Acupuncture Modulates NMDAR-PP1/Calpain1-KCC2 Pathway to Ameliorate Spinal Hyperexcitability and Spastic Hemiplegia Induced by Ischemic Stroke.

BACKGROUND

Post-stroke spastic hemiplegia (PSSH) frequently leads to severe motor dysfunction, with its primary pathology being spinal hyperexcitability arising from attenuated descending inhibition. We previously reported that acupuncture alleviated spastic hypertonia induced by middle cerebral artery occlusion (MCAO) via upregulating potassium-chloride cotransporter 2 (KCC2) expression. Cumulative evidence has indicated that N-methyl-D-aspartate receptor (NMDAR) can be a pivotal determinant of spinal excitability via modulating KCC2-mediated neuronal chloride homeostasis. The present study investigated whether acupuncture exerts its therapeutic effects through modulation of NMDAR-mediated activation of protein phosphatase 1 (PP1)/Calpain1-KCC2 pathway.

METHODS

Multiple functional assessments, in vivo electrophysiological test, 2,3,5-triphenyl tetrazolium chloride (TTC) staining, immunofluorescence, quantitative real-time PCR (RT-qPCR), and Western blot were used.

RESULTS

In the male MCAO rat model, assessments using the neurological-function score, muscle-tone scale, and footprint analysis demonstrated that acupuncture significantly attenuated spasticity and improved motor performance. H-reflex recordings and immediate early gene c-Fos (c-Fos) immunofluorescence indicated that acupuncture reduced hyperexcitability in spinal ventral horn. These observed effects of acupuncture were associated with its downregulation of N-methyl-D-aspartate receptor 1 (NMDAR1) expression and restoration of both the expression and function of KCC2 in spinal cord. Pharmacological interventions using NMDAR agonist and antagonist demonstrated that acupuncture upregulated KCC2 by inhibiting NMDAR-mediated activation of PP1 and Calpain1.

CONCLUSION

Acupuncture modulated the NMDAR-PP1/Calpain1-KCC2 pathway in the spinal cord to suppress neuronal hyperexcitability, thereby relieving spasticity and promoting motor function in rats with PSSH.