Activation of beta-catenin during hepatocarcinogenesis in transgenic mouse models: relationship to phenotype and tumor grade.

Mutations affecting phosphorylation sites in the beta-catenin gene have been implicated in the development of human and rodent hepatocellular carcinomas (HCCs). To further investigate the involvement of this gene in hepatocarcinogenesis, we used several transgenic mouse models of hepatic tumors induced by overexpression of c-myc in the liver either alone or in combination with transforming growth factor (TGF) alpha or TGF-beta1. Activation of beta-catenin, as judged by the presence of mutations and/or nuclear translocation of the protein, was most frequent in liver tumors from c-myc (4/17; 23.5%) and c-myc/TGF-beta1 (6/18; 33.3%) transgenic mice. However, it was very rare in faster growing and histologically more aggressive HCCs developed in c-myc/TGF-alpha mice (1/20; 5%). Administration of diethylnitrosamine, phenobarbital, or 2-amino-3,8-diethylimidazo[4,5-f]quinoxaline did not significantly affect the occurrence of beta-catenin mutations. Notably, nuclear accumulation of beta-catenin was observed only in adenomas and highly differentiated carcinomas with eosinophilic phenotype. Furthermore, preneoplastic lesions with eosinophilic phenotype frequently displayed focal nuclear positivity, colocalized with areas of high proliferation. In contrast, basophilic and clear-cell foci, as well as pseudo-glandular and poorly differentiated HCCs, exhibited a normal or reduced membranous immunoreactivity for beta-catenin. These studies suggest that nuclear translocation of beta-catenin and activation of Wingless/Wnt signaling may represent an early event in liver carcinogenesis, providing a growth advantage in a subset of hepatic tumors with a more differentiated phenotype.

Ciprofibrate and triiodothyronine do not suppress in vivo induction of placental glutathione S-transferase expression in rat hepatocytes.

Studies on hepatocyte primary cultures have suggested that loss of expression of the placental form of glutathione S-transferase in peroxisome proliferator (PP)-induced hepatocarcinogenesis is due to inhibition of glutathione S-transferase P (GSTP) transcription by the PPs. In the present study, we have analyzed the effect of a PP, ciprofibrate, and of another ligand of nuclear receptors, 3,3', 5-triiodo-L-thyronine (T3), on GSTP mRNA and protein levels in an in vivo model where GSTP expression was induced in Wistar rats by pre-treatment with a single dose of lead nitrate. Results indicate that administration of ciprofibrate or T3, immediately after lead nitrate treatment, did not exert any inhibitory effect on GSTP mRNA and protein levels, as revealed by both Western and immunohistochemical analysis. The results indicate that PPs do not inhibit hepatocyte GSTP expression induced in vivo by lead nitrate and suggest that inhibition of GSTP expression by PPs may not necessarily be the cause for the rapid disappearance of GSTP-positive preneoplastic lesions observed after a short term exposure to these agents.

Cell proliferation induced by triiodothyronine in rat liver is associated with nodule regression and reduction of hepatocellular carcinomas.

Previous studies have demonstrated that short-term treatment with peroxisome proliferators decreased the size and number of gamma-glutamyl transpeptidase or placental glutathione S-transferase (GSTP)-positive hepatic hyperplastic lesions. In this study, we have examined the effect of the hormone triiodothyronine (T3), which, similarly to peroxisome proliferators, is a strong liver mitogen and a ligand of nuclear receptors, on the growth of GSTP-positive nodules generated by the resistant hepatocyte model and on the development of hepatocellular carcinoma. Hepatic hyperplastic nodules were induced in male Fischer rats by a single dose (150 mg/kg) of diethylnitrosamine, followed by a 2-week exposure of the animals to 2-acetylaminofluorene and partial hepatectomy. Nine weeks after diethylnitrosamine administration, rats were switched to a diet containing 4 mg/kg T3 for 1 week (experiment 1) and sacrificed during T3 feeding or were exposed to seven cycles of T3-supplemented diet (1 week/month per 7 months), and sacrificed 6 months after the last cycle (experiment 2). Results showed that T3 treatment for 1 week caused a 70% reduction in the number of GSTP-positive nodules (14/cm2 in T3-fed rats versus 44/cm2 of control animals), as well as GSTP-positive area (12% versus 43% of controls). Reduction in the number of GSTP-positive nodules observed 1 week after T3 feeding was associated with a strong increase in the labeling index of enzyme-altered nodules compared with that of controls (labeling index was 64 and 31%, respectively). No significant differences in the apoptotic index were observed between the two groups. Results from experiment 2 did reveal that although rats treated with diethylnitrosamine + 2-acetylaminofluorene developed 100% hepatocellular carcinoma and 33% of them showed lung metastasis, only 50% of rats exposed to repeated cycles of triiodothyronine developed hepatocellular carcinoma with no lung metastasis. This study indicates that cell proliferation per se might not necessarily represent a promoting condition for putative preneoplastic lesions and demonstrates an anticarcinogenic effect of T3.

Early increase in cyclin-D1 expression and accelerated entry of mouse hepatocytes into S phase after administration of the mitogen 1, 4-Bis[2-(3,5-Dichloropyridyloxy)] benzene.

We have previously demonstrated that hepatocyte proliferation induced by the mitogen 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP) is independent of changes in cytokines, immediate early genes, and transcription factors that are considered to be necessary for regeneration of the liver after partial hepatectomy (PH) or necrosis. To further investigate the differences between mitogen-induced mouse hepatocyte proliferation and liver regeneration after PH, we have measured the expression of cyclin D1, cyclin D3, cyclin E, and cyclin A and of the cyclin-dependent kinases CDK2, CDK4, and CDK6. The involvement of the cyclin-dependent kinase inhibitors p21 and p27 and of the oncosuppressor gene p53 was also examined at different times after stimulation of hepatocyte proliferation. Results showed that a single administration of TCPOBOP caused a very rapid increase in the levels of cyclin D1, a G1 protein, when compared with two thirds PH (8 hours versus 30 hours). The early increase in cyclin D1 protein levels was associated with a faster onset of increased expression of S-phase-associated cyclin A (24 hours versus 36 hours with PH mice). Accordingly, measurement of bromodeoxyuridine (BrdU) incorporation revealed that, although approximately 8% of hepatocytes were BrdU-positive as early as 24 hours after TCPOBOP, no significant changes in BrdU incorporation were observed at the same time point after two thirds PH. The expression of other proteins involved in cell cycle control, such as cyclin-dependent kinases (CDK4, CDK2, CDK6), was also analyzed. Results showed that expression of CDK2 was induced much more rapidly in TCPOBOP-treated mice (2 hours) than in mice subjected to PH (36 hours). A different pattern of expression in the two models of hepatocyte proliferation, although less dramatic, was also observed for CDK4 and CDK6. Expression of the CDK inhibitors p21 and p27 and the oncosuppressor gene p53 variably increased after two thirds PH, whereas basically no change in protein levels was found in TCPOBOP-treated mice. The results demonstrate that profound differences in many cell cycle-regulatory proteins exist between direct hyperplasia and compensatory regeneration. Cyclin D1 induction is one of the earlier events in hepatocyte proliferation induced by the primary mitogen TCPOBOP and suggests that a direct effect of the mitogen on this cyclin may be responsible for the rapid onset of DNA synthesis observed in TCPOBOP-induced hyperplasia.

Cell proliferation induced by 3,3',5-triiodo-L-thyronine is associated with a reduction in the number of preneoplastic hepatic lesions.

Previous studies have suggested that liver cell proliferation is fundamental for the growth of carcinogen-initiated cells. To gain further information on the association between cell proliferation and hepatocarcinogenesis, we have examined the effect of the hormone 3,3',5-triiodo-L-thyronine (T3), a strong liver mitogen, on the growth of diethylnitrosamine (DENA)-induced hepatic lesions positive for the placental form of glutathione S-transferase (GSTP). Two weeks after a single initiating dose of DENA (150 mg/kg), cycles of liver cell proliferation were induced in male Fischer rats by feeding a T3-supplemented diet (4 mg/kg) 1 week/month for 7 months. Rats were killed at the end of the seventh cycle or 1 month later. Results indicate that, in spite of an increased labelling index, a 70% reduction in the number/cm(2) of GSTP-positive minifoci occurred in T3-treated rats. A decrease in the number of GSTP-positive foci was also observed in T3-treated rats killed 1 month after the last exposure to the hormone (40, versus 67 foci/cm(2) in controls), indicating that the reduction was not due to an inhibitory effect on GSTP exerted by the concomitant presence of T3. In a second series of experiments where DENA-treated rats were fed T3 for 1 week and then subjected to the resistant hepatocyte (RH) model, it was found that T3 treatment prior to promotion resulted in a decrease in the number of GSTP-positive foci (16 GSTP(+) foci/cm(2) in T3-fed animals versus 45 in the control group). The results indicate that cell proliferation associated with T3 treatment: (i) reduces the number of carcinogen-induced GSTP-positive lesions; (ii) does not exert any differential effect on the growth of the remaining foci; (iii) inhibits the capacity of putative DENA-initiated cells to be promoted by the RH model. Data suggest that cell proliferation may not necessarily represent a stimulus for the growth of putative preneoplastic lesions.

[Neuroendocrine carcinoma of the skin]. / Il carcinoma neuroendocrino della cute.

Merkel cell carcinoma is an unusual neuroendocrine tumour that arises in the derm. The case reported seemed to deserve the author's attention because of the clinical features, pathological findings and natural history (local recurrence, regional lymph node metachronous metastases, distant metastases). The authors believe that a differential diagnosis between Merkel cell carcinoma and other tumours located in the subcutaneous tissue is mandatory, in order to perform specific immunohistochemical and ultrastructural study.

[Ambulatory surgery: current status and prospects]. / Chirurgia ambulatoriale: stato attuale e prospettive.

Ambulatory Surgery (AS) was born some 20 years ago in USA pushed by economic requirements and rapidly spread over the European countries as one of the main factors of progress in health care. The Authors, after evaluating the actual situation of AS in the international literature, report their personal experience from January 1991 to December 1994. The series includes 810 surgical operations performed as outpatients procedures with immediate discharge. The following types of anaesthesia were used: local infiltration (86.6%), monolateral ultraselective spinal (10%), blended or general (3.4%). Hernias of the abdominal wall, varicose veins and anorectal diseases were the more frequent pathologies operated on. Results of surgery are satisfactory supporting the advantage of AS such as the absence of complications due to anaesthesia and hospital stay, the better relationship between patient and surgeon, the short return to working activities. AS proves its value on the clinical and socio-economic grounds provided that a well organised program and careful selection of patients are adopted. No extemporary organisation are advisable.

Cellular localization of inducible nitric oxide synthase in experimental endotoxic shock in the rat.

1. Endotoxin induces a shock-like syndrome with increased nitric oxide synthesis. To clarify the cellular source of NO in endotoxic shock we used immunohistochemistry and in situ hybridization to localize inducible NO synthase in rats given lipopolysaccharide or Corynebacterium parvum and lipopolysaccharide. Immunohistochemistry was carried out with an antibody raised against a synthetic peptide of mouse macrophage NO synthase. In situ hybridization was performed with 35S-labelled oligonucleotide probes corresponding to cDNA sequences common to mouse macrophage inducible NO synthase and rat vascular smooth inducible NO synthase. Monocytes and macrophages were identified by immunohistochemistry with the mouse monoclonal antibody ED1. 2. After lipopolysaccharide alone, the major site of NO synthase induction was monocytes and macrophages in multiple organs, principally liver and spleen. Bronchial, bile duct, intestinal and bladder epithelium and some hepatocytes also expressed inducible NO synthase. Expression peaked at 5 h and had returned to normal by 12 h except in spleen. 3. After priming with C. parvum, lipopolysaccharide led to a similar distribution of inducible NO synthase as lipopolysaccharide alone, but in addition there was more prominent hepatocyte staining, staining in macrophage granulomas in the liver and inducible NO synthase was present in some endothelial cells in the aorta. 4. These findings provide a direct demonstration of the cellular localization of inducible NO synthase after lipopolysaccharide.

PGD2 is an intermediate in agonist-stimulated nitric oxide release in rabbit skin microcirculation.

We investigated the role of endogenous prostaglandins and NO in the blood flow response of skin microcirculation in vivo. Test agents were injected intradermally in anesthetized rabbits and changes in skin blood flow measured with a laser-Doppler flow probe. Skin blood flow increased 75% at 7.33, 6.77, 11.63, 10.30, 10.55, 8.20, and < 7 -log mol/site with acetylcholine, ATP, bradykinin, prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), NO gas in solution, and nitroprusside respectively. Co-injection of indomethacin (3 x 10(-9) mol/site) or NG-nitro-L-arginine methyl ester (L-NAME; 10(-7) mol/site) with either acetylcholine or bradykinin abolished the effects. This suggests a link between NO and prostaglandin release. Arachidonic acid increased blood flow, which was inhibited by indomethacin, L-NAME, or the PGD2-receptor antagonist BW-A868C. Blood flow responses to either intradermal acetyl-choline or bradykinin, but not to NO in solution, were abolished by co-injection with BW-A868C. PGD2-mediated vasodilation was abolished by L-NAME or BW-A868C, but not by indomethacin. There was no evidence of a link between NO and prostaglandin release in precontracted rabbit aortic rings in vitro. The results suggest that, in the microcirculation of rabbit skin, acetylcholine- and bradykinin-mediated vasodilation involve the arachidonic acid-PGD2-NO pathway.

Opposing roles of cyclic AMP in the vascular control of edema formation.

Eight agents that increase the intracellular concentration of cyclic AMP were tested for their effect on edema formation. The specificity of the agents for vascular smooth muscle or the endothelium was determined by measuring vasodilation with a laser Doppler flow probe and cAMP production by endothelial cells and vascular smooth muscle cells in culture. The agents were injected intradermally in anesthetized rabbit skin and the local accumulation of 125I-labeled albumin in response to intradermal bradykinin was measured. Iloprost, prostaglandin E1, prostaglandin E2, pituitary adenylate cyclase activating polypeptide (PACAP), and vasoactive intestinal polypeptide (VIP) potentiated bradykinin-induced edema. These same agents also increased blood flow and vascular smooth muscle cAMP concentrations, but did not increase endothelial cell cAMP production. Albuterol suppressed edema formation, did not cause vasodilation, but did increase endothelial cell cAMP concentrations. The phosphodiesterase inhibitor rolipram did not cause vasodilation, but suppressed edema and potentiated the cAMP response to albuterol in cultured endothelial cells. L-Isoproterenol affected both cell types. At a lower concentration L-isoproterenol was a potent stimulus to endothelial cell cAMP production and inhibited edema formation; a higher dose had additional effects on vascular smooth muscle and significantly increased blood flow. These findings support the hypothesis that increasing intracellular cAMP concentrations in vascular smooth muscle promotes edema via increased blood flow. In contrast, increasing cAMP concentrations in endothelium may suppress edema by enhancing the permeability barrier.

Nitric oxide is inactivated by the bacterial pigment pyocyanin.

Pyocyanin is a phenazine pigment produced by the bacterium Pseudomonas aeruginosa and found in human lung secretions. Micromolar concentrations of pyocyanin inhibited the bioactivity of endothelium-derived relaxing factor (EDRF) generated from bovine pulmonary-artery endothelium in response to bradykinin. This inhibition was reversed by perfusing the EDRF-bioassay system with pyocyanin-free buffer for 15 min, but persisted in the presence of superoxide dismutase (20 units/ml). When nitric oxide, the major component of EDRF, was passed into an aqueous solution of pyocyanin in the absence of O2, a rapid colour change occurred from blue to pink; m.s. analysis of the products showed that the pyocyanin had been converted into a nitrosylated species.