Antimicrobial late cornified envelope (LCE) proteins: the psoriasis risk factor LCE3B/C-del affects microbiota composition

Antibacterial Activity of the p53 Tumor Suppressor Protein-How Strong Is the Evidence?

The p53 tumor suppressor is best known for controlling the cell cycle, apoptosis, DNA repair, and metabolism, but it also regulates immunity and is able to impede the live cycle of viruses. For this reason, these infectious agents encode proteins which inactivate p53. However, what is less known is that p53 can also be inactivated by human pathogenic bacteria. It is probably not due to collateral damage, but specific targeting, because p53 could interfere with their multiplication. The mechanisms of the antibacterial activity of p53 are poorly known. However, they can be inferred from the results of high-throughput studies, which have identified more than a thousand p53-activated genes. As it turns out, many of these genes code proteins which have proven or plausible antibacterial functions like the efficient detection of bacteria by pattern recognition receptors, the induction of pro-inflammatory pyroptosis, the recruitment of immune cells, direct bactericidal activity, and the presentation of bacterial metabolites to lymphocytes. Probably there are more antibacterial, p53-regulated functions which were overlooked because laboratory animals are kept in sterile conditions. In this review, we present the outlines of some intriguing antibacterial mechanisms of p53 which await further exploration. Definitely, this area of research deserves more attention, especially in light of the appearance of antibiotic-resistant bacterial strains.

Strengthening the Skin Barrier by Using a Late Cornified Envelope 6A-Derived Biomimetic Peptide

Changes in the expression of cornified envelope (CE) components are a hallmark of numerous pathological skin conditions and aging, underlying the importance of this stratum corneum structure in the homeostasis of the epidermal barrier. We performed a detailed characterisation of LCE6A, a member of the Late Cornified Envelope protein family. Immunohistochemical and immunoblot experiments confirmed that LCE6A is expressed late during epidermal differentiation. Crosslinking assays of recombinant LCE6A performed either in situ on human skin sections or in vitro demonstrated that LCE6A is indeed a substrate of transglutaminases and crosslinked to CEs. LCE6A-derived peptides containing a glutamine-lysine sequence retained these properties of the full-length protein and reinforced the mechanical resistance of CE submitted to sonication. We designed P26, a LCE6A-derived biomimetic peptide that similarly reinforced CE in vitro, and evaluated its protective properties ex vivo, on human skin explants, and in two double blind and vehicle-controlled clinical trials. P26 was able to protect the skin from barrier disruption, to limit the damage resulting from a defective barrier, and could improve the signs of aging such as loss of skin firmness and increased skin roughness. Hence, our detailed characterisation of LCE6A as a component of the CE enabled us to develop a LCE6A-derived peptide, biologically active with a new and original mode of action that could be of great interest as a cosmetic ingredient and a pharmacologic agent.

Atopic Dermatitis Complicated by Recurrent Eczema Herpeticum Is Characterized by Multiple, Concurrent Epidermal Inflammatory Endotypes

A subgroup of patients with atopic dermatitis (AD) suffers from recurrent, disseminated herpes simplex virus skin infection, termed eczema herpeticum. To determine the transcriptional mechanisms of the skin and immune system pathobiology that underlie development of AD with eczema herpeticum (ADEH), we performed RNA-sequencing analysis of nonlesional skin (epidermis, dermis) from AD patients with and without a history of ADEH (ADEH+, n = 15; ADEH-, n = 13) along with healthy controls (n = 15). We also performed RNA sequencing on participants' plasmacytoid dendritic cells infected in vitro with herpes simplex virus 1. ADEH+ patients exhibited dysregulated gene expression, limited in the dermis (14 differentially expressed genes) and more widespread in the epidermis (129 differentially expressed genes). ADEH+-upregulated epidermal differentially expressed genes were enriched in type 2 cytokine (IL4R , CCL22, CRLF2, IL7R), interferon (CXCL10, ICAM1, IFI44, IRF7), and IL-36γ (IL36G) inflammatory gene pathways. All ADEH+ participants exhibited type 2 cytokine and inteferon endotypes, and 87% were IL36G-high. In contrast, these endotypes were more variably expressed among ADEH- participants. ADEH+ skin also had dysregulated epidermal differentiation complex gene expression of the late-cornified envelope, S100A, and small proline-rich gene families, which are involved in skin barrier function and antimicrobial activities. Plasmacytoid dendritic cell transcriptional responses to herpes simplex virus 1 infection were unaltered by ADEH status. The study concluded that the pathobiology underlying ADEH+ risk is associated with a unique, multifaceted epidermal inflammation that accompanies dysregulation of epidermal differentiation complex genes. These findings will help direct future studies that define how these inflammatory patterns may drive risk of eczema herpeticum in AD.

Comparative genomics of sirenians reveals evolution of filaggrin and caspase-14 upon adaptation of the epidermis to aquatic life

The mammalian epidermis has evolved to protect the body in a dry environment. Genes of the epidermal differentiation complex (EDC), such as FLG (filaggrin), are implicated in the barrier function of the epidermis. Here, we investigated the molecular evolution of the EDC in sirenians (manatees and dugong), which have adapted to fully aquatic life, in comparison to the EDC of terrestrial mammals and aquatic mammals of the clade Cetacea (whales and dolphins). We show that the main subtypes of EDC genes are conserved or even duplicated, like late cornified envelope (LCE) genes of the dugong, whereas specific EDC genes have undergone inactivating mutations in sirenians. FLG contains premature stop codons in the dugong, and the ortholog of human CASP14 (caspase-14), which proteolytically processes filaggrin, is pseudogenized in the same species. As FLG and CASP14 have also been lost in whales, these mutations represent convergent evolution of skin barrier genes in different lineages of aquatic mammals. In contrast to the dugong, the manatee has retained functional FLG and CASP14 genes. FLG2 (filaggrin 2) is truncated in both species of sirenians investigated. We conclude that the land-to-water transition of sirenians was associated with modifications of the epidermal barrier at the molecular level.

Distinctive genes and signaling pathways associated with type 2 diabetes-related periodontitis: Preliminary study

The biological mechanisms underlying the pathogenesis of type 2 diabetes (T2DM)-related periodontitis remain unclear. This cross-sectional study evaluated the distinctive transcriptomic changes between tissues with periodontal health and with periodontitis in patients with T2DM. In this cross-sectional study, whole transcriptome sequencing was performed on gingival biopsies from non-periodontitis and periodontitis tissues from non-diabetic and diabetic patients. A differentially expressed gene (DEG) analysis and Ingenuity Pathway Analysis (IPA) assessed the genes and signaling pathways associated with T2DM-related periodontitis. Immunohistochemistry was performed to validate selected DEGs possibly involved in T2DM-related periodontitis. Four hundred and twenty and one thousand five hundred and sixty-three DEGs (fold change ≥ 2) were uniquely identified in the diseased tissues of non-diabetic and diabetic patients, respectively. The IPA predicted the activation of Phagosome Formation, Cardiac β-adrenergic, tRNA Splicing, and PI3K/AKT pathways. The IPA also predicted the inhibition of Cholesterol Biosynthesis, Adrenomedullin, and Inositol Phosphate Compounds pathways in T2DM-related periodontitis. Validation of DEGs confirmed changes in protein expression of PTPN2, PTPN13, DHCR24, PIK3R2, CALCRL, IL1RN, IL-6R and ITGA4 in diseased tissues in diabetic subjects. Thus, these preliminary findings indicate that there are specific genes and functional pathways that may be involved in the pathogenesis of T2DM-related periodontitis.

Atopic dermatitis complicated by recurrent eczema herpeticum is characterized by multiple, concurrent epidermal inflammatory endotypes

BACKGROUND

A subgroup of atopic dermatitis (AD) patients suffer from recurrent, disseminated herpes simplex virus (HSV) skin infections, termed eczema herpeticum (EH), which can be life-threatening and contribute to AD morbidity. The pathobiology underlying ADEH is unknown.

OBJECTIVE

To determine transcriptional mechanisms of skin and immune system pathobiology that underlie ADEH disease.

METHODS

We performed whole transcriptome RNA-sequencing of non-lesional skin samples (epidermis, dermis) of AD patients with (ADEH + , n=15) and without (ADEH - , n=13) recurrent EH history, and healthy controls (HC, n=15). We also performed RNA-sequencing on plasmacytoid dendritic cells (pDCs) collected from these participants and infected in vitro with HSV-1. Differential expression, gene set enrichment, and endotyping analyses were performed.

RESULTS

ADEH + disease was characterized by dysregulation in skin gene expression, which was limited in dermis (differentially expressed genes [DEGs]=14) and widespread in epidermis (DEGs=129). ADEH + -upregulated epidermal DEGs were enriched in type 2 cytokine (T2) ( IL4R, CCL22, CRLF2, IL7R ), interferon ( CXCL10, ICAM1, IFI44 , and IRF7) , and IL-36γ ( IL36G ) inflammatory pathway genes. At a person-level, all ADEH + participants exhibited T2 and interferon endotypes and 87% were IL36G-high. In contrast, these endotypes were more variably expressed among ADEH - participants. ADEH + patient skin also exhibited dysregulation in epidermal differentiation complex (EDC) genes within the LCE, S100 , and SPRR families, which are involved in skin barrier function, inflammation, and antimicrobial activities. pDC transcriptional responses to HSV-1 infection were not altered by ADEH status.

CONCLUSIONS

ADEH + pathobiology is characterized by a unique, multi-faceted epidermal inflammation that accompanies dysregulation in the expression of EDC genes.

Key Messages

AD patients with a history of recurrent EH exhibit molecular skin pathobiology that is similar in form, but more severe in degree, than in AD patients without this complication. Non-lesional skin of ADEH + patients concurrently exhibits excessive type 2 cytokine, interferon, and IL-36γ-driven epidermal inflammation. Expression of these inflammatory skin endotypes among ADEH + patients is associated with dysregulation in expression of epidermal differentiation complex genes involved in barrier function, inflammation, and antimicrobial activity.

Capsule Summary

AD patients with a history of recurrent disseminated HSV-1 skin infections form a unique molecular skin endotype group that concurrently exhibits type 2 cytokine, interferon, and IL-36γ-driven skin inflammation, accompanied by dysregulation in expression of epidermal differentiation complex genes involved in barrier function, inflammation, and antimicrobial activity.

CYSRT1: an antimicrobial epidermal protein that can interact with late cornified envelope (LCE) proteins

Late cornified envelope (LCE) proteins are small cationic epidermal proteins with antimicrobial properties, and the combined deletion of LCE3B and LCE3C genes is a risk factor for psoriasis that affects skin microbiome composition. In a yeast two-hybrid screen we identified cysteine-rich tail 1 protein (CYSRT1) as an interacting partner of members of all LCE groups except LCE6. These interactions were confirmed in a mammalian cell system by co-immunoprecipitation. CYSRT1 is a protein of unknown function that is specifically expressed in cutaneous and oral epithelia and spatially colocalizes with LCE proteins in the upper layers of the suprabasal epidermis. Constitutive CYSRT1 expression is present in fully differentiated epidermis and can be further induced in vivo by disruption of the skin barrier upon stratum corneum removal. Transcriptional regulation correlates to keratinocyte terminal differentiation but not to skin bacteria exposure. Similar to LCEs, CYSRT1 was found to have antibacterial activity against Pseudomonas aeruginosa. Comparative gene sequence analysis and protein amino acid alignment indicates that CYSRT1 is highly conserved among vertebrates and has putative antimicrobial activity. To summarize, we identified CYSRT1 in the outer skin layer, where it colocalizes with LCE proteins and contributes to the constitutive epidermal antimicrobial host defense repertoire.

Allergic Contact Cell-Mediated Hypersensitivity in Psoriasis: A Narrative Minireview

The dysfunctionality of the protective skin barrier in psoriasis allows easier cutaneous penetration of various contact haptens; thus, such patients can develop allergic contact hypersensitivity as a comorbidity. Both skin conditions involve T-cell-mediated mechanisms. Dermatologists and allergists should consider assessing allergic contact cell-mediated hypersensitivity in selected psoriasis patients, especially those with palmoplantar psoriasis and who are refractory to topical treatments, and in patients with psoriasis, with or without arthritis, treated with biologics that present skin lesions clinically suggestive of contact dermatitis.