Role and mechanism of the NOD-like receptor 3 inflammasome in ventilator-induced lung injury in rats / 中华危重病急救医学

ABSTRACT

ObjectiveTo investigate the role and its mechanism of the NOD-like receptor 3 (NLRP3) inflammasome in alveolar macrophages in ventilator-induced lung injury (VILI) in rats.Methods Thirty adult male Sprague-Dawley (SD) rats were randomly divided into three groups, with 10 rats in each group spontaneous breathing control group, normal tidal volume (VT) group (VT 8 mL/kg) and high VT group (VT 40 mL/kg). All of the rats underwent tracheotomy. Then rats in spontaneous breathing control group were kept to have spontaneous breathing, while rats in normal VT group and high VT group received mechanical ventilation. After 4 hours, the rats were sacrificed by carotid artery bleeding, and the bronchoalveolar lavage fluid (BALF), blood serum and lung tissue were collected. Lung wet/dry ratios (W/D) were measured. Light microscopy and electron microscopy were performed to observe the pathological changes in lung tissue, and the ultrastructural changes in alveolar macrophages. Enzyme linked immunosorbent assay (ELISA) was performed to measure the total protein content in the BALF and the interleukins (IL-1β and IL-18) in the serum and BALF. The mRNA expressions and protein levels of NLRP3, apoptosis-associated speck-like protein containing CARD (ASC), caspase-1, and nuclear factor-κB (NF-κB) in alveolar macrophages were assayed by real-time fluorescent quantization reverse transcription-polymerase chain reaction (RT-PCR) and Western Blot.Results The structure of lung tissue and alveolar macrophages of rats in spontaneous breathing control group and normal VT group appeared normal, while obvious inflammatory changes were found in high VT group. Compared with spontaneous breathing control group and normal VT group, the ratio of W/D (8.89±0.90 vs. 5.18±0.86, 5.71±0.82, bothP< 0.05), contents of total protein, IL-1β, IL-18 in BALF were significantly increased [total protein (g/L)2.34±0.41 vs. 1.77±0.14, 1.81±0.06, IL-1β (ng/L) 133.48±10.48 vs. 81.54±3.12, 83.80±5.22, IL-18 (μg/L)4.57±0.45 vs. 3.04±0.51, 3.43±0.43, allP< 0.05], and IL-1β and IL-18 in serum were also increased [IL-1β(ng/L) 105.06±10.18 vs. 65.11±8.58, 75.30±10.62, IL-18 (μg/L) 2.27±0.09 vs. 1.18±0.34, 1.43±0.15, all P< 0.05]. The mRNA and protein expressions of NLRP3, ASC, caspase-1 and NF-κB in alveolar macrophages of high VT group were significantly increased compared with that of spontaneous breathing control group and normal VT group. The mRNA expressions of NLRP3, ASC, caspase-1 and NF-κB in high VT group were (8.53±2.21), (5.75±1.17), (7.47±1.23) and (10.86±2.38) folds of those in spontaneous breathing control group, and the protein expressions of NLRP3, ASC, caspase-1 and NF-κB were (1.50±0.14), (1.49±0.04), (1.53±0.15) and (1.51±0.11) folds of those in spontaneous breathing control group (allP< 0.01). There were no significant differences in all the indexes between normal VT group and spontaneous breathing control group.ConclusionNLRP3 inflammasome in alveolar macrophages may be involved in the mechanism of occurrence of VILI.