Benzimidazolone p38 inhibitors

The synthesis and in vitro p38 alpha activity of a novel series of benzimidazolone inhibitors is described. The p38 alpha SAR is consistent with a mode of binding wherein the benzimidazolone carbonyl serves as the H-bond acceptor to Met109 of p38 alpha in a manner analogous to the pyridine nitrogen of prototypical pyridylimidazole p38 inhibitors. Potent p38 alpha activity comparable to that of several previously reported p38 inhibitors is observed for this novel chemotype.     

Large-scale exploration of growth inhibition caused by overexpression of genomic fragments in Saccharomyces cerevisiae

We have screened the genome of Saccharomyces cerevisiae for fragments that confer a growth-retardation phenotype when overexpressed in a multicopy plasmid with a tetracycline-regulatable (Tet-off) promoter. We selected 714 such fragments with a mean size of 700 base-pairs out of around 84,000 clones tested. These include 493 in-frame open reading frame fragments corresponding to 454 distinct genes (of which 91 are of unknown function), and 162 out-of-frame, antisense and intergenic genomic fragments, representing the largest collection of toxic inserts published so far in yeast.     

HMGB1 is an endogenous immune adjuvant released by necrotic cells

Immune responses against pathogens require that microbial components promote the activation of antigen-presenting cells (APCs). Autoimmune diseases and graft rejections occur in the absence of pathogens; in these conditions, endogenous molecules, the so-called 'innate adjuvants', activate APCs. Necrotic cells contain and release innate adjuvants; necrotic cells also release high-mobility group B1 protein (HMGB1), an abundant and conserved constituent of vertebrate nuclei. Here, we show that necrotic HMGB1(-/-) cells have a reduced ability to activate APCs, and HMGB1 blockade reduces the activation induced by necrotic wild-type cell supernatants. In vivo, HMGB1 enhances the primary antibody responses to soluble antigens and transforms poorly immunogenic apoptotic lymphoma cells into efficient vaccines.     

Increased glutathione biosynthesis plays a role in nickel tolerance in thlaspi nickel hyperaccumulators

Worldwide more than 400 plant species are now known that hyperaccumulate various trace metals (Cd, Co, Cu, Mn, Ni, and Zn), metalloids (As) and nonmetals (Se) in their shoots. Of these, almost one-quarter are Brassicaceae family members, including numerous Thlaspi species that hyperaccumulate Ni up to 3% of there shoot dry weight. We observed that concentrations of glutathione, Cys, and O-acetyl-l-serine (OAS), in shoot tissue, are strongly correlated with the ability to hyperaccumulate Ni in various Thlaspi hyperaccumulators collected from serpentine soils, including Thlaspi goesingense, T. oxyceras, and T. rosulare, and nonaccumulator relatives, including T. perfoliatum, T. arvense, and Arabidopsis thaliana. Further analysis of the Austrian Ni hyperaccumulator T. goesingense revealed that the high concentrations of OAS, Cys, and GSH observed in this hyperaccumulator coincide with constitutively high activity of both serine acetyltransferase (SAT) and glutathione reductase. SAT catalyzes the acetylation of l-Ser to produce OAS, which acts as both a key positive regulator of sulfur assimilation and forms the carbon skeleton for Cys biosynthesis. These changes in Cys and GSH metabolism also coincide with the ability of T. goesingense to both hyperaccumulate Ni and resist its damaging oxidative effects. Overproduction of T. goesingense SAT in the nonaccumulator Brassicaceae family member Arabidopsis was found to cause accumulation of OAS, Cys, and glutathione, mimicking the biochemical changes observed in the Ni hyperaccumulators. In these transgenic Arabidopsis, glutathione concentrations strongly correlate with increased resistance to both the growth inhibitory and oxidative stress induced effects of Ni. Taken together, such evidence supports our conclusion that elevated GSH concentrations, driven by constitutively elevated SAT activity, are involved in conferring tolerance to Ni-induced oxidative stress in Thlaspi Ni hyperaccumulators.     

Yeast lacking the SRO7/SOP1-encoded tumor suppressor homologue show increased susceptibility to apoptosis-like cell death on exposure to NaCl stress

Yeast cells deleted for the SRO7/SOP1 encoded tumor suppressor homologue show increased sensitivity to NaCl stress. On exposure to growth-inhibiting NaCl concentrations, sro7Delta mutants display a rapid loss in viability that is associated with markers of apoptosis: accumulation of reactive oxygen species, DNA breakage, and nuclear fragmentation. Additional deletion of the yeast metacaspase gene YCA1 prevents the primary fast drop in viability and diminishes nuclear fragmentation and DNA breakage. We also observed that NaCl induced loss in viability of wild-type cells is Yca1p dependent. However, a yeast strain deleted for both SRO7 and its homologue SRO77 exhibits NaCl-induced cell death that is independent on YCA1. Likewise, sro77Delta single mutants do not survive better after additional deletion of the YCA1 gene, and both sro77Delta and sro77Deltayca1Delta mutants display apoptotic characteristics when exposed to growth-inhibiting salinity, suggesting that yeast possesses Yca1p-independent pathway(s) for apoptosis-like cell death. The activity of Yca1p increases with increasing NaCl stress and sro7Delta mutants achieve levels that are higher than in wild-type cells. However, mutants lacking SRO77 do not enhance caspase activity when subject to NaCl stress, suggesting that Sro7p and Sro77p exert opposing effects on the cellular activity of Yca1p.     

PV1 is a key structural component for the formation of the stomatal and fenestral diaphragms

PV1 is an endothelial-specific integral membrane glycoprotein associated with the stomatal diaphragms of caveolae, transendothelial channels, and vesiculo-vacuolar organelles and the diaphragms of endothelial fenestrae. Multiple PV1 homodimers are found within each stomatal and fenestral diaphragm. We investigated the function of PV1 within these diaphragms and their regulation and found that treatment of endothelial cells in culture with phorbol myristate acetate (PMA) led to upregulation of PV1. This correlated with de novo formation of stomatal diaphragms of caveolae and transendothelial channels as well as fenestrae upon PMA treatment. The newly formed diaphragms could be labeled with anti-PV1 antibodies. The upregulation of PV1 and formation of stomatal and fenestral diaphragms by PMA was endothelium specific and was the highest in microvascular endothelial cells compared with their large vessel counterparts. By using a siRNA approach, PV1 mRNA silencing prevented the de novo formation of the diaphragms of caveolae as well as fenestrae and transendothelial channels. Overexpression of PV1 in endothelial cells as well as in cell types that do not harbor caveolar diaphragms in situ induced de novo formation of caveolar stomatal diaphragms. Lastly, PV1 upregulation by PMA required the activation of Erk1/2 MAP kinase pathway and was protein kinase C independent. Taken together, these data show that PV1 is a key structural component, necessary for the biogenesis of the stomatal and fenestral diaphragms.     

Oxysterol-induced toxicity in R28 and ARPE-19 cells

Studies have shown an intimate relationship between cholesterol and retinal diseases; we examined the effects of cholesterol oxides on cultured cells. Using the rat retinal precursor cell line R28 and the human RPE cell line ARPE-19, we investigated the potential cytotoxicity of cholesterol oxides. Cultured R28 and ARPE-19 cells were treated with either 25-hydroxycholesterol and 7-ketocholesterol (0–50 µg/ml). Cell viability was determined by the WST-1 colorimetric assay. Production of reactive oxygen intermediate (ROI) was assessed by a fluorescent probe–based assay (2,7-dichlorodihydrofluorescein diacetate [H₂DCFDA]). To detect the presence of apoptosis, DNA fragmentation gel analysis and Hoescht nuclear staining were performed. Both cholesterol oxides tested were toxic in a time- and dose-dependent fashion to the two cell lines used in this study. Treatment of R28 cells with either 25-hydroxycholesterol or 7-ketocholesterol at a concentration of 25 µg/ml resulted in greater than 50% loss of cell viability after 24 h. ARPE-19 cells were slightly less affected, with a loss of cell viability of approximately 20% and 40% after 24 h-exposure of 25-hydroxycholesterol and 7-ketocholesterol, respectively. DNA fragmentation and chromatin condensation demonstrated apoptotic events occurring in 7-ketocholesterol–treated cells. The fluorescent assay for ROI production showed that after an hour of exposure to 7-ketocholesterol, R28 cells responded with increased levels of ROIs, whereas no immediate production of ROIs were detected with treated ARPE-19 cells. These in vitro findings provide evidence that cholesterol oxides can directly damage cultured retinal and RPE cells. The oxysterol-induced oxidative stress in these cells may be a factor in the pathology of retinal degenerative diseases.     

VCAM-1-mediated Rac signaling controls endothelial cell-cell contacts and leukocyte transmigration

Leukocyte adhesion is mediated totally and transendothelial migration partially by heterotypic interactions between the ₁- and ₂-integrins on the leukocytes and their ligands, Ig-like cell adhesion molecules (Ig-CAM), VCAM-1, and ICAM-1, on the endothelium. Both integrins and Ig-CAMs are known to have signaling capacities. In this study we analyzed the role of VCAM-1-mediated signaling in the control of endothelial cell-cell adhesion and leukocyte transendothelial migration. Antibody-mediated cross-linking of VCAM-1 on IL-1-activated primary human umbilical vein endothelial cells (pHUVEC) induced actin stress fiber formation, contractility, and intercellular gaps. The effects induced by VCAM-1 cross-linking were inhibited by C3 toxin, indicating that the small GTPase p21Rho is involved. In addition, the effects of VCAM-1 were accompanied by activation of Rac, which we recently showed induce intercellular gaps in pHUVEC in a Rho-dependent fashion. With the use of a cell-permeable peptide inhibitor, it was shown that Rac signaling is required for VCAM-1-mediated loss of cell-cell adhesion. Furthermore, VCAM-1-mediated signaling toward cell-cell junctions was accompanied by, and dependent on, Rac-mediated production of reactive oxygen species and activation of p38 MAPK. In addition, it was found that inhibition of Rac-mediated signaling blocks transendothelial migration of monocytic U937 cells. Together, these data indicate that VCAM-1-induced, Rac-dependent signaling plays a key role in the modulation of vascular-endothelial cadherin-mediated endothelial cell-cell adhesion and leukocyte extravasation. human umbilical vein endothelial cells; vascular-endothelial cadherin; F-actin; reactive oxygen species; p38 mitogen-activated protein kinase; vascular cell adhesion molecule