Objective: To explore whether barium chloride (BaCl2) preconditioning has the protective effect on lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS) model in mice and the possible mechanism.
Methods: Sixty 8-12 week old healthy C57BL/6 male mice were randomly divided into control group, ARDS model group and BaCl2 pretreatment group, with 20 mice in each group. The BaCl2 pretreatment group was continuously injected with BaCl2 (4 mg/kg through the tail vein) for 3 days before ARDS model establishment. ARDS model was established by intratracheally injecting (3 mg/kg) LPS. The control group was intratracheally given the same volume of 0.9% normal saline. On 24th hour after ARDS model establishment, some mice were sacrificed for obtaining fresh lung tissue. And the right lower lobe of the lung was separated for observing the pathological changes of lung tissue while the left lung tissue was used to measure the wet/dry weight ratio (W/D) of the lung. Some mice were sacrificed for observing pulmonary microvascular permeability at 2nd hours after injecting Evans blue (EB) through tail vein. The left mice were killed for alveolar lavage to measure the levels of tumor necrosis factor-α (TNF-α) via enzyme linked immunosorbent assay (ELISA).
Results: Comparing with the control group, ARDS model group showed typical ARDS pathological changes, which included the increased W/D ratio (4.951±0.161 vs. 3.449±0.299, P < 0.01) and the content of EB in the lung tissue (μg/g: 0.130±0.027 vs. 0.085±0.011, P < 0.01), the damaged alveolar wall structure, lung congestion and exudates in the alveoli, as well as amounts of inflammatory cells. The pathological score of lung injury (10.33±1.15 vs. 1.67±0.58) and the level of TNF-α in BALF (ng/L: 900.85±247.80 vs. 68.21±5.79) were significantly increased in the ARDS model group (both P < 0.01). Comparing with the ARDS model group, the lung W/D ratio (4.620±0.125 vs. 4.951±0.161) and the EB content in the lung tissue (μg/g: 0.108±0.011 vs. 0.130±0.027) of BaCl2 pretreatment group were significantly reduced (both P < 0.01). And the damaged pulmonary structural BaCl2 pretreatment group were significantly alleviated. In addition, the pulmonary pathological score (5.00±1.00 vs. 10.33±1.15) and the level of TNF-α in BALF (ng/L: 169.16±73.33 vs. 900.85±247.80) were significantly decreased (both P < 0.01).
Conclusions: Barium chloride pretreatment can improve the lung histopathological changes of ARDS model mice induced by LPS by reducing the permeability of pulmonary capillaries and local inflammatory reaction.Barium chloride has the protective effect against LPS attack in mice model of ARDS.