Flightless I Alters the Inflammatory Response and Autoantibody Profile in an OVA-Induced Atopic Dermatitis Skin-Like Disease

Exogenous drug-induced mouse models of atopic dermatitis

Atopic dermatitis (AD) is an inflammatory skin disease characterized by intense pruritus. AD is harmful to both children and adults, but its pathogenic mechanism has yet to be fully elucidated. The development of mouse models for AD has greatly contributed to its study and treatment. Among these models, the exogenous drug-induced mouse model has shown promising results and significant advantages. Until now, a large amount of AD-related research has utilized exogenous drug-induced mouse models, leading to notable advancements in research. This indicates the crucial significance of applying such models in AD research. These models exhibit diverse characteristics and are highly complex. They involve the use of various strains of mice, diverse types of inducers, and different modeling effects. However, there is currently a lack of comprehensive comparative studies on exogenous drug-induced AD mouse models, which hinders researchers' ability to choose among these models. This paper provides a comprehensive review of the features and mechanisms associated with various exogenous drug-induced mouse models, including the important role of each cytokine in AD development. It aims to assist researchers in quickly understanding models and selecting the most suitable one for further investigation.

Skin barrier-inflammatory pathway is a driver of the psoriasis-atopic dermatitis transition

As chronic inflammatory conditions driven by immune dysregulation are influenced by genetics and environment factors, psoriasis and atopic dermatitis (AD) have traditionally been considered to be distinct diseases characterized by different T cell responses. Psoriasis, associated with type 17 helper T (Th17)-mediated inflammation, presents as well-defined scaly plaques with minimal pruritus. AD, primarily linked to Th2-mediated inflammation, presents with poorly defined erythema, dry skin, and intense itching. However, psoriasis and AD may overlap or transition into one another spontaneously, independent of biological agent usage. Emerging evidence suggests that defects in skin barrier-related molecules interact with the polarization of T cells, which forms a skin barrier-inflammatory loop with them. This loop contributes to the chronicity of the primary disease or the transition between psoriasis and AD. This review aimed to elucidate the mechanisms underlying skin barrier defects in driving the overlap between psoriasis and AD. In this review, the importance of repairing the skin barrier was underscored, and the significance of tailoring biologic treatments based on individual immune status instead of solely adhering to the treatment guidelines for AD or psoriasis was emphasized.

Mast cells in type 2 skin inflammation: Maintenance and function

Mast cells (MCs) are immune cells residing in tissues and playing indispensable roles in maintaining homeostasis and inflammatory states. Skin lesions associated with atopic dermatitis (AD) and type 2 skin inflammation display an increment in MCs, which have both pro- and anti-inflammatory effects. The direct and indirect activations of skin MCs by environmental factors such as Staphylococcus aureus can instigate type 2 skin inflammation in AD with poorly understood mechanisms. Furthermore, both IgE-dependent and -independent degranulation of MCs contribute to pruritus in AD. Conversely, MCs suppress type 2 skin inflammation by promoting Treg expansion through IL-2 secretion in the spleen. Moreover, skin MCs can upregulate gene expression involved in skin barrier function, thus mitigating AD-like inflammation. These functional variances of MCs in AD could stem from differences in experimental systems, their localization, and origins. In this review, we will focus on how MCs are maintained in the skin under homeostatic and inflammatory conditions, and how they are involved in the pathogenesis of type 2 skin inflammation.

Functional antibody delivery: Advances in cellular manipulation

The current therapeutic antibody market in the U.S. consists of 100 antibody-based products and their market value is expected to explode beyond $300 billion by 2025. These therapies are presently limited to extracellular targets due to the innate inability of antibodies to transverse membranes. To expand the number of accessible therapeutic targets, intracellular antibody delivery is necessary. Many delivery vehicles for antibodies have been used with some promising results, such as nanoparticles and cell penetrating polymers. Despite the success of these delivery platforms using model antibody cargo, there is a surprisingly small number of studies that focus on functional antibody delivery into the cytosol that also measures a cellular response. Antibodies can be designed for essentially unlimited targets, including proteins and DNA, that will ultimately control cell function once delivered inside cells. Advancement in cellular manipulation depends on the application of intracellularly delivering functional antibodies to achieve a desired result. This review focuses on the emerging field of functional antibody delivery which enables various cellular responses and cell manipulation.

Contribution of Dysregulated B-Cells and IgE Antibody Responses to Multiple Sclerosis

Multiple sclerosis (MS), a debilitating autoimmune inflammatory disease that affects the brain and spinal cord, causes demyelination of neurons, axonal damage, and neurodegeneration. MS and the murine experimental autoimmune encephalomyelitis (EAE) model have been viewed mainly as T-cell-mediated diseases. Emerging data have suggested the contribution of B-cells and autoantibodies to the disease progression. However, the underlying mechanisms by which dysregulated B-cells and antibody response promote MS and EAE remain largely unclear. Here, we provide an updated review of this specific subject by including B-cell biology and the role of B-cells in triggering autoimmune neuroinflammation with a focus on the regulation of antibody-producing B-cells. We will then discuss the role of a specific type of antibody, IgE, as it relates to the potential regulation of microglia and macrophage activation, autoimmunity and MS/EAE development. This knowledge can be utilized to develop new and effective therapeutic approaches to MS, which fits the scope of the Research Topic "Immune Mechanism in White Matter Lesions: Clinical and Pathophysiological Implications".

A Review of Acquired Autoimmune Blistering Diseases in Inherited Epidermolysis Bullosa: Implications for the Future of Gene Therapy

Gene therapy serves as a promising therapy in the pipeline for treatment of epidermolysis bullosa (EB). However, with great promise, the risk of autoimmunity must be considered. While EB is a group of inherited blistering disorders caused by mutations in various skin proteins, autoimmune blistering diseases (AIBD) have a similar clinical phenotype and are caused by autoantibodies targeting skin antigens. Often, AIBD and EB have the same protein targeted through antibody or mutation, respectively. Moreover, EB patients are also reported to carry anti-skin antibodies of questionable pathogenicity. It has been speculated that activation of autoimmunity is both a consequence and cause of further skin deterioration in EB due to a state of chronic inflammation. Herein, we review the factors that facilitate the initiation of autoimmune and inflammatory responses to help understand the pathogenesis and therapeutic implications of the overlap between EB and AIBD. These may also help explain whether corrections of highly immunogenic portions of protein through gene therapy confers a greater risk towards developing AIBD.

Multifunctional Roles of the Actin-Binding Protein Flightless I in Inflammation, Cancer and Wound Healing

Flightless I is an actin-binding member of the gelsolin family of actin-remodeling proteins that inhibits actin polymerization but does not possess actin severing ability. Flightless I functions as a regulator of many cellular processes including proliferation, differentiation, apoptosis, and migration all of which are important for many physiological processes including wound repair, cancer progression and inflammation. More than simply facilitating cytoskeletal rearrangements, Flightless I has other important roles in the regulation of gene transcription within the nucleus where it interacts with nuclear hormone receptors to modulate cellular activities. In conjunction with key binding partners Leucine rich repeat in the Flightless I interaction proteins (LRRFIP)1/2, Flightless I acts both synergistically and competitively to regulate a wide range of cellular signaling including interacting with two of the most important inflammatory pathways, the NLRP3 inflammasome and the MyD88-TLR4 pathways. In this review we outline the current knowledge about this important cytoskeletal protein and describe its many functions across a range of health conditions and pathologies. We provide perspectives for future development of Flightless I as a potential target for clinical translation and insights into potential therapeutic approaches to manipulate Flightless I functions.

Immunological Memory in Imiquimod-Induced Murine Model of Psoriasiform Dermatitis

Psoriasis is a common chronic inflammatory skin condition manifested by T cell responses and characterized by preferential recurrence at previously inflamed sites upon withdrawal of treatment. The site-specific disease memory in psoriasis has been linked to CD8⁺CD103⁺ tissue-resident memory T cells (Trm) in the epidermis which were previously thought to only provide “frontline” protection against pathogens and immunosurveillance during cancer development. In this study, we correlated the presence of a subset of the Trm cells which are also CD49a⁺ with disease severity in human psoriatic lesions with acute and chronic disease. Using an imiquimod (IMQ)-induced murine model of psoriasiform dermatitis, we also investigated the level of CD49a⁺ Trm cells in acute, chronic and resolved psoriatic lesions. Investigation of clinical human samples showed that patient disease severity highly correlated with the numbers of epidermal CD49a⁺ Trm cells. Additionally, this subset of Trm cells was shown to persist in resolved lesions of murine psoriasiform dermatitis once clinical disease features had subsided. Importantly, these CD49a⁺ Trm cells showed significantly higher levels of granzyme B (GzmB) production compared to acute disease, suggesting a potential role of CD49a⁺ Trm cells for psoriatic re-occurrence in resolved patients. Better understanding of epidermal CD49a⁺ Trm cell activity is necessary for development of advanced treatment strategies for psoriasis to permit long-term, continuous disease control.

Increasing the level of cytoskeletal protein Flightless I reduces adhesion formation in a murine digital flexor tendon model

Background

Surgical repair of tendons is common, but function is often limited due to the formation of flexor tendon adhesions which reduce the mobility and use of the affected digit and hand. The severity of adhesion formation is dependent on numerous cellular processes many of which involve the actin cytoskeleton. Flightless I (Flii) is a highly conserved cytoskeletal protein, which has previously been identified as a potential target for improved healing of tendon injuries. Using human in vitro cell studies in conjunction with a murine model of partial laceration of the digital flexor tendon, we investigated the effect of modulating Flii levels on tenocyte function and formation of adhesions.

Methods

Human tenocyte proliferation and migration was determined using WST-1 and scratch wound assays following Flii knockdown by siRNA in vitro. Additionally, mice with normal and increased levels of Flii were subjected to a partial laceration of the digital flexor tendon in conjunction with a full tenotomy to immobilise the paw. Resulting adhesions were assessed using histology and immunohistochemistry for collagen I, III, TGF-β1and -β3

Results

Flii knockdown significantly reduced human tenocyte proliferation and migration in vitro. Increasing the expression of Flii significantly reduced digital tendon adhesion formation in vivo which was confirmed through significantly smaller adhesion scores based on collagen fibre orientation, thickness, proximity to other fibres and crimping. Reduced adhesion formation was accompanied with significantly decreased deposition of type I collagen and increased expression of TGF-β1 in vivo.

Conclusions

These findings suggest that increasing the level of Flii in an injured tendon may be beneficial for decreasing tendon adhesion formation.

Flightless I exacerbation of inflammatory responses contributes to increased colonic damage in a mouse model of dextran sulphate sodium-induced ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by cytokine driven inflammation that disrupts the mucosa and impedes intestinal structure and functions. Flightless I (Flii) is an immuno-modulatory protein is a member of the gelsolin family of actin-remodelling proteins that regulates cellular and inflammatory processes critical in tissue repair. Here we investigated its involvement in UC and show that Flii is significantly elevated in colonic tissues of patients with inflammatory bowel disease. Using an acute murine model of colitis, we characterised the contribution of Flii to UC using mice with low (Flii+/-), normal (Flii+/+) and high Flii (FliiTg/Tg). High levels of Flii resulted in significantly elevated disease severity index scores, increased rectal bleeding and degree of colon shortening whereas, low Flii expression decreased disease severity, reduced tissue inflammation and improved clinical indicators of UC. Mice with high levels of Flii had significantly increased histological disease severity and elevated mucosal damage with significantly increased inflammatory cell infiltrate and significantly higher levels of TNF-α, IFN-γ, IL-5 and IL-13 pro-inflammatory cytokines. Additionally, Flii overexpression resulted in decreased β-catenin levels, inhibited Wnt/β-catenin signalling and impaired regeneration of colonic crypts. These studies suggest that high levels of Flii, as is observed in patients with UC, may adversely affect mucosal healing via mechanisms involving Th1 and Th2 mediated tissue inflammation and Wnt/β-catenin signalling pathway.