Marie Tani

Expression of specific chemokines and chemokine receptors in the central nervous system of multiple sclerosis patients

Chemokines direct tissue invasion by specific leukocyte populations. Thus, chemokines may play a role in multiple sclerosis (MS), an idiopathic disorder in which the central nervous system (CNS) inflammatory reaction is largely restricted to mononuclear phagocytes and T cells. We asked whether specific chemokines were expressed in the CNS during acute demyelinating events by analyzing cerebrospinal fluid (CSF), whose composition reflects the CNS extracellular space. During MS attacks, we found elevated CSF levels of three chemokines that act toward T cells and mononuclear phagocytes: interferon-gamma-inducible protein of 10 kDa (IP-10); monokine induced by interferon-gamma (Mig); and regulated on activation, normal T-cell expressed and secreted (RANTES). We then investigated whether specific chemokine receptors were expressed by infiltrating cells in demyelinating MS brain lesions and in CSF. CXCR3, an IP-10/Mig receptor, was expressed on lymphocytic cells in virtually every perivascular inflammatory infiltrate in active MS lesions. CCR5, a RANTES receptor, was detected on lymphocytic cells, macrophages, and microglia in actively demyelinating MS brain lesions. Compared with circulating T cells, CSF T cells were significantly enriched for cells expressing CXCR3 or CCR5. Our results imply pathogenic roles for specific chemokine-chemokine receptor interactions in MS and suggest new molecular targets for therapeutic intervention.

Astrocyte expression of mRNA encoding cytokines IP-10 and JE/MCP-1 in experimental autoimmune encephalomyelitis.

Mononuclear leukocytes preferentially accumulate in the central nervous system (CNS) during the course of experimental autoimmune encephalomyelitis (EAE). To address factors that govern leukocyte trafficking in EAE, we monitored expression of nxRNAs encoding IP‐10 and JE/MCP‐1, which are members of a family of chemoattractant cytokines. A transient burst of IP‐10 and JE/MCP‐1 mRNA accumulation in the CNS occurred, in close relation to the onset of histologic and clinical disease. In situ hybridizations showed, unexpectedly, that astrocytes were the major source of mRNAs encoding IP‐10 and JE/MCP‐1. These observations implicate astrocyte‐derived cytokines as potential chemoattractants for inflammatory cells during EAE.—Ransohoff, R. M., Hamilton, T. A., Tani, M., Stoler, M. H., Shick, H. E., Major, J. A., Estes, M. L., Thomas, D. M., Tuohy, V. K. Astrocyte expression of mRNA encoding cytokines IP‐10 and JE/MCP‐1 in experimental autoimmune encephalomyelitis. FASEB J. 7: 592‐600; 1993.

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.

Do chemokines mediate leukocyte recruitment in post-traumatic CNS inflammation?

Hematogenous leukocytes infiltrate the CNS after inflammatory stimuli, including infection, mechanical trauma and excitotoxic neuronal necrosis. However,the role of leukocytic inflammation in promoting or hindering tissue repair is poorly understood. Identification of signals that lead to leukocyte recruitment and activation is essential for the designing of interventions that modulate inflammation, thus improving neurological outcome. Chemokines are small pleiotropic chemoattractant cytokines whose target specificity suggests an important role in determining the cellular composition of inflammatory infiltrates. Chemokine expression profiles in the CNS during autoimmune and post-traumatic inflammation correlate well with the composition of leukocyte infiltrates, and expression studies in systems such as transgenic mice, suggest that chemokines have potent functional attributes in CNS physiology. We propose that selective chemokine expression by CNS cells is crucial for post-traumatic leukocyte accumulation.

Selective chemokine mRNA accumulation in the rat spinal cord after contusion injury

Following traumatic injury to the spinal cord, hematogenous inflammatory cells including neutrophils, monocytes, and lymphocytes infiltrate the lesion in a distinct temporal sequence. To examine potential mechanisms for their recruitment, we measured chemokine mRNAs in the contused rat spinal cord, using specific and sensitive reverse transcriptase polymerase chain reaction (RT‐PCR) dot‐blot hybridization assays. The neutrophil chemoattractant GRO‐α was 30‐fold higher than control values at 6 hr postinjury and decayed rapidly thereafter. LIX, a highly related α‐chemokine, also was elevated early postinjury. Monocyte chemoattractant peptide (MCP)‐1 and MCP‐5 mRNAs, potent chemoattractants for monocytes, were significantly elevated at the lesion epicenter at 12 and 24 hr postinjury and declined thereafter. Interferon‐γ‐inducible protein, 10 kDa (IP‐10), chemoattractant towards activated T‐lymphocytes, was significantly elevated at 6 and 12 hr postinjury. The dendritic cell chemoattractant MIP‐3α also was increased, perhaps contributing to the development of T‐cell autoreactivity to neural components after spinal cord injury (SCI) in rats. Other β‐chemokines, including MIP‐1α and RANTES (regulated on expression normal T‐cell expressed and secreted), were minimally affected by SCI. Expression of chemokines, therefore, directly precedes the influx of target neutrophils, monocytes, and T‐cells into the spinal cord postinjury, as noted previously. Thus, selective chemokine expression may be integral to inflammatory processes within the injured spinal cord as a mechanism of recruitment for circulating leukocytes. J. Neurosci. Res. 53:368–376, 1998.

Neutrophil infiltration, glial reaction, and neurological disease in transgenic mice expressing the chemokine N51/KC in oligodendrocytes

Chemokines (pro-inflammatory chemoattractant cytokines) are expressed in pathological conditions of the central nervous system (CNS). Previous studies suggested that the CNS is relatively resistant to leukocyte diapedesis after chemokine injection, leaving their functional role unresolved. The CNS function of N51/KC, a neutrophil-selective chemokine, was addressed by expressing N51/KC under control of the myelin basic protein (MBP) promoter in transgenic (tg) mice (MBP-N51/KC mice). CNS-specific N51/KC expression produced remarkable neutrophil infiltration into perivascular, meningeal, and parenchymal sites, demonstrating that this chemokine exerts the multiple functions in vivo required to recruit leukocytes into the CNS. MBP-N5 1/KC mice represent an incisive model for the molecular dissection of neutrophil entry into the CNS. Unexpectedly, MBP-N51/KC mice developed a neurological syndrome of pronounced postural instability and rigidity at high frequency beginning at 40 days of age, well after peak chemokine expression. 68/182 mice in one tg fine were found dead before one year of age, with prominent neurological symptoms premortem in 26 (38%). Florid microglial activation and blood-brain barrier disruption without dysmyelination were the major neuropathological alterations. Late-onset neurological symptoms in MBP-N51/KC mice may indicate unanticipated consequences of CNS chemokine expression.

Chronic expression of monocyte chemoattractant protein-1 in the central nervous system causes delayed encephalopathy and impaired microglial function in mice

Increased central nervous system (CNS) levels of monocyte chemoattractant protein 1 [CC chemokine ligand 2 (CCL2) in the systematic nomenclature] have been reported in chronic neurological diseases such as human immunodeficiency virus type 1‐associated dementia, amyotrophic lateral sclerosis, and multiple sclerosis. However, a pathogenic role for CCL2 has not been confirmed, and there is no established model for the effects of chronic CCL2 expression on resident and recruited CNS cells. We report that aged (>6 months) transgenic (tg) mice expressing CCL2 under the control of the human glial fibrillary acidic protein promoter (huGFAP‐CCL2hi tg+ mice) manifested encephalopathy with mild perivascular leukocyte infiltration, impaired blood brain barrier function, and increased CD45‐immunoreactive microglia, which had morphologic features of activation. huGFAP‐CCL2hi tg+ mice lacking CC chemokine receptor 2 (CCR2) were normal, showing that chemokine action via CCR2 was required. Studies of cortical slice preparations using video confocal microscopy showed that microglia in the CNS of huGFAP‐CCL2hi tg+ mice were defective in expressing amoeboid morphology. Treatment with mutant CCL2 peptides, a receptor antagonist and an obligate monomer, also suppressed morphological transformation in this assay, indicating a critical role for CCL2 in microglial activation and suggesting that chronic CCL2 exposure desensitized CCR2 on microglia, which in the CNS of huGFAP‐CCL2hi tg+ mice, did not up‐regulate cell‐surface expression of major histocompatibility complex class II, CD11b, CD11c, or CD40, in contrast to recruited perivascular macrophages that expressed enhanced levels of these markers. These results indicate that huGFAP‐CCL2hi tg+ mice provide a useful model to study how chronic CNS expression of CCL2 alters microglial function and CNS physiology.—Huang, D., Wujek, J., Kidd, G., He, T. T., Cardona, A., Sasse, M. E., Stein, E. J., Kish, J., Tani, M., Charo, I. F., Proudfoot, A. E., Rollins, B. J., Handel, T., Ransohoff, R. M. Chronic expression of monocyte chemoattractant protein‐1 in the central nervous system causes delayed encephalopathy and impaired microglial function in mice. FASEB J. 19, 761–772 (2005)

Astrocytes as antigen-presenting cells: expression of IL-12/IL-23

Interleukin‐12 (IL‐12, p70) a heterodimeric cytokine of p40 and p35 subunits, important for Th1‐type immune responses, has been attributed a prominent role in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Recently, the related heterodimeric cytokine, IL‐23, composed of the same p40 subunit as IL‐12 and a unique p19 subunit, was shown to be involved in Th1 responses and EAE. We investigated whether astrocytes and microglia, CNS cells with antigen‐presenting cell (APC) function can present antigen to myelin basic protein (MBP)‐reactive T cells, and whether this presentation is blocked with antibodies against IL‐12/IL‐23p40. Interferon (IFN)‐γ‐treated APC induced proliferation of MBP‐reactive T cells. Anti‐IL‐12/IL‐23p40 antibodies blocked this proliferation. These results support and extend our previous observation that astrocytes and microglia produce IL‐12/IL‐23p40. Moreover, we show that stimulated astrocytes and microglia produce biologically active IL‐12p70. Because IL‐12 and IL‐23 share p40, we wanted to determine whether astrocytes also express IL‐12p35 and IL‐23p19, as microglia were already shown to express them. Astrocytes expressed IL‐12p35 mRNA constitutively, and IL‐23 p19 after stimulation. Thus, astrocytes, under inflammatory conditions, express all subunits of IL‐12/IL‐23. Their ability to present antigen to encephalitogenic T cells can be blocked by neutralizing anti‐IL‐12/IL‐23p40 antibodies.

Do Chemokines Mediate Inflammatory Cell Invasion of the Central Nervous System Parenchyma

Inflammatory cell recruitment into the central nervous system (CNS) is a critical step in the response to diverse insults, including infection, trauma and infarction, as well as immune‐mediated disorders such as multiple sclerosis (MS). Despite considerable advances in understanding immune surveillance and antigen recognition in the CNS, the signals resulting in parenchymal inflammation are incompletely understood. Members of a novel family of chemo‐attractant cytokines, the chemokines, are made in the CNS and are emerging as likely mediators of inflammatory cell migration into the CNS.

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.