Exchangeable Self-Assembled Lanthanide Antennas for PLIM Microscopy.

Lanthanides have unique photoluminescence (PL) emission properties, including very long PL lifetimes. This makes them ideal for biological imaging applications, especially using PL lifetime imaging microscopy (PLIM). PLIM is an inherently multidimensional technique with exceptional advantages for quantitative biological imaging. Unfortunately, due to the required prolonged acquisitions times, photobleaching of lanthanide PL emission currently constitutes one of the main drawbacks of PLIM. In this study, we report a small aqueous-soluble, lanthanide antenna, 8-methoxy-2-oxo-1,2,4,5-tetrahydrocyclopenta[de]quinoline-3-phosphonic acid, PAnt, specifically designed to dynamically interact with lanthanide ions, serving as exchangeable dye aimed at mitigating photobleaching in PLIM microscopy in cellulo. Thus, self-assembled lanthanide complexes that may be photobleached during image acquisition are continuously replenished by intact lanthanide antennas from a large reservoir. Remarkably, our self-assembled lanthanide complex clearly demonstrated a significant reduction of PL photobleaching when compared to well-established lanthanide cryptates, used for bioimaging. This concept of exchangeable lanthanide antennas opens new possibilities for quantitative PLIM bioimaging.

Identification of IQM-266, a Novel DREAM Ligand That Modulates KV4 Currents.

Downstream Regulatory Element Antagonist Modulator (DREAM)/KChIP3/calsenilin is a neuronal calcium sensor (NCS) with multiple functions, including the regulation of A-type outward potassium currents (I A). This effect is mediated by the interaction between DREAM and KV4 potassium channels and it has been shown that small molecules that bind to DREAM modify channel function. A-type outward potassium current (I A) is responsible of the fast repolarization of neuron action potentials and frequency of firing. Using surface plasmon resonance (SPR) assays and electrophysiological recordings of KV4.3/DREAM channels, we have identified IQM-266 as a DREAM ligand. IQM-266 inhibited the KV4.3/DREAM current in a concentration-, voltage-, and time-dependent-manner. By decreasing the peak current and slowing the inactivation kinetics, IQM-266 led to an increase in the transmembrane charge ( Q K V 4.3 / DREAM ) at a certain range of concentrations. The slowing of the recovery process and the increase of the inactivation from the closed-state inactivation degree are consistent with a preferential binding of IQM-266 to a pre-activated closed state of KV4.3/DREAM channels. Finally, in rat dorsal root ganglion neurons, IQM-266 inhibited the peak amplitude and slowed the inactivation of I A. Overall, the results presented here identify IQM-266 as a new chemical tool that might allow a better understanding of DREAM physiological role as well as modulation of neuronal I A in pathological processes.

Conjugates of 2,4-Dihydroxybenzoate and Salicylhydroxamate and Lipocations Display Potent Antiparasite Effects by Efficiently Targeting the Trypanosoma brucei and Trypanosoma congolense Mitochondrion.

We investigated a chemical strategy to boost the trypanocidal activity of 2,4-dihydroxybenzoic acid (2,4-DHBA)- and salicylhydroxamic acid (SHAM)-based trypanocides with triphenylphosphonium and quinolinium lipophilic cations (LC). Three series of LC conjugates were synthesized that were active in the submicromolar (5a-d and 10d-f) to low nanomolar (6a-f) range against wild-type and multidrug resistant strains of African trypanosomes (Trypanosoma brucei brucei and T. congolense). This represented an improvement in trypanocidal potency of at least 200-fold, and up to >10 000-fold, compared with that of non-LC-coupled parent compounds 2,4-DHBA and SHAM. Selectivity over human cells was >500 and reached >23 000 for 6e. Mechanistic studies showed that 6e did not inhibit the cell cycle but affected parasite respiration in a dose-dependent manner. Inhibition of trypanosome alternative oxidase and the mitochondrial membrane potential was also studied for selected compounds. We conclude that effective mitochondrial targeting greatly potentiated the activity of these series of compounds.