Reactive oxygen species (ROS) are generated at sites of inflammation and injury, and at low levels, ROS can function as signaling molecules participating as signaling intermediates in regulation of fundamental cell activities such as cell growth and cell adaptation responses, whereas at higher concentrations, ROS can cause cellular injury and death. The vascular endothelium, which regulates the passage of macromolecules and circulating cells from blood to tissues, is a major target of oxidant stress, playing a critical role in the pathophysiology of several vascular diseases and disorders. Specifically, oxidant stress increases vascular endothelial permeability and promotes leukocyte adhesion, which are coupled with alterations in endothelial signal transduction and redox-regulated transcription factors such as activator protein-1 and nuclear factor-kappaB. This review discusses recent findings on the cellular and molecular mechanisms by which ROS signal events leading to impairment of endothelial barrier function and promotion of leukocyte adhesion. Particular emphasis is placed on the regulation of cell-cell and cell-surface adhesion molecules, the actin cytoskeleton, key protein kinases, and signal transduction events.

Intercellular adhesion molecule-1 (ICAM-1, CD54) is an inducible cell adhesion glycoprotein of the immunoglobulin supergene family expressed on the surface of a wide variety of cell types. ICAM-1 interactions with the beta2 integrins CD11a/CD18 (LFA-1) and CD11b/CD18 (MAC-1) on the surface of leukocytes are important for their transendothelial migration to sites of inflammation and their function as costimulatory molecules for T cell activation. ICAM-1 is constitutively expressed on the cell surface and is up-regulated in response to a variety of inflammatory mediators, including proinflammatory cytokines, hormones, cellular stresses, and virus infection. These stimuli increase ICAM-1 expression primarily through activation of ICAM-1 gene transcription. During the past decade much has been learned about the cell type- and stimulus-specific transcription of ICAM-1. The architecture of the ICAM-1 promoter is complex, containing a large number of binding sites for inducible transcription factors, the most important of which is nuclear factor-kappa B (NF-kappaB). NF-kappaB acts in concert with other transcription factors and co-activators via specific protein-protein interactions, which facilitate the assembly of distinct stereospecific transcription complexes on the ICAM-1 promoter. These transcription complexes presumably mediate the induction of ICAM-1 expression in different cell types and in response to different stimuli. In this review, we summarize our current understanding of ICAM-1 gene regulation with a particular emphasis on the transcription factors and signal transduction pathways critical for the cell type- and stimulus-specific activation of ICAM-1 gene transcription.

The hepatocyte nuclear factor 3␣ (HNF-3␣) and 3␤ proteins have homology in the winged helix/fork head DNA binding domain and regulate cell-specific transcription in hepatocytes and in respiratory and intestinal epithelia. In this study, we describe two novel isoforms of the winged helix transcription factor family, HNF-3/fork head homolog 11A (HFH-11A) and HFH-11B, isolated from the human colon carcinoma HT-29 cell line. We show that these isoforms arise via differential splicing and are expressed in a number of epithelial cell lines derived from tumors (HT-29, Caco-2, HepG2, HeLa, A549, and H441). We demonstrate that differentiation of Caco-2 cells toward the enterocyte lineage results in decreased HFH-11 expression and reciprocal increases in HNF-3␣ and HNF-3␤ mRNA levels. In situ hybridization of 16 day postcoitus mouse embryos demonstrates that HFH-11 expression is found in the mesenchymal and epithelial cells of the liver, lung, intestine, renal cortex, and urinary tract. Although HFH-11 exhibits a wide cellular expression pattern in the embryo, its adult expression pattern is restricted to epithelial cells of Lieberkühn's crypts of the intestine, the spermatocytes and spermatids of the testis, and the thymus and colon. HFH-11 expression is absent in adult hepatocytes, but its expression is reactivated in proliferating hepatocytes at 4, 24, and 48 h after partial hepatectomy. Consistent with these findings, we demonstrate that HFH-11 mRNA levels are stimulated by intratracheal administration of keratinocyte growth factor in adult lung and its expression in an adult endothelial cell line is reactivated in response to oxidative stress. These experiments show that the HFH-11 transcription factor is expressed in embryonic mesenchymal and epithelial cells and its expression is reactivated in these adult cell types by proliferative signals or oxidative stress.Cell-specific transcription relies on the combinatorial recognition of multiple cis-acting elements by families of cell-restricted transcription factors (80). One of these regulatory families is represented by the hepatocyte nuclear factor 3␣ (HNF-3␣), HNF-3␤, and HNF-3␥ proteins (43), which have homology in the winged helix DNA binding domain (12) and function in combination with other liver-enriched transcription factors to mediate hepatocyte-enriched transcription (17). The HNF-3␣ and -3␤ proteins also activate the transcription of genes important for respiratory epithelial cell function (7,14,35,40,60,82). The HNF-3 proteins thus appear to play an important transcriptional regulatory role in epithelial cell typespecific gene expression in adult tissues derived from gut endoderm.In the adult intestine, multipotent proliferative stem cells in Lieberkühn's crypts in the mouse intestine give rise to four terminally differentiated cell types: digestive and absorptive columnar enterocytes (representing the most abundant cell type), mucus-producing goblet cells, enteroendocrine cells, and Paneth cells (53). As the postmitotic enterocytes, goblet cells, and ente...

Interleukin-8 (IL-8), a member of the CXC chemokine family, is an important activator and chemoattractant for neutrophils and has been implicated in a variety of inflammatory diseases. IL-8 is secreted in a stimulus-specific manner by a wide variety of cell types and is regulated primarily at the level of gene transcription. Functional studies indicate that IL-8 transcriptional responses to proinflammatory mediators are rapid and require only 100 nucleotides of 5'-flanking DNA upstream of the TATA box. Within the IL-8 promoter sequence are DNA binding sites for the inducible transcription factors AP-1, NF-IL-6, and NF-kappaB. Transcription factors in these families bind the IL-8 promoter as dimers, and several distinct subunit combinations have been identified as important for IL-8 transcription. In addition, these factors can act in concert to synergistically activate the IL-8 promoter. AP-1 and NF-IL-6 physically interact with NF-kappaB, and functional cooperativity among the factors appears to be critical for optimal IL-8 promoter activity in different cell types. IL-8 transcription appears to be activated by a promoter recruitment mechanism where inducible transcription factor binding to the IL-8 promoter is required for binding of constitutively active TATA box-binding proteins and formation of a stable preinitiation complex. This review discusses the regulatory role these higher-order synergistic interactions play in IL-8 transcription and in generation of the stimulus-specific and cell type-specific patterns of IL-8 expression.

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We investigated the mechanisms by which H2O2 increases intercellular adhesion molecule 1 (ICAM-1; CD54) expression in endothelial cells. The H2O2-induced increase in ICAM-1 mRNA was inhibited by actinomycin D, by the antioxidant N-acetylcysteine, and by 3-amino-benzamide (which blocks oxidant-induced AP-1 activity), but not by pyrrolidine dithiocarbamate (which blocks oxidant-induced NF-kappa B activity). Nuclear run-on and transient transfections of ICAM-1 promoter constructs indicated that H2O2 stimulated ICAM-1 gene transcription by activation of a distinct region of the ICAM-1 promoter. The H2O2-responsive element was localized to sequences between -981 and -769 (relative to start codon). Located within this region are two 16-base pair repeats, each containing binding sites for the transcription factors AP-1 and Ets. A similar composite AP-1/Ets element isolated from the macrophage scavenger receptor gene conferred H2O2 responsiveness to a minimal promoter. Mutation of the 16-base pair repeats within the ICAM-1 promoter prevented H2O2-induced DNA binding activity, and their deletion abrogated the H2O2-induced transcriptional activity. In contrast, TNF alpha induced ICAM-1 transcription via activation of promoter sequences between -393 and -176, a region with C/EBP and NF-kappa B binding sites. The results indicate that H2O2 activates ICAM-1 transcription through AP-1/Ets elements within the ICAM-1 promoter, which are distinct from NF-kappa B-mediated ICAM-1 expression induced by TNF alpha.