Methamphetamine-induced nitric oxide promotes vesicular transport in blood–brain barrier endothelial cells

Abstract

Methamphetamine's (METH) neurotoxicity is thought to be in part due to its ability to induce blood–brain barrier (BBB) dysfunction. Here, we investigated the effect of METH on barrier properties of cultured rat primary brain microvascular endothelial cells (BMVECs). Transendothelial flux doubled in response to METH, irrespective of the size of tracer used. At the same time, transendothelial electrical resistance was unchanged as was the ultrastructural appearance of inter-endothelial junctions and the distribution of key junction proteins, suggesting that METH promoted vesicular but not junctional transport. Indeed, METH significantly increased uptake of horseradish peroxidase into vesicular structures. METH also enhanced transendothelial migration of lymphocytes indicating that the endothelial barrier against both molecules and cells was compromised. Barrier breakdown was only observed in response to METH at low micromolar concentrations, with enhanced vesicular uptake peaking at 1 μM METH. The BMVEC response to METH also involved rapid activation of endothelial nitric oxide synthase and its inhibition abrogated METH-induced permeability and lymphocyte migration, indicating that nitric oxide was a key mediator of BBB disruption in response to METH. This study underlines the key role of nitric oxide in BBB function and describes a novel mechanism of drug-induced fluid-phase transcytosis at the BBB.

Acetyl-L-Carnitine Prevents Methamphetamine-Induced Structural Damage on Endothelial Cells via ILK-Related MMP-9 Activity

“…This may occur by increased extravasation of neurotoxic proteins and pro-inflammatory molecules across the barrier, as well as deficits in both transcellular and paracellular transports [7,15]. We show also that ALC was effective in preventing the increased expression of ILK, thus preventing MMP-9 activation and preserving actin structure and TJ function.…”

“…In endothelial cells, these events may lead to loss of adhesion and/or relevant restructuration of the endothelium, thus contributing to increase METH neurotoxicity. Interestingly, although METH-induced internalization of both claudin and occludin through endocytosis was previously seen to be concomitant with TJ fragmentation and gap formation [3,13,14], the functional significance of such translocation remains unclear, since it can occur also in the absence of BBB structural changes [15]. As the anchoring protein ZO-1 and the transmembrane protein occludin are physically linked to the actin filaments, some authors have hypothesized that actin depolymerization could be secondary to the loss of these binding interactions.…”

“…Different mechanisms have been proposed for the lack of BBB tightness after METH exposure [3,4,10,11,13,15]. Among those, the activation and expression of MMPs, a common mechanism of BBB leakiness, was often referred after METH exposure [4,6,9].…”

“…Although pericytes, astrocytes, and the surrounding basement membrane play a structural and regulatory role on the neurovascular unit, the endothelial cells (ECs) are the barrier-conferring properties of the BBB [13,[15][16][17]. Its modulation is essentially a function of the TJ proteins [13,16,[18][19][20].…”

Methamphetamine promotes α-tubulin deacetylation in endothelial cells: The protective role of acetyl-l-carnitine

“…METH-induced permeability at the BBB level has been consistently reported both in vivo and in vitro (Conant et al, 2011;Martins et al, 2011;Urrutia et al, 2013), as a result of tight junction and cytoskeleton disarrangement (Dietrich, 2009;Kousik et al, 2012;Park et al, 2013). In endothelial cells, METH was also shown to trigger nitric oxide (NO)-mediated transcytosis (Martins et al, 2013). Recently, we showed, also in endothelial cells, that exposure to METH leads to disruption of actin filaments concomitant with claudin-5 translocation to the cytoplasm, promoted by MMP-9 activation in association with ILK overexpression (Fernandes et al, 2014).…”