Role of cyclooxygenase in inflammation and periapical bone resorption induced by bacterial lipopolyssacharide

Author(s)

Fernanda Regina Ribeiro Santos

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
• Defense date: 2015-03-27

Examining board members

Francisco Wanderley Garcia de Paula e Silva; Marianne de Vasconcelos Carvalho; Leonardo Biscaro Pereira; Alexandra Mussolino de Queiroz; Léa Assed Bezerra da Silva

• Advisor: Francisco Wanderley Garcia de Paula e Silva

Abstract

During the inflammatory process, mediators are released in order to stimulate cellular and humoral immune response. Through the action of the enzyme cyclooxygenase structural changes occur in the chain of arachidonic acid leading to prostaglandin synthesis, potentially responsible for regulating bone metabolism during inflammatory events. Thus, the aim of this study was to evaluate the role of the enzyme cyclooxygenase in pulp inflammation and periapical bone resorption after inoculation of bacterial lipopolysaccharide (LPS) in the pulp chamber of mouse molars. One hundred and forty four mice were C57BL/6 mice were inoculated in which the pulp chamber of the first molar with a solution containing E. coli LPS (1.0 mg / ml). After experimental periods of 7, 14, 21 and 28 days, the animals were euthanized and the blocks containing teeth and bone were removed to histotechnical processing and RNA extraction. The effects of pharmacologic blockade with indomethacin (non-selective COX inhibitor) and celecoxib (selective COX-2) on the expression of RANK, RANKL, OPG and other genes involved in bone metabolism were investigated. Histological sections were made and stained with hematoxylin and eosin, marked for immunohistochemistry for COX-2 and analyzed by conventional light microscopy. The recruitment of polymorphonuclear and mononuclear inflammatory cells to the pulp tissue was evaluated in three regions of the root pulp (cervical, middle and apical). Then, the evaluation of gene expression by reverse transcription and polymerase chain reaction was performed in real-time (qRT-PCR) using the TaqMan system and using a PCR assay Array (Osteogenesis profiler PCR array RT²). LPS inoculation of mice in the pulp chamber molar was able to induce the expression of Ptgs2 gene responsible for encoding COX-2 enzyme involved in the metabolism of arachidonic acid, as well as receptors for PGE2 Ptger1, Ptger3 and Ptger4. Simultaneously there was induction of the expression of genes Tnfrsf11a, Tnfrsf11b and Tnfsf11 responsible for encoding modulators of osteoclastogenesis RANK, OPG and RANKL, respectively. Celecoxib and Indomethacin, non-selective and selective inhibitors of COX-2, respectively, differentially modulate expression of genes Tnfrsf11a, Tnfrsf11b and Tnfsf11. Histologically, the drugs used did not inhibit the development of bone resorption in the periapical region. During the period of 28 days in the animals inoculated and LPS was administered Indomethacin was observed a significant increase of the periapical lesion. Some genes related to bone anabolism had to be increased in the initial stages of response to LPS inoculation in the pulp chamber, with the inhibition of the cyclooxygenase, such as Bmpr1b, Col10a1, Col14a1, Col17a1, Ahsg and Msx1. Considering that Celecoxibe and Indomethacin modulated differentially expression of genes involved in bone metabolism after inoculation of LPS, there seems to be a distinct role for COX-1 and COX-2 in periapical lesion development. (AU)

• FAPESP's process: 12/08421-2 - Investigation of the role of cyclooxygenase-2 in periapical bone resorption induced by bacterial lipopolysaccharide
• Grantee: Fernanda Regina Ribeiro Santos
• Support Opportunities: Scholarships in Brazil - Doctorate