5'-Methylthioadenosine administration prevents lipid peroxidation and fibrogenesis induced in rat liver by carbon-tetrachloride intoxication.

BACKGROUND: 5'-Methylthioadenosine (MTA), a product of S-adenosylmethionine (SAM) catabolism, could undergo oxidation by mono-oxygenases and auto-oxidation. MTA and SAM effects on oxidative liver injury were evaluated in CCl4-treated rats. METHODS: Male Wistar rats were killed 1-48 h after poisoning with a single intraperitoneal CCl4 dose (0.15 ml/100 g) or with the same dose twice a week for 14 weeks. Daily doses of MTA or SAM (384 micromol/kg), started 1 week before acute CCl4 administration or with chronic treatment, were continued up to the time of sacrifice. RESULTS: Acute and chronic CCl4 intoxication decreased MTA and, to a lesser extent, SAM and reduced glutathione (GSH) liver levels. MTA administration increased liver MTA without affecting SAM and GSH. SAM treatment caused complete/partial recovery of these compounds. MTA and, to a lesser extent, SAM prevented an increase in liver phospholipid hydroperoxides in acutely and chronically intoxicated rats and in prolyl hydroxylase activity and trichrome-positive areas in chronically treated rats. MTA prevented upregulation of Tgf-beta1, Collagen-alpha1 (I) and Tgf-alpha genes in liver of chronically intoxicated rats, and TGF-beta1-induced transdifferentiation to myofibroblasts and growth stimulation by platelet-derived growth factor-b of stellate cells in vitro. CONCLUSIONS: MTA and SAM protect against oxidative liver injury through partially different mechanisms.

Implication of Bcl-2 family genes in basal and D-amphetamine-induced apoptosis in preneoplastic and neoplastic rat liver lesions.

Molecular mechanisms of basal and D-amphetamine (AMPH)-induced apoptosis were studied in rat liver nodules, 12 (N12) and 30 (N30) weeks after initiation, and in hepatocellular carcinoma (HCC) induced by diethylnitrosamine in rats subjected to resistant hepatocyte model. Basal apoptosis in hematoxylin/eosin- and propidium iodide-stained sections was higher in nodules and HCC than in normal livers. It sharply increased in all tissues 4 hours after AMPH treatment (10 mg/kg), and declined to basal levels at 8 to 12 hours in liver and N12, but remained high up to 18 hours in N30 and HCC. c-myc, Tgf-alpha, p53, and Bcl-X(S) messenger RNA (mRNA) levels were higher, and Bcl-2 mRNA was lower in N12 and/or N30 and HCC than in normal liver. Four hours after AMPH injection, increase in c-myc and decreases in Bcl-2 and Bcl-X(L) mRNAs occurred in all tissues, whereas p53, Bax, and Bcl-X(S) mRNAs increased in N30 and HCC. These changes disappeared in liver and N12 at 18 hours, but persisted in N30 and HCC. c-Myc, P53, Bcl-2, and Bax proteins in normal liver and HCC +/- AMPH showed similar patterns. Tgf-beta1, Tgf-beta-RIII, CD95, and CD95L mRNA levels underwent slight or no changes in any tissue +/- AMPH. Basal Hsp27 expression was high in nodules and HCC, and was stimulated by AMPH in liver and N12, but not in N30 and HCC. These data suggest a role of dysregulation of Bcl-2 family genes and, at least in atypical lesions, of p53 overexpression, in basal and AMPH-induced apoptosis in nodules and HCCs. Hsp27 does not appear to sufficiently protect atypical lesions against apoptosis.

PCB and PAH impacts on cytochrome P-450-dependent oxidases in roach (Rutilus rutilus) from the Seine River (France).

Roach were sampled in the Seine River along a gradient of polyaromatic hydrocarbon (PAH) concentrations at three stations: Marnay upstream of Paris and Epinay and Poses downstream of Paris. Two hepatic monooxygenase activities: EROD (ethoxyresorufine-O-deethylase) and AE (aldrin epoxydase) and muscle residues of PCBs and PAHs were investigated during three periods of the year (before spawning, during spawning, and postspawning). Before spawning, EROD and AE activities were significantly correlated with muscle PCB levels (p

Analysis of loss of heterozygosity in neoplastic nodules induced by diethylnitrosamine in the resistant BFF1 rat strain.

Loss of heterozygosity (LOH) at specific chromosomal regions is a frequent event in poorly differentiated human hepatocellular carcinomas (HCCs), but rare in mouse HCCs. This behavior could depend on interspecies differences in mechanisms of hepatocarcinogenesis or in developmental stage of lesions. To verify if LOH is involved in rat hepatocarcinogenesis, we studied LOH frequency in slowly growing neoplastic nodules induced by Solt-Farber model in diethylnitrosamine-initiated BFF1 rats. We analyzed, with microsatellites, markers at 67 rat loci dispersed over all chromosomes, corresponding to regions homologous to those lost in human HCCs or containing hepatocellular susceptibility (Hcs) or resistance (Hcr) loci in rat and mouse. In agreement with previous findings with mouse HCCs, but at variance with human HCCs, no detectable LOH was found at any locus in rats, suggesting rare LOH involvement in neoplastic nodules, with low tendency to progress to full malignancy, of BFF1 rats.

Correlation of c-myc overexpression and amplification with progression of preneoplastic liver lesions to malignancy in the poorly susceptible Wistar rat strain.

Persistent liver nodules (PNs) and hepatocellular carcinomas (HCCs) induced in F344 rats by the resistant hepatocyte (RH) model exhibit c-myc overexpression and amplification. The role of these changes in progression of PN was investigated in nodules with different propensities to evolve to HCC in resistant Wistar rats and, for comparison, in susceptible F344 rats. Initiation of rats with diethylnitrosamine was followed by selection with 2-acetylaminofluorene (AAF) plus partial hepatectomy (RH groups). Two additional Wistar rat groups received a second AAF treatment without (RH+AAF) and with a necrogenic dose of CCl4 (RH+AAF/CCl4) 15 d after selection. The number to liver ratio and volume of glutathione-s-transferase placental form-positive lesions were lower in the Wistar than the F344 RH groups 9 and 32 wk after initiation and increased after a second AAF cycle treatment with and without CCl4. DNA synthesis in glutathione-s-transferase placental form-positive lesions was low in Wistar RH group at 9 wk and was stimulated by additional AAF treatments. HCCs developed at 57-60 wk in F344 RH, Wistar RH+AAF, and RH+AAF/CCl4 rats. Tumor incidence and multiplicity were lower in RH+AAF rats than in RH+AAF/CCl4 and F344 rats. At 32 wk, PN exhibited c-myc overexpression that increased from RH to RH+AAF rats and to RH+AAF/CCl4 Wistar rats. This was associated with c-myc amplification in Wistar RH+AAF/CCl4 rats. These results showed correlation of c-myc overexpression and amplification with nodule propensity to progress to HCC in poorly susceptible Wistar rats and suggested a possible genetic mechanism for susceptibility to hepatocarcinogenesis. The experimental system used in this work may be a valuable tool for studies on molecular mechanisms underlying liver growth and tumorigenesis supported by c-myc overexpression.

Partition of metallic and organochlorinated pollutants and monoorthosubstituted PCB pattern in the trophic web from different areas of the river Seine.

The partition of metals and organochlorines was studied along the trophic web at two different pollution level areas of the river Seine. The metal results along the trophic web were: (1) High concentration processes by the sediment (Kb from 0.7 x 10(2) to 32 x 10(2) according to metal). (2) Bioconcentration processes by the plants from the water and the sediment for all metals (Kb from 0.5 10(3) to 13.2 x 10(3)); (3) The mussel (benthic and fossorial) exhibited the highest metal levels; (4) the bream (benthic and detritivorous) had higher metal levels than the roach and the perch. No biomagnification was shown for the metals along the trophic web. The organochlorine results were: (1) High concentration in the sediment with Kb-values about 10(3). (2) A relationship between lipid and PCB levels in plants. (3) No rise in organochlorines along the trophic web at the slightly polluted areas. (4) Occurrence of organochlorine biomagnification in the highly polluted area. For the PCB pattern: (1) The profiles are similar in plants and the water. (2) Sediment and animals exhibited a rise in the more chlorinated congeners accompanied by an impoverishment of the less chlorinated and monoorthosubstituted ones with rising position in the trophic web.

Contamination of fish from different areas of the river Seine (France) by organic (PCB and pesticides) and metallic (Cd, Cr, Cu, Fe, Mn, Pb and Zn) micropollutants.

Organochlorine and metal pollution were studied in fish from different sites of the river Seine situated upstream and downstream of Paris. The metal content in roach were similar to those usually found in freshwater fish species. The PCB and the Pb pollutant levels in the fish evolved similarly along the river: from 1300 to 16,000 micrograms/kg dry weight for the PCBs and from 0.3 to 9.5 mg/kg for Pb, while the content of other metals did not change. The stations with the highest organochlorine contents are situated downstream from the Parisian discharges where there is a reduction of fish species present from 31 to 18. Fish caught at one station situated downstream from an industrial area (Guernes) contained a higher proportion of tri- and tetrachlorobiphenyls than fish from the other stations. Their muscle contents are above the French Food Standard of 2 ppm for PCB in fresh muscle.