| 1. |
- Eriksson, Hans, et al.
(författare)
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Evidence for the key role of the adipocyte cGMP-inhibited cAMP phosphodiesterase in the antilipolytic action of insulin
- 1995
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002. ; 1266:1, s. 101-107
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Tidskriftsartikel (refereegranskat)abstract
- Enhancement of cAMP degradation by increased cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) activity is thought to be an important component of the mechanism whereby insulin counteracts catecholamine-induced lipolysis in adipocytes. In this study the selective cGI-PDE inhibitor OPC3911 was used to evaluate this role of cGI-PDE activation in intact rat adipocytes with special reference to changes in cAMP levels measured as cAMP-dependent protein kinase (cAMP-PK) activity ratios. OPC3911 completely blocked (IC50 = 0.3 microM) the maximal inhibitory effect of insulin on noradrenaline-induced lipolysis and the net dephosphorylation of hormone-sensitive lipase and other intracellular target proteins for insulin action, whereas insulin-induced lipogenesis was not changed. The effect of OPC3911 on cAMP-PK activity ratios at different levels of lipolysis achieved by noradrenaline stimulation revealed that the reduction of cAMP-PK caused by 1 nM insulin was completely blocked by 3 microM OPC3911. The effect of OPC3911 was not due to an excessive increase in cellular cAMP resulting in 'supramaximal' lipolysis unresponsive to insulin. These data demonstrate that reduction in cAMP levels by the activation of cGI-PDE may be sufficient to account for the antilipolytic action of insulin.
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| 2. |
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| 3. |
- Belfrage, Hans
(författare)
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Activation of murine cytotoxic cells with interelukin-2 and the bacterial superantigen staphylococcal entertoxin A.
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Natural killer (NK) cells and T lymphocytes are the major effector cells that can recognize and kill tumor cells. NK cells have a constitutive cytotoxic activity and kill a wide spectrum of tumor cells while T cells recognize specific tumor antigens and need to be activated through their TCR to differentiate into cytotoxic T lymphocyte (CTL) killers or T helper cells. Interleukin-2 is the principal growth factor for both NK and T cells. Both in vitro and in vivo stimulation with IL-2 and the superantigen, Staphylococcal enterotoxin A (SEA) were used to characterize murine cytotoxic cells functionally and phenotypically. Culturing of lymphoid cells with IL-2 preferentially expanded NK cells and induced lymphokine activated killer (LAK) activity that preferentially was mediated by IL-2 activated NK cells (NK-LAK) and only to a minor extent by T cells (T-LAK). Stimulation of lymphoid cells with SEA preferentially expanded T cells expressing certain TCR variable beta elements both in in vitro culture and in vivo following intraperitoneal (i.p.) injections of SEA. T cells responded with induction of profound cytokine production and cytotoxic activity that could be targeted to tumor cells expressing MHC class II, this is termed staphylococcal enterotoxin dependent cell-mediated cytotoxicity (SDCC). However, SEA induced effects are transient and anergy and deletion eventually develop which lead to reduced endogenous IL-2 production and CTL activity. We could show that continuous IL-2/IL-2R stimulation through i.p. injections of rIL-2 twice a day had multiple effects on SEA induced T cell activity. Exogenous IL-2 increased T cell expansion and superinduced as well as prolonged CTL activity. Exogenous IL-2 also prevented SEA induced down-regulation of cytotoxic activity and cytokine production with maintained high levels of SDCC and endogenous IL-2 production. Combined treatment with SEA and IL-2 further superinduced cytokine production. Collectively, these data support that administration of continuous IL-2/IL-2R stimulation might be advantageous for SEA based tumor therapy.
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| 4. |
- Belfrage, Hans, et al.
(författare)
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Combined activation of murine lymphocytes with staphylococcal enterotoxin and interleukin-2 results in additive cytotoxic activity
- 1994
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Ingår i: Cancer Immunology and Immunotherapy. - 1432-0851. ; 38:4, s. 71-265
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Tidskriftsartikel (refereegranskat)abstract
- This report demonstrates that in vitro activation of murine spleen cells with interleukin-2 (IL-2) or the bacterial superantigen staphylococcal enterotoxin A (SEA) results in different patterns of activation and function of cytotoxic cells. Lymphokine-activated killer activity and antibody-dependent cellular cytotoxicity (ADCC) are mainly mediated by IL-2 activated natural killer (NK) cells. SEA is the most powerful T cell mitogen known so far and retargets cytotoxic T lymphocytes (CTL) to tumors expressing major histocompatibility complex (MHC) class II in staphylococcal-enterotoxin-dependent cellular cytotoxicity (SDCC). Culture of mouse spleen cells with SEA led to expansion and activation of T cells, which demonstrated strong SDCC activity and some NK-like cytotoxicity after 5 days in culture. Cell sorting revealed that both CD8+ and CD4+ T cells mediated SDCC but the former were more effective. Phenotypic analysis showed that SEA preferentially stimulated and expanded T cells expressing T cell receptor V beta 11, in particular CD8+ T cells. Combined activation with SEA and IL-2 resulted in simultaneous induction of T and NK cell cytotoxicity. Moreover, IL-2 had additive effects on SEA-induced SDCC. Combined treatment with SEA and IL-2 might therefore be an approach to induce maximal cytotoxicity against tumors and to recruit both T and NK cells in tumor therapy.
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| 5. |
- Belfrage, Hans, et al.
(författare)
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Enhanced and prolonged efficacy of superantigen-induced cytotoxic T lymphocyte activity by interleukin-2 in vivo
- 1995
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Ingår i: Cancer Immunology and Immunotherapy. - 1432-0851. ; 41:2, s. 87-94
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Tidskriftsartikel (refereegranskat)abstract
- The bacterial superantigen, staphylococcal enterotoxin A (SEA) activates T cells with high frequency and directs them to lyse MHC-class-II-expressing cells in superantigen-dependent cell-mediated cytotoxicity (SDCC). Treatment of mice with SEA induced strong CD8+ T-cell(CTL)-mediated SDCC, as well as abundant cytokine production from CD4+ and CD8+ T cells. However, both cytotoxicity and cytokine release were transient. In contrast, combined treatment with SEA and recombinant interleukin-2 (rIL-2) increased peak levels and maintained CTL activity. These effects were concomitant with an increased number of SEA-reactive V beta 11+ T cells. Both the CD4+ and CD8+ populations contained higher frequencies of cells expressing IL-2 receptor (IL-2R) alpha beta, which suggests that continuous IL-2R signaling preserves its high expression and subsequently prevents loss of growth factor signals necessary for expansion of T cells. Although IL-2R expression was increased among both CD4+ and CD8+ cells, only the cytotoxic function of CTL, but not cytokine production from either CD4 or CD8, was augmented. These findings demonstrate that treatment with rIL-2 potentiates superantigen-induced cytotoxicity and maintains high CTL activity. rIL-2 might therefore be useful in improving superantigen-based tumor therapy.
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| 6. |
- Belfrage, Hans, et al.
(författare)
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Functionally involved cell surface antigens on murine lymphokine activated killer cells
- 1987
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Ingår i: Immunology Letters. ; 14:4, s. 8-293
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the possible involvement of some cell surface structures on lymphoid cells in the functional activity of lymphokine activated killer (LAK) cells, a number of monoclonal antibodies (Mab) against such structures was studied for their ability to inhibit LAK activity in a standard cytotoxicity assay against the natural killer-insensitive target cell EL-4. Almost complete inhibition of LAK activity resulted from incubation with antibodies to the LFA-1 antigen, while blocking of the Lyt 2 antigen reduced cytotoxic activity about 50%. Mab to T-200 gave a weak and inconsistent inhibitory activity, while antibodies to Thy 1, L3T4, IL-2 receptor and MHC class I antigens were without effect. Mab to LFA-1 and Lyt 2 inhibited LAK activity towards EL-4, YAC-1 and differentiated F-9 teratocarcinoma cells, but did not affect LAK-mediated killing of undifferentiated F-9 cells. Experiments with separate preincubation of effector and target cells revealed that both LFA-1 and Lyt 2 inhibited LAK activity at the effector cell level only.
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| 7. |
- Belfrage, Hans, et al.
(författare)
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Prevention of superantigen induced down-regulation of T cell mediated cytotoxic activity by IL-2 in vivo. 1996 Accepted for publication in Immunology
- 1997
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Ingår i: Immunology. - 0019-2805. ; 90:2, s. 8-183
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Tidskriftsartikel (refereegranskat)abstract
- Administration of staphylococcal enterotoxin A (SEA) to mice induces profound activation, cytokine production and cytotoxic activity of both CD4+ and CD8+ T cells, but subsequently activated cells are deleted or become anergic. This study demonstrates that administration of interleukin-2 (IL-2) can prevent sea-induced hyporesponsiveness in CD8+ cytotoxic T lymphocytes (CTL). Repeated injections with sea every fourth day resulted in severely reduced cytotoxic activity in the spleen, which correlated with a reduced number of sea-responsive T-cell receptor (TCR)-V beta 11+ CD8+ cells. Studies of purified TCR-V beta 11+ CD8+ cells showed that they possessed intact cytotoxic activity per cell compared with cells from mice given a single injection of SEA, indicating that deletion was the main mechanism for the reduced cytotoxic activity. Combined treatment with SEA and IL-2 increased the number of cytotoxic cells in the spleen after each SEA injection and prevented the down-regulation of cytotoxic activity. Increased cytotoxic activity could be related to increased number and proliferation of CD8+ IL-2R alpha + cells, suggesting that administration of IL-2 maintained IL-2 responsiveness among CD8+ cells. Studies of sorted TCR-V beta 11+ CD8+ cells demonstrated that combined treatment with SEA and IL-2 also increased cytotoxic activity per cell compared with treatment with SEA alone. Taken together, IL-2 administration in vivo augmented SEA-induced expansion of T cells as well as the cytotoxic activity per CTL, and prevented SEA-induced cell deletion.
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| 8. |
- Belfrage, Hans, et al.
(författare)
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Prevention of superantigen-induced tolerance in vivo by interleukin-2 treatment. 1996 Submitted
- 1997
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Ingår i: Cancer Immunology and Immunotherapy. - 1432-0851. ; 44:2, s. 77-82
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Tidskriftsartikel (refereegranskat)abstract
- Injection of the superantigen staphylococcal enterotoxin A (SEA) activates both CD4+ and CD8+ T cells expressing certain families of T cell receptor (TCR) variable-region beta (V beta) chain. T cells respond with profound cytokine production and induction of cytotoxicity. Repeated injections, however, cause deletion and anergy of both CD4+ and CD8+ T cells, resulting in reduced frequency of SEA-responsive cells TCR-V beta11+ as well as reduced cytokine levels in serum upon challenge with SEA. Exogenous interleukin-2 (IL-2) in vivo rescued SEA-responsive CD4+ and CD8+ cells from SEA-induced deletion and/or increase expansion of SEA-primed cells as well as preventing downregulation of endogenous IL-2 production in vivo. Combined treatment with SEA and IL-2 also superinduced production of important cytokines for the cytotoxic function of T cells, tumour necrosis factor alpha, interferon gamma and IL-6, on a cellular level. These studies show that continuous stimulation with IL-2 in vivo could be useful for superantigen-based immunotherapy by induction of excessive T cell activation and by prevention of the development of T cell deletion and anergy.
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| 9. |
- Belfrage, Per, et al.
(författare)
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Alterations of lipid metabolism in healthy volunteers during long-term ethanol intake
- 1977
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Ingår i: European Journal of Clinical Investigation. - : Wiley. - 0014-2972 .- 1365-2362. ; 7:2, s. 127-131
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Tidskriftsartikel (refereegranskat)abstract
- Nine young, healthy male volunteers were given ethanol (75 g/day) for 5 weeks. The ethanol was divided into five daily doses and taken so that blood ethanol levels never exceeded 0.04% (w/v). During the latter part of the ethanol intake period, there was a significant, transient increase of plasma triglyceride (TG) concentrations followed by reduction to normal levels. A three-fold increase of lipoprotein lipase activity (LLA) occurred in biopsy specimens of adipose tissue. An increase of alpha-lipoprotein concentrations, which correlated significantly with the decrease in plasma TG levels and the increase in adipose LLA, was also observed during the ethanol intake period. No changes were observed in plasma cholesterol and beta-lipoprotein levels. A transient, three-fold increase of TG concentrations occurred in liver biopsy specimens. Ultrastructural and cytochemical examinations of the biopsy specimens showed hyperplasia of the smooth endoplasmic reticulum, and increased canallicular activity of gamma-glutamyl transferase (gamma-GT) activity in most subjects towards the end of and after the ethanol intake period. Serum gamma-GT levels also increased significantly.
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| 10. |
- Rahn, Tova, et al.
(författare)
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Essential role of phosphatidylinositol 3-kinase in insulin-induced activation and phosphorylation of the cGMP-inhibited cAMP phosphodiesterase in rat adipocytes. Studies using the selective inhibitor wortmannin
- 1994
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Ingår i: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 350:2-3, s. 314-318
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Tidskriftsartikel (refereegranskat)abstract
- Incubation of rat adipocytes with wortmannin, a potent and selective phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, completely blocked the antilipolytic action of insulin (IC50 = 100 nM), the insulin-induced activation and phosphorylation of cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) as well as the activation of the insulin-stimulated cGI-PDE kinase (IC50 = 10-30 nM). No direct effects of the inhibitor on the insulin-stimulated cGI-PDE kinase, the cGI-PDE and the hormone-sensitive lipase were observed. These data suggest that activation of PI 3-kinase upstream of the insulin-stimulated cGI-PDE kinase in the antilipolytic insulin signalchain has an essential role for insulin-induced cGI-PDE activation/phosphorylation and anti-lipolysis.
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