Brimonidine as a possible treatment for myopia.

BACKGROUND: Myopia is becoming a huge burden on the world's public health systems. The purpose of this study was to explore the effect of brimonidine in the treatment of form-deprivation myopia (FDM) and the relationship between intraocular pressure (IOP) and myopia development. METHODS: Monocular form deprivation myopia (FDM) was induced in three-week-old pigmented male guinea pigs. They were treated with 3 different methods of brimonidine administration (eye drops, and subconjunctival or intravitreal injections). Four different concentrations of brimonidine were tested for each method (2µg/µL, 4µg/µL, 20µg/µL, and 40µg/µL). All treatments continued for a period of 21 days. Tonometry, retinoscopy, and A-scan ultrasonography were used to monitor intraocular pressure, refractive error and axial length (AL), respectively. RESULTS: Treatment with subconjunctival brimonidine at 40µg/µL, and intravitreal brimonidine at 2µg/µL and 4µg/µL, inhibited the development of FDM. The myopic refraction, excessive axial length, and elevation of IOP were significantly decreased. Brimonidine in eye drops was ineffective. CONCLUSION: Brimonidine at appropriate doses significantly reduced the development of FD myopia in guinea pigs. The IOP may change with FD myopia.

A glycan receptor kinase facilitates intracellular accommodation of arbuscular mycorrhiza and symbiotic rhizobia in the legume Lotus japonicus.

Receptors that distinguish the multitude of microbes surrounding plants in the environment enable dynamic responses to the biotic and abiotic conditions encountered. In this study, we identify and characterise a glycan receptor kinase, EPR3a, closely related to the exopolysaccharide receptor EPR3. Epr3a is up-regulated in roots colonised by arbuscular mycorrhizal (AM) fungi and is able to bind glucans with a branching pattern characteristic of surface-exposed fungal glucans. Expression studies with cellular resolution show localised activation of the Epr3a promoter in cortical root cells containing arbuscules. Fungal infection and intracellular arbuscule formation are reduced in epr3a mutants. In vitro, the EPR3a ectodomain binds cell wall glucans in affinity gel electrophoresis assays. In microscale thermophoresis (MST) assays, rhizobial exopolysaccharide binding is detected with affinities comparable to those observed for EPR3, and both EPR3a and EPR3 bind a well-defined ß-1,3/ß-1,6 decasaccharide derived from exopolysaccharides of endophytic and pathogenic fungi. Both EPR3a and EPR3 function in the intracellular accommodation of microbes. However, contrasting expression patterns and divergent ligand affinities result in distinct functions in AM colonisation and rhizobial infection in Lotus japonicus. The presence of Epr3a and Epr3 genes in both eudicot and monocot plant genomes suggest a conserved function of these receptor kinases in glycan perception.

Enhanced hexamerization of insulin via assembly pathway rerouting revealed by single particle studies.

Insulin formulations with diverse oligomerization states are the hallmark of interventions for the treatment of diabetes. Here using single-molecule recordings we firstly reveal that insulin oligomerization can operate via monomeric additions and secondly quantify the existence, abundance and kinetic characterization of diverse insulin assembly and disassembly pathways involving addition of monomeric, dimeric or tetrameric insulin species. We propose and experimentally validate a model where the insulin self-assembly pathway is rerouted, favoring monomeric or oligomeric assembly, by solution concentration, additives and formulations. Combining our practically complete kinetic characterization with rate simulations, we calculate the abundance of each oligomeric species from nM to mM offering mechanistic insights and the relative abundance of all oligomeric forms at concentrations relevant both for secreted and administrated insulin. These reveal a high abundance of all oligomers and a significant fraction of hexamer resulting in practically halved bioavailable monomer concentration. In addition to providing fundamental new insights, the results and toolbox presented here can be universally applied, contributing to the development of optimal insulin formulations and the deciphering of oligomerization mechanisms for additional proteins.

Ca2+-Responsive Glyco-insulin.

Chemical modification of peptides and proteins, such as PEGylation and lipidation, creates conjugates with new properties. However, they are typically not dynamic or stimuli-responsive. Self-assembly controlled by a stimulus will allow adjusting properties directly. Here, we report that conjugates of oligogalacturonic acids (OGAs), isolated from plant-derived pectin, are Ca2+-responsive. We report the conjugation of OGA to human insulin (HI) to create new glyco-insulins. In addition, we coupled OGA to model peptides. We studied their self-assembly by dynamic light scattering, small-angle X-ray scattering, and circular dichroism, which showed that the self-assembly to form nanostructures depended on the length of the OGA sequence and Zn2+ and Ca2+ concentrations. Subcutaneous administration of OGA12-HI with Zn2+ showed a stable decrease in blood glucose over a longer period of time compared to HI, despite the lower receptor binding affinity.

Selective Acylation of Proteins at Gly and Lys in His Tags.

The chemical modification of proteins is of great importance in chemical biology, biotechnology, and for the production of modified biopharmaceuticals, as it enables introduction of fluorophores, biotin, half-life extending moieties, and more. We have developed two methods that use poly-His sequences to direct the highly selective acylation of proteins, either at the N-terminus or at a specific Lys residue. For the former, we used an N-terminal Gly-His6 segment (Gly-His tag) that directed acylation of the N-terminal Nα -amine with 4-methoxyphenyl esters, resulting in stable conjugates. Next, we developed the peptide sequences Hisn -Lys-Hism (Lys-His tags) that direct the acylation of the designated Lys Nϵ -amine under mild conditions and with high selectivity over native Lys residues. Both the Gly-His and Lys-His tags maintain the capacity for immobilized metal ion affinity chromatography. We have demonstrated the robustness of these methods by attaching different moieties such as azides, fluorophores, and biotin to different proteins, including antibodies.

Highly Selective Lysine Acylation in Proteins Using a Lys-His Tag Sequence.

Chemical modification of proteins has numerous applications, but it has been challenging to achieve the required high degree of selectivity on lysine amino groups. Recently, we described the highly selective acylation of proteins with an N-terminal Gly-His6 segment. This tag promoted acylation of the N-terminal Nα -amine resulting in stable conjugates. Herein, we report the peptide sequences Hisn -Lys-Hism , which we term Lys-His tags. In combination with simple acylating agents, they facilitate the acylation of the designated Lys Nϵ -amine under mild conditions and with high selectivity over native Lys residues. We show that the Lys-His tags, which are 7 to 10 amino acids in length and still act as conventional His tags, can be inserted in proteins at the C-terminus or in loops, thus providing high flexibility regarding the site of modification. Finally, the selective and efficient acylation of the therapeutic antibody Rituximab, pure or mixed with other proteins, demonstrates the scope of the Lys-His tag acylation method.

Controlling the fractal dimension in self-assembly of terpyridine modified insulin by Fe2+ and Eu3+ to direct in vivo effects.

Metal ion-induced self-assembly (SA) of proteins into higher-order structures can provide new, dynamic nano-assemblies. Here, the synthesis and characterization of a human insulin (HI) analog modified at LysB29 with the tridentate chelator 2,2':6',2''-terpyridine (Tpy) is described. SA of this new insulin analog (LysB29Tpy-HI) in the presence of the metal ions Fe2+ and Eu3+ at different concentrations was studied in solution by fluorescence luminescence and CD spectroscopy, dynamic light scattering, and small-angle X-ray scattering, while surface assembly was probed by AFM. Unique oligomerization was observed in solution, as Fe2+ yielded small magenta-colored discrete non-native assemblies, while Eu3+ caused the formation of large fractal assemblies. Binding of both metal ions to Tpy was demonstrated spectroscopically, and emission lifetime experiments revealed a distinct Eu3+ coordination geometry that included two water molecules. SAXS suggested that LysB29Tpy-HI with Fe2+ oligomerized to a discrete, roughly octameric species, while LysB29Tpy-HI with Eu3+ gave very large assemblies that could be modelled as fractals. The fractal dimensionality increased with the Eu3+ concentration. We propose that this is a consequence of Eu3+ binding to both Tpy and to free carboxylic acid groups on the insulin surface. LysB29Tpy-HI maintained insulin receptor affinity, and showed extended blood glucose lowering and plasma concentration after subcutaneous injection in rats. The combination of metal ion directed SA and native SA provides control of nano-scale fractal dimensionality and points towards use in therapeutics.

Carbohydrate-Derived Metal-Chelator-Triggered Lipids for Liposomal Drug Delivery.

Liposomes are versatile three-dimensional, biomaterial-based frameworks that can spatially enclose a variety of organic and inorganic biomaterials for advanced targeted-delivery applications. Implementation of external-stimuli-controlled release of their cargo will significantly augment their wide application for liposomal drug delivery. This paper presents the synthesis of a carbohydrate-derived lipid, capable of changing its conformation depending on the presence of Zn2+ : an active state in the presence of Zn2+ ions and back to an inactive state in the absence of Zn2+ or when exposed to Na2 EDTA, a metal chelator with high affinity for Zn2+ ions. This is the first report of a lipid triggered by the presence of a metal chelator. Total internal reflection fluorescence microscopy and a single-liposome study showed that it indeed was possible for the lipid to be incorporated into the bilayer of stable liposomes that remained leakage-free for the fluorescent cargo of the liposomes. On addition of EDTA to the liposomes, their fluorescent cargo could be released as a result of the membrane-incorporated lipids undergoing a conformational change.