Hypoxia-mediated impairment of the mitochondrial respiratory chain inhibits the bactericidal activity of macrophages.

In infected tissues oxygen tensions are low. As innate immune cells have to operate under these conditions, we analyzed the ability of macrophages (Mφ) to kill Escherichia coli or Staphylococcus aureus in a hypoxic microenvironment. Oxygen restriction did not promote intracellular bacterial growth but did impair the bactericidal activity of the host cells against both pathogens.

Toll-like receptor activation and hypoxia use distinct signaling pathways to stabilize hypoxia-inducible factor 1α (HIF1A) and result in differential HIF1A-dependent gene expression.

HIF1A is a transcription factor that plays a central role for the adaptation to tissue hypoxia and for the inflammatory response of myeloid cells, including DCs. HIF1A is stabilized by hypoxia but also by TLR ligands under normoxic conditions. The underlying signaling events leading to the accumulation of HIF1A in the presence of oxygen are still poorly understood.

Hypoxia-inducible protein 2 is a novel lipid droplet protein and a specific target gene of hypoxia-inducible factor-1.

Hypoxia-inducible protein 2 (HIG2) has been implicated in canonical Wnt signaling, both as target and activator. The potential link between hypoxia and an oncogenic signaling pathway might play a pivotal role in renal clear-cell carcinoma characterized by constitutive activation of hypoxia-inducible factors (HIFs), and hence prompted us to analyze HIG2 regulation and function in detail. HIG2 was up-regulated by hypoxia and HIF inducers in all cell types and mouse organs investigated and abundantly expressed in renal clear-cell carcinomas.

Small interfering RNA (siRNA) delivery into murine bone marrow-derived macrophages by electroporation.

Selective gene silencing by RNA interference (RNAi) is a valuable tool for the targeted manipulation of the development and/or function of cells. Using a fluorescein-labeled non-silencing siRNA duplex, we established a protocol for the electroporation of primary mouse macrophages which routinely yielded >95% transfected cells. Electroporation of siRNAs directed against MAPK1 and CD86 led to an efficient knock-down of cellular protein in bone marrow-derived mouse macrophages (BM-Mphi).