Blood-brain barrier permeability to ebiratide and TNF in acute spinal cord injury

β1 integrins play a critical role maintaining vascular integrity in the hypoxic spinal cord, particularly in white matter

Interactions between extracellular matrix (ECM) proteins and β1 integrins play an essential role maintaining vascular integrity in the brain, particularly under vascular remodeling conditions. As blood vessels in the spinal cord are reported to have distinct properties from those in the brain, here we examined the impact of β1 integrin inhibition on spinal cord vascular integrity, both under normoxic conditions, when blood vessels are stable, and during exposure to chronic mild hypoxia (CMH), when extensive vascular remodeling occurs. We found that a function-blocking β1 integrin antibody triggered a small degree of vascular disruption in the spinal cord under normoxic conditions, but under hypoxic conditions, it greatly enhanced (20-fold) vascular disruption, preferentially in spinal cord white matter (WM). This resulted in elevated microglial activation as well as marked loss of myelin integrity and reduced density of oligodendroglial cells. To understand why vascular breakdown is localized to WM, we compared expression levels of major BBB components of WM and grey matter (GM) blood vessels, but this revealed no obvious differences. Interestingly however, hypoxyprobe staining demonstrated that the most severe levels of spinal cord hypoxia induced by CMH occurred in the WM. Analysis of brain tissue revealed a similar preferential vulnerability of WM tracts to show vascular disruption under these conditions. Taken together, these findings demonstrate an essential role for β1 integrins in maintaining vascular integrity in the spinal cord, and unexpectedly, reveal a novel and fundamental difference between WM and GM blood vessels in their dependence on β1 integrin function during hypoxic exposure. Our data support the concept that the preferential WM vulnerability described may be less a result of intrinsic differences in vascular barrier properties between WM and GM, and more a consequence of differences in vascular density and architecture.

A TNF receptor 2 agonist ameliorates neuropathology and improves cognition in an Alzheimer's disease mouse model

Tumor necrosis factor-α (TNF-α) is a pleiotropic, proinflammatory cytokine related to different neurodegenerative diseases, including Alzheimer's disease (AD). Although the linkage between increased TNF-α levels and AD is widely recognized, TNF-α-neutralizing therapies have failed to treat AD. Previous research has associated this with the antithetic functions of the two TNF receptors, TNF receptor 1, associated with inflammation and apoptosis, and TNF receptor 2 (TNFR2), associated with neuroprotection. In our study, we investigated the effects of specifically stimulating TNFR2 with a TNFR2 agonist (NewStar2) in a transgenic Aβ-overexpressing mouse model of AD by administering NewStar2 in two different ways: centrally, via implantation of osmotic pumps, or systemically by intraperitoneal injections. We found that both centrally and systemically administered NewStar2 resulted in a drastic reduction in amyloid β deposition and β-secretase 1 expression levels. Moreover, activation of TNFR2 increased microglial and astrocytic activation and promoted the uptake and degradation of Aβ. Finally, cognitive functions were also improved after NewStar2 treatment. Our results demonstrate that activation of TNFR2 mitigates Aβ-induced cognitive deficits and neuropathology in an AD mouse model and indicates that TNFR2 stimulation might be a potential treatment for AD.

Association between Tumor Necrosis factor-Alpha(TNF-a) polymorphisms and Schizophrenia: an updated meta-analysis

BACKGROUND

Previous studies have explored associations between Tumour Necrosis factor-Alpha (TNF-a) polymorphisms and Schizophrenia. Their results were controversial. We conducted a meta-analysis to clarify the association between TNF-a - 308 G/A(rs1800629), -1031T/C(rs1799964), -863C/A(rs1800630) and -857 C/T (rs1799724) polymorphisms and Schizophrenia.

METHODS

All the studies that investigated the association between TNF-a polymorphisms and Schizophrenia published before 15 October 2020 were included in. The literature were comprehensively searched and identified in 2 English databases and 2 Chinese databases. The odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

For -1031 T/C polymorphism, at the overall analysis, significantly decreased Schizophrenia risk was found in T allele in the allele model (p = 0.006, OR = 0.88) and increased Schizophrenia risk was found in TC + CC genotype in the dominant model (p = 0.005, OR = 1.17). Similarly, the same results were obtained when pooled analyses were included in high-quality studies (allele model: p = 0.005, OR = 0.86; dominant model: p = 0.007, OR = 1.20). In addition, when stratified by ethnicity, the results showed that in allele model, the T allele decreased Schizophrenia risk in East Asian (p = 0.031, OR = 0.90).

CONCLUSION

The association may most likely result from less-credible, rather than from true associations or biological factors on the TNF-a - 1031 T/C polymorphism with Schizophrenia risk.KeypointsFor -1031T/C polymorphism, at the overall analysis, significantly decreased schizophrenia risk was found in T allele in the allele model, and increased schizophrenia risk was found in TC + CC genotype in the dominant model.In allele model, the T allele decreased schizophrenia risk in East Asian when stratified by ethnicity, and in the dominant model, TC + CC genotype increased schizophrenia risk in East Asian.

Delayed-onset white cord syndrome after anterior and posterior cervical decompression surgery for symptomatic ossification of spinal ligaments: illustrative cases

BACKGROUND

White cord syndrome is an extremely rare complication of cervical decompressive surgery, characterized by serious postoperative neurological deficits in the absence of apparent surgical complications. It is named after the characteristic ischemic-edematous intramedullary T2-hyperintense signal on postoperative magnetic resonance imaging and is believed to be caused by ischemic-reperfusion injury. Neurological deficits typically manifest immediately after surgery, and delayed occurrence has been reported only once.

OBSERVATIONS

The authors presented two cases of delayed white cord syndrome after anterior and posterior cervical decompression surgery for symptomatic ossification of the posterior longitudinal ligament and ligamentum flavum, respectively. Neurological deficits manifested on postoperative day 2 (case 1) and day 8 (case 2). The patients’ conditions were managed with high-dose corticosteroids, mean arterial pressure augmentation, and early physical therapy, after which they showed partial neurological recovery at discharge, which improved further by the 3-month follow-up visit.

LESSONS

The authors’ aim was to raise awareness among spine surgeons about this rare but severe complication of cervical decompressive surgery and to emphasize the mainstays of treatment based on current best evidence: high-dose corticosteroids, mean arterial pressure augmentation, and early physical therapy.

White cord syndrome in a pediatric patient: A case report and review

White cord syndrome is a rare condition involving sudden neurological deterioration following a decompressive cervical spinal surgery and characterized by the appearance of hyperintensity on T2-weighted magnetic resonance imaging. We present a report of a pediatric male patient who presented with the condition. This case shows that white cord syndrome can also be present in pediatric patients. We provide a brief review of the literature highlighting the main radiologic findings.

Regulation of the Blood-Brain Barrier by Circadian Rhythms and Sleep

The blood-brain barrier (BBB) is an evolutionarily conserved, structural, and functional separation between circulating blood and the central nervous system (CNS). By controlling permeability into and out of the nervous system, the BBB has a critical role in the precise regulation of neural processes. Here, we review recent studies demonstrating that permeability at the BBB is dynamically controlled by circadian rhythms and sleep. An endogenous circadian rhythm in the BBB controls transporter function, regulating permeability across the BBB. In addition, sleep promotes the clearance of metabolites along the BBB, as well as endocytosis across the BBB. Finally, we highlight the implications of this regulation for diseases, including epilepsy.

Late-onset "white cord syndrome" in an elderly patient after posterior cervical decompression and fusion: a case report

Introduction

In 2013, a rare early complication following cervical decompression the so-called "white cord syndrome" (WCS) was described for first time. This designation was given on the basis of the postoperative appearance of intramedullary hypertense areas in T2-MRI, resulting in devastating neurological damage. To our knowledge, only three cases of WCS have been published; we hereby present the fourth case, but the first one with late-onset presentation of this syndrome.

Case presentation

A 79-year-old male patient with Nurick grade 3 CSM was referred to our institution. He had already had a double-level C4-C6 anterior cervical decompression and fusion (ACDF) 2 years ago in another institution. The patient underwent posterior decompression from C3 to C6 plus C2-C7 lateral mass screw fusion. Within the first 24 h following surgery, he gradually developed C6 incomplete paraplegia (ASIA B). Cervical MRI disclosed a hypertensive signal in T2-weighted sequences at C6-C7 levels and the diagnosis of WCS was suspected. Revision surgery was made 30 h following our first surgery, with wider posterior decompression accompanied by intravenous methylprednisolone. The patient's neurologic status was improved, but the final neurologic outcome was worse (Nurick 4) than the preoperative status and subsequently did not change at all.

Discussion

To the best of our knowledge, this is the first report of a late-onset WCS and the fourth case of WCS per se. Spine surgeons should be aware of this rare but serious complication. We highlight possible risk factors and review the literature on the hypotheses about the pathophysiology of WCS.

Neuroimmune Axes of the Blood-Brain Barriers and Blood-Brain Interfaces: Bases for Physiological Regulation, Disease States, and Pharmacological Interventions

Central nervous system (CNS) barriers predominantly mediate the immune-privileged status of the brain, and are also important regulators of neuroimmune communication. It is increasingly appreciated that communication between the brain and immune system contributes to physiologic processes, adaptive responses, and disease states. In this review, we discuss the highly specialized features of brain barriers that regulate neuroimmune communication in health and disease. In section I, we discuss the concept of immune privilege, provide working definitions of brain barriers, and outline the historical work that contributed to the understanding of CNS barrier functions. In section II, we discuss the unique anatomic, cellular, and molecular characteristics of the vascular blood-brain barrier (BBB), blood-cerebrospinal fluid barrier, and tanycytic barriers that confer their functions as neuroimmune interfaces. In section III, we consider BBB-mediated neuroimmune functions and interactions categorized as five neuroimmune axes: disruption, responses to immune stimuli, uptake and transport of immunoactive substances, immune cell trafficking, and secretions of immunoactive substances. In section IV, we discuss neuroimmune functions of CNS barriers in physiologic and disease states, as well as pharmacological interventions for CNS diseases. Throughout this review, we highlight many recent advances that have contributed to the modern understanding of CNS barriers and their interface functions.

"White Cord Syndrome" of Acute Hemiparesis After Posterior Cervical Decompression and Fusion for Chronic Cervical Stenosis

BACKGROUND

"White cord syndrome" is a very rare condition thought to be due to acute reperfusion of chronically ischemic areas of the spinal cord. Its hallmark is the presence of intramedullary hyperintense signal on T2-weighted magnetic resonance imaging sequences in a patient with unexplained neurologic deficits following spinal cord decompression surgery. The syndrome is rare and has been reported previously in 2 patients following anterior cervical decompression and fusion. We report an additional case of this complication.

CASE DESCRIPTION

A 68-year-old man developed acute left-sided hemiparesis after posterior cervical decompression and fusion for cervical spondylotic myelopathy. The patient improved with high-dose steroid therapy.

CONCLUSIONS

The rare white cord syndrome following either anterior cervical decompression and fusion or posterior cervical decompression and fusion may be due to ischemic-reperfusion injury sustained by chronically compressed parts of the spinal cord. In previous reports, patients have improved following steroid therapy and acute rehabilitation.

Delayed spinal cord infarction following anterior cervical surgical decompression

Anterior cervical discectomy and fusion (ACDF) for cord compression is a safe and effective procedure with good outcomes. However, worsening of myelopathy is the most feared adverse event of the surgery. We report the case of a 36-year-old male patient who presented with an acute non-traumatic C5-6 cervical disc herniation causing incomplete quadriparesis. He underwent an uncomplicated ACDF at C5-6, and after an initial period of improvement, he developed a delayed onset of an anterior cord syndrome on day 3, without any discerning cause. We have reviewed similar cases reported in the literature and believe that our patient's postsurgical course is consistent with a delayed ischaemic/reperfusion injury to the cord following surgical decompression and restoration of blood flow through the anterior spinal artery and we make suggestions for management of such clinical events.

Propitious Therapeutic Modulators to Prevent Blood-Spinal Cord Barrier Disruption in Spinal Cord Injury

The blood-spinal cord barrier (BSCB) is a specialized protective barrier that regulates the movement of molecules between blood vessels and the spinal cord parenchyma. Analogous to the blood-brain barrier (BBB), the BSCB plays a crucial role in maintaining the homeostasis and internal environmental stability of the central nervous system (CNS). After spinal cord injury (SCI), BSCB disruption leads to inflammatory cell invasion such as neutrophils and macrophages, contributing to permanent neurological disability. In this review, we focus on the major proteins mediating the BSCB disruption or BSCB repair after SCI. This review is composed of three parts. Section 1. SCI and the BSCB of the review describes critical events involved in the pathophysiology of SCI and their correlation with BSCB integrity/disruption. Section 2. Major proteins involved in BSCB disruption in SCI focuses on the actions of matrix metalloproteinases (MMPs), tumor necrosis factor alpha (TNF-α), heme oxygenase-1 (HO-1), angiopoietins (Angs), bradykinin, nitric oxide (NO), and endothelins (ETs) in BSCB disruption and repair. Section 3. Therapeutic approaches discusses the major therapeutic compounds utilized to date for the prevention of BSCB disruption in animal model of SCI through modulation of several proteins.

Sleep fragmentation and sepsis differentially impact blood-brain barrier integrity and transport of tumor necrosis factor-α in aging

The factors by which aging predisposes to critical illness are varied, complex, and not well understood. Sepsis is considered a quintessential disease of old age because the incidence and mortality of severe sepsis increases in old and the oldest old individuals. Aging is associated with dramatic changes in sleep quality and quantity and sleep increasingly becomes fragmented with age. In healthy adults, sleep disruption induces inflammation. Multiple aspects of aging and of sleep dysregulation interact via neuroimmune mechanisms. Tumor necrosis factor-α (TNF), a cytokine involved in sleep regulation and neuroimmune processes, exerts some of its effects on the CNS by crossing the blood-brain barrier (BBB). In this study we examined the impact of sepsis, sleep fragmentation, and aging on BBB disruption and TNF transport into brain. We used the cecal ligation and puncture (CLP) model of sepsis in young and aged mice that were either undisturbed or had their sleep disrupted. There was a dichotomous effect of sepsis and sleep disruption with age: sepsis disrupted the BBB and increased TNF transport in young mice but not in aged mice, whereas sleep fragmentation disrupted the BBB and increased TNF transport in aged mice, but not in young mice. Combining sleep fragmentation and CLP did not produce a greater effect on either of these BBB parameters than did either of these manipulations alone. These results suggest that the mechanisms by which sleep fragmentation and sepsis alter BBB functions are fundamentally different from one another and that a major change in the organism's responses to those insults occurs with aging.

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.

Interleukin-1β transfer across the blood-brain barrier in the ovine fetus

Pro-inflammatory cytokines contribute to hypoxic-ischemic brain injury. Blood-brain barrier (BBB) dysfunction represents an important component of hypoxic-ischemic brain injury in the fetus. Hypoxic-ischemic injury could accentuate systemic cytokine transfer across the fetal BBB. There has been considerable conjecture suggesting that systemic cytokines could cross the BBB during the perinatal period. Nonetheless, evidence to support this contention is sparse. We hypothesized that ischemia-reperfusion increases the transfer of systemic interleukin-1β (IL-1β) across the BBB in the fetus. Ovine fetuses at 127 days of gestation were studied 4 hours after 30 minutes of bilateral carotid artery occlusion and compared with a nonischemic group. Recombinant ovine IL-1β protein was expressed from an IL-1β pGEX-2 T vector in E. coli BL-21 cells and purified. The BBB function was quantified in 12 brain regions using a blood-to-brain transfer constant with intravenous (125)I-radiolabeled IL-1β ((125)I-IL-1β). Interleukin-1β crossed the intact BBB in nonischemic fetuses. Blood-to-brain transport of (125)I-IL-1β was higher (P<0.05) across brain regions in fetuses exposed to ischemia-reperfusion than nonischemic fetuses. We conclude that systemic IL-1β crosses the intact fetal BBB, and that ischemia-reperfusion increases transfer of this cytokine across the fetal BBB. Therefore, altered BBB function after hypoxia-ischemia facilitates entry of systemic cytokines into the brain of the fetus.

Age- and location-related changes in microglial function

Inflammation in the central nervous system (CNS) is primarily regulated by microglia. No longer considered a homogenous population, microglia display a high degree of heterogeneity, immunological diversity and regional variability in function. Given their low rate of self-renewal, the microenvironment in which microglia reside may play an important role in microglial senescence. This study examines age-related changes in microglia in the brain and spinal cord. Using ex-vivo flow cytometry analyses, functional assays were performed to assess changes in microglial morphology, oxidative stress, cytokine production, and phagocytic activity with age in both the brain and spinal cord. The regional CNS environment had a significant effect on microglial activity with age. Blood-CNS barrier permeability was greater in the aging spinal cord compared with aging brain; this was associated with increased tissue cytokine levels. Aged microglia had deficits in phagocytosis at baseline and after stimulus-induced activation. The identification of age-specific, high scatter microglia together with the use of ex-vivo functional analyses provides the first functional characterization of senescent microglia. Age and regional-specificity of CNS disease should be taken into consideration when developing immune-modulatory treatments.

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.

Leukocyte infiltration across the blood-spinal cord barrier is modulated by sleep fragmentation in mice with experimental autoimmune encephalomyelitis

Background

We have recently shown that mice with experimental autoimmune encephalomyelitis (EAE) have increased sleep fragmentation (SF) and reduced sleep efficiency, and that the extent of SF correlates with the severity of disease. It is not yet clear whether and how sleep promotes recovery from autoimmune attacks. We hypothesized that SF promotes leukocyte infiltration across the blood-spinal cord barrier, impairs immune regulation, and thus worsens EAE.

Methods

Three groups of C57 mice were studied: Resting EAE; SF EAE with the mice subjected to the SF maneuver 12 h /day during zeitgeber time (ZT) 0–12 h; and naïve controls with neither EAE nor SF. Besides monitoring of the incidence and severity of EAE, the immune profiles of leukocytes in the spinal cord as well as those in the spleen were determined.

Results

When analyzed 16 days after EAE induction, at which time the SF was terminated, the SF group had a greater number of CD4⁺ T cells and a higher percent of CD4⁺ cells among all leukocytes in the spinal cord than the resting EAE group. When allowed to recover to 28 days after EAE induction, the SF mice had lower EAE scores than the resting EAE group. EAE induced splenomegaly and an increase of Gr1⁺CD11b⁺ myeloid-derived suppressor cells in the splenocytes. However, SF treatment had no additional effect on either peripheral splenocytes or granulocytes that reached the spinal cord.

Conclusion

The SF maneuver facilitated the migration of encephalopathic lymphocytes into the spinal cord. Paradoxically, these mice had a better EAE score after cessation of SF compared with mice without SF.

Sepsis-induced morbidity in mice: effects on body temperature, body weight, cage activity, social behavior and cytokines in brain

Infection negatively impacts mental health, as evidenced by the lethargy, malaise, and cognitive deficits experienced during illness. These changes in central nervous system processes, collectively termed sickness behavior, have been shown in animal models to be mediated primarily by the actions of cytokines in brain. Most studies of sickness behavior to date have used bolus injection of bacterial lipopolysaccharide (LPS) or selective administration of the proinflammatory cytokines interleukin-1β (IL-1β) or IL-6 as the immune challenge. Such models, although useful for determining mechanisms responsible for acute changes in physiology and behavior, do not adequately represent the more complex effects on central nervous system (CNS) processes of a true infection with replicating pathogens. In the present study, we used the cecal ligation and puncture (CLP) model to quantify sepsis-induced alterations in several facets of physiology and behavior of mice. We determined the impact of sepsis on cage activity, body temperature, food and water consumption and body weights of mice. Because cytokines are critical mediators of changes in behavior and temperature regulation during immune challenge, we also quantified sepsis-induced alterations in cytokine mRNA and protein in brain during the acute period of sepsis onset. We now report that cage activity and temperature regulation in mice that survive are altered for up to 23 days after sepsis induction. Food and water consumption are transiently reduced, and body weight is lost during sepsis. Furthermore, sepsis decreases social interactions for 24-48 h. Finally, mRNA and protein for IL-1β, IL-6, and tumor necrosis factor-α (TNFα) are upregulated in the hypothalamus, hippocampus, and brain stem during sepsis onset, from 6h to 72 h post sepsis induction. Collectively, these data indicate that sepsis not only acutely alters physiology, behavior and cytokine profiles in brain, but that some brain functions are impaired for long periods in animals that survive.

"White cord syndrome" of acute tetraplegia after anterior cervical decompression and fusion for chronic spinal cord compression: a case report

Paralysis is the most feared postoperative complication of ACDF and occurs most often due to an epidural hematoma. In the absence of a clear etiology, inadequate decompression or vascular insult such as ischemia/reperfusion injury are the usual suspects. Herewith we report a case of complete loss of somatosensory evoked potentials (SSEPs) during elective ACDF at C4-5 and C5-6 followed by postoperative C6 incomplete tetraplegia without any discernible technical cause. A postoperative MRI demonstrated a large area of high signal changes on T2-weighted MRI intrinsic to the cord "white cord syndrome" but no residual compression. This was considered consistent with spinal cord gliosis with possible acute edema. The acute decompression of the herniated disc resulted in cord expansion and rush-in reperfusion. We postulate that this may have led to disruption in the blood brain barrier (BBB) and triggered a cascade of reperfusion injuries resulting in acute neurologic dysfunction. At 16 months postoperatively our patient is recovering slowly and is now a Nurick Grade 4.

Cytokine signaling modulates blood-brain barrier function

The blood-brain barrier (BBB) provides a vast interface for cytokines to affect CNS function. The BBB is a target for therapeutic intervention. It is essential, therefore, to understand how cytokines interact with each other at the level of the BBB and how secondary signals modulate CNS functions beyond the BBB. The interactions between cytokines and lipids, however, have not been fully addressed at the level of the BBB. Here, we summarize current understanding of the localization of cytokine receptors and transporters in specific membrane microdomains, particularly lipid rafts, on the luminal (apical) surface of the microvascular endothelial cells composing the BBB. We then illustrate the clinical context of cytokine effects on the BBB by neuroendocrine regulation and amplification of inflammatory signals. Two unusual aspects discussed are signaling crosstalk by different classes of cytokines and genetic regulation of drug efflux transporters. We also introduce a novel area of focus on how cytokines may act through nuclear hormone receptors to modulate efflux transporters and other targets. A specific example discussed is the ATP-binding cassette transporter-1 (ABCA-1) that regulates lipid metabolism. Overall, cytokine signaling at the level of the BBB is a crucial feature of the dynamic regulation that can rapidly change BBB function and affect brain health and disease.

Blood-spinal cord barrier pericyte reductions contribute to increased capillary permeability

The blood-spinal cord barrier (BSCB) regulates molecular exchange between blood and spinal cord. Pericytes are presumed to be important cellular constituents of the BSCB. However, the regional abundance and vascular functions of spinal cord pericytes have yet to be determined. Utilizing wild-type mice, we show that spinal cord pericyte capillary coverage and number compared with the brain regions are reduced most prominently in the anterior horn. Regional pericyte variations are highly correlated with: (1) increased capillary permeability to 350 Da, 40,000 Da, and 150,000 Da, but not 2,000,000 Da fluorescent vascular tracers in cervical, thoracic, and lumbar regions and (2) diminished endothelial zonula occludens-1 (ZO-1) and occludin tight junction protein expression. Pericyte-deficient mutations (Pdgfrβ(F7/F7) mice) resulted in additional pericyte reductions in spinal cord capillaries leading to overt BSCB disruption to serum proteins, accumulation in motor neurons of cyotoxic thrombin and fibrin and motor neuron loss. Barrier disruption in perciyte-deficient mice coincided with further reductions in ZO-1 and occludin. These data suggest that pericytes contribute to proper function of the BSCB at the capillary level. Regional reductions in spinal cord pericytes may provide a cellular basis for heightened spinal cord barrier capillary permeability and motor neuron loss.

Cytokine and chemokine responses in serum and brain after single and repeated injections of lipopolysaccharide: multiplex quantification with path analysis

Administration of the proinflammatory molecule lipopolysaccharide (LPS) alters transport rates for many peptides across the blood-brain barrier (BBB). We and others have previously shown that effects of LPS on BBB transport are highly dependent on the injection paradigm used, and timing of the study. Cytokine expression in both brain and serum compartments influences the BBB response to an inflammatory stimulus, and mediates changes in BBB transport. Here, we used multianalyte technology to simultaneously determine the responses of 13 cytokines and chemokines (G-CSF, GM-CSF, IL-1α, IL-1β, IL-6, IL-10, IL-13, IP-10, KC, MCP-1, MIP-1α, RANTES, and TNF-α) in brain and blood to single and repeated injections of LPS and path analysis to determine the major relations among these analytes. Major findings are: (1) in comparison to measurements taken from a time course after a single injection of LPS, the three injection regimen of LPS produced significantly higher levels in brain for G-CSF, IL-1α, IL-6, MCP-1, MIP-1α, and TNF and in serum for G-CSF, IL-6, and GM-CSF and (2) path analysis distinguished direct from indirect correlations between analyte pairs, with MCP-1, IL-6, G-CSF, and KC mediating relations among these cytokines both within and between serum and brain compartments. These results suggest that potentiation of cytokine levels in brain and serum compartments could play important roles in the regulation of BBB transport, and that our novel application of an established statistical method can be used to assess direct correlations within multiplexed datasets.

The role of cerebral vascular NFkappaB in LPS-induced inflammation: differential regulation of efflux transporter and transporting cytokine receptors

BACKGROUND/AIMS

The transcription factor NFkappaB is a major mediator of lipopolysaccharide (LPS) signaling. We determined the role of NFkappaB activation in regulatory changes of the P-glycoprotein (Pgp) drug efflux transporter at the blood-brain barrier (BBB) and proinflammatory cytokine receptors.

METHODS

We treated NFkappaB knockout and wildtype mice with LPS or vehicle, obtained enriched cerebral microvessels, and determined target mRNA by qPCR for MDR1a/b, IL15Ralpha, IL2 Ralpha, IL2Rgamma, LIFR, gp130, and TNFR1/2, and protein expression by western blotting for P-gp, IL15Ralpha, IL2Rgamma, LIFR, and gp130.

RESULTS

The effects of LPS on the transporters and cytokine receptors showed differences between wildtype and NFkappaB knockout mice, and between mRNA and protein changes. NFkappaB not only mediated the LPS-induced increase of MDR1b, IL2Rgamma, and TNFR2 mRNA in the wildtype mice, but it showed opposite effects by elevating IL15Ralpha and TNFR1 mRNA and decreasing IL2Ralpha in the knockout mice. Although basal vinblastine uptake was unchanged in the NFkappaB knockout mice, LPS induced an increase of the uptake (depressed efflux transport) greater than that seen in the wildtype mice, indicating that NFkappaB helps to maintain Pgp efflux transporter function.

CONCLUSION

The results show differential involvement of NFkappaB signaling in response to LPS at the BBB.

Cerebral microvascular IL15 is a novel mediator of TNF action

The blood-brain barrier is a gatekeeper and modulatory interface for the CNS. Cerebral endothelial cells are the major component of the blood-brain barrier, and they modify inflammatory signals from the circulation to the CNS by production and secretion of secondary substances. The inflammatory mediators induced by tumor necrosis factor alpha (TNF) were determined by microarray analysis of RBE4 cerebral endothelial cells, at 0, 6, 12, or 24 h after TNF treatment. Interleukin (IL)-15 and its receptors were among the most robustly up-regulated genes. This was confirmed by real-time RT-PCR and western blotting. The three subunits of the IL15 receptor complex (IL15Ralpha, IL2Rbeta, and IL2Rgamma) showed differential regulation by TNF in their time course and amplitude of increased expression. Consistent with increased expression of the specific high affinity receptor IL15Ralpha, TNF increased cellular uptake of (125)I-IL15 and enhanced the fluorescent intensity of Alexa568-IL15 in RBE4 cells. TNF treatment in mice also increased the level of expression of IL15 receptors in enriched cerebral microvessels. We conclude that the cerebral microvascular IL15 system is a novel inflammatory mediator that transduces the actions of TNF.

Cytokine transport across the injured blood-spinal cord barrier

Spinal cord injury (SCI) induces dynamic changes of the blood-spinal cord barrier and even the more distant blood-brain barrier. Besides an immediate increase of paracellular permeability resulting from the direct impact of the injury, the transport systems for selective cytokines undergo regulatory changes. Since many of the transported molecules play essential roles in neuroregeneration, we propose that this altered peripheral tissue / CNS interaction benefits remodeling of the spinal cord and functional recovery after SCI. This review examines the transport of cytokines and neurotrophic factors into the spinal cord, emphasizing the upregulation of two cytokines--tumor necrosis factor alpha (TNF) and leukemia inhibitory factor (LIF)--during the course of SCI. The increased transport of TNF and LIF after SCI remains saturable and does not coincide with generalized BBB disruption, highlighting a pivotal regulatory role for the blood-spinal cord barrier.

Permeation of blood-borne IL15 across the blood-brain barrier and the effect of LPS

Interleukin15 (IL 15) is a proinflammatory cytokine with elevated concentrations in autoimmune diseases involving the periphery (e.g. rheumatoid arthritis) and CNS (e.g. multiple sclerosis). Its interactions with the blood-brain barrier (BBB) were studied in normal and lipopolysaccharide (LPS)-treated mice. (125)I-IL15 remained intact for at least 10 min after i.v. injection and reached CNS parenchyma with regional differences between brain and spinal cord. Both in vivo and in situ brain perfusion of (125)I-IL15 showed that its permeation of the BBB was non-saturable. LPS induced a significant increase of IL15 uptake by the brain and spinal cord, partly related to a higher general permeability of the BBB. The results suggest that the BBB is an interface for blood-borne IL15 to interact with the CNS in the basal state and during inflammation.

Elevated serum inflammatory markers in post-poliomyelitis syndrome

OBJECTIVES

To determine (i) whether serum inflammatory markers TNFalpha, IL-1beta. IL-6, and leptin are increased in post-poliomyelitis syndrome (PPS) compared to healthy controls; and (ii) whether an association exists between elevated inflammatory markers and clinical parameters in PPS. The cause of PPS is unknown, but abnormal inflammatory responses have been implicated in several small studies.

METHODS

Serum inflammatory markers were measured (by Luminex) in 51 PPS patients and 26 normal controls. Clinical parameters assessed included disease duration, muscle strength (Medical Research Council sumscore), fatigue (Fatigue Severity Scale and Multidimensional Fatigue Inventory), and pain (visual analog scale scores).

RESULTS

In PPS, TNFalpha levels, as well as IL-6 and leptin were significantly increased compared to controls (Wilcoxon rank-sum test, p=0.03 for TNFalpha, p=0.03 for IL-6, p=0.01 for leptin). The elevated TNFalpha levels in PPS were associated with increased pain due to illness (Spearman correlation coefficient r=0.36, 95% C.I. 0.09 to 0.57) and specifically, with muscle pain (r=0.38, 95% C.I. 0.11 to 0.59). There were no correlations between inflammatory markers in PPS and joint pain, muscle strength, fatigue, or disease duration.

CONCLUSIONS

Serum TNFalpha, IL-6 and leptin levels are abnormally increased in PPS patients. Elevated TNFalpha levels appear to be specifically associated with increased muscle pain.

Increased leptin permeation across the blood-brain barrier after chronic alcohol ingestion

Leptin, a polypeptide mainly produced in the periphery, crosses the blood-brain barrier (BBB) by receptor-mediated transport to exert multiple central nervous system actions including decreased food intake. The reciprocal interactions between leptin transport and alcohol drinking are not clear. In this study, we tested whether alcohol increases leptin entry into brain and, if this occurs, whether it is a consequence of a generalized increase in the permeability of the BBB. BBB permeability to albumin, the increased permeation of which indicates BBB disruption, as well as to leptin was measured after alcohol ingestion. CD1 and B6 mice ingested a 5% liquid alcohol diet or its isocaloric control for 2 weeks. Alcohol ingestion resulted in increased blood-alcohol levels, decreased blood-leptin concentrations, and increased permeation of radioactively labeled leptin across the BBB as shown by in situ perfusion. Although the increased influx of the vascular marker albumin into brain showed partial disruption of the BBB, the influx of (125)I-leptin still could be suppressed by excess unlabeled leptin, indicating persistence of its saturable transport system. When given a choice of either alcohol or control diet, even the alcohol-preferring B6 mice showed a significantly greater preference for the control liquid diet, and there was no evidence of BBB disruption or alterated leptin transport. Furthermore, acute alcohol intoxication induced by intraperitoneal injection of 20% alcohol did not result in BBB disruption or increased leptin permeation 4 h later. Thus, partial disruption of the BBB and increased permeation of leptin in both CD1 and B6 mice were only induced by chronic alcohol ingestion. The results showing increased leptin permeation across the BBB lead to the speculation that leptin may serve as a homeostatic feeding signal in these mice.

TNF reduces LIF endocytosis despite increasing NFkappaB-mediated gp130 expression

To examine how the proinflammatory cytokine tumor necrosis factor alpha (TNF) modulates the response of cerebral microvessels to other cytokines, we used rat cerebral microvessel endothelial RBE4 cells to simulate the in vitro blood-brain barrier (BBB). The gp130 receptor, which is shared by the interleukin (IL)-6 family of cytokines, showed specific upregulation by TNF. TNF treatment (5 ng/ml for 30 min to 24 h) increased gp130 at both the levels of transcription and protein expression. The stability of gp130 protein was mediated by NFkappaB activity, as the inhibitors quinazoline and MG132 not only blocked the increase induced by 6 h of TNF treatment, but also reduced its basal level of expression. By contrast, the lysosomal inhibitor chloroquine and the extracellular regulated kinase inhibitor U0126 showed no effect. Despite the increase of gp130, TNF caused a significant reduction in the cell binding and endocytosis of leukemia inhibitory factor (LIF), another proinflammatory cytokine that binds to the gp130 co-receptor and its unique gp190 receptor. This is consistent with our previous findings that TNF reduces gp190 expression and Stat3 activation. Thus, TNF stimulation results in decreased responsiveness of RBE4 cells to LIF, indicating complex regulatory interactions of cytokines at the BBB.

TNF is a key mediator of septic encephalopathy acting through its receptor, TNF receptor-1

In this study, we demonstrate that mice deficient in TNFR1 (TNFR1(-/-)) were resistant to LPS-induced encephalopathy. Systemic administration of lipopolysaccharide (LPS) induces a widespread inflammatory response similar to that observed in sepsis. Following LPS administration TNFR1(-/-) mice had less caspase-dependent apoptosis in brain cells and fewer neutrophils infiltrating the brain (p<0.039), compared to control C57Bl6 (TNFR1(+/+)) mice. TNFR1-dependent increase in aquaporin (AQP)-4 mRNA and protein expression was observed with a concomitant increase in water content, in brain (18% increase in C57Bl6 mice treated with LPS versus those treated with saline), similar to cerebral edema observed in sepsis. Furthermore, absence of TNFR1 partially but significantly reduced the activation of astrocytes, as shown by immunofluorescence and markedly inhibited iNOS mRNA expression (p<0.01). Septic encephalopathy is a devastating complication of sepsis. Although, considerable work has been done to identify the mechanism causing the pathological alterations in this setting, the culprit still remains an enigma. Our results demonstrate for the first time that endotoxemia leads to inflammation in brain, with alteration in blood-brain barrier, up-regulation of AQP4 and associated edema, neutrophil infiltration, astrocytosis, as well as apoptotic cellular death, all of which appear to be mediated by TNF-alpha signaling through TNFR1.

Tumor necrosis factor and stroke: role of the blood-brain barrier

The progression and outcome of stroke is affected by the intricate relationship between the blood-brain barrier (BBB) and tumor necrosis factor alpha (TNFalpha). TNFalpha crosses the intact BBB by a receptor-mediated transport system that is upregulated by CNS trauma and inflammation. In this review, we discuss intracellular trafficking and transcytosis of TNFalpha, regulation of TNFalpha transport after stroke, and the effects of TNFalpha on stroke preconditioning. TNFalpha can activate cytoprotective pathways by pretreatment or persistent exposure to low doses. This explains the paradoxical observation that transport of this proinflammatory cytokine improves the survival and function of hypoxic cells and of mice with stroke. The dual effects of TNFalpha may be related to differential regulation of TNFalpha trafficking downstream to TNFR1 and TNFR2 receptors. As we better understand how peripheral TNFalpha affects its own transport and modulates neuroregeneration, we may be in a better position to pharmacologically manipulate its regulatory transport system to treat stroke.

Adipokines and the blood-brain barrier

Just as the blood-brain barrier (BBB) is not a static barrier, the adipocytes are not inert storage depots. Adipokines are peptides or polypeptides produced by white adipose tissue; they play important roles in normal physiology as well as in the metabolic syndrome. Adipokines secreted into the circulation can interact with the BBB and exert potent CNS effects. The specific transport systems for two important adipokines, leptin and tumor necrosis factor alpha, have been characterized during the past decade. By contrast, transforming growth factor beta-1 and adiponectin do not show specific permeation across the BBB, but modulate endothelial functions. Still others, like interleukin-6, may reach the brain but are rapidly degraded. This review summarizes current knowledge and recent findings of the rapidly growing family of adipokines and their interactions with the BBB.

Immediate Damage to The Blood-Spinal Cord Barrier Due to Mechanical Trauma

Primary damage to the blood-spinal cord barrier (BSCB) is a nearly universal consequence of spinal cord injury that contributes significantly to the overall pathology, including the introduction of reactive species that induce cytotoxicity as well as secondary insults on the BSCB itself. We have characterized quantitatively the extent and severity of primary, physical disruption of the BSCB in adult rats 5 min after graded trauma induced with the Impactor weight-drop model of spinal cord contusion. Animals were injured by dropping a 10-g mass 12.5, 25, or 50 mm (n(level) = 8) on to the exposed mid-thoracic spinal cord. The volume of extravasation of three markers of distinct size--fluorescently labeled hydrazide ( approximately 730 Da), fluorescently labeled bovine serum albumin ( approximately 70 kDa), and immunohistochemically labeled red blood cells ( approximately 5 microm in diameter)--were quantified in both the gray and white matter. The results indicate that spinal cord trauma causes immediate, non-specific vascular changes that are well-predicted by mechanical parameters. Extravasation volume increased significantly with increasing drop height and decreasing marker size. Extravasation volumes for all three markers were greater in gray matter than in white matter, and were better correlated to the rate of spinal cord compression than to the depth of spinal cord compression, which suggests that tissue-level strain rate effects contribute to primary spinal cord microvasculature pathology. The relationship between the response of the spinal cord and the injury pattern points towards opportunities to control the distribution and extent of injury patterns in animal models of spinal cord injury through a precise understanding of model and tissue biomechanics, as well as potential improvements in means of preventing spinal cord injury.

TNFalpha trafficking in cerebral vascular endothelial cells

Using small tags, we tracked the pathway of tumor necrosis factor (TNF)alpha across cerebral vascular endothelial cells. In cerebral microvessel derived RBE4 cells, (125)I-TNFalpha had rapid endocytosis within the first 20 min and showed substantial exocytosis in the intact form. Biotinylated TNFalpha was detected at different time points after endocytosis by streptavidin-Quantum dots which showed its time-dependent colocalization with intracellular organelles. In mice, electron microscopic autoradiography after intravenous injection of (125)I-TNFalpha showed its transcytosis, as signals emerged on the abluminal side of the endothelial cells and reached brain parenchyma. The vesicular trafficking of TNFalpha reflects the immunomodulatory potential of peripheral cytokines for the CNS.

Recombinant human TNFalpha induces concentration-dependent and reversible alterations in the electrophysiological properties of axons in mammalian spinal cord

Increased expression of the proinflammatory cytokine tumor necrosis factor-alpha (TNFalpha) and its soluble receptors is evident within the central nervous system (CNS) following traumatic brain injury and spinal cord injury. TNFalpha is integral to the acute inflammatory cascade that follows neurotrauma and has been shown to have both beneficial and detrimental properties. We examined the effects of varying concentrations (1-5000 ng/mL) of recombinant human TNFalpha (rhTNFalpha) on select electrophysiological properties of excised guinea pig spinal cord tissue. Pulsed electrical stimuli (0.33 Hz) were delivered to strips of isolated ventral white matter in a double sucrose gap chamber. Recordings were made of the compound action potential (CAP) and membrane potential before, during, and after bathing the tissue with rhTNFalpha for 30 min. Increasing concentrations of rhTNFalpha yielded progressively greater reductions in amplitude of the CAP that were temporally associated with depolarization of the resting compound membrane potential. These effects were largely reversed on washout of rhTNFalpha and were not present when heat-denatured rhTNFalpha was introduced. The results provide evidence that elevated concentrations of TNFalpha induce reversible depolarization of the compound membrane potential and reduction in CAP amplitude, sometimes to the point of extinction of the CAP, suggestive of impaired axonal conduction. These observations point to a new mechanism of immune-mediated central conduction deficit. Cytokine-induced alterations in membrane properties and axonal conduction may contribute to neurological deficits following CNS injury by compounding trauma-induced myelinopathy and axonopathy.

Gamma glutamyl transpeptidase is a dynamic indicator of endothelial response to stroke

Gamma glutamyl transpeptidase (gammaGT) is enriched at the apical surface of the cerebral capillaries that constitute the blood-brain barrier (BBB). This study tested the effects of hypoxia and inflammation on gammaGT activity in mice after stroke induced by transient cerebral artery occlusion (tMCAO) and in cultured cerebral microvessel endothelial cells. In microvessel-enriched preparations from mice after tMCAO, gammaGT activity was higher than in the sham controls in both ipsilateral and contralateral hemispheres from 12 h to 5 days after stroke, but lower at later time points (10-15 days). To identify the roles of different cytotoxic and stimulatory signals in this event, we further studied the dynamic changes of gammaGT activity in rat brain endothelial (RBE4) cells. Tumor necrosis factor alpha and lipopolyssachride significantly increased gammaGT activity in a time-dependent manner, an effect not seen after re-oxygenation. Such endothelial activation correlated with reduced total cellular ATP production. Thus, hypoxia and inflammatory stimulation appeared to have opposite effects on endothelial function. With the co-existence of inflammation and hypoxia in the brain after ischemic stroke, dynamic changes of gammaGT activity reflect evolving changes of endothelial function.

Streptozotocin-induced diabetes progressively increases blood-brain barrier permeability in specific brain regions in rats

This study investigated the effects of streptozotocin-induced diabetes on the functional integrity of the blood-brain barrier in the rat at 7, 28, 56, and 90 days, using vascular space markers ranging in size from 342 to 65,000 Da. We also examined the effect of insulin treatment of diabetes on the formation and progression of cerebral microvascular damage and determined whether observed functional changes occurred globally throughout the brain or within specific brain regions. Results demonstrate that streptozotocin-induced diabetes produced a progressive increase in blood-brain barrier permeability to small molecules from 28 to 90 days and these changes in blood-brain barrier permeability were region specific, with the midbrain most susceptible to diabetes-induced microvascular damage. In addition, results showed that insulin treatment of diabetes attenuated blood-brain barrier disruption, especially during the first few weeks; however, as diabetes progressed, it was evident that microvascular damage occurred even when hyperglycemia was controlled. Overall, results of this study suggest that diabetes-induced perturbations to cerebral microvessels may disrupt homeostasis and contribute to long-term cognitive and functional deficits of the central nervous system.

Stroke upregulates TNFalpha transport across the blood-brain barrier

To determine how cytokine transport systems at the blood-brain barrier (BBB) participate in stroke progression and recovery, we generated a mouse model of transient middle cerebral artery occlusion (tMCAO). After 1 h of occlusion followed by nearly complete reperfusion, the neurological deficits lasted more than a week as shown by several behavioral tests. Despite the prominent infarct area indicated by reduced cerebral perfusion and confirmed by vital staining, the volume of distribution of (131)I-albumin in various brain regions was not significantly altered over time (12 h to 14 days). In sharp contrast, the blood-to-brain permeation of 125I-TNFalpha was significantly increased 5 days after tMCAO. Furthermore, excess unlabeled TNFalpha abolished this enhanced 125I-TNFalpha uptake. Thus, not only did the known saturable transport system for TNFalpha persist, but it functioned at a higher capacity in tMCAO mice. Upregulation of TNFR1 and TNFR2 partially explains the increased transport, as mRNA for both receptors showed the most pronounced increase (15-fold and 30-fold, respectively) in the ischemic hemisphere 5-7 days after tMCAO. However, even in the hemisphere contralateral to the ischemia induced by stroke, there was increased TNFalpha transport. The bilateral increase in 125I-TNFalpha entry from blood to brain suggests that TNFalpha trafficking in cerebral endothelial cells is influenced by global mediators in addition to the transporting receptors. Given the known multiple modulatory effects of TNFalpha after stroke, the results indicate that the TNFalpha transport system at the BBB facilitates neuroplasticity and plays an important role in stroke recovery.

Passage of erythropoietic agents across the blood-brain barrier: a comparison of human and murine erythropoietin and the analog darbepoetin alfa

Studies have suggested that erythropoietin (EPO) may be used to treat stroke in both animals and humans. It is thought to exert its effects directly on the brain and studies with therapeutic doses have shown that it can cross the blood-brain barrier. Here, we compared in a blinded fashion the ability of three erythropoietic agents (murine erythropoietin, human erythropoietin, and darbepoetin alfa, an analog of human erythropoietin in clinical use) to cross the blood-brain barrier of the mouse. High-performance liquid chromatography (HPLC) results showed that all three erythropoietic agents were enzymatically resistant in brain and blood. The unidirectional blood-to-brain influx rates (Ki) as measured by multiple-time regression analysis showed that all the erythropoietic agents crossed the blood-brain barrier at about the same rate as albumin, suggesting that they cross the blood-brain barrier by way of the extracellular pathways. No saturable component to influx was found, but indirect evidence suggested a brain-to-blood efflux system. The percent of the intravenously injected dose taken up per gram of brain (%Inj/g) ranged from 0.05 to 0.1 %Inj/g among the three erythropoietic agents and peaked about 3 h after IV injection. For other substances, this range of %Inj/g is known to produce direct effects on brain function. We conclude that erythropoietic agents cross the blood-brain barrier by way of the extracellular pathways in amounts that are likely sufficient to explain their neuroprotective effects.

Activation of complement pathways after contusion-induced spinal cord injury

Previous studies have shown that a cellular inflammatory response is initiated, and inflammatory cytokines are synthesized, following experimental spinal cord injury (SCI). In the present study, we tested the hypothesis that the complement cascade, a major component of both the innate and adaptive immune response, is also activated following experimental SCI. We investigated the pathways, cellular localization, timecourse, and degree of complement activation in rat spinal cord following acute contusion-induced SCI using the New York University (NYU) weight drop impactor. Mild and severe injuries (12.5 and 50 mm drop heights) at 1, 7, and 42 days post injury time points were evaluated. Classical (C1q and C4), alternative (Factor B) and terminal (C5b-9) complement pathways were strongly activated within 1 day of SCI. Complement protein immunoreactivity was predominantly found in cell types vulnerable to degeneration, neurons and oligodendrocytes, and was not generally observed in inflammatory or astroglial cells. Surprisingly, immunoreactivity for complement proteins was also evident 6 weeks after injury, and complement activation was observed as far as 20 mm rostral to the site of injury. Axonal staining by C1q and Factor B was also observed, suggesting a potential role for the complement cascade in demyelination or axonal degeneration. These data support the hypothesis that complement activation plays a role in SCI.

Autonomic neural regulation of immunity

The 'cytokine theory of disease' states that an overproduction of cytokines can cause the clinical manifestations of disease. Much effort has been expended to determine how cytokines are regulated in normal health. Transcriptional, translational and other molecular control mechanisms protect the host from excessive cytokine production. A recent discovery revealed an unexpected pathway that inhibits macrophage cytokine production. The inflammatory reflex is a physiological pathway in which the autonomic nervous system detects the presence of inflammatory stimuli and modulates cytokine production. Afferent signals to the brain are transmitted via the vagus nerve, which activates a reflex response that culminates in efferent vagus nerve signalling. Termed the 'cholinergic anti-inflammatory pathway', efferent activity in the vagus nerve releases acetylcholine (ACh) in the vicinity of macrophages within the reticuloendothelial system. ACh can interact specifically with macrophage alpha7 subunits of nicotinic ACh receptors, leading to cellular deactivation and inhibition of cytokine release. This 'hard-wired' connection between the nervous and immune systems can be harnessed therapeutically in animal models of inflammatory disease, via direct electrical stimulation of the vagus nerve, or through the use of cholinergic agonists that specifically activate the macrophage alpha7 subunit of the ACh receptor. Autonomic dysfunction has been associated with human inflammatory diseases including rheumatoid arthritis, diabetes and sepsis; whether this dysfunction results from the inflammatory component of these diseases, or is actually an underlying cause, is now less clear. The description of the cholinergic anti-inflammatory now brings to the fore several new therapeutic strategies for inflammatory disease, and suggests that many of these diseases may actually be diseases of autonomic dysfunction.

Effect of lipopolysaccharide on the transport of pituitary adenylate cyclase activating polypeptide across the blood–brain barrier

Pituitary adenylate cyclase activating polypeptide (PACAP) has neuroprotective effects against ischemia, even when given by intravenous (iv) administration 24 h after stroke. Transport of PACAP across the blood-brain barrier (BBB) by peptide transport system (PTS)-6 underlies its effectiveness after iv administration. However, PACAP transport is modified after central nervous system (CNS) injury, raising the question of whether cytokines or BBB disruption affects PTS-6 activity. Lipopolysaccharide (LPS) is derived from bacterial cell walls and affects the passage of other proteins across the BBB through its release of cytokines and disruption of the BBB. Here, we examined by several methods the transport of radioactively labeled PACAP (I-PACAP) across the BBB after intraperitoneal (ip) injection of LPS. After three doses of LPS, studies at a single time point found a differential effect of LPS on the brain/serum ratio for I-PACAP and radioactively labeled albumin (I-Albumin). Whereas LPS increased the ratio for I-Albumin, demonstrating BBB disruption, it decreased the ratio for I-PACAP. Multiple-time regression analysis, capillary depletion, and brain perfusion showed that this decrease was fully explained by a decrease in the initial, reversible binding of I-PACAP to brain endothelium, while the rate of transport of PACAP into the brain was not altered. These methods also showed that the LPS-treated mice were volume contracted. This volume contraction concentrated the amount of I-PACAP in the blood and so increased the amount of I-PACAP presented to the BBB. Lack of change in transport rate combined with volume contraction resulted in a net increase of about 30% of the iv dose of I-PACAP entering the brain. LPS did not alter the efflux of I-PACAP from the CNS. In conclusion, PTS-6 remains active and should be able to deliver therapeutic amounts of PACAP to the CNS in brain injuries involving cytokine release and BBB disruption.

Why study transport of peptides and proteins at the neurovascular interface

The blood-brain barrier (BBB) is an immense neurovascular interface. In neurodegenerative, ischemic, and traumatic disorders of the central nervous system (CNS), the BBB may hinder the delivery of many therapeutic peptides and proteins to the brain and spinal cord. Fortunately, the mistaken dogma that peptides and proteins do not cross the BBB has been corrected during the past two decades by the accumulating evidence that peptides and proteins in the periphery exert potent effects in the CNS. Not only can peptides and proteins serve as carriers for selective therapeutic agents, but they themselves may directly cross the BBB after delivery into the bloodstream. Their passage may be mediated by simple diffusion or specific transport, both of which can be affected by interactions in the blood compartment (outside the BBB) and within the endothelial cells (at the BBB level). Although the majority of current delivery strategies focuses on modification of the molecule to be delivered, understanding the mechanisms of transport will eventually facilitate regulation of the BBB directly. We review the different aspects of interactions and discuss recent advances in the cell biology of peptide/protein transport across the BBB. Better understanding of the nature and regulation of the transport systems at the BBB will provide a new direction to enhance the interactions of peripheral peptides and proteins with the CNS.

No association between the promoter variants of tumor necrosis factor alpha (TNF-α) and schizophrenia in Chinese Han population

An increasing amount of evidence suggests that the pathophysiology of schizophrenia is associated with activation of the immune system. Four studies have established an association of -308G/A polymorphism of tumor necrosis factor alpha (TNF-alpha), a cytokine involved in inflammatory processes, with schizophrenia [Mol. Psychiatry 6 (2001) 79; Mol. Psychiatry 8 (2003) 718; Schizophr. Res. 65 (2003) 19; Biol. Psychiatry 54 (2003) 1205]. In the present study, however, no significant positive association has been found between any individual SNP or haplotype constituted of the five promoter polymorphisms (-1031T/C, -863C/A, -857C/T, -308G/A and -238G/A) in the human TNF-alpha gene and schizophrenia (314 Chinese Han schizophrenic patients and 340 healthy control). A meta-analysis we did in this work, which is based on previous nine studies plus our own unpublished data including a total of 2399 schizophrenic patients (sporadic cases 2099, familial cases >505) and more than 3261 controls, failed to show significant difference of -308G/A distribution between patients and controls in both the whole sample and the pooled Asian sample. By contraries, the significant results in the pooled Caucasian sample imply an ethnic heterogeneity in -308G/A variation in the TNF-alpha gene in schizophrenia.

Topical application of TNF-alpha antiserum attenuates spinal cord trauma induced edema formation, microvascular permeability disturbances and cell injury in the rat

The possibility that antiserum to tumour necrosis factor-alpha (TNF-alpha) is neuroprotective in spinal cord injury (SCI) was examined in a rat model. SCI was produced by making an incision into the right dorsal horn at the T10-11 segments. Top TNF-alpha antiserum at three concentrations (1:10; 1:50 and 1:100) given 30 min before or 2 min, 5 min or 10 min after trauma resulted in marked reduction in visible swelling, edema formation, and leakage of radiolabelled iodine tracer within the T9 and T12 segments at 5 h in a dose dependent manner. This neuroprotective effect was most pronounced when the antiserum at the highest dose level (1:10) was applied 10 min after SCI. The TNF-alpha antiserum also reduced the SCI induced upregulation of neuronal nitric oxide synthase (nNOS) immunoreactivity in a concentration dependent manner. Taken together, these results suggest that local application of TNF-alpha antiserum is neuroprotective in SCI and that this effect is mediated through NOS regulation.

Upregulation of p55 and p75 receptors mediating TNF-alpha transport across the injured blood-spinal cord barrier

Tumor necrosis factor (TNF-alpha) is involved in the inflammation and tissue regeneration occurring after spinal cord injury (SCI). This study tests the specific role of p55 and p75 receptors in mediating the transport of TNF-alpha across the blood-spinal cord barrier (BSCB) after SCI by compression. Transcytosis of 125I-TNF-alpha across a monolayer of the cerebral endothelial cells that compose the blood-brain barrier was significantly reduced in the absence of functional p55 and p75 receptors. At 3 d after SCI, double receptor knockout mice had a significantly reduced increase in TNF-alpha uptake from blood to injured lumbar spinal cord as compared with their inbred controls, despite the similar extent of BSCB disruption (measured by 99mTc-albumin). The p75 single receptor knockout mice had a reduced increase in 125I-TNF-alpha uptake, whereas the p55 receptor knockout mice had no significant increase of 125I-TNF-alpha uptake after SCI, suggesting that the p55 receptor plays a major role. Hence, the increased uptake of TNF-alpha 3 d after SCI is not explained by nonspecific barrier disruption but by receptor-mediated upregulation of transport. Quantitative RT-PCR analysis further showed that upregulation of TNF-alpha transport was related to increased expression of mRNA for p55 and p75 receptors. The increase of p55 receptor expression was more robust and seen between 12 h and 1 wk after SCI, whereas the increase of p75 receptor expression occurred later and involved fewer regions. Thus, the differential upregulation of p55 and p75 receptors indicates that permeation of TNF-alpha across the injured BSCB remains a regulated process. Knowledge of receptor-mediated regulation could facilitate effective therapeutic manipulation of BSCB permeation of vascular cytokines important to CNS regeneration.