Biomarkers of free radical injury during spinal cord ischemia.

Plasma and urinary levels of 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha) were analysed at baseline and during the ischemia-reperfusion period in experimental spinal cord ischemia. A significant and immediate increase of 8-iso-PGF(2alpha) in plasma at the start and up to 60 min, and in the urine at 90-150 min following ischemia indicate an association of oxidative injury. The inflammatory response indicator 15-keto-dihydro-PGF(2alpha) in plasma increased significantly at the start and up to 60 min after ischemia. No such increase was seen in animals with no spinal cord ischemia. Thus, free radical mediated and cyclooxygenase catalysed products of arachidonic acid are increased during spinal cord ischemia as a consequence of oxidative injury and inflammation.     

Cardiopulmonary bypass as a cause of free radical-induced oxidative stress and enhanced blood-borne isoprostanes in humans

Free radicals are believed to be involved in postsurgery-related complications. We studied whether cardiopulmonary bypass (CPB) operation has any immediate impact on the initiation of oxidative stress and inflammatory response by measuring isoprostanes and prostaglandin F2alpha during and 24 h following CPB. The levels of 8-iso-PGF2alpha (a major F2-isoprostane and biomarker of oxidative stress) and 15-keto-dihydro-PGF2alpha (a major metabolite of PGF2alpha and biomarker of inflammatory response) were measured in frequently collected plasma samples before, during, and up to 24 h postsurgery in 21 patients. 8-Iso-PGF2alpha levels significantly increased within 3 min (p <.0001) and continued until 50 min (p <.0001) during CPB. On the contrary, no significant increase of inflammatory response indicator, 15-keto-dihydro-PGF2alpha was found during and up to 24 h postoperatively. These findings establish an increased free radical-induced oxidative stress activity rather than inflammatory response after CPB.     

F2-isoprostane, inflammation, cardiac function and oxygenation in the endotoxaemic pig

Prostaglandins are profoundly involved in endotoxaemic shock. Twenty pigs were given endotoxin at various doses (0.063-16 microg kg(-1) h(-1)). Three non-endotoxaemic pigs served as controls. Two eicosanoids were measured in plasma (8-iso-PGF(2alpha), a free radical-mediated lipid peroxidation product, and 15-keto-dihydro-PGF(2alpha) a major metabolite of COX activity) and evaluated against the pathophysiological responses that occur during endotoxaemic shock. Endotoxin mediates an increase in both 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha). An increase in the endotoxin dose induced significant log-linear responses in 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha). Oxidative injury correlated to the TNF-alpha, IL-6, reductions in cardiac performance and to oxygen delivery and utilisation. COX-mediated inflammatory responses correlated to TNF-alpha, IL-6 and to reductions in arterial oxygen tension. Thus, oxidative injury and COX-mediated inflammation play a central role in the manifestation of endotoxaemic shock. Furthermore, formation of these eicosanoids on endotoxin-mediated alterations in pulmonary hypertension, oxygen delivery and oxygen utilisation seems to be independent of the administered endotoxin dose.     

F(2)-isoprostane and prostaglandin F(2 alpha)metabolite excretion rate and day to day variation in healthy humans.

Isoprostanes are mainly formed in vivo by a non-enzymatic free radical catalysed oxidation of arachidonic acid. Studies have indicated that a major isoprostane, 8-iso-PGF(2 alpha)in plasma and urine is a reliable biomarker of oxidative stress. Prostaglandins are formed by enzymatic oxidation of arachidonic acid catalysed by cyclooxygenase (COX). 15-Keto-dihydro-PGF(2 alpha), a major metabolite of prostaglandin F(2 alpha)in plasma, and also found in urine, is considered to be a useful biomarker of inflammation. To investigate the excretion pattern and day to day variation of 8-iso-PGF(2 alpha)and 15-keto-dihydro-PGF(2 alpha)in healthy individuals, morning urine samples were collected from 13 volunteers on 10 successive days. The samples were analysed for free 8-iso-PGF(2 alpha)and 15-keto-dihydro-PGF(2 alpha)by radioimmunoassay. The mean excretion rate of 8-iso-PGF(2 alpha)was 0.27+/-0.11 nmol/mmol creatinine (mean+/-SD, n=13) and the coefficient of variation was 42% during the 10 days. The mean excretion rate of 15-keto-dihydro-PGF(2 alpha)was 0.46+/-0.19 nmol/mmol creatinine, giving a coefficient of variation of 41%. The mean values of 8-iso-PGF(2 alpha)were significantly correlated with the mean values of 15-keto-dihydro-PGF(2 alpha)(r=0.68, P=0.01). In conclusion, day to day biological variation in urinary excretion rate of 8-iso-PGF(2 alpha)and 15-keto-dihydro-PGF(2 alpha)should be taken into account in evaluating a clinical study unless a large increase or decrease of these parameters has been obtained.     

Oxidative stress and myocardial damage during elective percutaneous coronary interventions and coronary angiography. A comparison of blood-borne isoprostane and troponin release

The role of oxidative stress in clinical cardiology is still controversial. The aims of the present study were to examine if minor ischaemic episodes as may occur during elective percutaneous coronary intervention (PCI) induce oxidative stress and, eventually, if oxygen stress correlates with myocardial injury. Thirty eight and nine patients underwent PCI and diagnostic coronary angiography, respectively. Peripheral blood was sampled at different time points for plasma analyses of: 8-iso-PGF2alpha (free radical-mediated oxidative stress); 15-keto-dihydro-PGF2alpha (cyclooxygenase-mediated inflammation); troponin-T (myocardial injury); hsCRP, vitamin A and vitamin E; and, total antioxidants status (TAS). In both groups 8-iso-PGF2alpha increased transiently by approximately 80% (p < 0.001) during the procedure. There was a minor troponin-T release (p < 0.001) after PCI, but no correlation with 8-iso-PGF2alpha. Troponin-T did not increase after angiography. 15-keto-dihydro-PGF2alpha decreased by 50% after ended procedure, but increased by 100% after 24 h compared to baseline. hsCRP increased significantly (p < 0.001) from baseline to the next day in the PCI-group, but not in the angiography group. Vitamins and TAS decreased slightly after the procedures. It is concluded that a moderate oxidative stress was induced by both elective PCI and coronary angiography but that no correlation was found between oxidative stress and myocardial injury in this setting. This indicates that other mechanisms than ischaemia-reperfusion episodes caused an elevation in plasma isoprostane such like the injury at a vascular site mutual for both procedures. A secondary finding from the study was elevated markers of early inflammatory response, not only after PCI, but also after angiography.     

Oxidative stress and inflammatory response during and following coronary interventions for acute myocardial infarction

BACKGROUND: In acute myocardial infarction (AMI) treated with percutaneous coronary intervention (PCI), myocardial injury results from complex processes during both ischemia and reperfusion. Release of reactive oxygen species (ROS) may contribute to the accumulated myocardial damage. AIMS: To examine by frequent sampling of peripheral blood oxidative stress and early inflammation in patients undergoing primary PCI for AMI. Secondly, to assess whether a correlation exists between these parameters and the extent of myocardial damage. METHODS: Sixteen patients undergoing primary PCI within 6 h of AMI onset were included. Peripheral blood was sampled at start of procedure (t0) and repeatedly over 24 h following reperfusion. Main plasma analyses were: 8-iso-PGF2alpha (oxidative stress), 15-keto-dihydro-PGF2alpha (cyclooxygenase-mediated inflammation); and troponin-T (myocardial injury). Additional analyses included: total antioxidant status (TAS); vitamins; hsCRP and lipids. RESULTS: 8-Iso-PGF2alpha increased following restoration of blood flow, returned to t0 values after 3 h and was reduced below t0 the following day. TAS decreased significantly from t0 to the next day. There was no significant correlation between 8-iso-PGF2alpha and troponin T values. 15-Keto-dihydro-PGF2alpha was elevated during the first hour. There was a major rise in hsCRP after 24 h. CONCLUSION: Following reperfusion by primary PCI in AMI, oxidative stress and an inflammatory response are induced immediately. A rise in 8-iso-PGF2a during ischemia indicate that ROS generation may also take place during severely reduced coronary blood flow and hypoxia. No direct relationship between 8-iso-PGF2alpha or 15-keto-dihydro-PGF2alpha and troponin T was evident. The present study adds to the increasingly complex pathophysiological roles of ROS acting both as signal molecules and as mediators of tissue injury.     

Cardiopulmonary resuscitation in a rat model of chronic myocardial ischemia.

Our group has developed a rat model of cardiac arrest and cardiopulmonary resuscitation (CPR). However, the current rat model uses healthy adult animals. In an effort to more closely reproduce the event of cardiac arrest and CPR in humans with chronic coronary disease, a rat model of coronary artery constriction was investigated during cardiac arrest and CPR. Left coronary artery constriction was induced surgically in anesthetized, mechanically ventilated Sprague-Dawley rats. Echocardiography was used to measure global cardiac performance before surgery and 4 wk postsurgery. Coronary constriction provoked significant decreases in ejection fraction, increases in left ventricular end-diastolic volume, and increases left ventricular end-systolic volume at 4 wk postintervention, just before induction of ventricular fibrillation (VF). After 6 min of untreated VF, CPR was initiated on three groups: 1) coronary artery constriction group, 2) sham-operated group, and 3) control group (without preceding surgery). Defibrillation was attempted after 6 min of CPR. All the animals were resuscitated. Postresuscitation myocardial function as measured by rate of left ventricular pressure increase at 40 mmHg and the rate of left ventricular pressure decline was more significantly impaired and left ventricular end-diastolic pressure was greater in the coronary artery constriction group compared with the sham-operated group and the control group. There were no differences in the total shock energy required for successful resuscitation and duration of survival among the groups. In summary, this rat model of chronic myocardial ischemia was associated with ventricular remodeling and left ventricular myocardial dysfunction 4 wk postintervention and subsequently with severe postresuscitation myocardial dysfunction. This model would suggest further clinically relevant investigation on cardiac arrest and CPR.     

Cerebral Tissue Oxidative Ischemia-Reperfusion Injury in Connection with Experimental Cardiac Arrest and Cardiopulmonary Resuscitation: Effect of Mild Hypothermia and Methylene Blue

The present investigation is an expansion of previous studies which all share a basic experimental protocol of a porcine-induced cardiac arrest (CA) of 12 min followed by 8 min of cardiopulmonary resuscitation (CPR), different experimental treatments (immediate as well as postponed induced mild hypothermia and administration of much or less cool intravenous fluids), and a follow-up period of 3 h after which the animals were sacrificed. Another group of animals was studied according to the same protocol after 12-min CA and “standard CPR.” After death (within 1 min), the brains were harvested and frozen in liquid nitrogen awaiting analysis. Control brains of animals were collected in the same way after short periods of untreated CA (0 min, 5 min, and 15–30 min). Previous studies concerning chiefly neuropathological changes were now expanded with analyses of different tissue indicators (glutathione, luminol, leucigenin, malonialdehyde, and myeloperoxidase) of cerebral oxidative injury. The results indicate that a great part of oxidative injury occurs within the first 5 min after CA. Immediate cooling by administration of much intravenous fluid results in less cerebral oxidative injury compared to less intravenous fluid administration. A 30-min postponement of induction of hypothermia results in a cerebral oxidative injury comparable to that of “standard CPR” or the oxidative injury found after 5 min of untreated CA. Intravenous administration of methylene blue (MB) during and immediately after CPR in combination with postponed cooling resulted in no statistical difference in any of the indicators of oxidative injury, except myeloperoxidase, and glutathione, when this treatment was compared with the negative controls, i.e., animals subjected to anesthesia alone.     

Association between oxidative stress and bone mineral density

Free radicals have been shown to be involved in bone resorption in vitro and in rodents. We studied the effect of oxidative stress on bone mineral density (BMD) in 48 women and 53 men from a population-based study. The levels of 8-iso-PGF(2alpha) (a major F(2)-isoprostane and a biomarker of oxidative stress) and a control, 15-keto-dihydro-PGF(2alpha) (a biomarker of inflammatory response), were measured in urinary samples and their association with BMD and quantitative ultrasound (QUS) measurements were examined. In multivariate linear regression analyses, 8-iso-PGF(2alpha) levels were negatively associated with both BMD and QUS. In contrast, no association was found for 15-keto-dihydro-PGF(2alpha). Our findings establish a biochemical link between increased oxidative stress and reduced bone density and provide a rational for further studies investigating the role of pro- and antioxidants in osteoporosis.     

Time course and attenuation of ischaemia-reperfusion induced oxidative injury by propofol in human renal transplantation

Ischaemia-reperfusion injury resulting from interruption and restoration of blood flow might be related to free radical mediated oxidative stress and inflammation, and subsequently to post-surgery related complications. We studied the impact of renal transplantation on oxidative stress and inflammation by measuring F(2)-isoprostanes and prostaglandin F(2alpha), respectively, during transplantation and post-surgery. Additionally, due to earlier observations, two dissimilar anaesthetic agents (thiopentone and propofol) were compared to determine their antioxidative capacity rather than their anaesthetic properties. Blood samples were collected before, post-intubation, immediately, 30, 60,120, 240 min, and 12 and 24 h after reperfusion. Oxidative stress and inflammatory response were detected by measuring 8-iso-PGF(2alpha) (a major F(2)-isoprostane and a biomarker of oxidative stress) and 15-keto-dihydro-PGF(2alpha) (a major metabolite of PGF(2alpha) and a biomarker of COX-mediated inflammatory response), respectively. Reperfusion of the transplanted graft significantly increased plasma levels of 8-iso-PGF(2alpha). PGF(2alpha) metabolite levels, although elevated, did not reach statistical significance. In addition, significantly lower levels of 8-iso-PGF(2a) were observed in the propofol group compared to the thiopentone group. Together, these findings underline an augmented oxidative stress activity following an inflammatory response after human renal transplantation. Furthermore, propofol a well-known anaesthetic, counteracted oxidative stress by lowering the formation of a major F(2)-isoprostane.