Psoriasis in humans is associated with down-regulation of galectins in dendritic cells

Interactions between skin-resident dendritic and Langerhans cells and pain-sensing neurons

Various immune cells in the skin contribute to its function as a first line of defense against infection and disease, and the skin's dense innervation by pain-sensing sensory neurons protects the host against injury or damage signals. Dendritic cells (DCs) are a heterogeneous population of cells that link the innate immune response to the adaptive response by capturing, processing, and presenting antigens to promote T-cell differentiation and activation. DCs are abundant across peripheral tissues, including the skin, where they are found in the dermis and epidermis. Langerhans cells (LCs) are a DC subset located only in the epidermis; both populations of cells can migrate to lymph nodes to contribute to broad immune responses. Dermal DCs and LCs are found in close apposition with sensory nerve fibers in the skin and express neurotransmitter receptors, allowing them to communicate directly with the peripheral nervous system. Thus, neuroimmune signaling between DCs and/or LCs and sensory neurons can modulate physiologic and pathophysiologic pathways, including immune cell regulation, host defense, allergic response, homeostasis, and wound repair. Here, we summarize the latest discoveries on DC- and LC-neuron interaction with neurons while providing an overview of gaps and areas not previously explored. Understanding the interactions between these 2 defence systems may provide key insight into developing therapeutic targets for treating diseases such as psoriasis, neuropathic pain, and lupus.

The elevation of plasma galectin-9 levels in patients with psoriasis and its associations with inflammatory and immune checkpoint molecules in skin tissues

Psoriasis is a chronic, immune-mediated disorder that mainly affects the skin, with an estimated global prevalence of 2-3%. Galectin-9 (Gal-9) is a β-galactoside-binding lectin capable of promoting or suppressing the progression of infectious and immune-mediated diseases. Here, we determined if the expression of Gal-9 is observed in psoriasis. Gal-9 levels were measured in plasma of psoriasis (n = 62) and healthy control (HC) (n = 31) using an enzyme-linked immunosorbent assay. In addition, skin samples from seven patients were screened for RNA transcriptomes and the expression of Gal-9 was compared with inflammatory, immune checkpoint molecules (ICMs) and Foxp3. The plasma Gal-9 levels in patients with psoriasis were significantly higher (841 pg/mL) than in HCs (617 pg/mL) (P < 0.0001) and were associated with white blood cell numbers, eosinophils (%) and alanine transaminase. The levels of inflammatory molecules IL-36B, IL-17RA, IL-6R, IL-10, IRF8, TGFb1, and IL-37, and those of ICMs of Tim-3, CTLA-4, CD86, CD80, PD-1LG2, CLEC4G, and Foxp3 were significantly correlated with Gal-9 (LGALS9) in skin. However, HMGB1, CD44, CEACAM1 and PDL1-known to be associated with a variety of Gal-9 biological functions were not correlated with LGALS9. Thus, it is likely that Gal-9 expression affects the disease state of PS.

Evaluation of Plasma Concentrations of Galectins-1, 2 and 12 in Psoriasis and Their Clinical Implications

Psoriasis is a complex disease that nowadays is considered not only a dermatosis but a kind of systemic disorder associated with many accompanying diseases. Metabolic complications leading to cardiovascular incidences are the cause of increased mortality in psoriatic patients. Galectins (gal) are beta-galactoside-binding lectins that exert different functions, including engagement in metabolic processes. Our aim was to assess the concentrations of gal-1, 2 and 12 in psoriatics, to establish their potential clinical implications, including in metabolic complications. Plasma galectins were assessed by ELISA in 60 psoriatic patients and 30 controls without dermatoses and a negative family history of psoriasis. Plasma concentrations of all galectins were significantly higher in patients than controls (gal-1 with p < 0.001, gal-2 and 12 with p < 0.05). There were no correlations between galectins concentrations and psoriasis severity in PASI or disease duration (p > 0.05). Gal-1 and 12 were significantly negatively correlated with GFR (p < 0.05, p < 0.01, respectively) and gal-2 with HDL (p < 0.05). Gal-2 was significantly positively correlated with CRP (p < 0.05) and gal-12 with fasting glucose (p < 0.01). Based on the results and given the reported role of galectins in metabolic disorders we may conclude that gal-1, 2 and 12 could be potentially engaged in metabolic complications in psoriatics, most probably in atherosclerosis. Gal-2 could be perhaps further investigated as a marker of metabolically induced inflammation in psoriasis, gal-1 and gal-12 as predictors of renal impairment in psoriatics due to metabolic disorders. Potentially, gal-12 could be considered in the future as a marker of carbohydrate metabolism disorders in psoriatics.

Expression Pattern and Immunoregulatory Roles of Galectin-1 and Galectin-3 in Atopic Dermatitis and Psoriasis

The pathogenesis of atopic dermatitis (AD) and psoriasis (Ps) overlaps, particularly the activation of the immune response and tissue damage. Here, we evaluated galectin (Gal)-1 and Gal-3 levels, which are beta-galactoside-binding proteins with immunomodulatory functions and examined their effects on human keratinocytes stimulated with either interleukin (IL)-4 or IL-17A. Skin biopsies from AD, Ps, and control patients were evaluated using histological and immunohistochemical analyses. Six studies containing publicly available transcriptome data were individually analyzed using the GEO2R tool to detect Gal-1 and Gal-3 mRNA levels. In vitro, IL-4- or IL-17A-stimulated keratinocytes were treated with or without Gal-1 or Gal-3 to evaluate cytokine release and migration. Our findings showed different patterns of expression for Gal-1 and Gal-3 in AD and Ps skins. Densitometric analysis in skin samples showed a marked increase in the protein Gal-1 levels in Ps epidermis and in both AD and Ps dermis compared to controls. Protein and mRNA Gal-3 levels were downregulated in AD and Ps lesional skin compared with the control samples. In vitro, both galectins addition abrogated the release of IL-8 and RANTES in IL-17-stimulated keratinocytes after 24 h, whereas IL-6 release was downregulated by Gal-3 and Gal-1 in IL-4- and IL-17-stimulated cells, respectively. Administration of both galectins also increased the rate of keratinocyte migration under IL-4 or IL-17 stimulation conditions compared with untreated cells. Altogether, the immunoregulatory and migration effects of Gal-1 and Gal-3 on keratinocytes under inflammatory microenvironment make them interesting targets for future therapies in cutaneous diseases.

Participation of interferons in psoriatic inflammation

Interferons are multifunctional cytokines not expressed in the skin under normal physiological conditions. However, they are overexpressed in serum and skin lesions of patients with psoriasis and play an important role in the pathogenesis of the disease. Interferons act directly on skin resident cells and recruit and modulate inflammatory cells, thereby exacerbating psoriatic inflammation. They upregulate the expression of relevant cytokines and chemokines, facilitate excessive proliferation of keratinocytes, and enhance the formation of poorly differentiated dermal microvessels. In this review, we summarized the pathogenic effect of interferons on psoriasis and also discussed the therapeutic strategies targeting interferons.

Serum galectin-3 levels in patients with psoriasis

INTRODUCTION

Galectin-3 is a β-galactoside-binding lectin associated with cellular proliferation, inflammation and angiogenesis, which are the major characteristics of psoriatic skin.

OBJECTIVES

To investigate serum galectin-3 levels in psoriasis patients compared with healthy controls and to study its relationship with disease characteristics.

METHODS

Seventy-eight patients diagnosed with psoriasis and 78 age- and sex-matched healthy volunteers were included in the study. Serum galectin-3, IL-17, IL-6 and TNF-α levels were measured using Enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum Galectin-3, IL-17, IL-6 and TNF-α levels were significantly higher in psoriasis patients compared with control group (P < .001, P = .003, P < .001 and P < .001, respectively). A cut-off value of 10 ng/mL for galectin-3 was set after receiver operating characteristic analysis. A serum galectin-3 level >10 ng/mL increased the risk of psoriasis by 14.5 times (95% CI: 6.6-32.3, P < .001) and a serum galectin-3 level >10 ng/mL predicted psoriasis with 83.3% sensitivity and 74.3% specificity. No statistically significant association was observed between serum galectin-3 concentrations and disease characteristics including disease severity, presence of psoriatic arthritis, nail involvement and psoriatic comorbidity. No statistically significant correlation was observed between serum galectin-3 level and serum IL-17, IL-6 and TNF-α levels (all three P values > .05).

CONCLUSIONS

Elevated serum galectin-3 levels in psoriasis patients may indicate a possible role of galectin-3 in pathogenesis of psoriasis.

Novel archetype in psoriasis management bridging molecular dynamics in exploring novel therapies

Psoriasis is an autoimmune chronic inflammatory condition of skin affecting 125 million populaces around the globe. It is implicated as a result of multifaceted phenomena involving various cell and subcell activities with the aid of numerous cellular and molecular components including signaling aisle and regulatory proteins owing to the development of such hyperproliferative dermatological conditions. This involves a deeply complex and conflicting pathology owing to genetic and immunological deviations resulting from the unusual presentation of different signaling pathways and regulatory proteins. Explorations of these biomarkers and intervention of molecular and cellular processes in psoriasis are yet to be investigated and could be an exceptional aspect for understanding pathology with successful targeting of disease. In the presented study, we have integrated molecular insights, including signaling molecules, pathways, and proteins implicated in pathogenesis, and we have attempted to link this knowledge to the targeting of these phenomena in order to manage the conditions precisely. Further, therapeutic delivery approaches for targeting distinct layers of skin have also been investigated based on the application of different nanocarriers for successful psoriasis treatment.

Increased serum levels of galectin-9 in patients with chikungunya fever

Chikungunya fever (CHIKF) is an arboviral disease that has caused an epidemic burst of chronic inflammatory joint disease in Latin America in the last few years. Efforts are being spent in understanding the mechanisms by which it may cause such articular damage and in determining possible biomarkers of the disease. Galectins (GAL) are a family of animal lectins with an affinity for beta-galactosides. They have multiple functions including working as receptors in innate immunity and as a control for inflammatory responses in both innate and adaptive immunity. They regulate functions of immune cells, such as lymphocytes and macrophages, which have a main role in the chikungunya inflammatory process. Galectins are also involved in chronification of viral diseases, participate in the immunopathogenesis of chronic joint diseases such as rheumatoid arthritis, and have a role in inflammation in other arboviral diseases, such as dengue. Thus, we intended to determine the serum levels of galectin-1, -3, -4, -7, and -9 in patients with subacute and chronic articular manifestations of CHIKF and to evaluate their associations with clinical manifestations. We evaluated 44 patients with clinical manifestations of CHIKF and serological confirmation with IgM and/or IgG chikungunya virus (CHIKV) antibodies. Forty-nine age- and gender-matched healthy individuals served as controls. Anti-CHIKV IgM and IgG antibodies and galectins serum levels were measured by ELISA. We found higher levels of GAL-9 (patients median 2192 [1500-2631] pg/mL, controls median 46.88 [46.88-46.88] pg/mL, p < 0.0001) and lower levels of GAL-3 (patients median 235.5 [175.5-351.8] pg/mL, controls median 2236.0 [1256.0-2236.0] pg/mL, p < 0.0001) in patients than in controls. There was no statistical difference in levels of GAL-1, -4 and -7 between patients and control groups. There was no difference in GAL-9 serum levels between patients with subacute or chronic symptoms (median 2148 [1500-2722] pg/mL x 2212 [1844-2500] pg/mL, p = 0.3626). A significant association of GAL-9 with joint stiffness, both in its duration and intensity, was found. These results may reflect the participation of GAL-9 in the immunopathogenesis of the inflammatory process in chikungunya fever, as morning stiffness may reflect the systemic inflammatory process.

Role of Galectin-9 in Atopic Dermatitis - Is It Mediated Through E Selectin? A Clinical and Immunohistochemical Study

Background

Atopic dermatitis (AD) is a recognized T helper (Th)2, allergic, skin disease. Galectin-9 (gal-9) is a member of galectin family. It alters T-cell balance resulting in Th2 polarization. These Th2 cells yield various cytokines that may influence E selectin expression. Therefore, we hypothesized that gal-9 may have an active role in AD and this role could be mediated through E selectin.

Objective

To assess this hypothesis, immunohistochemical expression of gal-9 and E selectin was investigated in skin lesions, from atopic dermatitis patients, and compared.

Methods

Twenty-two atopic dermatitis patients and ten controls were included in this case-control study. SCORAD score was used to evaluate atopic dermatitis severity. Biopsies from skin lesions of AD patients and matched sites of controls were taken and stained immunohistochemically by gal-9 and E selectin polyclonal antibodies.

Results

Compared to controls, atopic dermatitis patients exhibited a significant increased gal-9 H score, percent of expression, cellular localization (P˂0.001) and intensity (P=0.04) as well as dermal cellular infiltrate (P˂0.001). Also, there were significant elevations in E selectin H score (P=0.002), percent of expression (P=0.001) and cellular localization (P<0.001) as well as dermal inflammatory infiltrates in AD cases than controls. In AD, 20 cases showed co expression of both gal-9 and E selectin in the epidermis with insignificant correlation between their H scores.

Study Limitations

This study only included a small number of studied subjects.

Conclusion

Galectin-9 and E selectin participates independently in atopic dermatitis pathogenesis, that may help in development of new therapeutic agents in atopic dermatitis management program.

Regulatory annotation of genomic intervals based on tissue-specific expression QTLs

MOTIVATION

Annotating a given genomic locus or a set of genomic loci is an important yet challenging task. This is especially true for the non-coding part of the genome which is enormous yet poorly understood. Since gene set enrichment analyses have demonstrated to be effective approach to annotate a set of genes, the same idea can be extended to explore the enrichment of functional elements or features in a set of genomic intervals to reveal potential functional connections.

RESULTS

In this study, we describe a novel computational strategy named loci2path that takes advantage of the newly emerged, genome-wide and tissue-specific expression quantitative trait loci (eQTL) information to help annotate a set of genomic intervals in terms of transcription regulation. By checking the presence or the absence of millions of eQTLs in a set of input genomic intervals, combined with grouping eQTLs by the pathways or gene sets that their target genes belong to, loci2path build a bridge connecting genomic intervals to functional pathways and pre-defined biological-meaningful gene sets, revealing potential for regulatory connection. Our method enjoys two key advantages over existing methods: first, we no longer rely on proximity to link a locus to a gene which has shown to be unreliable; second, eQTL allows us to provide the regulatory annotation under the context of specific tissue types. To demonstrate its utilities, we apply loci2path on sets of genomic intervals harboring disease-associated variants as query. Using 1 702 612 eQTLs discovered by the Genotype-Tissue Expression (GTEx) project across 44 tissues and 6320 pathways or gene sets cataloged in MSigDB as annotation resource, our method successfully identifies highly relevant biological pathways and revealed disease mechanisms for psoriasis and other immune-related diseases. Tissue specificity analysis of associated eQTLs provide additional evidence of the distinct roles of different tissues played in the disease mechanisms.

AVAILABILITY AND IMPLEMENTATION

loci2path is published as an open source Bioconductor package, and it is available at http://bioconductor.org/packages/release/bioc/html/loci2path.html.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Galectin 3: an extraordinary multifunctional protein in dermatology. Current knowledge and perspectives

Galectin 3 is a unique ~31 kDa protein that recognizes the N-acetyl-lactosamine structure of several glycoconjugates. It mainly occurs in epithelial and myeloid cells, but is also found in a variety of human cell types. In view of the crucial role played by galectin 3 in the regulation of cellular processes of essential importance and in the pathogenetic mechanisms of diverse disorders, it is not surprising that, particularly in the last three decades, the attention of the scientific community has been increasingly drawn to this extraordinary and multifunctional galectin. In this paper the authors summarize current knowledge on the expression of galectin 3 in normal and diseased human skin, its implications in the pathogenesis, diagnosis and prognosis of cutaneous disorders, and the perspectives of a novel approach to the treatment of the latter using galectin 3 or its inhibitors/antagonists.

The expression and function of galectins in skin physiology and pathology

The galectin family comprises β-galactoside-binding proteins widely expressed in many organisms. There are at least 16 family members, which can be classified into three groups based on their carbohydrate-recognition domains. Pleiotropic functions of different galectins in physiological and pathological processes through extracellular or intracellular actions have been revealed. In the skin, galectins are expressed in a variety of cells, including keratinocytes, melanocytes, fibroblasts, dendritic cells, lymphocytes, macrophages and endothelial cells. Expression of specific galectins is reported to affect cell status, such as activation or death, and regulate the interaction between different cell types or between cells and the extracellular matrix. In vitro cellular studies, in vivo animal studies and studies of human clinical material have revealed the pathophysiologic roles of galectins in the skin. The pathogenesis of diverse non-malignant skin disorders, such as atopic dermatitis, psoriasis, contact dermatitis and wound healing, as well as skin cancers, such as melanoma, squamous cell carcinoma, basal cell carcinoma and cutaneous haematologic malignancy can be regulated by different galectins. Revelation of biological roles of galectins in skin may pave the way to future development of galectin-based therapeutic strategies for skin diseases.

Elevated cerebrospinal fluid Galectin-9 is associated with central nervous system immune activation and poor cognitive performance in older HIV-infected individuals

We previously reported that galectin-9 (Gal-9), a soluble lectin with immunomodulatory properties, is elevated in plasma during HIV infection and induces HIV transcription. The link between Gal-9 and compromised neuronal function is becoming increasingly evident; however, the association with neuroHIV remains unknown. We measured Gal-9 levels by ELISA in cerebrospinal fluid (CSF) and plasma of 70 HIV-infected (HIV+) adults stratified by age (older > 40 years and younger < 40 years) either ART suppressed or with detectable CSF HIV RNA, including a subgroup with cognitive assessments, and 18 HIV uninfected (HIV-) controls. Gal-9 tissue expression was compared in necropsy brain specimens from HIV- and HIV+ donors using gene datasets and immunohistochemistry. Among older HIV+ adults, CSF Gal-9 was elevated in the ART suppressed and CSF viremic groups compared to controls, whereas in the younger group, Gal-9 levels were elevated only in the CSF viremic group (p < 0.05). CSF Gal-9 positively correlated with age in all groups (p < 0.05). CSF Gal-9 tracked with CSF HIV RNA irrespective of age (β = 0.33; p < 0.05). Higher CSF Gal-9 in the older viremic HIV+ group correlated with worse neuropsychological test performance scores independently of age and CSF HIV RNA (p < 0.05). Furthermore, CSF Gal-9 directly correlated with myeloid activation (CSF-soluble CD163 and neopterin) in both HIV+ older groups (p < 0.05). Among HIV+ necropsy specimens, Gal-9 expression was increased in select brain regions compared to controls (p < 0.05). Gal-9 may serve as a novel neuroimmuno-modulatory protein that is involved in driving cognitive deficits in those aging with HIV and may be valuable in tracking cognitive abnormalities.

Protein biomarker for psoriasis: A systematic review on their role in the pathomechanism, diagnosis, potential targets and treatment of psoriasis

Psoriasis is defined as a long-lasting multifactorial inflammatory autoimmune skin condition precisely characterized by delimited, erythematic papules with adherent shiny scales. The conditions are led by hyperproliferative responses of epidermis due to hyperactivation and immature keratinocytes production. The psoriatic skin consists of the thickened epidermal layer, in concurrence with inflammatory exudates in the dermis mainly of dendritic cells, neutrophils, T cells, and macrophages, contributing to the distinct manifestation of psoriatic lesions. It consents to multifaceted and discrete pathology due to the genetic and immunological alteration resulting from abnormal expression of various regulatory and structural proteins. These proteins are associated with various cellular and sub-cellular activities. Therefore, the presence of protein in a pathological cellular environment in the psoriatic lesions as well as in serum could be a great avenue for the insight of pathomechanism, anticipation and diagnosis of psoriasis. Research of protein biomarker in psoriasis is yet a developing realm to be explored by both fundamental and clinical researchers. This review is an attempt to assimilate the current discoveries and revelations of different proteins as a biomarker and their importance in pathogenesis, diagnosis, treatment, and anticipation of both the inflammatory and other dermatological aspects of psoriasis.

Dysfunctional immunoregulation in human liver allograft rejection associated with compromised galectin-1/CD7 pathway function

Regulatory T cells in rejected allograft patients display an inability to control responder T cells. Galectin-1 (Gal1) inhibits responder T cells through binding CD7. We investigated whether the dysfunctional immunoregulation in liver allograft rejection patients results from reduced regulatory T-cell Gal1 expression and/or responder T-cell CD7 expression. Circulating regulatory T cells and responder T cells were profiled from 31 acute rejection transplant patients, 85 transplant patients in remission, and 40 healthy controls. CD7+ and CD7− responder T cells were co-cultured with regulatory T cells to assess regulatory T-cell suppressor function. Gal1-small interfering RNA was used to silence regulatory T-cell Gal1. The CD7+ cell percentage was inversely correlated with AST, ALT, and GGT levels. The proportions of CD7+ responder T cells and Gal1+ regulatory T cells were higher in healthy controls than in transplant patients in remission and lowest in acute rejection transplant patients. Notably, CD7+ responder T-cell susceptibility to Gal1+ regulatory T-cell control was ranked in the same manner. Silencing Gal1 expression in regulatory T cells reduced their ability to suppress CD7+ (but not CD7−) responder T cells. Additionally, the proportions of CD43+ and CD45+ responder T cells were higher in healthy controls than in acute rejection transplant patients. CD43 co-expression (but not CD45 co-expression) on CD7+ responder T cells promoted their apoptosis in a Gal1-dependent manner. In sum, dysfunctional immunoregulation in liver allograft rejection patients can be partly attributed to reduced regulatory T-cell Gal1 expression and reduced responder T-cell CD7 expression. Responder T-cell CD43 downregulation in acute rejection patients may further contribute to reduced responder T-cell responsiveness to regulatory T-cell control.

Galectin-9 Is Critical for Mucosal Adaptive Immunity through the T Helper 17-IgA Axis

Impairment of the intestinal mucosal immunity significantly increases the risk of acute and chronic diseases. IgA plays a major role in humoral mucosal immunity to provide protection against pathogens and toxins in the gut. Here, we investigated the role of endogenous galectin-9, a tandem repeat-type β-galactoside-binding protein, in intestinal mucosal immunity. By mucosal immunization of Lgals9^-/- and littermate control mice, it was found that lack of galectin-9 impaired mucosal antigen-specific IgA response in the gut. Moreover, Lgals9^-/- mice were more susceptible to developing watery diarrhea and more prone to death in response to high-dose cholera toxin. The results indicate the importance of galectin-9 in modulating intestinal adaptive immunity. Furthermore, bone marrow chimera mice were established, and galectin-9 in hematopoietic cells was found to be critical for adaptive IgA response. In addition, immunized Lgals9^-/- mice exhibited lower expression of Il17 and fewer T helper 17 (Th17) cells in the lamina propria, implying that the Th17-IgA axis is involved in this mechanism. Taken together, these findings suggest that galectin-9 plays a role in mucosal adaptive immunity through the Th17-IgA axis. By manipulating the expression or activity of galectin-9, intestinal mucosal immune response can be altered and may benefit the development of mucosal vaccination.

Galectin-3: One Molecule for an Alphabet of Diseases, from A to Z

Galectin-3 (Gal-3) regulates basic cellular functions such as cell-cell and cell-matrix interactions, growth, proliferation, differentiation, and inflammation. It is not surprising, therefore, that this protein is involved in the pathogenesis of many relevant human diseases, including cancer, fibrosis, chronic inflammation and scarring affecting many different tissues. The papers published in the literature have progressively increased in number during the last decades, testifying the great interest given to this protein by numerous researchers involved in many different clinical contexts. Considering the crucial role exerted by Gal-3 in many different clinical conditions, Gal-3 is emerging as a new diagnostic, prognostic biomarker and as a new promising therapeutic target. The current review aims to extensively examine the studies published so far on the role of Gal-3 in all the clinical conditions and diseases, listed in alphabetical order, where it was analyzed.

Anti-inflammatory effect of galectin-1 in a murine model of atopic dermatitis

Atopic dermatitis (AD) is caused by both dysregulated immune responses and an impaired skin barrier. Although beta-galactoside-binding protein galectin-1 (Gal-1) has immunomodulatory effects in several inflammatory disorders, therapeutic strategies based on its anti-inflammatory properties have not been explored in AD. Thus, we evaluate pharmacological treatment with Gal-1 in the progression of an ovalbumin (OVA)-induced AD-like skin lesions. The skin of OVA-immunized male BALB/c mice was challenged with drops containing OVA on days 11, 14-18 and 21-24. Additionally, in the last week, a subset of animals was treated intraperitoneally with recombinant Gal-1 (rGal-1) or dexamethasone (Dex). Treatment with rGal-1 decreased the clinical signs of dermatitis in BALB/c mice and diminished local eotaxin and IFN-γ levels. The treatment also suppressed the infiltration of eosinophils and mast cells, which was verified by reduced expression of mouse mast cell protease 6 (mMCP6) and eosinophil peroxidase (EPX). These localized effects are associated with extracellular signal-regulated kinase (ERK) activation and downregulation of endogenous Gal-1. The inhibition of disease progression induced by rGal-1 was also correlated with reduced plasma IL-17 levels. Our results demonstrate that rGal-1 is an effective treatment for allergic skin inflammation in AD and may impact the development of novel strategies for skin inflammatory diseases.

KEY MESSAGES

Pharmacological treatment with rGal-1 reduces clinical signs of atopic dermatitis. Systemic treatment with rGal-1 inhibits eosinophil and mast cell influx in the skin of AD animals. rGal-1 reduced local eotaxin levels and systemic IL-17 levels. The inhibition of disease progression induced by rGal-1 was correlated with upregulation of phosphorylated ERK.

Systemic lupus erythematosus in the light of the regulatory effects of galectin-1 on T-cell function

Galectin-1 is an endogenous immunoregulatory lectin-type protein. Its most important effects are the inhibition of the differentiation and cytokine production of Th1 and Th17 cells, and the induction of apoptosis of activated T-cells. Galectin-1 has been identified as a key molecule in antitumor immune surveillance, and data are accumulating about the pathogenic role of its deficiency, and the beneficial effects of its administration in various autoimmune disease models. Initial animal and human studies strongly suggest deficiencies in both galectin-1 production and responsiveness in systemic lupus erythematosus (SLE) T-cells. Since lupus features widespread abnormalities in T-cell activation, differentiation and viability, in this review the authors wished to highlight potential points in T-cell signalling processes that may be influenced by galectin-1. These points include GM-1 ganglioside-mediated lipid raft aggregation, early activation signalling steps involving p56Lck, the exchange of the CD3 ζ-ZAP-70 to the FcRγ-Syk pathway, defective mitogen-activated protein kinase pathway activation, impaired regulatory T-cell function, the failure to suppress the activity of interleukin 17 (IL-17) producing T-cells, and decreased suppression of the PI3K-mTOR pathway by phosphatase and tensin homolog (PTEN). These findings place galectin-1 into the group of potential pathogenic molecules in SLE.

Galectin-3 in autoimmunity and autoimmune diseases

Galectin-3 (gal-3) is a β-galactoside-binding lectin, which regulates cell-cell and extracellular interactions during self/non-self-antigen recognition and cellular activation, proliferation, differentiation, migration and apoptosis. It plays a significant role in cellular and tissue pathophysiology by organizing niches that drive inflammation and immune responses. Gal-3 has some therapeutic potential in several diseases, including chronic inflammatory disorders, cancer and autoimmune diseases. Gal-3 exerts a broad spectrum of functions which differs according to its intra- or extracellular localization. Recombinant gal-3 strategy has been used to identify potential mode of action of gal-3; however, exogenous gal-3 may not reproduce the functions of the endogenous gal-3. Notably, gal-3 induces monocyte-macrophage differentiation, interferes with dendritic cell fate decision, regulates apoptosis on T lymphocytes and inhibits B-lymphocyte differentiation into immunoglobulin secreting plasma cells. Considering the influence of these cell populations in the pathogenesis of several autoimmune diseases, gal-3 seems to play a role in development of autoimmunity. Gal-3 has been suggested as a potential therapeutic agent in patients affected with some autoimmune disorders. However, the precise role of gal-3 in driving the inflammatory process in autoimmune or immune-mediated disorders remains elusive. Here, we reviewed the involvement of gal-3 in cellular and tissue events during autoimmune and immune-mediated inflammatory diseases.

Evolving mechanistic insights into galectin functions

Galectins are an evolutionarily ancient family of glycan-binding proteins (GBPs) and are found in all animals. Although they were discovered over 30 years ago, ideas about their biological functions continue to evolve. Current evidence indicates that galectins, which are the only known GBPs that occur free in the cytoplasm and extracellularly, are involved in a variety of intracellular and extracellular pathways contributing to homeostasis, cellular turnover, cell adhesion, and immunity. Here we review evolving insights into galectin biology from a historical perspective and explore current evidence regarding biological roles of galectins.

Localization and functional properties of two galectin-1 proteins in Atlantic cod (Gadus morhua) mucosal tissues

Galectin-1 is a β-galactoside binding lectin with multiple immune functions in higher vertebrates. We report the characterization of two galectin-1 proteins from Atlantic cod, with emphasis on mucosal tissues. Tissue distribution of these two ≈14kDa galectin-1 proteins (Codgal1-1 and Codgal1-2) was ascertained by western blotting of one dimensional (1D) and two dimensional (2DE) gels. The two galectin-1 proteins were differentially localized in the mucosal tissues of cod. Codgal1-1 was predominantly localized in the basal cells of skin and this protein was present in all the early developmental stages examined, indicating a likely involvement in developmental processes. The two lectins were also localized in the adherent macrophage-like cells (MLC) from cod head kidney and results gathered indicate their possible secretion during Francisella noatunensis infection, suggesting that they are active components of immune defence. Lactose affinity chromatography coupled with gel filtration co-purified the two cod galectin-1 proteins, which hemagglutinated horse red blood cells in a lactose inhibitable manner. They also could bind and agglutinate both Gram-positive and Gram-negative bacteria. This study suggests multiple functional roles for galectin-1, especially in development and innate immune response of Atlantic cod.

Reduced expression of galectin-1 and galectin-9 by leucocytes in asthma patients

Accumulating evidence shows that galectins play roles in the initiation and resolution phases of inflammatory responses by promoting anti- or proinflammatory effects. This study investigated the presence of three members of the galectin family (galectin-1, -3 and -9) in induced sputum samples of asthma patients, as well as their possible implication in the immunopathogenesis of human asthma. Levels of interleukin (IL)-5, IL-13, and galectins were determined in leucocytes isolated from induced sputum samples by reverse transcription-polymerase chain reaction (RT-PCR) immunofluorescence and flow cytometry. High levels of IL-5 and IL-13 mRNA were detected in sputum cells from asthma patients. In parallel, immunoregulatory proteins galectin-1 and galectin-9 showed a reduced expression on macrophages from sputum samples compared with cells from healthy donors. In-vitro immunoassays showed that galectin-1 and galectin-9, but not galectin-3, are able to induce the production of IL-10 by peripheral blood mononuclear cells from healthy donors. These findings indicate that macrophages from sputum samples of asthma patients express low levels of galectin-1 and galectin-9, favouring the exacerbated immune response observed in this disease.

Immunoregulatory molecules are master regulators of inflammation during the immune response

The balance between pro- and anti-inflammatory signalling is critical to maintain the immune homeostasis under physiological conditions as well as for the control of inflammation in different pathological settings. Recent progress in the signalling pathways that control this balance has led to the development of novel therapeutic agents for diseases characterized by alterations in the activation/suppression of the immune response. Different molecules have a key role in the regulation of the immune system, including the receptors PD-1 (Programmed cell Death 1), CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4) and galectins; or the intracellular enzyme IDO (indoleamine 2,3-dioxygenase). In addition, other molecules as CD69, AhR (Aryl hydrocarbon Receptor), and GADD45 (Growth Arrest and DNA Damage-inducible 45) family members, have emerged as potential targets for the regulation of the activation/suppression balance of immune cells. This review offers a perspective on well-characterized as well as emergent negative immune regulatory molecules in the context of autoimmune inflammatory diseases.