Melatonin does not prevent the protection of ischemic preconditioning in vivo despite its antioxidant effect against oxidative stress

Association of Hypoglycemia with Biomarkers of Oxidative Stress and Antioxidants: An Observational Study

Hypoglycemia has been associated with complications from the vasculature. The contributing effects of oxidative stress (OS) on these actions have not been sufficiently studied, especially in daily, routine clinical practice. We examined the association of hypoglycemia encountered in daily clinical practice with biomarkers of OS and endogenous antioxidant activity in persons with diabetes [type 1 (T1D) or type 2 (T2D)], as well as individuals without diabetes, with a history of hypoglycemia. Several biomarkers of OS (MDA, ADMA, ox-LDL, 3-NT, protein carbonyls, 4-HNE, TBARS) and antioxidant capacity (TAC, superoxide scavenging capacity, hydroxyl radical scavenging capacity, reducing power, ABTS) were measured. Blood was drawn at the time of hypoglycemia detection and under euglycemic conditions on a different day. A total of 31 participants (mean age [±SD] 52.2 ± 21.1 years, 45.2% males) were included in the study. There were 14 (45.2%) persons with T2D, 12 (38.7%) with T1D, and 5 (16.1%) without diabetes. We found no differences in the examined biomarkers. Only TBARS, a biomarker of lipid peroxidation, showed lower values during hypoglycemia (p = 0.005). This finding needs confirmation in more extensive studies, given that MDA, another biomarker of lipid peroxidation, was not affected. Our study suggests that hypoglycemia encountered in daily clinical practice does not affect OS.

CoenzymeQ10 and Ischemic Preconditioning Potentially Prevent Tourniquet-Induced Ischemia/Reperfusion in Knee Arthroplasty, but Combined Pretreatment Possibly Neutralizes Their Beneficial Effects

Tourniquet (TQ) use during total knee arthroplasty (TKA) induces ischemia/reperfusion (I/R) injury, resulting in mitochondrial dysfunction. This study aims to determine the effects of coenzyme Q10 (CoQ10) and ischemic preconditioning (IPC), either alone or in combination, on I/R-induced mitochondrial respiration alteration in peripheral blood mononuclear cells (PBMCs) and pain following TKA. Forty-four patients were allocated into four groups: control, CoQ10, IPC, and CoQ10 + IPC. CoQ10 dose was 300 mg/day for 28 days. IPC protocol was three cycles of 5/5-min I/R time. Mitochondrial oxygen consumption rates (OCRs) of PBMCs were measured seven times, at baseline and during ischemic/reperfusion phases, with XFe 96 extracellular flux analyzer. Postoperative pain was assessed for 48 h. CoQ10 improved baseline mitochondrial uncoupling state; however, changes in OCRs during the early phase of I/R were not significantly different from the placebo. Compared to ischemic data, IPC transiently increased basal OCR and ATP production at 2 h after reperfusion. Clinically, CoQ10 significantly decreased pain scores and morphine requirements at 24 h. CoQ10 + IPC abolished analgesic effect of CoQ10 and mitochondrial protection of IPC. In TKA with TQ, IPC enhanced mitochondrial function by a transient increase in basal and ATP-linked respiration, and CoQ10 provides postoperative analgesic effect. Surprisingly, CoQ10 + IPC interferes with beneficial effects of each intervention.

Melatonin and Nicotinamide Mononucleotide Attenuate Myocardial Ischemia/Reperfusion Injury via Modulation of Mitochondrial Function and Hemodynamic Parameters in Aged Rats

Ischemic heart diseases are the major reasons for disability and mortality in elderly individuals. In this study, we tried to examine the combined effects of nicotinamide mononucleotide (NMN) preconditioning and melatonin postconditioning on cardioprotection and mitochondrial function in ischemia/reperfusion (I/R) injury of aged male rats. Sixty aged Wistar rats were randomly allocated to 5 groups, including sham, control, NMN-receiving, melatonin-receiving, and combined therapy (NMN+melatonin). Isolated hearts were mounted on Langendorff apparatus and then underwent 30-minue ligation of left anterior descending coronary artery to induce regional ischemic insult, followed by 60 minutes of reperfusion. Nicotinamide mononucleotide (100 mg/kg/d intraperitoneally) was administered for every other day for 28 days before I/R. Melatonin added to perfusion solution, 5 minutes prior to the reperfusion up to 15 minutes early reperfusion. Myocardial hemodynamic and infarct size (IS) were measured, and the left ventricles samples were obtained to evaluate cardiac mitochondrial function and oxidative stress markers. Melatonin postconditioning and NMN had significant cardioprotective effects in aged rats; they could improve hemodynamic parameters and reduce IS and lactate dehydrogenase release compared to those of control group. Moreover, pretreatment with NMN increased the cardioprotection by melatonin. All treatments reduced oxidative stress and mitochondrial reactive oxygen species (ROS) levels and improved mitochondrial membrane potential and restored NAD⁺/NADH ratio. The effects of combined therapy on reduction of mitochondrial ROS and oxidative status and improvement of mitochondrial membrane potential were greater than those of alone treatments. Combination of melatonin and NMN can be a promising strategy to attenuate myocardial I/R damages in aged hearts. Restoration of mitochondrial function may substantially contribute to this cardioprotection.

The Anti-Oxidation and Mechanism of Essential Oil of Paederia scandens in the NAFLD Model of Chicken

Simple Summary

The essential oil of Paederia scandens can remedy non-alcoholic fatty liver disease of chicken, but the mechanisms remain unclear. In this study, proteomics technology was used to declare the anti-non-alcoholic fatty liver disease mechanism of Paederia scandens essential oil. The results show that the essential oil of Paederia scandens significant decreased the oxidative stress of non-alcoholic fatty liver disease in chicken, which was mainly due to the center regulation protein of HSP7C being significantly inhibited.

Abstract

The aim of the study is to determine the underlying pathogenic mechanisms of oxidative stress and detect the anti-oxidative target of essential oil of Paederia scandens in non-alcoholic fatty liver disease (NAFLD). Chicken NAFLD was modeled by feeding with a high-capacity diet and Paederia scandens essential oil was used to treat the disease. The levels of hepatic reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and the differential proteins and network of protein–protein interactions were investigated in model and drug-treated groups. The results showed that essential oil of Paederia scandens down regulated the hepatic ROS and MDA level significantly (p < 0.05 and 0.01, respectively). The heat shock cognate 71 kDa protein (HSP7C) was down regulated significantly, which was in the center of the network and interacted with 22 other proteins. The results showed that oxidative stress played an important role in the pathogenesis of chicken NAFLD. The essential oil of Paederia scandens showed good anti-oxidation activity by down regulating the HSP7C protein, which can be used as a potential therapeutic target in chicken NAFLD.

Empagliflozin Limits Myocardial Infarction in Vivo and Cell Death in Vitro: Role of STAT3, Mitochondria, and Redox Aspects

Empagliflozin (EMPA), a drug approved for type 2 diabetes management, reduced cardiovascular death but is unknown if it reduces myocardial infarction. We sought to investigate: (i) the effect of EMPA on myocardial function and infarct size after ischemia/reperfusion in mice fed with western diet (WD), (ii) the underlying signaling pathways, (iii) its effects on cell survival in rat embryonic-heart-derived cardiomyoblasts (H9C2) and endothelial cells (ECs). To facilitate the aforementioned aims, mice were initially randomized in Control and EMPA groups and were subjected to 30 min ischemia and 2 h reperfusion. EMPA reduced body weight, blood glucose levels, and mean arterial pressure. Cholesterol, triglyceride, and AGEs remained unchanged. Left ventricular fractional shortening was improved (43.97 ± 0.92 vs. 40.75 ± 0.61%) and infarct size reduced (33.2 ± 0.01 vs. 17.6 ± 0.02%). In a second series of experiments, mice were subjected to the above interventions up to the 10th min of reperfusion and myocardial biopsies were obtained for assessment of the signaling cascade. STAT3 was increased in parallel with reduced levels of malondialdehyde (MDA) and reduced expression of myocardial iNOS and interleukin-6. Cell viability and ATP content were increased in H9C2 and in ECs. While, STAT3 phosphorylation is known to bestow infarct sparing properties through interaction with mitochondria, we observed that EMPA did not directly alter the mitochondrial calcium retention capacity (CRC); therefore, its effect in reducing myocardial infarction is STAT3 dependent. In conclusion, EMPA improves myocardial function and reduces infarct size as well as improves redox regulation by decreasing iNOS expression and subsequently lipid peroxidation as shown by its surrogate marker MDA. The mechanisms of action implicate the activation of STAT3 anti-oxidant and anti-inflammatory properties.

"Pistacia lentiscus L." reduces the infarct size in normal fed anesthetized rabbits and possess antiatheromatic and hypolipidemic activity in cholesterol fed rabbits

HYPOTHESIS/PURPOSE

The aim of the present study was to evaluate in vivo the potential anti-ischemic and antiatheromatic activity of Chios Mastic gum, the resin of the trunk and branches of "Pistacia lentiscus var. chia", used since antiquity in traditional Greek medicine. The main compounds of mastic are triterpenes, possessing phytosterol-like structures. This led to the hypothesis that mastic and particularly its neutral fraction, enriched in phytosterol-like compounds, possess antiatheromatic activities.

METHODS

Total Mastic Extract without Polymer (TMEWP) and the neutral mastic fraction (NMF) were administered orally for 6 weeks to normal fed and to cholesterol fed rabbits in the form of sunflower oil solution. All the animals were randomly divided into 6 groups, anesthetized and subjected to 30min ischemia of the heart, followed by 3h reperfusion: At the end of the experiment the area at risk and the infarct zone were determined with the aid of fluorescent particles and triphenyl tetrazolium chloride staining, and small segments of the ascending and descending aorta and the heart were taken for histologic examination. Blood samples were collected at different time points of ischemia and reperfusion, for malondialdehyde (MDA) evaluation as an index of lipid peroxidation, for total and LDL cholesterol determination and for evaluation of oxidized LDL.

RESULTS

In the normal fed animals the NMF and the TMEWP reduced significantly the infarct size, while in the hypercholesterolemic rabbits both treatments were ineffective. Atherosclerosis was detected in all the animals fed cholesterol enriched diet in the form of subintimal accumulation of lipids and foamy macrophages. There was no detection of atherosclerosis in Groups treated with TMEWP and NMF, which both reduced the total cholesterol levels by 47 and 88% respectively, whilst had not effect on LDL oxidation. TMEWP and NMF reduced the MDA concentration in normal fed rabbits, but had no effect on MDA levels in cholesterol fed animals. TMEWP and NMPF reduce the infarct size in normal animals and possess significant antiatheromatic and hypolipidemic activities in rabbits fed cholesterol enriched diet.

Transient carotid ischemia as a remote conditioning stimulus for myocardial protection in anesthetized rabbits: Insights into intracellular signaling

BACKGROUND

We investigated the effectiveness of perconditioning (Perc) applied at different time points along with the role of RISK, SAFE, STAT5 and eNOS pathways.

METHODS AND RESULTS

Anesthetized rabbits were subjected to 30-min ischemia/3-hour reperfusion. Perc, consisted of 4 cycles of 1-min ischemia/reperfusion, was applied in the carotid artery at different time points. Perc was started and ended during ischemia, started during ischemia and ended at the beginning of reperfusion, started at the end of ischemia and ended at reperfusion and started and ended during reperfusion. The PI3K inhibitor wortmannin, or the JAK-2 inhibitor AG490, was also applied and the infarct size was assessed. In another series assigned to the previous groups, the phosphorylation of Akt, PI3K, ERKs1/2, GSK3β, STAT3, and STAT5 was evaluated. All Perc groups had smaller infarction compared to those without Perc, independently of PI3K or JAK-2 inhibition. STAT5 was the only molecule that was phosphorylated in parallel with cardioprotection. Since Src and angiotensin II mediate the STAT5 pathway, we administered the Scr inhibitor PP1 and the angiotensin II receptor antagonist valsartan. PP1 and valsartan prevented STAT5 phosphorylation, but did not abrogate the effect of Perc. Furthermore, the NOS inhibitor L-NAME was administered and abrogated the infarct size limiting effect of Perc. In parallel, the expression of cleaved caspase-3 was elevated only in the control and Perc-A-L-NAME groups.

CONCLUSION

Perc reduces infarction independently of RISK, SAFE and STAT5 pathways. Src kinase and angiotensin II play a predominant role in STAT5 activation. eNOS may protect the myocardium through inhibition of apoptosis.

Investigating the effect of antioxidant treatment on the protective effect of preconditioning in anesthetized rabbits

Reactive oxygen and nitrogen species are critical in preconditioning (PC). We sought to determine the effect of N-2-mercaptopropionyl glycine (MPG) on infarct size and on the oxidative status. Rabbits were exposed to 30-minute regional ischemia of the heart, which was followed by 3-hour reperfusion: (1) a control group without further intervention, (2) a PC1 group that was subjected to one cycle of PC, (3) a PC4 group that was subjected to 4 cycles of PC, (4) an MPG group that was treated with MPG for 60 minutes, starting 10 minutes before reperfusion, (5) MPG-PC1, and (6) the MPG-PC4 groups that were treated with the same dose of MPG and with 1 or 4 cycles of PC, respectively. Blood samples were drawn and collected for metabonomic analysis. In another series of experiments, 6 groups respective to the described ones were subjected to 30-minute regional ischemia of the heart and 20 minutes of reperfusion, after which pieces of heart tissue were quickly excised for malondialdehyde, nitrotyrosine, and glutathione content assessment. All PC and MPG groups developed smaller infarct size compared with control (16.5% ± 3.9%, 13.7% ± 3.1%, 18.6% ± 5.0%, 9.7% ± 2.0%, 15.0% ± 2.8% vs. 48.05% ± 7.2%; P < 0.05). MPG did not prevent lipid peroxidation and nitrotyrosine formation but enhanced the glutathione content. PC and MPG induced similar nuclear magnetic resonance changes. Long MPG infusion reduces the infarct size without abolishing the effect of PC, providing novel insights into the activity of MPG in PC.

Increased apoptosis in high-fat diet-induced nonalcoholic steatohepatitis in rats is associated with c-Jun NH2-terminal kinase activation and elevated proapoptotic Bax

Hepatocyte apoptosis in addition to oxidative stress could be a key component in the pathogenesis of nonalcoholic steatohepatitis (NASH). However, the underlying mechanisms of hepatocellular apoptotic response associated with oxidative stress have not been investigated in high-fat diet (HFD)-induced NASH models. In this study, Sprague-Dawley rats were fed either a Lieber-DeCarli control diet (CD; 35% energy from fat) or a HFD (71% energy from fat) for 6 wk. Pathologic lesions, lipid peroxidation products, and apoptotic hepatocytes in the liver were examined. The expressions of hepatic tumor necrosis factor-alpha (TNFalpha) and protein concentrations of cleaved caspase-3, cytochrome p4502E1 (CYP2E1), phosphorylated c-Jun NH(2)-terminal kinase (JNK), Bax, Bcl-2, and Bcl-xl were measured. Results showed that the key histological features of NASH, including steatosis, inflammatory cell infiltration, and ballooning degeneration of hepatocytes, were induced by HFD feeding, with increased hepatic TNFalpha mRNA expression. HFD-fed rats had elevated lipid peroxidation products and CYP2E1 protein in the liver. The apoptotic hepatocytes were significantly greater in livers of rats fed HFD than in those fed CD, and these were associated with a higher level of cleaved caspase-3. In addition, HFD feeding increased both hepatic phosphorylated JNK and pro-apoptotic Bax but did not affect anti-apoptotic Bcl-2 and Bcl-xl compared with CD feeding. These data indicate that the increased oxidative stress and its associated JNK activation as well as an imbalance of pro- and anti-apoptotic proteins in the Bcl-2 family all contribute to high hepatocyte apoptosis that may play an important role in the pathogenesis of NASH in this model.

Relationship between plasma osteopontin and oxidative stress in patients with coronary artery disease

BACKGROUND

It is known that oxidative stress plays an important role in the pathogenesis of atherosclerosis and that an association exists between osteopontin (OPN) and atherosclerosis.

OBJECTIVES

It was proposed that malondialdehyde (MDA), a biomarker of lipid peroxidation and oxidative stress, would be related to plasma OPN levels in patients with coronary artery disease (CAD).

METHODS/RESULTS

Plasma OPN and MDA levels were measured in 71 patients (60 males and 11 females; mean age 61.7 +/- 10 years). Fifty-eight patients had significant CAD (group I) and 13 patients were free of CAD as defined angiographically (group II). Plasma OPN was measured by enzyme-linked immunosorbent assay (ELISA), while MDA was determined spectrophotometrically. Multivariate regression analysis revealed that ln-transformed OPN levels were independently associated with MDA after adjustment for age, hypertension and diabetes mellitus (R(2) = 0.278, p = 0.0004 and beta regression coefficient = 0.252 [standard error = 0.0958], p = 0.011). OPN and MDA levels were higher in patients with diabetes (73.6 +/- 36.2 ng/ml versus 56.1 +/- 30.9 ng/ml, p = 0.02 and 2.5 +/- 0.5 microM versus 2.0 +/- 0.5 microM, p = 0.002, respectively).

CONCLUSIONS

The association between OPN and MDA levels in patients with CAD suggests an interaction between OPN and oxidative stress. This interaction may play a role in the pathogenesis of atherosclerosis.

Comparison of the protective effect of N-acetylcysteine by different treatments on rat myocardial ischemia-reperfusion injury

Reactive oxygen species have been known as important contributors to ischemia/reperfusion (I/R) injury. Studies on the beneficial effect of N-acetylcysteine (NAC), a potent antioxidant, on limiting infarct size induced by I/R yielded contrasting results. The present study was undertaken to compare the effect of NAC by different administration methods on infarct size in a rat myocardial I/R model. Rats underwent 30 min of left coronary occlusion followed by 4 h of reperfusion. Treatment with continuous infusion of NAC (150 mg/kg per hour) from 30 min before occlusion for 2 h (until 1 h after the start of reperfusion) produced a significant limitation of the infarct size as a percentage of the ischemic area (8%) compared to the non-treated control (60%). However, bolus injection of 150 mg/kg at 30 min prior to occlusion and 5 min prior to reperfusion failed to reduce it (56%) although the total dose is the same. The decreased total glutathione content and glutathione peroxidase activity in the ischemic region were recovered in the continuous infusion group, but not in the bolus injection group. The increased myeloperoxidase activity and phosphorylation of inhibitor kappaB after I/R were inhibited by the continuous treatment. These results indicate that the protective effect of NAC on myocardial infarction induced by I/R was different depending on the administration method. It is necessary to maintain blood concentration during the early period of reperfusion to obtain the beneficial effect of NAC.

Effect of the portacaval shunt on reperfusion injury after 65% hepatectomy in pigs

BACKGROUND

Portal flow diversion by portacaval shunts (PCS) has been shown to prevent primary graft nonfunction in liver transplantation using small-for-size grafts. In this study, we examine whether PCS can improve reperfusion injury after major hepatectomy in pigs.

MATERIALS AND METHODS

In 14 pigs, a partial PCS was constructed following 65% hepatectomy and 1 h of inflow ischemia. During 24 h of reperfusion, the shunt was either closed (group A, n = 7) or left open (group B, n = 7).

RESULTS

24 h after reperfusion, group A had higher levels of alanine aminotransferase (70 +/- 12 IU/l vs. 51 +/- 5.9 IU/l; p < 0.05), alanine aminotransferase per gram of liver remnant (0.41 +/- 0.07 IU/l/g vs. 0.21 +/- 0.05 IU/l/g; p < 0.05), prothrombin time (24.1 +/- 2.4 s vs. 14.3 +/- 2.9 s; p < 0.05), international normalized ratio (2.11 +/- 0.15 vs. 1.29 +/- 0.28; p < 0.05), hepatocyte necrosis scores and percentages of nuclei stained for proliferating cell nuclear antigen (52.57 +/- 8.9% vs. 36.71 +/- 6%; p < 0.05) compared to group B.

CONCLUSIONS

Partial portal flow diversion appears to attenuate reperfusion injury in a porcine model of major hepatectomy.

Design and synthesis of nitrate esters of aromatic heterocyclic compounds as pharmacological preconditioning agents

Ischemic preconditioning (IPC) constitutes an endogenous protective mechanism in which one or more brief periods of myocardial ischemia and reperfusion render the myocardium resistant to a subsequent more-sustained ischemic insult. Pharmacological preconditioning represents an ideal alternative of IPC. We now describe the design and synthesis of indole, quinoline, and purine systems with an attached pharmacophoric nitrate ester group. The indole and quinoline derivatives 4 and 5 possess structural features of the nitrate containing K(ATP) channel openers. Purine analogues 11 and 12, substituted at the position 6 by a piperidine moiety and at position 9 by an alkyl nitrate, could combine the effects of the nitrate containing K(ATP) channel openers and those of adenosine. Compound 13 bears the nicotinamide moiety of nicorandil instead of nitrate ester. Compounds 4, 5, and 11 reduced infarction and the levels of malondialdehyde (MDA) at reperfusion in anesthetized rabbits. Compounds 12 and 13 did not significantly reduce the infarct size. Analogues 4 and 5 increased cGMP and MDA during ischemia, while combined analogue 4 and mitoK(ATP) blocker 5-hydroxydecanoic acid (5-HD) abrogated this benefit suggesting an action through mitoK(ATP) channel opening. Treatment with derivative 11 combined with 5-HD as well as treatment with 11 and adenosine receptor blocker 8-(p-sulfophenyl)theophylline (SPT) did not abrogate cardioprotection. Compound 11 is a lead molecule for the synthesis of novel analogues possessing a dual mode of action through cGMP-mitoK(ATP) channel opening-free radicals and through adenosine receptors.

Effects of Levosimendan on circulating markers of oxidative and nitrosative stress in patients with advanced heart failure

BACKGROUND

Oxidative stress is associated with maladaptive cardiac remodeling and vascular dysfunction and may be an important contributor to chronic heart failure (CHF) deterioration. We sought to investigate if the calcium sensitizer levosimendan beneficially modulates circulating markers of oxidative and nitrosative stress thus lessening their deleterious effects in patients with advanced CHF.

METHODS

Thirty-nine patients with advanced CHF (mean NYHA 3.5+/-0.4; ischemic/dilated: 23/16; mean left ventricular ejection fraction: 26+/-7%) who were hospitalized due to syndrome worsening, were randomized (2:1) to receive either a 24-h levosimendan infusion of 0.1 microg/(kg min) (n=26) or placebo (n=13). Plasma b-type natriuretic peptide (BNP), circulating markers of oxidative [protein carbonyls, malondialdehyde (MDA)] and nitrosative (nitrotyrosine) stress, and cyclic GMP (cGMP) were measured at baseline and 48 h after each treatment.

RESULTS

Baseline characteristics and medications were well balanced in the two treatment groups. A significant improvement in left ventricular ejection fraction (P<0.01), NYHA class (P<0.01), and plasma BNP (P<0.01) was observed post-treatment only in the levosimendan group. Markers such as MDA, protein carbonyls and nitrotyrosine remained stable in the levosimendan-treated group, but significantly increased (P<0.05) in the placebo-treated patients. Neither therapeutic intervention changed the levels of circulating cGMP.

CONCLUSION

Levosimendan does not increase markers of oxidative and nitrosative stress in contrast to the placebo treatment, thus, exerting cardioprotective effects in advanced CHF patients. Moreover, levosimendan may exert its biologic action through non-cGMP-dependent biochemical pathways.

Malondialdehyde as an indicator of oxidative stress during abdominal aortic aneurysm repair

Ischemia-reperfusion injury significantly contributes to abdominal aortic aneurysm (AAA)- related mortality and morbidity; therefore, we measured oxidative stress during open AAA repair and investigated any potential associations with intraoperative or perioperative events (aortic clamping time, blood loss, and the need to transfer to the intensive care unit). Blood samples were collected at specific time points from 53 patients undergoing open AAA repair: (1) before induction of anesthesia; (2) 15, 30, 60, and 120 minutes after aortic clamping; (3) 15 and 60 minutes after clamp removal; and (4) 24 hours postoperatively. Malondialdehyde (MDA) levels were measured by a spectrophotometric method. Baseline MDA values in patients with AAA were significantly higher than in controls (P < .0001). A positive correlation was found between preoperative MDA levels and the size of AAAs (Pearson correlation = 0.578, P < .001). No difference was observed in MDA levels between ruptured and nonruptured AAAs; however, when all symptomatic patients (ruptured and elective symptomatic AAAs, n = 18) were considered, there was a significant elevation in MDA levels (P < .001). There was also a significant increase in MDA values in patients transferred postoperatively to the intensive care unit (P < .001). Finally, a positive association was found between the duration of aortic clamping with MDA values at 15 and 60 minutes after declamping, but not after 24 hours (Pearson correlation = 0.467, P < .001). MDA levels may predict the postoperative course of elective and ruptured AAAs.

Application of NMR-based metabonomics in the investigation of myocardial ischemia-reperfusion, ischemic preconditioning and antioxidant intervention in rabbits

NMR based metabonomics was applied in rabbit plasma samples during myocardial ischemia-reperfusion injury, with the following interventions: (1) Control (no intervention); (2) ischemic preconditioning (IpC); (3) administration of melatonin; (4) IpC+administration of melatonin; (5) treatment of the indole derivative C6458. The (1)H NMR signal intensity ratio of lactate/glucose was found to increase in Control samples during reperfusion compared to baseline, while lactate+alanine/acetate was decreased suggesting impairment of aerobic glycolysis and concomitant lipid utilization. In contrast, after IpC or treatment with C6458, the lactate/glucose ratio was similar to baseline in accordance with the previously reported decrease in infarct size. Multivariate statistical methods such as Principal Component Analysis (PCA), and Discriminant Analysis (DA) were used for the discrimination of samples. The use of ANOVA variable preselection prior to PCA was advantageous in producing adequate models. PCA could classify the Control group in three clusters according to the condition of the heart (baseline-ischemia-reperfusion) while in the IpC groups no classification was evident. PCA discrimination upon treatment with melatonin and C6458 provided further evidence of their effect on the metabolic profile. The supervised DA resulted in fine discrimination between the different subgroups. Plasma NMR spectra in combination with pattern recognition techniques proved to be an efficient and simple method to depict the metabolic changes produced upon ischemia-reperfusion of the myocardium.

The effects of tirofiban on peripheral markers of oxidative stress and endothelial dysfunction in patients with acute coronary syndromes

BACKGROUND

Endothelial dysfunction and oxidative stress are believed to be central mechanisms in atherogenesis. We aimed to determine the effects of tirofiban on oxidative stress and neutrophil-endothelium interaction markers in patients with acute coronary syndromes (ACS).

MATERIALS AND METHODS

We measured malondialdehyde (MDA), interleukin-6 (IL-6) and soluble endothelial intercellular and vascular adhesion molecules (sICAM-1 and sVCAM-1) on admission, at 48 and 72 h and on 5th day of hospitalization in 34 patients (age 66.5+/-1.8 years) with ACS. Patients with recurrent angina, changes on the electrocardiogram and/or elevated troponin I received intravenously tirofiban for 48 h and the others received normal saline.

RESULTS

Baseline concentrations of all markers did not differ significantly and compared with placebo, tirofiban infusion markedly reduced MDA, IL-6, sICAM-1 and sVCAM-1 at 48 h (-31+/-6% vs. 84+/-49%, p=0.007, -12+/-14% vs. 23+/-10%, p=0.05, -20+/-6% vs. 36+/-25%, p=0.04 and -10+/-5% vs. 6+/-5%, p=0.02, respectively). Relative to baseline, significant reductions were observed for all 4 markers at 72 h and day 5 (p<0.05).

CONCLUSION

Tirofiban potentiates the decline in oxidative stress and may reverse abnormal endothelial activation in patients with ACS. This benefit seems to remain over the following 5 days.

Acute administration of vitamin E triggers preconditioning via K(ATP) channels and cyclic-GMP without inhibiting lipid peroxidation

Vitamin E (VitE) is considered an antioxidant agent. One or more brief periods of ischemia (isc), followed by short reperfusion (rep), increase the tolerance of the heart to a subsequent prolonged ischemia, a phenomenon known as ischemic preconditioning (PC). Mitochondrial KATP channels (mitoKATP), cyclic-GMP (cGMP), and free radicals are involved in the mechanism of PC, whereas some antioxidants abolish this benefit. The purpose of this study was to evaluate the effect of VitE on infarct size, PC, and the oxidative status in vivo. Male rabbits were divided into seven groups and were subjected to myocardial ischemia (isc) and reperfusion (rep) with the following interventions: (1) control (no intervention); (2) E150 (iv VitE at a dose of 150 mg/kg for 75 min, starting 40 min before index isc and lasting through 5 min of rep); (3) E300 (iv VitE 300 mg/kg as previously described); (4) PC (two cycles of 5 min isc and 10 min rep), (5) combined E150-PC; and (6) combined E300-PC. In the last two groups VitE was given 40 min before index ischemia. Blood samples were taken for malondialdehyde (MDA) and conjugated dienes (CDs) measurement. In a second series of experiments heart tissue samples were taken at the time of long ischemia for MDA and CD determination and for cGMP assay. In order to test whether combined treatment with VitE (as the E150 group) and the mitoKATP blocker 5-hydroxydecanoic acid (5-HD) changes the infarct size, an additional group was assessed in the first series of experiments. Tissue VitE concentration was evaluated in myocardium. VitE at both doses reduced the infarct size (19.7 +/- 2.8% for E150 and 18.8 +/- 4.9% for E300 vs 47.4 +/- 2.6% in control, P < 0.05) without attenuating the effect of PC (10.2 +/- 3.1% for E150-PC, 12.4 +/- 2.2% for E300-PC, vs 13.5 +/- 3.3% for PC). Combined VitE and 5-HD treatment abrogates this benefit (37.4 +/- 6.5%, P < 0.05 vs E150 and NS vs control). VitE increases intracellular cGMP and CDs levels (P < 0.05 vs control) to the same extent as PC (P < 0.05 vs control), with no effect on MDA (P = NS between all the groups). Peripheral markers of oxidative stress are increased during reperfusion in all groups (P < 0.05 vs baseline). Overall, VitE limits infarct size via mitoKATP and cGMP, while preserving the benefit of ischemic PC.

The effectiveness of postconditioning and preconditioning on infarct size in hypercholesterolemic and normal anesthetized rabbits

BACKGROUND

Postconditioning with multiple very short coronary occlusions immediately after prolonged ischemia is a new endogenous mechanism for protection of the ischemic heart. We tested whether postconditioning is effective in limiting infarct size in hypercholesterolemic rabbits.

METHODS

Male rabbits were fed a cholesterol-enriched diet for 6 weeks. Animals were subjected to 30 min of regional ischemia of the heart and 3h of reperfusion with the following additional interventions: Control group no additional intervention, ischemic preconditioning (IPC) group to two cycles of 5 min ischemia separated by 10 min reperfusion before the index ischemia, 6/10 IPostC group to six cycles of 10s ischemia separated by 10s reperfusion and 4/30 IPostC group to four cycles of 30s ischemia separated by 30s reperfusion immediately after the end of the index ischemia. In a second series of experiments the same interventions were applied to animals fed with a normal diet. Infarct size (I) was determined by triphenyltetrazolium chloride staining.

RESULTS

The I/R in hypercholesterolemic rabbits was 55.2+/-5.9% in Control, 17.9+/-4.2% in IPC (P<0.01 versus Control), 63.4+/-4.8% in 6/10 IPostC and 55.6+/-8.2% in 4/30 IPostC (P=NS between them and the Control group). In the normal diet rabbits, the I/R was 48.2+/-4.3% in Control, 15.1+/-2.1% in IPC, 20.4+/-2.9% in 6/10 IPostC (P<0.01 versus Control) and 45.1+/-8.9% in 4/30 IPostC (P=NS versus Control). Blood cholesterol levels were increased and atheromatic lesions were present in the first series.

CONCLUSION

Postconditioning is ineffective in limiting the infarct size in rabbits with hypercholesterolemia and atherosclerosis while preconditioning continued to be effective under the same conditions.

The olive constituent oleuropein exhibits anti-ischemic, antioxidative, and hypolipidemic effects in anesthetized rabbits

Thgoal of this study was to evaluate the efficacy of the antioxidant olive constituent, oleuropein, on infarct size, oxidative damage, and the metabolic profile in rabbits subjected to ischemia. Oleuropein, 10 or 20 mg/(kg x d), was administered to 8 groups that consumed a normal or hypercholesterolemic diet for 6 wk or only the higher dose for 3 wk. Circulating levels of malondialdehyde, protein carbonyl, nitrite+nitrate, cholesterol, triglycerides, SOD activity, and the metabolic profile were measured using 1H NMR spectra. In rabbits that consumed the normal diet, the infarct size (percentage of infarct to risk areas) was reduced by the administration of 10 mg oleuropein/(kg x d) (16.1 +/- 2.9%) or 20 mg oleuropein/(kg x d) for 3 wk (21.7 +/- 2.2%) or for 6 wk (24.3 +/- 1.3%) compared with the control group (48.05 +/- 2.0%, P < 0.05). Only the higher dose of 20 mg/(kg x d) reduced the infarct size in hypercholesterolemic rabbits (34.7 +/- 4.4% for 6 wk and 34.8 +/- 6.1% for 3 wk) compared with the cholesterol-fed control group (52.8 +/- 2.4%, P < 0.05). Oleuropein decreased the plasma lipid peroxidation product and protein carbonyl concentrations compared with the control groups, in which these factors increased relative to baseline due to ischemia and reperfusion. Furthermore, in rabbits administered oleuropein, RBC superoxide dismutase activity did not change during ischemia and reperfusion. This activity was significantly higher than in both control groups in which it was reduced by ischemia and reperfusion compared with baseline. Treatment for 6 wk with both doses of oleuropein reduced total cholesterol and triglyceride concentrations. 1H NMR spectra revealed a different profile of glycolysis metabolites in the oleuropein-treated groups compared with the controls. Oleuropein, for 3 or 6 wk, reduced the infarct size, conferred strong antioxidant protection and reduced the circulating lipids. This is the first experimental study in vivo that suggests the possibility of using an olive constituent in the treatment of ischemia.

Therapeutic value of melatonin in an experimental model of liver injury and regeneration

Melatonin has marked antioxidant properties. The aim of the present study was to evaluate the therapeutic effect of melatonin on acute liver injury induced in rats by carbon tetrachloride (CCl4), allyl alcohol (AA) and their combination. A total of 108 male Wistar rats were divided into 12 experimental groups according to their treatment regimen (n = 5-10 rats in each group). Melatonin (100 mg/kg body weight, BW) was administered 6 hr (a) after a single dose of CCl4 (intragastrically 0. 66 mL/kg BW diluted 1:1 v/v with corn oil); (b) a single dose of AA (intraperitonealy, 0.62 mmol/kg BW 1:50 v/v in 0.9% saline solution); and (c) a combination of the above substances. Rats were sacrificed at 24 and 48 hr post-toxin administration and the therapeutic effect of melatonin was investigated by assessment of histopathological changes and lipid peroxidation alterations determined by measuring tissue malondialdehyde plus 4-hydroxy-nonenal (MDA + 4-HNE), plasma MDA and plasma levels of liver enzymes. The levels of a key antioxidant, glutathione (GSH), were measured in liver tissue homogenates. Hepatic necrosis was significantly reduced in the melatonin-treated rats 48 hr after administration of CCl4, AA and CCl4 + AA. The levels of hepatic enzymes in plasma were found to be significantly reduced at 24 and 48 hr in the CCl4 + AA treated rats after melatonin administration. Additionally, MDA and MDA + 4-HNE concentrations were significantly reduced at 24 and 48 hr time-points in all groups that received melatonin. GSH levels were decreased in liver after the toxic substances administration, whereas melatonin reversed this effect. In conclusion, a single dose of melatonin decreased hepatic injury induced by CCl4, AA and CCl4 + AA. The inhibition of the oxidative stress and therefore lipid peroxidation by melatonin in CCl4 and AA administered animals, may constitute the protective mechanism of melatonin against acute liver injury.

The Ca2+-sensitizer levosimendan improves oxidative damage, BNP and pro-inflammatory cytokine levels in patients with advanced decompensated heart failure in comparison to dobutamine

AIM

To investigate the effect of a new inotropic drug, levosimendan compared with dobutamine on levels of brain natriuretic peptide (BNP), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and malondialdehyde (MDA) in patients with severe decompensated heart failure.

METHODS AND RESULTS

Twenty-nine consecutive patients (22 males and 7 females), mean age 70.5+/-9.9 years, with decompensated heart failure on standard medical therapy, were randomised to receive either a 24 h infusion of levosimendan (n=15) or dobutamine (n=14). Blood samples were drawn at baseline, 48 h and 5 days post infusion. Levosimendan produced a significant reduction in BNP compared to baseline, at both 48 h (744.1+/-100 vs 1136.3+/-93.7 pg/ml, p=0.04) and 5 days (446+/-119.3 vs 1136.3+/-93.7 pg/ml, p=0.03), while IL-6 values decreased after 5 days (4.8+/-1.3 vs 8.6+/-1.5 pg/ml, p=0.01). MDA levels were significantly lower 5 days after levosimendan compared to baseline (2.3+/-0.2 vs 3+/-0.3 microM, p=0.01). TNF-alpha levels did not differ between the groups. The comparison of percentage alteration compared to baseline showed that BNP (-44.5+/-7.6% vs 4.8+/-18.7%, p=0.025), MDA (-21.8+/-5.1% vs 14.9+/-8.5%, p=0.001) and IL-6 (-38.8+/-12.5% vs 70.2+/-24%, p=0.001) levels were significantly lower in the levosimendan group 5 days after treatment compared to the dobutamine group.

CONCLUSIONS

Treatment with levosimendan in advanced decompensated heart failure exerts a beneficial hemodynamic, anti-inflammatory and antioxidant effect. These findings may give an insight into the favourable impact on mortality that levosimendan appears to have in published multicenter trials.