Association of thromboxane A2 receptor gene polymorphisms with cerebral infarction in a Chinese population

Genetic Association Study and Machine Learning to Investigate Differences in Platelet Reactivity in Patients with Acute Ischemic Stroke Treated with Aspirin

Aspirin resistance (AR) is a pressing problem in current ischemic stroke care. Although the role of genetic variations is widely considered, the data still remain controversial. Our aim was to investigate the contribution of genetic features to laboratory AR measured through platelet aggregation with arachidonic acid (AA) and adenosine diphosphate (ADP) in ischemic stroke patients. A total of 461 patients were enrolled. Platelet aggregation was measured via light transmission aggregometry. Eighteen single-nucleotide polymorphisms (SNPs) in ITGB3, GPIBA, TBXA2R, ITGA2, PLA2G7, HMOX1, PTGS1, PTGS2, ADRA2A, ABCB1 and PEAR1 genes and the intergenic 9p21.3 region were determined using low-density biochips. We found an association of rs1330344 in the PTGS1 gene with AR and AA-induced platelet aggregation. Rs4311994 in ADRA2A gene also affected AA-induced aggregation, and rs4523 in the TBXA2R gene and rs12041331 in the PEAR1 gene influenced ADP-induced aggregation. Furthermore, the effect of rs1062535 in the ITGA2 gene on NIHSS dynamics during 10 days of treatment was found. The best machine learning (ML) model for AR based on clinical and genetic factors was characterized by AUC = 0.665 and F1-score = 0.628. In conclusion, the association study showed that PTGS1, ADRA2A, TBXA2R and PEAR1 polymorphisms may affect laboratory AR. However, the ML model demonstrated the predominant influence of clinical features.

The Role of Thromboxane in the Course and Treatment of Ischemic Stroke: Review

Cardiovascular diseases are currently among the leading causes of morbidity and mortality in many developed countries. They are distinguished by chronic and latent development, a course with stages of worsening of symptoms and a period of improvement, and a constant potential threat to life. One of the most important disorders in cardiovascular disease is ischemic stroke. The causes of ischemic stroke can be divided into non-modifiable and modifiable causes. One treatment modality from a neurological point of view is acetylsalicylic acid (ASA), which blocks cyclooxygenase and, thus, thromboxane synthesis. The legitimacy of its administration does not raise any doubts in the case of the acute phase of stroke in patients in whom thrombolytic treatment cannot be initiated. The measurement of thromboxane B2 (TxB2) in serum (a stable metabolic product of TxA2) is the only test that measures the effect of aspirin on the activity of COX-1 in platelets. Measurement of thromboxane B2 may be a potential biomarker of vascular disease risk in patients treated with aspirin. The aim of this study is to present the role of thromboxane B2 in ischemic stroke and to present effective therapies for the treatment of ischemic stroke. Scientific articles from the PubMed database were used for the work, which were selected on the basis of a search for “thromboxane and stroke”. Subsequently, a restriction was introduced for works older than 10 years, those concerning animals, and those without full text access. Ultimately, 58 articles were selected. It was shown that a high concentration of TXB2 may be a risk factor for ischemic stroke or ischemic heart disease. However, there is insufficient evidence to suggest that thromboxane could be used in clinical practice as a marker of ischemic stroke. The inclusion of ASA in the prevention of stroke has a beneficial effect that is associated with the effect on thromboxane. However, its insufficient power in 25% or even 50% of the population should be taken into account. An alternative and/or additional therapy could be a selective antagonist of the thromboxane receptor. Thromboxane A2 production is inhibited by estrogen; therefore, the risk of CVD after the menopause and among men is higher. More research is needed in this area.

G-Protein-Coupled Receptors and Ischemic Stroke: a Focus on Molecular Function and Therapeutic Potential

In ischemic stroke, there is only one approved drug, tissue plasminogen activator, to be used in clinical conditions for thrombolysis. New neuroprotective therapies for ischemic stroke are desperately needed. Several targets and pathways have been shown to confer neuroprotective effects in ischemic stroke. G-protein-coupled receptors (GPCRs) are one of the most frequently targeted receptors for developing novel therapeutics for central nervous system disorders. GPCRs are a large family of cell surface receptors that response to a wide variety of extracellular stimuli. GPCRs are involved in a wide range of physiological and pathological processes. More than 90% of the identified non-sensory GPCRs are expressed in the brain, where they play important roles in regulating mood, pain, vision, immune responses, cognition, and synaptic transmission. There is also good evidence that GPCRs are implicated in the pathogenesis of stroke. This review narrates the pathophysiological role and possible targeted therapy of GPCRs in ischemic stroke.

Genetic Variants behind Cardiovascular Diseases and Dementia

Cardiovascular diseases (CVDs) and dementia are the leading causes of disability and mortality. Genetic connections between cardiovascular risk factors and dementia have not been elucidated. We conducted a scoping review and pathway analysis to reveal the genetic associations underlying both CVDs and dementia. In the PubMed database, literature was searched using keywords associated with diabetes mellitus, hypertension, dyslipidemia, white matter hyperintensities, cerebral microbleeds, and covert infarctions. Gene lists were extracted from these publications to identify shared genes and pathways for each group. This included high penetrance genes and single nucleotide polymorphisms (SNPs) identified through genome wide association studies. Most risk SNPs to both diabetes and dementia participate in the phospholipase C enzyme system and the downstream nositol 1,4,5-trisphosphate and diacylglycerol activities. Interestingly, AP-2 (TFAP2) transcription factor family and metabolism of vitamins and cofactors were associated with genetic variants that were shared by white matter hyperintensities and dementia, and by microbleeds and dementia. Variants shared by covert infarctions and dementia were related to VEGF ligand-receptor interactions and anti-inflammatory cytokine pathways. Our review sheds light on future investigations into the causative relationships behind CVDs and dementia, and can be a paradigm of the identification of dementia treatments.

The association between thromboxane A2 receptor gene polymorphisms and the risk of cerebral infarction

To explore the association between thromboxane A₂ receptor (TXA₂R) gene polymorphisms and the risk of cerebral infarction. We screened the relevant publications through the search engines in PubMed, Google Scholar, Embase, Web of Science, and China National Knowledge Infrastructure (the latest search update was performed on July 1, 2020). Gene-disease associations were measured using the estimation of OR (95 % CI) based on five genetic inheritance models. Totally three studies were included in this meta-analysis. TXA₂R rs768963 polymorphism in homozygote comparison (OR = 1.86, 95 % CI: 1.35-2.56), heterozygote comparison (OR = 1.81, 95 % CI: 1.37-2.39), and dominant model (OR = 1.82, 95 % CI: 1.39-2.37) emerged as risk factors for cerebral infarction. Besides, an increased cerebral infarction risk was observed in the heterozygote comparison (OR = 1.39, 95 % CI: 1.03-1.88) for TXA₂R rs2271875 polymorphism. None of the five models showed any association between TXA₂R rs4523 polymorphism and cerebral infarction risk. In conclusion, this is the first meta-analysis verifying that TXA₂R rs768963 polymorphism and TXA₂R rs2271875 polymorphism may be associated with the risk of cerebral infarction.

The TXA2R rs1131882, P2Y1 rs1371097 and GPIIIa rs2317676 three-loci interactions may increase the risk of carotid stenosis in patients with ischemic stroke

Background

The genetic risk factors for carotid stenosis are not fully understood. The aim of this study is to investigate the relationship between variants in platelet activation-relevant genes and carotid stenosis in patients with ischemic stroke (IS).

Methods

Eleven variants of platelet activation-relevant genes, aggregates of platelet-leukocyte, and platelet aggregation were examined in 236 IS patients with carotid stenosis and 378 patients without carotid stenosis. High-resolution B-mode ultrasound was used to assess carotid stenosis. Generalized multifactor dimensionality reduction (GMDR) methods were applied in analyzing gene-gene interactions to determine whether there was any interactive role of assessed variants in affecting risk of carotid stenosis.

Results

Platelet aggregation and aggregates of platelet-leukocyte showed higher value in patients with carotid stenosis, compared with patients without carotid stenosis. Excluding potential disturbance variables, these 11 variants were not associated with carotid stenosis. However, according to the GMDR analysis, gene-gene interactions among TXA2R rs1131882, P2Y1 rs1371097 and GPIIIa rs2317676 had a synergistic influence on carotid stenosis. The high-risk interactions between the three variants showed a relationship with higher platelet activation, and have independent associations with risk of carotid stenosis (OR = 2.72, 95% CI: 1.28–7.82, P = 0.001).

Conclusion

The interactions among rs1131882, rs1371097 and rs2317676 perhaps increase the risk of symptomatic carotid stenosis, and maybe a potential marker for carotid stenosis. In this study, the combinatorial analysis made good use in elucidating complex risk factors in the heredity of carotid stenosis.

Isoprostanes as potential cerebral vasospasm biomarkers

Despite enormous progress in medicine, symptomatic cerebral vasospasm (CVS), remains an unexplained clinical problem, which leaves both physicians and patients helpless and relying on chance, due to the lack of specific marker indicative of imminent danger as well as the lack of specific treatment. In our opinion CVS occurrence depends on dynamic disbalance between free radicals' formation (oxidative stress) and antioxidant activity. Isoprostanes are products of free-radical peroxidation of polyunsaturated fatty acids, and seem to mark a promising path for the research aiming to unravel its possible mechanism. Not only are they the biomarkers of oxidative stress in vivo and in vitro, but also have manifold biological effects (including vasoactive, inflammatory and mitogenic) via activation of the thromboxane A2 receptor (TBXA2R), both in physiological and pathophysiological processes. This review addresses the importance of isoprostanes in CVS in quest of appropriate biomarkers.

Interactions among variants in TXA2R, P2Y12 and GPIIIa are associated with carotid plaque vulnerability in Chinese population

PURPOSE

The associations between variants in platelet activation-relevant genes and carotid plaque vulnerability are not fully understood. The aim of the present study was to investigate the associations of the variants in platelet activation-relevant genes and interactions among these variants with carotid plaque vulnerability.

RESULTS

There were no significant differences in the frequencies of genotypes of the 11 variants between patients and controls. Among 396 patients, 102 patients had not carotid plaque, 106 had VP, and 188 had SP. The 11 variants were not independently associated with risk of carotid plaque vulnerability after adjusting for potential confounding variables. However, the GMDR analysis showed that there were synergistic effects of gene-gene interactions among TXA2Rr s1131882, GPIIIa rs2317676 and P2Y12 rs16863323 on carotid plaque vulnerability. The high-risk interactions among the three variants were associated with high platelet activation, and independently associated with the risk of carotid plaque vulnerability.

METHODS

Eleven variants in platelet activation-relevant genes were examined using mass spectrometry methods in 396 ischemic stroke patients and 291controls. Platelet-leukocyte aggregates and platelet aggregation were also measured. Carotid plaques were assessed by B-mode ultrasound. According to the results of ultrasound, the patients were stratified into three groups: non-plaque group, vulnerable plaque (VP) group and stable plaque (SP) group. Furthermore, gene-gene interactions were analyzed using generalized multifactor dimensionality reduction (GMDR) methods.

CONCLUSIONS

The rs1131882, rs2317676, and rs16863323 three-loci interactions may confer a higher risk of carotid plaque vulnerability, and might be potential markers for plaque instability.

Role of thromboxane A2 signaling in endothelium-dependent contractions of arteries

Thromboxane A₂ (TxA₂) plays a very important role in various cardiovascular diseases through its action on platelet aggregation, vasoconstriction, and proliferation. The present article focuses on the role of TxA₂ signaling in endothelium-dependent contractions of arteries. Arachidonic acid (AA) is metabolized by cyclooxygenase (COX) to form the unstable prostaglandin H₂ which is further converted into TxA₂. After being produced by thromboxane synthase (TxAS), TxA₂ ultimately stimulates TxA₂/prostanoid (TP) receptor to induce vasoconstriction. The calcium ionophore A23187, the prostanoid precursor AA, or the muscarinic receptor agonist acetylcholine (ACh) can evoke endothelium-dependent contractions associated with TxA₂. The endothelium-dependent contractions shown in hypertension, diabetes, atherogenesis, and other cardiovascular diseases have been significantly reduced by antagonism of COX, TxAS, or TP receptor. So inhibition of the bioavailability and/or effect of TxA₂ may be promising therapeutic targets to prevent these diseases. Especially some bioactive compounds isolated from medicinal plants will provide new pharmacological approaches to promote vascular health.

Association of FOXF2 gene polymorphisms with ischemic stroke in Chinese Han population

Recently, a novel locus at chromosome 6p25 (rs12204590, near FOXF2) associated with an increased risk of stroke in European populations was identified. However, whether polymorphisms in FOXF2 are also associated with the incidence of ischemic stroke in other populations remains unknown. In this case-control study, 803 Chinese Han patients with ischemic stroke and 803 matched control individuals were enrolled. Four tag SNPs and rs12204590 located in or near FOXF2 were selected, and the associations between genotypes/alleles and ischemic stroke were analyzed. In our study, we did not detect an association between the previously reported locus rs12204590 and ischemic stroke. By the genotype analysis, a novel SNP rs1711972, near FOXF2, was observed to be associated with an increased risk of ischemic stroke(CA genotype, adjusted OR = 1.35; 95% CI, 1.07 to 1.70), but not significantly after Bonferroni corrections for multiple tests. However, in the subgroup analysis, we discovered that rs1711972 was associated with an increased risk of large-artery atherosclerotic stroke in the additive model (P = 0.020; CA genotype, adjusted OR = 1.50; 95%CI, 1.09 to 2.07) and dominant model (P = 0.010; OR = 1.47; 95%CI, 1.09 to 1.99). Collectively, these results indicate that a novel SNP near FOXF2 may influence the risk of large-artery atherosclerotic stroke in Chinese Han population.

A Promising Approach to Integrally Evaluate the Disease Outcome of Cerebral Ischemic Rats Based on Multiple-Biomarker Crosstalk

Purpose

The study was designed to evaluate the disease outcome based on multiple biomarkers related to cerebral ischemia.

Methods

Rats were randomly divided into sham, permanent middle cerebral artery occlusion, and edaravone-treated groups. Cerebral ischemia was induced by permanent middle cerebral artery occlusion surgery in rats. To form a simplified crosstalk network, the related multiple biomarkers were chosen as S100β, HIF-1α, IL-1β, PGI₂, TXA₂, and GSH-Px. The levels or activities of these biomarkers in plasma were detected before and after ischemia. Concurrently, neurological deficit scores and cerebral infarct volumes were assessed. Based on a mathematic model, network balance maps and three integral disruption parameters (k, φ, and u) of the simplified crosstalk network were achieved.

Results

The levels or activities of the related biomarkers and neurological deficit scores were significantly impacted by cerebral ischemia. The balance maps intuitively displayed the network disruption, and the integral disruption parameters quantitatively depicted the disruption state of the simplified network after cerebral ischemia. The integral disruption parameter u values correlated significantly with neurological deficit scores and infarct volumes.

Conclusion

Our results indicate that the approach based on crosstalk network may provide a new promising way to integrally evaluate the outcome of cerebral ischemia.

Genetic variants of PTGS2, TXA2R and TXAS1 are associated with carotid plaque vulnerability, platelet activation and TXA2 levels in ischemic stroke patients

Eicosanoids may play a role in ischemic stroke. However, the associations of variants in cyclooxygenase (COX) pathway genes and interaction among these variants with carotid plaque vulnerability are not fully understood. In present study, twelve variants in COX pathway genes were examined using matrix-assisted laser desorption ionization time-of-flight mass spectrometry method in 396 patients with ischemic stroke and 291 controls. Platelet aggregation, platelet-leukocyte aggregates, and urine 11-dehydrothromboxane B2 (11-dTxB2) were also measured. According to the results of carotid high-resolution B-mode ultrasound, the patients were stratified into the following groups [i.e., non-carotid plaque and carotid plaque. The carotid plaque was further classified into subgroups of echolucent plaque (ELP) and echogenic plaque (EGP)]. Additionally, gene-gene interactions were analyzed to assess whether there was any interactive role for assessed variants in affecting carotid plaque vulnerability, platelet activation and 11-dTxB2 levels. There were no significant differences in the frequencies of genotypes of the twelve variants between patients and controls. Among 396 patients, 294 cases (74.2%) had carotid plaques (106 had ELP, 188 had EGP). Frequency of PTGS2 rs20417CC, TXAS1 rs2267679TT, TXAS1 rs41708TT, PTGIS rs5602CC, and TXA2R rs1131882TT genotype was significantly higher in patients with plaque compared with patients without plaque, or in patients with ELP compared with patients with EGP. 11-dTxB2 levels, platelet aggregation and platelet-leukocyte aggregates were significantly higher in patients with ELP compared with patients without plaque or with EGP. Multivariate logistic regression analysis revealed that PTGS2 rs20417CC, TXA2R rs1131882TT, and high-risk interaction among variants in PTGS2 rs20417, TXA2R rs1131882 and TXAS1 rs41708 were independently associated with the risk of ELP after adjusting for confounding variables. The variants in COX pathway genes and the high-risk interactions among variants in PTGS2 rs20417, TXA2R rs1131882 and TXAS1 rs41708 were associated with high 11-dTxB2 and platelet activation, and independently associated with the risk of carotid plaque vulnerability. These variants might be potential markers for plaque instability.

Associations of MDR1, TBXA2R, PLA2G7, and PEAR1 genetic polymorphisms with the platelet activity in Chinese ischemic stroke patients receiving aspirin therapy

AIM

Aspirin resistance has an incidence of 5%-65% in patients with ischemic stroke, who receive the standard dose of aspirin, but the platelet function is inadequately inhibited, thereby leading to thrombotic events. Numerous evidence shows that thromboxane A₂ receptor (TXA₂ receptor, encoded by TBXA2R), lipoprotein-associated phospholipase A₂ (Lp-PLA₂, encoded by PLA2G7) and platelet endothelial aggregation receptor-1 (PEAR1, encoded by PEAR1) are crucial in regulating platelet activation, and P-glycoprotein (P-gp, encoded by MDR1) influences the absorption of aspirin in the intestine. In this study we examined the correlation between MDR1, TBXA2R, PLA2G7, PEAR1 genetic polymorphisms and platelet activity in Chinese ischemic stroke patients receiving aspirin therapy.

METHODS

A total of 283 ischemic stroke patients receiving 100 mg aspirin for 7 d were genotyped for polymorphisms in MDR1 C3435T, TBXA2R (rs1131882), PLA2G7 (rs1051931, rs7756935), and PEAR1 (rs12566888, rs12041331). The platelet aggregation response was measured using an automatic platelet aggregation analyzer and a commercially available TXB₂ ELISA kit.

RESULTS

Thirty-three patients (11.66%) were insensitive to aspirin treatment. MDR1 3435TT genotype carriers, whose arachidonic acid (AA) or adenosine diphosphate (ADP)-induced platelet aggregation was lower than that of CC+CT genotype carriers, were less likely to suffer from aspirin resistance (odds ratio=0.421, 95% CI: 0.233-0.759). The TBXA2R rs1131882 CC genotype, which was found more frequently in the aspirin-insensitive group (81.8% vs 62.4%) than in the sensitive group, was identified as a risk factor for aspirin resistance (odds ratio=2.712, 95% CI: 1.080-6.810) with a higher level of AA-induced platelet aggregation. Due to the combined effects of PLA2G7 rs1051931 and rs7756935, carriers of the AA-CC haplotype had a higher level of ADP-induced platelet aggregation, and were at considerably higher risk of aspirin resistance than noncarriers (odds ratio=8.233, 95% CI: 1.590-42.638).

CONCLUSION

A considerable portion (11.66%) of Chinese ischemic stroke patients are insensitive to aspirin treatment, which may be correlated with the MDR1 C3435T, TBXA2R (rs1131882), and PLA2G7 (rs1051931-rs7756935) polymorphisms.

Thromboxane A2 receptor antagonist SQ29548 reduces ischemic stroke-induced microglia/macrophages activation and enrichment, and ameliorates brain injury

Thromboxane A2 receptor (TXA2R) activation is thought to be involved in thrombosis/hemostasis and inflammation responses. We have previously shown that TXA2R antagonist SQ29548 attenuates BV2 microglia activation by suppression of ERK pathway, but its effect is not tested in vivo. The present study aims to explore the role of TXA2R on microglia/macrophages activation after ischemia/reperfusion brain injury in mice. Adult male ICR mice underwent 90-min transient middle cerebral artery occlusion (tMCAO). Immediately and 24 h after reperfusion, SQ29548 was administered twice to the ipsilateral ventricle (10 μl, 2.6 μmol/ml, per dose). Cerebral infarction volume, inflammatory cytokines release and microglia/macrophages activation were measured using the cresyl violet method, quantitative polymerase chain reaction (qPCR), and immunofluorescence double staining, respectively. Expression of TXA2R was significantly increased in the ipsilateral brain tissue after ischemia/reperfusion, which was also found to co-localize with activated microglia/macrophages in the infarct area. Administration of SQ29548 inhibited microglia/macrophages activation and enrichment, including both M1 and M2 phenotypes, and attenuated ischemia-induced IL-1ß, IL-6, and TNF-α up-regulation and iNOS release. TXA2R antagonist SQ29548 inhibited ischemia-induced inflammatory response and furthermore reduced microglia/macrophages activation and ischemic/reperfusion brain injury.

Pharmacogenomics of Prostaglandin and Leukotriene Receptors

Individual genetic background together with environmental effects are thought to be behind many human complex diseases. A number of genetic variants, mainly single nucleotide polymorphisms (SNPs), have been shown to be associated with various pathological and inflammatory conditions, representing potential therapeutic targets. Prostaglandins (PTGs) and leukotrienes (LTs) are eicosanoids derived from arachidonic acid and related polyunsaturated fatty acids that participate in both normal homeostasis and inflammatory conditions. These bioactive lipid mediators are synthesized through two major multistep enzymatic pathways: PTGs by cyclooxygenase and LTs by 5-lipoxygenase. The main physiological effects of PTGs include vasodilation and vascular leakage (PTGE2); mast cell maturation, eosinophil recruitment, and allergic responses (PTGD2); vascular and respiratory smooth muscle contraction (PTGF2), and inhibition of platelet aggregation (PTGI2). LTB4 is mainly involved in neutrophil recruitment, vascular leakage, and epithelial barrier function, whereas cysteinyl LTs (CysLTs) (LTC4, LTD4, and LTE4) induce bronchoconstriction and neutrophil extravasation, and also participate in vascular leakage. PTGs and LTs exert their biological functions by binding to cognate receptors, which belong to the seven transmembrane, G protein-coupled receptor superfamily. SNPs in genes encoding these receptors may influence their functionality and have a role in disease susceptibility and drug treatment response. In this review we summarize SNPs in PTGs and LTs receptors and their relevance in human diseases. We also provide information on gene expression. Finally, we speculate on future directions for this topic.

A brief review on the mechanisms of aspirin resistance

Aspirin is the most widely prescribed drug for the primary and secondary prevention of cardiovascular and cerebrovascular diseases. However, a large number of patients continue to experience thromboembolic events despite aspirin therapy, a phenomenon referred to as aspirin resistance or treatment failure. Aspirin resistance is often observed along with a high incidence of unstable plaque, cardiovascular events and cerebrovascular accident. Studies have shown that aspirin reduces the production of TXA2, but not totally inhibits the activation of platelets. In this review, we analyze current and past research on aspirin resistance, presenting important summaries of results regarding the potential contributive roles of single nucleotide polymorphisms, inflammation, metabolic syndrome and miRNAs. The aim of this article is to provide a brief review on aspirin resistance and platelet function, which will provide important insights into the research of aspirin resistance.

Common genetic variants in platelet surface receptors and its association with ischemic stroke

Ischemic stroke has been named one of the leading causes of death worldwide. Whereas numerous biological mechanisms and molecules were found to be associated with stroke, platelets are particularly contributive to its pathogenesis. Recent data indicate considerable variability in platelet phenotype which accounts for differences in platelet surface receptor function, count and reactivity. These features collectively influence both the events leading to a disease and effectiveness of antiplatelet therapies. Consequently, genetic variants predisposing to cerebrovascular diseases can be sequenced using a wide array of techniques and become a useful tool in clinical setting. In this review, we provide an outline of common platelet polymorphisms that impose risk on ischemic stroke development and should be evaluated as targets to improve treatment. As study results are often inconsistent, partly due to differences in demographic characteristics between study populations and the fact that the functional impact of these variants has been relatively small, we conclude that both rare, low-frequency and common variants might account for genetic contribution on abnormal platelet response to antiplatelet drugs.

Thromboxane A2 Receptor Stimulation Enhances Microglial Interleukin-1β and NO Biosynthesis Mediated by the Activation of ERK Pathway

BACKGROUND AND PURPOSE

Thromboxane A2 (TXA2) receptors (TP) interact with the ligand TXA2 to induce platelet aggregation and regulate hemostasis. Recently TP-mediated signaling has been suggested to function in multiple cell types in the brain. In this report, we aim to study the expression and physiological role of TP in microglia, in particular after brain ischemia.

METHODS

Ischemic brain sections were analyzed for TP expression. Microglial cell line and primary microglia were cultured, or neuronal cell line co-culture system was used to determine the TP mediated signaling in inflammation and microglia activation.

RESULTS

We found that the TP level was significantly increased in ipsilateral mouse brain tissue at 24 h after ischemia-reperfusion, which was also found to partly co-localize with CD11b, a marker for microglial and infiltrated monocyte/macrophage, in peri-infarct area. Immunofluorescence staining of primary microglia and microglial cell line BV2 revealed the predominant membrane distribution of TP. Conditioned culture media from TP agonist U46619-treated BV2 cells decreased neuronal SH-SY5Y cell viability and induced apoptotic morphological changes. Furthermore, U46619 enhanced IL-1β, IL-6, and iNOS mRNA expression as well as IL-1β and NO releases in BV2 cells or primary microglia. Such stimulation could be attenuated by TP antagonist SQ29548 or MEK inhibitor U0126. The dose- and time-dependent extracellular-signal-regulated kinase (ERK) phosphorylation induced by U46619 further demonstrated ERK signaling-mediated microglia activation by TP agonist.

CONCLUSION

This study has shown a novel role of TP in microglia activation via the ERK signaling pathway, which provides insights for the management of neuroinflammation in diseases like cerebral infarction.