Application of Fluoro-Jade C in acute and chronic neurodegeneration models: utilities and staining differences

Neurodegeneration: Effects of calorie restriction on the brain sirtuin protein levels

BACKGROUND

Calorie restriction (CR) is suggested to activate protective mechanisms in neurodegenerative diseases (NDDs). Despite existing literature highlighting the protective role of Sirtuin (SIRT) proteins against age-related neurodegeneration (ND), no study has explored the total levels of SIRT 1, 3, and 6 proteins simultaneously in brain homogenates by ELISA following intermittent calorie restriction. Applying CR protocols in mice to induce stress, we aimed to determine whether ND would be more pronounced with ad libitum (AL) or with CR.

METHODS

Mice were randomly assigned to ad libitum (AL), Chronic CR (CCR), or Intermittent CR (ICR) groups at 10 weeks of baseline age (BL). SIRT 1, 3, and 6 protein levels were measured in the homogenized whole-brain supernatants of 49/50 weeks old mice by the ELISA method. Neuronal morphology was evaluated by the cresyl violet on the hippocampus. Neurodegeneration (ND) was assessed by the fluoro-jade and ImageJ was used for quantifications.

RESULTS

In the ICR group, SIRT1 levels were elevated compared to both the AL and BL groups. Similarly, the CCR group exhibited higher SIRT1 values compared to the AL and BL groups. While SIRT3 levels were higher in both the ICR and CCR groups compared to the AL and BL groups, this disparity did not reach statistical significance. SIRT6 levels were also higher in the ICR group compared to both the BL and AL groups, with the CCR group showing higher values compared to the BL and AL groups as well. Image quantification demonstrated significant neurodegeneration in the AL group compared to the CCR and ICR group, with no observed alterations in nerve cell morphology and number.

CONCLUSION

This study revealed that the levels of SIRT 1, SIRT 3, and SIRT 6 in brain tissue were notably elevated, and there was less evidence of ND at the 50-week mark in groups undergoing continuous calorie restriction and intermittent calorie restriction compared to baseline and ad libitum groups. Our findings illustrate that CR promotes increased SIRT expression in the mouse brain, thereby potentially mitigating neurodegeneration.

Localization of Melanocortin 1 Receptor in the Substantia Nigra

Recent findings have revealed that melanocortin 1 receptor (MC1R) deficiency leads to Parkinson's disease-like dopaminergic neurodegeneration in the substantia nigra (SN). However, its precise distribution and expressing-cell type in the SN remain unclear. Therefore, in this study, we analyzed the localization and characteristics of MC1R in the SN using histological methods, including in situ hybridization and immunohistochemistry. Our findings reveal that MC1R was slightly present in dopaminergic neurons in the ventral tier of SN pars compacta dorsal (vSNCD), a region particularly vulnerable to PD-related neurodegeneration. Notably, we discovered that MC1R is highly present in parvalbumin (PV)-positive neurons, which were also vesicular GABA transporter messenger RNA-expressing inhibitory neurons of the lateral SN pars reticulata (lSNR). Intracellular analysis demonstrated that MC1R was present not only in the plasma membrane but also in mitochondrial and endoplasmic reticulum membranes. Furthermore, MC1R co-localized with attractin (Atrn), a known MC1R modulator, in nearly all MC1R-positive neurons. Therefore, it has been suggested that MC1R and Atrn work together to regulate dopaminergic neurons in the SN through both direct expression and indirect modulation via PV-positive inhibitory neurons. These findings provide new insights into MC1R's role in the SN and its potential contribution to PD pathophysiology.

Systemic inflammation attenuates the repair of damaged brains through reduced phagocytic activity of monocytes infiltrating the brain

In this study, we examined how systemic inflammation affects repair of brain injury. To this end, we created a brain-injury model by stereotaxic injection of ATP, a damage-associated molecular pattern component, into the striatum of mice. Systemic inflammation was induced by intraperitoneal injection of lipopolysaccharide (LPS-ip). An analysis of magnetic resonance images showed that LPS-ip reduced the initial brain injury but slowed injury repair. An immunostaining analysis using the neuronal marker, NeuN, showed that LPS-ip delayed removal of dead/dying neurons, despite the fact that LPS-ip enhanced infiltration of monocytes, which serve to phagocytize dead cells/debris. Notably, infiltrating monocytes showed a widely scattered distribution. Bulk RNAseq analyses showed that LPS-ip decreased expression of genes associated with phagocytosis, with PCR and immunostaining of injured brains confirming reduced levels of Cd68 and Clec7a, markers of phagocytic activity, in monocytes. Collectively, these results suggest that systemic inflammation affects properties of blood monocytes as well as brain cells, resulting in delay in clearing damaged cells and activating repair processes.

Neurofilament light chain: A possible fluid biomarker in the intrahippocampal kainic acid mouse model for chronic epilepsy?

OBJECTIVE

In the management of epilepsy, there is an ongoing quest to discover new biomarkers to improve the diagnostic process, the monitoring of disease progression, and the evaluation of treatment responsiveness. In this regard, biochemical traceability in biofluids is notably absent in contrast to other diseases. In the present preclinical study, we investigated the potential of neurofilament light chain (NfL) as a possible diagnostic and response fluid biomarker for epilepsy.

METHODS

We gained insights into NfL levels during the various phases of the intrahippocampal kainic acid mouse model of temporal lobe epilepsy-namely, the status epilepticus (SE) and the chronic phase with spontaneous seizures. To this end, NfL levels were determined directly in the cerebral interstitial fluid (ISF) with cerebral open flow microperfusion as sampling technique, as well as in cerebrospinal fluid (CSF) and plasma. Lastly, we assessed whether NfL levels diminished upon curtailing SE with diazepam and ketamine.

RESULTS

NfL levels are higher during SE in both cerebral ISF and plasma in kainic acid-treated mice compared to sham-injected mice. Additionally, ISF and plasma NfL levels are lower in mice treated with diazepam and ketamine to stop SE compared with the vehicle-treated mice. In the chronic phase with spontaneous seizures, higher NfL levels could only be detected in ISF and CSF samples, and not in plasma. No correlations could be found between NfL levels and seizure burden, nor with immunohistological markers for neurodegeneration/inflammation.

SIGNIFICANCE

Our findings demonstrate the translational potential of NfL as a blood-based fluid biomarker for SE. This is less evident for chronic epilepsy, as in this case higher NfL levels could only be detected in ISF and CSF, and not in plasma, acknowledging the invasive nature of CSF sampling in chronic epilepsy follow-up.

Neurological Phenotypes in Mouse Models of Mitochondrial Disease and Relevance to Human Neuropathology

Mitochondrial diseases represent the most common inherited neurometabolic disorders, for which no effective therapy currently exists for most patients. The unmet clinical need requires a more comprehensive understanding of the disease mechanisms and the development of reliable and robust in vivo models that accurately recapitulate human disease. This review aims to summarise and discuss various mouse models harbouring transgenic impairments in genes that regulate mitochondrial function, specifically their neurological phenotype and neuropathological features. Ataxia secondary to cerebellar impairment is one of the most prevalent neurological features of mouse models of mitochondrial dysfunction, consistent with the observation that progressive cerebellar ataxia is a common neurological manifestation in patients with mitochondrial disease. The loss of Purkinje neurons is a shared neuropathological finding in human post-mortem tissues and numerous mouse models. However, none of the existing mouse models recapitulate other devastating neurological phenotypes, such as refractory focal seizures and stroke-like episodes seen in patients. Additionally, we discuss the roles of reactive astrogliosis and microglial reactivity, which may be driving the neuropathology in some of the mouse models of mitochondrial dysfunction, as well as mechanisms through which cellular death may occur, beyond apoptosis, in neurons undergoing mitochondrial bioenergy crisis.

A detection method for neuronal death indicates abnormalities in intracellular membranous components in neuronal cells that underwent delayed death

Acute neuronal degeneration is always preceded under the light and electron microscopes by a stage called microvacuolation, which is characterized by a finely vacuolar alteration in the cytoplasm of the neurons destined to death. In this study, we reported a method for detecting neuronal death using two membrane-bound dyes, rhodamine R6 and DiOC₆(3), which may be associated with the so-called microvacuolation. This new method produced a spatiotemporally similar staining pattern to Fluoro-Jade B in kainic acid-damaged brains in mice. Further experiments showed that increased staining of rhodamine R6 and DiOC₆(3) was observed only in degenerated neurons, but not in glia, erythrocytes, or meninges. Different from Fluoro-Jade-related dyes, rhodamine R6 and DiOC₆(3) staining is highly sensitive to solvent extraction and detergent exposure. Staining with Nile red for phospholipids and filipin III for non-esterified cholesterol supports that the increased staining of rhodamine R6 and DiOC₆(3) might be associated with increased levels of phospholipids and free cholesterol in the perinuclear cytoplasm of damaged neurons. In addition to kainic acid-injected neuronal death, rhodamine R6 and DiOC₆(3) were similarly useful for detecting neuronal death in ischemic models either in vivo or in vitro. As far as we know, the staining with rhodamine R6 or DiOC₆(3) is one of a few histochemical methods for detecting neuronal death whose target molecules have been well defined and therefore may be useful for explaining experimental results as well as exploring the mechanisms of neuronal death. (250 words).

Micrandilactone C, a Nortriterpenoid Isolated from Roots of Schisandra chinensis, Ameliorates Huntington's Disease by Inhibiting Microglial STAT3 Pathways

Huntington's disease (HD) is a neurodegenerative disease that affects the motor control system of the brain. Its pathological mechanism and therapeutic strategies have not been fully elucidated yet. The neuroprotective value of micrandilactone C (MC), a new schiartane nortriterpenoid isolated from the roots of Schisandra chinensis, is not well-known either. Here, the neuroprotective effects of MC were demonstrated in 3-nitropropionic acid (3-NPA)-treated animal and cell culture models of HD. MC mitigated neurological scores and lethality following 3-NPA treatment, which is associated with decreases in the formation of a lesion area, neuronal death/apoptosis, microglial migration/activation, and mRNA or protein expression of inflammatory mediators in the striatum. MC also inhibited the activation of the signal transducer and activator of transcription 3 (STAT3) in the striatum and microglia after 3-NPA treatment. As expected, decreases in inflammation and STAT3-activation were reproduced in a conditioned medium of lipopolysaccharide-stimulated BV2 cells pretreated with MC. The conditioned medium blocked the reduction in NeuN expression and the enhancement of mutant huntingtin expression in STHdh^Q111/Q111 cells. Taken together, MC might alleviate behavioral dysfunction, striatal degeneration, and immune response by inhibiting microglial STAT3 signaling in animal and cell culture models for HD. Thus, MC may be a potential therapeutic strategy for HD.

Aluminium exposure leads to neurodegeneration and alters the expression of marker genes involved to parkinsonism in zebrafish brain

Aluminium, despite being extremely widespread in the world, is a non-essential metal to human metabolism. This metal is known to have toxic effects on a variety of organs including the brain and is considered an etiological factor in neurodegenerative diseases. However, the molecular mechanisms by which aluminium exerts neurotoxic effects are not yet completely understood. Zebrafish is an animal model also used to study neurodegenerative diseases since the overall anatomical organization of the central nervous system is relatively conserved and similar to mammals. Adult zebrafish were exposed to 11 mg/L of Al for 10, 15, and 20 days and the neurotoxic effects of aluminium were analysed by histological, biochemical, and molecular evaluations. Histological stainings allowed to evaluation of the morphology of the brain parenchyma, the alteration of myelin and the activation of neurodegenerative processes. The expression of the Glial Fibrillary Acidic Protein, a marker of glial cells, was evaluated to observe the quantitative alteration of this important protein for the nervous system. In addition, the poly(ADP-ribose) polymerase activity was measured to verify a possible oxidative DNA damage caused by exposure to this metal. Finally, the evaluation of the markers involved in Parkinsonism was assessed by Real-Time PCR to better understand the role of aluminium in the regulation of genes related to Parkinson's neurodegenerative disease. Data showed that aluminium significantly affected the histology of cerebral tissue especially in the first periods of exposure, 10 and 15 days. This trend was also followed by the expression of GFAP. At longer exposure times, there was an improvement/stabilization of the overall neurological conditions and decrease in PARP activity. In addition, aluminium is involved in the deregulation of the expression of genes closely related to Parkinsonism. Overall, the data confirm the neurotoxicity induced by aluminium and shed a light on its involvement in neurodegenerative processes.

SARS-CoV-2 invades cognitive centers of the brain and induces Alzheimer's-like neuropathology

The neurotropism of SARS-CoV-2 and the phenotypes of infected neurons are still in debate. Long COVID manifests with "brain diseases" and the cause of these brain dysfunction is mysterious. Here, we analyze 34 age- and underlying disease-matched COVID-19 or non-COVID-19 human brains. SARS-CoV-2 RNA, nucleocapsid, and spike proteins are present in neurons of the cognitive centers of all COVID-19 patients, with its non-structural protein NSF2 detected in adult cases but not in the infant case, indicating viral replications in mature neurons. In adult COVID-19 patients without underlying neurodegeneration, SARS-CoV-2 infection triggers Aβ and p-tau deposition, degenerating neurons, microglia activation, and increased cytokine, in some cases with Aβ plaques and p-tau pretangles. The number of SARS-CoV-2 + cells is higher in patients with neurodegenerative diseases than in those without such conditions. SARS-CoV-2 further activates microglia and induces Aβ and p-tau deposits in non-Alzheimer's neurodegenerative disease patients. SARS-CoV-2 infects mature neurons derived from inducible pluripotent stem cells from healthy and Alzheimer's disease (AD) individuals through its receptor ACE2 and facilitator neuropilin-1. SARS-CoV-2 triggers AD-like gene programs in healthy neurons and exacerbates AD neuropathology. An AD infectious etiology gene signature is identified through SARS-CoV-2 infection and silencing the top three downregulated genes in human primary neurons recapitulates the neurodegenerative phenotypes of SARS-CoV-2. Thus, our data suggest that SARS-CoV-2 invades the brain and activates an AD-like program.

A companion to the preclinical common data elements and case report forms for neuropathology studies in epilepsy research. A report of the TASK3 WG2 Neuropathology Working Group of the ILAE/AES Joint Translational Task Force

The International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force initiated the TASK3 working group to create common data elements (CDEs) for various aspects of preclinical epilepsy research studies, which could help improve the standardization of experimental designs. This article addresses neuropathological changes associated with seizures and epilepsy in rodent models of epilepsy. We discuss CDEs for histopathological parameters for neurodegeneration, changes in astrocyte morphology and function, mechanisms of inflammation, and changes in the blood-brain barrier and myelin/oligodendrocytes resulting from recurrent seizures in rats and mice. We provide detailed CDE tables and case report forms (CRFs), and with this companion manuscript, we discuss the rationale and methodological aspects of individual neuropathological examinations. The CDEs, CRFs, and companion paper are available to all researchers, and their use will benefit the harmonization and comparability of translational preclinical epilepsy research. The ultimate hope is to facilitate the development of rational therapy concepts for treating epilepsies, seizures, and comorbidities and the development of biomarkers assessing the pathological state of the disease.

Effects of Long-Term Vagus Nerve Electrical Stimulation Therapy on Acute Cerebral Infarction and Neurological Function Recovery in Post MCAO Mice

Background

Vagus nerve stimulation therapy is proven to produce neuroprotective effects against central nervous system diseases and reduce neurological injury, having a positive effect on the recovery of neurological functions in mouse model of stroke.

Objective

This study was aimed at exploring a wider time window for VNS treatment, investigating the long-term behavioral improvement of long-term VNS in mice after pMCAO, and exploring the antiapoptotic properties of VNS and its role in autophagy, all of which may be a permanent deficiency potential mechanism of neuroprotection in hemorrhagic stroke.

Methods

Permanent focal cerebral ischemia and implantation of vagus nerve stimulator were performed through intracavitary occlusion of the right middle cerebral artery (MCA). The vagus nerve stimulation group received five times vagus nerve stimulation from 6 h after surgery for 5 days. Adhesive removal test and NSS neurological score were used to evaluate the neurological deficit of mice. TTC staining of mouse brain tissue was performed one week after surgery in order to assess the area of cerebral infarction. Additionally, frozen sections were stained with Fluoro-Jade B to observe the apoptotic cells in the ischemic penumbra of brain tissue. Finally, Western blot was used to detect the changes in the levels of apoptosis-related proteins such as cleaved-caspase3 and Bcl-2 and autophagy-related proteins such as mTOR, Beclin-1, and LC3-II in brain tissue.

Results

VNS can effectively reduce the behavioral score of pMCAO mice; TTC results showed that VNS could effectively reduce the infarct area after pMCAO (P < 0.05). After VNS intervention of the pMCAO group compared with the pMCAO+VNI group, the FJB-positive cells in the VNS group were significantly decreased (P < 0.05); Western Blot analysis showed that the expression of cleaved-caspase3 in the brain tissue of mice increased after pMCAO (P < 0.05), and the expression of Bcl-2 decreased (P < 0.05). This change could be effectively reversed after VNS intervention (P < 0.05).

Conclusion

VNS could effectively improve the behavioral performance of mice after permanent stroke in addition to significantly reducing the infarct size of the brain tissue. The mechanism may be related to the effective reduction of cell apoptosis and excessive autophagy after pMCAO by VNS.

Glycine-induced NMDA receptor internalization provides neuroprotection and preserves vasculature following ischemic stroke

Ischemic stroke is the second leading cause of death worldwide. Following an ischemic event, neuronal death is triggered by uncontrolled glutamate release leading to overactivation of glutamate sensitive N-methyl-d-aspartate receptor (NMDAR). For gating, NMDARs require not only the binding of glutamate, but also of glycine or a glycine-like compound as a co-agonist. Low glycine doses enhance NMDAR function, whereas high doses trigger glycine-induced NMDAR internalization (GINI) in vitro. Here, we report that following an ischemic event, in vivo, GINI also occurs and provides neuroprotection in the presence of a GlyT1 antagonist (GlyT1-A). Mice pretreated with a GlyT1-A, which increases synaptic glycine levels, exhibited smaller stroke volume, reduced cell death, and minimized behavioral deficits following stroke induction by either photothrombosis or endothelin-1. Moreover, we show evidence that in ischemic conditions, GlyT1-As preserve the vasculature in the peri-infarct area. Therefore, GlyT1 could be a new target for the treatment of ischemic stroke.

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GINI is a dynamic phenomenon which dampens NMDAR-mediated excitotoxicity during stroke

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GlyT1-antagonists (GlyT1-As) trigger GINI during stroke in vivo

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GlyT1-As mitigate post-stroke behavioral deficits and preserve peri-infarct vasculature

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GlyT1 could be a novel and viable therapeutic target for ischemic stroke

High-resolution fluorescence-guided transcranial ultrasound mapping in the live mouse brain

Understanding the physiological impact of transcranial ultrasound in rodent brains may offer an important preclinical model for human scale magnetic resonance–guided focused ultrasound methods. However, precision tools for high-resolution transcranial ultrasound targeting and real-time in vivo tracking of its effects at the mouse brain scale are currently lacking. We report a versatile bidirectional hybrid fluorescence-ultrasound (FLUS) system incorporating a 0.35-mm precision spherical-phased array ultrasound emission with a fiberscope-based wide-field fluorescence imaging. We show how the marriage between cortex-wide functional imaging and targeted ultrasound delivery can be used to transcranially map previously undocumented localized fluorescence events caused by reversible thermal processes and perform high-speed large-scale recording of neural activity induced by focused ultrasound. FLUS thus naturally harnesses the extensive toolbox of fluorescent tags and ultrasound’s localized bioeffects toward visualizing and causally perturbing a plethora of normal and pathophysiological processes in the living murine brain.

Absence of Apolipoprotein E is associated with exacerbation of prion pathology and promotes microglial neurodegenerative phenotype

Prion diseases or prionoses are a group of rapidly progressing and invariably fatal neurodegenerative diseases. The pathogenesis of prionoses is associated with self-replication and connectomal spread of PrP^Sc, a disease specific conformer of the prion protein. Microglia undergo activation early in the course of prion pathogenesis and exert opposing roles in PrP^Sc mediated neurodegeneration. While clearance of PrP^Sc and apoptotic neurons have disease-limiting effect, microglia-driven neuroinflammation bears deleterious consequences to neuronal networks. Apolipoprotein (apo) E is a lipid transporting protein with pleiotropic functions, which include controlling of the phagocytic and inflammatory characteristics of activated microglia in neurodegenerative diseases. Despite the significance of microglia in prion pathogenesis, the role of apoE in prionoses has not been established. We showed here that infection of wild type mice with 22L mouse adapted scrapie strain is associated with significant increase in the total brain apoE protein and mRNA levels and also with a conspicuous cell-type shift in the apoE expression. There is reduced expression of apoE in activated astrocytes and marked upregulation of apoE expression by activated microglia. We also showed apoE ablation exaggerates PrP^Sc mediated neurodegeneration. Apoe^−/− mice have shorter disease incubation period, increased load of spongiform lesion, pronounced neuronal loss, and exaggerated astro and microgliosis. Astrocytes of Apoe^−/− mice display salient upregulation of transcriptomic markers defining A1 neurotoxic astrocytes while microglia show upregulation of transcriptomic markers characteristic for microglial neurodegenerative phenotype. There is impaired clearance of PrP^Sc and dying neurons by microglia in Apoe^−/− mice along with increased level of proinflammatory cytokines. Our work indicates that apoE absence renders clearance of PrP^Sc and dying neurons by microglia inefficient, while the excess of neuronal debris promotes microglial neurodegenerative phenotype aggravating the vicious cycle of neuronal death and neuroinflammation.

Improvement in Double Staining With Fluoro-Jade C and Fluorescent Immunostaining: FJC Staining Is Not Specific to Degenerating Mature Neurons

Fluoro-Jade C (FJC) staining has been used to detect degenerating neurons in tissue sections. It is a simple and easy staining procedure and does not depend on the manner of cell death. In some experiments, double staining with FJC and fluorescent immunostaining (FI) is required to identify cell types. However, pretreatment for FJC staining contains some processes that are harsh to fluorophores, and the FI signal is greatly reduced. To overcome this issue, we improved the double staining protocol to acquire clear double-stained images by introducing the labeled streptavidin-biotin system. In addition, several studies indicate that FJC can label non-degenerating glial cells, including resting/reactive astrocytes and activated microglia. Moreover, our previous study indicated that degenerating mesenchymal cells were also labeled by FJC, but it is still unclear whether FJC can label degenerating glial cells. Acute encephalopathy model mice contained damaged astrocytes with clasmatodendrosis, and 6-aminonicotinamide-injected mice contained necrotic astrocytes and oligodendrocytes. Using our improved double staining protocol with FJC and FI, we detected FJC-labeled degenerating astrocytes and oligodendrocytes with pyknotic nuclei. These results indicate that FJC is not specific to degenerating neurons in some experimental conditions.

Expression of Low Level of VPS35-mCherry Fusion Protein Diminishes Vps35 Depletion Induced Neuron Terminal Differentiation Deficits and Neurodegenerative Pathology, and Prevents Neonatal Death

Vps35 (vacuolar protein sorting 35) is a key component of retromer that consists of Vps35, Vps26, and Vps29 trimers, and sortin nexin dimers. Dysfunctional Vps35/retromer is believed to be a risk factor for development of various neurodegenerative diseases. Vps35Neurod6 mice, which selectively knock out Vps35 in Neurod6-Cre+ pyramidal neurons, exhibit age-dependent impairments in terminal differentiation of dendrites and axons of cortical and hippocampal neurons, neuro-degenerative pathology (i.e., increases in P62 and Tdp43 (TAR DNA-binding protein 43) proteins, cell death, and reactive gliosis), and neonatal death. The relationships among these phenotypes and the underlying mechanisms remain largely unclear. Here, we provide evidence that expression of low level of VPS35-mCherry fusion protein in Vps35Neurod6 mice could diminish the phenotypes in an age-dependent manner. Specifically, we have generated a conditional transgenic mouse line, LSL-Vps35-mCherry, which expresses VPS35-mCherry fusion protein in a Cre-dependent manner. Crossing LSL-Vps35-mCherry with Vps35Neurod6 to obtain TgVPS35-mCherry, Vps35Neurod6 mice prevent the neonatal death and diminish the dendritic morphogenesis deficit and gliosis at the neonatal, but not the adult age. Further studies revealed that the Vps35-mCherry transgene expression was low, and the level of Vps35 mRNA comprised only ~5-7% of the Vps35 mRNA of control mice. Such low level of VPS35-mCherry could restore the amount of other retromer components (Vps26a and Vps29) at the neonatal age (P14). Importantly, the neurodegenerative pathology presented in the survived adult TgVps35-mCherry; Vps35Neurod6 mice. These results demonstrate the sufficiency of low level of VPS35-mCherry fusion protein to diminish the phenotypes in Vps35Neurod6 mice at the neonatal age, verifying a key role of neuronal Vps35 in stabilizing retromer complex proteins, and supporting the view for Vps35 as a potential therapeutic target for neurodegenerative diseases.

Corticosterone Administration Alters White Matter Tract Structure and Reduces Gliosis in the Sub-Acute Phase of Experimental Stroke

White matter tract (WMT) degeneration has been reported to occur following a stroke, and it is associated with post-stroke functional disturbances. White matter pathology has been suggested to be an independent predictor of post-stroke recovery. However, the factors that influence WMT remodeling are poorly understood. Cortisol is a steroid hormone released in response to prolonged stress, and elevated levels of cortisol have been reported to interfere with brain recovery. The objective of this study was to investigate the influence of corticosterone (CORT; the rodent equivalent of cortisol) on WMT structure post-stroke. Photothrombotic stroke (or sham surgery) was induced in 8-week-old male C57BL/6 mice. At 72 h, mice were exposed to standard drinking water ± CORT (100 µg/mL). After two weeks of CORT administration, mice were euthanised and brain tissue collected for histological and biochemical analysis of WMT (particularly the corpus callosum and corticospinal tract). CORT administration was associated with increased tissue loss within the ipsilateral hemisphere, and modest and inconsistent WMT reorganization. Further, a structural and molecular analysis of the WMT components suggested that CORT exerted effects over axons and glial cells. Our findings highlight that CORT at stress-like levels can moderately influence the reorganization and microstructure of WMT post-stroke.

Rosuvastatin Nanomicelles Target Neuroinflammation and Improve Neurological Deficit in a Mouse Model of Intracerebral Hemorrhage

Background

Intracerebral hemorrhage (ICH), a devastating subtype of stroke, has a poor prognosis. However, there is no effective therapy currently available due to its complex pathological progression, in which neuroinflammation plays a pivotal role in secondary brain injury. In this work, the use of statin-loaded nanomicelles to target the neuroinflammation and improve the efficacy was studied in a mouse model of ICH.

Methods

Rosuvastatin-loaded nanomicelles were prepared by a co-solvent evaporation method using polyethylene glycol-poly(ε-caprolactone) (PEG-PCL) copolymer as a carrier. The prepared nanomicelles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), and then in vitro and in vivo studies were performed.

Results

TEM shows that the nanomicelles are spherical with a diameter of about 19.41 nm, and DLS shows that the size, zeta potential, and polymer dispersity index of the nanomicelles were 23.37 nm, −19.2 mV, and 0.221, respectively. The drug loading content is 8.28%. The in vivo study showed that the nanomicelles significantly reduced neuron degeneration, inhibited the inflammatory cell infiltration, reduced the brain edema, and improved neurological deficit. Furthermore, it was observed that the nanomicelles promoted the polarization of microglia/macrophages to M2 phenotype, and also the expression of the proinflammatory cytokines, such as IL-1β and TNF-α, was significantly down-regulated, while the expression of the anti-inflammatory cytokine IL-10 was significantly up-regulated. The related mechanism was proposed and discussed.

Conclusion

The nanomicelles treatment suppressed the neuroinflammation that might contribute to the promoted nerve functional recovery of the ICH mouse, making it potential to be applied in clinic.

A central role for anterior cingulate cortex in the control of pathological aggression

Controlling aggression is a crucial skill in social species like rodents and humans and has been associated with anterior cingulate cortex (ACC). Here, we directly link the failed regulation of aggression in BALB/cJ mice to ACC hypofunction. We first show that ACC in BALB/cJ mice is structurally degraded: neuron density is decreased, with pervasive neuron death and reactive astroglia. Gene-set enrichment analysis suggested that this process is driven by neuronal degeneration, which then triggers toxic astrogliosis. cFos expression across ACC indicated functional consequences: during aggressive encounters, ACC was engaged in control mice, but not BALB/cJ mice. Chemogenetically activating ACC during aggressive encounters drastically suppressed pathological aggression but left species-typical aggression intact. The network effects of our chemogenetic perturbation suggest that this behavioral rescue is mediated by suppression of amygdala and hypothalamus and activation of mediodorsal thalamus. Together, these findings highlight the central role of ACC in curbing pathological aggression.

Epigenetic Blockade of Hippocampal SOD2 Via DNMT3b-Mediated DNA Methylation: Implications in Mild Traumatic Brain Injury-Induced Persistent Oxidative Damage

The recurrent events of mild trauma exacerbate the vulnerability for post-traumatic stress disorder; however, the underlying molecular mechanisms are scarcely known. The repeated mild traumatic brain injury (rMTBI) perturbs redox homeostasis which is primarily managed by superoxide dismutase 2 (SOD2). The current study investigates the role of DNA methylation in SOD2 gene regulation and its involvement in rMTBI-induced persistent neuropathology inflicted by weight drop injury paradigm. The oxidative damage, neurodegenerative indicators, and SOD2 function and its regulation in the hippocampus were analyzed after 48 h and 30 days of rMTBI. The temporal and episodic increase in ROS levels (oxidative stress) heightened 8-hydroxyguanosine levels indicating oxidative damage after rMTBI that was concomitant with decline in SOD2 function. In parallel, occupancy of DNMT3b at SOD2 promoter was higher post 30 days of the first episode of rMTBI causing hypermethylation at SOD2 promoter. This epigenetic silencing of SOD2 promoter was sustained after the second episode of rMTBI causing permanent blockade in SOD2 response. The resultant oxidative stress further culminated into the increasing number of degenerating neurons. The treatment with 5-azacytidine, a pan DNMT inhibitor, normalized DNA methylation levels and revived SOD2 function after the second episode of rMTBI. The release of blockade in SOD2 expression by DNMT inhibition also normalized the post-traumatic oxidative consequences and relieved the neurodegeneration and deficits in learning and memory as measured by novel object recognition test. In conclusion, DNMT3b-mediated DNA methylation plays a critical role in SOD2 gene regulation in the hippocampus, and the perturbations therein post rMTBI are detrimental to redox homeostasis manifesting into neurological consequences.

Early Adolescence Prefrontal Cortex Alterations in Female Rats Lacking Dopamine Transporter

Monoamine dysfunctions in the prefrontal cortex (PFC) can contribute to diverse neuropsychiatric disorders, including ADHD, bipolar disorder, PTSD and depression. Disrupted dopamine (DA) homeostasis, and more specifically dopamine transporter (DAT) alterations, have been reported in a variety of psychiatric and neurodegenerative disorders. Recent studies using female adult rats heterozygous (DAT+/-) and homozygous (DAT-/-) for DAT gene, showed the utility of those rats in the study of PTSD and ADHD. Currently, a gap in the knowledge of these disorders affecting adolescent females still represents a major limit for the development of appropriate treatments. The present work focuses on the characterization of the PFC function under conditions of heterozygous and homozygous ablation of DAT during early adolescence based on the known implication of DAT and PFC DA in psychopathology during adolescence. We report herein that genetic ablation of DAT in the early adolescent PFC of female rats leads to changes in neuronal and glial cell homeostasis. In brief, we observed a concurrent hyperactive phenotype, accompanied by PFC alterations in glutamatergic neurotransmission, signs of neurodegeneration and glial activation in DAT-ablated rats. The present study provides further understanding of underlying neuroinflammatory pathological processes that occur in DAT-ablated female rats, what can provide novel investigational approaches in human diseases.

GABAergic neurons are susceptible to BAX-dependent apoptosis following isoflurane exposure in the neonatal period

Exposure to volatile anesthetics during the neonatal period results in acute neuron death. Prior work suggests that apoptosis is the dominant mechanism mediating neuron death. We show that Bax deficiency blocks neuronal death following exposure to isoflurane during the neonatal period. Blocking Bax-mediated neuron death attenuated the neuroinflammatory response of microglia following isoflurane exposure. We find that GABAergic interneurons are disproportionately overrepresented among dying neurons. Despite the increase in neuronal apoptosis induced by isoflurane exposure during the neonatal period, seizure susceptibility, spatial memory retention, and contextual fear memory were unaffected later in life. However, Bax deficiency alone led to mild deficiencies in spatial memory and contextual fear memory, suggesting that normal developmental apoptotic death is important for cognitive function. Collectively, these findings show that while GABAergic neurons in the neonatal brain undergo elevated Bax-dependent apoptotic cell death following exposure to isoflurane, this does not appear to have long-lasting consequences on overall neurological function later in life.

Epigallocatechin-3-gallate PEGylated poly(lactic-co-glycolic) acid nanoparticles mitigate striatal pathology and motor deficits in 3-nitropropionic acid intoxicated mice

Aim: To compare free and nanoparticle (NP)-encapsulated epigallocatechin-3-gallate (EGCG) for the treatment of Huntington's disease (HD)-like symptoms in mice. Materials & methods: EGCG was incorporated into PEGylated poly(lactic-co-glycolic) acid NPs with ascorbic acid (AA). HD-like striatal lesions and motor deficit were induced in mice by 3-nitropropionic acid-intoxication. EGCG and EGCG/AA NPs were co-administered and behavioral motor assessments and striatal histology performed after 5 days. Results: EGCG/AA NPs were significantly more effective than free EGCG in reducing motor disturbances and depression-like behavior associated with 3-nitropropionic acid toxicity. EGCG/AA NPs treatment also mitigated neuroinflammation and prevented neuronal loss. Conclusion: NP encapsulation enhances therapeutic robustness of EGCG in this model of HD symptomatology. Together with our previous findings, this highlights the potential of EGCG/AA NPs in the symptomatic treatment of neurodegenerative diseases.

Early-life-trauma triggers interferon-β resistance and neurodegeneration in a multiple sclerosis model via downregulated β1-adrenergic signaling

Environmental triggers have important functions in multiple sclerosis (MS) susceptibility, phenotype, and trajectory. Exposure to early life trauma (ELT) has been associated with higher relapse rates in MS patients; however, the underlying mechanisms are not well-defined. Here we show ELT induces mechanistic and phenotypical alterations during experimental autoimmune encephalitis (EAE). ELT sustains downregulation of immune cell adrenergic receptors, which can be attributed to chronic norepinephrine circulation. ELT-subjected mice exhibit interferon-β resistance and neurodegeneration driven by lymphotoxin and CXCR2 involvement. These phenotypic changes are observed in control EAE mice treated with β1 adrenergic receptor antagonist. Conversely, β1 adrenergic receptor agonist treatment to ELT mice abrogates phenotype changes via restoration of immune cell β1 adrenergic receptor function. Our results indicate that ELT alters EAE phenotype via downregulation of β1 adrenergic signaling in immune cells. These results have implications for the effect of environmental factors in provoking disease heterogeneity and might enable prediction of long-term outcomes in MS.

Minocycline Alleviates Cluster Formation of Activated Microglia and Age-dependent Dopaminergic Cell Death in the Substantia Nigra of Zitter Mutant Rat

Microglial activation is a component of neurodegenerative pathology. Here, we examine whether activated microglia participate in age-related dopaminergic (DA) cell death in the substantia nigra pars compacta (SNc) of the zitter (zi/zi) rat, a mutant characterized by deletion of the attractin gene. Confocal microscopy with double-immunohistochemical staining revealed activated microglia-formed cell-clusters surrounding DA neurons in the SNc from 2 weeks after birth. An immunoelectron microscopic study showed that the cytoplasm of activated microglia usually contains phagosome-like vacuoles and lamellar inclusions. Expression levels of the pro-inflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) were increased in the midbrain of 2-month-old zi/zi rats. Chronic treatment with the anti-inflammatory agent minocycline altered the morphology of the microglia, reduced cluster formation by the microglia, and attenuated DA cell death in the SNc, and reduced the expression of IL-1β in the midbrain. These results indicate that activated microglia, at least in part and especially at the initial phase, contribute to DA cell death in the SNc of the zi/zi rat.

Novel Brain-Penetrating Oxime Acetylcholinesterase Reactivators Attenuate Organophosphate-Induced Neuropathology in the Rat Hippocampus

Organophosphate (OP) anticholinesterases cause excess acetylcholine leading to seizures which, if prolonged, result in neuronal damage in the rodent brain. Novel substituted phenoxyalkyl pyridinium oximes have previously shown evidence of penetrating the rat blood-brain barrier (BBB) in in vivo tests with a sarin surrogate (nitrophenyl isopropyl methylphosphonate, NIMP) or the active metabolite of the insecticide parathion, paraoxon (PXN), by reducing the time to cessation of seizure-like behaviors and accumulation of glial fibrillary acidic protein, whereas 2-PAM did not. The neuroprotective ability of our lead oximes (15, 20, and 55) was tested using NeuN, Nissl, and Fluoro-Jade B staining in the rat hippocampus. Following lethal-level subcutaneous challenge with NIMP or PXN, rats were intramuscularly administered a novel oxime or 2-PAM plus atropine and euthanized at 4 days. There were statistically significant increases in the median damage scores of the NeuN-stained NIMP, NIMP/2-PAM, and NIMP/Oxime 15 groups compared with the control whereas the scores of the NIMP/Oxime 20 and NIMP/Oxime 55 were not significantly different from the control. The same pattern of statistical significance was observed with PXN. Nissl staining provided a similar pattern, but without statistical differences. Fluoro-Jade B indicated neuroprotection from PXN with novel oximes but not with 2-PAM. The longer blood residence times of Oximes 20 and 55 compared with Oxime 15 might have contributed to their greater efficacy. These results suggest that novel oximes 20 and 55 were able to penetrate the BBB and attenuate neuronal damage after NIMP and PXN exposure, indicating potential broad-spectrum usefulness.

Attenuation of Acute Intracerebral Hemorrhage-Induced Microglial Activation and Neuronal Death Mediated by the Blockade of Metabotropic Glutamate Receptor 5 In Vivo

The activation of microglia in response to intracerebral hemorrhagic stroke is one of the principal components of the progression of this disease. It results in the formation of pro-inflammatory cytokines that lead to neuronal death, a structural deterioration that, in turn interferes with functional recovery. Metabotropic glutamate receptor 5 (mGluR5) is highly expressed in reactive microglia and is involved in the pathological processes of brain disorders, but its role in intracerebral hemorrhage (ICH) remains unknown. We hypothesized that mGluR5 regulates microglial activation and ICH maintenance. In this study, collagenase-induced ICH mice received a single intraperitoneal injection of the mGluR5 antagonist-, MTEP, or vehicle 2 h after injury. We found that acute ICH upregulated mGluR5 and microglial activation. mGluR5 was highly localized in reactive microglia in the peri-hematomal cortex and striatum on days 3 and 7 post-ICH. The MTEP-mediated pharmacological inhibition of mGluR5 in vivo resulted in the substantial attenuation of acute microglial activation and IL-6, and TNF-α release. We also showed that the blockade of mGluR5 markedly reduced cell apoptosis, and neurodegeneration and markedly elevated neuroprotection. Furthermore, the MTEP-mediated inhibition of mGluR5 significantly reduced the lesion volume and improved functional recovery. Taken together, our results demonstrate that ICH injury enhances mGluR5 expression in the acute and subacute stages and that mGluR5 is highly localized in reactive microglia. The blockade of mGluR5 reduces ICH-induced acute microglial activation, provides neuroprotection and promotes neurofunctional recovery after ICH. The inhibition of mGluR5 may be a relevant therapeutic target for intracerebral hemorrhagic stroke.

Characterization of a Parkinson's disease rat model using an upgraded paraquat exposure paradigm

Animal models of human diseases are crucial experimental tools to investigate the mechanisms involved in disease pathogenesis and to develop new therapies. In spite of the numerous animal models currently available that reproduce several neuropathological features of Parkinson disease (PD), it is challenging to have one that consistently recapitulates human PD conditions in both motor behaviors and biochemical pathological outcomes. Given that, we have implemented a new paradigm to expose rats to a chronic low dose of paraquat (PQ), using osmotic minipumps and characterized the developed pathologic features over time. The PQ exposure paradigm used lead to a rodent model of PD depicting progressive nigrostriatal dopaminergic neurodegeneration, characterized by a 41% significant loss of dopaminergic neuron in the substantia nigra pars compacta (SNpc), a significant decrease of 18% and 40% of dopamine levels in striatum at week 5 and 8, respectively, and a significant 1.5-fold decrease in motor performance. We observed a significant increase of microglia activation state, sustained levels of α-synucleinopathy and increased oxidative stress markers in the SNpc. In summary, this is an explorative study that allowed to characterize an improved PQ-based rat model that recapitulates cardinal features of PD and may represent an attractive tool to investigate several mechanisms underlying the various aspects of PD pathogenesis as well as for the validation of the efficacy of new therapeutic approaches that targets different mechanisms involved in PD neurodegeneration.

Coupling of terminal differentiation deficit with neurodegenerative pathology in Vps35-deficient pyramidal neurons

Vps35 (vacuolar protein sorting 35) is a key component of retromer that regulates transmembrane protein trafficking. Dysfunctional Vps35 is a risk factor for neurodegenerative diseases, including Parkinson’s and Alzheimer’s diseases. Vps35 is highly expressed in developing pyramidal neurons, and its physiological role in developing neurons remains to be explored. Here, we provide evidence that Vps35 in embryonic neurons is necessary for axonal and dendritic terminal differentiation. Loss of Vps35 in embryonic neurons results in not only terminal differentiation deficits, but also neurodegenerative pathology, such as cortical brain atrophy and reactive glial responses. The atrophy of neocortex appears to be in association with increases in neuronal death, autophagosome proteins (LC3-II and P62), and neurodegeneration associated proteins (TDP43 and ubiquitin-conjugated proteins). Further studies reveal an increase of retromer cargo protein, sortilin1 (Sort1), in lysosomes of Vps35-KO neurons, and lysosomal dysfunction. Suppression of Sort1 diminishes Vps35-KO-induced dendritic defects. Expression of lysosomal Sort1 recapitulates Vps35-KO-induced phenotypes. Together, these results demonstrate embryonic neuronal Vps35’s function in terminal axonal and dendritic differentiation, reveal an association of terminal differentiation deficit with neurodegenerative pathology, and uncover an important lysosomal contribution to both events.

S100 Calcium-Binding Protein A9 Knockout Contributes to Neuroprotection and Functional Improvement after Traumatic Brain Injury

S100 calcium-binding protein A9 (S100a9), a proinflammatory protein, has been shown to be involved in the development of neuroinflammatory disorders and neurodegenerative diseases. Upregulation of S100a9 in the brain during acute brain injury has been proposed to be associated with acute neuroinflammation. However, it remains unclear whether eliminating S100a9 expression will show beneficial outcomes after traumatic brain injury (TBI). Using S100a9 knockout mice, this study has demonstrated that S100a9 deletion ameliorates post-TBI anxiety, improves TBI-impaired motor and cognitive function, reduces lesion size, prevents perilesional neuron loss and neurodegeneration, diminishes neuroinflammation and TBI-induced neurogenesis, and enhances perilesional expression of neuroplasticity protein. These findings suggest that S100a9 plays a detrimental role in TBI. Genetic deletion of S100a9 enhances neuroprotection and improves functional outcome after TBI. This study sheds light on the pathological involvement of S100a9 in TBI, which would provide a new therapeutic target to minimize TBI-induced brain damage.

Cerebral dopamine neurotrophic factor-deficiency leads to degeneration of enteric neurons and altered brain dopamine neuronal function in mice

Cerebral dopamine neurotrophic factor (CDNF) is neuroprotective for nigrostriatal dopamine neurons and restores dopaminergic function in animal models of Parkinson’s disease (PD). To understand the role of CDNF in mammals, we generated CDNF knockout mice (Cdnf^−/−), which are viable, fertile, and have a normal life-span. Surprisingly, an age-dependent loss of enteric neurons occurs selectively in the submucosal but not in the myenteric plexus. This neuronal loss is a consequence not of increased apoptosis but of neurodegeneration and autophagy. Quantitatively, the neurodegeneration and autophagy found in the submucosal plexus in duodenum, ileum and colon of the Cdnf^−/− mouse are much greater than in those of Cdnf^+/+ mice. The selective vulnerability of submucosal neurons to the absence of CDNF is reminiscent of the tendency of pathological abnormalities to occur in the submucosal plexus in biopsies of patients with PD. In contrast, the number of substantia nigra dopamine neurons and dopamine and its metabolite concentrations in the striatum are unaltered in Cdnf^−/− mice; however, there is an age-dependent deficit in the function of the dopamine system in Cdnf^−/− male mice analyzed. This is observed as D-amphetamine-induced hyperactivity, aberrant dopamine transporter function, and as increased D-amphetamine-induced dopamine release demonstrating that dopaminergic axon terminal function in the striatum of the Cdnf^−/− mouse brain is altered. The deficiencies of Cdnf^−/− mice, therefore, are reminiscent of those seen in early stages of Parkinson’s disease.

Molecular Alterations and Effects of Acute Dehydroepiandrosterone Treatment Following Brief Bilateral Common Carotid Artery Occlusion: Relevance to Transient Ischemic Attack

Transient ischemic attack (TIA) represents brief neurological dysfunction of vascular origin without detectable infarction. Despite major clinical relevance characterization of post-TIA molecular changes using appropriate experimental model is lacking and no therapeutic agent has been established yet. Neurosteroid dehydroepiandrosterone (DHEA) arose as one of the candidates for cerebral ischemia treatment but its effects on TIA-like condition remain unknown. Seeking an animal model applicable for investigation of molecular alterations in mild ischemic conditions such as TIA, 15-min bilateral common carotid artery occlusion with 24-h reperfusion was performed to induce ischemia/ reperfusion (I/R) injury in adult male Wistar rats. Additionally, effects of 4-h post-operative DHEA treatment (20 mg/kg) were investigated in physiological and I/R conditions in hippocampus (HIP) and prefrontal cortex (PFC). The study revealed absence of sensorimotor deficits, cerebral infarcts and neurodegeneration along with preserved HIP and PFC overall neuronal morphology and unaltered malondialdehyde and reduced glutathione level following I/R and/or DHEA treatment. I/R induced nitric oxide burst in HIP and PFC was accompanied with increased neuronal nitric oxide synthase protein level exclusively in HIP. DHEA had no effects in physiological conditions, while increase of Bax/Bcl2 ratio and dissipation of mitochondrial membrane potential in treated I/R group suggested DHEA-mediated exacerbation of post-ischemic changes that might lead to pro-apoptotic events in HIP. Interestingly, DHEA restored I/R-induced NO to the control level in PFC. Obtained results indicated that I/R may serve as an appropriate model for investigation of molecular changes and treatment outcome following mild ischemic conditions such as TIA.

Fate of Astrocytes in The Gerbil Hippocampus After Transient Global Cerebral Ischemia

Neuronal death and reactive gliosis are major features of brain tissue damage following transient global cerebral ischemia (tgCI). This study investigated long-term changes in neuronal death and astrogliosis in the gerbil hippocampus for 180 days after 5 min of tgCI. A massive loss of pyramidal neurons was found in the hippocampal CA1 area (CA1) area between 5 and 30 days after tgCI by Fluoro-Jade B (FJB, a marker for neuronal degeneration) histofluorescence staining, but pyramidal neurons in the CA2/3 area did not die. The reaction of astrocytes (astrogliosis) was examined by glial fibrillary acidic protein (GFAP) immunohistochemistry. Morphological change or degeneration (death) of the astrocytes was found in the CA1 area after tgCI, but, in the CA2/3 area, astrogliosis was hardly shown. GFAP immunoreactive astrocytes in the CA1 area was significantly increased in number with time and peaked at 30 days after tgCI, and they began to be degenerated or dead from 40 days after tgCI. The effect was examined by double immunofluorescence staining for FJB and GFAP. The number of FJB/GFAP⁺ cells (degenerating astrocytes) was gradually increased with time after tgCI. At 180 days after tgCI, FJB/GFAP⁺ cells were significantly decreased, but FJB⁺ cells (dead astrocytes) were significantly increased. In brief, 5 min of tgCI induced a progressive degeneration of CA1 pyramidal neurons from 5 until 30 days with an increase of reactive astrocytes, and, thereafter, astrocytes were degenerated with time and dead at later times. This phenomenon might be shown due to the death of neurons.

Long-Term, Targeted Delivery of GDNF from Encapsulated Cells Is Neuroprotective and Reduces Seizures in the Pilocarpine Model of Epilepsy

Neurotrophic factors are candidates for treating epilepsy, but their development has been hampered by difficulties in achieving stable and targeted delivery of efficacious concentrations within the desired brain region. We have developed an encapsulated cell technology that overcomes these obstacles by providing a targeted, continuous, de novo synthesized source of high levels of neurotrophic molecules from human clonal ARPE-19 cells encapsulated into hollow fiber membranes. Here we illustrate the potential of this approach for delivering glial cell line-derived neurotrophic factor (GDNF) directly to the hippocampus of epileptic rats. In vivo studies demonstrated that bilateral intrahippocampal implants continued to secrete GDNF that produced high hippocampal GDNF tissue levels in a long-term manner. Identical implants robustly reduced seizure frequency in the pilocarpine model. Seizures were reduced rapidly, and this effect increased in magnitude over 3 months, ultimately leading to a reduction of seizures by 93%. This effect persisted even after device removal, suggesting potential disease-modifying benefits. Importantly, seizure reduction was associated with normalized changes in anxiety and improved cognitive performance. Immunohistochemical analyses revealed that the neurological benefits of GDNF were associated with the normalization of anatomical alterations accompanying chronic epilepsy, including hippocampal atrophy, cell degeneration, loss of parvalbumin-positive interneurons, and abnormal neurogenesis. These effects were associated with the activation of GDNF receptors. All in all, these results support the concept that the implantation of encapsulated GDNF-secreting cells can deliver GDNF in a sustained, targeted, and efficacious manner, paving the way for continuing preclinical evaluation and eventual clinical translation of this approach for epilepsy.SIGNIFICANCE STATEMENT Epilepsy is one of the most common neurological conditions, affecting millions of individuals of all ages. These patients experience debilitating seizures that frequently increase over time and can associate with significant cognitive decline and psychiatric disorders that are generally poorly controlled by pharmacotherapy. We have developed a clinically validated, implantable cell encapsulation system that delivers high and consistent levels of GDNF directly to the brain. In epileptic animals, this system produced a progressive and permanent reduction (>90%) in seizure frequency. These benefits were accompanied by improvements in cognitive and anxiolytic behavior and the normalization of changes in CNS anatomy that underlie chronic epilepsy. Together, these data suggest a novel means of tackling the frequently intractable neurological consequences of this devastating disorder.

Vdac1 Downregulation Causes Mitochondrial Disintegration Leading to Hippocampal Neurodegeneration in Scopolamine-Induced Amnesic Mice

Our previous report on hippocampal proteome analysis suggested the involvement of voltage-dependent anion channel (Vdac) 1 in scopolamine-induced amnesia. Further silencing of Vdac1 in young mice reduced the recognition memory. Vdac1 is a porin protein present abundantly on outer mitochondrial membrane. It acts as a transporter of energy metabolites ATP/ADP and Ca²⁺ ions and helps in communication between mitochondrial matrix and cytosol. As Vdac1-associated energy metabolism may be affected during amnesia, we determined the downstream function of Vdac1 in the present study. The expression of Vdac1 and total ATP level was decreased in the hippocampus of scopolamine-induced amnesic mice. Also, the mitochondrial membrane potential, cristae organization, and morphology were disrupted leading to increased ROS generation and reduced SOD and catalase activity. On the other hand, there was increase in the expression of pro-apoptotic marker proteins (Bax, Bad, Casp 3), leading to rising degenerated neuronal cells in the dentate gyrus and Cornu ammonis 3 and 1 subregions of the hippocampus during amnesia. Further, to check whether Vdac1 downregulation is associated with neurodegeneration, we infused Vdac1 siRNA stereotaxically in the hippocampus of normal young mice. As compared to control, Vdac1 silencing decreased ATP level and mitochondrial membrane potential leading to increase in the number of degenerated neuronal cells in subregions of the hippocampus. Taken together, our study shows that downregulation of Vdac1 causes neurodegeneration through mitochondrial disintegration in the hippocampus of scopolamine-induced amnesic mice.

TRPV4 Blockade Preserves the Blood-Brain Barrier by Inhibiting Stress Fiber Formation in a Rat Model of Intracerebral Hemorrhage

Blood–brain barrier (BBB) disruption and subsequent brain edema play important roles in the secondary neuronal death and neurological dysfunction that are observed following intracerebral hemorrhage (ICH). In previous studies, transient receptor potential vanilloid 4 (TRPV4), a calcium-permeable mechanosensitive channel, was shown to induce cytotoxicity in many types of cells and to play a role in orchestrating barrier functions. In the present study, we explored the role of TRPV4 in ICH-induced brain injury, specifically investigating its effect on BBB disruption. Autologous arterial blood was injected into the basal ganglia of rats to mimic ICH. Adult male Sprague Dawley rats were randomly assigned to sham and experimental groups for studies on the time course of TRPV4 expression after ICH. The selective TRPV4 antagonist HC-067047 and TRPV4 siRNA were administered to evaluate the effects of TRPV4 inhibition. GSK1016790A, a TRPV4 agonist, was administered to naive rats to verify the involvement of TRPV4-induced BBB disruption. A PKC inhibitor, dihydrochloride (H7), and a selective RhoA inhibitor, C3 transferase, were administered to clarify the involvement of the PKCα/RhoA/MLC2 pathway following ICH. Post-ICH assessments including functional tests, brain edema measurements, Evans blue extravasation, western blotting and immunohistochemical assays were performed. TRPV4 inhibition remarkably ameliorated neurological symptoms, brain edema, and neuronal death, as well as BBB disruption, 24–72 h following ICH. Meanwhile, TRPV4 blockade preserved the expression of adherens and tight junction proteins, as well as BBB integrity, by inhibiting stress fiber formation, which might be correlated with the regulation of components of the PKCα/RhoA/MLC2 pathway. Furthermore, adherens and tight junction protein degradation induced by GSK1016790A treatment in naive rats was also related to PKCα/RhoA/MLC2-pathway-mediated stress fiber formation. Based on these findings, therapeutic interventions targeting TRPV4 may represent a novel approach to ameliorate secondary brain injury following ICH.

Loss of SLC25A46 causes neurodegeneration by affecting mitochondrial dynamics and energy production in mice

Recently, we identified biallelic mutations of SLC25A46 in patients with multiple neuropathies. Functional studies revealed that SLC25A46 may play an important role in mitochondrial dynamics by mediating mitochondrial fission. However, the cellular basis and pathogenic mechanism of the SLC25A46-related neuropathies are not fully understood. Thus, we generated a Slc25a46 knock-out mouse model. Mice lacking SLC25A46 displayed severe ataxia, mainly caused by degeneration of Purkinje cells. Increased numbers of small, unmyelinated and degenerated optic nerves as well as loss of retinal ganglion cells indicated optic atrophy. Compound muscle action potentials in peripheral nerves showed peripheral neuropathy associated with degeneration and demyelination in axons. Mutant cerebellar neurons have large mitochondria, which exhibit abnormal distribution and transport. Biochemically mutant mice showed impaired electron transport chain activity and accumulated autophagy markers. Our results suggest that loss of SLC25A46 causes degeneration in neurons by affecting mitochondrial dynamics and energy production.

Dysregulation of LIMK-1/cofilin-1 pathway: A possible basis for alteration of neuronal morphology in experimental cerebral malaria

OBJECTIVE

Loss of cognition even after survival is the salient feature of cerebral malaria (CM). Currently, the fate of neuronal morphology is not studied at the ultrastructural level in CM. Recent studies suggest that maintenance of neuronal morphology and dendritic spine density (actin dynamics in particular) are essential for proper cognitive function. LIMK-1/cofilin-1 signaling pathway is known to be involved in the maintenance of actin dynamics through regulation of cofilin-1, and in executing learning and memory functions.

METHODS

Using an experimental mouse model, we analyzed the behavioral parameters of asymptomatic mice with CM by performing a rapid murine coma and behavior scale experiment. We performed Golgi-Cox staining to assess neuronal morphology, dendritic spine density, and arborization in brain cortex subjected to Plasmodium berghei ANKA infection compared to asymptomatic, anemic, and control groups. We studied the neural gene expression pattern of LIMK-1, cofilin-1, and β-actin in all the experimental groups by semiquantitative and quantitative polymerase chain reaction followed by immunoblotting and immunofluorescence.

RESULTS

We observed significant loss of dendritic spine density, abnormal spine morphology, reduced dendritic arborization, and extensive dendritic varicosities in the cortical neurons of CM-infected brain. Furthermore, these observations correlated with diminished protein levels of LIMK-1, cofilin-1, phospho-cofilin-1, and β-actin in the whole brain lysates as well as formation of actin-cofilin rods in the brain sections of symptomatic mice with CM.

INTERPRETATION

Overall, our findings suggest that the altered neuronal morphology and dysregulation of LIMK-1/cofilin-1 pathway could affect the cognitive outcome after experimental CM. Therefore, this study could help to establish newer therapeutic strategies addressing long-term cognitive impairment after CM. Ann Neurol 2017;82:429-443.

Increased 12/15-Lipoxygenase Leads to Widespread Brain Injury Following Global Cerebral Ischemia

Global ischemia following cardiac arrest is characterized by high mortality and significant neurological deficits in long-term survivors. Its mechanisms of neuronal cell death have only partially been elucidated. 12/15-lipoxygenase (12/15-LOX) is a major contributor to delayed neuronal cell death and vascular injury in experimental stroke, but a possible role in brain injury following global ischemia has to date not been investigated. Using a mouse bilateral occlusion model of transient global ischemia which produced surprisingly widespread injury to cortex, striatum, and hippocampus, we show here that 12/15-LOX is increased in a time-dependent manner in the vasculature and neurons of both cortex and hippocampus. Furthermore, 12/15-LOX co-localized with apoptosis-inducing factor (AIF), a mediator of non-caspase-related apoptosis in the cortex. In contrast, caspase-3 activation was more prevalent in the hippocampus. 12/15-lipoxygenase knockout mice were protected against global cerebral ischemia compared to wild-type mice, accompanied by reduced neurologic impairment. The lipoxygenase inhibitor LOXBlock-1 similarly reduced neuronal cell death both when pre-administered and when given at a therapeutically relevant time point 1 h after onset of ischemia. These findings suggest a pivotal role for 12/15-LOX in both caspase-dependent and caspase-independent apoptotic pathways following global cerebral ischemia and suggest a novel therapeutic approach to reduce brain injury following cardiac arrest.

Post-traumatic administration of the p53 inactivator pifithrin-α oxygen analogue reduces hippocampal neuronal loss and improves cognitive deficits after experimental traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Neuronal apoptosis in the hippocampus has been detected after TBI. The hippocampal dysfunction may result in cognitive deficits in learning, memory, and spatial information processing. Our previous studies demonstrated that a p53 inhibitor, pifithrin-α oxygen analogue (PFT-α (O)), significantly reduced cortical cell death, which is substantial following controlled cortical impact (CCI) TBI, and improved neurological functional outcomes via anti-apoptotic mechanisms. In the present study, we examined the effect of PFT-α (O) on CCI TBI-induced hippocampal cellular pathophysiology in light of this brain region's role in memory. To investigate whether p53-dependent apoptosis plays a role in hippocampal neuronal loss and associated cognitive deficits and to define underlying mechanisms, SD rats were subjected to experimental CCI TBI followed by the administration of PFT-α or PFT-α (O) (2mg/kg, i.v.) or vehicle at 5h after TBI. Magnetic resonance imaging (MRI) scans were acquired at 24h and 7days post-injury to assess evolving structural hippocampal damage. Fluoro-Jade C was used to stain hippocampal sub-regions, including CA1 and dentate gyrus (DG), for cellular degeneration. Neurological functions, including motor and recognition memory, were assessed by behavioral tests at 7days post injury. p53, p53 upregulated modulator of apoptosis (PUMA), 4-hydroxynonenal (4-HNE), cyclooxygenase-IV (COX IV), annexin V and NeuN were visualized by double immunofluorescence staining with cell-specific markers. Levels of mRNA encoding for caspase-3, p53, PUMA, Bcl-2, Bcl-2-associated X protein (BAX) and superoxide dismutase (SOD) were measured by RT-qPCR. Our results showed that post-injury administration of PFT-α and, particularly, PFT-α (O) at 5h dramatically reduced injury volumes in the ipsilateral hippocampus, improved motor outcomes, and ameliorated cognitive deficits at 7days after TBI, as evaluated by novel object recognition and open-field test. PFT-α and especially PFT-α (O) significantly reduced the number of FJC-positive cells in hippocampus CA1 and DG subregions, versus vehicle treatment, and significantly decreased caspase-3 and PUMA mRNA expression. PFT-α (O), but not PFT-α, treatment significantly lowered p53 and elevated SOD2 mRNA expression. Double immunofluorescence staining demonstrated that PFT-α (O) treatment decreased p53, annexin V and 4-HNE positive neurons in the hippocampal CA1 region. Furthermore, PUMA co-localization with the mitochondrial maker COX IV, and the upregulation of PUMA were inhibited by PFT-α (O) after TBI. Our data suggest that PFT-α and especially PFT-α (O) significantly reduce hippocampal neuronal degeneration, and ameliorate neurological and cognitive deficits in vivo via antiapoptotic and antioxidative properties.

Methylphenidate Causes Behavioral Impairments and Neuron and Astrocyte Loss in the Hippocampus of Juvenile Rats

Although the use, and misuse, of methylphenidate is increasing in childhood and adolescence, there is little information about the consequences of this psychostimulant chronic use on brain and behavior during development. The aim of the present study was to investigate hippocampus biochemical, histochemical, and behavioral effects of chronic methylphenidate treatment to juvenile rats. Wistar rats received intraperitoneal injections of methylphenidate (2.0 mg/kg) or an equivalent volume of 0.9 % saline solution (controls), once a day, from the 15th to the 45th day of age. Results showed that chronic methylphenidate administration caused loss of astrocytes and neurons in the hippocampus of juvenile rats. BDNF and pTrkB immunocontents and NGF levels were decreased, while TNF-α and IL-6 levels, Iba-1 and caspase 3 cleaved immunocontents (microglia marker and active apoptosis marker, respectively) were increased. ERK and PKCaMII signaling pathways, but not Akt and GSK-3β, were decreased. SNAP-25 was decreased after methylphenidate treatment, while GAP-43 and synaptophysin were not altered. Both exploratory activity and object recognition memory were impaired by methylphenidate. These findings provide additional evidence that early-life exposure to methylphenidate can have complex effects, as well as provide new basis for understanding of the biochemical and behavioral consequences associated with chronic use of methylphenidate during central nervous system development.

Neural ablation of the PARK10 candidate Plpp3 leads to dopaminergic transmission deficits without neurodegeneration

Parkinson’s disease (PD) is a multifactorial neurodegenerative disorder, characterised by the progressive loss of midbrain dopaminergic neurons and a variety of motor symptoms. The gene coding for the phospholipid phosphatase 3, PLPP3 (formerly PPAP2B or LPP3), maps within the PARK10 locus, a region that has been linked with increased risk to late-onset PD. PLPP3 modulates the levels of a range of bioactive lipids controlling fundamental cellular processes within the central nervous system. Here we show that PLPP3 is enriched in astroglial cells of the adult murine ventral midbrain. Conditional inactivation of Plpp3 using a Nestin::Cre driver results in reduced mesencephalic levels of sphingosine-1-phosphate receptor 1 (S1P₁), a well-known mediator of pro-survival responses. Yet, adult PLPP3-deficient mice exhibited no alterations in the number of dopaminergic neurons or in the basal levels of striatal extracellular dopamine (DA). Potassium-evoked DA overflow in the striatum, however, was significantly decreased in mutant mice. Locomotor evaluation revealed that, although PLPP3-deficient mice exhibit motor impairment, this is not progressive or responsive to acute L-DOPA therapy. These findings suggest that disruption of Plpp3 during early neural development leads to dopaminergic transmission deficits in the absence of nigrostriatal degeneration, and without causing an age-related locomotor decline consistent with PD.

Three-Dimensional Electron Microscopy Reconstruction of Degenerative Dopaminergic Neurons Surrounded by Activated Microglia in Substantia Nigra

There is an urgent need to investigate the reason for the pathogenic mechanism of intractable central neurological diseases such as Parkinson's disease. It has been reported that the activation of microglial cells is involved in the pathology of these diseases. However, due to technical difficulties, the relationship between degenerative neurons and activated microglial cells remains unclear. Therefore, we tried the improved analysis technique to clarify the spatial relationship between these cell types. We were able to establish an analysis technique that consists of a three-dimensional reconstruction method using serial immunoelectron micrographs after having identified both degenerative neurons and activated microglial cells under optical microscope. Using this technique, we have relatively easily been able to clarify the spatial relationship between degenerative neurons and activated microglial cells. Furthermore, using this technique it is possible to determine the neuronal degeneration process in detail, because it is able to identify structures implicated in degeneration, such as accumulation of lipofuscin in degenerated neuronal somata and phagocytotic structures of microglial cells. In future, this technical approach may be applied to elucidate the relationship between degenerative neurons and activated glial cells in human diseases.