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Engel K, Lee HN, Tewari BP, Lewkowicz AP, Ireland DDC, Manangeeswaran M, Verthelyi D. Neonatal Zika virus infection causes transient perineuronal net degradation. Front Cell Neurosci 2023; 17:1187425. [PMID: 37496706 PMCID: PMC10366369 DOI: 10.3389/fncel.2023.1187425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 06/21/2023] [Indexed: 07/28/2023] Open
Abstract
Perineuronal nets (PNNs) form a specialized extracellular matrix that predominantly surrounds parvalbumin (PV)-expressing GABAergic inhibitory interneurons and help regulate neuronal activity. Their formation early in the postnatal period is regulated by neuronal signaling and glial activation raising concerns that part of the long-term effects ascribed to perinatal viral infections could be mediated by altered PNN formation. Previously, we developed a model of neonatal Zika virus (ZIKV) infection where mice have lifelong neurological sequelae that includes motor disfunction and reduced anxiety coupled with a persistent low-grade expression in proinflammatory markers despite resolving the acute infection. Here, we demonstrate that ZIKV infection to P1 neonatal mice results in a reduction of PNN formation during the acute disease with significant reduction in Wisteria floribunda agglutinin (WFA) staining at the peak of infection [15 days post infection (dpi)] that persisted after the symptoms resolved (30 dpi). At 60 dpi, when there is residual inflammation in the CNS, the number of WFA+ cells and the level of WFA staining as well as levels of aggrecan and brevican in the brains of convalescent mice were not different from those in uninfected controls, however, there was increased frequency of PNNs with an immature phenotype. Over time the impact of the perinatal infection became less evident and there were no clear differences in PNN morphology between the groups at 1 year post infection. Of note, the reduction in PNNs during acute ZIKV infection was not associated with decreased mRNA levels of aggrecan or brevican, but increased levels of degraded aggrecan and brevican indicating increased PNN degradation. These changes were associated with increased expression of matrix metalloproteinase 12 (MMP12) and MMP19, but not MMP9, a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) or ADAMTS5. Together our findings indicate that infection at the time of PNN development interferes with PNN formation, but the nets can reform once the infection and inflammation subside.
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Affiliation(s)
- Kaliroi Engel
- Laboratory of Immunology, Center of Excellence in Infectious Disease and Inflammation, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Ha-Na Lee
- Laboratory of Immunology, Center of Excellence in Infectious Disease and Inflammation, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Bhanu P. Tewari
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA, United States
| | - Aaron P. Lewkowicz
- Laboratory of Immunology, Center of Excellence in Infectious Disease and Inflammation, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Derek D. C. Ireland
- Laboratory of Immunology, Center of Excellence in Infectious Disease and Inflammation, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Mohanraj Manangeeswaran
- Laboratory of Immunology, Center of Excellence in Infectious Disease and Inflammation, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Daniela Verthelyi
- Laboratory of Immunology, Center of Excellence in Infectious Disease and Inflammation, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
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Greco GA, Rock M, Amontree M, Lanfranco MF, Korthas H, Hong SH, Turner RS, Rebeck GW, Conant K. CCR5 deficiency normalizes TIMP levels, working memory, and gamma oscillation power in APOE4 targeted replacement mice. Neurobiol Dis 2023; 179:106057. [PMID: 36878326 PMCID: PMC10291850 DOI: 10.1016/j.nbd.2023.106057] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 02/16/2023] [Accepted: 02/26/2023] [Indexed: 03/07/2023] Open
Abstract
The APOE4 allele increases the risk for Alzheimer's disease (AD) in a dose-dependent manner and is also associated with cognitive decline in non-demented elderly controls. In mice with targeted gene replacement (TR) of murine APOE with human APOE3 or APOE4, the latter show reduced neuronal dendritic complexity and impaired learning. APOE4 TR mice also show reduced gamma oscillation power, a neuronal population activity which is important to learning and memory. Published work has shown that brain extracellular matrix (ECM) can reduce neuroplasticity as well as gamma power, while attenuation of ECM can instead enhance this endpoint. In the present study we examine human cerebrospinal fluid (CSF) samples from APOE3 and APOE4 individuals and brain lysates from APOE3 and APOE4 TR mice for levels of ECM effectors that can increase matrix deposition and restrict neuroplasticity. We find that CCL5, a molecule linked to ECM deposition in liver and kidney, is increased in CSF samples from APOE4 individuals. Levels of tissue inhibitor of metalloproteinases (TIMPs), which inhibit the activity of ECM-degrading enzymes, are also increased in APOE4 CSF as well as astrocyte supernatants brain lysates from APOE4 TR mice. Importantly, as compared to APOE4/wild-type heterozygotes, APOE4/CCR5 knockout heterozygotes show reduced TIMP levels and enhanced EEG gamma power. The latter also show improved learning and memory, suggesting that the CCR5/CCL5 axis could represent a therapeutic target for APOE4 individuals.
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Affiliation(s)
- Griffin A Greco
- Georgetown University School of Medicine (GUMC), Department of Pharmacology, United States of America
| | | | - Matthew Amontree
- GUMC, United States of America; Interdisciplinary Program in Neuroscience, United States of America
| | | | - Holly Korthas
- Interdisciplinary Program in Neuroscience, United States of America
| | - Sung Hyeok Hong
- GUMC, Department of Biochemistry and Molecular & Cellular Biology, United States of America
| | | | - G William Rebeck
- Interdisciplinary Program in Neuroscience, United States of America; GUMC, Department of Neuroscience, United States of America
| | - Katherine Conant
- Interdisciplinary Program in Neuroscience, United States of America; GUMC, Department of Neuroscience, United States of America.
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John U, Patro N, Patro I. Perineuronal nets: Cruise from a honeycomb to the safety nets. Brain Res Bull 2022; 190:179-194. [DOI: 10.1016/j.brainresbull.2022.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 09/17/2022] [Accepted: 10/05/2022] [Indexed: 11/30/2022]
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Coutens B, Yrondi A, Rampon C, Guiard BP. Psychopharmacological properties and therapeutic profile of the antidepressant venlafaxine. Psychopharmacology (Berl) 2022; 239:2735-2752. [PMID: 35947166 DOI: 10.1007/s00213-022-06203-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 07/26/2022] [Indexed: 10/15/2022]
Abstract
Major depression (MD) is one of the most common psychiatric disorders worldwide. Currently, the first-line treatment for MD targets the serotonin system but these drugs, notably the selective serotonin reuptake inhibitors, usually need 4 to 6 weeks before the benefit is felt and a significant proportion of patients shows an unsatisfactory response. Numerous treatments have been developed to circumvent these issues as venlafaxine, a mixed serotonin-norepinephrine reuptake inhibitor that binds and blocks both the SERT and NET transporters. Despite this pharmacological profile, it is difficult to have a valuable insight into its ability to produce more robust efficacy than single-acting agents. In this review, we provide an in-depth characterization of the pharmacological properties of venlafaxine from in vitro data to preclinical and clinical efficacy in depressed patients and animal models of depression to propose an indirect comparison with the most common antidepressants. Preclinical studies show that the antidepressant effect of venlafaxine is often associated with an enhancement of serotonergic neurotransmission at low doses. High doses of venlafaxine, which elicit a concomitant increase in 5-HT and NE tone, is associated with changes in different forms of plasticity in discrete brain areas. In particular, the hippocampus appears to play a crucial role in venlafaxine-mediated antidepressant effects notably by regulating processes such as adult hippocampal neurogenesis or the excitatory/inhibitory balance. Overall, depending on the dose used, venlafaxine shows a high efficacy on depressive-like symptoms in relevant animal models but to the same extent as common antidepressants. However, these data are counterbalanced by a lower tolerance. In conclusion, venlafaxine appears to be one of the most effective treatments for treatment of major depression. Still, direct comparative studies are warranted to provide definitive conclusions about its superiority.
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Affiliation(s)
- Basile Coutens
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université de Toulouse, CNRS, 31000, Toulouse, France
| | - Antoine Yrondi
- Département de psychiatrie, CHU Toulouse-Purpan, Toulouse NeuroImaging Center, ToNIC, Université de Toulouse, Inserm, 31059, Toulouse, France
| | - Claire Rampon
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université de Toulouse, CNRS, 31000, Toulouse, France
| | - Bruno P Guiard
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université de Toulouse, CNRS, 31000, Toulouse, France.
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Ye F, Alvarez-Carbonell D, Nguyen K, Leskov K, Garcia-Mesa Y, Sreeram S, Valadkhan S, Karn J. Recruitment of the CoREST transcription repressor complexes by Nerve Growth factor IB-like receptor (Nurr1/NR4A2) mediates silencing of HIV in microglial cells. PLoS Pathog 2022; 18:e1010110. [PMID: 35797416 PMCID: PMC9295971 DOI: 10.1371/journal.ppat.1010110] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 07/19/2022] [Accepted: 06/15/2022] [Indexed: 12/13/2022] Open
Abstract
Human immune deficiency virus (HIV) infection in the brain leads to chronic neuroinflammation due to the production of pro-inflammatory cytokines, which in turn promotes HIV transcription in infected microglial cells. However, powerful counteracting silencing mechanisms in microglial cells result in the rapid shutdown of HIV expression after viral reactivation to limit neuronal damage. Here we investigated whether the Nerve Growth Factor IB-like nuclear receptor Nurr1 (NR4A2), which is a repressor of inflammation in the brain, acts directly to restrict HIV expression. HIV silencing following activation by TNF-α, or a variety of toll-like receptor (TLR) agonists, in both immortalized human microglial cells (hμglia) and induced pluripotent stem cells (iPSC)-derived human microglial cells (iMG) was enhanced by Nurr1 agonists. Similarly, overexpression of Nurr1 led to viral suppression, while conversely, knock down (KD) of endogenous Nurr1 blocked HIV silencing. The effect of Nurr1 on HIV silencing is direct: Nurr1 binds directly to the specific consensus binding sites in the U3 region of the HIV LTR and mutation of the Nurr1 DNA binding domain blocked its ability to suppress HIV-1 transcription. Chromatin immunoprecipitation (ChIP) assays also showed that after Nurr1 binding to the LTR, the CoREST/HDAC1/G9a/EZH2 transcription repressor complex is recruited to the HIV provirus. Finally, transcriptomic studies demonstrated that in addition to repressing HIV transcription, Nurr1 also downregulated numerous cellular genes involved in inflammation, cell cycle, and metabolism, further promoting HIV latency and microglial homoeostasis. Nurr1 therefore plays a pivotal role in modulating the cycles of proviral reactivation by potentiating the subsequent proviral transcriptional shutdown. These data highlight the therapeutic potential of Nurr1 agonists for inducing HIV silencing and microglial homeostasis and ultimately for the amelioration of the neuroinflammation associated with HIV-associated neurocognitive disorders (HAND).
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Affiliation(s)
- Fengchun Ye
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - David Alvarez-Carbonell
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Kien Nguyen
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Konstantin Leskov
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Yoelvis Garcia-Mesa
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Sheetal Sreeram
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Saba Valadkhan
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Jonathan Karn
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
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Crapser JD, Arreola MA, Tsourmas KI, Green KN. Microglia as hackers of the matrix: sculpting synapses and the extracellular space. Cell Mol Immunol 2021; 18:2472-2488. [PMID: 34413489 PMCID: PMC8546068 DOI: 10.1038/s41423-021-00751-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/26/2021] [Indexed: 02/08/2023] Open
Abstract
Microglia shape the synaptic environment in health and disease, but synapses do not exist in a vacuum. Instead, pre- and postsynaptic terminals are surrounded by extracellular matrix (ECM), which together with glia comprise the four elements of the contemporary tetrapartite synapse model. While research in this area is still just beginning, accumulating evidence points toward a novel role for microglia in regulating the ECM during normal brain homeostasis, and such processes may, in turn, become dysfunctional in disease. As it relates to synapses, microglia are reported to modify the perisynaptic matrix, which is the diffuse matrix that surrounds dendritic and axonal terminals, as well as perineuronal nets (PNNs), specialized reticular formations of compact ECM that enwrap neuronal subsets and stabilize proximal synapses. The interconnected relationship between synapses and the ECM in which they are embedded suggests that alterations in one structure necessarily affect the dynamics of the other, and microglia may need to sculpt the matrix to modify the synapses within. Here, we provide an overview of the microglial regulation of synapses, perisynaptic matrix, and PNNs, propose candidate mechanisms by which these structures may be modified, and present the implications of such modifications in normal brain homeostasis and in disease.
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Affiliation(s)
- Joshua D. Crapser
- grid.266093.80000 0001 0668 7243Department of Neurobiology and Behavior, University of California, Irvine, CA USA
| | - Miguel A. Arreola
- grid.266093.80000 0001 0668 7243Department of Neurobiology and Behavior, University of California, Irvine, CA USA
| | - Kate I. Tsourmas
- grid.266093.80000 0001 0668 7243Department of Neurobiology and Behavior, University of California, Irvine, CA USA
| | - Kim N. Green
- grid.266093.80000 0001 0668 7243Department of Neurobiology and Behavior, University of California, Irvine, CA USA
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Hattori T, Iwasaki-Hozumi H, Bai G, Chagan-Yasutan H, Shete A, Telan EF, Takahashi A, Ashino Y, Matsuba T. Both Full-Length and Protease-Cleaved Products of Osteopontin Are Elevated in Infectious Diseases. Biomedicines 2021; 9:biomedicines9081006. [PMID: 34440210 PMCID: PMC8394573 DOI: 10.3390/biomedicines9081006] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/05/2021] [Accepted: 08/09/2021] [Indexed: 12/13/2022] Open
Abstract
Circulating full-length osteopontin (FL-OPN) is elevated in plasma from patients with various infectious diseases, such as adult T-cell leukemia, Mycobacterium tuberculosis (TB), hepatitis virus infection, leptospirosis, acquired immune deficiency syndrome (AIDS), AIDS/TB, and coronavirus disease 2019 (COVID-19). Proteolysis of OPN by thrombin, matrix metalloproteases, caspase 8/3, cathepsin D, plasmin, and enterokinase generates various cleaved OPNs with a variety of bioactivities by binding to different target cells. Moreover, OPN is susceptible to gradual proteolysis. During inflammation, one of the cleaved fragments, N-terminal thrombin-cleaved OPN (trOPN or OPN-Arg168 [OPN-R]), induces dendritic cell (DC) adhesion. Further cleavage by carboxypeptidase B2 or carboxypeptidase N removes Arg168 from OPN-R to OPN-Leu167 (OPN-L). Consequently, OPN-L decreases DC adhesion. In particular, the differences in plasma level over time are observed between FL-OPN and its cleaved OPNs during inflammation. We found that the undefined OPN levels (mixture of FL-OPN and cleaved OPN) were elevated in plasma and reflected the pathology of TB and COVID-19 rather than FL-OPN. These infections are associated with elevated levels of various proteases. Inhibition of the cleavage or the activities of cleaved products may improve the outcome of the therapy. Research on the metabolism of OPN is expected to create new therapies against infectious diseases.
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Affiliation(s)
- Toshio Hattori
- Research Institute of Health and Welfare, Kibi International University, Takahashi 716-8508, Japan; (H.I.-H.); (G.B.); (H.C.-Y.); (A.T.)
- Correspondence: ; Tel./Fax: +81-866-22-9469
| | - Hiroko Iwasaki-Hozumi
- Research Institute of Health and Welfare, Kibi International University, Takahashi 716-8508, Japan; (H.I.-H.); (G.B.); (H.C.-Y.); (A.T.)
| | - Gaowa Bai
- Research Institute of Health and Welfare, Kibi International University, Takahashi 716-8508, Japan; (H.I.-H.); (G.B.); (H.C.-Y.); (A.T.)
| | - Haorile Chagan-Yasutan
- Research Institute of Health and Welfare, Kibi International University, Takahashi 716-8508, Japan; (H.I.-H.); (G.B.); (H.C.-Y.); (A.T.)
- Mongolian Psychosomatic Medicine Department, International Mongolian Medicine Hospital of Inner Mongolia, Hohhot 010065, China
| | - Ashwnini Shete
- ICMR-National AIDS Research Institute, 73 G-Block, MIDC, Bhosari, Pune 411026, India;
| | - Elizabeth Freda Telan
- STD AIDS Cooperative Central Laboratory, San Lazaro Hospital, Manila 1003, Philippines;
| | - Atsushi Takahashi
- Research Institute of Health and Welfare, Kibi International University, Takahashi 716-8508, Japan; (H.I.-H.); (G.B.); (H.C.-Y.); (A.T.)
| | - Yugo Ashino
- Department of Respiratory Medicine, Sendai City Hospital, Sendai 982-8502, Japan;
| | - Takashi Matsuba
- Department of Animal Pharmaceutical Science, School of Pharmaceutical Science, Kyusyu University of Health and Welfare, Nobeoka 882-8508, Japan;
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Irollo E, Luchetta J, Ho C, Nash B, Meucci O. Mechanisms of neuronal dysfunction in HIV-associated neurocognitive disorders. Cell Mol Life Sci 2021; 78:4283-4303. [PMID: 33585975 PMCID: PMC8164580 DOI: 10.1007/s00018-021-03785-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 01/14/2021] [Accepted: 01/29/2021] [Indexed: 12/13/2022]
Abstract
HIV-associated neurocognitive disorder (HAND) is characterized by cognitive and behavioral deficits in people living with HIV. HAND is still common in patients that take antiretroviral therapies, although they tend to present with less severe symptoms. The continued prevalence of HAND in treated patients is a major therapeutic challenge, as even minor cognitive impairment decreases patient’s quality of life. Therefore, modern HAND research aims to broaden our understanding of the mechanisms that drive cognitive impairment in people with HIV and identify promising molecular pathways and targets that could be exploited therapeutically. Recent studies suggest that HAND in treated patients is at least partially induced by subtle synaptodendritic damage and disruption of neuronal networks in brain areas that mediate learning, memory, and executive functions. Although the causes of subtle neuronal dysfunction are varied, reversing synaptodendritic damage in animal models restores cognitive function and thus highlights a promising therapeutic approach. In this review, we examine evidence of synaptodendritic damage and disrupted neuronal connectivity in HAND from clinical neuroimaging and neuropathology studies and discuss studies in HAND models that define structural and functional impairment of neurotransmission. Then, we report molecular pathways, mechanisms, and comorbidities involved in this neuronal dysfunction, discuss new approaches to reverse neuronal damage, and highlight current gaps in knowledge. Continued research on the manifestation and mechanisms of synaptic injury and network dysfunction in HAND patients and experimental models will be critical if we are to develop safe and effective therapies that reverse subtle neuropathology and cognitive impairment.
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Affiliation(s)
- Elena Irollo
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA, 19102, USA
| | - Jared Luchetta
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA, 19102, USA
| | - Chunta Ho
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA, 19102, USA
| | - Bradley Nash
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA, 19102, USA
| | - Olimpia Meucci
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA, 19102, USA. .,Department of Microbiology and Immunology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA, 19102, USA. .,Center for Neuroimmunology and CNS Therapeutics, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA, 19102, USA.
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Osteopontin and Integrin Mediated Modulation of Post-Synapses in HIV Envelope Glycoprotein Exposed Hippocampal Neurons. Brain Sci 2020; 10:brainsci10060346. [PMID: 32512754 PMCID: PMC7349055 DOI: 10.3390/brainsci10060346] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 05/30/2020] [Accepted: 06/01/2020] [Indexed: 01/13/2023] Open
Abstract
The advent of Human Immunodeficiency Virus (HIV) antiretrovirals have reduced the severity of HIV related neurological comorbidities but they nevertheless remain prevalent. Synaptic degeneration due to the action of several viral factors released from infected brain myeloid and glia cells and inflammatory cytokines has been attributed to the manifestation of a range of cognitive and behavioral deficits. The contributions of specific pro-inflammatory factors and their interplay with viral factors in the setting of treatment and persistence are incompletely understood. Exposure of neurons to chemokine receptor-4(CXCR4)-tropic HIV-1 envelope glycoprotein (Env) can lead to post-synaptic degradation of dendritic spines. The contribution of members of the extracellular matrix (ECM) and specifically, of perineuronal nets (PNN) toward synaptic degeneration, is not fully known, even though these structures are found to be disrupted in post-mortem HIV-infected brains. Osteopontin (Opn, gene name SPP1), a cytokine-like protein, is found in abundance in the HIV-infected brain. In this study, we investigated the role of Opn and its ECM integrin receptors, β1- and β3 integrin in modifying neuronal synaptic sculpting. We found that in hippocampal neurons incubated with HIV-1 Env protein and recombinant Opn, post-synaptic-95 (PSD-95) puncta were significantly increased and distributed to dendritic spines when compared to Env-only treated neurons. This effect was mediated through β3 integrin, as silencing of this receptor abrogated the increase in post-synaptic spines. Silencing of β1 integrin, however, did not block the increase of post-synaptic spines in hippocampal cultures treated with Opn. However, a decrease in the PNN to βIII-tubulin ratio was found, indicating an increased capacity to support spine growth. From these results, we conclude that one of the mechanisms by which Opn counters the damaging impact of the HIV Env protein on hippocampal post-synaptic plasticity is through complex interactions between Opn and components of the ECM which activate downstream protective signaling pathways that help maintain the potential for effective post-synaptic plasticity.
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