ANALISI IMMUNOISTOCHIMICA E FUNZIONALE DEL SISTEMA ENDOCANNABINOIDE NELLA MALATTIA PARODONTALE

Immunohistochemical and functional analysis of Endocannabinoid System in periodontal disease Background: The amount of tissue destruction in periodontal disease depends on the equilibrium between pro- and anti-inflammatory mechanisms. Endocannabinoids, including anandamide (AEA) and 2-arachidonoilglicerol (2AG), are important lipid mediators for immunosuppressive effects and they may be involved in wound healing processes in several organs. The physiological role of endocannabinoids in periodontal healing is still unknown, although several studies have been conducted. The purpose of the present study was to elucidate the role of the endocannabinoid system (ECS) in periodontal healing, comparing the expression and distribution of CB1 and CB2 receptors, the production of AEA and the efficiency of the ECS, in the gingival tissue of individuals with chronic periodontitis and subjects non responders to periodontal therapy, versus healthy patients. Methods: In 10 periodontally healthy patients scheduled for tooth extraction, 11 patients with chronic periodontitis, and 8 patients “non-responders” to periodontal therapy, a biopsy of the interdental papilla was harvested and processed for immunohistochemistry, quantitative and functional analysis. The expression and distribution of CB1 and CB2 receptors, the amount of AEA and the efficiency of the ECS, through the ratio of G proteins activated on exposed receptors, was assessed within the three groups. Results: In patients with chronic periodontitis, the mean CB1 percentage on the connective tissue was 2.19 ± 0.76% and CB2 was 2.56 ± 0.80%; in non responders patients CB1 was 4.15 ± 1.39% and CB2 was 3.85 ± 0.73%; in healthy patients the values were 0.13 ± 0.18% and 0.08 ± 0.03% respectively. In patients with chronic periodontitis the mean CB1 value on the epithelium was 2.56 ± 0.80% and CB2 was 3.67 ± 0.73%; in non responders patients CB1 was 12.64 ± 2.65% while CB2 was 13.21 ± 2.58%; in healthy patients the values were respectively 0.06 ± 0.02% and 0.03 ± 0.02%. All the differences between the three groups were statistically significant (Kruskal–Wallis test p<0.05); moreover CB1 and CB2 expression resulted significantly higher in non responders than in chronic and in healthy patients (Wilcoxon-Mann-Whitney test, p<0.05). The values of AEA, extracted and quantified from gingival biopsies, were 52.02 ± 11.12 pg/mg in patients with chronic periodontitis, 16.38 ± 8.73 in non responders patients while 22.50 ± 9.59 pg/mg in healthy subjects. The production of AEA was significantly higher in chronic than in healthy and in non responders patients (Kruskal–Wallis test p=0,001). Furthermore there was a statistically significant difference between values obtained from active (52.02 ± 11.12 pg/mg) and healthy site of each chronic patient (22.50 ± 9.59 pg/mg) (Wilcoxon-Mann-Whitney test, p=0,004). As regards the functional analysis, the patients with chronic periodontitis shown 30% of G proteins, non responders patients 45%, while in healthy patients the value was about 55%. The ratio of G proteins activated on exposed receptors, which indicate the efficiency of the ECS, were 2.87 in chronic patients, 1.33 in non responders individuals and 183.33 in healthy patients. Conclusions: These results suggest that the ECS plays a role in periodontal diseases. Summarizing, the healthy patients have poor inflammation with minimal production of AEA, few receptors exposed but the ECS seems to be efficient; the patients with chronic periodontitis, that show a considerable tissue inflammation, produce about twice the amount of AEA, expose more receptors but the system is not efficient alone to contrast the disease. Indeed healing occurs only if the levels of plaque and inflammation are controlled. As regards the “non-responders” group we can conclude that the ECS produces fewer AEA, due to the lower level of inflammation but expose a lot of receptors in order to contrast the tissue destruction, but the system is not able to lead to healing.