Does a short-term exposure to cadmium chloride affects haemocyte parameters of the marine gastropod Haliotis tuberculata?

Status in molluscan cell line development in last one decade (2010–2020): impediments and way forward

Despite the attempts that have started since the 1960s, not even a single cell line of marine molluscs is available. Considering the vast contribution of marine bivalve aquaculture to the world economy, the prevailing viral threats, and the dismaying lack of advancements in molluscan virology, the requirement of a marine molluscan cell line is indispensable. This synthetic review discusses the obstacles in developing a marine molluscan cell line concerning the choice of species, the selection of tissue and decontamination, and cell culture media, with emphasis given on the current decade 2010-2020. Detailed accounts on the experiments on the virus cultivation in vitro and molluscan cell immortalization, with a brief note on the history and applications of the molluscan cell culture, are elucidated to give a holistic picture of the current status and future trends in molluscan cell line development.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-022-00539-x.

Effects of microplastics and mercury on manila clam Ruditapes philippinarum: Feeding rate, immunomodulation, histopathology and oxidative stress

Plastic pollution, which is one of the most important environmental problems at the present time, has been understood recently, and the effects of this pollution on ecosystem and biota are becoming a growing problem, especially in the aquatic ecosystems. Direct or indirect exposure to those particles leads to adverse effects on marine organisms. In the marine environment, plastic materials interact with other pollutants such as metals, thereby affecting the uptake levels of those pollutants in marine organisms. In the present study, the Manila clam Ruditapes philippinarum was exposed to polyethylene microbeads and mercury chloride in single, combined and incubated form at environmentally relative concentrations for one week in controlled laboratory conditions. The uptake and tissue distribution of both stressors as well as the vector role of microplastics on mercury uptake in the organisms were investigated. Filtration rates, biomarkers for immunomodulation and oxidative stress, and histological alterations were also evaluated. Microplastics were ingested by the clams, and translocated to the various tissues. However, contaminated microplastics displayed a negligible vector role in terms of mercury bioaccumulation in the clams. The single and interactive exposure of the stressors reduced the filtration rate in the clams. Both pollutants affected the immune system of the organisms. Histological alterations were determined in the gill and digestive gland tissues of the clams among the treatment groups, although oxidative stress biomarkers remained unchanged. This study suggests that the vector role of polyethylene microplastics in mercury uptake is negligible and reveals that the single and interactive one-week exposure of two pollutants induce toxicity in the manila clams.

Transcriptomic profile of oyster Crassostrea gigas hemocyte after short-term cadmium exposure and bacteria stimulation

Oyster Crassostrea gigas, is considered as a useful environmental indicator since it is widely distributed along the intertidal zone whereby it tends to accumulate cadmium and is always exposed to various pathogen agents. However, its molecular responses to both cadmium and pathogen stimulation remain unclear. In the present study, transcriptome data of hemocytes from oysters were analyzed to reveal specific molecular responses of oyster to cadmium or cadmium/bacteria stimulation. A total of 21591, 22872 and 20107 genes were detected in the BLANK, Cd24h and Cd/Bac24h group, respectively. Among them, there were 685 differentially expressed genes collected in the comparison of Cd24h versus BLANK. GO analysis of these genes found that sixteen terms into the Molecular Function category displayed transporter activities, and were all over-enrichment by cadmium exposure, whereas twelve terms into Biological Process category involved mainly in metabolic process of the various cellular components and two terms into Cellular Component category were all under-enrichment. The 330 immune responsive genes were shared by two gene lists of CdBac24h versus BLANK and CdBac24h versus Cd24h, and seven out of thirty terms in GO analysis were related to the immune process. Further annotation of these genes from the KEGG database revealed fourteen pathways, including two nervous system related pathways, arachidonic acid pathway, four immune pathways, MAPK cascade and other four cell signaling pathways, and two energy related pathways. Twenty-two differentially expressed genes were identified to responsive to both cadmium exposure and bacteria stimulation, but in different expression patterns, suggesting that bilateral responsive genes, such as alkaline phosphatase and sodium and chloride-dependent glycine transporter gene, could be candidate biomarkers for early warning of cadmium pollution. The present results collectively indicated that a profound neuro-endocrine-immune regulatory network was activated in response to cadmium and bacteria stimulation in oyster C. gigas, and the expression pattern of some cadmium responsive genes may be either reversed or strengthened by bacteria stimulation. The results provide knowledge on the transcriptomic response profile of oyster after short-term cadmium exposure and bacteria stimulation, which would be useful for future studies on stress response mechanism of mollusc, and some cadmium-bacteria responsive genes may be explored as potential biomarkers for monitoring marine pollution.

Differential sensitivity to cadmium of immunomarkers measured in hemocyte subpopulations of zebra mussel Dreissena polymorpha

Increasing discharge of industrial wastes into the environment results in pollution transfer towards hydrosystems. These activities release heavy metals such as cadmium, known as persistent pollutant that is accumulated by molluscs and exercise immunotoxicological effects. Among molluscs, the zebra mussel, Dreissena polymorpha constitutes a suitable support for freshwater ecotoxicological studies. In molluscs, homeostasis maintain is ensured in part by hemocytes that are composed of several cell populations involved in multiple physiological processes such as cell-mediated immune response or metal metabolism. Thus, hemocytes constitute a target of concern to study adverse effects of heavy metals. The objectives of this work were to determine whether immune-related endpoints assessed were of different sensitivity to cadmium and whether hemocyte functionalities were differentially affected depending on hemocyte subpopulation considered. Hemocytes were exposed ex vivo to concentrations of cadmium ranging from 10^-6 M to 10^-3 M for 21h prior flow cytometric analysis of cellular markers. Measured parameters (viability, phagocytosis, oxidative activity, lysosomal content) decreased in a dose-dependent manner with sensitivity differences depending on endpoint and cell type considered. Our results indicated that phagocytosis related endpoints were the most sensitive studied mechanisms to cadmium compared to other markers with EC₅₀ of 3.71±0.53×10^-4M for phagocytic activity and 2.79±0.19×10^-4M considering mean number of beads per phagocytic cell. Lysosomal content of granulocytes was less affected compared to other cell types, indicating lower sensitivity to cadmium. This suggests that granulocyte population is greatly involved in metal metabolism. Mitochondrial activity was reduced only in blast-like hemocytes that are considered to be cell precursors. Impairment of these cell functionalities may potentially compromise functions ensured by differentiated cells. We concluded that analysis of hemocyte activities should be performed at sub-population scale for more accurate results in ecotoxicological studies.

Responses of primary cultured haemocytes derived from the marine gastropod Haliotis tuberculata to an industrial effluent exposure

This study assessed the responses of primary cultured haemocytes from the marine gastropod Haliotis tuberculata exposed to the increasing concentrations of industrial effluent (0, 0.5, 1, 10, 15 and 20%) discharged into the Tunisian coastal area. Analyses showed the presence of metals such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), zinc (Zn), nickel (Ni) and lead (Pb) in the effluent. The effects of this mixture of pollutants on abalone haemocyte parameters were reflected by a significant decrease of cell viability, phagocytotic activity and reactive oxygen species (ROS) production as well as morphological and lysosomal membrane alterations. Thus, these results indicated that our primary culture system represents a suitable in vitro model for monitoring of anthropogenic contaminants in aquatic environments.

The cell cultures and the use of haemocytes from marine molluscs for ecotoxicology assessment

Among aquatic organisms suitable for biological monitoring, molluscs occupy a prominent place due to their wide geographic distribution, their abundance and accessibility in the field as well as in aquaculture. Molluscs reflect the degree of environmental contamination and are the most useful bioindicator tools. The study of modulation of immune system or immunomodulation in marine molluscs has become one of the privileged ways for evaluating the physiological effects of environmental factors. Physiological responses of molluscs to environmental stresses could be mediated by haemocytes. These cells are continually exposed to the external environment due to the open circulatory system of molluscs and are affected by pollutants. In fact, several studies showed the effects of different environmental contaminants on haemocyte functions (viability, phagocytosis, ROS production) as well as on proteins involved in cytoskeletal structure maintenance using the in vitro approaches. In ecotoxicology, in vitro approach is an alternative to animal testing due to the reduced use of experimental animals, low cost and rapid performance. Although several studies showed the importance of using in vitro cell models to determine the effects of different environmental contaminants on haemocyte parameters in marine molluscs, a few reviews highlight these effects. The main purpose of this paper is to summarize the recent data on the effect of some xenobiotics on haemocyte parameters in some mollusc species and then suggest future research prospects.