Preparation Of STVNa Inhalation Nebulizer And Its Therapeutic Effects On Bleomycin-induced Pulmonary Fibrosis

Idiopathic pulmonary fibrosis(IPF)is a chronic,progressive interstitial lung disease.The mortality of IPF is very high,and the median survival time from diagnosis is 2?4 years.The pathogenesis of IPF remains unclear.However,it is generally believed that the pathology of IPF is caused by the combination of inflammatory reaction,immune response,lung injury and fibrosis.Currently,pirfenidone and nintedanib are the only two approved oral drugs for the treatment of pulmonary fibrosis.However,the therapeutic effects of these two drugs are limited,and the gastrointestinal side effects are obvious.Therefore,there is an urgent clinical need to develop novel and effective drugs for the treatment of pulmonary fibrosis.Early research shows that isosteviol and its related derivatives have a wide range of pharmacological effects,such as anti-inflammatory activity,antioxidant and anti-fibrosis.In addition,the pulmonary fibrosis is a lung disease,and inhalation administration has the advantage of targeting the pulmonary region.This study will develop the inhaled solution of isosteviol sodium(STVNa)and investigate the therapeutic effects of STVNa solution inhaled on bleomycin-induced pulmonary fibrosis in rat.The main contents are as follows:1.Firstly,the development of STVNa inhalation nebulizer was evaluated based on the characteristics of lung function of pulmonary fibrosis patient and the physicochemical properties of STVNa.The particle size distribution(PSD)of aerosols are the main factors affecting the deposition of drugs in the lung.The PSD of aerosols are related to the type of nebulizer device,physicochemical properties of solution and the breathing pattern of patient.Currently,the measurement of PSD recommended by the Pharmacopoeia is tested at constant flow rate.This test condition is inconsistent with the state of airflow for clinical use of inhaled drugs.In this study,a laser diffractometer and a breathing simulator were connected in series to investigate the PSD of nebulizer in realistic breathing pattern.Therefore,as the established method for the measurement of PSD under realistic breathing pattern,the PSD of STVNa nebulizer was evaluated at the state of respiratory obstruction.In addition,the physicochemical properties of STVNa nebulizer were investigated,such as pH,osmolality,surface tension and dynamic viscosity.2.Secondly,due to therapeutic target of lung fibrosis was the alveolar septum,the imaging mass spectrometry(IMS)was used to explore the spatial distribution of drug aerosols in the lung.Furthermore,the in vivo and in vitro correlations of PSD were investigated by using different types of nebulizer,and in order to select an optimal nebulizer for the subsequent pharmacological studies3.Finally,the therapeutic effects of STVNa inhaled on pulmonary fibrosis were investigated.The lung fibrosis model of rat was established with bleomycin(BLM)via tracheal instillation.The therapeutic drugs were administered twice a day for 28 consecutive days after BLM administered.The lung imaging of micro-CT,pulmonary function test,histopathological analysis and collagen test of lung tissue were performed to evaluate the efficacy of STVNa inhaled.Meanwhile,the lung safeties after inhalation of STVNa solution for 28 consecutive days were evaluated from three aspects:lung imaging of micro-CT,pulmonary function test,histopathological analysis.The main results are as follows:1.It is feasible to use the laser diffractometer to measure the PSD of aerosols under realistic breathing pattern.The measurement of PSD should be made under specific breathing pattern represented patient's respiratory function.The testing results of STVNa nebulizer developed were within the acceptable limits.2.There was a trend showed by in vivo study of MSI that the relative signal strength of drug aerosol delivered by Pari nebulizer at the lung parenchyma was higher than the result obtained by Omron nebulizer.The result of in vitro study indicated that the ratio of small particles in the PSD produced by the Pari nebulizer was higher than that produced by the Omron nebulizer.The preliminary correlation between in vitro and in vivo study was showed.Compared with the Omron microAir NE-U22 nebulizer,the Pari LC sprint(blue baffle)was more suitable for drug delivery in the efficacy study.In addition,compared with oral administration,nebulized inhalation had the advantage of lung targeting.3.After the lung fibrosis model of rat was established with bleomycin via tracheal instillation,in the bleomycin group,the results of CT showed the characteristics of fibrosis focus such as ground-glass shadow and honeycomb shadow.The increased small airway resistance,reduced lung volume and compliance were showed in the pulmonary function test of bleomycin group.Meanwhile,the results of histopathological analysis showed that large areas of lung consolidation in the lung tissue of the bleomycin group,the lung interstitium was significantly thickened,collagen was deposited in large amounts,and obvious fibrotic lesions were appeared.However,the fibrosis and damage of lung caused by bleomycin were reduced after aerosol of STVNa inhaled.The lung function,infiltration of inflammatory cell and structural lesions of lung tissues were significantly improved,and the collagen deposition was reduced after the high dose of STVNa nebulizer inhaled.In summary,in the development and evaluation of nebulizer,it is necessary to conduct delivery performance testing and evaluation of inhaled formulation under specific breathing pattern represented patient's respiratory function.In addition,there are therapeutic effects on bleomycin-induced pulmonary fibrosis by STVNa inhaled.