Antioxidant deficit in gills of Pacific oyster (Crassostrea gigas) exposed to chlorodinitrobenzene increases menadione toxicity.
Disturbances in antioxidant defenses decrease cellular protection against oxidative stress and jeopardize cellular homeostasis. To knock down the antioxidant defenses of Pacific oyster Crassostrea gigas, animals were pre-treated with 1-chloro-2,4-dinitrobenzene (CDNB) and further challenged with pro-oxidant menadione (MEN). CDNB pre-treatment (10 μM for 18 h) was able to consume cellular thiols in gills, decreasing GSH (53%) and decrease protein thiols (25%). CDNB pre-treatment also disrupted glutathione reductase and thioredoxin reductase activity in the gills, but likewise strongly induced glutathione S-transferase activity (270% increase). Surprisingly, hemocyte viability was greatly affected 24 h after CDNB removal, indicating a possible vulnerability of the oyster immune system to electrophilic attack. New in vivo approaches were established, allowing the identification of higher rates of GSH-CDNB conjugate export to the seawater and enabling the measurement of the organic peroxide consumption rate. CDNB-induced impairment in antioxidant defenses decreased the peroxide removal rate from seawater. After showing that CDNB decreased gill antioxidant defenses and increased DNA damage in hemocytes, oysters were further challenged with 1 mM MEN over 24 h. MEN treatment did not affect thiol homeostasis in gills, while CDNB pre-treated animals recovered GSH and PSH to the control level after 24 h of depuration. Interestingly, MEN intensified GSH and PSH loss and mortality in CDNB-pre-treated animals, showing a clear synergistic effect. The superoxide-generating one-electron reduction of MEN was predominant in gills and may have contributed to MEN toxicity. These results support the idea that antioxidant-depleted animals are more susceptible to oxidative attack, which can compromise survival. Data also corroborate the idea that gills are an important detoxifying organ, able to dispose of organic peroxides, induce phase II enzymes, and efficiently export GSH-CDNB conjugates.
Departamento de Bioquímica, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, SC, Brazil.
Rafael
R
Trevisan
Miriam
M
Arl
Cássia Lopes
CL
Sacchet
Cristiano Severino
CS
Engel
Naissa Maria
NM
Danielli
Danielle Ferraz
DF
Mello
Caroline
C
Brocardo
Angelica Francesca
AF
Maris
Alcir Luiz
AL
Dafre
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D049896:Crassostrea / Q000187:drug effects* / Q000201:enzymology; D004137:Dinitrochlorobenzene / Q000633:toxicity*; D005880:Gills / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology; D006434:Hemocytes / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000032:analysis; D024483:Vitamin K 3 / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D000975:Antioxidants; D004137:Dinitrochlorobenzene; D013438:Sulfhydryl Compounds; D014874:Water Pollutants, Chemical; D024483:Vitamin K 3