Xiao-Yi Xiong

Toll-Like Receptor 4 Antagonist Attenuates Intracerebral Hemorrhage–Induced Brain Injury

Background and Purpose— Accumulating evidence indicates that inflammatory responses cause secondary injury after intracerebral hemorrhage (ICH). We recently demonstrated the involvement of toll-like receptor 4 (TLR4) signaling in these processes. The purpose of the current study was to investigate the protective effect and mechanism of TAK-242 (Ethyl (6R)-6-[N-(2-chloro-4-fluorophenyl) sulfamoyl] cyclohex-1-ene-1 -carboxylate, Takeda), a TLR4 antagonist, in an ICH mouse model. Methods— TAK-242 was intraperitoneally injected 6 hours after ICH once daily for 5 successive days. We assessed neurological deficit scores; changes in brain water content; and levels of inflammatory factors, DNA damage, and neuronal degeneration in perihematomal region 1, 3, and 5 days after ICH. Peripheral inflammatory cell infiltration was determined using flow cytometry; and the expression of TLR4 downstream signaling molecules was assessed by Western blot. Results— TAK-242 significantly reduced brain water content, neurological deficit scores, and levels of inflammatory factors. The levels of DNA damage and neuronal degeneration were also significantly decreased, as was peripheral inflammatory cell infiltration. The expression of TLR4 downstream signaling molecules, including myeloid differentiation primary response gene 88, toll/IR-1(TIR)-domain-containing adaptor protein inducing interferon-beta I&kgr;B&agr;, nuclear factor-&kgr;Bp65, and phosphorylated nuclear factor-&kgr;Bp65, was significantly downregulated. Conclusions— The results suggest that TLR4 antagonist reduced inflammatory injury and neurological deficits in a mouse model of ICH. The mechanism may involve decreased expression of signaling molecules downstream of TLR4.

Toll-like receptor 2/4 heterodimer mediates inflammatory injury in intracerebral hemorrhage

Inflammatory injury plays a critical role in intracerebral hemorrhage (ICH)‐induced secondary brain injury. However, the upstream events that initiate inflammatory responses following ICH remain elusive. Our previous studies suggested that Toll‐like receptor 4 (TLR4) may be the upstream signal that triggers inflammatory injury in ICH. In addition, recent clinical findings indicated that both TLR2 and TLR4 may participate in ICH‐induced brain injury. However, it is unclear how TLR2 functions in ICH‐induced inflammatory injury and how TLR2 interacts with TLR4.

CD36-Mediated Hematoma Absorption following Intracerebral Hemorrhage: Negative Regulation by TLR4 Signaling

Promoting hematoma absorption is a novel therapeutic strategy for intracerebral hemorrhage (ICH); however, the mechanism of hematoma absorption is unclear. The present study explored the function and potential mechanism of CD36 in hematoma absorption using in vitro and in vivo ICH models. Hematoma absorption in CD36-deficient ICH patients was examined. Compared with patients with normal CD36 expression, CD36-deficient ICH patients had slower hematoma adsorption and aggravated neurologic deficits. CD36 expression in perihematomal tissues in wild-type mice following ICH was increased, whereas the hematoma absorption in CD36−/− mice was decreased. CD36−/− mice also showed aggravated neurologic deficits and increased TNF-α and IL-1β expression levels. The phagocytic capacity of CD36−/− microglia for RBCs was also decreased. Additionally, the CD36 expression in the perihematoma area after ICH in TLR4−/− and MyD88−/− mice was significantly increased, and hematoma absorption was significantly promoted, which was significantly inhibited by an anti-CD36 Ab. In vitro, TNF-α and IL-1β significantly inhibited the microglia expression of CD36 and reduced the microglia phagocytosis of RBCs. Finally, the TLR4 inhibitor TAK-242 upregulated CD36 expression in microglia, promoted hematoma absorption, increased catalase expression, and decreased the H2O2 content. These results suggested that CD36 mediated hematoma absorption after ICH, and TLR4 signaling inhibited CD36 expression to slow hematoma absorption. TLR4 inhibition could promote hematoma absorption and significantly improve neurologic deficits following ICH.

Resveratrol counteracts lipopolysaccharide-induced depressive-like behaviors via enhanced hippocampal neurogenesis

Radial glial-like cells (RGLs) in the adult dentate gyrus (DG) function as progenitor cells for adult hippocampal neurogenesis, a process involved in the stress-related pathophysiology and treatment efficiency of depression. Resveratrol (RSV) has been demonstrated to be a potent activator of neurogenesis. The present study investigated whether chronic RSV treatment has antidepressant potential in relation to hippocampal neurogenesis. Mice received two weeks of RSV (20 mg/kg) or dimethylsulfoxide (DMSO) treatment, followed by lipopolysaccharide (LPS; 1 mg/kg) or saline injections for 5 days. We found that RSV treatment abrogated the increased immobility in the forced swimming test and tail suspension test induced by LPS. Immunohistochemical staining revealed that RSV treatment reversed the increase in microglial activation and the inhibition in DG neurogenesis. RSV treatment also attenuated LPS-induced defects in the expanding of RGLs through promoting symmetric division. In addition, RSV ameliorated LPS-induced NF-κB activation in the hippocampus coincides with the up-regulation levels of Sirt1 and Hes1. Taken together, these data indicated that RSV-induced Sirt1 activation counteracts LPS-induced depression-like behaviors via a neurogenic mechanism. A new model to understand the role of RSV in treating depression may result from these findings.

Function and mechanism of toll-like receptors in cerebral ischemic tolerance: from preconditioning to treatment

Increasing evidence suggests that toll-like receptors (TLRs) play an important role in cerebral ischemia-reperfusion injury. The endogenous ligands released from ischemic neurons activate the TLR signaling pathway, resulting in the production of a large number of inflammatory cytokines, thereby causing secondary inflammation damage following cerebral ischemia. However, the preconditioning for minor cerebral ischemia or the preconditioning with TLR ligands can reduce cerebral ischemic injury by regulating the TLR signaling pathway following ischemia in brain tissue (mainly, the inhibition of the TLR4/NF-κB signaling pathway and the enhancement of the interferon regulatory factor-dependent signaling), resulting in TLR ischemic tolerance. Additionally, recent studies found that postconditioning with TLR ligands after cerebral ischemia can also reduce ischemic damage through the regulation of the TLR signaling pathway, showing a significant therapeutic effect against cerebral ischemia. These studies suggest that the ischemic tolerance mediated by TLRs can serve as an important target for the prevention and treatment of cerebral ischemia. On the basis of describing the function and mechanism of TLRs in mediating cerebral ischemic damage, this review focuses on the mechanisms of cerebral ischemic tolerance induced by the preconditioning and postconditioning of TLRs and discusses the clinical application of TLRs for ischemic tolerance.

A20 Ameliorates Intracerebral Hemorrhage–Induced Inflammatory Injury by Regulating TRAF6 Polyubiquitination

Reducing excessive inflammation is beneficial for the recovery from intracerebral hemorrhage (ICH). Here, the roles and mechanisms of A20 (TNFAIP3), an important endogenous anti-inflammatory factor, are examined in ICH. A20 expression in the PBMCs of ICH patients and an ICH mouse model was detected, and the correlation between A20 expression and neurologic deficits was analyzed. A20 expression was increased in PBMCs and was negatively related to the modified Rankin Scale score. A20 expression was also increased in mouse perihematomal tissues. A20−/− and A20-overexpressing mice were generated to further analyze A20 function. Compared with wild-type (WT) mice, A20−/− and A20-overexpressing mice showed significant increases and decreases, respectively, in hematoma volume, neurologic deficit score, mortality, neuronal degeneration, and proinflammatory factors. Moreover, WT-A20−/− parabiosis was established to explore the role of A20 in peripheral blood in ICH injury. ICH-induced damage, including brain edema, neurologic deficit score, proinflammatory factors, and neuronal apoptosis, was reduced in A20−/− parabionts compared with A20−/− mice. Finally, the interactions between TRAF6 and Ubc13 and UbcH5c were increased in A20−/− mice compared with WT mice; the opposite occurred in A20-overexpressing mice. Enhanced IκBα degradation and NF-κB activation were observed in A20−/− mice, but the results were reversed in A20-overexpressing mice. These results suggested that A20 is involved in regulating ICH-induced inflammatory injury in both the central and peripheral system and that A20 reduces ICH-induced inflammation by regulating TRAF6 polyubiquitination. Targeting A20 may thus be a promising therapeutic strategy for ICH.

Association of CYP2C19 Polymorphisms with the Clinical Efficacy of Clopidogrel Therapy in Patients Undergoing Carotid Artery Stenting in Asia

The CYP2C19 gene plays a detrimental role in the metabolism of clopidogrel. This study aimed to investigate the association between CYP2C19 polymorphisms and the clinical efficacy of clopidogrel therapy in patients who have undergone carotid artery stenting (CAS). CYP2C19 genotype screening was performed on 959 ischemic stroke patients. Of these patients, 241 who had undergone CAS were enrolled in the study. They were all followed up for 1 year after stent surgery, and the primary clinical end-points were ischemic events. The frequencies of the CYP2C19*2 and *3 alleles among the 959 patients were 31.80% and 5.06%, respectively. Regarding the 241 participants who had undergone CAS, multivariate Cox regression analysis showed that the CYP2C19 loss-of-function (LOF) alleles (*2 and *3) were risk factors for post-CAS prognosis. Within 1 year of follow-up, the patients carrying the CYP2C19 LOF alleles were more likely to experience ischemic events than those carrying none. The occurrence of ischemic events did not significantly differ between the *2 and *3 allele carriers. Our results suggest that CYP2C19 LOF alleles (*2 and *3) significantly impact the prognosis of patients on clopidogrel therapy after CAS and that the CYP2C19*2 and CYP2C19*3 alleles have the same effects on prognosis.

Foxp3 exhibits antiepileptic effects in ictogenesis involved in TLR4 signaling

Inflammatory processes play critical roles in epileptogenesis, but the exact mechanisms that underlie these processes are still not completely understood. In this study, we investigated the role of forkhead transcription factor 3 (Foxp3), a transcription factor that is involved in T‐cell differentiation, in epileptogenesis. In both human epileptic tissues and experimental seizure models, we found significant up‐regulation of Foxp3 in neurons and glial cells. Of importance, Foxp3‐/‐ mice were susceptible to kainic acid–induced seizures, whereas overexpression of Foxp3 reduced acute seizure occurrence and decreased chronic seizure recurrence. In addition, in vitro experiments revealed that Foxp3 inhibited neuronal excitability via glial cells and not neurons. The protective effects of Foxp3 were manifested as a reduction in glial cell activation and proinflammatory cytokine production and increased neuronal survival. Moreover, we showed that beneficial effects of Foxp3 involved the attenuation of TLR4 signaling and inflammation, which led to the inactivation of NR2B‐containing NMDA receptors. These results suggest that Foxp3 in glial cells may play an antiepileptic role in epileptogenesis and may act as a modulator of TLR4. Taken together, our results indicate that Foxp3 may represent a novel therapeutic target for achieving anticonvulsant effects in patients with epilepsy that is currently resistant to drugs.—Wang, F.‐X., Xiong, X.‐Y., Zhong, Q., Meng, Z.‐Y., Yang, H., Yang, Q.‐W. Foxp3 exhibits antiepileptic effects in ictogenesis involved in TLR4 signaling. FASEB J. 31, 2948–2962 (2017). www.fasebj.org

Mfsd2a (Major Facilitator Superfamily Domain Containing 2a) Attenuates Intracerebral Hemorrhage–Induced Blood–Brain Barrier Disruption by Inhibiting Vesicular Transcytosis

Background Blood–brain barrier (BBB) disruption aggravates brain injury induced by intracerebral hemorrhage (ICH); however, the mechanisms of BBB damage caused by ICH remain elusive. Mfsd2a (major facilitator superfamily domain containing 2a) has been known to play an essential role in BBB formation and function. In this study, we investigated the role and underlying mechanisms of Mfsd2a in BBB permeability regulation after ICH. Methods and Results Using ICH models, we found that Mfsd2a protein expression in perihematomal brain tissues was significantly decreased after ICH. Knockdown and knockout of Mfsd2a in mice markedly increased BBB permeability, neurological deficit score, and brain water contents after ICH, and these were rescued by overexpressing Mfsd2a in perihematomas. Moreover, we found that Mfsd2a regulation of BBB permeability after ICH correlated with changes in vesicle number. Expression profiling of tight junction proteins showed no differences in Mfsd2a knockdown, Mfsd2a knockout, and Mfsd2a overexpression mice. However, using electron microscopy following ICH, we observed a significant increase in pinocytotic vesicle number in Mfsd2a knockout mice and decreased the number of pinocytotic vesicles in mouse brains with Mfsd2a overexpression. Finally, using multiple reaction monitoring, we screened out 3 vesicle trafficking–related proteins (Srgap2, Stx7, and Sec22b) from 31 vesicle trafficking‐related proteins that were markedly upregulated in Mfsd2a knockout mice compared with controls after ICH. Conclusions In summary, our results suggest that Mfsd2a may protect against BBB injury by inhibiting vesicular transcytosis following ICH.

The Efficacy of Prophylactic Antibiotics on Post-Stroke Infections: An Updated Systematic Review and Meta-Analysis

Post-stroke infections are common complications in acute stroke patients and are associated with an unfavorable functional outcome. However, reports on the effects of prophylactic antibiotics treatment on post-stroke infections are conflicting, especially those on post-stroke pneumonia and outcomes. We searched the PubMed, Embase, and Web of Knowledge databases up through March 11th, 2016. Seven randomized controlled trials including 4261 patients were analyzed among this systematic review and meta-analysis. We found preventive antibiotics treatment at the time of stroke onset did reduce the incidence of infections in adults with acute stroke (OR = 0.57, 95% CI: 0.38–0.85, P = 0.005), including reducing the number of urinary tract infections (OR = 0.34, 95% CI: 0.26–0.46, P < 0.001), but did not significantly decrease the rate of post-stroke pneumonia (OR = 0.91, 95% CI: 0.73–1.13, P = 0.385). Importantly, antibiotics treatment also showed no significant effect on the number of fatalities among stroke patients (OR = 1.07, 95% CI: 0.90–1.26, P = 0.743) and functional outcome scores on the modified Rankin Scale (OR = 1.76, 95% CI: 0.86–3.63, p = 0.124). Our study indicated that preventive antibiotics treatment not reduced the rate of post-stroke pneumonia or mortality, even though decreased the risk of infections, especially urinary tract infections. Thus, preventive antibiotics treatment may not be recommended for acute stroke patients.