Protective effect of ligustrazine against myocardial ischaemia reperfusion in rats: the role of endothelial nitric oxide synthase

1. The aim of the present study was to determine whether ligustrazine (2,3,5,6-tetramethylpyrazine; TMP) exerts a cardioprotective effect during myocardial ischaemia reperfusion (IR), and to investigate the underlying mechanisms and the role of endothelial nitric oxide synthase (eNOS) in cardioprotection. 2. Sprague-Dawley rats were divided into a sham group and five IR groups: IR control, TMP pretreated, TMP + wortmannin (a phosphatidylinositol 3-kinase (PI3K) inhibitor), N(G) -nitro-L-arginine methyl ester (L-NAME; a NOS inhibitor) and TMP + L-NAME. IR was produced by 35 min of regional ischaemia followed by 120 min of reperfusion. Myocardial infarct size, oxidative stress, myocardial apoptosis, nitric oxide (NO) production, and expression of phosphorylated protein kinase B (Akt) and eNOS were measured. 3. TMP markedly decreased infarct size and attenuated myocardial apoptosis, as evidenced by a decrease in the apoptotic index and reduced caspase-3 activity. TMP treatment caused a marked increase in NO production. Cotreatment with wortmannin or L-NAME completely blocked the TMP-induced NO increase. TMP induced phosphorylation of Akt at Ser 473 (1.61 ± 0.18 vs 0.79 ± 0.10 in the IR control group) and phosphorylation of eNOS at Ser1177 (1.87 ± 0.33 vs 0.94 ± 0.22 in the IR control group). Wortmannin abrogated the phosphorylation of Akt and eNOS induced by TMP. 4. These data suggest that ligustrazine has anti-apoptotic and cardioprotective effects against myocardial IR injury and that it acts through the PI3K/Akt pathway. In addition, the phosphorylation of eNOS with subsequent NO production was found to be an important downstream effector that contributes significantly to the cardioprotective effect of TMP.     

Hydroxysafflor yellow A reduces myocardial infarction size after coronary artery ligation in rats

This study was undertaken to determine the cardioprotective effect of hydroxysafflor yellow A (HSYA), at doses of 2, 4 or 8?mg/kg, extracted from the flower of the safflower plant, Carthamus tinctorius L. (Asteraceae), on acute myocardial ischemia induced by left anterior descending coronary artery (LAD) ligation in rats. The myocardial infarction size (MIS), creatine kinase (CK-MB) activity, endothelial nitric oxide synthase (eNOS) activity, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and nitric oxide (NO) content were measured. The results showed that administration with hydroxysafflor yellow A at doses of 4 or 8?mg/kg resulted in a reduction in myocardial infarction size. Hydroxysafflor yellow A (4 or 8?mg/kg) inhibited not only the elevation of creatine kinase activity and malondialdehyde content but also the reduction of superoxide dismutase activity, endothelial nitric oxide synthase activity and nitric oxide content. The findings suggested that hydroxysafflor yellow A (4 or 8?mg/kg) exerted cardioprotective effects against acute myocardial ischemic injury by regulating superoxide dismutase activity and endothelial nitric oxide synthase activity.     

Coconut kernel protein in diet protects the heart by beneficially modulating endothelial nitric oxide synthase,tumor necrosis factor-alpha,and nuclear factor-kappaB expressions in experimental myocardial infarction

Previous studies conducted in our laboratory revealed that coconut kernel protein has a significant cardioprotective effect on isoproterenol-induced myocardial infarction in rats. In the present study, we explored the possible protective mechanism of coconut kernel protein during acute myocardial infarction. Coconut kernel protein (50 mg/100 g) was administered to Sprague-Dawley rats orally for 45 days. Isoproterenol (20 mg/100 g) was injected subcutaneously at an interval of 24 hours twice to induce myocardial infarction. Myocardial infarction was confirmed by the abnormal activities of cardiac marker enzymes in serum. Activities of antioxidant enzymes such as superoxide dismutase (SOD) and catalase were decreased (p < 0.05) in the heart of isoproterenol-treated rats, whereas pretreatment with coconut kernel protein increased (p < 0.05) these activities. An improved antioxidant status in these rats was further confirmed by the increased level of reduced glutathione and decreased level of lipid peroxidation products. Nitric oxide synthase (NOS) activity in the heart and nitrite level in blood were increased (p < 0.05) in coconut kernel protein-treated rats administered with isoproterenol compared to isoproterenol control rats. Coconut protein pretreatment upregulated the expression of endothelial nitric oxide synthase (eNOS), whereas expressions of nuclear factor-kappaB (NF-κB) and tumor necrosis factor-alpha (TNF-α) were downregulated in isoproterenol-treated rats. These findings suggest that the protective effects of coconut kernel protein may be mediated in part through upregulation of nitric oxide production, antioxidant mechanisms, and its ability to inhibit TNF-α and NF-κB activation.     

The radioprotective effect of Nigella sativa on nitrosative stress in lens tissue in radiation-induced cataract in rat

Objective: The aim of this study was to investigate the antioxidant and radioprotective effects of Nigella sativa oil (NSO) and thymoquinone (TQ) against ionizing radiation-induced cataracts in lens after total cranium irradiation (IR) of rats with a single dose of 5 gray (Gy).

Materials and methods: Seventy-four Sprague-Dawley rats were used for the experiment. The rats were randomly divided into six groups. Group A received total cranium IR plus NSO (1?g?kg^–1?d^–1) orally through an orogastric tube. Group B received total cranium IR plus TQ (50?mgkg^–1?d^–1) daily by intraperitoneal injection. Group C received 5?Gy of gamma IR as a single dose to total cranium plus 1?ml saline. Group D₁ just received 1?ml saline. Group D₂ just received dimethyl sulfoxide. Group D₃ did not receive anything.

Results: At the end of the 10th d, cataract developed in 80% of the rats in IR group only. After IR, cataract rate dropped to 20% and 50% in groups which were treated with NSO and TQ, respectively, and was limited at grades 1 and 2. Nitric oxide synthase activity, nitric oxide and peroxynitrite levels in the radiotherapy group were higher than those of all other groups.

Conclusions: The results implicate a major role for NSO and TQ in preventing cataractogenesis in ionizing radiation-induced cataracts in the lenses of rats, wherein NSO were found to be more potent.     

Catalpol decreases peroxynitrite formation and consequently exerts cardioprotective effects against ischemia/reperfusion insult

Context: Peroxynitrite (ONOO^?) formation triggers oxidative/nitrative stress and contributes to exacerbated myocardial ischemia/reperfusion (MI/R) injury. Catalpol, an iridoid glycoside, abundantly found in the roots of Rehmannia glutinosa L. that is included in the family Phrymaceae in the order Lamiales, endemic to China, was found to have neuroprotective effects. However, the effect of catalpol on MI/R injury has not been identified.

Objective: This study investigated whether catalpol attenuates oxidative/nitrative stress in acute MI/R.

Materials and methods: Adult male rats were subjected to 30?min of myocardial ischemia and 3?h of reperfusion and were treated with saline, catalpol (5?mg/kg, i.p., 5?min before reperfusion) or catalpol plus wortmannin (15 µg/kg intraperitoneally injected 15?min before reperfusion).

Results: Pretreatment with catalpol significantly improved cardiac functions, reduced myocardial infarction, apoptosis and necrosis of cardiomyocytes after MI/R (all p < 0.05). Meanwhile, ONOO^? formation was markedly reduced after catalpol treatment (3.01?±?0.22 vs. 4.66?±?0.53 pmol/mg protein in vehicle, p < 0.05). In addition, catalpol increased Akt and endothelial nitric oxide synthase phosphorylation, nitric oxide (NO) production, anti-oxidant capacity and reduced MI/R-induced inducible nitric oxide synthase expression and superoxide anion (·O₂^?) production in I/R hearts. PI3K inhibitor wortmannin not only blocked catalpol-induced Akt activation, but also attenuated all the beneficial effects of catalpol. Suppression of ONOO^? formation by either catalpol or an ONOO^? scavenger uric acid (5?mg/kg) reduced myocardial infarct size in MI/R rats.

Discussion and conclusion: In conclusion, catalpol affords cardioprotection against MI/R insult by attenuating ONOO^? formation, which is attributable to increased physiological NO and decreased ·O₂^? production.     

Reduction of myocardial infarct size by tetrahydrobiopterin: possible involvement of mitochondrial KATP channels activation through nitric oxide production

This study examined whether intravenous administration of tetrahydrobiopterin (BH4) reduces myocardial infarct size following ischemia/reperfusion (I/R) in rats, and the mechanisms of its protective effect were also investigated. Rats were subjected to 30 minutes of ischemia by ligation of the left coronary artery and 2 hours of reperfusion. The infarct size was determined as a percentage of the area at risk by triphenyltetrazolium staining. Intravenous administration of BH4 (0.01 mg/kg-1 mg/kg) significantly reduced the myocardial infarct size. Nitrite plus nitrate (NOx) and cGMP levels in the hearts were significantly increased by the treatment with BH4, and the infarct size-limiting effect of BH4 was abolished by the co-administration of NG-nitro-L-arginine methyl ester, a specific inhibitor of nitric oxide synthase, or 5-hydroxydecanoic acid, a specific inhibitor of mitochondrial ATP-sensitive potassium channel (mitoKATP channel). These findings suggest that BH4 has a cardioprotective effect against I/R in vivo, and its protective effect appeared to be involved in the opening of mitoKATP channels through increased nitric oxide production.     

Regulation of endothelial nitric oxide synthase and asymmetric dimethylarginine by matrine attenuates isoproterenol-induced acute myocardial injury in rats

Objectives This study was designed to investigate the cardioprotective effects of matrine on regulation of endothelial nitric oxide synthase (eNOS) and asymmetric dimethylarginine (ADMA) in isoproterenol‐induced acute myocardial ischaemic rats. Methods Male Sprague–Dawley rats were pretreated with matrine (200, 100 and 50 mg/kg) orally for 10 days. Acute myocardial injury was induced in rats by subcutaneous injection of isoproterenol. Serum and haemodynamic parameters, histopathological variables and expression of protein levels were analysed. Key findings Oral administration of matrine (200, 100 and 50 mg/kg) significantly attenuated isoproterenol‐induced cardiac necrosis and left ventricular dysfunction. Matrine treatment restored impaired ventricular Akt and eNOS protein expression with concomitant increased phosphorylation of Akt (Ser473) and eNOS (Ser1177), and also restored glycogen synthase kinase 3β activity, as indicated by increased phosphorylation at Ser 9. Moreover, treatment with matrine had no effect on the isoproterenol‐induced elevated protein arginine methyltransferase 1 protein expression, but could significantly normalize the reduced dimethylarginine dimethylaminohydrolase 2 expression and attenuate the increased serum level of ADMA. The expression of catechol‐o‐methyltransferase and monoamine oxidase did not differ among all groups (all P > 0.05). Conclusions Our results suggested that matrine protects against isoproterenol‐induced myocardial ischaemia via eNOS and ADMA pathway.     

Cardioprotective effect of resvaratrol pretreatment on myocardial ischemia-reperfusion induced injury in rats

OBJECTIVE: The major objective of the present study was to examine the cardioprotective effect of resveratrol, an antioxidant presents in red wine, in the rat after ischemia-reperfusion (I/R). DESIGN: The left coronary artery was in occlusion for 30 min followed by a 120 min reperfusion in anesthetized rats. Animals were pretreated with and without resveratrol before occlusion. The post-ischemic ventricular function (left ventricle maximum systolic pressures and the maximal first derivative of developed pressure) and myocardial infarct size and myocardial nitric oxide (NO) and malonaldehyde (MDA) content were compared. RESULTS: Resveratrol pretreatment had dramatic cardioprotective effects on post-ischemic ventricular functional recovery and decreasing myocardial infarct size. Resveratrol pretreatment also increased NO and decreased MDA content in myocardium. CONCLUSIONS: Resveratrol has cardioprotective properties in I/R rats. The cardioprotective effects in the I/R rats may be correlated with its antioxidant activity and upregulation of NO production.     

Pharmacological characterization of mechanisms involved in the vasorelaxation produced by rosuvastatin in aortic rings from rats with a cafeteria‐style diet

The present study aimed to investigate the possible influence of several inhibitors and blockers on the vascular effect produced by the acute in vitro application of rosuvastatin to phenylephrine‐precontracted aortic rings from rats with a semi‐solid, cafeteria‐style (CAF) diet. It also aimed to examine the effects of rosuvastatin on the expression of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase, constitutive cyclooxygenase, and inducible cyclooxygenase in aortic rings from rats with a CAF diet. From comparisons of the effect on phenylephrine‐precontracted aortic rings extracted from rats with two different diets (a standard and a CAF diet), it was found that 10^?9–10^?5‐mol/L rosuvastatin produced lower concentration‐dependent vasorelaxation on rings from the CAF diet group. The vasorelaxant effect was unaffected by the vehicle, but it was significantly attenuated by 10^?5‐mol/L N^G‐nitro‐l ‐arginine methyl ester, 10^?2‐mol/L tetraethylammonium, 10^?3‐mol/L 4‐aminopyridine, 10^?7‐mol/L apamin plus 10^?7‐mol/L charybdotoxin, 10^?5‐mol/L indomethacin, or 10^?5‐mol/L cycloheximide. Moreover, in aortic rings from rats with a CAF diet, rosuvastatin enhanced the expression of eNOS, inducible nitric oxide synthase, constitutive cyclooxygenase, and inducible cyclooxygenase. The acute in vitro application of rosuvastatin to phenylephrine‐precontracted aortic rings from rats with a CAF diet had a vasorelaxant effect. Overall, the present results suggest that the stimulation of eNOS, the opening of Ca²⁺‐activated and voltage‐activated K⁺ channels, the stimulation of prostaglandin synthesis and enhanced protein levels of eNOS, inducible nitric oxide synthase, constitutive cyclooxygenase, and inducible cyclooxygenase are involved in this relaxant effect.     

Akt/GSK-3β/eNOS 通路在藏红花酸保护离体大鼠心肌缺血再灌注损伤中的作用

目的 研究藏红花酸 （CRO） 对离体大鼠心肌缺血再灌注损伤的保护作用, 探讨其与丝氨酸/苏氨酸蛋白激酶 （Akt） /糖原合成酶激酶 （GSK） -3β/一氧化氮合酶 （eNOS） 信号通路的关系。方法 SD 大鼠 40 只, 随机数字表法均分为正常（N）组、 缺血再灌注（IR）组及 5、 10、 15 mg/L 加药（CRO1、CRO2、 CRO3）组, 比较再灌注 30 min 时各组心率（HR）, 冠脉流量 （CF）, 左心室内压测定(LVDP、 LV+dp/dtmax、 LV-dp/dtmax)。灌流结束 TTC 心肌染色评估梗死范围,分光光度法测定肌浆乳酸脱氢酶 （LDH） 和肌酸激酶 （CK-MB); Western blot 检测各组心肌组织内 Akt、 磷酸化的丝氨酸/苏氨酸蛋白激酶(p-Akt )、 GSK-3β、 磷酸化的糖原合成酶激酶 (p-GSK) -3β、 eNOS、 磷酸化的一氧化氮合酶（pNOS）。结果 IR 组再灌注 30 min 时 HR、CF、LVDP、LV+dp/dtmax、 LV-dp/dtmax 较 N 组及加药组降低, 心肌梗死面积较加药组增大, LDH、 CK-MB 表达较 N 组及加药组增加 （均 P < 0.05）, CRO3组再灌注指标较 CRO1组升高, 梗死面积降低, LDH、 CK-MB 表达减少 （P < 0.05）。IR 组 Akt、 GSK-3b 及 eNOS 较 N 组及加药组的表达差异无统计学意义, 但 p-Akt、 p-GSK-3β及 p-NOS 与 N 组及加药组降低, 且 CRO3组较 CRO1组增加（均 P < 0.05）。结论 藏红花酸能够减轻大鼠心肌缺血再灌注损伤, 其作用机制可能与激活 Akt/GSK-3β/eNOS 通路并影响其磷酸化水平有关。     

Melatonin and Vitamin C Attenuates Alcohol‐Induced Oxidative Stress in Aorta

Abstract: Epidemiological studies have shown that low to moderate doses of alcohol consumption are beneficial to cardiac health. However, chronic high doses of alcohol ingestion cause cardiovascular complications. The aim of this study was to investigate both the effects of melatonin and vitamin C and expression of endothelial nitric oxide synthase in aorta of chronic alcoholic rats. Twenty‐four adult male Wistar rats weighing 200–250 g were used in the study. Rats were divided into four equal groups. Group I (control): rats were not fed on alcohol; Group II: rats were fed on alcohol; Group III: rats were fed on alcohol and 40 mg/kg vitamin C were injected intraperitoneally and Group IV: rats were fed on alcohol and 4 mg/kg melatonin were injected intraperitoneally. At the end of the experiment, rats were killed and aorta tissues were removed. Some parts of the aorta tissues were used for biochemical analyses and the other parts were used at histological procedures. In the control group, endothelial nitric oxide synthase immunoreactivity was (++) in smooth muscle cells and endothelial cells. Expression of endothelial nitric oxide synthase in the alcohol group was stronger than control group. Chronic ethanol ingestion significantly increased (p < 0.05); and melatonin significantly decreased both the plasma and tissue malondialdehyde levels. The superoxide dismutase levels and catalase activity did not change significantly in the Vitamin C and melatonin groups (p > 0.05) compared to the control and alcohol groups. The present results indicate that chronic alcohol consumption increase lipid peroxidation and cause endothelial nitric oxide synthase expression in the aorta. However, melatonin and vitamin C administration provide partial protection against alcohol‐induced damage.     

Effects of sildenafil on nanostructural and nanomechanical changes in mitochondria in an ischaemia‐reperfusion rat model

Sildenafil exerts cardioprotective effects by activating the opening of mitochondrial ATP‐sensitive potassium channels to attenuate ischaemia–reperfusion (IR) injury. In the present study, we used atomic force microscopy (AFM) to investigate changes in mitochondrial morphology and properties to assess sildenafil‐mediated cardioprotection in a rat myocardial infarction model. To investigate the cardioprotective effects of sildenafil, we used an in vivo Sprague‐Dawley rat model of IR. Rats were randomly divided into three groups: (i) sham‐operated rats (control; n = 5); (ii) IR‐injured rats treated with vehicle (normal saline; IR; n = 10); and (iii) IR‐injured rats treated with 0.75 mg/kg, i.p., sildenafil (IR + Sil; n = 10). Morphological and mechanical changes to mitochondria were analysed by AFM. Infarct areas were significantly reduced in sildenafil‐treated rats (7.8 ± 3.9% vs 20.4 ± 7.0% in the sildenafil‐treated and untreated IR groups, respectively; relative reduction 62%; P < 0.001). Analysis of mitochondria by AFM showed that IR injury significantly increased the areas of isolated mitochondria compared with control (24 150 ± 18 289 vs 1495 ± 1139 nm², respectively; P < 0.001), indicative of mitochondrial swelling. Pretreatment with sildenafil before IR injury reduced the mitochondrial areas (7428 ± 3682 nm²; P < 0.001; relative reduction 69.2% compared with the IR group) and ameliorated the adhesion force of mitochondrial surfaces. Together, these results suggest that sildenafil has cardioprotective effects against IR injury in a rat model by improving the morphological and mechanical characteristics of mitochondria.     

Effects of captopril,telmisartan and bardoxolone methyl (CDDO‐Me) in ischemia‐reperfusion‐induced acute kidney injury in rats: an experimental comparative study

Renal ischemia‐reperfusion (IR) injury is one of the most common causes of acute kidney injury. This study investigated the effects of captopril (CAP), telmisartan (TEL) and bardoxolone methyl (BM) in animals with renal IR injury. Adult male Wistar–Albino rats were divided into six groups: control, vehicle, IR, IR with CAP, IR with TEL and IR with BM. Before IR was induced, drugs were administered by oral gavage. After a 60‐min ischemia and a 120‐min reperfusion period, bilateral nephrectomies were performed. Serum urea, creatinine, neutrophil gelatinase‐associated lipocalin (NGAL) levels, tissue total oxidant status (TOS), total antioxidant status (TAS), total thiol (TT), asymmetric dimethylarginine (ADMA) levels, superoxide dismutase (SOD) activity and glutathione peroxidase (GSH‐Px) activity were measured. Tissue mRNA expression levels of peroxisome proliferator‐activated receptor‐? (PPAR‐?), nuclear factor erythroid 2‐related factor 2 (Nrf2) and nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) were analyzed. In addition, renal tissues were evaluated histopathologically and immunohistochemically. All tested drugs reduced renal damage, apoptosis, urea, creatinine, NGAL, TOS, nitric oxide (NO) and ADMA levels, NF‐κB, inducible nitric oxide synthase (iNOS) and endothelin‐1 (ET‐1) expressions (P < 0.001). All tested drugs increased SOD activity, GSH‐Px activity, TAS levels, TT levels, endothelial nitric oxide synthase (eNOS) expression, dimethylarginine dimethylaminohydrolases (DDAHs) expression, Nrf2 expression and PPAR‐? expression (P < 0.001, P < 0.003). These results suggest that CAP, TEL and BM pretreatment could reduce renal IR injury via anti‐inflammatory, antioxidant and anti‐apoptotic effects.     

UTP reduces infarct size and improves mice heart function after myocardial infarct via P2Y2 receptor

Pyrimidine nucleotides are signaling molecules, which activate G protein-coupled membrane receptors of the P2Y family. P2Y₂ and P2Y₄ receptors are part of the P2Y family, which is composed of 8 subtypes that have been cloned and functionally defined. We have previously found that uridine-5′-triphosphate (UTP) reduces infarct size and improves cardiac function following myocardial infarct (MI). The aim of the present study was to determine the role of P2Y₂ receptor in cardiac protection following MI using knockout (KO) mice, in vivo and wild type (WT) for controls. In both experimental groups used (WT and P2Y₂^−/− receptor KO mice) there were 3 subgroups: sham, MI, and MI + UTP. 24 h post MI we performed echocardiography and measured infarct size using triphenyl tetrazolium chloride (TTC) staining on all mice. Fractional shortening (FS) was higher in WT UTP-treated mice than the MI group (44.7 ± 4.08% vs. 33.5 ± 2.7% respectively, p < 0.001). However, the FS of P2Y₂^−/− receptor KO mice were not affected by UTP treatment (34.7 ± 5.3% vs. 35.9 ± 2.9%). Similar results were obtained with TTC and hematoxylin and eosin stainings. Moreover, troponin T measurements demonstrated reduced myocardial damage in WT mice pretreated with UTP vs. untreated mice (8.8 ± 4.6 vs. 12 ± 3.1 p < 0.05). In contrast, P2Y₂^−/− receptor KO mice pretreated with UTP did not demonstrate reduced myocardial damage. These results indicate that the P2Y₂ receptor mediates UTP cardioprotection, in vivo.     

Chronic β-AR activation-induced calpain activation and impaired eNOS–Akt signaling mediates cardiac injury in ovariectomized female rats

Objective: To address the pathophysiological relevance of ovarian hormones in chronic β-adrenergic stimulation-induced myocardial injury, we assessed impairments of Ca²⁺-mediated cell signaling in the left ventricle of ovariectomized female rats. Research design/methods: Female Wistar rats were subjected to bilateral ovariectomy and sham operation. Six weeks after ovariectomy (OVX), both OVX and sham rats were treated with isoproterenol (5mg/kg, intraperitoneally), a nonselective β-adrenergic agonist, once a day for 28 days. Results: We found that chronic β-adrenergic stimulation caused enhanced breakdown of sarcolemmal proteins such as dystrophin and utrophin in OVX rats compared to sham-operated rats. Generation of calpain-mediated 150 kDa-breakdown product of spectrin confirmed calpain activation following isoproterenol treatment. Marked breakdown of endogenous calpain inhibitor, calpastatin, in OVX rats was consistent with the calpain activation following chronic β-adrenergic stimulation. In addition to calpain activation, we also found marked reduction of endothelial nitric oxide synthase (eNOS) activity with concomitant deregulation by heat shock proteins 90 kDa and caveolin 3, both of which are eNOS-associated proteins. Finally, we documented decreased Akt phosphorylation with concomitant increased glycogen synthase kinase 3β phosphorylation underlying cell injury following chronic β-adrenergic stimulation. Conclusion: Taken together chronic β-adrenergic stimulation caused severe cardiac injury in OVX rats through calpain activation and impairments of Akt and eNOS signaling pathways.     

丹酚酸B预处理对心肌缺血/再灌注损伤能量代谢的影响

目的 观察丹酚酸B预处理对大鼠心肌缺血/再灌注损伤（MI/RI）能量代谢的作用。方法 通过结扎冠状动脉30min再灌注2 h建立大鼠MI/RI模型,随机分为4组：假手术组、模型组及丹酚酸B高、低（20、10 mg/kg）组,于建立模型前7 d开始ip给药,每天1次;再灌注结束后,采用比色法测定血清乳酸脱氢酶（LDH）、肌酸激酶（CK）活力,染色法测定心肌梗死面积（MIA）,定磷法测定心肌组织Na⁺-K⁺-ATP酶、Ca²⁺-Mg²⁺-ATP酶活性。结果 与模型组（42.60%）比较,丹酚酸B高、低剂量组的MIA分别缩小至35.93%和37.21%,差异显著（P<0.05）;与模型组比较,丹酚酸B高、低剂量组血清CK、LDH活力均显著降低（P<0.05、0.01）;与模型组比较,丹酚酸B高、低剂量组心肌组织Na⁺-K⁺-ATP酶、Ca²⁺-Mg²⁺-ATP酶活性均显著升高（P<0.05、0.01）。结论 丹酚酸B预处理可保护MI/RI所致心肌损伤,作用途径可能与改善心肌组织的能量代谢相关。     

Urantide对大鼠心肌缺血/再灌注后心肌细胞凋亡的作用及机制研究

目的观察urantide对大鼠缺血/再灌注心肌组织氧化应激损伤的作用和心肌细胞凋亡的影响及其与PI3K/Akt及PKC信号通路的关系。方法可逆性冠脉左前降支结扎造成心肌缺血/再灌注模型,给予大鼠心脏缺血30 min再灌注90 min。80只大鼠随机分为假手术组、缺血/再灌注(I/R)组、urantide低、中、高剂量组(3,10,30μg.kg-1)、维拉帕米对照组(1.6 mg.kg-1)、urantide+CHE组(30μg.kg-1+1 mg.kg-1)、urantide+LY294002组(30μg.kg-1+0.3 mg.kg-1)。Urantide低、中、高剂量组中urantide于缺血前5 min舌下静脉1 min内一次性推注,urantide+CHE组与urantide+LY294002组中,在穿线稳定后舌下静脉分别快速推注CHE与LY294002,5 min后舌下静脉快速推注uran-tide 30μg.kg-1,稳定10 min后再行缺血/再灌注操作。实验结束后测定大鼠血清中超氧化物歧化酶(SOD)、一氧化氮合酶(NOS)活力和丙二醛(MDA)含量以及一氧化氮(NO)含量。TUNEL法检测凋亡细胞指数(AI),免疫组化法检测心肌组织Bcl-2、Bax的蛋白表达。结果与I/R组相比,urantide 30μg.kg-1能明显升高SOD活性(P<0.01),明显减少血清中MDA的含量(P<0.05),明显提高NOS活力(P<0.01),使NO含量增加(P<0.01);Bax蛋白表达和心肌细胞凋亡指数降低(P<0.01),Bcl-2蛋白表达增加(P<0.05);urantide+CHE组与urantide+LY294002组与urantide30μg.kg-1组相比,SOD活力和NO含量下降,MDA含量上升,心肌组织中Bax蛋白表达和心肌细胞凋亡指数上升,而Bcl-2蛋白表达下降,与I/R组比较差异无统计学意义(P>0.01)。结论 Urantide能够通过激活PKC和PI3K/Akt信号转导通路,减少心肌组织氧自由基的含量,进一步调控Bcl-2和Bax蛋白的表达,抑制心肌缺血/再灌注大鼠心肌细胞的凋亡,从而对大鼠心肌缺血/再灌注具有一定保护作用。     

Comparative effects of selective and non-selective nitric oxide synthase inhibition in gentamicin-induced rat nephrotoxicity

Different nitric oxide synthase (NOS) isoforms are found in the kidney. Some studies provided evidences that increased endothelial NOS (eNOS) activity leads to restoration of renal function after injury, but activation of inducible NOS (iNOS) aggravates renal failure. In the present study, the beneficial effects of selective iNOS blockade in gentamicin (GM) induced nephrotoxicity have been investigated. Four groups of rats were studied. Untreated control rats received saline. In GM group, GM was injected (IV, 4 mg kg⁻¹). In GM + L-NAME group rats received L-NAME (N-omega-l-arginine methyl ester, a non-selective NOS inhibitor) simultaneously with GM (IV, 30 mg kg⁻¹). Additional doses of L-NAME were administered 2 and 4 h after GM (IP, 30 mg kg⁻¹). In GM + L-NIL group rats were treated by N-imino-ethyl lysine (L-NIL, a selective iNOS inhibitor). First dose (IV, 3 mg kg⁻¹) administrated simultaneously with GM. Next doses (IP, 3 mg kg⁻¹) were administered 2 and 4 h after GM. In all groups, serum and urine creatinine levels were measured. Creatinine clearance was calculated and considered as an estimation of glomerular filtration rate (GFR). Urine N-acetyl-b-d-glucose aminidase (NAG) activities were also determined. After experiments, kidney sections were histologically studied. Selective iNOS inhibition by L-NIL prevented the GM-induced decrease in GFR and increase in creatinine levels, while complete non-selective NOS inhibition by L-NAME aggravated the GFR reduction, elevation of creatinine levels and enzyme release (P < 0.05). Histological studies showed that GM-treated kidneys had evidences of tubular damages and these damages were less evident by the administration of L-NIL. In conclusion, selective inhibition of iNOS may prevent GM-induced nephrotoxicity, whereas non-selective inhibition of NOS aggravates it.     

诱导型一氧化氮合酶在GK糖尿病大鼠心肌梗死后的表达

目的本研究通过制作GK糖尿病大鼠及非糖尿病大鼠心肌梗死模型,观察诱导型一氧化氮合酶(iNOS)的表达在糖尿病大鼠合并心肌梗死时与非糖尿病大鼠心肌梗死时的变化,为冠心病合并糖尿病的心脏病理改变提供理论基础与科学依据。方法应用体质量在200～250g的雄性GK糖尿病大鼠及其对照雄性Wistar大鼠通过开胸手术结扎麻醉大鼠冠状动脉左前降支制作大鼠在体心肌梗死模型。心肌梗死模型制作前测量血糖。手术成功后分组饲养大鼠3周。3周后,测量血糖,活体剪取心脏,进行iNOS的免疫组织化学染色及实时聚合酶链反应(RT-PCR)检测。结果①GK糖尿病大鼠血糖明显高于Wistar大鼠血糖(P<0.05);②Wistar心肌梗死组与GK心肌梗死组在缺血区可见到心肌细胞iNOS大量阳性染色,但GK心肌梗死组与Wistar心肌梗死组相比,iNOS阳性染色减少,二者吸光度测定值差异有统计学意义(P<0.05);③Wistar心肌梗死组与GK心肌梗死组iNOSmRNA表达在缺血区明显增加,但GK心肌梗死组iNOSmRNA表达减少,二者之间差异有统计学意义(P<0.05)。结论iNOS在糖尿病大鼠合并心肌梗死时其在缺血区的表达是降低的,表明高血糖可能抑制iNOS的表达,使体内一氧化氮(NO)生成减少,不利于梗死后血供的恢复。     

Effects of Chronic Nitric Oxide Synthase Inhibition on TNB-induced Colitis in Rats

Nitric oxide (NO) synthesis is increased in ulcerative colitis, but the role of NO in colitis is poorly understood. The present study employed N^W-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, in rats to evaluate the effect of NO on 2,4,6-trinitrobenzenesulphonic acid (TNB)-induced colitis. L-NAME solutions were placed in subcutaneous, osmotic mini-pumps which continuously released L-NAME at 0.042, 0.208, 0.417, or 1.667mgkg^?1 h^?1. L-NAME dose-dependently enhanced lesions in TNB-induced colitis. The two higher doses of L-NAME significantly increased colonic mucosal damage, although there was slight, nonsignificant reduced lesion formation with the lowest dose of L-NAME, 0.042 mgkg^?1 h^?1. A single dose of L-NAME at 100 mgkg^?1 subcutaneously injected daily in TNB-treated rats also increased lesions, and these ulcerogenic actions of L-NAME were reversed by L-arginine but not by D-arginine (both at 500mgkg^?1, s.c). Only the highest dose of L-NAME (mini-pump) significantly depressed myeloperoxidase (MPO) activity. Faecal occult bleeding showed a close relationship with severity of colitis. These findings suggest that there may exist a balance between NO protective and aggressive effects. In TNB-induced colitis, antagonism of endogenous NO generation was intensified, whereas slight inhibition of NO synthesis reduced lesions. Variations in responses, related to timing or dose changes in L-NAME, may reflect the differences in inducible vs constitutive NO synthase isoforms.