Jordi Boada

Cells overexpressing fructose‐2,6‐bisphosphatase showed enhanced pentose phosphate pathway flux and resistance to oxidative stress

Changes in the content of fructose‐2,6‐bisphosphate, a modulator of glycolytic flux, also affect other metabolic fluxes such as the non‐oxidative pentose phosphate pathway. Since this is the main source of precursors for biosynthesis in proliferating cells, PFK‐2/FBPase‐2 has been proposed as a potential target for neoplastic treatments. Here we provide evidence that cells with a low content of fructose‐2,6‐bisphosphate have a lower energy status than controls, but they are also less sensitive to oxidative stress. This feature is related to the activation of the oxidative branch of the pentose phosphate pathway and the increased production of NADPH.

Fructose 1,6-bisphosphate reduced TNF-α-induced apoptosis in galactosamine sensitized rat hepatocytes through activation of nitric oxide and cGMP production

Fructose 1,6-P2 (F1,6BP) protects rat liver against experimental hepatitis induced by galactosamine (GalN) by means of two parallel effects: prevention of inflammation, and reduction of hepatocyte sensitization to tumour necrosis factor-alpha (TNF-alpha). In a previous paper we reported the underlying mechanism involved in the prevention of inflammation. In the present study, we examined the intracellular mechanisms involved in the F1,6BP inhibition of the apoptosis induced by TNF-alpha in parenchyma cells of GalN-sensitized rat liver. We hypothesized that the increased nitric oxide (NO) production in livers of F1,6BP-treated rats mediates the antiapoptotic effect. This hypothesis was evaluated in cultured primary rat hepatocytes challenged by GalN plus tumour necrosis factor-alpha (GalN+TNF-alpha), to reproduce in vitro the injury associated with experimental hepatitis. Our results show a reduction in apoptosis concomitant with an increase in NO production and with a reduction in oxidative stress. In such conditions, guanylyl cyclase is activated and the increase in cGMP reduces the TNF-alpha-induced apoptosis in hepatocytes. These results provide new insights in the protective mechanism activated by F1,6BP and confirm its interest as a hepatoprotective agent.

Enhanced antioxidant defenses and resistance to TNF-α in a glycolysis-depleted lung epithelial cell line

Glycolysis-depleted cells, obtained by stable transfection of fructose 2,6-bisphosphatase in mink lung epithelial cells (Mv1Lu), were less sensitive to serum withdrawal- and TNF-alpha-induced apoptosis than cells transfected with the empty vector pcDNA3 (control cells). We compared the differences in the redox status of the two transfectants and the changes produced by TNF-alpha treatment. The activities of the antioxidant enzymes catalase and glutathione peroxidase, as well as the content of reduced glutathione (GSH) and the activity of the nuclear transcription factor kappa B (NF-kappa B), were higher in pFBPase-2 clones than in control cells in all the conditions tested. TNF-alpha challenge sharpened the differences in glutathione peroxidase activity, GSH/GSSG ratios, and NF-kappa B activation between transfectants. These data indicate that glycolysis restriction at the PFK step protects cells against apoptotic stimuli by increasing the GSH content and NF-kappa B activity. This acquired feature may compromise antineoplastic treatments based on glycolytic depletion.

Adsorption of cyanuric chloride-activated polyethylene glycol on liposomes

Abstract One method for obtaining sterically stabilized liposomes consists of mixing an excess of cyanuric chloride-activated polyethylene glycol 5000 (activated PEG) with liposomes bearing distearoylphosphatidylethanolamine. Quantitative analysis of activated PEG present in extruded liposomes suggested that it can be found grafted as well as coated on the liposomal surface. Penetration kinetics at constant area and surface activity have shown the ability of activated PEG to adsorb on liposomes. This suggests that the interaction between activated PEG and lipid is primarily hydrophobic, and the triazine group of activated PEG must be embedded in the lipid. Microelectrophoretic measurements are consistent with the process of adsorption observed: Incorporation of PEG reduces the corresponding zeta potentials, but the presence of PEG in the bulk increases them in absolute terms. An experimental value lying between such extremes indicates that PEG is adsorbed.