Phase Ib dose-escalation study of the hypoxia-modifier myo-inositol trispyrophosphate in patients with hepatopancreatobiliary tumors

Objective

Hypoxia is present in most solid tumors and acts as a driver of malignancy. Myo-inositol trispyrophosphate (ITPP) is a novel re-oxygenating compound without apparent toxicity. In preclinical models, it potentiates the efficacy of subsequent chemotherapy through vascular normalization. We sought to assess the safety, tolerability, and preliminary efficacy of ITPP.

Methods

In this monocentric, open-label, dose-escalation study following a 3+3 design, eligible patients with advanced primary and secondary hepatopancreatobiliary tumors received nine 8-h infusions of ITPP during 3 weeks across eight dose levels (1866–14,500 mg/m2/dose), followed by standard chemotherapy. Primary endpoints were safety and tolerability. Secondary endpoints were pharmacokinetics and estimation of efficacy based on radiological responses and angiogenic serum markers. Registration number: NCT02528526.

Results

From April 2015 to July 2018, a total of 28 enrolled patients were assessed for the primary endpoints. ITPP was safe up to single doses of 12,390 mg/m2, and 32 ITPP-related adverse events occurred: 19 (67.8%) hypercalcemia, 5 (17.8%) hyponatremia, and 4 (14.2%) hypomagnesemia. Following ITPP monotherapy, 52% of patients displayed morphological disease stabilization. Following subsequent chemotherapy, 10% showed a partial response, and 60% had stable disease. Angiogenic markers were decreased in 60% after ITPP and tended to correlate with responses and survival after chemotherapy.

Conclusion

Administration of ITPP is safe up to 12,390 mg/m2 with favorable pharmacokinetics. Preliminary translational efficacy data show decreased angiogenic markers, which might indicate an anti-hypoxic effect and enhancement of chemotherapy through ITPP.

Efficacy of Retreatment After Failed Direct-acting Antiviral Therapy in Patients With HCV Genotype 1-3 Infections

Hepatitis C virus infection is causing chronic liver disease, cirrhosis, and hepatocellular carcinoma. By combining direct-acting antivirals (DAAs), high sustained virologic response rates (SVRs) can be achieved. Resistance-associated substitutions (RASs) are commonly observed after DAA failure, and especially nonstructural protein 5A (NS5A) RASs may impact retreatment options.^1-3 Data on retreatment of DAA failure patients using first-generation DAAs are limited.^4-7 Recently, a second-generation protease- and NS5A-inhibitor plus sofosbuvir (voxilaprevir/velpatasvir/sofosbuvir [VOX/VEL/SOF]) was approved for retreatment after DAA failure.⁸ However, this and other second-generation regimens are not available in many resource-limited countries or are not reimbursed by regular insurance, and recommendations regarding the selection of retreatment regimens using first-generation DAAs are very important. This study aimed to analyze patients who were re-treated with first-generation DAAs after failure of a DAA combination therapy.

Different pharmaceutical preparations of Δ9 -tetrahydrocannabinol differentially affect its behavioral effects in rats

Based on the contribution of the endocannabinoid system to the pathophysiology of schizophrenia, the primary pro-psychotic ingredient of Cannabis sativa, Δ-9-tetrahydrocannabinol (Δ-9-THC), is used in preclinical as well as clinical research to mimic schizophrenia-like symptoms. While it is common to administer lipid-based formulations of Δ-9-THC in human studies orally, intraperitoneal injections of water-based solutions are used in animal models. Because of the poor water solubility of Δ-9-THC, solubilizers such as ethanol and/or emulsifiers are needed for these preparations. In order to test whether a lipid-based solvent would be superior over a water-based vehicle in rats, we compared the effects on locomotor activity and prepulse inhibition (PPI) of the acoustic startle reaction, as well as pharmacokinetic data obtained from rats' serum and brain tissue samples. Up to 50 mg/kg Δ-9-THC in the lipid-based formulation was not able to induce any behavioral alterations, while already 5 mg/kg of the water-based Δ-9-THC preparation significantly reduced locomotor activity. This also induced a small but significant PPI reduction, which was prepulse intensity dependent. Interestingly, the reflexive motor response to the startle stimulus was not affected by the water-based Δ-9-THC solution. Analysis of serum and brain Δ-9-THC levels by high-performance liquid chromatography/mass spectrometry revealed that although the final concentration reached in the brain was comparable for both pharmaceutical preparations, the water-based formulation achieved a faster kinetic. We, therefore, conclude that the slope of the Δ-9-THC concentration-time curve and the resulting cannabinoid receptor type 1 activation per time unit are responsible for the induction of behavioral alterations.

Early blood-brain barrier dysfunction predicts neurological outcome following aneurysmal subarachnoid hemorrhage

BACKGROUND

Disease progression and delayed neurological complications are common after aneurysmal subarachnoid hemorrhage (aSAH). We explored the potential of quantitative blood-brain barrier (BBB) imaging to predict disease progression and neurological outcome.

METHODS

Data were collected as part of the Co-Operative Studies of Brain Injury Depolarizations (COSBID). We analyzed retrospectively, blinded and semi-automatically magnetic resonance images from 124 aSAH patients scanned at 4 time points (24-48 h, 6-8 days, 12-15 days and 6-12 months) after the initial hemorrhage. Volume of brain with apparent pathology and/or BBB dysfunction (BBBD), subarachnoid space and lateral ventricles were measured. Neurological status on admission was assessed using the World Federation of Neurosurgical Societies and Rosen-Macdonald scores. Outcome at ≥6 months was assessed using the extended Glasgow outcome scale and disease course (progressive or non-progressive based on imaging-detected loss of normal brain tissue in consecutive scans). Logistic regression was used to define biomarkers that best predict outcomes. Receiver operating characteristic analysis was performed to assess accuracy of outcome prediction models.

FINDINGS

In the present cohort, 63% of patients had progressive and 37% non-progressive disease course. Progressive course was associated with worse outcome at ≥6 months (sensitivity of 98% and specificity of 97%). Brain volume with BBBD was significantly larger in patients with progressive course already 24-48 h after admission (2.23 (1.23-3.17) folds, median with 95%CI), and persisted at all time points. The highest probability of a BBB-disrupted voxel to become pathological was found at a distance of ≤1 cm from the brain with apparent pathology (0·284 (0·122-0·594), p < 0·001, median with 95%CI). A multivariate logistic regression model revealed power for BBBD in combination with RMS at 24-48 h in predicting outcome (ROC area under the curve = 0·829, p < 0·001).

INTERPRETATION

We suggest that early identification of BBBD may serve as a key predictive biomarker for neurological outcome in aSAH. FUND: Dr. Dreier was supported by grants from the Deutsche Forschungsgemeinschaft (DFG) (DFG DR 323/5-1 and DFG DR 323/10-1), the Bundesministerium für Bildung und Forschung (BMBF) Center for Stroke Research Berlin 01 EO 0801 and FP7 no 602150 CENTER-TBI. Dr. Friedman was supported by grants from Israel Science Foundation and Canada Institute for Health Research (CIHR). Dr. Friedman was supported by grants from European Union's Seventh Framework Program (FP7/2007-2013; grant #602102).

Abstract P3-01-07: Enabling HER2 and androgen receptor (AR) protein expression and localization in circulating tumor cells (CTCs) of ER(+/-)HER2(-) metastatic breast cancer (MBC) patients (pts)

Background:

Upregulation of HER2 and AR are mechanisms of acquired resistance to endocrine therapy, and are being investigated as treatment-guiding biomarkers. However, measurement of these proteins and their localization requires metastatic biopsies, which are costly, invasive, and prone to under-sampling which limits their utility to guide treatment in late stage metastatic patients. A CTC-based test could expand the clinical utility of these biomarkers. Here we utilized the Epic Sciences CTC platform for CTC detection and characterization. MBC blood samples were characterized for CTC prevalence, HER2 and AR expression at time of disease progression.

Material and methods:

HER2 and AR expression levels were determined based on model cell lines. A total of 72 blood samples were acquired from ER(+/-)/HER2(-) patients (by standard tissue pathology) at disease progression. 72 samples were analyzed for HER2 and 64 were analyzed for AR using the Epic Platform. Single-cell whole genome sequencing was performed to assess clonality and inter-patient heterogeneity of CTCs detected.

Results:

55/72 (76.4%) of patients had CTCs detected across two slides. 13/72 (18.1%) had at least one HER2(+) CTC, 14/64 (21.9%) had at least one AR(+) CTC, and 7/64 (10.9%) had at both AR(+) and HER2(+) CTCs detected on replicate slides. HER2 expression on individual CTCs showed distinctive cytoplasmic membrane staining, and AR expression on individual CTCs showed frequent nuclear localization. Most patient samples showed heterogeneous expression of these markers at disease progression indicating subclonal sensitivity to targeted therapies. Subsequently, these cells will be individually sequenced to better determine the clonality of resistance.

Conclusions:

CTCs are detected in most MBC pts upon disease progression, with expression of known endocrine therapy resistance markers, HER2 and AR, observed that CTCs could guide subsequent therapy selection. Prospective evaluation of HER2 and AR on MBC pts' CTCs as predictive biomarkers of benefit from inhibitors of these proteins is needed.

Citation Format: Ontiveros P, Landaverde C, Graf R, Levin MK, Hippely S, Wang Y, Landers M, Dittamore R, O'Shaughnessy JA. Enabling HER2 and androgen receptor (AR) protein expression and localization in circulating tumor cells (CTCs) of ER(+/-)HER2(-) metastatic breast cancer (MBC) patients (pts) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-01-07.

Exocrine pancreas glutamate secretion help to sustain enterocyte nutritional needs under protein restriction

Glutamine (Gln) is the most concentrated amino acid in blood and considered conditionally essential. Its requirement is increased during physiological stress, such as malnutrition or illness, despite its production by muscle and other organs. In the malnourished state, Gln has been suggested to have a trophic effect on the exocrine pancreas and small intestine. However, the Gln transport capacity, the functional relationship of these two organs, and the potential role of the Gln-glutamate (Glu) cycle are unknown. We observed that pancreatic acinar cells express lower levels of Glu than Gln transporters. Consistent with this expression pattern, the rate of Glu influx into acinar cells was approximately sixfold lower than that of Gln. During protein restriction, acinar cell glutaminase expression was increased and Gln accumulation was maintained. Moreover, Glu secretion by acinar cells into pancreatic juice and thus into the lumen of the small intestine was maintained. In the intestinal lumen, Glu absorption was preserved and Glu dehydrogenase expression was augmented, potentially providing the substrates for increasing energy production via the TCA cycle. Our findings suggest that one mechanism by which Gln exerts a positive effect on exocrine pancreas and small intestine involves the Gln metabolism in acinar cells and the secretion of Glu into the small intestine lumen. The exocrine pancreas acinar cells not only avidly accumulate Gln but metabolize Gln to generate energy and to synthesize Glu for secretion in the pancreatic juice. Secreted Glu is suggested to play an important role during malnourishment in sustaining small intestinal homeostasis. NEW & NOTEWORTHY Glutamine (Gln) has been suggested to have a trophic effect on exocrine pancreas and small intestine in malnourished states, but the mechanism is unknown. In this study, we suggest that this trophic effect derives from an interorgan relationship between exocrine pancreas and small intestine for Gln-glutamate (Glu) utilization involving the uptake and metabolism of Gln in acinar cells and secretion of Glu into the lumen of the small intestine.

Hip Sonography: 20 Years Experience and Results

Hip sonography in the “Graf technique” is an important tool to detect early DDH cases and dysplastic hips in the German speaking countries, although hip sonography is still controversially discussed in the English speaking countries. The reason may be different techniques with different classification and outcome. Exact anatomical identification, measurement technique, typing, difference between instability and elasticity with a reproducible “standard plane” is absolutely necessary to make hip ultrasound (US) comparable and reliable.

US screening had reduced open reductions in Germany to 1:4000, in Austria to 0.23 per thousand. Because of the early screening and earlier less aggressive treatment, the overall costs could be reduced by 1/3 in comparison to the pre-ultrasound area.

US screening seems to prevent many, but not all operations and can be recommended as an important tool for prevention.

Standard-sampling microdialysis and spreading depolarizations in patients with malignant hemispheric stroke

Spreading depolarizations (SD) occur in high frequency in patients with malignant hemispheric stroke (MHS). Experimentally, SDs cause marked increases in glutamate and lactate, whereas glucose decreases. Here, we studied extracellular brain glutamate, glucose, lactate, pyruvate and the lactate/pyruvate ratio in relationship to SDs after MHS. We inserted two microdialysis probes in peri-infarct tissue at 5 and 15 mm to the infarct in close proximity to a subdural electrode strip. During 2356.6 monitoring hours, electrocorticography (ECoG) revealed 697 SDs in 16 of 18 patients. Ninety-nine SDs in electrically active tissue (spreading depressions, SD_d) were single (SD_ds) and 485 clustered (SD_dc), whereas 10 SDs with at least one electrode in electrically inactive tissue (isoelectric SDs, SD_i) were single (SD_is) and 103 clustered (SD_ic). More SDs and a significant number of clustered SDs occurred during the first 36 h post-surgery when glutamate was significantly elevated (> 100 µM). In a grouped analysis, we observed minor glutamate elevations with more than two SDs per hour. Glucose slightly decreased during SD_ic at 5 mm from the infarct. Directions of SD-related metabolic changes correspond to the experimental setting but the long sampling time of standard microdialysis precludes a more adequate account of the dynamics revealed by ECoG.

Recording, analysis, and interpretation of spreading depolarizations in neurointensive care: Review and recommendations of the COSBID research group

Spreading depolarizations (SD) are waves of abrupt, near-complete breakdown of neuronal transmembrane ion gradients, are the largest possible pathophysiologic disruption of viable cerebral gray matter, and are a crucial mechanism of lesion development. Spreading depolarizations are increasingly recorded during multimodal neuromonitoring in neurocritical care as a causal biomarker providing a diagnostic summary measure of metabolic failure and excitotoxic injury. Focal ischemia causes spreading depolarization within minutes. Further spreading depolarizations arise for hours to days due to energy supply-demand mismatch in viable tissue. Spreading depolarizations exacerbate neuronal injury through prolonged ionic breakdown and spreading depolarization-related hypoperfusion (spreading ischemia). Local duration of the depolarization indicates local tissue energy status and risk of injury. Regional electrocorticographic monitoring affords even remote detection of injury because spreading depolarizations propagate widely from ischemic or metabolically stressed zones; characteristic patterns, including temporal clusters of spreading depolarizations and persistent depression of spontaneous cortical activity, can be recognized and quantified. Here, we describe the experimental basis for interpreting these patterns and illustrate their translation to human disease. We further provide consensus recommendations for electrocorticographic methods to record, classify, and score spreading depolarizations and associated spreading depressions. These methods offer distinct advantages over other neuromonitoring modalities and allow for future refinement through less invasive and more automated approaches.

Large field-of-view movement-compensated intrinsic optical signal imaging for the characterization of the haemodynamic response to spreading depolarizations in large gyrencephalic brains

Haemodynamic responses to spreading depolarizations (SDs) have an important role during the development of secondary brain damage. Characterization of the haemodynamic responses in larger brains, however, is difficult due to movement artefacts. Intrinsic optical signal (IOS) imaging, laser speckle flowmetry (LSF) and electrocorticography were performed in different configurations in three groups of in total 18 swine. SDs were elicited by topical application of KCl or occurred spontaneously after middle cerebral artery occlusion. Movement artefacts in IOS were compensated by an elastic registration algorithm during post-processing. Using movement-compensated IOS, we were able to differentiate between four components of optical changes, corresponding closely with haemodynamic variations measured by LSF. Compared with ECoG and LSF, our setup provides higher spatial and temporal resolution, as well as a better signal-to-noise ratio. Using IOS alone, we could identify the different zones of infarction in a large gyrencephalic middle cerebral artery occlusion pig model. We strongly suggest movement-compensated IOS for the investigation of the role of haemodynamic responses to SDs during the development of secondary brain damage and in particular to examine the effect of potential therapeutic interventions in gyrencephalic brains.

The continuum of spreading depolarizations in acute cortical lesion development: Examining Leão's legacy

A modern understanding of how cerebral cortical lesions develop after acute brain injury is based on Aristides Leão's historic discoveries of spreading depression and asphyxial/anoxic depolarization. Treated as separate entities for decades, we now appreciate that these events define a continuum of spreading mass depolarizations, a concept that is central to understanding their pathologic effects. Within minutes of acute severe ischemia, the onset of persistent depolarization triggers the breakdown of ion homeostasis and development of cytotoxic edema. These persistent changes are diagnosed as diffusion restriction in magnetic resonance imaging and define the ischemic core. In delayed lesion growth, transient spreading depolarizations arise spontaneously in the ischemic penumbra and induce further persistent depolarization and excitotoxic damage, progressively expanding the ischemic core. The causal role of these waves in lesion development has been proven by real-time monitoring of electrophysiology, blood flow, and cytotoxic edema. The spreading depolarization continuum further applies to other models of acute cortical lesions, suggesting that it is a universal principle of cortical lesion development. These pathophysiologic concepts establish a working hypothesis for translation to human disease, where complex patterns of depolarizations are observed in acute brain injury and appear to mediate and signal ongoing secondary damage.

Local adaptation (mostly) remains local: reassessing environmental associations of climate-related candidate SNPs in Arabidopsis halleri

Numerous landscape genomic studies have identified single-nucleotide polymorphisms (SNPs) and genes potentially involved in local adaptation. Rarely, it has been explicitly evaluated whether these environmental associations also hold true beyond the populations studied. We tested whether putatively adaptive SNPs in Arabidopsis halleri (Brassicaceae), characterized in a previous study investigating local adaptation to a highly heterogeneous environment, show the same environmental associations in an independent, geographically enlarged set of 18 populations. We analysed new SNP data of 444 plants with the same methodology (partial Mantel tests, PMTs) as in the original study and additionally with a latent factor mixed model (LFMM) approach. Of the 74 candidate SNPs, 41% (PMTs) and 51% (LFMM) were associated with environmental factors in the independent data set. However, only 5% (PMTs) and 15% (LFMM) of the associations showed the same environment-allele relationships as in the original study. In total, we found 11 genes (31%) containing the same association in the original and independent data set. These can be considered prime candidate genes for environmental adaptation at a broader geographical scale. Our results suggest that selection pressures in highly heterogeneous alpine environments vary locally and signatures of selection are likely to be population-specific. Thus, genotype-by-environment interactions underlying adaptation are more heterogeneous and complex than is often assumed, which might represent a problem when testing for adaptation at specific loci.

Regulation of cerebral metabolism during cortical spreading depression

We analyzed the metabolic response to cortical spreading depression that drastically increases local energy demand to restore ion homeostasis. During single and multiple cortical spreading depressions in the rat cortex, we simultaneously monitored extracellular levels of glucose and lactate using rapid sampling microdialysis and glucose influx using 18 F-fluorodeoxyglucose positron emission tomography while tracking cortical spreading depression using laser speckle imaging. Combining the acquired data with steady-state requirements we developed a mass-conserving compartment model including neurons and glia that was consistent with the observed data. In summary, our findings are: (1) Early breakdown of glial glycogen provides a major source of energy during increased energy demand and leaves 80% of blood-borne glucose to neurons. (2) Lactate is used solely by neurons and only if extracellular lactate levels are >80% above normal. (3) Although the ratio of oxygen and glucose consumption transiently reaches levels <3, the major part (>90%) of the overall energy supply is from oxidative metabolism. (4) During cortical spreading depression, brain release of lactate exceeds its consumption suggesting that lactate is only a circumstantial energy substrate. Our findings provide a general scenario for the metabolic response to increased cerebral energy demand.

The Functional Networks of Prepulse Inhibition: Neuronal Connectivity Analysis Based on FDG-PET in Awake and Unrestrained Rats

Prepulse inhibition (PPI) is a neuropsychological process during which a weak sensory stimulus (“prepulse”) attenuates the motor response (“startle reaction”) to a subsequent strong startling stimulus. It is measured as a surrogate marker of sensorimotor gating in patients suffering from neuropsychological diseases such as schizophrenia, as well as in corresponding animal models. A variety of studies has shown that PPI of the acoustical startle reaction comprises three brain circuitries for: (i) startle mediation, (ii) PPI mediation, and (iii) modulation of PPI mediation. While anatomical connections and information flow in the startle and PPI mediation pathways are well known, spatial and temporal interactions of the numerous regions involved in PPI modulation are incompletely understood. We therefore combined [¹⁸F]fluoro-2-deoxyglucose positron-emission-tomography (FDG-PET) with PPI and resting state control paradigms in awake rats. A battery of subtractive, correlative as well as seed-based functional connectivity analyses revealed a default mode-like network (DMN) active during resting state only. Furthermore, two functional networks were observed during PPI: Metabolic activity in the lateral circuitry was positively correlated with PPI effectiveness and involved the auditory system and emotional regions. The medial network was negatively correlated with PPI effectiveness, i.e., associated with startle, and recruited a spatial/cognitive network. Our study provides evidence for two distinct neuronal networks, whose continuous interplay determines PPI effectiveness in rats, probably by either protecting the prepulse or facilitating startle processing. Discovering similar networks affected in neuropsychological disorders may help to better understand mechanisms of sensorimotor gating deficits and provide new perspectives for therapeutic strategies.

Transcranial direct current stimulation accelerates recovery of function, induces neurogenesis and recruits oligodendrocyte precursors in a rat model of stroke

BACKGROUND

Clinical data suggest that transcranial direct current stimulation (tDCS) may be used to facilitate rehabilitation after stroke. However, data are inconsistent and the neurobiological mechanisms underlying tDCS remain poorly explored, impeding its implementation into clinical routine. In the healthy rat brain, tDCS affects neural stem cells (NSC) and microglia. We here investigated whether tDCS applied after stroke also beneficially affects these cells, which are known to be involved in regeneration and repair.

METHODS

Focal cerebral ischemia was induced in rats by transient occlusion of the middle cerebral artery. Twenty-eight animals with comparable infarcts, as judged by magnetic resonance imaging, were randomized to receive a multi-session paradigm of either cathodal, anodal, or sham tDCS. Behaviorally, recovery of motor function was assessed by Catwalk. Proliferation in the NSC niches was monitored by Positron-Emission-Tomography (PET) employing the radiotracer 3'-deoxy-3'-[(18)F]fluoro-l-thymidine ([(18)F]FLT). Microglia activation was depicted with [(11)C]PK11195-PET. In addition, immunohistochemical analyses were used to quantify neuroblasts, oligodendrocyte precursors, and activation and polarization of microglia.

RESULTS

Anodal and cathodal tDCS both accelerated functional recovery, though affecting different aspects of motor function. Likewise, tDCS induced neurogenesis independently of polarity, while only cathodal tDCS recruited oligodendrocyte precursors towards the lesion. Moreover, cathodal stimulation preferably supported M1-polarization of microglia.

CONCLUSIONS

TDCS acts through multifaceted mechanisms that far exceed its primary neurophysiological effects, encompassing proliferation and migration of stem cells, their neuronal differentiation, and modulation of microglia responses.

Glucose consumption of inflammatory cells masks metabolic deficits in the brain

Inflammatory cells such as microglia need energy to exert their functions and to maintain their cellular integrity and membrane potential. Subsequent to cerebral ischemia, inflammatory cells infiltrate tissue with limited blood flow where neurons and astrocytes died due to insufficient supply with oxygen and glucose. Using dual tracer positron emission tomography (PET), we found that concomitant with the presence of inflammatory cells, transport and consumption of glucose increased up to normal levels but returned to pathological levels as soon as inflammatory cells disappeared. Thus, inflammatory cells established sufficient glucose supply to satisfy their energy demands even in regions with insufficient supply for neurons and astrocytes to survive. Our data suggest that neurons and astrocytes died from oxygen deficiency and inflammatory cells metabolized glucose non-oxidatively in regions with residual availability. As a consequence, glucose metabolism of inflammatory cells can mask metabolic deficits in neurodegenerative diseases. We further found that the PET tracer did not bind to inflammatory cells in severely hypoperfused regions and thus only a part of the inflammation was detected. We conclude that glucose consumption of inflammatory cells should be taken into account when analyzing disease-related alterations of local cerebral metabolism.

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Inflammatory cells consume high amounts of glucose in supply-limited brain regions.

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Glucose metabolism of inflammatory cells masks metabolic deficits in the brain.

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In vivo markers only reach inflammatory cells in regions with residual blood supply.

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Measuring inflammation and metabolism provide complementary information.

Transcranial direct current stimulation in the male mouse to promote recovery after stroke

Transcranial direct current stimulation (tDCS) constitutes a promising approach for promoting recovery of function after stroke, although the underlying neurobiological mechanisms are unclear. To conduct translational research in animal models, stimulation parameters should not lead to neuronal lesions. Liebetanz et al. recommend charge densities for cathodal stimulation in rats, but parameters for mice are not established. We established tDCS in the wild-type mouse, enabling studies with genetically-engineered mice (GEM). tDCS equipment was adapted to fit the mouse skull. Using different polarities and charge densities, tDCS was safe to apply in the mouse where the charge density was below 198 kC/m(2) for single or repeated stimulations. These findings are crucial for future investigations of the neurobiological mechanisms underlying tDCS using GEM.

Magnetic separation-based blood purification: a promising new approach for the removal of disease-causing compounds?

Recent studies report promising results regarding extracorporeal magnetic separation-based blood purification for the rapid and selective removal of disease-causing compounds from whole blood. High molecular weight compounds, bacteria and cells can be eliminated from blood within minutes, hence offering novel treatment strategies for the management of intoxications and blood stream infections. However, risks associated with incomplete particle separation and the biological consequences of particles entering circulation remain largely unclear. This article discusses the promising future of magnetic separation-based purification while keeping important safety considerations in mind.

The synthetic NCAM mimetic peptide FGL mobilizes neural stem cells in vitro and in vivo

The neural cell adhesion molecule (NCAM) plays a role in neurite outgrowth, synaptogenesis, and neuronal differentiation. The NCAM mimetic peptide FG Loop (FGL) promotes neuronal survival in vitro and enhances spatial learning and memory in rats. We here investigated the effects of FGL on neural stem cells (NSC) in vitro and in vivo. In vitro, cell proliferation of primary NSC was assessed after exposure to various concentrations of NCAM or FGL. The differentiation potential of NCAM- or FGL-treated cells was assessed immunocytochemically. To investigate its influence on endogenous NSC in vivo, FGL was injected subcutaneously into adult rats. The effects on NSC mobilization were studied both via non-invasive positron emission tomography (PET) imaging using the tracer [(18)F]-fluoro-L-thymidine ([(18)F]FLT), as well as with immunohistochemistry. Only FGL significantly enhanced NSC proliferation in vitro, with a maximal effect at 10 μg/ml. During differentiation, NCAM promoted neurogenesis, while FGL induced an oligodendroglial phenotype; astrocytic differentiation was neither affected by NCAM or FGL. Those differential effects of NCAM and FGL on differentiation were mediated through different receptors. After FGL-injection in vivo, proliferative activity of NSC in the subventricular zone (SVZ) was increased (compared to placebo-treated animals). Moreover, non-invasive imaging of cell proliferation using [(18)F]FLT-PET supported an FGL-induced mobilization of NSC from both the SVZ and the hippocampus. We conclude that FGL robustly induces NSC mobilization in vitro and in vivo, and supports oligodendroglial differentiation. This capacity renders FGL a promising agent to facilitate remyelinization, which may eventually make FGL a drug candidate for demyelinating neurological disorders.

Aromatic-turmerone induces neural stem cell proliferation in vitro and in vivo

Introduction

Aromatic (ar-) turmerone is a major bioactive compound of the herb Curcuma longa. It has been suggested that ar-turmerone inhibits microglia activation, a property that may be useful in treating neurodegenerative disease. Furthermore, the effects of ar-turmerone on neural stem cells (NSCs) remain to be investigated.

Methods

We exposed primary fetal rat NSCs to various concentrations of ar-turmerone. Thereafter, cell proliferation and differentiation potential were assessed. In vivo, naïve rats were treated with a single intracerebroventricular (i.c.v.) injection of ar-turmerone. Proliferative activity of endogenous NSCs was assessed in vivo, by using noninvasive positron emission tomography (PET) imaging and the tracer [¹⁸F]-fluoro-L-thymidine ([¹⁸F]FLT), as well as ex vivo.

Results

In vitro, ar-turmerone increased dose-dependently the number of cultured NSCs, because of an increase in NSC proliferation (P < 0.01). Proliferation data were supported by qPCR-data for Ki-67 mRNA. In vitro as well as in vivo, ar-turmerone promoted neuronal differentiation of NSCs. In vivo, after i.c.v. injection of ar-turmerone, proliferating NSCs were mobilized from the subventricular zone (SVZ) and the hippocampus of adult rats, as demonstrated by both [¹⁸F]FLT-PET and histology (P < 0.05).

Conclusions

Both in vitro and in vivo data suggest that ar-turmerone induces NSC proliferation. Ar-turmerone thus constitutes a promising candidate to support regeneration in neurologic disease.

Detecting tissue deterioration after brain injury: regional blood flow level versus capacity to raise blood flow

Regional cerebral blood flow (rCBF) is spatially and temporally adjusted to local energy needs. This coupling involves dilation of vessels both at the site of metabolite exchange and upstream of the activated region. Deficits in upstream blood supply limit the 'capacity to raise rCBF' in response to functional activation and therefore compromise brain function. We here demonstrate in rats that the 'capacity to raise rCBF' can be determined from real-time measurements of rCBF using laser speckle imaging during an energy challenge induced by cortical spreading depolarizations (CSDs). Cortical spreading depolarizations (CSDs) occur with high incidence in stroke and various other brain injuries and cause large metabolic changes. Various conditions of cerebral perfusion were induced, either by modifying microvascular tone, or by altering upstream blood supply independently. The increase in rCBF per unit of time in response to CSD was linearly correlated to the upstream blood supply. In an experimental model of stroke, we found that this marker of the capacity to raise rCBF which, in pathologic tissue may be additionally limited by impaired vasoactive signaling, was a better indicator of the functional status of cerebral tissue than local rCBF levels.

In-vivo detection of inflammation and neurodegeneration in the chronic phase after permanent embolic stroke in rats

Neuroinflammation with microglia activation (MA) constitutes a key tissue response in acute stroke. Until now, its course in the chronic stage is less well defined. Here, we investigated (i) neuroinflammation in the chronic stage of a rat model of embolic stroke (n=6), and (ii) whether this process can be visualized in vivo by multimodal imaging using Magnetic Resonance Imaging (MRI) and Positron-Emission-Tomography (PET). Imaging data were verified using histology and immunohistochemistry. Repetitive PET studies until week 6 after stroke reveal poststroke inflammation as a dynamic process that involved the infarct, the surrounding tissue and secondary degenerating areas in a complex fashion. At the end, 7 months after stroke, neuroinflammation had almost completely vanished at the lesion side. In contrast, remote from the primarily infarcted areas, a marked T2(*)- hypointensity was detected in the ipsilateral thalamus. In the corresponding area, [(11)C]PK11195-PET detected microglia activation. Immunohistochemistry confirmed activated microglia in the ipsilateral thalamus with signs of extensive phagocytosis and iron deposition around plaque-like amyloid deposition. Neuronal staining (NeuN) revealed pronounced neuronal loss as an endpoint of neurodegeneration in these areas. In conclusion, the data demonstrate not only ongoing thalamic neuroinflammation but also marked neurodegeneration remote from the lesion site in the chronic phase after stroke in rats. Both, neuroinflammation and neurodegeneration were accessible to (immuno-) histochemical methods as well as to in vivo methods using [(11)C]PK11195-PET and T2(*)-weighted MRI. Although the functional roles of these dynamic processes remain to be elucidated, ongoing destruction of neuronal tissue is conceivable. Its inhibition using anti-inflammatory substances may be beneficial in chronic post-stroke conditions, while multimodal imaging can be used to evaluate putative therapeutic effects in vivo.

Neural correlates of sensorimotor gating: a metabolic positron emission tomography study in awake rats

Impaired sensorimotor gating occurs in neuropsychiatric disorders such as schizophrenia and can be measured using the prepulse inhibition (PPI) paradigm of the acoustic startle response. This assay is frequently used to validate animal models of neuropsychiatric disorders and to explore the therapeutic potential of new drugs. The underlying neural network of PPI has been extensively studied with invasive methods and genetic modifications. However, its relevance for healthy untreated animals and the functional interplay between startle- and PPI-related areas during a PPI session is so far unknown. Therefore, we studied awake rats in a PPI paradigm, startle control and background noise control, combined with behavioral [(18)F]fluoro-2-deoxyglucose positron emission tomography (FDG-PET). Subtractive analyses between conditions were used to identify brain regions involved in startle and PPI processing in well-hearing Black hooded rats. For correlative analysis with regard to the amount of PPI we also included hearing-impaired Lister hooded rats that startled more often, because their hearing threshold was just below the lowest prepulses. Metabolic imaging showed that the brain areas proposed for startle and PPI mediation are active during PPI paradigms in healthy untreated rats. More importantly, we show for the first time that the whole PPI modulation network is active during "passive" PPI sessions, where no selective attention to prepulse or startle stimulus is required. We conclude that this reflects ongoing monitoring of stimulus significance and constant adjustment of sensorimotor gating.

Device for simultaneous positron emission tomography, laser speckle imaging and RGB reflectometry: validation and application to cortical spreading depression and brain ischemia in rats

Brain function critically relies on the supply with energy substrates (oxygen and glucose) via blood flow. Alterations in energy demand as during neuronal activation induce dynamic changes in substrate fluxes and blood flow. To study the complex system that regulates cerebral metabolism requires the combination of methods for the simultaneous assessment of multiple parameters. We developed a multimodal imaging device to combine positron emission tomography (PET) with laser speckle imaging (LSI) and RGB reflectometry (RGBR). Depending on the radiotracer, PET provides 3-dimensional quantitative information of specific molecular processes, while LSI and RGBR measure cerebral blood flow (CBF) and hemoglobin oxygenation at high temporal and spatial resolution. We first tested the functional capability of each modality within our system and showed that interference between the modalities is negligible. We then cross-calibrated the system by simultaneously measuring absolute CBF using (15)O-H2O PET (CBF(PET)) and the inverse correlation time (ICT), the LSI surrogate for CBF. ICT and CBF(PET) correlated in multiple measurements in individuals as well as across different animals (R(2)=0.87, n=44 measurements) indicating that ICT can be used for absolute quantitative assessment of CBF. To demonstrate the potential of the combined system, we applied it to cortical spreading depression (CSD), a wave of transient cellular depolarization that served here as a model system for neurovascular and neurometabolic coupling. We analyzed time courses of hemoglobin oxygenation and CBF alterations coupled to CSD, and simultaneously measured regional uptake of (18)F-2-fluoro-2-deoxy-D-glucose ((18)F-FDG) used as a radiotracer for regional glucose metabolism, in response to a single CSD and to a cluster of CSD waves. With this unique combination, we characterized the changes in cerebral metabolic rate of oxygen (CMRO2) in real-time and showed a correlation between (18)F-FDG uptake and the number of CSD waves that passed the local tissue. Finally, we examined CSD spontaneously occurring during focal ischemia also referred to as peri-infarct depolarization (PID). In the vicinity of the ischemic territory, we observed PIDs that were characterized by reduced CMRO2 and increased oxygen extraction fraction (OEF), indicating a limitation of oxygen supply. Simultaneously measured PET showed an increased (18)F-FDG uptake in these regions. Our combined system proved to be a novel tool for the simultaneous study of dynamic spatiotemporal alterations of cortical blood flow, oxygen metabolism and glucose consumption under normal and pathologic conditions.

Isoflurane suppresses cortical spreading depolarizations compared to propofol--implications for sedation of neurocritical care patients

Sedatives in the neurointensive care unit can strongly influence patients' risks of developing secondary brain damage. In particular, isoflurane, a volatile anesthetic, has been recently re-introduced to the neurointensive care unit, and first clinical studies suggest beneficial effects due to elevation of cerebral blood flow and reduction of metabolism. In contrast, propofol is a commonly used intravenous sedative that reduces cerebral blood flow and intra-cranial pressure. We have here studied the influence of these two sedatives on the occurrence of cortical spreading depolarizations (CSDs), which have emerged over the last decade as a major mechanism of delayed brain injury in stroke and brain trauma, constituting a substantial vascular and metabolic threat to peri-infarct tissue and being associated with poor patient outcome. Two experimental models were tested in Wistar rats anesthetized either with isoflurane or with propofol: KCl-evoked CSDs (n=10) and spontaneous CSDs after occlusion of the middle cerebral artery (n=14). Spatiotemporal patterns of CSD waves were observed by real-time laser speckle imaging of regional cerebral blood flow changes associated with the CSDs. During 30 min of cortical KCl application, 5.2±0.7 CSDs were induced under isoflurane compared to 10.2±1.8 CSDs under propofol (p<0.001). After focal ischemia, 2.43±1.0 CSDs/h emerged spontaneously under isoflurane versus 6.83±2.5 CSDs/h under propofol (p<0.001). Furthermore, baseline blood flow and glycemia were much higher under isoflurane compared to propofol, which may set the tissue in better metabolic conditions to recover from the occurrence of CSD waves. We conclude that isoflurane, in comparison to propofol, decreases the occurrence of CSDs and may improve recovery from these metabolically demanding waves. To reduce CSD induced secondary tissue damage, we suggest isoflurane to be favored over propofol to sedate acute stroke and trauma patients in the neurointensive care unit.

Intrafraction variations in linac-based image-guided radiosurgery of intracranial lesions

PURPOSE

This study investigated image-guided patient positioning during frameless, mask-based, single-fraction stereotactic radiosurgery of intracranial lesions and intrafractional translational and rotational variations in patient positions.

PATIENTS AND METHODS

A non-invasive head and neck thermoplastic mask was used for immobilization. The Exactrac/Novalis Body system (BrainLAB AG, Germany) was used for kV X-ray imaging guided positioning. Intrafraction displacement data, obtained by imaging after each new table position, were evaluated.

RESULTS

There were 269 radiosurgery treatments performed on 190 patients and a total of 967 setups within different angles. The first measured error after each table rotation (mean 2.6) was evaluated (698 measurements). Intrafraction translational errors were (1 standard deviation [SD]) on average 0.8, 0.8, and 0.7mm for the left-right, superior-inferior, and anterior-posterior directions, respectively, with a mean 3D-vector of 1.0mm (SD 0.9mm) and a range from -5mm to +5mm. On average, 12%, 3%, and 1% of the translational deviations exceeded 1, 2, and 3mm, respectively, in the three directions.

CONCLUSION

The range of intrafraction patient motion in frameless image-guided stereotactic radiosurgery is often not fully mapped by pre- and post-treatment imaging. In the current study, intrafraction motion was assessed by performing measurements at several time points during the course of stereotactic radiosurgery. It was determined that 12% of the intrafraction values in the three dimensions are above 1mm, the usual safety margin applied in stereotactic radiosurgery.

Continuous online microdialysis using microfluidic sensors: dynamic neurometabolic changes during spreading depolarization

Microfluidic glucose biosensors and potassium ion selective electrodes were used in an in vivo study to measure the neurochemical effects of spreading depolarizations (SD), which have been shown to be detrimental to the injured human brain. A microdialysis probe implanted in the cortex of rats was connected to a microfluidic PDMS chip containing the sensors. The dialysate was also analyzed using our gold standard, rapid sampling microdialysis (rsMD). The glucose biosensor performance was validated against rsMD with excellent results. The glucose biosensors successfully monitored concentration changes, in response to SD wave induction, in the range of 10-400 μM with a second time-resolution. The data show that during a SD wave, there is a time delay of 62 ± 24.8 s (n = 4) between the onset of the increase in potassium and the decrease in glucose. This delay can be for the first time demonstrated, thanks to the high-temporal resolution of the microfluidic sensors sampling from a single tissue site (the microdialysis probe), and it indicates that the decrease in glucose is due to the high demand of energy required for repolarization.

Lithium prevents early cytosolic calcium increase and secondary injurious calcium overload in glycolytically inhibited endothelial cells

Cytosolic free calcium concentration ([Ca(2+)]i) is a central signalling element for the maintenance of endothelial barrier function. Under physiological conditions, it is controlled within narrow limits. Metabolic inhibition during ischemia/reperfusion, however, induces [Ca(2+)]i overload, which results in barrier failure. In a model of cultured porcine aortic endothelial monolayers (EC), we addressed the question of whether [Ca(2+)]i overload can be prevented by lithium treatment. [Ca(2+)]i and ATP were analysed using Fura-2 and HPLC, respectively. The combined inhibition of glycolytic and mitochondrial ATP synthesis by 2-desoxy-d-glucose (5mM; 2-DG) plus sodium cyanide (5mM; NaCN) caused a significant decrease in cellular ATP content (14±1 nmol/mg protein vs. 18±1 nmol/mg protein in the control, n=6 culture dishes, P<0.05), an increase in [Ca(2+)]i (278±24 nM vs. 71±2 nM in the control, n=60 cells, P<0.05), and the formation of gaps between adjacent EC. These observations indicate that there is impaired barrier function at an early state of metabolic inhibition. Glycolytic inhibition alone by 10mM 2-DG led to a similar decrease in ATP content (14±2 nmol/mg vs. 18±1 nmol/mg in the control, P<0.05) with a delay of 5 min. The [Ca(2+)]i response of EC was biphasic with a peak after 1 min (183±6 nM vs. 71±1 nM, n=60 cells, P<0.05) followed by a sustained increase in [Ca(2+)]i. A 24-h pre-treatment with 10mM of lithium chloride before the inhibition of ATP synthesis abolished both phases of the 2-DG-induced [Ca(2+)]i increase. This effect was not observed when lithium chloride was added simultaneously with 2-DG. We conclude that lithium chloride abolishes the injurious [Ca(2+)]i overload in EC and that this most likely occurs by preventing inositol 3-phosphate-sensitive Ca(2+)-release from the endoplasmic reticulum. Though further research is needed, these findings provide a novel option for therapeutic strategies to protect the endothelium against imminent barrier failure.

Propagation of cortical spreading depolarization in the human cortex after malignant stroke

OBJECTIVE

To investigate hemodynamic response pattern and spatiotemporal propagation of cortical spreading depolarization in the peri-infarct region of malignant hemispheric stroke.

METHODS

In this prospective observational case study we used intraoperative laser speckle technology to measure cerebral blood flow in patients with malignant hemispheric stroke. Additionally, postoperative occurrence of cortical spreading depolarization was monitored using a subdural recording strip for electrocorticography and infarct progression was assessed by serial MRI.

RESULTS

In 7 of 20 patients, 19 blood flow changes typical of cortical spreading depolarizations occurred during a 20-minute period. Thirteen events were characterized by increase, 2 by biphasic response, and 4 by decrease of blood flow. Propagation velocity ranged from 1.7 to 9.2 mm/min and propagation area from 0.1 to 4.8 cm(2). Intrinsic optical signal alterations preceded and low-frequency vascular fluctuations were suppressed during the hemodynamic responses. A mean number of 56 ± 82 cortical spreading depolarizations per patient was recorded and a mean infarct progression of 30 ± 13 cm(3) was detected in 5 of 7 patients.

CONCLUSIONS

We visualize the spatiotemporal propagation of spreading depolarizations in the human cerebral cortex intraoperatively. In patients with focal ischemia, multiple cortical spreading depolarizations with either hyperemic or hypoemic flow responses occurred. Our data suggest that, in patients with focal ischemia, cortical spreading depolarizations are associated with both unfavorable and protective hemodynamic responses.

Simultaneous imaging of cortical blood flow and haemoglobin concentration with LASCA and RGB reflectometry

We demonstrate a system for the simultaneous imaging of cortical blood flow and haemoglobin oxygenation by laser speckle contrast analysis (LASCA) and RGB reflectometry. The sensitivity of the system was tested by observing changes of haemoglobin oxygenation and blood flow in rats in response to ischaemic stroke, hypercapnia, hyperoxia, hypoxia, cortical spreading depression and cortical activation following forepaw stimulation.