Search PubMed⌕ Search

Biomedical subjects

G Lonnemann

Publications and source records attributed to G Lonnemann.

At least 55 records · Page 3Linked to original sources
PubMed1992

Permeability of dialyzer membranes to TNF alpha-inducing substances derived from water bacteria.

Pro-inflammatory cytokine-inducing substances derived from cultured E. coli have previously been shown to pass across low-flux regenerated cellulosic dialyzer membranes. In the present study, a sterile filtrate of Pseudomonas maltophilia grown from standard bicarbonate dialysis fluid was used to test the permeability of various dialyzer membranes (regenerated cellulose, cellulose triacetate, polyacrylonitrile, polysulfone and polyamide) to TNF alpha-inducing bacterial substances. Pyrogen-free tissue culture medium (MEM) was recirculated for 60 minutes in the dialysate compartment of a closed-loop dialysis system, then P. maltophilia filtrate was added and recirculation was continued for a further hour. Samples from the dialysate (MEM) and the blood side (containing 10% human plasma in MEM) were incubated with donor mononuclear cells (MNC) for 18 hours and TNF alpha release was measured in MNC supernatants by radioimmunoassay. Five minutes after the addition of P. maltophilia filtrate, mean TNF alpha-inducing activity in the dialysate increased from (mean +/- SEM) 0.10 +/- 0.02 to 18.2 +2- 1.5 (ng/2.5 x 10(6) MNC/18 hr). TNF alpha-inducing activity in the blood side increased with regenerated cellulose from 0.10 +/- 0.01 to 4.57 +/- 1.55 (N = 8; P less than 0.001); with cellulose triacetate from 0.20 +/- 0.05 to 0.44 +/- 0.10 (N = 5; P less than 0.05), and with polyacrylonitrile from 0.10 +/- 0.02 to 1.16 +/- 0.45 (N = 5; P less than 0.03). No increased TNF alpha-inducing activity was observed in the blood side of polysulfone (N = 5) or polyamide dialyzers (N = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Complement C5a↗
PubMed1992

In vitro production of interleukin-1 from blood mononuclear cells of patients on chronic hemodialysis therapy.

A monocyte defect is thought to be involved in the impaired immune response in patients on regular hemodialysis therapy. As an indicator of cell function, we studied in vitro IL-1 beta production of mononuclear cells from hemodialysis patients in comparison to normal controls. Mononuclear cells were stimulated with endotoxin or Staphylococcus epidermidis in parallel with control incubations in tissue culture medium alone. Spontaneous as well as stimulated total IL-1 beta production (cell-associated plus extracellular) did not differ significantly in cells obtained from patients compared to those from normal controls. However, the relative amounts of IL-1 beta released into the cell supernatants were significantly reduced in mononuclear cells from hemodialysis patients when stimulated with endotoxin but not with Staphylococcus epidermidis. These data indicate a stimulus-dependent defect in the mechanism of IL-1 beta release. As IL-1 is necessary for T-cell activation this alteration in mononuclear cell function may play a role in the impaired cellular immunity observed in patients on chronic hemodialysis therapy.

Culture Media↗
PubMed1991

Regulation of TNF-alpha, IL-1 and IL-6 synthesis in differentiating human monoblastoid leukemic U937 cells.

The human monoblastoid tumor cell line U937 was induced to differentiate along the monocyte/macrophage lineage by treatment with 5 x 10(-9) M 12-O-tetradecanoyl phorbol-13-acetate (TPA). Between 2 h and 4 h following TPA-treatment U937 cells started to release significant amounts of TNF-alpha which remained detectable until 8-10 days. A significant IL-1 beta release was measured 24 h-48 h post stimulation and increased levels of IL-1 beta persisted until 20-22 days of culture. In contrast no release of either IL-1 alpha or IL-6 could be detected with 5 x 10(-9) M TPA during the whole time course of the experiments. The sequential induction of TNF-alpha and IL-1 beta appeared to be independently regulated since TNF-alpha release was not required for the onset of IL-1 beta production. Northern-blot analysis confirmed the sequential induction and the long term expression of TNF-alpha and IL-1 beta mRNAs. Western-blot analysis predominantly showed a high molecular weight IL-1 beta protein of about 35 kD. Further investigations on the regulation of cytokine production and release by TPA-differentiated U937 cells revealed that TNF-alpha and IL-1 beta synthesis was not influenced by exogenously added rhTNF-alpha or PGE2, whereas rh gamma-IFN specifically enhanced the IL-1 beta production. Thus, the regulation and intracellular processing of cytokines generated by differentiating U937 cells shows some differences when compared to mature monocytes/macrophages which may be related to the tumorigenic origin of U937 cells or to an incomplete differentiation.

Blotting, Northern↗
PubMed1990

Transcription, not synthesis, of interleukin-1 and tumor necrosis factor by complement.

Stimulation of interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF alpha) production was studied during in vitro hemodialysis (HD) of whole blood using cuprammonium (Cup) or polysulfone (PS) dialyzers. In the absence of LPS, circulation of whole blood for two hours through Cup or PS dialyzers was not sufficient to induce production of IL-1 beta or TNF alpha in peripheral blood mononuclear cells (PBMC) during subsequent 24 hour culture. However, compared to freshly isolated cells, post-HD PBMC were primed to produce more IL-1 beta and TNF alpha when subsequently stimulated with LPS. Despite the lack of spontaneous monokine synthesis after HD, we observed transcription of mRNA coding for IL-1 beta and TNF alpha after two hours of LPS-free HD. When compared to levels of mRNA induced by 5 ng/ml LPS (100%), Cup induced 27 +/- 6% whereas PS did not induce detectable transcription of IL-1 beta. In the case of TNF alpha mRNA, Cup induced 26 +/- 8% and PS 13 +/- 3%. Recombinant C5a induced mRNA for IL-1 beta in PBMC without detectable IL-1 beta protein synthesis. We conclude that transcription of mRNA for IL-1 beta and TNF alpha during HD is primarily caused by complement activation by Cup, but that LPS or other factors are required for translation of IL-1 beta and TNF alpha mRNA transcribed during HD.

Blotting, Northern↗
PubMed1990

Circulating interleukin-1 and tumor necrosis factor in septic shock and experimental endotoxin fever.

Interleukins (IL) -1 beta and -1 alpha and tumor necrosis factor (TNF-alpha) were measured by radioimmunoassay in plasma samples from 44 healthy individuals, 15 patients in septic shock, and 6 volunteers infused with endotoxin. Plasma IL-1 alpha levels were low (40 pg/ml) or undetectable in all situations. In 67% of the healthy subjects, plasma IL-1 beta levels were less than 70 pg/ml. Septic patients had higher plasma IL-1 beta levels (120 +/- 17 pg/ml, P = .001); those of surviving patients were higher than those of patients who died (P = .05). Plasma TNF-alpha concentrations in septic individuals were elevated (119 +/- 30 pg/ml) and correlated with severity of illness (r = .73, P = .003), but no correlation was observed between plasma IL-1 beta and TNF-alpha concentrations in individual samples. Infusion of endotoxin caused a twofold elevation of IL-1 beta, from a baseline of 35 +/- 5 pg/ml to a maximum of 69 +/- 27 pg/ml at 180 min (P less than .05). Peak TNF-alpha levels after endotoxin infusion were 15 times higher than IL-1 beta levels, were attained more rapidly (90 min), and as with the septic patients, did not correlate with IL-1 beta levels. These data support the concept that plasma IL-1 beta and TNF-alpha concentrations are regulated independently and are associated with different clinical outcomes.

Adolescent↗
PubMed1990

Hemodialysis-associated induction of cytokines.

The interleukin hypothesis relates chronic pathology in long-term end-stage renal disease (ESRD) patients to repeated stimulation of mononuclear cell cytokine production during hemodialysis. In vitro experiments demonstrated different possible mechanisms involved in hemodialysis-associated cytokine induction: adherence of mononuclear cells to the dialyzer membrane; complement activation, and the passage of cytokine-inducing bacterial fragments from contaminated dialysate through the dialyzer membrane into the blood. Studies investigating mononuclear cells from ESRD patients ex vivo suggest that these cells become activated during hemodialysis with complement-activating membranes and that the type of dialyzer membrane may influence mononuclear cell cytokine production in response to endotoxin. According to biological assays, plasma levels of interleukin-1 but not interleukin-6 activity seem to be elevated in ESRD patients compared to normal subjects and may increase further during treatment depending on the choice of the dialyzer membrane. However, to date, partly due to insufficient assay sensitivity and circulating inhibitors, measurements of interleukin-1, interleukin-6 and tumor necrosis factor in plasma by specific immunoassays could not finally prove elevated plasma cytokine levels in ESRD patients. Since circulating mononuclear cells are a major source of cytokines, studying the activation of these cells ex vivo seems to be the best approach to study hemodialysis-associated cytokine induction.

Cytokines↗
PubMed1989

The effect of dietary supplementation with n-3 polyunsaturated fatty acids on the synthesis of interleukin-1 and tumor necrosis factor by mononuclear cells.

We examined whether the synthesis of interleukin-1 or tumor necrosis factor, two cytokines with potent inflammatory activities, is influenced by dietary supplementation with n-3 fatty acids. Nine healthy volunteers added 18 g of fish-oil concentrate per day to their normal Western diet for six weeks. We used a radioimmunoassay to measure interleukin-1 (IL-1 beta and IL-1 alpha) and tumor necrosis factor produced in vitro by stimulated peripheral-blood mononuclear cells. With endotoxin as a stimulus, the synthesis of IL-1 beta was suppressed from 7.4 +/- 0.9 ng per milliliter at base line to 4.2 +/- 0.5 ng per milliliter after six weeks of supplementation (43 percent decrease; P = 0.048). Ten weeks after the end of n-3 supplementation, we observed a further decrease to 2.9 +/- 0.5 ng per milliliter (61 percent decrease; P = 0.005). The production of IL-1 alpha and tumor necrosis factor responded in a similar manner. Twenty weeks after the end of supplementation, the production of IL-1 beta, IL-1 alpha, and tumor necrosis factor had returned to the presupplement level. The decreased production of interleukin-1 and tumor necrosis factor was accompanied by a decreased ratio of arachidonic acid to eicosapentaenoic acid in the membrane phospholipids of mononuclear cells. We conclude that the synthesis of IL-1 beta, IL-1 alpha, and tumor necrosis factor can be suppressed by dietary supplementation with long-chain n-3 fatty acids. The reported antiinflammatory effect of these n-3 fatty acids may be mediated in part by their inhibitory effect on the production of interleukin-1 and tumor necrosis factor.

Adult↗
PubMed1989

Differences in the synthesis and kinetics of release of interleukin 1 alpha, interleukin 1 beta and tumor necrosis factor from human mononuclear cells.

Cell-associated and secreted interleukin 1 alpha (IL 1 alpha), IL 1 beta and tumor necrosis factor alpha (TNF-alpha), produced by human mononuclear cells (MNC) in vitro in response to lipopolysaccharide, were measured by radioimmunoassay. After 18 h of incubation, total production of IL 1 alpha in medium containing 1% heat-inactivated serum was two-to-three times higher than IL 1 beta. However, in the presence of 1% serum and 5% fresh plasma, IL 1 alpha and IL 1 beta were produced in similar amounts. Independent of the culture conditions, 90% of the IL 1 alpha remained cell associated whereas 80% of IL 1 beta was extracellular. The kinetics of production and release of IL 1 alpha, beta and TNF-alpha were also studied. IL 1 alpha and TNF-alpha reached maximal levels within 6 h of stimulation, whereas IL 1 beta reached maximal levels between 12 and 16 h. IL 1 alpha remained primarily cell associated (80%) for the first 24 h. After 48 h, extracellular IL 1 alpha exceeded cell-associated levels. IL 1 beta was primarily secreted (80%), appearing in the extracellular fluid within 6 h. TNF-alpha appeared in the extracellular fluid within 1 h of incubation, with less than 10% cell associated at any time during the 48 h of incubation. Although the three cytokines share many biological activities, this study provides evidence that MNC IL 1 alpha is predominantly a cell-associated cytokine acting on a cell-cell basis, whereas IL 1 beta and TNF-alpha are secreted as paracrine mediators.

Cells, Cultured↗
PubMed1989

In vitro production of IL 1 beta, IL 1 alpha, TNF and IL2 in healthy subjects: distribution, effect of cyclooxygenase inhibition and evidence of independent gene regulation.

Numerous studies have reported altered in vitro cytokine production in various diseases. In the present study we used specific immunoassays to quantitate production of interleukin 1 beta (IL 1 beta), IL 1 alpha, tumor necrosis factor (TNF) and IL 2 from human peripheral blood mononuclear cells (PBMC). The distribution of cell-associated and secreted cytokines was studied in PBMC of 21 individuals; in response to lipopolysaccharide (LPS) the proportion of cell-associated IL 1 beta ranged from 13% to 56%, for IL 1 alpha 29% to 98%, and for TNF 2% to 17%. In a larger cohort of 32 subjects, the total amount of immunoreactive cytokines produced in response to LPS or phytohemagglutinin was normally distributed within the study group. Mean production of IL 1 alpha in response to LPS was 10.1 ng/ml and exceeded production of IL 1 beta (5.6 ng/ml) and TNF (2.2 ng/ml). The distribution pattern was characterized by high intersubject variability extending over two orders of magnitude and the presence of high and low "producers". Production of IL 1 alpha and IL 1 beta correlated (R = 0.69). In contrast, production of IL 1 beta did not correlate with production of TNF or IL 2. Indomethacin present during stimulation of PBMC increased the amount of IL 1 beta produced and showed a high correlation (R = 0.83) compared to cultures without indomethacin. Thus, low production of IL 1 beta in certain subjects appears not to be due to inhibitable levels of cyclooxygenase products. In a retrospective study, PBMC from 12 subjects who had taken oral cyclooxygenase inhibitors during the preceding 7 days produced 43% more IL 1 beta than subjects who did not take these drugs (p less than 0.05). These studies demonstrate that the amount of cytokine synthesized by PBMC (a) is regulated independently for IL 1, TNF and IL 2; (b) correlates for IL 1 beta and IL 1 alpha; (c) is intrinsic for low and high "producers", and (d) production of IL 1 beta increases with the use of oral cyclooxygenase inhibitors.

Adult↗
PubMed1989

Erythropoietin in polycystic kidneys.

Erythropoietin (EPO) formation in kidneys of 18 patients with autosomal dominant polycystic kidney disease (ADPKD) was investigated. In 12 patients on hemodialysis and in 6 patients with preterminal renal failure serum, EPO was 29 +/- 7 and 16 +/- 1.5 mU/ml and hemoglobin concentrations were 11.0 +/- 0.6 and 12.7 +/- 1.2 g/dl, respectively. Cyst fluid from a total of 357 renal cysts was obtained by either in vivo aspiration or immediately after nephrectomy. The cysts contained variable concentrations of bioactive EPO from undectable values up to 3.2 U/ml. A pronounced enrichment of EPO was observed in cysts with sodium concentrations greater than 100 mmol/liter, suggesting an association with proximal tubular malformations. The EPO concentrations in the cysts were neither correlated with the protein concentration nor with the oxygen pressure of the cyst fluid. Using a cDNA probe for human EPO, mRNA for EPO was localized in stroma cells of the cyst walls by an in situ hybridization technique. Our findings suggest that single interstitial cells juxtaposed to proximal tubular cysts may produce EPO independent of the oxygen pressure inside the cysts, which ameliorates the anemia during end-stage polycystic kidney disease.

Animals↗
PubMed1988

C5a stimulates secretion of tumor necrosis factor from human mononuclear cells in vitro. Comparison with secretion of interleukin 1 beta and interleukin 1 alpha.

We have demonstrated that purified C5a is a potent stimulus to human PBMC secretion of TNF-alpha, IL-1 beta, and IL-1 alpha, which proceeds in a dose-dependent fashion. At a given concentration of C5a, TNF-alpha and IL-1 beta secretion did not differ significantly; both were secreted in significantly greater quantity than IL-1 alpha. Clinical conditions such as Gram-positive and Gram-negative bacterial infections, trauma, and immune complex diseases activate complement. Through the mediation of TNF and IL-1 secreted in response to C5a, these diverse disorders can share common features of fever, coagulopathy, acute phase protein production, and disordered metabolism.

Complement C5↗
PubMed1988

Concentrations of immunoreactive human tumor necrosis factor alpha produced by human mononuclear cells in vitro.

The concentrations of tumor necrosis factor (TNF) produced by human peripheral blood mononuclear cells (MNC) were measured using a radioimmunoassay (RIA) for human TNF. This was developed using a rabbit antiserum against human recombinant TNF (Hu rTNF), and Hu rTNF labeled with Na125I by a modification of the chloramine T method. This RIA does not detect human lymphotoxin, interleukin-1 alpha or beta, interleukin 2, interleukin 6, interferon alpha or gamma, granulocyte-macrophage-colony stimulating factor, and C5a des arg. A good correlation (r = 0.89) was found between the RIA and the cytolytic bioassay for TNF. The sensitivity of the RIA is between 3 and 78 pg/ml (median 11 pg/ml). The mean concentration of TNF in 24-h culture supernatants of human MNC exposed to different concentrations of lipopolysaccharide (LPS) was found to increase in dose-dependent fashion and then level off between 50 and 100 ng/ml. The concentrations of IL-1 beta and alpha detected by specific RIAs in these supernatants were between 0.2 and 19 ng/ml and 0.04 and 1 ng/ml, respectively. The amount of TNF produced by human MNC in vitro was determined in a cohort of 50 normal volunteers. Without exogenous stimuli, TNF concentrations were almost always below the detection limit; with 0.5 ng/ml LPS, the median concentration of TNF was 2 ng/ml, and with PHA the median was 3.8 ng/ml. In cultures performed in the presence of indomethacin significantly (p less than 0.005) more TNF was produced. Using this RIA, we could detect TNF in the circulation of mice injected with Hu rTNF. When plasma samples of patients with febrile illnesses were added directly to the RIA, TNF was not detectable, with the exception of patients with malaria. These studies demonstrate the range and sensitivity of LPS-induced and mitogen-induced production of immunoreactive TNF by human MNC in vitro without interference of similar cytokines in bioassays.

Animals↗