Background Giant-cell arteritis (GCA) is an inflammatory disease of large/medium-sized arteries, frequently involving the temporal arteries (TA). Inflammation-induced vascular remodelling leads to vaso-occlusive events. Circulating endothelin-1 (ET-1) is increased in patients with GCA with ischaemic complications suggesting a role for ET-1 in vascular occlusion beyond its vasoactive function.
Objective To investigate whether ET-1 induces a migratory myofibroblastic phenotype in human TA-derived vascular smooth muscle cells (VSMC) leading to intimal hyperplasia and vascular occlusion in GCA.
Methods and results Immunofluorescence/confocal microscopy showed increased ET-1 expression in GCA lesions compared with control arteries. In inflamed arteries, ET-1 was predominantly expressed by infiltrating mononuclear cells whereas ET receptors, particularly ET-1 receptor B (ETBR), were expressed by both mononuclear cells and VSMC. ET-1 increased TA-derived VSMC migration in vitro and α-smooth muscle actin (αSMA) expression and migration from the media to the intima in cultured TA explants. ET-1 promoted VSMC motility by increasing activation of focal adhesion kinase (FAK), a crucial molecule in the turnover of focal adhesions during cell migration. FAK activation resulted in Y397 autophosphorylation creating binding sites for Src kinases and the p85 subunit of PI3kinases which, upon ET-1 exposure, colocalised with FAK at the focal adhesions of migrating VSMC. Accordingly, FAK or PI3K inhibition abrogated ET-1-induced migration in vitro. Consistently, ET-1 receptor A and ETBR antagonists reduced αSMA expression and delayed VSMC outgrowth from cultured GCA-involved artery explants.
Conclusions ET-1 is upregulated in GCA lesions and, by promoting VSMC migration towards the intimal layer, may contribute to intimal hyperplasia and vascular occlusion in GCA.
- Giant-cell arteritis
- vascular inflammation
- cell migration
- focal adhesion kinase
- 5-bisphosphate 3-kinase (PI3K)
- Src kinase
- extracellular signal -regulated kinase
- matrix metaloproteinases. Heterotrimeric G proteins.
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Contributors MCC and EPR designed the experiments and wrote the manuscript. EPR, NTG and MCB performed the experimental work. EL and MS contributed preliminary results essential for the development of the study. MAA, GEF, SPG and JHR contributed to clinical selection and TA biopsy collection. SP and RL produced and provided BQ123. All authors read, made improvements and approved the final version.
Funding This study was supported by the Ministerio de Economía y Competitividad (SAF 14/57708-R, Marató TV3 2014/ 20150730) and Instituto de Salud Carlos III (PIE13/00033), both cofunded by Fondo Europeo de Desarrollo Regional (FEDER), Unión Europea, una manera de hacer Europa. SP and RL were supported by DGICYT-Spain (CTQ2015-67870-P) and Generalitat de Catalunya (2014 SGR 137).
Competing interests None declared.
Patient consent Obtained.
Ethics approval Ethics Committee Hospital Clinic of Barcelona.
Provenance and peer review Not commissioned; externally peer reviewed.
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