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101.
We tested the hypothesis that parental effort modulates the magnitude of corticosterone and prolactin responses to stress in a long-lived bird, the Black-legged kittiwake (Rissa tridactyla). To do so, we compared corticosterone and prolactin responses to capture/restraint stress between chick-rearing birds and failed breeders (no parental effort). We predicted that (1) the increase in plasma corticosterone levels in response to stress should be lower in chick-rearing birds, (2) the decrease in plasma prolactin levels in response to stress should be lower in chick-rearing birds, and (3) as both sexes care for the chick, there should be no sex difference in the hormonal response to stress. Baseline plasma corticosterone and prolactin levels were higher in chick-rearing birds and were not influenced by body condition. Failed breeders were in better condition than chick-rearing individuals. Corticosterone response to stress was unaffected by parental effort as both chick-rearing and failed birds exhibited a robust corticosterone increase. Prolactin response to stress was however clearly influenced by parental effort: chick-rearing birds showed a modest 9% prolactin decrease whereas in failed birds prolactin concentrations fell by 41%. Body condition did not influence hormonal responses to stress. When facing stressful condition, breeding kittiwakes attenuate their prolactin response to stress while enhancing their secretion of corticosterone. Increasing corticosterone secretion triggers foraging efforts and diminishes nest attendance whereas an attenuation of prolactin response to stress maintains parental behavior. We suggest that this hormonal mechanism facilitates a flexible time-budget that has been interpreted as a buffer against environmental variability. 相似文献
102.
Mithieux G Misery P Magnan C Pillot B Gautier-Stein A Bernard C Rajas F Zitoun C 《Cell metabolism》2005,2(5):321-329
Protein feeding is known to decrease hunger and subsequent food intake in animals and humans. It has also been suggested that glucose appearance into portal vein, as occurring during meal assimilation, may induce comparable effects. Here, we connect these previous observations by reporting that intestinal gluconeogenesis (i.e., de novo synthesis of glucose) is induced during the postabsorptive time (following food digestion) in rats specifically fed on protein-enriched diet. This results in glucose release into portal blood, counterbalancing the lowering of glycemia resulting from intestinal glucose utilization. Comparable infusions into the portal vein of control postabsorptive rats (fed on starch-enriched diet) decrease food consumption and activate the hypothalamic nuclei regulating food intake. Similar hypothalamic activation occurs on protein feeding. All these effects are absent after denervation of the portal vein. Thus, portal sensing of intestinal gluconeogenesis may be a novel mechanism connecting the macronutrient composition of diet to food intake. 相似文献
103.
Kim YS Kim JM Jung DL Kang JE Lee S Kim JS Seol W Shin HC Kwon HS Van Lint C Hernandez N Hur MW 《The Journal of biological chemistry》2005,280(22):21545-21552
104.
Bone marrow-derived dendritic cells reverse the anergic state of CD4+CD25+ T cells without reversing their suppressive function 总被引:2,自引:0,他引:2
Dendritic cells (DC) are potent inducers of immunity to foreign Ags, but also contribute to self-tolerance by induction of regulatory T cells or deletion/anergy of self-reactive T cells. In this study, we have studied the capacity of DC to activate naturally occurring CD4+CD25+ regulatory T cells as well as the ability of CD4+CD25+ T cells to suppress the DC-mediated activation of CD4+CD25- T cells. Mature bone marrow-derived dendritic cells, but not splenic DC, were able to induce the proliferation of CD4+CD25+ T cells in the presence of a polyclonal stimulus and in the absence of exogenous IL-2. The DC-induced proliferative response of the CD4+CD25+ T cells was partially dependent on IL-2 produced by a small number of contaminating CD25+ effector cells. Because bone marrow-derived dendritic cells induce proliferation of both CD4+CD25+ and CD4+CD25- T cells in vitro, it was impossible to assay the suppressive function of the CD4+CD25+ T cells using [3H]TdR uptake or CFSE dilution. We therefore measured IL-2 production in cocultures of CD4+CD25+ and CD4+CD25- T cells using the IL-2 secretion assay. Surprisingly, CD4+CD25+ T cells markedly suppressed IL-2 secretion by the CD4+CD25- T cells without inhibiting their proliferation. Collectively, these results suggest that Ag presentation by DC can induce the expansion of CD4+CD25+ T cells while simultaneously activating their ability to suppress cytokine secretion by effector T cells. 相似文献
105.
Vincent P Collette Y Marignier R Vuaillat C Rogemond V Davoust N Malcus C Cavagna S Gessain A Machuca-Gayet I Belin MF Quach T Giraudon P 《Journal of immunology (Baltimore, Md. : 1950)》2005,175(11):7650-7660
The semaphorin-signaling transducer collapsin response mediator protein 2 (CRMP2) has been identified in the nervous system where it mediates Sema3A-induced growth cone navigation. In the present study, we provide first evidence that CRMP2 is present in the immune system and plays a critical role in T lymphocyte function. CRMP2 redistribution at the uropod in polarized T cells, a structural support of lymphocyte motility, suggests that it may regulate T cell migration. This was evidenced in primary T cells by small-interfering RNA-mediated CRMP2 gene silencing and blocking Ab, as well as CRMP2 overexpression in Jurkat T cells tested in a chemokine- and semaphorin-mediated transmigration assay. Expression analysis in PBMC from healthy donors showed that CRMP2 is enhanced in cell subsets bearing the activation markers CD69+ and HLA-DR+. Heightened expression in T lymphocytes of patients suffering from neuroinflammatory disease with enhanced T cell-transmigrating activity points to a role for CRMP2 in pathogenesis. The elucidation of the signals and mechanisms that control this pathway will lead to a better understanding of T cell trafficking in physiological and pathological situations. 相似文献
106.
Reynolds LF de Bettignies C Norton T Beeser A Chernoff J Tybulewicz VL 《The Journal of biological chemistry》2004,279(18):18239-18246
Vav1 is a signaling protein required for both positive and negative selection of CD4(+)CD8(+) double positive thymocytes. Activation of the ERK MAPK pathway is also required for positive selection. Previous work has shown that Vav1 transduces T cell receptor (TCR) signals leading to an intracellular calcium flux. We now show that in double positive thymocytes Vav1 is required for TCR-induced activation of the ERK1 and ERK2 kinases via a pathway involving the Ras GTPase, and B-Raf, MEK1, and MEK2 kinases. Furthermore, we show that Vav1 transduces TCR signals to Ras by controlling the membrane recruitment of two guanine nucleotide exchange factors. First, Vav1 transduces signals via phospholipase Cgamma1 leading to the membrane recruitment of RasGRP1. Second, Vav1 is required for recruitment of Sos1 and -2 to the transmembrane adapter protein LAT. Finally, we show that Vav1 is required for TCR-induced LAT phosphorylation, a key event for the activation of both phospholipase Cgamma1 and Sos1/2. We propose that reduced LAT phosphorylation is the key reason for defective TCR-induced calcium flux and ERK activation in Vav1-deficient cells. 相似文献
107.
108.
Demozay D Rocchi S Mas JC Grillo S Pirola L Chavey C Van Obberghen E 《The Journal of biological chemistry》2004,279(8):6261-6270
Phosphatidylinositol 3-kinase signaling regulates the expression of several genes involved in lipid and glucose homeostasis; deregulation of these genes may contribute to insulin resistance and progression toward type 2 diabetes. By employing RNA arbitrarily primed-PCR to search for novel phosphatidylinositol 3-kinase-regulated genes in response to insulin in isolated rat adipocytes, we identified fatty aldehyde dehydrogenase (FALDH), a key component of the detoxification pathway of aldehydes arising from lipid peroxidation events. Among these latter events are oxidative stresses associated with insulin resistance and diabetes. Upon insulin injection, FALDH mRNA expression increased in rat liver and white adipose tissue and was impaired in two models of insulin-resistant mice, db/db and high fat diet mice. FALDH mRNA levels were 4-fold decreased in streptozotocin-treated rats, suggesting that FALDH deregulation occurs both in hyperinsulinemic insulin-resistant state and hypoinsulinemic type 1 diabetes models. Moreover, insulin treatment increases FALDH activity in hepatocytes, and expression of FALDH was augmented during adipocyte differentiation. Considering the detoxifying role of FALDH, its deregulation in insulin-resistant and type 1 diabetic models may contribute to the lipid-derived oxidative stress. To assess the role of FALDH in the detoxification of oxidized lipid species, we evaluated the production of reactive oxygen species in normal versus FALDH-overexpressing adipocytes. Ectopic expression of FALDH significantly decreased reactive oxygen species production in cells treated by 4-hydroxynonenal, the major lipid peroxidation product, suggesting that FALDH protects against oxidative stress associated with lipid peroxidation. Taken together, our observations illustrate the importance of FALDH in insulin action and its deregulation in states associated with altered insulin signaling. 相似文献
109.
Mounier CM Ghomashchi F Lindsay MR James S Singer AG Parton RG Gelb MH 《The Journal of biological chemistry》2004,279(24):25024-25038
Stable expression of human groups IIA and X secreted phospholipases A(2) (hGIIA and hGX) in CHO-K1 and HEK293 cells leads to serum- and interleukin-1beta-promoted arachidonate release. Using mutant CHO-K1 cell lines, it is shown that this arachidonate release does not require heparan sulfate proteoglycan- or glycosylphosphatidylinositol-anchored proteins. It is shown that the potent secreted phospholipase A(2) inhibitor Me-Indoxam is cell-impermeable. By use of Me-Indoxam and the cell-impermeable, secreted phospholipase A(2) trapping agent heparin, it is shown that hGIIA liberates free arachidonate prior to secretion from the cell. With hGX-transfected CHO-K1 cells, arachidonate release occurs before and after enzyme secretion, whereas all of the arachidonate release from HEK293 cells occurs prior to enzyme secretion. Immunocytochemical studies by confocal laser and electron microscopies show localization of hGIIA to the cell surface and Golgi compartment. Additional results show that the interleukin-1beta-dependent release of arachidonate is promoted by secreted phospholipase A(2) expression and is completely dependent on cytosolic (group IVA) phospholipase A(2). These results along with additional data resolve the paradox that efficient arachidonic acid release occurs with hGIIA-transfected cells, and yet exogenously added hGIIA is poorly able to liberate arachidonic acid from mammalian cells. 相似文献
110.
Nicot C Napal L Relat J González S Llebaria A Woldegiorgis G Marrero PF Haro D 《Biochemical and biophysical research communications》2004,325(3):660-664
Carnitine palmitoyltransferase I (CPT-I) and II (CPT-II) enzymes are components of the carnitine palmitoyltransferase shuttle system which allows entry of long-chain fatty acids into the mitochondrial matrix for subsequent oxidation. This system is tightly regulated by malonyl-CoA levels since this metabolite is a strong reversible inhibitor of the CPT-I enzyme. There are two distinct CPT-I isotypes (CPT-Ialpha and CPT-Ibeta), that exhibit different sensitivity to malonyl-CoA inhibition. Because of its ability to inhibit fatty acid synthase, C75 is able to increase malonyl-CoA intracellular levels. Paradoxically it also activates long-chain fatty acid oxidation. To identify the exact target of C75 within the CPT system, we expressed individually the different components of the system in the yeast Pichia pastoris. We show here that C75 acts on recombinant CPT-Ialpha, but also on the other CPT-I isotype (CPT-Ibeta) and the malonyl-CoA insensitive component of the CPT system, CPT-II. 相似文献