Baicalein Attenuates Lung Injury Induced by Myocardial Ischemia and Reperfusion

Baicalein is an active component of Scutellaria baicalensis Georgi, which has traditionally been used to treat cardiovascular diseases in China. In this study, we investigated if treatment with baicalein can attenuate the lung injury induced by myocardial ischemia and reperfusion (I/R). Myocardial I/R, induced by a 40-min occlusion of the left anterior descending coronary artery and a 3-h reperfusion, significantly increased histological damage and the wet-to-dry weight ratio of lungs in rats. The terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive nuclei and caspase-3 activation was significantly increased in the lungs. Serum and bronchoalveolar lavage fluid levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and interleukin-6 (IL-6) were significantly elevated, as were TNF-alpha levels in the lung. Intravenous administration with baicalein at doses of 3, 10, and 30 mg/kg for ten minutes before myocardial I/R significantly reduced histological damage, the wet-to-dry weight ratio, and apoptosis in the lung. Baicalein also significantly inhibited the increase in levels of TNF-alpha, IL-1 beta, and IL-6. Moreover, baicalein increased Bcl-2 and decreased p53, Bax, and cytochrome c in lungs. Phosphorylation of the prosurvival kinases, including Akt and extracellular signal-regulated kinases 1 and 2 (ERK1/2), was increased, while the phosphorylation of the pro-apoptotic mitogen-activated protein kinases, including p38 and c-Jun N-terminal kinase (JNK), was decreased. In conclusion, treatment with baicalein attenuates the lung injury induced by myocardial I/R. The mechanisms might be related to the limiting of apoptosis, possibly via the inhibition of both the extrinsic and intrinsic pathways of apoptosis, including the inhibition of TNF-alpha production and modulation of pro- and anti-apoptotic signaling elements.