Phenylalanine induces pulmonary hypertension through calcium-sensing receptor activation

Abstract

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.

Metabolic Reprogramming of the Right Ventricle and Pulmonary Arteries in a Flow-Associated Pulmonary Arterial Hypertension Rat Model

“…Phenylalanine, when substantially increased, is recognized to be involved in numerous pathophysiological processes, such as chronic obstructive pulmonary disease, persistent pulmonary hypertension, and coronary heart disease . Tan et al demonstrated that chronic phenylalanine administration induced PAH through binding to the calcium-sensing receptor and its subsequent activation in rats . According to this finding, they proposed a hypothesis that phenylalanine probably accumulates in the lungs of PAH, which was not previously reported but was confirmed by our current work.…”

“…53 Tan et al demonstrated that chronic phenylalanine administration induced PAH through binding to the calcium-sensing receptor and its subsequent activation in rats. 54 According to this finding, they proposed a hypothesis that phenylalanine probably accumulates in the lungs of PAH, which was not previously reported but was confirmed by our current work. Furthermore, tryptophan, an essential amino acid that could act as a precursor in serotonin production, was found to be upregulated in PAH PAs in our study.…”

Antihypertensive effect and underlying mechanism of tripeptide NCW on spontaneously hypertensive rats using metabolomics analysis

“…90 A study by Tan et al has the opposite view, and phenylalanine could induce pulmonary hypertension via binding to and activating calcium-sensing receptors. 91 Phenylalanine could be converted into tyrosine in the body, and tyrosine is a precursor to the norepinephrine, epinephrine, and dopamine. 92 High levels of these stress hormones are associated with the increased risk of hypertension.…”

Vasodilatory Effect of Guanxinning Tablet on Rabbit Thoracic Aorta is Modulated by Both Endothelium-Dependent and -Independent Mechanism

“…The mechanism of salvianolic acid B is different from that of GXNT, suggesting that the effect of GXNT on CaMKII may come from other active ingredients. In terms of ion channels, there were many compounds with calcium or potassium ion channel activities in vessels, including phenylalanine ( Tan et al, 2020 ), ferulic acid ( Zhou et al, 2017 ), and salvianolic acid B ( Lam et al, 2006 ), and more compounds had the activity in other cells, such as salvianolic acid A in cardiomyocytes ( Bao, 1993 ), isosalvianolic acid C ( Lin et al, 2019 ) in mast cells, and so on. In addition, compounds with calmodulin activity include phenylalanine ( VanScyoc et al, 2002 ), chlorogenic acid ( Tong et al, 2007 ), and salvianolic acid A ( Qiang et al, 2015 ), but only chlorogenic acid was reported to be related to endothelial calmodulin.…”