Biomedical subjects

M Brunetti

Publications and source records attributed to M Brunetti.

At least 37 records · Page 2Linked to original sources

PubMed2000

Pulsed intravenous high-dose dexamethasone in adults with chronic idiopathic thrombocytopenic purpura.

The role of pulsed high-dose dexamethasone (DXM) in the treatment of patients with chronic idiopathic thrombocytopenic purpura (ITP) is still uncertain. Following an early report in which it was described as an effective and well-tolerated treatment with a sustained platelet response in 100% of cases, a number of subsequent studies have failed to confirm such favorable results. As all these studies were conducted on small numbers of patients, we investigated further the effectiveness and side effects of this therapeutic modality in a larger cohort. Thirty-two patients with chronic ITP were scheduled to receive six monthly courses of intravenous DXM at the dose of 40 mg/day for 4 consecutive days. All patients had ITP that had been resistant to between two and five different therapeutic regimens, including 9 patients who had already failed splenectomy. All patients had to be seen 2 weeks after each cycle to asses their response as well as secondary effects. Three patients failed to respond and clinically required other therapy. Thirteen patients (41%) had a partial (platelet count between 50 and 100 x 10(9)/liter) or complete (platelet count >100 x 10(9)/liter) response to treatment, responses being mostly transient. Responses were observed early during the course of treatment, usually right after the first cycle of DXM. There were no late responses. Side effects were mild and did not require discontinuation of treatment. No clinical or laboratory parameter was found to predict treatment outcome. We conclude that high-dose DXM has a limited effect in patients with chronic ITP. Novel approaches and controlled multicenter trials may help identify new therapeutic strategies for this disease.

Adult↗

PubMed2000

Asymptotic evolution of nonlinear landau damping

The long-time evolution of nonlinear Landau damping in collisionless plasmas is analyzed by solving the Vlasov-Poisson system numerically. The value of the parameter marking the transition between Landau's and O'Neil's regimes is determined and compared with analytical results. The long-time evolution of a finite-amplitude electric field with wavelength lambda equal to the length of the simulation box L is given by a superposition of two counterpropagating "averaged" Bernstein-Greene-Kruskal (BGK) waves. When L>lambda and longer wavelength modes can be excited, the BGK waves correspond to an intermediate regime that is eventually modified by the excitation of the sideband instability. Ions dynamics is found not to affect these behaviors significantly.

Journal Article↗

PubMed2000

In vivo selection of protease cleavage sites by using chimeric Sindbis virus libraries.

Identifying protease cleavage sites contributes to our understanding of their specificity and biochemical properties and can help in designing specific inhibitors. One route to this end is the generation and screening of random libraries of cleavage sites. Both synthetic and phage-displayed libraries have been extensively used in vitro. We describe a novel system based on recombinant Sindbis virus which can be used to identify cleavage sites in vivo, thus eliminating the need for a purified enzyme and overcoming the problem of choosing the correct in vitro conditions. As a model we used the serine protease of the hepatitis C virus (HCV). We engineered the gene coding for this enzyme and two specific cleavage sites in the Sindbis virus structural gene and constructed libraries of viral genomes with a random sequence at either of the cleavage sites. The system was designed so that only viral genomes coding for sequences cleaved by the protease would produce viable viruses. With this system we selected viruses containing sequences mirroring those of the natural HCV protease substrates which were cleaved with comparable efficiencies.

Antibodies↗

PubMed2000

Polymorphonuclear leukocyte apoptosis is inhibited by platelet-released mediators, role of TGFbeta-1.

Platelets regulate several polymorphonuclear leukocyte (PMN) functions. We have found that thrombin-stimulated platelets potently inhibited PMN apoptosis. Cell-free supernatant from increasing concentrations of stimulated platelets inhibited PMN apoptosis in a dose-dependent manner, with an effect similar to that of corresponding concentrations of platelets. At the plateau, platelet supernatant inhibited PMN apoptosis by 54.6 +/- 6.8%, the anti-apoptotic activity being higher than that of GM-CSF and comparable to that of LPS. Neither IL-1ra nor a combination of anti-IL1alpha + betamAb affected the activity of platelet supernatant. In contrast a mAb recognizing the active form of TGF-beta1 significantly decreased this activity. Moreover, exogenous TGF-beta1 inhibited PMN apoptosis in a dose-dependent manner. The active form of this cytokine was indeed present in the supernatant of stimulated platelets at a concentration able to elicit an anti-apoptotic effect. The p38 MAPK inhibitor SB203580 prevented the anti-apoptotic effect of TGF-beta1 in a dose-dependent manner. Interestingly, it also prevented the anti-apoptotic effect of IL-1alpha, but not that of GM-CSF, LPS and dexamethasone. In conclusion, we report for the first time that PMN apoptosis is potently inhibited by platelet-released mediators, that TGF-beta1 mediates an important part of this effect, and that p38 MAPK is involved in the TGF-beta1 signaling leading to its anti-apoptotic effect. These results provide novel evidence to support the central role of platelets in inflammation.

Apoptosis↗

PubMed1999

Multiple determinants influence complex formation of the hepatitis C virus NS3 protease domain with its NS4A cofactor peptide.

The interaction of the hepatitis C virus (HCV) NS3 protease domain with its NS4A cofactor peptide (Pep4AK) was investigated at equilibrium and at pre-steady state under different physicochemical conditions. Equilibrium dissociation constants of the NS3-Pep4AK complex varied by several orders of magnitude depending on buffer additives. Glycerol, NaCl, detergents, and peptide substrates were found to stabilize this interaction. The extent of glycerol-induced stabilization varied in an HCV strain-dependent way with at least one determinant mapping to an NS3-NS4A interaction site. Conformational transitions affecting at least the first 18 amino acids of NS3 were the main energy barriers for both the association and the dissociation reactions of the complex. However, deletion of this N-terminal portion of the protease molecule only slightly influenced equilibrium dissociation constants determined under different physicochemical conditions. Limited proteolysis experiments coupled with mass spectrometric identification of cleavage fragments suggested a high degree of conformational flexibility affecting at least the first 21 residues of NS3. The accessibility of this region of the protease to limited chymotryptic digestion did not significantly change in any condition tested, whereas a significant reduction of chymotryptic cleavages within the NS3 core was detected under conditions of high NS3-Pep4AK complex affinity. We conclude the following: (1) The N-terminus of the NS3 protease that, according to the X-ray crystal structure, makes extensive contacts with the cofactor peptide is highly flexible in solution and contributes only marginally to the thermodynamic stability of the complex. (2) Affinity enhancement is accomplished by several factors through a general stabilization of the fold of the NS3 molecule.

Amino Acid Sequence↗

PubMed1999

A loop-mimetic inhibitor of the HCV-NS3 protease derived from a minibody.

We have been interested for some time in establishing a strategy for deriving lead compounds from macromolecule ligands such as minibody variants. A minibody is a minimized antibody variable domain whose two loops are amenable to combinatorial mutagenesis. This approach can be especially useful when dealing with 'difficult' targets. One such target is the NS3 protease of hepatitis C virus (HCV), a human pathogen that is believed to infect about 100 million individuals worldwide and for which an effective therapy is not yet available. Based on known inhibitor specificity (residues P6-P1) of NS3 protease, we screened a number of minibodies from our collection and we were able to identify a competitive inhibitor of this enzyme. We thus validated an aspect of recognition by HCV NS3 protease, namely that an acid anchor is necessary for inhibitor activity. In addition, the characterization of the minibody inhibitor led to the synthesis of a constrained hexapeptide mimicking the bioactive loop of the parent macromolecule. The cyclic peptide is a lead compound prone to rapid optimization through solid phase combinatorial chemistry. We therefore confirmed that the potential of turning a protein ligand into a low molecular weight active compound for lead discovery is achievable and can complement more traditional drug discovery approaches.

Binding Sites↗

PubMed1999

Costs of diabetes. A methodological analysis of the literature.

OBJECTIVE: To review studies on the costs of diabetes and its complications through a scheme designed specifically for assessing the quality of cost-of-illness (COI) studies. DESIGN AND SETTING: The methodology of COI studies in diabetes was analysed in order to assess the significance of quantitative results. The scheme adopted 7 items identified as the main points for discussing the methodological choices governing the results. We also used a checklist based on questions related to the 7 items. MAIN OUTCOME MEASURES AND RESULTS: The answers showed that many studies appear not to give technical details, so it is hard to understand the method. Methodological choices varied widely between the studies. This is probably due to the lack of consensus on the methodology of COI studies. Based on the findings of this review, we suggest also some specific points that could help produce more reliable results on the costs of diabetes. CONCLUSIONS: Clearly, a general consensus on COI studies is still remote, making the value of any comparison of results questionable.

Cost of Illness↗

PubMed1998

Design of selective eglin inhibitors of HCV NS3 proteinase.

Hepatitis C virus (HCV) infection is a major health problem that leads to cirrhosis and hepatocellular carcinoma in a substantial number of infected individuals, estimated to be 100-200 million worldwide. Unfortunately, immunotherapy or other effective treatments for HCV infection are not yet available, and interferon administration has limited efficacy. Different approaches to HCV therapy are being explored, and these include inhibition of the viral proteinase, helicase, and RNA-dependent RNA polymerase and development of a vaccine. Here we present the design of selective inhibitors with nanomolar potencies of HCV NS3 proteinase based on eglin c. These eglin c mutants were generated by reshaping the inhibitor active site-binding loop, and the results emphasize the role played by residues P5-P4' in enzyme recognition. In addition, alanine scanning experiments provide evidence that the N terminus of eglin c also contributes to NS3 binding. These eglin inhibitors offer a unique tool for accurately assessing the requirements for effective inhibition of the enzymatic activity of NS3 and at the same time can be considered lead compounds for the identification of other NS3 inhibitors in targeted design efforts.

Animals↗

PubMed1998

Product inhibition of the hepatitis C virus NS3 protease.

The nonstructural protein NS3 of the hepatitis C virus (HCV) harbors a serine protease domain that is responsible for most of the processing events of the nonstructural region of the polyprotein. Its inhibition is presently regarded as a promising strategy for coping with the disease caused by HCV. In this work, we show that the NS3 protease undergoes inhibition by the N-terminal cleavage products of substrate peptides corresponding to the NS4A-NS4B, NS4B-NS5A, and NS5A-NS5B cleavage sites, whereas no inhibition is observed with a cleavage product of the intramolecular NS3-NS4A junction. The Ki values of the hexamer inhibitory products [Ki(NS4A) = 0.6 microM, Ki(NS5A) = 1.4 microM, and Ki(NS4B) = 180 microM] are lower than the Km values of the respective substrate peptides [Km(NS4A-NS4B) = 10 microM, Km(NS5A-NS5B) = 3.8 microM, and Km(NS4B-NS5A) > 1000 microM]. Mutagenesis experiments have identified Lys136 as an important determinant for product binding. The phenomenon of product inhibition can be exploited to optimize peptide inhibitors of NS3 protease activity that may be useful in drug development.

Amino Acid Sequence↗

PubMed1998

The prognostic value of soluble interleukin-6 receptor in patients with multiple myeloma.

BACKGROUND: The effect of interleukin-6 (IL-6), the major growth factor for myeloma cells, may be enhanced by soluble IL-6 receptor (sIL-6R). Therefore, the current study investigated the clinical significance of serum sIL-6R in patients with multiple myeloma (MM). METHODS: Serum levels of sIL-6R were determined by enzyme-linked immunoassay in 55 normal controls, 81 individuals with monoclonal gammopathy of undetermined significance (MGUS), and 164 patients with MM in various phases of the disease. RESULTS: sIL-6R concentrations were higher in MM patients (162.0 +/- 134.6 ng/mL) than in individuals with MGUS (58.9 +/- 36.7 ng/mL) or in controls (45.6 +/- 22.3 ng/mL) (P = 0.0000). sIL-6R was not found to have a significant linear correlation with any other parameter, including IL-6, beta2-microglobulin (beta2-m), and neopterin, either in newly diagnosed cases or during the course of the disease. In addition, there were no statistically significant differences in sIL-6R concentrations between the clinical stages at the time of diagnosis. In univariate logistic regression analysis sIL-6R was a significant but weak prognostic indicator (P = 0.000000). Kaplan-Meier analysis showed that elevated levels of sIL-6R were associated with shorter survival (P = 0.00282). Patients also were stratified according to their serum beta2-m and sIL-6R levels. Patients with low levels of both parameters had a clear survival benefit over the other groups (P = 0.000000). CONCLUSIONS: The correlation between sIL-6R levels and survival is significant but weak, making it unlikely to be of much value in predicting the outcome of patients with MM alone. The results of the current study support the role of sIL-6R levels in improving the prognostic value of beta2-m and in discriminating patients with MM from individuals with MGUS.

Adult↗

PubMed1998

The economic cost of epilepsy: a review.

Epilepsy is the most prevalent chronic neurologic condition. In developed countries, its incidence is 30-50 per 100,000 population per year and the prevalence is approximately 5-8 cases per 1,000 population. The rapid growth of health care expenditures has led to increased interest in economic evaluation of health care programs. We reviewed studies on the costs of epilepsy to assess the significance of their quantitative results, through a specific scheme of analysis. The main findings of our study are that a general consensus on cost of illness evaluation is still remote and many studies lack technical details, making difficult any useful comparison of results. New efforts should be realized to achieve a major degree of standardization in methodological processes.

Cost of Illness↗

PubMed1998

Role of human leukocyte interferon-alpha in the treatment of patients with polycythemia vera.

Eighteen patients with polycythemia vera who were less than 60 years old received human leukocyte interferon-alpha subcutaneously at a starting dose of 3 MU three times a week. The interferon dose was escalated to 6 MU three times a week if it was well tolerated and disease was not controlled after 3 months of treatment at the lower dose. Hematologic response was defined as complete if the hematocrit was maintained at less than 45% in the absence of phlebotomy and partial if the hematocrit was kept at 45% to 50%, associated with a 50% or greater reduction of phlebotomy requirements; no response was defined as a response less than a partial response. Complete disease control was achieved in 11 patients, with partial control in a further six cases. One patient failed to respond. Median duration of response was 16 months (range 5 to 43 months), with 15 patients still under treatment. Therapy with human leukocyte interferon-alpha significantly improved (p <.01) phlebotomy requirements, the degree of splenomegaly, pruritus scores, iron stores and mean red cell volume values, and platelet and leukocyte counts. Interferon treatment did not produce remarkable side effects and no patient withdrew from the study because of intolerance. We conclude that subcutaneous human leukocyte interferon-alpha is an effective and well-tolerated therapy in the management of polycythemia vera-associated myeloproliferation and pruritus in patients less than 60 years old.

Adult↗

PubMed1998

Multiple enzymatic activities associated with recombinant NS3 protein of hepatitis C virus.

The hepatitis C virus (HCV) nonstructural 3 protein (NS3) contains at least two domains associated with multiple enzymatic activities; a serine protease activity resides in the N-terminal one-third of the protein, whereas RNA helicase activity and RNA-stimulated nucleoside triphosphatase activity are associated with the C-terminal portion. To study the possible mutual influence of these enzymatic activities, a full-length NS3 polypeptide of 67 kDa was expressed as a nonfusion protein in Escherichia coli, purified to homogeneity, and shown to retain all three enzymatic activities. The protease activity of the full-length NS3 was strongly dependent on the activation by a synthetic peptide spanning the central hydrophobic core of the NS4A cofactor. Once complexed with the NS4A-derived peptide, the full-length NS3 protein and the isolated N-terminal protease domain cleaved synthetic peptide substrates with comparable efficiency. We show that, as in the case of the isolated protease domain, the protease activity of full-length NS3 undergoes inhibition by the N-terminal cleavage products of substrate peptides corresponding to the NS4A-NS4B and NS5A-NS5B. We have also characterized and quantified the NS3 ATPase, RNA helicase, and RNA-binding activities under optimized reaction conditions. Compared with the isolated N-terminal and C-terminal domains, recombinant full-length NS3 did not show significant differences in the three enzymatic activities analyzed in independent in vitro assays. We have further explored the possible interdependence of the NS3 N-terminal and C-terminal domains by analyzing the effect of polynucleotides on the modulation of all NS3 enzymatic functions. Our results demonstrated that the observed inhibition of the NS3 proteolytic activity by single-stranded RNA is mediated by direct interaction with the protease domain rather than with the helicase RNA-binding domain.

Adenosine Triphosphatases↗

PubMed1998

IL-10 synergizes with dexamethasone in inhibiting human T cell proliferation.

We have evaluated the effects of dexamethasone (Dex) alone or in combination with interleukin (IL)-10 or transforming growth factor-beta 1 (TGF-beta 1) on human T cell proliferation. Both IL-10 and TGF-beta 1 significantly decreased the Dex concentration needed to inhibit T cell proliferation by 50% (IC50). Dex in combination with IL-10 completely inhibited T cell proliferation, even when IL-10 alone was ineffective, as in the case of phytohemagglutinin-induced T cell proliferation. The evaluation of the results according to the isobole method displayed a potent synergistic activity between Dex and IL-10, whereas the combination of Dex with TGF-beta 1 was additive. IL-10, but not TGF-beta 1, enhanced the inhibitory effect of Dex on IL-2 production. IL-2 and IL-4 only partly antagonized the antiproliferative effect of the combinations. IL-4 was as effective as IL-2 in antagonizing the combination of Dex with TGF-beta 1, but significantly less effective against the combination of Dex with IL-10. IL-10 and TGF-beta 1 are thus able to potentiate the Dex inhibitory effect on T cell proliferation and could be regarded as potential agents for future immunosuppressive protocols.

Dexamethasone↗

PubMed1997

Complex formation between the hepatitis C virus serine protease and a synthetic NS4A cofactor peptide.

The NS3 protein of the hepatitis C virus contains a serine protease that, upon binding to its cofactor, NS4A, is responsible for maturational cleavages that occur in the nonstructural region of the viral polyprotein. We have studied in vitro complex formation between the NS3 protease domain expressed in Escherichia coli and a synthetic peptide spanning the minimal domain of the NS4A cofactor. Complex dissociation constants in the low micromolar range were measured using different techniques such as activity titration, fluorescence titration, and pre-equilibrium analysis of complex formation. Cofactor binding was strictly dependent on the glycerol content of buffer solutions and was not significantly influenced by substrate saturation of the enzyme. NS4A peptide binding to NS3 was accompanied by changes in the circular dichroism spectrum in the region between 270 and 290 nm, as well as by an enhancement of tryptophan fluorescence. Conversely, no changes in the far UV region of the circular dichroism spectrum were detectable. These data are indicative of induced tertiary structure changes and suggest that the secondary structure content of the uncomplexed enzyme does not differ significantly from that of the NS3-cofactor complex. Pre-equilibrium measurements of complex formation showed very low values for k(on), suggesting conformational transitions to be rate limiting for the association reaction.

Amino Acid Sequence↗

PubMed1997

Serum interleukin-10 in plasma-cell dyscrasias.

Serum levels of interleukin-10 (IL-10) were measured by enzyme-linked immunosorbent assay in 115 patients with multiple myeloma (MM) in various phases of the disease (68 at diagnosis, 22 in plateau phase, 22 in relapse), in 71 individuals with monoclonal gammopathy of undetermined significance (MGUS), and in 53 normal volunteers. Detectable levels of serum IL-10 were found in 24 myelomas (20.9%), in 7 cases of MGUS (9.9%), and in 4 normal subjects (7.5%) (P = NS, chi2 test). In patients with MM, cytokine was detected with a comparable frequency in all pathologic stages and phases of the disease: 4/19 in stage I, 6/26 in stage II, 5/23 in stage III, 4/22 in plateau phase, and 5/25 in progressing or relapsed disease. IL-10 concentrations did not differ significantly between controls and patients with plasma-cell dyscrasia, between patients with MGUS and those with MM, between early vs. advanced MM, or between patients in different phases of the disease. In 36 patients with MM in whom IL-10 was measured serially, no significant changes were observed over the course of the disease. Also, when comparing the outcomes of individuals with detectable or undetectable IL-10 in single stages or in the whole myeloma group, no differences were revealed. Our results do not support an apparent involvement of IL-10 in the pathogenesis of MM in vivo. However, further studies are required to define the exact role of this cytokine within the complex cytokine network of this neoplastic disorder.

Adult↗

PubMed1997

Efficacy and safety of human leucocyte interferon-alpha treatment in patients younger than 60 years of age with polycythaemia vera.

OBJECTIVES: To evaluate the therapeutic activity and toxicity of human leucocyte interferon-alpha (lIFN-alpha) in patients with polycythaemia vera (PV) aged less than 60 years. DESIGN: An open clinical study. SETTING: Department of Medical Sciences, Regina Apostolorum Hospital, Albano Laziale, and Chair of Haematology, University of Rome 'Tor Vergata', S. Eugenio Hospital, Rome, Italy. SUBJECTS: Fourteen patients with PV and aged < 60 years who had active disease as indicated by the need for phlebotomy and/or cytoreductive therapy. INTERVENTIONS: lIFN-alpha administered subcutaneously at the starting dose of 3 MU thrice weekly. The interferon dose could be escalated to six MU thrice weekly if it was well tolerated and disease was not controlled after three months of treatment at the lower dose. MAIN OUTCOME MEASURES: Change in phlebotomy requirements, spleen size, pruritus score and haematological parameters after 6 months of treatment. Evaluation of lIFN-alpha side effects. RESULTS: Complete or partial disease control was achieved in 13 patients. Six patients achieved a complete response (CR) and four a partial response (PR) after 3 months of therapy. Dose escalation in partial or nonresponders resulted in two patients switching from a status of PR to CR, and three other patients achieving a partial response after being unresponsive to the lower dosage. Human leucocyte interferon-alpha therapy significantly improved (P < 01) phlebotomy requirements, the degree of splenomegaly, pruritus scores, iron stores and MCV values, and platelet and leucocyte counts. A mild flu-like syndrome (low-grade fever, nausea and myalgias) appeared during the early phase of therapy in the majority of patients, but no patient had to discontinue lIFN-alpha because of intolerance. CONCLUSIONS: Subcutaneous human leucocyte interferon-alpha appears an effective and well tolerated therapy in the management of PV-associated myeloproliferation and pruritus in patients aged less than 60 years.

Adult↗

PubMed1997

Affinity selection of a camelized V(H) domain antibody inhibitor of hepatitis C virus NS3 protease.

The HCV genome encodes, within the NS3 gene, a serine protease whose activity specifically cleaves the viral polyprotein precursor. Proteolytic processing of HCV polyprotein precursor by the viral NS3 proteinase is essential for virion maturation and designing specific inhibitors of this protease as possible anti-viral agents is a desirable and practical objective. With a view to studying both the function of HCV NS3 protease and to designing inhibitors of this enzyme, we directed our interest towards engineering macromolecular inhibitors of the viral protease catalytic activity. We describe here the affinity-selection and biochemical characterization of one inhibitor, cV(H)E2, a 'camelized' variable domain antibody fragment, isolated from a phage displayed synthetic repertoire, which is a potent and selective inhibitor of proteolysis by the NS3 enzyme. In addition to being useful as a biological probe to study the function of HCV protease, this inhibitor can serve as a potential pharmacophore model to design antivirals. Moreover, the results suggest a way of engineering improved human-derived small recognition units tailored for enzyme inhibition.

Animals↗