Biomedical subjects

Wen-Tsan Chang

Publications and source records attributed to Wen-Tsan Chang.

At least 19 recordsLinked to original sources

PubMed2006

Deregulation of AP-1 proteins in collagen gel-induced epithelial cell apoptosis mediated by low substratum rigidity.

In this study, we established that collagen gel, but not collagen gel coating, induced apoptosis exclusively in epithelial cell lines, which indicated that low substratum rigidity might trigger cell apoptosis. To confirm this, we used collagen gels with different rigidities due to cross-linking or physical disruption of collagen fibrils caused by sonication. We found that collagen gel-induced apoptosis was inversely correlated with substratum rigidity. Low substratum rigidity collagen gel-induced apoptosis was neither prevented by Bcl-2 overexpression nor preceded by mitochondrial release of cytochrome c. This suggested that the mitochondrial pathway was not involved in low substratum rigidity-induced apoptosis. Low substratum rigidity activated c-Jun N-terminal kinase (JNK) within 4 h, but it also rapidly down-regulated c-Jun within 1 h and triggered persistent aberrant expression of c-Fos for at least 24 h. Either reduced c-Jun expression or c-Fos overexpression induced apoptosis in several epithelial cells. Inhibiting low substratum rigidity-induced JNK activation prevented aberrant c-Fos expression but only partially blocked low substratum rigidity-induced apoptosis. Taking these results together, we conclude that low substratum rigidity collagen gel induced apoptosis in epithelial cells and that deregulated AP-1 proteins mediated that apoptosis, at least in part.

Animals↗

PubMed2006

Inhibition of cell migration by autophosphorylated mammalian sterile 20-like kinase 3 (MST3) involves paxillin and protein-tyrosine phosphatase-PEST.

MST3 is a member of the sterile-20 protein kinase family with a unique preference for manganese ion as a cofactor in vitro; however, its biological function is largely unknown. Suppression of endogenous MST3 by small interference RNA enhanced cellular migration in MCF-7 cells with reduced expression of E-cadherin at the edge of migrating cells. The alteration of cellular migration and protruding can be rescued by RNA interference-resistant MST3. The expression of surface integrin and Golgi apparatus was not altered, but phosphorylation on tyrosine 118 and tyrosine 31 of paxillin was attenuated by MST3 small interfering RNA (siRNA). Threonine 178 was determined to be one of the two main autophosphorylation sites of MST3 in vitro. Mutant T178A MST3, containing alanine instead of threonine at codon 178, lost autophosphorylation and kinase activities. Overexpression of wild type MST3, but not the T178A mutant MST3, inhibited migration and spreading in Madin-Darby canine kidney cells. MST3 could phosphorylate the protein-tyrosine phosphatase (PTP)-PEST and inhibit the tyrosine phosphatase activity of PTP-PEST. We conclude that MST3 inhibits cell migration in a fashion dependent on autophosphorylation and may regulate paxillin phosphorylation through tyrosine phosphatase PTP-PEST.

Amino Acid Sequence↗

PubMed2006

Expression of DPC4/Smad4 gene in stone-containing intrahepatic bile duct.

BACKGROUND AND OBJECTIVES: Hepatolithiasis is etiologically related to cholangiocarcinoma. We underwent this study with an attempt to examine the expression of DPC4/Smad4 gene in stone-containing intrahepatic bile ducts (IHD) and intrahepatic cholangiocarcinoma (ICC). PATIENTS AND METHODS: The immunohistochemical method and RT-PCR analysis were used to study the expression of DPC4/Smad4 gene in normal IHD, stone-containing IHD, and ICC. All the specimens were from hepatic resection. RESULTS: The immunohistochemical study showed that all specimens from 24 normal IHD had marked expression of DPC4/Smad4 gene, while there was 4.4% (2/46) and 33.3% (3/9) loss of DPC4/Smad4 expression in stone-containing IHD and ICC, respectively. Among the specimens of stone-containing IHD, all the hyperplastic epithelial cells showed normal expression of DPC4/Smad4 gene while dysplastic epithelial cells showed 20% (2/10) loss expression of DPC4/Smad4. The RT-PCR analysis showed that the normal IHD had the highest content of DPC4/Smad4 mRNA, which was threefold and sixfold higher than that of stone-containing IHD and ICC, respectively. CONCLUSION: Loss expression of DPC4/Smad4 gene was found both in stone-containing IHD and ICC. Dysplastic epithelium of stone-containing IHD had higher potential for malignant transformation.

Adult↗

PubMed2006

A novel siRNA validation system for functional screening and identification of effective RNAi probes in mammalian cells.

Small interfering RNAs (siRNAs) have become the most powerful and widely used gene silencing reagents for reverse functional genomics and molecular therapeutics. The key challenge for achieving effective gene silencing in particular for the purpose of the therapeutics is primarily dependent on the effectiveness and specificity of the RNAi targeting sequence. However, only a limited number of siRNAs is capable of inducing highly effective and sequence-specific gene silencing by RNA interference (RNAi) mechanism. In addition, the efficacy of siRNA-induced gene silencing can only be experimentally measured based on inhibition of the target gene expression. Therefore, it is important to establish a fully robust and comparative validating system for determining the efficacy of designed siRNAs. In this study, we have developed a reliable and quantitative reporter-based siRNA validation system that consists of a short synthetic DNA fragment containing an RNAi targeting sequence of interest and two expression vectors for targeting reporter and triggering siRNA expression. The efficacy of the siRNAs is measured by their abilities to inhibit expression of the targeting reporter gene with easily quantified readouts including enhanced green fluorescence protein (EGFP) and firefly luciferase. Using fully analyzed siRNAs against human hepatitis B virus (HBV) surface antigen (HBsAg) and tumor suppressor protein p53, we have demonstrated that this system could effectively and faithfully report the efficacy of the corresponding siRNAs. In addition, we have further applied this system for screening and identification of the highly effective siRNAs that could specifically inhibit expression of mouse matrix metalloproteinase-7 (MMP-7), Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1), and human serine/threonine kinase AKT1. Since only a readily available short synthetic DNA fragment is needed for constructing this novel reporter-based siRNA validation system, this system not only provides a powerful strategy for screening highly effective siRNAs but also implicates in the use of RNAi for studying novel gene function in mammals.

Animals↗

PubMed2006

The impact of prophylactic antibiotics on postoperative infection complication in elective laparoscopic cholecystectomy: a prospective randomized study.

BACKGROUND: The aim of this prospective randomized study was to investigate the necessity and impact of prophylactic antibiotics on postoperative infection complications in elective laparoscopic cholecystectomy. METHODS: At the time of induction of anesthesia, group A patients (n = 141) received 1 g cefazolin, and group B patients (control; n = 136) received 10 mL isotonic sodium chloride solution. Patients' characteristics and general operative outcomes were compared and analyzed. RESULTS: The overall rate of infection was 1.1% for total 277 patients (0.7% for group A patients and 1.5% for group B patients). No significant difference in infection complications was found between these 2 groups. Also any risk factors contributing to infection complications could not be found. CONCLUSIONS: We do not recommend the use of prophylactic antibiotics in elective laparoscopic cholecystectomy because they will not decrease the already-low rate of postoperative infectious complications.

Adult↗

PubMed2006

G-2548A polymorphism of the leptin gene is correlated with extreme obesity in Taiwanese aborigines.

We examined the genetic associations of the G-2548A polymorphism in the promoter of the leptin (LEP) gene and the Gln223Arg (Q223R) polymorphism of the leptin receptor (LEPR) gene with obesity. Two hundred twenty-six obese aboriginal subjects (BMI > or = 27 kg/m2) and 182 aboriginal subjects with normal weight (BMI < 25 kg/m2) participated in this study. The polymorphisms of LEP G-2548A and LEPR Q223R were genotyped by polymerase chain reaction/restriction fragment length polymorphism, and their anthropometric characteristics were measured. Levels of leptin, triglycerides, and cholesterol were measured after overnight fasting. We found that the frequencies of the LEP G/G homozygote (22.6%) with Mendelian recessive (chi2 = 7.89, p = 0.005) and codominant (chi2 = 7.93, p = 0.02) models to be higher in the extremely obese subjects (BMI > or = 35 kg/m2) than in normal weight subjects (6.9%) but not in moderately obese subjects (35 > BMI > or = 27 kg/m2). There was no difference in genotypic frequency of the LEPR Q223R polymorphism between the extreme obese and control groups. We suggest that the LEP -2548 G/G homozygote plays a genetic recessive role in the development of extreme obesity in Taiwanese aborigines.

Asian People↗

PubMed2006

Effect of SstI polymorphism of the apolipoprotein CIII gene and environmental factors on risks of hypertriglyceridemia in Taiwan aborigines.

BACKGROUND: Hypertriglyceridemia (HTG) is a heterogeneous metabolic disorder. The aim of this study was to examine associations among genetic polymorphisms, SstI polymorphism of apolipoprotein CIII (ApoCIII) and Hind III polymorphism of lipoprotein lipase (LPL), environmental factors and risks of HTG. METHODS AND RESULTS: Two hundred and forty-nine southern Taiwanese aborigines were recruited for a cross-sectional study, which included 90 subjects with triglyceride (TG)>150 mg/dl (HTG) and 159 with TG or=25 (OR=2.22, 95% CI: 1.18-4.16), starchy food consumption>or=3 times/week (OR=1.89, 95% CI: 1.00-3.59) and ApoCIII S2S2 genotype (OR=3.35, 95% CI: 1.10-10.19) were independently (p<0.05) associated with HTG risks. Among ApoCIII S1S1, S1S2 and S2S2 genotypes, ApoCIII and TG concentrations increased (p<0.01) in a dose-responsive manner. CONCLUSIONS: The ApoCIII S2 variant and environmental factors, including education, tribal background, BMI and starchy food intake, modulate the risks of HTG in aboriginal Taiwanese. Interaction between genetic and environmental factors warrants further investigation.

Aged↗

PubMed2005

A novel bidirectional expression system for simultaneous expression of both the protein-coding genes and short hairpin RNAs in mammalian cells.

RNA interference (RNAi) is an extremely powerful and widely used gene silencing approach for reverse functional genomics and molecular therapeutics. In mammals, the conserved poly(ADP-ribose) polymerase 2 (PARP-2)/RNase P bidirectional control promoter simultaneously expresses both the PARP-2 protein and RNase P RNA by RNA polymerase II- and III-dependent mechanisms, respectively. To explore this unique bidirectional control system in RNAi-mediated gene silencing strategy, we have constructed two novel bidirectional expression vectors, pbiHsH1 and pbiMmH1, which contained the PARP-2/RNase P bidirectional control promoters from human and mouse, for simultaneous expression of both the protein-coding genes and short hairpin RNAs. Analyses of the dual transcriptional activities indicated that these two bidirectional expression vectors could not only express enhanced green fluorescent protein as a functional reporter but also simultaneously transcribe shLuc for inhibiting the firefly luciferase expression. In addition, to extend its utility for the establishment of inherited stable clones, we have also reconstructed this bidirectional expression system with the blasticidin S deaminase gene, an effective dominant drug resistance selectable marker, and examined both the selection and inhibition efficiencies in drug resistance and gene expression. Moreover, we have further demonstrated that this bidirectional expression system could efficiently co-regulate the functionally important genes, such as overexpression of tumor suppressor protein p53 and inhibition of anti-apoptotic protein Bcl-2 at the same time. In summary, the bidirectional expression vectors, pbiHsH1 and pbiMmH1, should provide a simple, convenient, and efficient novel tool for manipulating the gene function in mammalian cells.

Animals↗

PubMed2005

Association of CD14 promoter polymorphisms and soluble CD14 levels in mite allergen sensitization of children in Taiwan.

CD14 is responsible for environmental lipopolysaccharide recognition and is a positional candidate gene for allergy. We hypothesized that genetic polymorphisms in the promoter region of the CD14 gene may be associated with Dermatophagoides pteronysinnus (Der p) allergen sensitization in children. Three single nucleotide polymorphisms (SNPs) of the CD14 promoter region, C(-159)T, A(-1,145)G, and G(-1,359)T were genotyped, and analyzed in 240 randomized case-control school-age children in Taiwan. Serum concentrations of IgE and soluble CD14 (sCD14) were also assayed. We found a significant inverse correlation of sCD14 and total serum IgE levels in our study population. Moreover, sCD14 binds Der p allergen in vitro in a dose-dependent manner. The distribution of three SNPs genotypes was similar in asthmatic children and the control group. However, there was a significant difference in the distribution of genotype CD14 G(-1,359)T, but not C(-159)T, between mite-sensitive and non-sensitive children. Haplotype analysis showed strong linkage disequilibrium among these three SNPs in the CD14 promoter region. Carriers of the CD14-159C/-1,145A/-1,359T haplotype had the highest IgE and lowest sCD14 levels as compared to other haplotypes. Our results support the hypothesis that CD14 gene variants may play an important role in influencing allergen sensitization of children in Taiwan.

Animals↗

PubMed2005

Toll-like receptor 4 plays an anti-HBV role in a murine model of acute hepatitis B virus expression.

AIM: Toll-like receptor 4 (TLR4) has been shown to be important for bacterial infection, especially to lipopolysaccharide signaling. Its possible role in HBV infection is studied in the present study. MATERIALS AND METHODS: pHBV3.6 plasmid, containing full-length HBV genome was used in the murine model of acute HBV expression by hydrodynamics in vivo transfection. TLR4 normal or mutant mouse strain was compared to investigate the possible role of TLR4 in acute HBV expression. RESULTS: After pHBV3.6 injection, the infiltrating leukocytes expressed TLR4 were observed nearby the HBsAg-expressing hepatocytes. The HBV antigenemia as well as the replication and transcription were higher in TLR4-mutant C3H/HeJ mice than in normal C3H/HeN mice. The HBV-specific immune responses were impaired in the liver or spleen of the C3H/HeJ mice. Their inducible nitric oxide synthase (iNOS) expression on the hepatic infiltrating cells was also impaired. When adoptively transferring splenocytes from C3H/HeN mice to C3H/HeJ mice, the HBV replication was inhibited to the level as that of C3H/HeN. CONCLUSION: These results suggest that TLR4 plays an anti-HBV role in vivo through the induction of iNOS expression and HBV-specific immune responses after HBV expression.

Adoptive Transfer↗

PubMed2005

Therapeutic inhibition of hepatitis B virus surface antigen expression by RNA interference.

RNA interference (RNAi) mediated inhibition of virus-specific genes has emerged as a potential therapeutic strategy against virus induced diseases. Human hepatitis B virus (HBV) surface antigen (HBsAg) has proven to be a significant risk factor in HBV induced liver diseases, and an increasing number of mutations in HBsAg are known to enhance the difficulty in therapeutic interventions. The key challenge for achieving effective gene silencing in particular for the purpose of the therapeutics is primarily based on the effectiveness and specificity of the RNAi targeting sequence. To explore the therapeutic potential of RNAi on HBV induced diseases in particular resulted from aberrant or persistent expression of HBsAg, we have especially screened and identified the most potent and specific RNAi targeting sequence that directly mediated inhibition of the HBsAg expression. Using an effective DNA vector-based shRNA expression system, we have screened 10 RNAi targeting sequences (HBsAg-1 to 10) that were chosen from HBsAg coding region, in particular the major S region, and have identified four targeting sequences that could mediate sequence specific inhibition of the HBsAg expression. Among these four shRNAs, an extremely potent and highly sequence specific HBsAg-3 shRNA was found to inhibit HBsAg expression in mouse HBV model. The inhibition was not only preventive in cotransfection experiments, but also had therapeutic effect as assessed by post-treatment protocols. Moreover, this HBsAg-3 shRNA also exhibited a great potency of inhibition in transgenic mice that constitutively expressed HBsAg. These results indicate that HBsAg-3 shRNA can be considered as a powerful therapeutic agent on HBsAg induced diseases.

Animals↗

PubMed2005

LrrA, a novel leucine-rich repeat protein involved in cytoskeleton remodeling, is required for multicellular morphogenesis in Dictyostelium discoideum.

Cell sorting by differential cell adhesion and movement is a fundamental process in multicellular morphogenesis. We have identified a Dictyostelium discoideum gene encoding a novel protein, LrrA, which composes almost entirely leucine-rich repeats (LRRs) including a putative leucine zipper motif. Transcription of lrrA appeared to be developmentally regulated with robust expression during vegetative growth and early development. lrrA null cells generated by homologous recombination aggregated to form loose mounds, but subsequent morphogenesis was blocked without formation of the apical tip. The cells adhered poorly to a substratum and did not form tight cell-cell agglomerates in suspension; in addition, they were unable to polarize and exhibit chemotactic movement in the submerged aggregation and Dunn chamber chemotaxis assays. Fluorescence-conjugated phalloidin staining revealed that both vegetative and aggregation competent lrrA(-) cells contained numerous F-actin-enriched microspikes around the periphery of cells. Quantitative analysis of the fluorescence-stained F-actin showed that lrrA(-) cells exhibited a dramatically increase in F-actin as compared to the wild-type cells. When developed together with wild-type cells, lrrA(-) cells were unable to move to the apical tip and sorted preferentially to the rear and lower cup regions. These results indicate that LrrA involves in cytoskeleton remodeling, which is needed for normal chemotactic aggregation and efficient cell sorting during multicellular morphogenesis, particularly in the formation of apical tip.

Actins↗

PubMed2005

Simple and efficient DNA vector-based RNAi systems in mammalian cells.

We have constructed four different RNA polymerase III (Pol III)-based expression vectors, containing H1 or U6 promoters from human and mouse, which enable the endogenous production of small RNA transcripts for gene silencing applications. In addition, to facilitate the selection of recombinant clones, we have further improved these vectors by constructing a stuffer of puromycin resistance gene (Puro(r)) between ClaI and HindIII sites, which makes the preparation of vectors easy for rapid and efficient cloning of targeting sequences. A comparative analysis of the silencing efficiency between shRNA, sense-RNA, antisense-RNA, and siRNA showed that both the shRNA and siRNA, but not the sense-RNA and antisense-RNA, dramatically inhibit the targeting gene firefly luciferase activity in mammalian cells. However, there were no significant differences in the inhibition of firefly luciferase expression by shRNA and siRNA expressed from these DNA vectors. In summary, these improved DNA vector-based RNAi systems should provide a simple, convenient, and efficient cloning strategy for studying gene functions in mammalian cells.

Base Sequence↗

PubMed2005

Bcl-2 rescues ceramide- and etoposide-induced mitochondrial apoptosis through blockage of caspase-2 activation.

Recent studies indicate that caspase-2 is involved in the early stage of apoptosis before mitochondrial damage. Although the activation of caspase-2 has been shown to occur in a large protein complex, the mechanisms of caspase-2 activation remain unclear. Here we report a regulatory role of Bcl-2 on caspase-2 upstream of mitochondria. Stress stimuli, including ceramide and etoposide, caused caspase-2 activation, mitochondrial damage followed by downstream caspase-9 and -3 activation, and cell apoptosis in human lung epithelial cell line A549. When A549 cells were pretreated with the caspase-2 inhibitor benzyloxycarbonyl-Val-Asp(-OMe)-Val-Ala-Asp(-OMe)-fluoromethyl ketone or transfected with caspase-2 short interfering RNA, both ceramide- and etoposide-induced mitochondrial damage and apoptosis were blocked. Overexpression of Bcl-2 prevented ceramide- and etoposide-induced caspase-2 activation and mitochondrial apoptosis. Furthermore, caspase-2 was activated when A549 cells were introduced with Bcl-2 short interfering RNA or were treated with Bcl-2 inhibitor, which provided direct evidence of a negative regulatory effect of Bcl-2 on caspase-2. Cell survival was observed when caspase-2 was inhibited in Bcl-2-silencing cells. Blockage of the mitochondrial permeability transition pore and caspase-9 demonstrated that Bcl-2-modulated caspase-2 activity occurred upstream of mitochondria. Further studies showed that Bcl-2 was dephosphorylated at serine 70 after ceramide and etoposide treatment. A protein phosphatase inhibitor, okadaic acid, rescued Bcl-2 dephosphorylation and blocked caspase-2 activation, mitochondrial damage, and cell death. Taken together, ceramide and etoposide induced mitochondria-mediated apoptosis by initiating caspase-2 activation, which was, at least in part, regulated by Bcl-2.

Animals↗

PubMed2005

Hepatitis B virus pre-S2 mutant upregulates cyclin A expression and induces nodular proliferation of hepatocytes.

Naturally occurring mutants with a deletion in the pre-S2 region of the large surface protein (Delta S2-LHBs) are prevalent in serum and livers of patients with chronic hepatitis B virus (HBV) infection associated with cirrhosis. The Delta S2-LHBs protein is retained in the endoplasmic reticulum (ER) and may induce ER stress. One interesting observation is the consistently clustered distribution of hepatocytes expressing Delta S2-LHBs. In this study, complementary DNA microarray analysis identified cyclin A and several groups of genes as being significantly upregulated by Delta S2-LHBs in the HuH-7 cell line. This observation was confirmed in liver tissues. The induction of cyclin A expression may occur via the specific transactivator function of Delta S2-LHBs independent of ER stress. In the presence of Delta S2-LHBs, hepatocytes sustained cyclin A expression and cell cycle progression under ER stress and displayed increased BrdU incorporation with multinuclear formation. Furthermore, Delta S2-LHBs could enhance anchorage-independent cell growth in a nontransformed human hepatocyte line and induced nodular proliferation of hepatocytes in transgenic mice. In conclusion, these in vitro and in vivo data support a role for Delta S2-LHBs in the hepatocyte hyperplasia and a likely role in the process of HBV-related tumorigenesis.

Animals↗

PubMed2004

Endoplasmic reticulum stress stimulates the expression of cyclooxygenase-2 through activation of NF-kappaB and pp38 mitogen-activated protein kinase.

Expression of mutant proteins or viral infection may interfere with proper protein folding activity in the endoplasmic reticulum (ER). Several pathways that maintain cellular homeostasis were activated in response to these ER disturbances. Here we investigated which of these ER stress-activated pathways induce COX-2 and potentially oncogenesis. Tunicamycin and brefeldin A, two ER stress inducers, increased the expression of COX-2 in ML-1 or MCF-7 cells. Nuclear translocation of NF-kappaB and activation of pp38 MAPK were observed during ER stress. IkappaBalpha kinase inhibitor Bay 11-7082 or IkappaBalpha kinase dominant negative mutant significantly inhibited the induction of COX-2. pp38 MAPK inhibitor SB203580 or eIF2alpha phosphorylation inhibitor 2-aminopurine attenuated the nuclear NF-kappaB DNA binding activity and COX-2 induction. Expression of mutant hepatitis B virus (HBV) large surface proteins, inducers of ER stress, enhanced the expression of COX-2 in ML-1 and HuH-7 cells. Transgenic mice showed higher expression of COX-2 protein in liver and kidney tissue expressing mutant HBV large surface protein in vivo. Similarly, increased expression of COX-2 mRNA was observed in human hepatocellular carcinoma tissue expressing mutant HBV large surface proteins. In ML-1 cells expressing mutant HBV large surface protein, anchorage-independent growth was enhanced, and the enhancement was abolished by the addition of specific COX-2 inhibitors. Thus, ER stress due either to expression of viral surface proteins or drugs can stimulate the expression of COX-2 through the NF-kappaB and pp38 kinase pathways. Our results provide important insights into cellular carcinogenesis associated with latent endoplasmic reticulum stress.

Active Transport, Cell Nucleus↗

PubMed2004

Sequential caspase-2 and caspase-8 activation upstream of mitochondria during ceramideand etoposide-induced apoptosis.

Recently, caspase-2 was shown to act upstream of mitochondria in stress-induced apoptosis. Activation of caspase-8, a key event in death receptor-mediated apoptosis, also has been demonstrated in death receptor-independent apoptosis. The regulation of these initiator caspases, which trigger the mitochondrial apoptotic pathway, is unclear. Here we report a potential regulatory role of caspase-2 on caspase-8 during ceramide-induced apoptosis. Our results demonstrate the sequential events of initiator caspase-2 and caspase-8 activation, Bid cleavage and translocation, and mitochondrial damage followed by downstream caspase-9 and -3 activation and cell apoptosis after ceramide induction in T cell lines. The expression of truncated Bid (tBid) and the reduction in mitochondrial transmembrane potential were blocked by caspase-2 or caspase-8, but not caspase-3, knockdown using an RNA interference technique. Ceramide-induced caspase-8 activation, mitochondrial damage, and apoptosis were blocked in caspase-2 short interfering RNA-expressing cells. Therefore, caspase-2 acts upstream of caspase-8 during ceramide-induced mitochondrial apoptosis. Similarly, sequential caspase-2 and caspase-8 activation upstream of mitochondria was also observed in etoposide-induced apoptosis. These data suggest sequential initiator caspase-2 and caspase-8 activation in the mitochondrial apoptotic pathway induced by ceramide or etoposide.

Animals↗

PubMed2004

Pre-S mutant surface antigens in chronic hepatitis B virus infection induce oxidative stress and DNA damage.

Ground glass hepatocytes (GGHs) are the historic hallmarks for the hepatocytes in the late and non-replicative stages of hepatitis B virus (HBV) infection. We have identified type I and type II GGHs that contain two mutant types of large HBV surface antigens (HBsAg) with deletions over the pre-S1 and pre-S2 regions, respectively. These pre-S mutant HBVsAg accumulate in endoplasmic reticulum (ER), resulting in strong ER stress. Type II GGHs often appear in hepatic nodules in the late phases of HBV infection and proliferate in clusters, suggesting that these mutant pre-S1/S2 HBsAg may be involved in HBV-related hepatocarcinogenesis, associated with ER stress. In this study, we investigated the potential genomic instability imposed by pre-S mutant HBsAg. Based on the analysis of comet assays, we found that the pre-S1 and pre-S2 mutant HBsAg caused oxidative stress and DNA damage. The DNA repair gene ogg1 was greatly induced by over-expression of pre-S mutant HBsAg. Induction of the DNA repair gene ogg1 was also detected in the pre-S2 HBsAg transgenic mice, as well as the type II GGHs from patients with hepatocellular carcinoma, strongly suggesting that the pre-S mutant HBsAg contributes to the oxidative DNA damage to hepatocytes. In addition, the mutation rates in the X-linked hprt gene were enhanced in mouse hepatoma ML1-4a cells, which constitutively expressed the pre-S1/S2 HBsAg. These results indicate that pre-S1/S2 mutant HBsAg, which make up GGHs, induce oxidative DNA damage and mutations in hepatocytes in the late stages of HBV infection.

Animals↗