Leukemia Inhibitory Factor in Rat Fetal Lung Development: Expression and Functional Studies

Background: Leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) are members of the family of the glycoprotein 130 (gp130)-type cytokines. These cytokines share gp130 as a common signal transducer, which explains why they show some functional redundancy. Recently, it was demonstrated that IL-6 promotes fetal lung branching. Additionally, LIF has been implicated in developmental processes of some branching organs. Thus, in this study LIF expression pattern and its effects on fetal rat lung morphogenesis were assessed. Methodology/Principal Findings: LIF and its subunit receptor LIFRa expression levels were evaluated by immunohistochemistry and western blot in fetal rat lungs of different gestational ages, ranging from 13.5 to 21.5 days post-conception. Throughout all gestational ages studied, LIF was constitutively expressed in pulmonary epithelium, whereas LIFRa was first mainly expressed in the mesenchyme, but after pseudoglandular stage it was also observed in epithelial cells. These results point to a LIF epithelium-mesenchyme cross-talk, which is known to be important for lung branching process. Regarding functional studies, fetal lung explants were cultured with increasing doses of LIF or LIF neutralizing antibodies during 4 days. MAPK, AKT, and STAT3 phosphorylation in the treated lung explants was analyzed. LIF supplementation significantly inhibited lung growth in spite of an increase in p44/42 phosphorylation. On the other hand, LIF inhibition significantly stimulated lung growth via p38 and Akt pathways

Tissue functions mediated by β3-adrenoceptors—findings and challenges

As β3-adrenoceptor agonists metamorphose from experimental tools into therapeutic drugs, it is vital to obtain a comprehensive picture of the cell and tissue functions mediated by this receptor subtype in humans. Human tissues with proven functions and/or a high expression of β3-adrenoceptors include the urinary bladder, the gall bladder, and other parts of the gastrointestinal tract. While several other β3-adrenoceptor functions have been proposed based on results obtained in animals, their relevance to humans remains uncertain. For instance, β3-adrenoceptors perform an important role in thermogenesis and lipolysis in rodent brown and white adipose tissue, respectively, but their role in humans appears less significant. Moreover, the use of tools such as the agonist BRL 37344 and the antagonist SR59230A to demonstrate functional involvement of β3-adrenoceptors may lead in many cases to misleading conclusions as they can also interact with other β-adrenoceptor subtypes or even non-adrenoceptor targets. In conclusion, we propose that many responses attributed to β3-adrenoceptor stimulation may need re-evaluation in the light of the development of more selective tools. Moreover, findings in experimental animals need to be extended to humans in order to better understand the potential additional indications and side effects of the β3-adrenoceptor agonists that are beginning to enter clinical medicine

Lymphocyte beta 2-adrenoceptors mirror precisely beta 2-adrenoceptor, but poorly beta 1-adrenoceptor changes in the human heart

To study the relationship of changes in human lymphocyte beta-adrenoceptors to changes potentially occurring in solid tissues we studied 16 patients undergoing elective coronary artery bypass grafting and determined the density of lymphocyte beta 2-adrenoceptors [by (-)125I-iodocyanopindolol (ICYP) binding] in comparison to beta-adrenoceptor density and responsiveness (contractile responses to isoprenaline) in the corresponding right atria. Lymphocyte beta 2-adrenoceptor density (with a range of 278-2442 ICYP binding sites/cell) was significantly correlated with beta-adrenoceptor density in the corresponding atria (54.8-171.6 fmol ICYP bound/mg protein, r = 0.784, P less than 0.001). In these atria the levels of beta 1- and beta 2-adrenoceptors (assessed by non-linear regression analysis of competition curves of the selective beta 2-adrenoceptor antagonist ICI 188,551 with ICYP binding) were approximately .70 and 30%, respectively. Lymphocyte beta 2-adrenoceptor density, however, correlated significantly better with atrial beta 2-adrenoceptor (r = 0.8441; P less than 0.001) than beta 1-adrenoceptor (r = 0.6226, P less than 0.05) density. On 12 of the 16 atria (electrically driven with 1 Hz at 37 degrees C) isoprenaline (10(-9) to 3 X 10(-6) mol/l) caused positive inotropic effects. The maximum increase in contractile force evoked by saturating concentrations of isoprenaline (mean: 3.52 +/- 0.62 mN), however, correlated equally well with beta 1- and beta 2-adrenoceptor density in the corresponding atria (r = 0.6834 and 0.6567, respectively). These results indicate that changes in lymphocyte beta 2-adrenoceptors can be taken as a precise index of changes of beta 2-adrenoceptors in other (solid) tissues; beta 1-adrenoceptor alterations, however, are only poorly reflected in the lymphocyte

Beta-2 adrenoceptor-mediated relaxation of the isolated human saphenous vein

On isolated strips of human saphenous vein, pretreated with 5 microM phenoxybenzamine and contracted with 10 mM KCl, the beta adrenoceptor mediating the relaxant effects of isoproterenol, procaterol and norepinephrine was characterized using the selective beta-1 adrenoceptor antagonist, bisoprolol, and the selective beta-2 adrenoceptor antagonist, ICI 118,551. All three agonists produced concentration-dependent relaxations of the isolated saphenous vein with an order of potency: procaterol (pD2 value, 7.69) greater than isoproterenol (pD2 value, 7.41) much greater than norepinephrine (pD2 value, 5.30). ICI 118,551 (3 X 10(-10) to 3 X 10(-9) M) was nearly 100 times more potent than bisoprolol (10(-7) to 10(-6) M) in antagonizing the relaxant effects of isoproterenol and procaterol. The slopes of the Schild plots for the antagonistic effects of ICI 118,551 and bisoprolol against isoproterenol- and procaterol-induced relaxations were not significantly different from unity indicating interaction with a homogeneous population of beta adrenoceptors. The pA2 value for ICI 118,551 amounted to 9.11 to 9.20 and for bisoprolol to 6.50 to 6.63. In addition, the concentration-response curve for the relaxant effect of norepinephrine was significantly shifted to the right by 10(-9) M ICI 118,551, but not affected by 10(-7) M bisoprolol. These results indicate that on the isolated strips of the human saphenous vein the beta adrenoceptor mediating relaxation is of the beta-2 subtyp

The role of cyclic AMP in the positive inotropic effect mediated by beta 1- and beta 2-adrenoceptors in isolated human right atrium

The time course of the effects of isoprenaline (3 X 10(-7) mol/l) on contractile force and on the cyclic AMP level was studied in the electrically driven isolated muscle strip of the human right atrium. Isoprenaline produced a rise in cyclic AMP content (maximum increase after 60 s) preceding the increase in contractile force. The effects of isoprenaline on contractile force and on the intracellular level of cyclic AMP were enhanced in the presence of the phosphodiesterase inhibitor papaverine (10(-5) mol/l). On the other hand, the beta-adrenoceptor antagonist propranolol (10(-7) mol/l) suppressed isoprenaline-induced cyclic AMP increases, but reduced the increase in force of contraction by only 35%. In addition, both the beta 1-selective antagonist bisoprolol (3 X 10(-9)-3 X 10(-8) mol/l) and the beta 2-selective antagonist ICI 118,551 (3 X 10(-9)-3 X 10(-8) mol/l) inhibited the isoprenaline-induced cyclic AMP increase concentration-dependently; ICI 118,551 produced more pronounced inhibition than bisoprolol. It is concluded that cyclic AMP is involved in the positive inotropic action of isoprenaline evoked by beta 1- and beta 2-adrenoceptor stimulation in isolated human right atrium; however, an additional cyclic AMP independent mechanism cannot be ruled ou

Beta-2 Adrenoceptor-Mediated Relaxation of the Isolated Human Saphenous Vein1

ABSTRAC