Role of copper accumulation in spontaneous renal carcinogenesis in Long-Evans Cinnamon rats

The Role of Ferric Nitrilotriacetate in Renal Carcinogenesis and Cell Death: From Animal Models to Clinical Implications

Iron is essential for cellular growth, and various ferroproteins and heme-containing proteins are involved in a myriad of cellular functions, such as DNA synthesis, oxygen transport, and catalytic reactions. As a consequence, iron deficiency causes pleiotropic effects, such as hypochromic microcytic anemia and growth disturbance, while iron overload is also deleterious by oxidative injury. To prevent the generation of iron-mediated reactive oxygen species (ROS), ferritin is synthesized to store excess iron in cells that are consistent with the clinical utility of the serum ferritin concentration to monitor the therapeutic effect of iron-chelation. Among the animal models exploring iron-induced oxidative stress, ferric nitrilotriacetate (Fe-NTA) was shown to initiate hepatic and renal lipid peroxidation and the development of renal cell carcinoma (RCC) after repeated intraperitoneal injections of Fe-NTA. Here, current understanding of Fe-NTA-induced oxidative stress mediated by glutathione-cycle-dependent iron reduction and the molecular mechanisms of renal carcinogenesis are summarized in combination with a summary of the relationship between the pathogenesis of human RCC and iron metabolism. In addition to iron-mediated carcinogenesis, the ferroptosis that is triggered by the iron-dependent accumulation of lipid peroxidation and is implicated in the carcinogenesis is discussed.

Mechanisms of Rodent Renal Carcinogenesis Revisited

The important renal tumors that can be induced by exposure of rats to chemical carcinogens are renal tubule tumors (RTTs) derived from tubule epithelium; renal pelvic carcinoma derived from the urothelial lining of the pelvis; renal mesenchymal tumors (RMTs) derived from the interstitial connective tissue; and nephroblastoma derived from the metanephric primordia. However, almost all of our knowledge concerning mechanisms of renal carcinogenesis in the rodent pertains to the adenomas and carcinomas originating from renal tubule epithelium. Currently, nine mechanistic pathways can be identified in either the rat or mouse following chemical exposure. These include direct DNA reactivity, indirect DNA reactivity through free radical formation, multiphase bioactivation involving glutathione conjugation, mitotic disruption, sustained cell proliferation from direct cytotoxicity, sustained cell proliferation by disruption of a physiologic process (alpha 2u-globulin nephropathy), exaggerated pharmacologic response, species-dominant metabolic pathway, and chemical exacerbation of chronic progressive nephropathy. Spontaneous occurrence of RTTs in the rat will be included since one example is a confounder for interpreting kidney tumor results in chemical carcinogenicity studies in rats.

Potential therapeutic effects of curcumin in gastric cancer

Despite recent advancements in understanding of the biology of gastric cancer, treatment of patients with advanced gastric cancer remains a major problem. Among different type of phytochemicals, curcumin, a welltable -known phytochemical, has been shown to be a promising cancer chemopreventive agent. Pharmacokinetics, safety, and efficacy of curcumin have been evaluated in several clinical trials against numerous diseases, and for the treatment of human cancer. In the present review, we have collected in vitro and in vivo investigations and studied the chemosensitizing and anticancer effects of curcumin against the gastric cancer cells. In summary, curcumin has been found to have efficient chemosensitizing effect and also inhibits viability, proliferation, and migration of gastric cancer cells mainly via cell cycle arrest and induction of apoptosis by both mitochondrial-dependent and -independent pathways.

Histological liver chances in Swiss mice caused by tannery effluent

Although tannery effluents are known for being highly toxic to organisms, reports about the effects of the intake of these xenobiotics on experimental mammal models are recent. Studies about the damages the chronic intake of these effluents can cause in the liver of outbred mice remain an unexplored field. Thus, the aim of the present study is to assess (histological) the hepatic condition of Swiss mice (outbred strain) chronically exposed to the intake of different raw tannery effluent concentrations diluted in water for 150 days. Accordingly, the mice (males and females) were divided in the following groups: control group-animals treated with drinking water, only; and groups 5 and 10%-treated with raw tannery effluent diluted in water. After exposure, the animals were subjected to euthanasia for liver fragment sample collection and histological analysis, respectively. Moderate hydropic degeneration was observed in the centrilobular regions of the liver of mice exposed to 5 and 10% tannery effluent, as well as greater amounts of hepatocytes presenting karyomegaly and necrotic hepatocytes, and a smaller amount of Kuffer cells in the liver of mice exposed to the xenobiotic. Finally, animals exposed to 10% tannery effluent showed mild hyperplasia of the bile ducts in the portal areas and fibroblast proliferation around the bile ducts, thus suggesting a fibrous process. Except for the frequency of hepatocytes presenting karyomegaly (lower in females), the herein observed hepatic changes were similar in male and female Swiss mice. Accordingly, the present data support the hypothesis that the chronic intake of tannery effluent by outbred mice (Swiss) causes damages in the liver, a fact that broadens the knowledge about the toxic potential of this pollutant, which goes beyond that of C57Bl/6J male mice (inbred strain).

Effects of N-Acetylcysteine, Quercetin, and Phytic Acid on Spontaneous Hepatic and Renal Lesions in LEC Rats

The effects of anti-oxidants were examined in Long-Evans Cinnamon (LEC) rats, which develop acute hepatic injury, and subsequent hepatic and renal tumors due to accumulation of excess Cu. The rats, at the age of 15 weeks, were supplied a diet containing either 1% of N-acetylcysteine (NAC), quercetin (QC), or phytic acid (PA), or basal diet alone. At weeks 2 and 6 posttreatment, animals were sacrificed for collection of blood and tissue samples. In the NAC-treated group, the development of hepatic and renal lesions was dramatically reduced. In addition, accumulation of Cu and Fe in the liver was suppressed. Acrolein-modified protein, a new marker for lipid peroxidation, was not detected in the liver or kidney of NAC treated rats, even though deposition was evident in control. Neither QC nor PA affected the development of spontaneous hepatic lesions. These results indicate that oxidative stress was reduced by NAC in the liver and kidney, and suggest that Cu and Fe may be involved in the generation of oxidative stress in the liver. In addition, it was suggested that the different effects of the anti-oxidants on lesion development in LEC rats might be related to different mechanisms of action with regard to oxidative stress.

Canine Gastric Pathology: A Review

Gastric disorders are common in dogs and are a major reason for veterinary consultation. In human medicine, the classification of gastric diseases based on histological features, genotypes and molecular phenotypes helps to better understand the characteristics of each subtype, and to improve early diagnosis, prevention and treatment. Canine gastric lesions often show strong histological similarities to their human counterparts. However, such conditions in the canine stomach are poorly studied and their cellular and molecular features are largely unknown. This article reviews the histopathological classification of inflammatory and neoplastic lesions of the canine stomach and provides an update on the application of molecular techniques within the field of canine gastric pathology. The canine disorders are compared with current knowledge of the equivalent human diseases.

Toxicologic assessment of Paecilomyces tenuipes in rats: renal toxicity and mutagenic potential

Paecilomyces tenuipes is entomogenous fungus that is called snow-flake Dongchunghacho in Korea. Although it is widely used in traditional medicines, its safety has not yet been comprehensively investigated. Therefore, the aim of this study was to evaluate the genotoxicity, acute and subchronic toxicity of P. tenuipes. The acute oral LD50 of P. tenuipes extract in rats was estimated to be greater than 2000mg/kg of body weight. In the subchronic study, the oral treatment of rats with 500, 1000 or 2000mg/kg P. tenuipes extract daily for 13weeks did not induce any dose-related changes (body weight, food consumption, clinical observation, urinalysis, hematology, clinical chemistry and organ weight). In contrast, histopathological observation revealed that P. tenuipes extract induced karyomegaly in outer medulla of kidney in all treated rats. Importantly, P. tenuipes extract exerted the mutagenic potential in Ames assay. Since karyomegalic alterations have been known to be associated with carcinogenicity, our finding on the mutagenicity of P. tenuipes extract supports the possibility on the potential involvement of P. tenuipes in carcinogenicity at least partially. In conclusion, the subchronic oral exposure of P. tenuipes may induce kidney abnormality at the concentration higher than 500mg/kg body weight, although further studies using other animal models are needed to identify the toxicity of P. tenuipes.

Gastric cancer: Classification, histology and application of molecular pathology

Gastric cancer remains one of the deadly diseases with poor prognosis. New classification of gastric cancers based on histologic features, genotypes and molecular phenotypes helps better understand the characteristics of each subtype, and improve early diagnosis, prevention and treatment. The objective of this article is to review the new classification of gastric cancers and the up-to-date guidance in the application of molecular testing.

Inhibitory effects of trientine, a copper-chelating agent, on induction of DNA strand breaks in kidney cells of Long-Evans Cinnamon (LEC) rats

The effects of treatment with trientine, a specific copper-chelating agent, on the accumulation of copper and induction of DNA strand breaks were investigated in Long-Evans Cinnamon (LEC) rats, an animal model for human Wilson's disease. Copper accumulated in the kidneys of LEC rats in an age-dependent manner from 12 to 18 weeks of age. When LEC rats were treated with trientine from 10 weeks of age, renal copper contents did not increase and were maintained at the same levels as those in 4-week-old LEC rats. Estimation of the amounts of DNA single-strand breaks (SSBs) by comet assay showed that SSBs of DNA were induced in a substantial population of LEC rat renal cortex cells around 12 weeks of age and that the amounts of SSBs increased in an age-dependent manner from 12 to 18 weeks of age. When LEC rats were treated with trientine from 10 weeks of age, the observed number of cells with DNA damage decreased, suggesting that induction of SSBs of DNA was inhibited and/or SSBs were repaired during the period of treatment with trientine. The results show that SSBs of DNA in LEC rat kidney cells are induced prior to occurrence of clinical signs of hepatic injury and that treatment of LEC rats with trientine decreases the number of DNA strand breaks.

Renal Fanconi syndrome and myopathy after liver transplantation: drug-related mitochondrial cytopathy?

Advances in the field of transplantation provide a better quality of life and allow more favorable conditions for growth and development in children. However, combinations of different therapeutic regimens require consideration of potential adverse reactions. We describe a 15-yr-old girl who had orthotopic liver transplantation because of Wilson's disease. Tacrolimus, MMF, and steroids were given as immunosuppressant. Lamivudine was added because of de nova hepatitis B infection during her follow-up. Three yr after transplantation she developed renal Fanconi syndrome with severe metabolic acidosis, hypophosphatemia, glycosuria, and aminoaciduria. Although tacrolimus was suspected to be the cause of late post-transplant renal acidosis and was replaced by sirolimus, acidosis, and electrolyte imbalance got worse. Proximal muscle weakness has developed during her follow-up. Fanconi syndrome, as well as myopathy, is well recognized in patients with mitochondrial disorders and caused by depletion of mtDNA. We suggest that our patient's tubular dysfunction and myopathy may have resulted from mitochondrial dysfunction which is triggered by tacrolimus and augmented by lamivudine.

A 13-week subchronic toxicity study of madder color in F344 rats

A 13-week repeated oral dose toxicity study of madder color (MC), a natural food colorant extracted from the roots of Rubia tinctorum L., was performed using F344 rats. Five groups of animals, each consisting of 10 males and 10 females, were fed diet containing 0, 0.6, 1.2, 2.5 or 5.0% MC for 13 weeks. During the experiment, lower body weight was evident from the 2.5% dose. Hematologically, fluctuation in red blood cell (RBC) parameters suggestive of weak anemia (females), and slight increases of platelet counts (both sexes) and white blood cell (WBC) counts (males) were observed at higher doses. Serum biochemically, slight fluctuations were observed in many parameters, including increased total protein (TP), conjugated bilirubin, Ca, and inorganic phosphate, and decrease of the albumin/globulin (A/G) ratio in both sexes, with dose-dependence for TP and A/G from 0.6% in females. Histopathological changes were mainly observed in the renal proximal tubules, such as microvesicular vacuolar degeneration in the cortex and karyomegaly in the outer medulla involving both sexes, lesions being evident even with 0.6%. In the outer medulla, elevation of cell proliferation activity as assessed with proliferating cell nuclear antigen was observed in males from 2.5%. Severity of focal necrosis of hepatocytes was increased only in females at 5.0%, while the increased relative liver weight as with the increased conjugated bilirubin was evident in both sexes from 1.2%. The results thus suggest that MC exerts mild toxicity, targeting liver, kidneys, and possibly RBCs and WBCs, some renal changes being evident from 0.6% in diet, that is attributable to be the lowest-observed adverse effect level (305.8-309.2mg/kg body weight/day).

Ferrous and ferric iron accumulates in the brain of aged Long–Evans Cinnamon rats, an animal model of Wilson's disease

The Long-Evans Cinnamon (LEC) rat, which accumulates excess copper (Cu) in its liver, is an animal model of Wilson's disease. We evaluated and compared the distributions of Cu, ferrous (Fe2+), and ferric (Fe3+) iron in four-brain regions, namely, in the cerebral cortex, cerebellum, substantia nigra (SN), and striatum of LEC and Long-Evans Agouti rats at 30 and 55 weeks. Cu levels were elevated in the striatum of LEC rats, and Fe2+ and Fe3+ were higher in the striatum and SN of LEC rats. Ratios of Fe2+ to Fe3+ were > 1 in four regions, and were highest in the striatum and SN of LEC rats. Cu and iron levels were found to be augmented during aging, and we suggest that these accumulations may exert deleterious effects in aged LEC rats. This study is the first report that demonstrates regional differences of Fe2+ and Fe3+ accumulation in the brain of aged LEC rats. Further studies are required to elucidate the mechanisms of Cu and iron accumulations and of their effects.

Copper induces histone hypoacetylation through directly inhibiting histone acetyltransferase activity

The abnormal accumulation of Cu2+ is closely correlated with the incidence of different diseases, such as Alzheimer's disease and Wilson disease. To study in vivo functions of Cu2+ will lead to a better understanding of the nature of these diseases. In the present study, effect of Cu2+ on histone acetylation was investigated in human hepatoma cells. Exposure of cells to Cu2+ resulted in a significant decrease of histone acetylation, as indicated by the decrease of the overall histone acetylation and the decrease of histone H3 and H4 acetylation. Since histone acetyltransferase (HAT) and histone deacetylase (HDAC) are the enzymes controlled the state of histone acetylation in vivo, we tested their contribution to the inhibition of Cu2+ on histone acetylation. One hundred nanomolar trichostatin A, the specific inhibitor of HDAC, did not attenuate the inhibitory effect of Cu2+ on histone acetylation. Combined with that Cu2+ showed no effect on the in vitro activity of HDAC, these results led to the conclusion that it is HAT, but not HDAC that is involved in Cu2+ -induced histone hypoacetylation. This conclusion was confirmed by the facts that (1) Cu2+ significantly inhibited the in vitro activity of HAT, (2) Cu2+ -treated cells possessed a lower HAT activity than control cells, and (3) 50 or 100 microM bathocuproine disulfonate, a chelator of Cu2+, significantly attenuated the inhibition of Cu2+ on HAT activity and histone acetylation in the similar pattern. Combined with that Cu2+ showed no or obvious cytotoxicity at 100 or 200 microM in human hepatoma cells, and the previous study that Cu2+ inhibits the histone H4 acetylation of yeast cells at nontoxic or toxic levels, the data presented here suggest that inhibiting histone acetylation is probably one general in vivo function of Cu2+, where HAT is its molecular target.

Evaluation of MT expression and detection of apoptotic cells in LEC rat kidneys

To confirm our previous observations on the effectiveness of long term treatment with Zn on Long-Evans Cinnamon (LEC) rats, we extended these studies determining the effects of Zn on trace elements, metallothionein (MT) concentrations and immunolocalization, and on the levels of both MT-1 and MT-2 mRNAs in the LEC rat kidneys. We also localized the renal cells that had chromatin condensation and nuclear fragmentation typical of apoptosis. The results demonstrate that the amount of Zn increased in the treated rats with respect to both untreated and basal rats. In the treated rats the amount of Cu and Fe was similar to that of the basal rats. MT concentrations did not change either with or without Zn treatment, but were higher than the basal group. However, if we consider the percentage of oxidized MT (MTox), we note that Zn treatment is very effective in reducing this value. MTox is not able to bind metals, so it does not perform a "scavenger" function. Moreover, quantification of mRNA indicates that the MT-1 isoform was significantly higher than the MT-2 isoform following Zn treatment. Untreated group sections showed a confocal fluorescent signal that highlighted the irregular nuclei and small apoptotic bodies. The intensity and quantity of fluorescence decreased in the treated group sections. These findings suggest that, in LEC rats, Zn may contribute to cytoprotection through the regulation of MT expression which may provide a cellular defence strategy in response to DNA damage.

Molecular mechanisms of DNA damage induced by procarbazine in the presence of Cu(II)

Procarbazine [N-isopropyl-alpha-(2-methylhydrazino)-p-toluamide], a hydrazine derivative, which has been shown to have effective antineoplastic activity, induces cancer in some experimental animals and humans. To clarify a new mechanism for its carcinogenic effect, we examined DNA damage induced by procarbazine in the presence of metal ion, using 32P-5'-end-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene. Procarbazine plus Cu(II) induced piperidine-labile and formamidopyrimidine-DNA glycosylase-sensitive lesions at the 5'-ACG-3' sequence, complementary to a hotspot of the p53 gene, and the 5'-TG-3' sequence. Catalase partially inhibited DNA damage, suggesting that not only H(2)O(2) but also other reactive species are involved. Procarbazine plus Cu(II) significantly increased the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine, which was completely inhibited by calatase. Electron spin resonance spin-trapping experiments revealed that methyl radicals were generated from procarbazine and Cu(II). On the basis of these findings, it is considered that procarbazine causes DNA damage through non-enzymatic formation of the Cu(I)-hydroperoxo complex and methyl radicals. In conclusion, in addition to alkylation, oxidative DNA damage may play important roles in not only antitumor effects but also mutagenesis and carcinogenesis induced by procarbazine.

Carcinogenic semicarbazide induces sequence-specific DNA damage through the generation of reactive oxygen species and the derived organic radicals

Semicarbazide, a hydrazine derivative, is carcinogenic to mice but shows no or little mutagenicity in the Salmonella-microsome test. To clarify whether or not the genotoxic mechanism contributes to the non-mutagenic carcinogenicity of semicarbazide, we investigated DNA damage induced by semicarbazide using 32P-5'-end-labeled DNA fragments obtained from the c-Ha-ras-1 protooncogene and the p53 tumor suppressor gene. Semicarbazide caused DNA damage frequently at the thymine and cytosine residues in the presence of Cu(II). Catalase and bathocuproine partially inhibited DNA damage, suggesting that hydrogen peroxide plus Cu(I) participates in DNA damage. When a high concentration of semicarbazide was used in the presence of catalase, DNA damage was induced, especially at G in 5'-AG and slightly at 5'-G in GG and GGG sequences. An electron paramagnetic resonance (EPR) spectroscopic study has confirmed that the reaction of semicarbazide with Cu(II) produces carbamoyl radicals (z.rad;CONH(2)), possibly generated via the nitrogen-centered radicals of semicarbazide. Azodicarbonamide also produced carbamoyl radicals and induced DNA damage frequently at 5'-G in GG and GGG sequences, suggesting that carbamoyl radicals participate in this sequence-specific DNA damage by semicarbazide. On the basis of our previous reports, we consider that the sequence-specific DNA damage at G in 5'-AG in the present study is due to the nitrogen-centered radicals. This study has shown that semicarbazide induces DNA damage in the presence of Cu(II) through the formation of hydrogen peroxide and Cu(I). In addition, semicarbazide-derived free radicals participate in DNA damage. DNA damage induced by these reactive species may be relevant to the carcinogenicity of semicarbazide.

Role of Atp7b gene in spontaneous and N-diethylnitrosamine-induced carcinogenesis in a new congenic strain, WKAH.C-Atp7b rats

To examine whether Long-Evans Cinnamon (LEC) rats, a mutant rat model of Wilson's disease, have a susceptibility gene(s) to hepatocarcinogenesis in addition to the causative gene, Atp7b, we established a new congenic strain, WKAH.C-Atp7b rats, in which the Atp7b gene of the LEC rats is inserted into the normal Wistar-King Aptekman Hokkaido (WKAH) background. Hepatocellular tumors developed spontaneously in both sexes of WKAH.C-Atp7b rats, their incidence being slightly lower than that in LEC rats. Incidences of spontaneous liver tumors in LEC, WKAH.C-Atp7b and WKAH rats correlated with hepatic copper and iron concentrations. Medium-term liver bioassay showed that LEC rats were more susceptible to the induction of glutathione S-transferase placental form-positive preneoplastic foci than WKAH.C-Atp7b rats, and WKAH.C-Atp7b rats were more susceptible than WKAH rats. In an N-diethylnitrosamine (DEN)-induced long-term carcinogenicity study, 1) LEC rats were similarly or rather less susceptible to hepatocellular tumors than WKAH.C-Atp7b and WKAH rats, indicating that the progression of the preneoplastic foci to liver cancer in LEC rats was worse than that in WKAH.C-Atp7b and WKAH rats, 2) the incidences of kidney tumors in LEC and WKAH.C-Atp7b rats were higher than that in WKAH rats and high copper concentrations in the kidneys were observed in LEC and WKAH.C-Atp7b rats, 3) LEC rats were resistant to lung carcinogenesis. These data indicate that the susceptibility of LEC rats to liver and kidney carcinogenesis could be explained by Atp7b gene mutation and that the susceptibility to lung carcinogenesis is controlled by gene(s) other than Atp7b.

Low susceptibility of Long-Evans Cinnamon rats to N-butyl-N-(4-hydroxybutyl)-nitrosamine-induced urinary bladder carcinogenesis and inhibitory effect of urinary copper

We studied the susceptibilities to N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced urinary bladder carcinogenesis of male Long-Evans Cinnamon (LEC), F344 and Long-Evans Agouti (LEA) rats. Male rats (n=21) were given 0.1% BBN in their drinking water from week 6, 8 and 10 for one week, and killed in week 56. The incidences of transitional cell tumors (papillomas plus carcinomas) in BBN-treated LEC and F344 rats were 12% and 76%, respectively (P<0.001, experiment 1), and those in LEC and LEA rats were 11% and 95%, respectively (P<0.001, experiment 2). When male LEC and F344 rats were given 0.1% BBN in their drinking water for 7 days, the intake of BBN and the urinary concentration of its active metabolite, N-butyl-N-(3-carboxypropyl)nitrosamine (BCPN), were higher in the LEC rats (P<0.01). The urinary pHs of untreated LEC and F344 rats were similar between week 6 and 30. The urinary copper concentration was lower in LEC rats before jaundice than in F344 rats, but its concentrations in 28- and 50-week-old LEC rats were 1.7 and 2.3 times those in F344 rats. In a two-stage carcinogenesis study using F344 rats, i.p. injections of cupric nitrilotriacetate increased urinary copper excretion, and inhibited BBN-induced bladder carcinogenesis. In a two-stage carcinogenesis study using LEC rats, oral administration of D-penicillamine decreased urinary copper excretion, and increased BBN-induced bladder cancer, although the difference was not significant. These data show that LEC rats are resistant to bladder carcinogenesis and suggest that urinary copper has a significant role in their resistance.