Carcinogen-induced early molecular events and its implication in the initiation of chemical hepatocarcinogenesis in rats: chemopreventive role of vanadium on this process

Carcinogen-induced formation of DNA adducts and other types of DNA lesions are the critical molecular events in the initiation of chemical carcinogenesis and modulation of such events by chemopreventive agents could be an important step in limiting neoplastic transformation in vivo. Vanadium, a dietary micronutrient has been found to be effective in several types of cancers both in vivo and in vitro and also possesses profound anticarcinogenicity against rat models of mammary, colon and hepatocarcinogenesis. Presently, we report the chemopreventive potential of vanadium on diethylnitrosamine (DEN)-induced early DNA damages in rat liver. Hepatocarcinogenesis was induced in male Sprague-Dawley rats with a single, necrogenic, intraperitoneal (i.p.) injection of DEN (200 mg/kg body weight) at week 4. There was a significant induction of tissue-specific ethylguanines, steady elevation of modified DNA bases 8-hydroxy-2'-deoxyguanosines (8-OHdGs) (P<0.0001; 89.93%) along with substantial increment of the extent of single-strand breaks (SSBs) (P<0.0001) following DEN exposure. Supplementation of 0.5 ppm of vanadium throughout the experiment abated the formations of O(6)-ethylguanines and 7-ethylguanines (P<0.0001; 48.71% and 67.54% respectively), 8-OHdGs (P<0.0001; 81.37%), length:width (L:W) of DNA mass (P<0.01; 62.12%) and the mean frequency of tailed DNA (P<0.001; 53.58%), and hepatic nodulogenesis in preneoplastic rat liver. The study indicates that 0.5 ppm vanadium is potentially and optimally effective, as derived from dose-response studies, in limiting early molecular events and preneoplastic lesions, thereby modulating the initiation stage of hepatocarcinogenesis. Vanadium is chemopreventive against DEN-induced genotoxicity and resulting hepatocellular transformation in rats.     

Molecular basis of anticlastogenic potential of vanadium in vivo during the early stages of diethylnitrosamine-induced hepatocarcinogenesis in rats

Carcinogen-induced DNA base modification and subsequent DNA lesions are the critical events for the expression of premalignant phenotype of the cell. We have therefore investigated the chemopreventive efficacy of a vanadium salt against diethylnitrosamine (DEN)-induced early DNA and chromosomal damages in rat liver. Hepatocarcinogenesis was induced in male Sprague-Dawley rats with a single, necrogenic, intraperitoneal injection of DEN (200mg/kg body weight). 8-Hydroxy-2'-deoxyguanosines (8-OHdGs), strand-breaks and DNA-protein crosslinks (DPCs) were measured by HPLC, comet assay and spectrofluorimetry, respectively. There was a significant and steady elevation of modified bases 8-OHdGs along with substantial increments of the extent of single-strand-breaks (SSBs), DPCs and chromosomal aberrations (CAs) following DEN exposure. Supplementation of vanadium as ammonium metavanadate (NH(4)VO(3), +V oxidation state) at a dose of 0.5ppm in terms of the salt weight throughout the experiment abated the formations of 8-OHdGs (P<0.0001; 79.54%), tailed DNA (P<0.05; 31.55%) and length:width of DNA mass (P<0.02; 61.25%) in preneoplastic rat liver. Vanadium treatment also inhibited DPCs (P<0.0001; 58.47%) and CAs (P<0.001; 45.17%) studied at various time points. The results indicate that the anticlastogenic potential of vanadium in vivo might be due to the observed reductions in liver-specific 8-OHdGs, SSBs and/or DPCs by this trace metal. We conclude that, vanadium plays a significant role in limiting DEN-induced genotoxicity and clastogenicity during the early stages of hepatocarcinogenesis in rats.     

Molecular basis of vanadium-mediated inhibition of hepatocellular preneoplasia during experimental hepatocarcinogenesis in rats

Carcinogen-induced early DNA lesions and metallothionein (MT) over-expression have been implicated in cell proliferation and thereby subsequent expression of premalignant phenotype of the cell. We have therefore investigated the chemopreventive potential of vanadium in a multi-biomarker approach, viz. 8-hydroxy-2'-deoxyguanosines (8-OHdGs), DNA single-strand breaks (SSBs), DNA-protein crosslinks (DPCs), chromosomal aberrations (CAs), in situ MT expression, and cell proliferation in rat liver preneoplasia. Hepatocarcinogenesis was induced in male Sprague-Dawley rats with a single, necrogenic, intraperitoneal (i.p.) injection of diethylnitrosamine (DEN) (200 mg/Kg body weight) at week 4 of the experimental protocol followed by promotion with phenobarbital (PB) (0.05% in basal diet), on and from week 8 and continued till 32 weeks in a long-term regimen. There was a significant and steady elevation of modified DNA bases 8-OHdGs (P < 0.0001; 90.69%) along with substantial increments of the extent of SSBs (P < 0.001) and CAs (P < 0.001) following DEN exposure. Supplementation of vanadium at a dose of 0.5 ppm abated the formations of 8-OHdGs (80.63%; P < 0.0001), SS-DNAs (P < 0.001) and SSBs/DNA unit (P < 0.01; 56.39%), DPCs (59.26%; P < 0.0001) and CAs (71.52%; P < 0.001) in preneoplastic rat liver studied at various time points. Low dose of vanadium treatment further reduced liver-MT immunoreactivity (P < 0.05) and BrdU-labeling index (P < 0.02) and a significant positive correlation (r = 0.92; r2 = 0.85; P = 0.0001) was noted between them. Continuous vanadium administration also decreased nodular incidence (66.67%) and nodule multiplicity (62.12%; P < 0.001) along with substantial improvement in the altered hepatocellular phenotype when compared to DEN + PB treatment alone. The study indicates that vanadium-mediated suppression of cell proliferation and resulting premalignant expression might be due to the observed reductions in hepatic 8-OHdGs, SSBs, DPCs, CAs, and MT immunoreactivity. Vanadium is chemopreventive for DEN-induced hepatocellular preneoplasia in rats.     

Cell proliferation and hepatocarcinogenesis in rat initiated by diethylnitrosamine and promoted by phenobarbital: potential roles of early DNA damage and liver metallothionein expression

Cell proliferation plays an important role in multistage chemical carcinogenesis. Again, several reports demonstrated that upregulation of metallothionein (MT) expression is associated with increased cell proliferation that may contribute to the pathogenesis of preneoplastic phenotype to frank malignancy. In this study, we evaluated the roles of early DNA damage, altered expressions of liver MT and Ki-67 nuclear antigen, and altered hepatic levels of zinc (Zn) and copper (Cu) on cell proliferation and the progression of hepatocarcinogenesis through premalignant, late premalignant and malignant transformation phases in male Sprague-Dawley rats. We have further studied the association between MT expression and cell proliferation in hepatocarcinogenesis. There was substantial induction of DNA single-strand breaks (SSBs) (P < 0.001) and development of hepatocellular premalignant lesions along with significant decrease in hepatic levels of Zn and increase in Cu content following a single, necrogenic, intraperitoneal (i.p.) injection (200 mg/Kg body weight) of diethylnitrosamine (DEN) at week 4 of the experimental protocol. Moreover, DEN + phenobarbital (PB)-treatment significantly elevated MT-, Ki-67-, and BrdU-immunoexpressions along with their immunolabeling indices. Furthermore, positive correlations between MT- and Ki-67- labeling (P = 0.0006) at various time intervals, as well as, between MT immunoreactivity and 5’-bromo-2’-deoxyuridine-labeling index (BrdU-LI) (P = 0.0007) indicate that, MT expression might be associated with Ki-67 expression and cell proliferation thereby. The study suggests that DEN treatment may lead to alteration of Zn and Cu levels resulting in early DNA damage along with elevation of MT expression that may ultimately lead to hepatic cell proliferation. The results thus provide evidence in support of the role of MT as a potential positive regulator of cell growth during the early stages of hepatocellular transformation in rats.     

Decreased density of beta1-adrenergic receptors in preneoplastic and neoplastic liver lesions of F344 rats

There is some evidence that rodent hepatocarcinogenesis is accompanied by changes in the adrenergic responsiveness of liver cells to catecholamines. In this study, immunohistochemical expression of beta1-adrenergic receptors (beta1-ARs) has been examined in spontaneous and chemically induced preneoplastic and neoplastic liver lesions of female and male Fischer 344 rats. An antibody specific for beta1-AR subtype was used. The study was carried out on archival formalin-fixed and paraffin-embedded livers from rats used in a previous study of hepatocarcinogenesis. One control group given distilled water by gavage, and two experimental groups, one initiated with a single dose of diethylnitrosamine (DEN) and one initiated with DEN and continuously treated with phenobarbital (PB) were examined. Rats were sacrificed after 2, 4, 8 and 21 months of experimentation. All types of liver putative preneoplastic lesions examined (basophilic, glycogen-retaining, or mixed cell foci) show a lower density of beta1-ARs than the surrounding normal liver parenchyma, either in control and in DEN-treated or DEN+PB-treated rats. No immunostaining is detectable in several altered cell foci. Hepatocellular adenomas and hepatocellular carcinomas also show a very low density of beta1-ARs, extensive areas completely devoid of beta1-ARs being mingled with areas showing a weak immunostaining.     

Supplementation of selenium reduces chemical hepatocarcinogenesis in male Sprague-Dawley rats

Selenium is an essential micronutrient mineral found mainly in soils and has been shown to prevent certain cancers in humans and animals. However, the dose and effects of selenium on liver cancer are controversial. The aim of this study was to investigate the effects of sodium selenite (4 mg/kg in drinking water) on chemically induced hepatocarcinogenesis in rats. Hepatocarcinogenesis was induced by a single intraperitoneal injection of diethyl nitrosamine (DEN) (200 mg/kg body weight) and 2 weeks later, the carcinogenic effect was promoted by 2-acetylaminofluorene (2-AAF) (0.02%). 44 Sprague-Dawley rats were divided into 6 groups: negative control, positive control (DEN+2-AAF), pre-selenium group (sodium selenite for 4 weeks, then DEN+2-AAF), pre-selenium control group (sodium selenite for 4 weeks, no DEN or 2-AAF), post-selenium group (sodium selenite for 8 weeks after 4 weeks of DEN injection) and post-selenium control group (sodium selenite for 8 weeks, no DEN or 2-AAF). Hematoxylin and eosin plus Gordon and Sweet’s methods were used to stain liver tissues. The results showed that the number and sizes of hepatic nodules in pre- and post-selenium treatment groups significantly decreased (P<0.05) compared with the positive control. Microscopic analysis of pre- and post-selenium groups showed that the majority of nodules were hyperplastic with preserved liver architecture, whereas the positive control was full of neoplastic nodules with a completely disrupted liver architecture. Hence, pre- and post-selenium treatments can reduce the extent of liver cancer on chemically induced hepatocarcinogenesis in rats.     

Effect of metanil yellow and malachite green on DNA synthesis in N-nitrosodiethylamine induced preneoplastic rat livers

Metanil yellow (MY) and malachite green (MG) are textile dyes, which, despite the ban occurs unsrupulously as food colouring agents. Accordingly they constitute a serious public health hazard and are of sufficient environmental concern. We have earlier reported that both MY and MG have tumor enhancing effects on the development of hepatic preneoplastic lesions induced by N-nitrosodiethylamine in rats. In order to understand the possible mechanisms by which MY and MG enhance tumor development, in this study we have tested the effects of MY and MG on DNA synthesis and PCNA expression in preneoplastic hepatic lesions during N-nitrosodiethylamine (DEN) induced hepatocarcinogenesis in male Wistar (WR) rats. Rats were administered 200 ppm DEN through drinking water for a period of one month. Administration of DEN for a period of one month showed an upregulation of cell cycle regulatory proteins namely cyclin D1, CDK4, cyclin E and CDK2. Accordingly, in other experiments, the animals were further administered MY and MG for a period of one month following one month DEN treatment. The effects of MY and MG were monitored on the basis of cell proliferation markers--DNA synthesis and PCNA expression both by immunohistochemical and immunoblotting. Following DEN administration, MY, MG and PB showed stimulation of DNA synthesis and increased PCNA expression when compared with either the corresponding controls or only DEN treated animals. In the present study, enhancing effect of MY, MG and PB on the cell proliferation markers during DEN-induced hepatic preneoplasia in rats was observed.     

Vanadium inhibits the development of 2-acetylaminofluorene-induced premalignant phenotype in a two-stage chemical rat hepatocarcinogenesis model

In recent years, research on the biological influence of micronutrients in cancer has grown enormously. Among these, vanadium, a dietary micronutrient present in mammalian tissues has received considerable attention as a limiting agent. In the present study, attempts have been made to investigate the in vivo antitumour potentials of this micronutrient at the 0.5 ppm dosage in drinking water in a defined model of a two-stage experimental rat hepatocarcinogenesis. The chemopreventive effect of vanadium was assessed by studying certain biomarkers, such as development of gamma-glutamyltranspeptidase (GGT)-positive foci, levels of some essential trace elements, in situ expression of proliferating cell nuclear antigen (PCNA) and chromosomal aberrations. Hepatocarcinogenesis was induced in male Sprague-Dawley rats by chronic feeding of 2-acetylaminofluorene (0.05% in basal diet) on and from week 4. Vanadium administration throughout the experiment reduced the relative liver weight, nodular incidence (66.70%), total number and multiplicity (79.93%) and restored hepatic levels of selenium (Se) and iron (Fe) (P < 0.001) when compared to the carcinogen control. Moreover, long-term vanadium treatment significantly abated the expressions of GGT (P < 0.001) and PCNA with concomitant reduction in PCNA immunolabeling index (P < 0.001; 36.62%). Finally, the anticlastogenic potential of vanadium was reflected through its ability to inhibit early chromosomal aberrations (P < 0.001; 45.17%) in 2-AAF-challenged rat hepatocytes. Our results suggest that supplementary vanadium at a dose of 0.5 ppm, when administered continuously throughout the study, than administered either in the initiation or promotion phase alone, is very much effective in suppressing neoplastic transformation in vivo. We conclude the significant role of vanadium in limiting cell proliferation and chromosomal aberrations during the preneoplastic stages of hepatocarcinogenesis in rats.     

Effect of Solanum trilobatum on the antioxidant status during diethyl nitrosamine induced and phenobarbital promoted hepatocarcinogenesis in rat

AIM: The methanolic extract of Solanum trilobatum (ST) is cytotoxic and exerts an inhibitory effect on tumor growth and in the present study, its role on the antioxidant status of N-diethylnitrosamine (DEN) induced and phenobarbital (PB) promoted hepatocarcinogenesis was assessed. METHODS: The protective role of ST on DEN induced and PB promoted hepatocarcinogenesis in Wistar rats was assessed from total nodular incidence, nodule multiplicity and volume of persistent nodules after an experimental period of 3 and 6 months following co-administration. The levels of thiobarbituric reactive substances (TBARS), glutathione (GSH) and activities of antioxidant enzymes were assessed in the haemolysate and liver of experimental animals to evaluate the antioxidant status. RESULTS: In DEN+PB+ST animals, the nodular incidence, multiplicity and volume reduced significantly compared to DEN+PB treated animals. In DEN+PB animals, the levels of TBARS increased significantly, whereas the levels of GSH and the activities of antioxidant enzymes-superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and glucose 6 phosphate dehydrogenase showed significant alterations compared to control both in the haemolysate and liver. However, in DEN+PB+ST animals, the levels of TBARS decreased significantly and the levels of GSH increased with favorable alterations in the activities of antioxidant enzymes in both the haemolysate and liver. CONCLUSION: The present results suggest that ST exerts its chemopreventive effects by modulating the antioxidant status during DEN induced hepatocarcinogenesis.     

Anticarcinogenic effect and modification of cytochrome P450 2E1 by dietary garlic powder in diethylnitrosamine-initiated rat hepatocarcinogenesis

The purpose of this study was to determine the effects of dietary garlic powder on diethylnitrosamine (DEN)- induced hepatocarcinogenesis and cytochrome P450 (CYP) enzymes in weaning male Sprague-Dawley rats by using the medium-term bioassay system of Ito et al. The rats were fed diets that contained 0, 0.5, 2.0 or 5.0% garlic powder for 8 weeks, beginning the diets with the intraperitoneal (i.p.) injection of DEN. The areas of placental glutathione S-transferase (GST-P) positive foci, an effective marker for DEN-initiated lesions, were significantly decreased in the rats that were fed garlic powder diets; the numbers were significantly decreased only in the 2.0 and 5.0% garlic-powder diets. The p-Nitrophenol hydroxylase (PNPH) activities and protein levels of CYP 2E1 in the hepatic microsomes of the rats that were fed the 2.0 and 5.0% garlic powder diet were much lower than those of the basal-diet groups. Pentoxyresorufin O-dealkylase (PROD) activity and CYP 2B1 protein level were not influenced by the garlic-powder diets and carcinogen treatment. Therefore, the suppression of CYP 2E1 by garlic in the diet might influence the formation of preneoplastic foci during hepatocarcinogenesis in rats that are initiated with DEN.     

Potential chemoprevention of diethylnitrosamine-initiated and 2-acetylaminofluorene-promoted hepatocarcinogenesis by zerumbone from the rhizomes of the subtropical ginger (Zingiber zerumbet)

Zerumbone (ZER), a monosesquiterpene found in the subtropical ginger (Zingiber zerumbet Smith), possesses antiproliferative properties to several cancer cells lines, including the cervical, skin and colon cancers. In this study, the antitumourigenic effects of ZER were assessed in rats induced to develop liver cancer with a single intraperitoneal injection of diethylnitrosamine (DEN, 200 mg/kg) and dietary 2-acetylaminofluorene (AAF) (0.02%). The rats also received intraperitoneal ZER injections at 15, 30 or 60 mg/kg body wt. twice a week for 11 weeks, beginning week four post-DEN injection. The hepatocytes of positive control (DEN/AAF) rats were smaller with larger hyperchromatic nuclei than normal, showing cytoplasmic granulation and intracytoplasmic violaceous material, which were characteristics of hepatocarcinogenesis. Histopathological evaluations showed that ZER protects the rat liver from the carcinogenic effects of DEN and AAF. Serum alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (AP) and alpha-fetoprotein (AFP) were significantly lower (P < 0.05) in ZER-treated than untreated rats with liver cancer. The liver malondialdehyde (MDA) concentrations significantly (P < 0.05) increased in the untreated DEN/AAF rats indicating hepatic lipid peroxidation. There was also significant (P < 0.05) reduction in the hepatic tissue glutathione (GSH) concentrations. The liver sections of untreated DEN/AAF rats also showed abundant proliferating cell nuclear antigen (PCNA), while in ZER-treated rats the expression of this antigen was significantly (P < 0.05) lowered. By the TUNEL assay, there were significantly (P < 0.05) higher numbers of apoptotic cells in DEN/AAF rats treated with ZER than those untreated. Zerumbone treatment had also increased Bax and decreased Bcl-2 protein expression in the livers of DEN/AAF rats, which suggested increased apoptosis. Even after 11 weeks of ZER treatment, there was no evidence of abnormality in the liver of normal rats. This study suggests that ZER reduces oxidative stress, inhibits proliferation, induces mitochondria-regulated apoptosis, thus minimising DEN/AAF-induced carcinogenesis in rat liver. Therefore, ZER has great potential in the treatment of liver cancers.     

Black tea polyphenols modulate xenobiotic-metabolizing enzymes,oxidative stress and adduct formation in a rat hepatocarcinogenesis model

The present study was designed to investigate the modulatory effects of black tea polyphenols (Polyphenon-B) on phase I and phase II xenobiotic-metabolizing enzymes and oxidative stress in a rat model of hepatocellular carcinoma (HCC). Liver tumours induced in male Sprague-Dawley rats by dietary administration of ρ-dimethylaminoazobenzene (DAB) increased cytochrome P450 (total and CYP1A1, 1A2 and 2B isoforms), cytochrome b₅, cytochrome b₅ reductase, glutathione S-transferase (GST total and GST-P isoform) and gamma-glutamyltranspeptidase (GGT) with decrease in quinone reductase (QR). This was accompanied by enhanced lipid and protein oxidation and compromised antioxidant defences associated with increased expression of the oxidative stress markers 4-hydroxynonenal (4-HNE), anti-hexanoyl lysine (HEL), dibromotyrosine (DiBrY) and 8-hydroxy 2-deoxyguanosine (8-OHdG). Dietary administration of Polyphenon-B effectively suppressed DAB-induced hepatocarcinogenesis, as evidenced by reduced preneoplastic and neoplastic lesions, modulation of xenobiotic-metabolizing enzymes and amelioration of oxidative stress. Thus, it can be concluded that Polyphenon-B acts as an effective chemopreventive agent by modulating xenobiotic-metabolizing enzymes and mitigating oxidative stress in an in vivo model of hepatocarcinogenesis.     

Transforming growth factor-alpha expression in rat experimental hepatocarcinogenesis.

Growth factors in general and transforming growth factor-alpha in particular have been related to cell proliferation and cell differentiation. This study was designed to clarify the distribution pattern of TGF-alpha in chemically-induced hepatocarcinogenesis. Sprague-Dawley rats were subjected to different non-intensive or intensive carcinogenic treatments using diethylnitrosamine (DEN) as carcinogen and ethinyl estradiol (EE) as promoter. The livers were fixed in 2% paraformaldehyde, dehydrated in a series of ethanol solutions, embedded in paraffin and sectioned. In the preneoplastic lesions no TGF-alpha immunoreactive cells were identified, but in some hepatic tumours cell immunostained with TGF-alpha antibody were observed. These results suggest that the cells capable of expressing TGF-alpha constitutively may be involved in neoplastic development in vivo.     

Vanadium induces apoptosis and modulates the expressions of metallothionein, Ki-67 nuclear antigen, and p53 during 2-acetylaminofluorene-induced rat liver preneoplasia

Our previous studies have shown that vanadium, a dietary micronutrient, has an inhibitory effect against experimentally induced rat hepatocarcinogenesis. In this study, we evaluated the role of vanadium on some potential protein expression markers of carcinogenesis, such as metallothionein (MT), an intracellular metal-binding protein linked with cell proliferation and apoptosis, Ki-67 nuclear antigen, and p53 tumor suppressor during 2-acetylaminofluorene (2-AAF)-induced (0.05% in basal diet) rat liver preneoplasia. In a short-term regimen, supplementation of vanadium at a dose of 0.5 ppm effectively suppressed the formation of DNA 'comets' (29.55%; P < 0.02), thereby indicating its nongenotoxicity at this particular dose. Vanadium administration throughout the study reduced relative liver weight (RLW), nodular incidence (57.15%), total number, and multiplicity (48.45%) with restoration of hepatic zinc (Zn), magnesium (Mg), selenium (Se), copper (Cu), iron (Fe), and calcium (Ca) contents when compared to the carcinogen control. Moreover, treatment with vanadium significantly abated the expressions of MT and Ki-67, studied at four sequential time points. An increased immunopositivity of p53 protein (1.03 +/- 0.23%; P < 0.02) was found in vanadium-treated rat liver with an elevated apoptotic-labeling index (AI; P < 0.001) as documented by TUNEL assay. Furthermore, a positive correlation between MT expression and Ki-67 labeling along with a strong negative correlation between MT immunoreactivity and AI (r = -0.9000, P = 0.0004 at week 24) at various time intervals suggest that, vanadium-mediated suppression of MT and Ki-67 expressions may be associated with induction of apoptosis. The results thus provide evidence for the first time in support of the potential role of vanadium on induction of p53 and apoptosis with concurrent suppression of MT and Ki-67 in order to have an understanding, in part, of the chemopreventive mechanism of this trace element in limiting neoplastic transformation in a defined model of experimental rat hepatocarcinogenesis.     

Association between M/L55-polymorphism of paraoxonase enzyme and oxidative DNA damage in patients with type 2 diabetes mellitus and in control subjects

The paraoxonase enzyme (PON) gene polymorphism causes a change of methionine (M-allele) to leucine (L-allele). PON may reduce low density lipoprotein oxidation and prevent atherosclerosis. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) is a sensitive index of oxidative DNA damage. We have studied the association between the PON genotypes and the urinary excretion of 8-OHdG. The study population consisted of 93 Finnish type 2 diabetes patients and 106 non-diabetic control subjects. The 24-h excretion of 8-OHdG was significantly higher in diabetic patients than in control subjects (P<0.001). In control subjects, the ratio of the 8-OHdG/glomerular filtration rate increased in order of genotype from MM to ML to LL (P<0.0412). These results suggest that lipid peroxidation may have an effect on DNA oxidation.     

Effects of supplemental oxygen on urinary 8-hydroxy-2’-deoxyguanosine levels in extremely low birth weight infants

Abstract

As the effects of supplementary oxygen on urinary excretion of 8-hydroxy-2’-deoxyguanosine (8-OHdG) are poorly understood, urinary 8-OHdG levels (ng/mg creatinine) were determined longitudinally on the postnatal day (PND) 1, 3, and 30 in 16 neonates with birth weight < 1000 g. No supplementary oxygen was required in 9 neonates during the first 24 h of life. Urinary 8-OHdG level on PND 1 was inversely correlated with birth weight in these 9 neonates (P = 0.0323) and was higher in four with birth weight < 750 g than five with birth weight > 750 g (41.0 ± 6.9 vs. 5.6 ± 2.7, respectively, P = 0.0200). Median urinary 8-OHdG on PND 1 of these 9 neonates was significantly lower than that of 7 neonates with oxygen (9.3 vs. 60.2, respectively), although there were no significant differences in clinical background, such as birth weight, between the two groups. Five of the 9 did not require supplemental oxygen at all during the first 30 days of life. Median urinary 8-OHdG levels were consistently significantly lower in the 5 neonates than in 11 neonates with oxygen transiently or persistently (9.3 vs. 54.6, 19.1 vs. 61.4, and 28.3 vs. 145 on PND 1, 3, and 30, respectively), although there were no differences in clinical background, such as birth weight, between the two groups. Urinary 8-OHdG on PND 30 was significantly positively correlated with supplemental oxygen dose on PND 30 (P < 0.0001), but not with birth weight in the 16 neonates. These results suggest that higher supplemental oxygen tension caused higher urinary 8-OHdG in this population.     

大鼠肝癌发生过程中增殖细胞核抗原（PCNA／Cyclin）的表达

应用免疫组织化学的ＡＢＣ法,对二乙基亚硝胺（ＤＥＮ）诱发大鼠发生过程中增殖细胞核抗原在肝组织中的表达进行了系统观察。结果显示：正常大鼠肝组织中仅见极少数ＰＣＮＡ阳性肝细胞,阳性率为０．０８％,随着诱癌进程发展,大鼠肝组织中ＰＣＮＡ阳性肝细胞逐渐增多,诱癌第４、８、１２周,大鼠肝组织中ＰＣＮＡ阳性肝细胞百分率分别为１．６％、３．８％、１６．２％,诱癌晚期癌结节内大部分肝癌细胞里ＰＣＮＡ阳性表达,阳性率为８０．６％。本研究结果表明原位检测ＰＣＮＡ表达比传统依据形态学分化程度来判断肿瘤发生可能性更为客观、可靠。     

Combined supplementation of vanadium and 1alpha,25-dihydroxyvitamin D3 inhibit placental glutathione S-transferase positive foci in rat liver carcinogenesis

The combined effects of vanadium (V) and 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] in inhibiting diethylnitrosamine (DEN)-induced and phenobarbital (PB) promoted hepatocarcinogenesis were examined in male Sprague-Dawley rats. All the rats were subjected to 70% partial hepatectomy (PH) at week 4 and 24h later were administered either solvent trioctanoin (Group B, D, F and H) or 10 mg DEN/kg (Group A, C, E and G) by gavage. Briefly after two weeks of DEN administration, PB were administered (0.05% in basal diet) to all the DEN-treated rats and continued till the completion of the experiment. Supplementary V at the dose of 0.5 ppm in drinking water ad libitum (Group C and D), 1,25(OH)2D3 at the dose of 3 microg/ml in propylene glycol per os twice a week (Group E and F) or both V and 1,25(OH)2D3 at the same above given doses (Group G and H) were started 4 weeks prior to DEN administration (week 0) and continued thereafter till week 15. The expression of the number and area of altered hepatocyte foci (AHF) positive for placental glutathione S-transferase (GST-P) was maximum in DEN-treated and PB promoted group (Group A). V (Group C) and 1,25(OH)2D3 (Group E) treatment significantly reduced the expression of GST-P-positive hepatocytes by 36.02% and 45.16% respectively but an additive protective action (61.46%) was found in Group G which received both V and 1,25(OH)2D3 for the entire period of the study. Moreover, histopathological examination and the incidence of hepatic hyperplastic nodules showed that combined action of V and 1,25(OH)2D3 can able to minimize the appearance of nodules as well and maintain the normal cellular architecture than V and 1,25(OH)2D3 when given alone. These results suggest that, when given together V and 1,25(OH)2D3 could be the chemopreventive agents for rat liver carcinogenesis.     

Altered transferrin gene expression in preneoplastic and neoplastic liver lesions induced in rats with N-nitrosomorpholine

The expression of the gene for the iron transport protein transferrin was found to be altered in preneoplastic and neoplastic lesions induced in the rat liver by N-nitrosomorpholine. The total RNA of ten hepatocellular carcinomas (HCC) was investigated by Northern blot analysis using a cDNA-probe comprising 150 bp of the 3′ region and compared with the total hepatic RNA in untreated rats. Seven hepatocellular carcinomas showed slight or pronounced reduction in transferrin expression. In situ hybridization of two additional hepatocellular carcinomas revealed marked reduction in the mRNA level for the transferrin gene compared with the surrounding tissue. In contrast, the majority of early preneoplastic lesions storing excess glycogen and tigroid cell foci expressed increased levels of transferrin mRNA. The loss of glycogen in mixed cell foci, which represent a later stage of hepatocarcinogenesis, was usually accompanied by a decrease in transferrin mRNA suggesting a close relationship between this change in gene expression and cellular dedifferentiation emerging during hepatocarcinogenesis.