M6P-modified solid lipid nanoparticles loaded with matrine for the treatment of fibrotic liver.

Liver fibrosis is a key pathological process shared by the progression of various chronic liver diseases. Treatment of liver fibrosis can effectively block the occurrence and development of hepatic cirrhosis or even carcinoma. Currently, there is no effective drug delivery vehicle for curing liver fibrosis. In this study, we designed matrine (MT)-loaded mannose 6-phosphate (M6P) modified human serum albumin (HSA) conjugated solid lipid nanoparticles (SLN), named M6P-HSA-MT-SLN for treatment of hepatic fibrosis. We demonstrated that M6P-HSA-MT-SLN exhibited controlled and sustained release properties and good stability over 7 days. The drug release experiments showed that M6P-HSA-MT-SLN exhibited slow and controlled drug release characteristics. In addition, M6P-HSA-MT-SLN showed a significant targeted ability to fibrotic liver. Importantly, in vivo studies indicated that M6P-HSA-MT-SLN could significantly improve histopathological morphology and inhibit the fibrotic phenotype. In addition, in vivo experiments demonstrate that M6P-HSA-MT-SLN could reduce the expression of fibrosis markers and alleviate the damage of liver structure. Hence, the M6P-HSA-MT-SLN provide a promising strategy to deliver therapeutic agents to fibrotic liver to prevent liver fibrosis.

A Novel Dantrolene Sodium-Loaded Mixed Micelle Containing a Small Amount of Cremophor EL: Characterization, Stability, Safety and Pharmacokinetics.

Dantrolene sodium (DS) is the only drug specifically used for the treatment of malignant hyperthermia. Nevertheless, its clinical application is significantly restricted due to its aqueous insolubility and the limited formulations available in clinical practice. In order to solve these problems, a novel mixed micelle composed of phospholipid and Cremophor EL was designed and evaluated. The mixed micelle was prepared using a stirring- ultrasonic method. The Dynamic Light Scattering (DLS) results showed that the micelle was small in size (12.14 nm) and narrowly distributed (PdI = 0.073). Transmission Electron Microscopy (TEM) images showed that the micelle was homogeneous and spherical. The stability study indicated that the system was stable for storage and dilution with distilled water, while the safety testing showed that the micelle was safe for intravenous administration with low hemolysis rates and low allergic reaction rates. In the pharmaceutics study, the Cmax and AUC0-t of the DS-loaded micelle were 4- and 4.5- folds higher than that of the DS. Therefore, the constructed phospholipid-Cremophor EL mixed micelle is a promising drug delivery system for DS.

Bimodal protein solubility distribution revealed by an aggregation analysis of the entire ensemble of Escherichia coli proteins.

Protein folding often competes with intermolecular aggregation, which in most cases irreversibly impairs protein function, as exemplified by the formation of inclusion bodies. Although it has been empirically determined that some proteins tend to aggregate, the relationship between the protein aggregation propensities and the primary sequences remains poorly understood. Here, we individually synthesized the entire ensemble of Escherichia coli proteins by using an in vitro reconstituted translation system and analyzed the aggregation propensities. Because the reconstituted translation system is chaperone-free, we could evaluate the inherent aggregation propensities of thousands of proteins in a translation-coupled manner. A histogram of the solubilities, based on data from 3,173 translated proteins, revealed a clear bimodal distribution, indicating that the aggregation propensities are not evenly distributed across a continuum. Instead, the proteins can be categorized into 2 groups, soluble and aggregation-prone proteins. The aggregation propensity is most prominently correlated with the structural classification of proteins, implying that the prediction of aggregation propensity requires structural information about the protein.

Asymmetry in membrane protein sequence and structure: glycine outside rule.

The growth in the number of known membrane protein structures enables us to conduct new statistical analyses that were not possible before. Using the recently developed Orientation of Protein in Membrane database that has explicit orientation information, here we address the asymmetry in sequence and structure of transmembrane helical proteins. We found that the Gly is markedly more populated at the outer side, the noncytoplasmic side, rather than the inner side, and that Lys, Arg, Leu, and Ile are biased toward the inner side. The asymmetry in Gly distribution is partly attributed to the fact that the coil is more populated in the outer side. Moreover, the frequency of Gly in the coil, but not in the helix, is weakly biased toward the outer side. The asymmetry in Gly distribution is confirmed by a genome-wide sequence-based analysis of membrane proteins accompanied by transmembrane helix prediction.

Applying a grid technology to protein structure predictor "ROKKY".

This paper describes a sub-project of BioGrid project called "HTC (High Throughput Computing) group." Generally, a protein structure prediction which requires large amount of computational resources is done by trial-and-error method. HTC group have been developing a high throughput computing system with a flexible workflow handling mechanism for a protein structure prediction. In this paper, we show how to apply our high throughput computing system to the protein structure predictor called "ROKKY."

Identification of a potent and highly efficacious, yet slowly desensitizing CB1 cannabinoid receptor agonist.

1 The relationship of agonist efficacy to the rate of G protein-coupled receptor signaling desensitization is controversial. 2 Expressing inwardly rectifying potassium channels (GIRKs) in Xenopus oocytes, we have devised a signaling assay that clearly identifies CB1 cannabinoid receptor agonists with low intrinsic efficacy. 3 In this assay, the synthetic CB1 agonists, AM411, AM782, AM1902, AM2233 and WIN55,212-2 and the endogenous cannabinoid, 2-arachidonoyl ester, were full agonists. 4 The synthetic CB1 agonist AM356 (methanandamide), the endogenous cannabinoids, anandamide and 2-arachidonoyl ether, and the phytocannabinoid, Delta9THC, were partial agonists. 5 The rate of desensitization of CB1 was independent of agonist efficacy. WIN55,212-2, AM782, AM1902, AM2233, and 2-arachidonoyl glycerol ester all desensitized quickly, with desensitization rates varying from 14% min(-1) to 10% min(-1). AM356, AM411, anandamide, and Delta9THC all desensitized considerably slower, at a rate of 5% min(-1). 6 Despite high potency and efficacy, AM411 desensitized as slowly as anandamide and Delta9THC. 7 CB1 agonist efficacy and rate of desensitization are not necessarily related.

Distinct domains of the mu-opioid receptor control uncoupling and internalization.

Homologous desensitization of the micro opioid receptor (muOR) can be resolved into distinct processes that include the uncoupling of the muOR from its G-protein effectors and internalization of cell surface receptors. Using electrophysiological recordings of muOR activation of G-protein-coupled K+ channels (Kir3) in Xenopus laevis oocytes and AtT20 cells, confocal microscopy of receptor localization, and radioligand binding of cell surface receptors, we resolved these desensitization mechanisms to determine the domain of muOR important for receptor uncoupling. Activation of muOR by saturating concentrations of [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO), methadone, or fentanyl, but not morphine, produced robust internalization of a green fluorescent protein-tagged muOR. A subsaturating concentration of DAMGO (100 nM) did not cause receptor internalization but markedly reduced the subsequent responsiveness of Kir3 by uncoupling muOR. muOR desensitization in AtT20 cells was confirmed to be homologous, because desensitization by 100 nM DAMGO was blocked by dominant-negative forms of either G protein-coupled receptor kinase (GRK) or arrestin, and pretreatment with DAMGO did not affect the Kir3 response to somatostatin receptor activation. Alanine substitution of a single threonine in the second cytoplasmic loop of the muOR (Threonine 180) blocked agonist-dependent receptor uncoupling without affecting receptor internalization. These results suggest that GRK-dependent phosphorylation of muOR required threonine 180 for uncoupling but that a different GRK and arrestin-dependent mechanism controlled muOR internalization in AtT20 cells.

Salvinorin A, an active component of the hallucinogenic sage salvia divinorum is a highly efficacious kappa-opioid receptor agonist: structural and functional considerations.

The diterpene salvinorin A from Salvia divinorum has recently been reported to be a high-affinity and selective kappa-opioid receptor agonist (Roth et al., 2002). Salvinorin A and selected derivatives were found to be potent and efficacious agonists in several measures of agonist activity using cloned human kappa-opioid receptors expressed in human embryonic kidney-293 cells. Thus, salvinorin A, salvinorinyl-2-propionate, and salvinorinyl-2-heptanoate were found to be either full (salvinorin A) or partial (2-propionate, 2-heptanoate) agonists for inhibition of forskolin-stimulated cAMP production. Additional studies of agonist potency and efficacy of salvinorin A, performed by cotransfecting either the chimeric G proteins Gaq-i5 or the universal G protein Ga16 and quantification of agonist-evoked intracellular calcium mobilization, affirmed that salvinorin A was a potent and effective kappa-opioid agonist. Results from structure-function studies suggested that the nature of the substituent at the 2-position of salvinorin A was critical for kappa-opioid receptor binding and activation. Because issues of receptor reserve complicate estimates of agonist efficacy and potency, we also examined the agonist actions of salvinorin A by measuring potassium conductance through G protein-gated K(+) channels coexpressed in Xenopus oocytes, a system in which receptor reserve is minimal. Salvinorin A was found to be a full agonist, being significantly more efficacious than (trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide methane-sulfonate hydrate (U50488) or (trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide methane-sulfonate hydrate (U69593) (two standard kappa-opioid agonists) and similar in efficacy to dynorphin A (the naturally occurring peptide ligand for kappa-opioid receptors). Salvinorin A thus represents the first known naturally occurring non-nitrogenous full agonist at kappa-opioid receptors.

G-protein receptor kinase 3 (GRK3) influences opioid analgesic tolerance but not opioid withdrawal.

1. Tolerance to opioids frequently follows repeated drug administration and affects the clinical utility of these analgesics. Studies in simple cellular systems have demonstrated that prolonged activation of opioid receptors produces homologous receptor desensitization by G-protein receptor kinase mediated receptor phosphorylation and subsequent beta-arrestin binding. To define the role of this regulatory mechanism in the control of the electrophysiological and behavioral responses to opioids, we used mice having a targeted disruption of the G-protein receptor kinase 3 (GRK3) gene. 2. Mice lacking GRK3 did not differ from wild-type littermates neither in their response latencies to noxious stimuli on the hot-plate test nor in their acute antinociceptive responses to fentanyl or morphine. 3. Tolerance to the electrophysiological response to the opioid fentanyl, measured in vitro in the hippocampus, was blocked by GRK3 deletion. In addition, tolerance to the antinociceptive effects of fentanyl was significantly reduced in GRK3 knockouts compared to wild-type littermate controls. 4. Tolerance to the antinociceptive effects of morphine was not affected by GRK3 deletion although morphine tolerance in hippocampal slices from GRK3 knockout mice was significantly inhibited. Tolerance developed more slowly in vitro to morphine than fentanyl supporting previous work in in vitro systems showing a correlation between agonist efficacy and GRK3-mediated desensitization. 5. The results of these studies suggest that GRK3-mediated mechanisms are important components of both electrophysiologic and behavioral opioid tolerance. Fentanyl, a high efficacy opioid, more effectively produced GRK3-dependent effects than morphine, a low efficacy agonist.

De novo design of foldable proteins with smooth folding funnel: automated negative design and experimental verification.

De novo sequence design of foldable proteins provides a way of investigating principles of protein architecture. We performed fully automated sequence design for a target structure having a three-helix bundle topology and synthesized the designed sequences. Our design principle is different from the conventional approach, in that instead of optimizing interactions within the target structure, we design the global shape of the protein folding funnel. This includes automated implementation of negative design by explicitly requiring higher free energy of the denatured state. The designed sequences do not have significant similarity to those of any natural proteins. The NMR and CD spectroscopic data indicated that one designed sequence has a well-defined three-dimensional structure as well as alpha-helical content consistent with the target.

C-fos-deficient mouse hippocampal CA3 pyramidal neurons exhibit both enhanced basal and kainic acid-induced excitability.

Excitotoxicity is a process in which glutamate or other excitatory amino acids induce neuronal cell death. To address whether and how c-fos is involved in neuronal excitotoxicity, we previously generated mice in which the c-fos expression is eliminated specifically in the hippocampus. We found that these mutant mice exhibit increased kainic acid (KA)-induced seizure severity, increased neuronal excitability as measured by electroencephalogram, and increased neuronal cell death compared to wild-type control mice. To further assess the role of c-fos in regulating neuronal excitability at a cellular level, we performed hippocampal slice recording in the current study. We found that c-fos-deficient CA3 pyramidal neurons exhibit both enhanced basal and KA-induced excitability compared to normal control neurons. Our results suggest that c-fos regulates CA3 neuronal excitability.