The regulatory effect of electro-acupuncture on the expression of NMDA receptors in a SCI rat model

Electroacupuncture induces analgesia by regulating spinal synaptic plasticity via the AMPA/NMDA receptor in a model of cervical spondylotic radiculopathy: secondary analysis of an experimental study in rats

OBJECTIVE

Cervical spondylotic radiculopathy (CSR) is characterized by neuropathic pain (NP). Although the analgesic effect of electroacupuncture (EA) has been widely recognized in clinical practice, the mechanism of EA in the treatment of CSR remains unknown. We previously reported that 7 days of EA improved behavioral markers of NP, attenuated increases in α-synuclein, synapsin 1 and 2, postsynaptic density (PSD)-95 and growth-associated protein (GAP)-43, and improved ultrastructural changes within synapses in a rat model of CSR. Herein, we present supplemental data from the same cohort of animals examining the timing of behavioral improvement within the first week (through additional measurements at 3 and 5 days into the EA treatment) and new data on the effects of EA on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and N-methyl-d-aspartic acid receptor (NMDAR) levels.

METHODS

As previously reported, the rats were divided into four groups at random: normal, sham, CSR and CSR + EA. EA at bilateral LI4 and LR3 was administered once a day for 7 days (20 min each) in the CSR + EA group after the CSR model was established by inserting a fishing line under the laminae. Behavioral assessments were carried out prior to initiation of EA and at 3, 5 and 7 days into the 7-day treatment course. Concentrations ofγ-aminobutyric acid (GABA) and glutamate (Glu) were determined using enzyme-linked immunosorbent assay and ultraviolet colorimetry, respectively, and AMPAR (glutamate receptor (GluR)1 and GluR2 membrane protein) expression was determined using Western blotting. Immunohistochemistry was used to detect the protein expression and average optical density (AOD) of NMDAR1 (NR1), NMDAR2A (NR2A) and NMDAR2B (NR2B). Quantitative reverse transcription-polymerase chain reaction was used to detect the mRNA expression of NR1, NR2A and NR2B. Transmission electron microscopy was used to observe changes in synaptic ultrastructure.

RESULTS

EA significantly improved the pressure pain threshold (PPT) and mechanical withdrawal threshold (MWT) 5 days into the intervention, although effects were less pronounced than at 7 days (at completion of treatment). However, significant effects on gait scores were not seen prior to 7 days. As previously reported, EA also improved markers of synaptic ultrastructure. In the spinal cord, GluR1 membrane protein expression was decreased, GluR2 membrane protein expression was increased, and the GluR1/GluR2 ratio was decreased. Protein and mRNA expression of NR1, NR2A and NR2B was significantly decreased. GABA concentration was markedly increased, while Glu concentration was markedly decreased.

CONCLUSION

Evidence of EA analgesia (higher PPT and MWT scores) was seen after 5 days of EA, while positive effects on motor function required 7 days of treatment. The underlying mechanism may be related to inhibition of AMPAR and NMDAR expression, regulation of the concentration of related neurotransmitters and improvement of spinal cord synaptic plasticity. This study establishes a preliminary theoretical foundation for the use of EA in the clinical treatment of CSR.

Electroacupuncture protective effects after cerebral ischemia are mediated through miR-219a inhibition

BACKGROUND

Electroacupuncture (EA) is a complementary and alternative therapy which has shown protective effects on vascular cognitive impairment (VCI). However, the underlying mechanisms are not entirely understood.

METHODS

Rat models of VCI were established with cerebral ischemia using occlusion of the middle cerebral artery or bilateral common carotid artery. The brain structure and function imaging were measured through animal MRI. miRNA expression was detected by chip and qPCR. Synaptic functional plasticity was detected using electrophysiological techniques.

RESULTS

This study demonstrated the enhancement of Regional Homogeneity (ReHo) activity of blood oxygen level-dependent (BOLD) signal in the entorhinal cortical (EC) and hippocampus (HIP) in response to EA treatment. miR-219a was selected and confirmed to be elevated in HIP and EC in VCI but decreased after EA. N-methyl-D-aspartic acid receptor1 (NMDAR1) was identified as the target gene of miR-219a. miR-219a regulated NMDAR-mediated autaptic currents, spontaneous excitatory postsynaptic currents (sEPSC), and long-term potentiation (LTP) of the EC-HIP CA1 circuit influencing synaptic plasticity. EA was able to inhibit miR-219a, enhancing synaptic plasticity of the EC-HIP CA1 circuit and increasing expression of NMDAR1 while promoting the phosphorylation of downstream calcium/calmodulin-dependent protein kinase II (CaMKII), improving overall learning and memory in VCI rat models.

CONCLUSION

Inhibition of miR-219a ameliorates VCI by regulating NMDAR-mediated synaptic plasticity in animal models of cerebral ischemia.

Electroacupuncture promotes nerve regeneration and functional recovery in rats with spinal cord contusion through the coordinate interaction of CD4 and BDNF

To explore the effect of electroacupuncture on spinal cord injury (SCI) involving immune-related factors and regeneration-related factors in rats. The model of spinal cord contusion was established by PCI 3000 instrument. Two types of acupuncture points were selected for electroacupuncture treatment on rats. The rats were tested once a week, and the fiber remodeling was detected by magnetic resonance imaging. Transcriptome sequencing was performed on spinal scar samples. Using Python to write code, statistical analysis and bioinformatics analysis of the correlation between transcriptome sequencing data and fiber reconstruction results are carried out. Lastly, the expression of CD4 and brain-derived neurotrophic factor (BDNF) in spinal cord scar was verified by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Electroacupuncture exhibited a positive effect on the recovery of motor function in rats after SCI. Bioinformatics analysis found a direct interaction between CD4 and BDNF. Transcriptome sequencing and PCR results verified that electroacupuncture significantly reduced the expression of CD4, and increased significantly the expression of BDNF, simultaneously corresponding to nerve regeneration in rats with SCI. Our results showed that electroacupuncture intervention in SCI rats improves neural behavior via inhibiting the expression of CD4 and increasing the expression of BDNF.

Mechanism Underlying Acupuncture Therapy in Spinal Cord Injury: A Narrative Overview of Preclinical Studies

Spinal cord injury (SCI) results from various pathogenic factors that destroy the normal structure and function of the spinal cord, subsequently causing sensory, motor, and autonomic nerve dysfunction. SCI is one of the most common causes of disability and death globally. It leads to severe physical and mental injury to patients and causes a substantial economic burden on families and the society. The pathological changes and underlying mechanisms within SCI involve oxidative stress, apoptosis, inflammation, etc. As a traditional therapy, acupuncture has a positive effect promoting the recovery of SCI. Acupuncture-induced neuroprotection includes several mechanisms such as reducing oxidative stress, inhibiting the inflammatory response and neuronal apoptosis, alleviating glial scar formation, promoting neural stem cell differentiation, and improving microcirculation within the injured area. Therefore, the recent studies exploring the mechanism of acupuncture therapy in SCI will help provide a theoretical basis for applying acupuncture and seeking a better treatment target and acupuncture approach for SCI patients.

GluN2A/ERK/CREB Signaling Pathway Involved in Electroacupuncture Regulating Hypothalamic-Pituitary-Adrenal Axis Hyperactivity

The hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis caused by stress will inevitably disrupt the homeostasis of the neuroendocrine system and damage physiological functions. It has been demonstrated that electroacupuncture (EA) can modulate HPA axis hyperactivity during the perioperative period. As the initiating factor of the HPA axis, hypothalamic corticotrophin-releasing hormone (CRH) is the critical molecule affected by EA. However, the mechanism by which EA reduces CRH synthesis and secretion remains unclear. Activated N-methyl-D-aspartate receptor (NMDAR) has been linked to over-secretion of hypothalamic CRH induced by stress. To determine whether NMDAR is involved in EA regulating the over-expression of CRH, a surgical model of partial hepatectomy (HT) was established in our experiment. The effect of EA on hypothalamic NMDAR expression in HT mice was examined. Then, we investigated whether the extracellular regulated protein kinases (ERK)/cyclic adenosine monophosphate response element-binding protein (CREB) signaling pathway mediated by NMDAR was involved in EA regulating HPA axis hyperactivity. It was found that surgery enhanced the expression of hypothalamic CRH and caused HPA axis hyperactivity. Intriguingly, EA effectively suppressed the expression of CRH and decreased the activation of GluN2A (NMDAR subunit), ERK, and CREB in HT mice. GluN2A, ERK, and CREB antagonists had similar effects on normalizing the expression of CRH and HPA axis function compared with EA. Our findings suggested that surgery enhanced the activation of the hypothalamic GluN2A/ERK/CREB signaling pathway, thus promoting the synthesis and secretion of CRH. EA suppressed the phosphorylation of GluN2A, ERK, and CREB in mice that had undergone surgery, indicating that the GluN2A/ERK/CREB signaling pathway was involved in EA alleviating HPA axis hyperactivity.

The Involvement of CaV1.3 Channels in Prolonged Root Reflexes and Its Potential as a Therapeutic Target in Spinal Cord Injury

Spinal cord injury (SCI) results in not only the loss of voluntary muscle control, but also in the presence of involuntary movement or spasms. These spasms post-SCI involve hyperexcitability in the spinal motor system. Hyperactive motor commands post SCI result from enhanced excitatory postsynaptic potentials (EPSPs) and persistent inward currents in voltage-gated L-type calcium channels (LTCCs), which are reflected in evoked root reflexes with different timings. To further understand the contributions of these cellular mechanisms and to explore the involvement of LTCC subtypes in SCI-induced hyperexcitability, we measured root reflexes with ventral root recordings and motoneuron activities with intracellular recordings in an in vitro preparation using a mouse model of chronic SCI (cSCI). Specifically, we explored the effects of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CPT), a selective negative allosteric modulator of Ca_V1.3 LTCCs. Our results suggest a hyperexcitability in the spinal motor system in these SCI mice. Bath application of CPT displayed slow onset but dose-dependent inhibition of the root reflexes with the strongest effect on LLRs. However, the inhibitory effect of CPT is less potent in cSCI mice than in acute SCI (aSCI) mice, suggesting changes either in composition of Ca_V1.3 or other cellular mechanisms in cSCI mice. For intracellular recordings, the intrinsic plateau potentials, was observed in more motoneurons in cSCI mice than in aSCI mice. CPT inhibited the plateau potentials and reduced motoneuron firings evoked by intracellular current injection. These results suggest that the LLR is an important target and that CPT has potential in the therapy of SCI-induced muscle spasms.

Low frequency pulsed electromagnetic field promotes the recovery of neurological function after spinal cord injury in rats

Low frequency pulsed electromagnetic field (LFPEMF) has been shown to provide anti-inflammatory and antioxidative effects. However, there are no reports on whether LFPEMF can treat spinal cord injury (SCI) and its therapeutic mechanism. Therefore, this study was conducted to investigate whether LFPEMF can promote the recovery of neurological function after SCI in rats and its therapeutic mechanism. Basso-Beattie-Bresnahan (BBB) score and transcranial magnetic motor-evoked potentials (tcMMEPs) were recorded to assess the recovery of neurological function. Hematoxylin and eosin (HE) staining and luxol fast blue (LFB) staining were performed to assess the severity of SCI. Immunofluorescence (IF) staining and western blotting (WB) were performed to assess the differentiation of oligodendrocyte precursor cells (OPCs) into oligodendrocytes (OLs). Toluidine blue (TB) staining was performed to assess remyelination. WB and enzyme-linked immunosorbent assays (ELISA) were performed to assess the expression of neurotrophins and inflammatory factors. Our results showed that following stimulation by LFPEMF, there were significant improvements in BBB scores, tcMMEP amplitudes, the extent of the damage, and reduced demyelination in rats after SCI. The mature OLs, the number of well-myelinated fibers, and the myelin sheath thickness significantly increased in rats stimulated by LFPEMF after SCI. The expression of neurotrophins significantly increased, and the expression of inflammatory factors significantly decreased in rats stimulated by LFPEMF after SCI. Therefore, we suggest that LFPEMF can promote the recovery of neurological function in rats after SCI by improving the differentiation of OPCs into OLs and promoting remyelination, as well as by inhibiting inflammation and promoting neurotrophic effects. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:449-456, 2019.