Bicarbonate correction of ketoacidosis alters host-pathogen interactions and alleviates mucormycosis
Teclegiorgis Gebremariam, … , Scott G. Filler, Ashraf S. Ibrahim
Teclegiorgis Gebremariam, … , Scott G. Filler, Ashraf S. Ibrahim
Published May 9, 2016
Citation Information: J Clin Invest. 2016;126(6):2280-2294. https://doi.org/10.1172/JCI82744.
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Research Article Infectious disease

Bicarbonate correction of ketoacidosis alters host-pathogen interactions and alleviates mucormycosis

Abstract

Patients with diabetic ketoacidosis (DKA) are uniquely predisposed to mucormycosis, an angioinvasive fungal infection with high mortality. Previously, we demonstrated that Rhizopus invades the endothelium via binding of fungal CotH proteins to the host receptor GRP78. Here, we report that surface expression of GRP78 is increased in endothelial cells exposed to physiological concentrations of β-hydroxy butyrate (BHB), glucose, and iron that are similar to those found in DKA patients. Additionally, expression of R. oryzae CotH was increased within hours of incubation with DKA-associated concentrations of BHB, glucose, and iron, augmenting the ability of R. oryzae to invade and subsequently damage endothelial cells in vitro. BHB exposure also increased fungal growth and attenuated R. oryzae neutrophil-mediated damage. Further, mice given BHB developed clinical acidosis and became extremely susceptible to mucormycosis, but not aspergillosis, while sodium bicarbonate reversed this susceptibility. BHB-related acidosis exerted a direct effect on both GRP78 and CotH expression, an effect not seen with lactic acidosis. However, BHB also indirectly compromised the ability of transferrin to chelate iron, as iron chelation combined with sodium bicarbonate completely protected endothelial cells from Rhizopus-mediated invasion and damage. Our results dissect the pathogenesis of mucormycosis during ketoacidosis and reinforce the importance of careful metabolic control of the acidosis to prevent and manage this infection.

Authors

Teclegiorgis Gebremariam, Lin Lin, Mingfu Liu, Dimitrios P. Kontoyiannis, Samuel French, John E. Edwards Jr., Scott G. Filler, Ashraf S. Ibrahim

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Figure 2

BHB, glucose, and iron concentrations consistent with those seen in DKA patients induce expression of CotH proteins in a time- and concentration-dependent manner.

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BHB, glucose, and iron concentrations consistent with those seen in DKA ...
(A–C) R. oryzae cells were incubated at various concentrations of BHB (A), glucose (B), or iron (C) often seen in DKA patients for 24 hours; then the expression of CotH genes was quantified by real-time RT-PCR (normalized to ACT1 housekeeping gene). (D–F) CotH protein cell surface expression in response to BHB (D), glucose (E), or iron (F) after 4 hours of incubation was quantified using FACS analysis following staining with anti-CotH polyclonal antibodies raised against CotH peptide in rabbits (primary antibody), then counterstaining with anti-rabbit Alexa Fluor 488–labeled antibody. Negative controls included staining of cells with serum collected from the same rabbit before vaccination with CotH peptide as primary antibody (preimmune serum). (G–I) Kinetics of cell surface R. oryzae CotH expression in response to elevated concentrations of BHB (G), glucose (H), or iron (I) as quantified by qRT-PCR. Data in qRT-PCR (n = 4–6 wells per group from 2 independent experiments) are expressed as median ± interquartile range relative to CotH expression in R. oryzae cells incubated without stimulus (A, C, G, and I) or with 1 mg/ml glucose (B and H). *P = 0.04 vs. 0 μM FeCl3 or 0 mM BHB; **P ≤ 0.02 vs. 0 or 15 μM FeCl3 or 5 mM BHB; ‡P < 0.02 vs. 1 mg/ml glucose; §P < 0.001 vs. no stimulus or 1 mg/ml glucose at the specified time point; #P < 0.05 vs. same condition at 6 or 12 hours by Wilcoxon rank sum test.