Transcriptomic Analysis of Effects of Developmental PCB Exposure in the Hypothalamus of Female Rats

This study investigated the consequences of perinatal exposure to Aroclor 1221 (A1221), a weakly estrogenic polychlorinated biphenyl (PCB) mixture and known endocrine-disrupting chemical (EDC), in female rats. Previous work has shown behavioral and physiological effects of A1221, and the current study extended this work to comprehensive transcriptomic profiling of two hypothalamic regions involved in the control of reproduction: the arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV). Female Sprague-Dawley rats were fed a cookie treated with a small volume of A1221 (1 mg/kg) or vehicle (3% DMSO in sesame oil) during pregnancy from gestational days 8-18 and after birth from postnatal (P) days 1-21, exposing the offspring via placental and lactational transfer. In female offspring, developmental, physiological, and hormonal effects of A1221 were relatively modest. However, because prior work has implicated this exposure in neurobehavioral disruptions, we sought to determine whether developmental programming of the brain transcriptome could underlie these phenotypes. We used 3' targeted RNA sequencing in the hypothalamus (arcuate nucleus, anteroventral periventricular nucleus) of experimental females at P8, 30, and 60 and identified significant alterations in gene expression and gene ontology (GO) terms in an age- and tissue-specific manner. Most notably, terms related to synaptic signaling, neurotransmitter regulation, immune response, and cellular structure were identified. Changes in pathways associated with synaptic functions and cellular metabolism were further identified, indicating that A1221 exposure can impact neurodevelopmental and neuroendocrine processes at a molecular level, even in the absence of overt developmental changes. These findings of molecular reprogramming may explain the behavioral effects of A1221 and highlight novel molecular targets and pathways that warrant further investigation to understand the effects of EDCs on the developing brain.