The central nervous system is protected by the blood-brain barrier (BBB). The tight junction (TJ) proteins
claudin-5 and zonula occludens-1 (ZO-1) as well as the cytoskeletal component F-actin play key roles in maintaining homeostasis
of the BBB. Increases in BBB permeability may be beneficial for the delivery of pharmacological substances
into the brain. Therefore, here, we assessed the use of ultrasound to induce transient enhancement of BBB permeability.
We used fluorescein isothiocyanate (FITC)-dextran 40 to detect changes in the membrane permeability of bEnd.3 cells
during ultrasound treatment. Ultrasound increased FITC-dextran 40 uptake into bEnd.3 cells for 2–6 h after treatment;
however, normal levels returned after 24 h. An insignificant increase in lactate dehydrogenase (LDH) leakage also occurred
3 and 6 h after ultrasound treatment, whereas at 24 h, LDH leakage was indistinguishable between the control and
treatment groups. Expression of claudin-5, ZO-1, and F-actin at the messenger RNA (mRNA) and protein levels was assessed
with real-time polymerase chain reaction and western blotting. Ultrasound induced a transient decrease in claudin-5
mRNA and protein expression within 2 h of treatment; however, no significant changes in ZO-1 and F-actin expression
were observed. Claudin-5, ZO-1, and F-actin immunofluorescence demonstrated that the cellular structures incorporating
these proteins were transiently impaired by ultrasound. In conclusion, our ultrasound technique can temporarily increase
BBB permeability without cytotoxicity to exposed cells, and the method can be exploited in the delivery of drugs to the
brain with minimal damage.