Jing-Zhou Wang

HMBG1 mediates ischemia–reperfusion injury by TRIF-adaptor independent Toll-like receptor 4 signaling

High-mobility group protein box-1 (HMGB1) has recently been recognized as a novel candidate in a specific upstream pathway promoting inflammation after brain ischemia. However, its downstream pathway and underlying mechanism have yet to be elucidated. The HMGB1 level in the acute cerebral infarct (ACI) group was significantly increased compared with that of control group, and correlated with the severity of neurologic impairment of ACI patients. Further, recombinant human HMGB1 (rhHMGB1) had no effect on microglia derived from mice lacking the Toll-like receptor 4 (TLR4−/–). Intracerebroventricular injection of rhHMGB1 in TLR4+/+ mice cause significantly more injury after cerebral ischemia–reperfusion than control group. But, TLR4−/– mice administered with rhHMGB1 showed moderate impairment after ischemia–reperfusion than TLR4+/+ mice. To determine the potential downstream signaling of HMGB1/TLR4 in cerebral ischemic injury, we used the ischemic–reperfusion model with Toll/interleukin-1 receptor domain-containing adaptor-inducing interferon-β knockout mice (TRIF−/–) and evaluated the activity and expression of TRIF pathway-related kinases. The results suggest that the TRIF pathway is not likely to be involved in TLR4-mediated ischemia brain injury. Finally, we found that TLR4 expressed by immigrant macrophages was involved in the development of ischemic brain damage. These results suggest that HMBG1 mediates ischemia–reperfusion injury by TRIF-adaptor independent Toll-like receptor 4 signaling. The TLR4 expressed by immigrant macrophages may be involved in the development of ischemic brain damage.

Upregulated expression of toll-like receptor 4 in monocytes correlates with severity of acute cerebral infarction

In the present study, we observed the expression of toll-like receptor 4 (TLR4) and its downstream signal pathway in peripheral blood monocytes (PBMs) from patients with acute cerebral infarct (ACI). The expression of TLR4 and MyD88 by PBMs was determined by flow cytometry and reverse transcriptase-polymerase chain reaction, and nuclear factor-κB (NF-κB) activity was detected by electrophoretic mobility shift assay. Ischemia/reperfusion injury-induced cerebral edema, infarction area, and neurologic impairment scores were determined in MyD88 gene knockout mice. The results indicated a significant increase in circulating TLR4+ monocytes in ACI patients as compared with the control group and the transient ischemia attack (TIA) group. This change paralleled an elevation in TLR4mRNA transcription and serum tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in the ACI and TIA groups. Correlation analysis showed TLR4 expression to significantly correlate with cytokine levels and stroke severity. MyD88mRNA differed insignificantly among the three groups. Compared with wild-type mice, 6 h of cerebral ischemia followed by 24 h of reperfusion did not significantly change cerebral edema, cerebral infarction area, and neurologic impairment scores in MyD88 gene knockout mice. Compared with the control group, serum heat shock protein (HSP) 60 increased significantly in the ACI and TIA groups, leading to NF-κB activation in TLR4/CD14-transfected HEK293 cells. It is suggested that upregulated TLR4 expression on PMBs may act as one of the peripheral mechanisms of inflammatory injury after ACI. Moreover, circulating HSP60 may be a ligand for TLR4, which is involved in the peripheral mechanism of inflammatory injury after ACI, possibly through an MyD88-independent signal pathway.

High-mobility group protein box-1 and its relevance to cerebral ischemia

High-mobility group box-1 (HMGB1) was originally identified as a ubiquitously expressed, abundant, nonhistone DNA-binding protein. It has well-established functions in the maintenance of nuclear homeostasis. The HMGB1 can either be passively released into the extracellular milieu in response to necrotic signals or actively secreted in response to inflammatory signals. Extracellular HMGB1 interacts with receptors, including those for advanced glycation endproducts (RAGEs) as well as Toll-like receptor 2 (TLR2) and TLR4. The HMGB1 functions in a synergistic manner with other proinflammatory mediators and acts as a potent proinflammatory cytokine-like factor that contributes to the pathogenesis of diverse inflammatory and infectious disorders. Numerous reports point to HMGB1 as a novel player in the ischemic brain. This review provides an appraisal of the emerging roles of HMGB1 in cerebral ischemia injury, highlighting the relevance of HMGB1-blocking agents as potent therapeutic tools for neuroprotection.

Association between apolipoprotein E gene polymorphism and the risk of vascular dementia: A meta-analysis

It remains controversial regarding the association between Apolipoprotein E (ApoE) gene polymorphism and the risk of vascular dementia (VaD). The present meta-analysis was performed to derive a more precise estimation of the relationship. The meta-analysis was performed by searching PubMed, Embase and Web of Science databases. A total of 29 studies included 1763 VaD cases and 4534 controls were identified. The results showed evidence for significant association between ApoE ɛ4 mutation and VaD risk (for ɛ3/ɛ4 vs. ɛ3/ɛ3: OR=1.65, 95% CI=1.40-1.94, p-value<0.00001; for ɛ4/ɛ4 vs. ɛ3/ɛ3: OR=3.17, 95% CI=2.09-4.80, p-value<0.00001; for ɛ4 allele vs. ɛ3 allele: OR=1.72, 95% CI=1.40-2.12, p-value<0.00001). The similar results were obtained in the subgroup analysis based on ethnicity. In summary, the present meta-analysis suggests an association between ApoE ɛ4 mutation and increased risk of VaD. However, due to the small sample size in most of the included studies and the selection bias existed in some studies, the results should be interpreted with caution.

Elevation of High-Mobility Group Protein Box-1 in Serum Correlates with Severity of Acute Intracerebral Hemorrhage

High-mobility group protein box-1 (HMGB1) is a proinflammatory involved in many inflammatory diseases. However, its roles in intracerebral hemorrhage (ICH) remain unknown. The purpose of this study was to examine the correlation between changes in serum levels of HMGB1 following acute ICH and the severity of stroke as well as the underlying mechanism. Changes in serum levels of HMGB1 in 60 consecutive patients with primary hemispheric ICH within 12 hours of onset of symptoms were determined. The correlation of HMGB1 with disease severity, IL-6, and TNF-α was analyzed. Changes in HMGB1 levels were detected with ELISA and Western blot. Compared with normal controls, patients with ICH had markedly elevated levels of HMGB1, which was significantly correlated with the levels of IL-6 and TNF-α, NIHSS score at the 10th day, and mRS score at 3 months. In comparison with the control group, the levels of HMGB1 in the perihematomal tissue in mice with ICH increased dramatically, peaked at 72 hours, and decreased at 5 days. Meanwhile, heme could stimulate cultured microglia to release large amounts of HMGB1 whereas Fe2+/3+ ions failed to stimulate HMGB1 production from microglia. Our findings suggest that HMGB1 may play an essential role in the ICH-caused inflammatory injury.

PPARγ attenuates intimal hyperplasia by inhibiting TLR4-mediated inflammation in vascular smooth muscle cells

AIMS Peroxisome proliferator-activated receptor γ (PPARγ) has been reported to attenuate intimal hyperplasia. This study aimed to test the hypothesis that PPARγ inhibits intimal hyperplasia through suppressing Toll-like receptor 4 (TLR4)-mediated inflammation in vascular smooth muscle cells. METHODS AND RESULTS TLR4(-/-) mice on a C57BL/6J background were used. Increased TLR4 and pro-inflammatory cytokines were observed in wire-injury-induced carotid neointima and in platelet-derived growth factor (PDGF)-activated vascular smooth muscle cells. The TLR4 deficiency protected the injured carotid from neointimal formation and impaired the cellular proliferation and migration in response to lipopolysaccharide and PDGF. Rosiglitazone attenuated intimal hyperplasia. Overexpression of PPARγ suppressed PDGF-induced proliferation and migration and inhibited TLR4-mediated inflammation in vascular smooth muscle cells, while PPARγ silencing exerted the opposite effect. Lipopolysaccharide counteracted the inhibitory effect of PPARγ on PDGF-induced proliferation and migration. Eritoran suppressed the proliferation and migration induced by PDGF and PPARγ silencing. Vascular smooth muscle cells derived from TLR4(-/-) mice showed impaired proliferation and migration upon PDGF activation and displayed no response to PPARγ manipulation. CONCLUSION PPARγ inhibits vascular smooth muscle cell proliferation and migration by suppressing TLR4-mediated inflammation and ultimately attenuates intimal hyperplasia after carotid injury.

Impaired Peroxisome Proliferator-activated Receptor-γ Contributes to Phenotypic Modulation of Vascular Smooth Muscle Cells during Hypertension

The phenotypic modulation of vascular smooth muscle cells (VSMCs) plays a pivotal role in hypertension-induced vascular changes including vascular remodeling. The precise mechanisms underlying VSMC phenotypic modulation remain elusive. Here we test the role of peroxisome proliferator-activated receptor (PPAR)-γ in the VSMC phenotypic modulation during hypertension. Both spontaneously hypertensive rat (SHR) aortas and SHR-derived VSMCs exhibited reduced PPAR-γ expression and excessive VSMC phenotypic modulation identified by reduced contractile proteins, α-smooth muscle actin (α-SMA) and smooth muscle 22α (SM22α), and enhanced proliferation and migration. PPAR-γ overexpression rescued the expression of α-SMA and SM22α, and inhibited the proliferation and migration in SHR-derived VSMCs. In contrast, PPAR-γ silencing exerted the opposite effect. Activating PPAR-γ using rosiglitazone in vivo up-regulated aortic α-SMA and SM22α expression and attenuated aortic remodeling in SHRs. Increased activation of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling was observed in SHR-derived VSMCs. PI3K inhibitor LY294002 rescued the impaired expression of contractile proteins, and inhibited proliferation and migration in VSMCs from SHRs, whereas constitutively active PI3K mutant had the opposite effect. Overexpression or silencing of PPAR-γ inhibited or excited PI3K/Akt activity, respectively. LY294002 counteracted the PPAR-γ silencing induced proliferation and migration in SHR-derived VSMCs, whereas active PI3K mutant had the opposite effect. In contrast, reduced proliferation and migration by PPAR-γ overexpression were reversed by the active PI3K mutant, and further inhibited by LY294002. We conclude that PPAR-γ inhibits VSMC phenotypic modulation through inhibiting PI3K/Akt signaling. Impaired PPAR-γ expression is responsible for VSMC phenotypic modulation during hypertension. These findings highlight an attractive therapeutic target for hypertension-related vascular disorders.

Association between NADPH Oxidase p22phox C242T Polymorphism and Ischemic Cerebrovascular Disease: A Meta-Analysis

Background Epidemiological studies have evaluated the association between nicotinamide adenine dinucleotide phosphate (NADPH) oxidase p22phox C242T polymorphism and risk of ischemic cerebrovascular disease (ICVD), but the results remain inconclusive. This meta-analysis was therefore designed to clarify these controversies. Methodology/Principal Findings Systematic searches of electronic databases Embase, PubMed and Web of Science, as well as hand searching of the references of identified articles and the meeting abstracts were performed. Statistical analyses were performed using software Review Manager (Version 5.1.7) and Stata (Version 11.0). The pooled odds ratios (ORs) with 95% confidence intervals (95%CIs) were performed. Fixed or random effects model was separately used depending on the heterogeneity between studies. Publication bias was tested by Beggs funnel plot and Eggers regression test. A total of 6 studies including 1,948 cases and 2,357 controls were combined showing no statistical evidence of association between NADPH oxidase p22phox C242T polymorphism and overall ICVD (allelic model: OR = 1.08, 95%CI = 0.93–1.26; additive model: OR = 1.33, 95%CI = 0.81–2.17; dominant model: OR = 1.00, 95%CI = 0.86–1.15; recessive model: OR = 1.06, 95%CI = 0.77–1.45). Significant association was found in large-artery atherosclerotic stroke subgroup (allelic model: OR = 1.12, 95%CI = 0.88–1.41; additive model: OR = 1.36, 95%CI = 0.60–3.09; dominant model: OR = 1.25, 95%CI = 0.74–2.11; recessive model: OR = 2.17, 95%CI = 1.11–4.23). No statistical evidence of significant association was observed for small-vessel occlusive stroke, as well as Asian subgroup and Caucasian subgroup. Statistical powers on the combined sample size (total and subgroup) were all lower than 80%. Conclusions/Significance This meta-analysis indicates that NADPH oxidase p22phox C242T polymorphism is more associated with large-artery atherosclerotic stroke than small-vessel occlusive stroke. However, this conclusion should be interpreted with caution due to the small sample size. Larger sample-size studies with homogeneous ICVD patients and well-matched controls are required.

Association between apolipoprotein E gene polymorphism and the risk of multiple sclerosis: A meta-analysis of 6977 subjects

Epidemiological studies have evaluated the association between apolipoprotein E (ApoE) gene polymorphism and multiple sclerosis (MS) risk. However, the results remain conflicting. Therefore, in order to derive a more precise association of ApoE gene polymorphism with MS risk, we performed this meta-analysis. Systematic searches of electronic databases PubMed, Embase and Web of Science, as well as hand searching of the references of identified articles were performed. Twenty studies were identified, covering a total of 4080 MS cases and 2897 controls. The results showed evidence for significant association between ApoE ε2 mutation and MS risk (for ε2/ε4 versus ε3/ε3: OR=1.74, 95% CI=1.12-2.71, p=0.01; for ε2 allele versus ε3 allele: OR=1.16, 95% CI=1.01-1.35, p=0.04). In the subgroup analysis by ethnicity, the similar results were obtained among Europeans (for ε2/ε4 versus ε3/ε3: OR=1.81, 95% CI=1.14-2.87, p=0.01; for ε2 allele versus ε3 allele: OR=1.19, 95% CI=1.02-1.38, p=0.03). After excluding the outlier studies by observing Galbraith plot, marginal association was found between ApoE ε3/ε4 genotype and the protective factor for MS (for ε3/ε4 versus ε3/ε3: OR=0.86, 95% CI=0.75-0.99, p=0.04). In summary, the present meta-analysis provides evidence that ApoE ε2 mutation is associated with MS risk. In addition, ApoE ε3/ε4 genotype appears to be a protective factor for MS.

Apolipoprotein A5 gene promoter region-1131T/C polymorphism is associated with risk of ischemic stroke and elevated triglyceride levels: a meta-analysis.

Background: The association between polymorphism -1131T/C in the promoter region of apolipoprotein A5 (APOA5) and ischemic stroke and plasma triglyceride (TG) levels remains controversial. To better clarify the association between APOA5-1131T/C and risk of ischemic stroke and plasma TG levels, we performed a meta-analysis to examine the allele and genotype of APOA5-1131T/C polymorphism in ischemic stroke cases and controls. Methods: Based on the search of PubMed, Embase, MEDLINE, CNKI (National Knowledge Infrastructure) and CBM (Chinese BioMedical Literature Database) databases, we identified and abstracted outcome data from all articles to evaluate the association between APOA5 and ischemic stroke/plasma TG levels. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were performed in dominant model (CC + TC vs. TT), recessive model (CC vs. TC + TT), homozygote comparison (CC vs. TT) and heterozygote comparison (TC vs. TT). The association between dominant model (CC + TC vs. TT) and plasma TG/total cholesterol/high-density lipoprotein cholesterol levels was measured by a weighted mean difference (WMD) with its corresponding 95% CI. To evaluate the ethnicity-specific effects, subgroup analyses were performed by ethnic group. Results: A meta-analysis containing 2,294 ischemic stroke cases and 1,858 controls from 8 case-control studies was performed. The results showed that APOA5-1131T/C polymorphism was significantly associated with ischemic stroke in all comparison models (CC + TC vs. TT, OR = 1.70, 95% CI = 1.24–2.32; CC vs. TC + TT, OR = 1.36, 95% CI = 0.98–1.90; CC vs. TT, OR = 1.73, 95% CI = 1.34–2.23; TC vs. TT, OR = 1.67, 95% CI = 1.19–2.36). On subgroup analysis by ethnicity, similarly significant associations were found in both Asians and Europeans, and the Europeans possessed a higher risk of ischemic stroke, especially in CC versus TT model (OR = 4.47, 95% CI = 1.33–15.06). Significant association between the C allele and elevated TG levels was detected in both ischemic stroke cases and controls; the TG levels were higher in the ischemic stroke cases and controls carrying the APOA5-1131C allele than in the noncarriers (CC + TC vs. TT, cases WMD = 0.43, 95% CI = 0.27–0.59; controls WMD = 0.51, 95% CI = 0.35–0.66). Similar within-group comparison of the total cholesterol and high-density lipoprotein cholesterol levels did not show any difference. Conclusions: Our meta-analysis revealed that the APOA5-1131T/C polymorphism is associated with a significant risk of ischemic stroke and elevated TG levels. The CC genotype and C allele might be a genetic risk factor that increases susceptibility of ischemic stroke and elevates plasma TG levels, and might be a useful target for clinical therapeutic intervention.