Histamine, Metabolic Remodelling and Angiogenesis: A Systems Level Approach.

Histamine is a highly pleiotropic biogenic amine involved in key physiological processes including neurotransmission, immune response, nutrition, and cell growth and differentiation. Its effects, sometimes contradictory, are mediated by at least four different G-protein coupled receptors, which expression and signalling pathways are tissue-specific. Histamine metabolism conforms a very complex network that connect many metabolic processes important for homeostasis, including nitrogen and energy metabolism. This review brings together and analyses the current information on the relationships of the "histamine system" with other important metabolic modules in human physiology, aiming to bridge current information gaps. In this regard, the molecular characterization of the role of histamine in the modulation of angiogenesis-mediated processes, such as cancer, makes a promising research field for future biomedical advances.

What Makes a Good Pore Former: A Study of Synthetic Melittin Derivatives.

Pore formation by membrane-active peptides, naturally encountered in innate immunity and infection, could have important medical and technological applications. Recently, the well-studied lytic peptide melittin has formed the basis for the development of combinatorial libraries from which potent pore-forming peptides have been derived, optimized to work under different conditions. We investigate three such peptides, macrolittin70, which is most active at neutral pH; pHD15, which is active only at low pH; and MelP5_Δ6, which was rationally designed to be active at low pH but formed only small pores. There are three, six, and six acidic residues in macrolittin70, pHD15, and MelP5_Δ6, respectively. We perform multi-microsecond simulations in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) of hexamers of these peptides starting from transmembrane orientations at neutral pH (all residues at standard protonation), low pH (acidic residues and His protonated), and highly acidic environments in which C-termini are also protonated. Previous simulations of the parent peptides melittin and MelP5 in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) are repeated in POPC. We find that the most potent pore-forming peptides exhibit strong interpeptide interactions, including salt bridges, H-bonds, and polar interactions. Protonation of the C-terminus promotes helicity and pore size. The proximity of the peptides allows fewer lipid headgroups to line the pores than in previous simulations, making the pores intermediate between barrel stave and toroidal. Based on these structures and geometrical arguments, we attempt to rationalize the factors that under different conditions can increase or decrease pore stability and propose mutations that could be tested experimentally.

Transmembrane Pore Structures of ß-Hairpin Antimicrobial Peptides by All-Atom Simulations.

Protegrin-1 is an 18-residue ß-hairpin antimicrobial peptide (AMP) that has been suggested to form transmembrane ß-barrels in biological membranes. However, alternative structures have also been proposed. Here, we performed multimicrosecond, all-atom molecular dynamics simulations of various protegrin-1 oligomers on the membrane surface and in transmembrane topologies. The membrane surface simulations indicated that protegrin dimers are stable, whereas trimers and tetramers break down. Tetrameric arcs remained stably inserted in lipid membranes, but the pore water was displaced by lipid molecules. Unsheared protegrin ß-barrels opened into ß-sheets that surrounded stable aqueous pores, whereas tilted barrels with sheared hydrogen bonding patterns were stable in most topologies. A third type of observed pore consisted of multiple small oligomers surrounding a small, partially lipidic pore. We also considered the ß-hairpin AMP tachyplesin, which showed less tendency to oligomerize than protegrin: the octameric bundle resulted in small pores surrounded by six peptides as monomers and dimers, with some peptides returning to the membrane surface. The results imply that multiple configurations of protegrin oligomers may produce aqueous pores and illustrate the relationship between topology and putative steps in protegrin-1's pore formation. However, the long-term stability of these structures needs to be assessed further.

The noni anthraquinone damnacanthal is a multi-kinase inhibitor with potent anti-angiogenic effects.

The natural bioactive compound damnacanthal inhibits several tyrosine kinases. Herein, we show that -in fact- damancanthal is a multi kinase inhibitor. A docking and molecular dynamics simulation approach allows getting further insight on the inhibitory effect of damnacanthal on three different kinases: vascular endothelial growth factor receptor-2, c-Met and focal adhesion kinase. Several of the kinases targeted and inhibited by damnacanthal are involved in angiogenesis. Ex vivo and in vivo experiments clearly demonstrate that, indeed, damnacanthal is a very potent inhibitor of angiogenesis. A number of in vitro assays contribute to determine the specific effects of damnacanthal on each of the steps of the angiogenic process, including inhibition of tubulogenesis, endothelial cell proliferation, survival, migration and production of extracellular matrix remodeling enzyme. Taken altogether, these results suggest that damancanthal could have potential interest for the treatment of cancer and other angiogenesis-dependent diseases.

Candidate gene study of TRAIL and TRAIL receptors: association with response to interferon beta therapy in multiple sclerosis patients.

TRAIL and TRAIL Receptor genes have been implicated in Multiple Sclerosis pathology as well as in the response to IFN beta therapy. The objective of our study was to evaluate the association of these genes in relation to the age at disease onset (AAO) and to the clinical response upon IFN beta treatment in Spanish MS patients. We carried out a candidate gene study of TRAIL, TRAILR-1, TRAILR-2, TRAILR-3 and TRAILR-4 genes. A total of 54 SNPs were analysed in 509 MS patients under IFN beta treatment, and an additional cohort of 226 MS patients was used to validate the results. Associations of rs1047275 in TRAILR-2 and rs7011559 in TRAILR-4 genes with AAO under an additive model did not withstand Bonferroni correction. In contrast, patients with the TRAILR-1 rs20576-CC genotype showed a better clinical response to IFN beta therapy compared with patients carrying the A-allele (recessive model: p = 8.88×10(-4), pc = 0.048, OR = 0.30). This SNP resulted in a non synonymous substitution of Glutamic acid to Alanine in position 228 (E228A), a change previously associated with susceptibility to different cancer types and risk of metastases, suggesting a lack of functionality of TRAILR-1. In order to unravel how this amino acid change in TRAILR-1 would affect to death signal, we performed a molecular modelling with both alleles. Neither TRAIL binding sites in the receptor nor the expression levels of TRAILR-1 in peripheral blood mononuclear cell subsets (monocytes, CD4+ and CD8+ T cells) were modified, suggesting that this SNP may be altering the death signal by some other mechanism. These findings show a role for TRAILR-1 gene variations in the clinical outcome of IFN beta therapy that might have relevance as a biomarker to predict the response to IFN beta in MS.

Structural perspective on the direct inhibition mechanism of EGCG on mammalian histidine decarboxylase and DOPA decarboxylase.

Histidine decarboxylase (HDC) and l-aromatic amino acid decarboxylase (DDC) are homologous enzymes that are responsible for the synthesis of important neuroactive amines related to inflammatory, neurodegenerative, and neoplastic diseases. Epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea, has been shown to target histamine-producing cells and to promote anti-inflammatory, antitumor, and antiangiogenic effects. Previous experimental work has demonstrated that EGCG has a direct inhibitory effect on both HDC and DDC. In this study, we investigated the binding modes of EGCG to HDC and DDC as a first step for designing new polyphenol-based HDC/DDC-specific inhibitors.