Non-alcoholic steatohepatitis patients exhibit reduced CD47, and increased sphingosine, cholesterol and MCP1 levels in the erythrocyte membranes

Abstract

ABSTRACTNon-alcoholic steatohepatitis (NASH) constitutes a significant cause of deaths, liver transplantations and economic costs worldwide. Despite extended research, investigations on the role of erythrocytes are scarce. Red blood cells from experimental animals and human patients with NASH, present phosphatidylserine exposure which is then recognized by Kupffer cells. This event leads to erythrophagocytosis, and amplification of inflammation through iron disposition. In addition, it has been shown that erythrocytes from NASH patients release the chemokine MCP1, leading to increased TNF-α release from macrophages RAW 264.7. However, erythrophagocytosis can also be caused by reduced CD47 levels. In addition, increased MCP1 release could be either signal-induced, or caused by higher MCP1 levels on the erythrocyte membrane. Finally, erythrocyte efferocytosis could provide additional inflammatory metabolites. In this study, we measured the erythrocyte membrane levels of CD47 and MCP1 by ELISA, and cholesterol and sphingosine with thin-layer chromatography. 18 patients (8 men, 10 women aged 56.7±11.5 years) and 14 healthy controls (7 men, 7 women aged 39.3±15.5 years) participated in our study. The erythrocyte CD47 levels were decreased in the erythrocyte membranes of NASH patients (844±409 pg/ml) compared to healthy controls (2969±1936 pg/ml) with P(Healthy>NAFLD)=99.1%, while the levels of MCP1 were increased in NASH patients (389±255 pg/ml), compared to healthy controls (230±117 pg/ml) with P(Healthy<NAFLD)=88.9%. Moreover, in erythrocyte membranes there was a statistically significant accumulation of sphingosine and cholesterol in NASH patients, compared to healthy controls. Our results imply that erythrocytes release chemotactic “find me” signals (MCP1), while containing reduced “do not eat me” signals (CD47). These molecules can lead to erythrophagocytosis. Next, increased “goodbye” signals (sphingosine and cholesterol) could augment inflammation by metabolic reprogramming.