Activation of JAK/STAT3 restores NK-cell function and improves immune defense after brain ischemia

Stroke-induced immune suppression predisposes the host to infections and can contribute to high morbidity and mortality in stroke patients. Because ischemic stroke has a profound effect on the systemic immune response, which may explain the increased susceptibility of stroke patients to infection, an urgent need persists for a better understanding of mechanisms associated with immune suppression; new and effective treatments for stroke can then be identified. NK cells play a key role in early host defense against pathogens by killing infected cells and/or producing cytokines such as IFN-γ. Because the phenotype and function of peripheral NK cells have been widely investigated in ischemic stroke, nCounter Inflammation Gene Array Analysis was used to build immune-related gene profiles of NK cells to comprehensively analyze the molecular signature of NK cells after ischemic brain injury. We observed distinct gene expression profiles reflecting different splenic NK-cell phenotypes and functional properties across the time course of transient middle cerebral artery occlusion (MCAO). Based on gene expression and pathway-network analysis, lower expression levels of signal transducer and activator of transcription-3 (STAT3) were observed in animals with MCAO compared with sham control animals. Genetic activation of STAT3 through the introduction of STAT3 clustered regularly interspaced short palindromic repeats (CRISPR) plasmid prevented the loss of NK-cell-derived IFN-γ production after MCAO, together with reduced bacterial burden and mortality. Our data suggest that brain ischemia impairs NK-cell-mediated immune defense in the periphery, at least in part through the JAK-STAT3 pathway, which can be readdressed by modulating STAT3 activation status.-Jin, W.-N., Ducruet, A. F., Liu, Q., Shi, S. X.-Y., Waters, M., Zou, M., Sheth, K. N., Gonzales, R., Shi, F.-D. Activation of JAK/STAT3 restores NK-cell function and improves immune defense after brain ischemia.

Low Free Triiodothyronine at Admission Predicts Poststroke Infection

BACKGROUND

Poststroke infection (PSI) is common and is usually associated with a severe prognosis. We investigated the association between PSI and thyroid hormones, which are critical to immune regulation, in patients with acute stroke.

METHODS

We retrospectively enrolled 520 consecutive patients with acute ischemic stroke (326 men; age, 71.9 ± 13.2 years) admitted to our department between September 2014 and June 2016. The impact of serum thyroid hormone levels measured at admission (thyroid-stimulating hormone [TSH], free triiodothyronine [FT3], and free thyroxine [FT4]) on the PSI was evaluated using multivariate logistic regression analysis.

RESULTS

We diagnosed 107 patients (20.6%; pneumonia, 65; urinary tract infection, 19; others, 23) with PSIs. While age (P <.001), body mass index (P = .0012), preadmission modified Rankin scale score (P = .0001), National Institutes of Health Stroke Scale score on admission (P <.001), admission FT3 level (P <.001), atrial fibrillation (P <.001), and ischemic heart disease (P = .0451) were significantly associated with PSI, we found no relationship among TSH levels, FT4 levels, and PSI occurrence. After multivariate adjustment, patients with PSIs were more frequently in the Q1 quartile (≤2.25 pg/mL) than in the Q2 (2.26-2.55 pg/mL; P = .0251), Q3 (2.56-2.89 pg/mL; P = .0007), or Q4 (≥2.90 pg/mL; P = .0010) quartiles of FT3 levels. Moreover, low FT3 levels (<2.29 pg/mL) were independently associated with PSI occurrence (P = .0013).

CONCLUSIONS

Low FT3 levels at admission are independently associated with PSI occurrence.

Early Dynamics of P-selectin and Interleukin 6 Predicts Outcomes in Ischemic Stroke

BACKGROUND

Thromboinflammatory molecules connect the prothrombotic state, endothelial dysfunction, and systemic/local inflammation in the acute phase of ischemic stroke.

METHODS

We prospectively investigated (1) serial changes in the levels of thromboinflammatory biomarkers in 76 patients with acute ischemic stroke (6, 24, and 72 hours after onset); (2) compared with 44 patients with asymptomatic severe (≥70%) carotid stenosis and 66 patients with Parkinson disease; and (3) we applied multiple regression methods, relating biological biomarkers combined with demographic data and comorbidities to poststroke infection, death, and functional outcome, and assessed the ability of the models to predict each outcome.

RESULTS

Interleukin 6 (IL-6) levels and change of IL-6 concentrations by 72 hours correlated with the size of tissue damage indicated by S100B titers. Levels of IL-6 and P-selectin at 72 hours were higher in patients with large-artery versus lacunar stroke. High concentration of IL-6, monocyte chemotactic protein 1, and S100B at 6 hours were associated with poststroke infections; high concentration of IL-6, S100B, and high-sensitivity C-reactive protein (hsCRP) correlated with death. Change of P-selectin from 6 to 72 hours by 1 unit increased the incidence of poststroke infections with an odds ratio of 22.7; each 100 units of IL-6 at baseline increased the odds of death by 9‰, and at 72 hours, the odds of poststroke infections by 4‰. Each unit of baseline hsCRP elevated the odds of death by 7%.

CONCLUSIONS

In regression models, in which biological, demographic, and comorbid factors were combined, those biological biomarkers predicted poor outcome with high accuracy, which were characterized by an increasing concentration by 72 hours. Two particular biomarkers emerged to predict outcomes besides hsCRP: early dynamic changes in the systemic levels of P-selectin and IL-6.