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 3

Induction of GRP78 or CotH3 expression is specific to BHB.

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Induction of GRP78 or CotH3 expression is specific to BHB. R. oryzae or ...
R. oryzae or endothelial cells were incubated with 10 mM BHB, lactic acid, or HCl for 6 hours in the absence of serum. All acid treatments resulted in dropping of the pH of the medium to 6.8. The expression of GRP78 (A) or CotH3 (C) was quantified by real-time RT-PCR after normalization of the data to GADPH or ACT1 housekeeping genes, respectively. GRP78 (B) or CotH3 (D) protein surface expression on endothelial or fungal cells using the above conditions was quantified using FACS analysis following staining with anti-GRP78 antibodies or CotH polyclonal antibodies (postimmune serum), respectively. Negative controls included staining of cells with an isotype matching control IgG (for GRP78 detection in B) or with serum collected from the same rabbit before vaccination with CotH peptide as primary antibody (preimmune serum in D). Data in qRT-PCR (n = 6 wells per group from 2 independent experiments) are expressed as median ± interquartile range relative to GRP78 or CotH3 expression in endothelial or R. oryzae cells, respectively, incubated in the media without any of the acids (Control). *P < 0.003 vs. all other treatments; **P < 0.05 vs. control or lactic acid by Wilcoxon rank sum test.