Background: Phenylalanine levels are associated with pulmonary hypertension in metabolic profiling clinical studies. However, the pathophysiologic role of phenylalanine on pulmonary circulation is still unclear. We experimentally addressed the direct impact of phenylalanine on pulmonary circulation in rats and explored the underlying molecular pathway. Methods and results: Phenylalanine was injected intraperitoneally into Sprague-Dawley rats (400 mg/100g body weight) as a single dose or daily in a chronic manner for 2, 3 and 4 weeks. Chronic injection of phenylalanine induced pulmonary hypertension with time-dependent severity evidenced by elevated pulmonary artery pressure and pulmonary vascular resistance, as well as pulmonary artery and right ventricular hypertrophy. Using tandem mass spectrometry analysis, we found a quick 2-fold increase in blood level of phenylalanine 2 hours following injection. This increase led to a significant accumulation of phenylalanine in lung after 4 hours which remained sustained at up to 3-fold increase after 4 weeks. In addition, cellular thermal shift assay with lung tissues from phenylalanine-injected rats reveals the binding of phenylalanine to the calcium-sensing receptor (CaSR). In vitro experiments with cultured pulmonary arterial smooth muscle cells showed that phenylalanine activated CaSR as indicated by the increase in intracellular calcium content, which was attenuated or diminished by the inhibition or knockdown of CaSR. Finally, the global knockout or lung-specific knockdown of CaSR significantly attenuated phenylalanine-induced pulmonary hypertension. Conclusions: Chronic phenylalanine injection induces pulmonary hypertension through binding to CaSR and its subsequent activation.

中文翻译：

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苯丙氨酸通过钙敏感受体的激活诱导肺动脉高压。

背景：在代谢谱分析临床研究中，苯丙氨酸水平与肺动脉高压相关。然而，苯丙氨酸对肺循环的病理生理作用仍不清楚。我们实验性地解决了苯丙氨酸对大鼠肺循环的直接影响，并探讨了潜在的分子途径。方法和结果：苯丙氨酸以单剂量或每天2次，3周和4周的慢性方式腹膜内注射到Sprague-Dawley大鼠（400 mg / 100g体重）中。长期注射苯丙氨酸可引起肺动脉高压，其严重程度与时间有关，表现为肺动脉压力升高，肺血管阻力增加以及肺动脉和右心室肥大。使用串联质谱分析，我们发现注射2小时后苯丙氨酸的血药浓度迅速增加了2倍。这种增加导致4小时后肺中苯丙氨酸的大量积累，并在4周后维持高达3倍的增加。此外，对来自注射苯丙氨酸的大鼠的肺组织进行细胞热位移分析，揭示了苯丙氨酸与钙敏感受体（CaSR）的结合。用培养的肺动脉平滑肌细胞进行的体外实验表明，苯丙氨酸激活的CaSR表现为细胞内钙含量的增加，而钙含量的增加则被CaSR的抑制或抑制所减弱或减弱。最后，CaSR的整体敲除或肺特异性敲除显着减轻了苯丙氨酸引起的肺动脉高压。结论：