SKINCARE


59


The role of lipid peroxidation in skin health


Norman E Miller and Irina P Miller - Kutanios


Although it has been known for many years that peroxidation of lipids in skin is increased by sunlight and atmospheric pollution, and that the products contribute to the ageing of skin, sunburn, and skin cancers, relatively little attention has been given to the process. This has largely been owing to the absence of a technology to protect tissues from the products of lipid peroxidation. However, this may be about to change,


thanks to a UK start-up created by two former Oxford medical scientists, one of whom was the co-discoverer of the protective effect of high- density lipoproteins (HDL, commonly known as ‘good’ cholesterol) against heart disease. The founders knew from their academic


cardiovascular research that one of the protein components of HDL particles is able to protect vascular cells from the toxic effects of lipid peroxides by sequestering them, and that peptides had been synthesized with even greater affinity for the molecules, even though they had no sequence homology to the HDL protein. The idea of transferring the technology


to skincare had been prompted when they discovered, when studying HDLs in tissue fluid collected from the skin of healthy volunteers, that the concentration of lipid peroxides in the fluid was many times greater than could be explained by the level in blood.


What are lipid peroxides? Lipid peroxides (more correctly lipid hydroperoxides) are formed in all tissues by the reaction of lipids with reactive oxygen species (ROS), commonly known as free


radicals. Only lipids containing one or more carbon-carbon double bonds can undergo peroxidation. Examples are unsaturated fatty acids, phospholipids, glycolipids, cholesterol and squalene. ROS are short-lived (lasting only


nanoseconds) but highly reactive molecules that are formed mostly in cellular organelles, such as mitochondria, the endoplasmic reticulum, and peroxisomes, particularly under conditions of metabolic stress. The most important are the hydroxyl and hydroperoxyl radicals.


Each cell produces on average about four


million of the former every day. Lipids are also oxidized by enzymes (e.g., lipoxygenases, cyclooxygenases) during the synthesis of physiological signalling molecules, such as prostaglandins.


How are they produced? Lipid peroxidation starts when a ROS molecule takes a hydrogen atom from an unsaturated lipid (Figure 1). The resulting lipid radical (L•) reacts with oxygen to produce a lipid peroxy radical (LOO•). When this takes a hydrogen from a second


lipid molecule, producing a lipid peroxide (LOOH) and another L• radical, it propagates a chain reaction that stops only when an antioxidant, such as vitamin E, donates a hydrogen to LOO• to form a vitamin E radical (which then reacts with another LOO• to form nonradical products). While LOOH molecules are the primary


end-products, several reactive aldehydes derived from them are more important in the context of skin health. Notable among them are malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE).


Figure 1: The three steps in the peroxidation of unsaturated lipids. ROS, reactive oxygen species. MDA, malondialdehyde. 4-HNE, 4-hydroxynonenal


www.personalcaremagazine.com


Why is lipid peroxidation important? Several products of lipid peroxidation have detrimental effects on physiology and cellular biochemistry, and have been implicated as


March 2023 PERSONAL CARE


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103