Expression of HMGB1 in septic serum induces vascular endothelial hyperpermeability

Abstract

The aim of the present study was to investigate the effects of high mobility group protein B1 (HMGB1), which is expressed in the serum of patients with sepsis, on vascular endothelial permeability. Sera from patients with sepsis were used to treat endothelial cells (ECs), and the effect on endothelial permeability was evaluated using immunofluorescence. The morphologies of endothelial cytoskeletal actin and vascular endothelial (VE)‑cadherin were assessed using laser scanning confocal microscopy. The protein expression levels of HMGB1, B‑cell lymphoma 2 (BCL‑2) and BCL‑2‑associated X protein (BAX) were detected using western blotting. EC apoptosis was measured using flow cytometry. The results demonstrated that HMGB1 was significantly expressed in the serum 24 h following the onset of sepsis, and the expression levels peaked at 48 h, which were sustained until 96 h post‑onset. Compared with the control group, treatment of the ECs with 20% septic serum in vitro significantly increased endothelial monolayer permeability (P<0.01), markedly induced transcellular filamentous (F)‑actin rearrangement with stress fiber formation, and resulted in the localization of VE‑cadherin fragmentations at the cell borders with increased gaps between ECs. Furthermore, flow cytometry showed that the apoptotic rate of ECs was significantly increased following treatment with septic serum. In addition, the expression levels of BAX were significantly increased, whereas the expression levels of BCL‑2 were significantly decreased. Pretreatment with an HMGBI inhibitor (ethyl pyruvate; 5 µM) 24 h prior to treatment with the septic serum attenuated the effects of septic serum treatment. Together, these findings suggested that treatment of ECs with sera from patients with sepsis may induce the loss of vascular endothelial monolayer integrity, elicit the formation of endothelial F‑actin stress fibers and initiate VE‑cadherin redistribution, which may be attributed to high levels of HMGB1 in the serum. This mechanism also appears to involve changes in the activation of BAX and BCL‑2, resulting in EC apoptosis.

Unfractionated Heparin Alleviates Human Lung Endothelial Barrier Dysfunction Induced by High Mobility Group Box 1 Through Regulation of P38–GSK3β–Snail Signaling Pathway

“…Using cultured human pulmonary microvascular endothelial cell, we were able to demonstrate that HMGB1 treatment/transfection increased endothelial permeability, disrupted endothelial barrier function and induced endothelial-to-mesenchymal transition. In addition, a similar function of HMGB1 on endothelial permeability has been reported in various type endothelial cells [18-20]. …”

Location is the key to function: HMGB1 in sepsis and trauma-induced inflammation

“…Endothelial cells also increase the production of proinflammatory IL‐8 and G‐CSF in response to HMGB1 . In addition to direct effects on proinflammatory mediator production and attraction of immune cells, HMGB1 also plays an important role in regulating endothelial cell cytoskeletal rearrangement and vascular permeability . High levels of HMGB1 in sera from patients with sepsis induce loss of vascular endothelial monolayer integrity, elicit formation of endothelial F‑actin stress fibers and initiate VE‑cadherin redistribution .…”

Ethyl pyruvate is a novel anti-inflammatory agent to treat multiple inflammatory organ injuries

“…In addition, EP improves sepsis outcome by reducing mitochondrial swelling and dysfunction in experimental sepsis [65]. Septic patients have significantly increased serum HMGB1 levels, which can induce endothelial cell hyperpermeability via BAX and BCL-2 regulated apoptosis, EP can reverse these detrimental effects to prevent endothelial cell injury in experimental sepsis [66]. Furthermore, EP can effectively reduce vascular endothelial inflammation and this effect at least partly depends on the attenuation of endoplasmic reticulum stress [67].…”