Increased vulnerability of hippocampal pyramidal neurons to the toxicity of kainic acid in OASIS-deficient mice

The endoplasmic reticulum (ER) stress response is a defense system for dealing with the accumulation of unfolded proteins in the ER lumen. Old astrocyte specifically induced substance (OASIS) is known to be expressed in astrocytes and involved in the ER stress response; however the function of OASIS in the injured brain has remained unclear. In this study, we examined the roles of OASIS in neuronal degeneration in the hippocampi of mice intraperitoneally injected with kainic acid (KA). OASIS mRNA was strongly induced in response to KA injection, with a similar time course to the induction of ER molecular chaperone immunoglobulin heavy chain binding protein mRNA. In situ hybridization showed that KA injection causes induction of immunoglobulin heavy chain binding protein mRNA in glial fibrillary acidic protein-positive astrocytes as well as in pyramidal neurons, although up-regulation of OASIS mRNA was only detected in glial fibrillary acidic protein-positive astrocytes. Primary cultured astrocytes, but not the neurons of OASIS −/− mice, revealed reduced vulnerability to ER stress. Furthermore, pyramidal neurons in the hippocampi of OASIS −/− mice were more susceptible to the toxicity induced by KA than those of wild-type mice. Taken together, these data suggest that OASIS expressed in astrocytes plays important roles in protection against the neuronal damage induced by KA.     

PolyADP-Ribosylation Is Required for Pronuclear Fusion during Postfertilization in Mice

Background

During fertilization, pronuclear envelope breakdown (PNEB) is followed by the mingling of male and female genomes. Dynamic chromatin and protein rearrangements require posttranslational modification (PTM) for the postfertilization development.

Methodology/Principal Findings

Inhibition of poly(ADP-ribose) polymerase activity (PARylation) by either PJ-34 or 5-AIQ resulted in developmental arrest of fertilized embryos at the PNEB. PARylation inhibition affects spindle bundle formation and phosphorylation of Erk molecules of metaphase II (MII) unfertilized oocytes. We found a frequent appearance of multiple pronuclei (PN) in the PARylation-inhibited embryos, suggesting defective polymerization of tubulins. Attenuated phosphorylation of lamin A/C by PARylation was detected in the PARylation-inhibited embryos at PNEB. This was associated with sustained localization of heterodomain protein 1 (HP1) at the PN of the one-cell embryos arrested by PARylation inhibition.

Conclusions/Significance

Our findings indicate that PARylation is required for pronuclear fusion during postfertilization processes. These data further suggest that PARylation regulates protein dynamics essential for the beginning of mouse zygotic development. PARylation and its involving signal-pathways may represent potential targets as contraceptives.     

Olfactory Imprinting of Amino Acids in Lacustrine Sockeye Salmon

Juvenile salmon have an olfactory ability to imprint their natal stream odors, but neither the odor properties of natal stream water nor the imprinting timing and duration have been clarified as yet. Here we show, using electrophysiological and behavioral experiments, that one-year-old lacustrine sockeye salmon (Oncorhynchus nerka) can be imprinted around the stage of parr-smolt transformation (PST) by a single amino acid, 1 µM L-proline (Pro), or L-glutamic acid (Glu). We also show by real-time PCR that changes occur in mRNA levels of the salmon olfactory imprinting-related gene (SOIG) around PST. The electro-olfactogram (EOG) responses of test fish exposed to Pro in March (before PST) and April–June (during PST) for 2 weeks were significantly (1.7-fold) greater than those of non-exposed control fish, but not those of test fish exposed in July (after PST). When Pro and control water were added to the water inlets of a two-choice test tank during the spawning season 2 years after the test water exposure, 80% of maturing and matured test fish exposed before and during PST showed a preference for Pro, whereas those exposed after PST did not. The EOG response of test fish exposed to Pro or Glu for 1 hour, 6 hours, 1 day, 7 days, or 14 days in May revealed that only the response after 14 days of exposure was significantly (1.8-fold) greater than the control. The expression levels of SOIG mRNA increased before and during PST, and decreased after PST. We conclude that one-year-old lacustrine sockeye salmon can be imprinted by a single amino acid before and during PST, and that imprinting requires exposure for at least 14 days.     

Isolation of a novel strain of Butyrivibrio fibrisolvens that isomerizes linoleic acid to conjugated linoleic acid without hydrogenation, and its utilization as a probiotic for animals

AIM: Isolation of a new strain of Butyrivibrio fibrisolvens possessing great capacity to produce conjugated linoleic acid (CLA) in order to utilize as a probiotic for animals. METHODS AND RESULTS: A novel strain (MDT-5) was isolated from the goat rumen, which exclusively converted linoleic acid (LA) to CLA, because of its high LA isomerase activity with virtually no CLA reductase activity. MDT-5 also converted linolenic acid to conjugated linolenic acid that may be more bioactive than CLA. The oral administration of MDT-5 every other day to mice for 2 weeks resulted in increased amounts of CLA in the contents of the large intestine (2.5-fold), as well as in adipose tissue (threefold). Feeding a high-LA diet, as well as prolonging the period of MDT-5 administration, further increased the CLA content in body fat. CONCLUSIONS: MDT-5 has by far greater ability to produce CLA than any other known bacteria. Administration of MDT-5 to mice increases CLA production in the large intestine, which results in increased CLA absorption. SIGNIFICANCE AND IMPACT OF THE STUDY: MDT-5 may be useful in pet animals as a probiotic to provide CLA continuously.     

Bone morphogenetic protein-3b (BMP-3b) gene expression is correlated with differentiation in rat calvarial osteoblasts

BMP-3b (also called GDF-10) is a novel BMP-3-related protein recently discovered in rat femur tissue. Gene expression of BMP-3b in osteoblastic cells and its regulation by prolonged culture, BMP-2 and transforming growth factor beta1 (TGF-beta1) were examined. The BMP-3b gene was highly expressed in rat osteoblasts obtained from calvarial bones but not in the osteoblastic cell lines (MC3T3-E1 and U2-OS). BMP-3b mRNA increased during osteoblastic differentiation in prolonged culture and was associated with increased alkaline phosphatase (ALPase) activity. When BMP-2, an enhancer of ALPase activity, was added to the primary osteoblast culture, BMP-3b mRNA increased 6.9-fold after 24 h. In contrast, TGF-beta1 treatment, which suppresses ALPase activity, rapidly and completely inhibited gene expression of BMP-3b. The regulation of BMP-3 mRNA differed from that of BMP-3b, even though both proteins share 81% identity. These findings indicate that BMP-3b gene expression is regulated by osteoblastic differentiation and BMP-3b functions in highly differentiated osteoblasts.     

Protective role of HSP27 against UVC-induced cell death in human cells

It is an intriguing problem whether heat shock proteins (HSPs) play a protective role in UVC-induced cell death in human cells, and the problem has not been solved. To search for the HSPs involved in UVC resistance, gene expression profiles using cDNA array were compared between UVC-sensitive human RSa cells and their UVC-resistant variant AP(r)-1 cells. The expression levels of heat shock protein 27 (HSP27) were lower in RSa cells than in AP(r)-1 cells. RSa cells transfected with sense HSP27 cDNA showed slightly lower sensitivity to UVC-induced cell death than the control cells transfected with a vector alone and much lower sensitivity than RSa cells transfected with the antisense HSP27 cDNA. Furthermore, the removal capacities of the two major types of UVC-damaged DNA (thymine dimers and (6-4)photoproducts) in the cells with the up-regulation of HSP27 were moderately elevated compared with those in the control cells, while those in the cells with down-regulation were remarkably suppressed. These results suggest that HSP27 is involved in the UVC-resistance of human cells, at least those tested, possibly via functioning in nucleotide excision repair.     

Roxithromycin downmodulates Th2 chemokine production by keratinocytes and chemokine receptor expression on Th2 cells: its dual inhibitory effects on the ligands and the receptors

Roxithromycin (RXM), an anti-bacterial macrolide, has various immunomodulatory activities. To investigate the ability of RXM to downregulate skin-infiltration of T-lymphocytes, we examined the effects of RXM on keratinocyte production of chemokines and T cell expression of chemokine receptors. Normal human and HaCaT keratinocytes were cultured with RXM and stimulants. RXM at 1 or 10 microM significantly suppressed the production/expression of Th2 chemokines MDC and TARC in these keratinocytes, but the production of IP-10 was not affected. The effect of RXM on T-cell expression of the corresponding chemokine receptors was also tested in Th2-rich peripheral blood lymphocytes. The IL-2-enhanced expression level of Th2 chemokine receptor CCR4 was decreased by RXM at 10 microM, whereas the expression of CXCR3 was unchanged. Thus, RXM downmodulates both the production and receptor expression of Th2 but not Th1 chemokines involved in cutaneous immunity, suggesting its beneficial therapeutic effects on Th2-mediated or allergic skin disorders.