Assessment of oxidative damage to DNA, transcriptional expression of key genes, lipid peroxidation and histopathological changes in carp Cyprinus carpio L. following exposure to chronic hypoxic and subsequent recovery in normoxic conditions

Abstract

In fish, a complex set of mechanisms deal with environmental stresses including hypoxia. In order to probe the hypothesis that hypoxia-induced stress could be manifested in varieties of pathways, a model species, mirror carp (Cyprinus carpio), were chronically exposed to hypoxic condition (dissolved oxygen level: 1.80 ± 0.6 mg/l) for 21 days and subsequently allowed to recover under normoxic condition (dissolved oxygen level: 8.2 ± 0.5 mg/l) for 7 days. At the end of these exposure periods, an integrated approach was applied to evaluate several endpoints at different levels of biological organisation. These included determination of (i) oxidative damage to DNA in erythrocytes (using modified comet assay), (ii) lipid peroxidation in liver samples by measuring the malondialdehyde production using the 2-thiobarbituric acid [i.e. thiobarbituric acid reactive substances (TBARS) assay] and (iii) histopathological changes in gills. In addition, transcriptional expression of hypoxia-inducible factor 1 α (HIF-1α) and genes involved in the repair of oxidative damage to DNA (i.e. ogg1) and base excision repair (i.e. xrcc1) using reverse transcription polymerase chain reaction in liver samples were also determined. The results suggested significantly enhanced expression of these genes in response to hypoxia compared to concurrent normoxic controls. While the expression of HIF-1α reverted to control values within 7 days exposure to normoxic condition (P < 0.05), the transcriptional expression of the two genes involved in DNA repair process remained significantly high under the recovery period, which complemented the induction of oxidative damage to DNA. Hypoxic groups showed significantly increased values for TBARS level (~2-fold) and histopathological changes in gill tissues compared to both normoxic and recovery groups. Overall, oxidative damage to DNA determined by modified comet assay reflected the observed biological responses in other tissues of the fish. Along with other parameters, this integrated experimental design further strengthens the applications of the comet assay as an important technique to assess stress-induced DNA damage in ecotoxicological studies.

Assessing relative sensitivity of marine and freshwater bivalves following exposure to copper: Application of classical and novel genotoxicological biomarkers

“…Modified comet assays using bacterial enzymes (e.g. FPG, Endo III) have been used by different workers to determine DNA oxidation in fish and mussels [5,107]. It would have been useful to determine DNA oxidation using the modified comet assay in this study as well, to determine relative contribution of DNA oxidation.…”

Effects of β-glucan on ROS production and energy metabolism in yellow croaker (Pseudosciaena crocea) under acute hypoxic stress

“…In mammals, numerous experimental studies have demonstrated that HIF-1a is a master regulator of transcription factor that activates the hypoxic expression of target genes involved in oxygen transport, glucose uptake, energetic homeostasis and so on (Semenza 2002;Huang et al 2004;Mason et al 2004;Rissanen et al 2009;Zhu et al 2013), especially in acute hypoxic stress (Lendahl et al 2009). Although there have recently been a few studies that addressed HIF-1a regulating oxidative stress and anaerobic metabolism induced by hypoxic stress in fish (Kim et al 2006;Mustafa et al 2015), little information is available regarding the role of HIF-1a in hypoxia-induced aerobic metabolism in fish.…”

Does Bougainvillea spectabilis protect Swiss Albino Mice from Aflatoxin-induced Hepatotoxicity?

“…The increased TBARS could be attributed to the reduction in detoxifying hyperperoxides in AFB 1 induced hepatocellular carcinoma (HCC). It is an autocatalytic free radical process and could be responsible for DNA damage (Shirali et al, 1994;Mustafa et al, 2015) which results in impaired membrane function, structural integrity (Gutteridge and Halliwell, 1988) and inactivation of number of membrane bound enzymes and protein receptor. Inclined level of TBARS content in AFB 1 treated rat and mice liver tissue has also been previously reported (Verma and Nair, 2002;El-Gibaly et al, 2003).…”