Selective recruitment of p160 coactivators on glucocorticoid-regulated promoters in Schwann cells

In the nervous system, glucocorticoid hormones play a major role during development and throughout life. We studied the mechanisms of action of the glucocorticoid receptor (GR) and its interactions with p160 coactivator family members [steroid receptor coactivator (SRC)-1 (a and e), SRC-2 and SRC-3] in mouse Schwann cells (MSC80). We found that the three p160s were expressed in MSC80 cells. We have shown by functional overexpression and RNA interference experiments that the recruitment of these coactivators by the GR is promoter dependent. A minimal promoter containing two glucocorticoid response elements, (GRE)2-TATA, recruits SRC-1 (a and e) and SRC-3, whereas SRC-2 is excluded. Within the context of the more complex mouse mammary tumor virus promoter, GR recruits SRC-1e and SRC-2, whereas SRC-1a and SRC-3 are not implicated. Furthermore, we have identified cytosolic aspartate aminotransferase as a GR target gene in MSC80 cells by microarray experiments. The GR recruits exclusively SRC-1e in the context of the cytosolic aspartate aminotransferase promoter. Because SRC-1 is the omnipresent coactivator of GR, we further investigated the interactions between GR and this coactivator in Schwann cells by reporter assays and immunocytochemistry experiments with deleted forms of SRC-1. We have shown that SRC-1 unexpectedly interacts with GR via its two nuclear receptor binding domains, thus providing a novel mechanism of GR signaling within the nervous system.     

Immunity,ageing and cancer

Compromised immunity contributes to the decreased ability of the elderly to control infectious disease and to their generally poor response to vaccination. It is controversial as to how far this phenomenon contributes to the well-known age-associated increase in the occurrence of many cancers in the elderly. However, should the immune system be important in controlling cancer, for which there is a great deal of evidence, it is logical to propose that dysfunctional immunity in the elderly would contribute to compromised immunosurveillance and increased cancer occurrence. The chronological age at which immunosenescence becomes clinically important is known to be influenced by many factors, including the pathogen load to which individuals are exposed throughout life. It is proposed here that the cancer antigen load may have a similar effect on "immune exhaustion" and that pathogen load and tumor load may act additively to accelerate immunosenescence. Understanding how and why immune responsiveness changes in humans as they age is essential for developing strategies to prevent or restore dysregulated immunity and assure healthy longevity, clearly possible only if cancer is avoided. Here, we provide an overview of the impact of age on human immune competence, emphasizing T-cell-dependent adaptive immunity, which is the most sensitive to ageing. This knowledge will pave the way for rational interventions to maintain or restore appropriate immune function not only in the elderly but also in the cancer patient.     

Essential‐Oil Composition of the Tunisian Endemic Cypress (Cupressus sempervirens L. var. numidica Trab.)

The essential oils isolated from leaves, wood, and cones of the Tunisian endemic cypress Cupressus sempervirens L. var. numidica Trab. collected from three natural populations were characterized by GC‐FID and GC/MS analyses. In the wood, leaf, and cone oils, 38, 35, and 26 constituents, representing 94.4, 97.8, and 98.5% of the total oil composition, respectively, were identified. Monoterpenes constituted the major fraction of the oils from all organs and for all populations. The oils were found to be of an α‐pinene (64.2%)/δ‐car‐3‐ene (11.1%) chemotype with considerable contents of α‐humulene (3.4%) in the leaf oil, cedrol (2.8%) in the wood oil, and sabinene (3.2%) in the cone oil, respectively. α‐Pinene, δ‐car‐3‐ene, limonene, carvacrol methyl ether, α‐humulene, and α‐amorphene were the main components that differentiated the oils of the three organs in the cypress of Makthar.     

cAMP induces ABCA1 phosphorylation activity and promotes cholesterol efflux from fibroblasts

ATP-binding cassette transporter A1 (ABCA1) plays a crucial role in apoA-I lipidation, a key step in reverse cholesterol transport. cAMP induces apoA-I binding activity and promotes cellular cholesterol efflux. We investigated the role of the cAMP/protein kinase A (PKA) dependent pathway in the regulation of cellular cholesterol efflux. Treatment of normal fibroblasts with 8-bromo-cAMP (8-Br-cAMP) increased significantly apoA-I-mediated cholesterol efflux, with specificity for apoA-I, but not for cyclodextrin. Concomitantly, 8-Br-cAMP increased ABCA1 phosphorylation in a time-dependent manner. Maximum phosphorylation was reached in <10 min, representing a 260% increase compared to basal ABCA1 phosphorylation level. Forskolin, a known cAMP regulator, increased both cellular cholesterol efflux and ABCA1 phosphorylation. In contrast, H-89 PKA inhibitor reduced cellular cholesterol efflux by 70% in a dose-dependent manner and inhibited almost completely ABCA1 phosphorylation. To determine whether naturally occurring mutants of ABCA1 may affect its phosphorylation activity, fibroblasts from subjects with familial HDL deficiency (FHD, heterozygous ABCA1 defect) and Tangier disease (TD, homozygous/compound heterozygous ABCA1 defect) were treated with 8-Br-cAMP or forskolin. Cellular cholesterol efflux and ABCA1 phosphorylation were increased in FHD but not in TD cells. Taken together, these findings provide evidence for a link between the cAMP/PKA-dependent pathway, ABCA1 phosphorylation, and apoA-I mediated cellular cholesterol efflux.     

T regulatory-1 cells induce IgG4 production by B cells: role of IL-10

The study was aimed to find out whether T cells with a regulatory profile could regulate the secretion of IgG4. Using tetanus Ag we found that PBMC of healthy human donors responded to exogenous IL-10 by down-regulating IgG1 and increasing IgG4 secretion. IgE was not affected. To investigate the direct effect of IL-10-producing T cells on B cells, we generated T cell clones (TCC) with two different cytokine profiles: first, IL-10high, IL-2low, IL-4low TCC, and second, IL-10low, IL-2high, IL-4high. The T cell-dependent Ab secretion was measured by coculturing purified CD19+ B cells and the TCC. Interestingly, we found that IgG4 production in the coculture correlated with the TCC production of IL-10 (r2 = 0.352, p = 0.0001), but not with IL-2, IL-4, nor IFN-gamma. IgE showed only a trend with regard to IL-4. Further, there was decreased Ab secretion in the absence of T-B cell contact. IL-10 also induced IgG4 when added to a Th1 TCC-B cell coculture system. The present study thus shows that in T-B cell coculture, IL-10, if induced by the TCC or added to the system, down-regulates the immune response by inducing IgG4 secretion. This establishes a direct implication of IL-10 in humoral hyporesponsiveness, particularly in compartments where the T-B cell interplay determines the subsequent immune response. The correlation between IgG4 and IL-10 (r2 = 0.352) indicates that IL-10 is an important but not the only factor for IgG4 induction.     

Presence and active synthesis of the 67 kDa elastin-receptor in human circulating white blood cells

Early after the identification of the elastin-receptor (El-R) on mesenchymal cells, it was demonstrated that phagocytic cells and lymphocytes could also respond to elastin peptides. Nevertheless, the level of El-R expression has never been demonstrated on immune cells and no data exist whether these cells actively synthesize this El-R. Thus, our aim in the present work was to study the expression and number of El-R on white blood cells (WBC) using a specific 67 kDa El-R antibody and to demonstrate the presence of mRNA corresponding to the gene coding for El-R. Our results show that messenger RNA corresponding to the presumptive gene coding for the 67 kDa El-R subunit could be detected in all three WBC-types investigated. On all of these WBC, the presence of El-R could be demonstrated, however their number and their function varied following the cell type. The presence of El-R is very important for the interaction of circulating cell with the matrix as these cells intervene during atherosclerosis and in host defence.