Ativação de receptores opioides na doença periodontal experimental: efeitos e mecanismos

Abstract

Beneficial effects of the kappa opioid agonist U-50,488 in preventing periodontal disease (PD) progression in rats were already described, but the mechanisms by which it ocurred were unknwon. The present study evaluated the expression of TNF-, IL-6, IL-8 and IL-10 in periodontal tissues of rats with ligature-induced PD, treated with U-50,488. It alsocorrelated the effects of such agonist with myeloperoxidase activity and the presence of osteoclasts in periodontal tissues. Male Holtzman rats weighing 250-300g were divided into four groups: (1) Naïve, (2) Ligature, (3) Ligature + Saline and 4) Ligature + Kappa agonist. Experimental PD was induced by placing a sterile silk ligature around the 2nd leftupper molar. Animals from groups 3 and 4 were locally administered with either saline or U-50,488, respectively, from the 3rd to the 5th day following ligation. After 5 or 11 days of ligature, animals were euthanized and periodontal tissue samples were collected for histological and morphometric analysis, for evalution of TNF-, IL-6, IL-8, IL-10 andMPO. Ligature placement induced a significant alveolar bone loss, inflammatory infiltrate, number of osteoclasts, MPO activy, IL-6, IL-8 and TNF- expression in periodontal tissues. U-50,488 decreased bone loss and the number of osteoclasts in periodontal tissues, although it did not alter histological inflammatory infiltrate and MPO activity. Furthemore,U-50,488 significantly reduced IL-6 and increased IL-10 levels, but it did not affect TNF- and IL-8. Lowering the levels of IL-6 and increasing IL-10 are important mechanisms by which U-50,488 decreases alveolar bone loss in ligature-induced periodontal disease.Keywords: alveolar bone loss, opioids, IL-6, IL-1