Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids

Skin surface lipids (SSLs) form the first barrier that protects the human organism from external stressors, disruption of the homeostasis of SSLs can result in severe skin abnormalities. One of the main causes of this disruption is oxidative stress that is primarily due to SSLs oxidation. Squalene (...

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Autores principales:	Saoussane Khalifa, Masaru Enomoto, Shunji Kato, Kiyotaka Nakagawa
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	SQ SQ-OOH cyclic peroxides photooxidation <sup>1</sup>O<sub>2</sub> <sup>3</sup>O<sub>2</sub> Therapeutics. Pharmacology RM1-950
Acceso en línea:	https://doaj.org/article/42b4085821fc452f9f9a6583e49c69fe
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spelling	oai:doaj.org-article:42b4085821fc452f9f9a6583e49c69fe2021-11-25T16:27:56ZNovel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids10.3390/antiox101117602076-3921https://doaj.org/article/42b4085821fc452f9f9a6583e49c69fe2021-11-01T00:00:00Zhttps://www.mdpi.com/2076-3921/10/11/1760https://doaj.org/toc/2076-3921Skin surface lipids (SSLs) form the first barrier that protects the human organism from external stressors, disruption of the homeostasis of SSLs can result in severe skin abnormalities. One of the main causes of this disruption is oxidative stress that is primarily due to SSLs oxidation. Squalene (SQ), the most abundant lipid among SSLs, was shown to first undergo singlet molecular oxygen (<sup>1</sup>O<sub>2</sub>) oxidation to yield 6 SQ-monohydroperoxide (SQ-OOH) isomers as the primary oxidation products. However, due to the instability and lability of hydroperoxides, we found that when total SQ-OOH isomers are further photooxidized, they form a unique higher molecular weight secondary oxidation product. To generate the compound, we photooxidized total SQ-OOH isomers in the presence of ground state molecular oxygen (<sup>3</sup>O<sub>2</sub>), after its isolation and purification, we studied its structure using MS/MS, NMR, derivatization reactions, and chemical calculations. The compound was identified as 2-OOH-3-(1,2-dioxane)-SQ. Photooxidation of individual SQ-OOH isomers revealed that 6-OOH-SQ is the precursor of 2-OOH-3-(1,2-dioxane)-SQ and indicated the possibility of the formation of similar cyclic peroxides from each isomer following the same photoinduced chain reaction mechanism. An HPLC-MS/MS method was developed for the analysis of 2-OOH-3-(1,2-dioxane)-SQ and its presence on the skin was confirmed in SSLs of six healthy individuals. Its quantity on the skin correlated directly to that of SQ and was not inversely proportional to its precursor, indicating the possibility of its accumulation on the skin surface and the constant regeneration of 6-OOH-SQ from SQ’s oxidation. In general, research on lipid cyclic peroxides in the human organism is very limited, and especially on the skin. This study shows for the first time the identification and presence of a novel SQ cyclic peroxide “2-OOH-3-(1,2-dioxane)-SQ” in SSLs, shedding light on the importance of further studying its effect and role on the skin.Saoussane KhalifaMasaru EnomotoShunji KatoKiyotaka NakagawaMDPI AGarticleSQSQ-OOHcyclic peroxidesphotooxidation<sup>1</sup>O<sub>2</sub><sup>3</sup>O<sub>2</sub>Therapeutics. PharmacologyRM1-950ENAntioxidants, Vol 10, Iss 1760, p 1760 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	SQ SQ-OOH cyclic peroxides photooxidation <sup>1</sup>O<sub>2</sub> <sup>3</sup>O<sub>2</sub> Therapeutics. Pharmacology RM1-950
spellingShingle	SQ SQ-OOH cyclic peroxides photooxidation <sup>1</sup>O<sub>2</sub> <sup>3</sup>O<sub>2</sub> Therapeutics. Pharmacology RM1-950 Saoussane Khalifa Masaru Enomoto Shunji Kato Kiyotaka Nakagawa Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids
description	Skin surface lipids (SSLs) form the first barrier that protects the human organism from external stressors, disruption of the homeostasis of SSLs can result in severe skin abnormalities. One of the main causes of this disruption is oxidative stress that is primarily due to SSLs oxidation. Squalene (SQ), the most abundant lipid among SSLs, was shown to first undergo singlet molecular oxygen (<sup>1</sup>O<sub>2</sub>) oxidation to yield 6 SQ-monohydroperoxide (SQ-OOH) isomers as the primary oxidation products. However, due to the instability and lability of hydroperoxides, we found that when total SQ-OOH isomers are further photooxidized, they form a unique higher molecular weight secondary oxidation product. To generate the compound, we photooxidized total SQ-OOH isomers in the presence of ground state molecular oxygen (<sup>3</sup>O<sub>2</sub>), after its isolation and purification, we studied its structure using MS/MS, NMR, derivatization reactions, and chemical calculations. The compound was identified as 2-OOH-3-(1,2-dioxane)-SQ. Photooxidation of individual SQ-OOH isomers revealed that 6-OOH-SQ is the precursor of 2-OOH-3-(1,2-dioxane)-SQ and indicated the possibility of the formation of similar cyclic peroxides from each isomer following the same photoinduced chain reaction mechanism. An HPLC-MS/MS method was developed for the analysis of 2-OOH-3-(1,2-dioxane)-SQ and its presence on the skin was confirmed in SSLs of six healthy individuals. Its quantity on the skin correlated directly to that of SQ and was not inversely proportional to its precursor, indicating the possibility of its accumulation on the skin surface and the constant regeneration of 6-OOH-SQ from SQ’s oxidation. In general, research on lipid cyclic peroxides in the human organism is very limited, and especially on the skin. This study shows for the first time the identification and presence of a novel SQ cyclic peroxide “2-OOH-3-(1,2-dioxane)-SQ” in SSLs, shedding light on the importance of further studying its effect and role on the skin.
format	article
author	Saoussane Khalifa Masaru Enomoto Shunji Kato Kiyotaka Nakagawa
author_facet	Saoussane Khalifa Masaru Enomoto Shunji Kato Kiyotaka Nakagawa
author_sort	Saoussane Khalifa
title	Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids
title_short	Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids
title_full	Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids
title_fullStr	Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids
title_full_unstemmed	Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids
title_sort	novel photoinduced squalene cyclic peroxide identified, detected, and quantified in human skin surface lipids
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/42b4085821fc452f9f9a6583e49c69fe
work_keys_str_mv	AT saoussanekhalifa novelphotoinducedsqualenecyclicperoxideidentifieddetectedandquantifiedinhumanskinsurfacelipids AT masaruenomoto novelphotoinducedsqualenecyclicperoxideidentifieddetectedandquantifiedinhumanskinsurfacelipids AT shunjikato novelphotoinducedsqualenecyclicperoxideidentifieddetectedandquantifiedinhumanskinsurfacelipids AT kiyotakanakagawa novelphotoinducedsqualenecyclicperoxideidentifieddetectedandquantifiedinhumanskinsurfacelipids
_version_	1718413132543557632

Novel Photoinduced Squalene Cyclic Peroxide Identified, Detected, and Quantified in Human Skin Surface Lipids

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