Cyclic adenosine monophosphate regulates the expression of the intercellular adhesion molecule and the inducible nitric oxide synthase in brain endothelial cells

Transport Across the Blood-Brain Barrier

The blood-brain barrier (BBB) is a dynamic barrier essential for maintaining the microenvironment of the brain. Although the special anatomical features of the BBB determine its protective role for the central nervous system (CNS) from blood-borne neurotoxins, however, the BBB extremely limits the therapeutic efficacy of drugs into the CNS, which greatly hinders the treatment of major brain diseases. This chapter summarized the unique structures of the BBB; described a variety of in vivo and in vitro experimental methods for determining the transport properties of the BBB and the permeability of the BBB to water, ions, and solutes including nutrients, therapeutic agents, and drug carriers; and presented recently developed mathematical models which quantitatively correlate the anatomical structures of the BBB with its barrier functions. Recent findings for modulation of the BBB permeability by chemical and physical stimuli were described. Finally, drug delivery strategies through specific trans-BBB routes were discussed.

A novel endothelial-derived anti-inflammatory activity significantly inhibits spontaneous choroidal neovascularisation in a mouse model

BACKGROUND

Endothelial cells (EC) grown on collagen particles inhibit intimal hyperplasia in animal models when applied perivascularly, and this effect appears to be, at least in part, the result of EC-derived soluble factors that suppress local vascular inflammation. To elucidate the molecular basis of the therapeutic effects of EC grown on collagen particles, the anti-inflammatory activity of conditioned medium from these cells was characterized.

METHODS

Human aortic EC (HAEC) and, for chromatin immunoprecipitation assays, human umbilical vein EC (HUVEC) were treated with tumor necrosis factor alpha (TNFα) in the presence of conditioned medium generated by HAEC grown on collagen particles (ECPCM), and the anti-inflammatory effects were evaluated by analysing the expression of the inflammation-related adhesion molecules E-selectin and vascular cell adhesion molecule-1 (VCAM-1). The therapeutic activity of ECPCM was studied using the mouse strain JR5558, which develops spontaneous choroidal neovascularisation (CNV) lesions driven by local inflammation.

RESULTS

ECPCM significantly suppressed TNFα-induced expression of E-selectin and VCAM-1. ECPCM did not affect the mRNA stability of the two genes, but suppressed TNFα-induced binding of the p65 subunit of NF-kB transcription factor to E-selectin and VCAM-1 promoters. In vivo, systemic ECPCM treatment significantly reduced the CNV area and the recruitment of activated macrophages to the lesions. Characterization of the molecule responsible for the anti-inflammatory activity in ECPCM indicates that it is unlikely to be a protein and that it is not any of the better characterized EC-derived anti-inflammatory molecules.

CONCLUSIONS

Medium conditioned by HAEC grown on collagen particles exhibits significant anti-inflammatory activity via inhibition of genes that mediate inflammatory responses in EC.

Prostaglandin E₂-induced intercellular adhesion molecule-1 expression is mediated by cAMP/Epac signalling modules in bEnd.3 brain endothelial cells

BACKGROUND AND PURPOSE

Prostaglandin E₂ (PGE₂) has been implicated in the regulation of adhesion molecules, leukocyte adhesion and infiltration into inflamed site. However, the underlying mechanism therein involved remains ill-defined. In this study, we explored its cellular mechanism of action in the regulation of the intercellular adhesion molecule-1 (ICAM-1) expression in the brain endothelial cells.

EXPERIMENTAL APPROACH

bEnd.3 cells, the murine cerebrovascular endothelial cell line and primary mouse brain endothelial cells were treated with PGE₂ with or without agonists/antagonists of PGE₂ receptors and associated signalling molecules. ICAM-1 expression, Akt phosphorylation and activity of NF-κB were determined by reverse transcription polymerase chain reaction (RT-PCR), immunoblot analysis, luciferase assay and immunocytochemistry.

KEY RESULTS

PGE₂ significantly up-regulated the expression of ICAM-1, which was blocked by EP4 antagonist (ONO-AE2-227) and knock-down of EP4. PGE₂ effects were mimicked by forskolin, dibutyryl cAMP (dbcAMP) and an exchange protein directly activated by cAMP (Epac) activator (8-Cpt-cAMP) but not a protein kinase A activator (N⁶-Bnz-cAMP). PGE₂-induced ICAM-1 expression was reduced by knock-down of Epac1. A PI3K specific inhibitor (LY294002), Akt inhibitor VIII (Akti) and NF-κB inhibitors (Bay-11-7082 and MG-132) attenuated the induction of ICAM-1 by PGE₂. PGE₂, dbcAMP and 8-Cpt-cAMP induced the phosphorylation of Akt, IκB kinase and IκBα and the translocation of p65 to the nucleus and increased NF-κB dependent reporter gene activity, which was diminished by Akti.

CONCLUSION AND IMPLICATIONS

Our findings suggest that PGE₂ induces ICAM-1 expression via EP4 receptor and Epac/Akt/NF-κB signalling pathway in bEnd.3 brain endothelial cells, supporting its pathophysiological role in brain inflammation.

Temporal effects of vascular endothelial growth factor and 3,5-cyclic monophosphate on blood-brain barrier solute permeability in vivo

To test the hypothesis that vascular endothelial growth factor (VEGF) can transiently increase the blood-brain barrier permeability, P, as for peripheral microvessels and that the elevation of 3,5-cyclic monophosphate (cAMP) levels can inhibit the VEGF-induced acute hyperpermeability, we employed multiphoton microscopy to quantify the cerebral microvessel permeability P to various-sized solutes under VEGF and cAMP treatments. The cerebral microcirculation was observed through a section of frontoparietal bone thinned with a microgrinder. Fluorescein (MW 376Da), fluorescein isothioyanate-dextran-20k (FITC-Dex-20k), FITC-Dex-70k, or Alexa Fluor 488-IgG in 1% bovine serum albumin mammalian Ringer's solution was injected into the cerebral circulation via the ipsilateral carotid artery with a syringe pump. Simultaneously, temporal images were collected from the brain parenchyma ∼100-200 μm below the pia mater. P was determined from the rate of tissue solute accumulation around individual microvessels. Exposure to 1 nM VEGF transiently increased P to 2.2, 10.5, 9.8, and 12.8 times control values, for fluorescein, Dex-20k, Dex-70k, and IgG, respectively, within 30 sec, and all returned to control levels within 2 min. After 20 min of pretreatment with 2 mM of the cAMP analog 8-bromo-cAMP, the initial increase by 1 nM VEGF was completely abolished in P of all solutes. The response pattern of P to VEGF and cAMP and the ratios of the peak to control values for rat cerebral microvessels are similar to those for rat mesenteric (peripheral) microvessels, except that the ratios are higher in P of cerebral microvessels for the intermediate and large solutes. These results imply a new approach for delivering large therapeutic agents to the brain.

Chlorella 11-peptide inhibits the production of macrophage-induced adhesion molecules and reduces endothelin-1 expression and endothelial permeability

The inflammation process in large vessels involves the up-regulation of vascular adhesion molecules such as endothelial cell selectin (E-selectin), intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) which are also known as the markers of atherosclerosis. We have reported that Chlorella 11-peptide exhibited effective anti-inflammatory effects. This peptide with an amino sequence Val-Glu-Cys-Tyr-Gly-Pro-Asn-Arg-Pro-Gln-Phe was further examined for its potential in preventing atherosclerosis in this study. In particular, the roles of Chlorella 11-peptide in lowering the production of vascular adhesion molecules, monocyte chemoattractant protein (MCP-1) and expression of endothelin-1 (ET-1) from endothelia (SVEC4-10 cells) were studied. The production of E-selectin, ICAM-1, VCAM-1 and MCP-1 in SVEC4-10 cells was measured with ELISA. The mRNA expression of ET-1 was analyzed by RT-PCR and agarose gel. Results showed that Chlorella 11-peptide significantly suppressed the levels of E-selectin, ICAM, VCAM, MCP-1 as well as ET-1 gene expression. The inhibition of ICAM-1 and VCAM-1 production by Chlorella 11-peptide was reversed in the presence of protein kinase A inhibitor (H89) which suggests that the cAMP pathway was involved in the inhibitory cause of the peptide. In addition, this peptide was shown to reduce the extent of increased intercellular permeability induced by combination of 50% of lipopolysaccharide (LPS)-activated RAW 264.7 cells medium and 50% normal SEVC cell culture medium (referred to as 50% RAW-conditioned medium). These data demonstrate that Chlorella 11-peptide is a promising biomolecule in preventing chronic inflammatory-related vascular diseases.

JNK/ERK/FAK mediate promigratory actions of basic fibroblast growth factor in astrocytes via CCL2 and COX2

While the role of cytokines in causing pro- and anti-inflammatory cascades in the brain and that of chemokines in promoting chemotaxis is well recognized, the immunomodulatory actions of neurotrophins released during brain injury remains largely undetermined. This knowledge gap affects basic fibroblast growth factor (FGF2), which in the brain is mainly produced by astrocytes and characteristically upregulated in reactive astrocytes. The goal of this study was to characterize the inflammatory actions of FGF2 in astrocytes using primary cultures. We report that FGF2 induced the upregulation of monocyte chemoattractant protein (CCL2) and cyclo-oxygenase type 2 (COX2), and the inhibition of lipopolysaccharide-elicited ICAM1 upregulation. The effects of FGF2 were: (i) dependent on gene transcription as revealed by the concomitant regulation of CCL2 or ICAM1 mRNAs; (ii) mediated by the FGF2 receptor type 2; (iii) dependent on ERK, JNK and FAK, and (iv) NF-κB-independent. FGF2 also caused accelerated wound closure dependent on CCL2, COX2, ERK, JNK and FAK in a scratch assay. We conclude that the signaling network triggered by FGF2 in astrocytes converged into accelerating directed motion. It follows that astrocyte migration to injury sites may be a key factor in the repair mechanisms orchestrated by FGF2.

Andrographolide inhibits ICAM-1 expression and NF-κB activation in TNF-α-treated EA.hy926 cells

Several lines of evidence indicate that inflammation and endothelial cell dysfunction are important initiating events in atherosclerosis. Tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine, induces the expression of cell adhesion molecules and results in monocyte adherence and atheromatous plaque formation. Andrographolide (AP) is a major bioactive diterpene lactone in Andrographis paniculata that has anti-inflammatory activity. A previous study demonstrated the role of heme oxygenase 1 (HO-1) in the inhibition of TNF-α-induced ICAM-1 expression by AP. The present study investigated the effect of AP on the IKK/NF-κB signaling pathway, which mediates TNF-α-induced ICAM-1 expression in EA.hy926 cells. Similar to the previous study, AP inhibited TNF-α-induced ICAM-1 mRNA and protein levels, its expression on the cell surface, and subsequent adhesion of HL-60 cells to EA.hy926 cells. AP inhibited TNF-α-induced κB inhibitor (IκB) kinase (IKK) and IκBα activation, p65 nuclear translocation, NF-κB and DNA binding activity, and promoter activity of ICAM-1. Although AP increased the intracellular cAMP concentration and induced the phosphorylation of cAMP response element-binding protein (CREB), knocking down CREB protein expression by transfecting the cells with CREB-specific small interfering RNA did not relieve the inhibition of ICAM-1 expression by AP. Taken together, these results suggest that AP down-regulates TNF-α-induced ICAM-1 expression at least in part via attenuation of activation of NF-κB in EA.hy926 cells rather than through activation of CREB. The results suggest that AP may have potential as a cardiovascular-protective agent.

Cerebral blood flow regulation by nitric oxide in neurological disorders

There has been a rapid increase in the amount of information on the physiological and pathophysiological roles of nitric oxide (NO) in the brain. This molecule, which is formed by the constitutive isoforms of NO synthase, endothelial (eNOS) and neuronal (nNOS), plays an obligatory role in the regulation of cerebral blood flow and cell viability and in the protection of nerve cells or fibres against pathogenic factors associated with Alzheimer's disease, Huntington's disease, seizures, and migraine. Cerebral blood flow is impaired by decreased formation of NO from endothelial cells, autonomic nitrergic nerves, or brain neurons and also by increased production of reactive oxygen species (ROS). The NO-ROS interaction is an important topic in discussing blood flow and cell viability in the brain. Excessive production of NO by inducible NOS (iNOS) and nNOS in the brain participates in neurotoxicity. Recent studies on brain circulation have provided useful information about the involvement of impaired NO availability or uncontrolled NO production in cerebral pathogenesis, including Alzheimer's disease, seizures, vascular headaches, and inflammatory disorders. Insight into the role of NO in the brain will contribute to our better understanding of cerebral hemodynamic dysfunction and will aid in developing novel therapeutic measures in diseases of the central nervous system.

Phosphorylation of GTP dissociation inhibitor by PKA negatively regulates RhoA

The cAMP-PKA cascade is a recognized signaling pathway important in inhibition of inflammatory injury events such as endothelial permeability and leucocyte trafficking, and a critical target of regulation is believed to be inhibition of Rho proteins. Here, we hypothesize that PKA directly phosphorylates GTP dissociation inhibitor (GDI) to negatively regulate Rho activity. Amino acid analysis of GDIalpha showed two potential protein kinase A (PKA) phosphorylation motifs, Ser(174) and Thr(182). Using in vitro kinase assay and mass spectrometry, we found that the purified PKA catalytic subunit phosphorylated GDIalpha-GST fusion protein and PKA motif-containing GDIalpha peptide at Ser(174), but not Thr(182). Transfection of COS-7 cells with mutated full-length GDIalpha at Ser(174) to Ala(174) (GDIalpha-Ser(174A)) abrogated the ability of cAMP to phosphorylate GDIalpha. However, mutation of Thr(182) to Ala(182) (GDIalpha-Thr(182A)) did not abrogate, and cAMP increased phosphorylation of GDIalpha to a similar extent as wild-type GDIalpha transfectants. The mutant GDIalpha-Ser(174A), but not GDIalpha-Thr(182A), was unable to prevent cAMP-mediated inhibition of Rho-dependent serum-response element reporter activity. Furthermore, the mutant GDIalpha-Ser(174A) was unable to prevent the thrombin-induced RhoA activation. Coprecipitation studies indicated that neither mutation of the PKA consensus sites nor phosphorylation alter GDIalpha binding with RhoA, suggesting that phosphorylation of Ser(174) regulated preformed GDIalpha-RhoA complexes. The findings provide strong support that the selective phosphorylation at Ser(174) by PKA is a signaling pathway in the negative regulation of RhoA activity and therefore could be a potential protective mechanism for inflammatory injury.

Influence of ischemic injury on vein graft remodeling: role of cyclic adenosine monophosphate second messenger pathway in enhanced vein graft preservation

OBJECTIVE

Endothelial injury during the harvest of saphenous vein grafts might play an important role in the development of vein graft disease after coronary artery bypass grafting. Using a murine autologous arterialized vein patch model, we tested whether the initial ischemic insult of vein grafts was linked to the later development of graft neointimal hyperplasia and whether the restoration of the cyclic adenosine monophosphate second messenger pathway would attenuate the development of neointimal hyperplasia.

METHODS

A segment of the external jugular vein of a mouse was grafted onto its abdominal aorta. Three weeks after the operation, the degree of neointimal hyperplasia of the implanted graft was compared among (1) grafts without preservation, (2) grafts with 2 hours of preservation (25 degrees C) in heparinized saline, and (3) grafts with 2 hours of preservation in heparinized saline in the presence of a cyclic adenosine monophosphate analog. In addition, cyclic adenosine monophosphate contents of vein grafts and leukocyte adherence to the graft endothelium were assessed.

RESULTS

Cyclic adenosine monophosphate contents were significantly decreased after 2 hours of preservation (212 +/- 8 vs 156 +/- 5 pmol/L, P < .01). The grafts preserved for 2 hours showed greater neointimal hyperplasia compared with the grafts without preservation (neointimal expansion, 68.7% +/- 9.6% vs 46.1% +/- 4.8%; P < .01). The addition of a cyclic adenosine monophosphate analog to the preservation solution significantly suppressed neointimal hyperplasia of grafts preserved for 2 hours (44.3% +/- 5.0%). Inhibiting the cyclic adenosine monophosphate-dependent protein kinase by adding Rp-cAMPS abrogated the beneficial effects. Furthermore, grafts preserved for 2 hours had significantly more leukocytes adhering to the graft endothelium 24 hours after the operation compared with nonpreserved grafts, which was significantly reduced by the cyclic adenosine monophosphate treatment.

CONCLUSIONS

Ischemic insult during vein graft harvest and preservation is a key factor in the development of vein graft neointimal hyperplasia at least in part caused by the depletion of cyclic adenosine monophosphate. We conclude that stimulation of the cyclic adenosine monophosphate second messenger pathway might be a potential strategy for the prevention of vein graft disease.

Intrinsic regulation of brain inflammatory responses

It is now well accepted that inflammatory responses in brain contribute to the genesis and evolution of damage in neurological diseases, trauma, and infection. Inflammatory mediators including cytokines, cell adhesion molecules, and reactive oxygen species including NO are detected in human brain and its animal models, and interventions that reduce levels or expression of these agents provide therapeutic benefit in many cases. Although in some cases, the causes of central inflammatory responses are clear--for example those due to viral infection in AIDS dementia, or those due to the secretion of proinflammatory substances by activated lymphocytes in multiple sclerosis--in other conditions the factors that allow the initiation of brain inflammation are not well understood; nor is it well known why brain inflammatory activation is not as well restricted as it is in the periphery. The concept is emerging that perturbation of endogenous regulatory mechanisms could be an important factor for initiation, maintenance, and lack of resolution of brain inflammation. Conversely, activation of intrinsic regulatory neuronal pathways could provide protection in neuroinflammatory conditions. This concept is the extension of the principle of "central neurogenic neuroprotection" formulated by Donald Reis and colleagues, which contends the existence of neuronal circuits that protect the brain against the damage initiated by excitotoxic injury. In this paper we will review work initiated in the Reis laboratory establishing that activation of endogenous neural circuits can exert anti-inflammatory actions in brain, present data suggesting that these effects could be mediated by noradrenaline, and summarize recent studies suggesting that loss of noradrenergic locus ceruleus neurons contributes to inflammatory activation in Alzheimer's disease.

Nitric oxide induces polarization of actin in encephalitogenic T cells and inhibits their in vitro trans-endothelial migration in a p70S6 kinase-independent manner

Nitric oxide (NO) inhibits both actively induced and transferred autoimmune encephalomyelitis. To explore potential mechanisms, we examined the ability of NO to inhibit migration of T lymphoblasts through both collagen matrices and monolayers of rat brain endothelial cells. The NO donor 1-hydroxy-2-oxo-3, 3-bis (2-aminoethyl)-1-triazene (HOBAT) inhibited migration in a concentration-dependent manner. NO pretreatment of T cells inhibited migration through untreated endothelial cells, but NO pretreatment of endothelial cells had no inhibitory effect on untreated T cells. Therefore NO's migration inhibitory action was mediated through its effect on T cells and not endothelial cells. HOBAT did not inhibit migration by inducing T-cell death but rather by polarizing the T cells, resulting in a morphology suggestive of migrating cells. P70S6 kinase, shown to have a role in NO-induced migration inhibition in fibroblasts, had no role in the inhibitory effect of NO on T-cell migration. Thus, HOBAT did not alter p70S6K activity nor did rapamycin, a specific inhibitor of p70S6K, inhibit HOBAT-induced T-cell morphological changes or T-cell migration. We suggest that NO-induced morphological changes result in T cells with predefined migratory directionality, thus limiting the ability of these cells to respond to other migratory signals.

Noradrenergic depletion increases inflammatory responses in brain: effects on IkappaB and HSP70 expression

The inflammatory responses in many cell types are reduced by noradrenaline (NA) binding to beta-adrenergic receptors. We previously demonstrated that cortical inflammatory responses to aggregated amyloid beta (Abeta) are increased if NA levels were first depleted by lesioning locus ceruleus (LC) noradrenergic neurons, which replicates the loss of LC occurring in Alzheimer's disease. To examine the molecular basis for increased responses, we used the selective neurotoxin DSP4 to lesion the LC, and then examined levels of putative anti-inflammatory molecules. Inflammatory responses were achieved by injection of aggregated Abeta1-42 peptide and IL-1beta into frontal cortex, which induced neuronal inducible nitric oxide synthase (iNOS) and microglial IL-1beta expression. DSP4-treatment reduced basal levels of nuclear factor kappa B (NF-kappaB) inhibitory IkappaB proteins, and of heat shock protein (HSP)70. Inflammatory responses were prevented by co-injection (ibuprofen or ciglitzaone) or oral administration (pioglitazone) of peroxisome proliferator-activated receptor gamma (PPARgamma) agonists. Treatment with PPARgamma agonists restored IkappaBalpha, IkappaBbeta, and HSP70 levels to values equal or above those observed in control animals, and reduced activation of cortical NF-kappaB. These results suggest that noradrenergic depletion reduces levels of anti-inflammatory molecules which normally limit cortical responses to Abeta, and that PPARgamma agonists can reverse that effect. These findings suggest one mechanism by which PPARgamma agonists could provide benefit in neurological diseases having an inflammatory component.

Noradrenergic regulation of inflammatory gene expression in brain

It is now well accepted that inflammatory events contribute to the pathogenesis of numerous neurological disorders, including multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease, and AID's dementia. Whereas inflammation in the periphery is subject to rapid down regulation by increases in anti-inflammatory molecules and the presence of scavenging soluble cytokine receptors, the presence of an intact blood-brain barrier may limit a similar autoregulation from occurring in brain. Mechanisms intrinsic to the brain may provide additional immunomodulatory functions, and whose dysregulation could contribute to increased inflammation in disease. The findings that noradrenaline (NA) reduces cytokine expression in microglial, astroglial, and brain endothelial cells in vitro, and that modification of the noradrenergic signaling system occurs in some brain diseases having an inflammatory component, suggests that NA could act as an endogenous immunomodulator in brain. Furthermore, accumulating studies indicate that modification of the noradrenergic signaling system occurs in some neurodiseases. In this article, we will briefly review the evidence that NA can modulate inflammatory gene expression in vitro, summarize data supporting a similar immunomodulatory role in brain, and present recent data implicating a role for NA in attenuating the cortical inflammatory response to beta amyloid protein.

Estrogen inhibits NF kappa B-dependent inflammation in brain endothelium without interfering with I kappa B degradation

The protective effects of 17beta-estradiol in cerebral ischemia may be partially due to the blockade of leukocyte adhesion in cerebral endothelial cells, although the molecular mechanisms are not well understood. We report that 17beta-estradiol (E(2)), but not the alpha-enantiomer, inhibited the basal and interleukin-1beta (IL-1beta)-mediated expression of the intercellular adhesion molecule type 1 (ICAM1) and NFkappaB activation, in cultured brain endothelial cells. However, the degradation of IkappaB-alpha, which is an essential requirement for the translocation of NFkappaB to the nucleus, and a common biological target to suppress NFkappaB activation, was not halted by E(2). These findings indicate that decreased expression of adhesion molecules may account for the capacity E(2) to reduce adhesion of leukocytes in cerebral endothelium in vivo, and suggest the existence of brain-specific, estrogen-sensitive pathways, other than IkappaB-alpha_-regulation, to modulate NFkappaB. The stereoselectivity of the E(2) effect is consistent with an estrogen receptor-mediated mechanism.

Interferon-beta counteracts inflammatory mediator-induced effects on brain endothelial cell tight junction molecules-implications for multiple sclerosis

To elucidate mechanisms of endothelial cell (EC) dysfunction in CNS inflammatory responses and beneficial effects of interferon-beta (IFN-gamma) in multiple sclerosis (MS), we analyzed effects of individual and combinations of soluble inflammatory mediators on the intracellular localization of the EC tight junction-associated molecules zonula occludens-1 and -2 (ZO-1 and ZO-2) in human brain ECs. The cytoplasm in the majority of cells in control EC cultures was clear; ZO-1 and ZO-2 were localized peripherally near sites of cell contact and associated with submembranous cytoplasmic filaments. H2O2 induced reversible time- and concentration-dependent translocation of ZO-1 and ZO-2 to a random distribution within EC cytoplasm and retraction of EC borders. For low concentrations, these effects were accompanied by less prominent submembranous filaments but not by evidence of cytotoxicity, increased cell death or altered amounts of ZO-1. Tumor necrosis factor-beta induced similar alterations but interferon-y did not. Co-treatment with either cytokine increased H2O2 effects whereas IFN-beta reversed H2O2-induced effects. In control white matter samples, EC cytoplasm was clear and ZO-1 was located on cell borders. In inflammatory/demyelinating lesions, EC ZO-1 was diffuse, indicating that the alterations induced in vitro mimic those in active MS lesions. These findings suggest that in MS patients, IFN-beta treatment may counteract inflammatory mediator effects on CNS EC tight junction molecules, thereby preserving EC barrier function.