Many everyday products contain
quaternary ammonium compounds (QAC) and some of them are known to be skin irritants such as
benzalkonium chloride. Others, such as
didecyldimethylammonium chloride, have been shown to cause
allergic contact dermatitis.
Ethylhexadecyldimethylammonium bromide (EHD) is a QAC for which sensitization potential is not clearly known. Therefore, we have studied its mechanism in human keratinocytes (KC), the main cells of the epidermis. We used the well-described human KC cell line KERTr exposed to EHD,
cinnamaldehyde (CinA), a well-known skin sensitizer, and a mixture of both. Since chemical sensitizers are known to activate the
transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF2), leading to cellular detoxification and suppressed proinflammatory
cytokines,
protein or
mRNA expression of NRF2 pathway-related
enzymes and pro-inflammatory
cytokines were investigated by Western blot and RT-qPCR. The activity of the NRF2 pathway on
inflammation was studied by RT-qPCR in NRF2-invalidated KERTr cells. We showed that EHD cannot induce the NRF2 pathway, unlike contact sensitizers like CinA. EHD triggers an inflammatory response by inducing the
mRNA expression of pro-inflammatory
cytokines such as IL-1β or
IL-6. Moreover, mixing EHD and CinA inhibits the effect of CinA on NRF2 expression and mitigates the inflammatory response induced by EHD alone. EHD treatment of KERTr cells in which NRF2 has been invalidated showed an exacerbation of the inflammatory response at the transcriptional level. Hence, EHD may elicit an inflammatory response in KC via the NF-κB pathway, which could lead to irritation when applied to the skin. This
inflammation is negatively controlled by the basal activity of the NRF2 pathway.