Induction of Tertiary Phase Epileptiform Discharges after Postasphyxial Infusion of a Toll-Like Receptor 7 Agonist in Preterm Fetal Sheep

Background: Toll-like receptor (TLR) agonists are key immunomodulatory factors that can markedly ameliorate or exacerbate hypoxic–ischemic brain injury. We recently demonstrated that central infusion of the TLR7 agonist Gardiquimod (GDQ) following asphyxia was highly neuroprotective after 3 days but not 7 days of recovery. We hypothesize that this apparent transient neuroprotection is associated with modulation of seizure-genic processes and hemodynamic control. Methods: Fetuses received sham asphyxia or asphyxia induced by umbilical cord occlusion (20.9 ± 0.5 min) and were monitored continuously for 7 days. GDQ 3.34 mg or vehicle were infused intracerebroventricularly from 1 to 4 h after asphyxia. Results: GDQ infusion was associated with sustained moderate hypertension that resolved after 72 h recovery. Electrophysiologically, GDQ infusion was associated with reduced number and burden of postasphyxial seizures in the first 18 h of recovery (p < 0.05). Subsequently, GDQ was associated with induction of slow rhythmic epileptiform discharges (EDs) from 72 to 96 h of recovery (p < 0.05 vs asphyxia + vehicle). The total burden of EDs was associated with reduced numbers of neurons in the caudate nucleus (r2 = 0.61, p < 0.05) and CA1/2 hippocampal region (r2 = 0.66, p < 0.05). Conclusion: These data demonstrate that TLR7 activation by GDQ modulated blood pressure and suppressed seizures in the early phase of postasphyxial recovery, with subsequent prolonged induction of epileptiform activity. Speculatively, this may reflect delayed loss of early protection or contribute to differential neuronal survival in subcortical regions.

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Toll-Like Receptor Agonists as Antecedent Therapy for Ischemic Brain Injury: Advancing Preclinical Studies to the Nonhuman Primate

Translational Stroke Research ◽

10.1007/978-1-4419-9530-8_10 ◽

2012 ◽

pp. 205-230

Author(s):

Frances Rena Bahjat ◽

Keri B. Vartanian ◽

G. Alexander West ◽

Mary P. Stenzel-Poore

Keyword(s):

Brain Injury ◽

Nonhuman Primate ◽

Preclinical Studies ◽

Ischemic Brain Injury ◽

Toll Like Receptor ◽

Ischemic Brain ◽

Receptor Agonists

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Propofol Ameliorates Ischemic Brain Injury by Blocking Toll-like Receptor 4-dependent Pathway and Suppressing Consequent Inflammatory Cytokine Production

10.21203/rs.3.rs-49562/v1 ◽

2020 ◽

Author(s):

Kazuha Mitsui ◽

Masakazu Kotoda ◽

Sohei Hishiyama ◽

Ayasa Takamino ◽

Sho Morikawa ◽

...

Keyword(s):

Brain Injury ◽

Inflammatory Cytokine ◽

Neuroprotective Effect ◽

Ischemic Brain Injury ◽

Toll Like Receptor ◽

Toll Like Receptor 4 ◽

Neuroprotective Effects ◽

Inflammatory Cytokine Production ◽

Ischemic Brain ◽

Dependent Pathway

Abstract BackgroundIschemic stroke is one of the leading causes of mortality and morbidity worldwide. Accumulated evidence suggests that the consequent excessive inflammation plays detrimental roles in the pathogenesis of secondary injury after cerebral infarction and exacerbates the brain tissue damage. Although regulation of the inflammation would be the potential strategy for the novel treatment option, effective methods that control the cerebral inflammation have not yet been established. Recent studies have suggested that propofol, a sedative agent widely used for management of patients with acute stroke, suppresses excessive inflammation and may have neuroprotective effects against ischemic brain injury. However, the available evidence is still limited and controversial, and the underlying mechanism remains unclear. This study aimed to investigate the neuroprotective effects of propofol against ischemic brain injury, with a specific focus on Toll-like receptor 4 (TLR4), the critical mediator of inflammation in the ischemic brain.ResultsTreatment with propofol significantly reduced infarct volume in wild-type mice (7.9 ± 1.4 vs. 12.6 ± 1.1 mm3, n = 10 each, p < 0.05). The propofol-treated mice exhibited lower levels of pro-inflammatory cytokine expressions compared with the control mice (IL-6: 0.57 ± 0.23 vs. 1.00 ± 0.39, p < 0.05, IL-1β: 0.53 ± 0.24 vs. 1.00 ± 0.36, p = 0.087, n = 15 each). The neuroprotective effect of propofol was abrogated by TLR4 gene knockout. Propofol treatment had no significant effects on hemodynamic parameters.ConclusionsPropofol attenuates brain injury by blocking the TLR4-dependent pathway and suppressing pro-inflammatory cytokine production. This insight into the mechanism underlying the neuroprotective effect of propofol against ischemic brain injury may lead to a new strategy for preventing exacerbation of cerebral infarction.

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Ischemic-Reperfusion Injury Increases Matrix Metalloproteinases and Tissue Metalloproteinase Inhibitors in Fetal Sheep Brain

Developmental Neuroscience ◽

10.1159/000489700 ◽

2018 ◽

Vol 40 (3) ◽

pp. 234-245 ◽

Cited By ~ 2

Author(s):

Xiaodi Chen ◽

Aparna Patra ◽

Grazyna B. Sadowska ◽

Barbara S. Stonestreet

Keyword(s):

Brain Injury ◽

Matrix Metalloproteinases ◽

Protein Expression ◽

Blood Brain Barrier ◽

Brain Barrier ◽

Ischemic Brain Injury ◽

Fetal Sheep ◽

Ischemic Brain ◽

Blood Brain ◽

Hypoxic Ischemic Brain Injury

Hypoxic-ischemic brain injury is a leading cause of neurodevelopmental morbidities in preterm and full-term infants. Blood-brain barrier dysfunction represents an important component of perinatal hypoxic-ischemic brain injury. The extracellular matrix (ECM) is a vital component of the blood-brain barrier. Matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) are important ECM components. They contribute to brain development, blood-brain barrier maintenance, and to regenerative and repair processes after hypoxic-ischemic brain injury. We hypothesized that ischemia at different durations of reperfusion affects the ECM protein composition of MMPs and TIMPs in the cerebral cortex of fetal sheep. Cerebral cortical samples were snap-frozen from sham control fetuses at 127 days of gestation and from fetuses after exposure to 30-min carotid occlusion and 4-, 24-, and 48-h of reperfusion. Protein expression of MMP-2, -8, -9, and -13 and TIMP-1, -2, -3, and -4 was measured by Western immunoblotting along with the gelatinolytic activity of MMP-2 and MMP-9 by zymography. The expression of MMP-8 was increased (Kruskal-Wallis, p = 0.04) in fetuses 48 h after ischemia. In contrast, changes were not observed in the protein expression of MMP-2, -9, or -13. The gelatinolytic activity of pro-MMP-2 was increased (ANOVA, p = 0.02, Tukey HSD, p = 0.05) 24 h after ischemia. TIMP-1 and -3 expression levels were also higher (TIMP-1, ANOVA, p = 0.003, Tukey HSD, p = 0.01; TIMP-3, ANOVA, p = 0.006, Tukey HSD, p = 0.01) 24 h after ischemia compared with both the sham controls and with fetuses exposed to 4 h of reperfusion. The changes in the expression of TIMP-1, -2, and -3 correlated with the changes in the MMP-8 and -13 protein expression. We speculate that regulation of MMP-8, MMP-13, and TIMPs contributes to ECM remodeling after is chemic-reperfusion injury in the fetal brain.

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Toll-Like Receptor 9: A New Target of Ischemic Preconditioning in the Brain

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/sj.jcbfm.9600606 ◽

2008 ◽

Vol 28 (5) ◽

pp. 1040-1047 ◽

Cited By ~ 117

Author(s):

Susan L Stevens ◽

Thomas MP Ciesielski ◽

Brenda J Marsh ◽

Tao Yang ◽

Delfina S Homen ◽

...

Keyword(s):

Brain Injury ◽

Ischemic Injury ◽

Ischemic Brain Injury ◽

Dependent Manner ◽

Cpg Odn ◽

Toll Like Receptor ◽

Ischemic Brain ◽

Cpg Oligodeoxynucleotide ◽

Tlr9 Ligand

Preconditioning with lipopolysaccharide (LPS), a toll-like receptor 4 (TLR4) ligand, provides neuroprotection against subsequent cerebral ischemic brain injury, through a tumor necrosis factor (TNF)α-dependent process. Here, we report the first evidence that another TLR, TLR9, can induce neuroprotection. We show that the TLR9 ligand CpG oligodeoxynucleotide (ODN) can serve as a potent preconditioning stimulus and provide protection against ischemic brain injury. Our studies show that systemic administration of CpG ODN 1826 in advance of brain ischemia (middle cerebral artery occlusion (MCAO)) reduces ischemic damage up to 60% in a dose- and time-dependent manner. We also offer evidence that CpG ODN preconditioning can provide direct protection to cells of the central nervous system, as we have found marked neuroprotection in modeled ischemia in vitro. Finally, we show that CpG preconditioning significantly increases serum TNFα levels before MCAO and that TNFα is required for subsequent reduction in damage, as mice lacking TNFα are not protected against ischemic injury by CpG preconditioning. Our studies show that preconditioning with a TLR9 ligand induces neuroprotection against ischemic injury through a mechanism that shares common elements with LPS preconditioning via TLR4.

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TLR7 agonist modulation of postasphyxial neurophysiological and cardiovascular adaptations in preterm fetal sheep

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00295.2019 ◽

2020 ◽

Vol 318 (2) ◽

pp. R369-R378 ◽

Cited By ~ 1

Author(s):

Kenta H. T. Cho ◽

Mhoyra Fraser ◽

Guido Wassink ◽

Simerdeep J. Dhillon ◽

Joanne O. Davidson ◽

...

Keyword(s):

Vascular Function ◽

Neuronal Excitability ◽

Epileptiform Activity ◽

Cell Loss ◽

High Amplitude ◽

Fetal Sheep ◽

Tlr Agonists ◽

Intracerebroventricular Infusion ◽

Tlr7 Agonist ◽

Neuroprotective Strategies

Activation of Toll-like receptors (TLRs) after hypoxic-ischemic brain injury can exacerbate injury but also alleviate cell loss, as recently demonstrated with the TLR7 agonist Gardiquimod (GDQ). However, TLR agonists also modulate vascular function and neuronal excitability. Thus, we examined the effects of TLR7 activation with GDQ on cardiovascular function and seizures after asphyxia in preterm fetal sheep at 0.7 gestation (104 days, term ∼147 days). Fetuses received sham asphyxia or asphyxia induced by umbilical cord occlusion for 25 min or asphyxia followed by a continuous intracerebroventricular infusion of 3.34 mg of GDQ from 1 to 4 h after asphyxia. Fetuses were monitored continuously for 72 h postasphyxia. GDQ treatment was associated with sustained, moderate hypertension for 72 h ( P < 0.05), with a transient increase in heart rate. Electroencephalographic (EEG) power was suppressed for the entire postasphyxial period in both groups, whereas EEG spectral edge transiently increased during the GDQ infusion compared with asphyxia alone ( P < 0.05), with higher β- and lower δ-EEG frequencies ( P < 0.05). This increase in EEG frequency was not related to epileptiform activity. After the GDQ infusion, there was earlier onset of high-amplitude stereotypic evolving seizures, with increased numbers of seizures and seizure burden ( P < 0.05). Hemodynamic function and seizure activity are important indices of preterm wellbeing. These data highlight the importance of physiological monitoring during preclinical testing of potential neuroprotective strategies.

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