ITE inhibits growth of human pulmonary artery endothelial cells

ABSTRACT

Aim: Pulmonary arterial hypertension (PAH), a deadly disorder is associated with excessive growth of human pulmonary artery endothelial (HPAECs) and smooth muscle (HPASMCs) cells. Current therapies primarily aim at promoting vasodilation, which only ameliorates clinical symptoms without a cure. 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) is an endogenous aryl hydrocarbon receptor (AhR) ligand, and mediates many cellular function including cell growth. However, the roles of ITE in human lung endothelial cells remain elusive. Herein, we tested a hypothesis that ITE inhibits growth of human pulmonary artery endothelial cells via AhR. Materials and Methods: Immunohistochemistry was performed to localize AhR expression in human lung tissues. The crystal violet method and MTT assay were used to determine ITE's effects on growth of HPAECs. The AhR activation in HPAECs was confirmed using Western blotting and RT-qPCR. The role of AhR in ITE-affected proliferation of HPAECs was assessed using siRNA knockdown method followed by the crystal violet method. Results: Immunohistochemistry revealed that AhR was present in human lung tissues, primarily in endothelial and smooth muscle cells of pulmonary veins and arteries, as well as in bronchial and alveolar sac epithelia. We also found that ITE dose- and time-dependently inhibited proliferation of HPAECs with a maximum inhibition of 83% at 20 µM after 6 days of treatment. ITE rapidly decreased AhR protein levels, while it increased mRNA levels of cytochrome P450 (CYP), family 1, member A1 (CYP1A1) and B1 (CYP1B1), indicating activation of the AhR/CYP1A1 and AhR/CYP1B1 pathways in HPAECs. The AhR siRNA significantly suppressed AhR protein expression, whereas it did not significantly alter ITE-inhibited growth of HPAECs. Conclusions: ITE suppresses growth of HPAECs independent of AhR, suggesting that ITE may play an important role in preventing excessive growth of lung endothelial cells.

KEYWORDS:

• ITE
• Aryl hydrocarbon receptor
• Growth
• Pulmonary artery endothelial cells

Acknowledgments

We would like to thank Loretta A. Uttech-Hanson, Research Administration Grant Writer & Project Manager at the Office of Grant Writing & Collaborative Project Development, School of Medicine and Public Health, University of Wisconsin-Madison for English language editing.

Declaration of interest

The authors report no conflicts of interest.

Funding

This work was supported by the US NIH grant PO1 HD38843 to JZ, a Dept. of Ob/Gyn R & D Grant, University of Wisconsin-Madison to JZ, Science & Technology Innovation Fund of Guangdong Medical University (Grant No. STIF201116) to SAH.