Artemin and an Artemin-Derived Peptide, Artefin, Induce Neuronal Survival, and Differentiation Through Ret and NCAM

Emerging evidence of artemin/GFRα3 signaling in musculoskeletal pain

Chronic musculoskeletal pain is highly prevalent and poses a significant personal, societal, and economic burden. Management of chronic musculoskeletal pain remains a challenge. Long-term use of common analgesic medications such as nonsteroidal anti-inflammatory drugs and opioids is associated with adverse events, and in the case of opioids, drug addiction. Additionally, many individuals do not experience sufficient pain relief with these therapeutic approaches. Thus, there is an urgent need to develop clinically efficacious and safe therapeutics for musculoskeletal pain. Recent advances in our understanding of musculoskeletal pain neurobiology have helped identify the role of neurotrophic factors, specifically, the glial cell line-derived neurotrophic factor (GDNF) family of ligands (GFL) and their associated signaling pathways. This review outlines our current understanding of the GFL signaling systems, discusses their role in inflammatory and chronic musculoskeletal pain and sensitivity, and comments on the analgesic therapeutic potential of targeting the GFL signaling system.

NOCICEPTOR NEURONS CONTROL POLLUTION-MEDIATED NEUTROPHILIC ASTHMA

The immune and sensory nervous systems, having evolved together, use a shared language of receptors and transmitters to maintain homeostasis by responding to external and internal disruptions. Although beneficial in many cases, neurons can exacerbate inflammation during allergic reactions, such as asthma. Our research modeled asthma aggravated by pollution, exposing mice to ambient PM2.5 particles and ovalbumin. This exposure significantly increased bronchoalveolar lavage fluid neutrophils and γδ T cells compared to exposure to ovalbumin alone. We normalized airway inflammation and lung neutrophil levels by silencing nociceptor neurons at inflammation's peak using intranasal QX-314 or ablating TRPV1-expressing neurons. Additionally, we observed heightened sensitivity in chemical-sensing TRPA1 channels in neurons from pollution-exacerbated asthmatic mice. Elevated levels of artemin were detected in the bronchoalveolar lavage fluid from pollution-exposed mice, with artemin levels normalizing in mice with ablated nociceptor neurons. Upon exposure PM2.5 particles, alveolar macrophages expressing pollution-sensing aryl hydrocarbon receptors, were identified as the source of artemin. This molecule enhanced TRPA1 responsiveness and increased neutrophil influx, providing a novel mechanism by which lung-innervating neurons respond to air pollution and suggesting a potential therapeutic target for controlling neutrophilic airway inflammation in asthma, a clinically intractable condition.

Diverse immunological dysregulation, chronic inflammation, and impaired erythropoiesis in long COVID patients with chronic fatigue syndrome

A substantial number of patients recovering from acute SARS-CoV-2 infection present serious lingering symptoms, often referred to as long COVID (LC). However, a subset of these patients exhibits the most debilitating symptoms characterized by ongoing myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS). We specifically identified and studied ME/CFS patients from two independent LC cohorts, at least 12 months post the onset of acute disease, and compared them to the recovered group (R). ME/CFS patients had relatively increased neutrophils and monocytes but reduced lymphocytes. Selective T cell exhaustion with reduced naïve but increased terminal effector T cells was observed in these patients. LC was associated with elevated levels of plasma pro-inflammatory cytokines, chemokines, Galectin-9 (Gal-9), and artemin (ARTN). A defined threshold of Gal-9 and ARTN concentrations had a strong association with LC. The expansion of immunosuppressive CD71+ erythroid cells (CECs) was noted. These cells may modulate the immune response and contribute to increased ARTN concentration, which correlated with pain and cognitive impairment. Serology revealed an elevation in a variety of autoantibodies in LC. Intriguingly, we found that the frequency of 2B4+CD160+ and TIM3+CD160+ CD8+ T cells completely separated LC patients from the R group. Our further analyses using a multiple regression model revealed that the elevated frequency/levels of CD4 terminal effector, ARTN, CEC, Gal-9, CD8 terminal effector, and MCP1 but lower frequency/levels of TGF-β and MAIT cells can distinguish LC from the R group. Our findings provide a new paradigm in the pathogenesis of ME/CFS to identify strategies for its prevention and treatment.

Peptides derived from growth factors: Exploring their diverse impact from antimicrobial properties to neuroprotection

Growth factor-derived peptides are bioactive molecules that play a crucial role in various physiological processes within the human body. Over the years, extensive research has revealed their diverse applications, ranging from antimicrobial properties to their potential in neuroprotection and treating various diseases. These peptides exhibit innate immune responses and have been found to possess potent antimicrobial properties against a wide range of pathogens. Growth factor-derived peptides have demonstrated the ability to promote neuronal survival, prevent cell death, and stimulate neural regeneration. As a result, they hold immense promise in the treatment of various neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis, as well as in the management of traumatic brain injuries. Moreover, growth factor-derived peptides have shown potential for supporting tissue repair and wound healing processes. By enhancing cell proliferation and migration, these peptides contribute to the regeneration of damaged tissues and promote a more efficient healing response. The applications of growth factor-derived peptides extend beyond their therapeutic potential in health; they also have a role in various disease conditions. For example, researchers have explored their influence on cancer cells, where some peptides have demonstrated anti-cancer properties, inhibiting tumor growth and promoting apoptosis in cancer cells. Additionally, their immunomodulatory properties have been investigated for potential applications in autoimmune disorders. Despite the immense promise shown by growth factor-derived peptides, some challenges need to be addressed. Nevertheless, ongoing research and advancements in biotechnology offer promising avenues to overcome these obstacles. The review summarizes the foundational biology of growth factors and the intricate signaling pathways in various physiological processes as well as diseases such as cancer, neurodegenerative disorders, cardiovascular ailments, and metabolic syndromes.

Examining Differences in the Genetic and Functional Architecture of Attention-Deficit/Hyperactivity Disorder Diagnosed in Childhood and Adulthood

Background

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder with diagnostic criteria requiring symptoms to begin in childhood. We investigated whether individuals diagnosed as children differ from those diagnosed in adulthood with respect to shared and unique architecture at the genome-wide and gene expression level of analysis.

Methods

We used genomic structural equation modeling (SEM) to investigate differences in genetic correlations (rg) of childhood-diagnosed (ncases = 14,878) and adulthood-diagnosed (ncases = 6961) ADHD with 98 behavioral, psychiatric, cognitive, and health outcomes. We went on to apply transcriptome-wide SEM to identify functional annotations and patterns of gene expression associated with genetic risk sharing or divergence across the ADHD subgroups.

Results

Compared with the childhood subgroup, adulthood-diagnosed ADHD exhibited a significantly larger negative rg with educational attainment, the noncognitive skills of educational attainment, and age at first sexual intercourse. We observed a larger positive rg for adulthood-diagnosed ADHD with major depression, suicidal ideation, and a latent internalizing factor. At the gene expression level, transcriptome-wide SEM analyses revealed 22 genes that were significantly associated with shared genetic risk across the subtypes that reflected a mixture of coding and noncoding genes and included 15 novel genes relative to the ADHD subgroups.

Conclusions

This study demonstrated that ADHD diagnosed later in life shows much stronger genetic overlap with internalizing disorders and related traits. This may indicate the potential clinical relevance of distinguishing these subgroups or increased misdiagnosis for those diagnosed later in life. Top transcriptome-wide SEM results implicated genes related to neuronal function and clinical characteristics (e.g., sleep).

[Effect and mechanism of human adipose-derived stem cell exosomes on diabetic peripheral neuropathy]

Objective: To investigate the changes of artemin protein expression in diabetic peripheral neuropathy (DPN) and to explore the regulatory effect of human adipose-derived stem cell (ADSC) exosomes on the change of artemin protein expression. Methods: This research was a prospective observational clinical research combined with experimental research. Thirteen DPN patients (9 males and 4 females, aged 32 to 68 years) who were admitted to the First Affiliated Hospital of Air Force Medical University (hereinafter referred to as our hospital) from May 2022 to October 2023 and met the inclusion criteria were selected as DPN group, and 5 non-diabetes patients (4 males and 1 female, aged 29 to 61 years) who were admitted to our hospital in the same period of time and met the inclusion criteria were selected as control group. The toe nerve or sural nerve tissue in the abandoned tissue after debridement or amputation of patients in the two groups was collected. The pathological changes of nerve tissue were observed after hematoxylin-eosin staining; the protein expressions of S100β and artemin in nerve tissue were observed after immunofluorescence staining, and the artemin protein expression was quantified; the protein and mRNA expressions of artemin were detected by Western blotting and real-time fluorescent quantitative reverse transcription polymerase chain reaction, respectively (the sample number in DPN group and control group was 13 and 5, respectively). Twelve male C57BL/6 mice aged 3 to 5 days were collected to isolate Schwann cells, and the cells were divided into conventional culture group cultured routinely, high glucose alone group (cultured with high concentration of glucose solution only), and high glucose+exosome group (cultured with high concentration of glucose solution and extracted human ADSC exosomes). After 24 hours of culture, the cell proliferation activity was detected by cell counting kit 8 (n=6). After 48 hours of culture, the protein expression of artemin was detected by Western blotting (n=3). Results: Compared with those in control group, the neural supporting cells decreased and the inflammatory cells increased in the nerve tissue of patients in DPN group, showing typical manifestations of nerve injury. Immunofluorescence staining showed that compared with those in control group, the nuclei was more, and the protein expression of S100β was lower in nerve tissue of patients in DPN group. The protein expression of artemin in nerve tissue of patients in DPN group was 71±31, which was significantly lower than 1 729±62 in control group (t=76.92, P<0.05). Western blotting detection showed that the protein expression of artemin in nerve tissue of patients in DPN group was 0.74±0.08, which was significantly lower than 0.97±0.06 in control group (t=5.49, P<0.05). The artemin mRNA expression in nerve tissue of patients in DPN group was significantly lower than that in control group (t=7.65, P<0.05). After 24 hours of culture, compared with that in conventional culture group, the proliferation activities of Schwann cells in high glucose alone group and high glucose+exosome group were significantly decreased (P<0.05); compared with that in high glucose alone group, the proliferation activity of Schwann cells in high glucose+exosome group was significantly increased (P<0.05). After 48 hours of culture, compared with those in conventional culture group, the protein expressions of artemin of Schwann cells in high glucose alone group and high glucose+exosome group were significantly decreased (P<0.05); compared with that in high glucose alone group, the protein expression of artemin of Schwann cells in high glucose+exosome group was significantly increased (P<0.05). Conclusions: The protein expression of artemin in nerve tissue of DPN patients is lower than that in normal nerve tissue, which may be related to the reduction of proliferation activity of Schwann cells by high glucose. Human ADSC exosomes may improve the proliferation activity of Schwann cells by increasing artemin protein expression, thereby delaying the progression of DPN.

Growth factors and their peptide mimetics for treatment of traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of disability in adults, caused by a physical insult damaging the brain. Growth factor-based therapies have the potential to reduce the effects of secondary injury and improve outcomes by providing neuroprotection against glutamate excitotoxicity, oxidative damage, hypoxia, and ischemia, as well as promoting neurite outgrowth and the formation of new blood vessels. Despite promising evidence in preclinical studies, few neurotrophic factors have been tested in clinical trials for TBI. Translation to the clinic is not trivial and is limited by the short in vivo half-life of the protein, the inability to cross the blood-brain barrier and human delivery systems. Synthetic peptide mimetics have the potential to be used in place of recombinant growth factors, activating the same downstream signalling pathways, with a decrease in size and more favourable pharmacokinetic properties. In this review, we will discuss growth factors with the potential to modulate damage caused by secondary injury mechanisms following a traumatic brain injury that have been trialled in other indications including spinal cord injury, stroke and neurodegenerative diseases. Peptide mimetics of nerve growth factor (NGF), hepatocyte growth factor (HGF), glial cell line-derived growth factor (GDNF), brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) will be highlighted, most of which have not yet been tested in preclinical or clinical models of TBI.

Traditional Use, Phytochemical Profiles and Pharmacological Properties of Artemisia Genus from Central Asia

The flora of Kazakhstan is characterized by its wide variety of different types of medicinal plants, many of which can be used on an industrial scale. The Traditional Kazakh Medicine (TKM) was developed during centuries based on the six elements of ancient Kazakh theory, associating different fields such as pharmacology, anatomy, pathology, immunology and food nursing as well as disease prevention. The endemic Artemisia L. species are potential sources of unique and new natural products and new chemical structures, displaying diverse bioactivities and leading to the development of safe and effective phytomedicines against prevailing diseases in Kazakhstan and the Central Asia region. This review provides an overview of Artemisia species from Central Asia, particularly traditional uses in folk medicine and the recent numerous phytochemical and pharmacological studies. The review is done by the methods of literature searches in well-known scientific websites (Scifinder and Pubmed) and data collection in university libraries. Furthermore, our aim is to search for promising and potentially active Artemisia species candidates, encouraging us to analyze Protein Tyrosine Phosphatase 1B (PTP1B), α-glucosidase and bacterial neuraminidase (BNA) inhibition as well as the antioxidant potentials of Artemisia plant extracts, in which endemic species have not been explored for their secondary metabolites and biological activities so far. The main result of the study was that, for the first time, the species Artemisia scopiformis Ledeb. Artemisia albicerata Krasch., Artemisia transiliensis Poljakov, Artemisia schrenkiana Ledeb., Artemisia nitrosa Weber and Artemisia albida Willd. ex Ledeb. due to their special metabolites, showed a high potential for α-glucosidase, PTP1B and BNA inhibition, which is associated with diabetes, obesity and bacterial infections. In addition, we revealed that the methanol extracts of Artemisia were a potent source of polyphenolic compounds. The total polyphenolic contents of Artemisia extracts were correlated with antioxidant potential and varied according to plant origin, the solvent of extraction and the analytical method used. Consequently, oxidative stress caused by reactive oxygen species (ROS) may be managed by the dietary intake of current Artemisia species. The antioxidant potentials of the species A. schrenkiana, A. scopaeformis, A. transiliensis and Artemisia scoparia Waldst. & Kitam. were also promising. In conclusion, the examination of details between different Artemisia species in our research has shown that plant materials are good as an antioxidant and eznyme inhibitory functional natural source.

Cell-Based HIF1α Gene Therapy Reduces Myocardial Scar and Enhances Angiopoietic Proteome, Transcriptomic and miRNA Expression in Experimental Chronic Left Ventricular Dysfunction

Recent preclinical investigations and clinical trials with stem cells mostly studied bone-marrow-derived mononuclear cells (BM-MNCs), which so far failed to meet clinically significant functional study endpoints. BM-MNCs containing small proportions of stem cells provide little regenerative potential, while mesenchymal stem cells (MSCs) promise effective therapy via paracrine impact. Genetic engineering for rationally enhancing paracrine effects of implanted stem cells is an attractive option for further development of therapeutic cardiac repair strategies. Non-viral, efficient transfection methods promise improved clinical translation, longevity and a high level of gene delivery. Hypoxia-induced factor 1α is responsible for pro-angiogenic, anti-apoptotic and anti-remodeling mechanisms. Here we aimed to apply a cellular gene therapy model in chronic ischemic heart failure in pigs. A non-viral circular minicircle DNA vector (MiCi) was used for in vitro transfection of porcine MSCs (pMSC) with HIF1α (pMSC-MiCi-HIF-1α). pMSCs-MiCi-HIF-1α were injected endomyocardially into the border zone of an anterior myocardial infarction one month post-reperfused-infarct. Cell injection was guided via 3D-guided NOGA electro-magnetic catheter delivery system. pMSC-MiCi-HIF-1α delivery improved cardiac output and reduced myocardial scar size. Abundances of pro-angiogenic proteins were analyzed 12, 24 h and 1 month after the delivery of the regenerative substances. In a protein array, the significantly increased angiogenesis proteins were Activin A, Angiopoietin, Artemin, Endothelin-1, MCP-1; and remodeling factors ADAMTS1, FGFs, TGFb1, MMPs, and Serpins. In a qPCR analysis, increased levels of angiopeptin, CXCL12, HIF-1α and miR-132 were found 24 h after cell-based gene delivery, compared to those in untreated animals with infarction and in control animals. Expression of angiopeptin increased already 12 h after treatment, and miR-1 expression was reduced at that time point. In total, pMSC overexpressing HIF-1α showed beneficial effects for treatment of ischemic injury, mediated by stimulation of angiogenesis.

Selective targeting of chronic social stress-induced activated neurons identifies neurogenesis-related genes to be associated with resilience in female mice

Prolonged social stress is a major cause for depression in humans and is associated with a wide range of subsequent pathophysiological changes such as elevated blood pressure. A routinely used model for investigating this kind of stress in mice is the chronic social defeat paradigm where a smaller intruder is exposed to an aggressive inhabitant of a home cage. This model is restricted to males and includes a high proportion of physical stress that might e.g., interfere with immunological aspects of the stress. The prevalence of depression in humans is even higher in women than in men. Therefore, expanding models to female individuals is desirable. We here tested the social instability model as a tool for administering chronic social stress to female C57BL/6J mice and analyzed short-term as well as long-lasting effects. Animals were housed in groups of four and were shuffled two times a week, resulting in a permanent re-structuration of their social hierarchy. While directly after the stress exposure, serum corticosterone was elevated, increased body weight and fat deposits were observed in stressed mice even one year after discontinuation of the stress. At the behavioral level, animals could be stratified into resilient and susceptible animals directly post-stress, but those subgroups were not distinguishable any more in the long-term analysis. To identify molecular contributors to resilience in the here presented social instability induced stress model, Arc-activity dependent trapping of neurons was conducted in Arc-creERT2/sun1sfGFP mice. RNA samples derived from activated nuclei from the ventral hippocampus, a brain region involved in stress-regulation during attacks or explorative behavior of mice, were subjected to a neurogenesis pathway array. While several genes were differentially regulated by stress, in particular, artemin, a neurotrophic factor was upregulated in resilient versus susceptible individuals.

The Circadian Oscillator of the Cerebellum: Triiodothyronine Regulates Clock Gene Expression in Granule Cells in vitro and in the Cerebellum of Neonatal Rats in vivo

The central circadian clock resides in the suprachiasmatic nucleus (SCN) of the hypothalamus, but an SCN-dependent molecular circadian oscillator is present in the cerebellar cortex. Recent findings suggest that circadian release of corticosterone is capable of driving the circadian oscillator of the rat cerebellum. To determine if additional neuroendocrine signals act to shape cerebellar clock gene expression, we here tested the role of the thyroid hormone triiodothyronine (T3) in regulation of the cerebellar circadian oscillator. In cultured cerebellar granule cells from mixed-gender neonatal rats, T3 treatment affected transcript levels of the clock genes Per2, Arntl, Nr1d1, and Dbp, suggesting that T3 acts directly on granule cells to control the circadian oscillator. We then used two different in vivo protocols to test the role of T3 in adult female rats: Firstly, a single injection of T3 did not influence clock gene expression in the cerebellum. Secondly, we established a surgical rat model combining SCN lesion with a programmable micropump infusing circadian physiological levels of T3; however, rhythmic infusion of T3 did not reestablish differential clock gene expression between day and night in SCN lesioned rats. To test if the effects of T3 observed in vitro were related to the developmental stage, acute injections of T3 were performed in mixed-gender neonatal rats in vivo; this procedure significantly affected cerebellar expression of the clock genes Per1, Per2, Nr1d1, and Dbp. Developmental comparisons showed rhythmic expression of all clock genes analyzed in the cerebellum of adult rats only, whereas T3 responsiveness was limited to neonatal animals. Thus, T3 shapes cerebellar clock gene profiles in early postnatal stages, but it does not represent a systemic circadian regulatory mechanism linking the SCN to the cerebellum throughout life.

Novel RET agonist for the treatment of experimental neuropathies

The glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) alleviate symptoms of experimental neuropathy, protect and stimulate regeneration of sensory neurons in animal models of neuropathic pain, and restore their functional activity. However, clinical development of GFL proteins is complicated by their poor pharmacokinetic properties and multiple effects mediated by several receptors. Previously, we have identified a small molecule that selectively activates the major signal transduction unit of the GFL receptor complex, receptor tyrosine kinase RET, as an alternative to GFLs, for the treatment of neuropathic pain. We then introduced a series of chemical changes to improve the biological activity of these compounds and tested an optimized compound named BT44 in a panel of biological assays. BT44 efficiently and selectively stimulated the GFL receptor RET and activated the intracellular mitogene-activated protein kinase/extracellular signal-regulated kinase pathway in immortalized cells. In cultured sensory neurons, BT44 stimulated neurite outgrowth with an efficacy comparable to that of GFLs. BT44 alleviated mechanical hypersensitivity in surgery- and diabetes-induced rat models of neuropathic pain. In addition, BT44 normalized, to a certain degree, the expression of nociception-related neuronal markers which were altered by spinal nerve ligation, the neuropathy model used in this study. Our results suggest that the GFL mimetic BT44 is a promising new lead for the development of novel disease-modifying agents for the treatment of neuropathy and neuropathic pain.

Radiotherapy and immunotherapy converge on elimination of tumor-promoting erythroid progenitor cells through adaptive immunity

Tumor-induced CD45^-Ter119⁺CD71⁺ erythroid progenitor cells, termed "Ter cells," promote tumor progression by secreting artemin (ARTN), a neurotrophic peptide that activates REarranged during Transfection (RET) signaling. We demonstrate that both local tumor ionizing radiation (IR) and anti-programmed death ligand 1 (PD-L1) treatment decreased tumor-induced Ter cell abundance in the mouse spleen and ARTN secretion outside the irradiation field in an interferon- and CD8⁺ T cell-dependent manner. Recombinant erythropoietin promoted resistance to radiotherapy or anti-PD-L1 therapies by restoring Ter cell numbers and serum ARTN concentration. Blockade of ARTN or potential ARTN signaling partners, or depletion of Ter cells augmented the antitumor effects of both IR and anti-PD-L1 therapies in mice. Analysis of samples from patients who received radioimmunotherapy demonstrated that IR-mediated reduction of Ter cells, ARTN, and GFRα3, an ARTN signaling partner, were each associated with tumor regression. Patients with melanoma who received immunotherapy exhibited favorable outcomes associated with decreased expression of GFRα3. These findings demonstrate an out-of-field, or "abscopal," effect mediated by adaptive immunity, which is induced during local tumor irradiation. This effect, in turn, governs the therapeutic effects of radiation and immunotherapy. Therefore, our results identify multiple targets to potentially improve outcomes after radiotherapy and immunotherapy.

Tumor Immune Evasion Induced by Dysregulation of Erythroid Progenitor Cells Development

Cancer cells harness normal cells to facilitate tumor growth and metastasis. Within this complex network of interactions, the establishment and maintenance of immune evasion mechanisms are crucial for cancer progression. The escape from the immune surveillance results from multiple independent mechanisms. Recent studies revealed that besides well-described myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs) or regulatory T-cells (Tregs), erythroid progenitor cells (EPCs) play an important role in the regulation of immune response and tumor progression. EPCs are immature erythroid cells that differentiate into oxygen-transporting red blood cells. They expand in the extramedullary sites, including the spleen, as well as infiltrate tumors. EPCs in cancer produce reactive oxygen species (ROS), transforming growth factor β (TGF-β), interleukin-10 (IL-10) and express programmed death-ligand 1 (PD-L1) and potently suppress T-cells. Thus, EPCs regulate antitumor, antiviral, and antimicrobial immunity, leading to immune suppression. Moreover, EPCs promote tumor growth by the secretion of growth factors, including artemin. The expansion of EPCs in cancer is an effect of the dysregulation of erythropoiesis, leading to the differentiation arrest and enrichment of early-stage EPCs. Therefore, anemia treatment, targeting ineffective erythropoiesis, and the promotion of EPC differentiation are promising strategies to reduce cancer-induced immunosuppression and the tumor-promoting effects of EPCs.

Simultaneous Treatment with Soluble Forms of GAS1 and PTEN Reduces Invasiveness and Induces Death of Pancreatic Cancer Cells

Introduction

Pancreatic carcinoma cells exhibit a pronounced tendency to invade along and through intra and extrapancreatic nerves, even during the early stages of the disease, a phenomenon called perineural invasion (PNI). Thus, we sought to determine the effects of the simultaneous expression of soluble forms of GAS1 and PTEN (tGAS1 and PTEN-L) inhibiting tumor growth and invasiveness.

Materials and Methods

We employed a lentiviral system to simultaneously express tGAS1 and PTEN-L; in order to determine the effects of the treatments, cell viability and apoptosis as well as the expression of the transgenes by ELISA and intracellular signaling as ascertained by the activation of AKT and ERK1/2 were measured; cell invasiveness was determined using a Boyden chamber assay; and the effects of the treatment were measured in vivo in a mouse model.

Results

In the present work, we show that the combined treatment with tGAS1 and PTEN-L inhibits the growth of pancreatic cancer cells, by reducing the activities of both AKT and ERK 1/2, decreases cell invasiveness, and restrains tumor growth in a mouse model.

Conclusion

The combined administration of tGAS1 and PTEN-L could be a valuable adjunct therapy for the treatment of pancreatic cancer.

Glial cell line-derived neurotrophic factors (GFLs) and small molecules targeting RET receptor for the treatment of pain and Parkinson's disease

Rearranged during transfection (RET), in complex with glial cell line-derived (GDNF) family receptor alpha (GFRα), is the canonical signaling receptor for GDNF family ligands (GFLs) expressed in both central and peripheral parts of the nervous system and also in non-neuronal tissues. RET-dependent signaling elicited by GFLs has an important role in the development, maintenance and survival of dopamine and sensory neurons. Both Parkinson's disease and neuropathic pain are devastating disorders without an available cure, and at the moment are only treated symptomatically. GFLs have been studied extensively in animal models of Parkinson's disease and neuropathic pain with remarkable outcomes. However, clinical trials with recombinant or viral vector-encoded GFL proteins have produced inconclusive results. GFL proteins are not drug-like; they have poor pharmacokinetic properties and activate multiple receptors. Targeting RET and/or GFRα with small molecules may resolve the problems associated with using GFLs as drugs and can result in the development of therapeutics for disease-modifying treatments against Parkinson's disease and neuropathic pain.

Small Molecules and Peptides Targeting Glial Cell Line-Derived Neurotrophic Factor Receptors for the Treatment of Neurodegeneration

Glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) are able to promote the survival of multiple neuronal populations in the body and, therefore, hold considerable promise for disease-modifying treatments of diseases and conditions caused by neurodegeneration. Available data reveal the potential of GFLs for the therapy of Parkinson's disease, neuropathic pain and diseases caused by retinal degeneration but, also, amyotrophic lateral sclerosis and, possibly, Alzheimer's disease. Despite promising data collected in preclinical models, clinical translation of GFLs is yet to be conducted. The main reasons for the limited success of GFLs clinical development are the poor pharmacological characteristics of GFL proteins, such as the inability of GFLs to cross tissue barriers, poor diffusion in tissues, biphasic dose-response and activation of several receptors in the organism in different cell types, along with ethical limitations on patients' selection in clinical trials. The development of small molecules selectively targeting particular GFL receptors with improved pharmacokinetic properties can overcome many of the difficulties and limitations associated with the clinical use of GFL proteins. The current review lists several strategies to target the GFL receptor complex with drug-like molecules, discusses their advantages, provides an overview of available chemical scaffolds and peptides able to activate GFL receptors and describes the effects of these molecules in cultured cells and animal models.

RET-independent signaling by GDNF ligands and GFRα receptors

The discovery in the late 1990s of the partnership between the RET receptor tyrosine kinase and the GFRα family of GPI-anchored co-receptors as mediators of the effects of GDNF family ligands galvanized the field of neurotrophic factors, firmly establishing a new molecular framework besides the ubiquitous neurotrophins. Soon after, however, it was realized that many neurons and brain areas expressed GFRα receptors without expressing RET. These observations led to the formulation of two new concepts in GDNF family signaling, namely, the non-cell-autonomous functions of GFRα molecules, so-called trans signaling, as well as cell-autonomous functions mediated by signaling receptors distinct from RET, which became known as RET-independent signaling. To date, the best studied RET-independent signaling pathway for GDNF family ligands involves the neural cell adhesion molecule NCAM and its association with GFRα co-receptors. Among the many functions attributed to this signaling system are neuronal migration, neurite outgrowth, dendrite branching, spine formation, and synaptogenesis. This review summarizes our current understanding of this and other mechanisms of RET-independent signaling by GDNF family ligands and GFRα receptors, as well as their physiological importance.

The role of glial cell line-derived neurotrophic factor family member artemin in neurological disorders and cancers

Artemin (ARTN) is a member of the glial cell line‐derived neurotrophic factor (GDNF) family ligands (GFLs), which encompasses family members, GDNF, neurturin (NRTN) and persephin (PSPN). ARTN is also referred to as Enovin or Neublastin, and bears structural characteristics of the TGF‐β superfamily. ARTN contains a dibasic cleavage site (RXXR) that is predicted to be cleaved by furin to yield a carboxy‐terminal 113 amino acid mature form. ARTN binds preferentially to receptor GFRα3, coupled to a receptor tyrosine kinase RET, forming a signalling complex for the regulation of intracellular pathways that affect diverse outcomes of nervous system development and homoeostasis. Standard signalling cascades activated by GFLs via RET include the phosphorylation of mitogen‐activated protein kinase or MAPK (p‐ERK, p‐p38 and p‐JNK), PI3K‐AKT and Src. Neural cell adhesion molecule (NCAM) is an alternative signalling receptor for ARTN in the presence of GFRα1, leading to activation of Fyn and FAK. Further, ARTN also interacts with heparan sulphate proteoglycan syndecan‐3 and mediates non‐RET signalling via activation of Src kinases. This review discusses the role of ARTN in spinal cord injury, neuropathic pain and other neurological disorders. Additionally, ARTN plays a role in non‐neuron tissues, such as the formation of Peyer's patch‐like structures in the lymphoid tissue of the gut. The emerging role of ARTN in cancers and therapeutic resistance to cancers is also explored. Further research is necessary to determine the function of ARTN in a tissue‐specific manner, including its signalling mechanisms, in order to improve the therapeutic potential of ARTN in human diseases.

Neurotrophic Effects of Vascular Endothelial Growth Factor B and Novel Mimetic Peptides on Neurons from the Central Nervous System

Vascular endothelial growth factor B (VEGFB) is a pleiotropic trophic factor, which in contrast to the closely related VEGFA is known to have a limited effect on angiogenesis. VEGFB improves survival in various tissues including the nervous system, where the effect was observed mainly for peripheral neurons. The neurotrophic effect of VEGFB on central nervous system neurons has been less investigated. Here we demonstrated that VEGFB promotes neurite outgrowth from primary cerebellar granule, hippocampal, and retinal neurons in vitro. VEGFB protected hippocampal and retinal neurons from both oxidative stress and glutamate-induced neuronal death. The VEGF receptor 1 (VEGFR1) is required for VEGFB-induced neurotrophic and neuroprotective effects. Using a structure-based approach, we designed short peptides, termed Vefin1-7, mimicking the binding interface of VEGFB to VEGFR1. Vefins were analyzed for their secondary structure and binding to VEGF receptors and compared with previously described peptides derived from VEGFA, another ligand of VEGFR1. We show that Vefins have neurotrophic and neuroprotective effects on primary hippocampal, cerebellar granule, and retinal neurons in vitro with potencies comparable to VEGFB. Similar to VEGFB, Vefins were not mitogenic for MCF-7 cancer cells. Furthermore, one of the peptides, Vefin7, even dose-dependently inhibited the proliferation of MCF-7 cells in vitro. Unraveling the neurotrophic and neuroprotective potentials of VEGFB, the only nonangiogenic factor of the VEGF family, is promising for the development of neuroprotective peptide-based therapies.