Peroxynitrite decomposition catalysts prevent myocardial dysfunction and inflammation in endotoxemic rats

OBJECTIVES: The aim of this study was to test whether peroxynitrite neutralizers would reduce peroxynitrite accumulation and improve myocardial contractile dysfunction and inflammation in endotoxin-treated rats. BACKGROUND: Release of endogenous proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha in response to endotoxin is responsible for the production of large amounts of nitric oxide (NO), which may exert detrimental effects on the myocardium in animal models, isolated hearts, and isolated cardiac myocytes. Recent studies have indicated that many of the deleterious effects of NO are mediated by peroxynitrite, a powerful oxidant generated from a fast diffusion-limited reaction of NO and superoxide anion. METHODS: We studied the effects of peroxynitrite neutralizers, such as mercaptoethylguanidine (MEG) sodium succinate (10 mg/kg) and 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrinato iron (III) (FeTPPS) (30 mg/kg) on peroxynitrite accumulation, in vivo endothelial cell-leukocyte activation on the mesenteric venule, and myocardial contractile dysfunction and inflammation in a model of sepsis induced by injection of endotoxin (10 mg/kg) in rats. RESULTS: Mercaptoethylguanidine sodium succinate and FeTPPS largely prevented the accumulation of peroxynitrite as measured by plasma rhodamine fluorescence and heart nitrotyrosine staining. Interestingly, MEG sodium succinate and FeTPPS improved endotoxin-induced myocardial contractile dysfunction, which was associated with reduced degradation of nuclear factor kappa B inhibitory protein I-kappa-B, plasma TNF-alpha levels, and microvascular endothelial cell-leukocyte activation. CONCLUSIONS: These observations suggest that the beneficial effects of MEG and FeTPPS on endotoxin-induced myocardial contractile dysfunction could be related to the unique effects of these compounds on cardiovascular inflammation processes.     

Habitual low-intensity exercise does not protect against myocardial dysfunction after ischemia in rats.

BACKGROUND: It is well established that participation in a chronic exercise program can reduce coronary heart disease (CHD) risk factors and improve myocardial tolerance to ischemia-reperfusion (I-R) injury. Low-intensity exercise programs are known to be effective in reducing CHD risk factors in humans and rats, but whether similar programs are of sufficient intensity to improve intrinsic tolerance to I-R injury has not been established. Thus, the purpose of this study is to determine whether low-intensity exercise provides self-protection to the heart against I-R injury. METHODS: Male, Sprague-Dawley rats were exercised on a treadmill at an intensity of 55-60% VO2max, 40 min/day, 5 days/week for 16 weeks. Reperfusion injury following 20 min of global ischemia was evaluated using the isolated perfused working heart model. Left ventricular content of the cytoprotective protein heat shock protein 70 (HSP70) was determined by Western blotting. RESULTS: The exercise program elevated HSP70 2.7-fold, but did not provide enhanced protection following 20 min of ischemia. Final post-ischemic recovery of cardiac external work was 63+/-9% of pre-ischemic value in the sedentary group (n=9) and 51+/-11% in the exercising group (n=9) (P>0.05). Post-ischemic lactate dehydrogenase release was also similar between groups and the magnitude of release was low, consistent with stunning. CONCLUSIONS: Regular exercise at 55-60% VO2max is below the threshold intensity necessary to induce intrinsic cardioprotection against I-R injury. Furthermore, elevated myocardial HSP70 is not necessarily a marker of improved protection against dysfunction associated with stunning.     

Nuclear factor-κB inhibition improves myocardial contractility in rats with cirrhotic cardiomyopathy

Background/Aims: Cytokines such as tumour necrosis factor (TNF-α) contribute to the pathogenesis of cirrhotic cardiomyopathy. Nuclear factor-κB (NF-κB) is crucial for cytokine regulation, and induces cardiac dysfunction in several heart disease models. We aimed to elucidate possible NF-κB involvement in cirrhotic cardiomyopathy. Methods: Rats were bile duct ligated (BDL) to produce cirrhosis; controls received sham operation. Animals were studied 4 weeks later. Two NF-κB inhibitors were used: pyrrolidine dithiocarbamate (PDTC) and Bay 11-7082. Four groups were studied in most protocols: sham control, sham+PDTC, BDL and BDL+PDTC. Additional contractility studies were performed with Bay 11-7082. Myocardial NF-κB and TNF-α expression was measured by Western blot and ELISA. The contractility of isolated cardiomyocytes was observed under direct microscopy. Results: Nuclear factor-κB and TNF-α levels were increased in cirrhotic hearts compared with controls. PDTC significantly reduced NF-κB activity and TNF-α expression in cirrhotic hearts; controls were unaffected. Cirrhotic cardiomyocytes showed decreased systolic and diatolic velocity compared with sham controls. Both PDTC and Bay 11-7082 restored contractile function in cirrhotic cardiomyocytes, but did not affect controls. Conclusions: Inhibition of the increased NF-κB activity in cirrhotic hearts was associated with improvement of attenuated cardiomyocyte contractility. NF-κB, via effects on cytokine expression, may contribute to the pathogenesis of cirrhotic cardiomyopathy.     

Hemodynamic and hepatic microcirculational changes in endotoxemic rats treated with different NOS inhibitors

BACKGROUND/AIMS: Severe septic shock may produce hypotension, which is due to the vasodilatational effect of nitric oxide. The effects of different nitric oxide synthase inhibitors on the hemodynamic and hepatic microcirculation of the endotoxemic rats were studied. METHODOLOGY: A prospective controlled study was performed. Eighteen Sprague-Dawley male rats (250-300 g) were anesthetized and studied. The rats were divided into three groups. The rats in group A (n = 6) were injected with lipopolysaccharide (50 mg/kg BW) and L-NAME (5 mg/kg BW). The rats in group B (n = 6) were injected with the same dose of lipopolysaccharide and aminoguanidine (400 mumole/kg BW). The rats in group C rats (n = 6) were injected with same dose of lipopolysaccharide and normal saline as a control. The rats were cannulated with femoral arterial, venous, and jugular venous catheters. Cardiac output was measured using a thermodilutional method, and liver sinusoidal microcirculation was measured with Laser Doppler Flowmetry. The cardiac output, stroke volume, heart rate, blood pressure, and microcirculational flux of the liver in the three groups were measured and compared at 0, 20, 40, 60 and 80 minutes after injection. RESULTS: The rats of group A showed significant decrease of their cardiac output, stroke volume and hepatic microcirculation after the drugs were infused though their blood pressure increased. The rats of group B showed decrease of their blood pressure and stroke volume initially, but no significant change of their cardiac output and hepatic microcirculation. At the 80th min, the rats of group B had the significantly highest cardiac output, stroke volume and hepatic microcirculation among three groups. CONCLUSIONS: The aminoguanidine prevents the hypotensive effect as well as L-NAME during severe sepsis, but it can maintain cardiac output, stroke volume and hepatic microcirculation better than L-NAME.     

红细胞生成素对大鼠心肌缺血-再灌注后抗氧化酶及NO等的影响

目的：探讨红细胞生成素（erythropoietin，EPO）对大鼠心肌缺血-再灌注损伤心肌组织中超氧化物岐化酶（SOD）、丙二醛（MDA）、谷胱甘肽过氧化物酶（GSH-px）、过氧化氢酶（CAT）、一氧化氮（NO）及一氧化氮合酶（NOS）表达的影响。方法：以左冠脉穿线结扎法制备心肌缺血再灌注模型，造模前24h开始给药。在大鼠心肌缺血30min再灌注24h后分别检测心肌组织的MDA，GSHpx，SOD，CAT，NO及NOS。结果：EPO干预组的SOD活力有明显增高，MDA含量明显下降（P均〈0．05），GSHpx及CAT含量均显著提高（P〈0．05）。同时，EPO的预处理也降低了NO和NOS的含量（P〈0．01）。结论：对于大鼠心肌缺血再灌注损伤，EPO干预可以提高多种抗氧化酶活性，同时对NO产生增多有一定的抑制作用。     

Angiotensin-converting enzyme inhibition restores endothelial but not medial connexin expression in hypertensive rats

OBJECTIVE AND DESIGN: Remodelling in the media and decreases in connexin (Cx) expression and size of endothelial cells occur in the caudal artery of spontaneously hypertensive rats (SHR). The objective of this study was to determine whether similar changes are found in the aorta and whether effects in both aorta and caudal artery are present in the pre-hypertensive period or can be reversed by antihypertensive treatment. METHODS AND RESULTS: In the aorta of SHR, there was no difference in endothelial cell size although Cxs 37 and 40 were decreased, compared with normotensive Wistar-Kyoto rats. Cxs 37 and 43 were also reduced in the media. These differences were not apparent in pre-hypertensive SHR. Inhibition of angiotensin-converting enzyme (ACE) in SHR decreased blood pressure and restored Cx expression in the endothelium of both aorta and caudal artery. The decreased endothelial cell size in the caudal artery or the reduced Cxs in the media of the aorta of SHR were unaffected by ACE inhibition. CONCLUSION: We conclude that cellular coupling is reduced in the endothelium of arteries of SHR, but this can be restored by inhibition of the renin-angiotensin system. Decreased cellular coupling in the media or decreased endothelial size in SHR were not reversed by this antihypertensive treatment.     

Night‐time sleep disturbance does not correlate with neuropsychiatric impairment in patients with cirrhosis

Background: Sleep–wake disturbances are common in patients with cirrhosis and are generally attributed to the presence of hepatic encephalopathy. Aim: To determine the relationship between sleep and neuropsychiatric disturbances in patients with cirrhosis. Methods: The study population comprised 87 patients, classified as neuropsychiatrically unimpaired or as having minimal/overt hepatic encephalopathy. Nineteen healthy volunteers served as controls. Validated questionnaires were used to assess sleep quality [Pittsburgh sleep quality index (PSQI)], day‐time sleepiness [Epworth sleepiness scale (ESS)] and diurnal preference. Health‐related quality of life (H‐RQoL) was assessed using the 36‐item short form health profile (SF‐36v1) and the chronic liver disease questionnaire. Results: Patients slept significantly less well than the healthy volunteers (PSQI score: 8.4 ± 4.9 vs. 4.6 ± 2.5, P<0.01) and had more pronounced day‐time sleepiness (abnormal ESS: 21 vs. 0%; χ²=3.8, P=0.05). No significant relationships were observed between sleep indices and the presence/degree of hepatic encephalopathy. H‐RQoL was significantly impaired in the patients (SF‐36v1 physical score: 36 ± 15 vs. 50 ± 10, P<0.001; SF‐36v1 mental score: 46 ± 11 vs. 50 ± 10, P<0.01); night‐time sleep disturbance was an independent predictor of poor H‐RQoL (P<0.01). Conclusions: Sleep–wake abnormalities are common in patients with cirrhosis; they significantly affect H‐RQoL but are not related to the presence of hepatic encephalopathy.     

Intravenous immunoglobulin does not reduce left ventricular remodeling in patients with myocardial dysfunction during hospitalization after acute myocardial infarction

Background

Left ventricular (LV) remodeling takes place after acute myocardial infarction (MI), potentially leading to overt heart failure (HF). Enhanced inflammation may contribute to LV remodeling. Our hypothesis was that the immunomodulating effects of intravenous immunoglobulin (IVIg) would be beneficial in patients with impaired myocardial function after MI by reducing myocardial remodeling and improving myocardial function.

Methods

Sixty-two patients with acute MI treated by percutaneous coronary intervention, with depressed LV ejection fraction (LVEF) were randomized in a double-blinded fashion to IVIg as induction therapy and thereafter as monthly infusions or placebo for 26 weeks. The primary end point was changes in LVEF from baseline to 6 months as assessed by MRI.

Results

Our main findings were: (i) LVEF increased significantly from 38 ± 10 (mean ± SD) to 45 ± 13% after IVIg and from 42 ± 9 to 49 ± 12% after placebo with no difference between the groups. (ii) The scar area decreased significantly by 3% and 5% in the IVIg and placebo group, respectively, with no difference between the groups. (iii) During the induction therapy (baseline to day 5), IVIg induced both inflammatory (e.g., increase in tumor necrosis factor α and monocyte chemoattractant protein-1) and anti-inflammatory (e.g., increase in interleukin-10 and decrease in leukocyte counts) variables, but during maintenance therapy there were no differences in changes of inflammatory mediators between IVIg and placebo.

Conclusions

IVIg therapy after ST elevation MI managed by primary PCI does not affect LV remodeling or function. This illustrates the challenges of therapeutic intervention directed against the cytokine network, to prevent post-MI remodeling.     

Lung elastic recoil does not correlate with pulmonary hemodynamics in severe emphysema

BACKGROUND: It has been postulated that right ventricular (RV) function may improve after lung volume reduction surgery (LVRS) for severe emphysema due to improvement in lung elastic recoil. Improved lung elastic recoil after LVRS is hypothesized to "tether" open extraalveolar vessels, thereby leading to a decrease in pulmonary vascular resistance (PVR) and improved RV function. Whether a relationship exists between static elastic lung recoil and pulmonary hemodynamics in severe emphysema, however, is unknown. METHODS: We prospectively studied 67 patients with severe emphysema (32 women; mean age, 65.3+/-6.6 years [SD]; mean FEV1, 0.79+/-0.25 L) who had hyperinflation (total lung capacity [TLC], 122.5+/-12.3% of predicted) and gas trapping (residual volume, 209.1+/-41.1% of predicted), and were referred to the National Emphysema Treatment Trial. Lung elastic recoil was measured both at TLC (coefficient of retraction [CR]) and at functional reserve capacity (CR at functional residual capacity [CRfrc]) in each patient. RESULTS: CR and CRfrc values were 1.3+/-0.6 cm H2O/L and 0.61+/-0.5 cm H2O/L, respectively. Hemodynamic measurements revealed a pulmonary artery (PA) systolic pressure of 35.9+/-8.9 mm Hg, mean PA pressure of 24.8+/-5.6 mm Hg, and PVR of 174+/-102 dyne*s*cm(-5). No significant correlations were found between CR and PVR (R=-0.046, p=0.71), PA systolic pressure (R=0.005, p=0.97), or mean PA pressure (R=-0.028, p=0.82). Additionally, no significant correlations were found between CRfrc and PVR (R=-0.002, p=0.99), PA systolic pressure (R=-0.062, p=0.62), or mean PA pressure (R=-0.041, p=0.74). CONCLUSIONS: We conclude there is no correlation between lung elastic recoil and pulmonary hemodynamics in severe emphysema, suggesting that elastic lung recoil is not an important determinant of secondary pulmonary hypertension in this group. Registered with www. clinicaltrials.gov, #NCT00000606.     

碘缺乏大鼠海马NO含量及NOS活性的研究

目的　研究碘缺乏与甲状腺功能低下对子代大鼠海马NO水平及NOS活性的影响,探讨在学习记忆低下中可能的作用。方法　以病区低碘粮食加去离子水复制碘缺乏、甲低动物模型。以硝酸还原酶法测定子代大鼠海马NO含量及NOS活性。结果　碘缺乏组子代大鼠尿碘及血清T3、T4含量明显降低,学习记忆力低下,海马组织内NO含量及NOS活性明显降低［NO含量（2.36±1.18）μmol/gPr;NOS活性（3.72±1.56）U/mgPr］。结论　碘缺乏、甲状腺功能低下可导致子代大鼠海马NO水平及NOS活性明显降低,提示海马内NO水平降低可能也是导致低碘动物学习记忆力低下的机制之一。     

Montelukast does not protect against hyperoxia-induced inhibition of alveolarization in newborn rats

Impaired lung development has been demonstrated in neonatal animals exposed to hyperoxia. High lung cys-leukotriene levels may be a contributing factor towards the increase in oxygen toxicity. We investigated the effect of cysteinyl-leukotriene inhibition using the receptor antagonist, montelukast (MK, Singulair), on hyperoxia-induced changes in lung parenchymal structure in neonatal rat pups. Rat pups were exposed to 21% O(2) (air) or 50% O(2) (moderate hyperoxia) from days 1-14 after birth, and were administered the cys-leukotriene receptor antagonist MK (1 mg/kg/day) or normal saline from days 4-14. Somatic growth and morphometric measurements were done on day 15. There was a significant increase in bronchoalveolar lavage fluid cysteinyl-leukotriene levels (+61.9%) when animals were exposed to hyperoxia. O(2) exposure significantly decreased the specific internal surface area by 13%. There was a nonsignificant 5.8% and 19.6% increase in mean chord length and mean alveolar diameter, respectively, as well as an 8.6% decrease in lung volume to body weight ratio. Inhibition of only one arm of the arachidonic-acid cascade by MK was not sufficient to prevent these oxygen-induced changes.     

NO、NOS在大鼠实验性结肠炎中的动态变化及意义

目的　观察大鼠实验性结肠炎发生发展过程中一氧化氮 (nitricoxide ,NO)、一氧化氮合酶 (nitricoxidesynthase ,NOS)的动态变化 ,了解NO、NOS同大鼠实验性结肠炎的关系。方法　采用 2 ,4 二硝基氯苯 (2 ,4 dinitrochlorobenzene ,DNCB)诱发大鼠实验性结肠炎模型 ;Wistar雄性大鼠 70只 ,检测造模前 (Ⅰ组 ) ,造模后第 1天 (Ⅱ组 )、第 1周 (Ⅲ组 )、第 2周 (Ⅳ组 )、第 4周 (Ⅴ组 )结肠粘膜NO、NOS的动态变化 ,同时观察其病理改变 ;结果用 x±s表示 ,采用单因素方差分析对数据进行统计学处理 ,以P <0 .0 5作为差异有显著性的检验水准。结果　 1、Ⅱ、Ⅲ、Ⅳ组同Ⅰ、Ⅴ组相比 ,结肠粘膜NOS的活性及NO的水平明显升高 ,经统计学分析差异显著(P <0 .0 1) ,而Ⅰ、Ⅴ组间上述指标差异无显著性 (P >0 .0 5 )。 2、病理学改变 :Ⅰ组未见明显病理学变化 ;Ⅱ、Ⅲ、Ⅳ组粘膜及粘膜下层明显充血、水肿 ,炎性细胞浸润 ,腺体杯状细胞减少 ,有糜烂及溃疡形成 ;Ⅴ组溃疡基本愈合 ,残存溃疡有明显修复性改变 ,如粘膜上皮修复、肉芽组织增生、瘢痕形成等。结论　NOS、NO过量生成和大鼠实验性结肠炎有关。     

Potentiation of bradykinin effect by angiotensin-converting enzyme inhibition does not correlate with angiotensin-converting enzyme activity in the rat mesenteric arteries

Angiotensin-converting enzyme (kininase II [ACE]) inhibitors are capable of potentiating bradykinin (BK) effects by enhancing the actions of bradykinin on B(2) receptors independent of blocking its inactivation. To investigate further the importance of ACE kininase activity on BK-induced vasodilation, we investigated the effect of inhibiting ACE, as well as other kininases, on both BK metabolism and vasodilator effect in preparations that exhibit increased ACE activity. Mesenteric arterial beds obtained from 1-kidney, 1-clip hypertensive rats presented augmented ACE and angiotensin I converting activities compared with normotensive rats. The isolated and perfused mesenteric beds were exposed to BK for 15 minutes in the absence or in the presence of kininase inhibitors; then, the perfusate was collected for analysis of the products of BK metabolism by high-performance liquid chromatography. BK was metabolized to the fragments BK(1-8), BK(1-7), and BK(1-5), and the recovery of intact BK was reduced by 47% in the hypertensive group. Recovery of BK was increased in both groups in the presence of a kininase I inhibitor and in the hypertensive group by neutral endopeptidase 24.11 inhibitor; however, ACE inhibition did not affect BK metabolism in both groups. In contrast, only the ACE inhibitor potentiated the vasodilator effect of BK in a mesenteric bed preconstricted with phenylephrine; the increase in BK effect, nevertheless, was not greater in arteries from hypertensive rats that presented an increased ACE activity when compared with those in the normotensive group. These data demonstrated that ACE inhibitor-induced potentiation of BK vasodilator effects is not related to their actions on BK degradation.     

Presence of low-grade inflammation in old rats does not worsen skeletal muscle loss under an endotoxemic and dietary stress

The study aimed to determine if age-associated low-grade inflammation aggravates the response to a stress, especially regarding to sarcopenia. Initial inflammatory status in 22-month-old rats was based on plasma α₂-macroglobulin and fibrinogen concentrations. The stress applied was a single intra-peritoneal injection of lipopolysaccharide followed by a 23-day period of malnutrition, i.e. a 4% casein diet distributed in quantity limited to 50% of spontaneous food intake. The response to the stress was analyzed in non-inflamed and low-grade inflamed rats and compared to non-inflamed and low-grade inflamed rats, which received the control treatment (i.e. no lipopolysaccharide injection and an 18% casein diet). The stress-induced body weight loss was higher in inflamed than non-inflamed rats, but the decrease in muscle weight was not worsened. Muscle protein turnover was not affected by the stress. Plasma α₂-macroglobulin levels increased after the stress, whatever the initial inflammatory status. However, fibrinogen levels decreased more in inflamed than non-inflamed rats and albumin levels were not affected by the stress. Independently of the initial inflammatory status, the liver glutathione content was strongly depleted by the stress. These results extend and support our previous findings by demonstrating that age-associated low-grade inflammation does not aggravate sarcopenia in old rats.