Giovanna Casalgrandi

Antioxidant activity of silybin in vivo during long-term iron overload in rats

BACKGROUND & AIMS Hepatic iron toxicity may be mediated by free radical species and lipid peroxidation of biological membranes. The antioxidant property of silybin, a main constituent of natural flavonoids, was investigated in vivo during experimental iron overload. METHODS Rats were fed a 2.5% carbonyl-iron diet and 100 mg.kg body wt-1.day-1 silybin for 4 months and were assayed for accumulation of hepatic lipid peroxidation by-products by immunocytochemistry, mitochondrial energy-dependent functions, and mitochondrial malondialdehyde content. RESULTS Iron overload caused a dramatic accumulation of malondialdehyde-protein adducts into iron-filled periportal hepatocytes that was decreased appreciably by silybin treatment. The same beneficial effect of silybin was found on the iron-induced accumulation of malondialdehyde in mitochondria. As to the liver functional efficiency, mitochondrial energy wasting and tissue adenosine triphosphate depletion induced by iron overload were successfully counteracted by silybin. CONCLUSIONS Oral administration of silybin protects against iron-induced hepatic toxicity in vivo. This effect seems to be caused by the prominent antioxidant activity of this compound.

Regulation of transferrin, transferrin receptor, and ferritin genes in human duodenum

To gain insights at the molecular level into the expression of iron-regulated genes [transferrin (Tf), transferrin receptor (TfR), and ferritin H and L subunits] in human intestinal areas relevant to iron absorption, the steady-state levels of specific messenger RNAs (mRNAs) were analyzed in gastric and duodenal samples obtained from 6 normal subjects, or 10 patients with anemia, 14 patients with untreated iron overload, and 8 patients with various gastrointestinal disorders. No Tf mRNA was detected in human gastroduodenal tissue, confirming earlier findings in the rat. In normal subjects, although higher levels of ferritin H- and L-subunit mRNAs were consistently found in duodenal than in gastric samples, no differences in the content of TfR transcripts were detected. However, a dramatic increase in TfR mRNA levels was specifically found in duodenal samples from subjects with mild iron deficiency but severe anemia. This response of the TfR gene is presumably secondary to decreased cellular iron content due to its accelerated transfer into the bloodstream, as also indicated by the low levels of ferritin subunit mRNAs found in the same tissue samples, and is not linked to faster growth rate of mucosal cells because no changes in duodenal expression of histone, a growth-related gene, were detected. In patients with secondary iron overload, a down-regulation of duodenal TfR gene expression and a concomitant increase in ferritin mRNA content were documented. On the contrary, a lack of TfR gene down-regulation and an abnormally low accumulation of ferritin H- and L-subunit mRNAs were detected in the duodenums of subjects with idiopathic hemochromatosis. Whether these molecular abnormalities in idiopathic hemochromatosis are relevant to the metabolic defect(s) of the disease is presently unknown.

Molecular and cellular aspects of iron-induced hepatic cirrhosis in rodents.

Hepatic fibrosis and cirrhosis are common findings in humans with hemochromatosis. In this study we investigated the molecular pathways of iron-induced hepatic fibrosis and evaluated the anti-fibrogenic effect of vitamin E. Male gerbils were treated with iron-dextran and fed a standard diet or a alpha-tocopherol enriched diet (250 mg/Kg diet). In gerbils on the standard diet at 6 wk after dosing with iron, in situ hybridization analysis documented a dramatic increase of signal for collagen mRNA around iron foci onto liver fat storing cells (FSC), as identified by immunocytochemistry with desmin antibody. After 4 mo, micronodular cirrhosis developed in these animals, with nonparenchymal cells surrounding hepatocyte nodules and expressing high level of TGF beta mRNA. In this group, in vivo labeling with [3H]-thymidine showed a marked proliferation of nonparenchymal cells, including FSC. In iron-dosed gerbils on the vitamin E-enriched diet for 4 mo, in spite of a severe liver iron burden, a normal lobular architecture was found, with a dramatic decrease of collagen mRNA accumulation and collagen deposition. At the molecular level, a total suppression of nonparenchymal cell proliferation was appreciable, although expression of collagen and TGF beta mRNAs was still present into microscopic iron-filled nonparenchymal cell aggregates scattered throughout the hepatic lobule. In conclusion, our study shows that anti-oxidant treatment during experimental hepatic fibrosis arrests fibrogenesis and completely prevents iron induced hepatic cirrhosis mainly through inhibition of nonparenchymal cell proliferation induced by iron.

Duodenal ferritin synthesis in genetic hemochromatosis

BACKGROUND/AIMS The molecular defect of genetic hemochromatosis (GH) is unknown. It is believed that low expression of duodenal ferritin in GH is caused by tissue or cell specific defect of ferritin synthesis. Our study was designed to ascertain whether the control of duodenal ferritin synthesis in GH was defective. METHODS Expression at the single cell level of H and L ferritin messenger RNAs and protein and activity of the iron regulatory factor, which controls the translation of ferritin messenger RNA, were assessed in 43 duodenal biopsy specimens from individuals with GH, secondary hemochromatosis (SH), anemia, or normal iron balance. RESULTS Signal for ferritin H and L subunit messenger RNAs was detected in both absorptive and nonabsorptive cells by in situ hybridization, but in 10 of 14 patients with untreated GH, the signal was lower than in patients with SH or normal subjects. However, immunostaining for ferritin protein documented a diffuse/cytoplasmic pattern, whereas a supranuclear/granular staining was found in normal subjects or patients with SH. The spontaneous activity of duodenal iron regulatory factor was consistently higher in patients with GH than in normal subjects or subjects with anemia or SH. CONCLUSIONS In patients with GH, ferritin gene transcription is preserved in both absorptive and nonabsorptive intestinal cells. Low accumulation of ferritin is not caused by a defective control of ferritin synthesis but by low expression of ferritin messenger RNA and sustained activity of iron regulatory factor.

Excess iron into hepatocytes is required for activation of collagen type I gene during experimental siderosis

BACKGROUND/AIMS Liver fibrosis and cirrhosis represent common pathological findings in humans with iron overload. This study was undertaken to assess whether in vivo targeting of iron to liver parenchymal or nonparenchymal cells would differently affect collagen gene activity. METHODS Rats were treated with an iron diet or intramuscular injections of iron dextran, and in situ hybridization analyses on liver samples were performed. RESULTS These iron treatments determined parenchymal or reticuloendothelial cell iron overload, respectively. The typical distribution of iron into different liver cells was documented by histochemistry and confirmed by in situ hybridization analysis with a ferritin L complementary RNA probe. In iron-fed rats, in situ hybridization analysis identified a signal for collagen type I messenger RNA into nonparenchymal cells in zones I and II. In rats with nonparenchymal cell iron overload, no activation of collagen gene expression was detected into or near iron-laden nonparenchymal cells. These findings were also confirmed by quantitative Northern blot analysis. CONCLUSIONS The results of this study indicate that, regardless of the total hepatic iron burden, selective localization of iron into liver cells (i.e., parenchymal cells) is required for the activation of collagen gene during long-term iron overload in rodents.

Antioxidant liposoluble vitamins and carotenoids in chronic hepatitis.

Background: It is known that antioxidant liposoluble vitamins and carotenoids are reduced in liver cirrhosis, but little is known about chronic viral hepatitis, where oxidative damage has to be taken into account. Methods: Fifty-five patients with chronic hepatitis, mainly C virus-related, were matched with 16 patients with biliary stones and 20 healthy controls. Plasma and liver analyses were carried out using a well-tried HPLC technique that affords an accurate quantification of retinol, tocopherol, alpha- and beta-carotene, cryptoxanthin, and lycopene. Results: Plasma concentration of retinol, tocopherol, beta-carotene, and lycopene was significantly decreased in both patient groups, particularly in those with chronic hepatitis. In contrast, liver concentration of both esterified and free retinol, tocopherol, and some carotenoids was better preserved in the hepatitis group than in the cholelithiasis group. A strict correspondence between aminotransferases and the amount of liver-stored retinol was documented. Conclusions: Plasma vitamin and carotenoid depletion co-existing with preserved liver storage may indicate a functional defect in liver pool mobilization or even a real depletion of the antioxidant defenses, which play a key role in averting cellular damage. The implications for nutrition and therapy need to be taken into account.

Standard or Branched-Chain Amino Acid Infusions as Short-Term Nutritional Support in Liver Cirrhosis?

The metabolic effects of selected and branched-chain amino acid (BCAA)-enriched parenteral solutions were studied in liver cirrhosis. After 3 days of an oral protein-free diet with balanced amino acid (AA) infusion, 36 cirrhotic patients without encephalopathy were randomly divided into four groups. Groups A and B were infused for 5 days with BCAA (valine, leucine, isoleucine) at doses of 0.5 and 1.0 g/kg/day, respectively, as the only nitrogen source. Group C received 0.8 g/kg of essential and nonessential AA solution with a prevalence of BCAA; the last group (D) continued the basic standard diet, as control. Routine chemistry, urinary nitrogen losses, nitrogen balance, and the whole plasma AA pattern were detected before and after the treatment period. BCAA alone led to an impressive and significant improvement in the basic AA pattern in both the A and B groups. The same results were obtained in group C for plasma AA. In particular, the ratio of BCAA to aromatic amino acids in groups A, B, and C was significantly increased (p less than 0.01, less than 0.02, less than 0.02, respectively). In group D the AA pattern and the BCAA/aromatic amino acid ratio remained unchanged. The negative nitrogen balance of the base state remained unchanged after 0.5 g of BCAA (A); it improved significantly and became positive during and after the infusions of a double dose of BCAA (B), as it did in the case of selective solutions (C), although to a lesser extent; the negative nitrogen balance of the control group showed only a slight improvement.(ABSTRACT TRUNCATED AT 250 WORDS)

Pro-oxidant and antioxidant factors in acute intermittent porphyria: Family studies

Summary: Given the crucial role of iron and porphyrins in oxidative cellular damage in the chronic porphyrias, we undertook an extensive study in families with acute porphyrias to evaluate the possible role of similar oxidative damage in these diseases, whose natural history is often also complicated by neoplastic evolution. Four unrelated patients with acute intermittent porphyria (AIP) were studied together with 37 members of four different families. Aminolevulinic acid and porphobilinogen were measured in urine, and porphyrins in urine, plasma and stools. The activity of the congenitally deficient enzyme, porphobilinogen deaminase, and the concentrations of plasma iron, transferrin, ferritin, and various antioxidants (ascorbic acid, retinol, tocopherol, α- and β-carotene, by a personal HPLC method) and the urinary and plasma metabolites of nitrous oxide were also assayed. The results showed no relationship between the observed increase of porphyrin metabolites and the presence of markers of oxidative damage or the decrease of circulating antioxidants: however, when such a decrease was registered, it depended on spontaneous or iatrogenic iron accumulation. We conclude that family screening, recommended for the identification of AIP carriers, must also include evaluation of iron stores with a view to preventing the oxidative damage and in order to forestall the neoplastic evolution of the disease.