OTULIN protects hyperoxia-induced neonatal lung injury and modulates mitochondrial protein OPA1 in association with the E3 ubiquitin ligase RNF31

The deubiquitinating enzyme OTULIN has been implicated in the development of lung injury, and regulating its expression may either exacerbate or alleviate pulmonary inflammatory damage. In this study, we aimed to investigate the role of deubiquitinating enzyme OTULIN in hyperoxia-induced lung injury and the underlying mechanisms involved. A bronchopulmonary dysplasia (BPD) model was established by exposing neonatal mice to a hyperoxic environment, and the effects of regulating OTULIN expression on mitochondrial homeostasis in pulmonary epithelial cells were further examined under hyperoxic conditions. In addition, we investigated the mechanisms through which OTULIN regulates mitochondrial-associated proteins and the ubiquitination mechanisms of differential mitochondrial protein OPA1. The results showed that hyperoxia induced significant lung injury in neonatal mice and was accompanied by upregulation of OTULIN expression. Additionally, hyperoxia disrupted mitochondrial homeostasis in neonatal mice lung tissue, as observed by a reduction in mitochondrial number and increased mitochondrial fusion and autophagy. After hyperoxia exposure, overexpression of OTULIN significantly reduced mitochondrial reactive oxygen species (ROS) levels in alveolar epithelial cells, maintained mitochondrial membrane potential, and promoted mitochondrial homeostasis. Mechanistically, OTULIN was found to directly interact with OPA1 and regulate its ubiquitination status. The E3 ubiquitin ligase RNF31 was identified as a key regulator of OPA1 stability, with knockdown of RNF31 reducing OPA1 levels. Moreover, OTULIN regulated the expression of both OPA1 and RNF31 and affected the stability of OPA1 and mitochondrial function through RNF31-dependent mechanisms. In vivo experiments further showed that knockdown of OTULIN aggravated hyperoxia-induced lung injury in neonatal mice, characterized by alveolar simplification, increased fibrosis, and further impairment of mitochondrial function, whereas overexpression of OTULIN alleviated these pathological changes. In conclusion, deubiquitinating enzyme OTULIN protected hyperoxia-induced neonatal lung injury and modulates mitochondrial protein OPA1 in association with the E3 ubiquitin ligase RNF31. These findings provide new insights into the pathogenesis of BPD and highlight the therapeutic potential of targeting the OTULIN/RNF31-OPA1 axis.