Evaluation of Antioxidants' Ability to Enhance Hyaluronic-acid Based Topical Moisturizers.

Background: Hyaluronic acid (HA) is a unique molecule of the extracellular matrix with multiple biological activities. In skin, HA plays an essential role as a humectant, capable of binding up to 1,000 times its mass with water, providing skin with moisture and viscoelastic properties. HA concentration and synthesis decrease significantly in aging skin, due to exogenous and endogenous factors, including photoaging and HA metabolism. A key driver for HA degradation and reduced concentration is mediated via induction of reactive oxygen species (ROS) and other free radicals. Objective: In this study, we evaluate antioxidant ingredients essential in the development of next-generation HA-based topical formulations aimed at leveraging HA's ability to maximize anti-aging properties. Methods: Two antioxidants, glycine saponin (Glycine soja germ extract) and glycyrrhetinic acid (enoxolone), were evaluated for stimulation of endogenous HA production and inhibition of endogenous hyaluronidase activity, respectively. Results: The antioxidant glycine saponin induced endogenous HA synthesis in fibroblasts, while the antioxidant glycyrrhetinic acid decreased the degradation rate of HA by 54 percent. Conclusion: While HA has been included in numerous topical skin products, critical aspects of HA metabolism, especially in aging skin, have often been overlooked, including decreases in HA synthesis with increasing age, and increases in HA degradation mediated by exogenously induced reactive oxygen species and free radicals and increased enzymatic degradation by endogenous hyaluronidases. Here, we describe a unique approach to inclusion of two antioxidants essential for the development of the next generation of antioxidant complex-based topical skin formulations to limit the signs of aging skin.

Redefine photoprotection: Sun protection beyond sunburn.

Excessive exposure to ultraviolet (UV) light leads to acute and chronic UV damage and is the main risk factor for the development of skin cancer. In most countries with western lifestyle, the topical application of sunscreens on UV-exposed skin areas is by far the most frequently used preventive measure against sunburn. Further than preventing sunburns, increasing numbers of consumers are appreciating sunscreens with a medium- to high-level sun protective factor (SPF) as basis for sustainable-skin ageing or skin cancer prevention programs. However, recent investigations indicate that clinically significant DNA damages as well as a lasting impairment of cutaneous immunosurveillance already occur far below the standard of one minimal erythema dose (MED) sunburn level, which contributes to the current discussion of the clinical value of high-protective SPF values. Ex vivo investigations on human skin showed that the application of SPF30 reduces DNA damage for a day long sun exposure (24 MED) drastically by about 53% but is significantly surpassed by SPF100 reducing DNA damage by approx. 73%. Further analysis on different SPF protection levels in UV-exposed cell culture assays focusing on IL-18, cell vitality and cis/trans-urocanic acid support these findings. Whereas SPF30 and SPF50+ sunscreens already offer a solid UVB cover for most indications, our results indicate that SPF100 provides significant additional protection against mutagenic (non-apoptotic-) DNA damage and functional impairment of the cutaneous immunosurveillance and therefore qualifies as an optimized sunscreen for specifically vulnerable patient groups such as immunosuppressed patients, or skin cancer patients.

N-acetyl-L-hydroxyproline - A potent skin anti-ageing active preventing advanced glycation end-product formation in vitro and ex vivo.

OBJECTIVE: Advanced glycation end-products (AGEs) represent a large group of compounds generated by a non-enzymatic reaction between reducing sugars and amino groups. The formation and accumulation of AGEs in the skin lead to protein crosslinking, dermal stiffening and yellowing, which ultimately contribute to cutaneous ageing. Amino acids have been described to exhibit anti-glycation effects. The objective of this study was to understand the inhibitory role of the amino acid derivative N-acetyl-L-hydroxyproline (NAHP) as an anti-glycation active for human skin. METHODS: A cell-free assay investigating the inhibition of glycation of serum albumin by NAHP was used to determine the capability of NAHP to decrease AGE formation. Also, by assessing the amount of the AGE N-(carboxymethyl)lysine (CML) the anti-glycation abilities of NAHP were investigated utilizing dot blot analysis. The improvement of cell-matrix interaction by NAHP was determined in vitro using a glycated fibroblast-populated collagen lattice (FPCL) dermis model. In skin biopsies, AGE autofluorescence was determined after treatment with NAHP and/or glucose ex vivo. RESULTS: NAHP significantly and dose-dependently inhibited levels of AGEs, which were induced by the glycation of a protein solution. This decrease could be visualized by showing that the brownish appearance as well as the AGE-specific fluorescence of glucose-treated samples were reduced after the application of increasing amounts of NAHP. Also, CML formation was dose-dependently inhibited by NAHP. In FPCLs, the contractile capacity of fibroblasts was significantly disturbed after glycation. This could be prevented by the addition of NAHP. Compared to glyoxal-treated samples, the co-application of NAHP significantly decreased the diameter as well as the weight of glycated FPCLs. Ex vivo application of glucose to skin explants showed a higher AGE fluorescence signal compared to control explants. Co-treatment with NAHP and glucose decreased the level of AGE fluorescence in comparison to glucose-treated explants. CONCLUSION: These data provide clear evidence that under glycation stress conditions treatment with NAHP inhibited AGE formation in vitro and ex vivo and prevented the loss of cellular contractile forces in a glycated dermis model. Thus, NAHP obviously provides a beneficial treatment option to counteract AGE-related changes in human skin such as dermal stiffening and yellowish skin appearance.

OBJECTIF: Les produits finis de glycation avancée (AGE) représentent un grand groupe de composés générés par une réaction non enzymatique entre des sucres réduits et des groupes amino. La formation et l'accumulation d'AGE dans la peau entraînent une réticulation protéique, un raidissement de la peau et un jaunissement, qui finissent par contribuer au vieillissement cutané. Les acides aminés ont été décrits comme ayant des effets d'anti­glycation. L'objectif de cette étude était de comprendre le rôle inhibiteur du dérivé d'acide aminé N­acétyl­L­hydroxyproline (NAHP) en tant qu'actif anti­glycation pour la peau humaine. MÉTHODES: Un test acellulaire étudiant l'inhibition de la glycation de l'albumine sérique par la NAHP a été utilisé pour déterminer la capacité de la NAHP à diminuer la formation d'AGE. En évaluant la quantité de l'AGE N­(carboxyméthyl)lysine (CML), les capacités d'anti­glycation de la NAHP ont également été étudiées à l'aide d'une analyse par dot blot. L'amélioration de l'interaction cellule­matrice par la NAHP a été déterminée in vitro à l'aide d'un modèle de derme de lattices de collagène composées de fibroblastes glyqués. Dans des biopsies cutanées, l'autofluorescence des AGE a été déterminée après un traitement par NAHP et/ou glucose ex vivo. RÉSULTATS: La NAHP a inhibé de manière significative et dose­dépendante les taux d'AGE induits par la glycation d'une solution protéique. Cette diminution a pu être visualisée en montrant que l'aspect brunâtre ainsi que la fluorescence spécifique aux AGE des échantillons traités par glucose ont été réduits après l'application de quantités croissantes de NAHP. En outre, la formation de CML était inhibée de manière dose­dépendante par la NAHP. Dans des lattices de collagène composées de fibroblastes, la capacité contractile des fibroblastes était significativement perturbée après la glycation. Cela a pu être évité par l'ajout de NAHP. Par rapport aux échantillons traités au glyoxal, la co­application de NAHP a significativement réduit le diamètre ainsi que le poids des lattices de collagène composées de fibroblastes glyquées. L'application ex vivo de glucose sur les explants de peau a montré un signal de fluorescence des AGE plus élevé que les explants témoins. Le traitement concomitant par NAHP et glucose a réduit le niveau de fluorescence des AGE par rapport aux explants traités par glucose. CONCLUSION: Ces données fournissent des preuves évidentes que, dans des conditions de stress par glycation, le traitement par NAHP a inhibé la formation d'AGE in vitro et ex vivo, et a prévenu la perte des forces contractiles cellulaires dans un modèle de derme glyqué. Ainsi, la NAHP constitue manifestement une option de traitement bénéfique pour contrer les changements liés aux AGE dans la peau humaine, tels que le raidissement du derme et l'aspect jaunâtre de la peau.

Ageing is associated with a reduction in markers of mitochondrial energy metabolism in the human epidermis.

The decline of mitochondrial function throughout the lifespan is directly linked to the development of ageing phenotypes of the skin. Here, we assessed alterations in markers of epidermal mitochondrial energy metabolism as a function of skin age. Human skin samples from distinct anatomical regions were obtained during routine dermatological surgery from 21 young (27.6 ± 1.71 year) and 22 old (76.2 ± 1.73 year) donors. Sections of skin samples were analysed by immunohistochemistry for mitochondrial subunits of each electron transport chain complex (I-V)/oxidative phosphorylation (OXPHOS), as well as proteins serving as a marker of mitochondrial mass (VDAC1) and the regulation of DNA transcription (TFAM). Staining intensities of ATP5F1A (comprising complex V) and TFAM in the epidermis of older subjects were significantly decreased compared with younger donors. Moreover, these effects were independent of UV exposure of the stained skin section. Overall, we demonstrate that ageing is associated with reduced protein levels of complex V of the mitochondrial respiratory chain and TFAM. These alterations may impair essential mitochondrial functions, exacerbating the cutaneous ageing process.

Assessing Cellular Uptake of Exogenous Coenzyme Q10 into Human Skin Cells by X-ray Fluorescence Imaging.

X-ray fluorescence (XRF) imaging is a highly sensitive non-invasive imaging method for detection of small element quantities in objects, from human-sized scales down to single-cell organelles, using various X-ray beam sizes. Our aim was to investigate the cellular uptake and distribution of Q10, a highly conserved coenzyme with antioxidant and bioenergetic properties. Q10 was labeled with iodine (I2-Q10) and individual primary human skin cells were scanned with nano-focused beams. Distribution of I2-Q10 molecules taken up inside the screened individual skin cells was measured, with a clear correlation between individual Q10 uptake and cell size. Experiments revealed that labeling Q10 with iodine causes no artificial side effects as a result of the labeling procedure itself, and thus is a perfect means of investigating bioavailability and distribution of Q10 in cells. In summary, individual cellular Q10 uptake was demonstrated by XRF, opening the path towards Q10 multi-scale tracking for biodistribution studies.

Anti-ageing effects of ubiquinone and ubiquinol in a senescence model of human dermal fibroblasts.

Coenzyme Q10 (CoQ10) is an endogenous lipophilic quinone found in equilibrium between its oxidised (ubiquinone) and reduced (ubiquinol) form, ubiquitous in biological membranes and endowed with antioxidant and bioenergetic properties, both crucial to the ageing process. CoQ10 biosynthesis decreases with age in different tissues including skin and its biosynthesis can be modulated by 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors such as statins. Statin-induced CoQ10 deprivation has previously been shown to be associated with the development of a senescence phenotype in cultured human dermal fibroblasts (HDF), hence this model was used to further investigate the role of CoQ10 in skin ageing. The present study aimed to compare the bioavailability of exogenously added CoQ10, in the form of ubiquinone or ubiquinol, to CoQ10-deprived HDF, and to determine their efficacy in rescuing the senescent phenotype induced by CoQ10 deprivation. First, additional senescence markers were implemented to further support the pro-ageing effect of statin-induced CoQ10 deprivation in HDF. Indeed, numerous senescence-associated secretory phenotype (SASP) markers such as p21, IL-8, CXCL1, and MMP-1 were upregulated, whereas components of the extracellular matrix were downregulated (elastin, collagen type 1). Next, we showed that CoQ10 supplementation to statin-treated HDF was able to counteract CoQ10 deprivation and rescued the development of selected senescence/ageing markers in HDF. Ubiquinol resulted more bioavailable than ubiquinone at the same concentration (15 µg/mL) and it significantly improved the cellular oxidative status even within isolated mitochondria highlighting an effective subcellular delivery. Ubiquinol was also more efficient compared to ubiquinone in reverting the expression of the senescent phenotype, quantified in terms of ß-galactosidase positivity, p21, collagen type 1, and elastin at the gene and protein expression levels. In conclusion, our results highlight the pivotal role of CoQ10 for skin vitality and strongly support the use of both forms as a beneficial and effective anti-ageing skin care treatment.

Modulation of Coenzyme Q10 content and oxidative status in human dermal fibroblasts using HMG-CoA reductase inhibitor over a broad range of concentrations. From mitohormesis to mitochondrial dysfunction and accelerated aging.

Coenzyme Q10 (CoQ10) is an endogenous lipophilic quinone, ubiquitous in biological membranes and endowed with antioxidant and bioenergetic properties, both crucial to the aging process. In fact, coenzyme Q10 synthesis is known to decrease with age in different tissues including skin. Moreover, synthesis can be inhibited by 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors such as statins, that are widely used hypocholesterolemic drugs. They target a key enzymatic step along the mevalonate pathway, involved in the synthesis of both cholesterol and isoprenylated compounds including CoQ10.In the present study, we show that pharmacological CoQ10 deprivation at concentrations of statins > 10000 nM triggers intracellular oxidative stress, mitochondrial dysfunction and generates cell death in human dermal fibroblasts (HDF). On the contrary, at lower statin concentrations, cells and mainly mitochondria, are able to partially adapt and prevent oxidative imbalance and overt mitochondrial toxicity. Importantly, our data demonstrate that CoQ10 decrease promotes mitochondrial permeability transition and bioenergetic dysfunction leading to premature aging of human dermal fibroblasts in vitro.

A tissue-engineered human dermal construct utilizing fibroblasts and transforming growth factor ß1 to promote elastogenesis.

Numerous studies have shown that extracellular matrix (ECM)-based scaffolds are suitable for dermal constructs for the differentiation of various cell types in vitro and for constructive tissue remodeling after implantation in vivo. However, a shortcoming of these ECM materials is its limited elastogenesis. Elastic fibers constitute an essential component of mammalian connective tissue and the presence of elastic fibers is crucial for the proper function of the cardiovascular, pulmonary, and intestinal systems. Since it is still largely unknown how cells coordinate the molecular events of elastic-fiber assembly, understanding the ability to regenerate elastic fibers in tissues remains a significant challenge. For this reason, human neonatal dermal fibroblasts (HDFneo) were analyzed for their potential to serve as a cell culture model for elastic fiber assembly. Using optical technologies such as multiphoton laser-scanning microscopy (MPSLM) we demonstrate that HDFneo stimulated with transforming growth factor ß1 (TGF-ß1) are able to produce a distinct and complex elastic fiber system in vitro. As shown by the desmosine and isodesmosine content, crosslinked elastic fibers were formed within the 3D ECM-based scaffold. This tissue-engineered dermal construct may prove to be an effective template for the development of medicinal approaches in regenerative soft skin tissue reconstruction through TGF-ß1 induction.

UV-mediated downregulation of the endocytic collagen receptor, Endo180, contributes to accumulation of extracellular collagen fragments in photoaged skin.

BACKGROUND: Collagen is the most abundant protein in human skin and is responsible for its resilience. In particular during photoaging, collagen homeostasis is out of balance leading to a continuous loss of intact collagen and to the observed signs of aged skin such as diminished tensile strength and wrinkle development. The process of collagen turnover is very slow and the relevance of cellular uptake of damaged collagen, most likely mediated via Endo180 or integrin α2ß1, still remains a matter of investigation. OBJECTIVE: We investigated the role of different collagen receptors on dermal fibroblasts for collagen internalization and their impact on collagen homeostasis during photoaging. METHODS: TaqMan Real-Time PCR, flow cytometry, UV irradiation, knockdown experiments and immunostaining. RESULTS: We show that Endo180 and integrin α2 are regulated in photoaged skin and after acute UV stress in vivo and in vitro. Knockdown experiments revealed that Endo180 is essential for cellular uptake of collagen fragments by dermal fibroblasts, whereas integrin α2 is important for initial binding of collagen. UV irradiation decreases collagen endocytosis. This correlates with reduced Endo180 expression and pericellular accumulation of collagen fragments during photoaging. CONCLUSION: Our findings correlate for the first time impaired collagen uptake via Endo180 with the pericellular accumulation of collagen fragments during photoaging. We assume an altered pericellular niche of fibroblasts in photoaged skin that has an impact on collagen homeostasis.

CEBP factors regulate telomerase reverse transcriptase promoter activity in whey acidic protein-T mice during mammary carcinogenesis.

Telomerase is activated in the majority of invasive breast cancers, but the time point of telomerase activation during mammary carcinogenesis is not clear. We have recently presented a transgenic mouse model to study human telomerase reverse transcriptase (TERT) gene expression in vivo (hTERTp-lacZ). In the present study, hTERTp-lacZxWAP-T bitransgenic mice were generated to analyze the mechanisms responsible for human and mouse TERT upregulation during tumor progression in vivo. We found that telomerase activity and TERT expression were consistently upregulated in SV40-induced invasive mammary tumors compared to normal and hyperplastic tissues and ductal carcinoma in situ (DCIS). Human and mouse TERT genes are regulated similarly in the breast tissue, involving the CEBP transcription factors. Loss of CEBP-α and induction of CEBP-ß expression correlated well with the activation of TERT expression in mouse mammary tumors. Transfection of CEBP-α into human or murine cells resulted in TERT repression, whereas knockdown of CEBP-α in primary human mammary epithelial cells resulted in reactivation of endogenous TERT expression and telomerase activity. Conversely, ectopic expression of CEBP-ß activated endogenous TERT gene expression. Moreover, ChIP and EMSA experiments revealed binding of CEBP-α and CEBP-ß to human TERT-promoter. This is the first evidence indicating that CEBP-α and CEBP-ß are involved in TERT gene regulation during carcinogenesis.

The promoter of human telomerase reverse transcriptase is activated during liver regeneration and hepatocyte proliferation.

BACKGROUND & AIMS: Telomerase activity has not been detected in healthy human liver biopsy samples, but it is up-regulated in most human liver tumors. It is not clear whether telomerase is activated in response to acute or chronic liver injury. Telomerase activity is closely associated with expression of its catalytic subunit, telomerase reverse transcriptase (TERT). We analyzed the activity of the human TERT (hTERT) promoter during liver regeneration in vivo and hepatocyte proliferation in vitro. METHODS: We used hTERTp-lacZ transgenic mice, which contain an 8.0-kilobase pair fragment of the hTERT gene promoter, to study the role of TERT in liver regeneration following partial hepatectomy. As an in vitro model, we used the HepaRG cell line as a new model system for human hepatocyte proliferation and differentiation. RESULTS: Activity of the hTERT promoter increased significantly after partial hepatectomy; it was also induced in hepatocytes, based on immunohistologic analysis. Similar to the in vivo results, telomerase activity and hTERT expression were up-regulated in proliferating HepaRG cells and repressed in response to growth arrest and differentiation. Promoter mapping revealed that a proximal 0.3-kilobase pair fragment contains all elements necessary for regulation of hTERT in HepaRG cells. We identified E2F2 and E2F7 as transcription factors that control the differential expression of hTERT in proliferating hepatocytes, in vitro and in vivo. CONCLUSIONS: hTERT is induced in hepatocytes during liver regeneration, indicating a functional role for telomerase in human liver.