NMR and molecular modelling studies on elastase inhibitor-peptides for wound management

Proteases play an important and critical role in the physiological process of wound repair. However, excessive and unregulated release of proteolytic enzymes (e.g., elastase) mediates abnormal degradation of healthy tissues, which leads to inflammatory disorders such as chronic wounds. Thus, it is of therapeutic interest to develop novel synthetic inhibitor-peptides of elastase, which can restore the balance between the free enzyme and the endogenous inhibitors in chronic wounds. In previous works, we have reported two different drug delivery systems to release novel elastase inhibitors to the wound site. In both systems synthetic peptides (KRCCPDTCGIKCL-Pep4 and KRMMPDTMGIKML-Pep4M) based on the primary structure of the endogenous elastase inhibitor, secretory leucocyte protease inhibitor, were used as active material. Phosphorylation of the reported peptides prompts significant structural differences, which reflects in distinct inhibitory capacity towards elastase. These structural modifications were prompted by electrostatic interactions and hydrogen bonds established from the peptide phosphoresidue. The current study was also extended to another synthetic peptide (WCTASVPPQCY-PepBBI) that is based on the reactive loop of another elastase inhibitor, the Bowmen-Birk inhibitor. PepBBI, phosphorylated and non-phosphorylated, displays similar behaviour to Pep4 and Pep4M. The structural modifications reported herein were evaluated by two-dimensional nuclear magnetic resonance and molecular modelling approaches.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (scholarship SFRH/BD/36522/2007 and PEst-OE/EQB/LA0004/2011), FEDER (European Fund for Regional Development)-COMPETE-QREN-EU and the European Project Lidwine - Multifunctional medical textiles for wound (e.g. Decubitus). We acknowledge CERMAX at ITQB-UNL and Rede Nacional de RMN for access to the facilities. Rede Nacional de RMN is supported with funds from FCT, Projecto de Re-equipamento Cientifico contract REDE/1517/RMN/2005, Portugal. Micaelo, N.M. acknowledges the contract research program "Compromisso corn a Ciencia" reference: C2008-UMINHO-CQ-03 and access to the Minho University GRIUM cluster

Advances in the synthesis of Homochiral (-)-1-azafagomine and (+)-5-epi-1-azafagomine. 1-N-phenyl carboxamide derivatives of both enantiomers of 1-azafagomine: leads for the synthesis of active α-Glycosidase inhibitors

- A new expeditious preparation of homochiral (-)-1-azafagomine, and (+)-5-epi-1-azafagomine has been devised. Stoodley´s diastereoselective cycloaddition of dienes bearing a 2,3,4,6-tetraacetyl glucosyl chiral auxiliary to 4-phenyl-1,2,4-triazole-3,5-dione, was merged with Bols protocol for functionalizing alkenes into molecules bearing a glucosyl framework. Homochiral (+)-5-epi-1-azafagomine was synthetized for the first time. Partial reductive cleavage of the phenyltriazolidinone moiety afforded new homochiral 1-N-phenyl carboxamide derivatives of 1-azafagomine. Both enantiomers of these derivatives were synthetized and tested, displaying a very good enzymatic inhibition towards baker´s yeast α-glucosidase. The molecular recognition mechanism of the 1-N-phenyl carboxamide derivative of 1-azafagomine by α-glucosidase from baker´s yeast was studied by molecular modelling. The efficient packing of the aromatic ring of the 1-N-phenyl carboxamide moiety into a hydrophobic sub-site (pocket) in the enzyme´s active site, seems to be responsible for the improved binding affinity in relation to underivatized (-)1-azafagomine and (+)1-azafagomine.We thank FCT for project funding PTDC/QUI/67407/2006 and FCT and FEDER for funding NMR spectrometer Bruker Avance III 400 as part of the National NMR Network. M.N.M. acknowledges the contract research program "Compromisso com a Ciencia" Reference C2008-UMINHO-CQ-03 and access to the Minho University GRIUM cluster

Tailoring cutinase activity towards polyethylene terephthalate and polyamide 6,6 fibers

Cutinase from Fusarium solani pisi was genetically modified near the active site, by site-directed mutagenesis, to enhance its activity towards polyethylene terephthalate (PET) and polyamide 6,6 (PA 6,6) fibers. The mutations L81A, N84A, L182A, V184A and L189A were done to enlarge the active site in order to better fit a larger polymer chain. Modeling studies have shown enhanced free energy stabilization of model substrate tetrahedral intermediate (TI) bound at the enzyme active site for all mutants, for both model polymers. L81A and L182A showed an activity increase of four- and five-fold, respectively, when compared with the wild type, for PET fibers. L182A showed the one- and two-fold higher ability to biodegrade aliphatic polyamide substrates. Further studies in aliphatic polyesters seem to indicate that cutinase has higher ability to recognize aliphatic substrates.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/22490/2005, SFRH/BD/22149/2005European Community - Biosyntex Project, no. G5RD-CT-2000-30110 “Competitive and Sustainable Growth

Assessment of the anthelmintic activity of medicinal plant extracts and purified condensed tannins against free-living and parasitic stages of Oesophagostomum dentatum

Background: Plant-derived condensed tannins (CT) show promise as a complementary option to treat gastrointestinal helminth infections, thus reducing reliance on synthetic anthelmintic drugs. Most studies on the anthelmintic effects of CT have been conducted on parasites of ruminant livestock. Oesophagostomum dentatum is an economically important parasite of pigs, as well as serving as a useful laboratory model of helminth parasites due to the ability to culture it in vitro for long periods through several life-cycle stages. Here, we investigated the anthelmintic effects of CT on multiple life-cycles stages of O. dentatum. Methods: Extracts and purified fractions were prepared from five plants containing CT and analysed by HPLC-MS. Anthelmintic activity was assessed at five different stages of the O. dentatum life cycle; the development of eggs to infective third-stage larvae (L3), the parasitic L3 stage, the moult from L3 to fourth-stage larvae (L4), the L4 stage and the adult stage. Results: Free-living larvae of O. dentatum were highly susceptible to all five plant extracts. In contrast, only two of the five extracts had activity against L3, as evidenced by migration inhibition assays, whilst three of the five extracts inhibited the moulting of L3 to L4. All five extracts reduced the motility of L4, and the motility of adult worms exposed to a CT-rich extract derived from hazelnut skins was strongly inhibited, with electron microscopy demonstrating direct damage to the worm cuticle and hypodermis. Purified CT fractions retained anthelmintic activity, and depletion of CT from extracts by pre-incubation in polyvinylpolypyrrolidone removed anthelmintic effects, strongly suggesting CT as the active molecules. Conclusions: These results suggest that CT may have promise as an alternative parasite control option for O. dentatum in pigs, particularly against adult stages. Moreover, our results demonstrate a varied susceptibility of different life-cycle stages of the same parasite to CT, which may offer an insight into the anthelmintic mechanisms of these commonly found plant compounds

Dietary fatty acid composition is sensed by the NLRP3 inflammasome: omega-3 fatty acid (DHA) prevents NLRP3 activation in human macrophages

The Nod-like receptor protein 3 (NLRP3) inflammasome is considered to be a pivotal host platform responsible for sensing of exogenous and endogenous danger signals, including those generated as a result of metabolic dysregulation, and for the subsequent, IL-1β-mediated orchestration of inflammatory and innate immunity responses. In this way, although the molecular link between diet-induced obesity and inflammasome activation is still unclear, free fatty acids (FFA) have been proposed as a triggering event. We report that dietary fatty acid (FA) composition is sensed by the NLRP3 inflammasome in human macrophages. For this purpose, we have analysed three roles of FA supplementation: as a priming signal for ATP-activated macrophages, in determining where the administration of dietary FAs interferes with LPS-mediated inflammasome activation and by inducing inflammasome activation per se. In this study, we confirm that saturated (SFAs) activated the NLRP3 inflammasome and stimulated the secretion of the IL-1β cytokine, while PUFAs were mainly inhibitors. Moreover, in general, DHA (n-3 PUFA) was more effective in preventing inflammasome activation than arachidonic acid (n-6 PUFA)

Membrane permeation properties of benzo[a]phenoxazinium fluorescent probes using molecular modelling techniques

Studies of membrane permeation properties of four benzo[a]phenoxazinium fluorescent probes with twenty carbon atoms at the 5- or 9-positions of the tetracyclic ring in 2,3-bis(palmitoyl-oxy)propyl-2-(trimethylammonio)ethyl phosphate, DPPC membranes using molecular modelling techniques were carried out. The molecular mechanism of interaction between the molecular probes and the DPPC lipids is described. It was showed that probes can be preferentially located at the membrane water interface interaction with the lipid polar groups, while others can be cross the membrane in a passive way. This processes is dependent on the tetracyclic substitutions and the alkyl chains present in the fluorescent probe. These findings can provide a detailed rational of the structural properties surrounding the molecular probes that could be correlated with the experimentally measured fluorescence.Fundação para a Ciência e Tecnologia (Portugal). National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT