Induce Keratinocyte Differentiation Research Articles

Non-psoriatic uses of calcipotriol: a concise updated review.

Calcipotriol (calcipotriene) is a synthetic vitamin D3 derivative that is a standard treatment option for psoriasis. It is generally well tolerated with minimal side effects. Due to its ability to reduce keratinocyte proliferation and induce keratinocyte differentiation as well as its immunomodulatory effects, calcipotriol has been used to treat a variety of skin disorders such as atopic dermatitis, actinic keratoses, lichen planus, seborrheic keratoses, and vitiligo [1]. We surveyed the literature examining the use of calcipotriol for non-psoriatic dermatologic disease.

Novel Electrospun Polycaprolactone/Calcium Alginate Scaffolds for Skin Tissue Engineering

After decades of research, fully functional skin regeneration is still a challenge. Skin is a multilayered complex organ exhibiting a cascading healing process affected by various mechanisms. Specifically, nutrients, oxygen, and biochemical signals can lead to specific cell behavior, ultimately conducive to the formation of high-quality tissue. This biomolecular exchange can be tuned through scaffold engineering, one of the leading fields in skin substitutes and equivalents. The principal objective of this investigation was the design, fabrication, and evaluation of a new class of three-dimensional fibrous scaffolds consisting of poly(ε-caprolactone) (PCL)/calcium alginate (CA), with the goal to induce keratinocyte differentiation through the action of calcium leaching. Scaffolds fabricated by electrospinning using a PCL/sodium alginate solution were treated by immersion in a calcium chloride solution to replace alginate-linked sodium ions by calcium ions. This treatment not only provided ion replacement, but also induced fiber crosslinking. The scaffold morphology was examined by scanning electron microscopy and systematically assessed by measurements of the pore size and the diameter, alignment, and crosslinking of the fibers. The hydrophilicity of the scaffolds was quantified by contact angle measurements and was correlated to the augmentation of cell attachment in the presence of CA. The in vitro performance of the scaffolds was investigated by seeding and staining fibroblasts and keratinocytes and using differentiation markers to detect the evolution of basal, spinous, and granular keratinocytes. The results of this study illuminate the potential of the PCL/CA scaffolds for tissue engineering and suggest that calcium leaching out from the scaffolds might have contributed to the development of a desirable biological environment for the attachment, proliferation, and differentiation of the main skin cells (i.e., fibroblasts and keratinocytes).

Bidirectional regulation of desmosome hyperadhesion by keratin isotypes and desmosomal components

Desmosomes are intercellular junctions which mediate cohesion and communication in tissues exposed to mechanical strain by tethering the intermediate filament cytoskeleton to the plasma membrane. While mature desmosomes are characterized by a hyperadhesive, Ca2+-independent state, they transiently loose this state during wound healing, pathogenesis and tissue regeneration. The mechanisms controlling the hyperadhesive state remain incompletely understood. Here, we show that upon Ca2+-induced keratinocyte differentiation, expression of keratin 17 (K17) prevents the formation of stable and hyperadhesive desmosomes, accompanied by a significant reduction of desmoplakin (DP), plakophilin-1 (PKP1), desmoglein-1 (Dsg1) and -3 (Dsg3) at intercellular cell borders. Atomic force microscopy revealed that both increased binding strength of desmoglein-3 molecules and amount of desmoglein-3 oligomers, known hallmarks of hyperadhesion, were reduced in K17- compared to K14-expressing cells. Importantly, overexpression of Dsg3 or DPII enhanced their localization at intercellular cell borders and increased the formation of Dsg3 oligomers, resulting in stable, hyperadhesive desmosomes despite the presence of K17. Notably, PKP1 was enriched in these desmosomes. Quantitative image analysis revealed that DPII overexpression contributed to desmosome hyperadhesion by increasing the abundance of K5/K17-positive keratin filaments in the proximity of desmosomes enriched in desmoglein-3. Thus, our data show that hyperadhesion can result from recruitment of keratin isotypes K5/K17 to desmosomes or from enhanced expression of DP and Dsg3 irrespective of keratin composition. The notion that hyperadhesive desmosomes failed to form in the absence of keratins underscores the essential role of keratins and suggest bidirectional control mechanisms at several levels.

Shotokuseki Extract Promotes Keratinocyte Differentiation Even at a Low Calcium Concentration

The switch between keratinocyte proliferation and differentiation is regulated by extracellular calcium levels, requiring high concentrations (>1 mol/L) of extracellular calcium to induce differentiation. The Shotokuseki extract (SE) contains various ions such as calcium, but its effect on keratinocytes is unknown. This study focused on calcium-induced differentiation of keratinocytes and investigated the effects of simultaneous application of calcium and other ions on keratinocyte differentiation. The expression of differentiation markers increased when SE was added to a keratinocyte culture but not when only calcium was added at the same concentration present in SE. The calcium concentration in SE was found to be too low (0.01 mol/L) to induce differentiation of keratinocytes. In addition, the application of SE increased intracellular calcium concentration compared with calcium solution alone. Therefore, the induction of keratinocyte differentiation by SE is not calcium-dependent, or SE may alter the calcium sensitivity of keratinocytes. In our study, we found that simultaneous application of multiple ions and/or the application of trace ions may alter calcium sensitivity and the epidermal cell response. The function of ion transporters associated with these ions and the response of cells to ions depends largely on the balance among various ions and the function of trace ions.

FGFR2 maintains cancer cell differentiation via AKT signaling in esophageal squamous cell carcinoma

ABSTRACT Fibroblast growth factors (FGFs) and their receptors (FGFRs) are important for signaling to maintain cancer stem-like cells (CSCs) in esophageal squamous cell carcinoma (ESCC). However, which FGF receptor, 1, 2, 3, 4, and L1, is essential or whether FGFRs have distinct different roles in ESCC-CSCs is still in question. This study shows that FGFR2, particularly the IIIb isoform, is highly expressed in non-CSCs. Non-CSCs have an epithelial phenotype, and such cells are more differentiated in ESCC. Further, FGFR2 induces keratinocyte differentiation through AKT but not MAPK signaling and diminishes CSC populations. Conversely, knockdown of FGFR2 induces epithelial–mesenchymal transition (EMT) and enriches CSC populations in ESCC. Finally, data analysis using The Cancer Genome Atlas (TCGA) dataset shows that expression of FGFR2 significantly correlated with cancer cell differentiation in clinical ESCC samples. The present study shows that each FGFR has a distinct role and FGFR2-AKT signaling is a key driver of keratinocyte differentiation in ESCC. Activation of FGFR2-AKT signaling could be a future therapeutic option targeting CSC in ESCC.

Differentiation-related zinc finger protein 750 suppresses cell growth in esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is a deadly squamous cell carcinoma (SCC) of the esophagus. Development of SCCs is associated with the deregulation of the squamous cell lineage program and/or keratinocyte terminal differentiation by genomic and genetic aberrations; thus, these processes must be tightly controlled to maintain normal squamous cell development. Zinc finger protein 750 (ZNF750) is a gene involved in keratinocyte terminal differentiation and is frequently mutated and putatively silenced in ESCC, which implicates its function as a potential differentiation-related suppressor of ESCC. The present study aimed to elucidate the relationship between ZNF750 function to induce keratinocyte differentiation and tumor suppression in ESCC. The results demonstrated that chemical manipulation of esophageal keratinocyte differentiation in mouse normal esophageal epithelial organoids (mNEEO) implicated the involvement of the mouse homologue of ZNF750, Zfp750, in keratinocyte differentiation in premalignant cells. Bioinformatics analyses of data from high ZNF750-expressing ESCC tumors obtained from public databases and ZNF750-overexpressing ESCC cells compared with low ZNF750-expressing ESCC tumors and GFP-expressing ESCC cells, respectively, revealed enrichment of keratinocyte differentiation-related gene sets in these samples. Finally, the induction through to terminal differentiation of the keratinocyte by all-trans retinoic acid on parental ESCC cell lines led to the upregulation of the terminal differentiation marker Involucrin and a decrease in cell viability similar to that observed in ZNF750-overexpressing ESCC cells. The results of the present study demonstrated a functional link between the ability of ZNF750 to induce cell differentiation through to terminal differentiation and its function as a growth suppressor in ESCC. This study provides improved understanding of the role of ZNF750, a frequently mutated differentiation-related gene in ESCC, and its effects in ESCC pathogenesis.

Exploration of novel candidate genes involved in epidermal keratinocyte differentiation and skin barrier repair in man

A proper skin barrier function requires constant formation of stratum corneum, i.e. the outermost layer of epidermis composed of terminally differentiated keratinocytes. The complex process of converting proliferative basal keratinocytes into corneocytes relies on programmed changes in the activity of many well-established genes. Much remains however to be investigated about this process, e.g. in conjunction with epidermal barrier defects due to genetic errors as in ichthyosis. To this end, we re-analyzed two sets of microarray-data comparing altered gene expression in differentiated vs. proliferating keratinocytes and in the skin of patients with autosomal recessive congenital ichthyosis (ARCI) vs. healthy controls, respectively. We thus identified 24 genes to be upregulated in both sets of array and not previously associated with keratinocyte differentiation. For 10 of these genes (AKR1B10, BLNK, ENDOU, GCNT4, GLTP, RHCG, SLC15A1, TMEM45B, TMEM86A and VSNL1), qPCR analysis confirmed the array results and subsequent immunostainings of normal epidermis showed superficial expression of several of the proteins. Furthermore, induction of keratinocyte differentiation using phorbol esters (PMA) resulted in increased expression of eight of the genes, whereas siRNA silencing of PPARδ, a transcription factor supporting differentiation, had the opposite effect.In summary, our results identify ten new candidate genes seemingly involved in human epidermal keratinocyte differentiation and possibly important for epidermal repair in a genetic skin disease characterized by barrier failure.

Lysosome-targeted photodynamic treatment induces primary keratinocyte differentiation

Photodynamic therapy is an attractive technique for various skin tumors and non-cancerous skin lesions. However, while the aim of photodynamic therapy is to target and damage only the malignant cells, it unavoidably affects some of the healthy cells surrounding the tumor as well. However, data on the effects of PDT to normal cells are scarce, and the characterization of the pathways activated after the photodamage of normal cells may help to improve clinical photodynamic therapy.In our study, primary human epidermal keratinocytes were used to evaluate photodynamic treatment effects of photosensitizers with different subcellular localization. We compared the response of keratinocytes to lysosomal photodamage induced by phthalocyanines, aluminum phthalocyanine disulfonate (AlPcS2a) or aluminum phthalocyanine tetrasulfonate (AlPcS4), and cellular membrane photodamage by m-tetra(3-hydroxyphenyl)-chlorin (mTHPC). Our data showed that mTHPC-PDT promoted autophagic flux, whereas lysosomal photodamage induced by aluminum phthalocyanines evoked differentiation and apoptosis. Photodamage by AlPcS2a, which is targeted to lysosomal membranes, induced keratinocyte differentiation and apoptosis more efficiently than AlPcS4, which is targeted to lysosomal lumen. Computational analysis of the interplay between these molecular pathways revealed that keratin 10 is the coordinating molecular hub of primary keratinocyte differentiation, apoptosis and autophagy.

Inhibition of sphingosine 1-phosphate lyase activates human keratinocyte differentiation and attenuates psoriasis in mice

Sphingosine 1-phosphate (S1P) lyase is an intracellular enzyme that catalyzes the irreversible degradation of S1P and has been suggested as a therapeutic target for the treatment of psoriasis vulgaris. Because S1P induces differentiation of keratinocytes, we examined whether modulation of S1P lyase and altered intracellular S1P levels regulate proliferation and differentiation of human neonatal epidermal keratinocyte (HEKn) cells. To identify the physiological functions of S1P lyase in skin, we inhibited S1P lyase in HEKn cells with an S1P lyase-specific inhibitor (SLI) and with S1P lyase 1 (SGPL1)-specific siRNA (siSGPL1). In HEKn cells, pharmacological treatment with the SLI caused G1 arrest by upregulation of p21 and p27 and induced keratin 1, an early differentiation marker. Similarly, genetic suppression by siSGPL1 arrested the cell cycle at the G1 phase and activated differentiation. In addition, enzyme suppression by siSGPL1 upregulated keratin 1 and differentiation markers including involucrin and loricrin. When hyperproliferation of HEKn cells was induced by interleukin (IL)-17 and IL-22, pharmacologic inhibition of S1P lyase by SLI decreased proliferation and activated differentiation of HEKn cells simultaneously. In addition, SLI administration ameliorated imiquimod-induced psoriatic symptoms including erythema, scaling, and epidermal thickness in vivo. We thus demonstrated that S1P lyase inhibition reduces cell proliferation and induces keratinocyte differentiation, and that inhibition may attenuate psoriasiform changes. Collectively, these findings suggest that S1P lyase is a modulating factor for proliferation and differentiation, and support its potential as a therapeutic target for psoriasis in human keratinocytes.

Abstract 4647: Keratinocyte specific deletion of TWIST1 promotes differentiation and inhibits UVB-induced hyperproliferation

Abstract Non-melanoma skin cancers (NMSC) have one of the highest incidences in the United States with over 5 million diagnoses every year. The major risk factor for the development of NMSC is solar ultraviolet radiation consisting of both UVA and UVB. In epidermal keratinocytes, UV radiation results in DNA damage as well as deregulation of both proliferative and survival signaling pathways that contribute to tumorigenesis. The transcription factor TWIST1 has been reported to be essential for the formation and invasiveness of chemically-induced tumors in skin. TWIST1 deletion in mouse epidermis results in arrested cell cycle progression in response to treatment with the tumor promoter, TPA, which in turn prevents skin tumor growth in two-stage skin carcinogenesis assays. However, the impact of the keratinocyte specific TWIST1 deletion on skin carcinogenesis caused by UV radiation has not been clarified. In preliminary experiments, we found that primary mouse keratinocytes with TWIST1 knockout (KO) displayed an increase in the G2/M phase population after a single exposure to 20mJ/cm2 of UVB radiation. Accordingly, protein levels of cell cycle regulator p21 increased while those of pMDM2 decreased after UVB exposure. Moreover, we found that primary mouse keratinocytes with TWIST1 KO displayed an increase in apoptosis as shown by augmented Annexin V staining that corresponded with the reduction in levels of anti-apoptotic regulators Bcl-2 and Bcl-XL and concomitant upregulation of cleaved PARP and cleaved caspase-7 after UVB exposure. Furthermore, deletion of TWIST1 in skin keratinocytes in vivo (using K5-Cre x TWIST1flox/flox mice) led to a significant reduction in UVB-induced epidermal hyperproliferation compared to wild-type mice assessed by both Ki67 immunofluorescence staining as well as BrdU incorporation. Additionally, the protein level for p21 was increased while the levels of c-myc, and Cyclin B1 were reduced in the TWIST1 deficient keratinocytes in vivo. Interestingly, expression of differentiation markers such as Loricrin, Keratin-10, Sca-1, and transglutaminase-1 were also increased in the epidermis of TWIST1 deficient mice. These results from the in vivo model show that TWIST1 deletion results in an interruption of UVB-induced hyperproliferation via cell cycle arrest and induction of keratinocyte differentiation. Collectively, our findings indicate that the deficiency of TWIST1 has significant effects on the proliferation, survival and differentiation of keratinocytes; processes important for UVB skin tumor development. Future experiments will continue to assess the changes in oncogenic signaling in epidermal keratinocytes in response to UVB exposure and further investigate the impact of the deletion of TWIST1 on UV-induced skin carcinogenesis. Research supported by CPRIT 2018 Grant RP150247 and by CONACYT Fellowship 671661. Citation Format: Fernando Eguiarte-Solomon, Okkyung Rho, John DiGiovanni. Keratinocyte specific deletion of TWIST1 promotes differentiation and inhibits UVB-induced hyperproliferation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4647.

LPA Induces Keratinocyte Differentiation and Promotes Skin Barrier Function through the LPAR1/LPAR5-RHO-ROCK-SRF Axis

The skin barrier protects the body from water loss, allergens, and pathogens. Profilaggrin is produced by differentiated keratinocytes and is processed into filaggrin monomers. These monomers cross-link keratin filaments and are also decomposed to natural moisturizing factors in the stratum corneum for skin hydration and barrier function. Deficits in FLG expression impair skin barrier function and underlie skin diseases such as dry skin and atopic dermatitis. However, intrinsic factors that regulate FLG expression and their mechanisms of action remain unknown. Here, we show that lysophosphatidic acid induces FLG expression in human keratinocytes via the LPAR1 and LPAR5 receptors and the downstream RHO-ROCK-SRF pathway. Comprehensive gene profiling analysis further showed that lysophosphatidic acid not only induces FLG expression but also facilitates keratinocyte differentiation. Moreover, lysophosphatidic acid treatment significantly up-regulated FLG production in a three-dimensional culture model of human skin and promoted barrier function in mouse skin invivo. Thus, our work shows a previously unsuspected role for lysophosphatidic acid and its downstream signaling in the maintenance of skin homeostasis, which may serve as a novel therapeutic target for skin barrier dysfunction.

β-1,3/1,4-Glucan Lichenan from Cetraria islandica (L.) ACH. induces cellular differentiation of human keratinocytes

Lichenan (molecular weight 275 kDa, β-D-1,3/1,4-glucopyranose ratio 1:3) from Cetraria islandica at a concentration of 100 μg/mL induced terminal cellular differentiation of primary human keratinocytes as demonstrated by immunofluorescence staining using cytokeratin 10 and involucrin as marker proteins. Lichenan-derived oligosaccharides (DP3 to 8), obtained by acid-catalyzed partial hydrolysis of the polymer, did not influence cellular differentiation. Cytokeratin, filaggrin, involucrin, loricrin and transglutaminase gene expression as typical differentiation markers was increased by lichenan in a time-dependent manner. Lichenan upregulated gene cluster which were mostly related to cellular differentiation with focus on MAPK signaling as was shown by Whole Human Genome Microarray. These gene expression data from the array experiments were subsequently confirmed by qPCR for selected genes. For identification of the molecular binding structures of lichenan 1- and 2-D PAGE of keratinocyte protein membrane preparations was performed, followed by blotting with FITC-labeled lichenan and subsequent mass spectrometric identification of the pinpointed proteins. Epidermal growth factor receptor (EGFR) and integrin β4, both proteins being strongly involved in induction of keratinocyte differentiation were identified. In addition, protein disulfide isomerase A3 (PDIA3) showed strong binding to FITC-lichenan, indicating this enzyme to be an intracellular target of the glucan for induction of the cellular differentiation of keratinocytes. As lichenan did not influence the EGFR phosphorylation and the phosphorylation of CREB transcription factor but strongly interacted with cytosolic proteins it is hypothized that the glucan may interact with EGFR and is subsequently internalized into the cell via endosomal uptake, interacting with PDIA3, which again alters TGFβ1 signaling towards keratinocyte differentiation.

170 Single low-dose radiation induced regulation of keratinocyte differentiation in calcium-induced HaCaT cells

Background: We are continually exposed to low-dose radiation(LDR) in the range 0.1 Gy from natural sources, medical devices, nuclear energy plants, and other industrial sourcesof ionizing radiation. There are three models for the biological mechanism of LDR: the linear no-threshold model, the hormetic model, and the threshold model. Objective: We used keratinocytes as a model system to investigate the molecular genetic effects of LDR on epidermal cell differentiation. Methods: To identify keratinocyte differentiation, we performed western blots using a specific antibody for involucrin, which is a precursor protein of the keratinocyte cornified envelope and a marker for keratinocyte terminal differentiation. We also performed quantitative polymerase chain reaction. We examined whether LDR induces changes in involucrin messenger RNA (mRNA) and protein levels in calcium-induced keratinocyte differentiation. Results: Exposure of HaCaT cells to LDR (0.1 Gy) induced p21 expression. p21 is a key regulator that induces growth arrest and represses stemness, which accelerates keratinocyte differentiation. We correlated involucrin expression with keratinocyte differentiation, and examined the effects of LDR on involucrin levels and keratinocyte development. LDR significantly increased involucrin mRNA and protein levels during calcium-induced keratinocyte differentiation. Conclusion: These studies provide new evidence for the biological role of LDR, and identify the potential to utilize LDR to regulate or induce keratinocyte differentiation.

Astilbin decreases proliferation and improves differentiation in HaCaT keratinocytes

Psoriasis is a common chronic dermatosis characterized by keratinocyte hyperproliferation accompanied by inflammatory reactions. Pathological changes upset the balance between keratinocyte proliferation, differentiation, and death in psoriatic lesions, suggesting that molecules with topical anti-inflammatory, anti-proliferation and anti-angiogenesis abilities may be useful for its treatment. The flavonoid astilbin is the major active component extracted from the rhizome of Smilax glabra, which has been widely used in China to treat inflammatory and autoimmune diseases. Here, we investigate the potential of astilbin as a treatment for psoriasis. We reveal that astilbin inhibits the growth of HaCaT keratinocytes. Detailed study shows that astilbin leads to S phase arrest of the cell cycle by induction of p53 and p21 and activated-AMPK. Additionally, astilbin induced keratinocyte differentiation correlated with suppression of keratin 5 (KRT5) and KRT14 proteins (the markers of epidermal basal layer) and induction KRT1 and KRT10 proteins (occurring in the upper layers). Moreover, astilbin regulates the expression of VEGF in human HaCaT keratinocytes. These results suggest that astilbin may be a promising agent for psoriasis treatment.

Overexpression of Psoriasin (S100A7) Contributes to Dysregulated Differentiation in Psoriasis.

Psoriasin, which is highly expressed in psoriasis, is encoded by a gene located within the epidermal differentiation complex. The aim of this study was to investigate the effect of endogenous psoriasin on disturbed keratinocyte differentiation in psoriasis. Immunohistochemical staining revealed a gradient of psoriasin expression in the psoriatic epidermis with highest expression in the suprabasal, differentiated layers. Induction of keratinocyte differentiation caused concurrent expression of psoriasin and the differentiation marker involucrin. The differentiation-induced psoriasin expression was found to be mediated by the protein kinase C pathway. The downregulation of psoriasin expression by small interfering RNA revealed that psoriasin mediates the expression of involucrin, desmoglein 1, transglutaminase 1 and CD24 in normal differentiation. The lentivirus-mediated overexpression of psoriasin, mimicking the psoriatic milieu, gave rise to an altered regulation of differentiation genes and an expression pattern reminiscent of that in psoriatic epidermis. These findings suggest that psoriasin contributes to the dysregulated differentiation process in the psoriasis epidermis.

Integrin-linked kinase and ELMO2 modulate recycling endosomes in keratinocytes

The formation of tight cell-cell junctions is essential in the epidermis for its barrier properties. In this tissue, keratinocytes follow a differentiation program tightly associated with their movement from the innermost basal to the outer suprabasal layers, and with changes in their cell-cell adhesion profile. Intercellular adhesion in keratinocytes is mediated through cell-cell contacts, including E-cadherin-based adherens junctions. Although the mechanisms that mediate E-cadherin delivery to the plasma membrane have been widely studied in simple epithelia, this process is less well understood in the stratified epidermis. In this study, we have investigated the role of Engulfment and Cell Motility 2 (ELMO2) and integrin-linked kinase (ILK) in the positioning of E-cadherin-containing recycling endosomes during establishment of cell-cell contacts in differentiating keratinocytes. We now show that induction of keratinocyte differentiation by Ca2+ is accompanied by localization of ELMO2 and ILK to Rab4- and Rab11a-containing recycling endosomes. The positioning of long-loop Rab11a-positive endosomes at areas adjacent to cell-cell contacts is disrupted in ELMO2- or ILK-deficient keratinocytes, and is associated with impaired localization of E-cadherin to cell borders. Our studies show a previously unrecognized role for ELMO2 and ILK in modulation of endosomal positioning, which may play key roles in epidermal sheet maintenance and permeability barrier function.

TLR3 activation induces S100A7 to regulate keratinocyte differentiation after skin injury

Human S100A7 (psoriasin) is highly expressed in psoriasis and other inflammatory diseases; however, the function of S100A7 in wound repair remains largely unknown. Here we demonstrated that skin injury increased the expression of S100A7. Damaged cells from wounded skin induced the expression of S100A7 via the activation of Toll-like receptor 3 (TLR3) followed by the activation of p38 MAPK. S100A7, in turn, acted on keratinocytes to induce the expression of terminal differentiation marker gene loricrin through the activation of p38 MAPK and caspase-1. The differentiation of keratinocytes induced by S100A7 resulted in skin stratification, thus efficiently promoting wound closure. Taken together, our results demonstrate that the activation of TLR3 accelerates wound closure via the induction of S100A7 to induce keratinocyte differentiation. These findings also provide new insights into the development of different forms of treatment with skin wounds.

The loss of ATP2C1 impairs the DNA damage response and induces altered skin homeostasis: Consequences for epidermal biology in Hailey-Hailey disease.

Mutation of the Golgi Ca2+-ATPase ATP2C1 is associated with deregulated calcium homeostasis and altered skin function. ATP2C1 mutations have been identified as having a causative role in Hailey-Hailey disease, an autosomal-dominant skin disorder. Here, we identified ATP2C1 as a crucial regulator of epidermal homeostasis through the regulation of oxidative stress. Upon ATP2C1 inactivation, oxidative stress and Notch1 activation were increased in cultured human keratinocytes. Using RNA-seq experiments, we found that the DNA damage response (DDR) was consistently down-regulated in keratinocytes derived from the lesions of patients with Hailey-Hailey disease. Although oxidative stress activates the DDR, ATP2C1 inactivation down-regulates DDR gene expression. We showed that the DDR response was a major target of oxidative stress-induced Notch1 activation. Here, we show that this activation is functionally important because early Notch1 activation in keratinocytes induces keratinocyte differentiation and represses the DDR. These results indicate that an ATP2C1/NOTCH1 axis might be critical for keratinocyte function and cutaneous homeostasis, suggesting a plausible model for the pathological features of Hailey-Hailey disease.

Luteolin-7-glucoside inhibits IL-22/STAT3 pathway, reducing proliferation, acanthosis, and inflammation in keratinocytes and in mouse psoriatic model.

The epidermis is a dynamic tissue in which keratinocytes proliferate in the basal layer and undergo a tightly controlled differentiation while moving into the suprabasal layers. The balance between keratinocyte proliferation, differentiation, and death is essential, and its perturbation can result in pathological changes. Some common skin diseases, such as psoriasis, are characterized by hyperproliferation accompanied by inflammatory reactions, suggesting that molecules with topical anti-inflammatory and ROS scavenging abilities may be useful for their treatment. Here we investigate the potential of the flavone Luteolin-7-glucoside (LUT-7G) as a treatment for psoriasis. We show that LUT-7G leads to a modification of the cell cycle and the induction of keratinocyte differentiation, with modification of energy, fatty acid, and redox metabolism. LUT-7G treatment also neutralizes the proliferative stimulus induced by the proinflammatory cytokines IL-22 and IL-6 in HEKn. Moreover, in the Imiquimod (IMQ) mouse model of psoriasis, topical administration of LUT-7G leads to a marked reduction of acanthosis and re-expression of epidermal differentiation markers. Dissection of the IL-22 signalling pathway, activated by IMQ treatment, demonstrates that LUT-7G impairs the nuclear translocation of phosphorylated (activated) STAT3, blocking the IL-22 signalling cascade. Thus LUT-7G appears to be a promising compound for the treatment of hyperproliferative and inflammatory skin diseases, such as psoriasis.

Photodynamic therapy inhibit Fibroblast Growth Factor-10 induced keratinocyte differentiation and proliferation through ROS in Fibroblast Growth Factor Receptor-2b pathway.

5-aminolevulinic acid-photodynamic therapy (ALA-PDT) is known to be effective in several skin diseases such as acne, actinic keratoses, condyloma acuminata. However, some detailed mechanisms of ALA-PDT to treat these skin diseases still remain elusive. In this study, we aimed to investigate mechanism of ALA-PDT in in-vitro and in-vivo models. For in vitro, we use human keratinocyte cell line (HaCaT) cells. CCK-8 was used to detect cell proliferation activity, immunofluorescence and western blotting method to detect the content of keratin (K)1, K6, K16, protein kinase C (PKC), fibroblast growth factor receptor-2b (FGFR2b) protein, ELISA and RT-PCR to detect expression of interleukin (IL) 1α in the cell supernatant, and detect reactive oxygen species (ROS). For in vivo, we use 20 rabbits to induce hyperkeratosis acne model in their ear. Dermatoscope was used to see follicle hyperkeratosis and skin biopsy to analyze histology and immunohistochemical of PKC, FGFR2b, K1, K6 and K16. Results from this study suggest that ROS stimulated by ALA-PDT lead to inhibition of FGFR2b pathway in PKC downstream to cause reduction of IL1α expression, and eventually, keratinocytes differentiation and proliferation. Our data thus reveal a treatment mechanism of ALA-PDT underlying hyperkeratosis related dermatoses.