Name: how the blood-brain barrier works
Uploaded: 2025-10-23T11:47:15.000Z
Duration: 49 s
Channel: JoVE

人間の脳は、中枢神経系の 毛細血管に並ぶ内皮細胞からなる 血液脳関門と呼ばれる保護関門を介して 保護関門を介して 循環系から隔離されています。血液脳関門はまた、基底膜および毛細血管と 密接に接触している星状細胞 と呼ばれる特殊化された神経細胞からなります。これらの成分は、不要な物質が 交差するのを防ぐのに役立ちます。このバリアは、接合部複合体を 形成するさまざまな種類のタンパク質を介して、血液と脳内の間質液との間の 化学交換を制御します。一般に、脂溶性化合物のみが 障壁を越えて拡散することができ、水溶性化合物は 能動的または受動的輸送を介して交差します。

「血液脳関門」 Cold Spring Harbor Perspectives in Biology 7, no. 1 (2015年1月).[<a href="https://doi.org/10.1101/cshperspect.a020412" target="__blank">ソース</a>]

Andreone、Benjamin J.、Baptiste Lacoste、およびChenghua Gu.「ニューロンと血管の相互作用」 Annual Review of Neuroscience 38(2015年7月8日):25–46。[<a href="https://doi.org/10.1146/annurev-neuro-071714-033835" target="__blank">ソース</a>]

血液脳関門

The Blood-brain Barrier

<h4>概要</h4>
 
 血液脳関門（BBB）とは、イオンや分子、病原体などの移動を厳密に制御しながら、血液中の栄養分を脳に供給する特殊な血管のことです。BBBは、片側が緊密に結合した内皮細胞、もう片側がアストロサイトの突起で構成されています。これらが一体となって半透膜のバリアを形成し、脳を保護するとともに、治療薬の送達に独自の課題を与えています。 
 
 <h4>細胞の構成要素</h4>
 
 BBBは、内皮細胞やアストロサイトなど、さまざまな細胞成分で構成されています。これらの細胞は共通の基底膜を共有しており、循環系と脳を取り巻く間質液の間の成分の通過を制御しています。
 
 最初の細胞成分である特殊な内皮細胞は、脳の毛細血管の壁を構成しています。まず、脳の毛細血管の壁を作っているのは、特殊な内皮細胞です。これらの細胞間接合部は、選択的な物理的障壁となり、ブドウ糖やインスリンなどの平均的な大きさの分子を含むほとんどの物質の単純な拡散を妨げます。
 
 第二の細胞タイプであるアストロサイトは、中枢神経系のグリア細胞の一種であり、脳血管系との相互作用や密接な関係を通じて、脳内の内皮細胞の機能や血流、イオンバランスに影響を与えます。グリア細胞は、血管と神経細胞を直接結びつける役割を果たしています。グリア細胞は、終足（エンドフィート、endfeet）と呼ばれる突起を伸ばし、一方では血管を包み込み、他方ではシナプスで神経細胞と密接に接触しています。
 
 <h4>化学的交換</h4>
 
 物質がBBBを通過する能力や交換の効率は、それぞれの分子やイオンの化学的・分子的特性に依存します。一般的に、酸素や二酸化炭素のような小さな脂溶性の成分は、内皮層を介して迅速かつ単純な拡散を行います。対照的に、大きい成分や水溶性の成分は、内皮細胞を介した受動的または能動的な輸送を含む、より選択的なプロセスを必要とすることが多いです。これらの物質の交換は、内皮細胞の表面にある分子特異的な受容体や輸送タンパク質の相対的な存在量や効率などに応じて、一般的にはよりゆっくりと行われるか、あるいは全く行われないこともあります。 
 
 <h4>BBBは脳を守る</h4>
 
 BBBによる神経保護は、脳の健康と機能を正常に保つために重要です。BBBの調節機能が低下すると、多発性硬化症、感染症、血液供給不足による虚血など、重篤な神経疾患を引き起こす可能性があります。逆に、BBBの活性化は、神経活性のある医薬の中枢神経系への通過を妨げたり、実質的に減少させたりすることで、一部の神経疾患の治療に悪影響を及ぼすことがあります。このため、神経疾患をターゲットとする医薬品は、BBBを通過しやすいように設計されなければなりません。

概要

血液脳関門(BBB)は、厳密には...

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主要用語と概念

how the blood-brain barrier works

The blood-brain barrier is a specialized system of blood vessels that helps control what enters the brain. It delivers nutrients from the blood while tightly regulating ions, molecules, pathogens, and other substances. This semipermeable barrier protects the brain and also makes it harder to deliver some therapies.

The blood-brain barrier includes several cellular parts, especially endothelial cells and astrocytes. These cells share a common basement membrane and regulate movement between the circulation and the fluid around the brain. Specialized endothelial cells form the walls of cerebral capillaries. They are joined by very tight intercellular junctions, which create a selective physical barrier. This barrier blocks simple diffusion of most substances, including molecules as large as glucose and insulin.

Astrocytes are glial cells in the central nervous system. They influence endothelial cell function, blood flow, and ion balance in the brain. Astrocytes connect closely with the cerebral vasculature. Their processes, called endfeet, wrap around blood vessels on one end and make contact with neurons at synapses on the other. This gives them a direct link between blood vessels and nerve cells.

What crosses the barrier depends on a molecule's chemical and molecular properties. Small lipid-soluble substances, such as oxygen and carbon dioxide, move across by rapid simple diffusion. Larger or water-soluble substances usually need a more selective process. They may move through an endothelial cell by passive or active transport. In many cases, this exchange is slower, or it may not occur at all, depending on receptors and transport proteins on the endothelial surface.

The blood-brain barrier is essential for brain health and normal function. When it does not work properly, severe neurological diseases can occur, including multiple sclerosis, infection, and ischemia from poor blood supply. The barrier can also make treatment difficult because it can reduce the passage of neuroactive drugs into the central nervous system. For that reason, medicines aimed at the brain must be designed to pass through the blood-brain barrier.

How the Blood-Brain Barrier Works

what is a nervous system?

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The nervous system is a network of specialized cells that keeps the body working and helps it respond to the world around it. It controls essential functions such as heart rate and breathing. It also supports movement that helps an organism escape danger. In vertebrates, the nervous system has two major parts: the central nervous system, or CNS, and the peripheral nervous system, or PNS. The CNS includes the brain, spinal cord, and retina, which is the sensory tissue of the visual system. The...

the parasympathetic nervous system

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The parasympathetic nervous system helps the body stay calm and return to a rested state. It is one of the two major divisions of the autonomic nervous system, which controls many unconscious functions such as heart rate and digestion. Its neurons are found in the brain and the peripheral nervous system, and they send axons to muscles, organs, and glands. This system is often called the “rest and digest” system because it supports body processes that restore homeostasis. It is most active...

the sympathetic nervous system

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The sympathetic nervous system helps the body respond to stress and danger. It is one of the two main divisions of the autonomic nervous system. When it turns on, it prepares the body for action and puts lower-priority functions, such as digestion, on hold. This response is often called the fight-or-flight system. A surprise exam can trigger it, and students may notice a tight stomach, a dry mouth, and a fast heartbeat. In a real threat, the system shifts blood away from the digestive system...

the blood-brain barrier

The blood-brain barrier is a specialized system of blood vessels that helps control what enters the brain. It delivers nutrients from the blood while tightly regulating ions, molecules, pathogens, and other substances. This semipermeable barrier protects the brain and also makes it harder to deliver some therapies. The blood-brain barrier includes several cellular parts, especially endothelial cells and astrocytes. These cells share a common basement membrane and regulate movement between the...

neuron structure

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Neurons send signals through a clear set of structures that let them receive, process, and pass on information. They are the main cells of the nervous system and use electrochemical signals to communicate. Neurons also talk to other cells through neurotransmitters at junctions called synapses. Most neurons share three main parts: a cell body, also called the soma, dendrites, and an axon. The soma holds the nucleus and other organelles needed for cell function. Dendrites usually receive...

glial cells

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Glial cells support the nervous system and work alongside neurons. They are one of the two main cell types in the nervous system. Unlike neurons, glia do not send electrical signals, but they help with nearly every other part of nervous system function. In humans, glial cells are about as numerous as neurons in the brain. In the central nervous system, glia include astrocytes, oligodendrocytes, microglia, and ependymal cells. Astrocytes are the most common glial cells. They form organized,...

action potentials

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the resting membrane potential

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Neurons keep a negative resting charge across their membrane. This electrical difference, called the membrane potential, comes from how ions move and how the membrane lets them pass. In a resting neuron, the inside is typically around -70 millivolts and is more negative than the outside, so the cell is polarized. Two main factors create this resting state. First, the membrane is selectively permeable, which means most ions and molecules cannot cross the lipid bilayer without help from ion...

long-term potentiation

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Long-term potentiation, or LTP, is a form of synaptic strengthening in the brain. It changes the strength of chemical synapses over time between pre- and postsynaptic neurons. LTP works against long-term depression, or LTD, which weakens synapses. Together, LTP and LTD are major mechanisms behind learning and memory. LTP can happen when a presynaptic neuron fires again and again and keeps stimulating a postsynaptic neuron. This is called Hebbian LTP, based on Donald Hebb’s idea that neurons...

long-term depression

Synaptic Pruning in Long-term Depression

Long-term depression, or LTD, is a form of synaptic plasticity that weakens chemical synapses over time. It acts between presynaptic and postsynaptic neurons. LTD works in opposition to long-term potentiation, or LTP, which strengthens synapses. Together, LTD and LTP are two of the main mechanisms behind learning and memory. LTD helps the brain avoid staying locked in a fully strengthened state. If synapses were always maximally strengthened, the brain would become less efficient and it would...

the synapse

How Neurons Signal at Synapses

Neurons communicate through synapses, the points where two neurons meet to pass on signals. At a synapse, the sending neuron is the presynaptic cell, and the receiving neuron is the postsynaptic cell. Most neurons can serve in both roles because they send and receive information. Electrical synapses move signals directly between cells. The presynaptic and postsynaptic cells are linked by gap junctions, which are proteins that physically connect them. This type of synapse can pass electrical...

key terms and concepts

Learn how the blood-brain barrier protects the brain, which cells build it, what can cross it, and why it matters for disease and drug delivery.

How the Blood-Brain Barrier Works | JoVE K12

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How the Blood-Brain Barrier Works

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