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Surface lipids as multifunctional mediators of skin responses to environmental stimuli.

De Luca C, Valacchi G - Mediators Inflamm. (2010)

Bottom Line: Its composition is unique for the high percentage of long chain fatty acids, and of the polyterpenoid squalene, absent in other human tissues, and in non-human Primates sebum.Qualitative modifications of SSL represent a pathogenetic sign of diagnostic value in dermatological disorders involving altered sebum production, like pytiriasis versicolor, acne, atopic or seborrheic dermatitis, as well as photo-aging.Achievements of nutriceutical interventions aimed at restoring normal SSL composition and homeostasis are discussed, as feasible therapeutic goals and major means of photo-protection.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Tissue Engineering and Skin Pathophysiology, Istituto Dermopatico dell'Immacolata (IDI IRCCS), Rome, Italy. c.deluca@idi.it

ABSTRACT
Skin surface lipid (SSL) film is a mixture of sebum and keratinocyte membrane lipids, protecting skin from environment. Its composition is unique for the high percentage of long chain fatty acids, and of the polyterpenoid squalene, absent in other human tissues, and in non-human Primates sebum. Here, the still incomplete body of information on SSL as mediators of external chemical, physical, and microbial signals and stressors is revised, focusing on the central event of the continuous oxidative modification induced by the metabolic activity of residential and pathological microbial flora, natural or iatrogenic UV irradiation, exposure to chemicals and cosmetics. Once alpha-tocopherol and ubiquinol-10 antioxidant defences of SSL are overcome, oxidation of squalene and cholesterol gives rise to reactive by-products penetrating deeper into skin layers, to mediate local defensive inflammatory, photo-protective, immune reactions or, at higher concentrations, inducing local but also systemic immune depression, ultimately implicating skin cancerogenesis. Qualitative modifications of SSL represent a pathogenetic sign of diagnostic value in dermatological disorders involving altered sebum production, like pytiriasis versicolor, acne, atopic or seborrheic dermatitis, as well as photo-aging. Achievements of nutriceutical interventions aimed at restoring normal SSL composition and homeostasis are discussed, as feasible therapeutic goals and major means of photo-protection.

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Chemical structures of squalene and of its main photo-oxidation labile or stable by-products, generated in vitro under UV irradiation.
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fig1: Chemical structures of squalene and of its main photo-oxidation labile or stable by-products, generated in vitro under UV irradiation.

Mentions: Among cutaneous SSL components, squalene is a most intriguing component. It represents indeed the most abundant peroxidable fraction in SSL. It was previously demonstrated that when human sebum is subjected to high-dosage UVB irradiation in vitro, SQ is markedly degraded as compared to cholesterol, sebum triglycerides, or mono-/diunsaturated free fatty acids (FFAs) [43, 44]. UVR, alone or in combination with photosensitizers or other physicochemical stimuli including microbial peroxidizing metabolism, induces oxidative degradation of SQ with the generation of a wide range of by-products of varying polarity and reactivity, that have been clearly characterised by ion mass spectrometry. These include SQ monohydroperoxide [43], different isomers of squalene epoxide, and shorter chain reactive aldehydes [45], in particular formaldehyde and malonyl dialdehyde (MDA) [46–48] ] (Figure 1). More recent studies have demonstrated that SQ is oxidized at a much higher rate in physiological conditions by UVA either than UVB, and that probably most previous results obtained with experimental UVB irradiation must be ascribed to the effects of minimal doses of UVA, always contaminating UVB emission sources [49].


Surface lipids as multifunctional mediators of skin responses to environmental stimuli.

De Luca C, Valacchi G - Mediators Inflamm. (2010)

Chemical structures of squalene and of its main photo-oxidation labile or stable by-products, generated in vitro under UV irradiation.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2963132&req=5

fig1: Chemical structures of squalene and of its main photo-oxidation labile or stable by-products, generated in vitro under UV irradiation.
Mentions: Among cutaneous SSL components, squalene is a most intriguing component. It represents indeed the most abundant peroxidable fraction in SSL. It was previously demonstrated that when human sebum is subjected to high-dosage UVB irradiation in vitro, SQ is markedly degraded as compared to cholesterol, sebum triglycerides, or mono-/diunsaturated free fatty acids (FFAs) [43, 44]. UVR, alone or in combination with photosensitizers or other physicochemical stimuli including microbial peroxidizing metabolism, induces oxidative degradation of SQ with the generation of a wide range of by-products of varying polarity and reactivity, that have been clearly characterised by ion mass spectrometry. These include SQ monohydroperoxide [43], different isomers of squalene epoxide, and shorter chain reactive aldehydes [45], in particular formaldehyde and malonyl dialdehyde (MDA) [46–48] ] (Figure 1). More recent studies have demonstrated that SQ is oxidized at a much higher rate in physiological conditions by UVA either than UVB, and that probably most previous results obtained with experimental UVB irradiation must be ascribed to the effects of minimal doses of UVA, always contaminating UVB emission sources [49].

Bottom Line: Its composition is unique for the high percentage of long chain fatty acids, and of the polyterpenoid squalene, absent in other human tissues, and in non-human Primates sebum.Qualitative modifications of SSL represent a pathogenetic sign of diagnostic value in dermatological disorders involving altered sebum production, like pytiriasis versicolor, acne, atopic or seborrheic dermatitis, as well as photo-aging.Achievements of nutriceutical interventions aimed at restoring normal SSL composition and homeostasis are discussed, as feasible therapeutic goals and major means of photo-protection.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Tissue Engineering and Skin Pathophysiology, Istituto Dermopatico dell'Immacolata (IDI IRCCS), Rome, Italy. c.deluca@idi.it

ABSTRACT
Skin surface lipid (SSL) film is a mixture of sebum and keratinocyte membrane lipids, protecting skin from environment. Its composition is unique for the high percentage of long chain fatty acids, and of the polyterpenoid squalene, absent in other human tissues, and in non-human Primates sebum. Here, the still incomplete body of information on SSL as mediators of external chemical, physical, and microbial signals and stressors is revised, focusing on the central event of the continuous oxidative modification induced by the metabolic activity of residential and pathological microbial flora, natural or iatrogenic UV irradiation, exposure to chemicals and cosmetics. Once alpha-tocopherol and ubiquinol-10 antioxidant defences of SSL are overcome, oxidation of squalene and cholesterol gives rise to reactive by-products penetrating deeper into skin layers, to mediate local defensive inflammatory, photo-protective, immune reactions or, at higher concentrations, inducing local but also systemic immune depression, ultimately implicating skin cancerogenesis. Qualitative modifications of SSL represent a pathogenetic sign of diagnostic value in dermatological disorders involving altered sebum production, like pytiriasis versicolor, acne, atopic or seborrheic dermatitis, as well as photo-aging. Achievements of nutriceutical interventions aimed at restoring normal SSL composition and homeostasis are discussed, as feasible therapeutic goals and major means of photo-protection.

Show MeSH
Related in: MedlinePlus