Variable neuroendocrine-immune dysfunction in individuals with unfavorable outcome after severe traumatic brain injury

Serial Measurements of Serum Glial Fibrillary Acidic Protein in Moderate-Severe Traumatic Brain Injury: Potential Utility in Providing Insights into Secondary Insults and Long-Term Outcome

In patients with traumatic brain injury (TBI), serum biomarkers may have utility in assessing the evolution of secondary brain injury. A panel of nine brain-injury- associated biomarkers was measured in archived serum samples over 10 days post-injury from 100 patients with moderate-severe TBI. Among the biomarkers evaluated, serum glial fibrillary acidic protein (GFAP) had the strongest associations with summary measures of acute pathophysiology, including intracranial pressure (ICP), cerebral perfusion pressure (CPP), and brain tissue pO2 (PbtO2). Group based trajectory (TRAJ) analysis was used to identify three distinct GFAP subgroups. The low TRAJ group (n = 23) had peak levels of 9.4 + 1.2 ng/mL that declined rapidly. The middle TRAJ group (n = 48) had higher peak values (31.5 + 5.0 ng/mL) and a slower decline over time. The high TRAJ group (n = 26) had very high, sustained peak values (59.6 + 12.5 ng/mL) that even rose among some patients over 10 days. Patients in the high TRAJ group had significantly higher mortality rate than patients in low and middle TRAJ groups (26.9% vs. 7.0%, p = 0.028). The frequency of poor neurological outcome (Glasgow Outcome Score Extended [GOS-E] 1-4) was 88.5% in the high TRAJ group, 54.2% in the middle TRAJ group, and 30.4% in the low TRAJ group (p < 0.001). ICP was highest in the high TRAJ group (median 17.6 mm Hg), compared with 14.4 mmHg in the low and 15.9 mm Hg in middle TRAJ groups (p = 0.002). High TRAJ patients spent the longest time with ICP >25 mm Hg, median 23 h, compared with 2 and 6 h in the low and middle TRAJ groups (p = 0.006), and the longest time with ICP >30 mm Hg, median 5 h, compared with 0 and 1 h in the low and middle TRAJ groups, respectively (p = 0.013). High TRAJ group patients more commonly required tier 2 or 3 treatment to control ICP. The high TRAJ group had the longest duration when CPP was <50 mm Hg (p = 0.007), and PbtO2 was <10 mm Hg (p = 0.002). Logistical regression was used to study the relationship between temporal serum GFAP patterns and 6-month GOS-E. Here, the low and middle TRAJ groups were combined to form a low-risk group, and the high TRAJ group was designated the high-risk group. High TRAJ group patients had a greater chance of a poor 6-month GOS-E (p < 0.0001). When adjusting for baseline injury characteristics, GFAP TRAJ group membership remained associated with GOS-E (p = 0.003). When an intensive care unit (ICU) injury burden score, developed to quantify physiological derangements, was added to the model, GFAP TRAJ group membership remained associated with GOS-E (p = 0.014). Mediation analysis suggested that ICU burden scores were in the causal pathway between TRAJ group and 6-month mortality or GOS-E. Our results suggest that GFAP may be useful to monitor serially in moderate-severe TBI patients. Future studies in larger cohorts are needed to confirm these results.

The Role of Neuroinflammatory Mediators in the Pathogenesis of Traumatic Brain Injury: A Narrative Review

Traumatic brain injury (TBI) is a debilitating acquired neurological disorder that afflicts nearly 74 million people worldwide annually. TBI has been classified as more than just a single insult because of its associated risk toward various long-term neurological and neurodegenerative disorders. This risk may be triggered by a series of postinjury secondary molecular and cellular pathology, which may be dependent on the severity of the TBI. Among the secondary injury mechanisms, neuroinflammation may be the most crucial as it may exacerbate brain damage and lead to fatal consequences when prolonged. This Review aimed to elucidate the influence of neuroinflammatory mediators on the TBI functional and pathological outcomes, particularly focusing on inflammatory cytokines which were associated with neuronal dysfunctions in the acute and chronic stages of TBI. These cytokines include interleukins (IL) such as IL-1(beta)β, IL-4, IL-6, IL8, IL-10, IL-18, IL-33 and tumor necrosis factor alpha (TNF-α), which have been extensively studied. Apart from these, IL-2, interferon gamma (IFN-γ), and transforming growth factor-beta (TGF-β) may also play a significant role in the pathogenesis of TBI. These neuroinflammatory mediators may trigger a series of pathological events such as cell death, microglial suppression, and increased catecholaminergic activity. Interestingly, in the acute phase of TBI, most of these mediators may also play a neuroprotective role by displaying anti-inflammatory properties, which may convert to a pro-inflammatory action in the chronic stages post TBI. Early identification and treatment of these mediators may help the development of more effective treatment options for TBI.

The role of the stress system in recovery after traumatic brain injury: A tribute to Bruce S. McEwen

Traumatic brain injury (TBI) represents a major public health concern. Although the majority of individuals that suffer mild-moderate TBI recover relatively quickly, a substantial subset of individuals experiences prolonged and debilitating symptoms. An exacerbated response to physiological and psychological stressors after TBI may mediate poor functional recovery. Individuals with TBI can suffer from poor stress tolerance, impairments in the ability to evaluate stressors, and poor initiation (and cessation) of neuroendocrine stress responses, all of which can exacerbate TBI-mediated dysfunction. Here, we pay tribute to the pioneering neuroendocrinologist Dr. Bruce McEwen by discussing the ways in which his work on stress physiology and allostatic loading impacts the TBI patient population both before and after their injuries. Specifically, we will discuss the modulatory role of hypothalamic-pituitary-adrenal axis responses immediately after TBI and later in recovery. We will also consider the impact of stressors and stress responses in promoting post-concussive syndrome and post-traumatic stress disorders, two common sequelae of TBI. Finally, we will explore the role of early life stressors, prior to brain injuries, as modulators of injury outcomes.

Early Antibiotic Administration is Independently Associated with Improved Survival in Traumatic Brain Injury

BACKGROUND

Central and systemic immune dysfunction after traumatic brain injury (TBI) can lead to infectious-related complications, which may result in delayed mortality. The role of early empiric antibiotics after TBI has not been characterized to date, but is recommended in select cases to decrease complications. We aimed to determine the relationship between early antibiotic use and in-hospital mortality in TBI patients.

METHODS

A retrospective review was conducted of TBI patients requiring ICU admission at an urban, academic, Level I trauma center from 01/2014 to 08/2016. Data collection included demographics, injury characteristics, details regarding antibiotic use, and outcomes. Early antibiotic administration was defined as any antibiotic given within 48 hs from admission. Patients given early antibiotics (EARLY) were compared to those who received their first dose later or did not receive any antibiotics (non-EARLY).

RESULTS

Of the 488 TBI patients meeting inclusion criteria, 189 (38.7%) received early antibiotics. EARLY patients were younger (EARLY 54.2 versus non-EARLY 61.5 ys, P <0.01) and more likely to be male (71.4% versus 60.9%, P = 0.02). Injury severity scores (23.6 versus 17.2, P <0.01) and regional head abbreviated injury scale scores (3.9 versus 3.7, P <0.01) were significantly higher in patients who received early antibiotics. Unadjusted in-hospital mortality rates were similar, however EARLY was associated with a lower mortality rate (AOR 0.17, 95% CI: 0.07 - 0.43, adjusted P <0.01) after adjusting for confounders.

CONCLUSIONS

Despite presenting with a higher injury burden, TBI patients who received early antibiotics had a lower associated mortality rate compared to their counterparts. Future investigations are necessary to understand the underlying mechanisms that result in this potential survival benefit.

Acute Cortisol Profile Associations With Cognitive Impairment After Severe Traumatic Brain Injury

BACKGROUND

Cognitive impairments commonly occur after traumatic brain injury (TBI) and affect daily functioning. Cortisol levels, which are elevated during acute hospitalization for most individuals after severe TBI, can influence cognition, but this association has not been studied previously in TBI.

OBJECTIVE

We hypothesized that serum and cerebral spinal fluid (CSF) cortisol trajectories over days 0-5 post-injury are associated with cognition 6-month post-injury.

METHODS

We examined 94 participants with severe TBI, collected acute serum and/or CSF samples over days 0-5 post-injury, and compared cortisol levels to those in 17 healthy controls. N = 88 participants had serum, and n = 84 had CSF samples available for cortisol measurement and had neuropsychological testing 6 months post-injury. Group based trajectory analysis (TRAJ) was used to generate temporal serum and CSF cortisol profiles which were examined for associations with neuropsychological performance. We used linear regression to examine relationships between cortisol TRAJ groups and both overall and domain-specific cognition.

RESULTS

TRAJ analysis identified a high group and a decliner group for serum and a high group and low group for CSF cortisol. Multivariable analysis showed serum cortisol TRAJ group was associated with overall cognitive composites scores (P = .024) and with executive function (P = .039) and verbal fluency (P = .029) domain scores. CSF cortisol TRAJ group was associated with overall cognitive composite scores (P = .021) and domain scores for executive function (P = .041), verbal fluency (P = .031), and attention (P = .034).

CONCLUSIONS

High acute cortisol trajectories are associated with poorer cognition 6 months post-TBI.

Profiling the Expression of Circulating Acute-Phase Proteins, Cytokines, and Checkpoint Proteins in Patients with Severe Trauma: A Pilot Study

Purpose

Severe trauma may lead to the systemic release of inflammatory mediators into the circulation with profound acute-phase responses; however, the understanding of the expression of these mediators remains limited. This study aimed to characterize the alterations in the expression of circulating acute-phase proteins, cytokines, and checkpoint proteins in patients with severe trauma injuries.

Patients and Methods

The study population included trauma patients in the intensive care unit (ICU) with an injury severity score equal to or greater than 16 and who had used a ventilator for 48 hours. A total of 12 female and 28 male patients were recruited for the study; six patients died and 34 survived. Blood samples collected at acute stages were compared with those drawn at the subacute stage, the time when the patients were discharged from the ICU, or before the discharge of the patients from the hospital.

Results

The study identified that the expression of acute-phase proteins, such as alpha-1-acid glycoprotein and C-reactive protein, and cytokines, including granulocyte colony-stimulating factor, interleukin-6, and interleukin-1 receptor antagonist, was elevated in the circulation after severe trauma. In contrast, the levels of acute-phase proteins, such as alpha-2-macroglobulin, serum amyloid P, and von Willebrand factor, and cytokines, including interleukin-4 and interferon gamma-induced protein 10, were reduced. However, there were no significant differences in the expression of checkpoint proteins in the circulation.

Conclusion

The dysregulated proteins identified in this study may serve as potential therapeutic targets or biomarkers for treating patients with severe trauma. However, the related biological functions of these dysregulated factors require further investigation to validate their functions.

A Histological and Morphometric Assessment of the Adult and Juvenile Rat Livers after Mild Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the most severe problems of modern medicine that plays a dominant role in morbidity and mortality in economically developed countries. Our experimental study aimed to evaluate the histological and morphological changes occurring in the liver of adult and juvenile mildly traumatized rats (mTBI) in a time-dependent model. The experiment was performed on 70 adult white rats at three months of age and 70 juvenile rats aged 20 days. The mTBI was modelled by the Impact-Acceleration Model-free fall of weight in the parieto-occipital area. For histopathological comparison, the samples were taken on the 1st, 3rd, 5th, 7th, 14th, and 21st days after TBI. In adult rats, dominated changes in the microcirculatory bed in the form of blood stasis in sinusoidal capillaries and veins, RBC sludge, and adherence to the vessel wall with the subsequent appearance of perivascular and focal leukocytic infiltrates. In juvenile rats, changes in the parenchyma in the form of hepatocyte dystrophy prevailed. In both groups, the highest manifestation of the changes was observed on 5–7 days of the study. On 14–21 days, compensatory phenomena prevailed in both groups. Mild TBI causes changes in the liver of both adult and juvenile rats. The morphological pattern and dynamics of liver changes, due to mild TBI, are different in adult and juvenile rats.

Early chronic systemic inflammation and associations with cognitive performance after moderate to severe TBI

BACKGROUND

Cognitive dysfunction adversely effects multiple functional outcomes and social roles after TBI. We hypothesize that chronic systemic inflammation exacerbates cognitive deficits post-injury and diminishes functional cognition and quality of life (QOL). Yet few studies have examined relationships between inflammation and cognition after TBI. Associations between early chronic serum inflammatory biomarker levels, cognitive outcomes, and QOL 6-months and 12-months after moderate-to-severe TBI were identified using unweighted (uILS) and weighted (wILS) inflammatory load score (ILS) formation.

METHODS

Adults with moderate-to-severe TBI (n ​= ​157) completed neuropsychological testing, the Functional Impairment Measure Cognitive Subscale (FIM-Cog) and self-reported Percent Back to Normal scale 6 months (n ​= ​139) and 12 months (n ​= ​136) post-injury. Serial serum samples were collected 1-3 months post-TBI. Cognitive composite scores were created as equally weighted means of T-scores derived from a multidimensional neuropsychological test battery. Median inflammatory marker levels associated with 6-month and 12-month cognitive composite T-scores (p ​< ​0.10) were selected for ILS formation. Markers were quartiled, and quartile ranks were summed to generate an uILS. Marker-specific β-weights were derived using penalized ridge regression, multiplied by standardized marker levels, and summed to generate a wILS. ILS associations with cognitive composite scores were assessed using multivariable linear regression. Structural equation models assessed ILS influences on functional cognition and QOL using 12-month FIM-Cog and Percent Back to Normal scales.

RESULTS

ILS component markers included: IL-1β, TNF-α, sIL-4R, sIL-6R, RANTES, and MIP-1β. Increased sIL-4R levels were positively associated with overall cognitive composite T-scores in bivariate analyses, while remaining ILS markers were negatively associated with cognition. Multivariable receiver operator curves (ROC) showed uILS added 14.98% and 31.93% relative improvement in variance captured compared to the covariates only base model (age, sex, education, Glasgow Coma Scale score) when predicting cognitive composite scores at 6 and 12 months, respectively; wILS added 33.99% and 36.87% relative improvement in variance captured. Cognitive composite mediated wILS associations with FIM-Cog scores at 12 months, and both cognitive composite and FIM-Cog scores mediated wILS associations with QOL.

CONCLUSIONS

Early chronic inflammatory burden is associated with cognitive performance post-TBI. wILS explains greater variance in cognitive composite T-scores than uILS. Linking inflammatory burden associated with cognitive deficits to functional outcome post-TBI demonstrates the potential impact of immunotherapy interventions aimed at improving cognitive recovery post-TBI.

MEK inhibitor trametinib attenuates neuroinflammation and cognitive deficits following traumatic brain injury in mice

Microglia-mediated neuroinflammation is one of the hallmark pathological features following traumatic brain injury (TBI) that contributes to aggravated brain damage and cognitive deficits. These pathologies require novel effective treatments to improve prognosis. Trametinib, a mitogen-activated protein kinase inhibitor approved by the Food and Drug Administration in treating various malignant tumors, has been shown to exert anti-inflammatory effects. The present study demonstrated that TBI mice treated with trametinib exhibited improved cognitive function. Trametinib treatment rescued oligodendrocytes and decreased infiltrating microglial density in the TBI area. Furthermore, this study revealed that ameliorated lipopolysaccharides (LPS) induced inflammatory reaction in microglial cells. Besides, trametinib attenuated inflammation factors expression during the early stages of TBI. In addition, trametinib inhibited LPS-induced microglial chemotactic activity. In conclusion, the results indicate that trametinib efficiently suppresses microglia-induced neuroinflammation and improves cognitive function of TBI mice, providing a potential therapy strategy for TBI patients.

Sex-Dependent Pathology in the HPA Axis at a Sub-acute Period After Experimental Traumatic Brain Injury

Over 2.8 million traumatic brain injuries (TBIs) are reported in the United States annually, of which, over 75% are mild TBIs with diffuse axonal injury (DAI) as the primary pathology. TBI instigates a stress response that stimulates the hypothalamic-pituitary-adrenal (HPA) axis concurrently with DAI in brain regions responsible for feedback regulation. While the incidence of affective symptoms is high in both men and women, presentation is more prevalent and severe in women. Few studies have longitudinally evaluated the etiology underlying late-onset affective symptoms after mild TBI and even fewer have included females in the experimental design. In the experimental TBI model employed in this study, evidence of chronic HPA dysregulation has been reported at 2 months post-injury in male rats, with peak neuropathology in other regions of the brain at 7 days post-injury (DPI). We predicted that mechanisms leading to dysregulation of the HPA axis in male and female rats would be most evident at 7 DPI, the sub-acute time point. Young adult age-matched male and naturally cycling female Sprague Dawley rats were subjected to midline fluid percussion injury (mFPI) or sham surgery. Corticotropin releasing hormone, gliosis, and glucocorticoid receptor (GR) levels were evaluated in the hypothalamus and hippocampus, along with baseline plasma adrenocorticotropic hormone (ACTH) and adrenal gland weights. Microglial response in the paraventricular nucleus of the hypothalamus indicated mild neuroinflammation in males compared to sex-matched shams, but not females. Evidence of microglia activation in the dentate gyrus of the hippocampus was robust in both sexes compared with uninjured shams and there was evidence of a significant interaction between sex and injury regarding microglial cell count. GFAP intensity and astrocyte numbers increased as a function of injury, indicative of astrocytosis. GR protein levels were elevated 30% in the hippocampus of females in comparison to sex-matched shams. These data indicate sex-differences in sub-acute pathophysiology following DAI that precede late-onset HPA axis dysregulation. Further understanding of the etiology leading up to late-onset HPA axis dysregulation following DAI could identify targets to stabilize feedback, attenuate symptoms, and improve efficacy of rehabilitation and overall recovery.

Temporal Acute Serum Estradiol and Tumor Necrosis Factor-α Associations and Risk of Death after Severe Traumatic Brain Injury

Severe traumatic brain injury (TBI) activates a robust systemic response that involves inflammatory and other factors, including estradiol (E2), associated with increased deaths. Tumor necrosis factor-alpha (TNFα) is a significant mediator of systemic shock, and it is an extra-gonadal transcription factor for E2 production. The study objectives were to test the hypotheses: (1) a positive feedback relationship exists between acute serum TNFα and E2; and (2) acute concentrations of E2 and TNFα are prognostic indicators of death after severe TBI. This prospective cohort study included N = 157 adults with severe TBI. Serum samples were collected for the first five days post-injury. The TNFα and E2 levels were averaged into two time epochs: first 72 h (T1) and second 72 h post-injury (T2). A cross-lag panel analysis conducted between T1 and T2 TNFα and E2 levels showed significant cross-lag effects: T1 TNFα and T1 E2 were related to T2 E2 and T2 TNFα, respectively. Cox proportional hazards multi variable regression models determined that increases in T1 E2 (hazard ratio [HR] = 1.79, 95% confidence interval [CI]: 1.15, 2.81), but not T2 E2 (HR = 0.91, 95% CI: 0.56, 1.47), were associated with increased risk of death. Increased T2 TNFα (HR = 2.47, 95% CI: 1.35, 4.53), and T1 TNFα (HR = 1.47, 95% CI: 0.99, 2.19), to a lesser degree, were associated with increased risk of death. Relationships of death with T2 TNFα and T1 E2 were mediated partially by cardiovascular, hepatic, and renal dysfunction. Both E2 and TNFα are systemic, reciprocally related biomarkers that may be indicative of systemic compromise and increased risk of death after severe TBI.

Incidence and risk factors of early postoperative complications in patients after decompressive craniectomy: a 5-year experience

PURPOSE

Decompressive craniectomy is an effective measure to reduce a pathologically elevated intracranial pressure. Patients' survival and life quality following this surgery have been a subject of several studies and significantly differ according to the primary diagnosis. Since this operation is often associated with a wide spectrum of possibly serious complications, we aimed to describe their incidence and possible associated risk factors.

METHODS

We evaluated 118 patients who underwent decompressive craniectomy at our clinic during years 2013-2017. The indications included traumatic brain injuries, ischaemic or haemorrhagic strokes and postoperative complications of planned neurosurgical procedures. Subsequently, we assessed the incidence of early postoperative complications (occurring during the first 3 postoperative weeks). The results were statistically analysed with relation to a wide selection of possible risk factors.

RESULTS

At least one early surgical postoperative complication occurred in 87 (73.73%) patients, the most frequent being a development of an extraaxial fluid collection in 41 (34.75%) patients. We were able to identify risk factors linked with extraaxial fluid collections, subcutaneous and extradural haematomas, postoperative seizures and meningitis. An overall need for reoperation was 13.56%. Neither the duration of the surgery nor the qualification of the operating surgeon had any effect on the complications' occurrence.

CONCLUSIONS

Decompressive craniectomy is associated with numerous early postoperative complications with a various degree of severity. Most cases of complications can, however, be managed in a conservative way. The risk factors linked with postoperative complications should be taken into account during the indication process in each individual patient.

Anti-Pituitary and Anti-Hypothalamus Autoantibody Associations with Inflammation and Persistent Hypogonadotropic Hypogonadism in Men with Traumatic Brain Injury

Traumatic brain injury (TBI) and can lead to persistent hypogonadotropic hypogonadism (PHH) and poor outcomes. We hypothesized that autoimmune and inflammatory mechanisms contribute to PHH pathogenesis. Men with moderate-to-severe TBI (n = 143) were compared with healthy men (n = 39). The TBI group provided blood samples 1-12 months post-injury (n = 1225). TBI and healthy control (n = 39) samples were assayed for testosterone (T) and luteinizing hormone (LH) to adjudicate PHH status. TBI samples 1-6 months post-injury and control samples were assayed for immunoglobulin M (IgM)/immunoglobulin G (IgG) anti-pituitary autoantibodies (APA) and anti-hypothalamus autoantibodies (AHA). Tissue antigen specificity for APA and AHA was confirmed via immunohistochemistry (IHC). IgM and IgG autoantibodies for glial fibrillary acid protein (GFAP) (AGA) were evaluated to gauge APA and AHA production as a generalized autoimmune response to TBI and to evaluate the specificity of APA and AHA to PHH status. An inflammatory marker panel was used to assess relationships to autoantibody profiles and PHH status. Fifty-one men with TBI (36%) had PHH. An age-related decline in T levels by both TBI and PHH status were observed. Injured men had higher APA IgM, APA IgG, AHA IgM, AHA IgG, AGA IgM, and AGA IgG than controls (p < 0.0001 all comparisons). However, only APA IgM (p = 0.03) and AHA IgM (p = 0.03) levels were lower in the PHH than in the non-PHH group in multivariate analysis. There were no differences in IgG levels by PHH status. Multiple inflammatory markers were positively correlated with IgM autoantibody production. PHH was associated with higher soluble tumor-necrosis-factor receptors I/II, (sTNFRI, sTNFRII), regulated on activation, normal T-cell expressed and secreted (RANTES) and soluble interleukin-2-receptor-alpha (sIL-2Rα) levels. Higher IgM APA, and AHA, but not AGA, in the absence of PHH may suggest a beneficial or reparative role for neuroendocrine tissue-specific IgM autoantibody production against PHH development post-TBI.

Blast traumatic brain injury and serum inflammatory cytokines: a repeated measures case-control study among U.S. military service members

Background

There is a paucity of human data on exposure to blast traumatic brain injury (bTBI) and the corresponding systemic cytokine immune response at later time points (i.e., months, years) post-injury.

Methods

We conducted a repeated measures, case-control study, examining associations of serum levels of pro- and anti-inflammatory cytokines, measured both pre- and post-deployment with having mild and moderate/severe bTBI. Utilizing serum from the Department of Defense Serum Repository cytokines were measured via an ELISA-based array for 15 cytokines. We compared pre- vs. post-levels among mild cases, moderate/severe cases, and controls and carried out case-control comparisons, using paired t- tests and generalized linear models.

Results

The average time between bTBI and post-deployment/bTBI serum among cases was 315.8 days. From pre- to post-deployment/bTBI, levels of interleukin 8 (IL-8) were decreased among both mild cases (μ = − 83.43 pg/ml; s.e. = 21.66) and moderate/severe cases (μ = − 107.67 pg/ml; s.e. = 28.74 pg/ml), while levels increased among controls (μ = 32.86 pg/ml; s.e. = 30.29). The same pattern occurred for matrix metallopeptidase 3 (MMP3), with levels decreasing for moderate/severe cases (μ = − 3369.24 pg/ml; s.e. = 1701.68) and increasing for controls (μ = 1859.60 pg/ml; s.e. = 1737.51) from pre- to post-deployment/bTBI. Evidence was also suggestive of case-control differences, from pre- to post-deployment/bTBI for interleukin 1 alpha (IL-1α), interleukin 4 (IL-4), and interleukin 6 (IL-6) among moderate/severe cases.

Conclusion

The findings of this longitudinal study indicate that in the chronic phase of bTBI, levels of IL-8 and MMP3 may be substantially lower than pre-injury. These results need confirmation in other studies, potentially those that account for treatment differences, which was not possible in our study.

Elevated Serum Levels of Inflammation-Related Cytokines in Mild Traumatic Brain Injury Are Associated With Cognitive Performance

Mild traumatic brain injury (mTBI) is the most common neurological insult and leads to long-lasting cognitive impairments. The immune system modulates brain functions and plays a key role in cognitive deficits, however, the relationship between TBI-induced changes in inflammation-related cytokine levels and cognitive consequences is unclear. This was investigated in the present study in two cohorts of individuals within 1 week of mTBI (n = 52, n = 43) and 54 matched healthy control subjects. Patients with mTBI were also followed up at 1 and 3 months post-injury. Measures included cognitive assessments and a 9-plex panel of serum cytokines including interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10, IL-12, chemokine ligand 2 (CCL2), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α). The contribution of cytokine levels to cognitive function was evaluated by multivariate linear regression analysis. The results showed that serum levels of IL-1β, IL-6, and CCL2 were acutely elevated in mTBI patients relative to controls; CCL2 level was remained high over 3 months whereas IL-1β and IL-6 levels were declined by 3 months post-injury. A high level of CCL2 was associated with greater severity of post-concussion symptoms (which survived in the multiple testing correction); elevated IL-1β was associated with worse working memory in acute phase (which failed in correction); and acute high CCL2 level predicted higher information processing speed at 3 months post-injury (which failed in correction). Thus, acute serum cytokine levels are useful for evaluating post-concussion symptoms and predicting cognitive outcome in participants with mTBI.

Interleukin-1 in cerebrospinal fluid for evaluating the neurological outcome in traumatic brain injury

Objective Severe traumatic brain injury (TBI) is associated with unfavorable outcomes secondary to injury from activation of the inflammatory cascade, the release of excitotoxic neurotransmitters, and changes in the reactivity of cerebral vessels, causing ischemia. Inflammation induced by TBI is complex, individual-specific, and associated with morbidity and mortality. The aim of the present study was to discover the differentially expressed cerebrospinal fluid (CSF) proteins and identify which can improve the clinical outcomes in TBI patients.

Methods In the present study, we reported 145 patients with TBI and found the change in patients’ leukocytes in serum and interleukin-1 (IL-1) in CSF, which strongly correlated with the neurological outcome. In terms of results of leukocytes in blood and IL-1 in CSF, we retained the patient’s CSF specimens and conducted a proteomic analysis.

Results A total of 119 differentially expressed proteins were detected between samples of TBI and the normal, which were commonly expressed in all samples, indicating the differentially expressed proteins. When the patients’ Glasgow outcome score (GOS) improved, IL-1 was down-regulated, and when the patients’ GCS score deteriorated, IL-1 was up-regulated accompanied with the progression in TBI.

Conclusion The differentially expressed proteins in CSF may be the novel therapeutic targets for TBI treatment. The leukocytes in blood samples and the IL-1 in CSF may be two important indicators for predicting the prognosis of TBI patients.

A Repeated Measures Pilot Comparison of Trajectories of Fluctuating Endogenous Hormones in Young Women with Traumatic Brain Injury, Healthy Controls

Objective

To compare baseline and 72-hour hormone levels in women with traumatic brain injury (TBI) and controls.

Setting

Hospital emergency department.

Participants

21 women ages 18-35 with TBI and 21 controls.

Design

Repeated measures.

Main Measures

Serum samples at baseline and 72 hours; immunoassays for estradiol (E2), progesterone (PRO), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and cortisol (CORT); and health history.

Results

Women with TBI had lower E2 (p = 0.042) and higher CORT (p = 0.028) levels over time. Lower Glasgow Coma Scale (GSC) and OCs were associated with lower FSH (GCS p = 0.021; OCs p = 0.016) and higher CORT (GCS p = 0.001; OCs p = 0.008).

Conclusion

Acute TBI may suppress E2 and increase CORT in young women. OCs appeared to independently affect CORT and FSH responses. Future work is needed with a larger sample to characterize TBI effects on women's endogenous hormone response to injury and OC use's effects on post-TBI stress response and gonadal function, as well as secondary injury.

TBI Rehabilomics Research: Conceptualizing a humoral triad for designing effective rehabilitation interventions

Most areas of medicine use biomarkers in some capacity to aid in understanding how personal biology informs clinical care. This article draws upon the Rehabilomics research model as a translational framework for programs of precision rehabilitation and intervention research focused on linking personal biology to treatment response using biopsychosocial constructs that broadly represent function and that can be applied to many clinical populations with disability. The summary applies the Rehabilomics research framework to the population with traumatic brain injury (TBI) and emphasizes a broad vision for biomarker inclusion, beyond typical brain-derived biomarkers, to capture and/or reflect important neurological and non-neurological pathology associated with TBI as a chronic condition. Humoral signaling molecules are explored as important signaling and regulatory drivers of these chronic conditions and their impact on function. Importantly, secondary injury cascades involved in the humoral triad are influenced by the systemic response to TBI and the development of non-neurological organ dysfunction (NNOD). Biomarkers have been successfully leveraged in other medical fields to inform pre-randomization patient selection for clinical trials, however, this practice largely has not been utilized in TBI research. As such, the applicability of the Rehabilomics research model to contemporary clinical trials and comparative effectiveness research designs for neurological and rehabilitation populations is emphasized. Potential points of intervention to modify inflammation, hormonal, or neurotrophic support through rehabilitation interventions are discussed. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Systemic Estrone Production and Injury-Induced Sex Hormone Steroidogenesis after Severe Traumatic Brain Injury: A Prognostic Indicator of Traumatic Brain Injury-Related Mortality

Extensive pre-clinical studies suggest that sex steroids are neuroprotective in experimental traumatic brain injury (TBI). However, clinical trials involving sex hormone administration have not shown beneficial results, and our observational cohort studies show systemic estradiol (E2) production to be associated with adverse outcomes. Systemic E2 is produced via aromatization of testosterone (T) or reduction of estrone (E1). E1, also produced via aromatization of androstenedione (Andro) and is a marker of T-independent E2 production. We hypothesized that E1 would be (1) associated with TBI-related mortality, (2) the primary intermediate for E2 production, and (3) associated with adipose tissue-specific aromatase transcription. We assessed 100 subjects with severe TBI and 8 healthy controls. Serum levels were measured on days 0-3 post-TBI for key steroidogenic precursors (progesterone), aromatase pathway intermediates (E1, E2, T, Andro), and the adipose tissue-specific aromatase transcription factors cortisol, tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6). E1 was elevated after TBI versus controls. High E1 was associated with higher progesterone, cortisol, and IL-6 (p < 0.05). Multivariable logistic regression demonstrated that those in the highest E1 tertile had increased odds for mortality (adjusted OR = 5.656, 95% CI = 1.102-29.045, p = 0.038). Structural equation models show that early serum E2 production is largely T independent, occurring predominantly through E1 metabolism. Acute serum E1 functions as a mortality marker for TBI through aromatase-dependent E1 production and T-independent E2 production. Further work should evaluate risk factors for high E2 production and how systemic E2 and its key intermediate E1 contribute to the extracerebral consequences of severe TBI.

Inflammation Relates to Chronic Behavioral and Neurological Symptoms in Military Personnel with Traumatic Brain Injuries

Studies have shown that the presence of acute inflammation during recovery is indicative of poor outcomes after a traumatic brain injury (TBI); however, the role of chronic inflammation in predicting post-TBI-related symptoms remains poorly understood. The purpose of this study was to compare inflammatory biomarkers (tumor necrosis factor [TNF]-α, interleukin [IL]-6, and IL-10) in active duty personnel who either sustained or did not sustain a TBI. Service members were also assessed for post-traumatic stress disorder (PTSD), depression, and quality of life through self-reported measures. IL-6 and TNF-α concentrations were greater in the TBI group than in the control group. Of those with a TBI, IL-6 and TNF-α concentrations were greater in the high-PTSD group than the low-PTSD group. No significant differences were found in IL-10 or the IL-6/IL-10 ratios between those with low and high PTSD. Exploratory factor analysis was conducted to describe the latent structure of variables relating to emotional and physical health (i.e., Short Form 36 subcomponents, etc.) and their relationships within the TBI group with inflammatory cytokines. Four symptom profiles were found, with the third component most relating to PTSD and depression symptoms and high inflammation. This study indicates that the comorbidity of TBI and PTSD is associated with inflammation in a military sample, emphasizing the necessity for intervention in order to mitigate the risks associated with inflammation.

An investigation of neuroinjury biomarkers after sport-related concussion: from the subacute phase to clinical recovery

OBJECTIVES

To characterise a panel of neuroinjury-related blood biomarkers after sport-related concussion (SRC). We hypothesised significant differences in biomarker profiles between athletes with SRC and healthy controls at both subacute and medical clearance time points.

METHODS

Thirty-eight interuniversity athletes were recruited over two athletic seasons (n = 19 SRC; n = 19 healthy matched-control). High-sensitivity immunoassay was used to evaluate 11 blood analytes at both the subacute phase after SRC and at medical clearance.

RESULTS

Univariate analysis identified elevated circulating peroxiredoxin-6 (PRDX-6) in athletes with SRC compared to healthy controls at the subacute time point. Multivariate analyses yielded similar results in the subacute phase, but identified both PRDX-6 and T-tau as significant contributors to class separation between athletes with SRC and controls at medical clearance.

CONCLUSIONS

Our results are consistent with the increasing recognition that physiological recovery after SRC extends beyond clinical recovery. Blood biomarkers appear to be useful in elucidating the biology of brain restitution after SRC. However, their implementation requires mindfulness of factors such as academic stress, exercise, and injury heterogeneity.

Levels of Interleukin-1β, Interleukin-18, and Tumor Necrosis Factor-α in Cerebrospinal Fluid of Aneurysmal Subarachnoid Hemorrhage Patients May Be Predictors of Early Brain Injury and Clinical Prognosis

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) is a severe cerebrovascular accident with high morbidity and mortality. The aim of this study is to investigate the relationship between level of inflammatory cytokines in cerebrospinal fluid (CSF) of aSAH patients, the severity of aSAH, and the outcome of aSAH patients.

METHODS

aSAH patients were prospectively included and followed-up for 6 months. CSF samples were collected at 1-3, 4-6, and 7-9 days after aSAH onset. Levels of interleukin (IL)-1β, IL-18, and tumor necrosis factor-α (TNF-α) in the CSF of aSAH patients were measured by enzyme-linked immunosorbent assay.

RESULTS

Eighty-one aSAH patients were enrolled. The levels of IL-1β, IL-18 and TNF-α in the CSF were especially higher in the group of aSAH patients with cerebral edema, cerebral vasospasm, and a high grade on Hunt-Hess scale, the high World Federation of Neurological Surgeons grades, and Fisher grade (P < 0.01). Higher levels of plasma C-reactive protein in the blood were correlated with poor outcome. The areas under the receiver operating characteristic curves for the levels of inflammatory cytokines in CSF were 0.85, 0.84, and 0.95, respectively. Clinical features (age, Hunt-Hess grade, etc.) were positively correlated with poor outcomes (P < 0.05).

CONCLUSIONS

The levels of IL-1β, IL-18, and TNF-α in CSF were elevated in aSAH patients and were positively associated with cerebral edema and acute hydrocephalus. Our findings suggest that CSF inflammatory cytokines might be biomarkers to assess severity and predict outcomes.

Altered Neuroendocrine Immune Responses, a Two-Sword Weapon against Traumatic Inflammation

During the occurrence and development of injury (trauma, hemorrhagic shock, ischemia and hypoxia), the neuroendocrine and immune system act as a prominent navigation leader and possess an inter-system crosstalk between the reciprocal information dissemination. The fundamental reason that neuroendocrinology and immunology could mix each other and permeate toward the field of traumatology is owing to their same biological languages or chemical information molecules (hormones, neurotransmitters, neuropeptides, cytokines and their corresponding receptors) shared by the neuroendocrine and immune systems. The immune system is not only modulated by the neuroendocrine system, but also can modulate the biological functions of the neuroendocrine system. The interactive linkage of these three systems precipitates the complicated space-time patterns for the courses of traumatic inflammation. Recently, compelling evidence indicates that the network linkage pattern that initiating agents of neuroendocrine responses, regulatory elements of immune cells and effecter targets for immune regulatory molecules arouse the resistance mechanism disorders, which supplies the beneficial enlightenment for the diagnosis and therapy of traumatic complications from the view of translational medicine. Here we review the alternative protective and detrimental roles as well as possible mechanisms of the neuroendocrine immune responses in traumatic inflammation.

Moderate blast exposure results in increased IL-6 and TNFα in peripheral blood

A unique cohort of military personnel exposed to isolated blast was studied to explore acute peripheral cytokine levels, with the aim of identifying blast-specific biomarkers. Several cytokines, including interleukin (IL) 6, IL-10 and tumor necrosis factor alpha (TNFα) have been linked to pre-clinical blast exposure, but remained unstudied in clinical blast exposure. To address this gap, blood samples from 62 military personnel were obtained at baseline, and daily, during a 10-day blast-related training program; changes in the peripheral concentrations of IL-6, IL-10 and TNFα were evaluated using an ultrasensitive assay. Two groups of trainees were matched on age, duration of military service, and previous history of blast exposure(s), resulting in moderate blast cases and no/low blast controls. Blast exposures were measured using helmet sensors that determined the average peak pressure in pounds per square inch (psi). Moderate blast cases had significantly elevated concentrations of IL-6 (F_1,60=18.81, p<0.01) and TNFα (F_1,60=12.03, p<0.01) compared to no/low blast controls; levels rebounded to baseline levels the day after blast. On the day of the moderate blast exposure, the extent of the overpressure (psi) in those exposed correlated with IL-6 (r=0.46, p<0.05) concentrations. These findings indicate that moderate primary blast exposure results in changes, specifically acute and transient increases in peripheral inflammatory markers which may have implications for neuronal health.

Neurotrophy and immunomodulation of induced neural stem cell grafts in a mouse model of closed head injury

Closed head injury (CHI) usually results in severe and permanent neurological impairments, which are caused by several intertwined phenomena, such as cerebral edema, blood-brain barrier (BBB) disruption, neuronal loss, astroglial scarring and inflammation. We previously reported that induced neural stem cells (iNSCs), similar to neural stem cells (NSCs), can accelerate neurological recovery in vivo and produce neurotrophic factors in vitro. However, the effects of iNSC neurotrophy following CHI were not determined. Moreover, whether iNSCs have immunomodulatory properties is unknown. Mouse models of CHI were established using a standardized weight-drop device and assessed by neurological severity score (NSS). Although these models fail to mimic the complete spectrum of human CHI, they reproduce impairment in neurological function observed in clinical patients. Syngeneic iNSCs or NSCs were separately transplanted into the brains of CHI mice at 12h after CHI. Neurological impairment post-CHI was evaluated by several tests. Animals were sacrificed for morphological and molecular biological analyses. We discovered that iNSC administration promoted neurological functional recovery in CHI mice and reduced cerebral edema, BBB disruption, cell death and astroglial scarring following trauma. Implanted iNSCs could up-regulate brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) levels to support the survival of existing neurons after CHI. In addition, engrafted iNSCs decreased immune cell recruitment and pro-inflammatory cytokine expression in the brain post-injury. Moreover, we found significant nuclear factor-kappaB (NF-κB) inhibition in the presence of iNSC grafts. In short, iNSCs exert neurotrophic and immunomodulatory effects that mitigate CHI-induced neurological impairment.

Cerebrospinal Fluid and Microdialysis Cytokines in Severe Traumatic Brain Injury: A Scoping Systematic Review

Objective

To perform two scoping systematic reviews of the literature on cytokine measurement in: 1. cerebral microdialysis (CMD) and 2. cerebrospinal fluid (CSF) in severe traumatic brain injury (TBI) patients.

Methods

Two separate systematic reviews were conducted: one for CMD cytokines and the second for CSF cytokines. Both were conducted in severe TBI (sTBI) patients only.

Data sources

Articles from MEDLINE, BIOSIS, EMBASE, Global Health, Scopus, Cochrane Library (inception to October 2016), reference lists of relevant articles, and gray literature were searched.

Study selection

Two reviewers independently identified all manuscripts utilizing predefined inclusion/exclusion criteria. A two-tier filter of references was conducted.

Data extraction

Patient demographic and study data were extracted to tables.

Results

There were 19 studies identified describing the analysis of cytokines via CMD in 267 sTBI patients. Similarly, there were 32 studies identified describing the analysis of CSF cytokines in 1,363 sTBI patients. The two systematic reviews demonstrated: 1. limited literature available on CMD cytokine measurement in sTBI, with some preliminary data supporting feasibility of measurement and associations between cytokines and patient outcome. 2. Various CSF measured cytokines may be associated with patient outcome at 6–12 months, including interleukin (IL)-1b, IL-1ra, IL-6, IL-8, IL-10, and tumor necrosis factor 3. There is little to no literature in support of an association between CSF cytokines and neurophysiologic or tissue outcomes.

Conclusion

The evaluation of CMD and CSF cytokines is an emerging area of the literature in sTBI. Further, large prospective multicenter studies on cytokines in CMD and CSF need to be conducted.

Cerebrospinal Fluid Cortisol Mediates Brain-Derived Neurotrophic Factor Relationships to Mortality after Severe TBI: A Prospective Cohort Study

Distinct regulatory signaling mechanisms exist between cortisol and brain derived neurotrophic factor (BDNF) that may influence secondary injury cascades associated with traumatic brain injury (TBI) and predict outcome. We investigated concurrent CSF BDNF and cortisol relationships in 117 patients sampled days 0–6 after severe TBI while accounting for BDNF genetics and age. We also determined associations between CSF BDNF and cortisol with 6-month mortality. BDNF variants, rs6265 and rs7124442, were used to create a gene risk score (GRS) in reference to previously published hypothesized risk for mortality in “younger patients” (<48 years) and hypothesized BDNF production/secretion capacity with these variants. Group based trajectory analysis (TRAJ) was used to create two cortisol groups (high and low trajectories). A Bayesian estimation approach informed the mediation models. Results show CSF BDNF predicted patient cortisol TRAJ group (P = 0.001). Also, GRS moderated BDNF associations with cortisol TRAJ group. Additionally, cortisol TRAJ predicted 6-month mortality (P = 0.001). In a mediation analysis, BDNF predicted mortality, with cortisol acting as the mediator (P = 0.011), yielding a mediation percentage of 29.92%. Mediation effects increased to 45.45% among younger patients. A BDNF^*GRS interaction predicted mortality in younger patients (P = 0.004). Thus, we conclude 6-month mortality after severe TBI can be predicted through a mediation model with CSF cortisol and BDNF, suggesting a regulatory role for cortisol with BDNF's contribution to TBI pathophysiology and mortality, particularly among younger individuals with severe TBI. Based on the literature, cortisol modulated BDNF effects on mortality after TBI may be related to known hormone and neurotrophin relationships to neurological injury severity and autonomic nervous system imbalance.

Induced neural stem cells modulate microglia activation states via CXCL12/CXCR4 signaling

We previously reported that induced neural stem cells (iNSCs) directly reprogrammed from mouse embryonic fibroblasts can expand and differentiate into neurons, astrocytes and oligodendrocytes. Whether iNSCs have immunoregulatory properties in addition to facilitating cell replacement remains uncertain. In this study, we aimed to characterize the immunomodulatory effects of iNSCs on the activation states of microglia and to elucidate the mechanisms underlying these effects. Using a mouse model of closed head injury (CHI), we observed that iNSC grafts decreased the levels of ED1⁺/Iba1⁺ and TNF-α⁺/Iba1⁺ microglia but increased the levels of IGF1⁺/Iba1⁺ microglia in the injured cortex. Subsequently, using a Transwell co-culture system, we discovered that iNSCs could modulate LPS-pretreated microglia phenotypes in vitro via CXCL12/CXCR4 signaling, which we demonstrated through the administration of the CXCR4 antagonist AMD3100 and CXCR4-specific siRNA treatment. An in vivo loss-of-function study also revealed that iNSC grafts regulated the behavior of resident microglia via CXCL12/CXCR4 signaling, influencing their activation state such that they promoted neurological functional recovery and neuron survival. Furthermore, the beneficial effects of iNSC transplantation were significantly diminished by CXCR4 knockdown. In short, iNSCs have the potential to influence microglia activation and the acquisition of neuroprotective phenotypes via CXCL12/CXCR4 signaling.

Biomarkers of Traumatic Brain Injury: Temporal Changes in Body Fluids

Traumatic brain injuries (TBIs) are caused by a hit to the head or a sudden acceleration/deceleration movement of the head. Mild TBIs (mTBIs) and concussions are difficult to diagnose. Imaging techniques often fail to find alterations in the brain, and computed tomography exposes the patient to radiation. Brain-specific biomolecules that are released upon cellular damage serve as another means of diagnosing TBI and assessing the severity of injury. These biomarkers can be detected from samples of body fluids using laboratory tests. Dozens of TBI biomarkers have been studied, and research related to them is increasing. We reviewed the recent literature and selected 12 biomarkers relevant to rapid and accurate diagnostics of TBI for further evaluation. The objective was especially to get a view of the temporal profiles of the biomarkers’ rise and decline after a TBI event. Most biomarkers are rapidly elevated after injury, and they serve as diagnostics tools for some days. Some biomarkers are elevated for months after injury, although the literature on long-term biomarkers is scarce. Clinical utilization of TBI biomarkers is still at a very early phase despite years of active research.

Cross-Phenotype Polygenic Risk Score Analysis of Persistent Post-Concussive Symptoms in U.S. Army Soldiers with Deployment-Acquired Traumatic Brain Injury

Traumatic brain injury (TBI) contributes to the increased rates of suicide and post-traumatic stress disorder in military personnel and veterans, and it is also associated with the risk for neurodegenerative and psychiatric disorders. A cross-phenotype high-resolution polygenic risk score (PRS) analysis of persistent post-concussive symptoms (PCS) was conducted in 845 U.S. Army soldiers who sustained TBI during their deployment. We used a prospective longitudinal survey of three brigade combat teams to assess deployment-acquired TBI and persistent physical, cognitive, and emotional PCS. PRS was derived from summary statistics of large genome-wide association studies of Alzheimer's disease, Parkinson's disease, schizophrenia, bipolar disorder, and major depressive disorder (MDD); and for years of schooling, college completion, childhood intelligence, infant head circumference (IHC), and adult intracranial volume. Although our study had more than 95% of statistical power to detect moderate-to-large effect sizes, no association was observed with neurodegenerative and psychiatric disorders, suggesting that persistent PCS does not share genetic components with these traits to a moderate-to-large degree. We observed a significant finding: subjects with high IHC PRS recovered better from cognitive/emotional persistent PCS than the other individuals (R² = 1.11%; p = 3.37 × 10^-3). Enrichment analysis identified two significant Gene Ontology (GO) terms related to this result: GO:0050839∼Cell adhesion molecule binding (p = 8.9 × 10^-6) and GO:0050905∼Neuromuscular process (p = 9.8 × 10^-5). In summary, our study indicated that the genetic predisposition to persistent PCS after TBI does not have substantial overlap with neurodegenerative and psychiatric diseases, but mechanisms related to early brain growth may be involved.

Multivariate projection method to investigate inflammation associated with secondary insults and outcome after human traumatic brain injury: a pilot study

BACKGROUND

Neuroinflammation has been proposed as a possible mechanism of brain damage after traumatic brain injury (TBI), but no consensus has been reached on the most relevant molecules. Furthermore, secondary insults occurring after TBI contribute to worsen neurological outcome in addition to the primary injury. We hypothesized that after TBI, a specific pattern of cytokines is related to secondary insults and outcome.

METHODS

A prospective observational clinical study was performed. Secondary insults by computerized multimodality monitoring system and systemic value of different cytokines were collected and analysed in the first week after intensive care unit admission. Neurological outcome was assessed at 6 months (GOSe). Multivariate projection technique was applied to analyse major sources of variation and collinearity within the cytokines dataset without a priori selecting potential relevant molecules.

RESULTS

Twenty-nine severe traumatic brain injury patients undergoing intracranial pressure monitoring were studied. In this pilot study, we demonstrated that after TBI, patients who suffered of prolonged and severe secondary brain damage are characterised by a specific pattern of cytokines. Patients evolving to brain death exhibited higher levels of inflammatory mediators compared to both patients with favorable and unfavorable neurological outcome at 6 months. Raised ICP and low cerebral perfusion pressure occurred in 21 % of good monitoring time. Furthermore, the principal components selected by multivariate projection technique were powerful predictors of neurological outcome.

CONCLUSIONS

The multivariate projection method represents a valuable methodology to study neuroinflammation pattern occurring after secondary brain damage in severe TBI patients, overcoming multiple putative interactions between mediators and avoiding any subjective selection of relevant molecules.

Principal components derived from CSF inflammatory profiles predict outcome in survivors after severe traumatic brain injury

Studies have characterized absolute levels of multiple inflammatory markers as significant risk factors for poor outcomes after traumatic brain injury (TBI). However, inflammatory marker concentrations are highly inter-related, and production of one may result in the production or regulation of another. Therefore, a more comprehensive characterization of the inflammatory response post-TBI should consider relative levels of markers in the inflammatory pathway. We used principal component analysis (PCA) as a dimension-reduction technique to characterize the sets of markers that contribute independently to variability in cerebrospinal (CSF) inflammatory profiles after TBI. Using PCA results, we defined groups (or clusters) of individuals (n=111) with similar patterns of acute CSF inflammation that were then evaluated in the context of outcome and other relevant CSF and serum biomarkers collected days 0-3 and 4-5 post-injury. We identified four significant principal components (PC1-PC4) for CSF inflammation from days 0-3, and PC1 accounted for the greatest (31%) percentage of variance. PC1 was characterized by relatively higher CSF sICAM-1, sFAS, IL-10, IL-6, sVCAM-1, IL-5, and IL-8 levels. Cluster analysis then defined two distinct clusters, such that individuals in cluster 1 had highly positive PC1 scores and relatively higher levels of CSF cortisol, progesterone, estradiol, testosterone, brain derived neurotrophic factor (BDNF), and S100b; this group also had higher serum cortisol and lower serum BDNF. Multinomial logistic regression analyses showed that individuals in cluster 1 had a 10.9 times increased likelihood of GOS scores of 2/3 vs. 4/5 at 6 months compared to cluster 2, after controlling for covariates. Cluster group did not discriminate between mortality compared to GOS scores of 4/5 after controlling for age and other covariates. Cluster groupings also did not discriminate mortality or 12 month outcomes in multivariate models. PCA and cluster analysis establish that a subset of CSF inflammatory markers measured in days 0-3 post-TBI may distinguish individuals with poor 6-month outcome, and future studies should prospectively validate these findings. PCA of inflammatory mediators after TBI could aid in prognostication and in identifying patient subgroups for therapeutic interventions.

Inflammatory cytokine and chemokine profiles are associated with patient outcome and the hyperadrenergic state following acute brain injury

Background

Traumatic brain injury (TBI) elicits intense sympathetic nervous system (SNS) activation with profuse catecholamine secretion. The resultant hyperadrenergic state is linked to immunomodulation both within the brain and systemically. Dysregulated inflammation post-TBI exacerbates secondary brain injury and contributes to unfavorable patient outcomes including death. The aim of this study was to characterize the early dynamic profile of circulating inflammatory cytokines/chemokines in patients admitted for moderate-to-severe TBI, to examine interrelationships between these mediators and catecholamines, as well as clinical indices of injury severity and neurological outcome.

Methods

Blood was sampled from 166 isolated TBI patients (aged 45 ± 20.3 years; 74.7 % male) on admission, 6-, 12-, and 24-h post-injury and from healthy controls (N = 21). Plasma cytokine [interleukin (IL)-1β, -2, -4, -5, -10, -12p70, -13, tumor necrosis factor (TNF)-α, interferon (IFN)-γ] and chemokine [IL-8, eotaxin, eotaxin-3, IFN-γ-induced protein (IP)-10, monocyte chemoattractant protein (MCP)-1, -4, macrophage-derived chemokine (MDC), macrophage inflammatory protein (MIP)-1β, thymus activation regulated chemokine (TARC)] concentrations were analyzed using high-sensitivity electrochemiluminescence multiplex immunoassays. Plasma catecholamines [epinephrine (Epi), norepinephrine (NE)] were measured by immunoassay. Neurological outcome at 6 months was assessed using the extended Glasgow outcome scale (GOSE) dichotomized as good (>4) or poor (≤4) outcomes.

Results

Patients showed altered levels of IL-10 and all chemokines assayed relative to controls. Significant differences in a number of markers were evident between moderate and severe TBI cohorts. Elevated IL-8, IL-10, and TNF-α, as well as alterations in 8 of 9 chemokines, were associated with poor outcome at 6 months. Notably, a positive association was found between Epi and IL-1β, IL-10, Eotaxin, IL-8, and MCP-1. NE was positively associated with IL-1β, IL-10, TNF-α, eotaxin, IL-8, IP-10, and MCP-1.

Conclusions

Our results provide further evidence that exaggerated SNS activation acutely after isolated TBI in humans may contribute to harmful peripheral inflammatory cytokine/chemokine dysregulation. These findings are consistent with a potentially beneficial role for therapies aimed at modulating the inflammatory response and hyperadrenergic state acutely post-injury.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0500-3) contains supplementary material, which is available to authorized users.

Brain-Derived Neurotrophic Factor (BDNF) in Traumatic Brain Injury-Related Mortality: Interrelationships Between Genetics and Acute Systemic and Central Nervous System BDNF Profiles

BACKGROUND

Older adults have higher mortality rates after severe traumatic brain injury (TBI) compared to younger adults. Brain-derived neurotrophic factor (BDNF) signaling is altered in aging and is important to TBI given its role in neuronal survival/plasticity and autonomic function. Following experimental TBI, acute BDNF administration has not been efficacious. Clinically, genetic variation in BDNF (reduced signaling alleles: rs6265, Met-carriers; rs7124442, C-carriers) can be protective against acute mortality. Postacutely, these genotypes carry lower mortality risk in older adults and greater mortality risk among younger adults.

OBJECTIVE

Investigate BDNF levels in mortality/outcome following severe TBI in the context of age and genetic risk.

METHODS

Cerebrospinal fluid (CSF) and serum BDNF were assessed prospectively during the first week following severe TBI (n = 203) and in controls (n = 10). Age, BDNF genotype, and BDNF levels were assessed as mortality/outcome predictors.

RESULTS

CSF BDNF levels tended to be higher post-TBI (P = .061) versus controls and were associated with time until death (P = .042). In contrast, serum BDNF levels were reduced post-TBI versus controls (P < .0001). Both gene * BDNF serum and gene * age interactions were mortality predictors post-TBI in the same multivariate model. CSF and serum BDNF tended to be negatively correlated post-TBI (P = .07).

CONCLUSIONS

BDNF levels predicted mortality, in addition to gene * age interactions, suggesting levels capture additional mortality risk. Higher CSF BDNF post-TBI may be detrimental due to injury and age-related increases in pro-apoptotic BDNF target receptors. Negative CSF and serum BDNF correlations post-TBI suggest blood-brain barrier transit alterations. Understanding BDNF signaling in neuronal survival, plasticity, and autonomic function may inform treatment.

Pathophysiology and clinical management of moderate and severe traumatic brain injury in the ICU

Moderate and severe traumatic brain injury (TBI) is the leading cause of morbidity and mortality among young individuals in high-income countries. Its pathophysiology is divided into two major phases: the initial neuronal injury (or primary injury) followed by secondary insults (secondary injury). Multimodality monitoring now offers neurointensivists the ability to monitor multiple physiologic parameters that act as surrogates of brain ischemia and hypoxia, the major driving forces behind secondary brain injury. The heterogeneity of the pathophysiology of TBI makes it necessary to take into consideration these interacting physiologic factors when recommending for or against any therapies; it may also account for the failure of all the neuroprotective therapies studied so far. In this review, the authors focus on neuroclinicians and neurointensivists, and discuss the developments in therapeutic strategies aimed at optimizing intracranial pressure and cerebral perfusion pressure, and minimizing cerebral hypoxia. The management of moderate to severe TBI in the intensive care unit is moving away from a pure "threshold-based" treatment approach toward consideration of patient-specific characteristics, including the state of cerebral autoregulation. The authors also include a concise discussion on the management of medical and neurologic complications peculiar to TBI as well as an overview of prognostication.