Biology subjects

Jones, A. T.

Publications and source records attributed to Jones, A. T..

4 recordsLinked to original sources

bioRxiv2024

The anti-inflammatory activity of IgG requires the co-engagement of types I and II Fc receptors

Intravenous immunoglobulin administered at high doses has been used for decades as an effective anti-inflammatory preparation to treat a wide array of autoimmune diseases. Studies in murine models have found this activity to be dependent on 1) sialylation of the N-linked glycan on the CH2 domain of IgG, 2) the type I IgG inhibitory Fc receptor Fc{gamma}RIIB, and 3) the type II Fc receptor DC-SIGN. Here, we demonstrate that the ectodomain glycan on Fc{gamma}RIIB interacts with the lectin domain of DC-SIGN to form a cell surface complex, thereby enabling the binding of sialylated IgG1. We have exploited this observation to Fc-engineer sialylated IgG1 to enhance its affinity for Fc{gamma}RIIB and demonstrate that the resulting molecule is at least 100-fold more potent in reducing the inflammatory sequelae of antibody or T cell mediated autoimmune diseases, providing the basis for a new class of anti-inflammatory therapeutics.

immunology↗

bioRxiv2023

Modification of the antibiotic, colistin, with dextrin causes enhanced cytotoxicity and triggers apoptosis in myeloid leukemia

Acute myeloid leukemia (AML) remains difficult to treat due to its heterogeneity in molecular landscape, epigenetics and cell signaling alterations. Precision medicine is a major goal in AML therapy towards developing agents that can be used to treat patients with different subtypes in combination with current chemotherapies. We have previously developed dextrin-colistin conjugates to combat the rise in multi-drug resistant bacterial infections and overcome dose-limiting nephrotoxicity. Recent evidence of colistins anticancer activity, mediated through inhibition of intracellular lysine-specific histone demethylase 1 (LSD1/KDM1A), suggests that dextrin-colistin conjugates could be used to treat cancer cells, including AML. This study aimed to evaluate whether dextrin conjugation (which reduces in vivo toxicity and prolongs plasma half-life) could enhance colistins cytotoxic effects in myeloid leukemia cell lines and compare the intracellular uptake and localization of the free and conjugated antibiotic. Our results identified a conjugate (containing 8,000 g/mol dextrin with 1 mol% succinoylation) that caused significantly increased toxicity in myeloid leukemia cells, compared to free colistin. Dextrin conjugation altered the mechanism of cell death by colistin, from necrosis to caspase 3/7-dependent apoptosis. In contrast, conjugation via a reversible ester linker, instead of an amide, had no effect on the mechanism of the colistin-induced cell death. Live cell confocal microscopy of fluorescently-labelled compounds showed both free and dextrin-conjugated colistin were endocytosed and co-localized in lysosomes and increasing the degree of modification by succinoylation of dextrin significantly reduced colistin internalization. Whilst clinical translation of dextrin-colistin conjugates for the treatment of AML is unlikely due to the potential to promote AMR and the relatively high colistin concentrations required for anticancer activity, the ability to potentiate the effectiveness of an anticancer drug by polymer conjugation, while reducing side effects and improving biodistribution of the drug, is very attractive, and this approach warrants further investigation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/565276v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@1cb7aaorg.highwire.dtl.DTLVardef@15e3574org.highwire.dtl.DTLVardef@7577aorg.highwire.dtl.DTLVardef@eb4_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2023

Sex- and age-dependent effects of locus coeruleus-originated tau dysfunction on olfaction and neurophysiology in rats

Braak and colleagues (2011) described human pretangle stages of abnormal tau protein originating in the locus coeruleus (LC) of young adults (Braaks Stages a-c, 1a-b), decades prior to the neurofibrillary tangle stages observed in Alzheimers disease. To capture the features of LC-originated pretangle tau stages, we used a rat model where male and female TH-Cre+/- rats received bilateral LC infusions of a hyperphosphorylated human tau (htauE14) gene via a viral vector. To assess the effects of age and sex on pretangle stage tau, we assayed physiological and behavioural changes 1-3mo (young) and 12+mo (aged) post LC-infusion (p.i.). Open field measures revealed age and sex-dependent differences in anxiety in LC-htauE14 infused rats and overall sex- and age-dependent differences in activity. Odour discrimination tests showed little impairment in LC-htauE14 infused rats at 1-3mo after LC infusion. At 12+mo p.i. however, LC-htauE14 male rats failed a difficult odour discrimination test and a further olfactory detection test (habituation-dishabituation), but male LC-Control rats and female rats were not impaired. LC neuronal firing rates were assessed in urethane-anesthetized aged (12+mo p.i.) male LC-htauE14 and LC-Control rats. The baseline level of firing of LC neurons in LC-htauE14 rats was higher than firing rates of LC-Control rats. Oscillatory patterns in LC firing were increased in amplitude and frequency by LC-htauE14. PSD95 density measures in piriform cortex were similar for LC-Control and LC-htauE14 male and female rats of young and aged groups. While synaptophysin density was higher in controls of the 1-3mo p.i. groups than in the LC-htauE14 rats, levels did not differ among aged groups. The increased excitability of LC cells observed may occur in relation to reduced LC axon arbours or may reflect a separate effect of htauE14 in LC neurons. The association of increased tonic LC activity to behavioural changes in the pretangle tau rat model merits further investigation.

neuroscience↗

bioRxiv2023

Dextrin conjugation to colistin inhibits its toxicity, cellular uptake and acute kidney injury in vivo.

The acute kidney injury (AKI) and dose-limiting nephrotoxicity, which occurs in 20-60% of patients following systemic administration of colistin, represents a challenge in the effective treatment of multi-drug resistant gram-negative infections. To reduce clinical toxicity of colistin and improve targeting to infected /inflamed tissues, we previously developed dextrin-colistin conjugates, whereby colistin is designed to be released by amylase-triggered degradation of dextrin in infected and inflamed tissues, after passive targeting by the enhanced permeability and retention effect. Whilst it was evident in vitro that polymer conjugation can reduce toxicity and prolong plasma half-life, without significant reduction in antimicrobial activity of colistin, it was unclear how dextrin conjugation would alter cellular uptake and localisation of colistin in renal tubular cells in vivo. We discovered that dextrin conjugation effectively reduced colistins toxicity towards human kidney proximal tubular epithelial cells (HK-2) in vitro, which was mirrored by significantly less cellular uptake of Oregon Green (OG)-labelled dextrin-colistin conjugate, when compared to colistin. Using live-cell confocal imaging, we revealed localisation of both, free and dextrin-bound colistin in endolysosome compartments of HK-2 and NRK-52E cells. Using a murine AKI model, we demonstrated dextrin-colistin conjugation dramatically diminishes both proximal tubular injury and renal accumulation of colistin. These findings reveal new insight into the mechanism by which dextrin conjugation can overcome colistins renal toxicity and show the potential of polymer conjugation to improve the side effect profile of nephrotoxic drugs. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/565265v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1ec6ac8org.highwire.dtl.DTLVardef@56a2b1org.highwire.dtl.DTLVardef@1d347fborg.highwire.dtl.DTLVardef@1ab7da_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗