Zhao Li-Min, Xu Yong-Jian, Zhang Zhen-Xiang, Ni Wang, Chen Shi-Xin
Department of Respiratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
Chin Med J (Engl). 2004 Nov;117(11):1630-6.
Potassium (K+) channels are important in regulating cell membrane potential and excitability. Although bronchial myocytes from asthmatic rats show a significant reduction in voltage-dependent delayed rectifier potassium channel (Kv) current density and higher excitability, the activity and expression of Kv in human bronchial smooth muscle cells (HBSMCs) have never been studied. The objective of this study was to investigate the effect of passive sensitization by asthmatic serum on the activity of Kv and the expression of Kv isoform Kv1.5 in HBSMCs.
HBSMCs were randomly divided into two groups: control group (containing 10% serum from nonatopic individuals) and sensitized group (containing 10% asthmatic serum), then cultured for 24 hours. Whole-cell patch clamp, immunofluorescence staining, reverse transcription-polymerase chain reaction and Western blot techniques were used to study the effect of passive sensitization on the activity of Kv and the expression of Kv1.5 in HBSMCs.
The membrane potential in passively sensitized HBSMCs was significantly depolarized to -(26.7 +/- 5.2) mV compared with -(41.3 +/- 6.4) mV in the control group (P < 0.01). Passive sensitization caused a significant inhibition of Kv currents in HBSMCs, resulting in a downward shift in the current-voltage (I-V) relationship curve. At +50 mV, the peak Kv current density of passively sensitized HBSMCs was significantly decreased from (54.6 +/- 8.7) picoamperes per picofarad (pA/pF) to (32.1 +/- 7.1) pA/pF (P < 0.01). The expression level of Kv1.5 mRNA in passively sensitized HBSMCs was significantly lower than that in the control group (0.76 +/- 0.07 vs 1.04 +/- 0.13, P < 0.05). The expression of Kv1.5 protein of passively sensitized HBSMCs was also significantly reduced compared to that from the control group (984 +/- 168 vs 2200 +/- 380, P < 0.05).
The activity and expression of Kv were all decreased in HBSMCs passively sensitized by asthmatic serum compared with nonsensitized cells. These changes might be involved in the mechanisms of formation and development of asthma.
钾（K+）通道在调节细胞膜电位和兴奋性方面起着重要作用。尽管哮喘大鼠的支气管肌细胞电压依赖性延迟整流钾通道（Kv）电流密度显著降低且兴奋性更高，但人类支气管平滑肌细胞（HBSMCs）中Kv的活性和表达从未被研究过。本研究的目的是探讨哮喘血清被动致敏对HBSMCs中Kv活性和Kv亚型Kv1.5表达的影响。
将HBSMCs随机分为两组：对照组（含10%非特应性个体血清）和致敏组（含10%哮喘血清），然后培养24小时。采用全细胞膜片钳、免疫荧光染色、逆转录-聚合酶链反应和蛋白质印迹技术研究被动致敏对HBSMCs中Kv活性和Kv1.5表达的影响。
被动致敏的HBSMCs膜电位显著去极化至-（26.7±5.2）mV，而对照组为-（41.3±6.4）mV（P<0.01）。被动致敏导致HBSMCs中Kv电流显著抑制，导致电流-电压（I-V）关系曲线下移。在+50 mV时，被动致敏的HBSMCs的峰值Kv电流密度从（54.6±8.7）皮安/皮法（pA/pF）显著降至（32.1±7.1）pA/pF（P<0.01）。被动致敏的HBSMCs中Kv1.5 mRNA的表达水平显著低于对照组（0.76±0.07对1.04±0.13，P<0.05）。与对照组相比，被动致敏的HBSMCs中Kv1.5蛋白的表达也显著降低（984±168对2200±380，P<0.05）。
与未致敏细胞相比，哮喘血清被动致敏的HBSMCs中Kv的活性和表达均降低。这些变化可能参与了哮喘形成和发展的机制。
