Neurofilaments: Novel findings and future challenges

Neurofilaments (NFs) are abundant cytoskeletal proteins that emerge as a critical hub for cell signalling within neurons. As we start to uncover essential roles of NFs in regulating microtubule and organelle dynamics, nerve conduction and neurotransmission, novel discoveries are expected to arise in genetics, with NFs identified as causal genes for various neurodegenerative diseases. This review will discuss how the latest advances in fundamental and translational research illuminate our understanding of NF biology, particularly their assembly, organisation, transport and degradation. We will emphasise the notion that filaments are not one entity and that future challenges will be to apprehend their diverse composition and structural heterogeneity and to scrutinize how this regulates signalling, sustains neuronal physiology and drives pathophysiology in disease.

Circulating Brain Injury Biomarkers: A Novel Method for Quantification of the Impact on the Brain After Tumor Surgery

BACKGROUND

Clinical methods to quantify brain injury related to neurosurgery are scarce. Circulating brain injury biomarkers have recently gained increased interest as new ultrasensitive measurement techniques have enabled quantification of brain injury through blood sampling.

OBJECTIVE

To establish the time profile of the increase in the circulating brain injury biomarkers glial fibrillary acidic protein (GFAP), tau, and neurofilament light (NfL) after glioma surgery and to explore possible relationships between these biomarkers and outcome regarding volume of ischemic injury identified with postoperative MRI and new neurological deficits.

METHODS

In this prospective study, 34 adult patients scheduled for glioma surgery were included. Plasma concentrations of brain injury biomarkers were measured the day before surgery, immediately after surgery, and on postoperative days 1, 3, 5, and 10.

RESULTS

Circulating brain injury biomarkers displayed a postoperative increase in the levels of GFAP ( P < .001), tau ( P < .001), and NfL ( P < .001) on Day 1 and a later, even higher, peak of NFL at Day 10 ( P = .028). We found a correlation between the increased levels of GFAP, tau, and NfL on Day 1 after surgery and the volume of ischemic brain tissue on postoperative MRI. Patients with new neurological deficits after surgery had higher levels of GFAP and NfL on Day 1 compared with those without new neurological deficits.

CONCLUSION

Measuring circulating brain injury biomarkers could be a useful method for quantification of the impact on the brain after tumor surgery or neurosurgery in general.

Regulation of neurofilament length and transport by a dynamic cycle of phospho-dependent polymer severing and annealing

Neurofilaments are cargoes of axonal transport which are unique among known intracellular cargoes in that they are long, flexible protein polymers. These polymers are transported into axons, where they accumulate in large numbers to drive the expansion of axon caliber, which is an important determinant of axonal conduction velocity. We reported previously that neurofilaments can be lengthened by joining ends, called end-to-end annealing, and that they can be shortened by severing. Here, we show that neurofilament annealing and severing are robust and quantifiable phenomena in cultured neurons that act antagonistically to regulate neurofilament length. We show that this in turn regulates neurofilament transport and that severing is regulated by N-terminal phosphorylation of the neurofilament subunit proteins. We propose that focal destabilization of intermediate filaments by site-directed phosphorylation may be a general enzymatic mechanism for severing these cytoskeletal polymers, providing a mechanism to regulate the transport and accumulation of neurofilaments in axons.

Sirtuin-2, NAD-Dependent Deacetylase, Is a New Potential Therapeutic Target for HIV-1 Infection and HIV-Related Neurological Dysfunction

The implementation and access to combined antiretroviral treatment (cART) have dramatically improved the quality of life of people living with HIV (PLWH). However, some comorbidities, such as neurological disorders associated with HIV infection still represent a serious clinical challenge. Soluble factors in plasma that are associated with control of HIV replication and neurological dysfunction could serve as early biomarkers and as new therapeutic targets for this comorbidity. We used a customized antibody array for determination of blood plasma factors in 40 untreated PLWH with different levels of viremia and found sirtuin-2 (SIRT2), an NAD-dependent deacetylase, to be strongly associated with elevated viral loads and HIV provirus levels, as well as with markers of neurological damage (a-synuclein [SNCA], brain-derived neurotrophic factor [BDNF], microtubule-associated protein tau [MAPT], and neurofilament light protein [NFL]). Also, longitudinal analysis in HIV-infected individuals with immediate (n = 9) or delayed initiation (n = 10) of cART revealed that after 1 year on cART, SIRT2 plasma levels differed between both groups and correlated inversely with brain orbitofrontal cortex involution. Furthermore, targeting SIRT2 with specific small-molecule inhibitors in in vitro systems using J-LAT A2 and primary glial cells led to diminished HIV replication and virus reactivation from latency. Our data thus identify SIRT2 as a novel biomarker of uncontrolled HIV infection, with potential impact on neurological dysfunction and offers a new therapeutic target for HIV treatment and cure. IMPORTANCE Neurocognitive disorders are frequently reported in people living with HIV (PLWH) even with the introduction of combined antiretroviral treatment (cART). To identify biomarkers and potential therapeutic tools to target HIV infection in peripheral blood and in the central nervous system (CNS), plasma proteomics were applied in untreated chronic HIV-infected individuals with different levels of virus control. High plasma levels of sirtuin-2 (SIRT2), an NAD+ deacetylase, were detected in uncontrolled HIV infection and were strongly associated with plasma viral load and proviral levels. In parallel, SIRT2 levels in the peripheral blood and CNS were associated with markers of neurological damage and brain involution and were more pronounced in individuals who initiated cART later in infection. In vitro infection experiments using specific SIRT2 inhibitors suggest that specific targeting of SIRT2 could offer new therapeutic treatment options for HIV infections and their associated neurological dysfunction.

Reactivity to neural tissue epitopes, aquaporin 4 and heat shock protein 60 is associated with activated immune-inflammatory pathways and the onset of delirium following hip fracture surgery

OBJECTIVES

Activation of the immune-inflammatory response system (IRS) and a deficiency in the compensatory immunoregulatory system (CIRS), neuronal injuries, and alterations in the glutamate receptor (GlutaR), aquaporin-4 (AQP4) and heat shock protein 60 (HSP60) are involved in delirium. Increased serum levels of neurofilament protein (NFP), glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) are biomarkers of neuronal injury. This investigation delineates whether elevated IgA/IgG reactivity against those self-antigens is associated with delirium severity and IRS activation.

METHODS

We measured peak Delirium Rating Scale (DRS) scores on days 2 and 3 following surgery in 59 hip fractured older adults, and IgA and IgG antibody levels against MBP, NFP, GFAP and myelin oligodendrocyte glycoprotein (MOG), metabotropic glutamate receptors mGluRs 1 and 5, N-Methyl-D-Aspartate receptor (NMDAR) GLU₁ (NR₁) and GLU₂ (NR₂), APQ4 and HSP60.

RESULTS

The IgA antibody levels against those self-antigens, especially GFAP, MBP and HSP60, strongly predict peak DRS scores on days 2 and 3 post-surgery. IgA reactivity against NMDAR and baseline DRS scores explained 40.6% of the variance in peak DRS scores, while IgA against NMDAR, IgG against MBP and age explained 29.1% of the variance in the IRS/CIRS ratio. There was no correlation between DRS scores and IgG directed against other self-antigens.

CONCLUSIONS

Increased IgA levels against neuronal self-antigens, AQP4 and HSP60 are risk factors for delirium. Polyreactive antibody-associated breakdown of immune tolerance, IRS activation and injuries in the neuronal cytoskeleton, oligodendrocytes, astrocytes, glial cells, and myelin sheath are involved in the pathophysiology of delirium.

Microglial inclusions and neurofilament light chain release follow neuronal α-synuclein lesions in long-term brain slice cultures

BACKGROUND

Proteopathic brain lesions are a hallmark of many age-related neurodegenerative diseases including synucleinopathies and develop at least a decade before the onset of clinical symptoms. Thus, understanding of the initiation and propagation of such lesions is key for developing therapeutics to delay or halt disease progression.

METHODS

Alpha-synuclein (αS) inclusions were induced in long-term murine and human slice cultures by seeded aggregation. An αS seed-recognizing human antibody was tested for blocking seeding and/or spreading of the αS lesions. Release of neurofilament light chain (NfL) into the culture medium was assessed.

RESULTS

To study initial stages of α-synucleinopathies, we induced αS inclusions in murine hippocampal slice cultures by seeded aggregation. Induction of αS inclusions in neurons was apparent as early as 1week post-seeding, followed by the occurrence of microglial inclusions in vicinity of the neuronal lesions at 2-3 weeks. The amount of αS inclusions was dependent on the type of αS seed and on the culture's genetic background (wildtype vs A53T-αS genotype). Formation of αS inclusions could be monitored by neurofilament light chain protein release into the culture medium, a fluid biomarker of neurodegeneration commonly used in clinical settings. Local microinjection of αS seeds resulted in spreading of αS inclusions to neuronally connected hippocampal subregions, and seeding and spreading could be inhibited by an αS seed-recognizing human antibody. We then applied parameters of the murine cultures to surgical resection-derived adult human long-term neocortical slice cultures from 22 to 61-year-old donors. Similarly, in these human slice cultures, proof-of-principle induction of αS lesions was achieved at 1week post-seeding in combination with viral A53T-αS expressions.

CONCLUSION

The successful translation of these brain cultures from mouse to human with the first reported induction of human αS lesions in a true adult human brain environment underlines the potential of this model to study proteopathic lesions in intact mouse and now even aged human brain environments.

SMI-32 labeling in Cajal-Retzius cells of feline primary visual cortex

Cajal-Retzius cells are one of the transient elements of the developing cerebral cortex. These cells express some characteristic molecules. One of them, heavy-chain neurofilaments, participating in the construction of the mature cerebral networks, are believed to be a specific feature of the human's Cajal-Retzius cells. Using histochemical stain for SMI-32 antibody to the non-phosphorylated heavy-chain neurofilaments, large neurons having horizontally oriented soma and bipolar processes were labeled in the molecular layer of the primary visual cortex of cats aged 0-2 postnatal days. Using DiI technique, similar neurons having a well-developed system of parallel vertical branches coming from the two horizontal processes were visualized in these areas. The location and general morphology of these neurons were similar to the Cajal-Retzius cells allowing to suppose for the carnivores to share similar with primates developmental mechanisms of the corticogenesis.

Transcriptomic Profile Reveals Deregulation of Hearing-Loss Related Genes in Vestibular Schwannoma Cells Following Electromagnetic Field Exposure

Hearing loss (HL) is the most common sensory disorder in the world population. One common cause of HL is the presence of vestibular schwannoma (VS), a benign tumor of the VIII cranial nerve, arising from Schwann cell (SC) transformation. In the last decade, the increasing incidence of VS has been correlated to electromagnetic field (EMF) exposure, which might be considered a pathogenic cause of VS development and HL. Here, we explore the molecular mechanisms underlying the biologic changes of human SCs and/or their oncogenic transformation following EMF exposure. Through NGS technology and RNA-Seq transcriptomic analysis, we investigated the genomic profile and the differential display of HL-related genes after chronic EMF. We found that chronic EMF exposure modified the cell proliferation, in parallel with intracellular signaling and metabolic pathways changes, mostly related to translation and mitochondrial activities. Importantly, the expression of HL-related genes such as NEFL, TPRN, OTOGL, GJB2, and REST appeared to be deregulated in chronic EMF exposure. In conclusion, we suggest that, at a preclinical stage, EMF exposure might promote the transformation of VS cells and contribute to HL.

Investigating the Presence of Interattack Astrocyte Damage in Neuromyelitis Optica Spectrum Disorder: Longitudinal Analysis of Serum Glial Fibrillary Acidic Protein

OBJECTIVES

Information on subclinical astrocyte damage can provide further insight into neuromyelitis optica spectrum disorder (NMOSD) pathophysiology and disease-monitoring strategies. To investigate whether astrocyte and neuroaxonal damage occurs during interattack periods in individuals with NMOSD through longitudinal measurement of serum glial fibrillary acidic protein (sGFAP) and neurofilament light chain (sNfL) at multiple time points.

METHODS

sGFAP and sNfL levels were measured in 187 serum samples from 20 participants with NMOSD treated with rituximab (median follow-up: 24 months) and 19 age-/sex-matched healthy controls using a highly sensitive single-molecule array assay. From the NMOSD cohort of National Cancer Center, Korea, 14 clinically stable participants were randomly selected for focused investigation of interattack periods, and 6 participants with clinical attacks despite treatment were enrolled for attack-related measurements.

RESULTS

Significant elevations of sGFAP levels were observed in all clinical attacks, and 95% (19/20) of patients showed reduction of sGFAP levels below the cutoff value (3 SDs above mean levels in age-/sex-matched healthy controls) within 3 months of their clinical attacks. The sGFAP levels were consistently low during interattack periods in 90% (17/19) of patients whose sGFAP levels returned to below the cutoff value. Changes in sNfL levels were similar to but slower than those in sGFAP levels.

CONCLUSIONS

Subclinical astrocyte damage represented by increasing sGFAP levels rarely occurred during interattack periods in individuals with NMOSD; however, a certain degree of astrocyte damage did occur at the time of clinical attacks without exception, but it was not evident within 3 months of the attack.

Altered sensory innervation and pain hypersensitivity in a model of young painful arthritic joints: short- and long-term effects

BACKGROUND

Early life experience can cause long-term alterations in the nociceptive processes underlying chronic pain, but the consequences of early life arthritic joint inflammation upon the sensory innervation of the joint is not known. Here, we measure pain sensitivity and sensory innervation in a young, juvenile and adult rodent model of arthritic joints and test the consequences of joint inflammation in young animals upon adult arthritic pain and joint innervation.

METHODS

Unilateral ankle joint injections of complete Freund's adjuvant (CFA) (6-20 µl) were performed in young, postnatal day (P)8, adolescent (P21) and adult (P40) rats. A separate cohort of animals were injected at P8, and again at P40. Hindpaw mechanical sensitivity was assessed using von Frey monofilaments (vF) for 10 days. Nerve fibres were counted in sections through the ankle joint immunostained for calcitonin gene-related peptide (CGRP) and neurofilament 200 kDa (NF200).

RESULTS

Ankle joint CFA injection increased capsular width at all ages. Significant mechanical pain hypersensitivity and increased number of joint CGRP + ve sensory fibres occurred in adolescent and adult, but not young, rats. Despite the lack of acute reaction, joint inflammation at a young age resulted in significantly increased pain hypersensitivity and CGRP+ fibre counts when the rats were re-inflamed as adults.

CONCLUSIONS

Joint inflammation increases the sensory nociceptive innervation and induces acute pain hypersensitivity in juvenile and adult, but not in young rats. However, early life joint inflammation 'primes' the joint such that adult inflammatory pain behaviour and nociceptive nerve endings in the joint are significantly increased. Early life joint inflammation may be an important factor in the generation and maintenance of chronic arthritic pain.

A possible mechanism for neurofilament slowing down in myelinated axon: Phosphorylation-induced variation of NF kinetics

Neurofilaments(NFs) are the most abundant intermediate filaments that make up the inner volume of axon, with possible phosphorylation on their side arms, and their slow axonal transport by molecular motors along microtubule tracks in a “stop-and-go” manner with rapid, intermittent and bidirectional motion. The kinetics of NFs and morphology of axon are dramatically different between myelinate internode and unmyelinated node of Ranvier. The NFs in the node transport as 7.6 times faster as in the internode, and the distribution of NFs population in the internode is 7.6 folds as much as in the node of Ranvier. We hypothesize that the phosphorylation of NFs could reduce the on-track rate and slow down their transport velocity in the internode. By modifying the ‘6-state’ model with (a) an extra phosphorylation kinetics to each six state and (b) construction a new ‘8-state’ model in which NFs at off-track can be phosphorylated and have smaller on-track rate, our model and simulation demonstrate that the phosphorylation-induced decrease of on-track rate could slow down the NFs average velocity and increase the axonal caliber. The degree of phosphorylation may indicate the extent of velocity reduction. The Continuity equation used in our paper predicts that the ratio of NFs population is inverse proportional to the ratios of average velocity of NFs between node of Ranvier and internode. We speculate that the myelination of axon could increase the level of phosphorylation of NF side arms, and decrease the possibility of NFs to get on-track of microtubules, therefore slow down their transport velocity. In summary, our work provides a potential mechanism for understanding the phosphorylation kinetics of NFs in regulating their transport and morphology of axon in myelinated axons, and the different kinetics of NFs between node and internode.

Squalenoyl siRNA PMP22 nanoparticles are effective in treating mouse models of Charcot-Marie-Tooth disease type 1 A

Charcot-Marie-Tooth disease type 1 A (CMT1A) lacks an effective treatment. We provide a therapy for CMT1A, based on siRNA conjugated to squalene nanoparticles (siRNA PMP22-SQ NPs). Their administration resulted in normalization of Pmp22 protein levels, restored locomotor activity and electrophysiological parameters in two transgenic CMT1A mouse models with different severity of the disease. Pathological studies demonstrated the regeneration of myelinated axons and myelin compaction, one major step in restoring function of myelin sheaths. The normalization of sciatic nerve Krox20, Sox10 and neurofilament levels reflected the regeneration of both myelin and axons. Importantly, the positive effects of siRNA PMP22-SQ NPs lasted for three weeks, and their renewed administration resulted in full functional recovery. Beyond CMT1A, our findings can be considered as a potent therapeutic strategy for inherited peripheral neuropathies. They provide the proof of concept for a new precision medicine based on the normalization of disease gene expression by siRNA.

Regulation of Prdx6 by Nrf2 Mediated Through aiPLA2 in White Matter Reperfusion Injury

Hypoxia and reperfusion produces overproduction of ROS (reactive oxygen species), which may lead to mitochondrial dysfunction leading to cell death and apoptosis. Here, we explore the hypothesis that Prdx6 protects the spinal cord white matter from hypoxia-reperfusion injury and elucidate the possible mechanism by which Prdx6 elicits its protective effects. Briefly, rats were deeply anesthetized with isoflurane. A 30-mm section of the spinal cord was rapidly removed and placed in cold Ringer's solution (2-4 °C). The dissected dorsal column was exposed to hypoxia with 95% N2 and 5% CO2 and reperfusion with 95% O2 and 5% CO2. The expression of Prdx6 significantly upregulated in white matter after hypoxia compared to the sham group, whereas reperfusion caused a gradual decrease in Prdx6 expression after reperfusion injury. For the first time, our study revealed the novel expression and localized expression of Prdx6 in astrocytes after hypoxia, and possible communication of astrocytes and axons through Prdx6. The gradual increase in Nrf2 expression suggests a negative regulation of Prdx6 through Nrf2 signaling. Furthermore, inhibition of aiPLA2 activity of Prdx6 by MJ33 shows that the regulation of Prdx6 by Nrf2 is mediated through aiPLA2 activity. The present study uncovers a differential distribution of Prdx6 in axons and astrocytes and regulation of Prdx6 in hypoxia-reperfusion injury. The low levels of Prdx6 in reperfusion injury lead to increased inflammation and apoptosis in the white matter; therefore, the results of this study suggest that Prdx6 has a protective role in spinal hypoxia-reperfusion injury.

The Role of Stress Granules in the Neuronal Differentiation of Stem Cells

creativecommons.org/licenses/by-nc-sa/3.0/. Cells assemble stress granules (SGs) to protect their RNAs from exposure to harmful chemical reactions induced by environmental stress. These SGs release RNAs, which resume translation once the stress is relieved. During stem cell differentiation, gene expression is altered to allow cells to adopt various functional and morphological features necessary to differentiate. This process induces stress within a cell, and cells that cannot overcome this stress die. Here, we investigated the role of SGs in the progression of stem cell differentiation. SGs aggregated during the neuronal differentiation of human bone marrow-mesenchymal stem cells, and not in cell lines that could not undergo differentiation. SGs were observed between one and three hours post-induction; RNA translation was restrained at the same time. Immediately after disassembly of SGs, the expression of the neuronal marker neurofilament-M (NFM) gradually increased. Assembled SGs that persisted in cells were exposed to salubrinal, which inhibited the dephosphorylation of eukaryotic translation initiation factor 2 subunit 1 (eIF2α), and in eIF2α/S51D mutant cells. When eIF2α/S51A mutant cells differentiated, SGs were not assembled. In all experiments, the disruption of SGs was accompanied by delayed NF-M expression and the number of neuronally differentiated cells was decreased. Decreased differentiation was accompanied by decreased cell viability, indicating the necessity of SGs for preventing cell death during neuronal differentiation. Collectively, these results demonstrate the essential role of SGs during the neuronal differentiation of stem cells.

Function study of vasoactive intestinal peptide on chick embryonic bone development

Embryonic bone development is a complicated procedure and modulated by neuro-osteogenic interaction. Vasoactive intestinal peptide (VIP) was first identified as a neural vasodilator and further proved to possess multiple biological functions such as neurotransmitter and immune regulator. However, as a key peptide regulator presented in skeletal nerve fibers, the function of VIP on innervation and early bone development regulation has not fully been uncovered yet. In this study, the chick embryo has been used as an experimental model to address the effect of VIP on embryonic bone development. Our study results confirmed the innervation of peripheral nerve fibers into limb bone tissue, which was revealed by the detection of neurofilament (NF) and class III β-tubulin (TUJ-1) in bone tissue at various developing stages. The VIP mRNA and peptide expression level in bone tissue were also increased upon innervation progress. A chick embryonic chemical sympathectomy model was constructed by exposing chick embryos with neurotoxin 6-OHDA. The 6-OHDA exposure of the early chick embryo caused the reduction of neural crest formation and NF expression. 6-OHDA treatment also inhibited distal limb bone development as well as VIP expression. Furthermore, co-application of VIP with 6-OHDA exposure could rescue the inhibited osteogenesis activity and delayed bone development during embryogenesis. Taken together, these results reveal that VIP played an important role during innervation at early stage of bone development. VIP could restore chemical sympathectomy induced osteogenesis inhibition and bone development impair in chick embryos.

Neurofilament light chain level in traumatic brain injury: A system review and meta-analysis

BACKGROUND

Neurofilament light (NfL) level was obviously increased in traumatic brain injury (TBI) individuals. But, no comprehensive meta-analysis has ever been conducted to assess the diagnostic performance of NfL. This study aims to evaluate the relationship between NfL level and TBI through a meta-analysis.

METHODS

Studies were selected from Pubmed, Web of science, Embase, Google Scholar, PMC and Chinese National Knowledge Infrastructure (CNKI), and the Chinese Biomedical Literature Database (CBM) through inclusion and exclusion criteria. The standard mean difference (SMD) and 95% confidence interval (CI) were calculated using the random-effect model or fixed-effect model to assess the association between NfL level and TBI. Subgroup analysis according to sample collection time, sample type and detection method was performed. The influence analysis and publication bias was also conducted. All analyses were performed using the RevMan 5.3 and Stata 12 software.

RESULTS

A total of 9 studies were included. Results indicated that TBI individuals had a higher NfL expression level compared with the non-TBI individuals (SMD = 2.48, 95% CI = 1.52-3.43, I = 96%, P < .01). Similar NfL increasing was also observed in Caucasian population, 0-48 hour and 6-10 days sample collection time, as well as cerebrospinal fluid (CSF), serum, plasma sample subgroup analysis. Moreover, the NfL increasing still existed no matter the NfL expression level was detected by ELISA or Simoa assay.

CONCLUSION

NfL expression level was increased in TBI individuals, which indicated that NfL could be a potential biomarker in the diagnosis of TBI and other neurodegenerative diseases.

Characterization of Fluid Biomarkers Reveals Lysosome Dysfunction and Neurodegeneration in Neuronopathic MPS II Patients

Mucopolysaccharidosis type II is a lysosomal storage disorder caused by a deficiency of iduronate-2-sulfatase (IDS) and characterized by the accumulation of the primary storage substrate, glycosaminoglycans (GAGs). Understanding central nervous system (CNS) pathophysiology in neuronopathic MPS II (nMPS II) has been hindered by the lack of CNS biomarkers. Characterization of fluid biomarkers has been largely focused on evaluating GAGs in cerebrospinal fluid (CSF) and the periphery; however, GAG levels alone do not accurately reflect the broad cellular dysfunction in the brains of MPS II patients. We utilized a preclinical mouse model of MPS II, treated with a brain penetrant form of IDS (ETV:IDS) to establish the relationship between markers of primary storage and downstream pathway biomarkers in the brain and CSF. We extended the characterization of pathway and neurodegeneration biomarkers to nMPS II patient samples. In addition to the accumulation of CSF GAGs, nMPS II patients show elevated levels of lysosomal lipids, neurofilament light chain, and other biomarkers of neuronal damage and degeneration. Furthermore, we find that these biomarkers of downstream pathology are tightly correlated with heparan sulfate. Exploration of the responsiveness of not only CSF GAGs but also pathway and disease-relevant biomarkers during drug development will be crucial for monitoring disease progression, and the development of effective therapies for nMPS II.

Biological and clinical characteristics of gene carriers far from predicted onset in the Huntington's disease Young Adult Study (HD-YAS): a cross-sectional analysis

BACKGROUND

Disease-modifying treatments are in development for Huntington's disease; crucial to their success is to identify a timepoint in a patient's life when there is a measurable biomarker of early neurodegeneration while clinical function is still intact. We aimed to identify this timepoint in a novel cohort of young adult premanifest Huntington's disease gene carriers (preHD) far from predicted clinical symptom onset.

METHODS

We did the Huntington's disease Young Adult Study (HD-YAS) in the UK. We recruited young adults with preHD and controls matched for age, education, and sex to ensure each group had at least 60 participants with imaging data, accounting for scan fails. Controls either had a family history of Huntington's disease but a negative genetic test, or no known family history of Huntington's disease. All participants underwent detailed neuropsychiatric and cognitive assessments, including tests from the Cambridge Neuropsychological Test Automated Battery and a battery assessing emotion, motivation, impulsivity and social cognition (EMOTICOM). Imaging (done for all participants without contraindications) included volumetric MRI, diffusion imaging, and multiparametric mapping. Biofluid markers of neuronal health were examined using blood and CSF collection. We did a cross-sectional analysis using general least-squares linear models to assess group differences and associations with age and CAG length, relating to predicted years to clinical onset. Results were corrected for multiple comparisons using the false discovery rate (FDR), with FDR <0·05 deemed a significant result.

FINDINGS

Data were obtained between Aug 2, 2017, and April 25, 2019. We recruited 64 young adults with preHD and 67 controls. Mean ages of participants were 29·0 years (SD 5·6) and 29·1 years (5·7) in the preHD and control groups, respectively. We noted no significant evidence of cognitive or psychiatric impairment in preHD participants 23·6 years (SD 5·8) from predicted onset (FDR 0·22-0·87 for cognitive measures, 0·31-0·91 for neuropsychiatric measures). The preHD cohort had slightly smaller putamen volumes (FDR=0·03), but this did not appear to be closely related to predicted years to onset (FDR=0·54). There were no group differences in other brain imaging measures (FDR >0·16). CSF neurofilament light protein (NfL), plasma NfL, and CSF YKL-40 were elevated in this far-from-onset preHD cohort compared with controls (FDR<0·0001, =0·01, and =0·03, respectively). CSF NfL elevations were more likely in individuals closer to expected clinical onset (FDR <0·0001).

INTERPRETATION

We report normal brain function yet a rise in sensitive measures of neurodegeneration in a preHD cohort approximately 24 years from predicted clinical onset. CSF NfL appears to be a more sensitive measure than plasma NfL to monitor disease progression. This preHD cohort is one of the earliest yet studied, and our findings could be used to inform decisions about when to initiate a potential future intervention to delay or prevent further neurodegeneration while function is intact.

FUNDING

Wellcome Trust, CHDI Foundation.

Functional Characterization of Neurofilament Light Splicing and Misbalance in Zebrafish

Neurofilaments (NFs), a major cytoskeletal component of motor neurons, play a key role in the differentiation, establishment and maintenance of their morphology and mechanical strength. The de novo assembly of these neuronal intermediate filaments requires the presence of the neurofilament light subunit (NEFL), whose expression is reduced in motor neurons in amyotrophic lateral sclerosis (ALS). This study used zebrafish as a model to characterize the NEFL homologue neflb, which encodes two different isoforms via a splicing of the primary transcript (neflbE4 and neflbE3). In vivo imaging showed that neflb is crucial for proper neuronal development, and that disrupting the balance between its two isoforms specifically affects the NF assembly and motor axon growth, with resultant motor deficits. This equilibrium is also disrupted upon the partial depletion of TDP-43 (TAR DNA-binding protein 43), an RNA-binding protein encoded by the gene TARDBP that is mislocalized into cytoplasmic inclusions in ALS. The study supports the interaction of the NEFL expression and splicing with TDP-43 in a common pathway, both biologically and pathogenetically.

Satellite glia activation in dorsal root ganglion contributes to mechanical allodynia after selective motor fiber injury in adult rats

Increasing evidence suggests that activation of satellite glia cells (SGCs) in sensory ganglia play important roles in the development of neuropathic pain. The present study aimed to investigate the involvement of SGC activation in a novel model of motor nerve injury induced pain hypersensitivity. The neuropathic pain model was established by cervical 8 ventral root avulsion (C8VA). Glial fibrillary acidic protein (GFAP) was used as a marker of SGC activation. Unilateral C8VA resulted in mechanical allodynia, but not thermal hyperalgesia in bilateral paws. Expectedly, SGCs were robustly activated on as early as 1 day and persisted for at least 7 days in the ipsilateral and contralateral dorsal root ganglia (DRG) of C6, C7 and C8 after C8VA. Double immunofluorescence showed that almost all the activated SGCs enveloped neurofilament 200 (NF200) positive myelinated neurons in DRG. Local application of fluorocitrate (FC), a glial metabolism inhibitor, significantly decreased the number of activated SGCs and alleviated bilateral mechanical allodynia. These results suggest that SGC activation contributed to ipsilateral and mirror-image pain hypersensitivity after C8VA. Inhibition of SGC activation represented a promising therapeutic strategy for the management of neuropathic pain following brachial plexus root avulsion.

The conserved DNMT1-dependent methylation regions in human cells are vulnerable to neurotoxicant rotenone exposure

BACKGROUND

Allele-specific DNA methylation (ASM) describes genomic loci that maintain CpG methylation at only one inherited allele rather than having coordinated methylation across both alleles. The most prominent of these regions are germline ASMs (gASMs) that control the expression of imprinted genes in a parent of origin-dependent manner and are associated with disease. However, our recent report reveals numerous ASMs at non-imprinted genes. These non-germline ASMs are dependent on DNA methyltransferase 1 (DNMT1) and strikingly show the feature of random, switchable monoallelic methylation patterns in the mouse genome. The significance of these ASMs to human health has not been explored. Due to their shared allelicity with gASMs, herein, we propose that non-traditional ASMs are sensitive to exposures in association with human disease.

RESULTS

We first explore their conservancy in the human genome. Our data show that our putative non-germline ASMs were in conserved regions of the human genome and located adjacent to genes vital for neuronal development and maturation. We next tested the hypothesized vulnerability of these regions by exposing human embryonic kidney cell HEK293 with the neurotoxicant rotenone for 24 h. Indeed,14 genes adjacent to our identified regions were differentially expressed from RNA-sequencing. We analyzed the base-resolution methylation patterns of the predicted non-germline ASMs at two neurological genes, HCN2 and NEFM, with potential to increase the risk of neurodegeneration. Both regions were significantly hypomethylated in response to rotenone.

CONCLUSIONS

Our data indicate that non-germline ASMs seem conserved between mouse and human genomes, overlap important regulatory factor binding motifs, and regulate the expression of genes vital to neuronal function. These results support the notion that ASMs are sensitive to environmental factors such as rotenone and may alter the risk of neurological disease later in life by disrupting neuronal development.

Demyelination associated with chronic arsenic exposure in Wistar rats

Inorganic arsenic is among the major contaminants of groundwater in the world. Worldwide population-based studies demonstrate that chronic arsenic exposure is associated with poor cognitive performance among children and adults, while research in animal models confirms learning and memory deficits after arsenic exposure. The aim of this study was to investigate the long-term effects of environmentally relevant arsenic exposure in the myelination process of the prefrontal cortex (PFC) and corpus callosum (CC). A longitudinal study with repeated follow-up assessments was performed in male Wistar rats exposed to 3 ppm sodium arsenite in drinking water. Animals received the treatment from gestation until 2, 4, 6, or 12 months of postnatal age. The levels of myelin basic protein (MBP) were evaluated by immunohistochemistry/histology and immunoblotting from the PFC and CC. As plausible alterations associated with demyelination, we considered mitochondrial mass (VDAC) and two axonal damage markers: amyloid precursor protein (APP) level and phosphorylated neurofilaments. To analyze the microstructure of the CC in vivo, we acquired diffusion-weighted images at the same ages, from which we derived metrics using the tensor model. Significantly decreased levels of MBP were found in both regions together with significant increases of mitochondrial mass and slight axonal damage at 12 months in the PFC. Ultrastructural imaging demonstrated arsenic-associated decreases of white matter volume, water diffusion anisotropy, and increases in radial diffusivity. This study indicates that arsenic exposure is associated with a significant and persistent negative impact on microstructural features of white matter tracts.

Neurofilament Light Chain as a Biomarker, and Correlation with Magnetic Resonance Imaging in Diagnosis of CNS-Related Disorders

The search for diagnostic and prognostic biomarkers for neurodegenerative conditions is of high importance, since these disorders may present difficulties in differential diagnosis. Biomarkers with high sensitivity and specificity are required. Neurofilament light chain (NfL) is a unique biomarker related to axonal damage and neural cell death, which is elevated in a number of neurological disorders, and can be detected in cerebrospinal fluid (CSF), as well as blood, serum, or plasma samples. Although the NfL concentration in CSF is higher than that in blood, blood measurement may be easier in practice due to its lesser invasiveness, reproducibility, and convenience. Many studies have investigated NfL in both CSF and serum/plasma as a potential biomarker of neurodegenerative disorders. Neuroimaging biomarkers can also potentially improve detection of CNS-related disorders at an early stage. Magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) are sensitive techniques to visualize neuroaxonal loss. Therefore, investigating the combination of NfL levels with indices extracted from MRI and DTI scans could potentially improve diagnosis of CNS-related disorders. This review summarizes the evidence for NfL being a reliable biomarker in the early detection and disease management in several CNS-related disorders. Moreover, we highlight the correlation between MRI and NfL and ask whether they can be combined.

Plasma and CSF neurofilament light: Relation to longitudinal neuroimaging and cognitive measures

OBJECTIVE

We aimed to (1) assess and compare baseline plasma and CSF neurofilament light (NfL) for cross-sectional and longitudinal associations with neuroimaging or cognition and (2) determine whether change in plasma NfL corresponded with change in these outcomes.

METHODS

Seventy-nine participants without dementia, median age 76 years, had plasma and CSF NfL, neuropsychological testing, and neuroimaging (MRI, amyloid PET, FDG-PET) at the same study visit, and a repeat visit (15 or 30 months later) with both plasma NfL and neuroimaging. Plasma NfL was measured on the Simoa-HD1 Platform and CSF NfL with an in-house ELISA. Linear mixed effects models were used to examine the associations between baseline plasma or CSF NfL and cognitive and neuroimaging outcomes adjusting for age, sex, and education. The relationship between change in plasma NfL and change in the outcomes was assessed using linear regression.

RESULTS

There were no cross-sectional associations between CSF or plasma NfL and any neuroimaging or cognitive measure. Longitudinally, higher baseline plasma NfL was associated with worsening in all neuroimaging measures, except amyloid PET, and global cognition. Higher baseline CSF NfL was associated with worsening in cortical thickness and diffusion MRI. The beta estimates for CSF NfL were similar to those for plasma NfL. Change in plasma NfL was associated with change in global cognition, attention, and amyloid PET.

CONCLUSION

Elevated baseline plasma NfL is a prognostic marker of cognitive decline and neuroimaging measures of neurodegeneration, and has similar effect sizes to baseline CSF NfL. Change in plasma NfL also tracked with short-term cognitive change.

Transcriptional Response and Morphological Features of the Neurovascular Unit and Associated Extracellular Matrix After Experimental Stroke in Mice

Experimental stroke studies yielded insights into single reactions of the neurovascular unit (NVU) and associated extracellular matrix (ECM). However, the extent of simultaneous processes caused by ischemia and their underlying transcriptional changes are still poorly understood. Strictly following the NVU and ECM concept, this study explored transcriptional responses of cellular and non-cellular components as well as their morphological characteristics following ischemia. Mice were subjected to 4 or 24 h of unilateral middle cerebral artery occlusion. In the neocortex and the striatum, cytoskeletal and glial elements as well as blood-brain barrier and ECM components were analyzed using real-time PCR. Western blot analyses allowed characterization of protein levels and multiple immunofluorescence labeling enabled morphological assessment. Out of 37 genes analyzed, the majority exhibited decreased mRNA levels in ischemic areas, while changes occurred as early as 4 h after ischemia. Down-regulated mRNA levels were predominantly localized in the neocortex, such as the structural elements α-catenin 2, N-cadherin, β-catenin 1, and βIII-tubulin, consistently decreasing 4 and 24 h after ischemia. However, a few genes, e.g., claudin-5 and Pcam1, exhibited increased mRNA levels after ischemia. For several components such as βIII-tubulin, N-cadherin, and β-catenin 1, matching transcriptional and immunofluorescence signals were obtained, whereas a few markers including neurofilaments exhibited opposite directions. In conclusion, the variety in gene regulation emphasizes the complexity of interactions within the ischemia-affected NVU and ECM. These data might help to focus future research on a set of highly sensitive elements, which might prospectively facilitate neuroprotective strategies beyond the traditional single target perspective.

[Transplanted adipose-derived stem cells promote the expression of deleted in colorectal cancer (DCC) and neurofilament-200 (NF-200) in peri-infarct cortex of rats]

Objective To investigate the effects of adipose-derived stem cells (ADSCs) transplantation on the expression of deleted in colorectal cancer (DCC) and neurofilament-200 (NF-200) in peri-infarct cortex of rats. Methods SD rats were randomly divided into sham group, model group and ADSCs group. The rat model of middle cerebral artery occlusion (MCAO) was established with the modified Longa's method. Twenty-four hours after MCAO, 50 μL of cell suspension containing about 2×10⁶ PKH-26-labeled ADSCs was injected into the carotid artery of rats in the ADSCs group, and the same dose of saline was given to the rats in the model group. Day 7 and 14 after MCAO, the migration of ADSCs in rat brains was observed under a fluorescence microscope, and the protein levels of DCC and NF-200 in the peri-infarct cortex were measured by Western blot analysis and the expression and distribution of DCC and NF-200 were detected by immunofluorescent histochemistry. Results PKH-26-labeled ADSCs were observed in the rat brains of ADSC group, and most of them were located in the peri-infarct cortex. At 7 and 14 days after MCAO, the expression of DCC in the model group was higher than that in the sham group, while the expression level of NF-200 was lower. Besides, the expression of DCC and NF-200 in the ADSC group was both higher than that in the model group. In the peri-infract cortex, DCC was mainly expressed in NF-200-positive neuronal axons. Conclusion The ADSCs can migrate to the peri-infarct cortex after transplantation via carotid artery, and may strengthen the axonal regeneration and repairment by promoting the expression of DCC and NF-200 in this region.

TRIM2, a novel member of the antiviral family, limits New World arenavirus entry

Tripartite motif (TRIM) proteins belong to a large family with many roles in host biology, including restricting virus infection. Here, we found that TRIM2, which has been implicated in cases of Charcot-Marie-Tooth disease (CMTD) in humans, acts by blocking hemorrhagic fever New World arenavirus (NWA) entry into cells. We show that Trim2-knockout mice, as well as primary fibroblasts from a CMTD patient with mutations in TRIM2, are more highly infected by the NWAs Junín and Tacaribe virus than wild-type mice or cells are. Using mice with different Trim2 gene deletions and TRIM2 mutant constructs, we demonstrate that its antiviral activity is uniquely independent of the RING domain encoding ubiquitin ligase activity. Finally, we show that one member of the TRIM2 interactome, signal regulatory protein α (SIRPA), a known inhibitor of phagocytosis, also restricts NWA infection and conversely that TRIM2 limits phagocytosis of apoptotic cells. In addition to demonstrating a novel antiviral mechanism for TRIM proteins, these studies suggest that the NWA entry and phagocytosis pathways overlap.

Levels of plasma neurofilament light chain and cognitive function in patients with Alzheimer or Parkinson disease

Plasma neurofilament light (NFL) has been proposed as a blood-based biomarker for neurodegeneration in Alzheimer's disease (AD) and parkinsonian disorders. However, the relationship between plasma NFL and cognitive decline in dementia due to Parkinson's disease (PD) remains to be elucidated. In this research, 119 AD, 56 mild cognitive impairment (MCI), 26 non-demented PD (PDND), and 23 Parkinson's disease dementia (PDD) patients, as well as 59 cognitively healthy controls (HC) were recruited. Each subject underwent a battery of neuropsychological testing. Plasma NFL levels were measured in duplicate using an NF-Light assay and transferred onto the Simoa platform with a home-brew kit. Plasma NFL was significantly increased in the AD group, compared with the control, MCI, PDND, and PDD groups. Plasma NFL was significantly higher in the PDD group, compared with the PDND group. High plasma NFL correlated with poor cognition in AD and PD, but not with motor symptoms in PD. Plasma NFL may represent a biomarker of cognitive decline in AD and PD, with more specificity for AD.

Axonal regrowth is impaired during digit tip regeneration in mice

Mice are intrinsically capable of regenerating the tips of their digits after amputation. Mouse digit tip regeneration is reported to be a peripheral nerve-dependent event. However, it is presently unknown what types of nerves and Schwann cells innervate the digit tip, and to what extent these cells regenerate in association with the regenerative response. Given the necessity of peripheral nerves for mammalian regeneration, we investigated the neuroanatomy of the unamputated, regenerating, and regenerated mouse digit tip. Using immunohistochemistry for β-III-tubulin (β3T) or neurofilament H (NFH), substance P (SP), tyrosine hydroxylase (TH), myelin protein zero (P0), and glial fibrillary acidic protein (GFAP), we identified peripheral nerve axons (sensory and sympathetic), and myelinating- and non-myelinating-Schwann cells. Our findings show that the digit tip is innervated by two digital nerves that each bifurcate into a bone marrow (BM) and connective tissue (CT) branch. The BM branches are composed of sympathetic axons that are ensheathed by non-myelinating-Schwann cells whereas the CT branches are composed of sensory and sympathetic axons and are ensheathed by myelinating- and non-myelinating-Schwann cells. The regenerated digit neuroanatomy differs from unamputated digit in several key ways. First, there is 7.5 fold decrease in CT branch axons in the regenerated digit compared to the unampuated digit. Second, there is a 5.6 fold decrease in myelinating-Schwann cells in the regenerated digit compared to the unamputated digit that is consistent with the decrease in CT branch axons. Importantly, we also find that the central portion of the regenerating digit blastema is aneural, with axons and Schwann cells restricted to peripheral and distal blastema regions. Finally, we show that even with impaired innervation, digits maintain the ability to regenerate after re-amputation. Taken together, these data indicate that nerve regeneration is impaired in the context of mouse digit tip regeneration.

Cancer Chemotherapy in Early Life Significantly Alters the Maturation of Pain Processing

Advances in pediatric cancer treatment have led to a ten year survival rate greater than 75%. Platinum-based chemotherapies (e.g. cisplatin) induce peripheral sensory neuropathy in adult and pediatric cancer patients. The period from birth through to adulthood represents a period of maturation within nociceptive systems. Here we investigated how cisplatin impacts upon postnatal maturation of nociceptive systems. Neonatal Wistar rats (Postnatal day (P) 7) were injected (i.p.) daily with either vehicle (PBS) or cisplatin (1mg/kg) for five consecutive days. Neither group developed mechanical or thermal hypersensitivity immediately during or after treatment. At P22 the cisplatin group developed mechanical (P < 0.05) and thermal (P < 0.0001) hypersensitivity versus vehicle group. Total DRG or dorsal horn neuronal number did not differ at P45, however there was an increase in intraepidermal nerve fiber density in cisplatin-treated animals at this age. The percentage of IB4+ve, CGRP+ve and NF200+ve DRG neurons was not different between groups at P45. There was an increase in TrkA+ve DRG neurons in the cisplatin group at P45, in addition to increased TrkA, NF200 and vGLUT2 immunoreactivity in the lumbar dorsal horn versus controls. These data highlight the impact pediatric cancer chemotherapy has upon the maturation of pain pathways and later life pain experience.

Internode length is reduced during myelination and remyelination by neurofilament medium phosphorylation in motor axons

The distance between nodes of Ranvier, referred to as internode length, positively correlates with axon diameter, and is optimized during development to ensure maximal neuronal conduction velocity. Following myelin loss, internode length is reestablished through remyelination. However, remyelination results in short internode lengths and reduced conduction rates. We analyzed the potential role of neurofilament phosphorylation in regulating internode length during remyelination and myelination. Following ethidium bromide induced demyelination, levels of neurofilament medium (NF-M) and heavy (NF-H) phosphorylation were unaffected. Preventing NF-M lysine-serine-proline (KSP) repeat phosphorylation increased internode length by 30% after remyelination. To further analyze the role of NF-M phosphorylation in regulating internode length, gene replacement was used to produce mice in which all KSP serine residues were replaced with glutamate to mimic constitutive phosphorylation. Mimicking constitutive KSP phosphorylation reduced internode length by 16% during myelination and motor nerve conduction velocity by ~27% without altering sensory nerve structure or function. Our results suggest that NF-M KSP phosphorylation is part of a cooperative mechanism between axons and Schwann cells that together determine internode length, and suggest motor and sensory axons utilize different mechanisms to establish internode length.

A Subset of Palisade Endings Only in the Medial and Inferior Rectus Muscle in Monkey Contain Calretinin

Purpose

To further chemically characterize palisade endings in extraocular muscles in rhesus monkeys.

Methods

Extraocular muscles of three rhesus monkeys were studied for expression of the calcium-binding protein calretinin (CR) in palisade endings and multiple endings. The complete innervation was visualized with antibodies against the synaptosomal-associated protein of 25 kDa and combined with immunofluorescence for CR. Six rhesus monkeys received tracer injections of choleratoxin subunit B or wheat germ agglutinin into either the belly or distal myotendinous junction of the medial or inferior rectus muscle to allow retrograde tracing in the C-group of the oculomotor nucleus. Double-immunofluorescence methods were used to study the CR content in retrogradely labeled neurons in the C-group.

Results

A subgroup of palisade and multiple endings was found to express CR, only in the medial and inferior rectus muscle. In contrast, the en plaque endings lacked CR. Accordingly, within the tracer-labeled neurons of the C-group, a subgroup expressed CR.

Conclusions

The study indicates that two different neuron populations targeting nontwitch muscle fibers are present within the C-group for inferior rectus and medial rectus, respectively, one expressing CR, one lacking CR. It is possible that the CR-negative neurons represent the basic population for all extraocular muscles, whereas the CR-positive neurons giving rise to CR-positive palisade endings represent a specialized, perhaps more excitable type of nerve ending in the medial and inferior rectus muscles, being more active in vergence. The malfunction of this CR-positive population of neurons that target nontwitch muscle fibers could play a significant role in strabismus.

Miconazole enhances nerve regeneration and functional recovery after sciatic nerve crush injury

INTRODUCTION

Improving axonal outgrowth and remyelination is crucial for peripheral nerve regeneration. Miconazole appears to enhance remyelination in the central nervous system. In this study we assess the effect of miconazole on axonal regeneration using a sciatic nerve crush injury model in rats.

METHODS

Fifty Sprague-Dawley rats were divided into control and miconazole groups. Nerve regeneration and myelination were determined using histological and electrophysiological assessment. Evaluation of sensory and motor recovery was performed using the pinprick assay and sciatic functional index. The Cell Counting Kit-8 assay and Western blotting were used to assess the proliferation and neurotrophic expression of RSC 96 Schwann cells.

RESULTS

Miconazole promoted axonal regrowth, increased myelinated nerve fibers, improved sensory recovery and walking behavior, enhanced stimulated amplitude and nerve conduction velocity, and elevated proliferation and neurotrophic expression of RSC 96 Schwann cells.

DISCUSSION

Miconazole was beneficial for nerve regeneration and functional recovery after peripheral nerve injury. Muscle Nerve 57: 821-828, 2018.

Geometric Navigation of Axons in a Cerebral Pathway: Comparing dMRI with Tract Tracing and Immunohistochemistry

Brain fiber pathways are presumed to follow smooth curves but recent high angular resolution diffusion MRI (dMRI) suggests that instead they follow 3 primary axes often nearly orthogonal. To investigate this, we analyzed axon pathways under monkey primary motor cortex with (1) dMRI tractography, (2) axon tract tracing, and (3) axon immunohistochemistry. dMRI tractography shows the predicted crossings of axons in mediolateral and dorsoventral orientations and does not show axon turns in this region. Axons labeled with tract tracer in the motor cortex dispersed in the centrum semiovale by microscopically sharp axonal turns and/or branches (radii ≤15 µm) into 2 sharply defined orientations, mediolateral and dorsoventral. Nearby sections processed with SMI-32 antibody to label projection axons and SMI-312 antibody to label all axons revealed axon distributions parallel to the tracer axons. All 3 histological methods confirmed preponderant axon distributions parallel with dMRI axes with few axons (<20%) following smooth curves or diagonal orientations. These findings indicate that axons navigate deep white matter via microscopic sharp turns and branches between primary axes. They support dMRI observations of primary fiber axes, as well as the prediction that fiber crossings include navigational events not yet directly resolved by dMRI. New methods will be needed to incorporate coherent microscopic navigation into dMRI of connectivity.

A novel histochemical method of simultaneous detection by a single- or double-immunofluorescence and Bielschowsky's silver staining in teased rat sciatic nerves

BACKGROUND

The Golgi silver method has been widely used in neuroscience for the study of normal and pathological morphology of neurons. The method has been steadily improved and Bielschowsky's silver staining method (BSSM) is widely used in various pathological conditions, like Alzheimer's disease.

NEW METHOD

In this work, teased sciatic nerves were silver impregnated using BSSM. We also developed simultaneous staining by silver impregnation and single- or double-immunofluorescence of the same section in teased nerve preparations. We immunostained against non-myelinating Schwann cells and different myelinating Schwann cell domains.

RESULTS

BSSM teased nerves show a strong staining of axons (black) and a gold-brown staining of myelinating and non-myelinating Schwann cells. We were also able to stain by immunofluorescence these BSSM teased nerves with specific molecular markers against non-myelinating Schwann cells, also against non-compact myelin such as the Schmidt-Lanterman incisures or paranodal regions and compact myelin, but not axons.

COMPARISON WITH EXISTING METHODS AND CONCLUSIONS

In peripheral nerves, several silver impregnation methods have been used to stain nerves in paraffin sections, but not in teased nerves to enable the assessment of isolated nerve fibers. In conclusion, BSSM gives accurate information of nerve morphology and combining the procedure with immunofluorescence it would be very useful to study the molecular nerve domain organization of the nerve fibers, and to study the molecular pathology of axon degeneration, or myelin disorders, or of any peripheral neuropathy, also to study demyelination diseases in the central nervous system.

Altered neurofilament protein expression in the lateral vestibular nucleus in Parkinson's disease

A major cause of morbidity in Parkinson's disease (PD) is postural instability. The neuropathology underlying postural instability is unknown. Postural control is mediated by Deiters' neurons of the lateral vestibular nucleus (LVN), which are the brainstem origin of descending vestibulospinal reflexes. Deiters' neurons express the cytostructural protein, non-phosphorylated neurofilament protein (NPNFP). In PD, reduced expression of NPNFP in substantia nigra (SN) neurons is believed to contribute to dysfunction. It was the aim of this study to determine if there is altered expression of NPNFP in the LVN in PD. We immunolabeled NPNFP in brainstem sections of six aged controls (mean age 92 yo) and six PD donors (mean age 83 yo). Our results show there was a ~ 50% reduction in NPNFP-positive Deiters' neurons compared to controls (13 ± 2.0/section vs 25.7 ± 3.0/section; p < 0.01, repeated measures ANOVA). In contrast, there was no difference in NPNFP-positive counts in the facial nucleus between control and PD. The normalized intensity of NPNFP labeling in LVN was also reduced in PD (0.87 ± 0.05 vs 1.09 ± 0.03; p < 0.01). There was a 35% concurrent reduction in NPNFP-positive neuropil in PD relative to controls (p < 0.01). We also show there was an 84% increase (p < 0.05) in somatic lipofuscin in PD patients compared to control. Lipofuscin aggregation has been shown to increase not only with age but also with neurodegeneration. Furthermore, decreased NPNFP intensity was strongly correlated with increasing lipofuscin autofluorescence across all cases (R ² = 0.81, p < 0.01). These results show two alterations in cellular content with PD, reduced expression and intensity of NPNFP and increased lipofuscin aggregation in Deiter's neurons. These changes may contribute to degeneration of postural reflexes observed in PD.

Abnormal neurofilament inclusions and segregations in dorsal root ganglia of a Charcot-Marie-Tooth type 2E mouse model

Charcot-Marie-Tooth (CMT) disease or hereditary motor and sensory neuropathy is the most prevalent inherited peripheral neuropathy and is associated with over 90 causative genes. Mutations in neurofilament light polypeptide gene, NEFL cause CMT2E, an axonal form of CMT that results in abnormal structures and/or functions of peripheral axons in spinal cord motor neurons and dorsal root ganglion neurons. We have previously generated and characterized a knock-in mouse model of CMT2E with the N98S mutation in Nefl that presented with multiple inclusions in spinal cord neurons. In this report, we conduct immunofluorescence studies of cultured dorsal root ganglia (DRG) from Nefl^N98S/+ mice, and show that inclusions found in DRG neurites can occur in embryonic stages. Ultrastructural analyses reveal that the inclusions are disordered neurofilaments packed in high density, segregated from other organelles. Immunochemical studies show decreased NFL protein levels in DRG, cerebellum and spinal cord in Nefl^N98S/+ mice, and total NFL protein pool is shifted toward the triton-insoluble fraction. Our findings reveal the nature of the inclusions in Nefl^N98S/+ mice, provide useful information to understand mechanisms of CMT2E disease, and identify DRG from Nefl^N98S/+ mice as a useful cell line model for therapeutic discoveries.

Neuronal Injury and Glial Changes Are Hallmarks of Open Field Blast Exposure in Swine Frontal Lobe

With the rapid increase in the number of blast induced traumatic brain injuries and associated neuropsychological consequences in veterans returning from the operations in Iraq and Afghanistan, the need to better understand the neuropathological sequelae following exposure to an open field blast exposure is still critical. Although a large body of experimental studies have attempted to address these pathological changes using shock tube models of blast injury, studies directed at understanding changes in a gyrencephalic brain exposed to a true open field blast are limited and thus forms the focus of this study. Anesthetized, male Yucatan swine were subjected to forward facing medium blast overpressure (peak side on overpressure 224-332 kPa; n = 7) or high blast overpressure (peak side on overpressure 350-403 kPa; n = 5) by detonating 3.6 kg of composition-4 charge. Sham animals (n = 5) were subjected to all the conditions without blast exposure. After a 3-day survival period, the brain was harvested and sections from the frontal lobes were processed for histological assessment of neuronal injury and glial reactivity changes. Significant neuronal injury in the form of beta amyloid precursor protein immunoreactive zones in the gray and white matter was observed in the frontal lobe sections from both the blast exposure groups. A significant increase in the number of astrocytes and microglia was also observed in the blast exposed sections compared to sham sections. We postulate that the observed acute injury changes may progress to chronic periods after blast and may contribute to short and long-term neuronal degeneration and glial mediated inflammation.

Preparation and Immunostaining of the Myenteric Plexus of Prion-Infected Mice

Intracerebral inoculation of mice with the M1000 strain of mouse-adapted human prions results in the consistent accumulation of PrP^Sc in the ileum of the gastrointestinal tract (GIT) of mice with clinical signs of prion disease. The accumulation of PrP^Sc in the ileum is accompanied by caspase activation and loss of immunoreactivity in subpopulations of neurons in the enteric nervous system. This suggests that like neurons in the central nervous system, cells in the enteric nervous system are also susceptible to prion-induced toxicity. In this chapter we describe the immunostaining of cells in myenteric plexus preparations of whole mounts prepared from the gastrointestinal tract of prion-infected mice.

Jujube-containing herbal decoctions induce neuronal differentiation and the expression of anti-oxidant enzymes in cultured PC12 cells

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Ziziphus jujuba (Mill.), known as Jujuba Fructus (JF) or jujube, is a well-known Traditional Chinese Medicine (TCM) for blood nourishment and sedation effect. Apart from prescribing as single herb alone, JF is very often being included in multi-herbal decoctions to prolong, enhance and harmonize pharmaceutical effects of decoctions while at the same time reducing toxicity. Here, we aimed to compare the protective and differentiating activities of three chemically standardized jujube-containing decoctions, including Guizhi Tang (GZT), Neibu Dangguijianzhong Tang (NDT) and ZaoTang (ZOT) in cultured PC12 cells.

MATERIALS AND METHODS

The protein expressions of neurofilaments, including NF68, NF160 and NF200, under the herbal treatment were revealed by western blot. The determination of neurite outgrowth in cultured PC12 cells upon the treatment of herbal extracts was performed by light microscope equipped with a phase-contrast condenser and SPOT imaging software. The protective effect against tBHP-induced cytotoxicity under the herbal treatment was measured by MTT assay. A luciferase reporter construct carrying four repeats of anti-oxidant response element (ARE) and a downstream luciferase reporter gene luc2P was transfected into PC12 cells to study the transcriptional activation of ARE. The mRNA expression of antioxidant enzymes under the herbal treatment was analyzed by quantitative real-time PCR.

RESULTS

These jujube-containing decoctions processed similar neuro-protective and brain beneficial properties. The herbal treatment induced the protein expression of neurofilaments. Neurite outgrowth was observed under the herbal treatment. In parallel, the pre-treatment of herbal extracts protected PC 12 cells against oxidative stress-induced apoptosis in a dose-dependent manner. Moreover, the herbal treatments triggered the mRNA expressions of relevant anti-oxidation genes, i.e. glutamate-cysteine ligase catalytic subunit (GCLC), glutamate-cysteine ligase modulatory subunit (GCLM), glutathione S-transferase (GST) and NAD(P)H quinone oxidoreductase (NQO1) via the activation of anti-oxidant response element (ARE).

CONCLUSION

The results therefore demonstrated neuro-protective and differentiating properties of the three closely related decoctions, and which subsequently illustrated the enhancement function of jujube within a multi-herbal decoction.

Repeated Closed Head Injury in Mice Results in Sustained Motor and Memory Deficits and Chronic Cellular Changes

Millions of mild traumatic brain injuries (TBIs) occur every year in the United States, with many people subject to multiple head injuries that can lead to chronic behavioral dysfunction. We previously reported that mild TBI induced using closed head injuries (CHI) repeated at 24h intervals produced more acute neuron death and glial reactivity than a single CHI, and increasing the length of time between injuries to 48h reduced the cumulative acute effects of repeated CHI. To determine whether repeated CHI is associated with behavioral dysfunction or persistent cellular damage, mice receiving either five CHI at 24h intervals, five CHI at 48h intervals, or five sham injuries at 24h intervals were evaluated across a 10 week period after injury. Animals with repeated CHI exhibited motor coordination and memory deficits, but not gait abnormalities when compared to sham animals. At 10wks post-injury, no notable neuron loss or glial reactivity was observed in the cortex, hippocampus, or corpus callosum. Argyrophilic axons were found in the pyramidal tract of some injured animals, but neither silver stain accumulation nor inflammatory responses in the injury groups were statistically different from the sham group in this region. However, argyrophilic axons, microgliosis and astrogliosis were significantly increased within the optic tract of injured animals. Repeated mild CHI also resulted in microgliosis and a loss of neurofilament protein 200 in the optic nerve. Lengthening the inter-injury interval from 24h to 48h did not effectively reduce these behavioral or cellular responses. These results suggest that repeated mild CHI results in persistent behavioral dysfunction and chronic pathological changes within the visual system, neither of which was significantly attenuated by lengthening the inter-injury interval from 24h to 48h.

The new Global Multiple Sclerosis Severity Score (MSSS) correlates with axonal but not glial biomarkers

This study investigated whether the new Global Multiple Sclerosis Severity Scale (MSSS) correlated with cerebrospinal fluid biomarkers for axonal and glial pathology. The MSSS correlated with the phosphorylated neurofilament heavy chain (NfH-SMI35, R=0.44, P=0.016). The degree of neurofilament phosphorylation (ratio NfH-SMI34 to NfH-SMI35) was 8-fold higher in severely (median MSSS 6.5) versus mildly (MSSS 3.2) disabled patients (7.3 versus 0.9, P=0.03). The MSSS may provide a statistically powerful tool for comparing overall disease severity and be useful for validating the biomarker concept in MS.

Neurometabolite Alterations Associated With Cognitive Performance in Perinatally HIV-Infected Children

Despite treatment with combination antiretroviral therapy (cART), cognitive impairment is still observed in perinatally HIV-infected children. We aimed to evaluate potential underlying cerebral injury by comparing neurometabolite levels between perinatally HIV-infected children and healthy controls. This cross-sectional study evaluated neurometabolites, as measured by Magnetic Resonance Spectroscopy (MRS), in perinatally HIV-infected children stable on cART (n = 26) and healthy controls (n = 36).Participants were included from a cohort of perinatally HIV-infected children and healthy controls, matched group-wise for age, gender, ethnicity, and socio-economic status. N-acetylaspartate (NAA), glutamate (Glu), myo-inositol (mI), and choline (Cho) levels were studied as ratios over creatine (Cre). Group differences and associations with HIV-related parameters, cognitive functioning, and neuronal damage markers (neurofilament and total Tau proteins) were determined using age-adjusted linear regression analyses.HIV-infected children had increased Cho:Cre in white matter (HIV-infected = 0.29 ± 0.03; controls = 0.27 ± 0.03; P value = 0.045). Lower nadir CD4+ T-cell Z-scores were associated with reduced neuronal integrity markers NAA:Cre and Glu:Cre. A Centers for Disease Control and Prevention (CDC) stage C diagnosis was associated with higher glial markers Cho:Cre and mI:Cre. Poorer cognitive performance was mainly associated with higher Cho:Cre in HIV-infected children, and with lower NAA:Cre and Glu:Cre in healthy controls. There were no associations between neurometabolites and neuronal damage markers in blood or CSF.Compared to controls, perinatally HIV-infected children had increased Cho:Cre in white matter, suggestive of ongoing glial proliferation. Levels of several neurometabolites were associated with cognitive performance, suggesting that MRS may be a useful method to assess cerebral changes potentially linked to cognitive outcomes.

Kolaviron was protective against sodium azide (NaN3) induced oxidative stress in the prefrontal cortex

Kolaviron is a phytochemical isolated from Garcina kola (G. kola); a common oral masticatory agent in Nigeria (West Africa). It is a bioflavonoid used--as an antiviral, anti-inflammatory and antioxidant--in relieving the symptoms of several diseases and infections. In this study we have evaluated the neuroprotective and regenerative effect of kolaviron in neurons of the prefrontal cortex (Pfc) before or after exposure to sodium azide (NaN3) induced oxidative stress. Separate groups of animals were treated as follows; kolaviron (200 mg/Kg) for 21 days; kolaviron (200 mg/Kg for 21 days) followed by NaN3 treatment (20 mg/Kg for 5 days); NaN3 treatment (20 mg/Kg for 5 days) followed by kolaviron (200 mg/Kg for 21 days); 1 ml of corn-oil (21 days-vehicle); NaN3 treatment (20 mg/Kg for 5 days). Exploratory activity associated with Pfc function was assessed in the open field test (OFT) following which the microscopic anatomy of the prefrontal cortex was examined in histology (Haematoxylin and Eosin) and antigen retrieval Immunohistochemistry to show astroglia activation (GFAP), neuronal metabolism (NSE), cytoskeleton (NF) and cell cycle dysregulation (p53). Subsequently, we quantified the level of Glucose-6-phosphate dehydrogenase (G6PDH) and lactate dehydrogenase (LDH) in the brain tissue homogenate as a measure of stress-related glucose metabolism. Kolaviron (Kv) and Kolaviron/NaN3 treatment caused no prominent change in astroglia density and size while NaN3 and NaN3/Kv induced astroglia activation and scar formation (astrogliosis) in the Pfc when compared with the control. Similarly, Kolaviron and Kv/NaN3 did not alter NSE expression (glucose metabolism) while NaN3 and NaN3/Kv treatment increased cortical NSE expression; thus indicating stress related metabolism. Further studies on enzymes of glucose metabolism (G6PDH and LDH) showed that NaN3 increased LDH while kolaviron reduced LDH in the brain tissue homogenate (P < 0.001). In addition kolaviron treatment before (P < 0.001) or after (P < 0.05) NaN3 treatment also reduced LDH expression; thus supporting its role in suppression of oxidative stress. Interestingly, NF deposition increased in the Pfc after kolaviron treatment while Kv/NaN3 showed no significant change in NF when compared with the control. In furtherance, NaN3 and NaN3/Kv caused a decrease in NF deposition (degeneration). Ultimately, the protective effect of KV administered prior to NaN3 treatment was confirmed through p53 expression; which was similar to the control. However, NaN3 and NaN3/Kv caused an increase in p53 expression in the Pfc neurons (cell cycle dysregulation). We conclude that kolaviron is not neurotoxic when used at 200 mg/Kg BW. Furthermore, 200 mg/Kg of kolaviron administered prior to NaN3 treatment (Kv/NaN3) was neuroprotective when compared with Kolaviron administered after NaN3 treatment (NaN3/Kv). Some of the observed effects of kolaviron administered before NaN3 treatment includes reduction of astroglia activation, absence of astroglia scars, antioxidation (reduced NSE and LDH), prevention of neurofilament loss and cell cycle regulation.

Cells Sensing Mechanical Cues: Stiffness Influences the Lifetime of Cell-Extracellular Matrix Interactions by Affecting the Loading Rate

The question of how cells sense substrate mechanical cues has gained increasing attention among biologists. By introducing contour-based data analysis to single-cell force spectroscopy, we identified a loading-rate threshold for the integrin α2β1-DGEA bond beyond which a dramatic increase in bond lifetime was observed. On the basis of mechanical cues (elasticity or topography), the effective spring constant of substrates k is mapped to the loading rate r under actomyosin pulling speed v, which, in turn, affects the lifetime of the integrin-ligand bond. Additionally, downregulating v with a low-dose blebbistatin treatment promotes the neuronal lineage specification of mesenchymal stem cells on osteogenic stiff substrates. Thus, sensing of the loading rate is central to how cells sense mechanical cues that affect cell-extracellular matrix interactions and stem cell differentiation.

Autophagy Promotes Peripheral Nerve Regeneration and Motor Recovery Following Sciatic Nerve Crush Injury in Rats

Autophagy maintains cellular homeostasis by stimulating the lysosomal degradation of cytoplasmic structures, including damaged organelles and dysfunctional proteins. The role of autophagy in the renewal and regeneration of injured peripheral nerves remains poorly understood. The current study investigated the role of autophagy in peripheral nerve regeneration and motor function recovery following sciatic nerve crush injury in rats by stimulating or suppressing autophagy and detecting the presence of autophagosomes and LC3-II expression by electron microscopy and Western blotting, respectively. Neurobehavioral function was tested by CatWalk gait analysis 1, 2, 3, and 6 weeks after injury, and the expression of neurofilament (NF)-200 and myelin basic protein (MBP) at the injury site was examined by immunocytochemistry. Apoptosis at the lesion site was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Treatment of injured rats with the autophagy inducer rapamycin increased the number of autophagosomes and LC3-II expression while reducing the number of apoptotic cells at the lesion; this was associated with an upregulation of MBP and NF-200 expression and increased motor function recovery as compared to sham-operated rats and those that were subjected to crush injury but untreated. The opposite effects were observed in rats treated with the autophagy inhibitor 3-methyladenine. These data indicate that the modulation of autophagy in peripheral nerve injury could be an effective pharmacological approach to promote nerve regeneration and reestablish motor function.

Neurofilament Light Chain Determination from Peripheral Blood Samples

The loss of neurological function is closely related to axonal damage. Neurofilament subunits are concentrated in neurons and axons and have emerged as promising biomarkers for neurodegeneration. Electrochemiluminescence (ECL) based assays are known to be of superior sensitivity and require less sample volume than conventional ELISAs. Here, we describe a highly sensitive ECL based immunoassay for quantification of neurofilament light chain (NfL) in blood and CSF.

[RECONSTRUCTION OF LOWER EXTREMITY FUNCTION OF COMPLETE SPINAL CORD INJURY RATS BY FIRST NEURON CONNECTION]

OBJECTIVE

To investigate the effects of the first neuron connection for the reconstruction of lower extremity function of complete spinal cord injury rats.

METHODS

Forty adult female Sprague Dawley rats of 300-350 g in weight were selected to prepare the models of L₁ transverse spinal cord injury. After 2 weeks of establishing model, the rats were randomly divided into control group (n = 20) and experimental group (n = 20). In the experimental group, the right hind limb function was reconstructed directly by the first neuron; in the control group, the other treatments were the same to the experimental group except that the distal tibial nerve and the proximal femoral nerve were not sutured. The recovery of motor function of lower extremity was observed by the Basso-Beattie-Bresnahan (BBB) scoring system on bilateral hind limbs at 7, 30, 50, and 70 days after operation. The changes of the spinal cord were observed by HE staining, neurofilament 200 immunohistochemistry staining, and the technique of horseradish peroxidase (HRP) tracing.

RESULTS

After establishing models, 6 rats died. The right hind limb had no obvious recovery of the motor function, with the BBB score of 0 in 2 groups; the left hind limb motor function was recovered in different degrees, and there was no significant difference in BBB score between 2 groups (P > 0.05). In the experimental group, HE staining showed that the spinal cord was reconstructed with the sciatic nerve, which was embedded in the spinal cord, and the sciatic nerve membrane was clearly identified, and there was no obvious atrophy in the connecting part of the spinal cord. In the experimental group, the expression of nerve fiber was stained with immunohistochemistry, and the axons of the spinal cord were positively by stained and the peripheral nerve was connected with the spinal cord. HRP labelled synapses were detected by HRP retrograde tracing in the experimental group, while there was no HRP labelled synapse in the control group.

CONCLUSION

Direct reconstruction of the first neurons is sufficient in the regeneration of corresponding neural circuit by the growth of residual axon; but the motor function recovery of the target muscles innervated by peripheral nerve is not observed.

Inosine Improves Neurogenic Detrusor Overactivity following Spinal Cord Injury

Neurogenic detrusor overactivity and the associated loss of bladder control are among the most challenging complications of spinal cord injury (SCI). Anticholinergic agents are the mainstay for medical treatment of detrusor overactivity. However, their use is limited by significant side effects such that a search for new treatments is warranted. Inosine is a naturally occurring purine nucleoside with neuroprotective, neurotrophic and antioxidant effects that is known to improve motor function in preclinical models of SCI. However, its effect on lower urinary tract function has not been determined. The objectives of this study were to determine the effect of systemic administration of inosine on voiding function following SCI and to delineate potential mechanisms of action. Sprague−Dawley rats underwent complete spinal cord transection, or cord compression by application of an aneurysm clip at T8 for 30 sec. Inosine (225 mg/kg) or vehicle was administered daily via intraperitoneal injection either immediately after injury or after a delay of 8 wk. At the end of treatment, voiding behavior was assessed by cystometry. Levels of synaptophysin (SYP), neurofilament 200 (NF200) and TRPV1 in bladder tissues were measured by immunofluorescence imaging. Inosine administration decreased overactivity in both SCI models, with a significant decrease in the frequency of spontaneous non−voiding contractions during filling, compared to vehicle−treated SCI rats (p<0.05), including under conditions of delayed treatment. Immunofluorescence staining demonstrated increased levels of the pan-neuronal marker SYP and the Adelta fiber marker NF200, but decreased staining for the C-fiber marker, TRPV1 in bladder tissues from inosine-treated rats compared to those from vehicle-treated animals, including after delayed treatment. These findings demonstrate that inosine prevents the development of detrusor overactivity and attenuates existing overactivity following SCI, and may achieve its effects through modulation of sensory neurotransmission.

High postnatal susceptibility of hippocampal cytoskeleton in response to ethanol exposure during pregnancy and lactation

Ethanol exposure to offspring during pregnancy and lactation leads to developmental disorders, including central nervous system dysfunction. In the present work, we have studied the effect of chronic ethanol exposure during pregnancy and lactation on the phosphorylating system associated with the astrocytic and neuronal intermediate filament (IF) proteins: glial fibrillary acidic protein (GFAP), and neurofilament (NF) subunits of low, medium, and high molecular weight (NFL, NFM, and NFH, respectively) in 9- and 21-day-old pups. Female rats were fed with 20% ethanol in their drinking water during pregnancy and lactation. The homeostasis of the IF phosphorylation was not altered in the cerebral cortex, cerebellum, or hippocampus of 9-day-old pups. However, GFAP, NFL, and NFM were hyperphosphorylated in the hippocampus of 21-day-old pups. PKA had been activated in the hippocampus, and Ser55 in the N-terminal region of NFL was hyperphosphorylated. In addition, JNK/MAPK was activated and KSP repeats in the C-terminal region of NFM were hyperphosphorylated in the hippocampus of 21-day-old pups. Decreased NFH immunocontent but an unaltered total NFH/phosphoNFH ratio suggested altered stoichiometry of NFs in the hippocampus of ethanol-exposed 21-day-old pups. In contrast to the high susceptibility of hippocampal cytoskeleton in developing rats, the homeostasis of the cytoskeleton of ethanol-fed adult females was not altered. Disruption of the cytoskeletal homeostasis in neural cells supports the view that regions of the brain are differentially vulnerable to alcohol insult during pregnancy and lactation, suggesting that modulation of JNK/MAPK and PKA signaling cascades target the hippocampal cytoskeleton in a window of vulnerability in 21-day-old pups. Our findings are relevant, since disruption of the cytoskeleton in immature hippocampus could contribute to later hippocampal damage associated with ethanol toxicity.