Prevention of adoptive transfer of murine Sjögren's syndrome into severe combined immunodeficient (SCID) mice by antibodies against intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1)

Differentially Expressed Gene Pathways in the Conjunctiva of Sjögren Syndrome Keratoconjunctivitis Sicca

Sjögren syndrome (SS) is an autoimmune condition that targets the salivary and lacrimal glands, with cardinal clinical signs of dry eye (keratoconjunctivitis sicca, KCS) and dry mouth. The conjunctiva of SS patients is often infiltrated by immune cells that participate in the induction and maintenance of local inflammation. The purpose of this study was to investigate immune-related molecular pathways activated in the conjunctiva of SS patients. Female SS patients (n=7) and controls (n=19) completed a series of oral, ocular surface exams. Symptom severity scores were evaluated using validated questionnaires (OSDI and SANDE). All patients fulfilled the ACR/EULAR criteria for SS and the criteria for KCS. Fluorescein and lissamine green dye staining evaluated tear-break-up time (TBUT), corneal and conjunctival disease, respectively. Impression cytology of the temporal bulbar conjunctiva was performed to collect cells lysed and subjected to gene expression analysis using the NanoString Immunology Panel. 53/594 differentially expressed genes (DEGs) were observed between SS and healthy controls; 49 DEGs were upregulated, and 4 were downregulated (TRAF5, TGFBI, KLRAP1, and CMKLRI). The top 10 DEGs in descending order were BST2, IFITM1, LAMP3, CXCL1, IL19, CFB, LY96, MX1, IL4R, CDKN1A. Twenty pathways had a global significance score greater or equal to 2. Spearman correlations showed that 29/49 upregulated DEGs correlated with either TBUT (inverse) or OSDI or conjunctival staining score (positive correlations). Venn diagrams identified that 26/29 DEGs correlated with TBUT, 5/26 DEGs correlated with OSDI, and 16/26 correlated with conjunctival staining scores. Five upregulated DEGs (CFB, CFI, IL1R1, IL2RG, IL4R) were uniquely negatively correlated with TBUT. These data indicate that the conjunctiva of SS patients exhibits a phenotype of immune activation, although some genes could be inhibitory. Some of the DEGs and pathways overlap with previous DEGs in salivary gland biopsies, but new DEGs were identified, and some of these correlated with symptoms and signs of dry eye. Our results indicate that gene analysis of conjunctiva imprints is a powerful tool to understand the pathogenesis of SS and develop new therapeutic targets.

Biologic therapy in Sjögren's syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease with complex and diverse clinical manifestations. It is characterized by lymphocyte infiltration of exocrine glands such as the salivary gland and lacrimal gland leading to insufficient secretion of the gland, manifested as dry mouth and dry eyes. In addition, it can involve extraglandular organs and cause systemic damage. The pathogenesis of SS is still unclear. At present, symptomatic treatment is the mainstay and there is a lack of effective therapy. With the development of molecular pathways underlying the pathogenesis of SS, more and more novel biological agents are used to treat SS. We summarized and analyzed the existing evidences on the efficacy of biological treatment of SS and their targets. Analysis of the efficacy of biological therapy and improvement of treatment strategies can help to give full play to its therapeutic advantages.

Sjögren's syndrome: Old and new therapeutic targets

Sjögren's syndrome (SS) is a prototype autoimmune disease characterized by oral and ocular mucosal dryness following chronic inflammation of salivary and lachrymal glands, respectively. Profound B cell hyperactivity along with systemic manifestations including fatigue, musculoskeletal complaints, features related to hepatic, pulmonary, renal and nervous system involvement, as well as lymphoma development can be also present. Despite that activation of both innate and adaptive immune pathways has been long well documented in SS pathogenesis, systemic immunosuppression in SS, in contrast to other autoimmune diseases, has been largely inefficacious. Biological agents previously implemented in successful therapeutic outcomes in rheumatoid arthritis (RA), such as anti-TNF agents, anakinra, tocilizumab and rituximab failed to reach primary outcomes in randomized double-blind controlled trials in the context of SS. Abatacept and belimumab, already licensed for the treatment of RA and lupus respectively, as well combination regimens of both rituximab and belimumab hold some promise in alleviation of SS-specific complaints, but data from large controlled trials are awaited. Recent advances in dissecting the molecular pathways underlying SS pathogenesis led to an expanding number of novel biological compounds directed towards type I interferon system, antigen presentation, costimulatory pathways, B and T cell activation, as well as germinal center formation. While targeting of cathepsin-S (Petesicatib), inducible costimulator of T cells ligand (prezalumab), and lymphotoxin beta receptor (baminercept) failed to fulfil the primary outcome measures, preliminary results from two randomized placebo controlled trials on CD40 blockade (Iscalimab) and B-cell activating factor receptor (Ianalumab) inhibition resulted in significant reduction of SS disease activity, with a favorable so far safety profile. Results from administration of other kinase inhibitors, a transmembrane activator and calcium-modulator and cytophilin ligand interactor TACI fusion protein (RC18), as well as low dose recombinant interleukin-2 to expand T-regulatory cells are currently awaited.

Inhibition of very late antigen-4 and leukocyte function-associated antigen-1 in experimental autoimmune uveoretinitis

B10.RIII mice were immunized with interphotoreceptor retinoid binding protein peptide to induce uveitis. Mice were injected intraperitoneally with anti-very late antigen-4 (VLA-4), anti-leukocyte function-associated antigen-1 (LFA-1), or a control Ab every other day from Day 5 to Day 13 post-immunization. The eyes and spleens were harvested on Day 14 or 28. The eyes were used for histologic/cytokine mRNA expression analyses. The spleens were used for Ag-recall cytokine production assays and intracellular cytokine assays. Treatment with both Abs led to a profoundly significant reduction in severity of uveitis and cytokine mRNA expression in the eye. However, cytokine production by splenocytes was significantly upregulated. Discontinuation of Ab treatment led to an increase in uveitis severity and cytokine mRNA expression in the eye, but led to a decrease in cytokine production and intracellular IFN-γ(+) and IL-17A(+)cytokine profile by splenocytes. Thus, blockade of these molecules using specific Abs may be a therapeutic option for patients with uveitis; however, such treatment must be continued.

Epigenetic dysregulation in salivary glands from patients with primary Sjögren's syndrome may be ascribed to infiltrating B cells

Sjögren's syndrome (SS) is an autoimmune exocrinopathy characterized by an epithelium injury with dense lymphocytic infiltrates, mainly composed of activated T and B cells. Present at the interface of genetic and environmental risk factors, DNA methylation is suspected to play a key role in SS. To clarify this point, global DNA methylation was tested within salivary gland epithelial cells (SGEC), peripheral T cells and B cells from SS patients. Global DNA methylation was reduced in SGEC from SS patients, while no difference was observed in T and B cells. SGEC demethylation in SS patients was associated with a 7-fold decrease in DNA methyl transferase (DNMT) 1 and a 2-fold increase in Gadd45-alpha expression. The other DNA methylation/demethylation partners, tested by real time PCR (DNMT3a/b, PCNA, UHRF1, MBD2, and MBD4), were not different. Interestingly, SGEC demethylation may be attributed in part to the infiltrating B cells as suspected in patients treated with anti-CD20 antibodies to deplete B cells. Such hypothesis was confirmed using co-culture experiments with human salivary gland cells and B cells. Furthermore, B cell-mediated DNA demethylation could be ascribed to an alteration of the PKC delta/ERK/DNMT1 pathway. As a consequence, part of the SGEC dysfunction in SS may be linked to epigenetic modifications, thus opening new therapeutic perspectives in SS.

ICAM-1 expression predisposes ocular tissues to immune-based inflammation in dry eye patients and Sjögrens syndrome-like MRL/lpr mice

PURPOSE

We previously reported that immune-based inflammation occurs on the ocular surface of humans as well as canines with keratoconjunctivitis sicca (KCS). Intercellular adhesion molecule-1 (ICAM-1) was found to be upregulated on lymphocytes and/or vascular endothelial cells resulting in lymphocytic diapedesis to the lacrimal and conjunctival tissues. The purpose of the current study was to demonstrate the role of ICAM-1 in (1) resident epithelial cell response during ocular inflammation, (2) local and/or peripheral lymphocyte activation or accumulation in the ocular tissues, and (3) whether anti-ICAM-1 is effective to attenuate immune-mediated ocular inflammation.

METHODS

ICAM-1 levels in various ocular tissues of human with KCS and/or MRL/lpr mouse were evaluated by immunohistochemistry and in situ hybridization for protein and messenger RNA (mRNA) expression, respectively. Soluble ICAM-1 concentrations in MRL/lpr mouse plasma over the course of disease development were measured by ELISA. Cell proliferation within ocular tissues was assessed by bromodeoxyuridine (BrdU) incorporation and immunohistochemical detection. The level of T cell activation was determined by IL-2 receptor (CD25, a marker of T cell activation and proliferation) and CD69 (a marker of T cell activation) immunoreactivity using FACS analysis. To examine the effectiveness of anti-ICAM-1/LFA-1 in elimination of lacrimal gland inflammation, MRL/lpr mice were injected intraperitoneally (i.p.) with or without monoclonal antibodies against ICAM-1 and LFA-1 at three or eight weeks of age.

RESULTS

Increased endogenous ICAM-1 expression at the level of protein and mRNA was detected in the epithelial cells present in the conjunctival and accessory lacrimal tissues in dry eye patients. In MRL/lpr mice, ICAM-1 expression by lacrimal acinar epithelial cells and conjunctival epithelial cells were detected in addition to inflammatory infiltrates and vascular endothelial cells at 16 weeks of age. Soluble ICAM-1 levels were markedly increased concomitantly with disease progression over time as compared with the controls. No significant lymphocytic proliferation (a lack of BrdU and CD25 immunoreactivities) was detected within lacrimal glands of MRL/lpr mice at the disease onset. However, a population of the infiltrated T cells were CD69 positive, indicating the activation stage of a T cell subset. Treatment using monoclonal antibodies against murine ICAM-1 and LFA-1 resulted in a decrease in the number of inflammatory infiltrates in MRL/lpr mice.

CONCLUSIONS

Our findings suggest that ICAM-1 upregulation locally and systemically promote lymphocyte activation and migration to the ocular surface (OS). Ocular resident epithelium is an active component of ocular surface and is capable of interacting with invasive lymphocytes by ICAM-1 production in response to immune activation and inflammation. ICAM-1 synthesized by epithelial cells may serve as a signaling molecule for predisposition of ocular surface inflammation and facilitate potential antigen presentation by epithelial cells. Lymphocytic infiltrates in the lacrimal gland of the MRL/lpr mouse appeared to be the result of the accumulation, but not proliferation of circulating lymphocytes diapodesed from the vasculature that had migrated into the local ocular tissues. The potential use of anti-ICAM-1 therapy in treating immune-based inflammatory diseases such as dry eye deserves further investigation.

EC3, a heterodimeric disintegrin from Echis carinatus, inhibits human and murine alpha4 integrin and attenuates lymphocyte infiltration of Langerhans islets in pancreas and salivary glands in nonobese diabetic mice

The venom of Echis carinatus suchoreki contains a monomeric disintegrin echistatin (Mr 5,500 Da) that strongly inhibits alphaIIbbeta3, alphavbeta3, and alpha5beta1 integrins and a heterodimeric disintegrin called EC3 (M(r) 14,762 Da). At nanomolar concentration, EC3 inhibits adhesion of human cell lines expressing alpha4beta1 and alpha4beta7 to immobilized VCAM-1; it has a lower inhibitory effect on alpha5beta1-mediated cell adhesion. In this study, we demonstrated that EC3, in contrast to echistatin, inhibited binding of monoclonal anti-alpha4 and anti-alpha5 antibodies to cells expressing alpha4beta7. In a dose-dependent manner and to the same extent, EC3 inhibited adhesion of Jurkat cells and murine splenic lymphocytes to immobilized VCAM-1, whereas echistatin was not active. EC3 injected intraperitoneally into nonobese diabetic (NOD mice) suppressed development of insulitis and sialoadenitis, whereas echistatin had no significant effect. We propose that the effect of EC3 is mediated, at least, in part, by blocking alpha4beta1 and alpha4beta7 on murine lymphocytes.

TNF-α and IL-1 Sequentially Induce Endothelial ICAM-1 and VCAM-1 Expression in MRL/lpr Lupus-Prone Mice

Dysfunctional leukocyte-endothelial interactions are thought to play a key role in systemic lupus erythematosus pathogenesis. We questioned the importance of TNF-α and IL-1 for endothelial activation in MRL/lpr lupus-prone mice. Endothelial ICAM-1 and VCAM-1 expression increased significantly with disease evolution in kidney, heart, and brain, as shown by i.v. injected radiolabeled Ab uptake. Lung endothelial VCAM-1 also increased, while lung endothelial ICAM-1 did not rise above a high basal level. Immunoassays showed a significantly raised circulating level of TNF-α by 14 wk, with levels of circulating IL-1α and IL-1β being additionally raised by 20 wk. With 14-wk-old MRL/lpr, anti-TNF-α antiserum inhibited expression of ICAM-1 and VCAM-1 by endothelial cells cultured with sera in vitro, and uptake of anti-ICAM-1 and anti-VCAM-1 mAb in lung, kidney, brain, and heart in vivo. In contrast, both anti-TNF-α and anti-IL-1 antisera were required for maximal inhibition in vitro and in vivo at 20 wk. These data indicate that TNF-α is largely responsible for the early up-regulation of endothelial ICAM-1 and VCAM-1, but that IL-1 enhances expression in late disease. Our observations provide novel insights of possible relevance to understanding endothelial activation in systemic lupus erythematosus, and highlight an approach that can be extended to dissecting other chronic inflammatory diseases.

CD44 variant isoform expression in a variety of skin-associated autoimmune diseases

CD44 variant isoforms are frequently expressed on tissue-infiltrating lymphocytes. By the high incidence of autoimmune reactions of the skin and aiming at new strategies of therapeutic intervention, we became interested in evaluating the CD44 isoform expression profile in autoimmune reactions of the skin. Expression of CD44s, CD44v3, v5, v6, v7, v7-v8, and v10 was evaluated in 55 biopsies of lupus erythematosus, bullous pemphigoid, vasculitis, morphea, and pemphigus vulgaris. Biopsies did not contain CD44v5-, CD44v6-, CD44v7-, or CD44v7-v8-positive leukocytes. Staining with anti-CD44v10 was seen in vasculitis and occasionally in lupus erythematosus, morphea, and bullous pemphigoid. All biopsies contained CD44v3(+) leukocytes, the percentage of CD44v3(+) leukocytes being increased in autoimmune infiltrates with the exception of pemphigus vulgaris. CD44v3 was expressed by CD4(+) cells as well as by part of CD8(+) cells, Langerhans cells, and monocytes. Vascular endothelium also contained CD44v3(+) cells. Only monocytes expressed CD44v10. We assume that CD44v3 and CD44v10 may be targeting leukocytes toward the skin or allow for their retention and expansion via binding of cytokines and chemokines harbored by activated, skin-associated endothelium or provided by cells surrounding the infiltrate. The absence of CD44v6, frequently associated with lymphocyte activation, appears to be a peculiarity of skin-infiltrating leukocytes.

Experimental graft versus host disease in the (BN x LEW) F1 rat hybrid as a model for autoimmune disease. Study of early adenitis in lacrimal and salivary glands

We analysed inflammatory changes at selected time intervals, of salivary and lacrimal glands in the developing immunostimulatory [BN-->(BN x LEW)F1] model of graft-versus-host (GVH) reaction. A focal mononuclear adenitis in lacrimal and salivary glands developed at day 7 and increased clearly in "onset"-rats. Inflammatory responses in submandibular and parotid glands were less consistent and weaker than in lacrimal glands. There was no significant focus score difference between males and females. The lacrimal infiltrates were characterised immunohistochemically with monoclonal antibodies. Our findings indicate that CD4+ cells of donor origin dominated infiltrates, whereas a moderate number of B cells appeared only in large (late) foci. At stages corresponding to the onset of GVH disease (GVHD) in skin/labial mucosa, numerous CD8+ lymphocytes and NK cells were found in lacrimal glands, adjacent to ductal/ vascular plexa, sometimes forming small foci and with evidence of epithelial damage. We conclude that GVHD-associated T cell migration into rat exocrine glands occurs as a result of the semi-alloantigen-activated phenotype properties of the T cells. This activation occurs initially in lymphoid tissue and migration into glands is secondary to this and unrelated to antigen specificity. We also found evidence of amplification and tissue damage, interpreted as due to local reactivation of the T cells.