Co-stimulatory and adhesion molecules of dendritic cells in rheumatoid arthritis

Immunomodulatory Nanoparticles for Modulating Arthritis Flares

Disease-modifying drugs have improved the treatment for autoimmune joint disorders, such as rheumatoid arthritis, but inflammatory flares are a common experience. This work reports the development and application of flare-modulating poly(lactic-co-glycolic acid)-poly(ethylene glycol)-maleimide (PLGA-PEG-MAL)-based nanoparticles conjugated with joint-relevant peptide antigens, aggrecan70-84 and type 2 bovine collagen256-270. Peptide-conjugated PLGA-PEG-MAL nanoparticles encapsulated calcitriol, which acted as an immunoregulatory agent, and were termed calcitriol-loaded nanoparticles (CLNP). CLNP had a ∼200 nm hydrodynamic diameter with a low polydispersity index. In vitro, CLNP induced phenotypic changes in bone marrow derived dendritic cells (DC), reducing the expression of costimulatory and major histocompatibility complex class II molecules, and proinflammatory cytokines. Bulk RNA sequencing of DC showed that CLNP enhanced expression of Ctla4, a gene associated with downregulation of immune responses. In vivo, CLNP accumulated in the proximal lymph nodes after intramuscular injection. Administration of CLNP was not associated with changes in peripheral blood cell numbers or cytokine levels. In the collagen-induced arthritis and SKG mouse models of autoimmune joint disorders, CLNP reduced clinical scores, prevented bone erosion, and preserved cartilage proteoglycan, as assessed by high-resolution microcomputed tomography and histomorphometry analysis. The disease protective effects were associated with increased CTLA-4 expression in joint-localized DC and CD4+ T cells but without generalized suppression of T cell-dependent immune response. The results support the potential of CLNP as modulators of disease flares in autoimmune arthropathies.

CD83 Regulates the Immune Responses in Inflammatory Disorders

Activating the immune system plays an important role in maintaining physiological homeostasis and defending the body against harmful infections. However, abnormalities in the immune response can lead to various immunopathological responses and severe inflammation. The activation of dendritic cells (DCs) can influence immunological responses by promoting the differentiation of T cells into various functional subtypes crucial for the eradication of pathogens. CD83 is a molecule known to be expressed on mature DCs, activated B cells, and T cells. Two isotypes of CD83, a membrane-bound form and a soluble form, are subjects of extensive scientific research. It has been suggested that CD83 is not only a ubiquitous co-stimulatory molecule but also a crucial player in monitoring and resolving inflammatory reactions. Although CD83 has been involved in immunological responses, its functions in autoimmune diseases and effects on pathogen immune evasion remain unclear. Herein, we outline current immunological findings and the proposed function of CD83 in inflammatory disorders.

Targeting protein–protein interaction for immunomodulation: A sunflower trypsin inhibitor analog peptidomimetic suppresses RA progression in CIA model

Protein–protein interactions (PPI) of co-stimulatory molecules CD2-CD58 are important in the early stage of an immune response, and increased expression of these co-stimulatory molecules is observed in the synovial region of joints in rheumatoid arthritis (RA) patients. A CD2 epitope region that binds to CD58 was grafted on to sunflower trypsin inhibitor (SFTI) template structure to inhibit CD2-CD58 PPI. The peptide was incorporated with an organic moiety dibenzofuran (DBF) in its structure. The designed peptidomimetic was studied for its ability to inhibit CD2-CD58 interactions in vitro, and its thermal and enzymatic stability was evaluated. Stability studies indicated that the grafted peptidomimetic was stable against trypsin cleavage. In vivo studies using the collagen-induced arthritis (CIA) model in mice indicated that the peptidomimetic was able to slow down the progress of arthritis, an autoimmune disease in the mice model. These studies suggest that with the grafting of organic functional groups in the stable peptide template SFTI stabilizes the peptide structure, and these peptides can be used as a template to design stable peptides for therapeutic purposes.

Impact of intrarectal chromofungin treatment on dendritic cells-related markers in different immune compartments in colonic inflammatory conditions

BACKGROUND

Chromofungin (CHR: chromogranin-A 47-66) is a chromogranin-A derived peptide with anti-inflammatory and anti-microbial properties. Ulcerative colitis (UC) is characterized by a colonic decrease of CHR and a dysregulation of dendritic CD11c⁺ cells.

AIM

To investigate the association between CHR treatment and dendritic cells (DCs)-related markers in different immune compartments in colitis.

METHODS

A model of acute UC-like colitis using dextran sulphate sodium (DSS) was used in addition to biopsies collected from UC patients.

RESULTS

Intrarectal CHR treatment reduced the severity of DSS-induced colitis and was associated with a significant decrease in the expression of CD11c, CD40, CD80, CD86 and interleukin (IL)-12p40 in the inflamed colonic mucosa and CD11c, CD80, CD86 IL-6 and IL-12p40 within the mesenteric lymph nodes and the spleen. Furthermore, CHR treatment decreased CD80 and CD86 expression markers of splenic CD11c⁺ cells and decreased NF-κB expression in the colon and of splenic CD11c⁺ cells. In vitro, CHR decreased CD40, CD80, CD86 IL-6 and IL-12p40 expression in naïve bone marrow-derived CD11c⁺ DCs stimulated with lipopolysaccharide. Pharmacological studies demonstrated an impact of CHR on the NF-κB pathway. In patients with active UC, CHR level was reduced and showed a negative linear relationship with CD11c and CD86.

CONCLUSION

CHR has protective properties against intestinal inflammation via the regulation of DC-related markers and CD11c⁺ cells. CHR could be a potential therapy of UC.

Modulation of co-stimulatory signal from CD2-CD58 proteins by a grafted peptide

Peptides were designed to inhibit the protein-protein interaction of CD2 and CD58 to modulate the immune response. This work involved the design and synthesis of eight different peptides by replacing each amino acid residue in peptide 6 with alanine as well as grafting the peptide to the sunflower trypsin-inhibitor framework. From the alanine scanning studies, mutation at position 2 of the peptide was shown to result in increased potency to inhibit cell adhesion interactions. The most potent peptide from the alanine scanning was further studied for its detailed three-dimensional structure and binding to CD58 protein using surface plasmon resonance and flow cytometry. This peptide was used to graft to the sunflower trypsin inhibitor to improve the stability of the peptide. The grafted peptide, SFTI-a1, was further studied for its potency as well as its thermal, chemical, and enzymatic stability. The grafted peptide exhibited improved activity compared to our previously grafted peptide and was stable against thermal and enzymatic degradation.

Immunostimulatory Potential of MoS2 Nanosheets: Enhancing Dendritic Cell Maturation, Migration and T Cell Elicitation

BACKGROUND

Due to their extraordinary physical and chemical properties, MoS2 nanosheets (MSNs) are becoming more widely used in nanomedicine. However, their influence on immune systems remains unclear.

MATERIALS AND METHODS

Two few-layered MSNs at sizes of 100-250 nm (S-MSNs) and 400-500 nm (L-MSNs) were used in this study. Bone marrow-derived dendritic cells (DCs) were exposed to both MSNs at different doses (0, 8, 16, 32, 64, 128 µg/mL) for 48 h and subjected to analyses of surface marker expression, cytokine secretion, lymphoid homing and in vivo T cell priming.

RESULTS

Different-sized MSNs of all doses did not affect the viability of DCs. The expression of CD40, CD80, CD86 and CCR7 was significantly higher on both S-MSN- and L-MSN-treated DCs at a dose of 128 μg/mL. As the dose of MSN increased, the secretion of IL-12p70 remained unchanged, the secretion of IL-1β decreased, and the production of TNF-α increased. A significant increase in IL-6 was observed in the 128 µg/mL L-MSN-treated DCs. In particular, MSN treatment dramatically improved the ex vivo movement and in vivo homing ability of both the local resident and blood circulating DCs. Furthermore, the cytoskeleton rearrangement regulated by ROS elevation was responsible for the enhanced homing ability of the MSNs. More robust CD4+ and CD8+ T cell proliferation and activation (characterized by high expression of CD107a, CD69 and ICOS) was observed in mice vaccinated with MSN-treated DCs. Importantly, exposure to MSNs did not interrupt LPS-induced DC activation, homing and T cell priming.

CONCLUSION

Few-layered MSNs ranging from 100 to 500 nm in size could play an immunostimulatory role in enhancing DC maturation, migration and T cell elicitation, making them a good candidate for vaccine adjuvants. Investigation of this study will not only expand the applications of MSNs and other new transition metal dichalcogenides (TMDCs) but also shed light on the in vivo immune-risk evaluation of MSN-based nanomaterials.

Constrained Cyclic Peptides as Immunomodulatory Inhibitors of the CD2:CD58 Protein-Protein Interaction

The interaction between the cell-cell adhesion proteins CD2 and CD58 plays a crucial role in lymphocyte recruitment to inflammatory sites, and inhibitors of this interaction have potential as immunomodulatory drugs in autoimmune diseases. Peptides from the CD2 adhesion domain were designed to inhibit CD2:CD58 interactions. To improve the stability of the peptides, β-sheet epitopes from the CD2 region implicated in CD58 recognition were grafted into the cyclic peptide frameworks of sunflower trypsin inhibitor and rhesus theta defensin. The designed multicyclic peptides were evaluated for their ability to modulate cell-cell interactions in three different cell adhesion assays, with one candidate, SFTI-a, showing potent activity in the nanomolar range (IC50: 51 nM). This peptide also suppresses the immune responses in T cells obtained from mice that exhibit the autoimmune disease rheumatoid arthritis. SFTI-a was resistant to thermal denaturation, as judged by circular dichroism spectroscopy and mass spectrometry, and had a half-life of ∼24 h in human serum. Binding of this peptide to CD58 was predicted by molecular docking studies and experimentally confirmed by surface plasmon resonance experiments. Our results suggest that cyclic peptides from natural sources are promising scaffolds for modulating protein-protein interactions that are typically difficult to target with small-molecule compounds.

Targeting dendritic cell function during systemic autoimmunity to restore tolerance

Systemic autoimmune diseases can damage nearly every tissue or cell type of the body. Although a great deal of progress has been made in understanding the pathogenesis of autoimmune diseases, current therapies have not been improved, remain unspecific and are associated with significant side effects. Because dendritic cells (DCs) play a major role in promoting immune tolerance against self-antigens (self-Ags), current efforts are focusing at generating new therapies based on the transfer of tolerogenic DCs (tolDCs) during autoimmunity. However, the feasibility of this approach during systemic autoimmunity has yet to be evaluated. TolDCs may ameliorate autoimmunity mainly by restoring T cell tolerance and, thus, indirectly modulating autoantibody development. In vitro induction of tolDCs loaded with immunodominant self-Ags and subsequent cell transfer to patients would be a specific new therapy that will avoid systemic immunosuppression. Herein, we review recent approaches evaluating the potential of tolDCs for the treatment of systemic autoimmune disorders.

Oral bacteria induce a differential activation of human immunodeficiency virus-1 promoter in T cells, macrophages and dendritic cells

INTRODUCTION

The human immunodeficiency virus (HIV) can integrate into T cells, macrophages and dendritic cells resulting in a latent infection. Reports have also demonstrated that various microbial and host cell factors can trigger HIV reactivation leading to HIV recrudescence, potentially undermining highly active antiretroviral therapies.

METHODS

This study evaluated the capacity of oral bacteria associated with chronic periodontal infections to stimulate HIV promoter activation in various cell models of HIV latency.

RESULTS

T cells (1G5) challenged with oral bacteria demonstrated a dose-response of HIV promoter activation with a subset of the bacteria, as well as kinetics that were generally similar irrespective of the stimuli. Direct bacterial challenge of the T cells resulted in increased activation of approximately 1.5- to 7-fold over controls. Challenge of macrophages (BF24) indicated different kinetics for individual bacteria and resulted in consistent increases in promoter activation of five fold to six fold over basal levels for all bacteria except Streptococcus mutans. Dendritic cells showed increases in HIV reactivation of 7- to 34-fold specific for individual species of bacteria.

CONCLUSION

These results suggested that oral bacteria have the capability to reactivate HIV from latently infected cells, showing a relationship of mature dendritic cells > immature dendritic cells > macrophages > or = T cells. Expression of various pattern recognition receptors on these various cell types may provide insight into the primary receptors/signaling pathways used for reactivation by the bacteria.

Recruitment of dendritic cells and macrophages during T cell-mediated synovial inflammation

Adoptive transfer of adjuvant-induced arthritis was used in this study to examine local macrophages and dendritic cells (DCs) during T cell-mediated synovial inflammation. We studied the influx of CD11b⁺CD11c⁺ putative myeloid DCs and other non-lymphoid CD45⁺ cells into synovium-rich tissues (SRTs) of the affected hind paws in response to a pulse of autoreactive thoracic duct cells. Cells were prepared from the SRTs using a collagenase perfusion-digestion technique, thus allowing enumeration and phenotypic analysis by flow cytometry. Numbers of CD45⁺ cells increased during the first 6 days, with increases in CD45⁺MHC (major histocompatibility complex) II⁺ monocyte-like cells from as early as day 3 after transfer. In contrast, typical MHC II^- monocytes, mainly of the CD4^- subset, did not increase until 12 to 14 days after cell transfer, coinciding with the main influx of polymorphonuclear cells. By day 14, CD45⁺MHC II^hi cells constituted approximately half of all CD45⁺ cells in SRT. Most of the MHC II^hi cells expressed CD11c and CD11b and represented putative myeloid DCs, whereas only approximately 20% were CD163⁺ macrophages. Less than 5% of the MHC II^hi cells in inflamed SRT were CD11b^-, setting a maximum for any influx of plasmacytoid DCs. Of the putative myeloid DCs, a third expressed CD4 and both the CD4⁺ and the CD4^- subsets expressed the co-stimulatory molecule CD172a. Early accumulation of MHC II^hiCD11c⁺ monocyte-like cells during the early phase of T cell-mediated inflammation, relative to typical MHC II^- blood monocytes, suggests that recruited monocytes differentiate rapidly toward the DC lineage at this stage in the disease process. However, it is possible also that the MHC II^hiCD11c⁺ cells originate from a specific subset of DC-like circulating mononuclear cells.

Enumeration and phenotypical analysis of distinct dendritic cell subsets in psoriatic arthritis and rheumatoid arthritis

Dendritic cells (DCs) comprise heterogeneous subsets of professional antigen-presenting cells, linking innate and adaptive immunity. Analysis of DC subsets has been hampered by a lack of specific DC markers and reliable quantitation assays. We characterised the immunophenotype and functional characteristics of psoriatic arthritis (PsA)-derived and rheumatoid arthritis (RA)-derived myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) to evaluate their potential role in arthritis. Circulating peripheral blood (PB) pDC numbers were significantly reduced in PsA patients (P = 0.0098) and RA patients (P = 0.0194), and mDCs were significantly reduced in RA patients (P = 0.0086) compared with healthy controls. The number of circulating mDCs in RA PB was significantly inversely correlated to C-reactive protein (P = 0.021). The phenotype of both DC subsets in PsA PB and RA PB was immature as compared with healthy controls. Moreover, CD62L expression was significantly decreased on both mDCs (PsA, P = 0.0122; RA, P = 0.0371) and pDCs (PsA, P = 0.0373; RA, P = 0.0367) in PB. Both mDCs and pDCs were present in PsA synovial fluid (SF) and RA SF, with the mDC:pDC ratio significantly exceeding that in matched PB (PsA SF, P = 0.0453; RA SF, P = 0.0082). pDCs isolated from RA SF and PsA SF displayed an immature phenotype comparable with PB pDCs. RA and PsA SF mDCs, however, displayed a more mature phenotype (increased expression of CD80, CD83 and CD86) compared with PB mDCs. Functional analysis revealed that both SF DC subsets matured following toll-like receptor stimulation. pDCs from PB and SF produced interferon alpha and tumour necrosis factor alpha on TLR9 stimulation, but only SF pDCs produced IL-10. Similarly, mDCs from PB and SF produced similar tumour necrosis factor alpha levels to TLR2 agonism, whereas SF mDCs produced more IL-10 than PB controls. Circulating DC subset numbers are reduced in RA PB and PsA PB with reduced CD62L expression. Maturation is incomplete in the inflamed synovial compartment. Immature DCs in SF may contribute to the perpetuation of inflammation via sampling of the inflamed synovial environment, and in situ presentation of arthritogenic antigen.

New therapeutics that treat rheumatoid arthritis by blocking T-cell activation

Despite the recent introduction of several new biological products, there remains a significant unmet medical need in rheumatoid arthritis. A focus on the aberrant activation of autoimmune T cells, which is integral to pathogenesis, is a promising approach involved in several of these new therapies. In choosing a molecular target for the modification of T-cell function, it is argued in this article, that within co-stimulatory pathways, CD80 could have a more compelling rationale than CD86. Data are presented showing that CD80-mediated T-cell activation can be inhibited using a small-molecule antagonist, which offers the potential to prevent the inflammatory process leading to joint destruction.

MHC II+ CD45+ cells from synovium-rich tissues of normal rats: phenotype, comparison with macrophage and dendritic cell lineages and differentiation into mature dendritic cells in vitro

Synovial tissues are frequent sites of inflammatory disorders in which dendritic cells (DCs) may play an important role. This study examines potential antigen-presenting cells obtained from synovium-rich tissues (SRTs) by vascular perfusion of rat hind limbs with collagenase and further enzymatic digestion of the disarticulated hind paws in vitro. The three sub-populations of interest were: CD45+MHC IIhi, mainly CD11c+ and CD163-; CD45+MHC IIlo, mainly CD11c- and CD163+ and CD45+MHC II-, mainly CD11c- and CD163+. Expression of CD11c and CD163 correlated with ruffled cell-surface (CD11c+CD163-) and highly vacuolated cytoplasm (CD11c-CD163+), respectively. Culture of the CD45+CD163- sub-population in granulocyte macrophage colony-stimulating factor (GM-CSF) yielded CD45+MHC IIhi CD11c+CD163- cells with veiled morphology, while the large vacuolated cells that expressed CD163 resembled type A synoviocytes in both surface antigen phenotype and morphology. These results demonstrate that SRTs contain indeterminate cells that can differentiate into mature DCs in vitro in response to GM-CSF, plus mature synovial lining macrophages.

MHC class II compartment, endocytosis and phagocytic activity of macrophages and putative dendritic cells isolated from normal tissues rich in synovium

The endocytic and phagocytic activities of a population of MHC IIhi CD11c+ dendritic cell (DC)-like cells in synovium-rich tissues (SRTs) of normal rat paws were compared with CD163+ cells (putative macrophages) from the same tissues and pseudo-afferent lymph DCs, peritoneal macrophages and blood monocytes. Fifty percent of CD11c+ cells and 75% of CD163+ cells isolated from SRT internalized fluorescein-conjugated dextran (FITC-DX). Of these endocytic cells, half of those expressing CD11c, but only 30% of those expressing CD163, were surface MHC class II+ (sMHC II+). CD11c+ cells were more endocytic than monocytes or pseudo-afferent lymph DC, but some CD163+ cells (type A synoviocytes) were found to be highly endocytic. CD163+ cells from SRT were more phagocytic (25%) than the general MHC class II+ population (16%). Of phagocytic cells, 40% of CD163+ cells were sMHC II(variable) and they constituted 60% of all MHC class II+ phagocytic cells. Only 18% of phagocytic MHC II+ cells expressed CD11c and the most of these were MHC IIhi. In comparison, 60% of CD163+ peritoneal macrophages were phagocytic, while blood monocytes were poorly phagocytic. Intracellular MHC class II-rich compartments (MIIC) were prominent in sMHC IIhi cells in SRT but rare in CD163+ cells. Most MHC IIhi CD11c+ cells did not have a detectable MIIC.

Phospholipase A2 modulates respiratory burst developed by neutrophils in patients with rheumatoid arthritis

Activated by bacterial peptides, phorbol esters, calcium ionophores and other agonists, neutrophils (PMNs) release the proinflammatory mediator, arachidonic acid (AA) via the intervention of phospholipase A(2) (PLA(2)). AA may play an essential role in activation of NADPH-oxidase, which is involved in the generation of superoxide anion by neutrophils. The present study is focused on the involvement of PLA(2) in the respiratory burst developed by PMNs isolated from patients with rheumatoid arthritis (RA). PLA(2) exists in very high levels in diseases such as rheumatoid arthritis and may cause acute inflammatory and proliferative changes in synovial structures. The respiratory burst was evaluated as superoxide anion release, using an amplified chemiluminescence method. The assays were performed using PMNs untreated or treated with different doses of stimulatory reagents (phorbol 12-myristate-13-acetate (PMA), calcium ionophore (A23187)). Our data suggested that PMA stimulated the production of superoxide anion in a dose-response manner, as compared with A23187, which did not induce a significant release of superoxide anion in PMNs-RA. The exogenous addition of AA significantly amplified the superoxide anion release by PMNs-RA stimulated with PMA and to a lesser extent, by PMNs stimulated with A23187. AA has also reversed the inhibitory effect of arachidonyl-trifluorometylketone and E-6-(bromomethylene)tetrahydro-3-(1-naphthalenyl)2H-pyran-2-one (BEL) on the superoxide anion release by PMNs-RA. In conclusion, the differential responses to these two agents suggested that different isoforms of PLA(2) were activated by A23187 or PMA, and support the idea that activation of these different PLA(2) served distinct functions of PMNs. Therefore, the inhibition of PLA(2) enzymes might be of great importance in the immunotherapy of rheumatoid arthritis.