Dataset Information

Dexamethasone Promotes Aspergillus fumigatus Growth in Macrophages by Triggering M2 Repolarization via Targeting PKM2.

ABSTRACT: Since long-term corticosteroid treatment is associated with emerging opportunistic fungal infections causing high morbidity and mortality in immune-suppressed individuals, here we characterized the impact of dexamethasone (Dex) treatment on Aspergillus fumigatus-related immune modulation. We found by high content screening and flow cytometric analyses that during monocyte-to-macrophage differentiation, as little as 0.1 µg/mL Dex resulted in a shift in macrophage polarization from M1 to M2-like macrophages. This macrophage repolarization mediated via Dex was characterized by significant upregulation of the M2 marker CD163 and downmodulation of M1 markers CD40 and CD86 as well as changes in phenotypic properties and adherence. These Dex-mediated phenotypic alterations were furthermore associated with a metabolic switch in macrophages orchestrated via PKM2. Such treated macrophages lost their ability to prevent Aspergillus fumigatus germination, which was correlated with accelerated fungal growth, destruction of macrophages, and induction of an anti-inflammatory cytokine profile. Taken together, repolarization of macrophages following corticosteroid treatment and concomitant switch to an anti-inflammatory phenotype might play a prominent role in triggering invasive aspergillosis (IA) due to suppression of innate immunological responses necessary to combat extensive fungal outgrowth.

SUBMITTER: Luvanda MK

PROVIDER: S-EPMC7909285 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Dexamethasone Promotes <i>Aspergillus fumigatus</i> Growth in Macrophages by Triggering M2 Repolarization via Targeting PKM2.

Luvanda Maureen K MK Posch Wilfried W Vosper Jonathan J Zaderer Viktoria V Noureen Asma A Lass-Flörl Cornelia C Wilflingseder Doris D

Journal of fungi (Basel, Switzerland) 20210120 2

Since long-term corticosteroid treatment is associated with emerging opportunistic fungal infections causing high morbidity and mortality in immune-suppressed individuals, here we characterized the impact of dexamethasone (Dex) treatment on <i>Aspergillus fumigatus</i>-related immune modulation. We found by high content screening and flow cytometric analyses that during monocyte-to-macrophage differentiation, as little as 0.1 µg/mL Dex resulted in a shift in macrophage polarization from M1 to M2 ...[more]

PMID: 33498318

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Project description:Allergic bronchopulmonary aspergillosis (ABPA) is an allergic immunological response to Aspergillus fumigatus (Af) exposure, which induces a strong T helper 2 (Th2) response via mechanisms that have yet to be elucidated. The aim of the present study was to investigate the hypothesis that T2 ribonuclease from Af (Af RNASET2) induces M2‑type macrophage polarization to produce a T helper 2 (Th2) immune response. Recombinant Af RNASET2 (rAf RNASET2) was expressed and purified in a prokaryotic pET system and BALB/c mice were immunized with rAf RNASET2 for in vivo analyses. Expression levels of M2 polarization factors were evaluated in RAW264.7 macrophages treated with rAf RNASET2 in vitro using flow cytometry, reverse transcription‑quantitative PCR, and western blot analysis. The results predicted that the mature Af RNASET2 protein (382 amino acids; GenBank no. MN593022) contained two conserved amino acid sequence (CAS) domains, termed CAS‑1 and CAS‑2, which are also characteristic of the RNASET2 family proteins. The protein expression levels of the Th2‑related cytokines interleukin (IL)‑4, IL‑10, and IL‑13 were upregulated in mice immunized with rAf RNASET2. RAW264.7 macrophages treated with rAf RNASET2 showed increased mRNA expression levels of M2 factors [arginase 1, Il‑10, and Il‑13]; however, there was no difference in cells treated with rAf RNASET2 that had been inactivated with a ribonuclease inhibitor (RNasin). The protein expression levels of IL‑10 in macrophage culture supernatant were also increased following stimulation with rAf RNASET2. In addition, rAf RNASET2 upregulated the expression of phosphorylated mitogen activated protein kinases (MAPKs) in RAW264.7 cells, whereas MAPK inhibitors attenuated rAf RNASET2‑induced IL‑10 expression in RAW264.7 cells. In conclusion, the present study reveals that high rAf RNASET2 activity is required for rAf RNASET2‑induced M2 polarization of macrophages and suggests an important immune regulatory role for Af RNASET2 in ABPA pathogenesis.

Project description:Invasive bronchopulmonary aspergillosis (IBPA) is a life-threatening disease in immunocompromised patients. Although Aspergillus terreus is frequently found in the environment, A. fumigatus is by far the main cause of IBPA. However, once A. terreus establishes infection in the host, disease is as fatal as A. fumigatus infections. Thus, we hypothesized that the initial steps of disease establishment might be fundamentally different between these two species. Since alveolar macrophages represent one of the first phagocytes facing inhaled conidia, we compared the interaction of A. terreus and A. fumigatus conidia with alveolar macrophages. A. terreus conidia were phagocytosed more rapidly than A. fumigatus conidia, possibly due to higher exposure of ?-1,3-glucan and galactomannan on the surface. In agreement, blocking of dectin-1 and mannose receptors significantly reduced phagocytosis of A. terreus, but had only a moderate effect on phagocytosis of A. fumigatus. Once phagocytosed, and in contrast to A. fumigatus, A. terreus did not inhibit acidification of phagolysosomes, but remained viable without signs of germination both in vitro and in immunocompetent mice. The inability of A. terreus to germinate and pierce macrophages resulted in significantly lower cytotoxicity compared to A. fumigatus. Blocking phagolysosome acidification by the v-ATPase inhibitor bafilomycin increased A. terreus germination rates and cytotoxicity. Recombinant expression of the A. nidulans wA naphthopyrone synthase, a homologue of A. fumigatus PksP, inhibited phagolysosome acidification and resulted in increased germination, macrophage damage and virulence in corticosteroid-treated mice. In summary, we show that A. terreus and A. fumigatus have evolved significantly different strategies to survive the attack of host immune cells. While A. fumigatus prevents phagocytosis and phagolysosome acidification and escapes from macrophages by germination, A. terreus is rapidly phagocytosed, but conidia show long-term persistence in macrophages even in immunocompetent hosts.

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Dataset Information

Dexamethasone Promotes Aspergillus fumigatus Growth in Macrophages by Triggering M2 Repolarization via Targeting PKM2.

Publications

Dexamethasone Promotes <i>Aspergillus fumigatus</i> Growth in Macrophages by Triggering M2 Repolarization via Targeting PKM2.

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