Recreational nitrous oxide and thrombotic events: a case series

Background

The study aimed to elucidate the prevalence of nitrous oxide (N2O) usage in patients with unexplained venous thromboembolism (VTE), highlighting the potential association with hyperhomocysteinaemia (HHcy).

Methods

We conducted a retrospective study at the Royal London Hospital, examining cases of N2O-related VTE from March to August 2023. Among 50 patients identified, four (8%) had recent unprovoked VTE. Patient data were collected based on N2O ambulatory emergency care pathway admissions.

Results

Among the 50 patients identified, four (8%) had recent or concurrent VTE. Three were male (75%), with an ethnic distribution of 50% Asian or Asian British and 50% Black or Black British. Patients were distributed across quintiles of the index of multiple deprivation. All had actual or functional vitamin B12 deficiency.

Discussion

The association between N2O use and VTE requires further investigation, though a plausible mechanism involving HHcy has been proposed. Clinicians should be vigilant for VTE in N2O users, especially those presenting with unexplained symptoms. VTE prophylaxis may be worth considering, particularly if continued exposure to nitrous oxide is anticipated.

Conclusion

N2O misuse may increase the risk of VTE, warranting attention from healthcare providers. Further research is needed to elucidate this association and inform preventive strategies. Public awareness about the risks of N2O remains essential.

The human liver microenvironment shapes the homing and function of CD4+ T-cell populations

OBJECTIVE

Tissue-resident memory T cells (TRM) are vital immune sentinels that provide protective immunity. While hepatic CD8+ TRM have been well described, little is known about the location, phenotype and function of CD4+ TRM.

DESIGN

We used multiparametric flow cytometry, histological assessment and novel human tissue coculture systems to interrogate the ex vivo phenotype, function and generation of the intrahepatic CD4+ T-cell compartment. We also used leukocytes isolated from human leukocyte antigen (HLA)-disparate liver allografts to assess long-term retention.

RESULTS

Hepatic CD4+ T cells were delineated into three distinct populations based on CD69 expression: CD69-, CD69INT and CD69HI. CD69HICD4+ cells were identified as tissue-resident CD4+ T cells on the basis of their exclusion from the circulation, phenotypical profile (CXCR6+CD49a+S1PR1-PD-1+) and long-term persistence within the pool of donor-derived leukcoocytes in HLA-disparate liver allografts. CD69HICD4+ T cells produced robust type 1 polyfunctional cytokine responses on stimulation. Conversely, CD69INTCD4+ T cells represented a more heterogenous population containing cells with a more activated phenotype, a distinct chemokine receptor profile (CX3CR1+CXCR3+CXCR1+) and a bias towards interleukin-4 production. While CD69INTCD4+ T cells could be found in the circulation and lymph nodes, these cells also formed part of the long-term resident pool, persisting in HLA-mismatched allografts. Notably, frequencies of CD69INTCD4+ T cells correlated with necroinflammatory scores in chronic hepatitis B infection. Finally, we demonstrated that interaction with hepatic epithelia was sufficient to generate CD69INTCD4+ T cells, while additional signals from the liver microenvironment were required to generate liver-resident CD69HICD4+ T cells.

CONCLUSIONS

High and intermediate CD69 expressions mark human hepatic CD4+ TRM and a novel functionally distinct recirculating population, respectively, both shaped by the liver microenvironment to achieve diverse immunosurveillance.

Genetic variation at mouse and human ribosomal DNA influences associated epigenetic states

BACKGROUND

Ribosomal DNA (rDNA) displays substantial inter-individual genetic variation in human and mouse. A systematic analysis of how this variation impacts epigenetic states and expression of the rDNA has thus far not been performed.

RESULTS

Using a combination of long- and short-read sequencing, we establish that 45S rDNA units in the C57BL/6J mouse strain exist as distinct genetic haplotypes that influence the epigenetic state and transcriptional output of any given unit. DNA methylation dynamics at these haplotypes are dichotomous and life-stage specific: at one haplotype, the DNA methylation state is sensitive to the in utero environment, but refractory to post-weaning influences, whereas other haplotypes entropically gain DNA methylation during aging only. On the other hand, individual rDNA units in human show limited evidence of genetic haplotypes, and hence little discernible correlation between genetic and epigenetic states. However, in both species, adjacent units show similar epigenetic profiles, and the overall epigenetic state at rDNA is strongly positively correlated with the total rDNA copy number. Analysis of different mouse inbred strains reveals that in some strains, such as 129S1/SvImJ, the rDNA copy number is only approximately 150 copies per diploid genome and DNA methylation levels are < 5%.

CONCLUSIONS

Our work demonstrates that rDNA-associated genetic variation has a considerable influence on rDNA epigenetic state and consequently rRNA expression outcomes. In the future, it will be important to consider the impact of inter-individual rDNA (epi)genetic variation on mammalian phenotypes and diseases.

A randomised controlled pilot trial of the influence of non-native English accents on examiners' scores in OSCEs

BACKGROUND

Objective structured clinical examinations (OSCEs) are important aspects of assessment in medical education. There is anecdotal evidence suggesting that students with non-native English accents (NNEA) may be subjected to unconscious bias. It is imperative to minimise the examiners' bias so that the difference in the scores reflects students' clinical competence. Research shows NNEAs can cause stereotyping, often leading to the speaker being negatively judged. However, no medical education study has looked at the influence of NNEAs in assessment.

METHODS

This is a randomized, single-blinded controlled trial. Four videos of one mock OSCE station were produced. A professional actor played a medical student. Two near identical scripts were prepared. Two videos showed the actor speaking with an Indian accent and two videos showed the actor speaking without the accent in either script. Forty-two OSCE examiners in the United Kingdom (UK) were recruited and randomly assigned to two groups. They watched two videos online, each with either script, each with a different script. One video with a NNEA and one video was without. Checklist item scores were analysed with descriptive statistics and non-parametric independent samples median test. Global scores were analysed with descriptive statistics and Mann-Whitney test.

RESULTS

Thirty-two examiners completed the study. The average scores for the checklist items (41.6 points) did not change when the accent variable was changed. Independent samples median test showed no statistically significant relationship between the accent and the scores (p = 0.787). For the global scores received by the videos with the NNEA, there were one less 'Good' grade and one more 'Fail' grade compared to those without the NNEA. Mann-Whitney test on global score showed lower scores for videos with NNEA (p = 0.661).

CONCLUSIONS

Examiners were not biased either positively or negatively towards NNEAs when providing checklist or global scores. Further study is required to validate the findings of this study. More discussion is warranted to consider how the accent should be considered in current medical education assessment.

REGISTRATION

Trial registration completed trial, ID: ISRCTN17360102, Retrospectively registered on 15/04/2020.

Dynamic trafficking and turnover of JAM-C is essential for endothelial cell migration

Junctional complexes between endothelial cells form a dynamic barrier that hinders passive diffusion of blood constituents into interstitial tissues. Remodelling of junctions is an essential process during leukocyte trafficking, vascular permeability, and angiogenesis. However, for many junctional proteins, the mechanisms of junctional remodelling have yet to be determined. Here, we used receptor mutagenesis, horseradish peroxidase (HRP), and ascorbate peroxidase 2 (APEX-2) proximity labelling, alongside light and electron microscopy (EM), to map the intracellular trafficking routes of junctional adhesion molecule-C (JAM-C). We found that JAM-C cotraffics with receptors associated with changes in permeability such as vascular endothelial cadherin (VE-Cadherin) and neuropilin (NRP)-1 and 2, but not with junctional proteins associated with the transmigration of leukocytes. Dynamic JAM-C trafficking and degradation are necessary for junctional remodelling during cell migration and angiogenesis. By identifying new potential trafficking machinery, we show that a key point of regulation is the ubiquitylation of JAM-C by the E3 ligase Casitas B-lineage lymphoma (CBL), which controls the rate of trafficking versus lysosomal degradation.

Reparative macrophage transplantation for myocardial repair: a refinement of bone marrow mononuclear cell-based therapy

Reparative macrophages play an important role in cardiac repair post-myocardial infarction (MI). Bone marrow mononuclear cells (BM-MNCs) have been investigated as a donor for cell therapy but with limited clinical success. These cells, however, may be utilized as a source for reparative macrophages. This translational study aimed to establish a robust in vitro protocol to produce functional reparative macrophages from BM-MNCs and to establish pre-clinical evidence of the efficacy of reparative macrophage transplantation for the treatment of MI. Mouse BM-MNCs were treated with M-CSF plus IL-4, IL-10, TGF-β1 or combinations of these in vitro. The concomitant administration of M-CSF and IL-4 produced the highest rate and largest number of CD11b+F4/80+CD206+ reparative macrophages. Expression and secretion of tissue repair-related factors including IGF-1, TGF-β1, VEGF and IL1-ra were remarkably enhanced in reparative macrophages compared to BM-MNCs. These cells were transplanted in a mouse MI model, resulting in evident improvement in cardiac function recovery, compared to BM-MNC transplantation. Histological studies showed that reparative macrophage transplantation enhanced myocardial tissue repair including augmented microvascular formation, reduced cardiomyocyte hypertrophy and attenuated interstitial fibrosis. Moreover, survival of reparative macrophages in the heart post-transplantation was increased compared to BM-MNCs. Reparative macrophage transplantation also increased host-derived reparative macrophages in part through TGF-β secretion. In conclusion, concomitant M-CSF + IL-4 treatment effectively produced reparative macrophages from BM-MNCs in vitro. Transplantation of produced reparative macrophage achieved a superior therapeutic efficacy, compared to BM-MNC transplantation, through the enhanced quantity and quality of donor cell engraftment. Further development of this advanced cell-based therapy is warranted.

Liver sampling: a vital window into HBV pathogenesis on the path to functional cure

In order to optimally refine the multiple emerging drug targets for hepatitis B virus (HBV), it is vital to evaluate virological and immunological changes at the site of infection. Traditionally liver biopsy has been the mainstay of HBV disease assessment, but with the emergence of non-invasive markers of liver fibrosis, there has been a move away from tissue sampling. Here we argue that liver biopsy remains an important tool, not only for the clinical assessment of HBV but also for research progress and evaluation of novel agents. The importance of liver sampling has been underscored by recent findings of specialised subsets of tissue-resident immune subsets capable of efficient pathogen surveillance, compartmentalised in the liver and not sampled in the blood. Importantly, the assessment of virological parameters, such as cccDNA quantitation, also requires access to liver tissue. We discuss strategies to maximise information obtained from the site of infection and disease pathology. Fine needle aspirates of the liver may allow longitudinal sampling of the local virus/host landscape. The careful utilisation of liver tissue and aspirates in conjunction with blood will provide critical information in the assessment of new therapeutics for the functional cure of HBV.

Interferon Alpha Induces Sustained Changes in NK Cell Responsiveness to Hepatitis B Viral Load Suppression In Vivo

NK cells are important antiviral effectors, highly enriched in the liver, with the potential to regulate immunopathogenesis in persistent viral infections. Here we examined whether changes in the NK pool are induced when patients with eAg-positive CHB are 'primed' with PegIFNα and importantly, whether these changes are sustained or further modulated long-term after switching to nucleos(t)ides (sequential NUC therapy), an approach currently tested in the clinic. Longitudinal sampling of a prospectively recruited cohort of patients with eAg+CHB showed that the cumulative expansion of CD56bright NK cells driven by 48-weeks of PegIFNα was maintained at higher than baseline levels throughout the subsequent 9 months of sequential NUCs. Unexpectedly, PegIFNα-expanded NK cells showed further augmentation in their expression of the activating NK cell receptors NKp30 and NKp46 during sequential NUCs. The expansion in proliferating, functional NK cells was more pronounced following sequential NUCs than in comparison cohorts of patients treated with de novo NUCs or PegIFNα only. Reduction in circulating HBsAg concentrations, a key goal in the path towards functional cure of CHB, was only achieved in those patients with enhancement of NK cell IFNγ and cytotoxicity but decrease in their expression of the death ligand TRAIL. In summary, we conclude that PegIFNα priming can expand a population of functional NK cells with an altered responsiveness to subsequent antiviral suppression by NUCs. Patients on sequential NUCs with a distinct NK cell profile show a decline in HBsAg, providing mechanistic insights for the further optimisation of treatment strategies to achieve sustained responses in CHB.

The BBaRTS Healthy Teeth Behaviour Change Programme for preventing dental caries in primary school children: study protocol for a cluster randomised controlled trial

BACKGROUND

Oral health behaviours such as establishing twice-daily toothbrushing and sugar control intake need parental self-efficacy (PSE) to prevent the development of childhood dental caries. A previous study has shown that behaviour change techniques (BCTs) delivered via a storybook can improve parental self-efficacy to undertake twice-daily toothbrushing.

OBJECTIVE

to determine whether an intervention (BBaRTS, Bedtime Brush and Read Together to Sleep), designed to increase PSE; delivered through storybooks with embedded BCTs, parenting skills and oral health messages, can improve child oral health compared to (1) an exactly similar intervention containing no behaviour change techniques, and (2) the BBaRTS intervention supplemented with home supply of fluoride toothpaste and supervised toothbrushing on schooldays.

METHODS/DESIGN

A 2-year, three-arm, multicentre, cluster randomised controlled trial.

PARTICIPANTS

children (estimated 2000-2600) aged 5-7 years and their families from 60 UK primary schools.

INTERVENTION

Test group 1: a series of eight children's storybooks developed by a psychologist, public health dentist, science educator, children's author and illustrators, with guidance from the Department for Education (England). The books feature animal characters and contain embedded dental health messages, parenting skills and BCTs to promote good oral health routines focused on controlling sugar intake and toothbrushing, as well as reading at bedtime. Books are given out over 2 years. Test group 2: as Test group 1 plus home supplies of fluoride toothpaste (1000 ppmF), and daily supervised toothbrushing in school on schooldays. Active Control group: series of eight books with exactly the same stories, characters and illustrations, but without BCTs, dental health messages or parenting skills. Annual child dental examinations and parental questionnaires will be undertaken. A sub-set of participants will be invited to join an embedded study of the child's diet and salivary microbiota composition.

PRIMARY OUTCOME MEASURE

dental caries experience in permanent teeth at age 7-8 years.

DISCUSSION

A multi-disciplinary team was established to develop the BBaRTS Children's Healthy Teeth Programme. The books were developed in partnership with the Department for Education (England), informed by a series of focus groups with children, teachers and parents.

TRIAL REGISTRATION

ISRCTN21461006 (date of registration 23 September 2015).