Serum amyloid A in geese; cloning and expression of recombinant protein

We defined the nucleotide-sequence of the full-length goose serum amyloid A and compared it to SAA sequences of the duck. The aim of this work was to clone and express recombinant goose SAA and to produce antibody against this protein: Total RNA was isolated from goose liver and used to synthesise first strand cDNA. The coding region of the goose SAA cDNA was amplified by PCR using primers corresponding to the appropriate conservative regions of duck SAA mRNA. The product was subcloned into pET-15b expression vector to result in a His*Tag fusion protein expression. The protein was purified by affinity chromatography. Rabbits were then immunized against the recombinant purified goose SAA protein. The anti-SAA serum was tested by Western blotting. Full-length goose SAA mRNA sequence has been obtained and sequenced.

[Inflammatory markers; C-reactive protein (CRP) and serum amyloid A (SAA)]

C-reactive protein (CRP) and serum amyloid A (SAA) are sensitive acute phase reactants. Both, but predominantly CRP in Japan, have long been used for monitoring inflammatory diseases. During the recent wave of measuring both at low concentration ranges and utilizing these values to clarity certain disorders involving low grade inflammation, we need to remain aware of factors other than apparent inflammation that can influence these values. These include age, obesity, hyperlipidemia, glucose intolerance, silent atherosclerosis, and therapeutic use of hypolipidemic agents or glucocorticoid. Genetic polymorphism may also be an influence; especially an allelic variant of SAA1 has been proposed to have a positive effect on SAA concentrations. Understanding this, these values should not be evaluated at a single sampling point but used kinetically in the individual.

Serum amyloid A serum concentrations and genotype do not explain low incidence of amyloidosis in Hyper-IgD syndrome

BACKGROUND

Hyper-IgD and periodic fever syndrome (HIDS) is an autosomal recessively inherited disorder characterized by recurrent episodes of fever and inflammation. Unlike other chronic inflammatory conditions, amyloidosis is very rare in HIDS. For deposition of amyloid of the AA type, high concentrations of SAA are a prerequisite, together with certain SAA1 gene polymorphisms. The SAA1.1 genotype predisposes for amyloidosis, while SAA1.5 genotype exerts a protective effect.

AIM OF THE STUDY

To determine if SAA concentrations and SAA1 gene polymorphisms could explain the virtual absence of amyloidosis in HIDS patients.

METHODS

We measured SAA and CRP concentrations in serum of 20 HIDS patients during an attack and during the asymptomatic phase. Genotype of SAA1 gene was determined in 60 HIDS patients.

RESULTS

SAA serum concentrations during attacks were very high (median 205 mg/l; range 75-520 mg/l, normal <3.1 mg/l). During attack-free periods 45% of patients still had elevated SAA concentrations. The distribution of the genotype of SAA1 gene in HIDS was similar to healthy controls (SAA1.1 0.41 vs. 0.50 p=0.32).

CONCLUSION

Patients with HIDS have high SAA during attacks and show sub-clinical inflammation when asymptomatic. The low incidence of amyloidosis cannot be explained by a predominance of non amyloidogenic SAA related genotypes.

Synergy between deacetylase inhibitors and IL-1beta in activation of the serum amyloid A2 gene promoter

Butyrate (NaBu) regulates intestinal inflammatory gene expression in part through inhibition of deacetylase activity, but the exact mechanisms involved remain to be determined. In this study, we showed by Northern blot a synergistic induction of the acute phase protein gene SAA2 with a combination of deacetylase inhibitors (Trichostatin A or NaBu) and IL-1beta in the colon carcinoma cell line Caco-2. While the NF-kappa B DNA-binding site was essential for SAA2 regulation by IL-1beta and deacetylase inhibitors, the C/EBP DNA-binding site modulated SAA2 expression levels, as assessed by transient transfection assays and mutagenesis studies. NaBu was sufficient to induce SAA2 expression after transient treatment with IL-1beta and, conversely, IL-1beta induced SAA2 after transient treatment with NaBu. These data suggest that pretreatment with either NaBu or IL-1beta predisposes the SAA2 promoter to further stimulation. Indeed, both NaBu and IL-1beta led to increased recruitment of NF-kappa B p65, C/EBPbeta, and C/EBP delta, and decreased NF-kappa B p50 and C/EBP alpha DNA-binding to the proximal SAA2 promoter, as assessed by chromatin immunoprecipitation assays. Interestingly, while IL-1beta, in contrast to NaBu, induced histone H4 acetylation, addition of IL-1beta and NaBu increased histone H4 acetylation and both C/EBPbeta and NF-kappa B p65 DNA-binding. Therefore, these results suggest that NaBu and IL- 1beta mediate SAA2 synergistic induction by establishing and maintaining similar and complementary chromatin modifications and transcription factor recruitment as well. In addition to global effects, NaBu specifically regulate gene expression, as exemplified by SAA2.

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.

Relative transcriptional activities of SAA1 promoters polymorphic at position -13(T/C): potential association between increased transcription and amyloidosis

The risk associated with the serum amyloid A (SAA) 1 gene and developing AA-amyloidosis is still controversial. In familial Mediterranean fever or Caucasoid rheumatoid arthritis (RA), the SAA1.1 allele is a risk factor for the development of AA-amyloidosis. However, individuals with the SAA1.3 allele are susceptible to AA-amyloidosis in the Japanese RA population, but those with the SAA1.1 are not. Previous reports have indicated that the -13T/C single nucleotide polymorphism (SNP) at the 5'-flanking region of SAA1 appears to be a better marker of AA-amyloidosis than the exon-3 based haplotype, i.e., SAA1.1 or SAA1.3, in both Japanese and American Caucasian populations. So far, it is unknown why the -13T SNP increases the amyloidogenicity of the patients. In the present study, a luciferase reporter gene assay showed that the transcriptional activity of the SAA1 having the -13T-containing promoter was significantly higher than activities of those with -13C-containing promoters (Fisher's protected least significance difference test). We suggest that having the -13T SNP in the SAA1 promoter correlates with the amyloidogenicity in part as a result of this increased transcriptional activity.

Serum amyloid A: production by human white adipocyte and regulation by obesity and nutrition

AIMS/HYPOTHESIS

The acute-phase proteins, serum amyloid As (SAA), are precursors of amyloid A, involved in the pathogenesis of AA amyloidosis. This work started with the characterisation of systemic AA amyloidosis concurrent with SAA overexpression in the subcutaneous white adipose tissue (sWAT) of an obese patient with a leptin receptor deficiency. In the present study a series of histopathological, cellular and gene expression studies was performed to assess the importance of SAA in common obesity and its possible production by mature adipocytes.

MATERIALS AND METHODS

Gene expression profiling was performed in the sWAT of two extremely obese patients with a leptin receptor deficiency. Levels of the mRNAs of the different SAA isoforms were quantified in sWAT cellular fractions from lean subjects and from obese subjects before and after a very-low-calorie diet. These values were subsequently compared with serum levels of SAA in these individuals. In addition, histopathological analyses of sWAT were performed in lean and obese subjects.

RESULTS

In sWAT, the expression of SAA is more than 20-fold higher in mature adipocytes than in the cells of the stroma vascular fraction (p<0.01). Levels of SAA mRNA expression and circulating levels of the protein are sixfold (p<0.001) and 3.5-fold (p<0.01) higher in obese subjects than in lean subjects, respectively. In lean subjects, 5% of adipocytes are immunoreactive for SAA, whereas the corresponding value is greater than 20% in obese subjects. Caloric restriction results in decreases of 45-75% in levels of the transcripts for the SAA isoforms and in circulating levels of the protein.

CONCLUSIONS/INTERPRETATION

The results of the present study indicate that SAA is expressed by sWAT, and its production at this site is regulated by nutritional status. If amyloidosis is seen in the context of obesity, it is possible that production of SAA by adipocytes could be a contributory factor.

Familial Alzheimer disease associated with A713T mutation in APP

Mutations in APP are associated with familial early-onset Alzheimer disease (FAD). Examination of the genomic sequence in one patient with FAD revealed a change located in the axon 17 of the APP gene at position 275329G>A (GenBank accession number: D87675; GI: 2429080); cDNA sequence 2137G>A (GenBank accession number: X06989; GI: 28720). This corresponds to the mutation A713T in APP. AD stage VI of neurofibrillary degeneration and stage C of Abeta-amyloid burden was found at the post-mortem neuropathological examination. Previous studies have suggested that the mutation A713T in APP is a silent mutation or polymorphism. However, we have not found this change in APP in a control population analyzed by the amplification-refractory mutation system (ARMS). It is concluded that A713T in APP is implicated in the pathogenesis of AD. Since the immunohistochemical study indicates that A713T mutation is not likely to relate with Abeta-amyloid processing, the causative role of this rare mutation remains to be warranted.

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.

Serum amyloid A3 expression is stimulated by dexamethasone and interleukin-6 in 3T3-L1 adipocytes

A chronic increase in systemic levels of acute-phase reactants contributes to the development of insulin resistance and associated disorders such as cardiovascular disease. Recently, serum amyloid A3 (SAA3) has been characterized as an adipocyte-secreted acute-phase reactant, expression of which is dramatically increased in insulin resistance and obesity. To further clarify expression and regulation of this adipocytokine in fat, SAA3 mRNA was measured by quantitative real-time reverse transcriptase PCR during differentiation of 3T3-L1 adipocytes and after treatment with various hormones known to induce insulin resistance and contribute to atherosclerosis. SAA3 mRNA was dramatically induced up to 77-fold during differentiation of 3T3-L1 preadipocytes. Furthermore, 100 nM dexamethasone and 30 ng/ml interleukin (IL)-6 induced SAA3 mRNA by up to 11- and 4.8-fold, respectively, in a time-dependent fashion with significant stimulation observed at concentrations as low as 10 nM dexamethasone and 1 ng/ml IL-6. In contrast, insulin, isoproterenol and growth hormone did not influence SAA3 synthesis. Inhibitor studies suggested that the positive effect of IL-6 on SAA3 expression is at least in part mediated by Janus kinase 2. Taken together, our results show a differential regulation of SAA3 by glucocorticoids and IL-6 supporting an integrative role of this acute-phase reactant in the pathogenesis of insulin resistance and its link to obesity and cardiovascular disease.

Transcriptional activity of serum amyloid A-activating factor-1 is regulated by distinct functional modules

Serum amyloid A-activating transcription factor-1 (SAF-1) plays a major role in regulating transcription of several inflammation-responsive genes, including SAA and matrix metalloproteinase-1, that are implicated in the pathogenesis of reactive secondary amyloidosis, atherosclerosis, and arthritis. SAF-1 is a 477-amino acid protein with six zinc fingers. Its activation during inflammatory condition by a phosphorylation event that leads to an altered structure suggested possible structural modification of this protein as a leading cause of higher activity. However, no information is available regarding structural features that might regulate its activity. Here, we have characterized its functional domains, delineating activation and repression modules, DNA binding, and nuclear localization activities. Using GAL4AD chimeras and a DNA-binding assay with proteins prepared from various deletion constructs, the core DNA-binding domain of SAF-1 is mapped between amino acids 282 and 361, which contain second, third, and fourth zinc fingers. Results from several deletion and point mutants using green fluorescent protein reporter show that SAF-1 contains two independent nuclear localization signals; one is composed of a stretch of basic amino acids, and the other is a bipartite signal located within the core DNA-binding domain. SAF-1 contains several negative and positively functioning transactivation modules clustered at the two ends of this protein. Removal of any one of the terminal negative modules renders the SAF-1 protein functionally very active. These findings suggest that the terminal repression modules act in conjunction to regulate the functional activity of this protein.

Cryopreserved bovine mammary cells to model epithelial response to infection

Mammary gland epithelial cells are likely to be important effectors in defending against mastitis, yet little is known about their response mechanisms. Here, we describe a cryopreserved bovine mammary epithelial cell model to study the infection response. Primary cell cultures from four Holstein cows were prepared, and frozen after two passages. The cell cultures from each cow were then thawed and maintained separately, yet simultaneously, and exposed to treatments that included infection with Staphylococcus aureus or exposure to LPS from Escherichia coli. A clear inflammatory response was shown by a significant (P < 0.05), dose dependent, increase of lactoferrin and IL-8 secretion within 24h in response to S. aureus or LPS. Marked increases (P < 0.05) in lactoferrin, TNF-alpha and serum amyloid A (SAA) mRNA expression were also observed. The results indicate the usefulness of our model to study infection responses of mammary epithelial cells, where all cells are simultaneously exposed to the same infection pressure. These responses can be studied over time, and most importantly, biological replication is provided by the four different genotypes being investigated individually. Finally, the results indicate that mammary epithelial cells play an important role in inflammatory response, through the production of pro-inflammatory cytokines, an acute phase protein, and lactoferrin.

Rapidly progressed secondary amyloidosis in a patient with mixed connective tissue disease

A 39-year-old woman with mixed connective tissue disease suddenly developed repeated watery diarrhea two years after the onset of the disease. A colonic biopsy specimen revealed amyloid A protein deposition and the diagnosis of secondary amyloidosis was established. The amyloid deposition disappeared after the 8-month course of the treatment with prednisolone and azathioprine. Molecular genetic analysis showed the presence of the gamma-allele in her serum amyloid A protein 1 gene. This might be associated with the early onset and progression of secondary amyloidosis in our case, just like cases reported in rheumatoid arthritis.

Serum Amyloid a promotes ABCA1-dependent and ABCA1-independent lipid efflux from cells

Serum amyloid A (SAA) is an acute phase protein that associates with HDL. In order to examine the role of SAA in reverse-cholesterol transport, lipid efflux was tested to SAA from HeLa cells before and after transfection with the ABCA1 transporter. ABCA1 expression increased efflux of cholesterol and phospholipid to SAA by 3-fold and 2-fold, respectively. In contrast to apoA-I, SAA also removed lipid without ABCA1; cholesterol efflux from control cells to SAA was 10-fold higher than for apoA-I. Furthermore, SAA effluxed cholesterol from Tangier disease fibroblasts and from cells after inhibition of ABCA1 by fixation with paraformaldehyde. In summary, SAA can act as a lipid acceptor for ABCA1, but unlike apoA-I, it can also efflux lipid without ABCA1, by most likely a detergent-like extraction process. These results suggest that SAA may play a unique role as an auxiliary lipid acceptor in the removal of lipid from sites of inflammation.

Molecular pathways to neurodegeneration

The molecular bases underlying the pathogenesis of neurodegenerative diseases are gradually being disclosed. One problem that investigators face is distinguishing primary from secondary events. Rare, inherited mutations causing familial forms of these disorders have provided important insights into the molecular networks implicated in disease pathogenesis. Increasing evidence indicates that accumulation of aberrant or misfolded proteins, protofibril formation, ubiquitin-proteasome system dysfunction, excitotoxic insult, oxidative and nitrosative stress, mitochondrial injury, synaptic failure, altered metal homeostasis and failure of axonal and dendritic transport represent unifying events in many slowly progressive neurodegenerative disorders.

Local expression of the serum amyloid A and formyl peptide receptor-like 1 genes in synovial tissue is associated with matrix metalloproteinase production in patients with inflammatory arthritis

OBJECTIVE

To evaluate the regulation of acute-phase serum amyloid A (A-SAA) production in inflamed synovial tissue, and to elucidate a possible pathophysiologic role in the induction of matrix metalloproteinase (MMP) release by fibroblast-like synoviocytes (FLS).

METHODS

Synovial tissue samples were obtained by arthroscopic biopsy from the knee joints of patients with inflammatory arthritis. Primary cultures of FLS from patients with rheumatoid arthritis (RA), psoriatic arthritis, sarcoid arthritis, and undifferentiated arthritis were established. Total RNA was extracted from FLS and analyzed by reverse transcription-polymerase chain reaction (PCR) using specific primers for A-SAA and formyl peptide receptor-like 1 (FPRL1), an A-SAA receptor. Southern blot analysis confirmed the PCR products generated. Immunohistochemical analysis demonstrated the expression of A-SAA protein production by several synovial cell populations, and immunofluorescence analysis confirmed A-SAA colocalization with the macrophage marker CD68. Primary FLS cultures stimulated with recombinant human A-SAA resulted in dose-dependent MMP-1 and MMP-3 production, as measured by an enzyme-linked immunosorbent assay.

RESULTS

A-SAA messenger RNA (mRNA) and FPRL1 mRNA were present in FLS, macrophages, and endothelial cells isolated from the synovial tissue of patients with RA and other categories of inflammatory arthritis. A-SAA expression was regulated by proinflammatory cytokines and occurred in association with FPRL1 expression in FLS and endothelial cells, which is consistent with a biologic role at the sites of inflammation. Recombinant human A-SAA induced both MMP-1 and MMP-3 secretion by FLS. The mean fold increases in A-SAA-induced MMP-1 and MMP-3 production were 2.6 and 10.6, respectively, compared with 7.6-fold and 41.9-fold increases in interleukin-1 beta-induced MMP-1 and MMP-3 production.

CONCLUSION

The up-regulation of the A-SAA and FPRL1 genes in inflamed synovial tissue suggests an important role in the pathophysiology of inflammatory arthritis. A-SAA induces the production of MMPs. Therapeutic targeting of A-SAA, or FPRL1, may modulate pathophysiologic pathways that are associated with matrix degradation in patients with RA and other forms of progressive inflammatory arthritis.

Influence of Serum Amyloid A (SAA1) and SAA2 gene polymorphisms on renal amyloidosis, and on SAA/C-reactive protein values in patients with familial mediterranean fever in the Turkish population

OBJECTIVE

To evaluate the effect of serum amyloid A (SAA) 1 and SAA2 gene polymorphisms on SAA levels and renal amyloidosis in Turkish patients with familial Mediterranean fever (FMF).

METHODS

SAA1 and SAA2 gene polymorphisms and SAA levels were determined in 74 patients with FMF (39 female, 35 male; median age 11.5 yrs, range 1.0-23.0). All patients were on colchicine therapy. SAA1 and SAA2 gene polymorphisms were analyzed using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). SAA and C-reactive protein (CRP) values were measured and SAA/CRP values were calculated.

RESULTS

The median SAA level was 75 ng/ml (range 10.2-1500). SAA1 gene polymorphisms were: a/a genotype in 23 patients (31.1%), a/beta genotype in 30 patients (40.5%), a/g genotype in one patient (1.4 %), beta/beta genotype in 14 patients (18.9%), beta/g genotype in 5 patients (6.8 %), and g/g genotype in one patient (1.4%). Of the 23 patients who had a/a genotype for the SAA1 polymorphism, 7 patients had developed renal amyloidosis (30.4%) compared to only one patient without this genotype (1/51; 2.0%); p < 0.001. SAA2 had no effect on renal amyloidosis. SAA1 and SAA2 genotypes had no significant effect on SAA levels. SAA/CRP values were significantly lower in patients with the SAA1a/a genotype, compared to other SAA1 genotypes: 0.16 (0.025-1.96) versus 0.23 (0.012-28.20), p < 0.05.

CONCLUSION

SAA1a/a genotype is one genetic factor that confers a significant risk for amyloidosis in the Turkish FMF population. Neither the SAA1 nor SAA2 genotypes had a significant effect on SAA level.

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.

The interaction between apolipoprotein serum amyloid A and high-density lipoprotein

Serum amyloid A (SAA) is a small apolipoprotein that binds to high-density lipoproteins (HDLs) via its N-terminus. The murine isoform SAA2.2 forms a hexamer in solution and the N-terminus is shielded from the solvent. Therefore, it is unclear how the SAA2.2 hexamer might bind HDL. In this study, the binding of SAA2.2 to murine HDL was investigated by glutaraldehyde cross-linking and polyacrylamide gel electrophoresis. The hexamer did not bind HDL significantly at 20 degrees C. However, at temperatures between 25-30 degrees C, SAA2.2 became destabilized and its monomeric form bound to HDL. SAA2.2 binding did not significantly replace Apo A-I in HDL particles. At 37-45 degrees C SAA2.2 binds less to HDL, suggesting that its binding is weak and sensitive to physiological and pathological temperatures, and thereby, potentially modulated, in vivo, by other factors.

TGF-β down-regulates IL-1α-induced TLR2 expression in murine hepatocytes

We have previously reported that the proinflammatory cytokine interleukin (IL)-1alpha can up-regulate functional Toll-like receptor 2 (TLR2) expression in primary-cultured murine hepatocytes, and bacterial lipopeptide (BLP) is capable of signaling through TLR2 to induce serum amyloid A (SAA) expression in hepatocytes. In the present study, we investigated the effect of the anti-inflammatory cytokine transforming growth factor-beta (TGF-beta) on TLR2 expression in primary-cultured murine hepatocytes. At the mRNA and protein levels, TGF-beta up-regulated TLR2 expression but inhibited TLR2 expression induced by IL-1alpha at 24 h. BLP-induced SAA promoter activity could be augmented by pretreatment with IL-1alpha but not TGF-beta or the combination of TGF-beta and IL-1alpha. TLR2 promoter activity and nuclear factor (NF)-kappaB activation by IL-1alpha were inhibited by TGF-beta treatment. Pretreatment with TGF-beta strongly suppressed IL-1alpha-induced TLR2 promoter activity and NF-kappaB activation, which was consistent with the down-regulation of type I IL-1 receptor (IL-1RI) mRNA expression. IL-1alpha up-regulated IL-1RI mRNA, but it was inhibited by the treatment with TGF-beta. These results suggest that TGF-beta suppresses the induction of TLR2 expression by IL-1alpha through down-regulation of IL-1RI expression. These results also demonstrate the disparity between IL-1alpha and TGF-beta in regulating TLR2-mediated SAA production in hepatocytes.

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.

Analysis of cDNA sequences of feline SAAs

Feline amyloidosis is an uncommon disorder caused by deposits of amyloid in a variety of organs. Most frequently encountered types are amyloid derived of pancreatic islet amyloid polypeptide (AIAPP) in older cats and of the apolipoprotein, apo-serum amyloid A (AA) in Abyssinian/Somali (Aby) and Siamese/Oriental (Siam) cats occurring at a relatively young age. For the AA protein of the Aby, Siam and domestic shorthair cat (DSH) breed different amino acid sequences have been described. It is not yet clear, however, whether the tendency to develop AA amyloidosis in Aby and Siam is associated with specific apoSAA protein sequences and whether this is breed specific. In this study, DNA from one Siam and two DSH cats revealed on Southern blot three bands suggesting at least three genes or gene clusters. The SAA cDNAs of hepatic mRNA from three Abys, five Siams and five DSHs were amplified by RT-PCR, cloned and sequenced. Siams and Abys had limited SAA sequence variability. All five Siams, three of which were positive for amyloid, had the amyloidogenic Siam SAA and the amyloidogenic Aby SAA sequence. Two of the Abys, both with amyloid, had the amyloidogenic Aby SAA sequence. The third Aby, without amyloid, missed its amyloidogenic sequence. The SAA sequences of the DSHs found in the present preliminary survey, suggested a possible tendency for more variability, whereas the amyloidogenic Siam as well as the amyloidogenic Aby sequence were found once. Up to five different sequences were found in a single animal. All five DSHs, moreover, had a specific sequence lacking in the Siams and Abys. The present results, especially those of the Siams, favor that in addition to the occurrence of amyloid associated SAA genes other factors such as infections and inflammatory processes are involved in the development of phenotypical amyloidosis.

Amyloidosis in familial Mediterranean fever patients: correlation with MEFV genotype and SAA1 and MICA polymorphisms effects

Background

Familial mediterranean fever (FMF) is a recessively inherited disease characterized by recurrent crises of fever, abdominal, articular and/or thoracic pain. The most severe complication is the development of renal amyloidosis. Over 35 mutations have been discovered so far in the gene responsible for the disease, MEFV. This article aims at determining a correlation between the MEFV genotype and the occurence of amyloidosis in FMF patients, in addition to the study of the modifying effects of the SAA1 (type 1 serum amyloid A protein) and MICA (Major Histocompatibility Complex (MHC) class-I-chain-related gene A) genes on this severe complication.

Methods

Fourteen MEFV mutations were screened and the SAA1 and MICA polymorphisms tested in 30 FMF patients with amyloidosis and 40 FMF patients without amyloidosis.

Results

The M694V and V726A allelic frequencies were, respectively, significantly higher and lower in the group with amyloidosis, compared to the control FMF group. The beta and gamma SAA1 alleles were more frequently encountered in the group without amyloidosis, whereas the alpha allele was significantly more observed in FMF patients with amyloidosis (p < 0.025). All the MICA alleles were encountered in both patients' groups, but none of them was significantly associated with amyloidosis.

Conclusions

The results suggest a protective effect of the SAA1 beta and gamma alleles on the development of amyloidosis and show the absence of a MICA modifying effect on amyloidosis development. Testing these polymorphisms on a larger sample will lead to more definite conclusions.