Exposure to sixty minutes of hyperoxia upregulates myocardial humanins in patients with coronary artery disease - a pilot study.

In experimental setting the concept of myocardial preconditioning by hyperoxia has been introduced and different intracellular protective mechanisms and their effects have been described. To study whether similar protective phenotype can be induced by hyperoxia also in humans, gene expression profile after hyperoxic exposure was analyzed. Adult patients were randomized to be ventilated with either FiO2 0.4 (n = 14) or 1.0 (n = 10) for 60 minutes before coronary artery bypass grafting. A tissue sample from the right atrial appendage was taken for gene analysis and expression profile analysis on genome wide level by RNA-seq analysis was applied. Exposure to > 96% oxygen for 60 minutes significantly changed the expression of 20 different genes, including upregulation of two different humanins - MTRNR2L2 and MTRNR2L8, and activated a "cell survival" network as detected by Ingenuity Pathway Analyses. We concluded that administration of > 96% oxygen for 1 hour changes gene expression in the myocardium of the patients with coronary artery disease and may enhance cell survival capability.

Measurement of mean arterial pressure: comparison of the Vasotrac monitor with the finger differential oscillometric device.

The Vasotrac monitor provides non-invasive near-continuous blood pressure monitoring and is designed to be an alternative to direct intra-arterial blood pressure (BP) measurement. As compared to radial artery invasive BP and upper arm non-invasive BP, Vasotrac readings have been found to have a good agreement with them. However, discrepancies have been reported when rapid changes in BP exist. In the present study we compared BP measured by the Vasotrac monitor on the radial artery with that recorded on the finger arteries by the differential oscillometric device allowing measurement on the beat-to-beat basis. Comparisons were performed on the mean arterial pressure (MAP) level. Special attention was paid to the signal conditioning before comparison of pressures of different temporal resolution. Altogether 383 paired MAP measurements were made in 14 healthy subjects. Based on all 383 paired measurements, the MAP values measured at the radial artery at rest were 4.8+/-6.0 mm Hg higher than those measured on fingers. The observed difference between the Vasotrac and differential oscillometric device can be explained by different measurement sites. This result is consistent with previous investigations, and the Vasotrac monitor can be considered to adequately track relatively rapid MAP changes on the radial artery. Attention should be paid to a proper signal conditioning before comparison of results obtained by different devices.

Exposure of rats to hyperoxia enhances relaxation of isolated aortic rings and reduces infarct size of isolated hearts.

Exposure of rats to hyperoxia before organ harvesting protected their isolated hearts against global ischaemia-reperfusion injury in a previous study. The present study investigates whether hyperoxia influences vasomotor function and regional ischaemia of the heart. Isolated rings of the thoracic aorta were obtained from rats immediately or 24 h after in vivo exposure to 60 min of hyperoxia (>95% O2), and the in vitro dose-response to phenylephrine (PHE), prostaglandin F2alpha (PGF2alpha) and endothelin-1 (ET-1), acetylcholine (Ach) and sodium nitroprusside (SNP) was assessed. Hyperoxia in vivo increased the relaxation of aortic rings to Ach and SNP, while it delayed contraction to PHE. The effect was more evident when the vessels were harvested immediately rather than 24 h after hyperoxic exposure. In separate experiments rat hearts were isolated immediately after hyperoxia, buffer-perfused, and subjected to 30 min of regional ischaemia and reperfused for 120 min. Infarct size was determined by triphenyl tetrazolium chloride staining. Hyperoxia significantly reduced infarct size. In normoxic controls 23.0 +/- 8.3% of the area at risk was infarcted, while in hyperoxic animals infarct size was 14.8 +/- 5.6% of the area at risk (P = 0.012). Exposure of rats to hyperoxia modifies the vasomotor response of isolated aortic rings, and reduces the infarct size of isolated rat heart. These novel aspects of hyperoxic treatment require further studies to explore the potential of its clinical application.

Cardioprotection by breathing hyperoxic gas-relation to oxygen concentration and exposure time in rats and mice.

OBJECTIVES: Breathing a hyperoxic gas (> or =95% O(2)) protects against ischaemia-reperfusion injury in rat and mouse hearts. The present study investigated how oxygen concentration and duration of hyperoxic exposure influenced cardioprotection, and whether hyperoxia might induce delayed cardioprotection (after 24 h). METHODS: Animals were kept in normal air or in a hyperoxic environment, and their hearts were isolated and Langendorff-perfused immediately or 24 h thereafter. Global ischaemia was induced for 25 min in rats and 40 min in mice, followed by 60 min of reperfusion. Infarct size was determined by triphenyl tetrazolium chloride staining. RESULTS: In rats exposure to > or =95, 80, and 60%, but not to 40% of oxygen immediately before heart isolation and perfusion improved postischaemic functional recovery. Eighty or more percent of oxygen also reduced infarct size. A preconditioning-like effect could be evoked by 60 or 180 min of hyperoxia, giving both immediate and delayed protection. In the mouse heart protection could be induced by pretreatment for 15 or 30, but not by 60 min with > or =95% oxygen. The protective effect of hyperoxia in mice could be evoked in the immediate model only. CONCLUSIONS: Hyperoxia protects the isolated rat and mouse heart against ischaemia-reperfusion injury, but some species-different responses exist. The protection depends on both oxygen concentration in inspired air, and duration of hyperoxic exposure.

Glucocorticoid pretreatment protects cardiac function and induces cardiac heat shock protein 72.

Acute administration of glucocortiocoids reduces inflammation. Increasing knowledge of the mechanisms of action indicate that pretreatment with glucocorticoids could have organ-protective effects. We investigated whether pretreatment with methylprednisolone (MP) protected the heart against ischemia-reperfusion dysfunction, and we hypothetized that this protection might be due to induction of the cardioprotective heat shock protein 72 (HSP72). Rats were given vehicle or MP-40 mg/kg im as a double injection starting either 24 or 120 h (5 days) before their hearts were excised for Langendorff perfusion (n = 6-11 hearts in each group). MP improved left ventricular function and coronary flow during reperfusion after 30 min of global ischemia and reduced infarct size. Cardiac HSP72 gradually increased in a 24-h time course after MP treatment, and the increase was sustained 5 days afterward (immunoblotting). HSP72 mRNA was either reduced or unchanged, indicating a posttranscriptional regulation. Pretreatment with hydrocortisone or dexamethasone (n = 7-8 hearts of each) similarily increased cardiac HSP72 24 h afterward. This paper demonstrates that glucocorticoids increase cardiac HSP72 and protect organ function against ischemia-reperfusion injury.

Pretreatment with methylprednisolone protects the isolated rat heart against ischaemic and oxidative damage.

Methylprednisolone (MP), a synthetic glucocorticoid, is widely used clinically and experimentally as acute antiinflammatory treatment. The molecular actions of MP indicate that pretreatment with this drug may be cardioprotective. We investigated if giving rats MP prior to excising their hearts for Langendorff-perfusion protected cardiac function against oxidative stress, and if this was mediated by increasing antioxidant defence or influencing myocardial nitric oxide synthase (NOS). Rats (n=6-11 in each group) were injected with MP (40mg/kg i.m.) or vehicle 24 and 12 h before Langendorff-perfusion with 30 min global ischaemia and 60 min reperfusion, or 10 min perfusion with 180 micromol/L hydrogen peroxide. Other hearts were exposed to 30 min global ischaemia 5 days after MP-injection. Additional hearts were sampled before, during, and after ischaemia for analyzing tissue activity of antioxidant enzymes. Tissue endothelial and inducible NOS (eNOS and iNOS) were investigated by immunoblotting and semiquantitative RT-PCR in a time-course after MP injection. Pretreatment with MP improved left ventricular function and increased coronary flow during postischaemic reperfusion, and this effect was sustained 5 days afterwards. When exposing hearts to hydrogen peroxide, MP improved coronary flow. Catalase, glutathione peroxidase, and oxidized glutathione were increased during reperfusion of MP-treated hearts compared to vehicle only. MP did not influence eNOS at protein or mRNA level. iNOS could not be detected by immunoblotting, indicating low cardiac enzyme content. Its mRNA initially increased the first hour after injection, thereafter decreased. In conclusions, pretreating rats with MP protects the heart against ischaemia-reperfusion dysfunction. This effect could be due to increase of tissue antioxidant activity during reperfusion. MP did not influence cardiac eNOS. mRNA for iNOS was influenced by MP, but the corresponding protein could not be detected.