Increased Siglec-1 expression in monocytes of patients with primary biliary cirrhosis

To evaluate Siglec-1 protein (CD169) and mRNA levels in peripheral blood monocytes of patients with primary biliary cirrhosis (PBC) and investigate its role in PBC pathogenesis by looking for correlations between Siglec-1 expression and key PBC associated biochemical indices.

FACS analysis was used to identify the percentage of peripheral blood monocytes positive for both CD14 and Siglec-1 in (a) 45 PBC patients, (b) 40 patients with liver cirrhosis after hepatitis B infection and (c) 36 healthy controls. Siglec-1 mRNA was measured by real-time RT-PCR and serum biomarkers by routine biochemistry.

The percentage of CD14-Siglec-1 double positive cells was significantly higher (p< 0.01) in PBC patients than in healthy controls or cirrhosis post-hepatitis patients (13.68 +/- 2.44%, 1.0 +/- 0.2 %, and 4.1 +/- 0.5 %, respectively). Siglec-1 mRNA expression in the PBC group was 3.42 times higher than in healthy controls (p < 0.01).

We investigated the role of Siglec-1 in PBC by assessing its expression in mononuclear cells of PBC patients and levels of secreted cytokines in cell supernatants after Siglec-1 RNA interference. It is possible that elevated Siglec-1 expression in peripheral blood monocytes of PBC patients is correlated with monocyte-mediated inflammatory responses during the development of PBC.