Investigating the effects of the disease-modifying anti-rheumatic drug methotrexate on the vascular endothelium

Abstract

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease that associates with increased mortality from cardiovascular disease (CVD). Methotrexate (MTX), a folate analogue used as disease-modifying anti-rheumatic drug (DMARD), reduces CVD morbidity and mortality in RA patients, possibly by improving endothelial function. The aim of this study was to investigate the molecular effects of MTX in quiescent and activated vascular endothelial cells (EC). In EC pre-treated with tumour necrosis factor (TNF)-alpha, MTX independently increased the activity of mitogen-activated protein kinase (MAPK) p38 and Akt and caused cell cycle arrest due to folate depletion. In contrast, MTX did not affect cell signalling, proliferation or gene expression in EC exposed to different types of shear stress. To tease out the underlying mechanism, folate or one carbon metabolism (OCM) was investigated in EC cultivated under static or shear stress conditions. Endothelial OCM was fundamentally altered by shear stress, with potentially important implications for MTX uptake and function. Using endothelial colony forming cells (ECFC) isolated from RA patients before and after treatment initiation with MTX and hydroxychloroquine, it was shown that systemic inflammation primes ECFC towards a pro-inflammatory state that may be reversible with DMARD treatment. These data suggest that MTX acts on vascular EC in a folate-dependent manner. However, since endothelial OCM was largely downregulated by shear stress, this implies that MTX may have limited direct effects on EC in vivo and provides a potential explanation for the controversies around the vascular effects of folate and anti-folate therapy. Although findings in ECFC from patients with RA support anti-inflammatory effects of MTX containing therapy, the data in this thesis do not support a direct MTX-mediated anti-atherogenic effect on the endothelium but suggest that the drug may limit EC dysfunction in combination with other drugs indirectly by reducing systemic inflammation.Open Acces