Polyamidoamine dendrimer impairs mitochondrial oxidation in brain tissue

Background: The potential nanocarrier polyamidoamine (PAMAM) generation 5 (G5-NH2) dendrimer has been shown to evoke lasting neuronal depolarization and cell death in a concentration-dependent manner. In this study we explored the early progression of G5-NH2 action in brain tissue on neuronal and astroglial cells.Results: In order to describe early mechanisms of G5-NH2 dendrimer action in brain tissue we assessed G5-NH2 trafficking, free intracellular Ca2+ and mitochondrial membrane potential (ΨMITO) changes in the rat hippocampal slice by microfluorimetry. With the help of fluorescent dye conjugated G5-NH2, we observed predominant appearance of the dendrimer in the plasma membrane of pyramidal neurons and glial cells within 30 min. Under this condition, G5-NH2 evoked robust intracellular Ca2+ enhancements and ΨMITO depolarization both in pyramidal neurons and astroglial cells. Intracellular Ca2+ enhancements clearly preceded ΨMITO depolarization in astroglial cells. Comparing activation dynamics, neurons and glia showed prevalence of lasting and transient ΨMITO depolarization, respectively. Transient as opposed to lasting ΨMITO changes to short-term G5-NH2 application suggested better survival of astroglia, as observed in the CA3 stratum radiatum area. We also showed that direct effect of G5-NH2 on astroglial ΨMITO was significantly enhanced by neuron-astroglia interaction, subsequent to G5-NH2 evoked neuronal activation.Conclusion: These findings indicate that the interaction of the PAMAM dendrimer with the plasma membrane leads to robust activation of neurons and astroglial cells, leading to mitochondrial depolarization. Distinguishable dynamics of mitochondrial depolarization in neurons and astroglia suggest that the enhanced mitochondrial depolarization followed by impaired oxidative metabolism of neurons may be the primary basis of neurotoxicity. © 2013 Nyitrai et al.; licensee BioMed Central Ltd

The Janus facet of nanomaterials

Application of nanoscale materials (NMs) displays a rapidly increasing trend in electronics, optics, chemical catalysis, biotechnology, and medicine due to versatile nature of NMs and easily adjustable physical, physicochemical, and chemical properties. However, the increasing abundance of NMs also poses significant new and emerging health and environmental risks. Despite growing efforts, understanding toxicity of NMs does not seem to cope with the demand, because NMs usually act entirely different from those of conventional small molecule drugs. Currently, large-scale application of available safety assessment protocols, as well as their furthering through case-by-case practice, is advisable. We define a standard work-scheme for nanotoxicity evaluation of NMs, comprising thorough characterization of structural, physical, physicochemical, and chemical traits, followed by measuring biodistribution in live tissue and blood combined with investigation of organ-specific effects especially regarding the function of the brain and the liver. We propose a range of biochemical, cellular, and immunological processes to be explored in order to provide information on the early effects of NMs on some basic physiological functions and chemical defense mechanisms. Together, these contributions give an overview with important implications for the understanding of many aspects of nanotoxicity

Biológiailag jelentős nem-kovalens kölcsönhatások tanulmányozása: fehérje-kötődés, nukleinsav-kötődés, önszerveződés = Investigations on non-covalent interactions of biological importance: protein binding, nucleic acid binding, self-assembly

Nem-kovalens kölcsönhatások (fehérjekötődés, aggregáció) kisérleti vizsgálatára UV-Vis, fluoreszcencia és kiroptikai spektroszkópiai módszereket alkalmaztak, a vizsgálati minták tisztítását kromatográfiás (HPLC, kapilláris elektroforézis) technikákkal végezték. A humán vérplazma minor fehérje komponensének (alfa-1 savas glikoprotein, AGP) részletes vizsgálata kimutatta, hogy az AGP genetikai variánsai eltérő, a kötődési erősségtől függő módon csökkentik a myeloid leukémia gyógyszerének (Imatinib, Glivec', Novartis) hatásosságát. Daganatos betegek klinikai vérmintáiból kidolgozták nagy tisztaságú AGP kinyerését és kapilláris elektroforézissel igazolták, hogy az AGP cukorláncának változatossága (glycoform heterogeneity) különféle daganatos megbetegedések érzékeny markere. Enantiomerek elválasztására egy ciklodextrin származékot tartalmazó új királis állófázist fejlesztettek ki. Megfigyelték, hogy AGP kötődésben királis inverzió következhet be. A kiroptikai spektrumokban megjelenő exciton sávpár intenzitását nem-kovalens kölcsönhatások esetére elméleti alapon indokolták. | UV-Vis, fluorescence and chiroptical spectroscopic methods have been applied for experimental studies of non-covalent interactions, the purification of the samples were done by chromatographic (HPLC, capillary electrophoresis) techniques. Detailed studies of the minor protein component of human blood plasma, alpha-1 acid glycoprotein (AGP) revealed that the decrease in the efficiency of the medication against chronic myelogenous leukaemia, Imatinib (Glivec', Novartis) brought about by the genetic variants of AGP was in correlation with their binding strength. Highly purified AGP samples were prepared from clinical blood samples of cancer patients and their capillary electrophoretic analysis proved the variability of sugar-chain of AGP (glycoform heterogeneity) to be a sensitive marker of several malignant diseases. New chiral stationary phase containing a cyclodextrin derivative has been developed for enantiomer separation. Chiral inversion has been demonstrated in AGP binding. The intensity of exciton couplets appearing in chiroptical spectra has been explained on theoretical grounds for non-covalent interactions