Reduced Serum Levels of Soluble Interleukin-15 Receptor α in Schizophrenia and Its Relationship to the Excited Phenotype.

Our previous studies documented that interleukin-15 receptor α (IL-15Rα) knockout (KO) mice exhibited hyperactivity, memory impairment, and desperate behavior, which are core features of schizophrenia and depression. Due to the overlapping symptomology and pathogenesis observed for schizophrenia and depression, the present study attempted to determine whether IL-15Rα was associated with the risk of schizophrenia or depression. One hundred fifty-six participants, including 63 schizophrenia patients, 29 depressive patients, and 64 age-matched healthy controls, were enrolled in the study. We investigated the circulating levels of soluble IL-15Rα and analyzed potential links between the IL-15Rα levels and clinical symptoms present in schizophrenia or depressive patients. We observed reduced serum IL-15Rα levels in schizophrenia patients, but not depressive patients compared with controls. Moreover, a significant negative association was observed between the circulating IL-15Rα levels and excited phenotypes in the schizophrenia patients. The IL-15Rα KO mice displayed pronounced pre-pulse inhibition impairment, which was a typical symptom of schizophrenia. Interestingly, the IL-15Rα KO mice exhibited a remarkable elevation in the startle amplitude in the startle reflex test compared to wild type mice. These results demonstrated that serum levels of soluble IL-15Rα were reduced in schizophrenia and highlighted the relationship of IL-15Rα and the excited phenotype in schizophrenia patients and mice.

Estrogen can abolish oxytocin-induced spinal anti-hyperalgesia.

Our previous study verified a sex difference of anti-hyperalgesia in rats and anti-allodynia in mice induced by intrathecal oxytocin (OT). In the model of intraplantar carrageenan-induced inflammatory hyperalgesia, intrathecal OT injection induced a substantial anti-hyperalgesia in male rats even at a low dose (0.125 nmol). In contrast, female rats only responded to an extremely high dose (1.25 nmol). This sex difference concurs with a lower expression of OT receptors and higher expression of insulin-regulated aminopeptidase (IRAP; OT degrading enzyme) in the spinal cords of female rats. In this study, we further determined the role of female hormones in this sex difference by using ovariectomized rats. Our results show that a low dose of intrathecal OT caused a significant anti-hyperalgesia effect in ovariectomized female rats, similar to that seen in male rats. Ovariectomy did not cause any change of paw edema except at the late stage of convalescence when compared with the sham-operated group. Ovariectomy-induced faster recovery from edema but did not affect the severity of hyperalgesia. Moreover, there was a similar amount of IRAP expression in ovariectomized and sham rats. When estradiol (E2) was given together with OT, OT-induced anti-hyperalgesia was abolished at the developmental stage of hyperalgesia in ovariectomized rats. These results show an inhibitory role of female hormones generated from ovaries (mainly estrogen) in the sex difference of anti-hyperalgesia induced by OT. This study suggests the feasibility of a novel OT-based remedy to treat hyperalgesia in men and in menopausal women no receiving hormonal supplements.

Intracellular interplay between cholecystokinin and leptin signalling for satiety control in rats.

Cholecystokinin (CCK) and leptin are satiety-controlling peptides, yet their interactive roles remain unclear. Here, we addressed this issue using in vitro and in vivo models. In rat C6 glioma cells, leptin pre-treatment enhanced Ca2+ mobilization by a CCK agonist (CCK-8s). This leptin action was reduced by Janus kinase inhibitor (AG490) or PI3-kinase inhibitor (LY294002). Meanwhile, leptin stimulation alone failed to mobilize Ca2+ even in cells overexpressing leptin receptors (C6-ObRb). Leptin increased nuclear immunoreactivity against phosphorylated STAT3 (pSTAT3) whereas CCK-8s reduced leptin-induced nuclear pSTAT3 accumulation in these cells. In the rat ventromedial hypothalamus (VMH), leptin-induced action potential firing was enhanced, whereas nuclear pSTAT3 was reduced by co-stimulation with CCK-8s. To further analyse in vivo signalling interplay, a CCK-1 antagonist (lorglumide) was intraperitoneally injected in rats following 1-h restricted feeding. Food access was increased 3-h after lorglumide injection. At this timepoint, nuclear pSTAT3 was increased whereas c-Fos was decreased in the VMH. Taken together, these results suggest that leptin and CCK receptors may both contribute to short-term satiety, and leptin could positively modulate CCK signalling. Notably, nuclear pSTAT3 levels in this experimental paradigm were negatively correlated with satiety levels, contrary to the generally described transcriptional regulation for long-term satiety via leptin receptors.

Phenotypic Resemblance to Neuropsychiatric Disorder and Altered mRNA Profiles in Cortex and Hippocampus Underlying IL15Rα Knockout.

BACKGROUND: Previous studies of the functions of IL15Rα have been limited to immune activities and skeletal muscle development. Immunological factors have been identified as one of the multiple causes of psychosis, and neurological symptoms have been described in IL15Rα knockout (KO) mice. Seeking to explore possible mechanisms for this in the IL15Rα-/- mouse brain, we analyzed gene expression patterns in the cortex and hippocampus using the RNA-seq technique. METHODS: IL15Rα KO mice were generated and littermate wildtype (WT) mice were used as a control group. A Y-maze was used to assess behavior differences between the two groups. The cortex and hippocampus of 3-month-old male mice were prepared and RNA-seq and transcriptome analysis were performed by gene set enrichment analysis (GSEA). RESULTS: Compared with the WT group, IL15Rα KO animals showed higher speed in the novel arm and more entrance frequency in the old arm in the Y-maze experiment. GSEA indicated that 18 pathways were downregulated and 13 pathways upregulated in both cortex and hippocampus from the GO, KEGG, and Hallmark gene sets. The downregulated pathways formed three clusters: respiratory chain and electron transport, regulation of steroid process, and skeletal muscle development. CONCLUSION: IL15Rα KO mice exhibit altered expression of multiple pathways, which could affect many functions of the brain. Lipid biosynthesis and metabolism in the central nervous system (CNS) should be investigated to provide insights into the effect of IL15Rα on psychosis in this murine model.

Schizophrenia Patient Shows a Rare Interleukin 15 Receptor alpha Variant Disrupting Signal Transduction.

BACKGROUND: Schizophrenia is a complex and debilitating mental disorder with strong heritability. Its pathogenesis involves immune dysregulation. Interleukin 15 and interleukin 15 receptor alpha(IL-15Rα) are classical immune molecules. They also help maintain normal brain function, leading to our hypothesis that IL-15Rα gene(IL- 15RA) variants contribute to the pathogenesis of schizophrenia. OBJECTIVE: We determine whether the genetic variants of IL-15RA are associated with the development and progression of schizophrenia and whether IL-15RA single nucleotide polymorphism(SNP) plays a key role in downstream signaling transduction. METHODS AND RESULTS: We sequenced IL-15RA exon from 132 Chinese schizophrenic patients and identified a rare variant(rs528238821) in a patient diagnosed with catatonic schizophrenia and ankylosing spondylitis(AS). We overexpressed this missense variant in cells driven by pBI-CMV vector. The cells showed attenuated STAT3 phosphorylation in response to interleukin15. CONCLUSION: IL-15RA mutation is rare in schizophrenic patients but interfered with IL- 15Rα intracellular signal transduction. Given the similarity of symptoms of catatonic schizophrenia and the known phenotype of IL-15Rα knockout mice, gene variation might offer diagnostic value for sub-types of schizophrenia.

The Amazon rain forest plant Uncaria tomentosa (cat's claw) and its specific proanthocyanidin constituents are potent inhibitors and reducers of both brain plaques and tangles.

Brain aging and Alzheimer's disease both demonstrate the accumulation of beta-amyloid protein containing "plaques" and tau protein containing "tangles" that contribute to accelerated memory loss and cognitive decline. In the present investigation we identified a specific plant extract and its constituents as a potential alternative natural solution for preventing and reducing both brain "plaques and tangles". PTI-00703 cat's claw (Uncaria tomentosa from a specific Peruvian source), a specific and natural plant extract from the Amazon rain forest, was identified as a potent inhibitor and reducer of both beta-amyloid fibrils (the main component of "plaques") and tau protein paired helical filaments/fibrils (the main component of "tangles"). PTI-00703 cat's claw demonstrated both the ability to prevent formation/aggregation and disaggregate preformed Aß fibrils (1-42 and 1-40) and tau protein tangles/filaments. The disaggregation/dissolution of Aß fibrils occurred nearly instantly when PTI-00703 cat's claw and Aß fibrils were mixed together as shown by a variety of methods including Thioflavin T fluorometry, Congo red staining, Thioflavin S fluorescence and electron microscopy. Sophisticated structural elucidation studies identified the major fractions and specific constituents within PTI-00703 cat's claw responsible for both the observed "plaque" and "tangle" inhibitory and reducing activity. Specific proanthocyanidins (i.e. epicatechin dimers and variants thereof) are newly identified polyphenolic components within Uncaria tomentosa that possess both "plaque and tangle" reducing and inhibitory activity. One major identified specific polyphenol within PTI-00703 cat's claw was epicatechin-4ß-8-epicatechin (i.e. an epicatechin dimer known as proanthocyanidin B2) that markedly reduced brain plaque load and improved short-term memory in younger and older APP "plaque-producing" (TASD-41) transgenic mice (bearing London and Swedish mutations). Proanthocyanidin B2 was also a potent inhibitor of brain inflammation as shown by reduction in astrocytosis and gliosis in TASD-41 transgenic mice. Blood-brain-barrier studies in Sprague-Dawley rats and CD-1 mice indicated that the major components of PTI-00703 cat's claw crossed the blood-brain-barrier and entered the brain parenchyma within 2 minutes of being in the blood. The discovery of a natural plant extract from the Amazon rain forest plant (i.e. Uncaria tomentosa or cat's claw) as both a potent "plaque and tangle" inhibitor and disaggregator is postulated to represent a potential breakthrough for the natural treatment of both normal brain aging and Alzheimer's disease.

The Blood-Brain Barrier: Regulatory Roles in Wakefulness and Sleep.

Sleep and its disorders are known to affect the functions of essential organs and systems in the body. However, very little is known about how the blood-brain barrier (BBB) is regulated. A few years ago, we launched a project to determine the impact of sleep fragmentation and chronic sleep restriction on BBB functions, including permeability to fluorescent tracers, tight junction protein expression and distribution, glucose and other solute transporter activities, and mediation of cellular mechanisms. Recent publications and relevant literature allow us to summarize here the sleep-BBB interactions in five sections: (1) the structural basis enabling the BBB to serve as a huge regulatory interface; (2) BBB transport and permeation of substances participating in sleep-wake regulation; (3) the circadian rhythm of BBB function; (4) the effect of experimental sleep disruption maneuvers on BBB activities, including regional heterogeneity, possible threshold effect, and reversibility; and (5) implications of sleep disruption-induced BBB dysfunction in neurodegeneration and CNS autoimmune diseases. After reading the review, the general audience should be convinced that the BBB is an important mediating interface for sleep-wake regulation and a crucial relay station of mind-body crosstalk. The pharmaceutical industry should take into consideration that sleep disruption alters the pharmacokinetics of BBB permeation and CNS drug delivery, being attentive to the chrono timing and activation of co-transporters in subjects with sleep disorders.

Involvement of the Blood-Brain Barrier in Metabolic Regulation.

Pertinent to pandemic obesity, the discovery of endogenous peptides that affect the ingestion of food has led to the question of how these ingestive peptides exert their actions in the brain. Whereas peripheral sources provide a ready reserve, the availability of ingestive peptides to their central nervous system targets can be regulated by the blood-brain barrier (BBB). Some of the peptides/polypeptides are transported by saturable mechanisms from blood to brain. Examples include leptin, insulin, mahogany, and pancreatic polypeptide. Some enter the brain by passive diffusion, such as neuropeptide Y, orexin A, cocaine- and amphetamine-regulated transcript, cyclo His-Pro, and amylin. Some others may have essentially no penetration of the BBB; this class includes agouti-related protein, melanin-concentrating hormone, and urocortin. The regulatory function of the BBB can be seen in various physiological states. Hyperglycemia may upregulate transport systems for leptin, urocortin, and galanin-like peptide, whereas fasting can down-regulate those for leptin and galanin-like peptide. Thus, the BBB plays a dynamic role in modulating the passage of ingestive peptides from blood to brain.

Spinal Cord Injury Changes Cytokine Transport.

Here we summarize three aspects of our understanding of the interactions of cytokines and neurotrophic peptides/proteins with the blood-brain and bloodspinal cord barriers (BBB): (a) pharmacokinetic analysis that has been reported for native cytokines and neurotrophic peptides/proteins; (b) landmark work on conjugated proteins to enhance their delivery across the normal BBB; and (c) regulatory changes under pathophysiological conditions in rodents, particularly after spinal cord injury (SCI). First, though the BBB restricts the permeation of large proteins, some cytokines and neurotrophic peptides/proteins in the periphery can reach the central nervous system (CNS) by specific transport systems. Moreover, SCI and some other disease processes may regulate these transport systems. The significance of studies of the transport systems is obvious because of the biological impact of these molecules on the CNS in health and disease. We have characterized the pharmacokinetic characteristics of some stable cytokines and neurotrophic peptides/proteins in mice after intravenous administration and also in the setting of in situ brain perfusion. In the particular case of SCI, there are time- and regionspecific changes of BBB permeability and transport systems. Tumor necrosis factor-α, a cytokine with dual actions in regeneration of the spinal cord, has a slow basal influx into the brain and spinal cord. After SCI, the increase in the entry of tumor necrosis factor-α to the CNS differs from leakage after BBB disruption and is related to upregulation of the transport system in a unique temporal and regional pattern. Overall, the permeation of cytokines across the BBB can be mediated by specific transport systems. The regulation of transport in pathophysiological conditions affects the extent of neuroinflammation and is implicated in neuroregeneration.

Circadian rhythm of autophagy proteins in hippocampus is blunted by sleep fragmentation.

Autophagy is essential for normal cellular survival and activity. Circadian rhythms of autophagy have been studied in several peripheral organs but not yet reported in the brain. Here, we measured the circadian rhythm of autophagy-related proteins in mouse hippocampus and tested the effect of sleep fragmentation (SF). Expressions of the autophagy-related proteins microtubule-associated protein 1 light chain 3 (LC3) and beclin were determined by western blotting and immunohistochemistry. Both the hippocampal LC3 signal and the ratio of its lipid-conjugated form LC3-II to its cytosolic form LC3-I showed a 24 h rhythm. The peak was seen at ZT6 (1 pm) and the nadir at ZT16 (1 am). The LC3 immunoreactivity in hippocampal CA1 pyramidal neurons also distributed differently, with more diffuse cytoplasmic appearance at ZT16. Chronic SF had a mild effect to disrupt the 24 h rhythm of LC3 and beclin expression. Interestingly, a greater effect of SF was seen after 24 h of recovery sleep when LC3-II expression was attenuated at both the peak and trough of circadian activities. Overall, the results show for the first time that the hippocampus has a distinct rhythm of autophagy that can be altered by SF.

From blood to brain through BBB and astrocytic signaling.

In this Festschrift, I discuss the career and guiding principles to which Abba J. Kastin has adhered during the last 20 years we worked together. I briefly describe the history of our joint laboratory group, the context of studies of peptide permeation across the blood-brain barrier (BBB), and newer developments in the BBB Group as Abba steps down after serving 35 years as the founding Editor-in-Chief for Peptides. Abba's BBB studies on peptides have contributed to concepts in the neuroendocrinology of feeding and developed information on molecular trafficking across BBB cells. The astroglial leptin signaling studies and the interactions of sleep and BBB are two major directions, whereas the long-term MIF-1 project demarcates a tortuous road on translational research.

Deletion of mouse FXR gene disturbs multiple neurotransmitter systems and alters neurobehavior.

Farnesoid X receptor (FXR) is a nuclear hormone receptor involved in bile acid synthesis and homeostasis. Dysfunction of FXR is involved in cholestasis and atherosclerosis. FXR is prevalent in liver, gallbladder, and intestine, but it is not yet clear whether it modulates neurobehavior. In the current study, we tested the hypothesis that mouse FXR deficiency affects a specific subset of neurotransmitters and results in an unique behavioral phenotype. The FXR knockout mice showed less depressive-like and anxiety-related behavior, but increased motor activity. They had impaired memory and reduced motor coordination. There were changes of glutamatergic, GABAergic, serotoninergic, and norepinephrinergic neurotransmission in either hippocampus or cerebellum. FXR deletion decreased the amount of the GABA synthesis enzyme GAD65 in hippocampus but increased GABA transporter GAT1 in cerebral cortex. FXR deletion increased serum concentrations of many bile acids, including taurodehydrocholic acid, taurocholic acid, deoxycholic acid (DCA), glycocholic acid (GCA), tauro-α-muricholic acid, tauro-ω-muricholic acid, and hyodeoxycholic acid (HDCA). There were also changes in brain concentrations of taurocholic acid, taurodehydrocholic acid, tauro-ω-muricholic acid, tauro-ß-muricholic acid, deoxycholic acid, and lithocholic acid (LCA). Taken together, the results from studies with FXR knockout mice suggest that FXR contributes to the homeostasis of multiple neurotransmitter systems in different brain regions and modulates neurobehavior. The effect appears to be at least partially mediated by bile acids that are known to cross the blood-brain barrier (BBB) inducing potential neurotoxicity.

Role of Astrocytes in Leptin Signaling.

To test the hypothesis that astrocytic leptin signaling induces an overall potentiation of the neuronal response to leptin, we generated a new line of astrocyte-specific leptin receptor knockout (ALKO-Δ1) mice in which no leptin receptor is expressed in astrocytes. Corresponding to cell-specific Cre recombinase expression in hypothalamic astrocytes but not neurons, this new strain of ALKO mice had attenuated pSTAT3 signaling in the arcuate nucleus of the hypothalamus 30 min after intracerebroventricular delivery of leptin. In response to high-fat diet for 2 months, the ALKO mice showed a greater increase of percent fat and blood leptin concentration. This coincided with a mild reactive gliosis in the hypothalamus. Overall, the absence of leptin receptors in astrocytes attenuated hypothalamic pSTAT3 signaling, induced a mild reactive morphology, and promoted the development of diet-induced obesity. We conclude that leptin signaling in astrocytes is essential for the homeostasis of neuroendocrine regulation in obesity.

Enriched environment inhibits mouse pancreatic cancer growth and down-regulates the expression of mitochondria-related genes in cancer cells.

Psycho-social stress has been suggested to influence the development of cancer, but it remains poorly defined with regard to pancreatic cancer, a lethal malignancy with few effective treatment modalities. In this study, we sought to investigate the impacts of enriched environment (EE) housing, a rodent model of "eustress", on the growth of mouse pancreatic cancer, and to explore the potential underlying mechanisms through gene expression profiling. The EE mice showed significantly reduced tumor weights in both subcutaneous (53%) and orthotopic (41%) models, while each single component of EE (inanimate stimulation, social stimulation or physical exercise) was not profound enough to achieve comparative anti-tumor effects as EE. The integrative transcriptomic and proteomic analysis revealed that in response to EE, a total of 129 genes in the tumors showed differential expression at both the mRNA and protein levels. The differentially expressed genes were mostly localized to the mitochondria and enriched in the citrate cycle and oxidative phosphorylation pathways. Interestingly, nearly all of the mitochondria-related genes were down-regulated by EE. Our data have provided experimental evidence in favor of the application of positive stress or of benign environmental stimulation in pancreatic cancer therapy.

Sleep fragmentation has differential effects on obese and lean mice.

Chronic sleep fragmentation (SF), common in patients with sleep apnea, correlates with the development of obesity. We hypothesized that SF differentially affects neurobehavior in lean wild-type (WT) and obese pan-leptin receptor knockout (POKO) mice fed the same normal diet. First, we established an SF paradigm by interrupting sleep every 2 min during the inactive light span. The maneuver was effective in decreasing sleep duration and bout length, and in increasing sleep state transition and waking, without significant rebound sleep in the dark span. Changes of sleep architecture were evident in the light span and consistent across days 1-10 of SF. There was reduced NREM, shortened sleep latency, and increased state transitions. During the light span of the first day of SF, there also was reduction of REM and increased delta power of slow-wave sleep. Potential effects of SF on thermal pain threshold, locomotor activity, and anxiety were then tested. POKO mice had a lower circadian amplitude of pain latency than WT mice in the hot plate test, and both groups had lowest tolerance at 4 pm (zeitgeber time (ZT) 10) and longest latency at 4 am (ZT 22). SF increased the pain threshold in WT but not in POKO mice when tested at 8 a.m. (ZT 2). Both the POKO mutation and SF resulted in reduced physical activity and increased anxiety, but there was no additive effect of these two factors. Overall, SF and the POKO mutation differentially regulate mouse behavior. The results suggest that obesity can blunt neurobehavioral responses to SF.

Can sleep apnea cause Alzheimer's disease?

Both obstructive sleep apnea (OSA) and Alzheimer's disease (AD) are increasing health concerns. The objective of this study is to review systematically the effects of OSA on the development of AD. The search was conducted in PubMed and Cochrane CENTRAL, and followed by a manual search of references of published studies. Cross-sectional, cohorts, and randomized clinical trials were reviewed. Besides clinical studies, we also discuss neuroimaging data, experimental animal evidence, and molecular mechanisms. Although a causal relationship between OSA and AD is not yet established, OSA induces neurodegenerative changes as a result of two major contributing processes: sleep fragmentation and intermittent hypoxia. As such, inflammation and cellular stress are sufficient to impair cell-cell interactions, synaptic function, and neural circuitry, leading to a decline of cognitive behavior. Sustained OSA could promote cognitive dysfunction, overlapping with that in AD and other neurodegenerative diseases. Early treatment by positive airway pressure and other current standards of care should have a positive impact to alleviate structural and functional deterioration. With better understanding of the cellular and neurophysiological mechanisms by which OSA contributes to AD, we may identify novel molecular targets for intervention.

Sleep restriction impairs blood-brain barrier function.

The blood-brain barrier (BBB) is a large regulatory and exchange interface between the brain and peripheral circulation. We propose that changes of the BBB contribute to many pathophysiological processes in the brain of subjects with chronic sleep restriction (CSR). To achieve CSR that mimics a common pattern of human sleep loss, we quantified a new procedure of sleep disruption in mice by a week of consecutive sleep recording. We then tested the hypothesis that CSR compromises microvascular function. CSR not only diminished endothelial and inducible nitric oxide synthase, endothelin1, and glucose transporter expression in cerebral microvessels of the BBB, but it also decreased 2-deoxy-glucose uptake by the brain. The expression of several tight junction proteins also was decreased, whereas the level of cyclooxygenase-2 increased. This coincided with an increase of paracellular permeability of the BBB to the small tracers sodium fluorescein and biotin. CSR for 6 d was sufficient to impair BBB structure and function, although the increase of paracellular permeability returned to baseline after 24 h of recovery sleep. This merits attention not only in neuroscience research but also in public health policy and clinical practice.

Efficacy of solution form of ethylenediaminetetraacetic acid on removing smear layer of root canal at different exposure time In Vitro.

This study was aimed to evaluate the effectiveness of solution form of 17% ethylenediaminetetraacetic acid (EDTA) on removing smear layer of root canals at different exposure time periods and to provide scientific basis for EDTA as a choice of root canal irrigation in clinical practice. Twenty-five single-rooted teeth were randomly divided into 5 groups: control group (group A) was given 2.5% NaOCl, and 4 experimental groups were given 2.5% NaOCl and 17% EDTA, including groups B, C, D and E with exposure time of 1, 3, 5 and 7 min, respectively. After preparation of the root canals, the teeth were split along their longitudinal axis, and the root sections were examined under scanning electron microscope for evaluation of smear layer removal and erosion on the surface of the root canal walls. The specimens in group B showed presence of smear layer on the walls of the root canal with no statistical difference from that in group A (P>0.05). In groups C and D, partial removal of smear layer was obtained, and there was no significant difference between the two groups (P>0.05), but there was significant difference in removal of smear layer between group C and group B (P<0.05). Root canal walls in group E specimens showed almost complete removal of smear layer, and the removal of smear layer was significantly different from that in group D (P<0.01). There was no significant change in the structure of the surface of root canal for each sample. It was concluded that combined irrigation with 17% EDTA and 2.5% NaOCl could remove the smear layer with no significant alteration in dentinal structure when the chelating agent was applied for 7 min. At 3 and 5 min of application, partial removal of smear layer was observed and at 1 min negligible removal of smear layer was achieved.

Leukocyte infiltration into spinal cord of EAE mice is attenuated by removal of endothelial leptin signaling.

Leptin, a pleiotropic adipokine, crosses the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) from the periphery and facilitates experimental autoimmune encephalomyelitis (EAE). EAE induces dynamic changes of leptin receptors in enriched brain and spinal cord microvessels, leading to further questions about the potential roles of endothelial leptin signaling in EAE progression. In endothelial leptin receptor specific knockout (ELKO) mice, there were lower EAE behavioral scores in the early phase of the disorder, better preserved BSCB function shown by reduced uptake of sodium fluorescein and leukocyte infiltration into the spinal cord. Flow cytometry showed that the ELKO mutation decreased the number of CD3 and CD45 cells in the spinal cord, although immune cell profiles in peripheral organs were unchanged. Not only were CD4(+) and CD8(+) T lymphocytes reduced, there were also lower numbers of CD11b(+)Gr1(+) granulocytes in the spinal cord of ELKO mice. In enriched microvessels from the spinal cord of the ELKO mice, the decreased expression of mRNAs for a few tight junction proteins was less pronounced in ELKO than WT mice, as was the elevation of mRNA for CCL5, CXCL9, IFN-γ, and TNF-α. Altogether, ELKO mice show reduced inflammation at the level of the BSCB, less leukocyte infiltration, and better preserved tight junction protein expression and BBB function than WT mice after EAE. Although leptin concentrations were high in ELKO mice and microvascular leptin receptors show an initial elevation before inhibition during the course of EAE, removal of leptin signaling helped to reduce disease burden. We conclude that endothelial leptin signaling exacerbates BBB dysfunction to worsen EAE.