N-Cadherin cleavage during activated hepatic stellate cell apoptosis is inhibited by tissue inhibitor of metalloproteinase-1. [In supplement: 11th International Symposium on the Cells of the Hepatic Sinusoid and their Relation to Other Cells]

Apoptosis of hepatic stellate cells (HSC) has previously been shown to occur during spontaneous resolution of experimental liver fibrosis. TIMP-1 has also been shown to have a key role because of its ability to inhibit apoptosis of HSC via matrix metalloproteinase (MMP) inhibition. This has led to further study of novel substrates for MMPs that might impact on HSC survival. N-Cadherin is known to mediate cell-cell contacts in fibroblasts. In this study we demonstrate that N-Cadherin is expressed by activated rat HSC. Furthermore, during apoptosis of HSC, the N-Cadherin is cleaved into smaller fragments. Apoptosis of HSC may be inhibited by TIMP-1. This is associated with reduced fragmentation of N-Cadherin. N-Cadherin may have an important role in supporting HSC survival while N-Cadherin cleavage may play a part in promoting HSC apoptosis in recovery from liver fibrosis

Bacterial expression of human kynurenine 3-monooxygenase:Solubility, activity, purification

AbstractKynurenine 3-monooxygenase (KMO) is an enzyme central to the kynurenine pathway of tryptophan metabolism. KMO has been implicated as a therapeutic target in several disease states, including Huntington’s disease. Recombinant human KMO protein production is challenging due to the presence of transmembrane domains, which localise KMO to the outer mitochondrial membrane and render KMO insoluble in many in vitro expression systems. Efficient bacterial expression of human KMO would accelerate drug development of KMO inhibitors but until now this has not been achieved. Here we report the first successful bacterial (Escherichia coli) expression of active FLAG™-tagged human KMO enzyme expressed in the soluble fraction and progress towards its purification

Tissue inhibitor of metalloproteinase-1 expression by human hepatic lipocytes and its role in liver disease

SIGLEAvailable from British Library Document Supply Centre-DSC:DX190393 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Case report of an arterioportal fistula, presenting with accelerated decompensation and sepsis, twenty-six years after initial liver biopsy

We describe the case of a 55-year-old lady who presented with accelerated hepatic decompensation from an arterioportal fistula (APF). There is histological evidence the APF proceeded a percutaneous liver biopsy performed 26 years ago. She had shown no symptoms or signs of liver disease in the intervening period. The clinical presentation initially was that of portal hypertension but evolved into a systemic inflammatory response syndrome associated with renal and liver failure. We describe how the APF was embolised by interventional radiology and how the timing of this decision was a balance between reversing abnormal haemodynamics and trying to avoid instrumentation of a potentially septic environment. This unusual case reflects the relationship between portal hypertension, sepsis and renal failure

Tissue inhibitor of metalloproteinase-1 messenger RNA expression is enhanced relative to interstitial collagenase messenger RNA in experimental liver injury and fibrosis

Liver fibrosis results from a relative imbalance between synthesis and degradation of matrix proteins. We have previously described release of the potent collagen-use inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP- 1), by culture-activated human hepatic stellate cells (HSCs). In this study, we have investigated the relative expression of TIMP-1 and interstitial collagenase in culture-activated rat HSCs and rat models of liver injury and fibrosis. The complementary DNA (cDNA) for rat TIMP-1 was obtained by homology polymerase chain reaction (PCR) and sequenced. By Northern analysis using this probe, TIMP-1 messenger RNA (mRNA) expression was up-regulated with HSC activation by culture on plastic as defined by cellular expression of procollagen-1. Interstitial collagenase mRNA was expressed in early culture (<4 days) but became undetectable in more activated cells (7-21 days). By activity assay of serum-free cell-conditioned media, TIMP-1 was found to be released in increasing concentrations with duration of culture on plastic. Expression of TIMP-1, interstitial collagenase, and procollagen-1 mRNAs were studied in rat models of biliary and parenchymal injury (bile duct ligation and CCl4 administration) by ribonuclease protection assay. TIMP-1 mRNA expression was increased at 6, 24 hours, and 3 days after bile duct ligation and was also shown to rise in acute CCl4 liver injury and remain elevated as the liver became fibrotic. TIMP-1 expression preceded procollagen-1 expression in both models. In contrast, interstitial collagenase mRNA levels remained similar to control values throughout both models of liver injury. Total cellular RNA from hepatocytes, HSCs, and Kupffer cells freshly isolated from livers after acute CCl4 injury was subjected to Northern analysis. TIMP-1 transcripts were observed in nonparenchymal cells only. We suggest that increased expression of TIMP-1 relative to interstitial collagenase by HSCs may promote progression of liver fibrosis in these rat models by preventing degradation of secreted collagens.Articl

Apoptosis of hepatic stellate cells: involvement in resolution of biliary fibrosis and regulation by soluble growth factors

Background: Activated hepatic stellate cells (HSC) are central to the pathogenesis of liver fibrosis, both as a source of fibrillar collagens that characterise fibrosis and matrix degrading metalloproteinases and their tissue inhibitors, the TIMPs.Aims: To test the hypothesis that HSC apoptosis is critical to recovery from biliary fibrosis and that soluble growth factors may regulate HSC survival and apoptosis.Methods: Rats (n=15) were subjected to bile duct ligation for 21 days, after which biliodigestive anastomosis was undertaken (n=13). Livers were harvested at fixed time points of recovery for periods of up to 42 days. Numbers of activated HSCs were quantified after alpha smooth muscle actin staining and HSC apoptosis was detected by terminal UDP-nick end labelling (TUNEL) staining and quantified at each time point. HSC apoptosis was quantified in vitro in the presence or absence of insulin-like growth factor (IGF)-1, IGF-2, platelet derived growth factor (PDGF), and transforming growth factor beta 1 (TGF-beta 1).Results: Following biliodigestive anastomosis after 21 days of bile duct ligation, rat liver demonstrated a progressive resolution of biliary fibrosis over 42 days, associated with a fivefold decrease in activated HSC determined by alpha smooth muscle actin staining. TUNEL staining indicated that loss of activated HSC resulted from an increase in the rate of apoptosis during the first two days post biliodigestive anastomosis. Serum deprivation and culture in the presence of 50 µM cycloheximide was associated with an increase in HSC apoptosis which was significantly inhibited by addition of 10 ng/ml and 100 ng/ml IGF-1, respectively (0.05>p, n=5). In contrast, 1 and 10 ng/ml of TGF-beta 1 caused a significant increase in HSC apoptosis compared with serum free controls (p<0.05, n=4). PDGF and IGF-2 were neutral with respect to their effect on HSC apoptosis.Conclusion: HSC apoptosis plays a critical role in the spontaneous recovery from biliary fibrosis. Both survival and apoptosis of HSC are regulated by growth factors expressed during fibrotic liver injury