Prospective Multicenter Observational Study of Overt Hepatic Encephalopathy.

BACKGROUND: Overt hepatic encephalopathy (OHE) is a frequent complication of decompensated cirrhosis. AIMS: A multicenter prospective observational study was performed to assess the most commonly recorded presenting manifestations of OHE and its associated health-care burden. METHODS: Qualifying patients must have experienced ≥1 OHE episode within 30 days of enrollment (qualifying OHE) and were followed for recurrence (on-study OHE). RESULTS: Two hundred and sixty-five patients were enrolled at 30 sites and followed for up to 9 months (mean 72 days). Seventy-two patients experienced 122 on-study episodes; with 72, 23, and 13 having ≥1, ≥2, or ≥3 on-study episodes with median days to occurrence of the 1st, 2nd, and 3rd episode of 34, 19, and 11, respectively. The most frequently recorded OHE manifestations included confusion (78 %), change in mental status (57 %), disorientation (48 %), lethargy (46 %), and asterixis (45 %). West Haven grade was used inconsistently and recorded for only 28 % of episodes. Most qualifying and on-study episodes occurred on rifaximin (60 and 82 %, respectively) and were associated with hospitalization (68 and 85 %, respectively). Twenty-three patients experienced ≥2 on-study episodes within 2 months of enrollment on average (median 45 days) and accounted for 60 % of on-study episodes. CONCLUSIONS: In this prospective study, OHE's most commonly recorded presenting manifestations included confusion, altered mental status, disorientation, lethargy, and asterixis. As reflected by frequent recurrence and hospitalizations, OHE, particularly the approximately 10 % of "high-resource-utilizing" patients with frequent recurrence, continues to pose a major unmet medical need and health-care burden despite the use of rifaximin.

Elevated phenylacetic acid levels do not correlate with adverse events in patients with urea cycle disorders or hepatic encephalopathy and can be predicted based on the plasma PAA to PAGN ratio.

BACKGROUND: Phenylacetic acid (PAA) is the active moiety in sodium phenylbutyrate (NaPBA) and glycerol phenylbutyrate (GPB, HPN-100). Both are approved for treatment of urea cycle disorders (UCDs) - rare genetic disorders characterized by hyperammonemia. PAA is conjugated with glutamine in the liver to form phenylacetyleglutamine (PAGN), which is excreted in urine. PAA plasma levels ≥ 500 µg/dL have been reported to be associated with reversible neurological adverse events (AEs) in cancer patients receiving PAA intravenously. Therefore, we have investigated the relationship between PAA levels and neurological AEs in patients treated with these PAA pro-drugs as well as approaches to identifying patients most likely to experience high PAA levels. METHODS: The relationship between nervous system AEs, PAA levels and the ratio of plasma PAA to PAGN were examined in 4683 blood samples taken serially from: [1] healthy adults [2], UCD patients of ≥ 2 months of age, and [3] patients with cirrhosis and hepatic encephalopathy (HE). The plasma ratio of PAA to PAGN was analyzed with respect to its utility in identifying patients at risk of high PAA values. RESULTS: Only 0.2% (11) of 4683 samples exceeded 500 µg/ml. There was no relationship between neurological AEs and PAA levels in UCD or HE patients, but transient AEs including headache and nausea that correlated with PAA levels were observed in healthy adults. Irrespective of population, a curvilinear relationship was observed between PAA levels and the plasma PAA:PAGN ratio, and a ratio>2.5 (both in µg/mL) in a random blood draw identified patients at risk for PAA levels>500 µg/ml. CONCLUSIONS: The presence of a relationship between PAA levels and reversible AEs in healthy adults but not in UCD or HE patients may reflect intrinsic differences among the populations and/or metabolic adaptation with continued dosing. The plasma PAA:PAGN ratio is a functional measure of the rate of PAA metabolism and represents a useful dosing biomarker.

Expression of variant fibronectins in wound healing: cellular source and biological activity of the EIIIA segment in rat hepatic fibrogenesis.

We have examined the cell-specific expression of two fibronectin isoforms, EIIIA and EIIIB, during experimental hepatic fibrosis induced by ligation of the biliary duct. AT the mRNA level, EIIIA and EIIIB were undetectable in normal liver but expressed early injury, preceding fibrosis. The cellular sources of these changes were determined by fractionating the liver at various time points after bile duct ligation into its constituent cell populations and extracting RNA from the fresh isolates. EIIIA-containing fibronectin mRNA was undetectable in normal sinusoidal endothelial cells but increased rapidly within 12 h of injury. By contrast, the EIIIB form was restricted to hepatic lipocytes (Ito or fat-storing cells) and appeared only after a lag of 12-24 h: it was minimal in sinusoidal endothelial cells. Both forms were minimal in hepatocytes. At the protein level, EIIIA-containing fibronectin was markedly increased within two days of injury and exhibited a sinusoidal distribution. Secretion of this form by endothelial cells was confirmed in primary culture. Matrices deposited in situ by endothelial cells from injured liver accelerated the conversion ("activation") of normal lipocytes to myofibroblast-like cells, and pretreatment of matrices with monoclonal antibody to the EIIIA segment blocked this response. Finally, recombinant fibronectin peptide containing the EIIIA segment was stimulatory to lipocytes in culture. We conclude that expression of EIIIA fibronectin by sinusoidal endothelial cells is a critical early event in the liver's response to injury and that the EIIIA segment is biologically active, mediating the conversion of lipocytes to myofibroblasts.

Endothelin antagonism in experimental hepatic fibrosis. Implications for endothelin in the pathogenesis of wound healing.

The liver's response to chronic injury is fibrosis, which is analogous to wound healing in other organs. Hepatic wounding is characterized by the "activation" of resident stellate cells (lipocytes, Ito cells) to myofibroblast-like cells that produce increased amounts of smooth muscle alpha-actin and extracellular matrix. Stellate cells possess abundant endothelin (ET) receptors (ETA/B) and, therefore, are subject to the effects of ET-1 and 3. In this study, we investigated whether ETs contribute to the activation of stellate cells and consequently, fibrogenesis. In cultured stellate cells, ET-1 and sarafotoxin S6C (a potent ETB receptor agonist) stimulated stellate cell activation, as assessed by expression of smooth muscle alpha-actin. Furthermore, the mixed ETA/B receptor antagonist, bosentan, blocked this process. Next, we administered bosentan during the induction of liver injury in two mechanistically distinct forms of hepatic wounding. Bosentan reduced levels of type I collagen and cellular fibronectin mRNAs in whole-liver tissue extracts in both models. In freshly isolated stellate cells from injured livers, bosentan reduced expression of activation markers, including smooth muscle alpha-actin and extracellular matrix mRNAs. We further demonstrate that endothelin antagonism after establishment of fibrosing injury reduced stellate cell activation and matrix production. These data indicate that ET contributes to stellate cell activation and fibrogenesis. Because ET is upregulated in diverse forms of parenchymal injury, we speculate that ET may play an important role in the wound-healing response.

Inducible nitric oxide synthase in rat hepatic lipocytes and the effect of nitric oxide on lipocyte contractility.

In liver injury, perisinusoidal cells known as lipocytes (Ito cells) undergo "activation," acquiring smooth muscle-like features and a contractile phenotype. To assess whether contraction of these cells is regulated by nitric oxide (NO), we examined the production of NO by lipocytes and the effect of NO on lipocyte contractility. Cultured lipocytes were exposed to cytokines and/or LPS. Single agents had little or no effect on the level of inducible NO synthase (iNOS) mRNA. However, interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), or LPS in combination with interferon-gamma (IFN-gamma) stimulated iNOS mRNA, which was present within 4 h after exposure. iNOS mRNA levels were paralleled by changes in nitrite (a metabolic product of NO). Intraperitoneal administration of IFN-gamma, TNF-alpha, and LPS led to rapid induction of iNOS mRNA in lipocytes, confirming in vivo the culture findings. Ligation of the common hepatic bile duct, which induces periportal-based liver injury, stimulated iNOS mRNA in lipocytes. Transforming growth factor-beta 1 decreased IFN-gamma/TNF-alpha--stimulated iNOS mRNA and nitrite. Finally, the effect of NO on lipocyte contractility was examined. In cells incubated with IFN-gamma and TNF-alpha, the contractile response to either serum or endothelin-1 was blocked. Contraction was restored entirely by an inhibitor of NO synthase, NG-monomethylarginine. Furthermore, 8-bromoguanosine 3':5'-cyclic monophosphate and sodium nitroprusside inhibited lipocyte contractility, consistent with the effect of NO induced by cytokines. We conclude that NO is a potent modulator of lipocyte contractility and may regulate this function by autocrine (or intracrine) mechanisms. Moreover, NO may play an important role in liver injury, countering the effect of contractile agonists on lipocytes.

Activation-dependent contractility of rat hepatic lipocytes in culture and in vivo.

Hepatic lipocytes are perisinusoidal cells that have been thought to be analogous to tissue pericytes, a cell type with purported vasoregulatory properties. However, we and others have recently demonstrated that lipocytes acquire markers of smooth muscle cells or myofibroblasts only after liver injury, via a process termed "activation." In this study, we document lipocyte contractility on collagen lattices and examine the importance of activation in this process. In culture, lipocytes became contractile only after spreading and activating, coincident with expression of smooth muscle alpha actin, a marker of activation (1990. Virchows Arch. B Cell Pathol. 59:349). After 5 d in culture, lipocytes induced rapid and sustained contraction of collagen lattices (to 43.7 +/- 2.3% of their original size 24 h after detachment). There was no contraction of lattices containing hepatocytes. Scanning electron microscopy demonstrated intimate associations of lipocyte cell membranes and collagen fibrils. Reduction in cell volume during contraction was also prominent. Lattice contraction by lipocytes was proportional to cell number. Serum was a potent stimulator of lipocyte contraction, as were endothelin types 1, 2, and 3; the effect of serum and endothelin 1 were additive. Neither thrombin, angiotensin-II, serotonin, nor the cytokines PDGF and TGF beta induced contraction. Cytochalasin B treatment resulted in concentration-dependent inhibition of contraction. As a test of the in vivo relevance of the culture findings, lipocytes were isolated from fibrotic animals and examined immediately after adherence. Whereas lipocytes from normal liver were initially compact, smooth muscle alpha actin negative and noncontractile, cells from animals with hepatic injury due to CCl4 displayed an activated appearance, expressed smooth muscle alpha actin, and were contractile immediately after adherence. Additionally, IFN-gamma, an agent which blocks lipocyte activation (1992. Hepatology. 16:776), inhibited lipocyte contraction. The data document that normal (i.e., quiescent) lipocytes are not contractile, but that activation is associated with the development of contractility. These findings suggest that a role for lipocytes in organ contraction or vasoregulation may be confined to injured, not normal liver.

Gene transfer of the neuronal NO synthase isoform to cirrhotic rat liver ameliorates portal hypertension.

Reduced production of nitric oxide (NO) in the cirrhotic liver results from a defect in hepatic endothelial cell nitric oxide synthase (ecNOS) and appears to contribute to the high intrahepatic resistance and portal hypertension typical of cirrhosis. Therefore, we postulated that targeting a heterologous NOS isoform to sinusoidal endothelial cells or other perisinusoidal cells, such as hepatic stellate cells, would counter the defect in NO production and reduce resistance to blood flow. Recombinant adenovirus (Ad) carrying the neuronal NOS gene (nNOS) targeted liver sinusoidal endothelial cells, stellate cells, and hepatocytes more efficiently than the corresponding cells in cirrhotic livers, but transduction rates were substantial even in cirrhotic animals. Expression of nNOS in each liver cell type, whether from normal or injured liver, caused increased NO production and inhibited endothelin-1-induced contractility of perisinusoidal stellate cells. Finally, in 2 different in vivo models of cirrhosis and portal hypertension, transduction of livers with recombinant Ad.nNOS significantly reduced intrahepatic resistance and portal pressure. The data highlight the feasibility of gene transfer to diseased liver and hepatic cells and demonstrate the potential of a novel therapy for portal hypertension caused by cirrhosis.

Analysis of air contrast barium enema, computed tomographic colonography, and colonoscopy: prospective comparison.

BACKGROUND: The usefulness of currently available colon imaging tests, including air contrast barium enema (ACBE), computed tomographic colonography (CTC), and colonoscopy, to detect colon polyps and cancers is uncertain. We aimed to assess the sensitivity of these three imaging tests. METHODS: Patients with faecal occult blood, haematochezia, iron-deficiency anaemia, or a family history of colon cancer underwent three separate colon-imaging studies--ACBE, followed 7-14 days later by CTC and colonoscopy on the same day. The primary outcome was detection of colonic polyps and cancers. Outcomes were assessed by building an aggregate view of the colon, taking into account results of all three tests. FINDINGS: 614 patients completed all three imaging tests. When analysed on a per-patient basis, for lesions 10 mm or larger in size (n=63), the sensitivity of ACBE was 48% (95% CI 35-61), CTC 59% (46-71, p=0.1083 for CTC vs ACBE), and colonoscopy 98% (91-100, p<0.0001 for colonoscopy vs CTC). For lesions 6-9 mm in size (n=116), sensitivity was 35% for ACBE (27-45), 51% for CTC (41-60, p=0.0080 for CTC vs ACBE), and 99% for colonoscopy (95-100, p<0.0001 for colonoscopy vs CTC). For lesions of 10 mm or larger in size, the specificity was greater for colonoscopy (0.996) than for either ACBE (0.90) or CTC (0.96) and declined for ACBE and CTC when smaller lesions were considered. INTERPRETATION: Colonoscopy was more sensitive than other tests, as currently undertaken, for detection of colonic polyps and cancers. These data have important implications for diagnostic use of colon imaging tests.

Inferior vena cava plethora with blunted respiratory response: a sensitive echocardiographic sign of cardiac tamponade.

To assess the diagnostic and prognostic value of the respiratory behavior of the inferior vena cava in pericardial effusions, clinical and two-dimensional echocardiographic data of 115 consecutive patients with a moderate or large effusion, including 33 who had cardiac tamponade, were reviewed. Echocardiograms were reviewed for effusion size, inferior vena cava diameter before and after deep inspiration and presence of right atrial and ventricular collapse. For the 83 patients (72%) with less than 50% decrease in inferior vena cava diameter after deep inspiration ("plethora"), inferior vena cava diameter decreased from 2.0 +/- 0.3 to 1.6 +/- 0.4 cm after inspiration (mean +/- SD) (mean decrease 18%). For the 32 patients (28%) without plethora, the diameter decreased from 1.6 +/- 0.5 to 0.6 +/- 0.3 cm (mean decrease 63%). Patients with plethora had significantly higher values for heart rate (111 +/- 21 versus 98 +/- 20 beats/min), pulsus paradoxus (24 +/- 15 versus 12 +/- 4 mm Hg), jugular venous distension (14 +/- 5 versus 8 +/- 3 cm H2O) and right atrial pressure (17 +/- 6 versus 12 +/- 6 mm Hg) and lower values for systolic blood pressure (109 +/- 22 versus 132 +/- 27 mm Hg) (all p less than 0.05) than did patients without plethora. Plethora was present in 58 (92%) of 63 patients who underwent a pericardial drainage procedure, 14 (88%) of 16 who developed constrictive physiology and 11 (92%) of 12 of those whose hospital death was related to pericardial effusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreaticopleural fistula. Report of 7 patients and review of the literature.

Pancreaticopleural fistula is an uncommon clinical condition. Its presentation is often confusing because of the paucity of clues suggestive of pancreatic disease and the preponderance of pulmonary symptoms and signs. Most patients are alcoholics but only one-half will have a clinical history of previous pancreatitis. Pleural effusions are large, recurrent, and highly exudative in nature. Many patients go through extensive pulmonary evaluation before the pancreas is identified as the site of primary pathology. An elevated serum amylase may be the first clue to the diagnosis. However, the key to the diagnosis is a dramatically elevated pleural fluid amylase. Effusions in association with acute pancreatitis, esophageal perforation, and thoracic malignancy are important to consider in the differential diagnosis of an elevated pleural fluid amylase but are usually easy to exclude. Computed tomography is excellent in defining pancreatic abnormalities and should be the first abdominal imaging study in suspected cases. Endoscopic retrograde cholangiopancreatography (ERCP) is used as a diagnostic tool only in confusing cases. Although no systematic study evaluates medical versus surgical therapy, we recommend an initial 2 to 4-week trial of medical therapy, including allowance of no oral intake, total parenteral nutrition, chest tube thoracostomy, and possibly a regimen of somatostatin or its analogs. The major complication in these patients is superinfection, which results in significant morbidity and mortality. Failure of medical therapy should be considered failure of pleural effusion(s) to clear, recurrence after reinstatement of oral intake, or superinfection. For those patients who fail to benefit from medical therapy, surgery is indicated.(ABSTRACT TRUNCATED AT 250 WORDS)

Pyogenic liver abscess. Changes in etiology, management, and outcome.

Pyogenic liver abscess (PLA) is an important entity with a changing clinical spectrum and may be more prevalent than previously reported. PLA remains most common in older patients, although we found a trend in age range downward. In contrast to earlier reports, PLA affected male and female patients with equal frequency. The most common known cause of PLA remains biliary tract disease, but the majority of patients with PLA were those in whom no underlying cause of PLA could be identified. Single PLA was more common than multiple PLA regardless of etiology. The clinical presentation of patients with PLA ia nonspecific and emphasizes the fact that a high index of suspicion is often required to make the diagnosis. Jaundice and a markedly elevated alkaline phosphatase are clues to the possibility of biliary tract involvement, but may not distinguish patients with liver abscess from those with other hepatic processes. While plain chest and abdominal X-rays were often abnormal and may point to the right upper quadrant as a source of abnormality, ultrasound (US) and abdominal computed tomography (CT) play a central role in this disease. Not only are they often paramount in elucidating the diagnosis of PLA, but US and CT are critical because of their ability to provide other useful information that may address the cause of PLA (that is the biliary tract, and in the case of abdominal CT, other structures). Further, our data suggest that in patients without clinical or imaging evidence of biliary tract disease or pylephlebitis, aggressive random evaluation of the intestinal tract is unwarranted. Percutaneous drainage combined with intravenous antibiotics was the most common therapeutic modality and resulted in cure in 76% of all patients in which it was used (compared to 65% with antibiotics alone and 61% with surgery) and has been successful in 90% of patients over the last 5 years (n = 50). In this study, percutaneous catheter drainage (PCD) appeared to result in a higher cure rate than percutaneous needle aspiration (PNA) but comparative studies are required to further address and determine their relative efficacies. Intravenous antibiotics alone are an important option in carefully selected patients. Surgical intervention as a primary mode of therapy has been almost completely replaced by less invasive approaches such as PCD/PNA, but remains an important consideration in patients who fail these therapies. Although PLA was once considered a fatal disease, the prognosis is now excellent. We have identified a subgroup of patients with no or low-level elevations in bilirubin and alkaline phosphatase and most often single right-sided PLA who do not have a readily identifiable cause of PLA (that is, cryptogenic), as having a particularly favorable prognosis. Death due to PLA is now limited primarily to those patients with severe underlying disease processes, including malignancy.

Ischemic hepatitis: clinical presentation and pathogenesis.

BACKGROUND: The pathophysiology of ischemic hepatitis, otherwise known as "shock liver," is poorly understood, although it is believed to be the result of a reduction in systemic blood flow as typically occurs in shock. The aim of this study was to investigate the importance of this phenomenon as well as other clinical features in patients with ischemic hepatitis. METHODS: We identified a cohort of 31 patients (case group) who met the most commonly accepted definition of ischemic hepatitis (an acute reversible elevation in either the serum alanine or aspartate aminotransferase level of at least 20 times the upper limit of normal, excluding known causes of acute hepatitis or hepatocellular injury, in an appropriate clinical setting). We also evaluated the clinical features and serum aminotransferase levels in a cohort (the control group) of 31 previously healthy patients who sustained major nonhepatic trauma at San Francisco General Hospital, a major trauma center. Both groups of patients had documented systolic blood pressures <75 mm Hg for at least 15 minutes. Clinical and hemodynamic (invasive and noninvasive) data were recorded. RESULTS: Despite the marked reduction in blood pressure, no patient in the control group developed ischemic hepatitis. The mean (+/- SD) peak serum aspartate aminotransferase level in the control group was only 78 +/- 72 IU, in contrast with a mean peak of 2,088 +/- 2,165 IU in the case group. All 31 patients with ischemic hepatitis had evidence of underlying organic heart disease, 29 (94%) of whom had right-sided heart failure. CONCLUSIONS: Systemic hypotension or shock alone did not lead to ischemic hepatitis in any patient. The vast majority of patients with ischemic hepatitis had severe underlying cardiac disease that had often led to passive congestion of the liver. These data lead us to propose that right-sided heart failure, with resultant hepatic venous congestion, may predispose the liver to hepatic injury induced by a hypotensive event.

Asymptomatic chronic gastrointestinal blood loss in patients taking aspirin or warfarin for cardiovascular disease.

OBJECTIVE: To determine whether low-dose aspirin or warfarin induces fecal occult blood loss. PATIENTS AND METHODS: A prospective, cross-over study, of 100 participants over 40 years of age in 1 of 3 groups, taking: (1) no aspirin or warfarin, (2) daily aspirin (either 81 or 325 mg), or (3) warfarin, but no aspirin. Stool samples were collected and analyzed for the presence of occult blood using HemoQuant and Hemoccult II. After collection of baseline samples, patients initially taking no aspirin (group 1) were asked to take regular aspirin (325 mg daily) for 2 months. Patients initially taking aspirin 81 mg daily (group 2) were switched to 325 mg daily for 2 months, and vice versa. RESULTS: Patients taking no aspirin had mean fecal blood of 0.68 +/- 0.05 mg hemoglobin/g stool, which increased to 1.41 +/- 0.36 mg/g after taking 325 mg of aspirin daily (P = 0.02). In contrast, patients in group 2, taking 81 mg and 325 mg of aspirin, had mean fecal blood of 0.82 +/- 0.08 mg/g (P = 0.57) and 1.04 +/- 0.23 mg/g (P = 0.13), respectively (comparisons with patients taking no aspirin). The mean blood loss in patients taking warfarin was 0.51 +/- 0.04 mg/g (P = 0.55), and fecal blood was not related to the degree of anticoagulation. There was no increase over normal in the rate of Hemoccult II-positive stool tests with aspirin or warfarin therapy. CONCLUSION: Aspirin, but not warfarin, caused a small but clinically insignificant increase in occult fecal blood. The small blood loss in patients taking aspirin or warfarin is unlikely to interfere with fecal occult blood test. Therefore, positive fecal occult blood tests, in patients taking either low-dose aspirin or warfarin, should be managed in the same fashion as patients not taking these medications.

Preliminary evaluation of 15-[18F]fluoro-3-oxa-pentadecanoate as a PET tracer of hepatic fatty acid oxidation.

UNLABELLED: The liver is an important site of fat oxidation. Abnormalities of hepatic mitochondrial fatty acid oxidation (HMFAO) are associated with obesity, type II diabetes, alcoholic hepatitis, and nonalcoholic steatohepatitis. Noninvasive assessment of HMFAO by PET has been impeded by the lack of a specific radiotracer. METHODS: No-carrier-added 15-[18F]fluoro-3-oxa-pentadecanoate (FOP) was synthesized and evaluated in living rats and isolated rat livers. RESULTS: FOP showed high uptake and slow clearance of radioactivity from livers in living rats. Inhibition of HMFAO by pretreatment of fasting rats with the carnitine palmitoyltransferase-I (CPT-I) inhibitor reduced the liver-to-blood ratio by 64%. In isolated rat livers, perfused in normoxic (95% O2) and hypoxic (15% O2) conditions with glucose (5 mmol/L) and palmitate (0.15 mmol/L), the externally measured kinetics of FOP showed reversible binding in tissue. The kinetics were adequately fit by a catenary 2-compartment model for estimation of tracer distribution volumes (DVs). The DVs of both compartments were found to correlate with fractional palmitate oxidation rate (FPOR) in experiments in normoxic and hypoxic conditions. The correlation was particularly strong for the slower second compartment (DV2 [mL/g dry weight] = 34.1 FPOR [mL/min/g dry weight] - 0.7, r = 0.89). Relatively small levels of diffusible metabolites of FOP were formed in vivo and in isolated rat liver. CONCLUSION: The selective uptake of FOP by liver and the high sensitivity of hepatic FOP DV to changes of HMFAO with CPT-I inhibition and hypoxia suggests potential usefulness for the 3-oxa fatty acid analog in assessments of hepatic mitochondrial oxidation of exogenous fatty acids with PET. These data emphasize that further studies are required to clarify the intracellular disposition of FOP in the liver and test its validity as a tracer of HMFAO over a broad range of conditions.

The cell and molecular biology of hepatic fibrogenesis. Clinical and therapeutic implications.

Much has been learned in the past 2 decades about the cellular and molecular mechanisms underlying hepatic fibrogenesis and about potential therapeutic approaches in patients with liver disease. The central event in fibrogenesis seems to be the activation of hepatic stellate cells. Stellate cell activation is characterized by several important features, including enhanced matrix synthesis and a prominent contractile phenotype, processes that probably contribute to the physical distortion and dysfunction of the liver in advanced disease. It is important to emphasize that the factors controlling activation are multifactorial and complex. The extracellular matrix is a dynamic, active constituent of the fibrogenic response and undergoes active remodeling, including synthesis and degradation. Effective therapy for hepatic fibrogenesis will probably also be multifactorial, based on the basic mechanisms underlying the fibrogenic process. The most effective therapies will probably be directed at the stellate cell. Approaches that address matrix remodeling (i.e., by enhancing matrix degradation or by inhibiting factors that prevent matrix breakdown) may be effective.

Cellular pathophysiology of portal hypertension and prospects for management with gene therapy.

In summary, regulation of sinusoidal blood flow in normal and injured liver involves structural, cellular, and humoral components. Available data suggest that stellate cells, resident perisinusoidal mesenchymal cells with a histologic orientation in the sinusoid analogous to [figure: see text] vasoregulatory pericytes, modulate sinusoidal blood flow. This regulation by stellate cells is most evident in the context of liver injury but may apply also to the normal liver. The endothelin and NO systems are important in modulating stellate cell contractility, and their degree of equilibrium is significant in determining the level of local intrahepatic resistance, especially in the injured liver. Manipulation of either or both of these systems is feasible and effective in experimental models. Such findings have obvious clinical implications and are expected to set the [figure: see text] stage for novel gene therapy approaches for treatment of patients with portal hypertension.

New concepts in the pathogenesis of portal hypertension: hepatic wounding and stellate cell contractility.

The pathogenesis of portal hypertension is multifactorial, and appears to result from interplay between fixed and dynamically modulable elements; the stellate cell is a newly recognized example of the latter. This perisinusoidal, pericyte-like cell has contractile features that are most prominent after liver injury, concomitant with their activation. These data imply an exaggerated contractile phenotype in the cirrhotic liver. This cell may contribute to increased intrahepatic portal hypertension via perisinusoidal constriction of the sinusoid or by contraction of fibrous extracellular matrix rich in type I collagen with concomitant disruption of lobular architecture. Endothelins and NO play a major role in the modulation of stellate cell contractility, and are therefore important in the pathogenesis of intrahepatic portal hypertension. These new data provide potential areas for therapeutic intervention in this clinical entity.

Systematic review: terlipressin in acute oesophageal variceal haemorrhage.

BACKGROUND: Controversy exists surrounding pharmacological therapy in acute variceal bleeding. AIM: To determine the efficacy and safety of terlipressin. METHODS: Randomized trials were identified and duplicate, independent, review identified 20 randomized trials involving 1609 patients that compared terlipressin with placebo, balloon tamponade, endoscopic treatment, octreotide, somatostatin or vasopressin for treatment of acute oesophageal variceal haemorrhage. RESULTS: Meta-analysis showed that compared to placebo, terlipressin reduced mortality (relative risk 0.66, 95% CI 0.49-0.88), failure of haemostasis (relative risk 0.63, 95% CI 0.45-0.89) and the number of emergency procedures per patient required for uncontrolled bleeding or rebleeding (relative risk 0.72, 95% CI 0.55-0.93). When used as an adjuvant to endoscopic sclerotherapy, terlipressin reduced failure of haemostasis (relative risk 0.75, 95% CI 0.58-0.96), and had an effect on reducing mortality that approached statistical significance (relative risk 0.74, 95% CI 0.53-1.04). No significant difference was demonstrated between terlipressin and endoscopic sclerotherapy, balloon tamponade, somatostatin or vasopressin. Haemostasis was achieved more frequently with octreotide compared to terlipressin (relative risk 1.62, 95% CI 1.05-2.50), but this result was based on unblinded studies. Adverse events were similar between terlipressin and the other comparison groups except for vasopressin, which caused more withdrawals due to adverse events. CONCLUSIONS: Terlipressin is a safe and effective treatment for acute oesophageal variceal bleeding, with or without adjuvant endoscopic sclerotherapy. Terlipressin appears to reduce mortality in acute oesophageal variceal bleeding compared to placebo, and is the only pharmacological agent shown to do so. Future studies will be required to detect potential mortality differences between terlipressin and other therapeutic approaches.

Interferon gamma inhibits lipocyte activation and extracellular matrix mRNA expression during experimental liver injury: implications for treatment of hepatic fibrosis.

BACKGROUND: A central feature of liver injury involves activation of hepatic lipocytes (perisinusoidal cells), a process characterized by their morphologic transformation to myofibroblast-like cells. Important features of this process include new expression of smooth muscle alpha actin and production of increased amounts of extracellular matrix. Interferon gamma is a cytokine with immunomodulatory and antifibrotic properties that has potent effects on lipocytes in a culture model of activation. The aim of this study was to determine if interferon gamma inhibited lipocyte activation in an in vivo model of liver injury and whether this effect resulted in an overall reduction in hepatic fibrosis. METHODS: Liver injury (with ensuing fibrosis) was induced by carbon tetrachloride. Interferon gamma was infused continuously by osmotic pump during the induction of liver fibrosis, after which lipocytes were isolated and features of lipocyte activation were examined. Finally, whole liver type I collagen mRNA was quantitated. RESULTS: Carbon tetrachloride caused histological fibrosis, which was significantly reduced on a quantitative basis by interferon gamma. Immunocytochemical analysis of livers from animals treated with interferon gamma demonstrated a significant reduction in the number of desmin positive cells (lipocytes) in portal and noncentral lobular areas as well as in bands of fibrosis, consistent with reduced lipocyte proliferation. Using discontinuous density centrifugation, two populations of lipocytes were isolated and characterized: one migrating in the upper layer of the gradient and another to the lower layer. Interferon gamma markedly reduced smooth muscle alpha actin expression (by immunoblot) in upper layer lipocytes and had significant inhibitory but less dramatic effects on lower layer lipocytes. Interferon gamma also reduced collagen I mRNA to 36% (p < 0.001, interferon gamma versus control) and 46% (p < 0.01) of control values in upper and lower layer lipocyte samples, respectively. Effects of interferon gamma on expression of cellular fibronectin mRNA were similar. Smooth muscle actin as well as type I collagen and cellular fibronectin mRNA were more abundant in lower than upper layer lipocytes in both control and interferon gamma treated animals. Finally, interferon gamma reduced collagen I mRNA in whole liver specimens to 36% of control values (p < 0.005, for interferon gamma compared to control, n = 6). CONCLUSIONS: The data indicate that interferon gamma inhibits lipocyte activation and extracellular matrix production in vivo during liver injury, which results in an overall decrease in hepatic fibrosis. Further, the data demonstrate heterogeneity in lipocytes during activation and identify a novel population of markedly activated lipocytes.