Bacterial lipopeptides induce nitric oxide synthase and promote apoptosis through nitric oxide-independent pathways in rat macrophages.

Stimulation of resident peritoneal macrophages with S-[2,3-bis(pamitoyloxy)-(2R,2S)-propyl]-N-palmytoyl-(R)-C ysSerLys4 or S(-)[2,3-bis(pamitoyloxy)-(2R,2S)-propyl]-N-palmytoyl-(R)-++ +CysAlaLys4, two synthetic bacterial lipopeptides, promoted the expression of the inducible form of nitric oxide synthase, exhibiting a temporal pattern of nitric oxide release that was delayed with respect to the induction elicited by bacterial lipopolysaccharide. Treatment of macrophages with genistein blocked the nitric oxide synthesis triggered by the lipopeptides or lipopolysaccharide. Simultaneous incubation with lipopolysaccharide and lipopeptide resulted in an antagonistic effect on nitric oxide synthase mRNA levels and on nitrite plus nitrate release to the medium.

Nitric oxide is released in regenerating liver after partial hepatectomy.

The induction of hepatic nitric oxide synthase (NOS) and the biosynthesis of nitric oxide (NO) were studied in liver after partial hepatectomy (PH). NOS activity in the liver remnant was observed 4 to 6 hours after PH, and no differences were evidenced between the proximal and distal surgical areas. The form of NOS expressed in liver was independent of calcium and calmodulin, and the messenger RNA levels were first detected 2 hours after hepatectomy using a probe corresponding to the cytokine-induced macrophage NOS.

Platelet-activating factor: the effector of protein-rich plasma extravasation and nitric oxide synthase induction in rat immune complex peritonitis.

1. The involvement of platelet-activating factor (PAF) in immune complex-induced/polymorphonuclear-mediated tissue injury was studied by use of a reverse passive Arthus (RPA) model in the peritoneal cavity of rats. 2.

Nitric oxide implication in the control of neurosecretion by chromaffin cells.

In this work, we have studied the effects of pure nitric oxide (NO) on the regulation of catecholamine (CA) secretion by chromaffin cells, as well as the possible presence of its synthesizing enzyme L-arginine:NO synthase (NOS) in these cells. Our results show that NO produces a large stimulation of basal CA secretion. This effect was calcium- and concentration-dependent (EC50 = 64 +/- 8 microM) and was not due to nonspecific damage of the tissue by NO.

Cocaine-induced liver injury in mice elicits specific changes in DNA ploidy and induces programmed death of hepatocytes.

Liver injury was induced by a single dose (60 mg/kg) of cocaine in male albino Swiss mice untreated or pretreated with phenobarbital (in drinking water 1 gm/L), for 5 days before cocaine administration. One parameter of liver injury, serum isocitrate dehydrogenase activity, showed sharp increases at 24 hr of cocaine treatment; we also noted decrease hepatic levels of ATP, GSH, cytochrome P-450 and NADPH/NADP+ ratio and increases in malondialdehyde concentration. Histopathological study of liver slices showed perivenous and periportal necrosis induced by cocaine in untreated mice and mice pretreated with phenobarbital, respectively.

CD2-CD48 interaction prevents apoptosis in murine B lymphocytes by up-regulating bcl-2 expression.

Antigen receptor engagement initiates clonal expansion and antibody secretion in B lymphocytes in response to foreign antigens. However, binding of self antigen to antigen receptors targets self-reactive B cell clones for elimination or inactivation. The antigen-triggered biochemical events and the eventual response of the cells are dependent on the simultaneous occupancy of co-stimulatory receptors.

Protein kinase C V3 domain mutants with differential sensitivities to m-calpain are not resistant to phorbol-ester-induced down-regulation.

Distinct linker sequences were introduced into the protease-sensitive V3 domain of protein kinase C-alpha and the mutant proteins were expressed in COS-1 cells. Partially purified preparations of these mutants were functionally similar to wild-type protein kinase C-alpha, however their susceptibility to m-calpain was quite distinct, with one mutant being insensitive to cleavage. The three mutants, after expression in COS-1 cells, were found to behave in a manner indistinguishable from wild-type protein kinase C-alpha with respect to subcellular distribution, acute responses to 12-O-tetradecanoyl-phorbol 13-acetate and 12-O-tetradecanoyl-phorbol-13-acetate-induced down-regulation.

Induction of nitric oxide release by MRC OX-44 (anti-CD53) through a protein kinase C-dependent pathway in rat macrophages.

Many membrane proteins are implicated in the control of cell function by triggering specific signaling pathways. There is a new family of membrane proteins, defined by its structural motifs, which includes several lymphoid antigens, but lacks a function. To study its biological role, we determined which signaling pathways are affected by the CD53 antigen, a prototypic member of this family, in rat macrophages.

[Changes in distribution and isoenzymatic expression of protein kinase C in B lymphocytes induced by alloantigenic stimulation].

Protein kinase C comprises a family of distinct isoenzymes that are involved in signal transduction pathway triggered by activation of membrane receptor. These isoenzymes differ in their tissue distribution, activation requirements and substrate specificity. Recent reports have shown the regulation of PKC-isoenzymes expression in physiological and pathological models.

Relationship between genomic DNA ploidy and parameters of liver damage during necrosis and regeneration induced by thioacetamide.

Thioacetamide proved to be a potent necrogenic agent when a single dose of 6.6 mmol/kg was administered intraperitoneally to rats. Its necrogenic ability was assessed on the basis of morphological and biochemical changes.

Rat liver messenger ribonucleic acid and enzyme activity of 6-phosphofructo 2-kinase/fructose 2,6-bisphosphatase impairment during the late period of pregnancy.

Fructose 2,6-bisphosphate concentration, 6-phosphofructo 2-kinase/fructose 2,6-bisphosphatase (PFK-2/FBPase2) activity, and messenger RNA decreased in maternal rat liver during the last days of gestation, and the recovery started after delivery. Phospho(enol)pyruvate carboxykinase activity and messenger RNA increased in contrast to PFK-2 changes. Measurement of the glycolytic capacity in isolated hepatocytes prepared from rats 1 h after parturition showed a low glucose consumption and an impaired capacity to metabolize glucose.

Early signals in alloantigen induced B-cell proliferation. Comparison between B-cell triggering by intact allogeneic cells and solubilized alloantigen.

Stimulation of B cells from BALB/c with allogeneic lymphocytes from C57BL/6 mice resulted in a slight increase in cytosolic Ca2+ but in the absence of proliferative response. Immunization of BALB/c mice with C57BL/6 total lymphocytes resulted in an enhancement of cytosolic Ca2+ and of B cell proliferation. Phosphatidylinositol specific phospholipase C was activated immediately after allogeneic stimulation as deduced by the concomitant rise in inositol 1,4,5-trisphosphate and 1,2-diacylglycerol.

Sulfonylureas activate glycogen phosphorylase and increase cytosolic free-Ca2+ levels in isolated rat hepatocytes.

Without causing significant changes in cellular levels of cyclic adenosine monophosphate (cAMP), the addition of either glibenclamide or gliquidone to isolated rat hepatocytes caused a transient dose- and Ca(2+)-dependent activation of glycogen phosphorylase. The calculated concentrations corresponding to half-maximal activation were 5 and 2 mumol/L, respectively. In connection with this, it was observed that glibenclamide provoked a dose-dependent increase in cytosolic free-calcium concentration ([Ca2+]i) in Fura-2-loaded hepatocytes.

Phorbol esters induce nitric oxide synthase and increase arginine influx in cultured peritoneal macrophages.

Incubation of peritoneal macrophages with beta-phorbol 12,13-dibutyrate promotes a time-dependent release of NO to the incubation medium. This effect was antagonized by LPS, a well known inducer of nitric oxide synthase (NOS) expression in macrophages, and was inhibited by NG-methyl-L-arginine and N omega-nitro-L-arginine. An increase in intracellular cGMP and NOS activity was observed in parallel with NO release.

Circular dichroism analysis of ligand-induced conformational changes in protein kinase C. Mechanism of translocation of the enzyme from the cytosol to the membranes and its implications.

The structural changes following the binding to protein kinase C (PKC) of activators that promote its translocation to lipid environments were studied by far-u.v. c.

Differential calcium mobilization by vasopressin, angiotensin II, gastrin-releasing peptide, and adenosine triphosphate in adult and fetal hepatocytes. Relevance for the activation of calcium-dependent enzymes.

Early signals elicited after membrane receptor binding of agonists, the transmembrane signaling pathway of which involves activation of phosphoinositide-specific phospholipase C, were compared in fetal (22 days gestation) and adult rat hepatocytes. Free cytosolic calcium changes varied depending on the agonist and type of stimulated cells. Angiotensin II and ATP elicited the maximal responses in both types of cells, whereas the maximal Ca2+ increase produced by vasopressin was twice as much in adult than in fetal hepatocytes.

Phorbol esters induce nitric oxide synthase activity in rat hepatocytes. Antagonism with the induction elicited by lipopolysaccharide.

The incubation of primary cultures of rat hepatocytes with lipopolysaccharide (LPS) or biologically active phorbol esters promotes the release of nitric oxide to the incubation medium. This process is the result of the induction of the Ca(2+)-and calmodulin-independent form of nitric oxide synthase. Both the release of nitric oxide to the incubation medium and the expression of nitric oxide synthase activity exhibited a lag period of about 45-60 min after cell stimulation.

Protein kinase C isoenzymes display differential affinity for phorbol esters. Analysis of phorbol ester receptors in B cell differentiation.

Protein kinase C (PKC) comprises a family of distinct isoenzymes that are involved in signal transduction pathways linking the cell to triggers perceived via membrane receptors. These isoenzymes differ in their tissue distribution, activation requirements, and substrate specificity. One common denominator among different PKC subspecies is their activation by phorbol esters.

Phorbol esters, bombesin and insulin elicit differential responses on the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase system in primary cultures of foetal and adult rat hepatocytes.

The effects of 4 beta-phorbol 12-myristate 13-acetate (PMA), bombesin and insulin on 6-phosphofructo-2-kinase (PFK-2) activity, on fructose 2,6-bisphosphate concentration and on the phosphorylation state of PFK-2 were investigated in primary cultures of hepatocytes from foetal and adult rats. Bombesin stimulated PFK-2 activity and increased hexose phosphate (glucose 6-phosphate and fructose 6-phosphate) and fructose 2,6-bisphosphate content in hepatocytes both in the foetal and adult state. However, PMA-treated foetal cells exhibited a marked stimulation in fructose 2,6-bisphosphate concentration and in PFK-2 activity as well as in the content of hexose phosphates, while no response was found in the case of adult hepatocytes.

Isoenzymes of carbohydrate metabolism in primary cultures of hepatocytes from thioacetamide-induced rat liver necrosis: responses to growth factors.

Hepatocytes isolated from the liver of rats after a necrotizing dose of thioacetamide (6.6 mmol/kg) were used to study the postnecrotic process of liver regeneration. Flow cytometry analysis revealed populations of dedifferentiated hepatocytes exhibiting physical properties (size and fluorescence emission at 530 nm) similar to those found in fetal (22 days old) liver cells.

Inhibition of 6-phosphofructo-2-kinase activity by mercaptopurines.

The activity of 6-phosphofructo-2-kinase (PFK-2), the enzyme that catalyses the synthesis of fructose 2,6-bisphosphate (Fru-2,6-P2), was inhibited by mercaptopurines in vitro. Inhibition was observed with the purified enzyme from rat liver and bovine heart, and in extracts from rat lymphocytes and hepatoma cells, chick embryo fibroblasts, and human HeLa and lymphoblastoid cells. Half-maximal effect was obtained with 0.