Effect of ischemic cerebral volume changes on behavior

Microglial TNFR2 signaling regulates the inflammatory response after CNS injury in a sex-specific fashion

Microglia, the resident immune cells of the central nervous system (CNS), play a major role in damage progression and tissue remodeling after acute CNS injury, including ischemic stroke (IS) and spinal cord injury (SCI). Understanding the molecular mechanisms regulating microglial responses to injury may thus reveal novel therapeutic targets to promote CNS repair. Here, we investigated the role of microglial tumor necrosis factor receptor 2 (TNFR2), a transmembrane receptor previously associated with pro-survival and neuroprotective responses, in shaping the neuroinflammatory environment after CNS injury. By inducing experimental IS and SCI in Cx3cr1CreER:Tnfrsf1bfl/fl mice, selectively lacking TNFR2 in microglia, and corresponding Tnfrsf1bfl/fl littermate controls, we found that ablation of microglial TNFR2 significantly reduces lesion size and pro-inflammatory cytokine levels, and favors infiltration of leukocytes after injury. Interestingly, these effects were paralleled by opposite sex-specific modifications of microglial reactivity, which was found to be limited in female TNFR2-ablated mice compared to controls, whereas it was enhanced in males. In addition, we show that TNFR2 protein levels in the cerebrospinal fluid (CSF) of human subjects affected by IS and SCI, as well as healthy donors, significantly correlate with disease stage and severity, representing a valuable tool to monitor the inflammatory response after acute CNS injury. Hence, these results advance our understanding of the mechanisms regulating microglia reactivity after acute CNS injury, aiding the development of sex- and microglia-specific, personalized neuroregenerative strategies.

Heartsick: psychiatric and inflammatory implications of cerebromicrovascular disease

BACKGROUND

Cerebromicrovascular disease (CMVD) strikes 87% of the population older than 65 years and is linked to an increased risk of ischemic stroke, depression, cognitive impairment, and Alzheimer's disease. Despite the wealth of knowledge on the consequences to the body stemming from poor vascular health, little focus has been placed on the consequences to the brain.

DESIGN

In this review, we present the preclinical and clinical evidence that supports the role of CMVD in behavioral dysfunction, argues for a clinical need for better recognition of the vascular depression phenotype, and calls for a more integrative translational approach to CMVD.

RESULTS AND CONCLUSIONS

Although the concept of cerebrovascular-induced behavioral change has existed for over 100 years, the difficulty of diagnosis, the slow progression of CMVD, and the lack of causative data have led to an underestimation of the patient population and poor treatment strategies. Preclinical studies have focused on the use of microsphere embolic models and vascular inflammation models to assess the mechanisms of, and treatment options for, CMVD. Though preclinical models provide support for correlative data collected in the clinic, translational reciprocity has not been established. The lack of clinical appreciation for the role of cerebrovascular health in brain function may result in missed diagnoses and inadequate treatment of underlying cardiovascular disease. Enhanced recognition of symptoms and disease presentation will allow for earlier prevention, detection, and identification of novel targets for drug development and other intervention strategies.

Direct thrombin inhibitor argatroban reduces stroke damage in 2 different models

BACKGROUND AND PURPOSE

We showed previously robust neuroprotection with the thrombin inhibitor argatroban and now sought additional support for its neuroprotective potential.

METHODS

We used behavioral and histological end points; rigorously blinded the study groups; extended the treatment window to 3 hours after ischemia onset; and used 2 separate models. First, 2-hour filament middle cerebral artery occlusion in 64 male Sprague-Dawley rats was followed by learning and memory testing and quantitative histomorphometry. Randomly assigned treatment was 0.45 mg argatroban, saline, or 0.4 U thrombin. Second, we used the quantal bioassay (n=272) after 2-hour middle cerebral artery occlusion to detect the longest time delay after which therapy failed.

RESULTS

Argatroban powerfully and significantly reversed learning and memory deficits because of focal ischemia compared with saline or thrombin (P<0.03; ANOVA). Argatroban was significantly (P<0.05; t test with Bonferroni) protective when given immediately or after 1, 2, 3, but not 4 hours delay.

CONCLUSIONS

We obtained supportive evidence for argatroban protection of the neurovascular unit using behavioral and histological measurements at realistic therapeutic time windows.

A standardized approach to the Fugl-Meyer assessment and its implications for clinical trials

BACKGROUND

Standardizing scoring reduces variability and increases accuracy. A detailed scoring and training method for the Fugl-Meyer motor assessment (FMA) is described and assessed, and implications for clinical trials considered.

METHODS

A standardized FMA scoring approach and training materials were assembled, including a manual, scoring sheets, and instructional video plus patient videos. Performance of this approach was evaluated for the upper extremity portion.

RESULTS

Inter- and intrarater reliability in 31 patients were excellent (intraclass correlation coefficient = 0.98-0.99), validity was excellent (r = 0.74-0.93, P < .0001), and minimal detectable change was low (3.2 points). Training required 1.5 hours and significantly reduced error and variance among 50 students, with arm FMA scores deviating from the answer key by 3.8 ± 6.2 points pretraining versus 0.9 ± 4.9 points posttraining. The current approach was implemented without incident into training for a phase II trial. Among 66 patients treated with robotic therapy, change in FMA was smaller (P ≤ .01) at the high and low ends of baseline FMA scores.

CONCLUSIONS

Training with the current method improved accuracy, and reduced variance, of FMA scoring; the 20% FMA variance reduction with training would decrease sample size requirements from 137 to 88 in a theoretical trial aiming to detect a 7-point FMA difference. Minimal detectable change was much smaller than FMA minimal clinically important difference. The variation in FMA gains in relation to baseline FMA suggests that future trials consider a sliding outcome approach when FMA is an outcome measure. The current training approach may be useful for assessing motor outcomes in restorative stroke trials.

Intensity of chronic cerebral hypoperfusion determines white/gray matter injury and cognitive/motor dysfunction in mice

We sought to establish a mouse model of subcortical ischemic vascular dementia (SIVD) that develops predominant white matter (WM) injury and cognitive dysfunction induced by chronic cerebral hypoperfusion. Adult C57Bl/6 male (n = 48) mice were subjected to bilateral common carotid artery stenosis with external microcoils (inner diameters: 0.16 mm, left; 0.18 mm, right). Mice were categorized according to left-side cerebral blood flow (CBF) value on day 6 into those with severe cerebral hypoperfusion (SCH; n = 16, < 30% of preoperative CBF baseline value) or moderate cerebral hypoperfusion (MCH; n = 21, 30-50% of preoperative value). Another 15 mice were sham operated. Neurological dysfunction was evaluated by Morris water maze, rotating rod, and open field tests. Histopathological examination was performed on day 35 after surgery. MCH animals showed persistent hyperlocomotion with reduced anxiety and spatial reference memory dysfunction. Rarefaction and small necrotic lesions were predominantly confined to the WM, with reactive astrocytosis, microglial infiltration, axonal loss, and myelin disruption, and these changes were dominant on the left side. SCH animals had persistent hyperlocomotion and motor dysfunction, and their ischemic lesions extended from the WM to the hippocampus and cortex. In MCH animals, myelin basic protein and neurofilament fiber densities in the WM were correlated with the time spent in the correct area in the water maze probe trials. Our MCH mouse model with the development of several types of neurological dysfunction with high reproducibility would be useful for investigating the pathomechanisms of WM injury in human SIVD.

Long-term survival and serial assessment of stroke damage and recovery - practical and methodological considerations

Impairments caused by stroke remain the main cause for adult disability. Despite a vigorous research effort, only 1 thrombolytic treatment has been approved in acute stroke (<3h). The limitations of preclinical studies and how these can be overcome have been the subject of various guidelines. However, often these guidelines focus on the acute stroke setting and omit long-term outcome measures, such as behaviour and neuroimaging. The considerations and practicalities of including the serial assessment of these approaches and their significance to establish therapeutic efficacy are discussed here.

Quantitative effects of nefiracetam on spatial learning of rats after cerebral embolism

Recent studies have shown that nefiracetam ameliorates cognitive dysfunction because of ischemia when behavioral testing occurs during treatment. We sought to determine if there was a persistent effect after treatment, by testing spatial learning of embolized rats after nefiracetam therapy.

METHODS

Male Sprague Dawley rats (250 to 300 g) were divided into 3 categories. The control group (n = 5) underwent no surgery or cerebral embolism. The vehicle group (n = 12) was anesthetized with halothane, underwent surgery, injected with intracarotid microspheres, and given orally 5 mL/kg of the vehicle (0.5% aqueous sodium carboxymethyl cellulose) for 21 days. The nefiracetam group (n = 12) was embolized and treated orally with 30 mg/kg nefiracetam (6 mg/mL in vehicle) for 21 days. Outcome was determined with visual spatial learning after the end of treatment.

RESULTS

Embolization caused a significant impairment in visual spatial learning, which nefiracetam completely ameliorated (group main effect, F(2,444) = 6.4, P = .002). Mean latency to the escape was 35 +/- 6 seconds for the vehicle group versus 18 +/- 4 seconds for the nefiracetam group, after 4 days of testing. This effect persisted after a further interval of 10 days (retention test). A reversal test (to assess working memory for new information) yielded mean latencies of 26 +/- 6 seconds for the control group, 49 +/- 5 seconds for vehicle, and 25 +/- 4 seconds for nefiracetam (group main effect, F(2,109) = 8.0, P = .0005, Newman-Keuls, P < .05), showing that both the control and nefiracetam groups were different from the vehicle group.

CONCLUSION

Nefiracetam therapy improves the learning behavior of embolized rats. The results are not caused by an activating effect of the drug because the animals are tested after the treatment period is over and because the beneficial effect is seen using the delayed retention test. Finally, working memory is markedly preserved by nefiracetam, an effect observed several weeks after treatment.

Stroke recovery and its imaging

Functional imaging of stroke recovery is a unique source of information that might be useful in the development of restorative treatments. Several features of brain function change spontaneously after stroke. Current studies define many of the most common events. Key challenges for the future are to develop standardized approaches to help address certain questions, determine the psychometric qualities of these measures, and define the clinical usefulness of these methods.

Strength of vital force in classical homeopathy: bio-psycho-social-spiritual correlates within a complex systems context

OBJECTIVE

To explore associations between a global rating for the classical homeopathic construct of vital force and clinician and patient ratings on previously validated bio-psycho-social-spiritual questionnaires.

METHODS

Sixty-two (62) community-recruited patients with fibromyalgia (FM) were assessed at baseline prior to a clinical trial of individualized homeopathy. Two homeopaths jointly performed case-taking interviews. A conventional medical provider independently evaluated patients with a standardized history and physical examination. Homeopaths rated each patient's vital force (five-point Likert scale, with 1 = very weak to 5 = very strong). Homeopaths and the conventional medical provider rated their Clinical Global Impression (CGI) of the severity of illness (1 = normal; 7 = among the most extremely ill). Patients completed self-rating scales on pain, global health, mood, quality of life, coping style, health locus of control, multidimensional well-being, spirituality, sense of coherence, positive states of mind, and social desirability.

RESULTS

Greater vital force ratings (mean 2.9 standard deviation [SD] 0.6) correlated moderately (p < or = 0.005) with less severe CGI illness ratings by the homeopaths (r =-0.59), decreased patient-rated mental confusion (r =-0.43), higher vigor (r = 0.38), and greater positive states of mind (r = 0.36). Vital force also showed correlations (p < 0.05) with lower CGI ratings by the conventional medical provider (r =-0.32), better selfrated quality of life (r = 0.33), lesser fatigue (r =-0.31), better global health (r = 0.29), greater sense of coherence (r = 0.28), powerful-others health locus of control (r = 0.27), increased emotional well-being (r = 0.27), and higher social desirability (r = 0.27), but not with age, pain, or illness duration.

CONCLUSION

Homeopathic vital force ratings reflect better perceived mental function, energy, and positive dimensions of the individual, beyond absence of disease.

Neuroprotection of ischemic brain by vascular endothelial growth factor is critically dependent on proper dosage and may be compromised by angiogenesis

Vascular endothelial growth factor (VEGF) is currently considered a potential pharmacologic agent for stroke therapy because of its strong neuroprotective and angiogenic capacities. Nonetheless, it is unclear how neuroprotection and angiogenesis by exogenous VEGF are related and whether they are concurrent events. In this study, the authors evaluated by stereology the effect of VEGF on neuronal and vascular volume densities of normal and ischemic brain cortices of adult male Sprague-Dawley rats. Ischemia was induced by a 4-hour occlusion of the middle cerebral artery. Low, intermediate, and high doses of VEGF165 were infused through the internal carotid artery for 7 days by an indwelling osmotic pump. The low and intermediate doses, which did not induce angiogenesis, significantly promoted neuroprotection of ischemic brains and did not damage neurons of normal brains. In contrast, the high dose that induced angiogenesis showed no neuroprotection of ischemic brains and damaged neurons of normal brains. These findings suggest that in vivo neuroprotection of ischemic brains by exogenous VEGF does not necessarily occur simultaneously with angiogenesis. Instead, neuroprotection may be greatly compromised by doses of VEGF capable of inducing angiogenesis. Stroke intervention efforts attempting to induce neuroprotection and angiogenesis concurrently through VEGF monotherapy should be approached with caution.

The selective A2A receptor antagonist SCH 58261 reduces striatal transmitter outflow, turning behavior and ischemic brain damage induced by permanent focal ischemia in the rat

Adenosine A(2A) receptor antagonists have been proved protective in different ischemia models. In this study we verified if the protective effect of the selective A(2A) antagonist, SCH 58261, could be attributed to the reduction of the excitatory amino acid outflow induced by cerebral focal ischemia. A vertical microdialysis probe was inserted into the striatum of male Wistar rats and, after 24 h, permanent right intraluminal middle cerebral artery occlusion (MCAo) was induced. Soon after waking, rats showed a definite contralateral turning behavior, which persisted up to 7 h after MCAo. During 4 h after MCAo, glutamate, aspartate, GABA, adenosine and taurine outflow increased. SCH 58261 (0.01 mg/kg, i.p.), administered 5 min after MCAo, suppressed turning behavior and significantly reduced the outflow of glutamate, aspartate, GABA and adenosine. At 24 h after MCAo, the rats showed severe sensorimotor deficit and damage in both the striatum and cortex. SCH 58261 significantly reduced cortical damage but did not protect against the sensorimotor deficit. The protective effect of SCH 58261 against turning behavior and increased outflow of excitatory amino acids in the first hours after MCAo suggests the potential utility of selective adenosine A(2A) antagonists when administered in the first hours after ischemia. Furthermore, this study, for the first time, proposes that turning behavior after permanent intraluminal MCAo, be used as a precocious index of neurological deficit and neuronal damage.

Xenon-129 MR imaging and spectroscopy of rat brain using arterial delivery of hyperpolarized xenon in a lipid emulsion

Hyperpolarized (129)Xe dissolved in a lipid emulsion constitutes an NMR tracer that can be injected into the blood stream, enabling blood-flow measurement and perfusion imaging. A small volume (0.15 ml) of this tracer was injected in 1.5 s in rat carotid and (129)Xe MR spectra and images were acquired at 2.35 T to evaluate the potential of this approach for cerebral studies. Xenon spectra consistently showed two resonances, at 194.5 ppm and 199.0 ppm relative to the gas peak. The signal-to-noise ratio (SNR) obtained for the two peaks was sufficient (ranging from 12 to 90) to follow their time courses. 2D transverse-projection xenon images were obtained with an in-plane resolution of 900 microm per pixel (SNR range 8-15). Histological analysis revealed no brain damage except in two rats that had received three injections.

Effect of intravenous recombinant tissue plasminogen activator on ischemic stroke lesion size measured by computed tomography. NINDS; The National Institute of Neurological Disorders and Stroke (NINDS) rt-PA Stroke Study Group

Background and Purpose-When given within 3 hours of symptom onset, recombinant tissue plasminogen activator (rtPA) improves outcome 3 months after ischemic stroke. Prespecified secondary end points of the National Institute of Neurological Disorders and Stroke (NINDS) rt-PA Stroke Trial were CT lesion volumes in the 2 treatment groups (tPA and placebo) at 24 hours, 7 to 10 days, and 3 months after stroke.

METHODS

-The trial included 2 independent studies, part I and part II, with identical methods of data collection. Before part I, uniform standards were established for CT scanning. CT images were obtained at baseline, 24 hours, 7 to 10 days, and 3 months after stroke onset and were reviewed centrally by reviewers blinded to treatment group and clinical findings. Since the individual studies were not powered to test for lesion volume differences, data from both parts of the trial were combined for all analyses. The primary analysis was conducted with the use of an intention-to-treat algorithm (including patients who died or were lost to follow-up). Measured lesion volume (excluding deaths and those lost to follow-up) was used as a secondary outcome in an exploratory analysis.

RESULTS

-After tPA treatment, there was a trend toward a reduction in 3-month median lesion volume in the tPA group: 15 cm(3) (interquartile range, 2 to 87) compared with 24 cm(3) (interquartile range, 4 to 101) in the placebo group (P:=0.06, log model) with a reduction of 11% in cumulative lesion volume, computed with Smirnov's D statistic. After exclusion of deaths and those lost to follow-up, similar trends toward positive treatment effects were seen at all time points.

CONCLUSIONS

-The direction of the effect of tPA on CT lesion volume at all time points was consistent with the observed clinical effects at 3 months. CT lesion volume may not be as sensitive a measure of treatment effect as clinical evaluation, at least as used in this study. An intention-to-treat analysis for the radiographic end point in this acute ischemic stroke clinical trial is a less biased approach to account for missing radiographic data than an analysis that uses only measured radiological data.

Distribution of AAV-TK following intracranial convection-enhanced delivery into rats

Adeno-associated virus (AAV)-based vectors are being tested in animal models as viable treatments for glioma and neurodegenerative disease and could potentially be employed to target a variety of central nervous system disorders. The relationship between dose of injected vector and its resulting distribution in brain tissue has not been previously reported nor has the most efficient method of delivery been determined. Here we report that convection-enhanced delivery (CED) of 2.5 x 10(8), 2.5 x 10(9), or 2.5 x 10(10) particles of AAV-thymidine kinase (AAV-TK) into rat brain revealed a clear dose response. In the high-dose group, a volume of 300 mm3 of brain tissue was partially transduced. Results showed that infusion pump and subcutaneous osmotic pumps were both capable of delivering vector via CED and that total particle number was the most important determining factor in obtaining efficient expression. Results further showed differences in histopathology between the delivery groups. While administration of vector using infusion pump had relatively benign effects, the use of osmotic pumps resulted in notable toxicity to the surrounding brain tissue. To determine tissue distribution of vector following intracranial delivery, PCR analysis was performed on tissues from rats that received high doses of AAV-TK. Three weeks following CED, vector could be detected in both hemispheres of the brain, spinal cord, spleen, and kidney.

Synergistic combinatorial stroke therapy: A quantal bioassay of a GABA agonist and a glutamate antagonist

We sought to prolong the window for stroke treatment using synergistic combinatorial therapy. We used the intraluminal filament occlusion model in rats to cause focal cerebral ischemia and a quantal bioassay to measure efficacy. The GABA agonist muscimol and the glutamate antagonist MK-801 were used alone and in combination at various times after ischemia onset. At progressively longer treatment delay intervals (30, 60, 75, 120, 240, and 360 min), higher doses of the single drugs were required to achieve neuroprotection. In contrast, the combination 1.0 mg/kg muscimol plus 0.5 mg/kg MK-801 was effective at all delay intervals studied except the longest (P < 0.05 at each time). After 240 min from ischemia onset, the combination was more effective than either single agent (P < 0.05 for each drug dose), suggesting synergism. The neuroprotective effect could not be demonstrated using morphometry. The treatment effects were probably not due to hypothermia because brain temperatures recorded in awake, unregulated subjects remained normo- or slightly hyperthermic following all treatments. Awake subjects kept on a heating pad exhibited mild brain hyperthermia. The combination caused a drop and MK-801 caused a significant increase in mean arterial blood pressure (main effects F(5,172) = 29, P < 0.0001). The combination of a GABA agonist and glutamate antagonist appears to possess synergistic neuroprotective effects when treatment is delayed up to 240 min following the onset of cerebral ischemia. Temperature regulation causes hyperthermia in awake subjects. The quantal bioassay is one method suitable for studies of synergistic stroke therapy.

Effect of ganaxolone in a rodent model of cerebral hematoma

BACKGROUND AND PURPOSE

Therapy with gamma-aminobutyric acid (GABA) agonists appears to improve outcome after experimental hematoma but with unacceptable side effects. We looked to synthetic GABA agonists, or positive GABA modulators, widely developed as anticonvulsants and anxiolytics, to find compounds that may be effective. Ganaxolone is a synthetic neuroactive steroid that positively modulates GABA. We sought to determine whether ganaxolone was beneficial using a model of intracerebral hematoma.

METHODS

We stereotaxically injected varying doses of bacterial collagenase into the caudate nucleus of rats to induce blood-brain barrier failure and hematoma formation. Four hours later, we administered intravenously 15 or 30 mg/kg ganaxolone (n=23 each group), 20 mg/kg pregnanolone (n=21), or vehicle (n=30). Forty-eight hours after collagenase injection, we rated each animal using a standard rodent neurological examination. The ratings were compared with the amounts of injected collagenase using the quantal bioassay procedure. Other sets of animals were tested later for visuospatial learning. Brains were then prepared for histomorphometry, and brain volumes were estimated.

RESULTS

We found that ganaxolone 30 mg/kg significantly increased the ED(50) in the bioassay, for a potency ratio of 1.8+/-0.41 compared with vehicle (P<0.05). Ganaxolone 15 mg/kg and pregnanolone did not affect neurological outcome. Ganaxolone 30 mg/kg did not clearly improve visuospatial learning several weeks after hemorrhage. Ganaxolone exhibited a weak effect on cerebral volumes 48 hours after stroke, but 3 months after hemorrhage no such effect could be detected.

CONCLUSIONS

Ganaxolone improves neurological outcome 48 hours after intracerebral hematoma but not visuospatial learning several weeks after intracerebral hematoma. Histological evidence of damage was reduced at 48 hours but not at 3 months.

Striatal outflow of adenosine, excitatory amino acids, gamma-aminobutyric acid, and taurine in awake freely moving rats after middle cerebral artery occlusion: correlations with neurological deficit and histopathological damage

BACKGROUND AND PURPOSE

While a number of studies have investigated transmitter outflow in anesthetized animals after middle cerebral artery occlusion (MCAO) performed by craniectomy, studies have never been performed after MCAO induced by intraluminal filament. In addition, it has been reported that after MCAO, infarct volume correlates with functional outcome and with transmitter outflow, although there are no studies that demonstrate a direct correlation between transmitter outflow and functional outcome. The purpose of the present study was to assess excitatory amino acids, gamma-aminobutyric acid, taurine, and adenosine outflow in awake rats after intraluminal MCAO and to determine whether, in the same animal, outflow was correlated with neurological outcome and histological damage.

METHODS

Vertical microdialysis probes were placed in the striatum of male Wistar rats. After 24 hours, permanent MCAO was induced by the intraluminal suture technique. The transmitter concentrations in the dialysate were determined by high-performance liquid chromatography. Twenty-four hours after MCAO, neurological deficit and histological outcome were evaluated.

RESULTS

All transmitters significantly increased after MCAO. Twenty-four hours after MCAO, the rats showed a severe sensorimotor deficit and massive ischemic damage in the striatum and in the cortex (9+/-2% and 25+/-6% of hemispheric volume, respectively). Significant correlations were found between the efflux of all transmitters, neurological score, and striatal infarct volume.

CONCLUSIONS

In this study, for the first time, amino acid and adenosine extracellular concentrations during MCAO by the intraluminal suture technique were determined in awake and freely moving rats, and a significant correlation was found between transmitter outflow and neurological deficit. The evaluation of neurological deficit, histological damage, and transmitter outflow in the same animal may represent a useful approach for studying neuroprotective properties of new drugs/agents against focal ischemia.