Copper Oxide and Zinc Oxide Nanomaterials Act as Inhibitors of Multidrug Resistance Transport in Sea Urchin Embryos: Their Role as Chemosensitizers

Abstract

The ability of engineered nanomaterials (NMs) to act as inhibitors of ATP-binding cassette (ABC) efflux transporters in embryos of white sea urchin (Lytechinus pictus) was studied. Nanocopper oxide (nano-CuO), nanozinc oxide (nano-ZnO), and their corresponding metal ions (CuSO4 and ZnSO4) were used as target chemicals. The results showed that nano-CuO, nano-ZnO, CuSO4, and ZnSO4, even at relatively low concentrations (0.5 ppm), significantly increased calcein-AM (CAM, an indicator of ABC transporter activity) accumulation in sea urchin embryos at different stages of development. Exposure to nano-CuO, a very low solubility NM, at increasing times after fertilization (>30 min) decreased CAM accumulation, but nano-ZnO (much more soluble NM) did not, indicating that metal ions could cross the hardened fertilization envelope, but not undissolved metal oxide NMs. Moreover, nontoxic levels (0.5 ppm) of nano-CuO and nano-ZnO significantly increased developmental toxicity of vinblastine (an established ABC transporter substrate) and functioned as chemosensitizers. The multidrug resistance associated protein (MRP, one of ABC transporters) inhibitor MK571 significantly increased copper concentrations in embryos, indicating ABC transporters are important in maintaining low intracellular copper levels. We show that low concentrations of nano-CuO and nano-ZnO can make embryos more susceptible to other contaminants, representing a potent amplification of nanomaterial-related developmental toxicity.

Comparative environmental fate and toxicity of copper nanomaterials

“…Conversely, while nCuO did not cause changes in mitochondrial membrane potential (MMP), CuSO 4 significantly (p < 0.05) decreased MMP even at 1 mg/L. Interestingly, nCuO (≥ 500 μg/L) and CuSO 4 (≥200 μg/L) acted as a chemosensitizers and increased the developmental toxicity of vinblastine, a cell division inhibitor (Torres-Duarte et al, 2016;Wu et al, 2015).…”

Developmental effects of two different copper oxide nanomaterials in sea urchin (Lytechinus pictus) embryos

“…Stock dispersions of 1000 ppm of both nano-CuO were prepared as previously reported (Fairbairn et al, 2011;Wu et al, 2015), and details are provided in the Supplemental Material. A range of nano-CuO suspensions were prepared in 0.45 mm FSW containing 0.2 ppm of alginic acid (Sigma-Aldrich, St. Louis, MO) and stored for 96 h at 16 C. Alginic acid is produced by brown algae and is a source of organic carbon and was used in concentrations similar to what can be found in natural marine environments; this also helps increase nanoparticle stability in the water column (Loosli et al, 2013).…”

“…The filtrate was acidified to pH 1.7 with trace metal grace HCl (Fisher Scientific, Fair Lawn, NJ) 6N and stored until analysis. Total copper concentration was also determined using chemiluminescence (Durand et al, 2013;Wu et al, 2015), which has a linear response (R 2 ¼ 0.9942) from 1 to 70 ppb copper (Supplementary Material).…”

“…Some of these NMs may be released from antifouling paint matrices into the aquatic environment, where they can exert their toxic effects in non-target organisms (Rawat et al, 2010). Previous toxicological studies of copper oxide nanomaterial (nano-CuO) in marine and estuarine organisms show that the NMs can accumulate in the tissue and cause oxidative stress, inhibit enzymatic activity, affect embryonic development and defense mechanisms at low concentrations, and at high doses, can cause mortality (Gomes et al, 2011;Hanna et al, 2014;Hanna et al, 2013;Hu et al, 2014;Wu et al, 2015). We selected the sea urchin as our model system for studying the potential impact of nano-CuO in coastal environments, focusing on the most sensitive developmental stages (Hamdoun & Epel, 2007).…”

“…Exposure to chemicals during early development has major impacts on the establishment of the embryonic axis of sea urchins, affecting their morphology, development and survival as larvae (Fernández & Beiras, 2001;Pillai et al, 2003). Though toxicity of nano-CuO in sea urchin embryos has been previously studied (Wu et al, 2015), detailed studies on the mechanisms of nano-CuO developmental toxicity are lacking. In the present study, we investigated the effects of soluble Cu 2+ and two nano-CuOs on sea urchin embryo development.…”