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Articles by K. S Park
Total Records ( 3 ) for K. S Park
  S. J Hwang , Y. H Jeong , I. S Kim , K. S Park , M. K Kang , J. S Koh , J. R Park , Y Park , E. H Koh , C. H Kwak , J. Y Hwang and S. Kim
  Background—

Among patients treated with clopidogrel, carriers of the cytochrome P450 (CYP) 2C19 loss-of-function allele have shown increased platelet reactivity and higher rates of ischemic events. Although adjunctive cilostazol to dual antiplatelet therapy (or "triple antiplatelet therapy") intensifies platelet inhibition, it remains unknown whether triple antiplatelet therapy after percutaneous coronary intervention can achieve adequate platelet inhibition in patients with the CYP2C19 mutant allele.

Methods and Results—

CYP2C19 genotyping for *1, *2, and *3 was performed in 134 high-risk patients undergoing elective percutaneous coronary intervention. After measurement of preprocedural platelet reactivity, patients were randomly assigned to receive either adjunctive cilostazol 100 mg twice daily (triple group; n=69) or high maintenance-dose (MD) clopidogrel of 150 mg daily (high-MD group; n=65). Using light transmittance aggregometry and the VerifyNow P2Y12 assay, platelet reactivity was assessed before the index procedure and at 30-day follow-up. The primary end point was absolute change in maximal platelet aggregation (Aggmax) according to CYP2C19 genotyping. High posttreatment platelet reactivity was defined as 5 µmol/L ADP–induced maximal platelet aggregation >50%. In noncarriers of the CYP2C19*2/*3 mutant allele, Aggmax values after 5 and 20 µmol/L ADP stimuli did not differ significantly between the triple (n=22) versus the high-MD group (n=22) (23.6±21.6% versus 16.6±15.4%, P=0.224 and 26.4±22.2% versus 18.6±14.9%, P=0.174, respectively). Absolute changes in late platelet aggregation and P2Y12 reaction unit were not different between the groups. The rate of high posttreatment platelet reactivity at 30-day follow-up also was comparable between the triple versus the high-MD group (4.5% versus 13.6%, P=0.607). In carriers of at least 1 CYP2C19*2/*3 mutant allele, the triple group (n=47) showed greater values of Aggmax after addition of 5 µmol/L (25.8±16.8% versus 11.1±19.8%, P<0.001) and 20 µmol/L ADP (26.3±16.0% versus 11.5±16.3%, P<0.001) compared with the high-MD group (n=43). Likewise, absolute changes in late platelet aggregation and P2Y12 reaction unit were consistently greater in the triple versus the high-MD group. Fewer patients in the triple group met the criteria of high posttreatment platelet reactivity at 30-day follow-up compared with the high-MD group (6.4% versus 37.2%, P<0.001).

Conclusions—

Among high-risk patients undergoing elective percutaneous coronary intervention, adjunctive cilostazol can achieve consistently intensified platelet inhibition and reduce the risk of high posttreatment platelet reactivity irrespective of CYP2C19 genotyping.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01012193.

  Y Horie , A Meguro , M Ota , N Kitaichi , Y Katsuyama , Y Takemoto , K Namba , K Yoshida , Y. W Song , K. S Park , E. B Lee , H Inoko , N Mizuki and S. Ohno
 

Objectives. HLA-B51 is strongly associated with Behçet's disease (BD) in any ethnic background. We recently reported that another gene, Toll-like receptor-4 (TLR4) is also implicated in BD in a Japanese population. To confirm these results, we investigated polymorphisms in the TLR4 gene in Korean patients with BD.

Methods. In this study, 119 patients with BD and 141 healthy controls were enrolled; every participant was a Korean. Nine single nucleotide polymorphisms previously detected in TLR4 by direct sequencing were analysed for an association with BD.

Results. The most frequent haplotype, TAGCGGTAA, was significantly increased in HLA-B*51-positive BD patients (49.5%), compared with healthy control participants [32.3%; P = 0.029; odds ratio (OR) = 2.01; 95% CI 1.25–3.23]. This haplotype was also significantly increased in BD patients with arthritis (48.2%; P = 0.003; OR = 1.96; 95% CI 1.26–3.26). There were no significant differences in the allele and genotype frequencies of patients and controls for each single nucleotide polymorphism.

Conclusions. The haplotype of TLR4 may increase the risk for developing BD and the complication of arthritis in the Korean population.

  S. J Park , Y. S Chun , K. S Park , S. J Kim , S. O Choi , H. L Kim and J. W. Park
 

Hypoxic inhibition of K+ current is a critical O2-sensing mechanism. Previously, it was demonstrated that the cooperative action of TASK-1 and NADPH oxidase-4 (NOX4) mediated the O2-sensitive K+ current response. Here we addressed the O2-sensing mechanism of NOX4 in terms of TASK-1 regulation. In TASK-1 and NOX4-coexpressing human embryonic kidney 293 cells, hypoxia (5% O2) decreased the amplitude of TASK-1 current (hypoxia-ITASK-1). To examine whether reactive oxygen species (ROS) mediate the hypoxia-ITASK-1, we treated the cells with carbon monoxide (CO) which is known to reduce ROS generation from the heme-containing NOX4. Unexpectedly, CO failed to mimic hypoxia in TASK-1 regulation, rather blocked the hypoxia-ITASK-1. Moreover, the hypoxia-ITASK-1 was neither recovered by H2O2 treatment nor prevented by antioxidant such as ascorbic acid. However, the hypoxia-ITASK-1 was noticeably attenuated by succinyl acetone, a heme synthase inhibitor. To further evaluate the role of heme, we constructed and expressed various NOX4 mutants, such as HBD(–) lacking the heme binding domain, NBD(–) lacking the NADPH binding domain, FBD(–) lacking the FAD binding domain, and HFBD(–) lacking both heme and FAD domains. The hypoxia-ITASK-1 was significantly reduced in HBD(–)-, FBD(–)-, or HFBD(–)-expressing cells, versus wild-type NOX4-expressing cells. However, NBD(–) did not affect the TASK-1 response to hypoxia. We also found that p22 is required for the NOX4-dependent TASK-1 regulation. These results suggest that O2 binding with NOX4 per se controls TASK-1 activity. In this process, the heme moiety and FBD seem to be responsible for the NOX4 regulation of TASK-1, and p22 might support the NOX4-TASK-1 interaction.

 
 
 
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