IgM and IgG but not cytokine secretion is restricted to the CD27+ B lymphocyte subset.

In a recent study we reported that CD27 is expressed on a subpopulation of human B lymphocytes and presented circumstantial phenotypic evidence that CD27 expression may be acquired late during B cell differentiation. Here we present functional data showing that, after in vitro stimulation, CD27+ but not CD27- B cells secrete large amounts of both IgM and IgG. Using double immunofluorescence staining of CD27 and IgD, three functionally different B cell subsets representing distinct stages of B cell differentiation can be isolated: 1) the CD27- IgD+ B cells, which do not secrete appreciable Ig; 2) the CD27+IgD+ B cells, which exclusively secrete IgM; and 3) the CD27+IgD- B cells, which comprise the IgG-producing cells. Furthermore, costimulation of CD27- B cells with low m.w. B cell growth factor, in the presence or in the absence of a CD40 mAb, does not induce these cells to become Ig-secreting cells. Although CD27- B cells hardly secrete Ig of any isotype in response to Staphylococcus aureus+IL-2, these cells proliferate vigorously and express the IL-2R alpha chain (CD25) under these stimulatory conditions. Furthermore, both CD27- and CD27+ B cells are capable of producing similar amounts of IL-6 and TNF-alpha. Taken together, these findings indicate that CD27 is a unique non-Ig surface marker discriminating naive from primed B lymphocytes. Furthermore, the capacity to proliferate and to secrete the B cell differentiation factors IL-6 and TNF-alpha already exists at an early B cell differentiation stage at which the cells lack CD27 expression and are not induced to produce Ig.     

Conventional and prospective molecular targets in antitumour drug design. Concepts in antitumour research.

To introduce a rationale in a drug development program the molecular base of the pathological lesion must be carefully considered both for selecting test compounds and to apply the most appropriate assay systems. From the beginning of antitumour drug research the principal aim has always been to select chemical compounds which could selectively inhibit tumour growth. This strategy was in full harmony with the concept that tumours are build up by fast proliferating cells. Research based on this concept has resulted in the development of more than 40 cytostatic agents, which are rather diverse in their chemical properties, but all act on one of the molecular mechanisms participating in cell proliferation. However the unsatisfactory therapeutic responses which could be obtained by the cytostatic agents focused the attention on those molecular events in the tumour cells which may be more closely related to the progression of the malignant disease.     

Oxidized hemoglobin forms contribute to NLRP3 inflammasome-driven IL-1β production upon intravascular hemolysis

Damage associated molecular patterns (DAMPs) are released form red blood cells (RBCs) during intravascular hemolysis (IVH). Extracellular heme, with its pro-oxidant, pro-inflammatory and cytotoxic effects, is sensed by innate immune cells through pattern recognition receptors such as toll-like receptor 4 and nucleotide-binding domain and leucine rich repeat containing family, pyrin domain containing 3 (NLRP3), while free availability of heme is strictly controlled. Here we investigated the involvement of different hemoglobin (Hb) forms in hemolysis-associated inflammatory responses.We found that after IVH most of the extracellular heme molecules are localized in oxidized Hb forms. IVH was associated with caspase-1 activation and formation of mature IL-1β in plasma and in the liver of C57BL/6 mice. We showed that ferrylHb (FHb) induces active IL-1β production in LPS-primed macrophages in vitro and triggered intraperitoneal recruitment of neutrophils and monocytes, caspase-1 activation and active IL-1β formation in the liver of C57BL/6 mice. NLRP3 deficiency provided a survival advantage upon IVH, without influencing the extent of RBC lysis or the accumulation of oxidized Hb forms. However, both hemolysis-induced and FHb-induced pro-inflammatory responses were largely attenuated in Nlrp3^?/? mice.Taken together, FHb is a potent trigger of NLRP3 activation and production of IL-1β in vitro and in vivo, suggesting that FHb may contribute to hemolysis-induced inflammation. Identification of RBC-derived DAMPs might allow us to develop new therapeutic approaches for hemolytic diseases.     

Hydroxyl free radicals induce cell differentiation in SK-N-MC neuroblastoma cells

The SK-N-MC cell line is frequently used as a model of neuronal differentiation induced by 5-bromodeoxyuridine (BrdU). In this study, the differentiation properties of this cell line were investigated under hydroxyl free radical generation, and compared to BrdU treatment. Hydroxyl free radicals were generated in the cultures by the Fenton reaction, i.e. by simultaneous addition of ADP-Fe2+ complex and H2O2. Microscopic morphological signs, as well as the acetylcholinesterase and ganglioside sialidase activities were considered as markers of neuronal differentiation of this cholinergic neuroblastoma cell line. Apart from the altered morphological appearance, the marker enzymes displayed significant increases after both types of intervention. We suggest that hydroxyl free radicals can induce in vitro cell differentiation. They apparently play a more complex role in cell physiology than simply causing oxidative damage.     

Supression of hemin-mediated oxidation of low-density lipoprotein and subsequent endothelial reactions by hydrogen sulfide (H2S)

Heme-mediated oxidative modification of low-density lipoprotein (LDL) plays a crucial role in early atherogenesis. It has been shown that hydrogen sulfide (H₂S) produced by vascular smooth muscle cells is present in plasma at a concentration of about 50 µmol/L. H₂S is a strong reductant which can react with reactive oxygen species like superoxide anion and hydrogen peroxide. The current study investigated the effect of H₂S on hemin-mediated oxidation of LDL and oxidized LDL (oxLDL)-induced endothelial reactions. H₂S dose dependently delayed the accumulation of lipid peroxidation products—conjugated dienes, lipid hydroperoxides (LOOH), and thiobarbituric acid reactive substances—during hemin-mediated oxidation. Moreover, H₂S decreased the LOOH content of both oxidized LDL and lipid extracts derived from soft atherosclerotic plaque, which was accompanied by reduced cytotoxicity. OxLDL-mediated induction of the oxidative stress responsive gene, heme oxygenase-1, was also abolished by H₂S. Finally we have shown that H₂S can directly protect endothelium against hydrogen peroxide and oxLDL-mediated endothelial cytotoxicity. These results demonstrate novel functions of H₂S in preventing hemin-mediated oxidative modification of LDL, and consequent deleterious effects, suggesting a possible antiatherogenic action of H₂S.     

Iron homeostasis in chronic inflammation

Inflammation induced anemia and resistance to erythropoietin are common features in patients with chronic kidney disease (CKD). Elevated levels of cytokines and enhanced oxidative stress, conditions associated with inflammatory states, are implicated in the development of anemia. Accumulating evidence suggests that activation of cytokine cascade and the associated acute-phase response, as it often occurs in patients with CKD, divert iron from erythropoiesis to storage sites within the reticuloendothelial system leading to functional iron deficiency and subsequently to anemia or resistance to erythropoietin. Other processes have also been shown to be involved in the pathogenesis of anemia provoked by the activated immune system including an inhibition of erythroid progenitor proliferation and differentiation, a suppression of erythropoietin production and a blunted response to erythropoietin. The present review concerns the underlying alterations in iron metabolism induced by chronic inflammation that result in anemia.