Oligodendrocyte-specific deletion of FGFR2 ameliorates MOG35-55 -induced EAE through ERK and Akt signalling

Immunopathogenesis of multiple sclerosis: molecular and cellular mechanisms and new immunotherapeutic approaches

BACKGROUND

Multiple sclerosis (MS) is a central nervous system (CNS) demyelinating autoimmune disease with increasing global prevalence. It predominantly affects females, especially those of European descent. The interplay between environmental factors and genetic predisposition plays a crucial role in MS etiopathogenesis.

METHODS

We searched recent relevant literature on reputable databases, which include, PubMed, Embase, Web of Science, Scopus, and ScienceDirect using the following keywords: multiple sclerosis, pathogenesis, autoimmunity, demyelination, therapy, and immunotherapy.

RESULTS

Various animal models have been employed to investigate the MS etiopathogenesis and therapeutics. Autoreactive T cells within the CNS recruit myeloid cells through chemokine expression, leading to the secretion of inflammatory cytokines driving the MS pathogenesis, resulting in demyelination, gliosis, and axonal loss. Key players include T cell lymphocytes (CD4+ and CD8+), B cells, and neutrophils. Signaling dysregulation in inflammatory pathways and the immunogenetic basis of MS are essential considerations for any successful therapy to MS. Data indicates that B cells and neutrophils also have significant roles in MS, despite the common belief that T cells are essential. High neutrophil-to-lymphocyte ratios correlate with MS severity, indicating their contribution to disease progression. Dysregulated signaling pathways further exacerbate MS progression.

CONCLUSION

MS remains incurable, but disease-modifying therapies, monoclonal antibodies, and immunomodulatory drugs offer hope for patients. Research on the immunogenetics and immunoregulatory functions of gut microbiota is continuing to provide light on possible treatment avenues. Understanding the complex interplay between genetic predisposition, environmental factors, and immune dysregulation is critical for developing effective treatments for MS.

Fibroblast growth factor receptor inhibitors mitigate the neuropathogenicity of Borrelia burgdorferi or its remnants ex vivo

In previous studies, we showed that fibroblast growth factor receptors (FGFRs) contribute to inflammatory mediator output from primary rhesus microglia in response to live Borrelia burgdorferi. We also demonstrated that non-viable B. burgdorferi can be as pathogenic as live bacteria, if not more so, in both CNS and PNS tissues. In this study we assessed the effect of live and non-viable B. burgdorferi in inducing FGFR expression from rhesus frontal cortex (FC) and dorsal root ganglion (DRG) tissue explants as well as their neuronal/astrocyte localization. Specific FGFR inhibitors were also tested for their ability to attenuate inflammatory output and apoptosis in response to either live or non-viable organisms. Results show that in the FC, FGFR2 was the most abundantly expressed receptor followed by FGFR3 and FGFR1. Non-viable B. burgdorferi significantly upregulated FGFR3 more often than live bacteria, while the latter had a similar effect on FGFR1, although both treatments did affect the expressions of both receptors. FGFR2 was the least modulated in the FC tissues by the two treatments. FGFR1 expression was more prevalent in astrocytes while FGFR2 and FGFR3 showed higher expression in neurons. In the DRG, all three receptor expressions were also seen, but could not be distinguished from medium controls by immunofluorescence. Inhibition of FGFR1 by PD166866 downregulated both inflammation and apoptosis in both FC and DRG in response to either treatment in all the tissues tested. Inhibition of FGFR1-3 by AZD4547 similarly downregulated both inflammation and apoptosis in both FC and DRG in response to live bacteria, while with sonicated remnants, this effect was seen in one of the two FC tissues and 2 of 3 DRG tissues tested. CCL2 and IL-6 were the most downregulated mediators in the FC, while in the DRG it was CXCL8 and IL-6 in response to FGFR inhibition. Downregulation of at least two of these three mediators was observed to downregulate apoptosis levels in general. We show here that FGFR inhibition can be an effective anti-inflammatory treatment in antibiotic refractive neurological Lyme. Alternatively, two biologics may be needed to effectively curb neuroinflammation and pathology in the CNS and PNS.

The small molecule fibroblast growth factor receptor inhibitor infigratinib exerts anti-inflammatory effects and remyelination in a model of multiple sclerosis

BACKGROUND AND PURPOSE

Fibroblast growth factors and receptors (FGFR) have been shown to modulate inflammation and neurodegeneration in multiple sclerosis (MS). The selective FGFR inhibitor infigratinib has been shown to be effective in cancer models. Here, we investigate the effects of infigratinib on prevention and suppression of first clinical episodes of myelin oligodendrocyte glycoprotein (MOG)35-55 -induced experimental autoimmune encephalomyelitis (EAE) in mice.

EXPERIMENTAL APPROACH

The FGFR inhibitor infigratinib was given over 10 days from the time of experimental autoimmune encephalomyelitis induction or the onset of symptoms. The effects of infigratinib on proliferation, cytotoxicity and FGFR signalling proteins were studied in lymphocyte cell lines and microglial cells.

KEY RESULTS

Administration of infigratinib prevented by 40% and inhibited by 65% first clinical episodes of the induced experimental autoimmune encephalomyelitis. In the spinal cord, infiltration of lymphocytes and macrophages/microglia, destruction of myelin and axons were reduced by infigratinib. Infigratinib enhanced the maturation of oligodendrocytes and increased remyelination. In addition, infigratinib resulted in an increase of myelin proteins and a decrease in remyelination inhibitors. Further, lipids associated with neurodegeneration such as lysophosphatidylcholine and ceramide were decreased as were proliferation of T cells and microglial cells.

CONCLUSION AND IMPLICATIONS

This proof of concept study demonstrates the therapeutic potential of targeting FGFRs in a disease model of multiple sclerosis. Application of oral infigratinib resulted in anti-inflammatory and remyelinating effects. Thus, infigratinib may have the potential to slow disease progression or even to improve the disabling symptoms of multiple sclerosis.

Fgf22 and Fgfr2b are required for neurogenesis and gliogenesis in the zebrafish forebrain

Fibroblast growth factors (Fgfs) play crucial roles in various developmental processes including brain development. We previously identified Fgf22 in zebrafish and found that fgf22 is involved in midbrain patterning during embryogenesis. Here, we investigated the role of Fgf22 in the formation of the zebrafish forebrain. We found that fgf22 was essential for determining the ventral properties of the telencephalon and diencephalon but not for cell proliferation. In addition, the knockdown of fgf22 inhibited the generation of glutamatergic neurons, γ-aminobutyric acid (GABA)ergic interneurons and astrocytes. Recently, Fgf signaling has received much attention because of its importance in the pathogenesis of multiple sclerosis, in which oligodendrocytes and myelin are destroyed. However, the effects of each Fgf on oligodendrocytes remain largely unknown. Therefore, we also investigated the role of Fgf22 in oligodendrocyte development and explored whether there is a difference between Fgf22 and other Fgfs. Knockdown of fgf22 promoted the generation of oligodendrocytes. Conversely, overexpression of fgf22 inhibited the generation of oligodendrocytes. Furthermore, the forebrain phenotypes of fgfr2b knockdown zebrafish were remarkably similar to those of fgf22 knockdown zebrafish. This establishes the Fgf22-Fgfr2b axis as a key ligand‒receptor partnership in neurogenesis and gliogenesis in the forebrain. Our results indicate that Fgf22 has a unique function in suppressing oligodendrocyte differentiation through Fgfr2b without affecting cell proliferation.

Overexpression of RBM34 Promotes Tumor Progression and Correlates with Poor Prognosis of Hepatocellular Carcinoma

BACKGROUND AND AIMS

Emerging evidence suggests that RNA-binding motif (RBM) proteins are involved in hepatocarcinogenesis and act either as oncogenes or tumor suppressors. The objective of this study was to investigate the role of RBM34, an RBM protein, in hepatocellular carcinoma (HCC).

METHODS

We first examined the expression of RBM34 across cancers. The correlation of RBM34 with clinicopathological features and the prognostic value of RBM34 for HCC was then investigated. Functional enrichment analysis of RBM34-related differentially expressed genes (DEGs) was performed to explore its biological function. RNA sequencing (RNA-seq) was applied to identify downstream genes and pathways affected upon RBM34 knockout. The correlation of RBM34 with immune characteristics was also analyzed. The oncogenic function of RBM34 was examined in in vitro and in vivo experiments.

RESULTS

RBM34 was highly expressed in hepatocellular carcinoma and correlated with poor clinicopathological features and prognosis. RBM34 was positively associated with tumor immune cell infiltration, biomarkers of immune cells, and immune checkpoint expression. A positive correlation was also observed between RBM34, T cell exhaustion, and regulatory T cell marker genes. Knockout of RBM34 significantly inhibited cell proliferation, migration, and xenograft tumor growth, and sensitized HCC cells to sorafenib treatment. RBM34 inhibition reduced FGFR2 expression and affected PI3K-AKT pathway activation in HCC cells.

CONCLUSIONS

Our study suggests that RBM34 may serve as a new prognostic marker and therapeutic target of HCC.

FGF/FGFR system in the central nervous system demyelinating disease: Recent progress and implications for multiple sclerosis

BACKGROUND

With millions of victims worldwide, multiple sclerosis is the second most common cause of disability among young adults. Although formidable advancements have been made in understanding the disease, the neurodegeneration associated with multiple sclerosis is only partially counteracted by current treatments, and effective therapy for progressive multiple sclerosis remains an unmet need. Therefore, new approaches are required to delay demyelination and the resulting disability and to restore neural function by promoting remyelination and neuronal repair.

AIMS

The article reviews the latest literature in this field.

MATERIALS AND METHODS

The fibroblast growth factor (FGF) signaling pathway is a promising target in progressive multiple sclerosis.

DISCUSSION

FGF signal transduction contributes to establishing the oligodendrocyte lineage, neural stem cell proliferation and differentiation, and myelination of the central nervous system. Furthermore, FGF signaling is implicated in the control of neuroinflammation. In recent years, interventions targeting FGF, and its receptor (FGFR) have been shown to ameliorate autoimmune encephalomyelitis symptoms in multiple sclerosis animal models moderately.

CONCLUSION

Here, we summarize the recent findings and investigate the role of FGF/FGFR signaling in the onset and progression, discuss the potential therapeutic advances, and offer fresh insights into managing multiple sclerosis.

Interferon Beta-1a versus Combined Interferon Beta-1a and Oligodendrocyte-Specific FGFR1 Deletion in Experimental Autoimmune Encephalomyelitis

Recombinant beta interferons-1 (IFNβ-1) are used as first line therapies in patients with relapsing multiple sclerosis (MS), a chronic inflammatory and neurodegenerative disease of the CNS. IFNβ-1a/b has moderate effects on the prevention of relapses and slowing of disease progression. Fibroblast growth factors (FGFs) and FGF receptors (FGFRs) are known to play a key role in the pathology of MS and its model EAE. To investigate the effects of short-term treatment with s.c. IFNβ-1a versus the combined application of s.c. IFNβ-1a and oligodendrocyte-specific deletion of FGFR1 (Fgfr1^ind−/− mice) in MOG_35-55-induced EAE. IFNβ-1a (30 mg/kg) was applied s.c. from days 0–7 p.i. of EAE in controls and Fgfr1^ind−/− mice. FGFR signaling proteins associated with inflammation/degeneration in MS/EAE were analyzed by western blot in the spinal cord. Further, FGFR1 in Oli-neu oligodendrocytes were inhibited by PD166866 and treated with IFNβ-1a (400 ng/mL). Application of IFNβ-1a over 8 days resulted in less symptoms only at the peak of disease (days 9–11) compared to controls. Application of IFNβ-1a in Fgfr1^ind−/− mice resulted in less symptoms primarily in the chronic phase of EAE. Fgfr1^ind−/− mice treated with IFNβ-1a showed increased expression of pERK and BDNF. In Oli-neu oligodendrocytes, treatment with PD166866 and IFNβ-1a also showed an increased expression of pERK and BDNF/TrkB. These data suggest that the beneficial effects in the chronic phase of EAE and on signaling molecules associated with ERK and BDNF expression are caused by the modulation of FGFR1 and not by interferon beta-1a. FGFR may be a potential target for therapy in MS.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Optical Coherence Tomography Angiography Characteristics Serve as Retinal Vein Occlusion Therapeutic Biomarkers for Dexamethasone Intravitreal Implant

Background

Retinal vein occlusion (RVO) is the second most common vision-threatening retinal vascular disease. Intravitreal dexamethasone implant has been applied to treat macular edema secondary to RVO (RVO-ME). However, the alteration of morphologic features detected with optical coherence tomography angiography (OCTA) has not been fully studied in RVO-ME patients before and after the treatment.

Objective

This study is aimed at identifying potential therapeutic targets in RVO with integrative bioinformatic analysis and compares the OCTA characteristics alterations in patients with RVO-ME receiving injection of dexamethasone intravitreal implant.

Methods

Bioinformatic analysis was analyzed in GSE101398 dataset from the Gene Expression Omnibus database. Multiple functional enrichment analyses were performed, and protein-protein interaction network was constructed to visualize the key node genes. Eleven eyes with RVO-ME were examined with OCTA before and after intravitreal dexamethasone implant. The OCTA parameters, including macular thickness, vessel density, foveal avascular zone parameters, the number of hyperreflective foci (HRF), area of cystoid edema, and subretinal fluid (SRF), were compared. The correlation was analyzed between best-corrected visual acuity (BCVA) and OCTA parameters.

Results

A total of 79 differentially expressed genes were identified. Functional enrichment analyses revealed the enriched inflammatory events in RVO. In RVO-ME, Pearson correlation revealed that baseline BCVA was positively correlated with the area of SRF and central macular thickness, while no correlation was detected between baseline BCVA and HRF number or the area of cystoid edema. The visual acuity improved, and the central macular thickness was decreased after intravitreal dexamethasone implant injection. Besides, the number of HRF, the area of cystoid edema, and SRF were significantly alleviated after dexamethasone intravitreal injection.

Conclusion

Retinal inflammation plays a crucial role in RVO pathogenesis. The imaging biomarkers of RVO including Müller glial intracellular edema, and retinal pigment epithelium dysfunction, could be assessed in OCTA and attenuated by intravitreal dexamethasone implant effectively.

Oligodendrocyte-Specific Deletion of FGFR1 Reduces Cerebellar Inflammation and Neurodegeneration in MOG35-55-Induced EAE

Multiple sclerosis (MS) is a chronic inflammatory and degenerative disease of the central nervous system (CNS). MS commonly affects the cerebellum causing acute and chronic symptoms. Cerebellar signs significantly contribute to clinical disability, and symptoms such as tremor, ataxia, and dysarthria are difficult to treat. Fibroblast growth factors (FGFs) and their receptors (FGFRs) are involved in demyelinating pathologies such as MS. In autopsy tissue from patients with MS, increased expression of FGF1, FGF2, FGF9, and FGFR1 was found in lesion areas. Recent research using mouse models has focused on regions such as the spinal cord, and data on the expression of FGF/FGFR in the cerebellum are not available. In recent EAE studies, we detected that oligodendrocyte-specific deletion of FGFRs results in a milder disease course, less cellular infiltrates, and reduced neurodegeneration in the spinal cord. The objective of this study was to characterize the role of FGFR1 in oligodendrocytes in the cerebellum. Conditional deletion of FGFR1 in oligodendrocytes (Fgfr1^ind−/−) was achieved by tamoxifen application, EAE was induced using the MOG_35-55 peptide. The cerebellum was analyzed by histology, immunohistochemistry, and western blot. At day 62 p.i., Fgfr1^ind−/− mice showed less myelin and axonal degeneration compared to FGFR1-competent mice. Infiltration of CD3(+) T cells, Mac3(+) cells, B220(+) B cells and IgG(+) plasma cells in cerebellar white matter lesions (WML) was less in Fgfr1^ind−/−mice. There were no effects on the number of OPC or mature oligodendrocytes in white matter lesion (WML). Expression of FGF2 and FGF9 associated with less myelin and axonal degeneration, and of the pro-inflammatory cytokines IL-1β, IL-6, and CD200 was downregulated in Fgfr1^ind−/− mice. The FGF/FGFR signaling protein pAkt, BDNF, and TrkB were increased in Fgfr1^ind−/− mice. These data suggest that cell-specific deletion of FGFR1 in oligodendrocytes has anti-inflammatory and neuroprotective effects in the cerebellum in the EAE disease model of MS.

Effects of FGFR Tyrosine Kinase Inhibition in OLN-93 Oligodendrocytes

Fibroblast growth factor (FGF) signaling is involved in the pathogenesis of multiple sclerosis (MS). Data from neuropathology studies suggest that FGF signaling contributes to the failure of remyelination in MS. In MOG_35–55-induced EAE, oligodendrocyte-specific deletion of FGFR1 and FGFR2 resulted in a less severe disease course, reduced inflammation, myelin and axon degeneration and changed FGF/FGFR and BDNF/TrkB signaling. Since signaling cascades in oligodendrocytes could not be investigated in the EAE studies, we here aimed to characterize FGFR-dependent oligodendrocyte-specific signaling in vitro. FGFR inhibition was achieved by application of the multi-kinase-inhibitor dovitinib and the FGFR1/2/3-inhibitor AZD4547. Both substances are potent inhibitors of FGF signaling; they are effective in experimental tumor models and patients with malignancies. Effects of FGFR inhibition in oligodendrocytes were studied by immunofluorescence microscopy, protein and gene analyses. Application of the tyrosine kinase inhibitors reduced FGFR1, phosphorylated ERK and Akt expression, and it enhanced BDNF and TrkB expression. Furthermore, the myelin proteins CNPase and PLP were upregulated by FGFR inhibition. In summary, inhibition of FGFR signaling in oligodendrocytes can be achieved by application of tyrosine kinase inhibitors. Decreased phosphorylation of ERK and Akt is associated with an upregulation of BDNF/TrkB signaling, which may be responsible for the increased production of myelin proteins. Furthermore, these data suggest that application of FGFR inhibitors may have the potential to promote remyelination in the CNS.

FGF/FGFR Pathways in Multiple Sclerosis and in Its Disease Models

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system (CNS) affecting more than two million people worldwide. In MS, oligodendrocytes and myelin sheaths are destroyed by autoimmune-mediated inflammation, while remyelination is impaired. Recent investigations of post-mortem tissue suggest that Fibroblast growth factor (FGF) signaling may regulate inflammation and myelination in MS. FGF2 expression seems to correlate positively with macrophages/microglia and negatively with myelination; FGF1 was suggested to promote remyelination. In myelin oligodendrocyte glycoprotein (MOG)35-55-induced experimental autoimmune encephalomyelitis (EAE), systemic deletion of FGF2 suggested that FGF2 may promote remyelination. Specific deletion of FGF receptors (FGFRs) in oligodendrocytes in this EAE model resulted in a decrease of lymphocyte and macrophage/microglia infiltration as well as myelin and axon degeneration. These effects were mediated by ERK/Akt phosphorylation, a brain-derived neurotrophic factor, and downregulation of inhibitors of remyelination. In the first part of this review, the most important pharmacotherapeutic principles for MS will be illustrated, and then we will review recent advances made on FGF signaling in MS. Thus, we will suggest application of FGFR inhibitors, which are currently used in Phase II and III cancer trials, as a therapeutic option to reduce inflammation and induce remyelination in EAE and eventually MS.