Multi-targeted loss of the antigen presentation molecule MR1 during HSV-1 and HSV-2 infection

Summary: The major histocompatibility complex (MHC), Class-I-related (MR1) molecule presents microbiome-synthesized metabolites to Mucosal-associated invariant T (MAIT) cells, present at sites of herpes simplex virus (HSV) infection. During HSV type 1 (HSV-1) infection there is a profound and rapid loss of MR1, in part due to expression of unique short 3 protein. Here we show that virion host shutoff RNase protein downregulates MR1 protein, through loss of MR1 transcripts. Furthermore, a third viral protein, infected cell protein 22, also downregulates MR1, but not classical MHC-I molecules. This occurs early in the MR1 trafficking pathway through proteasomal degradation. Finally, HSV-2 infection results in the loss of MR1 transcripts, and intracellular and surface MR1 protein, comparable to that seen during HSV-1 infection. Thus HSV coordinates a multifaceted attack on the MR1 antigen presentation pathway, potentially protecting infected cells from MAIT cell T cell receptor-mediated detection at sites of primary infection and reactivation

Adult obstructive sleep apnoea.

Obstructive sleep apnoea is an increasingly common disorder of repeated upper airway collapse during sleep, leading to oxygen desaturation and disrupted sleep. Features include snoring, witnessed apnoeas, and sleepiness. Pathogenesis varies; predisposing factors include small upper airway lumen, unstable respiratory control, low arousal threshold, small lung volume, and dysfunctional upper airway dilator muscles. Risk factors include obesity, male sex, age, menopause, fluid retention, adenotonsillar hypertrophy, and smoking. Obstructive sleep apnoea causes sleepiness, road traffic accidents, and probably systemic hypertension. It has also been linked to myocardial infarction, congestive heart failure, stroke, and diabetes mellitus though not definitively. Continuous positive airway pressure is the treatment of choice, with adherence of 60-70%. Bi-level positive airway pressure or adaptive servo-ventilation can be used for patients who are intolerant to continuous positive airway pressure. Other treatments include dental devices, surgery, and weight loss

Physiological mechanisms of upper airway hypotonia during REM sleep.

Study objectivesRapid eye movement (REM)-induced hypotonia of the major upper airway dilating muscle (genioglossus) potentially contributes to the worsening of obstructive sleep apnea that occurs during this stage. No prior human single motor unit (SMU) study of genioglossus has examined this possibility to our knowledge. We hypothesized that genioglossus SMUs would reduce their activity during stable breathing in both tonic and phasic REM compared to stage N2 sleep. Further, we hypothesized that hypopneas occurring in REM would be associated with coincident reductions in genioglossus SMU activity.DesignThe activity of genioglossus SMUs was studied in (1) neighboring epochs of stage N2, and tonic and phasic REM; and (2) during hypopneas occurring in REM.SettingSleep laboratory.Participants29 subjects (38 ± 13 y) (17 male).InterventionNatural sleep, including REM sleep and REM hypopneas.Measurement and resultsSubjects slept overnight with genioglossus fine-wire intramuscular electrodes and full polysomnography. Forty-two SMUs firing during one or more of stage N2, tonic REM, or phasic REM were sorted. Twenty inspiratory phasic (IP), 17 inspiratory tonic (IT), and five expiratory tonic (ET) SMUs were characterized. Fewer units were active during phasic REM (23) compared to tonic REM (30) and stage N2 (33). During phasic REM sleep, genioglossus IP and IT SMUs discharged at slower rates and for shorter durations than during stage N2. For example, the SMU peak frequency during phasic REM 5.7 ± 6.6 Hz (mean ± standard deviation) was less than both tonic REM 12.3 ± 9.7 Hz and stage N2 16.1 ± 10.0 Hz (P < 0.001). The peak firing frequencies of IP/IT SMUs decreased from the last breath before to the first breath of a REM hypopnea (11.8 ± 10.9 Hz versus 5.7 ± 9.4 Hz; P = 0.001).ConclusionGenioglossus single motor unit activity is significantly reduced in REM sleep, particularly phasic REM. Single motor unit activity decreases abruptly at the onset of REM hypopneas

Trazodone Effects on Obstructive Sleep Apnea and Non-REM Arousal Threshold.

RationaleA low respiratory arousal threshold is a physiological trait involved in obstructive sleep apnea (OSA) pathogenesis. Trazodone may increase arousal threshold without compromising upper airway muscles, which should improve OSA.ObjectivesWe aimed to examine how trazodone alters OSA severity and arousal threshold. We hypothesized that trazodone would increase the arousal threshold and improve the apnea/hypopnea index (AHI) in selected patients with OSA.MethodsSubjects were studied on two separate nights in a randomized crossover design. Fifteen unselected subjects with OSA (AHI ≥ 10/h) underwent a standard polysomnogram plus an epiglottic catheter to measure the arousal threshold. Subjects were studied after receiving trazodone (100 mg) and placebo, with 1 week between conditions. The arousal threshold was calculated as the nadir pressure before electrocortical arousal from approximately 20 spontaneous respiratory events selected randomly.Measurements and main resultsCompared with placebo, trazodone resulted in a significant reduction in AHI (38.7 vs. 28.5 events/h, P = 0.041), without worsening oxygen saturation or respiratory event duration. Trazodone was not associated with a significant change in the non-REM arousal threshold (-20.3 vs. -19.3 cm H2O, P = 0.51) compared with placebo. In subgroup analysis, responders to trazodone spent less time in N1 sleep (20.1% placebo vs. 9.0% trazodone, P = 0.052) and had an accompanying reduction in arousal index, whereas nonresponders were not observed to have a change in sleep parameters.ConclusionsThese findings suggest that trazodone could be effective therapy for patients with OSA without worsening hypoxemia. Future studies should focus on underlying mechanisms and combination therapies to eliminate OSA. Clinical trial registered with www.clinicaltrials.gov (NCT 01817907)

Trazodone Effects on Obstructive Sleep Apnea and Non-REM Arousal Threshold.

RationaleA low respiratory arousal threshold is a physiological trait involved in obstructive sleep apnea (OSA) pathogenesis. Trazodone may increase arousal threshold without compromising upper airway muscles, which should improve OSA.ObjectivesWe aimed to examine how trazodone alters OSA severity and arousal threshold. We hypothesized that trazodone would increase the arousal threshold and improve the apnea/hypopnea index (AHI) in selected patients with OSA.MethodsSubjects were studied on two separate nights in a randomized crossover design. Fifteen unselected subjects with OSA (AHI ≥ 10/h) underwent a standard polysomnogram plus an epiglottic catheter to measure the arousal threshold. Subjects were studied after receiving trazodone (100 mg) and placebo, with 1 week between conditions. The arousal threshold was calculated as the nadir pressure before electrocortical arousal from approximately 20 spontaneous respiratory events selected randomly.Measurements and main resultsCompared with placebo, trazodone resulted in a significant reduction in AHI (38.7 vs. 28.5 events/h, P = 0.041), without worsening oxygen saturation or respiratory event duration. Trazodone was not associated with a significant change in the non-REM arousal threshold (-20.3 vs. -19.3 cm H2O, P = 0.51) compared with placebo. In subgroup analysis, responders to trazodone spent less time in N1 sleep (20.1% placebo vs. 9.0% trazodone, P = 0.052) and had an accompanying reduction in arousal index, whereas nonresponders were not observed to have a change in sleep parameters.ConclusionsThese findings suggest that trazodone could be effective therapy for patients with OSA without worsening hypoxemia. Future studies should focus on underlying mechanisms and combination therapies to eliminate OSA. Clinical trial registered with www.clinicaltrials.gov (NCT 01817907)

Microrna-155 protects against pulmonary fibrosis by targeting the transcription regulator LXR alpha

Background/Purpose: MicroRNAs (miRs) are a novel class of posttranscriptional regulators. A single miR can have profound effects on cell activation due to its ability to modulate multiple pathways at once. We have previously shown that miR-155 is upregulated in rheumatoid arthritis (RA) synovial macrophages and promotes the development of autoimmunity and joint inflammation. Pre-clinical arthritis may be associated with lung changes e.g. bronchial wall thickening, thus the aim of this study was to investigate the contribution of miR-155 regulated pathways to lung homeostasis.<p></p> Methods: Normal human lung tissue was tested by in situ hybridisation with miR-155 and control probes. To model the fibrotic response, WT and miR-155 / mice were given bleomycin (0.06 unit/mouse) intranasally. Intervention included intraperitoneal injections of the Liver X Receptor (LXR) agonist (GW3965 daily; 40 mg/kg). End-points included bronchial lavage (BAL) cytology, lung tissue histology, evaluation of the expression of inflammatory and fibrotic genes by qPCR and concentrations of soluble mediators in serum and BAL fluid by multiplex assays. The validation of miR-155 binding to LXR, and the LXR response element in collagen gene promoters were performed with reporter assays.<p></p> Results: In situ hybridisation showed an abundant expression of miR-155 in the normal human lung suggesting that this miR may contribute to normal lung homeostasis. miR-155 / mice developed more severe bleomycininduced lung fibrosis compared to WT mice, as seen by increased collagen 1a/3a mRNA expression and protein deposition in the lungs, as well as accumulation of macrophages and lymphocytes in BAL. Gene expression analysis of lung extracts revealed an increase in the M2 pro-fibrotic macrophage markers Arginase 2, IL-13R and Ym1. In addition, the levels of pro-fibrotic cytokines such as VEGF and bFGF were significantly higher in BAL and serum of miR-155 / mice. Primary lung fibroblast lines derived from miR-155 / mice showed higher proliferation rates and motility compared to WT cells in wound healing assays. Computational analysis followed by functional luciferase assays revealed that the transcription activator LXR alpha is a direct target of miR-155 in the lungs. Expression of LXR alpha was significantly upregulated in the lungs of naive miR-155 / mice and was further increased in mice given bleomycin compared to similarly treated WT controls. Injection of the LXR agonist to WT mice increased LXR expression and mirrored the same phenotypic response to bleomycin as the miR-155 deficient mice; shown by increased collagen deposition and M2 macrophage and fibroblast activation. Promoter analysis revealed that LXRs could directly induce collagen production by binding to col1a and col3a promoters.<p>/</p> Conclusion: miR-155 appears important for lung homeostasis, likely by fine tuning levels of LXR thereby protecting from excessive remodelling. Given this and the emerging contribution of miR-155 to development of autoimmunity, this miR may act as a master-switch determining the duration of inflammation and the initiation of remodelling, as well as the balance between the immune and auto-immune responses.<p></p&gt

Mechanisms of the deep, slow-wave, sleep-related increase of upper airway muscle tone in healthy humans.

Upper airway muscle activity is reportedly elevated during slow-wave sleep (SWS) when compared with lighter sleep stages. To uncover the possible mechanisms underlying this elevation, we explored the correlation between different indices of central and reflex inspiratory drive, such as the changes in airway pressure and end-expiratory CO2 and the changes in the genioglossus (GG) and tensor palatini (TP) muscle activity accompanying transitions from the lighter N2 to the deeper N3 stage of non-rapid eye movement (NREM) sleep in healthy young adult men. Forty-six GG and 38 TP continuous electromyographic recordings were obtained from 16 men [age: 20 ± 2.5 (SD) yr; body mass index: 22.5 ± 1.8 kg/m2] during 32 transitions from NREM stages N2 to N3. GG but not TP activity increased following transition into N3 sleep, and the increase was positively correlated with more negative airway pressure, increased end-tidal CO2, increased peak inspiratory flow, and increased minute ventilation. None of these correlations was statistically significant for TP. Complementary GG and TP single motor unit analysis revealed a mild recruitment of GG units and derecruitment of TP units during the N2 to N3 transitions. These findings suggest that, in healthy individuals, the increased GG activity during SWS is driven primarily by reflex stimulation of airway mechanoreceptors and central chemoreceptors.NEW & NOTEWORTHY The characteristic increase in the activity of the upper airway dilator muscle genioglossus during slow-wave sleep (SWS) in young healthy individuals was found to be related to increased stimulation of airway mechanoreceptors and central chemoreceptors. No evidence was found for the presence of a central SWS-specific drive stimulating genioglossus activity in young healthy individuals. However, it remains to be determined whether a central drive exists in obstructive sleep apnea patients