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At least 19 recordsLinked to original sources
PubMed1992

Differences between ATP-mediated cytotoxicity and cell-mediated cytotoxicity.

There has been considerable recent interest in the possible role of extracellular ATP in cell-mediated cytotoxicity. To investigate the similarities and differences between ATP-mediated lysis and CTL-mediated lysis, we studied in detail the ATP-mediated lysis of EL-4 cells, which are highly susceptible to lysis by extracellular ATP. ATP-mediated lysis was time and concentration dependent; most lysis occurred within 4 to 6 h of incubation. The kinetics of ATP- and cell-mediated lysis were similar. However, in contrast to CTL-mediated lysis, ATP-mediated lysis of EL-4 cells did not appear to be accompanied by characteristic chromosomal degradation (apoptosis). In order to compare these cytotoxic processes in greater detail, ATP-resistant clones were derived by growing EL-4 cells continuously in the presence of high concentrations of ATP. These cloned EL-4 lines showed marked resistance to ATP-mediated cytotoxicity across a wide range of concentrations but were as susceptible as the parent EL-4 cells to cell-mediated cytotoxicity by an alloreactive effector population from a MLC. Thus, there appear to be a number of differences between ATP-mediated and cell-mediated cytotoxicity in this system; most notable is the identification of cell lines that are resistant to ATP but susceptible to CTL-mediated lysis.

Adenosine Triphosphate↗
PubMed1988

Phorbol ester and neomycin dissociate bradykinin receptor-mediated arachidonic acid release and polyphosphoinositide hydrolysis in Madin-Darby canine kidney cells. Evidence that bradykinin mediates noninterdependent activation of phospholipases A2 and C.

Many types of peptide hormone and neurotransmitter receptors mediate hydrolysis of phosphoinositides (PI) and arachidonic acid and arachidonic acid metabolite (AA) release, but the relation between these responses is not clearly defined. We have characterized bradykinin (BK)-mediated AA release and PI hydrolysis in clonal Madin-Darby canine kidney cells (MDCK-D1). Both responses occurred over a similar dose range in response to the B1 and B2 receptor agonist, BK, but not in response to the B1 receptor-selective agonist des-Arg-BK. To test whether AA release occurs via a mechanism which is sequential to and dependent upon PI hydrolysis, we used the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), which activates protein kinase C. TPA treatment blocked BK-mediated PI hydrolysis in MDCK-D1 cells, while at the same time and at similar concentrations enhancing BK-mediated AA release. Thus, TPA treatment dissociated BK-mediated AA release from PI hydrolysis. In addition, treatment of MDCK-D1 cells with neomycin blocked BK-mediated hydrolysis of phosphatidylinositol bisphosphate without reducing BK-mediated AA release. BK treatment increased formation of lysophospholipids with a time course in accord with BK-mediated AA release, indicating that at least part of the BK-mediated AA release was likely derived from activation of phospholipase A2. BK-mediated lysophospholipid production was enhanced by pretreatment with TPA, suggesting that the mechanism of AA release before and after treatment with TPA was the same. BK-mediated AA release and lysophospholipid production was dependent on the presence of extracellular calcium, while the enhanced responses to BK in the presence of TPA were not dependent on the presence of extracellular calcium. TPA treatment also enhanced AA release and lysophospholipid production in response to the calcium ionophore A23187. From these data we propose that BK, acting at B2 receptors, promotes AA release in MDCK cells via a mechanism which is 1) independent of polyphosphoinositide hydrolysis by phospholipase C, 2) dependent upon influx of extracellular calcium and activation of phospholipase A2, and 3) enhanced by activation of protein kinase C.

Animals↗
PubMed2025

S-GMAS: Genome-Wide Mediation Analysis With Brain Subcortical Shape Mediators.

Mediation analysis is widely utilized in neuroscience to investigate the role of brain image phenotypes in the neurological pathways from genetic exposures to clinical outcomes. However, it is still difficult to conduct mediation analyses with whole genome-wide exposures and brain subcortical shape mediators due to several challenges including (i) large-scale genetic exposures, that is, millions of single-nucleotide polymorphisms (SNPs); (ii) nonlinear Hilbert space for shape mediators; and (iii) statistical inference on the direct and indirect effects. To tackle these challenges, this paper proposes a genome-wide mediation analysis framework with brain subcortical shape mediators. First, to address the issue caused by the high dimensionality in genetic exposures, a fast genome-wide association analysis is conducted to discover potential genetic variants with significant genetic effects on the clinical outcome. Second, the square-root velocity function representations are extracted from the brain subcortical shapes, which fall in an unconstrained linear Hilbert subspace. Third, to identify the underlying causal pathways from the detected SNPs to the clinical outcome implicitly through the shape mediators, we utilize a shape mediation analysis framework consisting of a shape-on-scalar model and a scalar-on-shape model. Furthermore, the bootstrap resampling approach is adopted to investigate both global and spatial significant mediation effects. Finally, our framework is applied to the corpus callosum shape data from the Alzheimer's Disease Neuroimaging Initiative.

Humans↗
PubMed1991

Regional differences of beta 1- and beta 2-adrenoceptor-mediated functions in feline heart. A beta 2-adrenoceptor-mediated positive inotropic effect possibly unrelated to cyclic AMP.

The effects of (-)-adrenaline and (-)-noradrenaline were studied on isolated preparations of kitten heart. To define the contribution of beta 1-adrenoceptors (beta 1AR) and beta 2-adrenoceptors (beta 2AR) we used as tools the highly beta 1AR-selective antagonist CGP 20,712 A and non-linear analysis of antagonism. The beta 2AR-mediated responses to the catecholamines, disclosed by CGP 20,712 A, were verified by blockade with the beta 2AR-selective ICI 118,551. The relative density and contribution of beta 1AR and beta 2AR to (-)-adrenaline- and (-)-noradrenaline-induced adenylyl cyclase stimulation was also estimated in right ventricular membranes. 1. In the sinoatrial pacemaker (-)-adrenaline caused positive chronotropic effects through both beta 1AR and beta 2AR while (-)-noradrenaline does so predominantly through beta 1AR. During beta 1AR blockade (-)-adrenaline did cause the same maximum effects through beta 2AR as (-)-noradrenaline did through beta 1AR. 2. In left atria (-)-adrenaline caused positive inotropic effects predominantly through beta 1AR. CGP 20,712 A also uncovered a beta 2AR component at high (-)-adrenaline concentrations comprising one third of the maximum beta 1AR-mediated response. 3. Receptor binding assays revealed that 80% of right ventricular beta AR were beta 1AR and 20% beta 2AR. Consistent with this finding, around 80% of the adenylyl cyclase stimulation by both (-)-noradrenaline and (-)-adrenaline was mediated through beta 1AR, around 20% through beta 2AR. The positive inotropic effects of (-)-noradrenaline appeared to be nearly exclusively mediated through beta 1AR in right ventricular papillary muscles. 4. The positive inotropic effects of (-)-adrenaline were quite variable with regard to beta 1AR and beta 2AR in right ventricular papillary muscles. Although beta 1AR-mediated effects are predominant in many muscles with only a small contribution of beta 2AR, in some muscles beta 2AR mediated around 50% of the maximum effect elicited through beta 1AR. In 3 out of 17 muscles beta 2AR mediated the same maximum effect of (-)-adrenaline as beta 1AR. 5. On occasion, we found marked beta AR heterogeneity amongst two muscles from the same right ventricle. One muscle only exhibited beta 1AR-mediated effects of (-)-adrenaline whereas in the other muscle maximal effects could be elicited through beta 2AR.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic beta-Antagonists↗
PubMed2024

Mannose receptor (MRC1) mediates uptake of dextran in macrophages via receptor-mediated endocytosis.

UNLABELLED: Macrophages maintain surveillance of their environment using receptor-mediated endocytosis and pinocytosis. Receptor-mediated endocytosis allows macrophages to recognize and internalize specific ligands whereas macropinocytosis non-selectively internalizes extracellular fluids and solutes. Here, CRISPR/Cas9 whole-genome screens were used to identify genes regulating constitutive and growth factor-stimulated dextran uptake in murine bone-marrow derived macrophages (BMDM). The endocytic mannose receptor c-type 1 ( Mrc1 , also known as CD206) was a top hit in the screen. Targeted gene disruptions of Mrc1 reduced dextran uptake but had little effect on uptake of Lucifer yellow, a fluid-phase marker. Other screen hits also differentially affected the uptake of dextran and Lucifer yellow, indicating the solutes are internalized by different mechanisms. We further deduced that BMDMs take up dextran via MRC1-mediated endocytosis by showing that competition with mannan, a ligand of MRC1, as well as treatment with Dyngo-4a, a dynamin inhibitor, reduced dextran uptake. Finally, we observed that IL4-treated BMDM internalize more dextran than untreated BMDM by upregulating MRC1 expression. These results demonstrate that dextran is not an effective marker for the bulk uptake of fluids and solutes by macropinocytosis since it is internalized by both macropinocytosis and receptor-mediated endocytosis in cells expressing MRC1. This report identifies numerous genes that regulate dextran internalization in primary murine macrophages and predicts cellular pathways and processes regulating MRC1. This work lays the groundwork for identifying specific genes and regulatory networks that regulate MRC1 expression and MRC1-mediated endocytosis in macrophages. SIGNIFICANCE STATEMENT: Macrophages constantly survey and clear tissues by specifically and non-specifically internalizing debris and solutes. However, the molecular mechanisms and modes of regulation of these endocytic and macropinocytic processes are not well understood. Here, CRISPR/Cas9 whole genome screens were used to identify genes regulating uptake of dextran, a sugar polymer that is frequently used as a marker macropinocytosis, and compared with Lucifer yellow, a fluorescent dye with no known receptors. The authors identified the mannose receptor as well as other proteins regulating expression of the mannose receptor as top hits in the screen. Targeted disruption of Mrc1 , the gene that encodes mannose receptor, greatly diminished dextran uptake but had no effect on cellular uptake of Lucifer yellow. Furthermore, exposure to the cytokine IL4 upregulated mannose receptor expression on the cell surface and increased uptake of dextran with little effect on Lucifer yellow uptake. Studies seeking to understand regulation of macropinocytosis in macrophages will be confounded by the use of dextran as a fluid-phase marker. MRC1 is a marker of alternatively activated/anti-inflammatory macrophages and is a potential target for delivery of therapeutics to macrophages. This work provides the basis for mechanistic underpinning of how MRC1 contributes to the receptor-mediated uptake of carbohydrates and glycoproteins from the tissue milieu and distinguishes genes regulating receptor-mediated endocytosis from those regulating the bona fide fluid-phase uptake of fluids and solutes by macropinocytosis.

Journal Article↗
PubMed2026

Gut Microbiota, Lipidome, and Metabolites Mediate Immune Dysregulation in Diabetic Microvascular Disease: A Two-sample Mendelian Randomization and Mediation Analysis.

INTRODUCTION: Diabetic microvascular disease (DMiVD) involves dysregulated immune cell function, but the precise pathogenic mechanisms remain unclear. MATERIALS AND METHODS: We conducted a two-sample Mendelian randomization (MR) study using comprehensive GWAS and FinnGen summary statistics, encompassing 731 immune cell phenotypes, 473 gut microbial taxa, 91 inflammatory proteins, 179 lipid types, 1,400 plasma metabolites, 20 micronutrients, and DMiVD cases. The analysis aimed to evaluate causal associations between these variables and DMiVD. We further explored potential mediating roles of gut microbiota, plasma lipidome, and metabolites using mediation analysis, with multiple sensitivity tests confirming the robustness of our findings. RESULTS: We identified 20 immune cell phenotypes, 33 gut microbial taxa, 31 lipid types, and 83 plasma metabolites with significant causal associations with DMiVD. Mediation analysis revealed that the risk effect of CD3+ resting Tregs on diabetic nephropathy was partly mediated by phosphatidylcholine (16:0_18:2) (10.7%). Additionally, the protective effect of CX3CR1 on monocytes against DMiVD was partly mediated by Unclassified Bacilli A (35%), Species CAG-177 sp003538135 (22.6%), and triacylglycerol (52:6) (25.5%). DISCUSSION: These findings advance understanding of DMiVD pathogenesis, highlighting that modulation of key metabolic pathways and immune regulatory nodes may represent promising therapeutic strategies. Further experimental studies are needed to validate these potential causal relationships. CONCLUSION: Using causal inference approaches, this study identifies immune cell-mediated mechanisms underlying DMiVD, involving gut microbiota, plasma lipids, and metabolites. The results suggest potential intervention targets for mechanistic studies and therapeutic development.

Mendelian Randomization Analysis↗
PubMed1986

Studies on the receptor mediating cyclic AMP-independent enhancement by adenosine of IgE-dependent mediator release from rat mast cells.

Adenosine produced a concentration-related enhancement of antigen-induced 5-hydroxytryptamine (5-HT) release from rat serosal mast cells. This potentiation was maximal following the simultaneous addition of adenosine with antigen. Enhancement of 5-HT release was accompanied by potentiation of the adenosine 3':5'-cyclic monophosphate (cyclic AMP) response to challenge. The cyclic AMP response, which was antagonized by 8-phenyltheophylline, was characterized as an A2-purinoceptor-mediated effect by the use of 5'-N-ethylcarboxamideadenosine (NECA) and L-N6-phenylisopropyladenosine (L-PIA). Enhancement of 5-HT release, conversely, was not blocked by 8-phenyltheophylline suggesting it to be mediated by a cyclic AMP-independent mechanism. The effect of adenosine on 5-HT release was not reduced by the inhibition of the facilitated uptake of adenosine with dipyridamole, hexobendine or p-nitrobenzylthioguanosine, therefore, suggesting it to be mediated by a cell surface receptor. The receptor mediating enhancement of 5-HT does not appear to belong to the P2-purinoceptor subtype as adenosine was more potent than both adenosine monophosphate (AMP) and adenosine diphosphate (ADP) and alpha, beta-methylene ATP was inactive. Furthermore, the effects of AMP were blocked by alpha, beta-methylene ADP, which inhibits the conversion of AMP to adenosine. Adenosine, NECA, L- and D-PIA were all of equal potency in enhancing 5-HT release. Inosine and 3-deazaadenosine were also active. The rank order of potency of these adenosine analogues is not consistent with an effect at A1- or A2-purinoceptors. There appear to be two adenosine receptors on rat mast cells, an A2-purinoceptor which stimulates adenylate cyclase and a separate purinoceptor, stimulation of which produces enhancement of mediator release by an unknown mechanism. The effects mediated by these receptors appear to be independent of each other.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Synergism between calcium-mediated and cyclic AMP-mediated activation of chloride secretion in isolated guinea pig distal colon.

Synergistic effects of Ca2+-mediated secretagogues and cyclic AMP-mediated secretagogues on Cl- secretion by guinea pig distal colon were studied in vitro using Ussing chambers. Short-circuit current (Isc) and bidirectional fluxes of 22Na+ and 36Cl- were measured. Bethanechol (10(-4) M, a Ca2+-mediated secretagogue) caused an increase in Isc, which was enhanced 4-20 fold when the tissue was pretreated with prostaglandin E2 (10(-7)-10(-6) M), vasoactive intestinal polypeptide (5 x 10(-9)-10(-8) M) (cyclic AMP-mediated secretagogues), or 8-bromocyclic AMP (5 x 10(-4)-2 x 10(-3) M). Measurement of 36Cl flux showed that the increase in Isc in the presence of both 8-bromocyclic AMP and bethanechol resulted principally from increased Cl- secretion. On the other hand, the net absorptive flux of 22Na was not influenced under these conditions. Potentiation of the increase in Isc was also elicited by the combination of A23187 (5 x 10(-6) M) and 8-bromocyclic AMP (10(-3) M). The results are consistent with the notion that simultaneous activation of the cyclic AMP-mediated and Ca2+-mediated systems produces a synergistic increase in colonic Cl- secretion.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1985

Rejection of ticks from guinea pigs by anti-hapten-antibody-mediated degranulation of basophils at cutaneous basophil hypersensitivity sites: role of mediators other than histamine.

Previous studies have established that recruitment of basophils to sites of tick feeding in guinea pigs is required to effect immune resistance. In the current study, actively sensitized guinea pigs treated three times daily with H-1 (mepyramine) and H-2 (cimetidine) histamine receptor antagonists, during the challenge tick infestation period, expressed normal resistance to Amblyomma americanum larvae. Similarly, naive guinea pigs treated with anti-histamines four times daily, beginning 7 days before transfer of immune serum and tick challenge and continuing through the tick infestation period, also expressed normal antibody-mediated resistance to A. americanum. These results indicated that histamine was not an important basophil mediator of the resistance response. Ticks allowed to feed on tissue rich in basophils that were induced by sensitization and subsequent local challenge with non-tick protein antigen, keyhole limpet hemocyanin (KLH), expressed normal yield. Ticks that fed on similar tissue rich in basophils induced by sensitization and challenge with KLH, in which the basophils expressed anti-picryl specificity due to systemic passive transfer of anti-picryl antibodies, were rejected when basophils were induced to degranulate by i.v. challenge with picryl antigen at 6 hr (29% rejection), 12 hr (18% rejection), 24 hr (22% rejection), and 48 hr (37% rejection) post-tick attachment. However, basophil degranulation at 18, 72 and 96 hr post-tick attachment had no adverse effect on tick feeding. These hosts were protected from systemic anaphylaxis by treatment with the anti-histamine mepyramine. Release of histamine occurred at tick feeding sites, but vasoactive effects were blocked by mepyramine treatment as evidenced by a lack of increased vascular permeability (bluing) at these sites compared with non-tick-infested tissues, or to cutaneous basophil hypersensitivity (CBH) sites of animals not protected with mepyramine. These results indicate that local recruitment and subsequent degranulation of basophils via immune mechanisms dependent on non-tick antigens can lead to tick rejection, and that basophil-derived mediators other than histamine are involved in this immune resistance response to A. americanum ticks. The identity of the crucial basophil mediator(s) is not known. The significant susceptibility of ticks to basophil-mediator release at 6 to 12 hr and 24 to 48 hr post-attachment coincides with the tick attaching and fast-feeding phases, respectively, suggesting that these phases of tick parasitism are particularly susceptible to the effect of basophil mediators other than histamine.

Animals↗
PubMed1988

Murine trophoblast resists cell-mediated lysis. II. Resistance to natural cell-mediated cytotoxicity.

The susceptibility of murine trophoblast cells to natural cell-mediated cytotoxicity has been assessed. Primary short-term cultures of murine trophoblast cells isolated from 14-day placentas were found to be resistant to endogenous and interferon-activated natural killer (NK) cells and natural cytotoxic cells. That the relevant target structures are expressed on the surface of trophoblast cells and accessible to the effectors was demonstrated by their ability to inhibit the lysis of NK-sensitive target cells (YAC-1) in a dose-dependent manner. The lytic resistance of trophoblast cells was unaffected by neuraminidase treatment, inhibition of protein synthesis, or extending the assay time to 12 hr. Moreover, trophoblast cells were resistant to antibody-dependent cell-mediated cytotoxicity when coated with an alloantibody capable of mediating their lysis in the presence of heterologous complement. Neither the preincubation of effector cells in concentrated trophoblast culture supernatants nor the direct exposure of effectors to monolayers of trophoblast cells inhibited their NK lytic activity, indicating that the secretion of a suppressive factor or the direct inactivation of the NK cells was not responsible for the observed resistance to lysis. These observations, together with previous results showing the resistance of trophoblast to cytotoxic T cell-mediated lysis, reveal that murine trophoblast cells possess a resistance mechanism against several forms of cell-mediated lysis. This feature of trophoblast cells at the maternal-fetal interface is likely to play an important role in protecting the fetoplacental allograft from immune rejection.

Animals↗
PubMed1991

A novel cell-permeable cromoglycate derivative inhibits type I Fc epsilon receptor mediated Ca2+ influx and mediator secretion in rat mucosal mast cells.

Type I Fc epsilon receptor (Fc epsilon RI) mediated Ca2+ uptake and secretion of rat serosal mast cells have been shown to be inhibited by disodium 1,3-bis [(2'-carboxylatochromon-5'-yl) oxy]-2-hydroxypropane (disodium cromoglycate, DSCG), which is widely employed in the treatment of allergic asthma [Foreman et al. (1977) Br. J. Pharmacol. 59, 473P-474P; Cox (1967) Nature (London) 216, 1328-1329]. This drug was also found to modify the protein phosphorylation pattern of these mast cells. [Theoharides et al. (1980) Science 207, 80-82]. We have isolated by affinity chromatography on a water-insoluble cromoglycate-carrying matrix a cytosolic enzyme recently identified as a nucleoside 5'-diphosphate kinase. In order to examine a possible intracellular activity of the drug, a cell-permeant cromoglycate derivative, 1,3-bis [[2'-[[(acetoxymethyl)oxy]carbonyl]chromon-5'- yl]oxy]-2-hydroxypropane [bis(acetoxymethyl) cromoglycate, CG/AM], has been synthesized, and its uptake and effect on the Fc epsilon RI-mediated exocytosis of mast cells was investigated. A tritium-labeled CG/AM derivative, used as radioactive tracer, was found to permeate mucosal mast cells of the rat line RBL-2H3 and accumulate intracellularly up to 40-fold its extracellular concentration following hydrolysis by cytoplasmic hydrolases. A CG/AM dose dependent inhibition of the Fc epsilon RI-induced mediator secretion was observed in RBL-2H3 cells loaded with this compound (I50 approximately 40 microM extracellular CG/AM). A similar dose-dependent inhibition was observed for both the Fc epsilon RI-mediated transient rise in the concentration of cytosolic free Ca2+ ions [( Ca2+]i) and the net Ca2+ influx, as monitored by the fluorescent indicator Quin2 and the radioactive tracer 45Ca2+, respectively. These results clearly show that cell-permeant cromoglycate inhibits the Fc epsilon RI-mediated Ca2+ influx into the cell and further underscore the dominant role of this process in the coupling of stimulus to secretion in RBL cells. Furthermore, with the identification of nucleoside 5'-diphosphate kinase as a potential intracellular target for CG activity, distinct mechanisms of action may be inferred for cell-permeant and nonpermeant forms of CG.

Animals↗
PubMed1990

Separation of opioid from nonopioid mediation of affect in neonatal rats: nonopioid mechanisms mediate maternal contact influences.

A causal distinction is established in infant Norway rats between opioid- and nonopioid-mediated determinants of behavior. Contact influences are shown to be mediated by nonopioid pathways, whereas gustatory influences are shown to be opioid mediated. Specifically, naltrexone (0.5 and 1.0 mg/kg) did not at all diminish quieting exerted by contact with an anesthetized dam but completely reversed the quieting effects of morphine in isolated rats. Naloxone (5 mg/kg) did not affect the latencies with which nondeprived or 8-hr deprived rats 9, 12, 15, and 18 days of age attached to the nipples of anesthetized dams, nor did naloxone (5 and 10 mg/kg) cause any systematic change in nipple attachment in 10- and 18-day-old rats that had been deprived of their dam for either 0, 8, or 24 hr. In a 3rd experiment, naloxone (5 mg/kg) did not significantly reduce milk intake by 9-, 12-, 15-, or 18-day-old rats from the nipple when milk letdown was induced by oxytocin. Moreover, naloxone (5 and 10 mg/kg) did not reduce milk intake in Day-10 rats that, while suckling, received milk via a cannula placed in the posterior portion of the tongue at the level of the intermolar eminence or in rats that obtained milk directly from their awake mother. In contrast, milk intake was significantly reduced by naltrexone (0.25-1.0 mg/kg) in Day-10 rats that obtained milk (a) by licking it off a saturated substrate or (b) through an indwelling cannula located in the anterior portion of the lower jaw. (Milk delivered at this placement is thought to engage feeding systems by its taste and texture.) In a final set of experiments in Day-10 rats, intake of milk delivered via anterior jaw cannulae was reduced by naloxone (5 and 10 mg/kg) in rats that were either isolated, in contact with an anesthetized dam, or attached to her nipples. On the basis of resistance to naloxone and naltrexone administration, these experiments demonstrate that behavioral influences of the tactile (and possibly olfactory) qualities of the mother are not mediated by opioid systems. Implications for understanding the means through which mothers can influence their young and the infantile mediators of these maternal influences are discussed.

Affect↗
PubMed1988

Immunologically mediated regression of a murine lymphoma after treatment with anti-L3T4 antibody. A consequence of removing L3T4+ suppressor T cells from a host generating predominantly Lyt-2+ T cell-mediated immunity.

This study shows that intravenous injection of 1 mg of anti-L3T4 mAb (GK1.5) into thymectomized mice bearing the syngeneic L5178Y lymphoma results, after a delay of 2-3 d, in complete regression of this tumor and in long-term host survival. A flow cytofluorometric examination of the spleen cells of mAb-treated mice revealed that antibody treatment resulted in the elimination of greater than 98% of L3T4+ T cells, but had no effect on the Lyt-2+ T cells subset. Tumor regression was immunologically mediated, because L5178Y lymphoma cells were shown to be L3T4-, and regression of the tumor failed to occur in mice that had been lethally irradiated before anti-L3T4 mAb was given. Tumor regression was mediated by tumor-sensitized Lyt2+ T cells, as evidenced by the finding that treatment of tumor-bearing mice with anti-Lyt-2 mAb alone, or in combination with anti-L3T4 mAb, resulted in enhancement of tumor growth and a significant decrease in host survival time. Moreover, the spleens of mice whose tumors were undergoing regression in response to anti-L3T4 mAb treatment contained Lyt-2+ T cells capable, on passive transfer, of causing regression of a tumor in recipient mice. These results can be interpreted as showing that removal of tumor-induced L3T4+ suppressor T cells results in the release of Lyt-2+ effector T cells from suppression, and consequently in the generation of enough Lyt-2+ T cell-mediated immunity to cause tumor regression. This can only be achieved, however, if immunity to the tumor is mediated exclusively by Lyt-2+ T cells, as is the case for the L5178Y lymphoma. In the case of the P815 mastocytoma, treatment with anti-L3T4 mAb was without a therapeutic effect, and this was in keeping with the finding that immunity to this tumor is mediated by L3T4+, as well by Lyt-2+ T cells.

Animals↗
PubMed1991

Actions and interactions of mediator systems and mediators in the pathogenesis of ARDS and multiorgan failure.

A great variety of mediators and mediator systems are involved in the disturbance of the microcirculation and vascular permeability following polytrauma and sepsis. The locally accentuated, organ related activation and the cooperation of several of these mediators and mediator systems over a longer period of time seem to be responsible for the development of an acute organ failure in terms of ARDS and MOF. Cytokines from macrophages seem to be the determining factors converting a primarily functional and reversible systemic vascular reaction into organ related morphological lesions. This pathogenetic complexity has to be considered in future concepts for therapy and prophylaxis with regard to the hierarchical rank of the mediators involved.

Arachidonic Acid↗
PubMed1991

Two possibly distinct prostaglandin E1 receptors in N1E-115 clone: one mediating inositol trisphosphate formation, cyclic GMP formation, and intracellular calcium mobilization and the other mediating cyclic AMP formation.

Prostaglandin E1 (PGE1)-mediated transmembrane signal control systems were investigated in intact murine neuroblastoma cells (clone N1E-115). PGE1 increased intracellular levels of total inositol phosphates (IP), cyclic GMP, cyclic AMP, and calcium ([Ca2+]i). PGE1 transiently increased inositol 1,4,5-trisphosphate formation, peaking at 20 s. There was more than a 10-fold difference between the ED50 for PGE1 at cyclic AMP formation (70 nM) and its ED50 values at IP accumulation (1 microM), cyclic GMP formation (2 microM), and [Ca2+]i increase (5 microM). PGE1-mediated IP accumulation, cyclic GMP formation, and [Ca2+]i increase depended on both the concentration of PGE1 and extracellular calcium ions. PGE1 had more potent intrinsic activity in cyclic AMP formation, IP accumulation, and cyclic GMP formation than did PGE2, PGF2 alpha, or PGD2. A protein kinase C activator, 4 beta-phorbol 12 beta-myristate 13 alpha-acetate, had opposite effects on PGE1-mediated IP release and cyclic GMP formation (inhibitory) and cyclic AMP formation (stimulatory). These data suggest that there may be subtypes of the PGE1 receptor in this clone: a high-affinity receptor mediating cyclic AMP formation, and a low-affinity receptor mediating IP accumulation, cyclic GMP formation, and intracellular calcium mobilization.

Animals↗
PubMed1987

Influence of beta-adrenoceptor-mediated relaxation on alpha-adrenoceptor-mediated contraction of rat pulmonary artery to adrenaline or noradrenaline.

Concentration-response (contraction) curves to either adrenaline or noradrenaline were obtained on isolated ring preparations of pulmonary artery from rats. In preparations from young rats the curve for adrenaline was bell-shaped, unless beta-adrenoceptors were blocked with propranolol (1 X 10(-6) M). The maximum contraction to adrenaline was less in the absence than in the presence of propranolol. In preparations from aged rats the adrenaline curve was no longer bell-shaped, even in the absence of propranolol. This reflected a decrease in the beta-adrenoceptor-mediated relaxant responses of preparations from aged rats, seen as a separation between the concentration-response (relaxation) curves to adrenaline on preparations (phenoxybenzamine-treated, KCl-contracted) from young and aged rats. In preparations from young rats the noradrenaline curve was not bell-shaped, but if the preparations were from young rats treated with thyroxine (T4), then a bell-shaped curve for noradrenaline was obtained, unless beta-adrenoceptors were blocked by propranolol. These data could be explained by an increase in beta-adrenoceptor-mediated relaxant responses of preparations from T4-treated rats, seen as a separation in the concentration-response (relaxation) curves to noradrenaline on preparations from control and T4-treated rats, respectively. Thus alpha-adrenoceptor-mediated contractile responses of rat pulmonary artery preparations, to adrenaline or noradrenaline, can be attenuated by activation of beta-adrenoceptors, mediating relaxation, and the extent of this attenuation changes under the influence of factors, such as ageing or T4-treatment, which modify beta-adrenoceptor-mediated relaxation in this blood vessel type.

Aging↗
PubMed1989

Inhibitory effects of beta-adrenergic stimulants on increased vascular permeability caused by passive cutaneous anaphylaxis, allergic mediators, and mediator releasers in rats.

The effects of isoproterenol, salbutamol, theophylline, and forskolin on IgE antibody-mediated homologous passive cutaneous anaphylaxis (PCA) and on skin reactions caused by allergic mediators and mediator releasers were investigated in rats. Isoproterenol and salbutamol dose-dependently inhibited the PCA and skin reactions caused by histamine, serotonin, and leukotriene C4 (LTC4), elicited at the same time in the same rat. These agents also dose-dependently inhibited the skin reactions caused by platelet-activating factor (PAF), leukotriene D4 (LTD4), compound 48/80 (48/80), and calcium ionophore A23187 (A23187). Propranolol overcame the inhibitory effect of isoproterenol on PCA and skin reactions in a dose-dependent manner. Theophylline and forskolin showed similar effects as the beta-adrenergic stimulants. These results indicate that beta-adrenergic stimulants inhibit the increased vascular permeability caused by allergic mediators, and suggest that this activity of beta-adrenergic stimulants might play an important role in their antiallergic actions. Inhibition of increased vascular permeability might be mediated via beta-receptors and may be related to the increase in intracellular cyclic AMP levels.

Adrenergic beta-Agonists↗