Shinichiro Oda

Interleukin-6 inhibits long-term potentiation in rat hippocampal slices

The effects of recombinant human interleukin-6 (rhIL-6) on long-term potentiation (LTP) induced in the Schaffer collateral/commissural-CA1 pathway were examined using rat hippocampal slices. Field excitatory postsynaptic potential was recorded in the stratum radiatum of the CA1 region. Ten-min applications of rhIL-6 (50-2000 U/ml), started 5 min before the tetanus, significantly inhibited the induction of LTP, and in high doses of rhIL-6 also inhibited short-term potentiation (over 200 U/ml) and post-tetanic potentiation (over 500 U/ml). The effects of rhIL-6 (500 U/ml) were completely abolished by the preincubation of the slices with monoclonal anti-IL-6 receptor antibody (16 microg/ml) for 2 h. Heat-inactivated rhIL-6 had no effect on the synaptic potentiation. RhIL-6 affected neither the previously established LTP nor the basal synaptic transmission. These findings indicated that rhIL-6 modulated synaptic potentiation through the IL-6 receptor-mediated process in the hippocampus, probably by affecting post- and presynaptic sites in the CA1 region. The possible mechanisms of the IL-6-induced suppression of the synaptic potentiation were discussed.

Therapeutic Neovascularization by Nanotechnology-Mediated Cell-Selective Delivery of Pitavastatin Into the Vascular Endothelium

Objective—Recent clinical studies of therapeutic neovascularization using angiogenic growth factors demonstrated smaller therapeutic effects than those reported in animal experiments. We hypothesized that nanoparticle (NP)-mediated cell-selective delivery of statins to vascular endothelium would more effectively and integratively induce therapeutic neovascularization. Methods and Results—In a murine hindlimb ischemia model, intramuscular injection of biodegradable polymeric NP resulted in cell-selective delivery of NP into the capillary and arteriolar endothelium of ischemic muscles for up to 2 weeks postinjection. NP-mediated statin delivery significantly enhanced recovery of blood perfusion to the ischemic limb, increased angiogenesis and arteriogenesis, and promoted expression of the protein kinase Akt, endothelial nitric oxide synthase (eNOS), and angiogenic growth factors. These effects were blocked in mice administered a nitric oxide synthase inhibitor, or in eNOS-deficient mice. Conclusions—NP-mediated cell-selective statin delivery may be a more effective and integrative strategy for therapeutic neovascularization in patients with severe organ ischemia.

Nanoparticle-mediated endothelial cell-selective delivery of pitavastatin induces functional collateral arteries (therapeutic arteriogenesis) in a rabbit model of chronic hind limb ischemia

OBJECTIVES We recently demonstrated in a murine model that nanoparticle-mediated delivery of pitavastatin into vascular endothelial cells effectively increased therapeutic neovascularization. For the development of a clinically applicable approach, further investigations are necessary to assess whether this novel system can induce the development of collateral arteries (arteriogenesis) in a chronic ischemia setting in larger animals. METHODS Chronic hind limb ischemia was induced in rabbits. They were administered single injections of nanoparticles loaded with pitavastatin (0.05, 0.15, and 0.5 mg/kg) into ischemic muscle. RESULTS Treatment with pitavastatin nanoparticles (0.5 mg/kg), but not other nanoparticles, induced angiographically visible arteriogenesis. The effects of intramuscular injections of phosphate-buffered saline, fluorescein isothiocyanate (FITC)-loaded nanoparticles, pitavastatin (0.5 mg/kg), or pitavastatin (0.5 mg/kg) nanoparticles were examined. FITC nanoparticles were detected mainly in endothelial cells of the ischemic muscles for up to 4 weeks. Treatment with pitavastatin nanoparticles, but not other treatments, induced therapeutic arteriogenesis and ameliorated exercise-induced ischemia, suggesting the development of functional collateral arteries. Pretreatment with nanoparticles loaded with vatalanib, a vascular endothelial growth factor receptor (VEGF) tyrosine kinase inhibitor, abrogated the therapeutic effects of pitavastatin nanoparticles. Separate experiments with mice deficient for VEGF receptor tyrosine kinase demonstrated a crucial role of VEGF receptor signals in the therapeutic angiogenic effects. CONCLUSIONS The nanotechnology platform assessed in this study (nanoparticle-mediated endothelial cell-selective delivery of pitavastatin) may be developed as a clinically feasible and promising strategy for therapeutic arteriogenesis in patients.

Left ventricular performance in aortic valve replacement

We analyzed the mid-term left ventricular (LV) performance after aortic valve replacement (AVR). We measured LV contractility (end-systolic elastance: Ees), afterload (effective arterial elastance: Ea) and efficiency (ventriculoarterial coupling: Ea/Ees; ratio of stroke work and pressure-volume area: SW/PVA) based on transthoracic echocardiography data obtained before, after and approximately 1 year after isolated AVR in 263 patients with aortic stenosis (AS group; n=116), aortic regurgitation (AR group; n=93) or aortic stenosis and regurgitation (ASR group; n=54). The LV volume was calculated by the Teichholz M-mode method. Ees and Ea were approximated as follows: Ees=mean blood pressure/minimal LV volume; Ea=systolic blood pressure/(maximal LV volume-minimal LV volume). Thereafter, Ea/Ees and SW/PVA were calculated. Arterial blood pressure was measured using manchette methods. Ees and Ea decreased after AVR in the AS group, but increased in the AR group. Ea/Ees and SW/PVA worsened after AVR in the AR group, but improved during a 1-year period after AVR in all groups. Contrasting effects of AVR on LV contractility and afterload between AS and AR were clearly demonstrated. The mid-term LV contractility and efficiency after AVR were excellent and satisfactory. However, LV efficiency worsened early after AVR in AR patients.

Protective effects of cold spinoplegia with fasudil against ischemic spinal cord injury in rabbits.

OBJECTIVE Paraplegia remains a serious complication after surgical repair of thoracoabdominal aortic aneurysms. The aim of this study was to evaluate the neuroprotective efficacy of fasudil, a Rho kinase (ROCK) inhibitor, by reducing the number of infiltrating cells in the ventral horn and increasing the induction of eNOS against ischemic spinal cord injury in rabbits. METHODS Eighteen Japanese white rabbits were divided into three groups: saline (group 1, n = 7, 4 degrees C) and fasudil (group 2, n = 6, 4 degrees C) were immediately infused into the isolated segmental lumbar arteries over 30 seconds after aortic clamping. Group 3 (n = 5) was the sham-operated group. Hind limb function was evaluated 4 and 8 hours, and 1 and 2 days after 15 minutes of transient ischemia. Cell damage was analyzed by hematoxylin and eosin staining and temporal profiles of endothelial nitric oxide synthase immunoreactivity were performed. The number of intact motor neuron cells and infiltrating cells in the ventral horn were compared. RESULTS Two days after reperfusion, group 2 and group 3 showed better neurologic function, a greater number of intact motor neuron cells, and a smaller number of infiltrating cells in the ventral horn than group 1. The induction of endothelial nitric oxide synthase (eNOS) was prolonged up to 2 days after reperfusion in group 2. CONCLUSION These results indicate that fasudil has neuroprotective effects against ischemic spinal cord injury in rabbits by reducing the number of infiltrating cells in the ventral horn and prolonging the expression of eNOS.

A Rho-kinase inhibitor improves cardiac function after 24-hour heart preservation

OBJECTIVE The Rho-kinase signaling pathway is associated with coronary vasculopathy and myocardial dysfunction after cardiac transplantation. This study evaluated whether using a Rho-kinase inhibitor during allograft storage could limit early endothelial dysfunction and improve myocardial performance after reperfusion. METHODS This experiment was performed with an isolated working rabbit heart model and a support rabbit. Donor hearts (control group, n = 8) were arrested with an extracellular type of cardioplegia, preserved with University of Wisconsin solution, and then immersed in University of Wisconsin solution for 24 hours (1 degrees C). The Rho-kinase inhibitor (Rho-kinase inhibitor group, n = 8) was administrated in the cardioplegic solution, the preservation University of Wisconsin solution, and the storage University of Wisconsin solution. Left ventricular performance was evaluated from the modified Frank-Starling curve in the working mode. Coronary blood flow and donor heart rate were measured in Langendorff mode. Effective evaluation of the Rho-kinase inhibitor was inferred from phosphorylated myosin light chain. The expression of endothelial nitric oxide synthase mRNA was analyzed to assess endothelial function. RESULTS The Frank-Starling curve showed a significant left and upward shift in the Rho-kinase inhibitor group compared with the control group (P < .05). The coronary blood flow and heart rate in the Rho-kinase inhibitor group at 120 minutes was significantly higher than in the control group (P < .05). Phosphorylated myosin light chain was significantly suppressed in the Rho-kinase inhibitor group (P < .05). Endothelial nitric oxide synthase mRNA levels in the Rho-kinase inhibitor group increased 4-fold relative to those seen in the control group. CONCLUSIONS Treatment with Rho-kinase inhibitor during allograft harvest and storage enhanced coronary blood flow and ventricular recovery through nitric oxide-dependent endothelial protection after reperfusion. Rho-kinase inhibitor could help prevent early myocardial dysfunction after transplantation.

Experimental use of an elastomeric surgical sealant for arterial hemostasis and its long-term tissue response

OBJECTIVES Reliable suture line hemostasis should improve the outcome of aortic surgery. We examined the hemostatic effect and the tissue response of a novel elastomeric surgical sealant. METHODS Using porcine internal carotid arteries, we performed 16 end-to-end anastomoses with four stitches of simple interrupted sutures under full heparinization. The anastomoses were divided into two groups (eight anastomoses per group). Either novel sealant or fibrin glue was applied. The amount of bleeding was measured during the 30 s period after removing the vascular clamp. In a separate experiment, we applied the novel sealant around the abdominal aorta of rabbits (n=6) to assess the effect of the elastomeric property of the sealant on arterial wall histology. For comparison, we applied cyanoacrylate, which has no elastomeric property (n=6). A histological study was performed three months after the operation. RESULTS The novel sealant prevented arterial bleeding. The amount of bleeding from the anastomoses applied with novel sealant and fibrin glue was 0.12+/-0.03 g vs. 91.8+/-16.5 g, respectively (P<0.001). Thinning of the rabbit aortic wall was observed in the cyanoacrylate-treated abdominal aorta, whereas no thinning was observed in the novel sealant group. Histological examination revealed neither cell death nor necrosis in the novel sealant group. CONCLUSIONS The novel sealant effectively prevented arterial bleeding from the anastomosis under full heparinization. In addition, the elastomeric property of the sealant prevented thinning of the aortic wall. The novel sealant may be a promising hemostatic agent for arterial anastomosis.