Programmable microchip monitoring of post-stroke pyrexia: effects of aspirin and paracetamol on temperature and infarct size in the rat

A New NF-κB Inhibitor, MEDS-23, Reduces the Severity of Adverse Post-Ischemic Stroke Outcomes in Rats

Aim: Nuclear factor kappa B (NF-κB) is known to play an important role in the inflammatory process which takes place after ischemic stroke. The major objective of the present study was to examine the effects of MEDS-23, a potent inhibitor of NF-κB, on clinical outcomes and brain inflammatory markers in post-ischemic stroke rats. Main methods: Initially, a Toxicity Experiment was performed to determine the appropriate dose of MEDS-23 for use in animals, as MEDS-23 was analyzed in vivo for the first time. We used the middle cerebral artery occlusion (MCAO) model for inducing ischemic stroke in rats. The effects of MEDS-23 (at 10 mg/kg, ip) on post-stroke outcomes (brain inflammation, fever, neurological deficits, mortality, and depression- and anxiety-like behaviours) was tested in several efficacy experiments. Key findings: MEDS-23 was found to be safe and significantly reduced the severity of some adverse post-stroke outcomes such as fever and neurological deficits. Moreover, MEDS-23 significantly decreased prostaglandin E2 levels in the hypothalamus and hippocampus of post-stroke rats, but did not prominently alter the levels of interleukin-6 and tumor necrosis factor-α. Significance: These results suggest that NF-κB inhibition is a potential therapeutic strategy for the treatment of ischemic stroke.

Inhibition of cyclooxygenase-1 does not reduce mortality in post-ischemic stroke rats

BACKGROUND

Ischemic stroke is one of the leading causes of mortality and morbidity. The currently available non-invasive therapeutic options are not sufficiently efficacious. Post-ischemic brain is characterized by a prominent inflammatory response. Little is known about the involvement of cyclooxygenase (COX)-1 in the pathophysiology of ischemic stroke.

OBJECTIVE

This study was undertaken to examine the effects of a highly selective COX-1 inhibitor - mofezolac - on clinical outcomes and brain inflammatory markers in post-stroke rats.

METHODS

Stroke was induced by subjecting rats to permanent middle cerebral artery occlusion (MCAO). Control rats underwent a sham surgery. Rats were treated with mofezolac (50 mg/kg, intraperitoneally [ip]) once daily for 14 days. Control animals were treated with vehicle. Body temperature (BT), neurological score (NS) and cumulative mortality were monitored at different time points. At the end of the experiment, rats were euthanized and three brain regions (hypothalamus, hippocampus and frontal cortex) were extracted. Levels of interleukin (IL)-6, prostaglandin (PG)E₂ and tumor necrosis factor (TNF)-α in these brain regions were determined by ELISA kits.

RESULTS

BT, NS and cumulative mortality were all significantly higher in post-MCAO rats than in sham-operated rats, irrespective of the treatment given. BT, NS and mortality rate did not differ significantly between mofezolac-treated and vehicle-treated sham-operated animals. BT was significantly lower in mofezolac-treated as compared to vehicle-treated post-MCAO rats. Mofezolac did not significantly alter NS in post-MCAO rats at any time-point. Cumulative 14-day mortality was non-significantly higher in mofezolac-treated as compared to vehicle-treated post-MCAO rats (48 % vs. 21 %, respectively; P =  0.184). Mostly, IL-6 and TNF-α levels did not differ between post-MCAO and sham-operated rats and were not affected by mofezolac treatment. In contrast, mofezolac significantly decreased PGE₂ levels in post-MCAO rats' brains.

CONCLUSION

Overall, these results suggest that chronic treatment with the selective COX-1 inhibitor mofezolac did not reduce morbidity or mortality in post-stroke rats.

Automated recording of home cage activity and temperature of individual rats housed in social groups: The Rodent Big Brother project

Measuring the activity and temperature of rats is commonly required in biomedical research. Conventional approaches necessitate single housing, which affects their behavior and wellbeing. We have used a subcutaneous radiofrequency identification (RFID) transponder to measure ambulatory activity and temperature of individual rats when group-housed in conventional, rack-mounted home cages. The transponder location and temperature is detected by a matrix of antennae in a baseplate under the cage. An infrared high-definition camera acquires side-view video of the cage and also enables automated detection of vertical activity. Validation studies showed that baseplate-derived ambulatory activity correlated well with manual tracking and with side-view whole-cage video pixel movement. This technology enables individual behavioral and temperature data to be acquired continuously from group-housed rats in their familiar, home cage environment. We demonstrate its ability to reliably detect naturally occurring behavioral effects, extending beyond the capabilities of routine observational tests and conventional monitoring equipment. It has numerous potential applications including safety pharmacology, toxicology, circadian biology, disease models and drug discovery.

Effects of Acute Lithium Treatment on Brain Levels of Inflammatory Mediators in Poststroke Rats

Stroke is a leading cause of mortality and morbidity worldwide. Few therapeutic options with proven efficacy are available for the treatment of this disabling disease. Lithium is the gold standard treatment for bipolar disorder. Moreover, lithium has been shown to exhibit neuroprotective effects and therapeutic efficacy as a treatment of other neurological disorders. This study was undertaken to examine the effects of lithium on brain inflammatory mediators levels, fever, and mortality in postischemic stroke rats. Ischemic stroke was induced by occlusion of the mid cerebral artery (MCAO). Pretreatment with a single dose of lithium at 2 hours before MCAO induction significantly reduced the elevation in interleukin- (IL-) 6 and prostaglandin E₂ levels in brain of post-MCAO rats, as compared to vehicle-treated animals. On the other hand, lithium did not affect the elevation in IL-1α, IL-10, IL-12, and tumor necrosis factor-α levels in brain of post-MCAO rats. Moreover, pretreatment with lithium did not alter post-MCAO fever and mortality. These results suggest that acute pretreatment with a single dose of lithium did not markedly affect post-MCAO morbidity and mortality in rats.

Perioperative aspirin improves neurological outcome after focal brain ischemia possibly via inhibition of Notch 1 in rat

BACKGROUND

Perioperative discontinuation of aspirin is often considered due to bleeding concern. We determined whether this discontinuation affected neurological outcome after brain ischemia.

METHODS

Adult male Sprague-Dawley rats were subjected to a 90-minute right middle cerebral arterial occlusion (MCAO). They received 30 mg/kg/day aspirin via gastric gavage: 1) for 2 days at 5 days before MCAO; 2) for 2 days at 5 days before MCAO and for 3 days after MCAO; 3) for 7 days before MCAO; or 4) for 7 days before MCAO and for 3 days after MCAO. Neurological outcome was evaluated 3 days after the MCAO. Ischemic penumbral cortex was harvested 1 or 3 days after MCAO for determining Notch intracellular domain (NICD), IL-6 and IL-1β levels.

RESULTS

Aspirin given by regimen 2 and 3 but not by regimen 1 improved neurological outcome. Neuroprotection was achieved by N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), a Notch activation inhibitor. DAPT and aspirin given only by regimen 2 and 3 reduced NICD, IL-6 and IL-1β in the ischemic penumbral cortex. NICD was found in microglial nuclei. Microglial activation in the ischemic tissues was inhibited by aspirin.

CONCLUSION

Aspirin use during the perioperative period provides neuroprotection. Inhibition of Notch activation and neuroinflammation may contribute to the neuroprotection of aspirin.

Differential temporal evolution patterns in brain temperature in different ischemic tissues in a monkey model of middle cerebral artery occlusion

Brain temperature is elevated in acute ischemic stroke, especially in the ischemic penumbra (IP). We attempted to investigate the dynamic evolution of brain temperature in different ischemic regions in a monkey model of middle cerebral artery occlusion. The brain temperature of different ischemic regions was measured with proton magnetic resonance spectroscopy (¹H MRS), and the evolution processes of brain temperature were compared among different ischemic regions. We found that the normal (baseline) brain temperature of the monkey brain was 37.16°C. In the artery occlusion stage, the mean brain temperature of ischemic tissue was 1.16°C higher than the baseline; however, this increase was region dependent, with 1.72°C in the IP, 1.08°C in the infarct core, and 0.62°C in the oligemic region. After recanalization, the brain temperature of the infarct core showed a pattern of an initial decrease accompanied by a subsequent increase. However, the brain temperature of the IP and oligemic region showed a monotonously and slowly decreased pattern. Our study suggests that in vivo measurement of brain temperature could help to identify whether ischemic tissue survives.

Aspirin upregulates the expression of neuregulin 1 and survivin after focal cerebral ischemia/reperfusion in rats

Neuregulin 1 (NGR1) and survivin have been shown to be neuroprotective. However, the link between their expression and aspirin in the treatment of cerebral ischemia remains unclear. Here, we investigated the effect of aspirin on NGR1 and survivin expression after focal cerebral ischemia/reperfusion in rats. Sprague Dawley rats were randomly divided into an aspirin treatment group (n=40) and a control group (n=40). Each group was further divided into five subgroups according to the time after reperfusion. A middle cerebral artery model was established by an occlusion suture. At 24 h, 3, 5 and 7 days after reperfusion, the Bederson neurological deficit scores were 1.47±0.11, 1.22±0.08, 0.85±0.15 and 0.59±0.12 in the treatment group, and 1.87±0.18, 1.45±0.14, 1.05±0.08 and 0.75±0.15 in the control group, respectively, indicating a significant difference at each time point (P<0.05). In the infarct center, the number of NGR1- and survivin-positive cells reached the maximum at 6 h and decreased gradually to a minimum at 7 days, while in the peri-infarct area, the number was few at 6 h, peaked at 3 days and then was reduced gradually with significant differences between the two time points (P<0.05). There were more NGR1- and survivin-positive cells in the treatment group compared to the control group (P<0.05). In conclusion, the neuroprotective effect of aspirin is at least partly mediated by the upregulation of NGR1 and survivin expression after ischemia.

Neuroprotective effect of Z-ligustilide against permanent focal ischemic damage in rats

The present study investigated the effect of Z-Ligustilide (LIG), a characterized 3-n-alkyphthalide derivative existed in many medical Umbelliferae plants, on permanent focal ischemic brain injury in rats. Focal cerebral ischemia was induced by the occlusion of middle cerebral artery (MCA) for 24 h. LIG (20, or 80 mg/kg), orally administered at 2 h after ischemia, reduced the cerebral infarct volumes by 48.29% and 84.87% respectively compared to control group as visualized by 2,3,5-triphenyltetrazolium chloride (TTC) staining (p<0.01). Treatment with LIG could dose-dependently reduce brain swelling by 68.62% and 82.08% (p<0.01), and significantly improve behavioral deficits (p<0.01). In addition, LIG at the above used doses had no significant effect on rat body temperature. These data, along with previous findings in our lab demonstrating the neuroprotective effects of LIG in transient cerebral ischemia, suggest that LIG may be a potential neuroprotective agent for the treatment of ischemic stroke in future.

Therapeutic hypothermia in acute ischemic stroke

Increased body temperatures are common in the acute phase of stroke. Experimental and clinical studies have suggested that increased body temperatures are related to poor outcome. In animal studies of focal cerebral ischemia, early hypothermia consistently reduced infarct volume. Based on these findings, several Phase II clinical trials have been performed to study physical methods to reduce body temperature in patients with acute stroke. The feasibility and safety of these methods have not yet been established with sufficient certainty. Pharmacological lowering of body temperature may be an attractive alternative approach. In guidelines for the treatment of acute stroke, antipyretics are generally recommended to reduce fever, although their effect on functional outcome is unknown. There is currently no evidence from randomized trials to support routine use of physical or pharmacological cooling in acute stroke. Large randomized clinical trials are needed to study the effect of both physical and medical cooling on functional outcome after stroke.

Measurement of brain temperature with magnetic resonance spectroscopy in acute ischemic stroke

OBJECTIVE

Pyrexia is associated with poor outcome after stroke, but the temperature changes in the brain after stroke are poorly understood. We used magnetic resonance spectroscopic imaging (water-to-N-acetylaspartate frequency shift) to measure cerebral temperature noninvasively in stroke patients.

METHODS

We performed magnetic resonance diffusion, perfusion (diffusion- and perfusion-weighted imaging), and magnetic resonance spectroscopic imaging, compared temperatures in tissues as defined by the diffusion-weighted imaging appearance (definitely abnormal, possibly abnormal and immediately adjacent normal-appearing brain, and normal brain), and tested associations with lesion and patient characteristics.

RESULTS

Among 40 patients, temperature was higher in possibly abnormal (37.63 degrees C) than in definitely abnormal tissue (37.30 degrees C; p < 0.001) or in normal-appearing brain (ipsilateral, 37.16 degrees C; contralateral, 37.22 degrees C; both p < 0.001). Ischemic lesion temperature increased before normal brain temperature. Higher temperatures occurred in lesions that were large, had diffusion/perfusion-weighted imaging mismatch, had reduced cerebral blood flow, and in clinically severe strokes. Only 1 of 25 patients with ischemic lesion temperature greater than 37.5 degrees C was pyrexial.

INTERPRETATION

Temperature is elevated in acutely ischemic brain. More work is required to determine whether raised temperature results from ischemic metabolic reactions, impaired heat exchange from reduced cerebral blood flow, or early inflammatory cell activity (or a combination of these), but magnetic resonance spectroscopic imaging could be used in studies of temperature after brain injury and to monitor interventions.

Measurement of regional brain temperature using proton spectroscopic imaging: validation and application to acute ischemic stroke

A magnetic resonance proton spectroscopic imaging (SI) technique was developed to measure regional brain temperatures in human subjects. The technique was validated in a homogeneous phantom and in four healthy volunteers. Simulations and calculations determined the theoretical measurement precision as approximately +/-0.3 degrees C for individual 1-ml voxels. In healthy volunteers, repeated measurements on individual voxels had an S.D. = 1.2 degrees C. In a clinical study, 40 patients with acute ischemic stroke were imaged within 26 h (mean, 10 h) of onset. Temperatures were highest in the region that appeared abnormal (i.e., ischemic) on diffusion-weighted imaging (DWI) compared with a normal-appearing brain. The mean temperature difference between the DWI "lesion" area and the "normal brain" was 0.17 degrees C [P < 10(-3); range, 2.45 degrees C (hotter)-2.17 degrees C (cooler)]. Noninvasive temperature measurement by SI has sufficient precision to be used in studies of pathophysiology in stroke and in other brain disorders and to monitor therapies.

Strategies of neuroprotection for intracranial aneurysms

Neuroprotection for patients with intracranial aneurysms encompasses the preservation of brain cells endangered by a limited blood and oxygen supply due to aneurysm rupture, clipping or coiling, as well as vasospasm. A large variety of prophylactic and therapeutic neuroprotective strategies have been proposed, but success in human disease is quite limited. Topics of this chapter are the pathophysiology and treatment options of aneurysms, as well as promising neuroprotective strategies in further developmental stages: both physiologically based (hyperoxygenation, hypothermia, avoidance of hyperthermia and hyperglycaemia, hypertension, haemodilution and hypervolaemia) and pharmacologically based (antifibrinolytic drugs, calcium antagonists, anaesthetics, magnesium, erythropoietin and others). New concepts are ischaemic preconditioning, growth factors, and gene therapy. Each strategy is rated on underlying evidence, and research agendas are mentioned.

Complications and pitfalls in rat stroke models for middle cerebral artery occlusion: a comparison between the suture and the macrosphere model using magnetic resonance angiography

BACKGROUND AND PURPOSE

Investigating focal cerebral ischemia requires animal models that are relevant to human stroke. Complications and side effects are common among these models. The present study describes potential pitfalls in 3 techniques for middle cerebral artery occlusion (MCAO) in rats using magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA).

METHODS

Rats were subjected to temporary MCAO for 90 minutes using the suture technique (group I; n=10) or to permanent MCAO using the suture technique (group II; n=10) or the macrosphere technique (group III; n=10). Clinical evaluation was performed after 3 hours and 24 hours. After 24 hours, animals underwent MRI and MRA to determine lesion size and the intracranial vascular status.

RESULTS

Hemispheric lesion volume was significantly smaller in group I (14.6%) compared with groups II (35.2%; P<0.01) and III (21.3%; P<0.05). Two animals (1 each in group II and III) did not demonstrate neurological deficits and had no lesion on MRI and a patent MCA main stem on MRA. Subarachnoid hemorrhage was detected in 2 animals (1 each in group I and II). MRA indicated a patent MCA main stem in 2 animals (group II), although both rats displayed neurological deficits. Hypothalamic infarction with subsequent pathological hyperthermia was detected in all animals in group II and in 1 rat in group III.

CONCLUSIONS

Model failures occurred frequently in all groups. MRI and MRA helps to identify animals that need to be excluded from experimental stroke studies.

High-dose aspirin is neuroprotective in a rat focal ischemia model

Acetylsalicylic acid (ASA) is neuroprotective through various pharmacological action sites. We used a temporary middle cerebral artery occlusion (tMCAO) model in 56 Wistar rats to assess whether repeated ASA injections at 30 min, 6 h, 1, 2, 3, and 4 days after stroke onset are neuroprotective. Animals were sacrificed 5 days after MCAO; infarct size was analyzed with 2,3,5-triphenyltetrazolium chloride staining. As compared to saline (164+/-13 mm(3), n=14), only repeated injections of 40 mg/kg ASA (79+/-18 mm(3), n=14, P=0.0029), but not of 20 mg/kg ASA (129+/-19 mm(3), n=15), reduced infarct volume significantly. No significant change was noted with 40 mg/kg ASA injected only once at 30 min after MCAO (117+/-16 mm(3), n=13).

Delayed administration of interleukin-1 receptor antagonist protects against transient cerebral ischaemia in the rat

The cytokine interleukin-1 (IL-1) has been implicated in ischaemic, excitotoxic and traumatic brain damage in rodents. The naturally occurring IL-1 receptor antagonist (IL-1ra) markedly reduces neuronal injury in these conditions. However, the effects of IL-1ra on focal, transient cerebral ischaemia in the rat, which is of major clinical relevance, have not been reported. The objectives of this study were to test the effects of IL-1ra on cell death after temporary cerebral ischaemia, and to investigate the therapeutic time window for IL-1ra treatment. Ischaemia was induced by temporary (60 min) occlusion of the middle cerebral artery (MCAO) in rats, via surgical insertion (and subsequent removal) of a thread into the internal carotid artery. Damage was quantified at various times after MCAO to investigate the temporal progression of damage and establish an appropriate time to assess the effects of IL-1ra on cell death. Cell death was complete 18-24 h after temporary MCAO. Intracerebroventricular injection of IL-1ra (10 microg) at the time of MCAO and 60 min later reduced the lesion volume measured 24 h (57% reduction) or 48 h (52% reduction) after MCAO. Cell death was also significantly reduced when IL-1ra (20 microg) was administered as a single injection, 1 h (47%), 2 h (57%) or 3 h (46%) after MCAO, when compared to vehicle. These data show that IL-1ra markedly reduces cell death even when administration is delayed until 3 h after induction of reversible, focal cerebral ischaemia in the rat, and support our proposal that IL-1ra may be of therapeutic benefit in stroke.

Hyperthermia following traumatic brain injury: a critical evaluation

Hyperthermia, frequently seen in patients following traumatic brain injury (TBI), may be due to posttraumatic cerebral inflammation, direct hypothalamic damage, or secondary infection resulting in fever. Regardless of the underlying cause, hyperthermia increases metabolic expenditure, glutamate release, and neutrophil activity to levels higher than those occurring in the normothermic brain-injured patient. This synergism may further compromise the injured brain, enhancing the vulnerability to secondary pathogenic events, thereby exacerbating neuronal damage. Although rigorous control of normal body temperature is the current standard of care for the brain-injured patient, patient management strategies currently available are often suboptimal and may be contraindicated. This article represents a compendium of published work regarding the state of knowledge of the relationship between hyperthermia and TBI, as well as a critical examination of current management strategies.