Ligation of metabotropic glutamate receptor 3 (Grm3) ameliorates lupus-like disease by reducing B cells

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

Notch1/Hes1‑PTEN/AKT/IL‑17A feedback loop regulates Th17 cell differentiation in mouse psoriasis‑like skin inflammation

IL‑17A, the effector cytokine of T helper (Th) 17 cells, plays a crucial role in the pathogenesis of psoriasis. The Notch1 and PI3K/AKT signaling pathways are implicated in Th17 cell differentiation and IL‑17A production. The present study aimed to evaluate the regulatory effect of the Notch1/hairy and enhancer of split 1 (Hes1)‑PTEN/AKT/IL‑17A feedback loop on Th17 cell differentiation via the PI3K/AKT inhibitor LY294002 in a mouse model of psoriasis. Mice were randomly divided into 3 groups: a control group, a model group [5% imiquimod (IMQ)‑induced group] and an intervention group (5% IMQ‑induced plus LY294002‑treated group). Skin structural characteristics were recorded and evaluated by hematoxylin and eosin staining. The weights of the spleens and inguinal lymph nodes were measured. Th17 cell percentage, as well as the mRNA and protein expression levels of Notch1, Notch1 intracellular domain (NICD1), Hes1, PTEN, AKT, phosphorylated (p)‑AKT, mTOR complex 1 (mTORC1), p‑mTORC1, S6 kinase (S6K)1, S6K2 and IL‑17A were detected in skin samples of the three experimental groups. Additionally, splenic mononuclear cells from model mice were treated by 10 and 50 µM LY294002 to further evaluate its regulatory effect on Notch1/Hes1‑PTEN/AKT/IL‑17A feedback loop. Increased Th17 cell percentage, increased expression of Notch1, NICD1, Hes1, AKT, p‑AKT, mTORC1, p‑mTORC1, S6K1, S6K2 and IL‑17A, and decreased PTEN levels were observed in model mice alongside marked psoriasis‑like skin inflammation, splenomegaly and lymphadenopathy. LY294002 treatment significantly alleviated the severity of psoriasis‑like skin inflammation in the intervention mice, attenuated the degree of epidermal hyperplasia and dermal inflammatory cell infiltration, and mitigated splenomegaly and lymphadenopathy. In addition, LY294002 treatment reversed the increased Th17 cell percentage, as well as the increased expression of Notch1, NICD1, Hes1, AKT, p‑AKT, mTORC1, p‑mTORC1, S6K1, S6K2 and IL‑17A, and the decreased expression of PTEN. In vitro study from 5% IMQ‑induced mouse splenic mononuclear cells presented that high dose of LY294002 exerted more obviously regulatory effect on Notch1/Hes1‑PTEN/AKT/IL‑17A feedback loop. The current findings suggested that the Notch1/Hes1‑PTEN/AKT/IL‑17A feedback loop regulates Th17 cell differentiation within the disease environment of psoriasis. Blocking the Notch1/Hes1‑PTEN/AKT/IL‑17A feedback loop may thus be a potential therapeutic method for management of psoriatic inflammation.

Gm614 Protects Germinal Center B Cells From Death by Suppressing Caspase-1 Transcription in Lupus-Prone Mice

Only a few signaling pathways have been reported in germinal center (GC) B-cell proliferation and death. In this study, we showed that a novel uncharacterized Gm614 protein is highly expressed in GC B cells from lupus-prone mice. Critically, ablation of this GC B-cell-specific Gm614 promoted GC B-cell death and mitigation of autoimmune symptoms, whereas overexpression protected GC B cells from death and exacerbated autoimmune symptoms. We demonstrated that mechanistically, nuclear-localized Gm614 reduced caspase-1 expression in GC B cells by binding with caspase-1 promoter to suppress its activation. Our results suggest that Gm614 protects GC B cells from death by suppressing caspase-1 transcription in autoimmune diseases. This may provide some hints for targeting the cell proliferation involved in autoimmune diseases.

Hspa13 Promotes Plasma Cell Production and Antibody Secretion

The generation of large numbers of plasma cells (PCs) is a main factor in systemic lupus erythematosus (SLE). We hypothesize that Hspa13, a member of the heat shock protein family, plays a critical role in the control of PC differentiation. To test the hypothesis, we used lipopolysaccharide (LPS)-activated B cells and a newly established mouse line with a CD19^cre-mediated, B cell–specific deletion of Hspa13: Hspa13 cKO mice. We found that Hspa13 mRNA was increased in PCs from atacicept-treated lupus-prone mice and in LPS-stimulated plasmablasts (PBs) and PCs. A critical finding was that PBs and PCs [but not naïve B cells and germinal center (GC) B cells] expressed high levels of Hspa13. In contrast, the Hspa13 cKO mice had a reduction in BPs, PCs, and antibodies induced in vitro by LPS and in vivo by sheep red blood cells (SRCs)- or 4-hydroxy-3-nitrophenylacetyl (NP)-immunization. Accordingly, the Hspa13 cKO mice had reduced class-switched and somatically hypermutated antibodies with defective affinity maturation. Our work also showed that Hspa13 interacts with proteins (e.g., Bcap31) in the endoplasmic reticulum (ER) to positively regulate protein transport from the ER to the cytosol. Importantly, Hspa13 mRNA was increased in B220⁺ cells from patients with multiple myeloma (MM) or SLE, whereas Hspa13 cKO led to reduced autoantibodies and proteinuria in both pristane-induced lupus and lupus-prone MRL/lpr mouse models. Collectively, our data suggest that Hspa13 is critical for PC development and may be a new target for eliminating pathologic PCs.

Gm40600 suppressed SP 2/0 isograft tumor by reducing Blimp1 and Xbp1 proteins

Background

Multiple myeloma (MM), characterized by cancerous proliferation of plasmablasts (PB) and plasma cells (PC), remains incurable in many patients. Differentially expressed molecules between MM PCs and healthy PCs have been explored in order to identify novel targets for treating MM. In the present study, we searched for novel MM therapeutic targets by comparing mRNA expression patterns between the Mus musculus myeloma plasmablast-like SP 2/0 cell line and LPS-induced PB/PC.

Methods

Gene expression profiles of LPS-induced PB/PC and SP 2/0 cells were determined using RNA-sequencing. A predicted gene (Gm40600) was found to be expressed at a low level in SP 2/0 cells. To study the role of Gm40600 in malignant PC, Gm40600 cDNA was cloned into a lentiviral vector (LV201) containing a puromycin selectable marker that was then transfected into SP 2/0 cells. Stable Gm40600-expressing SP 2/0 cells were selected using puromycin. The effect of Gm40600 on SP 2/0 cell proliferation, cell cycle/apoptosis, and tumor progression was assessed by cell counting kit-8 (CCK8), flow cytometry (FACS), and the SP 2/0 isograft mouse model, respectively. The effect of Gm40600 on mRNA and protein expression was evaluated by RNA-sequencing and western blotting, respectively.

Results

We found that SP 2/0 cells expressed lower level of Gm40600 mRNA as compared to LPS-induced PB/PC. Overexpression of Gm40600 significantly suppressed SP 2/0 cell proliferation and isograft tumor progression in an isograft mouse model by promoting apoptosis. In addition, Gm40600 overexpression suppressed transcription of the gene encoding Bcl2. Gm40600 overexpression also reduced the expression of PC-associated transcription factors Blimp1 and Xbp1, which promote transcription of the gene that encodes Bcl2.

Conclusions

Gm40600 reduced SP 2/0 cell proliferation and isograft tumor growth and progression by suppressing Blimp1 and Xbp1-mediated Bcl2 transcription to induce apoptosis. Thus, regulation of a human homolog of Gm40600, or associated factors, may be a potential therapeutic approach for treating MM.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5848-1) contains supplementary material, which is available to authorized users.

Loc108167440 suppressed myeloma cell growth by P53-mediated apoptosis

Multiple myeloma (MM) results from biased proliferation of cancerous plasma cells (PC). Therapeutic strategies that target MM PC will provide immense value to the treatment of MM. For this, it is necessary to identify novel molecules that differ between MM PC and healthy PC. RNA sequencing was used to determine differences in gene expression profiles between LPS-induced plasmablasts (PB)/PC and the PB-like myeloma SP 2/0 cell line. Compared to LPS-induced PB/PC, SP 2/0 cells expressed significantly lower levels of Loc108167440 mRNA. Loc108167440 overexpression reduced the number of SP 2/0 cells by stimulating apoptotic cell death. In addition, Loc108167440 overexpression suppressed tumor progression in the SP 2/0 xenograft mouse model. Finally, we demonstrated that Loc108167440 overexpression up-regulated expression of p53 in SP 2/0 cells. These results suggest that Loc108167440 overexpression suppressed SP 2/0 cell growth by inducing p53-mediated apoptosis. Thus, Loc108167440 overexpression may be a potential therapy for treating MM.

The E3 ubiquitin ligase Itch is required for B-cell development

The E3 ubiquitin ligase Itch interacts with Foxo1 and targets it for ubiquitination and degradation during follicular helper T-cell differentiation, whereas the transcription factor Foxo1 plays a critical role in B-cell development. Thus, we proposed that Itch mediates B-cell differentiation. Unexpectedly, we found that Itch deficiency downregulated Foxo1 expression in B cells. Itch cKO (conditional knock out in B cells) mice had fewer pro-B cells in the bone marrow, more small resting IgM⁻IgD⁻B cells in the periphery, and lower B-cell numbers in the lymph nodes through decreased Foxo1-mediated IL-7Rα, RAG, and CD62L expression, respectively. Importantly, Itch deficiency reduced Foxo1 mRNA expression by up-regulating JunB-mediated miR-182. Finally, Foxo1 negatively regulated JunB expression by up-regulating Itch. Thus, we have identified a novel regulatory axis between Itch and Foxo1 in B cells, suggesting that Itch is essential for B-cell development.

BC094916 suppressed SP 2/0 xenograft tumor by down-regulating Creb1 and Bcl2 transcription

Background

Both multiple myeloma (MM) and systemic lupus erythematosus (SLE) are associated with abnormal production of plasma cells, although their pathological mechanism of each disease is different. The main characteristic of both diseases is uncontrolled differentiation of B cells into plasmablast/plasma cells. Despite continuous research on prognostic factors and the introduction of new agents for MM and SLE, treatments still do not exist for controlling plasmablast/plasma cells. Thus, it is necessary to identify novel therapeutic targets of plasmablast/plasma cells. Because of its plasmablast-like characteristics, the mus musculus myeloma SP 2/0 cell line was used in this study to test the effect of a novel therapeutic agent (BC094916 overexpression) on plasmablast/plasma cells.

Methods

We first determined gene expression profiles of plasma cells using Affymetrix microarrays and RNA-sequencing. The effect of BC094916 on SP 2/0 cell proliferation, cell cycle, and apoptosis was determined by CCK8 and fluorescence-activated cell sorting. The SP 2/0 xenograft mouse model was used to assess the impact of BC094916 on tumor progression. The luciferase reporter system was used to evaluate the effect of BC094916 on Creb1 and Bcl2 transcription.

Results

We found that BC094916 mRNA was decreased in plasma cells. The mouse myeloma cell line SP 2/0 expressed low levels of BC094916 mRNA, whereas BC094916 overexpression suppressed SP 2/0 cell proliferation by inducing apoptosis. BC094916 overexpression suppressed tumor progression in the SP 2/0 xenograft mouse model. We also found that BC094916 mediate apoptosis by suppressing transcription of the Creb1 and Bcl2 genes, which promote the transcription of eukaryotic translation initiation and elongation factor genes.

Conclusions

BC094916 overexpression suppressed Creb1 and Bcl2 transcription to induce cell apoptosis, which suppressed SP 2/0 proliferation and xenograft tumor progression. Thus, BC094916 overexpression may be a potential therapeutic agent for treatment of MM and autoimmune diseases such as SLE.

Synthesis and Pharmacological Characterization of C4β-Amide-Substituted 2-Aminobicyclo[3.1.0]hexane-2,6-dicarboxylates. Identification of (1 S,2 S,4 S,5 R,6 S)-2-Amino-4-[(3-methoxybenzoyl)amino]bicyclo[3.1.0]hexane-2,6-dicarboxylic Acid (LY2794193), a Highly Potent and Selective mGlu3 Receptor Agonist

Multiple therapeutic opportunities have been suggested for compounds capable of selective activation of metabotropic glutamate 3 (mGlu₃) receptors, but small molecule tools are lacking. As part of our ongoing efforts to identify potent, selective, and systemically bioavailable agonists for mGlu₂ and mGlu₃ receptor subtypes, a series of C4_β-N-linked variants of (1 S,2 S,5 R,6 S)-2-amino-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 1 (LY354740) were prepared and evaluated for both mGlu₂ and mGlu₃ receptor binding affinity and functional cellular responses. From this investigation we identified (1 S,2 S,4 S,5 R,6 S)-2-amino-4-[(3-methoxybenzoyl)amino]bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 8p (LY2794193), a molecule that demonstrates remarkable mGlu₃ receptor selectivity. Crystallization of 8p with the amino terminal domain of hmGlu₃ revealed critical binding interactions for this ligand with residues adjacent to the glutamate binding site, while pharmacokinetic assessment of 8p combined with its effect in an mGlu₂ receptor-dependent behavioral model provides estimates for doses of this compound that would be expected to selectively engage and activate central mGlu₃ receptors in vivo.

Anti‑IL‑39 (IL‑23p19/Ebi3) polyclonal antibodies ameliorate autoimmune symptoms in lupus‑like mice

The interleukin (IL)-12 family cytokines have been examined as therapeutic targets in the treatment of several autoimmune diseases. Our previous study showed that a novel IL-12 family cytokine, IL-39 (IL-23p19/Ebi3) mediates inflammation in lupus-like mice. In the present study, the effect of anti-mouse IL-39 polyclonal antibodies on autoimmune symptoms in lupus-like mice was investigated. Rabbit anti-mouse IL-39 polyclonal antibodies were produced by immunization with recombinant mouse IL-39, and purified using protein A chromatography. These antibodies were subsequently used to treat lupus-like mice. Flow cytometry, captured images, ELISA and H&E staining were used to determine the effect of anti-IL-39 polyclonal antibodies on inflammatory cells, autoantibody titers, proteinuria, infiltrating inflammatory cells and the structure of the glomerular region. The anti-IL-39 polyclonal antibodies effectively reduced the numbers of inflammatory cells, splenomegaly, autoantibody titers, proteinuria, infiltrating inflammatory cells, and restored the structure of the glomerular region in MRL/lpr mice. Taken together, these results suggested that anti-IL-39 polyclonal antibodies ameliorated autoimmune symptoms in lupus-like mice. Therefore, IL-39 may be used as a possible target for the treatment of systemic lupus erythematosus.

Both Notch1 and its ligands in B cells promote antibody production

Notch1 signaling regulates B and T lymphocyte development and also in vitro promotes antibody secretion upon B cell activation. However, it is still unclear about the role of Notch1 in antibody production upon in vitro and in vivo mixture lymphocytes activation. We first showed that Notch1 expressed in LPS-activated CD19^hi B cells and CD19^cre mediated Notch1 knock-down in LPS-activated B cells. Furthermore, we demonstrated that Notch1 knock-down in B cells reduced antibody production in LPS-stimulated B cells but did not affect antibody production in LPS-stimulated splenocytes and in experimental allergic encephalomyelitis (EAE) mice. Importantly, Notch1 ligands Dll1 and Jag1 expressed in B cells and pre-coated Notch1 protein promotes Notch1-knocked down B cells to produce antibody in LPS-stimulated B cells suggesting that Notch1 in other cells may promote antibody production by binding its ligands Dll1 and Jag1 in B cells. Together, our results suggest that both Notch1 and its ligands in B cells play an important role in antibody production.

B cells regulate thymic CD8+T cell differentiation in lupus-prone mice

Previous studies have shown that under normal physiological conditions thymic B cells play a critical function in T cell negative selection. We tested the effect of thymic B cells on thymic T-cell differentiation in autoimmune diseases including systemic lupus erythematosus (SLE). We found that thymic B cells and CD8^- CD4⁺ and CD4^-CD8⁺T cells increased, whereas CD4⁺CD8⁺T cells decreased in lupus-prone mice. Once B cells were reduced, the change was reversed. Furthermore, we found that B cells blocked thymic immature single positive (ISP) CD4^-CD8⁺CD3^lo/-RORγt^- T cells progression into CD4⁺CD8⁺T cells. Interestingly, we found a novel population of thymic immature T cells (CD4^-CD8⁺CD3^loRORγt⁺) that were induced into mature CD4^-CD8⁺CD3⁺RORγt⁺T cells by B cells in lupus-prone mice. Importantly, we found that IgG, produced by thymic B cells, played a critical role in the differentiation of thymic CD8⁺ISP and mature RORγt⁺CD8⁺ T cells in lupus-prone mice. In conclusion, B cells blocked the differentiation from thymic CD8⁺ISP and induced the differentiation of a novel immature CD4^-CD8⁺CD3^loRORγt⁺T cells into mature RORγt⁺CD8⁺ T cells by secreting IgG antibody in lupus-prone mice.

Foxd3 suppresses interleukin-10 expression in B cells

Interleukin-10-positive (IL-10⁺ ) regulatory B (Breg) cells play an important role in restraining excessive inflammatory responses by secreting IL-10. However, it is still unclear what key transcription factors determine Breg cell differentiation. Hence, we explore what transcription factor plays a key role in the expression of IL-10, a pivotal cytokine in Breg cells. We used two types of web-based prediction software to predict transcription factors binding the IL-10 promoter and found that IL-10 promoter had many binding sites for Foxd3. Chromatin immunoprecipitation PCR assay demonstrated that Foxd3 directly binds the predicted binding sites around the start codon upstream by -1400 bp. Further, we found that Foxd3 suppressed the activation of IL-10 promoter by using an IL-10 promoter report system. Finally, knocking out Foxd3 effectively promotes Breg cell production by up-regulating IL-10 expression. Conversely, up-regulated Foxd3 expression was negatively associated with IL-10⁺ Breg cells in lupus-prone MRL/lpr mice. Hence, our data suggest that Foxd3 suppresses the production of IL-10⁺ Breg cells by directly binding the IL-10 promoter. This study demonstrates the mechanism for Breg cell production and its application to the treatment of autoimmune diseases by regulating Foxd3 expression.

Interleukin (IL)-39 [IL-23p19/Epstein-Barr virus-induced 3 (Ebi3)] induces differentiation/expansion of neutrophils in lupus-prone mice

Interleukin (IL)-12 family cytokines play critical roles in autoimmune diseases. Our previous study has shown that IL-23p19 and Epstein-Barr virus-induced 3 (Ebi3) form a new IL-12 family heterodimer, IL-23p19/Ebi3, termed IL-39, and knock-down of p19 or Ebi3 reduced diseases by transferred GL7⁺ B cells in lupus-prone mice. In the present study, we explore further the possible effect of IL-39 on murine lupus. We found that IL-39 in vitro and in vivo induces differentiation and/or expansion of neutrophils. GL7⁺ B cells up-regulated neutrophils by secreting IL-39, whereas IL-39-deficient GL7⁺ B cells lost the capacity to up-regulate neutrophils in lupus-prone mice and homozygous CD19^cre (CD19-deficient) mice. Finally, we found that IL-39-induced neutrophils had a positive feedback on IL-39 expression in activated B cells by secreting B cell activation factor (BAFF). Taken together, our results suggest that IL-39 induces differentiation and/or expansion of neutrophils in lupus-prone mice.

A novel IL-23p19/Ebi3 (IL-39) cytokine mediates inflammation in Lupus-like mice

Interleukin-12 family cytokines have emerged as critical regulators of immunity with some members (IL-12, IL-23) associated with disease pathogenesis while others (IL-27, IL-35) mitigate autoimmune diseases. Each IL-12 family member is comprised of an α and a β chain, and chain-sharing is a key feature. Although four bona fide members have thus far been described, promiscuous chain-pairing between alpha (IL-23p19, IL-27p28, IL-12/IL-35p35) and beta (IL-12/IL-23p40, IL-27/IL-35Ebi3) subunits, predicts six possible heterodimeric IL-12 family cytokines. Here, we describe a new IL-12 member composed of IL-23p19 and Ebi3 heterodimer (IL-39) that is secreted by LPS-stimulated B cells and GL7(+) activated B cells of lupus-like mice. We further show that IL-39 mediates inflammatory responses through activation of STAT1/STAT3 in lupus-like mice. Taken together, our results show that IL-39 might contribute to immunopathogenic mechanisms of systemic lupus erythematosus, and could be used as a possible target for its treatment.