Neuronal damage in human immunodeficiency virus type 1 (HIV-1) infection in the brain is thought to occur at least in part through

The need for selective matrix metalloproteinase (MMP) inhibition is of interest because of the range of pathologies mediated by different MMP isoforms. The development of more selective MMP inhibitors (MMPi) may help to overcome some of the undesired side effects that have hindered the clinical success of these compounds. In an effort to devise new approaches to selective inhibitors, herein we describe several novel MMPi and show that their selectivity is dependent on the nature of the zinc-binding group (ZBG). This is in contrast to most current MMPi, which obtain isoform selectivity solely from the peptidomimetic backbone portion of the compound. In the present study, six different hydroxypyrone and hydroxypyridinone ZBGs were appended to a common biphenyl backbone and the inhibition efficiency of each inhibitor was determined in vitro (IC(50) values) against MMP-1, -2, -3, -7, -8, -9, -12, and -13. The results show that the selectivity profile of each inhibitor is different as a result of the various ZBGs. Computational modeling studies were used to explain some trends in the observed selectivity profiles. To assess the importance of the ZBG in a biological model, two of the semiselective, potent MMPi (and one control) were evaluated using an isolated perfused rat heart system. Hearts were subjected to ischemia reperfusion injury, and recovery of contractile function was examined. In this model, only one of the two MMPi showed significant and sustained heart recovery, demonstrating that the choice of ZBG can have a significant effect in a relevant pathophysiological endpoint.

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A chelator fragment library based on a variety of metal binding groups was screened against a metalloproteinase. Lead hits were identified and an expanded library of select compounds was synthesized, resulting in numerous high-affinity hits against several metalloprotein targets. The findings clearly demonstrate that chelators can be used to generate libraries suitable for fragmentbased lead design (FBLD) directed at important metalloproteins. Keywordschelators; fragment-based lead design; libraries; metalloproteins; zinc Fragment-based lead design (FBLD), sometimes referred to as fragment-based drug discovery (FBDD), is an increasingly important strategy for the discovery of biologically active compounds.[1] FBLD generally uses libraries consisting of modest collections (100-1000 compounds) of small molecular fragments (MW <300 amu) that are screened against targets of interest.[2] Although such fragments do not bind as tightly (K d values in the micro-to millimolar range) as more complex molecules, including those used in high-throughput screening (HTS) approaches, they can provide 'hits' that serve as efficient starting structures for the development of potent inhibitors. Fragments that bind to a target are identified, after which one of two approaches is generally pursued: a) a single fragment can be elaborated in order to obtain a tight binder; or b) multiple fragments binding at adjacent and distinct sites can be connected by an appropriate linker to obtain a potent inhibitor. Compared to HTS, FBLD is purported to have several advantages, including a more efficient exploration of chemically diverse space and higher ligand efficiencies.Although the application of FBLD to metalloprotein targets of medicinal interest has been described, [3] Matrix metalloproteinases (MMPs) represent one of the most well-established targets in the realm of metalloproteins. These zinc(II)-dependent enzymes have been extensively studied, and the development of MMP inhibitors (MMPi) has played an important role in the discovery of inhibitors for other zinc(II)-dependent metalloproteins, such as anthrax lethal factor (LF), histone deacetylases (HDACs), and others.[10] Indeed, the earliest application of FBLD to a metalloprotein target was directed at MMP-3.[3] Therefore, we focused our preliminary library screening efforts on MMPs, as a representative system for identifying fragments that would bind zinc(II) metalloproteins. Based on widely-reported criteria for fragment libraries, [2] an initial chelator fragment library (CFL-1) was assembled. A modest library containing 96 structural cores was prepared from chelators with two to four donor atoms for binding metal ions and sufficient solubility for screening ( Figure 1). The chelating groups included picolinic acids, hydroxyquinolones, pyrimidines, hydroxypyrones, hydroxypyridinones and salicylic acids, in addition to other compounds that are well-established components of metalloprotein inhibitors, such as hydroxamic acids and sulfonamides ( Figure 1). The CFL-1 librar...

Several G protein-coupled receptors (GPCRs) mediate neuronal cell migration and survival upon activation by their native peptide ligands but activate death-signaling pathways when activated by certain non-native ligands. In cultured neurons, we recently described expression of the unique seven-transmembrane (7TM) -G protein-coupled receptor, APJ, which is also strongly expressed in neurons in the brain and various cell types in other tissues. We now demonstrate that the endogenous APJ peptide ligand apelin activates signaling pathways in rat hippocampal neurons and modulates neuronal survival. We found that (i) both APJ and apelin are expressed in hippocampal neurons; (ii) apelin peptides induce phosphorylation of the cell survival kinases AKT and Raf/ERK-1/2 in hippocampal neurons; and (iii) apelin peptides protect hippocampal neurons against NMDA receptor-mediated excitotoxicity, including that induced by human immunodeficiency virus type 1. Thus, apelin/APJ signaling likely represents an endogenous hippocampal neuronal survival response, and therefore apelin should be further investigated as a potential neuroprotectant against hippocampal injury.