Dinko Berkovic

TNF activates NF-κB by phosphatidylcholine-specific phospholipase C-induced “Acidic” sphingomyelin breakdown

In this paper, we describe a phospholipid transmission pathway mediating tumor necrosis factor (TNF) activation of the nuclear transcription factor kappa B (NF-kappa B). Central to this TNF signaling route is the second messenger-like molecule ceramide, which is generated by sphingomyelin (SM) breakdown catalyzed by a sphingomyelinase (SMase). SMase activation is secondary to the generation of 1,2-diacylglycerol (DAG) produced by a TNF-responsive PC-specific phospholipase C (PC-PLC). The functional coupling of these two C type phospholipases is revealed by D609, a selective inhibitor of PC-PLC. SMase itself, or SMase-inducing regimens such as exogenous PLC or synthetic DAGs, induces NF-kappa B activation at pH 5.0, suggesting the operation of an acidic SMase. A model is proposed in which a TNF-responsive PC-PLC via DAG couples to an acidic SMase, resulting in the generation of ceramide, which eventually triggers rapid induction of nuclear NF-kappa B activity.

Utility of Procalcitonin Concentration in the Evaluation of Patients with Malignant Diseases and Elevated C-Reactive Protein Plasma Concentrations

BACKGROUNDnElevated plasma concentrations of the C-reactive protein (CRP) are frequently found in patients with malignant diseases. Discrimination between infection and noninfectious acute-phase reactions is essential for therapeutic decisions.nnnMETHODSnBecause increased procalcitonin (PCT) concentrations have been described predominantly in patients with a systemic infection, PCT plasma concentrations were measured prospectively in 111 patients with a hemato-oncological condition with a CRP concentration >8 mg/L.nnnRESULTSnDocumented cases of infection were identified in 42 patients, 39 patients had unexplained fever, and 30 patients had no signs of infection. Twenty patients in the latter group were classified as having an elevated CRP concentration caused by a high tumor load (tumor group), and 8 had elevated concentrations that were drug related (drug group). Median CRP concentrations did not differ significantly between groups of patients with and without infection. PCT concentrations were higher in patients with an infection than in patients without an infection and were within the normal range in all patients in the drug and tumor groups. As shown by receiver operating characteristic analysis, PCT concentration was a significant discriminator between having and not having infection, having infection and being in the tumor group, and having infection and being in the drug group. In contrast, CRP concentration was only a predictor of being in the drug group, when the cut-off point was set at 85.1 mg/L, which limited its clinical applicability.nnnCONCLUSIONSnPCT concentration contributes significantly to the differential diagnosis for elevated CRP concentrations in patients with hemato-oncological conditions and facilitates therapeutic decisions.

Investigations on the cellular uptake of hexadecylphosphocholine

The uptake of [(9,10)-3H]hexadecylphosphocholine (HePC) in six tumor cell lines was studied. All cell lines incorporated HePC in similar amounts, with the exception of the epidermoid cancer cell line KB, which took up higher amounts of HePC. The uptake of HePC at 37°C was shown to be time and concentration dependent. At 20°C, uptake was drastically reduced and at 4°C it was blocked completely. Binding of HePC, at 4°C, was not saturable at concentrations between 5 βg/mL (11.8 μM) and 100 μg/mL (235.3 μM), indicating that cell surface binding is not receptor-mediated. Furthermore, the effects of inhibitors of endocytosis were investigated. We observed a pronounced inhibitory effect by monensin and cytochalasin B. Colchicine was somewhat less effective whereas chloroquine was almost without effect. From these data we conclude that uptake of HePC is most probably mediatedvia a receptor-independent endocytotic mechanism.

Differential regulation of phospholipase A2 in human leukemia cells by the etherphospholipid analogue hexadecylphosphocholine

Hexadecylphosphocholine (HePC) is the main representative of a new group of antineoplastic agents, the alkylphosphocholines, which were originally derived from cytotoxic etherlysophospholipids. HePC shows antiproliferative action against a whole variety of tumor cells and tumors in vitro and in vivo. Furthermore, it also induces differentiation in some hematologic cell lines and prevents invasive growth of neoplastic cells in vitro. To date, the precise molecular mechanisms mediating the biological effects of HePC have not been identified yet. As etherlysophospholipids seem to inhibit some pathways of lipid-dependent intracellular signalling, similar effects may be relevant for HePC. We therefore investigated the influence of HePC on phospholipase A2 (PLA2-EC 3.1.1) in the human leukemia cell line U 937. HePC seems to inhibit enzyme activity independently of protein kinase C (PKC) in differentiated U 937 cells stimulated by tumor necrosis factor alpha (TNFalpha). Inhibition of purified secretory PLA2 from snake venom (EC 3.1.1.4) in vitro shows characteristics of a non-competitive mode. In contrast, HePC leads to an enhancement of PLA2 activity in immature cells which cannot be explained by changes in membrane composition. Our data suggest that PLA, inhibition is most probably not the mechanism by which HePC mediates its antiproliferative effects.

Gyriform Liver Foci in Chronic Hepatic Porphyria

A patient with suspected liver metastases detected by routine sonography of the abdomen was admitted to our clinic for further testing. Liver sonography disclosed multiple irregular gyriform foci of a hyperechoic structure with a maximum diameter of 3.5 cm. In magnetic resonance imaging, these foci appeared as hyperintense in T1-weighted images and isointense in T2-weighted images. A biopsy showed a discrete portal and periportal fibrosis. UV light fluorescence of the specimen was negative. Analysis of urine revealed an almost fourfold el-evation of total porphyrin of 591 µg/24 h, proving the diagnosis of chronic hepatic porphyria. Characteristic liver foci in hepatic porphyria are detected by sonography in some affected patients. Usually, they can also be depicted by magnetic resonance imaging and computed tomography. These foci often appear before any other symptoms of the disease and are reversible when triggering factors, such as certain drugs or alcohol, are discontinued.