Comparison of anti 60 and 52 kDa SS-A/Ro antibodies in the pathogenesis of cutaneous lupus erythematosus

Prevalence of Sjögren's syndrome according to 2016 ACR-EULAR classification criteria in patients with systemic lupus erythematosus

BACKGROUND

Diagnosis of SS is a complex task, as no symptom or test is unique to this syndrome. The American-European Consensus Group (AECG 2002) and the American-European classification criteria of 2016 (ACR/EULAR 2016) emerged through a search for consensus. This study aims to assess the prevalence of Sjögren's Syndrome (SS) in patients with Systemic Lupus Erythematosus (SLE), according to AECG 2002 and ACR-EULAR 2016 classifications, as well as clinical and histopathological features in this overlap. To date, there is no study that has evaluated SS in SLE, using the two current criteria.

METHODS

This cross-sectional study evaluated 237 SLE patients at the outpatient rheumatology clinic between 2016 and 2018. Patients were submitted to a dryness questionnaire, whole unstimulated salivary flow (WUSF), "Ocular Staining Score" (OSS), Schirmer's test I (ST-I), and labial salivary gland biopsy (LSGB).

RESULTS

After verifying inclusion and exclusion criteria, a total of 117 patients were evaluated, with predominance of females (94%) and mixed ethnicity (49.6%). The prevalence of SS was 23% according to AECG 2002 and 35% to ACR-EULAR 2016. Kappa agreement between AECG 2002 and ACR-EULAR 2016 were 0.7 (p < 0.0001). After logistic regression, predictors for SS were: anti/Ro (OR = 17.86, p < 0.05), focal lymphocytic sialadenitis (OR = 3.69, p < 0.05), OSS ≥ 5 (OR = 7.50, p < 0.05), ST I positive (OR = 2.67, p < 0.05), and WUSF ≤ 0.1 mL/min (OR = 4.13, p < 0.05).

CONCLUSION

The prevalence of SS in SLE was 23% (AECG 2002) and 35% (ACR-EULAR 2016). The presence of glandular dysfunction, focal lymphocytic sialadenitis, and anti/Ro were predictors of SS in SLE. The greatest advantage of the new ACR-EULAR 2016 criteria is to enable an early diagnosis and identify the overlapping of these two diseases. ACR-EULAR 2016 criteria is not yet validated for secondary SS and this study is a pioneer in investigating prevalence based on the new criteria.

Recent advances in cutaneous lupus

Cutaneous lupus erythematosus (CLE) is an inflammatory and autoimmune skin condition that affects patients with systemic lupus erythematosus (SLE) and exists as an isolated entity without associated SLE. Flares of CLE, often triggered by exposure to ultraviolet (UV) light result in lost productivity and poor quality of life for patients and can be associated with trigger of systemic inflammation. In the past 10 years, the knowledge of CLE etiopathogenesis has grown, leading to promising targets for better therapies. Development of lesions likely begins in a pro-inflammatory epidermis, conditioned by excess type I interferon (IFN) production to undergo increased cell death and inflammatory cytokine production after UV light exposure. The reasons for this inflammatory predisposition are not well-understood, but may be an early event, as ANA + patients without criteria for autoimmune disease exhibit similar (although less robust) findings. Non-lesional skin of SLE patients also exhibits increased innate immune cell infiltration, conditioned by excess IFNs to release pro-inflammatory cytokines, and potentially increase activation of the adaptive immune system. Plasmacytoid dendritic cells are also found in non-lesional skin and may contribute to type I IFN production, although this finding is now being questioned by new data. Once the inflammatory cycle begins, lesional infiltration by numerous other cell populations ensues, including IFN-educated T cells. The heterogeneity amongst lesional CLE subtypes isn't fully understood, but B cells appear to discriminate discoid lupus erythematosus from other subtypes. Continued discovery will provide novel targets for additional therapeutic pursuits. This review will comprehensively discuss the contributions of tissue-specific and immune cell populations to the initiation and propagation of disease.

Site-specific analysis of inflammatory markers in discoid lupus erythematosus skin

Prior studies identified T cells, B cells, and macrophages in the inflammatory infiltrate and up-regulation of their protein products in discoid lupus erythematosus (DLE) skin; however, they lacked rigorous analyses to define their specific locations in skin. Thus, we compared expressions of selected T cell, B cell, and macrophage markers in five areas of DLE, psoriasis, and normal skin. Immunostainings for CD3, CD4, CD8, CD20, CD68, CXCR3, CXCL10, and TIA-1 were performed in biopsies of 23 DLE lesional skin, 11 psoriasis lesional skin, and 5 normal skin. Three independent observers used a graded scale to rate each marker's presence in the epidermis, dermatoepidermal junction (DEJ), perivascular area, periadnexal area, and deep dermis. DLE lesional skin contained an increased abundance of CD3⁺, CD8⁺, and CD68⁺ cells at the DEJ, and CD20⁺ and CD68⁺ cells in the periadnexal area versus psoriasis and normal skin. CXCR3, CXCL10, and TIA-1 were elevated in periadnexal sites of DLE lesional skin versus psoriasis lesional skin. The aggregation of T cells, B cells, macrophages, and their protein products (CXCR3, CXCL10, and TIA-1) in the DEJ and periadnexal area of DLE lesional skin may contribute to the pathology of DLE through a coordinated, sophisticated process.

Common and specific associations of anti-SSA/Ro60 and anti-Ro52/TRIM21 antibodies in systemic lupus erythematosus

Little information exists about the association of anti-SSA/Ro60 and anti-Ro52/TRIM21 with systemic lupus erytematosus (SLE) features. In this work, we analysed the associations of both anti-Ro reactivities with clinical and immunological manifestations in 141 SLE patients. Photosensitivity and xerophtalmia/xerostomia were found to be positively associated with both anti-SSA/Ro60 (P = 0.024 and P = 0.019, resp.) and anti-Ro52/TRIM21 (P = 0.026 and P = 0.022, resp.). In contrast, a negative association was detected regarding anti-phospholipid antibodies, anti-SSA/Ro60 having a stronger effect (P = 0.014) than anti-Ro52/TRIM21. Anti-SSA/Ro60 showed a specific positive association with hypocomplementemia (P = 0.041), mainly with low C4 levels (P = 0.008), whereas anti-Ro52/TRIM21 was found to be positively associated with Raynaud's phenomenon (P = 0.026) and cytopenia (P = 0.048) and negatively associated with anti-dsDNA (P = 0.013). Lymphocytes are involved in the relationship between anti-Ro52/TRIM21 and cytopenia since positive patients showed lower cell levels than negative patients (P = 0.036). In conclusion, anti-SSA/Ro60 and anti-Ro52/TRIM21 showed both common and specific associations in SLE. These data thus increase evidence of the different associations of the two anti-Ro specificities even in a particular disease.

Immunologic and genetic considerations of cutaneous lupus erythematosus: a comprehensive review

Cutaneous lupus erythematosus (CLE) refers to those subtypes of lupus erythematosus (LE) that have predominantly skin manifestations. Discoid lupus erythematosus (DLE), subacute cutaneous lupus erythematosus (SCLE), LE panniculitis (LEP) and lupus erythematosus tumidus (LET) all fall into the category of CLE. The pathogenesis of CLE is likely multifactorial. UV irradiation has been shown to induce keratinocyte apoptosis. Impaired clearance of apoptotic cells is a potential mechanism for the development of CLE. UV irradiation can also induce externalization of autoantigens such as Ro/SSA, exposing them to circulating autoantibodies. Some drugs have been associated with CLE. Possible mechanisms include stimulation of an immune response through disruption of central tolerance and altered T cell function. T17 cells may also play a role in the pathogenesis of CLE as they have been detected in skin lesions of LE. Treg cells have been found to be decreased in LE lesions, which may contribute to the breakdown of self-tolerance. Epidermal Langerhans cells are reduced in CLE while plasmacytoid DCs are increased in the lesions of CLE, suggesting that DCs may also play an important role in the pathogenesis of CLE. Type I IFN- and TNF-α are both upregulated in lesions of CLE. Other cytokines such as IL-6 and IL-17 are also implicated in the pathogenesis of CLE. Cellular and cytokine networks can be impacted by environmental factors and genetic variations and this can result in an increased risk of developing autoimmune diseases such as CLE.

Anti-ribonucleoproteins autoantibodies in patients with systemic autoimmune diseases. Relation with cutaneous photosensitivity

A common feature between patients with a certain group of systemic autoimmune pathologies (SAPs) with rheumatic component, such as lupus erythematosus (LE) in all its forms, is the presence of cutaneous photosensitivity (CP) as well as the existence of autoantibodies (Aabs). These Aabs have also high incidence in other SAPs that do not present CP, like primary Sjögren's syndrome and rheumatoid arthritis. Cutaneous photosensitivity is a condition that consists of an exacerbated skin reaction to solar radiations; its incidence can reach 90% in systemic LE. The mechanisms involved in the development of CP have been extensively studied focusing on different approaches; however, the exact mechanism has not been fully elucidated yet. There are many theories that relate specifically the presence of circulating anti-Ro/SS-A Aabs with the CP phenomenon, though there are several studies which are in disagreement. In this study, we evaluated the Aabs profile (anti-Ro/SS-A 52 kDa, anti-Ro/SS-A 60 kDa, anti-La/SS-B, anti-Sm and ANAs) as well as their titer or reactivity, in a local cohort of 169 patients with SAPs. We related those Aabs profiles and titers with the presence or absence of CP, and we found that there was no significant association between the presence of anti-Ro/SS-A Aabs and the occurrence of CP. On the other hand, a statistically significant positive association was found between CP and high reactivity anti-Sm Aabs, though this fact could be biased by the incidence of both events in SLE patients. To sum up, in the particular population studied, there is no direct relationship between anti-Ro/SS-A Aabs and CP, which is in agreement with some authors and in disagreement with many others, contributing to the endless discussion of this issue.

Possible involvement of oxidative stress in salivary gland of patients with Sjogren's syndrome

OBJECTIVE

To determine the involvement of oxidative stress in the salivary gland of patients with Sjogren's syndrome (SS).

METHODS

Oxidative damage to the gland was measured by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and hexanoyl-lysine (HEL) using the SS saliva. In addition, lactate dehydrogenase (LDH) and mitochondrial glutamic-oxaloacetic transaminase (m-GOT), both general markers for cell damage, were also analyzed.

RESULTS

Increased levels of 8-OHdG and HEL were found in the saliva of SS patients, but not in that of patients with other salivary gland dysfunction or of healthy individuals. Levels of LDH and m-GOT were significantly correlated with 8-OHdG and HEL levels, respectively. Furthermore, the increased levels of 8-OHdG and HEL were also correlated in the SS saliva.

CONCLUSION

These findings suggested the involvement of oxidative stress in glandular tissue destruction in SS. It was indicated that the detection of 8-OHdG and HEL in the saliva may become a useful tool for the diagnosis of SS.

The intracellular 52-kd Ro/SSA autoantigen in keratinocytes is up-regulated by tumor necrosis factor ? via tumor necrosis factor receptor I

OBJECTIVE

Previous studies have shown that the nuclear Ro/SSA autoantigens involved in photosensitive cutaneous lupus manifestations are regulated by ultraviolet B (UVB) irradiation. UVB exposure triggers the release of tumor necrosis factor alpha (TNFalpha) from keratinocytes in the epidermis and from mast cells in the dermis. The present study aimed to characterize the effect of TNFalpha on messenger RNA (mRNA) and protein expression of the intracellular 52-kd Ro/SSA autoantigen in primary human keratinocytes and to elucidate the TNFalpha receptor (TNFR) signaling pathways mediating this effect.

METHODS

Expression of 52-kd Ro/SSA mRNA in primary human keratinocytes was investigated by quantitative real-time polymerase chain reaction (LightCycler system) using GAPDH as the housekeeping gene. Expression of 52-kd Ro/SSA protein was studied by flow cytometry after staining intracellular protein with IgG purified from an anti-52-kd Ro/SSA-positive serum. TNFR function was assessed by culturing cells in the presence and absence of neutralizing antibodies directed against the TNFR subunits TNFRI and TNFRII.

RESULTS

TNFalpha-induced up-regulation of 52-kd Ro/SSA mRNA expression peaked at 4 hours, followed by up-regulation of intracellular 52-kd Ro/SSA protein expression at 24 hours, independently of apoptosis. Between different donors, a high variability of both constitutive expression levels and TNFalpha-induced changes in 52-kd Ro/SSA mRNA and protein expression was observed. The up-regulatory effect of TNFalpha on 52-kd Ro/SSA mRNA and protein expression was inhibited by anti-TNFRI antibodies but enhanced by anti-TNFRII antibodies.

CONCLUSION

The finding that TNFalpha up-regulates 52-kd Ro/SSA expression in keratinocytes via TNFRI suggests that it may play a role in the pathogenesis of anti-Ro/SSA-associated cutaneous lupus erythematosus.

Photosensitivity in cutaneous lupus erythematosus: lessons from mice and men

Mouse models are similar but not identical to human diseases. However, they are important for research into the pathogenesis underlying autoimmune diseases because they allow us to evaluate similarities and differences between human diseases and mouse models. In fact, experimental models and inbred lupus-prone mice are tools that enable a better understanding of the 'photosensitivity' or 'photocytotoxicity' phenomena in relation to autoimmunity. Genetic studies of MRL/lpr mice revealed that the appearance of macroscopic lupus erythematosus (LE)-like skin lesions needs the lpr mutation plus an additional factor in an autosomal dominant fashion. The candidate is ultraviolet (UV) B light, the susceptibility to which is regulated by the genetic background. Such a genetic background is also speculated to be important in human cutaneous LE patients. The translocation of anti-SS-A/Ro on cultured keratinocytes irradiated with UVB light is quantitatively different from photocytotoxicity, and the quantitative levels are significantly higher in systemic LE and subacute cutaneous LE than in discoid LE and normal controls. This review focuses on the lessons gleaned from mouse and human models, and discusses photosensitivity in human cutaneous LE.