Responses of circulating fish phagocytes to paper mill effluent exposure

Rescheduling the process of nanoparticle removal used for water mercury remediation can increase the risk to aquatic organism: evidence of innate immune functions modulation in European eel (Anguilla anguilla L.)

This study aimed to assess the mechanisms of innate immune function responses to silica-coated iron oxide nanoparticle functionalized with dithiocarbamate groups (IONP) exposure alone and its associated mercury (Hg) in European eel (Anguilla anguilla L.) phagocytes isolated from peritoneum (P-phagocytes), gill (G-phagocytes), head kidney (HK-phagocytes) and spleen (S-phagocytes). The study evaluated viability, phagocytosis, oxidative burst activity (OBA) and lipid peroxidation (LPO). Four groups were made: (1) 2 × 10(6) phagocytes + RPMI-1640 (control), (2) 2 × 10(6) phagocytes + IONP (2.5 mg L(-1)), (3) 2 × 10(6) phagocytes + Hg (50 μg L(-1)) and (4) 2 × 10(6) phagocytes + IONP + Hg. Samplings were performed at 0, 2, 4, 8, 16, 24, 48 and 72 h of exposure. A. anguilla P-, G-, HK- and S-phagocytes in vitro exposure to IONP alone revealed either increased (except HK-phagocytes at 16 h) or no change in viability, suggesting that the cells are metabolically active and resistant to IONP exposure alone. In terms of phagocytes overactivation and reactive oxygen species (ROS) production as an indirect mechanism of immunotoxicity, the phagocytes responded in the following manner: P- > S- > HK- = G-phagocytes for IONP exposure alone, S- > HK- > P- = G-phagocytes for Hg exposure alone and HK- > G- = S- > P-phagocytes for concomitant exposure. Overall, considering Hg as a surrogate for metals and its association with IONP, as well as the likelihood that it could pose a serious threat to aquatic organisms by modulating their immune defense mechanisms if accidentally discharged into the aquatic environment, current results suggest that the step of IONP-metal complex removal must not be underrated and should be processed without any more ado.

Adverse effects of enrofloxacin when associated with environmental stress in Tra catfish (Pangasianodon hypophthalmus)

The aim of this study was to assess the adverse effects of enrofloxacin (EF) on Tra catfish, Pangasianodon hypophthalmus, in relation with density stress. Fish were held at 40, 80 or 120 fish m(-3) and fed with pellets containing either 1 g kg(-1) EF or no EF. Antibiotic exposure lasted 7d and all fish were fed without EF for another 7-d recovery period. Fish were sampled at 3, 7, 8, 10 and 14 d after the beginning of EF exposure. Lipid peroxidation (LPO) and total glutathione (GSH) levels, catalase (CAT), glutathione-s-transferase (GST) and acetylcholine-esterase (AChE) activities were assessed in gill, brain, liver and muscle. At day 7, LPO levels in gills of EF-fish reared at low or high density were significantly more than 5-fold higher than their respective control. On the contrary, LPO in gills of EF-fish reared at medium density was significantly 3-fold lower than the control fish. Similarly, CAT activities in gills of EF-fish reared under low or high density were higher than in their control groups, while this activity was lower in EF-fish of the medium density group. AChE activities in muscles of EF-fish reared at low or high density were lower than controls at days 3 and 7, respectively. These results suggest that EF exposure may lead to disorders like lipid peroxidation and neural dysfunction in fish. However, when reared under lower stress condition (medium density), they may cope better with EF-induced stress than chronically stressed fish (low or high density).

Wild juvenile Dicentrarchus labrax L. liver antioxidant and damage responses at Aveiro Lagoon, Portugal

The Aveiro Lagoon, at the north-western coast of Portugal, has been under considerable anthropogenic pressure for the last 5 decades. In order to perform an adequate survey of the effects induced by the contaminants in presence, wild juveniles Dicentrarchus labrax (sea bass) were selected. Thus, sea bass was captured at five sites: Torreira (TOR, as reference site), Gafanha (GAF), Rio Novo Príncipe (RIO), Laranjo (LAR) and Vagos (VAG) in autumn 2005. Liver defence responses such as catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (GSHt), total non-protein thiols (NP-SH) and metallothioneins (MT) were measured. Liver damage was determined as lipid peroxidation (LPO) and DNA integrity loss. RIO, LAR and VAG presented lower CAT, GR, GST activities and NP-SH and GSHt depletion in comparison to TOR. VAG and LAR showed higher GPx activity when compared to TOR. The highest MT level was found at GAF and VAG. The NP-SH and DNA integrity decreased at GAF compared to TOR. This field study demonstrated that not only antioxidant induction but also inhibitory responses must be considered as a signal of contamination.

Pro-apoptotic effect of fly ash leachates in hepatocytes of freshwater fish (Channa punctata Bloch)

The pro-apoptotic effect of fly ash leachates (FAL) was studied in the hepatocytes of an Indian freshwater fish, Channa punctata Bloch. Hepatocytes were exposed to different concentrations of '7-day' FAL for 24 and 48h and various parameters of apoptosis were studied using standardized procedures. FAL-induced apoptosis in hepatocytes was indicated by cytological examination, DNA fragmentation and DNA laddering. The induction in cytochrome-c release, caspases 3, 7, 10 and 9 activities and lactate dehydrogenase level provide mechanistic platform for FAL-induced apoptosis. Cytological examination showed an unambiguous apoptotic effect of ash leachates in fish hepatocytes. Exposed hepatocytes also showed increased production of H(2)O(2), superoxide ions and an increase in lipid peroxidation (LPO). The present study suggests a possible role of reactive oxygen species (ROS) in FAL-induced apoptosis in hepatocytes. Lactate dehydrogenase, LPO and apoptosis as biomarkers of cytotoxicity have recently been used for assessment of ecotoxicological impact of environmental chemicals. Our findings show that these biomarkers may also be used for evaluation of ecotoxicological impact of complex chemical mixture such as fly ash and its leachates.

Responses of European eel (Anguilla anguilla L.) circulating phagocytes to an in situ closed pulp mill effluent exposure and its association with organ-specific peroxidative damage

The effect of bleached kraft pulp mill effluent (BKPME) persistent compounds on phagocyte activities and its organ-specific influence in gill, kidney and liver was studied in European eel (Anguilla anguilla L.). Eels were caged and plunged at 3 different sites-50 m (site 1), 100 m (site 2) and 2,000 m (site 3) away from the end of the closed BKPME discharging channel for 8 and 48 h. Gill, head kidney and peritoneum phagocytes oxidative burst activity (OBA) was measured by the nitroblue tetrazolium reduction assay whereas lipid peroxidation (LPO) in eel gill, kidney and liver was measured by thiobarbituric acid reaction. A significant gill OBA induction was found at 8h on site 2, and on sites 1, 2 and 3 at 48 h exposure. However, in head kidney and peritoneal exudate phagocytes, OBA induction was significant only at sites 2 and 3 after 48 h exposure. In those particular sites, a significant increase in gill, kidney and liver LPO was measured that is assumed to result from OBA induction. Considering OBA and LPO, gill is the most affected tissue compared to kidney and liver. Gill vulnerability towards peroxidative damage was demonstrated at 8h on site 2 and at 48 h on sites 1, 2 and 3, whereas in kidney was observed at sites 2 and 3 only at 48 h. Liver LPO increased at site 2 only after 48 h exposure. Our results demonstrate that the OBA activation pattern in gill and kidney is associated with the induced peroxidative damage extent in those organ, together with water pollution the exposure route, resulting from previous BKPME effluent sediment contamination which may affect the activation pattern of circulating fish phagocytes.

Anguilla anguilla L. antioxidants responses to in situ bleached kraft pulp mill effluent outlet exposure

This study assesses the antioxidant enzymes activities viz., catalase, glutathione peroxidase, glutathione S-transferase and nonenzymatic antioxidant molecule such as glutathione in Anguilla anguilla L. gill, kidney and liver in response to 8- and 48-h exposure to bleached kraft pulp mill effluent (BKPME). A. anguilla were caged and plunged at three different sites-50 (Site 1), 100 (Site 2) and 2000 m (Site 3) away from the closed BKPME outlet. A significant gill (8 and 48 h) and kidney (48 h) catalase activity decrease was observed at site 2 exposure whereas liver showed a significant increase in catalase activity after 8 and 48 h to site 1 exposure. Glutathione peroxidase (GPX) activity was significantly decreased in gill after 8-h exposure to site 1 and 48-h exposures to sites 1 and 2, respectively. Concerning gill, kidney and liver glutathione S-transferase (GST) activity, a significant gill GST activity decrease after 8 h at site 2 and 48 h at sites 1 and 2 was observed; in kidney, a significant decrease in its activity was observed after 48 h at sites 1 and 2, respectively, whereas in liver, the decrease was significant only at site 2 after 48-h exposure. The in situ BKPME exposure caused a significant total gill and kidney reduced glutathione (GSH) decrease after 8 h at site 2 exposure and after 48 h at site 1 and 2 exposures, respectively. However, a biphasic response was observed in liver, i.e. initial significant increase after 8 h at site 2 followed by a significant decrease after 48 h to the same site exposure. The enzymatic and nonenzymatic antioxidants pattern in gill and kidney, as observed in this study, was different than liver, demonstrating that the liver was more resistant to oxidative damage than gill and kidney. In addition, A. anguilla gill, kidney and liver antioxidants adaptation potentials may serve as a surrogate biomarker to BKPME exposure.

Enzymatic and nonenzymatic antioxidants as an adaptation to phagocyte-induced damage in Anguilla anguilla L. following in situ harbor water exposure

Anguilla anguilla L. were caged for 8 and 48 h in harbor water of Aveiro Lagoon, Portugal. Respiratory burst activity (RBA) of peritoneal, head kidney, and gill phagocytes was measured. Lipid peroxidation (LPO) was estimated in gill, kidney, and liver. Liver ethoxyresorufin-O-deethylase (EROD) activity, cytochrome P450 (Cyt P450) content, and bile metabolites were assayed. Various antioxidant enzymes, viz., glutathione peroxidase, catalase, and glutathione S-transferase and nonenzymatic antioxidant, viz., total reduced glutathione were also studied. Harbor water xenobiotics induced a significant RBA increase in gill after 8 h; whereas in peritoneum and head kidney it increased after 48 h exposure. These responses were adversely associated with tissue-specific peroxidative damage since significant LPO increase was observed in gill (8 and 48 h), kidney (48 h), and liver (48 h). The tissue most affected was gill. Moreover, liver EROD activity, Cyt P450 content and bile metabolites remain unaltered after 8 h; in contrast, 48 h exposure showed significant EROD activity decrease and pyrene-type bile metabolites increase. Decreased EROD activity may be associated with concomitant liver damage, as increased LPO was observed after 48 h. Furthermore, the tissue-specific damage corresponded to the differences in the antioxidant potentials of the tissues, since the initial exposure period caused a significant increase in liver antioxidant activities, whereas gill and kidney showed a significant decrease, demonstrating that liver is highly adaptive to oxidative damage. However, at 48 h exposure gill, kidney, and liver showed a suppressive antioxidant effect, probably due to PAHs, since a significant induction at PAH-type bile metabolites has been seen. Our results demonstrate that phagocyte activation and associated peroxidative damage are concomitantly corroborated with enzymatic and nonenzymatic antioxidant activity differences. In addition, hepatic antioxidant induction after short-term exposure may serve as a potent biomarker for water pollutants in fish.

Naphthalene-induced differential tissue damage association with circulating fish phagocyte induction

The effect of naphthalene on phagocytes and associated abnormal cellular activities was studied in Anguilla anguilla L. Fish were exposed to sublethal concentrations (0.1, 0.3, 0.9, 2.7 microM) of naphthalene for 8, 16, 24, 48, and 72 h. Gill, head kidney, and peritoneum phagocyte respiratory burst activity (RBA) was measured by nitroblue tetrazolium reduction assay, whereas lipid peroxidation in fish gill, kidney, and liver was measured by thiobarbituric acid reaction substance. A significant increase (P < 0.05-P < 0.001) in total cell count (TCC) of phagocytes (TCCPH) isolated from gill, head kidney, and peritoneum was observed after 8 h of naphthalene exposure and persisting at 16 h exposure. However, long-term exposures (24, 48, and 72 h) induced a significant (P < 0.05-P < 0.001) decrease in TCC at all the concentration levels. Naphthalene exposure caused a significant (P < 0.05-P < 0.001) RBA induction after 8 and 16 h in gill, head kidney, and peritoneal phagocytes, which consequently resulted in a significant (P < 0.01 and P < 0.001) peroxidative tissue damage increase measured as lipid peroxidation (LPO) in gill, kidney, and liver at the same time intervals. Considering TCCPH, RBA, and LPO, the most affected tissues were gill and kidney after 8 and 16 h exposure to all naphthalene concentrations. RBA was significantly decreased after 24, 48, and 72 h of exposure (P < 0.05-P < 0.001), whereas peroxidative damage increased significantly (P < 0.05-P < 0.001) and persisted in long-term exposures (72 h) at all concentration levels in gill and kidney. Liver short-term exposure (8 and 16 h) to all naphthalene concentrations did not alter LPO activity. Long-term exposures (48 and 72 h) caused a significant (P < 0.01 and P < 0.001) LPO increase, which was more pronounced at 72 h. The results demonstrate that the activation pattern of RBA was corroborated by the extent of phagocyte-induced peroxidative damage in the tissues, as demonstrated by a significant increase of circulating phagocytes. However, the route of exposure and mode of entry of a pollutant may affect the activation pattern of circulating fish phagocytes. It is proposed that measurement of phagocyte-induced reactive oxygen species and their association with peroxidative damage in fish tissues may prove to be useful in biomonitoring fish exposure to aquatic pollutants.

Induction of hepatic antioxidants in freshwater catfish (Channa punctatus Bloch) is a biomarker of paper mill effluent exposure

Enzymatic and non-enzymatic antioxidants serve as an important biological defense against environmental oxidative stress. Information on antioxidant defense in fish is meager despite that fish are constantly exposed to a myriad of environmental stress including the oxidants. This study, therefore, assesses the activities of antioxidant enzymes viz., glutathione peroxidase, catalase and glutathione S-transferase and the non-enzymatic antioxidants viz., glutathione and metallothionein in various tissues of freshwater fish Channa punctatus (Bloch), in response to short-term and long-term exposures to paper mill effluent. The fish were exposed to the effluent at a concentration of 1.0% (v/v) for 15, 30, 60 and 90 days. The exposure caused a time-dependent increase in glutathione level (P < 0.001), activities of glutathione peroxidase (P < 0.05 to P < 0.001), glutathione S-transferase (P < 0.001) and a marginal initial decrease in catalase activity in the liver (P < 0.01 to P < 0.001). Metallothionein was induced in liver after 60 days of exposure. Two isoforms of metallothionein were detected. Catalase activity also increased 60 days afterwards. Antioxidant pattern was different in gill and kidney showing that liver was more resistant to oxidative damage as compared to gills and kidney. Our results demonstrate a pollutant-induced adaptive response in fish. In addition, levels of enzymatic and non-enzymatic tissue antioxidants may serve as surrogate markers of exposure to oxidant pollutants in fish.

Pollutant-induced over-activation of phagocytes is concomitantly associated with peroxidative damage in fish tissues

Pollutant-induced abnormal functioning of phagocytes and associated consequences were studied in freshwater catfish Heteropneustes fossilis (Bloch). Fish were exposed to effluent collected from bleached kraft type of paper mill at the concentration levels of 0.5, 1 and 2% for 15, 30, 60 and 90 days. Respiratory burst activity of peritoneal and head kidney phagocytes of exposed fish was measured by nitroblue tetrazolium reduction assay. Lipid peroxidation (LPO) was estimated in liver, gill and kidney of fish by measuring thiobarbituric acid reaction substances. It was observed that the phagocyte-activating xenobiotics of effluent induced an increase in the respiratory burst activity in phagocytes. The induction of respiratory burst activity was concomitantly associated with an increase in the peroxidative damage of tissues. The tissues most affected were kidney and gills. The change in LPO values in the gills of exposed fish was concentration- and time-dependent, showing significant increases (P<0.05 to <0.001) in all the exposed groups as compared with control fish. An almost similar pattern of LPO was observed in head kidney tissue (P<0.05 to <0.001). As regards liver, increase in LPO was not widespread, except at 0.5% for 90 days (P<0.05). In fact, reduced rates of LPO were observed in the livers of some groups. The results of respiratory burst corroborate with the phagocytic activation as well as with the extent of lipid peroxidation in the tissues, showing high population of circulatory phagocytes. Our results demonstrate that fish of polluted water are subjected to oxidative stress of multifarious dimensions.