Genetic and Histological Alterations Reveal Key Role of Prostaglandin Synthase and Cyclooxygenase 1 and 2 in Traumatic Brain Injury-Induced Neuroinflammation in the Cerebral Cortex of Rats Exposed to Moderate Fluid Percussion Injury

Comprehensive RNA Expression Analysis Revealed Biological Functions of Key Gene Sets and Identified Disease-Associated Cell Types Involved in Rat Traumatic Brain Injury

Traumatic brain injury (TBI) is a worldwide public health concern without major therapeutic breakthroughs over the past decades. Developing effective treatment options and improving the prognosis of TBI depends on a better understanding of the mechanisms underlying TBI. This study performed a comprehensive analysis of 15 RNA expression datasets of rat TBIs from the GEO database. By integrating the results from the various analyses, this study investigated the biological processes, pathways, and cell types associated with TBI and explored the activity of these cells during various TBI phases. The results showed the response to cytokine, inflammatory response, bacteria-associated response, metabolic and biosynthetic processes, and pathways of neurodegeneration to be involved in the pathogenesis of TBI. The cellular abundance of microglia, perivascular macrophages (PM), and neurons were found to differ after TBI and at different times postinjury. In conclusion, immune- and inflammation-related pathways, as well as pathways of neurodegeneration, are closely related to TBI. Microglia, PM, and neurons are thought to play roles in TBI with different activities that vary by phase of TBI.

Bioinformatics-based Identification of Key Pathways and Hub Genes of Traumatic Brain Injury in a Rat Model

Traumatic brain injury (TBI) is a common injury caused by external forces that lead to damaged brain function or pathological changes in the brain tissue. To explore the molecular mechanism and the hub genes of TBI, we downloaded gene expression profiles of the TBI model of rat and the sham control for the subsequent gene set enrichment analysis, pathway analysis and protein-protein interactions analysis. The results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis indicated that multiple biological pathways, including immune response, inflammatory response and cellular response to interleukin-1, as well as signaling pathways, such as tumor necrosis factor signaling pathway, chemokine signaling pathway, cytokine-cytokine receptor interaction, Toll-like receptor signaling pathway and nuclear factor kappa B signaling pathway were implicated in the TBI. In conclusion, this study provides insights into the molecular mechanism of TBI by screening the differentially expressed genes and hub genes that can be used as biomarkers and therapeutic targets.

Formyl Peptide Receptor 1 Signaling in Acute Inflammation and Neural Differentiation Induced by Traumatic Brain Injury

Traumatic brain injury (TBI) is a shocking disease frequently followed by behavioral disabilities, including risk of cerebral atrophy and dementia. N-formylpeptide receptor 1 (FPR1) is expressed in cells and neurons in the central nervous system. It is involved in inflammatory processes and during the differentiation process in the neural stem cells. We investigate the effect of the absence of Fpr1 gene expression in mice subjected to TBI from the early stage of acute inflammation to neurogenesis and systematic behavioral testing four weeks after injury. C57BL/6 animals and Fpr1 KO mice were subjected to TBI and sacrificed 24 h or four weeks after injury. Twenty-four hours after injury, TBI Fpr1 KO mice showed reduced histological impairment, tissue damage and acute inflammation (MAPK activation, NF-κB signaling induction, NRLP3 inflammasome pathway activation and oxidative stress increase). Conversely, four weeks after TBI, the Fpr1 KO mice showed reduced survival of the proliferated cells in the Dentate Gyrus compared to the WT group. Behavioral analysis confirmed this trend. Moreover, TBI Fpr1 KO animals displayed reduced neural differentiation (evaluated by beta-III tubulin expression) and upregulation of astrocyte differentiation (evaluated by GFAP expression). Collectively, our study reports that, immediately after TBI, Fpr1 increased acute inflammation, while after four weeks, Fpr1 promoted neurogenesis.

Modulating neuroinflammation and oxidative stress to prevent epilepsy and improve outcomes after traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability in young adults worldwide. TBI survival is associated with persistent neuropsychiatric and neurological impairments, including posttraumatic epilepsy (PTE). To date, no pharmaceutical treatment has been found to prevent PTE or ameliorate neurological/neuropsychiatric deficits after TBI. Brain trauma results in immediate mechanical damage to brain cells and blood vessels that may never be fully restored given the limited regenerative capacity of brain tissue. This primary insult unleashes cascades of events, prominently including neuroinflammation and massive oxidative stress that evolve over time, expanding the brain injury, but also clearing cellular debris and establishing homeostasis in the region of damage. Accumulating evidence suggests that oxidative stress and neuroinflammatory sequelae of TBI contribute to posttraumatic epileptogenesis. This review will focus on possible roles of reactive oxygen species (ROS), their interactions with neuroinflammation in posttraumatic epileptogenesis, and emerging therapeutic strategies after TBI. We propose that inhibitors of the professional ROS-generating enzymes, the NADPH oxygenases and myeloperoxidase alone, or combined with selective inhibition of cyclooxygenase mediated signaling may have promise for the treatment or prevention of PTE and other sequelae of TBI. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Synthesis and Biological Assessment of 2-Hydroxyiminoethanones as Anti-Inflammatory and β-Amyloid Aggregation Inhibitors

Alzheimer’s disease (AD) is a neuroinflammatory based pathologic state in which β-amyloid aggregates are major devastating agents. In this study, a series of 2-hydroxyiminoethanones were synthesized and evaluated as anti-inflammatory in carrageenan and formalin tests and inhibitors of β-amyloid aggregation. Compounds 1-10b were synthesized through a two-step reaction. Results: Compounds 1-5b showed more β-amyloid disaggregation ability than reference drugs rifampicin and donepezil and compound 2b was the best compound in this series and could reduce the extent of amyloid aggregation to 50.9%. Interestingly, compounds 1b and 3b showed significant anti-inflammatory activity in carrageenan-induced paw edema compared to control group and equivalent to the reference drug indomethacin. 2-Hydeoxyiminoethanones are privileged scaffold for further drug research and development as anti-neuroinflammatory and neuroprotective agents.

The potential roles of dopamine in traumatic brain injury: a preclinical and clinical update

Traumatic brain injury (TBI) is one of the leading causes of death and disability, particularly among the young and the elderly. Several therapeutic options have been investigated, including drug interventions or combinational therapies. Although many drugs have shown promising results in the preclinical stage, all have failed in large clinical trials. Targeting the dopamine system is a novel TBI approach that provides benefits to functional outcomes. TBI could damage the dopaminergic system. Alterations in dopamine levels can impact cellular dysfunction and central nervous system (CNS) inflammation. Experimental evidence suggests that dopamine should be considered a first-line treatment to protect cerebral autoregulation and promote cerebral outcomes in TBI. Furthermore, investigation of dopamine-related genetic factors in relation to injury severity could also be of great significance for promoting TBI treatment. Importantly, various clinical lines of evidence have indicated that many dopamine agonists are beneficial when administered following injury in TBI patients. However, side effects of dopamine treatment prevent their use in TBI treatment, and there is a need for ongoing large, prospective, double-blind randomized controlled trials (RCTs) with these medications by the use of standardized criteria and outcomes to fully understand their effectiveness in this patient group. Here, we review the roles of dopamine in TBI and discuss the role that dopaminergic therapies have in neuroprotective strategies.

Macrophage migration inhibitory factor facilitates prostaglandin E2 production of astrocytes to tune inflammatory milieu following spinal cord injury

Background

Astrocytes have been shown to produce several pro- and anti-inflammatory cytokines to maintain homeostasis of microenvironment in response to vast array of CNS insults. Some inflammation-related cytokines are responsible for regulating such cell events. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that can be inducibly expressed in the lesioned spinal cord. Unknown is whether MIF can facilitate the production of immunosuppressive factors from astrocytes to tune milieu following spinal cord injury.

Methods

Following establishment of contusion SCI rat model, correlation of PGE₂ synthesis-related protein levels with that of MIF was assayed by Western blot. ELISA assay was used to detect production of PGE₂, TNF-α, IL-1β, and IL-6. Immunohistochemistry was performed to observe colocalization of COX2 with GFAP- and S100β-positive astrocytes. The primary astrocytes were treated by various inhibitors to validate relevant signal pathway.

Results

The protein levels of MIF and COX2, but not of COX1, synchronously increased following spinal cord injury. Treatment of MIF inhibitor 4-IPP to the lesion sites significantly reduced the expression of COX2, mPGES-1, and as a consequence, the production of PGE₂. Astrocytes responded robustly to the MIF interference, by which regulated MAPK/COX2/PGE₂ signal pathway through coupling with the CD74 membrane receptor. MIF-induced production of PGE₂ from astrocytes was able to suppress production of TNF-α, but boosted production of IL-1β and IL-6 in LPS-activated macrophages.

Conclusion

Collectively, these results reveal a novel function of MIF-mediated astrocytes, which fine-tune inflammatory microenvironment to maintain homeostasis. These suggest an alternative therapeutic strategy for CNS inflammation.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1468-6) contains supplementary material, which is available to authorized users.

Incretin Mimetics as Rational Candidates for the Treatment of Traumatic Brain Injury

Traumatic brain injury (TBI) is becoming an increasing public health issue. With an annually estimated 1.7 million TBIs in the United States (U.S) and nearly 70 million worldwide, the injury, isolated or compounded with others, is a major cause of short- and long-term disability and mortality. This, along with no specific treatment, has made exploration of TBI therapies a priority of the health system. Age and sex differences create a spectrum of vulnerability to TBI, with highest prevalence among younger and older populations. Increased public interest in the long-term effects and prevention of TBI have recently reached peaks, with media attention bringing heightened awareness to sport and war related head injuries. Along with short-term issues, TBI can increase the likelihood for development of long-term neurodegenerative disorders. A growing body of literature supports the use of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and glucagon (Gcg) receptor (R) agonists, along with unimolecular combinations of these therapies, for their potent neurotrophic/neuroprotective activities across a variety of cellular and animal models of chronic neurodegenerative diseases (Alzheimer's and Parkinson's diseases) and acute cerebrovascular disorders (stroke). Mild or moderate TBI shares many of the hallmarks of these conditions; recent work provides evidence that use of these compounds is an effective strategy for its treatment. Safety and efficacy of many incretin-based therapies (GLP-1 and GIP) have been demonstrated in humans for the treatment of type 2 diabetes mellitus (T2DM), making these compounds ideal for rapid evaluation in clinical trials of mild and moderate TBI.

Neuroprotective Effects of Collagen-Glycosaminoglycan Matrix Implantation following Surgical Brain Injury

Background

Neurological deficits following neurosurgical procedures are inevitable; however, there are still no effective clinical treatments. Earlier reports revealed that collagen-glycosaminoglycan (CG) matrix implantation promotes angiogenesis, neurogenesis, and functional recovery following surgical brain injury (SBI). The present study was conducted to further examine the potential neuroprotective effects of collagen-glycosaminoglycan (CG) matrix implantation following neurosurgery.

Methods

CG implantation was performed in the lesion cavity created by surgical trauma. The Sprague-Dawley rat model of SBI was used as established in the previous study by the author. The rats were divided into three groups as follows: (1) sham (SHAM), (2) surgery-induced lesion cavity (L), and (3) CG matrix implantation following surgery-induced lesion cavity (L+CG). Proinflammatory (tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells)) and anti-inflammatory (IL-10 and granulocyte-macrophage colony-stimulating factor (GMCSF)) cytokine expression was evaluated by enzyme-linked immunosorbent assays. Microglial activation was evaluated by immunohistochemistry, and the neuroprotective effect of CG matrix implantation was evaluated by an immunohistochemical study of microglia ED-1 and IBA-1 (activated microglia) and myeloperoxidase (MPO) and by the analysis of IL-6, IL-10, TNF-α, NF-κB, and GMCSF cytokine levels. Apoptosis was also assessed using a TUNEL assay.

Results

The results showed that CG matrix implantation following surgically induced lesions significantly decreased the density of ED-1, IBA-1, and MPO (activated microglia). The tissue concentration of proinflammatory cytokines, such as TNF-α, IL-6, and NF-κB was significantly decreased. Conversely, the anti-inflammatory cytokines GMCSF and IL-10 were significantly increased.

Conclusions

Implantation of the CG matrix following SBI has neuroprotective effects, including the suppression of microglial activation and the production of inflammatory-related cytokines.

Effect of traumatic brain injury on nicotine-induced modulation of dopamine release in the striatum and nucleus accumbens shell

Background

Traumatic brain injury is associated with substantial alterations in reward processing, but underlying mechanisms are controversial.

Objective

A better understanding of alterations in dopamine (DA) release patterns from the dorsal striatum and nucleus accumbens shell (NAc) may provide insights into posttraumatic reward pathology.

Materials and Methods

The patterns of DA release with or without exposure to nicotine in brain slices with striatum and NAc, isolated from Sprague-Dawley rats with 6 psi fluid percussion (FPI) or sham injury were analysis by using fast-scan cyclic voltammetry. Tonic and phasic DA releases were assessed using single pulse and 10 pulses at 25 Hz, respectively. DA release relative to stimulation intensity, frequency, number of pulses, and paired-pulse facilitation was evaluated to determine release probability and response to bursting.

Results

There was a profound suppression in tonic DA release after nicotine desensitization after FPI, and the input/output curve for the DA release based on stimulation intensity was shifted to the right. FPI was associated with a significant decrease in frequency-dependent DA release augmentation, DA release induced by high frequency stimulation trains, and DA release in response to paired-pulse facilitation. The effect of nicotine desensitization was similar in FPI and sham-injured animals, although significantly smaller after FPI. Nicotine desensitization–induced differences between phasic and tonic release concentrations that contrasted with the reward-related signals then became less prominent in NAc after FPI.

Conclusions

TBI blunts DA release from mesolimbic reward centers, and more intense stimuli are required to produce context-dependent DA release sufficient to have a physiological effect.

Implications

The nicotine desensitization-related suppression in tonic DA release was profound with right-ward shift of the input/output curve for DA release after FPI. FPI was associated with a significant decrease in frequency-dependent DA release augmentation, DA release induced by high frequency stimulation trains, and DA release in response to paired-pulse facilitation. Nicotine desensitization–induced differences between phasic and tonic release concentrations that contrasted with the reward-related signals then became less prominent in NAc after FPI. TBI thus blunts DA release from mesolimbic reward centers, and more intense stimuli are required to produce context-dependent DA release sufficient to have a physiological effect.