Rose Mary Zumstein Georgetto Naal

Effects of the antimalarial drug primaquine on the dynamic structure of lipid model membranes.

Primaquine (PQ) is a potent therapeutic agent used in the treatment of malaria and its mechanism of action still lacks a more detailed understanding at a molecular level. In this context, we used differential scanning calorimetry (DSC), pressure perturbation calorimetry (PPC), and electron spin resonance (ESR) to investigate the effects of PQ on the lipid phase transition, acyl chain dynamics, and on volumetric properties of lipid model membranes. DSC thermograms revealed that PQ stabilizes the fluid phase of the lipid model membranes and interacts mainly with the lipid headgroups. This result was revealed by the great effect on the pretransition of phosphatidylcholines and the destabilization of the inverted hexagonal phase of a phosphatidylethanolamine bilayer. Spin probes located at different positions along the lipid chain were used to monitor different membrane regions. ESR results indicated that PQ is effective in changing the acyl chain ordering and dynamics of the whole chain of dimyristoylphosphatidylcholine (DMPC) phospholipid in the rippled gel phase. The combined ESR and PPC results revealed that the slight DMPC volume changes at the main phase transition induced by the presence of PQ is probably due to a less dense lipid gel phase. At physiological pH, the cationic amphiphilic PQ strongly interacts with the lipid headgroup region of the bilayers, causing considerable disorganization in the hydrophobic core. These results shed light on the molecular mechanism of primaquine-lipid interaction, which may be useful in the understanding of the complex mechanism of action and/or the adverse effects of this antimalarial drug.

In vitro anti-allergic activity of the fungal metabolite pyridovericin.

Mast cells play a critical role during the development of an allergic response. Upon activation by an antigen and IgE, via FcεRI receptors, mast cells release histamine and other mediators that initiate and propagate immediate hypersensitivity reactions. Mast cells also secrete cytokines that regulate the immune responses. In this way, inhibitors of mast cell activity could work as promising therapeutics for allergic disorders. In the present work, we investigated the capacity of pyridovericin, a natural product isolated from the entomopathogenic fungus Beauveria bassiana, to inhibit mast cell degranulation and cytokine secretion. It was found that pyridovericin strongly decreased the release of β-hexosaminidase, a marker for mast cell degranulation, when mast cells were stimulated by both FcεRI-dependent and independent pathways. In addition, pyridovericin strongly abrogated secretion of interleukin-4. Pyridovericin-mediated suppression of stimulated increase in intracellular Ca(2+) levels, a crucial signal for mounting of both degranulation and cytokine production responses, was ascribed as one of the inhibition targets of pyridovericin. Those initial studies identify pyridovericin as a potential new candidate for the development of new anti-allergic drugs.

Immune cells and mediators involved in the inflammatory responses induced by a P-I metalloprotease and a phospholipase A(2) from Bothrops atrox venom

&NA; Bothrops envenomations can promote severe inflammatory responses by inducing edema, pain, leukocyte recruitment and release of chemical mediators by local cells. In the present study, two toxins from Bothrops atrox venom (the P‐I metalloprotease Batroxase and the acidic phospholipase A2 BatroxPLA2) were evaluated in relation to their inflammatory effects induced in vivo and in vitro, mainly focusing on the participation of different immune cells and inflammatory mediators. Both toxins mainly promoted acute inflammatory responses with significant recruitment of neutrophils in the early hours (1–4 h) after administration into the peritoneal cavity of C57BL/6 mice, and increased infiltration of mononuclear cells especially after 24 h. Among the mediators induced by both toxins are IL‐6, IL‐10 and PGE2, with Batroxase also inducing the release of L‐1&bgr;, and BatroxPLA2 of LTB4 and CysLTs. These responses pointed to possible involvement of immune cells such as macrophages and mast cells, which were then evaluated in vitro. Mice peritoneal macrophages stimulated with Batroxase produced significant levels of IL‐6, IL‐1&bgr;, PGE2 and LTB4, whereas stimulus with BatroxPLA2 induced increases of IL‐6, PGE2 and LTB4. Furthermore, both toxins were able to stimulate degranulation of RBL‐2H3 mast cells, but with distinct concentration‐dependent effects. Altogether, these results indicated that Batroxase and BatroxPLA2 promoted local and acute inflammatory responses related to macrophages and mast cells and to the production of several mediators. Our findings should contribute for better understanding the different mechanisms of toxicity induced by P‐I metalloproteases and phospholipases A2 after snakebite envenomations. HighlightsWe assessed the inflammatory effects induced by two toxins from Bothrops atrox venom.Batroxase and BatroxPLA2 promoted local and acute inflammatory responses in vivo.Both toxins also stimulated immune cells such as macrophages and mast cells in vitro.Induced responses were related to the production of mediators such as IL‐6 and PGE2.These results should contribute for better understanding the toxicity of such toxins.

Novel binuclear μ-oxo diruthenium complexes combined with ibuprofen and ketoprofen: Interaction with relevant target biomolecules and anti-allergic potential.

This work presents the synthesis and characterization of two novel binuclear ruthenium compounds of general formula [Ru2O(carb)2(py)6](PF6)2, where py=pyridine and carb are the non-steroidal anti-inflammatory drugs ibuprofen (1) and ketoprofen (2). Both complexes were characterized by ESI-MS/MS spectrometry. The fragmentation patterns, which confirm the proposed structures, are presented. Besides that, compounds 1 and 2 present the charge transfer transitions within 325-330nm; and the intra-core transitions around 585nm, which is the typical spectra profile for [Ru2O] analogues. This suggests the carboxylate bridge has little influence in their electronic structure. The effects of the diruthenium complexes on Ig-E mediated mast cell activation were evaluated by measuring the enzyme β-hexosaminidase released by mast cells stimulated by antigen. The inhibitory potential of the ketoprofen complex against mast cell stimulation suggests its promising application as a therapeutic agent for treating or preventing IgE-mediated allergic diseases. In addition, in vitro metabolism assays had shown that the ibuprofen complex is metabolized by the cytochrome P450 enzymes.

Kinetic studies of the nucleophilic quenching of photoexcited nitroaryl ethers (NArE) by bromide ions in cationic micellar solution

Abstract Nucleophilic aromatic photosubstitution reactions of nitroaryl ethers (NArE) with sodium hydroxide were studied in aqueous solution containing N-hexadecyl-N,N,N-trimethylammonium chloride micelles. The increase of quantum yields depended on the length of the n-alkyl chain (maximum for methyl and minimum for decyl). The dependence on the surfactant concentration was in accordance with the mechanistic model of aromatic nucleophilic photosubstitution.