Cocktail Effect of Endocrine Disrupting Chemicals: Application to Chlorpyrifos in Lavender Essential Oils

Abstract

Chlorpyrifos is a pesticide that is toxic to human health and has been banned for the past decade. Due to its persistent and bioaccumulative properties, chlorpyrifos is still present in soil. Pregnant women can be exposed to chlorpyrifos through drinking water and herbal products, such as essential oils (EOs), resulting in adverse effects to the mother and fetus. Our objective was to evaluate and compare the potential endocrine disrupting effects of chlorpyrifos "free" or in contaminated lavender EO. We studied the release of four hormones and the activation of the P2X7 cell death receptor in human placental JEG-Tox cells as key biomarkers of endocrine toxicity for pregnant women (hPlacentox assay). We observed that "free" chlorpyrifos disrupted placental hormones and activated the P2X7 receptor, whereas chlorpyrifos in lavender EO disrupted only the placental hormones. We confirm that chlorpyrifos can be classified as an endocrine disrupting chemical (EDC) for pregnant women and point out that its endocrine disrupting effect may not be apparent when present in lavender EOs. Our results reveal the existence of specific reverse cocktail effects that may have protective properties against EDCs.

Keywords: P2X7 receptor; chlorpyrifos; lavender essential oil; polypeptide hormones; steroid hormones.

Figure 1

Cell viability was evaluated using the alamar blue assay after incubation of JEG-Tox cells with chlorpyrifos at 0.23 × 10⁻⁷ mg/mL, 0.23 × 10⁻⁶ mg/mL and 0.23 × 10⁻⁵ mg/mL or two lavender essential oils (EOs 1 and 2) at 0.17 × 10⁻³%, 0.17 × 10⁻²% and 0.17 × 10⁻¹% for 72 h. Triton^® X-100 at 0.016% was used as a positive control. Significance levels were *** p < 0.001.

Figure 2

Quantification of the release of (a) progesterone, (b) estradiol, (c) h-hCG and (d) hPL after incubation of JEG-Tox cells with chlorpyrifos 0.23 × 10⁻⁷ mg/mL, 0.23 × 10⁻⁶ mg/mL and 0.23 × 10⁻⁵ mg/mL or two lavender EOs (1 and 2) at 0.17 × 10⁻³%, 0.17 × 10⁻²% and 0.17 × 10⁻¹% for 72 h. AP at 10 µM, BPA at 20 µM, DES at 3.75 µM was used as a positive control. The significance levels were * p < 0.1 and ** p < 0.01.

Figure 3

P2X7 receptor activation was evaluated using the YO-PRO-1^® assay after incubation of JEG-Tox cells with chlorpyrifos at 0.23 × 10⁻⁷ mg/mL, 0.23 × 10⁻⁶ mg/mL and 0.23 × 10⁻⁵ mg/mL or two lavender EOs (1 and 2) at 0.17 × 10⁻³%, 0.17 × 10⁻²% and 0.17 × 10⁻¹% for 72 h. BPA at 20 µM was used as a positive control. The significance levels were * p < 0.1 and ** p < 0.01.