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I Kushner

Publications and source records attributed to I Kushner.

At least 37 records · Page 2Linked to original sources
PubMed1995

Kinetic modeling and mathematical analysis indicate that acute phase gene expression in Hep 3B cells is regulated by both transcriptional and posttranscriptional mechanisms.

To evaluate the possible role of posttranscriptional mechanisms in the acute phase response, we determined the kinetics of transcription (by nuclear run-on assay) and mRNA accumulation of five human acute phase genes in Hep 3B cells incubated with conditioned medium from LPS-stimulated monocytes. Increase in mRNA accumulation was comparable to increase in transcription rate for fibrinogen-alpha and alpha-1 protease inhibitor, suggesting largely transcriptional regulation. In contrast, mRNA accumulation was about 10-20-fold greater than transcriptional increase for serum amyloid A, C3, and factor B, suggesting participation of posttranscriptional mechanisms. Since finding a disparity between the magnitudes of increase in mRNA and transcription does not definitively establish involvement of posttranscriptional mechanisms, we subjected our data to modeling studies and dynamic mathematical analysis to evaluate this possibility more rigorously. In modeling studies, accumulation curves resembling those observed for these three mRNAs could be generated from the nuclear run-on results only if posttranscriptional regulation was assumed. Dynamic mathematical analysis of relative transcription rates and relative mRNA abundance also strongly supported participation of posttranscriptional mechanisms. These observations suggest that posttranscriptional regulation plays a substantial role in induction of some, but not all acute phase proteins.

Acute-Phase Reaction↗
PubMed1994

The acute phase response: general aspects.

The acute phase response in a given individual represents the integrated sum of multiple, separately regulated changes. Although many of these changes commonly occur together in affected individuals, clinical experience indicates that not all of them occur in all individuals, indicating that they must be individually regulated. For example, febrile patients may have normal blood levels of CRP and vice versa, leukocytosis does not always accompany other acute phase phenomena, and many instances of discordance between levels of the various acute phase proteins are seen. Cytokines function as part of a complex regulatory network, a signalling language in which information is conveyed to cells by combinations, and perhaps sequence, of intercellular messenger molecules. The effects of combinations of cytokines are complex. To use a somewhat crude simile, individual cytokines can be thought of as words which bear informational content and which may, on occasion, communicate a complete message. More commonly, however, the actual messages received by cells probably resemble sentences, in which combinations and sequences of words convey information. Currently available data suggest that hepatocytes receive a complex mixture of humoral or paracrine signals during the acute phase response. These are integrated by multiple interacting signal transducing mechanisms to cause finely regulated changes in plasma protein synthesis. Regulation largely occurs by transcriptional control, but post-transcriptional mechanisms, including translational regulation, may also participate. Both the extracellular and intracellular mechanisms that mediate the response of the hepatocyte to inflammatory stimuli appear to be highly complex and involve multiple overlapping, concurrent and parallel pathways. Enough is known at present to conclude that IL-6 is a major participant in these plasma protein changes. Regulation of non-hepatocyte acute phase phenomena has not been delineated as thoroughly, but clearly involves a number of inflammation-associated cytokines.

Acute-Phase Proteins↗
PubMed1993

IL-1 receptor antagonist affects the plasma protein response of Hep 3B cells to conditioned medium from lipopolysaccharide-stimulated monocytes.

The availability of the IL-1R antagonist (IL-1ra) has made it possible to assess the specific contributions of IL-1 to the acute phase changes induced by complex mixtures of cytokines. We utilized IL-1ra to define the contribution of IL-1 to the effects of conditioned medium from LPS-stimulated monocytes on production of the positive acute phase proteins C-reactive protein, serum amyloid A, fibrinogen, alpha 1-protease inhibitor, complement component C3, alpha 1-antichymotrypsin, alpha 1-acid glycoprotein, and ceruloplasmin and the negative acute phase proteins albumin and transferrin in Hep 3B cells. Induction of C-reactive protein and serum amyloid A was essentially abolished, induction of complement component C3 and alpha 1-acid glycoprotein was moderately decreased and induction of fibrinogen was enhanced. In contrast, there was no significant effect of IL-1ra on induction by conditioned medium of alpha 1-protease inhibitor, alpha 1-antichymotrypsin, or ceruloplasmin. IL-1ra partially blocked the down-regulatory effects of conditioned medium on both of the negative acute phase proteins we studied--albumin and transferrin. These findings enhance our understanding of the contribution of IL-1 to the acute phase response. In addition, they indicate that IL-1ra in vivo may influence synthesis of both positive and negative acute phase proteins.

Acute-Phase Proteins↗
PubMed1993

C-reactive protein increases production of IL-1 alpha, IL-1 beta, and TNF-alpha, and expression of mRNA by human alveolar macrophages.

The concentration of C-reactive protein (CRP) increases in human plasma up to a thousandfold during inflammatory states. Because tissue macrophages have been shown to have receptors for CRP, the question arises of whether these cells may respond to increased local concentrations of CRP by producing cytokines capable of participating in the inflammatory response. Accordingly, we examined the capacity of alveolar macrophages--relatively accessible human macrophages--to produce interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-alpha) in response to CRP. We found that production of IL-1 alpha, IL-1 beta, and TNF-alpha, as measured by bioassay and immunoassay, increased in a dose-dependent manner after stimulation by CRP and that the levels of the respective mRNAs analyzed by Northern blot increased proportionally. These findings suggest that one of the functions of CRP may be to stimulate the production of IL-1 and TNF by macrophages at inflammatory sites where alterations of capillary permeability combined with an increased serum level lead to enhanced local concentrations of this acute-phase protein.

Actins↗
PubMed1993

Regulation of the acute phase response by cytokines.

Cytokines appear to function as part of a complex regulatory network, a signaling language in which informational content resides in the combinations, and perhaps sequence, of cytokines and other extracellular messenger molecules received by a cell. The effects of combinations of cytokines are complex and often differ from their in vitro effects or when administered by themselves. (From this perspective, to use a somewhat crude simile, individual cytokines can be thought of as words which bear informational content. Although individual cytokines may, on occasion, communicate a complete message, more commonly the actual messages received by cells probably resemble sentences, in which it is the combination and sequence of words which convey information.) Currently available data suggest an in vivo scenario in the acute phase response in which the hepatocyte receives a complex mixture of humoral or paracrine signals which are integrated by multiple interacting post-receptor and gene regulatory mechanisms to cause finely regulated changes in plasma protein synthesis. Regulation often occurs by transcriptional control, but post-transcriptional mechanisms, including translational regulation, may participate. Both the extracellular and intracellular mechanisms that mediate the response of the hepatocyte to inflammatory stimuli appear to be highly complex and involve multiple overlapping, concurrent, and parallel pathways. Enough is known at present to conclude that IL-6 is a major participant in these changes in man. Regulation of non-hepatocyte acute phase phenomena has not been delineated as thoroughly, but clearly involves a number of cytokines.

Acute-Phase Reaction↗
PubMed1993

Aggressive therapy does not substantially alter the long-term course of rheumatoid arthritis. So what else is new?

A consensus has evolved that there is little evidence supporting the view that the second line agents significantly alter long-term outcomes in rheumatoid arthritis. Consequently, changes in approaches to treatment currently being employed include earlier use of existing second line agents, their use in combinations, and greater use of corticosteroids. Our awareness that our current drugs, at best, fall considerably short of attaining the therapeutic results we would like to achieve causes us to look forward to the development of rationally derived biologic agents with considerable anticipation.

Arthritis, Rheumatoid↗
PubMed1992

Effect of flurbiprofen on cytokine production by human monocytes and U-937 and THP-1 cell lines.

Possible effects of nonsteroidal antiinflammatory drugs (NSAID) on inflammatory mediators other than arachidonic acid metabolites which might contribute to the antiinflammatory effects of these drugs have not been fully explored. We investigated the effects of an NSAID, flurbiprofen, on production of the cytokines tumor necrosis factor alpha (TNF alpha), interleukin 1 beta (IL-1 beta) and interleukin 6 (IL-6) by human peripheral blood monocytes and by the human cell lines U-937 and THP-1. Cytokine production was induced by 1 microgram/ml bacterial lipopolysaccharide (LPS) in both monocytes and cell lines, and cytokine levels in supernatants were measured by enzyme immunoassay. In monocytes, IL-6 was the major product while in both cell lines, TNF alpha was the major product. Flurbiprofen caused moderate inhibition of IL-1 beta and TNF alpha production by stimulated monocytes, but did not affect IL-6 production. In contrast, flurbiprofen completely abolished IL-6 production by both cell lines and substantially inhibited IL-1 beta and TNF alpha production. These observations raise the possibility that inhibition of cytokine production by flurbiprofen may contribute to the antiinflammatory properties of this drug.

Cells, Cultured↗
PubMed1991

Effect of combinations of cytokines and hormones on synthesis of serum amyloid A and C-reactive protein in Hep 3B cells.

We have previously shown that induction of synthesis of the two major human acute phase proteins, serum amyloid A (SAA) and C-reactive protein (CRP), can be accomplished in the human hepatoma cell line Hep 3B, in the presence of dexamethasone, either by conditioned medium from LPS-stimulated monocytes or by the combination of IL-6 and IL-1. Neither of these cytokines alone caused significant induction of either SAA or CRP. In the present study we extended our earlier observations by evaluating the role of dexamethasone, the effect of different concentrations of IL-6 and IL-1 alpha in combination, and the possible role of TNF-alpha in regulating synthesis of SAA and CRP. Dexamethasone alone had no effect on induction of SAA or CRP. Incubation of Hep 3B cells with conditioned medium from LPS-stimulated monocytes, in the absence of dexamethasone, led to modest induction of SAA or CRP, but addition of dexamethasone potentiated this response in a dose-dependent manner. Similar results were obtained for the effect of dexamethasone on the induction of SAA by IL-6 plus IL-1 alpha. Checkerboard titration of IL-6 and IL-1 alpha revealed that increases in concentration of either cytokine led to dose-related increases in synthesis of both SAA and CRP as long as a minimal amount of the other cytokine was present. TNF-alpha alone had no significant effect on synthesis of either SAA or CRP, but the combination of IL-6 plus TNF-alpha led to substantial induction of SAA. This combination was less effective than the combination of IL-6 plus IL-1 alpha. No detectable effect of IL-6 plus TNF-alpha was observed on CRP synthesis. Both combinations of cytokines, IL-6 plus IL-1 alpha, and IL-6 plus TNF-alpha, caused increased SAA mRNA accumulation that roughly paralleled increase in synthesis. These data indicate that IL-6, IL-1 alpha, TNF-alpha, and dexamethasone in various combinations are all capable of influencing synthesis of SAA in Hep 3B cells, whereas only IL-6, IL-1 alpha, and dexamethasone can influence CRP synthesis.

C-Reactive Protein↗
PubMed1991

Effects of cytokine combinations on acute phase protein production in two human hepatoma cell lines.

We evaluated the effects of binary combinations of four cytokines on production of the positive acute phase proteins alpha-1 antichymotrypsin, haptoglobin and fibrinogen, and the negative acute phase proteins albumin and alpha-fetoprotein (AFP) in two human hepatoma cell lines. The effects of the cytokine combinations on the five proteins varied; each protein exhibited a unique and specific pattern of response to the cytokine combinations. In Hep G2 cells, antichymotrypsin was induced by all four cytokines, IL-6, IL-1, TNF-alpha, and transforming growth factor beta 1 alone, and their effects in binary combinations could be attributed to additive or minimally synergistic interactions. Fibrinogen was induced only by IL-6 and this induction was inhibited by IL-1 alpha, TNF-alpha or transforming growth factor beta 1. Haptoglobin was also induced only by IL-6, but TNF-alpha was the only cytokine that inhibited this induction at all concentrations of IL-6. Each of the four cytokines alone down regulated production of AFP and albumin. However, binary combinations of the four cytokines were simply additive, for the most part, in inhibiting AFP production, whereas the inhibitory effects of combinations of cytokines on albumin production differed significantly from simple additive effects. These observations, taken together with studies of effects of cytokine combinations on other acute phase proteins, indicate that the various acute phase proteins respond differently to different combinations of cytokines and that the potential exists for highly specific regulation of synthesis of individual plasma proteins by cytokine interactions. These findings imply that the acute phase response in vivo represents the integrated sum of multiple, separately regulated changes in gene expression.

Acute-Phase Proteins↗
PubMed1991

The primary structure of serum amyloid A protein in the rabbit: comparison with serum amyloid A proteins in other species.

Rabbit serum amyloid A (SAA) protein was isolated from acute-phase serum by ultracentrifugation, molecular seive chromatography, and ion-exchange chromatography. The complete amino acid sequence of the protein was established by sequence analysis of peptides derived from trypsin and Staphylococcus proteinase digestion of the protein. The molecule consisted of 104 amino acids and had an amino terminus that was blocked by pyrrolidonecarboxylic acid. Heterogeneity was not observed at any residue, which suggests that the material sequenced consisted of a single serum amyloid A species. The protein is highly homologous to serum amyloid A from humans and other animals, particularly in the middle portion of the molecule (positions 33 to 63), which suggests that this region may be important in its function. This highly conserved region may also contain the determinants for amyloid formation.

Amino Acid Sequence↗
PubMed1990

Induction of C-reactive protein by cytokines in human hepatoma cell lines is potentiated by caffeine.

Induction of C-reactive protein (CRP) by conditioned medium from lipopolysaccharide-stimulated human monocytes in two human hepatoma-cell lines, Hep 3B and NPLC/PRF/5, was potentiated 3-6-fold by the methylxanthine caffeine. The induction observed in the presence of conditioned medium plus caffeine was as much as 180-fold, comparable with that seen after many stimuli in vivo. This potentiation was accompanied by an increase in the levels of CRP mRNA. By contrast, no potentiating effect on CRP induction by conditioned medium was found when we tested theophylline, forskolin, 8-bromo cyclic AMP or two Ca2+ ionophores, namely ionomycin and A23187. None of the above compounds, including caffeine, when tested alone, had any detectable effect on the synthesis and secretion of CRP. Our previous study [Ganapathi, May, Schultz, Brabenec, Weinstein, Sehgal & Kushner (1988) Biochem. Biophys. Res. Commun. 157, 271-277], employing defined cytokines, had shown that induction of CRP in Hep 3B cells requires IL(interleukin)-6 plus IL-1, whereas, in the NPLC/PRF/5 cell line, IL-6 alone is effective. Caffeine similarly potentiated induction of CRP by these defined cytokine signals in these two cell lines. Changes in synthesis of other acute-phase proteins, including serum amyloid A (SAA), alpha 1-proteinase inhibitor, alpha 1-antichymotrypsin and albumin, induced by conditioned medium or, in some cases, by IL-6 and/or IL-1 alpha, were only minimally affected by caffeine. Thus these results indicate that the mechanism by which caffeine potentiates CRP induction by cytokines appears to be independent of increases in intracellular concentrations of the two second messengers, cyclic AMP and Ca2+; the precise nature of this mechanism is unclear at the present time. Our results also indicate that the intracellular mechanisms by which cytokines regulate synthesis of CRP may differ from those regulating synthesis of some other acute-phase proteins. The differential response of CRP and SAA to caffeine is of particular interest, since induction of both of these two major acute-phase proteins can be accomplished by identical extracellular signals.

8-Bromo Cyclic Adenosine Monophosphate↗