Effects of high-tidal-volume mechanical ventilation on the expression of P2X7 receptor and inflammatory response in lung tissue of rats

Ventilator-induced lung injury is a severe complication mainly caused from mechanical ventilation (MV), associated with the upregulation of inflammation response. The mechanism still remains unclear. This study aims to explore the effects of pathological damage, neutrophil infiltration, expression of P2X7 receptor, and activation of Caspase-1 in lung tissue using a rat model. Sprague Dawley (SD) rats were randomly divided into sham group, conventional MV group, and high-tidal-volume ventilation group and fed with clean water and rat food. The sham group received tracheotomy without MV; conventional MV group was given 7 mL/kg tidal volume ventilation, and high-tidal-volume MV group was given 28 mL/kg tidal volume ventilation. All the rats were sacrificed after 4 h of ventilation or spontaneous breath. Lung wet/dry ratio was measured, and paraffin sections were prepared for pathological injury assessment and immunohistochemistry of P2X7 and myeloperoxidase levels. Lung homogenate was used for Western blot analysis of P2X7 receptor and Caspase-1 levels and real-time polymerase chain reaction (PCR) analysis of P2X7 gene expression level. Compared to sham group and conventional MV group, high-tidal-volume MV led to an increase in lung wet/dry ratio and histology score. High-tidal-volume ventilation also led to chemotaxis of neutrophils. The expression levels of protein and messenger RNA (mRNA) of P2X7 receptor were significantly upregulated. Cleaved-caspase-1 expression was also upregulated. All data provide the evidence that high-tidal-volume MV can lead to lung injury, neutrophils infiltration, and upregulation of cleaved-Caspase-1 level. This result may be related to the upregulation of P2X7 receptor expression.