Cadmium nitrate and DNA methylation in gastropods: comparison between ovotestis and hepatopancreas

Abstract

Dietary ingestion is the main route of exposure to hazardous contaminants in land animals. Cadmium, a high-profile toxic metal, affects living systems at different organismal levels, including major storage organs (liver, kidneys), key organs for species survival (gonads), and epigenetic networks regulating gene expression. 5-methylcytosine (5mC) is the most common and best-characterized epigenetic mark among different modified nucleosides in DNA. This important player in methylation-driven gene expression is impacted by cadmium in sentinel terrestrial vertebrates. However, limited information exists regarding its impact on macroinvertebrates, especially land snails commonly used as (eco)toxicological models. We first investigate the methylomic effects of dietary cadmium given as cadmium nitrate on terrestrial mollusks. Mature specimens of the common brown garden snail, Cornu aspersum, were continuously exposed for four weeks to environmentally-relevant cadmium levels. We determined global genomic DNA methylation in hepatopancreas and ovotestis, as well as changes in the methylation status of CG pairs at the 5′ region close to the transcription site of gene encoding the Cd-selective metallothionein (Cd-MT). Weight gain/loss, hypometabolism tendency, and survival rates were also assessed. Although this exposure event did not adversely affect survival, gastropods exposed to the highest Cd dose revealed a significant reduction in body weight and a significant increase in hypometabolic behavior. The hepatopancreas, but not the ovotestis, displayed significant hypermethylation, but only for the aforementioned specimens. We also found that the 5′ end of the Cd-MT gene was unmethylated in both organs and its methylation status was insensitive to cadmium exposure. Our results are important since they provide scientists, for the first time, with quantitative data on DNA methylation in gastropod ovotestis and refine our understanding of Cd epigenetic effects on terrestrial mollusks.

DNA Methylation Machinery in Gastropod Mollusks

“…Cadmium induced an increase in the total 5mC content of hepatopancreas DNA, but only for relatively high exposure doses and times (as shown in Table 2). This effect seemed to be mediated by the type of inorganic anion bound to cadmium, with chloride ions having a stronger effect than either sulfate ions or nitrate ions [77][78][79]. The global DNA methylation levels in ovotestis, however, were not affected by exposure to cadmium nitrate [79] (as described in Table 2).…”

“…Geyer et al (2016) found that exposure to the demethylating agent 5-aza-C significantly inhibited egg production and embryo development in the planorbid snail, Biomphalaria glabrata [38]. In a study with sexually mature specimens of Cornu aspersum, Drăghici et al (2023) reported significant hypermethylation of the ovotestis compared to the hepatopancreas [79], possibly reflecting the more stringent regulation of genes crucial for reproductive processes in the former organ [83,85]. The foregoing authors also identified significantly elevated transcript levels for several key genes of the DNA methylation machinery in the gonadal structures of B. glabrata compared to somatic tissues, such as the head/foot, central nervous system, buccal mass, salivary glands, hepatopancreas, stomach, heart, kidneys, and mantle edge.…”

“…We focus on results originating from controlled experiments, since this approach allows for precise control over environmental conditions, isolation of variables, and high replicability of obtained data [34]. Among different trace metals derived from anthropogenic sources, toxicological studies to date have focused on cadmium (Cd)-a potent modulator of the DNA methylome [79]. These experiments have used C. aspersum as a study system and were conducted under controlled laboratory environments using different cadmium salts as a source of Cd [77][78][79].…”

“…Among different trace metals derived from anthropogenic sources, toxicological studies to date have focused on cadmium (Cd)-a potent modulator of the DNA methylome [79]. These experiments have used C. aspersum as a study system and were conducted under controlled laboratory environments using different cadmium salts as a source of Cd [77][78][79]. Cadmium induced an increase in the total 5mC content of hepatopancreas DNA, but only for relatively high exposure doses and times (as shown in Table 2).…”

Mass-Spectrometry-Based Research of Cosmetic Ingredients

“…Affects the fetus and the central nervous system in Children [230,231], probably carcinogenic to humans [232,233], neurotoxic, nephrotoxic, and hepatotoxic and can also produce effects on the reproductive system, and can also affect fetal development through its passage via the placenta [234][235][236][237][238][239]. Cadmium (Cd) 0.1 ppm -Damage of the kidneys, fragility of the bones, carcinogenic in humans [240][241][242]. Arsenic (As) 0.5 ppm 3 ppm (colorants) Skin eruptions, alopecia, and striation of the nails, but also skin cancer [243], circulatory and peripheral nervous disorders, an increased risk of lung cancer, and a possible increase in the risk of gastrointestinal tract and the urinary system cancers [244].…”