Transcriptional Downregulation of MicroRNA-19a by ROS Production and NF-κB Deactivation Governs Resistance to Oxidative Stress-initiated Apoptosis

Cell apoptosis is one of the main pathological alterations during oxidative stress (OS) injury. Previously, we corroborated that nuclear factor-κB (NF-κB) transactivation confers apoptosis resistance against OS in mammalian cells, yet the underlying mechanisms remain enigmatic. Here we report that microRNA-19a (miR-19a) transcriptionally regulated by reactive oxygen species (ROS) production and NF-κB deactivation prevents OS-initiated cell apoptosis through cylindromatosis (CYLD) repression. CYLD contributes to OS-initiated cell apoptosis, for which NF-κB deactivation is essential. MiR-19a directly represses CYLD via targeting 3' UTR of CYLD, thereby antagonizing OS-initiated apoptosis. CYLD repression by miR-19a restores the IKKβ phosphorylation, RelA disassociation from IκBα, IκBα polyubiquitination and degradation, RelA recruitment at gene promoter as well as VEGF secretion in the context of OS. Either pharmacological deactivation of NF-κB or genetic upregulation of CYLD compromises the apoptosis-resistant phenotypes of miR-19a. Furthermore, miR-19a is transcriptionally downregulated upon OS in two distinct processes that require ROS production and NF-κB deactivation. VEGF potentiates the ability of miR-19a to activate NF-κB and render apoptosis resistance. Our findings underscore a putative mechanism whereby CYLD repression-mediated and NF-κB transactivation-dependent miR-19a regulatory feedback loop prevents cell apoptosis in response to OS microenvironment.