Sexually dimorphic microglia and ischemic stroke

Ischemic stroke kills more women compared with men thus emphasizing a significant sexual dimorphism in ischemic pathophysiological outcomes. However, the mechanisms behind this sexual dimorphism are yet to be fully understood. It is well established that cerebral ischemia activates a variety of inflammatory cascades and that microglia are the primary immune cells of the brain. After ischemic injury, microglia are activated and play a crucial role in progression and resolution of the neuroinflammatory response. In recent years, research has focused on the role that microglia play in this sexual dimorphism that exists in the response to central nervous system (CNS) injury. Evidence suggests that the molecular mechanisms leading to microglial activation and polarization of phenotypes may be influenced by sex, therefore causing a difference in the pro/anti‐inflammatory responses after CNS injury. Here, we review advances highlighting that sex differences in microglia are an important factor in the inflammatory responses that are seen after ischemic injury. We discuss the main differences between microglia in the healthy and diseased developing, adult, and aging brain. We also focus on the dimorphism that exists between males and females in microglial‐induced inflammation and energy metabolism after CNS injury. Finally, we describe how all of the current research and literature regarding sex differences in microglia contribute to the differences in poststroke responses between males and females.

Sex-Dependent Differences in Physical Exercise-Mediated Cognitive Recovery Following Middle Cerebral Artery Occlusion in Aged Rats

Stroke remains a leading cause of death and disability in the United States. No current treatments exist to promote cognitive recovery in survivors of stroke. A previous study from our laboratory determined that an acute bout of forced treadmill exercise was able to promote cognitive recovery in 3 month old male rats after middle cerebral artery occlusion (MCAo). In this study, we tested the hypothesis that 6 days of intense acute bout of forced treadmill exercise (physical exercise – PE) promotes cognitive recovery in 11–14 month old male rats. We determined that PE was able to ameliorate cognitive deficits as determined by contextual fear conditioning. Additionally, we also tested the hypothesis that PE promotes cognitive recovery in 11–13 month old reproductive senescent female rats. In contrast to males, the same intensity of exercise that decrease cognitive deficits in males was not able to promote cognitive recovery in female rats. Additionally, we determined that exercise did not lessen infarct volume in both male and female rats. There are many factors that contribute to higher stroke mortality and morbidities in women and thus, future studies will investigate the effects of PE in aged female rats to identify sex differences.

Estrogen preconditioning: A promising strategy to reduce inflammation in the ischemic brain

During the premenopausal phase of a woman's life, estrogen naturally protects against ischemic brain damage and its debilitating consequence of cognitive decline. However, the decline in estrogen at menopause exponentially increases a women's risk for cerebral ischemia and its severity. Supplementation of estrogen during menopause is the most logical solution to abate this increased risk for cerebral ischemia; however, continuous therapy has proven to be contraindicative. Studies from our laboratory over the past decade have shown that a single bolus or long-term periodic 17β-estradiol treatment(s) two days prior to ischemia mimics ischemic preconditioning-conferred protection of the brain in ovariectomized or reproductively senescent female rats. These studies also demonstrated that 17β-estradiol-induced preconditioning (EPC) requires estrogen receptor (ER)-subtype beta (ER-β) activation. ER-β is expressed throughout the brain, including in the hippocampus, which plays a key role in learning and memory. Because periodic activation of ER-β mitigates post-ischemic cognitive decline in ovariectomized female rats, it can be surmised that EPC has the potential to reduce post-ischemic damage and cognitive decline in females. Estrogens are key anti-inflammatory agents; therefore this review discusses the effects of EPC on the inflammasome. Furthermore, as we now clearly know, the brain acts differently in males and females. Indeed, neurodegenerative diseases, including cerebral ischemia, and pharmacological drugs affect males and females in different ways. Thus, inasmuch as the National Institutes of Health and the Stroke Treatment Academic Industry Roundtable (STAIR) consortium mandate inclusion of female experimental animals, this review also discusses the need to close the gap in our knowledge in future studies of EPC in female animal models of cerebral ischemia.

Abstract TP124: Nicotine Alters Brain Energy Metabolism and Exacerbates Ischemic Brain Damage

Background: Smoking-derived nicotine (N) and oral contraceptives (OC) are known to synergistically magnify the risk and severity of cerebral ischemia in females. The underlying pathological mechanism remains elusive. Our studies have shown that N toxicity is exacerbated by OC via altered mitochondrial function, which involved a defect in activity of cytochrome c oxidase, the terminal enzyme of the electron transport chain. However, the effects of impaired mitochondrial function on brain metabolism remain to be investigated. To understand the impact in brain metabolisms, in the current study we investigated the global metabolomic profile of brains of adolescent and adult female rats exposed to N +/- OC.

Methods: Six and twelve weeks old Sprague-Dawley female rats were randomly (n = 8/group) exposed to either saline, N (4.5 mg/kg) +/- OC for 16-21 days. At the end of the treatment, brain tissue was harvested for metabolomic analysis (performed by Metabolon Inc.) The metabolomic profile was complemented with western blot analysis and enzyme activity measurements.

Results: Pathway enrichment analysis showed significant changes in energy metabolism (glycolysis and TCA cycle) and neurotransmitters in both adolescent and adult rats exposed to N, OC and N+OC in relation to saline treatment. The changes were more pronounced in adolescent rats with a significant decrease in glucose, glucose 6-phosphate, fructose-6-phosphate along with a significant increase in pyruvate in N and N+OC exposed groups when compared to saline (p<0.05), suggesting alterations in the glycolytic pathway. Western blot analyses of glycolytic enzymes support the observed metabolic changes.

Conclusion: Nicotine and N+OC exposure increased brain glycolysis in an age-dependent manner. Since glucose metabolism is critical for brain physiology, altered glycolysis deteriorates neural function thus exacerbating ischemic brain damage. Moreover, significant decrease in the neuroactive peptide GABA was observed in young female rats treated with N+OC when compared to saline group. Discerning the exact effects of N +/- OC on overall brain metabolism and the molecular mechanisms affecting mitochondrial function at different ages will open a new window for future therapeutic intervention.

Abstract TP118: Post-Stroke Whole Body Vibration Reduces Frailty in Nicotine Exposed Female Rats

Background: Stroke disproportionately kills more women than men and the risk of stroke remains high even at a young age among women smokers. Smoking prior to stroke is associated with increased post-stroke frailty. Frailty is characterized by an increased vulnerability to acute stressors and the reduced capacity of various bodily systems due to age-associated physiological deterioration. Such age related physiological deterioration of bone in laboratory animals and humans has shown to reverse after therapeutic intervention of whole body vibration (WBV). In the current study we aim to test the efficacy of WBV in reducing post-ischemic frailty and improving physical activity and cognition using a rat model of smoking attributed nicotine.

Methods: Nicotine or saline exposed adult female rats underwent transient middle cerebral artery occlusion (tMCAO; 90 min) / sham-surgery and randomly assigned (n = 6-8 per group) to either WBV or control groups. Animals placed in the WBV (40 Hz) group underwent 30 days of WBV treatment performed twice daily for 15 min each session for 5 days each week. We monitored the frailty index (FI) prior to and 1 month after tMCAO alone or in combination with WBV. The FI was composed of the following criteria: 1) activity levels, 2) blood pressure (BP), 3) basic metabolic status, and 4) cognitive performance of rats. Animals were sacrificed on the 30th day of WBV treatment, and brain tissue was harvested for histopathological analysis.

Results: Post-tMCAO WBV did not change activity levels or BP in nicotine or saline treated rats. Post-tMCAO WBV cognitive performance improved in saline group as compared to nicotine exposed rats. Sensorimotor function was also improved in tMCAO WBV saline group compared to nicotine-exposed rats. We observed 56% reduction in infarct volume of WBV treated rats as compared to control (p < 0.05). This difference was not seen in nicotine treated groups.

Conclusions: The post-ischemic WBV intervention had no detrimental effects on the frailty parameters, decreased brain damage, and reduced frailty in control female rats, but not in the nicotine-exposed group. This suggests that WBV may be a potential therapy for non-smokers to reduce post-ischemic frailty and improve functional and cognitive outcomes after stroke.

Preconditioning with CpG-ODN1826 reduces ischemic brain injury in young male mice: a replication study

Earlier studies established that ischemic tolerance can be induced in the brain using various strategies. An earlier study demonstrated that preconditioning with the toll-like receptor 9 ligand, CpG oligodeoxynucleotides (ODN), protects the brain against ischemic damage. To increase the potential translational value of the previous study, the goal of the present study was to replicate this earlier finding in a different animal cohort at a different site. In addition to these replication studies, following the Stroke Treatment Academic Industry Roundtable (STAIR) guidelines, we also conducted studies to evaluate the protective effect of CpG-ODN 1826 preconditioning on cerebral ischemic damage in ovariectomized (Ovx) female animals. Young male and female mice were treated with CpG-ODN 1826 or control ligand 3 days prior to the induction of transient (60 min) cerebral ischemia using a middle cerebral artery occlusion (MCAO) model. Infarct size was evaluated at ~24 h post-MCAO. We were able to replicate earlier findings that preconditioning with a low dose (20 μg/mouse) of CpG-ODN 1826 was able to lower cerebral ischemic damage in young male mice. However, we did not see any protective effect of low dose CpG-ODN 1826 preconditioning against cerebral ischemic damage in young Ovx female mice. Our study independently confirms the protective effect of CpG-ODN 1826 in inducing cerebral ischemia tolerance in male but not in Ovx female mice. Our study also demonstrates the feasibility of conducting such replication studies in rodent models of transient stroke.

Sexual dimorphism in inflammasome-containing extracellular vesicles and the regulation of innate immunity in the brain of reproductive senescent females

A woman's risk for stroke increases exponentially following the onset of menopause; however, the underlying mechanisms responsible for the increased risk remain unknown. The depletion of endogenous estrogen at menopause is known to activate the inflammatory response. Therefore, in this study we have used reproductively senescent (RS) rats to test the hypotheses that (1) inflammasome activation is significantly higher in the brain of RS females (RSF) as compared to their younger counterparts and age-matched senescent male rats, and that (2) RS triggers an innate immune response mediated in part by inflammasome-containing extracellular vesicles (EV) that originate in the female reproductive organs and then spreads to the brain. We tested these hypotheses using male and female Sprague-Dawley rats (Young: 6-7 months and RS: 9-13 months). Hippocampus, gonads and serum were collected. Additionally, cerebrospinal fluid (CSF) of pre- and post-menopausal women (ages 23 to 37 and 52 to 68) was purchased and extracellular vesicles (EV) were isolated from serum and CSF. The Inflammasome proteins caspase-1, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and IL-1β were then resolved by immunoblotting. We found that inflammasome protein expression increased significantly in the analyzed tissues in RSF as compared to young females (YF), such difference was not present in age-matched male rat brains. Interestingly, we found that Nik-related kinase (NRK), which is present in female reproductive organs was present in the CSF and serum-derived EV, suggesting that the source of the EV seen in the brain during RS/menopause originate, in part, in the female reproductive organs. Thus, this study shows for the first time an involvement of the inflammasome originating in the female reproductive system as a contributor to inflammation in the brain that makes the peri-menopausal women's brain more susceptible to neurodegenerative diseases such as stroke.

Nicotine Alters Estrogen Receptor-Beta-Regulated Inflammasome Activity and Exacerbates Ischemic Brain Damage in Female Rats

Smoking is a preventable risk factor for stroke and smoking-derived nicotine exacerbates post-ischemic damage via inhibition of estrogen receptor beta (ER-β) signaling in the brain of female rats. ER-β regulates inflammasome activation in the brain. Therefore, we hypothesized that chronic nicotine exposure activates the inflammasome in the brain, thus exacerbating ischemic brain damage in female rats. To test this hypothesis, adult female Sprague-Dawley rats (6–7 months old) were exposed to nicotine (4.5 mg/kg/day) or saline for 16 days. Subsequently, brain tissue was collected for immunoblot analysis. In addition, another set of rats underwent transient middle cerebral artery occlusion (tMCAO; 90 min) with or without nicotine exposure. One month after tMCAO, histopathological analysis revealed a significant increase in infarct volume in the nicotine-treated group (64.24 ± 7.3 mm³; mean ± SEM; n = 6) compared to the saline-treated group (37.12 ± 7.37 mm³; n = 7, p < 0.05). Immunoblot analysis indicated that nicotine increased cortical protein levels of caspase-1, apoptosis-associated speck-like protein containing a CARD (ASC) and pro-inflammatory cytokines interleukin (IL)-1β by 88% (p < 0.05), 48% (p < 0.05) and 149% (p < 0.05), respectively, when compared to the saline-treated group. Next, using an in vitro model of ischemia in organotypic slice cultures, we tested the hypothesis that inhibition of nicotine-induced inflammasome activation improves post-ischemic neuronal survival. Accordingly, slices were exposed to nicotine (100 ng/mL; 14–16 days) or saline, followed by treatment with the inflammasome inhibitor isoliquiritigenin (ILG; 24 h) prior to oxygen-glucose deprivation (OGD; 45 min). Quantification of neuronal death demonstrated that inflammasome inhibition significantly decreased nicotine-induced ischemic neuronal death. Overall, this study shows that chronic nicotine exposure exacerbates ischemic brain damage via activation of the inflammasome in the brain of female rats.

Cognitive Deficits after Cerebral Ischemia and Underlying Dysfunctional Plasticity: Potential Targets for Recovery of Cognition

Cerebral ischemia affects millions of people worldwide and survivors suffer from long-term functional and cognitive deficits. While stroke and cardiac arrest are typically considered when discussing ischemic brain injuries, there is much evidence that smaller ischemic insults underlie neurodegenerative diseases, including Alzheimer's disease. The "regenerative" capacity of the brain relies on several aspects of plasticity that are crucial for normal functioning; less affected brain areas may take over function previously performed by irreversibly damaged tissue. To harness the endogenous plasticity mechanisms of the brain to provide recovery of cognitive function, we must first understand how these mechanisms are altered after damage, such as cerebral ischemia. In this review, we discuss the long-term cognitive changes that result after cerebral ischemia and how ischemia alters several plasticity processes. We conclude with a discussion of how current and prospective therapies may restore brain plasticity and allow for recovery of cognitive function, which may be applicable to several disorders that have a disruption of cognitive processing, including traumatic brain injury and Alzheimer's disease.

Abstract TP91: Multiple Intra-arterial Dosing of the Mesenchymal Stem Cells Reduces Ischemic Brain Injury in a Rat Stroke Model

Background: Cell therapy is emerging as a promising novel treatment for ischemic stroke. Intra-arterial (IA) mesenchymal stem cells (MSCs) delivery in ischemic stroke has a high potential for clinical translation. Recently, we demonstrated the safety and efficacy of IA delivery of MSCs at 24h in a reversible middle cerebral artery occlusion (rMCAo) rodent model. Given the trophic mechanism of action of cell therapy in stroke, a second dose of cells may be beneficial. However, it is unclear if a second IA-MSCs administration is safe and efficacious. Therefore, we aimed to evaluate administration of two doses of IA-MSCs in the rodent stroke model.

Methods: Female ovariectomized Sprague–Dawley rats were exposed to MCAo for 90 min. Rats were treated with IA-MSCs (1x10 5 cells) or phosphate-buffered saline (PBS) at 1 and 6 days (1D-6D) after MCAo. To test neurological and motor function, the standardized neurobehavioral test battery and the rotarod test were performed. The mean duration (in seconds) on the device was recorded from 3 rotarod measurements. The rats were tested at 7, 15 and 30 days after MCAo. Rats were sacrificed at 30 days for infarct volume measurement using histology.

Results: There were no neurological worsening or mortality seen in either treatment group. We observed significant reduction in infarct volume in 1D-6D MSCs group (21 ± 15mm 3 ; n=5) compared to the PBS-treated group (86 ± 19 mm 3 ; n=8, p<0.05). The 1D-6D MSCs group also showed improvement in rotarod test results (16.8 ± 5.8% vs 7.9 ± 3.4%, p=0.075) at 30 days and neurological scores (5.6 ± 1.2 vs 7.75 ± 0.6, p=0.15) at 15 days.

Conclusions: Double dose IA-MSCs at 1D-6D post rMCAo is safe and reduces ischemic brain injury in female rats, with a trend towards functional improvement.

Abstract WP96: Whole Body Vibration After Ischemia Reduces Inflammation in the Brain of Reproductively Senescent Female Rats

Introduction: A woman’s risk of stroke increases exponentially after menopause, and even a mild ischemic episode can result in increased frailty. Studies performed in laboratory animals and humans support the hypothesis that whole body vibration (WBV) reduces or reverses pathological remodeling of bone and lessens frailty-related physiological deterioration. Using a rodent model of stroke, we have examined whether WBV reduces inflammation and post-ischemic damage and improves motor function in reproductively senescent (RS) female rats.

Methods: The estrous cycles of retired breeder Sprague–Dawley female rats (9–12 months; n = 4-6) were monitored for 14-20 days by daily vaginal smears. Rats that remained in constant diestrous were considered RS, exposed to transient middle cerebral artery occlusion (tMCAO; 60 min) and randomly assigned to either WBV or control groups. Animals placed in the WBV (40 Hz) group underwent 30 days of WBV treatment performed twice daily for 15 min each session for 5 days each week. During the treatment period, we tested motor function using a rotarod test intermittently after tMCAO. Animals were sacrificed on 30th day of WBV treatment and brain tissue was harvested for histopathological and inflammasome protein analysis performed by western blotting.

Results: WBV decreased protein levels of caspase-1, ASC and IL-1 β by 88% (p < 0.05), 57% (p < 0.05) and 148% (p < 0.05) in the peri-infarct area as compared to control-treated group. The rotarod test scores from the WBV treatment group were significantly higher than the control group on day 30 (p < 0.05), suggesting a significant improvement in functional activity of the WBV group. The histopathological assessment demonstrated a significant reduction in infarct volume in a mild-stroke model following WBV treatment as compared to control rats. We observed 56% reduction in infarct volume of WBV treated rats as compared to control. In parallel, we also monitored neurological deficit of rats that were exposed to WBV/control treatment after tMCAO.

Conclusion: The post-ischemic WBV intervention reduces brain damage and frailty in RS female rats, suggesting that WBV may be a potential therapy to reduce post-ischemic frailty and improve functional and cognitive outcomes after stroke in women.

Large animal canine endovascular ischemic stroke models: A review

BACKGROUND

Stroke is one of the leading causes of death and long-term disability worldwide. Recent exciting developments in the field with endovascular treatments have shown excellent outcomes in acute ischemic stroke. Prior to translating these treatments to human populations, a large-animal ischemic stroke model is needed. With the advent of new technologies in digital subtraction angiography, less invasive endovascular stroke models have been developed. Canines have gyrencephalic brain similar to human brain and accessible neurovascular anatomy for stroke model creation. Canine stroke model can be widely utilized to understand the disease process of stroke and to develop novel treatment. Less invasive endovascular internal carotid emboli injection and coil embolization methods can be used to simulate transient or permanent middle cerebral artery occlusion. Major restriction includes the extensive collateral circulation of canine cerebral arteries that can limit the stroke size. Transient internal carotid artery occlusion can decrease collateral circulation and increase stroke size to some degree. Additional method of manipulating the extent of collateral circulation needs to be studied. Other types of canine stroke models, including vertebral artery occlusion and basilar artery occlusion, can also be accomplished by endovascular thrombi injection.

CONCLUSIONS

We extensively review the literature on endovascular technique of creating canine ischemic stroke models and their application in finding new therapies for ischemic stroke.

Estrogen receptor beta signaling alters cellular inflammasomes activity after global cerebral ischemia in reproductively senescence female rats

Periodic treatments with estrogen receptor subtype-β (ER-β) agonist reduce post-ischemic hippocampal injury in ovariectomized rats. However, the underlying mechanism of how ER-β agonists protect the brain remains unknown. Global cerebral ischemia activates the innate immune response, and a key component of the innate immune response is the inflammasome. This study tests the hypothesis that ER-β regulates inflammasome activation in the hippocampus, thus reducing ischemic hippocampal damage in reproductively senescent female rats that received periodic ER-β agonist treatments. First, we determined the effect of hippocampal ER-β silencing on the expression of the inflammasome proteins caspase 1, apoptosis-associated speck-like protein containing a CARD (ASC), and interleukin (IL)-1β. Silencing of ER-β attenuated 17β-estradiol mediated decrease in caspase 1, ASC, and IL-1β. Next, we tested the hypothesis that periodic ER-β agonist treatment reduces inflammasome activation and ischemic damage in reproductively senescent female rats. Periodic ER-β agonist treatments significantly decreased inflammasome activation and increased post-ischemic live neuronal counts by 32% (p < 0.05) as compared to the vehicle-treated, reproductively senescent rats. Current findings demonstrated that ER-β activation regulates inflammasome activation and protects the brain from global ischemic damage in reproductively senescent female rats. Further investigation on the role of a periodic ER-β agonist regimen to reduce the innate immune response in the brain could help reduce the incidence and the impact of global cerebral ischemia in post-menopausal women. We propose that estrogen receptor subtype-β (ER-β) activation regulates inflammasome activation and protects the brain from global ischemic damage in reproductively senescent female rats.

Abstract 168: Intra-arterial Stem Cell Treatment Reduces Ischemic Brain Injury In Reproductively Senescent Female Rats

Background: Cell therapy is emerging as a promising treatment for stroke. We recently we demonstrated the efficacy of intra-arterial delivery of MSCs (IA MSCs) at 24h after a reversible middle cerebral artery occlusion (MCAo). Our study also identified a maximum tolerated dose of MSCs that could be delivered IA without compromising middle cerebral artery flow. The IA approach avoids first-pass trapping of MSCs in the lungs and liver as seen with intravenous delivery. Intra-arterial treatment is also minimally invasive and widely available in clinical practice and thus appealing for clinical translation. Since majority of ischemic strokes in women occur after onset of menopause it is crucial that we test the efficacy of IA MSCs in reproductively senescent females consistent with STAIR recommendations. We aimed to validate the efficacy of IA MSCs in reproductively senescent female rats. Methods: Retired breeder female (9-11 months; 280-350 g) Sprague-Dawley rats showing estrous acyclicity were exposed to MCAo (90 min). A day later, rats were treated with IA MSCs (1x10^5 cells) or phosphate-buffered saline (PBS). MSCs or PBS treated rats were sacrificed at 28-30 days for infarct volume measurement using histology. To test motor function, the rotarod test was performed. Rats were trained for 3 consecutive days for the rotarod test before undergoing the MCAo procedure. The mean duration (in seconds) on the device was recorded from 3 rotarod measurements 1 day before surgery. The rats were tested at 1, 7, 15 and 28-30 days after MCAo. Results: We observed significantly lower mean infarct volume in the MSC-treated group (12 ± 3 mm3; n=6) compared to the PBS-treated group (29 ± 7 mm3; Mean ± SEM; n=4, p<0.05). Treatment at 1 day after MCAO with MSCs significantly improved functional recovery, as evidenced by improved rotarod test results and neurological scores at 7, 15 and 30 days (P<0.05) compared with the PBS-treated group. Conclusions: Intra-arterial stem cell treatment reduces ischemic brain injury and improves functional outcomes in reproductively senescent female rats. Validating the efficacy of IA MSC treatment using a reproductively senescent animal stroke model suggests high potential for future clinical translation in a population at high risk for stroke.

Effect of sugar beet tubers as a partial replacer to green fodder on production performance and economics of lactating Surti buffaloes in lean period

Aim:

The objective of this study was to evaluate the effects of sugar beet tubers as a replacer to green fodder on production performance and economics of lactating Surti buffaloes.

Materials and Methods:

This trial was conducted at the Livestock Research Station, Navsari Agricultural University, Navsari. Twenty lactating Surti buffaloes in a changeover experimental design were selected to assess the effects of replacing green fodder with sugar beet (Beta vulgaris L.) tubers on production performance, economics of feeding sugar beet and blood biochemical profile. Half (50%) of the hybrid Napier was replaced with sliced sugar beet tubers in the ration of experimental animals.

Results:

Partial replacement of hybrid Napier with that of sugar beet tubers numerically improved dry matter intake, milk yield, 4% fat corrected milk and milk composition parameters such as fat, solid non-fat, protein and lactose, but not significantly. The blood parameters were in normal range and non-significant except that of glucose and triglycerides, which were increased in the sugar beet group. Replacing sugar beet tubers also proved to be cost-effective with improved net profit around Rs. 6.63/day.

Conclusion:

It can be concluded that 50% hybrid Napier fodder can be replaced with sugar beet tubers without any adverse effect on animal production performance, milk composition blood biochemical profile and economics of feeding.

Increased BDNF protein expression after ischemic or PKC epsilon preconditioning promotes electrophysiologic changes that lead to neuroprotection

Ischemic preconditioning (IPC) via protein kinase C epsilon (PKCɛ) activation induces neuroprotection against lethal ischemia. Brain-derived neurotrophic factor (BDNF) is a pro-survival signaling molecule that modulates synaptic plasticity and neurogenesis. Interestingly, BDNF mRNA expression increases after IPC. In this study, we investigated whether IPC or pharmacological preconditioning (PKCɛ activation) promoted BDNF-induced neuroprotection, if neuroprotection by IPC or PKCɛ activation altered neuronal excitability, and whether these changes were BDNF-mediated. We used both in vitro (hippocampal organotypic cultures and cortical neuronal-glial cocultures) and in vivo (acute hippocampal slices 48 hours after preconditioning) models of IPC or PKCɛ activation. BDNF protein expression increased 24 to 48 hours after preconditioning, where inhibition of the BDNF Trk receptors abolished neuroprotection against oxygen and glucose deprivation (OGD) in vitro. In addition, there was a significant decrease in neuronal firing frequency and increase in threshold potential 48 hours after preconditioning in vivo, where this threshold modulation was dependent on BDNF activation of Trk receptors in excitatory cortical neurons. In addition, 48 hours after PKCɛ activation in vivo, the onset of anoxic depolarization during OGD was significantly delayed in hippocampal slices. Overall, these results suggest that after IPC or PKCɛ activation, there are BDNF-dependent electrophysiologic modifications that lead to neuroprotection.

Efficacy and dose-dependent safety of intra-arterial delivery of mesenchymal stem cells in a rodent stroke model

Intra-arterial (IA) delivery of mesenchymal stem cells (MSCs) for acute ischemic stroke is attractive for clinical translation. However, studies using rat model of stroke have demonstrated that IA MSCs delivery can decrease middle cerebral artery (MCA) flow, which may limit its clinical translation. The goal of this study is to identify a dose of IA MSCs (maximum tolerated dose; MTD) that does not compromise MCA flow and evaluate its efficacy and optimal timing in a rat model of reversible middle cerebral artery occlusion (rMCAo). We sought to determine if there is a difference in efficacy of acute (1 h) versus sub-acute (24 h) IA MSCs treatment after rMCAo. Adult female Sprague-Dawley rats underwent rMCAo (90 min) and an hour later a single dose of MSCs (at de-escalating doses 1 × 10(6), 5 × 10(5), 2 × 10(5), 1 × 10(5) and 5 × 10(4)) was given using IA route. MSCs were suspended in phosphate buffered saline (PBS) and PBS alone was used for control experiments. We measured the percent change in mean laser Doppler flow signal over the ipsilateral MCA in de-escalating doses groups to determine MTD. The results demonstrated that the lowering of IA MSC dose to 1 × 10(5) and below did not compromise MCA flow and hence an IA MSC dose of 1 × 10(5) considered as MTD. Subsequently, 1 h and 24 h after rMCAo, rats were treated with IA MSCs or PBS. The 24 h delivery of IA MSCs significantly improved neurodeficit score and reduced the mean infarct volume at one month as compared to control, but not the 1 h delivery. Overall, this study suggests that the IA delivery of MSCs can be performed safely and efficaciously at the MTD of 1 × 10(5) delivered at 24 hours in rodent model of stroke.

Periodic 17β-estradiol pretreatment protects rat brain from cerebral ischemic damage via estrogen receptor-β

Although chronic 17β-estradiol (E2) has been shown to be a cognition-preserving and neuroprotective agent in animal brain injury models, concern regarding its safety was raised by the failed translation of this phenomenon to the clinic. Previously, we demonstrated that a single bolus of E2 48 hr prior to ischemia protected the hippocampus from damage in ovariectomized rats via phosphorylation of cyclic-AMP response element binding protein, which requires activation of estrogen receptor subtype beta (ER-β). The current study tests the hypothesis that long-term periodic E2-treatment improves cognition and reduces post-ischemic hippocampal injury by means of ER-β activation. Ovariectomized rats were given ten injections of E2 at 48 hr intervals for 21 days. Hippocampal-dependent learning, memory and ischemic neuronal loss were monitored. Results demonstrated that periodic E2 treatments improved spatial learning, memory and ischemic neuronal survival in ovariectomized rats. Additionally, periodic ER-β agonist treatments every 48 hr improved post-ischemic cognition. Silencing of hippocampal ER-β attenuated E2-mediated ischemic protection suggesting that ER-β plays a key role in mediating the beneficial effects of periodic E2 treatments. This study emphasizes the need to investigate a periodic estrogen replacement regimen to reduce cognitive decline and cerebral ischemia incidents/impact in post-menopausal women.

Oral contraceptives and nicotine synergistically exacerbate cerebral ischemic injury in the female brain

Oral contraceptives (OC) and smoking-derived nicotine (N) are known to synergistically increase the risk and severity of cerebral ischemia in women. Although it has been known for some time that long-term use of OC and nicotine will have an increased risk of peripheral thrombus formation, little is known about how the combination of OC and nicotine increases severity of brain ischemia. Recent laboratory studies simulating the conditions of nicotine exposure produced by cigarette smoking and OC regimen of women in female rats confirms that the severity of ischemic hippocampal damage is far greater in female rats simultaneously exposed to OC than to nicotine alone. These studies also demonstrated that the concurrent exposure of OC and nicotine reduces endogenous 17β-estradiol levels and inhibits estrogen signaling in the brain of female rats. The endogenous 17β-estradiol plays a key role in cerebrovascular protection in women during their pre-menopausal life and loss of circulating estrogen at reproductive senescence increases both the incidence and severity of cerebrovascular diseases. Therefore, OC and nicotine induced severe post-ischemic damage might be a consequence of lack of estrogen signaling in the brain. In the present review we highlight possible mechanisms by which OC and nicotine inhibits estrogen signaling that could be responsible for severe ischemic damage in females.

Nitrite therapy is neuroprotective and safe in cardiac arrest survivors

Cardiac arrest results in significant mortality after initial resuscitation due in most cases to ischemia-reperfusion induced brain injury and to a lesser degree myocardial dysfunction. Nitrite has previously been shown to protect against reperfusion injury in animal models of focal cerebral and heart ischemia. Nitrite therapy after murine cardiac arrest improved 22 h survival through improvements in myocardial contractility. These improvements accompanied transient mitochondrial inhibition which reduced oxidative injury to the heart. Based on preliminary evidence that nitrite may also protect against ischemic brain injury, we sought to test this hypothesis in a rat model of asphyxia cardiac arrest with prolonged survival (7d). Cardiac arrest resulted in hippocampal CA1 delayed neuronal death well characterized in this and other cardiac arrest models. Nitrite therapy did not alter post-arrest hemodynamics but did result in significant (75%) increases in CA1 neuron survival. This was associated with increases in hippocampal nitrite and S-nitrosothiol levels but not cGMP shortly after therapy. Mitochondrial function 1h after resuscitation trended towards improvement with nitrite therapy. Based on promising preclinical data, the first ever phase I trial of nitrite infusions in human cardiac arrest survivors has been undertaken. We present preliminary data showing low dose nitrite infusion did not result in hypotension or cause methemoglobinemia. Nitrite thus appears safe and effective for clinical translation as a promising therapy against cardiac arrest mediated heart and brain injury.

Abstract 3671: Intra-Carotid Mesenchymal Stem Cell Therapy is Superior to Intravenous delivery in Rat Model of Cerebral Ischemia

INTRODUCTION: There are multiple pre-clinical studies showing significant neurological functional benefit of Mesenchymal Stem Cells (MSCs) in cerebral ischemia. MSCs are adult bone marrow derived cells that have a high potential for clinical translation. The optimal route of MSC delivery has not been established. Intra-carotid (IC) delivery via catheters has several attributes attractive for clinical application & may be superior to intravenous (IV) delivery as it circumvents systemic trapping of cells and allows more cells to reach the target lesion. In our previous study using the rat rMCAo model, we found the maximum tolerated dose (MTD) of IC MSCs to be 1 x 10^5 HYPOTHESIS: We tested the hypothesis that the MTD of IC mesenchymal stem cells (MSCs) is more efficacious as compared to IV MSCs and IC control. We further hypothesized that the MTD of IC MSCs given at 24 hours is more efficacious as compared to IC MSCs at 60 minutes. METHODS: 34 female Sprague-Dawley rats underwent 90 minutes reversible middle cerebral artery occlusion (rMCAo). At 60 minutes or 24 hours post rMCAo, rats were assigned to receive: allogeneic IC MSCs at a dose of 1x 10^5 or IC phosphate buffered saline (PBS) 0.5ml or allogeneic intravenous (IV) MSCs 1 x 10^6 & rMCAo with no treatment (sham). Primary outcome measures were blinded neurodeficit score and infarct volume at 4 weeks.

RESULTS: At 24 hours post rMCAo, there was no significant difference in the neurodeficit score (NDS) amongst the groups. At four weeks post treatment, the IC MSC group showed a significantly lower NDS (7%_3.3) as compared to IV MSCs (10.2%_1.5, p=0.042); In subgroup analysis, IC MSCs given at 60 minutes showed no significant difference compared to other groups, but IC MSC given at 24 hours showed a significantly lower neurodeficit score (5.8 %_2.6) as compared to IC PBS (10.8%_1.2, p=0.003), IV MSCs (10.2 %_1.5, p=0.005) and Sham (10%_ 3.4, p=0.018) ( Fig1 .). The mean infarct volume of the group treated with IC MSCs was significantly lower as compared to IC PBS (18cc%_ 8 vs. 50cc%_17, p=0.043). On infarct topography frequency map comparison, we found a significantly decreased volume of infarction in the cortical regions in IC MSC group as compared to IC PBS group.

CONCLUSIONS: Treatment with maximum tolerated IC MSC dose of 1 x 10^5 post rMCAO results in superior functional outcome when compared with IV MSC 1 x 10^6, IC PBS and sham rats. Additionally, IC MSC at 24 hours is more efficacious than IC MSC at 60 minutes. There is also a significant decrease in infarct volume in IC MSC treated rats when compared with IC PBS. The IC MSCs may ameliorate injury in the cortex surrounding the core.

Abstract 2818: Safety, Feasibility and Signal of Activity of Intra-carotid Allogenic Mesenchymal Stem Cell therapy in a Large Animal Stoke Model

INTRODUCTION: Promising pre-clinical data shows benefits of intra-carotid allogenic mesenchymal stem cell (MSCs) therapy in ischemic stroke (IS) in small animal stroke models. Intra-carotid (IC) delivery of MSCs may be superior to intravenous (IV) delivery. However, due to the large size (15-50 microns) of MSCs, there is a concern that they may cause microvascular occlusion during IC administration. There is a need for large animal experiments to confirm positive results in small animal models as has been recommended by STAIR and STEPS consortia.

HYPOTHESIS: We tested the hypothesis that IC administration of allogeneic mesenchymal stem cells (MSCs) is feasible and safe in a large animal (canine) stroke model..

METHODS: We performed 1-3 hrs of reversible middle cerebral artery occlusion (rMCAo), in10 female mongrel dogs weighing 40-60 lbs, using an endovascular retrievable coil occlusion of the MCA with a transfemoral arterial approach. At 1 - 72 hrs after rMCAo, animals were assigned to the following treatment groups: A. IC saline placebo (saline) or B. IC allogeneic MSCs or C. IV allogeneic MSCs. Primary outcome measures were: development of angiographic occlusion post-IC MSC or saline infusion, change in MRI infarct volume or new ischemic lesions, and neurological deficit score (NDS) at 4 weeks. Dosing of MSCs was based on extrapolated maximum tolerated dose calculated in a rat study of IC MSCs in our laboratory.

RESULTS: Successful IC administration of MSCs was possible in all animals assigned to the treatment group. Animals receiving IC MSCs at 1× 10^6 or 10 × 10^6 (n=6) there were no clinical adverse events or neurological worsening during or 4 weeks post treatment. There were no angiographic decreases in flow or occlusions during or after IC MSC delivery. In the two animals with additional TCD monitoring during IC MSC delivery there were no changes in flow velocity or HITS signals indicating emboli. There was no worsening in MRI infarct volume ( Fig 1 .) amongst the IC MSC groups. A dramatic decrease in infarct volume was noted, in 2 animals in the IC MSC group with minimal infarct related atrophy at one month. None of the animals in the IV MSC or IC saline groups (n=2 in each group) showed a significant change in MRI infarct volume, and major infarct related atrophy was noted.

CONCLUSION: IC MSC administration in a large animal rMCAo model is feasible & safe. Fig1 : In vivo coronal MRI FLAIR sequences in IC delivery of MSCs in canine stroke model. There is a signal of biologic activity seen with IC MSC delivery. A. Baseline infarct at 48 hours after rMCAo. B. Infarct evolution at 29 days after IC administration of 10×10^6 MSCs.

Differential effects of delta and epsilon protein kinase C in modulation of postischemic cerebral blood flow

Cerebral ischemia causes cerebral blood flow (CBF) derangements resulting in neuronal damage by enhanced protein kinase C delta (δPKC) levels leading to hippocampal and cortical neuronal death after ischemia. Contrarily, activation of εPKC mediates ischemic tolerance by decreasing vascular tone providing neuroprotection. However, whether part of this protection is due to the role of differential isozymes of PKCs on CBF following cerebral ischemia remains poorly understood. Rats pretreated with a δPKC specific inhibitor (δV1-1, 0.5 mg/kg) exhibited attenuation of hyperemia and latent hypoperfusion characterized by vasoconstriction followed by vasodilation of microvessels after two-vessel occlusion plus hypotension. In an asphyxial cardiac arrest (ACA) model, rats treated with δ V1-1 (pre- and postischemia) exhibited improved perfusion after 24 h and less hippocampal CA1 and cortical neuronal death 7 days after ACA. On the contrary, εPKC-selective peptide activator, conferred neuroprotection in the CA1 region of the rat hippocampus 30 min before induction of global cerebral ischemia and decreased regional CBF during the reperfusion phase. These opposing effects of δ v. εPKC suggest a possible therapeutic potential by modulating CBF preventing neuronal damage after cerebral ischemia.