Strategies for specifically directing metal functionalization of protein nanotubes: constructing protein coated silver nanowires.

Biological molecules that self-assemble in the nanoscale range are useful multifunctional materials. Rotavirus VP6 protein self-assembles into tubular structures in the absence of other rotavirus proteins. Here, we present strategies for selectively directing metal functionalization to the lumen of VP6 nanotubes. The specific in situ metal reduction in the inner surface of nanotube walls was achieved by the simple modification of a method previously reported to functionalize the nanotube outer surface. Silver nanorods and nanowires as long as 1.5 µm were formed inside the nanotubes by coalescence of nanoparticles. Such one-dimensional structures were longer than others previously obtained using bioscaffolds. The interactions between silver ions and the nanotube were simulated to understand the conditions that allowed nanowire formation. Molecular docking showed that a naturally occurring arrangement of aspartate residues enabled the stabilization of silver ions on the internal surface of the VP6 nanotubes. This is the first time that such a spatial arrangement has been proposed for the nucleation of silver nanoparticles, opening the possibility of using such an array to direct functionalization of other biomolecules. These results demonstrate the natural capabilities of VP6 nanotubes to function as a versatile biotemplate for nanomaterials.

Oxidative phosphorylation is impaired by prolonged hypoxia in breast and possibly in cervix carcinoma.

It has been assumed that oxidative phosphorylation (OxPhos) in solid tumors is severely reduced due to cytochrome c oxidase substrate restriction, although the measured extracellular oxygen concentration in hypoxic areas seems not limiting for this activity. To identify alternative hypoxia-induced OxPhos depressing mechanisms, an integral analysis of transcription, translation, enzyme activities and pathway fluxes was performed on glycolysis and OxPhos in HeLa and MCF-7 carcinomas. In both neoplasias exposed to hypoxia, an early transcriptional response was observed after 8h (two times increased glycolysis-related mRNA synthesis promoted by increased HIF-1alpha levels). However, major metabolic remodeling was observed only after 24h hypoxia: increased glycolytic protein content (1-5-times), enzyme activities (2-times) and fluxes (4-6-times). Interestingly, in MCF-7 cells, 24h hypoxia decreased OxPhos flux (4-6-fold), and 2-oxoglutarate dehydrogenase and glutaminase activities (3-fold), with no changes in respiratory complexes I and IV activities. In contrast, 24h hypoxia did not significantly affect HeLa OxPhos flux; neither mitochondria related mRNAs, protein contents or enzyme activities, although the enhanced glycolysis became the main ATP supplier. Thus, prolonged hypoxia (a) targeted some mitochondrial enzymes in MCF-7 but not in HeLa cells, and (b) induced a transition from mitochondrial towards a glycolytic-dependent energy metabolism in both MCF-7 and HeLa carcinomas.

Targeting of cancer energy metabolism.

The main purpose of this review is to update and analyze the effect of several antineoplastic drugs (adriamycin, apoptodilin, casiopeinas, cisplatin, clotrimazole, cyclophosphamide, ditercalinium, NSAIDs, tamoxifen, taxol, 6-mercaptopurine, and alpha-tocopheryl succinate) and energy metabolism inhibitors (2-DOG, gossypol, delocalized lipophilic cations, and uncouplers) on tumor development and progression. The possibility that these antineoplastic drugs currently used in in vitro cancer models, in chemo-therapy, or under study in phase I to III clinical trials induce tumor cellular death by altering also metabolite concentration (i.e., ATP), enzyme activities, and/or energy metabolism fluxes is assessed. It is proposed that the use of energy metabolic therapy, as an alternative or complementary strategy, might be a promising novel approach in the treatment of cancer.

Post-conditioning preserves glycolytic ATP during early reperfusion: a survival mechanism for the reperfused heart.

BACKGROUND: Glycolytic activity during the transition period from anaerobic to aerobic metabolism has been demonstrated to be critical for heart recovery in isolated reperfused hearts. The purpose of this work was to investigate the relevance of the glycolytic pathway in preserving the cardiac function of post-conditioned hearts. METHODS: The activation of the glycolytic pathway in post-conditioned hearts was evaluated by measuring GLUT-4 insertion, glucose consumption and lactate production. Iodoacetic acid and 2-deoxy-D-glucose were administrated to the working hearts to evaluate the effect of glycolytic inhibition in the post-conditioning protective effect. RESULTS: Post-conditioning maneuvers applied to isolated rat hearts, after prolonged ischemia and before reperfusion, promoted recovery of cardiac mechanical function with sustained increase of GLUT-4 translocation and activation of the glycolytic pathway during ischemia and early reperfusion. Iodoacetate inhibited the protective effect of post-conditioning, without affecting the mitochondrial oxidative capacity. Glycolysis contribution to maintain mechanical function at early reperfusion was observed in post-conditioned hearts perfused with 2-deoxy-D-glucose and in hearts in which iodoacetate was administered only during reperfusion. CONCLUSION: It is concluded that in the post-conditioned heart, a functional compartmentation of anaerobic energy metabolism, at early reperfusion, plays a significant role in cardiac protection against reperfusion damage.

Energy metabolism transition in multi-cellular human tumor spheroids.

It is thought that glycolysis is the predominant energy pathway in cancer, particularly in solid and poorly vascularized tumors where hypoxic regions develop. To evaluate whether glycolysis does effectively predominate for ATP supply and to identify the underlying biochemical mechanisms, the glycolytic and oxidative phosphorylation (OxPhos) fluxes, ATP/ADP ratio, phosphorylation potential, and expression and activity of relevant energy metabolism enzymes were determined in multi-cellular tumor spheroids, as a model of human solid tumors. In HeLa and Hek293 young-spheroids, the OxPhos flux and cytochrome c oxidase protein content and activity were similar to those observed in monolayer cultured cells, whereas the glycolytic flux increased two- to fourfold; the contribution of OxPhos to ATP supply was 60%. In contrast, in old-spheroids, OxPhos, ATP content, ATP/ADP ratio, and phosphorylation potential diminished 50-70%, as well as the activity (88%) and content (3 times) of cytochrome c oxidase. Glycolysis and hexokinase increased significantly (both, 4 times); consequently glycolysis was the predominant pathway for ATP supply (80%). These changes were associated with an increase (3.3 times) in the HIF-1alpha content. After chronic exposure, both oxidative and glycolytic inhibitors blocked spheroid growth, although the glycolytic inhibitors, 2-deoxyglucose and gossypol (IC(50) of 15-17 nM), were more potent than the mitochondrial inhibitors, casiopeina II-gly, laherradurin, and rhodamine 123 (IC(50) > 100 nM). These results suggest that glycolysis and OxPhos might be considered as metabolic targets to diminish cellular proliferation in poorly vascularized, hypoxic solid tumors.