Insight into the structure-elastic property relationship of calcium silicate glasses: a multi-length scale approach.

Based on a combination of molecular dynamics simulations, and Raman and Brillouin light scattering spectroscopies, we investigate the structure and elastic properties relationship in an archetypical calcium silicate glass system. From molecular dynamics and Raman spectroscopy, we show that the atomic structure at the short and intermediate length scales is made up of long polymerized silicate chains, which adjusts itself by closing the Si-O-Si angles and leaving more space to [CaO]n edge shared polyhedra to strengthen the glass. Using Brillouin spectroscopy, we observe an increase of elastic constants of the glass with the calcium content, as the cohesion of the glass structure is enhanced through an increase of the binding between the cross-linked calcium-silicate frameworks. This result, albeit being simple in its nature, illustrates for the first time the implication of the calcium framework in the elastic behavior of the glass and will contribute substantially to the understanding of the composition-structure-property relationships in multi-component industrial glasses.

Betacellulin regulates schwann cell proliferation and myelin formation in the injured mouse peripheral nerve.

When a nerve fiber is cut or crushed, the axon segment that is separated from the soma degenerates distal from the injury in a process termed Wallerian degeneration (WD). C57BL/6OlaHsd-WldS (WldS ) mutant mice exhibit significant delays in WD. This results in considerably delayed Schwann cell and macrophage responses and thus in impaired nerve regenerations. In our previous work, thousands of genes were screened by DNA microarrays and over 700 transcripts were found to be differentially expressed in the injured sciatic nerve of WldS compared with wild-type (WT) mice. One of these transcripts, betacellulin (Btc), was selected for further analysis since it has yet to be characterized in the nervous system, despite being known as a ligand of the ErbB receptor family. We show that Btc mRNA is strongly upregulated in immature and dedifferentiated Sox2+ Schwann cells located in the sciatic nerve distal stump of WT mice, but not WldS mutants. Transgenic mice ubiquitously overexpressing Btc (Tg-Btc) have increased numbers of Schmidt-Lantermann incisures compared with WT mice, as revealed by Coherent anti-Stokes Raman scattering (CARS). Tg-Btc mice also have faster nerve conduction velocity. Finally, we found that deficiency in Btc reduces the proliferation of myelinating Schwann cells after sciatic nerve injury, while Btc overexpression induces Schwann cell proliferation and improves recovery of locomotor function. Taken together, these results suggest a novel regulatory role of Btc in axon-Schwann cell interactions involved in myelin formation and nerve repair. GLIA 2017 GLIA 2017;65:657-669.

Neurobehavioral Anomalies in the Pitx3/ak Murine Model of Parkinson's Disease and MPTP.

Pitx3/ak null mutants are characterized by basal ganglia pathology in a manner resembling Parkinson's disease (PD), with decline in substantia nigra cell numbers as well as striatal tyrosine hydroxylase expression. Although young adult Pitx3/ak mutants were deficient in motor coordination tests, they were more active than non-transgenic controls in the open-field, unlike PD-related bradykinesia. On the SHIRPA primary screen, the mutants displayed body tremor, hyperactivity in the viewing jar, anomalies in eye morphology as well as a higher degree of hindlimb clasping and myoclonic jumping. Increased hindlimb clasping time and rotorod deficits seen in mutants were also exhibited by mice injected with MPTP, indicating an influence of dopamine on these behaviors.

Toll-like receptor 4 stimulation with the detoxified ligand monophosphoryl lipid A improves Alzheimer's disease-related pathology.

Alzheimer's disease (AD) is the most common cause of dementia worldwide. The pathogenesis of this neurodegenerative disease, currently without curative treatment, is associated with the accumulation of amyloid ß (Aß) in brain parenchyma and cerebral vasculature. AD patients are unable to clear this toxic peptide, leading to Aß accumulation in their brains and, presumably, the pathology associated with this devastating disease. Compounds that stimulate the immune system to clear Aß may therefore have great therapeutic potential in AD patients. Monophosphoryl lipid A (MPL) is an LPS-derived Toll-like receptor 4 agonist that exhibits unique immunomodulatory properties at doses that are nonpyrogenic. We show here that repeated systemic injections of MPL, but not LPS, significantly improved AD-related pathology in APP(swe)/PS1 mice. MPL treatment led to a significant reduction in Aß load in the brain of these mice, as well as enhanced cognitive function. MPL induced a potent phagocytic response by microglia while triggering a moderate inflammatory reaction. Our data suggest that the Toll-like receptor 4 agonist MPL may be a treatment for AD.

Motor activity in young APPswe + PS1/A246E bigenic mice as a predicting variable for memory decline.

Reports of individuality in rodent species have been a subject of debate in pharmacology and other fields. In the current study, APPswe + PS1/A246E bigenic mice with Alzheimer's-like pathogenesis and wild-type controls were subdivided at 3 months of age into low, intermediate, and high responders in open-field activity. The mice were then evaluated longitudinally at 3 and 9 months for object recognition. Irrespective of genotype, mice with a high level of motor activity had better scores in object recognition. However, a significant correlation was established between open-field activity measured at 3 months of age and recognition memory measured at 9 months of age in the bigenic group only. These results indicate that motor activity in young mice with amyloid neuropathology may serve as a predicting variable for cognitive dysfunction in more mature mice.

GPR84 deficiency reduces microgliosis, but accelerates dendritic degeneration and cognitive decline in a mouse model of Alzheimer's disease.

Microglia surrounds the amyloid plaques that form in the brains of patients with Alzheimer's disease (AD), but their role is controversial. Under inflammatory conditions, these cells can express GPR84, an orphan receptor whose pathophysiological role is unknown. Here, we report that GPR84 is upregulated in microglia of APP/PS1 transgenic mice, a model of AD. Without GPR84, these mice display both accelerated cognitive decline and a reduced number of microglia, especially in areas surrounding plaques. The lack of GPR84 affects neither plaque formation nor hippocampal neurogenesis, but promotes dendritic degeneration. Furthermore, GPR84 does not influence the clinical progression of other diseases in which its expression has been reported, i.e., experimental autoimmune encephalomyelitis (EAE) and endotoxic shock. We conclude that GPR84 plays a beneficial role in amyloid pathology by acting as a sensor for a yet unknown ligand that promotes microglia recruitment, a response affecting dendritic degeneration and required to prevent further cognitive decline.

Effect of charge polydispersity and charge residence time on the dynamics of a micellar system.

We use dynamic light scattering to investigate the effects of charge polydispersity and charge residence time on the dynamics of a micellar system. While in the corresponding uncharged system only one exponential relaxation is observed, two relaxation modes are seen when charging the micelles by adding charged co-surfactant molecules with a long residence time. We attribute the existence of these two relaxation modes to the combined effect of size polydispersity and charge polydispersity, i.e. frozen fluctuations of the number of charges per micelle. Further support to this scenario is provided by control experiments on a similar charged system, but where the charge residence time is short compared to the time scales probed by dynamic light scattering. Here, charge polydispersity is effectively suppressed due to the rapid exchange of charged molecules between micelles and only one single relaxation mode is seen, thereby demonstrating the key role of frozen charge fluctuations in the complex dynamics of our micellar system.

Interactions between microemulsion droplets decorated with hydrophobically modified polymers: a small-angle neutron scattering study.

The shape and interactions between microemulsion droplets (R = 8.2 nm, polydispersity 20%) either decorated with PEO modified with a single hydrophobic end function (PEO-m: C12H25 - (EO)n, M(PEO) = 5.2 kg/mol), or with telechelic polymers of twice the mass (PEO-2m: C12H25 - (EO)2n - C12H25, M(PEO) = 10.4 kg/mol) have been studied by small-angle neutron scattering (SANS). The results as a function of droplet and polymer concentration have been compared to the reference case of the bare microemulsion which was shown to be unchanged using Porod representations. The interactions between bare and decorated droplets have been analyzed using the structure factor S(q), at first in a model-free way based on its low-q limit S(q → 0). This analysis provides clear evidence on the concentration-dependent repulsive or attractive nature of the contributions to the pair droplet-droplet pair potential of the polymers. Model pair potentials describing the steric repulsions and attractions by copolymer bridging are used to describe the low-q behavior of the structure factor based on an integral equation approach, giving an estimate of the range and amplitude of the potentials. Moreover, they provide an explanation for the observed transient clustering in terms of a shallow minimum of the total potential, as they establish the respective repulsive and attractive contributions of the polymer molecules.

Protein phosphatase 2A family members (PP2A and PP6) associate with U1 snRNP and the spliceosome during pre-mRNA splicing.

Protein phosphorylation and dephosphorylation are both important for multiple steps in the splicing pathway. Members of the PP1 and PP2A subfamilies of phospho-serine/threonine phosphatases play essential but redundant roles in the second step of the splicing reaction. PP6, a member of the PP2A subfamily, is the mammalian homolog of yeast Sit4p and ppe1, which are involved in cell cycle regulation; however, the involvement of PP6 in the splicing pathway remains unclear. Here we show that PP2A family members physically associate with the spliceosome throughout the splicing reaction. PP2A holoenzyme and PP6 were found stably associated with U1 snRNP. Together our findings indicate that these phosphatases regulate splicing catalysis involving U1 snRNP and suggest an important evolutionary conserved role of PP2A family phosphatases in pre-mRNA splicing.

Functional recovery after peripheral nerve injury is dependent on the pro-inflammatory cytokines IL-1ß and TNF: implications for neuropathic pain.

IL-1ß and TNF are potential targets in the management of neuropathic pain after injury. However, the importance of the IL-1 and TNF systems for peripheral nerve regeneration and the mechanisms by which these cytokines mediate effects are to be fully elucidated. Here, we demonstrate that mRNA and protein levels of IL-1ß and TNF are rapidly upregulated in the injured mouse sciatic nerve. Mice lacking both IL-1ß and TNF, or both IL-1 type 1 receptor (IL-1R1) and TNF type 1 receptor (TNFR1), showed reduced nociceptive sensitivity (mechanical allodynia) compared with wild-type littermates after injury. Microinjecting recombinant IL-1ß or TNF at the site of sciatic nerve injury in IL-1ß- and TNF-knock-out mice restored mechanical pain thresholds back to levels observed in injured wild-type mice. Importantly, recovery of sciatic nerve function was impaired in IL-1ß-, TNF-, and IL-1ß/TNF-knock-out mice. Notably, the infiltration of neutrophils was almost completely prevented in the sciatic nerve distal stump of mice lacking both IL-1R1 and TNFR1. Systemic treatment of mice with an anti-Ly6G antibody to deplete neutrophils, cells that play an essential role in the genesis of neuropathic pain, did not affect recovery of neurological function and peripheral axon regeneration. Together, these results suggest that targeting specific IL-1ß/TNF-dependent responses, such as neutrophil infiltration, is a better therapeutic strategy for treatment of neuropathic pain after peripheral nerve injury than complete blockage of cytokine production.

Reversal of neuropathy phenotypes in conditional mouse model of Charcot-Marie-Tooth disease type 2E.

Mutations in the gene encoding for the neurofilament light subunit (NF-L) are responsible for Charcot-Marie-Tooth (CMT) neuropathy type 2E. To address whether CMT2E disease is potentially reversible, we generated a mouse model with conditional doxycycline-responsive gene system that allows repression of mutant hNF-LP22S transgene expression in adult neurons. The hNF-LP22S;tTa transgenic (tg) mice recapitulated key features of CMT2E disease, including aberrant hindlimb posture, motor deficits, hypertrophy of muscle fibres and loss of muscle innervation without neuronal loss. Remarkably, a 3-month treatment of hNF-LP22S;tTa mice with doxycycline after onset of disease efficiently down-regulated expression of hNF-LP22S and it caused reversal of CMT neurological phenotypes with restoration of muscle innervation and of neurofilament protein distribution along the sciatic nerve. These data suggest that therapeutic approaches aimed at abolishing expression or neutralizing hNF-L mutants might not only halt the progress of CMT2E disease, but also revert the disabilities.

A critical role for chloride channel-3 (CIC-3) in smooth muscle cell activation and neointima formation.

OBJECTIVE: We have shown that the chloride-proton antiporter chloride channel-3 (ClC-3) is required for endosome-dependent signaling by the Nox1 NADPH oxidase in SMCs. In this study, we tested the hypothesis that ClC-3 is necessary for proliferation of smooth muscle cells (SMCs) and contributes to neointimal hyperplasia following vascular injury. METHODS AND RESULTS: Studies were performed in SMCs isolated from the aorta of ClC-3-null and littermate control (wild-type [WT]) mice. Thrombin and tumor necrosis factor-α (TNF-α) each caused activation of both mitogen activated protein kinase extracellular signal-regulated kinases 1 and 2 and the matrix-degrading enzyme matrix metalloproteinase-9 and cell proliferation of WT SMCs. Whereas responses to thrombin were preserved in ClC-3-null SMCs, the responses to TNF-α were markedly impaired. These defects normalized following gene transfer of ClC-3. Carotid injury increased vascular ClC-3 expression, and compared with WT mice, ClC-3-null mice exhibited a reduction in neointimal area of the carotid artery 28 days after injury. CONCLUSIONS: ClC-3 is necessary for the activation of SMCs by TNF-α but not thrombin. Deficiency of ClC-3 markedly reduces neointimal hyperplasia following vascular injury. In view of our previous findings, this observation is consistent with a role for ClC-3 in endosomal Nox1-dependent signaling. These findings identify ClC-3 as a novel target for the prevention of inflammatory and proliferative vascular diseases.

The ClC-3 Cl-/H+ antiporter becomes uncoupled at low extracellular pH.

Adenovirus expressing ClC-3 (Ad-ClC-3) induces Cl(-)/H(+) antiport current (I(ClC-3)) in HEK293 cells. The outward rectification and time dependence of I(ClC-3) closely resemble an endogenous HEK293 cell acid-activated Cl(-) current (ICl(acid)) seen at extracellular pH

Activation of swelling-activated chloride current by tumor necrosis factor-alpha requires ClC-3-dependent endosomal reactive oxygen production.

ClC-3 is a Cl(-)/H(+) antiporter required for cytokine-induced intraendosomal reactive oxygen species (ROS) generation by Nox1. ClC-3 current is distinct from the swelling-activated chloride current (ICl(swell)), but overexpression of ClC-3 can activate currents that resemble ICl(swell). Because H(2)O(2) activates ICl(swell) directly, we hypothesized that ClC-3-dependent, endosomal ROS production activates ICl(swell). Whole-cell perforated patch clamp methods were used to record Cl(-) currents in cultured aortic vascular smooth muscle cells from wild type (WT) and ClC-3 null mice. Under isotonic conditions, tumor necrosis factor-alpha (TNF-alpha) (10 ng/ml) activated outwardly rectifying Cl(-) currents with time-dependent inactivation in WT but not ClC-3 null cells. Inhibition by tamoxifen (10 microm) and by hypertonicity (340 mosm) identified them as ICl(swell). ICl(swell) was also activated by H(2)O(2) (500 microm), and the effect of TNF-alpha was completely inhibited by polyethylene glycol-catalase. ClC-3 expression induced ICl(swell) in ClC-3 null cells in the absence of swelling or TNF-alpha, and this effect was also blocked by catalase. ICl(swell) activation by hypotonicity (240 mosm) was only partially inhibited by catalase, and the size of these currents did not differ between WT and ClC-3 null cells. Disruption of endosome trafficking with either mutant Rab5 (S34N) or Rab11 (S25N) inhibited TNF-alpha-mediated activation of ICl(swell). Thrombin also activates ROS production by Nox1 but not in endosomes. Thrombin caused H(2)O(2)-dependent activation of ICl(swell), but this effect was not ClC-3- or Rab5-dependent. Thus, activation of ICl(swell) by TNF-alpha requires ClC-3-dependent endosomal H(2)O(2) production. This demonstrates a functional link between two distinct anion currents, ClC-3 and ICl(swell).

SHIRPA as a Neurological Screening Battery in Mice.

The SmithKline, Harwell, Imperial College, Royal Hospital, Phenotype Assessment (SHIRPA) is a rapid battery of tests comprising 42 measurements of motor activity, coordination, postural control, muscle tone, autonomic functions, and emotional reactivity, as well as reflexes dependent on visual, auditory, and tactile modalities. Individual scores in SHIRPA are sensitive in detecting phenotypes of several experimental models of neural disease, especially cerebellar degeneration and Alzheimer disease, and combined subscores have been useful in estimating the impact of vascular anomalies and exposure to infectious agents. In cerebellar degeneration, weak forelimb grip, impaired wire maneuver and air righting, and negative geotaxis appear as prevalent features. Most of the measures in the battery are susceptible to change after gene modifications or physiological alterations. SHIRPA can be used both in adult mice and mice in the preweaning period to screen for sensorimotor function and emotional reactivity, not selective attention or memory. © 2021 Wiley Periodicals LLC Basic Protocol: Step-by-step procedure for SHIRPA.

Powerful beneficial effects of macrophage colony-stimulating factor on beta-amyloid deposition and cognitive impairment in Alzheimer's disease.

Alzheimer's disease is a major cause of dementia in humans. The appearance of cognitive decline is linked to the overproduction of a short peptide called beta-amyloid (Abeta) in both soluble and aggregate forms. Here, we show that injecting macrophage colony-stimulating factor (M-CSF) to Swedish beta-amyloid precursor protein (APP(Swe))/PS1 transgenic mice, a well-documented model for Alzheimer's disease, on a weekly basis prior to the appearance of learning and memory deficits prevented cognitive loss. M-CSF also increased the number of microglia in the parenchyma and decreased the number of Abeta deposits. Senile plaques were smaller and less dense in the brain of M-CSF-treated mice compared to littermate controls treated with vehicle solution. Interestingly, a higher ratio of microglia internalized Abeta in the brain of M-CSF-treated animals and the phagocytosed peptides were located in the late endosomes and lysosomes. Less Abeta(40) and Abeta(42) monomers were also detected in the extracellular protein enriched fractions of M-CSF-treated transgenic mice when compared with vehicle controls. Finally, treating APP(Swe)/PS1 mice that were already demonstrating installed Abeta pathology stabilized the cognitive decline. Together these results provide compelling evidence that systemic M-CSF administration is a powerful treatment to stimulate bone marrow-derived microglia, degrade Abeta and prevent or improve the cognitive decline associated with Abeta burden in a mouse model of Alzheimer's disease.

Toll-like receptor 2 acts as a natural innate immune receptor to clear amyloid beta 1-42 and delay the cognitive decline in a mouse model of Alzheimer's disease.

Microglia are the immune cells of the brain, they are activated in the brain of Alzheimer's disease (AD) patients and mouse models of AD, and they express the innate immune receptor toll-like receptor 2 (TLR2). The present study investigated role of this receptor in the progression of AD-like pathologies. Here we show that amyloid beta (A beta) stimulates TLR2 expression in a small proportion of microglia. We then generated triple transgenic mice that are deficient in TLR2 from mice that harbor a mutant human presenelin 1 and a chimeric mouse/human amyloid precursor protein (APP) genes. TLR2 deficiency accelerated spatial and contextual memory impairments, which correlated with increased levels of A beta(1-42) and transforming growth factor beta1 in the brain. NMDA receptors 1 and 2A expression levels were also lower in the hippocampus of APP-TLR2(-/-) mice. Gene therapy in cells of the bone marrow using lentivirus constructs expressing TLR2 rescued the cognitive impairment of APP-TLR2(-/-) mice. Indeed, lenti-green fluorescent protein/TLR2 treatment had beneficial effects by restoring the memory consolidation process disrupted by TLR2 deficiency in APP mice. These data suggest that TLR2 acts as an endogenous receptor for the clearance of toxic A beta by bone-marrow-derived immune cells. The cognitive decline is markedly accelerated in a context of TLR2 deficiency. Upregulating this innate immune receptor may then be considered as a potential new powerful therapeutic approach for AD.

Requirement of myeloid cells for axon regeneration.

The role of CD11b+ myeloid cells in axonal regeneration was assessed using axonal injury models and CD11b-TK(mt-30) mice expressing a mutated HSV-1 thymidine kinase (TK) gene regulated by the myeloid-specific CD11b promoter. Continuous delivery of ganciclovir at a sciatic nerve lesion site greatly decreased the number of granulocytes/inflammatory monocytes and macrophages in the distal stump of CD11b-TK(mt-30) mice. Axonal regeneration and locomotor function recovery were severely compromised in ganciclovir-treated CD11b-TK(mt-30) mice. This was caused by an unsuitable growth environment rather than an altered regeneration capacity of neurons. In absence of CD11b+ cells, the clearance of inhibitory myelin debris was prevented, neurotrophin synthesis was abolished, and blood vessel formation/maintenance was severely compromised in the sciatic nerve distal stump. Spinal cord-injured axons also failed to regenerate through peripheral nerve grafts in the absence of CD11b+ cells. Therefore, myeloid cells support axonal regeneration and functional recovery by creating a growth-permissive milieu for injured axons.

Cytokine activation of nuclear factor kappa B in vascular smooth muscle cells requires signaling endosomes containing Nox1 and ClC-3.

Reactive oxygen species (ROS) are mediators of intracellular signals for a myriad of normal and pathologic cellular events, including differentiation, hypertrophy, proliferation, and apoptosis. NADPH oxidases are important sources of ROS that are present in diverse tissues throughout the body and activate many redox-sensitive signal transduction and gene expression pathways. To avoid toxicity and provide specificity of signaling, ROS production and metabolism necessitate tight regulation that likely includes subcellular compartmentalization. However, the constituent elements of NADPH oxidase-dependent cell signaling are not known. To address this issue, we examined cytokine generation of ROS and subsequent activation of the transcription factor nuclear factor kappaB in vascular smooth muscle cells (SMCs). Tumor necrosis factor-alpha and interleukin (IL)-1beta stimulation of SMCs resulted in diphenylene iodonium-sensitive ROS production within intracellular vesicles. Nox1 and p22(phox), integral membrane subunits of NADPH oxidase, coimmunoprecipitated with early endosomal markers in SMCs. ClC-3, an anion transporter that is primarily found in intracellular vesicles, also colocalized with Nox1 in early endosomes and was necessary for tumor necrosis factor-alpha and interleukin-1beta generation of ROS. Cytokine activation of nuclear factor kappaB in SMCs required both Nox1 and ClC-3. We conclude that in response to tumor necrosis factor-alpha and interleukin-1beta, NADPH oxidase generates ROS within early endosomes and that Nox1 cannot produce sufficient ROS for cell signaling in the absence of ClC-3. These data best support a model whereby ClC-3 is required for charge neutralization of the electron flow generated by Nox1 across the membrane of signaling endosomes.

Toll-like receptor signaling is critical for Wallerian degeneration and functional recovery after peripheral nerve injury.

Toll-like receptors (TLRs) bind specific components conserved among microorganisms as well as endogenous ligands produced by necrotic cells, injured axons, and the extracellular matrix. Here, we investigated whether TLRs are involved in regulating the immune response, Wallerian degeneration (WD), and nerve regeneration after sciatic nerve lesion. Early expression of interleukin-1beta and monocyte chemoattractant protein-1 was compromised in the sciatic nerve distal stump of mice deficient in TLR signaling. In addition, significantly fewer macrophages were recruited and/or activated in the sciatic nerve distal stump of TLR2-, TLR4-, and MyD88-deficient mice compared with wild-type littermates, whereas WD, axonal regeneration, and recovery of locomotor function were impaired. In contrast, animals that received a single microinjection of TLR2 and TLR4 ligands at the site of sciatic nerve lesion had faster clearance of the degenerating myelin and recovered earlier than saline-injected control rats. Finally, rats that had altered innate immune response through dexamethasone treatment exhibited three times more myelin debris in their sciatic nerve distal stump and a significant delay in recovery of locomotor function. Our results provide strong evidence that TLR signaling plays a critical role in orchestrating the innate immune response leading to efficient and rapid clearance of inhibitory myelin debris and nerve regeneration.