ADAR1 Inhibits ZBP1-Driven Neuronal Necroptosis After Intracerebral Hemorrhage.

Necroptosis is a critical response to secondary brain injury following intracerebral hemorrhage (ICH). Z-DNA Binding Protein 1 (ZBP1) binds to dsRNA and promotes the activation of Receptor-Interacting Protein Kinase 3 (RIPK3). This study investigated whether Adenosine Deaminase Acting on RNA 1 (ADAR1) inhibits neuronal necroptosis after ICH. ADAR1-knockdown mice and ZBP1flox/flox/Thy1-Cre+/- mice were subjected to collagenase VII-induced ICH. Brain edema and neurobehavioral deficits were assessed. The expressions of ADAR1 and ZBP1 were investigated by qPCR, western blot, immunofluorescence, and ELISA. Protein interactions were performed using co-immunoprecipitation. ADAR1p150 was reduced in both ICH patients and mice. ZBP1 and ADAR1 both bound to dsRNA. ADAR1p150 suppressed ZBP1 activation, potentially through functional antagonism and dsRNA editing, although causality remains to be established. Knockout of ZBP1 resulted in increased ADAR1p150 expression and reduced brain edema. Etanercept and shRNA-mediated ADAR1 knockdown promoted ZBP1 expression. Complementation of the ADAR1 Zα truncation did not reduce ZBP1 in ADAR1-knockdown cells. The inhibitory effect of ADAR1 on ZBP1 was attenuated in ADAR1Zα-/- cells. These data show that the Zα domain is required for ADAR1 to suppress ZBP1, but they do not establish whether this suppression depends on RNA editing or on dsRNA binding alone.