The exhausting work of acclimating to chronically elevated CO2

Protective effects of Tanshinone IIA preconditioning against hypobaric hypoxia-induced lung injury in a rat model

Tanshinone IIA (Tan-IIA), derived from Salvia miltiorrhiza, has been used in traditional Chinese medicine to treat cardiovascular diseases and pulmonary hypertension. This study investigates the potential of Tan-IIA preconditioning as a protective strategy against hypoxia-induced lung injury. Male Sprague-Dawley rats (200 ± 25 g) were divided into four groups: normoxia, normoxia with Tan-IIA, hypobaric hypoxia, and hypobaric hypoxia with Tan-IIA. Tan-IIA was administered intraperitoneally at doses of 10, 20, and 40 mg/kg body weight one hour before exposure to hypobaric hypoxia (simulated altitude of 25,000 feet for 48 h). Pulmonary edema was assessed by measuring transvacuolar leakage of sodium fluorescein dye and lung water content. Exposure to hypoxia triggered redox imbalances, inflammation, and changes in levels of nitric oxide (NOx), endothelin- 1, and Na/K ATPase, which contributed to pulmonary edema. Tan-IIA preconditioning, particularly at 20 mg/kg, was effective in reversing these disturbances. Tan-IIA modulated the expression of key signaling molecules, including c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38, as well as downstream activator protein- 1 (AP- 1) subunits (Jun and Fos), thus reducing inflammation. Its protective effects were partly due to increased NO levels and decreased endothelin, which lowered pulmonary vasoconstriction and permeability, respectively. Additionally, enhanced Na/K ATPase expression via hypoxia-inducible factor- 1 (HIF- 1) and AP- 1 pathways promoted alveolar fluid clearance, while interactions between nuclear factor erythroid 2-related factor 2 (Nrf2) and c-Jun highlighted the anti-oxidative properties of Tanshinone IIA. These findings demonstrate that Tanshinone IIA preconditioning protects against hypoxia-induced lung injury by mitigating pulmonary leakage. This highlights its potential therapeutic application in hypoxic lung conditions.