Lampidis T J, Kolonias D, Savaraj N, Rubin R W
Department of Oncology, Sylvester Comprehensive Cancer Center, University of Miami, School of Medicine, Veterans Administration Hospital, FL 33136.
Proc Natl Acad Sci U S A. 1992 Feb 15;89(4):1256-60. doi: 10.1073/pnas.89.4.1256.
Rhythmic, spontaneously pulsating cardiac cells cultured from newborn rats are immediately stimulated to beat faster by addition of a number of tubulin-binding agents but not by their non-tubulin-binding analogues. The tubulin-binding agents tested include vinblastine, vincristine, navelbine, two analogs of vinblastine (S12362 and S12363), nocodazole, colchicine, and podophylotoxin. In addition to binding tubulin, all of the above agents also depolymerize microtubules. In contrast, taxol, a tubulin-binding agent that stabilizes microtubules, does not stimulate cardiac cells. Moreover, the immediate and ensuing cardiac stimulation by vinblastine at 0.05 microgram/ml is completely blocked by pre- and cotreatment with taxol at 1.0 microgram/ml. The time necessary to reverse the cardiostimulatory effect of vinblastine is significantly longer than that required for nocodazole, further implicating depolymerization of microtubules in the cardiac activity of these agents. All of the tubulin-binding agents tested (including taxol) also immediately reverse adriamycin-induced arrhythmias. By using a monoclonal antibody to alpha-tubulin, typical filamentous microtubules are visualized in cardiac muscle and cocultured non-muscle cells by immunofluorescence. When cells are treated for 2 hr with vinblastine at 0.05 microgram/ml, fluorescence is detected in cross-striated patterns in cardiac muscle cells. Overall, these data open the possibility of uncovering an additional relationship between cytoskeletal elements (other than actin and myosin) and the contractility of cardiac muscle. They also suggest an alternative mechanism for affecting cardiac cell function in vitro (namely, by tubulin-binding agents). If these agents are shown to be cardioactive in vivo, they may provide another approach to the treatment and management of cardiac arrhythmias.
从新生大鼠培养的有节律、自发搏动的心脏细胞，加入多种微管蛋白结合剂后会立即被刺激而搏动加快，但加入它们的非微管蛋白结合类似物则不会。所测试的微管蛋白结合剂包括长春花碱、长春新碱、诺维本、长春花碱的两种类似物（S12362和S12363）、诺考达唑、秋水仙碱和鬼臼毒素。除了结合微管蛋白外，上述所有试剂还会使微管解聚。相比之下，紫杉醇是一种能稳定微管的微管蛋白结合剂，不会刺激心脏细胞。此外，用1.0微克/毫升的紫杉醇预处理和同时处理，能完全阻断0.05微克/毫升长春花碱立即产生的以及后续的心脏刺激作用。逆转长春花碱心脏刺激作用所需的时间明显长于诺考达唑所需的时间，这进一步表明微管解聚与这些试剂的心脏活性有关。所有测试的微管蛋白结合剂（包括紫杉醇）也能立即逆转阿霉素诱导的心律失常。通过使用抗α-微管蛋白单克隆抗体，通过免疫荧光在心肌和共培养的非肌肉细胞中观察到典型的丝状微管。当细胞用0.05微克/毫升长春花碱处理2小时时，在心肌细胞中可检测到横纹状的荧光。总体而言，这些数据揭示了细胞骨架成分（肌动蛋白和肌球蛋白之外）与心肌收缩性之间存在额外关系的可能性。它们还提出了一种体外影响心脏细胞功能的替代机制（即通过微管蛋白结合剂）。如果这些试剂在体内显示出心脏活性，它们可能为心律失常的治疗和管理提供另一种方法。
