, 2011). One must of course be careful when comparing in vivo brain
distribution and in vitro endothelial cell accumulation data. When observing GSK2118436 clinical trial the in vivo BBB endothelial cell pellet analysis for [3H]pentamidine previously published by our group, it was evident that the drug accumulated in the cells ( Sanderson et al., 2009). [3H]nifurtimox also accumulated in vivo in BBB endothelial cell pellets, and the effect on accumulation with CT were similar to those reported here with an increase observed with the addition of unlabelled pentamidine and little or no difference with the other drugs ( Jeganathan et al., 2011). The reasoning behind the improved cure rates of patients using NECT compared to eflornithine alone, based on our results, is unlikely to be due to the interactions of the drugs with membrane PCI-32765 nmr transporters at the level of the brain capillary endothelium. It has been stipulated that the arrestment of parasite defences caused by eflornithine allows the efficacy of nifurtimox to be improved and perhaps this is the main reason behind NECT success ( Priotto et al., 2009). The mechanism by which nifurtimox enters the cells remains unknown. It is likely
that the lipophilic properties of nifurtimox (with an octanol–saline partition coefficient of 5.46 Jeganathan et al., 2011) allow it to cross cell membranes by passive diffusion and previous work has shown that it not only appears to use a transcellular route of entry, but enters the mouse brain at sufficient amounts to be effective else in killing trypanosomes (Jeganathan et al., 2011). However, the role played, if any, by
blood-to-brain transporters remains elusive. Any effect that the drugs had on the expression of transporters in the hCMEC/D3 cell line has not been assessed here. It has been shown previously that some drugs can upregulate functional expression of drug transporters such as P-gp, and this is well documented with dexamethasone (Narang et al., 2008), but the 30 minute time frames of the experiments in this report were unlikely to be sufficient at inducing any significant increase in expression or activity. Studying nifurtimox entry and exit to the brain is crucial to improving treatment of second stage HAT, especially now that NECT is fast becoming the treatment of choice. Considering the current usage of NECT, it is somewhat surprising that very little is known about the mechanisms being used by these drugs to gain entry to the human brain. We report here that nifurtimox is a substrate of BCRP and possibly, to a lesser extent, members of the OATP transport family, in an in vitro model of the BBB.