Intrathecal Injection of Dual Zipper Kinase shRNA Alleviating the Neuropathic Pain in a Chronic Constrictive Nerve Injury Model

Deciphering the multifunctional role of dual leucine zipper kinase (DLK) and its therapeutic potential in disease

Dual leucine zipper kinase (DLK, MAP3K12), a serine/threonine protein kinase, plays a key role in neuronal development, as it regulates axon regeneration and degeneration through its downstream kinase. Importantly, DLK is closely related to the pathogenesis of numerous neurodegenerative diseases and the induction of β-cell apoptosis that leads to diabetes. In this review, we summarize the current understanding of DLK function, and then discuss the role of DLK signaling in human diseases. Furthermore, various types of small molecule inhibitors of DLK that have been published so far are described in detail in this paper, providing some strategies for the design of DLK small molecule inhibitors in the future.

Modulation of Aryl Hydrocarbon Receptor Expression Alleviated Neuropathic Pain in a Chronic Constriction Nerve Injury Animal Model

Neuropathic pain is well known to occur after damage to the somatosensory system. Aryl hydrocarbon receptor (AhR) has neuroprotective effects when the central nervous system is subjected to internal and external stimulations. However, the exact mechanism by which AhR regulates neuropathic pain is poorly understood. Nerve explant culture and the chronic constrictive nerve injury (CCI) model in wild or AhR-knockout mice were used in this study. In the nerve explant culture, the ovoid number increased in the AhR−/− condition and was decreased by omeprazole (AhR agonist) in a dose-dependent manner. Increased nerve degeneration and the associated inflammation response appeared in the AhR−/− condition, and these changes were attenuated by omeprazole. High expression of AhR in the injured nerve was noted after CCI. Deletion of AhR aggravated nerve damages and this was restored by omeprazole. Deletion of AhR increased NGF expression and reduced axon number in the paw skin, but this was attenuated by omeprazole. A highly expressed inflammation reaction over the dorsal spinal cord, somatosensory cortex, and hippocampus was noted in the AhR-deleted animals. Administration of omeprazole attenuated not only the inflammatory response, but also the amplitude of somatosensory evoked potential. Deletion of AhR further aggravated the neurobehavior compared with the wild type, but such behavior was attenuated by omeprazole. Chronic constrictive nerve injury augmented AhR expression of the injured nerve, and AhR deletion worsened the damage, while AhR agonist omeprazole counteracted such changes. AhR agonists could be potential candidates for neuropathic pain treatment.

Multitasking: Dual Leucine Zipper-Bearing Kinases in Neuronal Development and Stress Management

The dual leucine zipper-bearing kinase (DLK) and leucine zipper-bearing kinase (LZK) are evolutionarily conserved MAPKKKs of the mixed-lineage kinase family. Acting upstream of stress-responsive JNK and p38 MAP kinases, DLK and LZK have emerged as central players in neuronal responses to a variety of acute and traumatic injuries. Recent studies also implicate their function in astrocytes, microglia, and other nonneuronal cells, reflecting their expanding roles in the multicellular response to injury and in disease. Of particular note is the potential link of these kinases to neurodegenerative diseases and cancer. It is thus critical to understand the physiological contexts under which these kinases are activated, as well as the signal transduction mechanisms that mediate specific functional outcomes. In this review we first provide a historical overview of the biochemical and functional dissection of these kinases. We then discuss recent findings on regulating their activity to enhance cellular protection following injury and in disease, focusing on but not limited to the nervous system.