Publications by authors named "Jia-Ling Yang"

31 Publications

The Tip Region on VP2 Protein of Bluetongue Virus Contains Potential IL-4-Inducing Amino Acid Peptide Segments.

Pathogens 2020 Dec 22;10(1). Epub 2020 Dec 22.

School of Veterinary Medicine, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.

Bluetongue is an infectious viral hemorrhagic disease of domestic and wild ruminants that has a considerable economic impact on domestic ruminants. There are currently at least 29 serotypes of bluetongue virus (BTV) in the world. Noteworthily, the pathogenesis among BTV serotypes is different, even in the same animal species. In this study, BTV2/KM/2003 and BTV12/PT/2003 were used to investigate the differential immunological effects on bovine peripheral blood mononuclear cells (PBMCs). The BTV viral load and the expression of cytokine messenger RNA (mRNA) in PBMCs were measured by fluorescence-based real-time reverse-transcription PCR (qRT-PCR). The immunofluorescence assay (IFA) was applied to detect BTV signals in monocyte-derived macrophages (MDMs). The SWISS-MODEL and IL-4pred prediction tools were used to predict the interleukin 4 (IL-4)-inducing peptides in BTV-coat protein VP2. Synthetic peptides of VP2 were used to stimulate PBMCs for IL-4-inducing capability. This study demonstrated that the cytokine profiles of BTV-induced PBMCs were significantly different between BTV2/KM/2003 and BTV12/PT/2003. BTV2 preferentially activated the T helper 2 (Th2) pathway, represented by the early induction of IL-4, and likely fed back to inhibit the innate immunity. In contrast, BTV12 preferentially activated the innate immunity, represented by the induction of tumor necrosis factor -α (TNF-α) and interleukin 1 (IL-1), with only minimal subsequent IL-4. The BTV nonstructural protein 3 antibody (anti-BTV-NS3) fluorescent signals demonstrated that monocytes in PBMCs and MDMs were the preferred targets of BTV replication. Bioinformatics analysis revealed that the capability to induce IL-4 was attributed to the tip region of the VP2 protein, wherein a higher number of predicted peptide segments on BTVs were positively correlated with the allergic reaction reported in cattle. Synthetic peptides of BTV2-VP2 induced significant IL-4 within 12-24 h post-infection (hpi) in PBMCs, whereas those of BTV12 did not, consistent with the bioinformatics prediction. Bovine PBMCs and synthetic peptides together seem to serve as a good model for pursuing the BTV-induced IL-4 activity that precedes the development of an allergic reaction, although further optimization of the protocol is warranted.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/pathogens10010003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7822166PMC
December 2020

Type I hypersensitivity is induced in cattle PBMC during Bluetongue virus Taiwan isolate infection.

Vet Immunol Immunopathol 2020 Aug 21;226:110071. Epub 2020 May 21.

School of Veterinary Medicine, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei, 10617, Taiwan. Electronic address:

Bluetongue is a fatal viral disease in ruminants and has serious economic impacts on the livestock industry. Interactions between bluetongue virus (BTV) and immune cells are interesting because of the unique scenarios in each combination of animal species/breed and viral virulence/serotype. This study investigated the immune response in bovine peripheral blood mononuclear cells (PBMC) infected by the BTV2 Taiwan strain. The replication of the virus was limited in monocytes and monocyte-derived macrophages (MDM), and lymphocytes were less permissive. The cytokine mRNA of IL-4 in PBMC was expressed earlier and in greater quantities than that of innate immunity (TNFα, IL-1β) and cell mediated immunity (CMI) (IFNγ), and the IL-4 protein was stably present in the culture medium until 72 h post-infection (hpi). Even in MDM reconstituted with autologous lymphocyte (MDM-Lymphocyte), the IL-4 still had high mRNA expression level. The level of IgE antibody also increased at 24-72 hpi, suggestive of the engagement of type I hypersensitivity in the pathogenesis. The anti-viral activity contained in the culture supernatant was transferrable to recipient infected PBMC from other cows. However, in infected MDM largely free of lymphocytes, mRNA expressions of IL-1β, TNFα and IL-12p40 were normally expressed from 6 to 48 hpi, supporting the notion that IL-4 elaborated by lymphocytes in PBMC mediated the inhibition of both innate immunity and CMI to BTV2. The sum of responses subsequent to the early IL-4 expression likely constitutes part of the unique scenario in the current BTV2-Cow experimental combination biased toward Th2 response.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vetimm.2020.110071DOI Listing
August 2020

Heparan sulfate targeting strategy for enhancing liposomal drug accumulation and facilitating deep distribution in tumors.

Drug Deliv 2020 Dec;27(1):542-555

Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan.

Nanoparticles (NPs), such as liposomes, effectively evade the severe toxicity of unexpected accumulation and passively shuttle drugs into tumor tissues by enhanced permeability and retention. In the case of non-small cell lung cancer and pancreatic ductal adenocarcinoma, cancer-associated fibroblasts promote the aggregation of a gel-like extracellular matrix that forms a physical barrier in the desmoplastic stroma of the tumor. These stroma are composed of protein networks and glycosaminoglycans (GAGs) that greatly compromise tumor-penetrating performance, leading to insufficient extravasation and tissue penetration of NPs. Moreover, the presence of heparan sulfate (HS) and related proteoglycans on the cell surface and tumor extracellular matrix may serve as molecular targets for NP-mediated drug delivery. Here, a GAG-binding peptide (GBP) with high affinity for HS and high cell-penetrating activity was used to develop an HS-targeting delivery system. Specifically, liposomal doxorubicin (L-DOX) was modified by post-insertion with the GBP. We show that the uptake of L-DOX in A549 lung adenocarcinoma cells increased by GBP modification. Cellular uptake of GBP-modified L-DOX (L-DOX-GBP) was diminished in the presence of extracellular HS but not in the presence of other GAGs, indicating that the interaction with HS is critical for the cell surface binding of L-DOX-GBP. The cytotoxicity of doxorubicin positively correlated with the molecular composition of GBP. Moreover, GBP modification improved the distribution and anticancer efficiency of L-DOX, with enhanced desmoplastic targeting and extensive distribution. Taken together, GBP modification may greatly improve the tissue distribution and delivery efficiency of NPs against HS-abundant desmoplastic stroma-associated neoplasm.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/10717544.2020.1745326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7170378PMC
December 2020

Multicenter Study of Azole-Resistant Aspergillus fumigatus Clinical Isolates, Taiwan.

Emerg Infect Dis 2020 04;26(4):804-806

In a multicenter study, we determined a prevalence rate of 4% for azole-resistant Aspergillus fumigatus in Taiwan. Resistance emerged mainly from the environment (TR/L98H, TR/L98H/S297T/F495I, and TR/Y121F/T289A mutations) but occasionally during azole treatment. A high mortality rate observed for azole-resistant aspergillosis necessitates diagnostic stewardship in healthcare and antifungal stewardship in the environment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3201/eid2604.190840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7101115PMC
April 2020

Fruit Extract Ameliorates Experimental Autoimmune Encephalomyelitis through the Regulation of Th1/Th17 Cells.

Evid Based Complement Alternat Med 2019 14;2019:6797030. Epub 2019 Mar 14.

Department of Life Science, Institute of Biotechnology, National Tsing Hua University, Hsinchu 30013, Taiwan.

is a traditional Chinese medicine widely used for treating diarrhea, ulceration, and enuresis. Moreover, is effective for cognitive function improvement and nerve regeneration. Multiple sclerosis (MS) is a chronic neuronal inflammatory autoimmune disease that commonly affects young adults in high-latitude regions. The aim of this study was to evaluate the beneficial effects of in an experimental autoimmune encephalomyelitis (EAE) mouse model, which is an extensively used model for human MS. The ethanolic extract of fruit (AO-1) was orally administered to EAE mice. Our results showed AO-1 significantly reduced EAE symptoms. Histopathological analysis showed AO-1 reduced demyelination, inflammation, gliosis, and axonal swelling in the spinal cord. Furthermore, immunohistochemistry and quantitative polymerase chain reaction (qPCR) studies revealed that the infiltration of CD4, CD8 T cells, and CD11b monocytes into the spinal cord decreased in the AO-1-treated group. Mechanistically, the Th1 transcription factor T-bet, Th17 transcription factor retinoic acid receptor-related orphan receptor (RORt), and inflammatory cytokines interferon (IFN)- and interleukin (IL)-17 were reduced in the spinal cords of mice treated with AO-1. The expression levels of T-bet and RORt were also lowered in the spleens of those mice. Further study showed AO-1 inhibited production of IFN-, IL-2, and tumor necrosis factor- from MOG-peptide-stimulated splenocytes. One component isolated from AO-1, yakuchinone A, inhibited IL-17 production and reduced EAE symptoms in the mice. Collectively, our results indicate that AO-1 ameliorated the severity of EAE in mice and may involve the regulation of Th1/Th17 response. warrants further investigation, particularly regarding its clinical benefits for MS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1155/2019/6797030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6437745PMC
March 2019

Should we treat patients with only one set of positive blood cultures for extensively drug-resistant Acinetobacter baumannii the same as multiple sets?

PLoS One 2017 7;12(7):e0180967. Epub 2017 Jul 7.

Department of Internal Medicine, National Taiwan University Hospital Main Branch, and National Taiwan University College of Medicine, Taipei, Taiwan.

Acinetobacter species are not considered skin commensals and under-treatment is an overriding concern when caring for critically-ill patients who are mostly at risk of extensively drug-resistant Acinetobacter baumannii (XDRAB) infections. Hence even a single blood culture yielding XDRAB will tend to prompt intervention. However, field observations suggest that patients with single-positive blood cultures had milder disease and were more likely to be recruited in interventional studies than those with multiple-positive blood cultures, yet no distinction is made in current clinical or trial recruitment practices. To our knowledge, this is the first study to compare the clinical characteristics and outcomes of patients with single-positive versus multiple-positive blood cultures for XDRAB. In this multicenter prospective cohort study of XDRAB bacteremic patients from July 2010 to June 2015, only patients with at least two simultaneously drawn blood cultures were included. The patients were classified as having single-positive or multiple-positive blood cultures according to the number of positive blood cultures yielding XDRAB. The primary end-point was the 28-day mortality. Of a total of 155 patients enrolled, 69 had a single-positive and 86 had multiple-positive blood cultures. Leukopenia (37.2% vs. 16.2%; P = 0.004), thrombocytopenia (56.0% vs. 26.5%; P < 0.001), higher Pitt bacteremia scores (6.6 vs. 5.5, P = 0.03) and higher 28-day mortality rates (70.9% vs. 43.5%; P = 0.001) distinguished patients with multiple-positive from those with single-positive cultures. Multivariate logistic regression showed that multi-positivity independently predicted 28-day mortality (adjusted odds ratio, 2.34; 95% confidence interval (CI), 1.03-5.28; P = 0.04) and the Cox regression confirmed that multi-positivity (adjusted hazard ratio, 1.80; 95% CI, 1.13-2.85; P = 0.01) predicted rapid mortality. Patients with multiple versus single positive blood cultures yielding XDRAB had greater morbidity and mortality. Investigators and clinicians should be aware that the blood culture positivity rate impacts outcomes of XDRAB bacteremia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180967PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5501650PMC
September 2017

Gender-specific contributing risk factors and outcome of female cryptococcal meningoencephalitis patients.

BMC Infect Dis 2016 Jan 22;16:22. Epub 2016 Jan 22.

Department of Neurology, Nanfang Hospital, Southern Medical University, No.1838 North Guangzhou Avenue, Guangzhou City, Guangdong Province, People's Republic of China.

Background: Although male predominance was documented in previous studies on cryptococcal meningoencephalitis (CM), there has been no statistical study about female CM patients despite recently noticeable increase in female prevalence. In the current study, we aimed to investigate the independent gender-specific contributing risk factors for onset of CM and factors related to survival time in female patients by chosen statistical tools.

Methods: There have been 108 patients diagnosed with CM from July 1, 1998 to June 30, 2013 in Nanfang Hospital that were included in our study. This 15-year retrospective study compared demographic and clinical features of 31 female patients with 77 males. Multivariate analysis was performed for detection of the contributors to the onset of CM in female patients. The independent variables for multivariate analysis were selected according to statistical significance in univariate analysis. Furthermore, Cox regression model was used to evaluate the factors related to survival length.

Results: Use of corticosteroids or other immunosuppressants (32.3% versus 11.7%; p = 0.011) and history of systemic lupus erythematosus (SLE) and other autoimmune diseases (29% versus 3.9%; p < 0.001) were more common in females, but only the history of SLE or other autoimmune diseases was significant (OR 10.59, 95% CI 1.49-74.77, p = 0.02) by multivariate analysis. The ratio of cerebrospinal fluid (CSF) glucose-to-blood glucose was related to the survival time (p = 0.03, 95% CI 0-0.71).

Conclusions: The results showed that the history of SLE or other autoimmune diseases rather than chronic use of corticosteroids and/or immunosuppressants was the independent gender-specific contributing risk factor in female CM patients. Therefore, more attention should be made to the prevention of infection from the genus Cryptococcus spp. in female patients with SLE or other autoimmune diseases. In addition, decreased ratio of CSF glucose-to-blood glucose before antifungal therapy predicted the worse prognosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12879-016-1363-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4724144PMC
January 2016

The urinary shedding of porcine teschovirus in endemic field situations.

Vet Microbiol 2016 Jan 17;182:150-5. Epub 2015 Nov 17.

School of Veterinary Medicine, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan. Electronic address:

Porcine teschoviruses (PTVs) belong to the genus Teschovirus within the family Picornaviridae. PTVs are universal contaminants in pig herds in endemic and multi-infection statuses. Previous research has demonstrated PTV antigens and nucleic acid in renal glomeruli and tubular epithelia, suggesting the possibility that PTVs might be shed and transmitted via urine. The study aimed to demonstrate, in the context of pathogenesis, the presence of PTVs in the urine of naturally infected pigs. Viral loads of fluid and tissue samples quantified by an established qRT-PCR showed detection rates of 100% by head and in urine, feces, plasma and nasal swabs, and 38% in kidney. As predicted, PTVs were present in urine at 10(4.02 ± 1.45) copies/100 μl volume, equivalent to 17% of that in plasma. No significant differences were observed between healthy and culled pigs or among the 7 sampled herds. The presence of PTVs in urine was further substantiated by molecular serotyping. In particular, PTV-10 was identified in the urine of 3 piglets from 3 separate herds, consistent with the most prevalent serotype found in this study, and in plasma. The urine mixes with feces to form slurry making it easier for PTV to spread and contaminate the environment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vetmic.2015.11.008DOI Listing
January 2016

Excess Mortality Associated With Colistin-Tigecycline Compared With Colistin-Carbapenem Combination Therapy for Extensively Drug-Resistant Acinetobacter baumannii Bacteremia: A Multicenter Prospective Observational Study.

Crit Care Med 2015 Jun;43(6):1194-204

1Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan. 2Department of Internal Medicine, National Taiwan University Hospital Hsin-chu Branch, Hsin-chu, Taiwan. 3Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan. 4Department of Internal Medicine, Far Eastern Memorial Hospital, New Taipei City, Taiwan. 5Department of Internal Medicine, National Taiwan University Hospital Yun-Lin Branch, Yun-lin, Taiwan. 6Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan.

Objectives: Since few therapeutic options exist for extensively drug resistant Acinetobacter baumannii, an emerging threat in ICUs worldwide, and comparative prospective studies of colistin-based combination therapies are lacking, our objective was to compare the outcomes of patients with extensively drug-resistant A. baumannii bacteremia, treated with colistin-carbapenem and colistin-tigecycline combinations.

Design: Prospective, observational, multicenter study.

Setting, Patients, And Interventions: Adults with extensively drug-resistant A. baumannii bacteremia were prospectively followed from 2010 to 2013 at three hospitals in Taiwan. Extensively drug-resistant A. baumannii was defined as A. baumannii (genospecies 2) nonsusceptible to all drug classes except for colistin and tigecycline, and standard combination therapy as use of parenteral colistin-carbapenem or colistin-tigecycline for at least 48 hours after onset of bacteremia.

Measurements And Main Results: Primary outcome measure was 14-day mortality. Of the 176 episodes of extensively drug-resistant A. baumannii bacteremia evaluated, 55 patients with a median (interquartile range) age of 62 years (44-79 yr) and Sequential Organ Failure Assessment score of 9 (5-13) points received standard combination therapy: colistin-tigecycline in 29 patients and colistin-carbapenem in 26. Crude 14-day and in-hospital mortality rates for patients receiving colistin-tigecycline versus patients receiving colistin-carbapenem were 35% versus 15% (p=0.105) and 69% versus 50% (p=0.152), respectively. Breakthrough extensively drug-resistant A. baumannii bacteremia under steady state concentrations of combination therapy for colistin-tigecycline group was 18% and for colistin-carbapenem group was 0% (p=0.059). Eleven patients (20.0%) developed nephrotoxicity. After adjusting for age, sex, comorbidity, initial disease severity, loading colistin dose, polymicrobial infection, and primary infection site, excess 14-day mortality was associated with the use of colistin-tigecycline in the subgroup with tigecycline minimum inhibitory concentration greater than 2 mg/L compared with the use of colistin-carbapenem (hazard ratio, 6.93; 95% CI, 1.61-29.78; p=0.009).

Conclusions: Increased 14-day mortality was associated with colistin-tigecycline therapy given tigecycline minimum inhibitory concentration greater than 2 mg/L compared with colistin-carbapenem therapy for extensively drug-resistant A. baumannii bacteremia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/CCM.0000000000000933DOI Listing
June 2015

Trend in vancomycin susceptibility and correlation with molecular characteristics of methicillin-resistant Staphylococcus aureus causing invasive infections in Taiwan: results from the Tigecycline in vitro Surveillance in Taiwan (TIST) study, 2006-2010.

Diagn Microbiol Infect Dis 2014 Oct 21;80(2):162-7. Epub 2014 Jun 21.

Division of Infectious Diseases, Department of Internal Medicine, Kaohsiung Medical University Hospital, and Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.

This study was intended to investigate the trend in vancomycin susceptibility and correlation with molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) causing invasive infections. A total of 670 MRSA isolates were collected from patients with invasive infections as part of bacterial collection in the Tigecycline in vitro Surveillance in Taiwan (TIST) from 2006 to 2010. MICs of the isolates to vancomycin were determined using the agar dilution method. Characteristics of staphylococcal cassette chromosome mec (SCCmec), mec-associated hypervariable region (dru), and accessory gene regulator (agr) of the isolates were identified by polymerase chain reaction methods. MRSA isolates with SCCmec types I, II, and III were molecularly defined as hospital-associated MRSA (HA-MRSA), and those with SCCmec types IV, V, and VT were assigned as community-associated MRSA (CA-MRSA). All but 1 MRSA isolates exhibited vancomycin MICs ≤1 mg/L. A declining trend in vancomycin MICs among MRSA isolates was noted, which was associated with the decline in proportion of HA-MRSA. The percentage of CA-MRSA increased from 25.6% in 2006 to 46.0% in 2010. An increase in the geometric mean of vancomycin MICs was found in MRSA with particular molecular types such as SCCmec types II and III, agr groups I and II, and dru10-14. A significant correlation among particular molecular types was found, including SCCmecII-agr group II-dru4, SCCmecIII-agr group I-dru11-14, SCCmecIV-agr group II-dru9, and SCCmecVT-agr group I-dru9 and dru11. There was no vancomycin creep among MRSA isolates, and the declining trend of vancomycin MIC against MRSA was attributed to the increasing prevalence of CA-MRSA over time.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.diagmicrobio.2014.06.007DOI Listing
October 2014

Slow immunological progression in HIV-1 CRF07_BC-infected injecting drug users.

Emerg Microbes Infect 2013 Dec 11;2(12):e83. Epub 2013 Dec 11.

Departments of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine , Taipei, Taiwan.

Human immunodeficiency virus type 1 (HIV-1) circulating recombinant form (CRF) 07_BC has caused serious HIV-1 epidemics among injecting drug users (IDUs) in East Asia. Little is known about the characteristics of the virus and its impact on disease progression among the infected individuals. In this study, we compared immunological progression between 423 IDUs infected with CRF07_BC and 194 men who have sex with men (MSM) with primary subtype B infection, and a representative full-length CRF07_BC molecular clone, pCRF07_BC, was constructed to characterize the virus. We found that IDUs infected with CRF07_BC had significantly slower immunological progression in the Cox proportional hazards model (hazard ratio: 0.30; 95% confidence interval: 0.13-0.69; P=0.004). The constructed recombinant CRF07_BC viruses had a reduced processing of the Gag/Gag-Pol polyproteins, a decreased incorporation of Vpr in the virus particle, tethering of virus particles on the plasma membrane and decreased virus growth kinetics. These phenotypes are related to the unique 7-amino acid deletion in the p6 of CRF07_BC, since complementation of the 7-amino acid in pCRF07_BC could improve the defective phenotypes. In summary, compared with MSM infected with HIV-1 subtype B, IDUs infected with CRF07_BC had slower immunological progression, which is likely correlated with interference of virus particle maturation by the 7-amino acid deletion in p6.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/emi.2013.83DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3880871PMC
December 2013

Trends in the antimicrobial susceptibilities and serotypes of Streptococcus pneumoniae: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006-2010.

Int J Antimicrob Agents 2013 Oct 9;42(4):312-6. Epub 2013 Jul 9.

Section of Infectious Diseases, Department of Internal Medicine, Far Eastern Memorial Hospital, Taiwan.

Isolates of Streptococcus pneumoniae (n = 530) were collected from 20 hospitals in different parts of Taiwan from 2006 to 2010. MICs to 16 antimicrobial agents were determined by broth dilution method and serotypes were identified by latex agglutination. Based on meningitis (non-meningitis) criteria established by the CLSI, 11.7% (63.2%) of all isolates were susceptible to penicillin and 46.0% (83.8%) were susceptible to ceftriaxone. Of the isolates, 94.3% were non-susceptible to azithromycin and 5.8% and 7.2% were non-susceptible to moxifloxacin and levofloxacin, respectively. Susceptibility to penicillin by meningitis criteria increased significantly (P = 0.0012) with year, and that to clindamycin and amoxicillin/clavulanic acid declined significantly (P < 0.05). Six major serotypes were found, namely 19F (24.0%), 23F (18.5%), 14 (13.6%), 6B (12.5%), 19A (7.5%) and 3 (5.1%). Prevalence of serotypes 19F and 14 remained stationary, that of serotype 6B decreased significantly (P < 0.0001) and that of serotype 19A increased significantly (P < 0.0001) with year. The coverage rate of PCV-7 among the pneumococcal isolates declined from 80.5% in 2006 to 50% in 2010 (P < 0.0001) and that of PCV-13 declined from 91.5% in 2009 to 75% in 2010. The non-susceptibility rate to levofloxacin was highest among serotype 23F isolates (13.3%) and lowest among serotype 19A isolates (2.5%). Rates of resistance to the four agents penicillin, ceftriaxone, azithromycin and clindamycin were highest among serotype 19A isolates (70.0%) and 23F isolates (49.0%). All serotype 3 isolates were susceptible to four of the most commonly used antibiotics (penicillin, ceftriaxone, azithromycin and levofloxacin).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijantimicag.2013.05.013DOI Listing
October 2013

APE1/Ref-1 prevents oxidative inactivation of ERK for G1-to-S progression following lead acetate exposure.

Toxicology 2013 Mar 28;305:120-9. Epub 2013 Jan 28.

Molecular Carcinogenesis Laboratory, Institute of Biotechnology & Department of Life Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan.

Apurinic/apyrimidinic endonuclease 1 (APE1)/redox effector factor-1 is a multifunctional enzyme involved in DNA base excision repair and protein redox regulation. Previously, we have showed that lead acetate (Pb) elicits EGFR activation to initiate the SFK/PKCα/Ras/Raf-1/MKK1/2/ERK signaling cascade functioning against genotoxicity. Here, we explore whether APE1 and reactive oxygen species (ROS) affect ERK signaling and cell cycle progression following Pb exposure. We found that Pb induced APE1 expression and ROS generation in CL3 human lung cancer cells. The Pb-elicited ROS levels and cytotoxicity were further enhanced by introducing small interfering RNA specific for APE1 (siAPE1). E3330, an inhibitor of APE1 redox activity, also augmented the ROS levels and cytotoxicity in Pb-treated cells. Intriguingly, the capability of Pb to activate ERK was abolished under siAPE1 or E3330 co-treatments; conversely, forced expression of APE1 up-regulated the ERK activation by Pb or serum in both Cys65-redox activity dependent and independent manners. Moreover, APE1 formed complex with ERK2, and its redox activity could rescue ERK oxidative inactivation. APE1 redox activity also facilitated the Cyclin D1 expression and G1-to-S progression following Pb exposure. In summary, the results indicate that APE1 is a direct redox regulator of ERK for maintaining the kinase activity to promote cell proliferation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.tox.2013.01.010DOI Listing
March 2013

Trends in susceptibility of vancomycin-resistant Enterococcus faecium to tigecycline, daptomycin, and linezolid and molecular epidemiology of the isolates: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006 to 2010.

Antimicrob Agents Chemother 2012 Jun 9;56(6):3402-5. Epub 2012 Apr 9.

Section of Infectious Diseases, Department of Internal Medicine, Far Eastern Memorial Hospital, New Taipei City, Taiwan.

Among the 219 vancomycin-resistant Enterococcus faecium isolates collected in 20 Taiwanese hospitals from 2006 to 2010, all were susceptible to linezolid and daptomycin, and 98.6% were susceptible to tigecycline. There was a shift toward higher tigecycline MIC values (MIC(90)s) from 2006-2007 (0.06 μg/ml) to 2008-2010 (0.12 μg/ml). The MIC(90)s of daptomycin and linezolid remained stationary. Although pulsotypes among the isolates from the 20 hospitals varied, intrahospital spreading of several clones was identified in 13 hospitals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AAC.00533-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3370810PMC
June 2012

Trends in the susceptibility of clinically important resistant bacteria to tigecycline: results from the Tigecycline In Vitro Surveillance in Taiwan study, 2006 to 2010.

Antimicrob Agents Chemother 2012 Mar 27;56(3):1452-7. Epub 2011 Dec 27.

Division of Infectious Diseases, Department of Internal Medicine, Kaohsiung Medical University Hospital, and Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.

The Tigecycline In Vitro Surveillance in Taiwan (TIST) study, a nationwide, prospective surveillance during 2006 to 2010, collected a total of 7,793 clinical isolates, including methicillin-resistant Staphylococcus aureus (MRSA) (n = 1,834), penicillin-resistant Streptococcus pneumoniae (PRSP) (n = 423), vancomycin-resistant enterococci (VRE) (n = 219), extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (n = 1,141), ESBL-producing Klebsiella pneumoniae (n = 1,330), Acinetobacter baumannii (n = 1,645), and Stenotrophomonas maltophilia (n = 903), from different specimens from 20 different hospitals in Taiwan. MICs of tigecycline were determined following the criteria of the U.S. Food and Drug Administration (FDA) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST-2011). Among drug-resistant Gram-positive pathogens, all of the PRSP isolates were susceptible to tigecycline (MIC(90), 0.03 μg/ml), and only one MRSA isolate (MIC(90), 0.5 μg/ml) and three VRE isolates (MIC(90), 0.125 μg/ml) were nonsusceptible to tigecycline. Among the Gram-negative bacteria, the tigecycline susceptibility rates were 99.65% for ESBL-producing E. coli (MIC(90), 0.5 μg/ml) and 96.32% for ESBL-producing K. pneumoniae (MIC(90), 2 μg/ml) when interpreted by FDA criteria but were 98.7% and 85.8%, respectively, when interpreted by EUCAST-2011 criteria. The susceptibility rate for A. baumannii (MIC(90), 4 μg/ml) decreased from 80.9% in 2006 to 55.3% in 2009 but increased to 73.4% in 2010. A bimodal MIC distribution was found among carbapenem-susceptible A. baumannii isolates, and a unimodal MIC distribution was found among carbapenem-nonsusceptible A. baumannii isolates. In Taiwan, tigecycline continues to have excellent in vitro activity against several major clinically important drug-resistant bacteria, with the exception of A. baumannii.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AAC.06053-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294947PMC
March 2012

Agreement assessment of tigecycline susceptibilities determined by the disk diffusion and broth microdilution methods among commonly encountered resistant bacterial isolates: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2008 to 2010.

Antimicrob Agents Chemother 2012 Mar 12;56(3):1414-7. Epub 2011 Dec 12.

Division of Infectious Diseases, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University Medical College, Kaohsiung, Taiwan.

The Tigecycline In Vitro Surveillance in Taiwan (TIST) study, initiated in 2006, is a nationwide surveillance program designed to longitudinally monitor the in vitro activity of tigecycline against commonly encountered drug-resistant bacteria. This study compared the in vitro activity of tigecycline against 3,014 isolates of clinically important drug-resistant bacteria using the standard broth microdilution and disk diffusion methods. Species studied included methicillin-resistant Staphylococcus aureus (MRSA; n = 759), vancomycin-resistant Enterococcus faecium (VRE; n = 191), extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (n = 602), ESBL-producing Klebsiella pneumoniae (n = 736), and Acinetobacter baumannii (n = 726) that had been collected from patients treated between 2008 and 2010 at 20 hospitals in Taiwan. MICs and inhibition zone diameters were interpreted according to the currently recommended U.S. Food and Drug Administration (FDA) criteria and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. The MIC(90) values of tigecycline against MRSA, VRE, ESBL-producing E. coli, ESBL-producing K. pneumoniae, and A. baumannii were 0.5, 0.125, 0.5, 2, and 8 μg/ml, respectively. The total error rates between the two methods using the FDA criteria were high: 38.4% for ESBL-producing K. pneumoniae and 33.8% for A. baumannii. Using the EUCAST criteria, the total error rate was also high (54.6%) for A. baumannii isolates. The total error rates between these two methods were <5% for MRSA, VRE, and ESBL-producing E. coli. For routine susceptibility testing of ESBL-producing K. pneumoniae and A. baumannii against tigecycline, the broth microdilution method should be used because of the poor correlation of results between these two methods.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AAC.05879-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294924PMC
March 2012

Cdc20 proteolysis requires p38 MAPK signaling and Cdh1-independent APC/C ubiquitination during spindle assembly checkpoint activation by cadmium.

J Cell Physiol 2010 May;223(2):327-34

Molecular Carcinogenesis Laboratory, Department of Life Sciences, Institute of Biotechnology, National Tsing Hua University, Hsinchu 30013, Taiwan.

Cdc20, an activator of the anaphase promoting complex/cyclosome (APC/C) ubiquitin ligase, initiates the destruction of key mitotic regulators to facilitate mitosis, while it is negatively regulated by the spindle assembly checkpoint (SAC) to prevent premature anaphase entry. Activation of the p38 mitogen-activated protein kinase could contribute to mitotic arrest, but the underlying mechanism is unknown. Here we report a novel pathway in which the p38 signaling triggers Cdc20 destruction under SAC elicited by cadmium, a human carcinogen. We found that the cadmium-induced prometaphase arrest was linked to decreased Cdc20 and accumulated cyclin A protein levels in human cells, whereas the activity of cyclin B1-Cdk1 was unaffected. The Cdc20 half-life was markedly shortened along with its ubiquitination and degradation via 26S proteasome in cadmium-treated asynchronous or G(2)-enriched cells. Depletion of APC3 markedly suppressed the cadmium-induced Cdc20 ubiquitination and proteolysis, while depletion of Cdh1, another activator of APC/C, did not. Intriguingly, blockage of p38 activity restored the Cdc20 levels for continuing mitosis under cadmium, while inhibition of JNK activity had no effect. The cadmium-induced Cdc20 proteolysis was also suppressed during transient depletion of p38alpha or stable expression a dominant negative form of p38. Inhibition of p38 abolished the induction of Mad2-Cdc20-APC3 complex by cadmium. Moreover, forced expression of MKK6-p38 signaling could promote Cdc20 degradation in a Cdh1-independent APC/C pathway. In summary, accelerated ubiquitination and proteolysis of Cdc20 is essential for prometaphase arrest that is mediated via the p38 signaling during SAC activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jcp.22038DOI Listing
May 2010

Prevalence of extended-spectrum beta-lactamases in Enterobacter cloacae in Taiwan and comparison of 3 phenotypic confirmatory methods for detecting extended-spectrum beta-lactamase production.

J Microbiol Immunol Infect 2009 Aug;42(4):310-6

Department of Internal Medicine, National Taiwan University Hospital, Taipei 100, Taiwan.

Background And Purpose: The prevalence of extended-spectrum beta-lactamases (ESBLs) in Enterobacter cloacae remains unclear in Taiwan. This study was conducted to investigate the prevalence of ESBL-producing E. cloacae in Taiwan.

Methods: 116 clinical isolates of E. cloacae were tested for cefepime susceptibility. Isolates with a minimal inhibitory concentration (MIC) of > or = 0.25 microg/mL for cefepime were tested for the ESBL phenotype by the combination-disk synergy tests (CDSTs) using cefotaxime and ceftazidime alone or in combination with clavulanic acid, the ESBL Etest using cefepime with or without clavulanic acid, and the double-disk synergy test (DDST) using cefepime and amoxicillin-clavulanate.

Results: Thirty eight isolates had an MIC of > or = 0.25 microg/mL for cefepime. Of these, 27 had an ESBL phenotype; 24 were determined by DDST, 25 by CDST, and 21 by ESBL Etest. ESBL genes were identified in 24 isolates. One isolate without an ESBL phenotype but with an MIC of > or = 0.25 microg/mL for cefepime was confirmed to have the ESBL gene. DDST, CDSTs, and ESBL Etest detected 24, 22, and 21 of 25 isolates with the ESBL genotype, respectively. DDST had the highest sensitivity of 96.0% for detecting ESBLs among isolates and a specificity of 69.2%. CDSTs and ESBL Etest had sensitivities of 88.0% and 84.0%, respectively, and specificities of 69.2% and 100%, respectively. The overall prevalence of ESBL-producing E. cloacae was 21.6%.

Conclusions: A combination of DDST using cefepime and amoxicillin-clavulanate and CDSTs using cefotaxime and ceftazidime alone or in combination with clavulanic acid enhance the detection of ESBL production in Taiwan.
View Article and Find Full Text PDF

Download full-text PDF

Source
August 2009

Lead acetate induces EGFR activation upstream of SFK and PKCalpha linkage to the Ras/Raf-1/ERK signaling.

Toxicol Appl Pharmacol 2009 Mar 24;235(2):244-52. Epub 2008 Dec 24.

Molecular Carcinogenesis Laboratory, Institute of Biotechnology & Department of Life Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan.

Lead acetate (Pb), a probable human carcinogen, can activate protein kinase C (PKC) upstream of extracellular signal-regulated kinase 1 and 2 (ERK1/2). Yet, it remains unclear whether Pb activation of PKC --> ERK1/2 involves receptor/non-receptor tyrosine kinases and the Ras signaling transducer. Here we demonstrate a novel mechanism elicited by Pb for transmitting ERK1/2 signaling in CL3 human non-small-cell lung adenocarcinoma cells. Pb induction of higher steady-state levels of Ras-GTP was essential for increasing phospho-Raf-1(S338) and phospho-ERK1/2. Pre-treatment of the cells with a conventional PKC inhibitor Gö6976 or depleting PKCalpha using specific small interfering RNA blocked Pb induction of Ras-GTP. Pb also activated cellular tyrosine kinases. Specific pharmacological inhibitors, PD153035 for epidermal growth factor receptor (EGFR) and SU6656 for Src family tyrosine kinases (SFK), but not AG1296 for platelet-derived growth factor receptor, could suppress the Pb-induced tyrosine kinases, PKCalpha, Ras-GTP, phospho-Raf-1(S338) and phospho-ERK1/2. Furthermore, phosphorylation of tyrosines on the EGFR multiple autophosphorylation sites and the conserved SFK autophosphorylation site occurred during exposure of cells to Pb for 1-5 min and 5-30 min, respectively. Intriguingly, Pb activation of EGFR required the intrinsic kinase activity but not dimerization of the receptor. Inhibition of SFK or PKCalpha activities did not affect EGFR phosphorylation, while knockdown of EGFR blocked SFK phosphorylation and PKCalpha activation following Pb. Together, these results indicate that immediate activation of EGFR in response to Pb is obligatory for activation of SFK and PKCalpha and subsequent the Ras-Raf-1-MKK1/2-ERK1/2 signaling cascade.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.taap.2008.12.007DOI Listing
March 2009

Activation of protein kinase Calpha signaling prevents cytotoxicity and mutagenicity following lead acetate in CL3 human lung cancer cells.

Toxicology 2008 Aug 11;250(1):55-61. Epub 2008 Jun 11.

Molecular Carcinogenesis Laboratory, Institute of Biotechnology & Department of Life Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan.

Protein kinase C (PKC) family of serine/threonine protein kinases is sensitive signaling transducers in response to lead acetate (Pb) that could transmit phosphorylation cascade for proliferation and de-differentiation of neural cells. However, little is known as to the impact of PKC on Pb genotoxicity. Here we investigate whether Pb activates the conventional/classical subfamily of PKC (cPKC) signaling to affect cytotoxicity and mutagenicity in CL3 human non-small-cell lung adenocarcinoma cells. Pb specifically promoted membrane localization of the alpha isoform of PKC in CL3 cells. Pb also elicited Raf-1 activation as measured by the induction of phospho-Raf-1S338 and the dissociation from the Raf-1 kinase inhibitor protein. Inhibition of cPKC activity using Gö6976 or depletion of PKCalpha by introducing specific small interfering RNA blocked the induction of phospho-Raf-1S338, phospho-MKK1/2 and phospho-ERK1/2 in cells exposed to Pb. Intriguingly, declining PKCalpha enhanced the Pb cytotoxicity and revealed the Pb mutagenicity at the hprt gene. The results suggest that PKCalpha is obligatory for activation of the Raf-1-MKK1/2-ERK1/2 signaling module and plays a defensive role against cytotoxicity and mutagenicity following Pb exposure. Results obtained in this study also support our previous report showing that ERK1/2 activity is involved in preventing Pb genotoxicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.tox.2008.06.001DOI Listing
August 2008

Cyclin B1 proteolysis via p38 MAPK signaling participates in G2 checkpoint elicited by arsenite.

J Cell Physiol 2007 Aug;212(2):481-8

Molecular Carcinogenesis Laboratory, Institute of Biotechnology and Department of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan.

Timely induction of cyclin B1 controls mitotic entry, whereas its proteolysis is essential for mitotic exit. By contrast, cyclin B1 transcription is repressed during G(2) arrest induced by DNA damage. The p38 mitogen-activated protein kinase is involved in the G(2) checkpoint; yet, its impact on cyclin B1 protein levels remains unclear. Here we show that untimely proteolysis of cyclin B1 following p38 activation contributes to G(2) checkpoint. Exposing early G(2) cells to arsenite impeded cyclin B1 protein accumulation, Cdk1 activation, and G(2)-to-M progression. Conversely, cyclin B1 was non-degradable in late G(2) and mitotic cells after arsenite. Cyclin B1 proteolysis was enhanced by arsenite in early G(2) and asynchronous cells. This rapid destruction of cyclin B1 was mediated via the ubiquitin-proteasome pathway probably in a Cdc20 and Cdh1 independent mechanism. Under arsenite, inhibition of p38 activation or depletion of p38alpha suppressed cyclin B1 ubiquitination and proteolysis, while forced expression of MKK6-p38 accelerated these events. Inactivation of p38 in arsenite-treated early G(2) cells allowed G(2)-to-M progression, blocked apoptosis, increased cell viability, and decreased micronucleus formation. Thus, p38 signaling pathway triggering cyclin B1 proteolysis after arsenite may play an important role in connecting G(2) arrest with apoptosis or genome instability.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jcp.21042DOI Listing
August 2007

Environmental-sensitive micelles based on poly(2-ethyl-2-oxazoline)-b-poly(L-lactide) diblock copolymer for application in drug delivery.

Int J Pharm 2006 Jul 17;317(1):69-75. Epub 2006 Apr 17.

Department of Chemical Engineering, National Tsing Hua University, Hsinchu, 300 Taiwan, ROC.

Anticancer drug doxorubicin (DOX) was physically loaded into the micelles prepared from poly(2-ethyl-2-oxazoline)-b-poly(L-lactide) diblock copolymers (PEOz-PLLA). PEOz-PLLA consists of hydrophilic segment PEOz and hydrophobic segment PLLA showed pH-sensitivity in the aqueous solution. The DOX-loaded micelle exhibited a narrow size distribution with a mean diameter around 170 nm. The micellar structure can preserve hydrophobic drug DOX under the physiological condition (pH 7.4) and selectively release DOX by sensing the intracellular pH change in late endosomes and secondary lysosomes (pH 4-5). At 37 degrees C, the cumulated released rate of DOX from micelles was about 65% at pH 5.0 in the initial 24 h. Additionally, polymeric micelles had low cytotoxicity in human normal fibroblast HFW cells for 72 h by using MTT assay. Moreover, DOX-loaded micelles could slowly and efficiency decrease cell viability of non-small-cell lung carcinoma CL3 cells. Taken together, PEOz-b-PLLA diblock polymeric micelles may act as useful drug carriers for cancer therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijpharm.2006.03.002DOI Listing
July 2006

Cooperation of ERK and SCFSkp2 for MKP-1 destruction provides a positive feedback regulation of proliferating signaling.

J Biol Chem 2006 Jan 14;281(2):915-26. Epub 2005 Nov 14.

Molecular Carcinogenesis Laboratory, Institute of Biotechnology, Hsinchu, Taiwan.

The dual-specificity MAPK phosphatase MKP-1/CL100/DUSP1 is an inducible nuclear protein controlled by p44/42 MAPK (ERK1/2) in a negative feedback mechanism to inhibit kinase activity. Here, we report on the molecular basis for a novel positive feedback mechanism to sustain ERK activation by triggering MKP-1 proteolysis. Active ERK2 docking to the DEF motif (FXFP, residues 339-342) of N-terminally truncated MKP-1 in vitro initiated phosphorylation at the Ser(296)/Ser(323) domain, which was not affected by substituting Ala for Ser at Ser(359)/Ser(364). The DEF and Ser(296)/Ser(323) sites were essential for ubiquitin-mediated MKP-1 proteolysis stimulated by MKK1-ERK signaling in H293 cells, whereas the N-terminal domain and Ser(359)/Ser(364) sites were dispensable. ERK activation by serum increased the endogenous level of ubiquitinated phospho-Ser(296) MKP-1 and the degradation of MKP-1. Intriguingly, active ERK-promoted phospho-Ser(296) MKP-1 bound to SCF(Skp2) ubiquitin ligase in vivo and in vitro. Forced expression of Skp2 enhanced MKP-1 polyubiquitination and proteolysis upon ERK activation, whereas depletion of endogenous Skp2 suppressed such events. The kinetics of ERK signaling stimulated by serum correlated with the endogenous MKP-1 degradation rate in a Skp2-dependent manner. Thus, MKP-1 proteolysis can be achieved via ERK and SCF(Skp2) cooperation, thereby sustaining ERK activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M508720200DOI Listing
January 2006

Suppressive effect of 1-nitropyrene on benzo[a]pyrene-induced CYP1A1 protein expression in HepG2 cells.

Toxicol Lett 2006 Mar 8;161(3):236-43. Epub 2005 Nov 8.

Department of Biotechnology, Hung Kuang University, Taichung, Taiwan, ROC.

The genotoxicity of polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs may be influenced by the interaction of the compounds. In this study, our data showed that benzo[a]pyrene (BaP)-DNA adduct levels were decreased in a dose-dependent manner when the human hepatoma cell line HepG2 simultaneously treated with BaP and 1-nitropyrene (1-NP). To further investigate the molecular mechanism by which 1-NP interferes with the covalent binding of BaP to DNA, we conducted experiments to analyze the mRNA level and protein stability of cytochrome P450 1A1 (CYP1A1), which is engaged in the activation of BaP, leading to the generation of BaP-DNA adducts. Northern blot analysis presented that 1-NP attenuated BaP-induced CYP1A1 mRNA expression by 30.4-39.6% (p < 0.05). Western blot analysis revealed that the co-treatment with BaP and 1-NP resulted in a significant inhibition of BaP-induced CYP1A1 protein expression (70.7-88.2%, p < 0.05). However, the decrease in CYP1A1 protein levels was significantly larger than that in CYP1A1 mRNA levels. To confirm the effect of 1-NP on the CYP1A1 protein expression, in vitro proteolysis of CYP1A1 protein was evaluated. The results demonstrated that the addition of 1-NP enhanced CYP1A1 protein degradation and the proteolysis of CYP1A1 protein was inhibited by the addition of an antioxidant, dithiothreitol. In addition, the relative levels of reactive oxygen species (ROS) were elevated in HepG2 cells co-treated with BaP and 1-NP, indicating that the decrease of CYP1A1 protein level was probably attributed to the production of ROS generated by binary mixture. Taken together, these findings suggested that the transcriptional suppression and posttranslational mechanism may be involved in loss of CYP1A1 protein, causing the decrease of BaP-DNA adduct levels in the presence of binary mixtures of 1-NP and BaP.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.toxlet.2005.10.002DOI Listing
March 2006

ERK activation in arsenite-treated G1-enriched CL3 cells contributes to survival, DNA repair inhibition, and micronucleus formation.

Toxicol Sci 2006 Jan 5;89(1):164-72. Epub 2005 Oct 5.

Molecular Carcinogenesis Laboratory, Institute of Biotechnology and Department of Life Sciences, National Tsing Hua University, Hsinchu 300, Taiwan.

Arsenite is known to induce chromosomal damage and extracellular signal-regulated kinases 1/2 (ERK) signaling transduction pathway. Arsenite also perturbs mitotic spindle and induces G2/M prolongation, leading to genomic instability. However, little is known concerning whether G1 phase is susceptible to arsenite in causing genomic instability and ERK activation. In this study, we investigate the roles of ERK activation in survival, micronucleus formation, and nucleotide excision repair (NER) synthesis in arsenite-treated G1-enriched CL3 human non-small-cell lung carcinoma cells. We found that G1 was the most insensitive phase to arsenite cytotoxicity, yet it was highly susceptible to arsenite in micronucleus induction. After arsenite exposure, the G1 cells exhibited a marked retard in the formation of binucleated cells when they were cultured in cytochalasin B, an inhibitor of cytokinesis, suggesting that arsenite delays the cell cycle progression. Arsenite activated sustained-ERK signal in G1 cells whose suppression further decreased cell proliferation and survival and could lower the micronucleus induction. The NER synthesis activity of G1 cells was inhibited by arsenite as a function of the extent of ERK activation. Intriguingly, blockage of ERK activation recovered NER synthesis activity in the arsenite-treated G1 cells. Together, these results suggest that ERK activation in arsenite-treated G1 cells counteracts cytotoxicity and contributes to genomic instability via NER synthesis inhibition and micronucleus induction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/toxsci/kfj004DOI Listing
January 2006

Dual and opposing roles of ERK in regulating G(1) and S-G(2)/M delays in A549 cells caused by hyperoxia.

Exp Cell Res 2004 Jul;297(2):472-83

Molecular Carcinogenesis Laboratory, Department of Life Sciences, Institute of Biotechnology, National Tsing Hua University, Hsinchu 300, Taiwan.

This study explores the role of ERK activation in regulating G(1) and S-G(2)/M delays during hyperoxia. We demonstrate here that exposing A549 human alveolar type 2 adenocarcinoma cells to hyperoxia (95% O(2)) for 0.5-24 h time-dependently increases phospho-ERK, phospho-p53(Ser15), p53, and p21(CIP1) protein levels. Decreasing phospho-ERK with the pharmacological inhibitors, PD98059 and U0126, markedly suppresses hyperoxia-stimulated phospho-p53(Ser15), p53, and p21(CIP1), and also restores the hyperoxia-reduced kinase activities of cyclin D1/E1-Cdks. Our results suggest that ERK activation during hyperoxia contributes to the p53/p21-mediated G(1) checkpoint. However, inhibition of ERK signaling during hyperoxia further delays S-phase entry and progression. Hyperoxia induces significant expression of cyclin A/B1 and translocation of cyclin A into nuclei while marginally decreasing cyclin A/B1-Cdks kinase activities, which may be related to nuclear association with p21. Interestingly, inhibition of ERK signaling markedly suppresses the elevation of cyclin A/B1 proteins and cyclin A/B1-Cdks kinase activities during hyperoxia. Taken together, the results presented here suggest that hyperoxia-activated ERK acts upstream of p53 and p21 to suppress G(1)-Cdk activities; however, it is also required for induction of cyclin A/B1 and maintenance of cyclin A/B1-Cdk activities that oppose delays in S-phase entry and progression.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.yexcr.2004.03.033DOI Listing
July 2004

ERK1/2 achieves sustained activation by stimulating MAPK phosphatase-1 degradation via the ubiquitin-proteasome pathway.

J Biol Chem 2003 Jun 3;278(24):21534-41. Epub 2003 Apr 3.

Molecular Carcinogenesis Laboratory, Institute of Biotechnology, Department of Life Sciences, National Tsing Hua University, Hsinchu 300, Taiwan, Republic of China.

Sustained extracellular signal-regulated kinase 1/2 (ERK1/2) activation does not always correlate with its upstream Ras-Raf-mitogen-activated protein kinase kinase 1/2 (MKK1/2) signal cascade in cancer cells, and the mechanism remains elusive. Here we report a novel mechanism by which sustained ERK1/2 activation is established. We demonstrate that Pb(II), a carcinogenic metal, persistently induces ERK1/2 activity in CL3 human lung cancer cells and that Ras-Raf-MKK1/2 signaling cannot fully account for such activation. It is intriguing that Pb(II) treatment reduces mitogen-activated protein kinase phosphatase 1 (MKP-1) protein levels in time- and dose-dependent manners, which correlates with sustained ERK1/2 activation, and that Pb(II) also induces mRNA and de novo protein synthesis of MKP-1. In Pb(II)-treated cells, MKP-1 is polyubiquitinated, and proteasome inhibitors markedly alleviate the ubiquitination and degradation of MKP-1. Inhibiting the Pb(II)-induced ERK1/2 activation by PD98059 greatly suppresses MKP-1 ubiquitination and degradation. It is remarkable that constitutive activation of MKK1/2 triggers endogenous MKP-1 ubiquitination and degradation in various mammalian cell lines. Furthermore, expression of functional MKP-1 decreases ERK1/2 activation and the c-Fos protein level and enhances cytotoxicity under Pb(II) exposure. Taken together, these results demonstrate that activated ERK1/2 can trigger MKP-1 degradation via the ubiquitin-proteasome pathway, thus facilitating long-term activation of ERK1/2 against cytotoxicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M301854200DOI Listing
June 2003

Persistent activation of ERK1/2 by lead acetate increases nucleotide excision repair synthesis and confers anti-cytotoxicity and anti-mutagenicity.

Carcinogenesis 2003 Jan;24(1):53-61

Molecular Carcinogenesis Laboratory, Department of Life Sciences, National Tsing Hua University, Hsinchu 300, Taiwan, Republic of China.

Lead, a possible human carcinogen, affects signal transduction pathways in many aspects, yet exhibits low mutagenicity in human cells. In this study, we explore whether signaling pathways including the four MAPKs and AKT affect DNA repair and mutagenicity in the exposure of mammalian cells to lead acetate [Pb(II)]. Pb(II) increased the phosphorylated ERK1/2 and phosphorylated AKT but not the phosphorylated ERK5, phosphorylated p38 and JNK activity in human non-small cell lung adenocarcinoma CL3 cells. The duration of ERK1/2 activation was much longer than AKT activation and these two signals were independently activated by Pb(II) in CL3 cells. Intriguingly, a MKK1/2 inhibitor PD98059 (25-50 micro M) markedly suppressed ERK1/2 activation and greatly promoted the hprt mutation frequency and cytotoxicity in Pb(II)-treated CL3 cells. Conversely, inhibition of the AKT signal by wortmannin did not exhibit such effects. Inhibition of the persistently activated ERK1/2 in Pb(II)-treated diploid human fibroblasts by PD98059 also markedly increased the mutagenicity and cytotoxicity. The Pb(II)-induced mutagenicity and cytotoxicity were significantly higher in nucleotide excision repair (NER)-deficient UVL-10 rodent cells than their counterpart AT3-2 cells; also, ERK1/2 activation by Pb(II) was observed in AT3-2 but not UVL-10 cells. Furthermore, cellular NER synthesis was enhanced by Pb(II) exposure, which was markedly suppressed by PD98059. Activation of ERK1/2 by expressing a constitutively active form of MKK1 in CL3 cells also elevated cellular NER synthesis. Together, these results indicate that persistent activation of ERK1/2 signaling by Pb(II) enhances cellular NER synthesis, thereby conferring anti-cytotoxicity and anti-mutagenicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/carcin/24.1.53DOI Listing
January 2003

Short-term depletion of catalase suppresses cadmium-elicited c-Jun N-terminal kinase activation and apoptosis: role of protein phosphatases.

Carcinogenesis 2003 Jan;24(1):7-15

Molecular Carcinogenesis Laboratory, Department of Life Sciences, National Tsing Hua University, Hsinchu 300, Taiwan, Republic of China.

The c-Jun N-terminal kinase (JNK) is a vital stress-activated signal that can be regulated differentially under oxidant or antioxidant conditions. Recently, we have reported that activation of JNK by cadmium chloride (Cd) contributes to apoptosis in CL3 human lung adenocarcinoma cells. Although oxidative stress has been implicated in numerous biochemical effects altered by Cd, its role in Cd-elicited JNK activation has not been established. Here we report that catalase is crucial for the activation of JNK by Cd. Short-term treatment of 3-amino-1,2,4-triazole (3AT), a specific catalase inhibitor, completely suppressed the Cd-elicited JNK activation, conversely, exogenous addition of catalase increased the intensity and duration of JNK activation in Cd-treated CL3 cells. Co-administering high doses of H(2)O(2) (500-1000 micro M) with Cd also markedly decreased JNK activity, although at doses <200 micro M H(2)O(2) enhanced the Cd-elicited JNK activation in CL3 cells. 3AT also blocked JNK activation in Cd-treated normal human fibroblasts and Chinese hamster ovary cells, and in UV-irradiated CL3 cells. However, mannitol, a hydroxyl radical scavenger, did not alter the JNK activity in Cd-treated human and rodent cells. Intriguingly, sodium fluoride or okadaic acid, inhibitors for serine/threonine protein phosphatases (PP), recovered the JNK activity in CL3 cells exposed to Cd plus 3AT; however, the protein tyrosine phosphatases inhibitor sodium orthovanadate did not. Furthermore, 3AT decreased but catalase increased the Cd-induced cytotoxicity, apoptosis and procaspase-3 degradation in CL3 cells. Together, these results indicate that persistent activation of apoptotic JNK signal by Cd requires functional catalase and that short-term depletion of catalase activity may facilitate okadaic acid-sensitive PP to down-regulate the JNK activation and may predispose these cells to carcinogenic transformation upon Cd exposure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/carcin/24.1.7DOI Listing
January 2003