Upregulation of intercellular adhesion molecule-1 (ICAM-1) expression in primary cultures of human brain microvessel endothelial cells by cytokines and lipopolysaccharide

Influence of IFN-beta1b (Betaferon) on cytokine mRNA profiles in blood mononuclear cells and plasma levels of soluble VCAM-1 in multiple sclerosis

Inflammatory cell infiltration within the central nervous system (CNS) and upregulation of both pro- and anti-inflammatory cytokines are characteristic for multiple sclerosis (MS). Treatment with interferon-beta 1b (IFN-beta1b) reduces the number and severity of MS relapses. To examine whether treatment with IFN-beta1b affects levels of cytokine mRNA expressing blood mononuclear cells (MNC) we employed in-situ hybridization with synthetic oligonucleotide probes to detect and enumerate IFN-gamma, TNF-alpha, IL-10, TGF-beta and perforin mRNA expressing cells in MS patients before treatment with IFN-beta1b and during treatment for 3-6 weeks and for 3-6 months. Numbers of blood MNC spontaneously expressing TNF-alpha and IL-10 mRNA were lower after 3-6 months of treatment, while numbers of IFN-gamma, TGF-beta and perforin mRNA expressing MNC were not affected by treatment. IFN-beta1b had no influence on levels of MBP-reactive IFN-gamma, TNF-alpha, TGF-beta, IL-10 or perforin mRNA expressing blood MNC determined after 3-6 weeks or 3-6 months of treatment. Parallel measurements of plasma concentrations of soluble vascular cell adhesion molecule-1 (sVCAM-1) revealed elevated levels after 3-6 weeks of treatment and these levels remained higher after 3-6 months of treatment. The results suggest that IFN-beta1b treatment upregulates plasma levels of sVCAM-1, but has little effects on numbers of blood MNC expressing mRNA of the pro- and anti-inflammatory cytokines under study.Copyright Lippincott-Raven Publishers

Soluble intercellular adhesion molecule-I (sICAM-I) in serum and cerebrospinal fluid of demyelinating diseases of the central and peripheral nervous system

Serum and cerebrospinal fluid (CSF) soluble intercellular adhesion molecule-I (ICAM-I) levels were evaluated (ELISA) in 22 untreated and 13 corticosteroid-treated active relapsing remitting (RR) Multiple Sclerosis (MS), in 10 untreated and 10 corticosteroid-treated Guillain-Barré syndrome (GBS) and in 17 non-inflammatory neurological diseases (NIND). Twenty-eight clinically inactive RR MS were assayed for serum sICAM-I before and after 3 months treatment of 8 MIU rIFN beta-Ib taken s.c. every other day. High sICAM-I serum levels above the NIND values were found in untreated clinically active MS and in untreated GBS (P < 0.05) but not in the untreated clinically inactive MS group. The active MS group showed significantly (P = 0.0001) higher sICAM-I serum levels if compared to the inactive group. Corticosteroid-treated active MS and GBS patients showed lower (P < 0.05) serum sICAM-I levels than the corresponding untreated groups. Serum sICAM-I levels after 3 months of rIFN beta-Ib treatment (P < 0.0001, paired t-test) resulted increased compared to pretreatment values in MS. The mean values of CSF/serum sICAM-I:CSF/serum Albumin ratios (sICAM-I Index) in active untreated MS patients were higher compared to NIND (P < 0.005) and to corticosteroid-treated MS group (P = 0.01). sICAM Index values in GBS did not differ from those in NIND. The results seem to suggest potential roles for serum sICAM-I in downregulating the ongoing inflammatory response at the blood-brain barrier level and for CSF sICAM-I in the maintenance of a central nervous system local immune response.

Gene expression of IL-10 in relationship to TNF-alpha, IL-1beta and IL-2 in the rat brain following middle cerebral artery occlusion

To systematically elucidate the gene expression of inflammatory and immune modulators following middle cerebral artery occlusion (MCAO) in the rat, we studied interleukin-10 (IL-10) along with tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1beta) and interleukin-2 (IL-2). Gene expression of these cytokines was studied ipsilateral and contralateral to the MCAO, with mRNA expression levels evaluated 2, 4, 6, 8 and 12 h following permanent MCAO by reverse transcriptase polymerase chain reaction (RT-PCR). In the ischemic hemisphere TNF-alpha and IL-1beta mRNA increased at 2 h following MCAO and peaked at 6 h, with IL-10 mRNA detected only at 6 h. Contralaterally, both TNF-alpha and IL-1beta mRNAs were expressed with a similar pattern to that in the ischemic hemisphere, but at lower levels, with no contralateral IL-10 expression. There was no difference in IL-2 gene expression between control and experimental animals in either hemisphere. These results demonstrate that IL-10 and TNF-alpha, IL-1beta gene expression is induced early following MCAO. The temporal profile of these cytokines is similar to that seen in sepsis, where TNF-alpha induces IL-10; subsequently IL-10 inhibits TNF-alpha expression. The similarity of the temporal profile of cytokine expression in sepsis and cerebral ischemia suggests that IL-10 should be studied as a potential inhibitor of TNF-alpha production in ischemic brain tissue. The factors inducing contralateral expression of the inflammatory cytokines, TNF-alpha and IL-1beta, along with the potential clinical significance of this remote cytokine gene expression, merit further study.

Anti-intercellular adhesion molecule-1 (ICAM-1) antibody treatment prevents central and peripheral nervous system disease in autoimmune-prone mice

Abnormal neurological functioning similar to that seen in systemic lupus erythematosus (SLE) patients is detectable in an SLE-prone murine strain (MRL/lpr) by 8-10 weeks and is severe by 18 weeks of age. The purpose of this study was to evaluate the effectiveness of murine antiintercellular adhesion molecule-1 (ICAM-1) in suppressing neurological disease in MRL/lpr mice. Beginning at 6 weeks of age, five MRL/lpr mice received 5 weekly intraperitoneal injections of anti-ICAM-1-containing culture supernatant in phosphate-buffered saline (PBS) whereas four animals were treated with non-anti-ICAM-1 containing supernatant in PBS. A decline in neurological functioning began in control mice by 10 weeks, but anti-ICAM-1 treated mice remained normal throughout the study. All control mice had vasculitic skin lesions by 14 weeks of age whereas none of the anti-ICAM-1 treated mice ever developed skin lesions. Nerve conduction studies performed on all mice prior to sacrifice showed sciatic compound motor action potentials of anti-ICAM-1 treated mice that were of higher amplitude and shorter latency than those of controls. Inflammation in the sciatic nerve was more common in control mice. Brain histology revealed a similar degree of choroid plexus inflammation in both groups. Our study demonstrated that anti-ICAM-1 was effective in suppressing neurological abnormalities in MRL/lpr mice and may potentially be useful therapy in human SLE.

Expression of LFA-1alpha and ICAM-1 in the developing rat brain: a potential mechanism for the recruitment of microglial cell precursors

Several studies agree that microglial cells derive from monocytes that infiltrate the central nervous system during development, but the precise mechanism by which these cells enter into the nervous tissue is still unknown. In this way, the aim of the present study was to analyze the expression of two cell adhesion molecules involved in the recruitment of blood leukocytes into tissues, the lymphocyte function-associated antigen-1alpha (LFA-1alpha) and the intercellular adhesion molecule-1 (ICAM-1) in the developing rat brain (from E16 to P18). By means of immunohistochemistry, our observations showed that LFA-1alpha and ICAM-1 were expressed in the developing rat brain with a definite distribution pattern and a characteristic time course of appearance. In the embryonic period, LFA-1alpha immunoreactivity was displayed not only by intravascular blood cells but also by intraparenchymal round cells with a horseshoe-shaped nucleus, showing the typical morphological features of monocytes. Monocyte-like cells present in the embryonic brain parenchyma often displayed mitotic profiles. LFA-1alpha immunohistochemistry also revealed the presence of some LFA-1alpha-positive cells belonging to the ameboid microglial population (mostly in the white matter from E18). In the postnatal period, LFA-1alpha immunoreactivity was displayed by some ameboid microglial cells (P0-P9) and also by some ramified microglia. LFA-1alpha immunoreactivity observed in ramified microglia was weaker when compared to LFA-1alpha stained ameboid microglia. In contrast, ICAM-1 immunolabeling during the embryonic period was mainly located in endothelial cells of parenchymal brain blood vessels (principally from day E18). Blood vessels in choroid plexus and meninges also expressed ICAM-1 during the embryonic time. In postnatal animals, ICAM-1 immunoreactivity was found in relation to endothelial cells of blood vessels, but the density of ICAM-1-positive blood vessels was lower than that during the embryonic period. The gradual regulation in the expression of LFA-1alpha by monocyte-like cells and cells of the microglial lineage, and the expression of ICAM-1 by the brain vasculature strongly suggest that the LFA-1/ICAM-1 system may be a mechanism involved in the entry of microglial cell precursors into the developing rat brain.

Microvascular responses to cerebral ischemia/inflammation

Experimental occlusion of a brain-supplying artery triggers tissue ischemia and subsequent inflammatory events that are initiated at the blood microvessel interface. Cytokine production and molecular adhesive events occur in the early moments following cerebral blood flow reduction, which underlie the transition from ischemic to inflammatory injury. Events both within the microvascular lumen and in the immediately surrounding tissue are involved. Cytokines, including TNF-alpha, IL-1 beta, IL-6, and PAF, are produced from the ischemic parenchyma and contribute to the endothelial cell expression of P-selectin, ICAM-1, and E-selectin. Platelet activation occurs paris passu and probably involves alpha-granule P-selectin to mediate PMN leukocyte-platelet interactions. Other integrin heterodimers are also involved in the early microvascular responses to ischemia. The response of the basal lamina and ECM is somewhat slower, entailing yet unproven mechanisms that most probably include the proteolytic processes of leukocyte transmigration. The modifications to microvascular structure are likely to affect both endothelial and astrocyte relationships, promote erythrocyte extravasation and hemorrhage, and contribute to tissue injury. Remodeling of the microvasculature, apparent in other tissues, involves a number of these processes. However, the enzymatic participants and regulating mechanisms are coming under study: the unraveling of regulatory mechanisms of adhesion receptor expression and their modulation, and the companion roles of integrins as mediators of structural integrity and intercellular signaling.

Cerebral lupus vasculopathy. Mechanisms and clinical relevance

The most common neuropathological findings in SLE are a small vessel cerebral vasculopathy and microinfarcts. These findings may reflect the end result of repeated episodes of acute inflammation in the small vessels in the brain. There is experimental support for the local Shwartzman reaction as a paradigm to explain some of the CNS manifestations in SLE. Activation or "priming" of cerebral microvascular endothelial cells by anticardiolipin antibodies or other immunoglobulins in concert with intravascular activation of the complement system may combine to elicit leukothrombosis in the brain. Therapies aimed at inhibiting leukocyte-endothelial cell interactions in the brain may be of use in CNS lupus.

The effect of brain temperature on acute inflammation after traumatic brain injury in rats

The effect of varying brain temperature on neutrophil accumulation in brain and the expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1) on cerebrovascular endothelium after controlled cortical impact (CCI) was studied in rats. Sprague Dawley rats were anesthetized and subjected to CCI to the left parietal cortex. Ten minutes after CCI, brain temperature was modulated and maintained at 32 degrees C, 37 degrees C, or 39 degrees C (n = 8 per group) for 4 h. Rats were then decapitated and immunohistochemistry on brain sections was performed using monoclonal antibodies (MoAb) that recognize neutrophils (RP-3), ICAM-1 (TM-8, Athena Neurosciences), or MoAb that react with E-selectin (La-Roche). Each of these markers was quantified in 100 x fields. Neutrophil accumulation was also quantified with myeloperoxidase (MPO) assay. Absolute neutrophil count (ANC) was measured in blood samples before and 1 h and 4 h after CCI. Neutrophil accumulation in injured brain was decreased in rats maintained at 32 degrees C vs 39 degrees C (4-fold difference as assessed by immunohistochemistry, p < 0.05; 8-fold difference as assessed by MPO assay, p < 0.05). Peripheral blood ANC was not affected by temperature. E-selectin was induced on cerebrovascular endothelium after CCI (p < 0.05), but was only decreased modestly at 32 degrees C versus 39 degrees C (p = 0.11). ICAM-1 was not upregulated on cerebrovascular endothelium at this early time following CCI. Neutrophil accumulation is directly dependent on brain temperature during the initial 4 h after CCI. This appears to be mediated by mechanisms other than effects of temperature on E-selectin or ICAM-1 expression or systemic ANC.

Identification of cell types producing RANTES, MIP-1 alpha and MIP-1 beta in rat experimental autoimmune encephalomyelitis by in situ hybridization

The chemokines RANTES, macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta are members of the beta-family of chemokines and potent chemoattractants for lymphocytes and monocytes. To investigate the factors which regulate lymphocyte traffic in experimental autoimmune encephalomyelitis (EAE), we studied, by in situ hybridization analysis, the kinetics of mRNA expression and the potent cellular sources of RANTES, MIP-1 alpha and MIP-1 beta in the central nervous system (CNS) during the course of EAE. RANTES-positive cells appeared in the subarachnoid space and infiltrated the subpial region at around day 10, increased to a peak at days 12-13 and then decreased following the resolution of the acute phase of EAE, though elevated RANTES message expressions still remained on chronic subclinical stage. Most of RANTES positive cells were identified as T-lymphocytes located mainly around blood vessels, by combined studies of in situ hybridization and immunohistochemistry. The remainder of the RANTES-positive cells were astrocytes and macrophages/microglia. MIP-1 alpha and MIP-1 beta mRNA-positive cells appeared around day 10, increased further on days 12-13 and then gradually decreased. Most of the MIP-1 alpha- and MIP-1 beta-positive mononuclear cells were located around blood vessels. The kinetics of RANTES, MIP-1 alpha and MIP-1 beta expression paralleled those of the recruitment of infiltrating inflammatory cells and disease severity. Our observations support the possibility that chemokine production by T-cells, macrophages and astrocytes lead to the infiltration of inflammatory cells into the CNS parenchyma during the acute phase of EAE.

Distribution of endogenous tumour necrosis factor alpha in gliomas

AIMS

To determine the distribution and cellular origin of endogenous tumour necrosis factor alpha (TNF alpha) in the cellular components of human gliomas.

METHODS

Frozen sections of 26 gliomas (four astrocytomas (As); two oligoastrocytomas (OA); one ansplastic astrocytoma (AA); one anaplastic oligoastrocytoma (AOA); 18 glioblastomas (GB)) were examined immunohistochemically using antihuman TNF alpha and anti-Leu-M5 (CD11c) antibodies. Additional studies with double immunohistocchemical procedures were performed with anti-glial fibrillary acidic protein and anti-neurofilament antibodies.

RESULTS

Eighty per cent of the AA, AOA, and GB (16 of 20) had a positive reaction for TNF alpha, but only 17% of As and OA (one of six) were positive. Positive cells were seen in both the tumour tissue and adjacent brain tissues. TNF alpha protein was detected not only in the tumour cells but also in the endothelium of tumour vessels as well as reactive astrocytes and neurons.

CONCLUSIONS

Endogenous TNF alpha is present in cells of various origins in glial tumours including tumour vessels; however, the role of TNF alpha may be different in different types of cells or altered microenvironment.

Cytokine profile of myelin basic protein-reactive T cells in multiple sclerosis and healthy individuals

Myelin basic protein (MBP)-reactive T cells have been implicated in the autoimmune pathogenesis of multiple sclerosis (MS). In this study, we examined the cytokine profile of 531 primary MBP-reactive T-cell lines and 72 independently established clones from 32 patients with MS and 18 healthy controls (NS) by using highly sensitive enzyme-linked immunosorbent assays. An increased number of primary T-cell lines producing interferon-gamma (IFN gamma) and/or interleukin-4 (IL-4) in response to MBP were found in patients with MS compared with controls. No distinct Th1 or Th2 subtypes could be demonstrated among the MBP-reactive clones. IL-4 was more frequently observed among MS-derived clones. Clones derived from MS patients produced increased levels of IL-2, IL-4, tumor necrosis factor-alpha (TNF alpha), IFN gamma, and IL-10, but not IL-6. It is interesting that MBP-reactive T cells from MS patients expressing the disease-associated HLA-DRB1*15 allele produced increased quantities of TNF alpha, a cytokine suggested to play an important role in inflammation and demyelination. When challenged with either MBP or a bacterial superantigen, the clones expressed similar levels of the proinflammatory cytokine IFN gamma. Our study suggests a functional difference in T-cell responses to MBP in patients with MS compared with healthy individuals, and provides further insights into the role of MBP-reactive T cells and their cytokine profile in the inflammatory processes of MS.

Production of tumor necrosis factor-alpha and interleukin-1beta by human cerebral microvascular endothelium after percussive trauma

Intracerebral cytokine production is thought to be partially responsible for the brain edema and increased leukocyte adhesion seen after head injury by both a direct effect on vascular permeability and by causing leukocyte activation. Cerebrospinal fluid concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 are elevated after traumatic brain injury. The cerebral endothelium has not been investigated as a de novo source of cytokines after injury. We have found that conditioned media from cultured human cerebral microvascular endothelium (HCME) subjected to percussion trauma increases neutrophil chemotaxis. To test the hypothesis that percussive trauma increases the production of TNF-alpha and IL-1beta by HCME, serial supernatant samples from passage 2 HCME were collected for 24 hours and analyzed for TNF-alpha and IL-1beta concentration by enzyme-linked immunosorbent assay after trauma. HCME subjected to percussion injury secreted significantly more TNF-alpha at 8 and 24 hours and significantly more IL-1beta at 4 and 24 hours compared with uninjured controls (p < 0.05, Student's t test). These data suggest that HCME production of inflammatory cytokines occurs after traumatic brain injury independent of systemic influences. In situ cytokine production by HCME after percussion trauma may mediate the increased cerebral leukocyte accumulation and cerebrovascular dysfunction observed after focal brain injury.

The induction of ICAM-1 in human cerebromicrovascular endothelial cells (HCEC) by ischemia-like conditions promotes enhanced neutrophil/HCEC adhesion

Ischemic brain injury is exacerbated by leukocyte infiltration and formation of vasogenic edema. In this study we demonstrate that intercellular adhesion molecule-1 (ICAM-1) is dramatically (3 to 15-fold) up-regulated in human cerebromicrovascular endothelial cells (HCEC) by a 16 h exposure to the cytokine, IL-1 beta (50-200 u/ml), the phorbol ester, TPA (1-100 nM), or by simulated in vitro ischemia/reperfusion. These treatments also significantly increased the adhesion of allogeneic neutrophils to HCEC monolayers. Both IL-1 beta- and TPA-induced expression of ICAM-1 and increased neutrophil adhesion to HCEC were inhibited by the transcriptional inhibitor, actinomycin D (AcD; 1-10 micrograms/ml), and by an anti-ICAM-1 antibody (ICAM-1 Ab). By contrast, ischemia-induced neutrophil adhesion was only slightly affected by AcD and ICAM-1 Ab alone, but it was abolished by the combination of anti-ICAM-1 and anti-CD18 antibodies. The increase in surface expression of ICAM-1 and neutrophil adhesion by IL-1 beta, TPA and ischemia were significantly reduced by the cyclo-oxygenase (COX) inhibitors, indomethacin (100-300 microM) and dexamethasone (10-50 microM). These results indicate that ICAM-1 expression in HCEC can lead to enhanced neutrophil adhesion and that COX activation in HCEC likely plays a role in the processes by which leukocyte adhesion and recruitment take place in the brain during inflammation and ischemia in vivo.

Selective expression of adhesion molecules on human brain microvascular endothelial cells

Human microvascular endothelial cells were isolated from children's brain and examined for their morphological characteristics and upregulation of cell adhesion molecules in response to TNF alpha. Our human brain microvascular endothelial cells (HBMEC) were positive for factor VIII-Rag, carbonic anhydrase IV, Ulex Europeus Agglutinin I, took up fluorescently labeled acetylated low density lipoprotein and expressed gamma glutamyl transpeptidase, demonstrating their brain endothelial cell characteristics. Upon treatment with TNF alpha. VCAM and ICAM but little ELAM was expressed on HBMEC, while VCAM, ICAM and ELAM were clearly evident on HUVEC. This selective expression of cell adhesion molecules was also demonstrated by in situ stimulation of brain tissues. In conclusion, microvascular endothelial cells from childrens brains display selective expression of cell adhesion molecules, which differ from macrovascular endothelial cells. This may have consequences for leukocyte trafficking into the central nervous system.

Cytokines and perinatal brain injury

A rapidly expanding body of data provides support for the hypothesis that pro-inflammatory cytokines including interleukin-1 beta (IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha) are expressed acutely in injured brain and contribute to progressive neuronal damage. Little is known about the pathogenetic role of these cytokines in perinatal brain injury. Recent experimental studies have incorporated two closely related in vivo perinatal rodent brain injury models to evaluate the role(s) of pro-inflammatory cytokines in the progression of neuronal injury: a perinatal stroke model, elicited by unilateral carotid artery ligation and subsequent timed exposure to 8% oxygen in 7-day-old rats, and a model of excitotoxic injury, elicited by stereotactic intra-cerebral injection of the selective excitatory amino acid agonist NMDA. Each of these lesioning methods results in reproducible, quantifiable focal forebrain injury at this developmental stage. Acute brain injury, evoked by cerebral hypoxia-ischemia or excitotoxin lesioning, results in transient marked increases in expression of IL-1 beta, and TNF-alpha mRNA in brain regions susceptible to irreversible injury, and there is evidence that pharmacological antagonism of IL-1 receptors can attenuate injury in both models. Recent studies also suggest that complementary strategies, based on pharmacological antagonism of platelet activating factor and on neutrophil depletion can also limit the extent of irreversible injury. In summary, current data suggest that pro-inflammatory cytokines contribute to the progression of perinatal brain injury, and that these mediators are important targets for neuroprotective interventions in the acute post-injury period.

Adenovirus-mediated over-expression of interleukin-1 receptor antagonist reduces susceptibility to excitotoxic brain injury in perinatal rats

In seven-day-old rats, intracerebral injection of N-methyl-D-aspartate transiently stimulates expression of Interleukin-1 beta messenger RNA. To evaluate the role of Interleukin-1 beta in the pathogenesis of excitotoxic injury, we sought to determine if Interleukin-1 receptor antagonist, an endogenous competitive inhibitor of Interleukin-1 beta, could attenuate N-methyl-D-aspartate-induced injury. To induce sustained over-expression of Interleukin-1 receptor antagonist in the brain, a recombinant adenovirus encoding Interleukin-1 receptor antagonist was administered by intracerebroventricular injection into three-day-old rats. Increased brain concentrations of Interleukin-1 receptor antagonist two to six days later were documented by assays of tissue homogenates and by immunocytochemistry. To evaluate the impact of Interleukin-1 receptor antagonist on N-methyl-D-aspartate neurotoxicity, three-day-old animals received intracerebroventricular injections of either adenovirus encoding Interleukin-1 receptor antagonist or a control adenovirus encoding beta-galactosidase, followed four days later by right intrastriatal injections of N-methyl-D-aspartate (10 nmol/0.5 microliter), a dose that typically elicits excitotoxic injury in the ipsilateral striatum and adjacent hippocampus, or saline. Animals were killed five days later, and brain damage was quantitated by measurement of bilateral cross-sectional areas of the striatum and anterior hippocampus. In three independent experiments, in N-methyl-D-aspartate-lesioned animals, both striatal and hippocampal injuries were reduced in animals that had been infected with adenovirus that encoded Interleukin-1 receptor antagonist, in comparison with littermates infected with the control adenovirus (right striatal volume loss ranged from 16 to 24%, compared with 54-65% volume loss in control). There was no striatal atrophy in adenovirus-infected saline-injected animals. These results provide strong support for the hypothesis that Interleukin-1 beta is a mediator of excitotoxic brain injury in perinatal rats.

The trigeminal nerve and augmentation of regional cerebral blood flow during experimental bacterial meningitis

We investigated whether trigeminal nerve fibers contribute to enhanced regional cerebral blood flow (rCBF) in a rat model of experimental bacterial meningitis. rCBF was measured continuously for 6 h by laser Doppler flowmetry through thinned bone over the frontal cortex. Meningitis was induced with pneumococcal cell wall components and confirmed by a significant increase of (a) leukocytes within the cerebrospinal fluid, (b) brain water content, (c) intracranial pressure and (d) rCBF. The increase of rCBF was significantly attenuated (p < 0.05) at 3, 4, 5, and 6 h in animals after a chronic (200 +/- 21% versus 138 +/- 13% at 6 h on the intact and denervated sides, respectively) but not after an acute section of the nasociliary branch of the trigeminal nerve. We conclude that elevations in blood flow during the early phase of bacterial meningitis are mediated in part by the trigeminal nerve, probably by local perivascular release of neuropeptides from afferent axons innervating the meninges.

Experimental antileukocyte interventions in cerebral ischemia

White blood cells (WBCs) play vital roles in host defense. Recently, increasing interest has been directed toward the question of whether WBCs, particularly polymorphonuclear leukocytes, could also act as mediators of secondary brain damage in the setting of focal and global cerebral ischemia with and without reperfusion. Considerable insight into the importance of WBC-mediated tissue injury has been gained from studies employing antileukocyte interventions in experimental cerebral ischemia. The purpose of this article is to survey the different approaches taken to interfere with WBC inflammatory function. Emphasis is laid on a discussion of the efficacy of these interventions, their effects and side effects on cerebral and systemic parameters, and the power of evidence they provide for identification of WBCs as important factors in cerebral ischemia. The role of WBCs has been investigated in a great variety of global and focal cerebral ischemia models with and without reperfusion, leading to sometimes contradictory results. In the light of currently available data, it seems likely that WBCs contribute to secondary brain damage in the scenario of experimental transient focal cerebral ischemia, if the insult is not too severe.

Endothelial cells of the rat brain vasculature express cyclooxygenase-2 mRNA in response to systemic interleukin-1 beta: a possible site of prostaglandin synthesis responsible for fever

We previously showed that intraperitoneal injection of lipopolysaccharide induced cyclooxygenase-2 (COX-2) mRNA in as yet unidentified cells of blood vessels and leptomeninges in the rat brain and proposed a possible role of these cells as the source of prostaglandin E2 in the genesis of fever (Cao et al., Brain Res., 697 (1995) 187-196). In the present study, to proceed further with this line of research, we addressed the following two questions: first, does a pyrogenic dose of interleukin-1 beta (IL-1 beta), an endogenous pyrogen, induce COX-2 mRNA in the brain blood vessels and leptomeninges? Secondly, if it does, what type of cells are positive for COX-2 mRNA? Intraperitoneal injection of recombinant human IL-1 beta (30 micrograms/kg) induced fever in rats and an in situ hybridization study revealed that faint but significant COX-2 mRNA signals appeared in the blood vessels and leptomeninges at 1.5 h after the injection (the early rising phase of fever). The mRNA signals increased in number and intensity at 4 h (early plateau phase), decreased at 6.5 h (early recovery phase), and completely disappeared by 10 h after the injection (late recovery phase). The COX-2 mRNA positive cells in the blood vessels were likely to be the endothelial cells since the corresponding cells in the adjacent mirror-imaged section also expressed mRNAs for intracellular adhesion molecule-1 and the type-I interleukin-1 receptor, although those in the leptomeninges still remained unidentified. These results imply that circulating IL-1 beta acts on its receptor on the endothelial cells of the brain vasculature to induce COX-2 mRNA, which is possibly responsible for the elevated level of PGE2 seen during fever.

Platelet/endothelial cell adhesion molecule-1 (PECAM-1) expression by human brain microvessel endothelial cells in primary culture

PECAM-1 expression was investigated in primary cultures of human brain microvessel endothelial cells (HBMEC). HBMEC constitutively express PECAM-1 along their apical cell surface, advancing processes and on the basal surface at points of contact with the extracellular matrix. Surface expression is not altered by cytokine or lipopolysaccharide treatment. This distribution may mediate cell-cell contract and migration during angiogenesis and HBMEC-leukocyte interactions in CNS inflammation.

Influence of percussion trauma on expression of intercellular adhesion molecule-1 (ICAM-1) by human cerebral microvascular endothelium

OBJECTIVES

Brain injury is associated with the production of oxygen free radicals (OFR) and the accumulation of polymorphonuclear leukocytes (PMN) at the site of injury, both of which may be involved in the evolution of secondary cerebral injury. Intercellular adhesion molecule-1 (ICAM-1) is responsible for adherence of PMNs. We sought to determine whether percussion trauma altered the expression of ICAM-1 and to determine the effect of OFR scavengers on ICAM-1 expression after percussion trauma.

DESIGN

Prospective controlled laboratory research using passage 2 human cerebral microvascular endothelium (HCME).

MATERIALS AND METHODS

Cell lysates were collected over 24 hours and analyzed for ICAM-1 by enzyme-linked immunosorbent assay (ELISA) after trauma or incubation with tumor necrosis factor (TNF)-alpha. OFR scavengers were added immediately after trauma with or without previous incubation with TNF-alpha.

MEASUREMENTS AND MAIN RESULTS

Sublethal percussion trauma did not alter ICAM-1 expression by HCME. TNF-alpha upregulated ICAM-1 in percussed and nonpercussed cells with maximal ICAM-1 expression at 24 hours (p < 0.01, ANOVA). However, percussion trauma significantly blunted the response of HCME to TNF-alpha. The addition of OFR scavengers after percussion trauma alone had no effect on ICAM-1 expression at 24 hours, but restored the response of percussed HCME to TNF-alpha.

CONCLUSIONS

Percussion trauma alters the response of HCME to cytokine-induced ICAM-1 upregulation, and the normal response is restored by OFR scavengers. This suggests that HCME become dysfunctional after percussion trauma and this dysfunction may be mediated by OFR.

Intercellular adhesion molecule-1-deficient mice are less susceptible to cerebral ischemia-reperfusion injury

Neutrophil emigration is mediated by adhesion proteins that are highly expressed on the endothelial surface during inflammatory processes in the brain. Intercellular adhesion molecule-1 (ICAM-1) is an inducible adhesion molecule that binds to leukocyte integrins and facilitates neutrophil adhesion and transendothelial migration. To study the role of ICAM-1 during ischemia and reperfusion in the brain, we analyzed the effect of transient focal cerebral ischemia in ICAM-1-deficient mice generated by gene targeting in embryonic stem cells. Transient focal ischemia was induced by occluding the left middle cerebral artery for 3 hours followed by a 21- or 45-hour reperfusion period. When compared with their wild-type littermates, ICAM-1-deficient mice were less susceptible to cerebral injury as demonstrated by a 5.6- or 7.8-fold reduction in infarction volume, respectively. These data support the premise that neutrophil adhesion in ischemic areas may be deleterious and that ICAM-1 deficiency reduces neurological damage after transient focal cerebral ischemia.

Cytokines and adhesion molecules in stroke and related diseases

Once thought as immunologically naive, cells from the central nervous system have been shown to become immunologically reactive and produce various substances including cytokines and adhesion molecules. Recent investigations have revealed that mRNAs of certain cytokines such as tumor necrosis factor, interleukin-1, and interleukin-6 are expressed in the ischemic brain of the animals. Chemokines including CINC, MCP-1, and MIP-1, as well as adhesion molecules such as ICAM-1. ELAM and P-selectin were also found to be expressed. Although identification of the cells producing these cytokines were often difficult, neurons, endothelia, activated astrocytes and microglia/macrophages were the likely sources. The induction of these molecules in ischemic brain is time-locked and appears to be controlled in a highly regulated manner during the process of ischemic cascade. The functional role, interrelationship, and basic mechanism of action of these molecules are being increasingly recognized, while trials such as antiadhesion antibody molecules, growth factors, and anticytokine antibodies have been successful in reducing the neuronal damage in animals subjected to ischemic injury. Furthermore, changes of certain cytokines or adhesion molecules have been detected in the serum or cerebrospinal fluid of patients with stroke and related diseases suggesting that these molecules play a role in the pathogenesis of human stroke. Understanding of these cytokine-adhesion molecule cascades in the ischemic brain may allow us to develop new strategies for the treatment of stroke.

A pilot study investigating the effects of orally administered pentoxifylline on selected immune variables in patients with multiple sclerosis

Multiple sclerosis is probably mainly mediated by T-helper 1 (TH1)-lymphocytes. TH1-function can be down-regulated in vitro and in animal experiments by pentoxifylline. Therefore, we included 20 multiple sclerosis patients in an open label pilot trial of pentoxifylline. Outcome parameter was the effect of treatment on levels of various cytokines and adhesion molecules in cerebrospinal fluid and serum, on production of TH1- and TH2-cytokines using cell stimulation assays, as well as on measures of T-cell activation and proliferation. Kurtzke's EDSS was a secondary efficacy parameter. A convincing and consistent effect of pentoxifylline could not be demonstrated.

Serum and cerebrospinal fluid levels of soluble adhesion molecules in multiple sclerosis: predominant intrathecal release of vascular cell adhesion molecule-1

Activated cerebral vascular endothelial cells express leukocyte, vascular cell, and intracellular adhesion molecules (E-selectin, VCAM-1 and ICAM-1) which facilitate leukocyte adhesion to endothelium and migration into inflammatory lesions. Paired serum and cerebrospinal fluid (CSF) levels of soluble (s) E-selectin, sVCAM-1 and sICAM-1 were determined by ELISA in patients with clinically definite MS in relapse, and patients with other inflammatory (IND) and non-inflammatory neurological disease (NIND). CSF levels of sVCAM-1 and sICAM-1 were significantly increased in MS patients compared to IND and NIND patients. Elevation of CSF sVCAM-1 in MS patients was the most marked finding (P = 0.0001) and an increased sVCAM-1 index indicated that this was due to intrathecal release of sVCAM-1. There were no differences in serum and CSF sE-selectin levels between the study groups. Measurement of the sVCAM-1 index may provide a marker of disease activity in patients with clinically definite MS.

Immunoregulatory effects of interferon-beta and interacting cytokines on human vascular endothelial cells. Implications for multiple sclerosis autoimmune diseases

The mechanism(s) of action responsible for the anti-inflammatory effects mediated by interferon (IFN)-beta are still elusive although suggestions include anti-viral effects, the enhancement of natural killer (NK) or suppressor T cell activity and opposition to the effects of inflammatory cytokines. As vascular endothelial cells are active participants in inflammatory and demyelinating processes, we decided to examine the effects of IFN-beta on the expression of major histocompatibility complex (MHC) gene products and intercellular adhesion molecule (ICAM)-1 on human vascular endothelial cells (ECs). Human umbilical ECs demonstrated constitutive expression of ICAM-1 and MHC class I molecules but did not express MHC class II molecules. Basal expression of ICAM-1 molecules was enhanced by TNF alpha and to a lesser extent by IFN-beta, but was not affected by IFN-gamma. MHC class I expression on ECs was enhanced by IFN-beta, IFN-gamma, and tumor necrosis factor (TNF)-alpha. Furthermore, a synergistic effect was observed to combinations of these interacting cytokines. Incubation of ECs with IFN-gamma, but not IFN-beta, induced class II expression in a dose dependent manner. Moreover, co-incubation of ECs with IFN-beta and IFN-gamma resulted in significant down-regulation of class II molecules expression which was directly dependent on IFN-beta concentration. Northern blot analysis of DR alpha and Beta 2-microglobulin mRNA expression suggested that cytokine-mediated regulation of MHC molecules is at the transcriptional level, while modulation of ICAM-1 expression appears to be at the transcriptional as well as post-transcriptional level. Thus, our study demonstrated that IFN-beta and interacting cytokines exert complex immunoregulatory effects on endothelial cells with differential modulatory effects on various cell surface markers. Understanding the biological significance of these immunomodulatory effects mediated by IFN-beta may have important implications for cytokine-based strategies in the treatment of inflammatory and autoimmune diseases.

Cellular targets of exogenous tumour necrosis factor-alpha (TNF alpha) in human gliomas

To identify the cellular targets of TNF alpha in human gliomas, a total of 30 surgical specimens (12 glioblastomas, 4 anaplastic astrocytomas, 3 astrocytomas, 7 brains adjacent to tumour (BAT), 4 histologically normal-appearing brains) were examined by in vitro binding technique using biotinylated TNF alpha. The TNF-binding sites (TNF-BS) were recognized in the tumour cells in 8 of the 12 glioblastomas, 3 of the 4 anaplastic astrocytomas and in all the 3 astrocytomas. The TNF-BS were also recognized in the vascular endothelial cells in all these cases. The presence of TNF-BS in blood vessels ranged from 7.7 to 74.4% of the background vessels. This wide range of variation in the presence of TNF-BS within the tumour cells and tumour blood vessels may be relevant to the variable response of individual tumours to TNF alpha therapy. Since the tissue of normal brain, which lacks TNF-BS, might hardly be affected by this cytokine, administration of TNF alpha may be considered as an adjuvant therapy in selected groups of patients.

Time course of ICAM-1 expression and leukocyte subset infiltration in rat forebrain ischemia

The time course of ICAM-1 expression and leukocyte subset infiltration was studied in a model of CNS reperfusion injury in adult rats. Leukocyte adhesion and infiltration, mediated in part by intercellular adhesion molecule-1 (ICAM-1), appears to potentiate CNS reperfusion injury. The timing and relationship between ICAM-1 staining and leukocyte infiltration postglobal CNS ischemia is unknown. Reversible forebrain ischemia was produced in 32 adult Sprague-Dawley rats using the two-vessel occlusion model with histologic analysis performed at specific intervals postischemia: 1, 3, 6, 12, and 24 h, 4 and 7 d, or sham-operated controls (n = 4 each group). Monoclonal antibodies against ICAM-1 (1A29 and TM8), a specific granulocyte (PMN) (HIS48), and a specific monocyte/macrophage (M phi) (ED1) were used. No specific leukocyte and only rare ICAM-1 vessel immunoreactivity was observed in sham controls. ICAM-1: Significant expression in microvessels beginning at 1 h with additional diffuse CA1 pyramidal layer staining beginning at 4 d. Leukocytes: No PMN cells and rare M phi identified at 6 and 12 h. By 24 h: moderate infiltrate in areas of ICAM-1 expression of PMN and M phi. At 4 and 7 d: only M phi accumulation, cellular morphology now similar to microglia. The results of this study indicate that early and persistent ICAM-1 expression occurs following CNS ischemia with associated leukocyte infiltration.

Anti ICAM-1 (CD 54) monoclonal antibody reduces inflammatory changes in experimental bacterial meningitis

We investigated whether monoclonal antibodies directed against intracellular adhesion molecule 1 (ICAM-1 mAb) inhibit brain edema, increase of intracranial pressure (ICP), regional cerebral blood flow (rCBF) and recruitment of white blood cells (WBC) into the cerebrospinal fluid (CSF) in the rat model of the early phase of bacterial meningitis. Brain edema was assessed by brain water content determinations. rCBF measured by laser Doppler flowmetry and ICP were recorded continuously for 6 h after intracisternal challenge. Meningitis was induced with pneumococcal cell walls (PCW). Increase of ICP and brain water content were significantly inhibited (P <0.05) by intravenous treatment with ICAM-1 mAb (TM-8, 1 mg/kg). Furthermore, ICAM-1 mAb treatment profoundly attenuated (P <0.05) rCBF increase and WBC invasion into the CSF. These results suggest that the ICAM-1 pathway is critically involved in the early phase of bacterial meningitis.

Effects of TNF-alpha on the production of vasoactive substances by cerebral endothelial and smooth muscle cells in culture

The effects of tumor necrosis factor-alpha (TNF-alpha) on the production of the vasoactive substances nitric oxide (NO) and endothelin-1 (ET-1) were investigated in cerebrovascular cells in culture. Bovine cerebral endothelial cells (BCEC) stained positively for NADPH-diaphorase/NO synthase activity and spontaneously produced nitrite, a stable NO oxidation product, which accumulated in the culture medium in a linear way for 48 h. Low concentrations of TNF-alpha (0.5-2 ng/ml) significantly enhanced nitrite production after a 24-h incubation. Higher concentrations or longer exposure times resulted in a cytotoxic effect that altered cell morphology, released lactate dehydrogenase (LDH) to the culture medium, and reduced the protein content. Dexamethasone, but not the NO synthase inhibitor N-iminoethyl-L-ornithine (L-NIO), prevented the cytotoxic effect of TNF-alpha in BCEC. TNF-alpha also significantly enhanced nitrite production in bovine cerebral smooth muscle cells (BCSMC). The enhancement was detected at all times between 8 and 72 h and at all concentrations tested (2-100 ng/ml). Signs of cytotoxicity were not observed in BCSMC after incubation with TNF-alpha. ET-1 was constitutively secreted by BCEC. The production of ET-1 was stimulated by thrombin. TNF-alpha enhanced the release of ET-1 in BCEC, and this enhancement was not modified by the simultaneous addition of interferon-gamma (IFN-gamma). BCSMC did not produce ET-1, either spontaneously or in the presence of TNF-alpha, IFN-gamma, or of both together.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of acute phase gene expression by brain irradiation

PURPOSE

To investigate the in vivo acute phase molecular response of the brain to ionizing radiation.

METHODS AND MATERIALS

C3Hf/Sed/Kam mice were given midbrain or whole-body irradiation. Cerebral expression of interleukins (IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6), interferon (IFN-gamma), tumor necrosis factors (TNF-alpha and TNF-beta), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthetase (iNOS), von Willebrand factor (vWF), alpha 1-antichymotrypsin (EB22/5.3), and glial fibrillary acidic protein (GFAP) was measured at various times after various radiation doses by ribonuclease (RNase) protection assay. The effects of dexamethasone or pentoxifylline treatment of mice on radiation-induced gene expression were also examined.

RESULTS

Levels of TNF-alpha, IL-1 beta, ICAM-1, EB22/5.3 and to a lesser extent IL-1 alpha and GFAP, messenger RNA were increased in the brain after irradiation, whether the dose was delivered to the whole body or only to the midbrain. Responses were radiation dose dependent, but were not found below 7 Gy; the exception being ICAM-1, which was increased by doses as low as 2 Gy. Most responses were rapid, peaking within 4-8 h, but antichymotrypsin and GFAP responses were delayed and still elevated at 24 h, by which time the others had subsided. Pretreatment of mice with dexamethasone or pentoxifylline suppressed radiation-induced gene expression, either partially or completely. Dexamethasone was more inhibitory than pentoxifylline at the doses chosen.

CONCLUSIONS

The initial response of the brain to irradiation involves expression of inflammatory gene products, which are probably responsible for clinically observed early symptoms of brain radiotherapy. This mechanism explains the beneficial effects of the clinical use of steroids in such circumstances.

Intercellular adhesion molecule-1 (ICAM-1) upregulation in human brain tumors as an expression of increased blood-brain barrier permeability

The distribution of intercellular adhesion molecule (ICAM-1) binding sites was studied in the microvasculature of several types of human brain tumor biopsies (angioma, glioblastoma multiforme and meningioma). Immunoelectron microscopy was performed with the application of immuno-HRP or -gold probes using a pre-embedding technique. Ultrastructural analysis demonstrated a pronounced ICAM-1 upregulation on the luminal EC and/or perivascular surfaces. Reaction product for ICAM-1 was observed associated with some but not all blood vessels of the tumors examined. The strongest reaction product was noted associated with the angioma cases with lesser expression observed on the glioblastoma multiforme and meningioma cases. The reaction product using immuno-HRP probe was observed most pronounced on the luminal endothelial cell surface and also within vesiculo-tubular structures. Concentrated immunosignals with gold label were often expressed on EC microvilli. These data suggest that several types of brain tumors are actively involved in the process of upregulating ICAM-1, presumably for tumor cell adhesion and trafficking, the process of angiogenesis or both. We suggest that the ICAM-1-positive vesiculo-tubular structures reflect specialized, targeted regions on the ECs for tumor cell adhesion and eventual trans-BBB passage. Further, our studies also provide evidence that adhesion molecules may be a useful tool for the study of blood-brain barrier injury.

Adhesion molecule expression on murine cerebral endothelium following the injection of a proinflammagen or during acute neuronal degeneration

The acute inflammatory response in the murine CNS is different from that observed in other tissues. Few polymorphonuclear leukocytes are recruited to the brain parenchyma and there is a delay in the recruitment of monocytes. Leukocyte recruitment to sites of inflammation is dependent on adhesion molecules expressed on the endothelium. The atypical kinetics of leukocyte recruitment to the CNS may be the result of deficient or delayed adhesion molecule expression on the cerebral endothelium. Using immunohistochemistry, the present study demonstrates that following the intracranial injection of a proinflammagen, lipopolysaccharide, or following acute neuronal degeneration elicited with kainic acid, the adhesion molecules ICAM-1 and VCAM were readily upregulated on cerebral endothelium in a time course comparable with that demonstrated on non-CNS endothelium. Both molecules were expressed on vessels, irrespective of their size, at 24 h after kainic acid or 6 h after lipopolysaccharide injection but leukocyte recruitment was negligible. The expression of ICAM-1 was demonstrated not only on endothelium but also on microglia especially in response to nerve terminal degeneration. PECAM was constitutively expressed at high levels on cerebral endothelium and did not change during brain injury. However, PECAM was induced on astrocytes after lipopolysaccharide injection or during acute neuronal degeneration, the latter providing a particularly strong stimulus. This study indicates that the expression of these adhesion molecules on CNS endothelium is neither deficient or delayed and that they are unlikely to be limiting factors in leukocyte recruitment to the CNS.

Circulating selectin- and immunoglobulin-type adhesion molecules in acute ischemic stroke

BACKGROUND AND PURPOSE

Cellular adhesion molecules mediate adhesion between endothelial cells and leukocytes as a precondition for extravasation of leukocytes at sites of tissue injury. The pattern of release of circulating adhesion molecules has been characterized in patients with acute ischemic stroke.

METHODS

Serum concentrations of soluble selectin-type adhesion molecules (solube endothelial leukocyte adhesion molecule-1 [sELAM-1], soluble lymph node homing receptor [sL-selectin]) and immunoglobulin-type adhesion molecules (soluble vascular cell adhesion molecule-1 [sVCAM-1], soluble intercellular adhesion molecule-1 [sICAM-1]) were serially determined (at hours 4, 8, and 10 and at days 1, 3, and 5) in 22 patients with acute ischemic stroke. As control subjects, age- and sex-matched individuals with (n = 40) and without (n = 22) vascular risk factors were studied.

RESULTS

We observed increased concentrations of sICAM-1 and decreased levels of sL-selectin in patients with risk factors even in the absence of stroke. Patients with acute stroke had, in addition, an initial transient increase of sELAM-1 and a persistent increase of sVCAM-1.

CONCLUSIONS

The results suggest a chronic alteration of expression of adhesion molecules sICAM-1 and sL-selectin in subjects with risk factors for atherosclerosis; they also indicate acute changes of levels of sELAM-1 and sVCAM-1 in response to acute ischemic stroke. Determination of soluble adhesion molecules could allow in vivo monitoring of the initial steps of leukocyte-mediated brain damage in acute ischemic stroke.

Soluble forms of intercellular adhesion molecule-1 (ICAM-1) block lymphocyte attachment to cerebral endothelial cells

Serum levels of circulating ICAM-1 are increased in various disorders including inflammatory diseases of the central nervous system (CNS). We recently described an association between high sICAM-1 levels in the serum of patients with multiple sclerosis and disease activity. The functional consequences of increased circulating adhesion molecules are not fully understood. This may simply arise as a consequence of inflammation or may have immune modulating properties. ICAM-1 plays an important role in the recruitment of activated lymphocytes to sites of inflammation within the CNS. We therefore tested the ability of soluble forms of ICAM-1 to prevent adhesion of activated lymphocytes to cerebral endothelial cells. Mitogen-activated blood mononuclear cells (PBMC) as well as PBMCs from patients with active multiple sclerosis adhered to cerebral endothelial cell cultures in vitro. This adhesion could be blocked if lymphocytes were preincubated with a recombinant form of soluble ICAM-1. In addition, serum from patients with active multiple sclerosis and high sICAM-1 levels blocked adhesion in a dose-dependent manner which was abrogated by pre-adsorption to an anti ICAM-1 antibody. Since soluble forms of ICAM-1 are able to block lymphocyte adhesion to cerebral endothelial cells, they may provide new therapeutic tools to interfere with the pathogenesis of inflammatory diseases of the CNS.

Cerebral hypoxia-ischemia stimulates cytokine gene expression in perinatal rats

BACKGROUND AND PURPOSE

We tested the hypothesis that cerebral hypoxia-ischemia selectively stimulates interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) gene expression in brain regions susceptible to irreversible injury in perinatal rats.

METHODS

To elicit focal hypoxic-ischemic brain injury, 7-day-old perinatal (P7) rats were subjected to right carotid artery ligation followed by 3 hours of 8% O2 exposure and were killed 0 to 48 hours after hypoxia. Regional tissue IL-1 beta and TNF-alpha mRNA content were measured by reverse transcription followed by polymerase chain reaction amplification (RT-PCR) in samples prepared from cortex and hippocampus of the lesioned and contralateral hemispheres. cDNAs were amplified with primers specific for IL-1 beta, TNF-alpha, and the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which served as an internal control. The RT-PCR products were subjected to Southern blot analysis and hybridized with 32P-labeled gene-specific probes. Radioactivity was measured in excised bands, and results were normalized on the basis of levels of GAPDH expression.

RESULTS

In unlesioned P7 brain, IL-1 beta mRNA was barely detectable. In lesioned forebrain, there was a marked, transient stimulation of IL-1 beta mRNA expression, peaking at 4 hours after hypoxia. Hybridization signal was increased 16- to 30-fold over values from contralateral hemisphere samples in three independent assays (P < .05 comparing values in left and right cortex and in left and right hippocampus with the Kruskal-Wallis ranking test); by 24 hours after hypoxia, levels returned to normal. Similar transient increases in TNF-alpha mRNA expression were detected. In a closely related model of perinatal brain injury elicited by focal intracerebral N-methyl-D-aspartate injection, there was a corresponding acute stimulation of IL-1 beta and TNF-alpha mRNA expression at 4 hours after injection.

CONCLUSIONS

These results suggest that IL-1 beta and TNF-alpha may play important roles in the response of the developing brain to acute hypoxic-ischemic injury.

Signal transduction pathways in oligodendrocytes: role of tumor necrosis factor-alpha

We have used a combination of electrophysiological and biochemical approaches to investigate the effects and the mechanisms of action of tumor necrosis factor-alpha (TNF-alpha) on cultured oligodendrocytes (OLGs). Our studies have led to the following conclusions: (1) prolonged exposure of mature ovine OLGs to TNF-alpha leads to inhibition of process extension, membrane depolarization and a decrease in the amplitudes of both inwardly rectifying and outward K+ currents; (2) brief exposure of OLGs to TNF-alpha does not elicit membrane depolarization or consistent changes in cytosolic Ca2+ levels; (3) incubation of OLGs with TNF-alpha for 1 hr results in inhibition of phosphorylation of myelin basic protein and 2',3'-cyclic nucleotide phosphohydrolase. Ceramides, which have been shown to be effectors of TNF-alpha, are ineffective in inhibiting phosphorylation, whereas sphingomyelinase mimics TNF-alpha in this action. These observations suggest that other products of sphingomyelin hydrolysis may be the mediator(s) of TNF-alpha effect on protein phosphorylation. We have thus demonstrated that TNF-alpha can perturb the functions of OLGs via modulation of ion channels and of protein phosphorylation without necessarily inducing cell death. It is conceivable that modulation of ion channels and protein phosphorylation constitutes effective mechanisms for the participation of cytokines in signal transduction during myelination, demyelination and remyelination.

Chemokine expression in murine experimental allergic encephalomyelitis

Chemokines are a family of low molecular mass proteins with chemotactic and cell activating activities. Reverse transcription-polymerase chain reaction and Northern hybridization were used to examine their expression during murine experimental allergic encephalomyelitis (EAE), an autoimmune disease used as a model of multiple sclerosis. The mRNAs encoding RANTES, MIP-1 alpha, MIP-1 beta, TCA3 (I-309), IP-10, JE (MCP-1), KC (MGSA/gro), and MARC (MCP-3) were induced in the spinal cord 1-2 days before clinical signs were apparent. SDF, a cDNA predicted to encode a chemokine-like product, was expressed in normal as well as diseased spinal cords. No expression of C10 or MIP-2 was detected. Activated encephalitogenic T cells expressed message for RANTES, MIP-1 alpha, MIP-1 beta, and TCA3. These results define a subset of chemokines that may play an important role in the inflammatory process during murine EAE.

Selective binding of peripheral blood lymphocytes to the walls of cerebral vessels in frozen sections of human brain

In order to identify the factors that control the binding of blood leucocytes to cerebral blood vessels we have modified and applied the frozen section assay of Stamper and Woodruff to the study of human brain. Cryostat sections of brain tissue obtained at post mortem were overlaid with blood lymphocytes and experimental conditions were defined which permitted optimum binding of the cells to transected blood vessel walls. The maximal binding of lymphocytes to cerebral vessels occurred when 6 x 10(6) lymphocytes were overlaid onto brain sections for 30 min at 7 degrees C with gentle agitation. Only a small proportion (0.01%) of the added lymphocytes bound to exposed cerebral vessels. However, lymphocytes were far more adherent than monocytes and polymorphonuclear cells (7-fold and 11-fold respectively: p < 0.001) and activation of lymphocytes with IL-2 enhanced their binding to blood vessel walls (mean 130% increase; p < 0.03). Further analysis revealed that CD4-positive T lymphocytes were the predominant cell population binding to the blood vessels. Antibody blocking studies showed that lymphocyte binding to cerebral blood vessels was inhibited by pretreating the lymphocytes with anti-CD11a, anti-CD18 or anti-CD49d (p < or = 0.02) and immunohistochemical studies revealed the presence of the counter-receptors ICAM-1 (CD54) and VCAM-1 (CD106) for these adhesion molecules in addition to the presence of E-selectin (CD62E) and P-selectin (CD62P) on the cerebral blood vessels. The establishment of a technique in situ which measures selective binding of CD4-positive peripheral lymphocytes to sections of cerebral blood vessels will assist in the molecular characterization of factors that control the interaction of leucocytes with the blood-brain barrier in health and disease.

Cerebral endothelial cells are a major source for soluble intercellular adhesion molecule-1 in the human central nervous system

Immunohistological analysis of tissue sections from human brain revealed that intercellular adhesion molecule-1 (ICAM-1) is mainly expressed on endothelial cells of small vessels, including the subependymal vessels of the choroid plexus. In addition, it is expressed on cerebrospinal fluid (CSF) cells in patients with inflammatory diseases of the central nervous system. Stimulation of confluent monolayers of adult human cerebral endothelial cells with lipopolysaccharide (LPS) or recombinant human tumor necrosis factor-alpha (TNF-alpha) could induce expression and secretion of soluble ICAM-1 in a dose dependent manner. In addition, sICAM-1 was also present in the supernatant from U251 glioma cells. No sICAM was detected in the culture supernatant from activated blood or CSF lymphocytes. Cerebral endothelial cells are therefore a likely source for sICAM-1 in the CSF.

In vitro interaction of coronaviruses with primate and human brain microvascular endothelial cells

Primary human and primate brain microvascular endothelial cells were tested for permissiveness to coronaviruses JHM and 229E. While sub-genomic viral RNAs could be detected up to 72 hours post-infection, primate cells were abortively infected and neither virus caused cytopathology. Human cells were non-permissive for JHM but permissive for 229E replication; peak production of progeny 229E and observable cytopathic effects occurred approximately 22 and 32 hour post-infection, respectively. Using the criterion of cytopathology induction in infected endothelial cells, 229E was compared to other human RNA and DNA viruses. In addition, virus induced modulation of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and HLA I was monitored by immunostaining of infected cells.

Microvascular expression of MALA-2 correlates with in vivo lymphocyte trafficking and is preferentially enhanced in tumors by tumor necrosis factor-alpha and interleukin-1 alpha

The role of endothelial cell adhesion molecule expression in the immune response to tumors is unknown. We have investigated the expression of murine lymphocyte activation antigen (MALA-2), the murine equivalent of intercellular adhesion molecule-1 (ICAM-1), in blood vessels of normal murine tissues and in melanoma tumors and evaluated the relationship between MALA-2 expression and lymphocyte trafficking in vivo. C3H/HeN mice were injected both i.p. and s.c. with a clone of K-1735 syngeneic melanoma cells. Day 11 tumor-bearing mice were killed and vascular expression of MALA-2 was quantified using immunohistochemistry. MALA-2 expression was high in lung, liver and spleen and low in lymph node, small bowel, muscle and tumor. Systemic administration of either recombinant tumor necrosis factor alpha (rTNF alpha) or recombinant interleukin-1 alpha (rIL-1 alpha) over 2 days prior to organ harvest resulted in an increase in the number of tumor vessels expressing MALA-2, with no change in MALA-2 expression in other tissues. In vivo lymphocyte trafficking was evaluated using cultured, activated splenocytes radiolabeled with 111In. 111In-labeled splenocyte distribution correlated closely with MALA-2 expression, with high localization to spleen, liver and lung and poor localization to lymph node, small bowel, muscle and tumor. Systemic administration of rTNF alpha, but not rIL-1 alpha, resulted in a significant increase in 111In-labeled splenocyte distribution to tumor, but neither rTNF alpha nor IL-1 alpha altered 111In-labeled splenocyte distribution to normal organs. Our data demonstrate the in vivo pattern of vascular MALA-2 expression in normal murine tissues and tumors and suggest that the expression of MALA-2 can be preferentially enhanced in tumors by systemic administration of cytokines. Lymphocyte distribution in vivo correlates closely with the pattern of MALA-2 expression, and these data support the conclusion that MALA-2 plays an important role in the regulation of lymphocyte trafficking.

Upregulation of intercellular adhesion molecule 1 (ICAM-1) on brain microvascular endothelial cells in rat ischemic cortex

The expression of intercellular adhesion molecule 1 (ICAM-1) was studied in rat focal ischemic cortex. A significant increase in ICAM-1 mRNA expression in the ischemic cortex over levels in contralateral (nonischemic) site was observed by means of Northern blot analysis following either permanent or temporary occlusion with reperfusion of the middle cerebral artery (PMCAO or MCAO with reperfusion) in spontaneously hypertensive rats. In the ischemic cortex, levels of ICAM-1 mRNA increased significantly at 3 h (2.6-fold, n = 3, P < 0.05), peaked at 6 to 12 h (6.0-fold, P < 0.01) and remained elevated up to 5 days (2.5-fold, P < 0.05) after PMCAO. The profile of ICAM-1 mRNA expression in the ischemic cortex following MCAO with reperfusion was similar to that following PMCAO, except that ICAM-1 mRNA was significantly increased as early as 1 h (6.3-fold, n = 3, P < 0.05) and then gradually reached a peak at 12 h (12-fold, P < 0.01) after reperfusion. ICAM-1 mRNA expression in ischemic cortex following PMCAO was significantly greater in hypertensive rats than in two normotensive rat strains. Immunostaining using anti-ICAM-1 antibodies indicated that upregulated ICAM-1 expression was localized to endothelial cells of intraparenchymal blood vessels in the ischemic but not contralateral cortex. The data suggest that an upregulation of ICAM-1 mRNA and protein on brain capillary endothelium may play an important role in leukocyte migration into ischemic brain tissue.

Concomitant cortical expression of TNF-alpha and IL-1 beta mRNAs follows early response gene expression in transient focal ischemia

The expression of tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1 beta) mRNAs was significantly increased in the rat ischemic cortex following temporary occlusion of the middle cerebral artery (TMCAO) with reperfusion. Northern blot analysis demonstrated that the induction of TNF-alpha and IL-1 beta mRNAs occurred as early as 1 h after reperfusion, exhibiting a 4.6-fold increase (p < 0.05, n = 4) and 6.8-fold increase (p < 0.05, n = 4) in the ischemic cortex over control, respectively. TNF-alpha mRNA reached its peak at 3 h (8.0-fold, p < 0.05), whereas IL-1 beta mRNA reached its peak at 6 h (29.5-fold, p < 0.05). Both cytokine mRNA levels remained elevated for up to 2 d after reperfusion. In contrast to the time course of these cytokine mRNAs, c-fos and zif268 mRNAs, two early response genes, displayed a greater and earlier time-response profile. The early induction of c-fos and zif268 mRNAs in temporary brain ischemia with reperfusion suggests their roles in transcriptional regulation. The later concomitant expression of TNF-alpha and IL-1 beta suggests that these cytokines play an important role in the inflammatory response associated with focal ischemia.

Expression of ICAM-1, VCAM-1, L-selectin, and leukosialin in the mouse central nervous system during the induction and remission stages of experimental allergic encephalomyelitis

Adhesion molecules facilitate infiltration of leukocytes into the central nervous system (CNS) of mice with experimental allergic encephalomyelitis (EAE). Expression of the adhesion molecules ICAM-1 (CD54), VCAM-1 (CD106), L-selectin (CD62L), and leukosialin (CD43) was analyzed via immunocytochemistry 4-28 days after the injection of encephalitogen into EAE-susceptible SWXJ mice. Constitutive ICAM-1 expression on large-diameter CNS vessels was upregulated on post-injection days 8, 11, 14 and 18 (concurrent with de novo expression on smaller capillaries and glial cells), partially downregulated by day 23, and back to control levels by day 28. Constitutive VCAM-1 expression was upregulated by day 14 and back to control levels by day 28. Upregulation of ICAM-1 temporally coincided with the immigration of CD4+ lymphocytes and L-selectin+ leukocytes into the CNS, while downregulation coincided with their emigration. The infiltration of CD43+ leukocytes also coincided with the upregulation of vascular adhesion molecules, but CD43+ cells remained in the CNS after ICAM-1 and VCAM-1 had returned to control levels. Cellular infiltration and adhesion-molecule expression preceded EAE clinical symptoms by a minimum of 3 days, suggesting a causal role of adhesion molecules in the initiation of CNS inflammation. However, prophylactic injections of monoclonal antibodies against either ICAM-1, L-selectin, or CD43, did not ameliorate the clinical severity of EAE in this model.

Role of cell adhesion molecules in brain injury after transient middle cerebral artery occlusion in the rat

Activated neutrophils appear to be directly involved in tissue injury after focal cerebral ischemia and reperfusion. Intercellular adhesion molecules-1 (ICAM-1) and CD11/CD18 integrins have been implicated in ischemia-reperfusion induced neutrophil endothelial adhesion and transmigration. We therefore investigated the roles of CD11a/CD18 (LFA-1) and ICAM-1 in cerebral ischemia-reperfusion injury by using monoclonal antibodies, WT1 (anti-CD11a), WT3 (anti-CD18), and 1A29 (anti-ICAM-1). Rats were subjected to 1 h of middle cerebral artery occlusion (MCAO). Individual antibodies were administered at a dose of 5 mg/kg intraperitoneally at 15 min before ischemia and immediately after reperfusion. Rats were killed at 24 h after reperfusion, and brain edema, neutrophil infiltration and infarct size were measured. Sustained enhancement of ICAM-1 expression on capillaries was observed up to 24 h (beginning between 1 and 3 h after reperfusion). While, leukocytes began to infiltrate into the ischemic hemisphere between 6 and 12 h after reperfusion. Treatment with individual antibodies against cell adhesion molecules reduced edema formation and infarct size in addition to neutrophil accumulation 24 h after reperfusion. These results strongly implicate the invasion of neutrophils in the development of post-ischemic brain injury, and suggest that interactions between CD11a/CD18 and ICAM-1 contribute to neutrophil infiltration into the ischemic brain.