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Abarca-Merlin DM, Martínez-Durán JA, Medina-Pérez JD, Rodríguez-Santos G, Alvarez-Arellano L. From Immunity to Neurogenesis: Toll-like Receptors as Versatile Regulators in the Nervous System. Int J Mol Sci 2024; 25:5711. [PMID: 38891900 PMCID: PMC11171594 DOI: 10.3390/ijms25115711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/10/2024] [Accepted: 05/11/2024] [Indexed: 06/21/2024] Open
Abstract
Toll-like receptors (TLRs) are among the main components of the innate immune system. They can detect conserved structures in microorganisms and molecules associated with stress and cellular damage. TLRs are expressed in resident immune cells and both neurons and glial cells of the nervous system. Increasing evidence is emerging on the participation of TLRs not only in the immune response but also in processes of the nervous system, such as neurogenesis and cognition. Below, we present a review of the literature that evaluates the expression and role of TLRs in processes such as neurodevelopment, behavior, cognition, infection, neuroinflammation, and neurodegeneration.
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Affiliation(s)
- Daniela Melissa Abarca-Merlin
- Laboratorio de Investigación en Neurociencias, Hospital Infantil de México Federico Gómez, Av. Dr. Márquez 162. Colonia Doctores, Mexico City 06720, Mexico; (D.M.A.-M.)
| | - J. Abigail Martínez-Durán
- Laboratorio de Investigación en Neurociencias, Hospital Infantil de México Federico Gómez, Av. Dr. Márquez 162. Colonia Doctores, Mexico City 06720, Mexico; (D.M.A.-M.)
| | - J. David Medina-Pérez
- Laboratorio de Investigación en Neurociencias, Hospital Infantil de México Federico Gómez, Av. Dr. Márquez 162. Colonia Doctores, Mexico City 06720, Mexico; (D.M.A.-M.)
| | - Guadalupe Rodríguez-Santos
- Laboratorio de Investigación en Neurociencias, Hospital Infantil de México Federico Gómez, Av. Dr. Márquez 162. Colonia Doctores, Mexico City 06720, Mexico; (D.M.A.-M.)
| | - Lourdes Alvarez-Arellano
- Laboratorio de Investigación en Neurociencias, Hospital Infantil de México Federico Gómez, Av. Dr. Márquez 162. Colonia Doctores, Mexico City 06720, Mexico; (D.M.A.-M.)
- CONAHCYT-Hospital Infantil de México Federico Gómez, Mexico City 06720, Mexico
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Evans AK, Saw NL, Woods CE, Vidano LM, Blumenfeld SE, Lam RK, Chu EK, Reading C, Shamloo M. Impact of high-fat diet on cognitive behavior and central and systemic inflammation with aging and sex differences in mice. Brain Behav Immun 2024; 118:334-354. [PMID: 38408498 PMCID: PMC11019935 DOI: 10.1016/j.bbi.2024.02.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 02/16/2024] [Accepted: 02/21/2024] [Indexed: 02/28/2024] Open
Abstract
Aging and age-related diseases are associated with cellular stress, metabolic imbalance, oxidative stress, and neuroinflammation, accompanied by cognitive impairment. Lifestyle factors such as diet, sleep fragmentation, and stress can potentiate damaging cellular cascades and lead to an acceleration of brain aging and cognitive impairment. High-fat diet (HFD) has been associated with obesity, metabolic disorders like diabetes, and cardiovascular disease. HFD also induces neuroinflammation, impairs learning and memory, and may increase anxiety-like behavior. Effects of a HFD may also vary between sexes. The interaction between Age- and Sex- and Diet-related changes in neuroinflammation and cognitive function is an important and poorly understood area of research. This study was designed to examine the effects of HFD on neuroinflammation, behavior, and neurodegeneration in mice in the context of aging or sex differences. In a series of studies, young (2-3 months) or old (12-13 months) C57BL/6J male mice or young male and female C57Bl/6J mice were fed either a standard diet (SD) or a HFD for 5-6 months. Behavior was assessed in Activity Chamber, Y-maze, Novel Place Recognition, Novel Object Recognition, Elevated Plus Maze, Open Field, Morris Water Maze, and Fear Conditioning. Post-mortem analyses assessed a panel of inflammatory markers in the plasma and hippocampus. Additionally, proteomic analysis of the hypothalamus, neurodegeneration, neuroinflammation in the locus coeruleus, and neuroinflammation in the hippocampus were assessed in a subset of young and aged male mice. We show that HFD increased body weight and decreased locomotor activity across groups compared to control mice fed a SD. HFD altered anxiety-related exploratory behavior. HFD impaired spatial learning and recall in young male mice and impaired recall in cued fear conditioning in young and aged male mice, with no effects on spatial learning or fear conditioning in young female mice. Effects of Age and Sex were observed on neuroinflammatory cytokines, with only limited effects of HFD. HFD had a more significant impact on systemic inflammation in plasma across age and sex. Aged male mice had induction of microglial immunoreactivity in both the locus coeruleus (LC) and hippocampus an effect that HFD exacerbated in the hippocampal CA1 region. Proteomic analysis of the hypothalamus revealed changes in pathways related to metabolism and neurodegeneration with both aging and HFD in male mice. Our findings suggest that HFD induces widespread systemic inflammation and limited neuroinflammation. In addition, HFD alters exploratory behavior in male and female mice, and impairs learning and memory in male mice. These results provide valuable insight into the impact of diet on cognition and aging pathophysiology.
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Affiliation(s)
- Andrew K Evans
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304
| | - Nay L Saw
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304
| | - Claire E Woods
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304
| | - Laura M Vidano
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304
| | - Sarah E Blumenfeld
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304
| | - Rachel K Lam
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304
| | - Emily K Chu
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304
| | | | - Mehrdad Shamloo
- Stanford University School of Medicine, Department of Neurosurgery, 1050 Arastradero Road, Building A, Palo Alto, CA 94304.
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Dabi YT, Ajagbe AO, Degechisa ST. Toll-like receptors in pathogenesis of neurodegenerative diseases and their therapeutic potential. Immun Inflamm Dis 2023; 11:e839. [PMID: 37102648 PMCID: PMC10116887 DOI: 10.1002/iid3.839] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/17/2023] [Accepted: 03/29/2023] [Indexed: 04/28/2023] Open
Abstract
Toll-like receptors (TLRs) are a family of pattern-recognition receptors triggered by pathogen-derived and tissue-damage-related ligands. TLRs were previously believed to only be expressed in immune cells. However, it is now confirmed that they are ubiquitously expressed in cells within the body including neurons, astrocytes, and microglia of the central nervous system (CNS). Activation of TLRs is capable of inducing immunologic and inflammatory responses to injury or infection of CNS. This response is self-limiting that usually resolves once the infection has been eradicated or the tissue damage has been repaired. However, the persistence of inflammation-inducing insults or a failure in normal resolution mechanisms may result in overwhelming inflammation which may induce neurodegeneration. This implies that TLRs may play a role in mediating the link between inflammation and neurodegenerative diseases namely Alzheimer's disease, Parkinson's disease, Huntington's disease, stroke, and amyotrophic lateral sclerosis. So, new therapeutic approaches that specifically target TLRs may be developed by better understanding TLR expression mechanisms in the CNS and their connections to particular neurodegenerative disorders. Therefore, this review paper discussed the role of TLRs in neurodegenerative diseases.
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Affiliation(s)
- Yosef Tsegaye Dabi
- Department of Medical Laboratory Science, Institute of Health SciencesWollega UniversityNekemteEthiopia
| | - Abayomi O. Ajagbe
- Department of Anatomy, College of Health Sciences, Faculty of Basic Medical SciencesNile University of NigeriaAbujaNigeria
| | - Sisay T. Degechisa
- Department of Medical Biochemistry, School of Medicine, College of Health SciencesAddis Ababa UniversityAddis AbabaEthiopia
- Department of Medical Laboratory Sciences, College of Medicine and Health SciencesArba Minch UniversityArba MinchEthiopia
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Cuesta N, Fernández-Veledo S, Punzón C, Moreno C, Barrocal B, Sreeramkumar V, Desco M, Fresno M. Opposing Actions of TLR2 and TLR4 in Adipocyte Differentiation and Mature-Onset Obesity. Int J Mol Sci 2022; 23:ijms232415682. [PMID: 36555322 PMCID: PMC9779340 DOI: 10.3390/ijms232415682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 12/02/2022] [Accepted: 12/03/2022] [Indexed: 12/14/2022] Open
Abstract
Understanding the signaling cascades that govern adipocyte metabolism and differentiation is necessary for the development of therapies for obesity. Toll-like receptors (TLRs) are key mediators in adipogenesis, but their specific role is not completely understood. In this study, siRNA knockdown of Tlr2 in 3T3-L1 cells allowed them to differentiate more efficiently into adipocytes, whereas the opposite was observed for the knockdown of Tlr4. At the same time, we show that TLR2 knock-out mice spontaneously developed mature-onset obesity and insulin resistance. Besides a higher incidence of hyperplasia and hypertrophy in white adipose tissue (WAT), we found a significantly increased number of adipocyte precursor cells in TLR2-/- mice compared to TLR4-/- mice. Interestingly, genetic inactivation of Tlr4 in TLR2-/- mice reverted their increased adiposity, insulin resistance, and restored normal levels of adipocyte precursor cells. These findings provide evidence that TLR2 and TLR4 play opposing roles in WAT homeostasis and point to the existence of cross-regulation among TLR2 and TLR4 during adipocyte differentiation both in vitro and in vivo.
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Affiliation(s)
- Natalia Cuesta
- School of Medicine, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Correspondence:
| | - Sonia Fernández-Veledo
- Instituto de Investigación Sanitaria Pere Virgili, University Hospital of Tarragona Joan XXIII, 43007 Tarragona, Spain
| | - Carmen Punzón
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid—Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
| | - Cristóbal Moreno
- School of Medicine, Universidad Alfonso X el Sabio, Villanueva de la Cañada, 28691 Madrid, Spain
| | - Beatriz Barrocal
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid—Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
| | - Vinatha Sreeramkumar
- School of Health and Biomedical Sciences, Universidad Europea de Madrid, Villaviciosa de Odón, 28670 Madrid, Spain
| | - Manuel Desco
- Department of Bioengineering and Aerospace Engineering, Universidad Carlos III de Madrid, 28911 Leganés, Spain
| | - Manuel Fresno
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid—Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
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5
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Ceasrine AM, Bilbo SD. Dietary fat: a potent microglial influencer. Trends Endocrinol Metab 2022; 33:196-205. [PMID: 35078706 PMCID: PMC8881786 DOI: 10.1016/j.tem.2021.12.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/14/2021] [Accepted: 12/23/2021] [Indexed: 12/25/2022]
Abstract
Poor nutrition, lack of exercise, and genetic predisposition all contribute to the growing epidemic of obesity. Overweight/obesity create an environment of chronic inflammation that leads to negative physiological and neurological outcomes, such as diabetes, cardiovascular disease, and anxiety/depression. While the whole body contributes to metabolic homeostasis, the neuroimmune system has recently emerged as a key regulator of metabolism. Microglia, the resident immune cells of the brain, respond both directly and indirectly to dietary fat, and the environment in which microglia develop contributes to their responsiveness later in life. Thus, high maternal weight during pregnancy may have consequences for microglial function in offspring. Here, we discuss the most recent findings on microglia signaling in overweight/obesity with a focus on perinatal programming.
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Affiliation(s)
- Alexis M Ceasrine
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27710, USA
| | - Staci D Bilbo
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27710, USA; Department of Neurobiology, Duke University, Durham, NC 27710, USA; Department of Cell Biology, Duke University, Durham, NC 27710, USA.
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Bhusal A, Rahman MH, Suk K. Hypothalamic inflammation in metabolic disorders and aging. Cell Mol Life Sci 2021; 79:32. [PMID: 34910246 PMCID: PMC11071926 DOI: 10.1007/s00018-021-04019-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/01/2021] [Accepted: 10/29/2021] [Indexed: 12/15/2022]
Abstract
The hypothalamus is a critical brain region for the regulation of energy homeostasis. Over the years, studies on energy metabolism primarily focused on the neuronal component of the hypothalamus. Studies have recently uncovered the vital role of glial cells as an additional player in energy balance regulation. However, their inflammatory activation under metabolic stress condition contributes to various metabolic diseases. The recruitment of monocytes and macrophages in the hypothalamus helps sustain such inflammation and worsens the disease state. Neurons were found to actively participate in hypothalamic inflammatory response by transmitting signals to the surrounding non-neuronal cells. This activation of different cell types in the hypothalamus leads to chronic, low-grade inflammation, impairing energy balance and contributing to defective feeding habits, thermogenesis, and insulin and leptin signaling, eventually leading to metabolic disorders (i.e., diabetes, obesity, and hypertension). The hypothalamus is also responsible for the causation of systemic aging under metabolic stress. A better understanding of the multiple factors contributing to hypothalamic inflammation, the role of the different hypothalamic cells, and their crosstalks may help identify new therapeutic targets. In this review, we focus on the role of glial cells in establishing a cause-effect relationship between hypothalamic inflammation and the development of metabolic diseases. We also cover the role of other cell types and discuss the possibilities and challenges of targeting hypothalamic inflammation as a valid therapeutic approach.
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Affiliation(s)
- Anup Bhusal
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
| | - Md Habibur Rahman
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
- Division of Endocrinology, Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ, 08901, USA
| | - Kyoungho Suk
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea.
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea.
- Brain Science and Engineering Institute, Kyungpook National University, Daegu, 41944, Republic of Korea.
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7
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Zengeler KE, Lukens JR. Innate immunity at the crossroads of healthy brain maturation and neurodevelopmental disorders. Nat Rev Immunol 2021; 21:454-468. [PMID: 33479477 PMCID: PMC9213174 DOI: 10.1038/s41577-020-00487-7] [Citation(s) in RCA: 131] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2020] [Indexed: 12/29/2022]
Abstract
The immune and nervous systems have unique developmental trajectories that individually build intricate networks of cells with highly specialized functions. These two systems have extensive mechanistic overlap and frequently coordinate to accomplish the proper growth and maturation of an organism. Brain resident innate immune cells - microglia - have the capacity to sculpt neural circuitry and coordinate copious and diverse neurodevelopmental processes. Moreover, many immune cells and immune-related signalling molecules are found in the developing nervous system and contribute to healthy neurodevelopment. In particular, many components of the innate immune system, including Toll-like receptors, cytokines, inflammasomes and phagocytic signals, are critical contributors to healthy brain development. Accordingly, dysfunction in innate immune signalling pathways has been functionally linked to many neurodevelopmental disorders, including autism and schizophrenia. This review discusses the essential roles of microglia and innate immune signalling in the assembly and maintenance of a properly functioning nervous system.
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Affiliation(s)
- Kristine E Zengeler
- Department of Neuroscience, Center for Brain Immunology and Glia (BIG), Charlottesville, VA, USA.
- Neuroscience Graduate Program, Charlottesville, VA, USA.
- Cell and Molecular Biology Training Program, School of Medicine, University of Virginia, Charlottesville, VA, USA.
| | - John R Lukens
- Department of Neuroscience, Center for Brain Immunology and Glia (BIG), Charlottesville, VA, USA.
- Neuroscience Graduate Program, Charlottesville, VA, USA.
- Cell and Molecular Biology Training Program, School of Medicine, University of Virginia, Charlottesville, VA, USA.
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8
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Szentirmai É, Massie AR, Kapás L. Lipoteichoic acid, a cell wall component of Gram-positive bacteria, induces sleep and fever and suppresses feeding. Brain Behav Immun 2021; 92:184-192. [PMID: 33307170 PMCID: PMC7897295 DOI: 10.1016/j.bbi.2020.12.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/30/2020] [Accepted: 12/06/2020] [Indexed: 11/19/2022] Open
Abstract
Fragments of the bacterial cell wall are bioactive microbial molecules that have profound effects on the function of the brain. Some of the cell wall constituents are common to both Gram-positive and Gram-negative bacteria, e.g., peptidoglycans, while other cell wall components are specific to either Gram-positive or Gram-negative microbes. Lipopolysaccharide (LPS), also called endotoxin, is found exclusively in Gram-negative bacteria, while lipoteichoic acid (LTA) is specific to Gram-positive bacteria. The effects of peptidoglycans, their fragments, and LPS are well characterized, they induce sleep, fever and anorexia. In the present study, we investigated the sleep, body temperature and food intake modulating effects of LTA. We found that intraperitoneal injection of 100 and 250 μg LTA from B. subtilis and S. aureus increases non-rapid-eye movement sleep (NREMS) in mice. The effects were dose-dependent, and the changes were accompanied by decreased motor activity and feeding as well as febrile responses. Intraperitoneal injection of 10 μg LTA induced monophasic increases in body temperature, while 100 and 250 μg LTA from B. subtilis induced initial hypothermia followed by fever. Treatment with 250 μg LTA from S. aureus elicited monophasic hypothermia. Administration of 300 μg/kg LTA from S. aureus directly into the portal vein elicited similar sleep responses in rats but did not affect body temperature. The sleep-modulating effects of LTA were similar to that of LPS in mice, although LTA appears to be less potent. These findings suggest that the role of LTA in signaling by Gram-positive bacteria in the host body is analogous to the role of LPS/endotoxin in signaling by Gram-negative microbes. LTA may play a role in the development of sickness response in clinically manifest Gram-positive bacterial infections and may contribute to sleep signaling by the commensal intestinal microbiota.
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Affiliation(s)
- Éva Szentirmai
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University, Spokane, WA, United States; Sleep and Performance Research Center, Washington State University, Spokane, WA, United States.
| | - Ashley R Massie
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University, Spokane, WA, United States
| | - Levente Kapás
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University, Spokane, WA, United States; Sleep and Performance Research Center, Washington State University, Spokane, WA, United States
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9
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Aviello G, Cristiano C, Luckman SM, D'Agostino G. Brain control of appetite during sickness. Br J Pharmacol 2020; 178:2096-2110. [DOI: 10.1111/bph.15189] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 06/20/2020] [Accepted: 06/23/2020] [Indexed: 12/13/2022] Open
Affiliation(s)
- Gabriella Aviello
- Department of Pharmacy, School of Medicine and Surgery University of Naples Federico II Naples Italy
| | - Claudia Cristiano
- Department of Pharmacy, School of Medicine and Surgery University of Naples Federico II Naples Italy
| | - Simon M. Luckman
- Faculty of Biology, Medicine and Health, School of Medical Sciences University of Manchester Manchester UK
| | - Giuseppe D'Agostino
- Faculty of Biology, Medicine and Health, School of Medical Sciences University of Manchester Manchester UK
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10
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Chen CY, Shih YC, Hung YF, Hsueh YP. Beyond defense: regulation of neuronal morphogenesis and brain functions via Toll-like receptors. J Biomed Sci 2019; 26:90. [PMID: 31684953 PMCID: PMC6827257 DOI: 10.1186/s12929-019-0584-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 10/23/2019] [Indexed: 12/16/2022] Open
Abstract
Toll-like receptors (TLRs) are well known as critical pattern recognition receptors that trigger innate immune responses. In addition, TLRs are expressed in neurons and may act as the gears in the neuronal detection/alarm system for making good connections. As neuronal differentiation and circuit formation take place along with programmed cell death, neurons face the challenge of connecting with appropriate targets while avoiding dying or dead neurons. Activation of neuronal TLR3, TLR7 and TLR8 with nucleic acids negatively modulates neurite outgrowth and alters synapse formation in a cell-autonomous manner. It consequently influences neural connectivity and brain function and leads to deficits related to neuropsychiatric disorders. Importantly, neuronal TLR activation does not simply duplicate the downstream signal pathways and effectors of classical innate immune responses. The differences in spatial and temporal expression of TLRs and their ligands likely account for the diverse signaling pathways of neuronal TLRs. In conclusion, the accumulated evidence strengthens the idea that the innate immune system of neurons serves as an alarm system that responds to exogenous pathogens as well as intrinsic danger signals and fine-tune developmental processes of neurons.
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Affiliation(s)
- Chiung-Ya Chen
- Institute of Molecular Biology, Academia Sinica, 128, Academia Rd., Sec. 2, Taipei, 11529, Taiwan, Republic of China.
| | - Yi-Chun Shih
- Institute of Molecular Biology, Academia Sinica, 128, Academia Rd., Sec. 2, Taipei, 11529, Taiwan, Republic of China
| | - Yun-Fen Hung
- Institute of Molecular Biology, Academia Sinica, 128, Academia Rd., Sec. 2, Taipei, 11529, Taiwan, Republic of China
| | - Yi-Ping Hsueh
- Institute of Molecular Biology, Academia Sinica, 128, Academia Rd., Sec. 2, Taipei, 11529, Taiwan, Republic of China.
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11
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Dalby MJ, Aviello G, Ross AW, Walker AW, Barrett P, Morgan PJ. Diet induced obesity is independent of metabolic endotoxemia and TLR4 signalling, but markedly increases hypothalamic expression of the acute phase protein, SerpinA3N. Sci Rep 2018; 8:15648. [PMID: 30353127 PMCID: PMC6199263 DOI: 10.1038/s41598-018-33928-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 10/08/2018] [Indexed: 01/17/2023] Open
Abstract
Hypothalamic inflammation is thought to contribute to obesity. One potential mechanism is via gut microbiota derived bacterial lipopolysaccharide (LPS) entering into the circulation and activation of Toll-like receptor-4. This is called metabolic endotoxemia. Another potential mechanism is systemic inflammation arising from sustained exposure to high-fat diet (HFD) over more than 12 weeks. In this study we show that mice fed HFD over 8 weeks become obese and show elevated plasma LPS binding protein, yet body weight gain and adiposity is not attenuated in mice lacking Tlr4 or its co-receptor Cd14. In addition, caecal microbiota composition remained unchanged by diet. Exposure of mice to HFD over a more prolonged period (20 weeks) to drive systemic inflammation also caused obesity. RNAseq used to assess hypothalamic inflammation in these mice showed increased hypothalamic expression of Serpina3n and Socs3 in response to HFD, with few other genes altered. In situ hybridisation confirmed increased Serpina3n and Socs3 expression in the ARC and DMH at 20-weeks, but also at 8-weeks and increased SerpinA3N protein could be detected as early as 1 week on HFD. Overall these data show lack of hypothalamic inflammation in response to HFD and that metabolic endotoxemia does not link HFD to obesity.
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Affiliation(s)
- Matthew J Dalby
- Rowett Institute, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom
| | - Gabriella Aviello
- Rowett Institute, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom
| | - Alexander W Ross
- Rowett Institute, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom
| | - Alan W Walker
- Rowett Institute, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom
| | - Perry Barrett
- Rowett Institute, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom
| | - Peter J Morgan
- Rowett Institute, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom.
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12
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Spurthi KM, Sarikhani M, Mishra S, Desingu PA, Yadav S, Rao S, Maity S, Tamta AK, Kumar S, Majumdar S, Jain A, Raghuraman A, Khan D, Singh I, Samuel RJ, Ramachandra SG, Nandi D, Sundaresan NR. Toll-like receptor 2 deficiency hyperactivates the FoxO1 transcription factor and induces aging-associated cardiac dysfunction in mice. J Biol Chem 2018; 293:13073-13089. [PMID: 29929978 DOI: 10.1074/jbc.ra118.001880] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 06/09/2018] [Indexed: 12/17/2022] Open
Abstract
Toll-like receptors (TLRs) are a family of pattern-recognition receptors involved in innate immunity. Previous studies have shown that TLR2 inhibition protects the heart from acute stress, including myocardial infarction and doxorubicin-induced cardiotoxicity in animal models. However, the role of TLR2 in the development of aging-associated heart failure is not known. In this work, we studied aging-associated changes in structure and function of TLR2-deficient mice hearts. Whereas young TLR2-KO mice did not develop marked cardiac dysfunction, 8- and 12-month-old TLR2-KO mice exhibited spontaneous adverse cardiac remodeling and cardiac dysfunction in an age-dependent manner. The hearts of the 8-month-old TLR2-KO mice had increased fibrosis, cell death, and reactivation of fetal genes. Moreover, TLR2-KO hearts displayed reduced infiltration by macrophages, increased numbers of myofibroblasts and atrophic cardiomyocytes, and higher levels of the atrophy-related ubiquitin ligases MuRF-1 and atrogin-1. Mechanistically, TLR2 deficiency impaired the PI3K/Akt signaling pathway, leading to hyperactivation of the transcription factor Forkhead box protein O1 (FoxO1) and, in turn, to elevated expression of FoxO target genes involved in the regulation of muscle wasting and cell death. AS1842856-mediated chemical inhibition of FoxO1 reduced the expression of the atrophy-related ubiquitin ligases and significantly reversed the adverse cardiac remodeling while improving the contractile functions in the TLR2-KO mice. Interestingly, TLR2 levels decreased in hearts of older mice, and the activation of TLR1/2 signaling improved cardiac functions in these mice. These findings suggest that TLR2 signaling is essential for protecting the heart against aging-associated adverse remodeling and contractile dysfunction in mice.
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Affiliation(s)
- Kondapalli Mrudula Spurthi
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Mohsen Sarikhani
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Sneha Mishra
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Perumal Arumugam Desingu
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Shikha Yadav
- the Department of Biochemistry, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Swathi Rao
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Sangeeta Maity
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Ankit Kumar Tamta
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Shweta Kumar
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Shamik Majumdar
- the Department of Biochemistry, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Aditi Jain
- the Centre for Biosystems Science and Engineering, Indian Institute of Science, Bengaluru, Karnataka 560012, India, and
| | - Aishwarya Raghuraman
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Danish Khan
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Ishwar Singh
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Rosa J Samuel
- the Central Animal Facility, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Subbaraya G Ramachandra
- the Central Animal Facility, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Dipankar Nandi
- the Department of Biochemistry, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Nagalingam R Sundaresan
- From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, Karnataka 560012, India,
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13
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Caplan IF, Maguire-Zeiss KA. Toll-Like Receptor 2 Signaling and Current Approaches for Therapeutic Modulation in Synucleinopathies. Front Pharmacol 2018; 9:417. [PMID: 29780321 PMCID: PMC5945810 DOI: 10.3389/fphar.2018.00417] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 04/10/2018] [Indexed: 12/18/2022] Open
Abstract
The innate immune response in the central nervous system (CNS) is implicated as both beneficial and detrimental to health. Integral to this process are microglia, the resident immune cells of the CNS. Microglia express a wide variety of pattern-recognition receptors, such as Toll-like receptors, that detect changes in the neural environment. The activation of microglia and the subsequent proinflammatory response has become increasingly relevant to synucleinopathies, including Parkinson's disease the second most prevalent neurodegenerative disease. Within these diseases there is evidence of the accumulation of endogenous α-synuclein that stimulates an inflammatory response from microglia via the Toll-like receptors. There have been recent developments in both new and old pharmacological agents designed to target microglia and curtail the inflammatory environment. This review will aim to delineate the process of microglia-mediated inflammation and new therapeutic avenues to manage the response.
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Affiliation(s)
- Ian F Caplan
- Biology Department, Georgetown University, Washington, DC, United States
| | - Kathleen A Maguire-Zeiss
- Biology Department, Georgetown University, Washington, DC, United States.,Department of Neuroscience, Georgetown University Medical Center, Washington, DC, United States
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14
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Targeting pattern-recognition receptors to discover new small molecule immune modulators. Eur J Med Chem 2018; 144:82-92. [DOI: 10.1016/j.ejmech.2017.12.026] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 11/03/2017] [Accepted: 12/07/2017] [Indexed: 12/21/2022]
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15
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TLR2 agonism reverses chemotherapy-induced neutropenia in Macaca fascicularis. Blood Adv 2017; 1:2553-2562. [PMID: 29296907 DOI: 10.1182/bloodadvances.2017010611] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 11/09/2017] [Indexed: 11/20/2022] Open
Abstract
Neutropenia is a common consequence of radiation and chemotherapy in cancer patients. The resulting immunocompromised patients become highly susceptible to potentially life-threatening infections. Granulocyte colony-stimulating factor (G-CSF) is known to stimulate neutrophil production and is widely used as a treatment of chemotherapy-induced neutropenia. A small-molecule G-CSF secretagogue without a requirement for refrigerated supply chain would offer a more convenient and cost-effective treatment of chemotherapy-induced neutropenia. Bacterial lipopeptides activate innate immune responses through Toll-like receptor 2 (TLR2) and induce the release of cytokines, including G-CSF, from macrophages, monocytes, and endothelial. Pam2CSK4 is a synthetic lipopeptide that effectively mimics bacterial lipoproteins known to activate TLR2 receptor signaling through the TLR2/6 heterodimer. Substrate-based drug design led to the discovery of GSK3277329, which stimulated the release of G-CSF in activated THP-1 cells, peripheral blood mononuclear cells, and human umbilical vein endothelial cells. When administered subcutaneously to cynomolgus monkeys (Macaca fascicularis), GSK3277329 caused systemic elevation of G-CSF and interleukin-6 (IL-6), but not IL-1β or tumor necrosis factor α, indicating a selective cytokine-stimulation profile. Repeat daily injections of GSK3277329 in healthy monkeys also raised circulating neutrophils above the normal range over a 1-week treatment period. More importantly, repeated daily injections of GSK3277329 over a 2-week period restored neutrophil loss in monkeys given chemotherapy treatment (cyclophosphamide, Cytoxan). These data demonstrate preclinical in vivo proof of concept that TLR2 agonism can drive both G-CSF induction and subsequent neutrophil elevation in the cynomolgus monkey and could be a therapeutic strategy for the treatment of chemotherapy-induced neutropenia.
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16
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Silva VRR, Katashima CK, Bueno Silva CG, Lenhare L, Micheletti TO, Camargo RL, Ghezzi AC, Camargo JA, Assis AM, Tobar N, Morari J, Razolli DS, Moura LP, Pauli JR, Cintra DE, Velloso LA, Saad MJA, Ropelle ER. Hypothalamic S1P/S1PR1 axis controls energy homeostasis in Middle-Aged Rodents: the reversal effects of physical exercise. Aging (Albany NY) 2017; 9:142-155. [PMID: 28039439 PMCID: PMC5310661 DOI: 10.18632/aging.101138] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Accepted: 11/29/2016] [Indexed: 02/06/2023]
Abstract
Recently, we demonstrated that the hypothalamic S1PR1/STAT3 axis plays a critical role in the control of food consumption and energy expenditure in rodents. Here, we found that reduction of hypothalamic S1PR1 expression occurs in an age-dependent manner, and was associated with defective thermogenic signaling and weight gain. To address the physiological relevance of these findings, we investigated the effects of chronic and acute exercise on the hypothalamic S1PR1/STAT3 axis. Chronic exercise increased S1PR1 expression and STAT3 phosphorylation in the hypothalamus, restoring the anorexigenic and thermogenic signals in middle-aged mice. Acutely, exercise increased sphingosine-1-phosphate (S1P) levels in the cerebrospinal fluid (CSF) of young rats, whereas the administration of CSF from exercised young rats into the hypothalamus of middle-aged rats at rest was sufficient to reduce the food intake. Finally, the intracerebroventricular (ICV) administration of S1PR1 activators, including the bioactive lipid molecule S1P, and pharmacological S1PR1 activator, SEW2871, induced a potent STAT3 phosphorylation and anorexigenic response in middle-aged rats. Overall, these results suggest that hypothalamic S1PR1 is important for the maintenance of energy balance and provide new insights into the mechanism by which exercise controls the anorexigenic and thermogenic signals in the central nervous system during the aging process.
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Affiliation(s)
- Vagner Ramon Rodrigues Silva
- School of Applied Sciences, University of Campinas, Limeira, SP, Brazil.,Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | | | - Carla G Bueno Silva
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | - Luciene Lenhare
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | | | | | - Ana Carolina Ghezzi
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | | | | | - Natalia Tobar
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | - Joseane Morari
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | - Daniela S Razolli
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | | | - José Rodrigo Pauli
- School of Applied Sciences, University of Campinas, Limeira, SP, Brazil.,Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil.,CEPECE - Research Center of Sport Sciences, School of Applied Sciences, University of Campinas, Limeira, SP, Brazil
| | | | - Lício Augusto Velloso
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil.,Laboratory of Cell Signaling, Obesity and Comorbidities Research Center, University of Campinas, Campinas, 1308-970, Brazil
| | - Mario J A Saad
- Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil
| | - Eduardo Rochete Ropelle
- School of Applied Sciences, University of Campinas, Limeira, SP, Brazil.,Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil.,CEPECE - Research Center of Sport Sciences, School of Applied Sciences, University of Campinas, Limeira, SP, Brazil.,Laboratory of Cell Signaling, Obesity and Comorbidities Research Center, University of Campinas, Campinas, 1308-970, Brazil
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17
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Spiljar M, Merkler D, Trajkovski M. The Immune System Bridges the Gut Microbiota with Systemic Energy Homeostasis: Focus on TLRs, Mucosal Barrier, and SCFAs. Front Immunol 2017; 8:1353. [PMID: 29163467 PMCID: PMC5670327 DOI: 10.3389/fimmu.2017.01353] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 10/03/2017] [Indexed: 12/17/2022] Open
Abstract
The gut microbiota is essential for the development and regulation of the immune system and the metabolism of the host. Germ-free animals have altered immunity with increased susceptibility to immunologic diseases and show metabolic alterations. Here, we focus on two of the major immune-mediated microbiota-influenced components that signal far beyond their local environment. First, the activation or suppression of the toll-like receptors (TLRs) by microbial signals can dictate the tone of the immune response, and they are implicated in regulation of the energy homeostasis. Second, we discuss the intestinal mucosal surface is an immunologic component that protects the host from pathogenic invasion, is tightly regulated with regard to its permeability and can influence the systemic energy balance. The short chain fatty acids are a group of molecules that can both modulate the intestinal barrier and escape the gut to influence systemic health. As modulators of the immune response, the microbiota-derived signals influence functions of distant organs and can change susceptibility to metabolic diseases.
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Affiliation(s)
- Martina Spiljar
- Faculty of Medicine, Department of Cell Physiology and Metabolism, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland.,Diabetes Center, Faculty of Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Doron Merkler
- Faculty of Medicine, Department of Pathology and Immunology, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Mirko Trajkovski
- Faculty of Medicine, Department of Cell Physiology and Metabolism, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland.,Diabetes Center, Faculty of Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland
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18
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Abstract
The hypothalamus is an evolutionarily conserved brain structure that regulates an organism's basic functions, such as homeostasis and reproduction. Several hypothalamic nuclei and neuronal circuits have been the focus of many studies seeking to understand their role in regulating these basic functions. Within the hypothalamic neuronal populations, the arcuate melanocortin system plays a major role in controlling homeostatic functions. The arcuate pro-opiomelanocortin (POMC) neurons in particular have been shown to be critical regulators of metabolism and reproduction because of their projections to several brain areas both in and outside of the hypothalamus, such as autonomic regions of the brain stem and spinal cord. Here, we review and discuss the current understanding of POMC neurons from their development and intracellular regulators to their physiological functions and pathological dysregulation.
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Affiliation(s)
- Chitoku Toda
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, Connecticut 06520; .,Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Anna Santoro
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, Connecticut 06520; .,Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Jung Dae Kim
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, Connecticut 06520; .,Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Sabrina Diano
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, Connecticut 06520; .,Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut 06520.,Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut 06520.,Section of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut 06520
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19
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DeKorver NW, Chaudoin TR, Bonasera SJ. Toll-Like Receptor 2 Is a Regulator of Circadian Active and Inactive State Consolidation in C57BL/6 Mice. Front Aging Neurosci 2017; 9:219. [PMID: 28769782 PMCID: PMC5510442 DOI: 10.3389/fnagi.2017.00219] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 06/23/2017] [Indexed: 12/18/2022] Open
Abstract
Regulatory systems required to maintain behavioral arousal remain incompletely understood. We describe a previously unappreciated role that toll-like receptor 2 (Tlr2, a membrane bound pattern recognition receptor that recognizes specific bacterial, viral, and fungal peptides), contributes toward regulation of behavioral arousal. In 4–4.5 month old mice with constitutive loss of Tlr2 function (Tlr2−/− mice), we note a marked consolidation in the circadian pattern of both active and inactive states. Specifically, Tlr2−/− mice demonstrated significantly fewer but longer duration active states during the circadian dark cycle, and significantly fewer but longer duration inactive states during the circadian light cycle. Tlr2−/− mice also consumed less food and water, and moved less during the circadian light cycle. Analysis of circadian rhythms further suggested that Tlr2−/− mice demonstrated less day-to-day variability in feeding, drinking, and movement behaviors. Reevaluation of this same mouse cohort at age 8–8.5 months revealed a clear blunting of these differences. However, Tlr2−/− mice were still noted to have fewer short-duration active states during the circadian dark cycle, and continued to demonstrate significantly less day-to-day variability in feeding, drinking, and movement behaviors. These results suggest that Tlr2 function may have a role in promoting transitions between active and inactive states. Prior studies have demonstrated that Tlr2 regulates sickness behaviors including hypophagia, hyperthermia, and decreased activity. Our work suggests that Tlr2 function also evokes behavioral fragmentation, another aspect of sickness behavior and a clinically significant problem of older adults.
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Affiliation(s)
- Nicholas W DeKorver
- Division of Geriatrics, Department of Internal Medicine, Durham Research Center II, University of Nebraska Medical CenterOmaha, NE, United States
| | - Tammy R Chaudoin
- Division of Geriatrics, Department of Internal Medicine, Durham Research Center II, University of Nebraska Medical CenterOmaha, NE, United States
| | - Stephen J Bonasera
- Division of Geriatrics, Department of Internal Medicine, Durham Research Center II, University of Nebraska Medical CenterOmaha, NE, United States
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20
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Zilkha N, Kuperman Y, Kimchi T. High-fat diet exacerbates cognitive rigidity and social deficiency in the BTBR mouse model of autism. Neuroscience 2017; 345:142-154. [DOI: 10.1016/j.neuroscience.2016.01.070] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Revised: 01/26/2016] [Accepted: 01/29/2016] [Indexed: 12/13/2022]
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21
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Toll-like receptor 2 is increased in neurons in Parkinson's disease brain and may contribute to alpha-synuclein pathology. Acta Neuropathol 2017; 133:303-319. [PMID: 27888296 PMCID: PMC5250664 DOI: 10.1007/s00401-016-1648-8] [Citation(s) in RCA: 174] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 11/15/2016] [Accepted: 11/19/2016] [Indexed: 12/24/2022]
Abstract
Inflammation is likely a key contributor to the pathogenesis of Parkinson’s disease (PD), a progressively debilitating neurodegenerative disease that is accompanied by a pathological accumulation of the α-synuclein protein in a staged manner through the brain. What leads to the accumulation of α-synuclein in PD and how this relates to inflammatory pathways, however, is not entirely clear. Toll-like receptor (TLR) signaling is a major pathway mediating inflammation and, in particular, TLR2 is increasingly being implicated in PD. We have, therefore, examined the expression of TLR2 in postmortem brain tissue from PD patients and matched controls. We confirm that TLR2 is increased in PD brain, and find that levels of TLR2 correlate with the accumulation of pathological α-synuclein. TLR2 was expressed on neurons as well as microglia; however, the neuronal rather than glial expression of TLR2 was significantly increased in PD brain in accordance with disease staging, and TLR2 was strongly localized to α-synuclein positive Lewy bodies. In cell culture, activation of neuronal TLR2 induced an inflammatory response, including the secretion of inflammatory cytokines and microglial-activating chemokines, as well as the production of reactive oxygen species. Moreover, activation of neuronal TLR2 increased levels of endogenous α-synuclein protein, which was in turn associated with increased levels of the autophagy/lysosomal pathway marker p62. Finally, promoting autophagy with rapamycin or pharmacological inhibition of the TLR2 signaling pathway prevented the TLR2-mediated increase in α-synuclein in neuronal cell cultures. These results implicate neuronal TLR2 expression in human PD pathogenesis. In particular, the increased expression of TLR2 on neurons may provide new insight into disease pathogenesis and/or options for therapeutic intervention.
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22
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Tran DQ, Tse EK, Kim MH, Belsham DD. Diet-induced cellular neuroinflammation in the hypothalamus: Mechanistic insights from investigation of neurons and microglia. Mol Cell Endocrinol 2016; 438:18-26. [PMID: 27208620 DOI: 10.1016/j.mce.2016.05.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 05/17/2016] [Indexed: 12/31/2022]
Abstract
Diet-induced obesity can lead to detrimental chronic disorders. The severity of this global epidemic has encouraged ongoing research to characterize the mechanisms underlying obesity and its comorbidities. Recent evidence suggests that saturated fatty acids (SFA) in high-fat diets rapidly generate inflammation in the arcuate nucleus of the hypothalamus (ARC), which centrally regulates whole-body energy homeostasis. Herein, we will review the roles of hypothalamic neurons and resident microglia in the initiation of SFA-induced hypothalamic inflammation. Particularly, we focus on neuronal and microglial free fatty acid-sensing and capacity to produce inflammatory signaling. We also outline a potential role of peripherally-derived monocytes in this inflammation. And finally, we explore synaptic plasticity as a mechanism through which hypothalamic inflammation can modulate ARC circuitry, and thus disrupt energy homeostasis.
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Affiliation(s)
- Dean Q Tran
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Erika K Tse
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Mun Heui Kim
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Denise D Belsham
- Department of Physiology, University of Toronto, Toronto, ON, Canada; Department of Obstetrics and Gynaecology, University of Toronto, Toronto, ON, Canada; Department of Medicine, University of Toronto, Toronto, ON, Canada.
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23
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McDonald CL, Hennessy E, Rubio-Araiz A, Keogh B, McCormack W, McGuirk P, Reilly M, Lynch MA. Inhibiting TLR2 activation attenuates amyloid accumulation and glial activation in a mouse model of Alzheimer's disease. Brain Behav Immun 2016; 58:191-200. [PMID: 27422717 DOI: 10.1016/j.bbi.2016.07.143] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 07/08/2016] [Accepted: 07/09/2016] [Indexed: 12/11/2022] Open
Abstract
The effects of Toll-like receptor (TLR) activation in peripheral cells are well characterized but, although several TLRs are expressed on cells of the brain, the consequences of their activation on neuronal function remain to be fully investigated, particularly in the context of assessing their potential as therapeutic targets in neurodegenerative diseases. Several endogenous TLR ligands have been identified, many of which are soluble factors released from cells exposed to stressors. In addition, amyloid-β (Aβ) the main constituent of the amyloid plaques in Alzheimer's disease (AD), activates TLR2, although it has also been shown to bind to several other receptors. The objective of this study was to determine whether activation of TLR2 played a role in the developing inflammatory changes and Aβ accumulation in a mouse model of AD. Wild type and transgenic mice that overexpress amyloid precursor protein and presenilin 1 (APP/PS1 mice) were treated with anti-TLR2 antibody for 7months from the age of 7-14months. We demonstrate that microglial and astroglial activation, as assessed by MHCII, CD68 and GFAP immunoreactivity was decreased in anti-TLR2 antibody-treated compared with control (IgG)-treated mice. This was associated with reduced Aβ plaque burden and improved performance in spatial learning. The data suggest that continued TLR2 activation contributes to the developing neuroinflammation and pathology and may be provide a strategy for limiting the progression of AD.
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Affiliation(s)
- Claire L McDonald
- Trinity College Institute for Neuroscience, Trinity College, Dublin 2, Ireland
| | - Edel Hennessy
- Physical Therapy and Rehabilitation Science, Brain and Spinal Injury Center, University of California San Francisco, San Francisco General Hospital, 1001 Potrero av, Bld#1, Room#101, 94110 San Francisco, CA, United States
| | - Ana Rubio-Araiz
- Trinity College Institute for Neuroscience, Trinity College, Dublin 2, Ireland
| | - Brian Keogh
- Opsona Therapeutics LTD, 2nd Floor Ashford House, Tara Street, Dublin 2 D02 VX67, Ireland
| | - William McCormack
- Immune Regulation Research Group, Trinity Biomedical Sciences Institute, Trinity College Dublin, 152-160 Pearse St, Dublin 2, Ireland
| | - Peter McGuirk
- Opsona Therapeutics LTD, 2nd Floor Ashford House, Tara Street, Dublin 2 D02 VX67, Ireland
| | - Mary Reilly
- Opsona Therapeutics LTD, 2nd Floor Ashford House, Tara Street, Dublin 2 D02 VX67, Ireland
| | - Marina A Lynch
- Trinity College Institute for Neuroscience, Trinity College, Dublin 2, Ireland.
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24
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Jin S, Kim JG, Park JW, Koch M, Horvath TL, Lee BJ. Hypothalamic TLR2 triggers sickness behavior via a microglia-neuronal axis. Sci Rep 2016; 6:29424. [PMID: 27405276 PMCID: PMC4942617 DOI: 10.1038/srep29424] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 06/17/2016] [Indexed: 12/16/2022] Open
Abstract
Various pathophysiologic mechanisms leading to sickness behaviors have been proposed. For example, an inflammatory process in the hypothalamus has been implicated, but the signaling modalities that involve inflammatory mechanisms and neuronal circuit functions are ill-defined. Here, we show that toll-like receptor 2 (TLR2) activation by intracerebroventricular injection of its ligand, Pam3CSK4, triggered hypothalamic inflammation and activation of arcuate nucleus microglia, resulting in altered input organization and increased activity of proopiomelanocortin (POMC) neurons. These animals developed sickness behavior symptoms, including anorexia, hypoactivity, and hyperthermia. Antagonists of nuclear factor kappa B (NF-κB), cyclooxygenase pathway and melanocortin receptors 3/4 reversed the anorexia and body weight loss induced by TLR2 activation. These results unmask an important role of TLR2 in the development of sickness behaviors via stimulation of hypothalamic microglia to promote POMC neuronal activation in association with hypothalamic inflammation.
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Affiliation(s)
- Sungho Jin
- Department of Biological Sciences, University of Ulsan, Ulsan, 680-749, Republic of Korea
| | - Jae Geun Kim
- Division of Life Sciences, College of Life Sciences and Bioengineering, Incheon National University, Incheon, 406-772, Republic of Korea.,Program in Integrative Cell Signaling and Neurobiology of Metabolism, Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Jeong Woo Park
- Department of Biological Sciences, University of Ulsan, Ulsan, 680-749, Republic of Korea
| | - Marco Koch
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.,Institute of Anatomy, University of Leipzig, 04103 Leipzig, Germany
| | - Tamas L Horvath
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Byung Ju Lee
- Department of Biological Sciences, University of Ulsan, Ulsan, 680-749, Republic of Korea
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25
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Lee JK, Luchian T, Park Y. Effect of Regular Exercise on Inflammation Induced by Drug-resistant Staphylococcus aureus 3089 in ICR mice. Sci Rep 2015; 5:16364. [PMID: 26542343 PMCID: PMC4635399 DOI: 10.1038/srep16364] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 10/06/2015] [Indexed: 12/18/2022] Open
Abstract
Obesity is often associated with irregular dietary habits and reduced physical activity. Regular exercise induces a metabolic response that includes increased expression of various cytokines, signaling proteins and hormones, and reduced adipocyte size. In this study, mice performed a swimming exercise for 10 min/day, 5 days/week for 3 weeks. We then investigated the effect of this exercise regimen on inflammation induced by infection with drug-resistant Staphylococcus aureus strain 3089 (DRSA). In humans, DRSA causes dermatitis and pneumonitis. Similarly, DRSA induced inflammatory pneumonitis in both no-exercise (No-EX) and swim-trained (SW-EX) ICR mice. Regular exercise increased levels of the pro-inflammatory cytokines TNF-α and IL-1β and nitric oxide in both serum and whole lung tissue in SW-EX, as compared to No-EX control mice. Moreover, levels of the antimicrobial peptide cathelicidin were significantly increased in visceral adipose tissue and whole lung tissue in the SW-EX group, and this was accompanied by a reduction in the size of visceral adipocytes. In addition, levels of the inflammation marker peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) were not increased in the lung tissue of SW-EX mice. These findings suggest that in these model mice, regular exercise strengthens immune system responses, potentially preventing or mitigating infectious disease.
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Affiliation(s)
- Jong-Kook Lee
- Research Center for Proteinaceous Materials (RCPM), Chosun University, Gwangju, Korea
| | - Tudor Luchian
- Department of Physics, Alexandru I. Cuza University, Iasi, Romania
| | - Yoonkyung Park
- Department of Biotechnology &BK21-Plus Research Team for Bioactive Control Technology, Chosun University, Gwangju, Republic of Korea
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26
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Cheng K, Gao M, Godfroy JI, Brown PN, Kastelowitz N, Yin H. Specific activation of the TLR1-TLR2 heterodimer by small-molecule agonists. SCIENCE ADVANCES 2015; 1:e1400139. [PMID: 26101787 PMCID: PMC4474499 DOI: 10.1126/sciadv.1400139] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 03/12/2015] [Indexed: 05/14/2023]
Abstract
Toll-like receptor (TLR) agonists activate both the innate and the adaptive immune systems. These TLR agonists have been exploited as potent vaccine adjuvants and antitumor agents. We describe the identification and characterization of a small molecule, N-methyl-4-nitro-2-(4-(4-(trifluoromethyl)phenyl)-1 H-imidazol-1-yl)aniline (CU-T12-9), that directly targets TLR1/2 to initiate downstream signaling. CU-T12-9 specifically induces TLR1/2 activation, which can be blocked by either the anti-hTLR1 or the anti-hTLR2 antibody, but not the anti-hTLR6 antibody. Using a variety of different biophysical assays, we have demonstrated the binding mode of CU-T12-9. By binding to both TLR1 and TLR2, CU-T12-9 facilitates the TLR1/2 heterodimeric complex formation, which in turn activates the downstream signaling. Fluorescence anisotropy assays revealed competitive binding to the TLR1/2 complex between CU-T12-9 and Pam3CSK4 with a half-maximal inhibitory concentration (IC50) of 54.4 nM. Finally, we showed that CU-T12-9 signals through nuclear factor κB (NF-κB) and invokes an elevation of the downstream effectors tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10), and inducible nitric oxide synthase (iNOS). Thus, our studies not only provide compelling new insights into the regulation of TLR1/2 signaling transduction but also may facilitate future therapeutic developments.
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Affiliation(s)
- Kui Cheng
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100082, China
| | - Meng Gao
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100082, China
| | - James I. Godfroy
- Department of Chemistry and Biochemistry and the BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Peter N. Brown
- Department of Chemistry and Biochemistry and the BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Noah Kastelowitz
- Department of Chemistry and Biochemistry and the BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Hang Yin
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100082, China
- Department of Chemistry and Biochemistry and the BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA
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27
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Iyer A, Brown L, Whitehead JP, Prins JB, Fairlie DP. Nutrient and immune sensing are obligate pathways in metabolism, immunity, and disease. FASEB J 2015; 29:3612-25. [PMID: 26065858 DOI: 10.1096/fj.15-271155] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 06/02/2015] [Indexed: 12/13/2022]
Abstract
The growth and survival of multicellular organisms depend upon their abilities to acquire and metabolize nutrients, efficiently store and harness energy, and sense and fight infection. Systems for sensing and using nutrients have consequently coevolved alongside systems for sensing and responding to danger signals, including pathogens, and share many of the same cell signaling proteins and networks. Diets rich in carbohydrates and fats can overload these systems, leading to obesity, metabolic dysfunction, impaired immunity, and cardiovascular disease. Excessive nutrient intake promotes adiposity, typically altering adipocyte function and immune cell distribution, both of which trigger metabolic dysfunction. Here, we discuss novel mechanistic links between metabolism and immunity that underlie metabolic dysfunction in obesity. We aim to stimulate debate about how the endocrine and immune systems are connected through autocrine, paracrine, and neuroendocrine signaling in sophisticated networks that are only now beginning to be resolved. Understanding the expression and action of signaling proteins, together with modulating their receptors or pattern recognition using agonists or antagonists, will enable rational intervention in immunometabolism that may lead to novel treatments for obesity and metabolic dysfunction.
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Affiliation(s)
- Abishek Iyer
- *Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia; School of Health and Wellbeing, University of Southern Queensland, Toowoomba, Queensland, Australia; and Mater Research Institute-University of Queensland, Translational Research Institute, Queensland, Australia
| | - Lindsay Brown
- *Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia; School of Health and Wellbeing, University of Southern Queensland, Toowoomba, Queensland, Australia; and Mater Research Institute-University of Queensland, Translational Research Institute, Queensland, Australia
| | - Jonathan P Whitehead
- *Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia; School of Health and Wellbeing, University of Southern Queensland, Toowoomba, Queensland, Australia; and Mater Research Institute-University of Queensland, Translational Research Institute, Queensland, Australia
| | - Johannes B Prins
- *Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia; School of Health and Wellbeing, University of Southern Queensland, Toowoomba, Queensland, Australia; and Mater Research Institute-University of Queensland, Translational Research Institute, Queensland, Australia
| | - David P Fairlie
- *Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia; School of Health and Wellbeing, University of Southern Queensland, Toowoomba, Queensland, Australia; and Mater Research Institute-University of Queensland, Translational Research Institute, Queensland, Australia
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28
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Rodrigues FL, Silva LEV, Hott SC, Bomfim GF, da Silva CAA, Fazan R, Resstel LBM, Tostes RC, Carneiro FS. Toll-like receptor 9 plays a key role in the autonomic cardiac and baroreflex control of arterial pressure. Am J Physiol Regul Integr Comp Physiol 2015; 308:R714-23. [PMID: 25673780 DOI: 10.1152/ajpregu.00150.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 01/27/2015] [Indexed: 02/07/2023]
Abstract
The crosstalk between the immune and the autonomic nervous system may impact the cardiovascular function. Toll-like receptors are components of the innate immune system and play developmental and physiological roles. Toll-like receptor 9 (TLR9) is involved in the pathogenesis of cardiovascular diseases, such as hypertension and heart failure. Since such diseases are commonly accompanied by autonomic imbalance and lower baroreflex sensitivity, we hypothesized that TLR9 modulates cardiac autonomic and baroreflex control of arterial pressure (AP). Toll-like receptor 9 knockout (TLR9 KO) and wild-type (WT) mice were implanted with catheters into carotid artery and jugular vein and allowed to recover for 3 days. After basal recording of AP, mice received methyl-atropine or propranolol. AP and pulse interval (PI) variability were evaluated in the time and frequency domain (spectral analysis), as well as by multiscale entropy. Spontaneous baroreflex was studied by sequence technique. Behavioral and cardiovascular responses to fear-conditioning stress were also evaluated. AP was similar between groups, but TLR9 KO mice exhibited lower basal heart rate (HR). AP variability was not different, but PI variability was increased in TLR9 KO mice. The total entropy was higher in TLR9 KO mice. Moreover, baroreflex function was found higher in TLR9 KO mice. Atropine-induced tachycardia was increased in TLR9 KO mice, whereas the propranolol-induced bradycardia was similar to WT mice. TLR9 KO mice exhibit increased behavioral and decreased tachycardia responses to fear-conditioning stress. In conclusion, our findings suggest that TLR9 may negatively modulate cardiac vagal tone and baroreflex in mice.
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Affiliation(s)
- Fernanda Luciano Rodrigues
- Department of Pharmacology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil
| | - Luiz Eduardo V Silva
- Department of Physiology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil; and
| | - Sara Cristina Hott
- Department of Pharmacology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil
| | - Gisele F Bomfim
- Institute of Health Sciences, Federal University of Mato Grosso, Sinop, Mato Grosso, Brazil
| | - Carlos Alberto Aguiar da Silva
- Department of Physiology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil; and
| | - Rubens Fazan
- Department of Physiology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil; and
| | - Leonardo B M Resstel
- Department of Pharmacology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil
| | - Rita C Tostes
- Department of Pharmacology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil
| | - Fernando S Carneiro
- Department of Pharmacology, Ribeirao Preto Medical School, University of São Paulo, Ribeirao Preto, São Paulo, Brazil;
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29
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Barak B, Feldman N, Okun E. Toll-like receptors as developmental tools that regulate neurogenesis during development: an update. Front Neurosci 2014; 8:272. [PMID: 25221470 PMCID: PMC4148028 DOI: 10.3389/fnins.2014.00272] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 08/11/2014] [Indexed: 12/18/2022] Open
Abstract
Neurogenesis, the process of generating new neurons in the brain, fascinates researchers for its promise to affect multiple cognitive and functional processes in both health and disease. Many cellular pathways are involved in the regulation of neurogenesis, a complexity exemplified by the extensive regulation of this process during brain development. Toll-like receptors (TLRs), hallmarks of innate immunity, are increasingly implemented in various central nervous system plasticity-related processes including neurogenesis. As TLRs are involved in neurodegenerative disorders, understanding the involvement of TLRs in neurogenesis may hold keys for future therapeutic interventions. Herein, we describe the current knowledge on the involvement of TLRs in neurogenesis and neuronal plasticity and point to current knowledge gaps in the field.
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Affiliation(s)
- Boaz Barak
- McGovern Institute for Brain Research and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology Cambridge, MA, USA
| | - Noa Feldman
- The Mina and Everard Goodman Faculty of Life Sciences, The Gonda Multidisciplinary Brain Research Center, Bar Ilan University Ramat-Gan, Israel
| | - Eitan Okun
- The Mina and Everard Goodman Faculty of Life Sciences, The Gonda Multidisciplinary Brain Research Center, Bar Ilan University Ramat-Gan, Israel
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30
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Okun E, Griffioen KJ, Sarah R, Wan R, Cong WN, De Cabo R, Montalvo AM, Levette A, Maudsley S, Martin B, Arumugam TV, Mattson MP. Toll-like receptors 2 and 4 modulate autonomic control of heart rate and energy metabolism. Brain Behav Immun 2014; 36:90-100. [PMID: 24145051 PMCID: PMC3947180 DOI: 10.1016/j.bbi.2013.10.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 09/24/2013] [Accepted: 10/12/2013] [Indexed: 02/07/2023] Open
Abstract
Toll-like receptors (TLR) are innate immune receptors typically activated by microbial-associated molecular patterns (MAMPs) during infection or damage-associated molecular patterns (DAMPs) as a result of tissue injury. Recent findings suggest that TLR2 and TLR4 signaling play important roles in developmental and adult neuroplasticity, and in learning and memory. In addition, activation of TLR2 and TLR4 worsens ischemic injury to the heart and brain in animal models of myocardial infarction and stroke. TLR activation is also implicated in thermoregulation and fever in response to infection. However, it is not known whether TLRs participate in the regulation of the sympathetic and/or parasympathetic components of the autonomic nervous system (ANS). Here we provide evidence that TLR2 and TLR4 influence autonomic regulation of heart rate (HR) body temperature and energy metabolism in mice. We show that mice lacking TLR2 or TLR4 exhibit reduced basal HR, which results from an increase of parasympathetic tone. In addition, thermoregulatory responses to stress are altered in TLR2-/- and TLR4-/- mice, and brown fat-dependent thermoregulation is altered in TLR4-/- mice. Moreover, TLR2-/- and TLR4-/- mice consume less food and exhibit a greater mass compared to wild type mice. Collectively, our findings suggest important roles for TLR2 and TLR4 in the ANS regulation of cardiovascular function, thermoregulation, and energy metabolism.
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Affiliation(s)
- Eitan Okun
- The Mina and Everard Goodman Faculty of Life Sciences, The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan 52900, Israel.
| | - Kathleen J. Griffioen
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
| | - Rothman Sarah
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
| | - Ruiqian Wan
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
| | - Wei-Na Cong
- Laboratory of Clinical Investigation, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Rafael De Cabo
- Translational Gerontology Branch, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Alejandro Martin Montalvo
- Translational Gerontology Branch, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Andrew Levette
- Translational Gerontology Branch, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Stuart Maudsley
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
| | - Bronwen Martin
- Laboratory of Clinical Investigation, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | | | - Mark P. Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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31
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Innate sensors of pathogen and stress: linking inflammation to obesity. J Allergy Clin Immunol 2013; 132:287-94. [PMID: 23905917 DOI: 10.1016/j.jaci.2013.06.022] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 06/20/2013] [Accepted: 06/21/2013] [Indexed: 12/11/2022]
Abstract
Pathogen and nutrient response pathways are evolutionarily conserved and highly integrated to regulate metabolic and immune homeostasis. Excessive nutrients can be sensed by innate pattern recognition receptors as danger signals either directly or through production of endogenous ligands or modulation of intestinal microbiota. This triggers the activation of downstream inflammatory cascades involving nuclear factor κB and mitogen-activated protein kinase and ultimately induces the production of inflammatory cytokines and immune cell infiltration in various metabolic tissues. The chronic low-grade inflammation in the brain, islet, liver, muscle, and adipose tissue further promotes insulin resistance, energy imbalance, and impaired glucose/lipid metabolism, contributing to the metabolic complications of obesity, such as diabetes and atherosclerosis. In addition, innate pathogen receptors have now emerged as a critical link between the intestinal microbiota and host metabolism. In this review we summarize recent studies demonstrating the important roles of innate pathogen receptors, including Toll-like receptors, nucleotide oligomerization domain containing proteins, and inflammasomes in mediating the inflammatory response to metabolic stress in different tissues and highlight the interaction of innate pattern recognition receptors, gut microbiota, and nutrients during the development of obesity and related metabolic disorders.
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32
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Activation and regulation of the pattern recognition receptors in obesity-induced adipose tissue inflammation and insulin resistance. Nutrients 2013; 5:3757-78. [PMID: 24064574 PMCID: PMC3798933 DOI: 10.3390/nu5093757] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 08/14/2013] [Accepted: 09/11/2013] [Indexed: 12/19/2022] Open
Abstract
Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes mellitus, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various immune cells and signaling networks that link the immune and metabolic systems have contributed to our understanding of the pathogenesis of obesity-associated inflammation. Other recent studies have suggested that pattern recognition receptors in the innate immune system recognize various kinds of endogenous and exogenous ligands, and have a crucial role in initiating or promoting obesity-associated chronic inflammation. Importantly, these mediators act on insulin target cells or on insulin-producing cells impairing insulin sensitivity and its secretion. Here, we discuss how various pattern recognition receptors in the immune system underlie the etiology of obesity-associated inflammation and insulin resistance, with a particular focus on the TLR (Toll-like receptor) family protein Radioprotective 105 (RP105)/myeloid differentiation protein-1 (MD-1).
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