Mediating effect of sleep in the association between social media use and mental health among French adolescents during the COVID-19 sanitary crisis

OBJECTIVE/BACKGROUND

Social media use could have deleterious effects on mental health through short sleep duration and poor sleep quality among adolescents. This study aimed to investigate the mediating role of both sleep duration and sleep quality in the association between social media use and mental health among adolescents.

PATIENTS/METHODS

We used cross-sectional data collected from adolescents in the EXIST pilot project conducted during COVID-19 pandemic. Adolescents self-reported wellbeing (WEMWBS), anxiety and depression (HADS) as mental health outcomes. We used ad-hoc questionnaires to assess social media use during weekdays and weekend days, and sleep duration and quality. Mediation analyses were carried out following Baron and Kenny's method, using adjusted linear regression models.

RESULTS

A total of 340 adolescents (13.5 ± 0.6 years, 45.3 % girls) were included. Greater social media use, poorer sleep quality, and shorter sleep duration were associated with poorer mental health. Greater social media use was associated with poorer sleep quality only during the weekend days. The total effect of social media use during weekend days on anxiety (β = 2.54; 95%CI [-1.59; 6.68]) was significantly conveyed through sleep quality (β = 1.22; 95%CI [0.17; 2.62]; mediated proportion = 48.0 %) and duration (mediated proportion = 46.8 %). Mediated proportions ranged from 12.5 % to 20.6 % for wellbeing and depression. Mediating effects were not evident during weekdays.

CONCLUSIONS

Sleep duration and quality mediated the association between social media use and mental health among adolescents during weekend days but not weekdays. Our findings highlight the importance of promoting healthy social media habits, especially during periods of increased reliance on digital platforms, such as COVID-19 pandemic.

Mice humanized for MHC and hACE2 with high permissiveness to SARS-CoV-2 omicron replication

Human Angiotensin-Converting Enzyme 2 (hACE2) is the major receptor enabling host cell invasion by SARS-CoV-2 via interaction with Spike. The murine ACE2 does not interact efficiently with SARS-CoV-2 Spike and therefore the laboratory mouse strains are not permissive to SARS-CoV-2 replication. Here, we generated new hACE2 transgenic mice, which harbor the hACE2 gene under the human keratin 18 promoter, in "HHD-DR1" background. HHD-DR1 mice are fully devoid of murine Major Histocompatibility Complex (MHC) molecules of class-I and -II and express only MHC molecules from Human Leukocyte Antigen (HLA) HLA 02.01, DRA01.01, DRB1.01.01 alleles, widely expressed in human populations. We selected three transgenic strains, with various hACE2 mRNA expression levels and distinctive profiles of lung and/or brain permissiveness to SARS-CoV-2 replication. These new hACE2 transgenic strains display high permissiveness to the replication of SARS-CoV-2 Omicron sub-variants, while the previously available B6.K18-ACE22Prlmn/JAX mice have been reported to be poorly susceptible to infection with Omicron. As a first application, one of these MHC- and ACE2-humanized strains was successfully used to show the efficacy of a lentiviral-based COVID-19 vaccine.

The gut environment regulates bacterial gene expression which modulates susceptibility to bacteriophage infection

Abundance and diversity of bacteria and their viral predators, bacteriophages (phages), in the digestive tract are associated with human health. Particularly intriguing is the long-term coexistence of these two antagonistic populations. We performed genome-wide RNA sequencing on a human enteroaggregative Escherichia coli isolate to identify genes differentially expressed between in vitro conditions and in murine intestines. We experimentally demonstrated that four of these differentially expressed genes modified the interactions between E. coli and three virulent phages by either increasing or decreasing its susceptibility/resistance pattern and also by interfering with biofilm formation. Therefore, the regulation of bacterial genes expression during the colonization of the digestive tract influences the coexistence of phages and bacteria, highlighting the intricacy of tripartite relationships between phages, bacteria, and the animal host in intestinal homeostasis.

A Listeria monocytogenes Bacteriocin Can Target the Commensal Prevotella copri and Modulate Intestinal Infection

Understanding the role of the microbiota components in either preventing or favoring enteric infections is critical. Here, we report the discovery of a Listeria bacteriocin, Lmo2776, which limits Listeria intestinal colonization. Oral infection of conventional mice with a Δlmo2776 mutant leads to a thinner intestinal mucus layer and higher Listeria loads both in the intestinal content and deeper tissues compared to WT Listeria. This latter difference is microbiota dependent, as it is not observed in germ-free mice. Strikingly, it is phenocopied by pre-colonization of germ-free mice before Listeria infection with Prevotella copri, an abundant gut-commensal bacteria, but not with the other commensals tested. We further show that Lmo2776 targets P. copri and reduces its abundance. Together, these data unveil a role for P.copri in exacerbating intestinal infection, highlighting that pathogens such as Listeria may selectively deplete microbiota bacterial species to avoid excessive inflammation.

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L. monocytogenes secretes a bacteriocin (Lmo2776) homologous to the lactococcin 972

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Lmo2776 controls Listeria intestinal colonization in a microbiota-dependent manner

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Lmo2776 targets the abundant gut commensal Prevotella copri

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Presence of P. copri exacerbates infection

Neutrophil myeloperoxidase diminishes the toxic effects and mortality induced by lipopolysaccharide

Neutrophils have crucial antimicrobial functions but are also thought to contribute to tissue injury upon exposure to bacterial products, such as lipopolysaccharide (LPS). To study the role of neutrophils in LPS-induced endotoxemia, we developed a new mouse model, PMN^DTR mice, in which injection of diphtheria toxin induces selective neutrophil ablation. Using this model, we found, surprisingly, that neutrophils serve to protect the host from LPS-induced lethal inflammation. This protective role was observed in conventional and germ-free animal facilities, indicating that it does not depend on a particular microbiological environment. Blockade or genetic deletion of myeloperoxidase (MPO), a key neutrophil enzyme, significantly increased mortality after LPS challenge, and adoptive transfer experiments confirmed that neutrophil-derived MPO contributes importantly to protection from endotoxemia. Our findings imply that, in addition to their well-established antimicrobial properties, neutrophils can contribute to optimal host protection by limiting the extent of endotoxin-induced inflammation in an MPO-dependent manner.

Anticancer immunotherapy by CTLA-4 blockade relies on the gut microbiota

Antibodies targeting CTLA-4 have been successfully used as cancer immunotherapy. We find that the antitumor effects of CTLA-4 blockade depend on distinct Bacteroides species. In mice and patients, T cell responses specific for B. thetaiotaomicron or B. fragilis were associated with the efficacy of CTLA-4 blockade. Tumors in antibiotic-treated or germ-free mice did not respond to CTLA blockade. This defect was overcome by gavage with B. fragilis, by immunization with B. fragilis polysaccharides, or by adoptive transfer of B. fragilis-specific T cells. Fecal microbial transplantation from humans to mice confirmed that treatment of melanoma patients with antibodies against CTLA-4 favored the outgrowth of B. fragilis with anticancer properties. This study reveals a key role for Bacteroidales in the immunostimulatory effects of CTLA-4 blockade.

The intestinal microbiota modulates the anticancer immune effects of cyclophosphamide

Cyclophosphamide is one of several clinically important cancer drugs whose therapeutic efficacy is due in part to their ability to stimulate antitumor immune responses. Studying mouse models, we demonstrate that cyclophosphamide alters the composition of microbiota in the small intestine and induces the translocation of selected species of Gram-positive bacteria into secondary lymphoid organs. There, these bacteria stimulate the generation of a specific subset of "pathogenic" T helper 17 (pT(H)17) cells and memory T(H)1 immune responses. Tumor-bearing mice that were germ-free or that had been treated with antibiotics to kill Gram-positive bacteria showed a reduction in pT(H)17 responses, and their tumors were resistant to cyclophosphamide. Adoptive transfer of pT(H)17 cells partially restored the antitumor efficacy of cyclophosphamide. These results suggest that the gut microbiota help shape the anticancer immune response.

HLA-A*01:03, HLA-A*24:02, HLA-B*08:01, HLA-B*27:05, HLA-B*35:01, HLA-B*44:02, and HLA-C*07:01 monochain transgenic/H-2 class I null mice: novel versatile preclinical models of human T cell responses

We have generated a panel of transgenic mice expressing HLA-A*01:03, -A*24:02, -B*08:01, -B*27:05, -B*35:01, -B*44:02, or -C*07:01 as chimeric monochain molecules (i.e., appropriate HLA α1α2 H chain domains fused with a mouse α3 domain and covalently linked to human β2-microglobulin). Whereas surface expression of several transgenes was markedly reduced in recipient mice that coexpressed endogenous H-2 class I molecules, substantial surface expression of all human transgenes was observed in mice lacking H-2 class I molecules. In these HLA monochain transgenic/H-2 class I null mice, we observed a quantitative and qualitative restoration of the peripheral CD8(+) T cell repertoire, which exhibited a TCR diversity comparable with C57BL/6 WT mice. Potent epitope-specific, HLA-restricted, IFN-γ-producing CD8(+) T cell responses were generated against known reference T cell epitopes after either peptide or DNA immunization. HLA-wise, these new transgenic strains encompass a large proportion of individuals from all major human races and ethnicities. In combination with the previously created HLA-A*02:01 and -B*07:02 transgenic mice, the novel HLA transgenic mice described in this report should be a versatile preclinical animal model that will speed up the identification and optimization of HLA-restricted CD8(+) T cell epitopes of potential interest in various autoimmune human diseases and in preclinical evaluation of T cell-based vaccines.

RORγt+ innate lymphoid cells regulate intestinal homeostasis by integrating negative signals from the symbiotic microbiota

Lymphoid cells that express the nuclear hormone receptor RORγt are involved in containment of the large intestinal microbiota and defense against pathogens through the production of interleukin 17 (IL-17) and IL-22. They include adaptive IL-17-producing helper T cells (T(H)17 cells), as well as innate lymphoid cells (ILCs) such as lymphoid tissue-inducer (LTi) cells and IL-22-producing NKp46+ cells. Here we show that in contrast to T(H)17 cells, both types of RORγt+ ILCs constitutively produced most of the intestinal IL-22 and that the symbiotic microbiota repressed this function through epithelial expression of IL-25. This function was greater in the absence of adaptive immunity and was fully restored and required after epithelial damage, which demonstrates a central role for RORγt+ ILCs in intestinal homeostasis. Our data identify a finely tuned equilibrium among intestinal symbionts, adaptive immunity and RORγt+ ILCs.

Restricted microbiota and absence of cognate TCR antigen leads to an unbalanced generation of Th17 cells

Retinoic acid-related orphan receptor (ROR)γt(+) TCRαβ(+) cells expressing IL-17, termed Th17 cells, are most abundant in the intestinal lamina propria. Symbiotic microbiota are required for the generation of Th17 cells, but the requirement for microbiota-derived Ag is not documented. In this study, we show that normal numbers of Th17 cells develop in the intestine of mice that express a single TCR in the absence of cognate Ag, whereas the microbiota remains essential for their development. However, such mice, or mice monocolonized with the Th17-inducing segmented filamentous bacteria, fail to induce normal numbers of Foxp3(+) RORγt(+) T cells, the regulatory counterpart of IL-17(+)RORγt(+) T cells. These results demonstrate that a complex microbiota and cognate Ag are required to generate a properly regulated set of RORγt(+) T cells and Th17 cells.

Lymphoid tissue genesis induced by commensals through NOD1 regulates intestinal homeostasis

Intestinal homeostasis is critical for efficient energy extraction from food and protection from pathogens. Its disruption can lead to an array of severe illnesses with major impacts on public health, such as inflammatory bowel disease characterized by self-destructive intestinal immunity. However, the mechanisms regulating the equilibrium between the large bacterial flora and the immune system remain unclear. Intestinal lymphoid tissues generate flora-reactive IgA-producing B cells, and include Peyer's patches and mesenteric lymph nodes, as well as numerous isolated lymphoid follicles (ILFs). Here we show that peptidoglycan from Gram-negative bacteria is necessary and sufficient to induce the genesis of ILFs in mice through recognition by the NOD1 (nucleotide-binding oligomerization domain containing 1) innate receptor in epithelial cells, and beta-defensin 3- and CCL20-mediated signalling through the chemokine receptor CCR6. Maturation of ILFs into large B-cell clusters requires subsequent detection of bacteria by toll-like receptors. In the absence of ILFs, the composition of the intestinal bacterial community is profoundly altered. Our results demonstrate that intestinal bacterial commensals and the immune system communicate through an innate detection system to generate adaptive lymphoid tissues and maintain intestinal homeostasis.

Prolonged exposure of naïve CD8+ T cells to interleukin-7 or interleukin-15 stimulates proliferation without differentiation or loss of telomere length

Interleukin (IL)-7 and IL-15 are cytokines implicated in homeostatic control of the peripheral CD8 T-cell pool. We compared the effects of IL-7 and IL-15 on survival and proliferation of purified human CD8+ T-cell subsets. Low concentrations of either cytokine reduced the spontaneous apoptosis of all subsets, and enhancement of survival corresponded to the extent of Bcl-2 up-regulation. Surprisingly, although minimal proliferation of naïve CD8+ T cells was observed during the first week of culture with cytokines, a marked expansion of these cells occurred at later time points, particularly in response to IL-15. This occurred largely without phenotypic change or acquisition of effector function, indicating a dissociation of differentiation from proliferation. Notably, progression of naïve CD8+ T cells through several cell divisions resulted in up-regulation of telomerase and the maintenance of telomere length. These data show that IL-7 and IL-15 induce cell proliferation and rescue from apoptosis in a concentration, time and subset-dependent manner, and have implications for the homeostatic expansion of the naïve CD8+ T-cell pool.

[Therapeutic drug monitoring of mycophenolate mofetil, sirolimus and cyclosporine at C2]

The evolutions in treatments and clinical practices in organ transplantations led to modifications in the therapeutic drug monitoring (TDM) of immunosuppressive drugs. A focus is made regarding the C2 sampling of cyclosporin, as well as the TDM of mycophenolate mofetil and sirolimus. A review of literature about the evolution of drug monitoring, technical methods and sampling strategies is described. Arguments in favour of TDM are thus a decrease in the frequency of both graft rejection and adverse drug reactions, however, new strategies or new targets are needed in new associations or indications.

FLICE-inhibitory protein is a key regulator of germinal center B cell apoptosis

Affinity maturation of the B cell response to antigen (Ag) takes place in the germinal centers (GCs) of secondary follicles. Two sequential molecular mechanisms underpin this process. First, the B cell repertoire is diversified through hypermutation of the immunoglobulin (Ig) variable region genes. Second, mutant B cell clones with improved affinity for Ag are positively selected by Ag and CD40 ligand (L). This selection step is contingent upon "priming" of GC B cells for apoptosis. The molecular means by which B cell apoptosis is initiated and controlled in the GC remains unclear. Here, we show that GC B cell apoptosis is preceded by the rapid activation of caspase-8 at the level of CD95 death-inducing signaling complex (DISC). We found that GC B cells ex vivo display a preformed inactive DISC containing Fas-associated death domain-containing protein (FADD), procaspase-8, and the long isoform of cellular FADD-like IL-1beta-converting enzyme-inhibitory protein (c-FLIP(L)) but not the CD95L. In culture, c-FLIP(L) is rapidly lost from the CD95 DISC unless GC B cells are exposed to the survival signal provided by CD40L. Our results suggest that (a) the death receptor signaling pathway is involved in the affinity maturation of antibodies, and (b) c-FLIP(L) plays an active role in positive selection of B cells in the GC.

Intraindividual variability of paracetamol absorption kinetics after a semi-solid meal in healthy volunteers

OBJECTIVE

The absorption kinetics of paracetamol is dependent on gastric emptying and its measurement was proposed as a non-invasive method to estimate gastric emptying rate. The objective of this study was to evaluate the intraindividual variability of paracetamol absorption kinetics after a semi-solid meal.

METHODS

The pharmacokinetics of paracetamol was studied on two occasions in 15 healthy volunteers without Helicobacter pylori antibodies. A 1-g dose of paracetamol was given as a solution together with a standardised semi-solid meal and the subjects stayed in the supine position.

RESULTS

For most of the subjects, the time course of paracetamol concentrations was similar on the two occasions. The intraindividual variability was low, with coefficients of variation of 38.3%, 8.0% and 3.8% for time to maximum plasma concentration, maximum concentration and area under the plasma concentration - time curve until 6 h, respectively.

CONCLUSION

The assessment of paracetamol absorption kinetics is reproducible when the drug is given together with a semi-solid meal in Helicobacter pylori-negative healthy subjects.

Antiphospholipid antibody production during Mediterranean spotted fever

Antiphospholipid antibodies (aPLA) were discovered during the course of Mediterranean spotted fever (MSF) caused by Rickettsia conorii and characterized by endothelial cell (EC) damage resulting from this organism's tropism for EC. In two MSF patients, two types of aPLA were identified: antiphosphatidylethanolamine antibodies detected by immunological methods and lupus anticoagulant detected by clotting assays. The persistence of both aPLA for several months after the acute phase and clinical recovery might correspond to a durable immunological response to membrane damage of EC caused by R. conorii. Their possible role in the pathophysiology of microthrombi formation observed during MSF remains to be elucidated in a study on a larger number of patients.

Separation of fifteen non-steroidal anti-inflammatory drugs using micellar electrokinetic capillary chromatography

Micellar electrokinetic capillary chromatography with sodium dodecylsulfate as anionic surfactant was used to separate simultaneously fifteen non-steroidal anti-inflammatory drugs. UV detection was performed at 254 nm. The electroosmotic flow was carefully adjusted for optimal separation. Resolution of the drugs was obtained using a buffer containing 40 mmol l-1 NaH2PO4, 0.104 mol l-1 sodium dodecylsulfate and 3% (v/v) methanol, adjusted to pH 8 with sodium hydroxide. Lack of interference was checked with a number of drugs and metabolites. Between-day coefficients of variation ranged between 2 to 10%.

Guidelines for estimating the real cost of an objective structured clinical examination

A major impediment to the use of the objective structured clinical examination (OSCE) is that it is a labor-intensive and costly form of assessment. The cost of an OSCE is highly dependent on the particular model used, the extent to which hidden costs are reported, and the purpose of the examination. The authors detail hypothetical costs of running a four-hour OSCE for 120 medical students at one medical school. Costs are reported for four phases of this process: development, production, administration, and post-examination reporting and analysis. Costs are reported at two ends of the spectrum: the high end, where it is assumed that little is paid for by the institution and that faculty receive honoraria for work put into the examination; and the low end, where it is assumed that the sponsoring institution defrays basic costs and that faculty do not receive honoraria for their participation. The total costs reported for a first-time examination were $104,400 and $59,460 (Canadian dollars) at the high and low ends, respectively. These translate to per-student costs of $870 and $496. The cost of running an OSCE is high. However, the OSCE is uniquely capable of assessing many fundamental clinical skills that are presently not being assessed in a rigorous way in most medical schools.

Cytotoxic effect of serum on fibroblasts in one case of normolipidemic plane xanthoma and myeloma IgG lambda

Serum was examined for a cytotoxic effect on cultured human fibroblasts, using 8 normal controls and 4 patients. Three of the patients had secondary lipidoses associated with monoclonal gammapathies of IgA kappa, IgG kappa and IgG lambda types. The fourth had systemic lupus erythematosus (SLE) with hyperlipidemia. Only serum containing the monoclonal IgG lambda was found to be cytotoxic. This circulating IgG lambda was strongly bound to HDL and behaved like an antilipoprotein antibody. The circulating immune complexes may be the serum factor responsible for the cytotoxicity and the cutaneous plane xanthomas, thus giving another example of 'antibody-dependent' cellular cytotoxicity previously described for endothelial cells in other diseases.

Hexachlorophene and the central nervous system. Toxic effects in mice and baboons

A study on hexachlorophene encephalopathy in mice and baboons is reported. By light microscopy, a severe spongiform lesion of the central nervous system (CNS) was localized in the white matter, without myelin breakdown or cellular reaction. By electron microscopy, the myelin alteration was characterized by wide intralamellar spaces or "splitting" developed in the intraperiod line of compact sheaths. The acute changes described were induced by administration of the drug by the digestive or cutaneous routes at various dosage levels in an aqueous solution or in talcum powder. The toxic effects depended on the age of the animals, the survival times and the concentrations of hexachlorophene, i.e., 6%, 3%, and 0.5%. The findings are compared with previous reports on the neurotoxicity of hexachlorophene and other chemicals in human and experimental animals. Hexachlorophene cannot be recommended for use in young infants because of its neurotoxicity in very low doses as demonstrated in the present report.

[Hypertriglyceridemia and tumors. Production of stable cultures of Green's lymphoma]

In Golden Hamster the Greene malignant lymphoma is a subcutaneous and homotransplantable tumor whose development is associated with a constant hypertriglyceridemia and a large-decreased plasma post-heparin lipase activity. The tumoral cell line is well maintained on a human fibroblast monolayer culture and is demonstrated to secrete two IgG immunoglobulins.

[Olfactory esthesioneurocytoma: ultrastructural study of a case (author's transl)]

One case of malignant tumour of the left nasal cavity is reported in a woman 56 year old, affected by the disease 24 years. Numerous recurrences appeared and various histological diagnoses were performed. At the last surgery, the tumour invaded the ethmoid and was a typical olfactory esthesioneurocytoma. By electron microscopy, mature ganglion cells with dense cored vesicles (neurosecretory granules) were densely packed. Neuritic processes with microtubules were rarely normal in size and their content was most often abnormal; furthermore dystrophic axons were noted in great number.

[Hyperlipemia and tumors : post heparin lipase activity of the hamster bearing a malignant lymphoma]

Subcutaneous transplantation of Greene lymphoma in golden hamsters is followed by a type IV-V hyperlipoproteinemia with major hupertriglyceridemia and impairment of labelled triglyceride clearance. Postheparin lipase activity studies show that this hyperlipidemia is correlated with the decrease in the lipolytic enzyme, which plays an important role in triglyceride clearance. The role of the tumor is considered.