Intravenous pretreatment with magnolol protects myocardium against stunning

Magnolol, an antioxidant, has been reported to possess various protective effects on the cardiovascular system. However, its effect on myocardial stunning has not been elucidated. The purpose of this study was to investigate the antistunning effect of magnolol by evaluating the recovery of regional myocardial function after 10-minute coronary artery occlusion in anesthetized, open-chest rabbits. There was no significant hemodynamic change after intravenous infusion of magnolol. Systolic wall thickening fraction (WThF) measured with an epicardial Doppler sensor in animals pretreated with normal saline and vehicle solution remained significantly depressed (60 +/- 7% and 77 +/- 4% of baseline WThF, respectively) 3 hours after coronary artery reperfusion (CAR). Pretreatment with magnolol (10(-7) and 10(-6) g/kg, intravenous infusion) significantly enhanced the recovery of systolic wall thickening fraction (98 +/- 1 and 99 +/- 1% of baseline WThF, respectively) 60 minutes after CAR. This study demonstrated that intravenous pretreatment with magnolol protected myocardium against stunning.     

肢体缺血预处理对缺血/再灌注心肌保护作用及其机制

目的应用一氧化氮合酶(nitric oxide synthase,NOS)抑制剂及神经节阻滞剂,探讨非创伤性肢体缺血预处理对缺血/再灌注心肌保护作用的可能机制。方法Wistar大鼠64只,制备大鼠心肌缺血/再灌注的动物模型,随机分为4组,缺血/再灌注组(Ⅰ组),非创伤性肢体缺血预处理组(PL组),L-NAME+非创伤性肢体缺血预处理组(PL-N组),神经节阻滞剂六甲双胺+非创伤性肢体缺血预处理组(PL-H组)。实验结束,用TTC染色的方法测定大鼠心梗面积。每组另取8只大鼠,待实验结束后取缺血区心肌组织,测定NO、NOS及iNOS,应用反转录PCR技术,测定iNOS mRNA。结果PL组和PL-H组心肌梗死面积较Ⅰ组明显缩小(P<0.05),而PL-N组与Ⅰ组相比差异无显著性。PL组和PL-H组心肌组织NO含量较Ⅰ组明显升高,NOS、iNOS活性亦升高(P<0.05);PL-N组NO含量较I组略降低,但差异无统计学意义。PL组和PL-H组较I组心肌组织iNOS mRNA明显升高(P<0.05);而PL-N组iNOS mRNA表达较Ⅰ组无变化。结论内源性一氧化氮在肢体缺血预处理的早期心脏保护中起重要作用,而神经元途径在肢体缺血预处理的心肌保护中无明显作用。     

高效液相色谱法测定大鼠心肌中腺苷的含量

目的：建立高效液相色谱法测定大鼠心肌组织中腺苷的含量。方法 SD大鼠随机分为心肌缺血再灌注组（ IRI）、106 Treg细胞转输＋IRI组、107Treg细胞转输＋IRI 组和假手术对照组。色谱柱为 VP-ODS C18柱（250mm ×4.6mm,5μm）;流动相为甲醇：10mmol· L-1乙酸铵（10∶90）;流速为1.0mL· min -1;柱温25℃;检测波长260nm;进样量20μL。结果腺苷的标准液与峰面积均呈良好的线性关系（r＝1.000）,平均回收率分别为100.1％。日内和日间精密度分别在4.56％和4.84％以下。结论本法操作简便、准确、快速,可以用于测定大鼠心肌组织中腺苷的含量。     

Sodium tanshinone IIA sulfonate protects rat myocardium against ischemia-reperfusion injury via activation of PI3K/Akt/FOXO3A/Bim pathway

Aim： To investigate the mechanisms underlying the protective effects of sodium tanshinone IIA sulfonate （STS） in an ischemia- reperfusion （I/R）-induced rat myocardial injury model. Methods： Male SD rats were iv injected with STS, STS＋LY294002, or saline （NS） for 15 d. Then the hearts were subjected to 30 min of global ischemia followed by 2 h of reperfusion. Cardiac function, infarction size and area at risk were assessed. Cell apoptosis was evaluated with TUNEL staining, DNA laddering and measuring caspase-3 activity. In addition, isolated cardiomyocytes of neonatal rats were pretreated with the above drugs, then exposed to H202 （200 μmol/L） for I h. Cell apoptosis was detected using flow cytometric assay. The levels of p-Akt, p-FOXO3A and Bim were examined with immunoblotting. Results： Compared to NS group, administration of STS （20 mg/kg） significantly reduced myocardial infarct size （40.28%＋5.36% in STS group vs 59.52%±7.28% in NS group）, and improved the myocardial function as demonstrated by the increased values of dp/dt LVDP and coronary flow at different reperfusion time stages. Furthermore, STS significantly decreased the rate of apoptotic cells （15.11%±3.71% in STS group vs 38.21%±7.83% in NS group）, and reduced caspase-3 activity to nearly a quarter of that in NS group. Moreover, STS significantly increased the phosphorylation of Akt and its downstream target FOXO3A, and decreased the expression of pro-apoptotic gene Bim. Co-treatment with the PI3K inhibitor LY294002 （40 mg/kg） partially countered the protective effects induced by STS treatment. In isolated cardiomyocytes, STS exerted similar protective effects as shown in the ex vivo I/R model. Conclusion： STS pretreatment reduces infarct size and improves cardiac function in an I/R-induced rat myocardial injury model via activation of Akt/FOXO3A/Bim-mediated signal pathway.     

Demonstration of Ri-type adenosine receptors in bovine myocardium by radioligand binding

Summary Adenosine has been shown to have negative inotropic, chronotropic and dromotropic effects on the heart. The pharmacological profiles of these effects suggest that they are mediated via R_i (A₁) adenosine receptors, but a direct demonstration of these receptors is still missing. In the present study we report direct labelling of these receptors with (-)N⁶-[¹²⁵I]-p-hydroxyphenylisopropyladenosine ([¹²⁵I]HPIA). The radioligand bound in a saturable and reversible manner to a crude membrane preparation, the B _max-value was 30.5 fmol/mg protein and the K _D-value 1.1 nmol/l. A similar affinity of the ligand was obtained in kinetic and competition experiments. Competition experiments with a variety of adenosine analogues gave a pharmacological profile characteristic of R_i adenosine receptors with high affinities of N⁶-substituted derivatives and a marked stereospecificity for N⁶-phenylisopropyladenosine (PIA). Purification of the membrane preparation by density gradient centrifugation resulted in a 30-fold increase in the number of binding sites which was paralleled by a similar increase in the number of binding sites for [³H]ouabain. Guanine nucleotides decreased binding of [¹²⁵I]HPIA in a dose-dependent manner, but the IC₅₀-values were considerably higher than those reported in other tissues. Finally, binding of [¹²⁵I]HPIA appeared to be entropy-driven which has been shown to be characteristic of agonist binding to R_i adenosine receptors. These results suggest the presence of R_i adenosine receptors in ventricular myocardium which may be responsible for the mediation of the effects of adenosine and its analogues.Abbreviations [¹²⁵I]HPIA (-)N⁶-[¹²⁵I]-p-hydroxyphenylisopropyladenosine - (-)IHPIA (-)N⁶-iodo-p-hydroxyphenylisopropyladenosine - (+)/(-)PIA (+)/(-)N⁶-phenylisopropyladenosine - CHA N⁶-cyclohexyladenosine - NECA 5-N-ethylcarboxamidoadenosine - App(NH)p 5-adenylylimidodiphosphate - Gpp(NH)p 5-guanylylimidodiphosphate     

Dexmedetomidine protects mice against myocardium ischaemic/reperfusion injury by activating an AMPK/PI3K/Akt/eNOS pathway

Acute myocardial ischaemia/reperfusion (MIR) injury leads to severe arrhythmias and has a high rate of lethality. In the present study, we aim to determine the effect of dexmedetomidine (Dex) on heart injury parameters following MIR surgery. We examined the effects of Dex on heart function parameters and infarct size following MIR surgery. Proinflammatory cytokines, oxidative products and anti‐oxidative enzymes in the myocardium were measured to evaluate the anti‐inflammatory and anti‐oxidative effects of Dex. The role of the adenosine 5′‐monophosphate (AMP)‐activated protein kinase (AMPK)/phosphatidylino‐sitol 3‐kinase (PI3k)/Akt/endothelial nitric oxide synthase (eNOS) pathway was investigated using their inhibitors. The alteration of haemodynamic parameters, histopathological results, and infarct size caused by MIR was attenuated by Dex. The interleukine‐1 beta (IL‐1β), IL‐6, tumour necrosis factor‐a (TNF‐α) and myeloperoxidase (MPO) were all significantly decreased. Anti‐oxidative enzymes superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) were restored by Dex. Oxidative products8‐OHdG, MDA and protein carbonyl were all decreased by Dex (P<.05). Dex activated AMPK expression, eNOS and Akt phosphorylation. The influence of Dex on cardiac function was reversed by the inhibitors of the eNOS, AMPK and PI3K/Akt pathways. These results indicate that Dex protected the cardiac functional, histological changes, inflammation and oxidative stress induced by MIR. Our results present a novel signalling mechanism that Dex protects MIR injury by activating an AMPK/PI3K/Akt/eNOS pathway.     

Cochlear activation at low sound intensities by a fluid pathway

In order to assess the mechanisms responsible for cochlear activation at low sound intensities, a semi-circular canal was fenestrated in fat sand rats, and in other experiments a hole was made in the bone over the scala vestibuli of the first turn of the guinea-pig cochlea. Such holes, which expose the cochlear fluids to air, provide a sound pathway out of the cochlea which is of lower impedance than that through the round window. This should attenuate the pressure difference across the cochlear partition and thereby reduce the driving force for the base-to-apex traveling wave along the basilar membrane. The thresholds of the auditory nerve brainstem evoked responses (ABR) and of the cochlear microphonic potentials were not affected in the fenestration experiments. In addition, holes in the scala vestibuli of the first turn did not cause ABR threshold elevations. These results contribute further evidence that at low sound intensities the outer hair cells are probably not activated by a base-to-apex traveling wave along the basilar membrane. Instead it is possible that they are excited directly by the alternating condensation/rarefaction fluid pressures induced by the vibrations of the stapes footplate. The activated outer hair cells would then cause the localized basilar membrane movement.     

Prevention of ischemic brain injury by adenosine receptor activation

The abilities of the xanthine oxidase inhibitor, oxypurinol, and the adenosine deaminase inhibitor, deoxycoformycin, to alleviate cerebral ischemic damage were evaluated in gerbil and rat models. Cerebral ischaemia of 5 min duration was induced in unanesthetized Mongolian gerbils by bilateral occlusion of the carotid arteries. Cerebral damage was assessed behaviorally by the elevation of motor activity and by histological assesment of neuronal degeneration in the CA1 area of the hippocampus. Oxypurinol (40 mg/kg) administered either prior to or 30 min after and ischaemic episode significantly reduced both the hypermotility and hippocampal damage observed in saline-treated control ischemic gerbils. Deoxycoformycin (500 μg/kg) was effective only when administered prior to ischemia. Rats with a focal ischaemic lesion (unilateral occlusion of a middle cerebral artery combined with tandem occlusion of the ipsilateral common carotid artery) were used to model strokes. The degree of ischaemic damage was evaluated by measuring the contralateral neurological deficits at 24 and 48 h post infarction and by calculating the volume of infarcted tissue after brain slices had been stained with 2,3,5-triphenyl, 2H-tetrazolium chloride (TTC) solution. Oxypurinol (40 mg/kg) administered 30 min prior to or 1h after the onset of focal ischaemia significantly reduced the infarct size, brain swelling, and neurological deficits. Deoxycoformycin (500 μg/kg) was effective only when administered preischemia. These findings suggest that oxypurinol and deoxycoformycin may be useful for the prevention and treatment of ischaemic brain injuries. © 1993 Wiley-Liss, Inc.     

经静脉注射腺苷终止阵发性室上性心动过速

目的 :评估经静脉注射腺苷终止室上性心动过速 (室上速 )发作的疗效及安全性。方法 :有阵发性心动过速病史且体表心电图提示室上速的病人2 2例 ,经静脉序贯冲击给药 ,依次予腺苷 3,6 ,12 ,18mg ,直至室上速终止。所有病例在完成研究后 1wk内进行心内电生理检查 ,排除 2例非阵发性室上速的病人。结果 :腺苷递增给药 3,6 ,12 ,18mg中 ,累积成功率分别达 2 5 % ,6 5 % ,85 % ,95 %。副作用发生率累计达 30 % ,多不严重 ,为一过性 ,在停止给药后 2min内消失。结论 :腺苷经静脉序贯冲击给药可快速有效地终止阵发性室上速。该药重复性好。副作用常见 ,但多为一过性可耐受     

Cornel iridoid glycoside protects against white matter lesions induced by cerebral ischemia via activation of neuregulin-1 pathway in rats

Ischemic stroke often elicits profound white matter lesions, which results in poor neurological outcomes and impairing the recovery in post-stroke. However, few studies have focused on white matter lesions caused by cerebral ischemia. The present study was aimed to investigate the effects of cornel iridoid glycoside(CIG), a main active component extracted from Cornus officinalis, on the white matter injury induced by ischemic stroke. CIG(60 and 120 mg·kg~(-1)) were administered intragastrically 6 h after middle cerebral artery occlusion reperfusion(MCAO) surgery once a day for 7 d. A series of behavioral tests were carried out to evaluate the neurological function of MCAO rats. White matter structure was detected by luxol fast blue staining and transmission electron microscopy. Immunohistochemical staining was used to assess myelin loss, oligodendrocytes maturation and glial activation. Results showed that CIG remarkably decreased neurological deficit score, accelerated the recovery of somatosensory and motor functions, and ameliorated the memory deficit in MCAO rats. CIG alleviated white matter lesions and demyelination, increased myelin basic protein expression and the number of mature oligodendrocytes in the corpus callosum of MCAO rats. Besides, CIG inhibited the activation of microglia and astrocytes. Further data obtained by western blot analysis indicated that CIG increased the expression of brain-derived neurotrophic factor(BDNF)/p-Trk B, neuregulin-1/Erb B, and PI3 K p110α/p-Akt/p-m TOR in the corpus callosum of MCAO rats. Our findings demonstrated that CIG protected against white matter lesions induced by cerebral ischemia and the mechanisms were partially contributed to increasing BDNF and activating neuregulin-1/Erb B signaling and its downstream PI3 K/Akt/m TOR pathway in white matter.     

The administration of alpha-melanocyte-stimulating hormone protects the ischemic/reperfused myocardium

The contribution of alpha-melanocyte-stimulating hormone (alpha-MSH) treatment, an active fragment of adrenocorticotropic hormone (ACTH), to the recovery of postischemic cardiac function, infarct size, the incidence of reperfusion-induced ventricular fibrillation and apoptotic cell death was studied in ischemic/reperfused isolated rat hearts. Rats were subcutaneously injected with 40, 200 and 400 microg/kg of alpha-MSH, and 12 h later, hearts were isolated, perfused and subjected to 30 min of ischemia followed by 120 min of reperfusion. Thus, after 120 min of reperfusion, with the concentration of 200 microg/kg alpha-MSH, coronary flow, aortic flow and left ventricular developed pressure were significantly improved from their control values of 14.6+/-0.6 ml/min, 7.5+/-0.5 ml/min and 9.1+/-0.4 kPa to 20.2+/-0.4 ml/min (p<0.05), 31.5+/-0.9 ml/min (p<0.05) and 15.9+/-0.6 (p<0.05) kPa, respectively. With the doses of 40, 200 and 400 microg/kg of alpha-MSH, infarct size was reduced from its control value of 38+/-5% to 33+/-6% (NS), 17+/-3% (p<0.05) and 19+/-4% (p<0.05), respectively. The reduction in the incidence of reperfusion-induced ventricular fibrillation followed the same pattern. It is reasonable to assume that a reduction in infarct size, in the alpha-MSH-treated myocardium, resulted in a reduction as well in apoptotic cell death. Although we did not specifically study the exact mechanism(s) of alpha-MSH-afforded postischemic protection, we assume that this protection may be related to alpha-MSH-induced corticosterone release and corticosterone-induced de novo protein synthesis, which reflected in the recovery of postischemic cardiac function in isolated hearts. Thus, interventions that are able to increase plasma corticosterone or glucocorticoid release may prevent the development of ischemia/reperfusion-induced damage.     

Salidroside protects PC12 cells from MPP-induced apoptosis via activation of the PI3K/Akt pathway

Oxidative stress plays an important role in the pathogenesis of Parkinson’s disease (PD). Salidroside (SAL), a phenylpropanoid glycoside isolated from Rhodiola rosea L., can exert potent antioxidant properties. In this study, we investigated the protective effects, and the possible mechanism of action, of SAL against 1-methyl-4-phenylpyridinium (MPP⁺)-induced cell damage in rat adrenal pheochromocytoma PC12 cells. Pretreatment of PC12 cells with SAL significantly reduced the ability of MPP⁺ to induce apoptosis in a dose and time-dependent manner. SAL significantly and dose-dependently inhibited MPP⁺-induced chromatin condensation and MPP⁺-induced release of lactate dehydrogenase by PC12 cells. SAL enhanced Akt phosphorylation in PC12 cells, and the protective effects of SAL against MPP⁺-induced apoptosis were abolished by LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K) phosphorylation. These findings suggest that SAL prevents MPP⁺-induced apoptosis in PC12 cells, at least in part through activation of the PI3K/Akt pathway.     

Erythropoietin protects the human myocardium against hypoxia/reoxygenation injury via phosphatidylinositol-3 kinase and ERK1/2 activation

BACKGROUND AND PURPOSES: Erythropoietin (EPO) has been shown to protect against myocardial infarction in animal studies by activating phosphatidylinositol-3 kinase (PI3K)/Akt and ERK1/2. However these pro-survival pathways are impaired in the diabetic heart. We investigated the ability of EPO to protect human atrial trabeculae from non-diabetic and diabetic patients undergoing coronary artery bypass surgery, against hypoxia-reoxygenation injury. EXPERIMENTAL APPROACH: Human atrial trabeculae were exposed to 90min hypoxia and 120min reoxygenation. EPO was administered throughout reoxygenation. The developed force of contraction, calculated as a percentage of baseline force of contraction, was continuously monitored. The involvement of PI3K and ERK1/2 and the levels of activated caspase 3(AC3) were assessed. KEY RESULTS: EPO improved the force of contraction in tissue from non-diabetic patients (46.7+/-1.7% vs. 30.2+/-2.2% in control, p<0.001). These beneficial effects were prevented by the PI3K inhibitor, LY294002 and the ERK1/2 inhibitor, U0126. EPO also significantly improved the force of contraction in the diabetic tissue, although to a lesser degree. The levels of activated caspase 3 were significantly reduced in EPO treated trabeculae from both non-diabetic and diabetic patients, relative to their respective untreated controls. CONCLUSIONS AND IMPLICATIONS: EPO administered at reoxygenation protected human myocardial muscle by activating PI3K and ERK1/2 and reducing the level of activated caspase 3. This cardioprotection was also observed in the diabetic group. This data supports the potential of EPO being used as a novel cardioprotective strategy either alone or as an adjunct in the clinical setting alongside existing reperfusion therapies.     

Sevoflurane post-conditioning protects isolated rat hearts against ischemia-reperfusion injury via activation of the ERK1/2 pathway

Aim:

To investigate the role of extracellular signal-regulated kinases (ERKs) in sevoflurane post-conditioning induced cardioprotection in vitro.

Methods:

Isolated rat hearts were subjected to 30 min ischemia followed by 120 min reperfusion (I/R). Sevoflurane post-conditioning was carried out by administration of O₂-enriched gas mixture with 3% sevoflurane (SEVO) for 15 min from the onset of reperfusion. Cardiac functions, myocardial infarct size, myocardial ATP and NAD⁺ contents, mitochondrial ultrastructure, and anti-apototic and anti-oncosis protein levels were measured.

Results:

Sevoflurane post-conditioning significantly improved the heart function, decreased infarct size and mitochondria damage, and increased myocardial ATP and NAD⁺ content in the I/R hearts. Furthermore, sevoflurane post-conditioning significantly increased the levels of p-ERK and p-p70S6K, decreased the levels of porimin, caspase-8, cleaved caspase-3, and cytosolic cytochrome c in the I/R hearts. Co-administration of the ERK1/2 inhibitor PD98059 (20 μmol/L) abolished the sevoflurane-induced protective effects against myocardial I/R.

Conclusion:

Sevoflurane post-conditioning protects isolated rat hearts against myocardial I/R injury and inhibits cell oncosis and apoptosis via activation of the ERK1/2 pathway.     

Stimulation of nucleoside efflux and inhibition of adenosine kinase by A1 adenosine receptor activation

Adenosine is produced intracellularly during conditions of metabolic stress and is an endogenous agonist for four subtypes of G-protein linked receptors. Nucleoside transporters are membrane-bound carrier proteins that transfer adenosine, and other nucleosides, across biological membranes. We investigated whether adenosine receptor activation could modulate transporter-mediated adenosine efflux from metabolically stressed cells. DDT1 MF-2 smooth muscle cells were incubated with 10 microM [3H]adenine to label adenine nucleotide pools. Metabolic stress with the glycolytic inhibitor iodoacetic acid (1AA, 5 mM) increased tritium release by 63% (P < 0.01), relative to cells treated with buffer alone. The IAA-induced increase was blocked by the nucleoside transport inhibitor nitrobenzylthioinosine (1 microM), indicating that the increased tritium release was primarily a purine nucleoside. HPLC verified this to be [3H]adenosine. The adenosine A1 receptor selective agonist N6-cyclohexyladenosine (CHA, 300 nM) increased the release of [3H]purine nucleoside induced by IAA treatment by 39% (P < 0.05). This increase was blocked by the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (10 microM). Treatment of cells with UTP (100 microM), histamine (100 microM), or phorbol-12-myristate-13-acetate (PMA, 10 microM) also increased [3H]purine nucleoside release. The protein kinase C inhibitor chelerythrine chloride (500 nM) inhibited the increase in [3H]purine nucleoside efflux induced by CHA or PMA treatment. The adenosine kinase activity of cells treated with CHA or PMA was found to be decreased significantly compared with buffer-treated cells. These data indicated that adenosine A1 receptor activation increased nucleoside efflux from metabolically stressed DDT1 MF-2 cells by a PKC-dependent inhibition of adenosine kinase activity.     

桃叶珊瑚苷通过激活ERβ途径抑制心肌细胞凋亡

目的探讨桃叶珊瑚苷(aucubin,AU)抑制心肌细胞凋亡发挥抗心肌缺血损伤从而改善急性心肌梗死后心功能的作用与可能机制。方法采用冠状动脉左前降支结扎法制作小鼠急性心肌缺血(myocardial infarction,MI)模型。采用超声心动、Masson染色检测小鼠心功能及梗死面积。建立肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)/放线菌酮(cycloheximide,CHX)诱导的大鼠H9c2心肌细胞损伤模型。采用IncuCyte活细胞成像、TUNEL、Western blot等方法探讨了AU的抗心肌细胞损伤作用及其作用机制。结果研究结果表明,AU可以改善心肌梗死小鼠的心功能,降低梗死面积,减少由TNF-α/CHX诱导的心肌细胞凋亡,降低caspase-3蛋白质表达,上调Bcl2/Bax比值;同时AU可使ERβ(estrogen receptorβ,ERβ)表达升高,且雌激素受体β抑制剂可阻断AU的抗凋亡作用。结论该研究证实,AU可以通过抑制心肌细胞凋亡发挥抗心肌缺血损伤从而改善急性心肌梗死后心功能的作用,其部分作用机制与ERβ通路的激活有关。     

Oxyresveratrol protects human lens epithelial cells against hydrogen peroxide-induced oxidative stress and apoptosis by activation of Akt/HO-1 pathway

Oxidative stress induced by hydrogen peroxide (H₂O₂) triggers human lens epithelial cell (HLEC) apoptosis and initiates cataract formation. Oxyresveratrol (Oxy) was reported to possess antioxidant and free radical scavenging activities. Herein, we investigated the effects of Oxy on H₂O₂-induced oxidative stress and apoptosis in HLECs and the associated mechanisms. Cell viability was detected by MTT assay. The oxidative damage was assessed by measuring the activities of superoxide dismutases-1 (SOD-1), catalase (CAT), glutathione reductase (GSH), and malondialdehyde (MDA). Apoptosis was analyzed by flow cytometry analysis. The changed expressions of heme oxygenase-1 (HO-1) and protein kinase B (Akt) pathways were evaluated by qRT-PCR and western blot. We found that exposure to H₂O₂ dose-dependently reduced cell viability, and induced oxidative stress and apoptosis in HLECs, which were reversed by pretreatment with Oxy. Oxy increased p-Akt and HO-1 expressions in H₂O₂-stimulated HLECs. Akt and HO-1 expressions form a regulatory axis and Oxy activated the Akt/HO-1 pathway in H₂O₂-stimulated HLECs. Inhibition of the Akt/HO-1 pathway by LY294002 or ZnPP attenuated the effects of Oxy on oxidative stress and apoptosis in H₂O₂-stimulated HLECs. In conclusion, Oxy protected H₂O₂-induced oxidative stress and apoptosis through activating the Akt/HO-1 pathway, suggesting the protective effect of Oxy against H₂O₂-induced cataract.     

Enhancement of long-term potentiation by brain-derived neurotrophic factor requires adenosine A2A receptor activation by endogenous adenosine

The excitatory action of brain-derived neurotrophic factor (BDNF) on synaptic transmission is triggered by adenosine A2A receptor activation. Since high-frequency neuronal firing, such as that inducing long-term potentiation (LTP), favours both A2A receptor activation and BDNF effects on transmission, we now evaluated the influence of adenosine on the facilitatory action of BDNF upon CA1 hippocampal LTP. theta-Burst stimulation of the pyramidal inputs induced a significant and persistent increase in field EPSP slopes, and this potentiation was augmented in the presence of BDNF (20 ng/ml), an action prevented by the inhibitor of Trk receptor autophosphorylation, K252a (200 nM). Removal of endogenous extracellular adenosine with adenosine deaminase (ADA, 1 U/ml), as well as the antagonism of adenosine A2A receptors with SCH58261 (100 nM), prevented the excitatory action of BDNF upon LTP. In an adenosine depleted background (with ADA), activation of adenosine A2A receptors (with 10nM CGS21680) restored the facilitatory effect of BDNF on LTP; this was fully prevented by the protein kinase A inhibitor, H-89 (1 microM) and mimicked by the adenylate cyclase activator, forskolin (10 microM). In similar experiments, activation of adenosine inhibitory A1 receptors (with 5 nM CPA) did not affect the facilitatory effect of BDNF. In conclusion, the facilitatory action of BDNF upon hippocampal LTP is critically dependent on the presence of extracellular adenosine and A2A receptor activation through a cAMP/PKA-dependent mechanism. Since extracellular adenosine accumulates upon high-frequency neuronal firing, the present results reveal a key process to allow the influence of BDNF upon synaptic plasticity.     

Biochanin A protects lipopolysaccharide/D-galactosamine-induced acute liver injury in mice by activating the Nrf2 pathway and inhibiting NLRP3 inflammasome activation

Biochanin A, an isoflavone existed in red clover and peanuts, has been reported to possess a wide spectrum of pharmacological activities, such as anti-inflammatory and antioxidant effects. However, the protective effects and mechanism of biochanin A on liver injury have not been reported. In this study, acute liver injury was induced by intraperitoneal injection of lipopolysaccharide (LPS) and d-galactosamine (D-GalN). Biochanin A was administrated 1 h prior to LPS/D-GalN challenge. Serum ALT, AST, IL-1β, and TNF-α levels, hepatic malondialdehyde (MDA), GPx, SOD, and Catalase contents, tissue histology, IL-1β, TNF-α, NLRP3, and Nrf2 expression were detected. The results showed that serum ALT, AST, IL-1β, and TNF-α levels and hepatic MDA content increased after LPS/GalN treatment. These changes were attenuated by biochanin A. Meanwhile, biochanin A dose-dependently up-regulated the expression of Nrf2 and HO-1. Biochanin A also inhibited hepatic IL-1β and TNF-α expression in a dose-dependent manner. Biochanin A did not inhibit LPS/D-GalN-induced hepatic NLRP3, ASC, and caspase-1 expression. However, the interaction of NLRP3 with ASC and caspase-1 were inhibited by biochanin A. In addition, LPS/D-GalN-induced up-regulation of thioredoxin-interacting protein (TXNIP) and interaction between TXNIP and NLRP3 were also inhibited by biochanin A. In conclusion, biochanin A protected against LPS/GalN-induced liver injury by activating the Nrf2 pathway and inhibiting NLRP3 inflammasome activation.     

Taurine protects against low-density lipoprotein-induced endothelial dysfunction by the DDAH/ADMA pathway

Asymmetric dimethylarginine (ADMA), a major endogenous nitric oxide (NO) synthase inhibitor, is thought to be a key contributor for endothelial dysfunction. Decrease in activity of dimethylarginine dimethylaminohydrolase (DDAH), a major hydrolase of ADMA, causes accumulation of ADMA in some risk factors of atherosclerosis, including hypercholesterolemia. Taurine is a semi-essential amino acid that has previously been shown to have endothelial protective effects. The present study was to test whether the protective effect of taurine on endothelial function is related to modulation of the DDAH/ADMA pathway. A single injection of native LDL (4 mg/kg, i.v.) markedly reduced endothelium-dependent vasorelaxation and the plasma level of NO, and increased plasma concentrations of ADMA, malondialdehyde (MDA) and tumor necrosis factor-alpha (TNF-alpha). Treatment with taurine in vivo (60 or 180 mg/kg) significantly attenuated the inhibition of endothelium-dependent vasorelaxation and the reduced level of NO, and decreased the elevated levels of ADMA, MDA, and TNF-alpha. Incubation human umbilical vein endothelial cells (HUVECs) with ox-LDL (100 microg/ml) for 24 h markedly increased the medium levels of lactate dehydrogenase (LDH), ADMA, TNF-alpha and MDA, and decreased the level of NO in the medium and the intracellular activity of DDAH. Taurine (1 or 5 microg/ml) significantly attenuated the increases in the levels of LDH, ADMA, TNF-alpha and MDA, and the decrease in the level of NO and the activity of DDAH induced by ox-LDL in HUVECs. The present results suggested that taurine protected against endothelial dysfunction induced by native LDL in vivo or by ox-LDL in endothelial cells, and the protective effect of taurine on the endothelium is related to decrease in ADMA level by increasing of DDAH activity.