Journal of Biological Inorganic Chemistry最新文献

Human calprotectin (CP) is an innate immune protein that participates in the metal-withholding response to infection by sequestering essential metal nutrients from invading microbial pathogens. CP is comprised of S100A8 (α subunit, 10.8 kDa) and S100A9 (β subunit, 13.2 kDa). Two transition-metal binding sites of CP form at the S100A8/S100A9 dimer interface. Site 1 is a His₃Asp motif comprised of His83 and His87 from the S100A8 subunit and His20 and Asp30 from the S100A9 subunit. Site 2 is an unusual hexahistidine motif composed of S100A8 residues His17 and His27 and S100A9 residues His91, His95, His103, and His105. In the present study, the His₃Asp and His₆ sites of CP were further characterized by utilizing Co²⁺ as a spectroscopic probe. Magnetic circular dichroism spectroscopy was employed in conjunction with electron paramagnetic resonance spectroscopy and density functional theory computations to characterize the Co²⁺-bound S100A8(C42S)/S100A9(C3S) CP-Ser variant and six site variants that allowed the His₃Asp and His₆ sites to be further probed. Our results provide new insight into the metal-binding sites of CP-Ser and the effect of amino acid substitutions on the structure of site 2.

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Hyperthermophilic (‘superheat-loving’) archaea found in high-temperature environments such as Pyrobaculum aerophilum contain multicopper oxidases (MCOs) with remarkable efficiency for oxidizing cuprous and ferrous ions. In this work, directed evolution was used to expand the substrate specificity of P. aerophilum McoP for organic substrates. Six rounds of error-prone PCR and DNA shuffling followed by high-throughput screening lead to the identification of a hit variant with a 220-fold increased efficiency (k_cat/K_m) than the wild-type for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) without compromising its intrinsic activity for metal ions. The analysis of the X-ray crystal structure reveals four proximal mutations close to the T1Cu active site. One of these mutations is within the 23-residues loop that occludes this site, a distinctive feature of prokaryotic MCOs. The increased flexibility of this loop results in an enlarged tunnel and one additional pocket that facilitates bulky substrate-enzyme interactions. These findings underscore the synergy between mutations that modulate the dynamics of the active-site loop enabling enhanced catalytic function. This study highlights the potential of targeting loops close to the T1Cu for engineering improvements suitable for biotechnological applications.

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Transition metal complexes with characteristics of unique packaging in nanoparticles and remarkable cancer cell cytotoxicity have emerged as potential alternatives to platinum-based antitumor drugs. Here we report the synthesis, characterization, and antitumor activities of three new Ruthenium complexes that introduce 5-fluorouracil-derived ligands. Notably, encapsulation of one such metal complex, Ru3, within pluronic^® F-127 micelles (Ru3-M) significantly enhanced Ru3 cytotoxicity toward A549 cells by a factor of four. To determine the mechanisms underlying Ru3-M cytotoxicity, additional in vitro experiments were conducted that revealed A549 cell treatment with lysosome-targeting Ru3-M triggered oxidative stress, induced mitochondrial membrane potential depolarization, and drastically reduced intracellular ATP levels. Taken together, these results demonstrated that Ru3-M killed cells mainly via a non-apoptotic pathway known as oncosis, as evidenced by observed Ru3-M-induced cellular morphological changes including cytosolic flushing, cell swelling, and cytoplasmic vacuolation. In turn, these changes together caused cytoskeletal collapse and activation of porimin and calpain1 proteins with known oncotic functions that distinguished this oncotic process from other cell death processes. In summary, Ru3-M is a potential anticancer agent that kills A549 cells via a novel mechanism involving Ru(II) complex triggering of cell death via oncosis.

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Melanoma is the most aggressive and lethal type of skin cancer due to its characteristics such as high metastatic potential and low response rate to existing treatment modalities. In this way, new drug prototypes are being studied to solve the problem of treating patients with melanoma. Among these, ruthenium-based metallopharmaceuticals may be promising alternatives due to their antitumor characteristics and low systemic toxicity. In this context, the present study evaluated the antineoplastic effect of the ruthenium complex [Ru(mtz)(dppe)₂]PF₆-2-mercaptothiazoline-di-1,2-bis(diphenylphosphine) ethaneruthenium(II), namely RuMTZ, on human melanoma (A-375) and murine (B16-F10) cells, considering different approaches. Through XTT colorimetric and clonogenic efficiency assays, the complex revealed the selective cytotoxic activity, with the lowest IC₅₀ (0.4 µM) observed for A375 cells. RuMTZ also induced changes in cell morphology, increased cell population in the sub-G0 phase and inhibiting cell migration. The levels of γH2AX and cleaved caspase 3 proteins were increased in both cell lines treated with RuMTZ. These findings indicated that the cytotoxic activity of RuMTZ on melanoma cells is related, at least in part, to the induction of DNA damage and apoptosis. Therefore, RuMTZ exhibited promising antineoplastic activity against melanoma cells.

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The aim to access linked tetravanadate [V₄O₁₂]⁴⁻ anion with mixed copper(II) complexes, using α-amino acids and phenanthroline-derived ligands, resulted in the formation of four copper(II) complexes [Cu(dmb)(Gly)(OH₂)]₂[Cu(dmb)(Gly)]₂[V₄O₁₂]·9H₂O (1) [Cu(dmb)(Lys)]₂[V₄O₁₂]·8H₂O (2), [Cu(dmp)₂][V₄O₁₂]·C₂H₅OH·11H₂O (3), and [Cu(dmp)(Gly)Cl]·2H₂O (4), where dmb = 4,4′-dimethioxy-2,2′-bipyridine; Gly = glycine; Lys = lysine; and dmp = 2,9-dimethyl-1,10-phenanthroline. The [V₄O₁₂]⁴⁻ anion is functionalized with mixed copper(II) units in 1 and 2; while in 3, it acts as a counterion of two [Cu(dmp)]²⁺ units. Compound 4 crystallized as a unit that did not incorporate the vanadium cluster. All compounds present magnetic couplings arising from Cu⋯O/Cu⋯Cu bridges. Stability studies of water-soluble 3 and 4 by UV–Vis spectroscopy in cell culture medium confirmed the robustness of 3, while 4 appears to undergo ligand scrambling over time, resulting partially in the stable species [Cu(dmp)₂]⁺ that was also identified by electrospray ionization mass spectrometry at m/z = 479. The in vitro cytotoxicity activity of 3 and 4 was determined in six cancer cell lines; the healthy cell line COS-7 was also included for comparative purposes. MCF-7 cells were more sensitive to compound 3 with an IC₅₀ value of 12 ± 1.2 nmol. The tested compounds did not show lipid peroxidation in the TBARS assay, ruling out a mechanism of action via reactive oxygen species formation. Both compounds inhibited cell migration at 5 µM in wound-healing assays using MCF-7, PC-3, and SKLU-1 cell lines, opening a new window to study the anti-metastatic effect of mixed vanadium–copper(II) systems.

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The aim of this study was to investigate the effect and possible underlying mechanism of La₂(CO₃)₃ deposition on GI mucosal inflammation. Our results showed that La₂(CO₃)₃ can dissolve in artificial gastric fluids and form lanthanum phosphate (LaPO₄) precipitates with an average size of about 1 μm. To mimic the intestinal mucosa and epithelial barrier, we established a Caco-2/THP-1 macrophage coculture model and a Caco-2 monoculture model, respectively. Our findings demonstrated that the medium of THP-1 macrophages stimulated by LaPO₄ particles can damage the Caco-2 monolayer integrity in the coculture model, while the particles themselves had no direct impact on the Caco-2 monolayer integrity in the monoculture model. We measured values of trans-epithelial electrical resistance and detected images using a laser scanning confocal microscope. These results indicate that continuous stimulation of LaPO₄ particles on macrophages can lead to a disruption of intestinal epithelium integrity. In addition, LaPO₄ particles could stimulate THP-1 macrophages to secrete both IL-1β and IL-8. Although LaPO₄ particles can also promote Caco-2 cells to secrete IL-8, the secretion was much lower than that produced by THP-1 macrophages. In summary, the deposition of La₂(CO₃)₃ has been shown to activate macrophages and induce damage to intestinal epithelial cells, which may exacerbate inflammation in patients with chronic kidney disease. Therefore, patients taking lanthanum carbonate, especially those with gastrointestinal mucosal inflammation, should be mindful of the potential for drug deposition in the GI system.

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A schematic diagram of the effect and possible underlying mechanism of the deposition of La₂(CO₃)₃ on GI mucosal inflammation. 

Thiosemicarbazones are biologically active substances whose structural formula is formed by an azomethine, an hydrazine, and a thioamide fragments, to generate a R₂C=N–NR–C(=S)–NR₂ backbone. These compounds often act as ligands to generate highly stable metal–organic complexes. In certain experimental conditions, however, thiosemicarbazones undergo reactions leading to the cleavage of the chain. Sometimes, the breakage involves desulfurization processes. The present work summarizes the different chemical factors that influence the desulfurization reactions of thiosemicarbazones, such as pH, the presence of oxidant reactants or the establishment of redox processes as those electrochemically induced, the effects of the solvent, the temperature, and the electromagnetic radiation. Many of these reactions require coordination of thiosemicarbazones to metal ions, even those present in the intracellular environment. The nature of the products generated in these reactions, their detection in vivo and in vitro, together with the relevance for the biological activity of these compounds, mainly as antineoplastic agents, is discussed.

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Six aroylhydrazone di-m-chlorobenzyltin complexes {[X-C₆H₄(O)C=N–N=C(Me)COO](MeOH)(m-Cl-C₆H₄CH₂)₂Sn}₂ (X = p-Me- (1), p-MeO- (2), p–t-Bu- (3), p-NO₂- (4), p-OH- (5) or o-OH- (6)) were synthesized and characterized by HRMS (high-resolution mass spectrometry), NMR (nuclear magnetic resonance spectroscopy), IR (Fourier transform infrared spectroscopy), and TGA (thermogravimetric analysis) techniques. The molecular structure of complexes 1–6 was confirmed by single-crystal X-ray crystallography. The structure of complexes showed a distorted pentagonal bipyramidal configuration around the tin atom center, and the ligands adopted a tridentate chelating mode. Fascinatingly, either one-dimensional infinite chain structures or two-dimensional network structures were observed in the complexes through hydrogen bonds. Complex 2 has the strongest inhibitory effect on MCF7 and HepG2 cell proliferation, its effect was superior to that of the positive control drug cisplatin. The interaction of ct-DNA (calf-thymus DNA) with complex 2 was explored using UV absorption (ultraviolet absorption) and fluorescence spectroscopy. Complex 2 exhibited a moderate affinity for ct-DNA through intercalation modes. The interaction of complex 2 with ct-DNA has also been supported by molecular docking studies.

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Metallic titanium (Ti) implant surfaces need improvement for bioproperties and antibacterial behavior. For this purpose, a new boron-doped bioactive apatite–wollastonite (AW) coating was successfully developed on the Ti plate surface. The effects of boron addition on the microstructure, mechanical properties, and bioproperties of the AW coating were investigated. With the addition of boron (B), the AW coating morphology became less porous and compact. In terms of bio properties, the rate of apatite formation increased with the addition of B, and the cell viability rate increased from approximately 66–81%. B addition increased the elastic modulus of the AW coating from about 24–46 GPa and increased its hardness about 2.5 times. In addition, while no antibacterial activity was observed in the AW coating, the addition of boron slightly introduced antibacterial properties. The novel AW/B composite coating obtained is promising for Ti implant surfaces.

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