Zinc complexes of chloroquine and hydroxychloroquine versus the mixtures of their components: Structures, solution equilibria/speciation and cellular zinc uptake.

The zinc complexes of chloroquine (CQ; [Zn(CQH+)Cl3]) and hydroxychloroquine (HO-CQ; [Zn(HO-CQH+)Cl3]) were synthesized and characterized by X-Ray structure analysis, FT-IR, NMR, UV-Vis spectroscopy, and cryo-spray mass spectrometry in solid state as well as in aqueous and organic solvent solutions, respectively. In acetonitrile, up to two Zn2+ ions bind to CQ and HO-CQ through the tertiary amine and aromatic nitrogen atoms (KN-aminCQ = (3.8 ±â€¯0.5) x 104 M-1 and KN-aromCQ = (9.0 ±â€¯0.7) x 103 M-1 for CQ, and KN-aminHO-CQ = (3.3 ±â€¯0.4) x 104 M-1 and KN-aromHO-CQ = (1.6 ±â€¯0.2) x 103 M-1 for HO-CQ). In MOPS buffer (pH 7.4) the coordination proceeds through the partially deprotonated aromatic nitrogen, with the corresponding equilibrium constants of KN-arom(aq)CQ = (3.9 ±â€¯1.9) x 103 M-1and KN-arom(aq)HO-CQ = (0.7 + 0.4) x 103 M-1 for CQ and HO-CQ, respectively. An apparent partition coefficient of 0.22 was found for [Zn(CQH+)Cl3]. Mouse embryonic fibroblast (MEF) cells were treated with pre-synthesized [Zn((HO-)CQH+)Cl3] complexes and corresponding ZnCl2/(HO-)CQ mixtures and zinc uptake was determined by application of the fluorescence probe and ICP-OES measurements. Administration of pre-synthesized complexes led to higher total zinc levels than those obtained upon administration of the related zinc/(hydroxy)chloroquine mixtures. The differences in the zinc uptake between these two types of formulations were discussed in terms of different speciation and character of the complexes. The obtained results suggest that intact zinc complexes may exhibit biological effects distinct from that of the related zinc/ligand mixtures.

Select hyperactivating NLRP3 ligands enhance the TH1- and TH17-inducing potential of human type 2 conventional dendritic cells.

The detection of microorganisms and danger signals by pattern recognition receptors on dendritic cells (DCs) and the consequent formation of inflammasomes are pivotal for initiating protective immune responses. Although the activation of inflammasomes leading to secretion of the cytokine IL-1ß is typically accompanied by pyroptosis (an inflammatory form of lytic programmed cell death), some cells can survive and exist in a state of hyperactivation. Here, we found that the conventional type 2 DC (cDC2) subset is the major human DC subset that is transcriptionally and functionally poised for inflammasome formation and response without pyroptosis. When cDC2 were stimulated with ligands that relatively weakly activated the inflammasome, the cells did not enter pyroptosis but instead secreted IL-12 family cytokines and IL-1ß. These cytokines induced prominent T helper type 1 (TH1) and TH17 responses that were superior to those seen in response to Toll-like receptor (TLR) stimulation alone or to stronger, classical inflammasome ligands. These findings not only define the human cDC2 subpopulation as a prime target for the treatment of inflammasome-dependent inflammatory diseases but may also inform new approaches for adjuvant and vaccine development.

Improved tag-switch method reveals that thioredoxin acts as depersulfidase and controls the intracellular levels of protein persulfidation.

Hydrogen sulfide (H2S) has emerged as a signalling molecule capable of regulating several important physiological functions such as blood pressure, neurotransmission and inflammation. The mechanisms behind these effects are still largely elusive and oxidative posttranslational modification of cysteine residues (protein persulfidation or S-sulfhydration) has been proposed as the main pathway for H2S-induced biological and pharmacological effects. As a signalling mechanism, persulfidation has to be controlled. Using an improved tag-switch assay for persulfide detection we show here that protein persulfide levels are controlled by the thioredoxin system. Recombinant thioredoxin showed an almost 10-fold higher reactivity towards cysteine persulfide than towards cystine and readily cleaved protein persulfides as well. This reaction resulted in H2S release suggesting that thioredoxin could be an important regulator of H2S levels from persulfide pools. Inhibition of the thioredoxin system caused an increase in intracellular persulfides, highlighting thioredoxin as a major protein depersulfidase that controls H2S signalling. Finally, using plasma from HIV-1 patients that have higher circulatory levels of thioredoxin, we could prove depersulfidase role in vivo.