In mice transgenic for an autoantibody, self-reactive B cells have been shown to be eliminated upon interaction with membrane-bound self-antigens in the periphery as well as in the bone marrow, suggesting that both immature and mature B cells are eliminated by multimerization of surface immunoglobulins (sIg). Activation of mature B cells by antigens may thus require a second signal that inhibits sIg-mediated apoptosis. Such a second signal is likely to be provided by T helper cells, because B-cell tolerance is more easily induced in the absence of T helper cells. To assess the molecular nature of the signal that inhibits sIg-mediated apoptosis, we used anti-IgM-induced apoptotic death of WEHI-231 B lymphoma cells as a model system. Here we report that the signal for abrogating sIg-mediated apoptosis is generated by association of the CD40L molecule on T cells with the CD40 molecule on WEHI-231 cells. T-cell help through CD40 may thus determine whether B cells are eliminated or activated upon interaction with antigens.

Gliomas are the most common and lethal primary tumors of the central nervous system (CNS). Despite current rigorous treatment protocols, effect of chemotherapy has failed to improve patient outcome significantly. Curcumin is a potent antioxidant that possesses both anti-inflammatory and anti-tumor activities, can suppress the initiation, promotion, and metastasis of different tumors. Its anti-tumor properties in various cancer models and negligible toxicity in normal cells make it a promising chemotherapeutic candidate. But the effect and the molecular mechanism of curcumin on gliomas are still recognized limitedly. The goal of the study is to elucidate the inhibitory effect and possible mechanisms of curcumin on glioma. After the treatment of curcumin, glioma cells U251 growth in vitro were significantly inhibited in a dose-dependent manner, and the low dose of curcumin induced G2/M cell cycle arrest. The high dose of curcumin not only enhanced G2/M cell cycle arrest, but also induced S phase of cell cycle arrest. But no obvious pre-G1 peak was observed at the different doses of curcumin. Genome DNA electrophoresis further confirmed that no DNA ladder was formed after the treatment of curcumin in U251 cells. Results of Western blot analysis demonstrated that ING4 expression was almost undetectable in U251 cells, but significantly up-regulated during cell cycle arrest induced by curcumin, and p53 expression was up-regulated followed by induction of p21 WAF-1/CIP-1 and ING4. The results demonstrate that curcumin exerts inhibitory action on glioma cell growth and proliferation via induction of cell cycle arrest instead of induction of apoptosis in a p53-dependent manner, and ING4 possibly is in part involved in the signal pathways.

Highlights d ATP synthase c-subunit leak in Fragile X causes aberrant metabolism d Changes in ATP synthase component stoichiometry regulate protein synthesis rate d Inhibition of the leak normalizes synaptic spine morphology and Fragile X behavior

ABT-737 is a pharmacological inhibitor of the anti-apoptotic activity of B-cell lymphoma-extra large (Bcl-xL) protein; it promotes apoptosis of cancer cells by occupying the BH3-binding pocket. We have shown previously that ABT-737 lowers cell metabolic efficiency by inhibiting ATP synthase activity. However, we also found that ABT-737 protects rodent brain from ischemic injury in vivo by inhibiting formation of the pro-apoptotic, cleaved form of Bcl-xL, ΔN-Bcl-xL. We now report that a high concentration of ABT-737 (1 μM), or a more selective Bcl-xL inhibitor WEHI-539 (5 μM) enhances glutamate-induced neurotoxicity while a low concentration of ABT-737 (10 nM) or WEHI-539 (10 nM) is neuroprotective. High ABT-737 markedly increased ΔN-Bcl-xL formation, aggravated glutamate-induced death and resulted in the loss of mitochondrial membrane potential and decline in ATP production. Although the usual cause of death by ABT-737 is thought to be related to activation of Bax at the outer mitochondrial membrane due to sequestration of Bcl-xL, we now find that low ABT-737 not only prevents Bax activation, but it also inhibits the decline in mitochondrial potential produced by glutamate toxicity or by direct application of ΔN-Bcl-xL to mitochondria. Loss of mitochondrial inner membrane potential is also prevented by cyclosporine A, implicating the mitochondrial permeability transition pore in death aggravated by ΔN-Bcl-xL. In keeping with this, we find that glutamate/ΔN-Bcl-xL-induced neuronal death is attenuated by depletion of the ATP synthase c-subunit. C-subunit depletion prevented depolarization of mitochondrial membranes in ΔN-Bcl-xL expressing cells and substantially prevented the morphological change in neurites associated with glutamate/ΔN-Bcl-xL insult. Our findings suggest that low ABT-737 or WEHI-539 promotes survival during glutamate toxicity by preventing the effect of ΔN-Bcl-xL on mitochondrial inner membrane depolarization, highlighting ΔN-Bcl-xL as an important therapeutic target in injured brain.

AngII (angiotensin II) is a potent neurohormone responsible for cardiac hypertrophy, in which TGF (transforming growth factor)-β serves as a principal downstream mediator. We recently found that ablation of fibulin-2 in mice attenuated TGF-β signalling, protected mice against progressive ventricular dysfunction, and significantly reduced the mortality after experimental MI (myocardial infarction). In the present study, we investigated the role of fibulin-2 in AngII-induced TGF-β signalling and subsequent cardiac hypertrophy. We performed chronic subcutaneous infusion of AngII in fibulin-2 null (Fbln2−/− ), heterozygous (Fbln2+/− ) and WT (wild-type) mice by a mini-osmotic pump. After 4 weeks of subpressor dosage of AngII infusion (0.2 μg/kg of body weight per min), WT mice developed significant hypertrophy, whereas the Fbln2−/− showed no response. In WT, AngII treatment significantly up-regulated mRNAs for fibulin-2, ANP (atrial natriuretic peptide), TGF-β1, Col I (collagen type I), Col III (collagen type III), MMP (matrix metalloproteinase)-2 and MMP-9, and increased the phosphorylation of TGF-β-downstream signalling markers, Smad2, TAK1 (TGF-β-activated kinase 1) and p38 MAPK (mitogen-activated protein kinase), which were all unchanged in AngII-treated Fbln2−/− mice. The Fbln2+/− mice consistently displayed AngII-induced effects intermediate between WT and Fbln2−/− . Pressor dosage of AngII (2 mg/kg of body weight per min) induced significant fibrosis in WT but not in Fbln2−/− mice with comparable hypertension and hypertrophy in both groups. Isolated CFs (cardiac fibroblasts) were treated with AngII, in which direct AngII effects and TGF-β-mediated autocrine effects was observed in WT. The latter effects were totally abolished in Fbln2−/− cells, suggesting that fibulin-2 is essential for AngII-induced TGF-β activation. In conclusion our data indicate that fibulin-2 is essential for AngII-induced TGF-β-mediated cardiac hypertrophy via enhanced TGF-β activation and suggest that fibulin-2 is a potential therapeutic target to inhibit AngII-induced cardiac remodelling.