Diabetic neuropathic pain (DNP) is the most common disabling complication of diabetes. Emerging evidence has linked the pathogenesis of DNP to the aberrant sprouting of sensory axons into the epidermal area; however, the underlying molecular events remain poorly understood. Here we found that an axon guidance molecule, Netrin-3 (Ntn-3), was expressed in the sensory neurons of mouse dorsal root ganglia (DRGs), and downregulation of Ntn-3 expression was highly correlated with the severity of DNP in a diabetic mouse model. Genetic ablation of Ntn-3 increased the intra-epidermal sprouting of sensory axons and worsened the DNP in diabetic mice. In contrast, the elevation of Ntn-3 levels in DRGs significantly inhibited the intra-epidermal axon sprouting and alleviated DNP in diabetic mice. In conclusion, our studies identified Ntn-3 as an important regulator of DNP pathogenesis by gating the aberrant sprouting of sensory axons, indicating that Ntn-3 is a potential druggable target for DNP treatment.
Mice ; Animals ; Diabetes Mellitus, Experimental/metabolism* ; Axons/physiology* ; Diabetic Neuropathies ; Sensory Receptor Cells/metabolism* ; Neuralgia/metabolism*

Research on peripheral nervous injuries, especially the stretched injuries, is important to improve the clinical effectiveness and alleviate the patients's pain. In recent years, the biological changes and mechanics of stretched axons have been hot topics. This article reviews the recent advances in the morphological changes of axons as well as changes in cellular membrane, cytoskeleton, cellular metabolism, and action potential after axonal stretch.
Action Potentials ; Animals ; Axons ; metabolism ; pathology ; Cell Membrane ; pathology ; Cytoskeleton ; pathology ; Humans ; Stress, Mechanical

It has been well established that the recovery ability of central nervous system (CNS) is very poor in adult mammals. As a result, CNS trauma generally leads to severe and persistent functional deficits. Thus, the investigation in this field becomes a "hot spot". Up to date, accumulating evidence supports the hypothesis that the failure of CNS neurons to regenerate is not due to their intrinsic inability to grow new axons, but due to their growth state and due to lack of a permissive growth environment. Therefore, any successful approaches to facilitate the regeneration of injured CNS axons will likely include multiple steps: keeping neurons alive in a certain growth-state, preventing the formation of a glial scar, overcoming inhibitory molecules present in the myelin debris, and giving direction to the growing axons. This brief review focused on the recent progress in the neuron regeneration of CNS in adult mammals.
Animals ; Axons ; physiology ; Central Nervous System Diseases ; complications ; metabolism ; pathology ; Humans ; Mammals ; physiology ; Nerve Regeneration ; physiology

Neurons migrate from their birthplaces to the destinations, and extending axons navigate to their synaptic targets by sensing various extracellular cues in spatiotemporally controlled manners. These evolutionally conserved guidance cues and their receptors regulate multiple aspects of neural development to establish the highly complex nervous system by mediating both short- and long-range cell-cell communications. Neuronal guidance genes (encoding cues, receptors, or downstream signal transducers) are critical not only for development of the nervous system but also for synaptic maintenance, remodeling, and function in the adult brain. One emerging theme is the combinatorial and complementary functions of relatively limited classes of neuronal guidance genes in multiple processes, including neuronal migration, axonal guidance, synaptogenesis, and circuit formation. Importantly, neuronal guidance genes also regulate cell migration and cell-cell communications outside the nervous system. We are just beginning to understand how cells integrate multiple guidance and adhesion signaling inputs to determine overall cellular/subcellular behavior and how aberrant guidance signaling in various cell types contributes to diverse human diseases, ranging from developmental, neuropsychiatric, and neurodegenerative disorders to cancer metastasis. We review classic studies and recent advances in understanding signaling mechanisms of the guidance genes as well as their roles in human diseases. Furthermore, we discuss the remaining challenges and therapeutic potentials of modulating neuronal guidance pathways in neural repair.
Humans ; Axon Guidance/genetics* ; Neurons ; Axons/metabolism* ; Signal Transduction/genetics* ; Cell Communication

Spinal cord injury is a severe central nervous system disease, which will cause a series of complex pathophysiological changes and activate a variety of signaling pathways including Notch signaling. Studies have evidenced that activation of the Notch signaling pathway is not conducive to nerve repair and symptom improvement after spinal cord injury. Its mechanisms include inhibiting neuronal differentiation and axon regeneration, promoting reactive astrocyte proliferation, promoting M1 macrophage polarization and the release of proinflammatory factors, and inhibiting angiogenesis. Therefore, it has become a promising therapeutic strategy to inhibit Notch signal as a target in the treatment of spinal cord injury. In recent years, some researchers have used drugs, cell transplantation or genetic modification to regulate Notch signaling, which can promote the recovery of nerve function after spinal cord injury, thereby providing new treatment strategies for the treatment of spinal cord injury. This article will summarize the mechanism of Notch signaling pathway in spinal cord injury, and at the same time review the research progress in the treatment of spinal cord injury by modulating Notch signaling pathway in recent years, so as to provide new research ideas for further exploring new strategies for spinal cord injury.
Axons/metabolism* ; Cell Transplantation ; Humans ; Nerve Regeneration ; Signal Transduction/genetics* ; Spinal Cord/metabolism* ; Spinal Cord Injuries/metabolism*

Enhancing remyelination after injury is of utmost importance for optimizing the recovery of nerve function. While the formation of myelin by Schwann cells (SCs) is critical for the function of the peripheral nervous system, the temporal dynamics and regulatory mechanisms that control the progress of the SC lineage through myelination require further elucidation. Here, using in vitro co-culture models, gene expression profiling of laser capture-microdissected SCs at various stages of myelination, and multilevel bioinformatic analysis, we demonstrated that SCs exhibit three distinct transcriptional characteristics during myelination: the immature, promyelinating, and myelinating states. We showed that suppressor interacting 3a (Sin3A) and 16 other transcription factors and chromatin regulators play important roles in the progress of myelination. Sin3A knockdown in the sciatic nerve or specifically in SCs reduced or delayed the myelination of regenerating axons in a rat crushed sciatic nerve model, while overexpression of Sin3A greatly promoted the remyelination of axons. Further, in vitro experiments revealed that Sin3A silencing inhibited SC migration and differentiation at the promyelination stage and promoted SC proliferation at the immature stage. In addition, SC differentiation and maturation may be regulated by the Sin3A/histone deacetylase2 (HDAC2) complex functionally cooperating with Sox10, as demonstrated by rescue assays. Together, these results complement the recent genome and proteome analyses of SCs during peripheral nerve myelin formation. The results also reveal a key role of Sin3A-dependent chromatin organization in promoting myelinogenic programs and SC differentiation to control peripheral myelination and repair. These findings may inform new treatments for enhancing remyelination and nerve regeneration.
Animals ; Axons ; Chromatin/metabolism* ; Gene Expression Profiling ; Myelin Sheath/metabolism* ; Nerve Regeneration/physiology* ; Rats ; Schwann Cells/metabolism* ; Sciatic Nerve/injuries*

Galectin-4, a tandem repeat member of the β-galactoside-binding proteins, possesses two carbohydrate-recognition domains (CRD) in a single peptide chain. This lectin is mostly expressed in epithelial cells of the intestinal tract and secreted to the extracellular. The two domains have 40% similarity in amino acid sequence, but distinctly binding to various ligands. Just because the two domains bind to different ligands simultaneously, galectin-4 can be a crosslinker and crucial regulator in a large number of biological processes. Recent evidence shows that galectin-4 plays an important role in lipid raft stabilization, protein apical trafficking, cell adhesion, wound healing, intestinal inflammation, tumor progression, etc. This article reviews the physiological and pathological features of galectin-4 and its important role in such processes.
Animals ; Axons ; metabolism ; Endocytosis ; Galectin 4 ; blood ; genetics ; metabolism ; Humans ; Inflammatory Bowel Diseases ; metabolism ; pathology ; Membrane Microdomains ; metabolism ; Neoplasms ; metabolism ; pathology ; Neurons ; metabolism ; Wound Healing

OBJECTIVETo study the expression of tau-related protein in spinal cord of Chinese patients with Alzheimer's disease.

METHODSGallays-Braak stain and immunohistochemical study for tau protein (AT8) were carried out in the spinal cord tissue (T2, T8, T10, L2 and S2 segments) of 3 Chinese patients with Alzheimer's disease. Seven age-matched cases without evidence of dementia or neurologic disease were used as controls.

RESULTSNeurofibrillary tangles were identified in the neurons of anterior horn in 2 Alzheimer's disease cases but none was observed in the controls. Tau-positive axons and astroglia were detected in all Alzheimer's disease cases. Tau immunoreactivity in spinal cord of the patients correlated with that in brain tissue.

CONCLUSIONThe expression of tau-related protein is demonstrated in the spinal cord of Alzheimer's disease patients suggesting that axonal transport defect may play a role in the pathogenesis of Alzheimer's disease.

Aged ; Alzheimer Disease ; metabolism ; pathology ; Axonal Transport ; Axons ; metabolism ; pathology ; Humans ; Male ; Neurofibrillary Tangles ; metabolism ; pathology ; Phosphorylation ; Spinal Cord ; metabolism ; pathology ; tau Proteins ; metabolism

BACKGROUNDWallerian degeneration is a self-destructive process of axonal degeneration that occurs after an axonal injury or during neurodegenerative disorders such as Parkinson's or Alzheimer's disease. Recent studies have found that the activity of the nicotinamide adenine dinucleotide (NAD) synthase enzyme, nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) can affect the rate of Wallerian degeneration in mice and drosophila. NMNAT1 protects neurons and axons from degeneration. However, the role of NMNAT1 in neurons of central nervous system is still not well understood.

METHODSWe set up the culture of primary mouse neurons in vitro and manipulated the expression level of NMNAT1 by RNA interference and gene overexpression methods. Using electroporation transfection we can up-regulate or down-regulate NMNAT1 in cultured mouse dendrites and axons and study the neuronal morphogenesis by immunocytochemistry. In all functional assays, FK-866 (CAS 658084-64-1), a highly specific non-competitive inhibitor of nicotinamide phosphoribosyltransferase was used as a pharmacological and positive control.

RESULTSOur results showed that knocking down NMNAT1 by RNA interference led to a marked decrease in dendrite outgrowth and branching and a significant decrease in axon growth and branching in developing cortical neurons in vitro.

CONCLUSIONSThese findings reveal a novel role for NMNAT1 in the morphogenesis of developing cortical neurons, which indicate that the loss of function of NMNAT1 may contribute to different neurodegenerative disorders in central nervous system.

Animals ; Axons ; metabolism ; Blotting, Western ; Cells, Cultured ; Dendrites ; metabolism ; Immunohistochemistry ; Mice ; Morphogenesis ; genetics ; physiology ; Neurons ; cytology ; metabolism ; Nicotinamide-Nucleotide Adenylyltransferase ; genetics ; metabolism

OBJECTIVE AND METHODSTo evaluate synaptic changes using synaptophysin immunohistochemstry in rat and mouse, which spinal cords were subjected to graded compression trauma at the level of Th8-9.

RESULTSNormal animals showed numerous fine dots of synaptophysin immunoreactivity in the gray matter. An increase in synaptophysin immunoreactivity was observed in the neuropil and synapses at the surface of motor neurons of the anterior horns in the Th8-9 segments lost immunoreactivity at 4-hour point after trauma. The immunoreactive synapses reappeared around motor neurons at 9-day point. Unexpected accumulation of synaptophysin immunoreactivity occurred in injured axons of the white matter of the compressed spinal cord.

CONCLUSIONSynaptic changes were important components of secondary injuries in spinal cord trauma. Loss of synapses on motor neurons may be one of the factors causing motor dysfunction of hind limbs and formation of new synapses may play an important role in recovery of motor function. Synaptophysin immunohistochemistry is also a good tool for studies of axonal swellings in spinal cord injuries.

Animals ; Axons ; metabolism ; pathology ; Female ; Immunohistochemistry ; Male ; Mice ; Mice, Inbred Strains ; Rats ; Rats, Sprague-Dawley ; Spinal Cord Compression ; Spinal Cord Injuries ; metabolism ; pathology ; Synapses ; metabolism ; pathology ; Synaptophysin ; metabolism