Progression of Acute Lung Injury in Intratracheal LPS Rat Model: Efficacy of Fluticasone, Dexamethasone, and Pirfenidone

Introduction: We investigated the potential of LPS (10-300 mu g/rat) administered intratracheally (i.t.) to induce reproducible features of acute lung injury (ALI) and compared the pharmacological efficacy of anti-inflammatory glucocorticoids and antifibrotic drugs to reduce the disease. Additionally, we studied the time-dependent progression of ALI in this LPS rat model. Methods: We conducted (1) dose effect studies of LPS administered i.t. at 10, 30, 100, and 300 mu g/rat on ALI at 4 h timepoint; (2) pharmacological interventions using i.t. fluticasone (100 and 300 mu g/rat), i.t. pirfenidone (4,000 mu g/rat), and peroral dexamethasone (1 mg/kg) at 4 h timepoint; (3) kinetic studies at 0, 2, 4, 6, 8, 10, and 24 h post-LPS challenge. Phenotype or pharmacological efficacy was assessed using predetermined ALI features such as pulmonary inflammation, edema, and inflammatory mediators. Results: All LPS doses induced a similar increase of inflammation, edema, and inflammatory mediators, e.g., IL6, IL1 beta, TNF alpha, and CINC-1. In pharmacological intervention studies, we showed fluticasone and dexamethasone ameliorated ALI by inhibiting inflammation (>60-80%), edema (>70-100%), and the increase of cytokines IL6, IL1 beta, and TNF alpha (>= 70-90%). We also noticed some inhibition of CINC-1 (25-35%) and TIMP1 (57%) increase with fluticasone and dexamethasone. Conversely, pirfenidone failed to inhibit inflammation, edema, and mediators of inflammation. Last, in ALI kinetic studies, we observed progressive pulmonary inflammation and TIMP1 levels, which peaked at 6 h and remained elevated up to 24 h. Progressive pulmonary edema started between 2 and 4 h and was sustained at later timepoints. On average, levels of IL6 (peak at 6-8 h), IL1 beta (peak at 2-10 h), TNF alpha (peak at 2 h), CINC-1 (peak at 2-6 h), and TGF beta 1 (peak at 8 h) were elevated between 2 and 10 h and declined toward 24 h post-LPS challenge. Conclusion: Our data show that 10 mu g/rat LPS achieved a robust, profound, and reproducible experimental ALI phenotype. Glucocorticoids ameliorated key ALI features at the 4-h timepoint, but the antifibrotic pirfenidone failed. Progressive inflammation and sustained pulmonary edema were present up to 24 h, whereas levels of inflammatory mediators were dynamic during ALI progression. This study's data might be helpful in designing appropriate experiments to test the potential of new therapeutics to cure ALI.