ABSTRACT
Objective:To investigate the role of vitamin D analogue paricalcitol in activating vitamin D receptor/glutathione peroxidase 4 (VDR/GPX4) pathway in ventilator-induced lung injury (VILI).Methods:Twenty-four male C57BL/6J mice were randomly divided into control group, high tidal volume (HVT) induced VILI model group (HVT group), paricalcitol control group (P group), and paricalcitol pretreatment group (P+HVT group), with 6 mice in each group. The mice were endotracheal intubated and ventilated at 40 mL/kg tidal volume to prepare VILI model, while those in the control group were intubated without ventilation. The mice in the P+HVT group were intraperitoneally injected with paricalcitol 0.2 μg/kg once a day 1 week before modeling, while those in the P group were intraperitoneally injected paricalcitol 0.2 μg/kg once a day for 1 week before the experiment. After ventilation for 4 hours, the mice were sacrificed for lung tissue collection. Lung injury was evaluated by wet/dry (W/D) ratio, hematoxylin-eosin (HE) staining and Masson staining. The expressions of VDR and GPX4 were determined by Western blotting and immunohistochemistry. Malondialdehyde (MDA) and glutathione (GSH) contents were determined by micro method.Results:After HVT for 4 hours, compared with the control group, lung injury score and W/D ratio were significantly higher (lung injury score: 0.430±0.035 vs. 0.097±0.025, lung W/D ratio: 4.860±0.337 vs. 3.653±0.332, both P < 0.05), collagen fiber deposition was significantly increased, the content of MDA in lung tissue was significantly increased (nmol/g: 212.420±8.757 vs. 97.073±5.308, P < 0.05), GSH content and the protein expressions and immunoreactive score (IRS) of VDR and GPX4 were significantly decreased [GSH (μg/g): 44.229±1.690 vs. 70.840±0.781; VDR protein (VDR/GAPDH): 0.518±0.029 vs. 0.762±0.081, GPX4 protein (GPX4/GAPDH): 0.452±0.032 vs. 0.649±0.034; IRS score: VDR was 4.168±0.408 vs. 10.167±0.408, GPX4 was 4.333±1.033 vs. 10.333±0.516; all P < 0.05], which meant that the mice in HVT group showed obvious lung injury. After VDR was activated by paricalcitol, compared with the HVT group, lung injury score and W/D ratio were significantly decreased (lung injury score: 0.220±0.036 vs. 0.430±0.035, lung W/D ratio: 4.015±0.074 vs. 4.860±0.337, both P < 0.05), collagen fiber deposition was reduced, MDA content in lung tissue was decreased (nmol/g: 123.840±8.082 vs. 212.420±8.757, P < 0.05), GSH content and the protein expressions and IRS score of VDR and GPX4 were significantly up-regulated [GSH (μg/g): 63.094±0.992 vs. 44.229±1.690; VDR protein (VDR/GAPDH): 0.713±0.056 vs. 0.518±0.029, GPX4 protein (GPX4/GAPDH): 0.605±0.008 vs. 0.452±0.032; IRS score: VDR was 9.000±0.632 vs. 4.168±0.408, GPX4 was 8.833±0.408 vs. 4.333±1.033; all P < 0.05], which meant that lung injury in P+HVT group was significantly improved. Conclusion:Vitamin D analogue paricalcitol ameliorates pulmonary oxidation-reduction imbalance by activating the VDR/GPX4 pathway, thereby alleviating VILI.