Netherton syndrome subtypes share IL-17/IL-36 signature with distinct IFN-α and allergic responses.

BACKGROUND: Netherton syndrome (NS) is a rare recessive skin disorder caused by loss-of-function mutations in SPINK5 encoding the protease inhibitor LEKTI (lymphoepithelial Kazal-type-related inhibitor). NS patients experience severe skin barrier defects, display inflammatory skin lesions, and have superficial scaling with atopic manifestations. They present with typical ichthyosis linearis circumflexa (NS-ILC) or scaly erythroderma (NS-SE). OBJECTIVE: We used a combination of several molecular profiling methods to comprehensively characterize the skin, immune cells, and allergic phenotypes of NS-ILC and NS-SE patients. METHODS: We studied a cohort of 13 patients comprising 9 NS-ILC and 4 NS-SE. RESULTS: Integrated multiomics revealed abnormal epidermal proliferation and differentiation and IL-17/IL-36 signatures in lesion skin and in blood in both NS endotypes. Although the molecular profiles of NS-ILC and NS-SE lesion skin were very similar, nonlesion skin of each disease subtype displayed distinctive molecular features. Nonlesion and lesion NS-SE epidermis showed activation of the type I IFN signaling pathway, while lesion NS-ILC skin differed from nonlesion NS-ILC skin by increased complement activation and neutrophil infiltration. Serum cytokine profiling and immunophenotyping of circulating lymphocytes showed a TH2-driven allergic response in NS-ILC, whereas NS-SE patients displayed mainly a TH9 axis with increased CCL22/MDC and CCL17/TARC serum levels. CONCLUSIONS: This study confirms IL-17/IL-36 as the predominant signaling axes in both NS endotypes and unveils molecular features distinguishing NS-ILC and NS-SE. These results identify new therapeutic targets and could pave the way for precision medicine of NS.

A new tool to test active ingredient using lactic acid in vitro, a help to understand cellular mechanism involved in stinging test: An example using a bacterial polysaccharide (Fucogel® ).

The stinging test is an in vivo protocol that evaluates sensitive skin using lactic acid (LA). A soothing sensation of cosmetics or ingredients can be also appreciated through a decrease in stinging score. To predict the soothing sensation of a product before in vivo testing, we developed a model based on an LA test and substance P (SP) release using a co-culture of human keratinocytes and NGF-differentiated PC12 cells. A bacterial fucose-rich polysaccharide present in Fucogel® was evaluated as the soothing molecule in the in vivo stinging test and our in vitro model. Excluding toxic concentrations, the release of SP was significant from 0.2% of lactic acid for the PC12 cells and from 0.1% of lactic acid for the keratinocytes. When the pH was adjusted to approximately 7.4, LA did not provoke SP release. At these concentrations of LA, 0.1% of polysaccharide showed a significant decrease in SP release from the two cellular types and in co-cultures without modifying the pH of the medium. In vivo, a stinging test using the polysaccharide showed a 30% decrease in prickling intensity vs the placebo in 19 women between the ages of 21 and 69. Our in vitro model is ethically interesting and is adapted for cosmetic ingredients screening because it does not use animal experimentation and limits human volunteers. Moreover, Fucogel® reduced prickling sensation as revealed by the in vivo stinging test and inhibits the neurogenic inflammation as showed by our new in vitro stinging test based on SP release.

Self-maintenance of neurogenic inflammation contributes to a vicious cycle in skin.

Cutaneous neurogenic inflammation (CNI) is frequently associated with skin disorders. CNI is not limited to the retrograde signalling of nociceptive sensory nerve endings but can instead be regarded as a multicellular phenomenon. Thus, soluble mediators participating in communication among sensory nerves, skin and immune cells are key components of CNI. These interactions induce the self-maintenance of CNI, promoting a vicious cycle. Certain G protein-coupled receptors (GPCRs) play a prominent role in these cell interactions and contribute to self-maintenance. Protease-activated receptors 2 and 4 (PAR-2 and PAR-4, respectively) and Mas-related G protein-coupled receptors (Mrgprs) are implicated in the synthesis and release of neuropeptides, proteases and soluble mediators from most cutaneous cells. Regulation of the expression and release of these mediators contributes to the vicious cycle of CNI. The authors propose certain hypothetical therapeutic options to interrupt this cycle, which might reduce skin symptoms and improve patient quality of life.

Highly Efficient Ex Vivo Correction of COL7A1 through Ribonucleoprotein-Based CRISPR/Cas9 and Homology-Directed Repair to Treat Recessive Dystrophic Epidermolysis Bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare and severe genetic skin disease responsible for blistering of the skin and mucosa after minor trauma. RDEB is caused by a wide variety of variants in COL7A1 encoding type VII Collagen, the major component of anchoring fibrils that form key attachment structures for dermal-epidermal adherence. In this study, we achieved highly efficient COL7A1 editing in primary RDEB keratinocytes and fibroblasts from 2 patients homozygous for the c.6508C>T (p.Gln2170∗) variant through CRISPR/Cas9-mediated homology-directed repair. Three guide RNAs targeting the c.6508C>T variant or harboring sequences were delivered together with high-fidelity Cas9 as a ribonucleoprotein complex. Among them, one achieved 73% cleavage activity in primary RDEB keratinocytes and RDEB fibroblasts. Then, we treated RDEB keratinocytes and RDEB fibroblasts with this specific ribonucleoprotein complex and the corresponding donor template delivered as single-stranded oligodeoxynucleotide and achieved up to 58% of genetic correction as well as type VII Collagen rescue. Finally, grafting of corrected 3-dimensional skin onto nude mice induced re-expression and normal localization of type VII Collagen as well as anchoring fibril formation at the dermal-epidermal junction 5 and 10 weeks after grafting. With this promising nonviral approach, we achieved therapeutically relevant specific gene editing that could be applicable to all variants in exon 80 of COL7A1 in primary RDEB cells.

Chronic itch: emerging treatments following new research concepts.

Until recently, itch pathophysiology was poorly understood and treatments were poorly effective in relieving itch. Current progress in our knowledge of the itch processing, the numerous mediators and receptors involved has led to a large variety of possible therapeutic pathways. Currently, inhibitors of IL-31, IL-4/13, NK1 receptors, opioids and cannabinoids, JAK, PDE4 or TRP are the main compounds involved in clinical trials. However, many new targets, such as Mas-related GPCRs and unexpected new pathways need to be also explored.

Transgenic Kallikrein 14 Mice Display Major Hair Shaft Defects Associated with Desmoglein 3 and 4 Degradation, Abnormal Epidermal Differentiation, and IL-36 Signature.

Netherton syndrome is a rare autosomal recessive skin disease caused by loss-of-function mutations in SPINK5 encoding LEKTI protein that results in unopposed activity of epidermal kallikrein-related peptidases (KLKs), mainly KLK5, KLK7, and KLK14. Although the function of KLK5 and KLK7 has been previously studied, the role of KLK14 in skin homeostasis and its contribution to Netherton syndrome pathogenesis remains unknown. We generated a transgenic murine model overexpressing human KLK14 (TghKLK14) in stratum granulosum. TghKLK14 mice revealed increased proteolytic activity in the granular layers and in hair follicles. Their hair did not grow and displayed major defects with hyperplastic hair follicles when hKLK14 was overexpressed. TghKLK14 mice displayed abnormal epidermal hyperproliferation and differentiation. Ultrastructural analysis revealed cell separation in the hair cortex and increased thickness of Huxley's layer. Desmoglein (Dsg) 2 staining was increased, whereas Dsg3 and Dsg4 were markedly reduced. In vitro studies showed that hKLK14 directly cleaves recombinant human DSG3 and recombinant human DSG4, suggesting that their degradation contributes to hair abnormalities. Their skin showed an inflammatory signature, with enhanced expression of IL-36 family members and their downstream targets involved in innate immunity. This in vivo study identifies KLK14 as an important contributor to hair abnormalities and skin inflammation seen in Netherton syndrome.

Current pharmaceutical developments in atopic dermatitis.

Atopic dermatitis (AD) is an inflammatory, pruritic, chronic or chronically relapsing skin disease that typically begins in early childhood and is occurring frequently in families with other atopic diseases (bronchial asthma and/or allergic rhino-conjunctivitis). Thanks to immunological and neurobiological research, the era of new treatments is coming as well as it occurred with psoriasis 15 years ago. Many treatments targeting cytokines (IL-4, IL-13, IL-31, TSLP) or neurotransmitters (substance P, opioids) or their respective receptors as well as phosphodiesterase-4 or the Jak/Stat pathways are under development. Antagonists of cytokines and anti-jak have promising effects on pruritus while it is more difficult to discriminate the effects of other drugs from the placebo effect on itch, which is known to be high.

Major Role for TRPV1 and InsP3R in PAR2-Elicited Inflammatory Mediator Production in Differentiated Human Keratinocytes.

PAR2 activation in basal keratinocytes stimulates inflammation via the Ca2+-dependent production of mediators such as IL-1ß, TNF-α, and TSLP. In this study, we investigated PAR2 calcium signaling and the consequent production of inflammatory mediators in differentiated human primary keratinocytes (DhPKs). Stimulation with the PAR2-activating peptide SLIGKV promoted Ca2+ store depletion in both undifferentiated human primary keratinocytes and DhPKs. SLIGKV-evoked Ca2+ store depletion did not trigger the store-operated Ca2+ entry (i.e., SOCE) through ORAI1 in DhPKs compared with undifferentiated human primary keratinocytes. The inhibition of phospholipase C and the concomitant inhibition of TRPV1 and inositol triphosphate receptor in DhPKs abrogated the SLIGKV-evoked Ca2+ store depletion; NF-κB activity; and the production of inflammatory mediators such as IL-1ß, TNF-α, and TSLP. Taken together, these results indicate a key role for both InsP3R and TRPV1 in Ca2+ internal stores in the PAR2-evoked Ca2+ release and consequent skin inflammation in DhPKs. These findings may provide clues to understanding the pathological role of DhPKs in skin disorders in which PAR2 is known to be involved, such as atopic dermatitis, Netherton syndrome, and psoriasis.

TRPV1 and TRPA1 in cutaneous neurogenic and chronic inflammation: pro-inflammatory response induced by their activation and their sensitization.

Cutaneous neurogenic inflammation (CNI) is inflammation that is induced (or enhanced) in the skin by the release of neuropeptides from sensory nerve endings. Clinical manifestations are mainly sensory and vascular disorders such as pruritus and erythema. Transient receptor potential vanilloid 1 and ankyrin 1 (TRPV1 and TRPA1, respectively) are non-selective cation channels known to specifically participate in pain and CNI. Both TRPV1 and TRPA1 are co-expressed in a large subset of sensory nerves, where they integrate numerous noxious stimuli. It is now clear that the expression of both channels also extends far beyond the sensory nerves in the skin, occuring also in keratinocytes, mast cells, dendritic cells, and endothelial cells. In these non-neuronal cells, TRPV1 and TRPA1 also act as nociceptive sensors and potentiate the inflammatory process. This review discusses the role of TRPV1 and TRPA1 in the modulation of inflammatory genes that leads to or maintains CNI in sensory neurons and non-neuronal skin cells. In addition, this review provides a summary of current research on the intracellular sensitization pathways of both TRP channels by other endogenous inflammatory mediators that promote the self-maintenance of CNI.