In vivo hyperoxic preconditioning protects against rat-heart ischemia/reperfusion injury by inhibiting mitochondrial permeability transition pore opening and cytochrome c release.

In vivo hyperoxic preconditioning (PC) has been shown to protect against ischemia/reperfusion (I/R) myocardial damage. Mitochondrial permeability transition pore (MPTP) opening is an important event in cardiomyocyte cell death occurring during I/R and therefore a possible target for cardioprotection. We tested the hypothesis that in vivo hyperoxic PC, obtained by mechanical ventilation of animals, could protect heart against I/R injury by inhibiting MPTP opening and cytochrome c release from mitochondria. Mechanically ventilated rats were first exposed to a short period of hyperoxia and isolated hearts were subsequently subjected to I/R in a Langendorff apparatus. Hyperoxic PC significantly improved the functional recovery of hearts on reperfusion, reduced the infarct size, and decreased necrotic damage as shown by the reduced release of lactate dehydrogenase. Mitochondria from hyperoxic PC hearts were less sensitive than mitochondria from reperfused heart to MPTP opening. In addition, hyperoxic PC prevented mitochondrial NAD(+) depletion, an indicator of MPTP opening, and cytochrome c release as well as cardiolipin oxidation/depletion associated with I/R. Together, these results demonstrate that hyperoxic PC protects against heart I/R injury by inhibiting MPTP opening and cytochrome c release. Thus, in vivo hyperoxic PC may represent a useful strategy for the treatment of cardiac I/R injury and could have potential applications in clinical practice.

Acute subdural intracranial hematoma after combined spinal-epidural analgesia in labor.

Intracranial subdural hematoma is a rare, but well-described complication of epidural and spinal anesthesia, as documented by more than a decade of publications. Non-postural headache and vomiting are warning signs. A headache lasting more than 5 days should arouse suspicion of intracranial hemorrhage, whether or not it is associated with the appearance of neurological signs or the deterioration of neurological status. Urgent cranial computed tomography can confirm the diagnosis of subdural hematoma, which has the potential to cause a dramatic cerebral herniation syndrome. A combination of spinal epidural (CSE) anesthesia and analgesia is commonly used to obtain pain relief during caesarean sections and labor. We report the case of a patient who suffered from severe neurological deterioration and manifested signs of brain herniation due to the development of an acute intracranial subdural hematoma after CSE analgesia for labor. An emergency craniotomy was performed to remove the subdural hematoma and the patient recovered well. Close observation of patients undergoing CSE analgesia or anesthesia complaining of prolonged non-postural headaches, with or without neurological symptoms, is recommended.

Protective effect of melatonin against mitochondrial dysfunction associated with cardiac ischemia- reperfusion: role of cardiolipin.

Reactive oxygen species (ROS) are considered an important factor in ischemia/reperfusion injury to cardiac myocytes. Mitochondrial respiration, mainly at the level of complex I and III, is an important source of ROS generation and hence a potential contributor of cardiac reperfusion injury. Appropriate antioxidant strategies could be particularly useful to limit this ROS generation and associated mitochondrial dysfunction. Melatonin has been shown to effectively protect against ischemic-reperfusion myocardial damage. The mechanism by which melatonin exerts this cardioprotective effect is not well established. In the present study we examined the effects of melatonin on various parameters of mitochondrial bioenergetics in a Langerdoff isolated perfused rat heart model. After isolation of mitochondria from control, ischemic-reperfused and melatonin-treated ischemic-reperfused rat heart, various bioenergetic parameters were evaluated such as rates of mitochondrial oxygen consumption, complex I and complex III activity, H2O2 production as well as the degree of lipid peroxidation, cardiolipin content, and cardiolipin oxidation. We found that reperfusion significantly altered all these mitochondrial parameters, while melatonin treatment had strong protective effect attenuating these alterations. This effect appears to be due, at least in part, to the preservation, by ROS attack, of the content and integrity of cardiolipin molecules which play a pivotal role in mitochondrial bioenergetics. Protection of mitochondrial dysfunction was associated with an improvement of post-ischemic hemodynamic function of the heart. Melatonin had also strong protective effect against oxidative alterations to complex I and III as well as to cardiolipin in isolated mitochondria.

Mitochondrial dysfunction associated with cardiac ischemia/reperfusion can be attenuated by oxygen tension control. Role of oxygen-free radicals and cardiolipin.

Reactive oxygen species (ROS) are considered an important factor in ischemia/reperfusion injury to cardiac myocites. Mitochondrial respiration is an important source of ROS generation and hence a potential contributor to cardiac reperfusion injury. Appropriate treatment strategy could be particularly useful to limit this ROS generation and associated mitochondrial dysfunction. In the present study, we examined the effect of lowering the oxygen tension, at the onset of the reperfusion, on various parameters of mitochondrial bioenergetics in rat heart tissue. After isolation of mitochondria from control, ischemic, normoxic and hypoxic reperfused rat heart, various bioenergetic parameters were evaluated such as rates of mitochondrial oxygen consumption, complex I and complex III activity, H2O2 production and in addition, the degree of lipid peroxidation, cardiolipin content and cardiolipin oxidation. We found that normoxic reperfusion significantly altered all these mitochondrial parameters, while hypoxic reperfusion had a protective effect attenuating these alterations. This effect appears to be due, at least in part, to a reduction of mitochondrial ROS generation with subsequent preservation of cardiolipin integrity, protection of mitochondrial function and improvement of post-ischemic hemodynamic function of the heart.

Hypoxic reperfusion limits functional impairment following cardioplegic arrest in isolated rat heart.

BACKGROUND: Reperfusion injury decreases both systolic contractility and diastolic compliance. Several studies indicate that the sustained decrease in diastolic compliance is mainly due to reactive oxygen intermediates (ROI) generation and calcium overload. METHODS: Male Wistar isolated rat hearts were divided into 2 groups (n=10 each), perfused according to Langendorff technique and exposed to 45 min of ischemia. Hearts belonging to the first group were reperfused with Krebs-Henseleit solution at 600 mmHg pO2; a 150 mmHg pO2 perfusate was utilized in the second group during the first minute and switched to 600 mmHg pO2 thereafter. Modifications in diastolic compliance and systolic contractility were assessed by changes in left ventricular end-diastolic (LVEDP) and developed pressure (LVDP), and first derivative of the pressure curve (dP/dt). RESULTS: Increase in LVEDP values, with respect to pre-ischemic data, were detected at 1, 5, 10, 20 min following reperfusion at 600 mmHg pO2, and were respectively: +40.17+/-18.61, +57.5+/-28.8, +59.8+/-30.5 and +63.2+/-34.1 mmHg. At 150 mmHg pO2 they were: +15.69+/-13.13, +22.4+/-14.1, +26.2+/-13.7 and +28.9+/-15.8, with a significant difference within the first 20 min (p<0.05). At high pO2 levels, LVDP decreased of 53.0+/-27.35, 60.5+/-22.6, 59.8+/-23.3 and 50.7+/-25.0 mmHg, versus 42.7+/-25.7, 38.0+/-29.5, 39.2+/-30.9 and 38.7+/-32.7 mmHg at lower pO2 (p=NS). The correspondent values of the dP/dt were 37.8+/-27.7, 30.1+/-17.2, 32.2+/-13.6 and 35.4+/-14.0% of pre-ischemic values at high pO2, versus 43.3+/-27.09, 51.9+/-25.1, 50.1+/-24.6 and 53.1+/-29.9% at lower pO2. Statistical significance was lower for LVDP and dP/dt than LVEDP. CONCLUSIONS: Diastolic functional impairment was partially reduced within the first 20 min following low pO2 reperfusion, but without any significant improvement of contractility.

Lipid peroxidation and alterations to oxidative metabolism in mitochondria isolated from rat heart subjected to ischemia and reperfusion.

Ischemia-reperfusion injury to cardiac myocytes involves membrane damage mediated by oxygen free radicals. Lipid peroxidation is considered a major mechanism of oxygen free radical toxicity in reperfused heart. Mitochondrial respiration is an important source of these reactive oxygen species and hence a potential contributor to reperfusion injury. We have examined the effects of ischemia (30 min) and ischemia followed by reperfusion (15 min) of rat hearts, on the kinetic parameters of cytochrome c oxidase, on the respiratory activities and on the phospholipid composition in isolated mitochondria. Mitochondrial content of malonyldialdheyde (MDA), an index of lipid peroxidation, was also measured. Reperfusion was accompanied by a significant increase in MDA production. Mitochondrial preparations from control, ischemic and reperfused rat heart had equivalent Km values for cytochrome c, although the maximal activity of the oxidase was 25 and 51% less in ischemic and reperfused mitochondria than that of controls. These changes in the cytochrome c oxidase activity were associated to parallel changes in state 3 mitochondrial respiration. The cytochrome aa3 content was practically the same in these three types of mitochondria. Alterations were found in the mitochondrial content of the major phospholipid classes, the most pronounced change occurring in the cardiolipin, the level that decreased by 28 and by 50% as function of ischemia and reperfusion, respectively. The lower cytochrome c oxidase activity in mitochondria from reperfused rat hearts could be almost completely restored to the level of control hearts by exogenously added cardiolipin, but not by other phospholipids nor by peroxidized cardiolipin. It is proposed that the reperfusion-induced decline in the mitochondrial cytochrome c oxidase activity can be ascribed, at least in part, to a loss of cardiolipin content, due to peroxidative attack of its unsaturated fatty acids by oxygen free radicals. These findings may provide an explanation for some of the factors that lead to myocardial reperfusion injury.