The neurotoxicity of Paraquat and its degradation products on drosophila melanogaster

Abstract

Photodegradation is a promising technique for remediating contaminated environmental matrices. It demonstrates significant potential in transforming organic contaminants into carbon dioxide, water, and inorganic anions through degradation reactions that involve transient oxidizing species, mainly hydroxyl radicals generated by ultraviolet (UV) irradiation. In this study, we investigated whether the photodegradation of Paraquat (PQ) with UV irradiation reduced its toxicity in Drosophila melanogaster. Our results indicate that ingesting PQ degradation products by larvae resulted in a low axial ratio (pupal volume). In the adults, it resulted in markedly diminished climbing ability in a time-dependent manner after 10 days of feeding. In addition, exposure of D. melanogaster to photodegradation of PQ reduced acetylcholinesterase and citrate synthase activities but improved oxidative stress, as evidenced by protein carbonyl, and lactate production. These results suggest that the photodegradation of PQ with UV irradiation produced PQ fragments with higher toxicity than PQ, while the precise mechanism of its action requires further investigation.

Keywords: Drosophila melanogaster; Degradation products; Neurotoxicity; Photodegradation; UV irradiation.

Fig. 1

Full spectra of HRMS for a sample of PQ in (A) and 10 min (B) of PQ with UV irradiation.

Fig. 2

HRMS for Sample A. In (A) an expansion between 170 and 175 and a comparison with theoretical for the m/z 171.0915; in (B) an analysis in MS-MS mode for the m/z 171.

Fig. 3

Quantification of pupal volume in D. melanogaster by axial relationship. The body shape of a pupa can be described by length (L) / width (W). The values represent the mean ± S.E.M of five experiments. The results were considered statistically significant when *p < 0.05, **p < 0.01: ^avs. CTRL, ^bvs. PQ, ^cvs. 10 min, ^dvs. 15 min, and ^evs. 30 min of photolysis.

Fig. 4

Behavioral parameters. (A) Lifespan (percentual of survival) of D. melanogaster submitted to a diet supplemented with degradation products of PQ and (Figure S1) (B) Climbing ability of D. melanogaster fed a diet supplemented with degradation products of PQ and statistical analyses as supplementary material (Figure S2).

Fig. 5

Indirect measurement of ^•NO by the Griess Reaction in (A) thoraces and (B) heads of D. melanogaster fed on a diet supplemented with PQ and degradation products. The values represent the mean ± S.E.M of three independent experiments.

Fig. 6

Protein carbonyl content in (A) thoraces and (B) heads of D. melanogaster fed on a diet supplemented with PQ and degradation products. The values represent the mean ± S.E.M of three independent experiments. The results were considered statistically significant when *p < 0.05, **p < 0.01: ^avs. CTRL, ^bvs. PQ.

Fig. 7

Lactate concentration in (A) thoraces and (B) heads of D. melanogaster fed on a diet supplemented with PQ and degradation products. The values represent the mean ± S.E.M of three independent experiments. The results were statistically significant when *p < 0.05, **p < 0.01: ^avs. CTRL.

Fig. 8

CS activity in (A) thoraces and (B) heads of D. melanogaster fed on a diet supplemented with PQ and degradation products. The values represent the mean ± S.E.M of three independent experiments. The results were considered statistically significant when ***p < 0.001, ****p < 0.0001: ^avs. CTRL.

Fig. 9

AChE activity in (A) thoraces and (B) heads of D. melanogaster fed on a diet supplemented with PQ and degradation products. The values represent the mean ± S.E.M of three independent experiments. The results were considered statistically significant when ***p < 0.001, ****p < 0.0001: ^avs. CTRL.