The Role of Oxidative Stress in Environmental Responses of Fennoscandian Animals

All aerobic organisms have to deal with the toxicity of oxygen. Oxygen enables more efficient energy production compared to anaerobic respiration or fermentation, but at the same time reactive oxygen species (ROS) are being formed. ROS can also be produced by external factors such as UV-radiation and contamination. ROS can cause damage to biomolecules such as DNA, lipids and proteins and organisms try to keep the damage as small as possible by repairing biomolecules and metabolizing ROS. All ROS are not harmful, because they are used as signaling molecules. To cope against ROS organism have an antioxidant (AOX) system which consists both enzymatic and non-enzymatic AOX defense. Some AOX are produced by the organism itself and some are gained via diet. In this thesis I studied environmentally caused changes in the redox regulation of different wild vertebrate animals to gain knowledge on the temporal, spatial and pollution-derived-effects on the AOX systems. As study species I used barn swallow, ringed seal and the Baltic salmon. For the barn swallow the main interest was the seasonal fluctuation in the redox regulation and its connection to migration and breeding. The more contaminated ringed seals of the Baltic Sea were compared to seals from cleaner Svalbard to investigate whether they suffered from contaminant induced oxidative stress. The regional and temporal variation in redox regulation and regional variation in mRNA and protein expressions of Baltic salmon were studied to gain knowledge if the salmon from different areas are equally stressed. As a comparative aspect the redox responses of these different species were investigated to see which parts of the AOX system are substantial in which species. Certain parts of AOX system were connected to breeding and others to migration in barn swallows, there was also differences in biotransformation between birds caught from Africa and Finland. The Baltic ringed seal did not differ much from the seals from Svalbard, despite the difference in contaminant load. A possible explanation to this could be the enhanced AOX mechanisms against dive-associated oxidative stress in diving air-breathing animals, which also helps to cope with ROS derived from other sourses. The Baltic salmon from Gulf of Finland (GoF) showed higher activities in their AOX defense enzymes and more oxidative damage than fish from other areas. Also on mRNA and proteomic level, stress related metabolic changes were most profound in in the fish from GoF. Mainly my findings on species related differences followed the pattern of mammals showing highest activities and least damage and birds showing lower activities and most damage, fish being intermediate. In general, the glutathione recycling-related enzymes and the ratio of oxidized and reduced glutathione seemed to be the most affected parameters in all of the species.Kaikkien happea käyttävien eliöiden pitää tulla toimeen hapen myrkyllisyyden kanssa. Happi mahdollistaa paljon tehokkaamman energiantuotannon kuin hapettomat hengitys- tai käymisreaktiot, mutta samalla prosessissa vapautuu reaktiivisia happiradikaaleja (ROS). ROS:a voi muodostua myös ulkoisten tekijöiden, kuten UV-säteilyn ja saastumisen seurauksena. ROS:t voivat vaurioittaa biomolekyylejä kuten DNA:ta, rasvoja sekä proteiineja ja eliöt pyrkivätkin pitämään vaurioiden määrän niin pienenä kuin mahdollista, korjaamalla biomolekyylejä ja käsittelemällä ROS:ja. Kaikki ROS:t eivät ole vahingollisia, koska osa toimii mm. tiedonvälitysmolekyyleinä. Jotta eliöt pärjäisivät ROS:ja vastaan, on niille kehittynyt antioksidanttipuolustusjärjestelmä (AOX), johon kuuluvat entsymaattiset ja ei-entsymaattiset systeemit. Osan AOX:ta eliö tuottaa itse ja osa saadaan ravinnosta. Olen tutkinut väitöskirjassani ympäristön aiheuttamia muutoksia villien selkärankaisten hapetus-pelkistys säätelyyn saadakseni tietoa ajallisten, paikallisten ja saasteiden aiheuttamien muutosten vaikutusta AOX puolustukseen. Tutkimuslajeina käytin haarapääskyjä, Itämeren norppia ja Itämeren lohia. Haarapääskytutkimuksessa suurin mielenkiinto kohdistui hapetus-pelkistyssäätelyn vuodenaikaisvaihteluun ja sen yhteyteen lintujen muuttoon ja lisääntymiseen. Itämeren norppia verrattiin puhtaammissa oloissa eläviin Huippuvuorten norppiin, jotta saataisiin tietoa kärsivätkö ne saasteiden aiheuttamasta hapetusstressistä. Itämeren lohella tutkittiin sekä ajallista, että paikallista vaihtelua hapetus-pelkistys säätelyssä ja eroja mRNA- ja proteiinituotannossa, jotta saataisiin selville ovatko eri alueiden lohet yhtä stressaantuneita. Lisäksi näiden kolmen eri lajin hapetus-pelkistys vasteita vertailtiin, jotta tiedettäisiin mitkä osat AOX puolustuksesta ovat tärkeitä milläkin lajilla. Haarapääskyllä tietyt osat AOX systeemissä liittyivät lisääntymiseen ja toiset muuttoon, lisäksi Afrikasta pyydettyjen lintujen myrkkypuolustuksessa oli eroa Suomesta pyydettyihin lintuihin nähden. Itämeren norpat eivät eronneet paljoakaan Huippuvuorten norpista huolimatta suurista eroista saastepitoisuuksissa. Yksi mahdollinen syy tähän saattaisi olla sukeltavien, mutta ilmaa hengittävien eliöiden AOX puolustusentsyymeiden kohonnut tehokkuus, joka auttaa niitä selvitymään paremmin sukeltamiseen liittyvästä hapetusstressistä, sekä muista syistä johtuvasta liiallisesta ROS tuotannosta. Suomenlahden lohien AOX entsyymien aktiivisuudet olivat kohonneita muiden alueiden lohiin verrattuna. Lisäksi Suomenlahden lohilla havaittiin stressiaineenvaihduntaan liittyviä muutoksia mRNA- ja proteiinitasolla. Pääasiassa tulokseni eri lajienvälisistä eroista noudatti jo aiemmin havaittua linjaa: nisäkkäillä oli korkeimmat entsyymiaktiivisuudet ja vähiten vaurioita biomolekyyleissa, kun taas linnuilla oli matalimmat aktiivisuudet ja eniten vaurioita. Kalat puolestaan olivat tältä väliltä. Yleisesti ottaen glutationin hapetus-pelkistusreaktioihin liittyvien entsyymien aktiivisuudet, sekä glutationin pelkistyneen ja hapettuneen muodon suhde muuttuivat eniten kaikilla lajeilla.Siirretty Doriast

Metal and metalloid exposure and oxidative status in free-living individuals of Myotis daubentonii

Metal elements, ubiquitous in the environment, can cause negative effects in long-lived organisms even after low but prolonged exposure. Insectivorous bats living near metal emission sources can be vulnerable to such contaminants. Although it is known that bats can bioaccumulate metals, little information exists on the effects of metal elements on their physiological status. For example, oxidative status markers are known to vary after detoxification processes and immune reactions. Here, for two consecutive summers, we sampled individuals from a natural population of the insectivorous bat, Myotis daubentonii, inhabiting a site close to a metal emission source. We quantified metals and metalloids (As, Ca, Cd, Co, Cu, Mn, Ni, Pb, Se, Zn) from individual fecal pellets. We measured enzymatic antioxidants (GP, CAT, SOD), total glutathione (tGSH) and ratio between reduced and oxidized glutathione (GSH:GSSG) from their red blood cells together with biometrics, hematocrit and parasite prevalence. In general, metal concentrations in feces of M. daubentonii reflected the exposure to ambient contamination. This was especially evident in the higher concentrations of Cd, Co, Cu and Ni close to a smelter compared to a site with less contaminant exposure. Annual differences were also observed for most elements quantified. Sex-specific differences were observed for calcium and zinc excretion. SOD and CAT enzymatic activities were associated with metal levels (principal components of six metal elements), suggesting early signs of chronic stress in bats. The study also shows promise for the use of non-invasive sampling to assess the metal exposure on an individual basis and metal contamination in the environment.Peer reviewe

Different relationship between hsp70 mRNA and hsp70 levels in the heat shock response of two salmonids with dissimilar temperature preference

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Different relationship between hsp70 mRNA and hsp70 levels in the heat shock response of two salmonids with dissimilar temperature preference

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Variation of Basal EROD Activities in Ten Passerine Bird Species - Relationships with Diet and Migration Status

Inter-specific differences in animal defence mechanisms against toxic substances are currently poorly understood. The ethoxyresorufin-O-deethylase (EROD) enzyme plays an important role in defence against toxic chemicals in a wide variety of animals, and it is an important biomarker for environmental contamination. We compared basal hepatic EROD activity levels among ten passerine species to see if there is inter-specific variation in enzyme activity, especially in relation to their diet and migration status. Migratory insectivores showed higher EROD activity compared to granivores. We hypothesize that the variable invertebrate diet of migratory insectivores contains a wider range of natural toxins than the narrower diet of granivores. This may have affected the evolution of mixed function oxidases (MFO) system and enzyme activities. We further tested whether metabolic rates or relative liver size were associated with the variation in detoxification capacity. We found no association between EROD activity and relative (per mass unit) basal metabolic rate (BMR). Instead, EROD activity and relative liver mass (% of body mass) correlated positively, suggesting that a proportionally large liver also functions efficiently. Our results suggest that granivores and non- migratory birds may be more vulnerable to environmental contaminants than insectivores and migratory birds. The diet and migration status, however, are phylogenetically strongly connected to each other, and their roles cannot be fully separated in our analysis with only ten passerine species

Oxidative stress and antioxidant defense responses in Acartia copepods in relation to environmental factors

On a daily basis, planktonic organisms migrate vertically and thus experience widely varying conditions in their physico-chemical environment. In the Gulf of Finland, these changes are larger than values predicted by climate change scenarios predicted for the next century (up to 0.5 units in pH and 5 degrees C in temperature). In this work, we are interested in how temporal variations in physico-chemical characteristics of the water column on a daily and weekly scale influence oxidative stress level and antioxidant responses in the planktonic copepod of the genus Acartia. Responses were determined from samples collected during a two-week field survey in the western Gulf of Finland, Baltic Sea. Our results showed that GST (Glutathione-S-transferase) enzyme activity increased in the surface waters between Weeks I and II, indicating antioxidant defense mechanism activation. This is most likely due to elevating temperature, pH, and dissolved oxygen observed between these two weeks. During Week II also GSSG (oxidized glutathione) was detected, indicating that copepods responded to stressor(s) in the environment. Our results suggest that Acartia copepods seem fairly tolerant to weekly fluctuations in environmental conditions in coastal and estuarine areas, in terms of antioxidant defense and oxidative stress. This could be directly connected to a very efficient glutathione cycling system acting as antioxidant defense system for neutralizing ROS and avoiding elevated levels of LPX

Cardiovascular oxygen transport and peripheral oxygen extraction capacity contribute to acute heat tolerance in European seabass

This study evaluated whether different parameters describing cardiovascular function, energy metabolism, oxygen transport and oxidative stress were related to the critical thermal maximum (CTMAX) of European seabass (Dicentrarchus labrax) and if there were differential changes in these parameters during and after heat shock in animals with different CTMAX in order to characterize which physiological features make seabass vulnerable to heat waves. Seabass (n = 621) were tested for CTMAX and the physiological parameters were measured in individuals with good or poor temperature tolerance before and after a heat shock (change in temperature from 15 °C to 28 °C in 1.5 h). Fish with good thermal tolerance had larger ventricles with higher maximal heart rate during the heat shock than individuals with poor tolerance. Furthermore, they initially had a high ventricular Ca2+-ATPase activity, which was reduced to a similar level as in fish with poor tolerance following heat shock. The activity of heart lactate dehydrogenase increased in fish with high tolerance, when they were exposed to heat shock, while the aerobic enzyme activity did not differ between groups. The tolerant individuals had smaller red muscle fibers with higher myoglobin content than the poorly tolerant ones. The poorly tolerant individuals had higher hematocrit, which increased with heat shock in both groups. The poorly tolerant individuals had also higher activity of enzymes related to oxidative stress especially after heat shock. In general, CTMAX was not depending on merely one physiological factor but several organ and cellular parameters were related to the CTMAX of seabass and when working in combination they might protect the highly tolerant seabass from future heat waves. </p

Effects of calcium supplementation on oxidative status and oxidative damage in great tit nestlings inhabiting a metal-polluted area

Calcium has been proposed to diminish metal toxicity by the modulation of the oxidative stress. This study explores the effects of Ca availability and metal exposure on oxidative stress biomarkers in great tit (Parus major) nestlings. Nests were supplemented with Ca (Ca-supplemented group) or not supplemented (Control group) in a metal-polluted and a background zone in SW Finland. Metal concentrations were analyzed from feces. We analyzed antioxidants (tGSH, GSH:GSSG ratio, CAT, GST, GPx, SOD), protein carbonylation and lipid peroxidation in red cells of nestlings.Ca-supplemented and fast-growing nestlings showed higher CAT activity to cope with reactive oxygen species (ROS) generated during intensive growth and metabolism. SOD and GPx (the latter not statistically significant) were more active in the polluted area, possibly reflecting higher ROS production in nestlings from this zone due to the enhanced metal exposure and smaller size. Antioxidant levels changed over the range of metal concentrations depending on the Ca levels in plasma, suggesting that higher Ca levels stimulate antioxidants and mitigate the impacts of metals. Ca supplementation may improve nestling traits and reproductive output when antioxidants are enhanced in a situation of oxidative challenge. Therefore, Ca should be considered in future studies assessing metal exposure and effects on wild birds