Our major accomplishment this year was the publication of a study comparing the bioactivities of a series of stilbene compounds in C. elegans. The collection of stilbenes examined different by the presence of methoxylation or hydroxylation substitutions at four positions. In C. elegans, treatment with the hydroxylated stilbenes was generally benign in an adult lifespan assay. However, increasing methoxylation caused compounds to become toxic, and shorten adult survival. We next compared bioactivities in a C. elegans cancer model. Animals carrying a mutation in the gld-1 gene exhibit a germline tumor phenotype resulting from the inability of the germcells to exit mitosis. As for adult survival, the methoxylated stilbenes exhibited inhibitory activity on the growth of gld-1(q20) germline tumors, while hydroxylated stilbenes had minimal activity in this assay. Together, these results show that methoxylation enhanced stilbene bioactivity in C. elegans, both in terms of toxicity towards terminally-differentiated cells in adult animals and in proliferating cells in the germline tumors. This publication has generated great interest, and was flagged as Highly Accessed by the publisher. We hypothesize that the bioactivity differences between methoxylated and hydroxylated stilbenes reflect differences in bioavailability and/or target interactions. To examine these possibilities, transcriptional microarrays were used to compare gene expression in response to short-term exposures at high concentrations of resveratrol, an hydroxylated stilbene, and pterostilbene, a methoxylated stilbene. Preliminary results indicate that a resveratrol and pterostilbene may regulate some overlapping targets, which would be consistent with the idea that their differing bioactivities reflect bioavailability differences. In addition, pterostilbene affects expression of additional genes unaffected by resveratrol, which may reflect target-specific differences in these compounds. Analysis of the microarray results is ongoing. We are currently working on a second project which aims to identify compounds with hormetic activity in C. elegans. Hormesis is the ability of a toxic compound to induce beneficial, protective effects at subtoxic doses. Using C. elegans, we conducted a small screen to identify natural products that exerted hormetic activity in a C. elegans lifespan assay. This screen identified one compound which is able, in some experiments, to extend lifespan at a non-toxic dose. A parallel screen was conducted by collaborators in the LNS to identify compounds that induce a Nrf transcriptional response in cultured mammalian cells. The Nrf response screen identified the same compound, suggesting that prolongevity activity in C. elegans may be mediated by the homologous gene. Current work aims to identify the structural aspects of this compound required for prolongevity activity. In addition, we are examining target genes induced in C. elegans by this compound.
| Wilson, Mark A; Rimando, Agnes M; Wolkow, Catherine A (2008) Methoxylation enhances stilbene bioactivity in Caenorhabditis elegans. BMC Pharmacol 8:15 |
