Endothelial cells play a pivotal role in the inflammatory process by coordinating the recruitment of inflammatory cells to sites of tissue injury. Lipopolysaccharide (LPS) activates many of the proinflammatory and procoagulant responses of endothelial cells, and endothelial injury is thought to play a crucial role in the pathogenesis of septic shock due to Gram-negative bacteria. The receptor used by LPS to signal endothelial responses has not been identified. It is also not known how LPS induces endothelial injury/death. In this study, we demonstrate that LPS mediates endothelial apoptosis by a FADD-dependent pathway. FADD is a death domain-containing protein that binds to certain members of the tumor necrosis factor receptor family, namely TNFR1, Fas, and DR3. However, none of these receptors appear to be involved in LPS-mediated death, suggesting that LPS may utilize a novel death domain-containing protein to transduce a death signal. Lipopolysaccharide (LPS)1 is a critical glycolipid component of the outer wall of Gram-negative bacteria, and many of the cellular signals activated by Gram-negative bacteria are attributed to LPS (1). Several responses are evoked in endothelial cells by LPS, including up-regulation of adhesion molecules and expression of tissue factor. The endothelial cell is a prime target of the LPS molecule, and vascular complications of septic shock due to Gram-negative bacteria are related to endothelial injury (2, 3). Whereas LPS directly induces apoptosis of sheep and bovine endothelial cells, it is only toxic to human endothelial cells when the expression of new genes is blocked (4,5).Several intracellular molecules have been implicated in transducing LPS signals. Activation of NF-B, the Jak-STAT pathway, mitogen-activated protein kinases, and phosphatidylinositol 3-kinase have all been demonstrated to play a role in the intracellular signaling of LPS-mediated events (6 -8). LPS complexed with a serum protein, LPS-binding protein, signals through membrane-bound CD14 on monocytes and myeloid cells. In contrast, endothelial and epithelial cells, which are CD14-negative but still respond to LPS, require soluble CD14 present in serum in order to transduce LPS signals (6, 9, 10). It is still unclear how the LPS-soluble CD14 complex actually transmits a signal across the cell membrane. Evidence has been presented to suggest the presence of a signaling transmembrane receptor recognizing the LPS⅐CD14 complex (11). However, others (12, 13) have postulated that LPS is internalized by a vesicular transport mechanism and mediates signals, at least partly, by structurally mimicking ceramide. Transmembrane signaling by LPS has also been shown to be mediated by CD11/CD18 integrins independently of CD14 (14,15).How LPS activates the death pathway in endothelial or other cell types has not yet been investigated. On the other hand signaling of apoptosis by the TNF receptor 1 (TNFR1) and Fas has been extensively studied (16 -19). Engagement of TNFR1 or Fas results in cell death by the recruitment of a com...

Histone deacetylase inhibitors (HDACi) have been hailed as a powerful new class of anticancer drugs. The HDACi, trichostatin A (TSA), is thought to interfere with epigenetic control of cell cycle progression in G 1 and G 2 -M phase, resulting in growth arrest, differentiation, or apoptosis. Here, we describe a novel mechanism of action of HDACis in promoting immune responses against tumors. We report that treatment of carcinoma cells with TSA increases the expression of many components of the antigen processing machinery, including TAP-1, TAP-2, LMP-2, and Tapasin. Consistent with this result, we found that treatment of metastatic carcinoma cells with TSA also results in an increase in MHC class I expression on the cell surface that functionally translates into an enhanced susceptibility to killing by antigen-specific CTLs. Finally, we observed that TSA treatment suppresses tumor growth and increases tap-1 promoter activity in TAP-deficient tumor cells in vivo. Intriguingly, this in vivo anti-tumoral effect of TSA is entirely mediated by an increase in immunogenicity of the tumor cells, as it does not occur in immunodeficient mice. These novel insights into the molecular mechanisms controlling tumor immune escape may help revise immunotherapeutic modalities for eradicating cancers. [Cancer Res 2008;68(23):9601-7]

The transport of calcium ions (Ca(2+)) to the cytosol is essential for immunoreceptor signaling, regulating lymphocyte differentiation, activation, and effector function. Increases in cytosolic-free Ca(2+) concentrations are thought to be mediated through two interconnected and complementary mechanisms: the release of endoplasmic reticulum Ca(2+) "stores" and "store-operated" Ca(2+) entry via plasma membrane channels. However, the identity of molecular components conducting Ca(2+) currents within developing and mature T cells is unclear. Here, we have demonstrated that the L-type "voltage-dependent" Ca(2+) channel Ca(V)1.4 plays a cell-intrinsic role in the function, development, and survival of naive T cells. Plasma membrane Ca(V)1.4 was found to be essential for modulation of intracellular Ca(2+) stores and T cell receptor (TCR)-induced rises in cytosolic-free Ca(2+), impacting activation of Ras-extracellular signal-regulated kinase (ERK) and nuclear factor of activated T cells (NFAT) pathways. Collectively, these studies revealed that Ca(V)1.4 functions in controlling naive T cell homeostasis and antigen-driven T cell immune responses.