Damage to the Blood-brain Barrier
The blood-brain barrier (BBB) is lined with a layer of cells that separate the bloodstream from the brain. The barrier acts as a selective filter allowing specific substances like oxygen and hormones to enter the brain while preventing other substances from passing through the brain.
If this selective filter is damaged or not functioning correctly, the BBB may not properly prevent harmful substances from entering the brain. Some researchers argue that such a failure of the blood-brain barrier can result in damage from chemicals, inflammatory cytokines, and immune cells.
This damage caused by a “leaky brain” can potentially result in a variety of harmful health conditions and diseases including brain fog, Alzheimer’s disease, Huntington’s disease, and more.
Who Discovered the Blood-brain Barrier?
Around 100 years ago, a scientist named Paul Ehrlich discovered the blood-brain barrier. While studying animal physiology, Ehrlich injected blue dye into the bodies of these animals. The dye would be transported throughout the body but would not enter into the brain. When Ehrlich injected the dye directly into the brain he also saw the dye would remain there and did not pass to the rest of the body.
Ehrlich realized that there was an obstacle preventing the transfer of the dye. He determined that there must be a type of blood-brain barrier which acted as a special membrane that surrounded the brain and protected it from the bloodstream.
Similar to how past research has focused on the barrier in the gut, relatively new research has begun focusing on the blood-brain barrier and the potential effects if it is compromised. The compromise of the blood-brain barrier has become known as “leaky brain”.
What is the Blood-brain Barrier (In Detail)
Now, you may understand that the BBB is made of a thin layer of brain capillary endothelial cells. The endothelial cells are simple, flat cells that line the inside walls of the lymphatic system and blood vessels.
The entire barrier is composed of specialized components called neurovascular units (NVUs) which include:
- Endothelial cells, which line the barrier
- Astrocytic endfeet, which are part of astrocyte nerve cells that envelope the blood vessels
- Basement membrane that lines the epithelial cells
- Pericytes that provide structural support to the blood vessels, but may also control BBB development and permeability
All these different pieces form the blood-brain barrier, which acts as a semi-permeable, or selectively permeable barrier. The barrier plays an active role in controlling the exchange of materials between the blood, cerebrospinal fluid and brain through a system of transporters. It also acts as a protective barrier to prevent the free flow of potentially harmful materials between the blood and the brain.
The protective layer is composed of:
- A physical barrier of cells between the blood and the brain
- Transporters that carefully mediate the flow of compounds
- An enzymatic barrier with neurotransmitter and toxin metabolizing enzymes in the endothelial cells (blood) and epithelial cells (brain).
The blood-brain barrier is extremely important to your health, but it is also very delicate. The endothelial cells that line blood vessels are only one layer thick. It is true that there are additional layers of connective tissues and smooth muscle cells, particularly around large arteries and veins, but it is only the ultra-thin barrier that determines the passage of substances between the blood vessels and the brain.
The Result of a Damaged Blood-brain Barrier
Just like all cells in your body, the cells that make up the blood-brain barrier have a limited lifespan or can be damaged or destroyed. The cells in the body have a lifespan that can range from a couple of months to a couple of years like the cells in the brain endothelium. When the cells die they are naturally replaced by new cells produced by the body.
Cells can become damaged when exposed to detrimental compounds and physiological circumstances. When cells die prematurely, the body quickly begins to produce replacements.
When the body is unable to produce cells quickly enough to repair sustained damage, the blood-brain barrier is compromised and all sorts of issues can develop, like the leakage of plasma proteins, chemical toxins, pathogens into certain areas of the brain. These issues can result in exacerbated and potentially chronic inflammation coupled with neurodevelopmental disorders in children, autism, mental health disorders, and neurodegenerative disease. These chronic diseases and disorders are common complications from a “leaky brain”.
