Guarana (Paullinia cupana Mart.) attenuates methylmercury-induced toxicity in Caenorhabditis elegans

The influence of routine guarana (Paullinia cupana) consumption on apparent tolerance to mercury intoxication has been proposed. The present study investigated this hypothesis in Caenorhabditis elegans, a suitable experimental model for studies in toxicology. Wild type (WT) and skn-1 (ok2315) worm strains were pretreated with guarana ethanolic extract (GEE) from larvae 1 (L1) to L4 stage and then exposed for 6 hours to methylmercury (MeHg). The analyses included evaluation of GEE's effects on lethality, developmental delay, feeding, locomotion, gene expression (sod-3, gst-4, sir-2.1, hsf-1, snn-1, mtl-1, mtl-2, aat-1, aat-2 and aat-3) and antioxidant activity. GEE pre-treatment had no aberrant effects on WT worms exposed to MeHg, and protected skn-1 (ok2315) worms, which are more susceptible to environmental stresses. The protective effects of GEE might be dependent on modulation of genes other than those directly involved in antioxidant activity. GEE increased the expression of genes involved in metal transport (aat-2), metal detoxification (mtl-1 and mtl-2) and antioxidant responses (sir-2.1 and sod-3). Thus, routine consumption of guarana might be beneficial in protecting against MeHg-induced toxicity.