Morphological and Molecular Evidence of Active Principle Glyphosate Toxicity on the Liver of the Field LizardPodarcis siculus

Abstract

The expansion of agriculture causes a constant increase in habitat fragmentation and degradation due to the increased use of pesticides and herbicides. Habitat loss and alteration associated with agricultural expansion play an important role in the decline of reptiles and, among them, lizards are particularly endangered. This chapter describes the toxic effects of pure glyphosate on the liver of the common field lizard Podarcis siculus. Glyphosate (GLY) is the most widely used active ingredient in agrochemical formulations worldwide to maximize crop yields. The onset of liver damage was evaluated after oral administration of GLY to simulate a realistic situation of herbicide exposure in the lizard habitat. The results demonstrate a severe liver condition, with fibrotic formations that become scarring with increased exposure. Hepatocytes enhance their defense mechanism by activating their antioxidant systems and increasing the expression of p53. The results also confirm the xenoestrogenic nature of GLY. Altogether, the effects of GLY must be considered biologically relevant and could endanger the viability and survival of lizard populations, also unbalancing the trophic cascade. A more controlled and less intensive use of the herbicide GLY in areas devoted to crop production would therefore be advisable.

Glyphosate Interference in Follicular Organization in the Wall Lizard Podarcis siculus

“…The most evident damage in Podarcis ovaries is observed in the theca, the collagen-rich compartment, enveloping the follicles, which become very thick and compact. Collagen accumulation has already been reported in the liver [ 24 , 34 ] and in the testis in Podarcis lizards [ 25 , 35 , 36 ] and rats [ 37 ]. Therefore, thecal cells are markedly compressed among fibers and apparently reduced in number.…”

Could Exposure to Glyphosate Pose a Risk to the Survival of Wild Animals? A Case Study on the Field Lizard Podarcis siculus

“…Data on the effects of Gly in P. siculus tissues were obtained by exposing these animals to pure technical-grade Gly, as described in our previous works [ 53 , 54 , 55 , 56 ]. Briefly, sexually mature specimens were captured in uncontaminated wooded areas of the Campania region (Italy) and exposed orally to two different concentrations of the active ingredient (0.05 and 0.5 µg/kg body weight) three times a week for 3 weeks.…”

“…In these experiments, it was preferred to use low but repeated doses of Gly, thus mimicking the possible accumulation that these animals can suffer by feeding on contaminated food and water, even from a single spraying of the herbicide. After the treatments, animals were killed by decapitation after deep anesthesia (ketamine hydrochloride, 325 g/kg body weight); liver and gonads slices were removed and used fresh after fixation in Bouin’s and freezing for subsequent investigations, which led to the results described in [ 53 , 54 , 55 , 56 ] and summarized below.…”

“…Considering that the liver controls oocyte growth in oviparous vertebrates by producing vitellogenin (VTG) under estrogen signaling [ 58 ], it is clear that any impairment in this signaling can have deleterious effects on oogenesis [ 59 ]. Along with changes in estrogen receptor expression and synthesis, other Gly-induced structural and functional injuries similar to that found in the ovary have also been described in the liver; these damages were detected in the livers of both males and females [ 53 , 56 ].…”

“…Histological analysis showed massive deposition of type IV collagen, leading to the formation of large areas of fibrosis and fibrotic nodules ( Figure 2 ); the mechanical barrier created by the collagen fiber deposits also compressed the vessels, thus altering blood fluid dynamics and inducing the observed hypertrophy of blood vessels, as shown in Figure 2 . The stress condition induced by the herbicide on the liver was also manifested by the appearance of lipofuscin granules and melanomacrophages, the decrease of glycogen storage in the hepatocytes, as well as the overexpression of both enzymatic and non-enzymatic molecules involved in oxidative stress, such as superoxide dismutase 1 (Cu/Zn SOD, known as SOD1), glutathione peroxidase 1 (GPx1), metallothionein (MT), and tumor suppressor protein 53 (p53) [ 53 , 56 ].…”