Abstract
Camphor is widely used in pharmacy, the food industry, and cosmetics. In this study, we evaluate inhibitory and cytotoxic effects of camphor in the fission yeast (Schizosaccharomyces pombe), which presents a unicellular model in mechanistic toxicology and cell biology. Low-dose camphor exposure (0.4 mg/mL) activated autophagy, which was shown by GFP-Atg8 dots and transcriptional upregulation of Atg6 (Beclin-1 ortholog). Autophagy was also confirmed by using autophagy-deficient cells, which showed reduction in GFP-Atg8 dot formation. However, high-dose camphor exposure (0.8 mg/mL) caused dramatic cell death ratios, demonstrated by spot and colony-forming assays, even in autophagy-deficient cells. To unravel the underlying mechanism, this time, apoptosis-deficient cells were exposed to low- and high-dose camphor. Apoptosis was also confirmed by acridine orange/ethidium bromide staining. Among yeast apoptosis mediators, Aif1 was found to mediate camphor-induced cell death. In conclusion, differential regulation of autophagy and apoptosis, and switches between them, were found to be dose-dependent. The potential effects of camphor on autophagy and apoptotic cell death and underlying mechanisms were clarified in basic unicellular eukaryotic model, S. pombe.
Highlights
Terpenes and terpenoids are herbal extracts extracted from resins of medicinal and aromatic plants including Citrus, Lamiaceae, and Pinaceae, or produced from marine organisms such as Spongia (Gershenzon and Dudareva, 2007)
Autophagy activation was confirmed via atg6 (Beclin-1 ortholog in yeast) gene expression, which is known to play a key role in autophagy maturation and to be upregulated in transcriptional levels (Duncan et al, 2018)
We evaluated the effects of low-dose camphor exposure, in comparison to high-dose camphor exposure, on cell growth and viability of S. pombe cells
Summary
Terpenes and terpenoids are herbal extracts extracted from resins of medicinal and aromatic plants including Citrus, Lamiaceae, and Pinaceae, or produced from marine organisms such as Spongia (Gershenzon and Dudareva, 2007). The characteristics of fission yeast (Schizosaccharomyces pombe) that are analogous to mammals (Lin and Austriaco, 2014; Koyama et al, 2017, including mitochondrial biogenesis, cell cycle control, and evolutionarily conserved programmed/regulated cell death, in addition to a small and manipulated genome (Wood et al, 2002), make this yeast species an excellent model organism for molecular biology, biochemistry, and genetics studies (Hagan et al, 2016; Gerganova et al, 2019). Fission yeast provides a valuable opportunity to be used in cancer research, for its high proliferation rate resembles the Crabtree and Warburg effect (reprogrammed energy metabolism of cancer cells)
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