The restoration of hippocampal nerve de-myelination by methylcobalamin relates with the enzymatic regulation of homocysteine level in a rat model of moderate grade hepatic encephalopathy

This article describes how methylcobalamin (MeCbl) restores nerve myelination in a moderate- grade hepatic encephalopathy (MoHE) model of ammonia neurotoxicity. The comparative profiles of myelin basic protein (MBP), homocysteine (Hcy) and methionine synthase (MS: a MeCbl- dependent enzyme) activity versus nerve myelination status were studied in the hippocampus of the control, the MoHE (developed by administering 100 mg/kg bw thioacetamide i.p. for 10 days) and the MoHE rats treated with MeCbl (500 µg/kg BW i.p.) for 7 days. Compared to those of control rats, the hippocampal CA1 and CA3 regions of the MoHE rats showed significantly lower myelinated areas and MBP immunostaining. This coincided with the deranged myelin layering in TEM images, decreased MBP protein and its transcript levels in hippocampus of MoHE rats. However, all these parameters recovered to normal levels after MeCbl treatment. MeCbl is a cofactor of MS that catalyzes the conversion of Hcy to methionine as a feeder step of methylation reactions. We observed significantly increased serum and hippocampal Hcy levels in MoHE rats, however, these levels were restored to control values with a concordant activation of MS due to MeCbl treatment. A significant recovery in neurobehavioral impairments in the MoHE rats due to MeCbl treatment was also observed. These findings suggest that MoHE pathogenesis is associated with deranged nerve myelination in the hippocampus and that MeCbl treatment is able to restore it mainly by activating MS, a MeCbl-dependent Hcy-metabolizing enzyme.

Engineering chimeric autoantibody receptor T cells for targeted B cell depletion in multiple sclerosis model: An in-vitro study

Background

Recent evidence suggests that B cells and autoantibodies have a substantial role in the pathogenesis of Multiple sclerosis. T cells could be engineered to express chimeric autoantibody receptors (CAARs), which have an epitope of autoantigens in their extracellular domain acting as bait for trapping autoreactive B cells. This study aims to assess the function of designed CAAR T cells against B cell clones reactive to the myelin basic protein (MBP) autoantigen.

Methods

T cells were transduced to express a CAAR consisting of MBP as the extracellular domain. experimental autoimmune encephalomyelitis (EAE) was induced by injecting MBP into mice. The cytotoxicity, proliferation, and cytokine production of the MBP-CAAR T cells were investigated in co-culture with B cells.

Results

MBP-CAAR T cells showed higher cytotoxic activity against autoreactive B cells in all effector-to-target ratios compared to Mock T cell (empty vector-transduced T cell) and Un-T cells (un-transduced T cell). In co-cultures containing CAAR T cells, there was more proliferation and inflammatory cytokine release as compared to Un-T and Mock T cell groups.

Conclusion

Based on these findings, CAAR T cells are promising for curing or modulating autoimmunity and can be served as a new approach for clone-specific B cell depletion therapy in multiple sclerosis.

Myelin regulatory factor is a target of individual and interactive effects of HIV-1 Tat and morphine in the striatum and pre-frontal cortex

HIV-associated neurocognitive disorders (HAND) remain pervasive even with increased efficacy/use of antiretroviral therapies. Opioid use/abuse among HIV + individuals is documented to exacerbate CNS deficits. White matter (WM) alterations, including myelin pallor, and volume/structural alterations detected by diffusion tensor imaging are common observations in HIV + individuals, and studies in non-human primates suggest that WM may harbor virus. Using transgenic mice that express the HIV-1 Tat protein, we examined in vivo effects of 2-6 weeks of Tat and morphine exposure on WM using genomic and biochemical methods. RNA sequencing of striatal tissue at 2 weeks revealed robust changes in mRNAs associated with oligodendrocyte precursor populations and myelin integrity, including those for transferrin, the atypical oligodendrocyte marker N-myc downstream regulated 1 (Ndrg1), and myelin regulatory factor (Myrf/Mrf), an oligodendrocyte-specific transcription factor with a significant role in oligodendrocyte differentiation/maturation. Western blots conducted after 6-weeks exposure in 3 brain regions (striatum, corpus callosum, pre-frontal cortex) revealed regional differences in the effect of Tat and morphine on Myrf levels, and on levels of myelin basic protein (MBP), whose transcription is regulated by Myrf. Responses included individual and interactive effects. Although baseline and post-treatment levels of Myrf and MBP differed between brain regions, post-treatment MBP levels in striatum and pre-frontal cortex were compatible with changes in Myrf activity. Additionally, the Myrf regulatory ubiquitin ligase Fbxw7 was identified as a novel target in our model. These results suggest that Myrf and Fbxw7 contribute to altered myelin gene regulation in HIV.

Copper chelation and autoimmunity differentially impact myelin in the hippocampal-prefrontal circuit

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. About 50% of MS patients develop deficits in learning, memory and executive function, which are accompanied by demyelinating lesions in the hippocampus and/or prefrontal cortex (PFC). Why demyelination in these regions occurs in some patients but not in others and what is the underlying mechanism remain unclear. Here we report that myelin density in the hippocampus and PFC is markedly reduced in the cuprizone model, but not in the chronic experimental autoimmune encephalomyelitis. These two models can be used for studying different neuropathophysiological aspects of demyelinating diseases.

Myelin: Methods for Purification and Proteome Analysis

Molecular characterization of myelin is a prerequisite for understanding the normal structure of the axon/myelin-unit in the healthy nervous system and abnormalities in myelin-related disorders. However, reliable molecular profiles necessitate very pure myelin membranes, in particular when considering the power of highly sensitive "omics"-data acquisition methods. Here, we recapitulate the history and recent applications of myelin purification. We then provide our laboratory protocols for the biochemical isolation of a highly pure myelin-enriched fraction from mouse brains and for its proteomic analysis. We also supply methodological modifications when investigating posttranslational modifications, RNA, or myelin from peripheral nerves. Notably, technical advancements in solubilizing myelin are beneficial for gel-based and gel-free myelin proteome analyses. We conclude this article by exemplifying the exceptional power of label-free proteomics in the mass-spectrometric quantification of myelin proteins.

MAPK Assays in Arabidopsis MAMP-PRR Signal Transduction

Activation of MAPK (Mitogen-Activated Protein Kinase) cascades after MAMP (Microbe-Associated Molecular Pattern) perception through PRR (Pattern Recognition Receptor) is one of the first conserved responses when plants encounter microbial organisms. Phosphorylation of various cellular factors in the MAMP-PRR pathway by MAPK cascades is critical for broad-spectrum plant innate immunity. Measurement of MAPK activation and identification of MAPK phosphorylation targets in the MAMP-PRR signal transduction pathway are essential to understand how plants reprogram their cellular processes to cope with unfavorable microbial attack. Here, we describe detailed protocols of three assays measuring MAPK activity after MAMP perception: (1) immune-blotting analysis with anti-phospho ERK1/2 antibody; (2) in-gel kinase assay using a general substrate myelin basic protein (MBP); (3) an in vitro kinase assay to evaluate phosphorylation of MAPK substrate candidates during MAMP-PRR signaling based on a protoplast expression system.

Plant toxin abrin induced oxidative stress mediated neurodegenerative changes in mice

Abrin is a potent plant toxin. It is a heterodimeric protein toxin which is obtained from the seeds of Abrus precatorius plant. At cellular level abrin causes protein synthesis inhibition by removing the specific adenine residue (A4324) from the 28s rRNA of the 60S - ribosomal subunit. In the present study we investigated the role of oxidative stress in neurotoxic potential and demyelinating effects of abrin on brain. The mechanism by which abrin induces oxidative damage and toxicity in brain are relatively unknown. Animals were exposed to 0.4 and 1.0 LD50 abrin dose by intraperitoneal route and observed for 1 and 3 day post-toxin exposure. Oxidative stress occurred in brain due to abrin was confirmed in terms of increased reactive oxygen species (ROS), glutathione depletion and increased lipid peroxidation. Significant increase in blood and brain ROS was observed at day 3, 1 LD50. Abrin induced changes in the neurotransmitters (5-hydroxy tryptamine, norepinephrine, dopamine and monoamine oxidase) levels were evaluated by spectroflourometry. Increase in the levels of 5-HT and NE was observed after abrin exposure. MAO activity was found to be decreased in abrin exposed animals compared to control. Significant inhibition in the activity of acetylcholine esterase enzyme in brain and serum was reported for both the doses and time points. Western blot analysis of iNOS expression indicated that abrin treatment resulted in dose and time dependent increase. Furthermore, protein expression of myelin basic protein (MBP) was down regulated in a dose and time dependent manner. Brain histopathology was carried out and cortical brain region showed demyelination after abrin exposure. Results confirmed that abrin poisoning leads to neurodegeneration and neurotoxicity mediated through oxidative stress, AChE inhibition, lipid peroxidation and decrease in MBP levels.