Signalling profile of circulating leucocytes of subjects with Raynaud's phenomenon in relation to systemic sclerosis:...

Raynaud's phenomenon (RP) is a common symptom and may be an early sign of systemic sclerosis (SSc). To identify biomarkers distinguishing whether RP is associated with definitive SSc, we used phosphospecific flow cytometry to measure phosphorylated (p) signalling molecules [signal transducers and activators of transcription (pSTAT3, pSTAT6, pSTAT4), pSmad2/3, nuclear factor-κB (pNF-κB)] in peripheral blood leucocytes of RP patients undergoing nailfold videocapillaroscopy.

Leucocyte subsets (CD14⁺ monocytes, CD4⁺ and CD8⁺ T cells, CD19⁺ B cells) were identified by surface markers, and phosphorylation was measured after cytokine or lipopolysaccharide stimulation. Medical records were reviewed 9-10 years later, comparing RP subjects who developed SSc (SSc⁺, n = 8) with those who did not (SSc^-, n = 17) and healthy controls (HCs, n = 8).

SSc⁺ patients had significantly higher constitutive pSmad2/3 levels in CD4⁺ T cells than SSc^- or HCs (p = 0.005 and p = 0.034). SSc⁺ and SSc^- had higher stimulated pSTAT3(pY705) levels in CD4⁺ T cells than HCs (p = 0.001 and p = 0.026). SSc⁺ had higher stimulated pSTAT6 levels in CD4⁺ T cells compared with HCs (p = 0.017) and in CD19⁺ B cells compared with SSc^- and HCs (p = 0.006 and p < 0.001). SSc⁺ had higher stimulated pSTAT4 levels in CD4⁺ T cells compared with SSc^- and HCs (p = 0.004 and p = 0.037) and in CD8⁺ T cells compared with SSc^- (p = 0.007). No significant differences were found in pNF-κB and pSTAT3(pS727) levels.

The results give insights into the pathogenesis of SSc. Smad2/3, STAT3(pY705), STAT6, and STAT4 pathways may serve as novel SSc biomarkers.