Identification of Blood–Brain Barrier-Permeable Proteins Derived from a Peripheral Organ: In Vivo and in Vitro Evidence of Blood-to-Brain Transport of Creatine Kinase

Abstract

Certain proteins, such as inflammatory cytokines, that are released from injured or diseased organs are transported from the circulating blood through the blood–brain barrier (BBB) into the brain and contribute to the pathogenesis of related central nervous system dysfunctions. However, little is known about the protein transport mechanisms involved in the central nervous system dysfunctions. The aims of the present study were to identify BBB-permeable protein(s) derived from liver and to clarify their transport characteristics at the BBB. After administration of biotin-labeled liver cytosolic protein fraction to mice in vivo, we identified 9 biotin-labeled proteins in the brain. Among them, we focused here on creatine kinase (CK). In vitro uptake studies with human brain microvessel endothelial cells (hCMEC/D3 cells) showed preferential uptake of muscle-type CK (CK-MM) compared with brain-type CK (CK-BB) at the BBB. Integration plot analysis revealed that CK-MM readily penetrated into brain parenchyma from the circulating blood across the BBB. The uptake of CK-MM by hCMEC/D3 cells was decreased at 4 °C and in the presence of clathrin- and caveolin-dependent endocytosis inhibitors. These results indicate that entry of CK into the brain is mediated by a transport system(s) at the BBB.

Analysis of Clinical Related Factors of Neonatal Hand-Foot-Mouth Disease Complicated With Encephalitis

“…Under normal circumstances, the content of CK-BB in human blood and CSF is very low. When brain tissue lesions lead to brain cell edema and damage, CK-BB will be released into the cerebrospinal fluid, resulting in an increase in the concentration of CK-BB in the cerebrospinal fluid (4).…”

In Vitro Light‐Up Visualization of a Subunit‐Specific Enzyme by an AIE Probe via Restriction of Single Molecular Motion

“…Though a few works were reported to be able to identify the B subunit in serum, the ability for selective qualification of intracellular CK‐B in live samples remains unclear . On the other hand, the indirect immunofluorescence labelling by use of CK‐B antibody appears to be a good method for selective intracellular CK‐B mapping . However, some drawbacks, including instability, non‐negligible background signal, and complicated manipulation, further restrict the practical utility.…”