RNA特异性腺苷脱氨酶1与Caveolin 1在脓毒症相关肝损伤中的作用及机制

背景与目的 脓毒症相关肝损伤（SRLI）发病机制尚不清楚,细菌内毒素（LPS）对肝脏血管内皮细胞的炎症损害可能是重要环节。前期研究提示,RNA特异性腺苷脱氨酶1（ADAR1）可能通过调控内皮细胞功能相关蛋白Caveolin 1（Cav-1）在参与血管内皮应激中的局部和全身炎症反应。因此,本研究初步探讨ADAR1与Cav-1在SRLI中的作用,以期为SRLI的早期防治寻找新的方法。方法 取ADARl基因敲除小鼠（ADAR1^ECKO）与野生型小鼠（ADAR1^flox/flox）各20只,腹腔注射LPS（20 mg/kg）诱导脓毒症小鼠模型脓毒症模型,6 h后每组小鼠各取10只,获取肝脏组织,并分离肝窦内皮细胞（LSECs）,通过HE染色观察其肝脏病理学改变,用细胞免疫荧光法观察LSECs中Cav-1及其下游蛋白VE-cadherin的表达,两组其余小鼠用于生存率分析;用ADARl siRNA转染正常野生型小鼠的LSECs后,通过内皮细胞成管实验观察转染后LSECs的增殖情况、Western blot检测Cav-1下游相关蛋白的表达。结果 生存观察结果显示,注射LPS后,ADAR1^ECKO小鼠死亡时间早于ADAR1^flox/flox小鼠,存活率低于ADAR1^flox/flox小鼠（均P<0.05）;组织病理学观察显示,注射LPS 6 h后,ADAR1^ECKO小鼠的肝损伤比ADAR1^flox/flox小鼠更严重;细胞免疫荧光观察显示,注射LPS 6 h后,ADAR1^ECKO小鼠LSECs中Cav-1与VE-cadherin的表达低于ADAR1^flox/flox小鼠。正常野生型小鼠的LSECs转染ADARl siRNA后,成管能力明显减弱,Cav-1下游蛋白VE-cadherin的表达下调,但β-Catenin的表达无明显变化。结论 ADAR1的下调或功能缺失会导致SRLI加重,机制可能涉及其调控Cav-1/VE-cadherin通路的活性。因此,激活ADAR1/Cav-1/VE-cadherin通路可能是防治SRLI的有效策略。     

Lack of A1 adenosine receptors augments diabetic hyperfiltration and glomerular injury

Intraglomerular hypertension and glomerular hyperfiltration likely contribute to the pathogenesis of diabetic nephropathy, and tubuloglomerular feedback (TGF) has been suggested to play a role in diabetic hyperfiltration. A1 adenosine receptor (A1AR) null mice lack a TGF response, so this model was used to investigate the contribution of TGF to hyperfiltration in diabetic Ins2(+/-) Akita mice. TGF responses in Ins2(+/-) A1AR(-/-) double mutants were abolished, whereas they were attenuated in Ins2(+/-) mice. GFR, assessed at 14, 24, and 33 wk, was approximately 30% higher in Ins2(+/-) than in wild-type (WT) mice and increased further in Ins2(+/-) A1AR(-/-) mutants (P < 0.01 versus both WT and Ins2(+/-) mice at all ages). Histologic evidence of glomerular injury and urinary albumin excretion were more pronounced in double-mutant than single-mutant or WT mice. In summary, the marked elevation of GFR in diabetic mice that lack a TGF response indicates that TGF is not required to cause hyperfiltration in the Akita model of diabetes. Rather, an A1AR-dependent mechanism, possibly TGF, limits the degree of diabetic hyperfiltration and nephropathy.     

Isoflurane, but not halothane, induces protection of human myocardium via adenosine A1 receptors and adenosine triphosphate-sensitive potassium channels

BACKGROUND: Volatile anesthetics produce differing degrees of myocardial protection in animal models of ischemia. The purpose of the current investigation was to determine the influence of isoflurane and halothane on myocardial protection in a human model of simulated ischemia and the role of adenosine A1 receptors and adenosine triphosphate-sensitive potassium (KATP) channels in the anesthetic pathway. METHODS: Human atrial trabecular muscles were superfused with oxygenated Krebs-Henseleit buffer and stimulated at 1 Hz, with recording of maximum contractile force. Fifteen minutes before a 30-min anoxic insult, muscles were pretreated for 5 min with either anoxia, the A1 agonist N6-cyclohexyladenosine, 1% halothane or 1.2% isoflurane. These treatments were also performed in the presence of either the KATP channel antagonist glibenclamide or the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Anesthetic effects were also determined on KATP currents in isolated whole cell voltage-clamped human atrial myocytes. RESULTS: Recovery of force (recorded 60 min after anoxia) in isoflurane-pretreated muscles was reduced from 76.6 +/- 7.5% of baseline to 43.7 +/- 7.1% by pretreatment with glibenclamide, and to 52.5 +/- 6.2% by pretreatment with DPCPX. Halothane treatment provided no cardioprotection and seemed to inhibit protection by anoxic preconditioning. Halothane decreased whole cell KATP currents in atrial myocytes, whereas isoflurane had no effects. CONCLUSIONS: This study demonstrates the cardioprotective effects of isoflurane in contrast to the effects of halothane. Furthermore, A1 receptors and KATP channels seem to mediate the beneficial effects of anoxia and isoflurane in human myocardium.     

腺苷A1受体在全身麻醉中的作用研究进展

背景 由于腺苷在睡眠方面的作用与全身麻醉所产生的作用非常相似,近年来关于腺苷及其受体在全身麻醉过程作用的研究越来越多,但其机制尚无定论.目的 综述腺苷A1受体与全身麻醉的关系及在全身麻醉过程中可能的作用机制.内容 简述全身麻醉与腺苷A1受体在睡眠方面的相似之处以及全身麻醉相关的重要受体γ-氨基丁酸A型(γ-amino butyric acid A,GABAA)受体、N-甲基-D-天冬氨酸(N-methyl-D-aspartic acid,NMDA)受体与腺苷A1受体的关系,总结目前腺苷A1受体在全身麻醉中作用的研究结果.趋向 腺苷A1受体在全身麻醉中的作用机制尚不完全清楚,有待进一步的研究证实,研究腺苷A1受体和全身麻醉之间的关系对于临床麻醉工作及药物的研究应用有一定的指导意义.     

Natriuretic effect of adenosine A1-receptor blockade in rats

Background: Many effects of adenosine on renal function have been identified. The development of adenosine receptor blockers has made it possible to identify which of these effects are exerted by endogenous adenosine. At least four adenosine receptor subtypes, denoted A1, A2a, A2b, and A3 are currently known. In the present study the selective A1 receptor blocker 1,3-dipropyl-8[2-(5,6-epoxy) norbanyl] xanthine (CVT-117) was used to assess the effect of A1 activation by endogenous adenosine on renal function in rats. Methods: Clearance studies were performed before and after administration of 0.1 mg/kg and 0.8 mg/kg of CVT-117 in separate groups of rats and before and after administration of vehicle in time-control rats. Measurement of heart rate before and after administration of exogenous adenosine confirmed effective A1 receptor blockade. Results: At both the lower and higher doses, A1 receptor blockade with CVT-117 increased fractional sodium excretion and urine flow rate without altering GFR. The increase in sodium excretion following A1 blockade was not accompanied by increases in the excretion of phosphate or potassium. Conclusion: These results show that endogenous adenosine promotes sodium retention by activation of A1 receptors.     

Renal tubule necrosis and apoptosis modulation by A1 adenosine receptor expression

We have shown that A1 adenosine receptors (A1ARs) are cytoprotective against renal tubular necrosis and apoptosis both in vivo and in vitro. To study the role of A1AR numbers on renal epithelial cell survival, we stably overexpressed the human A1 receptor in a porcine renal tubule cell line and utilized primary cultures of proximal tubules obtained from A1AR knockout mice. Receptor-overexpressing cells were protected against peroxide-induced necrosis and tumor necrosis factor-alpha/cycloheximide-induced apoptosis. Conversely, cultured proximal tubule cells from receptor knockout mice showed more necrotic and apoptotic cell loss than corresponding cells from wild-type mice. Overexpression of the receptor resulted in a significantly higher baseline expression of both total and phosphorylated heat-shock protein (HSP)27; the latter due to A1 receptor enhancement of p38 and AP2 mitogen-activated protein kinase activities. The resistance to cell death in the porcine cells was reversed by selective A1 receptor antagonism and by a selective inhibitor of HSP synthesis. Receptor activation in wild-type mice in vivo led to increased total and phosphorylated HSP27, whereas receptor knockout mice showed decreased baseline and adenosine-mediated HSP phosphorylation. These studies show that endogenous A1AR activation produces cytoprotective effects in renal proximal tubules by modulating HSP27 signaling pathways.     

Natriuretic and diuretic actions of a highly selective adenosine A1 receptor antagonist

The natriuretic and diuretic action of a highly selective adenosine A1 receptor (A1AdoR) antagonist, 1,3-dipropyl-8-[2-(5,6-epoxy)norbornyl]xanthine (CVT-124), was investigated in anesthetized rats. CVT-124 (0.1 to 1 mg/kg) caused dose-dependent increases in urine flow and fractional and absolute sodium excretion of by six- to 10-fold and, at 0.1 mg/kg, increased the GFR (1.6+/-0.1 to 2.5+/-0.2 ml/min; P<0.01). There were no changes in BP or heart rate. CVT-124 reduced absolute proximal reabsorption (26+/-3 to 20+/-2 nl/min; P<0.05) despite unchanged proximally measured, single-nephron GFR (SNGFR) (42+/-5 to 44+/-4 nl/min; NS) and thereby decreased fractional proximal reabsorption (60+/-3 to 46+/-4%; P<0.05). Despite increasing distal tubular fluid flow rate (5.4+/-0.7 to 9.7+/-0.9 nl/min; P<0.001), it reduced the proximal-distal difference in SNGFR (before: 9.4+/-1.0 versus during CVT-124: 4.6+/-1.5 nl/min; P<0.01), suggesting that it had blunted the effects of the macula densa on SNGFR. Direct measurements of maximal tubuloglomerular feedback (TGF) responses were made from proximal stop flow pressure (PSF) during orthograde loop perfusion from the proximal tubule with artificial tubular fluid at 40 nl/min. TGF was blunted by intravenous CVT-124 (0.5 mg/kg; deltaPSF with vehicle: 8.3+/-0.6 versus CVT-124: 6.5+/-0.3 mm Hg; n = 9; P<0.01). In conclusion, A1AdoR blockade reduces proximal reabsorption and uncouples it from glomerular filtration. It increases distal delivery of fluid yet does not activate a macula densa-dependent fall in SNGFR because it blunts the TGF response. Natriuresis accompanied by blockade of proximal glomerulotubular balance and TGF characterizes a new class of diuretic drugs.     

Adenosine and adenosine uptake inhibitors potentiate the neuromuscular blocking action of rocuronium mediated by adenosine A1 receptors in isolated rat diaphragms

Background: Adenosine, which pre‐junctionally modulates neuromuscular transmission, and adenosine uptake inhibitors, which increase extracellular adenosine, have been used clinically. We investigated the effects of adenosine, dipyridamole and midazolam on the neuromuscular blocking action of rocuronium. Methods: Isometric twitch tensions of rat nerve‐hemidiaphragm preparations elicited by indirect (phrenic nerve) supra‐maximal stimulation at 0.1 Hz were evaluated (n=6 in all data). Results: Pre‐treatments with adenosine (0.1 and 1 μM) and CCPA (1 μM, adenosine A₁ receptor agonist), but not that with CGS21680 (0.5 μM, A₂ receptor agonist), shifted the rocuronium concentration–twitch tension curves to the left and decreased the rocuronium concentration for 50% twitch depression (IC₅₀) compared with the control (P<0.01). The leftward shift induced by 1 μM adenosine was inhibited by pre‐treatments with theophylline (50 μM, non‐selective adenosine receptor antagonist) and DPCPX (0.2 μM, A₁ receptor antagonist) but not by that with DPMA (5 μM, A₂ receptor antagonist). Pre‐treatments with dipyridamole and midazolam, adenosine uptake inhibitors, shifted the curve to the left and decreased IC₅₀ at supra‐therapeutic concentrations (10 and 2.5 μM, respectively) but not at clinical concentrations (2 and 0.5 μM, respectively), and the leftward shifts were inhibited by pre‐treatment with DPCPX (0.2 μM). Conclusion: The results indicate that adenosine potentiates the neuromuscular blocking action of rocuronium mediated by adenosine A₁ receptors and that supra‐therapeutic concentrations of dipyridamole and midazolam also potentiate the action of rocuronium by increasing endogenous adenosine concentration.     

腺苷A1受体诱导预处理延迟效应对供心保存的影响及机制探讨

目的　探讨腺苷A1受体激动剂预处理延迟效应对保存大鼠心脏的影响及其机制。方法　Wistar大鼠随机分为 8组 ,A、C组以高选择性腺苷A1受体激动剂 (CCPA)预处理 ;D、E、F组在CCPA预处理前分别注射锰 超氧化物歧化酶 (Mn SOD)反义、有意义、错配寡核苷酸 (ODN) ;B、G组注射生理盐水 ,H组只注射反义寡核苷酸。 2 4h后 ,A、B组用 4℃St.Thomas液保存 4h ,复灌 1h ,而另 6组采取低温缺血 3h ,复灌 1h。观测心功能、磷酸肌酸激酶 (CK mb)、三磷酸腺苷 (ATP)含量等。结果　A组左室内压上升与下降最大速率恢复率 (±dp/dtmax,% )为 6 2 .83± 17.2 7,6 6 .81± 18.99,心肌ATP含量 (10 3 μmol/g)为3.6 7± 1.4 2 ;而B组分别为 4 0 .4 1± 18.2 9,4 4 .70± 2 5 .14 ,1.4 6± 0 .5 4 ;A组均明显高于B组 ,差异均有显著性 (P <0 .0 1orP <0 .0 5 )。C组±dp/dtmax恢复率、ATP、Mn SOD活性均明显高于D、G、H组 (P <0 .0 1orP <0 .0 5 ) ,而与E、F组比较 ,差异无显著性。结论　腺苷A1受体激动剂能诱导预处理的延迟效应 ,改善离体大鼠心脏的保存效果 ,而该效应与Mn SOD的高表达有关。     

Involvement of A1 adenosine receptors in the acquisition of fertilizing capacity

Ejaculated mammalian spermatozoa acquire competence to fertilize oocytes by a two-step process: capacitation followed by acrosome reaction. The biochemical and biophysical modifications occurring in vivo in the female reproductive tract can be reproduced in vitro, and previous studies have suggested a capacitative role for adenosine A(1) receptor (A(1)R). Mice with a targeted disruption of the Adora 1 gene (A(1)R-/- mice) provide a useful model for better understanding the role of the A(1)R in fertility. Murine spermatozoa express A(1)R in the head, neck, midpiece region, and tail. The number of capacitated spermatozoa incubated in human tubal fluid was significantly reduced in A(1)R-/- compared with A(1)R+/+ and A(1)R+/- spermatozoa. The difference between A(1) R+/+ and A(1)R-/- mouse spermatozoa was mainly in the time necessary to reach the maximum percentage of capacitation. A(1)R+/+ murine sperm obtained the full state of capacitation within 90 minutes whereas A(1)R-/- sperm required 240 minutes. Caffeine, a known antagonist of A(1) and A(2A) adenosine receptors, lowered the number of capacitated sperm and affected the time of capacitation in a dose-dependent manner, mimicking the effects of the lack of A(1) receptors. Although number, motility, and viability of A(1)R-/- murine sperm was not significantly different from A(1)R+/+ mouse spermatozoa, a significant reduction of the number of pups produced by A(1)R-/- male mice suggests that A(1) receptors must be fully operative to accomplish the optimal degree of capacitation and thereby fertilization.     

Regulation of renal A(1) adenosine receptors in vivo.

We have compared renal A(1) adenosine receptor (AR) regulations in rats after chronic agonist and antagonist treatments. In one group, R-phenylisopropyladenosine (R-PIA), a selective A(1) AR agonist, was infused subcutaneously for 7 days. Another group was fed theophylline, a non-selective AR antagonist, for 2 weeks. Renal cortex membrane A(1) AR binding with 1,3-[(3)H]-dipropyl-8-cyclopentylxanthine demonstrated approximately 40% reduction in the B(max ) for the R-PIA group without any changes in the K(d) values. Neither the B(max) nor the K(d) changed following chronic theophylline treatment. Renal cortex G(i)alpha-proteins from the R-PIA treated rats decreased by approximately 30%. Renal G(i)alpha levels did not change in theophylline-treated rats. Consistent with the A(1) AR desensitization, R-PIA-treated rats had significantly higher basal renin release and showed attenuated A(1) AR-mediated inhibition of renin release. These data suggest that prolonged A(1) AR stimulation results in downregulation of renal A(1) ARs and G(i)alpha, accompanied by desensitization of A(1) AR-mediated inhibitory effects on renin release. Unlike cardiac and brain A(1) ARs, renal A(1) receptors are not subject to up-regulation following chronic antagonist treatment.     

Impaired glucose tolerance in the absence of adenosine A1 receptor signaling

OBJECTIVE

The role of adenosine (ADO) in the regulation of glucose homeostasis is not clear. In the current study, we used A1-ADO receptor (A1AR)-deficient mice to investigate the role of ADO/A1AR signaling for glucose homeostasis.

RESEARCH DESIGN AND METHODS

After weaning, A1AR^−/− and wild-type mice received either a standard diet (12 kcal% fat) or high-fat diet (HFD; 45 kcal% fat). Body weight, fasting plasma glucose, plasma insulin, and intraperitoneal glucose tolerance tests were performed in 8-week-old mice and again after 12–20 weeks of subsequent observation. Body composition was quantified by magnetic resonance imaging and epididymal fat-pad weights. Glucose metabolism was investigated by hyperinsulinemic-euglycemic clamp studies. To describe pathophysiological mechanisms, adipokines and Akt phosphorylation were measured.

RESULTS

A1AR^−/− mice were significantly heavier than wild-type mice because of an increased fat mass. Fasting plasma glucose and insulin were significantly higher in A1AR^−/− mice after weaning and remained higher in adulthood. An intraperitoneal glucose challenge disclosed a significantly slower glucose clearance in A1AR^−/− mice. An HFD enhanced this phenotype in A1AR^−/− mice and unmasked a dysfunctional insulin secretory mechanism. Insulin sensitivity was significantly impaired in A1AR^−/− mice on the standard diet shortly after weaning. Clamp studies detected a significant decrease of net glucose uptake in A1AR^−/− mice and a reduced glucose uptake in muscle and white adipose tissue. Effects were not triggered by leptin deficiency but involved a decreased Akt phosphorylation.

CONCLUSIONS

ADO/A1AR signaling contributes importantly to insulin-controlled glucose homeostasis and insulin sensitivity in C57BL/6 mice and is involved in the metabolic regulation of adipose tissue.Adenosine (ADO), a purine nucleoside, is a ubiquitous product of ATP breakdown, with a large variety of regulatory functions. ADO effects are mediated by four receptors (AR): A1, A2a, A2b, and A3, each showing an organ-specific expression pattern and different half-maximal effective concentration (EC50), thus facilitating differential effects (1). ARs mediate downstream effects mostly via G-protein–coupled receptors that are either stimulatory (A2a and A2b) or inhibitory (A1 and A3) to adenylate cyclase. The resulting increase or decrease of cAMP induces downstream signaling by triggering phosphorylation activation of key enzymes (2).A role of the metabolic byproduct of ATP utilization, adenosine, in the regulation of glucose uptake and utilization makes physiological sense. Nevertheless, previous studies of the effect of ADO on glucose transport have yielded conflicting results in that insulin sensitivity and/or glucose uptake were reported as either decreased (3–6) or increased (7–9). The availability of mice with adenosine receptor deletions offers a new way to assess the role of a chronic reduction in ADO signaling on glucose tolerance. Recently, we discovered a nephropathic phenotype in an A1AR-deficient Akita hybrid mouse model of type 1 diabetes, suggesting a relevant role for A1AR signaling in maintaining glucose homeostasis (10). Another recent study showed that mice with A1AR deletion have a higher fat content with aging (11). Because of the well-established relationship between excess body weight and insulin resistance, we considered it possible that the phenotype of A1AR-deficient mice may include the development of glucose intolerance and insulin resistance. In the current study, we have therefore used A1AR-deficient mice to examine the hypothesis that ADO signaling via A1AR contributes to glucose homeostasis. Our main findings support this notion in that A1AR-deficient mice show a defect in glucose tolerance that seems to be a result of insulin resistance.     

Bovine sperm adenylate cyclase. Inhibition by adenosine and adenosine analogs

Since both adenosine and cAMP affect sperm motility and metabolism, the authors have studied the mode of interaction of adenosine with the adenylate cyclase activity in either the presence or the absence of 15 mM caffeine. In general, structural analogs of adenosine containing alterations of the purine structure produce little or no inhibition, whereas analogs containing alterations of the ribose structure are effective inhibitors. Cyclic AMP and caffeine also inhibit the enzyme activity. The kinetics of the adenosine inhibition most closely resemble the linear noncompetitive type. Adenosine is a more effective inhibitor of adenylate cyclase activity in the presence of Mn2+ rather than Mg2+, and is more effective at higher metal ion concentrations. These observations are consistent with a P-site interaction of adenosine with adenylate cyclase.     

Involvement of peripheral adenosine A2 receptors in adenosine A1 receptor-mediated recovery of respiratory motor function after upper cervical spinal cord hemisection

BACKGROUND/OBJECTIVE: In an animal model of spinal cord injury, a latent respiratory motor pathway can be pharmacologically activated through central adenosine A1 receptor antagonism to restore respiratory function after cervical (C2) spinal cord hemisection that paralyzes the hemidiaphragm ipsilateral to injury. Although respiration is modulated by central and peripheral mechanisms, putative involvement of peripheral adenosine A2 receptors in functional recovery in our model is untested. The objective of this study was to assess the effects of peripherally located adenosine A2 receptors on recovery of respiratory function after cervical (C2) spinal cord hemisection. METHODS: Respiratory activity was electrophysiologically assessed (under standardized recording conditions) in C2-hemisected adult rats with the carotid bodies intact (H-CBI; n=12) or excised (H-CBE; n=12). Animals were administered the adenosine A2 receptor agonist, CGS-21680, followed by the A1 receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), or administered DPCPX alone. Recovered respiratory activity, characterized as drug-induced activity in the previously quiescent left phrenic nerve of C2-hemisected animals in H-CBI and H-CBE rats, was compared. Recovered respiratory activity was calculated by dividing drug-induced activity in the left phrenic nerve by activity in the right phrenic nerve. RESULTS: Administration of CGS-21680 before DPCPX (n=6) in H-CBI rats induced a significantly greater recovery (58.5 +/- 3.6%) than when DPCPX (42.6 +/- 4.6%) was administered (n=6) alone. In H-CBE rats, prior administration of CGS-21680 (n=6) did not enhance recovery over that induced by DPCPX (n=6) alone. Recovery in H-CBE rats amounted to 39.7 +/- 3.7% and 38.4 + 4.2%, respectively. CONCLUSIONS: Our results suggest that adenosine A2 receptors located in the carotid bodies can enhance the magnitude of adenosine A1 receptor-mediated recovery of respiratory function after C2 hemisection. We conclude that a novel approach of targeting peripheral and central adenosine receptors can be therapeutically beneficial in alleviating compromised respiratory function after cervical spinal cord injury.     

Inhibition of adenosine kinase attenuates interleukin-1- and lipopolysaccharide-induced alterations in articular cartilage metabolism

OBJECTIVE: To investigate the effect of adenosine kinase inhibition on interleukin (IL)-1beta- and lipopolysaccharide (LPS)-induced cartilage damage. DESIGN: Articular cartilage was obtained from the metacarpophalangeal joints of 10 young adult horses. Following a stabilization period, weighed cartilage explants were exposed to IL-1beta (10 ng/ml) or LPS (50 microg/ml) to induce cartilage degradation. To test the potential protective effects of adenosine, these explants were simultaneously exposed to adenosine (100 microM), the adenosine kinase inhibitor 5'iodotubercidin (ITU, 1 microM) or to both adenosine and ITU. After 72 h in culture, conditioned medium was collected for evaluation of glycosaminoglycan (GAG), nitric oxide (NO), prostaglandin E2 (PGE2) and matrix metalloproteinase (MMP)-3 release. RESULTS: IL-1beta and LPS stimulated significant release of GAG, NO, PGE2 and MMP-3. Incubation with ITU significantly inhibited both IL-1beta- and LPS-induced GAG release, but did not alter MMP-3 production. Exposure to ITU also reduced IL-1beta-induced PGE2 release and LPS-induced NO production. Direct adenosine supplementation did not attenuate the effects of IL-1beta or LPS, and the addition of adenosine or ITU in the absence of IL-1beta or LPS did not have any detectable effect on cartilage metabolism in this model. CONCLUSIONS: The adenosine kinase inhibitor ITU attenuated experimentally induced cartilage damage in an in vitro cartilage explant model. Release of adenosine from chondrocytes may play a role in the cellular response to tissue damage in arthritic conditions and modulation of these pathways in the joint may have potential for treatment of arthropathies.     

腺苷A1受体激动剂预处理对保存心脏效果的影响

目的探讨腺苷A1受体激动剂预处理延迟效应对低温St.Thomas液保存大鼠心脏的影响及其与心肌ATP敏感性钾通道的关系。方法Wistar大鼠随机分6组,A、C、D组在缺血前24h以高选择性A1受体激动剂CCPA预处理,B、E注射生理盐水;而D、F组在缺血前应用ATP敏感性钾通道阻滞剂氯磺环己脲。然后A、B组4℃St.Thomas液保存4h,复灌1h,而另4组低温缺血3h,复灌1h。观测心功能、CKMB、ATP含量等。结果A组左室内压上升与下降最大速率恢复率(±dp/dtmax,%)为62.83±17.27,66.81±18.99,心肌ATP含量(10-3μmol/wet.g)3.67±1.42;而B组分别为40.41±18.29,44.70±25.14,1.46±0.54;A组都明显高于B组,差异都有统计学意义(P<0.01或P<0.05)。C组±dp/dtmax恢复率、ATP含量都明显高于D、E、F组(P<0.01或P<0.05),而D、E、F组间差异无统计学意义(P>0.05)。结论以腺苷A1受体激动剂可诱导预处理的延迟效应,改善低温St.Thomas液保存离体大鼠心脏的保存效果,而该效应与心肌ATP敏感性钾通道开放有关。     

超氧化物歧化酶介导腺苷延迟预处理的研究

目的 探讨以腺苷介导延迟预处理与锰-超氧化物歧化酶(Mn-SOD)的关系。方法大鼠随机分 6组,B组以腺苷 A1受体激动剂 CCPA预处理,24 h后制成离体心脏,低温缺血 3 h,复灌1h。观测心功能、SOD等。A组为缺血对照;C、E、F组在预处理前分别静注Mn-SOD反义、意义、错配寡核苷酸(ODN)。结果 B、C组左室压力上升最大速率恢复率(％)分别为 72.62±16.28,50.00±17.02、Mn-SOD活性(IU/mg.prot)分别为67.81±19.12,35.70±15.02,B组都高于C组,差异有显著性(P<0.05)。结论 Mn-SOD参与腺苷 A1受体介导的延迟预处理。     

The effect of antagonism of adenosine A1 receptor against ischemia and reperfusion injury of the liver

BACKGROUND: Adenosine is known to exert protective roles in hepatic ischemia and reperfusion injury, while all adenosine receptors do not play the cytoprotective roles. We have tested our hypothesis that blockage of adenosine binding to A(1) receptor by its antagonist, KW3902 [8-(noradamantan-3-yl)-1,3-dipropylxanthine] attenuates hepatic ischemia-reperfusion injury. METHODS: Adult female beagle dogs underwent a 2 h total hepatic vascular exclusion (THVE) with a venovenous bypass. Nontreated animals that underwent THVE with a venovenous bypass alone were used as the control (Group CT, n=6). KW3902 was given to the animals by continuous intraportal infusion for 60 min before ischemia at a dose of 1 microg/kg/min (Group KW, n=6). Two wk survival, hemodynamics, hepatic tissue blood flow (HTBF), liver function, energy metabolism, cAMP concentration, and histopathological findings were studied. RESULTS: Two wk animal survival was significantly improved in group KW compared with that in group CT (group CT: 16.7% versus group KW: 83.3%). HTBF, liver function, and hepatic adenine nucleotide concentration were remarkably better in group KW than group CT. In addition, cAMP concentration in group KW was maintained significantly higher than group CT. Histopathological examination revealed preservation of hepatic architecture and suppression of neutrophil infiltration into hepatic tissue in group KW. CONCLUSION: Administration of adenosine A(1) receptor antagonist before ischemia attenuates hepatic ischemia-reperfusion injury. To elicit the beneficial effect of adenosine against ischemia and reperfusion injury of the liver, it is important to oppose adenosine A1 receptor activation.