Interleukin‐6 (IL‐6) induces either differentiation or growth of a variety of cells. Little is known about the molecular basis of this cellular decision. The family of signal transducer and activator of transcription (Stat) proteins are involved in signaling through a variety of cytokine and growth factor receptors, although their biological roles have not been established. To address whether Stat proteins play roles in IL‐6‐induced growth or differentiation, we introduced two types of mutant Stat3 acting in a dominant‐negative manner into M1 leukemic cells which respond to IL‐6 with growth arrest and terminal differentiation. We show that dominant‐negative forms of Stat3 inhibited both IL‐6‐induced growth arrest at G(0)/G1 and macrophage differentiation in the M1 transformants. Blocking of Stat activation resulted in inhibition of IL‐6‐induced repression of c‐myb and c‐myc. Furthermore, IL‐6 enhanced the growth of M1 cells primarily through shortening the length of the G1 period when Stat3 was suppressed. Thus IL‐6 generates both growth‐enhancing signals and growth arrest‐ and differentiation‐inducing signals at the same time. Stat3 may be a key molecule which determines the cellular decision from cell growth to differentiation in M1 cells.

Interleukin (IL)-18 was identified as a molecule that induces IFN-␥ production and enhances NK cell cytotoxicity. In this paper, we report upon the purification and characterization of human IL-18 receptor (hIL-18R). We selected the Hodgkin's disease cell line, L428, as the most strongly hIL-18R-expressing cell line based on the results of binding assays. Murine interleukin-18 (mIL-18) 1 was identified in the livers of mice sequentially injected with heat-killed Propionibacterium acnes and with lipopolysaccharide (1). Murine IL-18 cDNA was cloned from murine liver mRNA, and the factor was provisionally termed IFN-␥-inducing factor because it was first identified as an IFN-␥ inducer in mice. Consequently, human interleukin-18 (hIL-18) was cloned from normal human liver mRNA (2). IL-18 is a non-N-linked, glycosylated, 18.3-kDa cytokine in its mature form and exhibits biologic activities in the monomeric form.IL-18 has been found to have a variety of biologic actions, including the stimulation of the proliferation of activated T cells, enhancement of the lytic activity of NK cells, induction of interferon-␥ (IFN-␥), and granulocyte-macrophage colony-stimulating factor production by activated T cells and promotion of Th1-type helper (Th1) clone responses (1-4). It has also been reported that IL-18 inhibits osteoclast-like multinucleated cell formation in co-cultures of osteoblasts and hemopoietic cells of spleen or bone marrow origin (5). Thus, it is very obvious that IL-18 plays an important role in the immune system.IL-18 shares some of its biologic activities with IL-12, although the primary structures of the two cytokines show no homology (2). In addition, in the experiments using murine Th1 clones and enriched human T cells, IL-18 and IL-12 acted on the T cells synergistically to induce IFN-␥ production (1, 4). Interestingly, the amino acid sequence of IL-18 includes the IL-1 signature-like sequence (2) and has been shown to have 15% homology at the amino acid level with the IL-1␤ protein, but does not bear significant functional resemblance to the IL-1 family (2).The identification of the receptor for IL-18 is important for investigation of the physiological role of IL-18 in nature. In this report, we describe the purification and identification of hIL-18R from a Hodgkin's disease-derived cell line, L428, and present some characterization of this molecule. EXPERIMENTAL PROCEDURES Cell Lines and ReagentsC5/MJ, CCRF-HSB-2, HPB-ALL, JM, MOLT-3, MOLT-4, MOLT-16, PEER, SKW-3 (human T cell leukemia), ARH-77, BALL-1 (human B cell leukemia), KG-1, HL-60, U-937 (human myelomonocytic cell leukemia), NALM-16, HEL (human non-T, non-B cell leukemia), and L-428 and HDLM (human Hodgkin's disease) cell lines were maintained in culture at 37°C, in a 5% CO 2 air mixture in RPMI 1640 medium supplemented with 10% heat-inactivated fetal bovine serum (BioWhittaker Inc.). Recombinant human IL-1␤ (R&D Systems) and 125 -I-IL-1␤ (Amersham) were obtained commercially. Recombinant IL-18Recombinant human IL-18 (rhIL-18) was produced by cu...

If two good solvents become poor for a polymer when mixed, the solvent pair is called a co-nonsolvent pair for the polymer. The sharp depression of the LCST by the co-nonsolvency in solutions of poly(N-isopropylacrylamide) in the mixed solvent of water and methanol is shown to be caused by the competitive hydrogen bonding of water and methanol molecules onto the polymer chains. On the basis of a new statistical-mechanical model for competitive hydrogen bonds, the degree of hydration θ (w) and of methanol binding θ (m) , excess degree Δθ E of solvent binding, preferential adsorption coefficients Γ, LCST spinodal lines, and cloud-point depression ΔT cl are theoretically calculated and compared with the experimental results. The optimal composition x m (M) of methanol at which LCST takes the minimum value is studied as a function of the polymer molecular weight M. In the high molecular weight limit, it takes x m = 0.35. The solution recovers a uniform state in the region of higher methanol composition. Such a peculiar phase separation is caused by the dehydration of the polymer chains by the mixed methanol molecules in a cooperative way.

For the fermentative production of plant-specific flavanones (naringenin, pinocembrin) by Escherichia coli, a plasmid was constructed which carried an artificial biosynthetic gene cluster, including PAL encoding a phenylalanine ammonia-lyase from a yeast, ScCCL encoding a cinnamate/coumarate:CoA ligase from the actinomycete Streptomyces coelicolor A3(2), CHS encoding a chalcone synthase from a licorice plant and CHI encoding a chalcone isomerase from the Pueraria plant. The recombinant E. coli cells produced (2S)-naringenin from tyrosine and (2S)-pinocembrin from phenylalanine. When the two subunit genes of acetyl-CoA carboxylase from Corynebacterium glutamicum were expressed under the control of the T7 promoter and the ribosome-binding sequence in the recombinant E. coli cells, the flavanone yields were greatly increased, probably because enhanced expression of acetyl-CoA carboxylase increased a pool of malonyl-CoA that was available for flavanone synthesis. Under cultural conditions where E. coli at a cell density of 50 g/l was incubated in the presence of 3 mM tyrosine or phenylalanine, the yields of naringenin and pinocembrin reached about 60 mg/l. The fermentative production of flavanones in E. coli is the first step in the construction of a library of flavonoid compounds and un-natural flavonoids in bacteria.

Temperature dependent phase behavior of poly(N‐isopropylacylamide) (PNIPAM) microgels in water/methanol mixtures of different composition was studied with dynamic light scattering (DLS) and small‐angle neutron scattering (SANS). Using DLS, it is possible to measure the diffusion coefficient, and thus the size of particles exactly and directly; the variation of the phase transition temperature in the different solvents is also easy to detect by this method. With SANS measurements in D2O/MeOD mixtures, some of the DLS results were confirmed. Moreover, SANS measurements give valuable information on the particle structure in different solvents. The experiments were compared with the theory of competitive hydration introduced by Tanaka et al. We found a good agreement of theory and experiment, and obtained the theoretical predictions: around the transition temperature, the composition of the bound methanol along the chains is higher than that of the outer solution, while the whole methanol composition inside the gel is lower. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013, 51, 1100–1111

The concept of cooperative dehydration, defined as the simultaneous dissociation of the water molecules bound in correlated sequences to a polymer chain, has been applied to study the collapse of a poly(Nisopropylacrylamide) (PNIPAM) chain upon heating in aqueous solutions. We examined the applicability of this concept in three situations: (i) PNIPAM in water (in the absence of added force), (ii) PNIPAM in water subjected to a tension applied to the chain ends, and (iii) PNIPAM in a mixed solvent of water and a second water-miscible solvent. The transition becomes sharper as the cooperativity parameter of hydration increases. The tension-elongation curve of a hydrated chain at various temperatures, calculated following an approach similar to the classical theory of coil-helix transition, presents a flat plateau corresponding to the tension for which collapsed segments reel out of the globules. The reeled-out segments are hydrated immediately upon exposure to water. The calculations suggest a possible shift to higher temperatures of the cloud points of aqueous PNIPAM solutions under shear flow. The reentrant coil-globule-coil transition in mixed solvent of water and methanol is studied from the viewpoint of competitive hydrogen bonds between polymer-water and polymer-methanol.

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Cytokines play several roles in developing and/or reinforcing premature cellular senescence of young cells. One such cytokine, interleukin-6 (IL-6), regulates senescence in some systems in addition to its known functions of immune regulation and promotion of tumorigenesis. In this review, we describe recent advances in studies on the roles of IL-6 and its downstream signal transducer and activator of transcription 3 (STAT3) in regulating premature cellular senescence. IL-6/sIL-6Rα stimulation forms a senescence-inducing circuit involving the STAT3-insulin-like growth factor-binding protein 5 (IGFBP5) as a key axis triggering and reinforcing component in human fibroblasts. We describe how cytokines regulate the process of senescence by activating STAT3 in one system and anti-senescence or tumorigenesis in other systems. The roles of other STAT members in premature senescence also will be discussed to show the multiple mechanisms leading to cytokine-induced senescence.