Differential modulation of a radiation-induced bystander effect in glioblastoma cells by pifithrin-alpha and wortmannin

The implication of radiation-induced bystander effect (RIBE) for both radiation protection and radiotherapy has attracted significant attention, but a key question is how to modulate the RIBE. The present study found that, when a fraction of glioblastoma cells in T98G population were individually targeted with precise helium particles through their nucleus, micronucleus (MN) were induced and its yield increased non-linearly with radiation dose. After co-culturing with irradiated cells, additional MN could be induced in the non-irradiated bystander cells and its yield was independent of irradiation dose, giving direct evidence of a RIBE. Further results showed that the RIBE could be eliminated by pifithrin-alpha (p53 inhibitor) but enhanced by wortmannin (PI3K inhibitor). Moreover, it was found that nitric oxide (NO) contributed to this RIBE, and the levels of NO of both irradiated cells and bystander cells could be extensively diminished by pifithrin-alpha but insignificantly reduced by wortmannin. Our results indicate that RIBE can be modulated by p53 and PI3K through a NO-dependent and NO-independent pathway, respectively. (C) 2009 Elsevier B.V. All rights reserved.

5-aryl-pyrazolo[3,4-b]pyridazines: Potent inhibitors of glycogen synthase kinase-3 (GSK-3)

Introduction of a nitrogen atom into the 6-position of a series of pyrazolo[3,4-b]pyridines led to a dramatic improvement in the potency of GSK-3 inhibition. Rationalisation of the binding mode suggested participation of a putative structural water molecule, which was subsequently confirmed by X-ray crystallography. (C) 2003 Elsevier Science Ltd. All rights reserved.

3-anilino-4-arylmaleimides: Potent and selective inhibitors of glycogen synthase kinase-3 (GSK-3)

Potent 3-anilino-4-arylmaleimide glycogen synthase kinase-3 (GSK-3) inhibitors have been prepared using automated array methodology. A number of these are highly selective, having little inhibitory potency against more than 20 other protein kinases. (C) 2001 Elsevier Science Ltd. All rights reserved.

Selective small molecule inhibitors of glycogen synthase kinase-3 modulate glycogen metabolism and gene transcription

Background: Glycogen synthase kinase-3 (GSK-8) is a serine/threonine protein kinase, the activity of which is inhibited by a variety of extracellular stimuli including insulin, growth factors, cell specification factors and cell adhesion. Consequently, inhibition of GSK-3 activity has been proposed to play a role in the regulation of numerous signalling pathways that elicit pleiotropic cellular responses. This report describes the identification and characterisation of potent and selective small molecule inhibitors of GSK-3.

Non-thiazolidinedione antihyperglycaemic agents. Part 3: The effects of stereochemistry on the potency of alpha-methoxy-beta-phenylpropanoic acids.

Rhizopus delemar lipase catalyzed ester hydrolysis of the alpha-methoxy-beta-phenylpropanoate (I) affords the (R)-(+) and (S)-(-) isomers in > 84% enantiomeric excess. Abs. stereochem. was detd. by a single crystal X-ray anal. of a related synthetic analog. The activity of these two enantiomers on glucose transport in vitro and as anti-diabetic agents in vivo is reported and their unexpected equivalence attributed to an enzyme-mediated stereospecific isomerization of the (R)-(+) isomer. Binding studies using recombinant human PPAR-gamma (peroxisomal proliferator activated receptor gamma), now established as a mol. target for this compd. class, indicate a 20-fold higher binding affinity for the (S) antipode relative to the (R) antipode.