The blood-brain barrier (BBB)—a vital structure made up of endothelial cells, pericytes, astrocytes, microglia, and neurons—plays a crucial role in protecting the brain. It's like a bouncer at a club, ensuring only the right stuff gets in and the wrong stuff stays out. But this barrier isn't static; it's constantly challenged by factors from within and outside the body.

Hormones from peripheral organs, like the gonads and adrenal glands, can influence the BBB. They can do this in different ways depending on a person's sex and age. These hormones might talk to the brain through specific areas, such as the circumventricular organs, which have leaky blood vessels and can act as neurosensory or neurosecretory centers.

When illness strikes, such as liver, kidney, or lung diseases, harmful toxins and metabolites can enter the brain through the bloodstream. These can directly or indirectly affect the BBB by triggering the immune system. For instance, chronic kidney disease, which affects over 840 million people globally, can cause neurological issues like cognitive impairment and uremic encephalopathy due to uremic toxins.

It's essential to understand how these hormones, toxins, and immune reactions impact the brain's blood vessels. The BBB is the last line of defense for the brain, so figuring out how it communicates with the rest of the body is crucial for keeping our brains healthy.

How Peripheral Signals Affect the Blood-Brain Barrier

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