Spontaneous and optogenetically induced cortical spreading depolarization in familial hemiplegic migraine type 1 mutant mice.

Mechanisms underlying the migraine aura are incompletely understood, which to large extent is related to a lack of models in which cortical spreading depolarization (CSD), the correlate of the aura, occurs spontaneously. Here, we investigated electrophysiological and behavioural CSD features in freely behaving mice expressing mutant CaV2.1 Ca2+ channels, either with the milder R192Q or the severer S218L missense mutation in the α1 subunit, known to cause familial hemiplegic migraine type 1 (FHM1) in patients. Very rarely, spontaneous CSDs were observed in mutant but never in wildtype mice. In homozygous Cacna1aR192Q mice exclusively single-wave CSDs were observed whereas heterozygous Cacna1aS218L mice displayed multiple-wave events, seemingly in line with the more severe clinical phenotype associated with the S218L mutation. Spontaneous CSDs were associated with body stretching, one-directional slow head turning, and rotating movement of the body. Spontaneous CSD events were compared with those induced in a controlled manner using minimally invasive optogenetics. Also in the optogenetic experiments single-wave CSDs were observed in Cacna1aR192Q and Cacna1aS218L mice (whereas the latter also showed multiple-wave events) with movements similar to those observed with spontaneous events. Compared to wildtype mice, FHM1 mutant mice exhibited a reduced threshold and an increased propagation speed for optogenetically induced CSD with a more profound CSD-associated dysfunction, as indicated by a prolonged suppression of transcallosal evoked potentials and a reduction of unilateral forepaw grip performance. When induced during sleep, the optogenetic CSD threshold was particularly lowered, which may explain why spontaneous CSD events predominantly occurred during sleep. In conclusion, our data show that key neurophysiological and behavioural features of optogenetically induced CSDs mimic those of rare spontaneous events in FHM1 R192Q and S218L mutant mice with differences in severity in line with FHM1 clinical phenotypes seen with these mutations.

Optogenetic cortical spreading depolarization induces headache-related behaviour and neuroinflammatory responses some prolonged in familial hemiplegic migraine type 1 mice.

BACKGROUND: Cortical spreading depolarization (CSD), the neurophysiological correlate of the migraine aura, can activate trigeminal pain pathways, but the neurobiological mechanisms and behavioural consequences remain unclear. Here we investigated effects of optogenetically-induced CSDs on headache-related behaviour and neuroinflammatory responses in transgenic mice carrying a familial hemiplegic migraine type 1 (FHM1) mutation. METHODS: CSD events (3 in total) were evoked in a minimally invasive manner by optogenetic stimulation through the intact skull in freely behaving wildtype (WT) and FHM1 mutant mice. Related behaviours were analysed using mouse grimace scale (MGS) scoring, head grooming, and nest building behaviour. Neuroinflammatory changes were investigated by assessing HMGB1 release with immunohistochemistry and by pre-treating mice with a selective Pannexin-1 channel inhibitor. RESULTS: In both WT and FHM1 mutant mice, CSDs induced headache-related behaviour, as evidenced by increased MGS scores and the occurrence of oculotemporal strokes, at 30 min. Mice of both genotypes also showed decreased nest building behaviour after CSD. Whereas in WT mice MGS scores had normalized at 24 h after CSD, in FHM1 mutant mice scores were normalized only at 48 h. Of note, oculotemporal stroke behaviour already normalized 5 h after CSD, whereas nest building behaviour remained impaired at 72 h; no genotype differences were observed for either readout. Nuclear HMGB1 release in the cortex of FHM1 mutant mice, at 30 min after CSD, was increased bilaterally in both WT and FHM1 mutant mice, albeit that contralateral release was more pronounced in the mutant mice. Only in FHM1 mutant mice, contralateral release remained higher at 24 h after CSD, but at 48 h had returned to abnormal, elevated, baseline values, when compared to WT mice. Blocking Panx1 channels by TAT-Panx308 inhibited CSD-induced headache related behaviour and HMGB1 release. CONCLUSIONS: CSDs, induced in a minimally invasive manner by optogenetics, investigated in freely behaving mice, cause various migraine relevant behavioural and neuroinflammatory phenotypes that are more pronounced and longer-lasting in FHM1 mutant compared to WT mice. Prevention of CSD-related neuroinflammatory changes may have therapeutic potential in the treatment of migraine.

A Restricted Role for FcγR in the Regulation of Adaptive Immunity.

By their interaction with IgG immune complexes, FcγR and complement link innate and adaptive immunity, showing functional redundancy. In complement-deficient mice, IgG downstream effector functions are often impaired, as well as adaptive immunity. Based on a variety of model systems using FcγR-knockout mice, it has been concluded that FcγRs are also key regulators of innate and adaptive immunity; however, several of the model systems underpinning these conclusions suffer from flawed experimental design. To address this issue, we generated a novel mouse model deficient for all FcγRs (FcγRI/II/III/IV-/- mice). These mice displayed normal development and lymphoid and myeloid ontogeny. Although IgG effector pathways were impaired, adaptive immune responses to a variety of challenges, including bacterial infection and IgG immune complexes, were not. Like FcγRIIb-deficient mice, FcγRI/II/III/IV-/- mice developed higher Ab titers but no autoantibodies. These observations indicate a redundant role for activating FcγRs in the modulation of the adaptive immune response in vivo. We conclude that FcγRs are downstream IgG effector molecules with a restricted role in the ontogeny and maintenance of the immune system, as well as the regulation of adaptive immunity.

IgG-mediated anaphylaxis to a synthetic long peptide vaccine containing a B cell epitope can be avoided by slow-release formulation.

Synthetic long peptides (SLP) are a promising vaccine modality to induce therapeutic T cell responses in patients with chronic infections and tumors. We studied different vaccine formulations in mice using SLP derived from carcinoembryonic Ag. We discovered that one of the SLP contains a linear Ab epitope in combination with a CD4 epitope. Repeated vaccination with this carcinoembryonic Ag SLP in mice shows improved T cell responses and simultaneously induced high titers of peptide-specific Abs. These Abs resulted in unexpected anaphylaxis after a third or subsequent vaccinations with the SLP when formulated in saline. Administration of low SLP doses in the slow-release vehicle IFA prevented the anaphylaxis after repeated vaccination. This study underscores both the immunogenicity of SLP vaccination, for inducing T cell as well as B cell responses, and the necessity of safe administration routes.

Selective modulation of nuclear factor of activated T-cell function in restenosis by a potent bipartite peptide inhibitor.

RATIONALE: Nuclear factor of activated T-cells (NFAT) is importantly implicated in pathological cardiac remodeling and vascular lesion formation. NFAT functionality is mainly regulated by calcineurin, a Ca(2+)-dependent multi-effector phosphatase. Calcineurin inhibitors such as cyclosporine A (CsA) were shown to be effective in the treatment of restenosis and vascular inflammation but with adverse side effects. OBJECTIVE: This prompted the design of more selective inhibitors such as VIVIT and inhibitors of NFAT-calcineurin association, which unfortunately have a poor potency precluding clinical use. METHODS AND RESULTS: Here, we describe the rational design of a potent bipartite inhibitor of NFAT-calcineurin interaction, MCV1, which targets two separate calcineurin docking motifs. Modeling, site-directed mutagenesis, and functional studies demonstrated that MCV1 acts by allosteric modulation of calcineurin. Comparable to CsA, MCV1 prevents NFAT activation at nanomolar potency without impairing calcineurin phosphatase activity, nuclear factor-κB nuclear import, and general cell signaling. In contrast, CsA but not MCV1-activated basal level extracellular signal-regulated kinases activity and prevented nuclear import of calcineurin, independent of NFAT activation. In vivo MCV1 abrogated NFAT-mediated T-cell activation in a model of PMA-elicited peritonitis, whereas topical application of MCV1 markedly reduced neointima formation in a mouse model of restenosis. CONCLUSIONS: We designed a bipartite NFAT inhibitor that is more potent than VIVIT and more selective than CsA. MCV1 constitutes not only a powerful tool to unravel NFAT function but also a potential drug candidate for the treatment of diseases implicating NFAT activation.

IGF-1 has plaque-stabilizing effects in atherosclerosis by altering vascular smooth muscle cell phenotype.

Insulin-like growth factor-1 (IGF-1) signaling is important for the maintenance of plaque stability in atherosclerosis due to its effects on vascular smooth muscle cell (vSMC) phenotype. To investigate this hypothesis, we studied the effects of the highly inflammatory milieu of the atherosclerotic plaque on IGF-1 signaling and stability-related phenotypic parameters of murine vSMCs in vitro, and the effects of IGF-1 supplementation on plaque phenotype in an atherosclerotic mouse model. M1-polarized, macrophage-conditioned medium inhibited IGF-1 signaling by ablating IGF-1 and increasing IGF-binding protein 3, increased vSMC apoptosis, and decreased proliferation. Expression of α-actin and col3a1 genes was strongly attenuated by macrophage-conditioned medium, whereas expression of matrix-degrading enzymes was increased. Importantly, all of these effects could be corrected by supplementation with IGF-1. In vivo, treatment with the stable IGF-1 analog Long R3 IGF-1 in apolipoprotein E knockout mice reduced stenosis and core size, and doubled cap/core ratio in early atherosclerosis. In advanced plaques, Long R3 IGF-1 increased the vSMC content of the plaque by more than twofold and significantly reduced the rate of intraplaque hemorrhage. We believe that IGF-1 in atherosclerotic plaques may have a role in preventing plaque instability, not only by modulating smooth muscle cell turnover, but also by altering smooth muscle cell phenotype.

The neuropeptide substance P mediates adventitial mast cell activation and induces intraplaque hemorrhage in advanced atherosclerosis.

RATIONALE: Although we and others have recently shown that mast cells play an important role in plaque progression and destabilization, the nature of the actual trigger for (peri)vascular mast cell activation during atherosclerosis is still unresolved. OBJECTIVE: In this study, we confirm that perivascular mast cell content correlates with the number of nerve fibers in the adventitia of human coronary atherosclerotic plaque specimen. Because peripheral C-type nerve fibers secrete, among others, substance P, a potent mast cell activator, we set out to study effects of adventitial administration of this neuropeptide on mast cell dependent destabilization of carotid artery plaques in apolipoprotein E-deficient (apoE(-/-)) mice. METHODS AND RESULTS: Substance P treatment significantly enhanced the number and activation status of adventitial mast cells compared to controls and promoted intraplaque hemorrhages. These phenomena could be prevented by coadministration of the neurokinin-1 receptor antagonist spantide I and did not occur in mast cell deficient apoE(-/-) mice, establishing the critical involvement of mast cells in substance P-elicited plaque destabilization. CONCLUSIONS: Our data suggest that neurotransmitters such as substance P are capable of promoting mast cell dependent plaque destabilization and provide a new, direct link between neural factors and vascular inflammation.

BMP antagonists enhance myogenic differentiation and ameliorate the dystrophic phenotype in a DMD mouse model.

Duchenne Muscular Dystrophy (DMD) is an X-linked lethal muscle wasting disease characterized by muscle fiber degeneration and necrosis. The progressive pathology of DMD can be explained by an insufficient regenerative response resulting in fibrosis and adipose tissue formation. BMPs are known to inhibit myogenic differentiation and in a previous study we found an increased expression of a BMP family member BMP4 in DMD myoblasts. The aim of the current study was therefore to investigate whether inhibition of BMP signaling could be beneficial for myoblast differentiation and muscle regeneration processes in a DMD context. All tested BMP inhibitors, Noggin, dorsomorphin and LDN-193189, were able to accelerate and enhance myogenic differentiation. However, dorsomorphin repressed both BMP and TGFß signaling and was found to be toxic to primary myoblast cell cultures. In contrast, Noggin was found to be a potent and selective BMP inhibitor and was therefore tested in vivo in a DMD mouse model. Local adenoviral-mediated overexpression of Noggin in muscle resulted in an increased expression of the myogenic regulatory genes Myog and Myod1 and improved muscle histology. In conclusion, our results suggest that repression of BMP signaling may constitute an attractive adjunctive therapy for DMD patients.

VEGF and inhibitors of TGFbeta type-I receptor kinase synergistically promote blood-vessel formation by inducing alpha5-integrin expression.

Vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGFbeta) are potent regulators of angiogenesis. How VEGF and TGFbeta signaling pathways crosstalk is not well understood. Therefore, we analyzed the effects of the TGFbeta type-I-receptor inhibitors (SB-431542 and LY-2157299) and VEGF on endothelial cell (EC) function and angiogenesis. We show that SB-431542 dramatically enhances VEGF-induced formation of EC sheets from fetal mouse metatarsals. Sub-optimal doses of VEGF and SB-431542 synergistically induced EC migration and sprouting of EC spheroids, whereas overexpression of a constitutively active form of TGFbeta type-I receptor had opposite effects. Using quantitative PCR, we demonstrated that VEGF and SB-431542 synergistically upregulated the mRNA expression of genes involved in angiogenesis, including the integrins alpha5 and beta3. Specific downregulation of alpha5-integrin expression or functional blocking of alpha5 integrin with a specific neutralizing antibody inhibited the cooperative effect of VEGF and SB-431542 on EC sprouting. In vivo, LY-2157299 induced angiogenesis and enhanced VEGF- and basic-fibroblast-growth-factor-induced angiogenesis in a Matrigel-plug assay, whereas adding an alpha5-integrin-neutralizing antibody to the Matrigel selectively inhibited this enhanced response. Thus, induction of alpha5-integrin expression is a key determinant by which inhibitors of TGFbeta type-I receptor kinase and VEGF synergistically promote angiogenesis.

Stress hormone corticosterone enhances susceptibility to cortical spreading depression in familial hemiplegic migraine type 1 mutant mice.

Stress is a putative migraine trigger, but the pathogenic mechanisms involved are unknown. Stress and stress hormones increase neuronal excitability by enhancing glutamatergic neurotransmission, but inhibitory effects have also been reported. We hypothesise that an acute rise in stress hormones, such as corticosteroids which are released after stress, increase neuronal excitability and thereby may increase susceptibility to cortical spreading depression (CSD), the mechanism underlying the migraine aura. Here we investigated effects of acute restraint stress and of the stress hormone corticosterone on CSD susceptibility as surrogate migraine marker, in a transgenic mouse model of familial hemiplegic migraine type 1 (FHM1), which displays increased glutamatergic cortical neurotransmission and increased propensity for CSD. We found that 20-min and 3-h restraint stress did not influence CSD susceptibility in mutant or wild-type mice, despite elevated levels of plasma corticosterone. By contrast, subcutaneous administration of 20mg/kg corticosterone increased CSD frequency exclusively in mutant mice, while corticosterone plasma levels were similarly elevated in mutants and wild types. The effect of corticosterone on CSD frequency was normalised by pre-administration of the glucocorticoid receptor (GR) antagonist mifepristone. These findings suggest that corticosteroid-induced GR activation can enhance susceptibility to CSD in genetically susceptible individuals, and may predispose to attacks of migraine. Although corticosterone levels rise also during acute stress, the latter likely triggers a spatiotemporally more complex biological response with multiple positive and negative modulators which may not be adequately modeled by exogenous administration of corticosterone alone.

Large-scale mass spectrometry imaging investigation of consequences of cortical spreading depression in a transgenic mouse model of migraine.

Cortical spreading depression (CSD) is the electrophysiological correlate of migraine aura. Transgenic mice carrying the R192Q missense mutation in the Cacna1a gene, which in patients causes familial hemiplegic migraine type 1 (FHM1), exhibit increased propensity to CSD. Herein, mass spectrometry imaging (MSI) was applied for the first time to an animal cohort of transgenic and wild type mice to study the biomolecular changes following CSD in the brain. Ninety-six coronal brain sections from 32 mice were analyzed by MALDI-MSI. All MSI datasets were registered to the Allen Brain Atlas reference atlas of the mouse brain so that the molecular signatures of distinct brain regions could be compared. A number of metabolites and peptides showed substantial changes in the brain associated with CSD. Among those, different mass spectral features showed significant (t-test, P < 0.05) changes in the cortex, 146 and 377 Da, and in the thalamus, 1820 and 1834 Da, of the CSD-affected hemisphere of FHM1 R192Q mice. Our findings reveal CSD- and genotype-specific molecular changes in the brain of FHM1 transgenic mice that may further our understanding about the role of CSD in migraine pathophysiology. The results also demonstrate the utility of aligning MSI datasets to a common reference atlas for large-scale MSI investigations.

Targeting TGF-ß Signaling by Antisense Oligonucleotide-mediated Knockdown of TGF-ß Type I Receptor.

Duchenne muscular dystrophy (DMD) is caused by lack of functional dystrophin and results in progressive myofiber damage and degeneration. In addition, impaired muscle regeneration and fibrosis contribute to the progressive pathology of DMD. Importantly, transforming growth factor-ß (TGF-ß) is implicated in DMD pathology and is known to stimulate fibrosis and inhibit muscle regeneration. In this study, we present a new strategy to target TGF-ß signaling cascades by specifically inhibiting the expression of TGF-ß type I receptor TGFBR1 (ALK5). Antisense oligonucleotides (AONs) were designed to specifically induce exon skipping of mouse ALK5 transcripts. AON-induced exon skipping of ALK5 resulted in specific downregulation of full-length receptor transcripts in vitro in different cell types, repression of TGF-ß activity, and enhanced C2C12 myoblast differentiation. To determine the effect of these AONs in dystrophic muscles, we performed intramuscular injections of ALK5 AONs in mdx mice, which resulted in a decrease in expression of fibrosis-related genes and upregulation of Myog expression compared to control AON-injected muscles. In summary, our study presents a novel method to target TGF-ß signaling cascades with potential beneficial effects for DMD.

The effects of low levels of dystrophin on mouse muscle function and pathology.

Duchenne muscular dystrophy (DMD) is a severe progressive muscular disorder caused by reading frame disrupting mutations in the DMD gene, preventing the synthesis of functional dystrophin. As dystrophin provides muscle fiber stability during contractions, dystrophin negative fibers are prone to exercise-induced damage. Upon exhaustion of the regenerative capacity, fibers will be replaced by fibrotic and fat tissue resulting in a progressive loss of function eventually leading to death in the early thirties. With several promising approaches for the treatment of DMD aiming at dystrophin restoration in clinical trials, there is an increasing need to determine more precisely which dystrophin levels are sufficient to restore muscle fiber integrity, protect against muscle damage and improve muscle function.To address this we generated a new mouse model (mdx-Xist(Δhs)) with varying, low dystrophin levels (3-47%, mean 22.7%, stdev 12.1, n = 24) due to skewed X-inactivation. Longitudinal sections revealed that within individual fibers, some nuclei did and some did not express dystrophin, resulting in a random, mosaic pattern of dystrophin expression within fibers.Mdx-Xist(Δhs), mdx and wild type females underwent a 12 week functional test regime consisting of different tests to assess muscle function at base line, or after chronic treadmill running exercise. Overall, mdx-Xist(Δhs) mice with 3-14% dystrophin outperformed mdx mice in the functional tests. Improved histopathology was observed in mice with 15-29% dystrophin and these levels also resulted in normalized expression of pro-inflammatory biomarker genes, while for other parameters >30% of dystrophin was needed. Chronic exercise clearly worsened pathology, which needed dystrophin levels >20% for protection. Based on these findings, we conclude that while even dystrophin levels below 15% can improve pathology and performance, levels of >20% are needed to fully protect muscle fibers from exercise-induced damage.

Imaging mass spectrometry to visualize biomolecule distributions in mouse brain tissue following hemispheric cortical spreading depression.

MALDI mass spectrometry can simultaneously measure hundreds of biomolecules directly from tissue. Using essentially the same technique but different sample preparation strategies, metabolites, lipids, peptides and proteins can be analyzed. Spatially correlated analysis, imaging MS, enables the distributions of these biomolecular ions to be simultaneously measured in tissues. A key advantage of imaging MS is that it can annotate tissues based on their MS profiles and thereby distinguish biomolecularly distinct regions even if they were unexpected or are not distinct using established histological and histochemical methods e.g. neuropeptide and metabolite changes following transient electrophysiological events such as cortical spreading depression (CSD), which are spreading events of massive neuronal and glial depolarisations that occur in one hemisphere of the brain and do not pass to the other hemisphere , enabling the contralateral hemisphere to act as an internal control. A proof-of-principle imaging MS study, including 2D and 3D datasets, revealed substantial metabolite and neuropeptide changes immediately following CSD events which were absent in the protein imaging datasets. The large high dimensionality 3D datasets make even rudimentary contralateral comparisons difficult to visualize. Instead non-negative matrix factorization (NNMF), a multivariate factorization tool that is adept at highlighting latent features, such as MS signatures associated with CSD events, was applied to the 3D datasets. NNMF confirmed that the protein dataset did not contain substantial contralateral differences, while these were present in the neuropeptide dataset.

Mast cell chymase inhibition reduces atherosclerotic plaque progression and improves plaque stability in ApoE-/- mice.

AIMS: mast cells have been shown to accumulate in the adventitia of human atherosclerotic plaques and were recently demonstrated by us to contribute to plaque progression and instability. In this study, we investigated whether selective inhibition of mast cell chymases would affect the lesion development and stability. METHODS AND RESULTS: the protease inhibitor RO5066852 appeared to be a potent inhibitor of chymase activity in vitro and ex vivo. With this inhibitor, we provide three lines of evidence that chymase inhibition can prevent many pro-atherogenic activities. First, oral administration of RO5066852 reduced spontaneous atherosclerosis in the thoracic aorta of apoE(-/-) mice. Second, chymase inhibition prevented the accelerated plaque progression observed in apoE(-/-) mice that were exposed to repetitive episodes of systemic mast cell activation. Furthermore, RO5066852 enhanced lesional collagen content and reduced necrotic core size. Third, RO5066852 treatment almost completely normalized the increased frequency and size of intraplaque haemorrhages observed in apoE(-/-) mice after acute perivascular mast cell activation in advanced atherosclerosis. CONCLUSION: our data indicate that chymase inhibition can inhibit pro-atherogenic and plaque destabilizing effects which are associated with perivascular mast cell activation. Our study thus identifies pharmacological chymase inhibition as a potential therapeutic modality for atherosclerotic plaque stabilization.

Dual exon skipping in myostatin and dystrophin for Duchenne muscular dystrophy.

BACKGROUND: Myostatin is a potent muscle growth inhibitor that belongs to the Transforming Growth Factor-ß (TGF-ß) family. Mutations leading to non functional myostatin have been associated with hypermuscularity in several organisms. By contrast, Duchenne muscular dystrophy (DMD) is characterized by a loss of muscle fibers and impaired regeneration. In this study, we aim to knockdown myostatin by means of exon skipping, a technique which has been successfully applied to reframe the genetic defect of dystrophin gene in DMD patients. METHODS: We targeted myostatin exon 2 using antisense oligonucleotides (AON) in healthy and DMD-derived myotubes cultures. We assessed the exon skipping level, transcriptional expression of myostatin and its target genes, and combined myostatin and several dystrophin AONs. These AONs were also applied in the mdx mice models via intramuscular injections. RESULTS: Myostatin AON induced exon 2 skipping in cell cultures and to a lower extent in the mdx mice. It was accompanied by decrease in myostatin mRNA and enhanced MYOG and MYF5 expression. Furthermore, combination of myostatin and dystrophin AONs induced simultaneous skipping of both genes. CONCLUSIONS: We conclude that two AONs can be used to target two different genes, MSTN and DMD, in a straightforward manner. Targeting multiple ligands of TGF-beta family will be more promising as adjuvant therapies for DMD.