A geranyl acetophenone attenuates lipopolysaccharide-induced permeability and F-actin cytoskeleton rearrangement of endothelial cells

Our research group has previously demonstrated the anti-inflammatory effects of tHGA (2,4,6-trihydroxyl-3-geranylacetophenone), a geranyl acetophenone found in Melicope ptelefolia, via inhibition on lipoxygenase (LOX) and cyclooxygenase (COX), which further suppress the formation of leukotrienes and prostaglandins [1]. Leukotrienes and prostaglandins are two important proinflammatory mediators that cause F-actin cytoskeleton rearrangement followed by endothelial hyperpermeability, which is the central hallmark of many vascular inflammatory diseases [2]. This study aims to determine the effect of tHGA on lipopolysaccharide (LPS)-induced endothelial hyperpermeability and F-actin cytoskeleton rearrangement in human umbilical vein endothelial cells (HUVECs). HUVECs were pre-treated with increasing concentrations of tHGA for 6 hours before induced with LPS for 24 hours. MTT assay was performed to determine the non-toxic concentrations of tHGA. Transwell permeability assay was performed using Sodium Fluorescein (Na-F) and Evans Blue Albumin (EBA) to determine the degree of endothelial permeability upon small and large molecular weight molecules. The effect of tHGA on F-actin cytoskleton rearrangement was determined by staining F-actin with Alexa-Fluor 488 and examined under a fluorescense microscope. Results showed that tHGA was non-toxic at the concentration ≤20µM. At the concentration of 1.25, 5 and 20µM, tHGA significantly attenuated transcellular permeability of EBA as well as paracellular permeability of Na-F across HUVECs monolayer. EBA and Na-F permeability in HUVECs monolayer was decreased to 71% and 67% of the control at a concentration of 20µM (P < 0.005). The suppressive effect of tHGA on LPS-induced endothelial hyperpermeability was exerted through inhibition on F-actin cytoskeleton rearrangement. Thus, tHGA strengthened the endothelial barrier properties in HUVECS by reducing LPS-induced endothelial hyperpermeability and F-actin cytoskeleton rearrangement.

Keywords: Acetophenone, tHGA, permeability, F-actin, lipopolysaccharide, endothelial cells

References:

[1] Shaari K, Suppaiah V, Wai LK, Stanslas J, Tejo BA, Israf DA, Abas F, Ismail IS, Shuaib NH, Zareen S, Lajis NH. Bioassay-guided identification of an anti-inflammatory prenylated acylphloroglucinol from Melicope ptelefolia and molecular insights into its interaction with 5-lipoxygenase. Bioorg Med Chem 2011; 19: 6340 – 6347.

[2] Kumar P, Shen Q, Pivetti CD, Lee ES, Wu MH, Yuan SY. Molecular mechanisms of endothelial hyperpermeability: implications in inflammation. Expert Rev Mol Med 2009; 11: e19.