High-salt diet suppresses autoimmune demyelination by regulating the blood-brain barrier permeability.

Sodium chloride, "salt," is an essential component of daily food and vitally contributes to the body's homeostasis. However, excessive salt intake has often been held responsible for numerous health risks associated with the cardiovascular system and kidney. Recent reports linked a high-salt diet (HSD) to the exacerbation of artificially induced central nervous system (CNS) autoimmune pathology through changes in microbiota and enhanced TH17 cell differentiation [M. Kleinewietfeld et al., Nature 496, 518-522 (2013); C. Wu et al., Nature 496, 513-517 (2013); N. Wilck et al., Nature 551, 585-589 (2017)]. However, there is no evidence that dietary salt promotes or worsens a spontaneous autoimmune disease. Here we show that HSD suppresses autoimmune disease development in a mouse model of spontaneous CNS autoimmunity. We found that HSD consumption increased the circulating serum levels of the glucocorticoid hormone corticosterone. Corticosterone enhanced the expression of tight junction molecules on the brain endothelial cells and promoted the tightening of the blood-brain barrier (BBB) thereby controlling the entry of inflammatory T cells into the CNS. Our results demonstrate the multifaceted and potentially beneficial effects of moderately increased salt consumption in CNS autoimmunity.

Oligodendrocytes enforce immune tolerance of the uninfected brain by purging the peripheral repertoire of autoreactive CD8+ T cells.

Myelin-specific CD8(+) T cells are thought to contribute to the pathogenesis of multiple sclerosis. Here we modeled this contribution in mice with CD8(+) T cells recognizing ovalbumin (OVA) expressed in oligodendrocytes (ODCs). Surprisingly, even very high numbers of activated OVA-reactive CD8(+) T cells failed to induce disease and were cleared from the immune system after antigen encounter in the central nervous system (CNS). Peripheral infection with OVA-expressing Listeria (Lm-OVA) enabled CD8(+) T cells to enter the CNS, leading to the deletion of OVA-specific clones after OVA recognition on ODCs. In contrast, intracerebral infection allowed OVA-reactive CD8(+) T cells to cause demyelinating disease. Thus, in response to infection, CD8(+) T cells also patrol the CNS. If the CNS itself is infected, they destroy ODCs upon cognate antigen recognition in pursuit of pathogen eradication. In the sterile brain, however, antigen recognition on ODCs results in their deletion, thereby maintaining tolerance.

A Mouse Model of Post-Stroke Pneumonia Induced by Intra-Tracheal Inoculation with Streptococcus pneumoniae.

BACKGROUND: Stroke-induced immunodeficiency increases the risk of infectious complications, which adversely affects neurological outcome. Among those, pneumonia affects as many as one third of stroke patients and is the main contributor to mortality in the post-acute phase of stroke. Experimental findings on post-stroke susceptibility to spontaneous pneumonia in mice are contradictory. Here, we established a mouse model inducing standardized bacterial pneumonia and characterized the impaired pulmonary cellular and humoral immune responses after experimental stroke. METHODS: Bacterial pneumonia was induced by intra-tracheal inoculation with Streptococcus pneumoniae at different time points after transient middle cerebral artery occlusion (MCAO). Bacterial counts in lungs and blood, histological changes, and cytokine production in the lungs were assessed. Furthermore, we investigated the effect of pneumonia on stroke outcome. RESULTS: Intra-tracheal inoculation resulted in reproducible pneumonia and bacteraemia, and demonstrated post-stroke susceptibility to streptococcal pneumonia developing with a delay of at least 24 h after MCAO. Higher bacterial counts in mice infected 3 days after stroke induction correlated with reduced neutrophil and macrophage infiltration in the lungs and lower levels of pro-inflammatory cytokines in the broncho-alveolar lavage compared to sham-operated animals. Pneumonia increased mortality without affecting brain-infiltrating leukocytes. CONCLUSIONS: In this standardized mouse model of post-stroke pneumonia, we describe attenuated leukocyte infiltration and cytokine production in response to bacterial infection in the lungs that has a profound effect on outcome.

Clinical features of postoperative anastomotic bleeding after gastrectomy and efficacy of endoscopic hemostasis: a case-control study.

BACKGROUND: Postoperative anastomotic bleeding (PAB) is relatively rare; however, it can be lethal if not treated immediately. The aim of our study was to investigate the clinical features of PAB and the efficacy of endoscopic hemostasis (EH) for PAB. METHODS: Between January 2004 and May 2013, 16,591 patients underwent gastrectomy for gastric cancer at Asan Medical Center. Among them, 36 patients who experienced PAB within 2 months after the gastrectomy were enrolled as a case group. Each subject was matched at a ratio of 1:5 with randomly selected patients without bleeding during the same period (n = 180, control group). The clinical outcomes and risk factors for patients with PAB were compared with those of the control group, and the results of EH were evaluated retrospectively. RESULTS: The incidence of PAB was 0.22% (n = 36), and the median duration from gastrectomy to PAB was 34.5 h (interquartile range, 12.3-132.8 h). EH was attempted in 25 patients (69.4%); surgery was performed in 6 patients (16.7%); and conservative management was applied in 5 patients (13.9%). PAB-related death occurred in three patients (8.3%; one in each treatment modality). Among 25 patients with primary EH, 16 were treated successfully (64%) and hemoclip was the most commonly used endoscopic tool (52%). In the multivariate analysis, the type of gastrectomy was found to be a risk factor for PAB (odds ratio 3.448, 95% confidence interval, 1.138-10.448, p = .029). CONCLUSIONS: Although PAB is an infrequent and potentially life-threatening complication, endoscopy can be considered as a useful method to avoid additional surgery in properly selected patients.

DAMP signaling is a key pathway inducing immune modulation after brain injury.

Acute brain lesions induce profound alterations of the peripheral immune response comprising the opposing phenomena of early immune activation and subsequent immunosuppression. The mechanisms underlying this brain-immune signaling are largely unknown. We used animal models for experimental brain ischemia as a paradigm of acute brain lesions and additionally investigated a large cohort of stroke patients. We analyzed release of HMGB1 isoforms by mass spectrometry and investigated its inflammatory potency and signaling pathways by immunological in vivo and in vitro techniques. Features of the complex behavioral sickness behavior syndrome were characterized by homecage behavior analysis. HMGB1 downstream signaling, particularly with RAGE, was studied in various transgenic animal models and by pharmacological blockade. Our results indicate that the cytokine-inducing, fully reduced isoform of HMGB1 was released from the ischemic brain in the hyperacute phase of stroke in mice and patients. Cytokines secreted in the periphery in response to brain injury induced sickness behavior, which could be abrogated by inhibition of the HMGB1-RAGE pathway or direct cytokine neutralization. Subsequently, HMGB1-release induced bone marrow egress and splenic proliferation of bone marrow-derived suppressor cells, inhibiting the adaptive immune responses in vivo and vitro. Furthermore, HMGB1-RAGE signaling resulted in functional exhaustion of mature monocytes and lymphopenia, the hallmarks of immune suppression after extensive ischemia. This study introduces the HMGB1-RAGE-mediated pathway as a key mechanism explaining the complex postischemic brain-immune interactions.

Idarucizumab Improves Outcome in Murine Brain Hemorrhage Related to Dabigatran.

Lack of specific antidotes is a major concern in intracerebral hemorrhage (ICH) related to direct anticoagulants including dabigatran (OAC-ICH). We examined the efficacy of idarucizumab, an antibody fragment binding to dabigatran, in a mouse model of OAC-ICH. Dabigatran etexilate (DE) dose-dependently prolonged diluted thrombin time and tail-vein bleeding time, which were reversed by idarucizumab. Pretreatment with DE increased intracerebral hematoma volume and cerebral hemoglobin content. Idarucizumab in equimolar dose prevented excess hematoma expansion for both DE doses. In more extensive ICH, idarucizumab significantly reduced mortality. Thus, idarucizumab prevents excess intracerebral hematoma formation in mice anticoagulated with dabigatran and reduces mortality.

Amplification of regulatory T cells using a CD28 superagonist reduces brain damage after ischemic stroke in mice.

BACKGROUND AND PURPOSE: Neuroinflammation plays an important role in ischemic brain injury. Regulatory T cells (Treg) are important endogenous immune modulators. We tested the hypothesis that Treg amplification with a CD28 superagonistic monoclonal antibody (CD28SA) reduces brain damage in murine cerebral ischemia. METHODS: Cerebral ischemia was induced by coagulation of the distal middle cerebral artery or by 60 minutes filament occlusion of the proximal middle cerebral artery in C57BL6 mice. 150 µg CD28SA was injected intraperitoneally 3 or 6 hours after ischemia onset. Outcome was determined by infarct volumetry and behavioral testing. Brain-infiltrating leukocyte subpopulations were analyzed by flow cytometry and immunohistochemistry 3 and 7 days after middle cerebral artery occlusion. RESULTS: CD28SA reduced infarct size in both models and attenuated functional deficit 7 days after stroke induction. Mice treated with CD28SA increased numbers of Treg in spleen and brain. Tregs were functionally active and migrated into the brain where they accumulated and proliferated in the peri-infarct area. More than 60% of brain infiltrating Treg produced interleukin-10 in CD28SA compared with 30% in control. CONCLUSIONS: In vivo expansion and amplification of Treg by CD28SA attenuates the inflammatory response and improves outcome after experimental stroke.

Delayed Bleeding Rate According to the Forrest Classification in Second-Look Endoscopy After Endoscopic Submucosal Dissection.

BACKGROUND AND AIM: Forrest classification is a valid tool to predict rebleeding rate in peptic ulcer, not in post-endoscopic resection ulcer. We evaluated the delayed bleeding rate in Forrest classification II and III lesions when they were not treated in second-look endoscopy. METHODS: Between July 2011 and February 2012, 706 lesions in 656 consecutive patients who underwent second-look endoscopy performed on the second day after endoscopic submucosal dissection (ESD) were prospectively investigated. Endoscopic findings were described according to Forrest classification, and late delayed bleeding was defined as bleeding from second-look endoscopy to 1 month. We evaluated the rate of late delayed bleeding in untreated Forrest classification II and III lesions during second-look endoscopy. RESULTS: Among the 706 gastric tumors analyzed, late delayed bleeding after ESD occurred in 29 lesions (4.1%). At second-look endoscopy, Forrest I lesions (immediately treated by endoscopic hemostasis) were found in 63 cases [Ia, 8 lesions (1.1%); Ib, 55 lesions (7.8%)]; there was no further bleeding after discharge. Forrest II and III lesions (not treated in second-look endoscopy) were found in 643 cases [IIa, 62 lesions (8.8%); IIb, 119 lesions (16.9%); IIc, 460 lesions (65.2 %); III, 2 lesions (0.3%)]; and there was no significant difference in the late delayed bleeding rate between these groups [IIa, 2/62 (3.2%); IIb, 5/119 (4.2%); IIc and III, 22/462 (4.8%); P = 1.000]. CONCLUSIONS: The rate of late delayed bleeding of post-ESD ulcers with non-bleeding visible vessels was not significantly different from that of ulcers with non-visible vessels ( http://cris.nih.go.kr , identifier KCT0000268).

Boosting regulatory T cells limits neuroinflammation in permanent cortical stroke.

Inflammatory mechanisms contribute substantially to secondary tissue injury after brain ischemia. Regulatory T cells (Tregs) are key endogenous modulators of postischemic neuroinflammation. We investigated the potential of histone deacetylase inhibition (HDACi) to enhance Treg potency for experimental stroke in mice. HDACi using trichostatin A increased the number of Tregs and boosted their immunosuppressive capacity and interleukin (IL)-10 expression. In vivo treatment reduced infarct volumes and behavioral deficits after cortical brain ischemia, attenuated cerebral proinflammatory cytokine expression, and increased numbers of brain-invading Tregs. A similar effect was obtained using tubastatin, a specific inhibitor of HDAC6 and a key HDAC in Foxp3 regulation. The neuroprotective effect of HDACi depended on the presence of Foxp3(+) Tregs, and in vivo and in vitro studies showed that the anti-inflammatory cytokine IL-10 was their main mediator. In summary, modulation of Treg function by HDACi is a novel and potent target to intervene at the center of neuroinflammation. Furthermore, this novel concept of modulating endogenous immune mechanisms might be translated to a broad spectrum of diseases, including primary neuroinflammatory and neurodegenerative disorders.

Leukocyte invasion of the brain after experimental intracerebral hemorrhage in mice.

BACKGROUND AND PURPOSE: Neuroinflammatory processes contribute to secondary neuronal damage after intracerebral hemorrhage. We aimed to characterize the time course of brain immigration of different leukocyte subsets after striatal injection of either autologous blood or collagenase in mice. METHODS: Intracerebral hemorrhage was induced by injection of either autologous blood (20 µL) or collagenase (0.03 U) in C57Bl/6J mice. Hematoma volumetry was performed on cryosections. Blood volume was measured by hemoglobin spectrophotometry. Leukocytes were isolated from hemorrhagic hemisphere 1, 3, 5, and 14 days after intracerebral hemorrhage, stained for leukocyte markers, and measured by flow cytometry. Heterologous blood injection from CD45.1 mice was used to investigate the origin of brain-invading leukocytes. RESULTS: Collagenase injection induced a larger hematoma volume but a similar blood content compared with blood injection. Cerebral leukocyte infiltration in the hemorrhagic hemisphere was similar in both models. The majority of leukocytes isolated from the brain originated from the circulation. CD4+ T lymphocytes were the predominant brain leukocyte population in both models. However, cerebral granulocyte counts were higher after collagenase compared with blood injection. CONCLUSIONS: Brain infiltration of systemic immune cells is similar in both murine intracerebral hemorrhage models. The pathophysiological impact of invading leukocytes and, in particular, of T cells requires further investigation.

Constitutive Akt1 signals attenuate B-cell receptor signaling and proliferation, but enhance B-cell migration and effector function.

Ligation of the BCR induces a complex signaling network that involves activation of Akt, a family of serine/threonine protein kinases associated with B-cell development, proliferation, and tumor formation. Here, we analyzed the effect of enhanced Akt1 signals on B-cell maturation and function. Unexpectedly, we found that peripheral B cells overexpressing Akt1 were less responsive to BCR stimuli. This correlated with a decrease in Ca(2+) -mobilization and proliferation, in an impaired activation of Erk1/2 and mammalian target of rapamycin (mTOR) kinases and poor mobilization of NFATc1 and NF-κB/p65 factors. In contrast, activation of STAT5 and migration of B cells toward the chemokine SDF1α was found to be enhanced. Akt1 Tg mice showed an altered maturation of peritoneal and splenic B1 B cells and an enhanced production of IgG1 and IgG3 upon immunization with the T-cell independent Ag TNP-Ficoll. Furthermore, mice homo-zygous for Tg Akt1 showed a severe block in the maturation of B-cell precursors in BM and a strong enrichment of plasma cells in spleen. Altogether, our data reveal that enhanced Akt1 signals modify BCR signaling strength and, thereby, B-cell development and effector function.

Preculture of PBMCs at high cell density increases sensitivity of T-cell responses, revealing cytokine release by CD28 superagonist TGN1412.

Human volunteers receiving TGN1412, a humanized CD28-specific monoclonal antibody, experienced a life-threatening cytokine release syndrome during a recent trial. Preclinical tests using human PBMCs had failed to announce the rapid release of TNF, IFN-γ, and other toxic cytokines in response to this CD28 "superagonist" (CD28SA). CD28SA activate T-lymphocytes by ligating CD28 without overt engagement of the TCR. They do, however, depend on "tonic" TCR signals, which they amplify. Here we show that short-term preculture of PBMCs at high, but not at low, cell density results in massive cytokine release during subsequent stimulation with soluble TGN1412. Restoration of reactivity was cell-contact dependent, involved functional maturation of both monocytes and T cells, was sensitive to blockade by HLA-specific mAb, and was associated with TCR polarization and tyrosine phosphorylation. CD4 effector memory T cells were identified as the main source of proinflammatory cytokines. Importantly, responses to other T-cell activating agents, including microbial antigens, were also enhanced if PBMCs were first allowed to interact under tissue-like conditions. We provide a protocol, which strongly improves reactivity of circulating T cells to soluble stimulants, thereby allowing for more reliable preclinical testing of both activating and inhibitory immunomodulatory drugs.

A novel CD4 knockout mouse strain with a spontaneous frameshift mutation in the CD4 locus.

T cells express co-receptors CD4 and CD8, which are involved in the recognition of antigen presented to T cell receptors. The expression of CD4 in thymic hematopoietic cells is crucial for the thymic development and selection of T cells. In this study, we identified a novel CD4 mutant allele that emerged spontaneously in our mouse colony. The frameshift mutation led to a truncated CD4 protein which failed to reach the plasma membrane resulting in impaired development of CD4+ helper T cells. The CRISPR mediated correction of mutant allele restored the membrane CD4 expression. Further, using an adoptive transfer of T cells, we show that this model is an ideal recipient mouse for the study of CD4+ T cells.

Clinical significance of Propionibacterium acnes recovered from blood cultures: analysis of 524 episodes.

Of 522 patients with Propionibacterium acnes bacteremia (PAB), 18 (3.5%) had clinically significant PAB. Of these 18 patients, 10 (55.6%) had hospital-acquired bacteremia and 6 (33.3%) had undergone invasive procedures before development of PAB. One patient with a ventricular septal defect presented with infective endocarditis. After the exclusion of 1 patient whose outcome was not available, the overall mortality rate was 5.9% (1/17).

Duration of viral shedding in patients admitted to hospital with pandemic influenza A/H1N1 2009 infection.

Little is known about the kinetics of viral shedding of pandemic influenza A/H1N1 2009 virus. Influenza RNA, as a surrogate for viral clearance, was therefore measured on days 1, 5, 7, and 10 or more in patients admitted to hospital with pandemic influenza A/H1N1 2009 infection. A total of 72 patients who were admitted to hospital with confirmed pandemic influenza A/H1N1 2009 at a tertiary care hospital, Seoul, South Korea, between 1 September and 11 November 2009 were evaluated. The median duration of viral shedding, as assessed by RT-PCR, was 9 days, as determined by the Kaplan-Meier method. Patients who were positive by RT-PCR at their last assay, but who were discharged before the next RT-PCR test due to symptom improvement, were censored from the analysis. If such patients were included, with the assumption that they had negative viral status at discharge, the median duration of viral shedding was 5 days (interquartile range, 2-8 days). These calculations thus suggest that the true median duration of viral shedding is between 5 and 9 days. Univariate analysis showed that delayed administration of antiviral therapy and comorbidity were associated with slower viral clearance. Multivariate analysis showed that oseltamivir started after the first day of symptoms (OR 2.7, 95% CI 1.2-5.7) was associated independently with slower viral clearance. These findings indicate that, in about 50% of patients admitted to hospital with pandemic influenza A/H1N1 2009, virus can be positive as tested by RT-PCR on the eighth day after developing symptoms of influenza. The present findings also indicate that starting antiviral therapy within 24 hr of the onset of symptoms is associated with more rapid viral clearance.

Antigen-specific blockade of lethal CD8 T-cell mediated autoimmunity in a mouse model of multiple sclerosis.

Increasing evidence implies CD8 T cells in tissue-specific autoimmune diseases including multiple sclerosis. mAbs specific for MHC class I molecules presenting a dominant autoantigenic peptide may allow selective immunotherapy in such settings. We demonstrate the prophylactic and therapeutic efficacy of such a mAb in a transgenic mouse model of lethal demyelinating disease in which a neo-self Ag expressed by oligodendrocytes is targeted by CD8 T cells with transgenic Ag receptors. Mechanistic studies performed in vitro and in vivo indicate that it is the low expression of MHC class I on oligodendrocytes, which makes this form of Ag-specific intervention possible.

Prevalence and clinical features of pneumonia in patients with laboratory-confirmed pandemic influenza A H1N1 2009 infection in South Korea.

During the early stages of the pandemic influenza A H1N1 2009 (pH1N1) outbreak in South Korea, the government recommended antiviral therapy with laboratory confirmation in specialized hospitals. Hence we had a unique opportunity to test all patients suspected to have pH1N1, including those who initially presented with a mild illness, such as those who were not in at-risk groups and who had an uncomplicated illness. We therefore evaluated the proportion and clinical features of pneumonia in patients with laboratory-confirmed pH1N1. Of the 3253 patients who visited Asan Medical Center, Seoul, South Korea, between 24 August and 19 October 2009 for a suspected pH1N1 infection (temperature ≥ 37.5°C and at least 1 of the following symptoms: sore throat, cough, rhinorrhoea and nasal congestion), 553 (17%) were positive for pH1N1 by real-time reverse-transcriptase polymerase chain reaction. Chest radiographs were performed in 96 (17%) of the 553 patients. Of the 553 patients, 30 (5%; 95% confidence interval (CI) 4-8%) had pneumonia, including 26 (86%) with viral pneumonia and 4 (14%) with bacterial pneumonia. So, the proportion of pneumonia in patients with laboratory-confirmed pH1N1 was at least 5%. Multivariate analysis indicated that dyspnoea (odds ratio (OR) 57.8, p < 0.001), wheezing (OR 19.3, p = 0.02), vomiting (OR 18.5, p < 0.001) and diarrhoea (OR 11.0, p = 0.001) were independently associated with pneumonia. Antiviral therapy at >48 h after the onset of symptoms (OR 2.1, p = 0.09) tended to be more common in patients with pneumonia than in those without pneumonia.

Targeted Expression of Myelin Autoantigen in the Periphery Induces Antigen-Specific T and B Cell Tolerance and Ameliorates Autoimmune Disease.

There is a great interest in developing antigen-specific therapeutic approaches for the treatment of autoimmune diseases without compromising normal immune function. The key challenges are to control all antigen-specific lymphocyte populations that contribute to pathogenic inflammatory processes and to provide long-term protection from disease relapses. Here, we show that myelin oligodendrocyte glycoprotein (MOG)-specific tolerance can be established by ectopic expression of MOG in the immune organs. Using transgenic mice expressing MOG-specific CD4, CD8, and B cell receptors, we show that MOG expression in the bone marrow cells results in impaired development of MOG-specific lymphocytes. Ectopic MOG expression has also resulted in long-lasting protection from MOG-induced autoimmunity. This finding raises hope that transplantation of autoantigen-expressing bone marrow cells as a therapeutic strategy for specific autoantigen-driven autoimmune diseases.

The efficacy and safety of sunitinib in korean patients with advanced renal cell carcinoma: high incidence of toxicity leads to frequent dose reduction.

OBJECTIVE: The effects of sunitinib in a broad patient population, especially those of Asian ethnicity, have been rarely investigated. Here, we assessed the efficacy and safety of sunitinib in Korean patients with advanced renal cell carcinoma. METHODS: Between April 2006 and August 2008, 77 Korean patients with advanced renal cell carcinoma were treated with sunitinib. We performed retrospective analysis for efficacy in terms of survival outcomes and response rate. Toxicity profiles were also assessed. RESULTS: A total of 65 patients, including 39 (60%) patients without previous cytotoxic or immunotherapy, were eligible for the analysis. In 53 patients with measurable lesions, the objective response rate was 43% and disease control was achieved in 46 (86%) patients. The median time to treatment failure, time to progression and overall survival were 7.0, 11.8 and 22.8 months, respectively, with a median follow-up of 26.8 months in surviving patients. The most common treatment-related adverse events were fatigue (81%) and stomatitis (60%). The most common Grade 3 or 4 adverse events were hand-foot syndrome (16%), thrombocytopenia (16%) and stomatitis (10%). Dose reduction was required in 46% of patients. CONCLUSIONS: The efficacy was similar to a previous Phase III trial and a safety profile of sunitinib was manageable in Korean patients with advanced renal cell carcinoma, although the incidence of dose reduction and Grade 3 or 4 adverse events were higher than those of western reports. Future studies should investigate the ethnic differences in toxicity profiles of sunitinib.