Type III Intermediate Filaments Desmin, Glial Fibrillary Acidic Protein (GFAP), Vimentin, and Peripherin

Brain Injury Biomarkers and Applications in Neurological Diseases

ABSTRACT

Neurological diseases are a major health concern, and brain injury is a typical pathological process in various neurological disorders. Different biomarkers in the blood or the cerebrospinal fluid are associated with specific physiological and pathological processes. They are vital in identifying, diagnosing, and treating brain injuries. In this review, we described biomarkers for neuronal cell body injury (neuron-specific enolase, ubiquitin C-terminal hydrolase-L1, αII-spectrin), axonal injury (neurofilament proteins, tau), astrocyte injury (S100β, glial fibrillary acidic protein), demyelination (myelin basic protein), autoantibodies, and other emerging biomarkers (extracellular vesicles, microRNAs). We aimed to summarize the applications of these biomarkers and their related interests and limits in the diagnosis and prognosis for neurological diseases, including traumatic brain injury, status epilepticus, stroke, Alzheimer's disease, and infection. In addition, a reasonable outlook for brain injury biomarkers as ideal detection tools for neurological diseases is presented.

Glial fibrillary acidic protein is pathologically modified in Alexander disease

Here, we describe pathological events potentially involved in the disease pathogenesis of Alexander disease (AxD). This is a primary genetic disorder of astrocyte caused by dominant gain-of-function mutations in the gene coding for an intermediate filament protein glial fibrillary acidic protein (GFAP). Pathologically, this disease is characterized by the upregulation of GFAP and its accumulation as Rosenthal fibers. Although the genetic basis linking GFAP mutations with Alexander disease has been firmly established, the initiating events that promote GFAP accumulation and the role of Rosenthal fibers (RFs) in the disease process remain unknown. Here, we investigate the hypothesis that disease-associated mutations promote GFAP aggregation through aberrant posttranslational modifications. We found high molecular weight GFAP species in the RFs of AxD brains, indicating abnormal GFAP crosslinking as a prominent pathological feature of this disease. In vitro and cell-based studies demonstrate that cystine-generating mutations promote GFAP crosslinking by cysteine-dependent oxidation, resulting in defective GFAP assembly and decreased filament solubility. Moreover, we found GFAP was ubiquitinated in RFs of AxD patients and rodent models, supporting this modification as a critical factor linked to GFAP aggregation. Finally, we found that arginine could increase the solubility of aggregation-prone mutant GFAP by decreasing its ubiquitination and aggregation. Our study suggests a series of pathogenic events leading to AxD, involving interplay between GFAP aggregation and abnormal modifications by GFAP ubiquitination and oxidation. More important, our findings provide a basis for investigating new strategies to treat AxD by targeting abnormal GFAP modifications.

The main duct of von Ebner's glands is a source of Sox10 + taste bud progenitors and susceptible to pathogen infections

We have recently demonstrated that Sox10 -expressing ( Sox10 + ) cells give rise to mainly type-III neuronal taste bud cells that are responsible for sour and salt taste. The two tissue compartments containing Sox10 + cells in the surrounding of taste buds include the connective tissue core of taste papillae and von Ebner's glands (vEGs) that are connected to the trench of circumvallate and foliate papillae. In this study, we used inducible Cre mouse models to map the cell lineages of connective tissue (including stromal and Schwann cells) and vEGs and performed single cell RNA-sequencing of the epithelium of Sox10-Cre/tdT mouse circumvallate/vEG complex. In vivo lineage mapping showed that the distribution of traced cells in circumvallate taste buds was closely linked with that in the vEGs, but not in the connective tissue. Sox10 , but not the known stem cells marker Lgr5 , expression was enriched in the cell clusters of main ducts of vEGs that contained abundant proliferating cells, while Sox10-Cre/tdT expression was enriched in type-III taste bud cells and excretory ductal cells. Moreover, multiple genes encoding pathogen receptors are enriched in the vEG main ducts. Our data indicate that the main duct of vEGs is a source of Sox10 + taste bud progenitors and susceptible to pathogen infections.

Type III intermediate filaments in redox interplay: key role of the conserved cysteine residue

Intermediate filaments (IFs) are cytoskeletal elements involved in mechanotransduction and in the integration of cellular responses. They are versatile structures and their assembly and organization are finely tuned by posttranslational modifications. Among them, type III IFs, mainly vimentin, have been identified as targets of multiple oxidative and electrophilic modifications. A characteristic of most type III IF proteins is the presence in their sequence of a single, conserved cysteine residue (C328 in vimentin), that is a hot spot for these modifications and appears to play a key role in the ability of the filament network to respond to oxidative stress. Current structural models and experimental evidence indicate that this cysteine residue may occupy a strategic position in the filaments in such a way that perturbations at this site, due to chemical modification or mutation, impact filament assembly or organization in a structure-dependent manner. Cysteine-dependent regulation of vimentin can be modulated by interaction with divalent cations, such as zinc, and by pH. Importantly, vimentin remodeling induced by C328 modification may affect its interaction with cellular organelles, as well as the cross-talk between cytoskeletal networks, as seems to be the case for the reorganization of actin filaments in response to oxidants and electrophiles. In summary, the evidence herein reviewed delineates a complex interplay in which type III IFs emerge both as targets and modulators of redox signaling.

Impact of MG132 induced-proteotoxic stress on αB-crystallin and desmin phosphorylation and O-GlcNAcylation and their partition towards cytoskeleton

Small Heat Shock Proteins are considered as the first line of defense when proteostasis fails. Among them, αB-crystallin is expressed in striated muscles in which it interacts with desmin intermediate filaments to stabilize them, maintaining cytoskeleton's integrity and muscular functionalities. Desmin is a key actor for muscle health; its targeting by αB-crystallin is thus crucial, especially in stress conditions. αB-crystallin is phosphorylated and O-GlcNAcylated. Its phosphorylation increases consecutively to various stresses, correlated with its recruitment for cytoskeleton's safeguarding. However, phosphorylation as unique signal for cytoskeleton translocation remains controversial; indeed, O-GlcNAcylation was also proposed to be involved. Thus, there are still some gaps for a deeper comprehension of how αB-crystallin functions are finely regulated by post-translational modifications. Furthermore, desmin also bears both post-translational modifications; while desmin phosphorylation is closely linked to desmin intermediates filaments turnover, it is unclear whereas its O-GlcNAcylation could impact its proper function. In the herein paper, we aim at identifying whether phosphorylation and/or O-GlcNAcylation are involved in αB-crystallin targeting towards cytoskeleton in proteotoxic stress induced by proteasome inhibition in C2C12 myotubes. We demonstrated that proteotoxicity led to αB-crystallin's phosphorylation and O-GlcNAcylation patterns changes, both presenting a dynamic interplay depending on protein subfraction. Importantly, both post-translational modifications showed a spatio-temporal variation correlated with αB-crystallin translocation towards cytoskeleton. In contrast, we did not detect any change of desmin phosphorylation and O-GlcNAcylation. All together, these data strongly support that αB-crystallin phosphorylation/O-GlcNAcylation interplay rather than changes on desmin is a key regulator for its cytoskeleton translocation, preserving it towards stress.

Transcription Factors and Markers Related to Epithelial-Mesenchymal Transition and Their Role in Resistance to Therapies in Head and Neck Cancers

Head and neck cancers (HNCs) are heterogeneous and aggressive tumors of the upper aerodigestive tract. Although various histological types exist, the most common is squamous cell carcinoma (HNSCC). The incidence of HNSCC is increasing, making it an important public health concern. Tumor resistance to contemporary treatments, namely, chemo- and radiotherapy, and the recurrence of the primary tumor after its surgical removal cause huge problems for patients. Despite recent improvements in these treatments, the 5-year survival rate is still relatively low. HNSCCs may develop local lymph node metastases and, in the most advanced cases, also distant metastases. A key process associated with tumor progression and metastasis is epithelial-mesenchymal transition (EMT), when poorly motile epithelial tumor cells acquire motile mesenchymal characteristics. These transition cells can invade different adjacent tissues and finally form metastases. EMT is governed by various transcription factors, including the best-characterized TWIST1 and TWIST2, SNAIL, SLUG, ZEB1, and ZEB2. Here, we highlight the current knowledge of the process of EMT in HNSCC and present the main protein markers associated with it. This review focuses on the transcription factors related to EMT and emphasizes their role in the resistance of HNSCC to current chemo- and radiotherapies. Understanding the role of EMT and the precise molecular mechanisms involved in this process may help with the development of novel anti-cancer therapies for this type of tumor.

IOP and glaucoma damage: The essential role of optic nerve head and retinal mechanosensors

There are many unanswered questions on the relation of intraocular pressure to glaucoma development and progression. IOP itself cannot be distilled to a single, unifying value, because IOP level varies over time, differs depending on ocular location, and can be affected by method of measurement. Ultimately, IOP level creates mechanical strain that affects axonal function at the optic nerve head which causes local extracellular matrix remodeling and retinal ganglion cell death - hallmarks of glaucoma and the cause of glaucomatous vision loss. Extracellular tissue strain at the ONH and lamina cribrosa is regionally variable and differs in magnitude and location between healthy and glaucomatous eyes. The ultimate targets of IOP-induced tissue strain in glaucoma are retinal ganglion cell axons at the optic nerve head and the cells that support axonal function (astrocytes, the neurovascular unit, microglia, and fibroblasts). These cells sense tissue strain through a series of signals that originate at the cell membrane and alter cytoskeletal organization, migration, differentiation, gene transcription, and proliferation. The proteins that translate mechanical stimuli into molecular signals act as band-pass filters - sensing some stimuli while ignoring others - and cellular responses to stimuli can differ based on cell type and differentiation state. Therefore, to fully understand the IOP signals that are relevant to glaucoma, it is necessary to understand the ultimate cellular targets of IOP-induced mechanical stimuli and their ability to sense, ignore, and translate these signals into cellular actions.

[Validation of a C57/BL6J mouse model of focal cerebral ischemia established by electrocoagulation of the middle cerebral artery]

OBJECTIVE

To modify the method for establishing mouse models of middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia using electrocoagulation.

METHODS

Forty-six C57/BL6J male mice were divided into MCAO model group (n=34) and sham-operated group (n=12). In the model group, MCAO was induced by permanent coagulation of the right middle cerebral artery (MCA) using a coagulator, and cerebral blood flow perfusion was monitored before and at 20 min and 1 day after modeling. Neurological deficits of the mice at 1, 7, and 14 days after modeling were evaluated using Longa score, mNSS score, beam walking test, cylinder test and corner test. TTC staining was used to measure the cerebral infarct size, and Western blotting was performed to detect the expressions of BDNF, GFAP and DCX proteins in the ischemic cortex.

RESULTS

The mice in the model group showed significantly reduced cerebral blood flow in the MCA on the ischemic side and obvious neurological deficits with increased forelimb use asymmetry on days 1, 7 and 14 after modeling (P < 0.05). In the cerebral cortex on the ischemic side of the model mice, the expressions of GFAP and DCX increased significantly at 1, 7, and 14 days (P < 0.05) and the expression of BDNF increased at 1 day after modeling ischemia (P < 0.05).

CONCLUSION

We successfully prepared mouse models of MCAO using a modified method by changing the electrocoagulation location from the distal location of the junction between the MCA and the inferior cerebral vein to a 2 mm segment medial to the junction between the MCA and the olfactory bundle.

Desmin and Plectin Recruitment to the Nucleus and Nuclei Orientation Are Lost in Emery-Dreifuss Muscular Dystrophy Myoblasts Subjected to Mechanical Stimulation

In muscle cells subjected to mechanical stimulation, LINC complex and cytoskeletal proteins are basic to preserve cellular architecture and maintain nuclei orientation and positioning. In this context, the role of lamin A/C remains mostly elusive. This study demonstrates that in human myoblasts subjected to mechanical stretching, lamin A/C recruits desmin and plectin to the nuclear periphery, allowing a proper spatial orientation of the nuclei. Interestingly, in Emery-Dreifuss Muscular Dystrophy (EDMD2) myoblasts exposed to mechanical stretching, the recruitment of desmin and plectin to the nucleus and nuclear orientation were impaired, suggesting that a functional lamin A/C is crucial for the response to mechanical strain. While describing a new mechanism of action headed by lamin A/C, these findings show a structural alteration that could be involved in the onset of the muscle defects observed in muscular laminopathies.

Comparison of differentially expressed genes in longissimus dorsi muscle of Diannan small ears, Wujin and landrace pigs using RNA-seq

Introduction

Pig growth is an important economic trait that involves the co-regulation of multiple genes and related signaling pathways. High-throughput sequencing has become a powerful technology for establishing the transcriptome profiles and can be used to screen genome-wide differentially expressed genes (DEGs). In order to elucidate the molecular mechanism underlying muscle growth, this study adopted RNA sequencing (RNA-seq) to identify and compare DEGs at the genetic level in the longissimus dorsi muscle (LDM) between two indigenous Chinese pig breeds (Diannan small ears [DSE] pig and Wujin pig [WJ]) and one introduced pig breed (Landrace pig [LP]).

Methods

Animals under study were from two Chinese indigenous pig breeds (DSE pig, n = 3; WJ pig, n = 3) and one introduced pig breed (LP, n = 3) were used for RNA sequencing (RNA-seq) to identify and compare the expression levels of DEGs in the LDM. Then, functional annotation, Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and Protein-Protein Interaction (PPI) network analysis were performed on these DEGs. Then, functional annotation, Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and Protein-Protein Interaction (PPI) network analysis were performed on these DEGs.

Results

The results revealed that for the DSE, WJ, and LP libraries, more than 66, 65, and 71 million clean reads were generated by transcriptome sequencing, respectively. A total of 11,213 genes were identified in the LDM tissue of these pig breeds, of which 7,127 were co-expressed in the muscle tissue of the three samples. In total, 441 and 339 DEGs were identified between DSE vs. WJ and LP vs. DSE in the study, with 254, 193 up-regulated genes and 187, 193 down-regulated genes in DSE compared to WJ and LP. GO analysis and KEGG signaling pathway analysis showed that DEGs are significantly related to contractile fiber, sarcolemma, and dystrophin-associated glycoprotein complex, myofibril, sarcolemma, and myosin II complex, Glycolysis/Gluconeogenesis, Propanoate metabolism, and Pyruvate metabolism, etc. In combination with functional annotation of DEGs, key genes such as ENO3 and JUN were identified by PPI network analysis.

Discussion

In conclusion, the present study revealed key genes including DES, FLNC, PSMD1, PSMD6, PSME4, PSMB4, RPL11, RPL13A, ROS23, RPS29, MYH1, MYL9, MYL12B, TPM1, TPM4, ENO3, PGK1, PKM2, GPI, and the unannotated new gene ENSSSCG00000020769 and related signaling pathways that influence the difference in muscle growth and could provide a theoretical basis for improving pig muscle growth traits in the future.

Molecular biomarkers of diffuse axonal injury: recent advances and future perspectives

INTRODUCTION

Diffuse axonal injury (DAI), with high mortality and morbidity both in children and adults, is one of the most severe pathological consequences of traumatic brain injury. Currently, clinical diagnosis, disease assessment, disability identification, and postmortem diagnosis of DAI is mainly limited by the absent of specific molecular biomarkers.

AREAS COVERED

In this review, we first introduce the pathophysiology of DAI, summarized the reported biomarkers in previous animal and human studies, and then the molecular biomarkers such as β-Amyloid precursor protein, neurofilaments, S-100β, myelin basic protein, tau protein, neuron-specific enolase, Peripherin and Hemopexin for DAI diagnosis is summarized. Finally, we put forward valuable views on the future research direction of diagnostic biomarkers of DAI.

EXPERT OPINION

In recent years, the advanced technology has ultimately changed the research of DAI, and the numbers of potential molecular biomarkers was introduced in related studies. We summarized the latest updated information in such studies to provide references for future research and explore the potential pathophysiological mechanism on diffuse axonal injury.

Desmin and its molecular chaperone, the αB-crystallin: How post-translational modifications modulate their functions in heart and skeletal muscles?

Maintenance of the highly organized striated muscle tissue requires a cell-wide dynamic network through protein-protein interactions providing an effective mechanochemical integrator of morphology and function. Through a continuous and complex trans-cytoplasmic network, desmin intermediate filaments ensure this essential role in heart and in skeletal muscle. Besides their role in the maintenance of cell shape and architecture (permitting contractile activity efficiency and conferring resistance towards mechanical stress), desmin intermediate filaments are also key actors of cell and tissue homeostasis. Desmin participates to several cellular processes such as differentiation, apoptosis, intracellular signalisation, mechanotransduction, vesicle trafficking, organelle biogenesis and/or positioning, calcium homeostasis, protein homeostasis, cell adhesion, metabolism and gene expression. Desmin intermediate filaments assembly requires αB-crystallin, a small heat shock protein. Over its chaperone activity, αB-crystallin is involved in several cellular functions such as cell integrity, cytoskeleton stabilization, apoptosis, autophagy, differentiation, mitochondria function or aggresome formation. Importantly, both proteins are known to be strongly associated to the aetiology of several cardiac and skeletal muscles pathologies related to desmin filaments disorganization and a strong disturbance of desmin interactome. Note that these key proteins of cytoskeleton architecture are extensively modified by post-translational modifications that could affect their functional properties. Therefore, we reviewed in the herein paper the impact of post-translational modifications on the modulation of cellular functions of desmin and its molecular chaperone, the αB-crystallin.

Direct observation of oriented behavior of actin filaments interacting with desmin intermediate filaments

BACKGROUND

Associations between actin filaments (AFs) and intermediate filaments (IFs) are frequently observed in living cells. The crosstalk between these cytoskeletal components underpins cellular organization and dynamics; however, the molecular basis of filamentous interactions is not fully understood. Here, we describe the mode of interaction between AFs and desmin IFs (DIFs) in a reconstituted in vitro system.

METHODS

AFs (rabbit skeletal muscle) and DIFs (chicken gizzard) were labeled with fluorescent dyes. DIFs were immobilized on a heavy meromyosin (HMM)-coated collodion surface. HMM-driven AFs with ATP hydrolysis was assessed in the presence of DIFs. Images of single filaments were obtained using fluorescence microscopy. Vector changes in the trajectories of single AFs were calculated from microscopy images.

RESULTS

AF speed transiently decreased upon contact with DIF. The difference between the incoming and outgoing angles of a moving AF broadened upon contact with a DIF. A smaller incoming angle tended to result in a smaller outgoing angle in a nematic manner. The percentage of moving AFs decreased with an increasing DIF density, but the speed of the moving AFs was similar to that in the no-desmin control. An abundance of DIFs tended to exclude AFs from the HMM-coated surfaces.

CONCLUSIONS

DIFs agitate the movement of AFs with the orientation. DIFs can bind to HMMs and weaken actin-myosin interactions.

GENERAL SIGNIFICANCE

The study indicates that apart from the binding strength, the accumulation of weak interactions characteristic of filamentous structures may affect the dynamic organization of cell architecture.

Vimentin takes a hike - Emerging roles of extracellular vimentin in cancer and wound healing

Vimentin is a cytoskeletal protein important for many cellular processes, including proliferation, migration, invasion, stress resistance, signaling, and many more. The vimentin-deficient mouse has revealed many of these functions as it has numerous severe phenotypes, many of which are found only following a suitable challenge or stress. While these functions are usually related to vimentin as a major intracellular protein, vimentin is also emerging as an extracellular protein, exposed at the cell surface in an oligomeric form or secreted to the extracellular environment in soluble and vesicle-bound forms. Thus, this review explores the roles of the extracellular pool of vimentin (eVIM), identified in both normal and pathological states. It focuses specifically on the recent advances regarding the role of eVIM in wound healing and cancer. Finally, it discusses new technologies and future perspectives for the clinical application of eVIM.

Intermediate filaments in the heart: The dynamic duo of desmin and lamins orchestrates mechanical force transmission

The intermediate filament (IF) cytoskeleton supports cellular structural integrity, particularly in response to mechanical stress. The most abundant IF proteins in mature cardiomyocytes are desmin and lamins. The desmin network tethers the contractile apparatus and organelles to the nuclear envelope and the sarcolemma, while lamins, as components of the nuclear lamina, provide structural stability to the nucleus and the genome. Mutations in desmin or A-type lamins typically result in cardiomyopathies and recent studies emphasized the synergistic roles of desmin and lamins in the maintenance of nuclear integrity in cardiac myocytes. Here we explore the emerging roles of the interdependent relationship between desmin and lamins in providing resilience to nuclear structure while transducing extracellular mechanical cues into the nucleus.

Understanding Arrhythmogenic Cardiomyopathy: Advances through the Use of Human Pluripotent Stem Cell Models

Cardiomyopathies (CMPs) represent a significant healthcare burden and are a major cause of heart failure leading to premature death. Several CMPs are now recognized to have a strong genetic basis, including arrhythmogenic cardiomyopathy (ACM), which predisposes patients to arrhythmic episodes. Variants in one of the five genes (PKP2, JUP, DSC2, DSG2, and DSP) encoding proteins of the desmosome are known to cause a subset of ACM, which we classify as desmosome-related ACM (dACM). Phenotypically, this disease may lead to sudden cardiac death in young athletes and, during late stages, is often accompanied by myocardial fibrofatty infiltrates. While the pathogenicity of the desmosome genes has been well established through animal studies and limited supplies of primary human cells, these systems have drawbacks that limit their utility and relevance to understanding human disease. Human induced pluripotent stem cells (hiPSCs) have emerged as a powerful tool for modeling ACM in vitro that can overcome these challenges, as they represent a reproducible and scalable source of cardiomyocytes (CMs) that recapitulate patient phenotypes. In this review, we provide an overview of dACM, summarize findings in other model systems linking desmosome proteins with this disease, and provide an up-to-date summary of the work that has been conducted in hiPSC-cardiomyocyte (hiPSC-CM) models of dACM. In the context of the hiPSC-CM model system, we highlight novel findings that have contributed to our understanding of disease and enumerate the limitations, prospects, and directions for research to consider towards future progress.

Peripherin: A proposed biomarker of traumatic axonal injury triggered by mechanical force

Traumatic axonal injury (TAI) is one of the most common pathological features of severe traumatic brain injury (TBI). Our previous study using proteomics suggested that peripherin (PRPH) should be a potential candidate as a biomarker for TAI diagnosis. This study is to further elucidate the role and association of PRPH with TAI. In the animal study, we performed immunohistochemistry, ELISA and morphological analysis to evaluate PRPH level and distribution following a severe impact. PRPH-positive regions were widely distributed in the axonal tract throughout the whole brain. Axonal injuries with PRPH inclusion were observed post-TBI. Besides, PRPH was significantly increased in both cerebral spinal fluid and plasma at the early phase post-TBI. Colocalization analysis based on microscopy revealed that PRPH represents an immunohistological biomarker in the neuropathological diagnosis of TAI. Brain samples from patients with TBI were included to further test whether PRPH is feasible in the real practice of neuropathology. Immunohistochemistry of PRPH, NFH, APP and NFL on human brain tissues further confirmed PRPH as an immunohistological biomarker that could be applied in practice. Collectively, we conclude that PRPH mirrors the cytoskeleton injury of axons and could represent a neuropathological biomarker for TAI.

Desmin Reorganization by Stimuli Inducing Oxidative Stress and Electrophiles: Role of Its Single Cysteine Residue

The type III intermediate filament proteins vimentin and GFAP are modulated by oxidants and electrophiles, mainly through perturbation of their single cysteine residues. Desmin, the type III intermediate filament protein specific to muscle cells, is critical for muscle homeostasis, playing a key role in sarcomere organization and mitochondrial function. Here, we have studied the impact of oxidants and cysteine-reactive agents on desmin behavior. Our results show that several reactive species and drugs induce covalent modifications of desmin in vitro, of which its single cysteine residue, C333, is an important target. Moreover, stimuli eliciting oxidative stress or lipoxidation, including H2O2, 15-deoxy-prostaglandin J2, and CoCl2-elicited chemical hypoxia, provoke desmin disorganization in H9c2 rat cardiomyoblasts transfected with wild-type desmin, which is partially attenuated in cells expressing a C333S mutant. Notably, in cells lacking other cytoplasmic intermediate filaments, network formation by desmin C333S appears less efficient than that of desmin wt, especially when these proteins are expressed as fluorescent fusion constructs. Nevertheless, in these cells, the desmin C333S organization is also protected from disruption by oxidants. Taken together, our results indicate that desmin is a target for oxidative and electrophilic stress, which elicit desmin remodeling conditioned by the presence of its single cysteine residue.

A corneo-retinal hypercitrullination axis underlies ocular injury to nitrogen mustard

The vesicant sulfur mustard (SM) is a chemical warfare agent that causes acute and chronic injury to the cornea and proximal anterior segment structures. Despite clinical evidence of SM-exposure causing unexplained retinal deficits, there have been no animal studies conducted to examine the retinal toxicity of this vesciant. The cardinal hallmark of retinal response to stressors or injury is the activation of reactive gliosis, a cellular process largely governed by Müller glia. Previously we showed that corneal exposure to sodium hydroxide elicits rapid induction of reactive gliosis and results in retinal degeneration in a dose-related manner. Based on this evidence, we hypothesized that the vesicant nitrogen mustard (NM), an analog of SM, may also elicit reactive gliosis. To test this idea, we developed a mouse model of NM ocular injury and investigated corneal and retinal effects focusing on citrullination, a posttranslational modification (PTM) of proteins. This PTM was recently linked to alkali injury and has also been shown to occur in retinal degenerative conditions. Here, we demonstrate that corneal exposure to 1% NM causes a synchronous activation of citrullination in both the cornea and retina with hypercitrullination becoming apparent temporally and manifesting with altered cellular expression characteristics. A key finding is that ocular citrullination occurs acutely as early as 1-h post-injury in both the cornea and retina, which underscores a need for expeditious interception of this acute corneal and retinal response. Moreover, exploiting dose response and temporal studies, we uncoupled NM-induced retinal citrullination from its induction of retinal gliosis. Our findings demonstrate that hypercitrullination is a common corneo-retinal mechanism that sensitizes the eye to NM injury and suggests that counteracting hypercitrullination may provide a suitable countermeasure to vesicant injury.

Vimentin single cysteine residue acts as a tunable sensor for network organization and as a key for actin remodeling in response to oxidants and electrophiles

Cysteine residues can undergo multiple posttranslational modifications with diverse functional consequences, potentially behaving as tunable sensors. The intermediate filament protein vimentin has important implications in pathophysiology, including cancer progression, infection, and fibrosis, and maintains a close interplay with other cytoskeletal structures, such as actin filaments and microtubules. We previously showed that the single vimentin cysteine, C328, is a key target for oxidants and electrophiles. Here, we demonstrate that structurally diverse cysteine-reactive agents, including electrophilic mediators, oxidants and drug-related compounds, disrupt the vimentin network eliciting morphologically distinct reorganizations. As most of these agents display broad reactivity, we pinpointed the importance of C328 by confirming that local perturbations introduced through mutagenesis provoke structure-dependent vimentin rearrangements. Thus, GFP-vimentin wild type (wt) forms squiggles and short filaments in vimentin-deficient cells, the C328F, C328W, and C328H mutants generate diverse filamentous assemblies, and the C328A and C328D constructs fail to elongate yielding dots. Remarkably, vimentin C328H structures resemble the wt, but are strongly resistant to electrophile-elicited disruption. Therefore, the C328H mutant allows elucidating whether cysteine-dependent vimentin reorganization influences other cellular responses to reactive agents. Electrophiles such as 1,4-dinitro-1H-imidazole and 4-hydroxynonenal induce robust actin stress fibers in cells expressing vimentin wt. Strikingly, under these conditions, vimentin C328H expression blunts electrophile-elicited stress fiber formation, apparently acting upstream of RhoA. Analysis of additional vimentin C328 mutants shows that electrophile-sensitive and assembly-defective vimentin variants permit induction of stress fibers by reactive species, whereas electrophile-resistant filamentous vimentin structures prevent it. Together, our results suggest that vimentin acts as a break for actin stress fibers formation, which would be released by C328-aided disruption, thus allowing full actin remodeling in response to oxidants and electrophiles. These observations postulate C328 as a "sensor" transducing structurally diverse modifications into fine-tuned vimentin network rearrangements, and a gatekeeper for certain electrophiles in the interplay with actin.

Peptidyl arginine deiminase 4 deficiency protects against subretinal fibrosis by inhibiting Müller glial hypercitrullination

Retinal scarring with vision loss continues to be an enigma in individuals with advanced age-related macular degeneration (AMD). Müller glial cells are believed to initiate and perpetuate scarring in retinal degeneration as these glial cells participate in reactive gliosis and undergo hypertrophy. We previously showed in the murine laser-induced model of choroidal neovascularization that models wet-AMD that glial fibrillary acidic protein (GFAP) expression, an early marker of reactive gliosis, increases along with its posttranslational modification citrullination. This was related to increased co-expression of the citrullination enzyme peptidyl arginine deiminase-4 (PAD4), which also colocalizes to GFAP filaments. However, whether such hypercitrullination in Müller glial drives fibrotic pathology has remained understudied. Here, using male and female C57Bl6 mice subjected to laser injury, we investigated in a temporal study how citrullination impacts GFAP and PAD4 dynamics. We found that high molecular weight citrullinated species that accumulate in Müller glia corresponded with dynamic changes in GFAP and PAD4 showing their temporal redistribution from polymeric cytoskeletal to soluble protein fractions using immunostaining and western blot analysis. In conditional glial-specific PAD4 knockout (PAD4cKO) mice subjected to laser injury, there was a stark reduction of citrullination and of polymerized GFAP filaments. These injured PAD4cKO retinas showed improved lesion healing, as well as reduced fibronectin deposition in the subretinal space at 30 days. Taken together, these findings reveal that pathologically overexpressed PAD4 in reactive Müller glia governs GFAP filament dynamics and alters their stability, suggesting chronic PAD4-driven hypercitrullination may be a target for retinal fibrosis.

Gliovascular alterations in sporadic and familial Alzheimer's disease: APOE3 Christchurch homozygote glioprotection

In response to brain insults, astrocytes become reactive, promoting protection and tissue repair. However, astroglial reactivity is typical of brain pathologies, including Alzheimer's disease (AD). Considering the heterogeneity of the reactive response, the role of astrocytes in the course of different forms of AD has been underestimated. Colombia has the largest human group known to have familial AD (FAD). This group carries the autosomal dominant and fully penetrant mutation E280A in PSEN1, which causes early-onset AD. Recently, our group identified an E280A carrier who did not develop FAD. The individual was homozygous for the Christchurch mutation R136S in APOE3 (APOEch). Remarkably, APOE is the main genetic risk factor for developing sporadic AD (SAD) and most of cerebral ApoE is produced by astroglia. Here, we characterized astrocyte properties related to reactivity, glutamate homeostasis, and structural integrity of the gliovascular unit (GVU), as factors that could underlie the pathogenesis or protection of AD. Specifically, through histological and 3D microscopy analyses of postmortem samples, we briefly describe the histopathology and cytoarchitecture of the frontal cortex of SAD, FAD, and APOEch, and demonstrate that, while astrodegeneration and vascular deterioration are prominent in SAD, FAD is characterized by hyperreactive-like glia, and APOEch displays the mildest astrocytic and vascular alterations despite having the highest burden of Aβ. Notably, astroglial, gliovascular, and vascular disturbances, as well as brain cell death, correlate with the specific astrocytic phenotypes identified in each condition. This study provides new insights into the potential relevance of the gliovasculature in the development and protection of AD. To our knowledge, this is the first study assessing the components of the GVU in human samples of SAD, FAD, and APOEch.

Distribution of cytoskeletal proteins in the cat testis during the pre-pubertal and post-pubertal periods

Cytoskeletal proteins not only define the shape of cells, but also have critical roles in their proliferation, migration and motility, as well as in the establishment and maintenance of tissue organization and integrity. Furthermore, these proteins influence the physiological processes of the male reproductive system and are found in the structure of some cells. This study aimed to determine differences between the pre- and post-pubertal periods for the localization and distribution of actin, desmin, vimentin and cytokeratin-18 in the testes, epididymides and ductus deferentes of Persian and Turkish Angora and Van cats, using immunohistochemistry. The study material was grouped as belonging to the pre-pubertal and post-pubertal periods. The tissue samples of both groups were subjected to routine histological processing and embedded in paraffin. Serial sections cut from the paraffin-embedded tissue blocks were immunohistochemically stained with the indirect streptavidin-biotin complex method. Immunohistochemical findings demonstrated that there was no difference between the pre- and post-pubertal periods for the staining intensity and distribution of the proteins actin, vimentin, desmin and cytokeratin-18 in Persian and Turkish Angora and Van cats. On the other hand, differences were detected between the pre- and post-pubertal periods for the cellular expression and localization of these proteins in the testes, epididymides and ductus deferentes. Thus, the study results suggest that, based on the expression of actin, desmin, vimentin and cytokeratin-18 in the testes, epididymides and ductus deferentes during both periods, these molecular factors could have a contributory role in the development of the male reproductive system and the regulation of its physiological processes.

Laser-Induced Porcine Model of Experimental Retinal Vein Occlusion: An Optimized Reproducible Approach

Retinal vein occlusion (RVO) is a frequent visually disabling condition. The management of RVO continues to challenge clinicians. Macular edema secondary to RVO is often recurrent, and patients typically require intravitreal injections for several years. Understanding molecular mechanisms in RVO is a key element in improving the treatment of the condition. Studying the molecular mechanisms in RVO at the retinal level is possible using animal models of experimental RVO. Most studies of experimental RVO have been sporadic, using only a few animals per experiment. Here, we report on 10 years of experience of the use of argon laser-induced experimental RVO in 108 porcine eyes from 65 animals, including 65 eyes with experimental branch retinal vein occlusion (BRVO) and 43 eyes with experimental central retinal vein occlusion (CRVO). Reproducibility and methods for evaluating and controlling ischemia in experimental RVO are reviewed. Methods for studying protein changes in RVO are discussed in detail, including proteomic analysis, Western blotting, and immunohistochemistry. Experimental RVO has brought significant insights into molecular changes in RVO. Testing intravitreal interventions in experimental RVO may be a significant step in developing personalized therapeutic approaches for patients with RVO.

Postmortem 7T MRI for guided histopathology and evaluation of cerebrovascular disease

Postmortem (PM) magnetic resonance imaging (MRI) can serve as a bridge between in vivo imaging and histology by connecting MRI observed macrostructural findings to histological staining and microstructural changes. Data were acquired from 20 formalin-fixed brains including T2, T1, PD, and T2*-weighted images of left hemispheres and 6-mm-thick coronal slices. Tissue slices were bisected, aligned to MR images and used to guide histological sampling. Markers of myelin and oligodendroglia alterations were semiquantitatively rated and compared within white matter hyperintensities (WMHs) and normal-appearing white matter. Tissue priors were created from 3T in vivo data and used to guide segmentation of WMH. PM WMH and hemisphere volumes were compared to volumes derived from in vivo data. PM T2 WMH and T1 hemisphere volumes were correlated with in vivo 3T FLAIR WMH and T1 hemisphere volumes. WMH showed significant myelin loss, decreased GFAP expression and increased vimentin expression. MR-visible perivascular spaces and cortical microvascular lesions were successfully captured on histopathological sections. PM MRI can quantify cerebrovascular disease burden and guide tissue sampling, allowing for more comprehensive characterization of cerebrovascular disease that may be used to study etiologies of age-related cognitive change.

Cognitive dysfunction associated with COVID-19: Prognostic role of circulating biomarkers and microRNAs

COVID-19 is renowned as a multi-organ disease having subacute and long-term effects with a broad spectrum of clinical manifestations. The evolving scientific and clinical evidence demonstrates that the frequency of cognitive impairment after COVID-19 is high and it is crucial to explore more clinical research and implement proper diagnostic and treatment strategies. Several central nervous system complications have been reported as comorbidities of COVID-19. The changes in cognitive function associated with neurodegenerative diseases develop slowly over time and are only diagnosed at an already advanced stage of molecular pathology. Hence, understanding the common links between COVID-19 and neurodegenerative diseases will broaden our knowledge and help in strategizing prognostic and therapeutic approaches. The present review focuses on the diverse neurodegenerative changes associated with COVID-19 and will highlight the importance of major circulating biomarkers and microRNAs (miRNAs) associated with the disease progression and severity. The literature analysis showed that major proteins associated with central nervous system function, such as Glial fibrillary acidic protein, neurofilament light chain, p-tau 181, Ubiquitin C-terminal hydrolase L1, S100 calcium-binding protein B, Neuron-specific enolase and various inflammatory cytokines, were significantly altered in COVID-19 patients. Furthermore, among various miRNAs that are having pivotal roles in various neurodegenerative diseases, miR-146a, miR-155, Let-7b, miR-31, miR-16 and miR-21 have shown significant dysregulation in COVID-19 patients. Thus the review consolidates the important findings from the numerous studies to unravel the underlying mechanism of neurological sequelae in COVID-19 and the possible association of circulatory biomarkers, which may serve as prognostic predictors and therapeutic targets in future research.

Exosome biopotentiated hydrogel restores damaged skeletal muscle in a porcine model of stress urinary incontinence

Urinary incontinence afflicts up to 40% of adult women in the United States. Stress urinary incontinence (SUI) accounts for approximately one-third of these cases, precipitating ~200,000 surgical procedures annually. Continence is maintained through the interplay of sub-urethral support and urethral sphincter coaptation, particularly during activities that increase intra-abdominal pressure. Currently, surgical correction of SUI focuses on the re-establishment of sub-urethral support. However, mesh-based repairs are associated with foreign body reactions and poor localized tissue healing, which leads to mesh exposure, prompting the pursuit of technologies that restore external urethral sphincter function and limit surgical risk. The present work utilizes a human platelet-derived CD41a and CD9 expressing extracellular vesicle product (PEP) enriched for NF-κB and PD-L1 and derived to ensure the preservation of lipid bilayer for enhanced stability and compatibility with hydrogel-based sustained delivery approaches. In vitro, the application of PEP to skeletal muscle satellite cells in vitro drove proliferation and differentiation in an NF-κB-dependent fashion, with full inhibition of impact on exposure to resveratrol. PEP biopotentiation of collagen-1 and fibrin glue hydrogel achieved sustained exosome release at 37 °C, creating an ultrastructural “bead on a string” pattern on scanning electron microscopy. Initial testing in a rodent model of latissimus dorsi injury documented activation of skeletal muscle proliferation of healing. In a porcine model of stress urinary incontinence, delivery of PEP-biopotentiated collagen-1 induced functional restoration of the external urethral sphincter. The histological evaluation found that sustained PEP release was associated with new skeletal muscle formation and polarization of local macrophages towards the regenerative M2 phenotype. The results provided herein serve as the first description of PEP-based biopotentiation of hydrogels implemented to restore skeletal muscle function and may serve as a promising approach for the nonsurgical management of SUI.

Desmin variants: Trigger for cardiac arrhythmias?

Desmin (DES) is a classical type III intermediate filament protein encoded by the DES gene. Desmin is abundantly expressed in cardiac, skeletal, and smooth muscle cells. In these cells, desmin interconnects several protein-protein complexes that cover cell-cell contact, intracellular organelles such as mitochondria and the nucleus, and the cytoskeletal network. The extra- and intracellular localization of the desmin network reveals its crucial role in maintaining the structural and mechanical integrity of cells. In the heart, desmin is present in specific structures of the cardiac conduction system including the sinoatrial node, atrioventricular node, and His-Purkinje system. Genetic variations and loss of desmin drive a variety of conditions, so-called desminopathies, which include desmin-related cardiomyopathy, conduction system-related atrial and ventricular arrhythmias, and sudden cardiac death. The severe cardiac disease outcomes emphasize the clinical need to understand the molecular and cellular role of desmin driving desminopathies. As the role of desmin in cardiomyopathies has been discussed thoroughly, the current review is focused on the role of desmin impairment as a trigger for cardiac arrhythmias. Here, the molecular and cellular mechanisms of desmin to underlie a healthy cardiac conduction system and how impaired desmin triggers cardiac arrhythmias, including atrial fibrillation, are discussed. Furthermore, an overview of available (genetic) desmin model systems for experimental cardiac arrhythmia studies is provided. Finally, potential implications for future clinical treatments of cardiac arrhythmias directed at desmin are highlighted.

Astragaloside IV promotes pharmacological effect of Descurainia sophia seeds on isoproterenol-induced cardiomyopathy in rats by synergistically modulating the myosin motor

Descurainia sophia seeds (DS), Astragalus mongholicus (AM), and their formulas are widely used to treat heart failure caused by various cardiac diseases in traditional Chinese medicine practice. However, the molecular mechanism of action of DS and AM has not been completely understood. Herein, we first used mass spectrometry coupled to UPLC to characterize the chemical components of DS and AM decoctions, then applied MS-based quantitative proteomic analysis to profile protein expression in the heart of rats with isoproterenol-induced cardiomyopathy (ISO-iCM) before and after treated with DS alone or combined with AM, astragaloside IV (AS4), calycosin-7-glucoside (C7G), and Astragalus polysaccharides (APS) from AM. We demonstrated for the first time that DS decoction alone could reverse the most of differentially expressed proteins in the heart of the rats with ISO-iCM, including the commonly recognized biomarkers natriuretic peptides (NPPA) of cardiomyopathy and sarcomeric myosin light chain 4 (MYL4), relieving ISO-iCM in rats, but AM did not pronouncedly improve the pharmacological efficiency of DS. Significantly, we revealed that AS4 remarkably promoted the pharmacological potency of DS by complementarily reversing myosin motor MYH6/7, and further downregulating NPPA and MYL4. In contrast, APS reduced the efficiency of DS due to upregulating NPPA and MYL4. These findings not only provide novel insights to better understanding in the combination principle of traditional Chinese medicine but also highlight the power of mass spectrometric proteomics strategy combined with conventional pathological approaches for the traditional medicine research.

Glial Fibrillary Acidic Protein: A Biomarker and Drug Target for Alzheimer’s Disease

Glial fibrillary acidic protein (GFAP) is an intermediate filament structural protein involved in cytoskeleton assembly and integrity, expressed in high abundance in activated glial cells. GFAP is neuroprotective, as knockout mice are hypersensitive to traumatic brain injury. GFAP in cerebrospinal fluid is a biomarker of Alzheimer’s disease (AD), dementia with Lewy bodies, and frontotemporal dementia (FTD). Here, we present novel evidence that GFAP is markedly overexpressed and differentially phosphorylated in AD hippocampus, especially in AD with the apolipoprotein E [ε4, ε4] genotype, relative to age-matched controls (AMCs). Kinases that phosphorylate GFAP are upregulated in AD relative to AMC. A knockdown of these kinases in SH-SY5Y-APP_Sw human neuroblastoma cells reduced amyloid accrual and lowered protein aggregation and associated behavioral traits in C. elegans models of polyglutamine aggregation (as observed in Huntington’s disease) and of Alzheimer’s-like amyloid formation. In silico screening of the ChemBridge structural library identified a small molecule, MSR1, with stable and specific binding to GFAP. Both MSR1 exposure and GF AP-specific RNAi knockdown reduce aggregation with remarkably high concordance of aggregate proteins depleted. These data imply that GFAP and its phosphorylation play key roles in neuropathic aggregate accrual and provide valuable new biomarkers, as well as novel therapeutic targets to alleviate, delay, or prevent AD.

Vimentin Tail Segments Are Differentially Exposed at Distinct Cellular Locations and in Response to Stress

The intermediate filament protein vimentin plays a key role in cell signaling and stress sensing, as well as an integrator of cytoskeletal dynamics. The vimentin monomer consists of a central rod-like domain and intrinsically disordered head and tail domains. Although the organization of vimentin oligomers in filaments is beginning to be understood, the precise disposition of the tail region remains to be elucidated. Here we observed that electrophilic stress-induced condensation shielded vimentin from recognition by antibodies against specific segments of the tail domain. A detailed characterization revealed that vimentin tail segments are differentially exposed at distinct subcellular locations, both in basal and stress conditions. The 411–423 segment appeared accessible in all cell areas, correlating with vimentin abundance. In contrast, the 419–438 segment was more scantily recognized in perinuclear vimentin and lipoxidative stress-induced bundles, and better detected in peripheral filaments, where it appeared to protrude further from the filament core. These differences persisted in mitotic cells. Interestingly, both tail segments showed closer accessibility in calyculin A-treated cells and phosphomimetic mutants of the C-terminal region. Our results lead us to hypothesize the presence of at least two distinct arrangements of vimentin tail in cells: an “extended” conformation (accessible 419–438 segment), preferentially detected in peripheral areas with looser filaments, and a “packed” conformation (shielded 419–438 segment), preferentially detected at the cell center in robust filaments and lipoxidative stress-induced bundles. These different arrangements could be putatively interconverted by posttranslational modifications, contributing to the versatility of vimentin functions and/or interactions.

Desmin Modulates Muscle Cell Adhesion and Migration

Cellular adhesion and migration are key functions that are disrupted in numerous diseases. We report that desmin, a type-III muscle-specific intermediate filament, is a novel cell adhesion regulator. Expression of p.R406W mutant desmin, identified in patients with desmin-related myopathy, modified focal adhesion area and expression of adhesion-signaling genes in myogenic C2C12 cells. Satellite cells extracted from desmin-knock-out (DesKO) and desmin-knock-in-p.R405W (DesKI-R405W) mice were less adhesive and migrated faster than those from wild-type mice. Moreover, we observed mislocalized and aggregated vinculin, a key component of cell adhesion, in DesKO and DesKI-R405W muscles. Vinculin expression was also increased in desmin-related myopathy patient muscles. Together, our results establish a novel role for desmin in cell-matrix adhesion, an essential process for strength transmission, satellite cell migration and muscle regeneration. Our study links the patho-physiological mechanisms of desminopathies to adhesion/migration defects, and may lead to new cellular targets for novel therapeutic approaches.

Glial Fibrillary Acidic Protein in Blood as a Disease Biomarker of Neuromyelitis Optica Spectrum Disorders

Glial fibrillary acidic protein (GFAP) is a type III intermediate filament protein found in astrocytes in the brain. Damaged astrocytes release GFAP into cerebrospinal fluid and blood. Thus, GFAP levels in these body fluids may reflect the disease state of neuromyelitis optica spectrum disorder (NMOSD), which includes astrocytopathy, characterized by pathogenic antibodies against aquaporin 4 located on astrocytes. Recently, single-molecule array technology that can detect these synaptic proteins in blood, even in the subfemtomolar range, has been developed. Emerging evidence suggests that GFAP protein is a strong biomarker candidate for NMOSD. This mini-review provides basic information about GFAP protein and innovative clinical data that show the potential clinical value of blood GFAP levels as a biomarker for NMOSD.

Blood GFAP as an emerging biomarker in brain and spinal cord disorders

Blood-derived biomarkers for brain and spinal cord diseases are urgently needed. The introduction of highly sensitive immunoassays led to a rapid increase in the number of potential blood-derived biomarkers for diagnosis and monitoring of neurological disorders. In 2018, the FDA authorized a blood test for clinical use in the evaluation of mild traumatic brain injury (TBI). The test measures levels of the astrocytic intermediate filament glial fibrillary acidic protein (GFAP) and neuroaxonal marker ubiquitin carboxy-terminal hydrolase L1. In TBI, blood GFAP levels are correlated with clinical severity and extent of intracranial pathology. Evidence also indicates that blood GFAP levels hold the potential to reflect, and might enable prediction of, worsening of disability in individuals with progressive multiple sclerosis. A growing body of evidence suggests that blood GFAP levels can be used to detect even subtle injury to the CNS. Most importantly, the successful completion of the ongoing validation of point-of-care platforms for blood GFAP might ameliorate the decision algorithms for acute neurological diseases, such as TBI and stroke, with important economic implications. In this Review, we provide a systematic overview of the evidence regarding the utility of blood GFAP as a biomarker in neurological diseases. We propose a model for GFAP concentration dynamics in different conditions and discuss the limitations that hamper the widespread use of GFAP in the clinical setting. In our opinion, the clinical use of blood GFAP measurements has the potential to contribute to accelerated diagnosis and improved prognostication, and represents an important step forward in the era of precision medicine.

Biomarker Potential of Vimentin in Oral Cancers

Oral carcinogenesis is a multistep process. As much as 5% to 85% of oral tumors can develop from potentially malignant disorders (PMD). Although the oral cavity is accessible for visual examination, the ability of current clinical or histological methods to predict the lesions that can progress to malignancy is limited. Thus, developing biological markers that will serve as an adjunct to histodiagnosis has become essential. Our previous studies comprehensively demonstrated that aberrant vimentin expression in oral premalignant lesions correlates to the degree of malignancy. Likewise, overwhelming research from various groups show a substantial contribution of vimentin in oral cancer progression. In this review, we have described studies on vimentin in oral cancers, to make a compelling case for vimentin as a prognostic biomarker.

Update of the keratin gene family: evolution, tissue-specific expression patterns, and relevance to clinical disorders

Intermediate filament (IntFil) genes arose during early metazoan evolution, to provide mechanical support for plasma membranes contacting/interacting with other cells and the extracellular matrix. Keratin genes comprise the largest subset of IntFil genes. Whereas the first keratin gene appeared in sponge, and three genes in arthropods, more rapid increases in keratin genes occurred in lungfish and amphibian genomes, concomitant with land animal-sea animal divergence (~ 440 to 410 million years ago). Human, mouse and zebrafish genomes contain 18, 17 and 24 non-keratin IntFil genes, respectively. Human has 27 of 28 type I "acidic" keratin genes clustered at chromosome (Chr) 17q21.2, and all 26 type II "basic" keratin genes clustered at Chr 12q13.13. Mouse has 27 of 28 type I keratin genes clustered on Chr 11, and all 26 type II clustered on Chr 15. Zebrafish has 18 type I keratin genes scattered on five chromosomes, and 3 type II keratin genes on two chromosomes. Types I and II keratin clusters-reflecting evolutionary blooms of keratin genes along one chromosomal segment-are found in all land animal genomes examined, but not fishes; such rapid gene expansions likely reflect sudden requirements for many novel paralogous proteins having divergent functions to enhance species survival following sea-to-land transition. Using data from the Genotype-Tissue Expression (GTEx) project, tissue-specific keratin expression throughout the human body was reconstructed. Clustering of gene expression patterns revealed similarities in tissue-specific expression patterns for previously described "keratin pairs" (i.e., KRT1/KRT10, KRT8/KRT18, KRT5/KRT14, KRT6/KRT16 and KRT6/KRT17 proteins). The ClinVar database currently lists 26 human disease-causing variants within the various domains of keratin proteins.

Association between glial fibrillary acidic protein, glial-derived neurotrophic factor, and fatty acid-binding protein-2 at birth in the incidence of necrotizing enterocolitis in preterm infants

BACKGROUND

This study aimed to analyze the relationship between glial fibrillary acidic protein (GFAP), glial-derived neurotrophic factor (GDNF), and fatty acid-binding protein-2 (FABP-2) in preterm infants on the incidence of NEC.

METHODS

Preterm infants with a birth weight <1,500 g and gestational age <34 weeks were included in this study. Biomarker examination was performed using the umbilical vein blood at birth (first sample). Biomarker examination was repeated if the infant developed symptoms of NEC using peripheral vein blood (second sample). Infants were observed for 14 days. If NEC did not exist, a biomarker examination was performed at 14 days.

RESULTS

This study included 30 preterm infants, nine infants experienced NEC. The values of GFAP, GDNF, and FABP-2 (median and range) in the group with NEC were higher than those in the group without NEC in both the first samples {GFAP [1.40 (0.20-6.50) vs. 0.30 (0.10-1.30) P = 0.014], GDNF [2.84 (1.05-14.11) vs. 1.56 (1.07-3.48) P = 0.050], and FABP-2 [621.70 (278.40-2,207.00) vs. 294.20 (211.40-597.50) P = 0.002]} and second samples {GFAP [2.40 (0.30-3.10) vs. 0.30 (0.10-0.60) P = 0.003], GDNF [2.99 (0.56-10.30) vs. 1.46 (0.85-2.24) P = 0.019], and FABP-2 [646.8 (179.20-1,571.00) vs. 314.90 (184.70-521.60) P = 0.040]}. In infants with NEC, the median values of GFAP [2.40 (0.30-3.10) vs. 1.40 (0.20-6.50) P = 0.767], GDNF [2.99 (0.56-10.30) vs. 2.84 (1.05-14.11) P = 0.859], and FABP-2 [646.80 (179.20-1,571.00) vs. 621.70 (278.40-2,207.00) P = 0.953] in the second sample were higher than those in the first sample. Logistic regression demonstrated that GFAP at birth (Odds Ratio [OR] = 15.629, 95% Confidence Interval [CI] = 1.697-143.906, P = 0.015) and FABP-2 levels at birth (OR = 1.008, 95% CI = 1.001-1.015, P = 0.033) were significantly associated with an increased risk of NEC.

CONCLUSION

Increased GFAP, GDNF, and FABP-2 at birth are associated with NEC occurrence within two weeks of birth. These findings suggest that early-onset NEC is associated with intestinal injury that occurs during the perinatal or even prenatal period.

GFAP Alternative Splicing and the Relevance for Disease – A Focus on Diffuse Gliomas

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein that is characteristic for astrocytes and neural stem cells, and their malignant analogues in glioma. Since the discovery of the protein 50 years ago, multiple alternative splice variants of the GFAP gene have been discovered, leading to different GFAP isoforms. In this review, we will describe GFAP isoform expression from gene to protein to network, taking the canonical isoforms GFAPα and the main alternative variant GFAPδ as the starting point. We will discuss the relevance of studying GFAP and its isoforms in disease, with a specific focus on diffuse gliomas.

Antibody and Protein Profiles in Glaucoma: Screening of Biomarkers and Identification of Signaling Pathways

Simple Summary

Glaucoma is a chronic eye disease that is one of the leading causes of blindness worldwide. Currently, the only therapeutic option is to lower intraocular pressure. The onset of the disease is often delayed because patients do not notice visual impairment until very late, which is why glaucoma is also known as “the silent thief of sight”. Therefore, early detection and definition of specific markers, the so-called biomarkers, are immensely important. For the methodical implementation, high-throughput methods and omic-based methods came more and more into focus. Thus, interesting targets for possible biomarkers were already suggested by clinical research and basic research, respectively. This review article aims to join the findings of the two disciplines by collecting overlaps as well as differences in various clinical studies and to shed light on promising candidates concerning findings from basic research, facilitating conclusions on possible therapy options.

Abstract

Glaucoma represents a group of chronic neurodegenerative diseases, constituting the second leading cause of blindness worldwide. To date, chronically elevated intraocular pressure has been identified as the main risk factor and the only treatable symptom. However, there is increasing evidence in the recent literature that IOP-independent molecular mechanisms also play an important role in the progression of the disease. In recent years, it has become increasingly clear that glaucoma has an autoimmune component. The main focus nowadays is elucidating glaucoma pathogenesis, finding early diagnostic options and new therapeutic approaches. This review article summarizes the impact of different antibodies and proteins associated with glaucoma that can be detected for example by microarray and mass spectrometric analyzes, which (i) provide information about expression profiles and associated molecular signaling pathways, (ii) can possibly be used as a diagnostic tool in future and, (iii) can identify possible targets for therapeutic approaches.

Immunohistochemical analysis of vimentin expression in myocardial tissue from autopsy cases of ischemic heart disease

Vimentin is a type III intermediate filament cytoskeletal protein that is expressed mainly in cells of mesenchymal origin and is involved in a plethora of cellular functions. In this study, myocardial tissues from patients with ischemic heart disease and a mouse model of acute myocardial infarction were subjected to immunohistochemistry for vimentin. We first examined 26 neutral formalin-fixed, paraffin-embedded myocardial tissue samples from autopsies of patients that were diagnosed with ischemic heart disease within 48 h postmortem. Myocardial cells were negative for vimentin, whereas non-myocardial cells, including vascular endothelium, vascular smooth muscle, fibroblasts, nerve fibers, adipocytes and mesothelial cells, showed positivity. Elevated vimentin expression was observed around myocardial cells undergoing remodeling, suggesting fibroblastic and endothelial proliferation in these locations. By contrast, myocardial foci that were completely fibrotic did not show upregulated vimentin expression. Inflammatory foci including macrophages and neutrophils were clearly visualized with vimentin immunostaining. The same vimentin expression phenomena as those found in human samples were observed in the mouse model. Our study indicates that immunostaining of vimentin as a marker for myocardial remodeling and the dynamics of all non-myocardial cell types may be useful for supplementing conventional staining techniques currently used in the diagnosis of ischemic heart disease.

MicroSPECT Imaging-Guided Treatment of Idiopathic Pulmonary Fibrosis in Mice with a Vimentin-Targeting 99mTc-Labeled N-Acetylglucosamine-Polyethyleneimine

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic disease with poor prognosis. Evidence has shown that vimentin is a key regulator of lung fibrogenesis. ^99mTc-labeled N-acetylglucosamine-polyethyleneimine (NAG-PEI), a vimentin-targeting radiotracer, was used for the early diagnosis of IPF, and NAG-PEI was also used as a therapeutic small interfering RNA (siRNA) delivery vector for the treatment of IPF in this study. Single-photon emission-computed tomography (SPECT) imaging of bleomycin (BM)- and silica-induced IPF mice with ^99mTc-labeled NAG-PEI was performed to visualize pulmonary fibrosis and monitor the treatment efficiency of siRNA-loaded NAG-PEI, lipopolysaccharide (LPS, a tolerogenic adjuvant), or zymosan (ZYM, an immunostimulant). The lung uptakes of ^99mTc-NAG-PEI in the BM- and silica-induced IPF mice were clearly and directly correlated with IPF progression. The lung uptake of ^99mTc-NAG-PEI in the NAG-PEI/TGF-β1-siRNA treatment group or LPS treatment group was evidently lower than that in the control group, while the lung uptake of ^99mTc-NAG-PEI was significantly higher in the ZYM treatment group compared to that in the control group. These results demonstrate that NAG-PEI is a potent MicroSPECT imaging-guided theranostic platform for IPF diagnosis and therapy.

Senescent murine femoral arteries undergo vascular remodelling associated with accelerated stress-induced contractility and reactivity to nitric oxide

This work explored the mechanism of augmented stress-induced vascular reactivity of senescent murine femoral arteries (FAs). Mechanical and pharmacological reactivity of young (12-25 weeks, y-FA) and senescent (>104 weeks, s-FAs) femoral arteries was measured by wire myography. Expression and protein phosphorylation of selected regulatory proteins were studied by western blotting. Expression ratio of the Exon24 in/out splice isoforms of the regulatory subunit of myosin phosphatase, MYPT1 (MYPT1-Exon24 in/out), was determined by polymerase chain reaction (PCR). While the resting length-tension relationship showed no alteration, the stretch-induced-tone increased to 8.3 ± 0.9 mN in s-FA versus only 4.6 ± 0.3 mN in y-FAs. Under basal conditions, phosphorylation of the regulatory light chain of myosin at S19 was 19.2 ± 5.8% in y-FA versus 49.2 ± 12.6% in s-FA. Inhibition of endogenous NO release raised tone additionally to 10.4 ± 1.2 mN in s-FA, whereas this treatment had a negligible effect in y-FAs (4.8 ± 0.3 mN). In s-FAs, reactivity to NO donor was augmented (pD₂  = -4.5 ± 0.3 in y-FA vs. -5.2 ± 0.1 in senescent). Accordingly, in s-FAs, MYPT1-Exon24-out-mRNA, which is responsible for expression of the more sensitive to protein-kinase G, leucine-zipper-positive MYPT1 isoform, was increased. The present work provides evidence that senescent murine s-FA undergoes vascular remodelling associated with increases in stretch-activated contractility and sensitivity to NO/cGMP/PKG system.

The ependymal cell cytoskeleton in the normal and injured spinal cord of mice

The cytoskeleton of ependymal cells is fundamental to organize and maintain the normal architecture of the central canal (CC). However, little is known about the plasticity of cytoskeletal components after spinal cord injury. Here, we focus on the structural organization of the cytoskeleton of ependymal cells in the normal and injured spinal cord of mice (both females and males) using immunohistochemical and electron microscopy techniques. We found that in uninjured animals, the actin cytoskeleton (as revealed by phalloidin staining) was arranged following the typical pattern of polarized epithelial cells with conspicuous actin pools located in the apical domain of ependymal cells. Transmission electron microscopy images showed microvilli tufts, long cilia, and characteristic intercellular membrane specializations. After spinal cord injury, F-actin rearrangements paralleled by fine structural modifications of the apical domain of ependymal cells were observed. These changes involved disruptions of the apical actin pools as well as fine structural modifications of the microvilli tufts. When comparing the control and injured spinal cords, we also found modifications in the expression of vimentin and glial fibrillary acidic protein (GFAP). After injury, vimentin expression disappeared from the most apical domains of ependymal cells but the number of GFAP-expressing cells within the CC increased. As in other polarized epithelia, the plastic changes in the cytoskeleton may be critically involved in the reaction of ependymal cells following a traumatic injury of the spinal cord.

Elevated GFAP isoform expression promotes protein aggregation and compromises astrocyte function

Alexander disease (AxD) caused by mutations in the coding region of GFAP is a neurodegenerative disease characterized by astrocyte dysfunction, GFAP aggregation, and Rosenthal fiber accumulation. Although how GFAP mutations cause disease is not fully understood, Rosenthal fibers could be induced by forced overexpression of human GFAP and this could be lethal in mice implicate that an increase in GFAP levels is central to AxD pathogenesis. Our recent studies demonstrated that intronic GFAP mutations cause disease by altering GFAP splicing, suggesting that an increase in GFAP isoform expression could lead to protein aggregation and astrocyte dysfunction that typify AxD. Here we test this hypothesis by establishing primary astrocyte cultures from transgenic mice overexpressing human GFAP. We found that GFAP-δ and GFAP-κ were disproportionately increased in transgenic astrocytes and both were enriched in Rosenthal fibers of human AxD brains. In vitro assembly studies showed that while the major isoform GFAP-α self-assembled into typical 10-nm filaments, minor isoforms including GFAP-δ, -κ, and -λ were assembly-compromised and aggregation prone. Lentiviral transduction showed that expression of these minor GFAP isoforms decreased filament solubility and increased GFAP stability, leading to the formation of Rosenthal fibers-like aggregates that also disrupted the endogenous intermediate filament networks. The aggregate-bearing astrocytes lost their normal morphology and glutamate buffering capacity, which had a toxic effect on neighboring neurons. In conclusion, our findings provide evidence that links elevated GFAP isoform expression with GFAP aggregation and impaired glutamate transport, and suggest a potential non-cell-autonomous mechanism underlying neurodegeneration through astrocyte dysfunction.

Aging-Related Tau Astrogliopathy in Aging and Neurodegeneration

Astrocytes are of vital importance to neuronal function and the health of the central nervous system (CNS), and astrocytic dysfunction as a primary or secondary event may predispose to neurodegeneration. Until recently, the main astrocytic tauopathies were the frontotemporal lobar degeneration with tau (FTLD-tau) group of disorders; however, aging-related tau astrogliopathy (ARTAG) has now been defined. This condition is a self-describing neuropathology mainly found in individuals over 60 years of age. Astrocytic tau accumulates with a thorny or granular/fuzzy morphology and is commonly found in normal aging as well as coexisting with diverse neurodegenerative disorders. However, there are still many unknown factors associated with ARTAG, including the cause/s, the progression, and the nature of any clinical associations. In addition to FTLD-tau, ARTAG has recently been associated with chronic traumatic encephalopathy (CTE), where it has been proposed as a potential precursor to these conditions, with the different ARTAG morphological subtypes perhaps having separate etiologies. This is an emerging area of exciting research that encompasses complex neurobiological and clinicopathological investigation.

A report of two cases of bulbospinal form Alexander disease and preliminary exploration of the disease

Alexander disease (AxD) is a cerebral white matter disease affecting a wide range of ages, from infants to adults. In the present study, two cases of bulbospinal form AxD were reported, and a preliminary exploration of AxD was conducted thorough clinical, functional magnetic resonance imaging (fMRI) and functional analyses. In total, two de novo mutations in the glial fibrillary acidic protein (GFAP) gene (c.214G>A and c.1235C>T) were identified in unrelated patients (one in each patient). Both patients showed increased regional neural activity and functional connectivity in the cerebellum and posterior parietal cortex according to fMRI analysis. Notably, grey matter atrophy was discovered in the patient with c.214G>A variant. Functional experiments revealed aberrant accumulation of mutant GFAP and decreased solubility of c.1235C>T variant. Under pathological conditions, autophagic flux was activated for GFAP aggregate degradation. Moreover, transcriptional data of AxD and healthy human brain samples were obtained from the Gene Expression Omnibus database. Gene set enrichment analysis revealed an upregulation of immune‑related responses and downregulation of ion transport, synaptic transmission and neurotransmitter homeostasis. Enrichment analysis of cell‑specific differentially expressed genes also indicated a marked inflammatory environment in AxD. Overall, the clinical features of the two patients with bulbospinal form AxD were thoroughly described. To the best of our knowledge, the brain atrophy pattern and spontaneous brain functional network activity of patients with AxD were explored for the first time. Cytological experiments provided evidence of the pathogenicity of the identified variants. Furthermore, bioinformatics analysis found that inflammatory immune‑related reactions may play a critical role in AxD, which may be conducive to the understanding of this disease.

Astrocyte Activation in Neurovascular Damage and Repair Following Ischaemic Stroke

Transient or permanent loss of tissue perfusion due to ischaemic stroke can lead to damage to the neurovasculature, and disrupt brain homeostasis, causing long-term motor and cognitive deficits. Despite promising pre-clinical studies, clinically approved neuroprotective therapies are lacking. Most studies have focused on neurons while ignoring the important roles of other cells of the neurovascular unit, such as astrocytes and pericytes. Astrocytes are important for the development and maintenance of the blood-brain barrier, brain homeostasis, structural support, control of cerebral blood flow and secretion of neuroprotective factors. Emerging data suggest that astrocyte activation exerts both beneficial and detrimental effects following ischaemic stroke. Activated astrocytes provide neuroprotection and contribute to neurorestoration, but also secrete inflammatory modulators, leading to aggravation of the ischaemic lesion. Astrocytes are more resistant than other cell types to stroke pathology, and exert a regulative effect in response to ischaemia. These roles of astrocytes following ischaemic stroke remain incompletely understood, though they represent an appealing target for neurovascular protection following stroke. In this review, we summarise the astrocytic contributions to neurovascular damage and repair following ischaemic stroke, and explore mechanisms of neuroprotection that promote revascularisation and neurorestoration, which may be targeted for developing novel therapies for ischaemic stroke.

Skeletal and Cardiac Muscle Disorders Caused by Mutations in Genes Encoding Intermediate Filament Proteins

Intermediate filaments are major components of the cytoskeleton. Desmin and synemin, cytoplasmic intermediate filament proteins and A-type lamins, nuclear intermediate filament proteins, play key roles in skeletal and cardiac muscle. Desmin, encoded by the DES gene (OMIM *125660) and A-type lamins by the LMNA gene (OMIM *150330), have been involved in striated muscle disorders. Diseases include desmin-related myopathy and cardiomyopathy (desminopathy), which can be manifested with dilated, restrictive, hypertrophic, arrhythmogenic, or even left ventricular non-compaction cardiomyopathy, Emery–Dreifuss Muscular Dystrophy (EDMD2 and EDMD3, due to LMNA mutations), LMNA-related congenital Muscular Dystrophy (L-CMD) and LMNA-linked dilated cardiomyopathy with conduction system defects (CMD1A). Recently, mutations in synemin (SYNM gene, OMIM *606087) have been linked to cardiomyopathy. This review will summarize clinical and molecular aspects of desmin-, lamin- and synemin-related striated muscle disorders with focus on LMNA and DES-associated clinical entities and will suggest pathogenetic hypotheses based on the interplay of desmin and lamin A/C. In healthy muscle, such interplay is responsible for the involvement of this network in mechanosignaling, nuclear positioning and mitochondrial homeostasis, while in disease it is disturbed, leading to myocyte death and activation of inflammation and the associated secretome alterations.