High-cholesterol diet in combination with hydroxypropyl-beta-cyclodextrin induces NASH-like disorders in the liver of rats

Non-alcoholic fatty liver disease (NAFLD) is a general term for fatty liver disease not caused by viruses or alcohol. Fibrotic hepatitis, cirrhosis, and hepatocellular carcinoma can develop. The recent increase in NAFLD incidence worldwide has stimulated drug development efforts. However, there is still no approved treatment. This may be due in part to the fact that non-alcoholic steatohepatitis (NASH) pathogenesis is very complex, and its mechanisms are not well understood. Studies with animals are very important for understanding the pathogenesis. Due to the close association between the establishment of human NASH pathology and metabolic syndrome, several animal models have been reported, especially in the context of overnutrition. In this study, we investigated the induction of NASH-like pathology by enhancing cholesterol absorption through treatment with hydroxypropyl-beta-cyclodextrin (CDX). Female Sprague-Dawley rats were fed a normal diet with normal water (control group); a high-fat (60 kcal%), cholesterol (1.25 %), and cholic acid (0.5 %) diet with normal water (HFCC group); or HFCC diet with 2 % CDX water (HFCC+CDX group) for 16 weeks. Compared to the control group, the HFCC and HFCC+CDX groups showed increased blood levels of total cholesterol, aspartate aminotransferase, and alanine aminotransferase. At autopsy, parameters related to hepatic lipid synthesis, oxidative stress, inflammation, and fibrosis were elevated, suggesting the development of NAFLD/NASH. Elevated levels of endoplasmic reticulum stress-related genes were evident in the HFCC+CDX group. In the novel rat model, excessive cholesterol intake and accelerated absorption contributed to NAFLD/NASH pathogenesis.

Unilateral nephrectomized SHR/NDmcr-cp rat shows a progressive decline of glomerular filtration with tubular interstitial lesions

In patients with diabetic kidney disease (DKD), the estimated glomerular filtration rate (eGFR) or creatinine clearance rate (Ccr) is always used as an index of decline in renal function. However, there are few animal models of DKD that could be used to evaluate renal function based on GFR or Ccr. For this reason, it is desirable to develop animal models to assess renal function, which could also be used for the evaluation of novel therapeutic agents for DKD. Therefore, we aimed to develop such animal model of DKD by using spontaneously hypertensive rat (SHR)/NDmcr-cp (cp/cp) rats with the characteristics of obese type 2 diabetes and metabolic syndrome. As a result, we have found that unilateral nephrectomy (UNx) caused a chronic Ccr decline, development of glomerular sclerosis, tubular lesions, and tubulointerstitial fibrosis, accompanied by renal anemia. Moreover, losartan-mixed diet suppressed the Ccr decline in UNx-performed SHR/NDmcr-cp rats (UNx-SHR/cp rats), with improvement in renal anemia and histopathological changes. These results suggest that UNx-SHR/cp rats could be used as a DKD model for evaluating the efficacy of therapeutic agents based on suppression of renal function decline.

A rotating cerium anode X-ray system allows visualization of intramural coronary vessels after cardiac stem cell therapy for myocardial infarction

Conventional angiography is insufficient for evaluating the therapeutic effect of cardiac regeneration therapy. A microangiographic X-ray system using a cerium anode was developed. Cerium has a characteristic X-ray with a peak at 34.6 keV, which allows visualization of tiny amounts of iodine. The performance of the cerium anode X-ray system was evaluated in two excised normal canine hearts and in excised ischemic canine hearts treated with c-kit-positive cardiac stem cells (5 canines) or without cells (5 control canines). In the normal canines, branches penetrating from the left anterior descending artery into the myocardium were visualized, down to third-order branches. In just the treated hearts treated with stem cells, small vessels characterized by irregular vessel walls were observed. The cerium anode X-ray system allowed visualization of microvessels in excised ischemic canine hearts, and may evaluate the effect of cardiac stem cell therapy.

Evaluation of Intracranial Microvessel Visualization in Mouse and Dog Models by Using a New Rotating Cerium Anode X-ray System

OBJECTIVE

Lacunar stroke may be caused by infarction of small perforating branches of the middle cerebral artery. We developed a microangiographic X-ray system using a cerium anode to evaluate the perforating branches.

METHODS

Iodine has K-edges at 33.2 kilo electron volts. Cerium yields a characteristic X-ray of 34.6 kilo electron volts, therefore, the cerium anode X-ray system could detect tiny amounts of contrast material. First, an X-ray chart was used to evaluate the resolution. Second, the brains of mice were dissected and irradiated. Third, the brains of dogs were excluded and irradiated. Fourth, iodine was perfused into the carotid artery of living dogs during brain imaging.

RESULTS

In the first experiment, the cerium anode X-ray system elicited 4.86 clear line pairs. In mice, the perforating branches of the middle cerebral artery could be visualized. The perforating branches were clearly observed in dog brains ex situ even through an acrylic plate, but not in conventional X-ray images. Iodine moving inside the perforating branches was visualized in dog brains in situ using the cerium anode X-ray system.

CONCLUSION

The cerium anode X-ray system allowed us to visualize the perforating branches of the middle cerebral artery in living dogs.

Altered blood flow in cerebral perforating arteries of rat models of diabetes: A synchrotron radiation microangiographic study toward clinical evaluation of white matter hyperintensities

AIM

As altered blood flow in the cerebral perforating arteries (PA) might be related to development of cerebral white matter hyperintensities, we examined whether the hemodynamic relationship of the PA and middle cerebral artery (MCA) is altered in rat models of diabetes, compared with normal rats and a rat model of sinoatrial denervation (blood pressure fluctuation model).

METHODS

We used microangiography with monochromatic synchrotron radiation to measure the diameters of the PA and MCA at 4.5 μm resolution in five groups of rats: (i) Long-Evans Tokushima Otsuka (LETO); (ii) Otsuka Long-Evans Tokushima Fatty (a model of type 2 diabetes with obesity); (iii) LETO with sinoaortic denervation (LETO + SAD); (iv) F344; and (v) F344 + streptozotocin (a model of type 1 diabetes).

RESULTS

Compared with LETO, Otsuka Long-Evans Tokushima Fatty rats showed a significant reduction in the diameter of both PA and MCA, though the PA/MCA diameter ratio was unchanged. In contrast, compared with LETO, LETO + SAD rats showed an increased MCA diameter, and the PA/MCA diameter ratio was decreased. Compared with F344 rats, the MCA diameter was increased in F344 + streptozotocin rats, and the PA/MCA diameter ratio was decreased. Scatter diagrams showed that the diameters of the PA and MCA were essentially independent of each other in the two types of diabetic models.

CONCLUSION

PA were consistently visualized at high resolution by means of microangiography using synchrotron radiation. The present results show that rat diabetic models exhibit changes in PA diameter and PA/MCA diameter ratio, which might be related to the development of diabetes-associated cerebral white matter hyperintensities.

Development of Fingertip Synchrotron Radiation Microangiography toward Clinical Prediction of Diabetic Microangiopathy

OBJECTIVES

The spatial resolution of conventional angiographic systems is not enough to predict diabetic microangiopathy in arterioles (20-200 µm).

METHODS

To determine whether fingertip synchrotron (SR) radiation microangiography has enough spatial resolution to quantitate arteriolar diameter changes, and whether an arteriolar paradoxical vasoconstriction is a characteristic observation for diabetic microangiopathy, diameter reduction as arteriolar branching and difference of the diameter changes induced by acetylcholine between control (n = 5) and diabetic rats (n = 5) were analyzed.

RESULTS

Fingertip SR microangiography visualized the arterioles with a diameter range of 30-300 µm and demonstrated vascular diameter reduction as branching with a fixed ratio (r = 0.93, P < 0.004 and r = 0.73, P < 0.001). A vasodilatory reaction was induced by acetylcholine in the control (142.4 ± 61.9 to 190.9 ± 73.5, P < 0.05, n = 25), in contrast, paradoxical vasoconstriction in diabetic rats (201.6 ± 83.0 to 16 0.4 ± 67.9, P < 0.05, n = 37). Histological angiopathy was noted only in the diabetic rats.

CONCLUSION

In conclusion, the fingertip SR microangiography is useful to predict diabetic micrangiopahty.

Visualization of microvessels by angiography using inverse-Compton scattering X-rays in animal models

The fundamental performance of microangiography has been evaluated using the S-band linac-based inverse-Compton scattering X-ray (iCSX) method to determine how many photons would be required to apply iCSX to human microangiography. ICSX is characterized by its quasi-monochromatic nature and small focus size which are fundamental requirements for microangiography. However, the current iCSX source does not have sufficient flux for microangiography in clinical settings. It was determined whether S-band compact linac-based iCSX can visualize small vessels of excised animal organs, and the amount of X-ray photons required for real time microangiography in clinical settings was estimated. The iCSX coupled with a high-gain avalanche rushing amorphous photoconductor camera could visualize a resolution chart with only a single iCSX pulse of ∼3 ps duration; the resolution was estimated to be ∼500 µm. The iCSX coupled with an X-ray cooled charge-coupled device image sensor camera visualized seventh-order vascular branches (80 µm in diameter) of a rabbit ear by accumulating the images for 5 and 30 min, corresponding to irradiation of 3000 and 18000 iCSX pulses, respectively. The S-band linac-based iCSX visualized microvessels by accumulating the images. An iCSX source with a photon number of 3.6 × 10(3)-5.4 × 10(4) times greater than that used in this study may enable visualizing microvessels of human fingertips even in clinical settings.

Carperitide induces coronary vasodilation and limits infarct size in canine ischemic hearts: role of NO

Carperitide is effective for heart failure (HF) owing to its diuretic and vasodilatory effects. This recombinant peptide may also have direct cardioprotective effects because carperitide reduces the severity of heart failure and limits infarct size. Because coronary vasodilation is an important cardioprotective treatment modality, we investigated whether carperitide increased coronary blood flow (CBF) and improved myocardial metabolic and contractile dysfunction during ischemia in canine hearts. We also tested whether carperitide is directly responsible for limiting the infarct size. We infused carperitide at 0.025-0.2 μg kg(-1) min(-1) into the canine coronary artery. A minimum dose of 0.1 μg kg(-1) min(-1) was required to obtain maximal vasodilation. To test the effects of carperitide on ischemic hearts, we reduced perfusion pressure in the left anterior descending coronary artery such that CBF decreased to one-third of the baseline value. At 10 min after carperitide was infused at a dose of 0.1 μg kg(-1) min(-1), we observed increases in CBF, fractional shortening (FS) and pH levels in coronary venous blood without concomitant increases in cardiac nitric oxide (NO) levels; these changes were attenuated using either the atrial natriuretic peptide receptor antagonist HS-142-1 or the NO synthase inhibitor L(ω)-nitroarginine methyl ester (L-NAME). Cyclic guanosine monophosphate (GMP) levels in the coronary artery were elevated in response to carperitide that also limited the infarct size after 90 min of ischemia and subsequent reperfusion. Again, these effects were blunted by L-NAME. Carperitide increases CBF, reduces myocardial contractile and metabolic dysfunction and limits infarct size. In addition, NO is necessary for carperitide-induced vasodilation and cardioprotection in ischemic hearts.

Control of higher-order structures of zinc chlorophyll coordination polymers

The higher-order structures of the zinc chlorophyll coordination polymers were controlled by the regiochemistry of the coordination sites.

Local VEGF administration enhances healing of colonic anastomoses in a rabbit model

BACKGROUND/AIMS

Many studies report the role of vascular endothelial growth factor (VEGF) in wound healing, but few describe local VEGF administration to the digestive tract. Leakage from colonic anastomoses, including those due to ischemia, represents a major complication causing increased mortality and morbidity. Angiogenesis is crucial to anastomotic healing and restoration of blood supply, and VEGF is a potent angiogenic factor showing improved healing in various models of reconstruction and anastomosis. Here, we examine the effects of local VEGF-A(165) administration on postoperative rabbit colon anastomosis.

METHODS

Two colotomies per animal were made in the sinistral colon on opposite sides of the mesentery. Randomly assigned VEGF (10 microg/0.1 ml) or saline (0.1 ml) was injected into the muscularis propria on both sides of each colonic anastomosis before closing the access laparotomy using single-layer sutures. On postoperative days 3, 4 and 7, the bursting pressure of partially healed anastomoses was measured. On postoperative day 4, anastomotic tissues were examined for the following: hydroxyproline; histopathologically for inflammatory infiltrate and tissue organization and immunohistochemically for capillary proliferation and density; vessel density of midzone collaterals around anastomoses by microangiography.

RESULTS

Compared to saline, VEGF administration significantly improved bursting pressure (p = 0.014, paired t test) and increased hydroxyproline (p = 0.027, paired t test) on postoperative day 4. Inflammatory cell infiltration and fibroblast proliferation were prominent, and submucosal capillary vascular counts were significantly higher for VEGF.

CONCLUSIONS

Administration of VEGF to colonic anastomosis accelerates wound healing and strengthens the anastomosis by increased angiogenesis.

Effect of systemic blood pressure on microcollateral circulation evaluated by real-time contrast echocardiography

BACKGROUND

In acute myocardial infarction, residual collateral-derived myocardial blood flow (CBF) within the ischemic area is one of the major determinants of infarct size. Management of systemic blood pressure (sBP) related to maintain collateral circulation is still difficult. The aim of this study was to reveal the influence of sBP on the rescue of area at risk by collateral circulation.

METHODS

Real-time myocardial contrast echocardiography just after the onset of complete occlusion of the left circumflex coronary artery was performed in collateral-rich open-chest dogs. The video intensity of the ischemic area was evaluated during the occlusion and the CBF (A x beta) was calculated from a replenishment curve: y = A (1 - e(-beta t)). To analyze the effect of sBP on the collateral circulation, sBP was altered by infusion of nitroglycerin or etilefrine hydrochloride. To evaluate the defect size (%DS), every end-systolic myocardial contrast echocardiography image after left circumflex coronary artery occlusion was converted into binary images using custom offline software.

RESULTS

The %DS increased and CBF slightly decreased at low sBP. The %DS decreased and CBF increased at high sBP. At excessively high sBP, %DS increased and CBF decreased again.

CONCLUSION

Real-time myocardial contrast echocardiography, which is a useful noninvasive method to evaluate the collateral perfusion quantitatively, has a crucial role in the decision of patient treatment and management strategy of acute myocardial infarction.

Role of Cu,Zn-SOD in the synthesis of endogenous vasodilator hydrogen peroxide during reactive hyperemia in mouse mesenteric microcirculation in vivo

We have recently demonstrated that endothelium-derived hydrogen peroxide (H2O2) is an endothelium-derived hyperpolarizing factor and that endothelial Cu/Zn-superoxide dismutase (SOD) plays an important role in the synthesis of endogenous H2O2 in both animals and humans. We examined whether SOD plays a role in the synthesis of endogenous H2O2 during in vivo reactive hyperemia (RH), an important regulatory mechanism. Mesenteric arterioles from wild-type and Cu,Zn-SOD(-/-) mice were continuously observed by a pencil-type charge-coupled device (CCD) intravital microscope during RH (reperfusion after 20 and 60 s of mesenteric artery occlusion) in the cyclooxygenase blockade under the following four conditions: control, catalase alone, N(G)-monomethyl-L-arginine (L-NMMA) alone, and L-NMMA + catalase. Vasodilatation during RH was significantly decreased by catalase or L-NMMA alone and was almost completely inhibited by L-NMMA + catalase in wild-type mice, whereas it was inhibited by L-NMMA and L-NMMA + catalase in the Cu,Zn-SOD(-/-) mice. RH-induced increase in blood flow after L-NMMA was significantly increased in the wild-type mice, whereas it was significantly reduced in the Cu,Zn-SOD(-/-) mice. In mesenteric arterioles of the Cu,Zn-SOD(-/-) mice, Tempol, an SOD mimetic, significantly increased the ACh-induced vasodilatation, and the enhancing effect of Tempol was decreased by catalase. Vascular H(2)O(2) production by fluorescent microscopy in mesenteric arterioles after RH was significantly increased in response to ACh in wild-type mice but markedly impaired in Cu,Zn-SOD(-/-) mice. Endothelial Cu,Zn-SOD plays an important role in the synthesis of endogenous H(2)O(2) that contributes to RH in mouse mesenteric smaller arterioles.

Edaravone preserves coronary microvascular endothelial function after ischemia/reperfusion on the beating canine heart in vivo

We examined whether edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), a free radical scavenger, exerts its protective effect on coronary microvessels after ischemia/reperfusion (I/R) in vivo. Ninety-minute coronary occlusion followed by reperfusion was performed in 16 open-chest dogs with and without edaravone administration. Coronary small artery (> or = 100 microm in size) and arteriolar (< 100 microm) vasodilation, in the presence of endothelium-dependent (acetylcholine) or -independent (papaverine) vasodilators, was directly observed using intravital microscopy before and after I/R. I/R impaired microvascular vasodilation in response to acetylcholine, whereas administration of edaravone preserved the response in microvessels of both sizes, but to a greater extent in the coronary small arteries. No significant changes were noted with papaverine administration. In the edaravone group, the fluorescent intensity from reactive oxygen species (ROS) was lower, whereas nitric oxide (NO) intensity was higher relative to controls in the microvessels of the ischemic area. In conclusion, edaravone preserves coronary microvascular endothelial function after I/R in vivo. These effects, which were NO-mediated, were attributed to the ROS scavenging properties of edaravone.

Important role of endogenous hydrogen peroxide in pacing-induced metabolic coronary vasodilation in dogs in vivo

OBJECTIVES

We examined whether endogenous hydrogen peroxide (H2O2) is involved in pacing-induced metabolic vasodilation in vivo.

BACKGROUND

We have previously demonstrated that endothelium-derived H2O2 is an endothelium-derived hyperpolarizing factor in canine coronary microcirculation in vivo. However, the role of endogenous H2O2 in metabolic coronary vasodilation in vivo remains to be examined.

METHODS

Canine subepicardial small coronary arteries (> or =100 microm) and arterioles (<100 microm) were continuously observed by a microscope under cyclooxygenase blockade (ibuprofen, 12.5 mg/kg intravenous [IV]) (n = 60). Experiments were performed during paired right ventricular pacing under the following 7 conditions: control, nitric oxide (NO) synthase inhibitor (N(G)-monomethyl-L-arginine [L-NMMA], 2 micromol/min for 20 min intracoronary [IC]), catalase (a decomposer of H2O2, 40,000 U/kg IV and 240,000 U/kg/min for 10 min IC), 8-sulfophenyltheophylline (SPT) (an adenosine receptor blocker, 25 mug/kg/min for 5 min IC), L-NMMA+catalase, L-NMMA+tetraethylammonium (TEA) (K(Ca)-channel blocker, 10 microg/kg/min for 10 min IC), and L-NMMA+catalase+8-SPT.

RESULTS

Cardiac tachypacing (60 to 120 beats/min) caused coronary vasodilation in both-sized arteries under control conditions in response to the increase in myocardial oxygen consumption. The metabolic coronary vasodilation was decreased after L-NMMA in subepicardial small arteries with an increased fluorescent H2O2 production compared with catalase group, whereas catalase decreased the vasodilation of arterioles with an increased fluorescent NO production compared with the L-NMMA group, and 8-SPT also decreased the vasodilation of arterioles. Furthermore, the metabolic coronary vasodilation was markedly attenuated after L-NMMA+catalase, L-NMMA+TEA, and L-NMMA+catalase+8-SPT in both-sized arteries.

CONCLUSIONS

These results indicate that endogenous H2O2 plays an important role in pacing-induced metabolic coronary vasodilation in vivo.

Retinoic acids acting through retinoid receptors protect hippocampal neurons from oxygen-glucose deprivation-mediated cell death by inhibition of c-jun-N-terminal kinase and p38 mitogen-activated protein kinase

Retinoic acids (RAs), including all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA), play fundamental roles in a variety of physiological events in vertebrates, through their specific nuclear receptors: retinoic acid receptor (RAR) and retinoid X receptor (RXR). Despite the physiological importance of RA, their functional significance under pathological conditions is not well understood. We examined the effect of ATRA on oxygen/glucose-deprivation/reperfusion (OGD/Rep)-induced neuronal damage in cultured rat hippocampal slices, and found that ATRA significantly reduced neuronal death. The cytoprotective effect of ATRA was observed not only in cornu ammonis (CA) 1 but also in CA2 and dentate gyrus (DG), and was attenuated by selective antagonists for RAR or RXR. By contrast, in the CA3 region, no protective effects of ATRA were observed. The OGD/Rep also increased phosphorylated forms of c-jun-N-terminal kinase (P-JNK) and p38 (P-p38) in hippocampus, and specific inhibitors for these kinases protected neurons. ATRA prevented the increases in P-JNK and P-p38 after OGD/Rep, as well as the decrease in NeuN and its shrinkage, all of which were inhibited by antagonists for RAR or RXR. These findings suggest that the ATRA signaling via retinoid receptors results in the inhibition of JNK and p38 activation, leading to the protection of neurons against OGD/Rep-induced damage in the rat hippocampus.

Prolonged transient acidosis during early reperfusion contributes to the cardioprotective effects of postconditioning

We have previously reported that the prolonged transient acidosis during early reperfusion mediates the cardioprotective effects in canine hearts. Recently, postconditioning has been shown to be one of the novel strategies to mediate cardioprotection. We tested the contribution of the prolonged transient acidosis to the cardioprotection of postconditioning. Open-chest anesthetized dogs subjected to 90-min occlusion of the left anterior descending coronary artery and 6-h reperfusion were divided into four groups: 1) control group; no intervention after reperfusion ( n = 6); 2) postconditioning (Postcon) group; four cycles of 1-min reperfusion and 1-min reocclusion ( n = 7); 3) Postcon + sodium bicarbonate (NaHCO3) group; four cycles of 1-min reperfusion and 1-min reocclusion with the administration of NaHCO3( n = 8); and 4) NaHCO3group; administration of NaHCO3without postconditioning ( n = 6). Infarct size, the area at risk (AAR), collateral blood flow during ischemia, and pH in coronary venous blood were measured. The phosphorylation of Akt and extracellular signal-regulated kinase (ERK) in ischemic myocardium was assessed by Western blot analysis. Systemic hemodynamic parameters, AAR, and collateral blood flow were not different among the four groups. Postconditioning induced prolonged transient acidosis during the early reperfusion phase. Administration of NaHCO3completely abolished the infarct size-limiting effects of postconditioning. Furthermore, the phosphorylation of Akt and ERK in ischemic myocardium induced by postconditioning was also blunted by the cotreatment of NaHCO3. In conclusion, postconditioning mediates its cardioprotective effects possibly via prolonged transient acidosis during the early reperfusion phase with the activation of Akt and ERK.

Erythropoietin Enhances Neovascularization of Ischemic Myocardium and Improves Left Ventricular Dysfunction After Myocardial Infarction in Dogs

OBJECTIVES

We investigated the effects of erythropoietin (EPO) on neovascularization and cardiac function after myocardial infarction (MI).

BACKGROUND

Erythropoietin exerts antiapoptotic effects and mobilizes endothelial progenitor cells (EPCs).

METHODS

We intravenously administered EPO (1,000 IU/kg) immediately [EPO(0) group], 6 h [EPO(6h) group], or 1 week [EPO(1wk) group] after the permanent ligation of the coronary artery in dogs. Control animals received saline immediately after the ligation.

RESULTS

The infarct size 6 h after MI was significantly smaller in the EPO(0) group than in the control group (61.5 +/- 6.0% vs. 22.9 +/- 2.2%). One week after MI, the circulating CD34-positive mononuclear cell numbers in both the EPO(0) and the EPO(6h) groups were significantly higher than in the control group. In the ischemic region, the capillary density and myocardial blood flow 4 weeks after MI was significantly higher in both the EPO(0) and the EPO(6h) groups than in the control group. Four weeks after MI, left ventricular (LV) ejection fraction in the EPO(6h) (48.6 +/- 1.9%) group was significantly higher than that in either the control (41.9 +/- 0.9%) or the EPO(1wk) (42.6 +/- 1.2%) group but significantly lower than that in the EPO(0) group (56.1 +/- 2.3%). The LV end-diastolic pressure 4 weeks after MI in both the EPO(0) and the EPO(6h) groups was significantly lower than either the control or the EPO(1wk) group. Hematologic parameters did not differ among the groups.

CONCLUSIONS

In addition to its acute infarct size-limiting effect, EPO enhances neovascularization, likely via EPC mobilization, and improves cardiac dysfunction in the chronic phase, although it has time-window limitations.

Granulocyte Colony-Stimulating Factor Mediates Cardioprotection Against Ischemia/Reperfusion Injury via Phosphatidylinositol-3-Kinase/Akt Pathway in Canine Hearts

PURPOSE

Recent studies suggest that G-CSF prevents cardiac remodeling following myocardial infarction (MI) likely through regeneration of the myocardium and coronary vessels. However, it remains unclear whether G-CSF administered at the onset of reperfusion prevents ischemia/reperfusion injury in the acute phase. We investigated acute effects of G-CSF on myocardial infarct size and the incidence of lethal arrhythmia and evaluated the involvement of the phosphatidylinositol-3 kinase (PI3K) in the in vivo canine models.

METHODS

In open-chest dogs, left anterior descending coronary artery (LAD) was occluded for 90 minutes followed by 6 hours of reperfusion. We intravenously administered G-CSF (0.33 micro/kg/min) for 30 minutes from the onset of reperfusion. Wortmannin, a PI3K inhibitor, was selectively administered into the LAD after the onset of reperfusion.

RESULTS

G-CSF significantly (p<0.05) reduced myocardial infarct size (38.7+/-4.3% to 15.7+/-5.3%) and the incidence of ventricular fibrillation during reperfusion periods (50% to 0%) compared with the control. G-CSF enhanced Akt phospholylation in ischemic canine myocardium. Wortmannin blunted both the infarct size-limiting and anti-arrhythmic effects of G-CSF. G-CSF did not change myeloperoxidase activity, a marker of neutrophil accumulation, in the infarcted myocardium.

CONCLUSION

An intravenous administration of G-CSF at the onset of reperfusion attenuates ischemia/reperfusion injury through PI3K/Akt pathway in the in vivo model. G-CSF administration can be a promising candidate for the adjunctive therapy for patients with acute myocardial infarction.

Screening of novel nuclear receptor agonists by a convenient reporter gene assay system using green fluorescent protein derivatives

Nuclear receptors represent a very good family of protein targets for the prevention and treatment of diverse diseases. In this study, we screened natural compounds and their derivatives, and discovered ligands for the retinoic acid receptors (RARs) and the farnesoid X receptor (FXR). In the reporter assay systems of nuclear receptors presented here, two fluorescent proteins, enhanced yellow fluorescent protein (EYFP) and enhanced cyan fluorescent protein (ECFP), were used for detection of a ligand-based induction and as an internal control, respectively. By optimizing the conditions (e.g., of hormone response elements and promoter genes for reporter plasmids), we established a battery of assay systems for ligands of RARs, retinoid X receptor (RXR) and FXR. The screening using the reporter assay system can be carried out without the addition of co-factors or substrates. As a result of screening of more than 140 compounds, several compounds were detected which activate RARs and/or FXR. Caffeic acid phenylethyl ester (CAPE), known as a component of propolis from honeybee hives, and other derivatives of caffeic acid up-regulated the expression of reporter gene for RARs. Grifolin and ginkgolic acids, which are non-steroidal skeleton compounds purified from mushroom or ginkgo leaves, up-regulated the expression of the reporter gene for FXR.

Cardioprotective role of endogenous hydrogen peroxide during ischemia-reperfusion injury in canine coronary microcirculation in vivo

We have recently demonstrated that endogenous H2O2 plays an important role in coronary autoregulation in vivo. However, the role of H2O2 during coronary ischemia-reperfusion (I/R) injury remains to be examined. In this study, we examined whether endogenous H2O2 also plays a protective role in coronary I/R injury in dogs in vivo. Canine subepicardial small coronary arteries (>or=100 microm) and arterioles (<100 microm) were continuously observed by an intravital microscope during coronary I/R (90/60 min) under cyclooxygenase blockade (n=50). Coronary vascular responses to endothelium-dependent vasodilators (ACh) were examined before and after I/R under the following seven conditions: control, nitric oxide (NO) synthase (NOS) inhibitor NG-monomethyl-L-arginine (L-NMMA), catalase (a decomposer of H2O2), 8-sulfophenyltheophylline (8-SPT, an adenosine receptor blocker), L-NMMA+catalase, L-NMMA+tetraethylammonium (TEA, an inhibitor of large-conductance Ca2+-sensitive potassium channels), and L-NMMA+catalase+8-SPT. Coronary I/R significantly impaired the coronary vasodilatation to ACh in both sized arteries (both P<0.01); L-NMMA reduced the small arterial vasodilatation (both P<0.01), whereas it increased (P<0.05) the ACh-induced coronary arteriolar vasodilatation associated with fluorescent H2O2 production after I/R. Catalase increased the small arterial vasodilatation (P<0.01) associated with fluorescent NO production and increased endothelial NOS expression, whereas it decreased the arteriolar response after I/R (P<0.01). L-NMMA+catalase, L-NMMA+TEA, or L-NMMA+catalase+8-SPT further decreased the coronary vasodilatation in both sized arteries (both, P<0.01). L-NMMA+catalase, L-NMMA+TEA, and L-NMMA+catalase+8-SPT significantly increased myocardial infarct area compared with the other four groups (control, L-NMMA, catalase, and 8-SPT; all, P<0.01). These results indicate that endogenous H2O2, in cooperation with NO, plays an important cardioprotective role in coronary I/R injury in vivo.

Blockade of histamine H2 receptors protects the heart against ischemia and reperfusion injury in dogs

We have previously reported that histamine H(2) blockers may be cardioprotective in patients with chronic heart failure. Since both endogenous histamine and histamine H(2) receptors are present in heart tissue, we tested the hypothesis that the blockade of histamine H(2) receptors mediates protection against reversible or irreversible ischemia and reperfusion injury. In open-chest dogs, the left anterior descending coronary artery was occluded for 90 minutes, followed by reperfusion for 6 hours. Administration of famotidine and cimetidine from 10 minutes before occlusion until after 1 hour of reperfusion reduced infarct size (17.0 +/- 4.1% and 17.8 +/- 2.9% vs. 36.9 +/- 5.9% of the solvent group, respectively) Famotidine administration only during the reperfusion period for 1 hour also attenuated infarct size (22.5 +/- 3.5%). There were no differences in either area at risk or collateral flow among the groups. In another set of experiments, we decreased coronary perfusion pressure in dogs so that the coronary blood flow decreased to 50% of the non-ischemic level. In such conditions, we observed the increases in histamine release compared with non-ischemic conditions (0.04 +/- 0.03 to 0.28 +/- 0.13 ng/ml, p < 0.05). Famotidine improved anaerobic myocardial metabolism gauged by both lactate extraction ratio and myocardial oxygen consumption. We conclude that the blockade of histamine H(2) receptors mediates improvements in the anaerobic myocardial metabolism, and thus protects against ischemia and reperfusion injury.

Triiodothyronine acutely increases blood flow in the ventricles and kidneys of anesthesized rabbits

Thyroid hormone (triiodothyronine [T(3)]) has various nongenomic effects, including alterations in glucose and fatty acid metabolism, augmentation of intracellular Ca(2+), enhancement of myocardial contractility, and vascular dilatation. However, its effect on regional blood flow remains to be established. We have measured the effect of T(3) on blood flow in major organs of anesthetized rabbits in vivo using the microsphere method. Under artificial respiration, nonradioactive microspheres (5 x 10(5)) labeled with barium were injected to measure blood flow at control level. Then, T(3) (50 microg/kg per milliliter) was administered and microspheres labeled with iodine (5 x 10(5)) were injected. The atria, ventricles, kidneys, and right upper limb were excised and their contents of microspheres were evaluated. Blood flow in the ventricles was significantly increased by T(3) (2.9 +/- 0.3 versus 3.4 +/- 0.3 mL/min per gram, vehicle versus T(3)). Similarly, blood flow in the kidneys was significantly higher after T(3) injection (4.3 +/- 0.5 versus 5.1 +/- 0.5 mL/min per, vehicle versus T(3)). The blood flow in the atria and skeletal muscles remained unchanged. These results indicate that the vasodilatory response to T(3) is not uniform and occurs preferentially in major organs such as cardiac ventricles and kidneys; this may be relevant to the T(3)-induced improvement of cardiac function.

A role of opening of mitochondrial ATP-sensitive potassium channels in the infarct size-limiting effect of ischemic preconditioning via activation of protein kinase C in the canine heart

The opening of mitochondrial ATP-sensitive K+ (mitoK(ATP)) channels triggers or mediates the infarct size (IS)-limiting effect of ischemic preconditioning (IP). Because ecto-5'-nucleotidase related to IP is activated by PKC, we tested whether the opening of mitoK(ATP) channels activates PKC and contributes to either activation of ecto-5'-nucleotidase or IS-limiting effect. In dogs, IP procedure decreased IS and activated ecto-5'-nucleotidase, both of which were mimicked by transient exposure to either cromakalim or diazoxide, and these effects were blunted by either GF109203X (a PKC inhibitor) or 5-hydroxydecanoate (a mitoK(ATP) channel blocker), but not by HMR-1098 (a surface sarcolenmal K(ATP) channel blocker). Either cromakalim or diazoxide activated both PKC and ecto-5'-nucleotidase, which was blunted by either GF109203X or 5-hydroxydecanoate, but not by HMR-1098. We concluded that the opening of mitoK(ATP) channels contributes to either activation of ecto-5'-nucleotidase or the infarct size-limiting effect via activation of PKC in canine hearts.

Opening of Ca2+-activated K+ channels is involved in ischemic preconditioning in canine hearts

Brief periods of ischemia that precede sustained ischemia can markedly reduce infarct size (IS), a phenomenon that is known as ischemic preconditioning (IP). Several investigators have shown that elevation of the intracellular Ca(2+) level ([Ca(2+)](i)) during the antecedent brief periods of ischemia triggers the cardioprotective mechanism of IP. Since opening of Ca(2+) activated K(+) (K(Ca)) channels is reported to be cardioprotective, we hypothesized that these channels may be involved in the cardioprotective mechanism of IP. In anesthetized open-chest dogs, myocardial ischemia/reperfusion injury was created by occlusion of the left anterior descending coronary artery (LAD) for 90 min followed by 6 h of reperfusion. First, we showed that the treatment with NS1619, a K(Ca) channel opener, reduced IS (IS in NS1619 group and control group, 19.8 +/- 5.5% vs. 45.4 +/- 3.5% of the area at risk, P < 0.05). Next, four cycles coronary occlusion for 5 min and reperfusion (IP) were performed before the 90-min occlusion with or without the infusion of potent K(Ca) channel inhibitors, iberiotoxin (IbTX) and charybdotoxin (ChTX). IP markedly reduced IS (IS in the IP group was 8.2 +/- 1.8%, P < 0.01 vs. control group). Infusion of either of K(Ca) channel blockers during IP blunted the IS-limiting effect of IP (IS in the IP + IbTX and IP + ChTX groups was 30.7 +/- 7.0% and 35.5 +/- 3.7%, respectively, P < 0.05, vs. IP group). However, the cardioprotective effect of IP was not blunted by the treatment with ChTX when treated only during reperfusion (14.0 +/- 4.1%). Thus, we conclude that the opening of K(Ca) channel is involved in early trigger phase of the molecular mechanism of IP.

Beneficial effect of hydroxyfasudil, a specific Rho-kinase inhibitor, on ischemia/reperfusion injury in canine coronary microcirculation in vivo

OBJECTIVES

We examined whether hydroxyfasudil, a specific Rho-kinase inhibitor, exerts cardioprotective effect on coronary ischemia/reperfusion (I/R) injury and, if so, whether nitric oxide (NO) is involved.

BACKGROUND

Recent studies have demonstrated that Rho-kinase is substantially involved in the pathogenesis of cardiovascular diseases; however, it remains to be examined whether it is also involved in ischemia/reperfusion (I/R) injury.

METHODS

Canine subepicardial small arteries (SA, >or=100 microm) and arterioles (A, <100 microm) were observed by a charge-coupled device intravital microscope during I/R. Coronary vascular responses to endothelium-dependent (acetylcholine, intracoronary [IC]) and -independent (papaverine, IC) vasodilators were examined after I/R under the following four conditions: control (n = 7), NO synthase inhibitor alone (N(G)-monomethl-L-arginine [L-NMMA], IC, n = 4), hydroxyfasudil alone (IC, n = 7), and hydroxyfasudil plus L-NMMA (n = 7).

RESULTS

Hydroxyfasudil significantly attenuated serotonin (IC)-induced vasoconstriction of SA (-7 +/- 1% vs. 2 +/- 1%, p < 0.01). Coronary I/R significantly impaired coronary vasodilation to acetylcholine after I/R (SA, p < 0.05; and A, p < 0.01 vs. before I/R) and L-NMMA further reduced the vasodilation, whereas hydroxyfasudil completely preserved the responses. The vasoconstriction by L-NMMA after I/R was significantly improved by hydroxyfasudil in both-sized arteries (both p < 0.01). Expression of endothelial nitric oxide synthase (eNOS) protein in the ischemic endocardium of left anterior descending coronary artery area (as determined by Western blotting) significantly decreased (79 +/- 4%) compared with the nonischemic endocardium of LCX area (100 +/- 7%), which was improved by hydroxyfasudil (105 +/- 6%, p < 0.01). Hydroxyfasudil significantly reduced myocardial infarct size, and hydroxyfasudil with L-NMMA also reduced the infarct size compared with L-NMMA alone.

CONCLUSIONS

Hydroxyfasudil exerts cardioprotective effects on coronary I/R injury in vivo, in which NO-mediated mechanism may be involved through preservation of eNOS expression.

Erythropoietin Just Before Reperfusion Reduces Both Lethal Arrhythmias and Infarct Size via the Phosphatidylinositol-3 Kinase-Dependent Pathway in Canine Hearts

Although recent studies suggest that erythropoietin (EPO) may reduce multiple features of the myocardial ischemia/reperfusion injury, the cellular mechanisms and the clinical implications of EPO-induced cardioprotection are still unclear. Thus, in this study, we clarified dose-dependent effects of EPO administered just before reperfusion on infarct size and the incidence of ventricular fibrillation and evaluated the involvement of the phosphatidylinositol-3 (PI3) kinase in the in vivo canine model. The canine left anterior descending coronary artery was occluded for 90 min followed by 6 h of reperfusion. A single intravenous administration of EPO just before reperfusion significantly reduced infarct size (high dose (1,000 IU/kg): 7.7 +/- 1.6%, low dose (100 IU/kg): 22.1 +/- 2.4%, control: 40.0 +/- 3.6%) in a dose-dependent manner. Furthermore, the high, but not low, dose of EPO administered as a single injection significantly reduced the incidence of ventricular fibrillation during reperfusion (high dose: 0%, low dose: 40.0%, control: 50.0%). An intracoronary administration of a PI3 kinase inhibitor, wortmannin, blunted the infarct size-limiting and anti-arrhythmic effects of EPO. Low and high doses of EPO equally induced Akt phosphorylation and decreased the equivalent number of TUNEL-positive cells in the ischemic myocardium of dogs. These effects of EPO were abolished by the treatment with wortmannin. In conclusion, EPO administered just before reperfusion reduced infarct size and the incidence of ventricular fibrillation via the PI3 kinase-dependent pathway in canine hearts. EPO administration can be a realistic strategy for the treatment of acute myocardial infarction.

Optimal windows of statin use for immediate infarct limitation: 5'-nucleotidase as another downstream molecule of phosphatidylinositol 3-kinase

BACKGROUND

Although statins are reported to have a cardioprotective effect, their immediate direct influence on ischemia-reperfusion injury and the underlying mechanisms remain obscure. We investigated these issues an in vivo canine model.

METHODS AND RESULTS

Dogs were subjected to coronary occlusion (90 minutes) and reperfusion (6 hours) immediately after injection of pravastatin (0.2, 2, or 10 mg/kg), pitavastatin (0.01, 0.1, or 0.5 mg/kg), or cerivastatin (0.5, 5, or 50 microg/kg). Then myocardial phosphatidylinositol 3-kinase (PI3-K) and 5'-nucleotidase activities were measured, as well as infarct size. After 15 minutes of reperfusion, pravastatin caused dose-dependent activation of Akt and ecto-5'-nucleotidase in the ischemic zone, and the effect was significant at higher doses. Pitavastatin also significantly increased these activities, and its optimal dose was within the clinical range, whereas cerivastatin caused activation at the lowest dose tested. In all cases, both Akt and ecto-5'-nucleotidase showed activation in parallel, and this activation was completely abolished by wortmannin, a PI3-K inhibitor. The magnitude of the infarct-limiting effect paralleled the increase in Akt and ecto-5'-nucleotidase activity and was blunted by administration of wortmannin, alpha,beta-methyleneadenosine-5'-diphosphate, or 8-sulfophenyltheophylline during reperfusion. Both collateral flow and the area at risk were comparable for all groups.

CONCLUSIONS

Activation of ecto-5'-nucleotidase after ischemia by PI3-K activation may be crucial for immediate infarct-size limitation by statins. There seems to be an optimal dose for each statin that is independent of its clinical cholesterol-lowering effect.

Protein kinase A as another mediator of ischemic preconditioning independent of protein kinase C

BACKGROUND

We and others have reported that transient accumulation of cyclic AMP (cAMP) in the myocardium during ischemic preconditioning (IP) limits infarct size independent of protein kinase C (PKC). Accumulation of cAMP activates protein kinase A (PKA), which has been demonstrated to cause reversible inhibition of RhoA and Rho-kinase. We investigated the involvement of PKA and Rho-kinase in the infarct limitation by IP.

METHODS AND RESULTS

Dogs were subjected to 90-minute ischemia and 6-hour reperfusion. We examined the effect on Rho-kinase activity during sustained ischemia and infarct size of (1) preischemic transient coronary occlusion (IP), (2) preischemic activation of PKA/PKC, (3) inhibition of PKA/PKC during IP, and (4) inhibition of Rho-kinase or actin cytoskeletal deactivation during myocardial ischemia. Either IP or dibutyryl-cAMP treatment activated PKA, which was dose-dependently inhibited by 2 PKA inhibitors (H89 and Rp-cAMP). IP and preischemic PKA activation substantially reduced infarct size, which was blunted by preischemic PKA inhibition. IP and preischemic PKA activation, but not PKC activation, caused a substantial decrease of Rho-kinase activation during sustained ischemia. These changes were cancelled by preischemic inhibition of PKA but not PKC. Furthermore, either Rho-kinase inhibition (hydroxyfasudil or Y27632) or actin cytoskeletal deactivation (cytochalasin-D) during sustained ischemia achieved the same infarct limitation as preischemic PKA activation without affecting systemic hemodynamic parameters, the area at risk, or collateral blood flow.

CONCLUSIONS

Transient preischemic activation of PKA reduces infarct size through Rho-kinase inhibition and actin cytoskeletal deactivation during sustained ischemia, implicating a novel mechanism for cardioprotection by ischemic preconditioning independent of PKC and a potential new therapeutic target.

Beta-adrenoceptor blocker carvedilol provides cardioprotection via an adenosine-dependent mechanism in ischemic canine hearts

BACKGROUND

Carvedilol is a beta-adrenoceptor blocker with a vasodilatory action that is more effective for the treatment of congestive heart failure than other beta-blockers. Recently, carvedilol has been reported to reduce oxidative stress, which may consequently reduce the deactivation of adenosine-producing enzymes and increase cardiac adenosine levels. Therefore, carvedilol may also have a protective effect on ischemia and reperfusion injury, because adenosine mediates cardioprotection in ischemic hearts.

METHODS AND RESULTS

In anesthetized dogs, the left anterior descending coronary artery was occluded for 90 minutes, followed by reperfusion for 6 hours. Carvedilol reduced the infarct size (15.0+/-2.8% versus 40.9+/-4.2% in controls), and this effect was completely reversed by the nonselective adenosine receptor antagonist 8-sulfophenyltheophylline (45.2+/-5.4%) or by an inhibitor of ecto-5'-nucleotidase (44.4+/-3.6%). There were no differences of either area at risk or collateral flow among the various groups. When the coronary perfusion pressure was reduced in other dogs so that coronary blood flow was decreased to 50% of the nonischemic level, carvedilol increased coronary blood flow (49.4+/-5.6 to 73.5+/-7.5 mL x 100 g(-1) x min(-1); P<0.05) and adenosine release (112.3+/-22.2 to 240.6+/-57.1 nmol/L; P<0.05) during coronary hypoperfusion. This increase of coronary blood flow was attenuated by either 8-sulfophenyltheophylline or superoxide dismutase. In human umbilical vein endothelial cells cultured with or without xanthine and xanthine oxidase, carvedilol caused an increase of ecto-5'-nucleotidase activity.

CONCLUSIONS

Carvedilol shows a cardioprotective effect against ischemia and/or reperfusion injury via adenosine-dependent mechanisms.

Methotrexate and MX-68, a New Derivative of Methotrexate, Limit Infarct Size via Adenosine-Dependent Mechanisms in Canine Hearts

Methotrexate, an anti-rheumatic agent, has recently been reported to show an anti-inflammatory action via ecto-5'-nucleotidase- and adenosine-dependent mechanisms. Because ecto-5'-nucleotidase contributes to the production of adenosine and adenosine has a potent cardioprotective effect against ischemia/reperfusion injury, we investigated whether methotrexate or MX-68 [N-1-((2,4-diamino-6-pteridinyl) methyl)-3,4-dihydro-2H-1,4-benzothiazine-7- carbonyl]-N-2- aminoadipic acid] could reduce infarct size via adenosine-dependent mechanisms. In beagle dogs, the left anterior descending coronary artery was perfused through a bypass tube, which was occluded for 90 minutes followed by 6 hours of reperfusion. The size of infarcts was assessed by TTC staining. MX-68 reduced infarct size compared with that in untreated dogs (13.7 +/- 1.9 versus 38.6 +/- 5.3%, P < 0.01). This effect was completely blunted by either the adenosine receptor antagonist 8-sulfophenyltheophylline (8-SPT) (45.0 +/- 4.6% and 46.8 +/- 5.8% in the 8-SPT and MX-68 + 8-SPT groups, respectively) or by the ecto-5'-nucleotidase inhibitoralpha,beta-methylenadenosine 5'-diphosphate (AMP-CP) (44.0 +/- 4.5% and 46.7 +/- 5.8% in the AMP-CP and MX-68 + AMP-CP groups, respectively). Methotrexate also reduced infarct size to a level comparable with that in the MX-68 group, and its effect was also blunted by 8-SPT. There were no significant differences of collateral blood flow or risk area between the groups. We conclude that methotrexate and its derivative (MX-68) both limit infarct size via adenosine-dependent mechanisms.

Ectoparasites of the Pallas squirrel, Callosciurus erythraeus, introduced to Japan

The squirrel Callosciurus erythraeus (Pallas) (Rodentia: Sciuridae) was intentionally introduced to Japan in 1935 and has become established throughout much of the country. Although they live mainly in forests, Pallas squirrels come into gardens and are frequently fed by people or kept as pets, so their ectoparasites could be of potential medical as well as veterinary importance. During 2001-2003 we conducted the first ectoparasite survey of Pallas squirrels in Japan. From 105 C. erythraeus captured in Kamakura District of Kanagawa Prefecture on Honshu Island, three types of ectoparasite were found: 52 specimens of the sucking louse Neohaematopinus callosciuri Johnson (Anoplura: Haematopinidae), 26 fleas Ceratophyllus (Monopsyllus) anisus Rothschild (Siphonaptera: Ceratophyllidae) and four nymphs of the tick Haemaphysalis flava Neumann (Acari: Ixodidae) on 22, 13 and one squirrels, respectively. Evidently in Japan C. erythraeus carries relatively few ectoparasite species; this may be a contributory factor to their invasive success. Further investigations are needed to assess risks of zoonotic transmission of plague or murine typhus by C. anisus, of louse-borne typhus by N. callosciuri and of tularaemia and especially Japanese spotted fever (Rickettsia japonica) by H. flava.

Inhibition of matrix metalloproteinase-2 activity by siderophores of Pseudomonas species

To obtain a novel matrix metalloproteinase (MMP) inhibitor produced by bacteria, we have focused on the chelating activity of siderophores. Several siderophore-producing bacteria were isolated from soil using chrome azurol S agar plates and then the effect of siderophores on MMP-2 activity was assayed by gelatin zymography. The results showed that partially purified siderophores from ten isolated strains inhibited MMP-2 activity. Among these strains, two were non-fluorescent and eight were fluorescent Pseudomonas species. From these eight strains, pyoverdine-type siderophores were detected. The Zn(2+)-chelating activity of these siderophores correlated with the inhibition of MMP-2 activity. Therefore, it is considered that siderophores such as pyoverdines inhibit MMP-2 activity by chelating Zn(2+) on the active site of MMP-2.

Biodegradable gelatin hydrogel potentiates the angiogenic effect of fibroblast growth factor 4 plasmid in rabbit hindlimb ischemia

OBJECTIVES

We investigated the potentiation of gene therapy using fibroblast growth factor 4 (FGF4)-gene by combining plasmid deoxyribonucleic acid (DNA) with biodegradable gelatin hydrogel (GHG).

BACKGROUND

Virus vectors transfer genes efficiently but are biohazardous, whereas naked DNA is safer but less efficient. Deoxyribonucleic acid charges negatively; GHG has a positively charged structure and is biodegradable and implantable; FGF4 has an angiogenic ability.

METHODS

The GHG-DNA complex was injected into the hindlimb muscle (63 mice and 55 rabbits). Gene degradation was evaluated by using (125)I-labeled GHG-DNA complex in mice. Transfection efficiency was evaluated with reverse-transcription nested polymerase chain reaction and X-Gal histostaining. The therapeutic effects of GHG-FGF4-gene complex (GHG-FGF4) were evaluated in rabbits with hindlimb ischemia.

RESULTS

Gelatin hydrogel maintained plasmid in its structure, extending gene degradation temporally until 28 days after intramuscular delivery, and improving transfection efficiency. Four weeks after gene transfer, hindlimb muscle necrosis was ameliorated more markedly in the GHG-FGF4 group than in the naked FGF4-gene and GHG-beta-galactosidase (control) groups (p < 0.05, Kruskal-Wallis test). Synchrotron radiation microangiography (spatial resolution, 20 microm) and flow determination with microspheres confirmed significant vascular responsiveness to adenosine administration in the GHG-FGF4 group, but not in the naked FGF4-gene and the control.

CONCLUSIONS

The GHG-FGF4 complex promoted angiogenesis and blood flow regulation of the newly developed vessels possibly by extending gene degradation and improving transfection efficiency without the biohazard associated with viral vectors.

Inhomogeneous vasodilatory responses of rat tail arteries to heat stress: evaluation by synchrotron radiation microangiography

Tail blood flow is crucial for dissipating body heat in rats. Angiographies are convenient tools to evaluate tail circulation. However, conventional angiographies do not have sufficient sensitivity or spatial resolution for small vessels. Recently, we developed a novel microangiographic system using monochromatic synchrotron radiation and a high-definition video camera system. Here, we report an evaluation of rat tail circulation under heat stress using the synchrotron radiation microangiographic system. We performed an experiment using the microangiography of the caudal artery before and after heating up WKAH/HkmSlc rats to rectal temperature of 39 degrees C. The images were digitized and temporal subtraction was performed, and the diameters of caudal arteries were evaluated. After heating, the medial caudal artery was markedly dilated (320 +/- 53 to 853 +/- 243 micro m in diameter, p<0.001), while no significant change was observed in the lateral caudal arteries (139 +/- 42 to 167 +/- 73 micro m) and segmental anastomosing vessels. The heat stress allowed for visualization of the superficial caudal arteries with a diameter of approximately 60 micro m, not visible prior to heating. Thus, synchrotron radiation microangiography demonstrated that the rat tail possessed dual sets of arteries; one set was highly sensitive to heat-induced vasodilation (medial caudal artery and superficial caudal arteries) and the other set was less sensitive (lateral caudal arteries and segmental anastomosing vessels).

Amelioration of ischemia- and reperfusion-induced myocardial injury by the selective estrogen receptor modulator, raloxifene, in the canine heart

OBJECTIVES

We sought to investigate whether raloxifene reduces ischemia-reperfusion injury and what mechanisms are involved in the cardioprotective effects.

BACKGROUND

Estradiol-17-beta reduces myocardial infarct size in ischemia-reperfusion injury. Raloxifene, a selective estrogen receptor modulator, demonstrates immediate coronary artery vasorelaxing effects.

METHODS

The myocardial ischemia-reperfusion model included anesthetized open-chest dogs after 90-min occlusion of the left anterior descending coronary artery (LAD) and subsequent 6-h reperfusion. Raloxifene and/or other drugs were infused into the LAD from 10 min before coronary occlusion to 1 h after reperfusion without an occlusion period.

RESULTS

Infarct size was reduced in the raloxifene (5 microg/kg per min) group compared with the control group (7.2 +/- 2.5% vs. 40.9 +/- 3.9% of the area at risk, p < 0.01). Either N(G)-nitro-L-arginine methyl ester (L-NAME), the inhibitor of nitric oxide (NO) synthase, or charybdotoxin, the blocker of Ca(2+)-activated K+ (K(Ca)) channels, partially attenuated the infarct size-limiting effect, and both of them completely abolished the effect. The incidence of ventricular fibrillation was also less in the raloxifene group than in the control group (11% vs. 44%, p < 0.05). Activity of p38 mitogen-activated protein (MAP) kinase increased with 15-min ischemia, and raloxifene pretreatment inhibited the activity. Myeloperoxidase activity of the 6-h reperfused myocardium was also attenuated by raloxifene.

CONCLUSIONS

These data demonstrate that raloxifene reduces myocardial ischemia-reperfusion injury by mechanisms dependent on NO and the opening of K(Ca) channels in canine hearts. Deactivation of p38 MAP kinase and myeloperoxidase by raloxifene may be involved in the cellular mechanisms of cardioprotection.

Benidipine, a long-acting Ca channel blocker, limits infarct size via bradykinin- and NO-dependent mechanisms in canine hearts

Amlodipine increases NO levels in coronary vessels and aorta via bradykinin-dependent mechanisms in vitro. We have previously reported that a long-acting Ca channel blocker, benidipine, increases cardiac NO levels in ischemic canine hearts, suggesting that benidipine may also protect against ischemia and reperfusion injury via bradykinin- and NO-dependent mechanisms. We examined this possibility. In open chest dogs, the left anterior descending coronary artery was perfused with blood through a bypass tube and was occluded for 90 min followed by 6 hours of reperfusion. Infarct size was assessed by TTC staining at 6 hours of reperfusion. When benidipine doses of 50, 100, and 200 ng/kg/min were infused via the bypass tube between 10 min prior to the onset of ischemia and after 60 min of reperfusion, systemic blood pressure did not change significantly. Infarct size decreased with the administration of benidipine (50, 100, and 200 ng/kg/min) when compared to the untreated condition (24.8+/-2.5, 17.3+/-3.1, and 16.5+/-2.0 vs. 43.4+/-5.6%, respectively) associated with the increased release of NO and bradykinin in the coronary venous blood upon reperfusion. Myeloperoxidase activity of the myocardium increased after 6 hours of reperfusion, which was attenuated by benidipine. The limitation of infarct size and the increase in myeloperoxidase activity were completely blunted by either L-NAME or HOE140. There were no significant differences in collateral blood flow assessed by the microsphere method after 45 min of ischemia for any of the groups. Thus, we conclude that the Ca channel blocker, benidipine, limits infarct size via bradykinin- and NO-dependent mechanisms.

Nifedipine limits infarct size via NO-dependent mechanisms in dogs

OBJECTIVES

Amlodipine increases NO levels in coronary vessels and aorta via bradykinin-dependent mechanisms in vitro. We have previously reported that nifedipine increases cardiac NO levels in the ischemic canine hearts, suggesting that nifedipine may also have protective effects against ischemia and reperfusion injury, because the enhancement of NO production limits infarct size. We tested whether nifedipine limits infarct size via NO-dependent mechanisms.

METHODS

In open chest dogs, the left anterior descending coronary artery was perfused with blood through a bypass tube and occluded for 90 min followed by 6 hours of reperfusion. Infarct size was assessed at 6 hours of reperfusion. Nifedipine of 3 or 6 microg/kg/min was infused into the bypass tube between 10 min prior to the onset of ischemia and 60 min of reperfusion.

RESULTS

Neither systemic blood pressure nor heart rate changed during infusion of nifedipine. Infarct size was reduced by the administration of nifedipine (3 or 6 microg/kg/min) compared with the untreated condition (25.6+/-2.6 and 19.1+/-3.5 vs. 43.4+/-5.6%, respectively), which was completely blunted by L-NAME (45.0+/-3.6 and 45.4+/-4.2 vs. 47.9+/-3.9% in the nifedipine (3 or 6 microg/kg/min) with L-NAME groups vs. the L-NAME group). Myeloperoxidase activity of the myocardium increased after 6 hours of reperfusion, which was attenuated by nifedipine. The limitation of infarct size and the attenuation in myeloperoxidase actiivity were completely blunted by L-NAME. There were no significant differences in collateral blood flow at 45 min of ischemia between each group.

CONCLUSIONS

We conclude that the Ca channel blocker, nifedipine, limits infarct size via NO-dependent mechanisms.

Role of cellular acidosis in production of nitric oxide in canine ischemic myocardium

We tested the hypothesis that cellular acidosis modulates the production of nitric oxide (NO) in ischemic hearts. In canine hearts, we decreased coronary blood flow (CBF) to one third of the control by reduction of coronary perfusion pressure (105+/-3 to 41+/-5 mmHg), and thereafter we maintained CBF constant (89.8+/-1.6 to 30.0+/-0.5 ml/100 g/min) with an intracoronary administration of either saline, atropine, rauwolscine, HOE140, 8-sulfophenyltheophylline (8SPT), NaHCO3, or HOE642 (the inhibitor of Na+/H+ exchange). The cardiac NO levels defined as the differences of the nitrate and nitrite levels between coronary venous and arterial blood increased in the saline administration (2.9+/-0.2 to 12.7+/-1.7 micromol/l), and the extents of increases were identical in the condition of either saline, atropine, rauwolscine, HOE140 or 8SPT administration. In the condition with either NaHCO3 or HOE642, the increases in the cardiac NO levels were blunted (4.5+/-0.7 and 4.8+/-0.4 micromol/l, respectively). Cyclic GMP content of epicardial coronary artery in the ischemic area increased, which was also attenuated by either NaHCO3 or HOE642. We confirmed the acidosis-induced NO production in a more severe ischemic myocardium, and also showed that cellular acidosis produced by infusion of HCl increased NO production in non-ischemic myocardium. We conclude that cellular acidosis and subsequent activation of Na+/H+ exchanges modulate production of endogenous NO in canine ischemic myocardium.

Cardioprotective effect afforded by transient exposure to phosphodiesterase III inhibitors: the role of protein kinase A and p38 mitogen-activated protein kinase

BACKGROUND

Phosphodiesterase III inhibitors (PDEIII-Is) improve the hemodynamic status of heart failure via inotropic/vasodilatory effects attributable to the increase in intracellular cAMP level. Direct cardioprotection by PDEIII-Is and its underlying mechanisms, however, have not been identified. We tested the infarct size-limiting effect of PDEIII-Is and the roles of cAMP, protein kinase (PK) A, PKC, and mitogen-activated protein kinase (MAPK) families in open-chest dogs. Methods and Results-- Milrinone, olprinone (PDEIII-Is), or dibutyryl-cAMP (db-cAMP) was injected intravenously 30 minutes before 90-minute ischemia, followed by 6 hours of reperfusion. Olprinone was also examined with an intracoronary cotreatment with a PKA inhibitor (H89), a PKC inhibitor (GF109203X), an extracellular signal-regulated kinase kinase (MEK) inhibitor (PD98059), or a p38 MAPK inhibitor (SB203580) throughout the preischemic period. Either PDEIII-Is or db-cAMP caused substantial hemodynamic changes, which returned to control levels in 30 minutes. Collateral flow and percent risk area were identical for all groups. Both PDEIII-Is and db-cAMP increased myocardial p38 MAPK activity during the preischemic period, which was blocked by H89, but not by GF109203X. Both PDEIII-Is and db-cAMP reduced infarct size (19.1+/-4.1%, 17.5+/-3.3%, and 20.3+/-4.8%, respectively, versus 36.1+/-6.2% control, P<0.05 each). Furthermore, the effect of olprinone was blunted by either H89 (35.5+/-6.4%) or SB203580 (32.6+/-5.9%), but not by GF109203X or PD98059. H89, GF109203X, PD98059, or SB203580 alone did not influence infarct size.

CONCLUSIONS

Pretreatment with PDEIII-Is has cardioprotective effects via cAMP-, PKA-, and p38 MAPK-dependent but PKC-independent mechanisms in canine hearts.

Dantaxusins A and B, two new taxoids from Taxus yunnanensis

Two new taxane diterpenes, dantaxusin A [5 alpha-cinnamoyloxy-2 alpha,7 beta,13 alpha-triacetoxy-2(3-->20)abeo-taxa-4(20),11-diene-9,10-dione (1)] and dantaxusin B [5 alpha-cinnamoyloxy-9 alpha-hydroxy-10 beta,13 alpha-diacetoxytaxa-4(20),11-diene (2)], were isolated from an ethanol extract of the aerial parts of Taxus yunnanensis along with taxuspine B, 2-deacetoxytaxinine J, taxuyunnanine C, taxinine B, taxuspine C, and taxinine NN-4. The structures of 1 and 2 were established on the basis of 1D and 2D NMR and HRMS spectroscopic methods.

Role of phasic dynamism of p38 mitogen-activated protein kinase activation in ischemic preconditioning of the canine heart

Although ischemic stress, including ischemic preconditioning (IP), activates p38 mitogen-activated protein kinase (MAPK), the relationship between p38 MAPK activation and the underlying cellular mechanisms of cardioprotection by IP is not verified in vivo. We examined the effects of the selective p38 MAPK inhibition on the cardioprotective effect of IP in the open-chest dogs. The coronary artery was occluded 4 times for 5 minutes, separated by 5 minutes of reperfusion (IP) followed by 90 minutes of occlusion and 6 hours of reperfusion. We infused SB203580 into the coronary artery during IP and 1 hour of reperfusion, during IP alone, and during sustained ischemia in the IP group. p38 MAPK activity markedly increased during IP but did not additionally increase at the onset of ischemia and was even attenuated at 15 minutes of sustained ischemia, and heat-shock protein (HSP) 27 was phosphorylated and translocated from cytosol to myofibril or nucleus without affecting total protein level at the onset of ischemia compared with the control group. SB203580 treatment (1 micromol/L) only during IP blunted the infarct size limitation by IP (37.3+/-6.3% versus 7.4+/-2.1% in the IP group, P:<0.01) and attenuated either phosphorylation or translocation of HSP27 during IP. Although the SB203580 treatment throughout the preischemic and postischemic periods had no significant effect on infarct size (33.3+/-9.4%) in this model, treatment with SB203580 only during ischemia partially mimicked the infarct size limitation by IP (26.8+/-3.5%). Thus, transient p38 MAPK activation during ischemic preconditioning mainly mediates the cardioprotection followed by HSP27 phosphorylation and translocation in vivo in the canine heart.

Role of mitochondrial and sarcolemmal K(ATP) channels in ischemic preconditioning of the canine heart

We tested whether mitochondrial or sarcolemmal ATP-sensitive K(+) (K(ATP)) channels play a key role in ischemic preconditioning (IP) in canine hearts. In open-chest beagle dogs, the left anterior descending artery was occluded four times for 5 min each with 5-min intervals of reperfusion (IP), occluded for 90 min, and reperfused for 6 h. IP as well as cromakalim and nicorandil (nonspecific K(ATP) channel openers) markedly limited infarct size (6.3 +/- 1.2, 8.9 +/- 1.9, and 7.2 +/- 1.6%, respectively) compared with the control group (40.9 +/- 4.1%). A selective mitochondrial K(ATP) channel blocker, 5-hydroxydecanoate, partially blunted the limitation of infarct size in the animals subjected to IP and those treated with cromakalim and nicorandil (21.6 +/- 3.8, 25.1 +/- 4.6, and 19.8 +/- 5.2%, respectively). A nonspecific K(ATP) channel blocker, glibenclamide, completely abolished the effect of IP (38.5 +/- 6.2%). Intracoronary or intravenous administration of a mitochondria-selective K(ATP) channel opener, diazoxide, at >100 micromol/l could only partially decrease infarct size (19.5 +/- 4.3 and 20.1 +/- 4.4%, respectively). In conclusion, mitochondrial and sarcolemmal K(ATP) channels independently play an important role in the limitation of infarct size by IP in the canine heart.

Inhibition of drug metabolism in human liver microsomes by nizatidine, cimetidine and omeprazole

1. The inhibitory effects of cimetidine, nizatidine and omeprazole on the metabolic activity of CYP2C9, 2C19, 2D6 and 3A were investigated in human liver microsomes. Both cimetidine and omeprazole inhibited each of the CYP subfamily enzymes; in particular, omeprazole extensively inhibited the hydroxylation of S-mephenytoin (CYP2C19, Ki = 7.1 microM). Nizatidine exhibited no inhibition of any of the CYP isoforms examined. 2. Cimetidine inhibited the hydroxylation of tolbutamide but not of diclofenac, whereas omeprazole inhibited the hydroxylation of diclofenac but not that of tolbutamide. The ability to inhibit CYP2C9 varied with incubation time, as measured by the metabolic rate constant for the substrates. Therefore, suitable substrates and incubation times must be selected in inhibition studies examining metabolic clearance and the mechanism of inhibition of these drugs. 3. Nizatidine did not inhibit the metabolism of cisapride, glibenclamide, benidipine and simvastatin. Omeprazole inhibited the metabolism of cisapride (Ki = 0.4 microM), glibenclamide (11.7 microM) and benidipine (6.5 microM), whereas cimetidine inhibited the metabolism of glibenclamide (11.6 microM). To avoid drug-drug interactions, care needs to be taken to select suitable medicines for co-administration with anti-ulcer drugs.

Protein tyrosine kinase is not involved in the infarct size-limiting effect of ischemic preconditioning in canine hearts

Protein kinase C (PKC) plays an important role in ischemic preconditioning (IP). Because (1) tyrosine kinase is located at the downstream of PKC for IP in the rabbit hearts and (2) we have reported that ecto-5'-nucleotidase is the substrate for PKC and plays a crucial role for the infarct size-limiting effect, we tested whether tyrosine kinase activation contributes to either activation of ecto-5'-nucleotidase or the infarct size-limiting effect of the early phase of IP in the canine heart. In dogs, the IP procedure (4 cycles of 5-minute occlusion of coronary artery) and exposure to 12, 13-phorbol myristate acetate (PMA) each activated myocardial ecto-5'-nucleotidase and Lck tyrosine kinase. Genistein (10, 30, and 100 microg. kg(-)(1). min(-)(1) IC), an inhibitor of tyrosine kinase, attenuated the activation of Lck tyrosine kinase but did not attenuate the activation of ecto-5'-nucleotidase due to either IP or PMA. In the other canine hearts, IP attenuated infarct size (49+/-5 versus 11+/-3 or 16+/-3%, P<0.01) due to 90 minutes of coronary occlusion followed by 6 hours of reperfusion, which was not blunted by 3 or 2 (30 and 100 microg. kg(-)(1). min(-)(1)) doses of genistein (infarct sizes, 15+/-4, 13+/-4, and 13+/-3%, respectively, and 17+/-3 and 15+/-4%, respectively) or lavendustin A. Tyrosine kinase does not activate ecto-5'-nucleotidase or trigger the infarct size-limiting effect of the early phase of IP in canine hearts.

Intramyocardial vascular volume distribution studied by synchrotron radiation-excited X-ray fluorescence

We evaluated the vascular volume distribution with fine resolution (0.1-1.3 mg myocardial tissue) in the sagittal plane of the left ventricle by using the microsphere filling method in 21 dogs. The coronary arterial volume density in the sagittal plane did not exhibit normal distribution and was characterized by variability among the outer-to-inner layers and within the layers (+2SD/-2SD > 80 times), and the median values in the layers ranged from 4.7 to 22. 9 nl/mg myocardial tissue. The fractal analysis of vascular volume revealed a self-similar nature with a fractal dimension (D value) similar to that of flow distribution (1.20 +/- 0.05 and 1.24 +/- 0. 09 for vascular volume and flow distribution, respectively) and had a more marked variability than the flow. The correlation of the regional vascular volume between adjacent regions decreased as the distance increased. However, the correlation coefficients in the endocardial-to-epicardial direction were significantly higher than those in the anterior-to-posterior direction (P < 0.05 by paired t-test). In conclusion, we determined intramyocardial vascular volume density in the sagittal plane, and the distribution revealed considerable variability, self-similarity, and asymmetry in the correlation among the adjacent regions. These observations could be related to the characteristics of the intramural coronary vascular network.

Electrophysiologic and blood-flow responses in the endocardium and epicardium to disopyramide and MS-551 during myocardial ischemia in the dog

The aim of this study was to determine whether a quantitative relation exists between changes in regional myocardial blood flow (RMBF) and those in electrophysiologic determinants recorded via left ventricular endocardial and epicardial bipolar electrograms after administration of disopyramide (DP) and a class III antiarrhythmic drug, MS-551 (MS), during myocardial ischemia in the dog. Dogs were given DP (1 mg/kg, i.v., n = 14), MS (1 mg/kg, i.v., and 0.1 mg/kg/min, d.i.v., n = 13), or saline (n = 12). The effective refractory period (ERP) was determined by an S1-S2 extrastimulus method, and RMBF by a nonradioactive microsphere technique. The duration of regional electrograms (DRE) was measured as an indicator of conduction time in the myocardium. DP blunted ischemia-induced shortening of ERPs and lengthened DREs at the endocardial and epicardial sites, with a greater effect seen epicardially (p < 0.01 each). DP reduced RMBF, especially at the endocardial surfaces of the ischemic zone (p < 0.05). MS prolonged ERPs at the endocardial and epicardial sites in the ischemic and normal zones (p < 0.05-0.01), but there were no significant differences between the two sites. MS prolonged DREs (p < 0.05), but the magnitude of the prolongation of the DREs was similar to the values in the control group. MS had no effects on RMBF. DP treatment prolonged DREs at both sites in the ischemic zone more markedly than MS or saline treatment (p < 0.01 each). DP reduced RMBF at the endocardial site of the ischemic zone more markedly than MS or saline (p < 0.05 in each). Accordingly, MS prolonged ERPs, but did not increase disparities between endocardial and epicardial sites in the ischemic myocardium, whereas DP had a greater ERP-prolonging effect at the epicardial site than at the endocardial site. DP reduced endocardial RMBF more markedly than epicardial RMBF. These observations suggest that differences in ERPs between endocardial and epicardial ischemic myocardium caused by DP treatment are not due to the difference in RMBF reduction between the two tissue layers, and that DP and MS do not affect the same population of ion channel(s) when ERPs are prolonged.