Alginate oligosaccharides (AOS) with a weight average molecular weight of 5 kDa were efficiently amidated with amino acids and carbohydrates in aqueous media in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). Here, alanine, leucine, serine, as well as mannose and rhamnose, were amidated at high yields with a good control of the degree of substitution (DS). Amino acid- and carbohydrate-grafted AOS showed improved stability against degradation by alginate lyases having different specificities. This enzyme resistance was correlated with the DS: hydrolysis was reduced by 60-70% for low DS (0.1), whereas AOS with DS ranging from 0.4 to 0.6 remained unhydrolyzed. Competitive inhibition assays demonstrated multivalent binding of mannose-amidated AOS to concanavalin A lectin. A 178-fold affinity enhancement was observed for AOS (DS 0.38) over α-methyl-mannoside with an IC of 5.6 μM, lending further evidence for the promising potential of AOS as multivalent scaffolds.
Stress-induced premature senescence (SIPS) has been proposed as an in-vitro model for testing the long-term effects of stressful events and to find molecules/natural extracts that protect against such stress. Premature senescence of human skin diploid fibroblasts (HDFs) can be induced by repeated subcytotoxic exposure to UVB, with the appearance of so-called biomarkers of senescence such as growth arrest, senescence-associated beta-galactosidase activity, senescence-associated gene over-expression and the common 4977-bp mitochondrial DNA deletion. This model of UVB-induced premature senescence has been acknowledged as a robust in-vitro model in photoageing research. In this study, the potential anti-photoageing effects of a series of algal extracts were tested. The appearance of the biomarkers of UVB-induced premature senescence of HDFs was studied with or without algal extracts. One algal extract was shown to be particularly protective against UVB-induced SIPS. The results obtained here reinforce the notion that UVB-induced premature senescence of HDFs can be used to screen potential anti-photoageing compounds.
Background: Due to its immune system, the skin constitutes the first barrier against environmental attack such as chemical and physical agents or bacteria. The bacteria, viruses, archaea and fungi present on the superficial layers of the skin correspond to the cutaneous microbiota. Its composition is crucial to the balance of the immune system. It has already been shown that the composition of the microbiota affects the development of diseases such as atopic dermatitis (since an increase in Staphylococcus aureus has been described), but also diabetes and obesity. This microbiota imbalance (or dysbiosis) is mainly related to individual factors (age), diet, environmental (climate) and behavioral factors (hygiene, consumption of antibiotics). Aim: In our study, we are more interested in the effect of a stressful lifestyle on skin microbiota, and more especially on skin bacteria. Methods: We studied the skin microbiota from the faces of 70 healthy human subjects (aged 25 to 45 years). Firstly, we worked with 2 groups of 20 volunteers selected according to their stress level, using a validated stress score evaluation, known as the Perceived Stress Scale (PSS). Secondly, we tested the effect of a topical treatment on the skin microflora of a group of 30 volunteers who displayed a high stress index (PSS>27). Results: We identified a bacterial signature of stressed individuals in comparison to unstressed individuals in term of richness and diversity. We also identified some species that are more prevalent in stressed individuals, especially acidic and anaerobic bacteria, in relation to modified skin parameters (decreased skin pH, increased redness and a higher level of blemishes). We then identified some benefits to the skin microbiota of stressed individuals from a topical treatment, with an improvement in skin parameters (increased pH, reduced redness and fewer blemishes). Conclusion: This original study on healthy human skin microbiota will serve to direct future research addressing the role of skin microbiota in healthy people, and metagenomic projects addressing the complex physiological interactions between the skin and the microbes that populate this environment.
Vibrio alginolyticus (CNCM I-4994) secretes an exopolysaccharide that can be used as an ingredient in cosmetic applications. The structure was resolved using chromatography and one- and two-dimensional NMR spectroscopy experiments. The results show that the carbohydrate backbone is made of two residues: d-galacturonic acid and N-acetyl-d-glucosamine (GlcNac), which together constitute a tetrasaccharide repetition unit: [→3)-α-d-GalA-(1→4)-α-d-GalA-(1→3)-α-d-GalA-(1→3)-β-GlcNAc(1→]. Two amino acids, alanine and serine, are linked to GalA residues via amido linkages. The position and the distribution of the amino acids were characterized by two-dimensional NMR spectroscopy. To our knowledge, this is the first description of a structure for a marine exopolysaccharide decorated with an amino acid.
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