Cytokines and chemokines associated with Treg/Th17 response in chronic inflammatory periapical disease

Abstract Cytokines and chemokines have a fundamental role in the maintenance of inflammation and bone response, which culminate in the development of chronic periapical lesions. Regulatory (Treg) and Th17 cytokines play a key role in regulating the immune response involved in this process. The aim of this study was to investigate the role of Treg and Th17 cells in chronic inflammatory periapical disease, by comparing the expression of the immunoregulatory mediators TGF-β, IL-10, CCL4, and the proinflammatory IL-17 and CCL20 in the periapical tissue of teeth with pulp necrosis, with and without associated chronic lesions. Eighty-six periapical tissue samples were obtained from human teeth. The samples were divided into three groups: pulp necrosis with a periapical lesion (n=26); pulp necrosis without a periapical lesion (n=30), and control (n=30). All samples were submitted to histopathological analysis and cytokine and chemokine measurement through ELISA. Statistical analyses were done with Kruskal-Wallis and Mann-Whitney tests and Spearman correlation. The group with pulp necrosis and a periapical lesion showed a higher expression of CCL4 and TGF-β in comparison with pulp necrosis without a lesion. CCL20 was higher in the group with a periapical lesion when compared to the control. In all groups there was a weak positive correlation between IL-17/CCL20, IL-10/CCL4, and IL-17/TGF-β. Both types of cytokines, pro-inflammatory and immunoregulatory, occur simultaneously in periapical tissue. However, a rise in immunosuppressive cytokines and chemokines (CCL4 and TGF-β) in periapical lesions suggests a role of these cytokines in stable periapical disease.

Participação de citocinas relacionadas às respostas Th17/Treg na inflamação periapical inflamatória crônica / Role of cytokines related to responses Th17 / Treg in chronic inflammatory periapical disease

A doença periapical inflamatória é uma sequela da infecção e necrose pulpar. Ela representa a resposta de defesa do hospedeiro à agressão proveniente do canal radicular. Assim, lesões periapicais crônicas se desenvolvem como resposta à manutenção da inflamação e à reabsorção óssea. As células T reguladoras (Treg) e células T helper (Th) 17 (Th17) têm papel fundamental na regulação da resposta imunológica. Forkhead box P3 (FoxP3) é o fator de transcrição para as células Treg, mas a diferenciação e maturação das células T naive em Treg ou Th17 depende também de citocinas específicas como o fator transformador de crescimento ß (TGF-ß), interleucina 10 (IL-10), interleucina 17 (IL-17), interleucina 6 (IL-6) e interleucina 21 (IL-21). Outras citocinas participam na modulação da atividade de Treg e Th17 como as quimiocinas CCL4 e CCL20 com função de recrutamento destas células para atuação no processo inflamatório. O papel de Treg e Th17 tem sido muito estudado em doenças autoimunes, mas ainda pouco avaliado na patogenia das lesões inflamatórias periapicais crônicas. Para este estudo foram utilizadas oitenta e sete amostras de tecido periapical humano para realização de análises morfológicas e dosagem de citocinas por meio de ensaio imunoenzimático (ELISA) (TGF-ß, IL10, IL-17, CCL4, CCL20). As amostras de tecido periapical foram coletadas de três grupos: grupo controle (dentes hígidos), grupo de dentes com necrose pulpar e lesão periapical e grupo de dentes com necrose pulpar sem lesão periapical. Observamos alta expressão de CCL4 e TGF-ß no grupo com lesão periapical quando comparado com os grupos sem lesão e uma correlação positiva entre CCL20 e IL-17, além de um aumento na expressão de CCL20 no grupo com lesão periapical quando comparado ao controle. Nossas observações implicam que essas duas características, tanto pró-inflamatórias quanto imunossupressoras, estão presentes na lesão periapical crônica, ocorrendo de maneira simultânea e com características de co-estimulação, como resultado do intenso trabalho da resposta imunológica do hospedeiro contra o processo inflamatório proveniente das bactérias intracanais e seus subprodutos.(AU)

Inflammatory periapical disease is a sequel of the infection and pulp necrosis. It represents the host defense response to aggression from the root canal. Chronic periapical lesions are developed in response to the maintenance of inflammation and bone resorption. Regulatory T cells (Tregs) and Th17 cells play a key role in regulating the immune response with opposite functions. Forkhead box P3 (FoxP3) is the master transcription factor for Treg cells, but differentiation and maturation of naive T cells in Treg or Th17 also depend on specific cytokines such as transforming growth factor ß (TGFß), interleukin 10 (IL -10), interleukin17 (IL-17), interleukin-6 (IL-6) and interleukin-21 (IL-21). Other cytokines participate in the modulation of the Treg and Th17 activity, as the chemokines CCL4 and CCL20 with function of recruitment of these cells to act in the inflammatory process. The role of Treg and Th17 has been better studied in autoimmune diseases, but sparsely evaluated in the pathogenesis of chronic periapical inflammatory lesions. Eighty-six human samples were used to perform histologic analysis and the cytokine dosage by enzyme-linked immunosorbent assay (ELISA) (TGF-ß, IL-10, IL-17, CCL4, CCL20) in the periapical tissue of three groups: control group, group of teeth with pulp necrosis and periapical lesion and group of teeth with necrosis without periapical lesion. We observed high expression of CCL4 and TGF-ß in the group with periapical lesion in comparison with the groups without lesion and demonstrated increased expression of CCL20 in the group with periapical lesion when compared to control. Our findings imply that these two characteristics, pro-inflammatory and immunosuppressive, are present in the chronic periapical lesion, occurring simultaneously and with co-stimulation characteristics, as a result of the intense actionof the host's immune response against the inflammatory process coming from intracanal bacteria and their by-products.(AU)