21 March 2019 : Original article
Effect of Serum Deprivation Stress on Signal Induction Regulatory Protein-Alpha (SIRP-Alpha)-Mediated Erythrophagocytosis by MacrophagesZakaria Hindi1ABCDEFG*, AbdAllah Gad1ABCDE, Courtney Jarvis2ABCDEF, Talal Zahoor1AB, Craig Spellman1AE, Stephanie Filleur2ABCDEF
Med Sci Monit Basic Res 2019; 25:100-106
BACKGROUND: Hemophagocytic lymphohistiocytosis (HLH) is a rare syndrome that involves loss of macrophages’ self-cells recognition resulting in auto-phagocytosis of erythrocytes, leukocytes, and platelets and leading to multi-system effects. The pathogenesis of HLH is unclear but can be explained by malfunction of the physiologic inhibitory pathway through interaction between macrophage SIRP-α and erythrocyte CD 47. The goal of the present study was to evaluate if erythrocytes phagocytosis occurs as a result of altered macrophage SIRP-α expression during inflammatory/stressful conditions as seen in HLH.
MATERIAL AND METHODS: RAW264.7 macrophages were cultured in serum-free media (SFM) and complete media (CM) to simulate stressful and physiologic conditions, respectively. CD47+ mouse erythrocytes were used to test interactions with macrophages at different stages. SIRP-α expressions and phagocytosis assays were measured and analyzed at different steps. The study was in vitro and used murine cells to simulate in vivo human interactions.
RESULTS: SIRP-α expressions and phagocytosis rates were higher in SFM compared to CM. Interestingly, after adding SIRP-α blocking antibodies (Ab), phagocytosis rates significantly decreased.
CONCLUSIONS: Serum deprivation and LPS/INF-Gamma induction resulted in increased SIRP-α expression and erythrophagocytosis. Using SIRP-α Ab during this condition decreased the rate of erythrophagocytosis, which indicates that SIRP-α receptor can have pro-phagocytic activity.
Keywords: Lymphohistiocytosis, Hemophagocytic, Macrophages, CD47 Antigen, Culture Media, Serum-Free, Erythrocytes, Gene Expression Regulation, Phagocytosis, RAW 264.7 Cells, RNA, Messenger, Receptors, Immunologic
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