Chronic Low Dose Toxicity of Acrolein in C. elegans Mitochondria

Abstract

Acrolein (ACR) is a chemical of interest in the pathology and progression of mitochondrial disease and disorder. Chemical exposure to ACR may occur exogenously due to the use of herbicides or burning of fossil fuels, or endogenously as a by-product from various metabolic pathways. Several studies focus on the impact of high dose acute exposure of ACR with various model organisms, including live rats and mice, human spermatozoa, and several cell culture models. These models do not address the consequences of long term or chronic, low dose exposures and impacts on progeny. For these reasons, the model C. elegans was ideal because of its established genome, ability to self-fertilize or sexually reproduce, ability to yield three hundred progenies in its lifetime, and its short and understood lifespan. We hypothesized that C. elegans would experience mitochondrial dysfunction when chronically exposed to low doses of ACR, particularly with the 15 μM concentration. Based on previous research indicating another electrophilic aldehyde, 4-hydroxynonenal (4-HNE) inhibits SDH activity by forming a protein adduct with the redox subunit of SDH, we predicted that ACR may inhibit complex II (SDH) activity through protein adduct formation. We also predicted that ACR may also decrease lifespan and fecundity across generations of nematodes. To test our hypothesis and aims, we utilized C. elegans in experiments incorporating lifespan and fecundity assays, performed a histochemical stain to qualitatively measure SDH activity, used RT-PCR targeting specific genes related to oxidative stress and SDHA-1, and attempted to isolate mitochondria to perform SDH activity assays measured with spectrophotometry. Our results from the lifespan and fecundity assays suggested that low dose, chronic ACR exposure may decrease lifespan and fecundity in C. elegans. We also learned that C. elegans will attempt to leave the agar plate at ACR concentrations of 75 μM and 100 μM. Our RT-PCR results showed an upregulation in SDHA-1 and SOD-3 transcription in C. elegans after a 24-hour exposure to 100 μM ACR. These results suggest that higher doses of ACR may cause oxidative stress or damage to the mitochondria and SDH. Further experimentation may help better determine the interaction between ACR and the flavonoid subunit of SDH.