Mesencephalic Astrocyte-Derived Neurotrophic Factor Prevents Traumatic Brain Injury in Rats by Inhibiting Inflammatory Activation and Protecting the Blood-Brain Barrier

Astrocytes in functional recovery following central nervous system injuries

Astrocytes are increasingly recognised as partaking in complex homeostatic mechanisms critical for regulating neuronal plasticity following central nervous system (CNS) insults. Ischaemic stroke and traumatic brain injury are associated with high rates of disability and mortality. Depending on the context and type of injury, reactive astrocytes respond with diverse morphological, proliferative and functional changes collectively known as astrogliosis, which results in both pathogenic and protective effects. There is a large body of research on the negative consequences of astrogliosis following brain injuries. There is also growing interest in how astrogliosis might in some contexts be protective and help to limit the spread of the injury. However, little is known about how astrocytes contribute to the chronic functional recovery phase following traumatic and ischaemic brain insults. In this review, we explore the protective functions of astrocytes in various aspects of secondary brain injury such as oedema, inflammation and blood-brain barrier dysfunction. We also discuss the current knowledge on astrocyte contribution to tissue regeneration, including angiogenesis, neurogenesis, synaptogenesis, dendrogenesis and axogenesis. Finally, we discuss diverse astrocyte-related factors that, if selectively targeted, could form the basis of astrocyte-targeted therapeutic strategies to better address currently untreatable CNS disorders.

Neurotrophins and neural stem cells in posttraumatic brain injury repair

Traumatic brain injury (TBI) is the main cause of disability, mental health disorder, and even death, with its incidence and social costs rising steadily. Although different treatment strategies have been developed and tested to mitigate neurological decline, a definitive cure for these conditions remains elusive. Studies have revealed that various neurotrophins represented by the brain-derived neurotrophic factor are the key regulators of neuroinflammation, apoptosis, blood-brain barrier permeability, neurite regeneration, and memory function. These factors are instrumental in alleviating neuroinflammation and promoting neuroregeneration. In addition, neural stem cells (NSC) contribute to nerve repair through inherent neuroprotective and immunomodulatory properties, the release of neurotrophins, the activation of endogenous NSCs, and intercellular signaling. Notably, innovative research proposals are emerging to combine BDNF and NSCs, enabling them to synergistically complement and promote each other in facilitating injury repair and improving neuron differentiation after TBI. In this review, we summarize the mechanism of neurotrophins in promoting neurogenesis and restoring neural function after TBI, comprehensively explore the potential therapeutic effects of various neurotrophins in basic research on TBI, and investigate their interaction with NSCs. This endeavor aims to provide a valuable insight into the clinical treatment and transformation of neurotrophins in TBI, thereby promoting the progress of TBI therapeutics.

MANF protein expression is upregulated in immune cells in the ischemic human brain and systemic recombinant MANF delivery in rat ischemic stroke model demonstrates anti-inflammatory effects

Mesencephalic astrocyte-derived neurotrophic factor (MANF) has cytoprotective effects on various injuries, including cerebral ischemia, and it can promote recovery even when delivered intracranially several days after ischemic stroke. In the uninjured rodent brain, MANF protein is expressed almost exclusively in neurons, but post-ischemic MANF expression has not been characterized. We aimed to investigate how endogenous cerebral MANF protein expression evolves in infarcted human brains and rodent ischemic stroke models. During infarct progression, the cerebral MANF expression pattern both in human and rat brains shifted drastically from neurons to expression in inflammatory cells. Intense MANF immunoreactivity took place in phagocytic microglia/macrophages in the ischemic territory, peaking at two weeks post-stroke in human and one-week post-stroke in rat ischemic cortex. Using double immunofluorescence and mice lacking MANF gene and protein from neuronal stem cells, neurons, astrocytes, and oligodendrocytes, we verified that MANF expression was induced in microglia/macrophage cells in the ischemic hemisphere. Embarking on the drastic expression transition towards inflammatory cells and the impact of blood-borne inflammation in stroke, we hypothesized that exogenously delivered MANF protein can modulate tissue recovery processes. In an attempt to enhance recovery, we designed a set of proof-of-concept studies using systemic delivery of recombinant MANF in a rat model of cortical ischemic stroke. Intranasal recombinant MANF treatment decreased infarct volume and reduced the severity of neurological deficits. Intravenous recombinant MANF treatment decreased the levels of pro-inflammatory cytokines and increased the levels of anti-inflammatory cytokine IL-10 in the infarcted cortex one-day post-stroke. In conclusion, MANF protein expression is induced in activated microglia/macrophage cells in infarcted human and rodent brains, and this could implicate MANF's involvement in the regulation of post-stroke inflammation in patients and experimental animals. Moreover, systemic delivery of recombinant MANF shows promising immunomodulatory effects and therapeutic potential in experimental ischemic stroke.

Prognostic potential of serum mesencephalic astrocyte-derived neurotrophic factor in acute intracerebral hemorrhage: a prospective observational study

OBJECTIVE

Mesencephalic astrocyte-derived neurotrophic factor (MANF) expressions are dramatically up-regulated in injured brain tissues, thereby conferring neurological protective effects. We intended to determine significance of serum MANF as a prognostic biomarker of intracerebral hemorrhage (ICH).

METHODS

In this prospective, observational study done from February 2018 to July 2021, 124 patients with new-onset primary supratentorial ICH were consecutively enrolled. Also, a group of 124 healthy individuals constituted controls. Their serum MANF levels were detected using the Enzyme-Linked Immunosorbent Assay. National Institutes of Health Stroke Scale (NIHSS) and hematoma volume were designated as the two severity indicators. Early neurologic deterioration (END) was referred to as an increase of 4 or greater points in NIHSS scores or death at post-stroke 24 h. Post-stroke 90-day modified Rankin scale (mRS) scores of 3-6 was considered as a poor prognosis. Serum MANF levels were analyzed using multivariate analysis with respect to its association with stroke severity and prognosis.

RESULTS

Patients, in comparison to controls, displayed markedly elevated serum MANF levels (median, 24.7 versus 2.7 ng/ml; P < 0.001), and serum MANF levels were independently correlated with NIHSS scores (beta, 3.912; 95% confidence interval (CI), 1.623-6.200; VIF = 2.394; t = 3.385; P = 0.002), hematoma volumes (beta, 1.688; 95% CI, 0.764-2.612; VIF = 2.661; t = 3.617; P = 0.001) and mRS scores (beta, 0.018; 95% CI, 0.013-0.023; VIF = 1.984; t = 2.047; P = 0.043). Serum MANF levels significantly predicted END and poor 90-day prognosis with areas under receiver operating characteristic curve at 0.752 and 0.787 respectively. END and prognostic predictive abilities were similar between serum MANF levels and NIHSS scores plus hematoma volumes (all P > 0.05). Combination of serum MANF levels with NIHSS scores and hematoma volumes had significantly higher prognostic capability than each of them (both P < 0.05). Serum MANF levels above 52.5 ng/ml and 62.0 ng/ml distinguished development of END and poor prognosis respectively with median-high sensitivity and specificity values. Using multivariate analysis, serum MANF levels > 52.5 ng/ml predicted END with odds ratio (OR) value of 2.713 (95% CI, 1.004-7.330; P = 0.042) and > 62.0 ng/ml predicted a poor prognosis with OR value of 3.848 (95% CI, 1.193-12.417; P = 0.024). Using restricted cubic spline, there was a linear correlation between serum MANF levels and poor prognosis or END risk (both P > 0.05). Nomograms were well established to predict END and a poor 90-day prognosis. Under calibration curve, such combination models were comparatively stable (using Hosmer & Lemeshow test, both P > 0.05).

CONCLUSION

Increased serum MANF levels after ICH, in independent correlation with disease severity, independently distinguished risks of END and 90-day poor prognosis. Therefore, serum MANF may be a potential prognostic biomarker of ICH.

A prospective observational study on utility of serum mesencephalic astrocyte-derived neurotrophic factor as a promising prognostic biomarker of severe traumatic brain injury in humans

BACKGROUND

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is released under endoplasmic reticulum stress, thereby exerting neuroprotective effects. We determined whether serum MANF may be a prognostic biomarker of human severe traumatic brain injury (sTBI).

METHODS

Serum MANF concentrations of 137 sTBI patients and 137 controls were quantified in this prospective cohort study. Patients with extended Glasgow outcome scale (GOSE) scores of 1-4 at post-traumatic 6 months were considered to have poor prognosis. Relationships between serum MANF concentrations and severity plus prognosis were investigated using multivariate analyses. Area under receiver operating characteristic curve (AUC) was calculated for reflecting prognostic efficiency.

RESULTS

As compared to controls, there was a significant increase of serum MANF concentrations after sTBI (median, 18.5 ng/ml versus 3.0 ng/ml; P<0.001), which was independently correlated with Glasgow coma scale (GCS) scores [β, -3.000; 95% confidence interval (CI), -4.525--1.476; VIF, 2.216; P=0.001], Rotterdam computed tomography (CT) scores (β, 4.020; 95% CI, 1.446-6.593; VIF, 2.234; P=0.002) and GOSE scores (β, -0.056; 95% CI, -0.089--0.023; VIF, 1.743; P=0.011). Serum MANF concentrations substantially distinguished risk of poor prognosis with AUC of 0.795 (95% CI, 0.718-0.859) and its concentrations >23.9 ng/ml was predictive of poor prognosis with 67.7% sensitivity and 81.9% specificity. Serum MANF concentrations combined with GCS scores and Rotterdam CT scores displayed markedly higher prognostic predictive ability than each of them (all P<0.05). Using restricted cubic spline, there was a linear correlation between serum MANF concentrations and poor prognosis (P=0.256). Serum MANF concentrations > 23.9 ng/ml was independently associated with poor prognosis (odds ratio, 2.911; 95% CI, 1.057-8.020; P=0.039). A nomogram was built, where serum MANF concentrations > 23.9 ng/ml, GCS scores and Rotterdam CT scores were integrated. Hosmer and Lemeshow test, calibration curve and decision curve analysis demonstrated such a prediction model was comparatively stable and was of relatively high clinical benefit.

CONCLUSIONS

Substantially increased serum MANF concentrations after sTBI are highly correlated with traumatic severity and are independently predictive of long-term poor prognosis, suggesting that serum MANF may represent a useful prognostic biochemical marker of human sTBI.

A Focal Impact Model of Traumatic Brain Injury in Xenopus Tadpoles Reveals Behavioral Alterations, Neuroinflammation, and an Astroglial Response

Traumatic Brain Injury (TBI) is a global driver of disability, and we currently lack effective therapies to promote neural repair and recovery. TBI is characterized by an initial insult, followed by a secondary injury cascade, including inflammation, excitotoxicity, and glial cellular response. This cascade incorporates molecular mechanisms that represent potential targets of therapeutic intervention. In this study, we investigate the response to focal impact injury to the optic tectum of Xenopus laevis tadpoles. This injury disrupts the blood-brain barrier, causing edema, and produces deficits in visually-driven behaviors which are resolved within one week. Within 3 h, injured brains show a dramatic transcriptional activation of inflammatory cytokines, upregulation of genes associated with inflammation, and recruitment of microglia to the injury site and surrounding tissue. Shortly afterward, astrocytes undergo morphological alterations and accumulate near the injury site, and these changes persist for at least 48 h following injury. Genes associated with astrocyte reactivity and neuroprotective functions also show elevated levels of expression following injury. Since our results demonstrate that the response to focal impact injury in Xenopus resembles the cellular alterations observed in rodents and other mammalian models, the Xenopus tadpole offers a new, scalable vertebrate model for TBI.

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.

Mesencephalic astrocyte-derived neurotrophic factor attenuates acute lung injury via inhibiting macrophages' activation

Acute lung injury (ALI) is an urgent respiratory disease without effective treatment. Mesencephalic astrocyte-derived neurotrophic factor (MANF)has been demonstrated to play a suppressive role in some inflammatory conditions. However, the effect of MANF on ALI has not yet been reported. In this study, we collected bronchoalveolar lavage fluid (BALF) from the patients with or without pulmonary inflammation, and used lipopolysaccharide (LPS) to induce mice ALI model. Mono-macrophage-specific MANF knockout (MKO) mice were constructed and recombinant human MANF protein was used to ALI mice. We found that the endogenous MANF protein in both human BALF and mice lung tissues was increased in inflammatory conditions. MANF level in the macrophages of inflammatory lung was higher than that in normal controls in both human and mice. MANF deficiency in macrophages induced lung inflammation and aggravated LPS-induced lung injury. MANF lowered LPS-induced lung injury, inhibited macrophage polarization to M1 functional type. Meanwhile, MANF inhibited-LPS induced activation of NF-κB signal pathway by down regulating phosphorylated p65in lung tissue and macrophages. These results indicate that MANF acts as a suppressor in ALI via negatively regulating NF-κB activation and macrophages polarization, which may be a novel potential target and shed light on ALI therapy.

Reactive Astrocytes in Central Nervous System Injury: Subgroup and Potential Therapy

Traumatic central nervous system (CNS) injury, which includes both traumatic brain injury (TBI) and spinal cord injury (SCI), is associated with irreversible loss of neurological function and high medical care costs. Currently, no effective treatment exists to improve the prognosis of patients. Astrocytes comprise the largest population of glial cells in the CNS and, with the advancements in the field of neurology, are increasingly recognized as having key functions in both the brain and the spinal cord. When stimulated by disease or injury, astrocytes become activated and undergo a series of changes, including alterations in gene expression, hypertrophy, the loss of inherent functions, and the acquisition of new ones. Studies have shown that astrocytes are highly heterogeneous with respect to their gene expression profiles, and this heterogeneity accounts for their observed context-dependent phenotypic diversity. In the inured CNS, activated astrocytes play a dual role both as regulators of neuroinflammation and in scar formation. Identifying the subpopulations of reactive astrocytes that exert beneficial or harmful effects will aid in deciphering the pathological mechanisms underlying CNS injuries and ultimately provide a theoretical basis for the development of effective strategies for the treatment of associated conditions. Following CNS injury, as the disease progresses, astrocyte phenotypes undergo continuous changes. Although current research methods do not allow a comprehensive and accurate classification of astrocyte subpopulations in complex pathological contexts, they can nonetheless aid in understanding the roles of astrocytes in disease. In this review, after a brief introduction to the pathology of CNS injury, we summarize current knowledge regarding astrocyte activation following CNS injury, including: (a) the regulatory factors involved in this process; (b) the functions of different astrocyte subgroups based on the existing classification of astrocytes; and (c) attempts at astrocyte-targeted therapy.

Effects of cannabinoid (CBD) on blood brain barrier permeability after brain injury in rats

Cannabidiol is a natural herbal medicine known to protect the brain from traumatic brain injury (TBI). Here, a TBI rat model was established, with cannabidiol administered intraperitoneally at doses of 5, 10, or 20 mg/kg, 30 min before surgery and 6 h after surgery until sacrifice. Brain water content, body weight, and modified neurological severity scores were determined, and enzyme-linked immunosorbent assay, immunofluorescence staining, hematoxylin and eosin staining, Nissl staining, Evans-blue dye extravasation, and western blotting were performed. Results showed that cannabidiol decreased the number of aquaporin-4-positive and glial fibrillary acidic protein-positive cells. Cannabidiol also significantly reduced the protein levels of proinflammatory cytokines (TNF-α and IL-1β) and significantly increased the expression of tight junction proteins (claudin-5 and occludin). Moreover, cannabidiol administration significantly mitigated water content in the brain after TBI and blood-brain barrier disruption and ameliorated the neurological deficit score after TBI. Cannabidiol administration improved the integrity and permeability of the blood-brain barrier and reduced edema in the brain after TBI.

Glial Cell Line-Derived Neurotrophic Factor Family Ligands, Players at the Interface of Neuroinflammation and Neuroprotection: Focus Onto the Glia

Well-known effects of neurotrophic factors are related to supporting the survival and functioning of various neuronal populations in the body. However, these proteins seem to also play less well-documented roles in glial cells, thus, influencing neuroinflammation. This article summarizes available data on the effects of glial cell line derived neurotrophic factor (GDNF) family ligands (GFLs), proteins providing trophic support to dopaminergic, sensory, motor and many other neuronal populations, in non-neuronal cells contributing to the development and maintenance of neuropathic pain. The paper also contains our own limited data describing the effects of small molecules targeting GFL receptors on the expression of the satellite glial marker IBA1 in dorsal root ganglia of rats with surgery- and diabetes-induced neuropathy. In our experiments activation of GFLs receptors with either GFLs or small molecule agonists downregulated the expression of IBA1 in this tissue of experimental animals. While it can be a secondary effect due to a supportive role of GFLs in neuronal cells, growing body of evidence indicates that GFL receptors are expressed in glial and peripheral immune system cells. Thus, targeting GFL receptors with either proteins or small molecules may directly suppress the activation of glial and immune system cells and, therefore, reduce neuroinflammation. As neuroinflammation is considered to be an important contributor to the process of neurodegeneration these data further support research efforts to modulate the activity of GFL receptors in order to develop disease-modifying treatments for neurodegenerative disorders and neuropathic pain that target both neuronal and glial cells.

Pathophysiological Responses and Roles of Astrocytes in Traumatic Brain Injury

Traumatic brain injury (TBI) is immediate damage caused by a blow to the head resulting from traffic accidents, falls, and sporting activity, which causes death or serious disabilities in survivors. TBI induces multiple secondary injuries, including neuroinflammation, disruption of the blood–brain barrier (BBB), and brain edema. Despite these emergent conditions, current therapies for TBI are limited or insufficient in some cases. Although several candidate drugs exerted beneficial effects in TBI animal models, most of them failed to show significant effects in clinical trials. Multiple studies have suggested that astrocytes play a key role in the pathogenesis of TBI. Increased reactive astrocytes and astrocyte-derived factors are commonly observed in both TBI patients and experimental animal models. Astrocytes have beneficial and detrimental effects on TBI, including promotion and restriction of neurogenesis and synaptogenesis, acceleration and suppression of neuroinflammation, and disruption and repair of the BBB via multiple bioactive factors. Additionally, astrocytic aquaporin-4 is involved in the formation of cytotoxic edema. Thus, astrocytes are attractive targets for novel therapeutic drugs for TBI, although astrocyte-targeting drugs have not yet been developed. This article reviews recent observations of the roles of astrocytes and expected astrocyte-targeting drugs in TBI.

Hepatocyte-derived MANF alleviates hepatic ischaemia-reperfusion injury via regulating endoplasmic reticulum stress-induced apoptosis in mice

BACKGROUND

Endoplasmic reticulum (ER) perturbations are novel subcellular effectors involved in the ischaemia-reperfusion injury. As an ER stress-inducible protein, mesencephalic astrocyte-derived neurotrophic factor (MANF) has been proven to be increased during ischaemic brain injury. However, the role of MANF in liver ischaemia reperfusion (I/R) injury has not yet been studied.

METHODS

To investigate the role of MANF in the process of liver ischaemia-reperfusion, Hepatocyte-specific MANF knockout (MANF^hep-/- ) mice and their wild-type (WT) littermates were used in our research. Mice partial (70%) warm hepatic I/R model was established by vascular occlusion. We detected the serum levels of MANF in both liver transplant patients and WT mice before and after liver I/R injury. Recombinant human MANF (rhMANF) was injected into the tail vein before 1 hour occlusion. AST, ALT and Suzuki score were used to evaluate the extent of I/R injury. OGD/R test was performed on primary hepatocytes to simulate IRI in vitro. RNA sequence and RT-PCR were used to detect the cellular signal pathway activation while MANF knockout.

RESULTS

We found that MANF expression and secretion are dramatically up-regulated during hepatic I/R. Hepatocyte-specific MANF knockout aggravates the I/R injury through the over-activated ER stress. The systemic administration of rhMANF before ischaemia has the potential to ameliorate I/R-triggered UPR and liver injury. Further study showed that MANF deficiency activated ATF4/CHOP and JNK/c-JUN/CHOP pathways, and rhMANF inhibited the activation of the two proapoptotic pathways caused by MANF deletion.

CONCLUSION

Collectively, our study unravels a previously unknown relationship among MANF, UPR and hepatic I/R injury.

Basic Fibroblast Growth Factor (bFGF) Protects the Blood-Brain Barrier by Binding of FGFR1 and Activating the ERK Signaling Pathway After Intra-Abdominal Hypertension and Traumatic Brain Injury

Background

Intra-abdominal hypertension (IAH) is associated with high morbidity and mortality. IAH leads to intra-abdominal tissue damage and causes dysfunction in distal organs such as the brain. The effect of a combined injury due to IAH and traumatic brain injury (TBI) on the integrity of the blood–brain barrier (BBB) has not been investigated.

Material/Methods

Intracranial pressure (ICP) monitoring, brain water content, EB permeability detection, immunofluorescence staining, real-time PCR, and Western blot analysis were used to examine the effects of IAH and TBI on the BBB in rats, and to characterize the protective effects of basic fibroblast growth factor (bFGF) on combined injury-induced BBB damage.

Results

Combined injury from IAH and TBI to the BBB resulted in brain edema and increased intracranial pressure. The effects of bFGF on alleviating the rat BBB injuries were determined, indicating that bFGF regulated the expression levels of the tight junction (TJ), adhesion junction (AJ), matrix metalloproteinase (MMP), and IL-1β, as well as reduced BBB permeability, brain edema, and intracranial pressure. Moreover, the FGFR1 antagonist PD 173074 and the ERK antagonist PD 98059 decreased the protective effects of bFGF.

Conclusions

bFGF effectively protected the BBB from damage caused by combined injury from IAH and TBI, and binding of FGFR1 and activation of the ERK signaling pathway was involved in these effects.

Basic Fibroblast Growth Factor Reduces Permeability and Apoptosis of Human Brain Microvascular Endothelial Cells in Response to Oxygen and Glucose Deprivation Followed by Reoxygenation via the Fibroblast Growth Factor Receptor 1 (FGFR1)/ERK Pathway

Background

Disruption of the blood–brain barrier (BBB) is a mechanism in the pathogenesis of traumatic brain injury. Basic fibroblast growth factor (bFGF) is expressed in angiogenesis, neurogenesis, and neuronal survival. This study aimed to investigate the role of bFGF in vitro in human brain microvascular endothelial cells (HBMECs) challenged by oxygen-glucose deprivation/reperfusion (OGD/R).

Material/Methods

HBMECs were cultured in glucose-free medium and an environment with <0.5% oxygen in an anaerobic chamber. Immunocytochemistry, Western blot, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were used to measure the protein and mRNA expression levels of bFGF, tight junction, adherens junction, apoptotic proteins, and matrix metalloproteinases (MMPs). The effects of bFGF on the viability of HBMECs was evaluated using the cell counting kit-8 (CCK-8) assay. Cell apoptosis was evaluated using the TUNEL assay, and endothelial permeability was quantified using a transwell migration assay with fluorescein isothiocyanate (FITC) conjugated with dextran. The effects of bFGF were evaluated following inhibition of fibroblast growth factor receptor 1 (FGFR1) with PD173074 and inhibition of ERK with PD98059.

Results

Following OGD/R of HBMECs, bFGF significantly reduced cell permeability and apoptosis and significantly inhibited the down-regulation of the expressions of proteins associated with tight junctions, adherens junctions, apoptosis and matrix metalloproteinases (MMPs). The effects of bFGF were mediated by the activation of FGFR1 and ERK, as they were blocked by FGFR1 and ERK inhibitors.

Conclusions

Permeability and apoptosis of HBMECs challenged by OGD/R were reduced by bFGF by activation of the FGFR1 and the ERK pathway.

Profile of neuronal exosomes in HIV cognitive impairment exposes sex differences

OBJECTIVE

To use plasma neuron-derived exosomes (NDEs) to detect proteins that diagnose HIV-associated neurocognitive disorders (HAND). To compare NDE cargo from HAND with Alzheimer's disease.

DESIGN

Eighty plasma samples were assayed including men (n = 29) and women (n = 51) with and without HAND.

METHODS

Plasma NDEs were isolated by immunoadsorption with neuron specific L1 cell adhesion molecule antibody. NDE proteins were quantified by ELISA and proximity extension assays for 184 targets.

RESULTS

Neuronal enrichment of NDE was confirmed with elevated synaptophysin and normalized to the exosomal marker, apoptosis-linked gene-2-interacting protein X (ALIX). NDE from men and women had significant divergent results. High mobility group box 1 and neurofilament light were significantly increased in NDE from cognitively impaired men and were unchanged in women. NDE from HIV+ men had decreased p-T181-tau, a marker increased in Alzheimer's disease, compared with no difference in women. NDE amyloid beta was not increased in cognitive impairment. Proximity extension assays analysis showed 25 proteins were differentially expressed in HIV infection alone. Seven proteins identified asymptomatic and mild cognitive impairment in HIV+ women. NDE from women had significantly decreased cathepsin S, total tau, neuronal cell adhesion molecule and contactin 5 in mild impairment. Twelve proteins were increased in NDE from cognitively impaired men, including carboxypeptidase M, cadherin 3, colony stimulating factor 2 receptor alpha subunit and mesencephalic astrocyte-derived neurotropic factor.

CONCLUSION

NDE proteins differ in HIV infection alone and cognitive impairment between men and women suggesting mechanistic sex differences associated with HAND. Several NDE targets are different from that reported for Alzheimer's disease.

Neuroprotective and reparative effects of endoplasmic reticulum luminal proteins - mesencephalic astrocyte-derived neurotrophic factor and cerebral dopamine neurotrophic factor

Cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF) are proteins that have received increasing attention in the last decades. Although they are called neurotrophic factors they are drastically different from neurotrophic factors in their expression and physiological actions. They are located in the lumen of the endoplasmic reticulum (ER) and their basal secretion from neurons is very low. However their secretion is stimulated upon ER calcium depletion by chemical probes such as thapsigargin, a sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) pump inhibitor. Exogenous MANF and CDNF possess therapeutic properties in several neurological disease models, including Parkinson’s disease and stroke. Endogenous MANF expression has been shown to be neuroprotective, as well as administration of either CDNF or MANF into the extracellular space. In this review, we focus on their therapeutic effects, regulation of expression and secretion, comparison of their mechanisms of action, and their application to the brain parenchyma as recombinant proteins.

Secondary Pathology of the Thalamus after Focal Cortical Stroke in Rats is not Associated with Thermal or Mechanical Hypersensitivity and is Not Alleviated by Intra-Thalamic Post-Stroke Delivery of Recombinant CDNF or MANF

A stroke affecting the somatosensory pathway can trigger central post-stroke pain syndrome (CPSP). The symptoms often include hyperalgesia, which has also been described in rodents after the direct damage of the thalamus. Previous studies have shown that hemorrhagic stroke or ischemia caused by vasoconstriction in the thalamus induces increased pain sensitivity. We investigated whether inducing secondary damage in the thalamus by a cortical stroke causes similar pain hypersensitivity as has previously been reported with direct ischemic injury. We induced a focal cortical ischemia-reperfusion injury in male rats, quantified the amount of secondary neurodegeneration in the thalamus, and measured whether the thalamic neurodegeneration is associated with thermal or mechanical hypersensitivity. After one month, we observed extensive neuronal degeneration and found approximately 40% decrease in the number of NeuN+ cells in the ipsilateral thalamus. At the same time, there was a massive accumulation—a 30-fold increase—of phagocytic cells in the ipsilateral thalamus. However, despite the evident damage in the thalamus, we did not observe thermal or mechanical sensitization. Thus, thalamic neurodegeneration after cortical ischemia-reperfusion does not induce CPSP-like symptoms in rats, and these results suggest that direct ischemic damage is needed for CPSP induction. Despite not observing hyperalgesia, we investigated whether administration of cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF) into the ipsilateral thalamus would reduce the secondary damage. We gave a single injection (10 µg) of recombinant CDNF or MANF protein into the thalamus at 7 days post-stroke. Both CDNF and MANF treatment promoted the functional recovery but had no effect on the neuronal loss or the amount of phagocytic cells in the thalamus.

Mesencephalic astrocyte-derived neurotrophic factor (MANF) protects against Aβ toxicity via attenuating Aβ-induced endoplasmic reticulum stress

BACKGROUND

Extracellular accumulation of amyloid β-peptide (Aβ) is one of pathological hallmarks of Alzheimer's disease (AD) and contributes to the neuronal loss. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER) stress-inducible neurotrophic factor. Many groups, including ours, have proved that MANF rescues neuronal loss in several neurological disorders, such as Parkinson's disease and cerebral ischemia. However, whether MANF exerts its protective effect against Aβ neurotoxicity in AD remains unknown.

METHODS

In the present study, the characteristic expressions of MANF in Aβ_1-42-treated neuronal cells as well as in the brains of APP/PS1 transgenic mice were analyzed by immunofluorescence staining, qPCR, and Western blot. The effects of MANF overexpression, MANF knockdown, or recombination human MANF protein (rhMANF) on neuron viability, apoptosis, and the expression of ER stress-related proteins following Aβ_1-42 exposure were also investigated.

RESULTS

The results showed the increased expressions of MANF, as well as ER stress markers immunoglobulin-binding protein (BiP) and C/EBP homologous protein (CHOP), in the brains of the APP/PS1 transgenic mice and Aβ_1-42-treated neuronal cells. MANF overexpression or rhMANF treatment partially protected against Aβ_1-42-induced neuronal cell death, associated with marked decrease of cleaved caspase-3, whereas MANF knockdown with siRNA aggravated Aβ_1-42 cytotoxicity including caspase-3 activation. Further study demonstrated that the expressions of BiP, ATF6, phosphorylated-IRE1, XBP1s, phosphorylated-eIF2α, ATF4, and CHOP were significantly downregulated by MANF overexpression or rhMANF treatment in neuronal cells following Aβ_1-42 exposure, whereas knockdown of MANF has the opposite effect.

CONCLUSIONS

These findings demonstrate that MANF may exert neuroprotective effects against Aβ-induced neurotoxicity through attenuating ER stress, suggesting that an applicability of MANF as a therapeutic candidate for AD.