Microglia in the pathogenesis of MS

A forum to discuss research on the origins of MS and its development.

Microglia in the pathogenesis of MS

Postby frodo » Mon Jul 23, 2018 12:13 pm

Microglia in the pathogenesis of MS

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5499932/



We postulate that the immune reaction initiates in the CNS and immune cells (including T cells/B cell) infiltrate into the CNS as a result.

An unknown causative agent sets off a local inflammatory reaction, after which activated microglia are stimulated by the microenvironment to differentiate into many subgroups that then serve as APCs, phagocytes, and immune effector cells to activate T cells. Activated T cells can then cross the blood–brain barrier and result in a peripheral immune response.

Subsequently, activated T cells, B cells, and macrophages migrate from the periphery into the CNS, which exacerbates the inflammation or leads to relapse.

This hypothesis could explain some phenomena in MS patients. First, the APCs (microglia and macrophages) originate in the CNS, are recognized by CNS-resident cells, and remain localized within the CNS, which could explain why MS patients experience no peripheral complications, such as autoimmune nephritis and arthritis. Second, the inflammatory cascade occurs entirely within the CNS, which could explain the insufficiency or the absence of lymphocyte recruitment into the CNS after the initial relapsing phase of MS
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Re: Microglia in the pathogenesis of MS

Postby Petr75 » Tue Jul 24, 2018 9:14 am

frodo wrote:.. Second, the inflammatory cascade occurs entirely within the CNS, which could explain the insufficiency or the absence of lymphocyte recruitment into the CNS after the initial relapsing phase of MS


December 7, 2017
Department of neuroradiologie, Heidelberg University Hospital, Heidelberg, NěmeckoIn the Pipeline-Multiple Sclerosis: Neurographic MRI Reveals Peripheral Nerve Lesions in MS Patients
https://journals.lww.com/neurotodayonli ... hic.6.aspx

.. Current opinion is that pathological changes in MS are restricted to the central nervous system (CNS) and cranial nerves, but the new proof-of-concept study may offer new insights into the pathophysiology of the disease and help guide new treatment options, said lead author Jennifer Kollmer, MD, a neuroradiologist at Heidelberg University Hospital..
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Re: Microglia in the pathogenesis of MS

Postby NHE » Wed Jul 25, 2018 3:16 am

Petr75 wrote:December 7, 2017
Department of neuroradiologie, Heidelberg University Hospital, Heidelberg, NěmeckoIn the Pipeline-Multiple Sclerosis: Neurographic MRI Reveals Peripheral Nerve Lesions in MS Patients
https://journals.lww.com/neurotodayonli ... hic.6.aspx

.. Current opinion is that pathological changes in MS are restricted to the central nervous system (CNS) and cranial nerves, but the new proof-of-concept study may offer new insights into the pathophysiology of the disease and help guide new treatment options, said lead author Jennifer Kollmer, MD, a neuroradiologist at Heidelberg University Hospital..


It sounds like they may not be exactly sure of what the significance is of the lesions they're detecting.

Dr. Jacobs added that it is also worth noting that the healthy controls had quite a few lesions, implying that MRN may pick up very subtle disturbances of peripheral nerve myelin which don't have any functional importance.
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Re: Microglia in the pathogenesis of MS

Postby frodo » Wed Jul 25, 2018 1:26 pm

It looks like microglia is the root of all evil. Microglia activation is the first step in the so-called "preactive lesions" (with some doubts, see below), it appears in the "normal appearing white matter" and also in the cortical lesions.

Why that happens is unknown, but microglia activation is something that happens when a virus or antigen is present. Anyway it could be just a metabolic problem, because fingolimod prevents microglia activation without bad consequences.

There is a review about Microglia activation here:

Microglial Phenotypes and Functions in Multiple Sclerosis

http://perspectivesinmedicine.cshlp.org ... 28993.full

Some excerpts:

"In line with this concept, preactive lesions have been described in MS, which are defined by clusters of activated microglia in the white matter of MS patients, which develop without demyelination and peripheral cell infiltration (van Horssen et al. 2012), and thus may represent the early stage of inflammatory lesion (van Noort et al. 2011). However, these “preactive” lesions have been described in progressive MS, are very frequent and widespread, and it is therefore highly unlikely that such lesions develop into classical active MS plaques. In addition, they are poorly defined and may also reflect areas of diffuse microglia activation in the normal-appearing white matter of MS patients as well as areas of secondary Wallerian degeneration or even remyelination"

"From all these studies, it is clear that active demyelination and neurodegeneration is associated with microglia activation. Whether this microglia activation is the primary trigger of lesion formation, whether they are activated by T lymphocytes or B cells, or they are secondary to tissue injury mediated by soluble factors produced by cells of the adaptive immune system is currently unresolved. "

"A proof-of-principle, that inhibition of microglia activation has a beneficial effect on MS, has recently been obtained in a trial using minocycline. This drug, which has been shown to target microglia activation and has beneficial effects in several different experimental models of inflammation and neurodegeneration, reduced the conversion of clinically isolated syndrome (CIS) into definite MS in MS patients and reduced clinically or radiologically identified activity of the disease"
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Re: Microglia in the pathogenesis of MS

Postby Petr75 » Fri Jul 27, 2018 9:46 am

2018 Jul 3
Neuroscience Laboratory, Laval University, Quebec, QC, Canad
mCSF-Induced Microglial Activation Prevents Myelin Loss and Promotes Its Repair in a Mouse Model of Multiple Sclerosis
https://www.ncbi.nlm.nih.gov/pubmed/30018535

Abstract
A pathological hallmark of multiple sclerosis (MS) is myelin loss in brain white matter accompanied by compromised remyelination. Demyelinated lesions are deeply associated with oligodendrocyte apoptosis and a robust inflammatory response. Although various studies point towards a noxious role of inflammation in MS, others emphasize a positive role for the innate immune cells in disease progression. A cytokine well-known to stimulate cell survival, proliferation and differentiation of myeloid cells, macrophage colony-stimulating factor (mCSF), was administered to mice during a 5 week-long cuprizone diet. Treated mice exhibited reduced myelin loss during the demyelination phase, together with an increased number of microglia and oligodendrocyte precursor cells in lesion sites. Tamoxifen-induced conditional deletion of the mCSF receptor in microglia from cuprizone-fed mice caused aberrant myelin debris accumulation in the corpus callosum and reduced microglial phagocytic response. mCSF therefore plays a key role in stimulating myelin clearance by the brain innate immune cells, which is a prerequisite for proper remyelination and myelin repair processes.

full https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6037698/
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Re: Microglia in the pathogenesis of MS

Postby Petr75 » Mon Aug 27, 2018 8:00 am

2018 Aug 9
Department of Radiology/Nuclear Medicine, Weill Cornell Medicine, New York, New York City
Comparison of two different methods of image analysis for the assessment of microglial activation in patients with multiple sclerosis using (R)-[N-methyl-carbon-11]PK11195
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6084893/

Abstract
Chronic active multiple sclerosis (MS) lesions have a rim of activated microglia/macrophages (m/M) leading to ongoing tissue damage, and thus represent a potential treatment target. Activation of this innate immune response in MS has been visualized and quantified using PET imaging with [11C]-(R)-PK11195 (PK). Accurate identification of m/M activation in chronic MS lesions requires the sensitivity to detect lower levels of activity within a small tissue volume. We assessed the ability of kinetic modeling of PK PET data to detect m/M activity in different central nervous system (CNS) tissue regions of varying sizes and in chronic MS lesions. Ten patients with MS underwent a single brain MRI and two PK PET scans 2 hours apart. Volume of interest (VOI) masks were generated for the white matter (WM), cortical gray matter (CGM), and thalamus (TH). The distribution volume (VT) was calculated with the Logan graphical method (LGM-VT) utilizing an image-derived input function (IDIF). The binding potential (BPND) was calculated with the reference Logan graphical method (RLGM) utilizing a supervised clustering algorithm (SuperPK) to determine the non-specific binding region. Masks of varying volume were created in the CNS to assess the impact of region size on the various metrics among high and low uptake regions. Chronic MS lesions were also evaluated and individual lesion masks were generated. The highest PK uptake occurred the TH and lowest within the WM, as demonstrated by the mean time activity curves. In the TH, both reference and IDIF based methods resulted in estimates that did not significantly depend on VOI size. However, in the WM, the test-retest reliability of BPND was significantly lower in the smallest VOI, compared to the estimates of LGM-VT. These observations were consistent for all chronic MS lesions examined. In this study, we demonstrate that BPND and LGM-VT are both reliable for quantifying m/M activation in regions of high uptake, however with blood input function LGM-VT is preferred to assess longitudinal m/M activation in regions of relatively low uptake, such as chronic MS lesions.
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Re: Microglia in the pathogenesis of MS

Postby Petr75 » Fri Sep 28, 2018 10:26 am

2018 Sep 8
Università degli Studi di Milano, via Balzaretti, Milan, Italy
How to reprogram microglia toward beneficial functions
https://www.ncbi.nlm.nih.gov/pubmed/30195261

Abstract
Microglia, brain cells of nonneural origin, orchestrate the inflammatory response to diverse insults, including hypoxia/ischemia or maternal/fetal infection in the perinatal brain. Experimental studies have demonstrated the capacity of microglia to recognize pathogens or damaged cells activating a cytotoxic response that can exacerbate brain damage. However, microglia display an enormous plasticity in their responses to injury and may also promote resolution stages of inflammation and tissue regeneration. Despite the critical role of microglia in brain pathologies, the cellular mechanisms that govern the diverse phenotypes of microglia are just beginning to be defined. Here we review emerging strategies to drive microglia toward beneficial functions, selectively reporting the studies which provide insights into molecular mechanisms underlying the phenotypic switch. A variety of approaches have been proposed which rely on microglia treatment with pharmacological agents, cytokines, lipid messengers, or microRNAs, as well on nutritional approaches or therapies with immunomodulatory cells. Analysis of the molecular mechanisms relevant for microglia reprogramming toward pro-regenerative functions points to a central role of energy metabolism in shaping microglial functions. Manipulation of metabolic pathways may thus provide new therapeutic opportunities to prevent the deleterious effects of inflammatory microglia and to control excessive inflammation in brain disorders.
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Re: Microglia in the pathogenesis of MS

Postby NHE » Fri Sep 28, 2018 11:00 pm

Petr75 wrote:2018 Sep 8
Università degli Studi di Milano, via Balzaretti, Milan, Italy
How to reprogram microglia toward beneficial functions
https://www.ncbi.nlm.nih.gov/pubmed/30195261


Free full text at...

https://onlinelibrary.wiley.com/doi/pdf ... glia.23484
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Re: Microglia in the pathogenesis of MS

Postby Petr75 » Sat Oct 06, 2018 7:50 am

2018 Sep 12
Laboratory of Pathoneurochemistry, Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
Early P2X7R-dependent activation of microglia during the asymptomatic phase of EAE
https://www.ncbi.nlm.nih.gov/pubmed/30209761

Abstract
Microglia-mediated neuroinflammation accompanies many central nervous system (CNS) diseases, including multiple sclerosis (MS), and is strongly dependent on the purinergic P2X7 receptor. The nature of the inflammatory response in MS is studied for decades indicating, that proinflammatory microgliosis is involved in advanced stages of MS and is associated with active tissue damage and neurological dysfunctions. Evidence on the role of microgliosis in initial stages of the disease is scarce. Thus, in the present study, we investigated the time course of microglial activation in rat brain subjected to experimental autoimmune encephalomyelitis (EAE) which is the animal model of MS. We show that activation of microglia occurs in brains of immunized rats at a very early stage of EAE, well before the development of neurological symptoms of the disease. Enhanced immunoreactivity of microglia/macrophage-specific protein Iba-1, together with morphological features of microgliosis, was identified beginning at day 4 post immunization. Concomitantly, microglial expression of P2X7R was also examined. Moreover, our results reveal that administration of Brilliant Blue G, an antagonist of P2X7R, delays the onset of the disease and partially inhibits development of neurological symptoms in EAE rats. Blockage of P2X7R significantly reduces activation of microglia as confirmed by decreased Iba-1 immunoreactivity and suppresses neuroinflammation in EAE rat brains, as indicated by decreased protein levels of investigated proinflammatory cytokines: IL-1β, IL-6 and TNF-α. Our results indicate that microglia are involved in inducing neuroinflammation at a very early stage of MS/EAE via a P2X7R-dependent mechanism.

wiki P2RX7 https://en.wikipedia.org/wiki/P2RX7
.. The P2X7 receptor current can be blocked by zinc, calcium, magnesium, and copper
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