Ultraviolet radiation and skin aging: roles of reactive oxygen species, inflammation and protease activation, and strategies for prevention of inflammation-induced matrix degradation - a review

Repair of UVB-damaged skin by the antioxidant sulphated flavone glycoside thalassiolin B isolated from the marine plant Thalassia testudinum Banks ex König

Daily topical application of the aqueous ethanolic extract of the marine sea grass, Thalassia testudinum, on mice skin exposed to UVB radiation resulted in a dose-dependent recovery of the skin macroscopic alterations over a 6-day period. Maximal effect (90%) occurred at a dose of 240 microg/cm(2), with no additional effects at higher doses. Bioassay-guided fractionation of the plant extract resulted in the isolation of thalassiolin B (1). Topical application of 1 (240 microg/cm(2)) markedly reduces skin UVB-induced damage. In addition, thalassiolin B scavenged 2,2-diphenyl-2-picrylhydrazyl radical with an EC(50) = 100 microg/ml. These results suggest that thalassiolin B is responsible for the skin-regenerating effects of the crude extract of T. testudinum.

UV and pigmentation: molecular mechanisms and social controversies

Ultraviolet radiation (UVR) is an essential risk factor for the development of premalignant skin lesions as well as of melanoma and non-melanoma skin cancer. UVR exerts many effects on the skin, including tanning, carcinogenesis, immunomodulation, and production of vitamin D. Vitamin D (vit D) is important in the maintenance of healthy bones as well as other purported beneficial effects, amongst which is the potential for reducing risk of malignancy--though oral supplementation is fully capable of maintaining systemic levels. The known medical harm from UV exposure relates primarily to cancer of the skin--the most common organ in man to be affected by cancer. In this review, we summarize the knowledge about the ultraviolet (UV) response in regards to inflammation, immunosuppression, carcinogenesis and the tanning response. We also discuss vit D and UV, as well as public health implications of tanning behavior and commercial interests related to the promotion of UV exposure. As the most ubiquitous human carcinogen, UVR exposure represents both a challenge and enormous opportunity in the realm of skin cancer prevention.

Mapping of macrophage elastase cleavage sites in insoluble human skin elastin

Macrophage elastase (MMP-12) is a member of the family of matrix metalloproteinases (MMPs) and is active against multiple extracellular protein substrates such as elastin. Its effect on elastin is central to emphysema in the lung and photoaging of skin. Its expression in the skin increases on photodamaged skin and upon aging. Detecting and characterizing peptides cleaved in elastin, therefore, helps to understand such degradative disease processes in the skin and is also needed to assist in the rational design of agents that specifically inhibit the degradation. In this study, cleavage sites of MMP-12 in human skin elastin were extensively investigated. The peptides formed as a result of cleavages by this enzyme in the human skin elastin were characterized using mass spectrometry. A total of 41 peptides ranging from 4 to 41 amino acids were identified and 36 cleavage sites were determined. Amino acids encoded by exons 5, 6, 26, 28-31 were particularly susceptible to cleavages by MMP-12 and none or very few cleavages were detected from domains encoded by the remaining exons. The amino acid preferences of the different subsites on the catalytic domain of MMP-12 were analyzed.

Beneficial long-term effects of combined oral/topical antioxidant treatment with the carotenoids lutein and zeaxanthin on human skin: a double-blind, placebo-controlled study

BACKGROUND

The skin is exposed to numerous environmental assaults that can lead to premature aging. Of these agents, perhaps none is more ubiquitous than the ultraviolet (UV) wavelengths of sunlight. The primary immediate defense against environmental skin damage is the antioxidant capacity of the skin. However, this defense system can be compromised by moderate exposure to UV light. Therefore, bolstering the antioxidant defense system of the skin is a potentially important strategy for reducing environmentally induced skin damage.

AIM OF THE STUDY

This clinical trial was designed to study the efficacy of lutein and zeaxanthin, two potentially important antioxidants found naturally in the skin, upon five skin physiology parameters (surface lipids, hydration, photoprotective activity, skin elasticity and skin lipid peroxidation - malondialdehyde) of human subjects. These xanthophyllic carotenoids were administered either orally, topically, or in combination (both oral and topical routes).

RESULTS

The results obtained indicate that the combined oral and topical administration of lutein and zeaxanthin provides the highest degree of antioxidant protection. However, oral and topical administration of these antioxidants individually also provides significant activity in the skin. In addition, oral administration of lutein may provide better protection than that afforded by topical application of this antioxidant when measured by changes in lipid peroxidation and photoprotective activity in the skin following UV light irradiation.

Inhibition of inflammatory nitric oxide production and epidermis damages by Saccharomycopsis Ferment Filtrate

BACKGROUND

Yeast extracts have been shown to perform anti-inflammatory and cytoprotective activities. However, the effects of yeast extracts on lipopolysaccharide (LPS)-induced nitric oxide (NO) production and epidermal damages are still unclear.

OBJECTIVE

To investigate the effect of Saccharomycopsis Ferment Filtrate (SFF) on LPS-induced NO production in RAW264.7 macrophages and epidermal damages.

METHOD

RAW264.7 cells are incubated with LPS (25 ng/mL) and different concentrations of SFF. The amount of NO production is detected by Griess reaction. Additionally, the expression of inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1) are detected by Western blotting. Artificial epidermis is also used to mimic the in vivo condition to investigate the protective effects of SFF on LPS- or ultraviolet radiation (UVR)-induced damages by histology and electron microscopy.

RESULTS

The results show that SFF addition inhibits LPS-induced NO production and iNOS protein expression in a concentration-dependent manner without notable cytotoxicity in RAW264.7 cells, and induction of HO-1 protein expression by SFF was observed. Interestingly, both HO-1 inducers, hemin and CoCl2, significantly attenuated LPS-induced NO production and iNOS protein expression. The addition of CoCl2 potentiated the inhibitory effect of SFF on LPS-induced NO production. It seems that HO-1 protein participates in SFF inhibition of LPS-induced NO production. Furthermore, SFF exhibits significant protective effect on LPS- or UVR-induced damages in the artificial epidermis via histological and electron microscopic observations.

CONCLUSION

This study provided the first evidence to indicate the beneficial effects of SFF in preventing NO production in macrophages and damages in epidermis, respectively. It suggests that SFF possesses potential to be further developed.