Translating Animal Models of Ischemic Stroke to the Human Condition

Ischemic stroke is a leading cause of death and disability. However, very few neuroprotective agents have shown promise for treatment of ischemic stroke in clinical trials, despite showing efficacy in many successful preclinical studies. This may be attributed, at least in part, to the incongruency between experimental animal stroke models used in preclinical studies and the manifestation of ischemic stroke in humans. Most often the human population selected for clinical trials are more diverse than the experimental model used in a preclinical study. For successful translation, it is critical to develop clinical trial designs that match the experimental animal model used in the preclinical study. This review aims to provide a comprehensive summary of commonly used animal models with clear correlates between rodent models used to study ischemic stroke and the clinical stroke pathologies with which they most closely align. By improving the correlation between preclinical studies and clinical trials, new neuroprotective agents and stroke therapies may be more accurately and efficiently identified.

Functional recovery outcomes following acute stroke is associated with abundance of gut microbiota related to inflammation, butyrate and secondary bile acid

Accumulating evidence suggests that gut microbes modulate brain plasticity via the bidirectional gut-brain axis and play a role in stroke rehabilitation. However, the microbial species alterations associated with stroke and their correlation with functional outcome measures following acute stroke remain unknown. Here we measure post-stroke gut dysbiosis and how it correlates with gut permeability and cognitive functions in 12 stroke participants, 18 controls with risk factors for stroke, and 12 controls without risk factors. Stool samples were used to measure the microbiome with whole genome shotgun sequencing and leaky gut markers. We genotyped APOE status and measured diet composition and motor, cognitive, and emotional status using NIH Toolbox. We used linear regression methods to identify gut microbial associations with cognitive and emotional assessments. We did not find significance differences between the two control groups. In contrast, the bacteria populations of the Stroke group were statistically dissimilar from the control groups. Relative abundance analysis revealed notable decreases in butyrate-producing microbial taxa, secondary bile acid-producing taxa, and equol-producing taxa. The Stroke group had higher levels of the leaky gut marker alpha-1-antitrypsin in the stool than either of the groups and several taxa including Roseburia species (a butyrate producer) were negatively correlated with alpha-1-antitrypsin. Stroke participants scored lower on memory testing than those in the two control groups. Stroke participants with more Roseburia performed better on the picture vocabulary task; more Bacteroides uniformis (a butyrate producer) and less Escherichia coli (a pro-inflammatory species) reported higher levels of self-efficacy. Intakes of fiber, fruit and vegetable were lower, but sweetened beverages were higher, in the Stroke group compared with controls. Vegetable consumption was correlated with many bacterial changes among the participants, but only the species Clostridium bolteae, a pro-inflammatory species, was significantly associated with stroke. Our findings indicate that stroke is associated with a higher abundance of proinflammatory species and a lower abundance of butyrate producers and secondary bile acid producers. These altered microbial communities are associated with poorer functional performances. Future studies targeting the gut microbiome should be developed to elucidate whether its manipulation could optimize rehabilitation and boost recovery.

Abstract WP152: Changes In Thrombus Fibrin Content By Time In Patients Undergoing Thrombectomy

Introduction: Understanding clot composition and associated genomic, epigenomic, and proteomic signatures could provide insight into thrombus biology and etiology, and aid in prognosis in stroke. We report preliminary analysis of histology evaluations in subjects enrolled in the INSIGHT Registry, a multicentered ‘multi-omic’ analysis of thrombi associated with acute hemorrhagic and ischemic stroke this multi-omic clot collection registry. Our aim was to determine potential histology differences in thrombi as a consequence of infarct time (time from last known normal to thrombectomy).

Material and Methods: Subjects age ≥18 years, treated frontline with the Penumbra System for thrombectomy are included in this analysis. Patient demographics, medical history, radiographic, and procedural information are collected in conjunction with extracted clot and concurrent extracranial arterial blood. Enrollment, data collection, and data monitoring are ongoing for the INSIGHT registry. While the protocol includes analysis for proteomics and transcriptomics, for this analysis we used automated histology. An MSB Trichrome stain was used to evaluate the tissue. Composition was determined by automated pixel analysis, with the values representing ratios of the overall clot.

Results: Samples from 60 subjects who were enrolled from 10 sites between 02/2021 and 07/2021. Analysis of the thrombi successfully determined the relative portions of fibrin, red blood cells (RBCs), and platelets (PLT). The median percentage of fibrin in the thrombi was 44.0% (IQR 29.0 - 57.6; N=60). The median time interval from Last Known Well to recanalization was 4.0 hours (IQR 2.9-12.8 hours; N=55). There was no correlation between the time interval of stroke and the percent of fibrin in the thrombus (Pearson correlation coefficient -0.01, p 0.94).

Conclusion: These preliminary results demonstrate a lack of relationship between time interval of the stroke and clot histology composition with relation to fibrin. Thrombus fibrin composition is likely more related to other factors, and not predominantly related to time. We are currently investigating potential relationships to demographics and co-morbidities.

Short Chain Fatty Acids Taken at Time of Thrombectomy in Acute Ischemic Stroke Patients Are Independent of Stroke Severity But Associated With Inflammatory Markers and Worse Symptoms at Discharge

Introduction

Short chain fatty acids (SCFA) are gut microbiota-derived metabolites that contribute to the gut-brain axis and may impact stroke outcomes following gut dysbiosis. We evaluated plasma SCFA concentrations against stroke severity parameters and identified SCFA-associated protein networks.

Methods

The Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC), a continuously enrolling tissue bank, was used to obtain stroke samples. Arterial blood distal and proximal to the thrombus was obtained from Acute Ischemic Stroke (AIS) Patients (n=53) during thrombectomy. Patient demographics, stroke presentation and outcome parameters were reported. The SCFAs were isolated from proximal plasma via chemical derivatization UHPLC coupled tandem mass spectrometry using electrospray ionization and multiple reaction monitoring. Proteomic levels for 184 cardioembolic and inflammatory proteins was quantified from systemic and intracranial plasma by Olink. Arterial blood from cerebrovascular patients undergoing elective neurointerventional procedures was used as controls.

Results

Acetate positively correlated with time from last known normal (LKN) and was significantly lower in stroke patients compared to control. Isobutyrate, Butyrate and 2-Methylbutyrate negatively correlated with %ΔNIHSS. Isobutyrate and 2-Methylbutyrate positively correlated with NIHSS discharge. SCFA concentrations were not associated with NIHSS admission, infarct volume, or edema volume. Multiple SCFAs positively associated with systemic and pro-inflammatory cytokines, most notably IL-6, TNF-α, VCAM1, IL-17, and MCP-1.

Conclusions

Plasma SCFA concentrations taken at time of stroke are not associated with stroke severity at presentation. However, higher levels of SCFAs at the time of stroke are associated with increased markers of inflammation, less recovery from admission to discharge, and worse symptom burden at discharge.

Abstract P777: Statistical Modeling of Proteomic Signaling During Stroke in Patients Undergoing Thrombectomy

Introduction: The previously published Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) protocol (clinicaltrials.gov NCT03153683) utilizes mechanical thrombectomy to obtain tissue samples for banking. Peripheral blood proximal to the clot and intracranial blood distal from the clot were isolated. Proteomic and statistical analyses revealed normalized (intracranial-systemic) CCL19 expression was a predictor of infarct volume. Statistical modeling analyses were used determine the CCL19-associated proteomic signaling network occurring during ischemic stroke relating to infarct volume.

Methods: Arterial intracranial and systemic blood samples underwent analysis for inflammatory proteins using Proximity Extension Assay (PEA) via Olink (Olink Proteomics, Boston, MA). Systemic expression was used as an internal control to normalize expression in the intracranial blood. Bivariate regression was used to examine the relationship between the intracranial normalized CCL19 expression and infarct volume. A backwards stepwise regression was then used to determine a model of predictability of infarct volume by CCL19 and associated inflammatory proteins.

Results: 25 subjects (>18 yrs) with a mean infarct volume of 8,172 ± 82,284 mm 3 and mean infarct time of 513 ± 246 minutes were included in this study. Their median age was 64 (24-91) and 10 (40%) were male. 16 subjects (64%) had hypertension, 15 (60%) had BMI > 25, and 6 (24%) had a previous stroke. The stepwise regression model shows normalized expression of 16 proteins correlated with an increase in infarct volume (p<0.005): CCL20, CXCL1, OSM, CD6, OSMR, TGF-alpha, TRANCE, CXCL10, LIF-R, CCL19, CDCP1, Flt3L, CCL23, CD244, TRAIL, NOTCH1.

Conclusions: In our model, the expression of these proteins were consistently changed, though the directionality differed. LIF-R, NOTCH1, TRAIL, CD6, CCL23, TGF-alpha, and CCL20 were positively correlated, while the expressions of Flt3L, OSM, OSMR, TRANCE, CD244, CDCP1, CXCL1, CXCL10, and CCL19 were negatively correlated with infarct volume. This model depicts the proteomic signaling occurring during stroke in relationship to infarct volume, which reveals potential biomarkers and therapeutic targets for the early phase of ischemic stroke.

Abstract P778: Hypertension and Vascular Cell Adhesion Molecule 1 Relate To % Change in National Institutes of Health Stroke Scale Score in Ischemic Stroke After Mechanical Thrombectomy

Introduction: The University of Kentucky Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) protocol utilizes thrombectomy to isolate intracranial (i.e. distal to thrombus) arterial blood and systemic (i.e. carotid) arterial blood from thrombectomy procedures to study stroke. Here, we investigate the relationship among Vascular Cell Adhesion Molecule 1 (VCAM1), hypertension (HTN), and stroke recovery in patients undergoing mechanical thrombectomy for emergent large vessel occlusion (ELVO) stroke.

Methods: Intracranial and systemic plasma samples from 25 subjects underwent cardiometabolic proteomic analysis at Olink Proteomics. Demographic data including HTN status and both admission NIHSS and discharge NIHSS were included. Linear regression analysis was run on both intracranial and systemic VCAM1 expression levels against % change in NIHSS ((Admittance NIHSS - Discharge NIHSS)/Admittance NIHSS)) and two-tailed t-tests were run assessing VCAM1 expression with HTN vs. no HTN.

Results: Increased expression of intracranial VCAM1 significantly correlated with a smaller % change in NIHSS (p=0.001). Similarly, increased systemic VCAM1 expression was also found to have a significant relationship with smaller % change in NIHSS (p=0.005). Subjects with hypertension had significantly higher intracranial (p=0.03) and systemic (p=0.001) VCAM1 levels compared to those without HTN.

Discussion: VCAM1 mediates leukocyte-endothelial cell adhesion and has been shown to play a role in stroke. This study takes a novel approach of sampling both intracranial and systemic arterial blood during an ELVO stroke. We found increased intracranial and systemic VCAM1 independently correlate with a smaller % change in NIHSS, an indicator of poorer initial recovery. Although preliminary, these results suggest an informative role of VCAM1 levels at the time of infarct. Additionally, those with HTN had higher levels of intracranial and systemic VCAM1. These data are in line with previous studies suggesting VCAM1 is a marker of endothelial damage due to HTN leading to negative clinical outcomes. To better understand our findings, we plan to perform subset analyses investigating VCAM1 levels in relation to dyslipidemia, infarct time and infarct volume.

Abstract TP20: Protocol to Isolate Lymphocytes for Flow Cytometry From BACTRAC Samples

Introduction: Since 2015, mechanical thrombectomy is the standard treatment for emergent large vessel occlusion stroke. Using standard techniques during mechanical thrombectomy, the Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) protocol (clinicaltrials.gov NCT03153683) isolates distal blood within the artery immediately downstream from the clot, peripheral blood proximal to the clot, and the thrombus. BACTRAC is the first protocol utilizing the thrombectomy technique to collect local whole blood samples during brain infarction. We aimed to augment the current collection protocol to reproducibly obtain and study local leukocyte populations during human stroke.

Methods: We started with the established BACTRAC protocol previously published (PMID: 30064997). We modified the tissue collection protocol to isolate lymphocytes for flow cytometry and to bank the clot and plasma. We performed a flow cytometry panel that identifies CD3, 4, 8, 11b, 11c, 14, 19, 31, 45, 66b, 161, 183 markers to investigate populations of B-cells, T-cells, dendritic cells, NK cells, macrophages/monocytes, granulocytes, endothelial cells, and progenitors, respectively.

Results: The protocol was first established in healthy controls (n=9) by drawing venous blood and simulating a vial of distal blood and a vial of proximal blood. In healthy subjects, we were able to isolate on average 2x10 6 leukocytes/ml with a viability of 97.85%. Banked lymphocytes are also viable upon reconstitution and for flow cytometry. This protocol successfully isolates leukocytes in proximal and distal blood samples in subjects undergoing mechanical thrombectomy, with identification and analysis by flow cytometry currently ongoing.

Conclusions: This modification to the existing BACTRAC protocol provides the opportunity, for the first time, to study local leukocyte populations in the arteries undergoing ischemic stroke in the human condition. Efficient processing of these samples will provide insight into the neuroinflammatory microenvironment of the occlusion and accelerate translational stroke research towards new methods of diagnosis and treatment.

Evaluation of Patients with High National Institutes of Health Stroke Scale as Thrombectomy Candidates Using the Kentucky Appalachian Stroke Registry

INTRODUCTION

Mechanical thrombectomy has become standard of care for emergent large vessel occlusive stroke. Estimates of incidence for thrombectomy eligibility vary significantly. National Institutes of Health Stroke Scale (NIHSS) of 10 or greater is highly predictive of large vessel occlusion. Using our Kentucky Appalachian Stroke Registry (KApSR), we evaluated temporal trends in stroke admissions with NIHSS ≥10 to determine patient characteristics among that group along with effects and needs in thrombectomy utilization.

METHODS

Using the KApSR database that captures patients throughout the Appalachian region in our stroke network, we evaluated patients admitted with ischemic stroke with NIHSS ≥10. We recorded demographics, comorbidities, treatment (thrombectomy, decompressive craniectomy), and county of origin. Change in NIHSS from admission to discharge was used as an indicator of inpatient outcome.

RESULTS

Between 2010 and 2016, 1,510 patients were admitted with NIHSS ≥10. 87.2% had high blood pressure, 69.6% had dyslipidemia, and 41.7% used tobacco. There were significant sex differences in the types of patients presenting with NIHSS ≥10 with females being older on average and having more atrial fibrillation and obesity. There was an increase in thrombectomy utilization from 2010 to 2016, but only 7.5% of the potentially eligible patients underwent the procedure. In comparison to the period 2010-2014, the 2015-2016 period had higher rates of obesity and tobacco abuse.

CONCLUSION

Among patients with significant burden of ischemic stroke, the most common coexisting medical condition was high blood pressure. Patients who underwent thrombectomy had significantly better inpatient clinical improvement. These data support the need to maximize utilization of thrombectomy along with need to devote increased resources on modifiable stroke risk factors.

Immune System Activation in Perioperative Thrombectomy Patients: Preliminary Retrospective Study

BACKGROUND

Ischemic stroke is a devastating condition resulting in significant morbidity. Mechanical thrombectomy is now standard for large vessel occlusive stroke. Neuroinflammation is known to play important roles in ischemic stroke. Our aims were to examine our thrombectomy procedures and preliminarily examine systemic immune response in relation to thrombectomy changes.

METHODS

A retrospective review was conducted on mechanical thrombectomy cases from July 2011 through December 2015. Primary outcomes were time to recanalization, final Thrombolysis in Cerebral Infarction score, procedural complications, National Institutes of Health Stroke Scale improvement, and changes in white blood cell (WBC) count.

RESULTS

One-hundred and twenty-nine procedures were performed. We found a significant difference between WBC count on admission and WBC count post thrombectomy day 1 for patients with >90 minutes to recanalization (P = 0.006107). There was a positive association between WBC change and absolute National Institutes of Health Stroke Scale change among females (P = 0.0273) but not among males.

CONCLUSIONS

Overall, we found that systemic immune response has close relationships with speed of recanalization and preliminarily may shift differently on the basis of sex.

Abstract TMP107: Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) Protocol: Novel Method for Evaluating Human Stroke

Background: Research in ischemic stroke struggles from failures to translate stroke conditions between animal models and human patients. With mechanical thrombectomy, we have for the first time developed a protocol to facilitate tissue banking of intracranial thrombi as well as the blood immediately proximal and distal to it. These tissues provide a unique resource to correlate changes in the human condition to animal models. Our aim was to develop a reproducible protocol to bank these specimens for future gene expression and proteomic analysis.

Methods: We developed an IRB-approved protocol for tissue processing during thrombectomy (www.clinicaltrials.gov NCT03153683). The protocol was a joint clinical/basic science effort among multiple laboratories and the Neurointerventional Radiology Service Line. We placed laboratory supplies in the angio suite, and developed a step-by-step protocol for specimen retrieval and processing.

Results: Our protocol successfully yielded samples for analysis in all but one case. In our preliminary dataset, the protocol yielded adequate amounts of tissue for distal blood, proximal blood, and thrombus. We present the tissue banking protocol for dissemination, and highlight the training protocol and mechanics of on-call research staffing for 24/7 tissue processing. In addition, preliminary integrity analyses demonstrated high quality yields for RNA and protein.

Conclusion: We have developed a novel tissue banking protocol to capture thrombus, and both proximal and distal blood to the intracranial thrombus in human stroke patients. The specimens are captured during the thrombectomy procedure, and allow us to study the initial molecular response to ischemic stroke in the human condition in ways previously unavailable.

Abstract WMP113: Translational Evaluation of Acid/Base and Electrolyte Alterations in Acute Large Vessel Stroke

Background and Purpose: Monitoring for hypotension, hyperglycemia, hypoxia, and dehydration is key to reducing early death in stroke patients. Evaluation of physiological predictors of infarct volume and mortality may provide opportunities for effective interventions to improve outcomes. The purpose of this study is: 1) to describe and compare the predictive effects of venous blood gas (VBG) on infarct volume and mortality in acute stroke in rats; 2) and we have begun to collect arterial blood gas (ABG) to compare differences obtained proximal and distal to the occluded intracranial thrombi in acute ischemic stroke patients.

Methods: 3-month old Sprague-Dawey rats (n = 9) underwent permanent or transient middle cerebral artery occlusion (MCAO). Pre- and post-MCAO venous samples provided pH, pCO 2 , pO 2 , and electrolyte values (iCa 2+ , K + , and Na + ). Linear regression determined predictors of infarct volume from these values, and Cox regression analyzed VBG changes between tMCAO (n = 28) and pMCAO (n = 29) to determine predictors of mortality. We compared mean proximal and distal pH, pCO 2 , pO 2 , and electrolytes (iCa 2+ , K + , and Na + ) in stroke patients (n = 7) arterial samples using Wilcoxon Signed Ranks test.

Results: Animal studies demonstrated pH and iCa 2+ are predictors of infarct volume, but not mortality. After pMCAO (n = 9), change in pH or iCa 2+ significantly predicted infarct volume [F(1,7) = 7.351, β = -0.716, p = 0.03] and [F(1, 7) = 6.782, β = -0.701, p = 0.035]; as pH and calcium decreased, infarct volume increased. These variables explained 44% and 42% of the total variance in these models. In human patients (n = 7), there were significant differences in blood samples proximal and distal to the intracranial thrombus for pCO 2 (p = 0.018), HCO 3- (p = 0.028), iCa 2+ (p = 0.043), K + (p = 0.028), and Na + (p = 0.044).

Conclusions: In conclusion, there are acute changes in acid/base balance and electrolytes during stroke in rodent models and humans. In cross-species comparison ionized calcium changes were significant in both, with iCa 2+ changes predicting stroke volume in the rat model. These preliminary findings are novel, and warrant further exploration in human patients.

QUANTITATIVE MORPHOLOGICAL AND MOLECULAR PATHOLOGY OF THE HUMAN THYMUS CORRELATE WITH INFANT CAUSE OF DEATH

The objective of this study was to investigate and quantify the morphological and molecular changes in the thymus for common causes of human infant death. Thymic architecture and molecular changes apparent in human infant head trauma victims were assessed by microscopy and quantified by image analysis of digital whole slide images. Thymuses from victims of SIDS and suffocated infants displaying normal thymus architecture were used for comparison. Molecular expression of proliferation and serotonin receptor and transporter protein markers was evaluated. Duplicate morphological and molecular studies of rodent thymuses were completed with both mouse and rat models. Quantification of novel parameters of digital images of thymuses from human infants suffering mortal head trauma revealed a disruption of the corticomedullary organization of the thymus, particularly involving dissolution of the corticomedullary border. A similar result was obtained for related mouse and rat models. The human thymuses from head trauma cases also displayed a higher percentage of Ki-67-positive thymocytes. Finally, we determined that thymus expression of the human serotonin receptor, and the serotonin transporter, occur almost exclusively in the thymic medulla. Head trauma leads to a disruption of the thymic, corticomedullary border, and molecular expression patterns in a robust and quantifiable manner.

Abstract 2494: A Transient Decrease in Spleen Size Following Stoke Corresponds to Splenocyte Release into Systemic Circulation

Objective: Splenectomy is protective in ischemic injuries to renal, hepatic, and gastrointestinal systems, showing that the splenic response promotes cellular degeneration. Removal of the spleen is also protective in ischemic and hemorrhagic stroke. Therefore, we investigated the cellular response of the spleen to brain ischemia.

Hypothesis: Immune cells are released from the spleen following cerebral ischemia contributing to neural injury.

Methods: A time course was conducted to investigate splenic size changes in rats over time following permanent middle cerebral artery occlusion (MCAO) and sham-MCAO (n≥3). In a second experiment, splenocytes were labeled in situ with carboxyfluorescein diacetate, succinimidyl ester (CFSE). Five evenly spaced splenic injections, 4 mg/ml in DMSO, were given to all groups five days prior to MCAO or sham-MCAO. The experimental groups were: 48 hr post-MCAO (n=4), 48 hr post-sham-MCAO (n=4), 96 hr post-MCAO (n=6), 96 hr post-sham-MCAO (n=4), and a CFSE only group that was euthanized five days following injection of CFSE without undergoing MCAO (n=4). Spleen, brain, thymus, and blood smears were collected for all groups.

Results: The spleen was found to decrease in size at 48 hrs following MCAO in rats compared to controls (p<0.01). However, by 96 hrs post-MCAO the spleen size returned to levels not different from sham operated rats. CFSE was found to be non-toxic at the 4 mg/ml concentration and five days following injection 15% of the splenocytes were labeled. In the spleen, there was a significant increase (p<0.0001) in CFSE positive cells in the 48 hr sham group versus the 96 hr sham and both 48 and 96 hr MCAO groups. Blood smears showed a significant increase in total CFSE positive cells (p<0.0007) at 48 hrs post-MCAO. CFSE positive cells in the blood were identified by Giemsa staining. A significant increase of lymphocytes (p<0.005), monocytes (p<0.02), and neutrophils (p<0.0005) was found at 48 hrs post-MCAO when compared to the other groups.

Conclusion: These results demonstrate that CFSE is a viable and safe way to track immune cells in situ in an animal model of stroke. The spleen transiently decreases in size post-MCAO in rats and releases splenocytes into systemic circulation at 48 hrs following MCAO. These cells are migrating to the brain or other lymphoid organs, affecting the overall immune response to ischemia. Brains and thymi from the CFSE injected animals will be analyzed for the presence of these cells.

Nicotine inhibition of apoptosis in murine immune cells

Nicotine, the addictive component of tobacco, is thought to be at least partially responsible for the deleterious effects of smoking such as heart disease and cancer. Evidence shows that nicotine is an immunomodulator and that one of its possible mechanisms is regulation of apoptosis, or programmed cell death, in immune cells. This study examined the effects and the mechanisms of action of nicotine on dexamethasone (DEX)-induced apoptosis in murine immune cells by examining the expression of levels of the 17-kDa active caspase-3, a marker of apoptosis. Thymocytes and splenocytes from adult BALB/c female mice were incubated with concentrations of nicotine correlating to those found in the blood and tissue of smokers (0.01 microg/ml [0.022 microM] and 1 microg/ml [2.2 microM]), concurrently with 100 nM DEX, to induce apoptosis. Cytosolic protein fractions were analyzed by Western blotting with polyclonal antibodies that recognize the active form of caspase-3. The data showed that nicotine significantly blocked the formation of the DEX-induced 17-kDa caspase-3 subunit expression. This downregulation ranged from 65% to 100% of the active caspase-3 expressed in cultures treated with DEX alone. Addition of d-tubocurarine chloride (dTC), a general nicotinic receptor antagonist, inhibited nicotine downregulation of the DEX-induced active caspase-3 expression, providing evidence that this action of nicotine was receptor-mediated. These data support that nicotine is an important immunomodulator at the level of immune cell apoptosis, a process thought to be a contributory mechanism of autoimmunity, cardiovascular disease, and carcinogenesis.

Transcription factors in brain injury

After brain injury, neuronal genes are regulated to adjust to an altered environment; however, if neurons are damaged then genes related apoptosis are activated. Glial cells, astrocytes and microglia, respond to neuronal death by transcribing genes to enhance the survival of remaining neurons and for regeneration and repair. AP-1 transcription factors are induced in the neuronal response to injury. Depending on the AP-1 dimer combination, neuronal genes related to either apoptosis or survival are transcribed. A 35 kDa Fos-related antigen:JunD dimer is present in neurons that survive injury. Jun and JunD exists in neurons prior to undergoing apoptosis. Neuronal death activates gene expression in astrocytes and microglia. NFk beta transcription factors are induced in astrocytes reacting to neuronal injury. In the microglial response, STATs appear to be activated to regulate gene transcription. These transcription factors that modulate the genes involved in the cellular processes of brain injury are examined in this review.

Long-term expression of the 35,000 mol. wt fos-related antigen in rat brain after kainic acid treatment

Systemic injection of kainic acid, a rigid analogue of glutamate, induces both the short-term and the long-term expression of activator protein-1 transcription factors. The short-term responses of activator protein-1 factors such as c-fos and fos-related antigens have been well studied. However, the long-term expression of activator protein-1 factor(s) induced by kainic acid is poorly understood. The present study was designed to document the long-term expression (up to seven months) of the fos-related antigens and to map their distributions in the rat brain after systemic treatment with kainic acid. A single dose of kainic acid (8 mg/kg) was injected i.p. into Fischer 344 rats and their epileptic seizure behaviour was monitored. The rats with full limbic seizures were chosen for long-term study. By using immunocytochemistry with an antibody that cross-reacts with all known fos-related antigens, western blot analysis and a gel mobility-shift assay, we have now shown that a 35,000 mol. wt fos-related antigen was induced by kainic acid treatment and expressed at high levels for up to five months. This fos-related antigen still maintains the activator protein-1 DNA binding activity in the rat brain seven months after kainic acid treatment. The fos-related antigens and activator protein-1 binding activity were continuously expressed at high levels throughout the experimental period in the dentate granule cells where mossy fibre collateral sprouting occurred after kainic acid treatment. Our results suggested that long-term expression of fos-related antigen may reflect the pathophysiological changes after kainic acid administration.

Early in vitro genesis and differentiation of axons and dendrites by hippocampal neurons analyzed quantitatively with neurofilament-H and microtubule-associated protein 2 antibodies

Differentiating neurons initially extend neurites that are the precursors of axons and dendrites. The temporal pattern of neurite outgrowth has been studied extensively, but mostly qualitative analyses have been used to study this phenomenon. We have examined neurite outgrowth of hippocampal neurons in primary cultures using a polyclonal antibody against microtubule-associated protein 2 (MAP2) and a novel monoclonal antibody against the phosphorylated form of high neurofilament subunit (NF-H). These antibodies serve as markers for dendrites and axons, respectively. The neurite staining patterns were quantified during the first 10 days in culture and the analysis revealed that primary processes undergo three phases of differentiation: (i) in the first 24 h, the majority of primary neurites express MAP2 only and a small percentage express both MAP2 and NF-H; (ii) between 24 and 48 h, NF-H expression increases and it is coexpressed with MAP2 in many neurites as they begin to lengthen; and (iii) between 48 h and 4 days, MAP2 and NF-H protein expression occurs in separate populations of neurites. While most of the earliest forming primary neurites appear to be dendritic (MAP2 only), the coexpression of dendritic and axonal protein markers in a group of early forming processes suggests that these neurites may not be predetermined to become a dendrite or an axon. Our data also indicate that NF-H is detectable early in primary neurite development and that, based on in vivo localization and morphology of cultured neurites, the phosphorylated form of NF-H is concentrated in axons.