The Role of Neuroinflammation in Neuropsychiatric Disorders Following Traumatic Brain Injury: A Systematic Review

Efficacy of biomarkers and imaging techniques for the diagnosis of traumatic brain injury: challenges and opportunities

Concussion is a pervasive health issue in the present day. Increased prevalence in recent years has indicated a need to improve the current understanding of minor traumatic brain injury (mTBI). Effort has been devoted to understanding the underlying pathophysiology of TBIs, but some mechanisms remain unknown. Potentially lethal secondary effects of concussion include second impact syndrome and chronic traumatic encephalopathy (CTE), introducing long-term considerations for the management of mTBI. Post-concussion syndrome is another long-term consequence of concussion and may be influenced by both neuroinflammation and hormonal imbalances resulting from head trauma. Genetically mutated apolipoprotein E may also contribute to the severity and persistence of concussion symptoms, perhaps even acting as a risk factor for CTE. As it stands, the diagnosis of concussion is nuanced, depending primarily on subjective diagnostic tools that incorporate patient-reported symptoms and neurocognitive tests. Diagnostic tools provide some assistance in concussion diagnosis, but still lack accuracy and inherently leave room for uncertainty. To mitigate some of this uncertainty, considerable research has been devoted to the development of methods to diagnose concussions objectively. Biomarkers such as S100 calcium binding protein B (S100B), glial fibrillary acidic protein (GFAP), neurofilament light protein (Nf-L), interleukin-6 (IL-6) and microRNAs (miRNAs) as well as imaging techniques including diffusion tensor imaging (DTI) and blood-oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI) show great promise in this regard. This review aims to compile the relevant literature in these areas in the hopes of being used as a reference point for future research regarding concussions.

Early life factors and dementia risk: A study of adverse childhood experiences and later-life cognition and behaviour

OBJECTIVES

Adverse childhood experiences (ACE) are associated with brain alterations and cognitive decline. In later life, cognitive impairment and mild behavioural impairment (MBI) are associated with greater dementia risk. We investigated whether more severe ACE are cross-sectionally associated with worse later-life cognitive and behavioural symptoms.

STUDY DESIGN

Cross-sectional study.

METHODS

Data are from the Canadian Platform for Research Online to Investigate Health, Quality of Life, Cognition, Behaviour, Function, and Caregiving in Aging (CAN-PROTECT). Measures included the Childhood Trauma Screener (CTS-5), neuropsychological testing, Everyday Cognition (ECog)-II scale, and MBI Checklist (MBI-C). Linear regressions modelled associations between ACE severity and neuropsychological test scores. Multivariable negative binomial regressions (zero-inflated, if appropriate) modelled associations between ACE severity and ECog-II and MBI-C scores. All models controlled for age, sex, education, and ethnocultural origin. Clinical diagnoses of depression and/or anxiety were explored as covariates or mediators.

RESULTS

In adjusted analyses, higher ACE scores were associated with worse performance on Trail-Making B (standardized b = 0.10, q = 0.003), Switching Stroop (b = -0.08, q = 0.027), Paired Associates Learning (b = -0.08, q = 0.049), and Digit Span (b = -0.08, q = 0.029). Higher ACE scores were also associated with higher ECog-II (b = 1.08, q = 0.029) and MBI-C (b = 1.20, q < 0.001) scores; these associations were neither mediated by affective symptoms (ECog p = 0.16; MBI p = 0.13) nor moderated by sex (ECog p = 0.09; MBI p = 0.46).

CONCLUSION

Older adults with a history of more severe ACE show greater cognitive and behavioural risk markers for dementia that cannot be explained by previous psychiatric history. Further research into ACE as an early modifiable risk factor for dementia is warranted.

Electroacupuncture versus Escitalopram for mild to moderate Post-Stroke Depression: A randomized non-inferiority trial

Objective

To explore the efficacy of electroacupuncture in treating post-stroke depression (PSD) by modulating the inflammatory response pathway.

Methods

One hundred and fifty participants with mild or moderate PSD were randomly divided into 75 cases each in the electroacupuncture group (EA group) and escitalopram group (ESC group). In the EA group, 30 sessions of electroacupuncture were performed on the Baihui (GV 20), Yintang (GV 29), and the ipsilateral Taichong (LR 3) and Hegu (LI 4), simultaneous oral placebo for 40 days. The ESC group received oral escitalopram oxalate tablets 10mg to 20mg for 40 days, plus 30 sessions of sham electroacupuncture. The effectiveness of the treatment was evaluated by the Hamilton Depression Scale (HAMD-17), Self-Depression Scale (SDS), Modified Barthel Index Score (MBI), and the serum levels of IL-1β, IL-6, IL-10, TNF-α, and INF-γ.

Results

There was no statistically significant difference in the baseline data, HAMD-17, SDS, MBI scores, and serum IL-1β, IL-6, IL-10, TNF-α, and INF-γ levels between the two groups of participants before the intervention (P >0.05). After treatment, HAMD-17 and SDS scores continued to decrease and MBI scores continued to increase in both groups. The differences were statistically significant at the 6th week and baseline, the 10th week and baseline, and the 10th week and the 6th week (all P <0.001). The differences in HAMD-17, SDS, and MBI scores between the two groups at the 6th week were not statistically significant (P=0.110, 0.115, 0.516, respectively); HAMD-17 scores and SDS scores in the EA group were lower than those in the ESC group at the 10th week, and the differences were statistically significant (P=0.002,0.026, respectively). In the 6th week, the serum levels of pro-inflammatory factors such as IL-1β, IL-6, TNF-α, and INF-γ were significantly lower in both groups compared with the baseline, while the level of anti-inflammatory factor IL-10 was significantly higher. The difference between the pre-and post-intervention intra-group comparisons was statistically significant (P <0.001), and the difference between the inter-group comparisons was not statistically significant (P >0.05). No serious adverse events occurred throughout the trial. Both therapies could safely and effectively improve HAMD-17, SDS, and MBI scores and modulate neuroinflammatory responses in PSD participants. After the treatment was stopped, some parameters were better in the EA group than the ESC group in a short time.

Conclusion

Electroacupuncture is an effective, alternative to escitalopram for the treatment of mild-to-moderate PSD.

Clinical trial registration

Chinese Clinical Trial Registry (ChiCTR2300072576).

Altered serum TNF-α and MCP-4 levels are associated with the pathophysiology of major depressive disorder: A case-control study results

BACKGROUND

Major Depressive Disorder (MDD) is a debilitating mental health condition with complex etiology, and recent research has focused on pro-inflammatory cytokines and chemokines as potential contributors to its pathogenesis. However, studies investigating the roles of TNF-α and MCP-4 in MDD within the Bangladeshi population are scarce. This study aimed to assess the association between serum TNF-α and MCP-4 levels and the severity of MDD, exploring their potential as risk indicators for MDD development.

METHODS

This case-control study enrolled 58 MDD patients from Bangabandhu Sheikh Mujib Medical University (BSMMU) Hospital, Dhaka, Bangladesh, alongside 30 age, sex, and BMI-matched healthy controls. MDD diagnosis followed DSM-5 criteria and disease severity using the 17-item Hamilton Depression Rating Scale (Ham-D). We measured serum TNF-α and MCP-4 levels using ELISA assays according to the supplied protocols.

RESULTS

The study revealed significantly elevated serum TNF-α levels in MDD patients (47±6.6 pg/ml, mean±SEM) compared to controls (28.06±1.07 pg/ml). These increased TNF-α levels positively correlated with Ham-D scores (Pearson's r = 0.300, p = 0.038), suggesting a potential association between peripheral TNF-α levels and MDD pathology. Additionally, MDD patients exhibited significantly higher serum MCP-4 levels (70.49±6.45 pg/ml) than controls (40.21±4.08 pg/ml). However, serum MCP-4 levels showed a significant negative correlation (r = -0.270, P = 0.048) with Ham-D scores in MDD patients, indicating a more complex role for MCP-4 in MDD pathogenesis.

CONCLUSION

This study highlights that Bangladeshi MDD patients exhibit heightened inflammatory and immune responses compared to controls, supporting the cytokine hypothesis in MDD pathogenesis. Serum TNF-α, but not MCP-4, shows promise as a potential biomarker for assessing the risk of MDD development, which could aid in early detection. Future investigations involving larger populations and longitudinal studies are essential to confirm the utility of these cytokines as biomarkers for MDD.

Effect of Low Doses of Dexamethasone on Experimental Pulmonary Tuberculosis

Tuberculosis (TB) is the deadliest disease caused by a bacterial agent. Glucocorticoids (GCs) have a typical anti-inflammatory effect, but recently it has been shown that they can present proinflammatory activity, mainly by increasing molecules from innate immunity. In the current study, we evaluated the effect of low doses of dexamethasone on Mycobacterium tuberculosis in vivo and in vitro. We used an established mice model of progressing tuberculosis (TB) in the in vivo studies. Intratracheal or intranasal dexamethasone therapy administered with conventional antibiotics in the late stage of the disease decreased the lung bacilli load and lung pneumonia, and increased the survival of the animals. Finally, the treatment decreased the inflammatory response in the SNC and, therefore, sickness behavior and neurological abnormalities in the infected animals. In the in vitro experiments, we used a cell line of murine alveolar macrophages infected with Mtb. Low-dose dexamethasone treatment increased the clearance capacity of Mtb by MHS macrophages, MIP-1α, and TLR2 expression, decreased proinflammatory and anti-inflammatory cytokines, and induced apoptosis, a molecular process that contributes to the control of the mycobacteria. In conclusion, the administration of low doses of dexamethasone represents a promising adjuvant treatment for pulmonary TB.

KNT-127, a selective delta opioid receptor agonist, shows beneficial effects in the hippocampal dentate gyrus of a chronic vicarious social defeat stress mouse model

Delta opioid receptors (DOPs) play an important role in depression and other mood disorders. However, little is known about the underlying physiological mechanisms. The hypothalamic-pituitary-adrenal axis, adult hippocampal neurogenesis, and neuroinflammation are regarded as key pathophysiological factors in depression. In this study, we investigated the influence of DOP activation on those factors in a valid animal model of depression, chronic vicarious social defeat stress (cVSDS) mice. cVSDS mice (male C57BL/6J mice) were produced following a 10-day exposure to witness of social defeat stress, and each evaluation was performed more than 28 days after the stress period. Repeated administrations to cVSDS mice with a selective DOP agonist, KNT-127, both during (10 days) and after (28 days) the stress period respectively improved their decreased social interaction behaviors and increased serum corticosterone levels. When administered during the stress period, KNT-127 suppressed decreases in the hippocampal newborn neuron survival rate in cVSDS mice. Moreover, in both administration paradigms, KNT-127 reduced the number of Iba-1- and CD11b-positive cells in the subgranular zone and the granule cell layer of the hippocampal dentate gyrus, indicating a suppression of cVSDS-induced microglial overactivation. These results suggest that KNT-127 acts over the hypothalamic-pituitary-adrenal axis and regulates neurogenesis and neuroinflammation resulting in anti-stress effects, and the antidepressant-like effects of the DOP agonist are implicated in the suppression of the neuroinflammation. This study presents a new finding on the effects of repeated DOP activations on the pathophysiological states of depression.

The Putative Role of Neuroinflammation in the Interaction between Traumatic Brain Injuries, Sleep, Pain and Other Neuropsychiatric Outcomes: A State-of-the-Art Review

Sleep disturbances are widely prevalent following a traumatic brain injury (TBI) and have the potential to contribute to numerous post-traumatic physiological, psychological, and cognitive difficulties developing chronically, including chronic pain. An important pathophysiological mechanism involved in the recovery of TBI is neuroinflammation, which leads to many downstream consequences. While neuroinflammation is a process that can be both beneficial and detrimental to individuals' recovery after sustaining a TBI, recent evidence suggests that neuroinflammation may worsen outcomes in traumatically injured patients, as well as exacerbate the deleterious consequences of sleep disturbances. Additionally, a bidirectional relationship between neuroinflammation and sleep has been described, where neuroinflammation plays a role in sleep regulation and, in turn, poor sleep promotes neuroinflammation. Given the complexity of this interplay, this review aims to clarify the role of neuroinflammation in the relationship between sleep and TBI, with an emphasis on long-term outcomes such as pain, mood disorders, cognitive dysfunctions, and elevated risk of Alzheimer's disease and dementia. In addition, some management strategies and novel treatment targeting sleep and neuroinflammation will be discussed in order to establish an effective approach to mitigate long-term outcomes after TBI.

Blood glutamate scavenging as a novel glutamate-based therapeutic approach for post-traumatic brain injury anxiety and social impairment

Traumatic brain injury (TBI) is a serious condition that is associated with an increased risk of severe, long-term psychiatric consequences. Drugs that target the glutamatergic system have proven successful in treating both TBI and many of its psychiatric sequelae. Blood glutamate scavengers (BGS) cause a decrease in blood glutamate levels, leading to a reduction in glutamate's concentration gradient from the brain to the blood and decreased levels of brain glutamate. This study evaluated the BGS pyruvate as a treatment for TBI-related neuropsychiatric conditions in a rat model. 213 rats were divided into four groups in a 2 × 2 design: Sham or TBI rats treated with pyruvate or control treatment. Magnetic resonance imaging, neurological status, brain glutamate and blood glutamate levels were assessed following the injury. Four weeks after the start of treatment, all rats underwent behavioral tests to assess anxious behavior and social impairment (aggressive and hierarchical behavior). Rats responded positively to pyruvate in several tasks, lowering brain glutamate levels and reducing anxiety and depression, as well as modulating TBI-related changes in social behavior. Glutamate scavenging with pyruvate may be an effective therapeutic option for post-TBI behavioral changes by reducing associated elevations in brain glutamate levels.

Pharmacological, Neurochemical, and Behavioral Mechanisms Underlying the Anxiolytic- and Antidepressant-like Effects of Flavonoid Chrysin

Chrysin (5,7-dihydroxyflavone) is a flavonoid isolated from plants, such as Passiflora coerulea, Passiflora incarnata, and Matricaria chamomilla. This natural molecule exerts diverse pharmacological effects, which includes antioxidant, anti-inflammatory, anti-cancer, neuroprotective, and anti-apoptotic effects. Additionally, in brain structures, such as the hippocampus, prefrontal cortex, raphe nucleus, and striatum, involved in the physiopathology of anxiety and depression disorders, several neuropharmacological activities, including the activation of neurotransmitter systems (GABAergic, serotonergic, dopaminergic, and noradrenergic), neurotrophic factors, such as brain-derived neurotrophic factor and the nerve growth factor, and some signaling pathways are affected. The results showed that the anxiolytic and antidepressant-like effects of chrysin occurs through its interaction with specific neurotransmitter systems, principally the GABAergic and the serotonergic, and activation of other neurotrophic factors. However, it is not possible to discard the antioxidant and anti-inflammatory activities of chrysin while producing its anxiolytic- and antidepressant-like effects. Although these results have been obtained principally from pre-clinical research, they consistently demonstrate the potential therapeutic use of flavonoid chrysin as an anxiolytic and antidepressant agent. Therefore, this flavonoid could be considered as a promising novel therapy for anxiety and depression disorders.