Influence of Folate-Targeted Gold Nanoparticles on Subcellular Localization and Distribution into Lysosomes

The cell interaction, mechanism of cell entry and intracellular fate of surface decorated nanoparticles are known to be affected by the surface density of targeting agents. However, the correlation between nanoparticles multivalency and kinetics of the cell uptake process and disposition of intracellular compartments is complicated and dependent on a number of physicochemical and biological parameters, including the ligand, nanoparticle composition and colloidal properties, features of targeted cells, etc. Here, we have carried out an in-depth investigation on the impact of increasing folic acid density on the kinetic uptake process and endocytic route of folate (FA)-targeted fluorescently labelled gold nanoparticles (AuNPs). A set of AuNPs (15 nm mean size) produced by the Turkevich method was decorated with 0–100 FA-PEG3.5kDa-SH molecules/particle, and the surface was saturated with about 500 rhodamine-PEG2kDa-SH fluorescent probes. In vitro studies carried out using folate receptor overexpressing KB cells (KBFR-high) showed that the cell internalization progressively increased with the ligand surface density, reaching a plateau at 50:1 FA-PEG3.5kDa-SH/particle ratio. Pulse-chase experiments showed that higher FA density (50 FA-PEG3.5kDa-SH molecules/particle) induces more efficient particle internalization and trafficking to lysosomes, reaching the maximum concentration in lysosomes at 2 h, than the lower FA density of 10 FA-PEG3.5kDa-SH molecules/particle. Pharmacological inhibition of endocytic pathways and TEM analysis showed that particles with high folate density are internalized predominantly by a clathrin-independent process.

Anti-schistosomal activities of quinoxaline-containing compounds: From hit identification to lead optimisation

Schistosomiasis is a neglected disease of poverty that is caused by infection with blood fluke species contained within the genus Schistosoma. For the last 40 years, control of schistosomiasis in endemic regions has predominantly been facilitated by administration of a single drug, praziquantel. Due to limitations in this mono-chemotherapeutic approach for sustaining schistosomiasis control into the future, alternative anti-schistosomal compounds are increasingly being sought by the drug discovery community. Herein, we describe a multi-pronged, integrated strategy that led to the identification and further exploration of the quinoxaline core as a promising anti-schistosomal scaffold.

Firstly, phenotypic screening of commercially available small molecules resulted in the identification of a moderately active hit compound against Schistosoma mansoni (1, EC₅₀ = 4.59 μM on schistosomula). Secondary exploration of the chemical space around compound 1 led to the identification of a quinoxaline-core containing, non-genotoxic lead (compound 22). Compound 22 demonstrated substantially improved activities on both intra-mammalian (EC₅₀ = 0.44 μM, 0.20 μM and 84.7 nM, on schistosomula, juvenile and adult worms, respectively) and intra-molluscan (sporocyst) S. mansoni lifecycle stages. Further medicinal chemistry optimisation of compound 22, resulting in the generation of 20 additional analogues, improved our understanding of the structure-activity relationship and resulted in considerable improvements in both anti-schistosome potency and selectivity (e.g. compound 30; EC₅₀ = 2.59 nM on adult worms; selectivity index compared to the HepG2 cell line = 348). Some derivatives of compound 22 (e.g. 31 and 33) also demonstrated significant activity against the two other medically important species, Schistosoma haematobium and Schistosoma japonicum. Further optimisation of this class of anti-schistosomal is ongoing and could lead to the development of an urgently needed alternative to praziquantel for assisting in schistosomiasis elimination strategies.

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Lead compound 22 was identified with EC₅₀ of 0.44 µM and 84.7 nM for schistosomula and adult worms.

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20 analogues of the lead compound 22 were synthesised.

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Compounds 25, 30 and 32 showed the best selectivity profile.

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Compounds 31 and 33 are the most active on three medically important schistosome species.

FRI0561 PRO-INFLAMMATORY DIETS ARE ASSOCIATED WITH INCREASED C-REACTIVE PROTEIN AND RHEUMATOID ARTHRITIS IN THE UK BIOBANK COHORT

Background:

Several individual dietary components have been associated with the risk of rheumatoid arthritis (RA) and recent studies have suggested that dietary indices, which account for the consumption of multiple foods, can be used as more complete measures of risk.

Objectives:

In this study we aimed to use the Dietary Inflammatory Index (DII), an independent index of dietary variable associated with inflammatory biomarkers, to evaluate potential associations between pro-inflammatory exposures in the diet, an inflammation biomarker (C-reactive protein) and RA onset using the UK Biobank cohort.

Methods:

The DII was calculated from data obtained in 24-hour dietary recall questionnaires collected on healthy participants on four separate occasions over an approximate annual period between Feb 2011 and April 2012. Cases of RA in the UK Biobank cohort were identified from the participants with appropriate ICD10 codes and compared against a randomly selected subsample of controls matched (20:1) for age, sex, smoking status and BMI.

Results:

Among the 502,519 subjects enrolled in Biobank, 141,769 had completed 24-hour dietary recall questionnaires and had full data for the 18 dietary variables that were required to create the DII (mean=0.03, range: -3.88, 4.22). Higher (positive) DII values indicate more pro-inflammatory diets. This index was positively correlated (p<0.001) with C-reactive protein (CRP), attesting to the validity of this index for assessing dietary inflammatory potential. A total of 1,423 participants were classified as having RA (1% prevalence in ‘dietary’ cohort of 141,769) according to their ICD10 codes that were last updated in 2018. Their mean age at enrolment (2006-10) was 59 years. There was a significant association between DII and RA: OR 1.05 [1.01-1.09]; p=0.028) that suggested RA cases were more likely to be consuming a pro-inflammatory diet.

Conclusion:

These data show a significant association between diet, inflammation (CRP) and RA in the UK Biobank population. The findings are consistent with a recent analysis of the US Nurse’s Health Study which was based on data only from females, indicating that these findings are likely to be robust and generalisable. Diet is one of the few modifiable factors that has the potential to reduce the risk of future RA onset. These results open the way to providing evidence-based health advice and for designing clinical interventions.

References:

[1] Shivappa N, Steck SE, Hurley TG, Hussey JR, Hebert JR. Designing and developing a literature-derived, population-based dietary inflammatory index. Public health nutrition 2014;17:1689-96.

Acknowledgments:

This research has been conducted using the UK Biobank Resource under Application Number ‘33557’

Disclosure of Interests:

None declared

A sensitive method for the recovery of Escherichia coli serogroup O55 including Shiga toxin-producing variants for potential use in outbreaks

AIM

Shiga toxin-producing Escherichia coli (STEC) cause bloody diarrhoea, kidney failure and occasionally death. However, identifying the source of infection caused by STEC other than serogroup O157 is hampered by the availability of sensitive methods for detecting these pathogens. In this study, we developed novel tools for detecting E. coli O55 that is potentially associated with human outbreaks.

METHODS AND RESULTS

Overall specificity of immuno-magnetic separation (IMS) beads coated with anti-O55 serum was good with exception of cross-reactivity with E. coli O22 and O23, which was eliminated using an O55-specific PCR. Limit of detection for E. coli O55 using O55-IMS beads in spiked cattle faeces was on average 50 CFU per ml (range 1-90), and improved to <10 CFU per ml using the O55-specific PCR, following IMS on samples enriched for 2 h with E. coli O55. Application of these tools to test cattle faeces collected on-farm allowed the isolation of O55:H19, which through whole genome sequencing was compared to STEC O55:H7 human outbreak strains.

CONCLUSION

These tools provide a sensitive method which could be used to screen samples for STEC O55, whether environmental or human clinical.

SIGNIFICANCE AND IMPACT OF THE STUDY

Several human outbreaks reported in England were caused by STEC O55:H7. Tools developed here could assist in identification of the environmental source for these isolates, which has not yet been established.

Kinetic characterization of channel impaired mutants of tryptophan synthase

Tryptophan synthase, an alpha 2 beta 2 tetrameric complex, is a classic example of an enzyme that is thought to "channel" a metabolic intermediate (indole) from the active site of the alpha subunit to the active site of the beta subunit. The solution of the three-dimensional structure of the enzyme from Salmonella typhimurium provided physical evidence for a 25-A hydrophobic tunnel which connects the alpha and beta active sites (Hyde, C. C., Ahmed, S. A., Padlan, E. A., Miles, E. W., and Davies, D. R. (1988) J. Biol. Chem. 263, 17857-17871). Using rapid reaction kinetics, we have previously established that indole is indeed channeled and have identified three essential kinetic features which govern efficient channeling. In the current study we have probed the necessity of these features by using site-directed mutagenesis to alter these requirements. We now report the kinetic characterization of two mutants which contain substitutions to block or restrict the tunnel (beta C170F and beta C170W). Preliminary kinetic and structural evidence of a restricted tunnel in the beta C170W has been provided (Schlichting, I., Yang, X. W., Miles, E. W., Kim, A. Y., and Anderson, K. S. (1994) J. Biol. Chem. 269, 26591-26593). The rapid kinetic analysis of these mutant proteins shows that these mutations interfere with efficient channeling of the indole metabolite such that indole can be observed in single enzyme turnover of the physiologically relevant alpha beta reaction. In addition, the beta C170W mutant appears to be impaired in alpha beta intersubunit communication.