Increased circulating anti-α6-integrin autoantibodies in psoriasis and psoriatic arthritis but not in rheumatoid arthritis

Autoantibodies immuno-mechanically modulate platelet contractile force and bleeding risk

Altered mechanotransduction has been proposed as a putative mechanism for disease pathophysiology, yet evidence remains scarce. Here we introduce a concept we call single cell immuno-mechanical modulation, which links immunology, integrin biology, cellular mechanics, and disease pathophysiology and symptomology. Using a micropatterned hydrogel-laden coverslip compatible with standard fluorescence microscopy, we conduct a clinical mechanobiology study, specifically focusing on immune thrombocytopenia (ITP), an autoantibody-mediated platelet disorder that currently lacks a reliable biomarker for bleeding risk. We discover that in pediatric ITP patients (n = 53), low single platelet contraction force alone is a "physics-based" biomarker of bleeding (92.3% sensitivity, 90% specificity). Mechanistically, autoantibodies and monoclonal antibodies drive increases and decreases of cell force by stabilizing integrins in different conformations depending on the targeted epitope. Hence, immuno-mechanical modulation demonstrates how antibodies may pathologically alter mechanotransduction to cause clinical symptoms and this phenomenon can be leveraged to control cellular mechanics for research, diagnostic, and therapeutic purposes.

Biomarkers and biologics related with psoriasis and psoriatic arthritis

Over the past half century, psoriasis is considered as an immune-mediated inflammatory skin disease with the combined hallmarks of autoimmunity and autoinflammation, according to growing volumes of clinical and experimental findings. There is currently no cure for psoriasis, current treatment strategies focus on symptom control, disease minimization, and patient's quality of life enhancement. To meet these challenges, it keeps imperative to discover potential biomarkers, so that not only can they be used for the prediction and monitoring of psoriasis disease in clinic, but also can provide novel therapeutic targets or treatment strategies for psoriasis sufferers. This review systematically demonstrates the research progress of psoriasis-related biomarkers and elaborates their related mechanisms in the pathological development of psoriasis and psoriatic arthritis. In addition, we summarize the development of biologic therapies for psoriasis and psoriatic arthritis in order to drive the broader discussion of psoriasis as an autoimmune-mediated inflammatory skin disease.

Autoantibodies in psoriatic disease

Psoriasis is an inflammatory skin disease affecting over 8 million people in the US and Canada. Approximately, a quarter of psoriasis patients have an inflammatory arthritis termed psoriatic arthritis (PsA). Psoriatic disease encompassing both psoriasis and PsA is regarded as an immune-mediated inflammatory disease, exhibiting both autoimmune and autoinflammatory features. A review of the current literature on the presence and clinical significance of autoantibodies found in psoriatic disease are presented. The frequency of several autoantibodies in psoriasis and PsA patients as well as their clinical significance regarding disease diagnosis, disease activity and treatment response are reviewed. Additionally, the basic principles of antibody assays are presented, and the methods used for each study are analyzed. Despite historically described as a rheumatoid factor negative (seronegative) disease, an array of autoantibodies has been identified in patients with psoriatic disease. This points to an autoimmune component potentially playing a role in psoriatic disease; however, additional evidence is needed to determine the clinical utility of these autoantibodies.

Targeting integrin pathways: mechanisms and advances in therapy

Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.

ITGA9 Inhibits Proliferation and Migration of Dermal Microvascular Endothelial Cells in Psoriasis

Background

Cell proliferation, migration, and angiogenesis are aberrant in psoriatic human dermal microvascular endothelial cells (HDMECs), resulting in abnormal endothelial function and microvascular dilation in psoriasis.

Objective

To explore the role of Integrin subunit alpha 9 (ITGA9) in proliferation and migration of dermal microvascular endothelial cells.

Methods

HDMECs were isolated from the skin of 6 psoriatic patients and 6 healthy controls. Expression levels of ITGA9 mRNA and protein were assessed with qRT-PCR and Western blot, respectively, while miqRT-PCR was used to determine expression levels of miR-146a-3p. Cell proliferation and migration were assessed in human microvascular endothelial cell line (HMEC-1), following overexpression of either ITGA9 or miR-146a-3p, or co-transfection with miR-146a-3p-mimic and pLVX - ITGA9. Cell viability was detected by Cell Counting Kit-8 assay and 5-ethynyl-2'-deoxyuridine (EdU) cell proliferation assay. Cell apoptosis was assessed, using annexin V-FITC/PI apoptosis detection kit, while cell migration was detected by wound healing and transwell assay.

Results

Expression levels of ITGA9 were significantly decreased in psoriatic HDMECs compared to normal controls. Moreover, expression levels of miR-146a-3p were higher in psoriatic HDMECs than in normal controls. Overexpression of miR-146a-3p lowered expression levels of ITGA9, accompanied by increased proliferation and migration of HMEC-1 in vitro. In contrast, overexpression of ITGA9 inhibited proliferation and migration of HMEC-1, while increasing expression levels of cdc42, ki67, focal adhesion kinase (FAK), c-Src tyrosine kinase (Src), RAC1 and RhoA.

Conclusion

ITGA9 can repress the proliferation and migration of HMEC-1, suggesting utility of ITGA9 as a potential therapeutic intervention for psoriasis.

Remodeling of the Dermal Extracellular Matrix in a Tissue-Engineered Psoriatic Skin Model by n-3 Polyunsaturated Fatty Acids

Psoriasis is an inflammatory skin disease mainly associated with an epidermal disorder. However, the involvement of the dermal extracellular matrix (ECM) composition in psoriasis is still poorly understood. This study aimed to investigate the expression of ECM components in psoriatic skin substitutes (PS⁻) compared with healthy skin substitutes (HS⁻), as well as the effect of an n-3 polyunsaturated fatty acid, namely α-linolenic acid (ALA), on the psoriatic dermal compartment (PS^ALA+). Liquid chromatography tandem mass spectrometry analyses revealed that the lipidome of PS⁻ contained higher amounts of n-6 derived prostaglandins (PGE₂) and lipoxygenase products (9-HODE and 15-HETE). ALA supplementation increased the levels of PGE₃, 13-HOTrE, 15-HEPE, and 18-HEPE, and decreased the levels of PGE₂, 15-HETE, and 9-HOPE compared with PS⁻, indicating that ALA modulates the dermal lipidome of psoriatic skin substitutes. Gene expression profiling showed that several genes encoding for different ECM proteins were overexpressed in PS⁻ compared with HS⁻, namely COL1A1 (4.2-fold), COL1A2 (3-fold), COL3A1 (4.4-fold), COL4A1 (2.3-fold), COL4A2 (6.3-fold), COL5A1 (3.3-fold), COL5A2 (5.2-fold), and COL5A3 (4.6-fold). Moreover, the expression of collagen IV (Col IV), collagen VII (Col VII), and laminin was found to be increased in PS⁻ compared with HS⁻, and to be restored with ALA (PS^ALA+) according to immunofluorescence staining, while only the collagen I to collagen III ratio was altered according to dot blot analyses. Linear regression analysis revealed several positive correlations, including Col III with 14-HDHA levels, fibronectin with 12-HETE and 15-HETE levels, the dermo-epidermal junction Col IV with PGF_2α, 9-HODE, and 13-HODE levels, and laminin with levels of PGF_2α, 9-HODE, 13-HODE, 5-HETE, 12-HETE, and 15-HETE. These results suggest that the ECM plays an underestimated role in the pathogenesis of psoriasis and that ALA supplementation can regulate the ECM composition.

Integrin Regulated Autoimmune Disorders: Understanding the Role of Mechanical Force in Autoimmunity

The pathophysiology of autoimmune disorders is multifactorial, where immune cell migration, adhesion, and lymphocyte activation play crucial roles in its progression. These immune processes are majorly regulated by adhesion molecules at cell–extracellular matrix (ECM) and cell–cell junctions. Integrin, a transmembrane focal adhesion protein, plays an indispensable role in these immune cell mechanisms. Notably, integrin is regulated by mechanical force and exhibit bidirectional force transmission from both the ECM and cytosol, regulating the immune processes. Recently, integrin mechanosensitivity has been reported in different immune cell processes; however, the underlying mechanics of these integrin-mediated mechanical processes in autoimmunity still remains elusive. In this review, we have discussed how integrin-mediated mechanotransduction could be a linchpin factor in the causation and progression of autoimmune disorders. We have provided an insight into how tissue stiffness exhibits a positive correlation with the autoimmune diseases’ prevalence. This provides a plausible connection between mechanical load and autoimmunity. Overall, gaining insight into the role of mechanical force in diverse immune cell processes and their dysregulation during autoimmune disorders will open a new horizon to understand this physiological anomaly.

Autoantibodies in Psoriatic Disease

BACKGROUND

Psoriasis (Ps) is an inflammatory skin disease affecting over 8 million people in the USA and Canada. Approximately a quarter of patients with Ps have an inflammatory arthritis termed psoriatic arthritis (PsA). Psoriatic disease encompassing both Ps and PsA is regarded as an immune-mediated inflammatory disease, exhibiting both autoimmune and autoinflammatory features. Innate immune cell activation promotes inflammation and the cellular infiltrate in inflamed tissue is predominantly lymphocytic.

CONTENT

A narrative review of the current literature on the presence and clinical significance of autoantibodies found in psoriatic disease are presented. The frequency of several autoantibodies in Ps and PsA patients as well as their association with disease diagnosis, disease activity, and treatment response are reviewed.

SUMMARY

Despite historically described as a rheumatoid factor negative (seronegative) disease, an array of autoantibodies has been identified in patients with psoriatic disease. Many of the autoantibodies reviewed are elevated in Ps and PsA patients and are associated with disease activity, treatment response, and cardiovascular disease risk. The identification of autoantibodies in Ps and PsA patients points to an autoimmune component potentially playing a role in psoriatic disease; however, additional evidence is needed to determine the clinical utility of these autoantibodies and their contribution to disease pathogenesis.

Could basement membrane alterations, resembling micro-wounds at the dermo-epidermal junction in psoriatic non-lesional skin, make the skin susceptible to lesion formation?

Current data suggest that tissue microenvironment control immune functions. Therefore, understanding the tissue environment in which immune activation occurs will enhance our capability to interfere with abnormal immune pathology. Here, we argue that studying the constitutively abnormal functions of clinically uninvolved psoriatic skin in patients with plaque type psoriasis is very important to better understand psoriasis pathobiology, because non-lesional skin provides the tissue environment in which the psoriatic lesion develops. A key question in psoriasis is what initiates the abnormal, uncontrolled immune activation in the first place and the answer may lie in the skin. In light of this concept, we summarize abnormalities at the dermal-epidermal junction region which shows a special "non-healing-like" micro-wound phenotype in the psoriatic non-lesional skin that may act as a crucial susceptibility factor in the development of the disease.

Revisiting B cell tolerance and autoantibodies in seropositive and seronegative autoimmune rheumatic disease (AIRD)

Autoimmune rheumatic diseases (AIRD) are categorized seropositive or seronegative, dependent upon the presence or absence of specific autoreactive antibodies, including rheumatoid factor and anti-citrullinated protein antibodies. Autoantibody-based diagnostics have proved helpful in patient care, not only for diagnosis but also for monitoring of disease activity and prediction of therapy responsiveness. Recent work demonstrates that AIRD patients develop autoantibodies beyond those contained in the original categorization. In this study we discuss key mechanisms that underlie autoantibody development in AIRD: defects in early B cell development, genetic variants involved in regulating B cell and T cell tolerance, environmental triggers and antigen modification. We describe how autoantibodies can directly contribute to AIRD pathogenesis through innate and adaptive immune mechanisms, eventually culminating in systemic inflammation and localized tissue damage. We conclude by discussing recent insights that suggest distinct AIRD have incorrectly been denominated seronegative.

Current knowledge on autoantigens and autoantibodies in psoriasis

In the past decades, clinical and experimental evidence has demonstrated that psoriasis is an immune-mediated inflammatory disease of the skin that occurs in genetically susceptible individuals. Psoriasis also shows clear autoimmune pathomechanisms, but specific cellular targets for the onset and maintenance of psoriatic lesions were not established until 2014. Since then, four psoriasis autoantigens were discovered, namely cathelicidin LL-37, melanocytic ADAMTSL5, lipid antigen PLA2G4D and keratin 17. Autoreactive T cells against these autoantigens were found in a number of patients with moderate-to-severe plaque psoriasis. Moreover, the discovery of autoantibodies against LL-37 and ADAMTSL5 and their strong association with psoriatic arthritis (PsA) suggest a potential role of these autoantibodies in the pathogenesis of PsA. This review discusses the current studies on psoriatic autoantigens and the associated circulating autoantibodies and their mechanisms involved in the development and maintenance of psoriatic plaques. Recent autoimmune evidence fuelled the discussion on psoriasis as an autoimmune skin disorder and has the potential to develop new treatment strategies with protective and therapeutic antigen-targeted methods.

Biomechanical Factors in Psoriatic Disease: Defective Repair Exertion as a Potential Cause. Hypothesis Presentation and Literature Review

Joining main clinical manifestations of psoriatic skin disorder are inflammatory arthritis and nail lesions. Repetitive microdamage has been postulated as a main triggering factor in lesions of psoriatic arthritis. This concept of psoriatic disease might also be admissible for triggering nail lesions because the nail is a frequently traumatized structure. Here, we aimed to describe the conjectural injury mechanisms of nail complex with regard to acting biomechanical factors. Tissue repair response to physical microdamage may be altered in psoriatic disease. It is plausible to consider that a defective repair process in the dysregulated prepsoriatic tissue may lead to innate immune activation and further development of autoinflammatory lesions, although excessive inflammation is known to impair wound healing. Recently published data have revealed the importance of mechanosensitive Wingless-type (Wnt) signaling in the pathophysiology of psoriasis and ankylosing spondylitis. The Wnt signaling system is involved in morphogenesis, repair, and regeneration as a biologic process main regulator. Wnt5a seems to be a dominating mediator in both psoriatic plaques and during the spondylitis process that might also be a linking molecule of psoriatic response to mechanical stress. Future studies should focus on complex responsive interactions of tissue repair regulators regarded in psoriatic disease.

The contribution of IL-17 to the development of autoimmunity in psoriasis

Psoriasis is an (auto)immune-mediated disease that manifests as widespread desquamative erythema. The TNF-α/IL-23/IL-17A axis is crucial to its pathogenesis, which is demonstrated by its excellent therapeutic response to biologics that target this axis. There is a strong association between HLA-C*0602 and psoriasis, and researchers have identified autoantigens that are restricted to this major histocompatibility class I molecule. These auto-Ags include LL-37, A disintegrin and metalloprotease domain containing thrombospondin type 1 motif-like 5 (ADAMTSL5), and keratin 17. IL-17A-producing T cells have been identified in T cell populations that are reactive to these auto-Ags. In addition, lipid Ags have surfaced as candidate auto-Ags that activate IL-17A-producing T cells in a CD1a-restricted manner. In this article, we review the candidate auto-Ags that may contribute to the activation of the IL-17A-deviated immune response in psoriasis.

Differential efficacy of biologic treatments targeting the TNF-α/IL-23/IL-17 axis in psoriasis and psoriatic arthritis

Psoriasis and psoriatic arthritis cause significant physical and psychological burdens for afflicted individuals. An accelerated TNF-α/IL-23/IL-17 axis is their major pathomechanism; therefore, anti-TNF-α/IL-23/IL-17 biologics are very effective for the treatment of skin and joint lesions in psoriasis and psoriatic arthritis. Given that the IL-17 signature is more upregulated in the skin than in synovium in psoriatic arthritis, anti-IL-23/IL-17 agents seem to be superior to anti-TNF-α remedies in the treatment of skin lesions. In this review, we focus on the differential efficacy of anti-TNF-α/IL-23/IL-17 biologics in psoriasis and psoriatic arthritis.

Interaction of Psoriasis and Bullous Diseases

Patients with psoriasis are frequently complicated with autoimmune bullous diseases, especially, pemphigoid diseases. It has been known that one-third cases of anti-laminin gamma1 pemphigoid, formerly anti-p200 pemphigoid, are associated with psoriasis whereas bullous pemphigoid is the most frequently associated bullous disease in psoriasis cases regardless of the lack of detectable levels of the accompanying anti-laminin gamma1 autoantibodies. Despite several suggestions, however, the definitive reason of the striking association of psoriasis and these autoimmune bullous diseases remains elusive. In this review, we look over the epidemiological evidence of the association of psoriasis and autoimmune bullous diseases and the information of genetic susceptibilities of each disease, and discuss the possible mechanisms of their complication with reference to the recent understandings of each pathogenesis.

Autoimmunity and autoimmune co-morbidities in psoriasis

Psoriasis is characterized by widespread scaly erythematous plaques that cause significant physical and psychological burdens for the affected individuals. Accelerated inflammation driven by the tumour necrosis factor-α/interleukin-23/interleukin-17 axis is now known to be the major mechanism in the development of psoriasis. In addition, psoriasis has an autoimmune nature that manifests as autoreactive T cells and is co-morbid with other autoimmune diseases, such as autoimmune bullous diseases, vitiligo, alopecia and thyroiditis. In this article, we review the recent topics on autoimmunity and autoimmune co-morbidities in psoriasis.