Synergistic induction of CXCL10 by interferon-gamma and lymphotoxin-alpha in astrocytes: Possible role in cerebral malaria.

Cerebral malaria (CM) has a high mortality rate and incidence of neurological sequelae in survivors. Hypoxia and cytokine expression in the brain are two mechanisms thought to contribute to the pathogenesis of CM. The cytokines interferon (IFN)-γ and lymphotoxin (LT)-α and the chemokine CXCL10 are essential for the development of CM in a mouse model. Furthermore, serum IFN-γ protein levels are higher in human CM than in controls, and CXCL10 is elevated in both serum and cerebrospinal fluid in Ghanaian paediatric CM cases. Astrocytes actively participate in CNS pathologies, becoming activated in response to various stimuli including cytokines. Astrocyte activation also occurs in murine and human CM. We here determined the responsiveness of mouse and human astrocytes to IFN-γ and LT-α, with the aim of further elucidating the role of astrocytes in CM pathogenesis. Initially we confirmed that Ifn-γ and Cxcl10 are expressed in the brain in murine CM, and that the increased Cxcl10 expression is IFN-γ-dependant. IFN-γ induced CXCL10 production in human and murine astrocytes in vitro. The degree of induction was increased synergistically in the presence of LT-α. IFN-γ induced the expression of receptors for LT-α, while LT-α increased the expression of the receptor for IFN-γ, in the astrocytes. This cross-induction may explain the synergistic effect of the two cytokines on CXCL10 production. Expression of these receptors also was upregulated in the brain in murine CM. The results suggest that astrocytes contribute to CM pathogenesis by producing CXCL10 in response to IFN-γ and LT-α.

Multicenter Evaluation of a 0-Hour/1-Hour Algorithm in the Diagnosis of Myocardial Infarction With High-Sensitivity Cardiac Troponin T.

STUDY OBJECTIVE: We aim to prospectively validate the diagnostic accuracy of the recently developed 0-h/1-h algorithm, using high-sensitivity cardiac troponin T (hs-cTnT) for the early rule-out and rule-in of acute myocardial infarction. METHODS: We enrolled patients presenting with suspected acute myocardial infarction and recent (<6 hours) onset of symptoms to the emergency department in a global multicenter diagnostic study. Hs-cTnT (Roche Diagnostics) and sensitive cardiac troponin I (Siemens Healthcare) were measured at presentation and after 1 hour, 2 hours, and 4 to 14 hours in a central laboratory. Patient triage according to the predefined hs-cTnT 0-hour/1-hour algorithm (hs-cTnT below 12 ng/L and Δ1 hour below 3 ng/L to rule out; hs-cTnT at least 52 ng/L or Δ1 hour at least 5 ng/L to rule in; remaining patients to the "observational zone") was compared against a centrally adjudicated final diagnosis by 2 independent cardiologists (reference standard). The final diagnosis was based on all available information, including coronary angiography and echocardiography results, follow-up data, and serial measurements of sensitive cardiac troponin I, whereas adjudicators remained blinded to hs-cTnT. RESULTS: Among 1,282 patients enrolled, acute myocardial infarction was the final diagnosis for 213 (16.6%) patients. Applying the hs-cTnT 0-hour/1-hour algorithm, 813 (63.4%) patients were classified as rule out, 184 (14.4%) were classified as rule in, and 285 (22.2%) were triaged to the observational zone. This resulted in a negative predictive value and sensitivity for acute myocardial infarction of 99.1% (95% confidence interval [CI] 98.2% to 99.7%) and 96.7% (95% CI 93.4% to 98.7%) in the rule-out zone (7 patients with false-negative results), a positive predictive value and specificity for acute myocardial infarction of 77.2% (95% CI 70.4% to 83.0%) and 96.1% (95% CI 94.7% to 97.2%) in the rule-in zone, and a prevalence of acute myocardial infarction of 22.5% in the observational zone. CONCLUSION: The hs-cTnT 0-hour/1-hour algorithm performs well for early rule-out and rule-in of acute myocardial infarction.

Symptoms Predictive of Acute Myocardial Infarction in the Troponin Era: Analysis From the TRAPID-AMI Study.

The TRAPID-AMI (High Sensitivity Cardiac Troponin T assay for rapid Rule-out of Acute Myocardial Infarction) study evaluated a rapid "rule-out" acute myocardial infarction (AMI). We evaluated what symptoms were associated with AMI as part of a substudy of TRAPID-AMI. There were 1282 patients evaluated from 12 centers in Europe, the United States of America, and Australia from 2011 to 2013. Multiple symptom variables were prospectively obtained and evaluated for association with the final diagnosis of AMI. Multivariate logistic regression analysis was done, and odds ratios (OR) were calculated. There were 213/1282 (17%) AMIs. Four independent predictors for the diagnosis of AMI were identified: radiation to right arm or shoulder [OR = 3.0; confidence interval (CI): 1.8-5.0], chest pressure (OR = 2.5; CI: 1.3-4.6), worsened by physical activity (OR = 1.7; CI: 1.2-2.5), and radiation to left arm or shoulder (OR = 1.7; CI: 1.1-2.4). In the entire group, 131 (10%) had radiation to right arm or shoulder, 897 (70%) had chest pressure, 385 (30%) worsened with physical activity, and 448 (35%) had radiation to left arm or shoulder. Duration of symptoms was not predictive of AMI. There were no symptoms predictive of non-AMI. Relationship between AMI size and symptoms was also studied. For 213 AMI patients, cardiac troponins I values were divided into 4 quartiles. Symptoms including pulling chest pain, supramammillary right location, and right arm/shoulder radiation were significantly more likely to occur in patients with larger AMIs. In a large multicenter trial, only 4 symptoms were associated with the diagnosis of AMI, and no symptoms that were associated with a non-AMI diagnosis.

Characterization of an indoleamine 2,3-dioxygenase-like protein found in humans and mice.

Indoleamine 2,3-dioxygenase (INDO) and tryptophan 2,3-dioxygenase (TDO) each catalyze the first step in the kynurenine pathway of tryptophan metabolism. We describe the discovery of another enzyme with this activity, indoleamine 2,3-dioxygenase-like protein (INDOL1), which is closely related to INDO and is expressed in mice and humans. The corresponding genes have a similar genomic structure and are situated adjacent to each other on human and mouse chromosome 8. They are likely to have arisen by gene duplication before the origin of the tetrapods. The expression of INDOL1 is highest in the mouse kidney, followed by epididymis, and liver. Expression of mouse INDOL1 was further localized to the tubular cells in the kidney and the spermatozoa. INDOL1 was assigned its name because of its structural similarity to INDO. We demonstrate that INDOL1 catalyses the conversion of tryptophan to kynurenine therefore a more appropriate nomenclature for the enzymes might be INDO-1 and INDO-2, or the more commonly-used abbreviations, IDO-1 and IDO-2. Although the two proteins have similar enzymatic activities, their different expression patterns within tissues and during malaria infection, suggests a distinct role for each protein. This identification of INDOL1 may help to explain the regulation of the diversity of physiological and patho-physiological processes in which the kynurenine pathway is involved.

Investigation of the Tissue Distribution and Physiological Roles of Indoleamine 2,3-Dioxygenase-2.

Indoleamine 2,3-dioxygenase-2 (IDO2) is 1 of the 3 enzymes that can catalyze the first step in the kynurenine pathway of tryptophan metabolism. Of the 2 other enzymes, tryptophan 2,3-dioxygenase is highly expressed in the liver and has a role in tryptophan homeostasis, whereas indoleamine 2,3-dioxygenase-1 (IDO1) expression is induced by inflammatory stimuli. Indoleamine 2,3-dioxygenase-2 is reportedly expressed comparatively narrow, including in liver, kidney, brain, and in certain immune cell types, and it does not appear to contribute significantly to systemic tryptophan catabolism under normal physiological conditions. Here, we report the identification of an alternative splicing pattern, including the use of an alternative first exon, that is conserved in the mouse Ido1 and Ido2 genes. These findings prompted us to assess IDO2 protein expression and enzymatic activity in tissues. Our analysis, undertaken in Ido2 +/+ and Ido2-/- mice using immunohistochemistry and measurement of tryptophan and kynurenine levels, suggested an even more restricted pattern of tissue expression than previously reported. We found IDO2 protein to be expressed in the liver with a perinuclear/nuclear, rather than cytoplasmic, distribution. Consistent with earlier reports, we found Ido2 -/- mice to be phenotypically similar to their Ido2+/+ counterparts regarding levels of tryptophan and kynurenine in the plasma and liver. Our findings suggest a specialized function or regulatory role for IDO2 associated with its particular subcellular localization.

Prognostic Utility of a Modified HEART Score in Chest Pain Patients in the Emergency Department.

BACKGROUND: The TRAPID-AMI trial study (High-Sensitivity Troponin-T Assay for Rapid Rule-Out of Acute Myocardial Infarction) evaluated high-sensitivity cardiac troponin-T (hs-cTnT) in a 1-hour acute myocardial infarction (AMI) exclusion algorithm. Our study objective was to evaluate the prognostic utility of a modified HEART score (m-HS) within this trial. METHODS AND RESULTS: Twelve centers evaluated 1282 patients in the emergency department for possible AMI from 2011 to 2013. Measurements of hs-cTnT (99th percentile, 14 ng/L) were performed at 0, 1, 2, and 4 to 14 hours. Evaluation for major adverse cardiac events (MACEs) occurred at 30 days (death or AMI). Low-risk patients had an m-HS≤3 and had either hs-cTnT<14 ng/L over serial testing or had AMI excluded by the 1-hour protocol. By the 1-hour protocol, 777 (60%) patients had an AMI excluded. Of those 777 patients, 515 (66.3%) patients had an m-HS≤3, with 1 (0.2%) patient having a MACE, and 262 (33.7%) patients had an m-HS≥4, with 6 (2.3%) patients having MACEs (P=0.007). Over 4 to 14 hours, 661 patients had a hs-cTnT<14 ng/L. Of those 661 patients, 413 (62.5%) patients had an m-HS≤3, with 1 (0.2%) patient having a MACE, and 248 (37.5%) patients had an m-HS≥4, with 5 (2.0%) patients having MACEs (P=0.03). CONCLUSIONS: Serial testing of hs-cTnT over 1 hour along with application of an m-HS identified a low-risk population that might be able to be directly discharged from the emergency department.

The Use of Very Low Concentrations of High-sensitivity Troponin T to Rule Out Acute Myocardial Infarction Using a Single Blood Test.

BACKGROUND: Recent single-center and retrospective studies suggest that acute myocardial infarction (AMI) could be immediately excluded without serial sampling in patients with initial high-sensitivity cardiac troponin T (hs-cTnT) levels below the limit of detection (LoD) of the assay and no electrocardiogram (ECG) ischemia. OBJECTIVE: We aimed to determine the external validity of those findings in a multicenter study at 12 sites in nine countries. METHODS: TRAPID-AMI was a prospective diagnostic cohort study including patients with suspected cardiac chest pain within 6 hours of peak symptoms. Blood drawn on arrival was centrally tested for hs-cTnT (Roche; 99th percentile = 14 ng/L, LoD = 5 ng/L). All patients underwent serial troponin sampling over 4-14 hours. The primary outcome, prevalent AMI, was adjudicated based on sensitive troponin I (Siemens Ultra) levels. Major adverse cardiac events (MACE) including AMI, death, or rehospitalization for acute coronary syndrome with coronary revascularization were determined after 30 days. RESULTS: We included 1,282 patients, of whom 213 (16.6%) had AMI and 231 (18.0%) developed MACE. Of 560 (43.7%) patients with initial hs-cTnT levels below the LoD, four (0.7%) had AMI. In total, 471 (36.7%) patients had both initial hs-cTnT levels below the LoD and no ECG ischemia. These patients had a 0.4% (n = 2) probability of AMI, giving 99.1% (95% confidence interval [CI] = 96.7% to 99.9%) sensitivity and 99.6% (95% CI = 98.5% to 100.0%) negative predictive value. The incidence of MACE in this group was 1.3% (95% CI = 0.5% to 2.8%). CONCLUSIONS: In the absence of ECG ischemia, the detection of very low concentrations of hs-cTnT at admission seems to allow rapid, safe exclusion of AMI in one-third of patients without serial sampling. This could be used alongside careful clinical assessment to help reduce unnecessary hospital admissions.

Brain gene expression, metabolism, and bioenergetics: interrelationships in murine models of cerebral and noncerebral malaria.

Malaria infection can cause cerebral symptoms without parasite invasion of brain tissue. We examined the relationships between brain biochemistry, bioenergetics, and gene expression in murine models of cerebral (Plasmodium berghei ANKA) and noncerebral (P. berghei K173) malaria using multinuclear NMR spectroscopy, neuropharmacological approaches, and real-time RT-PCR. In cerebral malaria caused by P. berghei ANKA infection, we found biochemical changes consistent with increased glutamatergic activity and decreased flux through the Krebs cycle, followed by increased production of the hypoxia markers lactate and alanine. This was accompanied by compromised brain bioenergetics. There were few significant changes in expression of mRNA for metabolic enzymes or transporters or in the rate of transport of glutamate or glucose. However, in keeping with a role for endogenous cytokines in malaria cerebral pathology, there was significant up-regulation of mRNAs for TNF-alpha, interferon-gamma, and lymphotoxin. These changes are consistent with a state of cytopathic hypoxia. By contrast, in P. berghei K173 infection the brain showed increased metabolic rate, with no deleterious effect on bioenergetics. This was accompanied by mild up-regulation of expression of metabolic enzymes. These changes are consistent with benign hypermetabolism whose cause remains a subject of speculation.

A literature review of the feasibility of glial fibrillary acidic protein as a biomarker for stroke and traumatic brain injury.

Traumatic brain injuries (TBIs) are potentially lethal medical conditions, with symptoms that can overlap with symptoms of injuries outside the brain. In many cases, current diagnostic methods do not fully distinguish acute brain injury from other organ damage. In the management of stroke patients, the choice of treatment depends on whether the stroke is ischemic or hemorrhagic; however, no quick lab diagnostic tests are available to distinguish between the two types of strokes. As a result, patient triage, disposition, and patient management decisions may be delayed for patients with suspected TBI and stroke. Glial fibrillary acidic protein (GFAP), a brain-specific biomarker that is released into the blood following TBI and stroke, is being explored for potential diagnostic and prognostic value in these indications. We therefore conducted a review of MEDLINE-indexed publications from 2004 to 2011 to evaluate the current status of GFAP as a prognostic and diagnostic tool for TBI and stroke within the context of current published guidelines. Our review suggests that GFAP could provide clinically valuable information for the prognosis of TBI and stroke, but it is still at an early stage of development as a biomarker. Several TBI studies have shown elevated GFAP levels following a TBI event to be associated with greater severity of injury, poorer outcomes, and increased mortality. Clinical studies also indicate that GFAP has potential clinical utility in the differential diagnosis of various types of stroke. However, more clinical research will be required to determine the ability of GFAP levels to diagnose TBI in heterogeneous patient populations, as well as the ability of GFAP to differentiate between ischemic stroke (IS), intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), and non-stroke conditions in populations of patients with suspected rather than confirmed stroke. Additional clinical studies will also be required to define the temporal patterns of GFAP release in IS, ICH, SAH, and TBI, and their potential use in the differential diagnosis of these conditions. Finally, such research could demonstrate the ability of GFAP test results to provide unique clinical information that informs management decisions for TBI and stroke patients.

Indoleamine 2,3-dioxygenase-2; a new enzyme in the kynurenine pathway.

The kynurenine pathway of tryptophan metabolism converts the amino acid tryptophan into a number of biologically active metabolites. The first and rate-limiting step in this pathway is the conversion of tryptophan to N-formylkynurenine and until recently this reaction was thought to be performed by either of two enzymes, tryptophan 2,3-dioxygenase and indoleamine 2,3-dioxygenase. A third enzyme, indoleamine 2,3-dioxygenase-2, indoleamine 2,3-dioxygenase-like protein or proto-indoleamine 2,3-dioxygenase (IDO2, IDO-2, INDOL1 or proto-IDO), with this activity recently has been described. The gene encoding IDO2 is adjacent and structurally similar to the indoleamine 2,3-dioxygenase gene and both mouse genes use multiple promoters to express transcripts with alternate 5' exons. The IDO2 protein is expressed in the murine kidney, liver, male and female reproductive system. The two IDO enzymes can utilise a similar range of substrates, however they differ in their selectivity for some inhibitors. The selective inhibition of IDO2 by 1-methyl-D-tryptophan suggests that IDO2 activity may have a role in the inhibition of immune responses to tumours.

Interferon-gamma synergises with tumour necrosis factor and lymphotoxin-alpha to enhance the mRNA and protein expression of adhesion molecules in mouse brain endothelial cells.

Changes to the cerebral microvasculature are evident during cerebral malaria (CM). Activation of the endothelium is likely to be due to the actions of cytokines, circulating levels of which are elevated during CM. Endothelial cells are known to up-regulate the expression of cellular adhesion molecules, which can lead to cellular sequestration and obstruction of vessels. However, it is unknown whether cytokines synergise in the up-regulation of the adhesion molecules involved in CM. In this study, the mRNA and/or protein expression of the adhesion molecules vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), P-selectin and E-Selectin were examined in a mouse brain endothelial cell line. Endothelial cells were stimulated with interferon-gamma (IFN-gamma), tumour necrosis factor (TNF) and lymphotoxin-alpha (LT-alpha), alone or in combination. The expression of ICAM-1, VCAM-1, P-selectin and E-Selectin mRNA in mouse brain endothelial cells by TNF and/or LT-alpha was found to be significantly enhanced in the presence of IFN-gamma. The same synergistic effect was found when analyzing ICAM-1 protein expression in cytokine stimulated mouse brain endothelial cells. The findings show that cytokines can synergise to influence gene expression and protein expression in a mouse brain endothelial cell line.