The capability of Roundup to distort Zinc functionality in bivalve mollusk in the ex vivo and in vivo exposures

Abstract

BACKGROUND AND AIM: One of the common effects of herbicide Roundup (Rn, commercial formulation of glyphosate) is its adhesive activity towards metal ions. Zinc (Zn) plays the crucial role in plural biochemical reactions. The aim of this study was to elucidate the ability of Rn to distort Zn functionality in the ex vivo and in vivo exposures of bivalve mollusk. METHODS: In the ex vivo exposures, the digestive gland of Unio tumidus was exposed during 17 h to Rn (0.08 - 3.0 µM of glyphosate), 3.0 µM of Zn or Zn chelator TPEN (Tp) and their combinations ZnTp or ZnRn. In the in vivo exposures, the mussels were exposed to Rn (40 and 80 nM) during 14 days. The level of Zn in the tissue (Znt) and metallothioneins (Zn-MT), metallothioneins (MTSH) and glutathione (GSH&GSSG) concentrations, total antioxidant capacity (TAC), lysosomal membrane integrity (NRR test) and caspase-3 activity were determined. RESULTS:In the ex vivo exposures, the most consequent changes were indicated at 3 µM of Rn as the oxidative injury (decreased TAC and GSH levels). Similarly, in the in vivo exposures, the pro-oxidative effect of Rn was indicated at 80 nM. However, in the ex vivo exposure to ZnRn, the Znt or caspase-3 activity were not distorted, unlike under the effect of TPEN which caused opposite effects to Zn: decreased Znt and Zn-MT, increased caspase-3 activity. In the in vivo exposures, 80 nM of Rn caused a distortion of metallo-thiolome due to increased levels of insufficiently metalated MTSH and decreased Znt. The toxicity of Rn in the ex vivo and in vivo exposures was confirmed by the loss of lysosomal membrane integrity. CONCLUSIONS:Roundup does not affect directly the intracellular Zn functionality, unlike TPEN, but can distort it via the thiols oxidation. KEYWORDS: Bivalve mollusc, Roundup, Zinc, Metallothionein