Innovative Agents for Actinic Keratosis and Nanocarriers Enhancing Skin Penetration

Actinic keratosis and cutaneous squamous cell carcinoma are of increasing importance with aging and increased ultraviolet light exposure in Western societies. Efficient and well-tolerated therapy is still a matter of concern. As with tumours of other organs, new target sites and innovative drugs selectively addressing them are widely looked for. Due to the relevance for DNA synthesis and thus cell proliferation, human DNA polymerase alpha should be such a target, the more so as the three-dimensional structure of the active site has been proposed based on the application of molecular modelling methods and molecular dynamics simulations. The modelled structure of the active site was used for docking nucleotide analogues in order to design selective inhibitors. Consequently, well-fitting thymidine and guanosine analogues were synthesized and tested in vitro for their influence on normal and transformed human keratinocytes. In fact, the combination of modelling studies and in vitro tests allowed us to design antiproliferative and cytotoxic agents which are new drug candidates for the therapy of skin tumours, given the agents are no relevant substrates of nucleotide transporters (MRP-4, MRP-5) expressed by skin cancer cells. Essential kinases for nucleoside activation were detected, too, corresponding with the observed effects of nucleoside analogues. Due to the rather high molecular weight and poor solubility, however, skin penetration should be poor and thus topical therapy may require carriers to improve the uptake. This becomes feasible by lipidic and non-lipidic nanoparticles which can enhance the uptake of lipophilic agents up to 13-fold. Copyright (C) 2010 S. Karger AG, Base

A Systematic Approach from a Comparison of Three Glucocorticoids

Solid lipid nanoparticles (SLNs) can enhance drug penetration into the skin, yet the mechanism of the improved transport is not known in full. To unravel the influence of the drug-particle interaction on penetration enhancement, 3 glucocorticoids (GCs), prednisolone (PD), the diester prednicarbate (PC) and the monoester betamethasone 17-valerate (BMV), varying in structure and lipophilicity, were loaded onto SLNs. Theoretical permeability coefficients (cm/s) of the agents rank BMV (–6.38) ≧ PC (–6.57) > PD (–7.30). GC-particle interaction, drug release and skin penetration were investigated including a conventional oil-in-water cream for reference. Both with SLN and cream, PD release was clearly superior to PC release which exceeded BMV release. With the cream, the rank order did not change when studying skin penetration, and skin penetration is thus predominantly influenced by drug release. Yet, the penetration profile for the GCs loaded onto SLNs completely changed, and differences between the steroids were almost lost. Thus, SLNs influence skin penetration by an intrinsic mechanism linked to a specific interaction of the drug-carrier complex and the skin surface, which becomes possible by the lipid nature and nanosize of the carrier and appears not to be derived by testing drug release. Interestingly, PC and PD uptake from SLN even resulted in epidermal targeting. Thus, SLNs are not only able to improve skin penetration of topically applied drugs, but may also be of particular interest when specifically aiming to influence epidermal dysfunction

Specialized Peptidoglycan Hydrolases Sculpt the Intra-bacterial Niche of Predatory Bdellovibrio and Increase Population Fitness

Bdellovibrio are predatory bacteria that have evolved to invade virtually all Gram-negative bacteria, including many prominent pathogens. Upon invasion, prey bacteria become rounded up into an osmotically stable niche for the Bdellovibrio, preventing further superinfection and allowing Bdellovibrio to replicate inside without competition, killing the prey bacterium and degrading its contents. Historically, prey rounding was hypothesized to be associated with peptidoglycan (PG) metabolism; we found two Bdellovibrio genes, bd0816 and bd3459, expressed at prey entry and encoding proteins with limited homologies to conventional dacB/PBP4 DD-endo/carboxypeptidases (responsible for peptidoglycan maintenance during growth and division). We tested possible links between Bd0816/3459 activity and predation. Bd3459, but not an active site serine mutant protein, bound β-lactam, exhibited DD-endo/carboxypeptidase activity against purified peptidoglycan and, importantly, rounded up E. coli cells upon periplasmic expression. A ΔBd0816 ΔBd3459 double mutant invaded prey more slowly than the wild type (with negligible prey cell rounding) and double invasions of single prey by more than one Bdellovibrio became more frequent. We solved the crystal structure of Bd3459 to 1.45 Å and this revealed predation-associated domain differences to conventional PBP4 housekeeping enzymes (loss of the regulatory domain III, alteration of domain II and a more exposed active site). The Bd3459 active site (and by similarity the Bd0816 active site) can thus accommodate and remodel the various bacterial PGs that Bdellovibrio may encounter across its diverse prey range, compared to the more closed active site that “regular” PBP4s have for self cell wall maintenance. Therefore, during evolution, Bdellovibrio peptidoglycan endopeptidases have adapted into secreted predation-specific proteins, preventing wasteful double invasion, and allowing activity upon the diverse prey peptidoglycan structures to sculpt the prey cell into a stable intracellular niche for replication

Brain blood vessel autoantibodies in patients with NMDA and GABAA receptor encephalitis: identification of unconventional Myosin-X as target antigen

INTRODUCTION: The antibody repertoire from CSF-derived antibody-secreting cells and memory B-cells in patients with encephalitis contains a considerable number of antibodies that do not target the disease-defining autoantigen such as the GABA or NMDA receptors. This study focuses on the functional relevance of autoantibodies to brain blood vessels in patients with GABAA and NMDA receptor encephalitis. METHODS: We tested 149 human monoclonal IgG antibodies from the cerebrospinal fluid of six patients with different forms of autoimmune encephalitis on murine brain sections for reactivity to blood vessels using immunohistochemistry. Positive candidates were tested for reactivity with purified brain blood vessels, effects on transendothelial electrical resistance (TEER), and expression of tight junction proteins as well as gene regulation using human brain microvascular endothelial hCMEC/D3 cells as in vitro blood-brain barrier model. One blood-vessel reactive antibody was infused intrathecally by pump injection in mice to study in vivo binding and effects on tight junction proteins such as Occludin. Target protein identification was addressed using transfected HEK293 cells. RESULTS: Six antibodies reacted with brain blood vessels, three were from the same patient with GABAAR encephalitis, and the other three were from different patients with NMDAR encephalitis. One antibody from an NMDAR encephalitis patient, mAb 011-138, also reacted with cerebellar Purkinje cells. In this case, treatment of hCMEC/D3 cells resulted in decreased TEER, reduced Occludin expression, and mRNA levels. Functional relevance in vivo was confirmed as Occludin downregulation was observed in mAb 011-138-infused animals. Unconventional Myosin-X was identified as a novel autoimmune target for this antibody. DISCUSSION: We conclude that autoantibodies to blood vessels occur in autoimmune encephalitis patients and might contribute to a disruption of the blood-brain barrier thereby suggesting a potential pathophysiological relevance of these antibodies

Protist-Type Lysozymes of the Nematode Caenorhabditis elegans Contribute to Resistance against Pathogenic Bacillus thuringiensis

Pathogens represent a universal threat to other living organisms. Most organisms express antimicrobial proteins and peptides, such as lysozymes, as a protection against these challenges. The nematode Caenorhabditis elegans harbours 15 phylogenetically diverse lysozyme genes, belonging to two distinct types, the protist- or Entamoeba-type (lys genes) and the invertebrate-type (ilys genes) lysozymes. In the present study we characterized the role of several protist-type lysozyme genes in defence against a nematocidal strain of the Gram-positive bacterium Bacillus thuringiensis. Based on microarray and subsequent qRT-PCR gene expression analysis, we identified protist-type lysozyme genes as one of the differentially transcribed gene classes after infection. A functional genetic analysis was performed for three of these genes, each belonging to a distinct evolutionary lineage within the protist-type lysozymes (lys-2, lys-5, and lys-7). Their knock-out led to decreased pathogen resistance in all three cases, while an increase in resistance was observed when two out of three tested genes were overexpressed in transgenic lines (lys-5, lys-7, but not lys-2). We conclude that the lysozyme genes lys-5, lys-7, and possibly lys-2 contribute to resistance against B. thuringiensis, thus highlighting the particular role of lysozymes in the nematode's defence against pathogens

Identification and in vitro Analysis of the GatD/MurT Enzyme-Complex Catalyzing Lipid II Amidation in Staphylococcus aureus

The peptidoglycan of Staphylococcus aureus is characterized by a high degree of crosslinking and almost completely lacks free carboxyl groups, due to amidation of the D-glutamic acid in the stem peptide. Amidation of peptidoglycan has been proposed to play a decisive role in polymerization of cell wall building blocks, correlating with the crosslinking of neighboring peptidoglycan stem peptides. Mutants with a reduced degree of amidation are less viable and show increased susceptibility to methicillin. We identified the enzymes catalyzing the formation of D-glutamine in position 2 of the stem peptide. We provide biochemical evidence that the reaction is catalyzed by a glutamine amidotransferase-like protein and a Mur ligase homologue, encoded by SA1707 and SA1708, respectively. Both proteins, for which we propose the designation GatD and MurT, are required for amidation and appear to form a physically stable bi-enzyme complex. To investigate the reaction in vitro we purified recombinant GatD and MurT His-tag fusion proteins and their potential substrates, i.e. UDP-MurNAc-pentapeptide, as well as the membrane-bound cell wall precursors lipid I, lipid II and lipid II-Gly5. In vitro amidation occurred with all bactoprenol-bound intermediates, suggesting that in vivo lipid II and/or lipid II-Gly5 may be substrates for GatD/MurT. Inactivation of the GatD active site abolished lipid II amidation. Both, murT and gatD are organized in an operon and are essential genes of S. aureus. BLAST analysis revealed the presence of homologous transcriptional units in a number of gram-positive pathogens, e.g. Mycobacterium tuberculosis, Streptococcus pneumonia and Clostridium perfringens, all known to have a D-iso-glutamine containing PG. A less negatively charged PG reduces susceptibility towards defensins and may play a general role in innate immune signaling

A therapeutic non-self-reactive SARS-CoV-2 antibody protects from lung pathology in a COVID-19 hamster model

The emergence of SARS-CoV-2 led to pandemic spread of coronavirus disease 2019 (COVID-19), manifesting with respiratory symptoms and multi-organ dysfunction. Detailed characterization of virus-neutralizing antibodies and target epitopes is needed to understand COVID-19 pathophysiology and guide immunization strategies. Among 598 human monoclonal antibodies (mAbs) from 10 COVID-19 patients, we identified 40 strongly neutralizing mAbs. The most potent mAb, CV07-209, neutralized authentic SARS-CoV-2 with an IC(50) value of 3.1 ng/mL. Crystal structures of two mAbs in complex with the SARS-CoV-2 receptor-binding domain at 2.55 and 2.70 Å revealed a direct block of ACE2 attachment. Interestingly, some of the near-germline SARS-CoV-2-neutralizing mAbs reacted with mammalian self-antigens. Prophylactic and therapeutic application of CV07-209 protected hamsters from SARS-CoV-2 infection, weight loss, and lung pathology. Our results show that non-self-reactive virus-neutralizing mAbs elicited during SARS-CoV-2 infection are a promising therapeutic strategy