Mesencephalic astrocyte-derived neurotrophic factor reduces cell apoptosis via upregulating GRP78 in SH-SY5Y cells

Modulating Stress Proteins in Response to Therapeutic Interventions for Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative illness characterized by the degeneration of dopaminergic neurons in the substantia nigra, resulting in motor symptoms and without debilitating motors. A hallmark of this condition is the accumulation of misfolded proteins, a phenomenon that drives disease progression. In this regard, heat shock proteins (HSPs) play a central role in the cellular response to stress, shielding cells from damage induced by protein aggregates and oxidative stress. As a result, researchers have become increasingly interested in modulating these proteins through pharmacological and non-pharmacological therapeutic interventions. This review aims to provide an overview of the preclinical experiments performed over the last decade in this research field. Specifically, it focuses on preclinical studies that center on the modulation of stress proteins for the treatment potential of PD. The findings display promise in targeting HSPs to ameliorate PD outcomes. Despite the complexity of HSPs and their co-chaperones, proteins such as HSP70, HSP27, HSP90, and glucose-regulated protein-78 (GRP78) may be efficacious in slowing or preventing disease progression. Nevertheless, clinical validation is essential to confirm the safety and effectiveness of these preclinical approaches.

Upregulation of mesencephalic astrocyte-derived neurotrophic factor (MANF) expression offers protection against alcohol neurotoxicity

Alcohol exposure has detrimental effects on both the developing and mature brain. Endoplasmic reticulum (ER) stress is one of the mechanisms that contributes to alcohol-induced neuronal damages. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an ER stress-responsive protein and is neuroprotective in multiple neuronal injury and neurodegenerative disease models. MANF deficiency has been shown to exacerbate alcohol-induced ER stress and neurodegeneration. However, it is unknown whether MANF supplement is sufficient to protect against alcohol neurotoxicity. Alcohol alters MANF expression in the brain, but the mechanisms underlying alcohol modulation of MANF expression remain unclear. This study was designed to determine how alcohol alters MANF expression in neuronal cells and whether exogeneous MANF can alleviate alcohol neurotoxicity. We showed that alcohol increased MANF transcription and secretion without affecting MANF mRNA stability and protein degradation. ER stress was necessary for alcohol-induced MANF upregulation, as pharmacological inhibition of ER stress by 4-PBA diminished alcohol-induced MANF expression. In addition, the presence of ER stress response element II (ERSE-II) was required for alcohol-stimulated MANF transcription. Mutations or deletion of this sequence abolished alcohol-regulated transcriptional activity. We generated MANF knockout (KO) neuronal cells using CRISPR/Cas9. MANF KO cells exhibited increased unfolded protein response (UPR) and were more susceptible to alcohol-induced cell death. On the other hand, MANF upregulation by the addition of recombinant MANF protein or adenovirus gene transduction protected neuronal cells against alcohol-induced cell death. Further studies using early postnatal mouse pups demonstrated that enhanced MANF expression in the brain by intracerebroventricular (ICV) injection of MANF adeno-associated viruses ameliorated alcohol-induced cell death. Thus, alcohol increased MANF expression through inducing ER stress, which could be a protective response. Exogenous MANF was able to protect against alcohol-induced neurodegeneration.

Role of Astrocytes in Parkinson's Disease Associated with Genetic Mutations and Neurotoxicants

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons and the aggregation of Lewy bodies in the basal ganglia, resulting in movement impairment referred to as parkinsonism. However, the etiology of PD is not well known, with genetic factors accounting only for 10-15% of all PD cases. The pathogenetic mechanism of PD is not completely understood, although several mechanisms, such as oxidative stress and inflammation, have been suggested. Understanding the mechanisms of PD pathogenesis is critical for developing highly efficacious therapeutics. In the PD brain, dopaminergic neurons degenerate mainly in the basal ganglia, but recently emerging evidence has shown that astrocytes also significantly contribute to dopaminergic neuronal death. In this review, we discuss the role of astrocytes in PD pathogenesis due to mutations in α-synuclein (PARK1), DJ-1 (PARK7), parkin (PARK2), leucine-rich repeat kinase 2 (LRRK2, PARK8), and PTEN-induced kinase 1 (PINK1, PARK6). We also discuss PD experimental models using neurotoxins, such as paraquat, rotenone, 6-hydroxydopamine, and MPTP/MPP+. A more precise and comprehensive understanding of astrocytes' modulatory roles in dopaminergic neurodegeneration in PD will help develop novel strategies for effective PD therapeutics.

Chaperone-Dependent Mechanisms as a Pharmacological Target for Neuroprotection

Modern pharmacotherapy of neurodegenerative diseases is predominantly symptomatic and does not allow vicious circles causing disease development to break. Protein misfolding is considered the most important pathogenetic factor of neurodegenerative diseases. Physiological mechanisms related to the function of chaperones, which contribute to the restoration of native conformation of functionally important proteins, evolved evolutionarily. These mechanisms can be considered promising for pharmacological regulation. Therefore, the aim of this review was to analyze the mechanisms of endoplasmic reticulum stress (ER stress) and unfolded protein response (UPR) in the pathogenesis of neurodegenerative diseases. Data on BiP and Sigma1R chaperones in clinical and experimental studies of Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease are presented. The possibility of neuroprotective effect dependent on Sigma1R ligand activation in these diseases is also demonstrated. The interaction between Sigma1R and BiP-associated signaling in the neuroprotection is discussed. The performed analysis suggests the feasibility of pharmacological regulation of chaperone function, possibility of ligand activation of Sigma1R in order to achieve a neuroprotective effect, and the need for further studies of the conjugation of cellular mechanisms controlled by Sigma1R and BiP chaperones.

rmMANF prevents sepsis-associated lung injury via inhibiting endoplasmic reticulum stress-induced ferroptosis in mice

Ferroptosis plays a critical role in LPS-induced acute lung injury and is modulated by endoplasmic reticulum stress (ERS). As a typical ER stress-responsive protein, recently mesencephalic astrocyte-derived neurotrophic factor (MANF) has been demonstrated to attenuate LPS-induced acute lung injury (ALI) through repressing macrophage activation. However, whether MANF exerts a preventive role on ferroptosis and excess ER stress remains unclear. Here, we first built a protein-protein interaction (PPI) network to obtain potential interacting proteins related to MANF through STRING and GeneMANIA. Then, male C57BL/6J mice were used to build a model of LPS-induced lung injury. Two days before LPS injection, the tail vein injected recombinant murine MANF (rmMANF) at 750 μg/kg. Twenty-four hours after the LPS injection, the histopathological changes and damage in the lung tissues were detected and scored by HE staining and TUNEL assay, respectively. Endogenous MANF levels, oxidative stress markers (GSH, SOD, CAT, and MDA), ERS markers (GRP78, PERK, and ATF4), and the ferroptosis markers (iron, GPX4, and 4-HNE) in the lung tissues were measured by IHC, western blotting, and commercial kits. Our results showed that LPS induced significant lung injury to the increase in MPO, MDA, and 4-HNE, a decrease in GPX4 and GSH, SOD, CAT, and total iron accumulation in LPS-exposed mice. Simultaneously, GRP78/PERK/ATF4 pathway was notably activated by LPS, accompanied by the down-regulation of MANF. Furthermore, rmMANF pretreatment markedly prevented LPS-induced lung tissue injury and ferroptosis characteristics with the increased GPX4 level in sepsis mice. Finally, we found that LPS-induced oxidative stress and activation of the GRP78/PERK/ATF4 pathway were significantly restrained by rmMANF pretreatment, except for endogenous MANF level. Overall, rmMANF pretreatment can prevent sepsis-associated lung injury by inhibiting ER stress-induced ferroptosis in mice.

Mesencephalic astrocyte-derived neurotrophic factor (MANF) prevents the neuroinflammation induced dopaminergic neurodegeneration

BACKGROUND

The excessive activation of the microglia leads to the release of inflammatory factors that contribute to neuronal cell loss and neurodegeneration in Parkinson's Disease (PD). Mesencephalic astrocyte-derived neurotrophic factor (MANF) that belongs to a newly found neurotrophic factors (NTFs) family has been reported to promote neuronal survival in the PD models. However, the effects of the MANF on neuroinflammation in PD remain unclear.

METHODS

AAV8-MANF virus was constructed to determine whether the high expression of MANF can protect the neuroinflammation-induced dopaminergic neurodegeneration in rats with 6-OHDA-induced PD. Rotarod performance test, immunofluorescent staining and western bolt were employed to evaluate the behavioral dysfunction, dopaminergic neurodegeneration, microglia activation, and signal activation. 6-OHDA treated SH-SY5Y cells and LPS treated BV-2 cells were used as the in vitro model for MANF neuroprotective and neuroinflammation mechanisms. Cell vitality and apoptosis were evaluated with MTT, CCK-8 and flow cytometric analysis. The AKT/GSK3β-Nrf2 signaling and the TNF-α/IL6 expression were measured by Western Blot.

RESULTS

Our findings indicated that the elevated MANF expression by the AAV8-MANF administration ameliorated the motor dysfunction and protected the dopaminergic neurons in the 6-OHDA treated rats. The upregulated CD11b in the rat SN caused by the 6-OHDA administration was significantly attenuated by the pretreatment of the AAV8-MANF. Furthermore, the levels of p-AKT, p-GSK3β, BCL-2, and Nrf-2 were upregulated by the high expression of the MANF. Under the oxidative stress of the 6-OHDA, the MANF significantly reduced the apoptotic effect of the TNF-α on the SH-SY5Y cells. In the LPS treated BV-2 cells, the MANF reduced the production of the TNF-α and IL-6, via enhancing the Nrf-2, p-Akt, p-GSK3β, and p-NF-κβ level.

CONCLUSIONS

These results suggested that the MANF prevented the dopaminergic neurodegeneration caused by the microglia activation in PD via activation of the AKT/GSK3β-Nrf-2 signaling axis.

Mesencephalic astrocyte-derived neurotrophic factor (MANF): Structure, functions and therapeutic potential

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a novel evolutionarily conserved protein present in both vertebrate and invertebrate species. MANF shows distinct structural and functional properties than the traditional neurotrophic factors (NTF). MANF is composed of an N-terminal saposin-like lipid-binding domain and a C-terminal SAF-A/B, Acinus and PIAS (SAP) domain connected by a short linker. The two well-described activities of MANF include (1) role as a neurotrophic factor that plays direct neuroprotective effects in the nervous system and (2) cell protective effects in the animal models of non-neuronal diseases, including retinal damage, diabetes mellitus, liver injury, myocardial infarction, nephrotic syndrome, etc. The main objective of the current review is to provide up-to-date insights regarding the structure of MANF, mechanisms regulating its expression and secretion, physiological functions in various tissues and organs, protective effects during aging, and potential clinical applications. Together, this review highlights the importance of MANF in reversing age-related dysfunction and geroprotection.

Can the administration of platelet lysates to the brain help treat neurological disorders?

Neurodegenerative disorders of the central nervous system (CNS) and brain traumatic insults are characterized by complex overlapping pathophysiological alterations encompassing neuroinflammation, alterations of synaptic functions, oxidative stress, and progressive neurodegeneration that eventually lead to irreversible motor and cognitive dysfunctions. A single pharmacological approach is unlikely to provide a complementary set of molecular therapeutic actions suitable to resolve these complex pathologies. Recent preclinical data are providing evidence-based scientific rationales to support biotherapies based on administering neurotrophic factors and extracellular vesicles present in the lysates of human platelets collected from healthy donors to the brain. Here, we present the most recent findings on the composition of the platelet proteome that can activate complementary signaling pathways in vivo to trigger neuroprotection, synapse protection, anti-inflammation, antioxidation, and neurorestoration. We also report experimental data where the administration of human platelet lysates (HPL) was safe and resulted in beneficial neuroprotective effects in established rodent models of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, traumatic brain injury, and stroke. Platelet-based biotherapies, prepared from collected platelet concentrates (PC), are emerging as a novel pragmatic and accessible translational therapeutic strategy for treating neurological diseases. Based on this assumption, we further elaborated on various clinical, manufacturing, and regulatory issues that need to be addressed to ensure the ethical supply, quality, and safety of HPL preparations for treating neurodegenerative and traumatic pathologies of the CNS. HPL made from PC may become a unique approach for scientifically based treatments of neurological disorders readily accessible in low-, middle-, and high-income countries.

UPR Responsive Genes Manf and Xbp1 in Stroke

Stroke is a devastating medical condition with no treatment to hasten recovery. Its abrupt nature results in cataclysmic changes in the affected tissues. Resident cells fail to cope with the cellular stress resulting in massive cell death, which cannot be endogenously repaired. A potential strategy to improve stroke outcomes is to boost endogenous pro-survival pathways. The unfolded protein response (UPR), an evolutionarily conserved stress response, provides a promising opportunity to ameliorate the survival of stressed cells. Recent studies from us and others have pointed toward mesencephalic astrocyte-derived neurotrophic factor (MANF) being a UPR responsive gene with an active role in maintaining proteostasis. Its pro-survival effects have been demonstrated in several disease models such as diabetes, neurodegeneration, and stroke. MANF has an ER-signal peptide and an ER-retention signal; it is secreted by ER calcium depletion and exits cells upon cell death. Although its functions remain elusive, conducted experiments suggest that the endogenous MANF in the ER lumen and exogenously administered MANF protein have different mechanisms of action. Here, we will revisit recent and older bodies of literature aiming to delineate the expression profile of MANF. We will focus on its neuroprotective roles in regulating neurogenesis and inflammation upon post-stroke administration. At the same time, we will investigate commonalities and differences with another UPR responsive gene, X-box binding protein 1 (XBP1), which has recently been associated with MANF’s function. This will be the first systematic comparison of these two UPR responsive genes aiming at revealing previously uncovered associations between them. Overall, understanding the mode of action of these UPR responsive genes could provide novel approaches to promote cell survival.

Potential Role of MANF, an ER Stress Responsive Neurotrophic Factor, in Protecting Against Alcohol Neurotoxicity

Alcohol exposure during pregnancy is harmful to the fetus and causes a wide range of long-lasting physiological and neurocognitive impairments, collectively referred to as fetal alcohol spectrum disorders (FASD). The neurobehavioral deficits observed in FASD result from structural and functional damages in the brain, with neurodegeneration being the most destructive consequence. Currently, there are no therapies for FASD. It is exigent to delineate the underlying mechanisms of alcohol neurotoxicity and develop an effective strategy of treatment. ER stress, caused by the accumulation of unfolded/misfolded proteins in the ER, is the hallmark of many neurodegenerative diseases, including alcohol-induced neurodegeneration. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a newly discovered endoplasmic reticulum (ER) stress responsive neurotrophic factor that regulates diverse neuronal functions. This review summarizes the recent findings revealing the effects of MANF on the CNS and its protective role against neurodegeneration. Particularly, we focus the role of MANF on alcohol-induced ER stress and neurodegeneration and discuss the therapeutic potential of MANF in treating alcohol neurotoxicity such as FASD.

MANF: A Novel Endoplasmic Reticulum Stress Response Protein-The Role in Neurological and Metabolic Disorders

The mesencephalic astrocyte-derived neurotrophic factor (MANF), also named as arginine-rich protein (ARP) or arginine-rich mutated in early-stage tumors (ARMET), is a novel evolutionary conserved protein related to unfolded protein response. Growing evidence suggests that MANF critically involves in many ER stress-related diseases with a protective effect. Here, we review the function of MANF based on its structure in neurological and metabolic disorders and summarize its potential applications in disease diagnosis and therapies.

Endoplasmic reticulum stress-related secretory proteins as biomarkers of early myocardial ischemia-induced sudden cardiac deaths

Early myocardial ischemia-induced sudden cardiac deaths (EMI-SCD) remain a great diagnostic challenge for forensic pathologists due to no gross or non-specific histological pathology. The goal of this study was to assess whether three secretory proteins, related with cellular endoplasmic reticulum stress, can be applied in forensic diagnosis of EMI-SCD. These markers included LMAN2, CAPN-1, and VCP and were compared with two clinically used markers (CK-MB and cTnI). A total of 21 EMI-SCD cases with a mean age of 53.0 (± 10.5) years and a mean ischemia interval of < 2.77 (± 2.56) hours were collected. Another 23 cases (mean 44.6 ± 15.0 year old) that died from non-cardiac causes served as control. Enzyme-linked immunosorbent assay (ELISA) was performed to detect target proteins' serum concentrations in the EMI-SCD and control groups. We found that LMAN2, CAPN-1, and VCP were all significantly increased in the EMI-SCD group as compared with control serum, with the fold changes ranging from 1.48 (p = 0.0022, LMAN2), 1.33 (p = 0.041, CAPN-1), to 1.26 (p = 0.021, VCP), respectively. The concentrations of these proteins remained highly stable within 6 h and were not affected by death time, postmortem interval (< 4 h), age, and month at death. Receiver operating characteristic (ROC) curves showed that the areas under the curve (AUC) were 0.8178 (LMAN2), 0.6988 (CAPN-1), and 0.7267 (VCP), all of which were higher than CK-MB (AUC 0.5590) and cTn-I (AUC 0.5911). The diagnostic specificity (all above 60%) was obviously higher than CK-MB (43.48%) and cTnI (34.78%). In conclusion, LMAN-2, CAPN-1, and VCP could be stable serological biomarkers for diagnosis of EMI-SCD cases.

The cytoprotective protein MANF promotes neuronal survival independently from its role as a GRP78 cofactor

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER)-stress-regulated protein exhibiting cytoprotective properties through a poorly understood mechanism in various in vitro and in vivo models of neuronal and non-neuronal damage. Although initially characterized as a secreted neurotrophic factor for midbrain dopamine neurons, MANF has recently gained more interest for its intracellular role in regulating the ER homeostasis, including serving as a cofactor of the chaperone glucose-regulated protein 78 (GRP78). We aimed for a better understanding of the neuroprotective mechanisms of MANF. Here we show for the first time that MANF promotes the survival of ER-stressed neurons in vitro as a general unfolded protein response (UPR) regulator, affecting several UPR pathways simultaneously. Interestingly, MANF does not affect naïve neurons. We hypothesize that MANF regulates UPR signaling toward a mode more compatible with neuronal survival. Screening of MANF interacting proteins from two mammalian cell lines revealed a conserved interactome of 15 proteins including several ER chaperones such as GRP78, GRP170, protein disulfide isomerase family A member 1, and protein disulfide isomerase family A member 6. Further characterization confirmed previously published finding that MANF is a cofactor of GRP78 interacting with its nucleotide binding domain. Using microscale thermophoresis and nuclear magnetic resonance spectroscopy, we discovered that MANF is an ATP binding protein and that ATP blocks the MANF-GRP78 interaction. Interestingly, functional analysis of the antiapoptotic properties of MANF mutants in cultured neurons revealed divergent roles of MANF as a GRP78 cofactor and as an antiapoptotic regulator of UPR. We conclude that the co-factor type interaction with GRP78 is dispensable for the survival-promoting activity of MANF in neurons.

Attenuated Induction of the Unfolded Protein Response in Adult Human Primary Astrocytes in Response to Recurrent Low Glucose

AIMS/HYPOTHESIS

Recurrent hypoglycaemia (RH) is a major side-effect of intensive insulin therapy for people with diabetes. Changes in hypoglycaemia sensing by the brain contribute to the development of impaired counterregulatory responses to and awareness of hypoglycaemia. Little is known about the intrinsic changes in human astrocytes in response to acute and recurrent low glucose (RLG) exposure.

METHODS

Human primary astrocytes (HPA) were exposed to zero, one, three or four bouts of low glucose (0.1 mmol/l) for three hours per day for four days to mimic RH. On the fourth day, DNA and RNA were collected. Differential gene expression and ontology analyses were performed using DESeq2 and GOseq, respectively. DNA methylation was assessed using the Infinium MethylationEPIC BeadChip platform.

RESULTS

24 differentially expressed genes (DEGs) were detected (after correction for multiple comparisons). One bout of low glucose exposure had the largest effect on gene expression. Pathway analyses revealed that endoplasmic-reticulum (ER) stress-related genes such as HSPA5, XBP1, and MANF, involved in the unfolded protein response (UPR), were all significantly increased following low glucose (LG) exposure, which was diminished following RLG. There was little correlation between differentially methylated positions and changes in gene expression yet the number of bouts of LG exposure produced distinct methylation signatures.

CONCLUSIONS/INTERPRETATION

These data suggest that exposure of human astrocytes to transient LG triggers activation of genes involved in the UPR linked to endoplasmic reticulum (ER) stress. Following RLG, the activation of UPR related genes was diminished, suggesting attenuated ER stress. This may be a consequence of a successful metabolic adaptation, as previously reported, that better preserves intracellular energy levels and a reduced necessity for the UPR.

Mesencephalic astrocyte-derived neurotropic factor is an important factor in chondrocyte ER homeostasis

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER) resident protein that can be secreted due to an imperfect KDEL motif. MANF plays a cytoprotective role in several soft tissues and is upregulated in conditions resulting from intracellular retention of mutant protein, including two skeletal diseases, metaphyseal chondrodysplasia, Schmid type (MCDS) and multiple epiphyseal dysplasia (MED). The role of MANF in skeletal tissue homeostasis is currently unknown. Interestingly, cartilage-specific deletion of Manf in a mouse model of MED resulted in increased disease severity, suggesting its upregulation may be chondroprotective. Treatment of MED chondrocytes with exogenous MANF led to a decrease in the cellular levels of BiP (GRP78), confirming MANF's potential to modulate ER stress responses. However, it did not alleviate the intracellular retention of mutant matrilin-3, suggesting that it is the intracellular MANF that is of importance in the pathobiology of skeletal dysplasias. The Col2Cre-driven deletion of Manf from mouse cartilage resulted in a chondrodysplasia-like phenotype. Interestingly, ablation of MANF in cartilage did not have extracellular consequences but led to an upregulation of several ER-resident chaperones including BiP. This apparent induction of ER stress in turn led to dysregulated chondrocyte apoptosis and decreased proliferation, resulting in reduced long bone growth. We have previously shown that ER stress is an underlying disease mechanism for several skeletal dysplasias. The cartilage-specific deletion of Manf described in this study phenocopies our previously published chondrodysplasia models, further confirming that ER stress itself is sufficient to disrupt skeletal growth and thus represents a potential therapeutic target.

4-Phenylbutyric Acid Protects Against Ethanol-Induced Damage in the Developing Mouse Brain

BACKGROUND

Ethanol (EtOH) exposure during pregnancy may result in fetal alcohol spectrum disorders (FASD). One of the most deleterious consequences of EtOH exposure is neuronal loss in the developing brain. Previously, we showed that EtOH exposure induced neuroapoptosis in the brain of postnatal day 4 (PD4) mice but not PD12 mice. This differential susceptibility may result from an insufficient cellular stress response system such as unfolded protein response (also known as endoplasmic reticulum [ER] stress) in PD4 mice. In this study, we compared the effect of EtOH on ER stress in PD4 and PD12 mice and determined whether the inhibition of ER stress could protect the developing brain against EtOH damage.

METHODS

We used a third-trimester equivalent mouse model of FASD. PD4 and PD12 C57BL/6 mice were subcutaneously injected with saline (control), EtOH, EtOH plus 4-phenylbutyric acid (4-PBA), a chemical chaperone known as ER stress inhibitor, and 4-PBA alone. The expression of apoptosis marker, ER stress markers, and markers for glial cell activation was examined in the cerebral cortex.

RESULTS

EtOH induced neuroapoptosis and increased the expression of ER stress markers, such as activating transcription factor 6, 78-kDa glucose-regulated protein, inositol-requiring enzyme 1α, mesencephalic astrocyte-derived neurotrophic factor, and caspase-12 in PD4 but not PD12 mice. EtOH exposure also activated microglia and astrocytes. Interestingly, treatment with 4-PBA attenuated EtOH-induced neuroapoptosis. Moreover, 4-PBA inhibited the expression of the aforementioned ER stress markers and EtOH-induced glial activation in PD4 mice.

CONCLUSIONS

ER stress plays an important role in EtOH-induced damage to the developing brain. Inhibition of ER stress is neuroprotective and may provide a new therapeutic strategy for treating FASD.

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.

Cab45s inhibits neuronal apoptosis following intracerebral hemorrhage in adult rats

Recent studies have shown that Cab45s, belonging to the CREC family, can fight against apoptosis in the cancer cell lines. Here, we report that Cab45s may involve in neuronal apoptosis at the early stage of intracerebral hemorrhage (ICH) in pathophysiology. We found that expression of Cab45s was enhanced in areas contiguous to hematoma following ICH in adult rats, and that so were the expressions of Glucose-regulated protein 78 (GRP78), pro-apoptotic Bcl-2-associated X protein (Bax) and active caspase-3. In vitro, coimmunoprecipitation analysis indicated the interaction between Cab45s and GRP78. Depletion of Cab45s attenuated the expression of GRP78, but increased the expressions of Bax and caspase-3 in PC12 cells treated with hemin, which finally promoted apoptosis. Together, these results reveal that Cab45s might exert its anti-apoptotic function against neuronal apoptosis. Thus, the study may provide evidences for regulating Cab45s as a potentially reliable treatment for the secondary damage following ICH.

C. elegans MANF Homolog Is Necessary for the Protection of Dopaminergic Neurons and ER Unfolded Protein Response

Neurotrophic factors (NTFs) are important for the development, function, and survival of neurons in the mammalian system. Mesencephalic astrocyte-derived neurotrophic factor (MANF) and cerebral dopamine neurotrophic factor (CDNF) are two recently identified members of a novel family of NTFs in vertebrates that function to protect dopaminergic neurons. Although these genes are conserved across eukaryotes, their mechanism of neuroprotection is not fully understood. Sequence searches for MANF/CDNF homologs in invertebrates have identified a single ortholog that is most related to MANF. Here we report the in vivo characterization of the MANF gene, manf-1, in the nematode Caenorhabditis elegans. We found that manf-1 mutants have an accelerated, age-dependent decline in the survival of dopaminergic neurons. The animals also show increased endoplasmic reticulum (ER) stress, as revealed by reporter gene expression analysis of hsp-4, an ER chaperone BiP/GRP78 homolog, suggesting that a failure to regulate the ER unfolded protein response (ER-UPR) may be a contributing factor to dopaminergic neurodegeneration. Expression studies of manf-1 revealed that the gene is broadly expressed in a pattern that matches closely with hsp-4. Consistent with the requirements of manf-1 in the ER-UPR, we found that aggregates of α-Synuclein, a major constituent of Lewy bodies, were significantly increased in body wall muscles of manf-1 mutant animals. Overall, our work demonstrates the important role of manf-1 in dopaminergic neuronal survival and the maintenance of ER homeostasis in C. elegans.

MANF protects dopamine neurons and locomotion defects from a human α-synuclein induced Parkinson's disease model in C. elegans by regulating ER stress and autophagy pathways

Many studies have demonstrated that mesencephalic astrocyte-derived neurotrophic factor (MANF) has been shown protective effects on neurotoxin based models of Parkinson's disease (PD). It still remains unclear whether MANF can rescue dopaminergic (DA) neurons in an α-synuclein model. Glial cell line-derived neurotrophic factor (GDNF) and its related neurturin (NRTN) can protect DA neurons in the neurotoxin but not α-synuclein animal models of PD, it failed in the clinical trials. Since α-synuclein model can better mimic the progression of human PD, in our study we overexpressed MANF specifically in DA neurons by using an α-synuclein Caenorhabditis elegans (C. elegans) model. Our results showed MANF alleviated progressive neuronal degeneration and prevented locomotion defects. Indeed, MANF can protect cilia of DA neurons at an early stage, suggested that MANF participated in the whole process of neuronal degeneration. Furthermore, we found MANF facilitated the removal of misfolded α-synuclein proteins and rescued the function of damaged DA neurons. By using RNAi approach, we inhibited ER stress and autophagy related genes and effects of MANF were decreased, which demonstrated ER stress and autophagy pathways were involved in the MANF-mediated neuroprotection. Our study suggests MANF exhibits potential as a neuroprotective agent for PD therapy.

Neuroprotective effects of the gliopeptide ODN in an in vivo model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a progressive loss of dopamine (DA) neurons through apoptotic, inflammatory and oxidative stress mechanisms. The octadecaneuropeptide (ODN) is a diazepam-binding inhibitor (DBI)-derived peptide, expressed by astrocytes, which protects neurons against oxidative cell damages and apoptosis in an in vitro model of PD. The present study reveals that a single intracerebroventricular injection of 10 ng ODN 1 h after the last administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) prevented the degeneration of DA neurons induced by the toxin in the substantia nigra pars compacta of mice, 7 days after treatment. ODN-mediated neuroprotection was associated with a reduction of the number of glial fibrillary acidic protein-positive reactive astrocytes and a strong inhibition of the expression of pro-inflammatory genes such as interleukins 1β and 6, and tumor necrosis factor-α. Moreover, ODN blocked the inhibition of the anti-apoptotic gene Bcl-2, and the stimulation of the pro-apoptotic genes Bax and caspase-3, induced by MPTP in the substantia nigra pars compacta. ODN also decreased or even in some cases abolished MPTP-induced oxidative damages, overproduction of reactive oxygen species and accumulation of lipid oxidation products in DA neurons. Furthermore, DBI knockout mice appeared to be more vulnerable than wild-type animals to MPTP neurotoxicity. Taken together, these results show that the gliopeptide ODN exerts a potent neuroprotective effect against MPTP-induced degeneration of nigrostriatal DA neurons in mice, through mechanisms involving downregulation of neuroinflammatory, oxidative and apoptotic processes. ODN may, thus, reduce neuronal damages in PD and other cerebral injuries involving oxidative neurodegeneration.

MANF attenuates neuronal apoptosis and promotes behavioral recovery via Akt/MDM-2/p53 pathway after traumatic spinal cord injury in rats

The aim of this study was to investigate the potential effect and mechanism of action of MANF in attenuating neuronal apoptosis following t-SCI. A clip compressive model was used to induce a crush injury of the spinal cord in a total of 230 rats. The Basso, Beattie, and Bresnahan (BBB) score, spinal cord water content, and blood spinal cord barrier (BSCB) permeability were evaluated. The expression levels of MANF and its downstream proteins were examined by western blotting. Immunofluorescence staining of MANF, NeuN, GFAP, Iba-1, cleaved caspase-3, and TUNEL staining were also performed. Cells were counted in six randomly selected fields in the gray matter regions of the sections from two spinal cord sites (2 mm rostral and caudal to the epicenter of the injury) per sample. A cell-based mechanical injury model was also conducted using SH-SY5Y cells. Cell apoptosis and viability were assessed by flow cytometry, an MTT assay, and trypan blue staining. Subcellular structures were observed by transmission electron microscopy. MANF was mainly expressed in neurons. The expression levels of MANF, and its downstream target, p-Akt, were gradually increased and after t-SCI. Treatment with MANF increased Bcl-2 and decreased Bax and CC-3 levels; these effects were reversed on treatment with MK2206. The BBB score, spinal cord water content, and BSCB destruction were also ameliorated by MANF treatment. MANF decreases neuronal apoptosis and improves neurological function through Akt/MDM-2/p53 pathway after t-SCI. Therefore, MANF might be a potential treatment for patients with t-SCI.© 2018 BioFactors, 2018.

Bilberry extract administration prevents retinal ganglion cell death in mice via the regulation of chaperone molecules under conditions of endoplasmic reticulum stress

Purpose

To investigate the effect of bilberry extract anthocyanins on retinal ganglion cell (RGC) survival after optic nerve crush. Additionally, to determine details of the mechanism of the neuroprotective effect of bilberry extract anthocyanins and the involvement of endoplasmic reticulum stress suppression in the mouse retina.

Materials and methods

Anthocyanins in bilberry extract (100 mg/kg/day or 500 mg/kg/day) were administrated orally to C57BL/6J mice. The expression levels of various molecular chaperones were assessed with quantitative reverse-transcription polymerase chain reaction, Western blotting, and immunohistochemistry. RGC survival was evaluated by measuring the gene expression of RGC markers and counting retrogradely labeled RGCs after optic nerve crush.

Results

The protein levels of Grp78 and Grp94 increased significantly in mice after bilberry extract administration. Increased Grp78 and Grp94 levels were detected in the inner nuclear layer and ganglion cell layer of the retina, surrounding the RGCs. Gene expression of Chop, Bax, and Atf4 increased in mice after optic nerve crush and decreased significantly after oral bilberry extract administration. RGC survival after nerve crush also increased with bilberry extract administration.

Conclusion

These results indicate that oral bilberry extract administration suppresses RGC death. Bilberry extract administration increased Grp78 and Grp94 protein levels, an effect which may underlie the neuroprotective effect of bilberry extract after optic nerve crush. Thus, bilberry extract has a potential role in neuroprotective treatments for retinal injuries, such as those which occur in glaucoma.

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.

Mesencephalic astrocyte-derived neurotrophic factor reduces cell apoptosis via upregulating HSP70 in SHSY-5Y cells

Background

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a new candidate growth factor for dopaminergic neurons against endoplasmic reticulum stress (ER stress). HSP70 family, a chaperon like heat shock protein family, was proved to be involved in the MANF induced survival pathway in 6-OHDA treated SHSY-5Y cells. However, the ER stress relative transcriptome, in MANF signaling cascades is still investigated. The involvement of HSP70, a 70kd member of HSP70 family, need further to be verified.

Methods

The cell apoptosis was assayed by MTT, TUNEL staining and western blot of cleaved Caspase-3. The differentially expressed genes in SHSY-5Y cells under different conditions (control, 6-OHDA, 6-OHDA + MANF) were investigated by RNA-seq. Expression of HSP70 was further confirmed by real-time PCR. RNAi knockdown for HSP70 was performed to investigate the role of HSP70 in the MANF signaling pathway.

Results

MANF inhibits 6-OHDA-induced apoptosis in SHSY-5Y cells. Six ER stress relative genes (HSP70, GRP78, xbp-1, ATF-4, ATF-6, MAPK) were found enriched in 6-OHDA + MANF treatment group. HSP70 was the most significantly up-regulated gene under 6-OHDA + MANF treatment in SHSY-5Y cells. RNAi knockdown for HSP70 inhibits the protective effects of MANF against 6-OHDA toxicity in SHSY-5Y cells.

Conclusion

MANF exerts a protective role against 6-OHDA induced apoptosis in SHSY-5Y cells via up-regulating some ER stress genes, including HSP70 family members. The HSP70 expression level plays a key role in MANF-mediated survival pathway.

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.