Koji Sumikawa

Glutaredoxin Exerts an Antiapoptotic Effect by Regulating the Redox State of Akt

Glutaredoxin (GRX) is a small dithiol protein involved in various cellular functions, including the redox regulation of certain enzyme activities. GRX functions via a disulfide exchange reaction by utilizing the active site Cys-Pro-Tyr-Cys. Here we demonstrated that overexpression of GRX protected cells from hydrogen peroxide (H2O2)-induced apoptosis by regulating the redox state of Akt. Akt was transiently phosphorylated, dephosphorylated, and then degraded in cardiac H9c2 cells undergoing H2O2-induced apoptosis. Under stress, Akt underwent disulfide bond formation between Cys-297 and Cys-311 and dephosphorylation in accordance with an increased association with protein phosphatase 2A. Overexpression of GRX protected Akt from H2O2-induced oxidation and suppressed recruitment of protein phosphatase 2A to Akt, resulting in a sustained phosphorylation of Akt and inhibition of apoptosis. This effect was reversed by cadmium, an inhibitor of GRX. Furthermore an in vitro assay revealed that GRX reduced oxidized Akt in concert with glutathione, NADPH, and glutathione-disulfide reductase. Thus, GRX plays an important role in protecting cells from apoptosis by regulating the redox state of Akt.

Symptoms of spinal stenosis do not improve after epidural steroid injection.

OBJECTIVE This study was carried out to evaluate the therapeutic effect of epidural steroid injection on pseudoclaudication in patients with lumbar degenerative spinal canal stenosis. DESIGN Fifty-three patients who complained of pseudoclaudication of less than 20 m in walking distance were randomly divided into three groups. Group 1 (n = 16) underwent epidural injection with 8 ml of saline. Group 2 (n = 18) underwent epidural block with 8 ml of 1% mepivacaine. Group 3 (n = 19) underwent epidural block with a combination of 8 ml of 1% mepivacaine and 40 mg of methylprednisolone. The criteria of evaluation were as follows: excellent effect, > 100 m in walking distance; good effect, 20-100 m in walking distance; poor effect, <20 m in walking distance. RESULTS In group 1, the numbers of patients who showed a good effect were two (12.5%) after 1 week, one (6.5%) after 1 month, and one (6.5%) after 3 months. In group 2, the numbers of patients who showed a good or excellent result were 10 (55.5%) after 1 week, three (16.7%) after 1 month, and one (5.6%) after 3 months. In group 3, the numbers of patients who showed a good or excellent result were 12 (63.2%) after 1 week, three (15.8%) after 1 month, and one (5.3%) after 3 months. There was no significant difference in the effectiveness of treatment between group 2 and group 3 throughout the time course. CONCLUSION The results suggest that epidural steroid injection has no beneficial effect on the pseudoclaudication associated with spinal canal stenosis as compared with epidural block with a local anesthetic alone.

Effects of sevoflurane with and without nitrous oxide on human cerebral circulation : Transcranial Doppler study

Background This study was designed to evaluate the effects of sevoflurane with and without nitrous oxide on human middle cerebral artery (MCA) flow velocity, cerebrovascular carbon dioxide reactivity, and autoregulation compared with the awake state using transcranial Doppler ultrasonography. Methods In 14 patients, the time‐mean middle cerebral artery flow velocity (Vmca) was measured when the end‐tidal carbon dioxide level was approximately 30, 40, and 50 mmHg under the following conditions: (1) awake; (2) with 2% (1.2 MAC) sevoflurane; and (3) with 1.2 MAC sevoflurane‐60% nitrous oxide. In six other patients, the cerebrovascular autoregulation during anesthesia was determined using intravenous phenylephrine to increase blood pressure. Results Sevoflurane (1.2 MAC) significantly decreased Vmca compared with the awake value at each level of end‐tidal carbon dioxide, whereas 1.2 MAC sevoflurane‐60% nitrous oxide did not exert significant influence. The Vmca in normocapnic patients decreased from 69 cm/s to 55 cm/s with 1.2 MAC sevoflurane and then increased to 70 cm/s when nitrous oxide was added. Sevoflurane (1.2 MAC) with and without 60% nitrous oxide had a negligible effect on cerebrovascular carbon dioxide reactivity. A phenylephrine‐induced increase of mean arterial pressure did not influence Vmca during anesthesia. Conclusions Sevoflurane (1.2 MAC) reduced Vmca compared with the awake condition, whereas the addition of nitrous oxide caused Vmca to increase toward the values obtained in the awake condition. The cerebrovascular carbon dioxide reactivity and autoregulation were well maintained during 1.2 MAC sevoflurane with and without 60% nitrous oxide.

Dexmedetomidine Prevents Epinephrine-induced Arrhythmias Through Stimulation of Central α2 Adrenoceptors in Halothane-anesthetized Dogs

Since alpha 2-adrenergic agonists have important effects on the adrenergic system that have recently been applied to the anesthetic setting, we investigated the effect of stimulation of alpha 2 adrenoceptors on epinephrine-induced arrhythmias in halothane-anesthetized dogs. The arrhythmogenic threshold for epinephrine was determined during halothane anesthesia in the presence of dexmedetomidine, a selective alpha 2 agonist, and L-medetomidine, a stereoisomer of medetomidine that lacks alpha 2-agonist activity. Dexmedetomidine increased the arrhythmogenic threshold for epinephrine in a dose-dependent manner during halothane anesthesia. At the highest dose of dexmedetomidine, 0.5 microgram.kg-1.min-1, there was a three-fold increase in both the arrhythmogenic dose of epinephrine and the plasma epinephrine concentration that was reached at this dose. On the other hand, L-medetomidine over the same dose range did not effect the arrhythmogenic dose of epinephrine. Atipamezole, a central alpha 2 antagonist that crossed the blood-brain barrier, blocked the antiarrhythmic action of dexmedetomidine. L-659,066 a peripheral alpha 2 antagonist that does not penetrate the blood-brain barrier, did not affect the antiarrhythmic action of dexmedetomidine. Thus, dexmedetomidines antiarrhythmic effect on epinephrine-induced arrhythmias during halothane anesthesia appears to be mediated at least in part by stimulation of central alpha 2 adrenoceptors.

Isoflurane protects renal function against ischemia and reperfusion through inhibition of protein kinases, JNK and ERK.

Isoflurane has a pharmacological preconditioning effect against ischemia in the heart and brain, but whether this also occurs in the kidney is unclear. In this study, we investigated pharmacological preconditioning by isoflurane in the rat kidney. In the isoflurane preconditioning group (1.5% isoflurane for 20 min before renal ischemia) serum creatinine (1.2 ± 0.7 and 1.1 ± 0.2 mg/dL) and blood urea nitrogen (99 ± 29 and 187 ± 31 mg/dL) were significantly smaller at 24 and 48 h after reperfusion than in the nonpreconditioning group (creatinine; 2.4 ± 1.2 and 2.9 ± 0.9 mg/dL, urea; 62 ± 19 and 79 ± 20 mg/dL). We also investigated the intracellular signal transduction involved in isoflurane preconditioning in the kidney. The activities of the stress protein kinases, JNK and ERK but not p38, were significantly less in the kidneys of the preconditioning group than in those of the nonpreconditioning group (P < 0.05). We conclude that isoflurane has a preconditioning effect against renal ischemia/reperfusion injury when administered before ischemia. Inhibition of the protein kinases, JNK and ERK, might be involved in the mechanisms of isoflurane preconditioning.

Protective role of glutathione synthesis in response to oxidized low density lipoprotein in human vascular endothelial cells

Impairment of endothelial cells by oxidized low density lipoprotein (OxLDL) is believed to be the first step in atherogenesis. It is also believed that oxidative stress/antioxidant imbalance is involved in the cell damage by OxLDL. However, little is known about the interaction between OxLDL and antioxidants. In this study, we show that treatment of human vascular endothelial cells with OxLDL caused a gradual increase of glutathione (gamma-glutamylcysteinyl glycine, GSH) levels in 24 h. OxLDL increased the intracellular levels of reactive oxygen species (ROS) and stimulated the expression of gamma-glutamylcysteine synthetase (gamma-GCS), the rate-limiting enzyme for the GSH synthesis, the mitogen-activated protein kinase (MAPK) activity, and the AP-1-DNA binding activity. The luciferase activity of gamma-GCS promoter containing AP-1 site was activated by OxLDL. Collectively, OxLDL induces gamma-GCS expression mediated by AP-1 resulting in an increase of GSH levels. The MAPK activity stimulated by ROS may be involved in the activation of AP-1. The increase in GSH by OxLDL may afford cellular protection against OxLDL-induced oxidative stress.

Reactive oxygen species accelerate production of vascular endothelial growth factor by advanced glycation end products in RAW264.7 mouse macrophages.

Advanced glycation end products (AGEs) are believed to play an important role in the development of angiopathy in diabetes mellitus. Previous reports suggested a correlation between accumulation of AGEs and production of vascular endothelial growth factor (VEGF) in human diabetic retina. However, the mechanisms involved were not revealed. In this study, we investigated the transcriptional regulation of the expression of vascular endothelial growth factor (VEGF) by AGEs, and possible involvement of reactive oxygen species (ROS) in the induction. We employed an AGE of bovine serum albumin (BSA) prepared by an incubation of BSA with D-glucose for 40 weeks and N(epsilon)-(carboxymethyl)lysine (CML), a major AGE. The expression of VEGF was induced by CML-BSA in RAW264.7 mouse macrophage-like cells. CML-BSA stimulated the DNA-binding activity of activator protein-1 (AP-1). Promoter assay showed that the induction of VEGF was dependent on AP-1. The activity of Ras/Raf-1/MEK/ERK1/2 was involved in the CML-BSA-stimulated signaling pathways to activate the AP-1 transcription with a peak at 1 h. AGE-BSA also induced VEGF mediated by AP-1, however, there was a difference of effect between AGE-BSA and CML-BSA in the activation of AP-1. AGE-BSA-stimulated AP-1 activity showed a peak at 5 h, which paralleled the formation of ROS. Reduction of AGE-BSA with NaBH(4) or addition of vitamin E attenuated the AGE-BSA-stimulated signaling pathways leading to the same pattern as for CML-BSA-stimulated signals. These results suggest an important role for AGEs in stimulation of the development of angiogenesis observed in diabetic complications, and that ROS accelerates the AGE-stimulated VEGF expression.

Quantitative analysis of the relationship between sedation and resting energy expenditure in postoperative patients.

ObjectiveTo analyze quantitatively the relationship between sedation and resting energy expenditure or oxygen consumption in postoperative patients. DesignA prospective, clinical study. SettingAn eight-bed intensive care unit at a university hospital. PatientsThirty-two postoperative patients undergoing either esophagectomy or surgery of malignant tumors of the head and neck who required mechanical ventilation and sedation for ≥2 days postoperatively. InterventionsNone. Measurements and Main ResultsA total of 133 metabolic measurements were performed. Ramsay sedation scale (RSS), body temperature, and the dose of midazolam were evaluated at the time of the metabolic cart study. All patients received analgesia with buprenorphine at a fixed dose of 0.625 &mgr;g·kg−1·hr−1 continuously. Midazolam was used for induction and maintenance of intravenous sedation after admission to the intensive care unit. The initial dose was 0.04 mg·kg−1·hr−1 and was adjusted to achieve a desired depth of sedation at 3, 4, or 5 on the RSS every 4 hrs. The degree of sedation was classified into three states: light sedation (RSS 2–3; n = 49), moderate sedation (RSS 4; n = 39), and heavy sedation (RSS 5–6; n = 45). ResultsWith increasing the depth of sedation, oxygen consumption index (mL·min−1·m−2), resting energy expenditure index (REEI; kcal·day−1·m−2), and REE/basal energy expenditure (BEE) decreased significantly. Oxygen consumption index (mean ± sd), REEI, and REE/BEE were 151 ± 18, 1032 ± 120, and 1.29 ± 0.17 in the light sedation, 139 ± 22, 947 ± 143, and 1.20 ± 0.16 in the moderate sedation, and 125 ± 16, 865 ± 105, and 1.13 ± 0.12 in the heavy sedation, respectively. ConclusionAn increase in the depth of sedation progressively decreases in oxygen consumption index and REEI in postoperative patients.

The effects of propofol with and without ketamine on human cerebral blood flow velocity and CO2 response

UNLABELLED The combination of propofol and ketamine has been used for total IV anesthesia. This study was designed to clarify the effects of propofol-ketamine anesthesia on cerebral circulation by using transcranial Doppler ultrasonography. In Study 1, we examined the time course of time-mean middle cerebral artery blood flow velocity (Vmca) after ketamine (n = 10) or saline (n = 6) administration during propofol anesthesia. In Study 2, CO(2) responses were measured under the following conditions: awake (Group C, n = 7), propofol anesthesia (Group D, n = 7), and propofol-ketamine anesthesia (Group E, n = 8). Ketamine administration during propofol anesthesia administration did not affect Vmca, mean arterial pressure, or heart rate. Vmca under normocapnia in Groups D and E were 36 +/- 3 and 37 +/- 3 cm/s (mean +/- SE), respectively. The values were significantly lower than that of Group C (70 +/- 3 cm/s). The CO(2) response slopes of Groups D and E were significantly lower than that of Group C, although there was no significant difference between Groups D and E. These results suggest that ketamine does not influence Vmca or the cerebrovascular CO(2) response during propofol anesthesia administration, although the sample size in each group was small. IMPLICATIONS Our study suggests that ketamine does not influence middle cerebral artery blood flow velocity or the cerebrovascular CO(2) response assessed by transcranial Doppler ultrasonography during propofol anesthesia administration in patients without neurological complications.

Enhancement by propofol of epinephrine-induced arrhythmias in dogs

Although propofol is a widely used intravenous anesthetic, its effect on epinephrine-induced arrhythmias remains unknown. This study examined the possible interaction between propofol and epinephrine that might affect the induction of ventricular arrhythmias in dogs. The arrhythmogenic threshold of epinephrine was determined during anesthesia with halothane alone, propofol alone, etomidate alone, or etomidate plus varying doses of propofol. The arrhythmogenic dose and the corresponding plasma concentration of epinephrine during propofol anesthesia (blood propofol concentration 18.0 +/- 0.98 micrograms/ml) were 2.52 +/- 0.43 micrograms.kg-1.min-1 and 23.6 +/- 8.5 ng/ml, respectively. During halothane anesthesia (end-tidal 1.3 MAC), they were 2.66 +/- 0.21 micrograms.kg-1.min-1 and 35.7 +/- 1.9 ng/ml, respectively. During etomidate anesthesia, they were 9.67 +/- 1.06 micrograms.kg-1.min-1 and 205 +/- 27.5 ng/ml, respectively. The dose-effect relationship for propofol was examined during etomidate plus propofol anesthesia. Propofol reduced the arrhythmogenic plasma concentration of epinephrine in a concentration-dependent manner: at blood propofol concentrations of 2.33 +/- 0.46, 5.46 +/- 0.71, and 11.2 +/- 0.81 micrograms/ml, the corresponding plasma epinephrine concentrations were 182.6 +/- 52.5, 89.0 +/- 28.8, and 26.6 +/- 6.9 ng/ml, respectively. These results suggest that propofol enhances epinephrine-induced arrhythmias in a dose-dependent manner in dogs.