Dibutyl Phthalate Rather than Monobutyl Phthalate Facilitates Contact Hypersensitivity to Fluorescein Isothiocyanate in a Mouse Model

Abstract

Dibutyl phthalate (DBP) is a plasticizer used for many consumer products including cosmetics. Potential health concerns regarding DBP include reproductive and developmental toxicity, endocrine disruption and neurotoxicity. DBP is a high priority chemical as to reduction of exposure of children to it. Through reproductive toxicity studies, monobutyl phthalate (MBP) has been proposed to be the active metabolite derived from DBP. We previously demonstrated that DBP activates transient receptor potential ankyrin 1 (TRPA1) cation channels expressed on sensory neurons. We have also shown that DBP enhanced skin sensitization in a fluorescein isothiocyanate (FITC)-induced contact hypersensitivity (CHS) mouse model. Through MBP formation by esterase in the skin, it is possible that MBP exerts a major effect on the biological activity we observed. To test this possibility, we directly compared DBP and MBP. A more than 40-fold higher concentration of MBP as compared with DBP was required for activation of TRPA1 in vitro. Unlike DBP, MBP did not enhance skin sensitization to FITC. These results demonstrated that DBP directly, i.e., not through its metabolite MBP, activates TRPA1 and enhances FITC-CHS. It is noteworthy that butyl benzoate, a related compound, activated TRPA1 and enhanced FITC-CHS.Key words adjuvant; contact hypersensitivity; phthalate; skin; transient receptor potential ankyrin 1; mouse Di-n-butyl phthalate (DBP) is widely used as a plasticizer for consumer products such as paint, adhesives, paper coatings, printing ink and cosmetics.1-5) Regarding children's health concerns, DBP has become one of the highest priority chemicals as to reduction of exposure of children to it in consumer products.6) The health concerns include reproductive and developmental toxicity, endocrine disruption and neurotoxicity. [6][7][8] We have been studying DBP from an immuno-toxicological perspective. We employ a fluorescein isothiocyanate (FITC)-induced contact hypersensitivity (CHS) mouse model, in which DBP is empirically added to the solvent for FITC. 9) We found that DBP acts as an adjuvant during skin sensitization to FITC. 10) We also demonstrated that DBP had the ability to stimulate transient receptor potential ankyrin 1 (TRPA1) cation channels, which are expressed on sensory neurons. 11)We then compared several types of phthalate esters regarding adjuvant effects and TRPA1 stimulation. The immunological and nervous activation effects caused by phthalate esters were found to be well correlated. 11,12) In studies on reproductive toxicity, the role of monobutyl phthalate (MBP) as an active metabolite derived from DBP has been investigated. 13,14) Although studies on reproductive toxicity involve systemic administration of DBP, with which MBP is more likely to be produced in the body, topical application of DBP may yield MBP through esterase in the skin. Thus, there is a possibility that MBP has biological effects as an active metabolite. To examine this idea, we investigated whether MBP is more active than DBP regarding TR...

Update of the risk assessment of di‐butylphthalate (DBP), butyl‐benzyl‐phthalate (BBP), bis(2‐ethylhexyl)phthalate (DEHP), di‐isononylphthalate (DINP) and di‐isodecylphthalate (DIDP) for use in food contact materials

“…Jahreis et al (2018) found such effects even in the second (F2) generation after exposure to BBP of the parent mice. Enhanced antibody responses to thyroid globulin by exposure to DBP was observed by Wu et al (2017), and enhanced skin sensitisation by DBP, DINP, DIDP was described by Kang et al (2016Kang et al ( , 2017; Shen et al (2017) and Kurohane et al (2017).…”

Skin Sensitization to Fluorescein Isothiocyanate Is Enhanced by Butyl Paraben in a Mouse Model

“…Cells Chinese hamster ovary (CHO) cells expressing human TRPA1 (TRPA1-CHO) were used as described previously. 10,11,14,15) Animals Specific pathogen-free female BALB/c mice were purchased from Japan SLC Inc. (Shizuoka, Japan) at 7 weeks of age and held for 1 week before use for acclimatization. They were housed at 22 to 24°C with 50 to 60% humidity under artificial lighting conditions with a 12-h light/ dark cycle.…”

“…TRPA1 Activation in Vitro TRPA1-CHO cells were labeled with a calcium ion-sensitive fluorescent probe, Fluo 4-AM After automatic addition of a test sample (prepared in DMSO) in the presence or absence of a TRPA1 antagonist, HC-030031, the intracellular Ca 2+ level was measured over time with a fluorometric imaging plate reader, FLEXstation II (Molecular Devices, Sunnyvale, CA, U.S.A.) at 37°C as described previously. [12][13][14] The maximal Ca 2+ level was determined using 5 μM ionomycin.…”

“…Cytokine Production by Draining Lymh Nodes Cytokine production by draining lymph nodes after FITC sensitization was determined as described previously. 12,14,16) Mice were sensitized on forelimbs with 0.5% FITC in acetone in the presence or absence of a test sample on days 0 and 7. Twenty-four hours after the second sensitization, a single cell suspension of brachial lymph nodes was individually prepared from each mouse.…”

“…10) We propose a correlation between the ability of TRPA1 activation and the adjuvant effect on FITC-CHS. [10][11][12][13][14] In this study, we compared BP, which may enhance the allergic responses to other antigens, and EP, which may have little effect, using the FITC-CHS model. We found that BP is more potent than EP as to the activation of TRPA1 using a cell line expressing TRPA1.…”