A lipidomic approach towards identifying the effects of fragrance hydroperoxides on keratinocytes.

Background: Limonene and linalool are used in cosmetic products for their floral scents, but their oxidation products are strong contact allergens whose mechanisms of action are still not fully understood.

Objectives: The effects of limonene hydroperoxide (Lim-2-OOH) and linalool hydroperoxides (Lin-6/7-OOH) on the lipid profile of a human keratinocyte cell line (HaCaT) were evaluated. 2,4-Dinitrofluorobenzene (DNFB) was also included.

Methods: Lim-2-OOH and Lin-6/7-OOH were synthesised according to previous methods. HaCaT cells were treated with allergens (10 μM) for 24 h and the cellular lipid extracts were analysed by C18 liquid chromatography with tandem mass spectrometry (LC-MS/MS). Data analysis was performed using Lipostar software. Statistical analysis was carried out using Metaboanalyst and R software.

Results: All three sensitisers used caused significant changes in the lipidome of HaCaT cells in a similar trend. There was an upregulation in several plasmanyl/plasmenyl phospholipids (O-/P-phosphatidylcholines [PC] and O-/P-phosphatidylethanolamines [PE]), sphingolipids (HexCer) and triacylglycerol lipid species, and a decrease in some polyunsaturated fatty acids-containing phospholipid (PE and PC) species suggesting oxidative stress and inflammation.

Conclusions: This study is the first to evaluate the plasticity of the HaCaT cell lipidome in response to allylic hydroperoxide allergens Lim-2-OOH and Lin-6/7-OOH, together with the experimental contact allergen DNFB. These allergens are able to upregulate and downregulate certain lipid classes to a varying degree.