Browsing by Author "Koenig, CS"

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    Bile secretory function after warm hepatic ischemia-reperfusion injury in the rat
    (WILEY, 2003) Accatino, L; Pizarro, M; Solis, N; Arrese, M; Koenig, CS
    Hepatic ischemia-reperfusion (I-R) injury frequently is associated with cholestasis. However, the underlying mechanisms are not fully understood. The aim of the study is to assess bile secretory function in vivo in rats subjected to warm lobar hepatic ischemia at different times during reperfusion. A model of lobar 70% warm hepatic ischemia for 30 minutes was used with studies conducted at 1 and 6 hours and 1, 3, and 7 days after reperfusion. Bile secretory function was assessed after selective cannulation of bile ducts of ischemic (ILs) and nonischemic lobes (NILs). Serum activity of hepatic alanine and aspartate aminotransferase was slightly increased in rats subjected to I-R, whereas serum bile salt levels increased early during reperfusion, returning to control values after 7 days. ILs; showed mild reversible leukocyte infiltration and no significant necrosis. Bile flow and bile salt excretion were significantly decreased in ILs during the first 24-hour reperfusion period compared with shamoperated rats and NILs. A marked reduction in glutathione (GSH) excretion occurred at I and 6 hours and I and 3 days, which returned to control values after 7 days. Total GSH and both reduced and oxidized GSH levels in liver homogenate and arterial blood GSH levels were unchanged at all times. Protein mass of multidrug resistance protein 2 and its function, assessed by the hepatic maximum secretory rate of ceftriaxone, did not show significant changes in ILs or NILs compared with shamoperated rats. Liver tissue gamma-glutamyl transpeptidase (GGT) and gamma-glutamylcysteine synthetase activities remained unchanged, whereas biliary GGT and cysteine secretory rates were significantly increased in ILs; and NILs. Administration of acivicin, a GGT inhibitor, resulted in decreased secretion of this enzyme into bile and a parallel marked increase in biliary GSH secretion compared with untreated ischemic rats. In conclusion, warm hepatic I-R induces reversible cholestatic changes in ILs. GSH secretory rates from both ILs and NILs were markedly decreased during reperfusion. The reversibility of this effect after GGT inhibition, as well as increased release of active GGT into bile and cysteine biliary secretory rates, suggest increased GSH degradation in bile. These findings might be relevant for the I-R-induced clinical cholestasis, as well as cholangiocyte injury, seen after hepatic ischemia.
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    Differential expression of canalicular membrane Ca2+/Mg2+-ecto-ATPase in estrogen-induced and obstructive cholestasis in the rat
    (MOSBY, INC, 2000) Accatino, L; Pizarro, M; Solis, N; Arrese, M; Vollrath, V; Ananthanarayanan, M; Chianale, J; Koenig, CS
    Extracellular adenosine triphosphate (ATP) may regulate hepatocyte and cholangiocyte functions, and under some conditions it may have deleterious effects on bile secretion and cause cholestasis. The canalicular membrane enzyme Ca2+/Mg2+-ecto-ATPase (ecto-ATPase) hydrolyzes ATP/adenosine diphosphate (ATP/ADP) and regulates hepatic extracellular ATP concentration. Changes in liver ecto-ATPase in estrogen-induced cholestasis were examined in male rats receiving 17 alpha-ethinylestradiol (E groups) for 1, 3, or 5 days (5 mg/kg/day, sc) and compared with changes in rats subjected to obstructive cholestasis (O groups) for 1, 3, or 8 days. Activity of ecto-ATPase, protein mass in canalicular membranes and bile (estimated by Western blotting), steady state mRNA levels (by Northern blotting), and cellular and acinar distributions of the enzyme (histochemistry and immunocytochemistry) were assessed in these groups. Activity of ecto-ATPase, protein mass in isolated canalicular membranes, and enzyme mRNA levels were significantly increased in E group rats as compared with controls. In contrast, these parameters were markedly decreased in O group rats, and the enzyme protein was undetectable in bile. The ecto-ATPase histochemical reaction was markedly increased in the canalicular membrane of E group rats, extending from acinar zone 2 to zone 1,whereas it decreased in the O group. The ecto-ATPase immunocytochemical reaction was present in the canalicular membrane and pericanalicular vesicles in control and E group hepatocytes, but it decreased in obstructive cholestasis and was localized only to the canalicular membrane. Thus, significant changes in liver ecto-ATPase were apparent in 17 alpha-ethinylestradiol-induced cholestasis that were opposite to those observed in obstructive cholestasis. Assuming that the alterations observed in obstructive cholestasis are the result of the cholestatic phenomenon, we conclude that changes in ecto-ATPase in 17 alpha-ethinylestradiol-treated rats might be either primary events or part of an adaptive response in 17 alpha-ethinylestradiol-induced cholestasis.
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    Effects of diosgenin, a plant-derived steroid, on bile secretion and hepatocellular cholestasis induced by estrogens in the rat
    (W B SAUNDERS CO, 1998) Accatino, L; Pizarro, M; Solis, N; Koenig, CS
    Increased biliary secretion of cholesterol and lipid vesicles (unilamellae and multilamellae) induced by diosgenin (D), a plant-derived steroid, has cytoprotective effects in the rat liver subjected to obstructive cholestasis. In this study, our aims were to investigate the following: 1) the effects of D on the bile secretory process and on the cholestasis induced by estradiol-17 beta-(beta-D-glucuronide) (E17G) or 17 alpha-ethynylestradiol(E) administration; 2) whether the potentially protective effects of D are related to D-induced increase of biliary cholesterol and lipid lamellae; and 3) whether D has other effects capable of modifying specific bile secretory processes or preventing the cholestatic effects of estrogens. Rats were fed a standard ground chow (control group) or chow containing D for 6 days. E17G was administered i,v, to control and D-fed rats and bile flow, bile salt output, and alkaline phosphatase excretion were examined. 17 alpha-E was administered from days 4 to 6 to rats fed standard chow or chow plus D for 6 days and different functional parameters of the bile secretory process as well as the ultrastructure of hepatocytes and histochemistry of alkaline phosphatase and Mg2+-adenosine triphosphatase (ATPase:) were examined. D-treatment markedly increased cholesterol and lamellar structures in bile and attenuated the acute cholestatic effects of E17G, D-feeding prevented the decrease of taurocholate maximum secretory rate and the increase of biliary alkaline phosphatase and Ca2+,Mg2+-EctoATPase (EctoATPase) excretion, as well as the increase of cholesterol/ phospholipids ratio, alkaline phosphatase activity, and EctoATPase content in canalicular plasma membranes induced by E, D-feeding did not prevent E-induced decrease of basal bile flow, bile salt, cholesterol, and phospholipid secretory rates nor the decrease of Na+,K+-ATPase activity and Nac-taurocholate cotransporting polypeptide (Ntcp) content in isolated sinusoidal membranes. Cholestatic alterations of canalicular domain were apparent in E-treated rats. D administration was also associated with changes of ultraestructure and histochemistry of hepatocytes, E-induced alterations in ultrastructure and acinar distribution and intensity of histochemical reaction of both enzymes were partially prevented by D-feeding, We conclude that D administration, in addition to inducing a marked increase of biliary cholesterol and lipid lamellar structures output, was associated to changes in hepatocyte morphology and plasma membrane composition, enzymes activity, and histochemistry, D-feeding attenuated the acute cholestatic effects of E17G. D-induced increase of bile cholesterol and lipid lamellae content was not apparent when D-fed rats received E. Despite this fact, D administration prevented some cholestatic effects of E, probably through different metabolic effects and/or direct membrane effects, not related to increased lipid lamellae excretion.
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    Peroxisome proliferator-activated receptor gamma is expressed in hippocampal neurons and its activation prevents beta-amyloid neurodegeneration: role of Wnt signaling
    (ELSEVIER INC, 2005) Inestrosa, NC; Godoy, JA; Quintanilla, RA; Koenig, CS; Bronfman, M
    The molecular pathogenesis of Alzheimer's disease (AD) involves the participation of the amyloid-beta-peptide (Abeta), which plays a critical role in the neurodegeneration that triggers the disease. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors, which are members of the nuclear receptor family. We report here that (1) PPARgamma is present in rat hippocampal neurons in culture. (2) Activation of PPAR-gamma by troglitazone and rosiglitazone protects rat hippocampal neurons against Abeta-induced neurodegeneration, as shown by the 3-[4,5 -2yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay, immunofluorescence using an anti-heavy neurofilament antibody, and quantitative electron microscopy. (3) Hippocampal neurons treated with several PPAR-gamma agonists, including troglitazone, rosiglitazone, and ciglitazone, prevent the excitotoxic Abeta-induced rise in bulk-free Ca2+. (4) PPARgamma activation results in the modulation of Wnt signaling components, including the inhibition of glycogen synthase kinase-3beta (GSK-3beta) and an increase of the cytoplasmic and nuclear beta-catenin levels. We conclude that the activation of PPARgamma prevents Abeta-induced neurodegeneration by a mechanism that may involve a cross talk between neuronal PPAR-y and the Writ signaling pathway. More important, the fact that the activation of PPAR-y attenuated Abeta-dependent neurodegeneration opens the possibility to fight AD from a new therapeutic perspective. (C) 2004 Published by Elsevier Inc.