Red Blood Cell-Conditioned Media from Non-Alcoholic Fatty Liver Disease Patients Contain Increased MCP1 and Induce TNF-α Release

Background: Non-alcoholic fatty liver disease (NAFLD) constitutes a global pandemic. An intricate network among cytokines and lipids possesses a central role in NAFLD pathogenesis. Red blood cells comprise an important source of both cytokines and signaling lipids and have an important role in molecular crosstalk during immunometabolic deregulation. However, their role in NAFLD has not been thoroughly investigated. Methods: Conditioned media from erythrocytes derived from 10 NAFLD patients (4 men, 6 women, aged 57.875 +/- 15.16) and 10 healthy controls (4 men, 6 women, aged 39.3 +/- 15.55) was analyzed for the cytokines IFN-gamma, TNF-alpha, CCL2, CCL5, IL-8, IL-1 beta, IL-12p40, IL-17, MIP-1 beta, the signaling lipids sphingosine-1phosphate (S1P) and lysophosphatidic acid (LPA), and cholesterol. Their effect on the cytokine profile released by RAW 264.7 macrophages was also studied. Results: MCP1 levels were greater in conditioned growth medium from NAFLD patient erythrocytes than in that from healthy controls (37 +/- 40 vs 6.51 +/- 5.63 pg/ml). No statistically significant differences were found between patients and healthy controls with regard to SIP, LPA, cholesterol, or eight other cytokines. TNF-a release by RAW 264.7 cells was greater after incubation with patient-derived erythrocyte-conditioned medium than in medium without RAW 264.7 cells from either healthy or NAFLD subjects. Conclusions: Erythrocytes may contribute to liver infiltration by monocytes, and macrophage activation, partially due to CCL2 release, in the context of NAFLD.