Effect of spirocyclopiperazinium salt compound LXM-15 on spinal nerve injury in rats

Currently available therapies for neuropathic pain show limited efficacy. This study aimed to investigate the anti-nociceptive effect of the spirocyclopiperazinium salt compound LXM-15 in spinal nerve ligation (SNL) rats and to explore the potential mechanisms.

Mechanical allodynia and thermal hyperalgesia tests were used to evaluate the effects of LXM-15 in SNL rats. The expression of CaMKIIα, CREB, JAK2, STAT3, c-fos and TNF-α was detected by western blotting, ELISA or qRT-PCR analysis. Receptor blocking test was performed to explore possible target.

Administration of LXM-15 (1, 0.5, 0.25 mg/kg, i.g.) dose-dependently attenuated mechanical allodynia and thermal hyperalgesia in rats subjected to SNL (p < 0.01, p < 0.05), and the effects were completely blocked by peripheral α7 nicotinic or M4 muscarinic receptor antagonist (p > 0.05). LXM-15 significantly decreased the overexpression of phosphorylated CaMKIIα, CREB, JAK2 and STAT3 proteins and the mRNA levels of TNF-α and c-fos (p < 0.01, p < 05). All of the effects could be blocked by α7 or M4 receptor antagonist. Furthermore, LXM-15 reduced the protein expression of TNF-α and c-fos (p < 0.01, p < 0.05). No significant acute toxicity or abnormal hepatorenal function was observed.

This is the first study to report that LXM-15 exerts significant anti-nociceptive effect on SNL rats. This effect may occur by activating peripheral α7 nicotinic and M4 muscarinic receptors, further inhibiting the CaMKIIα/CREB and JAK2/STAT3 signalling pathways, and finally inhibiting the expression of TNF-α and c-fos.

Existing treatments for neuropathic pain show limited efficacy with severe adverse reactions. This paper is the first to report that LXM-15, a new spirocyclopiperazinium salt compound, exerts a significant anti-nociception in SNL rats without obvious toxicity. The underlying mechanisms include activating peripheral α7 nicotinic and M4 muscarinic receptors, then inhibiting the signalling pathways of CaMKIIα/CREB and JAK2/STAT3 and the expressions of TNF-α and c-fos. This study sheds new light on the development of novel analgesic drugs with fewer side effects.