Molecular Mechanism of Ventilator-associated Lung Injury Based on Keap1/Nfr2/ARE Signaling Pathway

  Objective  To explore the molecular mechanism of ventilation induced lung injury (VILI) formation based on Keap1/Nfr2/ARE signaling pathway.

  Methods  The VILI model was established by excessive mechanical ventilation in SD rats. HE staining was used to detect the pathological changes of lung tissue in the control group, normal tidal volume (VT) group and large VT group (VT 40 mL/kg). The wet weight of lung tissue was detected in each group. Dry weight (W/D) ratio change; BCA method was used to detect the changes of total protein in bronchoalveolar lavage fluid (BALF) of each group; ELISA was used to detect interleukin-1β (IL-1β) and leukocyte in BALF and serum of each group. The content of 8-OHdG in the lung tissue was detected by IL-8 and the content of malondialdehyde (MDA) in the lung tissue was detected by TBA method. The NLRP3, ASC and caspase-1 proteins in macrophages were detected by Western blotting. The changes of Keap1 and Nrf2 proteins in lung tissues were detected by RT-PCR. The expressions of SOD mRNA and HO-1 mRNA in lung tissues of each group were detected by RT-PCR.

  Results  Excessive mechanical ventilation could damage lung tissue, leading to alveolar rupture, inflammatory cell infiltration and erythrocytosis. Compared with the control group and normal VT group, the W/D value, 8-OHdG and MDA content in the large VT group, and total BALF, the contents of IL-1β and IL-18 in protein, IL-1β, IL-18 in serum increased significantly (P<0.05). Compared with the control group and normal VT group, NLRP3, ASC, in macrophage of large VT group, the content of Keap1 protein in caspase-1 protein and lung tissue increased significantly (P<0.05). The expression of Nrf2 protein, SOD mRNA and HO-1 mRNA in lung tissue decreased significantly.

  Conclusions  Large VT ventilation can cause acute inflammatory injury in lung tissue and lead to the occurrence of VILI. Inflammatory bodies of NLRP3 in alveolar macrophages are involved in this process, and the mechanism of NLRP3 inflammatory bodies is caused by hyperventilation in addition to mechanical injury. Decreased Keap1/Nrf2-ARE pathway inhibition and ROS clearance may also cause macrophage production of NLRP3 inflammatory bodies.