Permeability barrier disruption increases the level of serine palmitoyltransferase in human epidermis

Porcine Placenta Peptide Inhibits UVB-Induced Skin Wrinkle Formation and Dehydration: Insights into MAPK Signaling Pathways from In Vitro and In Vivo Studies

Excessive exposure to ultraviolet (UV) radiation from sunlight accelerates skin aging, leading to various clinical manifestations such as wrinkles, dryness, and loss of elasticity. This study investigated the protective effects of porcine placenta peptide (PPP) against UVB-induced skin photoaging. Female hairless SKH-1 mice were orally administered PPP for 12 weeks, followed by UVB irradiation. PPP significantly reduced wrinkle formation, improved skin moisture levels, and prevented collagen degradation. Mechanistically, PPP inhibited the expression of matrix metalloproteinases (MMPs) and upregulated collagen production. Moreover, PPP elevated hyaluronic acid levels, contributing to enhanced skin hydration. Additionally, PPP demonstrated antioxidant properties by increasing the expression of the antioxidant enzyme GPx-1, thereby reducing UVB-induced inflammation. Further molecular analysis revealed that PPP suppressed the activation of p38 MAP kinase and JNK signaling pathways, crucial mediators of UV-induced skin damage. These findings highlight the potential of porcine placental peptides as a natural and effective intervention against UVB-induced skin photoaging. The study provides valuable insights into the mechanisms underlying the protective effects of PPP, emphasizing its potential applications in skincare and anti-aging formulations.

Abnormalities of Sphingolipids Metabolic Pathways in the Pathogenesis of Psoriasis

Psoriasis is immune-mediated skin disorder affecting thousands of people. Sphingolipids (SLs) are bioactive molecules present in the epidermis, involved in the following cellular processes: proliferation, differentiation, and apoptosis of keratinocytes. Alterations in SLs synthesis have been observed in psoriatic skin. To investigate if the imbalance in lipid skin metabolism could be related to psoriasis, we analyzed the gene expression in non-lesioned and lesioned skin of patients with psoriasis available in two datasets (GSE161683 and GSE136757) obtained from National Center for Biotechnology Information (NCBI). The differentially expressed genes (DEGs) were searched for using NCBI analysis, and Gene Ontology (GO) biological process analyses were performed using the Database of Annotation, Visualization, and Integrated Discovery (DAVID) platform. Venn diagrams were done with InteractiVenn tool and heatmaps were constructed using Morpheus software. We observed that the gene expression of cytoplasmic phospholipase A₂ (PLA2G4D), glycerophosphodiester phosphodiesterase domain containing 3 (GDP3), arachidonate 12-lipoxygenase R type (ALOX12B), phospholipase B-like 1 (PLBD1), sphingomyelin phosphodiesterase 3 (SMPD3), ganglioside GM2 activator (GM2A), and serine palmitoyltransferase long chain subunit 2 (SPTLC2) was up-regulated in lesioned skin psoriasis when compared with the non-lesioned skin. These genes are related to lipid metabolism and more specifically to sphingolipids. So, in the present study, the role of sphingolipids in psoriasis pathogenesis is summarized. These genes could be used as prognostic biomarkers of psoriasis and could be targets for the treatment of patients who suffer from the disease.

Microbial dysbiosis in a mouse model of atopic dermatitis mimics shifts in human microbiome and correlates with the key pro-inflammatory cytokines IL-4, IL-33 and TSLP

BACKGROUND

Cutaneous bacterial dysbiosis is a characteristic hallmark of atopic dermatitis (AD) and it decisively influences the severity of the disease. Despite this, frequently used murine models of AD have not been characterized regarding the changes in skin microbiome communities.

OBJECTIVE

To analyze the skin microbiome of two frequently used murine models for AD for assessing their applicability in translational research.

METHODS

AD was induced in mice by topical application of calcipotriol, or oxazolone. Following comparable elicitation of AD-like dermatitis, including IgE induction, the skin microbial communities were analyzed and compared with human AD.

RESULTS

We detected critical differences in the microbiota composition of diseased skin. In contrast to calcipotriol treatment, application of oxazolone induced significant changes of the cutaneous microbiota and a drastic drop of bacterial richness. Furthermore, an expansion of Staphylococci, particularly S. xylosus was observed in the oxazolone group, also displaying positive correlations with AD key markers including pH, TEWL, IL-4, TSLP and IL-33.

CONCLUSIONS

In this article we show that i) the model of choice to investigate AD needs to be characterized for the cutaneous microbiota if applicable and ii) the oxazolone-mediated mixed Th1-Th2 immune response triggers microbiota-induced alterations which share similarities to dysbiosis in human AD and represents therefore a suitable model for translational research on AD if alterations of the microbiome are in the focus of the investigation.

Meta-analysis derived atopic dermatitis (MADAD) transcriptome defines a robust AD signature highlighting the involvement of atherosclerosis and lipid metabolism pathways

Background

Atopic dermatitis (AD) is a common inflammatory skin disease with limited treatment options. Several microarray experiments have been conducted on lesional/LS and non-lesional/NL AD skin to develop a genomic disease phenotype. Although these experiments have shed light on disease pathology, inter-study comparisons reveal large differences in resulting sets of differentially expressed genes (DEGs), limiting the utility of direct comparisons across studies.

Methods

We carried out a meta-analysis combining 4 published AD datasets to define a robust disease profile, termed meta-analysis derived AD (MADAD) transcriptome.

Results

This transcriptome enriches key AD pathways more than the individual studies, and associates AD with novel pathways, such as atherosclerosis signaling (IL-37, selectin E/SELE). We identified wide lipid abnormalities and, for the first time in vivo, correlated Th2 immune activation with downregulation of key epidermal lipids (FA2H, FAR2, ELOVL3), emphasizing the role of cytokines on the barrier disruption in AD. Key AD “classifier genes” discriminate lesional from nonlesional skin, and may evaluate therapeutic responses.

Conclusions

Our meta-analysis provides novel and powerful insights into AD disease pathology, and reinforces the concept of AD as a systemic disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0133-x) contains supplementary material, which is available to authorized users.

Circulating levels of sphingosine-1-phosphate are elevated in severe, but not mild psoriasis and are unresponsive to anti-TNF-α treatment

Sphingolipids are bioactive molecules with a putative role in inflammation. Alterations in sphingolipids, in particular ceramides, have been consistently observed in psoriatic skin. Herein, we quantified the circulating sphingolipid profile in individuals with mild or severe psoriasis as well as healthy controls. In addition, the effects of anti-TNF-α treatment were determined. Levels of sphingoid bases, including sphingosine-1-phosphate (S1P), increased in severe (P < 0.001; n = 32), but not in mild (n = 32), psoriasis relative to healthy controls (n = 32). These alterations were not reversed in severe patients (n = 16) after anti-TNF-α treatment despite significant improvement in psoriasis lesions. Circulating levels of sphingomyelins and ceramides shifted in a fatty acid chain length-dependent manner. These alterations were also observed in psoriasis skin lesions and were associated with changes in mRNA levels of ceramide synthases. The lack of S1P response to treatment may have pathobiological implications due to its close relation to the vascular and immune systems. In particular, increased levels of sphingolipids and especially S1P in severe psoriasis patients requiring biological treatment may potentially be associated with cardiovascular comorbidities. The fact that shifts in S1P levels were not ameliorated by anti-TNF-α treatment, despite improvements in the skin lesions, further supports targeting S1P receptors as therapy for severe psoriasis.

Epidermal Hydration Is Improved by Enhanced Ceramide Metabolism in Aged C57BL/6J Mice After Dietary Supplementation of Royal Jelly

Epidermal hydration is maintained by the epidermal lipid barrier, of which ceramide (Cer) is the major constituent. We examined the dietary effect of royal jelly (RJ) on epidermal hydration in aged mice. Altered Cer metabolism was further determined by measuring epidermal levels of individual Cer, glucosylceramide (GC), and sphingomyelin (SM) species, and of Cer-metabolizing enzymes. Aged C57BL/6J mice were fed a control diet (group AGED) or diets with 1% RJ harvested from two different areas (groups AGED+RJ1:AGED + RJ2) for 16 weeks. Aged C57BL/6J mice with no dietary intervention (the control group: group C) represented the onset of aging. In group AGED, epidermal levels of hydration, Cer1/2/5/6/7, GC-A/B/C/D, SM1/2/3, and β-glucocerebrosidase (GCase) protein, an enzyme of GC hydrolysis for Cer generation, were lower than in group C; these levels, as well as those of Cer3/4 and acidic sphingomyelinase (aSMase) protein, an enzyme of SM hydrolysis for Cer generation, were higher in group AGED + RJ1 than in group AGED. Despite increases in GC-B, SM1/2/3, and serine palmitoyltransferase2 protein, an enzyme of de novo Cer synthesis, in group AGED + RJ2 to levels higher than in group AGED, epidermal levels of hydration, Cer1-7, GC-A/C/D, GCase, and aSMase proteins were similar in these two groups. Expression of GCase and aSMase mRNAs, and of Cer synthase3 and ceramidase proteins, enzymes of de novo Cer synthesis and degradation, did not differ among groups. Dietary RJ1 improved epidermal hydration by enhancing Cer metabolism with increased levels of all Cer, GC, and SM species, and of GCase and aSMase proteins.

Transcriptional profiling of epidermal barrier formation in vitro

BACKGROUND

Barrier function is integral to the health of epithelial tissues. Currently, there is a broad need to develop and improve our knowledge with regard to barrier function for reversal of mild skin irritation and dryness. However, there are few in vitro models that incorporate modulations of both lipids and epidermal differentiation programs for pre-clinical testing to aid in the understanding of barrier health.

OBJECTIVE

We have generated a reconstituted epidermis on a decellularized dermis (DED) and characterized its barrier properties relative to human epidermis in order to determine its utility for modeling barrier formation and repair.

METHODS

We followed the process of epidermal differentiation and barrier formation through immunocytochemistry and transcriptional profiling. We examined barrier functionality through measurements of surface pH, lipid composition, stratum corneum water content, and the ability to demonstrate topical dose-dependent exclusion of surfactant.

RESULTS

Transcriptional profiling of the epidermal model during its formation reveals temporal patterns of gene expression associated with processes regulating barrier function. The profiling is supported by gradual formation and maturation of a stratum corneum and expression of appropriate markers of epidermis development. The model displays a functional barrier and a water gradient between the stratum corneum and viable layers, as determined by confocal Raman spectroscopy. The stratum corneum layer displays a normal acidic pH and an appropriate composition of barrier lipids.

CONCLUSION

The epidermal model demonstrates its utility as an investigative tool for barrier health and provides a window into the transcriptional regulation of multiple aspects of barrier formation.

Detergents with different chemical properties induce variable degree of cytotoxicity and mRNA expression of lipid-metabolizing enzymes and differentiation markers in cultured keratinocytes

The knowledge how detergents with different chemical properties influence epidermal keratinocytes is sparse. In the present study, the effects of five detergents were examined with respect to cell-toxicity and mRNA expression of key-enzymes in barrier lipid production and keratinocyte differentiation markers. First, the LD(50) for each detergent were determined. Secondly, keratinocytes were exposed to sub-toxic concentrations and the mRNA expression was analysed by real-time PCR after 24 h exposure to the detergents. SLS and CAPB induced a concentration-dependent increase in the expression of enzymes producing cholesterol and ceramides, while transcripts of enzymes producing fatty acids were unaffected. SLES and cocoglucoside increased the expression of certain enzymes involved in cholesterol and fatty acid synthesis while sodium cocoamphoacetate (SCAA) stimulated expression of transcripts involved in fatty acid synthesis. The expression of differentiation markers were increased by SLS, SLES and CAPB, while SCAA and cocoglucoside exhibited no effect. The present findings show that detergents have variable effects on lipid synthesis and keratinocyte differentiation, which could partly explain their barrier destruction potential in vivo.

Variations in the mRNA expression of inflammatory mediators, markers of differentiation and lipid-metabolizing enzymes caused by sodium lauryl sulphate in cultured human keratinocytes

Detergents are well known irritants. Effects of the detergent sodium lauryl sulphate (SLS) on cell toxicity using the XTT assay and mRNA expression of inflammatory mediators, markers of keratinocyte differentiation and enzymes synthesizing barrier lipids using real-time PCR were studied in cultured differentiated keratinocytes. After exposure for 24 h to SLS concentrations at 0.002% or above, toxic effects were observed. When a lower SLS concentration (0.00075%) was used the mRNA expression of inflammatory mediators peaked around 4-8 h. The expression of enzymes involved in the synthesis of cholesterol, fatty acids and ceramides and markers of keratinocyte differentiation also increased but after 24 h. In cells exposed to 0.000125-0.0015% SLS, a concentration-dependent induction of the expression of inflammatory mediators was found after 4 h. Similar changes were found after 24 h for involucrin and enzymes involved in ceramide synthesis. The mRNA expression of HMG-CoA synthase and reductase, long-chain acyl-CoA synthase and transglutaminase also peaked after 24 h, but maximal induction was observed already at 0.00075% SLS. In conclusion, SLS induces an inflammatory response in keratinocytes and alters the mRNA expression of important barrier lipid enzymes and markers of keratinocyte differentiation, of possible importance for the irritant properties of SLS.

Alterations of glucosylceramide-beta-glucosidase levels in the skin of patients with psoriasis vulgaris

Hydrolysis of glucosylceramides by the enzyme glucosylceramide-beta-glucosidase (GlcCer'ase) results in ceramide, a critical component of the intercellular lamellae that mediates the epidermal permeability barrier. A disturbance of ceramide formation is supposed to influence the transepidermal water loss in common skin diseases like atopic eczema or psoriasis. The aim of this study was to investigate whether GlcCer'ase levels were altered in the skin of subjects with psoriasis vulgaris. Skin punch biopsies were taken from lesional and non-lesional psoriatic skin and GlcCer'ase was evaluated both at the RNA and at the protein level. Normal skin from surgical patients provided the baseline GlcCer'ase expression in healthy subjects. Our results show that GlcCer'ase mRNA expression was decreased in psoriatic non-lesional skin compared to normal controls in all cases. Interestingly, in lesional psoriatic skin the level of GlcCer'ase was increased compared to non-lesional skin in all cases. For the immunohistochemical analysis, we used a newly synthesized monoclonal antibody anti-human GBC (GlcCer'ase-GST fusion protein). The results confirmed that GlcCer'ase, mainly present in the upper epidermis, was decreased in psoriatic skin compared to normal control and was increased in lesional compared to non-lesional psoriatic skin. Our findings support the concept that alteration in water permeability barrier in lesional psoriatic skin can serve as a trigger for the upregulation of the expression of enzymes like GlcCer'ase with consequent stimulation of ceramide generation.

Barrier function of the skin: "la raison d'être" of the epidermis

The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.