Reactive oxygen species (ROS) represent reactive products belonging to the partial reduction of oxygen. It has been reported that ROS are involved in different signaling pathways to control cellular stability. Under normal conditions, the correct function of redox systems leads to the prevention of cell oxidative damage. When ROS exceed the antioxidant defense system, cellular stress occurs. The cellular redox impairment is strictly related to tumorigenesis. Tumor cells, through the generation of hydrogen peroxide, tend to the alteration of cell cycle phases and, finally to cancer progression. In adults, the most common form of primary malignant brain tumors is represented by gliomas. The gliomagenesis is characterized by numerous molecular processes all characterized by an altered production of growth factor receptors. The difficulty to treat brain cancer depends on several biological mechanisms such as failure of drug delivery through the blood-brain barrier, tumor response to chemotherapy, and intrinsic resistance of tumor cells. Understanding the mechanisms of ROS action could allow the formulation of new therapeutic protocols to treat brain gliomas.

Background/aims: The erythrocyte is a cell exposed to a high level of oxygen pressure and to oxidative chemical agents. This stress involves SH-groups oxidation, cell shrinkage by activation of K-Cl cotransport (KCC) and elevation of the band 3 tyrosine phosphorylation level. The aim of our study was to test whether oxidative stress could influence band 3-mediated anion transport in human red blood cells. Methods: To evaluate this hypothesis, normal and pathological (glucose 6 phosphate dehydrogenase (G6PDH) defficient) erythrocytes were treated with known sulphydryl-blocking or thiol-oxidizing agents, such as N-ethylmaleimide (NEM), azodicarboxylic acid bis[dimethylamide] (diamide), orthovanadate, Mg 2+ and tested for sulphate (SO 4 -) uptake, K + efflux, G6PDH activity and glutathione (GSH) concentration. Results: In normal red blood cells, the rate constants of SO 4 -uptake decreased by about 28 % when cells were incubated with NEM, diamide and orthovanadate. In G6PDH-deficient red blood cells, in which oxidative stress occurs naturally, the rate constant of sulphate uptake was decreased by about 40% that of normal red cells. Addition of oxidizing and phosphatase inhibitor agents to pathological erythrocytes further decreased anion transport. In contrast, G6PDH activity was increased under oxidative stress in normal as well as in pathological cells and was lower in the presence of exogenous Mg 2+

TNF-α is a mediator of lethality in experimental infections by group B streptococcus (GBS), an important human pathogen. Little is known of signal transduction pathways involved in GBS-induced TNF-α production. Here we investigate the role of mitogen-activated protein kinases (MAPKs) and NF-κB in TNF-α production by human monocytes stimulated with GBS or LPS, used as a positive control. Western blot analysis of cell lysates indicates that extracellular signal-regulated kinase 1/2 (ERK 1/2), p38, and c-Jun N-terminal kinase MAPKs, as well as IκBα, became phosphorylated, and hence activated, in both LPS- and GBS-stimulated monocytes. The kinetics of these phosphorylation events, as well as those of TNF-α production, were delayed by 30–60 min in GBS-stimulated, relative to LPS-stimulated, monocytes. Selective inhibitors of ERK 1/2 (PD98059 or U0126), p38 (SB203580), or NF-κB (caffeic acid phenetyl ester (CAPE)) could all significantly reduce TNF-α production, although none of the inhibitors used alone was able to completely prevent TNF-α release. However, this was completely blocked by combinations of the inhibitors, including PD98059-SB203580, PD98059-CAPE, or SB203580-CAPE combinations, in both LPS- and GBS-stimulated monocytes. In conclusion, our data indicate that the simultaneous activation of multiple pathways, including NF-κB, ERK 1/2, and p38 MAPKs, is required to induce maximal TNF-α production. Accordingly, in septic shock caused by either GBS or Gram-negative bacteria, complete inhibition of TNF-α release may require treatment with drugs or drug combinations capable of inhibiting multiple activation pathways.

The effect of prostaglandin E 2 (PGE 2 ) in regulating the synthesis of the pro-inflammatory chemokine interleukin-8 (IL-8) in T lymphocytes is not yet defined, even though it may reduce or enhance IL-8 synthesis in other cell types. Here, we demonstrate that, in human T cells, PGE 2 induced IL-8 mRNA transcription through prostaglandin E 2 receptors 1-and 4-dependent signal transduction pathways leading to the activation of the transcription factor C/EBP homologous protein (CHOP), never before implicated in IL-8 transcription. Several kinases, including protein kinase C, Src family tyrosine kinases, phosphatidylinositol 3-kinase, and p38 MAPK, were involved in PGE 2 -induced CHOP activation and IL-8 production. The transactivation of the IL-8 promoter by CHOP was NF-B-independent. Our data suggest that PGE 2 acts as a potent pro-inflammatory mediator by inducing IL-8 gene transcription in activated T cells through different signal transduction pathways leading to CHOP activation. These findings show the complexity with which PGE 2 regulates IL-8 synthesis by inhibiting or enhancing its production depending on the cell types and environmental conditions.

To determine whether proliferative patterns in flat rectal mucosal samples can predict the recurrence of adenomatous colorectal polyps, after polypectomy, biopsy specimens from normal looking rectal mucosa were obtained at endoscopy from 55 patients diagnosed for the first time as having adenomatous colorectal polyps. Epithelial cell proliferation was assessed in biopsy specimens through 3H-thymidine autoradiography. After polypectomy, patients were followed for 24 months and underwent complete colonoscopy every 6 months to detect and remove any metachronous lesions. In 40 patients second biopsy specimens were taken during one of the follow up colonoscopies to evaluate the stability of proliferative indices over time. The ratio of labelled (S phase) to total cells (labelling index) for the entire crypt, as well as ratios for each of the five equal compartments into which the crypt had been divided longitudinally, was calculated for each patient. Mean labelling indices for upper crypt compartments 3 and 4+5 in the 22 patients in whom polyps recurred were significantly higher (respectively p<005 and p