Apoptosing cells are actively phagocytoscd in parenchymal tissues, thus preventin~ the inflammatory reaction which could derive from their slow uncontrolled degradation. The molecular mechanisms by which an apoptotic cell is recognized and taken up are largely unknown. We propose that the recognition of apoptotic hepatocytes is mediated by the sugar recognition systems of the liver, particularly the asialoglyeoproteln receptor (ASGP-R), The re~ults presented here demonstrate the participation of ASGP-R in the removal of apoptotie parenchymal cells, and indicate a new perspective for the understanding of its physiological role.

In the past years, the attention of scientists has mainly focused on the study of the genetic information and alterations that regulate eukaryotic cell proliferation and that lead to neoplastic transformation. An increasing series of data are emerging about the involvement of the initiation phase of translational processes in the control of cell proliferation. In this paper we review the novel insights on the biochemical and molecular events leading to the initiation and its involvement in cell proliferation and tumourigenesis. We describe the structure, regulation and proposed functions of the eukaryotic initiation factor 5A (eIF-5A) focusing the attention on its involvement in the regulation of apoptosis and cell proliferation. Moreover, we describe the modulation of its activity (through the reduction of hypusine synthesis) in apoptosis induced either by tissue transglutaminase or interferon a. Finally, we propose eIF-5A as an additional target of anti-cancer strategies.

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Basic fibroblast growth factor (bFGF) and platelet-derived growth factor-BB (PDGF-BB) modulate vascular wall cell function in vitro and angiogenesis in vivo. The aim of the current study was to determine how bovine aorta endothelial cells (BAECs) respond to the simultaneous exposure to PDGF-BB and bFGF. It was found that bFGF-dependent BAEC migration, proliferation, and differentiation into tubelike structures on reconstituted extracellular matrix (Matrigel) were inhibited by PDGF-BB. The role played by PDGF receptor ␣ (PDGF-R␣) was investigated by selective stimulation with PDGF-AA, by blocking PDGF-BB-binding to PDGF-R␣ with neomycin, or by transfecting cells with dominant-negative forms of the receptors to selectively impair either PDGF-R␣ or PDGF-R␤ function. In all cases, PDGF-R␣ impairment abolished the inhibitory effect of PDGF-BB on bFGF-directed BAEC migration. In addition, PDGF-R␣ phosphorylation was increased in the presence of bFGF and PDGF, as compared to PDGF alone, whereas mitogen-activated protein kinase phosphorylation was decreased in the presence of PDGF-BB and bFGF compared with bFGF alone. In vivo experiments showed that PDGF-BB and PDGF-AA inhibited bFGF-induced angiogenesis in vivo in the chick embryo chorioallantoic membrane assay and that PDGF-BB inhibited bFGF-induced angiogenesis in Matrigel plugs injected subcutaneously in CD1 mice. Taken IntroductionThe endothelial layer represents a physical and chemical barrier between the vessel lumen and the underlying tissues. Endothelial cells (ECs) exert a variety of functions and modulate underlying smooth muscle cells by releasing molecules with vasoactive and growth-regulatory properties. 1 Endothelial cells present an active replication phenotype in vitro, but in vivo they are quiescent. 2 The different expression of membrane-bound receptors 3,4 and the in vivo action of specific inhibitors 5-7 may account, at least in part, for the different replication pattern observed.Basic fibroblast growth factor (bFGF) is a potent EC growth factor; it is known to induce a proangiogenic phenotype in ECs and is released under acidosis conditions that induce EC protection from apoptosis. 8 bFGF plays a critical role in physiologic and pathologic angiogenesis, including tumor angiogenesis. 9,10 It exerts its functions by direct action, 11 by inducing vascular endothelial growth factor (VEGF) synthesis, 12 or by potentiating VEGF activity. 13,14 Platelet-derived growth factor (PDGF) is a growth factor known to be active on ECs. Three PDGF isoforms have been identified as disulfide-linked dimers, namely PDGF-AA, PDGF-BB, and PDGF-AB, expressed by ECs under various conditions. 15-19 They interact with different affinity with 2 tyrosine-kinase receptors, PDGF-R␣ and PDGF-R␤, which are expressed on ECs in normal 4,20-22 and in pathologic conditions. [23][24][25][26] Recently, PDGF-C and PDGF-D isoforms were also identified. 27,28 PDGF isoforms are reported to exert mitogenic and chemotactic action on EC, although PDGF-AA appears to be less potent or inactive...

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Both clinical and animal studies have shown that angiogenesis is impaired in diabetes mellitus; however, the mechanisms responsible for this effect are poorly characterized. The major aims of the present study were to evaluate the effect of hyperglycemia on fibroblast growth factor 2 (FGF2)-induced angiogenesis in vivo and to determine whether FGF2 non-enzymatic glycation occurs in hyperglycemic mice. New blood vessel formation was examined in reconstituted basement membrane protein (Matrigel) plugs containing FGF2 in control normoglycemic CD1 and in hyperglycemic nonobese diabetic (NOD) mice. FGF2-induced angiogenesis in NOD mice was inhibited by 75% versus control mice (P < 0.001). When recombinant FGF2 was mixed with Matrigel and injected in mice, it was found that recombinant FGF2 glycation was significantly enhanced in plugs from NOD versus control mice (P < 0.01). In the Boyden chamber assay, the chemotactic effect of glycated FGF2 toward endothelial cells was lower than that of unmodified FGF2 (P < 0.01). Further, FGF2 glycated in vitro and coinjected with Matrigel in CD1 mice was a weaker angiogenic stimulus than unglycated FGF2 (P < 0.005). These results indicate that FGF2-induced angiogenesis is inhibited in diabetic mice, FGF2 glycation is enhanced in hyperglycemic mice, and glycation markedly reduces FGF2 chemotactic effect in vitro and its angiogenic properties in vivo. Thus, FGF2 glycation may represent a mechanism responsible for the impairment of angiogenesis in diabetes mellitus. It has been previously shown that angiogenesis 1 and microvascular function are impaired in animal models of diabetes mellitus 2 and that collateral vessel development is inhibited in diabetic patients.3-5 The molecular mechanisms responsible for these effects are poorly characterized. As a consequence of increased glucose availability, free amino groups of proteins undergo a nonenzymatic reaction with reducing sugars, leading to the formation of unstable Schiff bases and, through the Amadori rearrangement, advanced glycation end-products (AGEs) are produced. 6,7 Several proteins, including hemoglobin, serum albumin, RNase, crystallins, ␤-lactoglobulin, extracellular matrix proteins. and many others undergo such non-enzymatic modification leading to precipitation of insoluble proteic material. 8 -11 This posttranslational modification of proteins is responsible for the thickening of the capillary basement membrane, a hallmark of diabetic microangiopathy 12 and AGEs have been shown to be involved in the etiology of both micro-and macrovascular complications in diabetes mellitus. [13][14][15][16][17][18][19][20] Further, it was reported that glycation reduces the mitogenic activity of basic fibroblast growth factor (FGF2) 21 in vitro and its ability to activate c-myc. 22 However, neither a cause-effect relationship between FGF2 glycation and diabetes nor the occurrence of FGF2 glycation in vivo have been shown. Therefore, the aims of the present study were: 1) to evaluate FGF2-induced angiogenesis in hyperglycemic mice; ...

Aloin, a natural anthracycline from aloe plant, is a hydroxyanthraquinone derivative shown to have antitumor properties. This study demonstrated that aloin exerted inhibition of cell proliferation, adhesion and invasion abilities of B16-F10 melanoma cells under non-cytotoxic concentrations. Furthermore, aloin induced melanoma cell differentiation through the enhancement of melanogenesis and transglutaminase activity. To improve the growth-inhibiting effect of anticancer agents, we found that the combined treatment of cells with aloin and low doses of cisplatin increases the antiproliferative activity of aloin. The results suggest that aloin possesses antineoplastic and antimetastatic properties, exerted likely through the induction of melanoma cell differentiation.

Considerable and intense progress has been made in the understanding of the chemistry, molecular biology and cell biology of transglutaminases (TGases: EC 2.3.2.13). The knowledge that very different processes such as cell growth, reproduction and death are dependent on the presence of adequate levels of these enzymes and that the amount of both free and protein-conjugated polyamines, formed by the enzyme, are capable of modulating the differentiation and proliferative capability of several cell types, has prompted a multitude of researchers to study the role of these fascinating molecules in cancer cell differentiation.