Systemic events in Clostridium difficile associated disease

描述（由申请方提供）：艰难梭菌在胃肠道中引发疾病，并通过向血流中释放毒素（TcdA和TcdB）引起结肠外损伤。不幸的是，虽然我们对这些毒素在感染部位的局部作用了解很多，但我们对这些毒素的全身作用的了解有限。最近，我们报道了TcdB是一种强有力的心脏毒素，其改变心脏功能并损害心脏。然而，心脏损伤可以完全缓解的半胱天冬酶-3抑制剂，在体外研究中，这表明只有部分保护TcdB使用这种抑制剂。这些结果表明，在体内凋亡细胞死亡不同于在体外研究。第一系列的实验将阐明细胞凋亡的步骤，因为它们发生在体内，以获得相关的洞察这种毒素在宿主内的活动。 迄今为止，几乎没有人知道TcdA的全身效应，尽管像TcdB一样，TcdA是一种有效的外毒素。在本研究的第二个目的中，我们将使用与TcdB相似的实验方法，阐明TcdA的全身效应，并确定这种毒素可能与TcdB联合作用。 最后，C.艰难梭菌相关疾病由于高水平的抗生素抗性菌株而难以治疗。在本研究的最终目的中，我们将探索几种旨在预防TcdB和TcdA引起的全身性损伤的新疗法。这项研究的具体目标如下： 具体目的1：探讨TcdB诱导心肌细胞凋亡的机制。 具体目标2：将确定TcdA对全身性损伤的贡献。 具体目标3：将评价TcdA和TcdB的候选抑制剂对全身损伤的保护作用。 相关性：C。在许多发达国家，艰难梭菌相关疾病是日益严重的医学问题。此外，与这种疾病相关的死亡率增加令人担忧，但对胃肠道以外的发病机制的步骤知之甚少。本文提出的研究将为这种疾病中发生的全身性损伤提供重要的见解，并测试新的候选疗法。

DESCRIPTION (provided by applicant): Clostridium difficile initiates disease in the gastrointestinal tract and causes extracolonic damage by releasing toxins (TcdA and TcdB) into the bloodstream. Unfortunately, while much is known about the localized effects of these toxins at the site of infection, our understanding of the systemic effects of these toxins is limited. Recently, we reported that TcdB is a potent cardiotoxin, which alters cardiac function and damages the heart. However, cardiac damage could be completely alleviated by a caspase-3 inhibitor, in contrast to in vitro studies, which show only partial protection against TcdB using this inhibitor. These results suggest in vivo apoptotic cell death differs from that studied in vitro. The first series of experiments will elucidate the steps in apoptosis as they occur in vivo, in order to gain relevant insight into the activities of this toxin within the host. To date, almost nothing is known about the systemic effects of TcdA, although like TcdB, TcdA is a potent exotoxin. Using experimental approaches similar to those employed for TcdB, in the second aim of this study, we will elucidate the systemic effects of TcdA and determine this toxin may work in combination with TcdB. Finally, C. difficile associated disease is difficult to treat due to a high level of antibiotic resistant strains. In the final aim of this study we will explore several novel therapeutics designed to prevent systemic damage by TcdB and TcdA. The specific aims of this study are as follows: Specific Aim 1: The mechanism of TcdB-induced apoptosis in cardiac tissue will be determined. Specific Aim 2: The contribution of TcdA to systemic damage will be determined. Specific Aim 3: Candidate inhibitors of TcdA and TcdB will be evaluated for protection against systemic damage. Relevance: C. difficile associated disease is an increasing medical problem in many developed countries. Furthermore, there has been a concerning increase in mortality associated with this illness, yet little is known about steps in pathogenesis outside of the gastrointestinal tract. The studies proposed herein will provide important insight into systemic damage occurring in this disease, and test new candidate therapeutics.