Three-Compartment Pharmacokinetics of Inhaled and Injected Sinapine Thiocyanate Manifest Prolonged Retention and Its Therapeutics in Acute Lung Injury.

<b>Background</b>: Acute lung injury (ALI) is driven by inflammatory cascades and reactive oxygen species (ROS) generation, with the progression to severe cases markedly increasing mortality. Sinapine thiocyanate (ST), a bioactive natural compound isolated from Sinapis Semen Albae (SSA), demonstrates both anti-inflammatory and antioxidant pharmacological activities. However, no monotherapeutic formulation of ST has been developed to date. A dry powder inhaler (DPI) enables targeted pulmonary drug delivery with excellent stability profiles and high inhalation efficiency. <b>Methods</b>: ST was purified and prepared as inhalable dry powder particles via an antisolvent crystallization technique. The therapeutic mechanisms of ST against ALI were elucidated by network pharmacology and pharmacokinetic analyses, with the therapeutic efficacy of the ST DPI in ALI mitigation being validated using LPS-induced rat models. <b>Results</b>: The ST DPI showed ideal aerodynamic characteristics. Notably, ST exhibited a three-compartment (triexponential) pharmacokinetic profile following both intravenous tail vein injection and inhalation administration. Furthermore, the inhaled formulation displayed a prolonged systemic residence time, which confers therapeutic advantages for pulmonary disease management. Furthermore, the inhalation administration of ST demonstrated a 2.7-fold increase in AUC compared with oral gavage, with a corresponding enhancement in systemic exposure. The ST DPI formulation demonstrated significant therapeutic efficacy against ALI in rats by downregulating inflammatory cytokines and modulating oxidative stress levels, mechanistically achieved through the MAPK-mediated regulation of cellular apoptosis via a positive feedback loop. <b>Conclusions</b>: The unique triexponential plasma level profiles of an ST DPI provide a promising pharmacokinetics-based therapeutic strategy for ALI, leveraging its marked efficacy in attenuating inflammation, oxidative stress, and pulmonary injury.