Inhibition of transforming growth factor beta-activated kinase 1 confers neuroprotection after traumatic brain injury in rats

Cardiomyocyte-specific knockout of ADAM17 alleviates doxorubicin-induced cardiomyopathy via inhibiting TNFα-TRAF3-TAK1-MAPK axis

The pathogenesis of doxorubicin-induced cardiomyopathy remains unclear. This study was carried out to test our hypothesis that ADAM17 aggravates cardiomyocyte apoptosis induced by doxorubicin and inhibition of ADAM17 may ameliorate doxorubicin-induced cardiomyopathy. C57BL/6J mice were intraperitoneally injected with a cumulative dose of doxorubicin to induce cardiomyopathy. Cardiomyocyte-specific ADAM17-knockout (A17α-MHCKO) and ADAM17-overexpressing (AAV9-oeA17) mice were generated. In addition, RNA sequencing of the heart tissues in different mouse groups and in vitro experiments in neonatal rat cardiomyocytes (NRCMs) receiving different treatment were performed. Mouse tumor models were constructed in A17fl/fl and A17α-MHCKO mice. In addition, cardiomyocyte-specific TRAF3-knockdown and TRAF3-overexpressing mice were generated. ADAM17 expression and activity were markedly upregulated in doxorubicin-treated mouse hearts and NRCMs. A17α-MHCKO mice showed less cardiomyocyte apoptosis induced by doxorubicin than A17fl/fl mice, and cardiomyocyte ADAM17 deficiency did not affect the anti-tumor effect of doxorubicin. In contrast, AAV9-oeA17 mice exhibited markedly aggravated cardiomyocyte apoptosis relative to AAV9-oeNC mice after doxorubicin treatment. Mechanistically, doxorubicin enhanced the expression of transcription factor C/EBPβ, leading to increased expression and activity of ADAM17 in cardiomyocyte, which enhanced TNF-α shedding and upregulated the expression of TRAF3. Increased TRAF3 promoted TAK1 autophosphorylation, resulting in activated MAPKs pathway and cardiomyocyte apoptosis. ADAM17 acted as a positive regulator of cardiomyocyte apoptosis and cardiac remodeling and dysfunction induced by doxorubicin by upregulating TRAF3/TAK1/MAPKs signaling. Thus, targeting ADAM17/TRAF3/TAK1/MAPKs signaling holds a promising potential for treating doxorubicin-induced cardiotoxicity.

Neuroprotective effects of takinib on an experimental traumatic brain injury rat model via inhibition of transforming growth factor beta-activated kinase 1

Transforming growth factor β-activated kinase 1 (TAK1) plays a significant role in controlling several signaling pathways involved with regulating inflammation and apoptosis. As such, it represents an important potential target for developing treatments for traumatic brain injury (TBI). Takinib, a small molecule and selective TAK1 inhibitor, has potent anti-inflammatory activity and has shown promising activity in preclinical studies using rat models to evaluate the potential neuroprotective impact on TBI. The current study used a modified Feeney's weight-drop model to cause TBI in mature Sprague-Dawley male rats. At 30 min post-induction of TBI in the rats, they received an intracerebroventricular (ICV) injection of Takinib followed by assessment of their histopathology and behavior. The results of this study demonstrated how Takinib suppressed TBI progression in the rats by decreasing TAK1, p-TAK1, and nuclear p65 levels while upregulating IκB-α expression. Takinib was also shown to significantly inhibit the production of two pro-inflammatory factors, namely tumor necrosis factor-α and interleukin-1β. Furthermore, Takinib greatly upregulated the expression of tight junction proteins zonula occludens-1 and claudin-5, reducing cerebral edema. Additionally, Takinib effectively suppressed apoptosis via downregulation of cleaved caspase 3 and Bax and reduction of TUNEL-positive stained cell count. As a result, an enhancement of neuronal function and survival was observed post-TBI. These findings highlight the medicinal value of Takinib in the management of TBI and offer an experimental justification for further investigation of TAK1 as a potential pharmacological target.

IRAK4 exacerbates traumatic brain injury via activation of TAK1 signaling pathway

Although multiple signaling pathways contributing to the pathophysiological process have been investigated, treatments for traumatic brain injury (TBI) against present targets have not acquired significant clinical progress. Interleukin-1 receptor-associated kinase 4 (IRAK4) is an important factor involved in regulating immunity and inflammation. However, the role of IRAK4 in TBI still remains largely unknown. Therefore, using a controlled cortical impact model (CCI), we investigated the function and molecular mechanism of IRAK4 in the context of TBI. IRAK4 was found to be activated in a time-dependent manner after TBI and mainly expressed in neurons. Inhibition of IRAK4 by siRNAs could significantly alleviates neuroinflammation, neuron apoptosis, brain edema, brain-blood barrier (BBB) dysfunction and improves neurological deficit in the context of CCI. Mechanistically, IRAK4 exacerbates CCI via activation of TAK1 signaling pathway. Interestingly, PF-0665083, an IRAK4 inhibitor, inhibits phosphorylation of IRAK4 and attenuates CCI-induced secondary injury. It could be conclude that IRAK4 plays a critical role in TBI-induced secondary injury and the underlining mechanism may be related to activation of TAK1 signaling pathway. PF-0665083 may serve as a potential treatment strategy to relieve TBI.

The Renin Angiotensin System as a potential treatment target for Traumatic Brain Injury

Traumatic brain injury (TBI) is a major health concern and leading cause of death and disability in young adults in the UK and worldwide, however, there is a paucity of disease modifying therapies for the treatment of TBI. This review investigates the potential of the renin-angiotensin system (RAS) as a treatment pathway for traumatic brain injury (TBI) in adults. Relevant electronic databases were searched on 18 December 2019, updated 16 May 2021. All English language articles with adult human or animal populations investigating RAS drugs as an intervention for TBI or reporting genetic evidence relevant to the RAS and TBI were screened. Eighteen preclinical RCTs (n=2269) and 2 clinical cohort studies (n=771) were included. Meta-analyses of 6 preclinical randomised-controlled trials (n=99) indicated candesartan improved neurological function short-term (<7 days: standardised mean difference (SMD) 0.61, 95% confidence interval (CI) 0.19 - 1.03, I2=0%) and long-term (≥7 days: SMD 1.06, 95% CI 0.38; 1.73, I2=0%) post-TBI. Findings were similar for most secondary outcomes. There was a suggestion of benefit from other RAS-targeting drugs, although evidence was limited due to few small studies. There was insufficient evidence to enable strong assessment of these drugs on mortality post-TBI. We conclude that angiotensin-receptor blockers, especially candesartan, show positive outcomes post-TBI in preclinical studies with moderate quality of evidence (GRADE). More research into the effect of regulatory-RAS targeting drugs is needed. Clinical trials of candesartan following TBI are recommended, due to strong and consistent evidence of neuroprotection shown by these preclinical studies.

Concussion susceptibility is mediated by spreading depolarization-induced neurovascular dysfunction

The mechanisms underlying the complications of mild traumatic brain injury, including post-concussion syndrome, post-impact catastrophic death, and delayed neurodegeneration remain poorly understood. This limited pathophysiological understanding has hindered the development of diagnostic and prognostic biomarkers and has prevented the advancement of treatments for the sequelae of mild traumatic brain injury.

We aimed to characterize the early electrophysiological and neurovascular alterations following repetitive mild traumatic brain injury and sought to identify new targets for the diagnosis and treatment of individuals at risk of severe post-impact complications. We combined behavioural, electrophysiological, molecular, and neuroimaging techniques in a rodent model of repetitive mild traumatic brain injury. In humans, we used dynamic contrast-enhanced MRI to quantify blood–brain barrier dysfunction after exposure to sport-related concussive mild traumatic brain injury.

Rats could clearly be classified based on their susceptibility to neurological complications, including life-threatening outcomes, following repetitive injury. Susceptible animals showed greater neurological complications and had higher levels of blood–brain barrier dysfunction, transforming growth factor β (TGFβ) signalling, and neuroinflammation compared to resilient animals. Cortical spreading depolarizations were the most common electrophysiological events immediately following mild traumatic brain injury and were associated with longer recovery from impact. Triggering cortical spreading depolarizations in mild traumatic brain injured rats (but not in controls) induced blood–brain barrier dysfunction. Treatment with a selective TGFβ receptor inhibitor prevented blood–brain barrier opening and reduced injury complications. Consistent with the rodent model, blood–brain barrier dysfunction was found in a subset of human athletes following concussive mild traumatic brain injury.

We provide evidence that cortical spreading depolarization, blood–brain barrier dysfunction, and pro-inflammatory TGFβ signalling are associated with severe, potentially life-threatening outcomes following repetitive mild traumatic brain injury. Diagnostic-coupled targeting of TGFβ signalling may be a novel strategy in treating mild traumatic brain injury.

Post-traumatic Neuroinflammation: Relevance to Pediatrics

Both detrimental and beneficial effects of post-traumatic neuroinflammation have become a major research focus as they offer the potential for immediate as well as delayed targeted reparative therapies. Understanding the complex interactions of central and peripheral immunocompetent cells as well as their mediators on brain injury and recovery is complicated by the temporal, regional, and developmental differences in their response to injuries. Microglia, the brain-resident macrophages, have become central in these investigations as they serve a major surveillance function, have the ability to react swiftly to injury, recruit various cellular and chemical mediators, and monitor the reparative/degenerative processes. In this review we describe selected aspects of this burgeoning literature, describing the critical role of cytokines and chemokines, microglia, advances in neuroimaging, genetics and fractal morphology analysis, our research efforts in this area, and selected aspects of pediatric post-traumatic neuroinflammation.

Protective Effects of Estrogen via Nanoparticle Delivery to Attenuate Myelin Loss and Neuronal Death after Spinal Cord Injury

Spinal cord injury (SCI) is associated with devastating neurological deficits affecting more than 11,000 Americans each year. Although several therapeutic agents have been proposed and tested, no FDA-approved pharmacotherapy is available for SCI treatment. We have recently demonstrated that estrogen (E2) acts as an antioxidant and anti-inflammatory agent, attenuating gliosis in SCI. We have also demonstrated that nanoparticle-mediated focal delivery of E2 to the injured spinal cord decreases lesion size, reactive gliosis, and glial scar formation. The current study tested in vitro effects of E2 on reactive oxygen species (ROS) and calpain activity in microglia, astroglia, macrophages, and fibroblasts, which are believed to participate in the inflammatory events and glial scar formation after SCI. E2 treatment decreased ROS production and calpain activity in these glial cells, macrophages, and fibroblast cells in vitro. This study also tested the efficacy of fast- and slow-release nanoparticle-E2 constructs in a rat model of SCI. Focal delivery of E2 via nanoparticles increased tissue distribution of E2 over time, attenuated cell death, and improved myelin preservation in injured spinal cord. Specifically, the fast-release nanoparticle-E2 construct reduced the Bax/Bcl-2 ratio in injured spinal cord tissues, and the slow-release nanoparticle-E2 construct prevented gliosis and penumbral demyelination distal to the lesion site. These data suggest this novel E2 delivery strategy to the lesion site may decrease inflammation and improve functional outcomes following SCI.

Inflammation in Traumatic Brain Injury

There is an increasing evidence that inflammation contributes to clinical and functional outcomes in traumatic brain injury (TBI). Many successful target-engaging, lesion-reducing, symptom-alleviating, and function-improving interventions in animal models of TBI have failed to show efficacy in clinical trials. Timing and immunological context are paramount for the direction, quality, and intensity of immune responses to TBI and the resulting neuroanatomical, clinical, and functional course. We present components of the immune system implicated in TBI, potential immune targets, and target-engaging interventions. The main objective of our article is to point toward modifiable molecular and cellular mechanisms that may modify the outcomes in TBI, and contribute to increasing the translational value of interventions that have been identified in animal models of TBI.

Model-based pathway enrichment analysis applied to the TGF-beta regulation of autophagy in autism

To differentiate between conditions of health and disease, current pathway enrichment analysis methods detect the differential expression of distinct biological pathways. System-level model-driven approaches, however, are lacking. Here we present a new methodology that uses a dynamic model to suggest a unified subsystem to better differentiate between diseased and healthy conditions. Our methodology includes the following steps: 1) detecting connections between relevant differentially expressed pathways; 2) construction of a unified in silico model, a stochastic Petri net model that links these distinct pathways; 3) model execution to predict subsystem activation; and 4) enrichment analysis of the predicted subsystem. We apply our approach to the TGF-beta regulation of the autophagy system implicated in autism. Our model was constructed manually, based on the literature, to predict, using model simulation, the TGF-beta-to-autophagy active subsystem and downstream gene expression changes associated with TGF-beta, which go beyond the individual findings derived from literature. We evaluated the in silico predicted subsystem and found it to be co-expressed in the normative whole blood human gene expression data. Finally, we show our subsystem's gene set to be significantly differentially expressed in two independent datasets of blood samples of ASD (autistic spectrum disorders) individuals as opposed to controls. Our study demonstrates that dynamic pathway unification can define a new refined subsystem that can significantly differentiate between disease conditions.

Astaxanthin ameliorates oxidative stress and neuronal apoptosis via SIRT1/NRF2/Prx2/ASK1/p38 after traumatic brain injury in mice

BACKGROUND AND PURPOSE

Oxidative stress and neuronal apoptosis play key roles in traumatic brain injury. We investigated the protective effects of astaxanthin against traumatic brain injury and its underlying mechanisms of action.

EXPERIMENTAL APPROACH

A weight-drop model of traumatic brain injury in vivo and hydrogen peroxide exposure in vitro model were established. Brain oedema, behaviour tests, western blot, biochemical analysis, lesion volume, histopathological study and cell viability were performed.

KEY RESULTS

Astaxanthin significantly reduced oxidative insults on Days 1, 3 and 7 after traumatic brain injury. Neuronal apoptosis was also ameliorated on Day 3. Additionally, astaxanthin improved neurological functions up to 3 weeks after traumatic brain injury. Astaxanthin treatment dramatically enhanced the expression of peroxiredoxin 2 (Prx2), nuclear factor-erythroid 2-related factor 2 (NRF2/Nrf2) and sirtuin 1 (SIRT1), while it down-regulated the phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) and p38. Inhibition of Prx2 by siRNA injection reversed the beneficial effects of astaxanthin against traumatic brain injury. Additionally, Nrf2 knockout prevented the neuroprotective effects of astaxanthin in traumatic brain injury. In contrast, overexpression of Prx2 in Nrf2 knockout mice attenuated the secondary brain injury after traumatic brain injury. Moreover, inhibiting SIRT1 by EX527 dramatically inhibited the neuroprotective effects of astaxanthin and suppressed SIRT1/Nrf2/Prx2/ASK1/p38 pathway both in vivo and in vitro.

CONCLUSION AND IMPLICATIONS

Astaxanthin improved the neurological functions and protected the brain from injury after traumatic brain injury, primarily by reducing oxidative stress and neuronal death via SIRT1/Nrf2/Prx2/ASK1/p38 signalling pathway and might be a new candidate to ameliorate traumatic brain injury.

TRAF3 mediates neuronal apoptosis in early brain injury following subarachnoid hemorrhage via targeting TAK1-dependent MAPKs and NF-κB pathways

Neuronal apoptosis has an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). TRAF3 was reported as a promising therapeutic target for stroke management, which covered several neuronal apoptosis signaling cascades. Hence, the present study is aimed to determine whether downregulation of TRAF3 could be neuroprotective in SAH-induced EBI. An in vivo SAH model in mice was established by endovascular perforation. Meanwhile, primary cultured cortical neurons of mice treated with oxygen hemoglobin were applied to mimic SAH in vitro. Our results demonstrated that TRAF3 protein expression increased and expressed in neurons both in vivo and in vitro SAH models. TRAF3 siRNA reversed neuronal loss and improved neurological deficits in SAH mice, and reduced cell death in SAH primary neurons. Mechanistically, we found that TRAF3 directly binds to TAK1 and potentiates phosphorylation and activation of TAK1, which further enhances the activation of NF-κB and MAPKs pathways to induce neuronal apoptosis. Importantly, TRAF3 expression was elevated following SAH in human brain tissue and was mainly expressed in neurons. Taken together, our study demonstrates that TRAF3 is an upstream regulator of MAPKs and NF-κB pathways in SAH-induced EBI via its interaction with and activation of TAK1. Furthermore, the TRAF3 may serve as a novel therapeutic target in SAH-induced EBI.

Cellular infiltration in traumatic brain injury

Traumatic brain injury leads to cellular damage which in turn results in the rapid release of damage-associated molecular patterns (DAMPs) that prompt resident cells to release cytokines and chemokines. These in turn rapidly recruit neutrophils, which assist in limiting the spread of injury and removing cellular debris. Microglia continuously survey the CNS (central nervous system) compartment and identify structural abnormalities in neurons contributing to the response. After some days, when neutrophil numbers start to decline, activated microglia and astrocytes assemble at the injury site—segregating injured tissue from healthy tissue and facilitating restorative processes. Monocytes infiltrate the injury site to produce chemokines that recruit astrocytes which successively extend their processes towards monocytes during the recovery phase. In this fashion, monocytes infiltration serves to help repair the injured brain. Neurons and astrocytes also moderate brain inflammation via downregulation of cytotoxic inflammation. Depending on the severity of the brain injury, T and B cells can also be recruited to the brain pathology sites at later time points.

Significance of tumor protein p53 mutation in cellular process and drug selection in brain lower grade (WHO grades II and III) glioma

Aim: Tumor protein p53 (TP53) mutant is one of the most frequently mutated genes in glioma. Results: The Cancer Genome Atlas data has shown that TP53 mutation is present in 49% of lower grade (World Health Organization [WHO] grades II and III) glioma patients. Data from The Genomics of Drug Sensitivity in Cancer database showed that three drugs: (5Z)-7-oxozeaenol, dabrafenib and nutlin-3a (-), have shown more resistance in patients with TP53 mutation. We identified 1100 differentially expressed genes. Functional enrichment analysis showed that the differentially expressed genes are mainly concentrated in the transport of ionic and cancer-related pathways. The top ten hub genes were identified and an outcome analysis revealed the most critical genes related to prognosis. Conclusion: Our results identified the key genes and pathways that might provide the basic proof to improve individualized treatment in patients with glioma.

NG25, an inhibitor of transforming growth factor‑β‑activated kinase 1, ameliorates neuronal apoptosis in neonatal hypoxic‑ischemic rats

Transforming growth factor (TGF)‑β‑activated kinase 1 (TAK1) was found to be activated by TGF‑β and acts as a central regulator of cell death in various types of disease. However, the expression and function of TAK1 in the neonatal brain following hypoxia‑ischemia (HI) remains unclear. In the present study, western blotting and immunofluorescence were employed to determine the expression and distribution of TAK1 in the brain cortex of a perinatal HI rat model. In addition, the specific inhibitor of TAK1, NG25 was administered via intracerebroventricular injection, prior to insult of the neonatal rat brains, for neuroprotection. Western blotting and double immunofluorescence indicated that an increased expression level of phosphorylated‑TAK1 was observed, and was localized with neurons and astrocytes, compared with the sham group. Further study demonstrated that injection of NG25 prior to insult significantly inhibited TAK1/c‑Jun N‑terminal kinases activity and dramatically ameliorated acute hypoxic‑ischemic cerebral injury by inhibiting cell apoptosis in perinatal rats. Thus, NG25 ameliorates neuronal apoptosis in neonatal HI rats by inhibiting TAK1 expression and cell apoptosis. In addition, NG25 may serve as a promising novel neuroprotective inhibitor for perinatal cerebral injury.

Transforming growth factor-beta 1 signaling regulates neuroinflammation and apoptosis in mild traumatic brain injury

Mild traumatic brain injury (mTBI) is a low-level injury, which often remains undiagnosed, and in most cases it leads to death and disability as it advances as secondary injury. Therefore, it is important to study the underlying signaling mechanisms of mTBI-associated neurological ailments. While transforming growth factor-beta1 (TGF-β1) has a significant role in inflammation and apoptosis in myriads of other pathophysiological conditions, the precise function of increased TGF-β1 after mTBI is unknown. In this study, our objective is to study the physiological relevance and associated mechanisms of TGF-β1-mediated inflammation and apoptosis in mTBI. Using an in vitro stretch-injury model in rat neuronal cultures and the in vivo fluid percussion injury (FPI) model in rats, we explored the significance of TGF-β1 activation in mTBI. Our study demonstrated that the activation of TGF-β1 in mTBI correlated with the induction of free radical generating enzyme NADPH oxidase 1 (NOX1). Further, using TGF-β type I receptor (TGF-βRI) inhibitor SB431542 and transfection of TGF-β1 siRNA and TGF-β antagonist Smad7, we established the neuroinflammatory and apoptotic role of TGF-β1 in mTBI. Inhibition of TGF-βRI or TGF-β1 diminished TGF-β1-induced inflammation and apoptosis. Further, the enhanced TGF-β1 activation increased the phosphorylation of R-Smads including Smad2 and Smad3 proteins. By immunofluorescence, western blotting, ELISA and TUNEL experiments, we demonstrated the up-regulation of pro-inflammatory cytokines IL-1β and TNF-α and apoptotic cell death in neurons. In conclusion, this study could establish the significance of TGF-β1 in transforming the pathophysiology of mTBI into secondary injury.

Rapid Activation of Transforming Growth Factor β-Activated Kinase 1 in Chondrocytes by Phosphorylation and K63 -Linked Polyubiquitination Upon Injury to Animal Articular Cartilage

Objective

Mechanical injury to cartilage predisposes to osteoarthritis (OA). Wounding of the articular cartilage surface causes rapid activation of MAP kinases and NF‐κB, mimicking the response to inflammatory cytokines. This study was undertaken to identify the upstream signaling mechanisms involved.

Methods

Cartilage was injured by dissecting it from the articular surface of porcine metacarpophalangeal (MCP) joints or by avulsing murine proximal femoral epiphyses. Protein phosphorylation was assayed by Western blotting of cartilage lysates. Immunolocalization of phosphorylated activating transcription factor 2 (ATF‐2) and NF‐κB/p65 was detected by confocal microscopy. Messenger RNA (mRNA) was measured by quantitative reverse transcriptase–polymerase chain reaction (qRT‐PCR). Receptor associated protein 80 (RAP‐80) ubiquitin interacting motif agarose was used in a pull‐down assay to obtain K⁶³‐polyubiquitinated proteins. Ubiquitin linkages on immunoprecipitated transforming growth factor β–activated kinase 1 (TAK‐1) were analyzed with deubiquitinases.

Results

Sharp injury to porcine cartilage caused rapid activation of JNK and NF‐κB pathways and the upstream kinases MKK‐4, IKK, and TAK‐1. Pharmacologic inhibition of TAK‐1 in porcine cartilage abolished JNK and NF‐κB activation and reduced the injury‐dependent inflammatory gene response. High molecular weight species of phosphorylated TAK‐1 were induced by injury, indicating its ubiquitination. An overall increase in K⁶³‐linked polyubiquitination was detected upon injury, and TAK‐1 was specifically linked to K⁶³‐ but not K⁴⁸‐polyubiquitin chains. In mice, avulsion of wild‐type femoral epiphyses caused similar intracellular signaling that was reduced in cartilage‐specific TAK‐1–null mice. Epiphyseal cartilage of MyD88‐null and TRAF‐6–null mice responded to injury, suggesting the involvement of a ubiquitin E3 ligase other than TRAF‐6.

Conclusion

Activation of TAK‐1 by phosphorylation and K⁶³‐linked polyubiquitination by injury indicates its role in driving cell activation. Further studies are needed to identify the upstream ubiquitination mechanisms, including the E3 ligase involved.

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

Accumulating evidence indicates that autophagy and inflammatory responses contributes to secondary brain injury after traumatic brain injury (TBI), and toll-like receptor 4 (TLR4) is considered to involvement of this cascade and plays an important role. The present study was designed to determine the hypothesis that administration of resatorvid (TAK-242), a TLR4 antagonist, might provide a neuroprotective effect by inhibit TLR4-mediated pathway in a TBI rat model. Rat subjected to controlled cortical impact injury were injected with TAK-242 (0.5 mg/kg, i.v. injected) 10 min prior to injury. The results demonstrated that TAK-242 treatment significantly attenuated TBI-induced neurons loss, brain edema, and neurobehavioral impairment in rats. Immunoblotting analysis showed that TAK-242 treatment reduced TBI-induced TLR4, Beclin 1, and LC3-II levels, and maintained p62 levels at 24 h. Double immunolabeling demonstrated that LC3 dots co-localized with the hippocampus pyramidal neurons, and TLR4 was localized with the hippocampus neurons and astrocytes. In addition, the expression of TLR4 downstream signaling molecules, including MyD88, TRIF, NF-κB, TNF-α, and IL-1β, was significantly downregulated in hippocampus tissue by Western blot analysis. In conclusion, our findings indicate that pre-injury treatment with TAK-242 could inhibit neuronal autophagy and neuroinflammation responses in the hippocampus in a rat model of TBI. The neuroprotective effects of TAK-242 may be related to modulation of the TLR4-MyD88/TRIF-NF-κB signaling pathway. Furthermore, the study also suggests that TAK-242, an attractive potential drug, may be a promising drug candidate for TBI.

Emerging Roles for the Immune System in Traumatic Brain Injury

Traumatic brain injury (TBI) affects an ever-growing population of all ages with long-term consequences on health and cognition. Many of the issues that TBI patients face are thought to be mediated by the immune system. Primary brain damage that occurs at the time of injury can be exacerbated and prolonged for months or even years by chronic inflammatory processes, which can ultimately lead to secondary cell death, neurodegeneration, and long-lasting neurological impairment. Researchers have turned to rodent models of TBI in order to understand how inflammatory cells and immunological signaling regulate the post-injury response and recovery mechanisms. In addition, the development of numerous methods to manipulate genes involved in inflammation has recently expanded the possibilities of investigating the immune response in TBI models. As results from these studies accumulate, scientists have started to link cells and signaling pathways to pro- and anti-inflammatory processes that may contribute beneficial or detrimental effects to the injured brain. Moreover, emerging data suggest that targeting aspects of the immune response may offer promising strategies to treat TBI. This review will cover insights gained from studies that approach TBI research from an immunological perspective and will summarize our current understanding of the involvement of specific immune cell types and cytokines in TBI pathogenesis.

Emerging Roles for the Immune System in Traumatic Brain Injury

Traumatic brain injury (TBI) affects an ever-growing population of all ages with long-term consequences on health and cognition. Many of the issues that TBI patients face are thought to be mediated by the immune system. Primary brain damage that occurs at the time of injury can be exacerbated and prolonged for months or even years by chronic inflammatory processes, which can ultimately lead to secondary cell death, neurodegeneration, and long-lasting neurological impairment. Researchers have turned to rodent models of TBI in order to understand how inflammatory cells and immunological signaling regulate the post-injury response and recovery mechanisms. In addition, the development of numerous methods to manipulate genes involved in inflammation has recently expanded the possibilities of investigating the immune response in TBI models. As results from these studies accumulate, scientists have started to link cells and signaling pathways to pro- and anti-inflammatory processes that may contribute beneficial or detrimental effects to the injured brain. Moreover, emerging data suggest that targeting aspects of the immune response may offer promising strategies to treat TBI. This review will cover insights gained from studies that approach TBI research from an immunological perspective and will summarize our current understanding of the involvement of specific immune cell types and cytokines in TBI pathogenesis.

A positive correlation exists between neurotrauma and TGF-β1-containing microglia in rats

BACKGROUND

Transforming growth factor-beta 1 (TGF-β1) regulates many processes after traumatic brain injury (TBI). Both Neuro AiD™ (MLC601) and astragaloside (AST) attenuate microglia activation in rats with TBI. The purpose of this study was to investigate whether MLC601 or AST improves output of TBI by affecting microglial expression of TGF-β1.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats (120 in number) were used to investigate the contribution of TGF-β1-containing microglia in the MLC601-mediated or the AST-mediated neuroprotection in the brain trauma condition using lateral fluid percussion injury.

RESULTS

Pearson correlation analysis revealed that there was a positive correlation between brain injury (evidenced by both brain contused volume and neurological severity score) and the cortical numbers of TGF-β1-containing microglia for the rats (n = 12) 4 days post-TBI. MLC601 or AST significantly (P < 0·05) attenuated TBI-induced brain contused volume (119 ± 14 mm³ or 108 ± 11 mm³ vs. 160 ± 21 mm³ ), neurological severity score (7·8 ± 0·3 or 8·1 ± 0·4 vs. 10·2 ± 0·5) and numbers of TGF-β1-containing microglia (6% ± 2% or 11% ± 3% vs. 79% ± 7%) for the rats 4 days post-TBI.

CONCLUSIONS

There was a positive correlation between TBI and cortical numbers of TGF-β1-containing microglia which could be significantly attenuated by astragaloside or NeuroAiD™ (MLC601) in rats.

Akt Specific Activator SC79 Protects against Early Brain Injury following Subarachnoid Hemorrhage

A growing body of evidence demonstrates that Akt may serve as a therapeutic target for treatment of early brain injury following subarachnoid hemorrhage (SAH). The purpose of the current study was to evaluate the neuroprotective effect of Akt specific activator SC79 in an experimental rat model of SAH. SAH was induced by injecting 300 μL of blood into the prechiasmatic cistern. Intracerebroventricular (ICV) injection of SC79 (30 min post-SAH) induced the p-Akt (Ser473) expression in a dose-dependent manner. A single ICV dose treatment of SC79 (100 μg/rat) significantly increased the expression of Bcl-2 and p-GSK-3β (Ser9), decreased the protein levels of Bax, cytoplasm cytochrome c, and cleaved caspase-3, indicating the antiapoptotic effect of SC79. As a result, the number of apoptotic cells was reduced 24 h post SAH. Moreover, SC79 treatment alleviated SAH-induced oxidative stress, restored mitochondrial morphology, and improved neurological deficits. Strikingly, treatment of SC79 provided a beneficial outcome against neurologic deficit with a therapeutic window of at least 4 h post SAH by ICV injection and 30 min post SAH by intraperitoneal injection. Collectively, SC79 exerts its neuroprotective effect likely through the dual activities of antioxidation and antiapoptosis. These data provide a basic platform to consider SC79 as a novel therapeutic agent for treatment of SAH.

Inhibition of myeloid differentiation factor 88(MyD88) by ST2825 provides neuroprotection after experimental traumatic brain injury in mice

Myeloid differentiation factor 88(MyD88) is an endogenous adaptor protein that plays an important role in coordinating intracellular inflammatory responses induced by agonists of the Toll-like receptor and interleukin-1 receptor families. MyD88 has been reported to be essential for neuronal death in animal models and may represent a therapeutic target for pharmacologic inhibition following traumatic brain injury (TBI). The purpose of the current study was to investigate the neuroprotective effect of MyD88 specific inhibitor ST2825 in an experimental mouse model of TBI. Intracerebroventricular (ICV) injection of high concentration (20μg/μL) ST2825 (15min post TBI) attenuated the development of TBI in mice, markedly improved neurological function and reduced brain edema. Decreased neural apoptosis and increased neuronal survival were also observed. Biochemically, the high concentration of ST2825 significantly reduced the levels of MyD88, further decreased TAK1, p-TAK1, nuclear p65 and increased IκB-α. Additionally, ST2825 significantly reduced the levels of Iba-1 and inflammatory factors TNF-α and IL-1β. These data provide an experimental rationale for evaluation of MyD88 as a drug target and highlight the potential therapeutic implications of ST2825 in TBI.

TAK1 determines susceptibility to endoplasmic reticulum stress and leptin resistance in the hypothalamus

Sustained endoplasmic reticulum (ER) stress disrupts normal cellular homeostasis and leads to the development of many types of human diseases, including metabolic disorders. TAK1 (also known as MAP3K7) is a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family and is activated by a diverse set of inflammatory stimuli. Here, we demonstrate that TAK1 regulates ER stress and metabolic signaling through modulation of lipid biogenesis. We found that deletion of Tak1 increased ER volume and facilitated ER-stress tolerance in cultured cells, which was mediated by upregulation of sterol-regulatory-element-binding protein (SREBP)-dependent lipogenesis. In the in vivo setting, central nervous system (CNS)-specific Tak1 deletion upregulated SREBP-target lipogenic genes and blocked ER stress in the hypothalamus. Furthermore, CNS-specific Tak1 deletion prevented ER-stress-induced hypothalamic leptin resistance and hyperphagic obesity under a high-fat diet (HFD). Thus, TAK1 is a crucial regulator of ER stress in vivo, which could be a target for alleviation of ER stress and its associated disease conditions.

Inhibition of the Receptor for Advanced Glycation End-Products (RAGE) Attenuates Neuroinflammation While Sensitizing Cortical Neurons Towards Death in Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a threatening and devastating neurological insult with high mortality and morbidity rates. Despite considerable efforts, the underlying pathophysiological mechanisms are still poorly understood. The receptor for advanced glycation end products (RAGE) is a multiligand receptor that has been implicated in various pathological conditions. We previously showed that RAGE was upregulated and may be involved in pathophysiology of SAH. In the current study, we investigated its potential role in SAH. We found that the upregulation of RAGE after SAH was NF-κB-dependent positive feedback regulation. Further, pharmacological inhibition of RAGE attenuated neuroinflammation, indicating a possible contributive role of RAGE in inflammation-associated brain injury after SAH. Conversely, however, inhibition of RAGE sensitized neurons, exacerbating cell death, which correlated with augmented apoptosis and diminished autophagy, suggesting that activation of RAGE may protect against SAH-induced neuronal injury. Furthermore, we demonstrate that inhibition of RAGE significantly reduced brain edema and improved neurological function at day 1 but not at day 3 post-SAH. Taken together, these results suggest that RAGE exerts dual role after SAH. Our findings also suggest caution should be exercised in setting RAGE-targeted treatment for SAH.

Upregulation of HMGB1 in wall of ruptured and unruptured human cerebral aneurysms: preliminary results

A growing body of evidence suggests that inflammation plays a crucial role in cerebral aneurysm initiation, progression, and rupture. High-mobility group box 1 (HMGB1) is a non-histone nuclear protein that can serve as an alarmin to drive the pathogenesis of inflammatory disease. The purpose of this study was to investigate the expression of HMGB1 in the wall of ruptured and unruptured human cerebral aneurysms. Human cerebral aneurysms (25 ruptured and 16 unruptured) were immunohistochemically stained for HMGB1. As controls, four specimens of the middle cerebral arteries obtained at autopsy were also immunostained. Immunofluorescence double staining was used to determine HMGB1 cellular distribution. HMGB1 was nearly undetectable in the controls. All aneurysm tissues stained positive for HMGB1 monoclonal antibody, and expression of HMGB1 was more abundant in ruptured aneurysm tissue than unruptured aneurysms (p < 0.05). Furthermore, the expression of HMGB1 had no correlation with aneurysm size and time resected after the rupture. HMGB1 nuclear immunoreactivity was co-localized with immunoreactivity of CD3 in T lymphocytes, CD20 in B lymphocytes, CD68 in macrophages, α-SMA in smooth muscle cells, and CD31 in endothelial cells. Cytoplasmic HMGB1 localization was also detected in macrophages and T lymphocytes. Taken together, HMGB1 is expressed in the wall of human cerebral aneurysms and is more abundant in ruptured aneurysms than in unruptured ones. These data indicate a possible role of HMGB1 in the pathophysiology of human cerebral aneurysms.

TAK1 inhibition-induced RIP1-dependent apoptosis in murine macrophages relies on constitutive TNF-α signaling and ROS production

Background

Transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) is a key regulator of signal cascades of TNF-α receptor and TLR4, and can induce NF-κB activation for preventing cell apoptosis and eliciting inflammation response.

Results

TAK1 inhibitor (TAKI) can decrease the cell viability of murine bone marrow-derived macrophages (BMDM), RAW264.7 and BV-2 cells, but not dermal microvascular endothelial cells, normal human epidermal keratinocytes, THP-1 monocytes, human retinal pigment epithelial cells, microglia CHME3 cells, and some cancer cell lines (CL1.0, HeLa and HCT116). In BMDM, TAKI-induced caspase activation and cell apoptosis were enhanced by lipopolysaccharide (LPS). Moreover, TAKI treatment increased the cytosolic and mitochondrial reactive oxygen species (ROS) production, and ROS scavengers NAC and BHA can inhibit cell death caused by TAKI. In addition, RIP1 inhibitor (necrostatin-1) can protect cells against TAKI-induced mitochondrial ROS production and cell apoptosis. We also observed the mitochondrial membrane potential loss after TAKI treatment and deterioration of oxygen consumption upon combination with LPS. Notably TNF-α neutralization antibody and inhibitor enbrel can decrease the cell death caused by TAKI.

Conclusions

TAKI-induced cytotoxicity is cell context specific, and apoptosis observed in macrophages is dependent on the constitutive autocrine action of TNF-α for RIP1 activation and ROS production.

Nanoparticle Estrogen in Rat Spinal Cord Injury Elicits Rapid Anti-Inflammatory Effects in Plasma, Cerebrospinal Fluid, and Tissue

Persons with spinal cord injury (SCI) are in need of effective therapeutics. Estrogen (E2), as a steroid hormone, is a highly pleiotropic agent; with anti-inflammatory, anti-apoptotic, and neurotrophic properties, it is ideal for use in treatment of patients with SCI. Safety concerns around the use of high doses of E2 have limited clinical application, however. To address these concerns, low doses of E2 (25 μg and 2.5 μg) were focally delivered to the injured spinal cord using nanoparticles. A per-acute model (6 h after injury) was used to assess nanoparticle release of E2 into damaged spinal cord tissue; in addition, E2 was evaluated as a rapid anti-inflammatory. To assess inflammation, 27-plex cytokine/chemokine arrays were conducted in plasma, cerebrospinal fluid (CSF), and spinal cord tissue. A particular focus was placed on IL-6, GRO-KC, and MCP-1 as these have been identified from CSF in human studies as potential biomarkers in SCI. S100β, an additional proposed biomarker, was also assessed in spinal cord tissue only. Tissue concentrations of E2 were double those found in the plasma, indicating focal release. E2 showed rapid anti-inflammatory effects, significantly reducing interleukin (IL)-6, GRO-KC, MCP-1, and S100β in one or all compartments. Numerous additional targets of rapid E2 modulation were identified including: leptin, MIP-1α, IL-4, IL-2, IL-10, IFNγ, tumor necrosis factor-α, etc. These data further elucidate the rapid anti-inflammatory effects E2 exerts in an acute rat SCI model, have identified additional targets of estrogen efficacy, and suggest nanoparticle delivered estrogen may provide a safe and efficacious treatment option in persons with acute SCI.

TGFβ-activated Kinase 1 (TAK1) Inhibition by 5Z-7-Oxozeaenol Attenuates Early Brain Injury after Experimental Subarachnoid Hemorrhage

Accumulating evidence suggests that activation of mitogen-activated protein kinases (MAPKs) and nuclear factor NF-κB exacerbates early brain injury (EBI) following subarachnoid hemorrhage (SAH) by provoking proapoptotic and proinflammatory cellular signaling. Here we evaluate the role of TGFβ-activated kinase 1 (TAK1), a critical regulator of the NF-κB and MAPK pathways, in early brain injury following SAH. Although the expression level of TAK1 did not present significant alternation in the basal temporal lobe after SAH, the expression of phosphorylated TAK1 (Thr-187, p-TAK1) showed a substantial increase 24 h post-SAH. Intracerebroventricular injection of a selective TAK1 inhibitor (10 min post-SAH), 5Z-7-oxozeaenol (OZ), significantly reduced the levels of TAK1 and p-TAK1 at 24 h post-SAH. Involvement of MAPKs and NF-κB signaling pathways was revealed that OZ inhibited SAH-induced phosphorylation of p38 and JNK, the nuclear translocation of NF-κB p65, and degradation of IκBα. Furthermore, OZ administration diminished the SAH-induced apoptosis and EBI. As a result, neurological deficits caused by SAH were reversed. Our findings suggest that TAK1 inhibition confers marked neuroprotection against EBI following SAH. Therefore, TAK1 might be a promising new molecular target for the treatment of SAH.

Alpha lipoic acid inhibits neural apoptosis via a mitochondrial pathway in rats following traumatic brain injury

Alpha lipoic acid (ALA) is a powerful antioxidant that has proven protective effects against brain damage following a traumatic brain injury (TBI) in rats. However, the molecular mechanisms underlying these effects are not well understood. This study investigated the effect of ALA on neural apoptosis and the potential mechanism of these effects in the weight-drop model of TBI in male Sprague-Dawley rats that were treated with ALA (20 or 100 mg/kg) or vehicle via intragastric administration 30 min after TBI. Brain samples were collected 48 h later for analysis. ALA treatment resulted in a downregulation of caspase-3 expression, reduced the number of positive cells in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and improved neuronal survival. Furthermore, the level of malondialdehyde and glutathione peroxidase activity were restored, while Bcl-2-associated X protein translocation to mitochondria and cytochrome c release into the cytosol were reduced by ALA treatment. These results demonstrate that ALA improves neurological outcome in rats by protecting neural cell against apoptosis via a mechanism that involves the mitochondria following TBI.

Involvement of neuronal TGF-β activated kinase 1 in the development of tolerance to morphine-induced antinociception in rat spinal cord

BACKGROUND AND PURPOSE

Tolerance induced by morphine and other opiates remains a major unresolved problem in the clinical management of pain. There is now good evidence for the importance of MAPKs in morphine-induced antinociceptive tolerance. A member of the MAPK kinase kinase family, TGF-β activated kinase 1 (TAK1) is the common upstream kinase of MAPKs. Here, we have assessed the involvement of TAK1 in the development of tolerance to morphine-induced analgesia.

EXPERIMENTAL APPROACH

The effects of an antagonist of TAK1 on morphine tolerance were investigated in vivo using the Randall-Selitto test, and the mechanism was investigated using Western blot and immunohistochemistry. The expression of TAK1 after chronic morphine exposure was also evaluated in vitro by immunohistochemistry.

KEY RESULTS

Chronic intrathecal morphine exposure up-regulated protein levels and phosphorylation of spinal TAK1. TAK1 immunoreactivity was co-localized with the neuronal marker NeuN. Intrathecal administration of 5Z-7-oxozeaenol (OZ), a selective TAK1 inhibitor, attenuated the loss of morphine analgesic potency and morphine-induced TAK1 up-regulation. Furthermore, OZ decreased the up-regulated expression of spinal p38 and JNK after repeated morphine exposure. In vitro studies demonstrated that sustained morphine treatment induced TAK1 up-regulation, which was reversed by co-administration of OZ. A bolus injection of OZ showed some reversal of established morphine antinociceptive tolerance.

CONCLUSIONS AND IMPLICATIONS

TAK1 played a pivotal role in the development of morphine-induced antinociceptive tolerance. Modulation of TAK1 activation by the selective inhibitor OZ in the lumbar spinal cord may prove to be an attractive adjuvant therapy to attenuate such tolerance.

Increased Expression of NLRP3 Inflammasome in Wall of Ruptured and Unruptured Human Cerebral Aneurysms: Preliminary Results

BACKGROUND

A growing body of evidence suggests that inflammation actively participates in cerebral aneurysm initiation, progression, and rupture. The primary objective of this study was to assess the expression of NLR family, Pyrin-domain containing 3 (NLRP3) inflammasome in human cerebral aneurysms.

METHODS

Aneurysmal domes (19 ruptured and 17 unruptured) from patients undergoing surgical treatment for ruptured or unruptured cerebral aneurysms were analyzed. A control sample comprising 4 middle cerebral arteries was obtained from autopsy subjects. The expression of NLRP3, apoptotic speck-containing protein with a card (ASC), caspase-1, and interleukin (IL)-1β were assessed by immunohistochemistry. Immunofluorescence double staining was used to determine NLRP3, ASC, and caspase-1 cellular distribution.

RESULTS

Expression of NLRP3, ASC, and caspase-1 were more abundant in ruptured aneurysm tissue than that in unruptured aneurysms, based on a semi-quantitative grading (P < .05). IL-1β was also overexpressed in the ruptured cerebral aneurysms and associated with increased expression of NLRP3, ASC, and caspase-1 (P < .05). Furthermore, NLRP3, ASC, and caspase-1 immunoreactivity were colocalized with immunoreactivity of CD3 in T lymphocytes and CD68 in macrophages.

CONCLUSIONS

NLRP3 inflammasome was expressed in the wall of human cerebral aneurysms and was more abundant in ruptured aneurysms than in unruptured. This study raises the possibility that NLRP3 inflammasome may be involved in the pathogenesis of human intracranial aneurysms, and this requires further study.

A cluster of protein kinases and phosphatases modulated in fetal Down syndrome (trisomy 21) brain

Down syndrome (DS; trisomy 21) is the most frequent cause of mental retardation with major cognitive and behavioral deficits. Although a series of aberrant biochemical pathways has been reported, work on signaling proteins is limited. It was, therefore, the aim of the study to test a selection of protein kinases and phosphatases known to be essential for memory and learning mechanisms in fetal DS brain. 12 frontal cortices from DS brain were compared to 12 frontal cortices from controls obtained at legal abortions. Proteins were extracted from brains and western blotting with specific antibodies was carried out. Primary results were used for networking (IntAct Molecular Interaction Database) and individual predicted pathway components were subsequently quantified by western blotting. Levels of calcium-calmodulin kinase II alpha, transforming growth factor beta-activated kinase 1 as well as phosphatase and tensin homolog (PTEN) were reduced in cortex of DS subjects and network generation pointed to interaction between PTEN and the dendritic spine protein drebrin that was subsequently determined and reduced levels were observed. The findings of reduced levels of cognitive-function-related protein kinases and the phosphatase may be relevant for interpretation of previous work and may be useful for the design of future studies on signaling in DS brain. Moreover, decreased drebrin levels may point to dendritic spine abnormalities.

Lipopolysaccharide-induced loss of cultured rat myenteric neurons - role of AMP-activated protein kinase

OBJECTIVE

Intestinal barrier function is vital for homeostasis. Conditions where the mucosal barrier is compromised lead to increased plasma content of lipopolysaccharide (LPS). LPS acts on Toll-like receptor 4 (TLR4) and initiates cellular inflammatory responses. TLR4 receptors have been identified on enteric neurons and LPS exposure causes neuronal loss, counteracted by vasoactive intestinal peptide (VIP), by unknown mechanisms. In addition AMP activated protein kinase (AMPK) stimulation causes loss of enteric neurons. This study investigated a possible role of AMPK activation in LPS-induced neuronal loss.

DESIGN

Primary cultures of myenteric neurons isolated from rat small intestine were used. Cultures were treated with LPS (0.2-20 µg/mL) with and without TAK1-inhibitor (5Z)-7-Oxozeaenol (10-6 M) or AMPK inhibitor compound C (10-5 M). AMPK-induced neuronal loss was verified treating cultures with three different AMPK activators, AICAR (10-4-3×10-3 M), metformin (0.2-20 µg/mL) and A-769662 (10-5-3×10-4 M) with or without the presence of compound C (10-5 M). Upstream activation of AMPK-induced neuronal loss was tested by treating cultures with AICAR (10-3 M) in the presence of TAK1 inhibitor (5Z)-7-Oxozeaenol (10-6 M). Neuronal survival and relative numbers of neurons immunoreactive (IR) for VIP were evaluated using immunocytochemistry.

RESULTS

LPS caused a concentration dependent loss of neurons. All AMPK activators induced loss of myenteric neurons in a concentration dependent manner. LPS-, AICAR- and metformin-,but not A-769662-, induced neuronal losses were inhibited by presence of compound C. LPS, AICAR or metformin exposure increased the relative number of VIP-IR neurons; co-treatment with (5Z)-7-Oxozeaenol or compound C reversed the relative increase in VIP-IR neurons induced by LPS. (5Z)-7-Oxozeaenol, compound C or A-769662 did not per se change neuronal survival or relative numbers of VIP-IR neurons.

CONCLUSION

AMPK activation mimics LPS-induced loss of cultured myenteric neurons and LPS-induced neuronal loss is counteracted by TAK1 and AMPK inhibition. This suggests enteric neuroimmune interactions involving AMPK regulation.

CPEB regulation of TAK1 synthesis mediates cytokine production and the inflammatory immune response

The cytoplasmic-element-binding (CPEB) protein is a sequence-specific RNA-binding protein that regulates cytoplasmic polyadenylation-induced translation. In mouse embryo fibroblasts (MEFs) lacking CPEB, many mRNAs encoding proteins involved in inflammation are misregulated. Correlated with this aberrant translation in MEFs, a macrophage cell line depleted of CPEB and treated with lipopolysaccharide (LPS) to stimulate the inflammatory immune response expresses high levels of interleukin-6 (IL-6), which is due to prolonged nuclear retention of NF-κB. Two proteins involved in NF-κB nuclear localization and IL-6 expression, IκBα and transforming growth factor beta-activated kinase 1 (TAK1), are present at excessively low and high steady-state levels, respectively, in LPS-treated CPEB-depleted macrophages. However, only TAK1 has an altered synthesis rate that is CPEB dependent and CPEB/TAK1 double depletion alleviates high IL-6 production. Peritoneal macrophages isolated from CPEB knockout (KO) mice treated with LPS in vitro also have prolonged NF-κB nuclear retention and produce high IL-6 levels. LPS-injected CPEB KO mice secrete prodigious amounts of IL-6 and other proinflammatory cytokines and exhibit hypersensitivity to endotoxic shock; these effects are mitigated when the animals are also injected with (5Z)-7-oxozeaenol, a potent and specific inhibitor of TAK1. These data show that CPEB control of TAK1 mRNA translation mediates the inflammatory immune response.

miR-21 improves the neurological outcome after traumatic brain injury in rats

The expression levels of microRNAs (miRNAs) including miR-21, have been reported to change in response to traumatic brain injury (TBI), suggesting that they may influence the pathophysiological process in brain injury. To analyze the potential effect of miR-21 on neurological function after TBI, we employed the fluid percussion injury rat model and manipulated the expression level of miR-21 in brain using intracerebroventricular infusion of miR-21 agomir or antagomir. We found that upregulation of miR-21 level in brain conferred a better neurological outcome after TBI by improving long-term neurological function, alleviating brain edema and decreasing lesion volume. To further investigate the mechanism underlying this protective effect, we evaluated the impact of miR-21 on apoptosis and angiogenesis in brain after TBI. We found that miR-21 inhibited apoptosis and promoted angiogenesis through regulating the expression of apoptosis- and angiogenesis-related molecules. In addition, the expression of PTEN, a miR-21 target gene, was inhibited and Akt signaling was activated in the procedure. Taken together, these data indicate that miR-21 could be a potential therapeutic target for interventions after TBI.

Intracranial injection of recombinant stromal-derived factor-1 alpha (SDF-1α) attenuates traumatic brain injury in rats

OBJECTIVE

This study was conducted to investigate the role of stromal-derived factor-1 alpha (SDF-1α) in a secondary brain injury after traumatic brain injury (TBI) in rats, and to further elucidate its underlying regulatory mechanisms.

MATERIALS AND METHODS

Male Sprague-Dawley rats underwent TBI for 30 min, and then received intracranial injections of recombinant SDF-1α, SDF-1α antibody, or saline as a vehicle control. At 24 h after TBI, brain tissues from the experimental animals were subjected to histology, immunohistochemistry, quantitative real-time polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and western blot analyses.

RESULTS

TBI-induced brain edema and blood-brain barrier disruption were ameliorated by post-injury injections of SDF-1α. TBI-induced neuronal degradation and apoptosis, accompanied by increased cleaved caspase-3, cleaved PARP and Bax, and decreased Bcl-2 were found to be attenuated by SDF-1α injection. Nitric oxide (NO) and inducible nitric oxide synthase (iNOS) levels decreased in SDF-1α treated animals after TBI. SDF-1α repressed inflammatory responses by inhibiting the expression of pro-inflammatory cytokines, such as TNF-α, IL-1β, and IL-6. However, neutralizing the effect of SDF-1α with its antibody abolished these therapeutic alterations in TBI animals. Importantly, SDF-1α attenuated the brain lesion by affecting the ERK and NF-κB signaling pathways after mechanical head trauma in rats.

CONCLUSIONS

SDF-1α ameliorates mechanical trauma-induced pathological changes via its anti-apoptotic and anti-inflammatory action in the brain.