Development of an effective single-chain variable fragment recognizing a novel epitope in the hepatitis C virus E2 protein that restricts virus entry into hepatocytes.

Previously, we reported a neutralizing monoclonal antibody, A8A11, raised against a novel conserved epitope within the hepatitis C virus (HCV) E2 protein, that could significantly reduce HCV replication. Here, we report the nucleotide sequence of A8A11 and demonstrate the efficacy of a single-chain variable fragment (scFv) protein that mimics the antibody, inhibits the binding of an HCV virus-like particle to hepatocytes, and reduces viral RNA replication in a cell culture system. More importantly, scFv A8A11 was found to effectively restrict the increase of viral RNA levels in the serum of HCV-infected chimeric mice harbouring human hepatocytes. These results suggest a promising approach to neutralizing-antibody-based therapeutic interventions against HCV infection.

BODIPY-attached zinc(II) complexes of curcumin drug for visible light assisted photo-sensitization, cellular imaging and targeted PDT.

Boron-dipyrromethene (BODIPY) based photosensitizers as porphyrinoids and curcumin as natural product possess exciting photophysical features suitable for theranostic applications, namely, imaging and photodynamic therapy (PDT). Limited aqueous solubility and insufficient physiological stability, however, reduce their efficacy significantly. We have designed a novel strategy to deliver these two unusable cytotoxins simultaneously in cancer cells and herein, report the synthesis, characterization and imaging-assisted photocytotoxicity of three zinc(II) complexes containing N3-donor dipicolylamine (dpa) ligands (L1-3) and O,O-donor curcumin (Hcur) viz. [Zn(L1)(cur)]Cl (1), [Zn(L2)(cur)]Cl (2) and [Zn(L3)(cur)]Cl (3), where L2 and L3 have pendant fluorescent BODIPY and non-emissive di-iodo-BODIPY moieties. Metal chelation imparted remarkable biological stability (pH ∼7.4) to the respective ligands and induces significant aqueous solubility. These ternary complexes could act as replacements of the existing metalloporphyrin-based PDT photosensitizers as their visible-light photosensitizing ability is reinforced by the dual presence of blue light absorbing curcumin and green light harvesting BODIPY units. Complex 2 having emissive BODIPY unit L2 and curcumin, showed mitochondria selective localization in HeLa, MCF-7 cancer cells and complex 3, the di-iodinated analogue of complex 2, exhibited type-I/II PDT activity via inducing apoptosis through mitochondrial membrane disruption in cancer cells while being significantly nontoxic in dark and to the healthy cells.

BODIPY-linked cis-dichlorido zinc(ii) conjugates: the strategic design of organelle-specific next-generation theranostic photosensitizers.

Dipicolylamine (dpa) based cis-dichlorido zinc(ii) complexes [Zn(L1-3)Cl2] (1-3), where L2 and L3 are non-iodo and di-iodo BODIPY-appended dpa in 2 and 3, and L1 is dpa in control complex 1, were prepared and characterized and their photocytotoxicity was studied. Complexes 2 and 3 were developed as potential substitutes for zinc(ii)-porphyrins/phthalocyanines that are photodynamic therapeutic agents with moderate activity owing to their inherent hydrophobicity and aggregation-induced deactivation mechanism. In our approach, we strategically designed hybrid inorganic-organic zinc-BODIPY conjugates as theranostic photosensitizers. The structurally characterized diamagnetic Zn(ii) cis-dichlorido complexes mimic cisplatin and serve as new-generation photosensitizers with enhanced aqueous solubility and mito-DNA targeting propensity while imparting significant physiological stability to the heavy atom tethered BODIPY ligand, L3. The BODIPY complexes showed a visible band near 500 nm (ε∼ 34 000-44 000 dm3 mol-1 cm-1) and an emission band at 507 nm for 2 in 1% DMSO-Dulbecco's phosphate buffered saline. The labile chlorido ligands (ΛM∼ 200 S m2 mol-1 in 9 : 1 H2O-DMSO) generated positively charged complexes inside the cellular medium enabling them to cross the mitochondrial membrane for this organelle-selective localization and singlet oxygen-mediated apoptotic photocytotoxicity at nanomolar concentrations for 3 in HeLa and MCF-7 cells in light (400-700 nm), while being less active in the dark.

Antibody-Conjugated Vitamin E-Derived Liposomes for Targeted Gene Transfer.

Construction of a vitamin E-based liposomal biomaterial and its ability to deliver therapeutic genes selectively across liver cancer cells are demonstrated herein. In humans, liver regulates the levels of α-tocopherol, i.e., vitamin E, and hepatic cells carry the machinery for its transport. To exploit the presence of tocopherol transport protein, we have selected an efficient gene transfecting α-tocopherol-based twin lipid bearing a hydroxyethylated headgroup and octamethylene spacer (TH8S) for liposome formation. Also, based on the abundancy of the low-density lipoprotein receptor (LDLr) on the cellular surface in the case of hepatocellular carcinoma, anti-LDLr monoclonal antibody is used to confer the targeting ability to liposomes. A facile thiol-maleimide click chemistry is used for antibody decoration on the liposomal surface. Selective delivery of reporter and therapeutic genes (GFP and p53) to cells of hepatic origin was observed using anti-LDLr-tagged TH8S liposomes. Cellular internalization by receptor-mediated endocytosis renders the bioconjugate highly specific as well as highly efficient. Compatibility of the designed material with human blood points to its safety of use in systemic circulation thereby highlighting its in vivo potential. Thus, we report here a versatile biomaterial derived from an essential vitamin that promises potential for targeted suicidal gene therapy.

Crystal structure, DNA crosslinking and photo-induced cytotoxicity of oxovanadium(IV) conjugates of boron-dipyrromethene.

Cis-dichloro-oxovanadium(IV) complexes [VO(L1/L2)Cl2], where L1 is N-(4-(5,5-difluoro-1,3,7,9-tetramethyl-5H-4ʎ4,5ʎ4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinin-10-yl)benzyl)-1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine in 1 and L2 is N-(4-(5,5-difluoro-2,8-diiodo-1,3,7,9-tetramethyl-5H-4ʎ4,5ʎ4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinin-10-yl)benzyl)-1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine in 2) having 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene as boron-dipyrromethene (BODIPY) appended dipicolylamine bases were prepared, characterized and their photocytotoxicity studied. X-ray crystal structure of 1 showed distorted octahedral geometry with a VIVON3Cl2 core having Cl-V-Cl angle of 91.93(4)°. The complexes showed variable solution conductivity properties. They were non-electrolytes in dry DMF at 25 °C but showed 1:1 electrolytic behavior in an aqueous medium due to dissociation of one chloride ligand as evidenced from the mass spectral study. Complexes 1 and 2 showed absorption bands at 500 and 535 nm, respectively. The calf thymus DNA melting study revealed their interaction through DNA crosslinking on exposure to light which was further confirmed from the alkaline agarose gel electrophoresis using plasmid supercoiled pUC19 DNA. Complex 2 showed disruption of the mitochondrial membrane potential in the JC-1 (1,1',3,3'-tetraethyl-5,5',6,6'-tetrachloroimidacarbocyanine iodide) assay. The complexes were photocytotoxic in visible light (400-700 nm, power: 10 J cm-2) in cervical cancer HeLa and breast cancer MCF-7 cells. Complex 2 having a photoactive diiodo­boron-dipyrromethene moiety gave a singlet oxygen quantum yield (ΦΔ) value of ~0.6. It showed singlet oxygen mediated apoptotic photodynamic therapy activity with remarkably low IC50 (half maximal inhibitory concentration) value of ~0.15 µM. The cis-disposition of chlorides gave a cis-divacant 4-coordinate intermediate structure from the density functional theory (DFT) study thus mimicking the DNA crosslinking property of cisplatin.

Glycodelin regulates the numbers and function of peripheral natural killer cells.

Natural killer (NK) cells comprise of ∼70% of the immune cell population in the maternal decidua and ∼15% of the mononuclear cells in the peripheral blood. The decidual NK cells capable of producing high levels of cytokines are functionally distinct from the peripheral NK cells that exhibit high cytotoxicity. The numbers of peripheral NK cells and their cytotoxicity potential have been correlated with pregnancy outcome. In the same context, glycodelin, an immunomodulatory protein, has been recognized to be essential for the establishment and maintenance of pregnancy, and its' reduced levels are associated with recurrent spontaneous abortions. We investigated the effect of glycodelin on the peripheral NK cells. Our results reveal that glycodelin suppresses the cytotoxicity of peripheral NK cells via downregulating perforin, granzyme B and IFNγ. Glycodelin also induces caspase-dependent death in only activated peripheral NK cells, the effect suggested to be mediated by glycodelin upon engaging with the CD7 cell surface receptor. Thus, during pregnancy, glycodelin modulates the function and the number of cytotoxic NK cells that pose a deleterious effect on the fetus, a semi-allograft. This study provides insights into the mechanism of the regulatory effect of glycodelin on NK cells and could possibly be exploited for the management of miscarriages.

A minimally-invasive cryogel based approach for the development of human ectopic liver in a mouse model.

Human liver tissue is preferable over nonhuman liver tissue for preclinical drug screening, as the former can better predict side effects specific to humans. However, due to limited supply and ethical issues with human liver tissue, it is desirable to develop an animal model having functional human liver tissue. In this study, we have established an ectopic functional human liver tissue in a mouse model, using a minimally-invasive method. Firstly, a human liver tissue mass using HepG2 cells and poly(N-isopropylacrylamide) (PNIPAAm) incorporated poly(ethylene glycol)-alginate-gelatin (PAG) cryogel matrix was developed in vitro. It was later implanted in mouse peritoneal cavity using a 16 G needle. Viscoelastic nature along with low Young's modulus provided injectable properties to the cryogel. We confirmed minimal cell loss/death while injecting. Further, by in vivo study efficacy of both injectable and surgical implantation approaches were compared. No significant difference in terms of cell infiltration, human serum albumin (HSA) secretion and enzyme activity confirmed efficacy. This model developed using a minimally-invasive approach can overcome the limitations of surgical implantation due to its cost effective and user friendly nature.

Correction: Endoplasmic reticulum targeting tumour selective photocytotoxic oxovanadium(iv) complexes having vitamin-B6 and acridinyl moieties.

Correction for 'Endoplasmic reticulum targeting tumour selective photocytotoxic oxovanadium(iv) complexes having vitamin-B6 and acridinyl moieties' by Samya Banerjee et al., Dalton Trans., 2016, 45, 783-796.

Correction: Impact of metal binding on the antitumor activity and cellular imaging of a metal chelator cationic imidazopyridine derivative.

Correction for 'Impact of metal binding on the antitumor activity and cellular imaging of a metal chelator cationic imidazopyridine derivative' by Mithun Roy et al., Dalton Trans., 2011, 40, 4855-4864.

Correction: Endoplasmic reticulum targeted chemotherapeutics: the remarkable photo-cytotoxicity of an oxovanadium(iv) vitamin-B6 complex in visible light.

Correction for 'Endoplasmic reticulum targeted chemotherapeutics: the remarkable photo-cytotoxicity of an oxovanadium(iv) vitamin-B6 complex in visible light' by Samya Banerjee et al., Chem. Commun., 2014, 50, 5590-5592.

New Water-Soluble Oxyamino Chitosans as Biocompatible Vectors for Efficacious Anticancer Therapy via Co-Delivery of Gene and Drug.

Among the many nonviral gene delivery vectors, chitosan, being a polysaccharide of natural origin, has gained special importance. In this report, chitosan (CS) has been solubilized in water by preparing its O-carboxymethyl derivative, CS(CH2COOH), with an optimum degree of carboxymethylation. This has been further derivatized to get the pyridine-substituted product (py)CS(CH2COOH), where the degree of pyridine substitution (47%) was optimized based on zeta potential measurements. The optimized formulation showed a high gene binding ability, forming nanosized positively charged polyelectrolyte complexes with DNA. These polyplexes were stable to DNase and physiological polyanions such as heparin. They also exhibited minimal toxicity in vitro and showed transfection levels comparable to the commercial standard Lipofectamine 2000 and much higher than polyethylenimine (MW, 25 kDa). Additionally, in this study, a hitherto unknown oxyamine derivative of chitosan has been prepared by phthaloyl protection, tosylation, and Gabriel's phthalimide synthesis. Nearly 40% of the primary alcohols were successfully converted to oxyamino functionality, which was used for forming oxime with the anticancer drug doxorubicin. The pH sensitivity of the oxime ether linkage and stability under biologically relevant conditions were then used to establish the compound as a versatile drug delivery vector. Co-delivery of functional gene (p53) and drug (doxorubicin) was accomplished in vitro and in vivo with the chitosan-pyridine imine vector (py)CS(CH2COOH) and the newly synthesized doxorubicin oxime ether CS(Dox). Complete tumor regression with no tumor recurrence and appreciable survivability point to the in vivo effectiveness and biocompatibility of the designed composite formulation. Overall, the pH sensitivity of the oxime linkage aiding slow and steady drug release, together with the sustained gene expression by pyridine-tethered carboxymethyl chitosan, allows us to generate a nanobiocomposite with significantly high anticancer therapeutic potential.

Development and Characterization of a Potent Tumor Necrosis Factor-Alpha-Blocking Agent.

Tumor necrosis factor-α (TNFα), one of the major proinflammatory cytokines, plays a key role in an effective immune response. However, the chronic presence of TNFα can lead to several inflammatory disorders, such as rheumatoid arthritis, psoriasis, Crohn's disease, etc. Inhibition of TNFα by pharmacological inhibitors or antibodies has proven to be effective in palliative treatment to some extent. The aim of this study was to develop an anti-TNFα antibody, which may be used as a therapeutic option to inhibit TNFα-mediated cytotoxicity. We characterized several hybridoma clones secreting monoclonal antibodies (mAbs) to human-TNFα. Four mAbs rescued L929 fibroblast cells from TNFα-triggered cell death and one of these, namely C8, was found to have the highest affinity. To gain insights into the mechanism by which mAb C8 inhibits human TNFα-mediated toxicity, the epitope corresponding to the mAb was delineated. The antigenic determinant was found to comprise of the stretch of amino acids 99-120, of which, 102-104 (glutamine, arginine, glutamic acid) form the core epitope. The observation was supported by bioinformatics analyses of an antigen/antibody complex model. In addition, the binding affinity of mAb C8 to TNFα was found to be comparable with that of infliximab, which is a commercially available anti-TNFα mAb.

Tumor Chemosensitization through Oncogene Knockdown Mediated by Unique α-Tocopherylated Cationic Geminis.

Herein, siRNA transfection efficiency of a unique set of α-tocopherylated gemini lipids has been established in vitro and in vivo. High efficacy of oncogene silencing achieved using the biomacromolecular assembly, formed from siRNA complexes of co-liposomes containing an α-tocopherylated gemini lipid, has been utilized for tumor regression via chemosensitization. Delivery studies with the gemini bearing hydroxyethyl headgroup with octamethylene spacer (TH8S) pointed to a higher siRNA transfection efficacy than its analog without hydroxyethyl group (T8S). Owing to p53 upregulation, transfected cells showed enhanced sensitivity to the chemotherapeutic agent, doxorubicin. Studies in murine model revealed significantly low levels of survivin mRNA in xenograft tumors injected with siRNA lipoplexes, leading to effective inhibition of tumor growth and an increase in sensitivity of the tumors toward doxorubicin. These findings enable us to propose the anti-survivin siRNA carrying TH8S co-liposomes as a potent member of cancer management strategies using suicide gene therapy.

Correction: Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions.

Correction for 'Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions' by Bappa Maiti et al., Org. Biomol. Chem., 2018, 16, 1983-1993.

Correlation of abrin-mediated inhibition of protein synthesis and apoptosis.

The plant toxin, abrin, a type-II ribosome inactivating protein, is extremely lethal, the human fatal dose being ~1 µg/kg body weight. Abrin has been classified as an agent for bioterrorism, which is of concern. Conversely, the high toxic property of abrin has been employed in generating immunotoxins, whereas its toxin moiety is conjugated to cell surface marker-specific antibodies for cell-targeted killing. Different cell types exhibit variable levels of sensitivity to abrin toxicity; therefore, adequate knowledge of the molecular mechanism that governs the activity of the protein would be a safeguard. To gain insights into this, two cell lines requiring strikingly different concentrations of abrin for inactivating ribosomes were studied. Employing conjugates of the wild-type and active site mutant of abrin A chain with the ricin B chain, it was found that abrin-induced apoptosis was dependent on inhibition of protein synthesis (PSI) leading to ER-stress in Ovcar-3 cells, but not in KB cells. Abrin was also observed to cause direct DNA damage in KB cells, while in Ovcar-3 cells abrin-induced DNA damage was found to be dependent on caspases. Overall, the study demonstrates that the correlation of abrin-mediated PSI and apoptosis is cell-specific and abrin can induce more than one pathway to cause cell death. © 2018 IUBMB Life, 71(3):357-363, 2019.

Identification of a co-target for enhancing efficacy of sorafenib in HCC through a quantitative modeling approach.

Sorafenib (SFB), a multi-kinase inhibitor, is the only approved drug for treating hepatocellular carcinoma (HCC). However, SFB shows low efficacy in many cases. HCC related mortality therefore remains to be high worldwide. SFB, a multi-kinase inhibitor is also known to modulate the redox homeostasis in cancer cells. To understand the effect of SFB on the redox status, a quantitative understanding of the system is necessary. Kinetic modeling of the relevant pathways is a useful approach for obtaining a quantitative understanding of the pathway dynamics and to rank the individual factors based on the extent of influence they wield on the pathway. Here, we report a comprehensive model of the glutathione reaction network (GSHnet ), consisting of four modules and includes SFB-induced redox stress. We compared GSHnet simulations for HCC of six different etiologies with healthy liver, and correctly identified the expected variations in cancer. Next, we studied alterations induced in the system upon SFB treatment and observed differential H2 O2 dynamics in all the conditions. Using metabolic control analysis, we identified glutathione S-transferase (GST) as the enzyme with the highest selective control coefficient, making it an attractive co-target for potentiating the action of SFB across all six etiologies. As a proof-of-concept, we selected ethacrynic acid (EA), a known inhibitor of GST, and verified ex vivo that EA synergistically potentiates the cytotoxic effect of SFB. Being an FDA approved drug, EA is a promising candidate for repurposing as a combination therapy with SFB for HCC treatment.

Mitochondria-localizing BODIPY-copper(ii) conjugates for cellular imaging and photo-activated cytotoxicity forming singlet oxygen.

Copper(ii) acetylacetonates of N,N,N-donor dipicolylamine (dpa) ligands, viz. [Cu(L1)(acac)]ClO4 (1), [Cu(L2)(acac)]ClO4 (2) and [Cu(L3)(acac)]ClO4 (3), where L1 is benzyldipicolylamine (bzdpa), L2 and L3 are non-iodinated and diiodinated BODIPY (borondipyrromethene) ligands and Hacac is acetylacetone, were synthesized and characterized and their photocytotoxicity was studied. The BODIPY complex 2, structurally characterized by X-ray crystallography, has copper(ii) in a distorted square-pyramidal geometry (degree of trigonality, τ5 = 0.28). The one-electron paramagnetic and redox active copper(ii) complexes displayed 1 : 1 electrolytic behaviour in polar organic solvents. The BODIPY complexes 2 and 3 showed respective visible bands at 498 and 539 nm in 5% DMSO-phosphate buffered saline (PBS). Complex 2 displayed an emission band at 511 nm in 5% DMSO-PBS (λex = 465 nm) with a fluorescence quantum yield (ΦF) value of 0.15. Cellular imaging using this complex showed significant mitochondrial localization in HeLa and MCF-7 cancer cells. Complex 3 with a diiodo-BODIPY moiety was non-emissive (ΦF = 0.01) but acted as an efficient photosensitizer with a singlet oxygen quantum yield value of 0.59 (ΦΔ). Complex 3 showed a remarkable PDT effect with apoptotic cell death due to singlet oxygen giving IC50 values within 0.04-0.06 µM in HeLa and MCF-7 cells using visible light (400-700 nm), while being less toxic in the dark.

Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions.

Herein, five new α-tocopheryl cationic gemini lipids with hydroxyethyl bearing headgroups (THnS, n = 4, 5, 6, 8, 12) have been synthesized for efficient plasmid DNA (pDNA) delivery into cancer cells. Among these gemini lipid formulations, the lipid with an octamethylene [-(CH2)8] spacer (TH8S) showed the highest transfection efficiency (TE) that was comparable to that of the commercial standard lipofectamine 2000 (L2K) in terms of luciferase expression in HepG2 (liver hepatocellular carcinoma) cells. The addition of the helper lipid DOPE (1,2-dioleoyl phosphatidyl ethanolamine) with cationic lipids in mixed liposomes further enhanced the TE and the optimized molar ratio was 2 : 1 (DOPE : cationic lipid). The optimized co-liposomal formulation of TH8S (DOPE : TH8S = 2 : 1) showed a higher TE in HepG2, A549 (human lung carcinoma) and MCF7 (human breast adenocarcinoma) cells than other optimized co-liposomal formulations and was also significantly more potent than L2K. The comparison of the TE of DOPE-TH8S (2 : 1) with the gemini lipid T8T (the headgroup devoid of the hydroxyl group) further demonstrated the importance of the hydroxyethyl functionality at the level of the headgroup. Relatively good binding efficiency and easy release of pDNA (pGL3) were also observed with DOPE-TH8S (2 : 1) in the ethidium bromide (EB)-exclusion and re-intercalation assay, which may be the plausible reason for high TE. The lipoplexes were also characterized by atomic force microscopy (AFM), dynamic light scattering (DLS), zeta potential and small angle X-ray diffraction experiments. Greater cellular internalization of fluorescein tagged pDNA was also observed with DOPE-TH8S (2 : 1) lipoplexes compared to that with L2K. Retention of the TE of DOPE-TH8S (2 : 1) lipoplexes under high serum conditions was conferred by the presence of the tocopherol backbone and also the hydroxyethyl functionalities. The cellular internalization pathway of the lipoplexes was characterized by performing transfection experiment in the presence of inhibitors of different endocytic pathways and it was found to be caveolae mediated. An MTT based cell viability assay indicated that the lipoplex mediated gene delivery vectors exhibited low toxicity in all the three cancer cell lines studied.

Identification of a flavonoid isolated from plum (Prunus domestica) as a potent inhibitor of Hepatitis C virus entry.

Hepatitis C virus (HCV) infection is a major cause of chronic liver diseases that often requires liver transplantation. The standard therapies are limited by severe side effects, resistance development, high expense and in a substantial proportion of cases, fail to clear the infection which bespeak the need for development of well-tolerated antivirals. Since most of the drug development strategies target the replication stage of viral lifecycle, the identification of entry inhibitors might be crucial especially in case of liver-transplant recipients. In the present study we have evaluated fruits which are known for their hepatoprotective effects in order to screen for entry inhibitors. We report the identification of a flavonoid, rutin, isolated from Prunus domestica as a new HCV entry inhibitor. Characterization and confirmation of the chemical structure was done by LC-ESI-MS, NMR and IR spectral analyses. Rutin significantly inhibited HCV-LP binding to hepatoma cells and inhibited cell-culture derived HCV (HCVcc) entry into hepatoma cells. Importantly, rutin was found to be non-toxic to hepatoma cells. Furthermore, rutin inhibits the early entry stage of HCV lifecycle possibly by directly acting on the viral particle. In conclusion, rutin is a promising candidate for development of anti-HCV therapeutics in the management of HCV infection.