Ana Rodríguez-Rodríguez

Melatonin: Buffering the Immune System

Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed.

Oxidative Stress in Traumatic Brain Injury

Traumatic brain injury (TBI) is a major healthcare concern, constituting a major cause of death and disability throughout the world. Among the factors leading to TBI outcome are biochemical cascades which occur in response to primary and secondary injury. These mechanisms generate oxidative stress, an imbalance between oxidant and antioxidant agents that can result in neural dysfunction and death. After TBI, an assembly of oxidative stress markers (carbonylated proteins, lipid peroxides, reactive oxygen and reactive nitrogen species) are produced in the brain, while antioxidant defense enzymes decrease (GSH, ratio GSH/GSSG, GPx, GR, GST, G-6PD, SOD, CAT). This imbalance is directly related to the pathogenesis of TBI. Therefore, the development of antioxidant strategies is of primary interest in ongoing efforts to optimize brain injury treatment. The success of any drug intervention strategy relies, in part, on knowledge of the optimal dosage and therapeutic window for its administration. But while the enzymes involved in oxidative stress have been identified, the temporal course of this imbalance following TBI has yet to be determined. This would explain why most antioxidant strategies developed to treat patients with TBI have failed.

Role of S100B protein in urine and serum as an early predictor of mortality after severe traumatic brain injury in adults

S100B is a calcium-binding protein released into the blood from astroglial cells due to brain injury. Some authors have described a correlation between S100B serum concentration and severity of brain damage. There is not much information about the accuracy of urinary S100B for predicting outcome after severe traumatic brain injury (TBI). 55 patients with severe TBI were included in the study. Blood and urine samples were drawn to determine S100B levels on admission and on the subsequent 24, 48, 72 and 96 h. S100B concentrations (serum and urine) were significantly higher in patients who were dead a month after the accident compared to survivors. ROC-analysis showed that S100B at 24h post-severe TBI is a useful tool for predicting mortality (serum: AUC 0.958, urine: AUC 0.778). The best cut-offs for S100B were 0.461 μg/L and 0.025 μg/L (serum and urine respectively), with a sensitivity of 90% for both measurements and a specificity of 88.4% (serum) and 62.8% (urine). We can state that the determination of S100B levels both in urine and serum acts as a sensitive and an effective biomarker for the early prediction of mortality after severe TBI.

S100B Protein May Detect Brain Death Development after Severe Traumatic Brain Injury

Despite improvements in the process of organ donation and transplants, the number of organ donors is progressively declining in developed countries. Therefore, the early detection of patients at risk for brain death (BD) is a priority for transplant teams seeking more efficient identification of potential donors. In the extensive literature on S100B as a biomarker for traumatic brain injury (TBI), no evidence appears to exist on its prognostic capacity as a predictor of BD after severe TBI. The objective of this study is to assess the value of including acute S100B levels in standard clinical data as an early screening tool for BD after severe TBI. This prospective study included patients with severe TBI (Glasgow Coma Scale score [GCS] ≤ 8) admitted to our Neurocritical Care Unit over a 30 month period. We collected the following clinical variables: age, gender, GCS score, pupillary alterations at admission, hypotension and pre-hospital desaturation, CT scan results, isolated TBI or other related injuries, Injury Severity Score (ISS), serum S100B levels at admission and 24 h post-admission, and a final diagnosis regarding BD. Of the 140 patients studied, 11.4% developed BD and showed significantly higher S100B concentrations (p<0.001). Multivariate analysis showed that bilateral unresponsive mydriasis at admission and serum S100B at 24 h post-admission had odds ratios (ORs) of 21.35 (p=0.005) and 4.9 (p=0.010), respectively. The same analysis on patients with photomotor reflex in one pupil at admission left only the 24 h S100B sample in the model (OR=15.5; p=0.009). Receiver operating characteristics (ROC) curve analysis on this group showed the highest area under the curve (AUC) (0.86; p=0.001) for 24 h S100B determinations. The cut off was set at 0.372 μg/L (85.7% sensitivity, 79.3% specificity, positive predictive value [PPV]=18.7% and negative predictive value [NPV]=98.9%). This study shows that pupillary responsiveness at admission, as well as 24 h serum S100B levels, could serve as screening tools for the early detection of patients at risk for BD after severe TBI.

Biomarkers of vasospasm development and outcome in aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a neurologic emergency caused by a brain aneurysm burst, resulting in a bleeding into the subarachnoid space. Its incidence is estimated between 4 and 28/10,000 inhabitants and it is the main cause of sudden death from stroke. The prognosis of patients with SAH is directly related to neurological status on admission, to the magnitude of the initial bleeding, as well as to the development of cerebral vasospasm (CVS). Numerous researchers have studied the role of different biomarkers in CVS development. These biomarkers form part of the metabolic cascade that is triggered as a result of the SAH. Hence, among these metabolites we found biomarkers of oxidative stress, inflammation biomarkers, indicators of brain damage, and markers of vascular pathology. However, to the author knowledge, none of these biomarkers has been demonstrated as a useful tool for predicting neither CVS development nor outcome after SAH. In order to reach success on future researches, firstly it should be stated which pathophysiological process is mainly responsible for CVS development. Once this process has been determined, the temporal course of this pathophysiologic cascade should be characterized, and then, perform further studies on biomarkers already analyzed, as well as on new biomarkers not yet studied in the SAH pathology, focusing attention on the temporal course of the diverse metabolites and the sampling time for its quantification.

S100B and Neuron-Specific Enolase as mortality predictors in patients with severe traumatic brain injury

Objective: To determine temporal profile and prognostic ability of S100B protein and neuron-specific enolase (NSE) for prediction of short/long-term mortality in patients suffering from severe traumatic brain injury (sTBI). Methods: Ninety-nine patients with sTBI were included in the study. Blood samples were drawn on admission and on subsequent 24, 48, 72, and 96 h. Results: 15.2% of patients died in NeuroCritical Care Unit, and 19.2% died within 6 months of the accident. S100B concentrations were significantly higher in patients who died compared to survivors. NSE levels were different between groups just at 48 h. In the survival group, S100B levels decreased from 1st to 5th sample (p < 0.001); NSE just from 1st to 3rd (p < 0.001) and then stabilized. Values of S100B and NSE in non-survival patients did not significantly vary over the four days post sTBI. ROC-analysis showed that all S100B samples were useful tools for predicting mortality, the best the 72 h sample (AUC 0.848 for discharge mortality, 0.855 for six-month mortality). NSE ROC-analysis indicated that just the 48-h sample predicted mortality (AUC 0.733 for discharge mortality, 0.720 for six-month mortality). Conclusion: S100B protein showed higher prognostic capacity than NSE to predict short/long-term mortality in sTBI patients.

Modelo experimental de lesión cerebral tipo masa en rata: expresión del daño cerebral mediante enolasa neuroespecífica y proteína S100B

OBJECTIVE To determine whether a model of transient mass-type brain damage (MTBD) in the rat produces early release of neurospecific enolase (NSE) and protein S100B in peripheral blood, as an expression of the induced brain injury. DESIGN An experimental study with a control group. SETTING Experimental operating room of the Institute of Biomedicine (IBiS) of Virgen del Rocío University Hospital (Seville, Spain). PARTICIPANTS Fourteen adult Wistar rats. INTERVENTIONS Blood was sampled at baseline, followed by: MTBD group, a trephine perforation was used to insert and inflate the balloon of a catheter at a rate of 500 μl/20 sec, followed by 4 blood extractions every 20 min. Control group, the same procedure as before was carried out, though without trephine perforation. PRIMARY STUDY VARIABLES Weight, early mortality, serum NSE and S100B concentration. RESULTS Differences in NSE and S100B concentration were observed over time within the MTBD group (P<.001), though not so in the control group. With the exception of the baseline determination, differences were observed between the two groups in terms of the mean NSE and S100B values. Following MTBD, NSE and S100B progressively increased at all measurement timepoints, with r=0.765; P=.001 and r=0.628; P=.001, respectively. In contrast, the control group showed no such correlation for either biomarker. CONCLUSIONS Serum NSE and S100B concentrations offer an early indication of brain injury affecting the gray and white matter in an experimental model of mass-type MTBD in the rat.

H-FABP: A new biomarker to differentiate between CT-positive and CT-negative patients with mild traumatic brain injury

The majority of patients with mild traumatic brain injury (mTBI) will have normal Glasgow coma scale (GCS) of 15. Furthermore, only 5%–8% of them will be CT-positive for an mTBI. Having a useful biomarker would help clinicians evaluate a patient’s risk of developing intracranial lesions. The S100B protein is currently the most studied and promising biomarker for this purpose. Heart fatty-acid binding protein (H-FABP) has been highlighted in brain injury models and investigated as a biomarker for stroke and severe TBI, for example. Here, we evaluate the performances of S100B and H-FABP for differentiating between CT-positive and CT-negative patients. A total of 261 patients with a GCS score of 15 and at least one clinical symptom of mTBI were recruited at three different European sites. Blood samples from 172 of them were collected ≤ 6 h after trauma. Patients underwent a CT scan and were dichotomised into CT-positive and CT-negative groups for statistical analyses. H-FABP and S100B levels were measured using commercial kits, and their capacities to detect all CT-positive scans were evaluated, with sensitivity set to 100%. For patients recruited ≤ 6 h after trauma, the CT-positive group demonstrated significantly higher levels of both H-FABP (p = 0.004) and S100B (p = 0.003) than the CT-negative group. At 100% sensitivity, specificity reached 6% (95% CI 2.8–10.7) for S100B and 29% (95% CI 21.4–37.1) for H-FABP. Similar results were obtained when including all the patients recruited, i.e. hospital arrival within 24 h of trauma onset. H-FABP out-performed S100B and thus seems to be an interesting protein for detecting all CT-positive mTBI patients with a GCS score of 15 and at least one clinical symptom.

Serologic behavior of S100B protein in patients who are brain dead: preliminary results.

OBJECTIVE The objective of this study is to assess the S100B protein serum concentrations from brain dead (BD) donors to understand whether its level could provide clinical information during BD diagnosis as a potential confirmatory test. METHODS During 12 months, 26 patients declared BD were prospectively included in this study. Once the diagnosis of BD was achieved, serum S100B protein levels were measured using an electrochemiluminescence assay. For analytical purposes, we selected the maximum S100B serum value reached during the first 5 days of evolution from a historical cohort of 124 survived patients after a severe brain injury (SBI), as well as from 18 healthy donors (HD) and a subgroup of patients who had severe traumatic brain injuries (TBIs) without extracranial injuries. RESULTS Mean age was 53.48 years (SD, 18.91 years). The BD group had significantly higher S100B serum levels (1.44 μg/L; interquartile ratio [IR], 0.63-3.68) than the SBI (0.34 μg/L; IR, 0.21-0.60) and HD groups (0.06 μg/L; IR, 0.03-0.07; P < .001). Analysis of S100B levels depending on the main cause responsible for BD development showed significant differences between subgroups (P = .012). S100B serum levels were higher in the isolated TBI BD group (P = .004). The S100B value showed an odds ratio for BD diagnosis of 8.38 (95% confidence interval [CI], 1.16-60.45; P = .035). Reciever operating characteristic analysis revealed an area under the curve of 0.92 (95% CI, 0.79-1.00; P = .007). We set a cut-off value of 2 μg/L in S100B serum concentrations. At this level, the diagnostic properties of S100B would reach 100% of specificity and positive predictive value (PPV), and sensitivity and negative predictive value (NPV) of 60% and 86.7%, respectively. CONCLUSION This preliminary analysis shows for the very first time that BD is associated with higher S100B serum levels, compared with other neurocritical care patients. We also found that the cause of BD development must be considered. Specifically, S100B serum levels in severe isolated TBI patients-with clinical exploration compatible with BD-could be used in a future as confirmatory test.

Serum brain injury biomarkers as predictors of mortality after severe aneurysmal subarachnoid hemorrhage: preliminary results

*Corresponding author: Zaida Ruiz de Azúa López, Virgen del Rocío University Hospital – Neurocritical Care Unit, Calle Marco Sancho número 26, Seville, Andalucia 41002, Spain, Phone: 340675669800, E-mail: zaida@azud.es; ruiz_azua_lopez_zaida@hotmail.com Juan José Egea-Guerrero, Gloria Rivera-Rubiales and Francisco Murillo-Cabezas: Virgen del Rocío University Hospital – Neurocritical Care Unit, Seville, Andalucia, Spain Ana Rodríguez-Rodríguez: University of Sevilla – IBIS/CSIC, Seville, Andalucia, Spain Ángel Vilches-Arenas: University of Seville – Department Preventive Medicine and Public Health, Seville, Andalucia, Spain Letter to the Editor