Artemisinin Facilitates Motor Function Recovery by Enhancing Motoneuronal Survival and Axonal Remyelination in Rats Following Brachial Plexus Root Avulsion

Artemisinin (ART), a well-known antimalarial medicine originally isolated from the plant Artemisia annua, exerts neuroprotective effects in the nervous system owing to an antioxidant effect. Here, we determined whether ART is capable of inhibiting the oxidative stress to enhance motoneuronal (MN) survival to promote motor function recovery of rats following brachial plexus root avulsion (BPRA) with reimplantation surgery. Rats following BPRA and reimplantation were subcutaneously injected with 500 μL of PBS or 16 mg/mL ART once daily for 7 days after surgery. Terzis grooming test (TGT), histochemical staining, real-time polymerase chain reaction, and Western blot were conducted to determine the recovery of motor function of the upper limb, the survival rate of MNs, the oxidative stress levels in the ventral horn of the spinal cord, the morphology of abnormal musculocutaneous nerve fibers, the remyelination of axons in musculocutaneous nerves, and the degree of bicep atrophy. ART significantly increased TGT score, improved the survival of MNs, inhibited the oxidative stress, ameliorated the abnormal morphology of fibers in the musculocutaneous nerve, promoted the remyelination of axons, and alleviated muscle atrophy. Take together, ART can improve the survival of MNs and axonal remyelination to promote the motor function recovery via inhibiting oxidative stress, suggesting that ART may represent a new approach to the therapy of spinal root avulsion.

Berberine enhances L1 expression and axonal remyelination in rats after brachial plexus root avulsion

BACKGROUND AND PURPOSE

Enhanced remyelination of the regenerated axons results in functional re-innervation and improved functional motor recovery after brachial plexus root avulsion (BPRA). The neural cell adhesion molecule L1 (L1CAM, L1) regulates myelination and promotes regeneration after acute injury in the nervous system. Berberine (BBR) can exert neuroprotective roles against the lesion. Herein, we investigated whether berberine (BBR) can affect the expression of L1 and enhance the axonal remyelination in rats following BPRA.

METHODS

The surgical procedures were performed to build the rat brachial plexus avulsion and re-implantation model, and then, the rats were treated with BBR. After the rehabilitation for 12 weeks, the musculocutaneous nerves were collected for quantitative real-time PCR, Western blot analysis, and histochemical and immunofluorescence staining.

RESULTS

We observed that, BBR treatment ameliorated the abnormal musculocutaneous nerve fibers morphology, up-regulated the L1 expression, increased the myelination-related genes, decreased the differentiated-associated genes, and up-regulated the phosphorylation of ERK.

CONCLUSION

These results suggest that BBR may enhance L1 expression and promote axonal remyelination after spinal root avulsion.

ERRγ is downregulated in injured motor neuron subpopulations following brachial plexus root avulsion

Estrogen-related receptor γ (ERRγ) is a member of a small group of orphan nuclear receptor transcription factors that have been implicated in several physiological and pathological processes, including placental development, regulation of metabolic genes or disease. The pattern of expression of ERRγ, its role in neuronal injury and its co-localization with other transcription factors in the spinal cord of rats with brachial plexus injury has not been determined. The expression profile of ERRγ and its co-localization with RNA binding protein fox-1 homolog 3 (NeuN) or cyclic AMP-dependent transcription factor 3 (ATF-3) in the motor neurons of rats that underwent brachial plexus root avulsion were assessed using western blot analysis, immunohistochemistry and immunofluorescence. Fluorogold (FG) was used to mark neurons whose axons were severed. ATF-3 was expressed in the nuclei of motor neurons whose axons were severed by root avulsion. On day 3 post-avulsion, FG and ATF-3 were all co-localized in the injured motor neurons. The level of ERRγ protein in the ipsilateral half of injured spinal cords was significantly decreased compared with that in the contralateral half on days 3, 14 and 28 post-avulsion (all P<0.05). The numbers of ERRγ-positive motor neurons (ERRγ^on) were also notably decreased in the ipsilateral side compared with that in the contralateral side on days 14 and 28 post-avulsion, implying that the expression occurred in α motor neurons that were progressively being lost, a phenomenon that was expected post-brachial plexus avulsion. Almost all large and small ERRγ-positive motor neurons were also NeuN-positive (NeuN^on). However, a few of these were ERRγ^on/NeuN^off (no NeuN signal). Therefore, these results suggested that ERRγ is a non-specific marker of γ motor neurons in rats, and therefore, this specific transcriptional program cannot be used to define functionally distinct motor neuron sub-populations. However, its downregulation on the injured side suggests that it is an important component of the response to injury in motor neurons.

Epigallocatechin gallate enhances the motor neuron survival and functional recovery after brachial plexus root avulsion by regulating FIG4

The survival of motor neurons (MNs) is the key to recovery of the motor function after brachial plexus root avulsion (BPRA). (-)-epigallocatechin-3-gallate (EGCG) exerts neuroprotective roles in neurons under different pathological conditions. However, the role of EGCG in regulating motor neurons under BPRA remains to be unclear. In the present study, we investigated the functional role of EGCG both <i><i><i>in vitro</i></i></i> and <i><i><i>in vivo</i></i></i>. In an <i><i><i>in vitro</i></i></i> study, we observed that EGCG obviously increased the cell survival rate of MNs and FIG4 protein levels compared with the vehicle control, with a peak level observed at 50 µM; EGCG can also upregulate FIG4 to reduce the cell death of MNs and increase the neurite outgrowth under oxidative stress; moreover, EGCG can upregulate FIG4 to promote the functional recovery and the survival of MNs in the ventral horn in mice after BPRA. These combined results may lay the foundation for EGCG to be a novel strategy for the treatment of BPRA.

Valproic acid protects neurons and promotes neuronal regeneration after brachial plexus avulsion

Valproic acid has been shown to exert neuroprotective effects and promote neurite outgrowth in several peripheral nerve injury models. However, whether valproic acid can exert its beneficial effect on neurons after brachial plexus avulsion injury is currently unknown. In this study, brachial plexus root avulsion models, established in Wistar rats, were administered daily with valproic acid dissolved in drinking water (300 mg/kg) or normal water. On days 1, 2, 3, 7, 14 and 28 after avulsion injury, tissues of the C5-T1 spinal cord segments of the avulsion injured side were harvested to investigate the expression of Bcl-2, c-Jun and growth associated protein 43 by real-time PCR and western blot assay. Results showed that valproic acid significantly increased the expression of Bcl-2 and growth associated protein 43, and reduced the c-Jun expression after brachial plexus avulsion. Our findings indicate that valproic acid can protect neurons in the spinal cord and enhance neuronal regeneration following brachial plexus root avulsion.

Electroacupuncture treatment contributes to the downregulation of neuronal nitric oxide synthase and motoneuron death in injured spinal cords following root avulsion of the brachial plexus

This study was performed in order to investigate the effect of electroacupuncture (EA) on motoneurons and the expression of neuronal nitric oxide synthase (nNOS) following brachial plexus root avulsion (BPRA). A total of 40 female Sprague-Dawley rats underwent BPRA (5th cervical-1st thoracic) and were randomly divided into the avulsion plus EA stimulation (AV+EA) and AV groups. The AV+EA group received a continuous 20-Hz asymmetric bidirectional disperse-dense wave at the acupuncture points (acupoints) of Dazhui (DU4) and Shousanli (LI10) for 15 min on alternate days until the animals were sacrificed, at 1, 2, 3 and 6 weeks. The AV group received no treatment. The cryostat sections of the 7th cervical segments were prepared and stained with neuronal nitric oxide synthase nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) and histochemically stained and counterstained with neutral red (NR). The number of nNOS-positive motoneurons on the lesion side and survived motoneurons on both sides of the 7th cervical segments were blindly counted and compared between the two groups. The results demonstrated that the number of nNOS-positive motoneurons was significantly lower in the AV+EA group compared with that in the AV group and the percentage of survived motoneurons was significantly higher compared with that of the AV group at 2 and 3 weeks. However, the number of nNOS-positive motoneurons and the percentage of survived motoneurons were not significantly different between the two groups at 1 and 6 weeks. These results indicated that, during the early period after BPRA, EA stimulation at the acupoints of Dazhui (DU4) and Shousanli (LI10) may significantly reduce the number of nNOS-positive motoneurons and protect against motoneuron death.