Targeting the Assembly of Bacterial Cell Division Protein FtsZ with Small Molecules

FtsZ is the key protein of bacterial cell division and an emergent target for new antibiotics. It is a filament-forming GTPase and a structural homologue of eukaryotic tubulin. A number of FtsZ-interacting compounds have been reported, some of which have powerful antibacterial activity. Here we review recent advances and new approaches in modulating FtsZ assembly with small molecules. This includes analyzing their chemical features, binding sites, mechanisms of action, the methods employed, and computational insights, aimed at a better understanding of their molecular recognition by FtsZ and at rational antibiotic design

Serotonin 5‑HT₆ Receptor Antagonists for the Treatment of Cognitive Deficiency in Alzheimer’s Disease

Alzheimer’s disease (AD) is one of the most frequent causes of death and disability worldwide and has a significant clinical and socioeconomic impact. In the search for novel therapeutic strategies, serotonin 5-HT₆ receptor (5-HT₆R) has been proposed as a promising drug target for cognition enhancement in AD. This manuscript reviews the compelling evidence for the implication of this receptor in learning and memory processes. We have summarized the current status of the medicinal chemistry of 5-HT₆R antagonists and the encouraging preclinical findings that demonstrate their significant procognitive behavioral effects in a number of learning paradigms, probably acting through modulation of multiple neurotransmitter systems and signaling pathways. The results of the ongoing clinical trials are eagerly awaited to shed some light on the validation of 5-HT₆R antagonists as a new drug class for the treatment of symptomatic cognitive impairment in AD, either as stand-alone therapy or in combination with established agents

New Serotonin 5‑HT_1A Receptor Agonists Endowed with Antinociceptive Activity <i>in Vivo</i>

We report the synthesis of new compounds <b>4–35</b> based on two different openings (A and B) of the chromane ring present in the previously identified 5-HT_1A receptor (5-HT_1AR) ligand <b>3</b>. The synthesized compounds were assessed for binding affinity, selectivity, and functional activity at the 5-HT_1AR. Selected candidates resulting from B opening were also evaluated for their potential antinociceptive effect <i>in vivo</i> and pharmacokinetic properties <i>in vitro</i>. Analogue <b>19</b> [2-(4-{[2-(2-ethoxyphenoxy)­ethyl]­amino}­butyl)­tetrahydro-1<i>H</i>-pyrrolo­[1,2-<i>c</i>]­imidazole-1,3­(2<i>H</i>)-dione] has been characterized as a high-affinity and potent 5-HT_1AR agonist (<i>K</i>_i = 2.3 nM; EC₅₀ = 19 nM). Pharmacokinetic studies indicated that compound <b>19</b> displays a good metabolic stability in human liver microsomes (<i>t</i>_1/2 ∼ 3 h and CL_int = 3.5 mL/min/kg, at 5 μM), and a low level of protein binding (25%, at 5 μM). Interestingly, <b>19</b> (3 mg/kg, ip, and 30 mg/kg, po) caused significant attenuation of formalin-induced behavior in early and late phases of the mouse intradermal formalin test of pain, and this <i>in vivo</i> effect was reversed by the selective 5-HT_1AR antagonist WAY-100635. Thus, the new 5-HT_1AR agonist identified in this work, <b>19</b>, exhibits oral analgesic activity, and the results herein represent a step toward identifying new therapeutics for the control of pain

The Extracellular Entrance Provides Selectivity to Serotonin 5‑HT₇ Receptor Antagonists with Antidepressant-like Behavior in Vivo

The finding that ergotamine binds serotonin receptors in a less conserved extended binding pocket close to the extracellular entrance, in addition to the orthosteric site, allowed us to obtain 5-HT₇R antagonist <b>6</b> endowed with high affinity (<i>K</i>_i = 0.7 nM) and significant 5-HT_1AR selectivity (ratio >1428). Compound <b>6</b> exhibits in vivo antidepressant-like effect (1 mg/kg, ip) mediated by the 5-HT₇R, which reveals its interest as a putative research tool or pharmaceutical in depression disorders

Development of a Fluorescent Bodipy Probe for Visualization of the Serotonin 5‑HT_1A Receptor in Native Cells of the Immune System

Serotonin (5-HT) modulates key aspects of the immune system. However, its precise function and the receptors involved in the observed effects have remained elusive. Among the different serotonin receptors, 5-HT_1A plays an important role in the immune system given its presence in cells involved in both the innate and adaptive immune responses, but its actual levels of expression under different conditions have not been comprehensively studied due to the lack of suitable tools. To further clarify the role of 5-HT_1A receptor in the immune system, we have developed a fluorescent small molecule probe that enables the direct study of the receptor levels in native cells. This probe allows direct profiling of the receptor expression in immune cells using flow cytometry. Our results show that important subsets of immune cells including human monocytes and dendritic cells express functional 5-HT_1A and that its activation is associated with anti-inflammatory signaling. Furthermore, application of the probe to the experimental autoimmune encephalomyelitis model of multiple sclerosis demonstrates its potential to detect the specific overexpression of the 5-HT_1A receptor in CD4+ T cells. Accordingly, the probe reported herein represents a useful tool whose use can be extended to study the levels of 5-HT_1A receptor in ex vivo samples of different immune system conditions

Synthetic Inhibitors of Bacterial Cell Division Targeting the GTP-Binding Site of FtsZ

Cell division protein FtsZ is the organizer of the cytokinetic Z-ring in most bacteria and a target for new antibiotics. FtsZ assembles with GTP into filaments that hydrolyze the nucleotide at the association interface between monomers and then disassemble. We have replaced FtsZ’s GTP with non-nucleotide synthetic inhibitors of bacterial division. We searched for these small molecules among compounds from the literature, from virtual screening (VS), and from our in-house synthetic library (UCM), employing a fluorescence anisotropy primary assay. From these screens we have identified the polyhydroxy aromatic compound UCM05 and its simplified analogue UCM44 that specifically bind to <i>Bacillus subtilis</i> FtsZ monomers with micromolar affinities and perturb normal assembly, as examined with light scattering, polymer sedimentation, and negative stain electron microscopy. On the other hand, these ligands induce the cooperative assembly of nucleotide-devoid archaeal FtsZ into distinct well-ordered polymers, different from GTP-induced filaments. These FtsZ inhibitors impair localization of FtsZ into the Z-ring and inhibit bacterial cell division. The chlorinated analogue UCM53 inhibits the growth of clinical isolates of antibiotic-resistant <i>Staphylococcus aureus</i> and <i>Enterococcus faecalis</i>. We suggest that these interfacial inhibitors recapitulate binding and some assembly-inducing effects of GTP but impair the correct structural dynamics of FtsZ filaments and thus inhibit bacterial division, possibly by binding to a small fraction of the FtsZ molecules in a bacterial cell, which opens a new approach to FtsZ-based antibacterial drug discovery

New Inhibitors of Angiogenesis with Antitumor Activity in Vivo

Angiogenesis is a requirement for the sustained growth and proliferation of solid tumors, and the development of new compounds that induce a sustained inhibition of the proangiogenic signaling generated by tumor hypoxia still remains as an important unmet need. In this work, we describe a new antiangiogenic compound (<b>22</b>) that inhibits proangiogenic signaling under hypoxic conditions in breast cancer cells. Compound <b>22</b> blocks the MAPK pathway, impairs cellular migration under hypoxic conditions, and regulates a set of genes related to angiogenesis. These responses are mediated by HIF-1α, since the effects of compound <b>22</b> mostly disappear when its expression is knocked-down. Furthermore, administration of compound <b>22</b> in a xenograft model of breast cancer produced tumor growth reductions ranging from 46 to 55% in 38% of the treated animals without causing any toxic side effects. Importantly, in the responding tumors, a significant reduction in the number of blood vessels was observed, further supporting the mechanism of action of the compound. These findings provide a rationale for the development of new antiangiogenic compounds that could eventually lead to new drugs suitable for the treatment of some types of tumors either alone or in combination with other agents