DLK inhibition has sex-specific effects on neuroprotection and locomotor recovery after spinal cord injury

Spinal cord injury (SCI) causes devastating functional deficits, in part due to neuroinflammation, oxidative stress, and excitotoxicity that drive death of lesion-adjacent viable neurons. One signaling protein that promotes neuronal apoptosis and activates stress-responsive genes is dual leucine zipper kinase (DLK), which is a neuron-enriched kinase that responds to extracellular stress by activating the c-Jun N-terminal kinase (JNK) pathway. We hypothesized that SCI would robustly activate DLK signaling and that acute pharmacological inhibition of DLK would suppress JNK pathway activation, thereby enhancing neuroprotection and locomotor recovery in our mouse model of moderate contusion SCI. Using western blotting, we observed that SCI induced strong and sustained activation of the JNK pathway in the injured spinal cord starting at 4 hours post-injury through 7 days. Complementary analysis of single-nucleus RNA-seq revealed that DLK expression is highly enriched in neurons across all injury phases. Following SCI, neurons exhibited robust, time-dependent upregulation of multiple DLK-responsive transcripts, consistent with sustained pathway activation during the acute and subacute periods. Systemic treatment with the selective DLK inhibitor IACS’825 effectively suppressed intraspinal JUN activation in a dose-dependent manner. However, unexpectedly, DLK inhibition delayed functional recovery in male mice and expanded lesion volume by 71%, with no significant effect in females. These findings highlight the complex roles of DLK signaling after SCI, revealing a need to understand the sex-specific molecular mechanisms that modulate injury outcomes. Future studies should further optimize timing, location, and cellular targeting of DLK therapeutic strategies to improve neuroprotection and neurologic recovery after SCI.