Hypoxia modulates expression of the 70-kD heat shock protein and reduces Leishmania infection in macrophages

Hypoxia, a microenvironmental factor present in diseased tissues, has been recognized as a specific metabolic stimulus or a signal of cellular response. Experimental hypoxia has been reported to induce adaptation in macrophages such as differential migration, elevation of proinflammatory cytokines and glycolytic enzyme activities, and decreased phagocytosis of inert particles. In this study we demonstrate that although exposure to hypoxia (5% O-2, 5% CO2, and balanced N-2) did not change macrophage viability, or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cleavage and proliferation, it significantly reduced expression of the 70-kD heat shock protein (HSP70), which was restored to prehypoxia levels after reoxygenation. The influence of low oxygen tension on macrophage functional activity was also studied, i.e. the ability of these cells to maintain or resist infection by a microorganism. We demonstrate that macrophages from two different sources (a murine cell line and primary cells) exposed to hypoxia were efficiently infected with Leishmania amazonensis, but after 24 h showed a reduction in the percentage of infected cells and of the number of intracellular parasites per macrophage, indicating that hypoxia induced macrophages to kill the intracellular parasites. These results support the notion that hypoxia, a microenvironmental factor, can modulate macrophage protein expression and functional activity. Copyright (C) 2004 National Science Council, ROC and S. Karger AG, Basel.11684785

The Influence of Low Oxygen on Macrophage Response to Leishmania Infection

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Hypoxia (low oxygen tension) is a common feature of inflamed and infected tissues. The influence of hypoxia on macrophage responses to micro-organisms has only recently been studied. This study demonstrates that hypoxia induced macrophages to control Leishmania amazonensis, an intracellular parasite that causes cutaneous and cutaneous metastatic lesions. The mechanisms that contribute to the control of macrophages against L. amazonensis infection under a hypoxic microenvironment are not known. Nitric oxide, TNF-alpha, IL-10 or IL-12 is not responsible for the decrease in parasitism under hypoxia. Live L. amazonensis entry or exocytosis of internalized particles as well as energetic metabolism was not impaired in infected macrophages; no apoptosis-like death was detected in intracellular parasites. Reactive oxygen species (ROS) is likely to be involved, because treatment with antioxidants N-acetylcysteine (NAC) and ebselen inhibits the leishmanicidal effect of macrophages under hypoxia. Leishmania amazonensis infection induces macrophages to express hypoxia-inducible factor-1 (HIF-1 alpha) and -2 (HIF-2 alpha). Data indicate that hypoxia affects the microbial activities and protein expression of macrophages leading to a different phenotype from that of the normoxic counterpart and that it plays a role in modulating Leishmania infection.742165175Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES