Neuroprotection and Enhancement of Neurite Outgrowth With Small Molecular Weight Compounds From Screens of Chemical Libraries

Discovery, Optimization, and Biological Evaluation of Sulfonamidoacetamides as an Inducer of Axon Regeneration

Axon regeneration after injury in the central nervous system is hampered in part because if an age-dependent decline in the intrinsic axon growth potential, and one of the strategies to stimulate axon growth in injured neurons involves pharmacological manipulation of implicated signaling pathways. Here we report phenotypic cell-based screen of chemical libraries and structure-activity-guided optimization that resulted in the identification of compound 7p which promotes neurite outgrowth of cultured primary neurons derived from the hippocampus, cerebral cortex, and retina. In an animal model of optic nerve injury, compound 7p was shown to induce growth of GAP-43 positive axons, indicating that the in vitro neurite outgrowth activity of compound 7p translates into stimulation of axon regeneration in vivo. Further optimization of compound 7p and elucidation of the mechanisms by which it elicits axon regeneration in vivo will provide a rational basis for future efforts to enhance treatment strategies.

Drug elucidation: invertebrate genetics sheds new light on the molecular targets of CNS drugs

Many important drugs approved to treat common human diseases were discovered by serendipity, without a firm understanding of their modes of action. As a result, the side effects and interactions of these medications are often unpredictable, and there is limited guidance for improving the design of next-generation drugs. Here, we review the innovative use of simple model organisms, especially Caenorhabditis elegans, to gain fresh insights into the complex biological effects of approved CNS medications. Whereas drug discovery involves the identification of new drug targets and lead compounds/biologics, and drug development spans preclinical testing to FDA approval, drug elucidation refers to the process of understanding the mechanisms of action of marketed drugs by studying their novel effects in model organisms. Drug elucidation studies have revealed new pathways affected by antipsychotic drugs, e.g., the insulin signaling pathway, a trace amine receptor and a nicotinic acetylcholine receptor. Similarly, novel targets of antidepressant drugs and lithium have been identified in C. elegans, including lipid-binding/transport proteins and the SGK-1 signaling pathway, respectively. Elucidation of the mode of action of anesthetic agents has shown that anesthesia can involve mitochondrial targets, leak currents, and gap junctions. The general approach reviewed in this article has advanced our knowledge about important drugs for CNS disorders and can guide future drug discovery efforts.

Drug discovery based on genetic and metabolic findings in schizophrenia

Recent progress in the genetics of schizophrenia provides the rationale for re-evaluating causative factors and therapeutic strategies for this disease. Here, we review the major candidate susceptibility genes and relate the aberrant function of these genes to defective regulation of energy metabolism in the schizophrenic brain. Disturbances in energy metabolism potentially lead to neurodevelopmental deficits, impaired function of the mature nervous system and failure to maintain neurites/dendrites and synaptic connections. Current antipsychotic drugs do not specifically address these underlying deficits; therefore, a new generation of more effective medications is urgently needed. Novel targets for future drug discovery are identified in this review. The coordinated application of structure-based drug design, systems biology and research on model organisms may greatly facilitate the search for next-generation antipsychotic drugs.

Triazolbenzo[d]thiazoles: efficient synthesis and biological evaluation as neuroprotective agents

A number of (1H-1,2,3-triazol-1-yl)benzo[d]thiazoles were synthesized utilizing a versatile Cu-catalyzed azide-alkyne click reaction (CuAAC) on tautomeric benzo[4,5]thiazolo[3,2-d]tetrazole (1) and 2-azidobenzo[d]thiazole (2) starting materials. Moreover, one of the resulting products of this investigation, triazolbenzo[d]thiazole 22, was found to possess significant neuroprotective activity in human neuroblastoma (SH-SY5Y) cells.

Structure-based discovery of low molecular weight compounds that stimulate neurite outgrowth and substitute for nerve growth factor

Olanzapine, an atypical antipsychotic drug, was previously shown to protect neuronal cells against nutrient deprivation and to enhance neurite outgrowth. In an effort to identify small molecules with greater potency, the structure of olanzapine was used as a template to search commercially available chemical inventories for compounds with similar features. These compounds were evaluated for their ability to protect cells against glutamine deprivation and low-serum conditions. Positive compounds, 'hits' from initial screening, were then tested for stimulation of neurite outgrowth, alone and in combination with suboptimum concentrations of nerve growth factor (NGF). Numerous neuroprotective compounds (mw < 550 Da) were identified that significantly stimulated neurite outgrowth in PC12 cells. These included 4', 6'-diamidino-2-phenylindole, a nuclear stain; staurosporine, an antibiotic and kinase inhibitor; and 2-phenylamino-adenosine, an adenosine analog. The small molecules were comparable with NGF, and in fact, replaced NGF in outgrowth assays. Pharmacophore analysis of the hits led to the design and synthesis of an active compound, LSU-D84, which represented an initial lead for drug discovery efforts.

Antipsychotic drugs: comparison in animal models of efficacy, neurotransmitter regulation, and neuroprotection

Various lines of evidence indicate the presence of progressive pathophysiological processes occurring within the brains of patients with schizophrenia. By modulating chemical neurotransmission, antipsychotic drugs may influence a variety of functions regulating neuronal resilience and viability and have the potential for neuroprotection. This article reviews the current literature describing preclinical and clinical studies that evaluate the efficacy of antipsychotic drugs, their mechanism of action and the potential of first- and second-generation antipsychotic drugs to exert effects on cellular processes that may be neuroprotective in schizophrenia. The evidence to date suggests that although all antipsychotic drugs have the ability to reduce psychotic symptoms via D(2) receptor antagonism, some antipsychotics may differ in other pharmacological properties and their capacities to mitigate and possibly reverse cellular processes that may underlie the pathophysiology of schizophrenia.