• Food Science and Biotechnology
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• v.15 no.5
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• pp.799-804
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• 2006

Ingestion of green tea has been shown to decrease prostaglandin $E_2$ levels in human colorectum, suggesting that tea constituents modulate arachidonic acid metabolism. In the present study, we investigated the effects of four purified green tea catechins, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epigallocatechin-3-gallate (EGCG), and (-)-epicatechin-3-gallate (ECG), on the catalytic activity of cytosolic phospholipase $A_2$ ($cPLA_2$) and release of arachidonic acid and its metabolites from intact cells. At $50\;{\mu}M$, EGCG and ECG inhibited $cPLA_2$ activity by 19 and 37%, respectively, whereas EC and EGC were less effective. The inhibitory effects of these catechins on arachidonic acid metabolism in intact cells were much more pronounced. At $10\;{\mu}M$, EGCG and ECG inhibited the release of arachidonic acid and its metabolites by 50-70% in human colon adenocarcinoma cells (HT-29) and human esophageal squamous carcinoma cells (KYSE-190 and 450). EGCG and ECG also inhibited arachidonic acid release induced by A23187, a calcium ionophore, in both HT-29 and KYSE-450 cell lines by 30-50%. The inhibitory effects of green tea catechins on $cPLA_2$ and arachidonic acid release may provide a possible mechanism for the prevention of human gastrointestinal inflammation and cancers.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.187-187
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• 1996

세포질에 존재하는 100 kDa Phospholipase $A_2$(cPLA$_2$)는 인지질의 sn-2 위치의 에스테르결합을 가수분해함으로서 Prostaglandin과 Leukotriene등 Eicosanoids 생합성의 전구체인 아라키돈산과 Platelet activating factor(PAF)를 생합성하는 전구체를 동시에 생성시키는 효소로 염증과 세포손상등에 중요한 역할이 기대된다. 본 효소의 활성화 기전을 규명하고자 하는 최근의 활발한 연구에도 불구하고 불명확한 점이 많은 것이 현실이다. 특히 세포를 자극하였을 때 유리되는 아라키돈산의 증가율과 세포를 파괴한 후 조제한 가용성분획에서 측정한 활성의 증가율과는 많은 차이를 나타냈다. 이러한 결과부터 cPLA$_2$ 효소 자체를 활성화시키는 어떤 인자를 가정하였다. 최근, PLA$_2$의 또다른 형태인 14 kDa의 분비성 PLA$_2$의 in vitro 활성을 증가시키는 인자가 동정되어 그 생화학적 특성이 규명되고 있으나 이 인자는 cPLA$_2$의 활성에는 아무런 증가효과를 나타내지 않았다. 본 연구자들은 소의 뇌조직에서 cPLA$_2$의 활성을 증가시키는 인자를 발견하고 그의 생화학적인 특성을 규명하였다. 돼지 비장에서 정제한 cPLA$_2$를 사용하였으며 소의 뇌 조직의 가용성 분획으로부터 본 활성화 인자를 동정하였으며 그 활성분획을 양이온 크로마토그라피로서 Mono S EPLC와 Superose 12 Sepharose gel filtration 크로마토그라피를 이용하여 더욱 분리한 결과 약 70 kDa과 25 kDa에서 각각 용출되었다. 이렇게 부분정제한 활성은 췌장에서 분리한 group I과 흰주의 group I과 흰주의 혈소판에서 분리한 group II PLA$_2$에 대해서는 아무런 증가효과를 나타내지 않는 반면, cPLA$_2$의 활성만을 약 5배 증가시켰다. 본 활성은 cPLA$_2$ 효소량의 증가에 따라 활성의 증가효과가 정차 감소하므로 화학량적인 반응(Stoichiometric reaction)일 것으로 예상되었다.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.250-252
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• 2014

Lipoprotein-associated phospholipase A2 (Lp-$PLA_2$) is a crucial enzyme in atherosclerosis as a potential drug target. The most remarkable Lp-$PLA_2$ inhibitory drug is Darapladib. We determined the binding pose of Darapladib to Lp-$PLA_2$ through docking study. Darapladib formed two hydrogen bonding interactions with the side chain of Tyr160 and Gln352 and several pi-pi interactions with aromatic and aliphatic hydrophobic residues of Lp-$PLA_2$. It is known that the dietylpropan-amine moiety of Darapladib has influence on the improvement of its oral bioavailability and we supposed this in our docking results.

• BMB Reports
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• v.41 no.8
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• pp.560-567
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• 2008

The importance of lipids in cell signaling and tissue physiology is demonstrated by the many CNS pathologies involving deregulated lipid metabolism. One such critical metabolic event is the activation of phospholipase $A_2$ ($PLA_2$), which results in the hydrolysis of membrane phospholipids and the release of free fatty acids, including arachidonic acid, a precursor for essential cell-signaling eicosanoids. Reactive oxygen species (ROS, a product of arachidonic acid metabolism) react with cellular lipids to generate lipid peroxides, which are degraded to reactive aldehydes (oxidized phospholipid, 4-hydroxynonenal, and acrolein) that bind covalently to proteins, thereby altering their function and inducing cellular damage. Dissecting the contribution of $PLA_2$ to lipid peroxidation in CNS injury and disorders is a challenging proposition due to the multiple forms of $PLA_2$, the diverse sources of ROS, and the lack of specific $PLA_2$ inhibitors. In this review, we summarize the role of $PLA_2$ in CNS pathologies, including stroke, spinal cord injury, Alzheimer's, Parkinson's, Multiple sclerosis-Experimental autoimmune encephalomyelitis and Wallerian degeneration.

• Journal of Chest Surgery
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• v.35 no.5
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• pp.343-349
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• 2002

background: In an attempt to investigate the role of oxidants in the activation of phospholipase $A_2$(PLA$_2$) and endogenous oxidative stress in the lung. acute inflammatory lung injury was induced by the instillation of hydrogen peroxide into the trachea of Sprague-Dawley rats. Material and Method: To prove the hypothesis thats released oxidants from neutrophils activate the PLA$_2$ retrogradely, activities of PLA$_2$ and lysoplatelet activating factor acetyltransferase(lysoPAF AT) were assayed i hours after instillation of hydrogen peroxide. In addition, to confirm the impairing effects of the activation of PLA$_2$ associated with endogenous oxidative stress, lung weight/body weight ratio(L$\times$10$^{-3}$ B), protein contents(mg/two lungs) in bronchoalveolar lavage(BAL) were measured. As neutrophilic respiratory burst has been known to play a pivotal role in the genesis of endogenous oxidative stress associated with acute inflammatory lung injury, BAL neutrophils counts and level of lung myelperoxidase(MPO) were measured after hydorgen peroxide insult. Morphological and histochemical studies were also performed to identify the effect of the endogenous oxidative stress. Result: Five hours after hydrogen peroxide instillation, lungs showed marked infiltration of neutrophils and increased weight. Protein contents in BAL increased significantly compared to those of normal rats. PLA$_2$ activity was enhanced in the hydrogen peroxide instilled group. Interestingly, the accelerated production of platelet activating factor(PAF) was confirmed by the increased activity of lysoPAF AT in the $H_2O$$_2$ employed lung. Morphologically, light microscopic findings of lungs after instillation of hydrogen peroxide showed atelectasis and infiltration of inflammatory cells, which was thought to be caused by lipid mediators produced by PLA$_2$ activation. In cerium chloride cytochemical electron microscopy, dense deposits of cerrous perhydroxide were identified. In contrast, no deposit of cerrous perhydroxide was found in the normal lung.

• Food Science and Biotechnology
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• v.17 no.6
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• pp.1289-1293
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• 2008

Fresh egg yolk (EY) was enzymatically modified using phospholipase $A_2$ ($PLA_2$) to produce an enzymatically modified-egg yolk powder (EM-EYP). The EM-EYP offered significantly higher emulsifying activity, emulsion stability, protein solubility, and mayonnaise stability than the control EYP. By employing $PLA_2$ in the enzymatic modification process, structural changes occurred in the phospholipids and lipoproteins of the yolk, and cleavage of apo-high density lipoprotein (HDL) components (Mw 105 kDa) was detected by sodium dodecyl sulfate-polyaerylamide gel electrophoresis (SDS-PAGE). Based on its functional properties, EM-EYP has great potential as a replacement for fresh EY in the production of processed food products such as mayonnaise.

• Korean Journal of Pharmacognosy
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• v.34 no.1 s.132
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• pp.100-108
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• 2003

The regulation of plasma lipid level, particularly LDL cholesterol, represents the focus of current therapy for atherosclerosis. And $Lp-PLA_2$ is able to hydrolyse oxidized phosphatidylcholine within LDL into lyso-PC and oxidized fatty acids. $Lp-PLA_2$ is a potential biomarker of coronary heart disease and plays an important proinflammatory role in the progression of atherosclerosis. We investigated the inhibitory effects of methanol extracts of 224 natural plants on $Lp-PLA_2$ activity. Seven kinds of methanol extracts of tested plants showed above 50% inhibitory effect with the concentration of $100\;{\mu}g/ml$. The concentrated aqueous suspensions of each methanol extract were partitioned with n-hexane, $CHCl_3$, and EtOAc. Among them, EtOAc extracts of Astilbe chinensis var. davidii (root) and Pourthiaea villosa var. brunnea (leaf) significantly inhibited $Lp-PLA_2$ activity at the same concentration.

• Tuberculosis and Respiratory Diseases
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• v.51 no.6
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• pp.503-516
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• 2001

Background : The present study was carried out in association with neutrophilic respiratory burst in the lung in order to clarify the pathogenesis of acute respiratory distress syndrome(ARDS) following acute severe hemorrhage. Because oxidative stress has been suggested as one of the principal factors causing tissue injury, the role of free radicals from neutrophils was assessed in acute hemorrhage-induced lung injury. Method : In Sprague-Dawley rats, hemorrhagic shock was induced by withdrawing blood(20 ml/kg of B.W) for 5 min and the hypotensive state was sustained for 60 min. To determine the mechanism and role of oxidative stress associated with phospholipase A2(PLA2) by neutrophils, the level of lung leakage, pulmonary myeloperoxidase(MPO), and the pulmonary PLA2 were measured. In addition, the production of free radicals was assessed in isolated neutrophils by cytochemical electron microscopy in the lung. Results : In hypotensive shock-induced acute lung injury, the pulmonary MPO, the level of lung leakage and the production of free radicals were higher. The inhibition of PLA2 with mepacrine decreased the pulmonary MPO, level of lung leakage and the production of free radicals from neutrophils. Conclusion : A. neutrophilic respiratory burst is responsible for the oxidative stress causing acute lung injury followed by acute, severe hemorrhage. PLA2 activation is the principal cause of this oxidative stress.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.5
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• pp.401-408
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• 2009

$K^+$-$Cl^-$-cotransport (KCC) has been reported to have various cellular functions, including proliferation and apoptosis of human cancer cells. However, the signal transduction pathways that control the activity of KCC are currently not well understood. In this study we investigated the possible role of phospholipase $A_2$ ($PLA_2$)-arachidonic acid (AA) signal in the regulatory mechanism of KCC activity. Exogenous application of AA significantly induced $K^+$ efflux in a dose-dependent manner, which was completely blocked by R-(+)-[2-n-butyl-6,7 -dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1Hinden-5-yl]oxy]acetic acid (DIOA), a specific KCC inhibitor. N-Ethylmaleimide (NEM), a KCC activatorinduced $K^+$ efflux was significantly suppressed by bromoenol lactone (BEL), an inhibitor of the calciumindependent $PLA_2$ ($iPLA_2$), whereas it was not significantly altered by arachidonyl trifluoromethylketone ($AACOCF_3$) and p-bromophenacyl bromide (BPB), inhibitors of the calcium-dependent cytosolic $PLA_2$ ($cPLA_2$) and the secretory $PLA_2$ ($sPLA_2$), respectively. NEM increased AA liberation in a doseand time-dependent manner, which was markedly prevented only by BEL. In addition, the NEM-induced ROS generation was significantly reduced by DPI and BEL, whereas $AACOCF_3$ and BPB did not have an influence. The NEM-induced KCC activation and ROS production was not significantly affected by treatment with indomethacin (Indo) and nordihydroguaiaretic acid (NDGA), selective inhibitors of cyclooxygenase (COX) and lipoxygenase (LOX), respectively. Treatment with 5,8,11,14-eicosatetraynoic acid (ETYA), a non-metabolizable analogue of AA, markedly produced ROS and activated the KCC. Collectively, these results suggest that $iPLA_2$-AA signal may be essentially involved in the mechanism of ROS-mediated KCC activation in HepG2 cells.

• Microbiology and Biotechnology Letters
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• v.21 no.2
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• pp.163-170
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• 1993

The effect of substrate micellization on the hydrolysis rate in the production of lysopho-sphatidylcholine (LPC) from phosphatidylcholine (PC) using hog pancreas phospholipase A2(PLA2) was studied. The optimal temperature and pH for the reactions in aqueous phase was found 42C and 7.2, respectively. For a given PC concentration, initial reaction rate was progressively increased with the addition of sodium deoxycholate (DOC), which could transform the bilayer of phospholipids into micellar structure.