Direct contacts between dendritic cells (DCs) and T cells or natural killer T (NKT) cells play important roles in primary and secondary immune responses. SR-PSOX/CXC chemokine ligand 16 (CXCL16), which is selectively expressed on DCs and macrophages, is a scavenger receptor for oxidized low-density lipoprotein and also the chemokine ligand for a G protein-coupled receptor CXC chemokine receptor 6 (CXCR6), expressed on activated T cells and NKT cells. SR-PSOX/CXCL16 is the second transmembrane-type chemokine with a chemokine domain fused to a mucin-like stalk, a structure very similar to that of fractalkine (FNK). Here, we demonstrate that SR-PSOX/CXCL16 functions as a cell adhesion molecule for cells expressing CXCR6 in the same manner that FNK functions as a cell adhesion molecule for cells expressing CX(3)C chemokine receptor 1 (CX(3)CR1) without requiring CX(3)CR1-mediated signal transduction or integrin activation. The chemokine domain of SR-PSOX/CXCL16 mediated the adhesion of CXCR6-expressing cells, which was not impaired by treatment with pertussis toxin, a Galphai protein blocker, which inhibited chemotaxis of CXCR6-expressing cells induced by SR-PSOX/CXCL16. Furthermore, the adhesion activity was up-regulated by treatment of SR-PSOX/CXCL16-expressing cells with a metalloprotease inhibitor, which increased surface expression levels of SR-PSOX/CXCL16. Thus, SR-PSOX/CXCL16 is a unique molecule that not only attracts T cells and NKT cells toward DCs but also supports their firm adhesion to DCs.

SR-PSOX and CXC chemokine ligand (CXCL)16, which were originally identified as a scavenger receptor and a transmembrane-type chemokine, respectively, are indicated to be identical. In this study, we demonstrate that membrane-bound SR-PSOX/CXCL16 mediates adhesion and phagocytosis of both Gram-negative and Gram-positive bacteria. Importantly, our prepared anti-SR-PSOX mAb, which suppressed chemotactic activity of SR-PSOX, significantly inhibited bacterial phagocytosis by human APCs including dendritic cells. Various scavenger receptor ligands inhibited the bacterial phagocytosis of SR-PSOX. In addition, the recognition specificity for bacteria was determined by only the chemokine domain of SR-PSOX/CXCL16. Thus, SR-PSOX/CXCL16 may play an important role in facilitating uptake of various pathogens and chemotaxis of T and NKT cells by APCs through its chemokine domain.

Insulin receptor substrate (IRS)-2؊/؊ mice develop diabetes because of insulin resistance in the liver and failure to undergo ␤-cell hyperplasia. Here we show by DNA chip microarray analysis that expression of the sterol regulatory element-binding protein (SREBP)-1 gene, a downstream target of insulin, was paradoxically increased in 16-week-old IRS-2 ؊/؊ mouse liver, where insulin-mediated intracellular signaling events were substantially attenuated. The expression of SREBP-1 downstream genes, such as the spot 14, ATP citratelyase, and fatty acid synthase genes, was also increased. Increased liver triglyceride content in IRS-2 ؊/؊ mice assures the physiological importance of SREBP-1 gene induction. IRS-2 ؊/؊ mice showed leptin resistance; low dose leptin administration, enough to reduce food intake and body weight in wild-type mice, failed to do so in IRS-2 ؊/؊ mice. Interestingly, high dose leptin administration reduced SREBP-1 expression in IRS-2 ؊/؊ mouse liver. Thus, IRS-2 gene disruption results in leptin resistance, causing an SREBP-1 gene induction, obesity, fatty liver, and diabetes.The pathogenesis of type 2 diabetes involves complex interactions among multiple physiological defects. Transgenic and knockout technology to create animal models of type 2 diabetes have had a major impact on assessment of the function of newly identified molecules implicated in the regulation of glucose homeostasis in vivo (1). The insulin receptor substrate (IRS) 1 proteins play a key role in signal transduction from the insulin receptor (reviewed in Refs. 2-4). These molecules are major intracellular phosphorylation targets of activated insulin receptor tyrosine kinase. The mammalian IRS protein family contains at least four members, ubiquitous IRS-1 (5) and IRS-2 (6), adipose tissue-predominant IRS-3 (7), and IRS-4, which are expressed in thymus, brain, and kidney (8). The physiological roles of each protein have been evaluated by gene targeting strategies. IRS-1 Ϫ/Ϫ mice are growth-retarded and insulin-resistant (9, 10) but do not develop diabetes, because an alternate substrate IRS-2 (10) or pp190 (11) compensates for the lack of IRS-1 in liver (11) and, at least in part, in skeletal muscle (12). In addition, hyperinsulinemia associated with ␤-cell hyperplasia effectively countervailed the insulin-resistant states (13). IRS-2 Ϫ/Ϫ mice, however, developed diabetes because of inadequate ␤-cell proliferation combined with liver-insulin resistance (14 -16). Mice lacking IRS-3 or IRS-4 had milder phenotypes (17, 18).Liver is a major target organ for insulin action, contributing to energy storage in the fed state by regulating catabolic and anabolic pathways. Liver-specific insulin receptor knockout mice exhibit dramatic insulin resistance (19). Insulin decreases gluconeogenic enzyme mRNAs (20) and increases lipogenic enzyme mRNAs. A transcription factor of sterol regulatory element-binding protein 1c (SREBP-1c) (21-23) or adipocyte differentiation and determination factor (24) plays a central role in insulin-mediated lipogen...

encoding AGIF that inhibits the process of adipogenesis as described [13], and exposed at -70% to an X-ray film with an intensifying screen.

A series of imidazopyridine thiazolidine-2,4-diones were designed and synthesized from their corresponding pyridines. These compounds represent conformationally restricted analogues of the novel hypoglycemic compound rosiglitazone (5). The series was evaluated for its effect on insulin-induced 3T3-L1 adipocyte differentiation in vitro and its hypoglycemic activity in the genetically diabetic KK mouse in vivo. The structure-activity relationships are discussed. On the basis of the in vivo potency, 5-[4-(5-methoxy-3-methyl-3H-imidazo[4, 5-b]pyridin-2-ylmethoxy)benzyl]thiazolidine-2,4-dione (19a) was selected as the candidate for further studies in a clinical setting.

Defects in Fas-mediated apoptosis are implicated in autoimmune diseases including rheumatoid arthritis (RA). Although induction of Fas-mediated apoptosis could have therapeutic effects on these diseases, it might cause deleterious effects in liver as Fas ligand or an agonistic anti-murine Fas antibody Jo2 causes severe hepatic injury in mice. We report here on the interesting characteristics of the newly obtained anti-Fas mAb, HFE7A, which cross-reacts with the Fas molecules of various species ranging from human to mouse and mitigates autoimmune symptoms without hepatotoxicity in mice. The administration of HFE7A to mice induced apoptosis in the thymocytes, although administration of HFE7A to mice or to marmosets did not induce any sign of hepatitis. The effect of HFE7A on liver is different from that of anti-murine Fas antibody Jo2, which causes acute and lethal hepatic injury to mice. Administration of HFE7A reduced lymphadenopathy and abnormal T cells in MRL-gld/gld mice. HFE7A induced apoptosis in synovial cells prepared from RA patients. Surprisingly, HFE7A protected mice from fulminant hepatitis induced by Jo2. Therefore, HFE7A is a potential therapeutic antibody not only for autoimmune diseases including RA but also for fulminant hepatitis.

Abstract. The pharmacological effects of rivoglitazone, a novel thiazolidinedione-derivative peroxisome proliferator-activated receptor (PPAR)-γ agonist, were characterized in vitro and in vivo. Rivoglitazone activated human PPARγ more potently compared with rosiglitazone and pioglitazone and had little effect on PPARα and PPARδ activity in luciferase reporter assays. In Zucker diabetic fatty (ZDF) rats, 14-day administration of rivoglitazone decreased the plasma glucose and triglyceride (TG) levels in a dose-dependent manner. The glucose-lowering effect of rivoglitazone was much more potent than those of pioglitazone (ED 50 : 0.19 vs. 34 mg/kg) and rosiglitazone (ED 50 : 0.20 vs. 28 mg/kg). In addition, rivoglitazone showed potent antidiabetic effects in diabetic db/db mice. In Zucker fatty rats, rivoglitazone at a dose of 0.1 mg/kg clearly ameliorated insulin resistance and lowered plasma TG levels by accelerating the clearance of plasma TG. Gene expression analysis in the liver and heart of ZDF rats treated with rivoglitazone for 14 days suggested that rivoglitazone may reduce hepatic glucose production and modulate the balance of the cardiac glucose/fatty acid metabolism in diabetic animals. In summary, we showed that rivoglitazone is a potent and selective PPARγ agonist and has a potent glucoselowering effect via improvement of the insulin resistance in diabetic animal models.

Tumor necrosis factor (TNF) is implicated in wasting syndromes and insulin resistance in chronic infection and obese-linked diabetes. TNF (10 ng/ml) inhibited adipocyte differentiation of 3T3-L1 cells, and in these TNF treated cells little insulin-stimulated glucose uptake was observed. Treatment of 3T3-L1 cells with troglitazone (1-10 microM) partially prevented this inhibitory effect of TNF on adipogenesis, and enhanced expression of C/EBP alpha and GLUT4, even in the presence of TNF. Troglitazone also prevented the inhibitory effects of interleukin-1, interleukin-6, and leukemia inhibitory factor, but not of transforming growth factor beta on adipocyte differentiation of 3T3-L1 cells. These effects might contribute to the antidiabetic effect of troglitazone in obese diabetic animals.