Objective:To explore the protective mechanism of dexmedetomidine (Dex) in a model of broncho-pulmonary dysplasia (BPD) in mice exposed to hyperoxia.Methods:Neonatal rats were randomly assigned to four groups:air control group,hyperoxia injury group,Dex control group,and hyperoxia+Dex group,with six animals in each group.The air control and Dex control groups were exposed to ambient air,while the hyperoxia injury and hyperoxia+Dex groups were exposed to 90% O 2.The Dex control and hyperoxia+Dex groups received daily intraperitoneal injections of Dex at a dosage of 500 μg/kg.Lung tissue samples were collected after 7 days.Histomorphological changes in lung tissue were evaluated using hematoxylin and eosin (HE) staining,and mitochondrial ultrastructural changes in type I epithelial cells of neonatal rat lung tissue were observed via transmission electron microscopy.The activity of Complex Ⅰ in neonatal rat lung tissue was assessed.The expression levels of PINK1 and Parkin in neonatal rat lung tissue were measured using quantitative PCR (qPCR).Western blot analysis was conducted to determine the protein expression levels of PINK1 and Parkin in lung tissues. Results:Under transmission electron microscopy,mitochondrial structures were intact in the lung tissues of both the air control group and the Dex control group.However,significant mitochondrial damage was observed in the hyperoxia injury group,while the hyperoxia+Dex group exhibited some relief from mitochondrial damage compared to the hyperoxia injury group.The activity of the oxidized respiratory chain Complex Ⅰ in the hyperoxia injury group was significantly lower than that in the air control group (4.824±0.804 vs.15.276±0.804, P<0.05) and the hyperoxia+Dex group(4.824±0.804 vs.9.648±0.804, P<0.05).After qPCR analysis,the expression levels of PINK1 and Parkin in the hyperoxia injury group were higher than those in the air control group(1.80±0.06 vs.1.00±0.07,2.10±0.14 vs.1.00±0.09, P<0.05),but lower than those in the hyperoxia+Dex group(1.80±0.06 vs.3.61±0.19,2.10±0.10 vs.4.24±0.43, P<0.05).Western blot analysis revealed that the expression levels of PINK1 and Parkin in the hyperoxia injury group were higher than those in the air control group(2.16±0.11 vs.1.00±0.01,3.82±0.13 vs.1.00±0.01, P<0.05),but lower than those in the hyperoxia+Dex group(2.16±0.11 vs.3.35±0.14,3.82±0.13 vs.5.48±0.15, P<0.05).There were no significant differences in mitochondrial structure integrity,Complex Ⅰ enzyme activity,or the expression levels of PINK1 and Parkin,as assessed by qPCR and Western blot analysis,between the air control and Dex control groups( P>0.05). Conclusion:Dex effectively mitigates mitochondrial ultrastructural damage in BPD model mice,enhances the activity of Complex Ⅰ in the oxidative respiratory chain,reduces mitochondrial damage,and increases the activation of the PINK1-Parkin-mediated mitophagy pathway,thereby promoting lung protection.

Objective:To explore the protective mechanism of dexmedetomidine (Dex) in a model of broncho-pulmonary dysplasia (BPD) in mice exposed to hyperoxia.Methods:Neonatal rats were randomly assigned to four groups:air control group,hyperoxia injury group,Dex control group,and hyperoxia+Dex group,with six animals in each group.The air control and Dex control groups were exposed to ambient air,while the hyperoxia injury and hyperoxia+Dex groups were exposed to 90% O 2.The Dex control and hyperoxia+Dex groups received daily intraperitoneal injections of Dex at a dosage of 500 μg/kg.Lung tissue samples were collected after 7 days.Histomorphological changes in lung tissue were evaluated using hematoxylin and eosin (HE) staining,and mitochondrial ultrastructural changes in type I epithelial cells of neonatal rat lung tissue were observed via transmission electron microscopy.The activity of Complex Ⅰ in neonatal rat lung tissue was assessed.The expression levels of PINK1 and Parkin in neonatal rat lung tissue were measured using quantitative PCR (qPCR).Western blot analysis was conducted to determine the protein expression levels of PINK1 and Parkin in lung tissues. Results:Under transmission electron microscopy,mitochondrial structures were intact in the lung tissues of both the air control group and the Dex control group.However,significant mitochondrial damage was observed in the hyperoxia injury group,while the hyperoxia+Dex group exhibited some relief from mitochondrial damage compared to the hyperoxia injury group.The activity of the oxidized respiratory chain Complex Ⅰ in the hyperoxia injury group was significantly lower than that in the air control group (4.824±0.804 vs.15.276±0.804, P<0.05) and the hyperoxia+Dex group(4.824±0.804 vs.9.648±0.804, P<0.05).After qPCR analysis,the expression levels of PINK1 and Parkin in the hyperoxia injury group were higher than those in the air control group(1.80±0.06 vs.1.00±0.07,2.10±0.14 vs.1.00±0.09, P<0.05),but lower than those in the hyperoxia+Dex group(1.80±0.06 vs.3.61±0.19,2.10±0.10 vs.4.24±0.43, P<0.05).Western blot analysis revealed that the expression levels of PINK1 and Parkin in the hyperoxia injury group were higher than those in the air control group(2.16±0.11 vs.1.00±0.01,3.82±0.13 vs.1.00±0.01, P<0.05),but lower than those in the hyperoxia+Dex group(2.16±0.11 vs.3.35±0.14,3.82±0.13 vs.5.48±0.15, P<0.05).There were no significant differences in mitochondrial structure integrity,Complex Ⅰ enzyme activity,or the expression levels of PINK1 and Parkin,as assessed by qPCR and Western blot analysis,between the air control and Dex control groups( P>0.05). Conclusion:Dex effectively mitigates mitochondrial ultrastructural damage in BPD model mice,enhances the activity of Complex Ⅰ in the oxidative respiratory chain,reduces mitochondrial damage,and increases the activation of the PINK1-Parkin-mediated mitophagy pathway,thereby promoting lung protection.