Suppressive activity of RGX-365 on HMGB1-mediated septic responses

Abstract RGX-365 is the main fraction of black ginseng conmprising protopanaxatriol (PPT)-type rare ginsenosides (ginsenosides Rg4, Rg6, Rh4, Rh1, and Rg2). No studies on the antiseptic activity of RGX-365 have been reported. High mobility group box 1 (HMGB1) is recognized as a late mediator of sepsis, and the inhibition of HMGB1 release and recovery of vascular barrier integrity have emerged as attractive therapeutic strategies for the management of sepsis. In this study, we examined the effects of RGX-365 on HMGB1-mediated septic responses and survival rate in a mouse sepsis model. RGX-365 was administered to the mice after HMGB1 challenge. The antiseptic activity of RGX-365 was assessed based on the production of HMGB1, measurement of permeability, and septic mouse mortality using a cecal ligation and puncture (CLP)-induced sepsis mouse model and HMGB1-activated human umbilical vein endothelial cells (HUVECs). We found that RGX-365 significantly reduced HMGB1 release from LPS- activated HUVECs and CLP-induced release of HMGB1 in mice. RGX-365 also restored HMGB1-mediated vascular disruption and inhibited hyperpermeability in the mice. In addition, treatment with RGX-365 reduced sepsis-related mortality in vivo. Our results suggest that RGX- 365 reduces HMGB1 release and septic mortality in vivo, indicating that it is useful in the treatment of sepsis.

RhoB controls endothelial barrier recovery by inhibiting Rac1 trafficking to the cell border.

Endothelial barrier dysfunction underlies chronic inflammatory diseases. In searching for new proteins essential to the human endothelial inflammatory response, we have found that the endosomal GTPase RhoB is up-regulated in response to inflammatory cytokines and expressed in the endothelium of some chronically inflamed tissues. We show that although RhoB and the related RhoA and RhoC play additive and redundant roles in various aspects of endothelial barrier function, RhoB specifically inhibits barrier restoration after acute cell contraction by preventing plasma membrane extension. During barrier restoration, RhoB trafficking is induced between vesicles containing RhoB nanoclusters and plasma membrane protrusions. The Rho GTPase Rac1 controls membrane spreading and stabilizes endothelial barriers. We show that RhoB colocalizes with Rac1 in endosomes and inhibits Rac1 activity and trafficking to the cell border during barrier recovery. Inhibition of endosomal trafficking impairs barrier reformation, whereas induction of Rac1 translocation to the plasma membrane accelerates it. Therefore, RhoB-specific regulation of Rac1 trafficking controls endothelial barrier integrity during inflammation.

Co-immobilization of adhesive peptides and VEGF within a dextran-based coating for vascular applications.

UNLABELLED: Multifunctional constructs providing a proper environment for adhesion and growth of selected cell types are needed for most tissue engineering and regenerative medicine applications. In this context, vinylsulfone (VS)-modified dextran was proposed as a matrix featuring low-fouling properties as well as multiple versatile moieties. The displayed VS groups could indeed react with thiol, amine or hydroxyl groups, be it for surface grafting, crosslinking or subsequent tethering of biomolecules. In the present study, a library of dextran-VS was produced, grafted to aminated substrates and characterized in terms of degree of VS modification (%VS), cell-repelling properties and potential for the oriented grafting of cysteine-tagged peptides. As a bioactive coating of vascular implants, ECM peptides (e.g. RGD) as well as vascular endothelial growth factor (VEGF) were co-immobilized on one of the most suitable dextran-VS coating (%VS=ca. 50% of saccharides units). Both RGD and VEGF were efficiently tethered at high densities (ca. 1nmol/cm(2) and 50fmol/cm(2), respectively), and were able to promote endothelial cell adhesion as well as proliferation. The latter was enhanced to the same extent as with soluble VEGF and proved selective to endothelial cells over smooth muscle cells. Altogether, multiple biomolecules could be efficiently incorporated into a dextran-VS construct, while maintaining their respective biological activity. STATEMENT OF SIGNIFICANCE: This work addresses the need for multifunctional coatings and selective cell response inherent to many tissue engineering and regenerative medicine applications, for instance, vascular graft. More specifically, a library of dextrans was first generated through vinylsulfone (VS) modification. Thoroughly selected dextran-VS provided an ideal platform for unbiased study of cell response to covalently grafted biomolecules. Considering that processes such as healing and angiogenesis require multiple factors acting synergistically, vascular endothelial growth factor (VEGF) was then co-immobilized with the cell adhesive RGD peptide within our dextran coating through a relevant strategy featuring orientation and specificity. Altogether, both adhesive and proliferative cues could be incorporated into our construct with additive, if not synergetic, effects.