Role of metallothionein against oxidative stress in the musselMytilus galloprovincialis

Abstract

Metallothionein (MT) is a sulfhydryl-rich protein involved mainly in heavy metal homeostasis and detoxification. In this study, the use of the mussel as an experimental model allowed us to test MT antioxidant properties at the molecular, cellular, and organism level. MT induction was achieved by mussel exposure to Cd (200 microg/l) in aquaria for 7 days followed by detoxification in the sea for 28 days. Cd-preexposed and nonexposed mussels were then treated with Fe (300-600 microg/l) in aquaria for 3 days. Biochemical assays on digestive gland tissue showed that treatment with Fe led to a significant increase in oxyradical production and malondialdehyde level only in mussels not preexposed to Cd. The Cd-dependent resistance to oxidative stress was ascribed to MT induction, as Cd produced no significant variation of reduced glutathione and major antioxidant enzymes. Digital imaging of isolated digestive gland cells showed lower oxyradical rise and higher viability in cells from Cd-preexposed mussels after treatments with 0.5-5 mM H2O2. Analyses on whole organisms showed that anoxic survival was lowered in mussels that had been treated with Fe, but such an effect was less pronounced in Cd-preexposed mussels compared with nonpreexposed ones. In conclusion, data suggest an antioxidant role for MT, which seems to occur through oxyradical scavenging and is able to protect both isolated cells and the entire organism from oxidative stress.

Exposure to excess dissolved iron in vivo affects oxidative status in the bivalve Mya arenaria

“…On day 17 only one half of the SOD activity in control animal DG was recorded. Further, induction of other protective mechanisms, such as metallothioneins, might act as effective transient control of heavy metal effects during the initial phase of heavy metal exposure, see also Viarengo et al (1999) and Alves de Almeida et al (2004), but this protective mechanism was not analyzed in our study.…”

“…ROS production by tissue homogenates DG samples were homogenized (1:5 w/v) in a 100 mM Tris-HCl, pH 7.75 buffer, with 2 mM EDTA and 5 mM MgCl 2 (Gallagher et al, 1992). Measurements were conducted according to Viarengo et al (1999) with modifications. Briefly, the homogenates were centrifuged at 4°C for 20 min at 10,000 g and the supernatants were employed.…”

“…Fe circulation in the hemolymph is an early event in Fe distribution to the tissues after the initial incorporation into the DG (Ahearn et al, 2004). Viarengo et al (1999) exposed Mytilus galloprovincialis to 600 μg/L Fe and observed significant Fe accumulation in DG after 3 days of treatment. This Fe accumulation led to an increase in ROS generation, assessed as oxidation of dihydrorhodamine, and lipid peroxidation (2-thiobarbituric acid reactive substances (TBARS) accumulation).…”

Oxidative Stress in Human Thyroid Gland Under Iodine Deficiency Nodular Goiter: From Harmlessness to Hazard Depending on Copper and Iodine Subcellular Distribution

“…1 No. 1 hodamine, which is converted to the fluorescent dye, rhodamine-123, while reacting with reactive oxygen species [18]. The fluorescence signal was detected by using af-max fluorescence plate-reader [excitation = 485 nm, emission = 538 nm] immediately, and in 20 min.…”

Ca2+homeostasis and redox balance in Antarctic sea organisms: Effects of temperature and of environmental contaminants

“…Variations of cytosolic free Ca 2+ were evaluated by digital imaging fluorescence microscopy using the probe fura-2, according to Burlando et al (1999). Cell viability assays were performed using the LIVE/DEAD® viability solution (Molecular Probes Inc., Eugene, OR), as reported in Viarengo et al (1999b). Starvation at 0° C and H 2 O 2 exposure at 4° C exacerbated these effects (Fig.…”