Long‐term effect of platelet lysate on primary fibroblasts highlighted with a proteomic approach

The use of platelets and platelet derivatives has acquired clinical relevance as a means of accelerating wound healing. Platelet beneficial effect is attributed to the release of growth factors and other bioactive substances able to regulate cellular activities. The purpose of this study was to evaluate the biological effects of platelet lysate (PL) on human primary skin fibroblasts. We studied cell viability, MAPK signalling and proteomic profile of fibroblasts exposed to a platelet lysate (PL) obtained from blood sample. Crystal violet and neutral red uptake assays showed the dose–response effects of PL on cell viability and metabolism at 3 and 6 days of exposure. Western blot demonstrated a more sustained activation of p38 than of ERK1/2. A proteomic approach was applied to identify soluble cellular components in primary fibroblasts that are differentially expressed in response to PL exposure. Protein identification was performed by mass spectrometry. The data demonstrate that human fibroblasts respond to PL exposure by modifying a number of proteins, related principally to stress response, metabolism and the cytoskeleton. Copyright © 2009 John Wiley & Sons, Ltd.     

Activation of Epstein-Barr virus/C3d receptor (gp140, CR2, CD21) on human cell surface triggers pp60src and Akt-GSK3 activities upstream and downstream to PI 3-kinase,respectively

We previously demonstrated that CR2 activation on human B lymphocyte surface specifically triggered tyrosine phosphorylation of the 95-kDa nucleolin, this leading to its binding on SH2 domains of p85 sub-unit of PI 3-kinase and to activation of this enzyme. The specificity of CR2 pathway was clearly demonstrated as neither CD19 nor BCR could induce tyrosine phosphorylation of nucleolin in normal B lymphocytes. These data led us to investigate herein additional molecular events, which were triggered by CR2 activation, upstream and downstream to PI 3-kinase activation. Upstream, we demonstrated that pp60src, a tyrosine kinase of the src family, was involved in tyrosine phosphorylation of nucleolin, while syk tyrosine kinase was not. We also demonstrated a direct protein-protein interaction of pp60src with nucleolin in a CR2-dependent and CD19-independent pathway. Downstream, we demonstrated that CR2 activation also triggered Akt and GSK3 enzyme activation, this pathway being under the control of pp60src tyrosine kinase activation. These regulatory functions of activated CR2 were specific as independent of syk tyrosine kinase and of CD19 and BCR activation. Thus, CR2 activation recruits a specific mechanism to activate PI 3-kinase and its subsequent pathways, this mechanism being different to those recruited by CD19 and BCR.     

The ultrastructural effects of beta-amyloid peptide on cultured PC12 cells: changes in cytoplasmic and intramembranous features

SummaryThe fine structural features of cultured PC12 cells were investigated after treatment for 1, 3, or 5 days with different concentrations of the vascular form of - 1–40 (-AP). PC12 cells treated with -AP showed time- and concentration-dependent lysosomal system activation and cell toxicity. We observed increases in the number and size of cytoplasmic lysosomes as indicated by increased acid phosphatase reactivity. Some lysosomes were in the form of multivesicular bodies or large residual bodies that appeared to arise by autophagia or by endocytotic uptake. Double-sided plasma membrane invaginations were observed to give rise to increasingly extensive intracytoplasmic vacuolization that was correlated with duration of -AP treatment. Freeze-fracture studies of the intramembranous particle (IMP) population in the plasma membrane P-face showed that both control and -AP treated cells had two major P-face IMP populations, small-diameter (4–8 nm) IMPs, and large-diameter ( 9nm) IMPs. The larger category of IMPs was found to possess a greater average diameter in the -AP treated cells than in the control cells. These IMPs could represent modifications to existing transmembranous receptors, channels, or transducing molecules by the -AP. These results demonstrate that -AP can induce time- and concentration-dependent ultrastructural changes in PC12 cell membranes.     

Increased expression of the CD80 accessory molecule by alveolar macrophages in asthmatic subjects and its functional involvement in allergen presentation to autologous TH2 lymphocytes

Background: Alveolar macrophages (AMs) are more efficient antigen-presenting cells in allergic individuals than in nonatopic subjects. Objective: We studied whether this difference may be correlated to increased expression of membrane costimulatory molecules, such as the B7 molecules (CD80 and CD86). Methods: Eleven subjects with allergic asthma sensitized to Dermatophagoides pteronyssinus and 5 healthy nonatopic volunteers underwent bronchoalveolar lavage, and the costimulatory molecule expression on AMs was evaluated. Peripheral blood T cells, either freshly isolated or as established D pteronyssinus -specific cell lines, were cultured with autologous monocytes or AMs as antigen-presenting cells. In vitro allergen-induced proliferation and cytokine production were evaluated in the presence of B7-blocking reagents. Results: Allergic individuals had a significantly higher proportion of AMs expressing the CD80 molecule than control subjects (28.5% ± 14.8% vs 1.4% ± 1.2%; P < .001), whereas no difference was observed in CD86 expression (2.0% ± 2.3% vs 1.1% ± 0.6; P > .1). In a large proportion of the asthmatic subjects we studied, AMs were presenting soluble antigens (tetanus toxoid and streptolysin-O) to freshly isolated T cells more efficiently than AMs from nonatopic control subjects. Finally, both T-cell proliferation and cytokine production of D pteronyssinus- specific established T-cell lines were inhibited by a CD80-blocking antibody in a dose-dependent manner. Conclusion: Costimulation by means of CD80 expressed by AMs is probably involved in the amplification of the allergen-specific T-lymphocyte response in the airways of asthmatic subjects. (J Allergy Clin Immunol 1999;103:1136-42.)