Gene expression profiles of normal human fibroblasts after exposure to ionizing radiation: a comparative study of low and high doses

Several types of cellular responses to ionizing radiation, such as the adaptive response or the bystander effect, suggest that low-dose radiation may possess characteristics that distinguish it from its high-dose counterpart. Accumulated evidence also implies that the biological effects of low-dose and high-dose ionizing radiation are not linearly distributed. We have investigated, for the first time, global gene expression changes induced by ionizing radiation at doses as low as 2 cGy and have compared this to expression changes at 4 Gy. We applied cDNA microarray analyses to G1-arrested normal human skin fibroblasts subjected to X irradiation. Our data suggest that both qualitative and quantitative differences exist between gene expression profiles induced by 2 cGy and 4 Gy. The predominant functional groups responding to low-dose radiation are those involved in cell-cell signaling, signal transduction, development and DNA damage responses. At high dose, the responding genes are involved in apoptosis and cell proliferation. Interestingly, several genes, such as cytoskeleton components ANLN and KRT15 and cell-cell signaling genes GRAP2 and GPR51, were found to respond to low-dose radiation but not to high-dose radiation. Pathways that are specifically activated by low-dose radiation were also evident. These quantitative and qualitative differences in gene expression changes may help explain the non-linear correlation of biological effects of ionizing radiation from low dose to high dose.     

Leukemic cell products down-regulate human dendritic cell differentiation

The microenvironment produced by solid tumors is inhibitory to the immune system, inducing dendritic cell (DC) alterations, but there is a paucity of information regarding haematological malignances. The aim of this study was to investigate DC differentiation under the influence of leukemic cell products. Monocytes from healthy volunteers were cultured in the presence of IL-4 and GM-CSF for the generation of immature DCs. Supernatants from leukemic cultures were added to monocyte cultures during differentiation. The lineages used were K562, a chronic myeloid leukemia, HL-60, a promyelocytic leukemia and DAUDI, originated from Burkitt lymphoma. It was observed that the expression of CD14 remained high and the CD1a was low in the presence of tumor supernatants, while non-malignant supernatants did not affect these parameters. Furthermore, IL-1β and TNF-α production by monocytes during differentiation was increased by the presence of tumor supernatants. The modifications on CD14 and CD1a expressions could be mimicked by the addition of exogenous IL-1β and partially inhibited by the neutralization of IL-1β. These results suggest that soluble products from leukemic cells interfere with DC differentiation and, in the present work, this effect could be mediated by monocyte-derived IL-1β in response to tumor supernatants.     

Heterologous expression of glycoside hydrolase family 2 and 42 β-galactosidases of lactic acid bacteria in Lactococcus lactis

This study characterized a glycoside hydrolase family 42 (GH42) β-galactosidase of Lactobacillus acidophilus (LacA) and compared lactose hydrolysis, hydrolysis of oNPG, pNPG and pNPG-analogues and galactooligosaccharides (GOSs) formation to GH2 β-galactosidases of Streptococcus thermophilus (LacZ type), Lactobacillus plantarum and Leuconostoc mesenteroides subsp. cremoris (both LacLM type). Beta-galactosidases were heterologously expressed in Lactococcus lactis using a p170 derived promoter; experiments were performed with L. lactis crude cell extract (CCE). The novel GH42 β-galactosidase of Lb. acidophilus had lower activity on lactose, oNPG and pNPG but higher relative activity on pNP analogues compared to GH2 β-galactosidases, and did not transgalactosylate at high lactose concentrations. Temperature and pH optima for lactose hydrolysis varied between GH2 β-galactosidases. oNPG and pNPG were the preferred substrates for hydrolysis; in comparison, activity on pNPG-analogues was less than 1.5%. GH2 β-galactosidases formed structurally similar GOS with varying preferences.     

Naphthylchalcones induce apoptosis and caspase activation in a leukemia cell line: The relationship between mitochondrial damage, oxidative stress, and cell death

In this study, we investigated the effects of 24 chalcone derivatives from 2-naphthylacetophenone toward a lymphoblastic leukemia cell line (L1210). Three compounds, called R7, R13, and R15, presented concentration- and time-dependent cytotoxicity and induced cellular death by apoptosis via mitochondrial injury and oxidative stress. The effects of these compounds appear to occur through different mechanisms because R13 and R7 induced a greater disturbance of mitochondrial potential, and all compounds induced disturbances of cellular ATP content and increased caspase-3 activity before cellular death. These compounds also interfered with antioxidant enzymes activities and GSH content through different mechanisms.     

Effect of Electroconvulsive Shock on Mitochondrial Respiratory Chain in Rat Brain

It is well described that impairment of energy production has been implicated in the pathogenesis of a number of diseases. Although several advances have occurred over the past 20 years concerning the use and administration of electroconvulsive therapy (ECT) to minimize its side effects, little progress has been made in understanding its mechanism of action. In this work, our aim was to measure the activities of mitochondrial respiratory chain complexes II and IV and succinate dehydrogenase from rat brain after acute and chronic electroconvulsive shock (ECS). Our results showed that mitochondrial respiratory chain enzymes activities were increased after acute ECS in hippocampus, striatum and cortex of rats. Besides, we also demonstrated that complex II activity was increased after chronic ECS in cortex, while hippocampus and striatum were not affected. Succinate dehydrogenase, however, was inhibited after chronic ECS in striatum, activated in cortex and not affected in hippocampus. Finally, complex IV was not affected by chronic ECS in hippocampus, striatum and cortex. Our findings demonstrated that brain metabolism is altered by ECS.     

Decreased Creatine Kinase Activity Caused by Electroconvulsive Shock

Although several advances have occurred over the past 20 years concerning the use and administration of electroconvulsive therapy to minimize side effects of this treatment, little progress has been made in understanding its mechanism of action. Creatine kinase is a crucial enzyme for brain energy homeostasis, and a decrease of its activity has been associated with neuronal death. This work was performed in order to evaluate creatine kinase activity from rat brain after acute and chronic electroconvulsive shock. Results showed an inhibition of creatine kinase activity in hippocampus, striatum and cortex, after acute and chronic electroconvulsive shock. Our findings demonstrated that creatine kinase activity is altered by electroconvulsive shock.     

Synapse development: still looking for the forest, still lost in the trees

Synapse development in the vertebrate central nervous system is a highly orchestrated process occurring not only during early stages of brain development, but also (to a lesser extent) in the mature nervous system. During development, the formation of synapses is intimately linked to the differentiation of neuronal cells, the extension of their axons and dendrites, and the course wiring of the nervous system. Subsequently, the stabilization, elimination, and strengthening of synaptic contacts is coupled to the refinement of axonal and dendritic arbors, to the establishment of functionally meaningful connections, and probably also to the day-to-day acquisition, storage, and retrieval of memories, higher order thought processes, and behavioral patterns.The authors acknowledge the support of the NIH (grant no. HD38760 DA016758) to C.C.G., the Ruth L. Kirchstein National Research Service Award (NRSA) to C.L.W., and the United States Israel Binational Science Foundation (grant no. 2003176) to C.C.G. and N.E.Z.