Butylated hydroxytoluene induces type-v collagen and overexpression of remodeling genes/proteins in experimental lung fibrosis
Vanessa Martins1, Walcy Rosolia Teodoro2, Ana Paula Pereira Velosa2, Priscila Andrade2, Cecília Farhat1, Alexandre Todorovic Fabro3 and Vera Luiza Capelozzi1
1Department of Pathology, 2Rheumatology Discipline, Faculty of Medicine, University of Sao Paulo and 3Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
Offprint requests to: Prof. Vera Luiza Capelozzi, Department of Pathology, Faculdade de Medicina da Universidade de São Paulo, Av. Dr. Arnaldo 455, room 1143, ZIP CODE 01296-903, São Paulo, SP, Brazil. e-mail: firstname.lastname@example.org
Summary. Anomalous histoarchitecture with increased levels of type-V collagen (Col V) in lungs of human idiopathic pulmonary fibrosis (IPF) and bleomycin (BLM) airway-centered interstitial fibrosis suggest that this collagen can be a possible trigger involved in the pathogenesis of these diseases. Butylated hydroxytoluene (BHT) injury model revealed a distal involvement of lung parenchyma with significant endothelial injury and fibrotic response, contrasting with the BLM airway-centered insult. We undertook this study to analyze whether BHT alters distal airway/alveolar epithelial cells (AECs) and extracellular matrix (ECM) signaling involved in the initiation and progression of pulmonary fibrosis in a different pathway concerning overexpression of Col V. Female mice C57BL/6 (n=6) were instilled intraperitoneally with 400 mg/kg of BHT dissolved in 1 mL of corn oil and euthanized at day 14 or 21 after BHT administration. Morphometry, immunohistochemistry and transmission electron microscopy were performed to characterize microscopic and submicroscopic changes of AECs and endothelial cells through transforming growth factor beta (TGF-β) basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) expression. Immunofluorescence and immunogold electron microscopy were performed to characterize Col V. Quantitative polymerase chain reaction (qPCR) was used to confirm differential levels of RNA messenger. BHT lungs showed marked fibrotic areas and hyperplastic AECs. The alveolar damage caused destruction of elastic fibers and a critical increase of Col V in ECM of distal lung parenchyma. Fibrogenesis-promoting markers TGF-β, bFGF and VEGF were also overexpressed in situ, coinciding with up-regulation in remodeling enzymes, growth factors, cytokines, transduction and transcription genes. BHT alters distal lung parenchyma signaling involved in pulmonary fibrosis highlighted similarities to human IPF in a pathway involving Col V arising as a promissory model to identify effective therapeutic targets. Histol Histopathol.
Key words: Pulmonary fibrosis, Butylated hydroxytoluene, Extracellular matrix, Type-V collagen, RT-PCR, Immunohistochemistry, Immunofluorescence, Electron microscopy