissues had a significant increase in iNOS expression by immunohistochemistry (P<0.001) compared to controls. There was no significant difference observed between patients with both diabetes and periodontitis and diabetic patients regarding iNOS(+) cells. Meanwhile, these two groups had significantly increased iNOS(+) cells when compared to periodontitis patients (P<0.001). There are significantly higher levels of iNOS mRNA expression of all patient groups compared to controls (P<0.0001). In addition, samples from patients with diabetes and periodontitis showed significantly higher levels of iNOS mRNA expression compared to samples from periodontitis patients and diabetic patients (P<0.0001) yet, without noting statistically significant differences between the latter two groups.
CONCLUSIONS: Although iNOS expression was prominent in the gingiva of patients with diabetes and periodontitis, periodontitis patients and diabetic patients, the higher mRNA for iNOS observed in diabetes and periodontitis may indicate a possible involvement of this mediator in the periodontal destruction of type 2 diabetes.