Influence of titanium dioxide nanoparticles on 2,3,7,8-tetrachlorodibenzo-p-dioxin bioconcentration and toxicity in the marine fish European sea bass (Dicentrarchus labrax)

Highlights

• Nano-TiO₂ did not interfere with 2,3,7,8-TCDD detoxification and bioconcentration in liver.

• Nano-TiO₂ affected immune response towards 2,3,7,8-TCDD exposure in spleen.

• Co-exposure caused a reduction of DNA strand breaks respect to single chemicals exposure.

• Nano-TiO2 alone and combined with 2,3,7,8-TCDD increased MN frequencies in erythrocytes.

Abstract

The present study investigated the influence of nano-TiO₂ (1 mg L⁻¹) on 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) (46 pg L⁻¹) bioconcentration and toxicity in the European sea bass (Dicentrarchus labrax) during 7 days in vivo exposure. A multimarkers approach was applied in different organs: detoxification in liver; innate immunity and pro-inflammatory response and adaptive immunity in gills and spleen; genotoxicity in peripheral erythrocytes and muscle. Bioconcentration of 2,3,7,8-TCDD in presence of nano-TiO2 was investigated in liver, skin and muscle as well as interaction between nano-TiO2 and organic pollutants in artificial sea water (ASW). Nano-TiO2 negatively influenced immune response induced by 2,3,7,8-TCDD in spleen but not in gills and reduced the DNA damage induced by 2,3,7,8-TCDD in erythrocytes. nano-TiO2 did not interfere with 2,3,7,8-TCDD detoxification and bioconcentration according to the observed no interaction of the nano-TiO2 with organic pollutants in ASW.

Introduction

Titanium dioxide (nano-TiO₂) is one the most widespread NP used in consumer and personal care products, as well as in many industrial sectors (Robichaud et al., 2009). It is also employed for environmental applications (i.e. nanoremediation) as efficient catalyst and adsorbent of organic contaminants and heavy metals (Karn et al., 2009). Nano-TiO₂ is thus released in huge amount in urban and industrial sewage and it is expected to occur in the aquatic environment at concentration of μg L⁻¹ (PEC in water 0.7–16 ug L⁻¹) (Batley et al., 2013). A significant input of nano-TiO₂ from sunscreen products in natural surface waters has been recently reported (Gondikasam et al., 2014). From its release into soil and waterways as well as for direct use on maritime technologies, nano-TiO₂ will end up in the sea, which might represents the ultimate sink such to represent an actual risk for marine organisms (Moore, 2006, Delay and Frimmel, 2012, Matranga and Corsi, 2012, Holden et al., 2013). Being listed as possible carcinogen for humans (B2, IARC, 2006), toxicological effects and ecological damage for many marine organisms cannot be excluded and need to be deeply investigated. In freshwater species, immunotoxicity, cytotoxicity and oxidative stress as well as physiological and reproductive alterations, have been well documented (Jovanovic et al., 2011, Jovanovic and Palic, 2012, Menard et al., 2011, Diniz et al., 2013, Hartmann et al., 2013, Ramdsen et al., 2013). Same effects have been already reported in invertebrate marine species (Galloway et al., 2010, Canesi et al., 2012, Barmo et al., 2013, D'Agata et al., 2014, Minetto et al., 2014). As for marine fish nano-TiO₂ has shown to induce sub-lethal adverse effects on the early life stages of the brackish species Oryzias latipes as premature hatching, pericardial edema and abnormal development (Paterson et al., 2011) while the effects on adults are largely unknown. Two in vitro studies on marine mammals clearly showed that nano-TiO₂ cause genotoxicity in bottle-nose dolphin leukocytes (Bernardeschi et al., 2010) and fibroblasts (Frenzilli et al., 2014). Besides toxicity caused by its inherent properties, nano-TiO₂ might also interact with other co-existing environmental pollutants -as metals and organic xenobiotics-thus modifying their availability, bioaccumulation and toxicity. Such effect is reported for freshwater species where adsorption on nano-TiO₂ enhances uptake and retention of Cd²⁺ in carp and Daphnia (Zhang et al., 2007; Hartmann et al., 2010, Hartmann et al., 2012, Hu et al., 2011, Yang et al., 2012), while bioavailability and metabolism of an organic contaminant as BDE209 is enhanced by nano-TiO₂ in zebrafish larvae (Wang et al., 2014). The interaction of nano-TiO₂ with organic pollutants has been also reported in sea water. Enhanced toxicity of TBT was reported in the presence of nano-TiO₂ in marine abalone embryos (Zhu et al., 2011). In our previous study (Canesi et al., 2014) using the marine mussel Mytilus galloprovincialis as model species, complex interactions between nano-TiO₂ with 2,3,7,8-tetracholorodibenzo-p-dioxin (2,3,7,8-TCDD) were reported on a wide range of molecular and physiological biomarkers measured in hemolymph, gills and digestive gland. The co-exposure with nano-TiO₂ increased accumulation of 2,3,7,8-TCDD in whole soft tissue of mussels. Both synergistic and antagonistic sub-lethal effects were observed depending on cell/tissue type and measured biomarker. A similar study with marine clam Scapharca subcrenata showed an enhanced uptake and accumulation of Phenanthrene (PhE) in the presence of nano-TiO₂ based on an high adsorption capability of nano-TiO₂ in sea water (Tian et al., 2014). So far any studies have evaluated this phenomenon in fish species that possess completely different mechanisms of uptake/detoxification/toxicity compared to bivalves.

Therefore presence of nano-TiO₂ in marine waters and its potential interaction with organic pollutants highlight the susceptibility of marine organisms and the need of more studies on interactive effects of nano-TiO₂ with existing toxic contaminants in marine waters with particular focus on piscine models.

Amon organic pollutants 2,3,7,8-TCDD is one of the most potent carcinogenic chemical, able to elicit a wide spectrum of biological effects following specific cellular pathways (Mandal, 2005, White and Birnbaum, 2009). 2,3,7,8-TCDD and other organochlorines are usually detected in marine organisms (up to pg g⁻¹ in fish for 2,3,7,8-TCDD (Greco et al., 2010, Nunes et al., 2011) and biomagnify through trophic webs (Corsolini et al., 2002).

In the present study we investigated the influence of nano-TiO₂ on 2,3,7,8-TCDD bioconcentration and sub-lethal toxicity (detoxification, immunotoxicity, genotoxicity) in the marine fish European sea bass Dicentrarchus labrax during 7 days in vivo exposure.

A multimarkers approach was applied in different organs: detoxification (CYP1A gene and EROD activity) in liver; innate immunity and pro-inflammatory response (IL-1β, IL-8, TNF-α and Cox-2) and adaptive immunity (IgM, and TRβ) in gills and spleen; DNA primary damage and micronuclei occurrence in peripheral erythrocytes; genomic stability in muscle. Bioconcentration of 2,3,7,8-TCDD in presence of nano-TiO₂ was also investigated in skin, muscle and liver tissues as well as interaction in artificial sea water (ASW) between nano-TiO₂ and organic pollutants.