Absence of polo-like kinase 3 in mice stabilizes Cdc25A after DNA damage but is not sufficient to produce tumors

Oxidative stress caused by hydrogen peroxide (H(2)O(2)) plays an important role in the pathogenesis of Alzheimer's disease (AD). The prominent damages caused by H(2)O(2) include the ruin of membrane integrity, loss of intracellular neuronal glutathione (GSH), oxidative damage to DNA as well as the subsequent caspase-3 and p53 activation. Icariin is a flavonoid extracted from the traditional Chinese herb Epimedium brevicornum Maxim. We have previously reported that icariin has a good curative effect on patients with mild cognitive impairment (MCI), AD animal and cell models. However, the molecular mechanism of how icariin exerts neuroprotective effects is still not well understood. To address this question, we exposed undifferentiated neuronal cell lines (PC12 cells) to hydrogen peroxide (H(2)O(2)) and investigated the possible neuroprotective mechanisms of icariin. Vitamin E was used as a positive control. We observed that H(2)O(2) activated the JNK/p38 mitogen-activated protein kinase (MAPK) and induced PC12 cells apoptosis in a concentration-dependent manner. More over, we demonstrated that icariin protected PC12 cells by attenuating LDH leakage, reducing GSH depletion, preventing DNA oxidation damage and inhibiting subsequent activation of caspase-3 and p53, which are the main targets of H(2)O(2)-induced cell damage. In addition, we also found that icariin's neuroprotective effect may partly correlate with its inhibitory effect on JNK/p38 MAPK pathways. Therefore, our findings suggest that icariin is a candidate for a novel neuroprotective drug to against oxidative-stress induced neurodegeneration.     

The Casein kinase 1α agonist pyrvinium attenuates Wnt-mediated CK1α degradation via interaction with the E3 ubiquitin ligase component Cereblon

The Cullin-RING ligase 4 E3 ubiquitin ligase component Cereblon (CRBN) is a well-established target for a class of small molecules termed immunomodulatory drugs (IMiDs). These drugs drive CRBN to modulate the degradation of a number of neosubstrates required for the growth of multiple cancers. Whereas the mechanism underlying the activation of CRBN by IMiDs is well described, the normal physiological regulation of CRBN is poorly understood. We recently showed that CRBN is activated following exposure to Wnt ligands and subsequently mediates the degradation of a subset of physiological substrates. Among the Wnt-dependent substrates of CRBN is Casein kinase 1α (CK1α), a known negative regulator of Wnt signaling. Wnt-mediated degradation of CK1α occurs via its association with CRBN at a known IMiD binding pocket. Herein, we demonstrate that a small-molecule CK1α agonist, pyrvinium, directly prevents the Wnt-dependent interaction of CRBN with CK1α, attenuating the consequent CK1α degradation. We further show that pyrvinium disrupts the ability of CRBN to interact with CK1α at the IMiD binding pocket within the CRBN–CK1α complex. Of note, this function of pyrvinium is independent of its previously reported ability to enhance CK1α kinase activity. Furthermore, we also demonstrate that pyrvinium attenuates CRBN-induced Wnt pathway activation in vivo. Collectively, these results reveal a novel dual mechanism through which pyrvinium inhibits Wnt signaling by both attenuating the CRBN-mediated destabilization of CK1α and activating CK1α kinase activity.     

Methods for averaging irregular respiratory flow profiles in awake humans.

Respiratory flow profiles have been of interest as an output of the respiratory controller. In determining average flow profiles, however, previous methods that align individual breaths in the time domain are susceptible to distortions caused by the great variability, both between breaths and within breaths. We aimed to develop a method for determining typical flow profiles that circumvents such distortions. Our method aligns different breaths by phase of respiratory cycle, which is defined as the angle associated with the point on the normalized flow-volume diagram (a phase-plane plot). Over a number of breaths, median values for flow, volume, and elapsed time from the start of the breath at each phase angle are determined. Because these estimates are mutually semi-independent and in general violate the laws of mass balance, an adjustment was performed such that the volume was precisely the time integral of the flow. The method produced typical flow profiles with characteristics that were significantly closer to the mean values obtained from the individual cycles than those obtained by the technique of Benchetrit and co-workers (Benchetrit G, Shea SA, Dinh TP, Bodocco S, Baconnier P, and Guz A, Respir Physiol 75: 199-210, 1989), which reconstructs the typical flow profile from Fourier coefficients.     

Possible Novel Therapy for Malignant Gliomas with Secretable Trimeric TRAIL

Malignant gliomas are the most common primary brain tumors. Despite intensive clinical investigation and many novel therapeutic approaches, average survival for the patients with malignant gliomas is only about 1 year. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown potent and cancer-selective killing activity and drawn considerable attention as a promising therapy for cancers, but concerns over delivery and toxicity have limited progress. We have developed a secretable trimeric TRAIL (stTRAIL) and here evaluated the therapeutic potential of this stTRAIL-based gene therapy in brain tumors. An adenovirus (Ad-stTRAIL) delivering stTRAIL was injected into intra-cranial human glioma tumors established in nude mice and tumor growth monitored using the magnetic resonance imaging (MRI). Ad-stTRAIL gene therapy showed potent tumor suppressor activity with no toxic side effects at therapeutically effective doses. When compared with 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU), a conventional therapy for malignant gliomas, Ad-stTRAIL suppressed tumor growth more potently. The combination of Ad-stTRAIL and BCNU significantly increased survival compared to the control mice or mice receiving Ad-stTRAIL alone. Our data indicate that Ad-stTRAIL, either alone or combined with BCNU, has promise as a novel therapy for malignant gliomas.     

Placental Syncytiotrophoblast Constitutes a Major Barrier to Vertical Transmission of Listeria monocytogenes

Listeria monocytogenes is an important cause of maternal-fetal infections and serves as a model organism to study these important but poorly understood events. L. monocytogenes can infect non-phagocytic cells by two means: direct invasion and cell-to-cell spread. The relative contribution of each method to placental infection is controversial, as is the anatomical site of invasion. Here, we report for the first time the use of first trimester placental organ cultures to quantitatively analyze L. monocytogenes infection of the human placenta. Contrary to previous reports, we found that the syncytiotrophoblast, which constitutes most of the placental surface and is bathed in maternal blood, was highly resistant to L. monocytogenes infection by either internalin-mediated invasion or cell-to-cell spread. Instead, extravillous cytotrophoblasts—which anchor the placenta in the decidua (uterine lining) and abundantly express E-cadherin—served as the primary portal of entry for L. monocytogenes from both extracellular and intracellular compartments. Subsequent bacterial dissemination to the villous stroma, where fetal capillaries are found, was hampered by further cellular and histological barriers. Our study suggests the placenta has evolved multiple mechanisms to resist pathogen infection, especially from maternal blood. These findings provide a novel explanation why almost all placental pathogens have intracellular life cycles: they may need maternal cells to reach the decidua and infect the placenta.     

The molting hormones from the embryonated egg of the tobacco hornworm, Manduca sexta (L.)

26-Hydroxyecdysone is the predominant molting hormone in 24- to 44-hour-old embryonated tobacco hornworm eggs, accounting for approximately 80% of the ecdysones present at this stage of development. This molting hormone was previously shown to be the major ecdysone present in 48- to 64-hour-old embryonated eggs of this insect. During both of these periods of embryonic development in the hornworm 20-hydroxyecdysone is a minor component, in contrast to its presence as the major ecdysone in the hornworm during certain stages of post-embryonic development.     

Examining the in vivo role of the amino terminus of the essential myosin light chain.

The functional significance of the actin binding region at the amino terminus of the cardiac essential myosin light chain (ELC) remains obscure. Previous experiments carried out in vitro indicated that modulation of residues 5-14 could induce an inotropic effect, increasing maximal ATPase activity at submaximal Ca(2+) concentrations (Rarick, H. M., Opgenorth, T. J., von Geldern, T. W., Wu-Wong, J. R., and Solaro, R. J. (1996) J. Biol. Chem. 271, 27039-27043). Using transgenesis, we effected a cardiac-specific replacement of ELC with a protein containing a 10-amino acid deletion at positions 5-14. Both the ventricular (ELC1vDelta5-14) and atrial (ELC1aDelta5-14) isoforms lacking this peptide were stably incorporated into the sarcomere at high efficiencies. Surprisingly when the kinetics of skinned fibers isolated from the ELC1vDelta5-14 or ELC1aDelta5-14 mice were examined, no alterations in either unloaded shortening or maximum shortening velocities were apparent. Myofibrillar Mg(2+)-ATPase activity was also unchanged in these preparations. No significant changes in the fiber kinetics in the cognate compartments were observed when either deletion-containing protein replaced endogenous ELC1v or ELC1a. The data indicate that the previously postulated importance of this region in mediating critical protein interactions between the cardiac ELCs and the carboxyl-terminal residues of actin in vivo should be reassessed.