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. 2023 Aug 30;12(17):2177.
doi: 10.3390/cells12172177.

Human Mast Cells Upregulate Cathepsin B, a Novel Marker of Itch in Psoriasis

Peter W West  1 , Chiara Tontini  1 , Haris Atmoko  1 , Orsolya Kiss  1 , Terence Garner  2 , Rajia Bahri  1 , Richard B Warren  1   3   4 , Christopher E M Griffiths  1   3   4 , Adam Stevens  2 , Silvia Bulfone-Paus  1   3   4
Affiliations

Human Mast Cells Upregulate Cathepsin B, a Novel Marker of Itch in Psoriasis

Peter W West et al. Cells. .

Abstract

Mast cells (MCs) contribute to skin inflammation. In psoriasis, the activation of cutaneous neuroimmune networks commonly leads to itch. To dissect the unique contribution of MCs to the cutaneous neuroinflammatory response in psoriasis, we examined their density, distribution, relation to nerve fibres and disease severity, and molecular signature by comparing RNA-seq analysis of MCs isolated from the skin of psoriasis patients and healthy volunteers. In involved psoriasis skin, MCs and Calcitonin Gene-Related Peptide (CGRP)-positive nerve fibres were spatially associated, and the increase of both MC and nerve fibre density correlated with disease severity. Gene set enrichment analysis of differentially expressed genes in involved psoriasis skin showed significant representation of neuron-related pathways (i.e., regulation of neuron projection along with dendrite and dendritic spine morphogenesis), indicating MC engagement in neuronal development and supporting the evidence of close MC-nerve fibre interaction. Furthermore, the analysis of 208 identified itch-associated genes revealed that CTSB, TLR4, and TACR1 were upregulated in MCs in involved skin. In both whole-skin published datasets and isolated MCs, CTSB was found to be a reliable indicator of the psoriasis condition. Furthermore, cathepsin B+ cells were increased in psoriasis skin and cathepsin B+ MC density correlated with disease severity. Therefore, our study provides evidence that cathepsin B could serve as a common indicator of the MC-dependent itch signature in psoriasis.

Keywords: cathepsin B; itch; mast cells; psoriasis.

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Conflict of interest statement

The authors declare no conflict of interest. C.T. and R.B. were supported by funding from the Medical Research Council (UK). R.B.W. is supported by the Manchester NIHR Biomedical Research Centre.

Figures

Figure 1
Figure 1
Mast cell and nerve fiber density, spatial association, and correlation with psoriasis severity. Immunofluorescence microscopy was used to identify and measure the density of (a) dermal MC tryptase and (b) PGP 9.5+ nerve fibres in normal (n = 8) and involved psoriasis skin (n = 11). Each subject is represented by a different symbol. (c,d) The distance in µm between MCs and PGP9.5+ nerves and the normalised frequency distribution of MCs within a given distance of a PGP9.5+ nerve fibre. (e,f) Representative photomicrographs of normal (e) and involved (f) skin show MC tryptase (cyan) and PGP9.5 (magenta). Discrete areas of PGP9.5 immunofluorescence in the dermis are identified (arrowheads). Scale bar = 20 µm. The tissue density of tryptase-positive MCs (g) and PGP9.5-positive nerve fibres (h) was correlated with the psoriasis severity index (PASI). * p < 0.05, ** p < 0.01, **** p < 0.0001, (unpaired t-test (a,b) Mann–Whitney U test (c), Pearson correlation (g,h)).
Figure 2
Figure 2
Calcitonin gene-related peptide density, spatial association with MCs, and correlation with severity of psoriasis. Immunofluorescence microscopy was used to identify and measure the density of MCs (tryptase), nerve fibres (PGP 9.5), and CGRP in normal (n = 6) and involved psoriasis skin (n = 10). (a) CGRP nerve fibre density and (b) proportion of CGRP+ nerve fibres in skin sections. (c) Distance between MC and CGRP+ nerve fibres and (d) normalised frequency distribution of MCs within a given distance of a CGRP+ nerve fibres in skin. (e) Correlation between CGRP density and severity index (PASI). (f,g) Representative photomicrographs of normal (f) and involved (g) skin show MC tryptase (cyan), PGP9.5 (yellow), and CGRP (magenta). The inset panel shows a magnified area with colocalized fluorescence. Scale bar = 20µm. Data are median ± IQR of n = 6 and n = 10 donors. * p < 0.05, **** p < 0.0001, ns: not significant (Mann–Whitney U test (a,c), unpaired t-test (b), Pearson correlation (e)).
Figure 3
Figure 3
RNA-seq analysis of mast cells isolated from normal and psoriasis skin. Mast cells (MCs) were isolated from normal (n = 7) and psoriasis-involved skin (n = 6, 2 donors pooled): (a) 3D PCA plot of log-transformed normalized matrix showing confidence ellipses (PCA1: 25.5%, PCA2: 12.42%, PCA3: 9.5% of explained variance) and (b) volcano plot of DEGs. Significantly different genes based on FDR-corrected p values and log2 fold change ± 2 are highlighted in red. (c) Z-score heatmap of the top 50 DEGs (q < 0.05) ordered by log2 fold change.
Figure 4
Figure 4
Canonical pathway (CP) analysis revealed functional enrichment of the CLEAR and Autophagy pathways in mast cells, with an upstream role for IL1B. Canonical pathway analysis was carried out on 203/249 differentially expressed genes (q < 0.05) using IPA. (a) CP analysis of DEGs, showing a Fisher exact test p-value < 0.05. Activation z-scores are displayed as orange for predicted activation. (b) Venn diagram of shared differentially-expressed genes identified in the CLEAR, Autophagy, and PI3K Signaling in B Lymphocytes (PI3K) canonical pathways. (c) Upstream regulator analysis of isolated MCs based on gene expression. Upregulated/downregulated genes (log2 fold change > 0/< 0) are respectively marked in magenta/cyan. Activation z-scores are displayed as orange arrows for predicted activation, blue for predicted inhibition, and grey for no prediction. Inconsistent findings are highlighted in yellow.
Figure 5
Figure 5
Neuron-associated ontology terms in psoriasis mast cells in gene set enrichment analysis. Gene set enrichment analysis of RNA isolated from MCs from healthy (n = 7) and psoriasis lesional skin (n = 6, 2 donors pooled). (a) Scatterplot of significantly enriched ontology terms obtained through the gseGO, gseKEGG, and gsePathway functions of ClusterProfiler/ReactomePA R tools. The cut-off for significance was set to the false discovery rate-corrected p value of < 0.05, and the analyses returned a total of 29 enriched ontology descriptions (23 GO, 2 KEGG, 4 REACTOME), as shown on the left of the plot. The colour of the dots represents the adjusted p-value, while the size of the dots represents the gene counts for each ontology term. The gene ratio is a measure of the total enrichment based on positive hits out of the total number of genes in that pathway. (b) Plot of enrichment scores and rank in the ordered dataset of the neuron-associated GO ontology terms GO:0048814, GO:0061001 and GO:0010975, with the highest-ranked genes showing the most enrichment.
Figure 6
Figure 6
Psoriasis mast cells share half of their differentially expressed genes with whole skin, while mast cells and neuronal signatures are unequally represented across studies and conditions. (a) Venn diagram of the number of overlapping differentially expressed genes between healthy donors and psoriasis patients in isolated MCs and microarray datasets. (b) Log2 fold change compared to healthy controls of 15 overlapping genes across datasets. (c) Cell type enrichment analysis of publicly available datasets and of MCs isolated from normal skin and psoriasis lesions, performed using xCell. The proportion of samples in which significant (p < 0.05) MC and neuron enrichment was detected is displayed per study. Isolated MCs were added as internal control for MC-specific signatures.
Figure 7
Figure 7
Random forest analysis of itch-associated genes and cathepsin B expression in mast cells. Random forest plot of differentially expressed genes in (a) psoriasis whole skin and (b) isolated MCs. Attributes that were significant (green bars), tentative, (yellow bars), or rejected (red bars) as indicative of the psoriasis condition are listed in order of importance. Worst, average and best shadow in each iteration are shown (blue bars). Gene names of significantly indicative attributes are enlarged below each plot. (c) Cathepsin B measured in the cell-free supernatant from human MCs stimulated with SP (concentrations shown) for 1 h. (d,e) Representative photomicrographs of the dermis of healthy (d) and psoriasis skin (e), showing cathepsin B (magenta) and MC tryptase (cyan) with nuclei stained with DAPI. Scale bar = 20 µm. Cathepsin B+ MCs are indicated by arrows. Examples of cathepsin-stained mast cells have been enlarged in each panel. (f,g) Number of total cathepsin B+ cells (f) and cathepsin B+ MCs (g) in normal skin (blue dots) and psoriasis skin (red dots). Data are mean± SEM (f) and median± IQR (g) of n = 9 donors. **** = p < 0.0001, ns: not significant (unpaired t-test). (h,i) total number of cathepsin B+ cells and cathepsin B+ MCs in psoriasis skin correlated with PASI. Significant positive correlation indicated by * p = 0.0225 (Pearson correlation).
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References

    1. Weitzmann A., Naumann R., Dudeck A., Zerjatke T., Gerbaulet A., Roers A. Mast Cells Occupy Stable Clonal Territories in Adult Steady-State Skin. J. Investig. Dermatol. 2020;120:2433–2441. doi: 10.1016/j.jid.2020.03.963. - DOI - PubMed
    1. Egan C.L., Viglione-Schneck M.J., Walsh L.J., Green B., Trojanowski J.Q., Whitaker-Menezes D., Murphy G.F. Characterization of unmyelinated axons uniting epidermal and dermal immune cells in primate and murine skin. J. Cutan. Pathol. 1998;25:20–29. doi: 10.1111/j.1600-0560.1998.tb01685.x. - DOI - PubMed
    1. Undem B.J., Taylor-Clark T. Mechanisms underlying the neuronal-based symptoms of allergy. J. Allergy Clin. Immunol. 2014;133:1521–1534. doi: 10.1016/j.jaci.2013.11.027. - DOI - PMC - PubMed
    1. Arizono N., Matsuda S., Hattori T., Kojima Y., Maeda T., Galli S.J. Anatomical variation in mast cell nerve associations in the rat small intestine, heart, lung, and skin. Similarities of distances between neural processes and mast cells, eosinophils, or plasma cells in the jejunal lamina propria. Lab. Investig. 1990;62:626–634. - PubMed
    1. Botchkarev V.A., Eichmüller S., Peters E.M., Pietsch P., Johansson O., Maurer M., Paus R. A simple immunofluorescence technique for simultaneous visualization of mast cells and nerve fibers reveals selectivity and hair cycle—Dependent changes in mast cell—Nerve fiber contacts in murine skin. Arch. Dermatol. Res. 1997;289:292–302. doi: 10.1007/s004030050195. - DOI - PubMed

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