Intracellular Cryptococcus neoformans disrupts the transcriptome profile of M1- and M2-polarized host macrophages

Abstract

Macrophages serve as a first line of defense against infection with the facultative intracellular pathogen, Cryptococcus neoformans ( Cn ). However, the ability of these innate phagocytic cells to destroy ingested Cn is strongly influenced by polarization state with classically (M1) activated macrophages better able to control cryptococcal infections than alternatively (M2) activated cells. While earlier studies have demonstrated that intracellular Cn minimally affects the expression of M1 and M2 markers, the impact on the broader transcriptome associated with these states remains unclear. To investigate this, an in vitro cell culture model of intracellular infection together with RNA sequencing-based transcriptome profiling was used to measure the impact of Cn infection on gene expression in both polarization states. The gene expression profile of both M1 and M2 cells was extensively altered to become more like naive (M0) macrophages. Gene ontology analysis suggested that this involved changes in the activity of the Janus kinase-signal transducers and activators of transcription (JAK-STAT), p53, and nuclear factor-κB (NF-κB) pathways. Analyses of the principle polarization markers at the protein-level also revealed discrepancies between the RNA- and protein-level responses. In contrast to earlier studies, intracellular Cn was found to increase protein levels of the M1 marker iNos. In addition, common gene expression changes were identified that occurred post- Cn infection, independent of polarization state. This included upregulation of the transcriptional co-regulator Cited1 , which was also apparent at the protein level in M1-polarized macrophages. These changes constitute a transcriptional signature of macrophage Cn infection and provide new insights into how Cn impacts gene expression and the phenotype of host phagocytes.

Transcriptional Changes in Pulmonary Phagocyte Subsets Dictate the Outcome Following Interaction With The Fungal Pathogen Cryptococcus neoformans

“…The identification of specific mechanisms that mediate intracellular C. neoformans survival and replication can aid in the development of novel therapies for the treatment of cryptococcosis. Previous studies have provided an investigation into the intracellular nature of C. neoformans and phagocytic cells using peripheral blood mononuclear cells (PBMCs), or macrophage cell lines ( 4 , 84 ). In addition, more recent fate-mapping studies have identified macrophage and DC subsets and have defined origins of both human and murine phagocytes ( 56 , 85 , 86 ) but few have analyzed how these phagocyte subsets initially interact with C. neoformans [reviewed in ( 60 )].…”

A Fun-Guide to Innate Immune Responses to Fungal Infections

“…Macrophages are a highly heterogenous population, existing on a spectrum of behaviours between M1, pro-inflammatory phenotypes and M2, wound healing phenotypes [ 64 ]. Proteomic analysis revealed a pro-inflammatory to wound healing phenotypic switch in C. albicans infection, whereas C. neoformans infection drives macrophages into a naïve M0 phenotype [ 65 , 66 ]. Stimulating an M1 phenotype led to decreased fungal burden and increased survival of mouse models in C. albicans and C. neoformans infection [ 67 , 68 ].…”

Influence of Pathogen Carbon Metabolism on Interactions With Host Immunity

“…As the yeasts reside in the macrophages, they work to maintain a naïve-type state of the macrophages. iNOS expression is also upregulated by the intracellular yeasts ( Subramani et al., 2020 ). Therefore, Cryptococcus has the insidious ability to hide within the host by manipulating the cytokine environment of the host.…”