Mechanisms of anti-inflammatory property of conserved dopamine neurotrophic factor: inhibition of JNK signaling in lipopolysaccharide-induced microglia

HER-096 is a CDNF-derived brain-penetrating peptidomimetic that protects dopaminergic neurons in a mouse synucleinopathy model of Parkinson's disease

Cerebral dopamine neurotrophic factor (CDNF) is an unconventional neurotropic factor that modulates unfolded protein response (UPR) pathway signaling and alleviates endoplasmic reticulum (ER) stress providing cytoprotective effects in different models of neurodegenerative disorders. Here, we developed a brain-penetrating peptidomimetic compound based on human CDNF. This compound called HER-096 shows similar potency and mechanism of action as CDNF, and promotes dopamine neuron survival, reduces α-synuclein aggregation and modulates UPR signaling in in vitro models. HER-096 is metabolically stable and able to penetrate to cerebrospinal (CSF) and brain interstitial fluids (ISF) after subcutaneous administration, with an extended CSF and brain ISF half-life compared to plasma. Subcutaneously administered HER-096 modulated UPR pathway activity, protected dopamine neurons, and reduced α-synuclein aggregates and neuroinflammation in substantia nigra of aged mice with synucleinopathy. Peptidomimetic HER-096 is a candidate for development of a disease-modifying therapy for Parkinson's disease with a patient-friendly route of administration.

CDNF and ER stress: Pharmacology and therapeutic possibilities

Cerebral dopamine neurotrophic factor (CDNF) is an endogenous protein in humans and other vertebrates, and it has been shown to have protective and restorative effects on cells in various disease models. Although it is named as a neurotrophic factor, its actions are drastically different from classical neurotrophic factors such as neurotrophins or the glial cell line-derived neurotrophic family of proteins. Like all secreted proteins, CDNF has a signal sequence at the N-terminus, but unlike common growth factors it has a KDEL-receptor retrieval sequence at the C-terminus. Thus, CDNF is mainly located in the ER. In response to adverse effects, such as ER stress, the expression of CDNF is upregulated and can alleviate ER stress. Also different from other neurotrophic factors, CDNF reduces protein aggregation and inflammation in disease models. Although it is an ER luminal protein, it can surprisingly directly interact with alpha-synuclein, a protein involved in the pathogenesis of synucleinopathies e.g., Parkinson's disease. Pleiotropic CDNF has therapeutic potential and has been tested as a recombinant human protein and gene therapy. The neuroprotective and neurorestorative effects have been described in a number of preclinical studies of Parkinson's disease, stroke and amyotrophic lateral sclerosis. Currently, it was successfully evaluated for safety in a phase 1/2 clinical trial for Parkinson's disease. Collectively, based on recent findings on the mode of action and therapeutic potential of CDNF, its use as a drug could be expanded to other ER stress-related diseases.

Rhein alleviates advanced glycation end products (AGEs)-induced inflammatory injury of diabetic cardiomyopathy in vitro and in vivo models

In diabetic patients, diabetic cardiomyopathy (DCM) is one of the most common causes of death. The inflammatory response is essential in the pathogenesis of DCM. Rhein, an anthraquinone compound, is extracted from the herb rhubarb, demonstrating various biological activities. However, it is unclear whether rhein has an anti-inflammatory effect in treating DCM. In our research, we investigated the anti-inflammatory properties as well as its possible mechanism. According to the findings in vitro, rhein could to exert an anti-inflammatory effect by reducing the production of NO, TNF-α, PGE2, iNOS, and COX-2 in RAW264.7 cells that had been stimulated with advanced glycosylation end products (AGEs). In addition, rhein alleviated H9C2 cells inflammation injury stimulated by AGEs/macrophage conditioned medium (CM). In vivo have depicted that continuous gavage of rhein could improve cardiac function and pathological changes. Moreover, it could inhibit the accumulation of AGEs and infiltration of inflammatory factors inside the heart of rats having DCM. Mechanism study showed rhein could suppress IKKβ and IκB phosphorylation via down-regulating TRAF6 expression to inhibit NF-κB pathway in AGEs/CM-induced H9C2 cells. Moreover, the anti-inflammation effect of rhein was realized through down-regulation phosphorylation of JNK MAPK. Furthermore, we found JNK MAPK could crosstalk with NF-κB pathway by regulating IκB phosphorylation without affecting IKKβ activity. And hence, the protective mechanism of rhein may involve the inhibiting of the TRAF6-NF/κB pathway, the JNK MAPK pathway, and the crosstalk between the two pathways. These results suggested that rhein may be a promising drug candidate in anti-inflammation and inflammation-related DCM therapy.

CDNF and MANF in the brain dopamine system and their potential as treatment for Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by gradual loss of midbrain dopamine neurons, leading to impaired motor function. Preclinical studies have indicated cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF) to be potential therapeutic molecules for the treatment of PD. CDNF was proven to be safe and well tolerated when tested in Phase I-II clinical trials in PD patients. Neuroprotective and neurorestorative effects of CDNF and MANF were demonstrated in animal models of PD, where they promoted the survival of dopamine neurons and improved motor function. However, biological roles of endogenous CDNF and MANF proteins in the midbrain dopamine system have been less clear. In addition to extracellular trophic activities, CDNF/MANF proteins function intracellularly in the endoplasmic reticulum (ER), where they modulate protein homeostasis and protect cells against ER stress by regulating the unfolded protein response (UPR). Here, our aim is to give an overview of the biology of endogenous CDNF and MANF in the brain dopamine system. We will discuss recent studies on CDNF and MANF knockout animal models, and effects of CDNF and MANF in preclinical models of PD. To elucidate possible roles of CDNF and MANF in human biology, we will review CDNF and MANF tissue expression patterns and regulation of CDNF/MANF levels in human diseases. Finally, we will discuss novel findings related to the molecular mechanism of CDNF and MANF action in ER stress, UPR, and inflammation, all of which are mechanisms potentially involved in the pathophysiology of PD.

Cyclic Hexapeptide from Bouvardia ternifolia (Cav.) Schltdl. and Neuroprotective Effects of Root Extracts

Bouvardia ternifolia (Cav.) Schltdl. is a shrub that belongs to the Rubiaceae family and is distributed throughout México; it has been used for its antioxidant, neuroprotective, and anti-inflammatory properties. This work aimed to evaluate the protective effects of B. ternifolia root extracts on the blood-brain barrier and the positive regulation of cytokines IL-1β, IL-6, and TNF-α, and the characterization of compounds present in the dichloromethane (BtD) and hexane (BtH) extracts. Male ICR mice were orally administered with B. ternifolia extracts for 5 days before a single injection of LPS. Administration of BtH and BtD significantly decreased Evans blue leakage into brain tissue by 70% and 68%, respectively. Meloxicam (MX) decreased the concentration of IL-1β by 39.6%; BtM by 53.9%; BtAq by 48.4%; BtD by 31.9%, and BtH by 37.7%. BtH was the only treatment that significantly decreased the concentration of IL-6 by 32.2%. The concentration of TNF-α declined with each of the treatments. The chemical composition of BtD and BtH was characterized by GC-MS, and the cyclic hexapeptide was identified by 13C, 1H NMR, and two-dimension techniques. In the BtD extract, seven compounds were found and in BtH 13 compounds were found. The methanolic (BtM) and aqueous (BtAq) extracts were not subjected to chemical analysis, because they did not show a significant difference in the BBB protection activity. Therefore, the results suggested that the extracts BtD and BtH protect the blood-brain barrier, maintaining stable its selective permeability, thereby preventing LPS from entering the brain tissue. Simultaneously, they modulate the production of IL-1β, IL-6, and TNF-α. It is important to note that this research only evaluated the complete extracts.

Glia-Neurotrophic Factor Relationships: Possible Role in Pathobiology of Neuroinflammation-Related Brain Disorders

Neurotrophic factors (NTFs) play an important role in maintaining homeostasis of the central nervous system (CNS) by regulating the survival, differentiation, maturation, and development of neurons and by participating in the regeneration of damaged tissues. Disturbances in the level and functioning of NTFs can lead to many diseases of the nervous system, including degenerative diseases, mental diseases, and neurodevelopmental disorders. Each CNS disease is characterized by a unique pathomechanism, however, the involvement of certain processes in its etiology is common, such as neuroinflammation, dysregulation of NTFs levels, or mitochondrial dysfunction. It has been shown that NTFs can control the activation of glial cells by directing them toward a neuroprotective and anti-inflammatory phenotype and activating signaling pathways responsible for neuronal survival. In this review, our goal is to outline the current state of knowledge about the processes affected by NTFs, the crosstalk between NTFs, mitochondria, and the nervous and immune systems, leading to the inhibition of neuroinflammation and oxidative stress, and thus the inhibition of the development and progression of CNS disorders.

Augmenting hematoma-scavenging capacity of innate immune cells by CDNF reduces brain injury and promotes functional recovery after intracerebral hemorrhage

During intracerebral hemorrhage (ICH), hematoma formation at the site of blood vessel damage results in local mechanical injury. Subsequently, erythrocytes lyse to release hemoglobin and heme, which act as neurotoxins and induce inflammation and secondary brain injury, resulting in severe neurological deficits. Accelerating hematoma resorption and mitigating hematoma-induced brain edema by modulating immune cells has potential as a novel therapeutic strategy for functional recovery after ICH. Here, we show that intracerebroventricular administration of recombinant human cerebral dopamine neurotrophic factor (rhCDNF) accelerates hemorrhagic lesion resolution, reduces peri-focal edema, and improves neurological outcomes in an animal model of collagenase-induced ICH. We demonstrate that CDNF acts on microglia/macrophages in the hemorrhagic striatum by promoting scavenger receptor expression, enhancing erythrophagocytosis and increasing anti-inflammatory mediators while suppressing the production of pro-inflammatory cytokines. Administration of rhCDNF results in upregulation of the Nrf2-HO-1 pathway, but alleviation of oxidative stress and unfolded protein responses in the perihematomal area. Finally, we demonstrate that intravenous delivery of rhCDNF has beneficial effects in an animal model of ICH and that systemic application promotes scavenging by the brain's myeloid cells for the treatment of ICH.

Involvement of Anti-Inflammatory and Stress Oxidative Markers in the Antidepressant-like Activity of Aloysia citriodora and Verbascoside on Mice with Bacterial Lipopolysaccharide- (LPS-) Induced Depression

Aloysia citriodora Palau is popularly used to treat nervous disorders. Experimental evidence has indicated that verbascoside (VBS) isolated from A. citriodora has pharmacological potential. In this study, we evaluated the antidepressant-like effects of a hydroalcoholic extract of A. citriodora (HEAc) and VBS against lipopolysaccharide- (LPS-) induced depressive-like behavior in mice. In the pretreatment protocol (performed to evaluate the preventive potential), mice were pretreated with HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg) before the administration of LPS. In the posttreatment protocol (performed to evaluate the therapeutic potential), mice were initially administered LPS and were subsequently given HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg). In both treatments, the mice were submitted to an open-field test and tail suspension test (TST) at 6 and 24 h after LPS administration. The posttreatment evaluation revealed that HEAc (30 or 300 mg/kg) and VBS produced an antidepressant-like effect, as indicated by a reduction in the time spent with no movement in the TST. Moreover, HEAc (30 or 300 mg/kg) was found to reduce interleukin-6 (IL-6) levels and N-acetyl-glycosaminidase activity in the hippocampus, increase glutathione (GSH) levels in the hippocampus and cortex, and enhance IL-10 in the cortex and, at a dose of 300 mg/kg, reduced myeloperoxidase activity in the cortex. Contrastingly, no comparable effects were detected in mice subjected to the pretreatment protocol. Administration of VBS similarly reduced the levels of IL-6 in the hippocampus and increased GSH levels in the cortex. Our observations indicate that both HEAc and VBS show promising antidepressant-like potential, which could be attributed to their beneficial effects in reducing neuroinflammatory processes and antioxidant effects in the central nervous system.

Cyclic AMP and biofilms reveal the synergistic proliferation strategy of Pseudomonas aeruginosa and Escherichia coli under the costimulation of high concentrations of microplastics and enrofloxacin

Microplastics (MPs) provide attachment sites for biofilm formation of microorganisms, which can promote their resistance to environmental stress has been proved. However, the effect of MPs on synergy survival among microorganisms under antibiotic stress remains unclear. In the present study, the proliferation of Escherichia coli and Pseudomonas aeruginosa was assessed under enrofloxacin stress with the influence of MPs. Here, MPs reduced the growth speed of E. coli and enhanced that of P. aeruginosa, especially at 12 h, but the final value of OD₆₀₀ and CFU of both bacteria not be influenced. E. coli was enrofloxacin sensitive (MIC = 0.25 μg/mL), and a high MP concentration in the presence of enrofloxacin notably enhanced the biofilm formation ability of P. aeruginosa, but proliferation decreased. In the coculture system, the proliferation of E. coli (increased 1.42-fold) and P. aeruginosa (increased 1.06-fold) both increased under enrofloxacin stress (0.25 μg/mL) with high-concentration MP addition. P. aeruginosa may provide the biofilm matrix for E. coli to resist the stress of enrofloxacin. The high concentration of cyclic AMP secreted by E. coli may slightly inhibited biofilm formation, leading to a decrease in the fitness cost of P. aeruginosa; thus, the proliferation of P. aeruginosa increased. The present study is the first to show that MP combined with antibiotics stimulates the metabolic cooperation of bacteria to promote proliferation.

Modulating Microglia/Macrophage Activation by CDNF Promotes Transplantation of Fetal Ventral Mesencephalic Graft Survival and Function in a Hemiparkinsonian Rat Model

Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons in substantia nigra pars compacta, which leads to the motor control deficits. Recently, cell transplantation is a cutting-edge technique for the therapy of PD. Nevertheless, one key bottleneck to realizing such potential is allogenic immune reaction of tissue grafts by recipients. Cerebral dopamine neurotrophic factor (CDNF) was shown to possess immune-modulatory properties that benefit neurodegenerative diseases. We hypothesized that co-administration of CDNF with fetal ventral mesencephalic (VM) tissue can improve the success of VM replacement therapies by attenuating immune responses. Hemiparkinsonian rats were generated by injecting 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle of Sprague Dawley (SD) rats. The rats were then intrastriatally transplanted with VM tissue from rats, with/without CDNF administration. Recovery of dopaminergic function and survival of the grafts were evaluated using the apomorphine-induced rotation test and small-animal positron emission tomography (PET) coupled with [¹⁸F] DOPA or [¹⁸F] FE-PE2I, respectively. In addition, transplantation-related inflammatory response was determined by uptake of [¹⁸F] FEPPA in the grafted side of striatum. Immunohistochemistry (IHC) examination was used to determine the survival of the grated dopaminergic neurons in the striatum and to investigate immune-modulatory effects of CDNF. The modulation of inflammatory responses caused by CDNF might involve enhancing M2 subset polarization and increasing fractal dimensions of 6-OHDA-treated BV2 microglial cell line. Analysis of CDNF-induced changes to gene expressions of 6-OHDA-stimulated BV2 cells implies that these alternations of the biomarkers and microglial morphology are implicated in the upregulation of protein kinase B signaling as well as regulation of catalytic, transferase, and protein serine/threonine kinase activity. The effects of CDNF on 6-OHDA-induced alternation of the canonical pathway in BV2 microglial cells is highly associated with PI3K-mediated phagosome formation. Our results are the first to show that CDNF administration enhances the survival of the grafted dopaminergic neurons and improves functional recovery in PD animal model. Modulation of the polarization, morphological characteristics, and transcriptional profiles of 6-OHDA-stimualted microglia by CDNF may possess these properties in transplantation-based regenerative therapies.

TRPV1 Suppressed NLRP3 Through Regulating Autophagy in Microglia After Ischemia-Reperfusion Injury

The microglia-mediated inflammatory response is one of the main causes of brain tissue damage after stroke. In recent years, it has been reported that autophagy in microglia played an important role in inflammatory response after stroke. Transient receptor potential vanilloid 1 (TRPV1) has been shown to regulate autophagy and inflammatory in microglia; however, the detailed mechanisms remain unclear. This study aimed to investigate whether autophagy regulates inflammatory is associated with TRPV1. Model of oxygen and glucose deprivation/reoxygenation (OGD/R) was established in vitro to induce cerebral ischemia-reperfusion injury (I/R). siRNA of Atg5, inhibitors, and agonists of both autophagy and TRPV1 were involved in our study. Autophagy was assayed by immunofluorescence staining LC-3 and autophagosome was observed using transmission electron microscopy (TEM). Autophagy/inflammation-related markers as Atg5, LC-3II/LC-3I, Beclin-1, NLRP3, IL-1β, and Caspase-1 were also measured in the present study. Results indicated that I/R injury-induced inflammatory injury may be impeded by inhibition of autophagy, and TRPV1 could suppress OGD/R-induced autophagy of microglia. However, the effect of TRPV1's inhibitor on inflammatory response was attenuated when the autophagy was blocked. These findings suggested that TRPV1 exhibits an anti-inflammatory effect on OGD/R-induced microglia, which was at least correlated with the anti-autophagy action of TRPV1 partially.

Cerebral dopamine neurotrophic factor protects and repairs dopamine neurons by novel mechanism

Midbrain dopamine neurons deteriorate in Parkinson's disease (PD) that is a progressive neurodegenerative movement disorder. No cure is available that would stop the dopaminergic decline or restore function of injured neurons in PD. Neurotrophic factors (NTFs), e.g., glial cell line-derived neurotrophic factor (GDNF) are small, secreted proteins that promote neuron survival during mammalian development and regulate adult neuronal plasticity, and they are studied as potential therapeutic agents for the treatment of neurodegenerative diseases. However, results from clinical trials of GDNF and related NTF neurturin (NRTN) in PD have been modest so far. In this review, we focus on cerebral dopamine neurotrophic factor (CDNF), an unconventional neurotrophic protein. CDNF delivered to the brain parenchyma protects and restores dopamine neurons in animal models of PD. In a recent Phase I-II clinical trial CDNF was found safe and well tolerated. CDNF deletion in mice led to age-dependent functional changes in the brain dopaminergic system and loss of enteric neurons resulting in slower gastrointestinal motility. These defects in Cdnf^-/- mice intriguingly resemble deficiencies observed in early stage PD. Different from classical NTFs, CDNF can function both as an extracellular trophic factor and as an intracellular, endoplasmic reticulum (ER) luminal protein that protects neurons and other cell types against ER stress. Similarly to the homologous mesencephalic astrocyte-derived neurotrophic factor (MANF), CDNF is able to regulate ER stress-induced unfolded protein response (UPR) signaling and promote protein homeostasis in the ER. Since ER stress is thought to be one of the pathophysiological mechanisms contributing to the dopaminergic degeneration in PD, CDNF, and its small-molecule derivatives that are under development may provide useful tools for experimental medicine and future therapies for the treatment of PD and other neurodegenerative protein-misfolding diseases.

Current knowledge and challenges associated with targeted delivery of neurotrophic factors into the central nervous system: focus on available approaches

During the last decades, numerous basic and clinical studies have been conducted to assess the delivery efficiency of therapeutic agents into the brain and spinal cord parenchyma using several administration routes. Among conventional and in-progress administrative routes, the eligibility of stem cells, viral vectors, and biomaterial systems have been shown in the delivery of NTFs. Despite these manifold advances, the close association between the delivery system and regeneration outcome remains unclear. Herein, we aimed to discuss recent progress in the delivery of these factors and the pros and cons related to each modality.

Cerebral dopamine neurotrophic factor transfection in dopamine neurons using neurotensin-polyplex nanoparticles reverses 6-hydroxydopamine-induced nigrostriatal neurodegeneration

Overexpression of neurotrophic factors in nigral dopamine neurons is a promising approach to reverse neurodegeneration of the nigrostriatal dopamine system, a hallmark in Parkinson's disease. The human cerebral dopamine neurotrophic factor (hCDNF) has recently emerged as a strong candidate for Parkinson's disease therapy. This study shows that hCDNF expression in dopamine neurons using the neurotensin-polyplex nanoparticle system reverses 6-hydroxydopamine-induced morphological, biochemical, and behavioral alterations. Three independent electron microscopy techniques showed that the neurotensin-polyplex nanoparticles containing the hCDNF gene, ranging in size from 20 to 150 nm, enabled the expression of a secretable hCDNF in vitro. Their injection in the substantia nigra compacta on day 21 after the 6-hydroxydopamine lesion resulted in detectable hCDNF in dopamine neurons, whose levels remained constant throughout the study in the substantia nigra compacta and striatum. Compared with the lesioned group, tyrosine hydroxylase-positive (TH⁺) nigral cell population and TH⁺ fiber density rose in the substantia nigra compacta and striatum after hCDNF transfection. An increase in βIII-tubulin and growth-associated protein 43 phospho-S41 (GAP43p) followed TH⁺ cell recovery, as well as dopamine and its catabolite levels. Partial reversal (80%) of drug-activated circling behavior and full recovery of spontaneous motor and non-motor behavior were achieved. Brain-derived neurotrophic factor recovery in dopamine neurons that also occurred suggests its participation in the neurotrophic effects. These findings support the potential of nanoparticle-mediated hCDNF gene delivery to develop a disease-modifying treatment against Parkinson's disease. The Institutional Animal Care and Use Committee of Centro de Investigación y de Estudios Avanzados approved our experimental procedures for animal use (authorization No. 162-15) on June 9, 2019.

Cerebral Dopamine Neurotrophic Factor (CDNF): Structure, Functions, and Therapeutic Potential

The cerebral dopamine neurotrophic factor (CDNF) together with the mesencephalic astrocyte-derived neurotrophic factor (MANF) form a unique family of neurotrophic factors (NTFs) structurally and functionally different from other proteins with neurotrophic activity. CDNF has no receptors on the cell membrane, is localized mainly in the cavity of endoplasmic reticulum (ER), and its primary function is to regulate ER stress. In addition, CDNF is able to suppress inflammation and apoptosis. Due to its functions, CDNF has demonstrated outstanding protective and restorative properties in various models of neuropathology associated with ER stress, including Parkinson's disease (PD). That is why CDNF already passed clinical trials in patients with PD. However, despite the name, CDNF functions extend far beyond the dopamine system in the brain. In particular, there are data on participation of CDNF in the maturation and maintenance of other neurotransmitter systems, regulation of the processes of neuroplasticity and non-motor behavior. In the present review, we discuss the features of CDNF structure and functions, its protective and regenerative properties.

Minocycline alleviates depression-like symptoms by rescuing decrease in neurogenesis in dorsal hippocampus via blocking microglia activation/phagocytosis

Clinical studies examining the potential of anti-inflammatory agents, specifically of minocycline, as a treatment for depression has shown promising results. However, mechanistic insights into the neuroprotective and anti-inflammatory actions of minocycline need to be provided. We evaluated the effect of minocycline on chronic mild stress (CMS) induced depressive-like behavior, and behavioral assays revealed minocycline ameliorate depressive behaviors. Multiple studies suggest a role of microglia in depression, revealing that microglia activation correlates with a decrease in neurogenesis and increased depressive-like behavior. The effect of minocycline on microglia activation in different areas of the dorsal or ventral hippocampus in stressed mice was examined by immunohistochemistry. We observed the increase in the number of activated microglia expressing CD68 after exposure to three weeks of chronic stress, whereas no changes in total microglia number were observed. These changes were observed throughout the DG, CA1 and CA2 regions in dorsal hippocampus but restricted to the DG of the ventral hippocampus. In vitro experiments including western blotting and phagocytosis assay were used to investigate the effect of minocycline on microglia activation. Activation of primary microglia by LPS in vitro causes and ERK1/2 activation, enhancement of iNOS expression and phagocytic activity, and alterations in cellular morphology that are reversed by minocycline exposure, suggesting that minocycline directly acts on microglia to reduce phagocytic potential. Our results suggest the most probable mechanism by which minocycline reverses the pathogenic phagocytic potential of neurotoxic M1 microglia, and reduces the negative phenotypes associated with reduced neurogenesis caused by exposure to chronic stress.

Cerebral dopamine neurotrophic factor promotes the proliferation and differentiation of neural stem cells in hypoxic environments

Previous research found that cerebral dopamine neurotrophic factor (CDNF) has a protective effect on brain dopaminergic neurons, and CDNF is regarded as a promising therapeutic agent for neurodegenerative diseases. However, the effects of CDNF on the proliferation, differentiation, and apoptosis of neural stem cells (NSCs), which are very sensitive to hypoxic environments, remain unknown. In this study, NSCs were extracted from the hippocampi of fetal rats and cultured with different concentrations of CDNF. The results showed that 200 nM CDNF was the optimal concentration for significantly increasing the viability of NSCs under non-hypoxic environmental conditions. Then, the cells were cultured with 200 nM CDNF under the hypoxic conditions of 90% N2, 5% CO2, and 5% air for 6 hours. The results showed that CDNF significantly improved the viability of hypoxic NSCs and reduced apoptosis among hypoxic NSCs. The detection of markers showed that CDNF increased the differentiation of hypoxic NSCs into neurons and astrocytes. CDNF also reduced the expression level of Lin28 protein and increased the expression of Let-7 mRNA in NSCs, under hypoxic conditions. In conclusion, we determined that CDNF was able to reverse the adverse proliferation, differentiation, and apoptosis effects that normally affect NSCs in a hypoxic environment. Furthermore, the Lin28/Let-7 pathway may be involved in this regulated function of CDNF. The present study was approved by the Laboratory Animal Centre of Southeast University, China (approval No. 20180924006) on September 24, 2018.

Trophic activities of endoplasmic reticulum proteins CDNF and MANF

Mesencephalic astrocyte-derived neurotrophic factor (MANF) and cerebral dopamine neurotrophic factor (CDNF) are endoplasmic reticulum (ER) luminal proteins that confer trophic activities in a wide range of tissues under diverse pathological conditions. Despite initially being classified as neurotrophic factors, neither protein structurally nor functionally resembles bona fide neurotrophic factors. Their highly homologous structures comprise a unique globular, saposin-like domain within the N-terminus joined by a flexible linker to a C-terminus containing a SAP-like domain, CXXC motif and an ER retention sequence. Neurotrophic factors exert effects by binding to cognate receptors in the plasma membrane; however, no cell surface receptors have been identified for MANF and CDNF. Both can act as unfolded protein response (UPR) genes that modulate the UPR and inflammatory processes. The trophic activity of MANF and CDNF extends beyond the central nervous system with MANF being crucial for the development of pancreatic β cells and both have trophic effects in a variety of diseases related to the liver, heart, skeletal tissue, kidney and peripheral nervous system. In this article, the unique features of MANF and CDNF, such as their structure and mechanisms of action related to ER stress and inflammation, will be reviewed. Recently identified interactions with lipids and membrane trafficking will also be described. Lastly, their function and therapeutic potential in different diseases including a recent clinical trial using CDNF to treat Parkinson's disease will be discussed. Collectively, this review will highlight MANF and CDNF as broad-acting trophic factors that regulate functions of the endoplasmic reticulum.

The role of innate immune responses and neuroinflammation in amyloid accumulation and progression of Alzheimer's disease

Alzheimer's disease (AD) is characterized by amyloid beta (Aβ) accumulation, tau pathology and neuroinflammation. Recently, there has been considerable interest in the role of neuroinflammation in directly contributing to the progression of AD. Studies in mice and humans have identified a role for microglial cells, the resident innate immune cells of the central nervous system, in AD. Activated microglia are a key hallmark of the disease and the secretion of proinflammatory cytokines by microglia may result in a positive feedback loop between neurons and microglia, resulting in ongoing low-grade inflammation. Traditionally, the pathways of Aβ production and neuroinflammation have been considered independently; however, recent studies suggest that these processes may converge to promote the pathology associated with AD. Here we review the importance of inflammation and microglia in AD development and effects of inflammatory responses on cellular pathways of neurons, including Aβ generation.

CDNF Protein Therapy in Parkinson's Disease

Neurotrophic factors (NTF) are a subgroup of growth factors that promote survival and differentiation of neurons. Due to their neuroprotective and neurorestorative properties, their therapeutic potential has been tested in various neurodegenerative diseases. Bioavailability of NTFs in the target tissue remains a major challenge for NTF-based therapies. Various intracerebral delivery approaches, both protein and gene transfer-based, have been tested with varying outcomes. Three growth factors, glial cell-line derived neurotrophic factor (GDNF), neurturin (NRTN) and platelet-derived growth factor (PDGF-BB) have been tested in clinical trials in Parkinson’s disease (PD) during the past 20 years. A new protein can now be added to this list, as cerebral dopamine neurotrophic factor (CDNF) has recently entered clinical trials. Despite their misleading names, CDNF, together with its closest relative mesencephalic astrocyte-derived neurotrophic factor (MANF), form a novel family of unconventional NTF that are both structurally and mechanistically distinct from other growth factors. CDNF and MANF are localized mainly to the lumen of endoplasmic reticulum (ER) and their primary function appears to be modulation of the unfolded protein response (UPR) pathway. Prolonged ER stress, via the UPR signaling pathways, contributes to the pathogenesis in a number of chronic degenerative diseases, and is an important target for therapeutic modulation. Intraputamenally administered recombinant human CDNF has shown robust neurorestorative effects in a number of small and large animal models of PD, and had a good safety profile in preclinical toxicology studies. Intermittent monthly bilateral intraputamenal infusions of CDNF are currently being tested in a randomized placebo-controlled phase I–II clinical study in moderately advanced PD patients. Here, we review the history of growth factor-based clinical trials in PD, and discuss how CDNF differs from the previously tested growth factors.

Trophic Factors in Inflammation and Regeneration: The Role of MANF and CDNF

Regeneration is an important process in multicellular organisms, responsible for homeostatic renewal and repair of different organs after injury. Immune cell activation is observed at early stages of the regenerative response and its regulation is essential for regenerative success. Thus, immune regulators play central roles in optimizing regenerative responses. Neurotrophic factors (NTFs) are secreted molecules, defined by their ability to support neuronal cell types. However, emerging evidence suggests that they can also play important functions in the regulation of immune cell activation and tissue repair. Here we discuss the literature supporting a role of NTFs in the regulation of inflammation and regeneration. We will focus, in particular, in the emerging roles of mesencephalic astrocyte-derived neurotrophic factor (MANF) and cerebral dopamine neurotrophic factor (CDNF) in the regulation of immune cell function and in the central role that immune modulation plays in their biological activity in vivo. Finally, we will discuss the potential use of these factors to optimize regenerative success in vivo, both within and beyond the nervous system.

Neurotrophic factors hold promise for the future of Parkinson's disease treatment: is there a light at the end of the tunnel?

Parkinson's disease (PD) is the second most common neurodegenerative disorder and is characterized by a spectrum of clinicopathologic signs and a complex etiology. PD results from the degeneration of dopaminergic (DAergic) neurons in the substantia nigra. Current therapies for PD are only able to alleviate symptoms without stopping disease progression. In addition, the available therapeutic strategies do not have long-lasting effects. Furthermore, these therapies cause different ranges of adverse side effects. There is great interest in neurotrophic factors (NTFs) due to their ability to promote the survival of different neural cells. These factors are divided into four families: neurotrophins, neurokines, the glial cell line-derived NTF family of ligands, and the newly recognized cerebral DA NTF/mesencephalic astrocyte-derived NTF family. The protective and therapeutic effects of these factors on DAergic neurons make them suitable for the prevention of progressive cell loss in PD. Based on the above premise, we focus on the protective effects of NTFs, especially CDNF and MANF, on nigrostriatal DAergic neurons in PD.

Outside in: Unraveling the Role of Neuroinflammation in the Progression of Parkinson's Disease

Neuroinflammation is one of the most important processes involved in the pathogenesis of Parkinson's disease (PD). The current concept of neuroinflammation comprises an inflammation process, which occurs in the central nervous system due to molecules released from brain-resident and/or blood-derived immune cells. Furthermore, the evidence of the contribution of systemic delivered molecules to the disease pathogenesis, such as the gut microbiota composition, has been increasing during the last years. Under physiological conditions, microglia and astrocytes support the well-being and well-function of the brain through diverse functions, including neurotrophic factor secretion in both intact and injured brain. On the other hand, genes that cause PD are expressed in astrocytes and microglia, shifting their neuroprotective role to a pathogenic one, contributing to disease onset and progression. In addition, growth factors are a subset of molecules that promote cellular survival, differentiation and maturation, which are critical signaling factors promoting the communication between cells, including neurons and blood-derived immune cells. We summarize the potential targeting of astrocytes and microglia and the systemic contribution of the gut microbiota in neuroinflammation process archived in PD.

Differential Regulation of Adhesion and Phagocytosis of Resting and Activated Microglia by Dopamine

Microglia, the immune competent cells of the central nervous system (CNS), normally exist in a resting state characterized by a ramified morphology with many processes, and become activated to amoeboid morphology in response to brain injury, infection, and a variety of neuroinflammatory stimuli. Many studies focused on how neurotransmitters affect microglia activation in pathophysiological circumstances. In this study, we tried to gain mechanistic insights on how dopamine (DA) released from neurons modulates cellular functions of resting and activated microglia. DA induced the reduction of the number of cellular processes, the increase of cell adhesion/spreading, and the increase of vimentin filaments in resting primary and BV₂ microglia. In contrast to resting cells, DA downregulated the cell spreading and phagocytosis of microglia activated by LPS. DA also significantly downregulated ERK1/2 phosphorylation in activated microglia, but not in resting microglia. Downregulation of ERK1/2 by DA in activated microglia required receptor signaling. In contrast, we found a significant increase of p38MAPK activity by DA treatment in resting, but not in activated microglia. These latter effects required the uptake of DA through the high-affinity transporter but did not require receptor signaling. Activation of p38MAPK resulted in the increase of focal adhesion number via phosphorylation of paxillin at Ser⁸³. These results indicate that DA might have a differential, depending upon the activation stage of microglia, impact on cellular functions such as adhesion and phagocytosis.

Cocaine‑ and amphetamine‑regulated transcript (CART) is associated with dopamine and is protective against ischemic stroke

Cocaine and amphetamine‑regulated transcript (CART) is a neuropeptide that can protect brains against ischemic injury. The aim of the present study was to investigate the effects of the CART within ischemic stroke and it possible mechanism. The expression levels of dopamine (DA) and CART in ischemic brain tissues of mice were measured following middle cerebral artery occlusion (MCAO). After receiving the treatment of DA and CART, the infarct volume of brain was measured in mice with MCAO. In addition, the function and potential mechanism of CART in ischemic stroke were further investigated. DA and CART expression was significantly decreased in mice with MCAO compared with normal control mice. Treatment of mice with MCAO with exogenous CART significantly decreased the extent of brain injury compared with untreated mice with MCAO. Treatment with exogenous CART promoted the survival of ex vivo neurons following oxygen‑glucose deprivation (OGD), while exogenous DA induced CART mRNA expression in a dose‑dependent manner, which suggested an association between CART and DA. Apoptosis of ex vivo neurons was significantly increased following OGD, however treatment with exogenous CART significantly inhibited this effect. The potential mechanism of CART was determined to be associated with inflammatory cytokines and related apoptotic genes. CART therefore appears to be associated with DA in its effect on ischemic stroke and is protective against brain injury following ischemic stroke by reducing inflammation activation; it may provide a promising means to treat ischemic stroke patients.

Cerebral Dopamine Neurotrophic Factor (CDNF) Has Neuroprotective Effects against Cerebral Ischemia That May Occur through the Endoplasmic Reticulum Stress Pathway

Cerebral dopamine neurotrophic factor (CDNF), previously known as the conserved dopamine neurotrophic factor, belongs to the evolutionarily conserved CDNF/mesencephalic astrocyte-derived neurotrophic factor MANF family of neurotrophic factors that demonstrate neurotrophic activities in dopaminergic neurons. The function of CDNF during brain ischemia is still not known. MANF is identified as an endoplasmic reticulum (ER) stress protein; however, the role of CDNF in ER stress remains to be fully elucidated. Here, we test the neuroprotective effect of CDNF on middle cerebral artery occlusion (MCAO) rats and neurons and astrocytes treated with oxygen–glucose depletion (OGD). We also investigate the expression of CDNF in cerebral ischemia and in primary neurons treated with ER stress-inducing agents. Our results show that CDNF can significantly reduce infarct volume, reduce apoptotic cells and improve motor function in MCAO rats, while CDNF can increase the cell viability of neurons and astrocytes treated by OGD. The expression of CDNF was upregulated in the peri-infarct tissue at 2 h of ischemia/24 h reperfusion. ER stress inducer can induce CDNF expression in primary cultured neurons. Our data indicate that CDNF has neuroprotective effects on cerebral ischemia and the OGD cell model and the protective mechanism of CDNF may occur through ER stress pathways.

IP-10 Promotes Blood-Brain Barrier Damage by Inducing Tumor Necrosis Factor Alpha Production in Japanese Encephalitis

Japanese encephalitis is a neuropathological disorder caused by Japanese encephalitis virus (JEV), which is characterized by severe pathological neuroinflammation and damage to the blood-brain barrier (BBB). Inflammatory cytokines/chemokines can regulate the expression of tight junction (TJ) proteins and are believed to be a leading cause of BBB disruption, but the specific mechanisms remain unclear. IP-10 is the most abundant chemokine produced in the early stage of JEV infection, but its role in BBB disruption is unknown. The administration of IP-10-neutralizing antibody ameliorated the decrease in TJ proteins and restored BBB integrity in JEV-infected mice. In vitro study showed IP-10 and JEV treatment did not directly alter the permeability of the monolayers of endothelial cells. However, IP-10 treatment promoted tumor necrosis factor alpha (TNF-α) production and IP-10-neutralizing antibody significantly reduced the production of TNF-α. Thus, TNF-α could be a downstream cytokine of IP-10, which decreased TJ proteins and damaged BBB integrity. Further study indicated that JEV infection can stimulate upregulation of the IP-10 receptor CXCR3 on astrocytes, resulting in TNF-α production through the JNK-c-Jun signaling pathway. Consequently, TNF-α affected the expression and cellular distribution of TJs in brain microvascular endothelial cells and led to BBB damage during JEV infection. Regarding regulation of the BBB, the IP-10/TNF-α cytokine axis could be considered a potential target for the development of novel therapeutics in BBB-related neurological diseases.

Mechanisms of multiple neurotransmitters in the effects of Lycopene on brain injury induced by Hyperlipidemia

BACKGROUND

Lycopene is a kind of carotenoid, with a strong capacity of antioxidation and regulating the bloodlipid. There has been some evidence that lycopene has protective effects on the central nervous system, but few studies have rigorously explored the role of neurotransmitters in it. Therefore, the present study was designed to investigate the effects of several neurotransmitters as lycopene exerts anti-injury effects induced by hyperlipidemia.

METHODS

Eighty adult SD rats, half male and half female, were randomly divided into eight groups on the basis of serum total cholesterol (TC) levels and body weight. There was a control group containing rats fed a standard laboratory rodent chow diet (CD); a hypercholesterolemic diet (rat chow supplemented with 4% cholesterol, 1% cholic acid and 0.5% thiouracil - this is also called a CCT diet) group; a positive group (CCT + F) fed CCT, supplemented with 10 mg·kg·bw^- 1·d^- 1 fluvastatin sodium by gastric perfusion; and lycopene groups at five dose levels (CCT + LYCO) fed with CCT and supplied lycopene at doses of 5, 25, 45, 65, and 85 mg·kg·bw^- 1·d^- 1. The levels of TC, triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-α), oxidized low density lipoprotein (ox-LDL), low-density lipoprotein receptor (LDLR), nerve growth factor (NGF), glutamic acid (Glu), Gamma aminobutyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT), N-methyl-D-aspartate (NMDA1R), GABA_A, 5-HT₁, D₁, and apoptosis-related proteins Caspase3, bax, and bcl-2 were measured after the experiment. Nissl staining was adopted to observe the morphological changes in neurons.

RESULTS

At the end of the experiment, the levels of TC, TG, LDL-C, IL-1, TNF-α, and ox-LDL in the serum and brain as well as the content of Glu, DA, NMDA, and D₁ in the brain of rats in the CCT group were higher than those in the control group (P<0.05); the levels of LDLR, NGF, GABA, 5-HT, GABA_A, 5-HT₁, and neuron quantities in the hippocampal CA1 and CA3 areas were lower than those in the control group (P<0.05). Compared to the CCT group, levels of TC, TG, LDL-C, IL-1, TNF-α, and ox-LDL in the serum and brain, as well as the content of Glu, DA and the expression of pro-apoptotic Caspase3 in the brain decreased in the rats with lycopene (25 mg to 85 mg) added to the diet (P<0.05); the levels of LDLR, NGF, GABA, 5-HT, GABA_A, and 5-HT₁ as well as the expression of anti-apoptotic bcl-2 and the neuron quantity in hippocampal CA1 and CA3 areas increased (P<0.05); further, the hippocampal cells were closely arranged. Lycopene dose was negatively correlated with the levels of TC, TG, and LDL-C in the serum and brain as well as levels of IL-1, TNF-α, ox-LDL, Glu/GABA, NMDA1R, and Caspase3 (P<0.05); it was positively correlated with the levels of LDLR, NGF, 5-HT, 5-HT₁, GABA_A, bcl-2, and the neuron quantity in hippocampal CA1 and CA3 areas (P<0.05).

CONCLUSIONS

Lycopene exerts anti-injury effects in the brain as-induced by hyperlipidemia. It can inhibit the elevation of serum TC, TG, and LDL-C in rats with hyperlipidemia while indirectly affecting the levels of TC, TG, and LDL-C in the brain, leading to a reduction in ox-LDL, IL-1, and TNF-α in the brain. This inhibits the release of Glu, which weakens nerve toxicity and downregulates pro-apoptotic Caspase3. Lycopene also plays an anti-injury role by promoting the release of the inhibitory neurotransmitter GABA and 5-HT, which enhances the protective effect, and by upregulating the anti-apoptotic bcl-2.

An evolutionary perspective on the role of mesencephalic astrocyte-derived neurotrophic factor (MANF): At the crossroads of poriferan innate immune and apoptotic pathways

The mesencephalic astrocyte-derived neurotrophic factor (MANF) belongs to a recently discovered family of neurotrophic factors. MANF can be secreted but is generally resident within the endoplasmic reticulum (ER) in neuronal and non-neuronal cells, where it is involved in the ER stress response with pro-survival effects. Here we report the discovery of the MANF homolog SDMANF in the sponge Suberites domuncula. The basal positioning of sponges (phylum Porifera) in the animal tree of life offers a unique vantage point on the early evolution of the metazoan-specific genetic toolkit and molecular pathways. Since sponges lack a conventional nervous system, SDMANF presents an enticing opportunity to investigate the evolutionary ancient role of these neurotrophic factors. SDMANF shares considerable sequence similarity with its metazoan homologs. It also comprises a putative protein binding domain with sequence similarities to the Bcl-2 family of apoptotic regulators. In Suberites, SDMANF is expressed in the vicinity of bacteriocytes, where it co-localizes with the toll-like receptor SDTLR. In transfected human cells, SDMANF was detected in both the organelle protein fraction and the cell culture medium. The intracellular SDMANF protein level was up-regulated in response to both a Golgi/ER transport inhibitor and bacterial lipopolysaccharides (LPS). Upon LPS challenge, transfected cells revealed a decreased caspase-3 activity and increased cell viability with no inducible Bax expression compared to the wild type. These results suggest a deep evolutionary original cytoprotective role of MANF, at the crossroads of innate immune and apoptotic pathways, of which a neurotrophic function might have arisen later in metazoan evolution.

Ethanol-induced damage to the developing spinal cord: The involvement of CCR2 signaling

Ethanol exposure during development causes fetal alcohol spectrum disorders (FASD). A large body of evidence shows that ethanol produces multiple abnormalities in the developing central nervous system (CNS), such as smaller brain size, reduced volume of cerebral white matter, permanent loss of neurons, and alterations in synaptogenesis and myelinogenesis. The effects of ethanol on the developing spinal cord, however, receive little attention and remain unclear. We used a third trimester equivalent mouse model to investigate the effect of ethanol on the developing spinal cord. Ethanol caused apoptosis and neurodegeneration in the dorsal horn neurons of mice of early postnatal days, which was accompanied by glial activation, macrophage infiltration, and increased expression of CCR2, a receptor for monocyte chemoattractant protein 1 (MCP-1). Ethanol-induced neuronal death during development resulted in permanent loss of spinal cord neurons in adult mice. Ethanol stimulated endoplasmic reticulum (ER) stress and oxidative stress, and activated glycogen synthase kinase 3β (GSK3β) and c-Jun N-terminal kinase (JNK) pathways. Knocking out MCP-1 or CCR2 made mice resistant to ethanol-induced apoptosis, ER stress, glial activation, and activation of GSK3β and JNK. CCR2 knock out offered much better protection against ethanol-induced damage to the spinal cord. Thus, developmental ethanol exposure caused permanent loss of spinal cord neurons and CCR2 signaling played an important role in ethanol neurotoxicity.

Potassium 2-(l-hydroxypentyl)-benzoate attenuates neuroinflammatory responses and upregulates heme oxygenase-1 in systemic lipopolysaccharide-induced inflammation in mice

A neuroinflammatory response is commonly involved in the progression of many neurodegenerative diseases. Potassium 2-(1-hydroxypentyl)-benzoate (PHPB), a novel neuroprotective compound, has shown promising effects in the treatment of ischemic stroke and Alzheimer׳s disease (AD). In the present study, the anti-inflammatory effects of PHPB were investigated in the plasma and brain of C57BL/6 mice administered a single intraperitoneal (i.p.) injection of lipopolysaccharide (LPS). Levels of iNOS and the cytokines TNFα, IL-1β and IL-10 were elevated in plasma, cerebral cortex and hippocampus after LPS injection and the number of microglia and astrocytes in cortex and hippocampus were increased. LPS also upregulated the expression of heme oxygenase-1 (HO-1) in the cortex and hippocampus. PHPB reduced the levels of iNOS and cytokines in the plasma and brain, decreased the number of microglia and astrocytes and further enhanced the upregulation of HO-1. In addition, PHPB inhibited the LPS-induced phosphorylation of ERK, P38 and JNK. These results suggest that PHPB is a potential candidate in the treatment of neurodegenerative diseases through inhibiting neuroinflammation.

Nutritional and Pharmacological Strategies to Regulate Microglial Polarization in Cognitive Aging and Alzheimer's Disease

The study of microglia, the immune cells of the brain, has experienced a renaissance after the discovery of microglia polarization. In fact, the concept that activated microglia can shift into the M1 pro-inflammatory or M2 neuroprotective phenotypes, depending on brain microenvironment, has completely changed the understanding of microglia in brain aging and neurodegenerative diseases. Microglia polarization is particularly important in aging since an increased inflammatory status of body compartments, including the brain, has been reported in elderly people. In addition, inflammatory markers, mainly derived from activated microglia, are widely present in neurodegenerative diseases. Microglial inflammatory dysfunction, also linked to microglial senescence, has been extensively demonstrated and associated with cognitive impairment in neuropathological conditions related to aging. In fact, microglia polarization is known to influence cognitive function and has therefore become a main player in neurodegenerative diseases leading to dementia. As the life span of human beings increases, so does the prevalence of cognitive dysfunction. Thus, therapeutic strategies aimed to modify microglia polarization are currently being developed. Pharmacological approaches able to shift microglia from M1 pro-inflammatory to M2 neuroprotective phenotype are actually being studied, by acting on many different molecular targets, such as glycogen synthase kinase-3 (GSK3) β, AMP-activated protein kinase (AMPK), histone deacetylases (HDACs), etc. Furthermore, nutritional approaches can also modify microglia polarization and, consequently, impact cognitive function. Several bioactive compounds normally present in foods, such as polyphenols, can have anti-inflammatory effects on microglia. Both pharmacological and nutritional approaches seem to be promising, but still need further development. Here we review recent data on these approaches and propose that their combination could have a synergistic effect to counteract cognitive aging impairment and Alzheimer's disease (AD) through immunomodulation of microglia polarization, i.e., by driving the shift of activated microglia from the pro-inflammatory M1 to the neuroprotective M2 phenotype.

In vivo screening reveals interactions between Drosophila Manf and genes involved in the mitochondria and the ubiquinone synthesis pathway

BACKGROUND

Mesencephalic Astrocyte-derived Neurotrophic Factor (MANF) and Cerebral Dopamine Neurotrophic Factor (CDNF) form an evolutionarily conserved family of neurotrophic factors. Orthologues for MANF/CDNF are the only neurotrophic factors as yet identified in invertebrates with conserved amino acid sequence. Previous studies indicate that mammalian MANF and CDNF support and protect brain dopaminergic system in non-cell-autonomous manner. However, MANF has also been shown to function intracellularly in the endoplasmic reticulum. To date, the knowledge on the interacting partners of MANF/CDNF and signaling pathways they activate is rudimentary. Here, we have employed the Drosophila genetics to screen for potential interaction partners of Drosophila Manf (DmManf) in vivo.

RESULTS

We first show that DmManf plays a role in the development of Drosophila wing. We exploited this function by using Drosophila UAS-RNAi lines and discovered novel genetic interactions of DmManf with genes known to function in the mitochondria. We also found evidence of an interaction between DmManf and the Drosophila homologue encoding Ku70, the closest structural homologue of SAP domain of mammalian MANF.

CONCLUSIONS

In addition to the previously known functions of MANF/CDNF protein family, DmManf also interacts with mitochondria-related genes. Our data supports the functional importance of these evolutionarily significant proteins and provides new insights for the future studies.

A biphenyl derivative from the twigs of Chaenomeles speciosa

In our continuing search for bioactive constituents of Korean medicinal sources, we investigated an 80% MeOH extract of the twigs of Chaenomeles speciosa. Column chromatographic purification of the CHCl₃ fraction resulted in the isolation of a new biphenyl derivative (1), along with four known biphenyl compounds (2-5) and six triterpenes (6-11). The chemical structure of the new compound was determined on the basis of spectroscopic analyses including 1D and 2D NMR data. Among isolates, compound 3 exhibited potent cytotoxic activities against SK-OV-3, SK-MEL-2, and XF498 cell lines (IC₅₀=5.91, 4.22, and 6.28μM, respectively). Also, Compounds 9 and 10 showed strong anti-neuroinflammatory activities (IC₅₀ 2.38, and 6.70μM, respectively).

Cerebral Dopamine Neurotrophic Factor: A Potential Therapeutic Agent for Parkinson's Disease

The application of neurotrophic factors (NTFs) is a promising therapeutic strategy for neurodegenerative disorders such as Parkinson's disease (PD). Many NTFs have been reported to enhance the survival, regeneration, and differentiation of neurons and to induce synaptic plasticity. However, because of their potential side-effects and low efficacy after clinical administration, more potent treatments for neurodegenerative disorders are being sought. Cerebral dopamine neurotrophic factor (CDNF), a newly-identified NTF homologous to mesencephalic astrocyte-derived NTF, is structurally and functionally different from other NTFs, providing new hope especially for PD patients. In various animal models of PD, CDNF is efficient in protecting and repairing dopaminergic neurons, and it inhibits endoplasmic reticulum stress, neuroinflammation, and apoptosis. Recent progress in all facets of CDNF research has enabled researchers to better understand its beneficial effects in the treatment of PD.

Recombinant AAV8-mediated intrastriatal gene delivery of CDNF protects rats against methamphetamine neurotoxicity

Methamphetamine (METH) exerts significant neurotoxicity in experimental animals and humans when taken at high doses or abused chronically. Long-term abusers have decreased dopamine levels, and they are more likely to develop Parkinson's disease (PD). To date, few medications are available to treat the METH-induced damage of neurons. Glial cell line-derived neurotrophic factor (GDNF) has been previously shown to reduce the dopamine-depleting effects of neurotoxic doses of METH. However, the effect of cerebral dopamine neurotrophic factor (CDNF), which has been reported to be more specific and efficient than GDNF in protecting dopaminergic neurons against 6-OHDA toxicity, in attenuating METH neurotoxicity has not been determined. Thus, the present study aimed to evaluate the neuroprotective effect of CDNF against METH-induced damage to the dopaminergic system in vitro and in vivo. In vitro, CDNF protein increased the survival rate and reduced the tyrosine hydroxylase (TH) loss of METH-treated PC12 cells. In vivo, METH was administered to rats following human CDNF overexpression mediated by the recombinant adeno-associated virus. Results demonstrated that CDNF overexpression in the brain could attenuate the METH-induced dopamine and TH loss in the striatum but could not lower METH-induced hyperthermia.

Unconventional neurotrophic factors CDNF and MANF: Structure, physiological functions and therapeutic potential

Cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF) promote the survival of midbrain dopaminergic neurons which degenerate in Parkinson's disease (PD). However, CDNF and MANF are structurally and functionally clearly distinct from the classical, target-derived neurotrophic factors (NTFs) that are solely secreted proteins. In cells, CDNF and MANF localize in the endoplasmic reticulum (ER) and evidence suggests that MANF, and possibly CDNF, is important for the maintenance of ER homeostasis. MANF expression is particularly high in secretory tissues with extensive protein production and thus a high ER protein folding load. Deletion of MANF in mice results in a diabetic phenotype and the activation of unfolded protein response (UPR) in the pancreatic islets. However, information about the intracellular and extracellular mechanisms of MANF and CDNF action is still limited. Here we will discuss the structural motifs and physiological functions of CDNF and MANF as well as their therapeutic potential for the treatment of neurodegenerative diseases and diabetes. Currently available knockout models of MANF and CDNF in mice, zebrafish and fruit fly will increase information about the biology of these interesting proteins.

Mesencephalic astrocyte-derived neurotrophic factor attenuates inflammatory responses in lipopolysaccharide-induced neural stem cells by regulating NF-κB and phosphorylation of p38-MAPKs pathways

Mesencephalic astrocyte-derived neurotrophic factor (MANF), a new evolutionary conserved neurotrophic factor (NTF), has been reported to protect midbrain dopaminergic neurons of neurodegenerative diseases such as Parkinson's disease (PD) model. Neural stem cells (NSCs) can play a role as the therapeutic tool in neurodegenerative diseases, but the inflammatory responses of central nervous system (CNS) appear to harm this function. Although studies have previously demonstrated the protective effect of MANF on neurons of CNS, it is lacking in making great efforts on the function of MANF on NSCs. The aim of this study was to investigate the antiinflammatory responses and signaling mechanisms of MANF on lipopolysaccharide (LPS)-induced NSCs. In the results, MANF decreased the proinflammatory cytokines of IL-1β, TNF-α, and IFN-γ induced by LPS by regulating NF-κB and phosphorylation of p38-mitogen-activated protein kinases (MAPKs) pathways, neither p-JNK nor p-ERK signaling. These findings suggest that MANF can facilitate to protect the inflammatory responses of NSCs, and provide beneficial function for the application of NSCs in the therapy.

Anti-Neuroinflammatory Effect of MC13, a Novel Coumarin Compound From Condiment Murraya, Through Inhibiting Lipopolysaccharide-Induced TRAF6-TAK1-NF-κB, P38/ERK MAPKS and Jak2-Stat1/Stat3 Pathways

MC13 is a novel coumarin compound found in Murraya, an economic crop whose leaves are widely used as condiment (curry) in cuisine. The aims of the present study were to investigate the neuroprotective effects of MC13 on microglia-mediated inflammatory injury model as well as potential molecular mechanism. Cell viability and apoptosis assay demonstrated that MC13 was not toxic to neurons and significantly protected neurons from microglia-mediated inflammatory injury upon lipopolysaccharide (LPS) stimulation. Results showed that MC13 markedly inhibited LPS-induced production of various inflammatory mediators, including nitrite oxide (Griess method), TNF-α and IL-6 (ELISA assay) in a concentration-dependent manner. Mechanism study showed that MC13 could suppress the activation of NF-κB, which was the central regulator for inflammatory response, and also decreased the interaction of TGF-β-activated kinase 1 (TAK1)-binding protein (TAB2) with TAK1 and TNF receptor associated factor (TRAF6), leading to the decreased phosphorylation levels of NF-κB upstream regulators such as IκB and IκB kinase (IKK). MC13 also significantly down-regulated the phosphorylation levels of ERK and p38 MAPKs, which played key roles in microglia-mediated inflammatory response. Furthermore, MC13 inhibited Jak2-dependent Stat1/3 signaling pathway activation by blocking Jak2 phosphorylation, Stat1/3 phosphorylation, and nuclear translocation. Taken together, our results demonstrated that MC13 protected neurons from microglia-mediated neuroinflammatory injury by inhibiting TRAF6-TAK1-NF-κB, p38/ERK MAPKs, and Jak2-Stat1/3 pathways. Finally, MC13 might interact with LPS and interfere LPS-binding to cell membrane surface. These findings suggested that coumarin might act as a potential medicinal agent for treating neuroinflammation as well as inflammation-related neurodegenerative diseases.

Therapeutic potential of the endoplasmic reticulum located and secreted CDNF/MANF family of neurotrophic factors in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder where dopamine (DA) neurons in the substantia nigra degenerate and die. Since no cure for PD exists, there is a need for disease-modifying drugs. Glial cell line-derived neurotrophic factor (GDNF) and related neurturin (NRTN) can protect and repair DA neurons in neurotoxin animal models of PD. However, GDNF was unable to rescue DA neurons in an α-synuclein model of PD, and both factors have shown modest effects in phase two clinical trials. Neurotrophic factors (NTFs), cerebral DA NTF (CDNF) and mesencephalic astrocyte-derived NTF (MANF) form a novel family of evolutionarily conserved, endoplasmic reticulum (ER) located and secreted NTFs. CDNF and MANF have a unique structure and an unparalleled dual mode of action that differs from other known NTFs. Both protect cells from ER stress, and regulate the unfolded protein response via interacting with chaperons, and CDNF dissolves intracellular α-synuclein aggregates. By binding to putative plasma membrane receptors, they promote the survival of DA neurons similarly to conventional NTFs. In animal models of PD, CDNF protects and repairs DA neurons, regulates ER stress, and improves motor function more efficiently than other NTFs.

Coumarin: A Privileged Scaffold for the Design and Development of Antineurodegenerative Agents

Drug development for neurodegenerative diseases (NDs) is foremost task for the medicinal chemists in the 21st century. Coumarins are exemplary of an assorted and aptitudinally useful set of drugs. Coumarins play a momentous role in several pharmacological and medicinal aspects. Its analogues are anticipated to play a significant role in the development of new therapeutic leads for NDs. Their promising applications in the field of ND medication are exemplified by clinical candidates such as nodakenin that have been potent for demoting memory impairment. Apart from ND, clinically used anticoagulant warfarin, anticoagulant dicoumarol, and antibiotic coumermycin, novobiocin and chartesium grab the interest of researchers in coumarins. It would be worthwhile to look at the different biological processes that could cause neurodegeneration, thereby establishing a link with distinct coumarin derivatives to serve the purpose of medication. This review undertakes estimation of the wide spectrum of studies focusing coumarin to the domain of drug research for ND. Herein, we search for multitarget coumarin-based inhibitors and their scope for NDs. Future challenges in coumarin-based drug development have been discussed, and emphases have been laid on the future perspectives of coumarins as possible drugs in the future for the treatment of NDs.

Benfotiamine attenuates inflammatory response in LPS stimulated BV-2 microglia

Microglial cells are resident immune cells of the central nervous system (CNS), recognized as key elements in the regulation of neural homeostasis and the response to injury and repair. As excessive activation of microglia may lead to neurodegeneration, therapeutic strategies targeting its inhibition were shown to improve treatment of most neurodegenerative diseases. Benfotiamine is a synthetic vitamin B1 (thiamine) derivate exerting potentially anti-inflammatory effects. Despite the encouraging results regarding benfotiamine potential to alleviate diabetic microangiopathy, neuropathy and other oxidative stress-induced pathological conditions, its activities and cellular mechanisms during microglial activation have yet to be elucidated. In the present study, the anti-inflammatory effects of benfotiamine were investigated in lipopolysaccharide (LPS)-stimulated murine BV-2 microglia. We determined that benfotiamine remodels activated microglia to acquire the shape that is characteristic of non-stimulated BV-2 cells. In addition, benfotiamine significantly decreased production of pro-inflammatory mediators such as inducible form of nitric oxide synthase (iNOS) and NO; cyclooxygenase-2 (COX-2), heat-shock protein 70 (Hsp70), tumor necrosis factor alpha α (TNF-α), interleukin-6 (IL-6), whereas it increased anti-inflammatory interleukin-10 (IL-10) production in LPS stimulated BV-2 microglia. Moreover, benfotiamine suppressed the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinases (JNK) and protein kinase B Akt/PKB. Treatment with specific inhibitors revealed that benfotiamine-mediated suppression of NO production was via JNK1/2 and Akt pathway, while the cytokine suppression includes ERK1/2, JNK1/2 and Akt pathways. Finally, the potentially protective effect is mediated by the suppression of translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in the nucleus. Therefore, benfotiamine may have therapeutic potential for neurodegenerative diseases by inhibiting inflammatory mediators and enhancing anti-inflammatory factor production in activated microglia.

Transient transfection of human CDNF gene reduces the 6-hydroxydopamine-induced neuroinflammation in the rat substantia nigra

BACKGROUND

The anti-inflammatory effect of the cerebral dopamine neurotrophic factor (CDNF) was shown recently in primary glial cell cultures, yet such effect remains unknown both in vivo and in 6-hydroxydopamine (6-OHDA) models of Parkinson's disease (PD). We addressed this issue by performing an intranigral transfection of the human CDNF (hCDNF) gene in the critical period of inflammation after a single intrastriatal 6-OHDA injection in the rat.

METHODS

At day 15 after lesion, the plasmids p3xNBRE-hCDNF or p3xNBRE-EGFP, coding for enhanced green florescent protein (EGFP), were transfected into the rat substantia nigra (SN) using neurotensin (NTS)-polyplex. At day 15 post-transfection, we measured nitrite and lipoperoxide levels in the SN. We used ELISA to quantify the levels of TNF-α, IL-1β, IL-6, endogenous rat CDNF (rCDNF) and hCDNF. We also used qRT-PCR to measure rCDNF and hCDNF transcripts, and immunofluorescence assays to evaluate iNOS, CDNF and glial cells (microglia, astrocytes and Neuron/Glial type 2 (NG2) cells). Intact SNs were additional controls.

RESULTS

In the SN, 6-OHDA triggered nitrosative stress, increased inflammatory cytokines levels, and activated the multipotent progenitor NG2 cells, which convert into astrocytes to produce rCDNF. In comparison with the hemiparkinsonian rats that were transfected with the EGFP gene or without transfection, 6-OHDA treatment and p3xNBRE-hCDNF transfection increased the conversion of NG2 cells into astrocytes resulting in 4-fold increase in the rCDNF protein levels. The overexpressed CDNF reduced nitrosative stress, glial markers and IL-6 levels in the SN, but not TNF-α and IL-1β levels.

CONCLUSION

Our results show the anti-inflammatory effect of CDNF in a 6-OHDA rat of Parkinson's disease. Our results also suggest the possible participation of TNF-α, IL-1β and IL-6 in rCDNF production by astrocytes, supporting their anti-inflammatory role.

Transplantation of Cerebral Dopamine Neurotrophic Factor Transducted BMSCs in Contusion Spinal Cord Injury of Rats: Promotion of Nerve Regeneration by Alleviating Neuroinflammation

Traumatic spinal cord injury (SCI) causes neuron death and axonal damage resulting in functional motor and sensory loss, showing limited regeneration because of adverse microenvironment such as neuroinflammation and glial scarring. Currently, there is no effective therapy to treat SCI in clinical practice. Bone marrow-derived mesenchymal stem cells (BMSCs) are candidates for cell therapies but its effect is limited by neuroinflammation and adverse microenvironment in the injured spinal cord. In this study, we developed transgenic BMSCs overexpressing cerebral dopamine neurotrophic factor (CDNF), a secretory neurotrophic factor that showed potent effects on neuron protection, anti-inflammation, and sciatic nerve regeneration in previous studies. Our results showed that the transplantation of CDNF-BMSCs suppressed neuroinflammation and decreased the production of proinflammatory cytokines after SCI, resulting in the promotion of locomotor function and nerve regeneration of the injured spinal cord. This study presents a novel promising strategy for the treatment of spinal cord injury.

Conserved dopamine neurotrophic factor-transduced mesenchymal stem cells promote axon regeneration and functional recovery of injured sciatic nerve

Peripheral nerve injury (PNI) is a common disease that often results in axonal degeneration and the loss of neurons, ultimately leading to limited nerve regeneration and severe functional impairment. Currently, there are no effective treatments for PNI. In the present study, we transduced conserved dopamine neurotrophic factor (CDNF) into mesenchymal stem cells (MSCs) in collagen tubes to investigate their regenerative effects on rat peripheral nerves in an in vivo transection model. Scanning electron microscopy of the collagen tubes demonstrated their ability to be resorbed in vivo. We observed notable overexpression of the CDNF protein in the distal sciatic nerve after application of CDNF-MSCs. Quantitative analysis of neurofilament 200 (NF200) and S100 immunohistochemistry showed significant enhancement of axonal and Schwann cell regeneration in the group receiving CDNF-MSCs (CDNF-MSCs group) compared with the control groups. Myelination thickness, axon diameter and the axon-to fiber diameter ratio (G-ratio) were significantly higher in the CDNF-MSCs group at 8 and 12 weeks after nerve transection surgery. After surgery, the sciatic functional index, target muscle weight, wet weight ratio of gastrocnemius muscle and horseradish peroxidase (HRP) tracing demonstrated functional recovery. Light and electron microscopy confirmed successful regeneration of the sciatic nerve. The greater numbers of HRP-labeled neuron cell bodies and increased sciatic nerve index values (SFI) in the CDNF-MSCs group suggest that CDNF exerts neuroprotective effects in vivo. We also observed higher target muscle weights and a significant improvement in muscle atrophism in the CDNF-MSCs group. Collectively, these findings indicate that CDNF gene therapy delivered by MSCs is capable of promoting nerve regeneration and functional recovery, likely because of the significant neuroprotective and neurotrophic effects of CDNF and the superior environment offered by MSCs and collagen tubes.