Oxidative stress-elicited YY1 potentiates antioxidative response via enhancement of NRF2-driven transcriptional activity: A potential neuronal defensive mechanism against ischemia/reperfusion cerebral injury.

Cerebral ischemia challenge evokes an adaptive defensive system through the induction of antioxidant enzymes. Many of such antioxidant enzymes are regulated essentially by the nuclear factor erythroid 2-related factor-2 (NRF2). Compelling evidence supports that targeting NRF2 signaling is a promising therapeutic strategy to alleviate post-I/R brain injury, but the molecular mechanisms underlying this strategy have yet to be elucidated. Herein, we show that the expression of transcription factor Yin Yang 1 (YY1) is significantly upregulated during the recovery following middle cerebral artery occlusion (MCAO). Ablation of endogenous YY1 using cerebral ventricle injection of siRNA exacerbated I/R-induced neuronal damage and attenuated the antioxidant defensive system. Mechanistically, low levels of reactive oxygen species (ROS) production stimulated neuronal YY1 expression, whereas high levels of ROS exhibited a noticeable inhibitory effect. The evoked YY1, in concert with other coregulators, recruited to the antioxidant responsive elements (AREs) binding site and then amplified the NRF2-mediated ARE transcription, thereby protecting cells against damage by potentiating antioxidant response. In this regard, compromise of YY1 expression by ROS overactivity is an important etiology that sabotages the antioxidant defensive system and consequently deteriorate s neuronal damage following I/R injury. Taken together, our findings provide novel evidence on a delicate and synergistical collaboration between YY1 and the master transcription factor NRF2 that functions to mobilize the cell's antioxidant machinery.