Effects of tail nerve electrical stimulation on the activation and plasticity of the lumbar locomotor circuits and the prevention of skeletal muscle atrophy after spinal cord transection in rats.

INTRODUCTION: Severe spinal cord injury results in the loss of neurons in the relatively intact spinal cord below the injury area and skeletal muscle atrophy in the paralyzed limbs. These pathological processes are significant obstacles for motor function reconstruction. OBJECTIVE: We performed tail nerve electrical stimulation (TNES) to activate the motor neural circuits below the injury site of the spinal cord to elucidate the regulatory mechanisms of the excitatory afferent neurons in promoting the reconstruction of locomotor function. METHODS: Eight days after T10 spinal cord transection in rats, TNES was performed for 7 weeks. Behavioral scores were assessed weekly. Electrophysiological tests and double retrograde tracings were performed at week 8. RESULTS: After 7 weeks of TNES treatment, there was restoration in innervation, the number of stem cells, and mitochondrial metabolism in the rats' hindlimb muscles. Double retrograde tracings of the tail nerve and sciatic nerve further confirmed the presence of synaptic connections between the tail nerve and central pattern generator (CPG) neurons in the lumbar spinal cord, as well as motor neurons innervating the hindlimb muscles. CONCLUSION: The mechanisms of TNES induced by the stimulation of primary afferent nerve fibers involves efficient activation of the motor neural circuits in the lumbosacral segment, alterations of synaptic plasticity, and the improvement of muscle and nerve regeneration, which provides the structural and functional foundation for the future use of cutting-edge biological treatment strategies to restore voluntary movement of paralyzed hindlimbs.

The therapeutic mechanism of transcranial iTBS on nerve regeneration and functional recovery in rats with complete spinal cord transection.

Background: After spinal cord transection injury, the inflammatory microenvironment formed at the injury site, and the cascade of effects generated by secondary injury, results in limited regeneration of injured axons and the apoptosis of neurons in the sensorimotor cortex (SMC). It is crucial to reverse these adverse processes for the recovery of voluntary movement. The mechanism of transcranial intermittent theta-burst stimulation (iTBS) as a new non-invasive neural regulation paradigm in promoting axonal regeneration and motor function repair was explored by means of a severe spinal cord transection. Methods: Rats underwent spinal cord transection and 2 mm resection of spinal cord at T10 level. Four groups were studied: Normal (no lesion), Control (lesion with no treatment), sham iTBS (lesion and no functional treatment) and experimental, exposed to transcranial iTBS, 72 h after spinal lesion. Each rat received treatment once a day for 5 days a week; behavioral tests were administered one a week. Inflammation, neuronal apoptosis, neuroprotective effects, regeneration and synaptic plasticity after spinal cord injury (SCI) were determined by immunofluorescence staining, western blotting and mRNA sequencing. For each rat, anterograde tracings were acquired from the SMC or the long descending propriospinal neurons and tested for cortical motor evoked potentials (CMEPs). Regeneration of the corticospinal tract (CST) and 5-hydroxytryptamine (5-HT) nerve fibers were analyzed 10 weeks after SCI. Results: When compared to the Control group, the iTBS group showed a reduced inflammatory response and reduced levels of neuronal apoptosis in the SMC when tested 2 weeks after treatment. Four weeks after SCI, the neuroimmune microenvironment at the injury site had improved in the iTBS group, and neuroprotective effects were evident, including the promotion of axonal regeneration and synaptic plasticity. After 8 weeks of iTBS treatment, there was a significant increase in CST regeneration in the region rostral to the site of injury. Furthermore, there was a significant increase in the number of 5-HT nerve fibers at the center of the injury site and the long descending propriospinal tract (LDPT) fibers in the region caudal to the site of injury. Moreover, CMEPs and hindlimb motor function were significantly improved. Conclusion: Neuronal activation and neural tracing further verified that iTBS had the potential to provide neuroprotective effects during the early stages of SCI and induce regeneration effects related to the descending motor pathways (CST, 5-HT and LDPT). Furthermore, our results revealed key relationships between neural pathway activation, neuroimmune regulation, neuroprotection and axonal regeneration, as well as the interaction network of key genes.

Tail nerve electrical stimulation promoted the efficiency of transplanted spinal cord-like tissue as a neuronal relay to repair the motor function of rats with transected spinal cord injury.

Following transected spinal cord injury (SCI), there is a critical need to restore nerve conduction at the injury site and activate the silent neural circuits caudal to the injury to promote the recovery of voluntary movement. In this study, we generated a rat model of SCI, constructed neural stem cell (NSC)-derived spinal cord-like tissue (SCLT), and evaluated its ability to replace injured spinal cord and repair nerve conduction in the spinal cord as a neuronal relay. The lumbosacral spinal cord was further activated with tail nerve electrical stimulation (TNES) as a synergistic electrical stimulation to better receive the neural information transmitted by the SCLT. Next, we investigated the neuromodulatory mechanism underlying the action of TNES and its synergism with SCLT in SCI repair. TNES promoted the regeneration and remyelination of axons and increased the proportion of glutamatergic neurons in SCLT to transmit brain-derived neural information more efficiently to the caudal spinal cord. TNES also increased the innervation of motor neurons to hindlimb muscle and improved the microenvironment of muscle tissue, resulting in effective prevention of hindlimb muscle atrophy and enhanced muscle mitochondrial energy metabolism. Tracing of the neural circuits of the sciatic nerve and tail nerve identified the mechanisms responsible for the synergistic effects of SCLT transplantation and TNES in activating central pattern generator (CPG) neural circuits and promoting voluntary motor function recovery in rats. The combination of SCLT and TNES is expected to provide a new breakthrough for patients with SCI to restore voluntary movement and control their muscles.

Cerebellar spreading depolarization mediates paroxysmal movement disorder.

Paroxysmal kinesigenic dyskinesia (PKD) is the most common paroxysmal dyskinesia, characterized by recurrent episodes of involuntary movements provoked by sudden changes in movement. Proline-rich transmembrane protein 2 (PRRT2) has been identified as the major causative gene for PKD. Here, we report that PRRT2 deficiency facilitates the induction of cerebellar spreading depolarization (SD) and inhibition of cerebellar SD prevents the occurrence of dyskinetic movements. Using Ca2+ imaging, we show that cerebellar SD depolarizes a large population of cerebellar granule cells and Purkinje cells in Prrt2-deficient mice. Electrophysiological recordings further reveal that cerebellar SD blocks Purkinje cell spiking and disturbs neuronal firing of the deep cerebellar nuclei (DCN). The resultant aberrant firing patterns in DCN are tightly, temporally coupled to dyskinetic episodes in Prrt2-deficient mice. Cumulatively, our findings uncover a pivotal role of cerebellar SD in paroxysmal dyskinesia, providing a potent target for treating PRRT2-related paroxysmal disorders.

UBE3A-mediated PTPA ubiquitination and degradation regulate PP2A activity and dendritic spine morphology.

Deficiency in the E3 ubiquitin ligase UBE3A leads to the neurodevelopmental disorder Angelman syndrome (AS), while additional dosage of UBE3A is linked to autism spectrum disorder. The mechanisms underlying the downstream effects of UBE3A gain or loss of function in these neurodevelopmental disorders are still not well understood, and effective treatments are lacking. Here, using stable-isotope labeling of amino acids in mammals and ubiquitination assays, we identify PTPA, an activator of protein phosphatase 2A (PP2A), as a bona fide ubiquitin ligase substrate of UBE3A. Maternal loss of Ube3a (Ube3am-/p+) increased PTPA level, promoted PP2A holoenzyme assembly, and elevated PP2A activity, while maternal 15q11-13 duplication containing Ube3a down-regulated PTPA level and lowered PP2A activity. Reducing PTPA level in vivo restored the defects in dendritic spine maturation in Ube3am-/p+ mice. Moreover, pharmacological inhibition of PP2A activity with the small molecule LB-100 alleviated both reduction in excitatory synaptic transmission and motor impairment in Ube3am-/p+ mice. Together, our results implicate a critical role of UBE3A-PTPA-PP2A signaling in the pathogenesis of UBE3A-related disorders and suggest that PP2A-based drugs could be potential therapeutic candidates for treatment of UBE3A-related disorders.

Targeting KPNB1 overcomes TRAIL resistance by regulating DR5, Mcl-1 and FLIP in glioblastoma cells.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine with potential anticancer effect, but innate and adaptive TRAIL resistance in majority of cancers limit its clinical application. Karyopherin ß1 (KPNB1) inhibition in cancer cells has been reported to abrogate the nuclear import of TRAIL receptor DR5 and facilitate its localization on the cell surface ready for TRAIL stimulation. However, our study reveals a more complicated mechanism. Genetic or pharmacological inhibition of KPNB1 potentiated TRAIL-induced apoptosis selectively in glioblastoma cells mainly by unfolded protein response (UPR). First, it augmented ATF4-mediated DR5 expression and promoted the assembly of death-inducing signaling complex (DISC). Second, it freed Bax and Bak from Mcl-1. Third, it downregulated FLIPL and FLIPS, inhibitors of caspase-8 cleavage, partly through upregulating ATF4-induced 4E-BP1 expression and disrupting the cap-dependent translation initiation. Meanwhile, KPNB1 inhibition-induced undesirable autophagy and accelerated cleaved caspase-8 clearance. Inhibition of autophagic flux maintained cleaved caspase-8 and aggravated apoptosis induced by KPNB1 inhibitor plus TRAIL, which were abolished by caspase-8 inhibitor. These results unveil new molecular mechanism for optimizing TRAIL-directed therapeutic efficacy against cancer.

Cloning and characterization of a trypsin-like serine protease gene, a novel regeneration-related gene from Apostichopus japonicus.

Trypsin-like serine protease (TLS) plays an important role in many physiological processes including wound healing, phlogosis reaction, blood clotting, regeneration etc. In this paper, a 1216 bp full-length cDNA sequence of TLS including 39 bp 5' UTR and 355 bp 3'UTR coding for a theoretical 273 amino acids protein was cloned from Apostichopus japonicus by means of the RACE technique for the first time. Bioinformatic analysis revealed that the gene with a 20 residues N-terminal signal peptide and a conserved C-terminal domain belongs to the trypsin-like serine protease superfamily. His78, Asp130 and Ser223 are the principal residues of the catalytic center. In-situ hybridization (ISH) analysis revealed that the TLS gene was widely distributed in different tissues. The expression patterns during different regeneration stages of the TLS gene in the body wall, intestine and respiratory trees were investigated using real-time quantitative PCR. The results show that there was a remarkable and temporary up-regulation of TLS gene expression in the body wall within 1h and subsequent down-regulation of TLS similar to intestine and respiratory trees. With the recovery of tissues, the expression level of the TLS gene was gradually up-regulated and finally reached normal levels. TLS was regulated during different regeneration stages suggesting that TLS is important in the regeneration process of A. japonicus.

Molecular cloning, characterization and expression analysis of a C-type lectin (AJCTL) from the sea cucumber Apostichopus japonicus.

For the sea cucumber Apostichopus japonicus, a C-type lectin (AJCTL) was identified using rapid amplification of cDNA ends (RACE) PCR techniques. The full-length cDNA of AJCTL is composed of 710bp with a 618bp open reading frame (ORF) that encodes a polypeptide of 205 amino acids with a N-terminal signal peptide and a C-terminal C-type lectin domain (CTLD). The calculated molecular mass of the whole protein is 22.5kDa and its predicted isoelectric point is 5.59. AJCTL belongs to the group VII of regulatory proteins and it might function as a Ca(2+)-dependent monosaccharide binding lectin specifically and recognizing mannose-type ligands. In situ hybridization demonstrated that the expression of AJCTL was located in the body wall, longitudinal muscles, intestinum and respiratory tree. This became apparent especially in the cytoplasm of epidermal cells and granular haemocytes. Real-time PCR data suggested that AJCTL was mostly synthesized in the longitudinal muscles and intestinum and less pronounced in the respiratory tree and body wall of adults. After 12h stimulation by Vibrio harveyi, at increasing bacterial concentration gradient, the expression of AJCTL in sea cucumber increased as well. This indicated that CTL is related to an innate immune response.