Combined effects of DDE and hyperlipidic diet on metallothionein expression and synthesis in rat tissues

Abstract

Metallothionein is well known for its detoxificant and anti-oxidant properties and has been shown to be effective to prevent hydroxyl radical-generated DNA degradation. The purpose of this investigation was to analyze the combined effect of two factors promoting cellular oxidative-stress, that is, the administration of the pesticide dichloro-diphenyl-dichloroethylene (DDE) and a high fat diet, on metallothionein expression and synthesis in rat liver and kidney.DDE is the main metabolite of dichloro-diphenyl-trichloroethane (DDT), and is commonly found in the food chain and in all tissues of living organisms, carried by the fats. Male Wistar rats were fed with a standard (N) or a high fat (HF) diet and exposed to DDE (10 mg/kg body mass, N + DDE and HF + DDE groups) or vehicle (corn oil, N, and HF groups) via gavage every day for 28 days. Tissues histology was determined by light microscopy analysis; differences in metallothionein gene expression and synthesis by real-time PCR and western blot, respectively.Finally, protein cellular localization was established by immunocytochemistry. The results showed a different involvement of metallothionein in defending tissues from HF-and DDEinduced oxidative stress, suggesting that hepatic and renal cells use different strategies against pro-oxidant species. In both cell types a marked increase in the metallothionein content was observed in the nucleus, with a concomitant drop of the cytoplasmatic protein, either under HFand DDE-stress conditions; however, no synergistic or additive effects were observed between the action of fats and pesticide. These findings reinforce the role of metallothionein in protecting DNA from oxidative damage. K E Y W O R D SDDE and oxidative stress, gene expression, high fat diet, metallothionein, protein synthesis and localization

Exposure to Dichlorodiphenyldichloroethylene (DDE) and Metallothionein Levels in Rats Fed with Normocaloric or High-Fat Diet: A Review

“…In particular, the relative amounts of MT transcripts were almost comparable between liver and testes; in kidneys, the MT mRNA level was about 5 times lower. A similar scenario was also found for MT proteins, whose relative amount in the three different organs was evaluated performing the Western blot analysis [56].…”

“…Recently, histological and molecular analysis indicated that oral exposure to a moderately low dose of DDE (10 mg/kg bw) for 4 weeks was able to elicit morphological alterations, cellular oxidative stress, and lipid peroxidation in rat tissues [47,48,56,58]. Studies also evidenced the presence of similar morphological and oxidative damage caused by the fat diet alone [47,48,56,58]. In the liver, an HF diet induced steatosis of hepatocytes, and DDE treatment-tissue inflammation and cellular vacuolization.…”

“…It has also been demonstrated that cells activated the endogenous antioxidant system to protect themselves from the oxidative damage generated in HF-and DDE-treated animals. In particular, increased synthesis and enzymatic activity of SOD1/2 and total GPx antioxidant enzymes and the induction of the mitochondrial uncoupling protein 2 (UCP2) were observed in the hepatocytes the to limit the mitochondrial damage produced by ROS [47,56]. On the contrary, testicular cells showed antioxidant system impairment in the HF-and DDE-treated animals associated with an increase in lipid peroxidation and the apoptotic rate.…”

“…The constitutive amount of MT mRNAs in tissues of male Wistar rats of 2 months of age was determined by real-time PCR analysis [54][55][56]. The MT primers used allow to amplify and quantify together both MT1 and MT2 isoforms [55,56].…”

“…This finding is quite surprising, because it is known that DDE, as well as saturated fatty acids, has a strong pro-oxidant activity that in theory was supposed to stimulate MT expression and synthesis in cells. It has been demonstrated that following the oral administration of DDE and saturated fatty acids, rat hepatocytes increase the amount and activity of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), thus suggesting that cells respond specifically to the oxidative stress [56]. The treatments also induce lipid peroxidation, a cellular condition previously associated with inhibition of MT synthesis in rat testes [45].…”