Reelin is overexpressed in the liver and plasma of bile duct ligated rats and its levels and glycosylation are altered in plasma of humans with cirrhosis

Abstract

Reelin is an extracellular matrix protein secreted by a variety of cell types in both embryonic and adult tissues, including the liver. However, the physiological significance of Reelin in normal and cirrhotic liver has thus far not been elucidated. We have investigated Reelin levels in the liver and plasma of bile duct ligated (BDL) rats. We observe a 115% increase in full-length Reelin and its 310- and 180-kDa fragments in liver extracts from BDL rats, compared to sham-operated controls (p = 0.005). The overall increase in protein levels was associated with a 30% increase of Reelin transcripts (p = 0.03). Immunohistochemical analysis demonstrated that hepatic stellate cells are the major source of Reelin in the injured liver. Increased liver Reelin in BDL rats leads to a pronounced 165% increase in the plasma levels (p < 0.001), particularly in the less abundant 180-kDa fragment (300% increase; p < 0.001). The data provides evidence that a fraction of plasma Reelin is synthesized in the liver. In human subjects suffering liver cirrhosis the level of the 180-kDa fragment was also increased by 140% in the plasma (p < 0.001). Analysis of Reelin glycosylation by lectin binding demonstrated that the 180- and predominant 310-kDa Reelin fragments in the plasma of cirrhotic patients are differentially glycosylated compared to non-diseased control subjects. The data show that Reelin is up-regulated in experimental liver cirrhosis and that its levels and glycosylation are altered in plasma from patients with cirrhosis, thereby supporting that Reelin is involved in the pathogenesis of liver disease.