Exploiting Host Polyamines for the Treatment of Skin and Wound Infections

描述（由申请人提供）：皮肤和软组织感染（SSTIs）及其相关并发症是美国发病率和死亡率的重要来源，特别是当由多药耐药（MDR）病原体引起时。耐多药相关的SSTI最常见的来源是耐甲氧西林金黄色葡萄球菌（MRSA）。在MRSA SSTIs中，宿主反应包括两个一般阶段：早期，典型的炎症反应随之而来，包括浸润的白细胞产生NO*，试图对伤口进行消毒。随后，宿主进入与抗炎介质和生长促进信号相关的伤口愈合和再生阶段，这些信号包括一类称为多胺的化合物（即腐胺、亚精胺和精胺）的产生。NO*和多胺都是由宿主精氨酸合成的，精氨酸的命运深刻影响金黄色葡萄球菌感染的结果。金黄色葡萄球菌对NO*的细胞毒性作用具有独特的抗性，然而多胺对这种病原体具有高毒性。事实上，考虑到溶解性皮肤病变的高度增殖性质，多胺在溶解阶段变得足够丰富，可以直接杀死MRSA。唯一的例外是属于新出现的社区相关MRSA USA300克隆的分离株。这些菌株获得精胺/亚精胺乙酰转移酶（SpeG），使其对宿主多胺具有完全的抗性，并有助于这些克隆的显著成功。在此，我们建议开发新的细菌speg同源物抑制剂，同时优化感染皮肤脓肿中宿主多胺水平。这种抗微生物/抗耐药性方法将允许治疗复杂的MRSA ssti，无论它们是否由表达speg的USA300菌株引起。有趣的是，我们发现从各种伤口相关的MDR病原体（如耐万古霉素的粪肠球菌、鲍曼不动杆菌和大肠杆菌）中去除speg活性通常会导致多胺敏感性。因此，这种方法可以扩展到治疗由许多耐多药细菌引起的伤口感染。我们计划开发一种基于荧光的检测方法来量化USA300 SpeG活性，该活性可以用一个小分子文库进行筛选，以确定先前鉴定的低亲和力SpeG抑制剂的结构-活性关系。我们的目标是找到可以安全应用的有效的SpeG拮抗剂

DESCRIPTION (provided by applicant): Skin and soft tissue infections (SSTIs) and their associated complications represent a significant source of morbidity and mortality in the US, particularly when caused by multidrug-resistant (MDR) pathogens. The most common source of MDR associated SSTI is methicillin-resistant Staphylococcus aureus (MRSA). The host response during MRSA SSTIs involves two general phases: early on, a classical inflammatory response ensues including infiltrating leukocytes generating NO* in an attempt to sterilize the wound. Later, the host shifts into a wound-resolution and regenerative phase associated with anti-inflammatory mediators and growth promoting signals including the production of a class of compounds known as polyamines (i.e. putrescine, spermidine, and spermine). Both NO* and polyamines are synthesized from host arginine and the fate of arginine profoundly affects the outcomes of S. aureus infections. S. aureus is uniquely resistant to the cytotoxic effects of NO*, however polyamines are highly toxic to this pathogen. In fact, given the highly proliferative nature of a resolving skin lesion, polyamines become abundant enough during the resolution phase to directly kill MRSA. The only exceptions are isolates belonging to the emerging community-associated MRSA USA300 clones. These strains acquired a spermine/spermidine acetyltransferase (SpeG) that confers complete resistance to host polyamines and contributes to the remarkable success of these clones. Here we propose to develop novel inhibitors of bacterial SpeG-homologues and simultaneously optimize host polyamine levels in infected skin abscesses. This antimicrobial/anti-resistance approach would allow for the treatment of complicated MRSA SSTIs regardless of whether they are caused by SpeG-expressing USA300 strains. Interestingly, we found that eliminating SpeG-activity from a variety of wound-related MDR pathogens (e.g. Vancomycin-resistant Enterococcus faecalis, Acinetobacter baumannii, and E. coli) generally leads to polyamine sensitivity. Thus, this approach can be extended to treat wound infections caused by a many MDR bacteria. We outline our plan to develop a fluorescence-based assay to quantify USA300 SpeG activity that can be screened with a small molecule library targeted to define structure-activity relationships to previously identified low-affinity SpeG-inhibitors. Our goal is to find effective SpeG antagonists that can be safely applied topically to skin lesions in which we have optimized polyamine levels. Polyamine optimization can be accomplished by direct topical administration of spermine and/or spermidine simultaneously with FDA-approved agents that limit polyamine catabolism. Alternatively, we propose a series of experiments that test the feasibility of immunomodulation as a mechanism of polyamine optimization. Upon completing our aims, we will determine the safest and most effective mechanism of optimizing tissue polyamines during an SSTI and combine this with potent anti-SpeG compounds that will render a number of wound-related pathogens susceptible to elevated polyamines. We will ascertain whether this is an effective treatment on its own, or better serves to augment current treatment strategies given the documented synergy between polyamine- killing and traditional antibiotics. In the end, we hope to harness the anti-inflammatory nature of polyamines and at the same time exploit their antibacterial effects to improve disease outcomes of SSTIs caused by a variety of MDR pathogens.