Synthesis of phospholipid-conjugated bile salts and interaction of bile salt-coated liposomes with cultured hepatocytes

To examine the possibility of targeting liposomes to hepatocytes via bile salts, the bile salt lithocholyltaurine was covalently linked to a phospholipid. The isomeric compounds disodium 3alpha-(2-(1,2-O-distearoyl-sn-glycero-3-phospho-2'-ethanolamidosuccinyloxy)ethoxy)-5beta-cholan-24-oyl-2'-aminoethansulfonate and disodium 3beta-(2-(1,2-O-distearoyl-sn-glycero-3-phospho-2'-ethanolamidosuccinyloxy)ethoxy-5beta-cholan-24-oyl-2'-aminoethansulfonate (DSPE-3beta-LCT) were synthesized and incorporated into liposomal membranes. Confocal laser scanning microscopy studies showed that bile salt-bearing liposomes (BSLs) attach to the surface of rat hepatocytes in culture. Studies with radioactively labeled liposomes revealed that the bile salt linked via the 3beta-conformation resulted in a higher attachment efficiency than that with the 3alpha-derivative. In the presence of BSLs corresponding to 2 mM liposomal phosphatidylcholine, uptake of 50 microM cholyltaurine (CT) into hepatocytes was reduced by approximately 40% by the 3beta-derivative and by approximately 17% by the 3alpha-derivative. When added simultaneously with the liposomes, CT up to 75 microM inhibited the binding of DSPE-3beta-LCT-bearing liposomes. By contrast, increasing concentrations reversed this inhibition and resulted in an increased bile salt-mediated binding. The same was true when CT was added 10 min before the liposomes were added. The attachment of BSLs to the surface of hepatocytes opens up promising possibilities for hepatocyte-specific drug delivery. More generally, not only substrates for cellular endocytosing receptors but also substrates for cellular carrier proteins should be suitable ligands for the cell-specific targeting of nanoscale particles such as liposomes.

[Seizures following Billroth II gastrectomy]

HISTORY

A 64-year old somnolent man was admitted to the emergency department with a reported seizure half an hour earlier. Due to similar episodes the patient had been treated with antiepileptics in the past. The patient s past history revealed a partial gastrectomy (Billroth II) more than ten years ago.

DIAGNOSTIC FINDINGS AND THERAPY

At the time of admission blood glucose was 31 mg/dl. Other routine laboratory analyses and the clinical examination were normal. In addition, a detailed neurological examination and a cranial CT-scan were normal. Due to the hypoglycemia a dumping syndrome was suspected. A three hour oral glucose tolerance test (OGTT) resulted in a late hypoglycemia, establishing the diagnosis of late dumping. After adaptation of the patient's diet no further hypoglycemic episodes occurred.

CONCLUSION

Manifestation of a dumping syndrome may occur even years after gastrectomy. Therefore, in patients presenting with hypoglycemia and a history of gut surgery, a dumping syndrome should be suspected. Furthermore, seizures due to hypoglycemia may be the only manifestation of late dumping.

Genetic variants of hepatitis B virus and their clinical relevance

Infection with hepatitis B virus (HBV) leads to a wide spectrum of clinical presentations ranging from an asymptomatic carrier state to self-limited acute or fulminant hepatitis to chronic hepatitis with progression to cirrhosis and hepatocellular carcinoma (HCC). Infection with HBV is one of the most common viral diseases affecting man. Both viral factors as well as the host immune response have been implicated in the pathogenesis and clinical outcome of HBV infection. Evidence has been accumulating that HBV mutants are associated with certain clinical disease manifestations, may affect the natural course of the infection and confer resistance to antivirals. Naturally occurring mutations have been identified in the structural and non-structural genes as well as regulatory elements of the virus. The best characterized mutants comprise the pre-core (pre-C) stop codon mutation resulting in a loss of hepatitis B e antigen (HBeAg), defined clusters of mutations in the core promotor resulting in enhanced viral replication and mutations in the hepatitis B core and surface antigens (HBcAg and HBsAg) altering the antigenicity of the virus. More recently, several mutations in the reverse transcriptase/polymerase gene have been identified conferring resistance to antivirals used for the treatment of chronic hepatitis B. In this review, we will focus on the biological phenotype of HBV genetic variants and discuss their clinical relevance for the pathogenesis of HBV-induced liver disease.

T cell response in hepatitis C virus infection

Hepatitis C virus (HCV) is a hepatotropic RNA virus that causes acute and chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. It is widely accepted that cellular immune responses play an important role in viral clearance and disease pathogenesis. However, HCV often evades effective immune recognition and has a propensity to persist in the majority of acutely infected individuals (ca. 80%). The immunological and virological basis for the inefficiency of the cellular immune response to clear or control the virus is not known. Recent studies, however, have provided new insights into the mechanisms of viral clearance and persistence that will be discussed in detail.

[Gene therapy for liver diseases--facts or fiction]

Molecular analyses have become an integral part of biomedical research as well as clinical medicine. The definition of the molecular and genetic basis of many human diseases has led to a better understanding of their pathogenesis and has in addition offered new perspectives for their diagnosis, treatment and prevention. Genetically, human diseases can be classified as hereditary monogenetic, acquired monogenetic and acquired complex genetic diseases. Based on this classification, gene therapy is based on four concepts: gene repair or substitution, block of gene expression (triple helix formation, sense strategy, ribozymes, small interfering (si) RNAs and gene augmentation as well as DNA vaccination. While recent developments are promising, various delivery, targeting and safety issues need to be addressed before gene therapy will enter clinical practice. In the future, gene therapy of liver diseases may become part of our patient management and complement existing therapeutic strategies.

[Diagnosis of hepatitis B and C]

Diagnosis of hepatitis B and C is based on sensitive and specific serological assays. Molecular assays for the detection of HBV DNA or HCV RNA are in some instances needed to confirm the diagnosis. However, their principal role is in the therapeutic decision making and in the monitoring of antiviral therapy.

[Esophageal carcinoma: non-surgical therapy]

Esophageal carcinoma is one of the most common cancers in the world. There is a rising incidence of adenocarcinoma of the esophagus in Western countries. The present standard of care of patients with early tumors (Tis-T1 N0-N1 M0) is surgery and there is no role for chemo- or radiotherapy. Surgical treatment of stage II patients with locally resectable tumors is associated with poor survival figures due to an increase of regional and distant lymph node metastases. Adjuvant chemotherapy should be used only in the setting of clinical trials. The role of neoadjuvant chemo-radiotherapy in patients with resectable tumors is controversial. There is also evidence that some patients with a complete response after chemo-radiotherapy do not have a further benefit from surgical treatment. Therefore, the appropriate application of these varied therapeutic interventions should be performed at specialized centers. The role of chemotherapy and radiation is now established in locally advanced inoperable disease. How best to deliver these modes of therapy has yet to be defined. Prospective randomised trials are the only way to define the best therapeutic strategies for the different subgroups of patients with esophageal carcinoma. Progress with newer chemotherapy agents, optimal radiotherapy protocols and innovations are likely to improve responses to combination treatments, but may more importantly limit associated toxicity. Future trials should also assess quality of life indices as end points, that are of particular importance in populations with a median survival of approx, one year. Patients with stage IVb esophageal carcinoma have a life expectancy of less than six months and palliative teatment strategies should primarily aim at the improvement of tumor related symptoms and the maintenance of nutrition.

[Hepatitis C]

Hepatitis C virus (HCV) infection is a leading cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Here, we briefly review the virology, diagnosis and therapy of hepatitis C. Standard therapy with pegylated interferon-alpha and ribavirin results in a sustained virological response in 40-50% of genotype 1- and in about 80% of genotype 2- or 3-infected patients. Recent progress has allowed the identification of novel antiviral targets and therapeutic strategies. These will likely complement existing therapeutic modalities in the near future.

["Medical futility": the doctor caught between the demands for and the limitations of treatment]

The term medical futility is applied to justify withholding treatments in patients who are likely to gain minimal benefit. Futility refers to limiting the moral obligation to provide medical treatment on the basis of clinical efficacy. Current discussions about the meaning of medical futility revolve around two distinct but related concerns. Firstly, whether it is possible to define medical futility in a way that enables objective assessment. Secondly, who should determine when a treatment is futile. In this article we summarize the debate about futility and discuss the relevance of this concept.

Cholestatische Hepatopathien

Zu den autoimmunen cholestatischen Hepatopathien rechnet man die primär biliäre Zirrhose (PBC), die Autoimmuncholangitis (AIC, Synonym: AMA-negative PBC) und die primär sklerosierende Cholangitis (PSC). Überlappungssyndrome weisen sowohl Charakteristika von cholestatischen Leberkrankungen als auch einer Autoimmunhepatitis auf. Bei der PBC sind alkalische Phosphatase und gamma-GT erhöht, in geringerem Ausmaß auch die Transaminasen, die Histologie zeigt Gallengangsläsionen. Anti-mitochondriale Antikörper sind charakteristisch. Die Gabe von Ursodeoxycholsäure (UDC) ist die etablierte Therapie und kann – zumindest in frühen Stadien – die Progredienz aufhalten oder verlangsamen. Bei fehlendem Ansprechen kann eine Immunsuppression versucht werden. Die PSC ist meist mit einer chronisch entzündlichen Darmerkrankung assoziiert. P-ANCA sind häufige Autoimmunmarker. Meist wird die Diagnose durch die typischen Veränderungen der Gallenwege bei der ERCP gestellt. UDC wird zur Therapie eingesetzt. Gallengangsstrikturen oder Cholangitiden sind sekundäre Folgen und können mit Antibiotika oder Dilatationen der Gallenwege behandelt werden. PBC und PSC führen letztlich zur Leberzirrhose. Bei fortgeschrittener Erkrankung ist eine Lebertransplantation indiziert.

Hereditäre Lebererkrankungen

In den vergangenen Jahren ist es gelungen, die genetischen Defekte, die zur Entstehung hereditärer Lebererkrankungen beitragen, zu identifizieren und darauf basierende Konzepte der Pathogenese der Erkrankungen zu entwickeln. Zu den häufigsten hereditären Lebererkrankungen gehören die Hämochromatose, der Morbus Wilson und der alpha1-Antitrypsin Mangel. Obgleich der Nachweis der Gendefekte zu einem besseren Verständnis der Erkrankungen führte, spielt der Nachweis der Mutationen nur eine untergeordnete diagnostische Rolle. In dieser Arbeit werden Klinik, Diagnostik und Therapie der häufigsten hereditären Lebererkrankungen zusammenfassend dargestellt.

[Suppressor T-cells: immunologic regulator cells and clinical perspectives]

Regulatory T cells modulate immune responses in different clinical settings. Here, we summarize the role of CD4(+)CD25(+) regulatory T cells in autoimmunity, transplantation, infectious diseases and tumor immunity.

[Best supportive care of hepatocellular carcinoma]

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in some areas of the world. The major etiologic risk factors include toxins (alcohol, aflatoxin B(1)), hepatitis B and C virus infection as well as various inherited metabolic disorders. The prognosis of HCC patients is generally very poor with a 5-year survival rate of less than 5%. The diagnosis is based on biochemical and imaging tests as well as histology. Therapeutic strategies include surgery (resection or liver transplantation) and non-surgical interventions, such as percutaneous ethanol injection or radiofrequency thermal ablation as well as transarterial embolization or chemoembolization. Radio- or chemotherapy are mostly ineffective. Therefore, the development and evaluation of novel HCC treatment strategies as well as the implementation of existing and the development of new measures to prevent HCC are of utmost importance. The better understanding of the clinical and molecular pathogenesis of HCC should lead to improved diagnostic, therapeutic and preventive strategies with the aim to reduce the incidence of HCC, one of the most devastating malignancies worldwide.

[Local ablation of malignant lesions of the liver - potential applications and limitations of the different methods]

Malignant lesions of the liver are among the most frequent and difficult problems in clinical practice. Liver tumors can be classified as primary (hepatocellular carcinoma HCC, cholangiocarcinoma CC) and secondary liver lesions (metastasis). The therapeutic principle of resecting liver tumours, applies to both types of liver lesions. Unfortunately many patients with primary and secondary liver lesions are inoperable because of technical difficulties or comorbidity. This stimulated the development of percutaneous ablation methods. These procedures allow to destroy tumors percutaneously with alcohol, acetic acid, radiofrequency, microwaves or laser. Potential applications and limitations of the methods are discussed.

[The role of the virus specific T-cell response in acute and chronic HBV and HCV infection]

Infections with hepatitis B (HBV) and hepatitis C virus (HCV) are worldwide one of the most frequent causes for chronic liver disease, liver cirrhosis and hepatocellular carcinoma. The mechanisms responsible for the elimination or the persistence of the virus are not well understood. The immunopathogenesis of HBV and HCV infection is primarily mediated by virus specific CD4+- and CD8+-T-cells. During acute infection a strong and multispecific T-cell response against different viral epitopes can be detected and is associated with the clearance of the virus. In case of viral persistence virus specific T-cells contribute to liver inflammation. In this article we summarize the current concepts about the role of the virus specific T-cell response in acute and chronic HBV and HCV infection.

Immunobiology and gene-based immunotherapy of hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is one of the major malignancies worldwide. For most patients with advanced or multifocal HCC treatment options are limited resulting in a poor prognosis. Several local ablation methods have been developed as minimally invasive strategies for HCC treatment. It is unclear, until now, whether these therapies will significantly improve the poor prognosis of patients with unresectable HCC. Novel therapeutic strategies and a better understanding of HCC imunobiology are, therefore, urgently required.

DESIGN

The scientific literature since 1970 in all languages cited in Medline was systematically reviewed.

RESULTS

Until now, a variety of specific and non-specific immunostimulatory strategies against HCC has been applied in preclinical experimental models with some promising results. The molecular characterization of HCC associated tumour antigens such as alpha-fetoprotein (AFP) and the increased understanding of the immunological pathways involved in liver and tumor immunology have paved the way for the design of promising gene-based cancer vaccines. The first phase I and II immunotherapeutic clinical trials based on dendritic cell immunotherapy and peptide vaccines are ongoing in HCC-patients. Clinical trials have, in general, demonstrated the safety of such strategies. Recently, exciting new immunological techniques and tools have been developed which allow to characterize antigen specific T cells at a single-cell level. In future, HCC specific tumor rejection antigens which can be used therapeutically have to be identified using microarray-based analysis. The different therapeutic modalities need to be compared directly resulting in optimised therapeutic approaches and the identification of sub-groups of HCC-patients responding favourably to treatment.

[Systemic treatment for hepatocellular carcinoma]

Hepatocellular carcinoma (HCC) is one of the most frequent malignancies worldwide. A variety of pharmacological strategies has been evaluated in the treatment of HCC: classical chemotherapy, tamoxifen, octreotide, thymostimulin, pravastatin, (131)I-lipiodol as well as transarterial chemoperfusion (TAC) and chemoembolisation (TACE). TACE monotherapy or TACE combined with pravastatin resulted in a survival benefit of selected HCC patients. New strategies such as immunotherapy, antiangiogenic agents or cyclooxygenase inhibitors are under clinical investigation and might play a role in future therapies for HCC. Efficient strategies for the primary prevention of HCC are available and promising concepts in the secondary prevention have been reported.