Mitochondrial gene expression, antioxidant responses, and histopathology after cadmium exposure

Abstract

The present study investigates cadmium effects on the transcription of mitochondrial genes of Procambarus clarkii after acute (0.05, 0.5, and 5 mg Cd/L; 4-10 days) and chronic exposures (10 μg Cd/L; 30-60 days). Transcriptional responses of cox1, atp6, and 12S using quantitative real-time RT-PCR were assessed in gills and hepatopancreas. Additionally, the expression levels of genes involved in detoxification and/or oxidative stress responses [mt, sod(Mn)] and enzymatic activities of antioxidants (SOD, CAT, GPX, and GST) were analyzed. The histopathological effects in hepatopancreas of crayfish were evaluated by light microscopy. Relationships between endpoints at different levels of biological organization and Cd bioaccumulation were also examined. Cd induced high levels of bioaccumulation, which was followed by mitochondrial dysfunction and histological alterations in both experiments. Moreover, perturbations in the defence mechanisms against oxidative stress tended to increase with time. Results also showed that molecular responses can vary depending on the intensity and duration of the chemical stress applied to the organisms and that the study of mt gene expression levels seemed to be the best tool to assess Cd intoxication.

Bioaccumulation and oxidative stress responses measured in the estuarine ragworm (Nereis diversicolor) exposed to dissolved, nano- and bulk-sized silver

“…However, compensatory mechanisms between antioxidants may occur. An increase in SeGPx activity is particularly relevant under severe oxidative challenge when CAT is inhibited, and cells may be critically dependent on SeGPx for detoxification of H 2 O 2 free radicals (Al Kaddissi et al, 2014). Increase in SeGPx activity was concomitant with a decrease in CAT activity indicating the necessity of this compensatory mechanisms during Ag NP and bulk Ag particle exposure treatments (Figs.…”

“…Finally, an early transient GST increase was found for both dissolved and bulk silver, while the activity was lowered in Ag NP at the last time point. It may be possible that such inhibition is due to either through direct action of metal on the enzyme or indirectly via the production of ROS (Ahn et al, 2014;Al Kaddissi et al, 2014). The accumulation of metals by N. diversicolor, including Ag, has been shown to occur primarily by sediment ingestion (Rainbow et al, 2009).…”

“…Biomarker responses have been well characterized against a range of xenobiotics including disinfectants (Elia et al, 2006a(Elia et al, , 2008, trace metals (Elia et al, 2000(Elia et al, , 2003(Elia et al, , 2006b(Elia et al, , 2007(Elia et al, , 2010Al Kaddissi et al, 2014) and metal-containing NPs (Buffet et al, 2011, 2012. Exposure to Ag NPs resulted in an increase of oxidative stress and a corresponding depletion of antioxidant defense mechanisms (Carlson et al, 2008;Kim et al, 2009).…”

How toxic is the depleted uranium to crayfish Procambarus clarkii compared with cadmium?

“…Fresh tissues were fixed with 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.4) for 48 h at 4°C, then washed three times for 5 min with 0.1 M sodium cacodylate buffer (pH 7.4), and then postfixed with 1% osmium tetroxide in the same buffer for 1 h (Al Kaddissi et al, ). Samples were subsequently dehydrated with successive baths of ethanol and propylene oxide, and finally embedded in Epon 812 (TAAB).…”

“…Groups of adult male crayfish were exposed to 0 and 40 µM of Cd or DU for 4–10 days (acute exposure) (Al Kaddissi et al, ) while others were exposed to 0 and 0.1 µM for 30–60 days (chronic exposure) (Al Kaddissi et al, , b). The impact of the metals on the survival rates of crayfish were reported in each study.…”