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Biomedical subjects

S H Han

Publications and source records attributed to S H Han.

At least 55 records · Page 3Linked to original sources
PubMed2000

Requirement of hydrogen peroxide generation in TGF-beta 1 signal transduction in human lung fibroblast cells: involvement of hydrogen peroxide and Ca2+ in TGF-beta 1-induced IL-6 expression.

Stimulation of human lung fibroblast cells with TGF-beta1 resulted in a transient burst of reactive oxygen species with maximal increase at 5 min after treatment. This reactive oxygen species increase was inhibited by the antioxidant, N-acetyl-l -cysteine (NAC). TGF-beta1 treatment stimulated IL-6 gene expression and protein synthesis in human lung fibroblast cells. Antioxidants including NAC, glutathione, and catalase reduced TGF-beta1-induced IL-6 gene expression, and direct H2O2 treatment induced IL-6 expression in a dose-dependent manner. NAC also reduced TGF-beta1-induced AP-1 binding activity, which is involved in IL-6 gene expression. It has been reported that Ca2+ influx is stimulated by TGF-beta1 treatment. EGTA suppressed TGF-beta1- or H2O2-induced IL-6 expression, and ionomycin increased IL-6 expression, with simultaneously modulating AP-1 activity in the same pattern. PD98059, an inhibitor of mitogen-activated protein kinase (MAPK) kinase/extracellular signal-related kinase kinase 1, suppressed TGF-beta1- or H2O2-induced IL-6 and AP-1 activation. In addition, TGF-beta1 or H2O2 increased MAPK activity which was reduced by EGTA and NAC, suggesting that MAPK is involved in TGF-beta1-induced IL-6 expression. Taken together, these results indicate that TGF-beta1 induces a transient increase of intracellular H2O2 production, which regulates downstream events such as Ca2+ influx, MAPK, and AP-1 activation and IL-6 gene expression.

Calcium↗
PubMed2000

2-Amino-3-methylimidazo[4,5-f]quinoline inhibits nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cells by blocking p38 kinase activation.

We show that 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a heterocyclic amine, significantly inhibits nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated macrophages. The decrease in NO production was found to correlate well with a decrease in inducible NO synthase (iNOS) mRNA expression as demonstrated by Northern blot analysis. Treatment of RAW 264.7 cells with IQ selectively inhibited the activation of NF-kappaB/Rel, an important transcription factor of iNOS gene expression, while neither AP-1 nor Oct was affected by IQ. Since iNOS transcription has been shown recently to be under the control of the p38 kinase signaling cascade, we assessed the effect of IQ on p38 kinase activation. Treatment of RAW 264.7 with IQ inhibited LPS-stimulated p38 kinase phosphorylation in a dose-related manner. IQ also inhibited the p38 kinase activity. Collectively, this series of experiments indicates that IQ inhibits LPS-induced expression of iNOS gene in RAW 264.7 cells. Based on our findings, the most likely mechanism that can account for this biological effect involves the negative regulation of NF-kappaB/Rel and p38 kinase pathway.

Animals↗
PubMed2000

Dexamethasone inhibits IL-1 beta gene expression in LPS-stimulated RAW 264.7 cells by blocking NF-kappa B/Rel and AP-1 activation.

In the present study, the mechanism by which dexamethasone (DEX) inhibited IL-1beta gene expression in bacterial lipopolysaccharide (LPS)-activated RAW 264.7 cells was investigated. The decrease in LPS-induced IL-1beta mRNA expression was demonstrated by quantitative reverse transcription polymerase chain reaction (RT-PCR). Since the promoter in IL-1beta gene contains binding motifs for NF-kappaB/Rel, AP-1, NF-IL6, and CREB/ATF, which appear to be important in LPS-mediated IL-1beta induction, the effects of DEX on the activation of these transcription factors were examined. Treatment of DEX to RAW 264.7 cells induced a dose-related inhibition of NF-kappaB/Rel and AP-1 in chloramphenicol acetyltransferase activity, while neither NF-IL6 nor CREB/ATF activation was affected by DEX. Treatment of RAW 264.7 cells with DEX inhibited DNA binding of NF-kappaB/Rel and AP-1 proteins to their cognate DNA sites as measured by electrophoretic mobility shift assay (EMSA). DEX treatment caused a significant reduction in nuclear c-rel, p65, and p50 protein contents, and these decreases were paralleled by the accumulation of cytoplasmic c-rel, p65, and p50. DEX treatment of RAW 264.7 cells did not inhibit the nuclear translocation of c-jun and c-fos. We found that the inhibition of IL-1beta production by DEX is not related to p38, which is important in the IL-1beta induction. These results suggest that DEX may inhibit IL-1beta gene expression by a mechanism involving the blocking of LPS-induced NF-kappaB/Rel and AP-1 activation.

Animals↗
PubMed2000

Chlorophyllin suppression of lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells.

Chlorophyllin (CHL), a water-soluble derivative of chlorophyll, functions as an anticarcinogen and antioxidant. In the present study, we investigated the effect of CHL on nitric oxide production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Treatment with CHL inhibited nitric oxide production in the LPS-stimulated RAW 264. 7 cells in a dose-related manner. Competitive RT-PCR analysis, using a DNA competitor as an internal standard, demonstrated that the treatment with 1, 10, and 50 microM CHL decreased LPS-induced iNOS mRNA expression in a concentration-dependent manner. Since the expression of the iNOS gene is mainly regulated by NF-kappaB, we then examined the effects of CHL on the NF-kappaB DNA binding activity, using an electrophoretic mobility shift assay. CHL down-regulated the NF-kappaB DNA binding on its cognate recognition site at the concentrations just noted. Employing a transfection and reporter gene expression system with p(NF-kappaB)(3)-chloramphenicol acetyl transferase (CAT), the treatment of CHL produced a dose-dependent inhibition of CAT activity in RAW 264.7 cells. Furthermore, CHL partially restored LPS-decreased IkappaBalpha, an inhibitory protein against NF-kappaB activation, in the cytosolic extract from the LPS-treated cells determined by immunoblot analysis. CHL also protected the hydroxyl radical-induced cytotoxicity in RAW 264.7 cells, indicating its antioxidant effect. These results suggest that CHL suppresses the nitric oxide production and iNOS mRNA expression mediated by the inhibition of NF-kappaB activation, and its action mechanism may be based on its antioxidant effect.

Animals↗
PubMed2000

Vitamin D3 up-regulated protein 1 mediates oxidative stress via suppressing the thioredoxin function.

As a result of identifying the regulatory proteins of thioredoxin (TRX), a murine homologue for human vitamin D3 up-regulated protein 1 (VDUP1) was identified from a yeast two-hybrid screen. Cotransfection into 293 cells and precipitation assays confirmed that mouse VDUP1 (mVDUP1) bound to TRX, but it failed to bind to a Cys32 and Cys35 mutant TRX, suggesting the redox-active site is critical for binding. mVDUP1 was ubiquitously expressed in various tissues and located in the cytoplasm. Biochemical analysis showed that mVDUP1 inhibited the insulin-reducing activity of TRX. When cells were treated with various stress stimuli such as H2O2 and heat shock, mVDUP1 was significantly induced. TRX is known to interact with other proteins such as proliferation-associated gene and apoptosis signal-regulating kinase 1. Coexpression of mVDUP1 interfered with the interaction between TRX and proliferation-associated gene or TRX and ASK-1, suggesting its roles in cell proliferation and oxidative stress. To investigate the roles of mVDUP1 in oxidative stress, mVDUP1 was overexpressed in NIH 3T3 cells. When cells were exposed to stress, cell proliferation was declined with elevated apoptotic cell death compared with control cells. In addition, c-Jun N-terminal kinase activation and IL-6 expression were elevated. Taken together, these results demonstrate that mVDUP1 functions as an oxidative stress mediator by inhibiting TRX activity.

3T3 Cells↗
PubMed2000

No association between alpha-1-antichymotrypsin polymorphism and Alzheimer's disease in Koreans.

To examine the possible involvement of the alpha-1-antichymotrypsin gene (ACT) polymorphism in the manifestation of Alzheimer's disease (AD), we analyzed genotypes of the ACT and apolipoprotein E gene (APOE) among 110 Korean patients with probable AD and 209 nondemented controls. No significant difference was obtained in genotypic (chi(2)=1.98, df=2, P>0.1) and allelic frequencies (chi(2)=1.61, df=1, P>0.1) of ACT between the AD and control groups. No overexpression of the ACT A/A genotype and ACT A allele was found when we analyzed the late-onset AD patients and the early-onset AD patients, separately. Then we stratified the ACT genotypes based on the presence or absence of the APOE epsilon4 allele to evaluate the possible interaction between them. In the APOE epsilon4-negative subjects, although the ACT A allele tended to be overexpressed in the AD group, the differences in the frequencies of the ACT A allele (chi(2)=2.79, df=1, P>0.1) and ACT A/A genotype (chi(2)=0.16, df=1, P>0.1) were not statistically significant. No significant overrepresentations of the ACT A allele (chi(2)=0.02, df=1, P>0.1) and ACT A/A genotype (chi(2)=0.17, df=1, P>0.1) were found in the APOE epsilon4-positive subjects, either. In addition, the status of the ACT genotype did not influence the age-at-onset of AD (F=0.03, df=2, P>0.1). Therefore, the ACT polymorphism does not contribute to the development of AD independently or interactively with the APOE epsilon4 allele in Koreans.

Age of Onset↗
PubMed2000

Kainic acid-induced seizures cause neuronal death in infant rats pretreated with lipopolysaccharide.

A major controversy in human epilepsy is whether severe seizures in infants or young children cause brain damage and subsequent epilepsy. Kainic acid (KA) produces severe seizures in infant rats, but hippocampal neuronal death and mossy fibre sprouting have not been previously demonstrated. There are similarities between lipopolysaccharide (LPS) pretreatment and KA-induced seizures in rats and the febrile convulsion of young children, in that both processes are associated with an immune stimulus and seizures. Infant rats, co-treated with LPS and KA, showed hippocampal neuronal death and mossy fibre sprouting. Taken together, our results suggest that severe febrile convulsion of young children may cause hippocampal damage and synaptic reorganization.

Animals↗
PubMed2000

Cellular invasion of Orientia tsutsugamushi requires initial interaction with cell surface heparan sulfate.

Role of transmembrane heparan sulfate proteoglycans on invasion of Orientia tsutsugamushi into host cells was investigated. Pretreatment with heparan sulfate and heparin inhibited the infection of O. tsutsugamushi for L cell, mouse fibroblast, whereas other glycosaminoglycans had little effect. These same treatments were also shown to reduce the infection in a dose-dependent manner, and enzymatic treatment of cells with heparitinase, but not chondroitinase ABC, inhibited the infection. In addition, mutant cell lines of Chinese hamster ovarian cell defective in heparan sulfate synthesis but not chondrotin sulfate synthesis and defective in all glycosaminoglycan synthesis showed marked reduction in susceptibility to infection by O. tsutsugamushi. Also mutant cell lines, which express heparan sulfate proteoglycans at low level, showed intermediate level of infectivity. Finally O. tsutsugamushi bind to(35)S-labelled heparin. Collectively, these findings provide strong evidence that heparan sulfate proteoglycans contribute to the attachment of O. tsutsugamushi to the cells.

Animals↗
PubMed2000

Liver transplantation. Selection, listing criteria, and preoperative management.

Although only the expansion of the donor pool will have a major impact on the survival of patients with decompensated cirrhosis awaiting OLT, anticipation of complications such as SBP may improve the likelihood of a patient surviving until OLT, and may ameliorate some of the major causes of morbidity of cirrhosis, such as osteoporosis. Close communication between the treating physicians and the transplant center is crucial to ensure that the patients' UNOS status can be appropriately adjusted if additional complications of cirrhosis, such as intractable ascites, have occurred.

Adult↗
PubMed2000

Production and characterization of monoclonal antibodies to serine proteinase allergens in Penicillium and Aspergillus species.

BACKGROUND: Alkaline and/or vacuolar serine proteinases are major allergens in prevalent airborne Penicillium and Aspergillus species. OBJECTIVE: The object of this study is to generate and characterize monoclonal antibodies against these serine proteinase allergens. METHODS: BALB/c mice were immunized individually with the Penicillium citrinum culture medium or the crude extract and culture medium preparations of Aspergillus fumigatus. Hybridoma cells that secrete monoclonal antibodies against serine proteinase allergens were selected by immunoblotting. Antigens in three different Penicillium (P. citrinum, P. notatum and P. oxalicum) and two different Aspergillus species (A. fumigatus, and A. flavus) recognized by these monoclonal antibodies were analysed by sodium dodecyl sulphate and two-dimensional polyacrylamide gel electrophoresis immunoblotting and N-terminal amino acid sequence analysis. RESULTS: Four (PCM8, PCM10, PCM16 and PCM39) and one (FUM20) monoclonal antibodies against serine proteinase allergens were generated after fusion of NS-1 cells with spleen cells obtained from BALB/c mice immunized with antigens from P. citrinum and A. fumigatus, respectively. Immunoblotting results showed that PCM8 reacted with an alkaline serine proteinase allergen in P. citrinum and P. notatum. PCM10 and PCM39 reacted with the alkaline serine proteinase in two Penicillium (P. citrinum, P. notatum) and two Aspergillus species (A. fumigatus, and A. flavus) tested. PCM16 reacted with the alkaline serine proteinase allergen in P. citrinum, A. fumigatus and A. flavus but not with that in P. notatum. MoAb FUM20 reacted with the alkaline serine proteinase allergen in two Aspergillus species (A. fumigatus and A. flavus) but not with that in two different Penicillium species (P. citrinum, P. notatum) tested. Among these five monoclonal antibodies generated, only PCM39 and FUM20 can react with the vacuolar serine proteinase allergen in P. notatum, P. oxalicum and in A. fumigatus. The 35 kDa P. citrinum component that reacted with FUM20 has an N-terminal amino acid sequence of DSPSVEKNAP. CONCLUSION: Five monoclonal antibodies against different epitopes of the serine proteinase major allergens in prevalent Penicillium and Aspergillus species were generated in the present study. Antibodies obtained may be useful in the characterization and standardization of serine proteinase allergens in crude fungal extracts.

Allergens↗
PubMed2000

Successful orthotopic liver transplantation for lamivudine-associated YMDD mutant hepatitis B virus.

YMDD hepatitis B virus (HBV) mutants emerge in more than one third of patients treated with lamivudine. The development of escape mutants potentially limits the efficacy of this new therapy for chronic HBV infection. Transplant centers may be hesitant to perform orthotopic liver transplantation (OLT) in patients with progressive liver disease who develop the YMDD mutant because of concerns of graft reinfection. We describe a 56-year-old man with chronic liver disease caused by HBV who successfully underwent OLT after the emergence of a YMDD mutant and progressive liver disease. Perioperatively, he received high-dose intravenous hepatitis B immune globulin (HBIG) treatment with continued lamivudine treatment. Thirty-two months after OLT, there was no evidence of HBV reinfection with the use of lamivudine and high-dose HBIG. Our experience suggests that the emergence of a YMDD HBV mutant is not a contraindication to OLT. The combination of lamivudine and high-dose HBIG can protect against reinfection of the hepatic allograft with the YMDD HBV escape mutant.

Hepatitis B virus↗
PubMed2000

An efficacy and cost-effectiveness analysis of combination hepatitis B immune globulin and lamivudine to prevent recurrent hepatitis B after orthotopic liver transplantation compared with hepatitis B immune globulin monotherapy.

Orthotopic liver transplantation (OLT) for hepatitis B virus (HBV) infection was limited until recently by poor graft and patient outcomes caused by recurrent HBV. Long-term immunoprophylaxis with hepatitis B immune globulin (HBIG) dramatically improved post-OLT survival, but recurrent HBV still occurred in up to 36% of the recipients. More recently, combination HBIG and lamivudine has been shown to effectively prevent HBV recurrence in patients post-OLT. The aim of the current study is to determine long-term outcome and cost-effectiveness of using combination HBIG and lamivudine compared with HBIG monotherapy in patients who undergo OLT for HBV. A retrospective chart review identified 59 patients administered combination HBIG and lamivudine and 12 patients administered HBIG monotherapy as primary prophylaxis against recurrent HBV. Lamivudine, 150 mg/d, was administered orally indefinitely. HBIG was administered under a standard protocol (10,000 IU intravenously during the anhepatic phase, then 10,000 IU/d intravenously for 7 days, then 10,000 IU intravenously monthly) indefinitely. A decision-analysis model was developed to evaluate the potential economic impact of prophylaxis against HBV with combination therapy compared with monotherapy. Recurrent HBV was defined as the reappearance of hepatitis B surface antigen (HBsAg) after its initial disappearance post-OLT. In the combination-therapy group, no patient redeveloped serum HBsAg or HBV DNA during mean follow-ups of 459 and 416 days, respectively. In the monotherapy group, 3 patients (25%) had reappearance of HBsAg in serum during a mean follow-up of 663 days. Combination therapy resulted in a dominant, cost-effective strategy with an average cost-effectiveness ratio of $252,111/recurrence prevented compared with $362,570/recurrence prevented in the monotherapy strategy. Combination prophylaxis with HBIG and lamivudine is highly effective in preventing recurrent HBV, may protect against the emergence of resistant mutants, and is significantly more cost-effective than HBIG monotherapy with its associated rate of recurrent HBV.

Adolescent↗
PubMed2000

Endoscopic management of biliary leaks after T-tube removal in liver transplant recipients: nasobiliary drainage versus biliary stenting.

This study presents the long-term sequelae of endoscopic retrograde cholangiopancreatography (ERCP)-managed biliary leakage in patients who underwent orthotopic liver transplantation (OLT) and compares the relative efficacy, safety, and charges of nasobiliary drainage (NBD) versus biliary stenting (BS). We identified all orthotopic liver transplant recipients from January 1, 1993, to December 31, 1997, who had undergone ERCP for biliary leakage. Clinical outcome and charges were calculated on an intention-to-treat basis according to initial endoscopic therapy. Of the 1,166 adult OLTs performed during the study period, 442 patients underwent elective T-tube removal. ERCP was attempted in 69 patients (16%) who developed biliary leakage after T-tube removal. Three patients (5%) in whom initial ERCP was unsuccessful underwent surgery. NBD and BS were used as primary therapy in 45 (68%) and 21 patients (32%), respectively. Three patients initially treated with NBD required reendoscopy or surgery compared with 6 patients initially treated with BS (P <.05). Although not statistically significant, there was a trend toward greater expense in the BS group compared with the NBD group. ERCP is a safe and effective method of managing biliary leakage after T-tube removal in orthotopic liver transplant recipients. However, our results suggest NBD is the preferred method because recurrent leaks were more common in patients treated initially with BS. With prompt use of ERCP, surgery is rarely needed for this complication of OLT.

Bile↗
PubMed2000

Complementary DNA cloning and immunologic characterization of a new Penicillium citrinum allergen (Pen c 3).

BACKGROUND: Penicillium citrinum has been identified as the most prevalent airborne Penicillium species in the Taipei area. It is important to understand the allergenic composition of this ubiquitous fungal species. OBJECTIVE: The complementary DNA (cDNA) clone of an allergen from P citrinum was isolated and expressed in Escherichia coli as a fusion protein. mAbs were prepared with the recombinant protein as antigen. The corresponding natural allergen in the fungal extracts was identified with the mAbs. METHODS: A Uni-Zap XR P citrinum cDNA library was screened with sera from asthmatic patients. An IgE-binding cDNA clone was isolated and expressed as a glutathione-S-transferase fusion protein. The frequency of IgE binding to the expressed protein was analyzed by immunoblotting. Spleen cells from BALB/c mice immunized with the recombinant protein were fused with NS-1 cells for mAb generation. RESULTS: A P citrinum cDNA library was screened with a mixture of serum samples from 4 asthmatic patients. An IgE-binding cDNA clone was obtained and designated as PCE2. PCE2 has a 694-bp insert that contains a 167 amino acids open reading frame. The deduced amino acid sequence of the encoded protein has 82.6% (138 amino acids) identity with an Aspergillus fumigatus peroxisomal membrane protein allergen (Asp f 3). PCE2 was expressed in E coli as a fusion protein and designated as Pen c 3. Sera from 13 (46%) of the 28 Penicillium-sensitized asthmatic patients demonstrated IgE binding to Pen c 3. In addition, 11 of the 13 Pen c 3-positive serum samples have IgE immunoblot reactivity to recombinant Asp f 3. The presence of IgE cross-reactivity between Pen c 3 and Asp f 3 was also detected by immunoblot inhibition. Four of the 6 mAbs generated against Pen c 3 cross-react with Asp f 3. The presence of the corresponding 18-k natural allergens in the crude extracts of P citrinum and A fumigatus were detected by immunoblot with use of the mAbs and sera from asthmatic patients. CONCLUSION: Results obtained suggest that the peroxisomal membrane protein (Pen c 3) is an important allergen of P citrinum. PCE2 is a full-length cDNA clone encoding this allergen. In addition, the mAbs generated may be useful in standardizing the diagnostic allergenic extracts.

Adult↗
PubMed2000

Stratified tests, stratified slopes, and random effects models for clinical trials with missing data.

Because missing observations may affect the size and power of statistical tests of equality, various analytical techniques explicitly or implicitly condition the analysis on the amount of information available per person. We illustrate the difference between stratifying a slope estimate and stratifying a test statistic based on slopes. We compare a nonparametric version of the latter approach with the parametric tests available from SAS Proc Mixed. Power and size of these two approaches are considered under different parametric settings, distributions, and missing data mechanisms.

Algorithms↗
PubMed2000

Marked hippocampal neuronal damage without motor deficits after mild concussive-like brain injury in apolipoprotein E-deficient mice.

Of various biological factors, only allele epsilon 4 of apolipoprotein E (apoE, protein; APOE4, gene) has been thus far suggested as a major determinant of genetic risk for sporadic and late-onset familial Alzheimer's disease (AD). Environmental influences such as lack of education, traumatic brain injury, oxidative stress, environmental toxins, hormonal imbalances, and alterations in immune or inflammatory responses may also contribute to the pathogenesis of AD. Thus genetic susceptibility and environmental risk factors may have synergistic effects on the development of AD. The purpose of present report was to assess whether the gene (APOE) and the environmental risk factor (traumatic brain injury) could interact in hippocampal neuronal degeneration. We investigated the histopathological changes of hipoccampal regions after mild concussive-like brain injury without motor deficits in apoE-deficient mice using the recently described novel weight-drop device. Control mice revealed minimal neurodegenerative changes limited to CA2 and CA3, while apoE-deficient mice showed widespread neuronal degeneration throughout hippocampal subfields and part of dentate gyrus. We also observed widespread glial fibrillary acidic protein (GFAP) immunoreactivity throughout the hippocampus, which was more intense in apoE-deficient mice. The results of this study indicate that even very mild traumatic brain injury could result in widespread hippocampal damage in apoE-deficient mice. This again supports the hypothesis that apoE might play a neurotrophic or neuroprotective function in the central nervous system.

Alzheimer Disease↗