Sequential expression of chemokines in experimental autoimmune neuritis

Antibiotics-Induced Intestinal Immunomodulation Attenuates Experimental Autoimmune Neuritis (EAN)

BACKGROUND

The composition of gut microbiota plays a pivotal role in priming the immune system and thus impacts autoimmune diseases. Data on the effects of gut bacteria eradication via systemic antibiotics on immune neuropathies are currently lacking. This study therefore assessed the effects of antibiotics-induced gut microbiota alterations on the severity of experimental autoimmune neuritis (EAN), a rat model of Guillain-Barré Syndrome (GBS). Myelin P0 peptide 180-199 (P0 180-199)-induced EAN severity was compared between adult Lewis rats (12 weeks old) that received drinking water with or without antibiotics (colistin, metronidazole, vancomycin) and healthy rats, beginning antibiotics treatment immediately after immunization (day 0), and continuing treatment for 14 consecutive days. Neuropathy severity was assessed via a modified clinical score, and then related to gut microbiota alterations observed after fecal 16S rRNA gene sequencing at baseline and after EAN induction. Effectors of gut mucosal and endoneurial immunity were assessed via immunostaining. EAN rats showed increased gut mucosal permeability alongside increased mucosal CD8+ T cells compared to healthy controls. Antibiotics treatment alleviated clinical EAN severity and reduced endoneurial T cell infiltration, decreased gut mucosal CD8+ T cells and increased gut bacteria that may be associated with anti-inflammatory mechanisms, like Lactobacillus or Parasutterella. Our findings point out a relation between gut mucosal immunity and the pathogenesis of EAN, and indicate that antibiotics-induced intestinal immunomodulation might be a therapeutic approach to alleviate autoimmunity in immune neuropathies. Further studies are warranted to evaluate the clinical transferability of these findings to patients with GBS.

CCL2 Knockdown Attenuates Inflammatory Response After Spinal Cord Injury Through the PI3K/Akt Signaling Pathway: Bioinformatics Analysis and Experimental Validation

Spinal cord injury (SCI) is a common clinical problem in orthopedics with a lack of effective treatments and drug targets. In the present study, we performed bioinformatic analysis of SCI datasets GSE464 and GSE45006 in the Gene Expression Omnibus (GEO) public database and experimentally validated CCL2 expression in an animal model of SCI. This was followed by stimulation of PC-12 cells using hydrogen peroxide to construct a cellular model of SCI. CCL2 expression was knocked down using small interfering RNA (si-CCL2), and PI3K signaling pathway inhibitors and activators were used to validate and observe the changes in downstream inflammation. Through data mining, we found that the inflammatory chemokine CCL2 and PI3K/Akt signaling pathways after SCI expression were significantly increased, and after peroxide stimulation of PC-12 cells with CCL2 knockdown, their downstream cellular inflammatory factor levels were decreased. The PI3K/Akt signaling pathway was blocked by PI3K inhibitors, and the downstream inflammatory response was suppressed. In contrast, when PI3K activators were used, the inflammatory response was enhanced, indicating that the CCL2-PI3K/Akt signaling pathway plays a key role in the regulation of the inflammatory response. This study revealed that the inflammatory chemokine CCL2 can regulate the inflammatory response of PC-12 cells through the PI3K/Akt signaling pathway, and blocking the expression of the inflammatory chemokine CCL2 may be a promising strategy for the treatment of secondary injury after SCI.

Extensive cytokine biomarker analysis in serum of Guillain-Barré syndrome patients

Guillain-Barré syndrome (GBS) is an acute idiopathic polyneuropathy which is related to infection and immune mechanism. The exact pathogenesis of the disease is unknown and treatment is limited. Thus, the purpose of the study is to identify biomarkers of GBS serum and elucidate their involvement in the underlying pathogenesis of GBS that could help to treat GBS more accurately. Antibody array technology was used to detect the expression levels of 440 proteins in serum of 5 GBS group and 5 healthy control group. Sixty-seven differentially expressed proteins (DEPs) were identified by antibody array, among which FoLR1, Legumain, ErbB4, IL-1α, MIP-1α and IGF-2 were down-regulated, while 61 proteins were up-regulated. Bioinformatics analysis indicated that most DEPs were associated with leukocytes, among which IL-1α, SDF-1b, B7-1, CD40, CTLA4, IL-9, MIP-1α and CD40L were in the center of protein-protein interaction (PPI) network. Subsequently, the ability of these DEPs to distinguish GBS from healthy control was further evaluated. CD23 was identified by means of Random Forests Analysis (RFA) and verified by enzyme-linked immunosorbent assay (ELISA). The ROC curve result of CD23 respectively displayed that its sensitivity, specificity and AUC were 0.818, 0.800 and 0.824. We speculate that activation of leukocyte proliferation and migration in circulating blood might be associated with inflammatory recruitment of peripheral nerves, leading to the occurrence and development of GBS, but this conclusion still requires deeper confirmation. More importantly, central proteins may play a pivotal role in the pathogenesis of GBS. In addition, we detected IL-1α, IL-9, and CD23 in the serum of GBS patients for the first time, which may be promising biomarkers for the treatment of GBS.

Immune-Mediated Neuropathies: Pathophysiology and Management

Dysfunction of the immune system can result in damage of the peripheral nervous system. The immunological mechanisms, which include macrophage infiltration, inflammation and proliferation of Schwann cells, result in variable degrees of demyelination and axonal degeneration. Aetiology is diverse and, in some cases, may be precipitated by infection. Various animal models have contributed and helped to elucidate the pathophysiological mechanisms in acute and chronic inflammatory polyradiculoneuropathies (Guillain-Barre Syndrome and chronic inflammatory demyelinating polyradiculoneuropathy, respectively). The presence of specific anti-glycoconjugate antibodies indicates an underlying process of molecular mimicry and sometimes assists in the classification of these disorders, which often merely supports the clinical diagnosis. Now, the electrophysiological presence of conduction blocks is another important factor in characterizing another subgroup of treatable motor neuropathies (multifocal motor neuropathy with conduction block), which is distinct from Lewis-Sumner syndrome (multifocal acquired demyelinating sensory and motor neuropathy) in its response to treatment modalities as well as electrophysiological features. Furthermore, paraneoplastic neuropathies are also immune-mediated and are the result of an immune reaction to tumour cells that express onconeural antigens and mimic molecules expressed on the surface of neurons. The detection of specific paraneoplastic antibodies often assists the clinician in the investigation of an underlying, sometimes specific, malignancy. This review aims to discuss the immunological and pathophysiological mechanisms that are thought to be crucial in the aetiology of dysimmune neuropathies as well as their individual electrophysiological characteristics, their laboratory features and existing treatment options. Here, we aim to present a balance of discussion from these diverse angles that may be helpful in categorizing disease and establishing prognosis.

Notch signaling dependent monocyte conversion alleviates immune-mediated neuropathies by regulating RBP-J/NR4A1 axis

Monocytes in peripheral blood and sciatic nerves play vital roles in immune-mediated neuropathies such as Guillain-Barré syndrome (GBS). Different subpopulations of monocytes, including classical and non-classical, exhibit distinct functions as well as phenotypic conversion potentials. However, the mechanisms underlying their development during immune-mediated neuropathy remain unclear. Notch signaling participates in monocyte differentiation and function. In this study, we used a myeloid-specific Notch signaling activation transgenic mouse (NIC^cA) and investigated the role of Notch signaling in monocytes during experimental autoimmune neuritis (EAN) in a mouse model of GBS. Clinical score assessment and histopathological examination revealed that sciatic nerve injury was attenuated in NIC^cA EAN mice compared to that in control mice. Flow cytometry and immunofluorescence staining suggested that increasing Ly6C^lo monocytes in the peripheral blood and nerve tissue might contribute to the alleviation of neuritis in NIC^cA mice. Meanwhile, an in vitro study suggested that bone marrow-derived monocytes from NIC^cA mice are more inclined toward Ly6C^lo cells than Ly6C^hi cells. Differential expression of monocyte development-associated genes was detected in NIC^cA and wild-type mice using RNA sequencing. The expression of Nr4a1 is upregulated remarkably when Notch signaling is activated. Treatment with Nr4a1 antagonist on NIC^cA mice-derived monocytes compromise their Ly6C^lo tendency. Consistently, a relationship between monocyte conversion and disease severity was observed in blood samples from patients with GBS. In conclusion, our current study showed that monocyte conversion modulated by Notch signaling plays an essential role in the EAN mouse model.

CX3CR1 But Not CCR2 Expression Is Required for the Development of Autoimmune Peripheral Neuropathy in Mice

One hallmark of Guillain-Barre syndrome (GBS), a prototypic autoimmune peripheral neuropathy (APN) is infiltration of leukocytes (macrophages and T cells) into peripheral nerves, where chemokines and their receptors play major roles. In this study, we aimed to understand the potential contribution of chemokine receptors CCR2 and CX3CR1 in APN by using a well-established mouse model, B7.2 transgenic (L31) mice, which possesses a predisposed inflammatory background. We crossbred respectively CCR2KO and CX3CR1KO mice with L31 mice. The disease was initiated by partial ligation on one of the sciatic nerves. APN pathology and neurological function were evaluated on the other non-ligated sciatic nerve/limb. Our results revealed that L31/CX3CR1KO but not L31/CCR2KO mice were resistant to APN. CX3CR1 is needed for maintaining circulating monocyte and CD8⁺ T cell survival. While migration of a significant number of activated CD8⁺ T cells to peripheral nerves is essential in autoimmune response in nerve, recruitment of monocytes into PNS seems optional. Disease onset is independent of CCR2 mediated blood-derived macrophage recruitment, which can be replaced by compensatory proliferation of resident macrophages in peripheral nerve. CX3CR1 could also contribute to APN via its critical involvement in maintaining nerve macrophage phagocytic ability. We conclude that blockade of CX3CR1 signaling may represent an interesting anti-inflammatory strategy to improve therapeutic management for GBS patients.

Ultrastructural characterization of mitochondrial damage in experimental autoimmune neuritis

Data are sparse about mitochondrial damage in GBS and in its most frequently employed animal model, experimental autoimmune neuritis (EAN). We here characterized changes in mitochondrial content and morphology at different time points during EAN by use of ultrastructural imaging and immunofluorescent labelling. Histological examination revealed that demyelinated axons and their adjacent Schwann cells showed reduced mitochondrial content and remaining mitochondria appeared swollen with greater diameter in Schwann cells and unmyelinated axons. Our findings indicate that in EAN, particularly mitochondria in Schwann cells are damaged. Further studies are warranted to address whether these changes are amenable to novel, mitoprotective treatments.

Evidence for a dynorphin-mediated inner ear immune/inflammatory response and glutamate-induced neural excitotoxicity: an updated analysis

Acoustic overstimulation (AOS) is defined as the stressful overexposure to high-intensity sounds. AOS is a precipitating factor that leads to a glutamate (GLU)-induced Type I auditory neural excitotoxicity and an activation of an immune/inflammatory/oxidative stress response within the inner ear, often resulting in cochlear hearing loss. The dendrites of the Type I auditory neural neurons that innervate the inner hair cells (IHCs), and respond to the IHC release of the excitatory neurotransmitter GLU, are themselves directly innervated by the dynorphin (DYN)-bearing axon terminals of the descending brain stem lateral olivocochlear (LOC) system. DYNs are known to increase GLU availability, potentiate GLU excitotoxicity, and induce superoxide production. DYNs also increase the production of proinflammatory cytokines by modulating immune/inflammatory signal transduction pathways. Evidence is provided supporting the possibility that the GLU-mediated Type I auditory neural dendritic swelling, inflammation, excitotoxicity, and cochlear hearing loss that follow AOS may be part of a brain stem-activated, DYN-mediated cascade of inflammatory events subsequent to a LOC release of DYNs into the cochlea. In support of a DYN-mediated cascade of events are established investigations linking DYNs to the immune/inflammatory/excitotoxic response in other neural systems.

Predicting the Response to Intravenous Immunoglobulins in an Animal Model of Chronic Neuritis

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a disabling autoimmune disorder of the peripheral nervous system (PNS). Intravenous immunoglobulins (IVIg) are effective in CIDP, but the treatment response varies greatly between individual patients. Understanding this interindividual variability and predicting the response to IVIg constitute major clinical challenges in CIDP. We previously established intercellular adhesion molecule (ICAM)-1 deficient non-obese diabetic (NOD) mice as a novel animal model of CIDP. Here, we demonstrate that similar to human CIDP patients, ICAM-1 deficient NOD mice respond to IVIg treatment by clinical and histological measures. Nerve magnetic resonance imaging and histology demonstrated that IVIg ameliorates abnormalities preferentially in distal parts of the sciatic nerve branches. The IVIg treatment response also featured great heterogeneity allowing us to identify IVIg responders and non-responders. An increased production of interleukin (IL)-17 positively predicted IVIg treatment responses. In human sural nerve biopsy sections, high numbers of IL-17 producing cells were associated with younger age and shorter disease duration. Thus, our novel animal model can be utilized to identify prognostic markers of treatment responses in chronic inflammatory neuropathies and we identify IL-17 production as one potential such prognostic marker.

Schwann cell differentiation inhibits interferon-gamma induction of expression of major histocompatibility complex class II and intercellular adhesion molecule-1

Interferon-gamma (IFN-γ) upregulates major histocompatibility complex class II (MHC class II) antigens and intercellular adhesion molecule-1 (ICAM-1) on Schwann cells (SC) in vitro, but in nerves of animals and patients MHC class II is primarily expressed on inflammatory cells. We investigated whether SC maturation influences their expression. IFN-γ induced MHC class II and upregulated ICAM-1; the axolemma-like signal 8-bromo cyclic adenosine monophosphate (8 Br cAMP) with IFN-γ inhibited expression. Delaying addition of 8 Br cAMP to SC already exposed to IFN-γ inhibited ongoing expression; addition of IFN-γ to SC already exposed to 8 Br cAMP resulted in minimal expression. Variability of cytokine-induced MHC class II and ICAM-1 expression by SC in vivo may represent the variability of signals from axolemma.

The role of nerve inflammation and exogenous iron load in experimental peripheral diabetic neuropathy (PDN)

BACKGROUND

Iron is an essential but potentially toxic metal in mammals. Here we investigated a pathogenic role of exogenous iron in peripheral diabetic neuropathy (PDN) in an animal model for type 1 diabetes.

METHODS

Diabetes was induced by a single injection of streptozotocin (STZ) in 4-month-old Sprague-Dawley rats. STZ-diabetic rats and non-diabetic rats were fed with high, standard, or low iron diet. After three months of feeding, animals were tested.

RESULTS

STZ-rats on standard iron diet showed overt diabetes, slowed motor nerve conduction, marked degeneration of distal intraepidermal nerve fibers, mild intraneural infiltration with macrophages and T-cells in the sciatic nerve, and increased iron levels in serum and dorsal root ganglion (DRG) neurons. While motor fibers were afflicted in all STZ-groups, only a low iron-diet led also to reduced sensory conduction velocities in the sciatic nerve. In addition, only STZ-rats on a low iron diet showed damaged mitochondria in numerous DRG neurons, a more profound intraepidermal nerve fiber degeneration indicating small fiber neuropathy, and even more inflammatory cells in sciatic nerves than seen in any other experimental group.

CONCLUSIONS

These results indicate that dietary iron-deficiency rather than iron overload, and mild inflammation may both promote neuropathy in STZ-induced experimental PDN.

Differential effects of CXCR4-CXCL12- and CXCR7-CXCL12-mediated immune reactions on murine P0106-125 -induced experimental autoimmune neuritis

AIM

The role of chemokines and their receptors, which regulate trafficking and homing of leucocytes to inflamed organs in human or murine autoimmune neuritis, has not yet been elucidated in detail, Therefore, the role of the chemokine receptors CXCR4 and CXCR7 and their ligand CXCL12 was studied in autoimmune-mediated inflammation of the peripheral nervous system.

METHODS

CXCL12/CXCR4 and/or CXCL12/CXCR7 interactions were specifically inhibited by the compounds AMD3100 or CCX771, respectively, in experimental autoimmune neuritis (EAN) of C57BL/6J mice immunized with P0106-125 peptide.

RESULTS

Disease activity was significantly suppressed by blocking CXCR7 while antagonization of CXCR4 enhanced disease activity. Enhanced disease activity was accompanied by significantly increased transcription of IFN-γ, IL-12 and TNF-α mRNA in regional lymph nodes and spleen as well as by increased serum levels of IFN-γ. Furthermore, by blocking CXCR4, expression of the cell adhesion molecules ICAM-1 and VCAM-1 was upregulated on vascular endothelial cells of the sciatic nerve, which coincided with significantly increased infiltration of the sciatic nerve by CD4+ T cells and macrophages. Remarkably, combined antagonization of both CXCR4 and CXCR7 significantly suppressed disease activity. This was accompanied by increased frequencies of activated and highly IFN-γ-expressing, P0106-125 -specific T cells in regional lymph nodes and spleen; however, these cells were unable to infiltrate the sciatic nerve.

CONCLUSION

These data suggest differential and hierarchically ordered roles for CXCR4/CXCL12- vs. CXCR7/CXCL12-dependent effects during EAN: CXCR7/CXCL12 interaction is a gatekeeper for pathogenic cells, regardless of their CXCR4/CXCL12-dependent state of activation.

FoxP3+ regulatory T cells determine disease severity in rodent models of inflammatory neuropathies

Inflammatory neuropathies represent disabling human autoimmune disorders with considerable disease variability. Animal models provide insights into defined aspects of their disease pathogenesis. Forkhead box P3 (FoxP3)+ regulatory T lymphocytes (Treg) are anti-inflammatory cells that maintain immune tolerance and counteract tissue damage in a variety of immune-mediated disorders. Dysfunction or a reduced frequency of Tregs have been associated with different human autoimmune disorders. We here analyzed the functional relevance of Tregs in determining disease manifestation and severity in murine models of autoimmune neuropathies. We took advantage of the DEREG mouse system allowing depletion of Treg with high specificity as well as anti-CD25 directed antibodies to deplete Tregs in mice in actively induced experimental autoimmune neuritis (EAN). Furthermore antibody-depletion was performed in an adoptive transfer model of chronic neuritis. Early Treg depletion increased clinical EAN severity both in active and adoptive transfer chronic neuritis. This was accompanied by increased proliferation of myelin specific T cells and histological signs of peripheral nerve inflammation. Late stage Treg depletion after initial disease manifestation however did not exacerbate inflammatory neuropathy symptoms further. We conclude that Tregs determine disease severity in experimental autoimmune neuropathies during the initial priming phase, but have no major disease modifying function after disease manifestation. Potential future therapeutic approaches targeting Tregs should thus be performed early in inflammatory neuropathies.

Thymic epithelium determines a spontaneous chronic neuritis in Icam1(tm1Jcgr)NOD mice

The NOD mouse strain spontaneously develops autoimmune diabetes. A deficiency in costimulatory molecules, such as B7-2, on the NOD genetic background prevents diabetes but instead triggers an inflammatory peripheral neuropathy. This constitutes a shift in the target of autoimmunity, but the underlying mechanism remains unknown. In this study, we demonstrate that NOD mice deficient for isoforms of ICAM-1, which comediate costimulatory functions, spontaneously develop a chronic autoimmune peripheral neuritis instead of diabetes. The disease is transferred by CD4(+) T cells, which infiltrate peripheral nerves together with macrophages and B cells and are autoreactive against peripheral myelin protein zero. These Icam1(tm1Jcgr)NOD mice exhibit unaltered numbers of regulatory T cells, but increased IL-17-producing T cells, which determine the severity, but not the target specificity, of autoimmunity. Ab-mediated ICAM-1 blockade triggers neuritis only in young NOD mice. Thymic epithelium from Icam1(tm1Jcgr)NOD mice features an altered expression of costimulatory molecules and induces neuritis and myelin autoreactivity after transplantation into nude mice in vivo. Icam1(tm1Jcgr)NOD mice exhibit a specifically altered TCR repertoire. Our findings introduce a novel animal model of chronic inflammatory neuropathies and indicate that altered expression of ICAM-1 on thymic epithelium shifts autoimmunity specifically toward peripheral nerves. This improves our understanding of autoimmunity in the peripheral nervous system with potential relevance for human diseases.

Cdc42 GTPases facilitate TNF-α-mediated secretion of CCL2 from peripheral nerve microvascular endoneurial endothelial cells

Trafficking of autoreactive leukocytes across the blood-nerve barrier and into peripheral nerves is an early pathological hallmark of Guillain-Barré syndrome (GBS). Tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, promotes transendothelial migration by upregulating endothelial expression of inflammatory mediators, including CCL2, a chemokine implicated in GBS. We sought to determine the mechanism by which TNF-α induces expression and secretion of CCL2 from peripheral nerve microvascular endoneurial endothelial cells (PNMECs). Expression of CCL2 mRNA and protein in quiescent PNMEC cultures was minimal. In contrast, cultures treated with TNF-α exhibited increased CCL2 mRNA and protein content, as well as protein secretion. Simvastatin significantly attenuated TNF-α-induced CCL2 secretion without affecting CCL2 mRNA or protein expression. Co-incubation with geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, prevented the effect of simvastatin. By comparison, inhibiting protein isoprenylation with GGTI-298, but not FTI-277, mimicked the effect of simvastatin and significantly attenuated transendothelial migration in vitro. Inhibition of the monomeric GTPase Cdc42, but not Rac1 or RhoA-C, attenuated TNF-α-mediated CCL2 secretion. TNF-α-mediated trafficking of autoreactive leukocytes into peripheral nerves during GBS may proceed by a mechanism that involves Cdc42-facilitated secretion of CCL2.

Intravenous immunoglobulin preparation attenuates neurological signs in rat experimental autoimmune neuritis with the suppression of macrophage inflammatory protein -1α expression

To clarify the mechanism of action of an intravenous immunoglobulin (IVIG) preparation in chronic inflammatory demyelinating polyneuropathy, the effects of IVIG were investigated using an experimental autoimmune neuropathy model in the rat. IVIG significantly suppressed the progression of neurologic signs and sciatic nerve conduction velocity with the inhibition of inflammatory cell infiltration, mainly of macrophages, to the peripheral nerves. A significant suppressive effect on the expression of macrophage inflammatory protein 1-α (MIP-1α) was simultaneously observed in the nerves. These results suggest that IVIG is effective for inflammatory demyelinating polyneuropathy by inhibiting the chemotactic factor of macrophages.

Chemokine-dependent signaling pathways in the peripheral nervous system

Chemokines and their G-protein-coupled receptors play important roles in development, homeostasis, and the innate and adaptive immune response. Pathologic chemokine signaling pathways in the peripheral nervous system can be studied in peripheral nerves using human in vitro models of the blood-nerve barrier (BNB) and a reliable model of acute peripheral nerve inflammation called severe murine experimental autoimmune neuritis (EAN). This chapter describes a flow-dependent human leukocyte-BNB trafficking assay and the reliable induction of EAN in female SJL/J mice as tools to study pro-inflammatory chemokine-dependent signaling in peripheral nerves.

Recent developments and future directions in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) encompasses a spectrum of acquired neuropathic conditions characterized by inflammatory demyelinating or axonal peripheral neuropathy with acute onset. Clinical and experimental studies in the past years have led to substantial progress in epidemiology, pathogenesis of GBS variants, and identification of prognostic factors relevant to treatment. In this review we provide an overview and critical assessment of the most recent developments and future directions in GBS research.

The role of chemokines in Guillain-Barré syndrome

INTRODUCTION

Chemokines and their receptors are important mediators of inflammation. Guillain-Barré syndrome (GBS) is the most common cause of acute paralysis worldwide. Despite current treatments, outcomes are suboptimal. Specific chemokine receptor antagonists have the potential to be efficacious against pathogenic leukocyte trafficking in GBS.

METHODS

A 36-year literature review was performed to summarize available data on chemokine expression in GBS and its representative animal model, experimental autoimmune neuritis (EAN).

RESULTS

Although there were a few observational human and animal studies demonstrating chemokine ligand/receptor expression in GBS and EAN, in vitro and in vivo functional studies using gene knockouts, neutralizing antibodies, or small molecular antagonists were limited. CCL2-CCR2, CCL5-CCR5, and CXCL10-CXCR3 have been most strongly implicated in EAN and GBS pathogenesis, providing targets for molecular blockade.

CONCLUSIONS

Preclinical human in vitro and in vivo EAN studies are needed to evaluate the potential efficacy of chemokine signaling inhibition in GBS.

Tumour necrosis factor α enhances CCL2 and ICAM-1 expression in peripheral nerve microvascular endoneurial endothelial cells

Recruitment and trafficking of autoreactive leucocytes across the BNB (blood-nerve barrier) is an early pathological insult in GBS (Guillain-Barré syndrome), an aggressive autoimmune disorder of the PNS (peripheral nervous system). Whereas the aetiology and pathogenesis of GBS remain unclear, pro-inflammatory cytokines, including TNFα (tumour necrosis factor α), are reported to be elevated early in the course of GBS and may initiate nerve injury by activating the BNB. Previously, we reported that disrupting leucocyte trafficking in vivo therapeutically attenuates the course of an established animal model of GBS. Here, PNMECs (peripheral nerve microvascular endothelial cells) that form the BNB were harvested from rat sciatic nerves, immortalized by SV40 (simian virus 40) large T antigen transduction and subsequently challenged with TNFα. Relative changes in CCL2 (chemokine ligand 2) and ICAM-1 (intercellular adhesion molecule 1) expression were determined. We report that TNFα elicits marked dose- and time-dependent increases in CCL2 and ICAM-1 mRNA and protein content and promotes secretion of functional CCL2 from immortalized and primary PNMEC cultures. TNFα-mediated secretion of CCL2 promotes, in vitro, the transendothelial migration of CCR2-expressing THP-1 monocytes. Increased CCL2 and ICAM-1 expression in response to TNFα may facilitate recruitment and trafficking of autoreactive leucocytes across the BNB in autoimmune disorders, including GBS.

α(M)β(2)-integrin-intercellular adhesion molecule-1 interactions drive the flow-dependent trafficking of Guillain-Barré syndrome patient derived mononuclear leukocytes at the blood-nerve barrier in vitro

The mechanisms of hematogenous leukocyte trafficking at the human blood-nerve barrier (BNB) are largely unknown. Intercellular adhesion molecule-1 (ICAM-1) has been implicated in the pathogenesis of Guillain-Barré syndrome (GBS). We developed a cytokine-activated human in vitro BNB model using primary endoneurial endothelial cells. Endothelial treatment with 10 U/ml tissue necrosis factor-α and 20 U/ml interferon-γ resulted in de novo expression of pro-inflammatory chemokines CCL2, CXCL9, CXCL11, and CCL20, with increased expression of CXCL2-3, CXCL8, and CXCL10 relative to basal levels. Cytokine treatment induced/enhanced ICAM-1, E- and P-selectin, vascular cell adhesion molecule-1 and the alternatively spliced pro-adhesive fibronectin variant, fibronectin connecting segment-1 expression in a time-dependent manner, without alterations in junctional adhesion molecule-A expression. Lymphocytes and monocytes from untreated GBS patients express ICAM-1 counterligands, α(M)- and α(L)-integrin, with differential regulation of α(M) -integrin expression compared to healthy controls. Under flow conditions that mimic capillary hemodynamics in vivo, there was a >3-fold increase in total GBS patient and healthy control mononuclear leukocyte adhesion/migration at the BNB following cytokine treatment relative to the untreated state. Function neutralizing monoclonal antibodies against human α(M)-integrin (CD11b) and ICAM-1 reduced untreated GBS patient mononuclear leukocyte trafficking at the BNB by 59% and 64.2%, respectively. Monoclonal antibodies against α(L)-integrin (CD11a) and human intravenous immunoglobulin reduced total leukocyte adhesion/migration by 22.8% and 17.6%, respectively. This study demonstrates differential regulation of α(M)-integrin on circulating mononuclear cells in GBS, as well as an important role for α(M)-integrin-ICAM-1 interactions in pathogenic GBS patient leukocyte trafficking at the human BNB in vitro.

TNF-α expression in Schwann cells is induced by LPS and NF-κB-dependent pathways

Lipopolysaccharide (LPS) is recognized by Toll-like receptor 4 and activates mitogen-activated protein kinase, which leads to the induction of proinflammatory cytokine gene expression. In vivo, Schwann cells (SCs) at the site of injury may also produce tumor necrosis factor-α (TNF-α). However, the precise mechanism that regulates TNF-α synthesis is still not clear. The nuclear transcription factor-κB (NF-κB) is an important transcription factor which is involved in the regulation of host immune responses. In the present study, we found that LPS possessed a comparable specific activity for activation of NF-κB-dependent gene expression in SCs. We also observed IκB-α/IκB-β degradation and the nuclear translocation of P65 due to LPS treatments. LPS-elicited TNF-α production in SCs was also drastically suppressed by SN50 (NF-κB inhibitor).

Erythropoietin ameliorates rat experimental autoimmune neuritis by inducing transforming growth factor-β in macrophages

Erythropoietin (EPO) is a pleiotropic cytokine originally identified for its role in erythropoiesis. In addition, in various preclinical models EPO exhibited protective activity against tissue injury. There is an urgent need for potent treatments of autoimmune driven disorders of the peripheral nervous system (PNS), such as the Guillain-Barré syndrome (GBS), a disabling autoimmune disease associated with relevant morbidity and mortality. To test the therapeutic potential of EPO in experimental autoimmune neuritis (EAN) - an animal model of human GBS--immunological and clinical effects were investigated in a preventive and a therapeutic paradigm. Treatment with EPO reduced clinical disease severity and if given therapeutically also shortened the recovery phase of EAN. Clinical findings were mirrored by decreased inflammation within the peripheral nerve, and myelin was well maintained in treated animals. In contrast, EPO increased the number of macrophages especially in later stages of the experimental disease phase. Furthermore, the anti-inflammatory cytokine transforming growth factor (TGF)-beta was upregulated in the treated cohorts. In vitro experiments revealed less proliferation of T cells in the presence of EPO and TGF-beta was moderately induced, while the secretion of other cytokines was almost not altered by EPO. Our data suggest that EPO revealed its beneficial properties by the induction of beneficial macrophages and the modulation of the immune system towards anti-inflammatory responses in the PNS. Further studies are warranted to elaborate the clinical usefulness of EPO for treating immune-mediated neuropathies in affected patients.

Pathogenesis and treatment of immune-mediated neuropathies

Immune-mediated neuropathies represent a heterogeneous spectrum of peripheral nerve disorders that can be classified according to time course, predominant involvement of motor/sensory fibers, distribution of deficits and paraclinical parameters such as electrophysiology and serum antibodies. In the last few years, significant advances have been achieved in elucidating underlying pathomechanisms, which made it possible to identify potential therapeutic targets. In this review, we discuss the latest development in pathogenesis and treatment of immune-mediated neuropathies.

Quinpramine ameliorates rat experimental autoimmune neuritis and redistributes MHC class II molecules

Activation of inflammatory cells is central to the pathogenesis of autoimmune demyelinating diseases of the peripheral nervous system. The novel chimeric compound quinpramine—generated from imipramine and quinacrine—redistributes cholesterol rich membrane domains to intracellular compartments. We studied the immunological and clinical effects of quinpramine in myelin homogenate induced Lewis rat experimental autoimmune neuritis (EAN), a model system for acute human inflammatory neuropathies, such as the Guillain-Barré syndrome. EAN animals develop paresis of all limbs due to autoimmune inflammation of peripheral nerves. Quinpramine treatment ameliorated clinical disease severity of EAN and infiltration of macrophages into peripheral nerves. It reduced expression of MHC class II molecules on antigen presenting cells and antigen specific T cell proliferation both in vitro and in vivo. Quinpramine exerted its anti-proliferatory effect on antigen presenting cells, but not on responder T cells. Our data suggest that quinpramine represents a candidate pharmaceutical for inflammatory neuropathies.

Targeting of myelin protein zero in a spontaneous autoimmune polyneuropathy

Elimination of the costimulatory molecule B7-2 prevents autoimmune diabetes in NOD mice, but leads to the development of a spontaneous autoimmune polyneuropathy (SAP), which resembles the human disease chronic inflammatory demyelinating polyneuropathy (CIDP). In this study, we examined the immunopathogenic mechanisms in this model, including identification of SAP Ags. We found that B7-2-deficient NOD mice exhibit changes in cytokine and chemokine gene expression in spleens over time. There was an increase in IL-17 and a decrease in IL-10 transcript levels at 4 mo (preclinical phase), whereas IFN-gamma expression peaked at 8 mo (clinical phase). There was also an increase in transcript levels of Th1 cytokines, CXCL10, and RANTES in sciatic nerves of mice that developed SAP. Splenocytes from SAP mice exhibited proliferative and Th1 cytokine responses to myelin P0 (180-199), but not to other P0 peptides or P2 (53-78). Adoptive transfer of P0-reactive T cells generated from SAP mice induced neuropathy in four of six NOD.SCID mice. Data from i.v. tolerance studies indicate that myelin P0 is one of the autoantigens targeted by T cells in SAP in this model. The expression of P0 by peri-islet Schwann cells provides a potential mechanism linking islet autoimmunity and inflammatory neuropathy.

Tumor necrosis factor-alpha antagonists and neuropathy

Tumor necrosis factor (TNF)-alpha plays an important role in many aspects of immune system development, immune-response regulation, and T-cell-mediated tissue injury. The evidence that TNF-alpha, released by autoreactive T cells and macrophages, may contribute to the pathogenesis of immune-mediated demyelinating neuropathies is reviewed. TNF-alpha antagonists (infliximab, etanercept, adalimumab) are indicated for the treatment of advanced inflammatory rheumatic and bowel disease, but these drugs can induce a range of autoimmune diseases that also attack the central and peripheral nervous systems. Case histories and series report on the association between anti-TNF-alpha treatment and various disorders of peripheral nerve such as Guillain-Barré syndrome, Miller Fisher syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy with conduction block, mononeuropathy multiplex, and axonal sensorimotor polyneuropathies. The proposed pathogeneses of TNF-alpha-associated neuropathies include both a T-cell and humoral immune attack against peripheral nerve myelin, vasculitis-induced nerve ischemia, and inhibition of signaling support for axons. Most neuropathies improve over a period of months by withdrawal of the TNF-alpha antagonist, with or without additional immune-modulating treatment. Preliminary observations suggest that TNF-alpha antagonists may be useful as an antigen-nonspecific treatment approach to immune-mediated neuropathies in patients with a poor response to, or intolerance of, standard therapies, but further studies are required.

Effective treatment of experimental autoimmune neuritis with Fc fragment of human immunoglobulin

IV immunoglobulin (IVIg) and its Fc fragment proved effective in preventing further progression of experimental autoimmune neuritis (EAN) in the rat induced by whole bovine peripheral nerve myelin and shortening disease duration. This effectiveness was associated with significant differences in electrophysiological parameters including less prolongation of somatosensory evoked potential (S wave) latencies, better maintained S wave amplitudes, less reduction of distal motor nerve conduction velocity, and better maintained amplitudes of compound muscle action potentials of dorsal foot muscles after stimulation at ankle and hip. Moreover, treatment with IVIg and Fc fragments resulted in less extensive inflammation and demyelination in nerve roots evidenced by significantly lower histological grades. The current study provides direct evidence for the first time that Fc fraction of IVIg is the effective component in the treatment of rat EAN.

Effective treatment of experimental autoimmune neuritis with human immunoglobulin

High-dose intravenous immunoglobulin (IVIg) is an effective treatment for inflammatory demyelinating neuropathies, although the mechanism(s) of action remain incompletely understood. Experimental autoimmune neuritis (EAN) is an animal model of inflammatory demyelinating neuropathies; however, there have been conflicting reports regarding the efficacy of human IVIg in EAN. To obtain a model suitable for the study of the mechanism(s) of action of IVIg in Guillain-Barré syndrome, we investigated the effect of IVIg in EAN in the rat using clinical, electrophysiological and morphological measures. Human IVIg administered at the onset of signs of disease proved effective in preventing further progression of disease and shortening disease duration. This effectiveness was associated with significant differences in electrophysiological parameters including less prolongation of somatosensory evoked potential (S wave) latencies, better maintained S wave amplitudes, less reduction of distal motor nerve conduction velocity, and better maintained amplitudes of compound muscle action potentials of the dorsal foot muscles after stimulation at ankle and hip. Moreover, treatment with IVIg resulted in significantly lower histological grades in rat EAN. The current study provides evidence that human IVIg is effective in the treatment of EAN in the rat, indicating that this model may facilitate further investigation of the mechanism(s) of action of IVIg in inflammatory demyelinating neuropathies.

Soluble TNFR1 inhibits the development of experimental autoimmune neuritis by modulating blood–nerve-barrier permeability and inflammation

The role of TNFalpha/LTalpha during EAN induced by active immunization with peripheral nerve myelin was examined by administering a recombinant soluble chimeric form of human TNF receptor 1 (TNFR1-IgG). TNFalpha and LTalpha do not directly contribute to neurological deficit during EAN since treatment with TNFR1-IgG after onset failed to alter the course of disease. Prophylaxis with a single dose of TNFR1-IgG delayed the onset of EAN and was accompanied initially by inhibition of blood-nerve-barrier permeability and inflammation. Subsequently, the number of infiltrating macrophages and blood-nerve-barrier permeability increased but the disease symptoms remained mild for five days (on average a limp tail) after which severe EAN developed. The antibody titer to peripheral nerve myelin was unaltered by prophylaxis with TNFR1-IgG. The markedly altered tempo of disease onset after TNFR1-IgG prophylaxis indicates that TNFalpha and/or LTalpha have a key role in the development of blood-nerve-barrier permeability and the coupling of macrophage activation and recruitment to peripheral nerve pathology during EAN.

Lovastatin attenuates nerve injury in an animal model of Guillain-Barré syndrome

Statins, widely used as clinically effective inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, exhibit anti-inflammatory properties that may be of therapeutic benefit for the management of some neurological disorders. In this study, a short-term course of lovastatin treatment is shown to markedly inhibit the development of experimental autoimmune neuritis (EAN) in the absence of hepatotoxic or myotoxic complications. Independent of cholesterol reduction, lovastatin treatment prevented EAN-induced peripheral nerve conduction deficits and morphologic nerve injury. Co-administration with mevalonate neutralized the prophylactic effects of lovastatin. When administered therapeutically, lovastatin significantly shortened the disease course. Autoreactive immunity, measured in vitro by myelin-stimulated proliferation of splenocytes, was significantly diminished by in vivo lovastatin treatment. Th1-dominant immune responses, measured by cytokine profiling, however, were not affected by lovastatin. Sciatic nerves of lovastatin-treated immunized rats showed markedly reduced levels of cellular infiltrates. Treating peripheral nerve endothelial monolayers with lovastatin significantly inhibited the in vitro migration of autoreactive splenocytes. Together, these data demonstrate that a short-term course of lovastatin attenuates the development and progression of EAN in Lewis rats by limiting the proliferation and migration of autoreactive leukocytes.

Immunolocalization and activation of nuclear factor-κB in the sciatic nerves of rats with experimental autoimmune neuritis

Recent data support an important role played by nuclear factor kappa B (NF-kappaB) in peripheral neuropathies. We investigated expression and activation of NF-kappaB in experimental autoimmune neuritis (EAN) in rat sciatic nerves removed after 7, 14 and 21 days after immunization. Immunoreactivity for the activated form of NF-kappaB was found in the nuclei of T cells and macrophages at days 14 and 21, and also in the nuclei of few Schwann cells and of vascular endothelial cells at all time points, especially during the peak stage. Western blot showed a single band corresponding to 65 kDa in all EAN animals. NF-kappaB DNA-binding activity was revealed by electrophoretic mobility shift assay. Our results support NF-kappaB activation in EAN during the induction stage as well as in the disease remission.

Pathogenesis of chronic inflammatory demyelinating polyradiculoneuropathy

The acute lesions of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) consist of endoneurial foci of chemokine and chemokine receptor expression and T cell and macrophage activation. The myelin protein antigens, P2, P0, and PMP22, each induce experimental autoimmune neuritis in rodent models and might be autoantigens in CIDP. The strongest evidence incriminates P0, to which antibodies have been found in 20% of cases. Failure of regulatory T-cell mechanism is thought to underlie persistent or recurrent disease, differentiating CIDP from the acute inflammatory demyelinating polyradiculoneuropathy form of Guillain-Barré syndrome. Corticosteroids, intravenous immunoglobulin and plasma exchange each provide short term benefit but the possible long-term benefits of immunosuppressive drugs have yet to be confirmed in randomised, controlled trials.

Inhibition of Ras attenuates the course of experimental autoimmune neuritis

EAN induced in Lewis rats by immunization with peripheral bovine myelin was treated by the Ras inhibitor farnesylthiosalicylate (FTS). Treatment from day 0 with FTS (5 mg/kg intraperitoneally twice daily) attenuated peak clinical scores (mean+/-S.E., 2.5+/-0.5 compared to 4.1+/-0.5 in saline treated controls, p=0.018, t-test) but not recovery. Treatment from day 10 with FTS attenuated peak disability (2.5+/-0.6, p=0.032 compared to saline treated controls) and improved recovery (0.84+/-0.42, untreated controls 2.4+/-0.6, p=0.028 by repeated measures ANOVA). Effects were confirmed by rotarod and nerve conduction studies. An inactive analogue, geranylthiosalicylate, had no clinical effect. Inhibition of Ras is of potential use in the treatment of inflammatory neuropathies.

Tumor necrosis factor-alpha-converting enzyme is expressed in the inflamed peripheral nervous system

Tumor necrosis factor-alpha (TNF-alpha) is considered to play a critical role in the pathogenesis of immune-mediated inflammatory demyelinating disorders of the peripheral nervous system (PNS). Processing of membrane-bound inactive pro-TNF-alpha into the active soluble cytokine is mediated by a sheddase, the so-called TNF-alpha-converting enzyme (TACE), a member of the A Disintegrin and Metalloproteinase (ADAM) family. We explored the expression of TACE (ADAM-17) in sciatic nerves from Lewis rats with experimental autoimmune neuritis (EAN), an animal model of the Guillain-Barré syndrome (GBS), an immune-mediated polyradiculoneuropathy. To extend our study to human disease, sural nerve biopsies from GBS patients were investigated by immunohistochemistry. In EAN, T lymphocytes could be defined as the cellular source of ADAM-17 with peak expression levels at maximum clinical disease severity. Similarly, in human sural nerves, ADAM-17-expressing T cells could be localized primarily within the epi- and perineurium, whereas in control sections from patients with non-inflammatory neuropathies, no expression could be depicted. Our findings indicate that ADAM-17 is upregulated during EAN and expressed in nerves of GBS patients and thus may contribute to the pathogenesis of inflammatory demyelination of the PNS.

Schwann cell overexpression of the GPR7 receptor in inflammatory and painful neuropathies

The human 7-transmembrane receptor GPR7 has sequence similarity to opioid and somatostatin receptors, and can be activated by the recently discovered neuropeptides NPB and NPW. This receptor is highly expressed in the nervous system, with suggested roles in neuroendocrine events and pain signaling. In this study, we investigated whether the GPR7 receptor is expressed in the peripheral nervous system under normal and pathological conditions. A low level of GPR7 receptor was observed in myelin-forming Schwann cells in both normal human and rat nerve, and in primary rat Schwann cell cultures. Peripheral nerve samples taken from patients exhibiting inflammatory/immune-mediated neuropathies showed a dramatic increase of GPR7 receptor expression restricted to myelin-forming Schwann cells. Complementary animal models of immune-inflammatory and ligation-induced nerve injury and neuropathic pain similarly exhibited an increased myelin-associated expression of GPR7 receptor. These results suggest a relationship between the pathogenesis of inflammatory/immune-mediated neuropathies, GPR7 receptor expression, and pain transmission.

CCR5 deficiency does not prevent P0 peptide 180–199 immunized mice from experimental autoimmune neuritis

Experimental autoimmune neuritis (EAN) is an inflammatory autoimmune demyelinating disease of peripheral nervous system (PNS) and represents an animal model of Guillain-Barré syndrome (GBS) in man. The inflammatory cell infiltrating into the PNS is a prerequisite for developing EAN. To explore the role of CC chemokine receptor 5 (CCR5) in the inflammatory process of EAN, we induced EAN in CCR5-deficient (CCR5(-/-)) mice with P0 protein peptide 180-199. We found that CCR5(-/-) mice showed a similar EAN clinical course and severity as well as profile of infiltrating macrophages and T cells in cauda equina (CE) of EAN and the same levels of spleen mononuclear cell (MNC) response to antigen and mitogen when compared with CCR5(+/+) control mice. However, increased IP-10 and MIP-1beta production in sciatic nerves were seen in CCR5(-/-) mice. These results suggest that CCR5 deficiency does not prevent P0 peptide 180-199-immunized mice from EAN. Increased MIP-1beta and IP-10 in sciatic nerves may compensate the CCR5 deficiency and contribute to inflammatory cells infiltrating to the PNS.

Expression of chemokine and receptors in Lewis rats with experimental autoimmune anterior uveitis

The purpose of this study is to investigate the sequential expression of certain chemokines and chemokine receptors in the iris-ciliary body and popliteal lymph nodes of Lewis rats and, thus, to establish their roles in experimental autoimmune anterior uveitis. Uveitis was induced with the injection of melanin-associated antigen intraperitoneally and into the left foot. The clinical severity of the uveitis was scored. At defined time points, CC chemokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-1, and regulated-upon-activation normal T-cell expressed and secreted), CXC chemokines (interferon gamma-inducible protein-10, stromal-derived factor-1, and interleukin-8), and receptor (CCR2, CCR3, CCR5, CXCR1, CXCR2, CXCR3, and CXCR4) mRNA expression were semiquantified by using a reverse-transcriptase reaction followed by polymerase chain reaction. The concentrations of macrophage inflammatory protein-1 and regulated-upon-activation normal T-cell expressed and secreted in aqueous humor were determined by means of enzyme-linked immunosorbent assay. Levels of monocyte chemoattractant protein-1, macrophage inflammatory protein-1 and interferon gamma-inducible protein-10 started increasing before the clinical onset of disease; these might have been involved in the initial recruitment of inflammatory cells. The level of regulated-upon-activation normal T-cell mRNA, however, started rising concurrently with the onset of clinical disease, suggesting that this chemokine may exert amplifying role in generating uveitis. Stromal-derived factor-1 exhibited an early and high level of expression with the increase of cognate receptor, CXCR4, indicating that stromal-derived factor-1 plays a role in either promoting angiogenesis or attracting for T-cells. Instead of upregulation like other chemokine receptors, interleukin-8 receptors, CXCR1and CXCR2, mRNA could not be detected in accord with the increase of interleukin-8. These findings appeared that downregulation of chemokine receptors on neutrophils may make themselves less respond to interleukin-8 and subsequently lead to decreased recruitment of neutrophils into the iris-ciliary body. In addition, the expression of chemokine receptors in popliteal lymph nodes were earlier than those in the iris-ciliary body. This sequence of expression may reflect the process of T lymphocytes maturation and differentiation. Monocyte chemoattractant protein-1 protein was immunohistologically detected in the ciliary epithelium and infiltrating leukocytes. The above results suggest that chemokines, which act on T cells and monocytes, are sequentially upregulated during the clinical course of experimental autoimmune anterior uveitis, and thus, may contribute to the pathogenesis of acute anterior uveitis.

CHEMOKINE EXPRESSION IN NERVE ALLOGRAFTS

OBJECTIVE

Chemokines (chemoattractant cytokines) play a major role in trafficking of cells to areas of inflammation. Infiltration of allograft tissues by immunocompetent cells is critical for rejection of donor tissues. The role of chemokines in nerve allograft rejection is not clear. We hypothesized that chemokines are responsible for attracting macrophages and T lymphocytes into nerve allograft tissue, initiating the graft rejection process.

METHODS

Lewis rats received 4-cm-long peroneal nerve allografts and isografts from ACI and Lewis rats, respectively. Twelve hours to 10 days after transplantation, grafts were removed and total cellular ribonucleic acid was extracted. Intragraft gene expression of several chemokines (cytokine-induced neutrophil chemoattractant, macrophage inflammatory protein [MIP]-2, monocyte chemoattractant protein-1, MIP-1 alpha, and regulated upon activation normal T-cell expressed and secreted [RANTES]) were analyzed by reverse transcription-polymerase chain reaction.

RESULTS

The cytokine-induced neutrophil chemoattractant was expressed in allografts and isografts at early time points (12 h to 6 d). Monocyte chemoattractant protein-1 messenger ribonucleic acid expression was similarly high in both isografts and allografts from 12 hours until 8 days after transplantation. MIP-1 alpha, MIP-2, and RANTES were expressed only in allografts. Kinetics of the neutrophil (MIP-2) and macrophage (MIP-1 alpha) chemokines revealed an early onset (12-24 h), a plateau from 1 to 4 days, and expression abruptly declining by Day 6. The lymphocyte chemoattractant RANTES had delayed kinetics, with a rise at Day 3, a peak at Day 4, and a gradual decline.

CONCLUSION

Induction of specific chemokine genes precedes nerve allograft infiltration by immunocompetent cells. MIP-1 alpha, MIP-2, and RANTES may be responsible for recruiting macrophages, granulocytes, and lymphocytes, respectively, to the rejecting allograft. In future studies, blockade of these specific chemokines or their receptors may prove to delay or prevent nerve allograft rejection.

Advances in understanding and treatment of immune-mediated disorders of the peripheral nervous system

During recent years, novel insights in basic immunology and advances in biotechnology have contributed to an increased understanding of the pathogenetic mechanisms of immune-mediated disorders of the peripheral nervous system. This increased knowledge has an impact on the management of patients with this class of disorders. Current advances are outlined and their implication for therapeutic approaches addressed. As a prototypic immune-mediated neuropathy, special emphasis is placed on the pathogenesis and treatment of the Guillain-Barré syndrome and its variants. Moreover, neuropathies of the chronic inflammatory demyelinating, multifocal motor, and nonsystemic vasculitic types are discussed. This review summarizes recent progress with currently available therapies and--on the basis of present immunopathogenetic concepts--outlines future treatment strategies.

Involvement of cyclooxygenase-1 and -2 in the sciatic nerve of rats with experimental autoimmune neuritis

The expression of both cyclooxygenase (COX)-1 and COX-2, which are representative enzymes in prostaglandin synthesis, was evaluated in the sciatic nerve of rats with experimental autoimmune neuritis (EAN). Western blot analysis showed that both COX-1 and COX-2 were significantly increased in the sciatic nerve at the peak stage of EAN and declined during the recovery stage. Vascular endothelial cells in normal sciatic nerves immunostained for both COX-1 and COX-2. COX-1 was mainly detected in macrophages, and not in other cell types, while COX-2 was detected in Schwann cells and axons as well as inflammatory macrophages in EAN lesions. This suggests that COXs are involved in the pathogenesis of peripheral demyelinating disease, including EAN, and the major cellular source of both COXs in EAN lesions is inflammatory macrophages. Furthermore, COX-2 is enhanced in some Schwann cells and neural elements, possibly mediating peripheral nervous system inflammation.

Aberrated levels of cerebrospinal fluid chemokines in Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy

Infiltration of spinal nerve roots and peripheral nerves by macrophages and T cells are rather consistent immunopathologic findings in patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Chemokines play a central role in recruitment of leukocytes to inflamed tissue. Chemokines have been implicated in the pathogenesis of the experimental autoimmune neuritis (EAN), which represents an animal model of GBS, but the role of chemokines in GBS and CIDP is not clear. Since chemokines may be released into CSF from inflamed spinal nerve roots, we studied the concentrations of the chemokines MCP-1, MIP-1beta, MIP-3beta, IP-10, SDF-1alpha, RANTES, and SLC in the CSF by sandwich ELISA in patients over the course of GBS and CIDP, before and after immunomodulatory treatment. Controls consisted of patients with noninflammatory neurological disorders. Patients examined in the acute phase of GBS prior to treatment with intravenous high dose immunoglobulins (IvIg) had elevated CSF levels of MCP-1 (a chemoattractant for blood monocytes and dendritic cells) and IP-10 (a chemoattractant for T cells). Patients with CIDP examined prior to immunomodulatory treatment had elevated CSF levels of MIP-3beta (a chemoattractant for mature dendritic cells, naïve and recently activated T cells) and IP-10. Levels of MIP-3beta tended to decreased during follow-up in those CIDP patients responding favorably to immunomodulatory treatment. CSF levels of MCP-1 and IP-10 correlated with the CSF:plasma albumin ratio in both GBS and CIDP patients. In CIDP patients, CSF levels of MIP-3beta also correlated with the CSF:plasma albumin ratio. These data implicate MCP-1 and IP-10 in the pathogenesis of GBS, and IP-10 and MIP-3beta in the pathogenesis of CIDP.

Changes in serum macrophage-related factors in patients with chronic inflammatory demyelinating polyneuropathy caused by intravenous immunoglobulin therapy

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a slowly progressive or recurrent neuropathy accompanied by infiltration of macrophages in the peripheral nerves. Macrophage colony-stimulating factor (M-CSF) and monocyte chemoattractant protein-1 (MCP-1) are a macrophage-related cytokine and chemokine, respectively. Although, intravenous immunoglobulin (IVIg) infusion therapy has been used for treating CIDP patients, not all CIDP patients have responded to IVIg infusion therapy. To determine the mechanisms of the action of IVIg, we examined serum M-CSF and MCP-1 levels during and after IVIg infusion therapy in 19 CIDP patients treated with IVIg (0.4 g/kg/day for 5 days). Ten of the 19 patients (52.6%) responded to IVIg therapy. Both M-CSF and MCP-1 concentrations in IVIg responders were significantly higher on day 1 postinfusion than those in nonresponders, but decreased to their pretreatment values on day 5 postinfusion. The results suggest that immunomodulation through M-CSF and MCP-1 is involved in the mechanisms underlying the effect of IVIg infusion therapy in CIDP patients.