Simvastatin Therapy in the Acute Stage of Traumatic Brain Injury Attenuates Brain Trauma-Induced Depression-Like Behavior in Rats by Reducing Neuroinflammation in the Hippocampus

Relationship among depression, fatigue, and sleep after traumatic brain injury: The role of physical exercise as a non-pharmacological therapy

Traumatic brain injury (TBI) is a burdensome condition frequently associated with an increased risk of psychiatric disorders. Although the exact molecular signaling pathways have not yet been fully defined, the compromised integrity of functional brain networks in regions such as the prefrontal cortex and anterior cingulate cortex has been linked to persistent symptoms, including depression, fatigue, and sleep disorders. Understanding how TBI affects neural physiology enables the development of effective interventions. One such strategy may be physical exercise, which promotes neural repair and behavioral rehabilitation after TBI. However, there are caveats to consider when interpreting the effects of physical exercise on TBI-induced mental health issues. This review will highlight the main findings from the literature investigating how different physical exercise protocols affect the progression of TBI-induced depression, fatigue, and sleep disturbances. Furthermore, we aim to explore potential neurobiological pathways that explain how physical exercise influences depression, fatigue, and sleep following TBI.

The Effect of Rosuvastatin on Facial Nerve Regeneration After Facial Nerve Injury: An Experimental Animal Study

OBJECTIVES

Rosuvastatin is an antihyperlipidemic statin group pharmacological agent with antioxidant, neuroprotective, and anti-inflammatory effects. In this study, we aimed to examine the functional, electrophysiological, and histopathological effects of rosuvastatin or in combination with corticosteroids on facial nerve regeneration in rats with traumatic peripheral facial paralysis (PFP).

METHODS

PFP was induced in 28 female Sprague Dawley rats that we divided into 4 groups: group 1, control group; group 2, methylprednisolone group; group 3, rosuvastatin group; group 4, rosuvastatin and methylprednisolone group. Electrophysiological, functional, and histopathological examinations were performed before and after the medications.

RESULTS

Electrophysiological threshold values of group 3 and group 4 were found to be significantly lower than the control group on day 21 after treatment (P = .002, P = .001; P < .01).In the histopathological evaluation, axonal degeneration, macrovacuolization, and vascular congestion levels were compared between the groups, and a statistically significant difference was observed in group 4 compared to the control group. The recovery time of the eye corneal reflex was found to be significantly higher in the control group than in groups 3 and 4 when comparing postoperative day 1 to day 7 and postoperative day 1 to day 14.

CONCLUSION

Rosuvastatin, especially when combined with methylprednisolone was found to significantly increase the facial nerve electrophysiological, functional, and histopathological recovery in injury-induced traumatic PFP.

Unraveling the Role of the Blood-Brain Barrier in the Pathophysiology of Depression: Recent Advances and Future Perspectives

Depression is a highly prevalent psychological disorder characterized by persistent dysphoria, psychomotor retardation, insomnia, anhedonia, suicidal ideation, and a remarkable decrease in overall well-being. Despite the prevalence of accessible antidepressant therapies, many individuals do not achieve substantial improvement. Understanding the multifactorial pathophysiology and the heterogeneous nature of the disorder could lead the way toward better outcomes. Recent findings have elucidated the substantial impact of compromised blood-brain barrier (BBB) integrity on the manifestation of depression. BBB functions as an indispensable defense mechanism, tightly overseeing the transport of molecules from the periphery to preserve the integrity of the brain parenchyma. The dysfunction of the BBB has been implicated in a multitude of neurological disorders, and its disruption and consequent brain alterations could potentially serve as important factors in the pathogenesis and progression of depression. In this review, we extensively examine the pathophysiological relevance of the BBB and delve into the specific modifications of its components that underlie the complexities of depression. A particular focus has been placed on examining the effects of peripheral inflammation on the BBB in depression and elucidating the intricate interactions between the gut, BBB, and brain. Furthermore, this review encompasses significant updates on the assessment of BBB integrity and permeability, providing a comprehensive overview of the topic. Finally, we outline the therapeutic relevance and strategies based on BBB in depression, including COVID-19-associated BBB disruption and neuropsychiatric implications. Understanding the comprehensive pathogenic cascade of depression is crucial for shaping the trajectory of future research endeavors.

CircSpna2 attenuates cuproptosis by mediating ubiquitin ligase Keap1 to regulate the Nrf2-Atp7b signalling axis in depression after traumatic brain injury in a mouse model

BACKGROUND

Depression is a common but often overlooked consequence in individuals with post-traumatic brain injury (TBI). Circular RNAs (circRNAs) play essential roles in the nervous system, yet their involvement in the cell death mechanism known as cuproptosis and in TBI-related depression remains unclear.

OBJECTIVES

This study aimed to investigate the role of circRNA, specifically circSpna2, in the regulation of cuproptosis and its association with depression in TBI patients.

METHODS

RNA sequencing (RNA-Seq) was used to assess the differential expression of circRNAs. Depression was evaluated using subjective and objective rating scales, and circSpna2 expression levels in plasma were measured. Further functional experiments were conducted in TBI mouse models, including knockdown and overexpression of circSpna2, to explore its impact on the Keap1-Nrf2-Atp7b pathway and cuproptosis.

RESULTS

TBI patients exhibited decreased levels of circSpna2, which correlated with depression (p < 0.0001). Knocking down circSpna2 in TBI mice aggravated depression-like symptoms (p < 0.0001). Mechanistically, circSpna2 was found to bind ubiquitin ligase Keap1, modulating the Nrf2-Atp7b signaling pathway and influencing cuproptosis (docking score: -331.88). Overexpression of circSpna2 alleviated cuproptosis after TBI through the Keap1/Nrf2/Atp7b axis.

CONCLUSIONS

CircSpna2 plays a regulatory role in cuproptosis and may serve as a novel biomarker and therapeutic target for depression following TBI. Enhancing circSpna2 expression could mitigate depression after TBI by modulating the Keap1/Nrf2/Atp7b pathway.

KEY POINTS

This study explores the role of circSpna2 in depression following traumatic brain injury (TBI). It was found that circSpna2 is significantly downregulated in TBI patients, and its expression levels correlate with depressive symptoms. In TBI mouse models, overexpression of circSpna2 alleviated depression-like behaviours, while its knockdown exacerbated these symptoms, suggesting its potential as both a biomarker and a therapeutic target for post-TBI depression. Mechanistically, circSpna2 regulates the Nrf2-Atp7b signalling pathway by binding to the DGR domain of Keap1, which prevents Nrf2 ubiquitination and enhances Nrf2 activity. This in turn promotes the transcription of Atp7b, a copper transport protein, helping to maintain copper homeostasis and mitigate copper-induced oxidative stress, a key driver of cell death (cuproptosis). The overexpression of circSpna2 also improved mitochondrial function and synaptic integrity, which are typically impaired by copper dysregulation. These findings highlight the therapeutic potential of circSpna2 in managing TBI-related depression through the regulation of oxidative stress and copper homeostasis.

Rosuvastatin attenuates total-tau serum levels and increases expression of miR-124-3p in dyslipidemic Alzheimer's patients: a historic cohort study

microRNAs are candidate diagnostic biomarkers for Alzheimer's disease. This study aimed to compare Silymarin with Rosuvastatin and placebo on total-Tau protein level and expression levels of microRNAs and TGF-β and COX-2 in Alzheimer's patients with secondary dyslipidemia. 36 mild AD patients with dyslipidemia were divided into three groups of 12. The first group received silymarin (140mg), the second group received placebo (140mg), and the third group recieved Rosuvastatin (10mg). Tablets were administered three times a day for Six months. The blood samples of the patients were collected before and after the intervention and the serum was separated. Using the RT-qPCR method, the expression levels of miR-124-3p and miR-125b-5p were assessed, and the serum levels of total-Tau, TGF-β, and COX-2 enzyme were measured using the ELISA method. Data were analyzed with SPSS software. In this study, the level of Δtotal-Tau was significantly lower in the Rosuvastatin group compared to the placebo (P = 0.038). Also, a significant reduction in the level of ΔTGF-β was observed in the Silymarin to Rosuvastatin group (p = 0.046) and ΔmiR-124-3p was significantly increased in the Rosuvastatin compared to the placebo group (p = 0.044). Rosuvastatin outperformed silymarin in decreasing Δtotal-Tau serum levels and enhancing expression of ΔmiR-124-3p, attributed to Rosuvastatin's capacity to lower cholesterol levels and inflammation concurrently. Conversely, silymarin was more effective than Rosuvastatin in reducing levels of ΔTGF-β. Serum miR-124-3p could serve as a promising diagnostic biomarker and a new therapeutic focus in AD.

The protective effects of statins in traumatic brain injury

Traumatic brain injury (TBI), often referred to as the "silent epidemic", is the most common cause of mortality and morbidity worldwide among all trauma-related injuries. It is associated with considerable personal, medical, and economic consequences. Although remarkable advances in therapeutic approaches have been made, current treatments and clinical management for TBI recovery still remain to be improved. One of the factors that may contribute to this gap is that existing therapies target only a single event or pathology. However, brain injury after TBI involves various pathological mechanisms, including inflammation, oxidative stress, blood-brain barrier (BBB) disruption, ionic disturbance, excitotoxicity, mitochondrial dysfunction, neuronal necrosis, and apoptosis. Statins have several beneficial pleiotropic effects (anti-excitotoxicity, anti-inflammatory, anti-oxidant, anti-thrombotic, immunomodulatory activity, endothelial and vasoactive properties) in addition to promoting angiogenesis, neurogenesis, and synaptogenesis in TBI. Supposedly, using agents such as statins that target numerous and diverse pathological mechanisms, may be more effective than a single-target approach in TBI management. The current review was undertaken to investigate and summarize the protective mechanisms of statins against TBI. The limitations of conducted studies and directions for future research on this potential therapeutic application of statins are also discussed.

Single Nucleotide Polymorphism in Cell Adhesion Molecule L1 Affects Learning and Memory in a Mouse Model of Traumatic Brain Injury

The L1 cell adhesion molecule (L1) has demonstrated a range of beneficial effects in animal models of spinal cord injury, neurodegenerative disease, and ischemia; however, the role of L1 in TBI has not been fully examined. Mutations in the L1 gene affecting the extracellular domain of this type 1 transmembrane glycoprotein have been identified in patients with L1 syndrome. These patients suffer from hydrocephalus, MASA (mental retardation, adducted thumbs, shuffling gait, aphasia) symptoms, and corpus callosum agenesis. Clinicians have observed that recovery post-traumatic brain injury (TBI) varies among the population. This variability may be explained by the genetic differences present in the general population. In this study, we utilized a novel mouse model of L1 syndrome with a mutation at aspartic acid position 201 in the extracellular domain of L1 (L1-201). We assessed the impact of this specific single nucleotide polymorphism (SNP) localized to the X-chromosome L1 gene on recovery outcomes following TBI by comparing the L1-201 mouse mutants with their wild-type littermates. We demonstrate that male L1-201 mice exhibit significantly worse learning and memory outcomes in the Morris water maze after lateral fluid percussion (LFP) injury compared to male wild-type mice and a trend to worse motor function on the rotarod. However, no significant changes were observed in markers for inflammatory responses or apoptosis after TBI.

Micromotion Derived Fluid Shear Stress Mediates Peri-Electrode Gliosis through Mechanosensitive Ion Channels

The development of bioelectronic neural implant technologies has advanced significantly over the past 5 years, particularly in brain-machine interfaces and electronic medicine. However, neuroelectrode-based therapies require invasive neurosurgery and can subject neural tissues to micromotion-induced mechanical shear, leading to chronic inflammation, the formation of a peri-electrode void and the deposition of reactive glial scar tissue. These structures act as physical barriers, hindering electrical signal propagation and reducing neural implant functionality. Although well documented, the mechanisms behind the initiation and progression of these processes are poorly understood. Herein, in silico analysis of micromotion-induced peri-electrode void progression and gliosis is described. Subsequently, ventral mesencephalic cells exposed to milliscale fluid shear stress in vitro exhibited increased expression of gliosis-associated proteins and overexpression of mechanosensitive ion channels PIEZO1 (piezo-type mechanosensitive ion channel component 1) and TRPA1 (transient receptor potential ankyrin 1), effects further confirmed in vivo in a rat model of peri-electrode gliosis. Furthermore, in vitro analysis indicates that chemical inhibition/activation of PIEZO1 affects fluid shear stress mediated astrocyte reactivity in a mitochondrial-dependent manner. Together, the results suggest that mechanosensitive ion channels play a major role in the development of a peri-electrode void and micromotion-induced glial scarring at the peri-electrode region.

The pharmacological bases for repurposing statins in depression: a review of mechanistic studies

Statins are commonly prescribed medications widely investigated for their potential actions on the brain and mental health. Pre-clinical and clinical evidence suggests that statins may play a role in the treatment of depressive disorders, but only the latter has been systematically assessed. Thus, the physiopathological mechanisms underlying statins' putative antidepressant or depressogenic effects have not been established. This review aims to gather available evidence from mechanistic studies to strengthen the pharmacological basis for repurposing statins in depression. We used a broad, well-validated search strategy over three major databases (Pubmed/MEDLINE, Embase, PsychINFO) to retrieve any mechanistic study investigating statins' effects on depression. The systematic search yielded 8068 records, which were narrowed down to 77 relevant papers. The selected studies (some dealing with more than one bodily system) described several neuropsychopharmacological (44 studies), endocrine-metabolic (17 studies), cardiovascular (6 studies) and immunological (15 studies) mechanisms potentially contributing to the effects of statins on mood. Numerous articles highlighted the beneficial effect of statins on depression, particularly through positive actions on serotonergic neurotransmission, neurogenesis and neuroplasticity, hypothalamic-pituitary axis regulation and modulation of inflammation. The role of other mechanisms, especially the association between statins, lipid metabolism and worsening of depressive symptoms, appears more controversial. Overall, most mechanistic evidence supports an antidepressant activity for statins, likely mediated by a variety of intertwined processes involving several bodily systems. Further research in this area can benefit from measuring relevant biomarkers to inform the selection of patients most likely to respond to statins' antidepressant effects while also improving our understanding of the physiopathological basis of depression.

An online experimental medicine trial on the effect of 28-day simvastatin administration on emotional processing, reward learning, working memory and salivary cortisol in healthy volunteers at risk for depression: OxSTEP protocol

BACKGROUND

Evidence suggests inflammation may be a key mechanism by which psychosocial stress, including loneliness, predisposes to depression. Observational and clinical studies have suggested simvastatin, with its anti-inflammatory properties, may have a potential use in the treatment of depression. Previous experimental medicine trials investigating 7-day use of statins showed conflicting results, with simvastatin displaying a more positive effect on emotional processing compared with atorvastatin. It is possible that statins require longer administration in predisposed individuals before showing the expected positive effects on emotional processing.

AIMS

Here, we aim to test the neuropsychological effects of 28-day simvastatin administration versus placebo, in healthy volunteers at risk for depression owing to loneliness.

METHOD

This is a remote experimental medicine study. One hundred participants across the UK will be recruited and randomised to either 28-day 20 mg simvastatin or placebo in a double-blind fashion. Before and after administration, participants will complete an online testing session involving tasks of emotional processing and reward learning, processes related to vulnerability to depression. Working memory will also be assessed and waking salivary cortisol samples will be collected. The primary outcome will be accuracy in identifying emotions in a facial expression recognition task, comparing the two groups across time.

Statins block mammalian target of rapamycin pathway: a possible novel therapeutic strategy for inflammatory, malignant and neurodegenerative diseases

Inflammation plays a critical role in several diseases such as cancer, gastric, heart and nervous system diseases. Data suggest that the activation of mammalian target of rapamycin (mTOR) pathway in epithelial cells leads to inflammation. Statins, the inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA), seem to be able to inhibit the mTOR. Statins are considered to have favorable effects on inflammatory diseases by reducing the complications caused by inflammation and by regulating the inflammatory process and cytokines secretion. This critical review collected data on this topic from clinical, in vivo and in vitro studies published between 1998 and June 2022 in English from databases including PubMed, Google Scholar, Scopus, and Cochrane libraries.

Neurobiological Mechanisms Of Depression Following Traumatic Brain Injury

OBJECTIVE

Depression is among the most pervasive and debilitating neuropsychiatric sequelae experienced by patients following a traumatic brain injury (TBI). While the individual mechanisms underlying depression and TBI have been widely studied, the neurobiological bases of depression after TBI remain largely unknown. This article highlights the potential mechanisms of action implicated in depression after TBI.

RESULTS

We review putative mechanisms of action including neuroinflammation, neuroendocrine dysregulation, metabolic abnormalities, and neurotransmitter and circuitry dysfunction. We also identify the current limitations in the field and propose directions for future research.

CONCLUSION

An improved understanding of the underlying mechanisms will aid the development of precision-guided and personalized treatments for patients suffering from depression after TBI.

Statins in depression: a repurposed medical treatment can provide novel insights in mental health

Depression has a large burden, but the development of new drugs for its treatment has proved difficult. Progresses in neuroscience have highlighted several physiopathological pathways, notably inflammatory and metabolic ones, likely involved in the genesis of depressive symptoms. A novel strategy proposes to repurpose established medical treatments of known safety and to investigate their potential antidepressant activity. Among numerous candidates, growing evidence suggests that statins may have a positive role in the treatment of depressive disorders, although some have raised concerns about possible depressogenic effects of these widely prescribed medications. This narrative review summarises relevant findings from translational studies implicating many interconnected neurobiological and neuropsychological, cardiovascular, endocrine-metabolic, and immunological mechanisms by which statins could influence mood. Also, the most recent clinical investigations on the effects of statins in depression are presented. Overall, the use of statins for the treatment of depressive symptoms cannot be recommended based on the available literature, though this might change as several larger, methodologically robust studies are being conducted. Nevertheless, statins can already be acknowledged as a driver of innovation in mental health, as they provide a novel perspective to the physical health of people with depression and for the development of more precise antidepressant treatments.

The Neurobiological Links between Stress and Traumatic Brain Injury: A Review of Research to Date

Neurological dysfunctions commonly occur after mild or moderate traumatic brain injury (TBI). Although most TBI patients recover from such a dysfunction in a short period of time, some present with persistent neurological deficits. Stress is a potential factor that is involved in recovery from neurological dysfunction after TBI. However, there has been limited research on the effects and mechanisms of stress on neurological dysfunctions due to TBI. In this review, we first investigate the effects of TBI and stress on neurological dysfunctions and different brain regions, such as the prefrontal cortex, hippocampus, amygdala, and hypothalamus. We then explore the neurobiological links and mechanisms between stress and TBI. Finally, we summarize the findings related to stress biomarkers and probe the possible diagnostic and therapeutic significance of stress combined with mild or moderate TBI.

Effects of RhoA on depression-like behavior in prenatally stressed offspring rats

Depression is a common mental disease that can lead to suicide when severe. Exposure to prenatal stress (PS) can lead to depression-like behavior in offspring, but the mechanism is unclear. RhoA (Ras homology family member A) plays an important role in stress-induced changes in synaptic plasticity, participating in the development of depression by activating the downstream effector ROCK (Rho-associated protein kinase). This study explored the influence in the expression of RhoA and downstream molecules ROCK1/2 in prenatally stressed rats, and the effect of RhoA inhibitor simvastatin on depression-like behavior induced by PS. Depression-like behavior in offspring was detected by sucrose preference test, forced swimming test, and open-field test. The mRNA and protein expression of RhoA and ROCK1/2 in the hippocampus and prefrontal cortex of offspring rats were detected by qRT-PCR and western blotting, respectively. Our results showed that PS causes depression-like behavior in offspring rats, associated with elevated expression of RhoA, ROCK1/2 in the hippocampus and prefrontal cortex. After administration of simvastatin to PS rats, the expression of RhoA and ROCK2 was significantly reduced, alleviating depression-like behavior. Our study demonstrated that RhoA participates in the depression-like behavior in prenatally stressed offspring rats, which may be a potential target for antidepressant therapy.

New diagnosis of cancer in mild and moderate/severe traumatic brain injury patients in a 12-year population-based study

Background

Traumatic brain injury (TBI) has been reported as a risk factor for brain cancer development. However, the magnitude of the impact of TBI on systemic cancer development has not been clarified.

Methods

A retrospective longitudinal cohort study was conducted using the Taiwan Longitudinal Health Insurance Database between January 2000 and December 2011. A total of 35,306 patients were initially enrolled, and 14,795 patients with mild TBI and 14,795 patients with moderate/severe TBI were matched using the National Health Insurance Research Database in Taiwan. The Cox proportional hazard regression model was used to estimate the hazard ratio (HR) of TBI adjusted for potential confounding factors.

Results

After matching, the results showed that patients with moderate/severe TBI had a high mortality rate (17.7% vs. 10.4%) and shorter time interval from TBI to death (mean 3.6 years vs. 5.8 years). No differences were observed in cancer incidence (4.1% vs. 4.1%) or risk factors for mortality between mild and moderate/severe TBI patients. However, patients aged between 46 and 55 years, female patients, and patients with pre-existing renal disease had a significant higher cancer incidence risk in moderate/severe TBI compared with mild TBI patients. The top 15 most common cancers showed that mild TBI patients had a higher percentage of head and neck cancer. The overall mortality rate in all TBI patients diagnosed with cancer was about 50%, and the cancer-specific mortality is approximately 85% in death of TBI patients with cancer.

Conclusions

We concluded that the incidence risk of a new cancer diagnosis and mortality risk of TBI patients with cancer between the mild TBI and moderate/severe TBI patients were not significantly different.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09416-4.

Chronic Anxiety- and Depression-Like Behaviors Are Associated With Glial-Driven Pathology Following Repeated Blast Induced Neurotrauma

Long-term neuropsychiatric impairments have become a growing concern following blast-related traumatic brain injury (bTBI) in active military personnel and Veterans. Neuropsychiatric impairments such as anxiety and depression are common comorbidities that Veterans report months, even years following injury. To understand these chronic behavioral outcomes following blast injury, there is a need to study the link between anxiety, depression, and neuropathology. The hippocampus and motor cortex (MC) have been regions of interest when studying cognitive deficits following blast exposure, but clinical studies of mood disorders such as major depressive disorder (MDD) report that these two regions also play a role in the manifestation of anxiety and depression. With anxiety and depression being common long-term outcomes following bTBI, it is imperative to study how chronic pathological changes within the hippocampus and/or MC due to blast contribute to the development of these psychiatric impairments. In this study, we exposed male rats to a repeated blast overpressure (~17 psi) and evaluated the chronic behavioral and pathological effects on the hippocampus and MC. Results demonstrated that the repeated blast exposure led to depression-like behaviors 36 weeks following injury, and anxiety-like behaviors 2-, and 52-weeks following injury. These behaviors were also correlated with astrocyte pathology (glial-fibrillary acid protein, GFAP) and dendritic alterations (Microtubule-Associated Proteins, MAP2) within the hippocampus and MC regions at 52 weeks. Overall, these findings support the premise that chronic glial pathological changes within the brain contribute to neuropsychiatric impairments following blast exposure.

Statins in Depression: An Evidence-Based Overview of Mechanisms and Clinical Studies

Background: Depression is a leading cause of disability, burdened by high levels of non-response to conventional antidepressants. Novel therapeutic strategies targeting non-monoaminergic pathways are sorely needed. The widely available and safe statins have several putative mechanisms of action, especially anti-inflammatory, which make them ideal candidates for repurposing in the treatment of depression. A large number of articles has been published on this topic. The aim of this study is to assess this literature according to evidence-based medicine principles to inform clinical practise and research. Methods: We performed a systematic review of the electronic databases MEDLINE, CENTRAL, Web of Science, CINAHL, and ClinicalTrials.gov, and an unstructured Google Scholar and manual search, until the 9th of April 2021, for all types of clinical studies assessing the effects of statins in depression. Results: Seventy-two studies were retrieved that investigated the effects of statins on the risk of developing depression or on depressive symptoms in both depressed and non-depressed populations. Fifteen studies specifically addressed the effects of statins on inflammatory-related symptoms of anhedonia, psychomotor retardation, anxiety, and sleep disturbances in depression. Most studies suggested a positive effect of statins on the occurrence and severity of depression, with fewer studies showing no effect, while a minority indicated some negative effects. Limitations: We provide a narrative report on all the included studies but did not perform any quantitative analysis, which limits the strength of our conclusions. Conclusions: Robust evidence indicates that statins are unlikely to lead to depressive symptoms in the general population. Promising data suggest a potential role for statins in the treatment of depression. Further clinical studies are needed, especially in specific subgroups of patients identified by pre-treatment assessments of inflammatory and lipid profiles.

Modulation of the Nitric Oxide/BH4 Pathway Protects Against Irradiation-Induced Neuronal Damage

The kynurenine pathway (KP, IDO/Kyn pathway) is an important metabolic pathway related to many diseases. Although cranial radiotherapy is the mainstay in metastatic tumors management, its efficacy is limited owing to the associated neuropsychiatric disorders. Sildenafil (SD) and simvastatin (SV) were reported to have antioxidant/anti-inflammatory effects and to serve as NO donor/BH4 regulator, respectively. Fluoxetine (Fx) is an FDA-approved anti-depressant agent and one of the selective serotonin reuptake inhibitor drugs (SSRI), used in neurological disorder treatment. The study objective was to investigate the role of cranial irradiation (C-IR) on KP signaling impairment and the possible intervention by SD and/or SV (as nitric oxide (NO) donor/Tetrahydrobiopterin (BH4) regulatory) on KP following C-IR-induced disruption compared with Fx (as standard drug).Herein, rats were exposed to C-IR at a single dose level of 25 Gy, then treated with sildenafil (SD) and/or simvastatin (SV), and fluoxetine (Fx) at doses of 75, 20, 10 mg/kg/day, respectively. The body weight gain and forced swimming test (FST) were used for evaluation along with the biochemical quantifications of KP intermediates and histopathological examination of cortex and hippocampus. The results indicated a significant activation of KP following C-IR as manifested by decreased Trp content and increased activities of indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) with a rise in kynurenine (KYN) and quinolinic acid (QA) hippocampal contents. In addition, a state of C-IR-induced oxidative stress, inflammation, NO-pathway dysregulation and neuronal apoptosis were observed as compared to the control group. However, significant modulations were recorded after the combined administration of SD and SV than those offered by each of them alone and by Fx. The biochemical assessment results were supported by the histopathological tissue examination. It could be concluded that the co-administration of SV and SD offers a neuroprotective effect against irradiation-induced brain injury due to its NO donor/BH4 regulatory activities, anti-inflammatory and antioxidant properties that modulate IDO/KYN pathway.

The Effect of Oral Simvastatin on the Clinical Outcome of Patients with Severe Traumatic Brain Injury: A Randomized Clinical Trial

Background

Despite recent promising pharmacological and technological advances in neurosurgical intensive care, the overall TBI-related mortality and morbidity remain high and still pose a major clinical problem. The aim of this study was to evaluate the effect of oral simvastatin on the clinical outcome of patients with severe TBI.

Methods

In a double-blind placebo-controlled randomized clinical trial a total of 98 patients with severe TBI in Imam Khomeini Hospital in Sari, Iran, were evaluated. Patients who meet the inclusion criteria were randomly allocated into two groups (n=49). In addition to supportive therapies, the intervention group received oral simvastatin (40 mg, daily) for 10 days, and the control group received the placebo (10 days). Patients' Glasgow coma scale (GCS) score, in hospital mortality, duration of mechanical ventilation and length of ICU and neurosurgery ward stay were evaluated during three-time intervals (T1: admission, T2: discharge and T3: one month after discharge).

Results

The percentage of conscious patients was 18.9% (7 cases) in the simvastatin group and 3.1% (1 case) in controls (P=0.06) at T2. One month after discharge (T3) the proportion of conscious patients significantly increased in the simvastatin group compared to control group (64.9 % versus 28.1 %; P=0.002). There was no significant difference for the mean of GCS score between the simvastatin group and control group at T1 (6.41 ± 1.30 versus 6.41 ± 1.28, respectively; P = 0.98). However, the mean score of GCS in patients who received simvastatin was significantly greater than controls at T2 and T3 (p<0.05). There was no significant differences between two group in-terms of length of mechanical ventilation, ICU and neurosurgery ward stay.

Conclusion

According to the results of this study it seems that using simvastatin may be an effective and promising therapeutic modality for improving GCS score during TBI recovery.

Comparative Efficacy and Acceptability of Anti-inflammatory Agents on Major Depressive Disorder: A Network Meta-Analysis

Background: With the growing importance of research about the association between neuroinflammation and major depressive disorder (MDD), anti-inflammatory agents have been used as a new antidepressant therapy in clinical practice. We conducted a network meta-analysis (NMA) with up-to-date evidence to compare different anti-inflammatory agents for improving the treatment of MDD patients.

Methods: To identify eligible randomized clinical trials, four databases (i.e, the Cochrane Library, Web of Science, PubMed and Embase) were searched from inception date to May 31, 2020. Anti-inflammatory agents were defined as non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, cytokine inhibitors, statins, pioglitazone, minocycline, N-acetylcysteine (NAC) and omega-3 fatty acid (Omega-3 FA). The main outcomes of this NMA were efficacy, acceptability and remission rate. Risk ratio (RR) was adopted for dichotomous outcomes, and the confidence interval (CI) was set at 95%. STATA 14.0 and R 3.6.3 were used to conduct the NMA. The study protocol was registered with PROSPERO (CRD42020182531).

Results: A total of 39 studies, involving 2871 participants, were included in quantitative data synthesis. For efficacy, NSAIDs (RR=0.50, 95%CI: 0.26-0.73) and pioglitazone (RR=0.45, 95%CI: 0.20-0.84) were more favorable than placebo. With respect to acceptability, NSAIDs were more acceptable than placebo (RR=0.89, 95%CI: 0.77-0.99) and minocycline (RR=1.22, 95%CI: 1.03-1.49). For remission, NSAIDs were more superior than placebo (RR=0.48, 95%CI: 0.27-0.79) and Omega-3 FA (RR=2.01, 95%CI: 1.09-3.90), while NACs were more favorable than placebo (RR=0.39, 95%CI: 0.13-0.99). Based on the surface under the cumulative ranking curve (SUCRA) value, corticosteroids (0.86) were the best anti-inflammatory agent for MDD patients in terms of efficacy, but the head-to-head comparisons for the efficacy of glucocorticoids and other agents were not statistically significant. As for acceptability, NSAIDs (0.81) were much better than other anti-inflammatory agents. Besides, NAC (0.80) was the best anti-inflammatory agent in the terms of remission.

Conclusions: In summary, we found that corticosteroids were more superior than other agents in terms of efficacy according to the SUCRA value. However, this result must be interpreted with caution because the head-to-head comparisons for the efficacy of glucocorticoids and other agents did not reach statistical significance. NSAIDs were recommended for acceptability and NAC for remission rate.

Simvastatin mitigates depressive-like behavior in ovariectomized rats: Possible role of NLRP3 inflammasome and estrogen receptors' modulation

It is well known that females are more vulnerable than males to stress-related psychiatric disorders, particularly during perimenopausal and postmenopausal periods. Hormone replacement therapy (HRT) has been widely used for the management of postmenopausal depression. However, HRT could be associated with severe adverse effects, including increased risk for coronary heart disease, breast cancer and endometrial cancer. Thus, there is a pressing demand for novel therapeutic options for postmenopausal depression without sacrificing uterine health. Simvastatin (SIM) was proven to have neuroprotective activities besides its hypocholesterolemic effect, the former can be attributed to its, antioxidant, anti-apoptotic and anti-inflammatory activities. Moreover, many reports highlighted that SIM has estrogenic activity and was able to induce the expression of estrogen receptors in rats. The present study showed that SIM (20 mg/kg, p.o.) markedly attenuated depressive-like behavior in ovariectomized (OVX) rats. Moreover, SIM prohibited hippocampal microglial activation, abrogated P2X7 receptor, TLR2 and TLR4 expression, inhibited NLRP3 inflammasome activation, with subsequent reduction in the levels of pro-inflammatory mediators; IL-1β and IL-18. Furthermore, a marked elevation in hippocampal expression of ERα and ERβ was noted in SIM-treated animals, without any significant effect on uterine relative weight or ERα expression. Taken together, SIM could provide a safer alternative for HRT for the management of postmenopausal depression, without any hyperplastic effect on the uterus.

Statins for major depressive disorder: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

The burden of depressive disorder is large and new treatment approaches are required. Repurposing widely available drugs such as statins may be a time- and cost-effective solution. Statins have anti-inflammatory and anti-oxidant properties which have been shown to be relevant to the pathophysiology of depression. This study assesses the efficacy, acceptability, tolerability, and safety of statins in major depressive disorder.

METHODS

Our study is an update and extension of a previous meta-analysis published in 2016 by Salagre et al. We performed a systematic review (PubMed/MEDLINE, Cochrane CENTRAL, ISI Web of Science, CINAHL, and ClinicalTrials.gov until the 1st September 2020) and meta-analysis of randomized controlled trials using any statin against placebo or any other statin in the treatment of major depressive disorder. Our primary efficacy outcome measure was the mean value on any standardized scale for depressive symptoms at 8 weeks of treatment. We also calculated outcomes for efficacy, response, and remission at 2, 4, and 12 weeks, as well as acceptability (dropouts for any cause), tolerability (dropouts due to any adverse event), and safety (any adverse event) outcomes at the studies' endpoints. Furthermore, we conducted an exploratory network meta-analysis for the primary efficacy outcome to identify potential differences between statins.

RESULTS

We retrieved five randomized controlled trials meeting our inclusion criteria: four used a statin in addition to an antidepressant and compared it to placebo plus antidepressant, and one compared two statins alone. and one comparing one statin with another. Statins compared to placebo in addition to antidepressants were efficacious at 8 weeks (N = 255, SMD = -0.48, 95% CI = -0.74 to -0. 22) and 12 weeks (N = 134, SMD = -0.47, 95% CI = -0.89 to -0.05, moderate certainty) with no difference for acceptability, tolerability, and safety (low certainty). An exploratory network meta-analysis suggested that the most lipophilic statins, especially simvastatin, could be more efficacious than less lipophilic or hydrophilic molecules.

CONCLUSIONS

This systematic review suggests the efficacy, acceptability, tolerability, and safety of statins in addition to antidepressants in patients with major depressive disorder. Further clinical trials in different settings are required to test this result.

TRIAL RGISTRATION

PROSPERO registration: CRD42020170938.

Aerobic Exercise Prevents Depression via Alleviating Hippocampus Injury in Chronic Stressed Depression Rats

(1) Background: Depression is one of the overwhelming public health problems. Alleviating hippocampus injury may prevent depression development. Herein, we established the chronic unpredictable mild stress (CUMS) model and aimed to investigate whether aerobic exercise (AE) could alleviate CUMS induced depression-like behaviors and hippocampus injury. (2) Methods: Forty-eight healthy male Sprague-Dawley rats (200 ± 20 g) were randomly divided into 4 groups (control, CUMS, CUMS + 7 days AE, CUMS + 14 days AE). Rats with AE treatments were subjected to 45 min treadmill per day. (3) Results: AE intervention significantly improved CUMS-induced depressive behaviors, e.g., running square numbers and immobility time assessed by the open field and forced swimming test, suppressed hippocampal neuron apoptosis, reduced levels of phosphorylation of NMDA receptor and homocysteine in hippocampus, as well as serum glucocorticoids, compared to the CUMS rats. In contrast, AE upregulated phosphorylation of AMPAR receptor and brain-derived neurotrophic factor (BDNF) hippocampus in CUMS depression rats. The 14 day-AE treatment exhibited better performance than 7 day-AE on the improvement of the hippocampal function. (4) Conclusion: AE might be an efficient strategy for prevention of CUMS-induced depression via ameliorating hippocampus functions. Underlying mechanisms may be related with glutamatergic system, the neurotoxic effects of homocysteine, and/or influences in glucocorticoids-BDNF expression interaction.

Simvastatin Improves Behavioral Disorders and Hippocampal Inflammatory Reaction by NMDA-Mediated Anti-inflammatory Function in MPTP-Treated Mice

The cognitive function impairment may be related to the inflammation of the hippocampus in Parkinson's disease. Simvastatin can play a positive role in Parkinson's disease. The purpose of this study was to investigate whether simvastatin could improve behavioral disorders, especially depression, anxiety and cognitive function in mouse PD models, and further explore the molecular mechanism. In the present study, C57BL-6 mice underwent intraperitoneal injection of MPTP (30 mg/kg) once a day for 5 consecutive days. At the same time, simvastatin (10 mg/kg) was pretreated for 2 days before the Parkinson's disease model was established, and then continued for 5 days, and the control group underwent intraperitoneal injection of MK801 (dizocilpine, 0.2 mg/kg) and saline solution. Depression status was tested by a tail suspension test and a sucrose splash test, followed by an open-field test and an elevated plus maze test to determine anxiety levels. Spatial behavior and muscle status were measured with a water maze and a rotarod test. The expression of RNA and protein of N-methyl-D-aspartate receptor subtype 2B (NMDAR2B), nerve growth factor IB (Nur77), cyclooxygenase-2 (COX-2), and tumor necrosis factor (TNF) α were assayed by real-time polymerase chain reaction and Western blot. Our results showed that simvastatin can improve the cognitive function, anxiety, and depression of PD mice with MPTP injury. Simvastatin reversed the NMDAR2B increase, restored Nur77 downward, and reduced the expression of COX-2 and TNF-α in MPTP-treated mice. This role of simvastatin was consistent with MK801 in increasing the expression of Nur77 and inhibiting NMDAR2B and cytokines in MPTP-lesioned PD mice. These findings suggest that reversed the NMDAR2B increase, restored Nur77 downward, and reduced the expression of COX-2 and TNF-α in MPTP-treated mice may be one of the mechanisms that simvastatin improves cognitive functions, depression, and anxiety in MPTP-lesioned mice.

Pathomechanisms of Non-Traumatic Acute Brain Injury in Critically Ill Patients

Delirium, an acute alteration in mental status characterized by confusion, inattention and a fluctuating level of arousal, is a common problem in critically ill patients. Delirium prolongs hospital stay and is associated with higher mortality. The pathophysiology of delirium has not been fully elucidated. Neuroinflammation and neurotransmitter imbalance seem to be the most important factors for delirium development. In this review, we present the most important pathomechanisms of delirium in critically ill patients, such as neuroinflammation, neurotransmitter imbalance, hypoxia and hyperoxia, tryptophan pathway disorders, and gut microbiota imbalance. A thorough understanding of delirium pathomechanisms is essential for effective prevention and treatment of this underestimated pathology in critically ill patients.

Rosuvastatin enhanced functional recovery after sciatic nerve injury in the rat

Posttraumatic nerve recovery remains a challenge in regenerative medicine. As such, there is a need for agents that limit nerve damage and enhance nerve regeneration. Here we investigate rosuvastatin, a 3-hydroxy-3-methylglutaryl coenzyme (HMG-CoA) reductase inhibitor, with anti-inflammatory and antioxidant properties. We explore its neuroprotective properties on sciatic nerve crush injury in male Wistar Rats. Rats were subjected to crush injury to the left sciatic nerve using a vessel clamp for 30 s. Rosuvastatin or vehicle was prepared daily and administrated by oral gavage for seven days post-injury. In rosuvastatin treatment groups, rosuvastatin was administrated at the doses of (5 or 10 mg/kg) in the treatment group. The control group was given a vehicle in the same manner. Behavioral, electrophysiological, morphological and molecular parameters were examined during the recovery process. Chronic administration of rosuvastatin at all doses after sciatic nerve crush markedly promoted nerve regeneration and significantly accelerated motor function recovery (P < 0.05). Electrophysiological, morphological and molecular parameters also improved in the rosuvastatin treatment groups compared to the controls. These findings suggest that neuroprotective effects of rosuvastatin could be due to its antioxidant and anti-inflammatory activity. It is clear that more research is needed to confirm these findings.

The effects of statins on microglial cells to protect against neurodegenerative disorders: A mechanistic review

Microglia are the primary innate immune system cells in the central nervous system (CNS). They are crucial for the immunity, neurogenesis, synaptogenesis, neurotrophic support, phagocytosis of cellular debris, and maintaining the CNS integrity and homeostasis. Invasion by pathogens as well as in CNS injuries and damages results in activation of microglia known as microgliosis. The activated microglia have the capacity to release proinflammatory mediators leading to neuroinflammation. However, uncontrolled neuroinflammation can give rise to various neurological disorders (NDs), especially the neurodegenerative diseases including Parkinson's disease (PD) and related disorders, Alzheimer's disease (AD) and other dementias, multiple sclerosis (MS), Huntington's disease (HD), spinocerebellar ataxia (SCA), spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), and stroke. Statins (HMG-CoA reductase inhibitors) are among the most widely prescribed medications for the management of hypercholesterolemia worldwide. It can be used for primary prevention in healthy individuals who are at higher risk of cardiovascular and coronary heart diseases as well as the secondary prevention in patients with cardiovascular and coronary heart diseases disease. A growing body of evidence has indicated that statins have the potential to attenuate the proinflammatory mediators and subsequent NDs by controlling the microglial activation and consequent reduction in neuroinflammatory mediators. In this review, we have discussed the recent studies on the effects of statins on microglia activation and neuroinflammation.

The Short-Term Effects of Isolated Traumatic Brain Injury on the Heart in Experimental Healthy Rats

BACKGROUND

To date, cardiac dysfunction after traumatic brain injury (TBI) has not been consistent. In this study, we hypothesized that TBI may play a role in the development of new-onset cardiac dysfunction in healthy experimental rats.

MATERIALS AND METHODS

Anesthetized healthy male Sprague-Dawley rats were divided into two groups: a sham-operated control group and a TBI group. The brain was injured with 2.4 atm percussion via a fluid percussion injury model. During the 120 min after TBI, we continuously measured brain parameters, including intracranial pressure (ICP) and cerebral perfusion pressure (CPP), and cardiac parameters, such as heart rate (HR), inter-ventricular septum dimension (IVSD), left ventricular internal dimension diastole (LVIDd), end-diastolic volume (EDV), ejection fraction (EF), fractional shortening (FS), and LV mass diastole (LVd mass) by cardiac echo. On days 1, 3, 7, and 14 after TBI, the brain damage volume was evaluated with triphenyltetrazolium chloride; the physiological parameters of the heart, including HR, IVSd, LVIDd, EDV, EF, FS, and LVd mass, were evaluated with cardiac echo; the morphology of cardiomyocytes was examined by hematoxylin and eosin (HE) and Masson trichrome staining; and the biomarkers of cardiac injury troponin I and B-type natriuretic peptide (BNP) were also examined.

RESULTS

Compared to sham-operated controls, the TBI groups had higher ICP, lower CPP, and higher brain neuronal apoptosis and infarction contusion volume. The impact of TBI on heart function showed hyperdynamic response trends in IVSd, LVIDd, EDV, EF, FS, and LVd mass within 30 min after TBI; however, EF and FS exhibited eventual decreasing trends. Simultaneously, the values of the biomarkers troponin I and BNP were within normal limits, and HE and Mass trichrome staining revealed no significant differences between the sham-operated control group and the TBI group.

CONCLUSIONS

Our results suggest that TBI due to 2.4 atm fluid percussion injury in healthy experimental rats may cause significant damage to the brain and affect the heart function as investigated by cardiac echo but not as investigated by HE and Masson trichrome stainings or troponin I and BNP evaluation.

The Neuroprotective Effects of Simvastatin on High Cholesterol Following Traumatic Brain Injury in Rats

BACKGROUND

High cholesterol has been correlated with a greater risk of cerebrovascular diseases. Whether pre-existing high cholesterol exacerbates traumatic brain injury (TBI), and whether treatment with the cholesterol-lowering agent simvastatin has neuroprotective effects, especially anti-neuroinflammatory effects, after TBI are not well investigated.

METHODS

Five-week-old male Sprague-Dawley rats were fed a high-fat diet for 8 weeks to induce hypercholesterolemia. Anesthetized male Sprague-Dawley rats were divided into 5 groups, including the sham-operated control, TBI control, and TBI with simvastatin treatment (4 mg/kg, 10 mg/kg, or 20 mg/kg) groups. Simvastatin was intraperitoneally injected at 0, 24, and 48 hours after TBI. Motor function was measured using an inclined plane. Neuronal apoptosis (maker Neu-N, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling), tumor necrosis factor-α expression in microglia (marker OX42) and astrocytes (marker glial fibrillary acidic protein), and Tumor necrosis factor-alpha receptor (TNFR) 1 and TNFR2 expression in neurons in the ischemic cortex were investigated using an immunofluorescence assay. All of the parameters were measured on the third day after TBI.

RESULTS

TBI significantly increased the serum levels of cholesterol. The TBI-induced motor deficit was significantly attenuated by 4, 10, and 20 mg/kg simvastatin therapy on the third day after TBI. TBI-induced neuronal TNFR1 activation and apoptosis, as well as tumor necrosis factor-α expression in astrocytes in the ischemic cortex, were significantly attenuated by simvastatin, particularly when 20 mg/kg was administered. Simultaneously, the serum cholesterol remained high despite simvastatin treatment.

CONCLUSIONS

The neuroprotection effects of simvastatin on the pre-existing hypercholesterolemia during TBI in rats may be related to its anti-neuroinflammatory effects but not to its cholesterol-lowing effects.

Innate Immune Signaling and Alcohol Use Disorders

Innate immune signaling is an important feature in the pathology of alcohol use disorders. Alcohol abuse causes persistent innate immune activation in the brain. This is seen in postmortem human alcoholic brain specimens, as well as in primate and rodent models of alcohol consumption. Further, in vitro models of alcohol exposure in neurons and glia also demonstrate innate immune activation. The activation of the innate immune system seems to be important in the development of alcohol use pathology, as anti-immune therapies reduce pathology and ethanol self-administration in rodent models. Further, innate immune activation has been identified in each of the stages of addiction: binge/intoxication, withdrawal/negative affect, and preoccupation/craving. This suggests that innate immune activation may play a role both in the development and maintenance of alcoholic pathology. In this chapter, we discuss the known contributions of innate immune signaling in the pathology of alcohol use disorders, and present potential therapeutic interventions that may be beneficial for alcohol use disorders.

Selective inhibition of intestinal 5-HT improves neurobehavioral abnormalities caused by high-fat diet mice

Recent literature reported the adverse effects of high-fat diet (HFD) on animal's emotional and cognitive function. An HFD-induced obesity/hyperlipidemia is accompanied by hormonal and neurochemical changes that can lead to depression. The important roles of gut-derived serotonin (5-Hydroxytryptamine, 5-HT) during this processing have been increasingly focused. Hence, to determine the potential role of gut-derived serotonin, HFD model was established in C57BL/6 mice. At the 4th week of feeding, a pharmacologic inhibitor of gut-derived 5-HT synthesis LP533401 (12.5 mg/kg/day), simvastatin (SIM) (5 mg/kg/day) and benzafibrate (BZ) (75 mg/kg/day) were administered for two weeks by oral gavage. Then, intraperitoneal glucose tolerance test (IPGTT), open field test (OFT), tail suspension test (TST), forced swim test (FST), sucrose preference test (SPT) were used to evaluate metabolic and neurobehavioral performances. Immunohistochemical staining, real-time quantitative PCR and other methods were to explore possible mechanisms. It was found that HFD feeding and drug treatments had some significant effects on neurobehaviors and brain: (1) All administrations reduced the total cholesterol (TC) and triglyceride (TG) parametric abnormality caused by HFD. LP533401 and SIM could significantly improve the impaired glucose tolerance, while BZ had no significant effect. (2) LP533401, SIM and BZ alleviated depression-like behavior of HFD mice in OFT, TST, FST and SPT. (3) LP533401 and SIM reversed the inhibition of Tryptophan Hydroxylase 2, Tph2 gene expression and the activation of Indoleamine 2,3-dioxy-Genase, IDO expression in HFD-treated brain, whereas BZ did not. (4) LP533401, SIM and BZ restored the inhibitory expression of 5-HT_1A receptor in HFD hippocampus. Conclusions: Selective inhibition of intestinal 5-HT can attenuate depressive-like behavior, reduce 5-HT_1AR impairment in hippocampus and correct abnormal 5-HT pathway in brain while ameliorating HFD-induced glucose intolerance. Further experiments are warranted to define the adequate strategy of targeting peripheral 5-HT for the treatment of such co-morbidity.

Cytokine Responses in Severe Traumatic Brain Injury: Where There Is Smoke, Is There Fire?

This scoping review will discuss the basic functions and prognostic significance of the commonly researched cytokines implicated in severe traumatic brain injury (sTBI), including tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, tissue inhibitor of matrix metalloproteinases-1 (TIMP-1), transforming growth factor-β (TGF-β), substance P, and soluble CD40 ligand (sCD40L). A scoping review was undertaken with an electronic search for articles from the Ovid MEDLINE, PUBMED and EMBASE databases from 1995 to 2017. Inclusion criteria were original research articles, and reviews including both animal models and human clinical studies of acute (< 3 months) sTBI. Selected articles included both isolated sTBI and sTBI with systemic injury. After applying the inclusion criteria and removing duplicates, 141 full-text articles, 126 original research articles and 15 review articles, were evaluated in compiling this review paper. A single reviewer, CC, completed the review in two phases. During the first phase, titles and abstracts of selected articles were reviewed for inclusion. A second evaluation was then conducted on the full text of all selected articles to ensure relevancy. From our current understanding of the literature, it is unlikely a single biomarker will be sufficient in accurately prognosticating patients with sTBI. Intuitively, a more severe injury will demonstrate higher levels of inflammatory cytokines which may correlate as a marker of severe injury. This does not mean, necessarily, these cytokines have a direct and causal role in the poor outcome of the patient. Further research is required to better delineate the complex systemic inflammatory and CNS interactions that occur during sTBI before they can be applied as a reliable prognostic tool.

Atorvastatin prevents lipopolysaccharide-induced depressive-like behaviour in mice

Clinical and pre-clinical evidences indicate an association between inflammation and depression since increased levels of pro-inflammatory cytokines are associated with depression-related symptoms. Atorvastatin is a cholesterol-lowering statin that possesses pleiotropic effects including neuroprotective and antidepressant actions. However, the putative neuroprotective effect of atorvastatin treatment in the acute inflammation mice model of depressive-like behaviour has not been investigated. In the present study, we aimed to investigate the effect of atorvastatin treatment on lipopolysaccharide (LPS) induced depressive-like behaviour in mice. Mice were treated with atorvastatin (1 or 10 mg/kg, v.o.) or fluoxetine (30 mg/kg, positive control, v.o.) for 7 days before LPS (0.5 mg/kg, i.p.) injection. Twenty four hours after LPS infusion, mice were submitted to the forced swim test, tail suspension test or open field test. After the behavioural tests, mice were sacrificed and the levels of tumour necrosis factor-α (TNF-α), brain-derived neurotrophic factor (BDNF), glutathione and malondialdehyde were measured. Atorvastatin (1 or 10 mg/kg/day) or fluoxetine treatment prevented LPS-induced increase in the immobility time in the forced swim and tail suspension tests with no alterations in the locomotor activity evaluated in the open field test. Atorvastatin (1 or 10 mg/kg/day) or fluoxetine treatment also prevented LPS-induced increase in TNF-α and reduction of BDNF levels in the hippocampus and prefrontal cortex. Treatment with atorvastatin (1 or 10 mg/kg/day) or fluoxetine prevented LPS-induced increase in lipid peroxidation and the reduction of glutathione levels in the hippocampus and prefrontal cortex. The present study suggests that atorvastatin treatment exerted neuroprotective effects against LPS-induced depressive-like behaviour which may be related to reduction of TNF-α release, oxidative stress and modulation of BDNF expression.

Simvastatin therapy in adolescent mice attenuates HFD-induced depression-like behavior by reducing hippocampal neuroinflammation

BACKGROUND

A high-fat diet (HFD)-induced obesity/hyperlipidemia is accompanied by hormonal and neurochemical changes that can be associated with depression. Emerging studies indicate that simvastatin (SMV, decreasing cholesterol levels) has therapeutic effects on neurological and neuropsychiatric diseases through hippocampal-dependent function. However, the studies on the HFD exposure in adolescent animals, which investigate the neuroprotective effects of SMV on the hippocampal morphology, serotonin (5-HT) system and inflammation, are limited. Hence, the aim of this study was to determine whether SMV attenuates HFD-induced major depressive disorders in adolescent animals and, more specifically, acts as an anti-neuroinflammatory response.

METHODS

Twenty-four male C57BL/6 mice were fed a control (n = 8), HFD (n = 8) and HFD + SMV (n = 8) for 14 weeks. In HFD + SMV group, SMV (10 mg/kg) was administrated from the 10th week of HFD feeding. The open field test (OFT) and the tail suspension test (TST) were used to examine the effect of SMV on behavioral performance. HE and Nissl staining were conducted to detect hippocampal morphology and neural survival. Expression of the inflammatory cytokine genes was assayed by quantitative polymerase chain reaction (Q-PCR).

RESULTS

Firstly, alterations in lipid parameters were minimized after SMV treatment. HFD-induced depression-like behavior, which was evidenced by an increase in immobility time in TST along with considerable decrease in locomotion activity, was significantly attenuated by SMV therapy for 4 weeks. Additionally, SMV could reduce HFD-induced structural abnormality, neuronal injury, serotonergic system disturbance and pro-inflammatory cytokine over-expression in the hippocampus. Neuroimmunological changes in central hippocampus displayed a similar characteristic (only IL-1β, IL-6, TNF-α) with that in periphery spleen, whereas they appeared in an entirely opposite trend with that in cerebral cortex.

CONCLUSION

Our results suggest that SMV may be a promising treatment for HFD-induced depression-like behavior during adolescent period through brain region-specific neuroninflammatory mechanisms.

Statins and the Brain: More than Lipid Lowering Agents?

BACKGROUND

Statins represent a class of medications widely prescribed to efficiently treat dyslipidemia. These drugs inhibit 3-βhydroxy 3β-methylglutaryl Coenzyme A reductase (HMGR), the rate-limiting enzyme of mevalonate (MVA) pathway. Besides cholesterol, MVA pathway leads to the production of several other compounds, which are essential in the regulation of a plethora of biological activities, including in the central nervous system. For these reasons, statins are able to induce pleiotropic actions, and acquire increased interest as potential and novel modulators in brain processes, especially during pathological conditions.

OBJECTIVE

The purpose of this review is to summarize and examine the current knowledge about pharmacokinetic and pharmacodynamic properties of statins in the brain. In addition, effects of statin on brain diseases are discussed providing the most up-to-date information.

METHODS

Relevant scientific information was identified from PubMed database using the following keywords: statins and brain, central nervous system, neurological diseases, neurodegeneration, brain tumors, mood, stroke.

RESULTS

315 scientific articles were selected and analyzed for the writing of this review article. Several papers highlighted that statin treatment is effective in preventing or ameliorating the symptomatology of a number of brain pathologies. However, other studies failed to demonstrate a neuroprotective effect.

CONCLUSION

Even though considerable research studies suggest pivotal functional outcomes induced by statin therapy, additional investigation is required to better determine the pharmacological effectiveness of statins in the brain, and support their clinical use in the management of different neuropathologies.

Unfolding the pleiotropic facades of rosuvastatin in therapeutic intervention of myriads of neurodegenerative disorders

Rosuvastatin, a 3-hydroxy-3-methylglutaryl-coenzyme (HMG-CoA) reductase inhibitor, and one of the most popular antihyperlipidemic medications have been found to possess pharmacodynamic activities much different from its usual indication. Recent research studies have revealed the efficacy of rosuvastatin in attenuating neuroinflammation, reducing the progression of Alzheimer's disease, providing protection against cerebral ischaemia and spinal cord injury as well as ameliorating epilepsy. Mechanisms behind the neuroprotective potential of rosuvastatin can be attributed to its pleiotropic effects, independent of its ability to inhibit HMG-CoA reductase. These processes include modulation of several cellular pathways, isoprenylation, effects on oxidative stress, nitrosative levels, inflammation, and immune response. This review aims to assimilate and summarize recent findings on the pharmacological actions of rosuvastatin in attenuating neurological disorders in order to guide future research in this space.

Lateral cerebellar nucleus stimulation promotes motor recovery and suppresses neuroinflammation in a fluid percussion injury rodent model

BACKGROUND

Many traumatic brain injury (TBI) survivors live with persistent disability from chronic motor deficits despite contemporary rehabilitation services, underscoring the need for novel treatment.

OBJECTIVE/HYPOTHESIS

We have previously shown that deep brain stimulation (DBS) of the lateral cerebellar nucleus (LCN) can enhance post-stroke motor recovery and increase the expression of markers of long-term potentiation in perilesional cerebral cortex. We hypothesize that a similar beneficial effect will be for motor deficits induced by unilateral fluid percussion injury (FPI) in rodents through long-term potentiation- and anti-inflammatory based mechanisms.

METHODS

Male Long Evans rats with a DBS macroelectrode in the LCN underwent FPI over contralateral primary motor cortex. After 4 weeks of spontaneous recovery, DBS treatment was applied for 4 weeks, with the pasta matrix, cylinder, and horizontal ladder tests used to evaluate motor performance. All animals were euthanized and tissue harvested for further analysis by histology, immunohistochemistry, RNA microarray assay and Western Blot.

RESULTS

LCN DBS-treated animals experienced a significantly greater rate of motor recovery than untreated surgical controls, with treated animals showing enhanced expression of RNA and protein for excitability related genes, suppressed expression of pro-inflammatory genes, suppressed microglial and astrocytic activation, but proliferation of c-fos positive cells. Finally, our data suggest a possible role for anti-apoptotic effects with LCN DBS.

CONCLUSION

LCN DBS enhanced the motor recovery following TBI, possibly by elevating the neuronal excitability at the perilesional area and mediating anti-apoptotic and anti-inflammatory effects.

Probability of New-Onset Cancer Between Patients with Traumatic Brain Injury and a Comparison General Population Cohort

BACKGROUND

Traumatic brain injury (TBI) has been reported as a risk factor for the development of brain tumors. However, whether TBI affects systemic cancer remains to be determined. We investigated the incidence and factors associated with cancer development in patients with TBI.

METHODS

A propensity score (age, gender, and comorbidity)-matched longitudinal cohort study of 34,556 patients with pre-existing TBI and 69,112 patients without TBI from January 2000 to December 2015 was presented using the Taiwan's National Health Insurance Research Database. The Cox proportional hazard regression model was used to estimate the hazard ratio of developing cancer adjusted by the potential confounding factors. The stratified analysis of age, gender, and comorbidities for each cancer type was evaluated using forest plot analysis.

RESULTS

The cancer incidence rate in the patients with TBI (4.38%) was greater than that in patients without TBI (3.88%). The interval to cancer development in those with TBI (5.65 ± 3.58 years) was shorter than that in those without TBI (6.02 ± 3.65 years). The cancer risk in those with TBI was increased 1.27-fold compared with that in the general population. Of the patients with TBI, age <55 years and male gender indicated a greater incidence of cancer than that of the general population. The patients with TBI had greater cancer frequencies in the head and neck structures compared with those in the general population.

CONCLUSIONS

TBI is a risk factor for cancer development, especially in males and those aged <55 years. We hope this information will remind physicians to consider the long-term effects of TBI on cancer development.

Novel therapies for combating chronic neuropathological sequelae of TBI

Traumatic brain injury (TBI) is a risk factor for development of chronic neurodegenerative disorders later in life. This review summarizes the current knowledge and concepts regarding the connection between long-term consequences of TBI and aging-associated neurodegenerative disorders including Alzheimer's disease (AD), chronic traumatic encephalopathy (CTE), and Parkinsonism, with implications for novel therapy targets. Several aggregation-prone proteins such as the amyloid-beta (Aβ) peptides, tau proteins, and α-synuclein protein are involved in secondary pathogenic cascades initiated by a TBI and are also major building blocks of the hallmark pathological lesions in chronic human neurodegenerative diseases with dementia. Impaired metabolism and degradation pathways of aggregation-prone proteins are discussed as potentially critical links between the long-term aftermath of TBI and chronic neurodegeneration. Utility and limitations of previous and current preclinical TBI models designed to study the link between TBI and chronic neurodegeneration, and promising intervention pharmacotherapies and non-pharmacologic strategies to break this link, are also summarized. Complexity of long-term neuropathological consequences of TBI is discussed, with a goal of guiding future preclinical studies and accelerating implementation of promising therapeutics into clinical trials. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Elucidating opportunities and pitfalls in the treatment of experimental traumatic brain injury to optimize and facilitate clinical translation

The aim of this review is to discuss the research presented in a symposium entitled "Current progress in characterizing therapeutic strategies and challenges in experimental CNS injury" which was presented at the 2016 International Behavioral Neuroscience Society annual meeting. Herein we discuss diffuse and focal traumatic brain injury (TBI) and ensuing chronic behavioral deficits as well as potential rehabilitative approaches. We also discuss the effects of stress on executive function after TBI as well as the response of the endocrine system and regulatory feedback mechanisms. The role of the endocannabinoids after CNS injury is also discussed. Finally, we conclude with a discussion of antipsychotic and antiepileptic drugs, which are provided to control TBI-induced agitation and seizures, respectively. The review consists predominantly of published data.

Depression following a traumatic brain injury: uncovering cytokine dysregulation as a pathogenic mechanism

A substantial number of individuals have long-lasting adverse effects from a traumatic brain injury (TBI). Depression is one of these long-term complications that influences many aspects of life. Depression can limit the ability to return to work, and even worsen cognitive function and contribute to dementia. The mechanistic cause for the increased depression risk associated with a TBI remains to be defined. As TBI results in chronic neuroinflammation, and priming of glia to a secondary challenge, the inflammatory theory of depression provides a promising framework for investigating the cause of depression following a TBI. Increases in cytokines similar to those seen in depression in the general population are also increased following a TBI. Biomarker levels of cytokines peak within hours-to-days after the injury, yet pro-inflammatory cytokines may still be elevated above physiological levels months-to-years following TBI, which is the time frame in which post-TBI depression can persist. As tumor necrosis factor α and interleukin 1 can signal directly at the neuronal synapse, pathophysiological levels of these cytokines can detrimentally alter neuronal synaptic physiology. The purpose of this review is to outline the current evidence for the inflammatory hypothesis of depression specifically as it relates to depression following a TBI. Moreover, we will illustrate the potential synaptic mechanisms by which tumor necrosis factor α and interleukin 1 could contribute to depression. The association of inflammation with the development of depression is compelling; however, in the context of post-TBI depression, the role of inflammation is understudied. This review attempts to highlight the need to understand and treat the psychological complications of a TBI, potentially by neuroimmune modulation, as the neuropsychiatric disabilities can have a great impact on the rehabilitation from the injury, and overall quality of life.

The role of neuroimmune signaling in alcoholism

Alcohol consumption and stress increase brain levels of known innate immune signaling molecules. Microglia, the innate immune cells of the brain, and neurons respond to alcohol, signaling through Toll-like receptors (TLRs), high-mobility group box 1 (HMGB1), miRNAs, pro-inflammatory cytokines and their associated receptors involved in signaling between microglia, other glia and neurons. Repeated cycles of alcohol and stress cause a progressive, persistent induction of HMGB1, miRNA and TLR receptors in brain that appear to underlie the progressive and persistent loss of behavioral control, increased impulsivity and anxiety, as well as craving, coupled with increasing ventral striatal responses that promote reward seeking behavior and increase risk of developing alcohol use disorders. Studies employing anti-oxidant, anti-inflammatory, anti-depressant, and innate immune antagonists further link innate immune gene expression to addiction-like behaviors. Innate immune molecules are novel targets for addiction and affective disorders therapies. This article is part of the Special Issue entitled "Alcoholism".

Hyperbaric Oxygen Effects on Depression-Like Behavior and Neuroinflammation in Traumatic Brain Injury Rats

OBJECTIVE

The aim of this study was to determine whether hyperbaric oxygen (HBO) therapy causes attenuation of traumatic brain injury (TBI)-induced depression-like behavior and its associated anti-neuroinflammatory effects after fluid percussion injury.

METHODS

Anesthetized male Sprague-Dawley rats were divided into 3 groups: sham operation plus normobaric air (NBA) (21% oxygen at 1 absolute atmosphere [ATA]), TBI plus NBA, and TBI plus HBO (100% oxygen at 2.0 ATA). HBO was applied immediately for 60 min/d after TBI for 3 days. Depression-like behavior was tested by a forced swimming test, motor function was tested by an inclined plane test, and infarction volume was tested by triphenyltetrazolium chloride (TTC) staining on days 4, 8, and 15. Neuronal apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labeling assay), microglial (marker OX42) activation, and tumor necrosis factor (TNF)-α expression in microglia in the hippocampus CA3 were measured by immunofluorescence methods.

RESULTS

Compared with the TBI controls, without significant changes in TTC staining or in the motor function test, TBI-induced depression-like behavior was significantly attenuated by HBO therapy by day 15 after TBI. Simultaneously, TBI-induced neuronal apoptosis, microglial (marker OX42) activation, and TNF-α expression in the microglia in the hippocampus CA3 were significantly reduced by HBO.

CONCLUSIONS

Our results suggest that HBO treatment may ameliorate TBI-induced depression-like behavior in rats by attenuating neuroinflammation, representing one possible mechanism by which depression-like behavior recovery might occur. We also recommend HBO as a potential treatment for TBI-induced depression-like behavior if early intervention is possible.

Th17 Cells Induce Dopaminergic Neuronal Death via LFA-1/ICAM-1 Interaction in a Mouse Model of Parkinson's Disease

T helper (Th)17 cells, a subset of CD4⁺ T lymphocytes, have strong pro-inflammatory property and appear to be essential in the pathogenesis of many inflammatory diseases. However, the involvement of Th17 cells in Parkinson's disease (PD) that is characterized by a progressive degeneration of dopaminergic (DAergic) neurons in the nigrostriatal system is unclear. Here, we aimed to demonstrate that Th17 cells infiltrate into the brain parenchyma and induce neuroinflammation and DAergic neuronal death in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- or 1-methyl-4-phenylpyridinium (MPP⁺)-induced PD models. Blood-brain barrier (BBB) disruption in the substantia nigra (SN) was assessed by the signal of FITC-labeled albumin that was injected into blood circulation via the ascending aorta. Live cell imaging system was used to observe a direct contact of Th17 cells with neurons by staining these cells using the two adhesion molecules, leukocyte function-associated antigen (LFA)-1 and intercellular adhesion molecule (ICAM)-1, respectively. Th17 cells invaded into the SN where BBB was disrupted in MPTP-induced PD mice. Th17 cells exacerbated DAergic neuronal loss and pro-inflammatory/neurotrophic factor disorders in MPP⁺-treated ventral mesencephalic (VM) cell cultures. A direct contact of LFA-1-stained Th17 cells with ICAM-1-stained VM neurons was dynamically captured. Either blocking LFA-1 in Th17 cells or blocking ICAM-1 in VM neurons with neutralizing antibodies abolished Th17-induced DAergic neuronal death. These results establish that Th17 cells infiltrate into the brain parenchyma of PD mice through lesioned BBB and exert neurotoxic property by promoting glial activation and importantly by a direct damage to neurons depending on LFA-1/ICAM-1 interaction.