Serum amyloid A in marine bivalves: An acute phase and innate immunity protein

Serum amyloid A (SAA) is among the most potent acute phase proteins (APP) in vertebrates. After injury, its early expression can dramatically increase to promote the recruitment of immuno-competent cells, expression of pro-inflammatory proteins and the activation of the innate immune defences. Although APP have been studied in many vertebrates, only recently their search was extended to invertebrates and the finding of SAA-like molecules has opened new questions on the immune-regulatory functions of these soluble proteins in the animal kingdom. Taking advantage of the considerable amount of genomic and transcriptomic data currently available, we retrieved 51 SAA-like proteins in several protostome taxa comprising 21 marine bivalve species and basal metazoans. In addition to vertebrate-like SAAs, we identified a second protein type with peculiar features. In the bivalves Crassostrea gigas and Mytilus galloprovincialis, both digital expression analysis and qPCR data indicated an induction of the classical SAA after bacterial challenge.

Immunization with pneumococcal polysaccharide serotype 3 and lipopolysaccharide modulates lung and liver inflammation during a virulent Streptococcus pneumoniae infection in mice

Vaccination reduces morbidity and mortality from pneumonia, but its effect on the tissue-level response to infection is still poorly understood. We evaluated pneumonia disease progression, acute-phase response, and lung gene expression profiles in mice inoculated intranasally with virulent Gram-positive Streptococcus pneumoniae serotype 3 (ST 3) with and without prior immunization with pneumococcal polysaccharide ST 3 (PPS3) or after coimmunization with PPS3 and a low dose of lipopolysaccharide (PPS3+LPS). Pneumonia severity was assessed in the acute phase at 5, 12, 24 and 48 h postinoculation (p.i.) and in the resolution phase at 7 days p.i. Primary PPS3-specific antibody production was upregulated, and IgM binding to pneumococci increased in PPS3-immunized mice. Immunizations with PPS3 or PPS3+LPS decreased bacterial recovery in the lung and blood at 24 and 48 h and increased survival. Microarray analysis of whole-lung RNA revealed significant changes in the acute-phase protein serum amyloid A (SAA) levels between noninfected and infected mice, and these changes were attenuated by immunization. SAA transcripts were higher in the liver and lungs of infected controls, and SAA protein was elevated in serum but decreased in PPS3-immunized mice. Thus, during a virulent pneumonia infection, prior immunization with PPS3 in an IgM-dependent manner as well as immunization with PPS3+LPS attenuated pneumonia severity and promoted resolution of infection, concomitant with significant regulation of cytokine gene expression levels in the lungs and acute-phase proteins in the lungs, liver, and serum.

Purification, identification and profiling of serum amyloid A proteins from sera of advanced-stage cancer patients

Surface-enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF-MS) is a powerful tool for screening potential biomarkers of various pathological conditions. However, low resolution and mass accuracy of SELDI-TOF-MS remain a major obstacle for determination of biological identities of potential protein biomarkers. We report here a refined workflow that combines ZipTip desalting, acetonitrile precipitation, high-performance liquid chromatography (HPLC) separation and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) analysis for the profiling, purification and identification of the targeted serum proteins found by SELDI-TOF-MS. By using this workflow, we purified ten targeted proteins from the sera of patients with various types of advanced stage (stage III–IV) cancers. These proteins were identified as isoforms of the human serum amyloid protein A (SAA) family with or without truncations at their N-terminals. This was confirmed by Western blot analysis. Different SAA expression patterns were observed by MALDI-TOF-MS profiling. SAA has long been reported as a biomarker for various cancer types such as lung cancer, ovarian cancer, and breast cancer. However, in this study we found increased SAA expression in the sera of advanced-stage cancer patients with different cancer types. Our results suggest that maybe SAA should not be used alone as a biomarker for any specific cancer type.

Effect of maternal restraint stress during gestation on temporal lipopolysaccharide-induced neuroendocrine and immune responses of progeny

The impact of gestational dam restraint stress on progeny immune and neuroendocrine temporal hormone responses to lipopolysaccharide (LPS) challenge was assessed. Maternal stress (5-min snout snare restraint stress during days 84 to 112 of gestation) increased (P < 0.05) the magnitude of tumor necrosis factor (TNF)-α, interleukin-6, epinephrine (E), norepinephrine, and serum amyloid A (SAA) production following LPS infusion in the offspring. Moreover, these effects appear to be dependent on gender for TNF-α, E, and cortisol production. However, maternal stress did not affect (P > 0.05) the normalization of proinflammatory cytokines or neuroendocrine hormones produced following LPS. Collectively, these results indicate that maternal stress impacts aspects of the proinflammatory cytokine and stress hormone response in their progeny following LPS dosing of the offspring. This response is potentially responsible in part for the resultant changes to SAA production. Because several of the changes observed here are dependent on pig gender, these results are also the first evidence that inherent epigenetic factors coupled with maternal stress impact the cumulative response to stress and LPS in young pigs.

Docosahexaenoic acid enhances hepatic serum amyloid A expression via protein kinase A-dependent mechanism

Serum amyloid A (SAA) reduces fat deposition in adipocytes and hepatoma cells. Human SAA1 mRNA is increased by docosahexaenoic acid (DHA) treatment in human cells. These studies asked whether DHA decreases fat deposition through SAA1 and explored the mechanisms involved. We demonstrated that DHA increased human SAA1 and C/EBPbeta mRNA expression in human hepatoma cells, SK-HEP-1. Utilizing a promoter deletion assay, we found that a CCAAT/enhancer-binding protein beta (C/EBPbeta)-binding site in the SAA1 promoter region between -242 and -102 bp was critical for DHA-mediated SAA1 expression. Mutation of the putative C/EBPbeta-binding site suppressed the DHA-induced SAA1 promoter activity. The addition of the protein kinase A inhibitor H89 negated the DHA-induced increase in C/EBPbeta protein expression. The up-regulation of SAA1 mRNA and protein by DHA was also inhibited by H89. We also demonstrated that DHA increased protein kinase A (PKA) activities. These data suggest that C/EBPbeta is involved in the DHA-regulated increase in SAA1 expression via PKA-dependent mechanisms. Furthermore, the suppressive effect of DHA on triacylglycerol accumulation was abolished by H89 in SK-HEP-1 cells and adipocytes, indicating that DHA also reduces lipid accumulation via PKA. The observation of increased SAA1 expression coupled with reduced fat accumulation mediated by DHA via PKA suggests that SAA1 is involved in DHA-induced triacylglycerol breakdown. These findings provide new insights into the complicated regulatory network in DHA-mediated lipid metabolism and are useful in developing new approaches to reduce body fat deposition and fatty liver.

Regulation of serum amyloid A3 (SAA3) in mouse colonic epithelium and adipose tissue by the intestinal microbiota

The gut microbiota has been proposed as an environmental factor that affects the development of metabolic and inflammatory diseases in mammals. Recent reports indicate that gut bacteria-derived lipopolysaccharide (LPS) can initiate obesity and insulin resistance in mice; however, the molecular interactions responsible for microbial regulation of host metabolism and mediators of inflammation have not been studied in detail. Hepatic serum amyloid A (SAA) proteins are markers and proposed mediators of inflammation that exhibit increased levels in serum of insulin-resistant mice. Adipose tissue-derived SAA3 displays monocyte chemotactic activity and may play a role in metabolic inflammation associated with obesity and insulin resistance. To investigate a potential mechanistic link between the intestinal microbiota and induction of proinflammatory host factors, we performed molecular analyses of germ-free, conventionally raised and genetically modified Myd88-/- mouse models. SAA3 expression was determined to be significantly augmented in adipose (9.9+/-1.9-fold; P<0.001) and colonic tissue (7.0+/-2.3-fold; P<0.05) by the presence of intestinal microbes. In the colon, we provided evidence that SAA3 is partially regulated through the Toll-like receptor (TLR)/MyD88/NF-kappaB signaling axis. We identified epithelial cells and macrophages as cellular sources of SAA3 in the colon and found that colonic epithelial expression of SAA3 may be part of an NF-kappaB-dependent response to LPS from gut bacteria. In vitro experiments showed that LPS treatments of both epithelial cells and macrophages induced SAA3 expression (27.1+/-2.5-fold vs. 1.6+/-0.1-fold, respectively). Our data suggest that LPS, and potentially other products of the indigenous gut microbiota, might elevate cytokine expression in tissues and thus exacerbate chronic low-grade inflammation observed in obesity.

Usefulness of haptoglobin and serum amyloid A proteins as biomarkers for atherothrombotic ischemic stroke diagnosis confirmation

OBJECTIVE

To identify protein biomarkers in order to classify ischemic stroke subtypes using proteomic analysis and immunoenzymatic tools for clinical validation.

METHODS AND RESULTS

We performed a proteomic analysis in serum samples of 24 patients with ischemic stroke (12 atherothrombotic patients and 12 cardioembolic patients). In this study, based on two-dimensional electrophoresis and mass spectrometry we found four spots whose expression intensity was at least four times stronger in atherothrombotic patients than in cardioembolic patients. These spots were identified as haptoglobin related protein, serum amyloid A (two spots) and haptoglobin alpha chain. We validated the possible value of haptoglobin and serum amyloid A in a larger series of patients (n=262) with ischemic stroke using ELISA techniques. Haptoglobin levels >1040microg/mL identified atherothrombotic patients with 95% sensitivity and 88% specificity whereas serum amyloid A levels >160microg/mL identified atherothrombotic patients with 91% sensitivity and 83% specificity.

CONCLUSIONS

Haptoglobin and serum amyloid A are useful biomarkers for atherothrombotic ischemic stroke diagnosis confirmation.

Therapeutic effects of triptolide on interleukin-10 gene-deficient mice with colitis

BACKGROUND

Triptolide, the principal active ingredient in the extract of Chinese herb Tripterygium wilfordii Hook , has both anti-inflammatory and immunomodulatory activities. However, the potential therapeutic role of triptolide in IBD was still unknown. Interleukin-10 deficient mice, a well characterized experimental model of inflammatory bowel disease, spontaneously developed a Th1 T cell-mediated colitis with many similarities to Crohn's disease. This study was designed to investigate the therapeutic effect of triptolide on the chronic colitis in IL-10-/- mice.

METHODS

Triptolide was intraperitoneally administrated every another day for 8 weeks to IL-10-/- mice. The gross and histological appearances of the colon, the level of inflammatory mediators and transcription factor activation in the colon were evaluated and compared with the control group.

RESULTS

The 8-week administration of triptolide resulted in a significant decrease in the severity of colitis, together with lower production of TNF-alpha ,IFN-gamma and IL-4 in colon. The level of serum amyloid A was decreased in triptolide-treated mice. Gene expressions of IL-12 and IL-23 in colon were also downregulated after treatment. Furthermore, administration of triptolide markedly reduced NF-small ka, CyrillicB activation in colon mucosa of IL-10-/- mice.

CONCLUSIONS

The efficacy of tritpolide treatment for the reduction of intestinal inflammation in IL-10-/- mice is a result of both anti-inflammatory and immunosuppressive activity. Triptolide holds significant potential for clinical applications for CD treatment.

Expression of serum amyloid A transcripts in human bone tissues, differentiated osteoblast-like stem cells and human osteosarcoma cell lines

Although the liver is the primary site of cytokine-mediated expression of acute-phase serum amyloid A (SAA) protein, extrahepatic production has also been reported. Besides its role in amyloidosis and lipid homeostasis during the acute-phase, SAA has recently been assumed to contribute to bone and cartilage destruction. However, expression of SAA in human osteogenic tissue has not been studied. Therefore, we first show that SAA1 (coding for the major SAA isoform) but not SAA2 transcripts are expressed in human trabecular and cortical bone fractions and bone marrow. Next, we show expression of (i) IL-1, IL-6, and TNF receptor transcripts; (ii) the human homolog of SAA-activating factor-1 (SAF-1, a transcription factor involved in cytokine-mediated induction of SAA genes); and (iii) SAA1/2 transcripts in non-differentiated and, to a higher extent, in osteoblast-like differentiated human mesenchymal stem cells. Third, we provide evidence that human osteoblast-like cells of tumor origin (MG-63 and SAOS-2) express SAF-1 under basal conditions. SAA1/2 transcripts are expressed under basal conditions (SAOS-2) and cytokine-mediated conditions (MG-63 and SAOS-2). RT-PCR, Western blot analysis, and immunofluorescence technique confirmed cytokine-mediated expression of SAA on RNA and protein level in osteosarcoma cell lines while SAA4, a protein of unknown function, is constitutively expressed in all osteogenic tissues investigated.

Regulation of Heparan Sulfate 6-O-Sulfation by β-Secretase Activity

The enzymes involved in glycosaminoglycan chain biosynthesis are mostly Golgi resident proteins, but some are secreted extracellularly. For example, the activities of heparan sulfate 6-O-sulfotransferase (HS6ST) and heparan sulfate 3-O-sulfotransferase are detected in the serum as well in the medium of cell lines. However, the biological significance of this is largely unknown. Here we have investigated by means of monitoring green fluorescent protein (GFP) fluorescence how C-terminally GFP-tagged HS6STs that are stably expressed in CHO-K1 cell lines are secreted/shed. Brefeldin A and monensin treatments revealed that the N-terminal hydrophobic domain of HS6ST3 is processed in the endoplasmic reticulum or cis/medial Golgi. Treatment of HS6ST3-GFP-expressing cells with various protease inhibitors revealed that the cell-permeable beta-secretase inhibitor N-benzyloxycarbonyl-Val-Leu-leucinal (Z-VLL-CHO) specifically inhibits HS6ST secretion, although this effect was specific for HS6ST3 but not for HS6ST1 and HS6ST2. However, Z-VLL-CHO treatment did not increase the molecular size of the HS6ST3-GFP that accumulated in the cell. Z-VLL-CHO treatment also induced the intracellular accumulation of SP-HS6ST3(-TMD)-GFP, a modified secretory form of HS6ST3 that has the preprotrypsin leader sequence as its N-terminal hydrophobic domain. Diminishment of beta-secretase activity by coexpressing the amyloid precursor protein of a Swedish mutant, a potent beta-secretase substrate, also induced intracellular HS6ST3-GFP accumulation. Moreover, Z-VLL-CHO treatment increased the 6-O-sulfate (6S) levels of HS, especially in the disaccharide unit of hexuronic acid-GlcNS(6S). Thus, the HS6ST3 enzyme in the Golgi apparatus and therefore the 6-O sulfation of heparan sulfates in the cell are at least partly regulated by beta-secretase via an indirect mechanism.

[Diagnostic value of serum amyloid A protein (SAA) determination]

Although serum amyloid A (SAA) was discovered almost 25 years ago, its biological role is still unknown. Similarly to C-reactive protein, SAA belongs to acute reaction proteins, synthesised in the liver after stimulation by proinflammatory cytokines like: TNFalpha, IL-1beta and IL-6. SAA level in acute inflammatory process of bacterial, mycotical, autoimmunological, oncological or extensive tissue damage is from 100 to 1000 mg/l. Additional SAA examination in patients with oncological disorders is accepted as a valuable survival index.

A patient with hyper-IgD syndrome responding to anti-TNF treatment

The hyperimmunoglobulinemia D periodic fever syndrome (HIDS) is caused by recessive mutations in the mevalonate kinase gene, which encodes an enzyme involved in cholesterol and nonsterol isoprenoid biosynthesis. The pathogenesis and treatment remains unclear. We describe a 6-year-old Turkish girl with severe disease. Her clinical features were accompanied with very high acute-phase reactants including a very high serum amyloid A level. The patient responded well to anti-tumor necrosis factor treatment. Our findings support the use of this anti-cytokine treatment in HIDS.

Inflammation-responsive transcription factor SAF-1 activity is linked to the development of amyloid A amyloidosis

Abundantly expressed serum amyloid A (SAA) protein under chronic inflammatory conditions gives rise to insoluble aggregates of SAA derivatives in multiple organs resulting in reactive amyloid A (AA) amyloidosis, a consequence of rheumatoid arthritis, Crohn's disease, ankylosing spondylitis, familial Mediterranean fever, and Castleman's disease. An inflammation-responsive transcription factor, SAF (for SAA activating factor), has been implicated in the sustained expression of amyloidogenic SAA under chronic inflammatory conditions. However, its role in the pathogenesis of AA amyloidosis has thus far remained obscure. In this paper we have shown that SAF-1, a major member of the SAF family, is abundantly present in human AA amyloidosis patients. To assess whether SAF-1 is directly linked to the pathogenesis of AA amyloidosis, we have developed a SAF-1 transgenic mouse model. SAF-1-overexpressing mice spontaneously developed AA amyloidosis at the age of 14 mo or older. Immunohistochemical analysis confirmed the nature of the amyloid deposits as an AA type derived from amyloidogenic SAA1. Furthermore, SAF-1 transgenic mice rapidly developed severe AA amyloidosis in response to azocasein injection, indicating increased susceptibility to inflammation. Also, during inflammation SAF-1 transgenic mice exhibited a prolonged acute phase response, leading to an extended period of SAA synthesis. Together, these results provide direct evidence that SAF-1 plays a key role in the development of AA amyloidosis, a consequence of chronic inflammation.

An explanation for the paradoxical induction and suppression of an acute phase response by ethanol

Binge ethanol (EtOH) consumption suppresses inflammatory responses and resistance to infection, but paradoxically it is associated with increased levels of acute phase proteins (which are indicators of inflammation) and an increased risk of inflammation-mediated pathologies such as cardiovascular disease and cirrhosis of the liver. The latter effect may be mediated by increased translocation of bacteria leading to activation of toll-like receptor 4 (TLR4). In this study, the dose-response and time course of the effects of EtOH alone or EtOH in conjunction with a TLR4 agonist (lipopolysaccharide [LPS]) were evaluated in mice. EtOH alone at a dosage of 6 g/kg induced an acute phase response (as indicated by enzyme-linked immunosorbent assay for serum amyloid A and serum amyloid P) that was maximal 24 h after dosing. Lower dosages of EtOH did not have this effect but did suppress the acute phase response to LPS and the production of interleukin-6 up to 3 h after dosing. EtOH at 6 g/kg did not induce an acute phase response in C3H/HeJ (TLR4 mutant) mice, indicating that this response is mediated through TLR4. These results provide a resolution for the apparently paradoxical pro- and anti-inflammatory actions of EtOH with regard to acute phase responses.

Extrahepatic production of acute phase serum amyloid A

Amyloidosis is a group of diseases characterized by the extracellular deposition of protein that contains non-branching, straight fibrils on electron microscopy (amyloid fibrils) that have a high content of beta-pleated sheet conformation. Various biochemically distinct proteins can undergo transformation into amyloid fibrils. The precursor protein of amyloid protein A (AA) is the acute phase protein serum amyloid A (SAA). The concentration of SAA in plasma increases up to 1000-fold within 24 to 48 h after trauma, inflammation or infection. Individuals with chronically increased SAA levels may develop AA amyloidosis. SAA has been divided into two groups according to the encoding genes and the source of protein production. These two groups are acute phase SAA (A-SAA) and constitutive SAA (C-SAA). Although the liver is the primary site of the synthesis of A-SAA and C-SAA, extrahepatic production of both SAAs has been observed in animal models and cell culture experiments of several mammalian species and chicken. The functions of A-SAA are thought to involve lipid metabolism, lipid transport, chemotaxis and regulation of the inflammatory process. There is growing evidence that extrahepatic A-SAA formation may play a crucial role in amyloidogenesis and enhances amyloid formation at the site of SAA production.

Expression of serum amyloid A transcripts in human trophoblast and fetal-derived trophoblast-like choriocarcinoma cells

The placenta comprises a highly specialized trophoblast layer, which arises from the embryo and differentiates during embryonic development to perform specialized functions, e.g., synthesis of pregnancy-associated hormones, growth factors and cytokines. As there is no evidence of maternal acute-phase protein transplacental transfer and trophoblast plays an important role in regulating immune responses at the feto-maternal interface, the expression of acute-phase serum amyloid A (A-SAA) was investigated in human first trimester trophoblast and trophoblast-like JAR and Jeg-3 choriocarcinoma cells. We here show expression of cytokine receptors and cytokine-dependent induction of A-SAA in JAR and Jeg-3 cells. While interleukin-1alpha/beta is a major agonist for A-SAA expression in JAR, tumor necrosis factor-alpha is the predominant agonist in Jeg-3. First trimester trophoblast and JAR/Jeg-3 cells further express the human homolog of SAA-activating factor-1, a transcription factor involved in cytokine-mediated induction of A-SAA genes. A-SAA1 and A-SAA2 transcripts were increased in first trimester trophoblast during pregnancy weeks 10 and 12 suggesting that A-SAA plays a role during early fetal development.

Differential influence of p38 mitogen activated protein kinase (MAPK) inhibition on acute phase protein synthesis in human hepatoma cell lines

BACKGROUND

Inhibition of intracellular signal transduction is considered to be an interesting target for treatment in inflammation. p38 MAPK inhibitors, especially, have been developed and are now in phase II clinical trials for rheumatoid arthritis (RA).

OBJECTIVE

To investigate the influence of p38 MAPK inhibition on acute phase protein (APP) production, which is dependent on both JAK/STAT and p38 MAPK pathways.

METHODS

The effects of p38 MAPK inhibition on APP production and mRNA expression in four human hepatoma cell lines was investigated, after stimulation with interleukin (IL)6 and/or IL1beta or tumour necrosis factor alpha.

RESULTS

Two out of four cell lines produced C reactive protein (CRP), especially after combined IL6 and IL1beta stimulation. CRP production was significantly inhibited by the p38 MAPK specific inhibitor RWJ 67657 at 1 micromol/l, which is pharmacologically relevant. Fibrinogen production was also inhibited at 1 micromol/l in all cell lines. Serum amyloid A (SAA) was produced in all four lines. In contrast with CRP, SAA production was not inhibited by RWJ 67657 at 1 micromol/l.

CONCLUSION

Production and mRNA expression of CRP and fibrinogen, but not SAA production and mRNA expression, were significantly inhibited by p38 MAPK specific inhibitor in hepatoma cell lines. For p38 MAPK inhibitor treatment in RA SAA might be a better marker of disease activity than CRP and fibrinogen, because SAA is not directly affected by p38 MAPK inhibition.

Differential expression and secretion of bovine serum amyloid A3 (SAA3) by mammary epithelial cells stimulated with prolactin or lipopolysaccharide

Serum amyloid A (SAA) proteins were originally identified as prominent acute phase serum reactants synthesized predominately by hepatocytes in response to infection, inflammation and trauma. In this study, we report the differential expression and secretion of serum amyloid A3 (SAA3) by bovine mammary epithelial cells following stimulation with either prolactin (PRL) or lipopolysaccharide (LPS). Reverse transcription-polymerase chain reaction analysis of PRL or LPS induced bovine mammary epithelial cells resulted in the detection of only the mammary-derived Saa3 (M-Saa3) transcript. Two-dimensional immunoblot analyses of colostrum and milk from healthy cows, as well as conditioned medium from PRL or LPS stimulated bovine mammary epithelial cells confirmed the differential production and secretion of M-SAA3 while other SAA isoforms were not detected. These data indicate that the bovine Saa3 gene is regulated differently from the other Saa genes with regard to the site of and stimulus for expression, suggesting an important tissue-specific function for bovine M-SAA3 during lactation and mammary infection.

Percutaneous coronary intervention triggers a systemic inflammatory response in patients treated for in-stent restenosis -- comparison with stable and unstable angina

OBJECTIVE AND DESIGN

It is believed that the magnitude of the systemic inflammatory response induced by percutaneous coronary intervention (PCI) impacts on the long-term outcomes in patients with stable angina (SA) and unstable angina (UA). We aimed to determine whether an inflammatory response appears in in-stent restenosis (ISR) patients undergoing balloon angioplasty and to assess its pattern and magnitude in relation to SA and UA subjects.

SUBJECTS

80 patients (59 with SA, 10 with UA, 11 with ISR) were enrolled into the prospective study.

TREATMENT

SA and UA patients undergoing single vessel coronary balloon angioplasty followed by stenting versus ISR subjects in whom only balloon angioplasty was performed.

METHODS

C-reactive protein (CRP), serum amyloid A (SAA), tumor necrosis factor alpha (TNF-alpha) and interleukin 10 (IL-10) were measured in blood samples collected before and 6, 24 h and 1 month after the procedure.

RESULTS

A comparable pattern of inflammatory response in terms of CRP and SAA concentrations in subjects undergoing PCI due to ISR and SA was discovered while in unstable patients its magnitude was substantially higher. CRP and SAA levels increased significantly in each group with the peak value at 24 h and the baseline levels remarkably correlated with the highest markers' concentrations. In contrast, preprocedural TNF-alpha concentrations were higher in ISR group when compared with SA and UA patients. Additionally, in ISR group a twofold increase in their values of borderline significance at 6 h was noted. SA and UA subjects were found to have significantly lower TNF-alpha levels at 6 and 24 h after the intervention though the marker concentrations markedly increased with peak values at 1 month. The levels of IL-10 did not differ at any time point between the groups.

CONCLUSIONS

We suggest that PCI triggers a systemic inflammatory response in patients with ISR and considerable differences in its pattern when compared with SA and UA patients were demonstrated. Moreover, a high preprocedural TNF-alpha level and its increase provoked by PCI in the ISR group warrant the need for further investigation of its possible involvement in the restenosis process.

Serum amyloid A-luciferase transgenic mice: response to sepsis, acute arthritis, and contact hypersensitivity and the effects of proteasome inhibition

Acute phase serum amyloid A proteins (A-SAAs) are multifunctional apolipoproteins produced in large amounts during the acute phase of an inflammation and also during the development of chronic inflammatory diseases. In this study we present a Saa1-luc transgenic mouse model in which SAA1 gene expression can be monitored by measuring luciferase activity using a noninvasive imaging system. When challenged with LPS, TNF-alpha, or IL-1beta, in vivo imaging of Saa1-luc mice showed a 1000- to 3000-fold induction of luciferase activity in the hepatic region that peaked 4-7 h after treatment. The induction of liver luciferase expression was consistent with an increase in SAA1 mRNA in the liver and a dramatic elevation of the serum SAA1 concentration. Ex vivo analyses revealed luciferase induction in many tissues, ranging from several-fold (brain) to >5000-fold (liver) after LPS or TNF-alpha treatment. Pretreatment of mice with the proteasome inhibitor bortezomib significantly suppressed LPS-induced SAA1 expression. These results suggested that proteasome inhibition, perhaps through the NF-kappaB signaling pathway, may regulate SAA1 expression. During the development of acute arthritis triggered by intra-articular administration of zymosan, SAA1 expression was induced both locally at the knee joint and systemically in the liver, and the induction was significantly suppressed by bortezomib. Induction of SAA1 expression was also demonstrated during contact hypersensitivity induced by topical application of oxazolone. These results suggest that both local and systemic induction of A-SAA occur during inflammation and may contribute to the pathogenesis of chronic inflammatory diseases associated with amyloid deposition.

Staphylococcus aureus lipotechoic acid induces differential expression of bovine serum amyloid A3 (SAA3) by mammary epithelial cells: Implications for early diagnosis of mastitis

Mastitis is one of the most costly diseases of agriculturally important animals and is a common problem for lactating cows. Current methods used to detect clinical and especially subclinical mastitis are either inadequate or problematic. Pathogens such as the gram-positive bacterium Staphylococcus aureus or the gram-negative bacterium Escherichia coli typically cause mastitis. E. coli induces clinical mastitis, whereas, S. aureus causes a subclinical, chronic infection of the mammary gland. In this study we report the differential expression and secretion of mammary-derived serum amyloid A3 (SAA3) by bovine mammary epithelial cells following stimulation with the S. aureus cell wall component, lipotechoic acid (LTA). Two-dimensional immunoblot analyses confirmed that bovine SAA3 is the predominant SAA isoform produced by LTA stimulated mammary epithelial cells. Our previous study showed that bovine SAA3 is also differentially expressed in response to the gram-negative bacterial endotoxin lipopolysaccharide. Collectively, these data indicate that the local production of SAA3 by mammary epithelial cells in response to either gram-positive or gram-negative bacterial components may provide a sensitive indicator for early detection and treatment of mastitis in vivo, minimizing chronic cases of infection, the spread of mastitis to other animals, and economic losses.

Distinctive serum protein profiles involving abundant proteins in lung cancer patients based upon antibody microarray analysis

Background

Cancer serum protein profiling by mass spectrometry has uncovered mass profiles that are potentially diagnostic for several common types of cancer. However, direct mass spectrometric profiling has a limited dynamic range and difficulties in providing the identification of the distinctive proteins. We hypothesized that distinctive profiles may result from the differential expression of relatively abundant serum proteins associated with the host response.

Methods

Eighty-four antibodies, targeting a wide range of serum proteins, were spotted onto nitrocellulose-coated microscope slides. The abundances of the corresponding proteins were measured in 80 serum samples, from 24 newly diagnosed subjects with lung cancer, 24 healthy controls, and 32 subjects with chronic obstructive pulmonary disease (COPD). Two-color rolling-circle amplification was used to measure protein abundance.

Results

Seven of the 84 antibodies gave a significant difference (p < 0.01) for the lung cancer patients as compared to healthy controls, as well as compared to COPD patients. Proteins that exhibited higher abundances in the lung cancer samples relative to the control samples included C-reactive protein (CRP; a 13.3 fold increase), serum amyloid A (SAA; a 2.0 fold increase), mucin 1 and α-1-antitrypsin (1.4 fold increases). The increased expression levels of CRP and SAA were validated by Western blot analysis. Leave-one-out cross-validation was used to construct Diagonal Linear Discriminant Analysis (DLDA) classifiers. At a cutoff where all 56 of the non-tumor samples were correctly classified, 15/24 lung tumor patient sera were correctly classified.

Conclusion

Our results suggest that a distinctive serum protein profile involving abundant proteins may be observed in lung cancer patients relative to healthy subjects or patients with chronic disease and may have utility as part of strategies for detecting lung cancer.

Expression of serum amyloid A, in normal, dysplastic, and neoplastic human colonic mucosa: implication for a role in colonic tumorigenesis

Serum amyloid A (SAA) is an acute phase reactant, whose level in the blood is elevated in response to trauma, infection, inflammation, and neoplasia. Elevated levels of SAA in the serum of cancer patients were suggested to be of liver origin rather than a tumor cell product. The role of SAA in human malignancies has not been elucidated. We investigated the expression of SAA at various stages of human colon carcinoma progression. Nonradioactive in situ hybridization applied on paraffin tissue sections from 26 colon cancer patients revealed barely detected SAA mRNA expression in normal looking colonic epithelium. Expression was increased gradually as epithelial cells progressed through dysplasia to neoplasia. Deeply invading colon carcinoma cells showed the highest levels of SAA. Expression was also found in colon carcinoma metastases. Cells of lymphoid follicles of the intestinal wall, inflammatory cells, ganglion cells, and endothelial cells, also expressed SAA mRNA. Immunohistochemical staining revealed SAA protein expression that colocalized with SAA mRNA expression. RT-PCR analysis confirmed the expression of the SAA1 and SAA4 genes in colon carcinomas, expression that was barely detectable in normal colon tissues. These findings indicate local and differential expression of SAA in human colon cancer tissues and suggest its role in colonic tumorigenesis.

Proteolysis of serum amyloid A and AA amyloid proteins by cysteine proteases: cathepsin B generates AA amyloid proteins and cathepsin L may prevent their formation

BACKGROUND

AA amyloidosis develops in patients with chronic inflammatory diseases. The AA amyloid proteins are proteolytic fragments obtained from serum amyloid A (SAA). Previous studies have provided evidence that endosomes or lysosomes might be involved in the processing of SAA, and contribute to the pathology of AA amyloidosis.

OBJECTIVE

To investigate the anatomical distribution of cathepsin (Cath) B and CathL in AA amyloidosis and their ability to process SAA and AA amyloid proteins.

METHODS

and results: CathB and CathL were found immunohistochemically in every patient with AA amyloidosis and displayed a spatial relationship with amyloid in all the cases studied. Both degraded SAA and AA amyloid proteins in vitro. With the help of mass spectrometry 27 fragments were identified after incubation of SAA with CathB, nine of which resembled AA amyloid proteins, and seven fragments after incubation with CathL. CathL did not generate AA amyloid-like peptides. When native human AA amyloid proteins were used as a substrate 26 fragments were identified after incubation with CathB and 18 after incubation with CathL.

CONCLUSION

The two most abundant and ubiquitously expressed lysosomal proteases can cleave SAA and AA amyloid proteins. CathB generates nine AA amyloid-like proteins by its carboxypeptidase activity, whereas CathL may prevent the formation of AA amyloid proteins by endoproteolytic activity within the N-terminal region of SAA. This is particularly interesting, because AA amyloidosis is a systemic disease affecting many organs and tissue types, almost all of which express CathB and CathL.

Serum amyloid A production by chicken fibroblast-like synoviocytes

In brown chicken with chronic inflammatory processes of the joints amyloid arthropathy easily develops. The amyloid has been shown to be of the AA type which is derived from serum amyloid A (SAA). The aim of the present study was to investigate whether fibroblast-like synoviocytes (FLS) originating from brown chicken and other chicken breeds express SAA mRNA and produce SAA protein. FLS were isolated from the knee joint synovium of healthy brown chickens, white chickens, and broilers. The absence of macrophages in FLS cultures was confirmed by assessment of the phagocytic capability and by immunohistochemistry. Additionally, cultured cells were identified by electron microscopy and immunohistochemical staining. Expression of SAA mRNA in normal and lipopolysaccharide (LPS)-stimulated cells was assessed by in situ hybridization, Northern blot analysis, reverse transcriptase-polymerase chain reaction (RT-PCR), Southern blot analysis and real-time quantitative PCR. SAA protein production was analyzed by Western blotting and ELISA. SAA mRNA was detected in unstimulated FLS isolated from the three different chicken breeds and more abundantly in those stimulated with LPS. However, SAA protein production was only detected in culture medium and cell lysate of LPS-stimulated FLS. Furthermore, FLS produced SAA in a concentration-dependent manner after stimulation with different amounts of LPS. The data suggest that during infection and inflammation chicken FLS may act as a source of articular SAA. This process may enhance development of amyloid from SAA in the joint.

A microarray search for genes predominantly expressed in human omental adipocytes: adipose tissue as a major production site of serum amyloid A

To identify genes predominantly expressed in omental adipocytes, microarray expression profiles from 33 human tissues or cell types were analyzed, using an algorithm developed for identification of transcripts predominantly expressed in a certain tissue. Both known adipocyte-specific and more unexpected genes were among the 28 genes identified. To validate the approach, adipocyte expression of three of these genes, acute-phase serum amyloid A (A-SAA), aquaporin 7, and transport secretion protein-2.2, was compared with 17 other human tissues by real-time PCR. The unexpectedly high expression of A-SAA in adipocytes was further verified by Northern blot and immunohistochemistry. The liver, reported to be the main production site for A-SAA, displayed the second highest expression using microarray and real-time PCR. In obese subjects, adipose tissue mRNA and serum A-SAA levels were down-regulated during an 18-wk diet regime (P < 0.05 and P < 0.0001, respectively). A-SAA serum levels were highly correlated to adipose tissue mRNA levels (P < 0.001) and to the total (P < 0.0001) and sc (P < 0.0001) adipose tissue areas, as analyzed by computed tomography. We show that adipose tissue is a major expression site of A-SAA during the nonacute-phase reaction condition. This provides a direct link between adipose tissue mass and a marker for low-grade inflammation and cardiovascular risk.

Serum amyloid A protein binds to outer membrane protein A of gram-negative bacteria

Serum amyloid A (SAA) is the major acute phase protein in man and most mammals. We observed SAA binding to a surprisingly large number of Gram-negative bacteria, including Escherichia coli, Salmonella typhimurium, Shigella flexneri, Klebsiella pneumoniae, Vibrio cholerae, and Pseudomonas aeruginosa. The binding was found to be high affinity and rapid. Importantly, this binding was not inhibited by high density lipoprotein with which SAA is normally complexed in serum. Binding was also observed when bacteria were offered serum containing SAA. Ligand blots following SDS-PAGE or two-dimensional gels revealed two major ligands of 29 and 35 kDa that bound SAA when probing with radiolabeled SAA or SAA and monoclonal anti-SAA. Following fractionation the ligand was found in the outer membrane fraction of E. coli and was identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry to be outer membrane protein A (OmpA). OmpA-deficient E. coli did not bind SAA, and following purification of OmpA the protein retained binding activity. The ligands on other bacteria were likely to be homologues of OmpA because wild type, but not OprF-deficient, P. aeruginosa bound SAA.

An active metabolite of leflunomide, A77 1726, inhibits the production of serum amyloid A protein in human hepatocytes

OBJECTIVE

Cytokine-induced hepatic serum amyloid A (SAA) synthesis is the critical step in the pathogenesis of AA amyloidosis secondary to rheumatoid arthritis (RA). This study was conducted to provide more insight into the mechanism of SAA production in hepatocytes and its regulation.

METHODS

Primary cultured normal human hepatocytes were stimulated with cytokines (IL-1beta, TNF-alpha and IL-6) and the culture supernatants were analysed for the production of SAA. Human hepatocytes, treated or not treated with A77 1726, were stimulated with IL-1beta and the cellular lysates were analysed by immunoblot using anti-phospho-specific mitogen-activated protein kinase (MAPK) and IkappaB-alpha. Acute phase-SAA (SAA1) mRNA expression was analysed by reverse transcription-polymerase chain reaction.

RESULTS

IL-1beta is a most potent inducer of SAA in normal hepatocytes. A77 1726 suppressed the production of SAA in human hepatocytes activated by IL-1beta in a dose-dependent manner (0-50 microM). A77 1726 inhibited IL-1beta-induced p38 and c-Jun N-terminal kinase 1/2 (JNK1/2) activation, whereas A77 1726 did not affect IL-1beta-induced NF-kappaB activation in hepatocytes.

CONCLUSION

These results indicate that MAPK signalling pathways are critical in IL-1beta-induced hepatic SAA synthesis. Leflunomide may suppress SAA synthesis by affecting these pathways and may therefore have some beneficial effect on AA amyloidosis secondary to RA.

Expression of serum amyloid A in chondrocytes and myoblasts differentiation and inflammation: possible role in cholesterol homeostasis

Serum amyloid A (SAA) is synthesized by the liver during the acute phase. Local expression of SAA mRNA has been reported also in non-liver cells, a potential local source of SAA protein not related to the systemic acute phase response. SAA function has not been established yet. In the present study, we identified SAA as a protein expressed by chondrocytes and myoblasts in response to inflammatory stimula. In both cell systems, SAA mRNA and protein expression is strongly stimulated by bacterial lipopolysaccharide treatment. SAA mRNA expression is also enhanced during terminal differentiation of cells of the chondrogenic and myogenic lineage; mRNA is barely detectable in prechondrogenic cells and is highly expressed in differentiated hyperthrophic chondrocytes. An increased level of SAA mRNA was also observed in vivo when we compared mRNA extracted from tibiae of 10 day embryos, still fully cartilaginous, with tibiae from 18 day embryos, a stage when the endochondral ossification process has already started. p38 activation, a well-known event of the chondrogenesis signaling cascade, controls expression of SAA in cartilage following inflammatory stimuli. SAA secreted by stimulated chondrocytes is associated with cholesterol. Cholesterol is synthesized by the same chondrocytes and is also increased in inflammatory conditions. A role of SAA in cholesterol homeostasis in chondrocytes is proposed.

Cholesterol secretion and homeostasis in chondrocytes: a liver X receptor and retinoid X receptor heterodimer mediates apolipoprotein A1 expression

Cholesterol is required for chondrocyte differentiation and bone formation. Apolipoprotein A1 (apoA-1) plays a major role in lipoprotein clearance and cholesterol redistribution. We report here that apoA-1 is expressed during chondrocyte differentiation in vitro and in vivo. In differentiating chondrocytes, the expression of the liver X receptor (LXR) is modulated and its expression correlates to the expression of apoA-1. The expression of other LXR target genes related to cholesterol homeostasis such as ABCA1 cholesterol transporter and sterol regulatory element-binding protein 1 (SREBP1) is similarly regulated. Small molecule ligands activating either LXR or retinoid X receptor (RXR) lead to a dramatic increase in apoA-1 mRNA and protein expression in cultured chondrocytes. These ligands strongly induce ABCA1 cholesterol transporter expression and effectively mediate cholesterol efflux from hypertrophic chondrocytes. In addition, we report that, in the same cells, the ligands down modulate Serum Amyloid A expression induced by bacterial lipopolysaccharide. Our studies provide evidence that LXR/RXR mediate a fine regulation of cholesterol homeostasis in differentiating chondrocytes.

Syntaxin 5 interacts with presenilin holoproteins, but not with their N- or C-terminal fragments, and affects beta-amyloid peptide production

Mutations in presenilins 1 and 2 (PS1 and PS2) account for the majority of cases of early-onset familial Alzheimer's disease. However, the trafficking and interaction of PSs with other proteins in the early secretory pathways are poorly understood. Using co-immunoprecipitation, we found that PS bound to Syx5 (syntaxin 5), which is a target-soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor involved in endoplasmic reticulum (ER)-Golgi vesicular transport in vivo. Syx5 interacted only with the full-length PS holoproteins and not with the naturally occurring N- or C-terminal fragments. The PS holoproteins co-immunoprecipitated with the mutant Syx5, which localized to the ER and Golgi compartments, despite the substitution of the transmembrane region with that of syntaxin 1A. In contrast, the transmembrane deletion mutant that localized to the cytosol, but not to the ER or Golgi compartments, did not co-immunoprecipitate the PS holoproteins. The PS1 variant linked to familial Alzheimer's disease (PS1DeltaE9), lacking the region that contains the endoproteolytic cleavage site in the cytoplasmic loop, showed markedly decreased binding to Syx5. Immunofluorescence and sucrose-density-gradient fractionation analyses showed that the full-length PS holoproteins co-localized with Syx5 to the ER and cis-Golgi compartments. Furthermore, Syx5 overexpression resulted in the accumulation of PS holoproteins and the beta-amyloid precursor protein, and reduced the secretion of the Abeta (amyloid beta) peptide in COS-7 cells. In summary, these results indicate that Syx5 binds to full-length PSs and affects the processing and trafficking of beta-amyloid precursor protein in the early secretory compartments.

Serum amyloid A binding to CLA-1 (CD36 and LIMPII analogous-1) mediates serum amyloid A protein-induced activation of ERK1/2 and p38 mitogen-activated protein kinases

Serum amyloid A protein (SAA) is an acute-phase reactant, known to mediate pro-inflammatory cellular responses. This study reports that CLA-1 (CD36 and LIMPII Analogous-1; human orthologue of the Scavenger Receptor Class B Type I (SR-BI)) mediates SAA uptake and downstream SAA signaling. Flow cytometry experiments revealed more than a 5-fold increase of Alexa-488 SAA uptake in HeLa cells stably transfected with CLA-1. Alexa 488-HDL uptake directly correlated with SAA uptake when determined in several CLA-1 stably transfected HeLa cell clones expressing various levels of CLA-1. SAA directly binds to CLA-1 as determined by cross-linking and colocalization of anti-CLA-1 antibody with SAA. SAA was co-internalized with transferrin to the endocytic recycling compartment pointing to a potential site of SAA metabolism. Alexa-488 SAA uptake in the CLA-1-overexpressing HeLa cells, as well as in THP-1 monocyte cell line, can be efficiently blocked by unlabeled SAA, high density lipoprotein, and other CLA-1 ligands. At the same time, markedly enhanced levels of phosphorylation of the mitogen-activated protein kinases (MAPKs), ERK1/2, and p38, were observed in cells stably transfected with CLA-1 cells following SAA stimulation when compared with mock transfected cells. The levels of the SAA-induced interleukin-8 (IL-8) secretion by CLA-1-overexpressing cells also significantly exceeded (5- to 10-fold) those detected for control cells. Synthetic amphipathic peptides possessing a structural alpha-helical motif inhibited SAA-induced activation of both MAPKs and IL-8 secretion in THP-1 cells. The results of this study demonstrate for the first time that CLA-1 functions as an endocytic SAA receptor and is involved in SAA-mediated cell signaling events associated with the immune-related and inflammatory effects of SAA.

Serum amyloid A is a ligand for scavenger receptor class B type I and inhibits high density lipoprotein binding and selective lipid uptake

Serum amyloid A is an acute phase protein that is carried in the plasma largely as an apolipoprotein of high density lipoprotein (HDL). In this study we investigated whether SAA is a ligand for the HDL receptor, scavenger receptor class B type I (SR-BI), and how SAA may influence SR-BI-mediated HDL binding and selective cholesteryl ester uptake. Studies using Chinese hamster ovary cells expressing SR-BI showed that (125)I-labeled SAA, both in lipid-free form and in reconstituted HDL particles, functions as a high affinity ligand for SR-BI. SAA also bound with high affinity to the hepatocyte cell line, HepG2. Alexa-labeled SAA was shown by fluorescence confocal microscopy to be internalized by cells in a SR-BI-dependent manner. To assess how SAA association with HDL influences HDL interaction with SR-BI, SAA-containing HDL was isolated from mice overexpressing SAA through adenoviral gene transfer. SAA presence on HDL had little effect on HDL binding to SR-BI but decreased (30-50%) selective cholesteryl ester uptake. Lipid-free SAA, unlike lipid-free apoA-I, was an effective inhibitor of both SR-BI-dependent binding and selective cholesteryl ester uptake of HDL. We have concluded that SR-BI plays a key role in SAA metabolism through its ability to interact with and internalize SAA and, further, that SAA influences HDL cholesterol metabolism through its inhibitory effects on SR-BI-mediated selective lipid uptake.

Lipopolysaccharide signaling induces serum amyloid A (SAA) synthesis in human hepatocytes in vitro

To investigate the role of lipopolysaccharide (LPS) in hepatocyte activation, we examined the expression of Toll-like receptor 4 (TLR4), the putative receptor for LPS in human hepatocytes. TLR4 mRNA and protein expression was confirmed in human hepatocytes. Stimulation of human hepatocytes with LPS results in rapid degradation of IkappaB-alpha and mitogen activated protein kinase activation. Human hepatocytes stimulated by LPS produced serum amyloid A protein. Our data suggest that human hepatocytes utilize components of TLR4 signal transduction pathways in response to LPS and these direct LPS-mediated effects on hepatocytes may contribute to liver inflammation and injury.

Tumor necrosis factor-alpha induces serum amyloid A3 in mouse granulosa cells

TNF-alpha has significant inhibitory effects on steroidogenesis and folliculogenesis and is associated with several inflammatory responses. Because ovulation is an inflammatory reaction, the effects of TNF on the family of acute-phase proteins in granulosa cells were investigated. Granulosa cells from immature mice at 28 d of age were cultured in the presence of 10 ng TNF/ml for 24 h. Serum amyloid A3 (SAA3), a main acute-phase protein, was induced by TNF in granulosa cells. The other isoforms of serum amyloid proteins SAA1, SAA2, and SAA4 were neither expressed in granulosa cells nor induced by TNF. TNF did not induce SAA3 mRNA in granulosa cells from TNF receptor type 1 (TNFR1) knockout mice, although SAA3 mRNA was induced within 3 h after TNF treatment in wild-type cells. Two SAA3 promoters, -617/+73 and -198/+73, were responsive to TNF and to p65, a component of the TNF signaling molecule nuclear factor (NF)-kappaB. The -106/+73 promoter of SAA3 lacking a NF-kappaB-like site was not responsive to TNF or p65. In granulosa cells from TNFR1 knockout mice, the SAA3 promoter (-198/+73) was responsive to transfection with the p65 component of NF-kappaB, but neither TNF treatment nor overexpression of the p50 component of NF-kappaB increased promoter activity. Similar results were observed in the murine ovarian granulosa tumor cell line (OV3121-1). Overexpression of the inhibitor of NF-kappaB (called IkappaB) blocked SAA3 promoter activity induced by TNF and by p65 in OV3121-1 cells. Closer analysis of deletion mutants of the SAA3 promoter revealed the necessity of a NF-kappaB like site for responsiveness to TNF in the OV3121-1 cells. TNF rapidly increased p65 in OV3121-1 nuclei when compared with controls not treated with TNF. TNF also increased phospho-IkB and SAA3 in whole-cell homogenates as determined by Western blots. Thus, TNF likely increased SAA3 promoter activity and protein by activating NF-kappaB signaling via TNFR1 in mouse granulosa cells. SAA3 is a novel gene in granulosa cells with yet unknown functions in the ovary.

Regulation of the human acute phase serum amyloid A genes by tumour necrosis factor-alpha, interleukin-6 and glucocorticoids in hepatic and epithelial cell lines

The major acute-phase protein serum amyloid A, A-SAA, is upregulated by a variety of inflammatory stimuli, including cytokines and glucocorticoids (GCs). Elevated systemic concentrations of both A-SAA and tumour necrosis factor (TNF)-alpha are a feature of inflammatory diseases, such as rheumatoid arthritis and inflammatory bowel disease. Here, we examine the roles of TNF-alpha, interleukin-6 (IL-6) and GCs on the transcriptional regulation of the two human A-SAA genes (SAA1 and SAA2) and show that these stimuli have different effects on the SAA1 and SAA2 promoters in HepG2 hepatoma and KB epithelial cell lines. Both genes are induced modestly by TNF-alpha and IL-6 alone and synergistically by TNF-alpha plus IL-6. The TNF-driven induction of SAA1, but not that of SAA2, can be enhanced by GCs in both cell lines, whereas GCs alone can upregulate SAA1 only in epithelial cells. The upregulation of both genes by cytokines, and of SAA1 by GCs, is more rapid in epithelial cells than hepatoma cells. We established that the order in which either cell line was treated with TNF-alpha and IL-6 influenced A-SAA promoter transcriptional activation. Treatment with TNF-alpha followed by IL-6 resulted in a much greater induction of both A-SAA genes than treatment with IL-6 followed by TNF-alpha.

Involvement of CD14 and Toll-Like Receptor 4 in the Acute Phase Response of Serum Amyloid A Proteins and Serum Amyloid P Component in the Liver After Burn Injury

Acute phase proteins such as serum amyloid A proteins (SAAs) and serum amyloid P component (SAP) are induced in the liver after various insults (e.g., infection, injury). The cellular and molecular mechanisms controlling the expression of these acute phase proteins may be specifically designed for different insults. The roles of two central molecules of the lipopolysaccharide (LPS)-mediated inflammation pathway (CD14 and toll-like receptor 4 [Tlr4]) were investigated for the regulation of SAAs and SAP in the liver of mice after an 18% total body surface area burn injury. RT-PCR analysis revealed a subtype- and time-dependent induction of SAA mRNAs between 3 h and 3 days, while there was a peak induction of SAP mRNA at day 1. Marked elevations of SAA and SAP protein levels at day 1 supported the mRNA data. Furthermore, a differential regulation of SAAs and SAP mRNAs was noted between CD14 knockout (KO) and their control mice after injury. SAA protein was induced to a lesser degree after injury in C3H/HeJ (Tlr4-defective) mice than in their control mice. In addition, in both CD14 KO and C3H/HeJ mice, the induction of SAP protein was significantly reduced compared with respective controls. These data provide evidence that CD14 and Tlr4 participate, at least in part, in a cascade of signaling events that control the immediate-early and differential induction of SAAs and SAP in the liver after injury. They also suggest that LPS may be one of the initial inducing agents associated with these acute phase responses in the liver after injury.

Cholesterol and cholate components of an atherogenic diet induce distinct stages of hepatic inflammatory gene expression

Atherosclerosis in inbred mouse strains has been widely studied by using an atherogenic (Ath) diet containing cholesterol, cholic acid, and fat, but the effect of these components on gene expression has not been systematically examined. We employed DNA microarrays to interrogate gene expression levels in liver of C57BL/6J mice fed the following five diets: mouse chow, the Ath diet, or modified versions of the Ath diet in which either cholesterol, cholate, or fat were omitted. Dietary cholesterol and cholate produced discrete gene expression patterns. Cholesterol was required for induction of genes involved in acute inflammation, including three genes of the serum amyloid A family, three major histocompatibility class II antigen genes, and various cytokine-related genes. In contrast, cholate induced expression of genes involved in extracellular matrix deposition in hepatic fibrosis, including five collagen family members, collagen-interacting proteins, and connective tissue growth factor. The gene expression findings were confirmed by biochemical measurements showing that cholesterol was required for elevation of circulating serum amyloid A, and cholate was required for accumulation of collagen in the liver. The possibility that these gene expression changes are relevant to atherogenesis in C57BL/6J mice was supported by the observation that the closely related, yet atherosclerosis-resistant, C57BL/6ByJ strain was largely resistant to dietary induction of the inflammatory and fibrotic response genes. These results establish that cholesterol and cholate components of the Ath diet have distinct proatherogenic effects on gene expression and suggest a strategy to study the contribution of acute inflammatory response and fibrogenesis independently through dietary manipulation.

Inhibition of IFN-gamma-inducible protein-10 abrogates colitis in IL-10-/- mice

A deficiency in understanding the steps responsible for colitis is the lack of comprehension for the role chemokines play in mucosal inflammation. IFN-gamma-inducible protein-10 (IP-10) and CXCR3 are highly expressed at sites of colitis. Our findings show that IP-10 significantly contributes to the development of Th1 and inflammatory responses. Specifically, IP-10 inhibition in IL-10(-/-) mice attenuates the associated increases in serum and/or local amyloid A, IL-2, IL-6, TNF-alpha, IFN-gamma, IL-1alpha, and IL-1beta with colitis as compared with IL-10(-/-) mice that develop colitis similar to human Crohn's disease. Correspondingly, the rate or intensity of inflammation in IL-10(-/-) mice treated with anti-IP-10 Abs showed improved scoring of inflammation, compared with control IL-10(-/-) mice. This study provides important and novel information regarding IP-10 as a target for the treatment of colitis.

Amyloid-enhancing factor mediates amyloid formation on fibroblasts via a nidus/template mechanism

OBJECTIVE

To determine the mechanism by which amyloid-enhancing factor (AEF) promotes amyloid deposition, and to test whether AEF seeds deposition of serum amyloid A (SAA) and facilitates conversion to beta-sheet structure.

METHODS

Fibroblasts were cultured with mouse recombinant SAA1.1 and AEF, SAA1.1, or AEF. AEF was prepared as a glycerol extract of spleen from amyloidotic mice. Amyloid was identified by staining with Congo red and examining for green birefringence under polarized light. SAA was localized immunohistochemically. Texas Red-labeled SAA was visualized in living cultures by fluorescence confocal microscopy. AEF was characterized by Western blot analysis using anti-SAA antiserum and N-terminal sequence analysis. Subunits comprising amyloid in fibroblast cultures were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

RESULTS

Amyloid was produced in fibroblast cultures by an AEF-dependent mechanism. AEF, added to culture medium as insoluble protein precipitates, adhered to fibroblast monolayers. SAA bound preferentially to the adherent precipitates. Coincident with SAA binding, precipitates developed an affinity for Congo red. Over time, as more SAA was added, networks of Congo red-positive material producing bright green birefringence also developed outward from AEF precipitates. Amyloid built upon AEF in this manner was composed of full-length SAA. No amyloid was produced in cultures treated with either SAA or AEF alone. SAA and SAA peptides processed in the C-terminal region were the most prominent proteins in the glycerol-extracted AEF preparation.

CONCLUSION

AEF binds to fibroblast monolayers and acts as a sink for SAA. SAA that collects on AEF assembles into an amyloid structure. Thus, it is concluded that AEF serves as both a nidus and a template for amyloid formation.

TRAF6-NF-kappaB pathway is essential for interleukin-1-induced TLR2 expression and its functional response to TLR2 ligand in murine hepatocytes

We have previously reported that the expressions of TLR2 and TLR4 mRNA are differentially regulated in mouse liver and in the parenchymal cells. In the present study, we investigated the mechanism of the up-regulatory effects of interleukin-1alpha (IL-1alpha), tumour necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS), or bacterial lipoprotein (BLP) on TLR2 mRNA expression in primary cultured murine hepatocytes. Although TLR2 mRNA stability was not affected, these treatments enhanced NF-kappaB activity and TLR2 gene transcription simultaneously. The up-regulation of TLR2 transcription in response to these reagents was completely inhibited by blocking the NF-kappaB activation pathway, demonstrating a pivotal role of NF-kappaB activation in the regulation of hepatocyte TLR2 transcription. The expression of TLR2 protein by hepatocytes was also remarkably up-regulated by IL-1alpha and, to a lesser extent, by TNF-alpha as well, but not by LPS or BLP. In addition, pretreatment of mice with IL-1alpha markedly increased the BLP (a ligand for TLR2)-induced serum level of serum amyloid A (SAA), an acute-phase protein predominantly produced by hepatocytes, indicating that IL-1alpha may also up-regulate functional TLR2 in vivo. These results demonstrate that IL-1alpha, through activating the TRAF6-NF-kappaB pathway, serves as the most potent inducer for TLR2 up-regulation, and plays an important role in the regulation of hepatocyte functions by augmenting the hepatocyte response to bacteria or bacterial products.

Human secretory phospholipase A2 mediates decreased plasma levels of HDL cholesterol and apoA-I in response to inflammation in human apoA-I transgenic mice

OBJECTIVE

Plasma levels of high density lipoprotein (HDL) cholesterol and apolipoprotein (apo)A-I are decreased in inflammatory states. Secretory phospholipase A2 (sPLA2), an acute-phase protein, may play a key role in the pathophysiology of this phenomenon.

METHODS AND RESULTS

To investigate the effects of sPLA2 on human-like HDL particles in vivo, we generated transgenic mice overexpressing human apoA-I and human sPLA2 (apoA-I/sPLA2 mice). Compared with apoA-I mice, apoA-I/sPLA2 mice had significantly lower plasma levels of phospholipids, HDL cholesterol, and apoA-I (each P<0.01). HDL from apoA-I/sPLA2 mice was significantly depleted in phospholipids and cholesteryl esters (each P<0.001) but was enriched in protein and triglycerides (each P<0.001). As assessed by gel filtration and nondenaturing gel electrophoresis, sPLA2 overexpression in apoA-I mice resulted in a dramatic shift of the HDL particle size toward smaller particles. Furthermore, virtually all plasma sPLA2 in apoA-I/sPLA2 mice was found in association with the HDL fraction. The acute-phase response was induced in apoA-I/sPLA2 double-transgenic and apoA-I single-transgenic mice by intraperitoneal lipopolysaccharide (LPS) injection. Plasma sPLA2 was significantly increased after LPS injection in apoA-I/sPLA2 mice. Twelve hours after LPS administration, plasma total cholesterol, HDL cholesterol, apoA-I, and phospholipids were unchanged in apoA-I transgenic control mice but had decreased significantly in the apoA-I/sPLA2 mice (-57%, -62%, and -54%, -61%, respectively; each P<0.001). Both groups of mice had increased plasma levels of serum amyloid A (SAA) in response to LPS. To test the hypothesis that SAA may be an in vivo activator of sPLA2, we specifically overexpressed SAA in apoA-I/sPLA2 mice by means of liver-directed gene transfer. Despite high plasma levels of SAA, plasma lipid and lipoprotein profiles were not different than those in control mice.

CONCLUSIONS

These results in a mouse model of human-like HDL indicate that sPLA2 expression significantly influences HDL particle size and composition and demonstrate that an induction of sPLA2 is required for the decrease in plasma HDL cholesterol in response to inflammatory stimuli in mice and that this effect is independent of SAA.

Differential glucocorticoid enhancement of the cytokine-driven transcriptional activation of the human acute phase serum amyloid A genes, SAA1 and SAA2

The human acute phase serum amyloid A (A-SAA) genes, SAA1 and SAA2, have a high degree of sequence identity that extends approximately 450 bp upstream of their transcription start sites. Each promoter contains analogously positioned functional binding sites for the transcription factors NF-kappaB and NF-IL6. In human HepG2 hepatoma cells transfected with SAA promoter luciferase reporter constructs, administration of IL-1 and IL-6, singly or in combination, induced SAA1 and SAA2 transcriptional readouts that were qualitatively indistinguishable. However, under induced conditions, the SAA2 promoter had a significant quantitative transcriptional advantage over the SAA1 promoter. The application of the synthetic glucocorticoid dexamethasone in the context of cytokine stimulation enhanced the transcriptional activity of the SAA1, but not the SAA2, promoter such that readout from the former became equivalent to that from the latter. A putative glucocorticoid response element (GRE) is present (between residues -208 and -194) only in the SAA1 gene; a similar sequence in the corresponding region of the SAA2 gene is disrupted by a nine-residue insertion. The SAA1 GRE was shown to be functionally active and the SAA2 disrupted GRE was shown to be functionally inactive in experiments using reporter constructs carrying SAA1 and SAA2 promoters that had been modified by site-specific mutagenesis. Quantitative analysis of transcript-specific RT-PCR products, derived from SAA1 and SAA2 mRNAs after treatment of HepG2 cells with cytokines in the presence or absence of dexamethasone, confirmed that the endogenous SAA1 gene has a cytokine-driven transcriptional disadvantage that is superseded by a marginal transcriptional advantage when glucocorticoids are present.

Decreases of apolipoprotein B-100 and A-I concentrations and induction of haptoglobin and serum amyloid A in nonfed calves

Reduced feed intake near parturition is suggested to be one of the major causal factors for the development of fatty liver in cows, and nonfeeding has been used as an experimental model for fatty liver. In cows with fatty liver, concentrations of lipoprotein lipids and proteins are decreased. In addition, the acute-phase protein haptoglobin is induced. The purpose of the present study was to examine whether the decrease of lipoprotein concentrations and the induction of acute-phase proteins were similarly reproduced by non-feeding. Holstein female calves (n=5) were nonfed for 3 days and thereafter refed. Serum concentrations of nonesterified fatty acids and beta-hydroxybutyric acid were initially increased by the nonfeeding, and followed by decreases in concentrations of cholesteryl esters, phospholipids, apolipoprotein (apo) B-100 and apoA-I. The apoC-III concentration was not distinctly decreased. Haptoglobin and serum amyloid A were induced during the nonfeeding and refeeding process. Haptoglobin was distributed in different proportions in the high-density lipoprotein, very high-density lipoprotein and the lipoprotein-deficient fractions, whereas almost all serum amyloid A was associated with the high-density lipoprotein fraction. These results suggest that the decreases in lipoprotein concentrations and induction of acute-phase proteins found in cows with fatty liver and those with fatty liver-related diseases such as ketosis are primarily due to the reduced feed intake near parturition.

Markers of inflammation and coronary artery disease

Many recent experimental and clinical studies have provided evidence for the presence of inflammation in atherosclerotic lesions. Ongoing inflammatory reactions within coronary atherosclerotic plaques are increasingly thought to be crucial determinants of the clinical course of patients with coronary artery disease (CAD). These facts lead to a search for reliable markers reflecting the inflammatory process in the atherosclerotic plaques. Circulating markers may consist of cytokines directly released from inflammatory cells present in the plaques and tissues exposed to recurrent ischemia as well as other reactants produced in response to these cytokines such as adhesion molecules and acute phase proteins. Recent studies suggest that markers of inflammation may reflect different aspects of the atherothrombotic process at different points in the continuum of acute coronary syndromes, have a potential role for the prediction of risk for developing CAD, and may correlate with severity and future risk for CAD. In spite of these findings, the clinical utility of measuring these markers is limited by the availability of reproducible diagnostic test assays. In addition, it remains to be determined whether markers of inflammation actually have a causal relation with cardiovascular disease, or simply reflect the underlying disease process. Such determination becomes important with the potential use of these markers in targeting preventive therapies. Therefore, further well-designed prospective evaluation of each of these markers is needed before their use in routine practice.

Elevated extrahepatic expression and secretion of mammary-associated serum amyloid A 3 (M-SAA3) into colostrum

Mammary-associated serum amyloid A 3 (M-SAA3) was secreted at highly elevated levels in bovine, equine and ovine colostrum and found at lower levels in milk 4 days postparturition. N-terminal sequencing of the mature M-SAA3 protein from all the three species revealed a conserved four amino acid motif (TFLK) within the first eight residues. This motif has not been reported to be present in any of the hepatically-produced acute phase SAA (A-SAA) isoforms. Cloning of the bovine M-Saa3 cDNA from mammary gland epithelial cells revealed an open reading frame that encoded a precursor protein of 131 amino acids which included an 18 amino acid signal peptide. The predicted 113 residue mature M-SAA3 protein had a theoretical molecular mass of 12,826Da that corresponded with the observed 12.8kDa molecular mass obtained for M-SAA3 in immunoblot analysis. The high abundance of this extrahepatically produced SAA3 isoform in the colostrum of healthy animals suggests that M-SAA3 may play an important functional role associated with newborn adaptation to extrauterine life and possibly mammary tissue remodeling.

Hyperglycemia-induced production of acute phase reactants in adipose tissue

Chronic elevation of systemic levels of acute phase reactants and inflammatory cytokines found in patients with diabetes and the often-associated metabolic syndrome X (hypertriglyceridemia, low serum high density lipoprotein cholesterol, hypertension, and accelerated atherosclerosis) may be responsible for the increased incidence of cardiovascular problems in this population. Here we examine the contribution of adipose tissue to the systemic elevation of acute phase reactants associated with chronic hyperglycemia. We demonstrate that adipose tissue expresses a number of acute phase reactants at high levels, including serum amyloid A3 (SAA3), alphal-acid glycoprotein, the lipocalin 24p3 as well as plasminogen activator inhibitor-1 (PAI-1). Additionally, we show SAA3 is expressed at low levels under normal conditions but in the diabetic state is dramatically up-regulated in adipose tissue while down-regulated in liver. Furthermore, pro-inflammatory stimuli and high glucose can lead to the induction of SAA3 in adipose tissue in vivo as well as in the 3T3-L1 adipocyte cell line. Adipose tissue may therefore play a major role in the pathogenic sequelae of Type II diabetes, in particular the cardiovascular problems associated with prolonged hyperglycemia.

Expression of serum amyloid A genes in mouse brain: unprecedented response to inflammatory mediators

Serum amyloid A (SAA) proteins were originally identified as prominent acute-phase serum proteins synthesized predominantly by hepatocytes. These small proteins are remarkably lipophilic, and we have sought evidence for their synthesis in mouse brain. RT-PCR showed constitutive expression of the murine SAA1 gene in the brains of normal BALB/cJ mice. After intracerebral inoculation with Sindbis virus, these mice predictably increase brain expression of tumor necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta), and IL-6. However, brain SAA1 expression fell after injecting either virus or control saline and remained low despite increases in TNF-alpha and IL-6, which are known to induce its expression in hepatocytes. Our data thus show that expression of the murine SAA1 gene has different, unprecedented control in mouse brain, suggesting that the protein itself may have a different physiological role there.