Haimei Zhu

Nanosized aspirin-Arg-Gly-Asp-Val: delivery of aspirin to thrombus by the target carrier Arg-Gly-Asp-Val tetrapeptide.

Resistance and nonresponse to aspirin dramatically decreases its therapeutic efficacy. To overcome this issue, a small-molecule thrombus-targeting drug delivery system, aspirin-Arg-Gly-Asp-Val (A-RGDV), is developed by covalently linking Arg-Gly-Asp-Val tetrapeptide with aspirin. The 2D ROESY NMR and ESI-MS spectra support a molecular model of an A-RGDV tetramer. Transmission electron microscopy images suggest that the tetramer spontaneously assembles to nanoparticles (ranging from 5 to 50 nm in diameter) in water. Scanning electron microscopy images and atomic force microscopy images indicate that the smaller nanoparticles of A-RGDV further assemble to bigger particles that are stable in rat blood. The delivery investigation implies that in rat blood A-RGDV is able to keep its molecular integrity, while in a thrombus it releases aspirin. The in vitro antiplatelet aggregation assay suggests that A-RGDV selectively inhibits arachidonic acid induced platelet aggregation. The mechanisms of action probably include releasing aspirin, modifying cyclic oxidase, and decreasing the expression of GPIIb/IIIa. The in vivo assay demonstrates that the effective antithrombotic dose of A-RGDV is 16700-fold lower than the nonresponsive dose of aspirin.

RGD-peptides modifying dexamethasone: to enhance the anti-inflammatory efficacy and limit the risk of osteoporosis

Dexamethasone (Dex) is one of the most effective anti-inflammatory glucocorticoids, while the side effect, osteoporosis seriously limits its clinical use. Cell adhesion is involved in the onset of inflammation and osteoporosis, and RGD-peptides are well known as anti-adhesion peptides. To enhance the anti-inflammatory efficacy and limit the osteoporotic risk of Dex three novel conjugates of RGDV, RGDS and RGDF covalently modified Dex are presented here. For the xylene-induced ear edema model the ear edema of the mice treated with the conjugates was significantly lower than that of the mice treated with Dex. Receiving 15 day therapy the total volumetric bonemineral density, the peripheral quantitative CT and the femur weight of the mice treated with the conjugates were significantly higher than those of the mice treated with Dex. Therefore covalently modifying Dex with RGDV, RGDS and RGDF not only increased the anti-inflammatory activity but also decreased the osteoporotic risk of Dex. In addition, the enhanced anti-inflammatory activity was correlated with the down-regulated DNA expression of the conjugates.

Cu(2+)-RGDFRGDS: exploring the mechanism and high efficacy of the nanoparticle in antithrombotic therapy.

Thrombosis disease has been the leading cause of morbidity and mortality worldwide. In the discovery of antithrombotic agents, three complexes of Cu2+ and repetitive arginine-glycine-aspartic acid (RGD) sequences, Cu(II)-Arg-Gly-Asp-Ser-Arg-Gly-Asp-Ser (Cu[II]-4a), Cu(II)-Arg-Gly-Asp-Val-Arg-Gly-Asp-Val (Cu[II]-4b), and Cu(II)-Arg-Gly-Asp-Phe-Arg-Gly-Asp-Phe (Cu[II]-4c), were previously reported, of which Cu(II)-4a and Cu(II)-4c possessed the highest in vitro and in vivo activity, respectively. Transmission electron microscopy (TEM) images visualized that Cu(II)-4a and Cu(II)-4c formed nanoaggregates and nanoparticles, respectively. However, the details of the formation of the nanospecies complexes and of the mechanism for inhibiting thrombosis remain to be clarified. For this purpose, this study designed a novel complex of Cu(II) and the RGD octapeptide, Arg-Gly-Asp-Phe-Arg-Gly-Asp-Ser (RGDFRGDS), consisting of Arg-Gly-Asp-Phe of Cu(II)-4c and Arg-Gly-Asp-Ser of Cu(II)-4a, to colligate their biological and nanostructural benefits. In contrast with Cu(II)-4a, -4b, and -4c, Cu(II)-RGDFRGDS (Cu2+-FS) had high antiplatelet and antithrombotic activities, with the formed nanoparticles having a porous surface. Additionally, this paper evidenced the dimer had the basic structural unit of Cu2+-FS in water, theoretically simulated the formation of Cu2+-FS nanoparticles, and identified that Cu2+-FS activity in decreasing glycoprotein IIb/IIIa, P-selectin, and IL-8 was responsible for the antithrombotic action. Finally, adherence onto the surface and entry into the cytoplasm were considered the steps of a two-step model for the blocking of platelet activation by Cu2+-FS nanoparticles. Findings indicated that the antiplatelet aggregation activity of Cu2+-FS was 10–52 times higher than that of RGDFRGDS, while the effective dose for antithrombotic action was 5,000 times lower than that of RGDFRGDS.

The application of tetrahydroisoquinoline-3-carbonyl-TARGD(F)F as an anti-thrombotic agent having dual mechanisms of action

Platelet surface glycoproteins P-selectin and GPIIb/IIIa are implicated in the formation of platelet-fibrin-leukocyte thrombus and platelet-fibrin-platelet thrombus, respectively. In the current study, taking N-(3S-tetrahydroisoquinoline-3-carbonyl)-Thr-Ala-Arg-Gly-Asp-(Phe)-Phe (IQCA-TAFF) as a model compound, the molecular modeling, synthesis, and an evaluation system for a novel anti-thrombotic agent were investigated. The synthesis of IQCA-TAFF was achieved by coupling 3S-tetrahydro-isoquinoline-3-carboxylic acid (IQCA) and Thr-Ala-Arg-Gly-Asp(Phe)-Phe (TAFF). The molecular modeling indicated that IQCA-TAFF was able to occupy the active site pocket of P-selectin with its IQCA moiety and to block GPIIb/IIIa fibrinogen-binding sites with its TAFF moiety, respectively. These are consistent with the dual inhibition of the expressions of P-selectin and GPIIb/IIIa, and with the in vitro anti-platelet aggregation activity of IQCA-TAFF. Besides, the dual suppression of P-selectin and GPIIb/IIIa leads to significant in vivo efficacy of IQCA-TAFF, 500-fold higher than those of IQCA and TAFF, respectively. Transmission electron microscopy (TEM) images indicated that in water, IQCA-TAFF concentration-dependently formed nano-globes. The molecular modeling, in vitro bioassay, in vivo bioassay, action mechanism investigation, and nano-image visualization together constitute a model system to characterize the anti-thrombotic agent capable of simultaneously inhibiting P-selectin and GPIIb/IIIa mediated thrombosis.

Energy minimized crystal structures of P-selectins based on molecular dynamics simulation: leading to two average structures capable of designing anti-thrombotic agents

In the most frequent cardiovascular events, deep vein thrombosis has been one of the most prominent causes of morbidity and mortality. Soluble P-selectin plays an essential role in the formation of thrombosis and has been considered a target of anti-thrombotic agents. With regard to molecular modeling, here the theoretical studies were performed on variant P-selectin structures. By removing SLex from PDB 1G1R or removing both SLex and PSGL-1 from PDB 1G1S, minimizing the energy of the formed structures, and performing molecular dynamics simulations, two average structures of P-selectins were obtained. A series of comparisons of the properties reflecting the quality of the two average structures, such as the backbone RMSD values, RMSF values, the change of the secondary structures, the conformation flexible regions and the correlated motions demonstrated that both of the two average structures are suitable and equally important for anti-thrombotic agent design.

Design, synthesis and evaluation of a novel π–π stacking nano-intercalator as an anti-tumor agent

Based on the knowledge that cyclohexane-1,4-dione, piperazine and β-carboline are the essential building blocks of DNA intercalators, β-carboline-3-carboxylic acid is a π–π stack-like DNA intercalator, and β-carboline derivatives can form nanoparticles, this paper hypothesized that (2′S,5′S)-tetrahydropyrazino[1′,2′:1,6]- di{2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole}-1′,4′-dione (THPDTPI) would be a π–π stacking lead nano-intercalator. The docking investigation found that THPDTPI can intercalate into DNA in a π–π stacking manner. The simple condensation of 3S-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid provided THPDTPI in good yield and high purity. The TEM, SEM and AFM imaging visualized that THPDTPI formed nanoparticles in ultrapure water, in the solid state and in rat plasma. The Faraday–Tyndall effect proved that THPDTPI exhibited nano-properties in pH 2.0 and pH 7.0 water. Spectrophotometric assays suggested that the interaction model of THPDTPI and CT DNA was π–π stacking intercalation. In vivo THPDTPI dose-dependently slowed the tumor growth of S180 mice with a minimal effective dose of 0.01 μmol kg−1 per day. In vitro THPDTPI exhibited anti-proliferation activities on S180 and HeLa cells with IC50 values of 0.39 and 3.5 μM, respectively. Even when the single dose was raised up to 10000 fold of the minimal effective dose, i.e. 100 μmol kg−1, THPDTPI still did not show liver, kidney and systemic toxicity in mice. These findings provide a strategy for designing THPDTPI-like π–π stacking nano-intercalators.

A novel lead of P-selectin inhibitor: Discovery, synthesis, bioassays and action mechanism.

By docking 126 derivatives of β-carboline-3-carboxylic acid, tetrahydro-β-carboline-3-carboxylic acid and indoloquinolizine into the active pocket of P-selectin (2-(3-(hydroxymethyl)-9H-pyrido[3,4-b]indol-1-yl)ethyl)-l-phenylalanine (HMCEF) was assigned a novel inhibitor. ELISA and flow cytometry experiments showed that HMCEF effectively down-regulated P-selectin expression and supported the rationality of the computer assistant screening, while UV spectrum experiments demonstrated that HMCEF directly bound to P-selectin. In vivo HMCEF dose dependently inhibited the rats and mice to form thrombus and had a minimal effective dose of 20nmol/kg, dose dependently inhibited inflammatory response of mice and had a minimal effective dose of 20nmol/kg. The decrease of serum TNFα and IL-8 of the treated mice was proposed to be the action mechanism of HMCEF inhibiting thrombosis and inflammation. All data imply that HMCEF is a novel lead of P-selectin inhibitor.

IQCA-TASS: a nano-scaled P-selectin inhibitor capable of targeting thrombus and releasing IQCA/TARGD(S)S in vivo

Thrombosis is a serious threat to human health worldwide. Tetrahydroisoquinoline-3-carboxylic acid (IQCA) is an antithrombotic agent, while Thr-Ala-Arg-Gly-Asp(Ser)-Ser (TASS) can target thrombus. Herein, tetrahydro-isoquinoline-3-carbonyl-Thr-Ala-Arg-Gly-Asp(Ser)-Ser (IQCA-TASS) was designed with the aim towards the discovery of a nano-delivery system for targeting thrombus. In vitro, IQCA-TASS acted on P-selectin and down-regulated P-selectin expression. The IC50 values of IQCA-TASS against the platelet aggregation induced by four aggregators were less than 0.45 nM. In vivo, IQCA-TASS targeted thrombus, released IQCA and TASS inside the thrombus, showed dose-dependent anti-thrombotic action, of which the minimal effective dose was 1 nmol kg-1, and showed anti-inflammatory action. Even with the dose up to 1 μmol kg-1, a dose of 1000 times the minimal effective dose, IQCA-TASS still induced no toxic reaction. In rat plasma, IQCA-TASS formed nanoparticles with diameters of less than 41 nm. The interactions of the nanoparticles with both resting and activated platelets were imaged. IQCA-TASS should be a safe nano-medicine capable of targeting thrombus and releasing anti-thrombotic/anti-inflammatory pharmacophores in disease sites.

DHDMIQK(KAP): a novel nano-delivery system of dihydroxyl-tetrahydro-isoquinoline-3-carboxylic acid and KPAK towards the thrombus

Vascular thrombosis is a major risk of the onset of stroke and so novel therapeutic candidates have been attracting interest. In this context, here docking based computer assisted screening and mesoscale simulation were used to design N-[(S)-6,7-dihydroxy-1,1-dimethyl-1,2,3,4-tetrahydroisoquinoline-3-carbonyl]-Lys(Pro-Ala-Lys), DHDMIQK(KAP), for inhibiting P-selectin expression. In vitro, 1 nM of DHDMIQK(KAP) effectively down-regulated P-selectin expression. In water, in rat plasma and in the solid state DHDMIQK(KAP) formed nanoparticles of a size capable of suitable delivery in the blood circulation. FT-MS and NOESY 2D NMR spectra showed DHDMIQK(KAP) formed hexamers, identified the intermolecular interactions of the hexamer, and assigned the hexamer a butterfly like conformation. Transmission electron microscopy, scanning electron microscopy and atomic force microscopy (AFM) imaged DHDMIQK(KAP) forming size-suitable nanoparticles for safe delivery in the blood circulation. In particular, AFM images showed that the nanoparticles effectively adhered onto the surfaces of the platelets. In vivo DHDMIQK(KAP) lysed the thrombus and inhibited thrombosis with a minimal effective dose of 0.01 nmol kg-1. FT-MS spectrum analyses defined a specific distribution of DHDMIQK(KAP) in the thrombus, but not in the blood and vital organs. Therefore, DHDMIQK(KAP) should be a novel nano-delivery system of 6,7-dihydroxyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid and KPAK to target the thrombus.

Enantiomeric diketopiperazines: getting insight into the impact of the configuration on the conformation, nanoimage, u-PA inhibition and anti-metastatic activity

The inhibition of urokinase-PA (u-PA) can block a series of pathological events, such as adhesion, migration and growth of malignant cells at the metastatic site. To discover new inhibitors the SS, RR, RS and SR of 3-(4-aminobutyl)-6-(1H-indole-3-ylmethyl)piperazine-2,5-dione (AIPZ) were designed, synthesized and evaluated. HPLC with a chiral column shows that their purity approaches 100%. The docking of these analogs toward the active site of u-PA resulted in high scores (118–134). The FT-MS spectra indicate that in aqueous solution the SS, RR, RS and SR of AIPZ exist as dimer, tetramer, trimer and trimer, respectively. The ROESY 2D NMR spectra give dimer, tetramer, trimer and trimer distinct conformations. The transmission electron microscopy and scanning electron microscopy show that the SS, RR, RS and SR can form distinct nano-species. The conversion of the plasminogen towards plasmin induced by UK is configuration-dependent, blocked by the SS, RR, RS and SR. The invasion and migration of HCCLM3 cells are configuration-dependent, inhibited by the SS, RR, RS and SR. The RR was selected as a representative for in vivo evaluation. At 5 μmol kg−1 of oral dose, RR not only blocked the metastasis of Lewis lung carcinoma cells towards the lung, but also slowed the growth of the primary solid tumors initiated either by S180 ascite tumor cells or by Lewis lung carcinoma cells, and it also prevented the mice from developing xylene-induced ear edema.