American journal of physiology. Lung cellular and molecular physiology

Importance of kynurenine in pulmonary hypertension.

PMID 28705908


The tryptophan metabolite kynurenine is significantly increased in pulmonary arterial hypertension (PAH) patients, and it is a potent vasodilator of systemic arteries. Our aim was to investigate the role of kynurenine in the pulmonary circulation. Serum tryptophan, kynurenine, and kynurenic acid levels were measured in 20 idiopathic PAH (IPAH) patients, 20 healthy controls, and 20 patients with chronic lung disease or metabolic syndrome without PH. Laser-dissected pulmonary arteries from IPAH and control lungs were tested for the expression of indoleamine-2, 3-dioxygenase (IDO), the rate-limiting enzyme for the conversion from tryptophan to kynurenine. Acute effects of kynurenine were tested in pulmonary vascular preparations, two different models of chronic pulmonary hypertension (PH), and in human pulmonary arterial smooth muscle cells (hPASMCs). In IPAH vs. control serum, kynurenine was significantly elevated (3.6 ± 0.2 vs. 2.6 ± 0.1 µM,