Roberto Caricato

Acetylcholinesterase as a Biomarker in Environmental and Occupational Medicine: New Insights and Future Perspectives

Acetylcholinesterase (AChE) is a key enzyme in the nervous system. It terminates nerve impulses by catalysing the hydrolysis of neurotransmitter acetylcholine. As a specific molecular target of organophosphate and carbamate pesticides, acetylcholinesterase activity and its inhibition has been early recognized to be a human biological marker of pesticide poisoning. Measurement of AChE inhibition has been increasingly used in the last two decades as a biomarker of effect on nervous system following exposure to organophosphate and carbamate pesticides in occupational and environmental medicine. The success of this biomarker arises from the fact that it meets a number of characteristics necessary for the successful application of a biological response as biomarker in human biomonitoring: the response is easy to measure, it shows a dose-dependent behavior to pollutant exposure, it is sensitive, and it exhibits a link to health adverse effects. The aim of this work is to review and discuss the recent findings about acetylcholinesterase, including its sensitivity to other pollutants and the expression of different splice variants. These insights open new perspective for the future use of this biomarker in environmental and occupational human health monitoring.

Carbonic Anhydrase as Pollution Biomarker: An Ancient Enzyme with a New Use

The measurement of cellular and sub-cellular responses to chemical contaminants (referred to as biomarkers) in living organisms represents a recent tool in environmental monitoring. The review focuses on carbonic anhydrase, a ubiquitous metalloenzyme which plays key roles in a wide variety of physiological processes involving CO2 and HCO3−. In the last decade a number of studies have demonstrated the sensitivity of this enzyme to pollutants such as heavy metals and organic chemicals in both humans and wildlife. The review analyses these studies and discusses the potentiality of this enzyme as novel biomarker in environmental monitoring and assessment.

Biomarker application for the study of chemical contamination risk on marine organisms in the taranto marine coastal area

This work represents a pilot study for monitoring the potential toxicological risk of commercial relevant marine resources along the South coast of Italy by using biomarkers as complementary tool to chemical analysis. The attention was focused on the industrialized area of Salento peninsula, such as Taranto, that, in spite of the presence of the big industry (oil, metal industry), sustains activities related to the sea resources, such as fishery and mussel-culture. The study was carried out in fish, such as Mullus barbatus and Trachurus mediterraneus, two important fish species for the fishery in this area, and in mussels (Mytilus galloprovincialis). As control area S. Maria di Leuca, area of naturalistic interest, was chosen. In fish, liver metallothionein levels (specific index of exposure to heavy metals such as Hg, Cd, Cu and Zn) and brain and muscular acetylcholinesterase (AChE) activity (specific index of exposure to organophosphate and carbamate pesticides) were measured. None of the two fish species showed significant differences in AChE activity and in pesticide trace level between the anthropogenic impact exposed site and the control group. On the other hand, metallothionein hepatic levels in M. barbatus were significantly increased in the organisms coming from Taranto with respect to the organisms coming from the control site, but chemical analysis, routinely performed on edible muscle for the evaluation of chemical quality of fish products, did not reveal high heavy metal concentration in the edible muscle of fish from Taranto. Mussels exposed for one month in the Mar Piccolo of Taranto, an important mussel farming area, showed increase in the level of catalase activity, an oxidative stress index, increase in the levels of metallothioneins and inhibition of AChE activity. The need to integrate chemical analysis with the study of biological responses to pollutants (biomarkers) in marine organisms is discussed for a better comprehension of the impact of chemical contaminants on the sea and its resources.

Subtle Effects of Biological Invasions: Cellular and Physiological Responses of Fish Eating the Exotic Pest Caulerpa racemosa

The green alga Caulerpa racemosa var. cylindracea has invaded Mediterranean seabed including marine reserves, modifying the structure of habitats and altering the distributional patterns of associated organisms. However, the understanding of how such invasion can potentially affect functional properties of Mediterranean subtidal systems is yet to be determined. In this study, we show that C. racemosa changes foraging habit of the native white seabream, Diplodus sargus. In invaded areas, we found a high frequency of occurrence of C. racemosa in the stomach contents of this omnivorous fish (72.7 and 85.7%), while the alga was not detected in fish from a control area. We also found a significant accumulation of caulerpin, one of the main secondary metabolites of C. racemosa, in fish tissues. The level of caulerpin in fish tissues was used here as an indicator of the trophic exposure to the invasive pest and related with observed cellular and physiological alterations. Such effects included activation of some enzymatic pathways (catalase, glutathione peroxidases, glutathione S-transferases, total glutathione and the total oxyradical scavenging capacity, 7-ethoxy resorufin O-deethylase), the inhibition of others (acetylcholinesterase and acylCoA oxidase), an increase of hepatosomatic index and decrease of gonadosomatic index. The observed alterations might lead to a detrimental health status and altered behaviours, potentially preventing the reproductive success of fish populations. Results of this study revealed that the entering of alien species in subtidal systems can alter trophic webs and can represent an important, indirect mechanism which might contribute to influence fluctuations of fish stocks and, also, the effectiveness of protection regimes.

Morphometric alterations in Mytilus galloprovincialis granulocytes: A new biomarker

Bivalve molluscs, particularly marine mussels, are used widely as sentinel organisms in environmental quality monitoring and assessment. Biochemical and cellular responses to pollutant exposure (i.e., biomarkers) increasingly are investigated in mussel tissues and their measurements largely used in marine environmental monitoring. The aim of the present study was to investigate possible pollutant-induced morphometric alterations in Mytilus galloprovincialis granulocytes in view of future applications as a sensitive, simple, and quick biomarker for monitoring and assessment applications. Granulocyte morphometric alterations were determined by image analysis on Diff-Quick® stained cells. For the first time, the rapid alcohol-fixed Diff-Quick stain protocol, utilized in clinical and veterinary applications for immediate interpretation of histological samples, was shown to be suitable for rapid cytological staining of M. galloprovincialis haemocytes. The present study was carried out in standardized laboratory conditions and further validated in field conditions. Results show consistent pollutant-induced enlargement of mussel granulocytes. This was verified by standardized biomarkers such as metallothionein concentrations in the digestive gland or lysosomal membrane stability in laboratory and field exposures. Results further suggest that the observed morphometric alterations can be used as a biomarker of chemical stress. Because no single biomarker generally is adequate for describing the complexity of effects induced by environmental pollutants on the organisms, we propose that morphometric alterations of granulocytes should be used in a biomarker battery in marine environmental monitoring programs such as Mussel Watch.

Potential application of carbonic anhydrase activity in bioassay and biomarker studies

Carbonic anhydrase (CA) (EC 4.2.1.1), a ubiquitous enzyme in bacteria, plant, and animal kingdoms, catalyses the reversible hydration of CO2 to produce H+ and using zinc as cofactor. CA plays a fundamental role in a number of physiological processes, such as respiration, ionic transport, acid–base regulation, and calcification. The aim of the present work was to investigate the sensitivity of this enzyme to heavy metals with a view to possible future applications of CA activity inhibition measurement in biomonitoring as either an in vitro bioassay or a biomarker. CA activity was determined by modifying a previously described electrometric method: briefly, CA activity units were calculated from the rate of H+ production in the reaction mixture (where CO2 was present as a substrate) against a blank containing the specific CA inhibitor acetazolamide. As regards the possible application as an in vitro bioassay, the sensitivity to heavy metals (cadmium, mercury, and copper) of the commercially available purified carbonic anhydrase (isozyme II) from bovine erythrocyte was tested in vitro. In our experimental set-up, bovine CA activity was significantly inhibited by micromolar concentrations of heavy metals, showing a dose–response behaviour. As regards the possible application as biomarkers, CA was investigated in the filter-feeding Mytilus galloprovincialis, widely used in pollution-monitoring programmes as a sentinel organism. Following in vitro and in vivo exposure to 1.785 μM cadmium chloride as a reference toxicant, mantle CA activity was significant inhibited. In conclusion, the sensitivity to chemical pollutants and low cost and simplicity of the assay method make CA activity measurement suitable for in vitro bioassay of the toxicity of environmental samples and for field biomarker applications in the sentinel organism M. galloprovincialis.

The Complex Relationship between Metals and Carbonic Anhydrase: New Insights and Perspectives

Carbonic anhydrase is a ubiquitous metalloenzyme, which catalyzes the reversible hydration of CO2 to HCO3− and H+. Metals play a key role in the bioactivity of this metalloenzyme, although their relationships with CA have not been completely clarified to date. The aim of this review is to explore the complexity and multi-aspect nature of these relationships, since metals can be cofactors of CA, but also inhibitors of CA activity and modulators of CA expression. Moreover, this work analyzes new insights and perspectives that allow translating new advances in basic science on the interaction between CA and metals to applications in several fields of research, ranging from biotechnology to environmental sciences.

Role of BK Channels in the Apoptotic Volume Decrease in Native Eel Intestinal Cells

High conductance Ca+-activated K+ channels (BK channels) have previously been demonstrated in the eel intestine. They are specifically activated following a hypotonic stress and sustain Regulatory Volume Decrease (RVD). The aim of the present work was to address the possible role of these channels in the Apoptotic Volume Decrease (AVD) of isolated eel enterocytes, and the possible interaction between BK channels and the progression of apoptosis. The detection of apoptosis was performed by confocal microscopy and annexin V and propidium iodide labelling; cell volume changes were monitored by video imaging. Within a few hours after isolation, enterocytes underwent anoikis (apoptosis induced by detachment from the extracellular matrix). They showed an early normotonic volume decrease (AVD) preceding the appearance of annexin V positivity. AVD occurred in correspondence with an increase in the [Ca2+]i, measured with Fura-2. When the cells were resuspended in high K+ solution or treated with iberiotoxin, AVD was completely abolished. In addition, treatment with high K+ or iberiotoxin significantly inhibited apoptosis progression. It was demonstrated for the first time in native enterocytes that BK channels, which are involved in RVD in these cells, plays also a crucial role in the AVD process and in the progression of apoptosis.

Carbonic anhydrase based environmental bioassay

Carbonic anhydrase (CA) is a metalloenzyme catalysing the reversible idratation of CO2 in H+ and . It is an ubiquitous enzyme in bacteria, plant and animal kingdoms, playing a fundamental role in a number of physiological processes. Previous studies demonstrated the sensitivity of CA activity to dichlorodiphenyl-dichloroethane (DDT) exposure in birds and to cadmium exposure in teleosts. The aim of the present work was to develop a new in vitro enzymatic bioassay for detecting toxic chemicals in environmental samples as a cost-effective tool in environmental monitoring. This bioassay uses the commercial available CA isozyme II from bovine erythrocytes whose sensitivity to the main classes of chemical pollutants of importance in water quality research was tested in this work. CA activity was determined by a modification of the electrometric method previously described by Wilbur and Anderson [K.M. Wilbur, G.N. Anderson. J. Biol. Chem., 176, 147 (1948).]: briefly, CA activity units were calculated from the rate of H+ production in the reaction mixture (where CO2 was present as substrate) against a blank containing the specific CA inhibitor acetazolamide. [H+] variation was followed at 0°C in the reaction mixture using a Mettler Delta 350 pH-meter. In our experimental set-up bovine CA activity was significantly inhibited by heavy metals (Cd, Cu and Hg), by the organochlorate compound arochlor and by the carbammate pesticides carbaryl in a dose-dependent manner. CA in vitro bioassay can represent a novel tool for rapid and low cost understanding of the toxicity of environmental samples, for assessing bioavailability of pollutants in environmental matrices and their additive or synergistic biological effects when present in mixtures.

Biomonitoring of water and soil quality: a case study of ecotoxicological methodology application to the assessment of reclaimed agroindustrial wastewaters used for irrigation

The aim of the work was to evaluate the ecotoxicity of reclaimed agroindustrial wastewaters used for irrigation through ecotoxicological bioassays and biomarkers. The ecotoxicological monitoring was addressed on both treated wastewaters and irrigated soils. Wastewater biomonitoring was performed by the acute test with Daphnia magna, the Microtox® test, and a new in vitro patented method. Soil quality monitoring was performed by the acute and chronic tests with the earthworm Eisenia fetida and biomarker analysis, such as lysosomal membrane stability, general stress biomarker of chemical pollution, and metallothionein, specific biomarker of exposure to heavy metals. Overall the integrated ecotoxicological analysis excluded the presence of ecotoxicity both in the reclaimed waters resulting from tertiary treatment and in the irrigated soils. In particular, the analysis of metallothionein allowed to exclude the accumulation of bioavailable heavy metals in the soil. This study suggests the suitability of ecotoxicological methods for the biomonitoring of water and soil during the reclaimed wastewaters reuse for irrigation, contributing to improving the process of agricultural re-use of wastewater in terms of assessment of the toxicological safety of the waters for the environment, for traders and consumers.