Schaeffer G, Wascher T C, Kostner G M, Graier W F
Department of Medical Biochemistry, University of Graz, Austria.
Diabetologia. 1999 Feb;42(2):167-76. doi: 10.1007/s001250051135.
Increased aggregation of platelets might contribute to the development of vascular complication in diabetes mellitus. In this study release of superoxide anions, intracellular Ca2+ signalling and nitric oxide formation stimulated by the receptor-dependent agonist adenosine 5 '-diphosphate (ADP) and the receptor-independent stimulus thapsigargin, were compared in platelets isolated from patients with Type II (non-insulin-dependent) diabetes mellitus and healthy control subjects. Diabetes augmented intracellular Ca2+ release and Ca2+ entry to ADP by 40 and 44% (control subjects: n = 11; diabetic: n = 6), while the median effective concentration (EC50) of ADP to initiate Ca2+ signalling was similar in both groups. The effect of thapsigargin on Ca2+ concentration was increased by 69% in diabetic patients (control subjects: n = 22; diabetic patients: n = 9). In addition, release of superoxide anions was 70% greater in diabetic patients (control subjects: n = 9; diabetic patients: n = 6). Treatment of platelets from control subjects with the superoxide anion-generating mixture xanthine oxidase and hypoxanthine or buthioninesulphoximine (BSO) mimicked the effect of diabetes on platelet Ca2+ signalling. The antioxidant glutathione normalized enhanced Ca2+ response in the diabetic group (control subjects: n = 5: diabetic patients: n = 6). Basal and thapsigargin-evoked nitric oxide synthase activity was reduced in the diabetic group by 85 and 64%, respectively (control subjects: n = 13; diabetic subjects: n = 13). The nitric oxide-donor 2-(N,N-diethylamino)-diazenolate-2-oxide sodium (DEA/NO) normalized enhanced Ca2+ signalling in platelets preincubated with xanthine oxidase and hypoxanthine (n = 12) and in those from diabetics (control subjects: n = 6; diabetic patients: n = 6). Inhibition of nitric oxide synthase by N-nitro-L-arginine (L-NA) augmented thapsigargin-induced Ca2+ signalling by 51% (n = 8). These data indicate that in diabetes platelet Ca2+ signalling might be enhanced by excessive superoxide production and an attenuated negative direct or indirect feedback control by nitric oxide, due to its reduced production.
血小板聚集增加可能促使糖尿病血管并发症的发生。在本研究中，比较了从II型（非胰岛素依赖型）糖尿病患者和健康对照者分离出的血小板中，受体依赖性激动剂5'-二磷酸腺苷（ADP）和受体非依赖性刺激剂毒胡萝卜素刺激产生的超氧阴离子释放、细胞内Ca2+信号传导及一氧化氮生成情况。糖尿病使细胞内Ca2+释放及Ca2+进入对ADP的反应分别增加40%和44%（对照者：n = 11；糖尿病患者：n = 6），而启动Ca2+信号传导的ADP半数有效浓度（EC50）在两组中相似。毒胡萝卜素对Ca2+浓度的影响在糖尿病患者中增加了69%（对照者：n = 22；糖尿病患者：n = 9）。此外，糖尿病患者的超氧阴离子释放量高出70%（对照者：n = 9；糖尿病患者：n = 6）。用超氧阴离子生成混合物黄嘌呤氧化酶和次黄嘌呤或丁硫氨酸亚砜胺（BSO）处理对照者的血小板，可模拟糖尿病对血小板Ca2+信号传导的影响。抗氧化剂谷胱甘肽使糖尿病组增强的Ca2+反应恢复正常（对照者：n = 5；糖尿病患者：n = 6）。糖尿病组基础及毒胡萝卜素诱发的一氧化氮合酶活性分别降低了85%和64%（对照者：n = 13；糖尿病患者：n = 13）。一氧化氮供体2-(N,N-二乙氨基)-重氮酸-2-氧化物钠（DEA/NO）使预先用黄嘌呤氧化酶和次黄嘌呤孵育的血小板（n = 12）以及糖尿病患者的血小板（对照者：n = 6；糖尿病患者：n = 6）中增强的Ca2+信号传导恢复正常。N-硝基-L-精氨酸（L-NA）抑制一氧化氮合酶使毒胡萝卜素诱导的Ca2+信号传导增加了51%（n = 8）。这些数据表明，在糖尿病中，由于一氧化氮生成减少，血小板Ca2+信号传导可能因超氧化物产生过多以及一氧化氮减弱的负向直接或间接反馈控制而增强。
