α4-integrin deficiency in B cells does not affect disease in a T-cell-mediated EAE disease model

Objective

The goal of this study was to investigate the role of CD 19⁺ B cells within the brain and spinal cord during CNS autoimmunity in a peptide-induced, primarily T-cell–mediated experimental autoimmune encephalomyelitis (EAE) model of MS. We hypothesized that CD19⁺ B cells outside the CNS drive inflammation in EAE.

Methods

We generated CD19.Cre^+/− α4-integrin^fl/fl mice. EAE was induced by active immunization with myelin oligodendrocyte glycoprotein peptide (MOG_p35-55). Multiparameter flow cytometry was used to phenotype leukocyte subsets in primary and secondary lymphoid organs and the CNS. Serum cytokine levels and Ig levels were assessed by bead array. B-cell adoptive transfer was used to determine the compartment-specific pathogenic role of antigen-specific and non–antigen-specific B cells.

Results

A genetic ablation of α4-integrin in CD19^+/− B cells significantly reduced the number of CD19⁺ B cells in the CNS but does not affect EAE disease activity in active MOG_p35-55-induced disease. The composition of B-cell subsets in the brain, primary lymphoid organs, and secondary lymphoid organs of CD19.Cre^+/− α4-integrin^fl/fl mice was unchanged during MOG_p35-55-induced EAE. Adoptive transfer of purified CD19⁺ B cells from CD19.Cre^+/− α4-integrin^fl/fl mice or C57BL/6 wild-type (WT) control mice immunized with recombinant rMOG_1-125 or ovalbumin_323-339 into MOG_p35-55-immunized CD19.Cre^+/− α4-integrin^fl/fl mice caused worse clinical EAE than was observed in MOG_p35-55-immunized C57BL/6 WT control mice that did not receive adoptively transferred CD19⁺ B cells.

Conclusions

Observations made in CD19.Cre^+/− α4-integrin^fl/fl mice in active MOG_p35-55-induced EAE suggest a compartment-specific pathogenic role of CD19⁺ B cells mostly outside of the CNS that is not necessarily antigen specific.

TLR3 agonism re-establishes CNS immune competence during α4-integrin deficiency

OBJECTIVE

Natalizumab blocks α4-integrin-mediated leukocyte migration into the central nervous system (CNS). It diminishes disease activity in multiple sclerosis (MS), but carries a high risk of progressive multifocal encephalopathy (PML), an opportunistic infection with JV virus that may be prompted by diminished CNS immune surveillance. The initial host response to viral infections entails the synthesis of type I interferons (IFN) upon engagement of TLR3 receptors. We hypothesized that TLR3 agonism reestablishes CNS immune competence in the setting of α4-integrin deficiency.

METHOD

We generated the conditional knock out mouse strain Mx1.Cre+ α4-integrinfl/fl, in which the α4-integrin gene is ablated upon treatment with the TLR3 agonist poly I:C. Adoptive transfer of purified lymphocytes from poly I:C-treated Mx1.Cre+ α4-integrinfl/fl donors into naive recipients recapitulates immunosuppression under natalizumab. Active experimental autoimmune encephalomyelitis (EAE) in Mx1.Cre+ α4-integrinfl/fl mice treated with poly I:C represents immune-reconstitution.

RESULTS

Adoptive transfer of T cells from poly I:C treated Mx1.Cre+ α4-integrinfl/fl mice causes minimal EAE. The in vitro migratory capability of CD45+ splenocytes from these mice is reduced. In contrast, actively-induced EAE after poly I:C treatment results in full disease susceptibility of Mx1.Cre+ α4-integrinfl/fl mice, and the number and composition of CNS leukocytes is similar to controls. Extravasation of Evans Blue indicates a compromised blood-brain barrier. Poly I:C treatment results in a 2-fold increase in IFN β transcription in the spinal cord.

INTERPRETATION

Our data suggest that TLR3 agonism in the setting of relative α4-integrin deficiency can reestablish CNS immune surveillance in an experimental model. This pathway may present a feasible treatment strategy to treat and prevent PML under natalizumab therapy and should be considered for further experimental evaluation in a controlled setting.

A Single Amino Acid Substitution Prevents Recognition of a Dominant Human Aquaporin-4 Determinant in the Context of HLA-DRB1*03:01 by a Murine TCR

Background

Aquaporin 4 (AQP4) is considered a putative autoantigen in patients with Neuromyelitis optica (NMO), an autoinflammatory disorder of the central nervous system (CNS). HLA haplotype analyses of patients with NMO suggest a positive association with HLA-DRB1* 03:01. We previously showed that the human (h) AQP4 peptide 281–300 is the dominant immunogenic determinant of hAQP4 in the context of HLA-DRB1*03:01. This immunogenic peptide stimulates a strong Th₁ and Th₁₇ immune response. AQP4_281-300-specific encephalitogenic CD4⁺ T cells should initiate CNS inflammation that results in a clinical phenotype in HLA-DRB1*03:01 transgenic mice.

Methods

Controlled study with humanized experimental animals. HLA-DRB1*03:01 transgenic mice were immunized with hAQP4_281-300, or whole-length hAQP4 protein emulsified in complete Freund’s adjuvant. Humoral immune responses to both antigens were assessed longitudinally. In vivo T cell frequencies were assessed by tetramer staining. Mice were followed clinically, and the anterior visual pathway was tested by pupillometry. CNS tissue was examined histologically post-mortem. Flow cytometry was utilized for MHC binding assays and to immunophenotype T cells, and T cell frequencies were determined by ELISpot assay.

Results

Immunization with hAQP4_281-300 resulted in an in vivo expansion of antigen-specific CD4⁺ T cells, and an immunoglobulin isotype switch. HLA-DRB1*03:01 TG mice actively immunized with hAQP4_281-300, or with whole-length hAQP4 protein were resistant to developing a neurological disease that resembles NMO. Experimental mice show no histological evidence of CNS inflammation, nor change in pupillary responses. Subsequent analysis reveals that a single amino acid substitution from aspartic acid in hAQP4 to glutamic acid in murine (m)AQP4 at position 290 prevents the recognition of hAQP4_281-300 by the murine T cell receptor (TCR).

Conclusion

Induction of a CNS inflammatory autoimmune disorder by active immunization of HLA-DRB1*03:01 TG mice with human hAQP4_281-300 will be complex due to a single amino acid substitution. The pathogenic role of T cells in this disorder remains critical despite these observations.

A rare adult cause of dizziness

A 55-year-old man was seen with progressively worsening dizziness over 10 months. The initial assessment with unremarkable laboratory and imaging studies suggested a peripheral vestibular disorder. He was then lost to follow-up but later was seen with worsening ataxia. Additional imaging studies showed subtle parenchymal lesions in the posterior fossa. The differential diagnoses included nutritional deficiencies, autoimmune disorders, systemic malignancies, and intracranial tumors. The final diagnosis was confirmed by a biopsy.

The neonatal CNS is not conducive for encephalitogenic Th1 T cells and B cells during experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is thought to be a CD4⁺ T cell mediated autoimmune demyelinating disease of the central nervous system (CNS) that is rarely diagnosed during infancy. Cellular and molecular mechanisms that confer disease resistance in this age group are unknown. We tested the hypothesis that a differential composition of immune cells within the CNS modulates age-associated susceptibility to CNS autoimmune disease. C57BL/6 mice younger than eight weeks were resistant to experimental autoimmune encephalomyelitis (EAE) following active immunization with myelin oligodendrocyte glycoprotein (MOG) peptide (p) 35–55. Neonates also developed milder EAE after transfer of adult encephalitogenic T cells primed by adult or neonate antigen presenting cells (APC). There was a significant increase in CD45⁺ hematopoietic immune cells and CD45⁺ high side scatter granulocytes in the CNS of adults, but not in neonates. Within the CD45⁺ immune cell compartment of adults, the accumulation of CD4⁺ T cells, Gr-1⁺ and Gr-1^- monocytes and CD11c⁺ dendritic cells (DC) was identified. A significantly greater percentage of CD19⁺ B cells in the adult CNS expressed MHC II than neonate CNS B cells. Only in the adult CNS could IFNγ transcripts be detected 10 days post immunization for EAE. IFNγ is highly expressed by adult donor CD4⁺ T cells that are adoptively transferred but not by transferred neonate donor cells. In contrast, IL-17 transcripts could not be detected in adult or neonate CNS in this EAE model, and neither adult nor neonate donor CD4⁺ T cells expressed IL-17 at the time of adoptive transfer.

Dantrolene is neuroprotective in Huntington's disease transgenic mouse model

Background

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a polyglutamine expansion in the Huntingtin protein which results in the selective degeneration of striatal medium spiny neurons (MSNs). Our group has previously demonstrated that calcium (Ca²⁺) signaling is abnormal in MSNs from the yeast artificial chromosome transgenic mouse model of HD (YAC128). Moreover, we demonstrated that deranged intracellular Ca²⁺ signaling sensitizes YAC128 MSNs to glutamate-induced excitotoxicity when compared to wild type (WT) MSNs. In previous studies we also observed abnormal neuronal Ca²⁺ signaling in neurons from spinocerebellar ataxia 2 (SCA2) and spinocerebellar ataxia 3 (SCA3) mouse models and demonstrated that treatment with dantrolene, a ryanodine receptor antagonist and clinically relevant Ca²⁺ signaling stabilizer, was neuroprotective in experiments with these mouse models. The aim of the current study was to evaluate potential beneficial effects of dantrolene in experiments with YAC128 HD mouse model.

Results

The application of caffeine and glutamate resulted in increased Ca²⁺ release from intracellular stores in YAC128 MSN cultures when compared to WT MSN cultures. Pre-treatment with dantrolene protected YAC128 MSNs from glutamate excitotoxicty, with an effective concentration of 100 nM and above. Feeding dantrolene (5 mg/kg) twice a week to YAC128 mice between 2 months and 11.5 months of age resulted in significantly improved performance in the beam-walking and gait-walking assays. Neuropathological analysis revealed that long-term dantrolene feeding to YAC128 mice significantly reduced the loss of NeuN-positive striatal neurons and reduced formation of Htt^exp nuclear aggregates.

Conclusions

Our results support the hypothesis that deranged Ca²⁺ signaling plays an important role in HD pathology. Our data also implicate the RyanRs as a potential therapeutic target for the treatment of HD and demonstrate that RyanR inhibitors and Ca²⁺ signaling stabilizers such as dantrolene should be considered as potential therapeutics for the treatment of HD and other polyQ-expansion disorders.

Lymph node-derived donor encephalitogenic CD4+ T cells in C57BL/6 mice adoptive transfer experimental autoimmune encephalomyelitis highly express GM-CSF and T-bet

Experimental autoimmune encephalomyelitis (EAE) is a relevant animal model for the human demyelinating inflammatory disorder of the central nervous system (CNS), multiple sclerosis (MS). Induction of EAE by adoptive transfer allows studying the role of the donor T lymphocyte in disease pathogenesis. It has been challenging to reliably induce adoptive transfer EAE in C57BL/6 (H-2b) mice. The goal of this study was to develop a reproducible and high yield protocol for adoptive transfer EAE in C57BL/6 mice. A step-wise experimental approach permitted us to develop a protocol that resulted in a consistent relatively high disease incidence of ~70% in recipient mice. Donor mice were immunized with myelin oligodendrocyte glycoprotein (MOG)p35-55 in complete Freund's adjuvant (CFA) followed by pertussis toxin (PT). Only lymph node cells (LNC) isolated at day 12 post immunization, and restimulated in vitro for 72 hours with 10 μg/mL of MOGp35-55 and 0.5 ng/mL of interleukin-12 (IL-12) were able to transfer disease. The ability of LNC to transfer disease was associated with the presence of inflammatory infiltrates in the CNS at day 12. Interferon gamma (IFNγ) was produced at comparable levels in cell cultures prepared from mice at both day 6 and day 12 post immunization. By contrast, there was a trend towards a negative association between IL-17 and disease susceptibility in our EAE model. The amount of GM-CSF secreted was significantly increased in the culture supernatants from cells collected at day 12 post immunization versus those collected at day 6 post-immunization. Activated CD4+ T cells present in the day 12 LNC cultures maintained expression of the transcription factor T-bet, which has been shown to regulate the expression of the IL-23 receptor. Also, there was an increased prevalence of MOGp35-55-specific CD4+ T cells in day 12 LNC after in vitro re-stimulation. In summary, encephalitogenic LNC that adoptively transfer EAE in C57BL/6 mice were not characterized by a single biomarker in our study, but by a composite of inflammatory markers. Our data further suggest that GM-CSF expression by CD4+ T cells regulated by IL-23 contributes to their encephalitogenicity in our EAE model.

Twelve testable hypotheses on the geobiology of weathering

Critical Zone (CZ) research investigates the chemical, physical, and biological processes that modulate the Earth's surface. Here, we advance 12 hypotheses that must be tested to improve our understanding of the CZ: (1) Solar-to-chemical conversion of energy by plants regulates flows of carbon, water, and nutrients through plant-microbe soil networks, thereby controlling the location and extent of biological weathering. (2) Biological stoichiometry drives changes in mineral stoichiometry and distribution through weathering. (3) On landscapes experiencing little erosion, biology drives weathering during initial succession, whereas weathering drives biology over the long term. (4) In eroding landscapes, weathering-front advance at depth is coupled to surface denudation via biotic processes. (5) Biology shapes the topography of the Critical Zone. (6) The impact of climate forcing on denudation rates in natural systems can be predicted from models incorporating biogeochemical reaction rates and geomorphological transport laws. (7) Rising global temperatures will increase carbon losses from the Critical Zone. (8) Rising atmospheric P(CO2) will increase rates and extents of mineral weathering in soils. (9) Riverine solute fluxes will respond to changes in climate primarily due to changes in water fluxes and secondarily through changes in biologically mediated weathering. (10) Land use change will impact Critical Zone processes and exports more than climate change. (11) In many severely altered settings, restoration of hydrological processes is possible in decades or less, whereas restoration of biodiversity and biogeochemical processes requires longer timescales. (12) Biogeochemical properties impart thresholds or tipping points beyond which rapid and irreversible losses of ecosystem health, function, and services can occur.

Acid increases MAPK-mediated proliferation in Barrett's esophageal adenocarcinoma cells via intracellular acidification through a Cl-/HCO3- exchanger

Abundant epidemiological evidence links acid reflux to adenocarcinoma in Barrett's esophagus, but few studies have examined the cellular mechanisms by which acid promotes this neoplastic progression. We hypothesized that extracellular acid exposure causes intracellular acidification that triggers MAPK signaling and proliferation in Barrett's epithelial cells. We tested that hypothesis in a Barrett's-derived esophageal adenocarcinoma cell line (SEG-1). SEG-1 cells were exposed to varying concentrations of acid, and intracellular pH (pH(i)) was measured by 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein microfluorimetry. After acid exposure, ERK and p38 MAPK activation were measured by Western blot analysis and an immune complex kinase assay. Proliferation was measured by Coulter counter cell counts and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide incorporation assay. Exposure of SEG-1 cells to solutions with a pH between 3 and 6.5 caused a rapid, reversible decrease in pH(i) to a level approximately equal to extracellular pH. Acid exposure caused a rapid activation of both ERK and p38 MAPKs and also resulted in pH-dependent increases in cell number, with a maximum increase of 41% observed at pH 6.0. The MAPK activation and proliferation in SEG-1 cells induced by acid exposure could be blocked by pretreatment with disodium 4,4'-diisothiocyanatostilbine-2,2'-disulfonate (DIDS), which prevents intracellular acidification by inhibiting the Cl(-)/HCO(3)(-) exchanger. In conclusion, in SEG-1 cells, extracellular acid exposure causes intracellular acidification, which activates MAPK and causes proliferation. The magnitude of these effects is pH dependent, and the effects can be inhibited by preventing intracellular acidification with DIDS.