Experimental Autoimmune Encephalomyelitis Rats Research Articles

Glutamate release machinery is altered in the frontal cortex of rats with experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is an animal model that mimics many of the clinical and pathological features of the human disease multiple sclerosis (MS). Both are inflammatory demyelinating and neurodegenerative pathologies of the central nervous system associated with motor, sensory, and cognitive deficits. In MS, gray matter atrophy is related to the emergence of cognitive deficits and contributes to clinical progression. In particular, prefrontal cortex injury and dysfunction have been correlated to the development of fatigue, one of the most common and disabling symptoms in MS. However, the molecular bases of these changes remain unknown. Taking advantage of EAE similitude, we herein analyze functional and morphological changes in isolated cortical presynaptic terminals (synaptosomes) from an acute rat model. We found impaired glutamate release in the frontal cortex from EAE rats. This defect appeared along with the onset of the disease, reversing when clinical signs were no more evident. Biochemical analysis of EAE synaptosomes revealed alterations in the presynaptic release machinery and in the response to depolarization, which was accompanied by abnormal synapsin I phosphorylation and dispersion. These changes were associated with reduced synaptic vesicle mobility, with no alterations in synaptosomal morphology as evidenced by electron microscopy. The present are the first pieces of evidence unraveling the molecular mechanisms of frontal cortex neuronal dysfunction in EAE and, possibly, MS.

Involvement of JAK/STAT signaling in the effect of cornel iridoid glycoside on experimental autoimmune encephalomyelitis amelioration in rats

In the present study, we investigated the therapeutic benefit of cornel iridoid glycoside (CIG), the main component extracted from Cornus officinalis, in experimental autoimmune encephalomyelitis (EAE) rats. CIG was intragastrically administered daily after EAE initiation for 20days and reduced disease severity, incidence, disease onset and ongoing paralysis. Histopathological staining showed that CIG could reduce T cell entry to the central nervous system and microglia activation, increased brain-derived neurotrophic factor (BDNF) expression and mature oligodendrocytes, and decreased oligodendrocyte progenitor cells (OPCs). Also, CIG treatment inhibited brain JAK/STAT1/3 and reduced proinflammatory cytokines. CIG might be a novel potential therapeutic agent for multiple sclerosis (MS).

PET imaging of disease progression and treatment effects in the experimental autoimmune encephalomyelitis rat model.

The experimental autoimmune encephalomyelitis model is a model of multiple sclerosis that closely mimics the disease characteristics in humans. The main hallmarks of multiple sclerosis are neuroinflammation (microglia activation, monocyte invasion, and T-cell infiltration) and demyelination. PET imaging may be a useful noninvasive technique for monitoring disease progression and drug treatment efficacy in vivo. Experimental autoimmune encephalomyelitis was induced by myelin-oligodendrocyte glycoprotein immunization in female Dark Agouti rats. Experimental autoimmune encephalomyelitis rats were imaged at baseline and at days 6, 11, 15, and 19 after immunization to monitor monocyte and microglia activation ((11)C-PK11195) and demyelination ((11)C-MeDAS) during normal disease progression and during treatment with dexamethasone. (11)C-PK11195 PET detected activation of microglia and monocytes in the brain stem and spinal cord during disease progression. The uptake of (11)C-PK11195 was elevated in dexamethasone-treated animals that had shown mild clinical symptoms that had resolved at the time of imaging. Demyelination was not detected by (11)C-MeDAS PET, probably because of the small size of the lesions (average, 0.13 mm). PET imaging of neuroinflammation can be used to monitor disease progression and the consequences of treatment in the experimental autoimmune encephalomyelitis rat model. PET imaging was more sensitive than clinical symptoms for detecting inflammatory changes in the central nervous system.

Matrine suppresses glutamate excitotoxicity in experimental autoimmune encephalomyelitis (HUM1P.323)

Abstract Multiple sclerosis (MS) is T cell-mediated inflammatory diseases characterized by lymphocyte infiltration and demyelination. Matrine (MAT) is a quinolizidine alkaloid derived from the herb Radix Sophorae Flave and has long been used in the treatment of hepatitis B in clinical without obvious side effects. Previous reports have revealed that MAT restrained the central inflammation after experimental autoimmune encephalomyelitis (EAE), the most common animal model of MS due to similar symptoms and mechanisms; however whether MAT is effective to inhibit glutamate excitotoxicity is still unclear. In this study, we provide evidence that MAT attenuated the EAE disease severity, accompanied by down-regulated glutamate level, increased GABA level, as well as promoted the expressions of two dependent glutamate transporters (GLT-1 and GLAST). In addition, MAT treatment significantly decreased the content of the NMDA- and AMPA- glutamate receptor in EAE rats. Together, these data indicate that MAT treatment inhibited glutamate excitotoxicity after EAE, and suggest that MAT may be a novel choice in MS therapy.

Upregulation of immunomodulatory molecules by matrine treatment in experimental autoimmune encephalomyelitis (HUM1P.316)

Abstract Dysfunction of the immunologic mechanism is a primary characteristic of experimental autoimmune encephalomyelitis (EAE), which is a classical experimental model of multiple sclerosis (MS). Matrine (MAT), a quinolizidine alkaloid, has been used for hepatitis B in clinical. Previous reports have suggested that MAT could ameliorate the clinical symptoms of EAE rats, but haven’t clarified the mechanism of action until now. Our present study showed that MAT reduced the neurological scores of EAE rats, suppressed infiltration of inflammatory cells and demyelination in the CNS significantly. Furthermore, we studied the possible immunologic mechanism underlying the treatment of MAT for EAE by measuring the expression of system and molecules related with immunoregulation mechanism. In our study, an administration of MAT significantly increased the expression and production in the CNS of Nrf2 and HO-1, the correlation factors of oxidative stress that confront inflammatory cells into the CNS. Furthermore, the expressions of Interleukin-4, Interleukin-5, Interleukin-10, transforming growth factor-1 and Foxp3, which play an important role in the balance between Th1 and Th2 cells in EAE, were also significantly increased. Our findings reveal that MAT could promote the expressions of factors for inhibiting the inflammation. In conclusion, our study clarifies the possible mechanisms underlying the treatment of MAT for EAE, implies that MAT may be a novel therapeutic option for MS.

Development of a selective S1P1 receptor agonist, Syl930, as a potential therapeutic agent for autoimmune encephalitis

Sphingosine-1-phosphate receptor subtype 1 (S1P1) is essential for lymphocyte egress from secondary lymphoid organs and is a validated drug target for the treatment of autoimmune disorders. However, during the preclinical and clinical trials of S1P1 modulators, the undesired activation of S1P3, a subtype of sphingosine 1-phosphate (S1P) receptors family, by S1P1 modulators often results in bradycardia in patients. Thus, we designed and synthesized a new series of selective S1P1 agonists. One of them, Syl930 (the prodrug), is preference to activate S1P1 but not S1P3. In this study, we further investigated the therapeutic potential of Syl930 on an experimental autoimmune encephalomyelitis (EAE) model in Lewis rats. We found that Syl930 can activate and internalize S1P1 receptors and effectively decreased the periphery blood lymphocytes (PBL) in SD rats, and subsequently rendered PBL insensitive to egress signal from secondary lymphoid organs (SLO). Intriguingly, the treatment of Syl930 did not bring any side effect on heart rate of the tested rats. Furthermore, the suppressed PBL caused by Syl930 was able to recover within 3 days after the last dose of treatment, which is correlated to the relatively short elimination half-life of Syl930. In the rat EAE model, therapeutic treatment with Syl930 significantly inhibited the progression of EAE and EAE-associated histological changes in brain and spinal cord of Lewis rats. These results illustrate that, as a selective S1P1 agonist, Syl930 exhibits a profound and rapidly reversible suppression of lymphocyte trafficking and it has the potential to serve as a therapeutic agent for autoimmune encephalitis.

Spinal Cord Brain Derived Neurotrophic Factor (BDNF) Responsive Cells in an Experimental Autoimmune Encephalomyelitis (EAE) Model of Multiple Sclerosis (MS): Implications in Myelin Repair

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that destroys central nervous system (CNS) myelin. Although, the exact pathophysiology of MS is unknown, it is associated with CNS infiltration of T-cells and monocytes, which subsequently activate phagocytic cells that directly damage myelin. Brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase receptor (TrkB), have recognized roles in myelin structure formation, maintenance, and repair. We used an experimental autoimmune encephalomyelitis (EAE) model of MS to determine changes in TrkB expression that may contribute to neurological recovery and myelin repair following an early inflammatory immune-mediated attack on CNS myelin. Spinal cord (SC) TrkB gene and protein expression were analyzed at various time intervals post-EAE induction. Analysis of gene and protein expression was conducted in animals with EAE relative to active controls (AC) and naive controls (NC). We showed significant increases in TrkB protein in the SC of EAE rats 12 days post-induction relative to controls. This elevated TrkB expression correlated with the onset of neurological recovery days 12 to 15 post-EAE induction. Furthermore, immunohistochemistry (IHC) analysis revealed up-regulated expression of TrkB in several SC cell types including a specific subset of BDNF responsive neuronal cells. Finally, transmission electron microscopy (TEM) showed the ultrastructural integrity of myelin is already compromised during the early, inflammatory stage of EAE prior to widespread demyelination. Therefore, the molecular signaling of SC BDNF via TrkB represents a key therapeutic target whose manipulation could facilitate myelin repair and neurological recovery following an MS-induced myelin attack.

Therapeutic effects of nonerythropoietic erythropoietin analog ARA290 in experimental autoimmune encephalomyelitis rat

ARA290 is a nonerythropoietic analog of erythropoietin (EPO) containing 11 amino acids which provides the anti-inflammatory and neuroprotective effects of EPO without stimulating hematopoiesis. Here we studied the therapeutic effects of ARA290 in experimental autoimmune encephalomyelitis (EAE) Lewis rats. Therapeutic (from Day 7 to Day 18 or from Day 9 to Day 19) administration of ARA290 (35, 70μg/kg, intra-peritoneal) to EAE rats once daily significantly reduced the severity and shortened the duration of clinical score, reduced the accumulation of inflammatory cells in EAE spinal cords and suppressed mRNA levels of interleukin-1β (IL-1β), IL-17, tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), inducible nitric oxide synthase (iNOS), matrix metalloproteinase 9 (MMP9) and transcription factor T-bet in spinal cords of EAE rats. Furthermore, ARA290 treatment reduced the helper T cell number in lymph nodes and circulation in EAE. In vitro study showed that ARA290 dose-dependently inhibited antigen specific- and antigen non-specific-lymphocyte proliferation as well. In addition, ARA290 altered the cytokine milieu to favor the polarization of Th2 and regulatory T (Treg) cells but suppressed the polarization of Th1 and Th17 cells in EAE lymph nodes. In summary, our study here showed that ARA290 could alter T cell function to suppress inflammation to ameliorate EAE, suggesting that ARA290 may be a new therapeutic candidate for multiple sclerosis.

Actively Induced Experimental Autoimmune Encephalomyelitis in Rats.

The rat and especially a number of inbred rat strains are very well suited for modeling multiple sclerosis (MS). Experimental autoimmune encephalomyelitis (EAE), the model of MS, can be induced by active or passive immunization. Active immunization can be performed with different myelin proteins or peptides thereof. Passive immunization is performed by transfer of myelin-specific T cells. Most known is EAE induced with myelin basic protein (MBP) in LEW (RT1(l)) rats that results in monophasic disease and EAE induced with myelin oligodendrocyte glycoprotein (MOG) in DA (RT1(av1)) rats that leads to relapsing remitting or chronic disease. Depending on the selected inbred rat strain, the immunogen and adjuvant used, different disease courses and pathologies can be induced that mimic different aspects of MS.

Protective effect of cytosolic phospholipase A2 inhibition against inflammation and degeneration by promoting regulatory T cells in rats with experimental autoimmune encephalomyelitis.

Cytosolic phospholipase A2 (cPLA2) is the rate-limiting enzyme that initiates the production of various inflammatory mediators. Previous studies have shown that inhibiting cPLA2 exerts a neuroprotective effect on experimental autoimmune encephalomyelitis (EAE) by ameliorating the severity of the disease and influencing Th1 and Th17 responses. However, it remains unclear whether treatment with a cPLA2 inhibitor will influence the regulatory T cells (Tregs) that play a critical role in maintaining immune homeostasis and preventing autoimmune diseases. In this study, the cPLA2 inhibitor AX059 reduced the onset and progression of EAE in Lewis rats. In addition, this effect was accompanied by activation of Tregs and alterations in the expression of their various cytokines. The study therefore demonstrated that Tregs are involved in the immunomodulatory effect mediated by cPLA2 inhibition. These findings may have clinical application in the treatment of multiple sclerosis.

Effects of Exercise Intensity in Experimental Autoimmune Encephalomyelitis

Background: Research on muscle contractile properties and disease progression following experimental autoimmune encephalomyelitis (EAE) and physical exercise remains conflicting. Objective: To investigate the effect of different exercise intensities on muscle contractile properties and hindquarter paralysis during EAE in Lewis rats. Methods: A control and EAE group were divided in sedentary, light, moderate and high intensity running subgroups. During EAE course, hind limb paralysis, body weight and food intake were registered. Following EAE recovery isokinetic foot extensor strength was measured during 115 maximal contractions and fiber characteristics of m. tibialis anterior (TA) and m. extensor digitorum longus (EDL) were analysed. Results: EAE reduced CSA of type IIb+x fibers of TA and EDL, while type I and IIa fibers CSA were not affected by EAE. Exercise did not change CSA of type I, IIa and IIb+x fibers of EDL nor TA, except for TA type IIa fibers CSA, which increased in EAE moderate and EAE high intensity groups. Muscle work peak was absent in all EAE animals during isokinetic muscle contractions. Intense exercise delayed onset of hindquarter paralysis in EAE, while disease peak and remission were not affected by exercise. Conclusion: This study suggests that EAE reduces CSA of type IIb+x fibers of TA and EDL. This possibly explains the absence of peak muscle work during the first of a series of isokinetic muscle contractions. Furthermore, exercise was not able to reduce muscle fiber atrophy, whereas high intensity exercise delayed onset of hindquarter paralysis.

Bacterial Melanin Ameliorates Symptoms of Experimental Autoimmune Encephalomyelitis in Rats

Experimental autoimmune encephalomyelitis (EAE) is a T cell autoimmune inflammatory disease of the central nervous system (CNS) that is a widely used animal model for the human demyelinating disease, multiple sclerosis. Bacterial melanin has proved to be a potent neuroprotector. It supports regeneration and motor recovery after CNS lesions. It is established that bacterial melanin can induce suppression of inflammatory process. Studies have revealed the negative correlation between skin pigmentation, vitamin D and the prevalence of autoimmune disease. Therefore we analyzed the anti-inflammatory effects of bacterial melanin in a rat EAE model. EAE was induced in adult albino male rats by immunizing with a rat spinal cord encephalitogenic emulsion. The development of EAE and neurological signs were evaluated by a standard protocol. Walking track analysis was conducted to evaluate motor recovery. Histomorphological analysis was applied to show cell infiltration into the spinal cord and effects of BM on the EAE pathomorphology. Pretreatment of EAE rats with bacterial melanin inhibited the development of disease, providing significant protective effect compared to control rats. BM treated rats showed lower degree of neurological deficit and higher level of motor recovery than controls. In treated rats histomorphological analysis demonstrated that brain infiltration with mononuclears was less expressed in bacterial melanin treated rats. Results show that bacterial melanin has protective effects in EAE and ameliorates symptoms of EAE.

RETRACTED: Matrine regulates glutamate-related excitotoxic factors in experimental autoimmune encephalomyelitis

It is increasingly accepted that glutamate excitotoxicity contributes to the death of nerve cells in multiple sclerosis (MS). Matrine (MAT) is a quinolizidine alkaloid that has long been used in the treatment of hepatitis B without obvious side effects. Previous reports have shown that MAT suppresses central nervous system inflammation and demyelination in experimental autoimmune encephalomyelitis (EAE), an animal model of MS; however whether MAT effectively inhibits excitotoxic molecules, such as glutamate-related factors, is still unclear. In this study, we provide data showing that MAT attenuated EAE disease severity, accompanied by downregulated glutamate and upregulated GABA levels, as well as enhanced expression of two dependent glutamate transporters (GLT-1 and GLAST). In addition, MAT treatment significantly reduced the level of the NMDA- and AMPA-glutamate receptor in EAE rats. Taken together, our data indicate that MAT treatment regulates glutamate-related molecules, and suggests that the neuroprotective role of MAT is a novel mechanism underlying its therapeutic effect in EAE.

GEMSP exerts a myelin-protecting role in the rat optic nerve

Objectives: Chronic experimental autoimmune encephalomyelitis (EAE) was induced in rats to evaluate the potential protective effect of GEMSP, a mixture made up of fatty acids (FA), vitamins, and amino acids or their derivatives, linked to Poly-L-Lysine, on the myelin sheath of the optic nerve.Methods: To evaluate the effects of GEMSP on the optic nerve, animals were divided into three experimental groups: (1) EAE rats treated with GEMSP; (2) EAE rats treated with 0·9% NaCl; and (3) control, non-EAE rats. Using electron microscopy, we investigated the possibility that this new drug candidate has a myelin-protective role.Results: A marginally significant reduction in the thickness of the myelin around optic nerve medium-size axons (diameter between 0·8–1·3 μm) was found in EAE rats. Treatment of EAE rats with GEMSP ameliorated myelin damage. Significantly increased myelin thickness was found when animals in groups 2 and 3 were compared. However, the number of myelinated axons studied was not altered in groups 1 or 2 when compared to controls.Discussion: Our results suggest that in a model of demyelination, GEMSP protects and enhances the formation of the myelin sheath of the optic nerve and therefore could be a potential drug candidate to reduce optic nerve pathogenesis in multiple sclerosis (MS).

123. Visual evoked potential latencies are significantly delayed in a new model of experimental autoimmune encephalomyelitis rat

Experimental autoimmune encephalomyelitis (EAE) is a pre-clinical disease model of Multiple Sclerosis (MS). In the present study we used a novel emulsion derived from the spinal cord – spinal cord homogenate (SCH) – to induce disease in Dark-Agouti (DA) rats, monitoring EAE course by using Visual Evoked Potentials (VEPs) to assess their usefulness as neurophysiological biomarker. 19 DA rats were used in the experiment: 7 immunized by injecting SCH (EAE RATS) and 12 controls (CTRL RATS). Flash epidural VEPs from both eyes were recorded 6 times once a week (first one the day before, then at days 6, 13, 20, 27, 34 post immunization). We measured P1 latency and amplitude from N1–P1–N2 complex by acquiring, for each session, the average of 4 waveforms (10 trains each) from each eye. There was significant difference in P1 latency between CTRL RATS and EAE RATS at days 13–20 and 27 post immunization ( p p > 0,05). The present results reveal that VEP P1 latencies are significantly delayed in EAE RATS, thus showing that VEPs could be a useful tool in monitoring disease course also in this new EAE animal model.

Visualization of acute focal lesions in rats with experimental autoimmune encephalomyelitis by magnetic nanoparticles, comparing different MRI sequences including phase imaging

To compare the sensitivity and specificity of phase imaging (PI) with other magnetic resonance imaging (MRI) methods in lesion detection in rats with experimental autoimmune encephalomyelitis (EAE), as an animal model for multiple sclerosis (MS). EAE was induced in rats (n = 14) by subcutaneous (s.c.) injection of myelin basic protein (MBP) and complete Freund's adjuvant (CFA). Control animals (n = 4) were given an s.c. injection of phosphate-buffered saline mixed with CFA. The development of local inflammatory processes, demyelinations, and blood-brain barrier (BBB) disruptions were monitored over 7 weeks in a 4.7T animal scanner by T1-, T2-, T2*-weighted images, magnetization transfer, and PI in the presence or absence of very small superparamagnetic iron oxide particles (VSOP) and confirmed by immunostaining using CD31, CD68, MBP, and albumin antibodies and Gallyas silver staining. EAE rats developed time-dependent local inflammations and BBB disruptions but no clear demyelinizations. In histological stainings these processes were trackable as accumulations of phagocytic monocytes and extravasal albumin. In MRI without application of VSOP inflammatory processes were not detectable. MRI in the presence of VSOP revealed inflammatory processes by the appearance of hypointense spots (hs). The specificity of PI to detect hs was similar to T1- and T2*-weighted images The calculated sensitivity was less than in corresponding T2*-weighted images. The diagnostic use of PI without VSOP as contrast agent to detect lesions is not recommended at field strength of 4.7T or lower.

Longitudinal positron emission tomography imaging for monitoring myelin repair in the spinal cord

Novel therapeutic interventions aimed at myelin repair are now under development for neuroprotection as well as functional recovery of patients with multiple sclerosis. However, development of myelin repair therapy necessitates a noninvasive approach for measuring changes in myelin content in vivo in a quantitative fashion not yet possible using magnetic resonance imaging. For this reason, we developed a novel positron emission tomography (PET) probe, termed [11C]MeDAS, that is capable of longitudinally imaging central nervous system myelin content. The binding properties of [11C]MeDAS for myelin were systematically evaluated by in vitro and in situ fluorescent staining of the spinal cord and the brain, and by in vivo competitive blocking studies. Longitudinal PET studies were conducted in 3 rat models involving acute focal neuroinflammation in the brain, lysophosphatidylcholine (LPC)-induced focal demyelination in the spinal cord, and experimental autoimmune encephalomyelitis (EAE). Image-guided myelin repair therapy was conducted in an LPC rat model using a mesenchymal stem cell-based hepatocyte growth factor (HGF). Biodistribution and acute toxicity studies of [11C]MeDAS were also conducted. MeDAS selectively stains myelin in the spinal cord and brain. Neuroinflammation did not affect [11C]MeDAS uptake in the brain as long as the myelin sheaths remained intact. Longitudinal PET studies in LPC and EAE rat models demonstrate that [11C]MeDAS uptake changes correlate with associated myelin loss in the spinal cord. Furthermore, using [11C]MeDAS-PET, the efficacy of myelin repair therapy with HGF was longitudinally monitored in vivo. [11C]MeDAS-PET is a promising imaging marker for monitoring myelin pathology in vivo, future applications of which in humans should be achievable.

AMP-Activated Protein Kinase Signaling Protects Oligodendrocytes that Restore Central Nervous System Functions in an Experimental Autoimmune Encephalomyelitis Model

AMP-activated protein kinase (AMPK) signaling is reported to protect neurons under pathologic conditions; however, its effect on oligodendrocytes (OLs) remains to be elucidated. We investigated whether AMPK signaling protects OLs to restore central nervous system (CNS) functions in an experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. Increased inflammation and demyelination in the CNS and peripheral immune responses were consistent with the observed clinical impairments in EAE animals, which were attenuated by treatment with metformin compared with vehicle. In addition, expressions of neurotrophic factors and of signatory genes of OL lineages were increased in the CNS of metformin-treated EAE animals. Likewise, metformin attenuated inflammatory response and enhanced expressions of neurotrophic factors, thereby protecting OLs via AMPK activation in mixed glial cultures stimulated with lipopolysaccharide/interferon γ invitro, as evidenced by analysis of the expression of signatory genes of O1(+)/MBP(+) OLs and their cellular populations. Metformin also attenuated oxidative stress and malondialdehyde-containing protein levels, with corresponding induction of antioxidative defenses in OLs exposed to cytokines via AMPK activation. These effects of metformin were evident in the CNS of EAE animals. These data provide evidence that AMPK signaling is crucial to protect OLs and, thus, CNS functions in EAE animals. We conclude that AMPK activators, including metformin, have the potential to limit neurologic deficits in multiple sclerosis and related neurodegenerative disorders.

Effects of antagonists of glutamate receptors on pro-inflammatory cytokines in the brain cortex of rats subjected to experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Inflammatory cytokines and glutamate neurotoxicity have been proposed as major determinants accompanying the demyelination and axonal degeneration observed during the course of MS. The present study using the animal model of MS known as experimental autoimmune encephalomyelitis (EAE) demonstrates that pharmacological inhibition of ionotropic NMDA glutamate receptors by their antagonists (amantadine and memantine) suppresses neurological symptoms of disease in EAE rats and reduces expression of pro-inflammatory cytokines in the brain. Conversely, antagonists of group I metabotropic glutamate receptors, mGluRs (LY 367385 and MPEP), do not affect the inflammatory process and the neurological condition of EAE rats.

Nitric oxide inhibits CXCL12 expression in neuroinflammation

Chemokine CXCL12 (C-X-C motif chemokine ligand 12) restricts immune cell invasion of the central nervous system (CNS) and limits neuroinflammation in experimental autoimmune encephalomyelitis (EAE), an animal model of inflammatory and demyelinating disease of the CNS, multiple sclerosis (MS). Nitric oxide (NO), by contrast, predominantly contributes to CNS tissue destruction in MS and EAE. Thus, the influence of NO on CXCL12 in the inflamed CNS was investigated. Excess expression of inducible NO synthase was inversely correlated to CXCL12 gene expression in spinal cord homogenates of rats immunized to develop EAE. NO inhibited gene expression of CXCL12 in astrocytes and endothelial cells in vitro. The inhibition was paralleled with reduction of p38 mitogen-activated protein kinase (MAPK) phosphorylation and it was mimicked with inhibitors of p38 MAPK activation in astrocytes. In vivo suppression of nitric generation recovered CXCL12 expression in the CNS and attenuated EAE in Dark Agouti rats. On the contrary, in vivo NO donation decreased CXCL12 expression in the CNS of EAE-resistant Albino Oxford (AO) rats. However, the effect was not paralleled with induction of EAE in AO rats. It is suggested that NO acting through suppression of p38 MAPK inhibits CXCL12 expression in neuroinflammation. These results imply that downregulation of NO release and protection of CXCL12 expression within the CNS might present the potential approaches in MS therapy.