Increased serum levels of adhesion molecules ICAM-1 and VCAM-1 in systemic sclerosis are not specific for pulmonary manifestations

Vivek Thakkar, Karen A. Patterson, Wendy Stevens, Michelle Wilson, Janet Roddy, Joanne Sahhar, Susanna Proudman, Pravin Hissaria, Mandana Nikpour

Studies suggest elevated serum intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) levels may be markers of pulmonary arterial hypertension in systemic sclerosis (SSc-PAH). We sought to evaluate whether ICAM-1 and VCAM-1 levels are useful screening biomarkers for incident SSc-PAH. In this cross-sectional study, four groups were selected from the Australian Scleroderma Cohort Study: group 1 (n = 15) had definite PAH; group 2 (n = 19) had interstitial lung disease (ILD); group 3 (n = 30) were SSc-controls; and group 4 (n = 34) were healthy controls. Serum ICAM-1 and VCAM-1 levels were measured using the Millipore Milliplex MAP Human 2-Plex Panel. There were no differences in ICAM-1 levels in the PAH versus ILD group (263.0 ± 85.4 vs 380.4 ± 168.3 ng/mL, p = 0.136), SSc-controls (263.0 ± 85.4 vs 253.1 ± 98.0 ng/mL, p = 1.00), or healthy controls (263.0 ± 85.4 vs 201.8 ± 57.2 ng/mL, p = 0.093). Similarly, there were no differences in VCAM-1 level in PAH versus ILD groups (1476.2 ± 434.9 vs 1424.8 ± 527.6 ng/mL, p = 1.00) and SSc-controls (1476.2 ± 434.9 vs 1409.5 ± 341.1 ng/mL, p = 1.00). SSc subjects had significantly higher levels of ICAM-1 (297.4 ± 134.0 vs 201.8 ± 57.2 ng/mL, p < 0.0001) and VCAM-1 compared to healthy controls (1432.7 ± 427.4 vs 1125.6 ± 273.4 ng/mL, p < 0.0001). Neither ICAM-1 nor VCAM-1 is a specific screening biomarker of SSc-PAH. Instead, increased levels of these adhesion molecules in SSc, irrespective of pulmonary complications, suggest that they may play a role in SSc pathogenesis.