Georgios I. Panoutsopoulos

Effect of serotonin receptor 2 blockage on liver regeneration after partial hepatectomy in the rat liver.

Abstract: The effect of serotonin receptor 2 blockade (5‐HT2) on liver regeneration after 30–34% and 60–70% partial hepatectomy in the rat liver was investigated.

The emerging role of serotonin in liver regeneration

Serotonin has a multifunctional role in many different organs serving either as a neurotransmitter in the central nervous system or a paracrine factor in the gastrointestinal tract. Over 90% of serotonin is synthesised in the enterochromaffin cells of the intestine and subsequently taken up by platelets. The involvement of platelet-derived serotonin in liver mass restoration after partial hepatectomy or toxic injury has been greatly investigated during the last decade. There is a growing body of evidence implicating serotonin in hepatic regeneration through altered expression of serotonin receptor subtypes in the liver. This review article provides a brief overview on the current knowledge about the actions of serotonin in liver regeneration.

Effect of Hepatic Stimulator Substance (HSS) on Cadmium-Induced Acute Hepatotoxicity in the Rat Liver

The hepatoprotective effect of HSS against cadmium-induced liver injury was investigated. Ratswere intoxicated with a dose of cadmium (3.5 mg/kg b.w.). The rats were treated with normalsaline (group I) or HSS (100 mg protein/kg b.w.; group II) 2 hr later and killed at different timepoints. Hematoxylin-eosin (HE) sections were assessed for necrosis, apoptosis, peliosis, mitoses,and inflammatory infiltration. Serum enzyme activities were assayed. Apoptosis was quantified by theTunel technique. Thymidine kinase activity and the rate of [ 3 H]thymidine incorporation into DNAwere also assayed. Necrosis, hepatocyte apoptosis, and peliosis were minimized in HSS-treatedrats (group II). Nonparenchymal cell apoptosis and liver regeneration were not quantitively alteredin the HSS-treated group, though the time profile was different. HSS protects hepatocytes againstcadmium-induced necrosis, apoptosis, and peliosis. Apoptosis was the major type of cell death fornonparenchymal liver cells and strongly correlated with the extent of peliosis. Interactions betweenhepatocytes and nonparenchymal liver cells seem to be important for the genesis of hepatic traumain acute cadmium hepatotoxicity.

Gadolinium chloride pretreatment ameliorates acute cadmium-induced hepatotoxicity.

Cadmium is a known industrial and environmental pollutant. It causes hepatotoxicity upon acute administration. Features of cadmium-induced acute hepatoxicity encompass necrosis, apoptosis, peliosis and inflammatory infiltration. Gadolinium chloride (GdCl3) may prevent cadmium-induced hepatotoxicity by suppressing Kupffer cells. The effect of GdCl3 pretreatment on a model of acute cadmium-induced liver injury was investigated. Male Wistar rats 4–5 months old were injected intraperitoneally with normal saline followed by cadmium chloride (CdCl2; 6.5 mg/kg) or GdCl3 (10 mg/kg) followed by CdCl2 (6.5 mg/kg; groups I and II, respectively). Rats of both the groups were killed at 9, 12, 16, 24, 48 and 60 h after cadmium intoxication. Liver sections were analyzed for necrosis, apoptosis, peliosis and mitoses. Liver regeneration was also evaluated by tritiated thymidine incorporation into hepatic DNA. Serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were also determined. Hepatic necrosis, hepatocyte and nonparenchymal cell apoptosis and macroscopic and microscopic types of peliosis hepatis were minimized by gadolinium pretreatment. Serum levels of AST and ALT were also greatly diminished in rats of group II. Tritiated thymidine incorporation into hepatic DNA was increased in gadolinium pretreatment rats. Kupffer cell activation was minimal in both the groups of rats. Gadolinium pretreatment attenuates acute cadmium-induced liver injury in young Wistar rats, with mechanisms other than Kupffer cell elimination.

Metabolism of Homovanillamine to Homovanillic Acid in Guinea Pig Liver Slices

Background/Aims: Homovanillamine is a biogenic amine that it is catalyzed to homovanillyl aldehyde by monoamine oxidase A and B, but the oxidation of its aldehyde to the acid derivative is usually ascribed to aldehyde dehydrogenase and a potential contribution of aldehyde oxidase and xanthine oxidase is usually ignored. Methods: The present investigation examines the metabolism of homovanillamine to its acid derivative by concurrent incubation with monoamine oxidase and aldehyde oxidase. In addition, the metabolism of homovanillamine in freshly prepared and cryopreserved liver slices is examined and the relative contribution of aldehyde oxidase, xanthine oxidase and aldehyde dehydrogenase activity by using specific inhibitors of each oxidizing enzyme is compared. Results: Homovanillamine was rapidly converted mainly to homovanillic acid when incubated with both momoamine oxidase and aldehyde oxidase. Homovanillic acid was also the main metabolite in the incubations of homovanillamine with freshly prepared or cryopreserved liver slices, via the intermediate homovanillyl aldehyde. The acid formation was 70-75 % inhibited by disulfiram (specific inhibitor of aldehyde dehydrogenase), whereas isovanillin (specific inhibitor of aldehyde oxidase) inhibited acid formation to a lesser extent (50-55 %) and allopurinol (specific inhibitor of xanthine oxidase) had almost no effect. Conclusions: Homovanillamine is rapidly oxidized to its acid, via homovanillyl aldehyde, by aldehyde dehydrogenase and aldehyde oxidase with little or no contribution from xanthine oxidase.

Phenylacetaldehyde oxidation by freshly prepared and cryopreserved guinea pig liver slices : The role of aldehyde oxidase

Phenylacetaldehyde is formed when the xenobiotic and biogenic amine 2-phenylethylamine is inactivated by a monoamine oxidase–catalyzed oxidative deamination. Exogenous phenylacetaldehyde is found in certain foodstuffs such as honey, cheese, tomatoes, and wines. 2-Phenylethylamine can trigger migraine attacks in susceptible individuals and can become fairly toxic at high intakes from foods. It may also function as a potentiator that enhances the toxicity of histamine and tyramine. The present investigation examines the metabolism of phenylacetaldehyde to phenylacetic acid in freshly prepared and in cryopreserved guinea pig liver slices. In addition, it compares the relative contribution of aldehyde oxidase, xanthine oxidase, and aldehyde dehydrogenase in the oxidation of phenylacetaldehyde using specific inhibitors for each oxidizing enzyme. The inhibitors used were isovanillin for aldehyde oxidase, allopurinol for xanthine oxidase, and disulfiram for aldehyde dehydrogenase. In freshly prepared liver slices, phenylacetaldehyde was converted mainly to phenylacetic acid, with traces of 2-phenylethanol being present. Disulfiram inhibited phenylacetic acid formation by 80% to 85%, whereas isovanillin inhibited acid formation to a lesser extent (50% to 55%) and allopurinol had little or no effect. In cryopreserved liver slices, phenylacetic acid was also the main metabolite, whereas the 2-phenylethanol production was more pronounced than that in freshly prepared liver slices. Isovanillin inhibited phenylacetic acid formation by 85%, whereas disulfiram inhibited acid formation to a lesser extent (55% to 60%) and allopurinol had no effect. The results in this study have shown that, in freshly prepared and cryopreserved liver slices, phenylacetaldehyde is converted to phenylacetic acid by both aldehyde dehydrogenase and aldehyde oxidase, with no contribution from xanthine oxidase. Therefore, aldehyde dehydrogenase is not the only enzyme responsible in the metabolism of phenylacetaldehyde, but aldehyde oxidase may also be important and thus its role should not be ignored.

The Hepatoprotective Effect of Hepatic Stimulator Substance (HSS) Against Liver Regeneration Arrest Induced by Acute Ethanol Intoxication

Male Wistar rats were randomized to receive ethanol (2.5 ml/kg by gastric intubation every 8 hr; group I), equal volumes of isocaloric to ethanol sucrose solution (group II), or ethanol and HSS (100 mg/kg intraperitoneally 10 and 16 hr after partial hepatectomy; groups III and IV, respectively) for up to 96 hr after partial hepatectomy, with ethanol administration starting 1 hr prior to partial hepatectomy. Animals were killed at 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 60, and 96 hr after partial hepatectomy. The rate of liver regeneration was evaluated by the mitotic index in H&E-stained sections, immunochemical detection of Ki67 nuclear antigen, rate of [3H]thymidine incorporation into hepatic DNA, and liver thymidine kinase enzymatic activity. The biological activity of HSS in groups I and II rats was evaluated using a bioassay. Ethanol administration arrested liver regeneration during the first 32 hr after partial hepatectomy and suppressed HSS activity throughout the period examined. Liver regeneration progressed after 32 hr despite the low levels of HSS activity. HSS administration at 10 and 16 hr reversed liver regeneration arrest induced by ethanol. Acute ethanol administration induces cell cycle arrest during the first 32 hr after partial hepatectomy and suppression of HSS biological activity seems to contribute to this effect. HSS administration reversed the inhibitory effect of ethanol on liver regeneration and caused synchronized entrance of hepatocytes in the S phase of the cell cycle. HSS seems to participate in the network of growth factors controlling the G1/S cell cycle checkpoint.

Contribution of Aldehyde Oxidizing Enzymes on the Metabolism of 3,4-Dimethoxy-2-phenylethylamine to 3,4-Dimethoxyphenylacetic Acid by Guinea Pig Liver Slices

Background/Aims: 3,4-Dimethoxy-2-phenylethylamine is catalyzed to its aldehyde derivative by monoamine oxidase B, but the subsequent oxidation into the corresponding acid has not yet been studied. Oxidation of aromatic aldehydes is catalyzed mainly by aldehyde dehydrogenase and aldehyde oxidase. Methods: The present study examines the metabolism of 3,4-dimethoxy-2-phenylethylamine in vitro and in freshly prepared and cryopreserved guinea pig liver slices and the relative contribution of different aldehyde-oxidizing enzymes was estimated by pharmacological means. Results: 3,4-Dimethoxy-2- phenylethylamine was converted into the corresponding aldehyde when incubated with monoamine oxidase and further oxidized into the acid when incubated with both, monoamine oxidase and aldehyde oxidase. In freshly prepared and cryopreserved liver slices, 3,4-dimethoxyphenylacetic acid was the main metabolite of 3,4-dimethoxy-2- phenylethylamine. 3,4-Dimethoxyphenylacetic acid formation was inhibited by 85% from disulfiram (aldehyde dehydrogenase inhibitor) and by 75-80% from isovanillin (aldehyde oxidase inhibitor), whereas allopurinol (xanthine oxidase inhibitor) inhibited acid formation by only 25-30%. Conclusions: 3,4- Dimethoxy-2-phenylethylamine is oxidized mainly to its acid, via 3,4-dimethoxyphenylacetaldehyde, by aldehyde dehydrogenase and aldehyde oxidase with a lower contribution from xanthine oxidase.

Ondansetron-droperidol combination vs. ondansetron or droperidol monotherapy in the prevention of postoperative nausea and vomiting

Introduction Laparoscopic cholecystectomy is associated with a high incidence of postoperative nausea and vomiting. In this study we investigated comparatively the efficacy of combination therapy with ondansetron plus droperidol versus monotherapy with each agent alone in preventing postoperative nausea and vomiting following elective laparoscopic cholecystectomy. Material and methods One hundred twenty-seven patients who underwent elective laparoscopic cholecystectomy under general anesthesia were included in the study, and assigned to one of the following three groups according to the antiemetic drug given intravenously at the end of the surgery: droperidol 1.25 mg in group D, ondansetron 4 mg in group O, and a combination of droperidol and ondansetron at the doses mentioned above in group D + O. Incidence of postoperative nausea and vomiting, and doses of given rescue antiemetics were recorded during the first postoperative day. The total drug cost per patient spent for postoperative nausea and vomiting management (including prophylactic antiemetics plus rescue postoperative antiemetics) was calculated. Results Combination therapy significantly reduced postoperative nausea and vomiting at 30 min, 3 h and 6 h after surgery compared with group D (p < 0.01 for all time points) and O (p < 0.01 at 30 min, p < 0.05 at 3 h) and required less rescue antiemetic treatment (p < 0.01). Total antiemetic cost analyses revealed no significant differences among the three groups (p > 0.05). Conclusions Pretreatment with ondansetron plus droperidol is more effective than monotherapy in preventing postoperative nausea and vomiting following laparoscopic cholecystectomy, without increasing the cost comparatively.

Gaucher disease: An orphan disease with significant osseous manifestations

Gaucher disease, the most common of the lysosomal storage diseases, is a systematic familial disease classified in “orphan diseases’’, a group of rare disorders with prevalence of 1:50,000 or lower in the general population. Gaucher disease results from mutations that impair the enzymatic activity of a lysosomal hydrolase called β-glucocerebrosidase and leads to the accumulation of glucocerebroside, its substrate, in the lysosomes of the macrophage/monocyte system. Macrophages are transformed to Gaucher cells by glucocerebroside accumulation which represent atypical activated macrophages that infiltrate various organs and secrete an array of pro-inflammatory cytokines. This results in organomegally and cytopenias in the peripheral blood due to hypersplenism and infiltration of the bone marrow by Gaucher cells. Cytokines exctreted by Gaucher cells are in the basis of bone pathology. Osteopenia, osteoporosis, painful bone crises, pathologic fractures, and osteonecrosis are the most common manifestations of osseous Gaucher disease. This disease is classified in three types based on CNS involvement and rate of progression. Therapy consists of β-glucocerebrosidase substitution and substrate reduction therapy. *Correspondence to: Georgios I. Panoutsopoulos, Director of Laboratory of Physiology-Pharmacology, Department of Nursing, Faculty of Human Movement and Quality of Life Sciences, University of Peloponnese, Efstathiou & Stamatikis Valioti and Plateon, Sparta 23100, Greece, E-mail: gpanouts@uop.gr