DLK silencing attenuated neuron apoptosis through JIP3/MA2K7/JNK pathway in early brain injury after SAH in rats

- The level of DLK was increased in the left cortex and peaked at 24 h after SAH.
- Reduction of DLK by siRNA led to decreased brain edema, neuronal apoptosis and improved neurological functions.
- Reducing DLK is neuroprotective and this effect may be mediated by JIP3 and MA2K7/JNK signal pathway.

ObjectiveDual leucine zipper kinase (DLK/MA3K12) has been reported involved in apoptosis and neuronal degeneration during neural development and traumatic brain injury. This study was designed to investigate the role of DLK with its adaptor protein JNK interacting protein-3 (JIP3), and its downstream MA2K7/JNK signaling pathway in early brain injury (EBI) after subarachnoid hemorrhage (SAH) in a rat model.DesignControlled in vivo laboratory study.SettingAnimal research laboratory.SubjectsTwo hundred and twenty-three adult male Sprague-Dawley rats weighing 280-320 g.InterventionsSAH was induced by endovascular perforation in rats. The SAH grade, neurological score, and brain water content were measured at 24 and 72 h after SAH. Immunofluorescence staining was used to detect the cells that expressed DLK. The terminal deoxynucleotid transferase-deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) was used to detect the neuronal apoptosis. In mechanism research, the expression of DLK, JIP3, phosphorylated-JNK (p-JNK)/JNK, and cleaved caspase-3 (CC-3) were analyzed by western blot at 24 h after SAH. The DLK small interfering RNA (siRNA), JIP3 siRNA, MA2K7 siRNA and recombinant DLK protein which injected intracerebroventricularly were given as the interventions.Measurements and main resultsThe DLK expression was increased in the left cortex neurons and peaked at 24 h after SAH. DLK siRNA attenuated brain edema, reduced neuronal apoptosis, and improved the neurobehavioral functions after SAH, but the recombinant DLK protein deteriorated neurobehavioral functions and brain edema. DLK siRNA decreased and recombinant DLK protein increased the expression of MA2K7/p-JNK/CC-3 at 24 h after SAH. The JIP3 siRNA reduced the level of JIP3/MA2K7/p-JNK/CC-3, combined DLK siRNA and JIP3 siRNA further decreased the expression of DLK/MA2K7/p-JNK/CC-3, and MA2K7 siRNA lowered the amount of MA2K7/p-JNK/CC-3 at 24 h after SAH.ConclusionsAs a negative role, DLK was involved in EBI after SAH, possibly mediated by its adaptor protein JIP3 and MA2K7/JNK signaling pathways. To reduce the level of DLK may be a new target as intervention for SAH.

100