In patients with systemic sclerosis (SSc), the relationship between innate immune activation, represented by increased expression of interferon (IFN)-regulated genes, and vascular injury/activation, manifest by increased endothelin-1 (ET-1), endothelin converting enzyme-1 (ECE1) and intercellular adhesion molecule-1, is uncertain.
Signaling pathways regulating intercellular adhesion molecule 1 expression by endothelin 1: comparison with interleukin-1beta in normal and scleroderma dermal fibroblasts.
Only IgG from SSc sera that were positive for antifibroblast antibody (AFA) induced a dose-dependent up-regulation of ICAM-1 expression and IL-6 production, enhancement of U937 cell adhesion, and increased levels of IL-1alpha, IL-1beta, and IL-6 mRNA in fibroblasts.
We investigated the potential modulation of cell surface intercellular adhesion molecule-1 (ICAM-1) expression and function by ET-1 in fibroblasts grown from skin biopsies of scleroderma (SSc) patients compared with healthy controls.
Increased expression of intercellular adhesion molecule 1 (ICAM-1) on systemic sclerosis fibroblasts is responsible for increased binding of T cells to those fibroblasts through ICAM-1/lymphocyte function-associated antigen 1 interactions. beta 1 and beta 2 integrins, ICAM-1, and endothelial leukocyte adhesion molecule 1 all may be involved in the homing of lymphocytes to involved skin in patients with systemic sclerosis.
These observations suggest that the complex interactions of beta 1 and beta 2 integrins, as well as ELAM-1 and ICAM-1, may be intimately involved in the pathogenesis of SSc, perhaps by mediating the homing and targeting of pathogenetic lymphocytes to the affected tissues.
MAb against intercellular adhesion molecule type 1 (ICAM-1) and LFA-1 also prevented binding of T lymphocytes, but had a more marked effect on adhesion to SSc fibroblasts than to normal fibroblasts; they also completely abolished the increased binding to fibroblasts treated with interleukin-1 alpha, tumor necrosis factor alpha, and interferon-gamma.
The increase in the number of ICAM-1-high fibroblasts in scleroderma patients may facilitate T cell activation and lymphokine production, and thus indirectly contribute to the fibrotic process.