Hyperammonemia is a feature of acute liver failure (ALF), which is associated with increased intracranial pressure (ICP) and brain herniation. We hypothesized that a combination of L-ornithine and phenylacetate (OP) would synergistically reduce toxic levels of ammonia by (1) L-ornithine increasing glutamine production (ammonia removal) through muscle glutamine synthetase and (2) I n patients with acute liver failure (ALF) increased intracranial pressure (ICP) leads to brain herniation, which accounts for 30% of deaths. 1 Liver failure results in hyperammonemia, which leads to toxic levels of ammonia in the brain. In patients with ALF, an arterial ammonia level of Ͼ150 mol/L has been shown to correlate with severity of intracranial hypertension 2 and deaths from brain herniation. 3 More recently, ammonia levels were shown to be predictive of increased ICP 4 and changes in blood ammonia concentration determined death due to cerebral edema in patients with ALF. 5Abbreviations: ALF, acute liver failure; GS, glutamine synthetase; HE, hepatic encephalopathy; ICP, intracranial pressure; OP, L-ornithine phenylacetate. From the

After parenchymal loss, the liver regenerates restoring normal mass and metabolic function. Prevailing theories on triggering events leading to regeneration include humoral, metabolic, and flow-mediated mechanisms, the latter emphasizing the importance of shear stress mediated nitric oxide regulation. We aimed to investigate whether the grade of resection and hence the portal venous pressure and sinusoidal shear stress increase would be reflected in the gene expression profiles in the liver remnant by using a global porcine cDNA microarray chip with ϳ23,000 genes represented. Six pig livers were resected with 62% (low portal pressure resection) and 75% (high portal pressure resection), resulting in a portal venous pressure increase from a baseline of 6.1-8.2 and 12 mmHg, respectively. By sampling consecutive biopsies from the liver remnants, we found differentially expressed genes in the high portal pressure resection group to have functions related primarily to apoptosis, nitric oxide metabolism and oxidative stress, whereas differentially expressed genes in the low portal pressure resection group potentially regulate the cell cycle. Common to both groups was the upregulation of genes regulating inflammation, transport, cell proliferation, development, and protein metabolism. Also common to both groups was both up-and downregulation of genes regulating cell-cell signaling, signal transduction, cell adhesion, and translation. Genes regulating the metabolism of lipids, hormones, amines, and alcohol were downregulated in both groups. In conclusion, the genetic regenerative response in the liver remnant to varies according to the level of resection. microarray; shear stress; partial hepatectomy; regeneration AFTER PARENCHYMAL LOSS, the liver regenerates restoring normal mass and metabolic function. Since Higgins and Anderson (33) formalized the study of liver regeneration in 1931, most studies on liver regeneration have been conducted in a model of 70% partial hepatectomy (PHx) in rodents. After PHx, several proapoptotic [transforming growth factor (TGF)-␤ and Fas ligand] and promitotic factors [IL-1, IL-6, EGF, hepatocyte growth factor (HGF), and TNF-␣; Refs. 22, 72] are known to be important humoral factors regulating induction, propagation, and termination of liver regeneration. Knockout studies in mice have demonstrated impaired regeneration in mice receptor negative for promitotic mediators (12) and hepatomegaly in mice receptor negative for proapoptotic mediators (16). Many of these humoral factors are detectable several hours after PHx (Refs. 50, 53, 76). However, later studies (65) have shown that liver regeneration commences already after 15 min post-PHx (via the detection of c-fos mRNA expression), suggesting more immediate triggering events. There is evidence indicating that the increased portal pressure and flow per gram of remaining liver tissue and hence sinusoidal shear stress after PHx may be a primary stimulus (53,63,64). Endothelial shear stress results in the production of nitric oxide (NO; Refs....

BackgroundAfter partial hepatectomy (PHx), the liver regeneration process terminates when the normal liver-mass/body-weight ratio of 2.5% has been re-established. To investigate the genetic regulation of the terminating phase of liver regeneration, we performed a 60% PHx in a porcine model. Liver biopsies were taken at the time of resection, after three weeks and upon termination the sixth week. Gene expression profiles were obtained using porcine oligonucleotide microarrays. Our study reveals the interactions between genes regulating the cell cycle, apoptosis and angiogenesis, and the role of Transforming Growth Factor-β (TGF-β) signalling towards the end of liver regeneration.ResultsMicroarray analysis revealed a dominance of genes regulating apoptosis towards the end of regeneration. Caspase Recruitment Domain-Containing Protein 11 (CARD11) was up-regulated six weeks after PHx, suggesting the involvement of the caspase system at this time. Zinc Finger Protein (ZNF490) gene, with a potential negative effect on cell cycle progression, was only up-regulated at three and six weeks after PHx indicating a central role at this time. TGF-β regulation was not found to be significantly affected in the terminating phase of liver regeneration. Vasohibin 2 (VASH2) was down-regulated towards the end of regeneration, and may indicate a role in preventing a continued vascularization process.ConclusionsCARD11, ZNF490 and VASH2 are differentially expressed in the termination phase of liver regeneration. The lack of TGF-β up-regulation suggests that signalling by TGF-β is not required for termination of liver regeneration.

No abstract

The therapeutic utility of endothelial progenitor cells (EPCs) in cardiovascular disease is potentially hampered by their low numbers in the circulation, impaired functional activity, and inhibitory factors in the recipient. These obstacles can possibly be circumvented by the use of proangiogenic cytokines and peptides. We sought to examine the effect of the endogenous vasoactive peptide adrenomedullin (AM) on the angiogenic potential of late outgrowth EPCs and their release of proangiogenic and proinflammatory cytokines/chemokines. Human peripheral blood mononuclear cells were cultured until the appearance of typical late outgrowth EPC colonies. The effect of AM on EPC proliferation was assessed using a colorimetric MTS proliferation assay while differentiation and formation of tubular structures in an EPC/fibroblast coculture or matrigel assay was used to assess the angiogenic potential of the cells. Finally, the release and mRNA transcripts of cytokines/chemokines were quantified in stimulated vs. nonstimulated EPCs using real-time PCR and a bead-based multiplex assay. The cultured EPCs possessed an endothelial phenotype and expressed the AM receptor (calcitonin receptor-like receptor/receptor activity modifying protein-2). AM stimulation induced proliferation of EPCs compared with controls (P < 0.05). Furthermore, AM produced a 36% and 80% increase in the formation of tubular networks in the EPC/fibroblast coculture and matrigel assay, respectively (P < 0.05). These effects seemed to be mediated through the phosphatidylinositol 3-kinase/Akt signaling pathway. AM did not seem to significantly influence the release or production of IL-6, IL-8, VEGF, stromal cell-derived factor 1, or the expression of CXCR-4 or VEGF receptor 2. In conclusion, adrenomedullin augmented the growth and angiogenic properties of late outgrowth EPCs, but did not influence their paracrine properties.