Cellular injury and lipid peroxidation induced by hexavalent chromium in isolated rat hepatocytes

In order to elucidate the relationship between cellular injury and lipid peroxidation induced by hexavalent chromium (CrVI), isolated rat hepatocytes treated with any one of scavengers of active oxygen species, antioxidants or antichromium agent were incubated with K2Cr2O7 as CrVI (1 mM Cr). After the incubation, the development of lipid peroxidation was determined as thiobarbituric acid (TBA)-reacting materials in total lipid extracts from the incubated hepatocytes. Cellular injury was observed as a leakage of lactate dehydrogenase (LDH) from hepatocytes into incubation medium. The contents of reduced glutathione (GSH) in hepatocytes were also assessed. Results obtained were as follows: (1) CrVI facilitated lipid peroxidation in isolated hepatocytes after 20 min of incubation. On the other hand, the cellular injury induced by CrVI was barely observed even after 60 min of incubation. (2) The CrVI-induced lipid peroxidation was inhibited by catalase and mannitol as scavengers of active oxygen species, or N,N'-diphenyl-p-phenylenediamine and alpha-tocopherol as antioxidants. However the cytotoxicity of CrVI could not be prevented by these chemicals. (3) CrVI depleted the contents of intracellular GSH and diminished the activities of glutathione reductase (GR) and glutathione-S-transferase (GST) except glutathione peroxidase. (4) The scavengers of active oxygen species and the antioxidants could not prevent the depletion of intracellular GSH induced by CrVI. (6) Ascorbic acid, antichromium agent, prevented all of the lipid peroxidation, the cellular injury and intracellular GSH depletion induced by CrVI.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protective effects of thiol compounds on chromate-induced cytotoxicity in HeLa cells.

The effects of several thiol compounds on the cytotoxicity induced by chromate (potassium dichromate) were examined. HeLa cells were incubated in Eagle's minimum essential medium (MEM) with or without the chromate alone, or with both chromate and any one of L-cysteine ethyl ester (LCysEE), L-cysteine methyl ester (LCysME), N-acetyl-L-(+)-cysteine, 2,3-dimercaptosuccinic acid (DMSA), 2, 3-dimercapto-1-propanesulfonic acid (DMPS), or dithiothreitol. After a given period of incubation, the number of viable cells was counted using the trypan blue exclusion test and the chromium content of the cells was estimated by atomic absorption spectrophotometry. The results obtained were as follows. 1) Chromate-induced cytotoxicity evaluated by inhibition of cell growth at 3 days of incubation was diminished by all of the thiol compounds tested when the cells were incubated in MEM with 2.5 to 10.0 microM chromate and 25 to 100 microM thiol compounds. 2) All of the thiol compounds produced a concentration-dependent reduction of chromate when a solution of the thiol compound (12.5 to 100 microM) was mixed with a solution of chromate (10 microM) in distilled water. 3) When cells were incubated in MEM with both 10 microM chromate and 25 to 100 microM thiol compounds, the chromium content of the cells at 6 hr of incubation was decreased in a concentration-dependent manner. 4) When these thiol compounds were added to MEM 1 hr before or after chromate, no or little protective effects of these thiol compounds against chromate-induced cytotoxicity and chromium uptake by the cells were observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of lipid peroxidation in mice by hexavalent chromium and its relation to the toxicity

Comparative effects of hexavalent (K2Cr2O7:Cr(VI)) and trivalent chromium (Cr(NO3)3:Cr(III)) on the development of lipid peroxidation, and the relationship between the lipid peroxidation and damage to tissues were studied using male ddY strain mice. The animals were administered with either of two chemicals at a dose of 20 mg Cr/kg by a single intraperitoneal injection. The results obtained were as follows: (1) Lipid peroxidation in the liver, as measured by the synthesis of thiobarbituric acid reactive substances (TBARS), showed a significant increase at 24 and 48 hr after Cr(VI) injection, while in the kidney it was observed only at 48 hr. In the mice administered with Cr(III), TBARS formation in the liver went down below the control levels, while no change was observed in the kidney. (2) Chromium contents in the liver and kidney showed a maximum level at 6 hr after injection of Cr(VI) and then those declined to the half of the maximum level at 48 hr, respectively. Chromium contents in the liver and kidney of the mice injected with Cr(III) were lower than those injected with Cr(VI) during the experimental period. (3) Increases of TBARS formation in the liver, chromium content in the liver and kidney, and ornithine carbamyl transferase (OCT) activity indicative of the liver cell damage, and urea nitrogen content in the serum, indicative of the kidney damage, observed at 24 hr after injection of Cr(VI) were inhibited by simultaneous injection of 100 mg/kg of L-ascorbic acid, as antichrome agent, respectively. These observations might suggest a possible causative role of lipid peroxidation in Cr(VI) toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)     

A participatory scenario method to explore the future of marine social‐ecological systems

Anticipating future changes in marine social‐ecological systems (MSES) several decades into the future is essential in the context of accelerating global change. This is challenging in situations where actors do not share common understandings, practices, or visions about the future. We introduce a dedicated scenario method for the development of MSES scenarios in a participatory context. The objective is to allow different actors to jointly develop scenarios which contain their multiple visions of the future. The method starts from four perspectives: “fisheries management,” “ecosystem,” “ocean climate,” and “global context and governance” for which current status and recent trends are summarized. Contrasted scenarios about possible futures are elaborated for each of the four single perspectives before being integrated into multiple‐perspective scenarios. Selected scenarios are then developed into storylines. Focusing on individual perspectives until near the end allows actors with diverse cultures, interests and horizons to confront their own notions of the future. We illustrate the method with the exploration of the futures of the Barents Sea MSES by 2050. We emphasize the following lessons learned: first, many actors are not familiar with scenario building and attention must be paid to explaining the purpose, methodology, and benefits of scenarios exercises. Second, although the Barents Sea MSES is relatively well understood, uncertainties about its future are significant. Third, it is important to focus on unlikely events. Fourth, all perspectives should be treated equally. Fifth, as MSES are continuously changing, we can only be prepared for future changes if we collectively keep preparing.