Neuroprotective Effects of Resatorvid Against Traumatic Brain Injury in Rat: Involvement of Neuronal Autophagy and TLR4 Signaling Pathway

Sevoflurane Postconditioning-Induced Anti-Inflammation via Inhibition of the Toll-Like Receptor-4/Nuclear Factor Kappa B Pathway Contributes to Neuroprotection against Transient Global Cerebral Ischemia in Rats

The anti-inflammatory actions of sevoflurane postconditioning are suggested as an important mechanism of sevoflurane postconditioning-induced neuroprotection against cerebral ischemia. Here, we determined whether the anti-inflammatory effects of sevoflurane postconditioning were mediated via inhibition of the toll-like receptor (TLR)-4/nuclear factor kappa B (NF-κB) pathway after global transient cerebral ischemia in rats. Forty-five rats were randomly assigned to five groups as follows: (1) control (10 min of ischemia, n = 10); (2) sevoflurane postconditioning (two periods of sevoflurane inhalation after ischemia for 10 min with a wash period of 10 min, n = 10); (3) resatorvid (intraperitoneal injection of a selective TLR-4 antagonist (3 mg/kg) 30 min before ischemia, n = 10); (4) sevoflurane postconditioning plus resatorvid (n = 10), and sham (n = 5). The numbers of necrotic and apoptotic cells in the hippocampal CA1 region, the expression levels of TLR-4, NF-κB, cleaved caspase-3, and tumor necrosis factor alpha (TNF-α) in the anterior part of each brain, and the serum levels of TNF-α, interleukin 6 (IL-6), and interleukin 1 beta (IL-1β) were assessed 1 day after ischemia. The necrotic cell counts and expression levels of TLR-4, NF-κB, caspase-3, and TNF-α in brain tissue as well as serum levels of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) were significantly higher in the control group than in the other groups. Our findings suggest that the anti-inflammatory actions of sevoflurane postconditioning via inactivation of the TLR-4/NF-κB pathway and subsequent reduction in pro-inflammatory cytokine production, in part, contribute to sevoflurane postconditioning-induced neuroprotection after global transient cerebral ischemia in rats.

FGF2 Attenuates Neural Cell Death via Suppressing Autophagy after Rat Mild Traumatic Brain Injury

Traumatic brain injury (TBI) can lead to physical and cognitive deficits, which are caused by the secondary injury process. Effective pharmacotherapies for TBI patients are still lacking. Fibroblast growth factor-2 (FGF2) is an important neurotrophic factor that can stimulate neurogenesis and angiogenesis and has been shown to have neuroprotective effects after brain insults. Previous studies indicated that FGF2's neuroprotective effects might be related to its function of regulating autophagy. The present study investigated FGF2's beneficial effects in the early stage of rat mild TBI and the underlying mechanisms. One hundred and forty-four rats were used for creating controlled cortical impact (CCI) models to simulate the pathological damage after TBI. Our results indicated that pretreatment of FGF2 played a neuroprotective role in the early stage of rat mild TBI through alleviating brain edema, reducing neurological deficits, preventing tissue loss, and increasing the number of surviving neurons in injured cortex and the ipsilateral hippocampus. FGF2 could also protect cells from various forms of death such as apoptosis or necrosis through inhibition of autophagy. Finally, autophagy activator rapamycin could abolish the protective effects of FGF2. This study extended our understanding of FGF2's neuroprotective effects and shed lights on the pharmacological therapy after TBI.

Non-invasive diagnosis and treatment strategies for traumatic brain injury: an update

PURPOSE OF REVIEW

Traumatic Brain Injury (TBI) remains the leading cause of morbidity and mortality in U.S. Since the last decade, there have been several advances in the understanding and management of TBI that have shown the potential to improve outcomes. The aim of this review is to provide a useful overview of these potential diagnostic and treatment strategies that have yet to be proven, along with an assessment of their impact on outcomes after a TBI.

RECENT FINDINGS

Recent technical advances in the management of a TBI are grounded in a better understanding of the pathophysiology of primary and secondary insult to the brain after a TBI. Hence, clinical trials on humans should proceed in order to evaluate their efficacy and safety.

SUMMARY

Mortality associated with TBI remains high. Nonetheless, new diagnostic and therapeutic techniques have the potential to enhance early detection and prevention of secondary brain insult.

Electroacupuncture Improved Hippocampal Neurogenesis following Traumatic Brain Injury in Mice through Inhibition of TLR4 Signaling Pathway

The protective role of electroacupuncture (EA) treatment in diverse neurological diseases such as ischemic stroke is well acknowledged. However, whether and how EA act on hippocampal neurogenesis following traumatic brain injury (TBI) remains poorly understood. This study aims to investigate the effect of EA on hippocampal neurogenesis and neurological functions, as well as its underlying association with toll-like receptor 4 (TLR4) signaling in TBI mice. BrdU/NeuN immunofluorescence was performed to label newborn neurons in the hippocampus after EA treatment. Water maze test and neurological severity score were used to evaluate neurological function posttrauma. The hippocampal level of TLR4 and downstream molecules and inflammatory cytokines were, respectively, detected by Western blot and enzyme-linked immunosorbent assay. EA enhanced hippocampal neurogenesis and inhibited TLR4 expression at 21, 28, and 35 days after TBI, but the beneficial effects of EA on posttraumatic neurogenesis and neurological functions were attenuated by lipopolysaccharide-induced TLR4 activation. In addition, EA exerted an inhibitory effect on both TLR4/Myd88/NF-κB and TLR4/TRIF/NF-κB pathways, as well as the inflammatory cytokine expression in the hippocampus following TBI. In conclusion, EA promoted hippocampal neurogenesis and neurological recovery through inhibition of TLR4 signaling pathway posttrauma, which may be a potential approach to improve the outcome of TBI.

Inflammation-dependent cerebrospinal fluid hypersecretion by the choroid plexus epithelium in posthemorrhagic hydrocephalus

The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type stress kinase SPAK, which binds, phosphorylates, and stimulates the NKCC1 co-transporter at the CPE apical membrane. Genetic depletion of TLR4 or SPAK normalizes hyperactive CSF secretion rates and reduces PHH symptoms, as does treatment with drugs that antagonize TLR4-NF-κB signaling or the SPAK-NKCC1 co-transporter complex. These data uncover a previously unrecognized contribution of CSF hypersecretion to the pathogenesis of PHH, demonstrate a new role for TLRs in regulation of the internal brain milieu, and identify a kinase-regulated mechanism of CSF secretion that could be targeted by repurposed US Food and Drug Administration (FDA)-approved drugs to treat hydrocephalus.

Pomalidomide mitigates neuronal loss, neuroinflammation, and behavioral impairments induced by traumatic brain injury in rat

BACKGROUND

Traumatic brain injury (TBI) is a global health concern that typically causes emotional disturbances and cognitive dysfunction. Secondary pathologies following TBI may be associated with chronic neurodegenerative disorders and an enhanced likelihood of developing dementia-like disease in later life. There are currently no approved drugs for mitigating the acute or chronic effects of TBI.

METHODS

The effects of the drug pomalidomide (Pom), an FDA-approved immunomodulatory agent, were evaluated in a rat model of moderate to severe TBI induced by controlled cortical impact. Post-TBI intravenous administration of Pom (0.5 mg/kg at 5 or 7 h and 0.1 mg/kg at 5 h) was evaluated on functional and histological measures that included motor function, fine more coordination, somatosensory function, lesion volume, cortical neurodegeneration, neuronal apoptosis, and the induction of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6).

RESULTS

Pom 0.5 mg/kg administration at 5 h, but not at 7 h post-TBI, significantly mitigated the TBI-induced injury volume and functional impairments, neurodegeneration, neuronal apoptosis, and cytokine mRNA and protein induction. To evaluate underlying mechanisms, the actions of Pom on neuronal survival, microglial activation, and the induction of TNF-α were assessed in mixed cortical cultures following a glutamate challenge. Pom dose-dependently ameliorated glutamate-mediated cytotoxic effects on cell viability and reduced microglial cell activation, significantly attenuating the induction of TNF-α.

CONCLUSIONS

Post-injury treatment with a single Pom dose within 5 h significantly reduced functional impairments in a well-characterized animal model of TBI. Pom decreased the injury lesion volume, augmented neuronal survival, and provided anti-inflammatory properties. These findings strongly support the further evaluation and optimization of Pom for potential use in clinical TBI.