Role of plasma membrane dicarboxylate transporters in the uptake and toxicity of diglycolic acid, a metabolite of diethylene glycol, in human proximal tubule cells

Thrombotic Microangiopathy and Acute Tubular Injury After Diethylene Glycol Ingestion: A Kidney Biopsy Teaching Case

We present a rare and unusual case of thrombotic microangiopathy (TMA) in a patient who ingested chafing fuel containing diethylene glycol. The patient showed a typical clinical course of initial gastrointestinal symptoms followed by acute kidney injury (AKI) and peripheral sensorimotor neuropathy. A kidney biopsy showed TMA and diffuse acute tubular injury. Diethylene glycol is widely used as a solvent in numerous consumer products, including brake fluid, antifreeze, chafing fuel, and artificial fog solutions. Diethylene glycol has been implemented in mass poisonings, and the incidence of AKI in diethylene glycol poisonings is linked to high-mortality rates. TMA, a pathologic lesion observed in a wide spectrum of diseases, is triggered by endothelial injury. Our case shows that TMA should be considered as a possible life-threatening complication in the setting of acute diethylene glycol poisoning. Direct toxic injury to endothelial cells by diethylene glycol is a possible mechanism. It is therefore plausible that patients with a genetic predisposition to endothelial injury may develop TMA following diethylene glycol exposure.

The dual role of citrate in cancer

Citrate is a key metabolite of the Krebs cycle that can also be exported in the cytosol, where it performs several functions. In normal cells, citrate sustains protein acetylation, lipid synthesis, gluconeogenesis, insulin secretion, bone tissues formation, spermatozoid mobility, and immune response. Dysregulation of citrate metabolism is implicated in several pathologies, including cancer. Here we discuss how cancer cells use citrate to sustain their proliferation, survival, and metastatic progression. Also, we propose two paradoxically opposite strategies to reduce tumour growth by targeting citrate metabolism in preclinical models. In the first strategy, we propose to administer in the tumor microenvironment a high amount of citrate, which can then act as a glycolysis inhibitor and apoptosis inducer, whereas the other strategy targets citrate transporters to starve cancer cells from citrate. These strategies, effective in several preclinical in vitro and in vivo cancer models, could be exploited in clinics, particularly to increase sensibility to current anti-cancer agents.

Variable sensitivity to diethylene glycol poisoning is related to differences in the uptake transporter for the toxic metabolite diglycolic acid

INTRODUCTION/CONTEXT

Poisonings with diethylene glycol are characterized by acute kidney injury and peripheral neuropathy. In animal studies on the toxicities of diethylene glycol and its metabolite diglycolic acid, remarkable differences in susceptibility to acute kidney injury were observed in identically-dosed rats. In those studies, only about 60% showed acute kidney injury, yet all rats with acute kidney injury showed marked diglycolic acid accumulation in tissues, while no diglycolic acid accumulated in rats without injury. Diglycolic acid is taken into renal cells via sodium-dependent dicarboxylate transporters. When sodium-dependent dicarboxylate transporter-1 is inhibited or knocked down in human kidney cells, diglycolic acid uptake and toxicity are reduced. We hypothesize that the variation in sensitivity to tissue diglycolic acid retention and to diethylene glycol/diglycolic acid toxicity is explained by differential expression of sodium-dependent dicarboxylate transporter-1 in rat kidneys.

METHODS

Using kidney tissue from previous studies, we performed rt-PCR analysis of sodium-dependent dicarboxylate transporter-1 mRNA. In those studies, Wistar-Han rats were either gavage with diethylene glycol 6 g/kg every 12 h for 7 days or with single doses of diglycolic acid 300 mg/kg. Kidney tissue was harvested after euthanasia and preserved in formalin. Tissue slices were homogenized and RNA was isolated using an RNAstorm FFPE RNA Isolation Kit. The expression of sodium-dependent dicarboxylate transporter-1 mRNA was compared between groups that showed diglycolic acid accumulation and acute renal injury with those that showed no diglycolic acid accumulation or toxicity.

RESULTS

Significantly higher expression of sodium-dependent dicarboxylate transporter-1 mRNA was present in the kidneys of rats with acute kidney injury and diglycolic acid accumulation compared to those in rats that had no diglycolic acid in their kidneys and no acute kidney injury.

DISCUSSION

The likelihood of acute kidney injury after dosing of rats with diethylene glycol or diglycolic acid is linked with an enhanced ability to take up diglycolic acid into renal cells via the sodium-dependent dicarboxylate transporter-1. The variability in diethylene glycol toxicity in humans, as reported in epidemiological studies, may also be linked with differences in tissue uptake of diglycolic acid.

CONCLUSIONS

Animals with acute kidney injury after exposure to diethylene glycol or diglycolic acid had higher sodium-dependent dicarboxylate transporter-1 expression and greater diglycolic acid accumulation in renal tissues than animals without acute kidney injury.