Dexmedetomidine's protective mechanism against hyperoxic injury in neonatal rats

Bronchopulmonary dysplasia (BPD) is a common serious complication of premature babies. No effective means control it. Hyperoxia damage is one of the important mechanisms of BPD. The reaserach confirmed pyroptosis existed in BPD. Dexmedetomidine is a new, high-specific α2 receptor agonist. Previous research foundation found that dexmedetomidine has a protective effect on BPD. To investigate how dexmedetomidine improves hyperoxic lung injury in neonatal mice by regulating pyroptosis. Neonatal rats were randomly divided into four groups: normal control group, hyperoxic injury group, air plus dexmedetomidine group, and hyperoxia plus dexmedetomidine group. After seven days the lungs of rats in each group were extracted, and the wet-to-dry weight ratio of the lung was measured. The lung injury in rats was observed using hematoxylin-eosin staining. Additionally, the expression and localization of nucleotide-binding oligomerization domain-like receptor thermal protein domain associated protein 3 (NLRP3), apoptosis-associated speck-like protein (ASC), and gasdermin D (GSDMD) proteins were examined in the lungs of rats using immunofluorescence staining. The mRNA levels of NLRP3, ASC, caspase-1, and interleukin 18 (IL-18) in the lungs of rats were determined using real-time PCR. Moreover, the protein levels of NLRP3, ASC, caspase-1/cleaved caspase-1, interleukin 1beta (IL-1β), IL-18, and tunor necrosis factor alpha (TNF-α) were detected in lungs of rats using Western blot. The extent of mitochondrial damage in lung tissues of each group was observed by transmission electron microscopy. The lung tissue injury of the neonatal rats was significantly improved in the hyperoxia plus dexmedetomidine group compared to the hyperoxic injury group. Furthermore, the expressions of pyroptosis-related proteins such as NLRP3, ASC, cleaved-caspase-1, and GSDMD were significantly decreased, along with the expressions of inflammatory factors in lung tissues. By inhibiting the NLRP3/caspase-1/GSDMD pyroptosis pathway, dexmedetomidine reduces the activation and release of inflammatory factors and provides a protective effect against hyperoxic lung injury in neonatal mice.