Fibroblasts enhance the in vitro survival of human memory and naïve B cells by maintaining intracellular levels of glutathione

To gain insight into the mechanism of memory B cell survival, we cultured highly purified subpopulations of tonsillar B cells with tonsillar fibroblasts. The fibroblasts greatly enhanced the survival of memory and na?ve B cells but did not delay the rapid apoptosis of germinal center B cells. B cell activation was not observed during the period of culture, as shown by the absence of activation markers and of cycling cells. These findings were reproduced when the B cells were physically separated from the fibroblasts by a semi-permeable transwell-membrane, indicating that the survival factor(s) were diffusible. Several cytokines including IL-6, IL-15, and VEGF were tested for survival activity but none could replace the fibroblasts. However, the addition of reduced glutathione (GSH) to the na?ve and memory B cells significantly enhanced their survival, and depletion of GSH resulted in rapid loss of B cell viability. Furthermore, intracellular glutathione levels were maintained when the B cells were co-cultured with fibroblasts. Our results suggest that glutathione plays an important role in the survival of memory and na?ve B cells in the presence of stromal cells.     

Expression of (pro)renin receptor in human erythroid cell lines and its increased protein accumulation by interferon-γ

The renin-angiotensin system is known to enhance erythropoiesis. (Pro)renin receptor ((P)RR), a specific receptor for renin and prorenin, has recently been identified. However, expression of (P)RR in erythroid cells has not been studied. The aim of the present study is to clarify expression of (P)RR in erythroid cells, and the effects of erythropoietin, angiotensin II, transforming growth factor-β1 (TGF-β1), interferon-γ (IFN-γ) and interleukin-1β (IL-1β) on its expression. Western blot analysis showed that (P)RR protein was expressed in human cultured erythroid cell lines, YN-1 and YN-1-0-A (a clonal variant cell line of YN-1). Erythropoietin (1IU/ml) increased (P)RR mRNA expression levels in YN-1-0-A cells (1.7-fold increase compared with control), but angiotensin II did not. Treatment of YN-1-0-A cells with IFN-γ (10ng/ml) for 48h increased the expression levels of (P)RR protein significantly (1.4-fold increase compared with control), whereas it had no significant effects on expression levels of (P)RR mRNA. Treatment of YN-1-0-A cells with TGF-β1 or IL-1β for 24 or 48h had no significant effects on expression levels of (P)RR. The present study has shown for the first time expression of (P)RR in erythroid cells, raising the possibility that (P)RR may have a role in erythropoiesis and the pathophysiology of certain types of anemia.     

Phosphodiesterase 7A1 is expressed in human CD4+ naïve T cells at higher levels than in CD4+ memory cells and is not required during their CD3/CD28-dependent activation

PDE7A1 is a cAMP-hydrolyzing phosphodiesterase expressed in lymphoid tissue, where its possible role during T cell activation remains unclear. We have characterized the functional relevance of PDE7A1 in the na?ve (CD4+CD45RA+) and memory (CD4+CD45RO+) subsets of human peripheral CD4+ T cells during CD3/CD28-dependent stimulation. Our results indicate that PDE7A1 is expressed in resting na?ve CD4+ T cells at higher levels than in the corresponding memory cells and that levels of PDE7A1 mRNA are not upregulated upon CD3/CD28 mediated stimulation of these T cell subsets. Treatment with a selective inhibitor of PDE7A1 does not impair CD3/CD28 induced activation of na?ve or memory CD4+ T cells, nor does it increase intracellular cAMP in CD4+ T cells. We conclude that PDE7A1 is not required during CD3/CD28-dependent activation of na?ve and memory CD4+ T cells, but cannot rule out other regulatory roles of PDE7A1 during maturation of CD4+ T cells.     

Suppression of iNOS expression by fucoidan is mediated by regulation of p38 MAPK,JAK/STAT,AP-1 and IRF-1, and depends on up-regulation of scavenger receptor B1 expression in TNF-α- and IFN-γ-stimulated C6 glioma cells

In neurodegenerative disorders, activated glial cells overproduce nitric oxide (NO), which causes neurotoxicity. Inducible NO synthase (iNOS) is a potential therapeutic target in neurodegenerative diseases. Here, we examined the action of fucoidan, a high-molecular-weight sulfated polysaccharide, on tumor necrosis factor-α (TNF-α)- and interferon-γ (IFN-γ)-induced NO production in C6 glioma cells. Fucoidan suppressed TNF-α- and IFN-γ-induced NO production and iNOS expression. In addition, fucoidan inhibited TNF-α- and IFN-γ-induced AP-1, IRF-1, JAK/STAT and p38 mitogen-activated protein kinase (MAPK) activation and induced scavenger receptor B1 (SR-B1) expression. Blocking of SR-B1 did not reverse the inhibitory effect of fucoidan on TNF-α- and IFN-γ- stimulated NO production. However, inhibition of SR-B1 expression by siRNA increased iNOS expression and p38 phosphorylation in TNF-α- and IFN-γ-stimulated C6 cells.Overall, p38 MAPK, AP-1, JAK/STAT and IRF-1 play an important role in the inhibitory effect of fucoidan on TNF-α- and IFN-γ-stimulated NO production, and intracellular SR-B1 expression may be related to the inhibition of iNOS expression by fucoidan via regulation of p38 phosphorylation. The present results also suggest that fucoidan could be a potential therapeutic agent for treating inflammatory-related neuronal injury in neurological disorders.