Loss of mutant p53 in HaCaT keratinocytes promotes cadmium-induced keratin 17 expression and cell death

BACKGROUND

Cadmium exposure induces dermatotoxicity and epidermal barrier disruption and leads to the development of various pathologies. HaCaT cells are immortalized human keratinocytes that are widely used as alternatives to primary human keratinocytes, particularly for evaluating cadmium toxicity. HaCaT cells bear two gain-of-function (GOF) mutations in the TP53 gene, which strongly affect p53 function. Mutant forms of p53 are known to correlate with increased resistance to various stimuli, including exposure to cytotoxic substances. In addition, keratin 17 (KRT17) was recently shown to be highly expressed in HaCaT cells in response to genotoxic stress. Moreover, p53 is a direct transcriptional repressor of KRT17. However, the impact of TP53 mutations in HaCaT cells on the regulation of cell death and keratin 17 expression is unclear. In this study, we aimed to evaluate the impact of p53 on the response to Cd-induced cytotoxicity.

METHODS AND RESULTS

Employing the MTT assay and Annexin V/propidium iodide staining, we demonstrated that knockout of TP53 leads to a decrease in the sensitivity of HaCaT cells to the cytotoxic effects of cadmium. Specifically, HaCaT cells with TP53 knockout (TP53 KO HaCaT) exhibited cell death at a cadmium concentration of 10 μM or higher, whereas wild-type cells displayed cell death at a concentration of 30 μM. Furthermore, apoptotic cells were consistently detected in TP53 KO HaCaT cells upon exposure to low concentrations of cadmium (10 and 20 μM) but not in wild-type cells. Our findings also indicate that cadmium cytotoxicity is mediated by reactive oxygen species (ROS), which were significantly increased only in TP53 knockout cells treated with 30 μM cadmium. An examination of proteomic data revealed that TP53 knockout in HaCaT cells resulted in the upregulation of proteins involved in the regulation of apoptosis, redox systems, and DNA repair. Moreover, RT‒qPCR and immunoblotting showed that cadmium toxicity leads to dose-dependent induction of keratin 17 in p53-deficient cells but not in wild-type cells.

CONCLUSIONS

The connection between mutant p53 in HaCaT keratinocytes and increased resistance to cadmium toxicity was demonstrated for the first time. Proteomic profiling revealed that TP53 knockout in HaCaT cells led to the activation of apoptosis regulatory circuits, redox systems, and DNA repair. In addition, our data support the involvement of keratin 17 in the regulation of DNA repair and cell death. Apparently, the induction of keratin 17 is p53-independent but may be inhibited by mutant p53.

Distinct induction pathways of heat shock protein 27 in human keratinocytes: Heat stimulation or capsaicin through phosphorylation of heat shock factor 1 at serine 326 and/or suppression of ΔNp63

Epidermal keratinocytes, forming the outermost layer of the human body, serve as a crucial barrier against diverse external stressors such as ultraviolet radiation. Proper keratinocyte differentiation and effective responses to external stimuli are pivotal for maintaining barrier integrity. Heat is one such stimulus that triggers the synthesis of heat shock proteins (HSPs) when cells are exposed to temperatures above 42 °C. Additionally, activation of the transient receptor potential cation channel subfamily V member 1 (TRPV1) occurs at 42 °C. Here, we explore the interplay between TRPV1 signaling and HSP induction in human keratinocytes. Both heat and capsaicin, a TRPV1 agonist, induce expression of HSP27, HSP70, and HSP90 in keratinocytes. Interestingly, pharmacological inhibition of TRPV1 attenuates heat-induced HSP27 expression, but not that of HSP70 or HSP90. Furthermore, both heat and capsaicin stimulation result in distinct phosphorylation patterns of heat shock factor 1 (HSF1), with phosphorylation at serine 326 being a common feature. Notably, genetic manipulation to mimic dephosphorylation of HSF1 at serine 326 reduces HSP27 levels. Additionally, ΔNp63, a key regulator of epidermal differentiation, negatively modulates HSP27 expression independently of HSF1 phosphorylation status. While heat stimulation has no effect on ΔNp63 expression, capsaicin reduces its levels. The precise role of TRPV1 signaling in keratinocytes warrants further investigation for a comprehensive understanding of its impact on barrier function.

Enhanced prokaryotic expression, purification, and biological activities of human keratinocyte growth factor

Keratinocyte growth factor (KGF), also known as fibroblast growth factor 7 (FGF7), plays a critical role in embryonic development, cell proliferation, and differentiation. However, efficient production of recombinant KGF remains a challenge due to its low expression levels and high tendency for aggregation in Escherichia coli. This study aimed to enhance the expression and solubility of KGF by employing different protein tags-PDIb'a', MBP, and His-fused to the N-terminus of KGF. Among these, H-PDIb'a'-KGF demonstrated superior stability and was selected for large-scale production and purification. The purified KGF was confirmed through liquid chromatography with tandem mass spectrometry analysis, which showed an 81% fragment mass identification coverage. Biological activity assessments using human breast cancer MCF-7 cells indicated that purified KGF significantly increased cell proliferation, with an EC50 of 6.4 ± 0.5 pM. Interestingly, PDIb'a' alone also exhibited a stimulatory effect on MCF-7 cells. Furthermore, the purified KGF enhanced the wound healing of HaCaT keratinocytes in a dose-dependent manner. These findings provide valuable insights into the efficient production and functional characterization of recombinant KGF for potential applications in therapeutic interventions.

Photoreactivity of polycyclic aromatic hydrocarbons (PAHs) and their mechanisms of phototoxicity against human immortalized keratinocytes (HaCaT)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic compounds in the environment. They are produced by many anthropogenic sources of different origins and are known for their toxicity, carcinogenicity, and mutagenicity. Sixteen PAHs have been identified as Priority Pollutants by the US EPA, which are often associated with particulate matter, facilitating their dispersion through air and water. When human skin is exposed to PAHs, it might occur simultaneously with solar radiation, potentially leading to phototoxic effects. Phototoxic mechanisms involve the generation of singlet oxygen and reactive oxygen species, DNA damage under specific light wavelengths, and the formation of charge transfer complexes. Despite predictions of phototoxic properties for some PAHs, there remains a paucity of experimental data. This study examined the photoreactive and phototoxic properties of the 16 PAHs enlisted in the Priority Pollutants list. Examined PAHs efficiently photogenerated singlet oxygen and superoxide anion in simple solutions. Furthermore, singlet oxygen phosphorescence was detected in PAH-loaded HaCaT cells. Phototoxicity against human keratinocytes was evaluated using various assays. At 5 nM concentration, examined PAHs significantly reduced viability and mitochondrial membrane potential of HaCaT cells following the exposure to solar simulated light. Analyzed compounds induced a substantial peroxidation of cellular proteins after light treatment. The results revealed that a majority of the examined PAHs exhibited substantial reactive oxygen species photoproduction under UVA and violet-blue light, with their phototoxicity corresponding to their photoreactive properties. These findings improve our comprehension of the interactions between PAHs and human skin cells under environmental conditions, particularly when exposed to solar radiation.

Delayed Collagen Production without Myofibroblast Formation Contributes to Reduced Scarring in Adult Skin Microwounds

In adult mammals, wound healing predominantly follows a fibrotic pathway, culminating in scar formation. However, cutaneous microwounds generated through fractional photothermolysis, a modality that produces a constellation of microthermal zones, exhibit a markedly different healing trajectory. Our study delineates the cellular attributes of these microthermal zones, underscoring a temporally limited, subclinical inflammatory milieu concomitant with rapid re-epithelialization within 24 hours. This wound closure is facilitated by the activation of genes associated with keratinocyte migration and differentiation. In contrast to macrothermal wounds, which predominantly heal through a robust myofibroblast-mediated collagen deposition, microthermal zones are characterized by absence of wound contraction and feature delayed collagen remodeling, initiating 5-6 weeks after injury. This distinct wound healing is characterized by a rapid re-epithelialization process and a muted inflammatory response, which collectively serve to mitigate excessive myofibroblast activation. Furthermore, we identify an initial reparative phase characterized by a heterogeneous extracellular matrix protein composition, which precedes the delayed collagen remodeling. These findings extend our understanding of cutaneous wound healing and may have significant implications for the optimization of therapeutic strategies aimed at mitigating scar formation.

Prenatal arsenic exposure alters keratinocyte stem cell fate through persistent activation of IGF2R-MAPK cascade leading to aggravated skin carcinogenesis in mice offspring

Chronic exposure to arsenic (As) promotes skin carcinogenesis in humans and potentially disturbs resident stem cell dynamics, particularly during maternal and early life exposure. In the present study, we demonstrate how only prenatal arsenic exposure disturbs keratinocyte stem cell (KSC) conditioning using a BALB/c mice model. Prenatal As exposure alters the normal stemness (CD34, KRT5), differentiation (Involucrin), and proliferation (PCNA) program in skin of offspring with progression of age as observed at 2, 10, and 18 weeks. Primary KSCs isolated from exposed animal at Day-2 showed increased survival (Bax:Bcl-xL, TUNEL assay), proliferation (BrdU), and differentiation (KRT5, Involucrin) potential through the activation of pro-carcinogenic IGF2R-MAPK cascade (IGF2R-G(α)q-MEK1-ERK1/2). This was associated with reduced enrichment of histone H3K27me3 and its methylase, EZH2 along with increased binding of demethylase, KDM6A at Igf2r promoter. Altered KSCs conditioning through disturbed Igf2r imprint contributed to impaired proliferation and differentiation and an aggravated tumor response in offspring.

Transcriptional landscape of human keratinocyte models exposed to 60-GHz millimeter-waves

The use of millimeter waves (MMW) will exponentially grow in the coming years due to their future utilization in 5G/6G networks. The question of possible biological effects at these frequencies has been raised. In this present study, we aimed to investigate gene expression changes under exposure to MMW using the Bulk RNA Barcoding and sequencing (BRB-seq) technology. To address this issue, three exposure scenarios were performed aiming at: i) comparing the cellular response of two primary culture of keratinocytes (HEK and NHEK) and one keratinocyte derivate cell line (HaCaT) exposed to MMW; ii) exploring the incident power density dose-effect on gene expression in HaCaT cell line; and, iii) studying the exposure duration at the new ICNIRP exposure limit for the general population. With the exception of heat effect induced by high power MMW (over 10 mW/cm2), those exposure scenarios have not enabled us to demonstrate important gene expression changes in the different cell populations studied. Very few differentially genes were observed between MMW exposed samples and heat shock control, and most of them were significantly associated with heat shock response that may reflect small differences in the heat generation. Together these results show that acute exposure to MMW has no effects on the transcriptional landscape of human keratinocyte models under athermal conditions.

An Ixodes persulcatus Inhibitor of Plasmin and Thrombin Hinders Keratinocyte Migration, Blood Coagulation, and Endothelial Permeability

The skin is the first host tissue that the tick mouthparts, tick saliva, and a tick-borne pathogen contact during feeding. Tick salivary glands have evolved a complex and sophisticated pharmacological arsenal, consisting of bioactive molecules, to assist blood feeding and pathogen transmission. In this work, persulcatin, a multifunctional molecule that targets keratinocyte function and hemostasis, was identified from Ixodes persulcatus female ticks. The recombinant persulcatin was expressed and purified and is a 25-kDa acidic protein with 2 Kunitz-type domains. Persulcatin is a classical tight-binding competitive inhibitor of proteases, targeting plasmin (Ki: 28 nM) and thrombin (Ki: 115 nM). It blocks plasmin generation on keratinocytes and inhibits their migration and matrix protein degradation; downregulates matrix metalloproteinase 2 and matrix metalloproteinase 9; and causes a delay in blood coagulation, endothelial cell activation, and thrombin-induced fibrinocoagulation. It interacts with exosite I of thrombin and reduces thrombin-induced endothelial cell permeability by inhibiting vascular endothelial-cadherin disruption. The multifaceted roles of persulcatin as an inhibitor and modulator within the plasminogen-plasmin system and thrombin not only unveil further insights into the intricate mechanisms governing wound healing but also provide a fresh perspective on the intricate interactions between ticks and their host organisms.

Roles for epithelial integrin α3β1 in regulation of the microenvironment during normal and pathological tissue remodeling

Integrin receptors for the extracellular matrix activate intracellular signaling pathways that are critical for tissue development, homeostasis, and regeneration/repair, and their loss or dysregulation contributes to many developmental defects and tissue pathologies. This review will focus on tissue remodeling roles for integrin α3β1, a receptor for laminins found in the basement membranes (BMs) that underlie epithelial cell layers. As a paradigm, we will discuss literature that supports a role for α3β1 in promoting ability of epidermal keratinocytes to modify their tissue microenvironment during skin development, wound healing, or tumorigenesis. Preclinical and clinical studies have shown that this role depends largely on ability of α3β1 to govern the keratinocyte's repertoire of secreted proteins, or the "secretome," including 1) matrix proteins and proteases involved in matrix remodeling and 2) paracrine-acting growth factors/cytokines that stimulate other cells with important tissue remodeling functions (e.g., endothelial cells, fibroblasts, inflammatory cells). Moreover, α3β1 signaling controls gene expression that helps epithelial cells carry out these functions, including genes that encode secreted matrix proteins, proteases, growth factors, or cytokines. We will review what is known about α3β1-dependent gene regulation through both transcription and posttranscriptional mRNA stability. Regarding the latter, we will discuss examples of α3β1-dependent alternative splicing (AS) or alternative polyadenylation (APA) that prevents inclusion of cis-acting mRNA sequences that would otherwise target the transcript for degradation via nonsense-mediated decay or destabilizing AU-rich elements (AREs) in the 3'-untranslated region (3'-UTR). Finally, we will discuss prospects and anticipated challenges of exploiting α3β1 as a clinical target for the treatment of cancer or wound healing.

WTAP-Mediated N6-Methyladenosine of RNAs Facilitate the Pathophysiology of Atopic Dermatitis

N6-methyladenosine (m6A) is the most abundant dynamic and reversible internal chemical modification of RNA in eukaryotic cells and is essential in multiple pathophysiological processes. However, it has not been reported in atopic dermatitis (AD). We used Arraystar m6A-mRNA epitranscriptomic microarray to screen for differentially expressed genes and their m6A levels and m6A-related enzymes in patients with AD. We confirmed that the m6A RNA methyltransferase WTAP and 2 candidate differentially expressed genes (S100A9 and SERPINB3) were significantly upregulated in keratinocytes in public data and epidermal lesions of patients with AD. In vitro cell experiments confirmed that WTAP influenced the expression of the 2 candidate differentially expressed genes and promoted primary human epidermal keratinocyte proliferation while inhibiting human epidermal keratinocyte differentiation. Furthermore, we showed that WTAP, S100A9, and SERPINB3 expression correlated with AD severity. Our findings revealed that WTAP-mediated m6A modification promoted the expression of S100A9 and SERPINB3 to aggravate human epidermal keratinocyte proliferation and dysdifferentiation contributing to the pathophysiological development of AD.

Epidermal loss of Bcl6 exacerbates MC903-induced atopic dermatitis-like skin inflammation

Atopic dermatitis (AD) is a chronic inflammatory skin disease where Th2-type immune responses are dominant. In the lesional skin of AD, keratinocytes show differentiation defects and secrete proinflammatory cytokines and chemokines, amplifying Th2-type responses in AD. We previously reported that inducible loss of B-cell lymphoma 6 (Bcl6), a transcription repressor and a master transcriptional regulator of follicular helper T cells and germinal center B cells, in the whole body results in upregulation of Th2-related cytokines in mouse skin. However, the role of Bcl6 in keratinocytes remains to be clarified. Here, we observed that BCL6 positively regulates the expression of keratinocyte differentiation markers and plasma membrane localization of adherence junctional proteins in keratinocyte cell culture. Although keratinocyte-specific loss of Bcl6 alone did not induce AD-like skin inflammation, it aggravates MC903-induced AD-like skin inflammation in mice. In addition, Bcl6 expression is decreased in the epidermis of lesional skin from MC903-induced AD-like skin inflammation in mice. These results strongly suggest that Bcl6 downregulation in keratinocytes contributes to the development and aggravation of AD-like skin inflammation in mice.

The crude extract obtained from Cinnamomum macrostemon Hayata regulates oxidative stress and mitophagy in keratinocytes

Four ethanol fractionated crude extracts (EFCEs [A-D]) purified from the leaves of Cinnamomum macrostemon Hayata were screened for antioxidative effects and mitochondrial function in HaCaT cells. The higher cell viability indicated that EFCE C was mildly toxic. Under the treatment of 50 ng/mL EFCE C, the hydrogen peroxide (H2O2)-induced cytosolic and mitochondrial reactive oxygen species levels were reduced as well as the H2O2-impaired cell viability, mitochondrial membrane potential (MMP), ATP production, and mitochondrial mass. The conversion of globular mitochondria to tubular mitochondria is coincident with EFCE C-restored mitochondrial function. The mitophagy activator rapamycin showed similar effects to EFCE C in recovering the H2O2-impaired cell viability, MMP, ATP production, mitochondrial mass, and also mitophagic proteins such as PINK1, Parkin, LC3 II, and biogenesis protein PGC-1α. We thereby propose the application of EFCE C in the prevention of oxidative stress in skin cells.

Lysophosphatidic acid down-regulates human RIPK4 mRNA in keratinocyte- derived cell lines

The tight control of proliferating keratinocytes is vital to the successful function of the skin. Differentiation of dividing cells is necessary to form a skin barrier. The same dividing cells are necessary to heal wounds and when malignant form tumors. RIPK4, a serine-threonine kinase, plays critical roles in these processes. Its loss of function was associated with pathological keratinocyte proliferation and development of squamous cell carcinoma (SCC) in humans and mice. The current study extends previous findings in the importance of RIPK4 in keratinocyte proliferation. A serum-derived phospholipid, lysophosphatidic acid (LPA), was identified as an important biologic inhibitor of RIPK4. LPA functions by inhibiting the transcription of RIPK4 mRNA. LPA treatment led to increased keratinocyte proliferation, and this was compromised in cells with reduced RIPK4 expression. The current study may help to explain the mechanism by which RIPK4 was downregulated during SCC progression and provide insights on RIPK4 functions. It may also allow for targeting of RIPK4 through a natural component of serum.

Interferon alpha promotes caspase-8 dependent ultraviolet light-mediated keratinocyte apoptosis via interferon regulatory factor 1

Introduction

Ultraviolet (UV) light is a known trigger of both cutaneous and systemic disease manifestations in lupus patients. Lupus skin has elevated expression of type I interferons (IFNs) that promote increased keratinocyte (KC) death after UV exposure. The mechanisms by which KC cell death is increased by type I IFNs are unknown.

Methods

Here, we examine the specific cell death pathways that are activated in KCs by type I IFN priming and UVB exposure using a variety of pharmacological and genetic approaches. Mice that overexpress Ifnk in the epidermis were exposed to UVB light and cell death was measured. RNA-sequencing from IFN-treated KCs was analyzed to identify candidate genes for further analysis that could drive enhanced cell death responses after UVB exposure.

Results

We identify enhanced activation of caspase-8 dependent apoptosis, but not other cell death pathways, in type I IFN and UVB-exposed KCs. In vivo, overexpression of epidermal Ifnk resulted in increased apoptosis in murine skin after UVB treatment. This increase in KC apoptosis was not dependent on known death ligands but rather dependent on type I IFN-upregulation of interferon regulatory factor 1 (IRF1).

Discussion

These data suggest that enhanced sensitivity to UV light exhibited by lupus patients results from type I IFN priming of KCs that drives IRF1 expression resulting in caspase-8 activation and increased apoptosis after minimal exposures to UVB.

The decline in cellular iron is crucial for differentiation in keratinocytes

Iron is a vital metal for most biological functions in tissues, and its concentration is exquisitely regulated at the cellular level. During the process of differentiation, keratinocytes in the epidermis undergo a noticeable reduction in iron content. Conversely, psoriatic lesions, characterized by disruptions in epidermal differentiation, frequently reveal an excessive accumulation of iron within keratinocytes that have undergone differentiation. In this study, we clarified the significance of attenuated cellular iron content in the intricate course of epidermal differentiation. We illustrated this phenomenon through the utilization of hinokitiol, an iron chelator derived from the heartwood of Taiwanese hinoki, which forcibly delivers iron into cells independent of the intrinsic iron-regulation systems. While primary cultured keratinocytes readily succumbed to necrotic cell death by this iron chelator, mild administration of the hinokitiol-iron complex modestly disrupts the process of differentiation in these cells. Notably, keratinocyte model cells HaCaT and anaplastic skin rudiments exhibit remarkable resilience against the cytotoxic impact of hinokitiol, and the potent artificial influx of iron explains a suppressive effect selectively on epidermal differentiation. Moreover, the augmentation of iron content induced by the overexpression of divalent metal transporter 1 culminates in the inhibition of differentiation in HaCaT cells. Consequently, the diminution in cellular iron content emerges as an important determinant influencing the trajectory of keratinocyte differentiation.

Cycloastragenol restrains keratinocyte hyperproliferation by promoting autophagy via the miR-145/STC1/Notch1 axis in psoriasis

BACKGROUND

Psoriasis is characterized by inflammation and hyperproliferation of epidermal keratinocytes. Cycloastragenol (CAG) is an active molecule of Astragalus membranaceus that potentially plays a repressive role in psoriasis. Activated cell autophagy is an effective pathway for alleviating psoriasis progression. Thus, we investigated the role of CAG in the proliferation and autophagy of interleukin (IL)-22-stimulated keratinocytes.

METHODS

A psoriasis model was established by stimulating HaCaT cells with IL-22. Gene or protein expression levels were measured by qRT-PCR or western blot. Autophagy flux was observed with mRFP-GFP-LC3 adenovirus transfection assay under confocal microscopy. Stanniocalcin-1 (STC1) secretion levels were determined using ELISA kits. The apoptosis rate was assessed using flow cytometry. Interactions between miR-145 and STC1 or STC1 and Notch1 were validated by luciferase reporter gene assays, RIP, and Co-IP assays.

RESULTS

CAG repressed cell proliferation and promoted apoptosis and autophagy in IL-22-stimulated HaCaT cells. Additionally, CAG promoted autophagy by enhancing miR-145. STC1 silencing ameliorated autophagy repression in IL-22-treated HaCaT cells. Moreover, miR-145 negatively regulated STC1, and STC1 was found to activate Notch1. Lastly, STC1 overexpression reversed CAG-promoted autophagy.

CONCLUSION

CAG alleviated keratinocyte hyperproliferation through autophagy enhancement via regulating the miR-145/STC1/Notch1 axis in psoriasis.

Glycyl-tRNA Synthetase Induces Psoriasis-Like Skin by Facilitating Skin Inflammation and Vascular Endothelial Cell Angiogenesis

Psoriasis is characterized by excessive keratinocyte proliferation and immunocyte infiltration, but the underlying pathogenesis remains unclear. Aminoacyl-tRNA synthetases are universally expressed enzymes that catalyze the first step of protein synthesis. Glycyl-tRNA synthetase (GARS) is a member of the aminoacyl-tRNA synthetase family. In addition to its canonical function, we found that GARS was overexpressed in the serum and skin lesions of patients with psoriasis. Moreover, GARS was highly expressed in human skin keratinocytes, and GARS knockdown in keratinocytes suppressed cell proliferation and promoted apoptosis through NF-κB/MAPK signaling pathway. Moreover, intradermal injection of recombinant GARS protein caused skin thickening, angiogenesis, and IFN/TNF-driven skin inflammation. Intriguingly, the reported functional receptor for GARS, cadherin 6 (CDH6), was specifically expressed in vascular endothelial cells, and we found that keratinocyte-derived GARS promotes inflammation and angiogenesis of vascular endothelial cells through CDH6. In addition, intradermal injection of GARS aggravated the phenotype and angiogenesis in imiquimod-induced psoriasiform dermatitis models, whereas the psoriatic phenotype and angiogenesis were relieved after knockdown of GARS by adeno-associated virus. Taken together, the results of this study identify the critical role of GARS in the pathogenesis of psoriasis and suggest that blocking GARS may be a therapeutic approach for alleviating psoriasis.

FOSL1 regulates hyperproliferation and NLRP3-mediated inflammation of psoriatic keratinocytes through the NF-kB signaling via transcriptionally activating TRAF3

Psoriasis is a common and immune-mediated skin disease related to keratinocytes hyperproliferation and inflammation. Fos-like antigen-1 (FOSL1) is an important transcription factor involved in various diseases. FOSL1 has been reported to be differentially expressed in psoriasis. However, the roles and mechanism of FOSL1 in psoriasis progression remain largely unknown. FOSL1 is an upregulated transcription factor in psoriasis and increased in M5-treated HaCaT cells. FOSL1 had a diagnostic value in psoriasis, and positively associated with PASI score, TNF-α and IL-6 levels in psoriasis patients. FOSL1 silencing attenuated M5-induced HaCaT cell hyperproliferation through decreasing cell viability and proliferative ability and increasing cell apoptosis. FOSL1 knockdown mitigated M5-induced NLRP3 inflammasome activation and it-mediated inflammatory cytokine (IL-6, IL-8 and CCL17) expression. TRAF3 expression was increased in psoriasis patients and M5-treated HaCaT cells. FOSL1 transcriptionally activating TRAF3 in HaCaT cells. TRAF3 overexpression reversed the suppressive effects of FOSL1 silencing on M5-induced hyperproliferation and NLRP3-mediated inflammation. FOSL1 knockdown attenuated M5-induced NF-κB signaling activation by reducing TRAF3. Activation of NF-κB signaling reversed the effects of FOSL1 knockdown on hyperproliferation and inflammation in M5-treated cells. FOSL1 silencing prevented M5-induced hyperproliferation and NLRP3-mediated inflammation of keratinocytes by inhibiting TRAF3-mediated NF-κB activity, indicating FOSL1 might act as a therapeutic target of psoriasis.

miR-129-5p inhibits anchorage-independent growth through silencing of ACTN1 and the ELK4/c-FOS axis in HPV-transformed keratinocytes

A persistent infection with human papillomavirus (HPV) can induce precancerous lesions of the cervix that may ultimately develop into cancer. Cervical cancer development has been linked to altered microRNA (miRNA) expression, with miRNAs regulating anchorage-independent growth being particularly important for the progression of precancerous lesions to cancer. In this study, we set out to identify and validate targets of miR-129-5p, a previously identified tumor suppressive miRNA involved in anchorage-independent growth and HPV-induced carcinogenesis. We predicted 26 potential miR-129-5p targets using online databases, followed by KEGG pathway enrichment analysis. RT-qPCR and luciferase assays confirmed that 3'UTR regions of six genes (ACTN1, BMPR2, CAMK4, ELK4, EP300, and GNAQ) were targeted by miR-129-5p. Expressions of ACTN1, CAMK4, and ELK4 were inversely correlated to miR-129-5p expression in HPV-transformed keratinocytes, and their silencing reduced anchorage-independent growth. Concordantly, miR-129-5p overexpression decreased protein levels of ACTN1, BMPR2, CAMK4 and ELK4 in anchorage-independent conditions. Additionally, c-FOS, a downstream target of ELK4, was downregulated upon miR-129-5p overexpression, suggesting regulation through the ELK4/c-FOS axis. ACTN1 and ELK4 expression was also upregulated in high-grade precancerous lesions and cervical cancers, supporting their clinical relevance. In conclusion, we identified six targets of miR-129-5p involved in the regulation of anchorage-independent growth, with ACTN1, BMPR2, ELK4, EP300, and GNAQ representing novel targets for miR-129-5p. For both ACTN1 and ELK4 functional and clinical relevance was confirmed, indicating that miR-129-5p-regulated ACTN1 and ELK4 expression contributes to HPV-induced carcinogenesis.

LIGHT signaling through LTβR and HVEM in keratinocytes promotes psoriasis and atopic dermatitis-like skin inflammation

Psoriasis (PS) and atopic dermatitis (AD) are common skin inflammatory diseases characterized by hyper-responsive keratinocytes. Although, some cytokines have been suggested to be specific for each disease, other cytokines might be central to both diseases. Here, we show that Tumor necrosis factor superfamily member 14 (TNFSF14), known as LIGHT, is required for experimental PS, similar to its requirement in experimental AD. Mice devoid of LIGHT, or deletion of either of its receptors, lymphotoxin β receptor (LTβR) and herpesvirus entry mediator (HVEM), in keratinocytes, were protected from developing imiquimod-induced psoriatic features, including epidermal thickening and hyperplasia, and expression of PS-related genes. Correspondingly, in single cell RNA-seq analysis of PS patient biopsies, LTβR transcripts were found strongly expressed with HVEM in keratinocytes, and LIGHT was upregulated in T cells. Similar transcript expression profiles were also seen in AD biopsies, and LTβR deletion in keratinocytes also protected mice from allergen-induced AD features. Moreover, in vitro, LIGHT upregulated a broad spectrum of genes in human keratinocytes that are clinical features of both PS and AD skin lesions. Our data suggest that agents blocking LIGHT activity might be useful for therapeutic intervention in PS as well as in AD.

Transport of CLCA2 to the nucleus by extracellular vesicles controls keratinocyte survival and migration

Chloride channel accessory 2 (CLCA2) is a transmembrane protein, which promotes adhesion of keratinocytes and their survival in response to hyperosmotic stress. Here we show that CLCA2 is transported to the nucleus of keratinocytes via extracellular vesicles. The nuclear localization is functionally relevant, since wild-type CLCA2, but not a mutant lacking the nuclear localization signal, suppressed migration of keratinocytes and protected them from hyperosmotic stress-induced cell death. In the nucleus, CLCA2 bound to and activated β-catenin, resulting in enhanced expression of Wnt target genes. Mass-spectrometry-based interaction screening and functional rescue studies identified RNA binding protein 3 as a key effector of nuclear CLCA2. This is of likely relevance in vivo because both proteins co-localize in the human epidermis. Together, these results identify an unexpected nuclear function of CLCA2 in keratinocytes under homeostatic and stress conditions and suggest a role of extracellular vesicles and their nuclear transport in the control of key cellular activities.

Cx31.1 can selectively intermix with co-expressed connexins to facilitate its assembly into gap junctions

Connexins are channel-forming proteins that function to facilitate gap junctional intercellular communication. Here, we use dual cell voltage clamp and dye transfer studies to corroborate past findings showing that Cx31.1 (encoded by GJB5) is defective in gap junction channel formation, illustrating that Cx31.1 alone does not form functional gap junction channels in connexin-deficient mammalian cells. Rather Cx31.1 transiently localizes to the secretory pathway with a subpopulation reaching the cell surface, which is rarely seen in puncta reminiscent of gap junctions. Intracellular retained Cx31.1 was subject to degradation as Cx31.1 accumulated in the presence of proteasomal inhibition, had a faster turnover when Cx43 was present and ultimately reached lysosomes. Although intracellularly retained Cx31.1 was found to interact with Cx43, this interaction did not rescue its delivery to the cell surface. Conversely, the co-expression of Cx31 dramatically rescued the assembly of Cx31.1 into gap junctions where gap junction-mediated dye transfer was enhanced. Collectively, our results indicate that the localization and functional status of Cx31.1 is altered through selective interplay with co-expressed connexins, perhaps suggesting Cx31.1 is a key regulator of intercellular signaling in keratinocytes.

Evaluation of mitochondrial stress following ultraviolet radiation and 5G radiofrequency field exposure in human skin cells

Whether human cells are impacted by environmental electromagnetic fields (EMF) is still a matter of debate. With the deployment of the fifth generation (5G) of mobile communication technologies, the carrier frequency is increasing and the human skin becomes the main biological target. Here, we evaluated the impact of 5G-modulated 3.5 GHz radiofrequency (RF) EMF on mitochondrial stress in human fibroblasts and keratinocytes that were exposed for 24 h at specific absorption rate of 0.25, 1, and 4 W/kg. We assessed cell viability, mitochondrial reactive oxygen species (ROS) production, and membrane polarization. Knowing that human skin is the main target of environmental ultraviolet (UV), using the same read-out, we investigated whether subsequent exposure to 5G signal could alter the capacity of UV-B to damage skin cells. We found a statistically significant reduction in mitochondrial ROS concentration in fibroblasts exposed to 5G signal at 1 W/kg. On the contrary, the RF exposure slightly but statistically significantly enhanced the effects of UV-B radiation specifically in keratinocytes at 0.25 and 1 W/kg. No effect was found on mitochondrial membrane potential or apoptosis in any cell types or exposure conditions suggesting that the type and amplitude of the observed effects are very punctual.

Mature IL-36γ Induces Stratum Corneum Exfoliation in Generalized Pustular Psoriasis by Suppressing Corneodesmosin

Loss-of-function sequence variations in the IL36RN gene encoding IL-36 receptor antagonist cause familial generalized pustular psoriasis, which begins shortly after birth and is difficult to treat, and its effects on the epidermis are unclear. This study investigated the involvement of IL-36 receptor agonists in the epidermal formation of generalized pustular psoriasis. We found that the IL-36 receptor agonists, especially mature IL-36γ, stimulated IL-8 and pro-IL-36γ production in the epidermis while downregulating the genes encoding epidermal cornified envelope-related proteins, for example, corneodesmosin. IL-36 receptor antagonist and monoclonal anti-IL-36γ antibodies counteracted the effect of mature IL-36γ on corneodesmosin in keratinocytes in a dose-dependent manner. In the epidermis of patients with generalized pustular psoriasis with IL36RN loss-of-function sequence variations, pro-IL-36γ was overproduced in the epidermis, and corneodesmosin protein expression was markedly decreased in the region of giant subcorneal pustules (Kogoj's spongiform pustules), with high neutrophil infiltration. IL-8 induced by mature IL-36γ stimulated the infiltration of several neutrophils in the epidermis. The newly produced pro-IL-36γ is cleaved to the mature form by neutrophil proteases. This newly produced mature IL-36γ was predicted to further suppress the gene expression of corneodesmosin, leading to significant stratum corneum exfoliation and formation of the pustules. Overall, our results elucidate the mechanism underlying the formation of Kogoj's spongiform pustules in generalized pustular psoriasis.

JNK inhibition enhances cell-cell adhesion impaired by desmoglein 3 gene disruption in keratinocytes

c-Jun NH2-terminal protein kinase (JNK) and p38 are stress-activated mitogen-activated protein kinases (MAPK) that are phosphorylated by various stimuli. It has been reported that the loss of desmoglein (DSG) 3, a desmosomal transmembrane core molecule, in keratinocytes impairs cell-cell adhesion accompanied by p38 MAPK activation. To understand the biological role of DSG3 in desmosomes and its relationship with stress-activated MAPKs, we established DSG3 knockout keratinocytes (KO cells). Wild-type cells showed a linear localization of DSG1 to cell-cell contacts, whereas KO cells showed a remarkable reduction despite the increased protein levels of DSG1. Cell-cell adhesion in KO cells was impaired over time, as demonstrated by dispase-based dissociation assays. The linear localization of DSG1 to cell-cell contacts and the strength of cell-cell adhesion were promoted by the pharmacological inhibition of JNK. Conversely, pharmacological activation of JNK, but not p38 MAPK, in wild-type cells reduced the linear localization of DSG1 in cell-cell contacts. Our data indicate that DSG1 and DSG2 in KO cells cannot compensate for the attenuation of cell-cell adhesion strength caused by DSG3 deficiency and that JNK inhibition restores the strength of cell-cell adhesion by increasing the linear localization of DSG1 in cell-cell contacts in KO cells. Inhibition of JNK signaling may improve cell-cell adhesion in diseases in which DSG3 expression is impaired.

Unconjugated bilirubin and its derivative ameliorate IMQ-induced psoriasis-like skin inflammation in mice by inhibiting MMP9 and MAPK pathway

Psoriasis is a chronic immune-mediated inflammatory skin disease that involves dysregulated proliferation of keratinocytes. Psoriatic skin lesions are characterized by redness, thickness, and scaling. The interleukin axis of IL-23/IL-17 is critically involved in the development of human psoriasis. Imiquimod (IMQ), an agonist of TLR7 is known to induce psoriatic-like skin inflammation in mice. The topical application of IMQ induces systemic inflammation with increased proinflammatory cytokines in serum and secondary lymphoid organs. Further, matrix metalloproteases (MMPs) have been implicated in the pathophysiology of psoriatic-like skin inflammation. The increased MMP9 activity and gene expression of proinflammatory cytokines in IMQ-induced psoriatic skin is mediated by the activation of the MAPK pathway. Moreover, the increased expression of neutrophil-specific chemokines confirmed the infiltration of neutrophils at the site of psoriatic skin inflammation. In contrast, expression of IL-10, an anti-inflammatory cytokine gene expression is reduced in IMQ-treated mice skin. Topical application of unconjugated bilirubin (UCB) and its derivative dimethyl ester of bilirubin (BD1) on IMQ-induced psoriatic mice skin significantly mitigated the symptoms of psoriasis by inhibiting the activity of MMP9. Further, UCB and BD1 reduced neutrophil infiltration as evidenced by decreased myeloperoxidase (MPO) activity and reduced gene expression of proinflammatory cytokines, and neutrophil-specific chemokines. Apart from these modulations UCB and BD1 reduced MAPK phosphorylation and upregulated anti-inflammatory cytokines. To conclude, UCB and BD1 immunomodulated the psoriatic skin inflammation induced by IMQ in mice by inhibiting neutrophil mediated MMP9, decreased proinflammatory cytokines gene expression and modulating the MAPK pathway.

Single-cell sequencing analysis and multiple machine-learning models revealed the cellular crosstalk of dendritic cells and identified FABP5 and KLRB1 as novel biomarkers for psoriasis

Background

Psoriasis is an immune-mediated disorder influenced by environmental factors on a genetic basis. Despite advancements, challenges persist, including the diminishing efficacy of biologics and small-molecule targeted agents, alongside managing recurrence and psoriasis-related comorbidities. Unraveling the underlying pathogenesis and identifying valuable biomarkers remain pivotal for diagnosing and treating psoriasis.

Methods

We employed a series of bioinformatics (including single-cell sequencing data analysis and machine learning techniques) and statistical methods to integrate and analyze multi-level data. We observed the cellular changes in psoriatic skin tissues, screened the key genes Fatty acid binding protein 5 (FABP5) and The killer cell lectin-like receptor B1 (KLRB1), evaluated the efficacy of six widely prescribed drugs on psoriasis treatment in modulating the dendritic cell-associated pathway, and assessed their overall efficacy. Finally, RT-qPCR, immunohistochemistry, and immunofluorescence assays were used to validate.

Results

The regulatory influence of dendritic cells (DCs) on T cells through the CD70/CD27 signaling pathway may emerge as a significant facet of the inflammatory response in psoriasis. Notably, FABP5 and KLRB1 exhibited up-regulation and co-localization in psoriatic skin tissues and M5-induced HaCaT cells, serving as potential biomarkers influencing psoriasis development.

Conclusion

Our study analyzed the impact of DC-T cell crosstalk in psoriasis, elucidated the characterization of two biomarkers, FABP5 and KLRB1, in psoriasis, and highlighted the promise and value of tofacitinib in psoriasis therapy targeting DCs.

Oct4 is a gatekeeper of epithelial identity by regulating cytoskeletal organization in skin keratinocytes

Oct4 is a pioneer transcription factor regulating pluripotency. However, it is not well known whether Oct4 has an impact on epidermal cells. We generated OCT4 knockout clonal cell lines using immortalized human skin keratinocytes to identify a functional role for the protein. Here, we report that Oct4-deficient cells transitioned into a mesenchymal-like phenotype with enlarged size and shape, exhibited accelerated migratory behavior, decreased adhesion, and appeared arrested at the G2/M cell cycle checkpoint. Oct4 absence had a profound impact on cortical actin organization, with loss of microfilaments from the cell membrane, increased puncta deposition in the cytoplasm, and stress fiber formation. E-cadherin, β-catenin, and ZO1 were almost absent from cell-cell contacts, while fibronectin deposition was markedly increased in the extracellular matrix (ECM). Mapping of the transcriptional and chromatin profiles of Oct4-deficient cells revealed that Oct4 controls the levels of cytoskeletal, ECM, and differentiation-related genes, whereas epithelial identity is preserved through transcriptional and non-transcriptional mechanisms.

Conditioned medium of induced pluripotent stem cell derived neuromesodermal progenitors enhances cell migration in vitro

BACKGROUND

Identification of novel cell-based therapy sources has been of great interest in recent years to provide alternative and available therapy options in clinics. Conditioned medium (CM) can be a valuable supply for growth factors, cytokines and chemokines as a source of stem cell secretome. Exploring the role of new CM sources for tissue regeneration might be a promising approach for therapeutic purposes.

METHODS AND RESULTS

In the current study, neuromesodermal progenitors (NMPs) derived from induced pluripotent stem cells (iPSCs) were used to collect CM. Fibroblast derived iPSCs were successfully differentiated into NMPs and NMPs were characterized by double positive T/Bra and Sox2 staining. CM was collected from NMPs, and the content was characterized by membrane analysis. In vitro wound healing assay was used as a model system to observe potential activity of CM on cell migration. Fibroblasts, keratinocytes and endothelial cells were used to evaluate the effect of NMP-derived CM (NMP-CM) on cell migration in vitro. Several important proteins related to wound healing such as ANGPT 1, ANGPT 2, MCP-1, PDGF-AA, SDF-1α, TIMP-1 and TIMP-2 were increased in NMP-CM. NMP-CM increased cell proliferation and migration in vitro.

CONCLUSIONS

In vitro data obtained from three distinct cell types suggest a promising role of NMP-CM on cell migration. NMP-CM can be used for wound management in the further future after detailed in vitro and in vivo research.

Activated fibroblasts modify keratinocyte stem niche through TET1 and IL-6 to promote their rapid transformation in a mouse model of prenatal arsenic exposure

Early life exposure to environmental pollutants such as arsenic (As) can increase the risk of cancers in the offspring. In an earlier study, we showed that only prenatal As exposure significantly increases epidermal stem cell proliferation and accelerates skin tumorigenesis in BALB/c mouse offspring. In the present work, we have examined the role of As-conditioned dermal fibroblasts (DFs) in creating pro-tumorigenic niches for Keratinocyte stem cells (KSCs) in the offspring. DFs isolated from prenatally exposed animals showed increased levels of activation markers (α-SMA, Fibronectin, Collagen IV), induction of ten-eleven translocation methylcytosine dioxygenase 1(TET1), and secreted high levels of niche modifying IL-6. This led to enhanced proliferation, migration, and survival of KSCs. Increased IL-6 production in As-conditioned fibroblast was driven through TET1 mediated 5-mC to 5-hmC conversion at -698/-526 and -856/-679 region on its promoter. IL-6 further acted through downstream activation of JAK2-STAT3 signaling, promoting epithelial-to-mesenchymal transition (EMT) in KSCs. Inhibition of pSTAT3 induced by IL-6 reduced the EMT process in KSCs resulting in a significant decrease in their proliferation, migration, and colony formation. Our results indicate that IL-6 produced by prenatally conditioned fibroblasts plays a major role in regulating the KSC niche and promoting skin tumor development in As-exposed offspring.

Formylpeptide receptor 1 contributes to epidermal barrier dysfunction-induced skin inflammation through NOD-like receptor C4-dependent keratinocyte activation

BACKGROUND

Skin barrier dysfunction may both initiate and aggravate skin inflammation. However, the mechanisms involved in the inflammation process remain largely unknown.

OBJECTIVES

We sought to determine how skin barrier dysfunction enhances skin inflammation and molecular mechanisms.

METHODS

Skin barrier defect mice were established by tape stripping or topical use of acetone on wildtype mice, or filaggrin deficiency. RNA-Seq was employed to analyse the differentially expressed genes in mice with skin barrier defects. Primary human keratinocytes were transfected with formylpeptide receptor (FPR)1 or protein kinase R-like endoplasmic reticulum (ER) kinase (PERK) small interfering RNA to examine the effects of these gene targets. The expressions of inflammasome NOD-like receptor (NLR)C4, epidermal barrier genes and inflammatory mediators were evaluated.

RESULTS

Mechanical (tape stripping), chemical (acetone) or genetic (filaggrin deficiency) barrier disruption in mice amplified the expression of proinflammatory genes, with transcriptomic profiling revealing overexpression of formylpeptide receptor (Fpr1) in the epidermis. Treatment with the FPR1 agonist fMLP in keratinocytes upregulated the expression of the NLRC4 inflammasome and increased interleukin-1β secretion through modulation of ER stress via the PERK-eIF2α-C/EBP homologous protein pathway. The activation of the FPR1-NLRC4 axis was also observed in skin specimens from old healthy individuals with skin barrier defect or elderly mice. Conversely, topical administration with a FPR1 antagonist, or Nlrc4 silencing, led to the normalization of barrier dysfunction and alleviation of inflammatory skin responses in vivo.

CONCLUSIONS

In summary, our findings show that the FPR1-NLRC4 inflammasome axis is activated upon skin barrier disruption and may explain exaggerated inflammatory responses that are observed in disease states characterized by epidermal dysfunction. Pharmacological inhibition of FPR1 or NLRC4 represents a potential therapeutic target.

Suppression of TCF4 promotes a ZC3H12A-mediated self-sustaining inflammatory feedback cycle involving IL-17RA/IL-17RE epidermal signaling

IL-17C is an epithelial cell-derived proinflammatory cytokine whose transcriptional regulation remains unclear. Analysis of the IL17C promoter region identified TCF4 as putative regulator, and siRNA knockdown of TCF4 in human keratinocytes (KCs) increased IL17C. IL-17C stimulation of KCs (along with IL-17A and TNF-α stimulation) decreased TCF4 and increased NFKBIZ and ZC3H12A expression in an IL-17RA/RE-dependent manner, thus creating a feedback loop. ZC3H12A (MCPIP1/Regnase-1), a transcriptional immune-response regulator, also increased following TCF4 siRNA knockdown, and siRNA knockdown of ZC3H12A decreased NFKBIZ, IL1B, IL36G, CCL20, and CXCL1, revealing a proinflammatory role for ZC3H12A. Examination of lesional skin from the KC-Tie2 inflammatory dermatitis mouse model identified decreases in TCF4 protein concomitant with increases in IL-17C and Zc3h12a that reversed following the genetic elimination of Il17c, Il17ra, and Il17re and improvement in the skin phenotype. Conversely, interference with Tcf4 in KC-Tie2 mouse skin increased Il17c and exacerbated the inflammatory skin phenotype. Together, these findings identify a role for TCF4 in the negative regulation of IL-17C, which, alone and with TNF-α and IL-17A, feed back to decrease TCF4 in an IL-17RA/RE-dependent manner. This loop is further amplified by IL-17C-TCF4 autocrine regulation of ZC3H12A and IL-17C regulation of NFKBIZ to promote self-sustaining skin inflammation.

MicroRNA-221-3p inhibits the inflammatory response of keratinocytes by regulating the DYRK1A/STAT3 signaling pathway to promote wound healing in diabetes

Diabetic foot ulcer (DFU), a serious complication of diabetes, remains a clinical challenge. MicroRNAs affect inflammation and may have therapeutic value in DFU. Here, we find that an miR-221-3p mimic reduces the inflammatory response and increases skin wound healing rates in a mouse model of diabetes, whereas miR-221-3p knockout produced the opposite result. In human keratinocytes cells, miR-221-3p suppresses the inflammatory response induced by high glucose. The gene encoding DYRK1A is a target of miR-221-3p. High glucose increases the expression of DYRK1A, but silencing DYRK1A expression decreases high glucose-induced inflammatory cytokine release via dephosphorylation of STAT3, a substrate of DYRK1A. Application of miR-221-3p mimic to human keratinocytes cells not only decreases DYRK1A expression but also inhibits high glucose-induced production of inflammatory cytokines to promote wound healing. This molecular mechanism whereby miR-221-3p regulates inflammation through the DYRK1A/STAT3 signaling pathway suggests targets and therapeutic approaches for treating DFU.

miR-26a-5p inhibits the proliferation of psoriasis-like keratinocytes in vitro and in vivo by dual interference with the CDC6/CCNE1 axis

Psoriasis is a chronic inflammatory proliferative dermatological ailment that currently lacks a definitive cure. Employing data mining techniques, this study identified a collection of substantially downregulated miRNAs (top 10). Notably, 32 targets were implicated in both the activation of the IL-17 signaling pathway and cell cycle dysregulation. In silico analysis revealed that one of these miRNAs, miR-26a-5p, is a highly conserved cross-species miRNA. Strikingly, the miR-26a-5p sequences in humans and mice are identical, and mmu-miR-26a-5p was found to target the same 7 cell cycle targets as its human counterpart, hsa-miR-26a-5p. Among these targets, CDC6 and CCNE1 were the most effective targets of miR-26a-5p, which was further validated in vitro using a dual luciferase reporter system and qPCR assay. The therapeutic assessment of miR-26a-5p revealed its remarkable efficacy in inhibiting the proliferation and G1/S transition of keratinocytes (HaCaT and HEKs) in vitro. In vivo experiments corroborated these findings, demonstrating that miR-26a-5p effectively suppressed imiquimod (IMQ)-induced psoriasis-like skin lesions in mice over an 8-day treatment period. Histological analysis via H&E staining revealed that miR-26a-5p treatment resulted in reduced keratinocyte thickness and immune cell infiltration into the spleens of IMQ-treated mice. Mechanistic investigations revealed that miR-26a-5p induced a cascade of downregulated genes associated with the IL-23/IL-17A axis, which is known to be critical in psoriasis pathogenesis, while concomitantly suppressing CDC6 and CCNE1 expression. These findings were corroborated by qPCR and Western blot analyses. Collectively, our study provides compelling evidence supporting the therapeutic potential of miR-26a-5p as a safe and reliable endogenous small nucleic acid for the treatment of psoriasis.

LncRNA H19 Inhibits Keratinocyte Cell Proliferation and Migration by Targeting miR-17-5p/RUNX1 Axis in Chronic Wounds

The migration and proliferation of keratinocytes are critical for re-epithelization during chronic wound healing. Runt-related transcription factor 1 (RUNX1) has been indicated to repress keratinocyte proliferation. Nonetheless, the potential molecular mechanism of RUNX1 in regulating keratinocyte proliferation and migration remains unclear. Cell counting kit-8 and wound-healing assays were implemented for examining keratinocyte viability and migration, respectively. Western blotting and real-time quantitative polymerase chain reaction were utilized for quantifying protein and RNA levels. Luciferase reporter assay was employed for verifying the interaction between RUNX1, miR-17-5p, and long noncoding RNA H19. The results showed that RUNX1 depletion promoted keratinocyte proliferation and migration and repressed extracellular matrix degradation. Mechanistically, H19 upregulated RUNX1 expression by competitively absorbing miR-17-5p. Rescue experiments revealed that overexpressing RUNX1 reversed H19 silencing-mediated effects on the phenotypes of keratinocytes. In conclusion, H19 knockdown promotes keratinocyte proliferation and migration and suppresses extracellular matrix degradation via the miR-17-5p/RUNX1 axis.

Keratinocyte integrin α3β1 induces expression of the macrophage stimulating factor, CSF-1, through a YAP/TEAD-dependent mechanism

The development of wound therapy targeting integrins is hampered by inadequate understanding of integrin function in cutaneous wound healing and the wound microenvironment. Following cutaneous injury, keratinocytes migrate to restore the skin barrier, and macrophages aid in debris clearance. Thus, both keratinocytes and macrophages are critical to the coordination of tissue repair. Keratinocyte integrins have been shown to participate in this coordinated effort by regulating secreted factors, some of which crosstalk to distinct cells in the wound microenvironment. Epidermal integrin α3β1 is a receptor for laminin-332 in the cutaneous basement membrane. Here we show that wounds deficient in epidermal α3β1 express less epidermal-derived macrophage colony-stimulating factor 1 (CSF-1), the primary macrophage-stimulating growth factor. α3β1-deficient wounds also have fewer wound-proximal macrophages, suggesting that keratinocyte α3β1 may stimulate wound macrophages through the regulation of CSF-1. Indeed, using a set of immortalized keratinocytes, we demonstrate that keratinocyte-derived CSF-1 supports macrophage growth, and that α3β1 regulates Csf1 expression through Src-dependent stimulation of Yes-associated protein (YAP)-Transcriptional enhanced associate domain (TEAD)-mediated transcription. Consistently, α3β1-deficient wounds in vivo display a substantially reduced number of keratinocytes with YAP-positive nuclei. Overall, our current findings identify a novel role for epidermal integrin α3β1 in regulating the cutaneous wound microenvironment by mediating paracrine crosstalk from keratinocytes to wound macrophages, implicating α3β1 as a potential target of wound therapy.

Elevated expression of interleukin-6 (IL-6) and serum amyloid A (SAA) in the skin and the serum of recessive dystrophic epidermolysis bullosa: Skin as a possible source of IL-6 through Toll-like receptor ligands and SAA

The effect of persistent skin inflammation on extracutaneous organs and blood is not well studied. Patients with recessive dystrophic epidermolysis bullosa (RDEB), a severe form of the inherited blistering skin disorder, have widespread and persistent skin ulcers, and they develop various complications including anaemia, hyperglobulinaemia, hypoalbuminaemia and secondary amyloidosis. These complications are associated with the bioactivities of IL-6, and the development of secondary amyloidosis requires the persistent elevation of serum amyloid A (SAA) level. We found that patients with RDEB had significantly higher serum levels of IL-6 and SAA compared to healthy volunteers and patients with psoriasis or atopic dermatitis. Both IL-6 and SAA were highly expressed in epidermal keratinocytes and dermal fibroblasts of the skin ulcer lesions. Keratinocytes and fibroblasts surrounding the ulcer lesions are continuously exposed to Toll-like receptor (TLR) ligands, pathogen-associated and damage-associated molecular pattern molecules. In vitro, TLR ligands induced IL-6 expression via NF-κB in normal human epidermal keratinocytes (NHEKs) and dermal fibroblasts (NHDFs). SAA further induced the expression of IL-6 via TLR1/2 and NF-κB in NHEKs and NHDFs. The limitation of this study is that NHEKs and NHDFs were not derived from RDEB patients. These observations suggest that TLR-mediated persistent skin inflammation might increase the risk of IL-6-related systemic complications, including RDEB.

Inhibitory effects of bioactive compounds on UVB-induced photodamage in human keratinocytes: modulation of MMP1 and Wnt signaling pathways

UVB radiation significantly threatens skin health, contributing to wrinkle formation and an elevated risk of skin cancer. This study aimed to explore bioactive compounds with potential UVB-protective properties. Using in silico analysis, we chose compounds to reduce binding energy with matrix metalloproteinase-1 (MMP1). Piperitoside, procyanidin C1, and mulberrofuran E emerged as promising candidates through this computational screening process. We investigated the UVB-protective efficacy of the selected compounds and underlying mechanisms in human immortalized keratinocytes (HaCaT). We also investigated the molecular pathways implicated in their action, focusing on the transforming growth factor (TGF)-β and wingless-related integration site (Wnt)/β-catenin signaling pathways. In UVB-exposed HaCaT cells (100 mJ/cm2 for 30 min), piperitoside, procyanidin C1, and mulberrofuran E significantly reduced reactive oxygen species (ROS) and lipid peroxides, coupled with an augmentation of collagen expression. These compounds suppressed MMP1, tumor necrosis factor-alpha (TNF-α), and inducible nitric oxide synthase (iNOS) expression, while they concurrently enhanced collagen-1 (COL1A1), β-catenin (CTNNB1), and superoxide dismutase type-1 (SOD1) expression. Furthermore, Wnt/β-catenin inhibitors, when administered subsequently, partially counteracted the reduction in MMP1 expression and alleviated inflammatory and oxidative stress markers induced by the bioactive compounds. In conclusion, piperitoside, procyanidin C1, and mulberrofuran E protected against UVB-induced damage in HaCaT cells by inhibiting MMP1 expression and elevating β-catenin expression. Consequently, these bioactive compounds emerge as promising preventive agents for UVB-induced skin damage, promoting skin health.

Collagen I protects human keratinocytes HaCaT against UVB injury via restoring PINK1/parkin-mediated mitophagy

Collagen I is a major component of extracellular matrix in human skin, and is also widely used in a variety of skin-care products. In this study, we investigated the modulatory roles of collagen I on human immortalized keratinocytes HaCaT, especially when cells were irradiated with UVB. Interestingly, the cells grown on plates coated by molecular collagen I, but not fibrillar collagen I, acquired certain resistance against UVB damages, as shown by increased survival and reduced apoptosis. The accumulation of dysfunctional mitochondria in UVB-treated cells was attenuated by molecular collagen I-coating. Interestingly, molecular collagen I rescued the loss of mitochondrial biogenesis in cells treated with UVB. Loss of PINK1/parkin-mediated mitophagy was dominant for the accumulation of dysfunctional mitochondria after UVB irradiation. Of note, cells cultured on molecular collagen I-precoated plates exhibited reserved mitophagy after UVB irradiation, as reflected by the enhanced protein level of PINK1/parkin, increased mitochondrial ubiquitin and the co-localization of lysosomes and mitochondria. Moreover, in UVB-treated cells, inhibiting mitophagy by Cyclosporin A, or by silencing PINK1 or parkin, disturbed the resolution of mitochondrial stress and reduced the protective effect of molecular collagen I, indicating that mitophagy is pivotal for the protection of collagen I against UVB damage in keratinocytes HaCaT. Collectively, this study reveals an unexpected protective role of collagen I, which facilitates mitophagy to rescue cells under UVB irradiation, providing a new direction for clinical application of collagen products.

Reconstructed human epidermis-based testing strategy of skin sensitization potential and potency classification using epidermal sensitization assay and in silico data

The hazards and potency of skin sensitizers are traditionally determined using animal tests such as the local lymph node assay (LLNA); however, significant progress has been made in the development of non-animal test methods addressing the first three mechanistic key events of adverse outcome pathway in skin sensitization. We developed the epidermal sensitization assay (EpiSensA), which is a reconstructed human epidermis-based assay, by measuring four genes related to critical keratinocyte responses during skin sensitization. Four in vitro skin sensitization test methods (EpiSensA, direct peptide reactivity assay [DPRA], KeratinoSens™, and human cell line activation test [h-CLAT]) were systematically evaluated using 136 chemicals including lipophilic chemicals and pre/pro-haptens, which may be related to assay-specific limitations. The constructed database included existing and newly generated data. The EpiSensA showed a broader applicability domain and predicted the hazards with 82.4% and 78.8% accuracy than LLNA and human data. The EpiSensA could detect 76 out of 88 sensitizers at lower concentrations than the LLNA, indicating that the EpiSensA has higher sensitivity for the detection of minor sensitizing constituents. These results confirmed the potential use of the EpiSensA in evaluating a mixture of unknown compositions that can be evaluated by animal tests. To combine different information sources, the reconstructed human epidermis-based testing strategy (RTS) was developed based on weighted multiple information from the EpiSensA and TImes MEtabolism Simulator platform for predicting Skin Sensitization (TIMES-SS; RTSv1) or Organization for Economic Cooperation and Development (OECD) QSAR Toolbox automated workflow (RTSv2). The predictivities of the hazards and Globally Harmonized System (GHS) subcategories were equal to or better than the defined approaches (2 out of 3, integrated testing strategy [ITS]v1, and ITSv2) adopted as OECD Guideline 497.

Comparative immunohistochemical analysis suggests a conserved role of EPS8L1 in epidermal and hair follicle barriers of mammals

The mammalian skin and its appendages depend on tightly coordinated differentiation of epithelial cells. Epidermal growth factor receptor (EGFR) pathway substrate 8 (EPS8) like 1 (EPS8L1) is enriched in the epidermis among human tissues and has also been detected in the epidermis of lizards. Here, we show by the analysis of single-cell RNA-sequencing data that EPS8L1 mRNA is co-expressed with filaggrin and loricrin in terminally differentiated human epidermal keratinocytes. Comparative genomics indicated that EPS8L1 is conserved in all main clades of mammals, whereas the orthologous gene has been lost in birds. Using a polyclonal antibody against EPS8L1, we performed an immunohistochemical screening of skin from diverse mammalian species and immuno-electron microscopy of human skin. EPS8L1 was detected predominantly in the granular layer of the epidermis in monotremes, marsupial, and placental mammals. The labeling was partly associated with cell membranes, and it was evident along the perimeter of keratinocytes at the transition with the cornified layer of the epidermis, similar to involucrin distribution. Basal, spinous, and the fully mature cornified layers lacked immunolabeling of EPS8L1. In addition to the epidermis, the hair follicle inner root sheath (IRS) was immunolabeled. Both epidermal granular layer and IRS contribute to the barrier function of the skin, suggesting that EPS8L1 is involved in the regulation of these barriers.

In vitro generation of epidermal keratinocytes from human CD34-positive hematopoietic stem cells

The epidermis is largely composed of keratinocytes (KCs), and the proliferation and differentiation of KCs from the stratum basale to the stratum corneum is the cellular hierarchy present in the epidermis. In this study, we explore the differentiation abilities of human hematopoietic stem cells (HSCs) into KCs. Cultured HSCs positive for CD34, CD45, and CD133 with prominent telomerase activity were induced with keratinocyte differentiation medium (KDM), which is composed of bovine pituitary extract (BPE), epidermal growth factor (EGF), insulin, hydrocortisone, epinephrine, transferrin, calcium chloride (CaCl2), bone morphogenetic protein 4 (BMP4), and retinoic acid (RA). Differentiation was monitored through the expression of cytokeratin markers K5 (keratin 5), K14 (keratin 14), K10 (keratin 10), K1 (keratin 1), transglutaminase 1 (TGM1), involucrin (IVL), and filaggrin (FLG) on day 0 (D0), day 6 (D6), day 11 (D11), day 18 (D18), day 24 (D24), and day 30 (D30) using immunocytochemistry, fluorescence microscopy, flow cytometry, qPCR, and Western blotting. The results revealed the expression of K5 and K14 genes in D6 cells (early keratinocytes), K10 and K1 genes in D11-D18 cells (mature keratinocytes) with active telomerase enzyme, and FLG, IVL, and TGM1 in D18-D24 cells (terminal keratinocytes), and by D30, the KCs were completely enucleated similar to cornified matrix. This method of differentiation of HSCs to KCs explains the cellular order exists in the normal epidermis and opens the possibility of exploring the use of human HSCs in the epidermal differentiation.

Metabolic re-programming of keratinocytes in response to contact allergens

BACKGROUND

Allergic contact dermatitis (ACD) is a common skin disease caused by the recognition of haptens by the immune system. Keratinocytes play an important role in the initiation and facilitation of inflammatory responses in ACD. Immune responses are associated with major changes in metabolism. However, metabolic re-programming is not well studied in ACD; specifically, knowledge of metabolic alterations in structural cells is lacking.

METHODS

Metabolic re-programming in ACD was studied using publicly available transcriptome datasets. Primary pooled keratinocytes and a keratinocyte cell line (HaCaT) were stimulated with contact allergens, and inflammatory responses and expression of metabolic markers were measured by qPCR and flow cytometry, respectively.

RESULTS

ACD is characterized by metabolic re-programming with a metabolic profile similar to atopic dermatitis. Exposure to contact allergens causes a wide array of metabolic alterations. Stimulation of keratinocytes with contact allergens induced inflammatory responses typical for ACD and was associated with an up-regulation of proteins representative for glucose uptake, fatty acid metabolism, oxidative phosphorylation and to some extent arginine biosynthesis. Changes in these metabolic pathways were also observed when comparing lesional with non-lesional contact dermatitis skin.

CONCLUSIONS

ACD is, similarly to other inflammatory skin diseases, characterized by metabolic re-programming. Contact allergen exposure induces expression of a wide array of metabolic pathways, which is at least in part mediated through metabolic re-programming of keratinocytes.

Induced pluripotent stem cell (iPSC) line MLi005-A derived from a patient with dominant dystrophic epidermolysis bullosa (DDEB)

We have generated MLi005-A, a new induced pluripotent stem cell (iPSC) line derived from skin fibroblasts of a male patient with dominant dystrophic epidermolysis bullosa (DDEB). This iPSC line may be used as a model system for studies on skin integrity, the extracellular matrix and skin barrier function. The characterization of the MLi005-A cell line consisted of molecular karyotyping, next-generation sequencing of the COL7A1 alleles, pluripotency and differentiation potentials testing by immunofluorescence of associated markers in vitro. The MLi-005A line has been also tested for ability to differentiate into fibroblasts and keratinocytes and markers associated with these cell types.

Epidermal turnover and iron metabolism in senile lentigo

Senile lentigo (SL) is a pigmentary disorder associated with disrupted epidermal turnover. Trace minerals in the skin are known to regulate keratinocyte proliferation and differentiation. To clarify the role of iron in SL, we compared the expression of molecules related to iron metabolism between SL lesion (lesion) and the surrounding normal skin (nonlesion). Our results revealed that proteins involved in iron uptake and utilization such as transferrin receptor 1, iron regulatory protein 1, mitoferrin 1, and divalent metal transporter 1 were expressed in the lower epidermis in the nonlesion, while expression of them was also observed in the upper epidermis in the lesion. Ferroportin (FPN), involved in iron export, was expressed in the upper epidermis in the nonlesion, but was only scarcely expressed in the upper epidermis in the lesion. Hepcidin, which promotes FPN degradation, was expressed in the lower epidermis in the nonlesion; however, its expression was also observed in the upper epidermis in the lesion. These changes in the expression of molecules involved in iron uptake/export/utilization might reflect the altered iron utilization state in SL, resulting in disruption of keratinocyte differentiation and disturbing epidermal turnover. Our results suggest that the metabolism of iron in keratinocytes in SL differs from that in the normal epidermis, and these changes could be associated with the abnormal epidermal turnover and decreased melanin excretion in SL.

Correlational analysis of PLIN1 with inflammation in diabetic foot ulcer wounds

BACKGROUND

The persistent presence of inflammation is a recognized pathogenic mechanisms of diabetic foot ulcers (DFUs). We aimed to investigate the expression of PLIN1 in tissues from DFU patients and assess its potential association with inflammation-induced damage.

METHODS

We performed transcriptome sequencing and correlation analysis of the foot skin from patients with or without DFUs. Additionally, we examined the correlation between PLIN1 and related inflammatory indicators by analyzing PLIN1 expression in tissue and serum samples and through high-glucose stimulation of keratinocytes (HaCaT cells).

RESULTS

PLIN1 is upregulated in the tissue and serum from DFU patients. Additionally, PLIN1 shows a positive correlation with leukocytes, neutrophils, monocytes, C-reactive protein, and procalcitonin in the serum, as well as IL-1β and TNF-α in the tissues. Experiments with Cells demonstrated that reduced expression of PLIN1 leads to significantly decreased expression of iNOS, IL-1β, IL-6, IL-18, and TNF-α. PLIN1 may mediate wound inflammatory damage through the NF-κB signaling pathway.

CONCLUSION

Our findings suggest that PLIN1 mediates the inflammatory damage in DFU, offering new prospects for the treatment of DFU.

A novel three-dimensional Nrf2 reporter epidermis model for skin sensitization assessment

Skin sensitization assessment has progressed from the use of animal models towards the application of New Approach Methodologies (NAMs). Several skin sensitization NAMs are accepted for regulatory use, but a majority relies on submerged in vitro cell cultures that limit their applicability domain, posing challenges for testing hydrophobic chemicals and mixtures. A newly developed three-dimensional (3D) Nrf2 reporter epidermis model for skin sensitization assessment is reported. This NAM may help to overcome these limitations. The NAM combines the in vivo-like biology and exposure conditions of 3D epidermis models with the reliability, convenience, and cost-effectiveness of secreted reporter gene technology. The Keap1-Nrf2-ARE pathway was chosen as the reporter gene read-out, as it is induced by most skin sensitizers and already adopted in OECD Test guideline 442D. Immortalized human primary keratinocytes (Ker-CT) were stably transfected with the pIGB-Nrf2-SEAP vector to construct a Nrf2 reporter cell line. Ker-CT Nrf2 reporter cells showed negligible basal expression of the Secreted Embryonic Alkaline Phosphatase (SEAP) reporter, which was induced 13.5-fold by exposure to the skin sensitizer cinnamic aldehyde (CA). Co-exposure to CA and the Nrf2 inhibitor glucocorticoid clobetasol propionate significantly suppressed the CA-induced SEAP expression, confirming dependance of the SEAP expression on Nrf2 activation. Using air-liquid interface and animal constituent free culture conditions, the Ker-CT Nrf2 reporter cells differentiated to stratified 3D epidermis models with an in vivo-like skin architecture and functional skin barrier. Evaluation of a Ker-CT Nrf2 reporter cell-based 2D assay by testing 10 conventional reference chemicals showed a predictive accuracy for skin sensitization potential of 80% and 70% compared to LLNA and human data in two independent laboratories and a high intra- and interlaboratory reproducibility. Moreover, the 3D epidermis models predicted 3 sensitizing and 2 non-sensitizing reference chemicals correctly in a first proof-of-concept study. Further investigations foresee the testing of additional chemicals, including hydrophobic compounds and mixtures to confirm the potential of the 3D epidermis models to broaden the applicability domain for NAM-based skin sensitization assessment.

Decreased TET2/5-hmC reduces the integrity of the epidermal barrier via epigenetic dysregulation of filaggrin in psoriatic lesions

BACKGROUND

TET2 participates in tumor progression and intrinsic immune homeostasis via epigenetic regulation. TET2 has been reported to be involved in maintaining epithelial barrier homeostasis and inflammation. Abnormal epidermal barrier function and TET2 expression have been detected in psoriatic lesions. However, the mechanisms underlying the role of TET2 in psoriasis have not yet been elucidated.

OBJECTIVE

To define the role of TET2 in maintaining epithelial barrier homeostasis and the exact epigenetic mechanism in the dysfunction of the epidermal barrier in psoriasis.

METHODS

We analyzed human psoriatic skin lesions and datasets from the GEO database, and detected the expression of TET2/5-hmC together with barrier molecules by immunohistochemistry. We constructed epidermal-specific TET2 knockout mice to observe the effect of TET2 deficiency on epidermal barrier function via toluidine blue penetration assay. Further, we analyzed changes in the expression of epidermal barrier molecules by immunofluorescence in TET2-specific knockout mice and psoriatic model mice.

RESULTS

We found that decreased expression of TET2/5-hmC correlated with dysregulated barrier molecules in human psoriatic lesions. Epidermal-specific TET2 knockout mice showed elevated transdermal water loss associated with abnormal epidermal barrier molecules. Furthermore, we observed that TET2 knockdown in keratinocytes reduced filaggrin expression via filaggrin promoter methylation.

CONCLUSION

Aberrant epidermal TET2 affects the integrity of the epidermal barrier through the epigenetic dysregulation of epidermal barrier molecules, particularly filaggrin. Reduced TET2 expression is a critical factor contributing to an abnormal epidermal barrier in psoriasis.