ERK/MAPK and PI3K/AKT signal channels simultaneously activated in nerve cell and axon after facial nerve injury

Clinical application and potential pluripotent effects of hepatocyte growth factor in spinal cord injury regeneration

INTRODUCTION

Spinal cord injury (SCI) is a condition in which the spinal cord parenchyma is damaged by various factors. The mammalian central nervous system has been considered unable to regenerate once damaged, but recent progress in basic research has gradually revealed that injured neural cells can indeed regenerate. Drug therapy using novel agents is being actively investigated as a new treatment for SCI. One notable treatment method is regeneration therapy using hepatocyte growth factors (HGF).

AREA COVERED

HGF has pluripotent neuroregenerative actions, as indicated by its neuroprotective and regenerative effects on the microenvironment and damaged cells, respectively. This review examines these effects in various phases of SCI, from basic research to clinical studies, and the application of this treatment to other diseases.

EXPERT OPINION

In regenerative medicine for SCI, drug therapies have tended to be more likely to be developed compared to cell replacement treatment. Nevertheless, there are still challenges to be addressed for these clinical applications due to a wide variety of pathology and animal experimental models of basic study, but HGF could be an effective treatment for SCI with expanded application.

Octanol alleviates chronic constriction injury of sciatic nerve-induced peripheral neuropathy by regulating AKT/mTOR signaling

OBJECTIVE

Activation of gap junction channels can induce neuropathic pain. Octanol can limit the conductance of gap junctions containing connexin 43 proteins. Thus, this study focused on the roles of octanol in chronic constriction injury (CCI)-induced peripheral neuropathy in mice and its mechanisms of action.

METHODS

Male mice were assigned into control, sham, CCI, CCI + Octanol-20 mg/kg, CCI + Octanol-40 mg/kg and CCI + Octanol-80 mg/kg groups. CCI was performed by applying three loose ligations to mouse sciatic nerve, and the mice with CCI was administered with 20 mg/kg, 40 mg/kg, or 80 mg/kg octanol. The neuropathic pain development was examined by assessing thermal withdrawal latency, paw withdrawal mechanical threshold, and sciatic functional index. Histopathological changes were evaluated by hematoxylin and eosin staining. The phosphorylation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR) was examined by western blotting. The expression of Akt and mTOR was also evaluated by immunofluorescence staining.

RESULTS

Octanol alleviated the CCI-induced mechanical and thermal hyperalgesia and sciatic functional loss. Additionally, octanol relieved the CCI-induced abnormal histopathological changes. Mechanistically, octanol inactivated the Akt/mTOR pathway in the mice with CCI.

CONCLUSION

In conclusion, octanol can alleviate CCI-induced peripheral neuropathic by regulating the Akt/mTOR pathway and might be a novel pharmacological intervention for neuropathic pain.

The role of kinases in peripheral nerve regeneration: mechanisms and implications

Peripheral nerve injury disease is a prevalent traumatic condition in current medical practice. Despite the present treatment approaches, encompassing surgical sutures, autologous nerve or allograft nerve transplantation, tissue engineering techniques, and others, an effective clinical treatment method still needs to be discovered. Exploring novel treatment methods to improve peripheral nerve regeneration requires more effort in investigating the cellular and molecular mechanisms involved. Many factors are associated with the regeneration of injured peripheral nerves, including the cross-sectional area of the injured nerve, the length of the nerve gap defect, and various cellular and molecular factors such as Schwann cells, inflammation factors, kinases, and growth factors. As crucial mediators of cellular communication, kinases exert regulatory control over numerous signaling cascades, thereby participating in various vital biological processes, including peripheral nerve regeneration after nerve injury. In this review, we examined diverse kinase classifications, distinct nerve injury types, and the intricate mechanisms involved in peripheral nerve regeneration. Then we stressed the significance of kinases in regulating autophagy, inflammatory response, apoptosis, cell cycle, oxidative processes, and other aspects in establishing conductive microenvironments for nerve tissue regeneration. Finally, we briefly discussed the functional roles of kinases in different types of cells involved in peripheral nerve regeneration.

Emerging role of extracellular vesicles and exogenous stimuli in molecular mechanisms of peripheral nerve regeneration

Peripheral nerve injuries lead to significant morbidity and adversely affect quality of life. The peripheral nervous system harbors the unique trait of autonomous regeneration; however, achieving successful regeneration remains uncertain. Research continues to augment and expedite successful peripheral nerve recovery, offering promising strategies for promoting peripheral nerve regeneration (PNR). These include leveraging extracellular vesicle (EV) communication and harnessing cellular activation through electrical and mechanical stimulation. Small extracellular vesicles (sEVs), 30-150 nm in diameter, play a pivotal role in regulating intercellular communication within the regenerative cascade, specifically among nerve cells, Schwann cells, macrophages, and fibroblasts. Furthermore, the utilization of exogenous stimuli, including electrical stimulation (ES), ultrasound stimulation (US), and extracorporeal shock wave therapy (ESWT), offers remarkable advantages in accelerating and augmenting PNR. Moreover, the application of mechanical and electrical stimuli can potentially affect the biogenesis and secretion of sEVs, consequently leading to potential improvements in PNR. In this review article, we comprehensively delve into the intricacies of cell-to-cell communication facilitated by sEVs and the key regulatory signaling pathways governing PNR. Additionally, we investigated the broad-ranging impacts of ES, US, and ESWT on PNR.

Index of consciousness monitoring during general anesthesia may effectively enhance rehabilitation in elderly patients undergoing laparoscopic urological surgery: a randomized controlled clinical trial

BACKGROUND

Based on electroencephalogram (EEG) analysis, index of consciousness (IoC) monitoring is a new technique for monitoring anesthesia depth. IoC is divided into IoC1 (depth of sedation) and IoC2 (depth of analgesia). The potential for concurrent monitoring of IoC1 and IoC2 to expedite postoperative convalescence remains to be elucidated. We investigated whether combined monitoring of IoC1 and IoC2 can effectively enhances postoperative recovery compared with bispectral index (BIS) in elderly patients undergoing laparoscopic urological surgery under general anesthesia.

METHODS

In this prospective, controlled, double-blinded trail, 120 patients aged 65 years or older were arbitrarily assigned to either the IoC group or the control group (BIS monitoring). All patients underwent blood gas analysis at T1 (before anesthesia induction) and T2 (the end of operation). The Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were administered to all patients at T0 (1 day before surgery) and T4 (7 days after surgery). Serum concentrations of C-reactive protein (CRP) and glial fibrillary acid protein (GFAP) were assessed at T1, T2, and T3 (24 h after surgery). Postoperative complications and the duration of hospitalization were subjected to comparative evaluation.

RESULTS

The incidence of postoperative cognitive dysfunction (POCD) was notably lower in the IoC group (10%) than in the control group (31.7%) (P = 0.003). Postoperative serum CRP and GFAP concentrations exhibited significant differences at time points T2 (CRP: P = 0.000; GFAP: P = 0.000) and T3 (CRP: P = 0.003; GFAP: P = 0.008). Postoperative blood glucose levels (P = 0.000) and the overall rate of complications (P = 0.037) were significantly lower in Group IoC than in Group control.

CONCLUSION

The employment of IoC monitoring for the management of elderly surgical patients can accelerate postoperative convalescence by mitigating intraoperative stress and reducing peripheral and central inflammatory injury.

TRIAL REGISTRATION

Chinese Clinical Trial Registry Identifier: ChiCTR1900025241 (17/08/2019).

The potential roles of dental pulp stem cells in peripheral nerve regeneration

Peripheral nerve diseases are significantly correlated with severe fractures or trauma and surgeries, leading to poor life quality and impairment of physical and mental health. Human dental pulp stem cells (DPSCs) are neural crest stem cells with a strong multi-directional differentiation potential and proliferation capacity that provide a novel cell source for nerve regeneration. DPSCs are easily extracted from dental pulp tissue of human permanent or deciduous teeth. DPSCs can express neurotrophic and immunomodulatory factors and, subsequently, induce blood vessel formation and nerve regeneration. Therefore, DPSCs yield valuable therapeutic potential in the management of peripheral neuropathies. With the purpose of summarizing the advances in DPSCs and their potential applications in peripheral neuropathies, this article reviews the biological characteristics of DPSCs in association with the mechanisms of peripheral nerve regeneration.

Unleashing Intrinsic Growth Pathways in Regenerating Peripheral Neurons

Common mechanisms of peripheral axon regeneration are recruited following diverse forms of damage to peripheral nerve axons. Whether the injury is traumatic or disease related neuropathy, reconnection of axons to their targets is required to restore function. Supporting peripheral axon regrowth, while not yet available in clinics, might be accomplished from several directions focusing on one or more of the complex stages of regrowth. Direct axon support, with follow on participation of supporting Schwann cells is one approach, emphasized in this review. However alternative approaches might include direct support of Schwann cells that instruct axons to regrow, manipulation of the inflammatory milieu to prevent ongoing bystander axon damage, or use of inflammatory cytokines as growth factors. Axons may be supported by a growing list of growth factors, extending well beyond the classical neurotrophin family. The understanding of growth factor roles continues to expand but their impact experimentally and in humans has faced serious limitations. The downstream signaling pathways that impact neuron growth have been exploited less frequently in regeneration models and rarely in human work, despite their promise and potency. Here we review the major regenerative signaling cascades that are known to influence adult peripheral axon regeneration. Within these pathways there are major checkpoints or roadblocks that normally check unwanted growth, but are an impediment to robust growth after injury. Several molecular roadblocks, overlapping with tumour suppressor systems in oncology, operate at the level of the perikarya. They have impacts on overall neuron plasticity and growth. A second approach targets proteins that largely operate at growth cones. Addressing both sites might offer synergistic benefits to regrowing neurons. This review emphasizes intrinsic aspects of adult peripheral axon regeneration, emphasizing several molecular barriers to regrowth that have been studied in our laboratory.

Transcriptomes of Injured Lamprey Axon Tips: Single-Cell RNA-Seq Suggests Differential Involvement of MAPK Signaling Pathways in Axon Retraction and Regeneration after Spinal Cord Injury

Axotomy in the CNS activates retrograde signals that can trigger regeneration or cell death. Whether these outcomes use different injury signals is not known. Local protein synthesis in axon tips plays an important role in axon retraction and regeneration. Microarray and RNA-seq studies on cultured mammalian embryonic or early postnatal peripheral neurons showed that axon growth cones contain hundreds to thousands of mRNAs. In the lamprey, identified reticulospinal neurons vary in the probability that their axons will regenerate after axotomy. The bad regenerators undergo early severe axon retraction and very delayed apoptosis. We micro-aspirated axoplasms from 10 growing, 9 static and 5 retracting axon tips of spinal cord transected lampreys and performed single-cell RNA-seq, analyzing the results bioinformatically. Genes were identified that were upregulated selectively in growing (n = 38), static (20) or retracting tips (18). Among them, map3k2, csnk1e and gtf2h were expressed in growing tips, mapk8(1) was expressed in static tips and prkcq was expressed in retracting tips. Venn diagrams revealed more than 40 components of MAPK signaling pathways, including jnk and p38 isoforms, which were differentially distributed in growing, static and/or retracting tips. Real-time q-PCR and immunohistochemistry verified the colocalization of map3k2 and csnk1e in growing axon tips. Thus, differentially regulated MAPK and circadian rhythm signaling pathways may be involved in activating either programs for axon regeneration or axon retraction and apoptosis.

The SELENOT mimetic PSELT promotes nerve regeneration by increasing axonal myelination in a facial nerve injury model in female rats

Peripheral nerve injury (PNI) is frequent and many patients suffer lifelong disabilities in severe cases. Although the peripheral nervous system is able to regenerate, its potential is limited. In this study, we tested in a nerve regeneration model in rat the potential beneficial effect of a short mimetic peptide, named PSELT, which derives from SELENOT, an essential thioredoxin-like selenoprotein endowed with neuroprotective and antioxidant activities. For this purpose, the right facial nerve of female Long-Evans rats was axotomized then bridged with a free femoral vein interposition graft. PSELT (1 μM) was injected into the vein immediately and 48 h after the injury, and the effects observed were compared to those found after an end-to-end suture used as a gold standard treatment. Whisking behavior, electrophysiological potential, and histological analyses were performed 3 months after injury to determine the effects of these treatments. These analyses revealed that PSELT-treated animals exhibit a better motor recovery in terms of protraction amplitude and velocity of vibrissae compared to control and end-sutured nerve animal groups. Moreover, administration of PSELT following injury enhanced muscle innervation, axonal elongation, and myelination of newly formed nerve fibers. Altogether, these results indicate that a PSELT-based treatment is sufficient to enhance facial nerve myelination and regeneration and could represent a new therapeutic tool to treat PNI.

SAM, a cystathionine beta-synthase activator, promotes hydrogen sulfide to promote neural repair resulting from massive cerebral infarction induced by middle cerebral artery occlusion

Neurologic deterioration after massive cerebral infarct should be identified at an early stage for medical and surgical treatments. We investigated the effect of hydrogen sulfide on the excitotoxity of PC12 cells exposed to oxygen-glucose deprivation (OGD) and its effect on the apoptosis of brain tissues in rats with middle cerebral artery occlusion (MCAO). Rats with MCAO were treated with SAM, a cystathionine beta-synthase (CBS) activator, or AOAA, a CBS inhibitor. Hydrogen sulfide content in the brain tissues of infarcted patients or rats with MCAO was decreased, whereas glutamate (GLU) content was increased. In addition, SAM reduced reactive oxygen species content, lactate dehydrogenase release, and apoptosis levels in the brain tissues of rats with MCAO. The PC12 cells that were exposed to OGD were also treated with 20 mM GLU and later treated with SAM or AOAA. In PC12 cells, SAM reduced the apoptosis caused by GLU after OGD. The protective effects of hydrogen sulfide was elicited through the sulfur-sulfhydrylation modification of NMDAR and the induction of ERK/MAPK signaling. Our results showed that hydrogen sulfide exerts a protective effect on the PC12 cells and the rats with MCAO, which might represent a possible therapeutic agent against massive cerebral infarct.

Signal Transduction Regulators in Axonal Regeneration

Intracellular signal transduction in response to growth factor receptor activation is a fundamental process during the regeneration of the nervous system. In this context, intracellular inhibitors of neuronal growth factor signaling have become of great interest in the recent years. Among them are the prominent signal transduction regulators Sprouty (SPRY) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN), which interfere with major signaling pathways such as extracellular signal-regulated kinase (ERK) or phosphoinositide 3-kinase (PI3K)/Akt in neurons and glial cells. Furthermore, SPRY and PTEN are themselves tightly regulated by ubiquitin ligases such as c-casitas b-lineage lymphoma (c-CBL) or neural precursor cell expressed developmentally down-regulated protein 4 (NEDD4) and by different microRNAs (miRs) including miR-21 and miR-222. SPRY, PTEN and their intracellular regulators play an important role in the developing and the lesioned adult central and peripheral nervous system. This review will focus on the effects of SPRY and PTEN as well as their regulators in various experimental models of axonal regeneration in vitro and in vivo. Targeting these signal transduction regulators in the nervous system holds great promise for the treatment of neurological injuries in the future.

Maresin 1 promotes nerve regeneration and alleviates neuropathic pain after nerve injury

Background

Peripheral nerve injury (PNI) is a public health concern that results in sensory and motor disorders as well as neuropathic pain and secondary lesions. Currently, effective treatments for PNI are still limited. For example, while nerve growth factor (NGF) is widely used in the treatment of PNI to promote nerve regeneration, it also induces pain. Maresin 1 (MaR1) is an anti-inflammatory and proresolving mediator that has the potential to regenerate tissue. We determined whether MaR1 is able to promote nerve regeneration as well as alleviating neuropathic pain, and to be considered as a putative therapeutic agent for treating PNI.

Methods

PNI models were constructed with 8-week-old adult male ICR mice and treated with NGF, MaR1 or saline by local application, intrathecal injection or intraplantar injection. Behavioral analysis and muscle atrophy test were assessed after treatment. Immunofluorescence assay was performed to examine the expression of ATF-3, GFAP, IBA1, and NF200. The expression transcript levels of inflammatory factors IL1β, IL-6, and TNF-α were detected by quantitative real-time RT-PCR. AKT, ERK, mTOR, PI3K, phosphorylated AKT, phosphorylated ERK, phosphorylated mTOR, and phosphorylated PI3K levels were examined by western blot analysis. Whole-cell patch-clamp recordings were executed to detect transient receptor potential vanilloid 1 (TRPV1) currents.

Results

MaR1 demonstrated a more robust ability to promote sensory and motor function recovery in mice after sciatic nerve crush injury than NGF. Immunohistochemistry analyses showed that the administration of MaR1 to mice with nerve crush injury reduced the number of damaged DRG neurons, promoted injured nerve regeneration and inhibited gastrocnemius muscle atrophy. Western blot analysis of ND7/23 cells cultured with MaR1 or DRG neurons collected from MaR1 treated mice revealed that MaR1 regulated neurite outgrowth through the PI3K–AKT–mTOR signaling pathway. Moreover, MaR1 dose-dependently attenuated the mechanical allodynia and thermal hyperalgesia induced by nerve injury. Consistent with the analgesic effect, MaR1 inhibited capsaicin-elicited TRPV1 currents, repressed the nerve injury-induced activation of spinal microglia and astrocytes and reduced the production of proinflammatory cytokines in the spinal cord dorsal horn in PNI mice.

Conclusions

Application of MaR1 to PNI mice significantly promoted nerve regeneration and alleviated neuropathic pain, suggesting that MaR1 is a promising therapeutic agent for PNI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02405-1.

Protective effect of Apremilast against LPS-induced acute lung injury via modulation of oxidative stress and inflammation: Possible involvement of Akt and ERK signaling pathways

Lung injuries are attributed due to exposure to Drugs or chemicals. One of the important challenging situations for the clinicians is to manage treatments of different diseases with acute lung injury (ALI). The objective of this study was to investigate the possible protective mechanisms and action of a novel Phosphodiesterase-4 inhibitor “Apremilast” (AP) in lipopolysaccharide (LPS)-induced lung injury. Blood sample from each animals were collected in a vacuum blood collection tube. The rat lungs were isolated for oxidative stress assessment, western blot analysis and their mRNA expressions using RT-PCR. Exposure of LPS in rats causes significant increase in oxidative stress, activates the pro-inflammatory cytokines release like tissue necrotic factor-alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6), modulated gene expression, protein expression and histopathological changes which were reversed by administration of AP. Finding of the research enlighten the protective role of AP against LPS-induced ALI.

Delayed inhibition of ERK and p38 attenuates neuropathic pain without affecting motor function recovery after peripheral nerve injury

Peripheral nerve injuries (PNIs) often result in persistent neuropathic pain, seriously affecting quality of life. Existing therapeutic interventions for PNI-induced neuropathic pain are far from satisfactory. Extracellular signal-regulated kinases (ERKs) and p38 have been found to participate in triggering and maintaining PNI-induced neuropathic pain. However, ERK and p38 also contribute to axonal regeneration and motor function recovery after PNI, making it difficult to inhibit ERK and p38 for therapeutic purposes. In this study, we simultaneously characterized neuropathic pain and motor function recovery in a mouse sciatic nerve crush injury model to identify the time window for therapeutic interventions. We further demonstrated that delayed delivery of a combination of ERK and p38 inhibitors at three weeks after PNI could significantly alleviate PNI-induced neuropathic pain without affecting motor function recovery. Additionally, the combined use of these two inhibitors could suppress pain markedly better than either inhibitor alone, possibly reducing the required dose of each inhibitor and alleviating the side effects and risks of the inhibitors when used individually.

Therapeutic Potential of Complementary and Alternative Medicines in Peripheral Nerve Regeneration: A Systematic Review

Despite the progressive advances, current standards of treatments for peripheral nerve injury do not guarantee complete recovery. Thus, alternative therapeutic interventions should be considered. Complementary and alternative medicines (CAMs) are widely explored for their therapeutic value, but their potential use in peripheral nerve regeneration is underappreciated. The present systematic review, designed according to guidelines of Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols, aims to present and discuss the current literature on the neuroregenerative potential of CAMs, focusing on plants or herbs, mushrooms, decoctions, and their respective natural products. The available literature on CAMs associated with peripheral nerve regeneration published up to 2020 were retrieved from PubMed, Scopus, and Web of Science. According to current literature, the neuroregenerative potential of Achyranthes bidentata, Astragalus membranaceus, Curcuma longa, Panax ginseng, and Hericium erinaceus are the most widely studied. Various CAMs enhanced proliferation and migration of Schwann cells in vitro, primarily through activation of MAPK pathway and FGF-2 signaling, respectively. Animal studies demonstrated the ability of CAMs to promote peripheral nerve regeneration and functional recovery, which are partially associated with modulations of neurotrophic factors, pro-inflammatory cytokines, and anti-apoptotic signaling. This systematic review provides evidence for the potential use of CAMs in the management of peripheral nerve injury.

The relation between mitogen activated protein kinase (MAPK) pathway and different genes expression in patients with beta Thalassemia

BACKGROUND

β-thalassemia is an inherited hemoglobinopathy resulting in quantitative changes in the β-globin chain. Understanding the molecular basis of that disorder requires studying the expression of genes controlling the pathways that affect the erythropoietic homeostasis especially the MAPK pathway. The MAPKs are a family of serine/threonine kinases that play an essential role in connecting cell-surface receptors to DNA in the nucleus of the cell.

AIM

to study the effect of expression of GNAI2, DUSP5 and ARRB1 genes on MAPK signaling pathway in pediatric patients with beta thalassemia.

METHODS

Forty children with beta thalassemia major (TM), forty children with beta thalassemia intermedia (TI) and forty age and gender matched healthy controls were enrolled in this study. Detection of GNAI2, DUSP5 and ARRB1 mRNA expression was done by real time polymerase chain reaction (RT-PCR).

RESULTS

revealed increased expression of ARRB1 (Arrestin Beta 1) gene, and decreased expression of both GNAI2 (Guanine nucleotide-binding protein G (i) subunit alpha-2) and DUSP5 (Dual specificity protein phosphatase 5) genes in both patient groups than control groups respectively.

CONCLUSIONS

Change in the rate of expression of ARRB1, GNAI2 and DUSP5 may have a role in the pathogenesis of abnormal hematopoiesis in cases of β thalassemia through affecting the MAPK pathway.

Blockade of metabotropic glutamate receptor 5 attenuates axonal degeneration in 6-hydroxydopamine-induced model of Parkinson's disease

Although there are numerous strategies to counteract the death of dopaminergic neurons in Parkinson's disease (PD), there are currently no treatments that delay or prevent the disease course, indicating that early protective treatments are needed. Targeting axonal degeneration, a key initiating event in PD, is required to develop novel therapies; however, its underlying molecular mechanisms are not fully understood. Here, we studied axonal degeneration induced by 6-hydroxydopamine (6-OHDA) in vitro and in vivo. We found that metabotropic glutamate receptor 5 (mGluR5) expression increased during 6-OHDA-induced axonal degeneration in primary neurons and that blockade of mGluR5 by its antagonists 2-methyl-6-(phenylethynyl)-pyridine (MPEP) and 3-[(2-methyl-1, 3-thiazol-4-yl) ethynyl]-pyridine (MTEP) almost completely attenuated the degenerative process in vitro. Furthermore, a rapid increase in intra-axonal calcium levels following 6-OHDA treatment was visualized using a calcium-sensitive fluorescence probe and a calcium chelator prevented the axonal degenerative process induced by 6-OHDA in vitro, whereas application of the mGluR5 antagonist MPEP partially attenuated the increase in intra-axonal calcium. The screening of calcium targets revealed that calpain activation and an increase in phosphorylated extracellular signal-regulated kinase (p-ERK) were calcium dependent during 6-OHDA-induced axonal degeneration in vitro. Consistent with these in vitro findings, blockade of mGluR5 with MPEP attenuated the degeneration of dopaminergic axons induced by 6-OHDA injection into the striatum prior to soma death in the early stage of PD in an in vivo animal model. In addition, MPEP inhibited the increase in mGluR5 expression levels, calpain activation and the elevation of p-ERK in the striatum triggered by 6-OHDA injection in vivo. Taken together, these data identify an mGluR5-calcium-dependent cascade that causes axonal degeneration, and suggest that mGluR5 antagonists could provide effective therapy to prevent the disease process of PD.

Activated Erk Is an Early Retrograde Signal After Spinal Cord Injury in the Lamprey

We previously reported that spinal cord transection (TX) in the lamprey causes mRNA to accumulate in the injured tips of large reticulospinal (RS) axons. We sought to determine whether this mRNA accumulation results from phosphorylation and transport of retrograde signals, similar to what has been reported in mammalian peripheral nerve. Extracellular signal-regulated protein kinase (Erk), mediates the neurite outgrowth-promoting effects of many neurotrophic factors. To assess the role of Erk in retrograde signaling of RS axon injury, we used immunoblot and immunohistochemistry to determine the changes in phosphorylated Erk (p-Erk) in the spinal cord after spinal cord TX. Immunostaining for p-Erk increased within axons and local cell bodies, most heavily within the 1-2 mm closest to the TX site, at between 3 and 6 h post-TX. In axons, p-Erk was concentrated in 3-5 μm granules that became less numerous with distance from the TX. The retrograde molecular motor dynein colocalized with p-Erk, but vimentin, which in peripheral nerve was reported to participate with p-Erk as part of a retrograde signal complex, did not colocalize with p-Erk, even though vimentin levels were elevated post-TX. The results suggest that p-Erk, but not vimentin, may function as a retrograde axotomy signal in lamprey central nervous system neurons, and that this signal may induce transcription of mRNA, which is then transported down the axon to its injured tip.

Bioactive Glasses and Glass/Polymer Composites for Neuroregeneration: Should We Be Hopeful?

Bioactive glasses (BGs) have been identified as highly versatile materials in tissue engineering applications; apart from being used for bone repair for many years, they have recently shown promise for the regeneration of peripheral nerves as well. They can be formulated in different shapes and forms (micro-/nanoparticles, micro-/nanofibers, and tubes), thus potentially meeting the diverse requirements for neuroregeneration. Mechanical and biological improvements in three-dimensional (3D) polymeric scaffolds could be easily provided by adding BGs to their composition. Various types of silicate, borate, and phosphate BGs have been examined for use in neuroregeneration. In general, BGs show good compatibility with the nervous system compartments both in vitro and in vivo. Functionalization and surface modification plus doping with therapeutic ions make BGs even more effective in peripheral nerve regeneration. Moreover, the combination of BGs with conductive polymers is suggested to improve neural cell functions at injured sites. Taking advantage of BGs combined with novel technologies in tissue engineering, like 3D printing, can open new horizons in reconstructive approaches for the nervous system. Although there are great potential opportunities in BG-based therapies for peripheral nerve regeneration, more research should still be performed to carefully assess the pros and cons of BGs in neuroregeneration strategies.

The Mechanism of MAPK Signal Transduction Pathway Involved with Electroacupuncture Treatment for Different Diseases

The mitogen-activated protein kinase (MAPK) signal transduction pathway plays an important role in the regulation of various diseases, such as cardiovascular and cerebrovascular diseases, and takes part in anti-inflammatory effects, analgesic effects, protection against injury, and maintenance of gastrointestinal functions. Electroacupuncture therapy is an external therapy used in traditional Chinese medicine. By adding external electrical stimulation to traditional acupuncture, the stimulus gets doubled and the therapeutic efficacy gets enhanced accordingly. It combines the benefits of both acupuncture and electrical stimulation. In recent years, some studies have explored the molecular mechanisms of MAPK signal pathways involved with electroacupuncture treatment. Based on these recent studies, this article summarizes the mechanisms of MAPK signal transduction pathways involved with electroacupuncture treatment. This adds great value to the studies of molecular mechanisms of electroacupuncture treatment and also provides an effective reference for its clinical use.

Promotion of Peripheral Nerve Regeneration by Stimulation of the Extracellular Signal-Regulated Kinase (ERK) Pathway

Peripherally projecting neurons undergo significant morphological changes during development and regeneration. This neuroplasticity is controlled by growth factors, which bind specific membrane bound kinase receptors that in turn activate two major intracellular signal transduction cascades. Besides the PI3 kinase/AKT pathway, activated extracellular signal‐regulated kinase (ERK) plays a key role in regulating the mode and speed of peripheral axon outgrowth in the adult stage. Cell culture studies and animal models revealed that ERK signaling is mainly involved in elongative axon growth in vitro and long‐distance nerve regeneration in vivo. Here, we review ERK dependent morphological plasticity in adult peripheral neurons and evaluate the therapeutic potential of interfering with regulators of ERK signaling to promote nerve regeneration. Anat Rec, 302:1261–1267, 2019. © 2019 Wiley Periodicals, Inc.

Fluorescence-Based Analysis of Noncanonical Functions of Aminoacyl-tRNA Synthetase-Interacting Multifunctional Proteins (AIMPs) in Peripheral Nerves

Aminoacyl-tRNA synthetase-interacting multifunctional proteins (AIMPs) are auxiliary factors involved in protein synthesis related to aminoacyl-tRNA synthetases (ARSs). AIMPs, which are well known as nonenzymatic factors, include AIMP1/p43, AIMP2/p38, and AIMP3/p18. The canonical functions of AIMPs include not only protein synthesis via multisynthetase complexes but also maintenance of the structural stability of these complexes. Several recent studies have demonstrated nontypical (noncanonical) functions of AIMPs, such as roles in apoptosis, inflammatory processes, DNA repair, and so on. However, these noncanonical functions of AIMPs have not been studied in peripheral nerves related to motor and sensory functions. Peripheral nerves include two types of structures: peripheral axons and Schwann cells. The myelin sheath formed by Schwann cells produces saltatory conduction, and these rapid electrical signals control motor and sensory functioning in the service of survival in mammals. Schwann cells play roles not only in myelin sheath formation but also as modulators of nerve degeneration and regeneration. Therefore, it is important to identify the main functions of Schwann cells in peripheral nerves. Here, using immunofluorescence technique, we demonstrated that AIMPs are essential morphological indicators of peripheral nerve degeneration, and their actions are limited to peripheral nerves and not the dorsal root ganglion and the ventral horn of the spinal cord.

Electroacupuncture promotes peripheral nerve regeneration after facial nerve crush injury and upregulates the expression of glial cell-derived neurotrophic factor

The efficacy of electroacupuncture in the treatment of peripheral facial paralysis is known, but the specific mechanism has not been clarified. Glial cell-derived neurotrophic factor (GDNF) has been shown to protect neurons by binding to N-cadherin. Our previous results have shown that electroacupuncture could increase the expression of N-cadherin mRNA in facial neurons and promote facial nerve regeneration. In this study, the potential mechanisms by which electroacupuncture promotes nerve regeneration were elucidated through assessing the effects of electroacupuncture on GDNF and N-cadherin expression in facial motoneurons of rabbits with peripheral facial nerve crush injury. New Zealand rabbits were randomly divided into a normal group (normal control, n = 21), injury group (n = 45) and electroacupuncture group (n = 45). Model rabbits underwent facial nerve crush injury only. Rabbits in the electroacupuncture group received facial nerve injury, and then underwent electroacupuncture at Yifeng (TE17), Jiache (ST6), Sibai (ST2), Dicang (ST4), Yangbai (GB14), Quanliao (SI18), and Hegu (LI4; only acupuncture, no electrical stimulation). The results showed that in behavioral assessments, the total scores of blink reflex, vibrissae movement, and position of apex nasi, were markedly lower in the EA group than those in the injury group. Hematoxylin-eosin staining of the right buccinator muscle of each group showed that the cross-sectional area of buccinator was larger in the electroacupuncture group than in the injury group on days 1, 14 and 21 post-surgery. Toluidine blue staining of the right facial nerve tissue of each group revealed that on day 14 post-surgery, there was less axonal demyelination and fewer inflammatory cells in the electroacupuncture group compared with the injury group. Quantitative real time-polymerase chain reaction showed that compared with the injury group, N-cadherin mRNA levels on days 4, 7, 14 and 21 and GDNF mRNA levels on days 4, 7 and 14 were significantly higher in the electroacupuncture group. Western blot assay displayed that compared with the injury group, the expression of GDNF protein levels on days 7, 14 and 21 were significantly upregulated in the electroacupuncture group. The histology with hematoxylin-eosin staining and Nissl staining of brainstem tissues containing facial neurons in the middle and lower part of the pons exhibited that on day 7 post-surgery, there were significantly fewer apoptotic neurons in the electroacupuncture group than in the injury group. By day 21, there was no significantly difference in the number of neurons between the electroacupuncture and normal groups. Taken together, these results have confirmed that electroacupuncture promotes regeneration of peripheral facial nerve injury in rabbits, inhibits neuronal apoptosis, and reduces peripheral inflammatory response, resulting in the recovery of facial muscle function. This is achieved by up-regulating the expression of GDNF and N-cadherin in central facial neurons.

Berberine promotes nerve regeneration through IGFR‑mediated JNK‑AKT signal pathway

Berberine presents therapeutic ability for various central nervous system disorders, including Alzheimer's disease and cerebral ischemia. The present study investigated the role of berberine in nerve regeneration and analyzed the potential mechanism mediated by berberine in hippocampal pyramidal neurons. Reverse transcription-quantitative poylmerase chain reaction, western blot, TUNEL assay and immunofluorescence were used to analyze the therapeutic effects of berberine on nerve regeneration. Berberine treatment increased growth and viability of hippocampal pyramidal neurons. Berberine treatment inhibited apoptosis of hippocampal pyramidal neurons and increased apoptosis regulator Bcl-2 and Bcl-w expression. Neuroinflammation of tumor necrosis factor α, interleukin (IL)1β, IL6 levels and autophagy-related proteins microtubule-associated proteins 1A/1B light chain 3B, autophagy related 16 like 1 and autophagy related 7 were downregulated by berberine treatment in hippocampal pyramidal neurons. Notably, study has found that berberine increased insulin-like growth factor receptor (IGFR) and decreased c-Jun N-terminal kinase (JNK) and protein kinase B (AKT) expression in hippocampal pyramidal neurons. IGFR antagonist abolished berberine-increased growth of hippocampal pyramidal neurons. In conclusion, these results indicate that berberine can promote nerve regeneration through IGFR-mediated JNK-AKT signal pathway.