Open AccessPreferential Silent Survival of Intracellular Bacteria in Hemoglobin-Primed Macrophages
Author(s) -
Karthik Subramanian,
Imelda Winarsih,
Chandrakumaran Keerthani,
Bow Ho,
Jeak Ling Ding
Publication year - 2014
Publication title -
journal of innate immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.078
H-Index - 64
eISSN - 1662-8128
pISSN - 1662-811X
DOI - 10.1159/000358236
Subject(s) - intracellular , proinflammatory cytokine , intracellular parasite , biology , microbiology and biotechnology , apoptosis , inflammation , immunology , biochemistry
Hemolysis releases hemoglobin (Hb), a prooxidant, into circulation. While the heme iron is a nutrient for the invading pathogens, it releases ROS, which is both microbicidal and cytotoxic, making it a double-edged sword. Previously, we found a two-pass detoxification mechanism involving the endocytosis of Hb into monocytes in collaboration with vascular endothelial cells to overcome oxidative damage. This prompted us to examine the effect of Hb priming on host cell viability and intracellular bacterial clearance during a hemolytic infection. Here, we demonstrate that Hb-primed macrophages harbor a higher intracellular bacterial load but with suppressed apoptosis. p-ERK and p-p38 MAPK were significantly downregulated, with concomitant impairment of Bax and downstream caspases. The Hb-primed cells harboring intracellular bacteria upregulated anti-inflammatory IL-10 and downregulated proinflammatory TNF-α, which further enhanced the infectivity of the neighboring cells. Our findings suggest that opportunistic intracellular pathogens exploit the Hb-scavenging machinery of the host to silently persist within the circulating phagocytes by suppressing apoptosis while escaping immune surveillance.