T cell deletional tolerance restricts AQP4 but not MOG CNS autoimmunity

Aquaporin-4 (AQP4)-specific Th17 cells are thought to have a central role in neuromyelitis optica (NMO) pathogenesis. When modeling NMO, only AQP4-reactive Th17 cells from AQP4-deficient (AQP4-/-), but not wild-type (WT) mice, caused CNS autoimmunity in recipient WT mice, indicating that a tightly regulated mechanism normally ensures tolerance to AQP4. Here, we found that pathogenic AQP4 T cell epitopes bind MHC II with exceptionally high affinity. Examination of T cell receptor (TCR) α/β usage revealed that AQP4-specific T cells from AQP4-/- mice employed a distinct TCR repertoire and exhibited clonal expansion. Selective thymic AQP4 deficiency did not fully restore AQP4-reactive T cells, demonstrating that thymic negative selection alone did not account for AQP4-specific tolerance in WT mice. Indeed, AQP4-specific Th17 cells caused paralysis in recipient WT or B cell-deficient mice, which was followed by complete recovery that was associated with apoptosis of donor T cells. However, donor AQP4-reactive T cells survived and caused persistent paralysis in recipient mice deficient in both T and B cells or mice lacking T cells only. Thus, AQP4 CNS autoimmunity was limited by T cell-dependent deletion of AQP4-reactive T cells. In contrast, myelin oligodendrocyte glycoprotein (MOG)-specific T cells survived and caused sustained disease in WT mice. These findings underscore the importance of peripheral T cell deletional tolerance to AQP4, which may be relevant to understanding the balance of AQP4-reactive T cells in health and in NMO. T cell tolerance to AQP4, expressed in multiple tissues, is distinct from tolerance to MOG, an autoantigen restricted in its expression.

Ammonia induced microglia activation was associated with limited effects on connexin 43 and aquaporin 4 expression in an astrocyte-microglia co-culture model

Background

Hepatic encephalopathy (HE) is a neurological complication resulting from acute or chronic liver disease. Hyperammonemia leading to astrocyte swelling and cerebral edema in combination with neuroinflammation including microglia activation, mainly contribute to the pathogenesis of HE. However, little is known about microglia and their inflammatory response, as well as their influence on astrocytic channels and astrocyte swelling under hyperammonemia.

Objective

To investigate the effects of ammonia on the microglial activation and morphology in different set-ups of an in vitro astrocyte-microglia co-culture model. Further, potential effects on glial viability, connexin 43 (Cx43) and aquaporin 4 (AQP4) expression were tested.

Methods

Primary rat glial co-cultures of astrocytes containing 5% (M5, representing "physiological" conditions) or 30% (M30, representing "pathological" conditions) of microglia were incubated with 3 mM, 5 mM, 10 mM and 20 mM ammonium chloride (NH4Cl) for 6 h and 24 h in order to mimic the conditions of HE. An MTT assay was performed to measure the viability, proliferation and cytotoxicity of cells. The microglial phenotypes were analyzed by immunocytochemistry. The expression of Cx43 and AQP4 were quantified by immunoblot analysis.

Results

A significant reduction of glial viability was observed in M30 co-cultures after incubation with 20 mM NH4Cl for 6 h, whereas in M5 co-cultures the viability remained unchanged. Microglial activation was detected by immunocytochemistry after incubation with 3 mM, 5 mM and 10 mM NH4Cl for 6 h and 24 h in M5 as well as in M30 co-cultures. The Cx43 expression was slightly increased in M30 co-cultures after 6 h incubation with 5 mM NH4Cl. Also, the AQP4 expression was slightly increased only in M5 co-cultures treated with 10 mM NH4Cl for 6 h. Under the other conditions, Cx43 and AQP4 expression was not affected by NH4Cl.

Conclusions

The novel aspect of our study was the significant microglial activation and decrease of viability after NH4Cl incubation in different set-ups of an in vitro astrocyte-microglia co-culture model, contributing to better understanding of pathophysiological mechanisms of HE. Hyperammonemia led to limited effects on Cx43 and AQP4 expression, the relevance of these minimal changes should be viewed with caution.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-021-00628-1.

Microglia complement astrocytes in neuromyelitis optica

Neuromyelitis optica (NMO) is a central nervous system (CNS) inflammatory autoimmune disease caused by antibodies against aquaporin-4 (AQP4) expressed on astrocytes. Binding of AQP4-specific antibodies (NMO-IgG) triggers activation of the complement cascade, which is responsible for astrocyte loss and secondary demyelination. Although the role for the cytolytic complement proteins in astrocyte destruction in NMO is well established, little is known regarding the initial phase of astrocyte injury. In this issue of the JCI, Chen and colleagues evaluated the precytolytic phase when NMO-IgG binds astrocytes in vivo in the absence of exogenous complement. NMO-IgG alone caused astrocyte activation and AQP4 loss. Surprisingly, microglia, CNS-resident innate immune cells that produce endogenous complement, were required for clinical manifestations of disease, a finding that suggests microglia may serve as a therapeutic target in NMO.

Evaluation of the risk of cervical cancer in patients with Multiple Sclerosis treated with cytotoxic agents: A cohort study

Background: Since most patients with relapsing-remitting multiple sclerosis (RRMS) are women, the present study aimed to determine whether treatment of patients with MS by cytotoxic agents is associated with an increased risk of cervical dysplasia. Cancer screening is often neglected in the chronic diseases such as MS, so more attention in this field was needed. Decreasing morbidity and mortality due to cervical cancer is the most important goal of screening in female MS patients especially in child bearing age. Thus, it can be said that this is the first study which investigated this important issue. Methods: A total of 129 individuals participated in this cohort study. They were assigned into 3 groups including 43 patients with MS who were treated with cytotoxic drugs, 43 patients with MS on immunomodulators, and 43 normal healthy controls. Pap smears were performed following standard methods and the results obtained from the three groups were compared by statistical analysis. Demographic data, Expanded Disability Status Scale (EDSS), and Pap smear changes were analyzed by SPSS software. Results: The most commonly detected abnormality in all examined patients and healthy controls was inflammation. Five patients with MS who were treated with cytotoxic agents revealed benign cellular changes (BCC) in their Pap smear that were statistically significant in comparison with other groups (P = 0.03). Patients who took Mitoxantrone presented BCC more than other groups [Odds ratio (OR) = 9.44, 95% confidence interval (CI): 1.46-60.70]. There was no significant difference between mean duration of MS diagnosis (P = 0.12), mean duration of previous MS treatments (P = 0.25), and mean duration of current MS treatments (P = 0.21) in patients with BCC compared to normal healthy controls or inflammatory change. Conclusion: According to the results of present study, BCC is more frequently observed in patients with MS who were treated with cytotoxic agents with immunosuppressive effect. Since BCC is a 'premalignant condition', the authors suggest that mandatory annual Pap smear should be performed for patients with MS who are treated with cytotoxic agents irrespective of their age in order to detect early signs of malignancy.

Dexamethasone and levetiracetam reduce hetero-cellular gap-junctional coupling between F98 glioma cells and glial cells in vitro

Gap junctions (GJs) in astrocytes and glioma cells are important channels for cell-to-cell communication that contribute to homo- and heterocellular coupling. According to recent studies, heterocellular gap-junctional communication (H-GJC) between glioma cells and their surrounding environment enhances glioma progression. Therefore, we developed a new in vitro model to examine H-GJC between glioma cells, astrocytes and microglia. Consequently, F98 rat glioma cells were double-labeled with GJ-impermeable (CM-DiI) and GJ-permeable dye (calcein AM) and were seeded on unlabeled astrocyte-microglia co-cultures. Dual whole cell voltage clamp recordings were carried out on selected cell pairs to characterize the functional properties of H-GJC in vitro. The expression of four types of connexins (Cxs), including Cx32, Cx36, Cx43 and Cx45, and microglial phenotypes were analyzed by immunocytochemistry. The H-GJC between glioma cells and astrocytes/microglia increased after a longer incubation period with a higher number of glioma cells. We provided evidence for the direct GJ coupling of microglia and glioma cells under native in vitro conditions. In addition, we exploited this model to evaluate H-GJC after incubation with levetiracetam (LEV) and/or dexamethasone (DEX). Previous in vitro studies suggest that LEV and DEX are frequently used to control seizure and edema in glioma. Our findings showed that LEV and/or DEX decrease the number of heterocellular coupled cells significantly. In conclusion, our newly developed model demonstrated H-GJC between glioma cells and both astrocytes and microglia. The reduced H-GJC by LEV and DEX suggests a potential effect of both drugs on glioma progression.

Epigenetic regulation of lateralized fetal spinal gene expression underlies hemispheric asymmetries

Lateralization is a fundamental principle of nervous system organization but its molecular determinants are mostly unknown. In humans, asymmetric gene expression in the fetal cortex has been suggested as the molecular basis of handedness. However, human fetuses already show considerable asymmetries in arm movements before the motor cortex is functionally linked to the spinal cord, making it more likely that spinal gene expression asymmetries form the molecular basis of handedness. We analyzed genome-wide mRNA expression and DNA methylation in cervical and anterior thoracal spinal cord segments of five human fetuses and show development-dependent gene expression asymmetries. These gene expression asymmetries were epigenetically regulated by miRNA expression asymmetries in the TGF-β signaling pathway and lateralized methylation of CpG islands. Our findings suggest that molecular mechanisms for epigenetic regulation within the spinal cord constitute the starting point for handedness, implying a fundamental shift in our understanding of the ontogenesis of hemispheric asymmetries in humans.

DOI:http://dx.doi.org/10.7554/eLife.22784.001

Estradiol Receptors Regulate Differential Connexin 43 Expression in F98 and C6 Glioma Cell Lines

Introduction

Glioma is the most common malignant primary brain tumour with male preponderance and poor prognosis. Glioma cells express variable amounts of connexin 43 (Cx43) and estrogen receptors (ERs). Both, Cx43 and ERs, play important roles in cell proliferation and migration. Therefore, we investigated the effects of 17-ß estradiol (E2) on Cx43 expression in two glioma cell lines with variable native expression of Cx43.

Materials and Methods

F98 and C6 rat glioma cells were cultured for 24 h in the presence of 10 nM or 100 nM E2, and the E2-antagonist, Fulvestrant. An MTT assay was performed to evaluate cell viability. ERα, ERβ and Cx43 protein expressions were analysed by western blotting and Cx43 mRNA expression was analysed by real-time polymerase chain reaction. To quantify cell migration, an exclusive zone migration assay was used. Functional coupling of cells via gap junctions was examined using whole-cell patch-clamp technique.

Results

E2 reduced Cx43 expression in C6 cells, but increased Cx43 expression in F98 cultures. These effects were mediated via ERs. Moreover, E2 promoted C6 cell migration, but it did not affect F98 cell migration. The expression level of ERα was found to be high in C6, but low in F98 cells. ERβ was exclusively expressed in C6 cells. In addition, E2 treatment induced a significant decrease of ERβ in C6 cultures, while it decreased ERα expression in F98 glioma cells.

Discussion

These findings show that E2 differentially modulates Cx43 expression in F98 and C6 glioma cells, likely due to the differential expression of ERs in each of these cell lines. Our findings point to the molecular mechanisms that might contribute to the gender-specific differences in the malignancy of glioma and could have implications for therapeutic strategies against glioma.

Systemic Escherichia coli infection does not influence clinical symptoms and neurodegeneration in experimental autoimmune encephalomyelitis

Background

Systemic infections can influence the course of multiple sclerosis (MS), especially by driving recurrent acute episodes. The question whether the infection enhances tissue damage is of great clinical importance and cannot easily be assessed in clinical trials. Here, we investigated the effects of a systemic infection with Escherichia coli, a Gram-negative bacterium frequently causing urinary tract infections, on the clinical course as well as on neurodegeneration in experimental autoimmune encephalomyelitis (EAE), an animal model of MS.

Methods

Rats were immunized with myelin oligodendrocyte glycoprotein (MOG_1–125) and challenged intraperitoneally with live E. coli K1 in the preclinical or in the clinical phase of the disease. To ensure the survival of animals, antibiotic treatment with ceftriaxone was initiated 36 h after the infection and continued for 3 consecutive days.

Results

Systemic infection with E. coli did not influence the onset of clinical EAE symptoms or disease severity. Analysis of the optic nerve and retinal ganglion cells revealed no significant changes in the extent of inflammatory infiltrates, demyelination and neurodegeneration after E. coli infection.

Conclusions

We could not confirm the detrimental effect of lipopolysaccharide-induced systemic inflammation, a model frequently used to mimic the bacterial infection, previously observed in animal models of MS. Our results indicate that the effect of an acute E. coli infection on the course of MS is less pronounced than suspected and underline the need for adequate models to test the role of systemic infections in the pathogenesis of MS.

Influence of drugs on gap junctions in glioma cell lines and primary astrocytes in vitro

Gap junctions (GJs) are hemichannels on cell membrane. Once they are intercellulary connected to the neighboring cells, they build a functional syncytium which allows rapid transfer of ions and molecules between cells. This characteristic makes GJs a potential modulator in proliferation, migration, and development of the cells. So far, several types of GJs are recognized on different brain cells as well as in glioma. Astrocytes, as one of the major cells that maintain neuronal homeostasis, express different types of GJs that let them communicate with neurons, oligodendrocytes, and endothelial cells of the blood brain barrier; however, the main GJ in astrocytes is connexin 43. There are different cerebral diseases in which astrocyte GJs might play a role. Several drugs have been reported to modulate gap junctional communication in the brain which can consequently have beneficial or detrimental effects on the course of treatment in certain diseases. However, the exact cellular mechanism behind those pharmaceutical efficacies on GJs is not well-understood. Accordingly, how specific drugs would affect GJs and what some consequent specific brain diseases would be are the interests of the authors of this chapter. We would focus on pharmaceutical effects on GJs on astrocytes in specific diseases where GJs could possibly play a role including: (1) migraine and a novel therapy for migraine with aura, (2) neuroautoimmune diseases and immunomodulatory drugs in the treatment of demyelinating diseases of the central nervous system such as multiple sclerosis, (3) glioma and antineoplastic and anti-inflammatory agents that are used in treating brain tumors, and (4) epilepsy and anticonvulsants that are widely used for seizures therapy. All of the above-mentioned therapeutic categories can possibly affect GJs expression of astrocytes and the role is discussed in the upcoming chapter.

Multiple sclerosis in Iran: a demographic study of 8,000 patients and changes over time

BACKGROUND

Iran was formerly considered to be located in a low prevalence zone for multiple sclerosis (MS). During the last decade the number of patients has increased. This study was conducted to estimate the prevalence of MS in the capital city of the country.

METHODS

We re-evaluated the files of all patients who had registered at the Iranian Multiple Sclerosis Society during a 10-year period.

RESULTS

8,146 patients (72.3% female, 27.7% male) with a female-to-male ratio of 2.60 had registered. Mean age of disease onset was 27.24 (SD: 8.32). A relapsing-remitting pattern was recognized in 84.9% of the patients. The number of new registrations tripled from 2002 to 2008 and the female-to-male ratio increased from 2 to 3.12. The prevalence of MS in Tehran is estimated to be at least 51.9 per 100,000. Visual impairment was the main presenting symptom.

CONCLUSIONS

It seems that the prevalence of MS has increased to a medium-to-high risk level in Iran. The mean age of onset was similar to other studies but the calculated prevalence of early onset MS was increased. The cumulative data indicates that the female-to-male ratio is increasing annually.

Relapsing neuromyelitis optica: demographic and clinical features in Iranian patients

BACKGROUND

Neuromyelitis Optica (NMO) is a severe inflammatory demyelinating disease of the central nervous system with distinguishing features from multiple sclerosis (MS). NMO has an unknown etiology with poor prognosis in which anti-aquaporin-4 receptor IgG seems to play a major role. The purpose of this study is to represent a clinical and demographic data of NMO in Iranian population.

METHODS

Of 1800 patients attending our MS clinic, 44 patients with NMO were recruited from 2006 to 2009.

RESULTS

Female to male ratio was 3:1 and the disease affected women in younger ages than men (P = 0.04). The median expanded disability status scale score was 3 and the mean duration of symptoms was 4.53 +/- 3.41 (median = 4) years with annual relapse rate of 1.13 year/patient. The most frequent symptoms at presentation were optic neuritis 22 (50%) and transverse myelitis 14 (31.8%). Out of 12 patients whose titer of NMO-IgG was measured, four (30.7%) patients were seropositive. Twenty-eight patients (63%) received azathioprine for a mean duration of 16.84 +/- 27.91 months with significantly lower annual relapse rate (0.4 year/patient).

CONCLUSIONS

Iranian patients as a Caucasian population living in Asia seem to have the same clinical features in comparison with the reported studies from Western countries. Although the duration of follow-up was not too long, but they may possibly have a more benign course.

A survey of pediatricians' knowledge on asthma management in children

Asthma is one of the most common acute and chronic conditions in children, and the pediatricians are expected to provide an important role for asthma care in this age group, however there is no published information describing the different aspects of their practices about children asthma in Iran. This study was done to characterize the knowledge of the Iranian pediatricians about the diagnosis, treatment and education of asthma in children. Validated questionnaires were completed by 193 pediatricians from different parts of Iran during the International Congress of Pediatrics in Tehran. A total of 193 returned questionnaires (96.5%) were eligible for the survey and analysis. About 49% of the respondents were male and 18% were sub-specialists. Wheezing was the most common mentioned symptoms in taking asthma into consideration. About 40% of these physicians had no plan for doing spirometry in eligible children and 35.2% of them did not have familiarity with peak flowmeter. Also about 17.6% of them paid no regular visits to their asthmatic patients. Only 29% of the respondents indicated that they would prescribe inhaled corticosteroids for a 6-year-old child with moderate persistent asthma and 73.3% of them would prescribe inhaled bronchodilator (Salbutamol) for an acute asthmatic attack as the first drug, while 17.1% of them used epinephrine injection for this purpose. About 42.2% of the respondents did not consider any education or action plan for their patients and only 60.6% of them had access to standard guidelines and educational programs. The results show that there are numerous aspects of children asthma management in Iran which are not consistent with standardized guidelines and recommendations. This survey and the attained information suggest areas for interventions to improve the pediatricians' knowledge about asthma and the disease management.