Modulation of the expression and activity of cathepsin S in reconstructed human skin by neohesperidin dihydrochalcone.

Dysregulation of cathepsin S (Cat S), a cysteine protease involved in extracellular-matrix and basement membrane (BM) degradation, is a concomitant feature of several inflammatory skin diseases. Therefore, Cat S has been suggested as a potential therapeutic target. Flavonoids, which were identified as regulatory molecules of various proteolytic enzymes, exert beneficial effects on skin epidermis. Herein, thirteen flavonoid compounds were screened in vitro and in silico and neohesperidin dihydrochalcone (NHDC) was identified as a potent, competitive, and selective inhibitor (Ki=8±1 µM) of Cat S. Furthermore, Cat S-dependent hydrolysis of nidogen-1, a keystone protein of BM architecture, as well elastin, collagens I and IV was impaired by NHDC, while both expression and activity of Cat S were significantly reduced in NHDC-treated human keratinocytes. Moreover, a reconstructed human skin model showed a significant decrease of both mRNA and protein levels of Cat S after NHDC treatment. Conversely, the expression of nidogen-1 was significantly increased. NHDC raised IL-10 expression, an anti-inflammatory cytokine, and mediated STAT3 signaling pathway, which in turn dampened Cat S expression. Our findings support that NHDC may represent a valuable scaffold for structural improvement and development of Cat S inhibitors to preserve the matrix integrity and favor skin homeostasis during inflammatory events.

Chemicals with weak skin sensitizing properties can be identified using low-density microarrays on immature dendritic cells.

A critical step in the induction of allergic contact dermatitis is the interaction of haptens with immature dendritic cells (iDC) leading to their activation. Therefore iDC appear as suitable targets for the evaluation of the sensitizing properties of haptens with the aim of developing in vitro toxicologic methods. Here, using a low-density cDNA-array, we analyzed the expression of 165 genes related to dendritic cell biology in human iDC following a 24h incubation with four haptens representative of strong (DNBS), moderate (isoeugenol) and weak (eugenol, hydroxycitronellal) contact sensitizers and with one irritant sodium dodecyl sulphate (SDS). Results show that 21/165 iDC genes were significantly modulated by hapten treatment. Some genes were preferentially modulated by a given chemical. Thus, DNBS, isoeugenol, eugenol and hydroxycitronellal consistently modulated CCR5, CCL27, CCL2 and CCR7, respectively, whereas the CXCL10 gene was regulated by SDS. When subjected to principal component analysis, the 21 target genes fell into four groups associated with a particular type of chemical endowed with distinct sensitizing or irritant properties. Thus, gene profiling of iDC using low-density microarray allows, for screening of chemicals, the indentification of weak haptens with potential skin sensitizing properties. These results suggest that gene profiling of iDC using low-density microarrays may be useful to identify chemicals with weak skin sensitizing properties.

DNA repair capacities of cutaneous fibroblasts: effect of sun exposure, age and smoking on response to an acute oxidative stress.

BACKGROUND: Sun irradiation causes skin ageing and cancer through the accumulation of damage to cell components. Intrinsic ageing is also associated with accumulation of oxidized macromolecules. OBJECTIVES: In this study we investigated the effects of sun exposure on response to an acute in vitro oxidative stress (H(2)O(2)) using normal human fibroblasts prepared from biopsies from 10 volunteers taken from sun-protected and sun-exposed sites. METHODS: Time-course experiments measuring repair of DNA strand-breaks and formamidopyrimidine DNA N-glycosylase-sensitive sites were conducted using the single-cell gel electrophoresis (comet) assay. RESULTS: Our results demonstrated that repair of strand-breaks was slower in sun-exposed compared with sun-protected cells. Interestingly, ageing was also associated with decreased DNA repair capacities for single-strand breaks in both sun-exposed and sun-protected cells whereas for formamidopyrimidine glycosylase (Fpg)-sensitive sites, this feature was in evidence only in sun-protected cells. Smoking, associated with age, was shown to have a markedly negative impact on DNA repair. CONCLUSIONS: Taken together our data suggest that stresses like ageing, sun exposure and smoking might have an additive effect contributing to the overall heterogeneity and decrease of DNA repair capacities in human cells and so increase the danger of sun exposure for health. They also emphasize the importance of the quality of the biological samples when repair studies on skin cells are to be conducted.

Responsiveness to androgens and effectiveness of antisense oligonucleotides against the androgen receptor on human epidermal keratinocytes is dependent on the age of the donor and the location of cell origin.

Local androgen excess has been associated with attenuation of wound healing in elderly individuals and with a decline in permeability barrier homeostasis in adult human skin. In this study we have applied specific antisense oligonucleotides, whose activity has already been investigated in SZ95 sebocytes, to inactivate transiently the androgen receptor in a reconstituted epidermis model and in primary human epidermal keratinocytes of different origin (breast, abdomen, foreskin) and donor age (females, 30- and 60-year-old). Further a possible interaction between blockage of androgen receptor and the expression of tissue inhibitors of matrix metalloproteinases was investigated. Androgen receptor levels were similar in pooled keratinocytes of the two age groups. Cell transfection with antisense oligonucleotides against the androgen receptor resulted in decreasing protein levels detected in all epidermal keratinocytes tested, whereas cells of aged donors (60-year-old) exhibited a stronger response than cells of young individuals (30-year-old). Keratinocytes from aged donors also responded to androgens with a stronger regulation of proliferation than keratinocytes of young individuals. The pattern of the androgen-induced response was dependent on the skin region of keratinocyte origin. The expression levels of tissue inhibitor of matrix metalloproteinase-1 were not age-related. Our results demonstrate an enhanced androgen sensitivity of keratinocytes from aged individuals associated with an origin-specific type of response.

Skin ultrastructure in senile lentigo.

Senile lentigo is a common component of photoaged skin. It is characterized by hyperpigmented macules which affect chronically irradiated skin mostly after the age of 50. This study was undertaken to assess the morphology of senile lentigo on the dorsum of the hands. A systematic comparison between lesional and perilesional skin using histology and transmission electron microscopy was done to determine whether melanocytes or keratinocytes are affected in the evolution of lesions and which tissue structure is modified. The histology study showed that lesional skin is characterized by a hyperpigmented basal layer and an elongation of the rete ridges, which seem to drive deeply into the dermis. The epidermis contained clusters of keratinocytes, which retained and accumulated the melanin pigment. Electron microscopy studies showed important modifications in the lesional skin ultrastructure in comparison with perilesional skin. In melanocytes from perilesional and lesional skin, we observed normal size melanosomes at all stages of maturation in the cytoplasm and in migration within dendrites. No pigment accumulation was observed. However, the morphology of melanocytes in lesional skin revealed an activated status with numerous mitochondria and a well-developed endoplasmic reticulum, which could reflect intense protein synthesis. In basal keratinocytes from lesional skin, we observed numerous melanosome complexes called polymelanosomes, which formed massive caps on the nuclei. Observations in colored semi-thin sections also revealed perturbed structures in the basal layer region, which could explain the skin perturbation. Indeed, we observed keratinocytes that presented important microinvaginations and pendulum melanocytes, which sank into the dermis, beneath the basal layer of keratinocytes. These cell modifications seemed to be due to a perturbation of the dermal-epidermal junction, which appeared disorganized and disrupted and could directly disturb the basal support of the cells.

Study of housekeeping gene expression in human keratinocytes using OLISA, a long-oligonucleotide microarray and q RT-PCR.

In recent years, applications of microarray platforms have been extended to different areas of research including cosmetic and pharmaceutical. Although microarray technology is still improving its sensitivity and flexibility, researchers often turn toward quantitative RT-PCR for data validation. Assessment of messenger RNA quantity by these methods is based on comparison with internal standard genes, mainly housekeeping genes, so called because their synthesis occurs normally at a constant level. However, numerous studies showed that expression of these genes could vary in given situations. Here, we report results on four housekeeping genes (GAPDH, beta-2 microglobulin, S40 and S26 ribosomal sub-units) with constant expression levels established on OLISA microarray using different keratinocyte cultures. Moreover, qRT-PCR validation demonstrates that S26 ribosomal is a good housekeeping gene on keratinocytes and skin studies. Our data indicate that S26 gene can be routinely used to standardize results to investigate differentially expressed genes in a healthy human skin.

Expression and function of neurotrophins and their receptors in human melanocytes.

Melanocytes and cells of the nervous system are of common ectodermal origin and neurotrophins (NT) have been shown to be released by human keratinocytes. We investigated the expression and function of NT [nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, NT-4/-5] and their receptors in human melanocytes. Human melanocytes produce all NT in different amounts, whereas they only release NT-4. NT-4 release is downregulated, whereas NT-3 is upregulated by ultraviolet (UVB) irradiation. Melanocytes treated with phorbol 12-myristate 13-acetate (PMA) express TrkA and TrkB, but not TrkC. NT fail to stimulate melanocyte proliferation, whereas they stimulate the synthesis of tyrosinase and tyrosinase-related protein-1 (TRP-1). Finally, NT-3, NT-4 and NGF increase melanin production. Taken together, these results demonstrate an intriguing interaction between melanocytes and the nervous system. We speculate that NT could be considered the target of therapy for disorders of skin pigmentation.

Photoageing shows histological features of chronic skin inflammation without clinical and molecular abnormalities.

BACKGROUND: Photodamage is characterized by degradation of collagen and accumulation of abnormal elastin in the superficial dermis. Mast cells and macrophages, which are found in higher numbers in photoaged skin, have been implicated in this process. OBJECTIVES: To analyse the phenotype of haematopoietic-derived infiltrating cells in photodamaged skin. METHODS: Chronically sun-exposed (preauricular) and control sun-protected (postauricular) skin was recovered from eight healthy subjects undergoing cosmetic surgery (facial lifting). RESULTS: Histological analysis showed that sun-exposed skin harboured more infiltrating mononuclear cells than sun-protected skin. Cellular infiltrates were found at the periphery of areas of elastolysis around hair follicles in sun-exposed sites, whereas they were found in the interfollicular dermis around blood vessels and around hair follicles in sun-protected samples. Immunohistochemical analysis revealed an increased number of mast cells, macrophages and CD4+ CD45RO+ T cells in sun-exposed dermis as well as a higher number of CD1a+ dendritic cells in sun-exposed epidermis, compared with the sun-protected samples. Thus photoageing displays histological features of chronic skin inflammation. However, no molecular sign of inflammation was observed and we even found a decreased expression of interleukin-1beta mRNA in sun-exposed compared with sun-protected sites. Furthermore, the patients' skin looked normal and did not display any clinical inflammation. CONCLUSIONS: Collectively, these data show that chronic ultraviolet irradiation induces alterations of innate immune cells which are recruited in sun-exposed skin without being activated.

Decreased expression of keratinocyte beta1 integrins in chronically sun-exposed skin in vivo.

BACKGROUND: Chronic exposure to ultraviolet (UV) radiation induces changes in the skin structure which are mostly found in the superficial dermis and at the dermal-epidermal junction. Keratinocytes and fibroblasts contribute both to the synthesis and to the degradation of the molecules important for the integrity of this skin site. While several studies have reported on alterations of dermal components and of the functions of fibroblasts in vivo and in vitro after UV exposure, recent data suggested that keratinocytes could be the main skin cell type involved in the photoageing process. OBJECTIVES: In this study, we analysed the expression of two keratinocyte molecules namely, beta1 integrin (a proliferation marker) and involucrin (a differentiation marker) in sun-exposed and sun-protected facial skin of 16 healthy patients undergoing facial lifting. METHODS: Methods included histology, immunohistochemistry and quantitative reverse transcriptase-polymerase chain reaction analysis. RESULTS: Sun-exposed skin displayed the characteristic morphological and molecular features of dermal photoageing, compared with sun-protected skin, including dermal elastosis, diminished fibrillin and type VII collagen expression. Analysis of the epidermis in sun-exposed vs. sun-protected skin showed no histological differences, but dramatic changes in the expression of beta1 integrin and involucrin. In sun-exposed skin, expression of beta1 integrin protein by epidermal basal cells was reduced, paralleling a downregulation of beta1 integrin mRNA, whereas involucrin protein expression was greatly enhanced in the superficial epidermal cell layers. Interestingly, the ratio between involucrin and beta1 integrin protein expression was consistently increased in sun-exposed skin sites. CONCLUSIONS: Collectively these results demonstrate that epidermal homeostasis is impaired by chronic UV exposure, and define beta1 integrin expression as a molecular marker of the epidermal photoageing process.

Automated RNA probe assay for the identification of Listeria monocytogenes.

Recent epidemics of human listeriosis have shown the importance of Listeria monocytogenes as a food-borne risk. We have developed an automated identification assay for L. monocytogenes using the specificity of the 16S rDNA probe described by Wang et al. (1991). Bacterial cultures were lysed quickly by a chemical step releasing the target nucleic acids. Extracts were loaded into the VIDAS automate (bioMérieux) which performed a non-radio-active hybridisation reaction for 2 h. This assay recognised specifically 68 out of 69 L. monocytogenes isolates from clinical and food origins, including serovars 4b and 1/2, without cross-hybridising to other Listeria species (103 strains) or other bacterial species (15 strains). The sensitivity of the assay was 10(7) bacteria. This automated technology is faster than conventional biochemical identification.

Monoclonal antibodies targeted to alpha-oligonucleotides. Characterisation and application in nucleic acid detection.

The aim of the present study was to test the antigenicity of alpha-deoxyribonucleotides in order to develop a new tool for the detection of nucleic acid sequences for use in diagnostic applications. We describe four monoclonal antibodies (Mabs) which recognize alpha-deoxyribonucleotides. Two were raised against a poly(alpha-dT) sequence and specifically recognized the alpha-dT nucleotide. Two were raised against a sequence containing all four common nucleotides as alpha-nucleotides and, surprisingly, only recognized the alpha-dG nucleotide. For all four Mabs, no cross reactivity was observed with beta-oligonucleotides. These Mabs were reactive with alpha-oligonucleotide sequences whether these sequences were single-stranded or hybridized to DNA or RNA. The four Mabs were tested in a sandwich hybridization assay that consisted of an alpha-oligonucleotide (for target sequence recognition), one of the four Mabs (for recognition of the hybridized alpha-oligonucleotide), and goat anti-mouse antibody conjugated to horse radish peroxidase (HRP) (for detection). One of the monoclonal antibodies, Mab 2E11D7, was directly conjugated to HRP and used in sandwich hybridization to detect PCR fragments of HPV 18 DNA. The sensitivity of this reaction was 1 pg of plasmid DNA containing the HPV 18 fragment. The specificity of the detection was demonstrated using HPV 6/11 and 16 DNA sequences.

Triple-helix formation by alpha oligodeoxynucleotides and alpha oligodeoxynucleotide-intercalator conjugates.

Base-pair sequences in double-stranded DNA can be recognized by homopyrimidine oligonucleotides that bind to the major groove at homopurine.homopyrimidine sequences thereby forming a local triple helix. To make oligodeoxynucleotides resistant to nucleases, we replaced the natural (beta) anomers of the nucleotide units by the synthetic (alpha) anomers. The 11-mer alpha oligodeoxynucleotide 5'-d(TCTCCTCCTTT)-3' binds to the major groove of DNA in an antiparallel orientation with respect to the homopurine strand, whereas a beta oligonucleotide adopts a parallel orientation. When an intercalating agent was attached to the 3' end of the alpha oligodeoxynucleotide, a strong stabilization of the triple helix was observed. A 16-base-pair homopurine.homopyrimidine sequence of human immunodeficiency virus proviral DNA was chosen as a target for a 16-mer homopyrimidine alpha oligodeoxynucleotide. A restriction enzyme that cleaves DNA at the junction of the homopurine.homopyrimidine sequence was inhibited by triple-helix formation. The 16-mer alpha oligodeoxynucleotide substituted by an intercalating agent was approximately 20 times more efficient than the unsubstituted oligomer. Nuclease-resistant alpha oligodeoxynucleotides offer additional possibilities to control gene expression at the DNA level.

Inhibition of translation initiation by antisense oligonucleotides via an RNase-H independent mechanism.

We have used alpha-oligomers as antisense oligonucleotides complementary to three different sequences of the rabbit beta-globin mRNA: a region adjacent to the cap site, a region spanning the AUG initiation codon or a sequence in the coding region. These alpha-oligonucleotides were synthesized either with a free 5' OH group or linked to an acridine derivative. The effect of these oligonucleotides on mRNA translation was investigated in cell-free extracts and in Xenopus oocytes. In rabbit reticulocyte lysate and in wheat germ extracts oligomers targeted to the cap site and the initiation codon reduced beta-globin synthesis in a dose-dependent manner, whereas the target mRNA remained intact. The anti-cap alpha-oligomer was even more efficient that its beta-counterpart in rabbit reticulocyte lysate. In contrast, only the alpha-oligomer, linked to the acridine derivative, complementary to the cap region displayed significant antisense properties in Xenopus oocytes. Therefore initiation of translation can be arrested by oligonucleotide/RNA hybrids which are not substrates for RNase-H.