The influence of alcohol on genioglossus single motor units in men and women during wakefulness.

NEW FINDINGS: What is the central question of this study? How does alcohol intake, which worsens obstructive sleep apnoea, alter motor control of the genioglossus muscle, an upper airway dilator, in healthy awake human volunteers, and does alcohol alter genioglossus muscle afterdischarge? What is the main finding and its importance? Alcohol consumption had a very minor effect on the activity of the genioglossus in healthy young individuals studied during wakefulness and did not alter afterdischarge, leaving open the possibility that alcohol worsens obstructive sleep apnoea via other mechanisms. ABSTRACT: Alcohol worsens obstructive sleep apnoea (OSA). This effect is thought to be due to alcohol's depressant effect on upper airway dilator muscles such as the genioglossus, but how alcohol reduces genioglossal activity is unknown. The aim of this study was to investigate the effect of alcohol consumption on genioglossus muscle single motor units (MUs). Sixteen healthy individuals were studied on two occasions (alcohol: breath alcohol concentration ∼0.07% and placebo). They were instrumented with a nasal mask, four intramuscular genioglossal EMG electrodes, and an ear oximeter. They were exposed to 8-12 hypoxia trials (45-60 s of 10% O2 followed by one breath of 100% O2 ) while awake. MUs were sorted according to their firing patterns and quantified during baseline, hypoxia and recovery. For the alcohol and placebo conditions, global muscle activity (mean ± SD peak inspiratory EMG = 119.3 ± 44.1 and 126.5 ± 51.9 µV, respectively, P = 0.53) and total number of MUs recorded at baseline (68 and 67, respectively) were similar. Likewise, the peak discharge frequency did not differ between conditions (21.2 ± 4.28 vs. 22.4 ± 4.08 Hz, P = 0.09). There was no difference between conditions in the number (101 vs. 88, respectively) and distribution of MU classes during hypoxia, and afterdischarge duration was also similar. In this study, alcohol had a very minor effect on genioglossal activity and afterdischarge in these otherwise healthy young individuals studied while awake. If similar effects are observed during sleep, it would suggest that the worsening of OSA following alcohol may be related to increased upper airway resistance/nasal congestion or arousal threshold changes.

A quantitative brain map of experimental cerebral malaria pathology.

The murine model of experimental cerebral malaria (ECM) has been utilised extensively in recent years to study the pathogenesis of human cerebral malaria (HCM). However, it has been proposed that the aetiologies of ECM and HCM are distinct, and, consequently, no useful mechanistic insights into the pathogenesis of HCM can be obtained from studying the ECM model. Therefore, in order to determine the similarities and differences in the pathology of ECM and HCM, we have performed the first spatial and quantitative histopathological assessment of the ECM syndrome. We demonstrate that the accumulation of parasitised red blood cells (pRBCs) in brain capillaries is a specific feature of ECM that is not observed during mild murine malaria infections. Critically, we show that individual pRBCs appear to occlude murine brain capillaries during ECM. As pRBC-mediated congestion of brain microvessels is a hallmark of HCM, this suggests that the impact of parasite accumulation on cerebral blood flow may ultimately be similar in mice and humans during ECM and HCM, respectively. Additionally, we demonstrate that cerebrovascular CD8+ T-cells appear to co-localise with accumulated pRBCs, an event that corresponds with development of widespread vascular leakage. As in HCM, we show that vascular leakage is not dependent on extensive vascular destruction. Instead, we show that vascular leakage is associated with alterations in transcellular and paracellular transport mechanisms. Finally, as in HCM, we observed axonal injury and demyelination in ECM adjacent to diverse vasculopathies. Collectively, our data therefore shows that, despite very different presentation, and apparently distinct mechanisms, of parasite accumulation, there appear to be a number of comparable features of cerebral pathology in mice and in humans during ECM and HCM, respectively. Thus, when used appropriately, the ECM model may be useful for studying specific pathological features of HCM.

IFN-γ-producing CD4+ T cells promote experimental cerebral malaria by modulating CD8+ T cell accumulation within the brain.

It is well established that IFN-γ is required for the development of experimental cerebral malaria (ECM) during Plasmodium berghei ANKA infection of C57BL/6 mice. However, the temporal and tissue-specific cellular sources of IFN-γ during P. berghei ANKA infection have not been investigated, and it is not known whether IFN-γ production by a single cell type in isolation can induce cerebral pathology. In this study, using IFN-γ reporter mice, we show that NK cells dominate the IFN-γ response during the early stages of infection in the brain, but not in the spleen, before being replaced by CD4(+) and CD8(+) T cells. Importantly, we demonstrate that IFN-γ-producing CD4(+) T cells, but not innate or CD8(+) T cells, can promote the development of ECM in normally resistant IFN-γ(-/-) mice infected with P. berghei ANKA. Adoptively transferred wild-type CD4(+) T cells accumulate within the spleen, lung, and brain of IFN-γ(-/-) mice and induce ECM through active IFN-γ secretion, which increases the accumulation of endogenous IFN-γ(-/-) CD8(+) T cells within the brain. Depletion of endogenous IFN-γ(-/-) CD8(+) T cells abrogates the ability of wild-type CD4(+) T cells to promote ECM. Finally, we show that IFN-γ production, specifically by CD4(+) T cells, is sufficient to induce expression of CXCL9 and CXCL10 within the brain, providing a mechanistic basis for the enhanced CD8(+) T cell accumulation. To our knowledge, these observations demonstrate, for the first time, the importance of and pathways by which IFN-γ-producing CD4(+) T cells promote the development of ECM during P. berghei ANKA infection.

Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.

IFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells.

Clinical experience with pemigatinib for previously treated metastatic cholangiocarcinoma: practical considerations from clinical cases.

The management of advanced cholangiocarcinoma (CCA) is challenging. In patients with advanced CCA, gemcitabine/cisplatin combination is the standard frontline chemotherapy, with 5-fluorouracil-based regimens preserved for subsequent lines; however, the expected survival is poor. Pemigatinib was approved for locally advanced or metastatic CCA with FGFR2 fusions or rearrangement. Pemigatinib has a manageable safety profile and achieves a durable response. Nearly 50 patients with CCA have been treated with pemigatinib in the United Kingdom. However, clinical experience with pemigatinib is lacking. We present our experience with three clinical cases to illustrate the position of pemigatinib in the management of CCA and related toxicities.

Essential role for IL-27 receptor signaling in prevention of Th1-mediated immunopathology during malaria infection.

Successful resolution of malaria infection requires induction of proinflammatory immune responses that facilitate parasite clearance; however, failure to regulate this inflammation leads to immune-mediated pathology. The pathways that maintain this immunological balance during malaria infection remain poorly defined. In this study, we demonstrate that IL-27R-deficient (WSX-1(-/-)) mice are highly susceptible to Plasmodium berghei NK65 infection, developing exacerbated Th1-mediated immune responses, which, despite highly efficient parasite clearance, lead directly to severe liver pathology. Depletion of CD4(+) T cells---but not CD8(+) T cells---prevented liver pathology in infected WSX-1(-/-) mice. Although WSX-1 signaling was required for optimal IL-10 production by CD4(+) T cells, administration of rIL-10 failed to ameliorate liver damage in WSX-1(-/-) mice, indicating that additional, IL-10-independent, protective pathways are modulated by IL-27R signaling during malaria infection. These data are the first to demonstrate the essential role of IL-27R signaling in regulating effector T cell function during malaria infection and reveal a novel pathway that might be amenable to manipulation by drugs or vaccines.

After-discharge in the upper airway muscle genioglossus following brief hypoxia.

STUDY OBJECTIVES: Genioglossus (GG) after-discharge is thought to protect against pharyngeal collapse by minimizing periods of low upper airway muscle activity. How GG after-discharge occurs and which single motor units (SMUs) are responsible for the phenomenon are unknown. The aim of this study was to investigate genioglossal after-discharge. METHODS: During wakefulness, after-discharge was elicited 8-12 times in healthy individuals with brief isocapnic hypoxia (45-60 s of 10% O2 in N2) terminated by a single breath of 100% O2. GG SMUs were designated as firing solely, or at increased rate, during inspiration (Inspiratory phasic [IP] and inspiratory tonic [IT], respectively); solely, or at increased rate, during expiration (Expiratory phasic [EP] or expiratory tonic [ET], respectively) or firing constantly without respiratory modulation (Tonic). SMUs were quantified at baseline, the end of hypoxia, the hyperoxic breath, and the following eight normoxic breaths. RESULTS: A total of 210 SMUs were identified in 17 participants. GG muscle activity was elevated above baseline for seven breaths after hyperoxia (p < 0.001), indicating a strong after-discharge effect. After-discharge occurred due to persistent firing of IP and IT units that were recruited during hypoxia, with minimal changes in ET, EP, or Tonic SMUs. The firing frequency of units that were already active changed minimally during hypoxia or the afterdischarge period (p > 0.05). CONCLUSION: That genioglossal after-discharge is almost entirely due to persistent firing of previously silent inspiratory SMUs provides insight into the mechanisms responsible for the phenomenon and supports the hypothesis that the inspiratory and expiratory/tonic motor units within the muscle have idiosyncratic functions.

Comparative analysis of the excretory-secretory proteome of the muscle larva of Trichinella pseudospiralis and Trichinella spiralis.

The nematodes Trichinella spiralis and Trichinella pseudospiralis are both intracellular parasites of skeletal muscle cells and induce profound alterations in the host cell resulting in a re-alignment of muscle-specific gene expression. While T. spiralis induces the production of a collagen capsule surrounding the host-parasite complex, T. pseudospiralis exists in a non-encapsulated form and is also characterised by suppression of the host inflammatory response in the muscle. These observed differences between the two species are thought to be due to variation in the proteins excreted or secreted (ES proteins) by the muscle larva. In this study, we use a global proteomics approach to compare the ES protein profiles from both species and to identify individual T. pseudospiralis proteins that complement earlier studies with T. spiralis. Following two-dimensional gel electrophoresis, tandem mass spectrometry was used to identify the peptide spots. In many cases identification was aided by the determination of partial peptide sequence from selected mass ions. The T. pseudospiralis spots identified included the major secreted glycoproteins and the secreted 5'-nucleotidase. Furthermore, two major groups of T. spiralis-specific proteins and several T. pseudospiralis-specific proteins were identified. Our results demonstrate the value of proteomics as a tool for the identification of ES proteins that are differentially expressed between Trichinella species and as an aid to identifying key parasite proteins that are involved in the host-parasite interaction. The value of this approach will be further enhanced by data arising out the current T. spiralis genome sequencing project.