[HTML][HTML] Induction of CD36 and thrombospondin-1 in macrophages by hypoxia-inducible factor 1 and its relevance in the inflammatory process

D Ortiz-Masia, I Díez, S Calatayud, C Hernandez… - PLoS …, 2012 - journals.plos.org
D Ortiz-Masia, I Díez, S Calatayud, C Hernandez, J Cosín-Roger, J Hinojosa, JV Esplugues
PLoS One, 2012journals.plos.org
Inflammation is part of a complex biological response of vascular tissue to pathogens or
damaged cells. First inflammatory cells attempt to remove the injurious stimuli and this is
followed by a healing process mediated principally by phagocytosis of senescent cells.
Hypoxia and p38-MAPK are associated with inflammation, and hypoxia inducible factor 1
(HIF-1) has been detected in inflamed tissues. We aimed to analyse the role of p38-MAPK
and HIF-1 in the transcriptional regulation of CD36, a class B scavenger receptor, and its …
Inflammation is part of a complex biological response of vascular tissue to pathogens or damaged cells. First inflammatory cells attempt to remove the injurious stimuli and this is followed by a healing process mediated principally by phagocytosis of senescent cells. Hypoxia and p38-MAPK are associated with inflammation, and hypoxia inducible factor 1 (HIF-1) has been detected in inflamed tissues. We aimed to analyse the role of p38-MAPK and HIF-1 in the transcriptional regulation of CD36, a class B scavenger receptor, and its ligand thrombospondin (TSP-1) in macrophages and to evaluate the involvement of this pathway in phagocytosis of apoptotic neutrophils. We have also assessed HIF-1α, p38-MAPK and CD36 immunostaining in the mucosa of patients with inflammatory bowel disease. Results show that hypoxia increases neutrophil phagocytosis by macrophages and induces the expression of CD36 and TSP-1. Addition of a p38-MAPK inhibitor significantly reduced the increase in CD36 and TSP-1 expression provoked by hypoxia and decreased HIF-1α stabilization in macrophages. Transient transfection of macrophages with a miHIF-1α-targeting vector blocked the increase in mRNA expression of CD36 and TSP-1 during hypoxia and reduced phagocytosis, thus highlighting a role for the transcriptional activity of HIF-1. CD36 and TSP-1 were necessary for the phagocytosis of neutrophils induced by hypoxic macrophages, since functional blockade of these proteins undermined this process. Immunohistochemical studies revealed CD36, HIF-1α and p38-MAPK expression in the mucosa of patients with inflammatory bowel disease. A positive and significant correlation between HIF-1α and CD36 expression and CD36 and p38-MAPK expression was observed in cells of the lamina propria of the damaged mucosa. Our results demonstrate a HIF-1-dependent up-regulation of CD36 and TSP-1 that mediates the increased phagocytosis of neutrophils by macrophages during hypoxia. Moreover, they suggest that CD36 expression in the damaged mucosa of patients with inflammatory bowel disease depends on p38-MAPK and HIF-1 activity.
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