Essential structure of opioid κ receptor agonist nalfurafine for binding to the κ receptor 3: Synthesis of decahydro(iminoethano)phenanthrene derivatives with an oxygen functionality at the 3-position and their pharmacologies

To clarify the essential structures of an opioid κ receptor selective agonist, nalfurafine, for binding to the κ receptor, we designed and synthesized the decahydro(iminoethano)phenanthrene derivatives with an oxygen functionality at the 3-position. The introduction of a hydroxy group to the derivatives increased the affinity and selectivity to the κ receptor regardless of the configuration at the 3-position. However, their affinities were lower than those of nalfurafine with the phenolic hydroxy group. The results suggested that the acidity of the hydroxy group would play an important role in the interaction with the opioid receptor. The low affinities of the 3-keto derivatives indicated that the 3-hydroxy group may participate in the hydrogen bonding with the receptor site not as a hydrogen acceptor but as a hydrogen donor. This is the first experimental evidence for a role as a hydrogen donor for the 3-hydroxy group in morphinans. Furthermore, the κ selectivities in these derivatives with the 6α-amide side chain were affected by the the 3-hydroxy group. The obtained structure–activity relationship information is expected to be useful for the design of more selective ligands for the κ receptor.     

Synthesis of quinolinomorphinan derivatives as highly selective δ opioid receptor ligands

We have reported previously the novel δ opioid agonist KNT-127 which showed high affinity and selectivity for the δ receptor. Moreover, the analgesic effect of subcutaneously administered KNT-127 was more potent than that of a prototypical δ agonist (?)-TAN-67 in the acetic acid writhing test. This study of the structure–activity relationship of KNT-127 derivatives focused on the introduction of substituents onto the 5′-, 6′-, 7′- or 8′-position of the quinoline ring and revealed that many derivatives with 5′- or 8′-substituents showed high affinities and selectivities for the δ receptor. Especially, SYK-153 with an 8′-OH group showed the highest affinity and the most balanced and highest selectivity for the δ receptor among the synthesized compounds.     

Dimerization of DOCK2 Is Essential for DOCK2-Mediated Rac Activation and Lymphocyte Migration

The migratory properties of lymphocytes depend on DOCK2, an atypical Rac activator predominantly expressed in hematopoietic cells. Although DOCK2 does not contain the Dbl homology domain typically found in guanine nucleotide exchange factors (GEFs), DOCK2 mediates the GTP-GDP exchange reaction for Rac via its DOCK homology region (DHR)-2 (also known as CZH2 or Docker) domain. DOCK2 DHR-2 domain is composed of three lobes, and Rac binding site and catalytic center are generated entirely from lobes B and C. On the other hand, lobe A has been implicated in dimer formation, yet its physiological significance remains unknown. Here, we report that lobe A-mediated DOCK2 dimerization is crucial for Rac activation and lymphocyte migration. We found that unlike wild-type DOCK2, DOCK2 mutant lacking lobe A failed to restore motility and polarity when expressed in thymoma cells and primary T cells lacking endogenous expression of DOCK2. Similar results were obtained with the DOCK2 point mutant having a defect in dimerization. Deletion of lobe A from the DHR-2 domain did not affect Rac GEF activity in vitro. However, fluorescence resonance energy transfer analyses revealed that lobe A is required for DOCK2 to activate Rac effectively during cell migration. Our results thus indicate that DOCK2 dimerization is functionally important under the physiological condition where only limited amounts of DOCK2 and Rac are localized to the plasma membrane.     

Determination of the number of active GroES subunits in the fused heptamer GroES required for interactions with GroEL

A double-heptamer ring chaperonin GroEL binds denatured substrate protein, ATP, and GroES to the same heptamer ring and encapsulates substrate into the central cavity underneath GroES where productive folding occurs. GroES is a disk-shaped heptamer, and each subunit has a GroEL-binding loop. The residues of the GroEL subunit responsible for GroES binding largely overlap those involved in substrate binding, and the mechanism by which GroES can replace the substrate when GroES binds to GroEL/substrate complex remains to be clarified. To address this question, we generated single polypeptide GroES by fusing seven subunits with various combinations of active and GroEL binding-defective subunits. Functional tests of the fused GroES variants indicated that four active GroES subunits were required for efficient formation of the stable GroEL/GroES complex and five subunits were required for the productive GroEL/substrate/GroES complex. An increase in the number of defective GroES subunits resulted in a slowing of encapsulation and folding. These results indicate the presence of an intermediate GroEL/substrate/GroES complex in which the substrate and GroES bind to GroEL by sharing seven common binding sites.     

Brain Atrophy in a Murine Model of Chronic Fatigue Syndrome and Beneficial Effect of Hochu-ekki-to (TJ-41)

Brain-derived neurotrophic factor (BDNF) is associated with the main symptoms of chronic fatigue sydrome (CFS) and neuron apoptosis. Nevertheless, no study has been performed directly to explore the relationship between CFS, BDNF and neuron apoptosis. We induced a CFS model by six injections of killed Brucella abortus antigen in BALB/c mice and treated them with Hochu-ekki-to (TJ-41). Daily running activity, body weight (BW), ratio of cerebral weight to BW (CW/BW) and expression levels of BDNF and Bcl-2 mRNA in the hippocampus were determined. The daily activity and CW/BW decreased significantly in the CFS model. BDNF and Bcl-2 mRNA expression levels in the hippocampus were suppressed in the CFS model and TJ-41 treated mice, while no significant difference was found between them. We improved a murine model to investigate the relationship between CFS and brain dysfunction. In this model, reduced daily activity might have been associated with decreased hippocampal BDNF mRNA expression, hippocampal apoptosis and brain atrophy. TJ-41 increased the daily running activity of the model, which was independent of brain recovery.     

Mutations in foregut SOX2+ cells induce efficient proliferation via CXCR2 pathway

Identification of the precise molecular pathways involved in oncogene-induced transformation may help us gain a better understanding of tumor initiation and promotion. Here, we demonstrate that SOX2⁺ foregut epithelial cells are prone to oncogenic transformation upon mutagenic insults, such as Kras^G12D and p53 deletion. GFP-based lineage-tracing experiments indicate that SOX2⁺ cells are the cells-of-origin of esophagus and stomach hyperplasia. Our observations indicate distinct roles for oncogenic KRAS mutation and P53 deletion. p53 homozygous deletion is required for the acquisition of an invasive potential, and Kras^G12D expression, but not p53 deletion, suffices for tumor formation. Global gene expression analysis reveals secreting factors upregulated in the hyperplasia induced by oncogenic KRAS and highlights a crucial role for the CXCR2 pathway in driving hyperplasia. Collectively, the array of genetic models presented here demonstrate that stratified epithelial cells are susceptible to oncogenic insults, which may lead to a better understanding of tumor initiation and aid in the design of new cancer therapeutics.     

Characterization and Modeling of Intermittent Locomotor Dynamics in Clock Gene-Deficient Mice

The scale-invariant and intermittent dynamics of animal behavior are attracting scientific interest. Recent findings concerning the statistical laws of behavioral organization shared between healthy humans and wild-type mice (WT) and their alterations in human depression patients and circadian clock gene (Period 2; Per2) mutant mice indicate that clock genes play functional roles in intermittent, ultradian locomotor dynamics. They also claim the clinical and biological importance of the laws as objective biobehavioral measures or endophenotypes for psychiatric disorders. In this study, to elucidate the roles of breakdown of the broader circadian regulatory circuit in intermittent behavioral dynamics, we studied the statistical properties and rhythmicity of locomotor activity in Per2 mutants and mice deficient in other clock genes (Bmal1, Clock). We performed wavelet analysis to examine circadian and ultradian rhythms and estimated the cumulative distributions of resting period durations during which locomotor activity levels are continuously lower than a predefined threshold value. The wavelet analysis revealed significant amplification of ultradian rhythms in the BMAL1-deficient mice, and instability in the Per2 mutants. The resting period distributions followed a power-law form in all mice. While the distributions for the BMAL1-deficient and Clock mutant mice were almost identical to those for the WT mice, with no significant differences in their parameter (power-law scaling exponent), only the Per2 mutant mice showed consistently and significantly lower values of the scaling exponent, indicating the increased intermittency in ultradian locomotor dynamics. Furthermore, based on a stochastic priority queuing model, we explained the power-law nature of resting period distributions, as well as its alterations shared with human depressive patients and Per2 mutant mice. Our findings lead to the development of a novel mathematical model for abnormal behaviors in psychiatric disorders.     

A Note on the Reactivation of the Fast Sodium Current in Spherical Clusters of Embryonic Chick Heart Cells

Reactivation of the fast sodium current in spherical clusters of embryonic chick heart cells was studied using the two-microelectrode voltage-clamp technique. The results show that there are at least two phases of reactivation. The contribution of the two phases to the overall reactivation process is highly dependent on the particular pulse protocol used to measure them.     

MRI-Based Analysis of Intracerebral Hemorrhage in Mice Reveals Relationship between Hematoma Expansion and the Severity of Symptoms

Intracerebral hemorrhage (ICH) is featured by poor prognosis such as high mortality rate and severe neurological dysfunction. In humans, several valuables including hematoma volume and ventricular expansion of hemorrhage are known to correlate with the extent of mortality and neurological dysfunction. However, relationship between hematoma conditions and the severity of symptoms in animal ICH models has not been clarified. Here we addressed this issue by using 7-tesla magnetic resonance imaging (MRI) on collagenase-induced ICH model in mice. We found that the mortality rate and the performance in behavioral tests did not correlate well with the volume of hematoma. In contrast, when hemorrhage invaded the internal capsule, mice exhibited high mortality and showed poor sensorimotor performance. High mortality rate and poor performance in behavioral tests were also observed when hemorrhage invaded the lateral ventricle, although worsened symptoms associated with ventricular hemorrhage were apparent only during early phase of the disease. These results clearly indicate that invasion of the internal capsule or the lateral ventricle by hematoma is a critical determinant of poor prognosis in experimental ICH model in mice as well as in human ICH patients. MRI assessment may be a powerful tool to refine investigations of pathogenic mechanisms and evaluations of drug effects in animal models of ICH.