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Caenorhabditis elegans presents functioning, biologically relevant phenotypes and is frequently used as a bioindicator of toxicity. However, most C. elegans in vivo effect-assessment methods are laborious and time consuming. Therefore, we developed a novel method to measure the oxygen consumption rate of C. elegans as a sublethal endpoint of toxicity. This protocol was tested by exposing 50 larval stage one C. elegans individuals for 48 h (at 20 °C) to different concentrations of two toxicants i.e. benzylcetyldimethylammonium chloride (BAC-C16) and cadmium (Cd). Following exposures, the oxygen consumption rate of the C. elegans individuals were measured using the high-throughput functionality of the Seahorse XFe96 Extracellular Flux Analyzer. Dose-response curves for BAC-C16 (R2 = 0.93; P = 0.001) and Cd (R2 = 0.98; P = 0.001) were created. Furthermore, a strong, positive correlation was evidenced between C. elegans oxygen consumption rate and a commonly used, ecologically relevant endpoint of toxicity (growth inhibition) for BAC-C16 (R2 = 0.93; P = 0.0001) and Cd (R2 = 0.91; P = 0.0001). The data presented in this study show that C. elegans oxygen consumption rate can be used as a promising functional measurement of toxicity.

Mitochondrial dysfunction has been proposed as one of the pathobiological underpinnings in Parkinson's disease. Environmental stressors, such as paraquat, induce mitochondrial dysfunction and promote reactive oxygen species production. Targeting oxidative stress pathways could prevent mitochondrial dysfunction and thereby halt the neurodegeneration in Parkinson's disease. Since curcumin is touted as an antioxidant and neuroprotective agent, the aim of this study was to investigate if curcumin is a suitable therapy to target mitochondrial dysfunction in Parkinson's disease using a paraquat-toxicity induced model in fibroblasts from LRRK2 -mutation positive Parkinson's disease individuals and healthy controls. The fibroblasts were exposed to five treatment groups, (i) untreated, (ii) curcumin only, (iii) paraquat only, (iv) pre-curcumin group: with curcumin for 2hr followed by paraquat for 24hr and (v) post-curcumin group: with paraquat for 24hr followed by curcumin for 2hr. Mitochondrial function was determined by measuring three parameters of mitochondrial respiration (maximal respiration, ATP-associated respiration, and spare respiratory capacity) using the Seahorse XF e 96 Extracellular Flux Analyzer. As expected, paraquat effectively disrupted mitochondrial function for all parameters. Pre-curcumin treatment improved maximal and ATP-associated respiration whereas, post-curcumin treatment had no effect. These findings indicate that curcumin may be most beneficial as a pre-treatment before toxin exposure, which has implications for its therapeutic use. These promising findings warrant future studies testing different curcumin dosages, exposure times and curcumin formulations in larger sample sizes of Parkinson's disease and control participants.

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