Molecular and phenotypic responses of Japanese medaka (Oryzias latipes) early life stages to environmental concentrations of cadmium in sediment

Abstract

Japanese medaka embryos were exposed to environmental concentrations of cadmium (Cd) to investigate adverse and adaptive responses in fish early life stages. Embryos were exposed during their whole development by static sediment-contact to environmental Cd concentrations (2 and 20 μg/g dry weight). Cd bioaccumulation, developmental defects, biochemical and biomolecular (qRT-PCR) responses were analyzed in embryos and hatchlings. A dose-dependent increase of Cd bioaccumulation and developmental defects was observed at hatching. Cd had clear impacts on heartbeat and cardiac morphogenesis and also induced to spinal deformities. The profile and the level of gene transcription were differentially modulated according to the Cd concentration, the duration of exposure and/or the developmental stage of fish. Pro-apoptotic bax and DNA repair rad51 transcripts were significantly repressed in embryos exposed to the highest Cd concentration. Repression of these genes was correlated to the increase of heart rate in 6-day-old embryos. NADH-dehydrogenase nd5 gene transcription was inhibited in larvae at the lowest concentration suggesting mitochondrial respiratory chain impairment, in association with Cd-induced teratogenicity. Finally, wnt1 gene was overexpressed indicating putative deregulation of Wnt signaling pathway, and suggested to be implied in the occurrence of some spinal and cardiac deformities. Results of this study permitted to propose some promising markers at the transcriptional and phenotypical level, responding to environmental concentrations of Cd. The present work also highlights the usefulness of the modified version of the medaka embryo-larval assay with sediment-contact exposure (MELAc) to investigate the toxicity and the modes of action of sediment-bound pollutants.

The longitudinal effects of early developmental cadmium exposure on conditioned place preference and cardiovascular physiology in zebrafish

“…We report an increase in baseline heart rate of Cd-treated larval zebrafish. A similar result was reported for Japanese medaka (Oryzias latipes) exposed to Cd-spiked sediments during early development (Barjhoux et al 2016). In that study, a concentration dependent increase in heart rate by 6 dpf was reported and followed by a progressive drop in heart rate by 7dpf.…”

“…These results are similar to those described in other studies looking at developmental and adult Cd exposure in zebrafish (Banni et al 2011; Favorito et al 2011; Matz et al 2007). Japanese medaka exposed to Cd-spiked sediments over the same approximate developmental time course as ours showed similar Cd bioaccumulation (Barjhoux et al 2016). These bioaccumulation levels are also similar to those quantified for bass found in waterways with moderate to levels of Cd in sediments, but not in surface waters (Andres et al 2000; Otter et al 2012).…”

“…The increased cell death might lower pumping efficiency, and the resulting drop in peripheral blood pressure could induce a compensatory baroreflex in heart rate. Alternatively, others have proposed that metal exposure might induce a stress response that progressively raises the heart rate (Barjhoux et al 2016). In longitudinal adults, the only fish whose base line heart rates were affected significantly by Cd were those treated with 1.0 μM.…”

Accumulation of Cd in the Early Stages of the Development of Rainbow Trout Oncorhynchus mykiss Exposed to Cd-Based Quantum Dots and Cd Salt

“…The decrease of Cd accumulation in larvae exposed to QDs could be the consequence of the loss of QDs bound to the chorion occurring at hatching. Several studies have previously reported that more than 94% of the total accumulated Cd from salt was located on the chorion of O. latipes embryos exposed to 10 mg Cd/L (Michibata 1981) and 93 % more of Cd were in larvae than in embryos exposed to 2 and 20 µg Cd/L (Barjhoux et al 2016). According to Meteyer et al (1988), negatively charged mucopolysaccharides and glutamic acid in the chorion could retain and limit Cd uptake by the embryo.…”

“…In addition, Cd is an extremely toxic metal and its amount has increased over past decades due to its widespread industrial use and also nanotechnology uses (Barjhoux et al 2016). Several field studies demonstrated that Cd contamination could persist for many years in the aquatic environment because of its storage in sediments and its further release into the water column under favorable hydrodynamic conditions (Coynel et al 2007).…”