Microglial secreted cathepsin B induces neuronal apoptosis

Activated microglia release a number of substances that can influence neuronal signalling and survival. Here we report that microglia stimulated with the peptide chromogranin A (CGA), secreted the cysteine protease, cathepsin B. Conditioned medium from CGA exposed microglia was neurotoxic to the HT22 hippocampal cell line and to primary cultures of cerebellar granule neurones. In both neuronal cell types, the neurotoxicity could be significantly attenuated with z-FA-fmk or by depletion of microglial conditioned medium with cathepsin B antibody. Conditioned medium from activated microglia or cathepsin B alone induced neuronal apoptosis and caspase 3 activation. Our data indicate that CGA-activated microglia can trigger neuronal apoptosis and that this may be mediated through the secretion of cathepsin B. Since cathepsins may also play a role in the amyloidogenic processing of amyloid precursor protein, these results may have significance for tissue damage and neuronal loss in the neuropathology of Alzheimer's disease.     

Changes in plasma membrane fluidity of immortal rodent cells induced by anticancer drugs doxorubicin, aclarubicin and mitoxantrone

The aim of this study was to examine the effect of three structurally different anticancer drugs-the pro-oxidative anthracyclines doxorubicin (DOX) and aclarubicin (ACL), and antioxidative anthraquinone mitoxantrone (MTX) on the fluidity of plasma membrane of immortalized rodent fibroblasts using fluorescence spectroscopy and electron spin resonance (ESR) techniques. Two kinds of fluorescent probes (TMA-DPH and 12-AS) and spin labels (5-DS and methyl-12-DS) were used to monitor fluidity in the hydrophobic core and in the polar headgroup region of the lipid bilayer. Immortalized hamster B14 and NIH 3T3 mouse fibroblasts were exposed to DOX, ACL and MTX. We demonstrate that these drugs influence predominantly the hydrophobic core of the lipid bilayer, inducing significant decrease in its fluidity at low concentrations (2-5 microM). A decreased membrane fluidity at the surface of the lipid bilayer was observed only at a higher concentration (20 microM) of the drugs, which indicates that DOX, ACL and MTX intercalate mainly into the hydrophobic core of the membrane, thereby perturbing its structure.     

An antitumor promoter from Moringa oleifera Lam.

In the course of studies on the isolation of bioactive compounds from Philippine plants, the seeds of Moringa oleifera Lam. were examined and from the ethanol extract were isolated the new O-ethyl-4-(α- -rhamnosyloxy)benzyl carbamate (1) together with seven known compounds, 4(α- -rhamnosyloxy)-benzyl isothiocyanate (2), niazimicin (3), niazirin (4), β-sitosterol (5), glycerol-1-(9-octadecanoate) (6), 3-O-(6′-O-oleoyl-β- -glucopyranosyl)-β-sitosterol (7), and β-sitosterol-3-O-β- -glucopyranoside (8). Four of the isolates (2, 3, 7, and 8), which were obtained in relatively good yields, were tested for their potential antitumor promoting activity using an in vitro assay which tested their inhibitory effects on Epstein–Barr virus-early antigen (EBV-EA) activation in Raji cells induced by the tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). All the tested compounds showed inhibitory activity against EBV-EA activation, with compounds 2, 3 and 8 having shown very significant activities. Based on the in vitro results, niazimicin (3) was further subjected to in vivo test and found to have potent antitumor promoting activity in the two-stage carcinogenesis in mouse skin using 7,12-dimethylbenz(a)anthracene (DMBA) as initiator and TPA as tumor promoter. From these results, niazimicin (3) is proposed to be a potent chemo-preventive agent in chemical carcinogenesis.