Regeneration mechanisms and therapeutic strategies for neuromuscular junctions in aging and diseases

The neuromuscular junction(NMJ)is an essential synaptic structure composed of motor neurons,skeletal muscles,and glial cells that orchestrate the critical process of muscle contraction(Li et al.,2018).The typical NMJ structure is classically described as having a“pretzel-like”shape in mice(Figure 1),whereas human NMJs have a smaller,fragmented structure throughout adulthood.Degenerated NMJs exhibit smaller or fragmented endplates,partial denervation,reduced numbers of synaptic vesicles,abnormal presynaptic mitochondria,and dysfunctional perisynaptic Schwann cells(Alhindi et al.,2022).

Gene expression profiling and endothelin in acute experimental pancreatitis

AIM:To analyze gene expression profiles in an experimental pancreatitis and provide functional reversal of hypersensitivity with candidate gene endothelin-1 antagonists.METHODS:Dibutyltin dichloride(DBTC) is a chemical used as a polyvinyl carbonate stabilizer/catalyzer,biocide in agriculture,antifouling agent in paint and fabric.DBTC induces an acute pancreatitis flare through generation of reactive oxygen species.Lewis-inbred rats received a single i.v.injection with either DBTC or vehicle.Spinal cord and dorsal root ganglia(DRG) were taken at the peak of inflammation and processed for transcriptional profiling with a cDNA microarray biased for rat brain-specific genes.In a second study,groups of animals with DBTC-induced pancreatitis were treated with endothelin(ET) receptor antagonists [ET-A(BQ123) and ET-B BQ788)].Spontaneous pain related mechanical and thermal hypersensitivity were measured.Immunohistochemical analysis was performed using anti-ET-A and ET-B antibodies on sections from pancreatic tissues and DRG of the T10-12 spinal segments.RESULTS:Animals developed acute pancreatic inflammation persisting 7-10 d as confirmed by pathological studies(edema in parenchyma,loss of pancreatic architecture and islets,infiltration of inflammatory cells,neutrophil and mononuclear cells,degeneration,vacuolization and necrosis of acinar cells) and the painrelated behaviors(cutaneous secondary mechanical and thermal hypersensitivity).Gene expression profile was different in the spinal cord from animals with pancreatitis compared to the vehicle control group.Over 260 up-regulated and 60 down-regulated unique genes could be classified into 8 functional gene families:circulatory/acute phase/immunomodulatory;extracellular matrix;structural;channel/receptor/transporter;signaling transduction;transcription/translation-related;antioxidants/chaperones/heat shock;pancreatic and other enzymes.ET-1 was among the 52 candidate genes upregulated greater than 2-fold in animals with pancreatic inflammation and visceral pain-related behavior.Treatments with the ET-A(BQ123) and ET-B(BQ-788) antagonists revealed significant protection against inflammatory pain related mechanical and thermal hypersensitivity behaviors in animals with pancreatitis(P < 0.05).Open field spontaneous behavioral activity(at baseline,day 6 and 30 min after drug treatments(BQ123,BQ788) showed overall stable activity levels indicating that the drugs produced no undesirable effects on normal exploratory behaviors,except for a trend toward reduction of the active time and increase in resting time at the highest dose(300 μmol/L).Immunocytochemical localization revealed that expression of ET-A and ET-B receptors increased in DRG from animals with pancreatitis.Endothelin receptor localization was combined in dual staining with neuronal marker NeuN,and glia marker,glial fibrillary acidic protein.ET-A was expressed in the cell bodies and occasional nuclei of DRG neurons in na ve animals.However,phenotypic expression of ET-A receptor was greatly increased in neurons of all sizes in animals with pancreatitis.Similarly,ET-B receptor was localized in neurons and in the satellite glia,as well as in the Schwann cell glial myelin sheaths surrounding the axons passing through the DRG.CONCLUSION:Endothelin-receptor antagonists protect against inflammatory pain responses without interfering with normal exploratory behaviors.Candidate genes can serve as future biomarkers for diagnosis and/or targeted gene therapy.

The suppressor of cytokine signalling 2(SOCS2),traumatic brain injury and microglial/macrophage regulation

Traumatic brain injury （TBI） results in a range of neuroinflam- matory events that vary depending on the type and extent of in- jury. Central to this is the activation of tissue resident microglia and infiltration of peripheral macrophages, which phagocytose debris and/or secrete a range of cytokines, chemokines and oth- er factors which modify the injured environment to promote or inhibit repair （Schwartz et al., 2013）. The reactive macro- phages/microglia are broadly divided into two categories.

Optimising validity and translational potential in rodent models of brain disorders

Neurological and psychiatric disorders collectively constitute the greatest burden of disease. However, the human brain is the most complex of biological systems and therefore accurately modeling brain disorders presents enormous challenges. A large range of therapeutic approaches across a diverse collection of brain disorders have been found to show great promise in preclinical testing and then failed during clinical trials. There are a variety of potential reasons for such failures, on both the preclinical and clinical sides of the equation. In this article, I wi l l focus on the key issues of validity in animal models. I wi l l discuss two forms of construct validity,‘genetic construct validity’ and ‘environmental construct val idity’,which model specific aspects of the genome and ‘envirome’ relevant to the disorder in question. The generation of new gene-edited animal models has been facilitated by new technologies, the most notable of which are CRISPR-Cas systems. These and other technologies can be used to enhance contruct validity. Finally, I wi l l discuss how face validity can be optimized, via more sophisticated cognitive, affective and motor behavioural tests, translational tools and the integration of molecular, cellular and systems data. Predictive validity cannot yet be assessed for the many preclinical models where we currently lack effective clinical interventions, however this wi l l change as the translational pipeline is honed to deliver therapies for a range of devastating disorders.

Convergence of neuro-endocrine-immune pathways in the pathophysiology of irritable bowel syndrome

Disordered signalling between the brain and the gut are generally accepted to underlie the functional bowel disorder, irritable bowel syndrome(IBS). However, partly due to the lack of disease-defining biomarkers, understanding the aetiology of this complex and multifactorial disease remains elusive. This common gastrointestinal disorder is characterised by alterations in bowel habit such as diarrhoea and/or constipation, bloating and abdominal pain, and symptom exacerbation has been linked with periods of stress, both psychosocial and infection-related. Indeed, a high level of comorbidity exists between IBS and stress-related mood disorders such as anxiety and depression. Moreover, studies have observed alterations in autonomic output and neuro-endocrine signalling in IBS patients. Accumulating evidence indicates that a maladaptive stress response, probably mediated by the stress hormone, corticotropin-releasing factor contributes to the initiation, persistence and severity of symptom flares.Other risk factors for developing IBS include a positive family history, childhood trauma, dietary factors and prior gastrointestinal infection. An emerging role has been attributed to the importance of immune factors in the pathophysiology of IBS with evidence of altered cytokine profiles and increased levels of mucosal immune cells. These factors have also been shown to have direct effects on neural signalling. This review discusses how pathological changes in neural, immune and endocrine pathways, and communication between these systems, contribute to symptom flares in IBS.

The potential of bone morphogenetic protein 2 as a neurotrophic factor for Parkinson’s disease

Parkinson’s disease is the second most common neurodegenerative disorder;it affects 1%of the population over the age of 65.The number of people with Parkinson’s disease is set to rapidly increase due to changing demographics and there is an unmet clinical need for disease-modifying therapies.The pathological hallmarks of Parkinson’s disease are the progressive degeneration of dopaminergic neurons in the substantia nigra and their axons which project to the striatum,and the aggregation ofα-synuclein;these result in a range of debilitating motor and non-motor symptoms.The application of neurotrophic factors to protect and potentially regenerate the remaining dopaminergic neurons is a major area of research interest.However,this strategy has had limited success to date.Clinical trials of two well-known neurotrophic factors,glial cell line-derived neurotrophic factor and neurturin,have reported limited efficacy in Parkinson’s disease patients,despite these factors showing potent neurotrophic actions in animal studies.There is therefore a need to identify other neurotrophic factors that can protect againstα-synuclein-induced degeneration of dopaminergic neurons.The bone morphogenetic protein(BMP)family is the largest subgroup of the transforming growth factor-βsuperfamily of proteins.BMPs are naturally secreted proteins that play crucial roles throughout the developing nervous system.Importantly,many BMPs have been shown to be potent neurotrophic factors for dopaminergic neurons.Here we discuss recent work showing that transcripts for the BMP receptors and BMP2 are co-expressed with several key markers of dopaminergic neurons in the human substantia nigra,and evidence for downregulation of BMP2 expression at distinct stages of Parkinson’s disease.We also discuss studies that explored the effects of BMP2 treatment,in in vitro and in vivo models of Parkinson’s disease.These studies found potent effects of BMP2 on dopaminergic neurites,which is important given that axon degeneration is increasingly recognized as a key early event in Parkinson’s disease.Thus,the aim of this mini-review is to give an overview of the BMP family and the BMP-Smad signalling pathway,in addition to reviewing the available evidence demonstrating the potential of BMP2 for Parkinson’s disease therapy.

Neurotrophic factor therapy for Parkinson's disease: past, present and future

One of the greatest unmet needs in the treatment of Parkinson’s disease（PD）is a disease-modifying therapy,which can halt the ongoing degeneration of dopaminergic neurons that is characteristic of this disorder.Current therapies focus on managing symptoms,rather than on addressing their cause.Promising candidates for disease-modifying therapies are the dopaminergic neurotrophic factors（NTFs）.

Regulation of cell adhesion in the testis： a new role for p73

The dramatic changes that male germ cells in the adult testis undergo in gene expression profile and morphology as they transition from spermatogonial stem cells through to mature spermatozoa is dependent upon their association with Sertoli cells. Sertoli cells are crucial for survival and maturation of male germ cells. Two recent papers, Holembowski et al？ and Inoue et a13 have described a surprising role for the p53 family member, p73, in regulation of germ cell-Sertoli cell adhesion.

A role for mitogen-activated protein kinase phosphatase 1(MKP1) in neural cell development and survival

The mitogen-activated protein kinase（MAPK）pathways are a group of conserved intracellular signalling pathways present in most cells including neurons and glia.These pathways respond to a variety of stimuli including growth factors,cytokines and oxidative stress to generate appropriate cellular responses such as modulation of gene expression,cell proliferation,differentiation and survival as well as the stress response（Korhonen and Moilanen,2014）.

Gastric pentadecapeptide BPC 157 in cytoprotection to resolve major vessel occlusion disturbances,ischemia-reperfusion injury following Pringle maneuver,and Budd-Chiari syndrome

The stable gastric pentadecapeptide BPC 157 counteracts various venous occlusion-induced syndromes.Summarized are all these arguments,in the Robert’s cytoprotection concept terms,to substantiate the resolution of different major vessel occlusion disturbances,in particular ischemia-reperfusion injury following the Pringle maneuver and Budd-Chiari syndrome,which was obtained by BPC 157 therapy.Conceptually,there is new point(bypassed occluded or ruptured vessel,the equation endothelium maintenance→epithelium maintenance=blood vessel recruitment and activation towards defect or bypassing vessel occlusion),the recruitment of collateral blood vessels to compensate for vessel occlusion and reestablish blood flow.In this paper,we summarize the evidence of the native cytoprotective gastric pentadecapeptide BPC 157,which is stable in the human gastric juice,is a membrane stabilizer and counteracts gut-leaky syndrome.As a particular target,it is distinctive from the standard peptide growth factors,with particular molecular pathways involved,controlling VEGF and NO pathways.In the early 1990s,BPC 157 appeared as a late outbreak of the Robert’s and Szabo’s cytoprotection-organoprotection concept,epithelium,endothelium protection as previous theoretical/practical breakthrough in the 1980s,and brain-gut axis and gut-brain axis.As the time went on,with its reported effects,it is likely most useful theory practical implementation and justification.Meantime,several reviews suggest that BPC 157,which does not have a lethal dose(LD1),has profound cytoprotective activity,used to be demonstrated in ulcerative colitis and invented to multiple sclerosis trials.Likely,it may bring the theory to practical application,starting with the initial argument,no degradation in human gastric juice for more than 24 h,and thereby,the therapeutic effectiveness(including therapeutic per-oral regimen)and pleiotropic beneficial effects.

Irritable bowel syndrome: A microbiome-gut-brain axis disorder?

Irritable bowel syndrome(IBS) is an extremely prevalent but poorly understood gastrointestinal disorder. Consequently, there are no clear diagnostic markers to help diagnose the disorder and treatment options are limited to management of the symptoms. The concept of a dysregulated gut-brain axis has been adopted as a suitable model for the disorder. The gut microbiome may play an important role in the onset and exacerbation of symptoms in the disorder and has been extensively studied in this context. Although a causal role cannot yet be inferred from the clinical studies which have attempted to characterise the gut microbiota in IBS, they do confirm alterations in both community stability and diversity. Moreover, it has been reliably demonstrated that manipulation of the microbiota can influence the key symptoms, including abdominal pain and bowel habit, and other prominent features of IBS. A variety of strategies have been taken to study these interactions, including probiotics, antibiotics, faecal transplantations and the use of germ-free animals. There are clear mechanisms through which the microbiota can produce these effects, both humoral and neural. Taken together, these findings firmly establish the microbiota as a critical node in the gut-brain axis and one which is amenable to therapeutic interventions.

Neurotrophic factors: from neurodevelopmental regulators to novel therapies for Parkinson's disease

Neuroprotection and neuroregeneration are two of the most promising disease-modifying ther- apies for the incurable and widespread Parkinson＇s disease. In Parkinson＇s disease, progressive degeneration of nigrostriatal dopaminergic neurons causes debilitating motor symptoms. Neurotrophic factors play important regulatory roles in the development, survival and maintenance of specific neuronal populations. These factors have the potential to slow down, halt or reverse the loss of nigrostriatal dopaminergic neurons in Parkinsoffs disease. Several neurotrophic fac- tors have been investigated in this regard. This review article discusses the neurodevelopmental roles and therapeutic potential of three dopaminergic neurotrophic factors： glial cell line-derived neurotrophic factor, neurturin and growth/differentiation factor 5.

Transient receptor potential channel A1 involved in calcitonin gene-related peptide release in neurons

Transient receptor potential channel A1 is one of the important transducers of noxious stimuli in the primary afferents, which may contribute to generation of neurogenic inflammation and hyperalgesia. The present study was designed to investigate if activation of transient receptor potential channel A1 may induce calcitonin gene-related peptide release from the primary afferent neurons. We found that application of allyl isothiocyanate, a transient receptor potential channel A1 activator, caused calcitonin gene-related peptide release from the cultured rat dorsal root ganglion neurons. Knock- down of transient receptor potential channel A1 with an antisense oligodeoxynucleotide prevented calcitonin gene-related peptide release by allyl isothiocyanate application in cultured dorsal root ganglion neurons. Thus, we concluded that transient receptor potential channel A1 activation caused calcitonin gene-related peptide release in sensory neurons.

Perspectives on neuroreparative therapies for treating multiple sclerosis

A need to develop neuroreparative therapies for multiple sclerosis（MS）：MS is the most common neurological disease of young Caucasian adults.This disease is characterized by inflammatory demyelination of the central nervous system（CNS）and involves activation of key inflammatory cells of both the adaptive and innate immune systems,which target and destroy both myelin and oligodendrocytes （the my- elin-forming glial cells in the CNS）. Key pathological features of the disease include autoimmune inflammation, axonal degeneration and demyelination （myelin loss）, latter of which can occur in both white matter and gray matter. The key cell type damaged in MS is oligodendrocytes, which produce the insulating myelin sheath surrounding many axons in the CNS. Myelin and oligodendrocytes have critical roles.

Growth differentiation factor 5:a neurotrophic factor with neuroprotective potential in Parkinson’s disease

Parkinson’s disease is the most common movement disorder worldwide,affecting over 6 million people.It is an age-related disease,occurring in 1%of people over the age of 60,and 3%of the population over 80 years.The disease is characterized by the progressive loss of midbrain dopaminergic neurons from the substantia nigra,and their axons,which innervate the striatum,resulting in the characteristic motor and non-motor symptoms of Parkinson’s disease.This is paralleled by the intracellular accumulation ofα-synuclein in several regions of the nervous system.Current therapies are solely symptomatic and do not stop or slow disease progression.One promising disease-modifying strategy to arrest the loss of dopaminergic neurons is the targeted delivery of neurotrophic factors to the substantia nigra or striatum,to protect the remaining dopaminergic neurons of the nigrostriatal pathway.However,clinical trials of two well-established neurotrophic factors,glial cell line-derived neurotrophic factor and neurturin,have failed to meet their primary end-points.This failure is thought to be at least partly due to the downregulation byα-synuclein of Ret,the common co-receptor of glial cell line-derived neurorophic factor and neurturin.Growth/differentiation factor 5 is a member of the bone morphogenetic protein family of neurotrophic factors,that signals through the Ret-independent canonical Smad signaling pathway.Here,we review the evidence for the neurotrophic potential of growth/differentiation factor 5 in in vitro and in vivo models of Parkinson’s disease.We discuss new work on growth/differentiation factor 5’s mechanisms of action,as well as data showing that viral delivery of growth/differentiation factor 5 to the substantia nigra is neuroprotective in theα-synuclein rat model of Parkinson’s disease.These data highlight the potential for growth/differentiation factor 5 as a disease-modifying therapy for Parkinson’s disease.

The Epigenome as a therapeutic target for Parkinson's disease

Parkinson＇s disease （PD） is a common, progressive neurodegenerative disease characterised by degeneration of nigrostriatal dopaminergic neurons, aggregation of α-synuclein and motor symptoms. Current dopamine-replacement strategies provide symptomatic relief, however their effectiveness wear off over time and their prolonged use leads to disabling side-effects in PD patients. There is therefore a critical need to develop new drugs and drug targets to protect dopaminergic neurons and their axons from degeneration in PD. Over recent years, there has been robust evidence generated showing that epigenetic dysregulation occurs in PD patients, and that epigenetic modulation is a promising therapeutic approach for PD. This ar- ticle first discusses the present evidence implicating global, and dopaminergic neuron-specific, akerations in the methylome in PD, and the therapeutic potential of pharmacologically targeting the methylome. It then focuses on another mechanism of epigenetic regulation, histone acetylation, and describes how the histone acetyltransferase （HAT） and histone deacetylase （HDAC） enzymes that mediate this process are attractive therapeutic targets for PD. It discusses the use of activators and/or inhibitors of HDACs and HATs in models of PD, and how these approaches for the selective modulation of histone acetylation elicit neuroprotective effects. Finally, it outlines the potential of employing small molecule epigenetic modulators as neuroprotective therapies for PD, and the future research that will be required to determine and realise this therapeutic potential.

Targeting transcriptional regulators to regenerate midbrain dopaminergic axons in Parkinson's disease

Introduction： Parkinson＇s disease （PD） is a chronic, age-re- lated neurodegenerative disorder that affects 1-2% of the population over the age of 65. PD is characterised by the progressive degeneration of nigrostriatal dopaminergic （DA） neurons. This leads to disabling motor symptoms, due to the striatal DA denervation. Despite decades of research, there is still no therapy that can slow, stop or regenerate the dying midbrain DA neurons in PD.

The bisulfite genomic sequencing protocol

The bisulfite genomic sequencing (BGS) protocol has gained worldwide popularity as the method of choice for analyzing DNA methylation. It is this popular because it is a powerful protocol and it may be coupled with many other applications. However, users often run into a slew ofproblems, including incomplete conversion,overly degraded DNA, sub-optimal PCR amplifications, false positives, uninformative results, or altogether failed experiments. We pinpoint the reasons why these problems arise and carefully explain the critical steps toward accomplishing a successful experiment step-by-step. This protocol has worked successfully (>99.9% conversion) on as little as 100 ng of DNA derived from nearly 10-year-old DNA samples extracted from whole blood stored at -80°C and resulted in enough converted DNA for more than 50 PCRreactions. The aim of this article is to makelearning and usage of BGS easier, more efficient and standardized for all users.

Ndfip1 represses cell proliferation by controlling Pten localization and signaling specificity

Pten controls a signaling axis that is implicated to regulate cell proliferation,growth,survival,migration,and metabolism.The molecular mechanisms underlying the specificity of Pten responses to such diverse cellular functions are currently poorly understood.Herewe report the control of Pten activity and signaling specificity during the cell cycle by Ndfip1 regulation of Pten spatial distribution.Genetic deletion of Ndfip1 resulted in a loss of Pten nuclear compartmentalization and increased cell proliferation,despite cytoplasmic Pten remaining active in regulating PI3K/Akt signaling.Cells lacking nuclear Pten were found to have dysregulated levels of Plk1 and cyclin D1 that could drive cell proliferation.In vivo,transgene expression of Ndfip1 in the developing brain increased nuclear Pten and lengthened the cell cycle of neuronal progenitors,resulting in microencephaly.Our results show that local partitioning of Pten from the cytoplasm to the nucleus represents a key mechanism contributing to the specificity of Pten signaling during cell proliferation.

Discovery of novel diarylamides as orally active diuretics targeting urea transporters

Urea transporters(UT)play a vital role in the mechanism of urine concentration and are recognized as novel targets for the development of salt-sparing diuretics.Thus,UT inhibitors are promising for development as novel diuretics.In the present study,a novel UT inhibitor with a diarylamide scaffold was discovered by high-throughput screening.Optimization of the inhibitor led to the identifi-cation of a promising preclinical candidate,N-[4-(acetylamino)phenyl]-5-nitrofuran-2-carboxamide(1 H),with excellent in vitro UT inhibitory activity at the submicromolar level.The half maximal inhibitory concentrations of 1 H against UT-B in mouse,rat,and human erythrocyte were 1.60,0.64,and0.13 mmol/L,respectively.Further investigation suggested that 8 mmol/L 1 H more powerfully inhibited UT-A1 at a rate of 86.8%than UT-B at a rate of 73.9%in MDCK cell models.Most interestingly,we found for the first time that oral administration of 1 H at a dose of 100 mg/kg showed superior diuretic effect in vivo without causing electrolyte imbalance in rats.Additionally,1 H did not exhibit apparent toxicity in vivo and in vitro,and possessed favorable pharmacokinetic characteristics.1 H shows promise as a novel diuretic to treat hyponatremia accompanied with volume expansion and may cause few side effects.