Targeted inhibition of hepatitis C virus-directed gene expression in human hepatoma cell lines

BACKGROUND & AIMS

The 5'-nontranslated region (NTR) of hepatitis C virus (HCV) contains important elements that control HCV translation. The aim of this study was to determine whether antisense oligonucleotides against the NTR of the HCV genome can be targeted to inhibit HCV gene expression.

METHODS

Antisense oligonucleotides directed against a sequence in the internal ribosomal binding site of the NTR (anti-III) and a portion of the NTR overlapping the core protein translational start site of HCV (anti-IV) were prepared. In transient transfections of a plasmid containing a luciferase gene immediately downstream from an HCV NTR insert, oligonucleotides anti-III and anti-IV in the form of asialoglycoprotein-polylysine complexes were administered to Huh7 cells, and luciferase activity generated by cytomegalovirus (CMV) HCVluc was measured.

RESULTS

Anti-III inhibited luciferase activity by 75% and 99% at 0.01 mumol/L and 0.1 mumol/L, respectively. Similarly, anti-IV inhibited luciferase activity 88% and 99% at 0.01 mumol/L and 0.1 mumol/L, respectively. In cell lines stably transfected with CMV HCVluc plasmid, complexed anti-III inhibited luciferase activity in Huh7 cells by 20% at 10 mumol/L and 85% at 60 mumol/L, and was competable by an excess of asialoglycoprotein.

CONCLUSIONS

Antisense oligonucleotides that bind to the NTR of HCV can be targeted by receptor-mediated endocytosis, and they specifically inhibit HCV-directed protein synthesis under intracellular conditions.

Pre-clinical trials using hepatic gene delivery

The development of gene therapy as a potential technique for treating serious metabolic or infectious disorders has generated much interest. The general applicability of gene therapy depends on the efficient transfer of the desired gene to specific tissues and cells. One of the most attractive sites for gene transfer is the liver because it plays a major role in many metabolic processes and is involved in a large variety of diseases. Nonviral strategies have been conceived for delivering genes to the liver but this approach is still at the preclinical stage. This review outlines the more commonly used approaches and discusses the progress that has been made toward developing a widely applicable, clinically relevant gene transfer procedure for the liver.

[Changes of activities of MLCK and dephosphatase in different arterial vessels from hypertensive rats]

The changes of activities of myosin light chain kinase (MLCK) and Ca2+/CaM-PP in different arterial vessels from hypertensive and normotensive rats were studied. The results were as follows. The MLCK activity of different arteries of spontaneous hypertensive rats (SHR) was different with the order of aorta (A) >> caudal artery (CA) >> mesenteric artery (MA), while in WKY rats the order of activity among different arteries is A << CA and MA and MA Ca2+/CaM-PP is obviously higher than in SHR. In renal hypertensive rats the activities of Ca2+/CaM-PP in different arteries are not quite different from those of the Wistar rats. The above results suggest that higher activities of MLCK or/and lower activity might be related to vasocontraction and hypertension.

Stabilization of dendritic arbor structure in vivo by CaMKII

Calcium-calmodulin-dependent protein kinase II (CaMKII) promotes the maturation of retinotectal glutamatergic synapses in Xenopus. Whether CaMKII activity also controls morphological maturation of optic tectal neurons was tested using in vivo time-lapse imaging of single neurons over periods of up to 5 days. Dendritic arbor elaboration slows with maturation, in correlation with the onset of CaMKII expression. Elevating CaMKII activity in young neurons by viral expression of constitutively active CaMKII slowed dendritic growth to a rate comparable to that of mature neurons. CaMKII overexpression stabilized dendritic structure in more mature neurons, whereas CaMKII inhibition increased their dendritic growth. Thus, endogenous CaMKII activity limits dendritic growth and stabilizes dendrites, and it may act as an activity-dependent mediator of neuronal maturation.

Serologic assay for secretory component distinguishes mechanical from hepatocellular cholestasis in humans

In rats, serum secretory component (SC) is elevated in mechanical but not hepatocellular cholestasis. To determine if serum SC might distinguish cholestatic syndromes in humans, serum samples were obtained from control subjects and patients with mechanical and hepatocellular cholestasis. Equal volumes of serum were assayed for SC by immunoblotting with an antibody specific for human SC. Quantitative densitometry of these immunoblots showed that in mechanically obstructed patients serum SC was reversibly elevated to a level approximately 10-fold higher than that of patients with hepatocellular cholestasis (P < 0.001). When comparing the two cholestatic groups, levels of serum alkaline phosphatase, but not bilirubin and alanine aminotransferase, were significantly higher in the group with mechanical cholestasis (P < 0.01). When comparing individual patients, serum SC was more reliable than alkaline phosphatase in distinguishing the two cholestatic syndromes (P < 0.05). Thus, serum SC may distinguish mechanical from hepatocellular cholestasis in humans.

Listeriolysin O potentiates immunotoxin and bleomycin cytotoxicity

Antitumor immunotoxins were formed by covalently attaching the ribosome-inactivating protein ricin A chain (RA) to the antitumor antibodies BR96 and L6. In vitro cytotoxicity assays established that BR96-RA was cytotoxic to H2987 human lung adenocarcinoma cells (IC50 = 6 nM), while L6-RA exhibited very low levels of cytotoxic activity (18% cell kill at 67 nM). The virulence factor from the intracellular pathogen Listeria monocytogenes, listeriolysin O (LLO), was able to potentiate the cytotoxicity of BR96-RA and L6-RA by 120- and > 1340-fold, respectively, resulting in IC50 values of approximately 50 pM. LLO also potentiated the cytotoxicity of the peptide anticancer drug bleomycin by a factor of > 2500 but had no effect on the cytotoxic activities of the anticancer drugs cytarabine and etoposide phosphate. In addition, LLO did not potentiate the cytotoxic activity of unconjugated ricin A chain or L6-RA on H2987 cells that were saturated with L6 prior to conjugate treatment. These results are attributed to LLO-induced alteration of the intracellular trafficking of molecules that are incorporated into acidic vesicles.

Design and preparation of a multimeric self-cleaving hammerhead ribozyme

The activity of a ribozyme can be impaired by additional sequences at the 5' and 3' termini of the catalytic sequence. To approach this problem, a system was designed that minimizes sequences upstream and downstream from active regions of a hammerhead ribozyme and allows delivery of a large number of active molecules. A self-cleavable multimeric molecule was prepared by placing a ribozyme target sequence (derived from the core region of the hepatitis B virus [HBV]) upstream and downstream from the catalytic sequence. This construct was cloned in tandem into in vitro expression vectors. 32P-UTP-labeled transcripts of the multimeric construct, as well as non-self-cleaved monomeric ribozyme controls, and substrate were synthesized. The multimeric ribozyme molecule efficiently self-cleaved to release monomeric ribozymes lacking any extra upstream and downstream sequences. In addition, monomers were substantially more active against the HBV target RNA than the non-self-cleavable ribozymes. Up to 80% degradation of the target RNA was achieved by a tenfold molar excess of a pentameric construct. We conclude that ribozymes can be produced as a multimeric tandem of self-cleavable molecules, the monomers of which are more active than monomeric ribozymes and highly efficient in cleavage of target transcripts.

Intracellular cleavage of hepatitis C virus RNA and inhibition of viral protein translation by hammerhead ribozymes

To determine the effects of hammerhead ribozymes against hepatitis C virus (HCV) RNA on viral protein translation, a luciferase reporter gene vector, pCMV/T7-NCRCdelta-luc, was constructed containing the 5'-noncoding region (5'-NCR) and part of the core region of HCV. Four ribozymes, Rz1-Rz4, were designed to cleave at nucleotide positions 136-160, 313-337, 496-520, and 373-388, respectively. Each ribozyme cleaved the target RNA at expected positions under cell-free conditions. Rz2 and Rz4 significantly suppressed translation of NCRCdelta-luc RNA by 71 and 49%, respectively. Translation of control luciferase mRNA lacking viral elements was not affected by the ribozymes. Furthermore, when NCRCdelta-luc RNA and ribozymes were cotransfected into cells, Rz2 and Rz4 significantly suppressed expression by 73 and 56%, respectively. In contrast, cleavage-deficient ribozymes with a point mutation in the hammerhead domain had no significant effect. To determine the effects of endogenously produced ribozymes, eukaryotic expression vectors for Rz2 and Rz4 were constructed. Cotransfection of the vectors with CMV/T7-NCRCdelta-luc showed suppression of luciferase activities to 50 and 61%, respectively. Moreover, transfection of pCMV/T7-NCRCdelta-luc into stable Rz2 and Rz4 producer cells also showed substantial inhibition of luciferase activity. Ribozymes directed against the HCV genome can substantially and specifically inhibit viral gene expression under intracellular conditions.

Delivery of a hammerhead ribozyme specifically down-regulates the production of fibrillin-1 by cultured dermal fibroblasts

The hammerhead ribozyme is a small catalytic RNA molecule. Potential hammerhead ribozymes that possess a catalytic domain and flanking sequence complementary to a target mRNA can cleave in trans at a putative cleavage site within the target molecule. We have investigated the potential of hammerhead ribozymes to down-regulate the product of the fibrillin-1 gene (FBN1). Fibrillin is a 347 kDa glycoprotein that is a major constituent of the elastin-associated microfibrils. Mutations in the FBN1 gene are responsible for Marfan syndrome (MFS), a common systemic disorder of the connective tissue. Many FBN1 mutations responsible for MFS appear to act in a dominant-negative fashion, raising the possibility that reduction of the amount of product from the mutant FBN1 allele might be a valid therapeutic approach for MFS. A trans-acting hammerhead ribozyme (FBN1-RZ1) targeted to the 5' end of the human FBN1 mRNA has been designed and synthesized, and shown to cleave its target efficiently in vitro. FBN1-RZ1 cleavage is magnesium dependent and efficient at both 37 and 50 degrees C. Delivery of the FBN1-RZ1 ribozyme into cultured dermal fibroblasts, by receptor-mediated endocytosis of a ribozyme-transferrin-polylysine complex, specifically reduces both cellular FBN1 mRNA and the deposition of fibrillin in the extracellular matrix. These results suggest that the use of hammerhead ribozymes is a valid approach to the study of fibrillin gene expression and possibly to the development of a therapeutic approach to MFS.

[Study of emotional disorders and their risk factors in patients hospitalized with lower extremity fracture]

111 adult patients hospitalized with lower extremity fracture (LEF) at three teaching hospitals of Beijing Medical University were interviewed by using STAI and CES-D. The results showed that the prevalence of depression in this group using CES-D is 69.4%, and there was a high correlation between STAI scores and CES-D scores. Multivariante analyses indicated that physical status, financial crisis, age, knowledge about disease, especially the patients' perceived threat of fracture, and social supports were the main factors that contribute to the patients' emotional distress.

Alternative splicing of the FMR1 gene in human fetal brain neurons

The alternative splicing expression of the FMR1 gene was reported in several human and mouse tissues. Five regions of FMR1 gene can be alternatively spliced, but the combination of them has not been investigated fully. We reported here the analysis of alternative splicing pattern of the FMR1 gene in cultured fetal human neurons, using a RT-PCR and cloning strategy. Eleven splicing types were cloned and different isoforms were not equally represented. The dominant isoform represents nearly 40%, and the other isoforms were relatively rare. One isoform has a different carboxylterminus. Most of the alternative spliced regions appear hydrophilic; thus, they may locate on the surface of the FMR1 protein.

Inhibition of hepatitis B virus replication by targeted pretreatment of complexed antisense DNA in vitro

We have shown that antisense oligonucleotides can be targeted to hepatitis B virus (HBV)-infected cells, resulting in specific inhibition of viral protein synthesis and replication in vitro. The targeting system was based on the internalization of DNA complexes by highly selective receptors for galactose-terminal glycoproteins, asialoglycoproteins, on the surface of hepatocytes. Our objective in this study was to determine whether antisense DNA could be targeted to hepatocytes to prevent subsequent infection by HBV. A 21-mer phosphorothioate-linked oligo DNA complementary to the HBV polyadenylation signal and 5'-upstream sequences was complexed to a targetable DNA carrier consisting of asialoglycoprotein coupled to polylysine. Pretreatment of Huh7, asialoglycoprotein receptor (+) cells, with antisense complexes before lipofection with an HBV-plasmid at a level of 6.5 x 10(6) copies of plasmid per cell inhibited the amount of newly synthesized, core-associated viral DNA in Huh7 cells to undetectable levels, less than 0.1 pg, as assessed by quantitative polymerase chain reaction (PCR). Hepatitis B viral RNA transcripts were decreased by 60% compared with controls as detected by RNase protection assays, and HBV surface antigen (HBsAg) accumulation was inhibited by 97%. The inhibition lasted for 6 days and was dose dependent. Controls consisting of antisense alone and a random oligo complex showed no significant effect on any of the parameters under identical conditions. We conclude that preexposure of cells to targeted complexed antisense DNA can substantially block viral gene expression and viral replication after transfection of HBV DNA.

A collagen enhancer-promoter construct in transgenic mice is markedly stimulated by ethanol administration

Type I collagen synthesis and deposition is generally indicative of irreversible damage in alcohol-induced cirrhosis in humans. However, in rodents, ethanol alone does not readily cause hepatic fibrosis. To determine whether this is because of a lack of ethanol-responsive elements, an artificial enhancer construct controlling rat type I collagen gene transcription was prepared in transgenic mice. The gene construct, ColCAT3.6, was a chimeric sequence containing the marker chloramphenicol acetyltransferase (CAT) gene linked to 3.5 kb of the rat alpha 1(I) 5'-flanking DNA, and 115 base pairs (bp) of transcribed collagen gene. Groups of transgenic mice were given 4 g/kg ethanol orally, twice daily for 4 weeks. As a positive control for hepatic fibrosis, transgenic mice were given intraperitoneal injections of CCl4, twice weekly for 4 weeks. Livers were assayed for CAT activity. Endogenous mouse collagen alpha 1(I) messenger RNA (mRNA) and transgene CAT mRNA were measured by RNase protection assays. Collagen synthesis in livers from the transgenic mice treated with ethanol were increased over controls, but the levels were not significantly different. Endogenous collagen alpha 1(I) steady-state mRNA levels in ethanol-treated mice were not significantly different compared with saline-treated controls. However, the transgene mRNA levels in ethanol-treated animals increased approximately 21-fold compared with saline-treated controls, as measured by RNase protection assays. Furthermore, the transgene product as measured by CAT activity in ethanol-treated mice was significantly increased threefold over saline-treated controls. We conclude that the 5'-flanking region of the rat alpha 1(I) collagen gene does contain regulatory elements that are strongly responsive to ethanol administration.

Microtubular disruption prolongs the expression of human bilirubin-uridinediphosphoglucuronate-glucuronosyltransferase-1 gene transferred into Gunn rat livers

DNA delivered to the liver by asialoglycoprotein receptor-mediated endocytosis is degraded in lysosomes within 48 h. To test the hypothesis that microtubular disruption should promote transgene persistence by interrupting endosomal translocation to lysosomes, plasmids containing bacterial chloramphenicol acetyltransferase (pSV2-CAT) or human bilirubin-UDP-glucuronosyltransferase-1 (pSVK3-hBUGT1) genes were complexed with asialoglycoprotein-polylysine conjugates, and 1 mg of the complexed DNA was injected intravenously into bilirubin-UDP-glucuronosyltransferase-deficient Gunn rats. 30 min before DNA injection, one group received 0.75 mg of colchicine/kg of body weight intraperitoneally, which was shown by immunofluorescent confocal microscopy to disrupt the microtubular network. Control rats received normal saline. In colchicine-pretreated rats receiving pSV2-CAT, hepatic chloramphenicol acetyltransferase activity persisted for 9-14 weeks, whereas in the saline-pretreated group the activity was detectable for 48 h only. In colchicine-pretreated Gunn rats receiving pSVK3-hBUGT1, the DNA persisted in liver for 10 weeks, bilirubin glucuronides were excreted in bile, and serum bilirubin levels declined by 25-35% in 2-4 weeks and remained reduced for 8 weeks. Without colchicine pretreatment, the DNA was detectable in liver for 2 days only, and serum bilirubin levels were not reduced. Thus, microtubular disruption provides a noninvasive method for prolonging the effect of liver-targeted gene therapy.

A hepatocyte-targeted conjugate capable of delivering biologically active colchicine in vitro

A derivative of colchicine was synthesized, in a manner that preserved its important structural features, and conjugated to an asialoglycoprotein. The conjugate was characterized by ultraviolet-visible spectrophotometry and protein analysis. An average coupling ratio of 2 mol of colchicine per mole of asialoglycoprotein was achieved. The conjugate was stable to incubation in serum but was split into its separate components under chemically reducing conditions. Incubation with cells in culture revealed that the conjugate had antiproliferative activity similar to that of colchicine, but only in asialoglycoprotein receptor-containing cells. There was no effect at all on asialoglycoprotein receptor (-) cells. Furthermore, the antiproliferative effect of the conjugate on receptor (+) cells was blocked by addition of a large molar excess of free asialoglycoprotein. Immunofluorescence microscopy revealed disruption of microtubules in cell cultures that were pretreated with the conjugate. These results indicate that a colchicine conjugate that is taken up specifically into cells by asialoglycoprotein receptors and released intracellularly in a biologically active form can be prepared.

Targeted delivery of antisense DNA in woodchuck hepatitis virus-infected woodchucks

An asialoglycoprotein-based DNA delivery system containing an antisense oligo DNA against the polyadenylation region and adjacent upstream sequences of woodchuck hepatitis virus (WHV) was prepared. Experimental woodchucks were inoculated neonatally with the woodchuck virus 23 weeks before initiating the study, and all animals subsequently developed hepatitis as evidenced by the presence of measurable levels of circulating viral DNA. Animals were injected intravenously (i.v.) with asialoorosomucoid (AsOR)-poly-L-lysine complexes containing 0.1 mg kg-1 antisense DNA for five consecutive days. Levels of surface antigen did not differ substantially between treated and control animals. However, intravenous administration of complexed antisense DNA significantly decreased viraemia, as shown by a five- to 10-fold decrease in circulating viral DNA 25 days post treatment. The decline lasted for at least 2 weeks, after which there was a gradual increase in DNA levels. Antisense DNA alone or a complex containing a random oligo DNA of the same size and linkage failed to have any significant effect on viral DNA levels. We conclude that antisense oligo DNA can be targeted to the liver in vivo, resulting in a substantial and prolonged decrease in viral DNA levels in WHV-infected woodchucks.

Excitatory and inhibitory neurotransmitters in the nucleus rotundus of pigeons

Rotundal neurons in pigeons (Columba livia) were examined for the effects of glutamate and its agonists NMDA and AMPA, antagonists CPP and CNQX, as well as of GABA and its antagonist bicuculline, on visual and tectal stimulation-evoked responses. Glutamate applied by iontophoresis excited all 48 rotundal cells tested, and this excitation was blocked by CNQX but not by CPP in 98% of cases, with 2% of cells being blocked by either CNQX or CPP. Out of 21 cells excited by AMPA, 20 were also excited by NMDA, indicating that AMPA and NMDA receptors may coexist in most rotundal cells. Action potentials were evoked in 36 additional cells by electrical stimulation applied to the tectum and they were also blocked by CNQX but not CPP. Visual responses recorded from a further eight luminance units and 21 motion-sensitive units were also blocked by CNQX and not CPP. On the other hand, GABA inhibited visual responses as well as responses evoked by tectal stimulation. An inhibitory period following tectal stimulation was eliminated by bicuculline. Taken together, these results indicate that glutamate may be an excitatory transmitter acting predominantly through non-NMDA receptors (AMPA receptors) in tectorotundal transmission. Meanwhile, GABA may be an inhibitory transmitter in the pigeon nucleus rotundus.

[Structure and function of FMR]

The widespread basal expression of fragile X gene (FMR1) suggests that it is a house keeping gene, essential to the survival and function of the cells, but unrelated to proliferation and phenogenesis. The spatial temporal specific expression of FMR1 further suggests that it is an important development-regulating gene, essential to development, particularly to the development of CNS and reproductive system, and may play an important role in cell migration and differantiation. It may also be a posttranscription regulator, by binding to mRNA, regulates the posttranscription processing, transportation, translation and localization of mRNAs. The diversity of pathogenesis of Fra(X) individuals may be caused by the variation of the downstream genes regulated by FMR1.

Infection of frog neurons with vaccinia virus permits in vivo expression of foreign proteins

Vaccinia virus can be used to infect cells in the CNS of frogs, Xenopus laevis, and Rana pipiens, both in vivo and in vitro. In vivo infections were accomplished by injection of viral solution into the tectal ventricle of stage 40-48 tadpoles or by local injections into distinct neural regions. Infections with high titer of virus injected into the ventricle resulted in the majority of cells in the brain expressing foreign protein, while cells in the retina and optic nerve showed no expression. Infection with lower viral titers resulted in fewer infected cells that were distributed throughout the otherwise normal tissue. Intense expression of foreign protein in the brain was observed 36 hr after injection and remained high for at least 4 days. Infected animals developed normally and had the same number of cells in the optic tectum as control animals. Infection with a recombinant virus carrying the gene for Green Fluorescent Protein labels neurons, so that infected cells can be observed in vivo. Vaccinia virus provides a versatile means to alter proteins in distinct populations of neurons in amphibia.

Avian Imc-tectal projection is mediated by acetylcholine and glutamate

In the bird, biochemical and histochemical data suggest that the neurotransmitter between nucleus isthmi pars magnocellularis (Imc) and tectum is either acetylcholine or glutamate. There are, however, discrepancies regarding the functional role of acetylcholine. In the present study we investigated the action of acetylcholine and glutamate and their specific antagonists on excitatory isthmo-tectal synaptic transmission using electrophysiological and microiontophoretic techniques. The results show two different population of cells: (1) excitatory cholinergic input, blocked by atropine sulphate but not by glutamate antagonist; (2) excitatory glutamatergic input of NMDA or non-NMDA receptor type, which is blocked or reduced by CPP or CNQX but not by atropine sulphate.