Beta-lactam chemical probes for GLT-1 transporter-related pathologies

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DESCRIPTION (provided by applicant): This application addresses broad challenge Area (06) Enabling Technologies and Specific Challenge Topic 06-GM-102*: Chemist/Biologist Collaborations facilitating tool development. This is a collaborative research project between the medicinal chemistry and biology groups at Temple University School of Pharmacy. The purpose is to design and synthesize novel b-lactam containing compounds to use as chemical probes to better understand the biology of glutamate transporter subtype 1 (GLT-1) upon activation by the b-lactam antibiotic ceftriaxone (CTX) and to investigate the impact of GLT-1 transporter activation in preclinical models of glutamate-related neurological and pathological disorders, including such as epilepsy, stroke, amyotrophic lateral sclerosis, multiple sclerosis, depression and addiction (Rothstein et al., 2005). This research is important to mankind because of the widely held belief among neuroscientists that GLT-1 transporter activation is a powerful - and understudied - approach for managing a broad range of glutamate-related diseases. Considering the combined social, medical, economic and criminal impact of these diseases and the lack of safe, efficacious, and convenient treatments currently available to treat them, the development of novel and attractive therapies targeting GLT-1 transporters might be useful in managing these disorders that affect a significant proportion of the population. Although a critical role for GLT- 1 in glutamate physiology and pathophysiology is indisputable, our knowledge of the biology underlying GLT-1 transporter activation and the pharmacological effects resulting from GLT-1 activation is lacking. The main reason is a lack of compounds that activate GLT-1. This perspective changed recently when a screen of 1040 FDA-approved drugs and nutritionals identified b-lactam antibiotics as the only practical pharmaceuticals capable of activating GLT-1 transporters. Preclinical studies using CTX have now demonstrated that GLT-1 activation is effective in animal models of glutamate-related pathologies. These studies have provided invaluable knowledge about GLT-1 biology and a proof-of-principle that GLT-1 activation should be explored as a powerful therapeutic approach. However, considering the resistance and diarrhea resulting from long-term antibiotic use, as well as the large doses of CTX (200 mg/kg) which are necessary in vivo, it is unlikely that direct antibiotic therapy will be used in the clinical management of pathologies caused by excessive glutamatergic transmission. This proposal directly addresses this therapeutic limitation by designing and synthesizing non-antibiotic, b-lactam containing compounds to eventually achieve the ultimate goal of developing a novel drug that will be useful in the clinical management of a broad range of glutamate-related neurological and pathological diseases. A primary step in the eventual development of potential therapeutic entities requires a structure-activity analysis of b-lactam derivatives towards a separation of GLT-1 and antibiotic activity. The establishment of a GLT-1-specific pharmacophore, with the ability to effectively cross the blood-brain barrier (BBB), will provide a structural template for the development of future compounds for further in vivo study. Therefore, emphasis in this proposal will be on designing b-lactam probes displaying three properties: enhanced BBB penetrability; GLT-1 activity; and reduced antibiotic efficacy. The in vivo GLT-1 activity of chemical probes satisfying these conditions will then be investigated using the biological endpoints of opiate tolerance, physical dependence and addiction, all of which are mediated in part by enhanced glutamatergic transmission. We will test the overall hypothesis that non-antibiotic, b-lactam containing compounds displaying enhanced brain penetrability and GLT-1 activity will block morphine tolerance and physical dependence and heroin and cocaine self-administration in rats through GLT-1 transporter activation. Taken together, experiments proposed herein will provide the first comprehensive investigation of the chemical and biological properties of b-lactam compounds as related to a broad range of glutamate-related neurological and pathological diseases. Temple University contributes substantially to the local economy, with a total annual economic impact of $2.7 billion. This includes annual operating spending of $850 million which creates or supports 6,439 jobs, $1.09 billion in employee spending that maintains an additional 5,299 jobs. Temple is currently spending $95.5 million on construction projects annually, creating 868 jobs. Temple graduates contribute to the economy, with an overall economic impact of $8.7 billion supporting 42,386 jobs. It is estimated the current proposal will create or retain the equivalent of 6-8 jobs in addition to providing purchasing power of ~$188,000 over two years. PUBLIC HEALTH RELEVANCE: A significant percentage of the United States population is affected by a broad range of glutamate-related neurological and pathological disorders which currently lack efficacious and safe treatments. One of the most promising - and understudied - strategies for managing such conditions is glutamate transporter subtype 1 (GLT-1) activation. The recent identification of b-lactam antibiotics as the only practical pharmaceuticals capable of activating GLT-1 indicates that a structure-activity analysis of b-lactam derivatives, directed towards a separation of GLT-1 and antibiotic activity, will result in the identification of one or more novel, non-antibiotic, b-lactam containing reference probes which will provide a structural template for the future development of attractive GLT-1-directed therapies.