Ischemia Enhances the Acute Stretch-Induced Increase in Calcium Spark Rate in Ventricular Myocytes
Ischemia Enhances the Acute Stretch-Induced Increase in Calcium Spark Rate in Ventricular Myocytes
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DOI：
10.3389/fphys.2020.00289
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发表时间：
2020-04-16
影响因子：
4
通讯作者：
Quinn, T. Alexander
中科院分区：
文献类型：
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作者：
Cameron, Breanne A.;Kai, Hiroaki;Quinn, T. Alexander
简介：在心室肌细胞中，由于牵张诱导的活性氧（ROS）增加，牵张可使肌浆网通过兰尼碱受体（“Ca 2+火花”）自发释放的钙（Ca 2+）急剧增加。在急性局部缺血中，缺血组织伸展，沿着增加Ca 2+火花率和ROS产生，其中每一个都与血管生成有关。然而，缺血是否对牵张诱导的Ca 2+火花和ROS增加有影响尚未研究。我们假设缺血会增强牵张引起的Ca 2+火花和ROS的增加。小鼠心室肌细胞分离（雄性，C57 BL/6 J）加载荧光染料以检测Ca 2+火花（4.6 μ M Fluo-4，10 min）或ROS（1 μ M DCF，20 min），暴露于正常台氏液（NT）或模拟缺血（SI）溶液（高钾血症[15 mM钾]、酸中毒[6.5 pH]和代谢抑制[1 mM氰化钠，20 mM 2-脱氧葡萄糖]），并通过碳纤维技术进行持续拉伸（类似于肌节长度增加10%，15 s）。结果：SI组基础Ca 2+放电率高于SI组（P < 0. 05），SI组基础Ca 2+放电率高于SI组（P < 0. 05（2.54 +/- 0.11火花中心点s（-1）中心点100 μ m（-2）; n = 103个细胞，N = 10只小鼠）（0.29 +/-0.05火花中心点s（-1）中心点100 μ m（-2）; n = 33个细胞，N = 9只小鼠; p < 0.0001）。拉伸导致两个SI中的Ca 2+火花率急剧增加（3.03 +/- 0.13火花中心点s（-1）中心点100 μ m（-2）; p < 0.0001）和NT（0.49 ± 0.07火花中心点s（-1）中心点100 μ m（-2）; p < 0.0001），SI的增加大于NT（+0.49 +/-0.04 vs. +0.20 +/-0.04火花中心点s（-1）中心点100 μ m（-2）; p < 0.0001）。在SI中，ROS产生的基线速率也更高。（1.01 +/- 0.01标准化斜率; n = 11，N = 8只小鼠）（0.98 +/-0.01标准化斜率; n = 12，N = 4只小鼠; p < 0.05），但在SI中仅随着牵拉而急剧增加。结论：缺血增强牵张诱导的心室肌细胞内Ca 2+火花的增加，并伴随牵张诱导的ROS产生的增强。这种效应可能是重要的过早兴奋和/或在急性局部缺血的促炎性底物的发展。
Introduction: In ventricular myocytes, spontaneous release of calcium (Ca2+) from the sarcoplasmic reticulum via ryanodine receptors ("Ca2+ sparks") is acutely increased by stretch, due to a stretch-induced increase of reactive oxygen species (ROS). In acute regional ischemia there is stretch of ischemic tissue, along with an increase in Ca2+ spark rate and ROS production, each of which has been implicated in arrhythmogenesis. Yet, whether there is an impact of ischemia on the stretch-induced increase in Ca2+ sparks and ROS has not been investigated. We hypothesized that ischemia would enhance the increase of Ca2+ sparks and ROS that occurs with stretch.Methods: Isolated ventricular myocytes from mice (male, C57BL/6J) were loaded with fluorescent dye to detect Ca2+ sparks (4.6 mu M Fluo-4, 10 min) or ROS (1 mu M DCF, 20 min), exposed to normal Tyrode (NT) or simulated ischemia (SI) solution (hyperkalemia [15 mM potassium], acidosis [6.5 pH], and metabolic inhibition [1 mM sodium cyanide, 20 mM 2-deoxyglucose]), and subjected to sustained stretch by the carbon fiber technique (similar to 10% increase in sarcomere length, 15 s). Ca2+ spark rate and rate of ROS production were measured by confocal microscopy.Results: Baseline Ca2+ spark rate was greater in SI (2.54 +/- 0.11 sparks center dot s(-1)center dot 100 mu m(-2); n = 103 cells, N = 10 mice) than NT (0.29 +/- 0.05 sparks center dot s(-1)center dot 100 mu m(-2); n = 33 cells, N = 9 mice; p < 0.0001). Stretch resulted in an acute increase in Ca2+ spark rate in both SI (3.03 +/- 0.13 sparks center dot s(-1)center dot 100 mu m(-2); p < 0.0001) and NT (0.49 +/- 0.07 sparks center dot s(-1)center dot 100 mu m(-2); p < 0.0001), with the increase in SI being greater than NT (+0.49 +/- 0.04 vs. +0.20 +/- 0.04 sparks center dot s(-1)center dot 100 mu m(-2); p < 0.0001). Baseline rate of ROS production was also greater in SI (1.01 +/- 0.01 normalized slope; n = 11, N = 8 mice) than NT (0.98 +/- 0.01 normalized slope; n = 12, N = 4 mice; p < 0.05), but there was an acute increase with stretch only in SI (+12.5 +/- 2.6%; p < 0.001).Conclusion: Ischemia enhances the stretch-induced increase of Ca2+ sparks in ventricular myocytes, with an associated enhancement of stretch-induced ROS production. This effect may be important for premature excitation and/or in the development of an arrhythmogenic substrate in acute regional ischemia.