Premenstrual Dysphoric Disorder (PMDD) Is Associated With Estradiol-Dependent Aberrations in Intracellular Calcium Homeostasis and the Endoplasmic Reticulum Stress Response

Abstract

Premenstrual Dysphoric Disorder (PMDD) is characterized by debilitating mood symptoms that vary with the menstrual cycle, with evidence suggesting that symptoms are due to an abnormal cellular response to reproductive hormones. However, the molecular and functional correlates of this abnormal hormone response are poorly understood. We performed RNA sequencing (RNAseq) on lymphoblastoid cell lines (LCLs) derived from women with PMDD and asymptomatic controls under untreated (i.e., steroid-free), estradiol-treated (E2), and progesterone-treated (P4) conditions. First, in a module-level analysis of RNAseq data, weighted gene correlation network analysis (WGCNA) identified four modules whose expression showed significant diagnosis x hormone interactions, including one module that was enriched for genes related to neuronal and synaptic function. Enrichment analysis of module hub genes underlying these neuronal enrichment signals revealed multiple pathways related to intracellular calcium dynamics. Next, in a gene-level analysis, a generalized linear model was fitted to RNAseq data and identified 1522 genes differentially responsive to E2 (E2-DRGs) and 480 differentially responsive to P4 (P4-DRGs). Analysis of top E2-DRGs revealed several genes (NUCB1, GCC2, GOLGB1) that were members of a physically interacting network involved in endoplasmic reticulum (ER)-Golgi body function. Independent qPCR validation reproduced a significant diagnosis x E2 interaction (F(1, 24) = 7.008, p = 0.0141) in NUCB1, a regulator of intracellular calcium and the ER stress response. Finally, we used a thapsigargin (Tg) challenge assay to test whether E2 induces differences in calcium homeostasis and the ER stress response in PMDD, measured by the spliced-to-unspliced XBP1 ratio. Upon Tg treatment, PMDD LCLs had a 27% decreased XBP1 splicing response compared to controls, and pre- treatment with E2 resulted in a statistically significant 38% decreased response (p = 0.005), with a significant diagnosis x treatment interaction (F(3,33) = 3.508, P = 0.0259). Our results suggest that hormone-dependent aberrations in intracellular calcium handling and the ER stress response may contribute to the pathophysiology of PMDD.