Effects of dehydroabietic acid on the physical state of cytoskeletal proteins and the lipid bilayer of erythrocyte membranes

Dehydroabietic acid cytotoxicity in goldfish radial glial cells in vitro

Dehydroabietic acid (DHAA) is a resin acid present in aquatic environments shown to induce cellular and molecular damage in aquatic animals. In this study, the cytotoxicity of DHAA on primary cultured goldfish radial glial cells (RGCs), an important component of the central nervous system, was evaluated. Here, it is reported that a concentration of 20mg/L DHAA affected cellular morphology and expression of genes involved in RGC steroidogenesis and metabolism. Higher concentration exposures of DHAA (40mg/L) lead to RGC death based on a lactate dehydrogenase leakage assay. Together, these data have implications in understanding the effects of DHAA on an integral central nervous system cell type important for neurogenesis, steroidogenesis and structural support. Due to the continuous presence of DHAA into water systems, results from this study provide indications as to the potential impacts of DHAA and demonstrate the importance of this class of chemicals on aquatic organisms.

Juvenile sea bass liver biotransformation and erythrocytic genotoxic responses to pulp mill contaminants

This research represents the first study concerning liver phase I biotransformation induction, measured as cytochrome P-450 (P450) and ethoxyresorufin-O-deethylase (EROD), and genotoxic responses, measured as erythrocytic micronuclei (EMN) and nuclear abnormalities (ENA), in Dicentrarchus labrax L. (sea bass) exposed to pulp and paper mill contaminants. Juvenile sea bass were exposed for 6 h to 0 (control) and 0.0125 microM concentrations of the resin acids (RAs) abietic acid (AA) and dehydroabietic acid (DHAA) or 7-isopropyl-1-methylphenanthrene (retene) (Experiment 1). Sea bass were exposed for 6 h to 0 (control), 0.78, 1.56, 3.12, 6.25, and 12.5% bleached kraft pulp mill environmental contaminated water (BKPMECW) collected at the old sewage outlet of a pulp and paper industry (Experiment 2). The time-dependent response was studied in sea bass at 0, 8, 16, 24, 48, and 72 h exposure to 0.78 and 12.5% BKPMECW (Experiment 3). The experimental results demonstrated the presence of genotoxic compounds in BKPMECW. AA, DHAA, and retene may be the constituents responsible for high BKPMECW genotoxicity, since they induced similar sea bass EMN and ENA frequency increases. The BKPMECW, the RAs, and retene failed to significantly increase liver EROD activity and P450 content at 6 h. Furthermore, 3.12% BKPMECW, 0.0125 microM AA, and 0.0125 microM retene significantly decreased liver EROD activity. However, P450 was significantly increased from 8 up to 72 h exposure to BKPMECW. Therefore, the low or inhibited EROD levels could be a consequence of a general membrane disturbance by BKPMECW, RAs, and retene. However, liver ALT results indicate significant liver damage or enzyme inhibition only at 8, 16, 48, and 72 h exposure to BKPMECW.

Juvenile sea bass liver biotransformation induction and erythrocytic genotoxic responses to resin acids

Juvenile Dicentrarchus labrax L. (sea bass) were exposed for 0, 2, 4, 6, and 8 h to abietic acid (AA) and dehydroabietic acid (DHAA) in concentration ranges 0, 0.0125, 0.025, 0.05, 0.1, 0.3, 0.9, and 2.7 microM. Liver cytochrome P-450 content (P450) and liver ethoxyresorufin-O-deethylase activity (EROD) were determined as phase I biotransformation biomarkers. Genotoxicity was measured as erythrocytic micronuclei (EMN) and nuclear abnormalities (ENA). Liver damage was assessed as liver alanine aminotransferase activity (ALT) and liver somatic index (LSI) was used as a general health indicator. AA inhibited EROD (at 2 h exposure to 0.05 microM) or failed to induce it, whereas a significant P450 increase was observed at 2 h exposure to 0.05 (2.3-fold) and 2.7 microM (6.3-fold). A significant P450 increase was also observed at 6 and 8 h exposure, respectively, to 0.0125 (3.4-fold) and 0.025 microM (4.9-fold) AA. EMN and ENA frequency were significantly increased at 2 h exposure to 0.9 microM AA. A significant EMN and ENA time-related increase was observed with an increased exposure length up to 8 h. Therefore, all the AA concentrations tested promoted an EMN and ENA increase at 8 h exposure. DHAA induced a significant EROD increase (3.2-fold) at 2 h exposure to the lowest concentration tested. Liver P450 was significantly increased at 2 h exposure to 0.025 (1.8-fold) and 0.3 microM (2.5-fold), at 4 h exposure to 0.1 microM (3.6-fold), and at 6 h exposure to 0.1 (3.2-fold) and 0.3 microM (2.8-fold), whereas it was significantly decreased (30% of control value) at 4 h exposure to 0.9 microM. EMN and ENA frequency were significantly increased from 0 to 2 h exposure to all DHAA concentrations tested and remained high from 2 to 8 h. EMN frequency was increased 20 times over control at 2 h exposure to 0.0125 microM DHAA, whereas it increased 9-fold at 2 h exposure to 0.9 microM AA. Furthermore, ENA frequency was increased 3 times over control at 2 h exposure to 0.0125 microM DHAA, and 2-fold after exposure to 0.9 microM AA. Maximal EMN and ENA induction was observed at 2 h exposure to 0.0125 microM DHAA and only at 4 h exposure to 2.7 microM AA. Therefore, the comparative analysis of the two resin acids genotoxic effects, measured as EMN and ENA, indicated that DHAA is more genotoxic than AA.

Occurrence of the toxin dehydroabietic acid in Salmonella typhimurium

Many strains of Salmonella typhimurium studied in our lab demonstrated marked differences in the pathogenicity for guinea pig, chicken and Hela cells. As a result, a pathogenic strain of S. typhimurium, strain 9SR2, was evaluated for lipophilic components that may be associated with virulence using gas chromatography/mass spectrometry. The hydroxylated fatty acids 2-hydroxytetradecanoic acid (2-OH-14:0) and 3-hydroxytetradecanoic acid (3-OH-14:0) often present in lipid A, a potent endotoxin, were observed as their methyl esters. The cyclic fatty acids methylene-hexadecanoic acid (C17delta) and methyleneoctadecanoic acid (C19delta) also were detected. The nephrotoxic and neurotoxic diterpenoid resin acid, dehydroabietic acid, was observed for the first time from S. typhimurium in both the total lipid and diglyceride fractions and determined as its methyl ester at m/z 314.2246. Due to its previously established toxicity, dehydroabietic acid may be a factor associated with virulence of S. typhimurium.

The reaction of lanthanide ions with n-doxyl stearic acids and its utilization for the ESR study on the permeability of lipid-bilayer of erythrocyte membrane to gadolinium ions

The reaction of lanthanide ions with n-doxyl stearic acid (nDS) spin labels (n = 5,7,12,16) was investigated by the electron spin resonance technique in aqueous solution. Among the lanthanides, the Gd3+, Tb3+, Tm3+ and Ce3+ ions strongly quenched the ESR signal of spin labels, but the effects of La3+, Eu3+ and Lu3+ are very weak. The quenching effects are featured by: (1) the dependence on the concentration of lanthanide ions; (2) no obvious changes of the ESR line shape in the presence of lanthanide ions; (3) the quenching constant decreases in the order: Gd3+ > Tb3+ > Tm3+ > Ce3+; (4) the quenching effects of lanthanide ions are found to strikingly correlate with their magnetic properties. These findings indicate that the interaction of lanthanide ions with nitroxide oxygen leading to the reduction of ESR signal amplitude is dominated by their magnetic characteristics rather than the coordination effect. By labeling erythrocyte membrane with nDS, n = 5,7,12,16 at different depths, we studied the diffusion of Gd3+ into the lipid-bilayer of erythrocyte membrane by monitoring the reduction processes of the ESR signals of nitroxide spin labels located at different depths of membrane lipid-bilayer after addition of Gd3+. These results revealed that the Gd3+ ions can penetrate into the lipid-bilayer, though the entry rate is slow. It was shown that the Gd3+ ions bind to the membrane and enhance the permeability of extracellular ascorbate into erythrocyte membrane. The transport mechanism of Gd3+ ions through the lipid-bilayer might be involved in the Gd3+ cation-induced pore formation in the surface of membrane.

Location of the toxic molecule abietic acid in model membranes by MAS-NMR

Abietic acid, the major component of conifer oleoresin, is an environmental toxic molecule with potential hazard to animal and plant life. Being amphipatic, the study of its location and the interaction with membrane components is important to get insight into the mechanism of its toxic action. High resolution magic angle spinning natural abundance 13C nuclear magnetic resonance studies have been undertaken in order to assess its location in egg yolk phosphatidylcholine multilamellar vesicles model membranes. 13C spin-lattice relaxation times in the presence of Gd3+, a paramagnetic agent, of both the phospholipid and abietic acid molecules have been measured in order to obtain information on molecular distances (see J. Villalaín, Eur. J. Biochem. 241 (1996) 586-593). The molecule of abietic acid is placed in the upper part of the palisade structure of the membrane, its carboxyl group is in close proximity to the phospholipid ester groups and it does not extend beyond the C4/C7 carbons of the phospholipid molecule.

The interaction of abietic acid with phospholipid membranes

Abietic acid is a major component of the oleoresin synthesized by many conifers and constitutes a major class of environmental toxic compounds with potential health hazard to animal, including human, and plant life. Being an amphipathic molecule, the study of the influence of abietic acid on the structure of membranes would be important to get insight into the mechanism of toxic action of the molecule. The interaction of abietic acid with model membranes of dipalmitoylphosphatidylcholine (DPPC) and dielaidoylphosphatidylethanolamine (DEPE) has been studied by differential scanning calorimetry and 31P-nuclear magnetic resonance spectroscopy. It has been found that abietic acid greatly affects the phase transition of DPPC, shifting the transition temperature to lower values, giving rise to the appearance of two peaks in the thermogram and to the presence of fluid immiscible phases. In a similar way, the phase transition of DEPE, in the presence of abietic acid, was shifted to lower temperatures, and two peaks appeared in the thermograms. The temperature of the lamellar to hexagonal H(II) phase transition was also decreased by the presence of abietic acid, but phase immiscibilities were not detected. The possible implications of these effects on the action of abietic acid on biological membranes are discussed.

Selective labeling of membrane protein sulfhydryl groups with methanethiosulfonate spin label

Electron paramagnetic resonance was used to characterize the first use of a thio-specific spin label in membranes. Procedures for use of the spin-label, 1-oxyl-2,2,5,5-tetramethyl-delta 3-pyrroline-3-methyl (methanethiosulfonate MTS) covalently attached to membrane proteins in human erythrocyte membranes are reported. The major findings are: (1) MTS was found to be thiol-specific in membranes as it is for soluble proteins; (2) MTS labels ghost proteins in as few as 30 min at room temperature, providing a distinct advantage when sensitive or fragile membranes are to be used; (3) the distribution of the spin label suggests that the major cytoskeletal protein, spectrin, and the major transmembrane protein (Band 3) incorporate the highest percentage of spin label. This procedure expands the tools with which the researcher can investigate the physical state of membrane proteins and its alteration upon interaction of membrane perturbants or in pathological conditions.