PPARalpha mediates the effects of the pesticide methyl thiophanate on liver of the lizard Podarcis sicula

The majority of environmental pollutants are potential peroxisomal proliferators which include a heterogeneous group of compounds known to determine massive peroxisomal proliferation and hepatocarcinogenesis in rodents. Peroxisomal proliferation is accompanied by the induction of the peroxisomal fatty acid beta-oxidation pathway mediated by a class of transcription factors named peroxisome proliferators activated receptors (PPARs). This phenomenon demonstrated also in ectotherm animals after exposition to environmental pollutants may be utilized as biomarker in environmental impact studies. In the present work we have tested the sensitivity to methyl thiophanate (TM) of the lizard Podarcis sicula in order to propose a biological model for monitoring the ecotoxicological effects of this pesticide on terrestrial sentinel species. The data obtained demonstrate that exposition to sub-lethal concentrations of TM leads to hepatocellular morphological changes and glycogen depletion, apoptosis, as well as probable peroxisomal proliferation attested by the increase of acyl-CoA oxidase (AOX). This effect seems to be mediated by the concomitant increase of PPARalpha. On the basis of these results we propose that also in Podarcis sicula, as just proposed for aquatic organisms, peroxisomal proliferation and AOX increase may be considered new biomarkers to evaluate pollution by organic compound in terrestrial environments.