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Matos ADO, Dantas PHDS, Queiroz HAGDB, Silva-Sales M, Sales-Campos H. TREM-2: friend or foe in infectious diseases? Crit Rev Microbiol 2024; 50:1-19. [PMID: 36403150 DOI: 10.1080/1040841x.2022.2146481] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 11/07/2022] [Indexed: 11/21/2022]
Abstract
The triggering receptor expressed on myeloid cells-2 (TREM-2) is an immune receptor expressed on immune and non-immune cells, more frequently investigated in neurodegenerative disorders and considered a marker for microglia activation. In infectious diseases, the receptor was initially believed to be an anti-inflammatory molecule, opposing the inflammation triggered by TREM-1. Currently, TREM-2 is associated with different aspects in response to infectious stimuli, including the induction of bacterial phagocytosis and clearance, containment of exacerbated pro-inflammatory responses, induction of M2 differentiation and activation of Th1 lymphocytes, besides of neurological damage after viral infection. Here, we present and discuss results published in the last two decades regarding the expression, activation and functions of TREM-2 during the course of bacterial, viral, fungal and parasitic infections. A surprisingly plasticity was observed regarding the roles of the receptor in the aforementioned contexts, which largely varied according to the cell/organ and pathogen type, besides influencing disease outcome. Therefore, our review aimed to critically overview the role of TREM-2 in infectious diseases, highlighting its potential to be used as a clinical biomarker or therapeutic target.
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Affiliation(s)
| | | | | | - Marcelle Silva-Sales
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Brazil
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Chen SL, Li XP, Gao L, Che YM, Zhang LL, Cheng XY. [Significance of triggering receptor expressed on myeloid cells-2 prognostic evaluation in hepatitis B virus-related acute-on-chronic liver failure]. Zhonghua Gan Zang Bing Za Zhi 2023; 31:1306-1312. [PMID: 38253075 DOI: 10.3760/cma.j.cn501113-20230214-00056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Objective: To explore the significance of triggering receptor expressed on myeloid cells-2 (TREM-2) prognostic evaluation so as to provide novel biological markers in clinical practice for patients with hepatitis B virus-related acute-on-chronic liver failure ( HBV-ACLF). Methods: The research subjects of this study were divided into an experimental group and a control group. Fifty HBV-ACLF cases admitted to the Department of Infectious Diseases of the First Affiliated Hospital of Nanchang University from January 1, 2019 to December 31, 2019 were selected as the experimental group. Patients were divided into survival and death groups according to the actual prognosis at discharge (self-discharge and dead patients were considered death groups, and all enrolled patients were hospitalized for more than 28 days). Twenty-five healthy subjects were chosen as the control group. Peripheral venous blood was collected from the experimental group and the control group. Plasma and peripheral blood mononuclear cells (PBMC) were isolated. The concentrations of TREM-2, interleukin (IL)-6, and IL-8 were detected in the plasma. TREM-2 mRNA expression was detected in PBMC. A single blood sample was collected from the control group, whereas five blood samples were dynamically collected from the experimental group on the day of admittance and at 7, 14, 21, and 28 days after treatment commenced. Simultaneously, upon admission, the relevant clinical indicators of HBV-ACLF patients were monitored, including the liver function test: alanine aminotransferase, aspartate aminotransferase, total bilirubin, albumin, coagulation function test: international normalized ratio, prothrombin time, and other indicators. Measurement data were expressed as mean±standard deviation (x±s). Count data were compared and analyzed using the χ(2) test. The intra-group factor mean was compared using a repeated measures ANOVA. The means were analyzed by t-tests between the two groups. Bivariate correlation analysis was used to analyze the correlation between the two variables. The value of TREM-2 as a diagnostic marker was analyzed using the receiver operating characteristic (ROC) curve. Results: The mRNA expression of TREM-2 in the PBMC of HBV-ACLF patients showed a gradually increasing trend at various time points and was significantly higher in the survival group than that of the control group at 28 days (P < 0.01), while the death group showed a gradually weakening trend at various time points and was significantly lower than the control group at 28 days (P < 0.01). (1) The levels of TREM-2 in the plasma of HBV-ACLF patients generally showed a gradually increasing trend at various time points in the survival group. The levels on the day of admission and 7, 14, 21, and 28 days after the initiation of treatment were (1.49±0.85), (1.62±0.58), (1.95±0.69), (2.33±0.71), and (2.00±0.67) ng/ml, respectively. The expression of TREM-2 in the death group showed a gradually weakening trend at various time points. The levels on the day of admission and 7, 14, 21, and 28 days after initiation of treatment were (1.40±0.73), (1.59±0.79), (1.56±0.80), (1.05±0.49), and (0.81±0.21) ng/ml, respectively. The survival group's various detection time points were higher than those of the death group, and the difference was statistically significant. The plasma level of TREM-2 in the healthy control group was (1.25±0.35) ng/ml. (2) The concentrations of IL-6 and IL-8 in the plasma of HBV-ACLF patients showed a gradually decreasing trend at various time points in the survival group. The levels on the day of admission and 7, 14, 21, and 28 days after initiation of treatment were (46.70±26.31), (33.98±20.28), (19.07±10.24), (14.76±7.84), (9.12±7.65) and (108.29±47.07), (93.85±26.53), (79.27±34.63), (56.72 ±18.30), (37.81±13.88) pg/ml, respectively. However, its concentration in the death group fluctuated within a relatively high range. The levels on the day of admission and 7, 14, 21, and 28 days after the initiation of treatment were (41.94±24.19), (36.99±19.78), (34.30±20.62), (34.14±14.52), (36.64±23.61) and (104.65±50.16), (112.98±45.03), (118.43±45.00), (111.67±40.44), (109.55±27.54) pg/ml, respectively. (3) Bivariate correlation analysis results indicated that the plasma TREM-2 content was negatively correlated with the plasma levels of pro-inflammatory cytokines IL-6 and IL-8 (r = -0.224, P = 0.025; r = - 0.223, P = 0.026). ROC curve analysis showed that the mRNA levels of TREM-2 in PBMCs at various time points for prognostic evaluation of HBV-ACLF patients were 1d=0.667, 7d=0.757, 14d=0.979, 21d=0.986, and 28d= 0.993. The areas under the ROC curve of the TREM-2 content in the plasma at various time points were 1d=0.522, 7d=0.571, 14d=0.658, 21d=0.927, and 28d=0.994. Conclusion: TREM-2 mRNA expression in PBMC and TREM-2 content in plasma have a significant relationship to the prognosis of HBV-ACLF patients and may inhibit the liver inflammatory response by regulating the secretion of pro-inflammatory cytokines IL-6 and IL-8. Dynamic monitoring of TREM-2 expression in peripheral blood is favorable for evaluating the prognostic condition of HBV-ACLF patients.
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Affiliation(s)
- S L Chen
- Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital of Nanchang University, Nanchang 330006, China Department of Gastroenteroloy, the Seventh Affiliated Hospital of Guangxi Medical University(Wuzhou Gongren Hospital), Wuzhou 543001, China
| | - X P Li
- The First Afliated Hospital Key Laboratory of Liver Regenerative Medicine of Jiangxi Province, Nanchang 330006, China
| | - L Gao
- Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital of Nanchang University, Nanchang 330006, China
| | - Y M Che
- Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital of Nanchang University, Nanchang 330006, China
| | - L L Zhang
- Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital of Nanchang University, Nanchang 330006, China
| | - X Y Cheng
- Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital of Nanchang University, Nanchang 330006, China
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Fan R, Cheng Z, Huang Z, Yang Y, Sun N, Hu B, Hou P, Liu B, Huang C, Liu S. TREM-1, TREM-2 and their association with disease severity in patients with COVID-19. Ann Med 2023; 55:2269558. [PMID: 37848000 PMCID: PMC10583614 DOI: 10.1080/07853890.2023.2269558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 09/28/2023] [Indexed: 10/19/2023] Open
Abstract
BACKGROUND Delayed diagnosis and inadequate treatment caused by limited biomarkers are associated with the outcomes of COVID-19 patients. It is necessary to identify other promising biomarkers and candidate targets for defining dysregulated inflammatory states. METHODS The triggering receptors expressed on myeloid cell (TREM)-1 and TREM-2 expression from hospitalized COVID-19 patients were characterized using ELISA and flow cytometry, respectively. Their correlation with disease severity and contrast with the main clinical indicators were evaluated. RESULTS Increased expression of soluble TREM-1 and TREM-2 in the plasma of COVID-19 patients was found compared to the control group. Moreover, membrane-bound TREM-1 and TREM-2 expression was upregulated on the cell surface of circulating blood T cells from COVID-19 patients. Correlation analysis showed that sTREM-2 levels were negatively correlated with PaO2/FiO2, but positively correlated with C-reactive protein (CRP), procalcitonin (PCT) and interleukin (IL)-6 levels. Receiver operating characteristic curve analysis indicated that the predictive efficacy of sTREM-1 and sTREM-2 was equivalent to CRP and IL-6, and a little better than absolute leukocyte or neutrophil count and PCT in distinguishing disease severity. CONCLUSION TREM-2 and TREM-1 are critical host immune factors that response to SARS-COV-2 infection and could serve as potential diagnostic biomarkers and therapeutic targets for COVID-19.
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Affiliation(s)
- Ruyue Fan
- Shandong Center for Disease Control and Prevention, Jinan, China
| | - Zuowang Cheng
- Department of Clinical Laboratory, Zhangqiu District People’s Hospital Affiliated to Jining Medical University, Jinan, China
| | - Zhisheng Huang
- Department of Pulmonary and Critical Care Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China
- Department of Pulmonary and Critical Care Medicine, National Regional Center for Respiratory Medicine, Jiangxi Hospital of China-Japan Friendship Hospital, Nanchang, China
| | - Ying Yang
- Shandong Center for Disease Control and Prevention, Jinan, China
| | - Na Sun
- Shandong Center for Disease Control and Prevention, Jinan, China
| | - Bin Hu
- Shandong Center for Disease Control and Prevention, Jinan, China
| | - Peibin Hou
- Shandong Center for Disease Control and Prevention, Jinan, China
| | - Bo Liu
- Department of Pulmonary and Critical Care Medicine, Zibo Municipal Hospital, Zibo, China
| | - Chuanjun Huang
- Department of Respiratory and Critical Care Medicine, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Shuai Liu
- Department of Respiratory and Critical Care Medicine, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
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Wu K, Liu YY, Shao S, Song W, Chen XH, Dong YT, Zhang YM. The microglial innate immune receptors TREM-1 and TREM-2 in the anterior cingulate cortex (ACC) drive visceral hypersensitivity and depressive-like behaviors following DSS-induced colitis. Brain Behav Immun 2023:S0889-1591(23)00141-1. [PMID: 37286175 DOI: 10.1016/j.bbi.2023.06.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 05/15/2023] [Accepted: 06/03/2023] [Indexed: 06/09/2023] Open
Abstract
Inflammatory bowel disease (IBD) is a chronic condition with a high recurrence rate. To date, the clinical treatment of IBD mainly focuses on inflammation and gastrointestinal symptoms while ignoring the accompanying visceral pain, anxiety, depression, and other emotional symptoms. Evidence is accumulating that bi-directional communication between the gut and the brain is indispensable in the pathophysiology of IBD and its comorbidities. Increasing efforts have been focused on elucidating the central immune mechanisms in visceral hypersensitivity and depression following colitis. The triggering receptors expressed on myeloid cells-1/2 (TREM-1/2) are newly identified receptors that can be expressed on microglia. In particular, TREM-1 acts as an immune and inflammatory response amplifier, while TREM-2 may function as a molecule with a putative antagonist role to TREM-1. In the present study, using the dextran sulfate sodium (DSS)-induced colitis model, we found that peripheral inflammation induced microglial and glutamatergic neuronal activation in the anterior cingulate cortex (ACC). Microglial ablation mitigated visceral hypersensitivity in the inflammation phase rather than in the remission phase, subsequently preventing the emergence of depressive-like behaviors in the remission phase. Moreover, a further mechanistic study revealed that overexpression of TREM-1 and TREM-2 remarkably aggravated DSS-induced neuropathology. The improved outcome was achieved by modifying the balance of TREM-1 and TREM-2 via genetic and pharmacological means. Specifically, a deficiency of TREM-1 attenuated visceral hyperpathia in the inflammatory phase, and a TREM-2 deficiency improved depression-like symptoms in the remission phase. Taken together, our findings provide insights into mechanism-based therapy for inflammatory disorders and establish that microglial innate immune receptors TREM-1 and TREM-2 may represent a therapeutic target for the treatment of pain and psychological comorbidities associated with chronic inflammatory diseases by modulating neuroinflammatory responses.
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Affiliation(s)
- Ke Wu
- NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, China
| | - Yue-Ying Liu
- NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, China
| | - Shuai Shao
- NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, China
| | - Wei Song
- NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, China
| | - Xing-Han Chen
- NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, China
| | - Yu-Ting Dong
- NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, China
| | - Yong-Mei Zhang
- NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, China.
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Kumar P, Mishra J, Kumar N. Mechanistic Role of Jak3 in Obesity-Associated Cognitive Impairments. Nutrients 2022; 14:nu14183715. [PMID: 36145091 PMCID: PMC9505565 DOI: 10.3390/nu14183715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 11/16/2022] Open
Abstract
Background and Aims: A compromise in intestinal mucosal functions is associated with several chronic inflammatory diseases. Previously, we reported that obese humans have a reduced expression of intestinal Janus kinase-3 (Jak3), a non-receptor tyrosine kinase, and a deficiency of Jak3 in mice led to predisposition to obesity-associated metabolic syndrome. Since meta-analyses show cognitive impairment as co-morbidity of obesity, the present study demonstrates the mechanistic role of Jak3 in obesity associated cognitive impairment. Our data show that high-fat diet (HFD) suppresses Jak3 expression both in intestinal mucosa and in the brain of wild-type mice. Methodology: Recapitulating these conditions using global (Jak3-KO) and intestinal epithelial cell-specific conditional (IEC-Jak3-KO) mice and using cognitive testing, western analysis, flow cytometry, immunofluorescence microscopy and 16s rRNA sequencing, we demonstrate that HFD-induced Jak3 deficiency is responsible for cognitive impairments in mice, and these are, in part, specifically due to intestinal epithelial deficiency of Jak3. Results: We reveal that Jak3 deficiency leads to gut dysbiosis, compromised TREM-2-functions-mediated activation of microglial cells, increased TLR-4 expression and HIF1-α-mediated inflammation in the brain. Together, these lead to compromised microglial-functions-mediated increased deposition of β-amyloid (Aβ) and hyperphosphorylated Tau (pTau), which are responsible for cognitive impairments. Collectively, these data illustrate how the drivers of obesity promote cognitive impairment and demonstrate the underlying mechanism where HFD-mediated impact on IEC-Jak3 deficiency is responsible for Jak3 deficiency in the brain, reduced microglial TREM2 expression, microglial activation and compromised clearance of Aβ and pTau as the mechanism during obesity-associated cognitive impairments. Conclusion: Thus, we not only demonstrate the mechanism of obesity-associated cognitive impairments but also characterize the tissue-specific role of Jak3 in such conditions through mucosal tolerance, gut–brain axis and regulation of microglial functions.
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Abstract
BACKGROUND The non-invasive identification of novel renal fibrosis biomarkers needs to be further studied. METHODS We collected urine samples from 77 biopsy-proven CKD patients and 15 healthy controls. The expression of urinary TREM-1 and TREM-2 was measured and the correlation with renal function parameter and pathological indicators was performed. The receiver operating characteristic (ROC) curve for the diagnosis of renal fibrosis was calculated. The protein expression of TREM-1 and TREM-2 in kidney tissues was measured. RESULTS The TREM-1/TREM-2 ratio was decreased in CKD patients and correlated with serum creatinine, estimated glomerular filtration rate and cystatin c. Further, the TREM-1/TREM-2 ratio was significantly decreased in moderate-severe fibrosis patients compared with none-mild renal fibrosis. TREM-1/TREM-2 ratio was correlated with the score of tubulointerstitial fibrosis (TIF) and the score of glomerular sclerosis. The ROC curve showed that the urinary TREM-1/TREM-2 ratio can diagnosemoderate-severe renal fibrosis at a cut-off value of 1.338 with a sensitivity of 86.4% and specificity of 81.8%. In human moderate-severe fibrosis kidney tissue, the protein expression of TREM-1 was lower and the TREM-2 was higher than none-mild fibrosis kidney tissue. CONCLUSION Urinary TREM-1/TREM-2 ratio was a potential biomarker for the diagnosis of renal fibrosis in CKD patients.
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Affiliation(s)
- Yuhan Cao
- Department of Nephrology, Yi Ji Shan Hospital Affiliated to Wan Nan Medical College, China.,Key Laboratory of Non-coding RNA Transformation Research of Anhui Higher Education Institution (Wann Nan Medical College), China
| | - Yuwei Wang
- Department of Nephrology, Yi Ji Shan Hospital Affiliated to Wan Nan Medical College, China
| | - Nana Peng
- School of Clinical Medicine, Wan Nan Medical College, China
| | - Jie Xiao
- School of Anesthesiology, Wan Nan Medical College, China
| | - Sufen Wang
- Department of Pathology, Yi Ji Shan hospital affiliated to Wan Nan Medical College, China
| | - Cong Fu
- Key Laboratory of Non-coding RNA Transformation Research of Anhui Higher Education Institution (Wann Nan Medical College), China.,Department of Cardiology, Yi Ji Shan hospital affiliated to Wan Nan Medical College, China
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Pei QG, Wang HC, Li L, Wang ZL. Triggering Receptor Expressed On Myeloid cells-2 Stimulates Osteoclast Differentiation and Bone Loss in Periodontitis. Oral Dis 2021; 28:1652-1661. [PMID: 34387017 DOI: 10.1111/odi.14004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 06/09/2021] [Accepted: 08/03/2021] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To investigate the expression of triggering receptor expressed on myeloid cells 2 (TREM-2) in the healthy and diseased tissue, including gingivitis or periodontitis, and then to assess if it has an impact on the development of periodontitis. METHODS AND MATERIALS The gingival tissues from healthy controls, gingivitis and periodontitis underwent haematoxylin-eosin and immunohistochemical staining, and the association of TREM-2 expression or TREM-2+ cell counts with clinical parameters was assessed. An anti-TREM-2 antibody was used to block the osteoclastogenesis in vitro and during the experimental periodontitis by injection into the gingiva. The relative gene expression of TREM-2 in different gingival tissues was analysed by quantitative PCR. RESULTS In the gingival tissues of periodontitis, TREM-2 expression and TREM-2+ cell counts were significantly higher than those of gingivitis and healthy controls (P<0.05). In the group of periodontitis showing moderate signs, the gingival tissues displayed significantly lower TREM-2 expression, in contrast with the group with advanced periodontal symptoms (P<0.05). Consistently, blocking TREM-2 significantly decreased osteoclast formation both in vitro and in vivo (P<0.05). CONCLUSION Increased TREM-2 expression and TREM-2+ cells were positively associated with the development of periodontitis. Osteoclast differentiation and stimulating alveolar bone loss were partly relied on TREM-2, which could be a target to be blocked for attenuating osteoclastogenesis in periodontitits.
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Affiliation(s)
- Qing-Guo Pei
- Department of Oral Implant, School & Hospital of Stomatology, Tongji University, Shanghai Engineering Research Centre of Tooth Restoration and Regeneration, 399 Yanchang Road, Shanghai, 200072, China
| | - Hai-Cheng Wang
- Department of Pathology, School & Hospital of Stomatology, Tongji University, Shanghai Engineering Research Center of Tooth Restoration and Regeneration, Shanghai, 200072, China
| | - Lin Li
- Department of Endodontics, School & Hospital of Stomatology, Tongji University, Shanghai Engineering Research Centre of Tooth Restoration and Regeneration, 399 Middle Yanchang Road, Shanghai, 200072, China
| | - Zuo-Lin Wang
- Department of Oral Implant, School & Hospital of Stomatology, Tongji University, Shanghai Engineering Research Centre of Tooth Restoration and Regeneration, 399 Yanchang Road, Shanghai, 200072, China
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Abstract
Macrophages are key multi-talented cells of the innate immune system and are equipped with receptors involved in damage and pathogen recognition with connected immune response guiding signaling systems. In addition, macrophages have various systems that are involved in the uptake of extracellular and intracellular cargo. The lysosomes in macrophages play a central role in the digestion of all sorts of macromolecules and the entry of nutrients to the cytosol, and, thus, the regulation of endocytic processes and autophagy. Simplistically viewed, two macrophage phenotype extremes exist. On one end of the spectrum, the classically activated pro-inflammatory M1 cells are present, and, on the other end, alternatively activated anti-inflammatory M2 cells. A unique macrophage population arises when lipid accumulation occurs, either caused by flaws in the catabolic machinery, which is observed in lysosomal storage disorders, or as a result of an acquired condition, which is found in multiple sclerosis, obesity, and cardiovascular disease. The accompanying overload causes a unique metabolic activation phenotype, which is discussed here, and, consequently, a unifying phenotype is proposed.
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Bandow K, Hasegawa H, Tomomura M, Tomomura A. Caldecrin inhibits lipopolysaccharide-induced pro-inflammatory cytokines and M1 macrophage polarization through the immunoreceptor triggering receptor expressed in myeloid cells-2. Biochem Biophys Res Commun 2020; 523:1027-1033. [PMID: 31973822 DOI: 10.1016/j.bbrc.2020.01.045] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 01/08/2020] [Indexed: 12/14/2022]
Abstract
Caldecrin was previously isolated as a serum calcium-decreasing factor from the pancreas and is known to suppress receptor activator of nuclear factor-κB ligand (RANKL)-induced calcium oscillation pathways in osteoclasts. Here, we explored the effects of caldecrin on lipopolysaccharide (LPS)-Toll-like receptor-4 (TLR-4) signaling pathways in macrophages. Caldecrin inhibited the LPS-induced gene expression of pro-inflammatory cytokines and M1 macrophage polarization in mouse bone marrow macrophages and the RAW264.7 mouse macrophage cell line. Next, we focused on triggering receptor expressed in myeloid cells-2 (TREM-2) as a co-receptor common to RANKL receptor and TLR-4, and established Trem2-KO RAW264.7 cells, in which Trem2 gene was deleted using the CRISPR/Cas9 system. Caldecrin-mediated alterations in pro-inflammatory cytokine expression and M1 macrophage polarization were not observed in Trem2-KO RAW264.7 cells. These results suggest that caldecrin is not only an inhibitor of osteoclast activation but also a negative regulator of LPS-induced inflammatory responses, functioning via TREM-2.
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Affiliation(s)
- Kenjiro Bandow
- Division of Biochemistry, Department of Oral Biology and Tissue Engineering, 1-1 Keyakidai, Sakado, Saitama, 350-0283, Japan
| | - Hiroya Hasegawa
- Division of Orthodontics, Department of Human Development and Fostering, Meikai University School of Dentistry, 1-1 Keyakidai, Sakado, Saitama, 350-0283, Japan
| | - Mineko Tomomura
- Division of Biochemistry, Department of Oral Biology and Tissue Engineering, 1-1 Keyakidai, Sakado, Saitama, 350-0283, Japan; Department of Oral Health Sciences, Meikai University School of Health Sciences, 1 Akemi, Urayasu, Chiba, 279-8550, Japan
| | - Akito Tomomura
- Division of Biochemistry, Department of Oral Biology and Tissue Engineering, 1-1 Keyakidai, Sakado, Saitama, 350-0283, Japan.
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Natale G, Biagioni F, Busceti CL, Gambardella S, Limanaqi F, Fornai F. TREM Receptors Connecting Bowel Inflammation to Neurodegenerative Disorders. Cells 2019; 8:E1124. [PMID: 31546668 DOI: 10.3390/cells8101124] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 09/16/2019] [Accepted: 09/21/2019] [Indexed: 02/07/2023] Open
Abstract
Alterations in Triggering Receptors Expressed on Myeloid cells (TREM-1/2) are bound to a variety of infectious, sterile inflammatory, and degenerative conditions, ranging from inflammatory bowel disease (IBD) to neurodegenerative disorders. TREMs are emerging as key players in pivotal mechanisms often concurring in IBD and neurodegeneration, namely microbiota dysbiosis, leaky gut, and inflammation. In conditions of dysbiosis, compounds released by intestinal bacteria activate TREMs on macrophages, leading to an exuberant pro-inflammatory reaction up to damage in the gut barrier. In turn, TREM-positive activated macrophages along with inflammatory mediators may reach the brain through the blood, glymphatic system, circumventricular organs, or the vagus nerve via the microbiota-gut-brain axis. This leads to a systemic inflammatory response which, in turn, impairs the blood-brain barrier, while promoting further TREM-dependent neuroinflammation and, ultimately, neural injury. Nonetheless, controversial results still exist on the role of TREM-2 compared with TREM-1, depending on disease specificity, stage, and degree of inflammation. Therefore, the present review aimed to provide an update on the role of TREMs in the pathophysiology of IBD and neurodegeneration. The evidence here discussed the highlights of the potential role of TREMs, especially TREM-1, in bridging inflammatory processes in intestinal and neurodegenerative disorders.
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Hasselmann J, Coburn MA, England W, Figueroa Velez DX, Kiani Shabestari S, Tu CH, McQuade A, Kolahdouzan M, Echeverria K, Claes C, Nakayama T, Azevedo R, Coufal NG, Han CZ, Cummings BJ, Davtyan H, Glass CK, Healy LM, Gandhi SP, Spitale RC, Blurton-Jones M. Development of a Chimeric Model to Study and Manipulate Human Microglia In Vivo. Neuron 2019; 103:1016-1033.e10. [PMID: 31375314 DOI: 10.1016/j.neuron.2019.07.002] [Citation(s) in RCA: 179] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 06/10/2019] [Accepted: 06/28/2019] [Indexed: 12/19/2022]
Abstract
iPSC-derived microglia offer a powerful tool to study microglial homeostasis and disease-associated inflammatory responses. Yet, microglia are highly sensitive to their environment, exhibiting transcriptomic deficiencies when kept in isolation from the brain. Furthermore, species-specific genetic variations demonstrate that rodent microglia fail to fully recapitulate the human condition. To address this, we developed an approach to study human microglia within a surrogate brain environment. Transplantation of iPSC-derived hematopoietic-progenitors into the postnatal brain of humanized, immune-deficient mice results in context-dependent differentiation into microglia and other CNS macrophages, acquisition of an ex vivo human microglial gene signature, and responsiveness to both acute and chronic insults. Most notably, transplanted microglia exhibit robust transcriptional responses to Aβ-plaques that only partially overlap with that of murine microglia, revealing new, human-specific Aβ-responsive genes. We therefore have demonstrated that this chimeric model provides a powerful new system to examine the in vivo function of patient-derived and genetically modified microglia.
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Affiliation(s)
- Jonathan Hasselmann
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA; Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA 92696, USA
| | - Morgan A Coburn
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA; Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA 92696, USA
| | - Whitney England
- Department of Pharmaceutical Sciences, University of California, Irvine, Irvine, CA 92697, USA
| | - Dario X Figueroa Velez
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA
| | - Sepideh Kiani Shabestari
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA
| | - Christina H Tu
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA
| | - Amanda McQuade
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA; Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA 92696, USA
| | - Mahshad Kolahdouzan
- Neuroimmunology Unit, Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC H3A 2B4, Canada
| | - Karla Echeverria
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA
| | - Christel Claes
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA
| | - Taylor Nakayama
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA
| | - Ricardo Azevedo
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA
| | - Nicole G Coufal
- Department of Pediatrics, University of California, San Diego, San Diego, CA 92093, USA
| | - Claudia Z Han
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, CA 92093, USA
| | - Brian J Cummings
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA
| | - Hayk Davtyan
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA; Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA 92696, USA
| | - Christopher K Glass
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, CA 92093, USA; Department of Medicine, University of California, San Diego, San Diego, CA 92093-0651, USA
| | - Luke M Healy
- Neuroimmunology Unit, Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC H3A 2B4, Canada
| | - Sunil P Gandhi
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA; Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, CA 92697, USA
| | - Robert C Spitale
- Department of Pharmaceutical Sciences, University of California, Irvine, Irvine, CA 92697, USA; Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, CA 92697, USA
| | - Mathew Blurton-Jones
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92696, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92696, USA; Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA 92696, USA; Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, CA 92697, USA.
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12
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Rossi E, Mracsko E, Papadimitropoulos A, Allafi N, Reinhardt D, Mehrkens A, Martin I, Knuesel I, Scherberich A. An In Vitro Bone Model to Investigate the Role of Triggering Receptor Expressed on Myeloid Cells-2 in Bone Homeostasis. Tissue Eng Part C Methods 2019; 24:391-398. [PMID: 29897015 DOI: 10.1089/ten.tec.2018.0061] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Triggering receptor expressed on myeloid cells-2 (TREM-2), a transmembrane receptor expressed by macrophages, microglia, and osteoclasts (OCs), plays a protective role in late-onset Alzheimer Disease (AD). To validate TREM-2 as a therapeutic target in AD, its potential secondary parallel effect on bone homeostasis should be clarified. However, animal models and monolayer cultures of human cells were shown poorly predictive of TREM-2 function in human. Therefore, this study aimed to engineer a tridimensional in vitro model using human progenitors differentiated into osteoblasts and OCs, recapitulating physiological bone homeostasis. Human bone marrow-derived mesenchymal cells were seeded and cultured under perfusion inside a collagen type I scaffold for 3 weeks, generating osteoblasts and mineralized matrix. Human peripheral blood-derived CD14+ monocytes were subsequently seeded through the generated tissue, thanks to perfusion flow, and further cultured for up to 3 weeks with an inductive medium, generating mature OCs. This culture system supported collagenous matrix deposition and resorption, allowing for the investigation of kinetic of soluble TREM-2 over the coculture time. Agonistic activation of TREM-2 in this model had no effect on OC activity or on mineralized matrix turnover. In conclusion, the engineered culture system represents a tridimensional, in vitro human bone model for drug testing and suggested no effect of TREM-2 agonist on bone resorption.
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Affiliation(s)
- Eleonora Rossi
- 1 Department of Biomedicine, University Hospital of Basel, University of Basel , Basel, Switzerland
| | - Eva Mracsko
- 2 Roche Pharmaceutical Research and Early Development, Roche Innovation Center , Basel, Switzerland
| | - Adam Papadimitropoulos
- 1 Department of Biomedicine, University Hospital of Basel, University of Basel , Basel, Switzerland
| | - Nima Allafi
- 1 Department of Biomedicine, University Hospital of Basel, University of Basel , Basel, Switzerland
| | - Dieter Reinhardt
- 2 Roche Pharmaceutical Research and Early Development, Roche Innovation Center , Basel, Switzerland
| | - Arne Mehrkens
- 1 Department of Biomedicine, University Hospital of Basel, University of Basel , Basel, Switzerland
| | - Ivan Martin
- 1 Department of Biomedicine, University Hospital of Basel, University of Basel , Basel, Switzerland
| | - Irene Knuesel
- 2 Roche Pharmaceutical Research and Early Development, Roche Innovation Center , Basel, Switzerland
| | - Arnaud Scherberich
- 1 Department of Biomedicine, University Hospital of Basel, University of Basel , Basel, Switzerland
- 3 Clinic of Plastic, Reconstructive and Aesthetic Surgery, University Hospital Basel , Basel, Switzerland
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13
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Yao Y, Li H, Chen J, Xu W, Yang G, Bao Z, Xia D, Lu G, Hu S, Zhou J. TREM-2 serves as a negative immune regulator through Syk pathway in an IL-10 dependent manner in lung cancer. Oncotarget 2018; 7:29620-34. [PMID: 27102437 PMCID: PMC5045421 DOI: 10.18632/oncotarget.8813] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 03/28/2016] [Indexed: 01/31/2023] Open
Abstract
During infection, triggering receptor expressed on myeloid cells-2 (TREM-2) restrains dendritic cells (DCs) and macrophages (MΦs) phagocytosis, as well as reduces pro-inflammatory cytokines release through DNAX-activation protein 12 (DAP12) signaling. However, the role of TREM-2 signaling in cancer has never been elucidated. In the current study, we found that TREM-2 was up-regulated on peripheral blood monocytes in tumor-bearing host. More TREM-2+DCs were detected in the lung of 3LL tumor-bearing mice. On the other hand, the level of TREM-2 on pulmonary MΦs positively correlated with the pathological staging of lung cancer. However, surgical or chemotherapeutic reduction of tumor burden led to the obvious decline of TREM-2. In vitro, TREM-2 expression of bone marrow (BM)-derived DCs and MΦs was induced by conditional medium (CM) containing the supernatant of 3LL cells. TREM-2+DCs from CM and/or tumor-bearing mice held altered phenotypes (CD80LowCD86LowMHCIILow) and impaired functions, such as, reduced interleukin (IL)-12 secretion, increased IL-10 production, and weakened ovalbumin (OVA)-endocytic capacity; also developed potent inhibitory effect on T cell proliferation that could be partially reversed by TREM-2 blockage. Moreover, spleen tyrosine kinase (Syk) inhibitor restrained IL-10 production of TREM-2+DC. Remarkably, IL-10 neutralizing antibody and Syk inhibitor both lowered the suppressive potential of TREM-2+DCs in T cell proliferation. Also, adoptive transfer of this TREM-2+DCs accelerated the tumor growth rather than jeopardized survival in lung cancer-bearing mice. In conclusion, these results indicate that TREM-2 might act as a negative immuno-regulatory molecule through Syk pathway in an IL-10 dependent manner and partially predicts prognosis in lung cancer patients.
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Affiliation(s)
- Yinan Yao
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Hequan Li
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Junjun Chen
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Weiyi Xu
- Department of Clinical Laboratory, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Guangdie Yang
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Zhang Bao
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Dajing Xia
- School of Public Health, Zhejiang University, Institute of Immunology, Zhejiang University, Hangzhou, China.,Institute of Immunology, Zhejiang University, Hangzhou, China
| | - Guohua Lu
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Shuwen Hu
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Jianying Zhou
- Department of Respiratory Diseases, First Affiliated Hospital of Zhejiang University, Hangzhou, China
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14
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Rudick CP, Miyamoto T, Lang MS, Agrawal DK. Triggering receptor expressed on myeloid cells in the pathogenesis of periodontitis: potential novel treatment strategies. Expert Rev Clin Immunol 2017; 13:1189-1197. [PMID: 29027827 DOI: 10.1080/1744666x.2017.1392855] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
INTRODUCTION Periodontal diseases are polymicrobial inflammatory disorders of the tissue, ligament, and bone structures supporting teeth. Periodontitis (inflammation with corresponding loss of attachment) affects 40-50% of adults. Recently, members of the Triggering Receptor on Myeloid Cell (TREM) family have been studied to determine their relationship to these diseases. Areas covered: TREM-1 is a receptor expressed on the surface of PMNs, monocytes, macrophages, dendritic cells, vascular smooth muscle cells, and keratinocytes upregulated in the presence of periodontal inflammation. TREM-1 expression can be upregulated by oral bacterium Porphyromonas gingivalis that can be abrogated by a sub-antimicrobial dose of doxycycline. When cleaved from the cell surface, a soluble form of TREM-1 (sTREM-1) can be used as a biomarker of inflammation and might also provide a link between oral and systemic inflammation. While less understood, TREM-2 has a role in osteoclastogenesis which could contribute to the alveolar bone destruction seen in more advanced periodontitis. Expert commentary: Additional studies to simulate biofilm microenvironment in TREM research are warranted. Longitudinal studies determining TREM-1, sTREM-1, and TREM-2 levels in tissues over time and progression of periodontal diseases would provide valuable information in the role of TREM receptors as indicators of or contributors to the disease process.
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Affiliation(s)
- Courtney P Rudick
- a Department of Clinical & Translational Science , Creighton University School of Medicine , Omaha , NE , USA
| | - Takanari Miyamoto
- b Department of Periodontology , Creighton University School of Medicine , Omaha , NE , USA
| | - Melissa S Lang
- b Department of Periodontology , Creighton University School of Medicine , Omaha , NE , USA
| | - Devendra K Agrawal
- a Department of Clinical & Translational Science , Creighton University School of Medicine , Omaha , NE , USA
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15
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Rosciszewski G, Cadena V, Murta V, Lukin J, Villarreal A, Roger T, Ramos AJ. Toll-Like Receptor 4 (TLR4) and Triggering Receptor Expressed on Myeloid Cells-2 ( TREM-2) Activation Balance Astrocyte Polarization into a Proinflammatory Phenotype. Mol Neurobiol 2017; 55:3875-3888. [PMID: 28547529 DOI: 10.1007/s12035-017-0618-z] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 05/12/2017] [Indexed: 01/07/2023]
Abstract
Astrocytes react to brain injury with a generic response known as reactive gliosis, which involves activation of multiple intracellular pathways including several that may be beneficial for neuronal survival. However, by unknown mechanisms, reactive astrocytes can polarize into a proinflammatory phenotype that induces neurodegeneration. In order to study reactive gliosis and astroglial polarization into a proinflammatory phenotype, we used cortical devascularization-induced brain ischemia in Wistar rats and primary astroglial cell cultures exposed to oxygen-glucose deprivation (OGD). We analyzed the profile of TLR4 expression and the consequences of its activation by gain- and loss-of-function studies, and the effects produced by the activation of triggering receptor expressed on myeloid cells-2 (TREM-2), a negative regulator of TLR4 signaling. Both OGD exposure on primary astroglial cell cultures and cortical devascularization brain ischemia in rats induced TLR4 expression in astrocytes. In vivo, astroglial TLR4 expression was specifically observed in the ischemic penumbra surrounding necrotic core. Functional studies showed that OGD increased the astroglial response to the TLR4 agonist lipopolysaccharide (LPS), and conversely, TLR4 knockout primary astrocytes had impaired nuclear factor kappa-B (NF-κB) activation when exposed to LPS. In gain-of-function studies, plasmid-mediated TLR4 over-expression exacerbated astroglial response to LPS as shown by sustained NF-κB activation and increased expression of proinflammatory cytokines IL-1β and TNFα. TREM-2 expression, although present in naïve primary astrocytes, was induced by OGD, LPS, or high-mobility group box 1 protein (HMGB-1) exposure. TREM-2 activation by antibody cross-linking or the overexpression of TREM-2 intracellular adaptor, DAP12, partially suppressed LPS-induced NF-κB activation in purified astrocytic cultures. In vivo, TREM-2 expression was observed in macrophages and astrocytes located in the ischemic penumbra. While TREM-2+ macrophages were abundant at 3 days post-lesion (DPL) in the ischemic core, TREM-2+ astrocytes persisted in the penumbra until 14DPL. This study demonstrates that TLR4 expression increases astroglial sensitivity to ligands facilitating astrocyte conversion towards a proinflammatory phenotype, and that astroglial TREM-2 modulates this response reducing the downstream NF-κB activation. Therefore, the availability of TLR4 and TREM-2 ligands in the ischemic environment may control proinflammatory astroglial conversion to the neurodegenerative phenotype.
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Affiliation(s)
- Gerardo Rosciszewski
- Universidad de Buenos Aires, Facultad de Medicina, Departamento de Histología, Embriología, Biología Celular y Genética, Buenos Aires, Argentina.,Laboratorio de Neuropatología Molecular, Instituto de Biología Celular y Neurociencia "Prof. E. De Robertis" Facultad de Medicina, Universidad de Buenos Aires, Calle Paraguay 2155 3er piso (1121),, Ciudad de Buenos Aires, Argentina
| | - Vanesa Cadena
- Universidad de Buenos Aires, Facultad de Medicina, Departamento de Histología, Embriología, Biología Celular y Genética, Buenos Aires, Argentina.,Laboratorio de Neuropatología Molecular, Instituto de Biología Celular y Neurociencia "Prof. E. De Robertis" Facultad de Medicina, Universidad de Buenos Aires, Calle Paraguay 2155 3er piso (1121),, Ciudad de Buenos Aires, Argentina
| | - Veronica Murta
- Universidad de Buenos Aires, Facultad de Medicina, Departamento de Histología, Embriología, Biología Celular y Genética, Buenos Aires, Argentina.,Laboratorio de Neuropatología Molecular, Instituto de Biología Celular y Neurociencia "Prof. E. De Robertis" Facultad de Medicina, Universidad de Buenos Aires, Calle Paraguay 2155 3er piso (1121),, Ciudad de Buenos Aires, Argentina
| | - Jeronimo Lukin
- Universidad de Buenos Aires, Facultad de Medicina, Departamento de Histología, Embriología, Biología Celular y Genética, Buenos Aires, Argentina.,Laboratorio de Neuropatología Molecular, Instituto de Biología Celular y Neurociencia "Prof. E. De Robertis" Facultad de Medicina, Universidad de Buenos Aires, Calle Paraguay 2155 3er piso (1121),, Ciudad de Buenos Aires, Argentina
| | - Alejandro Villarreal
- Universidad de Buenos Aires, Facultad de Medicina, Departamento de Histología, Embriología, Biología Celular y Genética, Buenos Aires, Argentina.,Department of Molecular Embryology, Institute for Anatomy and Cell Biology, University of Freiburg, 79104, Freiburg, Germany
| | - Thierry Roger
- Infectious Diseases Service, Department of Medicine, Lausanne University Hospital, Chemin des Boveresses 155, 1066, Epalinges, Switzerland
| | - Alberto Javier Ramos
- Universidad de Buenos Aires, Facultad de Medicina, Departamento de Histología, Embriología, Biología Celular y Genética, Buenos Aires, Argentina. .,Laboratorio de Neuropatología Molecular, Instituto de Biología Celular y Neurociencia "Prof. E. De Robertis" Facultad de Medicina, Universidad de Buenos Aires, Calle Paraguay 2155 3er piso (1121),, Ciudad de Buenos Aires, Argentina.
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16
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Hommes TJ, Dessing MC, Veer CV', Florquin S, Colonna M, de Vos AF, van der Poll T. Role of triggering receptor expressed on myeloid cells-1/3 in Klebsiella-derived pneumosepsis. Am J Respir Cell Mol Biol 2016; 53:647-55. [PMID: 25860078 DOI: 10.1165/rcmb.2014-0485oc] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Triggering receptor expressed on myeloid cells (TREM)-1 and -2 can affect Toll-like receptor-mediated activation of immune cells. Klebsiella pneumoniae is a common cause of pneumonia-derived sepsis. Here we studied the role of TREM-1/3 and TREM-2 in the host response during Klebsiella pneumonia. Macrophages lacking either TREM-1/3 or TREM-2 were tested for their responsiveness toward K. pneumoniae and for their capacity to internalize this pathogen in vitro. TREM-1/3- and TREM-2-deficient mice were infected with K. pneumoniae via the airways, and their responses were compared with those in wild-type mice. TREM-1/3-deficient macrophages produced lower cytokine levels upon exposure to K. pneumoniae, whereas TREM-2-deficient macrophages released higher cytokine concentrations. TREM-2-deficient, but not TREM-1/3-deficient, macrophages showed a reduced capacity to phagocytose K. pneumoniae. TREM-1/3-deficient mice showed an impaired host defense during Klebsiella pneumonia, as reflected by worsened survival and increased bacterial growth and dissemination. In contrast, TREM-2 deficiency did not affect disease outcome. Although TREM-1/3 and TREM-2 influence macrophage responsiveness to K. pneumoniae in vitro, only TREM-1/3 contribute to the host response during Klebsiella pneumonia in vivo, serving a protective role.
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Affiliation(s)
- Tijmen J Hommes
- 1 Center for Experimental and Molecular Medicine.,2 Center for Infection and Immunity
| | | | - Cornelis van 't Veer
- 1 Center for Experimental and Molecular Medicine.,2 Center for Infection and Immunity
| | | | - Marco Colonna
- 4 Department of Pathology, Washington University in St. Louis, St. Louis, Missouri
| | - Alex F de Vos
- 1 Center for Experimental and Molecular Medicine.,2 Center for Infection and Immunity
| | - Tom van der Poll
- 1 Center for Experimental and Molecular Medicine.,2 Center for Infection and Immunity.,5 Division of Infectious Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands; and
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Öhrfelt A, Axelsson M, Malmeström C, Novakova L, Heslegrave A, Blennow K, Lycke J, Zetterberg H. Soluble TREM-2 in cerebrospinal fluid from patients with multiple sclerosis treated with natalizumab or mitoxantrone. Mult Scler 2016; 22:1587-1595. [PMID: 26754805 DOI: 10.1177/1352458515624558] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 12/06/2015] [Indexed: 01/04/2023]
Abstract
BACKGROUND Microglia-mediated proteolysis of the triggering receptor expressed on myeloid cells-2 (TREM-2) produces soluble TREM-2 (sTREM-2) that can be measured in cerebrospinal fluid (CSF) samples. Loss-of-function mutations in TREM2 or in the gene encoding its adaptor protein cause the rare Nasu-Hakola disease (NHD). Multiple sclerosis (MS) is an autoimmune disease that in common with NHD is characterized by demyelination and microglial activation. OBJECTIVE To investigate the potential utility of sTREM-2 as a biomarker for MS and to follow treatment effects. METHODS sTREM-2 was analyzed in CSF samples from subjects with MS (N = 59); relapsing-remitting MS (RRMS) (N = 36), secondary progressive MS (SPMS) (N = 20) and primary progressive MS (PPMS) (N = 3), and controls (N = 27). CSF levels of sTREM-2 were also assessed before and after treatment of patients with natalizumab or mitoxantrone. RESULTS CSF levels of sTREM-2 were significantly increased in patients with RRMS, SPMS, and PPMS compared with controls. After natalizumab treatment, the levels of sTREM-2 were normalized to control levels. The levels of sTREM-2 were also reduced after mitoxantrone treatment. CONCLUSION Increased CSF levels of sTREM-2, a new marker of microglial activation, in MS and normalization upon treatment with either natalizumab or mitoxantrone support a role for microglial activation in active MS.
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Affiliation(s)
- Annika Öhrfelt
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Markus Axelsson
- Department of Neurology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Clas Malmeström
- Department of Neurology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lenka Novakova
- Department of Neurology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Amanda Heslegrave
- UCL Institute of Neurology, University College London (UCL), London, UK
| | - Kaj Blennow
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Jan Lycke
- Department of Neurology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Henrik Zetterberg
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden/UCL Institute of Neurology, University College London (UCL), London, UK
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18
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Nguyen AH, Koenck C, Quirk SK, Lim VM, Mitkov MV, Trowbridge RM, Hunter WJ, Agrawal DK. Triggering Receptor Expressed on Myeloid Cells in Cutaneous Melanoma. Clin Transl Sci 2015; 8:441-4. [PMID: 26184544 DOI: 10.1111/cts.12308] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The tumor microenvironment plays an important role in the progression of melanoma, the prototypical immunologic cutaneous malignancy. The triggering receptor expressed on myeloid cells (TREM) family of innate immune receptors modulates inflammatory and innate immune signaling. It has been investigated in various neoplastic diseases, but not in melanoma. This study examines the expression of TREM-1 (a proinflammatory amplifier) and TREM-2 (an anti-inflammatory modulator and phagocytic promoter) in human cutaneous melanoma and surrounding tissue. Indirect immunofluorescence staining was performed on skin biopsies from 10 melanoma patients and staining intensity was semiquantitatively scored. Expression of TREM-1 and TREM-2 was higher in keratinocytes than melanoma tissue (TREM-1: p < 0.01; TREM-2: p < 0.01). Whereas TREM-2 was the dominant isoform expressed in normal keratinocytes, TREM-1 expression predominated in melanoma tissue (TREM-1 to TREM-2 ratio: keratinocytes = 0.78; melanoma = 2.08; p < 0.01). The increased TREM ratio in melanoma tissue could give rise to a proinflammatory and protumor state of the microenvironment. This evidence may be suggestive of a TREM-1/TREM-2 paradigm in which relative levels dictate inflammatory and immune states, rather than absolute expression of one or the other. Further investigation regarding this paradigm is warranted and could carry prognostic or therapeutic value in treatment for melanoma.
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Affiliation(s)
- Austin Huy Nguyen
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
| | - Carleigh Koenck
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
| | - Shannon K Quirk
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
| | - Victoria M Lim
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
| | - Mario V Mitkov
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
| | - Ryan M Trowbridge
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
| | - William J Hunter
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
| | - Devendra K Agrawal
- Center for Clinical and Translational Science, Creighton University School of Medicine, Omaha, Nebraska, USA
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Abstract
Inflammation is tightly regulated by a vast system that is intricately interconnected with innate immunity. Aberrations in expression or signaling, such as in innate immune receptors, can create excessive inflammation and, when chronic, often promote oncogenesis. The triggering receptor expressed on myeloid cells receptor family has been characterized as a major player in the amplification and signaling of the inflammatory response. In a number of chronic inflammatory conditions and malignancies, the triggering receptor expressed on myeloid cells has been implicated in disease severity and progression. In this article, the current understanding of triggering receptor expressed on myeloid cells function in pre-malignant, malignant and chronic inflammatory conditions is critically reviewed. The potential for therapeutic application is also discussed.
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Affiliation(s)
- Austin Huy Nguyen
- Center for Clinical and Translational Science, Creighton University School of Medicine, 2500 California Plaza Omaha, NE 68178, USA
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Wei P, Lu Q, Cui G, Guan Z, Yang L, Sun C, Sun W, Peng Q. The role of TREM-2 in internalization and intracellular survival of Brucella abortus in murine macrophages. Vet Immunol Immunopathol 2014; 163:194-201. [PMID: 25563793 DOI: 10.1016/j.vetimm.2014.12.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2014] [Revised: 12/15/2014] [Accepted: 12/16/2014] [Indexed: 12/11/2022]
Abstract
Triggering receptor expressed on myeloid cells-2 (TREM-2) is a cell surface receptor primarily expressed on macrophages and dendritic cells. TREM-2 functions as a phagocytic receptor for bacteria as well as an inhibitor of Toll like receptors (TLR) induced inflammatory cytokines. However, the role of TREM-2 in Brucella intracellular growth remains unknown. To investigate whether TREM-2 is involved in Brucella intracellular survival, we chose bone marrow derived macrophages (BMDMs), in which TREM-2 is stably expressed, as cell model. Colony formation Units (CFUs) assay suggests that TREM-2 is involved in the internalization of Brucella abortus (B. abortus) by macrophages, while silencing of TREM-2 decreases intracellular survival of B. abortus. To further study the underlying mechanisms of TREM-2-mediated bacterial intracellular survival, we examined the activation of B. abortus-infected macrophages through determining the kinetics of activation of the three MAPKs, including ERK, JNK and p38, and measuring TNFα production in response to lipopolysaccharide (LPS) of Brucella (BrLPS) or B. abortus stimulation. Our data show that TREM-2 deficiency promotes activation of Brucella-infected macrophages. Moreover, our data also demonstrate that macrophage activation promotes killing of Brucella by enhancing nitric oxygen (NO), but not reactive oxygen species (ROS) production, macrophage apoptosis or cellular death. Taken together, these findings provide a novel interpretation of Brucella intracellular growth through inhibition of NO production produced by TREM-2-mediated activated macrophages.
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Affiliation(s)
- Pan Wei
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun 130062, People's Republic of China
| | - Qiang Lu
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun 130062, People's Republic of China
| | - Guimei Cui
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun 130062, People's Republic of China
| | - Zhenhong Guan
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun 130062, People's Republic of China
| | - Li Yang
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun 130062, People's Republic of China
| | - Changjiang Sun
- College of Veterinary Medicine, Jilin University, Changchun, People's Republic of China
| | - Wanchun Sun
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun 130062, People's Republic of China
| | - Qisheng Peng
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun 130062, People's Republic of China.
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Yaghmoor F, Noorsaeed A, Alsaggaf S, Aljohani W, Scholtzova H, Boutajangout A, Wisniewski T. The Role of TREM2 in Alzheimer's Disease and Other Neurological Disorders. J Alzheimers Dis Parkinsonism 2014; 4:160. [PMID: 25664220 PMCID: PMC4317331 DOI: 10.4172/2161-0460.1000160] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Alzheimer's disease (AD) is the leading cause of dementia worldwide. Late-onset AD (LOAD), is the most common form of Alzheimer's disease, representing about >95% of cases and early-onset AD represents <5% of cases. Several risk factors have been discovered that are associated with AD, with advancing age being the most prominent. Other environmental risk factors include diabetes mellitus, level of physical activity, educational status, hypertension and head injury. The most well known genetic risk factor for LOAD is inheritance of the apolipoprotein (apo) E4 allele. Recently, rare variants of TREM2 have been reported as a significant risk factor for LOAD, comparable to inheritance of apoE4. In this review we will focus on the role(s) of TREM2 in AD as well as in other neurodegenerative disorders.
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Affiliation(s)
- Faris Yaghmoor
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Ahmed Noorsaeed
- Pathology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Samar Alsaggaf
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Waleed Aljohani
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Henrieta Scholtzova
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Allal Boutajangout
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Psychiatry, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Physiology and Neuroscience, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY10016, USA
- King Abdulaziz University, School of Medicine, Jeddah, Saudi Arabia
| | - Thomas Wisniewski
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Pathology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Psychiatry, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
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Montalvo V, Quigley L, Vistica BP, Boelte KC, Nugent LF, Takai T, McVicar DW, Gery I. Environmental factors determine DAP12 deficiency to either enhance or suppress immunopathogenic processes. Immunology 2014; 140:475-82. [PMID: 23906311 DOI: 10.1111/imm.12158] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 06/28/2013] [Accepted: 07/29/2013] [Indexed: 12/30/2022] Open
Abstract
DNAX-activation protein 12 (DAP12), a transmembrane adapter, plays a major role in transducing activation signals in natural killer cells and various myeloid cells. Quantitative RT-PCR detected in normal mouse eyes considerable levels of DAP12 and multiple DAP12-coupled receptors, in particular TREM-1, Clec5a and SIRPb1. The role of DAP12 and its receptors in experimental autoimmune diseases has been controversial. Here, we analysed the effect of DAP12 deficiency on the capacity of mice to mount immunopathogenic cellular responses to the uveitogenic ocular antigen and interphotoreceptor retinoid-binding protein (IRBP), and to develop experimental autoimmune uveitis (EAU). Surprisingly, sequential analysis of EAU in mice deficient in DAP12 in two different animal facilities at first revealed enhanced disease as compared with wild-type mice, but when these mice were re-derived into a second, cleaner, animal facility, the response of control mice was essentially unchanged, whereas the DAP12 null mice were markedly hyporesponsive relative to controls in the new facility. Accordingly, when stimulated in vitro with IRBP, lymphocytes from the DAP12-deficient mice housed in the two facilities proliferated and produced opposite profiles of pro-inflammatory and anti-inflammatory cytokines, compared with their controls. These findings therefore demonstrate that the effects of DAP12 deficiency on development of autoimmune disease are dramatically affected by environmental factors.
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Affiliation(s)
- Vanessa Montalvo
- Laboratory of Immunology, National Eye Institute, NIH, Bethesda, MD, USA
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Sugimoto K, Nishioka R, Ikeda A, Mise A, Takahashi H, Yano H, Kumon Y, Ohnishi T, Tanaka J. Activated microglia in a rat stroke model express NG2 proteoglycan in peri-infarct tissue through the involvement of TGF-β1. Glia 2013; 62:185-98. [PMID: 24311432 DOI: 10.1002/glia.22598] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 10/20/2013] [Accepted: 10/22/2013] [Indexed: 12/12/2022]
Abstract
We investigated activated microglia in ischemic brain lesions from rats that had been subjected to transient middle cerebral artery occlusion. Activated microglia expressing NG2 chondroitin sulfate proteoglycan (NG2) were found only in the narrow zone (demarcation zone) that demarcated the peri-infarct tissue and ischemic core. NG2(-) activated microglia were abundantly distributed in the peri-infarct tissue outside the demarcation zone. NG2(+) microglia but not NG2(-) microglia expressed both CD68 and a triggering receptor expressed on myeloid cells 2 (TREM-2), suggesting that NG2(+) microglia eliminated apoptotic neurons. In fact, NG2(+) microglia often attached to degenerating neurons and sometimes internalized NeuN(+) or neurofilament protein(+) material. Kinetic studies using quantitative real-time RT-PCR revealed that expression of transforming growth factor-β1 (TGF-β1) was most evident in the ischemic core; with this marker produced mainly by macrophages located in this region. TGF-β receptor mRNA expression peaked at 3 days post reperfusion (dpr) in the peri-infarct tissue, including the demarcation zone. Primary cultured rat microglia also expressed the receptor mRNA. In response to TGF-β1, primary microglia enhanced the expression of NG2 protein and TREM-2 mRNA as well as migratory activity. A TGF-β1 inhibitor, SB525334, abolished these effects. The present results suggest that TGF-β1 produced in the ischemic core diffused toward the peri-infarct tissue, driving activated microglial cells to eliminate degenerating neurons. Appropriate control of NG2(+) microglia in the demarcation zone might be a novel target for the suppression of secondary neurodegeneration in the peri-infarct tissue.
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Affiliation(s)
- Kana Sugimoto
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Ehime University, Toon, Ehime, Japan
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Abstract
Microglia are critical nervous system-specific cells influencing brain development, maintenance of the neural environment, response to injury, and repair. They contribute to neuronal proliferation and differentiation, pruning of dying neurons, synaptic remodeling and clearance of debris and aberrant proteins. Colonization of the brain occurs during gestation with an expansion following birth with localization stimulated by programmed neuronal death, synaptic pruning, and axonal degeneration. Changes in microglia phenotype relate to cellular processes including specific neurotransmitter, pattern recognition, or immune-related receptor activation. Upon activation, microglia cells have the capacity to release a number of substances, e.g., cytokines, chemokines, nitric oxide, and reactive oxygen species, which could be detrimental or beneficial to the surrounding cells. With aging, microglia shift their morphology and may display diminished capacity for normal functions related to migration, clearance, and the ability to shift from a pro-inflammatory to an anti-inflammatory state to regulate injury and repair. This shift in microglia potentially contributes to increased susceptibility and neurodegeneration as a function of age. In the current review, information is provided on the colonization of the brain by microglia, the expression of various pattern recognition receptors to regulate migration and phagocytosis, and the shift in related functions that occur in normal aging.
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Affiliation(s)
- G Jean Harry
- National Toxicology Program Laboratory, National Institute of Environmental Health Sciences, MD C1-04, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA.
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