Successful protection by amantadine hydrochloride against lethal encephalitis caused by a highly neurovirulent recombinant influenza A virus in mice

A mouse model system for a lethal encephalitis due to influenza has been established by stereotaxic microinjection with the recombinant R404BP strain of influenza A virus into the olfactory bulb of C57BL/6 mice. The virus infection spread selectively to neurons in nuclei of the broad areas of the brain parenchyma that have anatomical connections to the olfactory bulb, leading to apoptotic neurodegeneration. The inflammatory reaction at the extended stage of viral infection involved the vascular structures affected by induction of inducible nitric oxide synthase and protein nitration; those were related to the etiology of fatal brain edema. The intraperitoneal administration of amantadine inhibited the viral growth in the brain and saved mice from the lethal encephalitis. The severity of neuronal loss paralleled the time lag between the virus challenge and the start of amantadine treatment. Thus, early pharmacological intervention is essential to minimize neurological deficits due to influenza virus-induced neurodegeneration.     

The inhibitory action of butyrate on lipopolysaccharide-induced nitric oxide production in RAW 264.7 murine macrophage cells

The effect of butyrate, a natural bacterial product of colonic bacterial flora, on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 murine macrophage cells was studied. Butyrate significantly reduced NO production in LPS-stimulated RAW cells. The inhibition was abolished by the removal of butyrate. Butyrate also inhibited the expression of inducible type NO synthase (iNOS) in LPS-stimulated RAW cells. Furthermore, butyrate prevented the activation of nuclear factor (NF)-kappaB through the stabilization of IkappaB-alpha and IkappaB-beta. Butyrate did not affect the phosphorylation of mitogen-activated protein (MAP) kinases by LPS. It was, therefore, suggested that butyrate down-regulated LPS-induced NO production in RAW cells through preventing the expression of iNOS, and that it was due to the inhibitory action of butyrate on the activation of NF-kappaB.     

Human erythroleukemia cell line (HEL) undergoes a drastic macrophage- like shift with TPA

We investigated the effect of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on the human erythroleukemia cell line, HEL, and found that TPA addition (10(-6)-10(-8) M) to HEL cell cultures induces morphological, functional, and biochemical changes in HEL cells that are characteristic for macrophage-like cells. Apart from the drastic changes in morphology, the cells greatly enhance their phagocytic ability and acquire receptors for binding and degradation of chemically modified lipoproteins. At the biochemical level, a newly synthesized 85K glycoprotein is observed, and the cells are unresponsive to inducers of globin synthesis. Comparative observations with K562 cells indicate that TPA inhibits, as in HEL cells, spontaneous and induced globin synthesis, but induces minimal macrophage-like properties in these cells. The results with HEL cells are interpreted to indicate that TPA uncovers a latent monocyte-like phenotype in these cells.     

Arginine residue 155 in the second intracellular loop plays a critical role in rat melanin-concentrating hormone receptor 1 activation

Melanin-concentrating hormone (MCH) receptor 1 (MCH1R) is a class A G protein-coupled receptor. The MCH system has been linked to a variety of physiological functions, including the regulation of feeding and energy metabolism. We recently reported the importance of a dibasic motif in the membrane-proximal C-terminal region for MCH1R function. Here we reveal that an Arg residue in intracellular loop 2 of MCH1R plays a critical role in receptor function. We analyzed the roles of two distinct motifs, BBXXB and BXBB (in which B is a basic residue and X is a nonbasic residue), located in the three intracellular loops of MCH1R. Triple-substitution mutants of intracellular loops 1 and 3 could still activate calcium mobilization, albeit with lower efficacy or potency. However, mutations in intracellular loop 2 led to a complete loss of induction of signal transduction without changing the high affinity constant (Kd) value. By analyzing a series of single-substitution mutants, a point mutation of Arg155 in intracellular loop 2 was found to be responsible for the signaling pathway elicited by MCH. In addition, substitution at positions corresponding to Arg155 in human MCH receptor 2 and rat somatostatin receptor 2 also markedly abolished their ligand-induced signaling capacities, indicating that this Arg is a recognition determinant in several G protein-coupled receptors.     

Role of intracellular Ca2+ and the calmodulin messenger system in pepsinogen secretion from isolated rabbit gastric mucosa.

Both carbachol (10(-4)-10(-3) mol/l) and cholecystokinin octapeptide (CCK-8) (10(-8)-10(-6) mol/l) significantly stimulated the release of pepsinogen from rabbit gastric mucosa maintained in organ culture (213-216% and 143-261% of control, respectively, p less than 0.05-0.01). The secretion was not affected by removing Ca2+ from the culture medium with ethylene glycol tetra-acetic acid. Verapamil failed to inhibit the secretion of pepsinogen induced by the drugs in ordinary culture medium containing Ca2+. In contrast, nicorandil (10(-6)-10(-4) mol/l) attenuated the release of pepsinogen by the drugs in a dose dependent manner, regardless of the presence or absence of Ca2+ in the culture medium. W-7 (10(-6)-10(-4) mol/l) and W-5 (10(-5) and 10(-4), or 10(-6) mol/l) reduced significantly the secretion of pepsinogen induced by carbachol (53-71% and 63-81% of control, respectively, p less than 0.05-0.01) and that by CCK-8 (49-67% and 66-76% of control, respectively, p less than 0.01) in the Ca2+ containing medium. However, W-7 did not show significant inhibition of cyclic adenosine monophosphate (cAMP) and forskolin induced pepsinogen secretion. These findings indicate that the calmodulin messenger branch that is activated by a rise of intracellular Ca2+ mobilised in cytosol from its intracellular, but not extracellular, source plays a critical role in pepsinogen secretion induced by carbachol and CCK-8. It seems likely that an increase in cAMP in cytosol does not provoke any calmodulin mediated pepsinogen secretion.