Polyamine metabolism in the exposure to organophosphorus pesticides of amphibian embryos from North Patagonia, Argentina

CESCHIN, DANILO GUILLERMO; PIRES, NATALIA SUSANA; LASCANO, CECILIA; VENTURINO, ANDRÉS

Tivoli

Conferencia; 4th International Conference on Polyamines: Biochemical, Physiological and Clinical Perspectives; 2016

ICGEB

The northern patagonic region is the mainproductive area of pears and apples in Argentina, whereorganophosphorus (OP)pesticides have been historically applied in large quantities for pest control.Inorder to contribute to responsible decision making, our group has analyzed theimpact of pesticide application on aquatic organisms for more than 35 years.For decades, the insecticide azinphos methyl (AM) was the main OP pesticideemployed; it has been detected in surface and groundwater in Northern Patagonia,exceeding the criteria for protection of aquatic life and remaining at highconcentrations throughout the season (Tosi et al., 2009). OP pesticides exerttheir toxic action through inhibition of the enzyme acetylcholinesterase.However, different cellular processes are altered in non-target organisms, and pesticideexposure is contributing to the decline of amphibian populations (Sparling etal., 2015). Rhinella arenarum is anative toad to Argentina which spends its embryonic and larval stages in waterbodies of the productive region and, therefore, water quality preservation isof great importance to this species. An integrated pest management approach iscurrently being implemented to reduce the utilization of OP pesticides in orderto meet the international requirements regarding the maximum residue levels ofpesticides on fruit and to protect environmental health.Although polyamines (PA)arerecognized as essential polycations forthe normal progression of embryonicdevelopmentand that their levels are consequently highly regulated, almost no studies havebeen conducted to analyze the influence of pesticides on PA metabolism. Consideringthe relevant role that amphibians play in the health of ecosystems, ourobjective is to analyze PA metabolism in R.arenarum embryos exposed to sublethal (0,5- and 2 mg/L) and lethal (9 mg/L)concentrations of AM. Control PA levels continuously increased along embryonicdevelopment. AM exposure increased ornithine decarboxylase(ODC) activity 18-foldat the end of embryonic development and alteredPA levels: putrescine increased(60%) while spermidine and spermine decreased (56% and not detectable,respectively). Besides, our aim is to establish whether oxidative stress is relatedto PA metabolism, particularly, through their oxidative degradation.In thisregard, we are currently investigating the effects of AM on the activity of N1-acetylpolyamineoxidase and diamine oxidase,according to Goodwin et al. (2011). Oxidativestress evidences were gradually observed during exposure to AMin thesignificant decrease of reduced glutathione and the inhibition of enzymeactivities such as superoxide dismutase. Besides, a transcriptomic analysis showedthat several genes encoding enzymes involved in PA metabolism modify theirexpression showing differential isoenzyme patterns when R. arenarum larvae are exposed to sublethal concentrations of OPpesticides.