In this study, we tested five compounds belonging to a novel series of piperazine arylideneimidazolones for the ability to inhibit the AcrAB-TolC efflux pump. The biphenylmethylene derivative (BM-19) and the fluorenylmethylene derivative (BM-38) were found to possess the strongest efflux pump inhibitor (EPI) activities in the AcrAB-TolC-overproducing Escherichia coli strain 3-AG100, whereas BM-9, BM-27, and BM-36 had no activity at concentrations of up to 50 μM in a Nile red efflux assay. MIC microdilution assays demonstrated that BM-19 at 1/4 MIC (intrinsic MIC, 200 μM) was able to reduce the MICs of levofloxacin, oxacillin, linezolid, and clarithromycin 8-fold. BM-38 at 1/4 MIC (intrinsic MIC, 100 μM) was able to reduce only the MICs of oxacillin and linezolid (2-fold). Both compounds markedly reduced the MIC of rifampin (BM-19, 32-fold; and BM-38, 4-fold), which is suggestive of permeabilization of the outer membrane as an additional mechanism of action. Nitrocefin hydrolysis assays demonstrated that in addition to their EPI activity, both compounds were in fact weak permeabilizers of the outer membrane. Moreover, it was found that BM-19, BM-27, BM-36, and BM-38 acted as near-infrared-emitting fluorescent membrane probes, which allowed for their use in a combined influx and efflux assay and thus for tracking of the transport of an EPI across the outer membrane by an efflux pump in real time. The EPIs BM-38 and BM-19 displayed the most rapid influx of all compounds, whereas BM-27, which did not act as an EPI, showed the slowest influx.

Background and Purpose: The histaminergic system is a promising target for the development of new analgesics, as histamine H₃ and H₄ receptors are expressed in regions concerned with nociceptive transmission. Here we have determined the analgesic effects of new H₃ and H₄ receptor antagonists in naive and neuropathic mice.Experimental Approach: We used chronic constriction injury (CCI) to the sciatic nerve in mice to model neuropathy. Effects of a new H₃ receptor antagonist, E‐162(1‐(5‐(naphthalen‐1‐yloxy)pentyl)piperidine) and H₄ receptor antagonist, TR‐7(4‐(4‐chlorophenyl)‐6‐(4‐methylpiperazin‐1‐yl)‐1,3,5‐triazin‐2‐amine) were assessed on mechanical (von Frey) and thermal (cold plate, tail flick) stimuli in mice with and without CCI (7 days after injury). Effects of these antagonists on morphine analgesia were also evaluated, along with the possible participation of H₁ receptors in their effects. We analysed the compounds in binding and functional cAMP assays at the H₃ and H₄ receptors and determined metabolic stability.Key Results: E‐162 and TR‐7 attenuated nociceptive responses and profound morphine analgesia in males with CCI. These antagonists showed analgesia in naive mice (tail flick test) and produced prolonged analgesia in neuropathic females. E‐162‐induced analgesia was reversed by pyrilamine, an H₁ receptor antagonist. E‐162 bound potently to H₃ receptors (K_i = 55 nM) and inhibited cAMP accumulation (IC₅₀ = 165 nM). TR‐7 showed lower affinity for H₄ receptors (K_i = 203 nM) and IC₅₀ of 512 nM.Conclusions and Implications: We describe a therapeutic use for new H₃ (E‐162) and H₄ receptor (TR‐7) antagonists in neuropathy. Targeting H₃ and H₄ receptors enhanced morphine analgesia, consistent with multimodal pain therapy.

In view of the pressing need to identify new antibacterial agents able to combat multidrug-resistant bacteria, we investigated a series of fused selenazolinium derivatives (1–8) regarding their in vitro antimicrobial activities against 25 ESKAPE-pathogen strains. Ebselen was used as reference compound. Most of the selenocompounds demonstrated an excellent in vitro activity against all S. aureus strains, with activities comparable to or even exceeding the one of ebselen. In contrast to ebselen, some selenazolinium derivatives (1, 3, and 7) even displayed significant actions against all Gram-negative pathogens tested. The 3-bromo-2-(1-hydroxy-1-methylethyl)[1,2]selenazolo[2,3-a]pyridinium chloride (1) was particularly active (minimum inhibitory concentrations, MICs: 0.31–1.24 µg/mL for MRSA, and 0.31–2.48 µg/mL for Gram-negative bacteria) and devoid of any significant mutagenicity in the Ames assay. Our preliminary mechanistic studies in cell culture indicated that their mode of action is likely to be associated with an alteration of intracellular levels of glutathione and cysteine thiols of different proteins in the bacterial cells, hence supporting the idea that such compounds interact with the intracellular thiolstat. This alteration of pivotal cysteine residues is most likely the result of a direct or catalytic oxidative modification of such residues by the highly reactive selenium species (RSeS) employed.

The clinical symptoms of Parkinson’s disease (PD) appear when dopamine (DA) concentrations in the striatum drops to around 20%. Simultaneous inhibitory effects on histamine H₃ receptor (H₃R) and MAO B can increase DA levels in the brain. A series of compounds was designed and tested in vitro for human H₃R (hH₃R) affinity and inhibitory activity to human MAO B (hMAO B). Results showed different activity of the compounds towards the two biological targets. Most compounds had poor affinity for hH₃R (K_i > 500 nM), but very good inhibitory potency for hMAO B (IC₅₀ < 50 nM). After further in vitro testing (modality of MAO B inhibition, permeability in PAMPA assay, cytotoxicity on human astrocyte cell lines), the most promising dual-acting ligand, 1-(3-(4-(tert-butyl)phenoxy)propyl)-2-methylpyrrolidine (13: hH₃R: K_i = 25 nM; hMAO B IC₅₀ = 4 nM) was selected for in vivo evaluation. Studies in rats of compound 13, in a dose of 3 mg/kg of body mass, confirmed its antagonistic effects for H₃R (decline in food and a water consumption), decline in MAO B activity (>90%) in rat cerebral cortex (CTX), and an increase in DA content in CTX and striatum. Moreover, compound 13 caused a slight increase in noradrenaline, but a reduction in serotonin concentration in CTX. Thus, compound 13 is a promising dual-active ligand for the potential treatment of PD although further studies are needed to confirm this.