MiR-15a/16 Regulates Apoptosis of Lung Epithelial Cells after Oxidative Stress.

Yong Cao,Lixin Xie,Jeffrey A Haspel,Yang Jin,Hyung-Geun Moon,Duo Zhang,Kebin Hu,Heedoo Lee

doi:10.2119/molmed.2015.00136

Abstract

Lung epithelial cell apoptosis is an important feature of hyperoxia-induced lung injury. Death receptor-associated extrinsic pathway and mitochondria-associated intrinsic pathway both mediate the development of lung epithelial cell apoptosis. Despite decades of research, molecular mechanisms of hyperoxia-induced epithelial cell apoptosis remain incompletely understood. Here we report a novel regulatory paradigm in response to hyperoxia-associated oxidative stress. Hyperoxia markedly up-regulated miR-15a/16 levels in lung epithelial cells, broncho-alveolar lavage fluid (BALF) and lung tissue. This effect was mediated by hyperoxia-induced reactive oxygen species (ROS). Functionally, miR-15a/16 inhibitors induced caspase 3-mediated lung epithelial cell apoptosis, in the presence of hyperoxia. MiR-15a/16 inhibitors robustly enhanced FADD level and down-regulated Bcl-2 expression. Consistently, cleaved caspase 8 and 9 were highly induced in the miR-15a/16 deficient cells, after hyperoxia. Using airway epithelial cell specific, miR-15a/16-/- mice, we found that Bcl-2 significantly reduced in lung epithelial cells in vivo after hyperoxia. In contrast, caspase 3, 8 and Bcl-2 associated death promoter (BAD) were highly elevated in the miR-15a/16-/- epithelial cells in vivo. Interestingly, in lung epithelial malignant cells, rather than benign cells, deletion of miR-15a/16 prevented apoptosis. Furthermore, deletion of miR-15a/16 in macrophages also prohibited apoptosis, opposite to what we have found in normal lung epithelial cells. Taken together, our data suggested that miR-15a/16 may exert differential roles in different cell types. MiR-15a/16 deficiency result in lung epithelial cell apoptosis in response to hyperoxia, via modulating both intrinsic and extrinsic apoptosis pathways.

Highlights

Acute lung injury (ALI) and its severe form, acute respiratory distress syndrome (ARDS), are serious clinical entities with substantial mortality and morbidity [1,2,3]
We found that microRNAs induced by hyperoxia-derived reactive oxygen species (ROS) modulated multiple pathways involved in apoptosis in lung epithelial cells
Induction of miR-15a/16 by hyperoxia was blunted when Beas2B cells were pretreated with the ROS scavenger, N-Acetyl cysteine (NAC) (Figure 1F)

Summary

Introduction

Acute lung injury (ALI) and its severe form, acute respiratory distress syndrome (ARDS), are serious clinical entities with substantial mortality and morbidity [1,2,3]. Oxidative stress is often present in these situations, in the setting of prolonged high-concentration oxygen (FIo2 > 0.8) [1,2,3]. In the past few decades, accumulating evidence demonstrates that prolonged exposure to toxic levels of oxygen causes fetal lung injury in animals [4,5]. HALI in mice has been used for decades as a model of oxidative stress mimicking clinical ARDS [6]. Since the 1950s, the underlying mechanisms of HALI are thought to result from ROS, which is generated directly or indirectly from high oxygen content and immune response, respectively [8,9,10,11].

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Results

Conclusion