Orhan Aktas

Sirt1 contributes critically to the redox-dependent fate of neural progenitors

Repair processes that are activated in response to neuronal injury, be it inflammatory, ischaemic, metabolic, traumatic or other cause, are characterized by a failure to replenish neurons and by astrogliosis. The underlying molecular pathways, however, are poorly understood. Here, we show that subtle alterations of the redox state, found in different brain pathologies, regulate the fate of mouse neural progenitor cells (NPCs) through the histone deacetylase (HDAC) Sirt1. Mild oxidation or direct activation of Sirt1 suppressed proliferation of NPCs and directed their differentiation towards the astroglial lineage at the expense of the neuronal lineage, whereas reducing conditions had the opposite effect. Under oxidative conditions in vitro and in vivo, Sirt1 was upregulated in NPCs, bound to the transcription factor Hes1 and subsequently inhibited pro-neuronal Mash1. In utero shRNA-mediated knockdown of Sirt1 in NPCs prevented oxidation-mediated suppression of neurogenesis and caused upregulation of Mash1 in vivo. Our results provide evidence for an as yet unknown metabolic master switch that determines the fate of neural progenitors.

Green Tea Epigallocatechin-3-Gallate Mediates T Cellular NF-κB Inhibition and Exerts Neuroprotection in Autoimmune Encephalomyelitis

Recent studies in multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), point to the fact that even in the early phase of inflammation, neuronal pathology plays a pivotal role in the sustained disability of affected individuals. We show that the major green tea constituent, (−)-epigallocatechin-3-gallate (EGCG), dramatically suppresses EAE induced by proteolipid protein 139–151. EGCG reduced clinical severity when given at initiation or after the onset of EAE by both limiting brain inflammation and reducing neuronal damage. In orally treated mice, we found abrogated proliferation and TNF-α production of encephalitogenic T cells. In human myelin-specific CD4+ T cells, cell cycle arrest was induced, down-regulating the cyclin-dependent kinase 4. Interference with both T cell growth and effector function was mediated by blockade of the catalytic activities of the 20S/26S proteasome complex, resulting in intracellular accumulation of IκB-α and subsequent inhibition of NF-κB activation. Because its structure implicates additional antioxidative properties, EGCG was capable of protecting against neuronal injury in living brain tissue induced by N-methyl-d-aspartate or TRAIL and of directly blocking the formation of neurotoxic reactive oxygen species in neurons. Thus, a natural green tea constituent may open up a new therapeutic avenue for young disabled adults with inflammatory brain disease by combining, on one hand, anti-inflammatory and, on the other hand, neuroprotective capacities.

TNF-related apoptosis inducing ligand (TRAIL) as a potential response marker for interferon-beta treatment in multiple sclerosis

BACKGROUNDnMany patients with multiple sclerosis do not respond to interferon beta, which is widely used as an immunomodulatory treatment in this disease. We aimed to assess the functional relevance of tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL), which is upregulated on incubation with interferon beta, for clinical treatment response.nnnMETHODSnWe quantified gene expression longitudinally by realtime-PCR of the peripheral immune cells of 82 patients with multiple sclerosis. In a first cohort of 62 patients, 20 were classified as first-year responders since they did not have relapses during treatment with interferon beta 1a; 19 were classified as first-year non-responders; and 23 developed neutralising antibodies to interferon beta. A second cohort, also characterised by MRI, consisted of 11 patients on interferon beta 1a and nine patients who were not treated. Concentrations of soluble TRAIL were determined by ELISA in serum samples of nine non-treated patients, 49 patients before treatment (29 responders, 20 non-responders), as well as longitudinally in a subset of 23 patients.nnnFINDINGSnIn both patient cohorts, drug-responders could be distinguished from non-responders by early and sustained induction of TRAIL (p<0.0001, each). In the presence of neutralising antibodies, initial upregulation of TRAIL expression was subsequently abrogated. Raised concentrations of soluble TRAIL in patients serum samples before the start of treatment allowed prediction of the treatment response in the first year (ROC analysis with area under the curve 0.879 [0.785-0.974]).nnnINTERPRETATIONnOur data suggest that TRAIL expression is a candidate for pretreatment assessment and might thus be used as a prognostic marker of treatment response to interferon beta in multiple sclerosis. Furthermore, our observations have implications for the development of future immunoregulatory strategies in multiple sclerosis therapy.

Neuronal Damage in Autoimmune Neuroinflammation Mediated by the Death Ligand TRAIL

Here, we provide evidence for a detrimental role of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in neural death in T cell-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Clinical severity and neuronal apoptosis in brainstem motor areas were substantially reduced upon brain-specific blockade of TRAIL after induction of EAE through adoptive transfer of encephalitogenic T cells. Furthermore, TRAIL-deficient myelin-specific lymphocytes showed reduced encephalitogenicity when transferred to wild-type mice. Conversely, intracerebral delivery of TRAIL to animals with EAE increased clinical deficits, while naive mice were not susceptible to TRAIL. Using organotypic slice cultures as a model for living brain tissue, we found that neurons were susceptible to TRAIL-mediated injury induced by encephalitogenic T cells. Thus, in addition to its known immunoregulatory effects, the death ligand TRAIL contributes to neural damage in the inflamed brain.

Antibody to aquaporin 4 in the diagnosis of neuromyelitis optica.

Background Neuromyelitis optica (NMO) is a demyelinating disease of the central nervous system (CNS) of putative autoimmune aetiology. Early discrimination between multiple sclerosis (MS) and NMO is important, as optimum treatment for both diseases may differ considerably. Recently, using indirect immunofluorescence analysis, a new serum autoantibody (NMO-IgG) has been detected in NMO patients. The binding sites of this autoantibody were reported to colocalize with aquaporin 4 (AQP4) water channels. Thus we hypothesized that AQP4 antibodies in fact characterize NMO patients. Methods and Findings Based on these observations we cloned human water channel AQP4, expressed the protein in a eukaryotic transcription/translation system, and employed the recombinant AQP4 to establish a new radioimmunoprecipitation assay (RIPA). Indeed, application of this RIPA showed that antibodies against AQP4 exist in the majority of patients with NMO (n = 37; 21 positive) as well as in patients with isolated longitudinally extensive transverse myelitis (n = 6; six positive), corresponding to a sensitivity of 62.8% and a specificity of 98.3%. By contrast, AQP4 antibodies were virtually absent in 291 other participants, which included patients with MS (n = 144; four positive), patients with other inflammatory and noninflammatory neurological diseases (n = 73; one positive), patients with systemic autoimmune diseases (n = 45; 0 positive), and healthy participants (n = 29; 0 positive). Conclusions In the largest series reported so far to our knowledge, we quantified AQP4 antibodies in patients with NMO versus various other diseases, and showed that the aquaporin 4 water channel is a target antigen in a majority of patients with NMO. The newly developed assay represents a highly specific, observer-independent, and easily reproducible detection method facilitating clinically relevant discrimination between NMO, MS, and other inflammatory diseases.

Activation of kinin receptor B1 limits encephalitogenic T lymphocyte recruitment to the central nervous system

Previous proteomic and transcriptional analyses of multiple sclerosis lesions revealed modulation of the renin-angiotensin and the opposing kallikrein-kinin pathways. Here we identify kinin receptor B1 (Bdkrb1) as a specific modulator of immune cell entry into the central nervous system (CNS). We demonstrate that the Bdkrb1 agonist R838 (Sar-[D-Phe]des-Arg9-bradykinin) markedly decreases the clinical symptoms of experimental autoimmune encephalomyelitis (EAE) in SJL mice, whereas the Bdkrb1 antagonist R715 (Ac-Lys-[D-βNal7, Ile8]des-Arg9-bradykinin) resulted in earlier onset and greater severity of the disease. Bdkrb1-deficient (Bdkrb1−/−) C57BL/6 mice immunized with a myelin oligodendrocyte glycoprotein fragment, MOG35–55, showed more severe disease with enhanced CNS-immune cell infiltration. The same held true for mixed bone marrow–chimeric mice reconstituted with Bdkrb1−/− T lymphocytes, which showed enhanced T helper type 17 (TH17) cell invasion into the CNS. Pharmacological modulation of Bdkrb1 revealed that in vitro migration of human TH17 lymphocytes across blood-brain barrier endothelium is regulated by this receptor. Taken together, these results suggest that the kallikrein-kinin system is involved in the regulation of CNS inflammation, limiting encephalitogenic T lymphocyte infiltration into the CNS, and provide evidence that Bdkrb1 could be a new target for the treatment of chronic inflammatory diseases such as multiple sclerosis.

Oral high-dose atorvastatin treatment in relapsing-remitting multiple sclerosis.

Background Recent data from animal models of multiple sclerosis (MS) and from a pilot study indicated a possible beneficial impact of statins on MS. Methodology/Principal Findings Safety, tolerability and effects on disease activity of atorvastatin given alone or in combination with interferon-beta (IFN-β) were assessed in a phase II open-label baseline-to-treatment trial in relapsing-remitting MS (RRMS). Patients with at least one gadolinium-enhancing lesion (CEL) at screening by magnetic resonance imaging (MRI) were eligible for the study. After a baseline period of 3 monthly MRI scans (months −2 to 0), patients followed a 9-month treatment period on 80 mg atorvastatin daily. The number of CEL in treatment months 6 to 9 compared to baseline served as the primary endpoint. Other MRI-based parameters as well as changes in clinical scores and immune responses served as secondary endpoints. Of 80 RRMS patients screened, 41 were included, among them 16 with IFN-β comedication. The high dose of 80 mg atorvastatin was well tolerated in the majority of patients, regardless of IFN-β comedication. Atorvastatin treatment led to a substantial reduction in the number and volume of CEL in two-sided multivariate analysis (pu200a=u200a0.003 and pu200a=u200a0.008). A trend towards a significant decrease in number and volume of CEL was also detected in patients with IFN-β comedication (pu200a=u200a0.060 and pu200a=u200a0.062), in contrast to patients without IFN-β comedication (pu200a=u200a0.170 and pu200a=u200a0.140). Immunological investigations showed no suppression in T cell response but a significant increase in IL-10 production. Conclusions/Significance Our data suggest that high-dose atorvastatin treatment in RRMS is safe and well tolerated. Moreover, MRI analysis indicates a possible beneficial effect of atorvastatin, alone or in combination with IFN-β, on the development of new CEL. Thus, our findings provide a rationale for phase II/III trials, including combination of atorvastatin with already approved immunomodulatory therapy regimens. Trial Registration ClinicalTrials.gov NCT00616187

Atorvastatin Induces T Cell Anergy via Phosphorylation of ERK1

Modulation of T cell response is a novel property of 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors. Previously we reported the benefits of atorvastatin treatment in experimental autoimmune encephalomyelitis, the murine model of the T cell-mediated autoimmune disorder multiple sclerosis, in which a blockade of the T cell cycle by atorvastatin was attributed to an accumulation of the negative regulator p27Kip1. We show in this report that, in line with the documented role of p27Kip1 in T cell anergy, treatment with atorvastatin results in a deficient response to a second productive stimulus in human T cells. This effect of atorvastatin was dependent on HMG-CoA reduction and required IL-10 signaling. Importantly, atorvastatin induced an early and sustained phosphorylation of ERK1, but not ERK2, which was crucial for the induction of anergy. On the basis of the therapeutic impact of HMG-CoA reductase inhibitors, the present findings should pave the way for future therapeutic concepts related to tolerance induction in neuroinflammatory disorders such as multiple sclerosis.

Systemic IFN-β treatment induces apoptosis of peripheral immune cells in MS patients

In multiple sclerosis (MS), an impaired apoptotic deletion of activated CNS-specific immune cells, leading to their pathogenic persistence, has been suggested to maintain chronic brain inflammation. We here investigated whether interferon-beta (IFN-beta) therapy induces apoptosis of peripheral immune cells. Serial blood samples from 127 relapsing-remitting MS patients were analyzed prior to the initiation of a weekly IFN-beta 1a therapy and 4, 26, and 52 weeks thereafter. Peripheral immune cells were investigated for apoptosis and for the expression of apoptosis-regulatory genes CD95, CD95 ligand, FLIP, Bcl-2, Bcl-X(L), Bag-1, and caspase 3 by quantitative real-time PCR. Biological efficacy of IFN-beta treatment was checked by quantification of Mx expression (ELISA and real-time PCR). We found a significant increase in the apoptosis rate of immune cells in response to IFN-beta treatment, compared to baseline levels. While Bcl-2 levels were permanently and Bag-1 levels transiently elevated upon therapy, other apoptosis-regulatory genes revealed no alterations. Upregulation of Mx expression confirmed the activity of IFN-beta in vivo. These findings indicate that immunomodulatory IFN-beta therapy involves the induction of apoptotic cell death with the observed RNA upregulation of Bcl-2 family members rather reflecting a possible compensatory mechanism. The increased apoptosis susceptibility of peripheral immune cells may contribute to the known reduction of brain inflammatory lesions during IFN-beta treatment.

Poor PASAT performance correlates with MRI contrast enhancement in multiple sclerosis

Background: Cognitive impairment is increasingly recognized as relevant clinical feature in multiple sclerosis (MS). We applied the Paced Auditory Serial Addition Test (PASAT), a recommended screening tool for cognitive dysfunction in MS, to investigate the relationship between cognitive performance and the presence of gadolinium (Gd)–enhancing lesions on brain MRI. Methods: In this longitudinal correlational research study, 75 patients with relapsing-remitting MS (48 women and 27 men, mean age 36 years, mean disease duration 5 years, mean Expanded Disability Status Scale [EDSS] 1.7) without clinical signs of a relapse underwent 2 MRI measurements (number and volume of T1 contrast-enhancing lesions and of T2 lesions) and clinical examinations (EDSS and Multiple Sclerosis Functional Composite [MSFC]) with a mean interscan interval of 10 weeks. Patients were divided into 3 groups: A (n = 38), Gd on 1 scan; B (n = 12), Gd on both scans; and C (n = 25), Gd on neither scan. Results: In group A, PASAT was better at the Gd-negative time point (p = 0.002), whereas the other MSFC subscores remained unchanged. Subgroup analysis confirmed the finding in patients with a Gd-positive scan first, whereas this was not the case for patients with a Gd-negative scan first, presumably owing to the small sample size of this subgroup. In groups B and C, there was no difference between both time points regarding MSFC and its subscores. EDSS remained stable in all groups during the investigation. Conclusions: Paced Auditory Serial Addition Test performance is affected by the appearance of Gd enhancement as surrogate marker of inflammatory activity in otherwise physically stable patients with multiple sclerosis, which may indicate that Gd enhancement causes a diffuse impairment of cerebral connectivity with a negative impact on cognitive functioning.