Investigation of Anti-Fibrotic Activity of Selected Herbal Drugs Against Bleomycin Induced Pulmonary Fibrosis In Rat

Abstract

Background: Pulmonary fibrosis is a lung disorder that affects the normal function of the respiratory system. It causes scars and thickness of lung tissues like bronchi, alveoli, etc. The pathophysiology of the fibrotic lungs involves the deposition of extracellular matrix on the airway which may lead to reduced oxygen diffusion capacity of alveoli inside the lungs which is irreversible. This results in the formation of fibrotic lungs. Various FDA approved synthetic drugs are available in market such as angio-kinase inhibitors, tyrosine kinase inhibitor, pyridones, corticosteroids, combination therapy etc. which provide only symptomatic relief. The researchers are exploring traditional medicines as an alternative to conventional treatment of pulmonary fibrosis. Terminalia chebula and Glycyrrhiza glabra are reported to possess anti- inflammatory and antioxidant activity. They also inhibit release of inflammatory mediators such as TNF- α, IL-6, IL- 1β. The ripe fruit extract of Terminalia chebula and aqueous extract of root of Glycyrrhiza glabra contain chebulic acid and glycyrrhizin respectively. In the light of existing reports, the present study was undertaken to explore the antifibrotic activity of Terminalia chebula and Glycyrrhiza glabra which may be exerted via inhibiting the inflammatory mediators and thereby myofibroblast and fibroblast production. Objectives: The aim of the present study was to investigate pharmacological action and mechanism of action of selected herbal drugs against bleomycin induced pulmonary fibrosis. Materials & Methods: Male/ female rats were divides into ten groups such as normal control (NC), disease control (DC), standard treatment (STD) (Methylprednisolone, 40mg/kg), and treatment groups of three doses of aqueous extract of T. Chebula (in the dose of 350mg/kg, 500 mg/kg, 750 mg/kg), two doses of Glycyrrhizin (in the dose of 250 mg/kg, 400 mg/kg) and two doses of Licorice extract (in the dose of 500 mg/kg, 1000 mg/kg respectively). For induction of pulmonary fibrosis, tracheostomy was performed. After 14th day, the development of pulmonary fibrosis was confirmed by histopathological examination. Treatment was started after confirmation of the disease induction and was continued up to 28 days. At the end of treatment, both lungs and blood were collected for the further histopathological and biochemical examination. The circulating eosinophil level was determined from blood samples of rat. Anti- inflammatory parameters such as level of IL-6 was measured from serum samples. TNF- α, IL- 1β, nuclear Factor- kappa B (NF-kβ) and level of hydroxyproline were measured from lung homogenate using ELISA kit. Immunohistochemical analysis was used for detection of α- SMA and collagen- I deposition. Results: Our results showed that T. Chebula aqueous extract as well as G. glabra aqueous extract and pure glycyrrhizin inhibits the release of various inflammatory mediators such as TNF- α, IL-6, IL- 1β, circulating eosinophils and NF-kβ expression which in turn inhibits formation of myofibroblast and fibroblast and thereby prevents chronic alveoli damage. It inhibits deposition of hydroxyproline and collagen- I which indicates inhibition the formation of extracellular matrix inside the lungs. Immunohistochemical analysis exhibited significant reduction in the production of α- SMA and collagen- I deposition inside the lungs confirming the protective action of both the drugs. Conclusion: Our study depicts that T. Chebula aqueous extract as well as G. glabra aqueous extract and pure glycyrrhizin has dose dependent protective action against bleomycin induced pulmonary fibrosis in rats.