Intracellular C. neoformans infection stimulates increased glycolytic activity in fetal liver-derived alveolar-like macrophages

Abstract

Alveolar macrophages (AMs) serve as a first line of defense against respiratory pathogens, including Cryptococcus neoformans, the primary causative agent of cryptococcosis, a deadly pulmonary mycosis which commonly afflicts immunocompromised individuals. While these innate immune cells are thought to play a pivotal role in controlling the outcome of C. neoformans infections, this critical host-pathogen interaction is more commonly studied in vitro using bone marrow-derived macrophages (BMDM) or immortalized macrophage cell lines that differ in ontogeny and phenotype from AMs. In this work, we characterized fetal liver-derived alveolar-like macrophages (FLAMs) as an alternate model to study the earliest stages of C. neoformans infection. Here, we show that the FLAM steady state transcriptome is more similar to primary AMs than peritoneal macrophages and the macrophage cell lines, RAW264.7 and J774, and that FLAMs exhibit distinct transcriptional responses to IFN{gamma} stimulation and C. neoformans infection compared to J774 cells. Specifically, transcriptome profiling and gene ontology analysis indicate that C. neoformans infection of FLAMs, but not J774 cells, increases the expression of canonical glycolytic genes, including Slc2a1, Pgk1, and Ldha, which is accompanied by a metabolic shift favoring glycolysis. Furthermore, activation or inhibition of hypoxia inducible factor 1 (HIF1) activity utilizing dimethyloxalylglycine (DMOG) and echinomycin, respectively, indicates that the expression of select glycolytic genes in C. neoformans-infected FLAMs is HIF1-dependent. Collectively, our results suggest that FLAMs serve as an appropriate tool for modeling AM:C. neoformans interactions and investigating the effects of this pathogen on host AM immunometabolism.