Role of Transforming Growth Factor-β in Pathogenesis of Pulmonary Fibrosis in COVID-19, Post-COVID Syndrome, Oncological and Chronic Inflammatory Lung Diseases

INTRODUCTION: Persistent post-COVID syndrome is the persistent physical, medical and cognitive sequelae of coronavirus disease 2019 (COVID-19), including persistent immunosuppression, pulmonary, cardiac and vascular fibrosis which lead to increased mortality and impair the quality of life of patients. АIM: To analyze the completed foreign and domestic studies on the pathophysiology of transforming growth factor-β (TGF-β) in conditions of COVID-19, post-COVID syndrome, oncological and chronic inflammatory lung diseases. Mast cells are among the main producers of inflammatory cytokines in COVID-19, their stimulation leads to the release of many proinflammatory cytokines, such as interleukin 1β, tumor necrosis factor α, interleukin 6, and also TGF-β. The basis of the pathogenesis of post-COVID syndrome is the overexpression of TGF-β leading to a prolonged state of immunosuppression and fibrosis. TGF-β acts as a tumor suppressor inhibiting proliferation and inducing apoptosis in the early stages of oncogenesis; plays an important role in most cellular biological processes leading to remodeling of the airway structures; is involved in epithelial changes, in subepithelial fibrosis, remodeling of smooth muscle of airways and in microvascular changes; induces resistance to glucocorticosteroids; stimulates the production of blood coagulation factor XII, thereby leading to development of potentially fatal complications, such as pulmonary embolism and ischemic stroke. CONCLUSION: In this literature review, a structured analysis of a multicomponent role of TGF-β in the pathogenesis of post-COVID syndrome, pulmonary fibrosis in COVID-19, tumors of respiratory system, chronic obstructive pulmonary disease, bronchial asthma, is given. A possible use of TGF-β as a biomarker of severe and moderate degree of COVID-19 is substantiated.