Mapping the Influence of the Gut Microbiota on Small Molecules across the Microbiome Gut Brain Axis

Microbes exert influence across the microbiome-gut-brain axis through neurotransmitter production, induction of host immunomodulators, or the release or induction of other microbial or host molecules. Here, we used mass spectrometry imaging (MSI), a label-free imaging tool, to map molecular changes in the gut and brain in germ-free, antibiotic-treated and control mice. We determined spatial distribution and relative quantification of neurotransmitters and their precursors in response to the microbiome. Using untargeted MSI, we detected a significant change in the levels of four identified small molecules in the brains of germ-free animals compared to controls. However, antibiotic treatment induced no significant changes in these same metabolites in the brain after 1 week of treatment. This work exemplifies the utility of MSI as a tool for the study of known and discovery of novel, mediators of microbiome-gut-brain axis communication.

Universal Sample Preparation Unlocking Multimodal Molecular Tissue Imaging

A new tissue sample embedding and processing method is presented that provides downstream compatibility with numerous different histological, molecular biology, and analytical techniques. The methodology is based on the low temperature embedding of fresh frozen specimens into a hydrogel matrix composed of hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP) and sectioning using a cryomicrotome. The hydrogel was expected not to interfere with standard tissue characterization methods, histologically or analytically. We assessed the compatibility of this protocol with various mass spectrometric imaging methods including matrix-assisted laser desorption ionization (MALDI), desorption electrospray ionization (DESI) and secondary ion mass spectrometry (SIMS). We also demonstrated the suitability of the universal protocol for extraction based molecular biology techniques such as rt-PCR. The integration of multiple analytical modalities through this universal sample preparation protocol offers the ability to study tissues at a systems biology level and directly linking results to tissue morphology and cellular phenotype.

Microbiome-derived carnitine mimics as previously unknown mediators of gut-brain axis communication

Alterations to the gut microbiome are associated with various neurological diseases, yet evidence of causality and identity of microbiome-derived compounds that mediate gut-brain axis interaction remain elusive. Here, we identify two previously unknown bacterial metabolites 3-methyl-4-(trimethylammonio)butanoate and 4-(trimethylammonio)pentanoate, structural analogs of carnitine that are present in both gut and brain of specific pathogen-free mice but absent in germ-free mice. We demonstrate that these compounds are produced by anaerobic commensal bacteria from the family Lachnospiraceae (Clostridiales) family, colocalize with carnitine in brain white matter, and inhibit carnitine-mediated fatty acid oxidation in a murine cell culture model of central nervous system white matter. This is the first description of direct molecular inter-kingdom exchange between gut prokaryotes and mammalian brain cells, leading to inhibition of brain cell function.

Nanoextraction Coupled to Liquid Chromatography Mass Spectrometry Delivers Improved Spatially Resolved Analysis

Direct analyte-probed nanoextraction (DAPNe) is a technique that allows extraction of drug and endogenous compounds from a discrete location on a tissue sample using a nano capillary filled with solvent. Samples can be extracted from spot diameters as low as 6 μm. Studies previously undertaken by our group have shown that the technique can provide good precision (5%) for analyzing drug molecules in 150 μm diameter areas of homogenized tissue, provided an internal standard is sprayed on to the tissue prior to analysis. However, without an isotopically labeled standard, the repeatability is poor, even after normalization to the spot area or matrix compounds. By application to tissue homogenates spiked with drug compounds, we can demonstrate that it is possible to significantly improve the repeatability of the technique by incorporating a liquid chromatography separation step. Liquid chromatography is a technique for separating compounds prior to mass spectrometry (LC-MS) which enables separation of isomeric compounds that cannot be discriminated using mass spectrometry alone, as well as reducing matrix interferences. Conventionally, LC-MS is carried out on bulk or homogenized samples, which means analysis is essentially an average of the sample and does not take into account discrete areas. This work opens a new opportunity for spatially resolved liquid chromatography mass spectrometry with precision better than 20%.

Intratumoral immunotherapy with TLR7/8 agonist MEDI9197 modulates the tumor microenvironment leading to enhanced activity when combined with other immunotherapies

Background

Immune checkpoint blockade (ICB) promotes adaptive immunity and tumor regression in some cancer patients. However, in patients with immunologically “cold” tumors, tumor-resident innate immune cell activation may be required to prime an adaptive immune response and so exploit the full potential of ICB. Whilst Toll-like receptor (TLR) agonists have been used topically to successfully treat some superficial skin tumors, systemic TLR agonists have not been well-tolerated.

Methods

The response of human immune cells to TLR7 and 8 agonism was measured in primary human immune cell assays. MEDI9197 (3M-052) was designed as a novel lipophilic TLR7/8 agonist that is retained at the injection site, limiting systemic exposure. Retention of the TLR7/8 agonist at the site of injection was demonstrated using quantitative whole-body autoradiography, HPLC-UV, and MALDI mass spectrometry imaging. Pharmacodynamic changes on T cells from TLR7/8 agonist treated B16-OVA tumors was assessed by histology, quantitative real time PCR, and flow cytometry. Combination activity of TLR7/8 agonism with immunotherapies was assessed in vitro by human DC-T cell MLR assay, and in vivo using multiple syngeneic mouse tumor models.

Results

Targeting both TLR7 and 8 triggers an innate and adaptive immune response in primary human immune cells, exemplified by secretion of IFNα, IL-12 and IFNγ. In contrast, a STING or a TLR9 agonist primarily induces release of IFNα. We demonstrate that the TLR7/8 agonist, MEDI9197, is retained at the sight of injection with limited systemic exposure. This localized TLR7/8 agonism leads to Th1 polarization, enrichment and activation of natural killer (NK) and CD8⁺ T cells, and inhibition of tumor growth in multiple syngeneic models. The anti-tumor activity of this TLR7/8 agonist is enhanced when combined with T cell-targeted immunotherapies in pre-clinical models.

Conclusion

Localized TLR7/8 agonism can enhance recruitment and activation of immune cells in tumors and polarize anti-tumor immunity towards a Th1 response. Moreover, we demonstrate that the anti-tumor effects of this TLR7/8 agonist can be enhanced through combination with checkpoint inhibitors and co-stimulatory agonists.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0724-8) contains supplementary material, which is available to authorized users.

Continuous inhibition of 11β-hydroxysteroid dehydrogenase type I in adipose tissue leads to tachyphylaxis in humans and rats but not in mice

BACKGROUND AND PURPOSE

11β-hydroxysteroid dehydrogenase type I (11β-HSD1), a target for Type 2 diabetes mellitus, converts inactive glucocorticoids into bioactive forms, increasing tissue concentrations. We have compared the pharmacokinetic-pharmacodynamic (PK/PD) relationship of target inhibition after acute and repeat administration of inhibitors of 11β-HSD1 activity in human, rat and mouse adipose tissue (AT).

EXPERIMENTAL APPROACH

Studies included abdominally obese human volunteers, rats and mice. Two specific 11β-HSD1 inhibitors (AZD8329 and COMPOUND-20) were administered as single oral doses or repeat daily doses for 7-9 days. 11β-HSD1 activity in AT was measured ex vivo by conversion of (3) H-cortisone to (3) H-cortisol.

KEY RESULTS

In human and rat AT, inhibition of 11β-HSD1 activity was lost after repeat dosing of AZD8329, compared with acute administration. Similarly, in rat AT, there was loss of inhibition of 11β-HSD1 activity after repeat dosing with COMPOUND-20 with continuous drug cover, but effects were substantially reduced if a 'drug holiday' period was maintained daily. Inhibition of 11β-HSD1 activity was not lost in mouse AT after continuous cover with COMPOUND-20 for 7 days.

CONCLUSIONS AND IMPLICATIONS

Human and rat AT, but not mouse AT, exhibited tachyphylaxis for inhibition of 11β-HSD1 activity after repeat dosing. Translation of observed efficacy in murine disease models to human for 11β-HSD1 inhibitors may be misleading. Investigators of the effects of 11β-HSD1 inhibitors should confirm that desired levels of enzyme inhibition in AT can be maintained over time after repeat dosing and not rely on results following a single dose.

Abstract 3678: Imaging AZD1152HQPA Accurin™ nanoparticle accumulation in preclinical tumors

AZD1152HQPA Accurin is a passively targeted nanoparticle containing the active metabolite of the Aurora B kinase prodrug AZD1152. In preclinical studies, AZD1152HQPA Accurin displays reduced bone marrow toxicity associated with AZD1152 together with increases in anti-tumour activity. Nanoparticles are proposed to enable delivery and retention of drug to the tumour thereby increasing efficacy and modifying therapeutic index. While it is possible to demonstrate increased duration of modulation of pharmacodynamic biomarkers and drug exposure by nanoparticle delivery, directly demonstrating that nanoparticles accumulate in the tumour is challenging. To investigate the intra tumoural distribution of AZD1152HQPA Accurin nanoparticles we have employed mass spectrometry techniques to image samples derived from human colorectal cancer SW620 studies in rats. We have separately identified the nanoparticle itself, drug encapsulated in nanoparticle, and drug released from nanoparticle; the latter by detecting a metabolite that is only generated from released drug. First MALDI (matrix assisted laser desorption ionization) which offers 20 μm spatial resolution, was used to detect AZD1152-hQPA (released and encapsulated). Second LESA (liquid extraction surface analysis), which offers 1000 μm spatial resolution, was used to detect drug and metabolite, enabling co-distribution to be demonstrated. Finally DESI (desorption electrospray ionization) which offers 100 μm spatial resolution was used to detect drug, metabolite and nanoparticle constituent showing the co-distribution in more detail. Using this combination of approaches it is possible to demonstrate the presence of nanoparticle-delivered AZD1152HQPA metabolite in the tumour at extended timepoints; co-located with nanoparticle and unchanged (encapsulated) drug. At these time points no drug remains if delivered as a simple IV infusion. Collectively this imaging mass spectrometry analysis demonstrates AZD1152HQPA Accurin accumulation in pre-clinical tumours and confirms that the Accurin accesses the tumour and achieves sustained drug release within the tumour.

Citation Format: Richard Goodwin, John Swales, Anna Nilsson, Per Andren, Nicola Strittmatter, Zoltan Takats, Colin Howes, Paula Taylor, Susan Ashton, Philip Jewsbury, Simon T. Barry. Imaging AZD1152HQPA Accurin™ nanoparticle accumulation in preclinical tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3678. doi:10.1158/1538-7445.AM2015-3678

The stability of amitriptyline N-oxide and clozapine N-oxide on treated and untreated dry blood spot cards

Procedures for drug monitoring based on Dried Blood Spot (DBS) sampling are gaining acceptance for an increasing number of clinical and preclinical applications, where ease of use, small sample requirement, and improved sample stability have been shown to offer advantages over blood tube sampling. However, to-date, the vast majority of this work has described the analysis of well characterized drugs. Using amitriptyline, clozapine, and their potentially labile N-oxide metabolites as model compounds, we consider the merits of using DBS for discovery pharmacokinetic (PK) studies where the metabolic fate of test compounds are often unknown. Both N-oxide metabolites reverted to parent compound under standard drying (2hr) and extraction conditions. Card type significantly affected the outcome, with 14% and 22% degradation occurring for clozapine-N-oxide and amitriptyline-N-oxide on a brand of untreated DBS cards, compared to 59 and 88% on a brand of treated DBS cards. Enrichment of the parent compound ex vivo leads to overestimation of circulating blood concentration and inaccurate determination of the PK profile.

Severe paediatric ulcerative colitis: incidence, outcomes and optimal timing for second-line therapy

BACKGROUND

Despite the predominance of extensive disease in children with ulcerative colitis, data concerning severe paediatric ulcerative colitis are sparse. We reviewed rates and predictors of response to intravenous-corticosteroid therapy in a single-centre cohort with long-term follow-up.

METHODS

99 children (49% males; age 2-17 years) were hospitalised (1991-2000) for treatment of severe ulcerative colitis (90% extensive; 49% new onset ulcerative colitis). Clinical, laboratory and radiographic data were reviewed. A population-based subset was used to assess incidence. Predictors of corticosteroid response were analysed using univariate and multivariate analyses at days 3 and 5 of therapy. Colectomy rates were calculated using Kaplan-Meier survival analyses.

RESULTS

28% (95% CI, 23 to 34%) of children with ulcerative colitis resident in the Greater Toronto Area required admission for intravenous corticosteroid therapy, of whom 53 (53%; 95% CI, 44 to 63%) responded. Several predictors were associated with corticosteroid failure, but in multivariable modelling only C-reactive protein [OR = 3.5 (1.4 to 8.4)] and number of nocturnal stools [OR = 3.2 (1.6 to 6.6)] remained significant at both days 3 and 5. The Pediatric Ulcerative Colitis Activity Index (PUCAI), Travis and Lindgren's indices strongly predicted non-response. Radiographically, the upper range of colonic luminal width was 40 mm in children younger than 11 years versus 60 mm in older patients. Cumulative colectomy rates at discharge, 1 year and 6 years were 42%, 58% and 61%, respectively.

CONCLUSIONS

Children with ulcerative colitis commonly experience at least one severe exacerbation. Response to intravenous corticosteroids is poor. The PUCAI, determined at day 3 (>45 points) should be used to screen for patients likely to fail corticosteroids and at day 5 (>70 points) to dictate the introduction of second-line therapies.

Kinetics of the time-dependent inactivation of CYP2D6 in cryopreserved human hepatocytes by methylenedioxymethamphetamine (MDMA)

Methylenedioxymethamphetamine (MDMA) was investigated in cryopreserved human hepatocytes as a time-dependent inactivator (TDI) of CYP2D6 using dextromethorphan (DEX) as a probe substrate. Inhibition kinetic parameters k(inact), the maximal rate of inactivation, and K(I), the inhibitor concentration at half the maximal activation rate, were determined. Time- and concentration-dependent inhibition were confirmed, and the influence of different elements of study design (e.g. cell number, stability of hepatocytes, dilution after preincubation) on estimated kinetic parameters were evaluated. Dilution factors (DF) of 1.2, 5 or total removal of inhibitor (by washing cells after preincubation, WR) resulted in k(inact) and K(I) (+/-S.E.) values of 0.02+/-0.002 min(-1) and 0.88+/-0.31 microM, 0.01+/-0.001 min(-1) and 1.23+/-0.70 microM, and 0.01+/-0.001 min(-1) and 2.10+/-1.32 microM, respectively; indicating that insufficient dilution may lead to overestimation of CYP2D6 inactivation. Accounting for MDMA depletion during the preincubation, corrected K(I) values were significantly lower (0.11+/-0.05 microM, 0.15+/-0.09 microM, 0.24+/-0.16 microM for DF of 1.2, 5, and WR, respectively). Inactivation efficiency in hepatocytes, as measured by k(inact)/K(I), was 10-fold less than that previously reported in human liver microsomes or recombinantly expressed systems. Possible causes for the observed differences between in vitro systems warrant further investigation. These may include differences in metabolic consumption of MDMA in each system, non-specific binding and presence of active efflux in hepatocytes.

Inhibition of 11beta-hydroxysteroid dehydrogenase type 1 reduces food intake and weight gain but maintains energy expenditure in diet-induced obese mice

AIMS/HYPOTHESIS

The 11beta-hydroxysteroid dehydrogenase type-1 inhibitor BVT.2733 lowers blood glucose and insulin in mutant mouse models of obesity and diabetes. Its effects on energy balance and body composition, and their contribution to improved glucose homeostasis have received little attention.

MATERIALS AND METHODS

BVT.2733 (100 mg/kg, orally) was given twice daily to lean and diet-induced obese mice for 16 or 17 days. A group of obese mice was pair-fed to the amounts consumed by BVT.2733-treated mice.

RESULTS

In both obese and lean mice, BVT.2733 reduced food intake and weight gain, but increased water intake. Pair-feeding caused almost as great a decrease in body weight as BVT.2733. Energy expenditure was 38+/-8% higher in the BVT.2733-treated obese mice than in the pair-fed mice. Terminal plasma corticosterone was raised, lean body weight reduced and percentage fat unchanged in the pair-fed mice (control, 47.8+/-2.6%; pair-fed, 47.1+/-1.9%), whereas BVT.2733 did not reduce lean mass, but did reduce percentage fat (40.9+/-2.0%). BVT.2733 but not pair-feeding reduced both the glucose tolerance AUC and the plasma insulin concentration 30 min after giving glucose.

CONCLUSIONS/INTERPRETATION

BVT.2733 reduced food intake but prevented a concomitant reduction in lean body mass and energy expenditure. The latter effects may have contributed to improved glucose tolerance.

Population advice on salt restriction: the social issues

The scientific evidence that underlies public health advice depends upon critical integration of information from several sources. The most informative evidence relating to the effects of population reduction in salt intake comes from systematic reviews of clinical trials. Recent rigorous reviews of salt restriction trials in normal subjects show extremely small effects ranging from 1 to 2 mm Hg for systolic blood pressure and 0.1 to 1.0 mm Hg for diastolic pressure. These are the result of much greater reductions in sodium intake than can be achieved by population advice, and may be further amplified by publication bias and effects of changes in other dietary components. There is little trial evidence to enable possible benefits and adverse effects to be balanced. Reviews biased by the inclusion of nonrandomized studies exaggerate the apparent blood pressure fall 5- to 50-fold and create spurious apparent progressive falls in blood pressure. Nevertheless, citation analysis shows that they are quoted much more frequently than rigorous reviews reaching more negative conclusions. This appears to be the result of an attempt to create an impression of scientific consensus. The salt debate has important implications for social policy.

Research and development in the NHS

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Management guidelines in essential hypertension: report of the second working party of the British Hypertension Society

Several important new issues have arisen in the management of patients with hypertension. A working party of the British Hypertension Society has therefore reviewed available intervention studies on anti-hypertensive treatment and made recommendations on blood pressure thresholds for intervention, on non-pharmacological and pharmacological treatments, and on treatment goals. This report also provides guidelines on blood pressure measurement, essential investigations, referrals for specialist advice, follow up, and stopping treatment.

Familial Conn's syndrome

We describe the occurrence of primary hyperaldosteronism in two sisters. Although this is only the second published report of familial Conn's syndrome, it does have implications for the relatives of patients with Conn's syndrome and these are discussed.

Reduction in vitro of red cell glutathione reproduces defects of cellular sodium transport seen in oedematous malnutrition

Red cells in oedematous malnutrition (kwashiorkor) have an increased sodium content, 'leakiness' to sodium and enhanced sodium pumping. In non-oedematous malnutrition (marasmus) there is a reduction in the sodium pump activity. The explanation has hitherto been unknown but the glutathione content of red cells is low in kwashiorkor and normal in marasmus. We artificially lowered the glutathione content of normal red cells to values characteristic of mild oedematous malnutrition, using the enzyme inhibitors bischloronitrosourea (BCNU) and buthionine sulfoximine (BSOX). After preincubation, the cells were washed to remove the inhibitors and oxidized glutathione. Cellular content of sodium and potassium, and 86Rb influx were then measured. The reduction in glutathione reproduced the abnormalities of sodium content and flux observed in kwashiorkor. We suggest that oxidant stress in kwashiorkor, by reducing cellular glutathione, may affect cell membrane electrolyte transport. This may act through alterations in membrane sulfhydryl groups. Glutathione depletion may therefore play an important role in the clinical picture and natural history of oedematous malnutrition and may have relevance to other conditions where oxidant stress occurs.