Objective: Approximately 15–20% of patients with giant-cell arteritis (GCA) develop ischaemic complications often preceded by transient ischaemia. The expression of the endothelin (ET) system in GCA lesions was investigated to assess its relationship with the development of ischaemic complications.
Methods: Plasma ET-1 was quantified by immunoassay in 61 patients with biopsy-confirmed GCA and 16 healthy donors. ET-1, endothelin-converting enzyme (ECE-1) and endothelin receptor (ETAR and ETBR) messenger RNA were measured by real-time quantitative reverse transcriptase–PCR in temporal arteries from 35 of these patients and 19 control arteries. Proteins were measured by immunoassay and Western blot.
Results: ET-1 concentration was increased at the protein level in temporal artery samples from GCA patients compared with controls (0.98 (SEM 0.32) vs 0.28 (SEM 0.098) fmol/mg, p = 0.028). ECE-1, ETAR and ETBR/actin ratios (Western blot) were also significantly higher in GCA patients. Intriguingly, mRNA expression of ET-1, ECE-1 and both receptors was significantly reduced in GCA lesions compared with control arteries. When investigating mechanisms underlying these results, platelet-derived growth factor and IL-1β, present in GCA lesions, were found to downregulate ET-1 mRNA in cultured human temporal artery-derived smooth muscle cells. Glucocorticoid treatment for 8 days did not result in significantly decreased endothelin tissue concentration (0.87 (SEM 0.2) vs 0.52 (SEM 0.08); p = 0.6). Plasma endothelin concentrations were higher in patients with ischaemic complications (1.049 (SEM 0.48) vs 1.205 (SEM 0.63) pg/ml, p = 0.032).
Conclusions: The endothelin system is increased at the protein level in GCA lesions creating a microenvironment prone to the development of ischaemic complications. Recovery induced by glucocorticoids is delayed, indicating persistent exposure to endothelin during initial treatment.
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Funding This study was supported by the Ministerio de Educación y Ciencia and Fondo Europeo de Desarrollo Regional (FEDER) (SAF 05/06250 and SAF 08/04328) and Marató-TV3 (06/0710). GE-F and MCC are supported by the Instituto de Salud Carlos III.
Competing interests None.
Ethics approval The study was approved by the Ethics Committee of the Hospital Clínic.
Patient consent Obtained.
The results were partly presented at the 71st Annual Meeting of the American College of Rheumatology. Boston, USA, November 2007.
Provenance and Peer review Not commissioned; externally peer reviewed.