The accumulation of blood leukocytes at sites of inflammation depends upon their localized adhesion to the vascular lining. We have investigated the hypothesis that this adhesive interaction involves inducible endothelial cell-surface structures that can bind leukocytes. Certain infammatory! immune cytokines, namely interleukin 1, tumor necrosis factor, and lymphotoxin, as well as bacterial endotoxin, act on cultured human endothelial cells (HEC) in a time-and proteinsynthesis-dependent fashion to increase leukocyte adhesion. (unpublished observations). In all cases, fusions of splenocytes to the NS-1 myeloma cell line and all subsequent procedures were done as described (15).

In an effort to further characterize conserved and species-specific mechanisms of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated toxicity, comparative temporal and dose-response microarray analyses were performed on hepatic tissue from immature, ovariectomized Sprague Dawley rats and C57BL/6 mice. For temporal studies, rats and mice were gavaged with 10 or 30 microg/kg of TCDD, respectively, and sacrificed after 2, 4, 8, 12, 18, 24, 72, or 168 h while dose-response studies were performed at 24 h. Hepatic gene expression profiles were monitored using custom cDNA microarrays containing 8567 (rat) or 13,361 (mouse) cDNA clones. Affymetrix data from male rats treated with 40 microg/kg TCDD were also included to expand the species comparison. In total, 3087 orthologous genes were represented in the cross-species comparison. Comparative analysis identified 33 orthologous genes that were commonly regulated by TCDD as well as 185 rat-specific and 225 mouse-specific responses. Functional annotation using Gene Ontology identified conserved gene responses associated with xenobiotic/chemical stress and amino acid and lipid metabolism. Rat-specific gene expression responses were associated with cellular growth and lipid metabolism while mouse-specific responses were associated with lipid uptake/metabolism and immune responses. The common and species-specific gene expression responses were also consistent with complementary histopathology, clinical chemistry, hepatic lipid analyses, and reports in the literature. These data expand our understanding of TCDD-mediated gene expression responses and indicate that species-specific toxicity may be mediated by differences in gene expression which may help explain the wide range of species sensitivities and will have important implications in risk assessment strategies.

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Metabolic Syndrome and Associated Diseases: From the Bench to the Clinic, a Society of Toxicology Contemporary Concepts in Toxicology (CCT) workshop was held on March 11, 2017. The meeting was convened to raise awareness of metabolic syndrome and its associated diseases and serve as a melting pot with scientists of multiple disciplines (eg, toxicologists, clinicians, regulators) so as to spur research and understanding of this condition. The criteria for metabolic syndrome include obesity, dyslipidemia (low high-density lipoprotein and/or elevated triglycerides), elevated blood pressure, and alterations in glucose metabolism. It can lead to a greater potential of type 2 diabetes, lipid disorders, cardiovascular disease, hepatic steatosis, and other circulatory disorders. Although there are no approved drugs specifically for this syndrome, many drugs target diseases associated with this syndrome thus potentially increasing the likelihood of drug-drug interactions. There is currently significant research focusing on understanding the key pathways that control metabolism, which would be likely targets of risk factors (eg, exposure to xenobiotics, genetics) and lifestyle factors (eg, microbiome, nutrition, and exercise) that contribute to metabolic syndrome. Understanding these pathways could also lead to the development of pharmaceutical interventions. As individuals with metabolic syndrome have signs similar to that of toxic responses (eg, oxidative stress and inflammation) and organ dysfunction, these alterations should be taken into account in drug development. With the increasing frequency of metabolic syndrome in the general population, the idea of a "normal" individual may need to be redefined. This paper reports on the substance and outcomes of this workshop.

Thrombospondins are a family of extracellular matrix proteins expressed throughout the developing nervous system that promote neurite outgrowth in vitro and help mediate the migration of granule cells across the molecular layer in explants of neonatal cerebellum. The receptors mediating these interactions have not previously been identified. In this study, monoclonal antibodies raised to the integrin alpha 3 beta 1 heterodimer are shown to inhibit neurite outgrowth by rat sympathetic neurons on thrombospondin-1. Alpha 3 beta 1 is found to be expressed on the cell body, neurites, and growth cones of sympathetic neurons in vitro and on sympathetic axons passing through the thrombospondin-rich outer sheath of the superior cervical ganglion in vivo, consistent with its role in mediating axon outgrowth. A receptor-ligand binding assay is used to demonstrate the direct binding of immunopurified alpha 3 beta 1 to thrombospondin-1. These results demonstrate a direct interaction between the integrin alpha 3 beta 1 and thrombospondin-1, which mediates neurite outgrowth in vitro and is likely to mediate the same interactions in vivo.