Regulation of Prdx6 by Nrf-2 is mediated through aiPLA2 in white matter reperfusion injury

Abstract

<jats:title>Abstract</jats:title> <jats:p>BackgroundMechanisms involving upregulation of cytoprotective genes under the control of transcription factors, such as Prdx6 and Nrf2, exist to protect cells from permanent damage and dysfunction under hypoxic conditions. Hypoxia and reperfusion produces overproduction of ROS (reactive oxygen species), which may lead to mitochondrial dysfunction leading to cell death and apoptosis. Here, we explore the hypothesis that Prdx6 protects the spinal cord white matter from hypoxia-reperfusion injury and elucidate the possible mechanism by which Prdx6 elicits its protective effects.MethodsBriefly, rats were deeply anesthetized with 5% isoflurane and maintained at 1.5%-2.5% isoflurane. A 30 mm section of spinal cord was rapidly removed and placed in cold Ringer’s solution (2-4 °C), and then a dorsal column segment was micro-dissected from the spinal cord and adjacent gray matter after longitudinal sectioning. The dissected dorsal column was exposed to hypoxia by perfusing 95% N 2 /5% CO 2 for 1 h. For reperfusion experiments, the Ringer’s was reperfused with 95% O 2 and 5% CO 2 for 2 h and 4 h.ResultsOur results show that the expression of Prdx6 significantly upregulated in white matter after hypoxia compared to the sham group, whereas reperfusion caused a gradual decrease in Prdx6 expression after 2 h and 4 h of reperfusion injury. For the first time, our study revealed the novel expression and localized expression of Prdx6 in astrocytes after hypoxia, and possible communication of astrocytes and axons through Prdx6. Interestingly we observed a gradual increase in Nrf2 expression, which suggests a negative regulation of Prdx6 through Nrf2 signaling. Furthermore, inhibition of aiPLA2 activity of Prdx6 by MJ33 shows that the regulation of Prdx6 by Nrf2 is mediated through aiPLA2 activity.ConclusionThe present study uncovers a differential distribution of Prdx6 in axons and astrocytes under a hypoxic environment of white matter, and regulation of Prdx6 in hypoxia-reperfusion injury. Our data show that low levels of Prdx6 in reperfusion injury leads to increased inflammation and apoptosis in white matter, therefore the results of this study suggests that Prdx6 has a protective role in spinal hypoxia-reperfusion injury.</jats:p>