Seulggie Choi

Identification of Porphyromonas gingivalis lipopolysaccharide-binding proteins in human saliva

Porphyromonas gingivalis causes periodontal diseases and its lipopolysaccharide (LPS) is considered as a major virulence factor responsible for pathogenesis. Since initial recognition of P. gingivalis LPS (Pg.LPS) in the oral cavity might be crucial for the host response, we identified Pg.LPS-binding proteins (Pg.LPS-BPs) using Pg.LPS-immobilized beads and a high-resolution mass spectrometry. LPS purified from P. gingivalis was conjugated onto N-hydroxysuccinimidyl-Sepharose(®) 4 Fast Flow beads. Notably, Pg.LPS-conjugated beads could stimulate Toll-like receptor 2 (TLR2) as determined by a TLR2-depdendent reporter expression system using CHO/CD14/TLR2. In addition, the Pg.LPS-conjugated beads induced the production of inflammatory mediators such as nitric oxide and interferon-gamma-inducible protein-10 in the macrophage cell-line, RAW 264.7. These results imply that Pg.LPS retained its immunological properties during the conjugation process. Then, the Pg.LPS-conjugated beads were mixed with a pool of saliva obtained from nine human subjects to capture Pg.LPS-BPs and molecular identities were determined by LTQ-Orbitrap hybrid fourier transform mass spectrometry. Pg.LPS-BPs captured at high frequencies included alpha-amylase, cystatin, prolactin-inducible protein, lysozyme C, immunoglobulin components, serum albumin, lipocalin-1, and submaxillary gland androgen-regulated protein 3B. These proteins are known to be involved in bacterial adhesion and colonization, anti-microbial functions or modulation of immune responses.

Effects of anode nozzle geometry on ambient air entrainment into thermal plasma jets generated by a non-transferred plasma torch

Summary form only given, as follows. In plasma spraying, higher temperature and velocity of thermal plasma jets are preferable for producing high qualities of protective coatings for their industrial uses, because the sprayed coating powders are melted and accelerated in the plasma flame ejected from a non-transferred DC arc torch through an ambient air toward a substrate. In the typical plasma spray process operated under an atmospheric-pressure condition, the entrainment, of ambient air into the thermal plasma jet is inevitable. An air inflow to the flame alters chemical compositions of the plasma species, cools the thermal plasma flame, and decreases the jet velocity. Furthermore, the dissociation of entrained air enhances the specific heat of plasma, and then the plasma temperatures decrease even when operation power level of the plasma torch is not changed. Consequently, the gradients of temperature and velocity in the plasma jet increase with the degree of air entrainment. Therefore, the ambient air entrainment should be controlled to the lower degree for getting the better quality of coating products with higher purity, density and bond strength. In this experimental work, the geometrical effects of anode nozzle of the non-transferred plasma torch on the air entrainment are examined by measurements using a quadruple mass spectrometer. Two different types of anode nozzle, i.e., tubular and stepped nozzles are employed for the torch. For each nozzle, air contents in the thermal plasma are measured to find the effects of nozzle geometry on the ambient air mixing with the plasma species. The radial and axial distributions of plasma temperature and velocity are also measured. By analyzing the measured results of the thermal plasma characteristics and the geometrical effects of nozzle shape on the air entrainment, the suitable design requirements of the nozzle are determined for optimal processes of plasma spraying.

Alpha-amylase is a human salivary protein with affinity to lipopolysaccharide of Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans lipopolysaccharide (Aa.LPS) is a major virulence factor associated with aggressive periodontitis. Although the recognition of Aa.LPS is potentially initiated by salivary proteins in the oral cavity, Aa.LPS-binding proteins (Aa.LPS-BPs) in saliva are poorly characterized. The purpose of this study was to capture and identify Aa.LPS-BPs in human saliva using a LTQ-Orbitrap hybrid Fourier transform mass spectrometry. Aa.LPS conjugated onto N-hydroxysuccinimidyl-Sepharose(®) 4 Fast Flow beads (Aa.LPS-beads) activated Toll-like receptor 4 and produced nitric oxide and Interferon gamma-inducible protein-10, implying that the conjugation process did not alter the biological properties of Aa.LPS. Aa.LPS-BPs were subsequently isolated from the nine human saliva samples from healthy individuals with the Aa.LPS-beads followed by identification with the mass spectrometry. Aa.LPS-BPs include α-amylase, serum albumin, cystatin, lysozyme C, submaxillary gland androgen-regulated protein 3B, immunoglobulin subunits, polymeric immunoglobulin receptor, deleted in malignant brain tumors 1, prolactin-inducible protein, lipocalin-1, and basic salivary proline-rich protein 2. Specific binding was validated using a pull-down assay with α-amylase which was captured at the highest frequency. Alpha-amylase demonstrated to interfere with the adherence and biofilm formation of A. actinomycetemcomitans. Even heat-inactivated α-amylase showed the interference to the same extent. Conclusively, we identified unique Aa.LPS-BPs that provide useful information to understand bacterial pathogenesis and host innate immunity in the oral cavity.

Identification of staphylococcal lipoteichoic acid-binding proteins in human serum by high-resolution LTQ-Orbitrap mass spectrometry.

Lipoteichoic acid (LTA), a major virulence factor of Gram-positive bacteria, is associated with bacterial adherence to host cells, biofilm formation, and inflammation. LTA-binding proteins (LTA-BPs) play an important role in the host immune response by initially recognizing and responding to LTA during infections. In this study, we screened for LTA-BPs in human serum using LTA-immobilized beads and high-throughput mass spectrometry. Highly pure and structurally intact LTA was prepared from Staphylococcus aureus and immobilized onto N-hydroxysuccinimide-activated Sepharose(®) 4 Fast Flow beads. The immobilization process does not seem to affect the biological activity of LTA since LTA-immobilized beads could stimulate macrophages and activate Toll-like receptor 2. Then, the LTA-immobilized beads were incubated with the human serum to capture LTA-BPs and their molecular identities were determined using high-resolution LTQ-Orbitrap hybrid Fourier transform mass spectrometry. LTA-BPs captured at high frequencies were neutrophil-activating peptide 2, prohibitin-2, alpha-1-anti-trypsin, histidine-rich glycoprotein, apolipoproteins, complements, and coagulation factor, most of which are known to be related with the host immune responses against infections. As high-throughput, efficient, accurate and sensitive, this screening method could be widely applicable to the identification of novel binding proteins to microbial virulence factors with glycolipid structures.

A duplex vibriocidal assay to simultaneously measure bactericidal antibody titers against Vibrio cholerae O1 Inaba and Ogawa serotypes.

Currently available cholera vaccines are formulated with killed-whole cells of Vibrio cholerae O1 Inaba and Ogawa serotypes. A serum vibriocidal assay has been widely used to evaluate the immunogenicity of cholera vaccines in clinical trials. In this study, we developed a duplex vibriocidal assay to obtain vibriocidal antibody titers against both serotypes simultaneously. Initially, serial dilutions of serum from vaccinees were incubated with guinea pig complements along with both streptomycin-resistant Inaba and ampicillin-resistant Ogawa strains for 1h. The mixture was then inoculated on separate agar plates containing each antibiotic to selectively culture each corresponding serotype and incubated at 37 degrees C for 16 to 20h. Bacterial colonies were enumerated using an automated colony counting system to obtain the vibriocidal antibody titers defined by the reciprocal of serum dilution inhibiting bacterial growth by 50%. Performance of the duplex vibriocidal assay was examined by comparison with a single serotype vibriocidal assay using 20 clinical sera consisting of ten-paired sera prepared at pre- and post-vaccination. Both assays showed a good correlation for vibriocidal titers against the two serotypes, respectively, as determined by Pearson correlation coefficient (r) and regression coefficient (beta) analyses; r=0.998, beta=1.003 for Inaba and r=0.997, beta=0.999 for Ogawa, respectively. The duplex vibriocidal assay can diminish the amount of sera required for the assay and enhance assay efficiency in terms of time, labor intensity, and expenditure.

Effect of post-cessation hyperglycemia on cardiovascular disease and mortality among middle-aged men: an eight-year longitudinal study

Smoking cessation reduces the risk of cardiovascular disease (CVD), but also elevates fasting serum glucose (FSG) levels. The effect of post-cessation hyperglycemia on cardiovascular disease is unknown. The study population consisted of 127,066 men without type 2 diabetes from the Korean National Health Insurance System – Health Screening Cohort database. Change in smoking habits and FSG was determined by the difference in smoking status and FSG levels from the first (2002 and 2003) and second (2004 and 2005) health examinations. Continual smokers, quitters, ex-smokers, and never smokers were stratified according to FSG elevation. The study participants were followed-up for CVD and CVD-related death from 2006 to 2013. Compared to continual smokers, quitters had decreased risk of CVD among those without FSG elevation (hazard ratio, HR, 0.76, 95% confidence interval, CI, 0.66–0.86) and with FSG elevation (HR 0.83, 95% CI 0.72–0.96). Similarly, quitters had a tendency towards reduced risk of CVD-related death among those without FSG elevation (HR 0.74, 95% CI 0.51–1.09) and with FSG elevation (HR 0.68, 95% CI 0.46–1.03). Post-cessation hyperglycemia did not attenuate the beneficiary risk-reducing effects of quitting on CVD and CVD-related death.

Cardiovascular health status between standard and nonstandard workers in Korea

Objectives The effect of employment insecurity on employee health is an important public health issue due to the recent effects of neoliberalism and the global financial crisis (2007–2008) on labor markets. This study aims to evaluate the differences in cardiovascular health status and the use of preventive screening services between standard and nonstandard workers. Methods Waged employees (N = 5,338) between the ages of 20 and 64 were grouped into standard (full-time, permanent) and nonstandard (part-time, temporary, or daily) employees. Data from the Fourth Korea National Health and Nutrition Examination Survey, 2007–2009, a nationwide representative survey, were examined, including cardiovascular health risk behaviors (tobacco, alcohol, physical inactivity), measured morbidities (blood pressure, blood glucose level, lipid profiles, body mass index), and the use of screening services for hypertension and diabetes mellitus. Results Female nonstandard employees tended to have higher blood pressure than did female standard employees (adjusted odds ratio, aOR 1.42, 95% confidence interval, CI 1.02 to 1.98). However, nonstandard employees (both men and women) were less likely to use preventive screening services for hypertension (aOR 0.72, 95% CI 0.54 to 0.94 in men; aOR 0.56, 95% CI 0.43 to 0.73 in women) and diabetes (aOR 0.58, 95% CI 0.43 to 0.79 in men; aOR 0.55, 95% CI 0.43 to 0.71 in women). Conclusion Nonstandard work is associated with the underuse of screening services and poorer cardiovascular health in a specific population. Policies to reduce employment insecurity and encourage nonstandard employees to receive health screening services should be prioritized.

Effects of smoking habit change on all-cause mortality and cardiovascular diseases among patients with newly diagnosed diabetes in Korea

This study aimed to investigate the effects of smoking habit change on the risks of all-cause mortality and cardiovascular diseases (CVDs) among patients with newly diagnosed diabetes using the Korean National Sample Cohort data. Survival regression analyses for the risks of all-cause mortality and CVDs were performed. Quitters without body mass index (BMI) change (adjusted hazard ratio [aHR], 0.68; 95% confidence interval [CI], 0.46–1.00) and quitters with BMI loss (aHR, 1.76; 95% CI, 1.13–2.73) showed significantly reduced and substantially the increased risk of all-cause mortality, respectively, compared with sustained smokers. Smoking reduction after diabetes diagnosis may have potential positive effects. However, definite benefits on the health outcomes were not identified in this study. Participants who started smoking after diabetes diagnosis had higher risks of all-cause mortality and CVDs than those who were never smokers or ex-smokers, although not statistically significant. In conclusion, smoking cessation after diabetes diagnosis could reduce the risks of all-cause mortality and cardiovascular events among patients with newly diagnosed diabetes when accompanied by proper weight management. Therefore, physicians should advice patients with newly diagnosed type 2 diabetes on the importance of smoking cessation in combination with long-term weight management to maximize the benefits of smoking cessation.

Utility values for age-related macular degeneration patients in Korea

Purpose Age-related macular degeneration (AMD) is one of the most important causes of blindness globally and may lead to decreased quality of life. Utility values for AMD patients according to sociodemographic and clinical characteristics have been little-studied, particularly among Asian populations. Methods A total of 1,283 AMD patients were identified from the Korean National Health and Nutrition Examination Survey from 2008 to 2012. A 45-degree digital retinal image for each eye was used to identify AMD patients. The utility values, calculated by the three level version of EuroQol-5D, of AMD patients according to sociodemographic and clinical characteristics were determined. The Kruskal-Wallis test was used to identify factors associated with reduced utility values among AMD patients. Results The mean utility value for AMD patients was 0.8765. Patients who were older (mean utility value 0.8339), were women (0.8488), had lower education levels (0.8287), were not employed (0.8467), and had lower household income (0.8022) had lower utility values (all p values <0.001). Utility values did not significantly differ according to AMD subtype (p value 0.729), likely due to the lack of enough power as only 48 patients had late AMD. Patients with lower best-eye visual acuity (BEVA) had lower utility values compared to those with high BEVA, even among those with high worst-eye visual acuity (WEVA) (p value <0.001). Conclusion Sociodemographic factors and visual acuity are important factors in determining the quality of life among AMD patients. Preserving BEVA, regardless of WEVA, may be associated with improved quality of life.

Utility values for glaucoma patients in Korea

Objectives Although determining the quality of life among glaucoma patients has important clinical and public health implications, the utility value of glaucoma patients has not yet been determined in Korea. Methods The Korean National Health and Nutrition Examination Survey database was used to identify 833 glaucoma patients based on ophthalmologic examinations. The adjusted mean utility values, calculated by EuroQol-5D (EQ-5D-3L), of glaucoma patients according to patient demographics and measures of glaucoma severity were determined using multivariate linear regression analysis. Results The mean utility value of glaucoma patients was 0.8968. Patients aged 70 years or more had significantly lower utility value (0.86, p value 0.005) compared to those aged less than 50 years (0.96). Patients within the lowest quartile of income had a utility value of 0.87, compared to a utility value of 0.96 for those within the highest quartile (p value 0.001). Patients who were not married had lower utility value (0.87) compared to married patients (0.93). Patients within the lowest quartile of worse eye frequency doubling technology (FDT) score had lower utility value (0.88) compared to those within the highest quartile (0.94). Finally, bilateral vision loss patients had significantly lower utility value (0.83, p value 0.013) compared to patients without vision loss (0.92). Conclusion The present study assessed utility values of Korean glaucoma patients. The quality of life determined by EQ-5D-3L in Korean glaucoma patients was higher compared to those in other countries. Patient demographics as well as measures of disease severity were important factors in determining the quality of life within glaucoma patients.