FHL2 is a novel target in pulmonary arterial hypertension

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): - Longfonds Nederland Background/ Objectives Pulmonary arterial hypertension (PAH) is a fatal disorder characterized by excessive proliferation of endothelial (EC) and smooth muscle cells, and impaired BMP signaling in small lung arteries. The LIM-only protein FHL2 is expressed in the vessel wall in ECs and smooth muscle cells and plays a crucial role in vessel wall homeostasis. However, the molecular mechanisms how FHL2 exerts its effects and its role in pulmonary artery EC function remain unclear. Here, we investigated the effect of FHL2 on EC proliferation and unraveled the underlying mechanisms involved. Methods/Results We found that FHL2 is highly expressed in lungs of PAH rats compared to control rats as evidenced by qPCR and western blot analysis. Human microvascular ECs (MVECs) derived from lungs of PAH patients displayed enhanced expression of FHL2. Ectopic expression of FHL2 in MVECs significantly increased mRNA levels of BMPR2 and Id1. To substantiate these results, luciferase assays were performed using BMP response element reporter construct and found that FHL2 increases Id1 expression. Furthermore, overexpression of FHL2 decreased TNF-α induced expression of pro-inflammatory cytokines. Finally, ectopic expression of FHL2 reduced proliferation of ECs. Conclusion Our data indicate that FHL2 is a novel negative regulator of MVEC proliferation through enhancing BMP signaling and inhibiting inflammation. Modulation of FHL2 may potentially represent a novel therapeutic strategy for the treatment of PAH.