Effect of dioxin exposure on several indices of blood redox status in lactating buffalo cows

Abstract

Dioxins are lipophilic compounds with a small molecular weight and are highly persistent, bioaccumulative and toxic. Dioxin detoxification is associated with an increased production of reactive oxygen species (ROS). In physiological conditions the body is protected against ROS and their toxic products by a wide range of antioxidant systems. We hypothesize that the imbalance between ROS production, associated with dioxin exposure, and the antioxidant defence capacity, may lead to oxidative stress, with consequent increased consumption of antioxidants and accumulation of toxic compounds in blood and tissues. The objective of this study was to evaluate the effect of exposure to dioxins on the plasma redox status of lactating buffalo cows. To this aim, the major liposoluble (retinol and α-tocopherol) and water-soluble (ascorbate) antioxidants, the superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, the total antioxidant capacity (TAC), as well as specific protein oxidation markers (protein bound carbonyls and nitro-tyrosine) and lipid oxidation markers (hydroperoxides), were chosen as indices of blood redox status. The concentration of antioxidants, protein-bound carbonyls (PC), nitro-tyrosine (N-Tyr), and hydroperoxides (LPO), the SOD and GPx activity, and the TAC were measured in plasma samples obtained from buffalo cows exposed to environmental levels of dioxins higher (n=21, group A) or lower (n=29; group B) than those permitted. Plasma titres of antioxidants, as measured by HPLC, and the total antioxidant capacity, as measured by trolox equivalents capacity, were higher in group B than in A. Similarly, SOD and GPx activities were higher in group B than in A. Conversely, plasma levels of PC, N-Tyr and LPO, as measured by ELISA, were higher in group A than in B. Our results suggest that exposure to dioxins impairs the plasma antioxidant defence system of lactating buffalo cows, and that metabolic processes associated with dioxin detoxification might induce or enhance oxidation of protein and lipids. This adverse effect on blood redox status might have negative implications for animal health and reproduction, and might compromise animal welfare.

Analysis of plasma indices of redox homeostasis in dairy cows reared in polluted areas of Piedmont (northern Italy)

“…These findings agree with the data previously obtained in buffalo cows (Spagnuolo et al, 2011), as well as in other laboratory species exposed to either 2,3,7,8 tetrachloro-dibenzo-p-dioxin (Stohs et al, 1984;Hassoun et al, 1998;Slezak et al, 2002) or to DL-PCBs (Lai et al, 2010), and support the hypothesis that the exposure to environmental pollutants, such as dioxins, severely impairs the blood antioxidant defence system. As expected, we found that the lower antioxidant capacity, observed in exposed cows, is associated with a significantly higher extent of oxidative modifications of protein and lipid.…”

“…Our findings suggest that in cows a significant part of the plasma antioxidant capacity, as measured by Trolox Equivalent Capacity, might be accounted for by Asc, and support the hypothesis that circulating Asc plays a major role in preventing protein oxidative modifications induced by carbonyls, as previously reported for humans (Krajcovicova-Kudlackova et al, 2006) and buffalo cows (Spagnuolo et al, 2011). Asc is a well known scavenger of peroxynitrite, and SOD is an enzymatic antioxidant involved in the scavenging of superoxide (Beckman and Koppenol, 1996;Halliwell and Gutteridge, 2000).…”

“…Plasma samples were processed for determination of Asc concentration as previously described (Spagnuolo et al, 2011), and analyzed by HPLC using an anion exchange column (Nucleosil 100-NH 2 , 5 μm, 250x4.6 mm i.d. ;…”

Characterization of blood redox status of early and mid-late lactating dairy cows

“…Determination of antioxidants and lipid hydroperoxides. Plasma samples were processed for determination of Asc concentration as previously described (Spagnuolo et al, 2011), and analyzed by high performance liquid chromatography (HPLC) using an anion exchange column (Nucleosil 100-NH 2 , 5 μm, 250 × 4.6 mm i.d.). Ret and Toc levels were measured according to a published procedure (Spagnuolo et al, 2003), and analyzed by HPLC using a reverse phase C18 column (Nova-PAK C18, 4 μm, 125 × 2 mm i.d.).…”

Influences of different space allowance on reproductive performances in buffalo

“…The damaging action of ROS, if not counteracted or prevented by antioxidant defenses, causes cell death, tissue oxidative stress and organ ageing or failure (Halliwell and Gutteridge, 1999). Ascorbate (Asc), α-tocopherol (Toc) and retinol (Ret) are able to scavenge ROS and prevent oxidative damage, in the hydrophilic and lipophilic compartment and their concentration in plasma could be used as marker of oxidative stress (Spagnuolo et al, 2011). The concentration of protein-bound carbonyls (PC) and nitro-tyrosine (N-Tyr) in blood plasma, is also a reliable method to evaluate the extent of oxidative protein damage (Beal, 2002;Dalle-Donne et al, 2003) as N-Tyr and PC are considered markers of ROS-mediated protein oxidation (Berlett and Stadtman, 1997).…”