Tumour necrosis factor‐α‐mediated disruption of cerebrovascular endothelial barrier integrity in vitro involves the production of proinflammatory interleukin‐6

Abstract

The co-involvement of tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) during blood-brain barrier (BBB) injury has been reported in various models of neuroinflammation, although the precise functional interplay between these archetypal proinflammatory cytokines remains largely undefined within this context. In the current paper, we tested the hypothesis that TNF-α-mediated BBB disruption is measurably attributable in-part to induction of microvascular endothelial IL-6 production. In initial experiments, we observed that treatment of human brain microvascular endothelial cells (HBMvECs) with TNF-α (0-100 ng/mL, 0-24 h) robustly elicited both time- and dose-dependent induction of IL-6 expression and release, as well as expression of the IL-6 family receptor, GP130. Further experiments demonstrated that the TNF-α-dependent generation of reactive oxygen species, down-regulation of adherens/tight junction proteins, and concomitant elevation of HBMvEC permeability, were all significantly attenuated by blockade of IL-6 signalling using either an anti-IL-6 neutralizing antibody or an IL-6 siRNA. Based on these observations, we conclude that TNF-α treatment of HBMvECs in vitro activates IL-6 production and signalling, events that were shown to synergize with TNF-α actions to elicit HBMvEC permeabilization. These novel findings offer a constructive insight into the specific contribution of downstream cytokine induction to the injurious actions of TNF-α at the BBB microvascular endothelium interface. The co-involvement of tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) during blood-brain barrier (BBB) injury has been widely reported. Using human brain microvascular endothelial cells (HBMvEC), we show that TNF-α-mediated BBB disruption is measurably attributable in-part to induction of endothelial IL-6 production and signalling. We demonstrate that the TNF-α-dependent generation of reactive oxygen species (ROS), down-regulation of interendothelial junctions, and concomitant elevation of HBMvEC permeability, could be significantly attenuated by using either an IL-6 neutralizing antibody or an IL-6-specific siRNA. These findings provide insight into the complex nature of proinflammatory cytokine injury at the BBB microvascular endothelium interface.

Virus entry and replication in the brain precedes blood-brain barrier disruption during intranasal alphavirus infection

“…In previous studies, we showed that in vivo BBB permeability increased after subcutaneous infection with West Nile virus (WNV), a neurotropic flavivirus, prior to initial neuroinvasion and during inflammatory infiltration (Daniels et al, 2014). Indeed, both WNV and VEEV induce increased expression of vascular adhesion molecules at endothelial barriers that recruit lymphocytes and monocytes (Schafer et al, 2009; Verma et al, 2009), which, via expression of BBB destabilizing cytokines including interleukin (IL)-2, IL-1 and TNF-α has recently been shown to decrease TJ integrity at the BBB via effects on RhoG-TPases and/or TJ expression (Daniels et al, 2014; Rochfort et al, 2016; Rochfort et al, 2014; Wylezinski and Hawiger, 2016). In contrast, CNS infection with rabies virus is associated with maintenance of BBB integrity, which has been shown to limit immune cell infiltration and virologic control, contributing to lethality (Roy and Hooper, 2007).…”

Differential transcription profiles of long non-coding RNAs in primary human brain microvascular endothelial cells in response to meningitic Escherichia coli

“…Accumulating evidence suggests that CNS-infecting bacteria enhance BBB permeability by damaging the tight junctions of BMECs12, and several molecules have been reported to mediate this enhancement of BBB permeability, such as the matrix metallopeptidase (MMP) family, transforming growth factor (TGF) β1, vascular endothelial growth factor (VEGF) A, interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF)-α131415. In the final stage of this process, a large number of inflammatory cells gain access to the cerebral parenchyma, triggering central inflammatory storm and CNS dysfunction16.…”

Commentary: Mycoplasma pneumoniae-associated mild encephalitis/encephalopathy with a reversible splenial lesion: Report of two pediatric cases and a comprehensive literature review

“…Serum levels of IL-6 and tumor necrosis factor (TNF)-α were increased in children with M.pneumoniae infection 32 . These factors enhance permeability of blood-brain barrier 33 , resulting in neuroinflammation, which renders microglia in the CC release proinflammatory cytokines and ROS. In fact, the levels of IL-6 were increased in cerebrospinal fluid (CSF) of children with MERS due to M.pneumoniae 34 …”