Selective alkylation and acylation of alpha and epsilon amino groups with PEG in a somatostatin analogue: tailored chemistry for optimized bioconjugates

The effects of the type and location of polymer grafting on the biological activity of different mono-PEG derivatives of the somatostatin analogue RC160 were evaluated. A chemical strategy to obtain mono-PEG alkylation or acylation of the peptide's alpha-terminal or lysil-epsilon primary amines was devised. Selective BOC protection of the two available primary amines, followed by reaction with two different PEG reagents and removal of the protecting group, was carried out. Chemical characterization, structural studies, and the evaluation of the biological activity of the bioconjugates synthesized allowed the identification of the one having characteristics more suitable for therapeutic application. This corresponds to the mono-epsilon-lysil-pegylated form, obtained by reductive alkylation, where the amine's positive charge is preserved. The results obtained suggest the importance of preliminary studies in the development of new polymer-peptide conjugates with improved pharmacological properties.     

Structural and functional characterization of hBD-1(Ser35), a peptide deduced from a DEFB1 polymorphism

beta-Defensins are mammalian antimicrobial peptides that share a unique disulfide-bonding motif of six conserved cysteines. An intragenic polymorphism of the DEFB1 gene that changes a highly conserved Cys to Ser in the peptide coding region has recently been described. The deduced peptide cannot form three disulfide bonds, as one of the cysteines is unpaired. We have determined the cysteine connectivities of a corresponding synthetic hBD-1(Ser35) peptide, investigated the structure by circular dichroism spectroscopy, and assayed the in vitro antimicrobial activity. Despite a different arrangement of the disulfides, hBD-1(Ser35) proved as active as hBD-1 against the microorganisms tested. This activity likely depends on the ability of hBD-1(Ser35) to adopt an amphipathic conformation in hydrophobic environment, similar to the wild type peptide, as suggested by CD spectroscopy.     

A crucial role for the vitamin D receptor in experimental inflammatory bowel diseases

The active form of vitamin D (1,25D3) suppressed the development of animal models of human autoimmune diseases including experimental inflammatory bowel disease (IBD). The vitamin D receptor (VDR) is required for all known biologic effects of vitamin D. Here we show that VDR deficiency (knockout, KO) resulted in severe inflammation of the gastrointestinal tract in two different experimental models of IBD. In the CD45RB transfer model of IBD, CD4+/CD45RBhigh T cells from VDR KO mice induced more severe colitis than wild-type CD4+/CD45RBhigh T cells. The second model of IBD used was the spontaneous colitis that develops in IL-10 KO mice. VDR/IL-10 double KO mice developed accelerated IBD and 100% mortality by 8 wk of age. At 8 wk of age, all of the VDR and IL-10 single KO mice were healthy. Rectal bleeding was observed in every VDR/IL-10 KO mouse. Splenocytes from the VDR/IL-10 double KO mice cells transferred IBD symptoms. The severe IBD in VDR/IL-10 double KO mice is a result of the immune system and not a result of altered calcium homeostasis, or gastrointestinal tract function. The data establishes an essential role for VDR signaling in the regulation of inflammation in the gastrointestinal tract.     

Three isoflavanones with cannabinoid-like moieties from Desmodium canum

Three further derivatives of 5,7,2',4'-tetrahydroxy-6-methyl isoflavanone have been isolated from the root extract of Desmodium canum and assigned the structures 2,3-dihydro-5,7-dihydroxy-6-methyl-3-(1a,2,3,3a,8b,8c-hexahydro-6-hydroxy-1,1,3a-trimethyl-1H-4-oxabenzo[f]cyclobut[c,d]inden-7-yl)-4H-1-benzopyran-4-one (1) 2,3-dihydro-5,7-dihydroxy-6-methyl-3-(6a,7,8,10a-tetrahydro-3-hydroxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-2-yl)-4H-1-benzopyran-4-one (2) 2,3-dihydro-5,7-dihydroxy-6-methyl-3-(3-hydroxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-2-yl) 4H-1-benzopyran-4-one (3). The three compounds and the previously isolated chromene 4 all derive from the geranylated precursor 5 by a series of cannabinoid-like oxidative rearrangements.     

Drug treatment in the development of mismatch repair defective acute leukemia and myelodysplastic syndrome

DNA from therapy-related acute leukemia/myelodysplastic syndrome cases (tAL/MDS) from the GIMEMA [Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto] Archive was examined for the microsatellite instability (MSI(+)) phenotype that is diagnostic for defective DNA mismatch repair. More than 60% (16/25) of tAL/MDS cases were MSI(+) in contrast to <4% (0/28) of de novo cases. hMLH1 gene silencing was rare and evidence of promoter methylation was found in less than one-third of the MSI(+) cases. Among the GIMEMA patients who had been treated for breast cancer there was an apparent trend towards early onset primary breast disease. This suggests that there might be common predisposing factors for breast cancer and tAL/MDS. There were also three examples of mutations in the MRE11 gene among the 25 tAL/MDS cases suggesting that defective recombinational DNA repair may promote the development of secondary malignancy. MSI(+) tAL/MDS was significantly associated with previous chemotherapy and the frequency of MSI(+) among radiotherapy patients was considerably lower. In view of the established relationship between drug resistance and mismatch repair defects, we suggest that selection for therapeutic drug resistance may contribute to the incidence of MSI(+) tAL/MDS.     

Oxidative damage of the gastric mucosa in Helicobacter pylori positive chronic atrophic and nonatrophic gastritis, before and after eradication

Background. Helicobacter pylori is the main cause of gastritis and a primary carcinogen. The aim of this study was to assess oxidative damage in mucosal compartments of gastric mucosa in H. pylori positive and negative atrophic and nonatrophic gastritis. Materials and methods. Five groups of 10 patients each were identified according to H. pylori positive or negative chronic atrophic (Hp‐CAG and CAG, respectively) and nonatrophic gastritis (Hp‐CG and CG, respectively), and H. pylori negative normal mucosa (controls). Oxidative damage was evaluated by nitrotyrosine immunohistochemistry in the whole mucosa and in each compartment at baseline and at 2 and 12 months after eradication. Types of intestinal metaplasia were classified by histochemistry. Results. Total nitrotyrosine levels appeared significantly higher in H. pylori positive than in negative patients, and in Hp‐CAG than in Hp‐CG (p < .001); no differences were found between H. pylori negative gastritis and normal mucosa. Nitrotyrosine were found in foveolae and intestinal metaplasia only in Hp‐CAG. At 12 months after H. pylori eradication, total nitrotyrosine levels showed a trend toward a decrease in Hp‐CG and decreased significantly in Hp‐CAG (p = .002), disappearing from the foveolae (p = .002), but remaining unchanged in intestinal metaplasia. Type I and II of intestinal metaplasia were present with the same prevalence in Hp‐CAG and CAG, and did not change after H. pylori eradication. Conclusions. Oxidative damage of the gastric mucosa increases from Hp‐CG to Hp‐CAG, involving the foveolae and intestinal metaplasia. H. pylori eradication induces a complete healing of foveolae but not of intestinal metaplasia, reducing the overall oxidative damage in the mucosa.     

Integrin function and regulation in development

Integrins are a large family of membrane receptors, consisting of alpha and beta subunits, that play a pivotal role in the interaction of cells with the extracellular matrix. Such interaction regulates the organization of cells in organs and tissues during development as well as cell differentiation and proliferation. We have shown that unfertilized oocytes express integrins that might be important during fertilization. We also analyzed nervous system and muscle tissue development showing that integrin expression is precisely regulated during organization of these tissues. The results indicate that two distinct integrin alpha subunits mediate the outgrowth of processes in nerve and glial cells. Alpha1 integrin, a laminin receptor, is up-regulated by nerve growth factor and other differentiation stimuli and is involved in neurite extension by nerve cells. In contrast, process extension by glial cells is likely to involve the alphaV integrin. Moreover, the latter integrin subunit is also transiently expressed in muscle of the embryo body where it localizes predominantly at developing myotendinous junctions. After birth this integrin disappears and is substituted by the alpha7 subunit. At the same time, important changes also occur in the expression of the associated beta subunit. In fact, the beta1A isoform which is expressed in fetal muscles, is substituted by beta1D. These isoforms are generated by alternative splicing and differ in only a few amino acid residues at the COOH terminus of the protein. This region of the molecule is exposed at the cytoplasmic face of the plasma membrane and is connected to the actin filaments. Our results show that beta1D, which is expressed only in striated muscle tissues, binds to both cytoskeletal and extracellular matrix proteins with an affinity higher than beta1A. Thus, beta1D provides a stronger link between the cytoskeleton and extracellular matrix necessary to support mechanical tension during muscle contraction. These results indicate that cells can regulate their interactions with the extracellular matrix by changing their expression of alpha integrin subunits and thus ligand specificity, or by more subtle changes involving alternative usage of different cytoplasmic domains. The important role of both alpha and beta integrin subunit cytoplasmic domains during development is further illustrated by the analysis of targeted mutations which we have generated by homologous recombination in mice.     

Hematopoietic growth factors in autologous transplantation

Hematopoietic growth factors (HGFs) sustain the survival, proliferation and differentiation of hematopoietic stem cells and some functions of mature blood cells. In man several HGFs have been characterised and cloned so far, and this has allowed investigators to confer the rationale for the clinical application of these molecules in hematology and oncology. In particular G-CSF and GM-CSF are currently utilised to abrogate the hematological toxicity of chemotherapy for standard and dose-intensified therapy, neutropenia following bone marrow and peripheral blood stem cell transplantation. Moreover there has recently been great interest in the ex vivo expansion of hematopoietic stem and progenitor cells for a variety of applications, such as in vitro tumor cell purging or for reducing the volume of blood processed by the leukapheresis. Several combinations of HGFs have been described to sustain the ex vivo survival and proliferation of these cells disclosing new opportunities in the field of stem cells transplants.