Hypoxia-inducible factor (HIF)1α is a
transcription factor involved in cellular metabolism and regulation of immune cell effector functions. Here, we studied the role of HIF1α in myeloid cells during
pneumonia caused by the major causative pathogen, Streptococcus pneumoniae (Spneu). Mice deficient for HIF1α in myeloid cells (LysMcreHif1αfl/fl) were generated to study the in vitro responsiveness of bone marrow-derived macrophages (BMDMs) and alveolar macrophages (AMs) to the Gram-positive bacterial wall component
lipoteichoic acid (LTA) and heat-killed Spneu, and the in vivo host response after
infection with Spneu via the airways. Both BMDMs and AMs released more
lactate upon stimulation with LTA or Spneu, indicative of enhanced glycolysis; HIF1α-deficiency in these cells was associated with diminished
lactate release. In BMDMs, HIF1α-deficiency resulted in reduced secretion of
tumor necrosis factor (TNF)α and
interleukin (IL)-6 upon activation with Spneu but not LTA, while HIF1α-deficient AMs secreted less TNFα and
IL-6 in response to LTA, and TNFα after Spneu stimulation. However, no difference was found in the host response of LysMcreHif1αfl/fl mice after Spneu
infection as compared to controls. Similar in vivo findings were obtained in neutrophil (Mrp8creHif1αfl/fl) HIF1α-deficient mice. These data suggest that myeloid HIF1α is dispensable for the host defense during
pneumococcal pneumonia.