Evaluation of Placental Toxicity of Five Essential Oils and Their Potential Endocrine-Disrupting Effects

Abstract

Pregnant women may use EOs in case of morning sickness, nausea, stress management, etc. Little is known about the potential danger that EOs represent for the placenta and therefore for the pregnancy. Our aim was to explore and compare the placental toxicity and potential endocrine disrupting effects of niaouli, orange, tea tree, wintergreen and ylang-ylang EOs, and their key compounds: 4-terpineol, 1,8-cineol, limonene, methyl salicylate and benzyl salicylate. We studied the release of four hormones and the activation of P2X7 receptor in JEG-Tox human placental cells as key biomarkers for endocrine toxicity. We observed that niaouli, orange, tea tree, wintergreen and ylang-ylang EOs and their key components disrupted at least one of the studied hormones but none of them activated the P2X7 cell death receptor. The tested EOs appear then to be more hormonal modulators rather than EDCs in human placental cells. The hormonal effects observed with the key components were very different from those observed with the EOs. EOs are very complex mixtures, and it is essential to study whole EOs rather than their components individually in safety assessment.

Keywords: P2X7 receptor; endocrine disruptor; essential oil; hormones; placental toxicity.

Figure 1

Effects of niaouli EO and 1,8-cineol on (a) cell viability (Alamar Blue assay), on released hormones: (b) progesterone (c) estradiol, (d) h-hCG and (e) hPL and on (f) P2X7 receptor activation (YO-PRO-1 assay) were evaluated, after incubation of JEG-Tox cells for 72 h. Triton^® X-100 at 0.016%, bisphenol A (BPA) at 20 µM, 4-tert-amylphenol (AP) at 10 µM and diethylstilbestrol (DES) at 3.75 µM were used as positive controls. The significance thresholds were * p < 0.1, ** p < 0.01, *** p < 0.001, # p < 0.1, and ## p < 0.01.

Figure 2

Effects of orange EO and limonene on (a) cell viability (Alamar Blue assay), on released hormones: (b) progesterone (c) estradiol, (d) h-hCG, (e) hPL and on (f) P2X7 receptor activation (YO-PRO-1 assay) were evaluated, after incubation of JEG-Tox cells for 72 h. Triton^® X-100 at 0.016%, bisphenol A (BPA) at 20 µM, 4-tert-amylphenol (AP) at 10 µM and diethylstilbestrol (DES) at 3.75 µM are used as positive controls. The significance thresholds were * p < 0.1, ** p < 0.01, *** p < 0.001, # p < 0.1, and ## p < 0.01.

Figure 3

Effects of tea tree EO and 4-terpineol on (a) cell viability (Alamar Blue assay), on released hormones: (b) progesterone (c) estradiol, (d) h-hCG, (e) hPL and on (f) P2X7 receptor activation (YO-PRO-1 assay) were evaluated, after incubation of JEG-Tox cells for 72 h. Triton^® X-100 at 0.016%, bisphenol A (BPA) at 20 µM, 4-tert-amylphenol (AP) at 10 µM and diethylstilbestrol (DES) at 3.75 µM are used as positive controls. The significance thresholds were * p < 0.1, ** p < 0.01, *** p < 0.001 and # p < 0.1.

Figure 4

Effects of wintergreen EO and methyl salicylate on (a) cell viability (Alamar Blue assay), on released hormones: (b) progesterone (c) estradiol, (d) h-hCG, and (e) hPL and on (f) P2X7 receptor activation (YO-PRO-1 assay) were evaluated, after incubation of JEG-Tox cells for 72 h. Triton^® X-100 at 0.016%, bisphenol A (BPA) at 20 µM, 4-tert-amylphenol (AP) at 10 µM and diethylstilbestrol (DES) at 3.75 µM are used as positive controls. The significance thresholds were * p < 0.1, ** p < 0.01, *** p < 0.001 and # p < 0.1.

Figure 5

Effects of ylang-ylang EO and benzyl salicylate on (a) cell viability (Alamar Blue assay), on released hormones: (b) progesterone (c) estradiol, (d) h-hCG, and (e) hPL and on (f) P2X7 receptor activation (YO-PRO-1 assay) were evaluated, after incubation of JEG-Tox cells for 72 h. Triton^® X-100 at 0.016%, bisphenol A (BPA) at 20 µM, 4-tert-amylphenol (AP) at 10 µM and diethylstilbestrol (DES) at 3.75 µM are used as positive controls. The significance thresholds were * p < 0.1, ** p < 0.01, *** p < 0.001 and #### p < 0.0001.