Investigation of the effect of quercetin on fibrosis by MiR-26b and MiR-27b expression in experimental pulmonary fibrosis

Introduction: Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive disease characterized by destruction of the alveolar wall, myofibroblast hyperplasia, extracellular matrix deposition and remodeling of the lung interstitium. Although the pathogenesis is not fully elucidated, alveolar epithelial cell injury and abnormal repair are the main mechanisms leading to pulmonary fibrosis. Currently, there are limited treatment options with unproven efficacy in IPF. Quercetin, a flavonoid found in various plants, has been noted by researchers to prevent cell injury caused by free radicals due to its strong antioxidant property, and there are studies reporting that it alleviates Bleomycin-induced pulmonary fibrosis. Recently, many studies have reported that miRNAs are effective in organ development, normal physiology and the pathogenesis of various diseases and play an important role in IPF. As a result of these studies, miR-27b was determined as an anti-fibrotic miRNA that inhibits fibroblast activation. In our study, it was aimed to reveal the role of miR-26b in the pathogenesis of the disease by showing the expression of miR-26b in Bleomycin-induced pulmonary fibrosis for the first time, and to evaluate the therapeutic effects of Quercetin by light and electron microscopic methods, and to compare the expression levels of miR-26b and miR-27b. Materials and Methods: In this study, 48 Wistar rats were randomly distributed and initially 4 experimental groups were formed. Groups 3 and 4 were further divided into 2 subgroups according to the treatment and life expectancy (n=8). In the 1st group (Control group), 10% saline (SF) was given intratracheally on the 0th day of the experiment. Starting from the 8th day, SF was administered intraperitoneally (i.p.) for 21 days. In the second group (Quercetin control group), Quercetin was given i.p. at a dose of 50 mg/kg for 21 days starting from the 8th day of the experiment. In Group 3 (Injury group), a single intratracheal dose of 10 mg/kg Bleomycin Sulfate was given on day 0 of the experiment. These animals are divided into 2 subgroups; half were sacrificed on the 22nd day (Group 3A) and the remaining half (Group 3B) on the 29th day. In the 4th group (Treatment group), a single intratracheal dose of 10 mg/kg Bleomycin Sulfate was given on the 0th day of the experiment. These animals are divided into 2 subgroups; half of them (Group 4A) were given 50 mg/kg of Quercetin starting from day 8 for 14 days, and the other half (Group 4B) was given i.p. at a dose of 50 mg/kg for 21 days starting from day 8. Lung tissues obtained after sacrification were examined using light and electron microscopic, immunohistochemical and molecular biological methods. Results: In light and electron microscopic examinations, it was observed that the alveolar structure was deteriorated by dense collagen accumulation in the interalveolar septum and a significant increase in the number of inflammatory cells was observed in the injury groups, while the fibrotic response was decreased and the alveolar structure improved with Quercetin treatment. Immunohistochemically, α-SMA expressions were higher in the injury groups, but lower in the treatment groups compared to the injury groups, while E-Cadherin expressions were decreased in the injury groups and showed stronger immunoreactivity in the treatment groups compared to the injury groups. It was found that miR-26b and miR-27b expressions were lower in the injury groups than in the control groups, and higher in the treatment groups than in the injury groups and approached the levels of the control groups. Conclusion: When the findings were evaluated, it was concluded that Quercetin can be considered as a new treatment agent in the Idiopathic Pulmonary Fibrosis model induced with Bleomycin, since it increases the expression levels of miR-26b and miR-27b, which decreases in fibrosis, and has therapeutic effects on the developing histopathological changes.