Icj. Van Der Sandt et al., P-glycoprotein inhibition leads to enhanced disruptive effects by anti-microtubule cytostatics at the in vitro blood-brain barrier, PHARM RES, 18(5), 2001, pp. 587-592
Purpose. To investigate whether P-glycoprotein (Pgp) protects the in vitro
BBB against the cytotoxic effects of anti-tumour drugs.
Methods. In an in vitro BBB coculture model the influence of the anti-micro
tubule drugs vinblastine. colchicine, paclitaxel and the non-antimicrotubul
e drugs doxorubicin, fluorouracil and etoposide in the absence or presence
of Pgp modulators on the trans-endothelial electrical resistance (TEER), wh
ich is an indicator for the integrity, was investigated.
Results. In the absence of Pgp modulators vinblastine, colchicine and pacli
taxel dose dependently decreased TEER values to less than 20% of control. N
on-anti-microtubule drugs did not affect TEER values. Following competitive
inhibition of Pgp by various Pgp modulators and substrates, even low conce
ntrations of vinblastine, colchicine and paclitaxel substantially decreased
TEER. IC50 values of LY 335979, SDZ-PSC 833, cyclosporin A, and verapamil
were 0.03, 0.25, 0.16. and 13.7 muM, respectively.
Conclusions. These results indicate that Pgp normally protects the in vitro
BBB against the disruptive effects of anti-microtubule drugs. but its inte
grity is lost when anti-microtubule drugs are used in combination with pote
nt Pgp modulators. In addition, this procedure offers the possibility to ch
aracterize Pgp modulators and substrates with respect to their efficacy and
to elucidate drug interactions at the level of Pgp.