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Articles by S. H Choi
Total Records ( 5 ) for S. H Choi
  S. H Nam , D. W Kim , T. S Jung , Y. S Choi , H. S Choi , S. H Choi and H. S. Park
 

Summary: We have developed a web server for the high-throughput annotation of expressed sequence tags (ESTs) called pipeline for EST analysis service (PESTAS). PESTAS processes entire datasets with an automated pipeline of 13 analytic services, then deposits the data into the MySQL database and transforms it into three kinds of reports: preprocessing, assembling and annotation. All annotated information is provided to the scientist and can be downloaded through a web browser. To get more relevant functional annotation results, a curation function was introduced with which biologists can easily change the best-hit annotation information. We included a gene chip module that detects gene expression differences between libraries by comparing accession number counts from BLAST search results. PESTAS also provides access to the pathway information of KEGG, which is useful for mapping the relationships among networks of annotated enzymes, and is especially valuable for those researchers interested in biological pathways.

  S. H Choi , R Harkewicz , J. H Lee , A Boullier , F Almazan , A. C Li , J. L Witztum , Y. S Bae and Y. I. Miller
 

Toll-like receptor (TLR)4 recognizes microbial pathogens, such as lipopolysaccharide, and mediates lipopolysaccharide-induced proinflammatory cytokine secretion, as well as microbial uptake by macrophages. In addition to exogenous pathogens, TLR4 recognizes modified self, such as minimally oxidized low-density lipoprotein (mmLDL). Here we report that mmLDL and its active components, cholesteryl ester hydroperoxides, induce TLR4-dependent fluid phase uptake typical of macropinocytosis. We show that mmLDL induced recruitment of spleen tyrosine kinase (Syk) to a TLR4 signaling complex, TLR4 phosphorylation, activation of a Vav1-Ras-Raf-MEK-ERK1/2 signaling cascade, phosphorylation of paxillin, and activation of Rac, Cdc42, and Rho. These mmLDL-induced and TLR4- and Syk-dependent signaling events and cytoskeletal rearrangements lead to enhanced uptake of small molecules, dextran, and, most importantly, both native and oxidized LDL, resulting in intracellular lipid accumulation. An intravenous injection of fluorescently labeled mmLDL in wild-type mice resulted in its rapid accumulation in circulating monocytes, which was significantly attenuated in TLR4-deficient mice. These data describe a novel mechanism leading to enhanced lipoprotein uptake in macrophages that would contribute to foam cell formation and atherosclerosis. These data also suggest that cholesteryl ester hydroperoxides are an endogenous ligand for TLR4. Because TLR4 is highly expressed on the surface of circulating monocytes in patients with chronic inflammatory conditions, and cholesteryl ester hydroperoxides are present in plasma, lipid uptake by monocytes in circulation may contribute to the pathological roles of monocytes in chronic inflammatory diseases.

  P Wiesner , S. H Choi , F Almazan , C Benner , W Huang , C. J Diehl , A Gonen , S Butler , J. L Witztum , C. K Glass and Y. I. Miller
 

Rationale: Oxidized low-density lipoprotein (LDL) is an important determinant of inflammation in atherosclerotic lesions. It has also been documented that certain chronic infectious diseases, such as periodontitis and chlamydial infection, exacerbate clinical manifestations of atherosclerosis. In addition, low-level but persistent metabolic endotoxemia is often found in diabetic and obese subjects and is induced in mice fed a high-fat diet.

Objective: In this study, we examined cooperative macrophage activation by low levels of bacterial lipopolysaccharide (LPS) and by minimally oxidized LDL (mmLDL), as a model for subclinical endotoxemia-complicated atherosclerosis.

Methods and Results: We found that both in vitro and in vivo, mmLDL and LPS (Kdo2-LipidA) cooperatively activated macrophages to express proinflammatory cytokines Cxcl2 (MIP-2), Ccl3 (MIP-1), and Ccl4 (MIP-1β). Importantly, the mmLDL and LPS cooperative effects were evident at a threshold LPS concentration (1 ng/mL) at which LPS alone induced only a limited macrophage response. Analyzing microarray data with a de novo motif discovery algorithm, we found that genes transcribed by promoters containing an activator protein (AP)-1 binding site were significantly upregulated by costimulation with mmLDL and LPS. In a nuclear factor–DNA binding assay, the cooperative effect of mmLDL and LPS costimulation on c-Jun and c-Fos DNA binding, but not on p65 or p50, was dependent on mmLDL-induced activation of extracellular signal-regulated kinase (ERK) 1/2. In addition, mmLDL induced c-Jun N-terminal kinase (JNK)-dependent derepression of AP-1 by removing nuclear receptor corepressor (NCoR) from the chemokine promoters.

Conclusions: The cooperative engagement of AP-1 and nuclear factor (NF)-B by mmLDL and LPS may constitute a mechanism of increased transcription of inflammatory cytokines within atherosclerotic lesions.

  Y. J Park , J. W Yoon , K. I Kim , Y. J Lee , K. W Kim , S. H Choi , S Lim , D. J Choi , K. H Park , J. H Choh , H. C Jang , S. Y Kim , B. Y Cho and C. Lim
  Background

Some studies have proposed that subclinical hypothyroidism (SCH) has adverse effects on the cardiovascular system, but little is known about the effect on patients undergoing cardiovascular operations. We examined the influence of preoperative SCH on postoperative outcome in patients undergoing coronary artery bypass grafting (CABG).

Methods

Among patients who underwent CABG between July 2005 and June 2007 at Seoul National University Bundang Hospital, 224 with normal thyroid function and 36 with SCH were enrolled. Preoperative risks and postoperative outcomes were evaluated prospectively without thyroid hormone replacement.

Results

There were no significant differences in primary outcomes (major adverse cardiovascular events) and secondary outcomes such as wound problems, mediastinitis, leg infection, respiratory complications, delirium, or reoperation during the same hospitalization. However, patients with SCH had a higher incidence of postoperative atrial fibrillation than those with normal thyroid function after adjustment for age, gender, body mass index, and other independent variables such as emergency operation, the use of cardiopulmonary bypass, combined valvular operation, preoperative creatinine levels, left ventricular systolic dysfunction, and nonuse of β-blockers (45.5% vs 29%; odds ratio, 2.552; 95% confidence interval, 1.117 to 5.830; p = 0.026).

Conclusions

SCH appears to influence the postoperative outcome for patients by increasing the development of postoperative atrial fibrillation. However, it is still unproven whether preoperative thyroxine replacement therapy for patients with SCH might prevent postoperative atrial fibrillation after CABG.

 
 
 
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