|Bin Umer, Anwar|
|Mc Laughlin, John|
Submitted to: Society of Toxicology
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/2011
Publication Date: 3/10/2011
Citation: Bin Umer, A., Mc Laughlin, J., Basu, D., Mccormick, S.P., Tumer, N. 2011. Identification of a direct role for mitochondria in the toxicity of ribotoxic stress inducing trichothecenes. Society of Toxicology. Interpretive Summary:
Technical Abstract: Trichothecenes are protein synthesis inhibitors that trigger a ribotoxic stress response leading to rapid activation of MAPKs, induction of proinflammatory responses, and cell death. These foodborne toxins include deoxynivalenol (DON), diacetoxyscirpenol (DAS), T-2, and trichothecin (Tcin). Identifying the molecular mechanisms underlying trichothecene toxicity is vital to understanding trichothecene toxicosis. To identify the genes that confer susceptibility to trichothecenes, we carried out a genome-wide screen of the 4720 yeast knockouts (YKOs) for increased resistance to Tcin. We identified mitochondria as a key target with 60% of the resistant YKOs associated with mitochondrial function (morphology, ribosome structure, genome maintenance). Growth of trichothecene-treated yeast cells was inhibited in non-fermentable media, which requires functional mitochondria, while cells devoid of mitochondria showed no such inhibition. [35S]-methionine incorporation of yeast cells treated with lower concentrations of trichothecenes showed ~50% inhibition of mitochondrial translation, but not total translation. When isolated yeast mitochondria were treated with 4µM and 8µM Tcin, [35S]-methionine incorporation decreased by 40% and 78%, respectively. Trichothecene-treated yeast cells were stained for mitochondrial membrane potential (Rh123), ROS generation (DCFH-DA) and cell death (PI) and analyzed using flow cytometry. Median fluorescence intensities for all three markers increased when yeast cells were treated with trichothecenes. These results demonstrate a direct role for mitochondria in trichothecene toxicity. Mitochondrial translation is inhibited by trichothecenes. Furthermore, flow cytometry results indicate that trichothecenes trigger ROS generation, resulting in hyperpolarization of the mitochondrial membrane, which eventually leads to cell death.