ObjectiveTo estimate whether alpha 1-antitrypsin (AAT) can reduce ventilator-induced lung injury (VILI) in acute respiratory distress syndrome (ARDS) rats after mechanical ventilation.MethodsThe rats were randomly divided into 3 groups: a sham (S) group, a mechanical ventilation (V) group and a mechanical ventilation/AAT (VA) group. The rats in the S group only received anesthesia, and the rats in the V and VA groups received endotoxin to simulate ARDS followed by mechanical ventilation for 4 hours. At the beginning of ventilation, the rats in the V group received saline, and the rats in the VA group received AAT. The PaO2/FiO2 ratio and the lung wet/dry (W/D) weight ratio were tested. The total protein and neutrophil elastase concentrations and the neutrophil and macrophage counts in bronchoalveolar lavage fluid (BALF) were tested. Proinflammatory factors in BALF and intercellular cell adhesion molecule-1 (ICAM-1) and microphage inflammatoryprotein-2 (MIP-2) in the serum were also detected. Furthermore, the oxidative stress response was detected, and histological injury and apoptosis were evaluated.ResultsCompared with the S group, PaO2/FiO2 was significantly decreased in the V group and the VA group, the protein concentration in the BALF and the lung W/D weight ratio were significantly increased, the concentration of inflammatory factors in BALF and peripheral blood was significantly increased, and inflammatory cells in BALF also increased. Meanwhile, malondialdehyde (MDA) concentration, myeloperoxidase (MPO) and nicotinamide adeninedinucleotide phosphate (NADPH) activity increased significantly. The V group and VA group were severely damaged, and the number of apoptotic cells increased significantly. Compared with the V group, the PaO2/FiO2 in the VA group significantly increased; the W/D weight ratio and the BALF protein concentration decreased; the number of macrophages and neutrophils in the BALF, and the concentration of elastase significantly decreased; tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 in BALF decreased, IL-10 increased; ICAM-1 and MIP-2 in peripheral blood decreased. At the same time, the MDA concentration, MPO and NADPH activities in the VA group were significantly lower than those in the V group; the tissue damage was significantly reduced, and the number of apoptosis was significantly reduced. In addition, compared with the V group, the expression of Bax, gelsolin and cleaved caspase-3 decreased in the VA group, but the expression of Bcl-2 was increased (all P<0.05).ConclusionsAAT can relieve VILI in ARDS rats. The protection conferred by AAT may be associated with the anti-inflammatory, antioxidative stress response and antiapoptotic effect of AAT.