ursodoxicoltaurine and Necrosis

N. We first conducted transcriptome-wide m. We identified an overwhelming proportion of m. We demonstrate the essential role of Mettl14 in facilitating liver regeneration by modulating polypeptide-processing proteins in the ER in an m

Topics: Adenosine; Animals; Apoptosis; Cell Proliferation; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Gene Deletion; Hepatectomy; Hepatocytes; Homeostasis; Liver; Liver Regeneration; Male; Methyltransferases; Mice, Knockout; Necrosis; Organ Specificity; Peptides; RNA Stability; RNA, Messenger; Taurochenodeoxycholic Acid; Transcriptome

The goal of this investigation was to determine whether chenodeoxycholic acid (CDCA)-induced apoptosis is prevented by ursodeoxycholic acid (UDCA) or tauroursodeoxycholic acid (TUDC) and to characterize the involvement of mitochondria in the process. Cultured human HepG2 cells were treated in a dose- and time-dependent protocol in order to establish a sufficiently low exposure to CDCA that causes apoptosis but not necrosis. Low-dose CDCA induced an S-phase block and G2 arrest of the cell cycle, as determined by flow cytometry. As a result, cell proliferation was inhibited. CDCA-induced apoptosis, as determined by fluorescence microscopy of Hoechst 33342-stained nuclei, was evident upon coincubation with TUDC. Additionally, after exposure to UDCA plus CDCA, the cell membrane was permeable to fluorescent dyes. Caspase-9-like activity, poly(ADP-ribose) polymerase (PARP) cleavage, and extensive DNA fragmentation were detected in CDCA-exposed cells and in cells coincubated with TUDC, but not UDCA. CDCA caused a decrease in mitochondrial membrane potential and depletion of ATP, both of which were potentiated by UDCA but not TUDC. The results suggest that UDCA potentiates CDCA cytotoxicity, probably at the level of induction of the mitochondrial permeability transition (MPT). Consequently, as suggested by the lack of the main hallmarks of the apoptotic pathway, in the presence of UDCA, CDCA-induced apoptosis is not properly executed but degenerates into necrosis.

Topics: Adenosine Triphosphate; Apoptosis; Bile Acids and Salts; Bromodeoxyuridine; Caspase 9; Caspases; Cell Cycle; Cell Division; Cell Line; Cell Membrane Permeability; Cell Survival; Chenodeoxycholic Acid; Chromatin; Cytochromes c; DNA; DNA Fragmentation; Dose-Response Relationship, Drug; Drug Synergism; Humans; Mitochondrial Diseases; Necrosis; Poly(ADP-ribose) Polymerases; Taurochenodeoxycholic Acid; Time Factors; Tubulin; Ursodeoxycholic Acid

In cholestatic liver disease, bile acids may initiate or aggravate hepatocellular damage. Cellular necrosis and cell death may be due to detergent effects of bile acids, but apoptosis may also play a role. In cholestasis, the conditions determining either apoptotic or cytolytic cell death are still unclear. Primary rat hepatocytes in culture represent a suitable model to study bile-acid-induced liver damage.. Glycochenodeoxycholic acid, a hydrophobic bile acid, was used to induce cell damage. Tauroursodeoxycholic acid, a hydrophilic bile acid, served as substrate to study possible protective effects of such compounds. To study the time and concentration dependency of bile-acid-induced cytolysis and apoptosis, morphologic alterations, hepatocellular enzyme release and nucleosomal DNA fragmentation were evaluated.. Bile-acid-induced cytolysis, as indicated by hepatocellular enzyme release and by morphologic signs of membrane destruction, increased with concentration and time. Addition of tauroursodeoxycholic acid to the incubation medium reduced cytolysis significantly, indicating a direct hepatoprotective effect of this bile acid against the detergent action of hydrophobic bile acids. In contrast to cytolysis, apoptosis with DNA fragmentation was induced by low concentrations of glycochenodeoxycholic acid a few hours after incubation. Coincubation with tauroursodeoxycholic acid in equimolar concentrations significantly reduced apoptosis, indicating another direct hepatoprotective effect of tauroursodeoxycholic acid.. It seems likely that in severe cholestasis, bile-acid-induced injury of hepatocytes is due mainly to cytolysis, whereas in moderately severe cholestasis apoptosis represents the predominant mechanism of bile acid toxicity. Tauroursodeoxycholic acid may reduce both bile-acid-induced apoptosis and cytolysis.

Topics: Animals; Apoptosis; Aspartate Aminotransferases; Bile Acids and Salts; Cell Death; Cells, Cultured; DNA Fragmentation; Glycochenodeoxycholic Acid; L-Lactate Dehydrogenase; Liver; Male; Necrosis; Rats; Rats, Wistar; Taurochenodeoxycholic Acid

Taurochenodeoxycholate (TCDC) (or taurocholate, TC) excessively i.v. infused in rats causes an acute cholestasis accompanied by an excessive excretion of various proteins (lactate dehydrogenase, LDH, albumin, etc.) into the bile. This cholestasis was initially found to be effectively prevented by a simultaneous infusion of tauroursodeoxycholate (TUDC). Later this property was found to be shared by glycoursodeoxycholate (GUDC) and tauro (and glyco) alpha and beta-muricholate (MC) all known to be relatively hydrophilic. The extent of the preventative effect appears to be comparable for taurine and glycine conjugates of all three bile salts (UDC, alpha-MC and beta-MC). An albumin leakage into the bile enhanced by TCDC infusion appears to be mainly from albumin in the serum, since i.v. injected 125I-human serum albumin excretion into the bile paralled the rat albumin excretion. Despite very drastic biochemical abnormalities induced by TCDC infusion, morphological correlates in the liver are scarce both from light and electron microscopic examinations, the only correlate with biochemical parameters being a sporadic necrosis of hepatocytes, especially in the periportal areas. Although there is not sufficient morphological evidence, it appears that TCDC infusion causes a direct communication between serum and bile leading to a rapid leakage of large molecules such as albumin and even gamma-globulin. Conjugates of hydrophilic bile salts such as UDC, alpha-MC and beta-MC efficiently prevent such bile abnormalities but their hydrophilicity is not the sole determinant of this property since a more hydrophilic bile salt such as taurodehydrocholate does not possess this property. The underlying mechanism(s) for this protective property remains uncertain.

Topics: Albumins; Animals; Bile; Bile Acids and Salts; Cholestasis; Cholic Acids; L-Lactate Dehydrogenase; Liver; Male; Necrosis; Rats; Rats, Wistar; Taurochenodeoxycholic Acid

Continuous intravenous infusion of taurochenodeoxycholate at a rate of 0.4 mumol.min-1.100 gm-1 for only 30 min in rats caused threefold to tenfold greater release of proteins (alkaline phosphatase, lactate dehydrogenase and albumin) into bile in comparison with animals infused with tauroursodeoxycholate at much higher rates (1.8 mumol.min-1.100 gm-1) for 2 hr. The simultaneous infusion of tauroursodeoxycholate and taurochenodeoxycholate (0.6 and 0.4 mumol.min-1.100 gm-1, respectively) for 2 hr prevented the marked biochemical changes in the bile induced by taurochenodeoxycholate for 15 to 60 min exhibited significantly more necrotic hepatocytes, especially in zone 1, in comparison with animals infused with tauroursodeoxycholate or a combination of taurochenodeoxycholate and tauroursodeoxycholate. A good correlation was observed between biochemical and morphological indices of bile acid-induced hepatocyte injury. These data suggest that (a) primary events induced by the acute infusion of toxic bile salts responsible for cholestasis include zone 1 hepatocellular necrosis and (b) this can be prevented by the simultaneous infusion of tauroursodeoxycholate.

Topics: Animals; Bile; Bile Acids and Salts; Liver; Male; Necrosis; Proteins; Rats; Rats, Inbred Strains; Taurochenodeoxycholic Acid; Taurocholic Acid