The Blood Brain Barrier

In an article published today in the prestigious journal Science, a team of researchers led by Dr Alexander Prat and postgraduate fellow Jorge Alvarez at the University of Montreal Hospital Research Centre (CRCHUM) sheds light on how the blood-brain-barrier (BBB) works to prevent the incursion of the immune system into the brain. "Our findings provide a better understanding of the mechanisms used by the brain in mounting a natural defence against immune system aggression, as is the case in Multiple Sclerosis" explains Dr Prat.

There is no known cure for this auto-immune disease of the central nervous system (CNS). One of the characteristics of this debilitating disease is the inability of the BBB to restrict and control the passage of immune cells into the brain. This intrusion of the body's immune system into the brain affects the ability of neurons in the brain and in the spinal cord to communicate efficiently with one another, producing extensive and recurrent central nervous system damage.

As such, Multiple Sclerosis (MS) symptoms can include paralysis, pricking or numbness, visual problems, repetitive difficulties with coordination and balance and in moving, which lead to chronic clinical handicap in MS patients.

The BBB is a physical and metabolic barrier that prevents unwanted cells or molecules from entering the CNS. It is composed of, among other things, tightly bound endothelial cells (cells that line the interior surface of blood cells) and perivascular astrocytes (star-shaped cells that regulate the transmission of electrical signals in the brain) that maintain CNS balance. Prat and Alvarez show that these astrocytes also play a key role in secreting Sonic hedgehog, a protein that is involved in how the brain is organized, and that endothelial cells express Hedgehog receptors, which together promote proper BBB formation and integrity during embryonic development and adulthood.

More importantly, they show, in a laboratory setting with animal and human brain cells, that the so-called Hedgehog pathway plays an important role in decreasing the adhesion and migration of immune cells into the brain. These findings demonstrate that the Hedgehog pathway provides a barrier-promoting effect and an endogenous anti-inflammatory balance to CNS-directed immune attacks. Its dysregulation is one of the pathological hallmarks of Multiple Sclerosis.

"The results of this research open the door to designing therapeutic approaches to control immune cell migration to the CNS and thus improve their delivery to affected areas," notes Dr Prat.

With more than 75,000 MS patients, Canada has the highest incidence of multiple sclerosis in the world.

This study was supported by grants from the Canadian Institutes of Health Research and the Multiple Sclerosis Society of Canada.

Source: CNW Canadian Newswire © 2011 CNW Group Ltd (02/12/11)

Cornell University researchers may have solved a 100-year puzzle: How to safely open and close the blood-brain barrier so that therapies to treat Alzheimer's disease, multiple sclerosis and cancers of the central nervous system might effectively be delivered. (Journal of Neuroscience, Sept. 14, 2011.)

The researchers found that adenosine, a molecule produced by the body, can modulate the entry of large molecules into the brain. For the first time, the researchers discovered that when adenosine receptors are activated on cells that comprise the blood-brain barrier, a gateway into the blood-brain barrier can be established.

Although the study was done on mice, the researchers have also found adenosine receptors on these same cells in humans. They also discovered that an existing FDA-approved drug called Lexiscan, an adenosine-based drug used in heart imaging in very ill patients, can also briefly open the gateway across the blood-brain barrier.

The blood-brain barrier is composed of the specialized cells that make up the brain's blood vessels. It selectively prevents substances from entering the blood and brain, only allowing such essential molecules as amino acids, oxygen, glucose and water through. The barrier is so restrictive that researchers couldn't find a way to deliver drugs to the brain until now.

"The biggest hurdle for every neurological disease is that we are unable to treat these diseases because we cannot deliver drugs into the brain," said Margaret Bynoe, associate professor of immunology at Cornell's College of Veterinary Medicine and senior author of a paper appearing Sept. 14 in the Journal of Neuroscience. Aaron Carman, a former postdoctoral associate in Bynoe's lab, is the paper's lead author. The study was funded by the National Institutes of Health.

"Big pharmaceutical companies have been trying for 100 years to find out how to traverse the blood-brain barrier and still keep patients alive," said Bynoe, who with colleagues have patented the findings and have started a company, Adenios Inc., which will be involved in drug testing and preclinical trials.

Researchers have tried to deliver drugs to the brain by modifying them so they would bind to receptors and "piggyback" onto other molecules to get across the barrier, but so far, this modification process leads to lost drug efficacy, Bynoe said.

"Utilizing adenosine receptors seems to be a more generalized gateway across the barrier," she added. "We are capitalizing on that mechanism to open and close the gateway when we want to."

In the paper, the researchers describe successfully transporting such macromolecules as large dextrans and antibodies into the brain. "We wanted to see the extent to which we could get large molecules in and whether there was a restriction on size," Bynoe said.

The researchers also successfully delivered an anti-beta amyloid antibody across the blood-brain barrier and observed it binding to beta-amyloid plaques that cause Alzheimer's in a transgenic mouse model. Similar work has been initiated for treating multiple sclerosis, where researchers hope to tighten the barrier rather than open it, to prevent destructive immune cells from entering and causing disease.

Although there are many known antagonists (drugs or proteins that specifically block signaling) for adenosine receptors in mice, future work will try to identify such drugs for humans.

Source: Medical News Today © MediLexicon International Ltd 2004-2011

A new way of delivering drugs to the brain has been developed by scientists at the University of Oxford.

They used the body's own transporters - exosomes - to deliver drugs in an experiment on mice.

The authors say the study, in Nature Biotechnology, could be vital for treating diseases such as Alzheimer's, Parkinson's and Muscular Dystrophy.

The Alzheimer's Society said the study was "exciting" and could lead to more effective treatments.

Research barrier
 
One of the medical challenges with diseases of the brain is getting any treatment to cross the blood-brain barrier.

The barrier exists to protect the brain, preventing bacteria from crossing over from the blood, while letting oxygen through.

However, this has also produced problems for medicine, as drugs can also be blocked.

In this study the researchers used exosomes to cross that barrier.

Exosomes are like the body's own fleet of incredibly small vans, transporting materials between cells.

The team at Oxford harvested exosomes from mouse dentritic cells, part of the immune system, which naturally produce large numbers of exosomes.

They then fused the exosomes with targeting proteins from the rabies virus, which binds to acetylcholine receptors in brain cells, so the exosome would target the brain.

They filled the exosomes with a piece of genetic code, siRNA, and injected them back into the mice.

The siRNA was delivered to the brain cells and turned off a gene, BACE1, which is involved in Alzheimer's disease.

The authors reported a 60% reduction in the gene's activity.

"These are dramatic and exciting results" said the lead researcher Dr Matthew Wood.

"This is the first time this natural system has been exploited for drug delivery."

Customised
 
The research group believes that the method could modified to treat other conditions and other parts of the body.

Dr Wood said: "We are working on sending exosomes to muscle, but you can envisage targeting any tissue.

"It can also be made specific by changing the drug used."

The researchers are now going to test the treatment on mice with Alzheimer's disease to see if their condition changes.

The team expect to begin trials in human patients within five years.

Dr Susanne Sorensen, head of research at the Alzheimer's Society, said: "In this exciting study, researchers may have overcome a major barrier to the delivery of potential new drugs for many neurological diseases including Alzheimer's."

She said the blood-brain barrier had been an "enormous issue as many potential drugs have not been properly tested because you couldn't get enough of them into the brain."

She added: "If this delivery method proves safe in humans, then we may see more effective drugs being made available for people with Alzheimer's in the future."

Dr Simon Ridley, head of research at Alzheimer's Research UK, said: "This is innovative research, but at such an early stage it's still a long way from becoming a treatment for patients.

"Designing drugs that cross the blood brain barrier is a key goal of research that holds the promise of improving the effectiveness of Alzheimer's treatments in the future."

Source: BBC News © British Broadcasting Corporation 2011 (22/03/11)

The University of South Florida's Department of Neurosurgery and Brain Repair has been granted a patent for a cell transplantation procedure combining human umbilical cord blood (HUCB) cells and a sugar-alcohol compound called "mannitol" that may make a big difference in treating life-threatening neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and stroke, among others.

The technology administers the neuroprotective effect of umbilical cord blood cells along with mannitol to permeabilize the blood-brain barrier, allowing for the increased entry of therapeutic growth factors. Saneron CCEL Therapeutics, Inc., a biotechnology R&D USF spin-out company located at the Tampa Bay Technology Incubator, has licensed the technology.

"Approximately 750,000 strokes occur every year in the United States, and nearly one third of them are fatal," said Saneron's President and COO, Nicole Kuzmin-Nichols, MBA. "Given the devastating effects of stroke, it is imperative that we develop new therapies to minimize damage to the brain as well as repair the damage. We are excited about this new technology and its potential to help us develop a variety of new products and therapies to do just that."

While transplanted HUCB cells may benefit several neurological diseases, getting them past the blood-brain-barrier has presented a problem. The blood-brain barrier separates circulating blood and cerebral spinal fluid in the central nervous system. The newly patented technology is based on mannitol acting as a blood-brain barrier permeabilizer to help get the therapeutic substances secreted by HUCB cells past the blood-brain barrier and into the central nervous system. Mannitol, which temporarily shrinks the tight cells that make up the barrier, allows HUCB cells, via their secreted factors, to reach the site of injury or disease.

"Human umbilical cord blood contains a high percentage of stem cells that when intravenously administered can survive and differentiate into neurons in the damaged brain. Equally appealing is their ability to secrete beneficial molecules that potentially promote behavioral recovery," said Dr. Cesar Borlongan, co-inventor and a USF neuroscientist and professor and consultant for Saneron. "Because the blood-brain barrier regulates the entry of many blood-borne substances into the brain, it may exclude potentially therapeutic substances."

"The use of stem cell therapy as a treatment for neurodegenerative disorders shows exciting promise, though several hurdles must be overcome and getting the cells correctly positioned is one of those," said Nicole Kuzmin-Nichols. "This technology provides the means to deliver the HUCB cells directly to the damaged brain to maximize their effect."

Source: Medical News Today © 2010 MediLexicon International Ltd (09/07/10)

In diseases such as multiple sclerosis, cells of the immune system infiltrate the brain tissue, where they cause immense damage.

For many years, it was an enigma as to how these cells can escape from the bloodstream.

This is no trivial feat, given that specialised blood vessels act as a barrier between the nervous system and the bloodstream. Until now, tissue sections provided the sole evidence that the immune cells really do manage to reach the nerve cells.

Now, a team of scientists from the Max Planck Institute of Neurobiology, the University Medical Center Göttingen, and other institutes, has witnessed the movements of these cells "live" under the microscope for the very first time. In the process, they discovered several new behavioural traits of the immune cells.

The consolidated findings mark a significant step forward in our understanding of this complex disease ("Effector T cell interactions with meningeal vascular structures in nascent autoimmune CNS lesions").

The picture shows the movement of creeping T-cells (green) inside blood vessels (red) over a period of about 20 minutes. It clearly shows that some T-cells leave the blood vessels - the long exposure lets them leave a green trail as the cells make their way through the brain tissue. (Image: Max Planck Institute of Neurobiology / Bartholomäus)

The brain and the spinal cord monitor and control the functions of all body parts and co-ordinate the whole organism's movements, senses and behaviour. Adequate protection of the brain and spinal cord are therefore of the utmost importance. Physical influences and injuries are warded off by the cranial bone and the vertebral column. Dangers lurking within the body, such as viruses circulating in the bloodstream, are kept at bay by highly specialized blood vessels. The vessels' walls form a barrier that cannot be penetrated by the cells or various other small particles, thus serving to protect the delicate nerve cells.

There are, however, exceptions to the rule. In diseases such as multiple sclerosis (MS), aggressive cells in the immune system manage to break through the blood vessels' barrier. Having invaded the brain tissue, these cells wreak havoc by triggering off inflammatory reactions and attacking nerve cells. In Germany alone, the resulting adverse effects afflict over 120,000 MS-patients.

Tracking down the culprits
Since there is normally a clear division between the blood circulatory system and the central nervous system (i.e. brain plus spinal cord), scientists were baffled as to how immune cells manage to cross the blood-brain-barrier. This knowledge may aid in understanding the origins of multiple sclerosis. In the 1980s, scientists were able to prove conclusively that, under certain conditions, so called T-cells can recognize and attack components of the body's own brain cells. Thanks to tissue sections performed over the last few decades, scientists now have much better knowledge of the migration of these cells from their point of origin to their point of penetration into the brain and the damage that they cause. However, actual observations of such movements long remained impossible.

Observing aggressive cells in action
Scientists at the Max Planck Institute of Neurobiology, the University Medical Center Göttingen and their colleagues have now overcome this impossibility. Using a two-photon microscope, the researchers succeeded in tracing the movements of aggressive T-cells labelled with the green fluorescent protein (GFP) in the living tissue of rats. The systematic observation of these cells during the course of the disease provided amazing new insights into the cell's behaviour.

The scientists discovered that the aggressive T-cells overcome the barrier between blood and nerve tissue in a number of steps. Outside the nervous system, the labelled cells moved just as we would expect them to; most cells were floating along with the flow of the bloodstream. Only now and again did a cell attach itself briefly onto the vascular wall. Here they rolled in the direction of the blood stream or were being carried off again by the current. Yet, once the cells reached the blood vessels of the nervous system, they began to act in a completely different manner.

The scientists observed here far more cells clinging to the vascular walls. "Things got really exciting when we observed that the cells can actually creep, a behaviour so far unheard of for T-cells", Ingo Bartholomäus relates his observations. Here, "creeping" describes an active cell movement, usually against the flow of the bloodstream. The scientists watched T-cells as they took anything between a few minutes and several hours to creep along the vessels' walls. At the end of such a search movement, the cells were either swept away again by the bloodstream or they managed to squeeze through the vascular wall.

Ominous encounters
Having successfully penetrated the blood-brain-barrier, the cells continued their search in the vicinity of the blood vessels. It was thus only a question of time before the T-cells encountered one of the phagocytic cells abundant on the outer linings of blood vessels and on the surface of the nerve tissue. When a mobile T-cell came across such a phagocyte, the two cells formed a closely connected pair. Some of these pairs remained inseparable for several minutes.
Although the scientists already knew that T-cells must make contact with phagocytes in order to become immune-activated, they were now able to observe these interactions right where they happened, i.e. at the blood-brain-barrier. And indeed, the T-cells did not launch their attack on the nervous system by releasing their inflammatory neurotransmitters until they had bonded with the phagocytes.

As a result of the T-cells' activation, more and more T-cells passed through the vascular walls. "The activation of T-cells at the border to the nerve tissue appears to be a decisive signal for the invasion of the immune cells", concludes Alexander Flügel, supervisor of the study and director of the Department of Experimental and Clinical Neuroimmunology at the University Medical Center Göttingen and Head of the MS Hertie-Institute.

Light bulb moments
Thanks to their sophisticated observation methods, the scientists also established that some of the antibodies already being used in MS-therapy cause the creeping cells to disappear. As Ingo Bartholomäus explains "Up to now, it was only known that these antibodies prevented the T-cells' escaping from the blood vessels, but as our observations now show, they actually prevent them from creeping".

Thanks to the scientists' observations, we now have a much clearer picture of how the immune cells move and obtain access to the nervous system. This knowledge is likely to also increase our knowledge of the immune system's security system functions in healthy tissue. However, as is often the case, new insights and information also give rise to many new questions.

How do the immune cells manage to cling to the lining of the blood vessels and how do they recognize the weak spots, where they can slip through the barrier between the bloodstream and the nervous system? What governs the cells once they have surmounted the blood-brain-barrier?

These are some of the questions the scientists will be addressing next. The long-term goal will be to develop new forms of therapy and medication for multiple sclerosis and other diseases.

Source: Nanowerk ©2009, Nanowerk LLC. (06/11/09)

It was nine years ago that University of Maryland School of Medicine researchers discovered that a mysterious human protein called zonulin played a critical role in celiac disease and other autoimmune disorders, such as multiple sclerosis and diabetes. Now, scientists have solved the mystery of zonulin’s identity, putting a face to the name, in a sense. Scientists led by Alessio Fasano, M.D., have identified zonulin as a molecule in the human body called haptoglobin 2 precursor.

Pinpointing the precise molecule that makes up the mysterious protein will enable a more detailed and thorough study of zonulin and its relationship to a series of inflammatory disorders. The discovery was reported in a new study by Dr. Fasano, published the week of September 7, 2009 in the online version of the Proceedings of the National Academy of Sciences.

Dr. Fasano is a professor of pediatrics, medicine and physiology and director of the Mucosal Biology Research Center and the Center for Celiac Research at the University of Maryland School of Medicine.

Haptoglobin is a molecule that has been known to scientists for many years. It was identified as a marker of inflammation in the body. Haptoglobin 1 is the original form of the haptoglobin molecule, and scientists believe it evolved 800 million years ago. Haptoglobin 2 is a permutation found only in humans. It’s believed the mutation occurred in India about 2 million years ago, spreading gradually among increasing numbers of people throughout the world.

Dr. Fasano’s study revealed that zonulin is the precursor molecule for haptoglobin 2 — that is, it is an immature molecule that matures into haptoglobin 2. It was previously believed that such precursor molecules served no purpose in the body other than to mature into the molecules they were destined to become. But Dr. Fasano’s study identifies precursor haptoglobin 2 as the first precursor molecule that serves another function entirely — opening a gateway in the gut, or intestines, to let gluten in. People with celiac disease suffer from a sensitivity to gluten.

“While apes, monkeys and chimpanzees do not have haptoglobin 2, 80 percent of human beings have it,” says Dr. Fasano. “Apes, monkeys and chimpanzees rarely develop autoimmune disorders. Human beings suffer from more than 70 different kinds of such conditions. We believe the presence of this pre-haptoglobin 2 is responsible for this difference between species.”

“This molecule could be a critical missing piece of the puzzle to lead to a treatment for celiac disease, other autoimmune disorders and allergies and even cancer, all of which are related to an exaggerated production of zonulin/pre-haptoglobin 2 and to the loss of the protective barrier of cells lining the gut and other areas of the body, like the blood brain barrier,” says Dr. Fasano.

“The only current treatment for celiac disease is cutting gluten from the diet, but we have confidence Dr. Fasano’s work will someday bring further relief to these patients. Zonulin, with its functions in health and disease as outlined in Dr. Fasano’s paper, could be the molecule of the century,” says E. Albert Reece, M.D., Ph.D., M.B.A., dean of the School of Medicine, vice president for medical affairs of the University of Maryland and John Z. and Akiko K. Bowers Distinguished Professor. Dr. Fasano, as a physician scientist, fulfills two of the core missions of the University of Maryland School of Medicine: making basic science discoveries that can impact human health, and finding ways to translate those discoveries into treatments and diagnostic tools.

People who suffer from celiac disease have a sensitivity to gluten, a protein found in wheat, and suffer gastrointestinal distress and other serious symptoms when they eat it. In celiac patients, gluten generates an exaggerated release of zonulin that makes the gut more permeable to large molecules, including gluten. The permeable gut allows these molecules, such as gluten, access to the rest of the body. This triggers an autoimmune response in which a celiac patient’s immune system identifies gluten as an intruder and responds with an attack targeting the intestine instead of the intruder.

An inappropriately high level of production of zonulin also seems responsible for the passage through the intestine of intruders other than zonulin, including those related to conditions such as diabetes, multiple sclerosis and even allergies. Recently, other groups have reported elevated production of zonulin affecting the permeability of the blood brain barrier of patients suffering from brain cancer.

“We hope pre-haptoglobin 2 will be a door to a better understanding of not just celiac disease, but of several other devastating conditions that continue to affect the quality of life of millions of individuals,” says Dr. Fasano. “This is quite a remarkable molecule that was just flying under the radar. We would have never have thought it would be the key. Now that we have identified this molecule, we are able to replicate it in the lab to use for research purposes. We hope to learn much more about it and its potential for treating and diagnosing celiac disease and other autoimmune conditions. This molecule has opened innumerable doors for our research.”

Source: Linker Land © 2009 Linker Land (08/09/09)

According to the research team, led by Carlos Lopez-Otin, their findings can provide potential new target for multiple sclerosis therapy.

Collagenase-2 is a member of a protein family called matrix metalloproteinases (MMPs, collagenase-2 is MMP8), which is a large group of enzymes that break down collagen and other components of the body's connective tissue.

MMPs are responsible to cause MS by degrading the tissue that maintains the blood-brain barrier, thus making it possible for unwanted cells to invade and break down nerves. Besides, increased amounts of MMPs are found in the blood and spinal fluid of diseased individuals.

Using a mouse model of MS, Lopez-Otin and colleagues performed two analyses on MMP8 to determine how relevant this protein is to the disease.

Initially, mutant mice deficient in the gene for MMP8 was developed and it was found that these mice had a fewer invading cells in the brain, fewer damaged nerves, and a general improvement in their clinical profile.

In fact, the researchers also gave diseased mice a drug that blocked MMP8 activity and found that this, too, could reduce the severity of disease symptoms.

These findings, when taken together, provide the first causal evidence for MMP8 in the development of MS, and offer a new therapeutic target, the researchers said.

Source: NewKerela.com (c) 2007 NewKerala.Com (29/03/08)

An international team of scientists that includes a Saint Louis University researcher suggest several strategies to propel research for treatments of brain diseases that include multiple sclerosis, Alzheimer's disease, obesity and stroke in the January issue of the Lancet Neurology.

Their review article, which focuses on surmounting obstacles posed by the blood-brain barrier (BBB), is available in an early online edition of the prestigious medical journal on Dec. 17.

The blood-brain barrier is a gate-keeping system of cells that protects the brain from toxins and lets in nutrients. Because it passes no judgment on which foreign substances are there to treat diseases and which are penetrating the brain to do harm, it locks all of them out. That makes getting drugs into the brain where they can do their work in treating brain diseases difficult.

"A big part of our work is raising the awareness about the blood-brain barrier as an intimate part of the disease process," said William A. Banks, M.D., professor of geriatrics and pharmacological and physiological science at Saint Louis University School of Medicine, and a member of the research team.

"You can't get drugs into the brain or understand brain disease without understanding the blood-brain barrier, which is among our most significant recommendations for future research."

The blood-brain barrier is woefully misunderstood, said Banks, who also is a staff physician at Veterans Affairs Medical Center in St. Louis.

"The general theme of our review article is the blood-brain barrier is not a brick wall but a regulating interface between the brain and the rest of the body. Look at the brain as an island, where all raw materials have to be imported. The blood-brain barrier is the shipping and communications system that connects the island (the brain) to the rest of the world (the body)."

Sometimes the blood-brain barrier lets in things that it shouldn't and doesn't let out things that it should. Learning more about the secrets of the blood-brain barrier system is critical in understanding Alzheimer's disease, for instance, because the BBB makes it difficult to target medication where it's needed in the brain and won't allow toxic amyloid beta proteins, believed to cause Alzheimer's, to drain out of the brain.

Much of Banks' work focuses on the function of the blood-brain barrier in regulating the immune system, the body's natural defense in fighting disease. The cells that make up the blood-brain barrier help the brain and immune system communicate, he explained.

The crash of that communication system can impact diseases including Alzheimer's disease, stroke and multiple sclerosis. In the Lancet Neurology article, Banks and his colleagues called for more research to better understand how the blood-brain barrier relates to immune cells.

The article also recommended wider use of state-of-the-art imaging to examine how the blood-brain barrier and the rest of central nervous system interact, particularly in patients who have spinal cord injuries, head trauma and stroke. Changes to the blood-brain barrier could give important clues about injuries to the central nervous system and the growth of tumors.

The review also called for investigators from various disciplines and who work in different institutions and laboratories to collaborate on blood-brain barrier research to take research from an animal model to patient clinical trials.

An international committee of 14 scientists who specialize in blood-brain barrier research wrote the review article. In addition to SLU and the VA, participating institutions included Oregon Health & Science University, King's College, Memorial Sloan-Kettering Cancer Center, University of Manitoba, University of Arizona, University of Bern, Texas Tech University Health Sciences Center, University of Rochester, University of California Los Angeles, University of New Mexico and University of Minnesota Medical School.

Source: Medical News Today © 2007 MediLexicon International Ltd (18/12/07)

The findings, reported online in the Proceedings of the National Academy of Sciences, can be used for testing potential MS therapies and for better understanding the role of the blood-brain barrier in disease processes.

Scientists led by D. Craig Hooper, Ph.D., associate professor of cancer biology at Jefferson Medical College of Thomas Jefferson University in Philadelphia, and Hilary Koprowski, M.D., professor of cancer biology at Jefferson Medical College and director of Jefferson’s Center for Neurovirology and the Biotechnology Foundation Laboratories, wanted to find out what factors might affect the onset and severity of EAE (experimental allergic encephalomyelitis), an MS-like autoimmune disease often used as a model. They studied various strains of mice, each lacking some genes associated with inflammation and immunity, and looked at what happened to the blood-brain barrier.

They discovered that the amount of blood-brain barrier damage and subsequent permeability increase correlated to the severity of disease, and surprisingly, in nearly every case, the mouse’s genetic make-up didn’t matter. The mice developed EAE even without supposedly crucial factors in inflammation and autoimmunity – and disease.

“We’ve now shown in all of these mice missing certain components of the immune system that, as expected, opening the blood-brain barrier and letting cells and factors in from the circulation is critical to the development of disease,” Dr. Hooper says. “The fact that the extent of the permeability change correlates with the severity of clinical disease signs shows that this is an important element in determining how sick these animals can get.

“This puts an emphasis on the fact that blood brain permeability changes are an important aspect of the development of a CNS inflammatory disease like EAE, an animal model of MS,” he says.

According to Dr. Hooper, previous studies by his group and other researchers have shown that blood-brain barrier permeability is critical in the development of MS. To study this permeability, he and his co-workers looked at a range of mice lacking certain genes for various types of immune system and inflammatory cells such as NF kappaB, TNF-alpha, and interferon alpha, beta and gamma that contribute to disease. The researchers established EAE in each mouse strain and examined what was common to all of the animals when they developed disease.

“What’s astounding is that mice that wouldn’t be expected to develop EAE because they have major defects in their immune system are still able to develop disease,” though at different rates, he notes.

However, mice missing the immune protein TNF-alpha often did not show disease, despite the increase in brain barrier permeability, causing the scientists to speculate about its role in the disease. “This is the first proof that there are permeability changes in all of these animals and the first hint that permeability doesn’t always equal disease,” he says.

Dr. Hooper notes that the work is part of the long-range goal of determining the exact role of blood-brain barrier permeability in disease. “These results tell us a great deal about the mechanisms that damage the blood-brain barrier,” he says. “All of these factors that are missing in the mice aren’t essential to opening the blood brain barrier.”

Source: Thomas Jefferson University (08/04/07)

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