Andrzej Glabinski

Chemokines and chemokine receptors in inflammation of the nervous system: manifold roles and exquisite regulation

This article focuses on the production of chemokines by resident glial cells of the nervous system. We describe studies in two distinct categories of inflammation within the nervous system: immune-mediated inflammation as seen in experimental autoimmune encephalomyelitis (EAE) or multiple sclerosis (MS) and post-traumatic inflammation. We provide evidence that chemokines play a role in amplifying the inflammatory reaction in EAE (and, probably, MS). In the context of neural trauma, chemokines appear to be primary stimuli for leukocyte recruitment. Strikingly, expression of monocyte chemoattractant protein (MCP)-1 and interferon-gamma-inducible protein-10 (IP-10) are largely restricted to astrocytes or other glial cells in these diverse pathological states. The remainder of the review focuses on studies that address the molecular mechanisms which underlie transcriptional regulation of three astrocyte-derived chemokines: MCP-1, IP-10 and beta-R1/interferon-gamma-inducible T-cell chemoattractant (I-TAC). Based on these studies, we propose that the complex promoters of these genes are marvelously organized for flexible and efficient response to challenge. In the case of MCP-1, several different stimuli can elicit gene transcription, acting through a conserved mechanism that includes binding of inducible transcription factors and recruitment of the constitutive factor Sp1. For IP-10 and beta-R1/I-TAC, it appears that efficient gene transcription occurs only in highly inflammatory circumstances that produce aggregates of simultaneous stimuli. These characteristics, in turn, mirror the expression patterns of the endogenous genes: MCP-1 is expressed under a variety of circumstances, while IP-10 appears primarily during immune-mediated processes that feature exposure of resident neuroglia to high levels of inflammatory cytokines.

Chemokines and chemokine receptors in CNS pathology

Chemokines are small proinflammatory cytokineswhich stimulate migration of inflammatory cells invitro and in vivo. They can be divided according tostructure, function and gene localization into fourdifferent subfamilies. Chemokines have been as-cribed diverse additional functions, including reg-ulation of angiogenesis, control of cell proliferationand developmental tissue patterning.The suspicion that chemokines could be involvedin CNS pathology emerged from considering theirtarget-cell specificity, in light of the selectiverecruitment of leukocyte populations to the in-trathecal compartment in diverse disease processes.Initial studies of chemokine expression in the CNSwere performed in models including experimentalautoimmune encephalomyelitis (EAE), stroke andmeningitis. Early results from these investigationsprovided the exciting insight that parenchymal CNScells were among the most abundant sources ofchemokines, bothin vitro and in vivo. A landmarkobservation from Karpus et al (1995) was that EAEcould be abrogated by passive immunization withantibodies to a single chemokine, MIP-1a.Chemokine receptors have also found a place inthe unique pathologies of the nervous system.Evident relationships between chemokines thatfunction in specific processes and response byappropriate hematogenous receptor-bearing cellshave been demonstrated. Of more novelty (if lesswell understood) has been the finding that chemo-kine receptors such as CXCR4, CXCR2, CX3CR1 andthe Duffy antigen receptor for chemokines (DARC)are expressed by resident neuroepithelial cells.These varied observations point to a fascinating,diverse and complex array of biological roles forthese products in the CNS. Preliminary results inthis field are reviewed in this manuscript andsummarized in the Tables.

Prevention of chronic relapsing experimental autoimmune encephalomyelitis by soluble tumor necrosis factor receptor I

We have evaluated the effect of the type I (p-55, type beta) soluble tumor necrosis factor receptor (sTNFrI) in an animal model of multiple sclerosis. Experimental autoimmune encephalomyelitis (EAE) was induced in SJL/J mice by adoptive transfer of T lymphocytes sensitized to myelin basic protein (MBP). sTNFrI completely blocked both clinical signs of disease and pathological changes that included CNS demyelination and inflammatory cell infiltration. Effective inhibition of disease expression was obtained using several different regimens of subcutaneous (s.c.) injection. These included daily doses starting at day 0, every other day injections starting at day 0, daily doses starting on day 4, and two doses separated by 12 h on day 1 and 2. Furthermore, treatment with sTNFrI for 15 days completely protected these animals from the recurrent episodes of disease normally associated with adoptively transferred EAE. These findings suggest that TNF plays a major causative role in EAE and that the sTNFrI may prove to be a useful therapeutic approach in multiple sclerosis.

Expression of Chemokines RANTES, MIP-1α and GRO-α Correlates with Inflammation in Acute Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an investigator-initiated disorder that serves as an animal model for the common human demyelinating disease multiple sclerosis. Both diseases are typified by disseminated perivascular and submeningeal cuffs in the central nervous system (CNS). It was shown recently that chemokines are integral to the pathogenesis of EAE. In the present study we analyzed the gene expression of three chemokines, RANTES, MIP-1α and GRO-α, at the onset of acute EAE, and correlated that expression with the intensity of inflammatory changes in the CNS. We showed that all three chemokines are upregulated simultaneously with symptom onset of acute EAE, and that chemokine expression correlates with the intensity of inflammation in the CNS. This consistent relationship supports the hypothesis that chemokines are relevant to leukocyte accumulation in CNS parenchyma.

Chemokine expression in GKO mice (lacking interferon-gamma) with experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the central nervous system (CNS) considered to be an animal model for multiple sclerosis (MS). The detailed mechanism that specifies accumulation of inflammatory cells within the CNS in these conditions remains a subject of active investigation. Chemokines including IP-10, GRO-alpha, MCP-1 are produced in EAE tissues selectively by parenchymal astrocytes, but the regulatory stimuli that govern this expression remain undetermined. The unexpected occurrence of increased EAE susceptibility in Balb/c GKO mice (lacking IFN-gamma) offered an opportunity to examine the spectrum of chemokine expression during immune-mediated inflammation in the absence of a single regulatory cytokine. We found that chemokines MCP-1 and GRO-alpha were upregulated in the CNS of mice with EAE despite the GKO genotype. IP-10, which is highly expressed in the CNS of mice with an intact IFN-gamma gene and EAE, was strikingly absent. In vitro experiments confirmed that IFNgamma selectively stimulates astrocytes for IP-10 expression. These results indicate that IP-10 is dependent upon IFN-gamma for its upregulation during this model disease, and document directly that astrocyte expression of chemokines during EAE is governed by pro-inflammatory cytokines.

Regulation and function of central nervous system chemokines.

In this paper, we discuss the potential involvement of a new family of cytokines, termed chemokines, in CNS inflammatory pathology. Chemokines are a family of proinflammatory cytokines which are able to stimulate target‐cell‐specific directional migration of leukocytes. Because of this feature, chemokines may be potent mediators of inflammatory processes. We have previously reported observations indicating that chemokines may be involved in the process of lesion formation during autoimmune inflammation within CNS, and, in particular, are likely participants in the process of influx of inflammatory cells into the CNS parenchyma. We observed also that mechanical injury of brain and subsequent post‐traumatic inflammation may in part be mediated by chemokines. Chemokines undoubtedly co‐operate with cell‐associated adhesion molecules during recruitment of leukocytes from blood to CNS. The sequential expression of soluble and membrane‐bound signals for leukocyte migration is an intricate process that can be interrupted by a variety of strategies. Our data suggest that chemokines may represent a promising target for future therapy of inflammatory conditions, including CNS inflammation resulting from varied insults.

Expression of monocyte chemoattractant protein (MCP-1) and nitric oxide synthase-2 following cerebral trauma

Abstract Traumatic injury to the brain initiates multiple interrelated processes that involve parenchymal, vascular, and infiltrating inflammatory cells. Nitric oxide (NO) and chemokines have been implicated as regulators of the central nervous system injury response. Following a cryogenic lesion of the cerebral cortex in mice, mRNA for NO synthase (NOS)-2 was detected by reverse transcriptase polymerase chain reaction ipsilaterally 12 h after injury and persisted for 2 weeks. While mRNA was also detected contralaterally, the time course of expression was shorter (1 week). By immunohistochemistry, NOS-2 protein was initially detected ipsilaterally 12 h after injury in infiltrating inflammatory cells. Astroglial cells expressed NOS-2 from 24 to 72 h after injury. The expression of monocyte chemoattractant protein (MCP-1) mRNA peaked at 6 h on the lesion side, remained for 24 h and then declined by 48 h. On the unlesioned side, MCP-1 mRNA was expressed to a much lesser extent and had declined by 24 h. The up-regulation of MCP-1 was relatively specific as a closely related mRNA encoding IP-10 was not significantly increased. These findings implicate a role for NOS-2 and MCP-1 as potential regulators of cellular events following cryogenic cerebral trauma.

Treatment with BBB022A or rolipram stabilizes the blood-brain barrier in experimental autoimmune encephalomyelitis: an additional mechanism for the therapeutic effect of type IV phosphodiesterase inhibitors

We examined the treatment effects of two structurally distinct phosphodiesterase type IV (PDE IV) inhibitors, BBB022 and rolipram, in murine and rat models of experimental autoimmune encephalomyelitis (EAE). Based on our data, we propose a mechanism of action which may supplement immunomodulatory effects of PDE IV inhibitors. In particular, PDE inhibitors promote elevation of intracellular cAMP levels, increasing the electrical resistance of endothelial monolayers by stabilizing intercellular junctional complexes. Such an effect on central nervous system (CNS) vascular endothelium has the potential to reduce disease severity in EAE, because both inflammatory cells and humoral factors readily cross a disrupted blood-brain barrier (BBB). In this report, we demonstrate the capacity of BBB022 and rolipram to decrease clinical severity of EAE. further, PDE IV inhibitors significantly reduced BBB permeability in the spinal cords of mice with EAE. These results provide evidence that PDE IV-inhibitors may exert therapeutic effects in EAE by modifying cerebrovascular endothelial permeability, reducing tissue edema as well as entry of inflammatory cells and factors.

Chemokine Upregulation Follows Cytokine Expression in Chronic Relapsing Experimental Autoimmune Encephalomyelitis

Chronic relapsing experimental autoimmune encephalomyelitis (ChREAE) is an autoimmune disease of the central nervous system (CNS) induced by CNS myelin components. In the early active stage, both ChREAE and multiple sclerosis (MS) are characterized by the presence of perivascular inflammatory cuffs disseminated in the CNS. There is growing evidence that chemoattractant cytokines (chemokines) play an important role in this process. The main goal of the present study was to analyse the hypothesis that chemokine expression in the CNS during autoimmune inflammation is regulated by proinflammatory cytokines. To address this concept, we analysed temporal relations between chemokine and cytokine expression during ChREAE. Phasic upregulation of gene expression for chemokines T‐cell activation gene 3 (TCA‐3)/CCL1, monocyte chemoattractant protein‐1 (MCP‐1)/CCL2, macrophage inflammatory protein‐1 alpha (MIP‐1α)/CCL3, MIP‐1β/CCL4, regulated on activation normal T cell expressed and secreted (RANTES)/CCL5 and MIP‐2/CXCL2–3 as well as cytokines tumour necrosis factor‐α (TNF‐α), ‐β, LT‐β, interferon‐γ (IFN‐γ) and transforming growth factor‐β1 (TGF‐β1) in the CNS was observed during attacks of ChREAE. Expression of cytokines TNF‐β and LT‐β preceded, and the expression of TGF‐β1 followed chemokine upregulation. Our results suggest that chemokine expression during CNS autoimmune inflammation may be regulated by some proinflammatory cytokines.

TNF-α microinjection upregulates chemokines and chemokine receptors in the central nervous system without inducing leukocyte infiltration

Chemokines (chemoattractant cytokines) are key players in the initiation of inflammatory cell accumulation in the central nervous system (CNS). Mechanisms leading to upregulation of chemokines in CNS pathologic conditions remain largely unknown. Numerous in vitro studies showed that inflammatory cytokines stimulate cultured CNS cells to produce chemokines. The main goal of this study was to analyze if an individual proinflammatory cytokine is sufficient to upregulate the chemokine system in the adult CNS in vivo. We analyzed CC chemokine ligand and receptor expression in brains from two different strains of mice (SJL and BALB) after stereotaxic, intracerebral injection of tumor necrosis factor-alpha (TNF-alpha). In both strains, we detected similarly increased expression of chemokines RANTES/CCL5, macrophage inflammatory protein-1alpha (MIP-1alpha)/CCL3, MIP-1beta/CCL4, and MIP-2, as well as chemokine receptors CCR1, CCR2, and CCR5. Interestingly, we did not observe parenchymal leukocyte infiltrates after local TNF-alpha delivery. This observation shows that upregulation of chemokines by TNF-alpha is not sufficient to cause accumulation of leukocytes in the CNS parenchyma in both strains of mice.