Protective effects of MnM2Py4P and Mn-salen against small bowel ischemia/reperfusion injury in rats using an in vivo and an ex vivo electron paramagnetic resonance technique with a spin probe

BACKGROUND

Reperfusion of ischemic tissues results in the formation of toxic reactive oxygen species (ROS), such as superoxide anion, hydroxyl radicals, hydroperoxide, and peroxynitrite. ROS are potent oxidizing agents, capable of damaging cellular membranes by lipid peroxidation. In the present study, we applied an in vivo electron paramagnetic resonance (EPR)/spin probe and an ex vivo EPR technique to provide direct evidence of ROS following experimentally induced small bowel ischemia/reperfusion (I/R) injury.

MATERIALS AND METHODS

We used a rat model of small bowel I/R injury to explore the possibility that MnM2Py4P or Mn-salen can prevent the accumulation of ROS species following experimentally induced I/R injury. We examined the ability of MnM2Py4P and Mn-salen to scavenge radicals in living Sprague-Dawley (SD) rats using an in vivo and an ex vivo EPR technique with a spin probe.

RESULTS

The CP decay rates in the MnM2Py4P- and Mn-salen-treated rats were significantly higher than those in the untreated rats and almost equal to those in sham group rats. There were no significant differences between the MnM2Py4P-treated group and the Mn-salen-treated group. Superoxide scavenging activities (SSA) in the MnM2Py4P- and EUK-8-treated group were higher than those in the untreated group and almost equal to the sham group.

CONCLUSION

The present study suggested that the protective effects of MnM2Py4P and Mn-salen against small bowel IR injury were mediated by the inhibition of O2, H2O2, and NO production.

Pigment Epithelium-derived Factor Inhibits Vascular Endothelial Growth Factor-induced Vascular Hyperpermeability Both In Vitro and In Vivo

Administration of pigment epithelium-derived factor (PEDF) inhibits advanced glycation end products-elicited retinal vascular hyperpermeability, as well as cold injury-induced brain oedema in rats. However, the underlying molecular mechanism by which PEDF blocks the hyperpermeability in vivo is not fully understood. This study investigated whether PEDF could inhibit vascular endothelial growth factor (VEGF)-induced vascular hyperpermeability both in vitro and in vivo. The Miles assay revealed that, after intradermal injection of VEGF in nude mice, simultaneous administration of PEDF inhibited vascular hyperpermeability in a dose-dependent manner. The in vitro permeability assay also showed that PEDF blocked the VEGF-induced barrier dysfunction in endothelial cells. These results demonstrated that PEDF could inhibit the VEGF-induced vascular hyperpermeability both in vitro and in vivo, and suggest that PEGF may be suitable to be considered as a novel therapeutic agent for various vasopermeable disorders in which VEGF is involved.

Measurement of Radical-Scavenging Ability in Small Bowel Ischemia/Reperfusion Injury in Rats Using an In Vivo and Ex Vivo Electron Paramagnetic Resonance Technique

Reperfusion of ischemic tissues results in the formation of toxic reactive oxygen species (ROS), such as superoxide anion, hydroxyl radicals, hydroperoxide, and peroxynitrite. ROS are potent oxidizing agents, fully capable of damaging cellular membranes by lipid peroxidation. In this study, we applied for the first time the in vivo electron paramagnetic resonance (EPR)/spin probe and ex vivo EPR technique to provide direct evidence of ROS following experimentally induced small bowel ischemia/reperfusion (I/R) injury. The decay rate (spin clearance rate) was determined over the first 3 minutes at 6 hours after reperfusion. Decay rates in rats subjected to I/R injury were lower than those in the sham group. Superoxide scavenging activity (SSA) in rats subjected to I/R injury was significantly lower than that in the sham group. In conclusion, this study demonstrated that it is possible to detect the accumulation of ROS following experimentally induced small intestine I/R injury using an in vivo and an ex vivo EPR technique with a spin probe.

Molecular mechanisms for vascular injury in the metabolic syndrome

The metabolic syndrome is strongly associated with insulin resistance and has been recognized as a cluster of risk factors for cardiovascular diseases such as visceral obesity, hypertension, diabetes and dyslipidemia. Recently, insulin resistance in the absence of overt diabetes or the metabolic syndrome itself has been shown to be associated with endothelial dysfunction, one of the initial steps in the process of atherosclerosis. In the present article we review the molecular mechanisms by which the metabolic syndrome causes endothelial dysfunction and subsequently promotes atherosclerosis. We also discuss promising therapeutic strategies that specifically target the mechanisms responsible for vascular alterations in the metabolic syndrome.

Efficacy of intermittent etidronate therapy for corticosteroid-induced osteoporosis in patients with diffuse connective tissue disease

We conducted a one-year comparative study of 25 patients with corticosteroid-induced osteoporosis associated with diffuse connective tissue disease. The patients were randomly divided into 2 groups: group A (9 patients), monotherapy with active vitamin D3 (V.D3); and group B (16 patients), combination therapy with V.D3 and etidronate. Four markers were employed: as an bonegenic marker, serum alkaline phosphatase (ALP); as a bone resorption marker, urinary deoxypyridinoline (DPD); as a bone salt minerals assay level, young adult mean (YAM); and bonefracture ratio. Results showed that: ALP decreased in both groups with no significant difference between groups; DPD increased significantly from baseline (p < 0.05) in group A, but it decreased significantly from baseline (p < 0.05) in group B, but again without a significant difference between groups; YAM resulted in no significant improvement in group A, but a significant improvement from baseline (p < 0.01) was shown in group B, with a significant difference between groups (p < 0.05); and a new spinal compression fracture ratio was extremely lower in group A than in group B. The findings indicated cyclical/intermittent etidronate therapy is effective in preventing corticosteroid-induced osteoporosis.

[Changes of arterial blood pressure and heart rate during induction of anesthesia with propofol--efficacy of propofol titration using bispectral index as an indicator]

Bispectral index (BIS) is a processed EEG parameter that measures the hypnotic effects of anesthetic and sedative agents on the brain. We studied whether propofol titration using BIS allows us to prevent hemodynamic changes during induction of anesthesia and endotracheal intubation. Thirty patients without hypertension and obesity were studied. In the titration group (n = 15), BIS was maintained at 40 during induction of anesthesia with propofol. In the bolus group, anesthesia was induced with a bolus infusion of propofol 2 mg.kg-1 (n = 15). Arterial blood pressure and heart rate were recorded before induction of anesthesia, during induction of anesthesia, immediately after, and 1 min, 2 min, and 3 min after intubation. Diastolic blood pressure and heart rate increased significantly after endotracheal intubation in both groups. Systolic blood pressure significantly increased immediately after intubation in the bolus group, but was unchanged in the titration group. These results suggest that BIS is useful to prevent significant increases in systolic blood pressure associated with endotracheal intubation during induction of anesthesia with propofol.

Glycolaldehyde-modified low density lipoprotein leads macrophages to foam cells via the macrophage scavenger receptor

It was shown that proteins modified with advanced glycation end products (AGE) are effectively endocytosed by macrophages or macrophage-derived cells in vitro, and immunohistochemical studies involving anti-AGE antibodies demonstrated the accumulation of AGE-modified proteins (AGE-proteins) in macrophage-derived foam cells in human atherosclerotic lesions in situ, suggesting the involvement of AGE-modified LDL in the atherogenic process in vivo. To examine this suggestion, LDL was modified with glycolaldehyde, a highly reactive intermediate of the Maillard reaction. Physicochemically, glycolaldehyde-modified LDL (GA-LDL) was characterized by increases in negative charge, fluorescence intensity, and reactivity to anti-AGE antibodies, properties highly similar to those of AGE-proteins. The cellular interaction of GA-LDL with mouse peritoneal macrophages showed that GA-LDL was specifically recognized and endocytosed, followed by lysosomal degradation. The endocytic uptake of GA-LDL by these cells was competitively inhibited by acetylated LDL (acetyl-LDL), and the endocytic degradation of acetyl-LDL was also competed for by GA-LDL. Furthermore, incubation of GA-LDL with these macrophages and Chinese hamster ovary cells overexpressing the macrophage scavenger receptor (MSR), but not with peritoneal macrophages from MSR-knockout mice, led to the intracellular accumulation of cholesteryl esters (CE). These results raised the possibility that AGE-modified LDL, if available in situ, is taken up by macrophages mainly via MSR and then contributes to foam cell formation in early atherosclerotic lesions.

Insulin enhances macrophage scavenger receptor-mediated endocytic uptake of advanced glycation end products

Hyperglycemia accelerates the formation and accumulation of advanced glycation end products (AGE) in plasma and tissue, which may cause diabetic vascular complications. We recently reported that scavenger receptors expressed by liver endothelial cells (LECs) dominantly mediate the endocytic uptake of AGE proteins from plasma, suggesting its potential role as an eliminating system for AGE proteins in vivo (Smedsrod, B., Melkko, J., Araki, N., Sano, H., and Horiuchi, S. (1997) Biochem. J. 322, 567-573). In the present study we examined the effects of insulin on macrophage scavenger receptor (MSR)-mediated endocytic uptake of AGE proteins. LECs expressing MSR showed an insulin-sensitive increase of endocytic uptake of AGE-bovine serum albumin (AGE-BSA). Next, RAW 264.7 cells expressing a high amount of MSR were overexpressed with human insulin receptor (HIR). Insulin caused a 3.7-fold increase in endocytic uptake of 125I-AGE-BSA by these cells. The effect of insulin was inhibited by wortmannin, a phosphatidylinositol-3-OH kinase (PI3 kinase) inhibitor. To examine at a molecular level the relationship between insulin signal and MSR function, Chinese hamster ovary (CHO) cells expressing a negligible level of MSR were cotransfected with both MSR and HIR. Insulin caused a 1.7-fold increase in the endocytic degradation of 125I-AGE-BSA by these cells, the effect of which was also inhibited by wortmannin and LY294002, another PI3 kinase inhibitor. Transfection of CHO cells overexpressing MSR with two HIR mutants, a kinase-deficient mutant, and another lacking the binding site for insulin receptor substrates (IRS) resulted in disappearance of the stimulatory effect of insulin on endocytic uptake of AGE proteins. The present results indicate that insulin may accelerate MSR-mediated endocytic uptake of AGE proteins through an IRS/PI3 kinase pathway.

Hydroxyl radical mediates N epsilon-(carboxymethyl)lysine formation from Amadori product

Recent studies demonstrated N epsilon-(carboxymethyl)lysine (CML) in several tissue proteins. Incubation of proteins with glucose leads through a Schiff base to Amadori products. Oxidative cleavage of Amadori products is considered as a major route to CML formation in vivo, whereas it is not known which reactive oxygen species (ROS) is involved. The present study is undertaken to identify such a ROS. We prepared heavily glycated human serum albumin (HSA) which contained a high level of Amadori products, but an undetectable level of CML. Incubation of glycated HSA with FeCl2, but not with H2O2, led to CML formation which was enhanced by H2O2, but inhibited by catalase or mannitol, whereas superoxide dismutase had no effect. Similar data were obtained by experiments using Boc-fructose-lysine as a model Amadori compound. These data indicate that hydroxyl radical generated by the reaction of Fe2+ with H2O2 mediates CML formation from Amadori compounds.

The receptor for advanced glycation end products mediates the chemotaxis of rabbit smooth muscle cells

Long-term incubation of proteins with glucose leads to advanced glycation end products (AGEs) with fluorescence and a brown color. We recently demonstrated immunologically the intracellular AGE accumulation in smooth muscle cell (SMC)-derived foam cells in advanced atherosclerotic lesions. To understand the mechanism of AGE accumulation in these foam cells, we have now characterized the interaction of AGE proteins with rabbit-cultured arterial SMCs. In experiments at 4 degrees C, 125I-labeled AGE-bovine serum albumin (AGE-BSA) showed a dose-dependent saturable binding to SMCs with an apparent dissociation constant (Kd) of 4.0 microg/ml. In experiments at 37 degrees C, AGE-BSA underwent receptor-mediated endocytosis and subsequent lysosomal degradation. The endocytic uptake of 125I-AGE-BSA was effectively inhibited by unlabeled AGE proteins such as AGE-BSA and AGE-hemoglobin, but not by acetylated LDL and oxidized LDL, well-known ligands for the macrophage scavenger receptor (MSR). Moreover, the binding of 125I-AGE-BSA to SMCs was affected neither by amphoterin, a ligand for one type of the AGE receptor, named RAGE, nor by 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole-hexanoic acid-BSA, a ligand for the other AGE receptors, p60 and p90. This indicates that the endocytic uptake of AGE proteins by SMCs is mediated by an AGE receptor distinct from MSR, RAGE, p60, and p90. To examine the functional role of this AGE receptor, the migratory effects of AGE-BSA on these SMCs were tested. Incubation with 1-50 microg/ml of AGE-BSA for 14 h resulted in significant dose-dependent cell migration. The AGE-BSA-induced SMC migration was chemotactic in nature and was significantly inhibited (approximately 80%) by an antibody against transforming growth factor-beta (TGF-beta), and the amount of TGF-beta secreted into the culture medium from SMC by AGE-BSA was sevenfold higher than that of control, indicating that TGF-beta is involved in the AGE-induced SMC chemotaxis. These data suggest that AGE may play a role in SMC migration in advanced atherosclerotic lesions.

Advanced glycation end products and their recognition by macrophage and macrophage-derived cells

Modification of proteins by long-term incubation with glucose leads to the formation of advanced glycation end products (AGEs). AGE proteins are taken up by macrophages via the AGE receptor, which is similar to the macrophage scavenger receptor (MSR). In the present study, we compared the ligand specificity of the AGE receptor with that of MSR by three different experiments. The endocytic uptake of 125I-acetyl-LDL by RAW cells was effectively inhibited by unlabeled AGE-bovine serum albumin (BSA), whereas the inhibitory effect of acetyl-LDL on 125I-AGE-BSA was partial. Polyanions showing an effective inhibition for endocytic uptake of AGE-BSA were not always inhibitory for endocytic degradation of acetyl-LDL. These data, together with those obtained by three-dimensional fluorescence-activated cell sorter analysis, indicate that AGE proteins are recognized by more than two receptors, of which MSR is at least one. Finally, we examined whether MSR could mediate the endocytic uptake of AGE proteins by Chinese hamster ovary cells overexpressing bovine type II MSR (CHO-SRII cells). 125I-AGE-BSA underwent endocytic degradation by CHO-SRII cells, and this was effectively inhibited by unlabeled acetyl-LDL. These results clearly show that MSR mediates the endocytic uptake of AGE proteins, suggesting a new role of MSR in biological recognition of AGE in vivo.

N (epsilon)-(carboxymethyl)lysine protein adduct is a major immunological epitope in proteins modified with advanced glycation end products of the Maillard reaction

Long-term incubation of proteins with glucose leads to the formation of advanced glycation end products (AGE). Recent immunological studies have suggested the potential role of AGE in atherosclerosis, aging, and diabetic complications. We previously prepared a monoclonal (6D12) as well as a polyclonal anti-AGE antibody and proposed the presence of a common AGE structure(s) that may act as a major immunochemical epitope [Horiuchi, S., Araki, N., & Morino, Y. (1991) J. Biol. Chem. 266, 7329-7332]. The purpose of the present study was to determine the major epitope. Amino acid analysis of AGE-proteins indicated that N(epsilon)-(carboxymethyl)lysine (CML) was a major modified lysine residue. Immunologic studies demonstrated the positive reaction of 6D12 not only to all CML-modified proteins tested, but also to BSA modified with several aldehydes known to generate a CML-protein adduct, and a linear correlation between the CML contents of CML-BSA and their immunoreactivity to 6D12 up to approximately 8 mol/mol of protein. Further experiments with CML analogs revealed that the epitope of 6D12 is a CML-protein adduct with an important carbonyl group. In contrast to 6D12, our polyclonal anti-AGE antibody showed a significant but much weaker immunoreactivity to CML-BSA, suggesting that the polyclonal antibody contains two populations, one reactive to CML (CML-PA) and the other unreactive to CML (Non-CML-PA). Non-CML-PA separated from CML-PA by CML-BSA affinity chromatography did not react with all CML-modified preparations, but retained its property to react commonly with AGE preparations obtained from proteins, lysine derivatives, and monoaminocarboxylic acids. Therefore, it is clear that a CML-protein adduct is a major immunological epitope in AGE structures, but there still exist other major epitope(s) expressed commonly in AGE-proteins.

Advanced glycation end products stimulate plasminogen activator activity via GM-CSF in RAW 264.7 cells

The effects of advanced glycation end products (AGE) on the plasminogen activator (PA) activity were investigated with murine macrophage cell line RAW 264.7 cells. AGE-bovine serum albumin (BSA) showed a dose-dependent induction for the urokinase-type PA (uPA) activity. The uPA induction by AGE-BSA was effectively suppressed by the antibody against granulocyte-macrophage colony-stimulating factor (GM-CSF). The uPA activity of these cells was also induced by ligands for the macrophage scavenger receptor (MSR). These data provide evidence that AGE-BSA stimulates the uPA activity via GM-CSF through MSR in RAW cells. These findings, taken together with a recent demonstration of endocytic uptake of AGE-proteins by MSR in vitro and the presence of AGE-proteins in atherosclerotic lesions, strongly suggest that the uPA induction by AGE-proteins via MSR plays an important role in human atherogenesis.

Echocardiographic assessment of left ventricular function and wall motion at high altitude in normal subjects

To understand the effects of high-altitude hypoxia on cardiac function and the change in cardiac function during high-altitude acclimatization, precise studies were first performed at greater than 5,000 m of altitude in Himalaya by 2-dimensional echocardiography. In addition to examining well-known indexes of cardiac function, the centerline method was used to assess regional wall motion, which has not been examined under conditions of high-altitude hypoxia. The subjects were 11 climbing members (aged 21 to 43 years) of the Kyoto University Medical Research Expedition of Xixabangma (8,027 m) in 1990. Examinations were performed at sea level, at the base camp (5,020 m), and twice at the advanced base camp (5,650 m). Heart rate, left ventricular (LV) end-diastolic volume, cardiac output, mean rate of circumferential fiber shortening, ejection fraction, % fractional shortening, and regional LV wall motion were measured. At high altitude, heart rate increased to 136% of the sea level value, but gradually decreased in the degree of increment at the early and late advanced base camp measurements. LV end-diastolic volume decreased significantly by 70%. At base camp there were significant increases in ejection fraction, mean rate of circumferential fiber shortening, and % fractional shortening, which showed little change during the long-term stay at high altitude. Regional wall motion at high altitude (measured by the center-line method) decreased at the septal wall and increased at the posterolateral wall. These results demonstrate that: (1) LV cardiac performance at high altitude is enhanced significantly in spite of reduced preload. After good acclimatization, cardiac performance remains augmented, but there is a tendency to decrease the degree of augmentation. (2) In regional LV wall motion, septal wall motion is impaired, but LV posterolateral wall motion shows a compensatory increase.

[Imaging diagnosis of hepatobiliary system and pancreas--computed tomography, ultrasound and angiography]

CT, US and angiography have become the most important examinations in the diagnosis of hepatobiliary and pancreatic diseases. Therefore updated and precise knowledge of these modalities are mandatory not only for the diagnosis but also for the interventional radiology in this field. General review on the advantages and limitations of these medical images are described.

Computed tomography of renal metastases

The CT manifestations of renal metastases from nonurinary tract carcinomas were evaluated in five autopsy-proven cases. Three cases resembled renal inflammatory disease or renal cysts. The wide variety of CT manifestations of renal metastases underscores the need to bear renal metastases in mind when renal abnormalities are observed in any case of advanced malignancy.