Do you know about this amazing wall that protects the brain? (Blood-Brain Barrier)

Think of your brain as a very valuable, sensitive fortress. And there is a gatekeeper who checks everything that enters that fortress, keeping the bad things out and only letting the good things in. Similarly, today we are going to talk about a special gatekeeper, or filter, located in the blood vessels around our brain, protecting the brain. In medicine, we call this the Blood-Brain Barrier (BBB).

Simply put, what is the Blood-Brain Barrier (BBB)?

This is not just a barrier. In fact, it is like a guard for our brain. This protective wall is located on the inside of the blood vessels surrounding the brain. Its main function is to prevent harmful substances, germs, and unwanted chemicals in the blood from entering the brain . It also controls the proper intake of nutrients and oxygen to the brain and the removal of waste products from the brain.

In other parts of our body, the cells in our blood vessels (we call these endothelium cells) have small gaps between them. But in the blood vessels in the brain, these cells are very tightly packed, connected to each other, and there are no gaps. It's like a plastered wall without holes. So even large molecules, or even things that are just soluble in water, can't easily pass through it.

What can go inside this security wall?

Not everything stops at this wall. Some things can pass through it.

• Very small molecules: Small molecules like oxygen and carbon dioxide can easily pass through this.
• Lipid-soluble: The outer covering of these protective wall cells is made of lipids, so lipid-soluble substances can easily pass through it.

Think about why things like alcohol, anesthetics, and caffeine affect our brains so quickly. The reason is that they can easily pass through the Blood-Brain Barrier. Also, many medications, such as antidepressants, anxiolytics, and epilepsy medications, are designed to cross this barrier and reach the brain.

That means, if a drug is to directly affect the brain, it must be able to cross the Blood-Brain Barrier.

What are the situations where this defense wall can be weakened?

Although this protective barrier is very strong, it can sometimes weaken or start to "leak." This can happen mainly in conditions such as inflammation . When this barrier is weakened, harmful substances that normally wouldn't be able to enter the brain can enter.

The table below lists some of the main medical conditions that can weaken the Blood-Brain Barrier.

Are there any signs that this might be a problem?

In fact, there are no direct symptoms that indicate a problem with the Blood-Brain Barrier. What we see are symptoms of the underlying disease that affects it (for example, stroke or Alzheimer's disease). Although there is currently no clear way to test the condition of this barrier, various methods are being explored at the research level.

What should we do to keep this valuable defense strong?

Although we can't directly treat the Blood-Brain Barrier, we can avoid the factors that weaken it. That means maintaining a healthy lifestyle is the best thing to do.

• Maintain a balanced diet and a healthy weight: Things like high blood pressure, diabetes, and cholesterol damage our blood vessels. This damage can also affect the blood vessels in the brain. Therefore, it is very important to control these diseases through a good diet and exercise.
• Don't ignore infections: Sometimes, if ear, eye, or dental infections are not treated properly, the germs can travel through the bloodstream to the brain. So, see your doctor immediately for any infection and get treatment.
• Wear safety gear: Head injuries can directly damage this barrier. Therefore, be sure to wear a helmet when riding a bicycle or motorbike, and fasten your seat belt when riding in a vehicle.
• Manage your chronic diseases properly: If you have diseases like diabetes, high blood pressure, or cholesterol, take the medications your doctor prescribes exactly and on time. Also, go to clinics on time to check your condition.

How do doctors use this knowledge?

Knowledge about the Blood-Brain Barrier is very useful for doctors and scientists. It is both a challenge and an opportunity.

• The challenge: Sometimes, a drug for a brain tumor or infection can't get through to the brain because of this barrier. The barrier thinks the drug is "bad." In these cases, special methods (such as a "Trojan horse" method, which involves attaching itself to another molecule) are used to deliver the drug through the barrier.
• Case: Parkinson's disease occurs when there is a decrease in the chemical dopamine in the brain. Even if dopamine is given directly as a medicine, it cannot cross this barrier and enter the brain. Therefore, doctors give a medicine called levodopa. This levodopa can cross the barrier. Once it enters the brain, levodopa turns into dopamine. Isn't this a great idea?

That is, some drugs are designed to bypass this barrier. Other drugs are designed to bypass it, because if the drug gets into the brain, it can cause unwanted side effects.