Abstract
Lipopolysaccharide (LPS) causes microvascular barrier disruption, leading to albumin leakage from microvessels resulting in a range of disastrous sequels. Salvianolic acid B (SalB) is a major water-soluble component derived from Salvia miltiorrhiza. Previous studies showed its potential to attenuate microvascular barrier dysfunction, but the underlying mechanism is not fully understood. The present study was intended to investigate the impact of SalB on endothelial cell barrier in vivo in rat mesenteric venules as well as in vitro in human umbilical vein endothelial cells (HUVECs), aiming at disclosing the mechanism thereof, particularly the role of Src in its action. Male Wistar rats were challenged by infusion of LPS (2 mg/kg/h) through left femoral vein for 90 min. SalB (5 mg/kg/h) was administrated either simultaneously with LPS or 30 min after LPS infusion through the left jugular vein. Vesicles in venular walls were observed by electron microscopy. HUVECs were incubated with LPS with or without SalB. The expression of Zonula occluden-1 (ZO-1), VE-cadherin, caveolin-1 and Src in HUVECs was assessed by Western blot and confocal microscopy, binding of SalB to Src was measured using Surface Plasmon Resonance and BioLayer Interferometry. Treatment with SalB inhibited albumin leakage from rat mesenteric venules and inhibited the increase of vesicle number in venular endothelial cells induced by LPS. In addition, SalB inhibited the degradation of ZO-1, the phosphorylation and redistribution of VE-cadherin, the expression and phosphorylation of caveolin-1, and phosphoirylation of Src in HUVECs exposed to LPS. Furthermore, SalB was found able to bind to Src. This study demonstrates that protection of SalB against microvascular barrier disruption is a process involving both para- and trans-endothelial cell pathway, and highly suggests Src as the key enzyme for SalB to work.
Highlights
Lipopolysaccharide (LPS) is an essential component of the cell wall of Gram negative bacteria, which causes a series of inflammatory reactions in the infected subjects, including microvascular barrier disruption
The present study demonstrated the potential of Salvianolic acid B (SalB) to ameliorate the LPS-induced microvascular hyperpermeability, as shown by the decrease in albumin leakage from rat mesenteric venules
As to the mechanism we observed an ability of SalB to reduce the caveola number in rat mesenteric venular endothelial cells after LPS challenge, and decrease the expression and phosphorylation of caveolin-1, the redistribution and phosphorylation of VE-cadherin, and the degradation of Zonula occluden-1 (ZO-1) in HVUECs exposed to LPS
Summary
Lipopolysaccharide (LPS) is an essential component of the cell wall of Gram negative bacteria, which causes a series of inflammatory reactions in the infected subjects, including microvascular barrier disruption. LPS recognition by TLR4 activates the c-Src [10], which in turn phosphorylates caveolin-1 at tyrosine 14, promotes caveolae to shuttle across endothelial cells and transport plasma albumin [11, 12]. No strategy is available as yet in clinic to prevent or attenuate LPS-induced microvascular barrier dysfunction by acting on Src. Salvianolic acid B (SalB), is a major water-soluble component derived from Salvia miltiorrhiza with a phenolic hydroxyl group. We hypothesized that SalB preserves microvascular endothelium barrier via interference in Src activation To test this hypothesis, in the present study, we assessed the effect of SalB on LPS-elicited rat mesenteric venular hyperpermeability, and explored the underlying mechanism both in vivo in rat and in vitro in HUVECs with focusing on the role of Src
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