Mitochondria-containing extracellular vesicles from mouse vs . human brain endothelial cells for ischemic stroke therapy

Ischemic stroke-induced mitochondrial dysfunction in the blood-brain barrier-forming brain endothelial cells ( BECs ) results in long-term neurological dysfunction post-stroke. We previously reported that intravenous administration of human BEC ( hBEC )-derived mitochondria-containing extracellular vesicles ( EVs ) showed a potential efficacy signal in a mouse middle cerebral artery occlusion ( MCAo ) model of stroke. We hypothesized that EVs harvested from donor species homologous to the recipient species ( e.g., mouse) may improve therapeutic efficacy, and therefore, use of mouse BEC ( mBEC )-derived EVs may improve post-stroke outcomes in MCAo mice. We investigated if EVs derived from the same species as the recipient cell (mBEC-EVs and recipient mBECs or hBECs-EVs and recipient hBECs) show a greater EV mitochondria delivery efficiency than cross-species EVs and recipient cells (mBEC-EVs and recipient hBECs or vice versa ). Our results showed that mBEC-EVs outperformed hBEC-EVs in transferring EV mitochondria to the recipient ischemic mBECs, and improved mBEC mitochondrial function via increasing oxygen consumption rate. mBEC-EVs significantly reduced brain infarct volume and improved behavioral recovery compared to vehicle-injected MCAo mice. Our data suggests that mBEC-EVs show superior therapeutic efficacy in a mouse MCAo stroke model compared to hBEC-EVs-supporting the continued use of mBEC-EVs to optimize the therapeutic potential of mitochondria-containing EVs in preclinical studies.

Mitochondria-containing extracellular vesicles (EV) reduce mouse brain infarct sizes and EV/HSP27 protect ischemic brain endothelial cultures

Ischemic stroke causes brain endothelial cell (BEC) death and damages tight junction integrity of the blood-brain barrier (BBB). We harnessed the innate mitochondrial load of BEC-derived extracellular vesicles (EVs) and utilized mixtures of EV/exogenous 27 kDa heat shock protein (HSP27) as a one-two punch strategy to increase BEC survival (via EV mitochondria) and preserve their tight junction integrity (via HSP27 effects). We demonstrated that the medium-to-large (m/lEV) but not small EVs (sEV) transferred their mitochondrial load, that subsequently colocalized with the mitochondrial network of the recipient primary human BECs. Recipient BECs treated with m/lEVs showed increased relative ATP levels and mitochondrial function. To determine if the m/lEV-meditated increase in recipient BEC ATP levels was associated with m/lEV mitochondria, we isolated m/lEVs from donor BECs pre-treated with oligomycin A (OGM, mitochondria electron transport complex V inhibitor), referred to as OGM-m/lEVs. BECs treated with naïve m/lEVs showed a significant increase in ATP levels compared to untreated OGD cells, OGM-m/lEVs treated BECs showed a loss of ATP levels suggesting that the m/lEV-mediated increase in ATP levels is likely a function of their innate mitochondrial load. In contrast, sEV-mediated ATP increases were not affected by inhibition of mitochondrial function in the donor BECs. Intravenously administered m/lEVs showed a reduction in brain infarct sizes compared to vehicle-injected mice in a mouse middle cerebral artery occlusion model of ischemic stroke. We formulated binary mixtures of human recombinant HSP27 protein with EVs: EV/HSP27 and ternary mixtures of HSP27 and EVs with a cationic polymer, poly (ethylene glycol)-b-poly (diethyltriamine): (PEG-DET/HSP27)/EV. (PEG-DET/HSP27)/EV and EV/HSP27 mixtures decreased the paracellular permeability of small and large molecular mass fluorescent tracers in oxygen glucose-deprived primary human BECs. This one-two punch approach to increase BEC metabolic function and tight junction integrity may be a promising strategy for BBB protection and prevention of long-term neurological dysfunction post-ischemic stroke.

Abstract WMP111: MicroRNAs As A Therapeutic Target To Reduce Microglial Activation After Post-stroke Social Isolation

Introduction: Social isolation (SI) and loneliness are linked to all-cause mortality, as well as mortality from stroke and other vascular diseases. However, the mechanisms mediating the effects of social factors on stroke recovery are unknown. We hypothesized that differential expression of miRNAs contributes to the deleterious effects of post-stroke SI.

Methods: Aged (18-20 months) C57BL/6 male mice were used to examine the detrimental effects of post-stroke SI on miRNA profiles in the brain. Mice were randomly assigned to either pair housing (PH), or single housing (SI) three days after a 60-minute transient right middle cerebral artery occlusion (MCAO). At this time point (post-stroke day 3), the infarct is complete, and was equivalent between groups, avoiding potential changes seen with differing infarct sizes. Temporal miRNA profiling of the ipsilateral hemisphere was assessed at two-time points (post-stroke SI D4 and D27). Brain cells were analyzed by flow cytometry.

Results: Post-stroke SI resulted in significant alterations of distinct miRNA profiles within the brain across both acute and chronic time points (n=4/grp, FDR adjusted * p <0.05). MiRNA-mRNA interactional analysis revealed miR-10a-5p and miR-10b-5p as pivotal nodes within the pool of miRNAs that interacted with the largest subset of miRNAs for post-stroke at SI D4 and D27, respectively. Downstream pathway analysis utilizing an independent repository, the KEGG pathway showed 4 days of isolation resulted in the enrichment of pathways related to microglial activation and 27 days of isolation lead to the activation of neuronal-specific pathways that regulate cognition and motivation (FDR adjusted * p <0.05). Independent validation cohorts demonstrated significant activation of microglia at post-stroke SI D4 as assessed by the median fluorescence intensity (MFI) of purinergic receptor P2Y12 (P2RY12), in CD45 int CD11b + P2RY12 + cells in the brain. MFI of P2RY12 was significantly downregulated in post-stroke SI mice at D4 (n=7-8/grp, * p <0.05) compared to PH mice.

Conclusions: These results support our hypothesis that post-stroke SI exacerbates microglia activation, and results in the differential expression of microglial pathway-related miRNAs.

Abstract 83: Stroke-induced Gut Microbiota Dysbiosis Regulates Microfold Cells In Peyer’s Patches

Microfold or membranous cells (M cells) are specialized antigen sampling cells residing in the epithelium of Peyer’s patches (PPs), the gut-associated lymphoid tissue in the small intestine. M cells are in continuous crosstalk with luminal microbes and host immune cells. The detrimental shift of the microbiota seen with aging and after stroke contribute to bacterial antigen translocation. This axis has emerged as an epicenter for post-stroke immune dysfunction and systemic infection. The role of M cells in the PPs as an initiation site for host mucosal immunity after stroke is undefined.

Hypothesis: Stroke-induced gut dysbiosis and M cell ablation leads to impaired antigen sampling mechanisms and clearance of translocating bacteria in PPs after stroke. We used a 60-minute reversible middle cerebral artery occlusion model in young (8-10 wks) C57BL/6 male mice to investigate how brain ischemia affects M cells in the PPs. We performed microbiota transplants from the cecal contents of stroke mice to naïve age-matched recipients via oral gavage for three consecutive days before tissue harvest on day four. We determined that stroke-induced changes in gut microbiota alone can cause M cell dysfunction. We found that both the number of PPs and M cells decrease 24 hours after stroke (n=8/gp, p=0.0104 and p=0.0054, respectively). Our imaging studies revealed disruption of tissue architecture and reduction in size of PPs after stroke. Microbiota transplant from stroke mice cecum to naïve recipients showed a similar effect on the number of PPs and M cells (n=10/gp, p=0.0568 and p=0.0299 ). The decrease in the number of M cells after microbiota transplantation was associated with immune dysregulation in the PPs, such as a reduction in the number of regulatory T cells (n=5/gp, p=0.0084 ). This is the first study that specifically examined M cells in a mouse model of stroke. Our results show that 1) stroke reduces the number of PPs and M cells and 2) stroke-induced gut dysbiosis can independently reduce the number of PPs and likely M cells and may regulate gut-originated immune responses after stroke. Future studies are needed to understand the effects of stroke-induced dysbiosis on M cell-mediated antigen processing in the gut and their immunoregulatory functions.

Abstract TMP111: The Detrimental Effects Of Post-stroke Social Isolation On Microglial Activation Is Mediated By MicroRNAs

Introduction: Social Isolation (SI) is a risk factor for a wide array of psychological disorders. SI significantly enhances the incidence of developing neurological diseases, including stroke within the elderly population. Recent studies have shown microRNA (miRNA) signatures in the brain and the circulation are altered in social defeat models and under stressful environmental conditions. Although SI has shown to influence post-stroke recovery, potential targetable interventions to mitigate these inflammatory events are limited.

Hypothesis: Post-stroke SI influences temporally distinct miRNA networks in the brain that regulate acute microglial activation and contribute to chronic depressive phenotypes.

Methods: Aged (18-20 month) C57BL/6 male mice were subjected to 60-minute middle cerebral artery occlusion (MCAO) followed by reperfusion. Mice were randomly assigned to either continued pair housing (PH), or SI three days after a 60-minute MCAO. Mice were euthanized at post-stroke SI Day 1, 4, and 27 and ipsilateral hemispheres were collected for miRNA sequencing and downstream analysis. Behavioral tests and brain cell analysis using flow cytometry were performed using independent experimental cohorts.

Results: The top 10 differentially expressed miRNAs were identified in SI vs. PH mice across three time points (FC ≥ 1.5, FDR adjusted P <0.05, n=4/group). Interactional network analysis revealed miR-466i-3p, miR-10a-5p, and miR-10b-5p as pivotal nodes that regulated the expression of the largest subset of genes involved in microglial-specific immune activation and chronic depression after stroke at SI D4 and D27, respectively. Flow cytometry analysis showed that microglia are significantly activated at post-stroke SI Day 4, as assessed by the downregulation of microglia-specific homeostatic protein purinergic receptor P2RY12 ( P <0.05, n=7-8/group) and interestingly, chronic SI induced depressive-like behaviors in aged stroke mice; consistent with our miRNA-based pathway analysis.

Conclusion: This is the first comprehensive miRNA expression profiling study using NGS technique in aging, stroke, and SI. Our data revealed that SI-specific miRNAs are involved in microglial activation and chronic depression in aged mice.

Sex-Specific Differences in Autophagic Responses to Experimental Ischemic Stroke

Ischemic stroke triggers a series of complex pathophysiological processes including autophagy. Differential activation of autophagy occurs in neurons derived from males versus females after stressors such as nutrient deprivation. Whether autophagy displays sexual dimorphism after ischemic stroke is unknown. We used a cerebral ischemia mouse model (middle cerebral artery occlusion, MCAO) to evaluate the effects of inhibiting autophagy in ischemic brain pathology. We observed that inhibiting autophagy reduced infarct volume in males and ovariectomized females. However, autophagy inhibition enhanced infarct size in females and in ovariectomized females supplemented with estrogen compared to control mice. We also observed that males had increased levels of Beclin1 and LC3 and decreased levels of pULK1 and p62 at 24 h, while females had decreased levels of Beclin1 and increased levels of ATG7. Furthermore, the levels of autophagy markers were increased under basal conditions and after oxygen and glucose deprivation in male neurons compared with female neurons in vitro. E2 supplementation significantly inhibited autophagy only in male neurons, and was beneficial for cell survival only in female neurons. This study shows that autophagy in the ischemic brain differs between the sexes, and that autophagy regulators have different effects in a sex-dependent manner in neurons.

Long Noncoding RNA Fos Downstream Transcript Is Developmentally Dispensable but Vital for Shaping the Poststroke Functional Outcome

[Figure: see text].

Young versus aged microbiota transplants to germ-free mice: increased short-chain fatty acids and improved cognitive performance

Aging is associated with cognitive decline and decreased concentrations of short-chain fatty acids (SCFAs) in the gut. SCFAs are significant in that they are protective to the gut and other organs. We tested the hypothesis that the aged gut microbiome alone is sufficient to decrease SCFAs in the host and produce cognitive decline. Fecal transplant gavages (FTGs) from aged (18-20 months) or young (2-3 months) male C57BL/6 mice into germ-free male C57BL/6 mice (N = 11 per group) were initiated at ~3 months of age. Fecal samples were collected and behavioral testing was performed over the study period. Bacterial community structures and relative abundances were measured in fecal samples by sequencing the bacterial 16S ribosomal RNA gene. Mice with aged and young microbiomes showed clear differences in bacterial β diversity at 30, 60, and 90 d (P = .001 for each) after FTGs. The fecal SCFAs, acetate, propionate, and butyrate (microbiome effect, P < .01 for each) were decreased in mice with an aged microbiome. Mice with an aged microbiome demonstrated depressive-like behavior, impaired short-term memory, and impaired spatial memory over the 3 months following the initial FTG as assessed by the tail suspension (P = .008), the novel object recognition (P < .001), and the Barnes Maze (P = .030) tests, respectively. We conclude that an aged microbiome alone is sufficient to decrease SCFAs in the host and to produce cognitive decline.

Early Post-stroke Depressive Symptoms are Associated with Low Peripheral Levels of Soluble Triggering Receptor Expressed on Myeloid Cells-1 (sTREM-1) and Glial Cell-derived Neurotrophic Factor (GDNF)

BACKGROUND

Stroke is a major cause of death and disability worldwide. Among its complications, post-stroke depression (PSD) leads to a significant burden. The diagnosis of PSD is complex, and there are no biomarkers that can assist in its early identification and adequate management.

OBJECTIVE

The aim of the present study is to investigate peripheral biomarkers in the acute phase of stroke and their potential association with depressive symptoms.

METHODS

We evaluated 60 patients in the acute phase of stroke by using standardized instruments of psychiatric and neurological assessment (Mini International Neuropsychiatric Interview-Plus- MINI-Plus, Hospital Anxiety and Depression Scale-HADS, and National Institutes of Health Stroke Scale-NIHSS) and measured peripheral biomarkers.

RESULTS

In multivariate analysis, low peripheral levels of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) and higher NIHSS scores were associated with PSD. The severity of depressive symptoms was inversely correlated with sTREM-1 and glial cell-derived neurotrophic factor (GDNF) levels.

CONCLUSION

This is the first study indicating an association between sTREM-1 and PSD. Our results may point to the involvement of glial mechanisms in the manifestation of depressive symptoms after stroke.

Abstract WP143: Identification of Socially-Regulated Circulating Microrna Signatures in Stroke

Introduction: Epidemiological and clinical studies strongly support that social isolation (SI) is associated with higher mortality after stroke. SI has been identified as a risk factor in a wide variety of diseases, including stroke. However, few studies have attempted to identify the underlying mechanisms contributing to the detrimental effect of SI. To better understand systemic and global regulation networks governed by social factors, and in an attempt to identify viable biomarkers, we profiled changes in circulating microRNA (miRNA) expression in aged stroke mice after SI.

Methods: Aged C57BL/6 mice (18-20 months) of both sexes were pair-housed (PH) or socially isolated (SI) for two weeks prior to sham or a 60-minute middle cerebral artery occlusion surgery. Mice were sacrificed two weeks after surgery and blood samples were obtained for profiling of plasma miRNAs. Using whole miRNAome analysis, differentially expressed miRNAs by isolation, stroke and sex differences were comprehensively identified and compared using bioinformatics. We further used mimic and antagomiR treatments to confirm a potential role of the identified miRNAs.

Results: Stroke significantly changed 8 miRNAs including miR-467d-3p ( P =0.0014), miR-376b-3p ( P =0.013) and miR-297c-5p ( P =0.016) in PH groups (sham vs. stroke). In a comparison between PH vs. SI in stroke mice, stroke SI mice showed a differential miRNA profile (11 miRNAs) including let-7 family potentially targeting Dicer protein, a key enzyme for miRNA biogenesis. Interestingly, compared to sham SI mice, stroke SI mice had a 2-fold increase in the number of altered miRNAs (21 miRNAs) including miR-129-1-3p ( P =0.0075), miR-28a-3p ( P =0.0091) and miR-204-5p ( P =0.016). Finally, we found a strong sex difference in miRNA expression in response to SI.

Conclusions: We identified several key miRNAs as potential biomarkers for 1) stroke, 2) SI and 3) SI/stroke. These miRNA signatures are highly unique and create a complex gene-regulatory network that depends on the social environment. Our data provide potential biomarkers and identify several miRNAs that could lead to significant improvements in diagnosis of elderly patients at elevated risk for the detrimental effects of loneliness.

Abstract 108: Sex Differences in Stroke-induced Lymphocyte Responses in the Gut Epithelia

Introduction: Stroke is a sexually dimorphic disease. Notably, emerging evidence suggests that stroke leads to gut dysbiosis and pathological shifts in the gut microbiota. However, little is known about how the gut epithelial surface maintains homeostasis after stroke. In this study, we isolated intraepithelial lymphocytes (IELs), which are mainly CD8 + T cells and do not need priming against antigens, as well as intestinal epithelial cells (IECs). We examined their responses to stroke-induced gut epithelial damage.

Methods: C57BL/6 (2-3 months) mice of both sexes were subjected to either 60-minute middle cerebral artery occlusion or sham surgery. At day 7 after stroke, IECs and IELs, which are intercalated between IECs, were isolated from mouse colonic tissues using Percoll density gradients. RNA was isolated from the cells and amplified to quantitate expression levels of cell-specific genes for antibacterial proteins and chemotactic cytokines. Tissues were then used for histological analysis by hematoxylin and eosin staining and bacterial fluorescence in situ hybridization (FISH).

Results: Stroke caused significant colonic damage in male mice, compared to female mice. Bacterial FISH demonstrated microbial encroachment into the host gut epithelium in males after stroke; whereas female mice maintained spatial segregation between the host gut and bacteria. Stroke increased expression levels of pro-inflammatory cytokine genes in male IELs including IL-1β (28.3 fold increase, P <0.05), KC or CXCL1 (5.8 fold increase, P <0.05) and MIP2α or CXCL2 (9.9 fold increase, P <0.05) after stroke compared with sham mice. Additionally, both IELs and IECs of male stroke mice exhibited an up-regulation of antimicrobial protein gene, regenerating islet-derived protein 3 (Reg3γ, P <0.05). This pattern of up-regulation, however, was not present in female mice.

Conclusions: This is the first study that demonstrates robust sex differences in lymphocyte responses at the gut mucosal surface between males and females following stroke. The closer proximity of the gut microbiota with the host may direct gene expression related to microbial responses in the injured epithelium after brain injury. Our study provides novel insight into host-microbial homeostasis in stroke.

Systematic Review on the Involvement of the Kynurenine Pathway in Stroke: Pre-clinical and Clinical Evidence

Background: Stroke is the second leading cause of death after ischemic heart disease and the third leading cause of disability-adjusted life-years lost worldwide. There is a great need for developing more effective strategies to treat stroke and its resulting impairments. Among several neuroprotective strategies tested so far, the kynurenine pathway (KP) seems to be promising, but the evidence is still sparse.

Methods: Here, we performed a systematic review of preclinical and clinical studies evaluating the involvement of KP in stroke. We searched for the keywords: (“kynurenine” or “kynurenic acid” or “quinolinic acid”) AND (“ischemia” or “stroke” or “occlusion) in the electronic databases PubMed, Scopus, and Embase. A total of 1,130 papers was initially retrieved.

Results: After careful screening, forty-five studies were included in this systematic review, being 39 pre-clinical and six clinical studies. Despite different experimental models of cerebral ischemia, the results are concordant in implicating the KP in the pathophysiology of stroke. Preclinical evidence also suggests that treatment with kynurenine and KMO inhibitors decrease infarct size and improve behavioral and cognitive outcomes. Few studies have investigated the KP in human stroke, and results are consistent with the experimental findings that the KP is activated after stroke.

Conclusion: Well-designed preclinical studies addressing the expression of KP enzymes and metabolites in specific cell types and their potential effects at cellular levels alongside more clinical studies are warranted to confirm the translational potential of this pathway as a pharmacological target for stroke and related complications.

Abstract TMP30: Mucin is a Novel Target for Gut Protective Immunity in Stroke

Introduction: Infections are a common cause of post-stroke morbidity and mortality. Recent studies suggest that gut microbiota are a major source of post-stroke infection. Gut mucus layers are a major area of communication between gut microbiota and host immune cells. To our knowledge there have been no studies evaluating the role of colonic epithelial mucins, where most of the gut bacteria reside, after ischemic stroke.

Hypothesis: Epithelial mucin plays a protective role in stroke-induced colonic disruption.

Methods: Mice were subjected to either sham or 60-minute middle cerebral artery occlusion (MCAO). Neurological deficit score (NDS) and levels of lipopolysaccharide-binding protein (LBP) in plasma were assessed at day 7 after stroke. Mice were sacrificed at day 7 after stroke and colonic epithelial cells (ECs) were isolated for a gene expression study. Tissues were used for histology and bacterial in situ hybridization. Fecal samples were collected for 16S sequencing and IgA ELISA.

Results: Young female mice had lower NDS and LBP levels, with intact colonic structures (n=4/group, P <0.05). Young mice ECs significantly increased 1) regenerating islet-derived protein (Reg) family-specific antimicrobial proteins in males (24.3, 21.3 and 2.5 fold change in Reg3β, -γ and -4, respectively) and 2) mucin genes in females (1.8 and 1.4 fold change in Muc2 and -4, respectively, n=4-5/group, P <0.05). Young ovariectomized mice switched their protective strategies from enhanced expression of mucin genes to a “male-like” pattern in which Reg genes were increased after stroke (n=3-5/group, P <0.05). Aged mice failed to express these sex-specific genes after stroke. Interestingly, after stroke, bacteria from young female but not male mice were found at a farther distance from the colonic epithelium secondary to intact mucus layers. Finally, young female mice increased mucin-regulating Akkermansia bacteria and IgA in the feces after stroke (n=4/group, P <0.05).

Conclusions: Our data demonstrates that 1) stroke provokes a colonic epithelial response and 2) mucin is critical for colonic protection in stroke. In conclusion, mucin should be considered as a novel target to improve post-stroke recovery as well as an important element in maintaining colonic structure.

Abstract 26: Stroke Impairs Epithelial Microfold Cells in Intestinal Peyer’s Patches

Introduction: Peyer’s patches (PP) are lymphatic tissue in the small intestine. Tissue-resident specialized epithelial cells [microfold (M) cells] are essential for immune surveillance in the gut by sensing pathogens and eliciting immune responses by lymphocytes. Emerging evidence highlights the importance of gut microbiota as an epicenter for post-stroke infection, however the role of PP and M cells in stroke is still undefined.

Hypothesis: Ischemic stroke influences the antigen-sampling systems in intestinal PPs.

Methods: Young (8-10 wks) and aged (18-20 months) C57BL/6N male mice were subjected to either sham or 60-minute middle cerebral artery occlusion (MCAO) followed by reperfusion. Mice were sacrificed at day 3 after stroke. The small intestines were isolated and PP tissue was obtained. The numbers and structure of the PP and M cells were assessed using whole-mounts and confocal microscopy. Gene expression in PP was examined using real-time qPCR. Finally, immune cells in PPs were evaluated using flow cytometry.

Results: The number of PPs was dramatically reduced at day 3 after stroke. Sham mice had 7 to 10 PPs in their small intestines, whereas stroke mice only retained 2 to 5 PPs (n=4/group, P <0.05). Aging also decreased the numbers of PPs both in sham (5 to 6) and stroke mice (1 to 4) (n=4/group, P <0.05). Whole-mount assays revealed that stroke impaired the number of UEA-1 + WGA - M cells as well as the structure of the PP. Stroke induced the loss and shrinkage of villus and decreased both villus M cells and fucosylated epithelial cells in the distal ileum. Additionally, stroke abrogated the mRNA expression of Gp2 and RANKL pathway genes such as Tnfsf11 (RANK) and Tnfsf11a (RANKL) that are responsible for M cell maturation and function, respectively (1.95, 1.31 and 2.67 fold change in Gp2, Tnfsf11 and Tnfsf11a, respectively, n=4/group, P <0.05). However, we did not observe a significant change of immune cells in PP after stroke.

Conclusions: The response of PP in stroke was highly epithelial M cell-specific. Although the understanding of interactions between luminal antigens including bacteria and PP is still needed, our data provides us with a new insight into how brain damage can alter antigen sampling and shape adaptive immunity in the host.

Abstract TMP25: Short Chain Fatty Acids Mediate the Beneficial Effects of Young Microbiome on Recovery in Aged Mice after Ischemic Stroke

Introduction: Age is a non-modifiable risk factor for stroke. The elderly have high mortality and delayed recovery after a stroke compared to younger patients, a finding that is recapitulated in murine models. Young animals that received aged biome after stroke had lower short chain fatty acids (SCFAs) in their feces and delayed recovery compared to young mice receiving young biome. SCFAs, generated primarily by gut bacteria are important signaling molecules for gut homeostasis. We hypothesize that fecal transplant from young donor/ SCFA producing bacteria into aged mice will improve recovery compared to mice that received aged biome.

Methods: Aged C57BL/6 male mice (18-20 months) were subjected to middle cerebral artery occlusion and randomly assigned to one of two groups, either received: 1. aged biome or 2. young biome. In addition, a separate cohort of aged mice were randomized as above, and divided into two groups: 1. received a cocktail of SCFA producers + Inulin as substrate or 2. received vehicle control group. Mice were tested for motor and cognitive recovery for 14 days. Fecal samples were subjected to 16s sequencing and metabolomics. Tissues were collected at sacrifice and used for flow cytometry and IHC.

Results: Aged mice that received young fecal transplants after stroke expressed higher SCFAs in their fecal samples (p<0.05) and demonstrated significantly improved stroke recovery in comparison to mice that received aged biome (n=9-10/grp; p<0.05). Young biome treated mice demonstrated rapid improvement in hang time (54.6±7.9s vs 32.6±3.3s; p<0.05) and better outcomes in open field (p<0.05). Aged mice with young biome had better cognitive outcomes compared to the aged biome group. Consistently, our ongoing studies show that transplanting selected strains of SCFA producing bacteria is sufficient to enhance recovery, as tested in hang wire test (64.7±20.4% vs vehicle 25.0±12.5%; n=4/grp; p<0.05).

Conclusions: Metabolites produced by young microbiome improve post-stroke recovery in aged mice, enhance SCFAs, and reduce inflammation. Although SCFA production appears to be a key contributor to recovery, more studies are needed to elucidate the underlying mechanisms in order to develop a therapeutic strategy for the treatment of stroke patients.

Abstract 181: Stroke Induces a Differential Colonic Epithelial Response and Leads to Impaired Gut Integrity and Increased Post-Stroke Infections in Aged Mice

Introduction: Infection is an important complication in the acute phase after stroke which effects up to 65% of stroke patients. These infections can in turn cause sepsis, which is a major contributor to hospital mortality. Emerging evidence indicates that these infections originate from the host commensal microbiota. We have found that stroke leads to increased gut permeability and bacterial translocation and that aged mice are more susceptible to post-stroke infections compared to young. We further investigated the possibility of how the response to infection differs between young and aged mice.

Hypothesis: Impaired gut epithelial-specific response after stroke in aged mice leads to increased risk of infections and impaired recovery.

Methods: Young (8-10 wks) and aged (18-20 mos) male mice (n=4-5/group) were subjected to either sham or 60-minute middle cerebral artery occlusion (MCAO) followed by reperfusion. Mice were sacrificed at day 8 after stroke. One cohort of mice (n=3/group) was evaluated for the histology and hypoxic barrier integrity. Finally, colonic epithelial cells (cECs) were isolated and changes of the gene expression in cECs were examined (n=4-5/group).

Results: Epithelial dysfunction was observed in aged mice, including a decrease in goblet cells and mucus layer ( P <0.05). Furthermore, stroke induced the loss of hypoxic barrier in the gut of aged mice. Intriguingly, multiple epithelial antimicrobial peptides of the regenerating islet-derived protein (Reg) family genes, which are produced by epithelial cells including deep secretory cells, were highly up-regulated following stroke only in young mice [~20 fold change in Reg3β and Reg3γ ( P <0.05); ~2 fold change in Reg4 ( P <0.05)]. In addition, aged mice showed decreased expression levels of goblet cell-secreting mucin (Muc) (~1.4 fold change in Muc2, P <0.05), whereas young mice retained expression after stroke.

Conclusions: Our data indicates that 1) both aging and stroke impairs gut integrity and possibly leads to increase of infections and 2) epithelial cells could differentially respond to external stimuli after stroke, in an age-dependent manner. The current study provides the first insight into how intestinal epithelium is involved in the brain-gut axis in stroke.

Ischemic stroke induces gut permeability and enhances bacterial translocation leading to sepsis in aged mice

Aging is an important risk factor for post-stroke infection, which accounts for a large proportion of stroke-associated mortality. Despite this, studies evaluating post-stroke infection rates in aged animal models are limited. In addition, few studies have assessed gut microbes as a potential source of infection following stroke. Therefore we investigated the effects of age and the role of bacterial translocation from the gut in post-stroke infection in young (8-12 weeks) and aged (18-20 months) C57Bl/6 male mice following transient middle cerebral artery occlusion (MCAO) or sham surgery. Gut permeability was examined and peripheral organs were assessed for the presence of gut-derived bacteria following stroke. Furthermore, sickness parameters and components of innate and adaptive immunity were examined. We found that while stroke induced gut permeability and bacterial translocation in both young and aged mice, only young mice were able to resolve infection. Bacterial species seeding peripheral organs also differed between young (Escherichia) and aged (Enterobacter) mice. Consequently, aged mice developed a septic response marked by persistent and exacerbated hypothermia, weight loss, and immune dysfunction compared to young mice following stroke.

Deletion of the P2X4 receptor is neuroprotective acutely, but induces a depressive phenotype during recovery from ischemic stroke

INTRODUCTION

Acute ischemic injury leads to severe neuronal loss. One of the key mechanisms responsible for this effect is inflammation, which is characterized by the activation of myeloid cells, including resident microglia and infiltrating monocytes/macrophages. P2X4 receptors (P2X4Rs) present on these immune cells modulate the inflammatory response. For example, excessive release of adenosine triphosphate during acute ischemic stroke triggers stimulation of P2X4Rs, leading to myeloid cell activation and proliferation and further exacerbating post-ischemic inflammation. In contrast, during recovery P2X4Rs activation on microglia leads to the release of brain-derived neurotrophic factor (BDNF), which alleviate depression, maintain synaptic plasticity and hasten post-stroke behavioral recovery. Therefore, we hypothesized that deletion of the P2X4R specifically from myeloid cells would have differential effects on acute versus chronic recovery following stroke.

METHODS

We subjected global or myeloid-specific (MS) P2X4R knock-out (KO) mice and wild-type littermates of both sexes to right middle cerebral artery occlusion (60min). We performed histological, behavioral (sensorimotor and depressive), and biochemical (quantitative PCR and flow cytometry) analyses to determine the acute (three days after occlusion) and chronic (30days after occlusion) effects of receptor deletion.

RESULTS

Global P2X4R deletion led to reduced infarct size in both sexes. In MS P2X4R KO mice, only females showed reduced infarct size, an effect that did not change with ovariectomy. MS P2X4R KO mice of both sexes showed swift recovery from sensorimotor deficits during acute recovery but exhibited a more pronounced post-stroke depressive behavior phenotype that was independent of infarct size. Quantitative PCR analysis of whole cell lysate as well as flow-sorted myeloid cells from the perilesional cortex showed increased cellular interleukin 1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) mRNA levels but reduced plasma levels of these cytokines in MS P2X4R KO mice after stroke. The expression levels of BDNF and other depression-associated genes were reduced in MS P2X4R KO mice after stroke.

CONCLUSIONS

P2X4R deletion protects against stroke acutely but predisposes to depression-like behavior chronically after stroke. Thus, a time-sensitive approach should be considered when targeting P2X4Rs after stroke.

Abstract 46: The Influence of Age and Stroke on Gut Inflammation and Microbiota

Introduction: Earlier work by our laboratory and other groups has identified that aging leads to changes in both the immune system and the microbiome. The elderly have high mortality and more disability after a stroke, a finding that is recapitulated in murine model. Recently, pro-inflammatory γδ T cells have received increasing attention as a major contributor to gut immune responses. These cells may be a link in the bidirectional communication between the microbiome and the central nervous system. We hypothesize that fecal transplant of aged biome into young animals will enhance inflammation, γδ T cell numbers, and worsen functional recovery after stroke in young mice.

Methods: Young C57BL/6 male mice, were randomized and subjected to sham surgery/right middle cerebral artery occlusion (MCAO-60min) followed by reperfusion. All mice received streptomycin treatment at 24h and 48h after MCAO. Subsequently, mice were gavaged with biome from either young or aged animals at 72 and 96 h post-stroke. Behavioral and functional outcomes were evaluated. Animals were sacrificed 15 days after stroke. Brain atrophy was quantified, and Flow Cytometry (FACS) and immunohistochemistry was performed on gut tissue and spleen to determine if stroke or the aged biome influence γδ T cells.

Results: Young mice transplanted with aged biome take a longer time to regain their pre-stroke body weight. These mice have higher post-stroke hyperactivity compared with mice treated with young biome, as measured by average velocity (p<.006) and total distance traveled (p<.006) in the Open Field. Young mice given aged biome had poorer grip strength, as well as a depressive phenotype, when compared with mice transplanted with young biome. FACS analysis shows higher levels of γδ T cell in the gut with stroke and with fecal transplant of aged biome (sham vs. stroke p=0.0443; young vs. aged biome p=0.0199).

Conclusion: Collectively our findings suggests that the gut microbiome plays an important role in post-stroke recovery. Understanding the underlying mechanisms may identify novel therapeutic targets for the treatment of stroke patients.

Alterations in the gut microbiota can elicit hypertension in rats

Gut dysbiosis has been linked to cardiovascular diseases including hypertension. We tested the hypothesis that hypertension could be induced in a normotensive strain of rats or attenuated in a hypertensive strain of rats by exchanging the gut microbiota between the two strains. Cecal contents from spontaneously hypertensive stroke prone rats (SHRSP) were pooled. Similarly, cecal contents from normotensive WKY rats were pooled. Four-week-old recipient WKY and SHR rats, previously treated with antibiotics to reduce the native microbiota, were gavaged with WKY or SHRSP microbiota, resulting in four groups; WKY with WKY microbiota (WKY g-WKY), WKY with SHRSP microbiota (WKY g-SHRSP), SHR with SHRSP microbiota (SHR g-SHRSP), and SHR with WKY microbiota (SHR g-WKY). Systolic blood pressure (SBP) was measured weekly using tail-cuff plethysmography. At 11.5 wk of age systolic blood pressure increased 26 mmHg in WKY g-SHRSP compared with that in WKY g-WKY (182 ± 8 vs. 156 ± 8 mmHg, P = 0.02). Although the SBP in SHR g-WKY tended to decrease compared with SHR g-SHRSP, the differences were not statistically significant. Fecal pellets were collected at 11.5 wk of age for identification of the microbiota by sequencing the 16S ribosomal RNA gene. We observed a significant increase in the Firmicutes:Bacteroidetes ratio in the hypertensive WKY g-SHRSP, as compared with the normotensive WKY g-WKY (P = 0.042). Relative abundance of multiple taxa correlated with SBP. We conclude that gut dysbiosis can directly affect SBP. Manipulation of the gut microbiota may represent an innovative treatment for hypertension.

Abstract T MP14: The Critical Role of Macrophage Migration Inhibitory Factor on Post-Stroke Recovery

Objective: One-third of stroke survivors are affected by post-stroke depression. Evidence from epidemiological and clinical studies demonstrates that depression either before or after stroke is associated with poor recovery and high mortality. Recently it was found that loss of macrophage migration inhibitory factor (MIF) is associated with depressive behavior and impaired neurogenesis. Therefore, here we tested the hypothesis that MIF plays a role in stroke recovery and that chronic MIF inhibition contributes to post-depressive phenotypes and poor stroke outcomes.

Methods: C57BL/6 male mice (20-25g; Charles River), were subjected to a 60min right middle cerebral artery occlusion (MCAO) and randomly assigned to vehicle or MIF antagonist, ISO-1 (7mg/kg/day intraperitoneal) treatment. Infarcts quantified with TTC. Recovery was investigated using neurological deficit scores (NDS), corner test, the forced swim test (FST) and the tail suspension test (TST). MIF levels were assessed by ELISA and western-blot (n=4/grp). Further, the effects of MIF loss were tested using knockout (KO) mice. Data are expressed as mean±sem. P value < .05 was set for statistical significance.

Results: Post-stroke chronic ISO-1 treatment significantly increased immobility in TST at 14d (126±8 vs 83±6s; p<.05), delayed stroke recovery in the corner test (p<.05) and NDS (p<.05) compared to vehicle group. These detrimental effects were observed in parallel to reduced plasma MIF levels (p<.05). Stroke alone did not affect mobility in FST compared to sham (p>.05). Infarct size was similar in ISO-1 and vehicle groups (48±3.2% versus 46±2.8%; p>.05). When subjected MIF KO mice to stroke, similar pattern of delayed post-stroke recovery is observed suggesting that MIF plays a critical role in pre- or post-stroke depression and recovery.

Conclusions: MIF KO mice had a depressive phenotype at baseline, and poor recovery after stroke compared to WT. Post-stroke MIF inhibition led to the development of a post-stroke depressive phenotype and also led to poorer recovery. These effects are independent of stroke volume. These findings suggest that targeting MIF might be a novel therapeutic strategy to treat post-stroke depression and to enhance recovery in stroke survivors.

Chronic metformin treatment improves post-stroke angiogenesis and recovery after experimental stroke

Metformin is currently the first-line treatment drug for type 2 diabetes. Metformin is a well-known activator of AMP-activated protein kinase (AMPK). In experimental studies, metformin has been shown to exert direct vascular effects by increasing vascular endothelial growth factor expression and improving microvascular density. As stroke is the leading cause of long-term disability and angiogenesis is implicated as an important mechanism in functional recovery, we hypothesized that chronic metformin treatment would improve post-stroke functional recovery by enhancing functional microvascular density. For this study, C57BL/6N male mice were subjected to a 60-min middle cerebral artery occlusion, and were given 50 mg/kg/day metformin beginning 24 h post-stroke for 3 weeks. Behavioral recovery was assessed using adhesive-tape removal and the apomorphine-induced turning test. The role of angiogenesis was assessed by counting vessel branch points from fluorescein-conjugated lectin-perfused brain sections. Importantly even if metformin treatment was initiated 24 h after injury it enhanced recovery and significantly improved stroke-induced behavioral deficits. This recovery occurred in parallel with enhanced angiogenesis and with restoration of endogenous cerebral dopaminergic tone and revascularization of ischemic tissue. We assessed if the effects on recovery and angiogenesis were mediated by AMPK. When tested in AMPK α-2 knockout mice, we found that metformin treatment did not have the same beneficial effects on recovery and angiogenesis, suggesting that metformin-induced angiogenic effects are mediated by AMPK. The results from this study suggest that metformin mediates post-stroke recovery by enhancing angiogenesis, and these effects are mediated by AMPK signaling.

Abstract W P88: Impact of Post Stroke Isolation on Sociability and Depressive Behavior

Background and Purpose: Social isolation (SI) has been linked epidemiologically with high rates of morbidity and mortality following stroke. Clinically, social support and coping strategies have been shown to be significant factors in caregiver’s health-related quality of life. In order to discover the biological mechanisms underlying the benefits of social interaction the development of pre-clinical animal models are needed. The goal of our study was to examine the effect of post stroke pair housing and SI in different behavioral paradigms, which can be used as a validated model to assess chronic functional recovery.

Methods: C57BL/6 male mice (8-12 weeks) were paired for 14 days before 60 min of transient intraluminal middle cerebral artery occlusion (MCAO) or sham surgery (n=8-10/group) and randomly assigned to six different housing conditions: 1. Stroke isolated (STiso), 2. Stroke pair housed (PH) with sham, 3. Stroke PH with stroke and their respective sham controls (Gps 4, 5, and 6). Behavioral assessments (3 Chamber sociability task, tail suspension test and sucrose consumption test), were performed at 42 days (Cohort 1) or every 7Th day for 6 weeks (Cohort 2). Brain atrophy was calculated using cresyl violet staining and blood samples were collected for interleukin-6 (IL-6) measurements.

Results: Post stroke PH mice, either with sham or stroke partner showed significantly higher (p<0.05) sociability after MCAO. In the 2nd cohort, a two-factor interaction ‘group versus days’ showed a significant difference between post stroke SI and PH groups (F 3,24 = 5.41; p< 0.01, RM ANOVA with Bonferroni correction). Post stroke SI mice showed reduced sucrose consumption (p<0.05) and increased immobility (p<0.05) indicating a depressive phenotype. Post stroke SI mice had significantly more tissue loss (40.8 ± 1.3% in SI vs. 17.5 ± 1.5% in PH; p<0.001) and showed higher levels of IL-6, a biomarker of social stress and inflammation.

Conclusions: Our findings suggest that post stroke isolation reduces sociability and exacerbates depressive behavior, whereas pair housing aids early functional recovery. Moreover, the sociability (“empathy”) task can be a useful model for chronic post stroke behavioral recovery.

Abstract W MP48: Post-stroke Administration of Exogenous Inter-alpha Inhibitor Proteins is Neuroprotective

Background and Purpose: Current stroke therapies approved for human use are limited by time constraints and carry significant hemorrhagic risk. Down regulation of pro-inflammatory cytokines, modulation of peripheral leukocyte infiltration and reduced microglial activation benefit the ischemic brain. A novel immunomodulator protein family extracted from human plasma (Inter-alpha Inhibitor Proteins - IAIP) has been developed that has desirable anti-inflammatory properties in addition to an advantageous long half-life (8-12 hours).

Methods: C57BL/6 mice were subjected to transient focal ischemia by middle cerebral artery occlusion (MCAO) for 90 minutes. One cohort was given IAIP (30mg/kg) immediately at reperfusion (90 minutes after stroke). A second “delayed treatment” cohort was given IAIP 6 hours after stroke onset. Both cohorts were given a second dose 24 hours post-stroke. Motor and sensory deficits were assessed using the neurological deficit score (NDS). Infarct was assessed at either 48 hours or 7 day time points. Infarct data presented as mean ±SEM, NDS data are presented as median±IQR.

Results: At 48 hours mice given IAIP at reperfusion had significantly smaller cortical (59.26%±1.80% versus 31.58%±8.53%, n=8, p<.05) and hemisphere (46.05%±1.55% vs. 22.53%±6.55%, n=8, p<.05) infarct volumes. Delayed IAIP treated mice also had significantly smaller cortical (52.44%±1.73% vs. 22.99%±4.59%, n=6, p<.05) and hemispheric infarcts (43.86%±2.11% vs. 19.45%±3.59%, n=6, p<.05) at 48 hours. Analysis at 7 days showed significantly smaller cortical (23.30%±2.53% vs. 3.46%±0.46%, n=6, p<.05) and total hemisphere (22.33%±2.87% vs 5.90%±0.86%, n=6, p<.05) infarcts in mice treated with IAIP 6 hrs after stroke suggesting durability of neuroprotective effects. Significant improvement in NDS (1±1, n=19 versus 2±1, n=18) was also seen in mice treated with IAIP vs. controls. Similar beneficial effects of IAIP were seen in aged mice.

Conclusions: Delayed administration of IAIP at 6 and 24 hours post-stroke results in significantly smaller infarcts and improved functional outcomes, indicating IAIP could potentially be translated into an important novel treatment strategy for adults with brain ischemia.

Social interaction plays a critical role in neurogenesis and recovery after stroke

Stroke survivors often experience social isolation. Social interaction improves quality of life and decreases mortality after stroke. Male mice (20-25 g; C57BL/6N), all initially pair housed, were subjected to middle cerebral artery occlusion (MCAO). Mice were subsequently assigned into one of three housing conditions: (1) Isolated (SI); (2) Paired with their original cage mate who was also subjected to stroke (stroke partner (PH-SP)); or (3) Paired with their original cage mate who underwent sham surgery (healthy partner (PH-HP)). Infarct analysis was performed 72 h after stroke and chronic survival was assessed at day 30. Immediate post-stroke isolation led to a significant increase in infarct size and mortality. Interestingly, mice paired with a healthy partner had significantly lower mortality than mice paired with a stroke partner, despite equivalent infarct damage. To control for changes in infarct size induced by immediate post-stroke isolation, additional cohorts were assessed that remained pair housed for three days after stroke prior to randomization. Levels of brain-derived neurotrophic factor (BDNF) were assessed at 90 days and cell proliferation (in cohorts injected with 5-bromo-2'-deoxyuridine, BrdU) was evaluated at 8 and 90 days after stroke. All mice in the delayed housing protocol had equivalent infarct volumes (SI, PH-HP and PH-SP). Mice paired with a healthy partner showed enhanced behavioral recovery compared with either isolated mice or mice paired with a stroke partner. Behavioral improvements paralleled changes in BDNF levels and neurogenesis. These findings suggest that the social environment has an important role in recovery after ischemic brain injury.

Social isolation after stroke leads to depressive-like behavior and decreased BDNF levels in mice

Social isolation prior to stroke leads to poorer outcomes after an ischemic injury in both animal and human studies. However, the impact of social isolation following stroke, which may be more clinically relevant as a target for therapeutic intervention, has yet to be examined. In this study, we investigated both the sub-acute (2 weeks) and chronic (7 weeks) effects of social isolation on post-stroke functional and histological outcome. Worsened histological damage from ischemic injury and an increase in depressive-like behavior was observed in isolated mice as compared to pair-housed mice. Mice isolated immediately after stroke showed a decrease in the levels of brain-derived neurotrophic factor (BDNF). These changes, both histological and behavioral, suggest an overall negative effect of social isolation on stroke outcome, potentially contributing to post-stroke depression and anxiety. Therefore, it is important to identify patients who have perceived isolation post-stroke to hopefully prevent this exacerbation of histological damage and subsequent depression.

Abstract 3432: Sex-dependent Differences in Autophagy After Experimentally-induced Stroke

Background and Purpose: Autophagy is a catabolic process where the cell consumes pieces of itself as a part of normal cellular growth, development, and homeostasis. In response to nutrient challenge or other stressors, including ischemia, autophagy levels may rise, enabling the cell to survive. Autophagy has been shown to play a role in the cellular response to neonatal cerebral ischemia, and sex differences have been found in cell culture models of neuronal nutrient starvation. However, the role of sex in the autophagic response to stroke has not been investigated in vivo . The objective of this study was to examine the impact of sex on autophagy following experimental stroke.

Methods: Stroke was induced by reversible right middle cerebral artery occlusion (MCAO - 90 minutes) in male, gonadally-intact female, and ovariectomized (OVX) WT C57BL/6 mice (20-25 gm). Autophagy activity was assessed at 6 and 24 hours following MCAO with LC3-I/II and Atg7 protein levels by western blot (n=3 MCAO; n=3 sham/group). Beta-actin was utilized as a loading control.

Results: Atg7 levels were higher in sham males at both the 6h and 24h timepoint compared to intact females and OVX females. After MCAO, males and OXV females showed increased levels of Atg7 relative to sham at 6h, while intact female levels were unchanged. By 24h, Atg7 levels in MCAO males and OVX females remained higher than sham, while intact females showed no difference. LC3-II levels were higher in MCAO for OVX females at 6h and 24h, while intact females saw transiently-elevated LC3-II levels at 6h and no elevation by 24h. Males had higher levels of LC3-II in both MCAO and sham relative to intact females at both 6h and 24h and higher levels than OVX females at 6h.

Conclusions: This study demonstrates that autophagy activation in response to stroke differs between the sexes. We found that males had overall higher levels of autophagy than both OVX females and intact females at both 6h and 24h. Both males and OVX females showed higher levels of autophagy at 24h and 6h after MCAO relative to sham, while females showed no change. Our study suggests that changes in autophagy may contribute to the differential outcome after stroke between the sexes. Studies examining sex differences in infarct size after MCAO after inhibition of autophagy with 3-methyladenine (3-MA, Sigma-Aldrich, St. Louis, MO) are ongoing in our laboratory.

Abstract 197: Post-stroke Inhibition of TGF-β-activated Kinase by 5Z-7-oxozeaenol Improves Histological and Behavioral Outcomes in a Mouse Model of Ischemic Stroke

Background: Transforming growth factor-β activated kinase 1 (TAK1) activates several intracellular signaling cascades, affecting cell proliferation, inflammation, and apoptosis. It is also a putative kinase for adenosine monophosphate protein kinase (AMPK). 5Z-7-oxozeaenol is a selective inhibitor of TAK1. We and others have previously reported that this drug reduced infarct volume and levels of activated TAK1when administered prior to ischemia in a mouse model of ischemic stroke. We investigated the possible clinical utility of the drug by administering it after ischemia and measuring infarct volumes and behavioral outcomes at 7 days. We also explored the relationship between TAK1 and AMPK by examining outcomes of TAK1 inhibition in AMPK knockout (KO) mice.

Methods: Stroke was induced by 90 minutes of reversible middle cerebral artery occlusion (MCAO) in male mice. In one cohort, wild-type (WT) and AMPK KO mice were treated with drug or vehicle via intraperitoneal (IP) injection 2 hours after stroke onset and stroke severity was measured by tissue staining at 24 hours. In a second cohort, WT and AMPK KO mice were treated with drug or vehicle 3.5 hours after stroke onset and stroke severity was measured using the novel-object recognition test (NORT) and by tissue staining at 7 days. Proteins were analyzed by western blot in a third cohort of mice that were sacrificed 4 hours after onset of ischemia.

Results: IP injection of 5.0 mg/kg of drug 2 hours after onset of MCAO resulted in a significant reduction in whole-hemisphere infarct volume after 24 hours of reperfusion (49.18±4.18% vehicle vs.17.81±5.86% drug, p=0.001, n=7 vehicle, 8 drug) and after 7 days of reperfusion (57.16±2.38% vehicle vs. 38.35±8.97% drug, p=0.049, n=8 vehicle, 8 drug), and significantly increased the percentage of time that the mice spent exploring a novel object (59.85 ± 3.62% drug vs. 33.15 ± 5.04% vehicle, p=0.001, n=7 vehicle, 7 drug). In AMPK KO mice, there was also a reduction in whole-hemisphere infarct volume. The drug reduced levels of the TAK1 target JNK as well as the JNK target c-Jun.

Conclusions: Post-stroke inhibition of TAK1 was neuroprotective and this effect was sustained for 7 days. It was also associated with improvement in the NORT, suggesting preservation of memory function. Together, these findings suggest that 5Z-7-oxozeaenol may have clinical utility for patients suffering ischemic stroke. 5Z-7-oxozeaenol reduced levels of the TAK1 target JNK and its target, c-Jun, suggesting that the benefits of inhibition are due to decreased levels of the transcription factor complex AP-1, of which c-Jun is a major component. The sustained protective effect in AMPK KO mice suggests that AMPK is not important to the mechanism of neuroprotection following TAK1 inhibition.

Abstract 3133: Impact of Post-stroke Isolation on Stroke Outcome

Background: Psychosocial factors are increasingly accepted as critical factors in post-stroke recovery, mortality and morbidity. Although, emerging data from clinical and population based studies support the role of social support in improved functional recovery and reducing the risk of mortality, to date no experimental studies have investigated such effects in post-stroke animal models. The aim of this study is to investigate for the impact of post stroke housing and the effects of long-term social isolation and pair housing with either a healthy or a stroked partner, and explored for the mechanisms.

Methods: Male mice (20-25g; C57BL/6N, Charles River Labs), all initially pair housed, were subjected to right middle cerebral artery occlusion (MCAO - 60min) and then randomly assigned to a specific housing condition - isolated, paired with a stroke partner or paired with a healthy partner. Infarct size was quantified with TTC 72h after stroke (n=8/grp). We then investigated the effects of housing on long-term functional recovery using corner test, cylinder test, forced swim test (FST) and tail suspension test (TST). We further explored the mechanisms underlying the improved behavioral recovery by injecting BrDU 150mg/kg/day i.p. for 5 days starting from day 3 post-stroke (n=8/grp), and assessing changes in BDNF levels by western-blot analysis (n=4/grp). Data were expressed as mean±sem. Two-way ANOVA was performed and P value < .05 was set for statistical significance.

Results: Post-stroke housing conditions can significantly impact infarct size; we observed that mice isolated after stroke had increased infarct volume compared to pair housed mice in all three brain regions (Cortex: 63.2±2.5 vs 40.0±6.2; p<0.01); (Striatum: 86.6±2.2 vs 67.7±2.9; p<0.01); (Total: 60.9±1.3 vs 32.6±4.3; p<0.01). Although post-stroke housing with healthy vs a stroked partner did not influenced infarct size (p>0.05), animals pair housed with healthy partner showed a significantly improved functional recovery by as early as day 15 in the cylinder and corner tests (p<0.05). Increased mobility was observed in FST and TST in PH mice compared to SI mice at day 90 (p<0.05). Consistently, housing with a healthy partner increased BrDU positive cells (p<0.05) and enhanced BDNF expression compared to other cohorts (SI 1±0.1; PH with stroke partner 1.9±0.2; PH with healthy partner 2.6±0.1; n=4/grp), no changes were seen in sham mice.

Conclusions: Post-stroke housing has an important impact on stroke outcome; isolation has a detrimental effect on infarct size compared to pair housed cohorts. Interestingly, independent of infarct size, housing with a healthy partner hastened recovery compared to those stroke mice housed with partner that had also been subjected to stroke. Molecular analysis indicates the involvement of BDNF and neurogenesis may be important regulators of post-stroke housing induced functional recovery.