Evaluation of macrophages infiltration, inflammatory signal and skeletal muscle atrophy of rats with periapical lesion

Abstract

Currently, there is some consensus within the dentistry area related to the fact that chronic inflammation in teeth may eventually lead to systemic disorders. Periapical lesion (PL) is characterized as an oral inflammation and it is associated with increased levels of proinflammatory cytokines such as IL-6 and TNF-alpha, that possibly induce insulin resistance. Insulin resistance can be defined as the state in which there is a decreased tissue glucose uptake in response to insulin stimulus, however, the mechanisms that cause insulin resistance are not fully understood. Previous studies from our laboratory observed that PL promotes increased plasma concentrations of TNF-alpha, impairments in insulin signal transduction and reduced GLUT4 content in plasma membrane in skeletal muscle tissue, showing a relationship between PL and insulin resistance. These findings highlight the need for further studies to verify the mechanisms involved in these hormonal resistance. This way, current evidence suggest that infiltrated macrophages in tissues may contribute to the development of insulin resistance This condition is related to the activation of the "toll-like receptor 4" (TLR4) that is highly expressed by macrophages. It should be noted that activation of TLR4 in macrophages triggers pro-inflammatory signals which are related to the insulin signal inhibition. In addition, it is known to conditions with high inflammatory component such as heart failure and sepsis are related to morphological changes in muscle tissue. Therefore, it is also important to find out whether the inflammatory state present in LP can promote changes in this tissue. Thus, in order to verify if macrophage infiltration and inflammatory signaling are changed in PL rats, This study, aimed to: 1) to verify the presence of infiltrated macrophages(proteína F4/80) in this tissue; 2) to analyze the cross-sectional area of muscle fibers; 3) to evaluate the gene expression and total content (JNK, IKKalpha/beta, TNF-alpha,)and TLR4 in muscle tissue; 4) to verify the phosphorylation status of JNK, IKKalpha/beta; 5) to analyze the plasma concentrations of LPS, HSP70, INFgama, TNF-alpha, IL-4, TGF-beta; 6) to quantify the expression of transcription factors involved in the differentiation of lymphocytes in spleen tissue (T-bet, GATA-3 e FOXP3); 7) 7) to quantify the gene expression of proteins related to muscular atrophy (Murf1 and atrogin-1). For this purpose, 45 Wistar rats (2 months old) will be distributed into three groups: a) control rats without PL; b) rats with induced PL in the first upper right molar (only one lesion); c) rats with induced PL in first and second molars of the upper and lower right side (total of four lesions) employing a drill carbon steel with a sphere of 0.1 mm in the edge. Statistical analysis will be performed by analysis of variance (ANOVA) followed by Tukey test. The significance level adopted will be 5% (alpha = 5%). (AU)