A metabolic inhibitor arms macrophages to kill intracellular fungal pathogens by manipulating zinc homeostasis

Abstract

Macrophages deploy numerous strategies to combat invasion by microbes. One tactic is to restrict acquisition of diverse nutrients including trace metals, a process termed nutritional immunity. Intracellular pathogens adapt to a resource poor environment by marshalling mechanisms to harvest nutrients. Carbon acquisition is crucial for pathogen survival; compounds that reduce availability are a potential strategy to control intracellular replication. Treatment of macrophages with the glucose analog, 2-deoxy-D-glucose (2-DG), armed phagocytes to eliminate the intracellular fungal pathogen Histoplasma capsulatum in vitro and in vivo. Killing did not rely on altering access to carbon-containing molecules, or changes in ATP, ER stress, or autophagy. Unexpectedly, 2-DG undermined import of exogenous zinc into macrophages decreasing the quantity of cytosolic and phagosomal zinc. The fungus perished as a result of zinc starvation. This change in metal ingress was not ascribed to a defect in a single importer; rather, there was a collective impairment in transporter activity. This undescribed effect promotes the antifungal machinery of macrophages and expands the complexity of 2-DG activities far beyond manipulating glycolysis. Mechanistic metabolic studies employing 2-DG will have to consider its effect on zinc transport. Our preclinical data support consideration of this agent as a possible adjunctive therapy for histoplasmosis.

Characterization and functional analysis of zinc trafficking in the human fungal pathogen Candida parapsilosis

“…Macrophages play key roles in controlling pathogenic fungi. Interestingly, these phagocytes can mount either zinc-starvation or intoxification responses against phagocytosed fungi [7,31]. We therefore assessed the interaction between C. parapsilosis ZnT mutant strains and J774.2 murine macrophages.…”

“…Interestingly, these phagocytes can mount either zinc- royalsocietypublishing.org/journal/rsob Open Biol. 12: 220077 starvation or intoxification responses against phagocytosed fungi [7,31]. We therefore assessed the interaction between C. parapsilosis ZnT mutant strains and J774.2 murine macrophages.…”

“We've got to get out”—Strategies of human pathogenic fungi to escape from phagocytes

“…A Zrc1 homolog also protects C. neoformans from high zinc in vitro, but is dispensable in murine infections, suggesting that Zn toxicity is not a factor in protection from Cryptococcosis (Cho et al, 2018). Going even further, H. capsulatum instead is faced with phagosomal zinc limitation when macrophages are activated with GM‐CSF (Subramanian Vignesh et al, 2013), and blocking import of exogenous zinc into macrophages decreases the survival of H. capsulatum within the phagosome (Rossi et al, 2021). It remains to be seen which factors influence the macrophage's decision to starve the pathogen for zinc or bombard it − is it the fungal or the host species, the immune environment, or is there a temporal component to these kinetics?…”

Utilization of aHistoplasma capsulatumzinc reporter reveals the complexities of fungal sensing of metal deprivation

“…H. capsulatum RNA was isolated by mechanical disruption with 0.5 mm glass beads, extraction with TRIzol™ (Invitrogen), and precipitated with ethanol, as previously described (44,45). Genomic DNA was removed via DNase digestion and column purification using the PureLink™ RNA Mini Kit (Invitrogen).…”