Liposome Click Membrane Permeability Assay for Identifying Permeable Peptides.

PURPOSE: To develop a novel, target agnostic liposome click membrane permeability assay (LCMPA) using liposome encapsulating copper free click reagent dibenzo cyclooctyne biotin (DBCO-Biotin) to conjugate azido modified peptides that may effectively translocate from extravesicular space into the liposome lumen. METHOD: DBCO-Biotin liposomes were prepared with egg phosphatidylcholine and cholesterol by lipid film rehydration, freeze/thaw followed by extrusion. Size of DBCO-Biotin liposomes were characterized with dynamic light scattering. RESULTS: The permeable peptides representing energy independent mechanism of permeability showed higher biotinylation in LCMPA. Individual peptide permeability results from LCMPA correlated well with shifts in potency in cellular versus biochemical assays (i.e., cellular/ biochemical ratio) demonstrating quantitative correlation to intracellular barrier in intact cells. CONCLUSION: The study provides a novel membrane permeability assay that has potential to evaluate energy independent transport of diverse peptides.

The atlastin membrane anchor forms an intramembrane hairpin that does not span the phospholipid bilayer.

The endoplasmic reticulum (ER) is composed of flattened sheets and interconnected tubules that extend throughout the cytosol and makes physical contact with all other cytoplasmic organelles. This cytoplasmic distribution requires continuous remodeling. These discrete ER morphologies require specialized proteins that drive and maintain membrane curvature. The GTPase atlastin is required for homotypic fusion of ER tubules. All atlastin homologs possess a conserved domain architecture consisting of a GTPase domain, a three-helix bundle middle domain, a hydrophobic membrane anchor, and a C-terminal cytosolic tail. Here, we examined several Drosophila-human atlastin chimeras to identify functional domains of human atlastin-1 in vitro Although all chimeras could hydrolyze GTP, only chimeras containing the human C-terminal tail, hydrophobic segments, or both could fuse membranes in vitro We also determined that co-reconstitution of atlastin with reticulon does not influence GTPase activity or membrane fusion. Finally, we found that both human and Drosophila atlastin hydrophobic membrane anchors do not span the membrane, but rather form two intramembrane hairpin loops. The topology of these hairpins remains static during membrane fusion and does not appear to play an active role in lipid mixing.

Lunapark stabilizes nascent three-way junctions in the endoplasmic reticulum.

The endoplasmic reticulum (ER) consists of a polygonal network of sheets and tubules interconnected by three-way junctions. This network undergoes continual remodeling through competing processes: the branching and fusion of tubules forms new three-way junctions and new polygons, and junction sliding and ring closure leads to polygon loss. However, little is known about the machinery required to generate and maintain junctions. We previously reported that yeast Lnp1 localizes to ER junctions, and that loss of Lnp1 leads to a collapsed, densely reticulated ER network. In mammalian cells, only approximately half the junctions contain Lnp1. Here we use live cell imaging to show that mammalian Lnp1 (mLnp1) affects ER junction mobility and hence network dynamics. Three-way junctions with mLnp1 are less mobile than junctions without mLnp1. Newly formed junctions that acquire mLnp1 remain stable within the ER network, whereas nascent junctions that fail to acquire mLnp1 undergo rapid ring closure. These findings imply that mLnp1 plays a key role in stabilizing nascent three-way ER junctions.

A comprehensive lipid binding and activity validation of a cancer-specific peptide-peptoid hybrid PPS1.

We recently identified a peptide-peptoid hybrid, PPS1, which recognizes lipids that have an overall negative charge, such as phosphatidylserine (PS), phosphatidylglycerol (PG), phosphatidic acid (PA), and phosphatidylinositol (PI), but that does not bind to neutral lipids, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), and sphingomyelin (SM). The simple dimeric version of PPS1, PPS1D1, displayed strong cytotoxicity to cancer cells over normal cells in vitro and tumor burden in vivo. In this study, we comprehensively characterized the direct binding and activity of PPS1 on PS, PG, and PA using liposome-based assays and lung cancer cell lines that express these negatively charged lipids. First, the fluorescence polarization (FP) binding studies of fluoresceinated-PPS1 (PPS1-FITC) to PS-, PG-, and PA-containing PC-liposomes showed that the binding of PPS1 to PC-liposomes increased as concentrations of these lipids increased. In terms of activity, PPS1D1 induced the release of calcein from large, unilamellar PC-liposomes containing 15-30% PS, PG, and PA. PPS1D1 had no activity when the liposomes were composed of 100% PC. This effect was higher at 30% lipids than 15%, and the EC50 for PG and PA were higher than that of PS, indicating that PPS1D1 is more specific towards PS. PPS1D1 binds to and induces significant cytotoxicity in lung cancer cell lines H1693, HCC95, and H1395, which express negatively charged lipids, but had no effect on normal HBEC30KT cells, which has mostly PC in the outer layer. In addition, a series of previously developed PPS1D1 derivatives, which retain or lose activity, were tested with these liposome-based assays, and the data were equivalent to previous observations. This study provides comprehensive binding and activity validations of a unique peptide-peptoid hybrid, PPS1, on negatively charged lipids PS, PA, and PG that are elevated on cancer cell surfaces relative to normal human cell surfaces.

Salsalate improves glycaemia in overweight persons with diabetes risk factors of stable statin-treated cardiovascular disease: A 30-month randomized placebo-controlled trial.

OBJECTIVE: To assess long-term efficacy and safety of salsalate to improve glycemia in persons with diabetes risk, who are overweight with statin-treated, stable coronary heart disease. METHODS: Glycemic status was assessed in 192 persons without diabetes at baseline in a pre-specified secondary analysis from Targeting INflammation Using SALsalate in CardioVascular Disease (TINSAL-CVD), a multi-center, double-masked, randomized (1:1), placebo-controlled, parallel clinical trial. RESULTS: Participants were mostly Caucasian males, age 60±7 years, BMI 31.4±3.0 kg/m2 , fasting glucose 92.8±11.0 mg/dL, and HbA1c 5.8±0.3%. Reductions in mean fasting glucose -5.70 mg/dL (95%CI: -7.44 to -3.97 mg/dL, P<0.001), HbA1c -0.11% (95%CI: -0.210 to -0.002%, P=0.046) and glycated serum protein -81.8 µg/mL (95%CI: -93.7 to -69.9 µg/mL, P<0.001) were demonstrated in salsalate compared to placebo-assigned groups over 30 months. Reductions in fasting glucose and glycated serum protein were greater with salsalate compared to placebo in participants with prediabetes compared to a normoglycemic sub-group (Pinteraction =0.018). Salsalate lowered total white blood cell counts (mean difference -0.7x103 /µL, 95%CI: -1.0 to -0.4 x103 /µL, P<0.001) and increased adiponectin (mean difference 1.8 µg/mL, 95%CI: 0.9 to 2.6 µg/mL, P<0.001) and albuminurea (16.7 µg/mg, 95%CI: 6.4 to 27.1 µg/mg, P<0.001) compared to placebo, consistent with previous results for patients with type 2 diabetes taking salsalate for shorter times. CONCLUSIONS: Salsalate improves glycemia in obese persons at increased risk for diabetes, and hence may decrease risk of incident type 2 diabetes. Salsalate may inform new therapeutic approaches for diabetes prevention, but renal safety may limit clinical utility.

The Atlastin C-terminal tail is an amphipathic helix that perturbs the bilayer structure during endoplasmic reticulum homotypic fusion.

Fusion of tubular membranes is required to form three-way junctions found in reticular subdomains of the endoplasmic reticulum. The large GTPase Atlastin has recently been shown to drive endoplasmic reticulum membrane fusion and three-way junction formation. The mechanism of Atlastin-mediated membrane fusion is distinct from SNARE-mediated membrane fusion, and many details remain unclear. In particular, the role of the amphipathic C-terminal tail of Atlastin is still unknown. We found that a peptide corresponding to the Atlastin C-terminal tail binds to membranes as a parallel α helix, induces bilayer thinning, and increases acyl chain disorder. The function of the C-terminal tail is conserved in human Atlastin. Mutations in the C-terminal tail decrease fusion activity in vitro, but not GTPase activity, and impair Atlastin function in vivo. In the context of unstable lipid bilayers, the requirement for the C-terminal tail is abrogated. These data suggest that the C-terminal tail of Atlastin locally destabilizes bilayers to facilitate membrane fusion.

Identification of the minimum pharmacophore of lipid-phosphatidylserine (PS) binding peptide-peptoid hybrid PPS1D1.

We previously reported a unique peptide-peptoid hybrid, PPS1 that specifically recognizes lipid-phosphatidylserine (PS) and a few other negatively charged phospholipids, but not neutral phospholipids, on the cell membrane. The dimeric version of PPS1, i.e., PPS1D1 triggers strong cancer cell cytotoxicity and has been validated in lung cancer models both in vitro and in vivo. Given that PS and other negatively charged phospholipids are abundant in almost all tumor microenvironments, PPS1D1 is an attractive drug lead that can be developed into a globally applicable anti-cancer agent. Therefore, it is extremely important to identify the minimum pharmacophore of PPS1D1. In this study, we have synthesized alanine/sarcosine derivatives as well as truncated derivatives of PPS1D1. We performed ELISA-like competitive binding assay to evaluate the PS-recognition potential and standard MTS cell viability assay on HCC4017 lung cancer cells to validate the cell cytotoxicity effects of these derivatives. Our studies indicate that positively charged residues at the second and third positions, as well as four hydrophobic residues at the fifth through eighth positions, are imperative for the binding and activity of PPS1D1. Methionine at the first position was not essential, whereas the positively charged Nlys at the fourth position was minimally needed, as two derivatives that were synthesized replacing this residue were almost as active as PPS1D1.

In vivo quantitative study of sized-dependent transport and toxicity of single silver nanoparticles using zebrafish embryos.

Nanomaterials possess distinctive physicochemical properties (e.g., small sizes and high surface area-to-volume ratios) and promise a wide variety of applications, ranging from the design of high quality consumer products to effective disease diagnosis and therapy. These properties can lead to toxic effects, potentially hindering advances in nanotechnology. In this study, we have synthesized and characterized purified and stable (nonaggregation) silver nanoparticles (Ag NPs, 41.6 ± 9.1 nm in average diameter) and utilized early developing (cleavage-stage) zebrafish embryos (critical aquatic and eco- species) as in vivo model organisms to probe the diffusion and toxicity of Ag NPs. We found that single Ag NPs (30-72 nm diameters) passively diffused into the embryos through chorionic pores via random Brownian motion and stayed inside the embryos throughout their entire development (120 hours-post-fertilization, hpf). Dose- and size-dependent toxic effects of the NPs on embryonic development were observed, showing the possibility of tuning biocompatibility and toxicity of the NPs. At lower concentrations of the NPs (≤0.02 nM), 75-91% of embryos developed into normal zebrafish. At the higher concentrations of NPs (≥0.20 nM), 100% of embryos became dead. At the concentrations in between (0.02-0.2 nM), embryos developed into various deformed zebrafish. Number and sizes of individual Ag NPs embedded in tissues of normal and deformed zebrafish at 120 hpf were quantitatively analyzed, showing deformed zebrafish with higher number of larger NPs than normal zebrafish and size-dependent nanotoxicity. By comparing with our previous studies of smaller Ag NPs (11.6 ± 3.5 nm), we found striking size-dependent nanotoxicity that, at the same molar concentration, the larger Ag NPs (41.6 ± 9.1 nm) are more toxic than the smaller Ag NPs (11.6 ± 3.5 nm).

Single nanoparticle spectroscopy for real-time in vivo quantitative analysis of transport and toxicity of single nanoparticles in single embryos.

Nanomaterials exhibit distinctive physicochemical properties and promise a wide range of applications from nanotechnology to nanomedicine, which raise serious concerns about their potential environmental impacts on ecosystems. Unlike any conventional chemicals, nanomaterials are highly heterogeneous, and their properties can alter over time. These unique characteristics underscore the importance of study of their properties and effects on living organisms in real time at single nanoparticle (NP) resolution. Here we report the development of single-NP plasmonic microscopy and spectroscopy (dark-field optical microscopy and spectroscopy, DFOMS) and ultrasensitive in vivo assay (cleavage-stage zebrafish embryos, critical aquatic species) to study transport and toxicity of single silver nanoparticles (Ag NPs, 95.4 ± 16.0 nm) on embryonic developments. We synthesized and characterized purified and stable (non-aggregation) Ag NPs, determined their sizes and doses (number), and their transport mechanisms and effects on embryonic development in vivo in real time at single-NP resolution. We found that single Ag NPs passively entered the embryos through their chorionic pores via random Brownian diffusion and stayed inside the embryos throughout their entire development (120 h), suggesting that the embryos can bio-concentrate trace NPs from their environment. Our studies show that higher doses and larger sizes of Ag NPs cause higher toxic effects on embryonic development, demonstrating that the embryos can serve as ultrasensitive in vivo assays to screen biocompatibility and toxicity of the NPs and monitor their potential release into aquatic ecosystems.

Study of the multidrug membrane transporter of single living Pseudomonas aeruginosa cells using size-dependent plasmonic nanoparticle optical probes.

Multidrug membrane transporters (efflux pumps) in both prokaryotes and eukaryotes are responsible for impossible treatments of a wide variety of diseases, including infections and cancer, underscoring the importance of better understanding of their structures and functions for the design of effective therapies. In this study, we designed and synthesized two silver nanoparticles (Ag NPs) with average diameters of 13.1 +/- 2.5 nm (8.1-38.6 nm) and 91.0 +/- 9.3 nm (56-120 nm) and used the size-dependent plasmonic spectra of single NPs to probe the size-dependent transport kinetics of MexAB-OprM (multidrug transporter) in Pseudomonas aeruginosa in real time at nanometer resolution. We found that the level of accumulation of intracellular NPs in wild-type (WT) cells was higher than in nalB1 (overexpression of MexAB-OprM) but lower than in DeltaABM (deletion of MexAB-OprM). In the presence of proton ionophores (CCCP, inhibitor of proton motive force), we found that intracellular NPs in nalB1 were nearly doubled. These results suggest that MexAB-OprM is responsible for the extrusion of NPs out of cells and NPs (orders of magnitude larger than conventional antibiotics) are the substrates of the transporter, which indicates that the substrates may trigger the assembly of the efflux pump optimized for the extrusion of the encountered substrates. We found that the smaller NPs stayed inside the cells longer than larger NPs, suggesting the size-dependent efflux kinetics of the cells. This study shows that multisized NPs can be used to mimic various sizes of antibiotics for probing the size-dependent efflux kinetics of multidrug membrane transporters in single living cells.

In silico evaluation of apoptogenic potential and toxicological profile of triterpenoids.

AIM: Caspases-3 and 8 are key mediators of intrinsic and extrinsic pathway of apoptosis, respectively. Triterpenoids of natural and synthetic origin reported as anticancer agents with apoptotic potential and hence may prove to be good candidates for in silico testing against caspases-3 and 8. MATERIALS AND METHODS: Various naturally-occurring and synthetic triterpenoids were subjected to activity prediction using PASS Online software, and among them, 67 compounds were selected for further processing. Protein structure of caspase-3 (3DEI) and caspase-8 (3KJQ) was obtained from the protein data bank and docked with selected triterpenoids using AutoDock Tools and AutoDock Vina. Toxicological profile was predicted based on clinical manifestations using PASS online software. RESULTS: The high docking score of -10.0, -9.9, -9.8, and -9.5 were shown by friedelin, tingenone, albiziasaponin A, and albiziasaponin C, respectively, for caspase-3, and -11.0, -9.6, -9.6, and -9.4 by ß-boswellic acid, bryonolic acid, canophyllic acid, and CDDO, respectively, for caspase-8. Possible adverse events were predicted with varying degree of probability and major relevant effects were reported. Hydrostatic interactions along with formation of hydrogen bonds with specific amino acids in the binding pocket were identified with each triterpenoid. CONCLUSION: Lead molecules identified through this in silico study such as friedelin, tingenone, albiziasaponin, bryonolic acid, and canophyllic acid may be utilized for further in vitro/in vivo studies as apoptotic agents targeting caspases-3 and 8.

Anticancer activity of saponin isolated from Albizia lebbeck using various in vitro models.

ETHNOPHARMACOLOGICAL RELEVANCE: Albizia lebbeck (L.) Benth. (Family: Mimosaceae) is commonly known as Sirisha in Sanskrit. The leaves and pods of A. lebbeck were claimed to be used against cancer in traditional medicine. Previous studies using bark, leaves, seeds and pods of A. lebbeck showed cytotoxic activity against hepatic, colon, larynx, cervical and breast cancer cell lines. AIM OF THE STUDY: To evaluate the anticancer activity of saponin rich fraction of Albizia lebbeck by using various in vitro models. MATERIALS AND METHODS: Albiziasaponins (A-E) are oleanene triterpene presents in Albizia lebbeck were used for in silico studies. In silico testing of albiziasaponins for structure based pharmacological activity prediction using PASS Online software and docking with Autodock tool and Autodock Vina revels it's anticancer and apoptogenic potential. Antiproliferative activity of saponin rich fraction of A. lebbeck was performed using MCF-7 human breast cancer cells by MTT assay methods. Anti-angiogenic property of saponin rich fraction of A. lebbeck was evaluated in in vitro shell less chick embryo cultures with different concentrations (0.1 µg/ml, 0.5 µg/ml, and 1 µg/ml) by using ImageJ software. In vitro cultured lymphocytes chromosomal aberration assay was performed to determine the physical integrity of chromosomes in cells and effect of saponin rich fraction of A. lebbeck on cell cycle. Apoptogenic potential was evaluated using Caspases-3 and Caspase-8 ELISA assay in MCF-7 cells. RESULTS: Result of MTT assay showed IC50 of saponin rich fraction of A. lebbeck at 1 µg/ml in MCF-7 cells. Treatment with saponin rich fraction of A. lebbeck significantly (p < 0.05) reduced angiogenic parameters. Significant chromosomal aberrations (hypodiploid, hyperdiploid, ring, premature separation, Dicentric fragments, Acentric fragment, chromatid break, and chromosomal gap) were observed in saponin rich fraction of A. lebbeck treated groups. Treatment with saponin rich fraction of A. lebbeck increased levels of Caspases-3 (optical density of 0.24 at 450 nm) and Caspase-8 (optical density of 0.31 at 450 nm) as compared to staurosporine (optical density of 2.47 and 2.65 for caspases-3 and -8 respectively at 450 nm). CONCLUSION: In our study, saponin rich fraction of A. lebbeck showed antiproliferative, antiangiogenic and apoptogenic potential using various in-vitro models. It also found to increase chromosomal aberration and thereby may affect cell cycle.

Role of NAADP for calcium signaling in the salivary gland.

Coordination of intracellular Ca2+ signaling in parotid acini is crucial for controlling the secretion of primary saliva. Previous work from our lab has demonstrated acidic-organelle Ca2+ release as a participant in agonist-evoked signaling dynamics of the parotid acinar cell. Furthermore, results implicated a potential role for the potent Ca2+ releasing second messenger NAADP in these events. The current study interrogated a direct role of NAADP for Ca2+ signaling in the parotid salivary gland acinar cell. Use of live-cell Ca2+ imaging, patch-clamp methods, and confocal microscopy revealed for the first time NAADP can evoke or enhance Ca2+ dynamics in parotid acini. These results were compared with pancreatic acini, a morphologically similar cell type previously shown to display NAADP-dependent Ca2+ signals. Findings presented here may be relevant in establishing new therapeutic targets for those suffering from xerostomia produced by hypofunctioning salivary glands.

Identification of lipid-phosphatidylserine (PS) as the target of unbiasedly selected cancer specific peptide-peptoid hybrid PPS1.

Phosphatidylserine (PS) is an anionic phospholipid maintained on the inner-leaflet of the cell membrane and is externalized in malignant cells. We previously launched a careful unbiased selection targeting biomolecules (e.g. protein, lipid or carbohydrate) distinct to cancer cells by exploiting HCC4017 lung cancer and HBEC30KT normal epithelial cells derived from the same patient, identifying HCC4017 specific peptide-peptoid hybrid PPS1. In this current study, we identified PS as the target of PPS1. We validated direct PPS1 binding to PS using ELISA-like assays, lipid dot blot and liposome based binding assays. In addition, PPS1 recognized other negatively charged and cancer specific lipids such as phosphatidic acid, phosphatidylinositol and phosphatidylglycerol. PPS1 did not bind to neutral lipids such as phosphatidylethanolamine found in cancer and phosphatidylcholine and sphingomyelin found in normal cells. Further we found that the dimeric version of PPS1 (PPS1D1) displayed strong cytotoxicity towards lung cancer cell lines that externalize PS, but not normal cells. PPS1D1 showed potent single agent anti-tumor activity and enhanced the efficacy of docetaxel in mice bearing H460 lung cancer xenografts. Since PS and anionic phospholipid externalization is common across many cancer types, PPS1 may be an alternative to overcome limitations of protein targeted agents.

Effect of Targeting Inflammation With Salsalate: The TINSAL-CVD Randomized Clinical Trial on Progression of Coronary Plaque in Overweight and Obese Patients Using Statins.

IMPORTANCE: Inflammation may contribute to pathological associations among obesity, diabetes mellitus, and cardiovascular disease. OBJECTIVE: To determine whether targeting inflammation using salsalate compared with placebo reduces progression of noncalcified coronary artery plaque. DESIGN, SETTING, AND PARTICIPANTS: In the Targeting Inflammation Using Salsalate in Cardiovascular Disease (TINSAL-CVD) trial participants were randomly assigned between September 23, 2008, and July 5, 2012, to 30 months of salsalate or placebo in addition to standard, guideline-based therapies. Randomization was computerized and centrally allocated, with patients, health care professionals, and researchers masked to treatment assignment. Participants were overweight and obese statin-using patients with established, stable coronary heart disease. INTERVENTIONS: Salsalate (3.5 g/d) or placebo orally over 30 months. MAIN OUTCOMES AND MEASURES: The primary outcome was progression of noncalcified coronary artery plaque assessed by multidetector computed tomographic angiography. Secondary outcomes were other measures of safety and efficacy. RESULTS: Two hundred fifty-seven participants were randomized to salsalate (n = 129) or placebo (n = 128). Their mean (SD) age was 60.8 (7.0) years, and 94.0% (236 of 251) were male. One hundred ninety participants (89 in the salsalate group and 101 in the placebo group) completed the study. Compared with baseline, there was no increase in noncalcified plaque volume in the placebo-treated patients and no difference in change between the salsalate and placebo groups (mean difference, -1 mm3; 95% CI, -11 to 9 mm3; P = .87). Salsalate treatment decreased total white blood cell, lymphocyte, monocyte, and neutrophil counts and increased adiponectin levels without change in C-reactive protein levels. Fasting glucose, triglycerides, uric acid, and bilirubin levels were decreased in the salsalate group compared with the placebo group, while hemoglobin levels were increased. Urinary albumin levels increased, with tinnitus and atrial arrhythmias more common, in the salsalate group compared with the placebo group. CONCLUSIONS AND RELEVANCE: Salsalate when added to current therapies that include a statin does not reduce progression of noncalcified coronary plaque volume assessed by multidetector computed tomographic angiography in statin-using patients with established, stable coronary heart disease. The absence of progression of noncalcified plaque volume in the placebo group may limit interpretation of the trial results. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00624923.