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 9

NaHCO3 bicarbonate enhances survival of BHB-treated mice with mucormycosis.

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NaHCO3 bicarbonate enhances survival of BHB-treated mice with mucormycos...
(A) Mice were injected 5 times with BHB (n = 5 per group) or BHB followed by NaHCO3 before determination of the blood pH. (B) LPI concentrations were measured in samples collected from normal immunocompetent mice and mice treated with BHB or with BHB followed by sodium bicarbonate. Data in A and B are expressed as median ± interquartile range. *P < 0.05 vs. normal mice or BHB + NaHCO3 for A and vs. normal mice for B. (C) Survival of mice treated with BHB (n = 20), BHB + NaHCO3 (prophylaxis, n = 8), or BHB + NaHCO3 (therapy, n = 10). Mice were infected with R. oryzae intratracheally with 2.5 × 105 spores (average delivered inoculum is 4.5 × 103 from 3 independent experiments). **P = 0.0085 by log-rank test vs. BHB-treated and infected. (D) Lung and brain fungal burden of mice (n = 10 per group) treated with BHB or BHB + NaHCO3 (prophylactically) was determined by qPCR 48 hours after infection. Data are expressed as median ± interquartile range. y axis value represents the lower limit of detection in the assay. ‡P < 0.04 vs. lungs or brains from BHB-treated mice. (E) Histopathological images (H&E) and cumulative score of inflammation, hemorrhage, and edema scores of lungs harvested from mice treated with BHB or BHB + NaHCO3 (prophylactically) 48 hours after infection with R. oryzae, showing significantly extensive signs of pneumonia with neutrophil infiltration (black arrows) and hemorrhage (white arrows) in the lungs of mice treated with BHB. Original magnification, ×100 (top); ×400 (bottom). #P = 0.04. (F) Survival of mice (n = 9 per group) infected intratracheally with R. oryzae transformed with empty plasmid (6.4 × 103 spores) or with plasmids attenuating CotH2/CotH3 (4.1 × 103 spores) or FTR1 expression (5.2 × 103 spores). ***P < 0.03 vs. mice infected with R. oryzae transformed with empty plasmid.