Protective effects of an anti-4-HNE monoclonal antibody against liver injury and lethality of endotoxemia in mice.

4-hydroxy-2-nonenal (4-HNE) is a lipid peroxidation product that is known to be elevated during oxidative stress. During systemic inflammation and endotoxemia, plasma levels of 4-HNE are elevated in response to lipopolysaccharide (LPS) stimulation. 4-HNE is a highly reactive molecule due to its generation of both Schiff bases and Michael adducts with proteins, which may result in modulation of inflammatory signaling pathways. In this study, we report the production of a 4-HNE adduct-specific monoclonal antibody (mAb) and the effectiveness of the intravenous injection of this mAb (1 mg/kg) in ameliorating LPS (10 mg/kg, i.v.)-induced endotoxemia and liver injury in mice. Endotoxic lethality in control mAb-treated group was suppressed by the administration of anti-4-HNE mAb (75 vs. 27%). After LPS injection, we observed a significant increase in the plasma levels of AST, ALT, IL-6, TNF-α and MCP-1, and elevated expressions of IL-6, IL-10 and TNF-α in the liver. All these elevations were inhibited by anti-4-HNE mAb treatment. As to the underlining mechanism, anti-4-HNE mAb inhibited the elevation of plasma high mobility group box-1 (HMGB1) levels, the translocation and release of HMGB1 in the liver and the formation of 4-HNE adducts themselves, suggesting a functional role of extracellular 4-HNE adducts in hypercytokinemia and liver injury associated with HMGB1 mobilization. In summary, this study reveals a novel therapeutic application of anti-4-HNE mAb for endotoxemia.

Histidine-rich glycoprotein ameliorates endothelial barrier dysfunction through regulation of NF-κB and MAPK signal pathway.

BACKGROUND AND PURPOSE: Microvascular barrier breakdown is a hallmark of sepsis that is associated with sepsis-induced multiorgan failure. Histidine-rich glycoprotein (HRG) is a 75-kDa plasma protein that was demonstrated to improve the survival of septic mice through regulation of cell shape, spontaneous ROS production in neutrophils, and adhesion of neutrophils to vascular endothelial cells. We investigated HRG's role in the LPS/TNF-α-induced barrier dysfunction of endothelial cells in vitro and in vivo and the possible mechanism, to clarify the definitive roles of HRG in sepsis. EXPERIMENTAL APPROACH: EA.hy 926 endothelial cells were pretreated with HRG or human serum albumin before stimulation with LPS/TNF-α. A variety of biochemical assays were applied to explore the underlying molecular mechanisms on how HRG protected the barrier function of vascular endothelium. KEY RESULTS: Immunostaining results showed that HRG maintains the endothelial monolayer integrity by inhibiting cytoskeleton reorganization, losses of VE-cadherin and ß-catenin, focal adhesion kinase degradation, and cell detachment induced by LPS/TNF-α. HRG also inhibited the cytokine secretion from endothelial cells induced by LPS/TNF-α, which was associated with reduced NF-κB activation. Moreover, HRG effectively prevented the LPS/TNF-α-induced increase in capillary permeability in vitro and in vivo. Finally, Western blot results demonstrated that HRG prevented the phosphorylation of MAPK family and RhoA activation, which are involved mainly in the regulation of cytoskeleton reorganization and barrier permeability. CONCLUSIONS AND IMPLICATIONS: Taken together, our results demonstrate that HRG has protective effects on vascular barrier function in vitro and in vivo, which may be due to the inhibition of MAPK family and Rho activation.