Portal hemodynamic changes after hepatocyte transplantation in acute hepatic failure

Hepatocyte transplantation has been proposed as an alternative for rescuing patients with acute hepatic failure. However, portal hemodynamic changes and issues of safety after hepatocyte transplantation in acute hepatic failure have not been systemically evaluated because of the lack of a suitable experimentation system. In this study, we created a novel spring-guidewire introducer needle to simplify the technique for long-term portal cannulation in F-344 rats. The portal cannula was capable of being used for blood sampling, infusion of hepatocytes, and measurement of portal hemodynamic changes. One week after portal cannulation, rats were injected withD-galactosamine (1.35 g/kg, i.p.) to induce hepatic failure. Hepatocytes (2×10⁷) were infused intraportally 24–26 h after induction of liver injury. Portal pressures were recorded for up to 60 min after hepatocyte transplantation. Intraportal infusion of 2×10⁷ hepatocytes caused an instantaneous onset of portal hypertension. The magnitude of the rise in portal pressure was similar in both normal rats and rats with acute hepatic failure (33.0±7.1 vs. 37.7±0.5 mm Hg; p=0.23). However, the resolution rate of portal hypertension was remarkably delayed in rats with acute hepatic failure, and the portal pressure was significantly higher than that in normal rats 60 min after hepatocyte transplantation (25.0±2.8 vs. 14.5±2.4 mm Hg; p=0.007). In conclusion, we have established a simple new technique for long-term portal cannulation of rats. Our studies provide critical insights into the delayed resolution of portal hemodynamics after hepatocyte transplantation in subjects with acute hepatic failure.     

Functional expression, purification, and characterization of the extra stable human placental alkaline phosphatase in the Pichia pastoris system

Human placental alkaline phosphatase was successfully cloned in the yeast system Pichia pastoris. The recombinant enzyme was over-expressed as a secreted protein in the cultured medium. The enzyme was extremely stable, which resulted in a total recovery of the enzyme activity after the purification process. The purified enzyme preparation was apparently homogeneous as examined by the polyacrylamide gel electrophoresis, analytical gel-permeation chromatography, and analytical ultracentrifugation. The final enzyme preparation showed a purification of 803-fold from the culture medium with a specific activity of 578 U/mg of protein. Fluorescence spectroscopic analyses showed multiple unfolding steps in the urea denaturation process of the homodimeric recombinant enzyme. Extensive conformational change of the enzyme in urea was detected by the analytical ultracentrifugation and the size-exclusive chromatography. The quaternary structure of the enzyme is quite stable. No indication of dissociation was observed after extensive tertiary structural changes.     

Links between CD147 function, glycosylation, and caveolin-1

Cell surface CD147 shows remarkable variations in size (31-65 kDa) because of heterogeneous N-glycosylation, with the most highly glycosylated forms functioning to induce matrix metalloproteinase (MMP) production. Here we show that all three CD147 N-glycosylation sites make similar contributions to both high and low glycoforms (HG- and LG-CD147). l-Phytohemagglutinin lectin binding and swainsonine inhibition experiments indicated that HG-CD147 contains N-acetylglucosaminyltransferase V-catalyzed, beta1,6-branched, polylactosamine-type sugars, which account for its excess size. Therefore, CD147, which is itself elevated on invasive tumor cells, may make a major contribution to the abundance of beta1,6-branched polylactosamine sugars that appear on invasive tumor cells. It was shown previously that caveolin-1 associates with CD147, thus inhibiting CD147 self-aggregation and MMP induction; now we show that caveolin-1 associates with LG-CD147 and restricts the biosynthetic conversion of LG-CD147 to HG-CD147. In addition, HG-CD147 (but not LG-CD147) was preferentially captured as a multimer after treatment of cells with a homobifunctional cross-linking agent and was exclusively recognized by monoclonal antibody AAA6, a reagent that selectively recognizes self-associated CD147 and inhibits CD147-mediated MMP induction. In conclusion, we have 1) determined the biochemical basis for the unusual size variation in CD147, 2) established that CD147 is a major carrier of beta1,6-branched polylactosamine sugars on tumor cells, and 3) determined that caveolin-1 can inhibit the conversion of LG-CD147 to HG-CD147. Because it is HG-CD147 that self-aggregates and stimulates MMP induction, we now have a mechanism to explain how caveolin-1 inhibits these processes. These results help explain the previously established tumor suppressor functions of caveolin-1.     

A transporter of<Emphasis Type="Italic"> Escherichia coli</Emphasis> specific for<Emphasis Type="SmallCaps"> l</Emphasis>- and<Emphasis Type="SmallCaps"> d</Emphasis>-methionine is the prototype for a new family within the ABC superfamily

An ABC-type transporter in Escherichia coli that transports both l- and d-methionine, but not other natural amino acids, was identified. This system is the first functionally characterized member of a novel family of bacterial permeases within the ABC superfamily. This family was designated the methionine uptake transporter (MUT) family (TC #3.A.1.23). The proteins that comprise the transporters of this family were analyzed phylogenetically, revealing the probable existence of several sequence-divergent primordial paralogues, no more than two of which have been transmitted to any currently sequenced organism. In addition, MetJ, the pleiotropic methionine repressor protein, was shown to negatively control expression of the operon encoding the ABC-type methionine uptake system. The identification of MetJ binding sites (in gram-negative bacteria) or S-boxes (in gram-positive bacteria) in the promoter regions of several MUT transporter-encoding operons suggests that many MUT family members transport organic sulfur compounds. Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

ATR kinase activity regulates the intranuclear translocation of ATR and RPA following ionizing radiation

Upon damage of DNA in eukaryotic cells, several repair and checkpoint proteins undergo a dramatic intranuclear relocalization, translocating to nuclear foci thought to represent sites of DNA damage and repair. Examples of such proteins include the checkpoint kinase ATR (ATM and Rad3-related) as well as replication protein A (RPA), a single-stranded DNA binding protein required in DNA replication and repair. Here, we used a microscopy-based approach to investigate whether the damage-induced translocation of RPA is an active process regulated by ATR. Our data show that in undamaged cells, ATR and RPA are uniformly distributed in the nucleus or localized to promyelocytic leukemia protein (PML) nuclear bodies. In cells treated with ionizing radiation, both ATR and RPA translocate to punctate, abundant nuclear foci where they continue to colocalize. Surprisingly, an ATR mutant that lacks kinase activity fails to relocalize in response to DNA damage. Furthermore, this kinase-inactive mutant blocks the translocation of RPA in a cell cycle-dependent manner. These observations demonstrate that the kinase activity of ATR is essential for the irradiation-induced release of ATR and RPA from PML bodies and translocation of ATR and RPA to potential sites of DNA damage.     

Anti-tumor activity of the farnesyl-protein transferase inhibitors arteminolides, isolated from Artemisa

Members of the Artemisia genus are important medicinal plants found throughout the world. Arteminolides A-D (1-4), isolated from the aerial parts of Artemisia, have an inhibitory activity on farnesyl-protein transferase (FPTase; EC 2.5.1.29) in in vitro assay. This study was carried out with the purpose of validating anti-tumor effects of the compounds in human tumor cells and mouse xenograft model. The arteminolides inhibited tumor cell growth in a dose-dependent manner. Furthermore, arteminolide C (3) blocked in vivo growth of human colon and lung tumor xenograft without the loss of body weight in nude mice.     

Signaling via histamine receptors in cat duodenal smooth muscle cells

Histamine produced concentration-dependent contractions in cat duodenal smooth muscle cells that were obtained by enzymatic digestion of smooth muscle with collagenase F. Pyrilamine, an H1 receptor antagonist, inhibited the contractile response while famotidine, an H2 receptor antagonist, augmented it. In cells with selectively preserved H1 receptors, produced by pretreatment with pyrilamine followed by inactivation of all unprotected receptors with N-ethylmaleimide, histamine-induced contraction was significantly augmented as compared with control cells. Pertussis toxin (PTX) had no effect on contraction, suggesting that the H1 receptor is coupled to a PTX-insensitive G protein. Gi2, Gi3, Go, Gs, and Gq subunits were present in cat duodenum, and histamine-induced contraction was inhibited by Gq antibody after cell permeabilization. Neomycin, a PLC inhibitor, inhibited the histamine-induced cell contraction, but not rhoCMB, a PLD inhibitor, or DEDA, a PLA2 inhibitor. Heparin, an IP3 receptor inhibitor, inhibited contraction whereas chelerythrine, a PKC inhibitor, had no effect. We conclude that histamine-induced contraction in cat duodenal smooth muscle cells is mediated by H1 receptors coupled to a PTX-insensitive Gq protein and results in activation of phosphatidylinositol-specific phospholipase C (PI-PLC).     

Trafficking defects in endogenously synthesized cholesterol in fibroblasts,macrophages, hepatocytes,and glial cells from Niemann-Pick type C1 mice

Niemann-Pick type C1 disease (NPC1) is an inherited neurovisceral lipid storage disorder, hallmarked by the intracellular accumulation of unesterified cholesterol and glycolipids in endocytic organelles. Cells acquire cholesterol through exogenous uptake and endogenous biosynthesis. NPC1 participation in the trafficking of LDL-derived cholesterol has been well studied; however, its role in the trafficking of endogenously synthesized cholesterol (endoCHOL) has received much less attention. Previously, using mutant Chinese hamster ovary cells, we showed that endoCHOL moves from the endoplasmic reticulum (ER) to the plasma membrane (PM) independent of NPC1. After arriving at the PM, it moves between the PM and internal compartments. The movement of endoCHOL from internal membranes back to the PM and the ER for esterification was shown to be defective in NPC1 cells. To test the generality of these findings, we have examined the trafficking of endoCHOL in four different physiologically relevant cell types isolated from wild-type, heterozygous, and homozygous BALB/c NPC1NIH mice. The results show that all NPC1 homozygous cell types (embryonic fibroblasts, peritoneal macrophages, hepatocytes, and cerebellar glial cells) exhibit partial trafficking defects, with macrophages and glial cells most prominently affected. Our findings suggest that endoCHOL may contribute significantly to the overall cholesterol accumulation observed in selective tissues affected by Niemann-Pick type C disease.