Pharmacologic activation of activating transcription factor 6 contributes to neuronal survival after spinal cord injury in mice

Abstract

The impact of primary and secondary injuries of spinal cord injury (SCI) results in the demise of numerous neurons, and there is still no efficacious pharmacological intervention for it. Recently, studies have shown that endoplasmic reticulum stress (ERS) plays a pivotal role in recovery of neurological function after spinal cord injury. As a process to cope with intracellular accumulation of misfolded and unfolded proteins which triggers ERS, the unfolded protein response (UPR) plays an important role in maintaining protein homeostasis. And, a recently disclosed small molecule AA147, which selectively activates activating transcription factor 6 (ATF6), has shown promising pharmacological effects in several disease models. Thus, it seems feasible to protect the neurons after spinal cord injury by modulating UPR. In this study, primary neurons were isolated from E17-19 C57BL/6J mouse embryos and we observed that AA147 effectively promoted the survival of neurons and alleviated neuronal apoptosis after oxygen–glucose deprivation/reoxygenation (OGD/R) in vitro. This was evident through a decrease in the proportion of PI-positive and TUNEL-positive cells, an increase in BCL-2 expression, and a decrease in the expression of BAX and C-caspase3. In in-vivo experiments, these findings were corroborated by TUNEL staining and immunohistochemistry. It was also found that AA147 enhanced three arms of the unfolded protein response with reduced CHOP expression. Besides, AA147 mitigated the accumulation of ROS in neurons probably by upregulating catalase expression. Furthermore, spinal cord injury models of C57BL/6J mice were established and behavioral experiments revealed that AA147 facilitated the recovery of motor function following SCI. Thus, pharmacologic activation of ATF6 represents a promise therapeutic approach to ameliorate the prognosis of SCI.