Growth factors and chemokines: a comparative functional approach between invertebrates and vertebrates.

Growth factors and cytokines control and coordinate a broad spectrum of fundamental cellular functions, and are evolutionarily conserved both in vertebrates and invertebrates. In this review, we focus our attention on the functional phylogenetic aspects of growth factors/cytokines like the Transforming Growth Factor-beta (TGF-beta), the Connective Tissue Growth Factor (CTGF), and the Vascular Endothelial Growth Factor (VEGF). We will also delve into the activites of two chemokine families, interleukin (IL)-8 (or CXCL8) and CC chemokine ligand 2/monocyte chemoattractant protein-1 (CCL2). These molecules have been selected for their involvement in immune responses and wound healing processes, where they mediate and finely regulate various regeneration processes like angiogenesis or fibroplasia, not only in vertebrates, but also in invertebrates.

Cytokines and chemokines as regulators of angiogenesis in health and disease.

The intricate interplay between the endothelium and immune cells has been well recognized in the context of immune responses. However, the fact that this inter-relation extends well beyond immune regulation is becoming increasingly recognized, with particular regards to the influence of the immune system on the essential endothelial process of angiogenesis, where the contribution of cytokines drives the angiogenic process. As angiogenesis is an important component of numerous pathological states, among these chronic inflammatory conditions and cancer, understanding the role of cytokines and chemokines in guiding new vessel formation provides key insight into novel therapeutic modalities. Here we review the actions of principal cytokines and chemokines on the angiogenic process and discuss how both can be considered potential pharmaceutical targets or pharmaceuticals themselves for modulation of angiogenesis in chronic inflammation associated with cancer, rheumatoid arthritis and other inflammatory diseases.

Anti-angiogenesis and angioprevention: mechanisms, problems and perspectives.

The recognition that angiogenesis is a key early event in tumor progression and metastasis has led to the development of new strategies for cancer therapy. The generation of a new blood vessel network under physiological conditions is regulated by the concerted action of activators and inhibitors. Perturbation of this balance, as it occurs in solid tumor growth and metastasis, appears to be a critical point in tumorigenesis. This has led to the "angiogenic switch" hypothesis: the point at which a tumor acquires the potential to induce angiogenesis is a critical step towards malignancy. Based on experimental evidence, prevention of blood vessel development appears to be the mechanism of action of many successful chemopreventive drugs of natural or synthetic origin: a novel concept that we termed "angioprevention". The hypothesis that anti-angiogenesis is at the basis of tumor prevention also suggests that many anti-angiogenic drugs could be used for chemoprevention in higher risk populations or in early intervention. There is a growing body of experimental evidence that anti-angiogenic strategies will contribute to the future therapy of cancer, several compounds with anti-angiogenic properties are now under clinical investigation including anti-inflammatory compounds, as inflammation may play a key role in angiogenesis. We must persevere in the development of novel, powerful and safer angiogenesis inhibitors and in the use of anti-angiogenic drugs in combination with other natural or synthetic anti-cancer agents in a biological therapy strategy.

Antiangiogenic activity of chemopreventive drugs.

Tumors growing within the host form dynamic aberrant tissue that consists of host components, including the stroma, an expanding vasculature and often chronic inflammation, in addition to the tumor cells themselves. These host components can contribute to, rather than limit, tumor expansion, whereas deprivation of vessel formation has the potential to confine tumors in small, clinically silent foci. Therapeutic inhibition of vessel formation could be best suited to preventive strategies aimed at the suppression of angiogenesis in primary tumors in subjects at risk, or of micrometastases after surgical removal of a primary tumor. Our analysis of potential cancer chemopreventive molecules including N-acetylcysteine, green tea flavonoids and 4-hydroxyphenyl-retinamide has identified antiangiogenic activities that could account--at least in part--for the tumor prevention effects observed with these compounds. These drugs appear to target common mechanisms of tumor angiogenesis that may permit identification of critical targets for antiangiogenic therapy and antiangiogenic chemoprevention.

HIV type 1 Tat protein is a survival factor for Kaposi's sarcoma and endothelial cells.

The HIV-1 Tat protein has been directly implicated in the pathogenesis of AIDS-related Kaposi's sarcoma (KS); however, its effects on KS spindle-shaped and endothelial cell apoptosis are largely unexplored. Since susceptibility to apoptosis is relevant for tumor development and response to therapy, we investigated the effects of Tat on KS and endothelial cell survival from apoptosis. The effect of Tat was evaluated in three KS cell lines (KS-imm, KS-C1, and KS-L3) exposed to the chemotherapy agent vincristine, currently used for the treatment of this tumor, and in human umbilical vein-derived endothelial cells (HUVECs) induced to undergo apoptosis by serum withdrawal. Apoptosis was assessed by enzymatic assays, microscopic examination of chromatin and cytoskeleton, evaluation of plasma membrane integrity and subdiploid DNA content, TUNEL assays, and measurement of caspase-3 activity. Tat, in a dose-dependent manner, protected the three KS cell lines and HUVECs from apoptosis induced by vincristine or serum starvation, respectively. This effect appeared to be independent of modulation of Fas, Bcl-2, or Bax expression. In contrast, Tat upregulated Bcl-X(L) expression and induced a relevant decrease in caspase-3 activity in vincristine-treated KS cells. Taken together, these results suggest that the HIV-1 Tat protein may factor KS development and progression by sustaining endothelial and transformed cell survival.

Tumor gelatinases and invasion inhibited by the green tea flavanol epigallocatechin-3-gallate.

BACKGROUND: Given the association of consumption of green tea with prevention of cancer development, metastasis, and angiogenesis, the effect of the main flavanol present, epigallocatechin-3-gallate (EGCG), on two gelatinases most frequently overexpressed in cancer and angiogenesis (MMP-2 and MMP-9) and on tumor cell invasion and chemotaxis were examined. METHODS: Zymography, Western blotting, and enzyme linked immuoadsorbent assay were used to analyze the effect of EGCG on MMP-2 and MMP-9 activity, whereas its effect on tumor cell invasion and chemotaxis was examined using modified Boyden chamber assays. RESULTS: A Zn2+ chelation-independent, dose-dependent, noncompetitive inhibition by EGCG of both gelatinases was found at concentrations 500 times lower than that reported to inhibit urokinase. Tumor cell invasion of a reconstituted basement membrane matrix, but not chemotaxis, was reduced by 50% with EGCG concentrations equivalent to that in the plasma of moderate green tea drinkers, and 2 orders of magnitude below those of tissue inhibitors of MMPs. Although higher concentrations of EGCG were associated with increased levels of both cell-associated gelatinases and their activator MT1-MMP, no increased gelatinase activation was found, and TIMP-1 and TIMP-2 inhibitors were up-regulated. Finally, concentrations of EGCG active in restraining proliferation and inducing apoptosis of transformed cells were more than 100 times lower than those reported for normal cells. CONCLUSIONS: Epigallocatechin-3-gallate is a potent inhibitor of gelatinases and an orally available pharmacologic agent that may confer the antiangiogenic and antimetastatic activity associated with green tea.

Growth factor supplemented matrigel improves ectopic skeletal muscle formation--a cell therapy approach.

Following damage to skeletal muscle, satellite cells become activated, migrate towards the injured area, proliferate, and fuse with each other to form myotubes which finally mature into myofibers. We tested a new approach to muscle regeneration by incorporating myoblasts, with or without the exogenous growth factors bFGF or HGF, into three-dimensional gels of reconstituted basement membrane (matrigel). In vitro, bFGF and HGF induced C2C12 myoblast proliferation and migration and were synergistic when used together. In vivo, C2C12 or primary i28 myoblasts were injected subcutaneously together with matrigel and growth factors in the flanks of nude mice. The inclusion of either bFGF or HGF increased the vascularization of the gels. Gels supplemented with bFGF showed myogenesis accompanied by massive mesenchymal cell recruitment and poor organization of the fascicles. Samples containing HGF showed delayed differentiation with respect to controls or bFGF, with increased myoblast proliferation and a significantly higher numbers of cells in myotubes at later time points. HGF samples showed limited mesenchymal cell infiltration and relatively good organization of fascicles. The use of both bFGF and HGF together showed increased numbers of nuclei in myotubes, but with bFGF-mediated fibroblast recruitment dominating. These studies suggest that an appropriate combination of basement membrane components and growth factors could represent a possible approach to enhance survival dispersion, proliferation, and differentiation of myogenic cells during muscle regeneration and/or myoblast transplantation. This model will help develop cell therapy of muscle diseases and open the future to gene therapy approaches.

Human immunodeficiency virus transactivator protein (Tat) stimulates chemotaxis, calcium mobilization, and activation of human polymorphonuclear leukocytes: implications for Tat-mediated pathogenesis.

The extracellular activities of the human immunodeficiency virus (HIV) transactivator protein (Tat) include induction of angiogenesis and stimulation of monocyte migration. Here it is shown that polymorphonuclear leukocytes (PMNL), mostly neutrophils, rapidly invade in response to Tat in vivo and initiate the formation of new vessels. In vitro, Tat was chemotactic for PMNL and induced calcium (Ca(2+)) mobilization. Tat proteins with inactivating substitutions in the arginine-glycine-aspartic acid or basic domain were still active in inducing PMNL migration, whereas Tat peptides mapped the migration and Ca(2+) mobilization activity to a cysteine-rich core domain, previously described as a Tat "chemokine-like" region (peptide CysL(24-51)). Tat and the CysL(24-51) peptide also induced PMNL superoxide production and the release of the angiogenic factors interleukin-8 and vascular endothelial growth factor from PMNL. CysL(24-51) did not induce endothelial cell migration but was angiogenic in vivo. These data indicate that the Tat activity on PMNL is mediated by its chemokine-like region and that PMNL recruitment by Tat is linked to angiogenesis.

Kaposi's sarcoma cells of different etiologic origins respond to HIV-Tat through the Flk-1/KDR (VEGFR-2): relevance in AIDS-KS pathology.

Kaposi's sarcoma (KS) is an hyperplastic lesion whose main histological features are typical spindle shaped cells with a mixed endothelial-mesenchymal-macrophage phenotype, an intense vascularization and an inflammatory infiltrate. The etiology of KS appears to be linked to activation of a latent HHV8 infection. Sporadic and iatrogenic KS are slow progressing lesions that can undergo spontaneous regression. In contrast, KS, which is frequently associated with HIV infection, is found in a highly aggressive form in AIDS patients. The HIV-1 Tat has been shown to activate the VEGF receptor KDR in endothelial and KS spindle cells, suggesting this HIV protein could contribute to KS pathogenesis. We used primary 'reactive' KS cell culture from sporadic and epidemic KS, and an immortal KS-line (KS-Imm) isolated in our laboratory from a iatrogenic KS lesion, to verify if Tat-induced cell signaling is able to mediate cellular responses. We demonstrate that KS cells migrated in response to Tat and that VEGF is able to compete with the Tat chemotactic activity towards these cells. A function-blocking anti-KDR antibody was able to abrogate both VEGF and Tat-induced KS chemotactic response, indicating a direct involvement of this receptor. Our data show that HIV-Tat can also activate KS cells derived from sporadic or iatrogenic lesions, suggesting that in AIDS patients Tat could cooperate with VEGF in activation of KDS on KS precursor spindle and endothelial cells, and contribute to the aggressiveness of AIDS-KS lesions.

Distinct chemotactic and angiogenic activities of peptides derived from Kaposi's sarcoma virus encoded chemokines.

The vMIPs are chemokine-like proteins expressed by the Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) during the lytic phase of viral infection. vMIP-I activates CCR8, a chemokine receptor expressed by Th2 lymphocytes and cultured monocytes. vMIP-II is an agonist for CCR3, a receptor expressed by eosinophils, and an antagonist for several other chemokine receptors. Both are highly angiogenic in the chick chorio-allantoic membrane. We designed and tested three 26-mer peptides, derived from vMIP-I (pK-I), from vMIP-II (pK-II) and from the control MIP-1alpha (pM), spanning key residues of chemokines. pK-I, pK-II and pM all were able to activate a strong chemotactic response in monocytes, higher than parental vMIP-I and II. This corresponded to induction of calcium fluxes in these cells, typical of chemokines. Interestingly, pK-II and pM were also active on PMN neutrophils. In vivo studies (matrigel sponge and rabbit cornea models) showed that pK-I retains the strong angiogenic potential exerted by vMIP-I, while pK-II and pM induced an inflammatory response, probably mediated by PMN recruitment. Our observations indicate that chemokine-derived peptides can show biological activity at pharmacological concentrations. pK-I, in particular, displays the angiogenic activity of full-length vMIP-I, while all peptides appear to have acquired additional properties, stimulating new cellular targets.

Inhibition of CXCR4-dependent HIV-1 infection by extracellular HIV-1 Tat.

Certain chemokines inhibit HIV replication through binding to cell surface receptors which also act as viral coreceptors. Based on our previous observations that HIV-1 Tat can interact with alpha- and beta-chemokine receptors, we investigated the potential effect of extracellular Tat (ecTat) on infection and replication of CCR5-dependent (R5) and CXCR4-using (X4) HIV-1 strains in primary activated peripheral blood mononuclear cells (PBMC) of uninfected donors. Receptor desensitization and binding competition studies were used to determine chemokine receptor binding by ecTat. Standard HIV replication assays based on reverse transcriptase (RT) activity determination in culture supernatants of PBMC and real time PCR for HIV-1 gag DNA were used to determine potential effects on early (entry or RT) steps of infection. ecTat bound to CXCR4 expressing monocytes and mitogen-activated PBMC, and competed with the natural ligand of CXCR4, SDF-1alpha (stromal cell-derived factor-1alpha) in calcium mobilization assays. EcTat inhibited replication of the X4 HIV-1 (LAI/IIIB strain) in activated PBMC at concentrations close to those of SDF-1alpha, whereas it only modestly interfered with R5 HIV-1 (BaL) replication in PBMC. Both SDF-1alpha and ecTat inhibited accumulation of X4 HIV-1 gag DNA, indicating interference with viral entry and/or RT. Our data show the surprising and counter-intuitive observation that ecTat selectively represses X4 HIV replication. This could favour spreading of R5 viruses, a condition observed in vivo immediately after transmission and in the early asymptomatic phase of infection.

Inhibition of angiogenesis and vascular tumor growth by interferon-producing cells: A gene therapy approach.

We developed an in vivo gene therapy approach to characterize and optimize the anti-angiogenic activity of class I interferons (IFNs), using packaging cell lines producing an amphotropic LXSN-based retrovirus expressing either IFN-alpha1 (alpha1Am12), IFN-beta (betaAm12) murine cDNAs, or the vector alone (neoAm12). Pretreatment of endothelial-like Eahy926 cells in vitro with conditioned media (CM) from alpha1Am12 or betaAm12 cells for 48 hours significantly inhibited their migration and invasion as compared to neoAm12-CM-treated cells. betaAm12-CM also inhibited the formation of capillary-like structures on Matrigel by EAhy926 cells. In vivo, inclusion of the betaAm12 cells strongly inhibited, and alpha1Am12 partially inhibited, the angiogenic response in the Matrigel sponge model in both immune-competent and athymic nude mice. Electron microscopy showed a reduction of host cell infiltration in alpha1Am12- and betaAm12-containing sponges and reduction of invading tubular clefts of host cells as compared to controls. Finally, inoculation of either alpha1Am12 or betaAm12 cells (10%) along with a highly angiogenic Kaposi's sarcoma cell line (90%) resulted in a powerful reduction of tumor growth in nude mice in vivo, as did infection with the interferon-alpha-producing retroviruses. These data suggest that a gene therapy approach using class I interferons can effectively inhibit tumor angiogenesis and growth of vascular tumors.

Tissue inhibitors of metalloproteases: regulation and biological activities.

A central role in tissue invasion is played by proteases that degrade extracellular matrices; in particular specific metalloproteases (MMPs) have been frequently correlated with the invasive potential of tumor cells and with the angiogenic process. MMPs are tightly regulated by molecules controlling their activation and by specific inhibitors of MMPs, known as the Tissue Inhibitors of MetalloProteases or TIMPs. Four TIMP family members are currently known. An imbalance between MMPs and TIMPs is linked to the degradation of the extracellular matrix associated with several physiologic and pathologic events including angiogenesis, invasion and metastasis. TIMPs are not only the 'guardians' of tissue degradation, they are able to control cell proliferation and cell survival as well. Given the critical role that TIMPs play, it is vital to know how the expression of TIMPs is controlled. Here we review the major biological properties and the molecular regulation of the TIMP expression.

[Unexplained male infertility and testicular microlithiasis]. / Infertilità maschile inspiegata e microlitiasi testicolare.

In this study we analyse the frequency of testicular microlithiasis in a group of otherwise infertile healthy men, visited at the Andrology Service of Prato Hospital. Here the ultrasound machine is located in the ambulatory and it is possible to use it during the first visit of the patient, as we have done in 250 consecutive infertile men. This examination, easy and not invasive, has been performed to evaluate the pampiniform plexus to find possible varicocele, epydidimis for obstructive signs and testes for the presence or absence of parenchymal calcifications or masses. We found 106 positive sonographic records (42.4%) for scrotal diseases. Between them, two cases of testicular microlithiasis (0.8% of 250 consecutive ultrasound examinations and 1.7% in the last twelve months). Our data, although with a lower incidence than literature, show the importance of ultrasound examination in absence of specific diagnostic questions too, in the study of male infertility. Clinical management of testicular microlithiasis is difficult, due to loss of treatment and to cancer risk. A long term follow up is request, with periodical (6-12 months) sonographic controls. A classification (here we propose) can be useful for a more precise monitoring.

HIV-Tat dependent chemotaxis and invasion, key aspects of tat mediated pathogenesis.

Extracellular Tat acts as a pleiotropic molecule inducing several biological effects on different target cells. Tat stimulates the chemotaxis of numerous cell types and it appears to have oncogenic activities, including acting as a co-factor for Kaposi's sarcoma. The Tat protein has been shown to bind integrins through an RGD amino acid motif. Tat is an angiogenic factor able to induce the migration and invasion of endothelial and KS cells through the interaction of its basic domain with the VEGF receptor VEGFR2 (Flk-1/KDR). We have also found that Tat is able to mimic chemokines, activating monocyte migration through the chemokine like' cysteine-core domain. Tat is a chemoattractant for dendritic cells, and both the RGD and basic domains appear to be involved in this response. In a recent study we demonstrated that Tat is chemotactic for PMN and induces Ca2+ mobilization in vitro. Experiments using synthetic peptides showed that Tat activities on PMN are mediated by the chemokine like' region. Finally Tat is also able to induce B cell chemotaxis, while its activity on helper T cells has not yet been clarified. Here we review data on Tat-dependent chemotaxis and discuss the possible implications in Tat mediated pathogenesis.

Thrombospondin-1 inhibits Kaposi's sarcoma (KS) cell and HIV-1 Tat-induced angiogenesis and is poorly expressed in KS lesions.

Kaposi's sarcoma (KS), a neoplasm often associated with iatrogenic and acquired immunosuppression, is characterized by prominent angiogenesis. Angiogenic factors released by both KS and host cells, as well as HHV-8 and HIV viral products, have been implicated in the pathogenesis of this lesion. Angiogenesis is the result of imbalance among angiogenesis promoters and inhibitors, which disrupts homeostasis. The aim of this study was to investigate the expression and mechanism of KS control of thrombospondin-1 (TSP), a physiological inhibitor of angiogenesis. Immunohistochemical analysis of four KS lesions showed only spotty reactivity for TSP in the stroma and in less than 10 per cent of lesional blood vessels. In addition, the typical KS spindle cells were not stained. In agreement with these findings, decreased levels of TSP were measured with an ELISA assay in the supernatants of cultured KS cells, compared with endothelial cells. In vitro, TSP inhibited the endothelial cell proliferation and motility induced by KS cell supernatants. TSP also prevented endothelial cell motility induced by Tat, a product of HIV-1 endowed with angiogenic potential and implicated in the pathogenesis of AIDS-KS. In vivo, TSP inhibited the angiogenic activity exerted by Tat in the Matrigel sponge model. These results suggest that TSP down-regulation might be permissive for the development of KS-associated angiogenesis.

In vitro models of angiogenesis: the use of Matrigel.

Tumor-induced angiogenesis is a key event for neoplastic progression. In vitro assays are important for identification of potential angiogenic agents and rapid screening for pharmacological inhibitors. The increased interest in this field of study has generated several in vitro assays that recapitulate the steps of endothelial cell activation and differentiation. In this short report we emphasize the utility of Matrigel, a reconstituted basement membrane, to define two different steps in the angiogenic process: invasion in response to growth factors and organization of microvessels into a network with branching morphology on a Matrigel substrate.

Inhibition of angiogenesis by type I interferons in models of Kaposi's sarcoma.

Kaposi's Sarcoma (KS) is a pathology which occurs with increased frequency and in a particularly aggressive form in AIDS patients. The HIV-1 Tat protein appears to be an important co-factor in the induction of the extensive neo-vascularization associated with AIDS-KS. Tat acts as a chemoattractant for endothelial cells in vitro, inducing both chemotactic and invasive responses. Several clinical trials have been performed testing the effectiveness of diverse biological agents in therapy of KS, among these the type I interferons. Type I IFNs have diverse biological functions besides their anti-viral activity, including anti-angiogenic properties. We have shown that IFN alpha and IFN beta are potent inhibitors of both primary and immortalized endothelial cell migration and morphogenesis in vitro as well as neo-angiogenesis induced by HIV-1 Tat in vivo. The inhibitory effect of IFN class I on HIV-Tat associated angiogenesis further supports its use as a therapy for epidemic Kaposi's sarcoma. The use of recombinant IFNs at the levels required to obtain a therapeutic effect are associated with side effects and toxicity, therefore we are now developing a gene therapy approach for constant and local delivery type I IFNs.