Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS 66160, USA.
Cardiovasc Diabetol. 2010 Feb 1;9:8. doi: 10.1186/1475-2840-9-8.
Diminished calcium (Ca2+) transients in response to physiological agonists have been reported in vascular smooth muscle cells (VSMCs) from diabetic animals. However, the mechanism responsible was unclear.
METHODOLOGY/PRINCIPAL FINDINGS: VSMCs from autoimmune type 1 Diabetes Resistant Bio-Breeding (DR-BB) rats and streptozotocin-induced rats were examined for levels and distribution of inositol trisphosphate receptors (IP3R) and the SR Ca2+ pumps (SERCA 2 and 3). Generally, a decrease in IP3R levels and dramatic increase in ryanodine receptor (RyR) levels were noted in the aortic samples from diabetic animals. Redistribution of the specific IP3R subtypes was dependent on the rat model. SERCA 2 was redistributed to a peri-nuclear pattern that was more prominent in the DR-BB diabetic rat aorta than the STZ diabetic rat. The free intracellular Ca2+ in freshly dispersed VSMCs from control and diabetic animals was monitored using ratiometric Ca2+ sensitive fluorophores viewed by confocal microscopy. In control VSMCs, basal fluorescence levels were significantly higher in the nucleus relative to the cytoplasm, while in diabetic VSMCs they were essentially the same. Vasopressin induced a predictable increase in free intracellular Ca2+ in the VSMCs from control rats with a prolonged and significantly blunted response in the diabetic VSMCs. A slow rise in free intracellular Ca2+ in response to thapsigargin, a specific blocker of SERCA was seen in the control VSMCs but was significantly delayed and prolonged in cells from diabetic rats. To determine whether the changes were due to the direct effects of hyperglycemica, experiments were repeated using cultured rat aortic smooth muscle cells (A7r5) grown in hyperglycemic and control conditions. In general, they demonstrated the same changes in protein levels and distribution as well as the blunted Ca2+ responses to vasopressin and thapsigargin as noted in the cells from diabetic animals.
CONCLUSIONS/SIGNIFICANCE: This work demonstrates that the previously-reported reduced Ca2+ signaling in VSMCs from diabetic animals is related to decreases and/or redistribution in the IP3R Ca2+ channels and SERCA proteins. These changes can be duplicated in culture with high glucose levels.
已经有报道称，在糖尿病动物的血管平滑肌细胞（VSMCs）中，对生理激动剂的钙（Ca2+）瞬变反应减弱。然而，导致这种现象的机制尚不清楚。
方法/主要发现：检查了来自自身免疫型 1 型糖尿病抗性生物繁殖（DR-BB）大鼠和链脲佐菌素诱导大鼠的 VSMCs 中肌醇三磷酸受体（IP3R）和肌浆网 Ca2+泵（SERCA2 和 3）的水平和分布。一般来说，糖尿病动物的主动脉样本中 IP3R 水平降低，Ryanodine 受体（RyR）水平显著升高。特定的 IP3R 亚型的重新分布取决于大鼠模型。SERCA2 被重新分布到核周模式，在 DR-BB 糖尿病大鼠的主动脉中比 STZ 糖尿病大鼠更为明显。使用通过共焦显微镜观察的比率型 Ca2+敏感荧光染料监测来自对照和糖尿病动物的新鲜分散的 VSMCs 中的细胞内游离 Ca2+。在对照 VSMCs 中，核相对于细胞质的基础荧光水平明显更高，而在糖尿病 VSMCs 中则基本相同。血管加压素诱导的控制 VSMCs 中的游离细胞内 Ca2+可预测增加，而糖尿病 VSMCs 的反应则延长且明显减弱。在对照 VSMCs 中观察到对 thapsigargin（SERCA 的特异性阻断剂）的反应中，细胞内游离 Ca2+缓慢升高，但在糖尿病大鼠的细胞中明显延迟和延长。为了确定这些变化是否是由于高血糖的直接作用，使用在高血糖和对照条件下生长的培养的大鼠主动脉平滑肌细胞（A7r5）重复了实验。总的来说，它们表现出与从糖尿病动物的细胞中观察到的相同的蛋白水平和分布变化以及对血管加压素和 thapsigargin 的 Ca2+反应减弱。
结论/意义：这项工作表明，先前报道的糖尿病动物 VSMCs 中 Ca2+信号转导减弱与 IP3R Ca2+通道和 SERCA 蛋白的减少和/或重新分布有关。这些变化可以在高糖水平的培养中复制。
