Jan Thöne

Dietary Fatty Acids Directly Impact Central Nervous System Autoimmunity via the Small Intestine

Growing empirical evidence suggests that nutrition and bacterial metabolites might impact the systemic immune response in the context of disease and autoimmunity. We report that long-chain fatty acids (LCFAs) enhanced differentiation and proliferation of T helper 1 (Th1) and/or Th17 cells and impaired their intestinal sequestration via p38-MAPK pathway. Alternatively, dietary short-chain FAs (SCFAs) expanded gut T regulatory (Treg) cells by suppression of the JNK1 and p38 pathway. We used experimental autoimmune encephalomyelitis (EAE) as a model of T cell-mediated autoimmunity to show that LCFAs consistently decreased SCFAs in the gut and exacerbated disease by expanding pathogenic Th1 and/or Th17 cell populations in the small intestine. Treatment with SCFAs ameliorated EAE and reduced axonal damage via long-lasting imprinting on lamina-propria-derived Treg cells. These data demonstrate a direct dietary impact on intestinal-specific, and subsequently central nervous system-specific, Th cell responses in autoimmunity, and thus might have therapeutic implications for autoimmune diseases such as multiple sclerosis.

Modulation of Autoimmune Demyelination by Laquinimod via Induction of Brain-Derived Neurotrophic Factor

Laquinimod is a promising, orally available compound that has been successfully evaluated in placebo-controlled phase II/III studies of relapsing-remitting multiple sclerosis (MS). Studies are ongoing to further define laquinimods modulatory mechanisms. Analyses in the animal model of experimental autoimmune encephalomyelitis (EAE) demonstrate that laquinimod reduces infiltration of leukocytes into the central nervous system, induces a Th1 to Th2/3 shift, and suppresses Th17 responses. To evaluate the potential neuroprotective capacity of laquinimod via modulation of brain-derived neurotrophic factor (BDNF), we analyzed the expression of BDNF in blood samples from 203 MS patients treated with laquinimod. Furthermore, we investigated the effect of laquinimod in EAE using a conditional BDNF knockout strain lacking BDNF expression in myeloid cells and T cells (LLF mice). Treatment with laquinimod resulted in a significant and persistent increase in BDNF serum levels of MS patients when compared to baseline and placebo-treated patients. LLF mice treated with laquinimod display a more severe EAE disease course in comparison to wild-type mice. Furthermore, laquinimod-treated wild-type monocytes secreted an anti-inflammatory cytokine pattern in comparison to untreated wild-type monocytes and treated LLF monocytes. Adoptive transfer of laquinimod stimulated monocytes into mice with EAE ameliorated the disease course. Consistent with immunomodulatory properties, laquinimod skewed monocytes toward a regulatory phenotype and also acted via modulation of BDNF, which may contribute to neuroprotection in MS patients.

Impact of aerobic exercise training on cognitive functions and affect associated to the COMT polymorphism in young adults

Physical fitness can serve as a means to enhance cognitive functioning by modulating particular aspects of brain functioning. However, mechanisms underlying this modulating effect remain widely unresolved. To examine the impact and to clarify the mechanisms of physical fitness training in a young and healthy population, it was investigated whether an increase in fitness would result in improvements in executive control processes and positive and negative affect. Moreover, genotype of the Val158Met polymorphism in catechol-O-methyltransferase (COMT) as an index of relative central dopamine bioavailability was determined to elucidate dopamine tuning efficiency and its association with performance in the applied cognitive tasks. Seventy-five individuals participated and underwent an incremental fitness test to assess physical fitness. An exercising group subsequently engaged in a 17 weeks running training consisting of three running sessions at moderate to high, individually adjusted intensities. Associated with increased fitness improved cognitive flexibility and cognitive control were observed, whereas working memory remained unaffected. In runners, Val/Val participants improved cognitive performance to a greater extent compared to individuals carrying a Met allele. From the present results it is concluded that an increase in physical fitness provides a means to improve cognitive functioning via dopaminergic modulation.

Inflammation modulates anxiety in an animal model of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by inflammation, but also degenerative changes. Besides neurological deficits, the rate of affective disorders such as depression and anxiety is at least six fold increased. Many aspects of MS can be mimicked in the animal model of myelin oligodendrocyte glycoprotein experimental autoimmune encephalomyelitis (MOG-EAE). Here we investigate behavioral changes in C57BL/6 mice suffering from mild MOG-EAE. In the later phase of the disease, mice were subjected to behavioral tests including the light-dark-box (LD Box), the acoustic startle response (SR) with a pre-pulse inhibition protocol as well as the learned helplessness (LH) paradigm. Behavioral data were correlated with the motor performance in an open field and rotarod test (RR). In the RR and open field, there was no significant difference in the motor performance between controls and mice suffering from mild MOG-EAE. Yet EAE mice displayed an increased anxiety-like behavior with a 23% reduction of the time spent in the bright compartment of the LD Box as well as an increased SR. In the LH paradigm, mice suffering from MOG-EAE were twice as much prone to depressive-like behavior. These changes correlate with an increase of hippocampal tissue tumor necrosis factor alpha levels and neuronal loss in the hippocampus. Modulation of monoaminergic transmission by chronic application of the antidepressant amitriptyline resulted in a decreased startle reaction and increased hippocampal norepinephrine levels. These data imply that chronic inflammation in the CNS may impact on emotional responses in rodent models of anxiety.

Anti-inflammatory effects of the anticonvulsant drug levetiracetam on electrophysiological properties of astroglia are mediated via TGFβ1 regulation

BACKGROUND AND PURPOSE The involvement of astrocytes as immune‐competent players in inflammation and the pathogenesis of epilepsy and seizure‐induced brain damage has recently been recognized. In clinical trials and practice, levetiracetam (LEV) has proven to be an effective antiepileptic drug (AED) in various forms of epileptic seizures, when applied as mono‐ or added therapy. Little is known about the mechanism(s) of action of LEV. Evidence so far suggests a mode of action different from that of classical AEDs. We have shown that LEV restored functional gap junction coupling and basic membrane properties in an astrocytic inflammatory model in vitro.

Topiramate modulates pH of hippocampal CA3 neurons by combined effects on carbonic anhydrase and Cl−/HCO3− exchange

Topiramate (TPM) is an anticonvulsant whose impact on firing activity and intracellular pH (pHi) regulation of CA3 neurons was investigated. Using the 4‐aminopyridine‐treated hippocampal slice model bathed in bicarbonate‐buffered solution, TPM (25–50 μM) reduced the frequency of epileptiform bursts and action potentials without affecting membrane potential or input resistance. Inhibitory effects of TPM were reversed by trimethylamine‐induced alkalinization. TPM also lowered the steady‐state pHi of BCECF‐AM‐loaded neuronal somata by 0.18±0.07 pH units in CO2/HCO3−‐buffered solution. Subsequent to an ammonium prepulse, TPM reduced the acidotic peak but clearly slowed pHi recovery. These complex changes were mimicked by the protein phosphatase inhibitor okadaic acid. Alkalosis upon withdrawal of extracellular Cl− was augmented by TPM. Furthermore, at decreased pHi due to the absence of extracellular Na+, TPM reversibly increased pHi. These findings demonstrate that TPM modulates Na+‐independent Cl−/HCO3− exchange. In the nominal absence of extracellular CO2/HCO3− buffer, both steady‐state pHi and firing of epileptiform bursts remained unchanged upon adding TPM. However, pHi recovery subsequent to an ammonium prepulse was slightly increased, as was the case in the presence of the carbonic anhydrase (CA) inhibitor acetazolamide. Thus, a slight reduction of intracellular buffer capacity by TPM may be due to an inhibitory effect on intracellular CA. Together, these findings show that TPM lowers neuronal pHi most likely due to a combined effect on Na+‐independent Cl−/HCO3− exchange and CA. The apparent decrease of steady‐state pHi may contribute to the anticonvulsive property of TPM.

Constitutive activity of NF-kappa B in myeloid cells drives pathogenicity of monocytes and macrophages during autoimmune neuroinflammation

The NF-κB/REL-family of transcription factors plays a central role in coordinating the expression of a wide variety of genes controlling immune responses including autoimmunity of the central nervous system (CNS). The inactive form of NF-κB consists of a heterodimer which is complexed with its inhibitor, IκB. Conditional knockout-mice for IκBα in myeloid cells (lysMCreIκBαfl/fl) have been generated and are characterized by a constitutive activation of NF-κB proteins allowing the study of this transcription factor in myelin-oligodendrocyte-glycoprotein induced experimental autoimmune encephalomyelitis (MOG-EAE), a well established experimental model for autoimmune demyelination of the CNS.In comparison to controls, lysMCreIκBαfl/fl mice developed a more severe clinical course of EAE. Upon histological analysis on day 15 p.i., there was an over two fold increased infiltration of T-cells and macrophages/microglia. In addition, lysMCreIκBαfl/fl mice displayed an increased expression of the NF-κB dependent factor inducible nitric oxide synthase in inflamed lesions. These changes in the CNS are associated with increased numbers of CD11b positive splenocytes and a higher expression of Ly6c on monocytes in the periphery. Well in accordance with these changes in the myeloid cell compartment, there was an increased production of the monocyte cytokines interleukin(IL)-12 p70, IL-6 and IL-1beta in splenocytes. In contrast, production of the T-cell associated cytokines interferon gamma (IFN-gamma) and IL-17 was not influenced.In summary, myeloid cell derived NF-κB plays a crucial role in autoimmune inflammation of the CNS and drives a pathogenic role of monocytes and macrophages independently from T-cells.

Levetiracetam inhibits Na+-dependent Cl−/HCO3− exchange of adult hippocampal CA3 neurons from guinea-pigs

The novel anticonvulsant levetiracetam (LEV) was tested for effects on bioelectric activity and intracellular pH (pHi) regulation of hippocampal CA3 neurons from adult guinea‐pigs. In 4‐aminopyridine‐treated slices, LEV (10–100 μM) reduced the frequency of action potentials and epileptiform bursts of CA3 neurons by 30–55%, while the shape of these potentials remained largely unchanged. Suppressive effects were reversed by an increase of pHi with trimethylamine (TMA). Using BCECF‐AM‐loaded slices, we found that LEV (10–50 μM) reversibly lowered neuronal steady‐state pHi by 0.19±0.07 pH units in the presence of extracellular CO2/HCO3− buffer. In the nominal absence of extracellular CO2/HCO3− or in Na+‐free CO2/HCO3−‐buffered solution, LEV had no effect on steady‐state pHi. Recovery of pHi subsequent to ammonium prepulses remained unchanged in the absence of CO2/HCO3− buffer, but was significantly reduced by LEV in the presence of CO2/HCO3− buffer. These findings show that LEV inhibits HCO3−‐dependent acid extrusion, but has no effect on Na+/H+ exchange. LEV did not affect Na+‐independent Cl−/HCO3− exchange because intracellular alkalosis upon withdrawal of extracellular Cl− remained unchanged. These data show that LEV at clinically relevant concentrations inhibits Na+‐dependent Cl−/HCO3− exchange, lowers neuronal pHi, and thereby may contribute to its anticonvulsive activity.

Laquinimod: a promising oral medication for the treatment of relapsing-remitting multiple sclerosis

Introduction: MS is a chronic immunological disease of the CNS. Due to a lack of curative treatment approaches, current principles aim at the reduction of inflammatory disease activity. Today, many different substances are under investigation in Phase III clinical trials and hold promise in the treatment of relapsing-remitting MS (RRMS). Laquinimod is a promising new orally administered substance which has demonstrated beneficial effects in placebo-controlled trials in patients with RRMS and is currently under investigation in two global Phase III trials. Areas covered: The authors review the pharmaceutical properties of laquinimod, its suggested mechanisms of action, clinical efficacy and adverse profile. This review contains data that have been presented by experts in the field at international meetings and congresses and that have been published in peer-reviewed journals. Expert opinion: While laquinimod has been shown to have a promising safety profile, its mechanisms of action are not completely understood and further research is necessary to clarify this. Studies conducted in EAE, the mouse model of MS, have demonstrated immunomodulatory and neuroprotective mechanisms of action. Hopefully, the two current pivotal Phase III trials currently underway will shed some light on laquinimod confirming its clinical potential and add to the current armamentarium for the treatment of RRMS.

Effective immunosuppressant therapy with cyclophosphamide and corticosteroids in paraneoplastic cerebellar degeneration

Paraneoplastic cerebellar degeneration (PCD) is a rare immune mediated phenomenon often associated with cancer of the ovarian. Hitherto, tumor dissection is the mainstay in therapy while immunomodulatory treatment regimes often fail. Here we report on an 86 year old female patient who developed a severe pancerebellar syndrome. Clinical course, onconeural (anti-Yo) antibodies and detection of ovarian cancer suggest the assumption of PCD as the most probable diagnosis. We initiated a high-dose course of corticosteroids followed by a single dose of cyclophosphamide (600 mg/day). Surprisingly patients condition improved and stabilized within days subsequent to cyclophosphamide application. This case demonstrates the benefit of immunosuppressive therapy in an anti-Yo positive patient with severe PCD secondary to an ovarian cancer.