Exploring geometric properties of gold nanoparticles using TEM images to explain their chaperone like activity for citrate synthase

Study on geometric properties of nanoparticles and their relation with biomolecular activities, especially protein is quite a new field to explore. This work was carried out towards this direction where images of gold nanoparticles obtained from transmission electron microscopy were processed to extract their size and area profile at different experimental conditions including and excluding a protein, citrate synthase. Since the images were ill-posed, texture of a context-window for each pixel was used as input to a back-propagation network architecture to obtain decision on its membership as nanoparticle. The segmented images were further analysed by k-means clustering to derive geometric properties of individual nanoparticles even from their assembled form. The extracted geometric information was found to be crucial to give a model featuring porous cage like configuration of nanoparticle assembly using which the chaperone like activity of gold nanoparticles can be explained.     

Multispectroscopic studies on the molecular interactions between bovine γ-globulin and borohydride-capped silver nanoparticles

Interactions between bovine γ-globulin (BGG) and borohydride-capped silver nanoparticles (BAgNPs) were studied using dynamic light scattering (DLS) and spectroscopic techniques such as UV–vis spectroscopy, fluorescence, and circular dichroism. The results were compared with earlier reported interactions between γ-globulin and citrate-coated AgNPs (CAgNPs). BAgNPs were synthesized and characterized. Irrespective of the coating on AgNPs, nanoparticles had formed ground-state complexes with the protein. CAgNPs, as well as BAgNPs had caused static quenching of tryptophan (Trp) fluorescence of the protein. The change in the capping agent from citrate to borohydride weakened the binding of nanoparticles with the protein. But the same change in capping agent had increased the fluorescence quenching efficiency of AgNPs. Hydrogen bonding and van der Waals interactions were involved in BGG–BAgNPs complex similar to the CAgNPs complex with γ-globulin. Polarity of the Trp microenvironment in BGG was not altered using BAgNPs as opposed to CAgNPs, as supported using synchronous and three-dimensional fluorescence. Resonance light scattering experiments also suggested nano-bio conjugation. Far-UV and near-UV circular dichroism (CD) spectra respectively pointed towards changes in the secondary and tertiary structure of BGG by BAgNPs, which was not observed for CAgNPs.     

CpG-ODN Class C Mediated Immunostimulation in Rabbit Model of Trypanosoma evansi Infection

CpG oligodeoxynucleotides (CpG-ODN) stimulate immune cells from a wide spectrum of mammalian species. Class C CpG-ODN is relatively stable and has the combined immune effects of both A and B classes of CpG-ODN. Trypanosoma evansi produces the state of immuno-suppression in the infected hosts. The current chemotherapeutic agents against this parasite are limited in number and usually associated with severe side effects. The present work aimed to determine the immunostimulatory effects of CpG-ODN class C in T. evansi infected rabbits. Rabbits inoculated with CpG C and challenged with T. evansi resulted in delayed onset of clinical signs with reduced severity in comparison to that of T. evansi infected rabbits. The treatment also enhanced humoral immune responses. Histopathological findings in liver and spleen revealed enhancement of mononuclear cell infiltration and secondary B cell follicles. These results demonstrate that CpG-ODN class C, has immunostimulatory properties in rabbit model of trypanosomosis. The use of booster doses or sustained delivery of CpG-ODN will further elucidate the prolonged CpG-ODN generated immune responses.     

Discovery of an ergosterol-signaling factor that regulates Trypanosoma brucei growth

Ergosterol biosynthesis and homeostasis in the parasitic protozoan Trypanosoma brucei was analyzed by RNAi silencing and inhibition of sterol C24β-methyltransferase (TbSMT) and sterol 14α-demethylase [TbSDM (TbCYP51)] to explore the functions of sterols in T. brucei growth. Inhibition of the amount or activity of these enzymes depletes ergosterol from cells at <6 fg/cell for procyclic form (PCF) cells or <0.01 fg/cell for bloodstream form (BSF) cells and reduces infectivity in a mouse model of infection. Silencing of TbSMT expression by RNAi in PCF or BSF in combination with 25-azalanosterol (AZA) inhibited parasite growth and this inhibition was restored completely by adding synergistic cholesterol (7.8 μM from lipid-depleted media) with small amounts of ergosterol (1.2 μM) to the medium. These observations are consistent with the proposed requirement for ergosterol as a signaling factor to spark cell proliferation while imported cholesterol or the endogenously formed cholesta-5,7,24-trienol act as bulk membrane components. To test the potential chemotherapeutic importance of disrupting ergosterol biosynthesis using pairs of mechanism-based inhibitors that block two enzymes in the post-squalene segment, parasites were treated with AZA and itraconazole at 1 μM each (ED₅₀ values) resulting in parasite death. Taken together, our results demonstrate that the ergosterol pathway is a prime drug target for intervention in T. brucei infection.     

Amelioration of cisplatin-induced nephrotoxicity in mice by oral administration of diphenylmethyl selenocyanate

Cisplatin is one of the most potent and active cytotoxic drug in the treatment of cancer. However, side-effects in normal tissues and organs, notably nephrotoxicity in the kidneys, limit the promising efficacy of cisplatin. The present study was designed to ascertain the possible in vivo protective potential of a synthetic organoselenium compound diphenylmethyl selenocyanate (3 mg/kg.b.w.) against the nephrotoxic damage induced by cisplatin (5 mg/kg.b.w. for 5 days) in Swiss albino mice. Treatment with diphenylmethyl selenocyanate markedly reduced cisplatin-induced lipid peroxidation, serum creatinine and blood urea nitrogen levels. Renal antioxidant defense systems, such as glutathione-S-transferase, glutathione peroxidase, superoxide dismutase, catalase, activities and reduced glutathione level, depleted by cisplatin therapy, were restored to normal by the selenium compound. The selenium compound also reduced renal tubular epithelial cell damage, nitric oxide levels and expression of COX-2, and iNOS in kidneys injured by cisplatin. These results demonstrate the protective effect of diphenylmethyl selenocyanate against cisplatin-induced nephrotoxicity in mice.     

Monitoring Shifts in the Conformation Equilibrium of the Membrane Protein Cytochrome P450 Reductase (POR) in Nanodiscs

Nanodiscs are self-assembled ∼50-nm² patches of lipid bilayers stabilized by amphipathic belt proteins. We demonstrate that a well ordered dense film of nanodiscs serves for non-destructive, label-free studies of isolated membrane proteins in a native like environment using neutron reflectometry (NR). This method exceeds studies of membrane proteins in vesicle or supported lipid bilayer because membrane proteins can be selectively adsorbed with controlled orientation. As a proof of concept, the mechanism of action of the membrane-anchored cytochrome P450 reductase (POR) is studied here. This enzyme is responsible for catalyzing the transfer of electrons from NADPH to cytochrome P450s and thus is a key enzyme in the biosynthesis of numerous primary and secondary metabolites in plants. Neutron reflectometry shows a coexistence of two different POR conformations, a compact and an extended form with a thickness of 44 and 79 Å, respectively. Upon complete reduction by NADPH, the conformational equilibrium shifts toward the compact form protecting the reduced FMN cofactor from engaging in unspecific electron transfer reaction.     

Vanadium(III)-L-cysteine protects cisplatin-induced nephropathy through activation of Nrf2/HO-1 pathway

Cisplatin (CDDP) is one of the first-line anticancer drugs; however, the major limitation of CDDP therapy is development of nephrotoxicity (25–35% cases), whose precise mechanism mainly involves oxidative stress, inflammation and cell death. Therefore, in search of a potential chemoprotectant, an organovanadium complex, viz., vanadium(III)-L-cysteine (VC-III) was evaluated against CDDP-induced nephropathy in mice. CDDP was administered intraperitoneally (5?mg/kg b.w.) and VC-III was given by oral gavage (1?mg/kg b.w.) in concomitant and pre-treatment schedule. The results showed that VC-III administration reduced (p?<?0.001) serum creatinine and blood urea nitrogen levels, suggesting amelioration of renal dysfunction. VC-III treatment also significantly (p?<?0.001) prevented CDDP-induced generation of reactive oxygen species, reactive nitrogen species, and onset of lipid peroxidation in kidney tissues of the experimental mice. In addition, VC-III also substantially (p?<?0.001) restored CDDP-induced depleted activities of the renal antioxidant enzymes such as, superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, and glutathione (reduced) level. Furthermore, histopathological study also confirmed the renoprotective efficacy of VC-III. Western blotting analysis appended by immunohistochemical data showed that VC-III treatment quite effectively reduced the expression of proinflammatory mediators such as, NFκβ, COX-2 and IL-6. VC-III administration also stimulated Nrf2-mediated antioxidant defense system by promotion of downstream antioxidant enzymes, such as HO-1. Moreover, treatment with VC-III significantly (p?<?0.001) enhanced CDDP-mediated cytotoxicity in MCF-7 and NCI-H520 human cancer cell lines. Thus, VC-III can serve as a suitable chemoprotectant and increase the therapeutic window of CDDP in cancer patients.