PPARgamma antagonists reverse the inhibition of neural antigen-specific Th1 response and experimental allergic encephalomyelitis by Ciglitazone and 15-deoxy-Delta12,14-prostaglandin J2

We have recently shown that de novo formation of lymphoid structures resembling B-cell follicles occurs in the inflamed central nervous system (CNS) meninges in a subset of patients with secondary progressive multiple sclerosis and in SJL mice with relapsing-remitting experimental autoimmune encephalomyelitis (EAE). Because lymphotoxin (LT) alpha(1)beta(2) is essential for lymphoid tissue organization, we used real-time PCR to examine LTbeta and LTbeta receptor (LTbetaR) gene expression in the CNS of SJL mice immunized with PLP 139-151 peptide. Moreover, we used the decoy receptor LTbetaR-immunoglobulin fusion protein to block the interaction of lymphotoxin (LT) alpha(1)beta(2) with the LTbeta receptor (LTbetaR) in mice with established EAE and evaluate the effect of systemic and local treatments with the fusion protein on disease progression, CNS lymphocytic infiltration and formation of meningeal B-cell follicles. The present findings indicate that both LTbeta and LTbetaR are upregulated at EAE onset and during subsequent relapses and that systemic and local blockade of the LT pathway with LTbetaR-Ig results in protracted and transient inhibition of EAE clinical signs, respectively. LTbetaR-Ig treatment also reduces T- and B-cell infiltration and prevents the induction of the chemokines CXCL10 and CXCL13 and the formation of organized ectopic follicles in the EAE-affected CNS. Targeting of molecules involved in lymphoid organogenesis could represent a valid strategy to inhibit CNS inflammation and formation of ectopic follicles, which may play a role in maintaining an abnormal, intrathecal humoral immune response in CNS autoimmune disease.     

Therapeutic effect of ghrelin in experimental autoimmune encephalomyelitis by inhibiting antigen-specific Th1/Th17 responses and inducing regulatory T cells

Ghrelin is an important gastrointestinal hormone that regulates feeding and metabolism. Moreover, ghrelin is produced by immune cells and shows potent anti-inflammatory activities. Here, we investigated its effect in two models of experimental autoimmune encephalomyelitis (EAE) that mirror chronic and relapsing-remitting multiple sclerosis. A short systemic treatment with ghrelin after the disease onset reduced clinical severity and incidence of both forms of EAE, which was associated with a decrease in inflammatory infiltrates in spinal cord and in the subsequent demyelination. This therapeutic effect was exerted through the reduction of the autoimmune and inflammatory components of the disease. Ghrelin decreased the presence/activation of encephalitogenic Th1 and Th17 cells in periphery and nervous system, down-regulated various inflammatory mediators, and induced regulatory T cells. In summary, our findings provide a powerful rationale for the assessment of the efficacy of ghrelin as a novel therapeutic approach for treating multiple sclerosis through distinct immunomodulatory mechanisms and further support the concept that the neuroendocrine and immune systems crosstalk to finely tune the final immune response of our body.     

1,25 Dihydroxyvitamin-D3 modulates JAK-STAT pathway in IL-12/IFNgamma axis leading to Th1 response in experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is a Th1 cell-mediated autoimmune disease model of multiple sclerosis (MS). Vitamin D deficiency is commonly observed in MS patients and vitamin D supplements reduce the clinical symptoms of EAE and MS. Earlier studies have shown that in vivo treatment with vitamin D analogs ameliorates EAE in association with the inhibition of IL-12 production and Th1 differentiation. The mechanisms in the regulation of Th1 response by vitamin D in EAE/MS are, however, not known. We show that in vivo treatment of C57BL/6 and SJL/J mice (i.p.) with 100 ng of 1,25 dihydroxyvitamin D3, on every other day from Day 0-30, ameliorates EAE in association with the inhibition of IL-12 production and neural antigen-specific Th1 response. In vitro treatment with 1,25(OH)2D3 inhibited IFNgamma-induced tyrosine phosphorylation of STAT1, without affecting JAK2, in EOC-20 microglial cells. Treatment of activated T cells with 1,25(OH)2D3 also inhibited the IL-12-induced tyrosine phosphorylation of JAK2, TYK2, STAT3, and STAT4 in association with a decrease in T cell proliferation in vitro. These findings highlight the fact that vitamin D modulates JAK-STAT signaling pathway in IL-12/IFNgamma axis leading to Th1 differentiation and further suggest its use in the treatment of MS and other Th1 cell-mediated autoimmune diseases.     

Chronic relapsing experimental allergic encephalomyelitis

Summary The vascular permeability in the nervous system to Evans blue-albumin and horseradish peroxidase was studied in chronic relapsing EAE in strain 13 and Hartley guinea pigs. The disease was induced by single sensitization of immature animals and was characterized clinically by remissions and relapses. Recent and old demyelinating plaques in the spinal cord were present. These showed an increased permeability to the protein tracers. The blood-brain barrier in these plaques are therefore disturbed and also in this respect the condition is similar to the multiple sclerosis lesions.     

Pentoxifylline inhibits experimental allergic encephalomyelitis

Pentoxifylline, a widely used methylxanthine, has been proven to inhibit the production and action of the cytokine TNF α. Since it has been suggested that TNF α is the major cytokine involved in the pathogenesis of multiple sclerosis, we tested pentoxifylline for its capacity to prevent experimental allergic encephalomyelitis (EAE). 26 Lewis rats with acute EAE were treated with either pentoxifylline or saline. The pentoxifylline treated rats showed a significantly lower incidence of clinical signs as well as significantly lower histological inflammation. The exact mechanism of this preventive effect remains to be clarified but it might be mainly related to inhibition of TNF α release from central nervous system macrophages.     

Intraventricular transplantation of neural precursor cell spheres attenuates acute experimental allergic encephalomyelitis

Brain transplantation of neural precursor cells (NPCs) has been proposed to enhance CNS regeneration. As the pathogenesis of most acute CNS diseases involves an inflammatory component, we studied whether NPC transplantation affects brain inflammation. Newborn rat multipotential NPCs were transplanted intraventriculary into acute experimental allergic encephalomyelitis (EAE) rats, a model for disseminated brain inflammation. Cells migrated into inflamed white matter and differentiated into glial cells. NPC transplantation attenuated the clinical severity of EAE and the brain inflammation, indicated by reduction in perivascular infiltrates and decreased expression of ICAM-1 and LFA-1. NPCs inhibited basal proliferation and proliferative responses to Concavalin-A and to MOG peptide of EAE rat-derived lymphocytes in vitro. Purified astrocytes inhibited lymphocyte proliferation in vitro, but did not migrate into EAE brains in vivo, and did not reduce EAE severity or brain inflammation. Thus, transplanted NPCs attenuate acute EAE via an anti-inflammatory mechanism which depends on cell ability to migrate into inflamed brain tissue.     

Hypothalamic response to experimental allergic encephalomyelitis: role of substance P

Adjuvant-induced arthritis (AA) is thought to be a model for experimental chronic stress that has as main features decreased adrenocorticotropin hormone (ACTH) plasma levels and a rise in median eminence content of arginine vasopressin (AVP) due to the activity of substance P. In experimental allergic encephalomyelitis (EAE), another chronic stress model, the role of substance P action is not clear. In this paper we tried to clarify the role of substance P in Lewis rats, which are susceptible to this disease. EAE was induced using myelin basic protein plus complete Freund's adjuvant injected into the hind limbs. One day later injections of an antagonist to substance P (RP 67580), saline, and substance P were administered daily for 12-14 days through a stainless steel cannula into the lateral ventricle of the brain, and then the rats were killed. The rats were divided into groups of controls, sham, diseased controls (no intracerebroventricular injections) and EAE (injected intracerebroventricularly). Plasma was used for the quantification of ACTH and corticosterone but not AVP which was assayed in hypothalamic median eminence extracts. In noninjected diseased rats the plasma levels of ACTH and corticosterone were significantly higher than in noninjected control rats, whereas the AVP concentrations in the median eminence were unchanged. The substance P antagonist did not affect the levels of these hormones in plasma or the median eminence. Substance P decreased the plasma levels of ACTH and corticosterone but did not increase the median eminence content of vasopressin. Administration of the antagonist 30 min before an equivalent dose of substance P increased the plasma levels of the two hormones, but did not change the content of AVP. Based on the lack of response to the antagonist RP 67580 we suggest that the substance P has different roles in EAE and AA at least in the later stages of EAE (after 11 days of immunization).     

Adoptive transfer of experimental allergic encephalomyelitis

We have previously shown that adoptive transfer of experimental allergic encephalomyelitis can be greatly enhanced by culturing sensitized lymph node cells (LNC) with specific antigen, myelin basic protein (BP). In the present study, successful transfer was accomplished with 5×10⁶ Lewis rat LNC after 48 h culture with BP. Disease transfer was inhibited by the addition to culture of dibutyryl adenosine 3’,5’-cyclic monophosphate (Bt₂ cAMP) or the phosphodiesterase inhibitor, isobutyl methylxanthine (MIX), but not by Bt₂cGMP. BP-induced lymphoproliferation was also inhibited, but with a slightly different dose-response relationship. An early step in the lymphocyte activation process appears to be most sensitive to the inhibitory effects of Bt₂cAMP.     

Immunomodulation of relapsing experimental allergic encephalomyelitis

Mice immunized to produce relapsing experimental allergic encephalomyelitis (R-EAE) were treated with immunomodulating agents known to affect acute monophasic experimental allergic encephalomyelitis. Pretreatment with either mouse spinal cord or myelin basic protein in incomplete Freund's adjuvant decreased the incidence of R-EAE from 77% to 28 and 31%, respectively. Single doses of cyclophosphamide (CY) at the time of immunization did not affect development of R-EAE. CY given repetitively in low doses decreased the incidence of R-EAE to 10%. Therefore, R-EAE can be altered by immunomodulation, but the patterns differ from those seen in acute EAE.     

Heme oxygenase-1 in SJL mice with experimental allergic encephalomyelitis

The expression of heme oxygenase-1 (HO-1) is increased in the CNS of mice and rats with experimental allergic encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). To investigate the role of HO-1 in EAE, a putative inhibitor [tin-protoporphyrin IX (Sn-PP IX)] of HO-1 was administered to SJL mice during active disease. Sn-PP IX (200 micromol/kg) attenuated clinical scores, weight loss, and some signs of pathology in comparison to vehicle treatment. Glutathione levels were greater in treated EAE mice than in those receiving vehicle, indicating lower oxidative stress in the former group. These data suggest that inhibition of HO-1 attenuated disease and suppressed free radical production. In the SJL model of EAE, extravasated blood is present in the CNS, and iron released by HO-1 from this heme source may not be adequately sequestered by ferritin, allowing for iron-mediated tissue damage. Thus, HO-1 may act to amplify the disease process in this model.     

Accelerated response to reinoculation in experimental allergic encephalomyelitis: histopathologic study.

Experimental allergic encephalomyelitis (EAE) was induced in Lewis rats by the injection of spinal cord tissue or myelin basic protein and adjuvants (Freund's or carbonyl iron or pertussis vaccine), or by adoptive immunization. After an interval of five to 12 weeks, the recovered rats were reinoculated by a different route and usually with a different adjuvant. The onset of the second attack was determined by the histologic detection of EAE lesions at intervals during the incubation period. In each of ten experiments, the second attack of EAE occurred one or two days earlier than in naive controls injected at the same time. Residual EAE lesions left over from the first attack could not explain the findings in the reinoculated rats. The accelerated response to the second inoculation may be related to the anamnestic response of classical immunology or to residual damage to the blood-brain barrier. Resistance to a second attack was not encountered in this histopathologic study.     

Mature bone marrow-derived dendritic cells polarize Th2 response and suppress experimental autoimmune encephalomyelitis

Distinct subsets of dendritic cells (DCs) based on the origin, phenotypes, and the nature of the signals that promote DC maturation can determine polarized immune responses of T cells. In this study, DCs were cultured from mouse bone marrow (BM) progenitors in granulocyte-macrophage colony-stimulating factor (GM-CSF). To generate mature DCs (mDCs), lipopolysaccharide (LPS) was used in the culture for 24 h. LPS-stimulated DCs were phenotypically mature, which exhibited strongly upregulated CD40, B7.1, and B7.2 compared to non-LPS-stimulated immature DCs (imDCs). Both mDCs and imDCs expressed high levels of MHC class II but low level of CD54. mDCs produced higher levels of IL-10 and lower IL-12 compared to imDCs. No IFN-gamma or IL-4 was found in both groups. When mDCs were injected intraperitoneally (i.p.) to the mice with experimental autoimmune encephalomyelitis (EAE), the severity of clinical signs and inflammation in the CNS was significantly suppressed compared to imDC-injected mice (p<0.01) and PBS-injected mice (p<0.02). Moreover, lymphocytes from mDC-injected mice produced lower level of IL-12, IFN-gamma, but higher level of IL-10, compared to imDC-injected and non-DC-injected mice. We conclude that BM-mDCs, but not BM-imDCs, promote Th2 differentiation and have the potential for suppression of inflammatory demyelination.     

Demyelination and neurological signs in experimental allergic encephalomyelitis

Because of the reported absence of demyelination in some animals with neurological signs of experimental allergic encephalomyelitis (EAE), it has been suggested that these signs are not due to demyelination. The present study demonstrates that there is ample demyelination in the central nervous system (CNS) and peripheral nervous system (PNS) to account for the neurological signs in rats with myelin basic protein (MBP)-induced acute EAE as well as in rats and rabbits with whole-spinal-cord-induced acute EAE. The main reasons for failure to detect demyelination in animals with neurological signs of EAE appear to be inadequate histological techniques and incomplete examination of the nervous system, particularly the PNS and the lumbar, sacral and coccygeal segments of the spinal cord.     

Neuroimmunology of multiple sclerosis and experimental allergic encephalomyelitis

The potential causes, immunopathology, and treatment of multiple sclerosis (MS) are summarized in this article. Findings from a well-examined animal model for MS, experimental allergic encephalomyelitis (EAE), are described and used to illustrate the paths of research in MS. Data from a recent clinical trial with a modified myelin peptide provide support for concepts deduced from EAE. The authors stress that the complexity of the disease requires new techniques to capture the influence of single or combined treatment approaches.