Vinculin and Rab5 complex is required [correction of requited]for uptake of Staphylococcus aureus and interleukin-6 expression.

Vinculin, a 116-kDa membrane cytoskeletal protein, is an important molecule for cell adhesion; however, little is known about its other cellular functions. Here, we demonstrated that vinculin binds to Rab5 and is required for Staphylococcus aureus (S. aureus) uptake in cells. Viunculin directly bound to Rab5 and enhanced the activation of S. aureus uptake. Over-expression of active vinculin mutants enhanced S. aureus uptake, whereas over-expression of an inactive vinculin mutant decreased S. aureus uptake. Vinculin bound to Rab5 at the N-terminal region (1-258) of vinculin. Vinculin and Rab5 were involved in the S. aureus-induced phosphorylation of MAP kinases (p38, Erk, and JNK) and IL-6 expression. Finally, vinculin and Rab5 knockdown reduced infection of S. aureus, phosphorylation of MAPKs and IL-6 expression in murine lungs. Our results suggest that vinculin binds to Rab5 and that these two molecules cooperatively enhance bacterial infection and the inflammatory response.

POT1b regulates phagocytosis and NO production by modulating activity of the small GTPase Rab5.

The protection of telomeres 1 (POT1) protein is a 75-kDa protein that plays an important role in telomere protection, which is related to telomere elongation. Although POT1 is present in and acts in the nuclei, little is known about the functions of POT1 in the cytosol. We here examined the role of POT1b in phagocytosis in a macrophage-like RAW 264 cell line. We found that POT1 was present in the cytosol, where it was bound to Rab5, which is a protein important for endocytosis. POT1b knockdown in RAW 264 cells increased Rab5 activity and facilitated the phagocytosis of whole cells of Escherichia coli and Staphylococcus aureus. Furthermore, POT1b knockdown enhanced the expression of inducible nitric oxide synthase (iNOS), followed by the promotion of nitric oxide (NO) generation in response to stimulation by bacterial whole cells. These results suggest that POT1b negatively regulates phagocytosis by controlling Rab5 activity and thereby modulates bacteria-induced NO generation. These findings suggest that POT1b participates in innate immune responses.

Acacetin inhibits expression of E-selectin on endothelial cells through regulation of the MAP kinase signaling pathway and activation of NF-κB.

Since E-selectin-mediated adhesion of leukocytes or tumor cells to the vascular endothelium is a key early event in the initiation of inflammatory response and cancer metastasis, E-selectin inhibition is thought to be a good target for therapeutic intervention. Several flavones have been shown to have anti-inflammatory and anticancer properties. In the present study, we investigated the effects of plant flavones on expression of E-selectin in human umbilical vein endothelial cells. Among 11 flavones, acacetin strongly inhibited TNF-α-induced E-selectin expression in HUVECs. Acacetin suppressed the TNF-α-induced phosphorylation of p38 but did not inhibit TNF-α-induced phosphorylations of JNK and ERK. Acacetin also inhibited the activation of NF-κB by stimulation with TNF-α. Furthermore, adhesion of monocytes to TNF-α-treated endothelial cells was inhibited by cotreatment with acacetin. These results suggest that acacetin inhibits the expression of E-selectin by regulation of the p38 MAPK signaling pathway and activation of NF-κB.

E-selectin mediates Porphyromonas gingivalis adherence to human endothelial cells.

Porphyromonas gingivalis, a major periodontal pathogen, may contribute to atherogenesis and other inflammatory cardiovascular diseases. However, little is known about interactions between P. gingivalis and endothelial cells. E-selectin is a membrane protein on endothelial cells that initiates recruitment of leukocytes to inflamed tissue, and it may also play a role in pathogen attachment. In the present study, we examined the role of E-selectin in P. gingivalis adherence to endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with tumor necrosis factor alpha (TNF-α) to induce E-selectin expression. Adherence of P. gingivalis to HUVECs was measured by fluorescence microscopy. TNF-α increased adherence of wild-type P. gingivalis to HUVECs. Antibodies to E-selectin and sialyl Lewis X suppressed P. gingivalis adherence to stimulated HUVECs. P. gingivalis mutants lacking OmpA-like proteins Pgm6 and -7 had reduced adherence to stimulated HUVECs, but fimbria-deficient mutants were not affected. E-selectin-mediated P. gingivalis adherence activated endothelial exocytosis. These results suggest that the interaction between host E-selectin and pathogen Pgm6/7 mediates P. gingivalis adherence to endothelial cells and may trigger vascular inflammation.

Valproic acid increases susceptibility to endotoxin shock through enhanced release of high-mobility group box 1.

High-mobility group box 1 (HMGB1) is a nuclear factor and a secreted protein. During inflammation, HMGB1 is secreted into the extracellular space where it can interact with the receptor for advanced glycation end products and trigger proinflammatory signals. Extracellular HMGB1 plays a critical role in several inflammatory diseases such as sepsis and rheumatoid arthritis. Valproic acid (VPA) is one of the most frequently prescribed antiepileptic drugs. The present study was undertaken to investigate the effect of VPA on secretion of HMGB1 in systemic inflammatory responses induced by lipopolysaccharide. Pretreatment with VPA increased the susceptibility of mice to lipopolysaccharide in endotoxemia. Valproic acid induced HMGB1 release and nuclear factor κB activation in RAW-blue cells. Valproic acid promoted the phosphorylation of ERK1/2 but not that of p38 or JNK. The MEK1/2 inhibitor PD98059 also suppressed HMGB1 release and activation of nuclear factor κB induced by VPA. Valproic acid induced expression of γ-aminobutyric acid receptors in macrophages, and picrotoxin, a γ-aminobutyric acid A receptor antagonist, inhibited the VPA-activated phosphorylation of ERK and VPA-induced HMGB1 release. These results suggest that VPA may exacerbate innate immune responses to endotoxin through enhanced release of HMGB1.

Morroniside cinnamic acid conjugate as an anti-inflammatory agent.

A morroniside cinnamic acid conjugate was prepared and evaluated on E-selectin mediated cell-cell adhesion as an important role in inflammatory processes. 7-O-Cinnamoylmorroniside exhibited excellent anti-inflammatory activity (IC(50)=49.3 microM) by inhibiting the expression of E-selectin; further, it was more active than another cinnamic-acid-conjugated iridoid glycoside (harpagoside; IC(50)=88.2 microM), 7-O-methylmorroniside, and morroniside itself. As a result, 7-O-cinnamoylmorroniside was observed to be a potent inhibitor of TNF-alpha-induced E-selectin expression.