Filaggrin Polymorphisms and the Uptake of Chemicals through the Skin-A Human Experimental Study

BACKGROUND: The filaggrin protein is important for skin barrier structure and function. Loss-of-function (null) mutations in the filaggrin gene FLG may increase dermal absorption of chemicals. OBJECTIVE: The objective of the study was to clarify if dermal absorption of chemicals differs depending on FLG genotype. METHOD: We performed a quantitative real-time polymerase chain reaction (qPCR)-based genetic screen for loss-of-function mutations (FLG null) in 432 volunteers from the general population in southern Sweden and identified 28 FLG null carriers. In a dermal exposure experiment, we exposed 23 FLG null and 31 wild-type (wt) carriers to three organic compounds common in the environment: the polycyclic aromatic hydrocarbon pyrene, the pesticide pyrimethanil, and the ultraviolet-light absorber oxybenzone. We then used liquid-chromatography mass-spectrometry to measure the concentrations of these chemicals or their metabolites in the subjects' urine over 48 h following exposure. Furthermore, we used long-range PCR to measure FLG repeat copy number variants (CNV), and we performed population toxicokinetic analysis. RESULTS: Lag times for the uptake and dermal absorption rate of the chemicals differed significantly between FLG null and wt carriers with low (20-22 repeats) and high FLG CNV (23-24 repeats). We found a dose-dependent effect on chemical absorption with increasing lag times by increasing CNV for both pyrimethanil and pyrene, and decreasing area under the urinary excretion rate curve (AUC((0-40h))) with increasing CNV for pyrimethanil. FLG null carriers excreted 18% and 110% more metabolite (estimated by AUC((0-40h))) for pyrimethanil than wt carriers with low and high CNV, respectively. CONCLUSION: We conclude that FLG genotype influences the dermal absorption of some common chemicals. Overall, FLG null carriers were the most susceptible, with the shortest lag time and highest rate constants for skin absorption, and higher fractions of the applied dose excreted. Furthermore, our results indicate that low FLG CNV resulted in increased dermal absorption of chemicals.

Automated summary

The study showed that FLG genotype influences the dermal absorption of some common chemicals. FLG null carriers were the most susceptible, with the shortest lag time and highest rate constants for skin absorption, excreting higher fractions of the applied dose. Additionally, results indicated that low FLG CNV resulted in increased dermal absorption of chemicals.