New classes of antibiotics are urgently needed to counter increasing levels of pathogen resistance. Peptide
deformylase (PDF) was originally selected as a specific bacterial target, but a human homologue, the inhibition
of which causes cell death, was recently discovered. We developed a dual-screening strategy for selecting
highly effective compounds with low inhibition effect against human PDF. We selected a new scaffold in
vitro that discriminated between human and bacterial PDFs. Analyses of structure−activity relationships
identified potent antibiotics such as 2-(5-bromo-1H-indol-3-yl)-N-hydroxyacetamide (6b) with the same
mode of action in vivo as previously identified PDF inhibitors but without the apoptotic effects of these
inhibitors in human cells.
Activation of cell signaling by reactive chemicals and pollutants is an important issue for human health. It has been shown that lipophilic nitro-benzoxadiazole (NBD) compounds rapidly move across the plasma membrane and enhance Epidermal Growth Factor Receptor (EGFR) tyrosine phosphorylation in cancer cells. Unlike ligand-dependent activation, the mechanism of this induction relies on the generation of hydrogen peroxide, which is involved in the activation of the catalytic site of the receptor and the inactivation of protein tyrosine phosphatase PTP-1B. Production of H2O2 during redox transformation of NBD compounds is associated with the transition of a monomeric form of Cu/Zn superoxide dismutase 1 (SOD1) to stable dimers. The highly stable and functionally active SOD1 dimer, in the absence of adequate activities in downstream reactions, promotes the disproportionate production and accumulation of intracellular hydrogen peroxide shortly after exposure to NBD compounds. The intrinsic fluorescence of small compounds was used to demonstrate their binding to SOD1. Our data indicate that H2O2 and concomitantly generated electrophilic intermediates behave as independent entities, but all contribute to the biological reactivity of NBD compounds. This study opens a promising path to identify new biomarkers of oxidative/electrophilic stress in the progression of cancer and other diseases.
Current antidepressants act principally by blocking monoamine reuptake by high-affinity transporters in the brain. However, these antidepressants show important shortcomings such as slow action onset and limited efficacy in nearly a third of patients with major depression disorder. Here, we report the development of a prodrug targeting organic cation transporters (OCT), atypical monoamine transporters recently implicated in the regulation of mood. Using molecular modeling, we designed a selective OCT2 blocker, which was modified to increase brain penetration. In a rodent model of chronic depression induced by corticosterone exposure, daily administration of this compound, H2-cyanome, induced positive effects on several behaviors mimicking symptoms of depression, including anhedonia, anxiety, social withdrawal, and memory impairment. Importantly, in this validated model, H2-cyanome compared favorably with the classical antidepressant fluoxetine, with a faster action on anhedonia and better anxiolytic effects. Integrated Z-scoring across these depression-like variables revealed a lower depression score for mice treated with H2-cyanome than for mice treated with fluoxetine for 3 weeks. Repeated H2-cyanome administration increased VTA dopaminergic neuron firing, which may underlie its rapid action on anhedonia. H2-cyanome also modulated in a similar way than fluoxetine several intracellular signaling pathways previously involved in antidepressant response. Our findings provide proof-of-concept of long-term antidepressant efficacy of an OCT blocker, and a mechanistic framework for the development of new classes of antidepressants and therapeutic alternatives for resistant depression and other psychiatric disturbances such as anxiety.
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