scholarly journals Distinct cellular mediators drive the Janus Faces of Toll-like Receptor 4 regulation of network excitability which impacts working memory performance after brain Injury

2019 ◽  
Author(s):  
Akshata A. Korgaonkar ◽  
Ying Li ◽  
Susan Nguyen ◽  
Jenieve Guevarra ◽  
Kevin C H Pang ◽  
...  
Keyword(s):  
Working Memory ◽  
Brain Injury ◽  
Memory Performance ◽  
Memory Function ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Tlr4 Signaling ◽  
Injured Brain ◽  
Cellular Mediators

AbstractThe mechanisms by which the neurophysiological and inflammatory responses to brain injury contribute to memory impairments are not fully understood. Recently, we reported that the innate immune receptor, toll-like receptor 4 (TLR4) enhances AMPA receptor (AMPAR) currents and excitability in the dentate gyrus after fluid percussion brain injury (FPI) while limiting excitability in controls. Here we examine the cellular mediators underlying TLR4 regulation of dentate excitability and its impact on memory performance. In ex vivo slices, astrocytic and microglial metabolic inhibitors selectively abolished TLR4 antagonist modulation of excitability in controls, without impacting FPI rats, demonstrating that glial signaling contributes to TLR4 regulation of excitability in controls. In glia-depleted neuronal cultures from naïve mice, TLR4 ligands bidirectionally modulated AMPAR charge transfer demonstrating the ability of neuronal TLR4 to regulate excitability, as observed after brain injury. In vivo TLR4 antagonism reduced early post-injury increases in mediators of MyD88-dependent and independent TLR4 signaling without altering expression in controls. Blocking TNFα, a downstream effector of TLT4, mimicked effects of TLR4 antagonist and occluded TLR4 agonist modulation of excitability in slices from both control and FPI rats. Functionally, transiently blocking TLR4 in vivo improved impairments in working memory observed one week and one month after FPI, while the same treatment impaired memory function in uninjured controls. Together these data identify that distinct cellular signaling mechanisms converge on TNFα to mediate TLR4 modulation of network excitability in the uninjured and injured brain and demonstrate a role for TLR4 in regulation of working memory function.HighlightsTLR4 suppresses dentate excitability in controls through signaling involving gliaNeuronal TLR4 signaling underlies enhanced dentate excitability after brain injuryTNFα contributes to TLR4 regulation of excitability in the injured brainAltering TLR4 signaling impacts working memory performanceTLR4 signaling is a potential target to improve working memory after brain trauma

scholarly journals The Absence of Toll-Like Receptor 4 Signaling in C3H/HeJ Mice Predisposes Them to Overwhelming Rickettsial Infection and Decreased Protective Th1 Responses

2008 ◽  
Vol 76 (8) ◽  
pp. 3717-3724 ◽  
Author(s):  
Jeffrey M. Jordan ◽  
Michael E. Woods ◽  
Juan Olano ◽  
David H. Walker
Keyword(s):  
Rickettsia Conorii ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Necrosis Factor Alpha ◽  
Tlr4 Signaling ◽  
Rickettsial Infections ◽  
Factor Alpha ◽  
Intravenous Inoculation

ABSTRACT The importance of toll-like receptor 4 (TLR4) in immunity to rickettsiae remains elusive. To investigate the role of TLR4 in protection against rickettsioses, we utilized C3H/HeJ mice, which are naturally defective in TLR4 signaling, and compared the responses of C3H/HeN and C3H/HeJ mice following intravenous inoculation with Rickettsia conorii. Mice genetically defective in TLR4 signaling developed overwhelming, fatal rickettsial infections when given an inoculum that was nonfatal for TLR4-competent mice. In addition, mice lacking the ability to signal through TLR4 had significantly greater rickettsial burdens in vivo. Moreover, we observed greater concentrations of the cytokines interleukin 6 (IL-6), tumor necrosis factor alpha, IL-12p40, IL-12p70, and IL-17 in the sera of mice with intact TLR4 function as well as significantly greater quantities of activated CD4+ and CD8+ T lymphocytes. Additionally, we also observed that Th17 cells were present only in TLR4-competent mice, suggesting an important role for TLR4 ligation in the activation of this subset. In agreement with these data, we also observed significantly greater percentages of immunosuppressive regulatory T cells in the spleen during infection in TLR4-defective mice. Together, these data demonstrate that, while rickettsiae do not contain endotoxic lipopolysaccharide, they nevertheless initiate TLR4-specific immune responses, and these responses are important in protection.

scholarly journals Serum Amyloid A1/Toll-Like Receptor-4 Axis, an Important Link between Inflammation and Outcome of TBI Patients

Biomedicines ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 599
Author(s):  
Víctor Farré-Alins ◽  
Alejandra Palomino-Antolín ◽  
Paloma Narros-Fernández ◽  
Ana Belen Lopez-Rodriguez ◽  
Céline Decouty-Perez ◽  
...  
Keyword(s):  
Injury Severity ◽  
White Blood Cells ◽  
Serum Amyloid ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Important Link ◽  
Tlr4 Mrna ◽  
Serum Amyloid A1

Traumatic brain injury (TBI) is one of the leading causes of mortality and disability worldwide without any validated biomarker or set of biomarkers to help the diagnosis and evaluation of the evolution/prognosis of TBI patients. To achieve this aim, a deeper knowledge of the biochemical and pathophysiological processes triggered after the trauma is essential. Here, we identified the serum amyloid A1 protein-Toll-like receptor 4 (SAA1-TLR4) axis as an important link between inflammation and the outcome of TBI patients. Using serum and mRNA from white blood cells (WBC) of TBI patients, we found a positive correlation between serum SAA1 levels and injury severity, as well as with the 6-month outcome of TBI patients. SAA1 levels also correlate with the presence of TLR4 mRNA in WBC. In vitro, we found that SAA1 contributes to inflammation via TLR4 activation that releases inflammatory cytokines, which in turn increases SAA1 levels, establishing a positive proinflammatory loop. In vivo, post-TBI treatment with the TLR4-antagonist TAK242 reduces SAA1 levels, improves neurobehavioral outcome, and prevents blood–brain barrier disruption. Our data support further evaluation of (i) post-TBI treatment in the presence of TLR4 inhibition for limiting TBI-induced damage and (ii) SAA1-TLR4 as a biomarker of injury progression in TBI patients.

Lack of Toll-like receptor 4 decreases lipopolysaccharide-induced bone resorption in C3H/HeJ mice in vivo

2008 ◽  
Vol 23 (3) ◽  
pp. 190-195 ◽  
Author(s):  
H. Nakamura ◽  
Y. Fukusaki ◽  
A. Yoshimura ◽  
C. Shiraishi ◽  
M. Kishimoto ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4

scholarly journals Low-Level Light in Combination with Metabolic Modulators for Effective Therapy of Injured Brain

2015 ◽  
Vol 35 (9) ◽  
pp. 1435-1444 ◽  
Author(s):  
Tingting Dong ◽  
Qi Zhang ◽  
Michael R Hamblin ◽  
Mei X Wu
Keyword(s):  
Learning And Memory ◽  
Memory Function ◽  
Light Illumination ◽  
Low Level ◽  
Metabolic Substrates ◽  
Secondary Damage ◽  
Injured Brain ◽  
Combinational Treatment

Vascular damage occurs frequently at the injured brain causing hypoxia and is associated with poor outcomes in the clinics. We found high levels of glycolysis, reduced adenosine triphosphate generation, and increased formation of reactive oxygen species and apoptosis in neurons under hypoxia. Strikingly, these adverse events were reversed significantly by noninvasive exposure of injured brain to low-level light (LLL). Low-level light illumination sustained the mitochondrial membrane potential, constrained cytochrome c leakage in hypoxic cells, and protected them from apoptosis, underscoring a unique property of LLL. The effect of LLL was further bolstered by combination with metabolic substrates such as pyruvate or lactate both in vivo and in vitro. The combinational treatment retained memory and learning activities of injured mice to a normal level, whereas other treatment displayed partial or severe deficiency in these cognitive functions. In accordance with well-protected learning and memory function, the hippocampal region primarily responsible for learning and memory was completely protected by combination treatment, in marked contrast to the severe loss of hippocampal tissue because of secondary damage in control mice. These data clearly suggest that energy metabolic modulators can additively or synergistically enhance the therapeutic effect of LLL in energy-producing insufficient tissue–like injured brain.

scholarly journals Prefrontal modulation of working memory performance in brain injury and disease

2006 ◽  
Vol 27 (11) ◽  
pp. 837-847 ◽  
Author(s):  
Frank G. Hillary ◽  
Helen M. Genova ◽  
Nancy D. Chiaravalloti ◽  
Bart Rypma ◽  
John DeLuca
Keyword(s):  
Working Memory ◽  
Brain Injury ◽  
Memory Performance

scholarly journals Toll-Like Receptor 4 Signaling and Drug Addiction

2020 ◽  
Vol 11 ◽  
Author(s):  
Ruyan Wu ◽  
Jun-Xu Li
Keyword(s):  
Drug Addiction ◽  
Multiple Drug ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Tlr4 Signaling ◽  
Drug Classes ◽  
Downstream Effectors ◽  
Potential Efficacy ◽  
Proinflammatory Responses

The emphasis of neuronal alterations and adaptations have long been the main focus of the studies of the mechanistic underpinnings of drug addiction. Recent studies have begun to appreciate the role of innate immune system, especially toll-like receptor 4 (TLR4) signaling in drug reward-associated behaviors and physiology. Drugs like opioids, alcohol and psychostimulants activate TLR4 signaling and subsequently induce proinflammatory responses, which in turn contributes to the development of drug addiction. Inhibition of TLR4 or its downstream effectors attenuated the reinforcing effects of opioids, alcohol and psychostimulants, and this effect is also involved in the withdrawal and relapse-like behaviors of different drug classes. However, conflicting results also argue that TLR4-related immune response may play a minimal part in drug addiction. This review discussed the preclinical evidence that whether TLR4 signaling is involved in multiple drug classes action and the possible mechanisms underlying this effect. Moreover, clinical studies which examined the potential efficacy of immune-base pharmacotherapies in treating drug addiction are also discussed.

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