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Composition of the Blood Brain Barrier (BBB)
The BBB consists of highly specialized endothelial cells that express tight junction proteins, including zonula occludens-1 (ZO-1), occludin, and Claudin-1 / CLDN1, -3, and -5.
In addition to this endothelial barrier, the BBB also consists of pericytes and astrocytic end-feet surrounding the endothelial cells
MDR1 (Multidrug Resistance Protein 1) / P-Glycoprotein 1, is an importat determinant of permeability
"Leaks" in the Blood Brain Barrier (BBB)?
In some regions of the brain called circumventricular organs (CVOs), the BBB is fenestrated, leading to direct contact between the brain and the circulatory system: neurons in these areas pick up signals from the blood or secrete hormones into the circulatory system away
One of these areas is the median eminence in the mediobasal hypothalamus (MBH)
How leaks can be made
The increased blood-brain-barrier permeability was associated with reduced expression of the tight junction proteins Occludin and Claudin-5
Lipopolysaccharides (LPS) mainly produced by Gram-negative bacteria (Proteobacteria and Bacteroidetes: pro-inflammatory bacteria) can induce inflammation and disrupt the blood–brain barrier function
Drugs, which cannot passage through the Blood Brain Barrier (BBB)
Delivering substances intranasally via the olfactory epithelium (OE) has become a promising noninvasive technique. This method allows for bypassing the blood-brain barrier (BBB), enabling direct therapeutic delivery to the brain.
The blood-brain barrier (BBB) hinders the penetration of many drugs
Monoclonal antibodies of approx. 150 kDa cannot cross the blood brain barrier
see also:
Extracellular Vesicles (EV)
Intranasal drug delivery
Olfactory epithelium
Olfactory system