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The Effect of the Endocrine Disrupting Chemical Bisphenol A on Pro‐opiomelanocortin, Circadian Rhythm and Neuroinflammatory Marker Gene Expression in Hypothalamic Cell Models

Obesity is a global health crisis that has doubled in prevalence since 1980 and is associated with co‐morbidities, such as type 2 diabetes mellitus and circadian rhythm disruption. Therefore, understanding the cellular mechanisms responsible for obesity has relevance for improving human health. A number of endocrine‐disrupting chemicals, such as bisphenol A (BPA), an industrial chemical present in 95% of human urine samples, have been linked to obesity. However, the effect of BPA on the pro‐opiomelanocortin (POMC) neurons of the hypothalamus has yet to be explored. POMC neurons produce a precursor polypeptide that is cleaved into the anorexigenic peptide MSH, known to inhibit feeding behaviour. Altering POMC expression could therefore disrupt energy homeostasis in the hypothalamus, ultimately leading to weight gain. We hypothesized that BPA induces a neuroinflammatory response to alter the gene expression of POMC, thereby impairing feeding regulation. We also hypothesized that BPA may alter the expression of circadian clock genes. This study utilized two characterized hypothalamic neuronal models, the adult‐derived mHypoA‐POMC/GFP‐2 and embryonic mHypoE‐43/5 cell‐lines. Both cell‐lines were chosen for their expression of inflammatory markers, circadian genes and POMC transcripts. We examined the effect of 100 M BPA on the transcription of POMC, pro‐inflammatory genes IL6, NFκB, IκB, and the endoplasmic reticulum (ER) stress marker CHOP, over a 24 h timecourse by real‐time quantitative PCR (RT‐qPCR). Analysis of circadian clock genes Bmal1, Per2 and Rev‐Erb was also undertaken. In the mHypoA‐POMC/GFP‐2 cell‐line, BPA significantly upregulated POMC, IL6, IκB and CHOP mRNA levels. Furthermore, BPA significantly altered the mRNA levels of Bmal1 and Per2 at specific time points, indicating a disruption of the circadian clock. Similar to the adult‐derived POMC line, BPA significantly altered the mRNA levels of POMC, IL6, IκB, NFκB and CHOP, Bmal1, Rev‐Erb and Per2 in the mHypoE‐43/5 cell‐line. Given the altered expression of feeding‐related peptides, BPA could have an inflammation‐mediated mechanism of action that is being explored. Additionally, the disruption of circadian genes by BPA could further alter cellular function necessary for proper energy homeostasis. In ongoing studies, we are employing anti‐inflammatory compounds to determine whether induction of inflammation causes POMC and circadian gene expression disruption. In conclusion, our study is the first to explore the direct effects of BPA on POMC neuronal cell models, demonstrating altered expression of genes associated with obesity. We therefore have the necessary tools to understand this process at a more mechanistic level.