Participation of T cell immunoglobulin and mucin domain-3 (TIM-3) and its ligand (galectin-9) in the pathogenesis of active generalized vitiligo

Modulation of the Gal-9/TIM-3 Immune Checkpoint with α-Lactose. Does Anomery of Lactose Matter?

Simple Summary

The disaccharide lactose is a common excipient in pharmaceutical products. In addition, the two anomers α- and β-lactose can exert immuno-modulatory effects. α-Lactose functions as a major regulator of the T-cell immunoglobulin mucin-3 (Tim-3)/Galectin-9 (Gal-9) immune checkpoint, through direct binding to the β-galactoside-binding lectin galectin-9. The blockade of TIM-3 with monoclonal antibodies or small molecules represents a promising approach to combat onco-hematological diseases, in particular myelodysplastic syndromes, and acute myeloid leukemia. Alternatively, the activity of the checkpoint can be modulated via targeting of Gal-9 with both α- and β-lactose. In fact, lactose is a quasi-pan-galectin ligand, capable of modulating the functions of most of the 16 galectin molecules. This review discusses the capacity of lactose and Gal-9 to modulate the TIM-3/Gal-9 and PD-1/PD-L1 immune checkpoints in oncology. The immuno-regulatory roles of lactose and Gal-9 are highlighted.

Abstract

The disaccharide lactose is an excipient commonly used in pharmaceutical products. The two anomers, α- and β-lactose (α-L/β-L), differ by the orientation of the C-1 hydroxyl group on the glucose unit. In aqueous solution, a mutarotation process leads to an equilibrium of about 40% α-L and 60% β-L at room temperature. Beyond a pharmaceutical excipient in solid products, α-L has immuno-modulatory effects and functions as a major regulator of TIM-3/Gal-9 immune checkpoint, through direct binding to the β-galactoside-binding lectin galectin-9. The blockade of the co-inhibitory checkpoint TIM-3 expressed on T cells with anti-TIM-3 antibodies represents a promising approach to combat different onco-hematological diseases, in particular myelodysplastic syndromes and acute myeloid leukemia. In parallel, the discovery and development of anti-TIM-3 small molecule ligands is emerging, including peptides, RNA aptamers and a few specifically designed heterocyclic molecules. An alternative option consists of targeting the different ligands of TIM-3, notably Gal-9 recognized by α-lactose. Modulation of the TIM-3/Gal-9 checkpoint can be achieved with both α- and β-lactose. Moreover, lactose is a quasi-pan-galectin ligand, capable of modulating the functions of most of the 16 galectin molecules. The present review provides a complete analysis of the pharmaceutical and galectin-related biological functions of (α/β)-lactose. A focus is made on the capacity of lactose and Gal-9 to modulate both the TIM-3/Gal-9 and PD-1/PD-L1 immune checkpoints in oncology. Modulation of the TIM-3/Gal-9 checkpoint is a promising approach for the treatment of cancers and the role of lactose in this context is discussed. The review highlights the immuno-regulatory functions of lactose, and the benefit of the molecule well beyond its use as a pharmaceutical excipient.

Expression analysis of PD-1 and Tim-3 immune checkpoint receptors in patients with vitiligo; positive association with disease activity

The contribution of immune checkpoint receptors in the immunopathogenesis of various autoimmune diseases has been addressed in previous reports. In this study,  the expression profile of T-cell immunoglobulin and mucin-domain containing-3 (Tim-3) and programmed cell death-1 (PD-1) checkpoint molecules was investigated in CD8⁺ T cells of Vitiligo patients. The association of Tim-3 and PD-1 expression with disease activity was also explored. The frequency of Tim-3⁺ /PD-1⁺ /CD8⁺ T cells in 30 patients with vitiligo and 30 sex- and age-matched controls was determined by flow cytometry. CD8⁺ T cells were then positively isolated by magnetic beads, and the mRNA expression of PD-1 and Tim-3 was determined by TaqMan-based real-time PCR. To measure the cytokines production, PBMCs were stimulated with PMA/ionomycin and concentrations of IL-4, IFN-γ and TNF-α were measured in culture supernatants by ELISA. Disease activity of patients with vitiligo was determined using the Vitiligo Area Severity Index. Patients with vitiligo have significantly shown more expression of Tim-3 and PD-1 on their CD8⁺ T cells compared with controls. Expression analysis of Tim-3 mRNA, but not PD-1, confirmed the results obtained from flow cytometry. While the production levels of TNF-α and IFN-γ were found higher by patients with vitiligo, IL-4 production was lower in patients compared with controls. A direct association was observed between the Tim-3 and PD-1 expression and also the production of pro-inflammatory cytokines with disease activity of patients with vitiligo. Our results indicate that Tim-3 and PD-1 are involved in immune dysregulation mechanisms of CD8⁺ T cells in vitiligo and may introduce as potential biomarkers for disease progression and targeted immunotherapy.

Emerging role of immune cell network in autoimmune skin disorders: An update on pemphigus, vitiligo and psoriasis

Autoimmune skin diseases are a group of disorders that arise due to a deregulated immune system resulting in skin tissue destruction. In the majority of these conditions, either autoreactive immune cells or the autoantibodies are generated against self-antigens of the skin. Although the etiology of these diseases remains elusive, biochemical, genetic, and environmental factors such as infectious agents, toxins damage the skin tissue leading to self-antigen generation, autoantibody attack and finally results in autoimmunity of skin. Immune dysregulation, which involves predominantly T helper 1/17 (Th1/Th17) polarization and the inability of regulatory T cells to regress immune response, is implicated in autoimmune skin diseases. The emerging roles of immune cells, cytokines, and chemokines in the pathogenesis of common autoimmune skin diseases like pemphigus, vitiligo, and psoriasis are discussed in this review. The main focus is on the interplay between immune cell network including the innate and adaptive immune system, regulatory cells, immune checkpoints and recently identified tissue-resident memory cells (TRMs) in disease pathogenesis and relapse. We also attempt to highlight on the immune mechanisms common to these diseases which can be targeted for designing novel therapeutics.

Vitiligo blood transcriptomics provides new insights into disease mechanisms and identifies potential novel therapeutic targets

BACKGROUND

Significant gaps remain regarding the pathomechanisms underlying the autoimmune response in vitiligo (VL), where the loss of self-tolerance leads to the targeted killing of melanocytes. Specifically, there is incomplete information regarding alterations in the systemic environment that are relevant to the disease state.

METHODS

We undertook a genome-wide profiling approach to examine gene expression in the peripheral blood of VL patients and healthy controls in the context of our previously published VL-skin gene expression profile. We used several in silico bioinformatics-based analyses to provide new insights into disease mechanisms and suggest novel targets for future therapy.

RESULTS

Unsupervised clustering methods of the VL-blood dataset demonstrate a "disease-state"-specific set of co-expressed genes. Ontology enrichment analysis of 99 differentially expressed genes (DEGs) uncovers a down-regulated immune/inflammatory response, B-Cell antigen receptor (BCR) pathways, apoptosis and catabolic processes in VL-blood. There is evidence for both type I and II interferon (IFN) playing a role in VL pathogenesis. We used interactome analysis to identify several key blood associated transcriptional factors (TFs) from within (STAT1, STAT6 and NF-kB), as well as "hidden" (CREB1, MYC, IRF4, IRF1, and TP53) from the dataset that potentially affect disease pathogenesis. The TFs overlap with our reported lesional-skin transcriptional circuitry, underscoring their potential importance to the disease. We also identify a shared VL-blood and -skin transcriptional "hot spot" that maps to chromosome 6, and includes three VL-blood dysregulated genes (PSMB8, PSMB9 and TAP1) described as potential VL-associated genetic susceptibility loci. Finally, we provide bioinformatics-based support for prioritizing dysregulated genes in VL-blood or skin as potential therapeutic targets.

CONCLUSIONS

We examined the VL-blood transcriptome in context with our (previously published) VL-skin transcriptional profile to address a major gap in knowledge regarding the systemic changes underlying skin-specific manifestation of vitiligo. Several transcriptional "hot spots" observed in both environments offer prioritized targets for identifying disease risk genes. Finally, within the transcriptional framework of VL, we identify five novel molecules (STAT1, PRKCD, PTPN6, MYC and FGFR2) that lend themselves to being targeted by drugs for future potential VL-therapy.