OKT3-induced nephrotoxicity is associated with release of group II secretory phospholipase A2

Abstract. Administration of the murine IgG2a CD3 monoclonal antibody OKT3 exerts a transient nephro-toxic effect. Increased levels of group II secretory phospholipase A₂ (sPLA₂-II) might account for this nephrotoxicity as sPLA₂-II induces the biosynthesis of prostaglandins, vasoactive lipid mediators that influence glomerular haemodynamics and renal function. Furthermore, extracellular phospholipases seem to be involved in proximal tubular cell injury. We studied plasma sPLA₂-II levels in relation to circulating creatinine, tumour necrosis factor α, interleukin 6 and C-reactive protein levels in 15 renal allograft recipients receiving rejection treatment with OKT3. As a control group, we studied 15 renal allograft recipients receiving rejection treatment with methyl-prednisolone. A maximal fourfold increase in sPLA₂-II levels was observed 48 h after the first OKT3 administration, preceded by increased tumour necrosis factor α and interleukin 6 levels and accompanied by increased C-reactive protein levels. Creatinine levels reached a maximal increase 72 h after initiation of treatment. During methylprednisolone treatment no increase in any of the studied parameters was observed. Thus, administration of OKT3 induces increased sPLA₂-II levels, presumably via generation of cytokines. We hypothesize that sPLA₂-II may contribute to the nephrotoxic effect of OKT3 by inducing vasoconstrictive prostaglandins and renal tubular cell injury.     

Secreted and intracellular phospholipases A2 inhibition by 1-decyl 2-octyl-glycerophosphocholine in rat peritoneal macrophages

Summary— Compounds able to inhibit phospholipases A₂ can be considered as potential anti-inflammatory drugs. In this respect, the inhibitory effect of the phospholipid analogue 1-decyl 2-octyl-rac-glycero-3-phosphocholine (decyloctyl-GPC) added to the culture medium of rat peritoneal macrophages stimulated with ionophore A23187 was determined, (a) The substrate of phospholipase A₂ 1-octadecanoyl 2-[¹⁴C]eicosatetraenoyl-sn-glycero-3-phosphocholine ([¹⁴C]20:4-GPC) was added to the culture medium. In macrophages + extracellular fluids, its hydrolysis at the 2-position, produced [¹⁴C]non-phosphorous lipids which reached 12% of the dose at 0.14 μM, 73% at 0.9 and > 90% at 1.6 μM; in experiments where macrophages and extracellular fluids were analyzed separately, decyloctyl-GPC initially added at 4 μM, significantly inhibited the release of [¹⁴C]fatty acids and the eicosanoid synthesis, demonstrating its ability to inhibit secreted and/or intracellular phospholipases A₂. (b) Extracellular fluids were separated from the macrophages and incubated with [¹⁴C]20:4-GPC: 48% of the dose was hydrolyzed by extracellular fluid-associated secreted phospholipase A₂ and decyloctyl-GPC at 3 μM, reduced this hydrolysis by 50%. (c) [³H]arachidonic acid ([³H]20:4) was added to the culture medium and was esterified in the macrophage membrane phospholipids. Activation of intracellular phospholipase A₂ induced the release of [³H] fatty acids and eicosanoid synthesis. These releases were inhibited by 50% with decyloctyl-GPC added at 4 μM. (d) [³H]20:4 and [¹⁴C]20:4-GPC were added to the culture medium of the macrophages. [³H] and [¹⁴C] fatty acids and eicosanoids were released in macrophages or extracellular fluids. They were significantly reduced by the phospholipid analogue added at 4 μM. It is concluded that secreted and intracellular phospholipases A₂ were both inhibited by decyloctyl-GPC which extensively reduced the 20:4 release from exogenous and membrane phospholipids and therefore eicosanoid synthesis.     

Thromboxane A2 and related prostaglandins in airways

Summary— Asthma is now thought to be a chronic inflammatory disease of the airways. The roles of prostanoids, thromboxane A₂ (TXA₂) and the prostaglandins (PGs) in the pathogenesis and pathophysiology of asthma have fostered a wealth of studies but remain controversial. TXA₂ and the bronchoconstrictor PGs, PGD₂ and PGF_2α, are generated in greater amounts in asthmatic than in normal subjects. TXA₂ is a potent constrictor of airway smooth muscle, an inducer of acetylcholine release and of airway microvascular leakage. It may participate in the thickening and the remodeling of the airway wall which may contribute to the airway hyperresponsiveness, a typical feature of asthma. Strategies for inhibition of TXA₂ effects include antagonism of the TXA₂ receptor (TP receptor) and inhibition of the thromboxane synthase. TP receptor antagonists could block the effects of all the bronchoconstrictor prostanoids because TXA₂ as well as the bronchoconstrictor PGs act through activation of lung TP receptor. The recent development of specific and potent TP receptor antagonists and inhibitors of thromboxane synthase has provided tools to assess the role of TXA₂ and bronchoconstrictor PGs in the pathophysiology of asthma.     

Renal and Cardiovascular Effect of Prostaglandin A2 in Hypertensive Patients

Abstract. The haemodynamic and renal effects of synthetic prostaglandin A₂ (PGA₂) have been studied in 10 hypertensive subjects during a) a short lasting infusion of hypotensive doses of 3–9μg/kg min. of PGA₂; b) a continuous infusion starting with subdepressive doses and extended with hypotensive doses.—The rapid hypotensive effect observed with high doses was accompanied by an increase in cardiac output and renal blood flow without significant changes in the peripheral vascular bed. Hepatic blood flow was decreased. These observations show a preferential renal redistribution of cardiac output. During the administration of subdepressive doses of PGA., a marked renal effect was observed, consisting in an increase in free water clearance and diuresis with no significant modifications of general haemodynamics. The natriuretic effect was much less pronounced suggesting that PGA₂ is not a specific natriuretic hormone.—The haemodynamic and renal effects of endogenous PGs may play an important role in renal functions and in blood pressure regulation.     

Adenosine reduces airway excitatory non-cholinergic (e-NC) contraction through both A1 and A2 adenosine receptor activation in the guinea pig

Summary— The influence of adenosine and selective A₁ and A₂ agonists and antagonists was investigated on the cholinergic and the excitatory non-cholinergic (e-NC) contractions induced by electrical field stimulation in the guinea-pig bronchi. Adenosine (10 nM-1 mM) induced a concentration-dependent inhibition of the e-NC contraction (EC₅₀ = 90 ± 14 μM), whereas the cholinergic peak was only slightly affected. Preincubation of the tissue with the adenosine uptake blocker dipyridamole (10 μM) significantly shifted the concentration-inhibition curve to adenosine to the left (EC₅₀ = 10 ± 1 μM), suggesting an interaction with extracellular adenosine receptors of A₁ and/or A₂ subtype. To characterize the receptor type involved in this effect, selective adenosine derivatives were studied. The agonist to both A₁ and A₂ adenosine receptors, 5′-N-ethylcarboxamidoadenosine (NECA) was more potent than the selective A₁ agonist, (-)-R-6-phenylisopropyladenosine (R-PIA), in inhibiting the e-NC contraction (EC₅₀ = 0.10 ± 0.04 and 0.60 ±0.12 μM, respectively, with a maximal inhibition of 70 and 45%, respectively). The concentration-response curve to NECA was shifted to the right by the A₂ receptor selective antagonist 3,7-dimethyl-1-propargylxanthine (DMPX) (10 μM) (EC₅₀ = 1.4 ± 0.5 μ) as well as by the specific A₁ receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (10 μM) (EC₅₀ = 0.7 ± 0.3 μM). The inhibitory effect induced by the association of both antagonists, DPCPX and DMPX, was considerably potentiated (EC₅₀ > 22 ± 2.5 μM). The effect of R-PIA was also shifted to the right by DPCPX (EC₅₀ = 8.2 ± 1.6 μM) but was not modified by DMPX. The contractile response to exogenous substance P was unaffected by NECA pretreatment (0.3 μM). Altogether, these results suggest that adenosine-induced inhibition of e-NC contraction of guinea-pig bronchi is mediated through activation of both A₁ and A₂ adenosine receptors linked to inhibition of the release of neuropeptides from C-fibre nerve endings.     

Increased biosynthesis of thromboxane A2 by diabetic platelets

Abstract. Because ADP has been reported to produce a secondary wave of platelet aggregation in diabetic subjects, and since ADP is known to enhance normal platelet biosynthesis of pro-aggregating thromboxane A₂, we tested whether or not the reported increased sensitivity of diabetic platelets to ADP may also result in increased platelet biosynthesis of thromboxane A₂. To test this hypothesis, ¹⁴C-arachidonic acid (¹⁴C-AA) was incubated in vitro with washed human platelets' in the presence or absence of ADP. These studies included platelets isolated from thirty normal volunteers, twenty-six diabetic subjects with and without known vascular complications, eighteen non-diabetic pregnant females and fourteen pregnancy-induced diabetic females. Data from these studies demonstrated: (i) a significant increase in the capability of diabetic platelets in response to ADP to biosynthesize thromboxane A₂ from arachidonic acid when compared to platelets from normal controls (P < 0.001); (ii) a significant increase in thromboxane A₂ biosynthesis by platelets from pregnancy-induced diabetic subjects over nondiabetic pregnant females (P < 0.001); (iii) a two-fold increase in thromboxane A₂ biosynthesis by platelets from diabetic subjects with vascular complications when compared to those without vascular complications. Although our data also showed approximately a twofold increase in thromboxane A₂ biosynthesis by platelets from diabetic subjects with greater than 10 years of the disease when compared to diabetic subjects with less than 10 years, these latter results were, however, not statistically significant. Results from these studies suggest that a relationship may exist between the markedly increased ADP-induced platelet aggregation in diabetes mellitus and the vascular complications associated with this disease. Whether or not increased capacity of the diabetic platelet to biosynthesize pro-aggregating thromboxane A₂ in response to ADP or other pro-aggregating agents is per se a triggering factor in occlusive vascular diseases reported in diabetic subjects must await further studies.     

Platelet and vessel associated prostacyclin and thromboxane A2/prostaglandin endoperoxide receptors

Synthetic stable analogues of thromboxane A2 (TXA2), cyclic endoperoxides (PGH2) and prostacyclin (PGI2) opened up new opportunities for investigating the mechanisms of action of these compounds. They proved to be useful pharmacological probes for characterizing PGI2 and TXA2/PGH2 receptors. Over the past few years, new synthetic antagonists with high specificity allowed the modulation of biological responses to endogenous eicosanoids. These compounds will, therefore, considerably promote our understanding of the biological function and significance of arachidonate metabolites. The present review summarizes current concepts that have arisen concerning platelet and vascular PGI2 and TXA2/PGH2 receptors, their transmembrane signal transduction, as well as their possible implications in the pathophysiology of cardiovascular disease.     

脂蛋白相关性磷脂酶A2的活性与冠心病风险预测的相关性研究

目的观察血清中脂蛋白相关磷脂酶A2酶活性(Lp-PLA2)与冠心病(CHD)的相关性,探讨Lp-PLA2是否是冠心病的危险因子。方法分别对239例经降脂治疗的冠心病患者(CHD1组)、154例未经降脂治疗的冠心病患者(CHD2组)和378例健康对照者(NC组)的各种生化指标以及临床基本资料进行检测和调查。应用免疫比浊法(美国Cayman公司提供PAF-AH活性测定试剂盒),测定Lp-PLA2的酶活性。结果未经降脂治疗的冠心病组和经降脂治疗的冠心病组的Lp-PLA2活性明显高于对照组,差异有统计学意义[35.01(15.96,53.32)nmol/ml/min,28.74(16.72,53.58)nmol/ml/min,22.67(15.55,28.62)nmol/ml/min,P<0.001];校正传统冠心病危险因子(CHO,TG,Hs-CRP,Lp(a),GLU)后,Lp-PLA2活性的最高四分位数与最低四分位数相比,CHD的OR值为3.15(95%CI:1.05-9.50)。结论 Lp-PLA2的活性在冠心病患者中显著升高,是冠心病的危险因子。     

脂蛋白相关磷脂酶A2酶活性水平及其I198T基因多态性与2型糖尿病的相关性研究

目的 探讨脂蛋白相关磷脂酶A2酶活性水平及I198T多态性是否是2型糖尿病的危险因素.方法应用TaqMan-ARMS PCR方法,检测117例2型糖尿病患者（T2DM组）和203例健康对照组I198T基因多态性,并对Lp-PLA2酶活性水平、各种生化指标以及临床基本资料进行测定和调查.结果 2型糖尿病组Lp-PLA2酶活性水平明显高于对照组,差异有统计学意义（29.44（16.10,55.81）,21.39（12.42,52.82）,19.77（14.63,26.61） nmol·ml-1·min-1,P〈0.01）;校正各项混杂因素（CHO,TG,Hs-CRP和 Lp（a））后,Lp-PLA2酶活性的最高组与最低组相比,2型糖尿病的OR值为12.21（95%CI,2.88~51.80）;Lp-PLA2酶活性水平在基因型II的Lp-PLA2酶活性最高[22.79（15.49,36.11） nmol·ml-1·min-1,P〈0.05],基因型TT的Lp-PLA2酶活性最低[15.70（8.83,22.60） nmol·ml-1·min-1,P〈0.05）,基因型IT与2型糖尿病的关联显著（OR：2.13 CI：（1.11-4.07） P〈0.05）.结论 Lp-PLA2的酶活性水平在2型糖尿病患者中显著升高,是其独立的危险因子; 基因型IT与2型糖尿病的关联显著.     

脂蛋白相关磷脂酶A2酶活性水平及其基因多态性与冠心病的相关性研究

目的 建立脂蛋白相关磷脂酶A2(Lp-PLA2)基因A379V点突变等位基因特异-荧光定量PCR(TaqMan-ARMS)测定方法,探讨Lp-PLA2的酶活性水平及SNPs是否是冠心病的危险因素.方法 采用等位基因特异性PCR(ARMS)技术结合荧光定量PCR技术(TaqMan探针),通过对不同基因型引物3’端正配与错配扩增效率差别的比较,建立TaqMan-ARMS检测Lp-PLA2基因(PLA2G7)A379V点突变的方法,并对方法进行评价.应用TaqMan-ARMS PCR力法,检测395例冠心病患者(CAD组)和396例非冠心病对照者(NCAD组)PLA2G7的A379V基因频率,并对Lp-PLA2的酶活性水平、年龄、CHO、GLU 、TG、HDL、LDL、Hs-CRP、Lp(a)进行测定和调查,运用独立样本t检验、卡方检验、方差分析、logistic回归对数据进行分析.结果 CAD组的Lp-PLA2酶活性水平明显高于NCAD组(31.51 nmol·ml-1·min-1＞21.31 nmol·ml-1·min-1),差异有统计学意义(F=16.40,P＜0.001);校正传统冠心病危险因子[CHO,TG,Hs-CRP,Lp(a),GLU]后,Lp-PLA2酶活性的最高四分化数与最低四分位数相比,CAD的比值比(OR)为7.50(95％ CI:2.34～24.05);在校正年龄、性别后,A379V点突变基因型VV的OR值为2.95(95％ CI:1.22～7.15,P＜0.05).结论 成功建立了基于TaqMan-ARMS PCR技术的定性检测A379V基因突变的方法;Lp-PLA2的酶活性水平在冠心病患者中显著升高,是冠心病的危险因子;A379V点突变基因型VV是冠心病的危险因子.     

Antithrombotic effects of S 18886, a novel orally active thromboxane A2 receptor antagonist

Summary. Platelet activation and thrombus formation play a critical role in the onset of acute coronary syndromes. Thromboxane A₂ (TxA₂) is among the different chemical modulators released by activated platelets. TxA₂ is considered one of the most powerful agonists for platelet activation. In addition, TxA₂ exerts a vasoconstrictor effect by serving as an agonist of the thromboxane receptor (TP) on the vascular smooth muscle cell membranes. The putative effect of TxA₂ on thrombosis is demonstrated by the clinical effectiveness of acetylsalicylic acid (ASA) in the prevention of acute coronary syndromes. Among the clinically used antiplatelet agents, clopidogrel has shown to be slightly more effective than ASA in the prevention of atherothrombotic events in patients with peripheral arterial disease, and is one of the most widely used after aspirin. The aims of the study were to study the antithrombotic effects of escalating doses of the TP‐receptor antagonist, S 18886 and to compare its effects with those achieved by the administration of ASA (5 mg kg^?1 day^?1), and clopidogrel (3 mg kg^?1 day^?1). The study was undertaken at high and low shear rate conditions using the Badimon perfusion chamber in a porcine model. Antithrombotic effects were assessed as changes on platelet and fibrin(ogen) deposition. The doses of 30 and 100 µg kg^?1 day^?1 were selected based on a previous platelet aggregation study. S 18886 shows a dose‐dependent antithrombotic response. The dose of S‐100 develops similar antithrombotic effects to those of clopidogrel and superior to those of aspirin. The antithrombotic effects were statistically significant at both studied shear rate conditions. Therefore, the orally active TP‐receptor antagonist, S 18886, appears to be a new and effective agent to prevent atherothrombotic complications.     

TRA-418, a novel compound having both thromboxane A2 receptor antagonistic and prostaglandin I2 receptor agonistic activities: its antiplatelet effects in human and animal platelets

Summary.  TRA-418 is a novel compound that has been found in our screening for compounds having both thromboxane A₂ (TP) receptor antagonistic and prostaglandin I₂ (IP) receptor agonistic activities. In the binding assays, TRA-418 showed a 10-fold higher affinity to TP-receptors than IP-receptors. TRA-418 inhibited platelet aggregation induced by the TP-receptor agonist, U-46619 and by arachidonic acid at concentrations lower than those required for inhibition of ADP-induced aggregations. Furthermore, TRA-418 inhibited not only platelet aggregation induced by ADP alone, but also that induced by ADP in the presence of the TP-receptor antagonist, SQ-29548. When the IC₅₀ values of TRA-418 for platelet aggregation were estimated in platelet preparations from monkeys, dogs, cats, and rats using ADP and arachidonic acid as the platelet stimulating agents, it was found that the values estimated in monkey platelets were quite similar to those estimated in human platelets. In ex vivo platelet aggregation in monkeys, TRA-418 exhibited significant inhibitory effects on arachidonic acid-induced aggregation in platelet preparations from monkeys treated at 3 µg kg min⁻¹ or higher doses, where neither a significant decrease in blood pressure nor a significant increase in heart rate was observed. These results are consistent with the fact that TRA-418 has a relatively potent TP-receptor antagonistic activity together with a relatively weak IP-receptor agonistic activity.     

Biosynthesis of prostacyclin and thromboxane A2 during chronic hypoxaemia in children with cyanotic congenital heart disease

The high risk of vaso-occlusive events in children younger than 4 years with cyanotic congenital heart disease and polycythaemia has been attributed to increased thromboxane (Tx) A₂ formation. In older children with cyanotic congenital heart disease, however, the risk of vaso-occlusive events is much lower. We therefore hypothesized that the formation of TxA₂ and prostacyclin is not disturbed in this age group. We measured urinary excretion of stable index metabolites of in vivo TxA₂ and prostacyclin formation by gas chromatography–mass spectrometry in nine children (age 5.9–14.4, median 8.7 years) with cyanotic congenital heart disease, and in nine healthy, age-matched control subjects. The patients excreted less 2,3-dinor-TxB₂ (systemic TxA₂ formation, P =0.03), 2,3-dinor-6-keto-PGF_1α (systemic prostacyclin formation, P =0.03) and TxB₂ (renal TxA₂ formation, P =0.01) than the control subjects. We conclude that in children older than 5 years with cyanotic congenital heart disease, endogenous synthesis of TxA₂ and prostacyclin is not stimulated. This result may explain the lower risk of vaso-occlusive events in this age group as compared with younger children. In addition, our results suggest that chronic hypoxaemia may affect the in vivo formation of TxA₂ and prostacyclin and the metabolic disposition of TxB₂.     

P2Y12 receptor-mediated potentiation of thrombin-induced thromboxane A2 generation in platelets occurs through regulation of Erk1/2 activation

BACKGROUND: Thromboxane A2 (TXA2) is a positive feedback lipid mediator that is generated upon stimulation of platelets with various agonists. Aspirin works as an antithrombotic drug by blocking the generation of TXA2. The aim of this study was to evaluate the role of the purinergic P2Y receptors in thrombin-induced TXA2 generation. RESULTS: PAR1-activating peptide (SFLLRN), PAR4-activating peptide (AYPGKF), and thrombin, induced the activation of cytosolic phospholipase A2 (cPLA2), release of arachidonic acid (AA) from membrane-bound phospholipids, and subsequent TXA2 generation in human platelets. The actions of these agonists were significantly inhibited in the presence of the P2Y12 receptor antagonist, AR-C69931MX, but not the P2Y1 receptor antagonist, MRS2179. In addition, AYPGKF- and thrombin-induced TXA2 generation was significantly reduced in platelets from mice dosed with clopidogrel, confirming the results obtained with the human platelets. Also, Pearl mouse platelets that lack releasable nucleotides generated significantly less TXA2 when compared with the wild-type littermates in response to PAR stimulation. Inhibition of extracellular signal-regulated protein kinase 1/2 (Erk 1/2) activation using U0126, an inhibitor of MAP kinase kinase (MEK), suppressed PAR-mediated cPLA2 phosphorylation and TXA2 generation. Further, platelets that were pretreated with AR-C69931MX, as well as Pearl mouse platelets, displayed the reduced levels of Erk1/2 phosphorylation upon stimulation with the PAR agonists. CONCLUSIONS: Based on these findings, we conclude that thrombin-induced Erk1/2 activation is essential for PAR-mediated TXA2 generation, which is potentiated by the P2Y12 receptor-mediated signaling pathway but not the P2Y1 receptor-mediated signaling pathway. Finally, using selective inhibitors of Src kinases, we show that PAR-mediated Src activation precedes Erk1/2 activation.     

Cisplatin-induced renal effects and thromboxane A2 receptor blockade

The aim of this study was to evaluate the renal protective effect of linotroban, a thromboxane A₂ receptor antagonist, in 25 patients with malignant tumours scheduled for cisplatin therapy. Cisplatin was administered 1 h after the start of a 24-h continuous infusion of linotroban or placebo. Glomerular filtration rate and effective renal plasma flow were measured. Infusions of cisplatin decreased glomerular filtration rate by 17 ± 25 mL min⁻¹ ( P  = 0.049 vs. baseline) and effective renal plasma flow by 94 ± 150 mL min⁻¹ ( P  = 0.049 vs. baseline) in the placebo group. In the linotroban group a decrease in glomerular filtration rate by 11 ± 18 mL min⁻¹ ( P  = 0.050 vs. baseline) and in effective renal plasma flow by 26 ± 63 mL min⁻¹ ( P  = 0.2 vs. baseline) was noted. However, no difference was noted between groups in response to treatment. Our findings indicate that linotroban may not be useful for prevention of cisplatin's acute nephrotoxic effects.     

冠心病患者血清脂蛋白相关磷脂酶A2与氧化低密度脂蛋白水平

摘要：目的：分析冠心病(CAD)患者血清脂蛋白相关磷脂酶A2(Lp-PLA2)、氧化低密度脂蛋白(ox-LDL)水平。 方法：分别检测100例急性冠脉综合征(ACS)、75例稳定性心绞痛(SAP)患者和50例健康人对照者的血清Lp-PLA2、ox-LDL水平及CAD病变程度,分析其相关关系。 结果：与健康人对照组相比,CAD患者血清Lp-PLA2、ox-LDL水平均显著升高(P<0.01);与SAP组相比,ACS组血清Lp-PLA2、ox-LDL、肌钙蛋白I(TnI)水平及Gensini积分均显著升高(P<0.01)。相关性分析显示,CAD患者Gensini积分分别与血清Lp-PLA2(r=0.426,P<0.01)、ox-LDL(r=0.331,P<0.01)水平呈正相关,Lp-PLA2与ox-LDL之间亦显著正相关(r=0.238,P<0.01)。多元回归分析显示,CAD患者血清Lp-PLA2(β=0.366,P<0.01)和ox-LDL(β=0.253,P<0.01)水平共同决定了22.7%的Gensini积分变化;Gensini积分是血清Lp-PLA2的唯一显著的独立预测因子(β=0.420,P<0.01);LDL胆固醇(LDL-C) (β=0.411,P<0.01)、Gensini积分(β=0.285,P<0.01)共同决定了25.9%的ox-LDL变化。 结论：CAD患者血清Lp-PLA2、ox-LDL水平升高,且与动脉粥样硬化(As)病变程度密切相关。     

Potentiating effects of nicorandil on the adenosine A2 receptor-mediated vasodepression in rats: potential role for KATP channels

Summary— The effects of nicorandil on systemic blood pressure (SBP) and heart rate (HR) responses to adenosine were compared with those to N⁶-cyclopentyladenosine (CPA), a selective adenosine A, receptor agonist, and 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA), a selective adenosine A₂ receptor agonist, in anesthetized rats. When injected intravenously (iv), single bolus doses of CPCA (0.01–1.0 μg/kg), like adenosine (30 μg/kg), elicited dose-dependent decreases in SBP scarcely affecting HR, while CPA (0.03–1.0 μg/kg) produced only reduction of HR without influencing SBP. The enhancement of the vasodepressor response to CPCA, like adenosine, was induced by the iv infusion of either nicorandil (10 μg/kg per min) or cromakalim (0.1 μg/kg per min), but the response to CPA in HR remained unmodified during the infusion of nicorandil as well as cromakalim. After iv treatment with glibenclamide (20 mg/kg), an adenosine triphosphate (ATP)-sensitive K⁺ channel blocker, or 3,7-dimethyl-1-propargylxanthine (DMPX) (1 mg/kg), a selective antagonist of adenosine A₂ receptor, not only CPCA action but also the enhancement of CPCA action by nicorandil and cromakalim were significantly attenuated. Similar results were obtained in the case of single bolus iv adenosine. The present result indicates that the augmentation of the adenosine action by nicorandil appears to be mediated by activation of ATP-sensitive K⁺ channels, closely linked with stimulation on A₂ receptors by adenosine.     

The A1 (B) phenomenon: a monoclonal anti-B (BS-85) demonstrates low levels of B determinants on A1 red cells

A monoclonal anti-B (BS 85) that reacts strongly with red cells from weak B variants (B3, Bint and Bv) has demonstrated the presence of a trace of B on A1 red cells. The agglutination of group A1 red cells by an anti-B antibody is called the A1 (B) phenomenon and is the converse of the B(A) phenomenon seen with certain monoclonal anti-A antibodies. Fragile A1 (B) agglutination is best seen by spin-tube techniques and A1 red cells negative in saline tests are agglutinated by albumin and protease enzyme-enhanced tests, but no reactions are seen with A2 red cells. The A1 (B) reaction is specifically inhibited by B substance, and D-galactose and the galactose-containing sugars melibiose and lactose. Red cells from B variants showed differential inhibition patterns with various sugars. A1 transferase levels were normal even in the strongest A1 (B) reactive blood samples, although the plasma H transferase levels and H status of these red cells were elevated. This is in contrast to the B(A) phenomenon which is associated with elevated levels of B transferase. It is suggested that A1(B) overlapping specificity can occur because of a combination of higher H activity (and thus more H sites) together with normal levels of A transferase activity as they are 20% higher than normal levels of B transferase. The production of anti-B reagents free of the A1 (B) phenomenon with BS-85 is achieved by suitable dilution using quality control tests with protease-treated A1 red cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

The promoting effect of epinephrine on lipopolysaccharide-induced interleukin-8 production in whole blood may be mediated by thromboxane A2

Summary.  Epinephrine is known to enhance lipopolysaccharide (LPS)-induced interleukin (IL)-8 secretion in a platelet dependent manner. To determine whether thromboxane A₂ (TxA₂; a product from activated platelets) is involved in this process, blood samples drawn either before or 2 h after oral administration of 440 mg acetylsalicylic acid (ASA) were stimulated with LPS (5 ng mL⁻¹) and different concentrations of epinephrine were added (0.1–100.0 µmol L⁻¹). ASA ingestion significantly (global P  < 0.05) reduced the enhancing effect of epinephrine on LPS-induced IL-8 release by 15–28%. To further explore whether TxA₂ may be involved in this process, a TxA₂ agonist (U46619) was added to whole blood together with LPS instead of epinephrine. U46619 mimicked the epinephrine effect: 20 ng mL⁻¹ U46619 enhanced LPS-induced IL-8 release by 39% ( P  < 0.05). Furthermore, preincubation of whole blood with 75 µmol L⁻¹ or 150 µmol L⁻¹ SQ29548, a TxA₂ receptor antagonist, completely blocked epinephrine's promoting effect on LPS-induced IL-8 release. Since thrombin-activated platelets have been reported to be important in the production of IL-8 in monocytes through the activation of monocytes by exposed RANTES in a P-selectin-dependent reaction, we suggest that the epinephrine effect is mediated by enhanced TxA₂ production and subsequent rise in the exposure of RANTES and P-selectin on the platelets of whole blood.     

特发性膜性肾病患者血清抗M型磷脂酶A2受体抗体阳性率与肾间质损伤的关系

目的观察特发性膜性肾病(idiopathic membranous nephropathy,IMN)患者血清抗M型磷脂酶A₂受体(phospholipase A₂receptor,PLA₂R)抗体阳性率变化,探讨其对IMN患者发生肾间质损伤的预测价值。方法268例IMN患者,发生肾间质损伤219例为损伤组,未发生肾间质损伤49例为未损伤组。比较2组一般资料及24h尿蛋白定量、血肌酐、血尿酸、估算肾小球滤过率、血清白蛋白水平等;比较2组血清抗M型PLA₂R抗体阳性率;多因素logistic回归分析IMN患者发生肾间质损伤的影响因素;绘制ROC曲线,评估血清抗M型PLA₂R抗体阳性联合血肌酐、血清白蛋白、24h尿蛋白定量预测IMN患者发生肾间质损伤的价值。结果损伤组年龄[(46.32±13.20)岁]大于未损伤组[(35.16±9.53)岁](P<0.05),24h尿蛋白定量[(6.58±3.50)g]、血肌酐[(72.53±32.62)mmol/L]、血尿酸(352.26±96.48)mmol/L]水平均高于未损伤组[(4.04±1.78)g、(60.21±17.36)mmol/L、(309.05±72.64)mmol/L](P<0.05),估算肾小球滤过率[(92.83±18.71)mL/(min·1.73m²)]、血清白蛋白水平[(21.76±4.80)g/L]低于未损伤组[(122.03±32.05)mL/(min·1.73m²)、(28.91±6.18)g/L](P<0.05);2组性别比例、民族、体质量指数及血清三酰甘油、总胆固醇、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇水平比较差异均无统计学意义(P>0.05)。损伤组血清抗M型PLA₂R抗体阳性(1∶10)率、血清抗M型PLA₂R抗体阳性(1∶100)率(49.8%、35.6%)均高于未损伤组(24.5%、12.2%)(P<0.05)。多因素logistic回归分析结果显示,24h尿蛋白定量(OR=1.503,95%CI:1.164~1.940,P=0.002)、血肌酐(OR=0.971,95%CI:0.944~1.000,P=0.047)、估算肾小球滤过率(OR=0.911,95%CI:0.867~0.958,P<0.001)、血尿酸(OR=1.011,95%CI:1.003~1.018,P=0.005)、血清白蛋白(OR=0.804,95%CI:0.720~0.898,P<0.001)、血清抗M型PLA₂R抗体(OR=19.939,95%CI:5.558~71.530,P<0.001)是IMN患者发生肾间质损伤的影响因素。ROC曲线分析结果显示,血清抗M型PLA₂R抗体阳性预测IMN患者发生肾间质损伤的AUC为0.813(95%CI:0.736~0.889,P<0.001),灵敏度为89.0%,特异度为73.5%;血肌酐、血清白蛋白、24h尿蛋白定量分别以79.5mmol/L、23.01g/L、6.45g/L为最佳截断值,联合血清抗M型PLA₂R抗体阳性预测IMN患者发生肾间质损伤的AUC分别为0.859(95%CI:0.802~0.916,P<0.001)、0.907(95%CI:0.861~0.952,P<0.001)、0.923(95%CI:0.886~0.960,P<0.001),灵敏度分别为89.0%、88.6%、79.0%,特异度分别为73.5%、83.7%、91.8%。结论24h尿蛋白定量、血肌酐、估算肾小球滤过率、血尿酸、血清白蛋白、血清抗M型PLA₂R抗体是IMN患者发生肾间质损伤的影响因素,血清抗M型PLA₂R抗体阳性联合24h尿蛋白定量检测对IMN患者肾间质损伤有较高的预测价值。