Survival and infectivity of Toxoplasma gondii and Cryptosporidium parvum oocysts bioaccumulated by Dreissena polymorpha

AIMS

The study was aimed to understand the depuration process of Cryptosporidium parvum and Toxoplasma gondii oocysts by zebra mussel (Dreissena polymorpha), to consider the use of the zebra mussel as a bioremediation tool.

MATERIALS AND METHODS

Two experiments were performed: (i) individual exposure of mussel to investigate oocyst transfers between bivalves and water and (ii) in vivo exposure to assess the ability of the zebra mussel to degrade oocysts.

RESULTS

(i) Our results highlighted a transfer of oocysts from the mussels to the water after 3 and 7 days of depuration; however, some oocysts were still bioaccumulated in mussel tissue. (ii) Between 7 days of exposure at 1000 or 10 000 oocysts/mussel/day and 7 days of depuration, the number of bioaccumulated oocysts did not vary but the number of infectious oocysts decreased.

CONCLUSION

Results show that D. polymorpha can release oocysts in water via (pseudo)faeces in depuration period. Oocysts remain bioaccumulated and infectious oocyst number decreases during the depuration period in zebra mussel tissues. Results suggest a degradation of bioaccumulated C. parvum and T. gondii oocysts.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlighted the potential use of D. polymorpha as a bioremediation tool to mitigate of protozoan contamination in water resources.

Aerobic and anaerobic energy production in juvenile roach (Rutilus rutilus): regulation of glycolytic process by ethofumesate at two temperatures

The aim of this study was to evaluate the coupled impact of an herbicide, ethofumesate, and temperature on the cellular energy metabolism of juvenile roach, especially on the glycolysis pathway. Juvenile roach were exposed to 0, 0.5, 5, and 50 μg/L of ethofumesate for 7 days in laboratory conditions at two temperatures (10 and 17 °C). The energy reserves (carbohydrate, lipid, and protein) were quantified, since the availability of substrates regulates the glycolysis. Then, the glycolysis was studied at the biochemical level by the measurement of the glycolytic flux and at the molecular level with the measurement of the relative expression of four genes encoding for glycolysis enzymes. This study revealed different effect of ethofumesate on the glycolysis pathway according to the temperature of exposure. Indeed, at 10 °C, it appeared that only the molecular regulation level was affected, whereas, at 17 °C, ethofumesate acted on the biochemical level. The differences observed between the two exposures imply the establishment of different strategies in order to maintain to cope with stress according to the temperature of exposure.

Motility of adherent hemocytes as a potential marker of immunocompetence and immunotoxic effects in bivalves

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Short-term immunotoxic effects of an anti-cancer drug (Etoposide) on the freshwater pondsnail Lymnaea stagnalis

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Multi-metallic contamination around former uranium mines induces adverse effects and acclimation disturbance in three-spined stickleback (Gasterosteus aculeatus)

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Effect of ethofumesate herbicide on energy metabolism in roach (Rutilus rutilus)

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Effects of aluminium and bacterial lipopolysaccharide on oxidative stress and immune parameters in roach, Rutilus rutilus L

Aluminium is used in diverse anthropogenic processes at the origin of pollution events in aquatic ecosystems. In the Champagne region (France), high concentrations of aluminium (Al) are detected due to vine-growing practices. In fish, little is known about the possible immune-related effects at relevant environmental concentrations. The present study analyzes the simultaneous effects of aluminium and bacterial lipopolysaccharide (LPS), alone and in combination, on toxicological biomarkers in the freshwater fish species Rutilus rutilus. For this purpose, roach treated or not with LPS were exposed to environmental concentrations of aluminium (100 μg/L) under laboratory-controlled conditions for 2, 7, 14 and 21 days. After each exposure time, we assessed hepatic lipoperoxidation, catalase activity, glutathione reductase activity and total glutathione content. We also analyzed cellular components related to the LPS-induced inflammatory response in possible target tissues, i.e. head kidney and spleen. Our results revealed a significant prooxidant effect in the liver cells and head kidney leukocytes of roach exposed to 100 μg of Al/L for 2 days. In liver, we observed more lipoperoxidation products and lower endogenous antioxidant activity levels such as glutathione reductase activity and total glutathione content. These prooxidant effects were associated with a higher oxidative burst in head kidney leukocytes, and they were all the more important in fish stimulated by LPS injection. These findings demonstrate that environmental concentrations of Al induce oxidative and immunotoxic effects in fish and are associated to an immunomodulatory process related to the inflammatory response.

Detection of immunotoxic effects of estrogenic and androgenic endocrine disrupting compounds using splenic immune cells of the female three-spined stickleback, Gasterosteus aculeatus (L.)

Today, the list of endocrine disrupting compounds (EDCs) in freshwater and marine environments that mimic or block endogenous hormones is expanding at an alarming rate. As immune and reproductive systems may interact in a bidirectional way, some authors proposed the immune capacities as attractive markers to evaluate the hormonal potential of environmental samples. Thus, the present work proposed to gain more knowledge on direct biological effects of natural and EDCs on female fish splenic leucocyte non-specific immune activities by using ex vivo assays. After determining the optimal required conditions to analyze splenic immune responses, seven different EDCs were tested ex vivo at 0.01, 1 and 100nM over 12h on the leucocyte functions of female three-spined stickleback, Gasterosteus aculeatus. In summary, we found that natural hormones acted as immunostimulants, whilst EDCs were immunosuppressive.

Energy metabolism and pesticides: biochemical and molecular responses to copper in roach Rutilus rutilus

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Effects of depleted uranium on immune parameters of zebrafish, Danio rerio, measured by flow cytometry

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Polychlorinated biphenyls in freshwater salmonids from the Kerguelen Islands in the Southern Ocean

The Subantarctic Kerguelen Islands (49°S, 70°E) contain freshwater ecosystems among the most isolated in the world. Concentrations of polychlorinated biphenyls (PCBs) were assessed in the muscle of 48 brook trout and 38 brown trout caught during summer and spring 2006 in the rivers, lakes and ponds of Kerguelen. The sum of 29 PCBs averaged 404 and 358 ng g(-1) lipid, and dioxin-like PCB was 19 and 69 ng g(-1) lipid, in brook and brown trout, respectively. The values showed a high variability and some fish accumulated PCBs at levels similar to those of fish from impacted areas. While inter-sex differences were limited, the season and the morphotype appeared to have the most influence. Fish captured in summer had muscle PCB concentrations about three times higher than those caught in spring and the 'river' morphotype of brook trout showed the highest PCB levels.

Investigation of the ability of the Pneumonia Severity Index to accurately predict clinically relevant outcomes: a European study

In order to confirm the validity of the Pneumonia Severity Index (PSI) for patients in Europe, data from adults with pneumonia who were enrolled in two prospective multicentre studies, conducted in France (Pneumocom-1, n = 925) and Spain (Pneumocom-2, n = 853), were compared with data from the original North American study (Pneumonia PORT, n = 2287). The primary outcome was 28-day mortality; secondary outcomes were subsequent hospitalisation for outpatients, and intensive care unit admission and length of stay for inpatients. All outcomes within individual risk classes, and mortality rates in low-risk (PSI I-III) and higher-risk patients, were compared across the three cohorts. Overall mortality rates were 4.7% in Pneumonia PORT, 6.3% in Pneumocom-2 and 10.6% in Pneumocom-1 (p <0.01), ranging from 0.4% to 1.6% (p 0.06) for low-risk patients and from 13.0% to 19.1% (p 0.24) for high-risk patients. Despite significant differences in baseline patient characteristics, none of the study outcomes differed within the low-risk classes. The sensitivity and negative predictive value of low-risk classification for mortality exceeded 93% and 98%, respectively. Thus, in two independent European cohorts, the PSI predicted patient outcomes accurately and reliably, particularly for low-risk patients. These findings confirm the validity of the PSI when applied to patients from Europe.

Immunology-related perturbations induced by copper and chitosan in carp (Cyprinus carpio L.)

Copper is used in treatment mixtures to control fungal diseases in vineyards. Its concentrations are relatively high in some aquatic ecosystems, and the main problem observed in this study was the antioxidant stress induced by this heavy metal. Copper toxicologic effects in aquatic organisms have prompted the demand for alternative use of low-toxicity molecules in culture treatments. Chitosan is a polymer with antifungal property similar to copper and may be an interesting biopesticide. Thus, it is necessary to investigate the potential toxicity of chitosan for aquatic animal health, either alone or in conjunction with copper. In this study, carp were exposed to two sublethal chitosan concentrations (75 and 150 mg/L) or to two sublethal copper concentrations (0.1 and 0.25 mg/L) or to a mixture of chitosan plus copper (75 mg/L and 0.1 mg/L, respectively). The results of the present study show that exposure to copper at environmentally realistic levels or to chitosan at sublethal concentrations may significantly stimulate various aspects of immune functions in carp such as nonspecific cellular immunity, represented by total immunoglobulin level, ceruloplasmin activity, and oxidative activity of phagocytes. This acute-phase inflammatory response induced separately by the two treatments was not observed, especially on phagocyte oxidative activity, when carp were exposed to the copper-chitosan mixture. This fact could be explained by a possible chelation of copper by chitosan decreasing the biodisponibility of the two products for immune cells. Thus, the immunotoxicologic impact of copper and chitosan on fish immune response would be less pronounced with the combined treatments than with separate treatments in an aquatic environment.

Stimulation of antioxidant enzymes levels in carp (Cyprinus carpio L.) infected by Ptychobothrium sp. (Cestoda)

Increased antioxidant enzymatic activities were observed in carp parasitised by Ptychobothrium sp. when compared with healthy fish. This antioxidant response could contribute to neutralise the oxidative stress normally induced by parasitism.

Lindane increases macrophage-activating factor production and intracellular calcium in rainbow trout (Oncorhynchus mykiss) leukocytes

The authors studied the in vitro effects of lindane on macrophage-activating factor (MAF) production by peripheral blood leukocytes (PBLs) in rainbow trout. MAF production by PBLs induced normally by mitogens concanavalin A (ConA) and phorbol myristate acetate (PMA) was not modified by a pretreatment with lindane (from 2.5 to 50 microM). Only a concentration of 100 microM lindane decreased MAF production, associated with cellular death. Moreover, MAF activities were detected in supernatants of PBL cultures treated with lindane from 2.5 to 10 microM in absence of ConA/PMA stimulation. Factors present in these supernatants remain to be identified. Lindane, at concentrations which did not induce MAF production (50 and 100 microM) led to an increase in PBL calcium levels by acting on the endoplasmic reticulum calcium stores. Although the intracytosolic calcium concentration ([Ca(2+)](i)) increase seems to be associated with cell death, lindane-induced MAF production may be linked with other intracellular mechanisms.

Antioxidant response modulated by copper in healthy or parasitized carp (Cyprinus carpio L.) by Ptychobothrium sp. (Cestoda)

An increased antioxidant response (catalase, glutathione S-transferase (GST) and glutathione reductase (GRd) activities in liver and GST activity in head kidney) was observed in carp parasitized by Ptychobothrium sp. compared to healthy fish. In case of a copper contamination of these fish, the decrease in enzymatic activities observed was less pronounced in parasitized than in healthy carp.

Lindane differently modulates intracellular calcium levels in two populations of rainbow trout (Oncorhynchus mykiss) immune cells: head kidney phagocytes and peripheral blood leucocytes

We studied the in vitro effects of high concentrations of the insecticide lindane (from 2.5 to 100 microM) on intracellular calcium levels ([Ca(2+)](i)) in rainbow trout head kidney phagocytes and peripheral blood leucocytes (PBLs). [Ca(2+)](i) was measured during 6 min by spectrofluorimetry using Indo-1/AM as fluorescent probe. Lindane, from 5 to 100 microM, increased [Ca(2+)](i) in PBLs and from 25 microM in phagocytes. In Ca(2+)-free medium, only 50 and 100 microM lindane increased significantly [Ca(2+)](i) in PBLs and only 100 microM lindane in phagocytes. However, lindane at 5 and 10 microM, induced a decrease in [Ca(2+)](i) in phagocytes suspended in Ca(2+)-free medium. Lindane needed extracellular calcium to rise [Ca(2+)](i) in phagocytes but not in PBLs. Lindane effects on endoplasmic reticulum (ER) calcium store was examined. In spite of mobilisation by lindane of ER calcium store in phagocytes, it had an opposite effect in PBLs. The composition of the two cell population can explain the differences in calcium modulation observed. [Ca(2+)](i) is an extremely important signal transduction element in physiology and modulation of [Ca(2+)](i) by lindane can be responsible for modulations of immune cell functions. Moreover, sustained rises in [Ca(2+)](i) as observed in our study may be associated with cell death and explained partially the cytotoxicity of this organochlorine insecticide on fish immune cells.

Lindane increases in vitro respiratory burst activity and intracellular calcium levels in rainbow trout (Oncorhynchus mykiss) head kidney phagocytes

Phagocytic cells are the main actors of the fish immune system. They secrete reactive oxygen species (ROS) involved in their bactericidal activity. The effects of lindane on ROS production in rainbow trout phagocytes are contradictory. Here, we study the effects of high concentrations of lindane on ROS production (by chemiluminescence) and on intracellular calcium levels ([Ca(2+)](i)) (by spectrofluorimetry) in trout phagocytes. In these cells, lindane from 2.5 to 10 µM, increases ROS production and has no effect on [Ca(2+)](i). From 25 to 200 µM, lindane leads to a rise in ROS production (maximal value measured: 41152+/-6253 RLU for 100 µM lindane) associated with an increase in [Ca(2+)](i) (+3149+/-96 nM for 100 µM lindane) and with cytotoxicity which appears 2 min after addition of 100 µM lindane (25.4+/-3.75%; P<0.05). In the absence of extracellular calcium, ROS production of lindane-treated cells remains significantly higher than in controls (maximal value measured: 1899+/-254 RLU for 25 µM lindane), a significant decrease in [Ca(2+)](i) is observed in cells treated with 5 or 10 µM lindane (-54+/-35 nM for 10 µM lindane), and an increase in [Ca(2+)](i) in cells treated with 100 µM lindane (330+/-33 nM). The rise in [Ca(2+)](i) induced by lindane is inhibited when cells are preincubated with thapsigargin (Thaps). We conclude that lindane induces an increase in [Ca(2+)](i)50 µM) alter Ca(2+) homeostasis in the absence of extracellular Ca(2+), confirming that lindane can affect other intracellular stores of Ca(2+). At low concentrations (<25 µM), lindane stimulates ROS production by Ca(2+)-independant mechanisms without inducing cytotoxicity. From 25 µM, lindane increases [Ca(2+)](i) and maximal cytotoxicity appears from 100 µM lindane. Lindane toxicity in fish phagocytes may be associated with high [Ca(2+)](i) and high ROS production. Thus, ROS are beneficial in protection of the organism but when ROS are produced in excess, they can be toxic for cells and tissues.

[Antibody response, cortisolemia and prolactinemia in rainbow trouts]

We have studied the humoral immune response (production of anti-Yersinia ruckeri antibodies), and measured the levels of plasmatic hormones (cortisol and prolactin) in rainbow trout (Oncorhynchus mykiss) subjected to hyperosmotic stress (NaCl, 22 / 1000). Under acute stressful conditions (saline stress during 7 days), high blood cortisol and prolactin (PRL) levels were correlated with a weak anti-Yersinia ruckeri antibody response, as evidenced by late and low antibody titres as compared to normal fish. Interestingly, the group of fish subjected to chronic stress (till 30 days) exhibited no significant differences in blood cortisol and prolactin levels despite low antibody titres as compared to control group. Hence, it is possible that in acute stress, cortisol and prolactin levels might exert immunosuppressive effects on antibody production, whereas in chronic stress other neuroendocrine hormones might result in curtailed humoral immunity.