Indication of the impact of environmental stress on the responses of the bivalve mollusk Unio tumidus to ibuprofen and microplastics based on biomarkers of reductive stress and apoptosis

Reductive stress and cytotoxicity in the swollen river mussel (Unio tumidus) exposed to microplastics and salinomycin

Multistress effects lead to unpredicted consequences in aquatic ecotoxicology and are extremely concerning. The goal of this study was to trace how specific effects of the antibiotic salinomycin (Sal) and microplastics (MP) on the bivalve molluscs are manifested in the combined environmentally relevant exposures. Unio tumidus specimens were treated with Sal (0.6 μg L-1), MP (1 mg L-1, 2 μm size), and both at 18 °C (Mix) and 25 °C (MixT) for 14 days. The redox stress and apoptotic enzyme responses and the balance of Zn/Cu in the digestive gland were analyzed. The shared signs of stress included a decrease in NAD+/NADH and Zn/Cu ratios and lysosomal integrity and an increase in Zn-metallothioneins and cholinesterase levels. MP caused a decrease in the glutathione (GSH) concentration and redox state, total antioxidant capacity, and Zn levels. MP and Mix induced coordinated apoptotic/autophagy activities, increasing caspase-3 and cathepsin D (CtD) total and extralysosomal levels. Sal activated caspase-3 only and increased by five times Cu level in the tissue. Due to the discriminant analysis, the cumulative effect was evident in the combined exposure at 18 °C. However, under heating, the levels of NAD+, NADH, GSH, GSH/GSSG and metallothionein-related thiols were decreased, and coordination of the cytosolic and lysosomal death stimuli was distorted, confirming that heating and pollution could exert unexpected synergistic effects on aquatic life.

The odd couple: Caffeine and microplastics. Morphological and physiological changes in Mytilus galloprovincialis

In recent years, the presence of pharmaceuticals and microplastics (MPs) in aquatic ecosystems has raised concerns about their environmental impact. This study explores the combined effects of caffeine, a common pharmaceutical pollutant, and MPs on the marine mussel Mytilus galloprovincialis. Caffeine, at concentrations of 20.0 μg L-1, and MPs (1 mg L-1, 35-50 μm size range), was used to mimic real-world exposure scenarios. Two hundred M. galloprovincialis specimens were divided into four groups: caffeine, MPs, Mix (caffeine + MPs), and Control. After a two-week acclimation period, the mollusks were subjected to these pollutants in oxygen-aerated aquariums under controlled conditions for 14 days. Histopathological assessments were performed to evaluate gill morphology. Cellular volume regulation and digestive gland cell viability were also analyzed. Exposure to caffeine and MPs induced significant morphological changes in M. galloprovincialis gills, including cilia loss, ciliary disk damage, and cellular alterations. The chitinous rod supporting filaments also suffered damage, potentially due to MP interactions, leading to hemocyte infiltration and filament integrity compromise. Hemocytic aggregation suggested an inflammatory response to caffeine. In addition, viability assessments of digestive gland cells revealed potential damage to cell membranes and function, with impaired cell volume regulation, particularly in the Mix group, raising concerns about nutrient metabolism disruption and organ function compromise. These findings underscore the vulnerability of M. galloprovincialis to environmental pollutants and emphasize the need for monitoring and mitigation efforts. RESEARCH HIGHLIGHTS: The synergy of caffeine and microplastics (MPs) in aquatic ecosystems warrants investigation. MPs and caffeine could affect gill morphology of Mytilus galloprovincialis. Caffeine-exposed cells had lower viability than the control group in the NR retention test. MPs and mix-exposed cells struggled to recover their volume.

Nano-scale and micron-scale plastics amplify the bioaccumulation of benzophenone-3 and ciprofloxacin, as well as their co-exposure effect on disturbing the antioxidant defense system in mussels, Perna viridis

Plastics ranging from nano-scale to micron-scale are frequently ingested by many marine animals. These particles exhibit biotoxicity and additionally perform as vectors that convey and amass adsorbed chemicals within organisms. Meanwhile, the frequency of detection of the benzophenone-3 and ciprofloxacin can be adsorbed on plastic particles, then accumulated in bivalves, causing biotoxicity. To understand their unknown accumulative kinetics in vivo affected by different plastic sizes and toxic effect from co-exposure, several scenarios were set up in which the mode organism were exposed to 0.6 mg/L of polystyrene carrying benzophenone-3 and ciprofloxacin in three sizes (300 nm, 38 μm, and 0.6 mm). The live Asian green mussels were chosen as mode organism for exposure experiments, in which they were exposed to environments with plastics of different sizes laden with benzophenone-3 and ciprofloxacin, then depurated for 7 days. The bioaccumulation and depuration kinetics of benzophenone-3 and ciprofloxacin were measured using HPLC-MS/MS after one week of exposure and depuration. Meanwhile, their toxic effect were investigated by measuring the changes in six biomarkers (condition index, reactive oxygen species, catalase, glutathione, lipid peroxidation, cytochrome P450 and DNA damage). The bioconcentration factors in mussels under different exposure conditions were 41.48-111.75 for benzophenone-3 and 6.45 to 12.35 for ciprofloxacin. The results suggested that microplastics and nanoplastics can act as carriers to increase bioaccumulation and toxicity of adsorbates in mussels in a size-dependent manner. Overproduction of reactive oxygen species caused by microplastics and nanoplastics led to increased DNA damage, lipid peroxidation, and changes in antioxidant enzymes and non-enzymatic antioxidants during exposure. Marked disruption of antioxidant defenses and genotoxic effects in mussels during depuration indicated impaired recovery. Compared to micron-scale plastic with sizes over a hundred micrometers that had little effect on bivalve bioaccumulation and toxicity, nano-scale plastic greatly enhanced the biotoxicity effect.

Chlorpromazine's impact on Mytilus galloprovincialis: a multi-faceted investigation

The antipsychotic chlorpromazine (Cpz) has raised concern as a pharmaceutical effluent due to its wide medical applications. Moreover, its potent pro-oxidant properties and impact on the cell viability of the marine mollusc Mytilus galloprovincialis, even at low concentrations (ng/L), have been noted. Based on this evidence, in this study, we investigated the physiological effects of Cpz on M. galloprovincialis, to elucidate its fate within the organism, in terms of bioaccumulation, biotransformation, byssus changes and stress responses of the cellular thiolome. Histological and indicators of vitality analyses were also performed to better evaluate the influence of the drug on the morphology and cell viability of the digestive gland. To this end, two different concentrations of Cpz (Cpz I (12 ng/L or 37 pM) and Cpz II (12 μg/L or 37 nM)) were administered to mussels over 14 days. Cpz accumulation in the digestive gland significantly increased with water concentration (BCF of Cpz I and Cpz II). Biochemical analyses indicated lysosomal dysfunction, reflected in elevated total Cathepsin D activity and compromised lysosomal membrane stability. Stress-related and metal-buffering proteins (GST and metallothionein) responded to both Cpz concentrations. Cpz I induced phase I biotransformation activity (CYP450-dependent EROD), while Cpz II triggered caspase-3 activation, indicative of detoxification overload. Histological analysis revealed digestive gland atrophy, epithelial thinning, haemocyte infiltration, and brown cell presence. Byssus analysis showed significant alterations. In conclusion, our study underscores Cpz-induced physiological and histological changes in M. galloprovincialis, posing potential implications for mussel health and confirming the utilisation of this mussel as an indication of Cpz ecotoxicity.

Biochemical basis of resistance to multiple contaminations in the native and invasive populations of Dreissena polymorpha

The zebra mussel Dreissena polymorpha (Pallas, 1771) is an invasive species and a valuable bioindicator in the inland waters. Nevertheless, the biochemical reasons for the unique competitiveness of zebra mussels are not clear. This study aimed to compare the native and invasive populations of D. polymorpha in their ability to withstand the same multiple environmental challenges (i.e. chemical: microplastics and caffeine; physical: temperatures). The specimens from the invasive population in west Ukraine (Tn) and native population at lower streams of river Dnipro (south Ukraine, Kh) were sampled in the August of 2021 y. Molluscs from both populations were treated simultaneously with microplastics (MP, 1 mg L-1, pore size 2 μm); caffeine (Caf, 20.0 μg L-1) at 18 °C, elevated temperature (25 °C) and MP and Caf combinations at 18 °C and 25 °C for 14 days. Untreated molluscs exposed at 18 °C represented control groups. A set of the 20 markers of oxidative stress, biotransformation, detoxification and apoptosis were assayed in the total soft tissues. From the two controls, Kh-group indicated lower stressful impact. However, both populations increased caspase-3 and GST activities and lysosomal instability in most exposures, and cholinesterase and phenoloxidase activities under the heating and combine exposures, indicating the remarkable properties to respond to new challenges and synergistic effect of mixtures. Inter-population differences were related to the metallothionein, cathepsin D, cytochrome P540 and oxidative stress responses that reflect population-dependent adverse outcome pathways. The discriminant analysis separated two populations with a substantially lesser magnitude of responses in the invasive population as a sign of higher resistance.

Cellular and oxidative stress responses of Mytilus galloprovincialis to chlorpromazine: implications of an antipsychotic drug exposure study

Introduction: Bivalve molluscs like Mytilus galloprovincialis are valuable bioindicators due to their filter-feeding lifestyle, wide distribution, and ability to concentrate xenobiotics. Studying the effects of pharmaceuticals on these molluscs is crucial given their presence in surface waters. This study investigated the response of M. galloprovincialis to chlorpromazine (Cpz), an antipsychotic with antiviral activity against influenza, HIV, and coronaviruses in human cells. Methods: In this study, we examined the 14-day impact of chlorpromazine (Cpz) on the model species M. galloprovincialis at two concentrations (Cpz 1: 12 ng L-1 or 37 pM; Cpz 2: 12 µg L-1 or 37 nM). To ensure controlled exposure, a stock solution of Cpz was prepared and introduced into the tanks to match the intended concentrations. Seawater and stock solutions were refreshed every 48 h. The primary focus of this study centered on evaluating cell viability, cell volume regulation, and oxidative stress indicators. Results: Although cell volume regulation, as assessed by decreasing regulatory volume Regulation volume decrease, did not show statistically significant changes during the experiment, digestive cell viability, on the other hand, showed a significant decrease (p < 0.01) in the Cpz 2 group, suggesting effects on the general health and survival of these cells. Biochemically, in both Cpz 1 and Cpz 2, superoxide dismutase activity increased, while catalase (CAT) decreased, causing an elevated lipid peroxidation thiobarbituric acid-reactive substances and protein carbonyls, particularly in the Cpz 2 group. The level of reduced glutathione (GSH) increased in both exposures, whereas the level of GSSG increased only in the Cpz 1 group. Consequently, the GSH/GSSG ratio was elevated in the Cpz 2 group only. Discussion: A comparison of the magnitudes of anti- and pro-oxidative manifestations indicated a pro-oxidative shift in both exposures. These findings show that Cpz induces non-specific symptoms of biochemical and cellular disturbances in M. galloprovincialis even at the low picomolar concentration.

Immunotoxic effects of exposure to the antifouling copper(I) biocide on target and nontarget bivalve species: a comparative in vitro study between Mytilus galloprovincialis and Ruditapes philippinarum

Edible bivalves constitute an important bioresource from an economic point of view, and studies on their immune responses to environmental pollutants are crucial for both the preservation of biodiversity and economic reasons. The worldwide diffusion of copper(I)-based antifouling paints has increased copper leaching into coastal environments and its potential impact on both target and nontarget organisms. In this study, immunotoxicity assays were carried out with short-term (60 min) cultures of hemocytes from the bivalves Mytilus galloprovincialis-a mussel dominant in the macrofouling community-and Ruditapes philippinarum-a clam dominant in the soft-sediment community-exposed to CuCl to compare the toxic effects on their immune responses. The LC50 values were similar, 40 μM (3.94 mg L-1) for the mussel and 44 μM (4.33 mg L-1) for the clam. In both species, apoptosis occurred after exposure to 1 µM (98.9 μg L-1) CuCl, the concentration able to significantly increase the intracellular Ca2+ content. Biomarkers of cell morphology and motility revealed microfilament disruption, a significant decrease in yeast phagocytosis and lysosome hydrolase (β-glucuronidase) inhibition beginning from 0.5 µM (49.5 μg L-1) CuCl in both the mussel and clam. The same concentration of CuCl affected biomarkers of oxidative stress, as a significant decrease in reduced glutathione content in the cytoplasm and inhibition of mitochondrial cytochrome-c oxidase (COX) were detected in both species. Comparison of the biomarkers showed that clam is more sensitive than the mussel regarding alterations to the lysosomal membrane and reactive oxygen species (ROS) production, which supports the potential harmful effects of antifouling biocides on the survival of nontarget pivotal species in the coastal community.

Combined effect of microplastic, salinomycin and heating on Unio tumidus

Microplastic (MP) and heating (T) suspected to modulate biological effects of aquatic contaminants. Salinomycin (Sal) is veterinary antibiotic and anticancer agent. The goal of this study was to examine the multistress effect of MP, Sal and T on the bioindicator bivalve mollusc. The Unio tumidus were treated with MP (1 mg L^-1), Sal (0.6 µg L^-1), their combination under 18° C (Mix) and 25° C (MixT) for 14 days. The digestive glands were analyzed. MP and Sal did not cause changes of Mn- and Cu,Zn-SOD, lipid peroxidation and Cyp-450-depended EROD levels, whereas catalase, GST and protein carbonyls (Sal-group) increased compared to control. In the Mix-group, enzymes, particularly EROD and GST (by 34% and 115% respectively) were up-regulated. However, in the MixT-group, they were corresponding to control or lesser (EROD, catalase). Our findings emphasize the need to take into account multistress interactions in the MP environmental risk assessment.