Biomedical subjects

J D Sipe

Publications and source records attributed to J D Sipe.

At least 37 records · Page 2Linked to original sources

PubMed1997

Evidence for local production of acute phase response apolipoprotein serum amyloid A in Alzheimer's disease brain.

Acute phase serum amyloid A (A-apoSAA), but not constitutive apoSAA (C-apoSAA), was identified by Western blotting experiments in brain protein extracts from eight of nine patients with Alzheimer's disease (AD), one with a brain tumor and one with multiple sclerosis. A-apoSAA was not detected in six subjects with Pick's or Lewy Body disease or three other non-AD brain specimens. Apolipoprotein A-I and albumin were not found in any of the brain protein extracts. A-apoSAA mRNA was detected in AD brain by reverse transcription-polymerase chain reaction (RT-PCR). These data suggest that apoSAA is locally produced in AD brain and that investigation of the neuroinflammatory effects of this injury specific apolipoprotein is warranted.

Aged↗

PubMed1997

Response to local inflammation of IL-1 beta-converting enzyme- deficient mice.

IL-1 beta-converting enzyme (ICE) cleaves pro-IL-1 beta to the mature, released form. Although other proteases can process pro-IL-1 beta, ICE-deficient (ICE -/-) mice do not release mature IL-1 beta in response to endotoxin. The purpose of our study was to investigate the response of ICE -/- mice in two models of local inflammation, turpentine-induced tissue damage and zymosan-induced peritonitis. No differences were observed in the development of the systemic acute phase response after turpentine administration between wild-type and ICE -/- mice, but this response was completely impaired in IL-1 beta -/- mice. Accordingly, the levels of mature IL-1 beta produced in response to turpentine did not differ between wild-type and ICE -/- mice. In contrast, following zymosan-induced peritonitis, the levels of mature IL-1 beta were significantly lower in ICE -/- mice. This was associated with a 50% decrease in cellular infiltrate in ICE -/- mice compared with that in wild-type controls. The reduced production of zymosan-induced mature IL-1 beta in ICE -/- mice was also observed from cultured peritoneal or spleen cells. Our results demonstrate that in turpentine-induced tissue necrosis, precursor IL-1 beta is processed by non-ICE proteases, but in complement-mediated inflammation, ICE participates in the processing of the IL-1 beta precursor.

Animals↗

PubMed1997

Regulation of extrahepatic apolipoprotein serum amyloid A (ApoSAA) gene expression by interleukin-1 alpha alone: synthesis and secretion of ApoSAA by cultured aortic smooth muscle cells.

Serum amyloid A apolipoproteins (apoSAA) appear to compromise the ability of high density lipoprotein to protect against atherosclerosis and it is of interest to determine whether aortic smooth muscle cells can contribute to local pools of apoSAA in the presence of cytokines that are known to stimulate acute phase apoSAA (A-apoSAA) synthesis in the liver. In this study, the regulation of A-apoSAA synthesis was monitored in cultured neonatal rabbit aortic smooth muscle cells. Constitutive apoSAA3 gene expression was minimal, and only detectable by amplification of the mRNA by reverse transcriptase-polymerase chain reaction. ApoSAA3 gene expression and protein synthesis were stimulated by IL-1 alpha; as little as 0.01 ng/ml of IL-1 alpha stimulated an increase in steady state levels of apoSAA3 mRNA. Interestingly, IL-6 (which is required in addition to IL-1 alpha for the optimal synthesis of A-apoSAA by human hepatoma cells) had little if any effect on apoSAA3 synthesis by the smooth muscle cells. In a time course, it was shown that the stimulation of apoSAA3 mRNA levels was apparent by 1-2 h after the addition of cytokine, and that levels remained elevated in the presence of the cytokine for at least 48 h. Immunoprecipitation using an antiserum directed against apoSAA3 revealed that IL-1 alpha stimulated the synthesis and secretion of apoSAA3 protein in a manner that was consistent with apoSAA3 mRNA expression. The implications of these findings in atherogenesis are discussed.

Amino Acid Sequence↗

PubMed1997

Rheumatoid arthritis exhibits reduced acute phase and enhanced constitutive serum amyloid A protein in synovial fluid relative to serum. A comparison with C-reactive protein.

OBJECTIVE: There are 2 classes of serum amyloid A (SAA) protein, acute phase (A-SAA) and constitutive (C-SAA). Hepatic synthesis of A-SAA is dramatically upregulated by inflammatory cytokines, while C-SAA is constitutively produced in the absence of inflammation. A-SAA has been shown to attract monocytes, neutrophils, and T lymphocytes, but the function of C-SAA remains to be determined. SAA proteins have been found in both serum and synovial fluid (SF) of patients with rheumatoid arthritis (RA), but have not been characterized with respect to isoform distribution. We determined the relative distribution of A-SAA and C-SAA in serum and SF of patients with RA and compared their abundance to the classic acute phase response protein, C-reactive protein (CRP). METHODS: A-SAA (isoforms SAA1, SAA2) and CRP were measured by commercially available ELISA kits. ELISA were developed for C-SAA (SAA4) and apolipoprotein AI (apo AI) in paired serum and SF from 56 patients with RA. RESULTS: Concentrations (mean +/- SD) of A-SAA (SAA1,2) in serum and SF are 124 +/- 247, 20 +/- 32 micrograms/ml; CRP 75 +/- 70, 33 +/- 37 micrograms/ml; C-SAA (SAA4) 106 +/-49, 91 +/- 39 micrograms/ml; and apo AI 1.19 +/- 0.32, 0.37 +/- 0.12 mg/ml, respectively. CRP correlated positively with A-SAA in serum or SF and negatively with apo AI in serum. There was no correlation with apo AI in SF. In contrast, there was no correlation between C-SAA and CRP, A-SAA, or apo AI in serum or in SF. Median concentrations of A-SAA in serum and SF (44, 10 micrograms/ml) and CRP (46, 20 micrograms/ml), respectively, markedly differed from the mean values, whereas median concentrations of C-SAA (104, 85 micrograms/ml) and apo AI (1.17, 0.37 mg/ml), respectively, did not. CONCLUSION: C-SAA concentrations vary in serum and SF independently of A-SAA and CRP levels. The lower concentration of A-SAA relative to C-SAA and CRP in SF suggests that A-SAA could be selectively catabolized in SF or alternatively not well transported into the synovial space.

Acute-Phase Proteins↗

PubMed1996

Effect of endotoxin in IL-1 beta-deficient mice.

IL-1 plays an important role in the pathophysiologic responses to infection and inflammation, in part by mediating its own production and that of other proinflammatory cytokines. However, the relative contribution of IL-1 alpha and IL-1 beta to the inflammatory response has not been well clarified. Using IL-1 beta-deficient (IL-1 beta -/-) mice, we investigated the specific role of IL-1 beta in the in vivo and in vitro response to LPS. No differences between IL-1 beta +/+ and IL-1 beta -/- mice were observed in circulating levels for IL-1 alpha, IL-6, or TNF-alpha after the systemic administration of either a low (5 micrograms/kg) or high (5 mg/kg) dose of LPS. IL-1 beta -/- mice also had a normal response to LPS in terms of activation of the hypothalamus-pituitary-adrenal axis, hypoglycemia, serum amyloid A production, and anorexia. IL-1 beta -/- mice were normally sensitive to the lethal effect of LPS and were protected against LPS toxicity when pretreated with low-dose LPS. However, in vitro, peritoneal macrophages from IL-1 beta -/- mice stimulated with LPS produced significantly less IL-1 alpha than macrophages from IL-1 beta +/+ mice (p < 0.05). No differences in IL-6 or TNF-alpha synthesis were observed between macrophages from IL-1 beta +/+ and IL-1 beta -/- mice. In summary, our results suggest that either IL-1 beta is not essential for the in vivo systemic response to LPS or that its role can be fulfilled by other cytokines with overlapping activities.

Animals↗

PubMed1996

Six different cytokines that share GP130 as a receptor subunit, induce serum amyloid A and potentiate the induction of interleukin-6 and the activation of the hypothalamus-pituitary-adrenal axis by interleukin-1.

Ciliary neurotrophic factor (CNTF) and interleukin-6 (IL-6) potentiate the elevation of serum corticosterone induced by suboptimal doses of interleukin-1 (IL-1). CNTF also potentiates IL-1-induced serum IL-6. Here, we report that four other cytokines (leukemia inhibitory factor [LIF], oncostatin M [OSM], interleukin-11 and cardiotrophin-1) also potentiated the elevation of serum corticosterone and IL-6 levels induced by IL-1. Furthermore, all the six cytokines studied induced the acute-phase protein serum amyloid A when administered alone. Because these cytokines differ both in structure and in function, but share gp130 as a subunit of their receptors, these results indicate that signaling through gp130 mediates potentiation of IL-1 activities. The potentiation of IL-1-induced serum corticosterone levels is not a consequence of the increased serum IL-6 observed after IL-1 administration. In fact, in IL-6 deficient mice, IL-1 increased serum corticosterone to a level comparable to that observed in wild-type mice. Thus, either endogenous IL-6 does not mediate IL-1-induced corticosterone increase, or its role may be fulfilled by other cytokines. To the extent that gp130-dependent cytokines may serve this role, they may be important feedback regulators of inflammation through the activation of the hypothalamus-pituitary-adrenal axis and the potentiation of acute-phase protein synthesis.

Acute-Phase Reaction↗

PubMed1996

The fibril forming region of the beta-amyloid precursor differs from that of the amyloid A precursor in its interaction with lipids.

Since the amyloid A (AA) precursoir, serum amyloid A (apoSAA), has been shown to bind cholesterol (C) in the AA fibril forming region, we investigated the interaction of the beta-amyloid precursor protein (AbetaPP) and beta-amyloid (Abeta) peptide with C and phosphatidyl choline (PC) by measuring changes in binding to microtiter wells at physiological pH and ionic strength. While either C or PC inhibited AbetaPP binding to the same extent that C inhibited apoSAA binding, neither C nor PC had any effect on binding of the Abeta peptide, although antibodies to Abeta1-40 did block binding. The binding of (125)I-Abeta1-40 and (125)I-AbetaPP was inhibited by apoE3 and apoE4, but not by either apoSAA or bovine serum albumin. Bound (125)I-AbetaPP was partially released into medium containing C, PC, apoE3, apoE4, or antibodies to AbetaPP. Our results indicate that AbetaPP but not Abeta peptide can be retained in solution in the presence of C and PC and suggest that this failure to interact with lipids may account for the greater insolubility of Abeta fibrils than AA fibrils.

Amyloid beta-Protein Precursor↗

PubMed1996

Polymorphism of acute-phase serum amyloid A isoforms and amyloid resistance in wild-type Mus musculus czech.

Until CE/J mice and their offspring were characterized as amyloid-resistant, all mice were thought to be amyloid-susceptible to multiple injections of azocasein or a single injection of silver nitrate following administration of amyloid enhancing factor. We now report, for the first time, that wild-type Mus musculus czech and F1 hybrids bred by crossing M. musculus czech with amyloid-susceptible CBA/J mice are also amyloid resistant. Based on the derived amino acid sequences of two serum amyloid A (SAA) cDNA clones, we describe two unusual SAA gene isoforms in M. musculus czech, one of which differs from four previously characterized acute-phase apoSAA isoforms at several amino acid residues. Our findings support the hypothesis that protection against amyloid fibril formation in wild-type M. musculus czech mice and their offspring is linked to apoSAA gene mutations (molecular motif).

Amino Acid Sequence↗

PubMed1996

Reduced susceptibility to IL-1 and endotoxin in transgenic mice expressing IL-1 in their lens.

To learn about the effects of chronic exposure to IL-1 we generated a transgenic (Tg) mouse line that expresses human IL-1 beta under the control of the lens alpha-A crystallin promoter. Expression of human IL-1 beta was restricted to the eye; neither the protein nor its mRNA were detected in various other organs of the Tg mice. The Tg mice develop severe ocular inflammation shortly after birth, which affects the lens and other eye tissues and apparently allows the release of IL-1 into the circulation. Here we report that the Tg mice exhibit decreased responsiveness to IL-1 and lipopolysaccharide (LPS), as compared to their wild-type littermate controls: (1) when injected with IL-1 the Tg mice produced lower levels of serum amyloid A than their controls; (2) thymocytes of the Tg mice responded less vigorously in culture to stimulation with IL-1; and (3) Tg mice showed lower morbidity and mortality than their controls when injected with toxic amounts of LPS. These data suggest that chronic exposure to IL-1 in the Tg mice induces partial resistance to this cytokine, analogous to the reduced responsiveness to IL-1 in animals pretreated with this proinflammatory cytokine.

Animals↗

PubMed1996

Degradation of serum amyloid A in amyloid-susceptible and amyloid-resistant mouse strains.

Degradation of serum amyloid A (apoSAA) by resident peritoneal cells (RPCS) and conditioned medium (CDM), prepared with RPCS, from amyloid-susceptible CBA/J mice, amyloid-resistant CE/J mice and their amyloid-resistant CBA/J x CE/J F1 progeny was investigated in vitro. Serum amyloid A was derived from murine acute phase (AP) plasma and associated with high density lipoprotein (HDL). Degradation of apoSAA by RPCS and CDM from CBA/J mice was complete while degradation by RPCS and CDM from CE/J mice did not occur. Degradation of apoSAA by RPCS and CDM from CBA/J x CE/J F1 hybrid mice was indistinguishable from that by RPCS and CDM from the CBA/J parent. Intermediate fragments were not detected with either RPCS or CDM from CBA/J mice or CBA/J x CE/J F1 hybrid mice. Degradation of apoSAA was inhibited by phenylmethanylsulfonyl fluoride (PMSF) indicating that the enzyme, secreted into the fluid phase, was a serine esterase. Unlike apoSAA, HDL-associated apoA-1 remained intact. It was thus concluded that while selective degradation of HDL-associated apoSAA (apoSAA-HDL) by RPCS from the CBA/J and CE/J mice was significantly different, the genetic study did not support the hypothesis that there was direct linkage between impaired degradation of apoSAA-HDL in the CE/J mouse strain and protection against amyloid fibril formation. As amyloid resistance in CBA/J x CE/J F1 hybrid mice is not attributable to failure to express the amyloidogenic isoform apoSAA2, the study supports the original hypothesis that amyloid resistance may be linked to expression of apoSAAcej.

Amyloid↗

PubMed1996

Quantitative and qualitative alterations of acute-phase proteins in healthy elderly persons.

To assess acute-phase proteins in relation to ageing, we measured serum concentrations of C-reactive protein of AGP in 131 healthy elderly individuals (aged >/= 65 years) living independently in the community, and 47 healthy younger individuals. Concentrations of CRP in the older persons (median = 3.0 microg/ml) were significantly greater than in the younger group (median = 0.9 microg/ml, p = 0. 0003). Concentrations of SAA and AGP were similar in the two groups, but AGP glycosylation forms with reduced binding affinity for concanavalin-A (changes that have been observed in chronic inflammatory states) were increased in the elderly sample (p<0.0001). These findings suggest that both quantitative and qualitative alterations of acute-phase proteins occur with physiological ageing in humans.

Activities of Daily Living↗

PubMed1996

Amino terminal region of acute phase, but not constitutive, serum amyloid A (apoSAA) specifically binds and transports cholesterol into aortic smooth muscle and HepG2 cells.

The human apoSAA proteins comprise both acute phase (apoSAA1, apoSAA2) and constitutive (apoSAA4) isoforms; all are expressed in human atherosclerotic lesions as well as in liver. Recombinant acute phase apoSAA binds cholesterol with an affinity of approximately 170 nM and enhances cholesterol uptake by HepG2 cells (J. Lipid Res. 1995. 36:37-46). In the present study, we sought to define the region of acute phase apoSAA involved in cholesterol binding and to investigate the ability of constitutive apoSAA4 to bind cholesterol. Binding of [3H]cholesterol to apoSAAp was inhibited by unlabeled cholesterol (1-100 nM), but not significantly by vitamin D and estradiol. Direct binding of acute phase, but not constitutive, apoSAA to the surfaces of polystyrene microtiter wells was strongly diminished in the presence of cholesterol. The ability of apoSAAp to bind cholesterol was inhibited by antibodies to human apoSAA1 and to peptide 1-18 of apoSAA1. There was only slight inhibition of cholesterol binding by antibodies to peptide 40-63, and no inhibition by antibodies to peptides spanning regions containing amino acid residues 14-44 and 59-104. [3H]cholesterol uptake by neonatal rabbit aortic smooth muscle and HepG2 cells was enhanced by a synthetic peptide corresponding to amino acids 1-18 of hSAA1, but not by peptides corresponding to amino acids 1-18 of hSAA4. [3H]cholesterol uptake by HepG2 cells was slightly increased by a peptide corresponding to amino acids 40-63 of hSAA1. These findings suggest that apoSAA modulates the local flux of cholesterol between cells and lipoproteins during inflammation and atherosclerosis.

Amino Acid Sequence↗

PubMed1995

Linkage of protection against amyloid fibril formation in the mouse to a single, autosomal dominant gene.

Inbred strains of mice provide a model for studies of the pathogenesis of amyloid A (AA) amyloidosis. All susceptible strains of mice described to date codominantly express two serum amyloid A (apoSAA) isoforms, apoSAA1 and apoSAA2, of which only apoSAA2 serves as a precursor for amyloid fibrils. In previous studies, we have shown that the CE/J strain, which produces a single, novel apoSAA isoform, apoSAACE/J, is amyloid resistant. In the present study amyloid-resistant CE/J females were mated with amyloid-susceptible CBA/J males to produce F1 hybrid offspring which were then backcrossed to the parental CBA/J mouse strain. Amyloid susceptibility was determined in 30 backcrossed mice 72 h after injection of murine amyloid enhancing factor and silver nitrate. ApoSAA isoforms in plasma were separated by isoelectric focusing gel electrophoresis and visualized after immunoblotting with anti-AA antiserum. Amyloid A fibrils in spleen homogenates were denatured by formic acid and AA protein was quantified by ELISA using anti-mouse apoSAA antibodies. Values < 5 apoSAA equivalent units were considered negative. 13 mice expressed an apoSAA1 and apoSAA2 doublet characteristic of CBA/J mice, whereas 17 mice, expressed the apoSAACE/J isoform codominantly with apoSAA1 and apoSAA2. The correlation of amyloid resistance to expression of the apoSAACE/J isoform was absolute (17/17 were negative; mean score 2.6 +/- 0.17 [standard error of the mean] apoSAA equivalent units) and the correlation between amyloid susceptibility and the expression of apoSAA2/apoSAA1 was also striking (12/13 were amyloid positive; mean score 47.9 +/- 9.0 [standard error of the mean] apoSAA equivalent units (P < 0.001). This is not significantly different from the 50% segregation of apoSAA phenotypes expected for linkage to a single gene. These results indicate that a single gene governs apoSAACE/J expression and thus confers protection against amyloid deposition even in the presence of apoSAA1 and apoSAA2 isoforms and show for the first time that resistance to AA amyloidosis is a dominant trait governed by a single gene.

Amino Acid Sequence↗

PubMed1995

The down-regulation of IL-6-stimulated fibrinogen steady state mRNA and protein levels by human recombinant IL-1 is not PGE2-dependent: effects of IL-1 receptor antagonist (IL-1RA).

Infections, trauma and inflammatory processes induce a host response with increases in a large group of structurally and functionally diverse plasma proteins. Parental administration of foreign proteins also induce an increase in plasma fibrinogen. Interleukin-6 (IL-6) is a monocyte-derived mediator and has regulatory effects on acute phase protein genes which result in the induction of fibrinogen synthesis in primary hepatocytes, while the addition of interleukin-1 (IL-1) exerts a negative modulating influence on the IL-6-stimulated fibrinogen. In order to understand the mechanisms by which IL-1 inhibits IL-6-stimulated fibrinogen transcription and translation, and since IL-1 is believed to act through PGE2 stimulation, we have studied the influence of PGE2 in IL-6 or IL-1, alone and in combination, on Fg mRNA expression (by Northern blot analysis) and the influence of PGE2, indomethacin, and arachidonic acid on Fg secretion. Moreover, since human recombinant interleukin-1 receptor antagonist (hrIL-1ra) is a strong inhibitor of IL-1 induced IL-1 transcription and translation and has an inhibitory effect on PGE2, we have studied the effects of IL-1ra on the down-regulation of IL-6 stimulated fibrinogen by IL-1, using an Fg ELISA method.(ABSTRACT TRUNCATED AT 250 WORDS)

Arachidonic Acid↗

PubMed1995

Ciliary neurotrophic factor (CNTF) induces serum amyloid A, hypoglycaemia and anorexia, and potentiates IL-1 induced corticosterone and IL-6 production in mice.

Ciliary neurotrophic factor (CNTF) supports the survival of ciliary ganglion neurons and was shown to induce the synthesis of acute-phase proteins and fever. We studied the effect of CNTF, alone or in association with IL-1, on levels of corticosterone (CS), glucose, serum amyloid A (SAA), and IL-6. We also compared the effect of CNTF with that of IL-6, since the gp130 receptor subunit for CNTF is shared with that of IL-6. A single intravenous injection of CNTF induced hypoglycaemia and SAA and potentiated IL-1-induced CS and IL-6. Chronic CNTF, but not IL-6, resulted in decreased food intake and body weight up to days 6-7. After this time, body weight and food intake recovered even if CNTF treatment was continued, indicating that a phenomenon of tolerance occurred. Finally, CNTF (unlike IL-1) was not toxic in adrenalectomized mice. Therefore the similarities of CNTF activities with those of other cytokines, particularly IL-6, might go beyond the activation of the same receptor-signal transduction pathway of IL-6.

Animals↗

PubMed1995

Acute-phase proteins in osteoarthritis.

The joint destruction of osteoarthritis (OA) comprises loss of articular cartilage resulting from an imbalance of enzyme-catalized cartilage breakdown and regeneration. OA is thought to derive from defective chondrocyte metabolism and thus to inherently lack the large-scale systemic response that is the hallmark of rheumatoid arthritis (RA). Because of the apparent absence of systemic inflammation in OA, acute-phase response proteins have not been as extensively studied in OA as they have been in RA. The diagnosis of OA almost always involves radiographic assessment of joint damage, which is useful only after the disease process has been underway for several months. Radiographic evaluation cannot give a good assessment of current disease activity and is a relatively insensitive indicator of prognosis. Cartilage breakdown products can potentially serve as direct surrogate markers of OA disease activity, but have not been extensively used because of their limited sensitivity and the technical difficulties associated with their measurement. Markers of disease activity in RA are indirect and are derived from the acute-phase response, a cycle of temporal changes in cellular and metabolic function. The early part of the acute-phase response involves the local action and production of cytokines such as interleukin-1 (IL-1), tumor necrosis factor (TNF-alpha) and IL-6. In the late acute-phase response, these cytokines can effect many systemic changes, including increased production of acute-phase proteins (APP). Three valuable surrogate markers of disease activity in RA are provided by the acute-phase response: the time-honored erythrocyte sedimentation rate (ESR) and the newer APPs C-reactive protein (CRP) and serum amyloid A (SAA). As in RA, the joint destruction of OA involves IL-1, TNF-alpha, and IL-6; however, OA can be viewed as an indolent stimulus of the later (systemic) acute-phase response. Recent studies of the acute-phase response in OA suggest that the concentrations of CRP and SAA are elevated in OA, but to a lesser extent than in RA. In the future, long-term monitoring of CRP concentrations in the blood may permit the earlier detection and more effective treatment of OA.

Acute-Phase Proteins↗

PubMed1995

Recombinant human serum amyloid A (apoSAAp) binds cholesterol and modulates cholesterol flux.

During acute inflammation, the serum amyloid A (apoSAA) proteins apoSAA1 and apoSAA2 are transiently associated with high density lipoproteins (HDL) in concentrations of as much as 1000-fold more than their concentrations during homeostasis; however, their effect on HDL function is unclear. Recombinant apoSAAp, a hybrid of the closely related human apoSAA1 and apoSAA2 isoforms, was found to exhibit a high affinity for cholesterol. The adsorption of apoSAAp to polystyrene microtiter wells at physiological pH, temperature, and salt concentration was inhibited and reversed by cholesterol. ApoSAAp, to a greater extent than apoA-I, albumin, or fetal bovine serum, enhanced diffusion of cholesterol from HDL across a membrane that retained molecules > 3.5 kDa. Cholesterol from 25 nM to 125 microM inhibited binding of [3H]cholesterol to 167 nM apoSAAp. A cholesterol binding assay was developed to determine the dissociation constant for binding of [3H]cholesterol to apoSAAp; Kd = 1.7 +/- 0.3 x 10(-7) M and the maximum binding capacity (Bmax) is 1.1 +/- 0.1 mol/mol. After binding cholesterol, the apparent size of apoSAAp as determined by gel filtration on Sephacryl S-100 was increased from 12 to 23 kDa. ApoSAAp enhanced free [14C]cholesterol uptake from tissue culture medium by HepG2 cells, an effect that was dose dependent and blocked by polyclonal antibodies to human apoSAA1 and apoSAA2. ApoSAAp, unlike apoA-I, was taken up from serum-free medium by HepG2 cells and appeared to be degraded by cell-associated enzymes. Unlike peritoneal exudate cells, human HepG2 hepatoma cells do not secrete an enzyme that degrades apoSAAp. These results suggest that apoSAA can potentially serve as a transient cholesterol-binding protein.

Adsorption↗

PubMed1995

Ciliary neurotrophic factor inhibits brain and peripheral tumor necrosis factor production and, when coadministered with its soluble receptor, protects mice from lipopolysaccharide toxicity.

BACKGROUND: The receptor of ciliary neurotrophic factor (CNTF) contains the signal transduction protein gp130, which is also a component of the receptors of cytokines such as interleukin (IL)-6, leukemia-inhibitory factor (LIF), IL-11, and oncostatin M. This suggests that these cytokines might share common signaling pathways. We previously reported that CNTF augments the levels of corticosterone (CS) and of IL-6 induced by IL-1 and induces the production of the acute-phase protein serum amyloid A (SAA). Since the elevation of serum CS is an important feedback mechanism to limit the synthesis of proinflammatory cytokines, particularly tumor necrosis factor (TNF), we have investigated the effect of CNTF on both TNF production and lipopolysaccharide (LPS) toxicity. MATERIALS AND METHODS: To induce serum TNF levels, LPS was administered to mice at 30 mg/kg i.p. and CNTF was administered as a single dose of 10 micrograms/mouse i.v., either alone or in combination with its soluble receptor sCNTFR alpha at 20 micrograms/mouse. Serum TNF levels were the measured by cytotoxicity on L929 cells. In order to measure the effects of CNTF on LPS-induced TNF production in the brain, mice were injected intracerebroventricularly (i.c.v.) with 2.5 micrograms/kg LPS. Mouse spleen cells cultured for 4 hr with 1 microgram LPS/ml, with or without 10 micrograms CNTF/ml, were also analyzed for TNF production. RESULTS: CNTF, administered either alone or in combination with its soluble receptor, inhibited the induction of serum TNF levels by LPS. This inhibition was also observed in the brain when CNTF and LPS were administered centrally. In vitro, CNTF only marginally affected TNF production by LPS-stimulated mouse splenocytes, but it acted synergistically with dexamethasone (DEX) in inhibiting TNF production. Most importantly, CNTF administered together with sCNTFR alpha protected mice against LPS-induced mortality. CONCLUSIONS: These data suggest that CNTF might act as a protective cytokine against TNF-mediated pathologies both in the brain and in the periphery.

Animals↗