Effects of lysophosphatidylcholine and arachidonic acid on the regulation of intracellular Ca2+ transport

Summary The role of lysophosphatidylcholine and arachidonic acid in signal transduction was investigated using subcellular organelles and permeabilized cells from liver. Both substances can be generated intracellularly by the action of phospholipase A₂ on phosphatidy1choline. Lysophosphatidylcholine as well as arachidonic acid raised the free Ca²⁺ concentration in the incubation media of permeabilized cells, isolated mitochondria and microsomes. The half maximally effective concentrations for Ca²⁺ release from mitochondria were 78 ± 1 mol/l for lysophosphatidylcholine and 80 ± 11 mol/l for arachidonic acid. Though isolated microsomes released Ca²⁺ in response to both agents, the combined presence of mitochondria and microsomes did not exhibit a synergism in Ca²⁺ release in response to arachidonic acid; the increase in the free Ca²⁺ concentration in response to lysophosphatidylcholine was even smaller than with mitochondria alone. It is concluded that the two reaction products of phospholipase A₂ can raise the cytoplasmic Ca²⁺ concentration and therefore may participate in cellular signal transduction. Send offprint requests to I. Rustenbeck at the above address     

Different metabolic profiles of K1 serotype and non-serotype K1 and K2 Klebsiella pneumoniae isolates in oral infection mice model

K1 or K2 serotype Klebsiella pneumoniae isolate caused clinical pyogenic liver abscess (KLA) infection is prevalent in many areas. It has been identified that K1 or K2 serotype K. pneumoniae isolates caused KLA infection in mice by oral inoculation. In our study, K1 serotype K. pneumoniae isolate Kp1002 with hypermucoviscosity (HV)-positive phenotype caused KLA infection in C57BL/6 mice by oral inoculation. Simultaneously, non-serotype K1 and K2 isolate Kp1014 with HV-negative phenotype failed to cause KLA infection in the same manner. It seems that gastrointestinal tract translocation is the pathway by which K1 or K2 serotype K. pneumoniae caused KLA infection. Liquid chromatography-tandem mass spectrometry was used to further analyze metabolic profile changes in mice with KLA infection. Data showed that after Kp1002 or Kp1014 oral inoculation, serum Phosphatidylcholine (PC) and Lysophosphatidylcholine (LPC) levels significantly changed in mice. Some PC and LPC molecules showed changes both in the Kp1002 KLA group and the Kp1014 no-KLA group compared with the control group. The level of 18:1/18:2-PC significantly changed in the Kp1002 KLA group compared with the control group, but showed no change between the Kp1014 no-KLA group and the control group. The level of 18:1/18:2-PC might have been particularly affected by KLA infection caused by K1 serotype K. pneumoniae Kp1002. It may be a potential biomarker for KLA infection.     

Cell membrane-derived lysophosphatidylcholine activates cardiac ryanodine receptor channels

Lysophosphatidylcholine (LPC) is metabolized from a membrane phospholipid and modulates a variety of channels in the plasma membrane (PM). We examined LPC modulation of cardiac ryanodine receptor (RyR) channels in the sarcoplasmic reticulum (SR) using the planar lipid bilayer method to measure the single-channel currents. Micromolar concentrations of LPC increased the open probability of the reconstituted RyR channels irrespective of whether LPC was added to the cis or trans chamber. LPC also increased the membrane capacitance of the bilayer. The effects of LPC contrasted well with those of sphingosylphosphorylcholine (SPC). Taken together, these results suggest that amphipathic lipid LPC does not bind directly to the RyR channel protein, but rather, is incorporated into the bilayer membrane and activates the channel. Thus, we consider cell membrane-derived LPC to be a putative endogenous mediator that activates not only plasma membrane channels but also RyR channels and induces arrhythmogenic Ca²⁺ mobilization in cardiomyocytes.     

溶血磷脂酰胆碱对内皮细胞表面粘附分子表达的影响

大量的单核细胞募集是动脉粥样损伤形成的早期表现之一,相关的内皮细胞粘附分子在其中具有积极作用。本文研究了溶血磷脂酰胆碱（Ｌｙｓｏｐｈｏｓｐｈａｔｉｄｙｌｃｈｏｌｉｎｅ,Ｌｙｓｏ－ＰＣ）对培养的人脐静脉内皮细胞（ＨＵＶＥＣｓ）膜上细胞间粘附分子－（Ｉｎｔｅｒｃｅｌｌｕｌａｒ ａｄｈｅｓｉｏｎ ｍｏｌｅｃｕｌｅ－１,ＩＣＡＭ－１）、Ｅ选择素（Ｅｎｄｏｔｈｅｌｉａｌ－ｌｅｕｋｏｃｙｔｅ ａｄｈｅｓｉｏｎ     

葛根素对溶血磷脂酰胆碱损伤血管内皮依赖性舒张功能的影响

目的 探讨葛根素（puerarin）对溶血磷脂酰胆碱（lysophosphatidylcholine，LPC）损伤家兔血管内皮依赖性舒张功能的影响。方法 采用离体血管环张力实验法检测乙酰胆碱诱导的内皮依赖性舒张反应来评价LPC对血管内皮功能的损害和葛根素的保护作用。结果 分别用2．5～10mg／LLPC孵育血管环30min，出现剂量依赖性抑制乙酰胆碱诱导的内皮依赖性舒张反应。用0．25～1g／L葛根素分别孵育血管环15min，再与5mg／LLPC共同孵育30min，明显改善LPC所致的血管舒张功能的损害。结论 葛根素对LPC所致的血管内皮依赖性舒张功能的损伤具有明显的保护作用。     

The ischemic metabolite lysophosphatidylcholine increases rat coronary arterial tone by endothelium-dependent mechanisms

Lysophosphatidylcholine (LPC), a hydrolysis product of phospholipid degradation, accumulates in the ischemic myocardium. Using isolated hearts or rat coronary septal arteries, we tested the impact of LPC in modulating basal function or the responses to vasoactive agents. Sustained perfusion of hearts with LPC augmented coronary perfusion pressure (CPP) and reduced left ventricular developed pressure (LVDP). By mechanisms that have yet to be identified, these effects on CPP and LVDP were exaggerated when LPC was removed from the perfusate. Although LPC (or its washout) had no direct effect on vascular tone in the isolated coronary artery, it selectively potentiated the receptor-coupled vasoconstrictor response to U-46619, a thromboxane A₂ mimetic. Interestingly, when LPC was washed out, the potentiation to U-46619 was even more pronounced. Both the immediate and residual effects of LPC were endothelium-dependent. EDHF was likely the sole mediator responsible for the direct effects of LPC on U-46619-vasoconstriction, whereas the augmented vasoconstrictor responses following LPC washout may in part be related to an increase in ET-1, and a striking reduction in the bioavailability of NO. Our data suggest that in addition to reducing the accumulation of LPC to prevent ischemia-reperfusion (I/R) damage, efforts targeting an improved endothelium-dependent regulation of vascular tone could be an attractive approach to limit the cardiac damage induced by I/R.     

Lysophosphatidylcholine suppresses apoptotic cell death by inducing cyclooxygenase-2 expression via a Raf-1 dependent mechanism in human cholangiocytes

Purpose The high incidence of biliary tract carcinoma in patients with anomalous pancreaticobiliary ductal junction (APBDJ) implicates that a compositional alteration in bile may contribute to the genesis of this cancer. Lysophosphatidylcholine (LPC) is generated in the bile of these patients. Given the role of cyclooxygenase-2 (COX-2) in biliary tract carcinogenesis, we postulated that LPC induces COX-2 in cholangiocytes.Methods The effect of LPC on COX-2 expression in cholangiocytes was evaluated by immunoblot analysis, real-time PCR and reporter gene assay. Apoptosis was induced by TRAIL treatment, and quantified using DAPI staining.Results Lysophosphatidylcholine increased COX-2 protein expression in cholangiocytes in a concentration- and time-dependent manner. LPC-induced Raf-1 activation was responsible for this COX-2 induction. Accordingly, LPC increased COX-2 mRNA levels in a Raf-1 dependent manner by stabilizing COX-2 mRNA. Finally, LPC attenuated TRAIL-mediated apoptosis through a COX-2/PgE2 dependent mechanism.Conclusions Collectively, these results implicate that LPC inhibits cholangiocyte apoptosis by inducing COX-2 expression via a Raf-1 dependent mechanism. This anti-apoptotic signaling may participate in biliary tract carcinogenesis in APBDJ patients, and therefore, its interruption may be a viable chemopreventative strategy.This work was presented at the European Association for the Study of the Liver in Paris in 2005.     

溶血磷脂酰胆碱对牛视网膜微血管内皮细胞PDGF-B表达的影响

[目的]探讨溶血磷脂酰胆碱(lysophosphatidylcholine,LPC)对牛视网膜微血管内皮细胞(bovine retinal microvascular endothelial cells,BRECs)表达血小板衍生生长因子-B (platelet derived growth factor B,PDGF-B)的影响.[方法]原代培养的牛视网膜微血管内皮细胞分为4组:对照组,LPC(20、40、60 μmol/L)3组;LPC各组根据不同作用时间(6、12、24 h)又分为3个亚组,用PDGF-B试剂盒检测各组内皮细胞培养上清液中PDGF-B蛋白的含量;用RT-PCR法检测PDGF-B mRNA的表达.[结果]LPC可使BRECs表达PDGF-B增加,具有时间和剂量依赖性,LPC(60 μmol/L)作用12h时效果最明显,差异有统计学意义(P＜0.05).[结论]LPC可引起BRECs表达PDGF-B增加,在糖尿病视网膜病变(diabetic retinopathy,DR)早期保护周细胞.     

Cut-off phenomenon in the protective effect of alcohols against lysophosphatidylcholine-induced calcium overload

We studied the effect of chain length on the protective effect of alcohols against lysophosphatidylcholine (LPC)-induced Ca²⁺ overload in neonatal rat cardiomyocytes. We previously found that ethanol retards Ca²⁺ elevation. Cells were loaded with the Ca²⁺-sensitive fluorophore fura-2, and changes in fluorescence were followed. The addition of 10 M LPC increased Ca²⁺, which reached a plateau after an 8–10 min delay. The presence of 88 mM n-propanol, n-butanol, tert-butanol, or 2,2-dimethylpropanol significantly increased the delay by 94–213%. However, n-pentanol at 2 mM or 88 mM had no protective effect. Among n-alcohols, the increase in lag time was inversely proportional to the length of the carbon chain. Chain length, rather than molecular weight determines the effect, because 2,2-dimethylpropanol had a protective effect. The influence of alcohols on LPC micelle formation was estimated from the increase in octadecyl rhodamine B fluorescence; the increase by n-alcohols was directly proportional to chain length, indicating that micelle formation was not involved in the extension of lag time. The absence of the protective effect when the alcohol aliphatic chain exceeds four carbons suggests that the effect of ethanol may be mediated via a small lipophilic pocket on a protein, or to lateral pressure perturbation in the membrane.     

串联质谱法在过氧化物酶体病筛查中的应用

目的：探讨串联质谱法检测极长链酰基肉碱（VLCAC）和溶血磷脂酰胆碱（LPC）在过氧化物酶体病筛查中的价值。方法：选取2017年1月至2021年3月以发育迟缓等神经系统异常就诊于上海市儿童医院,根据临床症状、磁共振成像和基因检测结果明确诊断为X-连锁肾上腺脑白质营养不良（X-ALD）患儿14例和脑肝肾综合征（ZS）患儿4例。另选取同年龄段体检儿童200名为健康对照组。使用含稳定同位素内标的溶剂萃取所有对象干血斑标本中的VLCAC和LPC,直接采用串联质谱法检测二十碳酰基肉碱（C20）、二十二碳酰基肉碱（C22）、二十四碳酰基肉碱（C24）、二十六碳酰基肉碱（C26）、二十碳溶血磷脂酰胆碱（C20:0-LPC）、二十二碳溶血磷脂酰胆碱（C22:0-LPC）、二十四碳溶血磷脂酰胆碱（C24:0-LPC）和二十六碳溶血磷脂酰胆碱（C26:0-LPC）水平,并计算C24/C20、C24/C22、C26/C20、C26/C22、C24:0-LPC/C20:0-LPC、C24:0-LPC/C22:0-LPC、C26:0-LPC/C20:0-LPC、C26:0-LPC/C22:0-LPC比值。采用Kruskal-Wallis H检验和Mann-WhitneyU检验比较各组间VLCAC和LPC各指标检测值及比值,采用偏最小二乘法和变量投影重要度权重评分分析各指标对判断疾病的贡献度。结果：除C24:0-LPC/C20:0-LPC外,所有指标和比值在各组间差异均有统计学意义（P<0.05或P<0.01）;X-ALD组与健康对照组、ZS组与健康对照组间,各指标有不同程度的差异,但X-ALD组与ZS组间差异无统计学意义（P>0.05）;偏最小二乘法分析显示X-ALD和ZS组与健康对照组能够完全分离,C26的变量投影重要度值最大。结论：串联质谱法检测VLCAC和LPC可作为过氧化物酶体病筛查的方法,其中C26或可作为诊断敏感指标。