Nitric oxide‐sensitive guanylyl cyclase is the only nitric oxide receptor mediating platelet inhibition

See also Gordge MP. Nitric oxide: a one‐trick pony? This issue, pp 1340–2. Summary. Background: The nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling cascade is involved in the precise regulation of platelet responses. NO released from the endothelium is known to activate NO‐sensitive guanylyl cyclase (NO‐GC) in platelets. By the generation of cGMP and subsequent activation of cGMP‐dependent protein kinase (PKG), NO‐GC mediates the reduction of the intracellular calcium and inhibits platelet adhesion and aggregation. However, NO has been postulated to influence these platelet functions also via cGMP‐independent mechanisms. Objective: We studied the effect of NO on platelets lacking NO‐sensitive guanylyl cyclase with regards to aggregation, adhesion, calcium mobilization and bleeding time. Methods and results: Here, we show that NO signaling leading to inhibition of agonist‐induced platelet aggregation is totally abrogated in platelets from mice deficient in NO‐GC (GCKO). Even at millimolar concentrations none of the several different NO donors inhibited collagen‐induced aggregation of GCKO platelets. In addition, NO neither affected adenosine 5′‐diphosphate (ADP)‐induced adhesion nor thrombin‐induced calcium release in GCKO platelets. Although the NO‐induced cGMP signal transduction was totally abrogated cyclic adenosine monophosphate (cAMP) signaling was still functional; however, cGMP/cAMP crosstalk was disturbed on the level of phosphodiesterase type 3 (PDE3). These in vitro data are completed by a reduced bleeding time indicating the lack of NO effect in vivo. Conclusions: We conclude that NO‐GC is the only NO receptor in murine platelets mediating the inhibition of calcium release, adhesion and aggregation: lack of the enzyme leads to disturbance of primary hemostasis.     

Effect of nebivolol on blood oxygen transport indices and endothelial dysfunction in patients with arterial hypertension

Endothelial dysfunction, which is characterized by impairment of nitric oxide (NO) bioavailability, plays an important role in the development of arterial hypertension. The L‐arginine‐NO pathway is closely related to oxygen transport to tissue. Endothelial dysfunction in patients with arterial hypertension can affect haemoglobin‐oxygen affinity and tissue oxygen supply. Alterations in blood oxygen transport indices may play role in the pathogenesis of arterial hypertension. The aim of the present study was to investigate the effect of the beta‐selective adrenoblocker nebilet (nebivolol) on blood oxygen transport indices and on endothelial dysfunction in patients with arterial hypertension. The study population included 52 patients with grade II and grade III arterial hypertension. The results of our studies indicate that endothelial dysfunction in hypertensive patients significantly changes blood oxygen indices. The endothelium can be involved in formation of these impairments because only NO synthesized in sufficient amounts can maintain normal blood flow and oxygen transport to tissues. Endothelial dysfunction impairs formation of different haemoglobin NO‐derivatives, that influence not only on the release of NO at different sites of the vascular bed, but also on haemoglobin‐oxygen affinity, and accordingly, on optimal blood oxygenation in capillaries of pulmonary circulation and its deoxygenation in capillaries of systemic circulation. Treatment of hypertensive patients with nebivolol corrects the blood oxygen transport indices, stimulates NO production and improves endothelium‐dependent dilatation. Normalization of blood oxygen transport indices may regulate the activity of the L‐arginine‐NO pathway. Thus, nebivolol may improve efficiency of the treatment of hypertension.     

Exogenous nitric oxide regulates activity and synthesis of vascular endothelial nitric oxide synthase

Background Nitric oxide (NO) – a major signalling molecule of the vascular system – is constitutively produced in endothelial cells (EC) by the endothelial NO synthase (eNOS). Since a reduced NO synthesis is an early sign of endothelial dysfunction and NO delivering drugs are used to substitute the impaired endothelial NO production, we addressed the effect of exogenous NO on eNOS in human umbilical venous endothelial cell cultures. Materials and methods The synthetic NO donor DETA/NO (trade name, but in the following we refer to detNO), that releases NO in a strictly first order reaction with a half life of 20 h, was used in our experiments. Results Short‐term (20–30 min) detNO treatment of EC increases the Ser¹¹⁷⁷ phosphorylation of the constitutively expressed endothelial NOS and the production of endogenous NO generated by eNOS from [³H]arginine. The phosphorylation of eNOS is Akt‐dependent and completely reverted by the phosphatidylinositol‐3 kinase (PI‐3K) inhibitor LY294002. A prolonged continuous exposure of EC to detNO 150 µmol L^?1 over a period of 24–48 h causes a reversible cell cycle arrest at G₁‐phase associated with a larger cell volume and increased cell protein content (hypertrophic phenotype of EC). The eNOS protein and mRNA of the hypertrophic cells and the generation of endogenous NO are reduced but eNOS phosphorylation could still be elevated by stimulation with vascular endothelial growth factor. Conclusions Our data explain clinical studies describing a short‐term but not a long‐term benefit of NO treatment for patients with cardiovascular risk factors. The results could be a rational approach to develop a generation of NO donors accomplishing a retarded release from NO donors that mimic the low continuous pulsatile stress‐induced release of endogenous NO.     

Wound healing action of nitric oxide‐releasing self‐expandable collagen sponge

Mounting evidence showing that local nitric oxide (NO) delivery may significantly improve the wound healing process has stimulated the development of wound dressings capable of releasing NO topically. Herein, we describe the preparation of a self‐expandable NO‐releasing hydrolyzed collagen sponge (CS), charged with the endogenously found NO donor, S‐nitrosoglutathione (GSNO). We show that cold pressed and GSNO‐charged CS (CS/GSNO) undergo self‐expansion to its original 3D shape upon water absorption to a swelling degree of 2,300 wt%, triggering the release of free NO. Topical application of compressed CS/GSNO on wounds in an animal model showed that exudate absorption by CS/GSNO leads to the release of higher NO doses during the inflammatory phase and progressively lower NO doses at later stages of the healing process. Moreover, treated animals showed significant increase in the mRNA expression levels of monocyte chemoattractant protein‐1 (MCP‐1), murine macrophage marker (F4/80), transforming growth factor beta (TGF‐β), stromal cell‐derived factor 1 (SDF‐1), insulin‐like growth factor‐1 (IGF‐1), nitric oxide synthase(iNOS), and matrix metalloproteinase(MMP‐9). Cluster differentiation 31 (CD31), vascular endothelial growth factor (VEGF), and F4/80 were measured on Days 7 and 12 by immunohistochemistry in the cicatricial tissue. These results indicate that the topical delivery of NO enhances the migration and infiltration of leucocytes, macrophages, and keratinocytes to the wounded tissue, as well as the neovascularization and collagen deposition, which are correlated with an accelerated wound closure. Thus, self‐expandable CS/GSNO may represent a novel biocompatible and active wound dress for the topical delivery of NO on wounds.     

Delta2-Specific Opioid Receptor Agonist and Hibernating Woodchuck Plasma Fraction Provide Ischemic Neuroprotection

Objectives: The authors present evidence that the δ opioid receptor agonist Deltorphin‐D_variant (Delt‐D_var) and hibernating woodchuck plasma (HWP), but not summer‐active woodchuck plasma (SAWP), can provide significant neuroprotection from focal ischemia in mice by a mechanism that relies in part on reducing nitric oxide (NO) release in ischemic tissue. Methods: Cerebral ischemia was produced in wild‐type and NO synthase–deficient (NOS^–/–) mice by transient, 1‐hour middle cerebral artery occlusion (MCAO). Behavioral deficits were determined at 22 hours and infarct volume was assessed at 24 hours after MCAO. Mice were treated with saline or Delt‐D_var at 2.0 and 4.0 mg/kg, or 200 μL of HWP or SAWP. NOS^–/– mice were treated with either saline or Delt‐D_var at 4.0 mg/kg. NO release was determined using an N9 microglial cell line pretreated with δ‐ or μ‐specific opioids and HWP or SAWP prior to activation with lipopolysaccharide and interferon‐γ. Nitrate in the medium was measured as an indicator of NO production. Results: Infusion of Delt‐D_var or HWP (but not SAWP) decreased infarct volume and improved behavioral deficits following 1 hour of MCAO and 24 hours of reperfusion. In NOS^–/– mice, endothelial NOS^+/+ is required to provide Delt‐D_var–induced neuroprotection. Delt‐D_var and HWP dose‐dependently decreased NO release in cell culture, while SAWP and other δ‐ and μ‐specific opioids did not. Conclusions: Delt‐D_var and HWP, but not SAWP, are effective neuroprotectant agents in a mouse model of transient MCAO. In cell culture, the mechanism of this ischemic neuroprotection may rely in part on their ability to block NO release.     

Low‐intensity ultrasound increases endothelial cell nitric oxide synthase activity and nitric oxide synthesis

Summary. Low‐intensity ultrasound (US) increases tissue perfusion in ischemic muscle through a nitric oxide (NO)‐dependent mechanism. We have developed a model to expose endothelial cells to well‐characterized acoustic fields in vitro and investigate the physical and biological mechanisms involved. Human umbilical vein endothelial cells (HUVEC) or bovine aortic endothelial cells (BAEC) were grown in tissue culture plates suspended in a temperature‐controlled water bath and exposed to US. Exposure to 27 kHz continuous wave US at 0.25 W cm^?2 for 10 min increased HUVEC media NO by 102 ± 19% (P < 0.05) and BAEC by 117 ± 23% (P < 0.01). Endothelial cell NO synthase activity increased by 27 ± 24% in HUVEC and by 32 ± 16% in BAEC (P < 0.05 for each). The cell response was rapid with a significant increase in NO synthesis by 10 s and a maximum increase after exposure for 1 min. By 30 min post‐exposure NO synthesis declined to baseline, indicating that the response was transient. Unexpectedly, pulsing at a 10% duty cycle resulted in a 46% increase in NO synthesis over the response seen with continuous wave US, resulting in an increase of 147 ± 18%. Cells responded to very low intensity US, with a significant increase at 0.075 W cm^?2 (P < 0.01) and a maximum response at 0.125 W cm^?2. US caused minor reversible changes in cell morphology but did not alter proliferative capacity, indicating absence of injury. We conclude that exposure of endothelial cells to low‐intensity, low‐frequency US increases NO synthase activity and NO production, which could be used to induce vasodilatation experimentally or therapeutically.     

Nitric Oxide-based Possibilities for Pharmacotherapy

The goal of nitric oxide (NO) based pharmacotherapy is to reach proper homeostasis of NO metabolism in the target tissue where endogenous production of NO is either too weak or excessively increased. In addition to the classic NO-based therapy of cardiovascular conditions with nitrates, a variety of new therapeutic possibilities have emerged including sexual disorders, gastrointestinal system, immunology, tumour growth regulation and respiratory disorders. NO levels of target tissues can be affected directly by NO donors, or indirectly by increasing the level of L-arginine, a substrate of nitric oxide synthase (NOS). While increased production of NO by induceable NOS (iNOS) by, for example, cytokines does not at present seem therapeutically meaningful, increased NO production by constitutive NOS (cNOS) may be involved in the beneficial effects of ACE inhibitors or oestrogens. NO production may be pharmacologically decreased by inhibition of expression of iNOS by glucocorticoids while both cNOS and iNOS derived NO production is inhibited by administration of false substrates, for example L-NAME. Additionally, the respiratory system and related vessels can be reached directly and more selectively by inhalation of pure NO gas. Possible problems in administering NO and perhaps some NO-donors include the toxic nature of the compound itself whereby vital enzyme systems may be inhibited and tissue damaging radicals formed. Future prospects of NO-based pharmocotherapy may feature selective ligands to different NOS isoforms and tissue selective donors that release NO in a controlled fashion.     

氯胺酮对脑缺血诱导大鼠海马、皮层一氧化氮变化的影响

目的 :探讨一氧化氮在急性全脑缺氧缺血的病理作用机制。方法 :用硝酸还原酶特异性还原一氧化氮 (NO)产物的方法 ,测定大鼠前脑缺血模型中海马、皮层一氧化氮释放量的异常变化及离子通道拮抗剂氯胺酮对这些变化的影响。结果 :①急性脑缺血后海马、皮层胞内一氧化氮含量有不同程度的增高 ,呈先升后降的趋势。②预先腹腔注射氯胺酮 ,大鼠海马、皮层NO释放量明显低于对照组 ,5 0mg/kg的给药量差异显著 (P <0 0 5 )。结论 :一定量的离子通道拮抗剂氯胺酮能部分抑制缺血性中枢神经元一氧化氮的异常释放 ,且早期脑缺血诱生一氧化氮的异常升高很可能是脑组织对外界刺激的应激反应     

脊髓伤后脊髓组织中一氧化氮合酶活性变化与兴奋性氨基酸释放间的联系

目的探明脊髓伤后脊髓组织中一氧化氮合酶(NOS)活性变化与兴奋性氨基酸(EAA)释放间的关系.方法首先通过蛛网膜下腔注射谷氨酸(GLU)观测其对大鼠脊髓组织NOS活性动态变化的影响;然后通过微透析技术及高效液相色谱荧光法动态地探测不同NOS活性水平对伤段脊髓局部EAA含量变化的影响.结果外源性GLU迅速激活了脊髓组织NOS的活性,而抑制NOS活性则明显降低了伤段脊髓组织EAA的浓度.结论脊髓伤后脊髓组织中一氧化氮(NO)与EAA的释放相互促进,因而在继发性脊髓损伤中形成级联放大的神经毒性因子释放.     

Pharmacological mechanisms involved in the antinociceptive effects of dexmedetomidine in mice

Dexmedetomidine (DEX) is a α₂‐adrenoceptor (α₂‐AR) agonist used as an anesthetic adjuvant and as sedative in critical care settings. Typically, α₂‐AR agonists release nitric oxide (NO) and subsequently activate NO‐GMPc pathway and have been implicated with antinociception. In this study, we investigate the pharmacological mechanisms involved in the antinociceptive effects of DEX, using an acetic acid‐induced writhing assay in mice. Saline or DEX (1, 2, 5, or 10 μg/kg) was intravenously injected 5 min before ip administration of acetic acid and the resulting abdominal constrictions were then counted for 10 min. To investigate the possible mechanisms related to antinociceptive effect of DEX (10 μg/kg), the animals were also pretreated with one of the following drugs: 7‐nitroindazole (7‐NI; 30 mg/kg ip); 1H‐[1,2,4] oxadiazole [4,3‐a] quinoxaline‐1‐one (ODQ; 2.5 mg/kg, ip); yohimbine (YOH; 1 mg/kg, ip); atropine (ATRO; 2 mg/kg, ip); glibenclamide (GLIB; 1 mg/kg, i.p.) and naloxone (NAL; 0.2 mg/kg, ip). A rotarod and open‐field performance test were performed with DEX at 10 μg/kg dose. DEX demonstrated its potent antinociceptive effect in a dose‐dependent manner. The pretreatment with 7‐NI, ODQ, GLIB, ATRO, and YOH significantly reduced the antinociceptive affects of DEX. However, NAL showed no effecting DEX‐induced antinociception. The rotarod and open‐field tests confirmed there is no detectable sedation or even significant motor impairment with DEX at 10 μg/kg dose. Our results suggest that the α₂‐AR and NO‐GMPc pathways play important roles in the systemic antinociceptive effect of DEX in a murine model of inflammatory pain. Furthermore, the antinociceptive effect exerted by DEX appears to be dependent on K_ATP channels, independent of opioid receptor activity.     

COX-2 and iNOS are critical in advanced glycation end product-activated chondrocytes in vitro

Background The advanced glycation end products (AGEs) accumulate in joints of osteoarthritis patients. This study aimed to investigate the roles of cyclooxygenase‐2 (COX‐2) and inducible nitric oxide synthase (iNOS) pathways in AGE‐mediated cartilage damage. Materials and methods Methylglyoxal‐modified albumin was used as the source of AGE. Porcine and human chondrocytes were prepared from the joint cartilage of pigs and osteoarthritis patients. The activation of COX‐2, iNOS, nuclear factor‐kappaB (NF‐κB), activator protein‐1 (AP‐1) and protein kinases was determined by Western blotting, kinase assay, electrophoretic mobility shift assay (EMSA) or transfection assay. Prostaglandin E₂ (PGE₂) and NO concentrations were determined by enzyme‐linked immunosorbent assay (ELISA) and Griess reaction respectively. The enzymatic activity of COX was determined by measuring the conversion of arachidonic acid to PGE₂. The release of sulphated glycosaminoglycan and the intensity of Safranin O staining were used to measure cartilage degradation. Results AGE potently induced COX‐2‐PGE₂ and iNOS‐NO activation in porcine and human chondrocytes. Meanwhile, the upstream molecules regulating COX‐2/iNOS activation, such as AP‐1, NF‐κB, extracellular signal regulated protein kinase (ERK) and c‐jun N‐terminal kinase (JNK), were activated by AGE. Although AGE could not activate p38 directly, by measuring COX enzyme activity, the inhibition of p38 resulted in suppressing AGE‐induced conversion of arachidonic acid to PGE₂. Furthermore, successful blockage of either COX‐2 or NOS activity significantly reduced AGE‐mediated proteoglycan release and cartilage degradation. Conclusions This study highlights the significance of COX‐2 and iNOS pathways in AGE‐mediated OA pathogenesis and their potential as therapeutic targets that are beyond pain killing for OA treatment.     

Anticonvulsive effect of atorvastatin on pentylenetetrazole‐induced seizures in mice: the role of nitric oxide pathway

Atorvastatin has shown to possess neuroprotective, antiexcitotoxic, and antiepileptic effects besides its cholesterol‐lowering properties. Nitric oxide (NO) may be responsible for a group of these effects. In the present study, a model of clonic seizure induced by pentylenetetrazole (PTZ) in male NMRI mice was used to investigate the anticonvulsive effects of atorvastatin through NO‐dependent pathways. Atorvastatin (5 mg/kg) significantly increased the seizure threshold (P < 0.001). Moreover, L‐arginine (a precursor of NO) significantly (P < 0.01) potentiated the anticonvulsive effects of subeffective doses of atorvastatin (1 mg/kg). Finally, L‐NAME [L‐arginine methyl ester dihydrochloride], a nonspecific NO synthase inhibitor, completely abolished the anticonvulsive properties of atorvastatin. Our findings demonstrated the role of atorvastatin as an anticonvulsive agent and showed the effects to be mediated through NO‐related pathways.     

Nitric oxide and its relationship to thrombotic disorders

Summary.  Nitric oxide (NO) is released by the endothelium preventing platelet adhesion to the vessel wall. When released by platelets, NO inhibits further recruitment of platelets to a growing thrombus. Modulation of endogenous NO release may be a mechanism by which the thrombotic response can be regulated as suggested by several clinical diseases associated with impaired bioactive NO. Diseases including atrial fibrillation and coronary atherothrombotic disease have been associated with impaired NO release or decrease in NO bioavailability.     

Evaluation of endothelium‐dependent vasodilation in the human peripheral circulation

Flow‐mediated vasodilation (FMD) in the brachial artery measured by ultrasound, and the increase in forearm blood flow (FBF) induced by local infusion of a muscarinic‐receptor agonist have both frequently been used to evaluate endothelium‐dependent vasodilation (EDV) in the human forearm. The present study intended to evaluate the relationship between these techniques and to investigate if vasodilation induced by the muscarinic receptor‐agonist methacholine (MCh) was owing to production of nitric oxide (NO). FMD during hyperaemia was assessed by ultrasound and FBF was measured by venous occlusion plethysmography during local infusion of MCh or L ‐arginine in the human forearm. Both these methods were applied in 26 individuals. In another 12 individuals forearm arterial and venous plasma concentrations of nitrate/nitrite (NOx) were measured together with FBF before and during local MCh infusion.While the change in brachial artery diameter induced by sublingually given nitroglycerine and the vasodilatory response to sodium nitroprusside (SNP) given locally in the forearm were significantly correlated (r=0·70, P<0·01), FMD showed no relationship with the vasodilation evoked by MCh (r=–0·03) or L ‐arginine (r=0·04). The five‐fold increase in FBF during MCh infusion was associated with a significant increase in venous plasma NOx concentrations (P<0·05) and a more than 11‐fold increase in forearm NOx‐release (P<0·01). Thus, a significant relationship between the two methods regarding the evaluation of endothelium‐independent vasodilation evoked by NO‐donors was found, but no relationship was found between the two methods regarding the evaluation of endothelium‐dependent vasodilation. Furthermore, vasodilation induced by MCh in the forearm seems to be induced by NO‐release.     

SB-220453, a potential novel antimigraine agent, inhibits nitric oxide release following induction of cortical spreading depression in the anaesthetized cat

Profound nitric oxide release associated with cortical spreading depression (SD), has been implicated in stroke, traumatic brain injury and migraine pathophysiology. SB-220453 represents a mechanistically novel, well-tolerated class of compounds which may have therapeutic potential in the treatment of conditions associated with neuronal hyperexcitability and inflammation. The aim of the present study was to investigate the effects of SB-220453 on the nitric oxide (NO) release associated with SD in the anaesthetized cat. In vehicle treated animals, KCl application for 6 min to the cortical suface produced repeated changes in extracellular direct current field potential with associated NO release. This activity was sustained for a median duration of 55 min (25-75% range, 32-59 min) and 59 min (25-75% range, 34-59 min), respectively. SB-220453 (1, 3 and 10 mg/kg i.p.) produced a dose-related inhibition of this activity and at the highest dose tested, the median duration of changes in extracellular field potential and NO release were reduced to 4 min (25-75% range, 4-5 min) and 5 min (25-75% range, 5-5 min), respectively. No effect was observed on basal systemic haemodynamic parameters or resting cerebral laser Doppler blood flux at any of the doses of SB-220453 tested. SB-220453 therefore represents a novel compound to assess the potential benefit of inhibiting SD associated nitric oxide release in neurological disease.     

Nitric oxide in the human uterine cervix: endogenous ripening factor

The human uterine cervix can produce nitric oxide (NO), a free radical with an ultra-short half-life. The release of NO changes during pregnancy and is increased in early nonviable pregnancies compared to normal uncomplicated pregnancies. This review concentrates on the role of NO release in cervical ripening in pregnant women. Also some suggestions on future aspects are discussed.     

Pharmacological evidence of involvement of nitric oxide pathway in anti‐pruritic effects of sumatriptan in chloroquine‐induced scratching in mice

Chloroquine (CQ) induces histamine‐independent itch in human and mice. We recently reported the role of intradermal nitric oxide (NO)/cyclic guanosine monophosphate pathway in CQ‐evoked scratching in mice. Chloroquine stimulates neuronal nitric oxide synthase (nNOS) activity to over‐producing NO in the skin. Sumatriptan, a 5‐hydroxytryptamine 1b/1d receptors (5‐HTR1b/1d) agonist, is involved in pain and used to treat migraine and cluster headaches. According to previous studies, sumatriptan inhibits NOS activity. Thus, we aimed to investigate the effect of sumatriptan on CQ‐induced scratching. We used the rostral back model of itch. Chloroquine was injected intradermally into the rostral back of NMRI mice, and the scratching behavior was evaluated by measuring the number of bouts over 30 min. We evaluated the effect of sumatriptan and combination of sumatriptan and a non‐selective NO synthase inhibitor, L‐N‐nitro arginine methyl ester (L‐NAME), on the scratching behavior. Additionally, the changes of skin, hippocampus, and cortical nitrite level after different treatments were studied. Intraperitoneal and intradermal sumatriptan attenuates CQ‐induced itch which reversed by GR‐127935, the selective 5‐HTR1b and 5‐HTR1d antagonist. Co‐administration of subeffective doses of sumatriptan and L‐NAME significantly decreases the scratching behavior. Intradermal injection of CQ significantly increases the intradermal nitrite levels while it does not have any significant effects on hippocampal or cortical nitrite concentrations. Likewise, the effective doses of intraperitoneal and intradermal sumatriptan significantly reduce intradermal nitrite levels. We concluded that sumatriptan suppresses CQ‐induced itch most likely by activating 5‐HT1b/1d receptors. This effect probably mediates through NO pathway.     

芦荟多糖对体外培养人表皮细胞分泌细胞因子及一氧化氮的影响

目的研究芦荟多糖对体外培养人表皮细胞分泌细胞因子及一氧化氮(NO)的影响。方法测定经25、50、100、200和400mg/L,不同浓度芦荟多糖作用后的人表皮细胞培养上清液中转化生长因子-α(TGF-α)、TGF-β、白细胞介素-1β(IL-1β)、IL-6、IL-8、肿瘤坏死因子(TNF)及NO的水平;对照组则用等体积的细胞培养液处理。结果与对照组比较,经芦荟多糖作用后,培养液中TGF-α、TGF-β1、IL-1β、IL-6、IL-8和TNF水平呈不同程度升高,其差异有显著性(P<0.05或P<0.01);且随着芦荟多糖作用浓度的增加,其效应与剂量明显相关(P<0.01);而NO水平与对照组比较呈显著性下降(P<0.01),量-效关系明显(P<0.01)。结论芦荟多糖促进人表皮细胞分泌TGF-α、TGF-β1、IL-1β、IL-6、IL-8及TNF,而对NO释放则具有抑制作用。     

Enhanced nitric oxide release during cortical spreading depression following infusion of glyceryl trinitrate in the anaesthetized cat

Intravenous infusion of glyceryl trinitrate (GTN) into migraineurs induces an immediate headache followed by migraine. We studied the effect of GTN 10.25 g kg¹ min ¹) on local cerebrovascular laser Doppler flux (rCBF_LDF), artery diameter and NO concentration (selective NO microelectrode) in the pial middle cerebral artery perfusion territory of the anaesthetized cat, at rest and during cortical spreading depression (SD). GTN infusion induced a significant increase in pial artery diameter, rCBF_LDF, and NO concentration. Following termination of infusion, NO concentrations remained significantly elevated above controls for 60 min, other parameters returned to baseliae within 10 min ( p 0.05, ANOVA, post hoc Dunnett's multiple comparison procedure). Two hours after termination of infusion KCl-evoked SD was initiated. GTN-treated animals exhibited significantly ( p 0.05, Kruskal-Wallis) elevated SD-induced NO release compared to controls. All other parameters remained unaffected. Our results demonstrate that GTN induces a prolonged increase in local NO concentrations and enhances SD-induced NO release.     

Erythropoietin attenuates hypertrophy of neonatal rat cardiac myocytes induced by angiotensin‐II in vitro

Objective: Erythropoietin (EPO) is a haematopoietic hormone that has been confirmed as a novel cardioprotective agent. In this study, we test the hypothesis that EPO inhibits angiotensin‐II (Ang‐II)‐induced hypertrophy in cultured neonatal rat cardiomyocytes. Material and methods: Cultured neonatal rat cardiomyocytes were used to evaluate the effects of EPO on Ang‐II‐induced hypertrophy in vitro. The surface area and mRNA expression of atrial natriuretic (ANF) myocytes were employed to detect cardiac hypertrophy. A phosphatidylinositol 3′‐kinase (PI3K) inhibitor LY294002 and an endothelial nitric oxide synthase (eNOS) inhibitor l‐NAME were also employed to detect the underlying mechanism of EPO. Intracellular signal molecules, such as Akt (PKB), phosphorylated Akt, eNOS and transforming growth factor‐β1 (TGF‐β1) protein expression were determined by Western blot. Nitric oxide (NO) levels in the supernatant of cultured cardiomyocytes were assayed using an NO assay kit. Results: The results indicate that EPO significantly attenuates Ang‐II‐induced hypertrophy shown as inhibition of increases in cell surface area and ANF mRNA levels. NO production was also increased proportionally in the EPO‐treated group. EPO enhanced Akt activation and eNOS protein expression, whereas LY294002 or l‐NAME partially abolished the anti‐hypertrophic effect of EPO, accompanied by a decrease in Akt activation, eNOS protein expression and/or a reduction of NO production. EPO also down‐regulated the protein expression of TGF‐β1. Conclusion: We conclude that EPO attenuates cardiac hypertrophy via activation of the PI3K‐Akt‐eNOS‐NO pathway and the down‐regulation of TGF‐β1.