Autoantibodies to angiotensin and endothelin receptors in systemic sclerosis induce cellular and systemic events associated with disease pathogenesis

We conclude that angiotensin and endothelin-receptor activation via anti-AT&sub1;R and anti-ETAR Abs mediate pathogenic effects, indicating their contribution to pathogenesis of SSc. Therefore, anti-AT&sub1;R and anti-ETAR Abs could provide novel targets for therapeutic intervention in the treatment of SSc.

Anti-AT&sub1;R and anti-ETAR Ab-positive immunoglobulin G (IgG) from SSc patients (SSc-IgG) was used for experiments. Healthy donor IgG served as a normal control, and AT&sub1;R and ETAR activation was inhibited by antagonists. Protein expression was measured with ELISA, mRNA expression with real time-PCR, endothelial repair with a scratch assay, and collagen expression with immunocytochemistry. Transendothelial neutrophil migration was measured with a culture insert system, and neutrophil ROS activation with immunofluorescence. Neutrophils in bronchoalveolar lavage fluids (BALFs) were analyzed microscopically after passive transfer of SSc-IgG or NC-IgG into naïve C57BL/6J mice. KC plasma levels were quantified by a suspension array system. Histologic analyses were performed by using light microscopy.

Anti-AT&sub1;R and anti-ETAR Ab-positive SSc-IgG induced activation of human microvascular endothelial cells (HMEC-1). Elevated protein and mRNA levels of the proinflammatory chemokine interleukin-8 (IL-8, CXCL8) and elevated mRNA levels of the vascular cell adhesion molecule-1 (VCAM-1) were induced in HMEC-1. Furthermore, activation of HMEC-1 with SSc-IgG increased neutrophil migration through an endothelial cell layer and activation of reactive oxygen species (ROS). SSc-IgG decreased HMEC-1 wound repair and induced type I collagen production in healthy donor skin fibroblasts. Effects of migration, wound repair, and collagen expression were dependent on the Ab-levels. Passive transfer of anti-AT1R and anti-ETAR Ab-positive SSc-IgG into naïve C57BL/6J mice increased neutrophil BALF counts. In parallel, increased levels of the murine functional IL-8 homologue, chemokine KC, were found in the plasma of SSc-IgG-treated mice as well as structural alterations of the lungs. Conclusions: We conclude that angiotensin and endothelin-receptor activation via anti-AT&sub1;R and anti-ETAR Abs mediate pathogenic effects, indicating their contribution to pathogenesis of SSc. Therefore, anti-AT&sub1;R and anti-ETAR Abs could provide novel targets for therapeutic intervention in the treatment of SSc.