Biomedical subjects

R N Spengler

Publications and source records attributed to R N Spengler.

28 records · Page 2Linked to original sources

PubMed1994

Endogenous norepinephrine regulates tumor necrosis factor-alpha production from macrophages in vitro.

Evidence for the extraneuronal accumulation of norepinephrine has been demonstrated to occur in macrophage (M phi), yet the physiologic role of this system remains undefined. We have assessed the response of murine peritoneal M phi to adrenergic antagonists. We have also defined a physiologic role of a M phi-associated pool of the nonspecific adrenergic agonist norepinephrine. We investigated the constitutive involvement of alpha-adrenergic and beta-adrenergic receptors in LPS-induced TNF-alpha production. CFA-elicited M phis were incubated with LPS (1 microgram/ml) in the presence or absence of adrenergic agonists and/or antagonists. Although stimulation of alpha-adrenergic receptors increased TNF production and gene expression, beta-adrenergic receptors decreased it. Interestingly, when adrenergic antagonists along with LPS alone were added to M phi, they generated the response opposite to that produced by their suitable agonist, suggesting a role for endogenous norepinephrine in M phi. Thus, although alpha 2-adrenergic antagonists attenuated TNF production, beta-adrenergic antagonists augmented TNF expression in a concentration-dependent manner. Norepinephrine and epinephrine were found in M phi as determined by HPLC and LPS stimulation induced a significant decrease in their content. M phis were also incubated with LPS or medium only, washed, and then challenged 12 h later with LPS. When given a second LPS stimulation, M phis were found to have an increased response to alpha 2-adrenergic agonists and decreased response to alpha 2-adrenergic antagonists. Therefore, M phi-associated norepinephrine appears to regulate LPS-induced TNF production in an autocrine fashion.

Animals↗

PubMed1990

Stimulation of alpha-adrenergic receptor augments the production of macrophage-derived tumor necrosis factor.

Accumulating evidence supports the hypothesis that neuroendocrine hormones may participate in immunologic processes. In our study we have determined that UK-14304 (UK) and norepinephrine (NE), both alpha 2-adrenergic agonists, can augment LPS-stimulated TNF from elicited macrophages (MO). The increase in TNF production was concentration dependent with an EC50 for UK and NE of 8.1 +/- 2.6 and 0.52 +/- 0.17 nM, respectively. The concentration-effect curve for UK and NE was shifted to the right by the alpha 2-antagonist yohimbine (10(-6) M), with new EC50 of 49.7 +/- 12.2 (p less than 0.001) nM and 10.3 +/- 22 nM. The augmenting effect of UK on MO TNF production was assessed over a 7 log LPS response curve. Within a single population of MO 10 nM UK shifted the LPS-induced TNF curve eightfold to the left with the greatest increase in TNF production at lower LPS concentrations. At the transcriptional level, Northern blot analysis demonstrated that UK increased LPS-induced TNF mRNA accumulation. This augmentation in TNF mRNA accumulation was blocked by yohimbine. The presence of a MO alpha-adrenergic receptor was established by demonstrating binding of the alpha 2-adrenergic antagonist 3H-yohimbine to membranes prepared from MO. This binding was rapid, saturable, reversible, and blocked by UK, clonidine, and phentolamine. These investigations support the role of alpha 2 adrenergic agonists as immunostaining compounds that may regulate cytokine production during an inflammatory response.

Animals↗

PubMed1989

Modulation of tumor necrosis factor-alpha gene expression. Desensitization of prostaglandin E2-induced suppression.

PGE2, an immune mediator, is an inhibitor of LPS-stimulated TNF production and gene transcription. In the present study we determined whether pretreatment with PGE2 could desensitize the suppressive function of PGE2 for the production of macrophage (MO)-derived TNF. CFA-elicited MO were incubated with PGE2 or medium only, washed, and then challenged with graded doses of LPS (0.001 to 1000 ng/ml) in the presence or absence of new PGE2. The concomitant addition of PGE2 with LPS shifted the LPS concentration-effect curve 16-fold to the right with a 52% decrease in the maximum LPS response, while MO pretreated with PGE2, washed, and incubated with LPS plus new PGE2 were desensitized to TNF regulation. These latter conditions resulted in a complete loss of the ability of PGE2 to inhibit MO TNF production as demonstrated by no significant change in the EC50 of LPS. In addition, the PGE2 concentration effect curve was shifted to the right after pretreatment of MO, suggesting a desensitized PGE2 receptor system. At the transcriptional level, pretreatment of MO with PGE2 attenuated the ability of new PGE2 to inhibit LPS-dependent TNF mRNA expression. Further studies demonstrated that, although the concomitant addition of the cyclooxygenase inhibitor indomethacin plus LPS could increase TNF production, MO pretreated with indomethacin, washed, and then challenged with LPS demonstrated an inhibition of TNF expression. MO pretreated with indomethacin also demonstrated an increased sensitivity for exogenous PGE2-induced suppression of TNF mRNA and bioactivity. These investigations further support the role of PGE2 as an immunomodulating compound that may effectively regulate the local concentration of specific monokines needed to maintain an inflammatory lesion.

Adjuvants, Immunologic↗

PubMed1989

Changes in alpha 2-adrenoceptor number and function in brains of morphine-dependent rats.

The effects of long-term treatment of rats with morphine sulfate were assessed upon the specific binding of [3H]clonidine to alpha 2-adrenoceptors on neural membranes isolated from various brain areas and upon the function of presynaptic alpha 2-adrenoceptors during field stimulation of hippocampal slices. Rats were injected with morphine every 8 h for 14 days with doses which started at 10 mg/kg per injection i.p., and which increased every 3 days to a final dose of 100 mg/kg per injection on the last 2 days. At 8 and 32 h after the last injection the Bmax for [3H]clonidine binding to neural membranes from various brain areas was significantly decreased. At the same times, the fractional release of [3H]noradrenaline during field stimulation of hippocampal slices was increased and the sensitivity of the hippocampal slice to clonidine was reduced which indicated the development of a functional subsensitivity of the presynaptic alpha 2-adrenoceptor. These changes in receptor function persisted at 72 h after the last morphine injection although at this time there were marked increases over control values in [3H]clonidine binding to membranes from all rat brain areas except the caudate nucleus. These findings suggest that changes in alpha 2-adrenoceptor number and function which develop during long-term morphine administration might play an important role in opiate dependence.

Animals↗

PubMed1989

Dynamics of dibutyryl cyclic AMP- and prostaglandin E2-mediated suppression of lipopolysaccharide-induced tumor necrosis factor alpha gene expression.

The regulation of lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF) production by prostaglandin E2 (PGE2), forskolin, and dibutyryl cyclic AMP (cAMP) was examined at the cellular and molecular levels. The above three agents could suppress LPS (100 ng/ml)-stimulated TNF production by immunologically activated murine macrophages (M phi s) in a dose-dependent manner. The concomitant addition of PGE2, dibutyryl cAMP, or forskolin to LPS-challenged M phi s resulted in 50% inhibition of TNF production at 10(-7), 3 X 10(-6), and 3 X 10(-5) M, respectively. Interestingly, delaying the addition of PGE2 or dibutyryl cAMP by 1.5 h post-LPS stimulation was also effective in suppressing the production of TNF bioactivity, but only dibutyryl cAMP was effective when its addition was delayed by 3 h. Northern (RNA) blot analysis of mRNA isolated from LPS-challenged M phi s treated with PGE2 or dibutyryl cAMP corroborated the bioactivity data. The delayed addition of PGE2 or dibutyryl cAMP by 1.5 h post-LPS stimulation resulted in a suppression of TNF mRNA accumulation by 50 to 70%. These data support the concept that LPS is a potent stimulus for M phi-derived TNF production and that this mediator is a very proximal signal in LPS-mediated disease states. Thus, therapeutic approaches that target the suppression of TNF in LPS-dependent disease states may be limited by the rapid expression of this mediator.

Adjuvants, Immunologic↗

PubMed1989

Interleukin-2-induced tumor necrosis factor-alpha (TNF-alpha) gene expression in human alveolar macrophages and blood monocytes.

Recent investigations have demonstrated interleukin-2 receptor (IL-2R) expression on both human alveolar macrophages (AM phi) and blood monocytes (PBM), but the function of these receptors has not been fully elucidated. In this study, we demonstrate that human AM phi, as well as PBM, can be induced to express biologically active TNF-alpha after challenge with interleukin-2 (IL-2). Furthermore, we examined the expression of TNF-alpha at the mRNA level via Northern blot and in situ hybridization analysis. Normal AM phi, obtained by bronchoalveolar lavage, and PBM were stimulated with either IL-2 (2,000 U/ml) or lipopolysaccharide (LPS) (10 micrograms/ml) for 18 h. Specificity was demonstrated by neutralizing TNF-alpha activity with a polyclonal rabbit anti-human TNF-alpha antibody. PBM TNF-alpha biologic activity from 11 subjects challenged with either IL-2 or LPS was 19 +/- 6 and 85 +/- 15 U/ml/10(6) cells, respectively, which represented 5-fold and 21-fold increases over control values. AM phi TNF-alpha biologic activity from nine subjects was 110 +/- 28 (IL-2-mediated) and 304 +/- 69 (LPS-mediated) U/ml/10(6) cells, which represented 2- and 6-fold increases over controls. AM phi exhibited statistically greater (p less than 0.05) TNF production in response to both IL-2 and LPS as compared to PBM. IL-2 challenge resulted in an induction of TNF-alpha mRNA accumulation, as demonstrated by Northern blot and in situ hybridization analyses. TNF-alpha mRNA was quantitated by laser densitometry for Northern blots or by counting the number of silver grains/mononuclear phagocytic cell in the in situ hybridization analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Cellular and molecular regulation of tumor necrosis factor-alpha production by pentoxifylline.

Tumor necrosis factor-alpha (TNF), a mononuclear phagocyte (MO)-derived peptide, is increasingly being recognized for its pleomorphic immunologic effects. A number of investigations have demonstrated that lipopolysaccharide (LPS) can induce TNF synthesis, yet mechanisms that regulate TNF expression at the cellular and molecular levels have not been fully elucidated. In this study, we present data demonstrating pentoxifylline, a methylxanthine, is efficacious in suppressing LPS-induced MO-derived TNF at the level of both TNF mRNA accumulation and TNF supernatant bioactivity. Pentoxifylline, at a dose of 1 x 10(-5)M, suppressed the production of both biologically active TNF and TNF mRNA expression by more than 50%. Furthermore, additional methylxanthines and dibutyryl cAMP have similar effects on TNF expression. These data support the mechanism for this suppressive effect is via the generation of intracellular cAMP.

1-Methyl-3-isobutylxanthine↗

PubMed1986

Presynaptic alpha 2 adrenoreceptor function in dependent rats before and after morphine withdrawal.

Changes in the number of alpha 2 adrenoreceptors in the hippocampus, as measured by the specific binding of 3H-clonidine, were compared to changes in presynaptic alpha 2 adrenoreceptor function in electrically stimulated hippocampal slices. In dependent rats the specific binding of 3H-clonidine was reduced significantly. At 32 h after withdrawal binding began to return toward normal values, and at 72 h after withdrawal was significantly greater than that seen in saline-treated rats. In hippocampal slice experiments sensitivity to clonidine was significantly decreased in morphine-dependent animals and returned toward normal values after withdrawal. At 72 h after withdrawal, the sensitivity to clonidine of the presynaptic alpha 2 adrenoreceptor remained depressed although receptor density as measured in the binding studies was increased. This study suggests that the changes in the function of presynaptic alpha 2 adrenoreceptors might be important in the development of dependence upon morphine.

Animals↗

PubMed1981

Facioliasis: is the anemia caused by hematophagia?

In fascioliasis, anemia is a well-recognized symptom but its etiology is controversial. There is disagreement on whether hematophagia occurs, and if it does, whether it is sufficient to produce the anemic symptoms observed. Another opinion is that a toxic substance emanating from the fluke causes the anemia. In the present study the anemia was investigated in rats. Hematological parameters measured over the course of infection showed significant decreases in erythrocyte counts and hemoglobin after the flukes entered the bile duct. Significant increases were observed in reticulocyte counts and mean corpuscular volume upon entry of flukes into the bile duct. Urobilinogen levels increased in early stages of infection but returned to near normal levels after the worms reached the bile duct. To determine whether Fasciola hepatica could produce an anemia in rats when hematophagia was prevented, uninfected rats were peritoneally implanted with worms in fine-mesh sacks which prevented worms from feeding on blood. Hematological parameters indicated that the anemia produced in rats with implanted worms was very similar to that produced by mature, per os infections. This study indicates that the anemia is caused by a substance released by the worms and supports previous work suggesting that proline released from the worms may be inducing the anemia.

Anemia↗

PubMed1979

Fascioliasis: similarities of the anemia in rats to that produced by infused proline.

Fasciola hepatica releases large amounts of proline into the bile of its host. Significant increases in the levels of other amino acids in the bile also occur. The present investigation examines whether proline and these other amino acids may play a role in inducing the anemia that frequently accompanies fascioliasis. In experiments, rats were infused intra-abdominally for 2 weeks with 1 of 3 solutions: 20.0 mM proline in saline, a mixture of 8 amino acids (excluding proline) each at 2.0 mM in saline, or saline only. At the end of the experiments 2 cc of blood was removed from each rat, via cardiac puncture. The heparinized blood was used to count erythrocytes and reticulocytes, and to measure hematocrit and mean corpuscular volume (MCV). Analysis of variance disclosed highly significant differences in erythrocyte counts, MCV, and reticulocyte counts among the 5 groups. A Student-Newman-Keuls test indicated that the Proline and Infected groups were not different from each other (except for MCV, where proline's effect was more severe) and that both groups differed significantly from the Amino Acid group, the Saline group, and the Control group. Hence, it appears that infused proline can cause an anemia similar to that induced by Fasciola.

Amino Acids↗