A high-throughput microfluidic mechanoporation platform to enable intracellular delivery of cyclic peptides in cell-based assays

Cyclic peptides are poised to target historically difficult to drug intracellular protein-protein interactions, however, their general cell impermeability poses a challenge for characterizing function. Recent advances in microfluidics have enabled permeabilization of the cytoplasmic membrane by physical cell deformation (i.e., mechanoporation), resulting in intracellular delivery of impermeable macromolecules in vector- and electrophoretic-free approaches. However, the number of payloads (e.g., peptides) and/or concentrations delivered via microfluidic mechanoporation is limited by having to pre-mix cells and payloads, a manually intensive process. In this work, we show that cells are momentarily permeable (t 1/2 = 1.1-2.8 min) after microfluidic vortex shedding (μVS) and that lower molecular weight macromolecules can be cytosolically delivered upon immediate exposure after cells are processed/permeabilized. To increase the ability to screen peptides, we built a system, dispensing-microfluidic vortex shedding (DμVS), that integrates a μVS chip with inline microplate-based dispensing. To do so, we synced an electronic pressure regulator, flow sensor, on/off dispense valve, and an x-y motion platform in a software-driven feedback loop. Using this system, we were able to deliver low microliter-scale volumes of transiently mechanoporated cells to hundreds of wells on microtiter plates in just several minutes (e.g., 96-well plate filled in <2.5 min). We validated the delivery of an impermeable peptide directed at MDM2, a negative regulator of the tumor suppressor p53, using a click chemistry- and NanoBRET-based cell permeability assay in 96-well format, with robust delivery across the full plate. Furthermore, we demonstrated that DμVS could be used to identify functional, low micromolar, cellular activity of otherwise cell-inactive MDM2-binding peptides using a p53 reporter cell assay in 96- and 384-well format. Overall, DμVS can be combined with downstream cell assays to investigate intracellular target engagement in a high-throughput manner, both for improving structure-activity relationship efforts and for early proof-of-biology of non-optimized peptide (or potentially other macromolecular) tools.

Feasibility of a combined supervised and home-based whole-body vibration intervention in children after inpatient oncological treatment

Purpose

Reduced physical performance due to therapy-related dysfunctions in children diagnosed with cancer contributes to insufficient physical activity levels. It is therefore essential that relevant functions are restored. Whole-body vibration (WBV) training, a neuromuscular stimulating exercise intervention, could have the potential to target those functions adequately. Therefore, the aim of this study was to evaluate the feasibility of a combined supervised and home-based WBV intervention with children after inpatient oncological treatment.

Methods

Eight children aged 6–21 years were included after cessation of their inpatient oncological treatment. They performed a 12-week WBV training including one supervised and two home-based sessions per week according to a standardized training protocol. Feasibility, adherence and compliance to the vibration protocol were documented. Subjective benefits and satisfaction were assessed using a questionnaire.

Results

Study participants attended 84.03 ± 13.09% of WBV sessions. No serious adverse events occurred. Some patients reported side effects partially resulting in modifications of the vibration protocol by therapists. Almost all children regarded the intervention as beneficial.

Conclusion

A combined supervised and home-based WBV intervention with children after inpatient oncological treatment is feasible and safe. The beneficial potential regarding relevant sensory and motor dysfunctions is now to be investigated.

Trial registration number and date of registration

DRKS00014713 15.05.2018

Motives of contributing personal data for health research: (non-)participation in a Dutch biobank

Background

Large-scale, centralized data repositories are playing a critical and unprecedented role in fostering innovative health research, leading to new opportunities as well as dilemmas for the medical sciences. Uncovering the reasons as to why citizens do or do not contribute to such repositories, for example, to population-based biobanks, is therefore crucial. We investigated and compared the views of existing participants and non-participants on contributing to large-scale, centralized health research data repositories with those of ex-participants regarding the decision to end their participation. This comparison could yield new insights into motives of participation and non-participation, in particular the behavioural change of withdrawal.

Methods

We conducted 36 in-depth interviews with ex-participants, participants, and non-participants of a three-generation, population-based biobank in the Netherlands. The interviews focused on the respondents’ decision-making processes relating to their participation in a large-scale, centralized repository for health research data.

Results

The decision of participants and non-participants to contribute to the biobank was motivated by a desire to help others. Whereas participants perceived only benefits relating to their participation and were unconcerned about potential risks, non-participants and ex-participants raised concerns about the threat of large-scale, centralized public data repositories and public institutes, such as social exclusion or commercialization. Our analysis of ex-participants’ perceptions suggests that intrapersonal characteristics, such as levels of trust in society, participation conceived as a social norm, and basic societal values account for differences between participants and non-participants.

Conclusions

Our findings indicate the fluidity of motives centring on helping others in decisions to participate in large-scale, centralized health research data repositories. Efforts to improve participation should focus on enhancing the trustworthiness of such data repositories and developing layered strategies for communication with participants and with the public. Accordingly, personalized approaches for recruiting participants and transmitting information along with appropriate regulatory frameworks are required, which have important implications for current data management and informed consent procedures.

Identification of platelet-derived growth factor C as a mediator of both renal fibrosis and hypertension

Platelet-derived growth factors (PDGF) have been implicated in kidney disease progression. We previously found that PDGF-C is upregulated at sites of renal fibrosis and that antagonism of PDGF-C reduces fibrosis in the unilateral ureteral obstruction model. We studied the role of PDGF-C in collagen 4A3^-/- ("Alport") mice, a model of progressive renal fibrosis with greater relevance to human kidney disease. Alport mice were crossbred with PDGF-C^-/- mice or administered a neutralizing PDGF-C antibody. Both PDGF-C deficiency and neutralization reduced serum creatinine and blood urea nitrogen levels and mitigated glomerular injury, renal fibrosis, and renal inflammation. Unexpectedly, systolic blood pressure was also reduced in both Alport and wild-type mice treated with a neutralizing PDGF-C antibody. Neutralization of PDGF-C reduced arterial wall thickness in the renal cortex of Alport mice. Aortic rings isolated from anti-PDGF-C-treated wildtype mice exhibited reduced tension and faster relaxation than those of untreated mice. In vitro, PDGF-C upregulated angiotensinogen in aortic tissue and in primary hepatocytes and induced nuclear factor κB (NFκB)/p65-binding to the angiotensinogen promoter in hepatocytes. Neutralization of PDGF-C suppressed transcript expression of angiotensinogen in Alport mice and angiotensin II receptor type 1 in Alport and wildtype mice. Finally, administration of neutralizing PDGF-C antibodies ameliorated angiotensin II-induced hypertension in healthy mice. Thus, in addition to its key role in mediating renal fibrosis, we identified PDGF-C as a mediator of hypertension via effects on renal vasculature and on the renin-angiotensin system. The contribution to both renal fibrosis and hypertension render PDGF-C an attractive target in progressive kidney disease.

The efforts of direct support professionals to facilitate inclusion: the role of psychological determinants and work setting

BACKGROUND

Various studies have found that direct support professionals (DSPs) play an important role in determining the degree to which people with intellectual disabilities (ID) are included in society. However, less research has been conducted on the psychological processes that may influence the behavioural intentions of DSPs to actually engage with and invest effort in supporting their clients' inclusion. Five possible psychological variables are identified in the literature: attitudes, social norms, experienced competencies, identity and meta-evaluation. In our research, we tested whether these processes influence the (intended) efforts DSPs make to facilitate their clients' inclusion.

METHOD

A structured questionnaire was sent to 927 DSPs working in one of three different locations (an ordinary non-segregated setting, a reversed non-segregated setting and a residential facility). Of these, 336 DSPs completed the questionnaire.

RESULTS

Several variables revealed differences between the three locations, specifically in efforts to facilitate inclusion, attitudes, social norms, experienced competencies and professional identity. Looking at the overall means, we found (relatively) high scores for the experienced competencies, role identity and meta-evaluation. In contrast, the means were relatively negative regarding the DSPs' attitudes to inclusion and their assumed social norms.

CONCLUSIONS

Direct support professionals' efforts to facilitate inclusion depend on their attitude towards inclusion, the experienced competencies, their role identity, the DSPs' meta-evaluation and, indirectly through attitudes, also on the assumed social norms of the relevant stakeholders. Organizations responsible for supporting people with ID and which may want their DSPs to make greater efforts to facilitate inclusion should pay attention to these psychological variables.

Reduced Cellular Toxicity of a New Silver-Containing Antimicrobial Dressing and Clinical Performance in Non-Healing Wounds

Bacterial colonisation of wounds may delay wound healing. Modern silver-containing dressings are antimicrobial, yet cellular toxicity is a serious side-effect. We provide data for a newly formulated silver-containing ointment dressing, Atrauman Ag, for antimicrobial activity and cytotoxicity. Atrauman Ag effectively killed a panel of commensal skin as well as pathogenic bacterial strains while cytotoxicity for HaCaT keratinocytes was only around 10%. With these favourable in vitro tests, Atrauman Ag was analysed in 86 patients with traumatic and non-healing wounds of different aetiologies. The wound state was evaluated for 3 subsequent dressing changes. The slough score was reduced from 59.2 to 35.8%, granulation tissue increased from 27 to 40% and epithelialisation went up from 12.1 to 24%. We conclude that Atrauman Ag has a superior profile of antimicrobial activity over cellular toxicity and the low silver ion release rate may prevent interference with wound-healing mechanisms.

Isolation of novel tRNA(Ala) mutants by library selection in a tRNA(Ala) knockout strain

The relationship between tRNA structure and function has been widely investigated by site-directed mutagenesis. This method has been a very useful tool to reveal the critical bases in tRNAs that are important for recognition and aminoacylation, but has been limited by the large number of possible base combinations in tRNA molecules. We have devised a new method that uses tRNA knockout cells for selection of functional tRNAs from a mutant tRNA gene library to overcome this limitation. To explore the mechanism of tRNA(Ala) recognition, the bases of the acceptor-stem region were randomized and active mutants were selected in a tRNA(Ala) knockout strain. Mutants of tRNA(Ala) having diverse sequence combinations in the acceptor-stem region and a broad range of functional activity to support knockout cell growth were isolated. The mutant tRNAs selected by the method included molecules containing novel base substitutions as well as extensively altered base combinations that would not be readily generated by rationally designed site-directed mutagenesis. Our results emphasize the importance of the acceptor stem as a structural unit in which some nucleotides may carry more weight than others, but in summation every nucleotide contributes to the interaction with the enzyme.

ActA from Listeria monocytogenes can interact with up to four Ena/VASP homology 1 domains simultaneously

The facultative intracellular human pathogenic bacterium Listeria monocytogenes actively recruits host actin to its surface to achieve motility within infected cells. The bacterial surface protein ActA is solely responsible for this process by mimicking fundamental steps of host cell actin dynamics. ActA, a modular protein, contains an N-terminal actin nucleation site and a central proline-rich motif of the 4-fold repeated consensus sequence FPPPP (FP(4)). This motif is specifically recognized by members of the Ena/VASP protein family. These proteins additionally recruit the profilin-G-actin complex increasing the local concentration of G-actin close to the bacterial surface. By using analytical ultracentrifugation, we show that a single ActA molecule can simultaneously interact with four Ena/VASP homology 1 (EVH1) domains. The four FP(4) sites have roughly equivalent affinities with dissociation constants of about 4 microm. Mutational analysis of the FP(4) motifs indicate that the phenylalanine is mandatory for ActA-EVH1 interaction, whereas in each case exchange of the third proline was tolerated. Finally, by using sedimentation equilibrium centrifugation techniques, we demonstrate that ActA is a monomeric protein. By combining these results, we formulate a stoichiometric model to describe how ActA enables Listeria to utilize efficiently resources of the host cell microfilament for its own intracellular motility.

Physical and genetic map of the Listeria monocytogenes EGD serotype 1/2a chromosome

Listeria monocytogenes is a facultative intracellular pathogen responsible for both invasive and non-invasive food-borne illness in animals and humans. In this study, macrorestriction analysis following pulsed-field gel electrophoresis was used to show that Listeria monocytogenes serovar 1/2a strain EGD has a single chromosome containing eight NotI fragments of 1100, 850, 365, 320, 275, 40, 30 and 20 kb in size and 11 AscI fragments of 860, 470, 410, 360, 320, 250, 110, 80, 50, 30 and 20 kb. The total genome therefore comprises 3000 +/- 50 kb. The creation of a physical and genetic map of the Listeria genome was achieved by generating NotI linking clones and their use in subsequent hybridisation analysis. Using isogenic mutants harbouring additional artificial NotI restriction sites, we were able to precisely map the positions of all currently known virulence genes on the chromosome.

Serospecific antigens of Legionella pneumophila

Serospecific antigens isolated by EDTA extraction from four serogroups of Legionella pneumophila were analyzed for their chemical composition, molecular heterogeneity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and immunological properties. The antigens were shown to be lipopolysaccharides and to differ from the lipopolysaccharides of other gram-negative bacteria. The serospecific antigens contained rhamnose, mannose, glucosamine, and two unidentified sugars together with 2-keto-3-deoxyoctonate, phosphate, and fatty acids. The fatty acid composition was predominantly branched-chain acids with smaller amounts of 3-hydroxymyristic acid. The antigens contain periodate-sensitive groups; mannosyl residues were completely cleaved by periodate oxidation. Hydrolysis of the total lipopolysaccharide by acetic acid resulted in the separation of a lipid A-like material that cross-reacted with the antiserum to lipid A from Salmonella minnesota but did not comigrate with it on sodium dodecyl sulfate gels. None of the four antigens contained heptose. All of the antigen preparations showed endotoxicity when tested by the Limulus amebocyte lysate assay. The results of this study indicate that the serogroup-specific antigens of L. pneumophila are lipopolysaccharides containing an unusual lipid A and core structure and different from those of other gram-negative bacteria.

Microbial transformations of natural antitumor agents: conversion of lapachol to dehydro-alpha-lapachone by Curvularia lunata

Microbial transformation of lapachol, a naturally occurring naphthoquinone, was carried out by Curvularia lunata (NRRL 2178). The fungus brings about oxidative cyclization of the substrate to dehydro-alpha-lapachone, which was isolated and characterized by nuclear magnetic resonance and mass spectral analyses; its structure was verified by chemical synthesis. The metabolite is a naturally occurring chromene possessing antibacterial and antitumor activities.

Microbial transformations of natural antitumor agents: oxidation of lapachol by Penicillium notatum

The naphthoquinone lapachol (1) is readily metabolized by several fungi and streptomycetes. Preparative-scale fermentations with Penicillium notatum (UI 1602) provided a major polar metabolite (4), which was isolated and identified as an intermediate of the Hooker oxidation. The metabolite was synthesized by reacting lapachol with hydrogen peroxide under alkaline conditions.