Increased expression of soluble fractalkine (CX3CL1) in systemic sclerosis – possible role in vascular inflammation

Abstract

IntroductionThe pathogenesis of systemic sclerosis (SSc) involves interplay between obliterative vasculopathy in multiple vascular beds, inflammation, autoimmunity and progressive fibrosis. Vascular injury and activation are the earliest and possibly primary events in the pathogenesis of SSc. Aim of the workTo determine levels of serum soluble fractalkine (sFKN) and its receptor CX3CR1 in peripheral blood mononuclear cells (PBMCs) in systemic sclerosis (SSc) patients and healthy controls. In addition, to assess any possible association between sFKN and clinical features of SSc. Patients and methodsSerum levels of soluble fractalkine (sFKN, CX3CL1) assessed by enzyme linked immunosorbent assay (ELISA) and expression of its receptor (CX3CR1) on peripheral blood mononuclear cells by flow cytometric analysis, were measured in 18 systemic sclerosis (SSc) patients and 15 age and sex matched healthy controls. The degree of skin involvement was estimated by modified Rodnan skin thickness score (mRSS), pulmonary involvement was assessed in all patients by high resolution computerized tomography (HRCT) and pulmonary function tests (PFTs). ResultsSerum sFKN levels and expression of its receptor CX3CR1 were significantly elevated in SSc patients than in healthy controls (P<0.0.05). SSc patients with pulmonary fibrosis had sFKN levels three times higher than those without PF. Serum sFKN correlated inversely with forced vital capacity of lungs (FVC%) but correlated positively with severity of pulmonary fibrosis, extent of skin fibrosis (mRSS), pitting scars, skin ulcers, anti topo-isomerase1antibody and CRP. ConclusionSerum sFKN may play an important role in the pathogenesis of SSc, including tissue inflammation and vascular injury, hence, its measurement may be a useful serologic marker for the diagnosis and follow up of pulmonary and skin complications. So strategies to target CX3CL1–CX3CR1 interaction could provide a new therapeutic approach in SSc, potentially by blocking endothelial cell injury, leucocyte infiltration, and vascular injury.