Cristina Maria Failla

Vascular endothelial growth factor receptor-1 is deposited in the extracellular matrix by endothelial cells and is a ligand for the alpha 5 beta 1 integrin.

Vascular endothelial growth factor receptor-1 (VEGFR-1) is a tyrosine kinase receptor for several growth factors of the VEGF family. Endothelial cells express a membrane-spanning form of VEGFR-1 and secrete a soluble variant of the receptor comprising only the extracellular region. The role of this variant has not yet been completely defined. In this study, we report that the secreted VEGFR-1 is present within the extracellular matrix deposited by endothelial cells in culture, suggesting a possible involvement in endothelial cell adhesion and migration. In adhesion assays, VEGFR-1 extracellular region specifically promoted endothelial cell attachment. VEGFR-1-mediated cell adhesion was divalent cation-dependent, and inhibited by antibodies directed against the α5β1 integrin. Moreover, VEGFR-1 promoted endothelial cell migration, and this effect was inhibited by anti-α5β1 antibodies. Direct binding of VEGFR-1 to theα 5β1 integrin was also detected. Finally, binding to VEGFR-1 initiated endothelial cell spreading. Altogether these results indicate that the soluble VEGFR-1 secreted by endothelial cells becomes a matrix-associated protein that is able to interact with the α5β1 integrin, suggesting a new role of VEGFR-1 in angiogenesis, in addition to growth factor binding.

A central hydrophobic domain of the hepatitis C virus NS4A protein is necessary and sufficient for the activation of the NS3 protease

The processing at the NS3/4A, NS4A/4B, NS4B/5A and NS5A/5B junctions in the non-structural region of the hepatitis C virus (HCV) polyprotein is performed by a viral serine protease activity contained within the N-terminal 180 amino acids of the NS3 protein. Full protease activity is only achieved upon the interaction of a region at the N terminus of NS3 with the NS4A protein, this region is also involved in the modulation of the protease activity. Using the rabbit reticulocyte expression system, we have defined the minimal domain of NS4A that is necessary to increase the cleavage efficiency of NS3. A synthetic peptide containing the same region, NS4A amino acids 21 to 32, stimulates the proteolytic activity of NS3 at all the trans-cleavage sites.

STAT3-dependent effects of IL-22 in human keratinocytes are counterregulated by sirtuin 1 through a direct inhibition of STAT3 acetylation

IL‐22 has a pathogenetic role in psoriasis, where it is responsible for the altered proliferation and differentiation of keratinocytes and induces inflammatory molecules. The IL‐22‐induced effects are mediated by STAT3, whose activity is proportional to acetylation in lysine (Lys)685 and phosphorylation in tyrosine (Tyr)705. Lys 685 acetylation of STAT3 is inhibited by sirtuin (SIRT)1, a class III deacetylase promoting keratinocyte differentiation. Due to the opposite effects of IL‐22 and SIRT1, we investigated whether IL‐22‐induced effects in keratinocytes could be regulated by SIRT1 through control of STAT3. We found that SIRT1 opposes the IL‐22‐induced STAT3 activity by deacetylating STAT3 and reducing STAT3 Tyr705 phosphorylation. By controlling STAT3, SIRT1 also influences the IL‐22‐induced expression of molecules involved in proliferation and inflammation as well as proliferation and migration processes in cultured keratinocytes. Although SIRT1 levels were similar in keratinocytes of healthy individuals and patients with psoriasis, they were reduced in psoriatic skin lesions, with the lymphokine IFN‐γ inhibiting SIRT1 expression. Concomitantly, IFN‐γ enhanced basal acetylation of STAT3 and its phosphorylation induced by IL‐22. In conclusion, STAT3‐dependent IL‐22 signaling and effects in keratinocytes are negatively regulated by SIRT1. In skin affected by psoriasis, SIRT1 is down‐regulated by IFN‐y, which thus renders psoriatic keratinocytes more prone to respond to IL‐22.—Sestito, R., Madonna, S., Scarponi, C., Cianfarani, F., Failla, C. M., Cavani, A., Girolomoni, G., Albanesi, C. STAT3‐dependent effects of IL‐22 in human keratinocytes are counterregulated by sirtuin 1 through a direct inhibition of STAT3 acetylation. FASEB J. 25, 916–927 (2011). www.fasebj.org

Granulocyte/macrophage colony-stimulating factor treatment of human chronic ulcers promotes angiogenesis associated with de novo vascular endothelial growth factor transcription in the ulcer bed

Background  Granulocyte/macrophage colony‐stimulating factor (GM‐CSF), a cytokine with pleiotropic functions, has been successfully employed in the treatment of chronic skin ulcers. The biological effects underlying GM‐CSF action in impaired wound healing have been only partly clarified.

Integrin α3β1 Is an Alternative Cellular Receptor for Adenovirus Serotype 5

ABSTRACT Many adenovirus serotypes enter cells by high-affinity binding to the coxsackievirus-adenovirus receptor (CAR) and integrin-mediated internalization. In the present study, we analyzed the possible receptor function of α3β1 for adenovirus serotype 5 (Ad5). We found that penton base and integrin α3β1 could interact in vitro. In vivo, both Ad5-cell binding and virus-mediated transduction were inhibited in the presence of anti-α3 and anti-β1 function-blocking antibodies, and this occurred in both CAR-positive and CAR-negative cell lines. Peptide library screenings and data from binding experiments with wild-type and mutant penton base proteins suggest that the Arg-Gly-Asp (RGD) in the penton base protein, the best known integrin binding motif, is only part of the binding interface with α3β1, which involved multiple additional contact sites.

Sirtinol Treatment Reduces Inflammation in Human Dermal Microvascular Endothelial Cells

Histone deacetylases (HDAC) are key enzymes in the epigenetic control of gene expression. Recently, inhibitors of class I and class II HDAC have been successfully employed for the treatment of different inflammatory diseases such as rheumatoid arthritis, colitis, airway inflammation and asthma. So far, little is known so far about a similar therapeutic effect of inhibitors specifically directed against sirtuins, the class III HDAC. In this study, we investigated the expression and localization of endogenous sirtuins in primary human dermal microvascular endothelial cells (HDMEC), a cell type playing a key role in the development and maintenance of skin inflammation. We then examined the biological activity of sirtinol, a specific sirtuin inhibitor, in HDMEC response to pro-inflammatory cytokines. We found that, even though sirtinol treatment alone affected only long-term cell proliferation, it diminishes HDMEC inflammatory responses to tumor necrosis factor (TNF)α and interleukin (IL)-1β. In fact, sirtinol significantly reduced membrane expression of adhesion molecules in TNFã- or IL-1β-stimulated cells, as well as the amount of CXCL10 and CCL2 released by HDMEC following TNFα treatment. Notably, sirtinol drastically decreased monocyte adhesion on activated HDMEC. Using selective inhibitors for Sirt1 and Sirt2, we showed a predominant involvement of Sirt1 inhibition in the modulation of adhesion molecule expression and monocyte adhesion on activated HDMEC. Finally, we demonstrated the in vivo expression of Sirt1 in the dermal vessels of normal and psoriatic skin. Altogether, these findings indicated that sirtuins may represent a promising therapeutic target for the treatment of inflammatory skin diseases characterized by a prominent microvessel involvement.

Redesigning the substrate specificity of the hepatitis C virus NS3 protease.

Backgound. Hepatitis C Virus (HCV) non-structural protein 3 (NS3) encodes a trypsin-like serine protease that catalyzes the cleavages at the NS3/NS4A, NS4A/NS4B, NS4B/NS5A and NS5A/NS5B junctions in the viral polyprotein and that shows a preference for a cysteine as the P1 residue. Results. We describe here a partial model of the HCV NS3 protease which allowed us to predict the position of the secondary structure elements of the enzyme and of the residues involved in its specificity. By replacing these with the corresponding residues of Streptomyces griseus protease B, we obtained a protease that, similar to the bacterial protein and unlike the wild-type enzyme, is able to cleave a substrate containing a phenylalanine in the P1 position. Conclusion. These results confirm the reliability of our model and represent one of the few examples of redesign of a serine protease substrate specificity directed by molecular modelling.

Interleukin-17 and interleukin-22 promote tumor progression in human nonmelanoma skin cancer.

Interleukin‐17 (IL‐17) and IL‐22 have been reported to play critical roles in autoimmunity and inflammation but information about their role in cancer is limited. In this study, we investigated the role of IL‐17 and IL‐22 in the progression of human skin basal‐cell carcinoma (BCC) and squamous‐cell carcinoma (SCC). We found that both tumor types are infiltrated with an high number of IL‐17+ and IL‐22+ T lymphocytes, as demonstrated by immunohistochemistry and by FACS analysis performed on peritumoral T‐cell lines isolated from skin biopsies. In vitro studies demonstrated that proliferation and migration of the BCC‐ and SCC‐cell lines M77015 and CAL27 were increased by IL‐17 and IL‐22. Moreover, IL‐17, alone or in combination with TNF‐α, was able to induce the production of two cytokines important for tumor progression, IL‐6 and IL‐8, in CAL27. We also showed that IL‐17 upregulated NF‐κB signaling, while IL‐22 activated the STAT3 pathway and the antiapoptotic AKT protein in M77015 and CAL27. Finally, in vivo experiments demonstrated that IL‐17 and IL‐22 enhanced tumor growth in nude mice injected with CAL27. Altogether, our findings indicate that high levels of IL‐22 and IL‐17 in the BCC and SCC microenvironment promote tumor progression.

A proangiogenic peptide derived from vascular endothelial growth factor receptor-1 acts through α5β1 integrin

Vascular endothelial growth factor receptor-1 (VEGFR-1) is a tyrosine kinase receptor for growth factors of the VEGF family. Endothelial cells express a membrane-bound and a soluble variant of this protein, the latter being mainly considered as a negative regulator of VEGF-A signaling. We previously reported that the soluble form is deposited in the extracellular matrix produced by endothelial cells in culture and is able to promote cell adhesion and migration through binding to alpha5beta1 integrin. In this study, we demonstrate that the Ig-like domain II of VEGFR-1, which contains the binding determinants for the growth factors, is involved in the interaction with alpha5beta1 integrin. To identify domain regions involved in integrin binding, we designed 12 peptides putatively mimicking the domain II surface and tested their ability to inhibit alpha5beta1-mediated endothelial cell adhesion to soluble VEGFR-1 and directly support cell adhesion. One peptide endowed with both these properties was identified and shown to inhibit endothelial cell migration toward soluble VEGFR-1 as well. This peptide directly binds alpha5beta1 integrin, but not VEGF-A, inducing endothelial cell tubule formation in vitro and neoangiogenesis in vivo. Alanine scanning mutagenesis of the peptide defined which residues were responsible for its biologic activity and integrin binding.

Expression of the soluble vascular endothelial growth factor receptor-1 in cutaneous melanoma: role in tumour progression.

Background  Vascular endothelial growth factor (VEGF)‐A, placenta growth factor (PlGF) and their corresponding membrane receptors are involved in autocrine and paracrine regulation of melanoma growth and metastasis. Besides the membrane receptors, a soluble form of the VEGF receptor (VEGFR)‐1 (sVEGFR‐1) has been identified, that behaves both as a decoy receptor, sequestering VEGF‐A and PlGF, and as an extracellular matrix (ECM) molecule, promoting endothelial cell adhesion and migration through the interaction with α5β1 integrin.