Publications by authors named "Laurence Morel"

125 Publications

Suppressor of cytokine signaling-1 mimetic peptides attenuate lymphocyte activation in the MRL/lpr mouse autoimmune model.

Sci Rep 2021 Mar 18;11(1):6354. Epub 2021 Mar 18.

Department of Microbiology & Cell Science, University of Florida, Museum Road Building 981, PO Box 110700, Gainesville, FL, 32611, USA.

Autoimmune diseases are driven largely by a pathogenic cytokine milieu produced by aberrantly activated lymphocytes. Many cytokines, including interferon gamma (IFN-γ), utilize the JAK/STAT pathway for signal propagation. Suppressor of Cytokine Signaling-1 (SOCS1) is an inducible, intracellular protein that regulates IFN-γ signaling by dampening JAK/STAT signaling. Using Fas deficient, MRL/MpJ-Fas/J (MRL/lpr) mice, which develop lupus-like disease spontaneously, we tested the hypothesis that a peptide mimic of the SOCS1 kinase inhibitory region (SOCS1-KIR) would inhibit lymphocyte activation and modulate lupus-associated pathologies. Consistent with in vitro studies, SOCS1-KIR intraperitoneal administration reduced the frequency, activation, and cytokine production of memory CD8 and CD4 T lymphocytes within the peripheral blood, spleen, and lymph nodes. In addition, SOCS1-KIR administration reduced lymphadenopathy, severity of skin lesions, autoantibody production, and modestly reduced kidney pathology. On a cellular level, peritoneal SOCS1-KIR administration enhanced Foxp3 expression in total splenic and follicular regulatory T cells, reduced the effector memory/naïve T lymphocyte ratio for both CD4 and CD8 cells, and reduced the frequency of GL7 germinal center enriched B cells. Together, these data show that SOCS1-KIR treatment reduced auto-reactive lymphocyte effector functions and suggest that therapeutic targeting of the SOCS1 pathway through peptide administration may have efficacy in mitigating autoimmune pathologies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-021-86017-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7973732PMC
March 2021

D-mannose ameliorates autoimmune phenotypes in mouse models of lupus.

BMC Immunol 2021 Jan 5;22(1). Epub 2021 Jan 5.

Department of Pathology, Immunology and Laboratory Medicine, University of Florida, JHMHC 275, Box 100275, Gainesville, FL, 32610-0275, USA.

Background: Systemic lupus erythematosus is an autoimmune disease characterized by an overproduction of autoantibodies resulting from dysregulation in multiple immune cell types. D-mannose is a C epimer of glucose that exhibits immunoregulatory effects in models of autoimmune diseases, such as type 1 diabetes, induced rheumatoid arthritis, and airway inflammation. This study was conducted to evaluate the efficacy of D-mannose treatment in mouse models of lupus.

Results: Firstly, the effect of D-Mannose was evaluated by flow cytometry on the in vitro activation of non-autoimmune C57BL/6 (B6) bone marrow-derived dendritic cells (BMDCs) and their ability to induce antigen-specific CD4 T cell proliferation and activation. D-mannose inhibited the maturation of BMDCs and their induction of antigen-specific T cell proliferation and activation. In vivo, D-mannose increased the frequency of Foxp3 regulatory T cells in unmanipulated B6 mice. To assess the effect of D-mannose in mouse models of lupus, we used the graft-versus-host disease (cGVHD) induced model and the B6.lpr spontaneous model. In the cGVHD model, D-mannose treatment decreased autoantibody production, with a concomitant reduction of the frequency of effector memory and follicular helper T cells as well as germinal center B cells and plasma cells. These results were partially validated in the B6.lpr model of spontaneous lupus.

Conclusion: Overall, our results suggest that D-mannose ameliorates autoimmune activation in models of lupus, at least partially due to its expansion of Treg cells, the induction of immature conventional dendritic cells and the downregulation of effector T cells activation. D-Mannose showed however a weaker immunomodulatory effect in lupus than in other autoimmune diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12865-020-00392-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7786459PMC
January 2021

Effects of metformin on disease flares in patients with systemic lupus erythematosus: post hoc analyses from two randomised trials.

Lupus Sci Med 2020 10;7(1)

Rheumatology, Renji Hospital South Campus, Shanghai Jiaotong University School of Medicine, Shanghai, China

Objective: To confirm that metformin prevents flares in patients with SLE with low disease activity, we performed a post hoc analysis combining our previous two randomised trials.

Methods: Post hoc analyses were performed on data from the open-labelled proof-of-concept trial (n=113, ChiCTR-TRC-12002419) and placebo-controlled 'Met Lupus' trial (n=140, NCT02741960) comparing the efficacy of metformin versus placebo/nil add-on to standard therapy in patients with SLE with low disease activity (SELENA-SLEDAI ≤4). The primary endpoint was defined by the SELENA-SLEDAI Flare Index at 12-month follow-up. A subgroup analysis was performed.

Results: Overall, 201 eligible patients were included, with 99 allocated to metformin group and 102 allocated to the placebo/nil group. By 12 months of follow-up, 21 patients (21.2%) flared in the metformin group, as compared with 36 (35.3%) in the placebo/nil group (p=0.027, risk ratio=0.68, 95% CI 0.46 to 0.96). Subgroup analysis showed that patients with negative anti-dsDNA antibody and normal complement at baseline, and a disease duration <5 years with concomitant use of hydroxychloroquine had a better response to metformin.

Conclusion: Post hoc pooled analyses suggested that metformin reduced subsequent disease flares in patients with SLE with low disease activity, especially for serologically quiescent patients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/lupus-2020-000429DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7583791PMC
October 2020

Immunophenotyping reveals distinct subgroups of lupus patients based on their activated T cell subsets.

Clin Immunol 2020 Dec 29;221:108602. Epub 2020 Sep 29.

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL, USA; Division of Rheumatology and Clinical Immunology, Department of Medicine, University of Florida, Gainesville, FL, USA. Electronic address:

Objective: This study performed an integrated analysis of the cellular and transcriptional differences in peripheral immune cells between patients with Systemic Lupus Erythematosus (SLE) and healthy controls (HC).

Methods: Peripheral blood was analyzed using standardized flow cytometry panels. Transcriptional analysis of CD4 T cells was performed by microarrays and Nanostring assays.

Results: SLE CD4 T cells showed an increased expression of oxidative phosphorylation and immunoregulatory genes. SLE patients presented higher frequencies of activated CD38HLA-DR T cells than HC. Hierarchical clustering identified a group of SLE patients among which African Americans were overrepresented, with highly activated T cells, and higher frequencies of Th1, Tfh, and plasmablast cells. T cell activation was positively correlated with metabolic gene expression in SLE patients but not in HC.

Conclusions: SLE subjects presenting with activated T cells and a hyperactive metabolic signature may represent an opportunity to correct aberrant immune activation through targeted metabolic inhibitors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clim.2020.108602DOI Listing
December 2020

Intestinal Dysbiosis and Tryptophan Metabolism in Autoimmunity.

Front Immunol 2020 4;11:1741. Epub 2020 Aug 4.

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL, United States.

The development of autoimmunity involves complex interactions between genetics and environmental triggers. The gut microbiota is an important environmental constituent that can heavily influence both local and systemic immune reactivity through distinct mechanisms. It is therefore a relevant environmental trigger or amplifier to consider in autoimmunity. This review will examine recent evidence for an association between intestinal dysbiosis and autoimmune diseases, and the mechanisms by which the gut microbiota may contribute to autoimmune activation. We will specifically focus on recent studies connecting tryptophan metabolism to autoimmune disease pathogenesis and discuss evidence for a microbial origin. This will be discussed in the context of our current understanding of how tryptophan metabolites regulate immune responses, and how it may, or may not, be applicable to autoimmunity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2020.01741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7417361PMC
April 2021

Gut microbiota dysbiosis and altered tryptophan catabolism contribute to autoimmunity in lupus-susceptible mice.

Sci Transl Med 2020 07;12(551)

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL 32610, USA.

The autoimmune disease systemic lupus erythematosus (SLE) is characterized by the production of pathogenic autoantibodies. It has been postulated that gut microbial dysbiosis may be one of the mechanisms involved in SLE pathogenesis. Here, we demonstrate that the dysbiotic gut microbiota of triple congenic (TC) lupus-prone mice (B6.) stimulated the production of autoantibodies and activated immune cells when transferred into germfree congenic C57BL/6 (B6) mice. Fecal transfer to B6 mice induced autoimmune phenotypes only when the TC donor mice exhibited autoimmunity. Autoimmune pathogenesis was mitigated by horizontal transfer of the gut microbiota between co-housed lupus-prone TC mice and control congenic B6 mice. Metabolomic screening identified an altered distribution of tryptophan metabolites in the feces of TC mice including an increase in kynurenine, which was alleviated after antibiotic treatment. Low dietary tryptophan prevented autoimmune pathology in TC mice, whereas high dietary tryptophan exacerbated disease. Reducing dietary tryptophan altered gut microbial taxa in both lupus-prone TC mice and control B6 mice. Consequently, fecal transfer from TC mice fed a high tryptophan diet, but not a low tryptophan diet, induced autoimmune phenotypes in germfree B6 mice. The interplay of gut microbial dysbiosis, tryptophan metabolism and host genetic susceptibility in lupus-prone mice suggest that aberrant tryptophan metabolism may contribute to autoimmune activation in this disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/scitranslmed.aax2220DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7739186PMC
July 2020

Efficacy of the Combination of Metformin and CTLA4Ig in the (NZB × NZW)F1 Mouse Model of Lupus Nephritis.

Immunohorizons 2020 06 15;4(6):319-331. Epub 2020 Jun 15.

Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32610;

CTLA4Ig, a reagent that inhibits CD28 signaling, has shown therapeutic efficacy in mouse models of lupus nephritis (LN) when combined with several other biologics or standard of care drugs. Unfortunately, clinical trials treating LN patients with CTLA4Ig (abatacept) have not met endpoints. Metformin, a drug used to control hyperglycemia that inhibits mitochondrial metabolism, lowered the effective dose of glucocorticoids and prevented major flares when added on to the standard of care treatment of lupus patients with low disease activity. Metformin combined with inhibition of glycolysis by 2-deoxyglucose showed therapeutic efficacy in multiple mouse models of LN. Because CD28 signaling triggers glucose metabolism in T cells, we hypothesized that combining CTLA4Ig treatment with metformin would have the same effect. In this study, we showed that the combination of metformin and CTLA4Ig decreased the development of LN in (NZB × NZW)F1 mice treated at the early stage of disease. This preventive effect was associated with a decreased expansion of CD4 T cell effector subsets. However, contrary to the combination with 2-deoxyglucose, metformin combined with CTLA4Ig did not alter autoantibody production, suggesting different mechanisms of symptom mitigation. Overall, this study shows therapeutic efficacy of the combination of metformin and CTLA4Ig, two drugs with established safety records, in a preclinical mouse model of LN.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/immunohorizons.2000033DOI Listing
June 2020

T cells expressing the lupus susceptibility allele Pbx1d enhance autoimmunity and atherosclerosis in dyslipidemic mice.

JCI Insight 2020 06 4;5(11). Epub 2020 Jun 4.

Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, Florida, USA.

Patients with systemic lupus erythematosus (SLE) present a high incidence of atherosclerosis, which contributes significantly to morbidity and mortality in this autoimmune disease. An impaired balance between regulatory (Treg) and follicular helper (Tfh) CD4+ T cells is shared by both diseases. However, whether there are common mechanisms of CD4+ T cell dysregulation between SLE and atherosclerosis remains unclear. Pre-B cell leukemia transcription factor 1 isoform d (Pbx1d) is a lupus susceptibility gene that regulates Tfh cell expansion and Treg cell homeostasis. Here, we investigated the role of T cells overexpressing Pbx1d in low-density lipoprotein receptor-deficient (Ldlr-/-) mice fed with a high-fat diet, an experimental model for atherosclerosis. Pbx1d-transgenic T cells exacerbated some phenotypes of atherosclerosis, which were associated with higher autoantibody production, increased Tfh cell frequency, and impaired Treg cell regulation, in Ldlr-/- mice as compared with control T cells. In addition, we showed that dyslipidemia and Pbx1d-transgenic expression independently impaired the differentiation and function of Treg cells in vitro, suggesting a gene/environment additive effect. Thus, our results suggest that the combination of Pbx1d expression in T cells and dyslipidemia exacerbates both atherosclerosis and autoimmunity, at least in part through a dysregulation of Treg cell homeostasis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1172/jci.insight.138274DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7308052PMC
June 2020

Metabolic determinants of lupus pathogenesis.

Immunol Rev 2020 05 12;295(1):167-186. Epub 2020 Mar 12.

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL, USA.

The metabolism of healthy murine and more recently human immune cells has been investigated with an increasing amount of details. These studies have revealed the challenges presented by immune cells to respond rapidly to a wide variety of triggers by adjusting the amount, type, and utilization of the nutrients they import. A concept has emerged that cellular metabolic programs regulate the size of the immune response and the plasticity of its effector functions. This has generated a lot of enthusiasm with the prediction that cellular metabolism could be manipulated to either enhance or limit an immune response. In support of this hypothesis, studies in animal models as well as human subjects have shown that the dysregulation of the immune system in autoimmune diseases is associated with a skewing of the immunometabolic programs. These studies have been mostly conducted on autoimmune CD4 T cells, with the metabolism of other immune cells in autoimmune settings still being understudied. Here we discuss systemic metabolism as well as cellular immunometabolism as novel tools to decipher fundamental mechanisms of autoimmunity. We review the contribution of each major metabolic pathway to autoimmune diseases, with a focus on systemic lupus erythematosus (SLE), with the relevant translational opportunities, existing or predicted from results obtained with healthy immune cells. Finally, we review how targeting metabolic programs may present novel therapeutic venues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/imr.12847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7180129PMC
May 2020

Immune metabolism regulation of the germinal center response.

Exp Mol Med 2020 03 4;52(3):348-355. Epub 2020 Mar 4.

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL, USA.

The humoral immune response requires germinal centers to produce high-affinity antigen-specific antibodies that counter pathogens. Numerous studies have provided a better understanding of how metabolic pathways regulate the development, activation and functions of immune cells. Germinal centers are transient, highly dynamic microanatomic structures that develop in lymphoid organs during a T-cell-dependent humoral immune response. Analysis of germinal centers provides an opportunity to understand how metabolic programs control the differentiation and function of highly specialized germinal center B cells and follicular helper CD4 T cells. Targeting immunometabolism during the germinal center response may afford the possibility to improve vaccine design and to develop new therapies to alleviate autoimmunity. In this review, we discuss the major metabolic pathways that are used by germinal center B and T cells, as well as the plasma cells that they produce, all of which are influenced by the microenvironment of this unique structure of the adaptive immune system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s12276-020-0392-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7156389PMC
March 2020

Editorial: Mechanisms by Which SLE-Associated Genetic Variants Contribute to SLE Pathogenesis.

Front Immunol 2019 3;10:2808. Epub 2019 Dec 3.

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL, United States.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2019.02808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6901671PMC
November 2020

Emergency myelopoiesis contributes to immune cell exhaustion and pulmonary vascular remodelling.

Br J Pharmacol 2021 Jan 4;178(1):187-202. Epub 2020 Feb 4.

Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, College of Medicine, University of Florida, Gainesville, Florida.

Background And Purpose: Pulmonary hypertension (PH) secondary to chronic lung disease (World Health Organization Group 3 PH) is deadly, with lung transplant being the only available long-term treatment option. Myeloid-derived cells are known to affect progression of both pulmonary fibrosis and PH, although the mechanism of action is unknown. Therefore, we investigated the effect of myeloid cell proliferation induced by emergency myelopoiesis on development of PH and therapy directed against programmed death-ligand 1 (PD-L1), expressed by myeloid cells in prevention of pulmonary vascular remodelling.

Experimental Approach: LysM.Cre-DTR ("mDTR") mice were injected with bleomycin (0.018 U·g , i.p.) while receiving either vehicle or diphtheria toxin (DT; 100 ng, i.p.) to induce severe PH. Approximately 4 weeks after initiation of bleomycin protocol, right ventricular pressure measurements were performed and tissue samples collected for histologic assessment. In a separate experiment, DT-treated mice were given anti-PD-L1 antibody (αPD-L1; 500 μg, i.p.) preventive treatment before bleomycin administration.

Key Results: Mice undergoing induction of emergency myelopoiesis displayed more severe PH, right ventricular remodelling and pulmonary vascular muscularization compared to controls, without a change in lung fibrosis. This worsening of PH was associated with increased pulmonary myeloid-derived suppressor cell (MDSC), particularly polymorphonuclear MDSC (PMN-MDSC). Treatment with αPD-L1 normalized pulmonary pressures. PD-L1 expression was likewise found to be elevated on circulating PMN-MDSC from patients with interstitial lung disease and PH.

Conclusions And Implications: PD-L1 is a viable therapeutic target in PH, acting through a signalling axis involving MDSC.

Linked Articles: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/bph.14945DOI Listing
January 2021

Type I IFN Sensing by cDCs and CD4 T Cell Help Are Both Requisite for Cross-Priming of AAV Capsid-Specific CD8 T Cells.

Mol Ther 2020 03 15;28(3):758-770. Epub 2019 Nov 15.

Department Pediatrics, University of Florida, Gainesville, FL, USA; Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN, USA. Electronic address:

Adeno-associated virus (AAV) vectors are widely used in clinical gene therapy to correct genetic disease by in vivo gene transfer. Although the vectors are useful, in part because of their limited immunogenicity, immune responses directed at vector components have complicated applications in humans. These include, for instance, innate immune sensing of vector components by plasmacytoid dendritic cells (pDCs), which sense the vector DNA genome via Toll-like receptor 9. Adaptive immune responses employ antigen presentation by conventional dendritic cells (cDCs), which leads to cross-priming of capsid-specific CD8 T cells. In this study, we sought to determine the mechanisms that promote licensing of cDCs, which is requisite for CD8 T cell activation. Blockage of type 1 interferon (T1 IFN) signaling by monoclonal antibody therapy prevented cross-priming. Furthermore, experiments in cell-type-restricted knockout mice showed a specific requirement for the receptor for T1 IFN (IFNaR) in cDCs. In contrast, natural killer (NK) cells are not needed, indicating a direct rather than indirect effect of T1 IFN on cDCs. In addition, co-stimulation by CD4 T cells via CD40-CD40L was required for cross-priming, and blockage of co-stimulation but not of T1 IFN additionally reduced antibody formation against capsid. These mechanistic insights inform the development of targeted immune interventions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ymthe.2019.11.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054715PMC
March 2020

Regulating colonic dendritic cells by commensal glycosylated large surface layer protein A to sustain gut homeostasis against pathogenic inflammation.

Mucosal Immunol 2020 01 16;13(1):34-46. Epub 2019 Oct 16.

Department of Infectious Diseases and Immunology, University of Florida, Gainesville, FL, 32611, USA.

Microbial interaction with the host through sensing receptors, including SIGNR1, sustains intestinal homeostasis against pathogenic inflammation. The newly discovered commensal Propionibacterium strain, P. UF1, regulates the intestinal immunity against pathogen challenge. However, the molecular events driving intestinal phagocytic cell response, including colonic dendritic cells (DCs), by this bacterium are still elusive. Here, we demonstrate that the glycosylation of bacterial large surface layer protein A (LspA) by protein O-mannosyltransferase 1 (Pmt1) regulates the interaction with SIGNR1, resulting in the control of DC transcriptomic and metabolomic machineries. Programmed DCs promote protective T cell response to intestinal Listeria infection and resist chemically induced colitis in mice. Thus, our findings may highlight a novel molecular mechanism by which commensal surface glycosylation interacting with SIGNR1 directs the intestinal homeostasis to potentially protect the host against proinflammatory signals inducing colonic tissue damage.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41385-019-0210-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6917853PMC
January 2020

Alpha-1-Antitrypsin Ameliorates Pristane Induced Diffuse Alveolar Hemorrhage in Mice.

J Clin Med 2019 Aug 29;8(9). Epub 2019 Aug 29.

Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA.

Diffuse alveolar hemorrhage (DAH) is a fatal complication in patients with lupus. DAH can be induced in B6 mice by an intraperitoneal injection of pristane. Since human alpha-1-antitrypsin (hAAT) is an anti-inflammatory and immuno-regulatory protein, we investigated the protective effect of hAAT against pristane-induced DAH in B6 mice and hAAT transgenic (hAAT-Tg) mice. We first showed that hAAT Tg expression lowers TNF-α production in B cells, as well as CD4+ T cells in untreated mice. Conversely, the frequency of regulatory CD4+CD25+ and CD4+CD25-IL-10+ cells was significantly higher in hAAT-Tg than in B6 mice. This confirmed the anti-inflammatory effect of hAAT that was observed even at steady state. One week after a pristane injection, the frequency of peritoneal Ly6C inflammatory monocytes and neutrophils in hAAT-Tg mice was significantly lower than that in B6 mice. Importantly, pristane-induced DAH was completely prevented in hAAT-Tg mice and this was associated with a modulation of anti- to pro-inflammatory myeloid cell ratio/balance. We also showed that treatment with hAAT decreased the severity of DAH in B6 mice. These results showed for the first time that hAAT has a therapeutic potential for the treatment of DAH.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/jcm8091341DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6780888PMC
August 2019

Metabolic regulation of pathogenic autoimmunity: therapeutic targeting.

Curr Opin Immunol 2019 12 15;61:10-16. Epub 2019 Aug 15.

Department of Pathology, Immunology, and Laboratory Medicine, 1395 Center Drive, University of Florida, Gainesville, FL, 32610, USA. Electronic address:

Metabolism has recently emerged as an essential mechanism that regulates the immune system. Studies in healthy mice and, to a lesser extent, humans, have defined the metabolism of immune cells in response to various challenges. It is increasingly recognized that the overactive immune system that drives autoimmune diseases presents metabolic abnormalities that offer therapeutic opportunities. These novel therapeutic venues are supported by a few studies using metabolic inhibitors in mouse models and in small clinical trials. Reaching the full potential of targeting immuno-metabolism in autoimmune diseases requires a systemic cell-specific characterization of metabolic pathways in mouse models and cells from patients. Here, we review recent reports of immuno-metabolic alterations in autoimmune diseases, as well as alterations in immune effector pathways that have been implicated in autoimmunity, with a focus on systemic lupus erythematosus.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.coi.2019.07.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6901716PMC
December 2019

Metformin Inhibits the Type 1 IFN Response in Human CD4 T Cells.

J Immunol 2019 07 3;203(2):338-348. Epub 2019 Jun 3.

Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL 32610;

In systemic lupus erythematosus, defective clearance of apoptotic debris and activation of innate cells result in a chronically activated type 1 IFN response, which can be measured in PBMCs of most patients. Metformin, a widely used prescription drug for Type 2 diabetes, has a therapeutic effect in several mouse models of lupus through mechanisms involving inhibition of oxidative phosphorylation and a decrease in CD4 T cell activation. In this study, we report that in CD4 T cells from human healthy controls and human systemic lupus erythematosus patients, metformin inhibits the transcription of IFN-stimulated genes (ISGs) after IFN-α treatment. Accordingly, metformin inhibited the phosphorylation of pSTAT1 (Y701) and its binding to IFN-stimulated response elements that control ISG expression. These effects were independent of AMPK activation or mTORC1 inhibition but were replicated using inhibitors of the electron transport chain respiratory complexes I, III, and IV. This indicates that mitochondrial respiration is required for ISG expression in CD4 T cells and provides a novel mechanism by which metformin may exert a therapeutic effect in autoimmune diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1801651DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6615983PMC
July 2019

Targeting T Cell Activation and Lupus Autoimmune Phenotypes by Inhibiting Glucose Transporters.

Front Immunol 2019 17;10:833. Epub 2019 Apr 17.

Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL, United States.

CD4 T cells have numerous features of over-activated cellular metabolism in lupus patients and mouse models of the disease. This includes a higher glycolysis than in healthy controls. Glucose transporters play an essential role in glucose metabolism by controlling glucose import into the cell from the extracellular environment. We have previously shown that treatment of lupus-prone mice with 2-deoxy-D-glucose, which inhibits the first step of glycolysis was sufficient to prevent autoimmune activation. However, direct targeting of glucose transporters has never been tested in a mouse model of lupus. Here, we show that CG-5, a novel glucose transporter inhibitor, ameliorated autoimmune phenotypes in a spontaneous lupus-prone mouse model, B6.NZM2410. (Triple-congenic, TC), and in a chronic graft- vs. host-disease (cGVHD) model of induced lupus. , CG-5 blocked glycolysis in CD4 T cells, and limited the expansion of CD4 T cells induced by alloreactive stimulation. CG-5 also modulated CD4 T cell polarization by inhibiting Th1 and Th17 differentiation and promoting regulatory T (Treg) induction. Moreover, CG-5 treatment reduced lupus phenotypes including the expansion of germinal center B (GC B) cells, as well as the production of autoantibodies in both TC mice and cGVHD models. Finally, CG-5 blocked glycolysis in human T cells. Overall, our data suggest that blocking glucose uptake with a small molecule inhibitor ameliorates autoimmune activation, at least partially due to its inhibition of glycolysis in CD4 T cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2019.00833DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478810PMC
September 2020

A Variant of the Histone-Binding Protein sNASP Contributes to Mouse Lupus.

Front Immunol 2019 2;10:637. Epub 2019 Apr 2.

Department of Immunology, Weifang Medical University, Weifang, China.

The () sublocus is derived from the mouse lupus susceptibility 2 () locus identified in the NZM2410 model. Our current study dissected the functional characters and the genetic basis of the locus relative to lupus when co-expressed with the Fas mutation, an established inducer of autoimmunity. The rec1c.lpr mice exhibited mild expansion of lymph nodes and had a normal T cell cellularity, but developed significantly kidney and lung inflammation, indicating that the amplifies -induced autoimmune pathogenesis. A variant of somatic nuclear autoantigenic sperm protein (sNASP) was identified from the interval as a substitution of two consecutive amino acid residues in the histone-binding domain, resulting in an increased binding affinity to histone H4 and H3.1/H4 tetramer. To determine the role of the allele in mouse lupus, a novel strain was generated by introducing the mutations into the B6 genome. In this transgenic model, the allele synergized with the mutation leading to moderate autoimmune phenotypes and aggravating inflammatory pathology alterations in kidney and lung that were similar to those observed in the rec1c.lpr mice. These results establish that the allele is a pathogenic genetic element in the sublocus, which not only promotes autoimmunity, but also exacerbates the inflammation reaction of end organs in mouse lupus pathogenesis. It also shows the complexity of the locus, initially mapped as the major locus associated with B1a cell expansion. In addition to , which regulates this expansion, we have now identified in the same locus a protective allele of , a variant of Skint6 associated with T cell activation, and now a variant of that amplifies autoimmunity and tissue damage.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2019.00637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6454087PMC
June 2020

Immune Response-Dependent Assembly of IMP Dehydrogenase Filaments.

Front Immunol 2018 29;9:2789. Epub 2018 Nov 29.

Department of Oral Biology, University of Florida, Gainesville, FL, United States.

Inosine monophosphate dehydrogenase (IMPDH) catalyzes the conversion of IMP to xanthosine monophosphate, the rate-limiting step in guanosine monophosphate (GMP) synthesis. In cultured cells, IMPDH polymerizes into micron-scale filamentous structures when GMP synthesis is inhibited by depletion of purine precursors or by various drugs, including mycophenolic acid, ribavirin, and methotrexate. IMPDH filaments also spontaneously form in undifferentiated mouse embryonic stem cells and induced pluripotent stem cells, hinting they might function in various highly proliferative cell types. Therefore, we investigated IMPDH filament formation in human and murine T cells, which rely heavily on guanine nucleotide synthesis to rapidly proliferate in response to antigenic challenge. We discovered extensive IMPDH filament formation in mature T cells, B cells, and other proliferating splenocytes of normal, adult B6 mice. Both cortical and medullary thymocytes in young and old mice also showed considerable assembly of IMPDH filaments. We then stimulated primary human peripheral blood mononuclear cells with T cell mitogens phytohemagglutinin (PHA), concanavalin A (ConA), or antibodies to CD3 and CD28 for 72 h. We detected IMPDH filaments in 40-60% of T cells after activation compared to 0-10% of unstimulated T cells. Staining of activated T cells for the proliferation marker Ki-67 also showed an association between IMPDH filament formation and proliferation. Additionally, we transferred ovalbumin-specific CD4 T cells from B6.OT-II mice into B6.Ly5a recipient mice, challenged these mice with ovalbumin, and harvested spleens 6 days later. In these spleens, we identified abundant IMPDH filaments in transferred T cells by immunofluorescence, indicating that IMPDH also polymerizes during antigen-specific T cell activation. Overall, our data indicate that IMPDH filament formation is a novel aspect of T cell activation and proliferation, and that filaments might be useful morphological markers for T cell activation. The data also suggest that IMPDH filament formation could be occurring in a variety of proliferating cell types throughout the body. We propose that T cell activation will be a valuable model for future experiments probing the molecular mechanisms that drive IMPDH polymerization, as well as how IMPDH filament formation affects cell function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2018.02789DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6283036PMC
October 2019

Alpha 1 Antitrypsin Gene Therapy Extends the Lifespan of Lupus-Prone Mice.

Mol Ther Methods Clin Dev 2018 Dec 18;11:131-142. Epub 2018 Oct 18.

Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA.

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease characterized by high levels of pathogenic autoantibodies and tissue damage. Multiple studies showed that dendritic cell (DC) activation plays a critical role in SLE pathogenesis. Human alpha 1 antitrypsin (hAAT) is a serine proteinase inhibitor with potent anti-inflammatory and cytoprotective properties. In this study, we first examined the effects of hAAT on the functions of DCs from lupus-prone mice, and we showed that hAAT treatment efficiently inhibited CpG- (TLR9 agonist) induced activation of bone marrow-derived conventional and plasmacytoid DCs as well as the production of pro-inflammatory cytokines. The hAAT treatment also attenuated DC help for B cell proliferation and immunoglobulin M (IgM) production. We next tested the protective effect of hAAT protein and gene therapy using recombinant adeno-associated virus 8 (rAAV8-CB-hAAT) in a spontaneous lupus mouse model, and we showed that both treatments decreased autoantibody levels. Importantly, rAAV8-CB-hAAT did not induce an immune response to its transgene product (hAAT), but it showed more pronounced therapeutic effects in reducing urine protein levels and extending the lifespan of these mice. These results indicate that AAT has therapeutic potential in the treatment of SLE in humans.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.omtm.2018.10.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6258868PMC
December 2018

Impaired innate immune signaling due to combined Toll-like receptor 2 and 4 deficiency affects both periodontitis and atherosclerosis in response to polybacterial infection.

Pathog Dis 2018 11 1;76(8). Epub 2018 Nov 1.

Department of Periodontology, College of Dentistry, University of Florida, Gainesville, FL 32610, USA.

Plasma membrane-associated Toll-like receptor (TLR2 and TLR4) signaling contributes to oral microbe infection-induced periodontitis and atherosclerosis. We recently reported that either TLR2 or TLR4 receptor deficiency alters recognition of a consortium of oral pathogens, modifying host responses in periodontitis and atherosclerosis. We evaluated the effects of combined TLR2-/-TLR4-/- double knockout mice on innate immune signaling and induction of periodontitis and atherosclerosis after polybacterial infection with Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia and Fusobacterium nucleatum in a mouse model. Multispecies infections established gingival colonization in all TLR2-/-TLR4-/- mice and induced production of bacterial-specific IgG antibodies. In combined TLR2-/-TLR4-/- deficiency there was, however, reduced alveolar bone resorption and mild gingival inflammation with minimal migration of junctional epithelium and infiltration of inflammatory cells. This indicates a central role for TLR2 and TLR4 in periodontitis. Atherosclerotic plaque progression was markedly reduced in infected TLR2-/-TLR4-/- mice or in heterozygotes indicating a profound effect on plaque growth. However, bacterial genomic DNA was detected in multiple organs in TLR2-/-TLR4-/- mice indicating an intravascular dissemination from gingival tissue to heart, aorta, kidney and lungs. TRL2 and TLR4 were dispensable for systemic spread after polybacterial infections but TLR2 and 4 deficiency markedly reduces atherosclerosis induced by oral bacteria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/femspd/fty076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251349PMC
November 2018

Inhibition of glucose metabolism selectively targets autoreactive follicular helper T cells.

Nat Commun 2018 10 22;9(1):4369. Epub 2018 Oct 22.

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, 1395 Center Drive, Gainesville, FL, 32610, USA.

Follicular helper T (T) cells are expanded in systemic lupus erythematosus, where they are required to produce high affinity autoantibodies. Eliminating T cells would, however compromise the production of protective antibodies against viral and bacterial pathogens. Here we show that inhibiting glucose metabolism results in a drastic reduction of the frequency and number of T cells in lupus-prone mice. However, this inhibition has little effect on the production of T-cell-dependent antibodies following immunization with an exogenous antigen or on the frequency of virus-specific T cells induced by infection with influenza. In contrast, glutaminolysis inhibition reduces both immunization-induced and autoimmune T cells and humoral responses. Solute transporter gene signature suggests different glucose and amino acid fluxes between autoimmune T cells and exogenous antigen-specific T cells. Thus, blocking glucose metabolism may provide an effective therapeutic approach to treat systemic autoimmunity by eliminating autoreactive T cells while preserving protective immunity against pathogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-018-06686-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6197193PMC
October 2018

Inhibition of Glycolysis Reduces Disease Severity in an Autoimmune Model of Rheumatoid Arthritis.

Front Immunol 2018 3;9:1973. Epub 2018 Sep 3.

Immunology, and Laboratory Medicine, Department of Pathology, University of Florida, Gainesville, FL, United States.

The K/BxN mouse is a spontaneous model of arthritis driven by T cell receptor transgenic CD4 T cells from the KRN strain that are activated by glucose-6-phosphate isomerase (GPI) peptides presented by the H-2 allele from the NOD strain. It is a model of autoimmune seropositive arthritis because the production of anti-GPI IgG is necessary and sufficient for joint pathology. The production of high levels of anti-GPI IgG requires on the expansion of CD4 follicular helper T (Tfh) cells. The metabolic requirements of this expansion have never been characterized. Based on the therapeutic effects of the combination of metformin and 2-deoxyglucose (2DG) in lupus models that normalized the expansion of effector CD4 T cells. We showed that the CD4 T cells and to a lesser extent, the B cells from K/BxN mice are more metabolically active than the KRN controls. Accordingly, preventive inhibition of glycolysis with 2DG significantly reduced joint inflammation and the activation of both adaptive and innate immune cells, as well as the production of pathogenic autoantibodies. However, contrary to the lupus-prone mice, the addition of metformin had little beneficial effect, suggesting that glycolysis is the major driver of immune activation in this model. We propose that K/BxN mice are another model in which autoreactive Tfh cells are highly glycolytic and that their function can be limited by inhibiting glucose metabolism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2018.01973DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6130222PMC
September 2019

Protective Role of Myeloid Cells Expressing a G-CSF Receptor Polymorphism in an Induced Model of Lupus.

Front Immunol 2018 9;9:1053. Epub 2018 May 9.

Department of Pathology, Immunology, Laboratory Medicine, University of Florida Diabetes Institute, University of Florida, Gainesville, FL, United States.

The genetic analysis of the lupus-prone NZM2410 mouse has identified a suppressor locus, , which confers resistance to spontaneous lupus in combination with NZM2410 susceptibility loci, or in the chronic graft-versus-host disease (cGVHD) induced model of lupus in the B6. congenic strain. The candidate gene for , the gene encoding the granulocyte colony-stimulating factor receptor (G-CSF-R/CD114), was validated when cGVHD was restored in B6. mice after treatment with G-CSF. The goal of the project reported herein was to investigate the myeloid cells that confer resistance to cGVHD and to ascertain if the mechanism behind their suppression involves the G-CSF pathway. We showed that despite expressing the highest levels of G-CSF-R, neutrophils play only a modest role in the autoimmune activation induced by cGVHD. We also found reduced expression levels of G-CSF-R on the surface of dendritic cells (DCs) and a differential distribution of DC subsets in response to cGVHD in B6. versus B6 mice. The CD8α DC subset, known for its tolerogenic phenotype, was expanded upon induction of cGVHD in B6. mice. In addition, the deficiency of CD8α DC subset enhanced the severity of cGVHD in B6. and B6 mice, confirming their role in suppression of cGVHD. B6.DCs presented lowered activation and antigen presentation abilities and expressed lower levels of genes associated with DC activation and maturation. Exposure to exogenous G-CSF reversed the majority of these phenotypes, suggesting that tolerogenic DCs maintained through a defective G-CSF-R pathway mediated the resistance to cGVHD in B6. mice.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2018.01053DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5954343PMC
July 2019

Proliferation of hippocampal progenitors relies on p27-dependent regulation of Cdk6 kinase activity.

Cell Mol Life Sci 2018 Oct 4;75(20):3817-3827. Epub 2018 May 4.

Laboratory of Developmental Neurobiology, GIGA-Neurosciences, Quartier Hôpital, University of Liège, Avenue Hippocrate 15, B36 +1, 4000, Liège, Belgium.

Neural stem cells give rise to granule dentate neurons throughout life in the hippocampus. Upon activation, these stem cells generate fast proliferating progenitors that complete several rounds of divisions before differentiating into neurons. Although the mechanisms regulating the activation of stem cells have been intensively studied, little attention has been given so far to the intrinsic machinery allowing the expansion of the progenitor pool. The cell cycle protein Cdk6 positively regulates the proliferation of hippocampal progenitors, but the mechanism involved remains elusive. Whereas Cdk6 functions primarily as a cell cycle kinase, it can also act as transcriptional regulator in cancer cells and hematopoietic stem cells. Using mouse genetics, we show here that the function of Cdk6 in hippocampal neurogenesis relies specifically on its kinase activity. The present study also reveals a specific regulatory mechanism for Cdk6 in hippocampal progenitors. In contrast to the classical model of the cell cycle, we observe that the Cip/Kip family member p27, rather than the Ink4 family, negatively regulates Cdk6 in the adult hippocampus. Altogether, our data uncover a unique, cell type-specific regulatory mechanism controlling the expansion of hippocampal progenitors, where Cdk6 kinase activity is modulated by p27.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00018-018-2832-xDOI Listing
October 2018

Relative Contributions of B Cells and Dendritic Cells from Lupus-Prone Mice to CD4 T Cell Polarization.

J Immunol 2018 05 21;200(9):3087-3099. Epub 2018 Mar 21.

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL 32610;

Mouse models of lupus have shown that multiple immune cell types contribute to autoimmune disease. This study sought to investigate the involvement of B cells and dendritic cells in supporting the expansion of inflammatory and regulatory CD4 T cells that are critical for lupus pathogenesis. We used lupus-prone B6.NZM2410.Sle1.Sle2.Sle3 (TC) and congenic C57BL/6J (B6) control mice to investigate how the genetic predisposition of these two cell types controls the activity of normal B6 T cells. Using an allogeneic in vitro assay, we showed that TC B1-a and conventional B cells expanded Th17 cells significantly more than their B6 counterparts. This expansion was dependent on CD86 and IL-6 expression and mapped to the lupus-susceptibility locus. In vivo, TC B cells promoted greater differentiation of CD4 T cells into Th1 and follicular helper T cells than did B6 B cells, but they limited the expansion of Foxp3 regulatory CD4 T cells to a greater extent than did B6 B cells. Finally, when normal B6 CD4 T cells were introduced into Rag1 mice, TC myeloid/stromal cells caused their heightened activation, decreased Foxp3 regulatory CD4 T cell differentiation, and increased renal infiltration of Th1 and Th17 cells in comparison with B6 myeloid/stromal cells. The results show that B cells from lupus mice amplify inflammatory CD4 T cells in a nonredundant manner with myeloid/stromal cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1701179DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5915918PMC
May 2018

Regulatory T cells and TLR9 activation shape antibody formation to a secreted transgene product in AAV muscle gene transfer.

Cell Immunol 2019 08 1;342:103682. Epub 2017 Aug 1.

Department of Pediatrics, Division of Cellular and Molecular Therapy, University of Florida, Gainesville, FL, United States. Electronic address:

Adeno-associated viral (AAV) gene delivery to skeletal muscle is being explored for systemic delivery of therapeutic proteins. To better understand the signals that govern antibody formation against secreted transgene products in this approach, we administered an intramuscular dose of AAV1 vector expressing human coagulation factor IX (hFIX), which does not cause antibody formation against hFIX in C57BL/6 mice. Interestingly, co-administration of a TLR9 agonist (CpG-deoxyoligonucleotide, ODN) but not of lipopolysaccharide, caused a transient anti-hFIX response. ODN activated monocyte-derived dendritic cells and enhanced T follicular helper cell responses. While depletion of regulatory T cells (Tregs) also caused an antibody response, TLR9 activation combined with Treg depletion instead resulted in prolonged CD8 T cell infiltration of transduced muscle. Thus, Tregs modulate the response to the TLR9 agonist. Further, Treg re-population eventually resolved humoral and cellular immune responses. Therefore, specific modes of TLR9 activation and Tregs orchestrate antibody formation in muscle gene transfer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cellimm.2017.07.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5794662PMC
August 2019

An update on lupus animal models.

Curr Opin Rheumatol 2017 Sep;29(5):434-441

Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, Florida, USA.

Purpose Of Review: The complexity and heterogeneity of the clinical presentation in systemic lupus of erythematosus (SLE), combined to the inherent limitations of clinical research, have made it difficult to investigate the cause of this disease directly in patients. Various mouse models have been developed to dissect the cellular and genetic mechanisms of SLE, as well as to identify therapeutic targets and to screen treatments. The purpose of this review is to summarize the major spontaneous and induced mouse models of SLE and to provide an update on the major advances they have contributed to the field.

Recent Findings: Mouse models of SLE have continued to contribute to understand the cellular, signaling and metabolic mechanisms contributing to the disease and how targeting these pathways can provide therapeutic targets. Whenever possible, we discuss the advantage of using one model over the others to test a specific hypothesis.

Summary: Spontaneous and induced models of lupus models are useful tools for the study of the cause of the disease, identify therapeutic targets and screen treatments in preclinical studies. Each model shares specific subsets of attributes with the disease observed in humans, which provides investigators a tool to tailor to their specific needs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/BOR.0000000000000412DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5815391PMC
September 2017

B Cell Tolerance to Deiminated Histones in BALB/c, C57BL/6, and Autoimmune-Prone Mouse Strains.

Front Immunol 2017 30;8:362. Epub 2017 Mar 30.

Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, TN, USA.

Deimination, a posttranslational modification of arginine to citrulline carried out by peptidylarginine deiminases, may compromise tolerance of self-antigens. Patients with connective tissue autoimmunity, particularly rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), or Felty's syndrome, present with autoantibodies to deiminated histones (dH), which thus form a category of antibodies to citrullinated protein antigens (ACPA). In general, ACPA are a sensitive diagnostic for RA and may form in response to the release of nuclear chromatin (DNA plus dH) from granulocytes, usually referred to as neutrophil extracellular traps. The aim of this study was to examine spontaneously autoimmune mice for autoantibodies and T cell responses to dH. We compared IgG binding to deiminated and non-deiminated histones (nH) by ELISA and Western blotting in spontaneously autoimmune strains of (NZB × NZW) F and NZM2410 together with their derivative congenic strains, C57BL/6. and C57BL/6., which display profound autoreactivity against nuclear self-antigens. The splenocyte proliferation against the two antigens was determined in the spontaneously autoimmune (NZB × NZW) F strain from which other autoimmune strains used in the study were derived. Immunizations with dH and nH were attempted in BALB/c mice to assess their splenocyte response. Splenocytes from BALB/c mice and from autoimmune mice at the time of conversion to autoimmunity proliferated strongly in response to dH, yet serum IgG from autoimmune (NZB × NZW) F, NZM2410, and C57BL/6. mice displayed a remarkable bias against binding to dH. At the time of seroconversion, the antibodies already exhibited preference for nH, and only nH were recovered from circulating immune complexes. Analysis of histone deimination showed constitutive deimination in thymic extracts from C57BL/6 and C57BL/6. triply congenic mice and in spleens of autoimmune triply congenic mice. Our study demonstrates that tolerance mechanisms against dH are intact in BALB/c and C57BL/6 mice and continue to be effective in mice with overt autoimmunity to nH. We conclude that, in contrast to human RA and SLE patients, where we frequently observe autoantibodies against dH, autoimmune mice maintain strong tolerance mechanisms to prevent the development of autoantibodies to dH.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2017.00362DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371714PMC
March 2017