The Global Plastics Treaty: An Endocrinologist's Assessment

Plastics are everywhere. They are in many goods that we use every day. However, they are also a source of pollution. In 2022, at the resumed fifth session of the United Nations Environment Assembly, a historic resolution was adopted with the aim of convening an Intergovernmental Negotiating Committee to develop an international legally binding instrument on plastic pollution, including in the marine environment, with the intention to focus on the entire life cycle of plastics. Plastics, in essence, are composed of chemicals. According to a recent report from the secretariat of the Basel, Rotterdam, and Stockholm conventions, around 13 000 chemicals are associated with plastics and plastic pollution. Many of these chemicals are endocrine-disrupting chemicals and, according to reports by members of the Endocrine Society and others, exposure to some of these chemicals causes enormous costs due to the development of preventable diseases. The global plastics treaty brings the opportunity for harmonized, international regulation of chemicals with endocrine disrupting properties present in plastic products.

Benzophenones alter autophagy and ER stress gene expression in pancreatic beta cells in vitro

Benzophenones (BPs) are endocrine disruptors frequently used in sunscreens and food packaging as UV blockers. Our goal was to assess the effect of benzophenone 2 (BP2) and 3 (BP3) on gene expression related to autophagy process and ER stress response in pancreatic beta cells. To that end, the mouse pancreatic beta cell line MIN6B1 was treated with 10 µM BP2 or BP3 in the presence or absence of the autophagy-inhibitor chloroquine (CQ, 10 µM) or the autophagy-inducer rapamycin (RAPA, 50 nM) during 24 h. BP3 inhibited the expression of the autophagic gene Ulk1, and additional effects were uncovered when autophagy was modified by CQ and RAPA. BP3 counteracted CQ-induced Lamp2 expression but did not compensate CQ-induced Sqstm1/p62 gene transcription, neither BP2. Nevertheless, the BPs did not alter the autophagic flux. In relation to ER stress, BP3 inhibited unspliced and spliced Xbp1 mRNA levels in the presence or absence of CQ, totally counteracted CQ-induced Chop gene expression, and partially reverted CQ-induced Grp78/Bip mRNA levels, while BP2 also partially inhibited Grp78/Bip mRNA induction by CQ. In conclusion, BPs, principally BP3, affect cellular adaptive responses related to autophagy, lysosomal biogenesis, and ER stress in pancreatic beta cells, indicating that BP exposure could lead to beta cell dysfunction.

In-Vitro Exposure to Endocrine Disruptors Alters Inflammatory Markers in Whole Hypothalami and Immortalized GnRH Neurons

Bisphenol A (BPA), a monomer of polycarbonate plastics, and Benzophenones (BPs), used as UV-filters, are endocrine disrupting chemicals (EDC) found in everyday products. Previously, we showed that the in-vitro exposure to BPA decreased Kiss-induced GnRH expression in GN11 cells (donated by Dr. Susan Wray, NIH), immature GnRH neurons, and that exposure to all the EDC decreased Kiss-induced GnRH gene expression in GT1-7 cells (donated by Dr. Pamela Mellon, UCSD), mature GnRH neurons. In this study, we analyzed the effect of in-vitro exposure to the same EDC (BPA, BP2 or BP3, Sigma, 1x10^-9 M) or medium as control (C) in mature GnRH neurons (GT1-7 cells), and isolated hypothalami from adult Balb/c males on Glial fibrillary acidic protein (GFAP) and cytokine gene expression. Cells were exposed to the compounds for 12 or 24 h, in DMEM (high glucose) with charcoal-stripped FBS, and the hypothalami for 6 h to the EDC, in Krebs-Ringer buffer. After the incubations, RNA was extracted using Tri-Reagent (Molecular Research Center, OH, USA), 1-2 µg RNA was reverse transcribed and Real-Time PCR performed using specific primers. Results were expressed as Mean±SE and analyzed by T-test or ANOVA using Statistica v12 (StatSoft Inc, USA) Twenty-four hour BPA exposure increased il18 in GT1-7 cells (C=1.0±0.04, BPA=1.2±0.1, T-test p<0.05, n=7), whereas neither BP2 nor BP3 had an effect on il18 expression (ANOVA: ns, n=7). When il6 was analyzed, 24-hour BPA decreased its expression relative to C and to 12-hour BPA, whereas BP3 had a dual effect depending on the time-point analyzed, increasing the expression at 12-hour stimulation and decreasing it after 24-hour stimulation (DMSO-12h=0.82±0.08, DMSO-24h= 1.01±0.13, BPA-12h=1.00±0.11, BPA-24h=0.68±0.06, BP2-12h=0.75±0.12, BP2-24h=0.82±0.18, BP3-12h=1.20±0.10, BP3-24h=0.83±0.05; Repeated Measures Two-way ANOVA: BPA-24h different from DMSO-24h and BPA-12h p<0.05, BP3-12h different from DMSO-12h and from BP3-24h p<0.05, n=4). In the hypothalami, 6-hour BPA exposure increased gfap gene expression (C=0.8±0.2, BPA=1.7±0.4; T-test p<0.05, n=9), whereas neither BP2 nor BP3 had any significant effect (C=0.8±0.2, BP2=1.4±0.3, BP3=1.0±0.3, ANOVA ns, n=9). There was no significant change in il18, il6 or il1b gene expression in whole hypothalami with any of the EDC tested (ANOVA ns). Our results show that the EDC herein studied have the potential to alter the inflammatory state of mature GnRH neurons and to activate astrocytes in the hypothalamus. The pattern for cytokine expression in the whole tissue could be different from the one observed in GnRH neurons, as the hypothalamus contain multiple cell types, and effects can be different in the different cells. More experiments are needed to dissect the mechanisms involved in the effects observed. Funding: CONICET, ANPCyT, UBA, International Society for Neurochemistry, Asoc. ORT Arg., Fund. R. Barón, Fund. Williams.

Differential gonadotropin releasing hormone (GnRH) expression, autoregulation and effects in two models of rat luteinized ovarian cells

GnRH has been suggested to participate in corpus luteum function. Here we studied the expression of GnRH mRNA and peptide in two models of rat luteinized tissues: ovarian cells from PMSG-hCG treated prepubertal rats (SPO) and from intrasplenic ovarian tumors (Luteoma). A GnRH autoregulatory effect was evaluated as well as its action on cell proliferation and apoptosis. GnRH mRNA was present in SPO, isolated corpora lutea from SPO and Luteoma from 1 week to 7 months of development. In vitro cultures of Luteoma cells expressed 2-fold higher GnRH mRNA and 10-fold higher GnRH peptide than SPO cells. Buserelin (GnRH analog) increased GnRH mRNA and peptide expression in SPO but not in Luteoma cells. While basal proliferation was very low in Luteoma cells, SPO cells showed a significant increase in cell number by both the thymidine and the MTS methods after 72 h in culture. Buserelin induced a decrease in cell number in both cell types to a similar degree. Although basal apoptosis levels were higher in SPO than in Luteoma cells, Buserelin-induced apoptosis was only detected in Luteoma cells after 48 h treatment. These results show that the two types of rat, luteinized tissues, Luteoma and SPO, markedly differed in some intrinsic properties and in their local GnRH systems. Luteoma cells proliferate very weakly, express and secrete high amounts of GnRH, do not show an autoregulatory effect and respond to the decapeptide with apoptosis stimulation. In contrast SPO cells proliferate significantly, secrete low levels of GnRH but possess a positive, autoregulatory mechanism and respond to GnRH stimulation with impairment of proliferation.