Endotoxin leads to rapid subcellular re-localization of hepatic RXRα: A novel mechanism for reduced hepatic gene expression in inflammation

BACKGROUND: Lipopolysaccharide (LPS) treatment of animals down-regulates the expression of hepatic genes involved in a broad variety of physiological processes, collectively known as the negative hepatic acute phase response (APR). Retinoid X receptor alpha (RXRalpha), the most highly expressed RXR isoform in liver, plays a central role in regulating bile acid, cholesterol, fatty acid, steroid and xenobiotic metabolism and homeostasis. Many of the genes regulated by RXRalpha are repressed during the negative hepatic APR, although the underlying mechanism is not known. We hypothesized that inflammation-induced alteration of the subcellular location of RXRalpha was a common mechanism underlying the negative hepatic APR. RESULTS: Nuclear RXRalpha protein levels were significantly reduced (~50%) within 1-2 hours after low-dose LPS treatment and remained so for at least 16 hours. RXRalpha was never detected in cytosolic extracts from saline-treated mice, yet was rapidly and profoundly detectable in the cytosol from 1 hour, to at least 4 hours, after LPS administration. These effects were specific, since the subcellular localization of the RXRalpha partner, the retinoic acid receptor (RARalpha), was unaffected by LPS. A potential cell-signaling modulator of RXRalpha activity, c-Jun-N-terminal kinase (JNK) was maximally activated at 1-2 hours, coincident with maximal levels of cytoplasmic RXRalpha. RNA levels of RXRalpha were unchanged, while expression of 6 sentinel hepatic genes regulated by RXRalpha were all markedly repressed after LPS treatment. This is likely due to reduced nuclear binding activities of regulatory RXRalpha-containing heterodimer pairs. CONCLUSION: The subcellular localization of native RXRalpha rapidly changes in response to LPS administration, correlating with induction of cell signaling pathways. This provides a novel and broad-ranging molecular mechanism for the suppression of RXRalpha-regulated genes in inflammation.     

High-level expression of whiG——A key gene for Streptomyces differentiation in Escherichia coli

Six nucleotides located in the region of translation start site of whiG were changed. whiG was amplified by PCR technique. Reformed sequences were determined. This gene was directly subcloned into expression vector pET11c containing strong T7 promoter, and the recombinant plasmid was introduced into E. coli BL21(DE3), which could be induced by IPTG to produce T7 RNA polymerase. The SDS-PAGE result showed that whiG highly expressed in E. coli BL21(DE3), and the yield of whiG product was about 20% of insoluble proteins in cell. whiG product (σwhiG) was further identified by Western blot hybridization after making its antibody. whiG gene was subcloned into Streptomyces plasmid pIJ6021, and then it was introduced into sporulation deficient mutant C71 from Streptomyces coelicolor. The result showed that C71 could restore sporulation and σwhiG has biological functions.     

Induction of apoptosis in host cells: a survival mechanism for Leishmania parasites?

Leishmania parasites invade host macrophages, causing infections that are either limited to skin or spread to internal organs. In this study, 3 species causing cutaneous leishmaniasis, L. major, L. aethiopica and L. tropica, were tested for their ability to interfere with apoptosis in host macrophages in 2 different lines of human monocyte-derived macrophages (cell lines THP-1 and U937) and the results confirmed in peripheral blood mononuclear cells (PBMC). All 3 species induced early apoptosis 48 h after infection (expression of phosphatidyl serine on the outer membrane). There were significant increases in the percentage of apoptotic cells both for U937 and PBMC following infection with each of the 3 species. Early apoptotic events were confirmed by mitochondrial membrane permeabilization detection and caspase activation 48 and 72 h after infection. Moreover, the percentage of infected THP-1 and U937 macrophages increased significantly (up to 100%) following treatment with an apoptosis inducer. Since phosphatidyl serine externalization on apoptosing cells acts as a signal for engulfment by macrophages, induction of apoptosis in the parasitized cells could actively participate in spreading the infection. In summary, parasite-containing apoptotic bodies with intact membranes could be released and phagocytosed by uninfected macrophages.     

Studies for the large scale isolation of membrane-associated progesterone 11α-hydroxylase: Enzyme stability in Rhizopus nigricans ATCC 6277b cells

Factors influencing the stability of the membrane-associated enzyme progesterone 11α-hydroxylase of Rhizopus nigricans are reported. stability of the enzyme activity was enhanced over 18 h by glucose (2.5% w/v) and more so by aeration and by operations performed below 20°C. The results are related to the requirements of large-scale enzyme isolation.     

Fetal genes in mother's blood: A novel mechanism for telegony?

Telegony is a discredited genetic phenomenon that a previous male may influence the characteristics of offspring subsequently borne by the same female to another male. Although its reality was acknowledged by such authorities as Charles Darwin and Herbert Spencer, it has been met with skepticism because of a lack of understanding of the theoretical basis for telegony. With the discovery of fetal genes in mother's blood, the penetration of somatic cells by sperm, and the ability of RNA to program genome rearrangement, mechanisms might exist for telegony.     

VEGF selectively induces Down syndrome critical region 1 gene expression in endothelial cells: a mechanism for feedback regulation of angiogenesis?

The Down syndrome critical region 1 (DSCR1) gene (also known as MCIP1, Adapt78) encodes a regulatory protein that binds to calcineurin catalytic A subunit and acts as a regulator of the calcineurin-mediated signaling pathway. We show in this study that DSCR1 is greatly induced in endothelial cells in response to VEGF, TNF-alpha, and A23187 treatment, and that this up-regulation is inhibited by inhibitors of the calcineurin-NFAT (nuclear factor of activated T cells) signaling pathway as well as by PKC inhibition and a Ca(2+) chelator. We hypothesized that the up-regulation of DSCR1 gene expression in endothelial cells could act as an endogenous feedback inhibitor for angiogenesis by regulating the calcineurin-NFAT signaling pathway. Our transient transfection analyses confirm that the overexpression of DSCR1 abrogates the up-regulation of reporter gene expression driven by both the cyclooxygenase 2 and DSCR1 promoters in response to stimulators. Our results indicate that DSCR1 up-regulation may represent a potential molecular mechanism underlying the regulation of angiogenic genes activated by the calcineurin-NFAT signaling pathway in endothelial cells.     

Polyunsaturated fatty acids stimulate superoxide formation in tumor cells: A mechanism for specific cytotoxicity and a model for tumor necrosis factor?

Some neoplastic cell lines are readily killed when incubated in the presence of polyunsaturated fatty acids (PUFA). In an attempt to elucidate this phenomenon, we studied PUFA-driven superoxide (O2-) production by cultured NS-1 cells (murine lymphoid tumor cells). We find: (1) Even in the absence of added PUFA, NS-1 cells generate O2- (i.e., reduce nitroblue tetrazolium). (2) addition of PUFA increases O2- by greater than 50%. (3) Artificial loading of NS-1 cells with liposome encapsulated superoxide dismutase prevents the majority of spontaneous and PUFA-driven NBT reduction. We conclude that PUFA drives O2- generation by tumor cells, that this generation is largely intracellular, and that this phenomenon may help explain toxicity of PUFA for tumor cells.     

The intramandibular joint in Girella: A mechanism for increased force production?

Intramandibular joints (IMJ) are novel articulations between bony elements of the lower jaw that have evolved independently in multiple fish lineages and are typically associated with biting herbivory. This novel joint is hypothesized to function by augmenting oral jaw expansion during mouth opening, which would increase contact between the tooth‐bearing area of the jaws and algal substratum during feeding, resulting in more effective food removal from the substrate. Currently, it is not understood if increased flexibility in a double‐jointed mandible also results in increased force generation during herbivorous biting and/or scraping. Therefore, we selected the herbivore Girella laevifrons for a mechanical study of the IMJ lower jaw lever system. For comparative purposes, we selected Graus nigra, a non–IMJ‐bearing species, from a putative sister genus. Shortening of the lower jaw, during flexion at the IMJ, resulted in a more strongly force‐amplifying closing lever system in the lower jaw, even in the absence of notable changes to the sizes of the muscles that power the lever system. To explain how the IMJ itself functions, we use a four‐bar linkage that models the transmission of force and velocity to and through the lower jaw via the IMJ. When combined, the functionally interrelated lever and linkage models predict velocity to be amplified during jaw opening, whereas jaw closing is highly force modified by the presence of the IMJ. Moreover, the function of the IMJ late during jaw closure provides enough velocity to detach sturdy and resilient prey. Thus, this novel jaw system can alternate between amplifying the force or the velocity exerted onto the substrate where food items are attached. This unique mechanical configuration supports the argument that IMJs are functional innovations that have evolved to meet novel mechanical challenges and constraints placed on the feeding apparatus by attached and sturdy food sources. J. Morphol. 2010. © 2009 Wiley‐Liss, Inc.     

HDAC inhibitors induce apoptosis but not cellular senescence in Gadd45α-deficient E1A+Ras cells

HDAC inhibitors (HDIs) induce irreversible cell cycle arrest and senescence in E1A+Ras expressing cells. Furthermore, HDIs activate Gadd45α/NF-κB signaling pathway to suppress apoptosis thereby promoting the cell survival. Here, to clarify the role of Gadd45α in realization of the antiapoptotic program, we compared wild-type E1A+Ras cells and the cells with knockout of gadd45α gene (Gadd45α−/− cells). As in Gadd45α-expressing E1A+Ras cells, HDIs induce irreversible cell cycle arrest in Gadd45α−/− cells, but the arrested cells do not senesce and eventually die due to activation of the apoptotic death program. These data suggest that the expression of Gadd45α is involved in maintaining the balance of pro- and anti-apoptotic stimuli, while lack or loss of Gadd45 directs the cells to apoptosis after HDIs treatment. Appropriately Gadd45α-deficient cells demonstrate a higher level of pro-apoptotic signals, whereas the anti-apoptotic program is suppressed. The elevated apoptotic background of Gadd45α−/− cells is accompanied by higher levels of Ser15-phosphorylated p53 and p21/Waf1 proteins that additionally commit the cells to HDIs-induced apoptosis. Additionally, loss of Gadd45α protein activates the DDR signaling pathway as demonstrated by nuclear pATM staining, accumulation of γH2AX foci and an increase of single-strand DNA breaks. Thus, in wild-type E1A+Ras cells the p53-dependent expression of Gadd45α is necessary not only for DNA repair and HDI-induced cellular senescence, but also to withstand to apoptosis after DNA damage and stress. Therefore the use of HDIs in combination with agents that block Gadd45α function may have promise for cancer therapy.     

Modulating the expression of aquaporin genes in planta: A key to understand their physiological functions?

Aquaporins (AQPs) are believed to act as "cellular plumbers", allowing plants to rapidly alter their membrane water permeability in response to environmental cues. This study of AQP regulation at both the RNA and protein levels has revealed a large number of possible mechanisms. Currently, modulation of AQP expression in planta is considered the strategy of choice for elucidating the role of AQPs in plant physiology. This review highlights the fact that this strategy is complicated by many factors, such as the incomplete characterization of transport selectivity of the targeted AQP, the fact that AQPs might act as multifunctional channels with multiple physiological roles, and the number of post-translational regulation mechanisms. The classification of AQPs as constitutive or stress-responsive isoforms is also proposed.     

Resistin up-regulates fractalkine expression in human endothelial cells: Lack of additive effect with TNF-α

Resistin is a cytokine and fractalkine (Fk) a cell adhesion molecule and chemokine that contribute to human vascular inflammation by mechanisms not clearly defined. We questioned whether resistin induces Fk expression in human endothelial cells (HEC), compared the effect with that of the pro-inflammatory cytokine, TNF-α, and evaluated the consequences of co-stimulating HEC with both activators on Fk induction and on the signalling molecules involved. We found that resistin up-regulated Fk expression at comparable level to that of TNF-α by a mechanism involving P38 and JNK MAPK and NF-κB. Co-stimulation of cells with resistin and TNF-α did not increase Fk expression induced by every single inducer. Moreover resistin reduced the expression induced by TNF-α in HEC. The new data uncover Fk as a novel molecular link between resistin and inflammation and show that resistin and TNF-α have no additive effect in Fk up-regulation or on the signalling molecules implicated.     

Modulating the expression of aquaporin genes in planta: A key to understand their physiological functions?

Aquaporins (AQPs) are believed to act as “cellular plumbers”, allowing plants to rapidly alter their membrane water permeability in response to environmental cues. This study of AQP regulation at both the RNA and protein levels has revealed a large number of possible mechanisms. Currently, modulation of AQP expression in planta is considered the strategy of choice for elucidating the role of AQPs in plant physiology. This review highlights the fact that this strategy is complicated by many factors, such as the incomplete characterization of transport selectivity of the targeted AQP, the fact that AQPs might act as multifunctional channels with multiple physiological roles, and the number of post-translational regulation mechanisms. The classification of AQPs as constitutive or stress-responsive isoforms is also proposed.     

Elevated ZIPK is required for TNF-α-induced cell adhesion molecule expression and leucocyte adhesion in endothelial cells

Leucocyte adhesion to the vascular endothelium is a critical event in the early inflammatory response to infection and injury.This process is primarily regulate...     

α7 nicotinic acetylcholine receptor (α7nAChR) expression in bone marrow-derived non-T cells is required for the inflammatory reflex

The immune response to infection or injury coordinates host defense and tissue repair, but also has the capacity to damage host tissues. Recent advances in understanding protective mechanisms have found neural circuits that suppress release of damaging cytokines. Stimulation of the vagus nerve protects from excessive cytokine production and ameliorates experimental inflammatory disease. This mechanism, the inflammatory reflex, requires the α7 nicotinic acetylcholine receptor (α7nAChR), a ligand-gated ion channel expressed on macrophages, lymphocytes, neurons and other cells. To investigate cell-specific function of α7nAChR in the inflammatory reflex, we created chimeric mice by cross-transferring bone marrow between wild-type (WT) and α7nAChR-deficient mice. Deficiency of α7nAChR in bone marrow-derived cells significantly impaired vagus nerve-mediated regulation of tumor necrosis factor (TNF), whereas α7nAChR deficiency in neurons and other cells had no significant effect. In agreement with recent work, the inflammatory reflex was not functional in nude mice, because functional T cells are required for the integrity of the pathway. To investigate the role of T-cell α7nAChR, we adoptively transferred α7nAChR-deficient or WT T cells to nude mice. Transfer of WT and α7nAChR-deficient T cells restored function, indicating that α7nAChR expression on T cells is not necessary for this pathway. Together, these results indicate that α7nAChR expression in bone marrow-derived non-T cells is required for the integrity of the inflammatory reflex.     

Distribution and fate of DCX/PSA-NCAM expressing cells in the adult mammalian cortex: A local reservoir for adult cortical neuroplasticity?

The expression of early developmental markers such as doublecortin (DCX) and the polysialylated-neural cell adhesion molecule (PSA-NCAM) has been used to identify immature neurons within canonical neurogenic niches. Additionally, DCX/PSA-NCAM+ immature neurons reside in cortical layer II of the paleocortex and in the paleo- and entorhinal cortex of mice and rats, respectively. These cells are also found in the neocortex of guinea pigs, rabbits, some afrotherian mammals, cats, dogs, non-human primates, and humans. The population of cortical DCX/PSA-NCAM+ immature neurons is generated prenatally as conclusively demonstrated in mice, rats, and guinea pigs. Thus, the majority of these cells do not appear to be the product of adult proliferative events. The immature neurons in cortical layer II are most abundant in the cortices of young individuals, while very few DCX/PSA-NCAM + cortical neurons can be detected in aged mammals. Maturation of DCX/PSA-NCAM+ cells into glutamatergic and GABAergic neurons has been proposed as an explanation for the age-dependent reduction in their population over time. In this review, we compile the recent information regarding the age-related decrease in the number of cortical DCX/PSA-NCAM+ neurons. We compare the distribution and fates of DCX/PSA-NCAM + neurons among mammalian species and speculate their impact on cognitive function. To respond to the diversity of adult neurogenesis research produced over the last number of decades, we close this review by discussing the use and precision of the term “adult non-canonical neurogenesis.”