Metabolic Effects of Sodium Fluorocitrate and Meclizine on Saccharomyces cerevisiae: Changes in Oxygen Consumption

Abstract

Sodium fluoroacetate (1080) is a colorless, odorless, tasteless, water‐soluble metabolic poison. In the body, fluoroacetate is converted to fluorocitrate (FC) which blocks the citric acid cycle and drastically decreases ATP production. Symptoms of exposure include nausea, vomiting, abdominal pains, salivation, irrational fear, weakness, tachypnea, cyanosis, sweating, increased temperature, and death. Signs and symptoms of 1080 poisoning are nonspecific, complicating diagnosis. 1080 is tightly regulated within the United States, but it is commonly used in Australia, New Zealand, Mexico, Japan, South Korea, and Israel as a rodenticide to control invasive and predatory species. An eco‐terrorist scare in New Zealand (2015) and findings reported by the CIA (2007) have led 1080 to being identified as a potential terrorist weapon.Saccharomyces cerevisiae is a useful model to assess the impact of FC on cellular respiration and to screen therapeutics. In response to FC, yeast shows depressed mitochondrial activity as measured by oxygen consumption rate (OCR). Meclizine, an antihistamine used to treat nausea, vomiting, and dizziness, shows promise as a potential treatment in this model. Toxicity of meclizine was also assessed.Assays were performed in yeast extract peptone galactose (YPG) media, a metabolically restrictive media. To assess the effect of FC on OCR, cells were exposed to 50 μM, 100 μM, and 200 μM FC in liquid culture for 1, 4, or 24 hours. After incubation, mitochondrial respiration was assessed via the MitoXpress assay (Agilent), a fluorescence‐based assay which measures OCR. Once established as a viable model, yeast was then used to screen meclizine as a therapeutic to improve cellular respiration. Yeast was co‐incubated with fluorocitrate (200 μM) and meclizine (1 μM, 5 μM, and 15 μM) for 4 hours, and the effects on mitochondrial respiration were assessed via the MitoXpress assay.OCR decreased in yeast exposed to FC. Treatment with meclizine rescued mitochondrial function as demonstrated by an increase in OCR. Higher concentrations of meclizine (15 μM) improved mitochondrial activity. However, studies analyzing the effect of meclizine on yeast growth showed high concentrations of meclizine (15μM) inhibit growth, suggesting a toxic effect. Lower concentrations of meclizine (1μM) improved growth compared to untreated yeast exposed to FC. Future studies will continue to characterize the effectiveness of meclizine as a treatment and to use yeast as a screening method for other potential treatments for sodium fluoroacetate.Support or Funding InformationDISCLAIMER: The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.N.A.A., M.C.R., and M.K.A. were supported in part by an appointment to the Internship/Research Participation Program for USAMRICD, administered by the Oak Ridge Institute for Science and Education through an agreement between the US Department of Energy and the USAMRDC.