Estrogen receptors in giant cell arteritis. An immunocytochemical, western blot and RT-PCR study

Giant cell arteritis (GCA) is a chronic form of vasculitis which predominantly affects women over 50 years of age. The aim of this study was to analyse the presence of estrogen receptor alpha (ER) in the temporal arteries of patients with GCA.

Inflamed temporal artery biopsies from 43 GCA patients were stained with monoclonal antibodies to two different segments of the ER and compared with non-inflamed arteries from age- and sex-matched controls who had not received a clinical diagnosis of GCA. The protein that was extracted from 4 GCA-positive biopsies and 4 non-GCA controls was analysed using the Western blot method with a monoclonal antibody to ER. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis using primer pairs specific to ER-cDNA was performed on the total RNA from 4 GCA-positive biopsies and 4 non-GCA controls.

The inflamed arteries expressed distinct cytoplasmic immunoreactivity to ER in activated mononuclear inflammatory cells and in giant cells. Biopsies from GCA patients and controls displayed cytoplasmic ER positivity in smooth muscle cells. Western blot analysis revealed two bands corresponding to approximately 64 and 54 kDa, respectively, in the inflamed arteries and controls. In the inflamed biopsies and non-GCA controls, RT-PCR analysis revealed a strong band corresponding to approximately 670 bp, as expected, and a weaker band corresponding to approximately 440 bp.

In inflamed arteries from GCA patients, smooth muscle cells, activated mononuclear inflammatory cells and giant cells express cytoplasmic ER. Non-inflamed control arteries also express cytoplasmic ER in smooth muscle cells. The accumulation of cytoplasmic ER may suggest the involvement of estrogen not only in GCA but also in normal vascular aging. The results justify further investigations into the pathogenetic roles of estrogen metabolism in GCA.