Abstract
African trypanosomes are tsetse fly transmitted protozoan parasites responsible for
human African trypanosomiasis, a disease characterized by a plethora of neurological
symptoms and death. How the parasites under microvascular shear stress (SS) flow conditions
in the brain cross the blood–brain barrier (BBB) is not known. In vitro studies using
static models comprised of human brain microvascular endothelial cells (BMEC) show
that BBB activation and crossing by trypanosomes requires the orchestration of parasite
cysteine proteases and host calcium-mediated cell signaling. Here, we examine BMEC
barrier function and the activation of extracellular signal-regulated kinase (ERK)1/2
and ERK5, mitogen-activated protein kinase family regulators of microvascular permeability,
under static and laminar SS flow and in the context of trypanosome infection. Confluent
human BMEC were cultured in electric cell-substrate impedance sensing (ECIS) and parallel-plate
glass slide chambers. The human BMEC were exposed to 2 or 14 dyn/cm2 SS in the presence or absence of trypanosomes. Real-time changes in transendothelial
electrical resistance (TEER) were monitored and phosphorylation of ERK1/2 and ERK5
analyzed by immunoblot assay. After reaching confluence under static conditions human
BMEC TEER was found to rapidly increase when exposed to 2 dyn/cm2 SS, a condition that mimics SS in brain postcapillary venules. Addition of African
trypanosomes caused a rapid drop in human BMEC TEER. Increasing SS to 14 dyn/cm2, a condition mimicking SS in brain capillaries, led to a transient increase in TEER
in both control and infected human BMEC. However, no differences in ERK1/2 and ERK5
activation were found under any condition tested. African trypanosomiasis alters BBB
permeability under low shear conditions through an ERK1/2 and ERK5 independent pathway.
Keywords
African trypanosomes - blood–brain barrier - brain microvascular endothelial cells
- trypanosoma brucei rhodesiense - shear stress - MAPK
