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The Controversial Role of LPS in Platelet Activation In Vitro. Int J Mol Sci 2022; 23:ijms231810900. [PMID: 36142813 PMCID: PMC9505944 DOI: 10.3390/ijms231810900] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 09/12/2022] [Accepted: 09/13/2022] [Indexed: 11/16/2022] Open
Abstract
Circulating platelets are responsible for hemostasis and thrombosis but are also primary sensors of pathogens and are involved in innate immunity, inflammation, and sepsis. Sepsis is commonly caused by an exaggerated immune response to bacterial, viral, and fungal infections, and leads to severe thrombotic complications. Among others, the endotoxin lipopolysaccharide (LPS) found in the outer membrane of Gram-negative bacteria is the most common trigger of sepsis. Since the discovery of the expression of the LPS receptor TLR4 in platelets, several studies have investigated the ability of LPS to induce platelet activation and to contribute to a prothrombotic phenotype, per se or in combination with plasma proteins and platelet agonists. This issue, however, is still controversial, as different sources, purity, and concentrations of LPS, different platelet-purification protocols, and different methods of analysis have been used in the past two decades, giving contradictory results. This review summarizes and critically analyzes past and recent publications about LPS-induced platelet activation in vitro. A methodological section illustrates the principal platelet preparation protocols and significant differences. The ability of various sources of LPS to elicit platelet activation in terms of aggregation, granule secretion, cytokine release, ROS production, and interaction with leukocytes and NET formation is discussed.
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Li RHL, Nguyen N, Tablin F. Canine platelets express functional Toll-like receptor-4: lipopolysaccharide-triggered platelet activation is dependent on adenosine diphosphate and thromboxane A2 in dogs. BMC Vet Res 2019; 15:245. [PMID: 31307465 PMCID: PMC6632210 DOI: 10.1186/s12917-019-1997-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 07/08/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Functional Toll-like receptor 4 (TLR4) has been characterized in human and murine platelets indicating that platelets play a role in inflammation and hemostasis during sepsis. It is unclear whether canine platelets could express functional TLR4 by responding to its ligand, lipopolysaccharide (LPS). We sought to determine if dogs express functional TLR4 and if LPS-induced platelet activation requires co-stimulation with ADP or thromboxane A2 (TxA2). Canine platelets were unstimulated (resting) or activated with thrombin or ADP prior to flow cytometric or microscopic analyses for TLR4 expression. We treated resting or ADP-primed platelets with LPS in the absence or presence of acetylsalicylic acid (ASA) and inhibited TLR4 with function blocking antibody or LPS from Rhodobacter sphaeroides (LPS-RS). RESULTS We discovered that dog platelets have variable TLR4 expression, which was upregulated following thrombin or ADP activation. LPS augmented P-selectin expression and thromboxane B2 secretion in ADP-primed platelets via TLR4. Inhibition of cyclooxygenase by ASA attenuated LPS-mediated P-selectin expression demonstrating that TLR4 signaling in platelets is partially dependent on TxA2 pathway. CONCLUSION Expression of functional TLR4 on canine platelets may contribute to hypercoagulability in clinical septic dogs. Cyclooxygenase and TxA2 pathways in TLR4-mediated platelet activation may present novel therapeutic targets in dogs with sepsis.
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Affiliation(s)
- Ronald H L Li
- Department of Veterinary Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, California, USA.
| | - Nghi Nguyen
- Department of Veterinary Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Fern Tablin
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, California, USA
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Liu T, Liu M, Zhang T, Liu W, Xu H, Mu F, Ren D, Jia N, Li Z, Ding Y, Wen A, Li Y. Z-Guggulsterone attenuates astrocytes-mediated neuroinflammation after ischemia by inhibiting toll-like receptor 4 pathway. J Neurochem 2018; 147:803-815. [PMID: 30168601 DOI: 10.1111/jnc.14583] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 08/11/2018] [Accepted: 08/24/2018] [Indexed: 02/05/2023]
Abstract
Inflammatory damage plays a pivotal role in ischemic stroke pathogenesis and may represent one of the therapeutic targets. Z-Guggulsterone (Z-GS), an active component derived from myrrh, has been used to treat various diseases. The traditional uses suggest that myrrh is a good candidate for anti-inflammatory damage. This study was to investigate the anti-inflammatory and neuroprotective effects of Z-GS following cerebral ischemic injury, as well as the exact mechanisms behind them. Rat middle cerebral artery occlusion (MCAO) model and in vitro astrocytes oxygen-glucose deprivation (OGD) model were adopted to simulate ischemic stroke. Z-GS (30 or 60 mg/kg) was administered intraperitoneally immediately after reperfusion, while astrocytes were maintained in 30 or 60 μM Z-GS before OGD treatment. The results indicated that Z-GS significantly alleviated neurological deficits, infarct volume and histopathological damage in vivo, and increased the astrocytes viability in vitro. Moreover, the treatment of Z-GS inhibited the astrocytes activation and down-regulated the mRNA levels of pro-inflammatory cytokines. Furthermore, the activated TLR4-NF-κB signaling pathways induced by MCAO or OGD were significantly suppressed by Z-GS treatment, which was achieved via inhibiting the phosphorylation of JNK. Our results demonstrated that Z-GS exerted neuroprotective and anti-inflammatory properties through preventing activation of TLR4-mediated pathway in the activated astrocytes after ischemia injury. Therefore, Z-GS could be considered as a promising candidate for the treatment of ischemic stroke.
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Affiliation(s)
- Tianlong Liu
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Minna Liu
- Department of Nephrology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Tiejun Zhang
- Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China
| | - Wenxing Liu
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Hang Xu
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Fei Mu
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Danjun Ren
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Na Jia
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Zhengjun Li
- Department of Dermatology, Qi Lu Hospital, Shandong University, Jinan, China
| | - Yi Ding
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Aidong Wen
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Yuwen Li
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, China.,Department of Pharmacy, The First Affiliated Hospital of SooChow University, Suzhou, China
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Toll-Like Receptor 4 Signalling and Its Impact on Platelet Function, Thrombosis, and Haemostasis. Mediators Inflamm 2017; 2017:9605894. [PMID: 29170605 PMCID: PMC5664350 DOI: 10.1155/2017/9605894] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 08/17/2017] [Accepted: 09/12/2017] [Indexed: 11/18/2022] Open
Abstract
Platelets are anucleated blood cells that participate in a wide range of physiological and pathological functions. Their major role is mediating haemostasis and thrombosis. In addition to these classic functions, platelets have emerged as important players in the innate immune system. In particular, they interact with leukocytes, secrete pro- and anti-inflammatory factors, and express a wide range of inflammatory receptors including Toll-like receptors (TLRs), for example, Toll-like receptor 4 (TLR4). TLR4, which is the most extensively studied TLR in nucleated cells, recognises lipopolysaccharides (LPS) that are compounds of the outer surface of Gram-negative bacteria. Unlike other TLRs, TLR4 is able to signal through both the MyD88-dependent and MyD88-independent signalling pathways. Notably, despite both pathways culminating in the activation of transcription factors, TLR4 has a prominent functional impact on platelet activity, haemostasis, and thrombosis. In this review, we summarise the current knowledge on TLR4 signalling in platelets, critically discuss its impact on platelet function, and highlight the open questions in this area.
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Tsai CS, Huang CY, Chen CH, Lin YW, Shih CM, Tsao NW, Chiang KH, Lee CY, Jeng H, Lin FY. Eotaxin-2 increased toll-like receptor 4 expression in endothelial cells in vitro and exacerbates high-cholesterol diet-induced atherogenesis in vivo. Am J Transl Res 2016; 8:5338-5353. [PMID: 28078007 PMCID: PMC5209487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 11/05/2016] [Indexed: 06/06/2023]
Abstract
Eotaxin-2 is a potent chemoattractant. High concentration of eotaxin-2 triggers the inflammation and tumor metastasis. Inhibition of eotaxin-2 may protect experimental atherogenesis although the mechanism is still unclear. Toll-like receptor 4 (TLR4) plays a major role mediating vascular inflammation, which is related to atherogenesis. In the results, we demonstrated that eotaxin-2 potentially impairs the tube formation capacity of human coronary artery endothelial cells (HCAECs). Eotaxin-2 augments the monocytic adhesion in lipopolysaccharides (LPS)-induced HCAECs, and which were reversed by TLR4 siRNA. Thus this study was conducted to investigate whether eotaxin-2 increases TLR4 expression, and then enhances the sensitivity of cells to antigen stimulation in HCAECs, which mediates the increasing of the development of serious atherosclerosis. In fact, we showed that JNK/SAPK, p38 MAPK, and ERK1/2 activation contribute to the transcriptional signaling pathway, JNK/SAPK and p38 MAPK regulate post-transcriptional modification, as well as protein-trafficking pathway in eotaxin-2-treated HCAECs TLR4 expression. RNA binding proteins, such as human antigen R (HuR) and tristetraprolin (TTP) mediate stability of TLR4 mRNA and chaperone, such as PRAT4A (a protein associated with TLR4) regulate trafficking of TLR4 protein might confer eotaxin-2 responsiveness. Eotaxin-2 administration led to a significant elevation of high cholesterol diet-induced atherosclerosis, and of TLR4 expression in B6.129S7-Ldlrtm1Her /J but not Ldlr-/--/-/Tlr4-/- mice. Our results revealed that eotaxin-2 induced overexpression TLR4 via mitogen-activated protein kinases (MAPK) signaling pathways, RNA binding proteins-mediated mRNA stabilization, and PRAT4A-regulated trafficking in HCAECs. These effects may lead to amplification of inflammatory responses contribute to the pathogenesis of cardiovascular disorders.
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Affiliation(s)
- Chien-Sung Tsai
- Division of Cardiovascular Surgery, Department of Surgery, Taoyuan Armed Forces General HospitalTaoyuan, Taiwan
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General HospitalTaipei, Taiwan
- Department and Graduate Institute of Pharmacology, National Defense Medical CenterTaipei, Taiwan
| | - Chun-Yao Huang
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical UniversityTaipei, Taiwan
- Division of Cardiology and Cardiovascular Research Center, Department of Internal Medicine, Taipei Medical University HospitalTaipei, Taiwan
| | - Chien-Ho Chen
- School of Medical Laboratory Science and Biotechnology Taipei Medical UniversityTaipei, Taiwan
| | - Yi-Wen Lin
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General HospitalTaipei, Taiwan
- Institute of Oral Biology, National Yang-Ming UniversityTaipei, Taiwan
| | - Chun-Ming Shih
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical UniversityTaipei, Taiwan
- Division of Cardiology and Cardiovascular Research Center, Department of Internal Medicine, Taipei Medical University HospitalTaipei, Taiwan
| | - Nai-Wen Tsao
- Division of Cardiovascular Surgery, Taipei Medical University HospitalTaipei, Taiwan
| | - Kuang-Hsing Chiang
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical UniversityTaipei, Taiwan
- Division of Cardiology and Cardiovascular Research Center, Department of Internal Medicine, Taipei Medical University HospitalTaipei, Taiwan
| | - Chi-Yuan Lee
- Graduate Institute of Clinical Medical Sciences, China Medical UniversityTaichung, Taiwan
| | - Hellen Jeng
- Division of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical UniversityTaipei, Taiwan
| | - Feng-Yen Lin
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical UniversityTaipei, Taiwan
- Division of Cardiology and Cardiovascular Research Center, Department of Internal Medicine, Taipei Medical University HospitalTaipei, Taiwan
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