Hollow Mesoporous Molybdenum Single-Atom Nanozyme-Based Reactor for Enhanced Cascade Catalytic Antibacterial Therapy.

Purpose: The remarkable peroxidase-like activity of single-atom nanozymes (SAzymes) allows them to catalyze the conversion of H2O2 to •OH, rendering them highly promising for antibacterial applications. However, their practical in vivo application is hindered by the near-neutral pH and insufficient H2O2 levels present in physiological systems. This study was aimed at developing a SAzyme-based nanoreactor and investigating its in vivo antibacterial activity. Methods: We developed a hollow mesoporous molybdenum single-atom nanozyme (HMMo-SAzyme) using a controlled chemical etching approach and pyrolysis strategy. The HMMo-SAzyme not only exhibited excellent catalytic activity but also served as an effective nanocarrier. By loading glucose oxidase (GOx) with HMMo-SAzyme and encapsulating it with hyaluronic acid (HA), a nanoreactor (HMMo/GOx@HA) was constructed as glucose-triggered cascade catalyst for combating bacterial infection in vivo. Results: Hyaluronidase (HAase) at the site of infection degraded HA, allowing GOx to convert glucose into gluconic acid and H2O2. An acid environment significantly enhanced the catalytic activity of HMMo-SAzyme to promote the further catalytic conversion of H2O2 to •OH for bacterial elimination. In vitro and in vivo experiments demonstrated that the nanoreactor had excellent antibacterial activity and negligible biological toxicity. Conclusion: This study represents a significant advancement in developing a cascade catalytic system with high efficiency based on hollow mesoporous SAzyme, promising the advancement of biological applications of SAzyme.

Improved Synthesis of a Novel Biodegradable Tunable Micellar Polymer Based on Partially Hydrogenated Poly(ß-malic Acid-co-benzyl Malate).

Poly(benzyl malate) (PBM), together with its derivatives, have been studied as nanocarriers for biomedical applications due to their superior biocompatibility and biodegradability. The acquisition of PBM is primarily from chemical routes, which could offer polymer-controlled molecular weight and a unique controllable morphology. Nowadays, the frequently used synthesis from L-aspartic acid gives an overall yield of 4.5%. In this work, a novel synthesis route with malic acid as the initiator was successfully designed and optimized, increasing the reaction yield up to 31.2%. Furthermore, a crystalline form of PBM (PBM-2) that polymerized from high optical purity benzyl-ß-malolactonate (MLABn) was discovered during the optimization process. X-ray diffraction (XRD) patterns revealed that the crystalline PBM-2 had obvious diffraction peaks, demonstrating that its internal atoms were arranged in a more orderly manner and were different from the amorphous PBM-1 prepared from the racemic MLABn. The differential scanning calorimetry (DSC) curves and thermogravimetric curves elucidated the diverse thermal behaviors between PBM-1 and PBM-2. The degradation curves and scanning electron microscopy (SEM) images further demonstrated the biodegradability of PBM, which have different crystal structures. The hardness of PBM-2 implied the potential application in bone regeneration, while it resulted in the reduction of solubility when compared with PBM-1, which made it difficult to be dissolved and hydrogenated. The solution was therefore heated up to 75 °C to achieve benzyl deprotection, and a series of partially hydrogenated PBM was sequent prepared. Their optimal hydrogenation rates were screened to determine the optimal conditions for the formation of micelles suitable for drug-carrier applications. In summary, the synthesis route from malic acid facilitated the production of PBM for a shorter time and with a higher yield. The biodegradability, biosafety, mechanical properties, and adjustable hydrogenation widen the application of PBM with tunable properties as drug carriers.

A Nano Drug Delivery System Based on Angelica sinensis Polysaccharide for Combination of Chemotherapy and Immunotherapy.

Combination of chemotherapy and immunotherapy has been a promising strategy in cancer treatment. Polysaccharides from Angelica sinensis (AP), a well-known Chinese herbal medicine, have been proved to have good immunomodulatory activity. In the present study, an enzyme-sensitive tumor-targeting nano drug delivery system (AP-PP-DOX (doxorubicin), PP stood for peptide) was constructed. In this system, Angelica polysaccharides act as not only carriers to targeted delivery of drugs to tumor tissue but also effectors to improve tumor microenvironment and enhance immune function, resulting in synergistic antitumor effect with chemotherapy drugs. The structure of this conjugate was confirmed by FI-IR and 1H-NMR. The particle size and zeta potential of the nanoparticles were 129.00 ± 3.32 nm and -28.45 ± 0.22 mV, respectively. Doxorubicin (DOX) and AP could be quickly released from the AP-PP-DOX under the presence of matrix metalloproteinase 2 (MMP2). The released DOX showed good antitumor efficacy in vitro. The treatment of released AP moiety increased the expression of IL-2, while that of IL-10 was decreased, showing potential in restoring Th1/Th2 immune balance in tumor microenvironment. In a word, this drug delivery system, with specific tissue targeting and tumor microenvironment improvement, will open a new avenue for combination treatment of cancer.

Construction of a novel "ball-and-rod" MSNs-pp-PEG system: a promising antitumor drug delivery system with a particle size switchable function.

To utilize the advantages of drug carriers of different sizes, a size switchable "ball-and-rod" drug delivery system was constructed, which could switch its size in response to enzymes in tumors. It would be a promising system with long circulation and deep penetration properties, which enable its application in tumor treatment.

Enhanced Endocytic and pH-Sensitive Poly(malic acid) Micelles for Antitumor Drug Delivery.

Poly(ß-benzyl malate) (PBM), a derivative of poly(ß-malic acid) (PMLA), is a potential antitumor drug carrier due to its desirable biocompatibility and nontoxicity. In this study, micelles based on PBM-PEG polymers were prepared, which possessed several key features, including (i) micelle formation via self-assembly with a size of approximately 100 nm, (ii) π-π stacking interactions between the polymer chains and between the polymer and the drug, improving the stability of micelles and drug loading capacity (drug loading rate increased to 20 wt%), (iii) the cell penetrating peptide (TAT) was shielded by a long PEG chain before reaching the tumor site and exposed to tumor tissue, and (iv) high efficiency tumor uptake via exposure to TAT. At the site of a tumor, the extracellular pH level caused cleavage of the hydrazine bond, which led to the exposure of TAT on the polymeric micelles, thus enhancing cellular internalization. Then, the polymeric micelles disintegrated and DOX was released in response to the acidic pH in the lysosomal and endosomal compartments within the tumor cells. Both in vitro and in vivo efficacy studies indicated that this pH-sensitive PBM polymeric micelle is a promising antitumor drug carrier.

Stimuli-responsive polymeric micelles for drug delivery and cancer therapy.

Polymeric micelles (PMs) have been widely investigated as nanocarriers for drug delivery and cancer treatments due to their excellent physicochemical properties, drug loading and release capacities, facile preparation methods, biocompatibility, and tumor targetability. They can be easily engineered with various functional moieties to further improve their performance in terms of bioavailability, circulation time, tumor specificity, and anticancer activity. The stimuli-sensitive PMs capable of responding to various extra- and intracellular biological stimuli (eg, acidic pH, altered redox potential, and upregulated enzyme), as well as external artificial stimuli (eg, magnetic field, light, temperature, and ultrasound), are considered as "smart" nanocarriers for delivery of anticancer drugs and/or imaging agents for various therapeutic and diagnostic applications. In this article, the recent advances in the development of stimuli-responsive PMs for drug delivery, imaging, and cancer therapy are reviewed. The article covers the generalities of stimuli-responsive PMs with a focus on their major delivery strategies and newly emerging technologies/nanomaterials, discusses their drawbacks and limitations, and provides their future perspectives.

Optimal Design of Novel Functionalized Nanoconjugates Based on Polymalic Acid for Efficient Tumor Endocytosis with Enhanced Anticancer Activity.

To overcome the strong negative charge and improve the endocytosis of poly-ß-malic acid (PMLA) as a drug carrier, a pH-sensitive nanoconjugate of PMLA/hyd-PEG5000/PEG2000-TAT/DOX (PHPTD) was developed. The trans activator of transcription (TAT) modified with polyethylene glycol2000(PEG2000) was conjugated with the PMLA backbone which improved the endocytosis of PMLA. PEG5000 was utilized to shield TAT by a pH-sensitive hydrazone (Hyd) bond. In order to decrease the potential risk of accelerated blood clearance (ABC) phenomenon by anti-PEG IgM, the minimal content of TAT for penetrating tumor cells and the optimal protecting layer density of PEG5000 were screened. The result showed that 0.3 mol% TAT was enough to efficiently improve cellular uptake of PMLA (30 kda). The cytotoxicity and the 1H-NMR results indicated that 3.6 mol% PEG5000-modified nanoconjugates could shield 0.3 mol% TAT. The antitumor effect in breast cancer cells (MDA-MB-231) in tumor-bearing BALB/C mice demonstrated that this nanoconjugates exhibits high therapeutic efficiency in artificial solid tumors and low toxicity to normal tissues. It is indicated that TAT could be hidden in the long chain of PEG5000 at a neutral pH, when arrival to the tumor extracellular microenvironment, PEG5000 was cleaved from the nanoconjugates through the hydrazone bond due to the acidic tumor environment. Then, TAT was exposed, allowing the nanoconjugates to be transported into tumor cells. Our findings provide important and detailed information regarding the optimal content of TAT and the shielded density of PEG5000 and reveal their abilities of tumor penetration and potential for the efficient drug carrier.

Dual-pH Sensitive Charge-reversal Nanocomplex for Tumor-targeted Drug Delivery with Enhanced Anticancer Activity.

Poly(ß-L-malic acid) (PMLA), a natural aliphatic polyester, has been proven to be a promising carrier for anti-cancer drugs. In spite of excellent bio-compatibility, the application of PMLA as the drug carrier for cancer therapy is limited by its low cellular uptake efficiency. The strong negative charge of PMLA impedes its uptake by cancer cells because of the electrostatic repulsion. In this study, a dual pH-sensitive charge-reversal PMLA-based nanocomplex (PMLA-PEI-DOX-TAT@PEG-DMMA) was developed for effective tumor-targeted drug delivery, enhanced cellular uptake, and intracellular drug release. The prepared nanocomplex showed a negative surface charge at the physiological pH, which could protect the nanocomplex from the attack of plasma proteins and recognition by the reticuloendothelial system, so as to prolong its circulation time. While at the tumor extracellular pH 6.8, the DMMA was hydrolyzed, leading to the charge reversal and exposure of the TAT on the polymeric micelles, thus enhancing the cellular internalization. Then, the polymeric micelles underwent dissociation and drug release in response to the acidic pH in the lyso/endosomal compartments of the tumor cell. Both in vitro and in vivo efficacy studies indicated that the nanocomplex significantly inhibited the tumor growth while the treatment showed negligible systemic toxicity, suggesting that the developed dual pH-sensitive PMLA-based nanocomplex would be a promising drug delivery system for tumor-targeted drug delivery with enhanced anticancer activity.

Synthesis and properties of poly(DEX-GMA/AAc) microgel particle as a hemostatic agent.

Immediate hemorrhage control without secondary injury is pivotal for saving lives. In this study, polymerized glycidyl methacrylate derivative dextran/acrylic acid (poly(DEX-GMA/AAc)) microgel particles were prepared via emulsion polymerization method as a hemostatic agent. Microgel particles with size distribution of 500-800 nm were chosen because they showed more appropriate characteristics of swelling ratio and gelation time. The results revealed that the microgel particles had excellent swelling ratio of 68.95 g g-1 (w/w), which was 8.4 times that of counterpart clinically used microporous polysaccharide hemospheres, Arista. And poly(DEX-GMA/AAc) showed very short gelation time of 10-13 s. As a result, a gelled film could be formed rapidly after poly(DEX-GMA/AAc) absorbed water in blood when used on wounds, and then staunched bleeding. Poly(DEX-GMA/AAc) microgel particles showed better clotting ability than commercial hemostatic agent Flashclot in vitro. In addition, poly(DEX-GMA/AAc) did not cause exothermic burn when absorbing liquid, which was superior to Flashclot. No obvious toxicity was found in cytotoxicity study and skin irritancy test. Blood loss and hemostasis time were dramatically reduced by poly(DEX-GMA/AAc) microgel particles in hemorrhage models of ear vein, ear artery, liver and femoral artery in rabbits. These results indicated that the poly(DEX-GMA/AAc) microgel particles are a potential hemostatic agent with almost no cytotoxicity and good biocompatibility.

Preparation of Two Types of Polymeric Micelles Based on Poly(ß-L-Malic Acid) for Antitumor Drug Delivery.

Polymeric micelles represent an effective delivery system for poorly water-soluble anticancer drugs. In this work, two types of CPT-conjugated polymers were synthesized based on poly(ß-L-malic acid) (PMLA) derivatives. Folic acid (FA) was introduced into the polymers as tumor targeting group. The micellization behaviors of these polymers and antitumor activity of different self-assembled micelles were investigated. Results indicate that poly(ethylene glycol)-poly(ß-L-malic acid)-campotothecin-I (PEG-PMLA-CPT-I, P1) is a grafted copolymer, and could form star micelles in aqueous solution with a diameter of about 97 nm, also that PEG-PMLA-CPT-II (P2) is an amphiphilic block copolymer, and could form crew cut micelles with a diameter of about 76 nm. Both P1 and P2 micelles could improve the cellular uptake of CPT, especially the FA-modified micelles, while P2 micelles showed higher stability, higher drug loading efficiency, smaller size, and slower drug release rate than that of P1 micelles. These results suggested that the P2 (crew cut) micelles possess better stability than that of the P1 (star) micelles and might be a potential drug delivery system for cancer therapy.

Characterization of Compounds in Psoralea corylifolia Using High-Performance Liquid Chromatography Diode Array Detection, Time-of-Flight Mass Spectrometry and Quadrupole Ion Trap Mass Spectrometry.

High-performance liquid chromatography with diode array detection (HPLC-DAD), time-of-flight mass spectrometry (HPLC-TOFMS) and quadrupole ion trap mass spectrometry (HPLC-QITMS) were used for separation and identification of multi-components in Psoralea corylifolia. Benefiting from combining the accurate mass measurement of HPLC-TOFMS to generate elemental compositions, the complementary multilevel structural information provided by HPLC-QITMS and the characteristic UV spectra obtained from HPLC-DAD, 24 components in P. corylifolia were identified. The five groups of isomers were differentiated based on the fragmentation behaviors in QITMS and UV spectra. It can be concluded that an effective method based on the combination of HPLC-DAD, HPLC-TOFMS and HPLC-QITMS for identification of chemical components in P. corylifolia was established. The results provide essential data for further pharmacological and clinical studies of P. corylifolia and facilitate the rapid quality control of the crude drug.

Preparation of poly(ß-L-malic acid)-based charge-conversional nanoconjugates for tumor-specific uptake and cellular delivery.

In this study, a multifunctional poly(ß-L-malic acid)-based nanoconjugate with a pH-dependent charge conversional characteristic was developed for tumor-specific drug delivery. The short branched polyethylenimine-modified poly(ß-L-malic acid) (PEPM) was first synthesized. Then, the fragment HAb18 F(ab')2 and 2,3-dimethylmaleic anhydride were covalently attached to the PEPM to form the nanoconjugate, HDPEPM. In this nanoconjugate, the 2,3-dimethylmaleic anhydride, the shielding group, could shield the positive charge of the conjugate at pH 7.4, while it was selectively hydrolyzed in the tumor extracellular space (pH 6.8) to expose the previously-shielded positive charge. To study the anticancer activity, the anticancer drug, doxorubicin, was covalently attached to the nanoconjugate. The doxorubicin-loaded HDPEPM nanoconjugate was able to efficiently undergo a quick charge conversion from -11.62 mV to 9.04 mV in response to the tumor extracellular pH. The electrostatic interaction between the positively charged HDPEPM nanoconjugates and the negatively charged cell membrane significantly enhanced their cellular uptake, resulting in the enhanced anticancer activity. Also, the tumor targetability of the nanoconjugates could be further improved via the fragment HAb18 F(ab')2 ligand-receptor-mediated tumor cell-specific endocytosis.

Novel protective role of endogenous cardiac myocyte P2X4 receptors in heart failure.

BACKGROUND: Heart failure (HF), despite continuing progress, remains a leading cause of mortality and morbidity. P2X4 receptors (P2X4R) have emerged as potentially important molecules in regulating cardiac function and as potential targets for HF therapy. Transgenic P2X4R overexpression can protect against HF, but this does not explain the role of native cardiac P2X4R. Our goal is to define the physiological role of endogenous cardiac myocyte P2X4R under basal conditions and during HF induced by myocardial infarction or pressure overload. METHODS AND RESULTS: Mice established with conditional cardiac-specific P2X4R knockout were subjected to left anterior descending coronary artery ligation-induced postinfarct or transverse aorta constriction-induced pressure overload HF. Knockout cardiac myocytes did not show P2X4R by immunoblotting or by any response to the P2X4R-specific allosteric enhancer ivermectin. Knockout hearts showed normal basal cardiac function but depressed contractile performance in postinfarct and pressure overload models of HF by in vivo echocardiography and ex vivo isolated working heart parameters. P2X4R coimmunoprecipitated and colocalized with nitric oxide synthase 3 (eNOS) in wild-type cardiac myocytes. Mice with cardiac-specific P2X4R overexpression had increased S-nitrosylation, cyclic GMP, NO formation, and were protected from postinfarct and pressure overload HF. Inhibitor of eNOS, L-N(5)-(1-iminoethyl)ornithine hydrochloride, blocked the salutary effect of cardiac P2X4R overexpression in postinfarct and pressure overload HF as did eNOS knockout. CONCLUSIONS: This study establishes a new protective role for endogenous cardiac myocyte P2X4R in HF and is the first to demonstrate a physical interaction between the myocyte receptor and eNOS, a mediator of HF protection.

An apple oligogalactan suppresses endotoxin-induced cyclooxygenase-2 expression by inhibition of LPS pathways.

Colorectal cancer (CRC) is one of the most common cancers and a leading cause of cancer-related mortality in developed countries. Many ingredients of apples have been proven to have anti-inflammatory and anti-carcinogenic characteristics, and show benefits for CRC prevention. The aim of this study, therefore, was to evaluate inhibitory effect of an apple oligogalactan (AOG) on pro-inflammatory endotoxin lipopolysaccharide (LPS)-activated human colon carcinoma cells HT-29 and SW-620 and investigate the possible mechanisms. The two cell lines were pretreated with AOG (0.1-1 g/L) for 30 min and then treated with 10 µg/mL LPS. Real time PCR, Western blot, electrophoretic mobility shift assay (EMSA), and ELISA were used to detect the expression and activity of cyclooxygenase-2 (COX-2), NF-κB and MAPKs pathways. AOG significantly inhibited the expression and activity of COX-2 in LPS-activated human colon carcinoma cells HT-29 and SW-620. The mechanisms of AOG-suppressed COX-2 expression may be through inhibiting the phosphorylation of MAPKs and the activation of NF-κB and AP-1. These data may provide another molecular basis for understanding how apples act to prevent CRC and indicate that AOG may be useful for treatment of colitis and prevention of carcinogenesis.

Chemical constituents of the root of Jasminum giraldii.

Two new compounds, ethylconiferin and (-)-lariciresinol 4-(6'''-O-cinnamyl-ß-D-glucopyranoside), along with the three known compounds (+)-pinoresinol, (+)-cycloolivil, nobiletin, were isolated from the root of Jasminum girialdii. All these compounds were isolated for the first time from this source. Their structures were elucidated on the basis of extensive spectroscopic analysis and chemical methods. In addition, the in vitro cytotoxic activity of these compounds was evaluated. The results showed that none of the compounds had any significant inhibitory activities on the proliferation of HCT-116 and SW-620 cells.

The therapeutic effect of 2-cyclohexylthio-AMP in heart failure.

AIM: : The aim of this study was to investigate the therapeutic effect of 2-cyclohexylthio-adenosine 5'-monophosphate (AMP) in mice with heart failure (HF). METHODS: : 2-Cyclohexylthio-AMP was dissolved in phosphate-buffered saline and infused in mice with ischemic HF after permanent left coronary [left anterior descending (LAD)] ligation and in calsequestrin (CSQ) mice with HF. Myocardial function ex vivo was determined in the working heart model. Cardiac function in vivo was assessed by echocardiography. RESULTS: : Injection of 2-cyclohexylthio-AMP induced a dose-dependent increase in +dP/dt, -dP/dt, and left ventricular developed pressure in normal wild-type mice and in CSQ mice with HF using the ex vivo working heart model. Spontaneous heart rate did not change after the injection of 2-cyclohexylthio-AMP. Compared with normal saline-treaded mice, chronic infusion of 2-cyclohexylthio-AMP in mice with ischemic HF after left coronary artery (LAD) ligation and in CSQ mice resulted in improved +dP/dt, -dP/dt, left ventricular developed pressure, and fractional shortening, restored the ß-adrenergic response and decreased heart weight/body weight ratios. CONCLUSIONS: : 2-Cyclohexylthio-AMP improved the cardiac contractile performance and rescued mice from HF. This salutary action may result from the reduction of myocardial hypertrophy and the restoration of the ß-adrenergic response in both LAD ligation and CSQ mouse models of HF. The fact that this agent can increase contractile performance without heart rate increase should be desirable in HF therapy.

Oligosaccharide from apple induces apoptosis and cell cycle arrest in HT29 human colon cancer cells.

It is reported that apple polysaccharide can prevent colon cancer growth and impede colon cancer progression. Apple oligosaccharide was prepared by the combination of alkaline hydrolysis and enzymolysis of apple polysaccharides, and purified by anion column chromatography. The aim of this study is to explore the effect of apple oligosaccharide on the cellular viability of human colon carcinoma cells (HT29 cells) and its mechanism. The results showed that apple oligosaccharide decreased the cellular viability of HT29 cells in dose-dependent manner. Meanwhile it enhanced the expression of Bax; and decreased the levels of Bcl-2 and Bcl-xl. Apple oligosaccharide induced cell cycle arrest in S phase, which correlated with the decreased expression of Cdk 2 and cyclin B1. These results indicated that apple oligosaccharide attenuated HT29 cell viability by inducing cell apoptosis and cell cycle arrest. Apple oligosaccharide is a potential chemoprevention agent or anti-tumor agent and is worthy of further study.

Comparision of piceid and resveratrol in antioxidation and antiproliferation activities in vitro.

BACKGROUND: The clinic therapeutic effect of resveratrol is limited due to its low oral bioavailability. Piceid, a precursor of resveratrol, is the most abundant form of resveratrol in nature. A number of studies have hypothesized that piceid may have the same bioactivities like those of resveratrol. The aim of this work is to compare piceid with resveratrol in antioxidation and antiproliferation activities in vitro. METHODS: The antioxidative effects of resveratrol and piceid were evaluated by phenanthroline-Fe²âº method and H2O2-induced oxidative injury cell model. The antiproliferation effects were determined by MTT method in human liver tumor HepG2 cells, human breast cancer MDA-MB-231 cells and MCF-7 cells. The effects of resveratrol and piceid on the cell cycle and the apoptosis were evaluated by flow cytometry. Additionally, the uptake profiles of resveratrol and piceid in cancer cells were observed using fluorescence microscopy and clarified by LC-MS/MS. CONCLUSION: Piceid exhibited higher scavenging activity against hydroxyl radicals than resveratrol in vitro. Resveratrol showed a significant protective effect against H2O2-induced cell damage. What is more, resveratrol had biphasic effects on tumor cells. Resveratrol and piceid only showed significant cytotoxicity on tumor cells at high concentration (≥50 µmol/L), while low concentration of resveratrol (<30 µmol/L) increased the cell viability. The principal effect of resveratrol and piceid on the viability of tumor cells was caused by the cell cycle arrest, while the effect on apoptosis was relatively minor. The reason that piceid showed lower biological activity than resveratrol at the same concentration was probably because piceid was more difficult in being uptaken by cells.

5'-Phosphate and 5'-phosphonate ester derivatives of (N)-methanocarba adenosine with in vivo cardioprotective activity.

Activation of a cardiac myocyte P2X4 receptor protects against heart failure. 5'-Phosphonate and 5'-phosphate analogues of AMP containing a (N)-methanocarba (bicyclo[3.1.0]hexane) system could protect from heart failure by potentially activating this cardioprotective channel. Phosphoesters and phosphonodiesters were synthesized and administered in vivo via a miniosmotic pump in a mouse ischemic heart failure model and most significantly increased intact heart contractile function (echocardiography) compared to vehicle infusion. Several new thio and deuterated phosphate derivatives were protective in a calsequestrin (CSQ) overexpressing heart failure model. Diethyl (7, MRS4084) and diisopropyl (8, MRS4074) phosphotriesters were highly protective in the ischemic model. Substitution of 2-Cl with iodo reduced protection in the CSQ model. Diisopropyl ester 16 (MRS2978) of (1'S,2'R,3'S,4'R,5'S)-4'-(6-amino-2-chloropurin-9-yl)-2',3'-(dihydroxy)-1'-(phosphonoethylene)bicyclo[3.1.0]hexane was highly efficacious (CSQ), while lower homologue 1'-phosphonomethylene derivative 14 was inactive. Thus, we identified uncharged carbocyclic nucleotide analogues that represent potential candidates for the treatment of heart failure, suggesting this as a viable and structurally broad approach.