Abstract: Jiang Yueming, Zhao Xiaomin, Qu Xin Ashland China Holdings Co., Ltd, Shanghai 200233, China Corresponding author: Zhao Xiaomin, Email: rzhao@ashland.com 【Abstract】 Objective To evaluate the effect of air pollution on carbonylated protein level in the stratum corneum, and to assess the protective effect of pink pepper tree extracts and lipid mixtures on skin damage. Methods After the investigation of influencing factors in the preliminary experiment, fluorescence labelling assay was performed to detect the carbonylated protein level in the skin stratum corneum at different body sites of 34 healthy testees. Cigarette smoke was used to simulate pollutants, and the forearms of 15 healthy testees were exposed in the customized pollution simulation chamber with the flexor aspects facing upwards. After 0, 1, 2, 4, 5 hours of exposure, stratum corneum samples were collected by using D-squame tapes. In each of 14 selected healthy testees, 3 adjacent areas on the flexor aspect of unilateral forearm were divided into 3 groups: pink pepper tree group treated with 1% aqueous solution of pink pepper tree extracts, control group treated with deionized water, and blank group receiving no treatment. Then, the forearms of the 14 testees were exposed in the pollution simulation chamber for 5 hours, and stratum corneum samples were collected from the 3 areas before and after the exposure. Another 16 healthy testees were included, and 3 adjacent areas on the flexor aspect of their unilateral forearms were divided into 3 groups: lipid mixture group treated with 5% lipid mixture emulsion, control group treated with lipid mixture-free placebo emulsion, and blank group receiving no treatment. Then, the forearms of the 16 testees were exposed in the pollution simulation chamber for 5 hours, and stratum corneum samples were collected from the 3 areas before and after the exposure. Moreover, twenty healthy testees were enrolled into the double-blind split-face clinical trial. That is, one half of the face was randomly chosen to be treated with 1% emulsion of pink pepper tree extracts, and the other facial side was treated with placebo emulsion. Before and after 56-day treatment, stratum corneum samples were collected from the cheeks of testees by using D-squame tapes. Fluorescence labelling assay was conducted to detect the carbonylated protein level in the above stratum corneum samples. Results The analysis of 34 testees showed that carbonylated protein levels （average fluorescence intensity） significantly differed among different body sites （P < 0.001）, and the carbonylated protein levels were significantly higher in the cheeks （26.3 ± 7.1） and forehead （22.9 ± 7.9） than in the forearm （14.7 ± 4.9） and waist and back （12.6 ± 4.2）（P < 0.001）, and higher in the forearm than in the waist and back （P = 0.046）. In the short-term simulated accelerated exposure experiment, the carbonylated protein level increased along with the increase of the duration of exposure to pollution （R2 = 0.995 9）. After 5-hour exposure, the pink pepper tree group and lipid mixture group both showed significantly lower elevated levels of carbonylated protein in the stratum corneum （9.7 ± 5.2, 5.8 ± 4.9） compared with the corresponding blank groups （19.0 ± 10.0, 17.4 ± 8.8; P < 0.005） and control groups （18.5 ± 7.3, 15.9 ± 6.4; P < 0.005）. In the long-term human trial, the carbonylated protein levels significantly decreased in the facial side treated with 1% emulsion of pink pepper tree extracts for 8 weeks compared with the placebo-treated facial side. Conclusion Air pollution aggravates skin damage induced by protein carbonylation in the stratum corneum, and pink pepper tree extracts and lipid mixtures can effectively reduce the carbonylated protein level.

Key words: Skin, Air pollution, Oxidative stress, Protein carbonylation, Pink pepper extract, Lipid mixture