Protective role of heme oxygenase-1 in the intestinal tissue injury in an experimental model of sepsis.

OBJECTIVE: The aim of this study was to examine the role of heme oxygenase-1 induction in the intestinal tissue injury in a rat model of sepsis. DESIGN: Randomized, masked, controlled animal study. SETTING: University-based animal research facility. SUBJECTS: Sprague-Dawley male rats, weighing 220-250 g (n = 126). INTERVENTIONS: Rats were injected with lipopolysaccharide (10 mg/kg) intraperitoneally. Another group of rats was injected with interleukin-6 (10 microg/kg) intravenously. In some rats, tin mesoporphyrin (1 micromol/kg) was administered intravenously 1 hr before lipopolysaccharide treatment. MEASUREMENTS AND MAIN RESULTS: Following lipopolysaccharide treatment, expression of heme oxygenase-1 and nonspecific delta-aminolevulinate synthase (ALAS-N), the rate-limiting enzymes of heme catabolism and biosynthesis, respectively, was examined in various regions of the intestine. Lipopolysaccharide treatment markedly increased heme oxygenase-1 messenger RNA and protein concentrations in the mucosal epithelial cells in the duodenum and the jejunum, whereas its expression in the ileum and the colon was hardly detectable and was not influenced by the treatment. ALAS-N messenger RNA was also more markedly increased in the duodenum, the jejunum, and the ileum than in the colon following lipopolysaccharide treatment. Interleukin-6 administration also induced heme oxygenase-1 and ALAS-N gene expression in a pattern similar to that following lipopolysaccharide treatment. In contrast to the marked heme oxygenase-1 expression in the upper intestine, lipopolysaccharide-induced mucosal injury and inflammation in the upper intestine were far less than observed in the lower intestine as judged both by tumor necrosis factor-alpha gene expression and by histologic analysis. Of note, inhibition of heme oxygenase activity by tin mesoporphyrin produced a significant tissue injury in the upper intestine of the lipopolysaccharide-treated animals. CONCLUSIONS: Intestinal heme oxygenase-1 and ALAS-N gene expression was regulated in a site-specific manner in a rat model of sepsis. Our findings also suggest that heme oxygenase-1 induction may play a fundamental role in protecting mucosal epithelial cells of the intestine from oxidative damages that occur in sepsis.

Relationship between adrenomedullin and vasopressin-aquaporin system under general anesthesia.

AIM: The roles of adrenomedullin (AM) in body fluid balance under general anesthesia were investigated. METHODS: Time course changes in plasma osmolality, AM, arginine vasopressin (AVP), and urinary aquaporin 2 (AQP2) in 17 patients undergoing abdominal surgery under general anesthesia were examined. RESULTS: Increases in plasma AM levels were observed in parallel with increases in the levels of urinary AQP2/creatinine (Cr) before induction and 90 and 180 min after initiation of anesthesia. Significant correlations between plasma AM and urinary AQP2/Cr (r = 0.62, p < 0.0001) as well as urinary AVP/Cr and AQP2/Cr (r = 0.60, p < 0.0001) were uncovered. Multivariate stepwise analysis identified plasma AM as the critical independent factor affecting urinary AQP2/Cr level. CONCLUSION: A novel correlation of AM and AQP2 which overlays an AVP-AQP2 system may play a key role in fluid homeostasis during general anesthesia.

Quantitative evaluation of the neuroprotective effects of hypothermia ranging from 34 degrees C to 31 degrees C on brain ischemia in gerbils and determination of the mechanism of neuroprotection.

OBJECTIVE: The present study was designed to determine whether the predominant factor responsible for neuroprotection of hypothermia ranging from 31 to 34 degrees C is prolongation of onset of ischemic depolarization or suppression of neuronal injury during ischemic depolarization and to quantitatively determine the neuroprotective effects of hypothermia of 34 degrees C and 31 degrees C. DESIGN: Prospective animal study. SETTING: A university research laboratory. SUBJECTS: Eighty-nine gerbils. INTERVENTIONS: Bilateral common carotid arteries were occluded for 3-20 mins. The brain temperature was set at 37 degrees C, 34 degrees C, or 31 degrees C before and during ischemic depolarization. MEASUREMENTS AND MAIN RESULTS: DC potentials were measured in the CA1 region, where histologic evaluation was performed 7 days later. Onset times of ischemic depolarization were 1.3 +/- 0.2, 1.6 +/- 0.4, and 2.4 +/- 0.7 mins at 37 degrees C, 34 degrees C, and 31 degrees C, respectively. The logistic regression curve demonstrated a close relationship between duration of ischemic depolarization and neuronal damage and showed a rightward shift by lowering the brain temperature. In the 37 degrees C, 34 degrees C, and 31 degrees C groups, the durations of ischemic depolarization causing 50% neuronal damage were estimated to be 8.0, 14.2, and 26.0 mins, respectively, and the ischemia times causing 50% neuronal damage were estimated to be 4.9, 8.1, and 14.2 mins, respectively. CONCLUSIONS: The onset of ischemic depolarization was prolonged in the 34 degrees C and 31 degrees C groups by only 0.3 and 1.1 mins, respectively, compared with that in the 37 degrees C group. Most of the neuroprotection by hypothermia was attributed to the suppression of neuronal injury during ischemic depolarization, suggesting that hypothermia has neuroprotective effects if it is initiated during the ischemic depolarization period. The results also indicate that the neuroprotective effect at 31 degrees C is about three times greater than that at 34 degrees C and that neuronal cells can withstand 2.9 times longer duration of ischemia at 31 degrees C than at 37 degrees C.

Evaluation of the safety of recent surgical microscopes equipped with xenon light sources.

Although recent surgical microscopes for neurosurgery are equipped with xenon light sources to obtain bright fields of vision, the safety of a xenon beam, which has strong energy intensity in a long ultraviolet light, for cortical neurons has not been evaluated. Cranial windows were made in the parietal bones of gerbils. The skull of each gerbil was covered with warmed saline (0.5 mm in depth) to maintain the brain temperature. Ultraviolet irradiation (365-nm) was performed for 30 minutes at energy levels of 9.6, 4.4, 1.3, and 0.3 mwatts/cm(2), and neuronal damage was observed in 90 +/- 4%, 42 +/- 23%, 9 +/- 6%, and 0 +/- 0% of pyramidal cells in the parietal cortex 24 hours later. With the use of a logistic regression curve, the energy level causing 50% of neuronal damage was estimated to be 5.4 mwatts/cm(2). By increasing the thickness of the saline layer over the skull surface (1 mm and 2 mm), neuronal damages were significantly attenuated (21 +/- 18% and 10 +/- 8%, respectively, 4.4 mwatts/cm(2). Because the highest energy levels of 365-nm ultraviolet rays emitted from surgical microscopes measured in the present study (0.379 mwatts/cm (2)) were much closer to the dose causing 0% damage than to the dose causing 9% damage, the risk of neuronal injury occurring during microsurgery could be negligible. However, care should be taken in patients who take medicine classified as photosensitizing agents, such as diphenylhydantoin, which are thought to concentrate ultraviolet energy. The use of saline over the cortical surface may be beneficial for reducing the detrimental effects of 365-nm ultraviolet light.

[A case of severe acute hyperkalemia during pre-anhepatic stage in living-related liver transplantation].

We reported a case of severe acute hyperkalemia during pre-anhepatic stage in living-related liver transplantation. The serum potassium concentration was elevated from 5.1 mmol.l-1 to 7.3 mmol.l-1 after hepatic artery ligation. Inspite of administration of diuretics, calcium and glucose-insulin, T wave on ECG was elevated and premature ventricular contractions occurred frequently. Finally, ventricular tachycardia occurred three times. After hepatic vein ligation, in anhepatic stage, serum potassium decreased gradually to 3.7 mmol.l-1 and arrhythmia disappeared. We consider that the main cause of hyperkalemia in this case is flowing out of potassium from the ischemic liver by surgical manipulation. It is necessary to take care of the change of serum potassium concentration not only in postreperfusion but also pre-anhepatic stage in living-related liver transplantation.

Tin chloride pretreatment prevents renal injury in rats with ischemic acute renal failure.

OBJECTIVE: To investigate whether tin chloride pretreatment ameliorates renal injury in rats with ischemic acute renal failure (IARF) by virtue of its kidney-specific heme oxygenase-1 induction. DESIGN: Randomized, masked, controlled animal study. SETTING: University-based animal research facility. SUBJECTS: Sprague-Dawley male rats, weighing 200-230 g (n = 359). INTERVENTIONS: Rats were injected with tin chloride subcutaneously, because subcutaneous administration of tin chloride is known to specifically and potently induce renal heme oxygenase activity in the rat. Anesthetized rats were subjected to bilateral flank incisions, and the right kidney was removed. Renal ischemia for 40 mins was performed by left renal microvascular clamping, followed by reflow of the blood. MEASUREMENTS AND MAIN RESULTS: Tin chloride treatment specifically induced heme oxygenase-1 mRNA and protein in the proximal tubular epithelial cells of the kidney without apparent cell injury in the rat. Tin chloride treatment before renal ischemia augmented the induction of heme oxygenase-1 in IARF rats at both transcriptional and protein concentrations in the renal epithelial cells compared with IARF animals. Tin chloride pretreatment, which decreased microsomal heme concentration, ameliorated the ischemic renal injury as judged by the significant decrease in serum creatinine and blood urea nitrogen concentrations and the lesser tubular epithelial cell injuries. In contrast, inhibition of heme oxygenase activity by treatment with tin mesoporphyrin, which increased microsomal heme concentration, abolished the beneficial effect of tin chloride pretreatment. CONCLUSION: These findings indicate that tin chloride pretreatment significantly ameliorates renal injury in rats with IARF by virtue of its specific heme oxygenase-1 induction in renal epithelial cells. These findings also suggest that heme oxygenase-1 induction plays an important role in protecting renal cells from oxidative damage caused by heme.

Dynamic changes in cortical NADH fluorescence and direct current potential in rat focal ischemia: relationship between propagation of recurrent depolarization and growth of the ischemic core.

Forty rats were subjected to 3 hours of focal ischemia by occluding the left middle cerebral and left common carotid arteries. The propagation of recurrent depolarization around the ischemic core was analyzed using direct-current potential and NADH (reduced nicotinamide adenine dinucleotide) fluorescence images by irradiating the parietal-temporal cortex with ultraviolet light. Based on histological evaluation at direct-current recording sites, the total time of depolarization causing 50% neuronal injury was estimated to be 18.2 minutes. The sites showing recurrent depolarizations resulted in 23 +/- 29% neuronal injury due to the short depolarization time, whereas the sites showing recurrent depolarizations and eventually persistent depolarization resulted in infarction. The NADH fluorescence images showed that recurrent depolarizations propagated along the margin of the ischemic core. In 85.9% of the recurrent depolarizations, the fluorescence disappeared without leaving any traces and did not affect the area of the ischemic core. However, in 47.5% of the animals, 14.1% of recurrent depolarizations merged with the ischemic core and increased the area by 6 +/- 4 mm(2). These findings suggest that recurrent depolarization increases the severity of neuronal injury but does not cause infarction by itself if persistent depolarization does not follow, and that the area of persistent depolarization is enlarged with 14.1% of recurrent depolarizations.

Temperature-dependent postextrasystolic potentiation and Ca(2+) recirculation fraction in canine hearts.

We have found that cardiac temperature proportionally changes O(2) cost of contractility, defined as O(2) consumption for myocardial total Ca(2+) handling normalized to contractility in terms of the end-systolic pressure-volume ratio (maximal elastance, E(max)), in the canine left ventricle (temperature sensitivity, Q(10) = 2). We have separately found that a decrease in the recirculation fraction (RF) of Ca(2+) within myocardial cells underlies an increased O(2) cost of E(max) in stunned hearts. We therefore hypothesized that a similar change in RF would underlie the Q(10) of O(2) cost of E(max). We tested this hypothesis by analyzing RF calculated from an exponential decay component of the transiently alternating postextrasystolic potentiation in the canine left ventricle. RF decreased from 0.7 to 0.5 as cardiac temperature increased from 33 to 38 degrees C with Q(10) of 0.5, reciprocal to that of O(2) cost of E(max). We conclude that Q(10) of ATP-consuming reactions involved in Ca(2+) handling and E(max) response to it could reasonably account for the reciprocal Q(10) of RF and O(2) cost of E(max).

Effect of anesthetics on the self-sustained oscillation in an artificial membrane induced by repetitive conformational change of DOPH molecules between hydrophilic and hydrophobic phases.

PURPOSE: The mechanism of anesthesia was approached from a study of an artificial excitable membrane that well reproduced the active electrical properties of the nerve membrane. METHODS: Self-sustained oscillations of the membrane potential in a model membrane in which dioleyl phosphate (DOPH) was infiltrated into the pores of a millipore filter were utilized to investigate the effect of volatile anesthetic agents on the repetitive conformational change of DOPH molecules between hydrophilic multibilayers and hydrophobic oil droplets, while this process was coupled with diffusion of K+ across the membrane placed between KCl aqueous solutions. RESULTS: The period of the self-sustained oscillations increased due to the addition of volatile anesthetics to the aqueous solutions, and there were critical values of concentrations of volatile anesthetics above which the self-sustained oscillations disappeared. CONCLUSION: The volatile anesthetic agents affected the hydrophobic oil droplets of the DOPH molecules and impeded their repetitive conformational change between the hydrophilic and hydrophobic phases, just as local anesthetics had been reported to do.