Brain Ischemia Suppresses Immunity in the Periphery and Brain via Different Neurogenic Innervations.

Brain ischemia inhibits immune function systemically, with resulting infectious complications. Whether in stroke different immune alterations occur in brain and periphery and whether analogous mechanisms operate in these compartments remains unclear. Here we show that in patients with ischemic stroke and in mice subjected to middle cerebral artery occlusion, natural killer (NK) cells display remarkably distinct temporal and transcriptome profiles in the brain as compared to the periphery. The activation of catecholaminergic and hypothalamic-pituitary-adrenal axis leads to splenic atrophy and contraction of NK cell numbers in the periphery through a modulated expression of SOCS3, whereas cholinergic innervation-mediated suppression of NK cell responses in the brain involves RUNX3. Importantly, pharmacological or genetic ablation of innervation preserved NK cell function and restrained post-stroke infection. Thus, brain ischemia compromises NK cell-mediated immune defenses through mechanisms that differ in the brain versus the periphery, and targeted inhibition of neurogenic innervation limits post-stroke infection.

Skin Autofluorescence is an Independent Predictor of Post Stroke Infection in Diabetes.

Post stroke infection occurs in 15-20% of acute stroke patients and is associated with a poor longterm outcome. In a prospective study on 113 acute ischemic stroke patients with diabetes mellitus 15.9% suffered nosocomial infection. We found chronic hyperglycemia measured by skin autofluorescence in arbitrary units to be an independent predictor of a nosocomial infection post stroke (OR = 3.24 [CI 95%: 1.13; 9.26], p = 0.029). Skin autofluorescence represents the glycemic memory beyond HbA1c. Potential mechanisms leading from increased skin autofluorescence to vulnerability for infectious complications include more severe strokes due to preexisting vasculopathy and exacerbated post stroke immunosuppression.

The value of serum procalcitonin in the anti-infection therapy of acute stroke patients.

OBJECTIVES: To investigate the value of dynamic monitoring of serum procalcitonin (PCT) in anti-infective therapy of patients with acute stroke. METHODS: This is a case control retrospective study of acute stroke patients conducted from July 2016 to October 2018, in the Department of Neurology, Affiliated Hospital of Hebei University, who who reached within twenty four hours. They, were selected as the study subjects who were divided into infection group and non-infection group according to the inclusion and exclusion criteria. The serum PCT and CRP levels were compared between the two groups at 24 hours, 48 hours and 72 hours. In order to judge the changes of PCT level and the infection of stroke patients, different kinds of antibiotics were used for corresponding treatment. Retrospective analysis of the cases that did not monitor PCT anti infective treatment before July 2016 were compared with the cases that monitored PCT to guide anti infective treatment after July 2016, and compared the efficacy of antibiotics. RESULTS: The serum PCT level of patients in the infection group was significantly higher than that of patients in the noninfection group (P<0.001). For the patients whose PCT<0.5 ng/ml within 72 hour, anti-infective therapy was not administered. However, for those patients whose PCT<0.5 ng/ml and CRP rose significantly, WBC, body temperature and chest CT were closely monitored. For the patients whose PCT increased slightly (0.5 ng/mlPCT>2 ng/ml), mezlocillin/ sulbactam or ceftriaxone/ tazobactam was administered. For patients whose PCT increased significantly (PCT>5 ng/ml), carbapenem antibiotic or a combination of two antibiotics was administered. CONCLUSION: Dynamic detection of serum PCT concentration can make accurate judgment on the severity of bacterial infection in patients with acute stroke and guide the rational application of antibiotics.

Clopidogrel may decrease the risk of post-stroke infection after ischaemic stroke.

BACKGROUND AND PURPOSE: The P2Y12 receptor, a well-known factor in the platelet activation pathway, plays a role in thrombosis as well as systemic inflammation. Clopidogrel, a prototype P2Y12 receptor antagonist, reportedly decreases inflammation and systemic infection. The aim of this study was to evaluate whether clopidogrel use decreases the risk of post-stroke infection following ischaemic stroke. METHODS: A total of 1643 patients with acute ischaemic stroke (within 7 days after onset) were included for analysis between March 2010 and December 2015. Patients were categorized into two groups (clopidogrel users versus clopidogrel non-users), and clinical characteristics and risks of post-stroke infection were compared between the two groups. The inverse probability of treatment weighting using propensity scores for baseline imbalance adjustments was applied. RESULTS: Of the included patients (mean age 67.7 years; men 60.6%), 670 (40.8%) patients were clopidogrel users and 164 (10.0%) patients had post-stroke infection. The proportion of patients with post-stroke infection was significantly lower in clopidogrel users compared to clopidogrel non-users (6.7% vs. 12.2%, P ≤ 0.001). Moreover, clopidogrel users were less likely to be admitted to the intensive care unit (13.3% vs. 35.3%, P = 0.006). A multivariate analysis with inverse probability of treatment weighting revealed that clopidogrel users exhibited a lower risk of post-stroke infection (odds ratio 0.56, 95% confidence interval 0.42-0.75) and intensive care unit admission (odds ratio 0.34, 95% confidence interval 0.22-0.53). CONCLUSIONS: The study suggested that clopidogrel users exhibit a lower risk of infection and develop less severe infections after ischaemic stroke. Further prospective studies are needed.

Statin Treatment in the Acute Phase and the Risk of Post-stroke Pneumonia: A Retrospective Cohort Study.

Background: We aimed to investigate the impact of statin treatment in the acute phase on the risk and severity of post-stroke pneumonia because of the uncertain effects of statins on post-stroke pneumonia. Methods: Consecutive cases of acute ischemic stroke (AIS) between January 2014 and February 2019 were retrospectively analyzed. Additionally, the association of statin treatment in the acute phase with the risk and severity of post-stroke pneumonia was estimated with logistic regression. We registered the present study in the Chinese Clinical Trial Registry (ChiCTR 2000032838). Results: Of the 1,258 enrolled patients, no significant difference was observed in post-stroke pneumonia risk between the two groups (with/without statin treatment in the acute phase) after propensity score matching (35.1 vs. 27.9%, p = 0.155). We did not find statin treatment in the acute phase to significantly increase the risk of post-stroke pneumonia both before and after matched analysis [odds ratio (OR) = 1.51, 95% confidence interval (CI) = 0.85-2.67, p = 0.157; OR = 1.57, 95% CI = 0.77-3.18, p = 0.213, respectively]. In the 271 patients with post-stroke pneumonia, no significant difference was found in its severity between two groups (19.6 vs. 19.4%, p = 0.964). No significant association was found between statin treatment and post-stroke pneumonia severity (OR = 0.95, 95% CI = 0.39-2.31, p = 0.918). Conclusions: There appeared to be no additional benefits of statin treatment in the acute phase for post-stroke pneumonia reduction among AIS patients. Clinical Trial Registration:http://www.chictr.org.cn, identifier: ChiCTR2000032838.

Ischemic stroke and infection: A brief update on mechanisms and potential therapies.

Ischemic stroke triggers a multifaceted inflammatory response in the brain that contributes to secondary brain injury and infarct expansion. In parallel with brain inflammation, ischemic stroke also leads to post-stroke immunosuppression. Stroke-induced leukopenia then predisposes patients to opportunistic infections potentially leading to pneumonia or unrinary tract infections and a worsened stroke outcome. There is evidence that the hypothalamic-pituitaryadrenal axis plays an important role in the etiology of post-stroke immunosuppression, by which prolonged glucocorticoid signalling leads to changes in immune responses. While opportunistic microbes in hospitals have been thought to be the source of infection, recent studies have reported that gut flora may also be a cause of post-stroke infection as a consequence of compromised integrity of the gut barrier after stroke. While antimicrobial drugs would appear to be a rational form of treatment for bacterial infections in stroke patients, the rise in drug-resistant bacteria and possible adverse effects of disrupting beneficial gut flora represent major challenges with these drugs. Considering the prominent role of gut microbiota in modulating immune responses, protecting and restoring the post-stroke gut bacteriome may provide significant benefit in the context of post-stroke infection. With such broad aspects of post-stroke infection occurring together with an extensive inflammatory response in the brain, a carefully considered administration of therapies for ischemic stroke is warranted.

Urinary tract infection after stroke: A narrative review.

BACKGROUND: Urinary tract infection (UTI) is one of the most common infections seen in patients hospitalized for acute stroke, resulting in greater utilization of hospital resources in addition to patient discomfort. Although post-stroke infections (PSIs) are commonly referenced for interference with stroke recovery as well as associations with worse clinical outcome, factors associated specifically with UTI after stroke remain unclear. AIM: To provide a comprehensive narrative synthesis covering literature published with results specific to the topic of UTI in stroke patients. METHODS: Literature review was performed searching the keywords "stroke" and "urinary tract infection" in Pubmed. All manuscripts published in English were appraised for information relevant to UTI in stroke patients. Applicable content was obtained, synthesized, and summarized. RESULTS: Post-stroke UTI is found to be associated with prolongation of hospital length of stay (LOS), discharge to a Care Home, and increased medical care costs. This process possibly reflects the consequences of greater stroke severity and clinical courses requiring urinary catheterization in hospitalized patients. However, UTI does not share an independent association with long-term clinical outcomes including morbidities and mortality. CONCLUSIONS: A narrative review was performed, including the following topics: classifications and epidemiology, pathogenesis, clinical features, and future directions. The heterogeneous nature of reports on UTI in stroke patients remains as a major limitation in literature.

Old Dog New Tricks; Revisiting How Stroke Modulates the Systemic Immune Landscape.

Infections in the post-acute phase of cerebral ischaemia impede optimal recovery by exacerbating morbidity and mortality. Our review aims to reconcile the increased infection susceptibility of patients post-stroke by consolidating our understanding of compartmentalised alterations to systemic immunity. Mounting evidence has catalogued alterations to numerous immune cell populations but an understanding of the mechanisms of long-range communication between the immune system, nervous system and other organs beyond the involvement of autonomic signalling is lacking. By taking our cues from established and emerging concepts of neuro-immune interactions, immune-mediated inter-organ cross-talk, innate immune training and the role of microbiota-derived signals in central nervous system (CNS) function we will explore mechanisms of how cerebral ischaemia could shape systemic immune function. In this context, we will also discuss a key question: how are immune requirements critical for mediating repair of the ischaemic insult balanced by the need for anti-microbial immunity post-stroke, given that they are mediated by mutually exclusive immune networks? Our reformed understanding of the immune landscape post-stroke and novel mechanisms at play could guide targeted therapeutic interventions and initiate a step-change in the clinical management of these infectious complications post-stroke.

Post-stroke infections and preventive antibiotics in stroke: Update of clinical evidence.

This review provides an update of evidence on post-stroke infections and the use of preventive antibiotics in stroke. Infection is a common complication after stroke, affecting between 15% and 30% of the patients. The predictors for post-stroke infection can be divided into three categories: clinical factors, anatomical (stroke related) factors and immunological factors. The relation between the occurrence of a post-stroke infection and functional outcome remained subject of debate, but it seems likely that the occurrence of these infections has a causal relation with poor functional outcome and mortality. In the first meta-analysis on preventive antibiotic therapy, almost a decade ago, its beneficial effect on post-stroke infection rate was clear; however, the effect on functional outcome remained uncertain because included studies were small and heterogeneous. Afterwards, three large phase-3 RCTs were published and a Cochrane meta-analysis was performed. It has now become clear that, despite the finding that overall infections are reduced, preventive antibiotic therapy in the acute phase of stroke does neither improve functional outcome, nor decrease mortality rates. This does not yet mean that further research on preventive antibiotics in stroke is useless: the pathophysiology and etiology of post-stroke infections are unclear and the use of preventive antibiotics in specific subgroups of stroke patients could still be very effective. This is currently being studied. Besides, preventive antibiotic therapy might be cost-effective by increasing quality-adjusted life years. Thirdly, research for the upcoming years might put more emphasis on the effect of stroke on immunological alterations.

Predictors of early infection in cerebral ischemic stroke.

BACKGROUND: Infection is the most common complication of stroke. AIM: To determine the risk factors and predictors of post-stroke infection (PSI), which developed within 7 days from the onset of acute ischemic stroke. SUBJECTS: The study included 60 ischemic stroke patients admitted in the Neurology Department of Zagazig University, Egypt, who were subdivided into: [Non Stroke Associated Infection group (nSAI); 30 patients having stroke without any criteria of infection within 7 days from the onset and Stroke Associated Infection group (SAI); 30 patients having stroke with respiratory tract infection (RTI) or urinary tract infection within 7 days], in addition to 30 healthy sex and age-matching subjects as control. METHODS: All the patients had a detailed history taking, thorough clinical general and neurological examination, laboratory tests (Urine analysis & urine culture, blood sugar, lipid profile and serum tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-10), a chest radiography to assess RTI and brain computed tomography (CT) to exclude the hemorrhagic stroke and to confirm the ischemic stroke. RESULTS: SAI patients were found to be significantly older with higher baseline blood glucose level. Also the number of patients with tube feeding, lower conscious level, more stroke severity and more large size infarcts were significantly higher in SAI patients. There was a significant elevation in the IL-10, a significant decrease in the TNF-α and a significant decrease in the TNF-α/ IL-10 ratio, in the SAI group. The baseline serum level of IL-10 ≥ 14.5 pg/ ml and size of infarct area > 3.5 cm3 were found to be the independent predictors of PSI. CONCLUSION: Patients with older age, tube feeding, lower conscious level, worse baseline stroke severity, large cerebral infarcts in CT scan, and increased IL-10 serum level were more susceptible to infection. The baseline serum level of IL-10 ≥ 14.5 pg/ ml and the size of infarct area > 3.5 cm3 were the independent predictors of PSI.

Acquired Immunoglobulin G deficiency in stroke patients and experimental brain ischemia.

BACKGROUND AND PURPOSE: Acute brain injuries induce a systemic immune depression syndrome (SIDS) that predisposes patients to bacterial infections. While cellular compartments of this syndrome have been well characterized, the contribution of humoral immune mechanisms and particularly immunoglobulins to SIDS has not been investigated so far. METHODS: We determined serum immunoglobulin levels and infectious complications at several time points in 159 ischemic and hemorrhagic stroke patients. Additionally, findings were verified in a transient middle cerebral artery occlusion model. A novel immunoassay was established to analyze the IgG excretion ratio in mice. RESULTS: We identified a transient IgG reduction in patients suffering from substantial ischemic or hemorrhagic brain injuries. The IgG-reduction was associated with subsequent bacterial infections. Similarly, transient hypogammaglobulinemia was detected in a murine stroke model. We then used this animal model to further distinguish the mechanism of the IgG reduction by an IgG transfer paradigm. Excretional loss rather than deficient production of IgG was demonstrated to underlay hypogammaglobulinemia. CONCLUSIONS: This is the first report of transient hypogammaglobulinemia after ischemic and hemorrhagic stroke suggesting involvement in infectious complications. These findings pave the road for further studies investigating post-stroke hypogammaglobulinemia as a druggable target for stroke-induced complications.

Impact of early enteral nutrition on short term prognosis after acute stroke.

We hypothesized that early enteral nutritional support would improve the short term prognosis of acute stroke patients with dysphagia, demonstrated by lower malnutrition rates, lower complication rates, and lower National Institutes of Health Stroke Scale (NIHSS) scores at 90 days post stroke. Nutrition support is an essential element in the care of stroke patients and many studies have investigated the effect of specific nutritional elements on stroke patients. However, few studies have looked at the impact of complete enteral nutrition on Chinese patients with acute stroke. To investigate this, we conducted a randomized controlled trial of 146 patients with acute stroke and dysphagia, among whom 75 were supported with nasogastric nutrition and 71 received family managed nutrition after randomization. Nutritional status, nosocomial infection and mortality rates were recorded on day 21 of hospitalization. Neurological deficits were evaluated by the NIHSS activities of daily living Barthel index (ADLBI) and the modified Rankin scale (mRS) and compared between the two groups. We found that the nasogastric nutrition group had a better nutritional status and reduced nosocomial infection and mortality rates after 21 days compared with patients in the family managed nutrition group. In addition, the nasogastric nutrition group showed a lower score on the NIHSS than the control group. However, the differences in the scores of the ADLBI and the 90 day mRS between the groups were not significant. Taken together, the present study shows that early enteral nutrition support improves the short term prognosis of acute stroke patients with dysphagia.

Prognostic value of blood interleukin-6 in the prediction of functional outcome after stroke: a systematic review and meta-analysis.

We aimed to quantify the association of blood interleukin-6 (IL-6) concentrations with poor outcome after stroke and its added predictive value over clinical information. Meta-analysis of 24 studies confirmed this association with a weighted mean difference of 3.443 (1.592-5.294) pg/mL, despite high heterogeneity and publication bias. Individual participant data including 4112 stroke patients showed standardized IL-6 levels in the 4th quartile were independently associated with poor outcome (OR=2.346 (1.814-3.033), p<0.0001). However, the additional predictive value of IL-6 was moderate (IDI=1.5%, NRI=5.35%). Overall these results indicate an unlikely translation of IL-6 into clinical practice for this purpose.