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Examination of Tight Junction Protein Expression and Distribution both in Enterocytes and Brain Capillary Endothelial Cells in an Experimental Model for Multiple sclerosis - A Link between Two Barriers

Bereber Goiricelaya, Aitor (2015) MOBN01 20151
Degree Projects in Molecular Biology
Popular Abstract
How tight junctions are affected in a Multiple Sclerosis model

In Multiple Sclerosis (MS), unusual immune cells of unknown origin, which are supposed to protect us from infections, attack the central nervous system (CNS). Their main target is the myelin shield surrounding neuronal axons, which is essential for proper transmission of neuronal signals. These autoreactive cells can enter the CNS through brain capillaries. However, brain capillaries are able to restrict the passage of cells and molecules and form the so-called blood-brain-barrier (BBB). Therefore, CNS infiltration of self-attacking immune cells requires BBB disruption in MS. In addition, dysregulation of the intestinal barrier (IB), which allows the passage of nutrients... (More)
How tight junctions are affected in a Multiple Sclerosis model

In Multiple Sclerosis (MS), unusual immune cells of unknown origin, which are supposed to protect us from infections, attack the central nervous system (CNS). Their main target is the myelin shield surrounding neuronal axons, which is essential for proper transmission of neuronal signals. These autoreactive cells can enter the CNS through brain capillaries. However, brain capillaries are able to restrict the passage of cells and molecules and form the so-called blood-brain-barrier (BBB). Therefore, CNS infiltration of self-attacking immune cells requires BBB disruption in MS. In addition, dysregulation of the intestinal barrier (IB), which allows the passage of nutrients while halting the entrance of pathogens, has also been observed in experimental autoimmune encephalomyelitis (EAE), the animal model used to investigate the human MS. A key component of these barriers are the tight junctions (TJs), the connections that tightly link their cells. TJs regulate the permeability of such barriers and thus, are believed to play an important role in these MS-related disruptive processes. However, little is known about how each particular TJ can affect barrier permeability, which is why this work aimed to evaluate TJ arrangement and expression (amount of protein produced by the cells) in EAE, in both barriers.

Methods and results

Immunohistochemistry and fluorescence microscopy were used to qualitatively assess the distribution of three different TJs (occludin, ZO-1 and JAM-A) on intestines and cerebral capillaries of EAE mice. Immunohistochemistry is a technique that allows us to label a desired protein by using antibodies that specifically bind such protein. Moreover, if these antibodies carry molecules that emit fluorescence, as in this case, the labeled proteins can be visualized using fluorescence microscopy. In addition, analysis of TJ immunosignals with an image processing software also allowed to measure the expression of these proteins in relative terms. Our data showed that occludin, ZO-1 and JAM-A underwent equivalent expression changes in both the BBB and the IB during EAE progression. Concretely, occludin expression remained rather unaltered through disease development, whereas ZO-1 and JAM-A expression tended to diminish with the course of the disease.

Discussion

For the first time, reduced ZO-1 and JAM-A levels have been associated with increased intestinal permeability in EAE. In addition, the same reduction observed in brain capillaries confirms previous studies and seems to correlate with increased BBB permeability both in MS and EAE. Conversely, occludin might play a minor role in EAE as well as other murine models; although occludin downregulation has been associated with BBB dysfunction in MS and even IB disruption in other disorders. Unravelling the mechanisms underlying the dysfunction of cellular barriers will help to better understand MS and many other diseases, and perhaps, will facilitate the development of new drug delivery methods through the BBB.

Advisor: Mehrnaz Nouri
Master’s Degree Project in Molecular Biology 2015 (45 credits)
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Bereber Goiricelaya, Aitor
supervisor
organization
course
MOBN01 20151
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8314965
date added to LUP
2015-12-16 11:19:28
date last changed
2015-12-16 11:19:28
@misc{8314965,
  author       = {Bereber Goiricelaya, Aitor},
  language     = {eng},
  note         = {Student Paper},
  title        = {Examination of Tight Junction Protein Expression and Distribution both in Enterocytes and Brain Capillary Endothelial Cells in an Experimental Model for Multiple sclerosis - A Link between Two Barriers},
  year         = {2015},
}