Silvano Focardi

Oxidative stress in ecotoxicology: from the analysis of individual antioxidants to a more integrated approach.

An integrate approach will be discussed for investigations on oxidative stress in xenobiotic toxicity. While the analysis of individual antioxidants is useful for their sensitivity and to understand the mode of action of a stressor, the integration with the analysis of the total antioxidant capacity provides a more holistic assessment of the overall biological significance of such variations. TOSC has a greater predictive value on the health condition of the organisms and allows to discriminate the different role of specific ROS in oxidative stress syndrome.

CONGENER PROFILE AND TOXICITY ASSESSMENT OF POLYCHLORINATED BIPHENYLS IN DOLPHINS, SHARKS AND TUNA COLLECTED FROM ITALIAN COASTAL WATERS

Abstract Bottlenose and Rissos dolphins found dead along the Italian coast in 1992 were analysed for the presence of PCB isomers and DDT. High concentrations of PCBs (90–1400 μg/g wet wt) were detected in the blubber of stranded carcasses. The concentrations were higher than those found in animals showing reproductive failure and physiological impairment following prolonged PCB exposure, suggesting that the contamination by PCBs as well as DDT may be a major causative factor for the large-scale deaths of dolphins in the Mediterranean Sea. The 2,3,7,8-TCDD toxic equivalents estimated for bottlenose and Rissos dolphins were 18.8 and 20.8 ng/g, respectively, with a major contribution from mono-ortho PCBs. The monoortho congeners of IUPAC Nos 105, 118 and 156 accounted for most of the toxicity exerted by PCBs in these dead dolphins. An increase in the proportion of non-ortho coplanar PCB congener of IUPAC No. 169 to No. 126 with an increase in the total PCB concentration in the blubber suggested a strong induction of drug metabolizing enzymes. It is possible to use CB-169 CB-126 concentration ratio to indicate whether there has been a strong activation of cytochrome P450 enzyme system in severely exposed/contaminated dolphin populations. The total PCB concentrations in the adipose fat of sharks from Italian coasts ranged from 70 to 4000 ng/g wet wt and that of DDT from 14 to 300 ng/g wet wt. In bluefin tuna, the total PCB and DDT concentrations were 170–2200 and 56–780 ng/g wet wt, respectively. These values were comparable to those reported for the same species in the Mediterranean Sea during the 1970s, suggesting the existence of PCB sources near this marine ecosystem.

Isomer-specific analysis and toxic evaluation of polychlorinated biphenyls in striped dolphins affected by an epizootic in the western Mediterranean sea.

Isomer-specific concentrations of polychlorinated biphenyls (PCBs) including planar, mono- and di-ortho congeners and concentrations of DDT were determined in striped dolphins affected by a morbillivirus epizootic in the western Mediterranean in 1990. Extremely high concentrations of PCBs ranging from 94 to 670 μg/g (wet wt) were detected in the blubber. Similarly, DDT concentrations were high, between 22 and 230 μg/g (wet wt). The concentrations of three non-ortho coplanar PCBs were 43 (3,3′,4,4′-T4CB), 6.8 (3,3′,4,4′,5-P5CB), and 7.8 (3,3′,4,4′,5,5′-H6CB) ng/g (wet wt), respectively, the highest residue levels reported to date. The estimated 2,3,7,8-TCDD toxic equivalents of non-, mono- and di-ortho PCB congeners in striped dolphins were several times higher than those observed for other marine mammals and humans. Mono-ortho congeners contributed greater 2,3,7,8-TCDD toxic equivalents than non-ortho members. The higher ratio of 3,3′,4,4′,5,5′-H6CB/3,3′,4,4′,5-P5CB (IUPAC 169/126) suggested a strong induction of mixed function oxidase enzymes and highlighted the possibility of using this ratio as an index for risk assessment of PCB contamination in marine mammals. Elevated concentrations of PCBs may have played a role in the immune depression in striped dolphins, ultimately leading to the development of morbillivirus disease.

Integrating enzymatic responses to organic chemical exposure with total oxyradical absorbing capacity and DNA damage in the European eel Anguilla anguilla.

In this work, susceptibility to oxidative stress was analyzed under laboratory conditions in the European eel Anguilla anguilla. Eels were treated with increasing concentrations of benchmark environmental pollutants, namely, benzo[a]pyrene ([BaP], at 0, 0.1, 1, 10, and 50 mg/kg), beta-naphthoflavone ([BNF], at 0, 0.1, 1, 10, and 50 mg/kg), Arochlor 1254 (at 0, 0.1, 1, 10, and 50 mg/kg), and 2,3,7,8-tetrachlorodibenzo p-dioxin ([TCDD], at 0, 0.01, 0.1, 1, and 2 microg/kg). The integral relationships were analyzed between induction of ethoxyresorufin O-deethylase (EROD) activity, its involvement in perturbing oxyradical metabolism, and the role of cytochrome P450 and/or oxidative stress in mediating genotoxic effects. To reveal whether the oxidative status in exposed organisms was altered as a result of chemical exposure, measurements of the main endogenous antioxidant defenses were integrated with the measurement of total oxyradical scavenging capacity (TOSC) toward peroxyl radicals and hydroxyl radicals (*OH). This approach permits discriminating the resistance of a tissue toward different forms of oxyradicals, thereby indicating a differential role for specific reactive oxygen species (ROS) in perturbing the balance between prooxidant and antioxidant mechanisms. All the analyzed chemicals promoted EROD induction (reflective of CYP1A) and altered either the levels or the activities of the antioxidants studied, which might be anticipated to exert alterations in oxyradical metabolism. Analysis of TOSC suggested the prevalence of metabolic oxidative pathways leading to the more reactive *OH on exposure to the chemicals studied. Of these chemicals, enhanced EROD activity correlated with genotoxic damage only in the cases of the nonhalogenated hydrocarbons BaP and BNF. The highest degree of genotoxic damage was consistently observed in organisms in which the capacity to absorb or scavenge OH was lowest. These data suggest a general relationship between oxidative stress and loss of DNA integrity in juvenile eels exposed to the chemicals studied herein.

Sex differences in Adélie penguin foraging strategies

Abstract Consistent sex differences in foraging trip duration, feeding locality and diet of breeding Adélie penguins (Pygoscelis adeliae) were demonstrated at two widely separated locations over several breeding seasons. Differences in foraging behaviour were most pronounced during the guard stage of chick rearing. Female penguins made on average longer foraging trips than males, ranged greater distances more frequently and consumed larger quantities of krill. In contrast, males made shorter journeys to closer foraging grounds during the guard period and fed more extensively on fish throughout chick rearing. Mean guard stage foraging trip durations over four seasons at Béchervaise Island, Eastern Antarctica and over two seasons at Edmonson Point, Ross Sea ranged between 31 and 73 h for females and 25 and 36 h for males. Ninety percent of males tracked from Béchervaise Island by satellite during the first 3 weeks post-hatch foraged within 20 km of the colony, while the majority (60%) of females travelled to the edge of the continental shelf (80–120 km from the colony) to feed during this period.

Elevated cadmium accumulation in marine organisms from Terra Nova Bay (Antarctica)

As a contribution towards identification of the principal environmental factors involved in cadmium accumulation in Antarctic marine organisms and the establishment of a baseline near the Italian Antarctic Station “Baia Terra Nova”, surface sediments, plankton and benthic organisms were studied in coastal waters of Terra Nova Bay (Ross Sea). The cadmium content of sediments was similar to that regarded as background in most marine coastal areas, whereas in surface water, phytoand Zooplankton it was similar to values measured in areas of enhanced upwelling. Algal and animal taxa dominating benthic associations had a higher cadmium content than related species from other seas. Very high concentrations of the metal were found in sponges (10–80 μg/g dw) and in the digestive gland of molluscs (up to 345 μg/g inNeobuccinum eatoni). The rapid regeneration of cadmium and its natural occurrence and bioavailability in highly productive coastal waters seem to be responsible for cadmium accumulation in the tissues of marine organisms near the “Baia Terra Nova” station.

Accumulation Pattern of Butyltin Compounds in Dolphin, Tuna, and Shark Collected from Italian Coastal Waters

Tributyltin (TBT) and its breakdown products, mono-(MBT) and dibutyltin (DBT) were determined in bottlenose dolphin (Tursiops truncatus), bluefin tuna (Thunnus thynnus thynnus) and blue shark (Prionace glauca) collected from the Italian coast of the Mediterranean Sea in 1992–1993. Concentrations of total butyltin (BTs) in the liver of dolphin (1,200–2,200 ng/g wet wt) were an order of magnitude higher than in the blubber (48–320 ng/g wet wt). TBT was the predominant butyltin species in the blubber while DBT accounted for an higher proportion in the liver of dolphins. Butyltin concentrations in bluefin tuna were lower than those in dolphins, with TBT highest in the muscle and DBT in the liver. Concentrations of BTs in blue sharks were lower than those in dolphin and tuna, with kidney having the highest concentrations. TBT was the predominant form of butyltin derivatives in all the tissues of shark. Accumulation of butyltin compounds in liver/kidney seems to be associated with the presence of proteins such as glutathione.

Heavy metals and selenium in stranded dolphins of the Northern Tyrrhenian (NW Mediterranean)

Heavy metal (Hg, Cd, Pb and Zn) and selenium levels were determined in striped (Stenella coeruleoalba) and bottle-nosed dolphins (Tursiops truncatus) stranded along the coast of Tuscany and Latium, Italy in the period 1987-1989. Lead and zinc concentrations were quite low and there was modest accumulation of cadmium in the kidney of both species. Mercury levels were very high, especially in the liver where they reached peaks of 4400 ppm (dry weight) in the striped dolphin and 13,150 ppm (dry weight) in the bottle-nosed dolphin. Selenium levels were also high and were significantly correlated with mercury levels in some organs and tissues. The toxicological significance of the selenium-mercury interaction is discussed.

The use of non-destructive biomarker in Mediterranean cetaceans: Preliminary data on MFO activity in skin biopsy

Abstract Cetaceans have been subjected to heavy anthropogenic pressure in the last century. In addition to hunting there is now the subtle threat of pollution which may be responsible for metabolic impairment and involved in stranding episodes and population decline. The need to study pollutants and their effect on cetacean populations is often in contrast with the need to protect these animals. In this paper a new method of collecting skin and hypodermic biopsies in the Fin whale (Balaenoptera physalus) and Striped dolphin (Stenella coeruleoalba) in order to analyse Mixed Function Oxidase (MFO) activity and organochlorine contents, is described. The results show marked differences between the two species. MFO activity in skin and organochlorines in blubber are higher in Striped dolphin than the Fin whale. The new method enables the main effects of exposure to lipophilic contaminants to be assessed in a nondestructive way in biomarker studies.

Organochlorine levels in subcutaneous blubber biopsies of fin whales (Balaenoptera physalus) and striped dolphins (Stenella coeruleoalba) from the Mediterranean Sea.

Polychlorinated biphenyls (PCBs) and DDT compounds were determined in subcutaneous blubber of fin whales (Balaenoptera physalus) and striped dolphins (Stenella coeruleoalba) from the Mediterranean Sea. From 1990 to 1993, 68 fin whale and 89 dolphin blubber biopsies were analysed. The whales were sampled while passing through the Ligurian Sea, whereas the dolphins were collected in different areas of the Mediterranean: the Ligurian, Tyrrhenian and Ionian Seas. Total PCBs and DDTs were 5.5-7.1 ppm and 4.2-9.5 ppm, respectively, in the whales and 15.5-86.0 ppm and 15.6-63.5 ppm, respectively, in the dolphins. Thirty PCB congeners were identified for each sample, IUPAC numbers 153, 138, 187, 180 and 170 being the most abundant, totalling an average of 55% of total PCBs in the whale and 60% in the dolphin. The large differences in accumulation are related to position in the food chain. In striped dolphins significant differences were found in relation to sampling site, and in fin whales in relation to sex.