SEROTONIN LIMITS GENERATION OF CHROMAFFIN CELLS DURING ADRENAL ORGAN DEVELOPMENT

Adrenal gland is the major organ releasing catecholamines and regulating our stress response. The mechanisms balancing adrenal hormone-producing cells and protecting against neuroblastoma or other tumors are still enigmatic. Here we revealed that adrenergic chromaffin cells release serotonin (5HT), which acts upon their immediate progenitor “bridge” cells via 5-hydroxytryptamine receptor 3A (HTR3A). Consistently, the aggressive HTR3Ahigh human neuroblastoma cell lines reduce proliferation in response to HTR3A-specific agonists, suggesting the mechanism of anti-tumor protection. Physiological increase of 5HT in vivo caused prolongation of a cell cycle length in “bridge” progenitors leading to smaller chromaffin population and changing the balance of hormones and behavioral patterns in resulting adult rodents. These behavioral effects and smaller adrenals were mirrored in a progeny of pregnant females subjected to experimental stress, suggesting novel maternal-fetal link controlling developmental adaptations. Finally, these findings corresponded to a size-distribution of adrenals found in wild rodents with different coping strategies. Wnt1-Cre+/-;R26RTomato+/+ E13.5 embryos prenatally treated with 5HTP (40 mg/kg) or vehicle (PBS) for control at E11.5 and E12.5 were harvested in iced cold PBS for smartseq2 sequencing

肾上腺是分泌儿茶酚胺（catecholamines）、调节机体应激反应的核心器官。目前，肾上腺激素分泌细胞的稳态维持机制，以及其抵御神经母细胞瘤（neuroblastoma）等肿瘤的潜在调控通路仍不明晰。本研究揭示：肾上腺素能嗜铬细胞（adrenergic chromaffin cells）可释放血清素（5-羟色胺，5HT），后者通过5-羟色胺受体3A（HTR3A）作用于其直接祖细胞——“桥接”祖细胞。实验结果一致显示，高表达HTR3A的侵袭性人神经母细胞瘤细胞系在HTR3A特异性激动剂处理后增殖受到抑制，这提示了该通路的抗肿瘤保护机制。体内血清素的生理性升高可延长“桥接”祖细胞的细胞周期（cell cycle）时长，进而导致嗜铬细胞群体规模缩小，并改变成年啮齿类动物的激素平衡与行为模式。该行为改变与肾上腺体积缩小的表型，同样出现在经受实验性应激的孕鼠后代中，这提示存在一条全新的母胎调控通路以控制发育适应性过程。最后，上述研究发现与不同应对策略的野生啮齿类动物的肾上腺体积分布特征相符。我们对在胚胎发育E11.5与E12.5时经产前给予5-羟色氨酸（5HTP，40 mg/kg）或对照溶剂（磷酸盐缓冲液，PBS）的Wnt1-Cre+/-;R26RTomato+/+ E13.5胚胎，于冰预冷的磷酸盐缓冲液中取材，并采用Smart-seq2测序开展转录组分析。