Modulation of pacemaker channel function in a model of thalamocortical hyperexcitability by demyelination and cytokines.

A consensus is yet to be reached regarding the exact prevalence of epileptic seizures or epilepsy in multiple sclerosis (MS). In addition, the underlying pathophysiological basis of the reciprocal interaction among neuroinflammation, demyelination, and epilepsy remains unclear. Therefore, a better understanding of cellular and network mechanisms linking these pathologies is needed. Cuprizone-induced general demyelination in rodents is a valuable model for studying MS pathologies. Here, we studied the relationship among epileptic activity, loss of myelin, and pro-inflammatory cytokines by inducing acute, generalized demyelination in a genetic mouse model of human absence epilepsy, C3H/HeJ mice. Both cellular and network mechanisms were studied using in vivo and in vitro electrophysiological techniques. We found that acute, generalized demyelination in C3H/HeJ mice resulted in a lower number of spike-wave discharges, increased cortical theta oscillations, and reduction of slow rhythmic intrathalamic burst activity. In addition, generalized demyelination resulted in a significant reduction in the amplitude of the hyperpolarization-activated inward current (Ih) in thalamic relay cells, which was accompanied by lower surface expression of hyperpolarization-activated, cyclic nucleotide-gated channels, and the phosphorylated form of TRIP8b (pS237-TRIP8b). We suggest that demyelination-related changes in thalamic Ih may be one of the factors defining the prevalence of seizures in MS.

Dietary conjugated linoleic acid links reduced intestinal inflammation to amelioration of CNS autoimmunity.

A close interaction between gut immune responses and distant organ-specific autoimmunity including the CNS in multiple sclerosis has been established in recent years. This so-called gut-CNS axis can be shaped by dietary factors, either directly or via indirect modulation of the gut microbiome and its metabolites. Here, we report that dietary supplementation with conjugated linoleic acid, a mixture of linoleic acid isomers, ameliorates CNS autoimmunity in a spontaneous mouse model of multiple sclerosis, accompanied by an attenuation of intestinal barrier dysfunction and inflammation as well as an increase in intestinal myeloid-derived suppressor-like cells. Protective effects of dietary supplementation with conjugated linoleic acid were not abrogated upon microbiota eradication, indicating that the microbiome is dispensable for these conjugated linoleic acid-mediated effects. Instead, we observed a range of direct anti-inflammatory effects of conjugated linoleic acid on murine myeloid cells including an enhanced IL10 production and the capacity to suppress T-cell proliferation. Finally, in a human pilot study in patients with multiple sclerosis (n = 15, under first-line disease-modifying treatment), dietary conjugated linoleic acid-supplementation for 6 months significantly enhanced the anti-inflammatory profiles as well as functional signatures of circulating myeloid cells. Together, our results identify conjugated linoleic acid as a potent modulator of the gut-CNS axis by targeting myeloid cells in the intestine, which in turn control encephalitogenic T-cell responses.

Maladaptive cortical hyperactivity upon recovery from experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) patients exhibit neuropsychological symptoms in early disease despite the immune attack occurring predominantly in white matter and spinal cord. It is unclear why neurodegeneration may start early in the disease and is prominent in later stages. We assessed cortical microcircuit activity by employing spiking-specific two-photon Ca2+ imaging in proteolipid protein-immunized relapsing-remitting SJL/J mice in vivo. We identified the emergence of hyperactive cortical neurons in remission only, independent of direct immune-mediated damage and paralleled by elevated anxiety. High levels of neuronal activity were accompanied by increased caspase-3 expression. Cortical TNFα expression was mainly increased by excitatory neurons in remission; blockade with intraventricular infliximab restored AMPA spontaneous excitatory postsynaptic current frequencies, completely recovered normal neuronal network activity patterns and alleviated elevated anxiety. This suggests a dysregulation of cortical networks attempting to achieve functional compensation by synaptic plasticity mechanisms, indicating a link between immune attack and early start of neurodegeneration.

Intravenous Iron Carboxymaltose as a Potential Therapeutic in Anemia of Inflammation.

Intravenous iron supplementation is an effective therapy in iron deficiency anemia (IDA), but controversial in anemia of inflammation (AI). Unbound iron can be used by bacteria and viruses for their replication and enhance the inflammatory response. Nowadays available high molecular weight iron complexes for intravenous iron substitution, such as ferric carboxymaltose, might be useful in AI, as these pharmaceuticals deliver low doses of free iron over a prolonged period of time. We tested the effects of intravenous iron carboxymaltose in murine AI: Wild-type mice were exposed to the heat-killed Brucella abortus (BA) model and treated with or without high molecular weight intravenous iron. 4h after BA injection followed by 2h after intravenous iron treatment, inflammatory cytokines were upregulated by BA, but not enhanced by iron treatment. In long term experiments, mice were fed a regular or an iron deficient diet and then treated with intravenous iron or saline 14 days after BA injection. Iron treatment in mice with BA-induced AI was effective 24h after iron administration. In contrast, mice with IDA (on iron deficiency diet) prior to BA-IA required 7d to recover from AI. In these experiments, inflammatory markers were not further induced in iron-treated compared to vehicle-treated BA-injected mice. These results demonstrate that intravenous iron supplementation effectively treated the murine BA-induced AI without further enhancement of the inflammatory response. Studies in humans have to reveal treatment options for AI in patients.

Nuclear export inhibitors avert progression in preclinical models of inflammatory demyelination.

Axonal damage has been associated with aberrant protein trafficking. We examined a newly characterized class of compounds that target nucleo-cytoplasmic shuttling by binding to the catalytic groove of the nuclear export protein XPO1 (also known as CRM1, chromosome region maintenance protein 1). Oral administration of reversible CRM1 inhibitors in preclinical murine models of demyelination significantly attenuated disease progression, even when started after the onset of paralysis. Clinical efficacy was associated with decreased proliferation of immune cells, characterized by nuclear accumulation of cell cycle inhibitors, and preservation of cytoskeletal integrity even in demyelinated axons. Neuroprotection was not limited to models of demyelination, but was also observed in another mouse model of axonal damage (that is, kainic acid injection) and detected in cultured neurons after knockdown of Xpo1, the gene encoding CRM1. A proteomic screen for target molecules revealed that CRM1 inhibitors in neurons prevented nuclear export of molecules associated with axonal damage while retaining transcription factors modulating neuroprotection.

Thalamic involvement in patients with neurologic impairment due to Shiga toxin 2.

OBJECTIVE: The outbreak of hemolytic-uremic syndrome and diarrhea caused by Shiga toxin-producing Escherichia coli O104:H4 in Germany during May to July 2011 involved severe and characteristic neurologic manifestations with a strong female preponderance. Owing to these observations, we designed a series of experimental studies to evaluate the underlying mechanism of action of this clinical picture. METHODS: A magnetic resonance imaging and electroencephalographic study of patients was performed to evaluate the clinical picture in detail. Thereafter, combinations of different experimental settings, including electrophysiological and histological analyses, as well as calcium imaging in brain slices of rats, were conducted. RESULTS: We report on 7 female patients with neurologic symptoms and signs including bilateral thalamic lesions and encephalopathic changes indicative of a predominant involvement of the thalamus. Experimental studies in rats revealed an enhanced expression of the Shiga toxin receptor globotriaosylceramide on thalamic neurons in female rats as compared to other brain regions in the same rats and to male animals. Incubation of brain slices with Shiga toxin 2 evoked a strong membrane depolarization and intracellular calcium accumulation in neurons, associated with neuronal apoptosis, predominantly in the thalamic area. INTERPRETATION: These findings suggest that the direct cytotoxic effect of Shiga toxin 2 in the thalamus might contribute to the pathophysiology of neuronal complications in hemolytic-uremic syndrome.