👤 Cuevas JV

Ru(II) polypyridyl complexes are widely used in biological fields, due to their physico-chemical and photophysical properties. In this paper, a series of new chiral Ru(II) polypyridyl complexes (1-5) with the general formula {Δ/Λ-[Ru(bpy)₂(X,Y-sal)]BF₄} (bpy = 2,2'-bipyridyl; X,Y-sal = 5-bromosalicylaldehyde (1), 3,5-dibromosalicylaldehyde (2), 5-chlorosalicylaldehyde (3), 3,5-dichlorosalicylaldehyde (4) and 3-bromo-5-chlorosalicylaldehy (5)) were synthesized and characterized by elemental analysis, FT-IR, and ¹H/¹³C NMR spectroscopy. Also, the structures of complexes 1 and 5 were determined by X-ray crystallography; these results showed that the central Ru atom adopts a distorted octahedral coordination sphere with two bpy and one halogen-substituted salicylaldehyde. DFT and TD-DFT calculations have been performed to explain the excited states of these complexes. The singlet states with higher oscillator strength are correlated with the absorption signals and are mainly described as ¹MLCT from the ruthenium centre to the bpy ligands. The lowest triplet states (T₁) are described as ³MLCT from the ruthenium center to the salicylaldehyde ligand. The theoretical results are in good agreement with the observed unstructured band at around 520 nm for complexes 2, 4 and 5. Biological studies on human cancer cells revealed that dihalogenated ligands endow the Ru(II) complexes with enhanced cytotoxicity compared to monohalogenated ligands. In addition, as far as the type of halogen is concerned, bromine is the halogen that provides the highest cytotoxicity to the synthesized complexes. All complexes induce cell cycle arrest in G0/G1 and apoptosis, but only complexes bearing Br are able to provoke an increase in intracellular ROS levels and mitochondrial dysfunction. Show less

The regulation of hydrogen ion concentration (pH) is fundamental to cell viability, metabolism, and enzymatic function. Within the nervous system, the control of pH is also involved in diverse and dynamic processes including development, synaptic transmission, and the control of network excitability. As pH affects neuronal activity, and can also itself be altered by neuronal activity, the existence of tools to accurately measure hydrogen ion fluctuations is important for understanding the role pH plays under physiological and pathological conditions. Outside of their use as a marker of synaptic release, genetically encoded pH sensors have not been utilized to study hydrogen ion fluxes associated with network activity. By combining whole-cell patch clamp with simultaneous two-photon or confocal imaging, we quantified the amplitude and time course of neuronal, intracellular, acidic transients evoked by epileptiform activity in two separate in vitro models of temporal lobe epilepsy. In doing so, we demonstrate the suitability of three genetically encoded pH sensors: deGFP4, E(2)GFP, and Cl-sensor for investigating activity-dependent pH changes at the level of single neurons. Show less

Aminophosphines 2-(diphenylphosphino)-1-methylimidazole (dpim) and diphenyl-2-pyridylphosphine (PPh(2)py) have been used to prepare two series of Ru(II) arene complexes of formulae [(η(6)-p-cymene)Ru(κ(2)-O,O'-X)(κ(1)-P-dpim)]Y (series a: 1a·Y-3a·Y) and [(η(6)-p-cymene)Ru(κ(2)-O,O'-X)(κ(1)-P-PPh(2)py)]Y (series b: 1b·Y-3b·Y) (where X=acac, acetylacetonate; bzac, benzoyl acetonate; dbzm, dibenzoyl methanoate; Y=BF(4), BPh(4)). The structures of 1a·BF(4), 1a·BPh(4), 3a·BF(4), 1b·BPh(4) and 3b·BPh(4) were determined by X-ray diffraction. The tetrafluoroborate derivatives are more soluble in organic solvents than their tetraphenylborate counterparts. Five BF(4)(-) derivatives (all except the unstable 1b·BF(4)) were selected to evaluate the cytotoxic behavior in vitro against the human cancer cell lines MCF-7 (breast cancer) and CAPAN-1 (pancreatic cancer). 2b·BF(4) and 3b·BF(4) exhibited IC(50) values similar to those of cisplatin. Electrophoresis and AFM studies showed good correspondence between the biological activity levels of 2b·BF(4) and 3b·BF(4) and their ability to modify the DNA structure. Hydrolytic studies indicate that aquation could be involved in the activation mechanism of these complexes and confirm that the hydrolysis rate of 3b·BF(4) is higher than that of 3a·BF(4). Thus, the cytotoxic activity trends are explained in terms of the higher reactivity of derivatives from series b, which in turn is rationalized as being the result of the electronic features of dpim and PPh(2)py established by cyclic voltammetry measurements. Show less

The bZIP transcription factor Nrf2 controls a genetic program that protects cells from oxidative damage and maintains cellular redox homeostasis. Keap1, a BTB-Kelch protein, is the major upstream regulator of Nrf2 and controls both the subcellular localization and steady-state levels of Nrf2. In this report, we demonstrate that Keap1 functions as a substrate adaptor protein for a Cul3-dependent E3 ubiquitin ligase complex. Keap1 assembles into a functional E3 ubiquitin ligase complex with Cul3 and Rbx1 that targets multiple lysine residues located in the N-terminal Neh2 domain of Nrf2 for ubiquitin conjugation both in vivo and in vitro. Keap1-dependent ubiquitination of Nrf2 is inhibited following exposure of cells to quinone-induced oxidative stress and sulforaphane, a cancer-preventive isothiocyanate. A mutant Keap1 protein containing a single cysteine-to-serine substitution at residue 151 within the BTB domain of Keap1 is markedly resistant to inhibition by either quinone-induced oxidative stress or sulforaphane. Inhibition of Keap1-dependent ubiquitination of Nrf2 correlates with decreased association of Keap1 with Cul3. Neither quinone-induced oxidative stress nor sulforaphane disrupts association between Keap1 and Nrf2. Our results suggest that the ability of Keap1 to assemble into a functional E3 ubiquitin ligase complex is the critical determinant that controls steady-state levels of Nrf2 in response to cancer-preventive compounds and oxidative stress. Show less