Frontline Sodium Channel-Blocking Antiseizure Medicine Use Promotes Future Onset of Drug-Resistant Chronic Seizures

The mechanisms of treatment-resistant epilepsy remain unclear. We have previously shown that frontline administration of therapeutic doses of lamotrigine (LTG), which preferentially inhibits the fast-inactivation state of sodium channels, during corneal kindling of mice promotes cross-resistance to several other antiseizure medicines (ASMs). However, whether this phenomenon extends to monotherapy with ASMs that stabilize the slow inactivation state of sodium channels is unknown. Therefore, this study assessed whether lacosamide (LCM) monotherapy during corneal kindling would promote future development of drug-resistant focal seizures in mice. Male CF-1 mice (n = 40/group; 18-25 g) were administered an anticonvulsant dose of LCM (4.5 mg/kg, i.p.), LTG (8.5 mg/kg, i.p.), or vehicle (0.5% methylcellulose) twice daily for two weeks during kindling. A subset of mice (n = 10/group) were euthanized one day after kindling for immunohistochemical assessment of astrogliosis, neurogenesis, and neuropathology. The dose-related antiseizure efficacy of distinct ASMs, including LTG, LCM, carbamazepine, levetiracetam, gabapentin, perampanel, valproic acid, phenobarbital, and topiramate, was then assessed in the remaining kindled mice. Neither LCM nor LTG administration prevented kindling: 29/39 vehicle-exposed mice were kindled; 33/40 LTG-exposed mice were kindled; and 31/40 LCM-exposed mice were kindled. Mice administered LCM or LTG during kindling became resistant to escalating doses of LCM, LTG, and carbamazepine. Perampanel, valproic acid, and phenobarbital were less potent in LTG- and LCM-kindled mice, whereas levetiracetam and gabapentin retained equivalent potency across groups. Notable differences in reactive gliosis and neurogenesis were also appreciated. This study indicates that early, repeated administration of sodium channel-blocking ASMs, regardless of inactivation state preference, promotes pharmacoresistant chronic seizures. Inappropriate ASM monotherapy in newly diagnosed epilepsy may thus be one driver of future drug resistance, with resistance being highly ASM class specific.

A Subpopulation of Microglia Generated in the Adult Mouse Brain Originates from Prominin-1-Expressing Progenitors

Microglia maintain brain health and play important roles in disease and injury. Despite the known ability of microglia to proliferate, the precise nature of the population or populations capable of generating new microglia in the adult brain remains controversial. We identified Prominin-1 (Prom1; also known as CD133) as a putative cell surface marker of committed brain myeloid progenitor cells. We demonstrate that Prom1-expressing cells isolated from mixed cortical cultures will generate new microglia in vitro To determine whether Prom1-expressing cells generate new microglia in vivo, we used tamoxifen inducible fate mapping in male and female mice. Induction of Cre recombinase activity at 10 weeks in Prom1-expressing cells leads to the expression of TdTomato in all Prom1-expressing progenitors and newly generated daughter cells. We observed a population of new TdTomato-expressing microglia at 6 months of age that increased in size at 9 months. When microglia proliferation was induced using a transient ischemia/reperfusion paradigm, little proliferation from the Prom1-expressing progenitors was observed with the majority of new microglia derived from Prom1-negative cells. Together, these findings reveal that Prom1-expressing myeloid progenitor cells contribute to the generation of new microglia both in vitro and in vivo Furthermore, these findings demonstrate the existence of an undifferentiated myeloid progenitor population in the adult mouse brain that expresses Prom1. We conclude that Prom1-expressing myeloid progenitors contribute to new microglia genesis in the uninjured brain but not in response to ischemia/reperfusion.SIGNIFICANCE STATEMENT Microglia, the innate immune cells of the CNS, can divide to slowly generate new microglia throughout life. Newly generated microglia may influence inflammatory responses to injury or neurodegeneration. However, the origins of the new microglia in the brain have been controversial. Our research demonstrates that some newly born microglia in a healthy brain are derived from cells that express the stem cell marker Prominin-1. This is the first time Prominin-1 cells are shown to generate microglia.

Development of an antiepileptogenesis drug screening platform: Effects of everolimus and phenobarbital

Objective

The kainic acid (KA)‐induced status epilepticus (SE) model in rats is a well‐defined model of epileptogenesis. This model closely recapitulates many of the clinical and pathological characteristics of human temporal lobe epilepsy (TLE) that arise following SE or another neurological insult. Spontaneous recurrent seizures (SRS) in TLE can present after a latent period following a neurological insult (traumatic brain injury, SE event, viral infection, etc.). Moreover, this model is suitable for preclinical studies to evaluate the long‐term process of epileptogenesis and screen putative disease‐modifying/antiepileptogenic agents. The burden of human TLE is highly variable, similar to the post‐KA SE rat model. In this regard, this model may have broad translational relevance. This report thus details the pharmacological characterization and methodological refinement of a moderate‐throughput drug screening program using the post‐KA‐induced SE model of epileptogenesis in male Sprague Dawley rats to identify potential agents that may prevent or modify the burden of SRS. Specifically, we sought to demonstrate whether our protocol could prevent the development of SRS or lead to a reduced frequency/severity of SRS.

Methods

Rats were administered either everolimus (2–3 mg/kg po) beginning 1, 2, or 24 h after SE onset, or phenobarbital (60 mg/kg ip) beginning 1 h after SE onset. All treatments were administered once/day for 5–7 days. Rats in all studies (n = 12/treatment dose/study) were then monitored intermittently by video‐electroencephalography (2 weeks on, 2 weeks off, 2 weeks on epochs) to determine latency to onset of SRS and disease burden.

Results

Although no adverse side effects were observed in our studies, no treatment significantly modified disease or prevented the presentation of SRS by 6 weeks after SE onset.

Significance

Neither phenobarbital nor everolimus administered at several time points after SE onset prevented the development of SRS. Nonetheless, we demonstrate a practical and moderate‐throughput screen for potential antiepileptogenic agents in a rat model of TLE.

Chemical Sympathectomy, but not Adrenergic Blockade, Improves Stroke Outcome

BACKGROUND

A robust adrenergic response following stroke impairs lymphocyte function, which may prevent the development of autoimmune responses to brain antigens. We tested whether inhibition of the sympathetic response after stroke would increase the propensity for developing autoimmune responses to brain antigens.

METHODS

Male Lewis rats were treated with 6-hydroxydopamine (OHDA) prior to middle cerebral artery occlusion (MCAO), labetalol after MCAO, or appropriate controls. Behavior was assessed weekly and animals survived to 1 month at which time ELISPOT assays were done on lymphocytes from spleen and brain to determine the Th1 and Th17 responses to myelin basic protein (MBP), ovalbumin (OVA), and concanavalin A. A subset of animals was sacrificed 72 hours after MCAO for evaluation of infarct volume and lymphocyte responsiveness. Plasma C-reactive protein (CRP) was measured as a biomarker of systemic inflammation.

RESULTS

Despite similar initial stroke severity and infarct volumes, 6-OHDA-treated animals lost less weight and experienced less hyperthermia after stroke. 6-OHDA-treated animals also had decreased CRP in circulation early after stroke and experienced better neurological outcomes at 1 month. The Th1 and Th17 responses to MBP did not differ among treatment groups at 1 month, but the Th1 response to OVA in spleen was more robust in labetalol and less robust in 6-OHDA-treated animals.

CONCLUSIONS

Chemical sympathectomy with 6-OHDA, but not treatment with labetalol, decreased systemic markers of inflammation early after stroke and improved long-term outcome. An increase in Th1 and Th17 responses to MBP was not seen with inhibition of the sympathetic response.

Splenectomy Does Not Improve Long-Term Outcome After Stroke

BACKGROUND AND PURPOSE

Immune responses to brain antigens after stroke contribute to poor outcome. We hypothesized that splenectomy would lessen the development of such responses and improve outcome.

METHODS

Male Lewis rats (275-350 g) underwent 2-hour middle cerebral artery occlusion immediately after splenectomy or sham splenectomy. Animals were survived to 4 weeks (672 hrs), and immune responses to myelin basic protein determined at euthanasia. Infarct volume was determined in a subset of animals euthanized at 72 hours. Behavioral outcomes were assessed to 672 hours.

RESULTS

Splenectomy was associated with worse neurological scores early after stroke, but infarct size at 72 hours was similar in both groups. Behavioral outcomes and immune responses to myelin basic protein were also similar among splenectomized and sham-operated animals 672 hours after middle cerebral artery occlusion.

CONCLUSIONS

Splenectomy did not alter the immune responses to brain antigens or improve outcome after stroke. Differences between this study and other studies of splenectomy and stroke are examined.

Antibodies to myelin basic protein are associated with cognitive decline after stroke

B lymphocytes cause post-stroke cognitive decline in mice. We therefore evaluated the association between autoantibodies and post-stroke cognitive decline in a prospectively collected human cohort. The mini-mental state exam (MMSE) was administered 30, 90, 180, and 365days after stroke. Antibody titers to myelin basic protein (MBP), proteolipid protein, and several non-specific proteins were determined. Among 58 subjects with initial MMSE≥20 and at least 2 MMSE examinations in the year after stroke, cognitive decline (MMSE decrease ≥2) occurred in 10 (17%) subjects. In multivariate analysis, MBP antibody titers were the only independent predictor of cognitive decline (OR=9.02 [1.18, 68.90]; P=0.03).

Effect of Antibiotic Class on Stroke Outcome

BACKGROUND AND PURPOSE

Infections are common after stroke and associated with worse outcome. Clinical trials evaluating the benefit of prophylactic antibiotics have produced mixed results. This study explores the possibility that antibiotics of different classes may differentially affect stroke outcome.

METHODS

Lewis rats were subjected to transient cerebral ischemia (2 hours) and survived for 1 month. The day after stroke they were randomized to therapy with ceftiofur (a β-lactam antibiotic), enrofloxacin (a fluoroquinolone antibiotic), or vehicle (as controls) and underwent the equivalent of 7 days of treatment. Behavioral tests were performed weekly until euthanization. In a subset of animals, histology was done.

RESULTS

There were no differences in outcomes at 24 hours or 1 week after stroke among the different groups. At 1 month after stroke, however, performance on the rotarod was worse in enrofloxacin-treated animals when compared with control animals.

CONCLUSIONS

Independent of infection, the antibiotic enrofloxacin was associated with worse stroke outcome. These data echo the clinical observations to date and suggest that the secondary effects of antibiotics on stroke outcome should be considered when treating infection in subjects with stroke. The mechanism by which this antibiotic affects outcome needs to be elucidated.

Poststroke fatigue: hints to a biological mechanism

BACKGROUND

Poststroke fatigue (PSF) is common, but the biological basis of this fatigue is unknown. We explored the possibility that PSF is related to systemic inflammation by investigating polymorphisms in 2 genes that affect the immune response.

METHODS

In a substudy of a larger trial that evaluated the role of the immune response on stroke outcome, fatigue was assessed at 30, 90, 180, and 365 days after ischemic stroke using the Fatigue Assessment Scale. Subjects were genotyped for 3 single nucleotide polymorphisms, one in the interleukin-1 receptor antagonist gene (IL1RN; rs4251961, a T/C substitution) and two in the in toll-like receptor-4 (TLR4) gene (1063 A/G [Asp299Gly] rs4986790 and 1363 C/T [Thr399Ile] rs4986791).

RESULTS

Of the 39 participants, 22 (56%) endorsed fatigue during the study. The degree of fatigue was remarkably constant over time and independent of stroke outcome. The C allele of the rs4251961 single nucleotide polymorphism (SNP) in IL1RN was associated with self-reported fatigue (P = .03), whereas the cosegregating polymorphisms in TLR4 were associated with lower levels of fatigue (P= .04).

CONCLUSIONS

SNPs in 2 genes with opposing effects on inflammatory immune responses were significantly, but differentially, associated with PSF. These findings suggest a direct link between immune signaling dysregulation and PSF.

Strain differences in fatigue and depression after experimental stroke

Fatigue and depression are common symptoms after stroke. Animal models of poststroke fatigue (PSF) and poststroke depression (PSD) would facilitate the study of these symptoms. Spontaneous locomotor activity is as an objective measure of fatigue and learned helplessness an accepted correlate of depression. We used different rat strains to evaluate stroke-induced changes in behavior in hopes that interstrain differences would provide insights into the biological basis of these symptoms. Male Lewis, Wistar, and Sprague-Dawley (SD) rats underwent experimental stroke. Spontaneous activity was assessed continually after stroke (for up to 50 days). In a subset of animals, the forced swim test was performed prior to and 1 month after stroke to assess learned helplessness; blood was obtained at sacrifice for cytokine assay. Stroke induced strain-related differences in activity; Lewis rats increased spontaneous activity during the dark cycle, while Wistar and SD rats increased activity during the light cycle. The velocity of movement decreased during the dark cycle in Wistar and SD rats and during the light cycle in Lewis rats. Stroke also led to an increase in learned helplessness in Lewis rats. In summary, different patterns of behaviors emerge in different rat strains after stroke. Lewis rats displayed behavior consistent with depression but not fatigue, while Wistar and SD rats displayed behavior consistent with fatigue but not depression. These data argue that PSF and PSD are different biological constructs and suggest that analysis of strain-related differences may provide insight into symptom pathophysiology.

Variation in behavioral deficits and patterns of recovery after stroke among different rat strains

Pre-clinical models of stroke therapeutics depend upon the ability to detect differences in infarct volume as well as in the short- and long-term outcomes of treated animals. Little attention has been paid to interstrain differences in these outcomes and the importance of defining the most appropriate behavioral tests. In this study, we evaluate long-term outcome from stroke in three different rat strains. Lewis, Wistar, and Sprague Dawley (SD) rats were subjected to 2-h middle cerebral artery occlusion and survived for up to 49 days. Behavioral tests were performed weekly. There was continuous assessment of rotational/circling activity in the home cage by use of an automated software program. A separate group of animals was sacrificed at 24 h to determine infarct volume. Infarct volume was similar in all three strains. Mortality was significantly higher in SD rats (P < 0.001). Rotational/circling activity at 24 h was correlated with cortical infarct volume in Wistar and SD rats (ρ = 0.67, P = 0.04 and ρ = 0.72, P = 0.01, respectively). Wistar and SD rats displayed more rotational/circling activity following stroke than Lewis rats, but Lewis rats evidenced more impairment on complex motor tasks like the rotarod. Further, computer automated analysis of rotational activity was more sensitive than subjective assessment, with SD rats showing a preference for clockwise rotations to 49 days after stroke despite normalization of the neurological score after 21 days. There are significant interstrain differences in survival and in the patterns of neurological impairment and recovery after stroke. These differences must be taken into account in pre-clinical studies, but may also be capitalized upon to understand genetic contributions to injury. Finally, computerized assessment of behavior is more sensitive than subjective assessment for detecting behavioral changes.

Abstract T MP119: Forced Swim Test as an Index of Post-Stroke Depression in Rats

Background: Depression is common after stroke. The Porsolt Forced Swim Test (FST) is used to screen for depression and response to therapy in rodent models. The duration of immobility is considered to be an indication of learned helplessness. In this study we aimed to characterize post-stroke depression using the FST.

Methods: Male Lewis (N=6), Wistar (N=5), and Sprague Dawley (SD; N=11) rats were subjected to the FST (10 minutes) prior to 2 hours middle cerebral artery occlusion (MCAO) and then again at 28 days after MCAO. Sham-operated animals were used as controls. The latency to immobility and the duration of immobility were assessed along with the maximum velocity of movement. Blood was obtained at the time of sacrifice and assayed for interleukin (IL)-1α, IL-1β and IL-10. Statistics are non-parametric; data are displayed as median and interquartile range.

Results: Prior to stroke, the latency to immobility was similar in all strains, but the duration of immobility was greater in Lewis rats (201 [159, 294] secs; P =0.039) than in Wistar (148 [106, 184] secs) and SD rats (136 [112, 200] secs). The maximal velocity of movement in Lewis rats (47 [42, 55] cm/sec; P =0.007) was faster than Wistar (29 [25, 41] cm/sec) and SD (39 [34, 46] cm/sec) rats. In comparison to strain matched sham-operated animals, stroke was associated with an increase in the period of immobility (P=0.088), a decrease in latency to immobility ( P =0.019) and an increase in the maximal velocity of movements ( P =0.033) in Lewis rats. No significant differences in FST behavior were seen in Wistar or SD rats. Plasma concentrations of IL-1α (P=0.001) and IL-10 (P=0.011) were highest in Lewis rats at the time of sacrifice. The duration of immobility was most highly correlated with IL-1β (r=0.663, P =0.003) and IL-10 (r=0.575, P =0.013).

Summary: At baseline, Lewis rats exhibit more depressive behavior than Wistar and SD rats, and stroke appears to enhance these differences. The change in behavior on the FST is associated with an increase in markers of systemic inflammation. The FST could be used to study interventions for post-stroke depression.

Abstract T P81: Long-Term Activity Levels Vary by Rat Strain Following Stroke: A Disruption of the Circadian Rhythm?

Background: Assessment of long-term behavioral outcome after experimental cerebral ischemia is important for evaluating potential therapeutic interventions. In this study, we explored strain related differences in baseline behavior and in response to stroke.

Methods: Spontaneous cage activity was monitored (cm moved per hr) and analyzed before and after 2 hour middle cerebral artery occlusion (MCAO) in male Lewis, Wistar, and Sprague Dawley (SD) rats using the Noldus PhenoTyper® cages and EthoVision® Software system. Stroke severity was assessed using the neuroscore, foot fault errors, and performance on the rotarod. Infarct volume at 24 hours was determined in a second cohort of animals. Animals were sacrificed 56 days after MCAO. Data are analyzed using non-parametric statistics.

Results: Prior to stroke, the median distance moved per hour during the dark was similar among the 3 strains, but Lewis rats were more active during the light cycle (P=0.001). Neuroscores did not differ between strains at 3 hrs after MCAO nor did infarct volumes at 24 hours after MCAO. Lewis rats, however, performed worse on the rotarod in the month following MCAO (P<0.05 at each time point). Foot fault errors were similar throughout the study period. After stroke, Lewis rats became more active during the dark cycle while Wistar and SD rats became more active during the light cycle (Figure).

Summary: The 3 strains of rats evaluated in this study had different patterns in the change in activity after MCAO. Lewis rats showed an increase in activity during the dark cycle while Wistar and SD rats showed an increase in activity during the light cycle. This observation suggests that there are genetic differences in the response to stroke that may alter the circadian rhythm after stroke.

Abstract W P229: Reduction of Peroxiredoxin 5 Concentration in Patients following Ischemic Stroke

Background: There is a marked inflammatory response within the brain after stroke. Peroxiredoxins (PRXs) are endogenous anti-oxidant proteins, but recent data suggest that PRXs may be responsible for initiating inflammation in the brain following cerebral ischemia. In this study we evaluated the relationship between PRX5 and biomarkers of inflammation following ischemic stroke.

Methods: In a prospective study of patients with ischemic stroke, PRX5 concentrations were determined by standard ELISA in plasma samples (N=98) obtained at 3 days after stroke onset. Relationships between stroke severity, biomarkers of inflammation and stroke outcome were explored.

Results: At 3 days after stroke, PRX5 concentrations were significantly lower in patients with severe stroke (NIHSS ≥17; 37.6 ng/mL [28.5, 45.3]) as compared to patients with moderate stroke (NIHSS 6-16; 48.0 ng/mL [36.5, 88.6]) or mild stroke (NIHSS ≤5; [40.5, 76.3]); P =0.001. PRX5 was inversely correlated with the number of white blood cells, neutrophils, and monocytes as well as with plasma CRP, TNF-α, IL-6, IL-10 and IL-2. None of these correlations remained significant after controlling for stroke severity. Patients with higher plasma PRX5 at 3 days were more likely to have good outcome (mRS≤2) at 3 months ( P =0.019), but this relationship was lost after controlling for stroke severity.

Discussion: Plasma concentrations of PRX5 are decreased in patients with severe stroke and inversely correlated with biomarkers of inflammation. These data suggest that the initiator of systemic inflammation after stroke is not PRX5. Further, they show that severe brain injury leads to a loss of circulating anti-oxidant proteins.

Peroxiredoxin 5 (PRX5) is correlated inversely to systemic markers of inflammation in acute stroke

BACKGROUND AND PURPOSE

Peroxiredoxins are endogenous antioxidants that function as peroxide and peroxynitrite scavengers. Extracellular peroxiredoxins, however, are shown to initiate inflammation within the ischemic brain through activation of Toll-like receptors. Based on this observation, we hypothesized that plasma peroxiredoxin concentrations in ischemic stroke would correlate biomarkers of inflammation and predict poor outcome.

METHODS

In a prospective study of patients with ischemic stroke, plasma peroxiredoxin 5 (PRX5) concentrations and inflammatory biomarkers at day 3 after stroke onset were correlated and the association between PRX5 at day 3 and outcome at 3 months assessed.

RESULTS

PRX5 concentrations were available for 98 patients and were lower in those with more severe strokes (P=0.001). PRX5 was inversely correlated to biomarkers of inflammation at day 3 after stroke and did not predict 3-month outcome.

CONCLUSIONS

Plasma PRX5 is decreased in severe stoke and inversely correlated to biomarkers of systemic inflammation. These data suggest that PRX5 is not a proinflammatory mediator in acute stroke. Moreover, the inverse relationship between PRX5 and stroke severity suggests that PRX5 is either consumed or its production is impaired in severe stroke. Further study is needed to define the potential role of PRX5 in stroke.

The immunologic profile of adoptively transferred lymphocytes influences stroke outcome of recipients

Animals that have myelin basic protein (MBP) specific lymphocytes with a Th1(+) phenotype have worse stroke outcome than those that do not. Whether these MBP specific cells contribute to worsened outcome or are merely a consequence of worse outcome is unclear. In these experiments, lymphocytes were obtained from donor animals one month after stroke and transferred to naïve recipient animals at the time of cerebral ischemia. The MBP specific phenotype of donor cells was determined prior to transfer. Animals that received either MBP specific Th1(+) or Th17(+) cells experienced worse neurological outcome, and the degree of impairment correlated with the robustness of MBP specific Th1(+) and Th17(+) responses. These data demonstrate that the immunologic phenotype of antigen specific lymphocytes influences stroke outcome.

Abstract TP114: Post-stroke Fatigue Is Linked To The IL1RN Polymorphism rs4251961

Background: Post-stroke fatigue (PSF) is common, but the biological basis of PSF is unknown. We explored the relationship between PSF, systemic inflammation and genetic polymorphisms that affect the immune response.

Methods: In a substudy of a larger trial that evaluated the role of the immune response on stroke outcome, patients were asked about their level of fatigue at 30, 90, 180, and 365 days after ischemic stroke. (The degree fatigue of was quantified using the Fatigue Assessment Scale [FAS], with possible scores of 10 (minimal fatigue) to 50 (severe fatigue). Plasma cytokine concentrations were analyzed and patients genotyped for polymorphisms in the promoter of the interleukin-1 receptor antagonist (IL-1ra) gene (IL1RN; rs4251961). The minor allele (C) is associated with decreased IL-1ra in healthy adults in comparison with the major (T) allele.

Results: Of patients for whom FAS scores were available (N=38), there were 16 (41%) with TT, 14 (36%) with CT and 8 (21%) with CC genotypes. The degree of fatigue (median [interquartile range]) was remarkably constant over time (22 [16, 29]) and tended to be higher in patients with a C allele (Figure). The FAS scores for patients with the minor C allele was 26 (17, 32) and was 18 in those without (13, 26; P=0.046). If fatigue is defined as an FAS score greater than the 75th percentile value for all patients (>29), 8/22 (36%) of patients with the C allele experienced fatigue while only 1/16 (6%) patients with TT did (P=0.031). Controlling for stroke severity, age and gender, the odds ratio (95% confidence interval) for developing fatigue (FAS>29) with a C allele was 9.96 (1.13-87.42; P=0.038). The concentration of IL-1ra did not differ among patients with the C allele and those without at any time point and was not associated with the FAS score.

Conclusions: The rs4251961 polymorphism of IL1RN appears to be associated with PSF. This finding, and the relationship to systemic markers of inflammation, will need to be validated in a larger cohort.

Severe stroke induces long-lasting alterations of high-mobility group box 1

BACKGROUND AND PURPOSE

The signals that initiate the poststroke inflammatory response are unknown. High-mobility group box (HMGB) 1 protein is a nuclear protein that is passively released from necrotic tissue and is able to activate leukocytes, which in turn secrete HMGB1. HMGB1 is also able to activate antigen-presenting cells and therefore stands at the crossroads of innate and adaptive immunity.

METHODS

Plasma HMGB1 concentrations were determined at multiple time points after ischemic stroke (N=110) and correlated to stroke severity and biomarkers of inflammation. The relationships between HMGB1, stroke outcome, and autoimmune responses to brain antigens were also assessed.

RESULTS

Stroke resulted in an increase in HMGB1 that persisted for 30 days. Plasma HMGB1 was correlated with the number of circulating leukocytes but was not predictive of either stroke outcome or the development of autoimmune responses to brain antigens. Patients with a Th1(+) response to myelin basic protein at 90 days after stroke, however, had higher plasma HMGB1.

CONCLUSIONS

HMGB1 appears to be involved in the postischemic inflammatory response, but it remains unclear whether HMGB1 initiates this response or merely reflects activation of leukocytes by another signal.

Myelin basic protein autoantibodies, white matter disease and stroke outcome

Antibodies to brain antigens are present in stroke survivors. In this study, we assessed autoantibody responses to white matter antigens, their correlation to white matter disease and stroke outcome. Antibody titers (immunoglobulin G [igG]) to myelin basic protein (MBP), proteolipid protein (PLP) and tetanus toxoid (TT) were available at one or more time points for 112 subjects with ischemic stroke. In comparison to the control subjects (N=40), there was a global decrease in IgG titers to TT early after stroke. Patients with white matter disease on magnetic resonance imaging had elevated titers of antibodies to both MBP and PLP at 30days after stroke, and anti-MBP antibodies were associated with worse outcome. The potential pathologic consequences of antibodies to white matter, especially MBP, is deserving of further investigation.

Higher plasma fractalkine is associated with better 6-month outcome from ischemic stroke

BACKGROUND AND PURPOSE

Fractalkine (CX3CL1) is a unique chemokine that is constitutively expressed on neurons where it serves as an adhesion molecule for lymphocytes and monocytes. CX3CL1 may also be cleaved from the surface of these cells and enter the circulation to act as a traditional chemokine. CX3CL1 could thus influence the inflammatory response after stroke. We hypothesized that patients with higher plasma CX3CL1 after stroke would have a more robust inflammatory response and experience worse outcome.

METHODS

Plasma CX3CL1 concentrations were assessed in 85 patients who were part of a larger study evaluating immune responses after ischemic stroke; CX3CL1 values were available from Day 1 to Day 180 after stroke onset. CX3CL1 was correlated to measures of inflammation and its effect on outcome assessed.

RESULTS

At 1 day after stroke, CX3CL1 was lower in patients with severe strokes. At 180 days after stroke, CX3CL1 concentrations were lower in patients with poor outcome. The association of CX3CL1 and outcome at 180 days was independent of initial stroke severity. Plasma CX3CL1 at 180 days was inversely associated with systemic markers of inflammation, including white blood cell counts and high-sensitivity C-reactive protein.

CONCLUSIONS

In contrast to our original hypothesis, lower concentrations of CX3CL1 are associated with worse stroke outcome. In light of recent studies suggesting an immunomodulatory and neuroprotective role for CX3CL1 in a variety of neurodegenerative diseases, a therapeutic role for CX3CL1 in stroke recovery should be considered.

Abstract 2874: Functional Polymorphisms in Toll-like Receptor 4 Predict Worse Outcome in Acute Ischemic Stroke Patients

Background: Toll-like receptor-4 (TLR4) plays a central role in the pathophysiology of acute ischemic stroke (AIS). Specific single nucleotide polymorphisms (SNPs) in TLR4 including 1063 A/G [Asp299Gly] and 1363 C/T [Thr399Ile] alter immune cell responsiveness to lipopolysaccharide (LPS) and are associated with increased rates of infection. The effect of these TLR4 SNPs on outcome following AIS is unknown.

Methods: Patients were prospectively enrolled after onset of AIS. Clinical and demographic data were collected and neurological outcomes assessed at 3 months. Blood was drawn at multiple time points to quantify leukocyte subsets and assess plasma levels of C-reactive protein and a panel of cytokines. Genotyping for the TLR4 SNPs was also performed on blood samples. Uni- and multivariate analyses were performed to assess associations between TLR4 SNP haplotype and (i) each laboratory parameter noted above, (ii) infection risk and (iii) stroke outcome.

Results: Of the 42 patients included; 6 (14%) were heterozygous for either one or both TLR4 SNPs. Baseline characteristics were similar in patients with or without a TLR4 SNP. In analyses adjusted for both initial stroke severity and age, the presence of a TLR4 SNP was associated with increases in blood leukocytes, plasma C-reactive protein and the cytokine interleukin-1 receptor antagonist (IL-1ra). The presence of either TLR4 SNP was also associated with a trend toward increased rates of infection (adjusted odds ratio and 95% confidence interval of 8.20 and 0.826-81.5, respectively) and a decreased likelihood of favorable outcome as defined by a modified Rankin Scale score of two or less at three months from stroke onset (0.014, 0.00-0.759).

Conclusions: In AIS patients, functionally significant genetic variations in TLR4 influence both rates of stroke-associated infection and neurological outcome. These data suggest a direct connection between TLR4 function and stroke pathophysiology.

Abstract 2686: Plasma HMGB1 Concentration Correlates With The Inflammatory Response Following Stroke

Background: There is an inflammatory response following ischemic stroke that appears to contribute to brain injury and worsen outcome. High-mobility group box 1 (HMBG1) is a nuclear protein that is released from necrotic cells and serves as a “danger signal” which can initiate an inflammatory response in a non-infectious environment. We assessed whether early systemic HMGB1 could serve as a marker for infarct size and predict outcome and whether plasma HMGB1 would correlate with systemic markers of inflammation.

Methods: Plasma HMGB1 concentrations were analyzed in 114 patients with ischemic stroke at 1 (N=38), 3 (N=98), 7 (N=95), 30 (N=89), 90 (N=71), 180 (N=70) and 365 (N=24) days (blood samples were not available for all patients at all time points). A group of 40 “healthy” volunteers served as controls. Infarct volume was determined on diffusion weighted MRI and stroke severity by NIHSS score. The association between plasma HMGB1 and laboratory markers of inflammation was analyzed at each time point. Significance was set at P <0.05.

Results: There was only a modest correlation between the NIHSS score, infarct volume and early plasma HMGB1 (highest value by day 3) after stroke (r=0.248, P =0.009 and r=0.217, P =0.024, respectively). In comparison to controls, plasma HMGB1 was elevated to 30 days after stroke; patients with more severe strokes had higher plasma HMGB1 than patients with less severe stroke ( Figure ). There was a robust correlation between plasma HMGB1 and white blood cell (WBC) counts that was independent of stroke severity at 1 day after stroke (r=0.449, P =0.005). This relationship between plasma HMGB1 and WBC count persisted to 1 year after stroke (r=0.551, P =0.008) and was driven by polymorphonuclear cells (PMNs). Initial plasma HMGB1 was not predictive of long term outcome.

Conclusions: Plasma HMGB1 is elevated following ischemic stroke, and is higher in patients with more severe strokes. The robust and independent association of HMGB1 with WBC counts following stroke suggests that these cells may be the primary source of plasma HMGB1 following stroke.

Plasma α-melanocyte stimulating hormone predicts outcome in ischemic stroke

BACKGROUND AND PURPOSE

α-Melanocyte stimulating hormone (α-MSH) is an endogenously produced neuropeptide derived from the same precursor as adrenocorticotropic hormone. α-MSH has profound immunomodulatory properties and may also be neuroprotective. Nothing is known about α-MSH and changes in its plasma concentrations in patients with acute ischemic stroke.

METHODS

In this prospective observational study, plasma concentrations of α-MSH, adrenocorticotropic hormone, cortisol, and interleukin 6 were assessed longitudinally over the course of 1 year after stroke onset in 111 patients. Logistic regression was used to the effect of initial plasma α-MSH, adrenocorticotropic hormone, cortisol, and interleukin 6 on long-term outcome.

RESULTS

There was an early decrease in plasma α-MSH in patients with severe stroke (National Institutes of Health Stroke Scale≥17) that normalized over the course of the year; these same patients evidenced elevations in plasma cortisol and interleukin 6. Higher initial plasma α-MSH, but not adrenocorticotropic hormone, cortisol, or interleukin 6, was independently predictive of good long-term outcome.

CONCLUSIONS

This research is the first to study endogenous changes in plasma α-MSH after stroke. The independent effect of early plasma α-MSH on stroke outcome, as well as a growing body of experimental data demonstrating improved stroke outcome with exogenous α-MSH administration, suggests a potential therapeutic role for α-MSH in the treatment of stroke.

Post-stroke infection: a role for IL-1ra?

BACKGROUND

Infection is common following stroke and is independently associated with worse outcome. Clinical studies suggest that infections occur more frequently in those individuals with stroke-induced immunologic dysfunction. This study sought to explore the contribution of immunomodulatory cytokines and hormones to lymphocyte function and infection risk.

METHODS

Patients (N = 112) were enrolled as soon as possible after the onset of ischemic stroke. Blood was drawn to assess plasma cortisol, IL-10, IL-1ra, lymphocyte numbers, and lymphocyte function at 72 h after stroke onset; infections were censored through 21 days after stroke onset.

RESULTS

Infection occurred in 25% of patients. Stroke severity was the most important predictor of infection risk. Increased plasma cortisol, IL-10, and IL-1ra, as well as decreased lymphocyte numbers, at 72 h after stroke onset were associated with risk of subsequent infection. After controlling for stroke severity, only IL-1ra was independently associated with infection risk, and the degree of risk was consistent throughout the post-stroke period. Infection, but not IL-1ra itself, was associated with worse outcome at 3 months.

CONCLUSIONS

In this study cohort, increased plasma IL-1ra was independently associated with the risk of post-stroke infection. Further studies are needed to validate this finding, which could have important implications for stroke therapy.

α-MSH: a potential neuroprotective and immunomodulatory agent for the treatment of stroke

Alpha-melanocyte-stimulating hormone (MSH) is a neuropeptide with profound immunomodulatory properties; we evaluated the effects of α-MSH on stroke outcome and its ability to modulate the postischemic immune response. In Lewis rats subjected to 3 hours of middle cerebral artery occlusion (MCAO), plasma concentrations of α-MSH rapidly decreased and returned to baseline over the course of days. Exogenous administration of α-MSH (100 or 500 μg/kg) improved 24 hour outcome in animals subjected to 2 hours MCAO; α-MSH 500 μg/kg also decreased infarct volume at this time point. Both doses of α-MSH were ineffective in improving outcome or decreasing infarct volume in animals subjected to 3 hours MCAO. The splenocyte response to phytohemagglutin in animals treated with α-MSH was attenuated at 24 hours after MCAO. At 1 month after MCAO, treatment with α-MSH 500 μg/kg at the time of stoke was associated with a decrease in TH1 response to myelin basic protein (MBP) in animals subjected to 2 hours MCAO, although treatment was not associated with improved outcome at this time point. Given the early benefits of α-MSH treatment and its effect on immunologic outcome, further studies to evaluate the utility of α-MSH for the treatment of cerebral ischemia are warranted.

Anamnestic recall of stroke-related deficits: an animal model

BACKGROUND AND PURPOSE

Anamnestic recall of stroke-related deficits is a common clinical observation, especially during periods of systemic infection. The pathophysiology of this transient re-emergence of neurological dysfunction is unknown.

METHODS

Male Lewis rats underwent 3 hours middle cerebral artery occlusion and were treated with lipopolysaccharide or saline at the time of reperfusion. The delayed-type hypersensitivity (DTH) response to myelin basic protein was examined 28 days after middle cerebral artery occlusion. Changes in behavioral outcomes were assessed after DTH testing and repeat administration of lipopolysaccharide or saline at 34 days. At the time of euthanasia (36 days), the immunologic response of splenocytes to myelin basic protein, neuron-specific enolase, and proteolipid protein was determined by enzyme-linked immunospot assay and the number of lymphocytes in the brain determined by immunocytochemistry.

RESULTS

Animals treated with lipopolysaccharide at middle cerebral artery occlusion had a greater DTH response to myelin basic protein than animals treated with saline. Among those animals that had fully recovered on a given behavioral test before DTH testing, those treated with lipopolysaccharide at middle cerebral artery occlusion displayed more neurological deterioration after DTH testing and had more CD8(+) lymphocytes within the ischemic core of the brain. Furthermore, the Th1 immune response to brain antigens in the spleen was more robust among those animals that deteriorated after DTH testing and there were more CD4(+) lymphocytes in the penumbral region of animals with a Th1 response to myelin basic protein.

CONCLUSIONS

Our data suggest that an immune response to the brain contributes to the phenomenon of anamnestic recall of stroke-related deficits after an infection. The contribution of the immune response to this phenomenon deserves further investigation.

Long term immunologic consequences of experimental stroke and mucosal tolerance

Background

An inflammatory insult following middle cerebral artery occlusion (MCAO) is associated with a predisposition to develop a deleterious autoimmune response to the brain antigen myelin basic protein (MBP). Induction of immunologic tolerance to brain antigens prior to MCAO prevents this deleterious autoimmune response and is associated with better functional outcome early after stroke. In this study, we sought to determine the long term immunologic consequences of experimental stroke and induction of mucosal tolerance.

Methods

Male Lewis rats were tolerized to MBP or ovalbumin (OVA) by intranasal administration prior to MCAO and administration of lipopolysaccharide (LPS). Neurological outcome was assessed at set points after MCAO and animals sacrificed at 3 months; the immune response to MBP in brain and spleen was determined using ELISPOT assay and degree of cellular inflammatory brain infiltrate assessed by immunocytochemistry.

Results

Animals that developed a pro-inflammatory (TH1) response to MBP experienced worse outcome, while those that developed a regulatory response (TREG) experienced better outcome. A TREG response in spleen was also associated with decreased inflammation and an increase in the number of FoxP3 positive cells in brain. In this study, tolerization to MBP prior to MCAO was associated with a tendency to develop a TH1 response to MBP by 3 months after MCAO.

Conclusion

These data show that induction of immunological tolerance to MBP is associated with improved outcome after stroke. This study, however, raises concern about the potential for inadvertent induction of detrimental autoimmunity through mucosal administration of antigen.

Morphological plasticity in an infant monkey model of temporal lobe epilepsy

PURPOSE/METHODS

Seizures in early life are thought to contribute to the development of human temporal lobe epilepsy. To examine the consequences of early seizures, we elicited status epilepticus in immature, 5.5- to 7.0-month-old pigtailed macaques by unilateral microinfusion of bicuculline methiodide into the entorhinal cortex.

RESULTS

This report focuses on neuropathological changes in the hippocampus. Bicuculline infusion consistently elicited limbic-like seizures with prolonged, relatively localized electrographic activity. Magnetic resonance imaging revealed enhanced signal intensity in the ipsilateral hippocampus after seizures; in some cases, there was also progressive hippocampal atrophy. Histological changes were variable; in two of five monkeys, there was significant hippocampal neuron loss, gliosis, granule cell dispersion, and mossy fiber reorganization.

CONCLUSIONS

The histopathological findings and associated magnetic resonance imaging abnormalities after bicuculline-induced status epilepticus in infant monkeys mimic common aspects of human temporal lobe epilepsy.