Normal Human Epithelial Keratinocytes Research Articles

P19 Defining the mechanism of skin barrier restoration by Lactobacillus rhamnosus

Abstract Introduction and aims We aim to investigate the lysate of Lactobacillus rhamnosus GG (LGG), a bacterium previously established as a gut probiotic, and to examine its postulated ability to enhance and restore human skin barrier function. Compromised skin barriers are implicated in various skin conditions including atopic dermatitis. Furthermore, skin barrier function decreases with age leading to dryness and sensitivity. Previous research has shown promising effects of LGG lysates on keratinocytes, including increasing transepidermal electrical resistance, increasing tight junction protein expression, cell migration promotion and mitigation of Staphylococcus aureus toxicity. This study aims to take a closer look at the molecular mechanisms behind the effect of LGG lysates on the skin, including terminal differentiation, lamin dispersal and nuclear degradation in keratinocytes. Methods Normal human epithelial keratinocytes and rat epithelial keratinocytes were grown and treated with the LGG lysate. Western blot analysis was used to determine the relative concentrations of tight junction proteins and other differentiation markers. A phosphoproteomic study was performed to identify key pathways activated by the LGG lysate. A Staphylococcus epidermidis lysate control was used to filter out any nonspecific bacterial effects. Immunostaining of nuclear proteins was used to visualize the effects of LGG lysate on lamin dispersal and nuclear degradation. short hairpin RNA filaggrin knockdown normal human keratinocytes were developed to create a ‘barrier impaired’ model to assess ability of the lysate to ‘rescue’ the skin barrier. Results The LGG lysate was shown to increase tight junction protein expression in normal human keratinocytes and increase keratinocyte terminal differentiation markers. We present Results that show decreased tight junction protein expression in filaggrin knockdown cells. Conclusions These Results show the potential for LGG lysate to enhance and restore skin barrier function and begin to suggest potential mechanisms for this effect.

Manuka honey activates the aryl hydrocarbon receptor: Implications for skin inflammation

Manuka honey (MH) is a complex nutritional material with antimicrobial, antioxidant and anti-inflammatory activity. We have previously shown that MH down regulates IL-4-induced CCL26 expression in immortalized keratinocytes. As MH contains potential ligands of the Aryl Hydrocarbon Receptor (AHR), a key regulator of skin homeostasis, we hypothesize that this effect is mediated via AHR activation. Here, we treated HaCaT cell lines, either stable transfected with an empty vector (EV-HaCaT) or in which AHR had been stable silenced (AHR-silenced HaCaT); or primary normal human epithelial keratinocytes (NHEK) with 2% MH for 24 h. This induced a 15.4-fold upregulation of CYP1A1 in EV-HaCaTs, which was significantly reduced in AHR-silenced cells. Pre-treatment with the AHR antagonist CH223191 completely abrogated this effect. Similar findings were observed in NHEK. In vivo treatment of the Cyp1a1Cre x R26ReYFP reporter mice strain’s skin with pure MH significantly induced CYP1A1 expression compared with Vaseline. Treatment of HaCaT with 2% MH significantly decreased baseline CYP1 enzymatic activity at 3 and 6 h but increased it after 12 h, suggesting that MH may activate the AHR both through direct and indirect means. Importantly, MH downregulation of IL-4-induced CCL26 mRNA and protein was abrogated in AHR-silenced HaCaTs and by pre-treatment with CH223191. Finally, MH significantly upregulated FLG expression in NHEK in an AHR-dependent manner. In conclusion, MH activates AHR, both in vitro and in vivo, thereby providing a mechanism of its IL4-induced CCL26 downregulation and upregulation of FLG expression. These results have potential clinical implications for atopic diseases and beyond.

Bardoxolone-Methyl (CDDO-Me) Impairs Tumor Growth and Induces Radiosensitization of Oral Squamous Cell Carcinoma Cells.

Radiotherapy represents a common treatment strategy for patients suffering from oral squamous cell carcinoma (OSCC). However, application of radiotherapy is immanently limited by radio-sensitivity of normal tissue surrounding the tumor sites. In this study, we used normal human epithelial keratinocytes (NHEK) and OSCC cells (Cal-27) as models to investigate radio-modulating and anti-tumor effects of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9,-dien-28-oic acid methyl ester (CDDO-Me). Nanomolar CDDO-Me significantly reduced OSCC tumor xenograft-growth in-ovo applying the chick chorioallantoic membrane (CAM) assay. In the presence of CDDO-Me reactive oxygen species (ROS) were found to be reduced in NHEK when applying radiation doses of 8 Gy, whereas ROS levels in OSCC cells rose significantly even without radiation. In parallel, CDDO-Me was shown to enhance metabolic activity in malignant cells only as indicated by significant accumulation of reducing equivalents NADPH/NADH. Furthermore, antioxidative heme oxygenase-1 (HO-1) levels were only enhanced in NHEK and not in the OSCC cell line, as shown by immunoblotting. Clonogenic survival was left unchanged by CDDO-Me treatment in NHEK but revealed to be abolished almost completely in OSCC cells. Our results indicate anti-cancer and radio-sensitizing effects of CDDO-Me treatment in OSCC cells, whereas nanomolar CDDO-Me failed to provoke clear detrimental consequences in non-malignant keratinocytes. We conclude, that the observed differential aftermath of CDDO-Me treatment in malignant OSCC and non-malignant skin cells may be utilized to broaden the therapeutic range of clinical radiotherapy.

Toluene downregulates filaggrin expression via the extracellular signal-regulated kinase and signal transducer and activator of transcription–dependent pathways

Toluene downregulates filaggrin expression via the extracellular signal-regulated kinase and signal transducer and activator of transcription–dependent pathways

Proliferation of Human Keratinocytes and Cocultured Human Keratinocytes and Fibroblasts in Three-Dimensional Fibrin Constructs

Over the last several years, our in vitro and in vivo studies have focused on optimizing the use of fibrin to deliver cells. We have shown that some three-dimensional (3D) fibrin constructs with specific fibrinogen and thrombin concentration support robust proliferation of normal human dermal fibroblasts, whereas different fibrinogen and thrombin concentrations support high mesenchymal stem cell proliferation in 3D fibrin constructs. In this article, we found that normal human epithelial keratinocytes proliferate well in 3D fibrin constructs consist of fibrinogen concentration ranging from 17 to 33 mg/mL and thrombin concentration of 1 U/mL. Further, using a new proliferation assay, we studied the proliferation of fibroblasts and keratinocytes cocultured in various 3D fibrin constructs of different fibrinogen and thrombin concentrations. We found that 3D fibrin constructs with a range of fibrinogen concentration (5-34 mg/mL) and a thrombin concentration of 1 U/mL produce an optimal cell proliferation for both cell types when cocultured. This profile of proliferation is different from that seen when keratinocytes or fibroblasts are incorporated separately in 3D fibrin constructs. In conclusion, we found that one needs to choose the fibrinogen and thrombin concentration carefully depending on the cell type to deliver; that is, different fibrin constructs with different fibrinogen and thrombin concentration are required to deliver fibroblasts or keratinocytes alone or to codeliver both cell types. Moreover, there seems to be a cross-talk between keratinocytes and fibroblasts when they are cointroduced in 3D fibrin constructs. This feedback could be due to the effects of growth factors produced by the two cell types in the 3D fibrin constructs.

Effects of UVB-induced oxidative stress on protein expression and specific protein oxidation in normal human epithelial keratinocytes: a proteomic approach

BackgroundThe UVB component of solar ultraviolet irradiation is one of the major risk factors for the development of skin cancer in humans. UVB exposure elicits an increased generation of reactive oxygen species (ROS), which are responsible for oxidative damage to proteins, DNA, RNA and lipids. In order to examine the biological impact of UVB irradiation on skin cells, we used a parallel proteomics approach to analyze the protein expression profile and to identify oxidatively modified proteins in normal human epithelial keratinocytes.ResultsThe expression levels of fifteen proteins - involved in maintaining the cytoskeleton integrity, removal of damaged proteins and heat shock response - were differentially regulated in UVB-exposed cells, indicating that an appropriate response is developed in order to counteract/neutralize the toxic effects of UVB-raised ROS. On the other side, the redox proteomics approach revealed that seven proteins - involved in cellular adhesion, cell-cell interaction and protein folding - were selectively oxidized.ConclusionsDespite a wide and well orchestrated cellular response, a relevant oxidation of specific proteins concomitantly occurs in UVB-irradiated human epithelial Keratinocytes. These modified (i.e. likely dysfunctional) proteins might result in cell homeostasis impairment and therefore eventually promote cellular degeneration, senescence or carcinogenesis.

Leucine-Aspartic Acid-Valine Sequence as Targeting Ligand and Drug Carrier for Doxorubicin Delivery to Melanoma Cells: In Vitro Cellular Uptake and Cytotoxicity Studies

To study the feasibility of Leucine-Aspartic Acid-Valine (LDV) as targeting ligand and drug carrier for targeted delivery to integrin alpha(4)beta(1) over-expressing cancer cells. Poly(L,D,V) was randomly copolymerized using N-carboxyanhydrides of leucine, beta-benzyl-aspartic acid, and valine. Oligo(LDV), consisting of 2-6 LDV units, were synthesized by solid phase protein synthesis (SPPS) method. Binding of Leu-Asp-Val, Val-Asp-Leu, and Leu-Asn-Val, and internalization of FITC labeled LDV by wild-type and integrin alpha(4) knock-down A375 cells were studied. Cytotoxicity of poly(L,D,V)-Dox, oligo(LDV)-Dox, and doxorubicin (Dox) was also determined on wild-type, integrin alpha(4) knock-down A375 cells, and normal human epithelial keratinocytes (NHEK). LDV was essential for the specific binding and internalization by cells expressing integrin alpha(4)beta(1). Cytotoxicity of poly(L,D,V)-Dox and oligo(LDV)-Dox was integrin alpha(4)-dependent, while free Dox did not show this differential effect. No observable cytotoxicity trend was found when increasing LDV repeating unit. Poly(L,D,V) was relatively more effective than oligo(LDV) for the delivery of Dox to A375. LDV containing moieties bind specifically to integrin alpha(4)beta(1) expressing cancer cells. The binding, internalization, and cytotoxicity depend on the level of integrin alpha(4)beta(1) expression. Poly(L,D,V) and oligo(LDV) were both effective in the in vitro targeted delivery of Dox to integrin alpha(4)beta(1) over-expressing A375 cells.

The Regulatory Element in the 3′-Untranslated Region of Human Papillomavirus 16 Inhibits Expression by Binding CUG-binding Protein 1

The 3'-untranslated regions (UTRs) of human papillomavirus 16 (HPV16) and bovine papillomavirus 1 (BPV1) contain a negative regulatory element (NRE) that inhibits viral late gene expression. The BPV1 NRE consists of a single 9-nucleotide (nt) U1 small nuclear ribonucleoprotein (snRNP) base pairing site (herein called a U1 binding site) that via U1 snRNP binding leads to inhibition of the late poly(A) site. The 79-nt HPV16 NRE is far more complicated, consisting of 4 overlapping very weak U1 binding sites followed by a poorly understood GU-rich element (GRE). We undertook a molecular dissection of the HPV16 GRE and identify via UV cross-linking, RNA affinity chromatography, and mass spectrometry that is bound by the CUG-binding protein 1 (CUGBP1). Reporter assays coupled with knocking down CUGBP1 levels by small interfering RNA and Dox-regulated shRNA, demonstrate CUGBP1 is inhibitory in vivo. CUGBP1 is the first GRE-binding protein to have RNA interfering knockdown evidence in support of its role in vivo. Several fine-scale GRE mutations that inactivate GRE activity in vivo and GRE binding to CUGBP1 in vitro are identified. The CUGBP1.GRE complex has no activity on its own but specifically synergizes with weak U1 binding sites to inhibit expression in vivo. No synergy is seen if the U1 binding sites are made weaker by a 1-nt down-mutation or made stronger by a 1-nt up-mutation, underscoring that the GRE operates only on weak sites. Interestingly, inhibition occurs at multiple levels, in particular at the level of poly(A) site activity, nuclear-cytoplasmic export, and translation of the mRNA. Implications for understanding the HPV16 life cycle are discussed.

UVB irradiation down-regulates HPV-16 RNA expression: Implications for malignant progression of transformed cells

A new cell line obtained from normal human epithelial keratinocytes transfected with the whole HPV-16 genome has been extensively characterised. This cell line, named HK-168, has a basal/para-basal keratinocyte phenotype, requires the use of serum-free chemically defined media and maintains the ability to differentiate toward pluri-stratified epithelia. Although immortalised it is not capable of anchorage independent growth and is not tumorigenic. HK-168 has a distinctive kariotype, with a complete, transcriptionally active HPV-16 genome integrated at an almost 1:1 ratio into the host haploid genome thus providing a convenient experimental model for viral transformed pre-neoplastic cell phenotype. The oxidative stress, induced by mild UVB irradiation, caused in HK-168 a general suppression of viral transcription, accompanied by a moderate growth arrest, an appropriated response of cellular antioxidant enzymes, the activation of cell repair mechanisms and a mild induction of apoptosis. This response is similar to the one observed in the highly resistant diploid keratinocytes. Conversely, transformed cells devoid of HPV sequences (HaCaT), appeared extremely susceptible to apoptosis. We propose that reported suppression of viral oncogenes, restoring the cell control on growth and repair mechanisms, allows the damage repair, ultimately resulting in a surviving response.

Ultraviolet B Light Stimulates lnterleukin‐20 Expression by Human Epithelial Keratinocytes

The proinflammatory cytokine interleukin-20 (IL-20) may exert the majority of its activity in the skin. We examined the effect of various treatments including several forms of phototherapy on IL-20 expression using cultured normal human epithelial keratinocytes (NHEK). Broadband UVB light, recombinant (r) IL-1 and rIL-8 increased, while hydrocortisone reduced, NHEK supernatant IL-20 levels. Elevation of NHEK IL-20 mRNA and maximal supernatant IL-20 levels occurred with a UVB light dose (40 mJ cm(-2)) that reduced cell viability by approximately 50%. While this UVB light dose also elevated supernatant IL-1 alpha and IL-8 levels, antibody neutralization studies indicated that neither of these cytokines was directly responsible for this increase in IL-20 expression. However, the elevation in IL-20 levels was fully inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB-203580, suggesting involvement of this stress signaling pathway in this UVB light response. Photodynamic therapy (PDT) with the photosensitizer lemuteporfin, UVA light, cisplatin, lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) or recombinant interferon-gamma (rIFN-gamma) either had little effect or decreased NHEK supernatant IL-20 levels. Reduced IL-20 levels paralleled the cytotoxic actions of PDT, UVA light or cisplatin and the antiproliferative effect of rIFN-gamma. Neither rIL-20 supplementation nor anti-IL-20 antibody treatments affected cell viability indicating that soluble IL-20 did not affect the short-term survival of UVB light-irradiated NHEK. Stimulation of IL-20 expression in keratinocytes by UVB light suggests that this cytokine might participate in skin responses to this ever-present environmental factor and potentially has a role in UV light-associated dermatoses.

Expression of the novel tumour suppressor p33(ING1)is independent of p53.

A recently cloned tumour suppressor candidate, p33ING1, has been shown in vitro to collaborate with p53 to execute growth arrest and apoptosis. However, it is unclear as to how the expression of ING1 is regulated in normal and stress conditions. Using a p53-knockout mouse model, we investigated if the expression of ING1 was dependent on p53. We found that there was no difference in ING1 mRNA and protein levels between p53+/+ and p53–/– murine organs. In addition, when normal human epithelial keratinocytes (NHEK) and a keratinocyte cell line, HaCaT, which lacks wild-type p53 function, were exposed to UVB irradiation, the expression levels of ING1 were elevated in both NHEK and HaCaT cells. It is interesting, however, that UVB irradiation did not induce ING1 expression in dermal fibroblasts isolated from p53+/+ and p53–/– mice. Based on our findings, we therefore conclude that the expression of ING1 is independent of p53 status. UV induction of ING1 in keratinocytes suggests that ING1 may play a role in cellular stress response and skin carcinogenesis. © 2000 Cancer Research Campaign http://www.bjcancer.com

Laser and daunomycin chemophototherapy of human carcinoma cells.

Adriamycin and daunomycin anticancer drugs are detectable in leukemias and solid tumors by cell fluorescence. We observed initial cytoplasmic fluorescence followed by slow nuclear localization of adriamycin and daunomycin after incubation with cultured human squamous cell (P3, FADU) and adenocarcinoma (HT29, SW620) lines by digital video imaging microscopy. Tumor cells incubated with 10 mug/ml of these drugs exhibited increased uptake for more than 3 h with intracellular levels in the range 0.5-2.5 mug/10 6 cells measured by dimethyl sulfoxide (DMSO) extraction and fluorescence spectrophotometry. Daunomycin had 10- to 100-fold higher toxicity for these carcinoma cells than for normal human epithelial keratinocytes measured by in vitro MTT tetrazolium assays. The viability of daunomycin-sensitized carcinoma cells was decreased 2- to 10-fold further by argon laser illumination at 488 nm (5W, T max = 8 degrees C) for 2-3 minutes. The results suggest that adriamycin derivatives may be useful targeting agents for adjuvant treatment and chemophototherapy of human solid tumors by MR-guided laser fiberoptic endoscopy.