15-keto-prostaglandin E2 activates host peroxisome proliferator-activated receptor gamma (PPAR-γ) to promote Cryptococcus neoformans growth during infection

Abstract

Cryptococcus neoformans is one of the leading causes of invasive fungal infection in humans worldwide. C . neoformans uses macrophages as a proliferative niche to increase infective burden and avoid immune surveillance. However, the specific mechanisms by which C . neoformans manipulates host immunity to promote its growth during infection remain ill-defined. Here we demonstrate that eicosanoid lipid mediators manipulated and/or produced by C . neoformans play a key role in regulating pathogenesis. C . neoformans is known to secrete several eicosanoids that are highly similar to those found in vertebrate hosts. Using eicosanoid deficient cryptococcal mutants Δplb1 and Δlac1 , we demonstrate that prostaglandin E 2 is required by C . neoformans for proliferation within macrophages and in vivo during infection. Genetic and pharmacological disruption of host PGE 2 synthesis is not required for promotion of cryptococcal growth by eicosanoid production. We find that PGE 2 must be dehydrogenated into 15-keto-PGE 2 to promote fungal growth, a finding that implicated the host nuclear receptor PPAR-γ. C . neoformans infection of macrophages activates host PPAR-γ and its inhibition is sufficient to abrogate the effect of 15-keto-PGE 2 in promoting fungal growth during infection. Thus, we describe the first mechanism of reliance on pathogen-derived eicosanoids in fungal pathogenesis and the specific role of 15-keto-PGE 2 and host PPAR-γ in cryptococcosis.

Blood vessel occlusion byCryptococcus neoformansis a mechanism for haemorrhagic dissemination of infection

“…Deletion of Δplb1 has previously been shown to exhibit increased cell size during infection of macrophages in vitro and in a mouse model of cryptococcosis (25,26). We have recently demonstrated that several phenotypes associated with plb1 deletion were due to differences in fungal eicosanoid production, differences also present in a second cryptococcal mutant strain lac1 (27). We first wanted to ensure enlarged cryptococcal size also occurs in the zebrafish infection model; we measured the size of Δplb1 and Δlac1 cryptococcal cells at 1dpi, and found that there was a significant increase in cell diameter compared to wild type, with a 100% increase in the number of cryptococci with a diameter >5µm (Fig.…”

“…The C. neoformans variety grubii strain KN99, its GFP-expressing derivative KN99:GFP and mCherry-expressing derivative KN99:mCherry were used in this study (39). We used GFP expressing Δplb1-H99, Δlac1-H99 or parental H99-GFP (27) and Δgsc, Δsmt, Δsld8 and parental strain (24). Cultures were grown in 2□ml of yeast extract peptone dextrose (YPD) (all reagents are from Sigma-Aldrich, Poole, UK unless otherwise stated) inoculated from YPD agar plates and grown for 18□hours at 28□°C, rotating horizontally at 20□rpm.…”

The mouse lung early cellular innate immune response is not sufficient to control fungal infection with Cryptococcus neoformans

“…Mice were randomised into treatment groups using the Google random number generator. Animals were infected by intranasal inoculation -mice were lightly anaesthetised using gaseous isofluorane and inoculated with 50μl of either 50,000cfu Cryptococcus neoformans KN99α GFP (18) or H99 ∆Plb1 GFP (42,43) or 50,000 6μm Fluoresbrite® YG Microspheres Polysciences (Hamburg, Germany). 0hpi mice were sacrificed by pentobarbital injection and exsanguination following recovery from the intranasal dosing anaesthesia.…”

“…Long term 24hr imaging was done using a widefield Nikon Ti (Kingston Upon Thames, UK), imaged at 20x using the settings, lens and camera described in Evans et al (43). All data was captured using NIS element AR software.…”

“…C. neoformans has evolved multiple virulence mechanisms related to an ecological niche in the soil and tree saprophyte in response to natural predators such as amoebae that have allowed this fungus to cause disease (5,6). These include a polysaccharide capsule, production of oxygen scavenging melanin and the ability to modulate host immunity (7)(8)(9)(10). The majority of cryptococcosis patients present late in disease, following dissemination of infection to the CNSmeaning most experimental and clinical research is focussed on these later stages (14,15,16,17).…”