Mink Steven N, Jacobs Hans, Bose Deepak, Duke Krika, Cheng Zhao Qin, Liu Gang, Light R Bruce
Department of Medicine, University of Manitoba, Manitoba R3E-0Z3, Winnipeg, Canada.
J Mol Cell Cardiol. 2003 Mar;35(3):265-75. doi: 10.1016/s0022-2828(03)00004-x.
The objective of the present study was to identify the nature of a filterable cardiodepressant substance (FCS) that contributes to myocardial dysfunction in a canine model of Escherichia coli septic shock. In a previous study, it was found that FCS increased in plasma after 4 h of bacteremia (Am J Physiol 1993;264:H1402) in which FCS was identified by a bioassay that included a right ventricular trabecular (RVT) preparation. In that study, FCS was only partially identified by pore filtration techniques and was found to be a protein of molecular weight between 10 and 30 K. In the present study, FCS was further purified by size exclusion high-pressure liquid chromatography, until a single band was identified on one-dimensional gel electrophoresis. This band was then subjected to tandem mass spectrometry and protein-sequencing techniques and both techniques identified FCS as lysozyme c (Lzm-S), consistent with that originating from the canine spleen. Confirmatory tests showed that purified Lzm-S produced myocardial depression in the RVT preparation at concentrations achieved during sepsis in the in vivo preparation. In addition, Lzm-S inhibited the adrenergic response induced by field stimulation and the beta- agonist isoproterenol in in vitro preparations, these results suggesting that Lzm-S may inhibit the sympathetic response in sepsis. The present findings indicate that Lzm-S originating from disintegrating leukocytes from organs such as the spleen contributes to myocardial dysfunction in this model. The mechanism may relate to its binding or hydrolysis of a cardiac membrane glycoprotein thereby interfering with myocardial excitation-contraction coupling in sepsis.
本研究的目的是确定一种可滤过的心脏抑制物质（FCS）的性质，该物质在大肠杆菌败血症休克犬模型中导致心肌功能障碍。在先前的一项研究中发现，菌血症4小时后血浆中FCS增加（《美国生理学杂志》1993年；264:H1402），其中FCS通过包括右心室小梁（RVT）制备的生物测定法进行鉴定。在该研究中，FCS仅通过孔径过滤技术部分鉴定，发现其为分子量在10至30K之间的蛋白质。在本研究中，FCS通过尺寸排阻高压液相色谱进一步纯化，直到在一维凝胶电泳上鉴定出一条单一谱带。然后对该谱带进行串联质谱和蛋白质测序技术分析，两种技术均将FCS鉴定为溶菌酶c（Lzm-S），这与源自犬脾脏的物质一致。确证试验表明，纯化的Lzm-S在体内制备的败血症过程中达到的浓度下，在RVT制备中产生心肌抑制。此外，Lzm-S在体外制备中抑制场刺激和β-激动剂异丙肾上腺素诱导的肾上腺素能反应，这些结果表明Lzm-S可能在败血症中抑制交感反应。目前的研究结果表明，源自脾脏等器官中解体白细胞的Lzm-S在该模型中导致心肌功能障碍。其机制可能与其与心肌膜糖蛋白的结合或水解有关，从而在败血症中干扰心肌兴奋-收缩偶联。
