Induction of reactive oxygen species from isolated rat glomeruli by protein kinase C activation and TNF-α stimulation, and effects of a phosphodiesterase inhibitor

大学院医学系研究科環境社会医学Diabetic nephropathy is a major complication of diabetes leading to end-stage renal disease, which requires hemodialysis. Although the mechanism by which it progresses is largely unknown, the role of hyperglycemia-derived oxidative stress has recently been the focus of attention as the cause of diabetic complications. Constituent cells of the renal glomeruli have the capacity to release reactive oxygen species (ROS) upon stimulation of NADPH oxidase activated by protein kinase C (PKC). Hyperglycemia and insulin resistance in the diabetic state are often associated with activation of PKC and tumor necrosis factor (TNF)-α, respectively. The aim of this study is to clarify the signaling pathway leading to ROS production by PKC and TNF-α in rat glomeruli. Isolated rat glomeruli were stimulated with phorbol 12-myristate 13-acetate (PMA) and TNF-α, and the amount of ROS was measured using a chemiluminescence method. Stimulation with PMA (10 ng/ml) generated ROS with a peak value of 136 ± 1.2 cpm/mg protein (mean ± SEM). The PKC inhibitor H-7, the NADPH oxidase inhibitor diphenylene iodonium and the phosphatidylinositol-3 (PI-3) kinase inhibitor wortmannin inhibited PMA-induced ROS production by 100%, 100% and 80%, respectively. In addition, TNF-α stimulated ROS production (283 ± 5.8/mg protein/20 min). The phosphodiesterase inhibitor cilostazol activates protein kinase A and is reported to improve albuminuria in diabetic rats. Cilostazol (100 μg/ml) inhibited PMA, and TNF-α-induced ROS production by 78 ± 1.8, and 19 ± 2.7%, respectively. The effects of cilostazol were not additive with wortmannin. Cilostazol arrests oxidative stress induced by PKC activation by inhibiting the PI-3 kinase-dependent pathway, and may thus prevent the development of diabetic nephropathy. © 2007 Elsevier Inc. All rights reserved

Antegrade and retrograde cardioplegia: Alternate or simultaneous?

AbstractNeither antegrade nor retrograde cardioplegic protection provides homogeneous distribution, and a combination may be required to avoid anaerobic metabolism and depressed postoperative ventricular function. Tepid cardioplegia (29° C) avoids the delayed recovery of cardiac function and metabolism associated with cold cardioplegia (15° C) and reduces the anaerobic metabolism seen with warm (37° C) cardioplegia. We compared two techniques that combine antegrade and retrograde tepid cardioplegia: alternate and simultaneous. Methods: Sixty patients undergoing elective isolated coronary artery bypass grafting were randomized to receive near continuous tepid retrograde and either intermittent antegrade cardioplegia (the alternate technique) or antegrade cardioplegia with the solution delivered concurrently through each completed vein graft (the simultaneous technique). Results: Myocardial lactate extraction was greater after crossclamp release following simultaneous than alternate cardioplegia. Postoperative ventricular function was better after alternate than simultaneous cardioplegia. Conclusion: Both techniques permitted rapid postoperative recovery of myocardial metabolism and ventricular function. However, simultaneous cardioplegia was simpler and did not require deairing the aortic root between antegrade infusions. (J THORAC CARDIOVASC SURG 1996;112:787-96

Adequate distribution of warm cardioplegic solution

AbstractSeventy-five patients undergoing coronary artery bypass grafting were randomized to receive warm antegrade (N = 25), warm retrograde (N = 25), or a combination of warm antegrade and retrograde (N = 25) delivery of blood cardioplegic solution. Myocardial oxygen utilization, lactate and acid metabolism, and adenine nucleotides and their degradation products were measured during the operation and cardiac function was assessed postoperatively. Warm retrograde delivery of cardioplegic solution increased lactate and acid release during cardioplegia and reperfusion, decreased left ventricular adenosine triphosphate concentrations, and reduced the washout of adenine nucleotide degradation products from both left and right ventricles. Warm antegrade delivery of cardioplegic solution resulted in less lactate and acid release during cardioplegia but more lactate accumulated in the territory of the left anterior descending artery during the crossclamp period. Intermittent antegrade delivery of the cardioplegic solution during combination cardioplegia washed out lactate and acid, which suggested inhomogeneous delivery of the cardioplegic solution during continuous retrograde cardioplegia. Combination cardioplegia best preserved adenosine triphosphate in the left ventricle and resulted in the best postoperative left and right ventricular function. A combination of intermittent antegrade and continuous retrograde delivery of cardioplegic solution provided better myocardial protection than either antegrade or retrograde delivery of cardioplegic solution alone. (J THORAC CARDIOVASC SURG 1995;110: 800-12