Calcium modulation activates Epstein-Barr virus genome in latently infected cells.

In many viral infections the host cell carries the viral genome without producing viral particles, a phenomenon known as viral latency. The cellular mechanisms by which viral latency is maintained or viral replication is induced are not known. The modulation of intracellular calcium concentrations by calcium ionophores induced Epstein-Barr viral antigens in lymphoblastoid cell lines that carry the virus. When calcium ionophores were used in conjunction with direct activators of protein kinase C (12-O-tetradecanoyl phorbol-13-acetate and a synthetic diacylglycerol), a greater induction of viral antigens was observed than with either agent alone. Activation of protein kinase C may be required for the expression of the viral genome.

Sch proteins are localized on endoplasmic reticulum membranes and are redistributed after tyrosine kinase receptor activation.

The intracellular localization of Shc proteins was analyzed by immunofluorescence and immunoelectron microscopy in normal cells and cells expressing the epidermal growth factor receptor or the EGFR/erbB2 chimera. In unstimulated cells, the immunolabeling was localized in the central perinuclear area of the cell and mostly associated with the cytosolic side of rough endoplasmic reticulum membranes. Upon epidermal growth factor treatment and receptor tyrosine kinase activation, the immunolabeling became peripheral and was found to be associated with the cytosolic surface of the plasma membrane and endocytic structures, such as coated pits and endosomes, and with the peripheral cytosol. Receptor activation in cells expressing phosphorylation-defective mutants of Shc and erbB-2 kinase showed that receptor autophosphorylation, but not Shc phosphorylation, is required for redistribution of Shc proteins. The rough endoplasmic reticulum localization of Shc proteins in unstimulated cells and their massive recruitment to the plasma membrane, endocytic structures, and peripheral cytosol following receptor tyrosine kinase activation could account for multiple putative functions of the adaptor protein.

HCV derived from sera of HCV-infected patients induces pro-fibrotic effects in human primary fibroblasts by activating GLI2.

Hepatitis C virus (HCV) infection is a leading cause of liver fibrosis, especially in developing countries. The process is characterized by the excess accumulation of ECM that may lead, over time, to hepatic cirrhosis, liver failure and also to hepatocarcinoma. The direct role of HCV in promoting fibroblasts trans-differentiation into myofibroblasts, the major fibrogenic cells, has not been fully clarified. In this study, we found that HCV derived from HCV-infected patients infected and directly induced the trans-differentiation of human primary fibroblasts into myofibroblasts, promoting fibrogenesis. This effect correlated with the activation of GLI2, one of the targets of Hedgehog signaling pathway previously reported to be involved in myofibroblast generation. Moreover, GLI2 activation by HCV correlated with a reduction of autophagy in fibroblasts, that may further promoted fibrosis. GLI2 inhibition by Gant 61 counteracted the pro-fibrotic effects and autophagy inhibition mediated by HCV, suggesting that targeting HH/GLI2 pathway might represent a promising strategy to reduce the HCV-induced fibrosis.

Partition of epidermal growth factor receptors on freeze-fractured plasma membranes of A431 cells is affected by the ligand.

The fracture immunolabel technique, which permits assessment of the partition of transmembrane proteins with the inner or outer leaflets of the freeze-fractured membrane, was used to analyze the behavior on fracture of epidermal growth factor (EGF) receptors over the plasma membranes of A431 cells. The receptors partition mainly with the outer leaflet of the freeze-fractured plasma membranes, whereas they become associated with the inner leaflet when they are occupied by the ligand. This modified partition is even more evident after receptor clustering induced by incubation with EGF at 37 degrees C. Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) decreases the number of receptors over both inner and outer leaflets. An effect similar to that induced by the ligand is obtained when receptor aggregation is achieved using anti-receptor monoclonal antibodies (MAb). The modified partition therefore indicates receptor activation and appears to be a consequence of receptor cross-linking rather than to reflect a conformational change of the receptor molecule. Parallel immunolabeling with anti-phosphotyrosine antibodies of freeze-fractured EGF-treated A431 cells reveals that the receptors, when activated, are associated only with the inner leaflet of the plasma membrane.

Infection of human T lymphoid cells by human herpesvirus 6 is blocked by two unrelated protein tyrosine kinase inhibitors, biochanin A and herbimycin.

Human herpesvirus 6 is a T lymphotropic herpesvirus that causes exanthem subitum in infants and is considered a potential cofactor in AIDS etiopathogenesis and progression owing to its in vivo and in vitro interactions with human immunodeficiency virus. We report that no differences in phosphorylation on tyrosine residues of cellular proteins were detectable at early times following HHV-6 infection in comparison to uninfected cells. On the contrary, several cellular proteins appeared phosphorylated on tyrosine at 24-48 hr postinfection. In addition, when tyrosine phosphorylation induced by HHV-6 infection was inhibited by the tyrosine kinase inhibitor biochanin A, the infection of HSB-2 cells was also coordinately reduced, as judged by inhibition of cytopathic effect and by inhibition of early and late viral antigen expression. Similar results were obtained with a second unrelated tyrosine kinase inhibitor, herbimycin. The inhibitors seem to act at a late stage of the viral infectious cycle, since neither viral binding nor internalization were affected. Thus, our results indicate that HHV-6 infection leads to the phosphorylation of protein tyrosine kinases, which may play a role in the course of viral infection, probably by participating in the cytopathic effect induced by the virus.

Human herpesvirus 6 variant A, but not variant B, infects EBV-positive B lymphoid cells, activating the latent EBV genome through a BZLF-1-dependent mechanism.

Human herpesvirus 6, a predominantly T lymphotropic virus, has been recently shown to infect some EBV-positive B cell lines, and to induce in them the activation of the EBV lytic cycle. Here we have confirmed and extended such observations, showing that (1) this phenomenon is restricted to the variant A of HHV-6: in fact two isolates belonging to the HHV-6 variant B (BA92 and Z29) were neither able to infect any B cell line, independently of the EBV status, nor to induce the EBV genome expression. The only exception is represented by the P3HR1 cells, in which, however, the infection by the variant B does not determine induction of EBV antigens; (2) the presence of the EBV genome contributes to the susceptibility of the B cell lines to HHV-6 infection, increasing the binding sites and the percentage of infectable cells, as detected by immunoelectron microscopy; and (3) HHV-6 infected T cells, transfected with plasmids bearing the promoter regions of the EBV early genes BZLF1 and BMRF1, show a strong transactivation of these promoters.

Infection by human herpesvirus 6 (HHV-6) of human lymphoid T cells occurs through an endocytic pathway.

We have analyzed by immunoelectron microscopy the early events of binding and internalization of human herpesvirus 6 (HHV-6, strain GS) on a susceptible T-lymphoblastoid cell line, HSB-2. The virions bound to the cell surface at 4 degrees C were tightly associated with the plasma membrane. Gold immunolabeling of the viral envelope proteins was strong and specific. Warming at 37 degrees C for different times showed viral internalization through smooth surfaced pits and vesicles. Fusion events of the virions with the cell plasma membrane were never observed. Gold immunolabeling performed in parallel experiments before or after viral internalization showed: (1) absence of viral envelope proteins on the cell plasma membranes at all times of internalization, again excluding fusion events; (2) entry of the virions with their envelopes. Treatment of the cells with chloroquine, a drug known to affect the endocytic pathway, led to an almost complete inhibition of viral infectivity, suggesting that the endocytosed virions are responsible for a successful infection. Comparable results were obtained using a second strain of HHV-6 (BA92), with biologic and molecular characteristics similar to the prototype strain Z29. The chloroquine inhibition was effective on two different T cell lines (HSB-2 and J-Jhan), as well as on phytohemagglutinin-stimulated peripheral blood mononuclear cells.

Mechanism of antitumoral activity of catechols in culture.

Cell lines Raji and K 562, lacking tyrosinase, and two melanotic human melanoma cell lines (IRE 1 and IRE 2), were exposed to concentrations from 5 X 10(-3) M to 10(-5) M of different phenols which are substrates of tyrosinase, i.e. l-dopa, dopamine, hydroquinone, terbutylcatechol, and of phenols which are not substrates of the tyrosinase, i.e. resorcinol, butylated hydroxyanisole and hydroquinone dimethyl ether. Cultures were carried out in the presence or in the absence of oxygen radical scavenger enzymes superoxide dismutase, catalase and peroxidase. The stability of each substance in culture medium was assayed by high performance liquid chromatography (HPLC). Results showed that: catechols which are substrates of tyrosinase decompose fully after 24 hr in medium; they are equally toxic for melanoma and non-melanoma cell lines; their toxicity increases when they are preincubated in medium for 24 hr and 48 hr before addition of cells; their toxicity is significantly reduced by addition of scavenger enzymes; on the contrary, phenols not substrates of tyrosinase are stable in medium and their toxicity is not reduced by scavenger enzymes. It is concluded that tyrosinase does not play a major role in catechol toxicity in vitro, which is probably due to some products of catechol decomposition, especially oxygen radicals, acting outside the cells.

Epstein-Barr virus serology in nasopharyngeal carcinomas and other head and neck neoplasms in Italy.

This paper reports the results of the EBV-specific antibody response in 17 Italian nasopharyngeal carcinoma (NPC) patients, 15 other head and neck tumor patients and 15 normal controls. Nucleic acid hybridization has been performed on the biopsy tissue from 4 of the NPC patients, and EBV-DNA was present in two undifferentiated (WHO 3) tumors, and absent in two samples of the keratinizing (WHO 1) type. EBV serology appears to be specifically related to NPC, more evidently for VCA-IgA and EA-IgG antibodies, and useful as an aid in diagnosis of NPC. However, in order to assess a prognostic value of the above markers, a greater number of patients followed for a longer period of time (at least 5 years) is needed, and is currently being pursued.

Differential platelet proaggregating activity of three Burkitt's lymphoma-derived human cell lines.

We demonstrate a differential platelet in vitro proaggregating activity in three Burkitt's lymphoma--derived human B cell lines, i.e. Daudi, Raji and P3H-R1. Functional and ultrastructural findings indicated the ability of Daudi cells to induce a marked secondary irreversible platelet aggregation, while the Raji cells only induced a primary-type reversible platelet response; no evidence of proaggregating activity has been obtained for P3H-R1 cells. Luminometric assays indicated that contact of Daudi and Raji, but not P3H-R1, cells with platelet rich plasma (PRP) or platelet poor plasma (PPP) was followed by ADP release, in the range of 2,2-3,5 microM and 0.4-0.6 microM respectively for Daudi and Raji cells. After preincubation of PRP with apyrase Daudi cells induced a reversible platelet response similar to that obtained with the use of Raji cells: then, the irreversible complete platelet response induced by Daudi cells was to be related to ADP release from degranulating platelets. Experiments in gel-filtered platelet systems showed that the plasma co-factor inducing ADP release from Daudi and Raji cells was not fibrinogen. Specific inhibition of platelet thrombin receptors, as well as of cycloxygenase and lipoxygenase pathways, did not modify the proaggregating activity of Daudi and Raji cells. Work is in progress to characterize the plasma factor interacting with Daudi and Raji, but not P3H-R1 cells, and the differences between the three cell lines which support this differential interaction.

Role of skin surface lipids in UV-induced epidermal cell changes.

Ultraviolet irradiation is capable of affecting skin surface lipids, especially squalene and cholesterol, both in vitro and in vivo, with generation of active lipoperoxides. The photodecomposition of the skin lipid component was carefully evaluated by capillary gas-chromatography. The effects of UV-induced lipoperoxides on human keratinocytes in culture and on guinea pig ear slices were compared with those of synthetic lipoperoxides, i.e. cumene hydroperoxide and 13-hydroperoxylinoleate. A time- and dose-dependent effect on protein synthesis and mitotic activity was observed. In cell culture low concentrations (0.05-5 micrograms/ml) of peroxidated squalene and synthetic lipoperoxides stimulated the incorporation of radiolabelled thymidine and phenylalanine, while higher concentrations (greater than 10 micrograms/ml), or longer periods of treatment, induced cellular damage. In guinea pig ear slices, the lipoperoxides (5-50 micrograms/ml) increased aminoacid incorporation and the number of epidermal pigment cells; higher concentrations (greater than 100 micrograms/ml) caused a derangement of epidermal structure. The results suggest that UV irradiation of skin generates lipoperoxides from the surface lipids which, in vitro, are capable of producing a number of changes in epidermal cells.

[Diagnostic accuracy of computerized tomography. Preoperative staging of gastric cancer]. / Accuratezza diagnostica della tomografia computerizzata. Stadiazione preoperatoria del cancro gastrico.

"Imaging techniques" have assumed greater clinical value in the further assessment of an endoscopically or radiologically verified neoplastic lesion of the stomach through the ability to evaluate its extent of invasion, metastatic involvement of lymphnodes and/or distant organs. US, CT, and more recently NMR are non-invasive modalities that provide an accurate preoperative assessment of potential surgery decision making. Common current practice of preoperative CT in gastric cancer and relevant results documented in letterature, have inclined many clinicians in its use in staging this disease. The aim of the study is to evaluate and assign the efficacy of CT imaging in the preoperative staging of gastric cancer by comparing the results obtained with this imaging technique with the postoperative histopatologic findings of 25 patients with adenocarcinoma of the stomach. CT demonstrates the primitive lesion as a gastric wall differentiate T1 (parietal invasion extending to the lamina propria and submucosa) and T2 (invasion of the muscolaris propria and the submucosa). The performance values of CT in detecting tumor extension to the sierosa were as follows: sensitivity of 78%, specificity of 63%; and overall accuracy of 72%. The sensitivity and specificity of CT in demonstrating adjacent organ involvement were approximately 75% and 85% respectively, and overall accuracy of 84%. In the detection of metastatic involvement of lymphnodes CT demonstrated to be 70% sensitive, 62% specific with an efficacy of 68%. In terms of M-stage, CT imaging identified liver metastases in 3 patients (2 located in the VII segment and 1 in the IV) and 1 metastasis to the adrenal gland. All were confirmed by specimen histopathologic findings.

[Telescopic termino-terminal pancreatico-jejunostomy after duodenopancreatectomy]. / La pancreatico-digiunostomia termino-terminale telescopica dopo duodenocefalopancreatectomia.

The Authors report their experience in pancreatic stump management after pancreaticoduodenectomy. "Telescope" end-to-end pancreaticojejunostomy realized with some safe technical details represents a valid reconstructive procedure especially when the pancreatic remnant has a normal parenchyma without dilated duct.

TPA induction of Epstein-Barr virus early antigens in Raji cells is blocked by selective protein kinase-C inhibitors.

We have shown that modulation of intracellular calcium in EBV latently infected cells could induce the expression of viral antigens, and suggested that a protein kinase-C (PKC) may play a major role in the EBV genome activation. We now report further investigations on the role of PKC using 2 selective enzymatic inhibitors [1-(5-Isoquinolinylsulfonyl)-2-methylpiperazine] (H-7) and Staurosporine. We show that these inhibitors can abrogate the inductive effect of TPA or the combination of TPA plus n-butyrate. The inhibitors have no effect on induction by calcium ionophores or by viral superinfection. In this context the effect of verapamil (a specific calcium channel blocker) and of several calmodulin antagonists was investigated. No inhibitory effect of these agents could be demonstrated on any of the induction systems examined. These observations strengthen the idea that in some instances cellular PKC plays a role in the expression of viral antigens; however, alternative regulatory mechanisms cannot be excluded.

Surface distribution and internalization of erbB-2 proteins.

We report the localization over the cell surface and the early steps of antibody-induced internalization of the product of the erbB-2 proto-oncogene, structurally related to the epidermal growth factor receptor (EGFR). We show that erbB-2/p 185 is mostly excluded from endocytic pits on the cell surface. Incubation at 37 degrees C with an anti-erbB-2/p185 monoclonal antibody induces the rapid entry of the protein into the cell. Similar internalization is shown by a chimeric molecule EGFR/erbB-2 in response to EGF. Both the timing and the pathway of internalization followed by the erbB-2/p185 appear totally similar to those described for the EGFR. At variance with the normal erbB-2/p185, two mutant activated erbB-2 proteins are frequently localized within endocytic pits of the cell surface, indicating that mutations in the transmembrane regions may determine constitutive internalization of the protein.

Paraphenylene diamine, a contact allergen, induces oxidative stress in normal human keratinocytes in culture.

During the course of evaluating the interaction between allergens and keratinocytes in the pre-immunological phase of contact sensitization, we have studied the effects of paraphenylene diamine (pPD) on membrane lipid peroxidation and on intracellular antioxidant levels in cultured human keratinocytes. pPD is an aromatic amine which undergoes spontaneous oxidation in culture medium, generating short-lived free radical species including oxyradicals. Following exposure to non-toxic concentrations of pPD (0.5-10 micrograms/ml), we have evaluated the fatty acid pattern of membrane phospholipids as a target of peroxidative damage, and the intracellular level of reduced glutathione (GSH), the activity of superoxide dismutase (SOD), and that of catalase (CAT) as parameters of the antioxidant system. Depending on pPD concentration and the period of exposure, peroxidative damage with a significant decrease in membrane polyunsaturated fatty acids, was detected. Concentrations between 0.5 and 2 micrograms/ml produced an initial increase and then a decrease in both SOD and CAT activities, and in the oxidation of GSH, up to 12 h. After 24 h, when all the pPD had decomposed, recovery of the initial levels of the antioxidants was detected. Concentrations over 5 micrograms/ml induced a progressive decrease in both the enzymatic activities and the GSH concentrations. These results are consistent with the view that oxidative stress can be an essential event in the pre-immunological phase of contact sensitization.

Nonrandom distribution of epidermal growth factor receptors on the plasma membrane of human A431 cells.

The localization of epidermal growth factor (EGF) receptors over the plasma membranes of human epidermoid carcinoma A431 cells was analyzed at the electron microscopic level using surface replica techniques and conventional thin sections, in combination with immunocytochemistry. Immunolabeling was performed using two distinct monoclonal antibodies directed against the extracellular portion of the receptor, followed by protein A-colloidal gold conjugates. Unexpectedly, with the first monoclonal antibody used, the distribution of the receptors in both unfixed and glutaraldehyde-fixed cells was clearly regionalized, showing a preferential localization of the immunolabeling at the cell periphery as well as over the areas rich in microvilli and in coated and uncoated pits. A similar pattern of distribution was observed also with the other monoclonal antibody, but only when the cells were fixed with glutaraldehyde before immunolabeling. Treatment with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate modifies this distribution, inducing a more disperse pattern. Our observations suggest that a minor group of EGF receptors, which may represent the high-affinity receptors, presents a regional distribution, similar to that described for typical recycling receptors.

Early interactions of human herpesvirus 6 with lymphoid cells: role of membrane protein components and glycosaminoglycans in virus binding.

A microassay was developed to detect human herpesvirus 6 (HHV-6) binding to its cellular receptor using flow cytometry. Comparable results were obtained either by using HHV-6 preparations conjugated with fluorescein isothiocyanate or by indirect immunofluorescent labeling of membrane-bound virus using as primary antibody a monoclonal antibody specific for the HHV-6 gp60/110 envelope glycoprotein. Virus attachment to the plasma membrane was specific and saturable. As expected, among cell lines of various origin, maximum binding was detected on human T-lymphoid cells (HSB-2). Papain digestion of HSB-2 cells prevented HHV-6 attachment and reduced significantly virus infection, indicating the involvement of a protein-based receptor in the attachment step. After removal of the protease, virus receptors were resynthesized and their regeneration was prevented partially by cycloheximide, an inhibitor of protein synthesis. Unexpectedly, only high concentrations (mg/ml) of soluble heparan sulfate and heparin inhibited HHV-6 binding and infection. Under the same conditions, few micrograms (per ml) of heparin suppressed completely herpes simplex type 1 (HSV-1) attachment to the same cell line. Treatment of HSB-2 cells with heparitinase and heparinase, at doses that reduced significantly HSV-1 attachment, had little effect on HHV-6 binding to the cell membrane, indicating a different requirement of heparan sulfate-containing glycosaminoglycans for the two herpesviruses. These data suggest that protein components of the cellular membrane play an essential role in HHV-6 binding and infection while heparan sulfate-glycos-aminoglycans appear to be involved only partially in virus-receptor interaction.

Squalene peroxides may contribute to ultraviolet light-induced immunological effects.

Ultraviolet (UV) irradiation is capable of producing a dose-dependent decomposition of skin surface lipids and particularly of squalene, with the concomitant generation of active lipoperoxides. The biological effects of UV-peroxidated squalene were tested, compared with those produced by synthetic lipoperoxides (cumene hydroperoxide), on some immunological parameters in vivo modified by UVB irradiation. Application of UV-peroxidated squalene as well as cumene hydroperoxide significantly inhibited the induction of contact hypersensitivity to dinitrofluorobenzene in mice, which was associated with a decrease in the number of ATPase positive cells. The effect was dose-dependent (over 40 micrograms for peroxidated squalene and over 20 micrograms for cumene) and relevant after 2 d of treatment. Down-regulation towards the applied hapten was demonstrated. The results indicate that UV-induced lipoperoxides of squalene are capable of inhibiting the induction of contact hypersensitivity in mice and suggest that, among the other photoproducts generated in humans, squalene peroxides may play a role as biochemical messengers of the biological effects of UV irradiation of the skin.