I. Venturini

Up-regulation of peripheral benzodiazepine receptor system in hepatocellular carcinoma

Increased number of peripheral benzodiazepine receptors (PBRs) have been found in some tumors outside the liver. The present study was to verify whether the PBR system is altered in hepatocellular carcinoma (HCC). The levels of endogenous benzodiazepine-like compounds (BZDs), measured by radioreceptor binding technique after HPLC purification and the endogenous ligand for PBRs, termed diazepam binding inhibitor (DBI), measured by radioimmunoassay utilizing a specific antibody for human DBI, were studied in the blood of 15 normal subjects, 12 liver cirrhosis and 10 patients with HCC. The levels of BZDs in serum were increased hundred fold in liver cirrhosis patients and slightly elevated in HCC patients. DBI was found to be increased in HCC patients. The binding recognition sites for PBRs (Bmax) were increased 4 to 7 fold in HCC tissue in comparison with that found in non-tumoral liver tissue (NTLT). On the contrary the concentrations of DBI were found to be significantly decreased in HCC tissue in comparison with the respective NTLT. These results seem to suggest an implication of PBRs and of their putative endogenous ligands in the metabolism of these neoplastic cells and possibly in their proliferation. The up-regulation of PBRs found in HCC tissue seems to indicate an increased functional activity of these receptors and opens up the possibility of new pharmacological and diagnostic approaches while the changes in the circulating endogenous ligands for the above receptors might be envisaged as early markers of tumorigenesis in liver cirrhosis.

INCREASED EXPRESSION OF PERIPHERAL BENZODIAZEPINE RECEPTORS AND DIAZEPAM BINDING INHIBITOR IN HUMAN TUMORS SITED IN THE LIVER

The peripheral benzodiazepine receptor system triggers intracellular metabolic events and has been associated with cell proliferation. Its endogenous ligand, the diazepam binding inhibitor, contributes to steroidogenesis by promoting cholesterol delivery to the inner mitochondrial membrane. The present study was undertaken to verify whether this system is altered in tumors sited in the liver. Peripheral benzodiazepine receptors and diazepam binding inhibitor were studied using immunocytochemistry and in situ hybridization in 9 human tumors sited in the liver, in liver hyperplasia, cirrhotic nodular regeneration, intestinal adenocarcinoma and in surrounding non-tumoral tissue. Immunocytochemical staining and in situ hybridization demonstrated that peripheral benzodiazepine receptors and diazepam binding inhibitor were more prominently expressed in neoplastic cells than in non-tumoral tissue. They were present in the same cells, suggesting that diazepam binding inhibitor may act in an intracrine manner in these cells. Higher peripheral benzodiazepine receptors and diazepam binding inhibitor expression in tumor cells suggest an implication of this system in the metabolism of neoplastic cells. Furthermore the evaluation of peripheral benzodiazepine receptor and diazepam binding inhibitor expression might be useful in evaluating malignancy and in diagnostic approaches of tumors in liver tissue.

Management of hepatic encephalopathy: Role of rifaximin

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, which develops in patients with acute or chronic liver failure. It is widely accepted to be due to impairment of hepatic clearance of toxic products from the gut such as ammonia. Accumulation of ammonia induces a glutamate neurotoxicity leading to an increased tone of the γ-aminobutyric acid A (GABA-A) receptor system in the brain which results in HE. Factors either increasing the ammonia levels (protein load, constipation, sepsis, or gastrointestinal bleeding) or potentiating the functional activity of the GABAergic system [natural benzodiazepine-like compounds (NBZDs) or exogenous benzodiazepines] may act as precipitating factors of HE. NBZDs are present in trace amounts in the blood of normal subjects and have been found to be increased in the blood of patients with liver cirrhosis, with or without HE. These compounds may derive either from the diet since they have been found in plants, vegetables and animals or from gut bacteria. The observation that intestinal bacterial flora is involved in the production of both primary agent of HE (ammonia) and precipitating factors (NBZDs) suggests that the use of nonabsorbable antibiotics such as rifaximin may be useful in preventing episodes of HE in patients with liver cirrhosis.

Natural endogenous ligands for benzodiazepine receptors in hepatic encephalopathy.

Benzodiazepines of natural origin (NBZDs) have been found in human blood and brains as well as in medicinal plants and foods. In plasma and brain tissue there are i.e. diazepam and nordiazepam equal to commercial drugs but there are also other benzodiazepine-like compounds termed “endozepines”, which act as agonists at the benzodiazepine receptors of central type (CBR). A synthetic pathway for the production of NBZDs has not yet been found, but it has been suggested that micro-organisms may synthesize molecules with benzodiazepine-like structures. Hence NBZDs could be of both endogenous and exogenous source and be considered as natural anxyolitic and sedative. Interestingly there are also natural compounds, such as the polypeptide Diazepam Binding Inhibitor (DBI) acting as an “inversive agonist” implicated in fair and panic disorders. It has been suggested that NBZDs may play a role in the pathogenesis of hepatic encephalopathy (HE). Multidirectional studies evaluated NBZDs levels (1) in the blood of normal subjects, of cirrhotic with or without HE and in commercial benzodiazepine consumers; (2) in the blood of cirrhotic treated or not with a non-absorbable antibiotic; (3) in several constituents of our diet. In conclusion, NBZDs increase sometime in cirrhotics with or without HE but they reach concentrations not higher than those found in commercial benzodiazepines consumers. Hence NBZDs must be considered as occasional precipitating factor of HE and benzodiazepine antagonists only symptomatic drugs. The finding that NBZDs may be in part synthesized by intestinal bacterial flora and in part constituent of our diet underlines the importance to feed cirrhotic patients with selected food.

Oxindole in pathogenesis of hepatic encephalopathy

concentrations in their plasma than those without (0·249 [0·05] vs 0·96 [0·25] nmol/mL). Because plasma and brain concentrations of oxindole rapidly equilibrate, it is reasonable to assume that hepatic encephalopathy patients have elevated brain concentrations of this endogenous sedative agent. Studies involving a larger number of patients, correlating selected neurological signs with plasma oxindole levels are necessary in order to further evaluate the role this endogenous sedative plays in the neurological diseases associated with acute or chronic liver failure.

CagA and VacA Helicobacter Pylori Antibodies in Gastric Cancer

BACKGROUND Infection with different genotypes of virulent Helicobacter pylori strains (cytotoxin-associated gene A [CagA]- and/or vacuolating cytotoxin A [VacA]-positive) can play a role in the development of atrophic gastritis, duodenal ulcer (DU) and gastric cancer (GC). OBJECTIVE To determine whether patients with GC and H pylori-negative histological staining had previously been infected with H pylori CagA- and/or VacA-positive virulent strains. METHODS Twenty-three GC patients with a mean (+/- SD) age of 68.14+/-9.8 years who tested H pylori-negative on histological staining took part in the study. Three control groups were included. The first group comprised 19 patients with past H pylori infection and DUs eradicated 10 years earlier, with a mean age of 58+/-18.2 years. H pylori-negative status for this group was determined every year with Giemsa staining, and follow-up testing occured 120+/-32 months (mean +/- SD) after therapy. The subsequent control groups included 20 asymptomatic children, with a mean age of 7+/-4.47 years, and with H pylori-negative fecal tests; the final group contained 30 patients without clinical symptoms of H pylori infection, with a mean age of 68+/-11.6 years, who tested H pylori-negative by histological staining. RESULTS Prevalence of CagA and VacA seropositivity, respectively was 82.6% and 73.91% in GC patients; 84.2% and 84.2% in H pylori-negative DU patients; 25% and 5% in H pylori-negative children; and 36.6% and 16.6% in the patients without clinical symptoms on histological staining. CagA and VacA antibody positivity was not significantly different between GC patients and patients with DUs that had been eradicated 10 years earlier. Significant positivity was found between the childrens group and the H pylori-negative (with past DUs) group (P<0.001). A statistically significant difference was found in age between groups (P<0.03). CONCLUSIONS Patients with GC, even when H pylori-negative at the time of the present study, may have been infected by H pylori before the onset of the disease, as confirmed by CagA and VacA seropositivity. These data reinforce the hypothesis that H pylori may be a direct carcinogenic agent of GC.

Hepatic encephalopathy in liver transplant recipients precipitated by benzodiazepines present in transfused blood

The observation that there are episodes of encephalopathy in liver cirrhosis patients after orthotopic liver transplantation, despite a well functioning graft and despite the lack of cerebral complications, prompted us to investigate the potential role of circulating benzodiazepine-like compounds in these episodes. The plasma levels of benzodiazepines were examined in 14 liver cirrhotic patients before and after transplantation. The benzodiazepines in the fluids infused during surgery and in individual bags of blood administered after surgery to 4 of these patients were also assayed. Herein we report that benzodiazepines accumulating in the blood of some transplanted patients appear to derive from blood transfusions utilized during surgery. The analysis of the types of benzodiazepines present in the blood utilized for transfusions suggests the use of commercial benzodiazepines by the donors. These compounds seem to be able to precipitate hepatic encephalopathy in patients with preexisting encephalopathy. Hence we suggest not using benzodiazepine consumers as blood donors, at least for patients with encephalopathy undergoing to liver transplantation.

Tryptophan Metabolism and Hepatic Encephalopathy

Oxindole administration (1-100 mg/kg i.p.) to mammals decreases locomotor activity, reduces muscular tone and blood pressure and at larger doses causes coma and death. Utilizing both HPLC and GC/MS, we showed that oxindole is present in the blood, brain and other organs of several animal species, including humans. We demonstrated that oxindole is a tryptophan metabolite able to significantly decrease neuronal excitability by modifying the function of voltage-operated sodium channels. Its synthesis requires the availability of indole, which is formed in the gut. When liver function is impaired, a sufficient amount of indole reaches systemic circulation and is oxidized into oxindole, which seems to be one of the responsible agents for the neurological symptoms found in the course of liver impairment.

Ammonia and 1,4-benzodiazepines in encephalopathic patients with fulminant hepatic failure

AMMONIA AND 1,4-BENZODIAZEPINES IN ENCEPHALOPATHIC PATIENTS WITH FULMINANT HEPATIC FAILURE. M.L. Zeneroli*, I. Venturini*, L, Corsi °, R. Avallone °, F. Farina*, G. Ardizzone , M. Centanaro , A. Arrigo , L. Miglioli*, P. Schreier**, M. Kleinschnitz**, and M. Baraldi °. *Cattedra di Semeiotica e Metodologia Medica e °Dip. Scienze Farmaceutiche Universit~t di Modena; ^Centro Trapianti Universit~ di Genova, Italy; and **Lehrstuhlfur Lebensmittelchemie Universiflit Wtirzburg, Germany.