Transforming growth factor beta-3 crystals as reservoirs for slow release of active TGF-beta3

Transforming growth factor betas (TGF-betas) play critical roles in many diseased states and injury repair processes. Exogenous delivery of TGF-beta may thus have therapeutic applications. Here, crystals of TGF-beta3 (TGF-beta3) are being evaluated as protected reservoirs for sustained local release. A sensitive Mv1Lu cell growth inhibition assay established that in vitro, active TGF-beta3 can be delivered from physically stable crystals. Non-sink release experiments revealed that crystal solubility at pH 7.4 was higher in cell culture medium (2.7+/-0.1 microg/ml) than in saline buffers (approximately 1-1.5 microg/ml, P<0.05). Addition of serum induced a five-fold delay in equilibration of soluble-crystal TGF-beta3. Semi-sink experiments cumulated in higher TGF-beta3 release than under non-sink conditions; the observed steady states correlated with crystal solubility and the frequency of buffer exchange. Release of TGF-beta3 from crystals was also strongly dependent on solubility changes as affected by pH. At neutral pH the solubilities were the lowest, and increased with both higher and lower pH. The results indicate that TGF-beta3 crystals may have promising features for local pH-triggered sustained-release applications.

Anti-inflammatory effects of CGP 47969A, a novel inhibitor of proinflammatory cytokine synthesis, in rabbit immune colitis

BACKGROUND & AIMS

Proinflammatory cytokines such as interleukin (IL) 1, IL-8, and tumor necrosis factor (TNF) have been implicated as primary mediators of intestinal inflammation. The aim of the present study was to determine the effects of a novel cytokine antagonist (CGP 47969A) in a rabbit model of acute colitis.

METHODS

Colitis was induced using the formalin-immune complex technique. Animals were pretreated intrarectally with CGP 47969A (30, 10, or 3 mg/kg), hydrocortisone (0.8 mg/kg), or vehicle (4 mL saline) 2 hours before the induction of colitis and twice daily thereafter until death 48 hours after the induction of colitis. The severity of inflammation of colonic tissue was assessed using histological analysis and myeloperoxidase activity assay, and IL-1 alpha, IL-8, TNF-alpha, and IL-1 receptor antagonist levels were determined.

RESULTS

Compared with vehicle, CGP 47969A (10 mg/kg) significantly reduced the acute inflammatory index by 58%, edema by 67%, necrosis by 99%, and myeloperoxidase activity by 49% (all P < 0.02) with efficacy similar to that of steroids. These effects were associated with a significant inhibition of colonic IL-1 alpha and IL-8 by 56% and 90%, respectively (p < 0.01).

CONCLUSIONS

Administration of CGP 47969A reduces inflammation and tissue damage in rabbit immune complex colitis through mechanisms involving the inhibition of mucosal proinflammatory cytokines.

Differential effects of prednisolone and indomethacin on zymosan-induced inflammation in a modified murine tissue-chamber model

A tissue-chamber model of inflammation in mice has been modified and used to investigate the kinetics of zymosan-induced inflammatory mediators such as tumour necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta) and prostaglandin E2 (PGE2). In addition, the influx of polymorphonuclear leukocytes (PMN) into the chamber fluid and the granuloma surrounding the chamber was measured by myeloperoxidase (MPO) activity using a new microtitre plate assay. TNF alpha and IL-1 beta reached a peak concentrations at 3 and 6 h respectively after zymosan injection. Intermediate high concentrations of IL-1 beta were observed until the end of the experiment at 72 h, but TNF alpha concentrations decreased from 24 h to biologically insignificant values. In contrast, exudate PGE2 and MPO activity increased up to 24 h after zymosan injection and remained high until 72 h. At 6 h after zymosan challenge, oral pre-treatment with prednisolone (3 to 30 mg/kg) dose-dependently reduced TNF alpha, IL-1 beta and PGE2 concentrations while indomethacin (0.3 to 3 mg/kg) significantly attenuated PGE2, slightly enhanced TNF alpha and had no effect on IL-1 beta concentrations in the exudate. Both drugs had similar potencies against exudate and tissue MPO activities. Prednisolone inhibited IL-1 beta at 72 h post-zymosan. Indomethacin was more potent than prednisolone against PGE2 (ID50 of< 0.3 versus 0.6 mg/kg). The data obtained confirm the usefulness and reliability of this model in evaluating the effects of anti-inflammatory agents on inflammatory mediators induced by zymosan.

Hydrogen peroxide as a potent bacteriostatic antibiotic: implications for host defense

Host defense against bacterial pathogens in higher organisms is mediated in part by the generation of reactive oxygen species (ROS) by PMN. In this study, we determined the following effects of exposure of constant concentrations of H2O2 on E. coli in a culture continuously monitored for H2O2 concentration, numbers, and viabilities of cells: (1) E. coli growth rates monitored for 1 h were profoundly affected by concentrations of H2O2, between 25-50 microM. (2) Complete bacteriostasis was observed at 100 microM. (3) Significant cell killing was not observed until the concentration of H2O2 was greater than 500 microM. (4) Bacteriostatic (25-50 microM) concentrations of H2O2 appeared not to be toxic to human skin fibroblasts for a 2-h exposure. (4) Bacteriostasis by H2O2 could not be explained by metabolic inhibition, because intracellular ATP levels were not compromised at bacteriostatic doses of H2O2. (5) Measurements of H2O2 concentrations in subcutaneous abscess fluid infected with both E. coli and S. aureus indicated prevailing concentrations of the oxidant consistent with a proposed role of H2O2 in host defense.

CGP 47969A: a novel inhibitor of the synthesis of inflammatory cytokines

CGP 47969A is a novel piperazine derivative that inhibits the synthesis of inflammatory cytokines, such as interleukin-1 alpha (IL-1), IL-1 beta and tumor necrosis factor alpha (TNF), in human monocytes stimulated with lipopolysaccharide (LPS), zymosan or IL-1 itself. IC50 values are in the range of 0.3-5 mumol/l. CGP 47969A does not inhibit total protein or RNA synthesis indicating selectivity for cytokine inhibition. CGP 47969A exerts its inhibitory effect at a post-transcriptional level, most probably by reducing translational efficiency of IL-beta mRNA, as steady-state levels of IL-1 beta mRNA are not inhibited while the primary translation product, the 31 kD IL-1 beta precursor molecule, is dose-dependently inhibited by CGP 47969A. The compound is devoid of cyclooxygenase and phospholipase A2 inhibitory activity but efficiently inhibits the generation of PGE2 and LTC4 in zymosan-stimulated mouse macrophages with an IC50 of 1.2 and 0.6 mumol/l, respectively. Antagonism of IL-1 and/or TNF is thought to have a beneficial effect on the course of inflammatory diseases. CGP 47969A may therefore represent a mechanistically new approach to the treatment of such diseases.

CGP 47969A: effect on collagen induced arthritis in DBA/1 mice

OBJECTIVE

CGP 47969A is a novel and potent inhibitor of cytokine biosynthesis in human and murine monocytic cells. The effect of CGP 47969A on collagen induced arthritis (CIA) in DBA/1 mice was investigated and compared to that of prednisolone.

METHODS

CIA was induced by intradermal injection of type II collagen in CFA at Day 0. CGP 47969A was applied orally, 5 times/week, starting at Day 15 after immunization. Arthritic signs were recorded 3 times/week for clinical scoring and radiographic analysis was performed at the end of the experiment at Day 60. Serum amyloid P (SAP) and anticollagen antibody titers were determined by ELISA at Day 60.

RESULTS

CGP 47969A dose dependently reduced the incidence of arthritis from 93% in the positive control group to 60, 40, 30 and 10% at doses of 1, 5, 25 and 60 mg/kg/day, respectively. At a dose of 120 mg/kg, CGP 47969A totally prevented the occurrence of arthritis (ED50 between 1 and 5 mg/kg). Prednisolone at 3 and 30 mg/kg reduced the arthritis incidence to 70 and 30%, respectively. CGP 47969A dose dependently inhibited the joint destruction, as measured by radiographic scoring and its potency was comparable to that of prednisolone. The elevated serum levels of the positive acute phase protein SAP in arthritic animals were completely normalized by CGP 47969A at a dose of 60 mg/kg, however, neither CGP 47969A nor prednisolone influenced the plasma levels of anticollagen antibodies (IgG).

CONCLUSION

Our results demonstrate that CGP 47969A is highly effective in CIA with a potency comparable to that of prednisolone. These promising results justify the expectation that this novel antiarthritic compound now under development might also be effective in the treatment of rheumatoid arthritis in man.

A mutational analysis of receptor binding sites of interleukin-1 beta: differences in binding of human interleukin-1 beta muteins to human and mouse receptors

The 3-D crystal structure of interleukin-1 beta (IL-1 beta) has been used to define its receptor binding surface by mutational analysis. The surface of IL-1 beta was probed by site-directed mutagenesis. A total of 27 different IL-1 beta muteins were constructed, purified and analyzed. Receptor binding measurements on mouse and human cell lines were performed to identify receptor affinities. IL-1 beta muteins with modified receptor affinity were evaluated for structural integrity by CD spectroscopy or X-ray crystallography. Changes in six surface loops, as well as in the C- and N-termini, yielded muteins with lower binding affinities. Two muteins with intact binding affinities showed 10- to 100-fold reduced biological activity. The surface region involved in receptor binding constitutes a discontinuous area of approximately 1000 A2 formed by discontinuous polypeptide chain stretches. Based on these results, a subdivision into two distinct local areas is proposed. Differences in receptor binding affinities for human and mouse receptors have been observed for some muteins, but not for wild-type IL-1 beta. This is the first time a difference in binding affinity of IL-1 beta muteins to human and mouse receptors has been demonstrated.

Monoclonal antibody based enzyme-linked and chemiluminescent assays for the human interleukin-1 receptor antagonist. Application to measure hIL-1ra levels in monocyte cultures and synovial fluids

Interleukin-1 receptor antagonist (IL-1ra) has the potential to counteract at least part of the biological effects of interleukin-1. The outcome of an inflammatory reaction may therefore be determined by the balance between IL-1 and IL-1ra, rather than by IL-1 alone. We have developed an immunoassay to address this issue as well as to assess the effects of anti-inflammatory agents on the expression of IL-1 and IL-1ra in vitro or in body fluids. Recombinant human IL-1ra was expressed in an E. coli system, purified to homogeneity, and used to derive monoclonal antibodies in mice as well as polyclonal antibodies in rabbits. A sandwich ELISA was constructed with F(ab')2 fragments of a high affinity monoclonal antibody and the rabbit serum as a source of secondary antibody. The assay required no sample treatment to avoid interference by rheumatoid factor. The measuring range was 0.020-2 ng/ml. By labelling a second monoclonal antibody with an acridinium ester, a chemiluminescence assay with a wider measuring range (0.050-15 ng/ml) was generated. In accord with published data, we found that IL-1ra was secreted by human monocytes stimulated with LPS, Zymosan, IL-1 alpha, or human IgG. After an induction phase of ca. 4 hours and depending on the stimulus, IL-1ra accumulated linearly for periods up to 96 h. IL-1ra levels in synovial fluids of 19 patients suffering from various inflammatory joint diseases were compared with the cytokine levels of IL-1 beta, IL-6, IL-8, and TNF-alpha. Highest positive correlations were found with IL-8 and IL-1 beta. In normal blood donors IL-1ra serum levels were 150-800 pg/ml (Median: 387 pg/ml). Owing to its sensitivity and large measuring range the newly developed assays appear to be suitable for measuring IL-1ra in cell cultures as well as in biological fluids.

Interferon-gamma overcomes the glucocorticoid-mediated and the interleukin-4-mediated inhibition of interleukin-1 beta synthesis in human monocytes

Interleukin-1 (IL-1) has been implicated in the tissue destruction of rheumatoid arthritis, a disease that is widely treated with glucocorticoids. In this study we investigated the effect of the T cell product interferon-gamma (IFN-gamma) on the glucocorticoid-mediated and on the IL-4-mediated inhibition of IL-1 beta mRNA and IL-1 beta protein synthesis in highly purified human monocytes. Both dexamethasone and IL-4 dose-dependently inhibited IL-1 beta mRNA and IL-1 beta protein synthesis after stimulation with LPS (300 ng/ml); maximal inhibition of 80-90% was achieved. IFN-gamma (1-100 U/ml) did not influence IL-1 beta mRNA and IL-1 beta protein levels in unstimulated cells, but potentiated the LPS-induced synthesis of IL-1 beta mRNA and IL-1 beta protein. After a preincubation time of 1 h, 100 U/ml of IFN-gamma increased the LPS-induced IL-1 beta production by about 20-40%. When human monocytes were preincubated for 1 h with IFN-gamma (100 U/ml) prior to the addition of dexamethasone (10(-6) M) and prior to the stimulation with LPS, the dexamethasone-mediated inhibition of IL-1 beta mRNA and IL-1 beta protein synthesis was totally neutralized by IFN-gamma. In addition, IFN-gamma totally overcame the negative effect of IL-4 (100 pM) on IL-1 beta protein synthesis. A preincubation period of at least 1 h with IFN-gamma was necessary for the neutralization of the dexamethasone effect. If IFN-gamma was given at the same time or after dexamethasone, only a weak effect was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Neutralization of interleukin-1 beta activity in vivo with a monoclonal antibody alleviates collagen-induced arthritis in DBA/1 mice and prevents the associated acute-phase response

Interleukin-1 (IL-1) has been implicated in the development and progression of a variety of acute and chronic inflammatory diseases. Due to its pro-inflammatory and tissue-degrading activities, IL-1 is regarded as a major mediator of chronic inflammatory joint diseases, including rheumatoid arthritis in man, adjuvant arthritis in rats and collagen-induced arthritis in mice. However, conclusive experimental evidence for the crucial role of IL-1 in the development of joint destruction has not been presented as yet. In the present study, we investigated the effect of a neutralizing monoclonal mouse antibody against mouse IL-1 beta (IgG1 isotype) on the development and progression of collagen-induced arthritis in DBA/1 mice. The antibody was injected intraperitoneally 3 times a week, either from day 3 or from day 21 after primary immunization, to day 60. In the positive control group an arthritis incidence of 80% was observed after 60 days. The injection of a control antibody of the same isotype did not influence the incidence of arthritis, whereas injection of anti-IL-1 beta from day 21 reduced the arthritis incidence to about 30%. Injection of anti-IL-1 beta starting at day 3 totally prevented both the development of arthritis and the associated increase of the acute phase protein serum amyloid P (SAP). Anti-collagen antibody titers, which increased significantly after immunization, were not influenced by the injection of anti-IL-1 beta antibodies, in spite of the suppressive effect on arthritis development.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance imaging and morphometric quantitation of cartilage histology after chronic infusion of interleukin 1 in rabbit knees

Cartilage pathology in rabbit knees was monitored by noninvasive magnetic resonance imaging (MRI) and evaluated using morphometric histologic measurements. Infusion of rabbit knees with the cytokine interleukin 1 induces cartilage degradation and inflammation. A miniosmotic pump was implanted subcutaneously to deliver interleukin 1 through a polyethylene catheter inserted into the rabbit knee. Rabbit knees were imaged using MRI and prepared for histologic examination at 5 and 12 days after chronic infusion of interleukin 1. MRI obtained 0.7-mm sections for three-dimensional reconstruction of cartilage image. Cartilage deterioration near the site of infusion was visible on MRI. MRI measurements indicated a reduction in cartilage thickness. Histology revealed a loss of staining of cartilage matrix proteoglycan, synovial hypertrophy, and perichondral bone resorption. Morphometric analysis of cartilage histology indicated a reduction in both cellularity (chondrocytes/m mu 2 area) and cell to matrix area ratio. These observations suggest that a loss of proteoglycan, an early event in cartilage degeneration, can be detected by MRI.

Interleukin-1 (IL-1) production in a mouse tissue chamber model of inflammation. II. Identification of (tissue) macrophages as the IL-1 producing cells and the effect of anti-inflammatory drugs

We have used our newly described mouse tissue chamber model [1], to investigate the process of IL-1 production in more detail. The inflammatory reaction in the tissue surrounding the implanted chambers was investigated histologically and by using the polymerase chain reaction (PCR). The inflammatory response included influx of leucocytes into the granuloma surrounding the tissue chamber, expression of IL-1 beta on macrophages present in the inflamed tissue and an increase in the mRNA coding for IL-1 beta and IL-6 proteins in the granuloma. The effects of three anti-inflammatory or immunosuppressive drugs, prednisolone, indomethacin and cyclosporin A, on IL-1 beta and PGE2 production in zymosan and Bordetella-pertussis-vaccine (BPV)-challenged tissue chambers were also examined. Oral treatment with prednisolone and cyclosporin A of zymosan-challenged animals showed a dose-dependent reduction of IL-1 beta concentrations, but no effect of indomethacin. Both prednisolone and indomethacin dose-dependently reduced PGE2 concentrations to control levels, while cyclosporin A was effective only at the highest dose tested (100 mg/kg/day p.o.). In drug-treated BPV-challenged animals, prednisolone and cyclosporin A also showed a dose-dependent reduction of IL-1 beta, while indomethacin was again ineffective. Prednisolone and indomethacin also dose-dependently reduced the PGE2 concentrations to control levels, whereas cyclosporin A was effective only at the highest dose tested (100 mg/kg/day p.o.). This model will be useful for investigating the mechanisms controlling the production of IL-1 beta from the mRNA level to the secretion of mature biologically active protein [1], and in the search for new drugs which could selectively interfere with this process.

Interleukin-1 (IL-1) production in a mouse tissue chamber model of inflammation. I. Development and initial characterisation of the model

A simple and reliable animal model to quantify interleukin-1 (IL-1) production at a site of inflammation has been developed and characterised. This model involves the subcutaneous implantation of sterile Teflon chambers (30 mm x 10 mm diameter) into the backs of mice. After 14 days, a straw coloured transudate fluid was present in the lumen of the implanted chamber which was withdrawn for the determination of baseline measurements of various inflammatory parameters. A localised chronic inflammatory response was then induced in the chambers by injection of 1% zymosan or Bordetella pertussis vaccine (BPV) (in presensitised animals). The local inflammatory reaction in the chamber, over a 30 day time course, was characterised by leucocyte infiltration, and marked increases in protein, prostaglandin E2, IL-1 and IL-6 concentrations in the chamber fluid. A rapid increase in plasma concentrations of the acute-phase reactant serum amyloid P (SAP) also occurred. This model allows repeated samples to be obtained from the same animal for the assessment of inflammatory parameters and may be useful for investigating the mechanisms controlling the production of IL-1 during the inflammatory response in vivo.

Transforming growth factors type-beta and dexamethasone attenuate group II phospholipase A2 gene expression by interleukin-1 and forskolin in rat mesangial cells

Treatment of rat mesangial cells with interleukin-1 beta (IL-1 beta) and forskolin induced, in a synergistic fashion, the expression of group II phospholipase A2 (PLA2) mRNA, with subsequent increased synthesis and secretion of PLA2. In contrast, interleukin-6 did not increase PLA2 mRNA levels of PLA2 activity. Transforming growth factor (TGF) beta 1, TGF beta 2 and TGF beta 3 equipotently attenuated the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, as well as PLA2 synthesis and secretion. The glucocorticoid dexamethasone only partially suppressed the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, but totally inhibited PLA2 synthesis and secretion.

Recombinant human C5a induces transcription but not translation of interleukin 1 beta mRNA in human monocytes

The effect of recombinant human C5a (rhC5a) on the synthesis of interleukin 1 beta (IL-1 beta) was investigated in human monocytes, isolated by leukapheresis and countercurrent elutriation. rhC5a induced IL-1 beta mRNA synthesis in a dose- and time-dependent manner. Maximal induction was achieved at 3 h with rhC5a concentrations of 200 to 500 ng/ml. The maximal rhC5a-stimulated mRNA induction was about 75% of that observed using LPS as the stimulus (300 ng/ml). The inducing activity of rhC5a could be neutralized by preincubation with a polyclonal anti-C5a antibody. On the other hand rhC5a in optimal concentrations only weakly stimulated IL-1 beta protein synthesis, as measured by a two-site directed enzyme-linked immunoassay. When compared on Northern blots, a slightly reduced mobility of C5a-stimulated IL-1 beta mRNA was observed relative to LPS-stimulated RNA. To exclude the possibility that structural defects in the IL-1 beta mRNA are responsible for the weak translational efficiency after C5a stimulation a primer extension experiment was performed. No difference in the length of the extended fragment was detected between LPS and C5a-stimulated RNA, suggesting that the 5'-regions of the RNAs are identical. When LPS- or C5a-stimulated RNA was used to program IL-1 beta synthesis in an in vitro translation system from rabbit reticulocytes, no difference in translational efficiency was observed. Our results indicate that in human monocytes two signals for IL-1 beta gene expression are necessary, a signal for transcriptional activation and another signal to induce translation of the mRNA.

Recombinant human C5a induces transcription but not translation of interleukin-1 beta mRNA in human monocytes

The effect of recombinant human C5a (rhC5a) on the synthesis of interleukin-1 beta (IL 1 beta) was investigated in highly purified human monocytes, isolated by leukapheresis and counter-current elutriation. RhC5a induced IL 1 beta mRNA synthesis in a dose- and time-dependent manner; maximal induction was achieved at 3 h with rhC5a concentrations of 200 to 500 ng/ml. The IL 1 beta mRNA induction with rhC5a was about 75% of the response observed using lipopolysaccharide (LPS) as the stimulus (300 ng/ml). On the other hand, rhC5a in optimal concentrations only weakly stimulated IL 1 beta protein synthesis, as measured by a two-site-directed enzyme-linked immunoassay. When LPS- or C5a-stimulated RNA was used to program IL 1 beta synthesis in an in vitro translation system from rabbit reticulocytes, no difference in translational efficiency was observed. Our results indicate that, in human monocytes, two signals for IL 1 beta gene expression are necessary, one signal for transcriptional activation and a second signal to induce translation of the mRNA.

Interleukin 1beta and tumour necrosis factor alpha induce a macrophage-type of nitric oxide synthase in rat renal mesangial cells

Treatment of mesangial cells with interleukin 1 beta (IL-1 beta) or tumour necrosis factor alpha (TNF alpha) has been shown to increase cGMP formation, most probably due to induction of nitric oxide synthase. Here we report that maximum stimulation of cGMP formation over a 24-h period required the presence of IL-1 beta or TNF alpha during the first 18 h of induction. N4-monomethyl-L-arginine (L-NMMA) was a potent inhibitor of cytokine-induced cGMP formation while N4-nitro-L-arginine (L-NNA) was less active. Formation of nitric oxide was detected in the cytosol of cytokine-treated mesangial cells by activation of purified soluble guanylate cyclase and was stimulated by tetrahydrobiopterin, but not by calcium calmodulin. Treatment of cells with IL-1 beta or TNF alpha markedly attenuated the contractile response to a subsequent challenge with angiotensin II. Furthermore, conditioned medium from IL-1 beta-treated cells increased cGMP in untreated control cells.

PDGF suppresses the activation of group II phospholipase A2 gene expression by interleukin 1 and forskolin in mesangial cells

Treatment of rat mesangial cells with interleukin 1 beta (IL-1 beta) and forskolin greatly enhanced the expression of group II phospholipase A2 (PLA2) mRNA, with subsequent increased synthesis and secretion of PLA2, as detected by PLA2 activity measurements and immunoprecipitation of culture media of [35S]methionine-labelled mesangial cells. PDGF-BB dose-dependently suppressed the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, as well as PLA2 synthesis and secretion. In contrast, PDGF-AA had no inhibitory effect. The tyrosine kinase inhibitor genistein dose-dependently antagonized the inhibitory effect of PDGF-BB on IL-1 beta-stimulated PLA2 secretion, thus suggesting that tyrosine phosphorylation may be required for PDGF-BB inhibition of PLA2 gene expression in mesangial cells.

Transforming growth factor beta 2 inhibits interleukin 1 beta- and tumour necrosis factor alpha-induction of nitric oxide synthase in rat renal mesangial cells

Treatment of mesangial cells with interleukin 1 beta (IL-1 beta) or tumour necrosis factor alpha (TNF alpha) has been shown to induce nitric oxide (NO) synthase with subsequent autocrine stimulation of soluble guanylate cyclase (Pfeilschifter and Schwarzenbach, 1990, FEBS Lett. 273, 185-187). Here we report that transforming growth factor beta 2 (TGF beta 2) dose-dependently inhibits IL-1 beta- and TNF alpha-stimulated cGMP formation in mesangial cells. Half-maximal inhibition is observed at concentrations of 0.4 and 0.06 ng/ml of TGF beta 2, respectively. Maximum inhibition of cGMP formation over a 24 h period requires the presence of TGF beta 2 during the first 4 h of induction. In addition, the inhibitory effect of TGF beta 2 on cytokine-induced cGMP formation is not affected by the potent cyclo-oxygenase inhibitor indomethacin, thus excluding prostaglandins as mediators.

Mapping the receptor binding domain of interleukin-1 beta by means of binding studies using overlapping sequence fragments: why did it fail?

Interleukin-1 (IL-1) alpha and beta are polypeptide hormones that mediate a broad range of biological activities and interact with surface receptors on numerous cell types. Great efforts are made at present to define the interaction domain of IL-1 with its receptor. We have tried to map the domain of IL-1 beta by assessing the receptor interaction of synthetic octapeptide acid amides representing overlapping segments of the IL-1 beta primary sequence. Since the tertiary structure of IL-1 beta is known, the selection of octapeptides could be confined to the surface exposed residues. More than a 100 octapeptides were tested for binding in a competitive binding assay, using a mouse thymoma cell line (EL 4.61) as a receptor source and 125I-IL-1 alpha and beta as radioligands. No binding was found at up to a one hundred fold excess of octapeptide over radioligand. From this lack of binding we conclude that the entropic cost of conformationally freezing the octapeptide is high and that the conformation of the binding domain is per se in terms of free energy and is stabilized by the overall tertiary structure of IL-1.

Cyclic AMP mimics, but does not mediate, interleukin-1- and tumour-necrosis-factor-stimulated phospholipase A2 secretion from rat renal mesangial cells

We have previously shown that recombinant interleukin 1 (IL-1) and recombinant tumour necrosis factor (TNF) synergistically stimulate phospholipase A2 release from mesangial cells. We now report that treatment of mesangial cells with the beta-agonist salbutamol, prostaglandin E2 (PGE2), cholera toxin or forskolin, which all activate adenylate cyclase, increased release of phospholipase A2 activity. Likewise, addition of a membrane-permeant cyclic AMP (cAMP) analogue or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine enhanced release of phospholipase A2 activity from mesangial cells. There was a lag period of about 8 h before a significantly enhanced secretion could be detected. Furthermore, actinomycin D or cycloheximide completely suppressed cAMP-stimulated secretion of phospholipase A2. Angiotensin II, the phorbol ester phorbol 12-myristate 13-acetate, the Ca2+ ionophore A23187 and a membrane-permeant cGMP analogue did not stimulate phospholipase A2 release from the cells. Treatment with indomethacin completely inhibited IL-1 beta- and TNF-stimulated PGE2 synthesis, without having any effect on phospholipase A2 secretion, thus excluding cytokine-induced PGE2 synthesis as the mediator of phospholipase A2 release. Neither IL-1 beta nor TNF induced any increase in intracellular cAMP in mesangial cells. Furthermore, incubation of the cells with 2',5'-dideoxyadenosine, an inhibitor of adenylate cyclase, did not block cytokine-stimulated phospholipase A2 secretion. In addition, IL-1 beta and TNF synergistically interacted with forskolin to stimulate phospholipase A2 release from the cells. The protein kinase inhibitors H-8, staurosporine, K252a and amiloride inhibited IL-1 beta- and TNF-stimulated phospholipase A2 secretion. However, high concentrations that inhibit other protein kinases were needed. These observations suggest that IL-1 beta and TNF cause secretion of phospholipase A2 by a mechanism independent of cAMP. The signalling pathways used by IL-1 beta and TNF may involve a protein kinase that is probably different from protein kinase A or protein kinase C.

Priming of polymorphonuclear granulocytes by lipopolysaccharides and its complexes with lipopolysaccharide binding protein and high density lipoprotein

Human peripheral blood neutrophils are primed, or enabled to respond to formyl peptide, by prior exposure to bacterial lipopolysaccharide (LPS). The activity of LPS and the size of its aggregates are altered by plasma constituents such as high density lipoprotein (HDL) and the recently discovered acute phase reactant lipopolysaccharide binding protein (LBP) Tobias et al.: J. Exp. Med. 164,777, 1986]. The ability of LPS, LPS-LBP, and LPS-HDL complexes to activate a number of cellular responses have been compared. LPS-LBP and LPS-HDL were prepared using LBP and HDL from rabbit serum. LPS from Salmonella minnesota Re595 and its LPS-LBP and LPS-HDL complexes differed in their ability to prime PMN O2- production in response to formyl peptide (f-Nle-Leu-Phe-Nle-Tyr-Leu [FNLPNTL]). Human PMN prepared under conditions in which O2- production is minimal (less than 1 nmol O2-/10(6) PMN/10 min) after exposure to 10(-7) M FNLPNTL can be primed with 0.1-100 ng/ml LPS in a dose- and time-dependent manner to produce up to 12 nmol O2-/10(6) PMN/10 min. LBP complexation accelerated the priming induced by LPS, whereas HDL complexation retarded it. Priming was accompanied by a parallel two- to threefold increase in formyl peptide receptor number as determined by FACS analysis of fluoresceinated FNLPNTL binding and SDS-PAGE autoradiographic analysis of photoaffinity ligand binding. Thus binding of LPS to plasma proteins changes the response of the PMS to LPS and may represent one way in which the response of the PMN is regulated during infection. Since LBP concentrations change during an acute phase response, complexation of LPS with LBP is a mechanism that may regulate neutrophil responses in vivo during inflammation.

Resistance of Escherichia coli to rifampicin and sorangicin A--a comparison

Sorangicin A, a macrolide polyether antibiotic and the ansamycin antibiotic rifampicin inhibit DNA-dependent RNA polymerase to a similar extent. Resistance to sorangicin A is due to a mutation in the RNA polymerase which renders the enzyme less sensitive. Parallel investigations with rifampicin revealed partial cross-resistance, which was more marked in sorangicin A-resistant mutants than in rifampicin-resistant mutants.

Interleukin 1 and tumor necrosis factor synergistically stimulate prostaglandin synthesis and phospholipase A2 release from rat renal mesangial cells

Treatment of rat glomerular mesangial cells with recombinant human interleukin 1 alpha (rIL-1 alpha), recombinant human interleukin 1 beta (rIL-1 beta) or recombinant human tumor necrosis factor (rTNF) induces prostaglandin E2 (PGE2) synthesis and the release of a phospholipase A2 (PLA2) activity. rIL-1 beta is significantly more potent than rIL-1 alpha or rTNF in stimulating PGE2 as well as PLA2 release from mesangial cells. When given together, rTNF interacts in a synergistic fashion with rIL-1 alpha and rIL-1 beta to enhance both, PGE2 synthesis and PLA2 release. The released PLA2 has a neutral pH optimum and is calcium-dependent. Pretreatment of cells with actinomycin D or cycloheximide inhibits basal and cytokine-stimulated PGE2 and PLA2 release.

Role of oxidants in DNA damage. Hydroxyl radical mediates the synergistic DNA damaging effects of asbestos and cigarette smoke

The mechanism by which cigarette smoking and asbestos exposure synergistically increase the incidence of lung cancer is unknown. We hypothesized that cigarette smoke and asbestos might synergistically increase DNA damage. To test this hypothesis we exposed isolated bacteriophage PM2 DNA to cigarette smoke and/or asbestos, and assessed DNA strand breaks as an index of DNA damage. Our results supported our hypothesis. 78 +/- 12% of the DNA exposed to both cigarette smoke and asbestos developed strand breaks, while only 9.8 +/- 7.0 or 4.3 +/- 3.3% of the DNA exposed to cigarette smoke or asbestos, respectively, developed strand breaks under the conditions of the experiment. Our experimental evidence suggested that cigarette smoke and asbestos synergistically increased DNA damage by stimulating .OH formation. First, significant amounts of .OH were detected by electron paramagnetic resonance (EPR) in DNA mixtures containing both cigarette smoke and asbestos, but no .OH was detected in mixtures containing cigarette smoke alone or asbestos alone. Second, the .OH scavengers, dimethylsulfoxide (DMSO), mannitol, or Na benzoate decreased both .OH detection by EPR and strand breaks in DNA mixtures exposed to cigarette smoke and asbestos. Third, the H2O2 scavenger, catalase, and the iron chelators, 1,10-phenanthroline and desferrithiocin, decreased both .OH detection and strand breaks in DNA mixtures exposed to cigarette smoke and asbestos. These latter findings suggest that iron contained in asbestos may catalyze the formation of .OH from H2O2 generated by cigarette smoke. In summary, our study indicates that cigarette smoke and asbestos synergistically increase DNA damage and suggests that this synergism may involve .OH production.

Induction of inflammatory mediators from human polymorphonuclear granulocytes and rat mast cells by haemolysin-positive and -negative E. coli strains with different adhesins

We investigated the role of various E. coli strains that expressed different adhesins and/or generated haemolysin with regard to the induction of inflammatory mediators, e.g. histamine release from rat mast cells as well as the chemiluminescence response and the release of lipoxygenase transformation products from human polymorphonuclear neutrophils. Our data show that the degree of haemagglutination did not parallel the induction of the chemiluminescence response. Haemolysin-negative bacteria with different adhesins induced more 5-hydroxyeicosatetraenoic acid as compared to haemolysin-positive bacteria, which generated more leukotriene B4 as compared to 5-hydroxyeicosatetraenoic acid. Among the leukotrienes, more leukotriene B4 as compared to leukotriene C4 was released from peripheral leucocytes. Studies with rat mast cells showed that histamine release was dependent on the haemolysin activity expressed by washed bacteria or present within the bacterial culture supernatant. Histamine release was markedly diminished when haemolysin activity decayed. Several haemolysin-negative bacteria with defined adhesins also released histamine, suggesting that, in addition to haemolysin, other factors contribute to mediator release. Thus, various properties of bacteria (e.g. adhesins, haemolysin) may participate to varying degrees in the induction of inflammatory mediators, e.g. oxygen radicals, lipoxygenase transformation products, leucotrienes and histamine.

Uptake, intracellular activity, and influence of rifampin on normal function of polymorphonuclear leukocytes

Quinone and hydroquinone forms of rifampin accumulated in normal polymorphonuclear leukocytes (PMN) (maximal cellular to extracellular concentration ratio [C/Emax] +/- standard error of the mean, 9.36 +/- 0.54 and 8.82 +/- 0.65, respectively, after 5 to 10 min) and chronic granulomatous disease PMN (C/Emax, 13.76 +/- 0.77 and 14.29, respectively). Uptake of rifampin was influenced by incubation temperature and extracellular pH but not by phorbol myristate acetate stimulation or metabolic inhibitors. At extracellular concentrations between 0.06 and 5.0 mg/liter, rifampin significantly reduced the number of staphylococci surviving inside chronic granulomatous disease PMN, thus compensating for the bactericidal defect inherent with this disease. Spontaneous migration and chemotaxis of normal PMN were unaffected by rifampin. However, phagocytosis of yeast particles and oxygen consumption of stimulated PMN were moderately depressed, and O2- production and chemiluminescence were significantly depressed in a dose-dependent manner. The bactericidal activity of normal PMN was not impaired. Inhibition of chemiluminescence and O2- release were also observed in a cell-free system. We conclude that rifampin possesses favorable characteristics for the effective elimination of intracellular microorganisms. Further studies are needed to evaluate the in vivo significance of ion scavenging by rifampin, which could be hazardous to immunocompromised patients.

Experimental hematogenous infection of subcutaneously implanted foreign bodies

Implanted foreign bodies are highly susceptible to pyogenic infection. Whereas infection up to 3 months after surgery is probably due to perioperative bacterial contamination, little is known about the pathogenesis of late prosthetic infections. We employed an animal model to determine whether subcutaneously implanted foreign bodies were susceptible to experimental bacteremia. Tissue cages were implanted into guinea pigs, which were infected at the earliest 4 weeks later by intracardiac injection of Staphylococcus aureus Wood 46. The injection of 2 X 10(6) cfu did not result in any infection. Inoculation of 5 X 10(7) cfu resulted in a bacteremia of 10(2)-10(3) cfu/ml after 5 min and led to 11/26 selective tissue cage infections with no microbiological evidence of infection elsewhere. Higher inocula caused systemic infections with foci in different organs. Rifampin (7.5 mg/kg b.i.d.) was administered for 48 h, starting at different times after infection to establish the best timing for efficacious short-term therapy. When treatment was begun 1 h before or 3 h after inoculation, complete protection was observed, whereas 1/12 and 3/15 tissue cages remained infected when the first dose was not given until 24 h and 48 h, respectively, after inoculation. These experiments illustrate that implanted prostheses are highly susceptible even to bacteremias with low density of microorganisms. Prophylaxis can prevent such infections, whereas delayed short-term treatment may fail.

Duodeno-pancreatic secretions enhance bactericidal activity of antimicrobial drugs

We have studied the action of various antimicrobial agents in microbiological media and in human duodeno-pancreatic secretions. In the latter medium, clioquinol exhibited a rapid bactericidal effect on both growing and stationary bacteria at concentrations near its MIC. However, it was merely bacteriostatic in microbiological media, even at high concentrations. Phanquinone, chlorquinaldol, and, to a lesser extent, also chloramphenicol and trimethoprim likewise displayed enhanced bactericidal activity in duodeno-pancreatic secretions, but various other antibacterial agents did not. These findings suggest that duodeno-pancreatic secretions contain a factor augmenting the antibacterial activity of a number of drugs.

Antibiotic action on phagocytosed bacteria measured by a new method for determining viable bacteria

Antibiotics such as rifampin that act on phagocytosed bacteria have clinical advantages. The investigation of such intraphagocytic activity of antibiotics is, however, hampered by the time-consuming and cumbersome procedures necessary for enumerating viable bacteria. We have developed a semiautomatic biophotometric method for this purpose that permits the processing of relatively large numbers of samples. Using this method with Staphyloccus aureus Wood 46 as a test organism, we studied the dose dependence of the activities of a number of antibiotics against intraphagocytic bacteria. We could confirm the very good intracellular activity of rifampin. Its activity at low concentrations was slightly better against intracellular than against extracellular bacteria. In contrast, clindamycin and erythromycin, both of which have been reported to accumulate within phagocytes, did not exhibit a correspondingly enhanced intracellular activity, erythromycin being active intracellularly only at high concentrations. Clindamycin and vancomycin were effective against intracellular organisms, but only at relatively high concentrations owing to their low bactericidal activity against S. aureus Wood 46. Penicillin G, ampicillin, gentamicin, and streptomycin exhibited no useful intracellular activity. These results demonstrate that radioactive accumulation studies of antibacterial agents are not sufficient to show intracellular activity. Intracellular activity must be demonstrated in a functional test, preferably with graded concentrations of the test substance.

Fimbria-specific antibodies detach Escherichia coli from human cells

Antibodies obtained from rabbits immunized with purified adhesion-mediating fimbriae of Escherichia coli SS142 were specific for the fimbriae of the homologous strain; they did not cross-react with isolated fimbriae of three different E. coli strains or with protein extracts from nine other adhesive E. coli strains. The antibodies inhibited adhesion to Intestine 407 tissue culture cell monolayers and hemagglutinating activity of E. coli SS142 but not of several other E. coli strains. The antibodies were able not only to prevent but also to reverse the adhesion of E. coli SS142 to Intestine 407 cells or human erythrocytes. Analysis of the kinetics of inhibition suggested that the antibodies did not competitively inhibit adhesion. Such antibodies can be useful for distinguishing different mechanistic steps of bacterial adhesion. Their ability to reverse bacterial adhesion in vitro may be of clinical relevance.

Effect of swainsonine on the processing of the asparagine-linked carbohydrate chains of alpha 1-antitrypsin in rat hepatocytes. Evidence for the formation of hybrid oligosaccharides

The biosynthesis of the proteinase inhibitor alpha 1-antitrypsin has been studied in rat hepatocyte primary cultures. Newly synthesized alpha 1-antitrypsin was found in hepatocytes as a glycoprotein of an apparent molecular weight of 49,000 carrying oligosaccharide side chains of the high mannose type. In the hepatocyte medium a secreted alpha 1-antitrypsin of an apparent molecular weight of 54,000 could be identified as a glycoprotein with carbohydrate chains of the complex type. Pulse-chase experiments revealed a precursor-product relationship for the two forms of alpha 1-antitrypsin. When the hepatocytes were treated with swainsonine, an intracellular form of alpha 1-antitrypsin with an apparent molecular weight of 49,000 indistinguishable from that of control cells was found. However, the alpha 1-antitrypsin secreted from swainsonine-treated hepatocytes was different from that present in control media. It was characterized by a lower apparent molecular weight (51,000), a higher amount of [3H]mannose incorporation, half as much incorporation of [3H]galactose, and the same amount of [3H]fucose incorporation compared to alpha 1-antitrypsin of control media. In contrast to the 54,000 complex type alpha 1-antitrypsin from control media the 51,000 alpha 1-antitrypsin from the medium of swainsonine-treated cells was found to be susceptible to the action of endoglucosaminidase H, even when fucose was attached to the proximal GlcNAc residue. alpha 1-Antitrypsin secreted from swainsonine-treated cells combines features usually associated with either high mannose or complex type oligosaccharides and therefore represents a hybrid structure. In spite of its effect on the carbohydrate part of alpha 1-antitrypsin swainsonine did not impair the secretion of the incompletely processed glycoprotein.

Lectin-resistant variants of mouse melanoma cells. II. In vitro characteristics

Lectin-resistant variants of B-16 melanoma cells were selected with wheat-germ agglutinin, ricin and concanavalin A. They exhibited altered metastasizing capacity and tumorigenicity in C57BL mice. Several in vitro properties were defined and compared including homotypic adhesiveness, microfilament organization, melanin release, activity of tyrosine hydroxylase, DNA content, and karyotypes. The possible relevance of these properties in vitro for the malignant behavior displayed in vivo is discussed. The usefulness of this approach of selecting surface variants to study the problem of metastasis is also discussed.

Properties of pili from Escherichia coli SS142 that mediate mannose-resistant adhesion to mammalian cells

We isolated pili from Escherichia coli SS142. These pili had a diameter of 6 nm and an average length of 400 nm. They were composed of subunits with a molecular weight of 18,000. Their amino acid composition was determined; methionine and proline were not detected. The isolated pili retained mannose-resistant hemagglutinating activity. Proteolytic digestion and glutaraldehyde fixation led to partial or complete loss of the hemagglutinating activity of the pili without causing any detectable damage to their supramolecular structure, which was only disintegrated by treatment with hot sodium dodecyl sulfate. The hemagglutinating activity of E. coli SS142 was inhibited by the glycoproteins fetuin and Tamm-Horsfall protein, as well as by the glycolipids phytyl lactoside, dansyl-sphingosine lactoside, and digalactosyl diglyceride. Isolated pili inhibited the adhesion of the homologous strain E. coli SS142 to Intestine 407 cell monolayers, but did not inhibit the adhesion of E. coli strain B-413, B-506, or 2699. This indicates that E. coli SS142 binds to a receptor different from those recognized by the other strains and that mannose-resistant adhesion to tissue culture cells can be classified into different subtypes.

Effects of low concentrations of antibiotics on Escherichia coli adhesion

We have previously shown that subinhibitory concentrations of antibiotics may influence the adhesion of Escherichia coli SS142 to human epithelioid tissue culture cells. This report shows that these effects are not limited to E. coli SS142 or to our tissue culture system. Most of the 10 E. coli strains studied showed decreased adhesion to Intestine 407 tissue culture cells after growth in 25% of the minimum inhibitory concentration of streptomycin, tetracycline, trimethoprimsulfametrole, chloramphenicol, and clindamycin. Nalidixic acid at 25% of the minimum inhibitory concentration caused an increase of adhesion. The hemagglutinating activity of the five hemagglutinating strains and the adhesiveness of E. coli SS142 to human buccal cells were similarly affected by low concentrations of the above-mentioned antibiotics. We conclude that E. coli adhesion to human epithelioid tissue culture cells is a valid model of bacterial adhesion because of its high accuracy and reproducibility.

Swainsonine prevents the processing of the oligosaccharide chains of influenza virus hemagglutinin

Swainsonine, an indolizidine alkaloid, inhibits the alpha-mannosidase that is involved in glycoprotein processing. Thus, in cultured animal cells, this alkaloid causes an increase in the surface content of high mannose glycoproteins and a decrease in the amount of complex type glycoproteins (Elbein, A. D., Solf, R., Dorling, P. R., and Vosbeck, K. (1982) Proc. Natl. Acad. Sci. U. S. A., 78, 7393-7397). In this report, the effect of swainsonine on the synthesis virus hemagglutinins was examined. Primary calf kidney cultures were infected with influenza virus and viral replication was allowed to proceed in the absence or presence of swainsonine. Several hours after the addition of swainsonine, [2-3H]mannose or [6-3H]glucosamine were added to label the hemagglutinins and the mature virus particles were isolated. Virus particles raised in the presence of this alkaloid had the same infectivity and hemagglutination titer as virus particles from control cells. However, when the hemagglutinins were examined on sodium dodecyl sulfate gels, the major hemagglutinin (HA0) and its subunits, HA1 and HA2, from swainsonine-treated cells, migrated faster, indicating that they were of lower molecular weights. The labeled hemagglutinins were digested with pronase and the resulting glycopeptides were chromatographed on Bio-Gel P-4. Both the mannose-labeled and glucosamine-labeled glycopeptides from swainsonine-treated virus migrated more slowly on these columns than those of controls cells, suggesting that they were altered in structure. Furthermore, when the glycopeptides were digested with endoglucosaminidase H, 90% of the glycopeptides from swainsonine-treated cells were susceptible to this enzyme, whereas only 30% of those from control cells were digested. The major oligosaccharide released from inhibited cells by endoglucosaminidase H was digestible with alpha-mannosidase, whereas that of control cells was resistant to this enzyme. However, the control cell glycopeptide was digested by a combination of neuraminidase, beta-galactosidase, beta-N-acetylhexosaminidase, and alpha-mannosidase. These data show that swainsonine prevents the formation of complex glycoproteins and gives rise to increased amounts of high-mannose glycoproteins.

An assay for measuring specific adhesion of an Escherichia coli strain to tissue culture cells

Escherichia coli SS142 has been found to adhere specifically to the human epithelioid tissue culture cell line Intestine 407, but not to other tissue culture cells. This paper describes an accurate, reproducible and objective method of assessing the rate of adhesion of radiolabelled bacteria to these cellular monolayers. Adhesion was found to be linear with time for 60 min and with bacterial concentrations up to 10(9) bacteria/ml. The binding appeared to be irreversible. Adhesion was not affected by changes in the composition of the medium, its pH or ionic strength, or by the assay temperature within physiological limits, but was diminished at very high ionic strength or low temperature. It increased with increasing cell density of the monolayers. Under appropriate conditions the assay could be used for comparative determinations of the rate of adhesion of different, or differently treated bacteria.

Bacterial adhesion in the pathogenesis of infective endocarditis. Effect of subinhibitory antibiotic concentrations on streptococcal adhesion in vitro and the development of endocarditis in rabbits

Bacterial adhesion to the constituents of nonbacterial thrombotic endocarditis (NBTE) is important in the pathogenesis of endocarditis. Subinhibitory concentrations (subMIC) of some antibiotics decrease bacterial adhesion to epithelial cells in vitro. We utilized an in vitro assay system to study the effect of subMIC of various antibiotics on streptococcal adhesion to a fibrin-platelet matrix (simulating NBTE). The results were (a) bacterial adhesion of Streptococcus sanguis and Streptococcus faecalis to NBTE was significantly reduced by vancomycin, penicillin, tetracycline, chloramphenicol and streptomycin (P less than 0.01 vs. controls) but not rifampin or trimethoprimsulfametrole; (b) the effect was dose-dependent and increased with duration of exposure to antibiotic; (c) reduction in bacterial adhesion did not correlate with altered retention by hydrophobic-interaction chromatography. This reduction in adhesion correlated with a diminished capacity of subMIC exposed Streptococcus sanguis (1/4 vancomycin minimum inhibitory concentration (MIC) X 4 h) to produce endocarditis in vivo. After intravenous inoculation of 10(6) colony-forming units of preincubated organisms into rabbits with traumatized aortic valves, 6 of 22 developed endocarditis vs. 17 of 22 controls (P = 0.03). These results may be relevant to prophylaxis of endocarditis since exposure of bacteria to subMIC of various antibiotics may reduce bacterial adherence both, to mucosal surfaces, and to damaged cardiac valves.

Escherichia coli adhesion to Saccharomyces cerevisiae and mammalian cells: role of piliation and surface hydrophobicity

A number of Escherichia coli strains isolated from patients with urinary tract infections, bacteremia, or diarrhea were studied with respect to their (i) capacity to agglutinate human AB, bovine, and guinea pig erythrocytes as well as yeast (Saccharomyces cerevisiae) cells; (ii) adhesion to monolayers of cells from human intestine (intestine 407; ATCC CCL6), monkey kidney (Vero; ATCC CCL81), feline embryo (Flow no. 05-552), and porcine kidney (PK1; ATCC CRL1392) and of primary rat kidney cell cultures; and (iii) surface hydrophobicity as measured by hydrophobic interaction chromatography. No correlation could be found between the capacity of the bacteria to adhere to the different cultured mammalian cells and their agglutination patterns. The results indicated not only a complexity of bacterial receptors on the eucaryotic cells, but also a multiplicity of bacterial adhesions as expressed by the selectivity of bacterial binding. Binding of bacteria was found to be attributed to the presence of pili on the bacterial surface. It was observed that the bacteria were differently piliated: some had only common type I or related pili which gave rise to mannose-sensitive (MS) adhesion or agglutination (MS pili), some had only pili which gave rise to mannose-resistant (MR) adhesion or agglutination (MR pili), and some had both MS and MR pili. Bacteria with MS pili were more hydrophobic than those with MR pili or with none at all.

Effects of subminimal inhibitory concentrations of antibiotics on adhesiveness of Escherichia coli in vitro

The adhesion of radiolabeled Escherichia coli (strain SS142) to monolayers of Intestine 407, a human epithelioid tissue culture cell line, was investigated. In this assay the adhesion of bacteria grown in the presence of subminimal inhibitory concentrations of tetracycline, clindamycin,, or trimethoprim-sulfametrole was reduced in a manner that was dose dependent. In contrast, at such concentrations nalidixic acid enhanced the adhesion of this bacterial strain, and other antibiotics-e.g., penicillin G, ampicillin, mecillinam, cephacetrile, cephalexin, cefotaxime, chloramphenicol, and streptomycin-did not affect its adhesiveness.

Assay of intercellular adhesiveness using cell-coated Sephadex beads as collecting particles

A simple, rapid and precise method, based on a previous method, for measuring relative rates of intercellular adhesion is described. DEAE-Sephadex beads were treated with nitrocellulose in order to allow cells to grow on their surfaces. Balb/c 3T3 and Balb/c 3T12 cells were used to characterize the assay. They formed confluent cell layers on nitrocellulose-treated DEAE-Sephadex. These cell-coated beads were employed to collect 32P-labelled cells from single cell suspensions. Since they formed statistically uniform, large collecting surfaces, the collection of labelled cells was markedly improved as compared to the original assay. The cell-coated beads collected a large percentage of the labelled cells in a short time. The percentage of cells collected was independent of the concentration of labelled cells in the assay mixture, and the collection was linear for approximately 60 min. The variability between replicate assays was usually +/− 5%. The assay allows the rapid and precise determination of intercellular adhesion in large numbers of individual samples. These features make it useful to screen for effects of different treatments on intercellular adhesions.