Disruption of the Non-classical ERα-PCYT1A-Phospholipid-NR5A2 Axis impairs kisspeptin signaling in hypothalamic KNDy neurons and drives postpartum depression

Postpartum depression (PPD) is a common neuroendocrine disorder associated with the rapid decline in estrogen levels following childbirth. However, the precise molecular mechanisms through which estrogen withdrawal disrupts hypothalamic signaling, particularly in key reproductive neurons, remain poorly understood. To investigate this, we developed an in vitro PPD-like model using primary embryonic hypothalamic Kisspeptin/Neurokinin B/Dynorphin (KNDy) neurons subjected to estradiol (E2) exposure and subsequent withdrawal. Multi-omics analyses, including proteomics, lipidomics, and transcriptomics, were integrated with functional studies. We discovered that the transcription factor NR5A2 is critical for initiating Kisspeptin rebound after short-term E2 withdrawal by directly binding to the Kiss1 promoter. However, under prolonged withdrawal conditions, this recovery fails. This failure is driven by a disruption in neuronal phospholipid metabolism, characterized by the downregulation of the rate-limiting enzyme PCYT1A and a consequent reduction in specific phosphatidylcholines, PC(32:1) and LPC(24:0), which we identified as crucial stabilizers of NR5A2 activity. Further mechanistic analysis revealed that prolonged E2 withdrawal impairs non-classical Estrogen Receptor α (ncERα) signaling, which upstream regulates PCYT1A expression. Reactivating this ncERα pathway restored phospholipid synthesis and NR5A2-mediated Kisspeptin expression. The entire ncERα-PCYT1A-phospholipid-NR5A2-Kiss1 axis was validated in an in vivo rat model of PPD, where direct intracerebroventricular administration of phospholipids successfully alleviated depressive-like behaviors. Our study defines a novel signaling cascade that links estrogen dynamics with neuronal lipid metabolism to control postpartum neuroendocrine recovery, offering fresh mechanistic and therapeutic insights into PPD.