ABSTRACT
BACKGROUND: Hepatitis C virus (HCV) infection is a major cause of human hepatocellular carcinoma (HCC). The precise mechanism of hepatocarcinogenesis in humans by HCV is currently unclear. It was recently shown, however, that transgenic mice with the HCV core gene often develop HCC, suggesting tumorigenic activity of the HCV core protein. Further, the HCV core protein expressed in HepG2 cells transfected with the core gene was shown to stimulate proliferation of transfectants through activation of nuclear factor-kappaB (NF-kappaB). The downstream target molecule(s) of NF-kappaB activated by the HCV core protein to evoke cell proliferation is not yet identified. Transforming growth factor (TGF) alpha, which is often overexpressed in various tumour tissues such as HCC, has been shown to stimulate hepatocyte proliferation through activation of the mitogen-activated protein kinase or extracellular signal-related protein kinase (MAPK/ERK) cascade. AIMS: To explore the possibility that TGFalpha might be a target molecule for NF-kappaB activated by the HCV core, and that TGFalpha participates in the growth promotion of the core transfectants in an autocrine manner, activating the MAPK/ERK pathway. METHODS: A HCV core expression vector was transfected into human hepatoma Huh-7, HepG2 and Hep3B cells. NF-kappaB activity was examined by an electrophoretic mobility shift assay. TGFalpha transcription was assessed by a luciferase reporter assay. TGFalpha protein was determined by immunoblot and ELISA. MAPK/ERK activity was examined by an in vitro kinase assay. Cell proliferation was assessed by a water-soluble tetrazolium salt-1 assay. RESULTS: In the HCV core transfectants, NF-kappaB bound to the kappaB site in the TGFalpha proximal promoter region, resulting in an increase in TGFalpha transcription. Immunoblot as well as ELISA showed increased TGFalpha expression in the HCV core transfectants. SN50, a specific inhibitory peptide for NF-kappaB, cancelled HCV core-induced TGFalpha expression. HCV core protein increased cell proliferation as well as ERK activity of the HCV core transfectants as compared with the mock transfectants. The growth-promoting activity and activation of ERK by the HCV core protein were negated by treatment with anti-TGFalpha antibodies. CONCLUSIONS: These results suggest that the HCV core protein promotes proliferation of human hepatoma cells by activation of the MAPK/ERK pathway through up regulation of TGFalpha transcription via activation of NF-kappaB. Our finding provides a new insight into the mechanism of hepatocarcinogenesis by HCV infection.
Subject(s)
Carcinoma, Hepatocellular/physiopathology , Hepacivirus/metabolism , Liver Neoplasms/physiopathology , NF-kappa B/metabolism , Transforming Growth Factor alpha/metabolism , Viral Core Proteins/metabolism , Carcinoma, Hepatocellular/genetics , Carcinoma, Hepatocellular/metabolism , Cell Division/physiology , Cell Line, Tumor , Enzyme Activation , Hepacivirus/genetics , Humans , Liver Neoplasms/genetics , Liver Neoplasms/metabolism , Mitogen-Activated Protein Kinases/metabolism , NF-kappa B/antagonists & inhibitors , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Peptides/pharmacology , Transcription, Genetic/drug effects , Transcription, Genetic/genetics , Transfection , Transforming Growth Factor alpha/analysis , Transforming Growth Factor alpha/genetics , Viral Core Proteins/geneticsABSTRACT
Acute axonal polyneuropathy and Wernicke-Korsakoff encephalopathy developed simultaneously in three patients. Nerve conduction studies (NCS) detected markedly decreased compound muscle action potentials (CMAPs) and sensory nerve action potentials (SNAPs) with minimal conduction slowing; sympathetic skin responses (SSRs) were also notably decreased. Sural nerve biopsies showed only mild axonal degeneration with scattered myelin ovoid formation. The symptoms of neuropathy lessened within two weeks after an intravenous thiamine infusion. CMAPs, SNAPs, and SSRs also increased considerably. We suggest that this is a new type of peripheral nerve impairment: physiological conduction failure with minimal conduction delay due to thiamine deficiency.
Subject(s)
Axons/physiology , Korsakoff Syndrome/etiology , Korsakoff Syndrome/physiopathology , Neural Conduction/physiology , Polyneuropathies/etiology , Polyneuropathies/physiopathology , Thiamine Deficiency/complications , Thiamine Deficiency/physiopathology , Acute Disease , Adult , Axons/drug effects , Humans , Korsakoff Syndrome/drug therapy , Male , Middle Aged , Neural Conduction/drug effects , Polyneuropathies/drug therapy , Thiamine/therapeutic use , Thiamine Deficiency/drug therapyABSTRACT
We developed new sandwich cup method to assay the penetration of various antimicrobial agents through Pseudomonas exopolysaccharides. Using alginate extracted from mucoid-type Pseudomonas aeruginosa and gellan gum from Pseudomonas elodea, the role of exopolysaccharides as a barrier against drug penetration was examined. The penetration of positively charged hydrophilic drugs such as aminoglycosides and polypeptides was markedly inhibited by the gels tested, but that of beta-lactams, quinolones, and macrolides was not inhibited. The penetration of gentamicin was strongly influenced by the gel concentration, the solution to be used, and the presence of Ca2+. These results suggest that the microenvironment at the infection site could greatly influence drug penetration through biofilms in vivo.
