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The ability to follow phospholipid (Plp) metabolism is of paramount importance in many circumstances in which cell survival and cell proliferation are of concern-for example in neurological disorders and cancer (1,2). NMR spectroscopy has long been known to be important tool for exploring Plp metabolism (3-6). Novel NMR developments, such as high-resolution magic angle spinning (HRMAS) probes, have provided improved spectra of cultured cells (7) and normal (8,9) and cancer (10 -12) tissues. Recently, using HRMAS together with proton total correlation spectroscopy (TOCSY), we showed that a mousebearing B16 melanoma tumor responded to chloroethyl nitrosourea (CENU) treatment in vivo by altering its Plp metabolism (12).The first purpose of the present study was to demonstrate on cultured B16 melanoma cells in vitro that HRMAS proton TOCSY cross-peak signal variations of Plp derivatives reflected concentration variations. The second purpose was to determine the Plp metabolism response of cultured B16 melanoma cells to CENU treatment in vitro, as a model for Plp metabolism alterations previously observed in vivo.The Plp derivatives that were simultaneously observed using proton TOCSY were choline (Cho), phosphocholine (PC), cytidyl-diphosphate-choline (CDP-Cho), ethanolamine (Eth), phosphoethanolamine (PE), CDP-ethanolamine (CDP-Eth) (all of which are derivatives of the phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEth) biosynthetic pathways), and glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE) (derivatives of PtdCho and PtdEth hydrolysis) (1-3).As regards the most expressed Plp derivatives in cultured B16 melanoma cells, HRMAS proton TOCSY signals revealed linearity with 1D saturation recovery signals, the NMR spectroscopy reference for quantifying concentrations. Therefore, HRMAS proton TOCSY was used to quantify concentration changes of water-soluble Plp derivatives in CENU-treated cultured melanoma cells. The response of cultured B16 melanoma cells to CENU treatment involved a transient accumulation of GPC and GPE, a down-regulation of PC and increase of CDP-Eth during cell proliferation inhibition, and a dramatic and irreversible rise of PE during and after cell proliferation inhibition. These data are discussed in relation to mouse-bearing B16 melanoma tumor response to CENU in vivo, and to Plp metabolism enzymatic involvement. METHODS ChemicalsNЈ-[2-chloroethyl]-N[2-(methylsulfonyl)ethyl]-NЈ-nitrosourea (cystemustine) is a CENU antineoplastic agent (13) that has been proposed for the treatment of human malignant melanoma and glioma. Cystemustine (Orphachem, Clermont-Ferrand, France) was supplied as a 5-mM solution in 0.9% NaCl. D 2 O (SDS, Peypin, France) was used to lock the spectrometer. Cell CulturesTransplantable B16 melanoma cells originating from C57BL6/6J Ico mice (ICIG, Villejuif, France) were adapted

Abstract. Protein phosphatase 2A (PP2A), an Akt pathway inhibitor, is considered to be activated by methylation of its catalytic subunit. Also PP2A downregulation was proposed to take part in carcinogenesis. Recently, PP2A activation was shown to be activated in response to DNA damage. To obtain further information on the role of PP2A in tumors and response to DNA damage, we investigated the relationship between PP2A methylation and activity, cell proliferation, Akt activation, c-Myc expression and PTEN activity in B16 melanoma cells untreated and after chloroethylnitrosourea (CENU) treatment. In untreated cells, okadaic acid, an antagonist of PP2A methylation, inhibited PP2A activity, stimulated cell proliferation, increased Akt activation and c-Myc expression. Xylulose-5-phosphate, an agonist of PP2A methylation, increased PP2A activity, decreased cell proliferation, Akt activation and c-Myc expression. However, both PP2A methylation modulators increased PTEN activity. During the response to CENU treatment, PP2A methylation and activity were strongly increased, Akt activation and c-Myc expression were decreased. However PTEN activity was increased. After tumor cell growth recovery, these modifications were moderately decreased. PP2A methylation was quantified and correlated positively with PP2A activity, and negatively with criteria for cell aggressiveness (cell proliferation, Akt activation, c-Myc expression). Based on these data, PP2A methylation status controls PP2A activity and oncoproteins expression and PP2A is strongly activated after CENU treatment thus partly explaining the growth inhibition in response to this agent. It follows that PP2A promethylating agents are potential candidates for anticancer drugs.

The use of isotopic substitution to delay the oxidative metabolism of the anesthetic propofol 1 was studied. The aromatic hydrogens of propofol 1 were replaced by deuterium to produce the mono- and trideuterated derivatives 4 and 5. In vitro metabolic studies on human hepatic microsomes showed no isotopic effect in the para hydroxylation of propofol, and 1, 4, and 5 display similar hypnotic activity and toxicity in mice.

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