Cultured human endothelial cells (EC) exposed to atherogenic low-density lipoprotein levels have increased reactive oxygen species (ROS) generation. The enzyme responsible for this ROS production elevation is unknown. We have examined for the presence of a functional leukocyte-type NADPH oxidase in EC to elucidate whether this enzyme could be the ROS source. The plasma membrane fraction of disrupted EC showed a reduced-minus-oxidized difference spectra with absorption peaks identical to those observed in the spectra of the leukocyte NADPH oxidase component, cytochrome b558. Western-blot analysis, using anti-gp91 -phox. anti -p22-phox. anti -p47-phox. and anti -p67-phox antibodies, demonstrated the protein expression of NADPH oxidase subunits in EC. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed the mRNA expression of gp91-phox, p22-phox, p47-phox, and p67-phox in EC. Sonicates from unstimulated EC produced no measurable superoxide; whereas, exogenously applied arachidonic acid activated superoxide generation in a manner that was dependent upon the presence of NADPH and both membrane and cytosolic fractions combined. Apocynin, a specific leukocyte NADPH oxidase inhibitor, was shown by Western-blot analysis of membrane and cytoplasmic fractions to inhibit the translocation of p47-phox to the membrane of stimulated EC. These findings support the presence of a functionally active leukocyte-type NADPH oxidase in EC. NADPH oxidase could be the major cellular ROS source in EC perturbation, which has been hypothesized to be a major contributing factor in the pathogenesis of atherosclerosis.

In order to study the major cellular source of reactive oxygen species (ROS) in perturbed human endothelial cells (EC), the effect of thrombin, a phospholipase A2 activator, on cultured EC ROS generation has been investigated. EC were incubated with 0.1-1 unit/ml thrombin and cellular superoxide anion (O(-)2) release and hydrogen peroxide (H2O2) production measured. Thrombin exposure caused an elevation in EC O(-)2 release and H2O2 production. The effects of protein kinase C, arachidonic acid metabolism, NADPH oxidase, and phospholipase A2 inhibitors on thrombin-induced EC H2O2 production were examined. EC were exposed to 0.5 unit/ml thrombin and cellular H2O2 production measured in the presence and absence of the protein kinase C inhibitor, H-7; arachidonic acid metabolism inhibitors, indomethacin, nordihydroguaiaretic acid, and SKF525A; NADPH oxidase inhibitor, apocynin; and phospholipase A2 inhibitor, 4-bromophenacyl bromide. All inhibitors, with the exception of H-7 and indomethacin, suppressed thrombin-induced EC H2O2 production. The pattern of effects of these metabolic antagonists on thrombin-induced EC ROS production is similar to that previously reported on ROS production in EC exposed to high low-density lipoprotein levels, and in stimulated leukocytes. These findings further implicate NADPH oxidase as a major ROS source in EC.

beta-glucanases are prominent proteins in pea endocarp tissue responding to fungal infection. We have cloned and sequenced a partial pea cDNA clone, pPIG312, corresponding to a beta-1,3-glucanase in pea pods challenged with the incompatible pathogen Fusarium solani f. sp. phaseoli. The insert from the partial pea cDNA was used to probe a genomic library derived from pea leaves of the same cultivar. One of the genomic clones, pPIG4-3, contained the complete coding sequence for a mature beta-1,3-glucanase protein. The predicted amino acid sequence of the pea beta-1,3-glucanase has 78% identity to bean beta-1,3-glucanase, 62% and 60% to two tobacco beta-1,3-glucanases, 57% to soybean beta-1,3-glucanase, 51% to barley beta-1,3-glucanase, and 48% to barley beta-1,3-1,4-glucanase. Genomic Southern analysis indicates that the pea genome contains only one beta-1,3-glucanase gene corresponding to the probe used in this study. Accumulation of beta-1,3-glucanase mRNA homologous with the pPIG312 probe was detected in pea pods within 4 to 8 h after challenge with F. solani f. sp. phaseoli, f. sp. pisi, a compatible strain, or the elicitor, chitosan. In the incompatible reaction, mRNA accumulation remained high for 48h, whereas it rapidly decreased in the compatible reaction. After fungal inoculation of whole pea seedlings, the enhanced mRNA accumulation occurred mainly in the basal region (lower stem and root). This beta-1,3-glucanase mRNA was constitutively expressed in the roots of pea seedlings.(ABSTRACT TRUNCATED AT 250 WORDS)

The fungicidal class I endochitinases (E.C.3.3.1.14, chitinase) are associated with the biochemical defense of plants against potential pathogens. We isolated and sequenced a genomic clone, DAH53, corresponding to a class I basic endochitinase gene in pea, Chi1. The predicted amino acid sequence of this chitinase contains a hydrophobic C-terminal domain similar to the vacuole targeting sequences of class I chitinases isolated from other plants. The pea genome contains one gene corresponding to the chitinase DAH53 probe. Chitinase RNA accumulation was observed in pea pods within 2 to 4 h after inoculation with the incompatible fungal strain Fusarium solani f. sp. phaseoli, the compatible strain F. solani f.sp. pisi, or the elicitor chitosan. The RNA accumulation was high in the basal region (lower stem and root) of both fungus challenged and wounded pea seedlings. The sustained high levels of chitinase mRNA expression may contribute to later stages of pea's non-host resistance.

The effects of known leukocyte NADPH oxidase inhibitors on general cellular oxidant production in cultured human endothelial cells (EC) has been investigated. EC were stimulated with 10 nM phorbol 12-myristate 13-acetate and cellular oxidant production measured in the presence and absence of inhibitors that act on various substituents of the oxidase complex and its activation pathways. The effects of the cytosolic oxidase subunit translocation inhibitors, catechols (3,4-dihydroxybenzaldehyde, caffeic acid, and protocatechuic acid), ortho-methoxy-substituted catechols (apocynin, vanillin, and 4-nitroguaiacol), and quinone, 1,4-naphthoquinone; flavoprotein inhibitors, diphenylene iodonium and quinacrine; haem ligands, imidazole and pyridine; directly acting thiol reagents, disulfiram and penicillamine; NADPH analogue, Cibacron Blue; redox active inhibitors, quercetin and esculetin; intracellular calcium antagonist, TMB-8; and calmodulin antagonists, W-7 and trifluoperazine, were determined. All compounds reduced oxidant production in stimulated EC. These findings add to previous observations suggesting the presence of a functionally active NADPH oxidase in EC. Identifying the major cellular reactive oxygen species source in perturbed EC will provide new insights into our understanding of endothelial dysfunction, which has been hypothesized to be a major contributing factor in the pathogenesis of atherosclerosis.