HTR1B regulates mitochondrial homeostasis and mitophagy by activating the ERK/ MAPK signalling pathway during human embryonic arrest.

Background: Previous studies have shown that serotonin and its receptors are widely distributed in mammalian reproductive tisssues and play an important role in embryonic development. However, the specific effects of the serotonergic system on embryonic arrest (EA) and the underlying mechanism require further investigation.

Methods: Chorionic villi were collected from patients with EA and healthy pregnant women. Western blotting (WB) and immunohistochemistry (IHC) were used to detect serotonin receptor 1B (HTR1B) levels and evaluate mitochondrial function. Additionally, HTR-8/SVneo cells were transfected with an HTR1B overexpression plasmid. Quantitative real-time polymerase chain reaction(qRT-PCR), Cell Counting Kit-8 (CCK-8), and wound healing assays were utilized to evaluate mitophagy level, cell proliferation and cell migration, respectively.

Results: We discovered elevated HTR1B levels in the chorionic villi of the patients with EA compared to controls. Concurrently, we observed enhanced levels of nucleus-encoded proteins including mitofilin, succinate dehydrogenase complex subunit A (SDHA), and cytochrome oxidase subunit 4 (COXIV), along with the mitochondrial fusion protein optic atrophy 1(OPA1), fission proteins mitochondrial fission protein 1(FIS1) and mitochondrial fission factor (MFF) in the EA group. Additionally, there was an excessive mitophagy levels in EA group. Furthermore, a notable activation of mitogen-activated protein kinase (MAPK) signaling pathway proteins including extracellular regulating kinase (ERK), c-Jun N-terminal kinase (JNK), and P38 was observed in the EA group. By overexpressing HTR1B in HTR-8/SVneo cells, we observed a significant reduction in cell proliferation and migration. HTR1B overexpression also caused an increase in levels of SDHA and FIS1, as well as an upregulation of mitophagy. Notably, the ERK inhibitor U0126 effectively mitigated these effects.

Conclusion: These findings show that HTR1B influences mitochondrial homeostasis, promoting excessive mitophagy and impairing cell proliferation and migration by activating the MAPK signalling pathway during post-implantation EA. Therefore, HTR1B may serve as a potential therapeutic target for patients with EA.