Degradation of serum amyloid A protein by surface-associated enzymes of human blood monocytes

Advanced systemic amyloidosis secondary to metastatic renal cell carcinoma

Secondary amyloidosis is a rare complex complication related to chronic inflammatory disease. This complication is sparsely associated to malignant neoplasms. Renal cell carcinoma (RCC) is the most common solid organ malignancy related with this paraneoplastic syndrome. Some case reports have described stabilisation or even remission of amyloidosis with cytoreductive nephrectomy. Majority of those reports were based on locally advanced RCC. We report the first case of early aggressive systemic secondary amyloidosis in high-volume metastatic RCC. The subject was diagnosed with metastatic RCC within 6 months of secondary amyloidosis; on month 5 of initiation of targeted therapy (pazopanib) developed nephrotic syndrome with a heavy proteinuria (>18 g/day), severe hypoalbuminaemia (1.53 g/dL), intense and progressive oedema, severe pancolitis and mild dyspnoea with hypotension. A colon biopsy and the immunohistochemistry confirmed the histological diagnosis of a secondary amyloidosis. The multidisciplinary tumour board decided to perform cytoreductive nephrectomy in order to reduce the pro-inflammatory status. Pathology report showed a complete resection of clear cell RCC plus renal amyloid deposits. The patient died within 4 days of surgery due to multiorgan failure.

Serum amyloid A: A potential biomarker of lung disorders

Serum amyloid A is an acute-phase protein with multiple immunological functions. Serum amyloid A is involved in lipid metabolism, inflammatory reactions, granuloma formation, and cancerogenesis. Additionally, serum amyloid A is involved in the pathogenesis of different autoimmune lung diseases. The levels of serum amyloid A has been evaluated in biological fluids of patients with different lung diseases, including autoimmune disorders, chronic obstructive pulmonary diseases, obstructive sleep apnea syndrome, sarcoidosis, asthma, lung cancer, and other lung disorders, such as idiopathic pulmonary fibrosis, tuberculosis, radiation pneumonitis, and cystic fibrosis. This review focuses on the cellular and molecular interactions of serum amyloid A in different lung diseases and suggests this acute-phase protein as a prognostic marker.

Multiplex Assay for Quantification of Acute Phase Proteins and Immunoglobulin A in Dried Blood Spots

Inflammation is the first line defense mechanism against infection, tissue damage, or cancer development. However, inappropriate inflammatory response may also trigger diseases. The quantification of inflammatory proteins is essential to distinguish between harmful and beneficial immune response. Currently used immunoanalytical assays may suffer specificity issues due to antigen-antibody interaction and possible cross-reactivity of antibody with other protein species. In addition, immunoanalytical assays typically require invasive blood sampling and additional logistics; they are relatively costly and highly challenging to multiplex. We present a multiplex assay based on selected reaction monitoring (SRM) for quantification of seven acute-phase proteins (i.e., SAA1, SAA2-isoform1, SAA4, CRP, A1AT-isoform1, A1AG1, A1AG2) and the adaptive immunity effector IGHA1 in dried blood spots. This type of sample is readily available from all human subjects including newborns. The study utilizes proteotypic isotopically labeled peptides with trypsin-cleavable tag and presents optimized and reproducible workflow and several important practical remarks regarding quantitative SRM assays development. The panel of inflammatory proteins was quantified with sequence specificity capable to differentiate protein isoforms with intra- and interday precision (<16.4% coefficient of variation (CV) and <14.3% CV, respectively). Quantitative results were correlated with immuno-nephelometric assay (typically greater than 0.9 Pearson's R).

Serum amyloid A - a review

Serum amyloid A (SAA) proteins were isolated and named over 50 years ago. They are small (104 amino acids) and have a striking relationship to the acute phase response with serum levels rising as much as 1000-fold in 24 hours. SAA proteins are encoded in a family of closely-related genes and have been remarkably conserved throughout vertebrate evolution. Amino-terminal fragments of SAA can form highly organized, insoluble fibrils that accumulate in “secondary” amyloid disease. Despite their evolutionary preservation and dynamic synthesis pattern SAA proteins have lacked well-defined physiologic roles. However, considering an array of many, often unrelated, reports now permits a more coordinated perspective. Protein studies have elucidated basic SAA structure and fibril formation. Appreciating SAA’s lipophilicity helps relate it to lipid transport and metabolism as well as atherosclerosis. SAA’s function as a cytokine-like protein has become recognized in cell-cell communication as well as feedback in inflammatory, immunologic, neoplastic and protective pathways. SAA likely has a critical role in control and possibly propagation of the primordial acute phase response. Appreciating the many cellular and molecular interactions for SAA suggests possibilities for improved understanding of pathophysiology as well as treatment and disease prevention.

Human SR-BII mediates SAA uptake and contributes to SAA pro-inflammatory signaling in vitro and in vivo

Serum amyloid A (SAA) is an acute phase protein with cytokine-like and chemotactic properties, that is markedly up-regulated during various inflammatory conditions. Several receptors, including FPRL-1, TLR2, TLR4, RAGE, class B scavenger receptors, SR-BI and CD36, have been identified as SAA receptors. This study provides new evidence that SR-BII, splice variant of SR-BI, could function as an SAA receptor mediating its uptake and pro-inflammatory signaling. The uptake of Alexa Fluor488 SAA was markedly (~3 fold) increased in hSR-BII-expressing HeLa cells when compared with mock-transfected cells. The levels of SAA-induced interleukin-8 secretion by hSR-BII-expressing HEK293 cells were also significantly (~3-3.5 fold) higher than those detected in control cells. Moderately enhanced levels of phosphorylation of all three mitogen-activated protein kinases, ERK1/2, and p38 and JNK, were observed in hSR-BII-expressing cells following SAA stimulation when compared with control wild type cells. Transgenic mice with pLiv-11-directed liver/kidney overexpression of hSR-BI or hSR-BII were used to assess the in vivo role of each receptor in SAA-induced pro-inflammatory response in these organs. Six hours after intraperitoneal SAA injection both groups of transgenic mice demonstrated markedly higher (~2-5-fold) expression levels of inflammatory mediators in the liver and kidney compared to wild type mice. Histological examinations of hepatic and renal tissue from SAA-treated mice revealed moderate level of damage in the liver of both transgenic but not in the wild type mice. Activities of plasma transaminases, biomarkers of liver injury, were also moderately higher in hSR-B transgenic mice when compared to wild type mice. Our findings identify hSR-BII as a functional SAA receptor that mediates SAA uptake and contributes to its pro-inflammatory signaling via the MAPKs-mediated signaling pathways.

Serum Amyloid A Stimulates PKR Expression and HMGB1 Release Possibly through TLR4/RAGE Receptors

Serum amyloid A (SAA) proteins are known to be surrogate markers of sepsis, but their pathogenic roles remain poorly elucidated. Here we provide evidence to support a possible role of SAA as a pathogenic mediator of lethal sepsis. In a subset of septic patients for which serum high mobility group box 1 (HMGB1) levels paralleled the clinical scores, some anti-HMGB1 antibodies detected a 12-kDa protein belonging to the SAA family. In contrast to the most abundant SAA1, human SAA induced double-stranded RNA-activated protein kinase R (PKR) expression and HMGB1 release in the wild-type, but not toll-like receptor 4/receptor for advanced glycation end products (TLR4/RAGE)-deficient, macrophages. Pharmacological inhibition of PKR phosphorylation blocked SAA-induced HMGB1 release, suggesting an important role of PKR in SAA-induced HMGB1 release. In animal models of lethal endotoxemia and sepsis, recombinant SAA exacerbated endotoxemic lethality, whereas SAA-neutralizing immunoglobulins G (IgGs) significantly improved animal survival. Collectively, these findings have suggested SAA as an important mediator of inflammatory diseases. Highlights of this study include: human SAA is possibly only expressed in a subset of septic patients; SAA induces HMGB1 release via TLR4 and RAGE receptors; SAA supplementation worsens the outcome of lethal endotoxemia; whereas SAA-neutralizing antibodies confer protection against lethal endotoxemia and sepsis.

Renal cell carcinoma presenting as AA amyloidosis: a case report and review of the literature

A 47-year-old Caucasian man developed mild diarrhoea associated with more than 10 kg weight loss, severe fatigue and anaemia. Endoscopy demonstrated deposits of AA amyloid within the gastrointestinal tract. He had heavy proteinuria with a serum albumin of 15 g/L consistent with systemic AA amyloidosis. He had no symptoms to suggest an underlying chronic inflammatory condition but had CRP 130 mg/L and SAA 474 mg/L. In an attempt to identify the source of his inflammatory response, he underwent a contrast-enhanced whole-body computed tomography scan, which revealed a necrotising mass lesion in the right kidney consistent with a renal cell carcinoma. It also showed non-mechanical obstruction of the small bowel and, immediately post-imaging, the patient developed intractable vomiting followed by oliguric renal failure requiring haemodialysis. Despite his renal and gut failure, he underwent right radical nephrectomy without further complications. Histology showed complete resection of a clear cell renal cell carcinoma and renal amyloid deposits. Post-surgery, his acute-phase response decreased to normal, consistent with the renal cell carcinoma acting as the inflammatory stimulus. Although he remains dialysis dependent, his gut function improved and he has regained both normal weight and serum albumin. Our case demonstrates partial resolution of AA amyloidosis with removal of the inflammatory source.

Serum amyloid A uptake by feline peripheral macrophages

Serum amyloid A (SAA) is one of the major acute phase proteins in cats and humans. SAA concentrations increase in response to the inflammatory status and secondary amyloid A amyloidosis has been documented in cats. In order to control the SAA concentration, it is important to clarify how the SAA protein is metabolized. Although the details of SAA metabolism in the body remain unknown, human and murine research indicates that macrophages play a key role in SAA uptake. The objectives of this study were to demonstrate SAA uptake by feline macrophages and to evaluate the effects of lipopolysaccharide (LPS) and dexamethasone (Dex) on SAA uptake. The concentration of recombinant feline SAA added to a feline macrophage culture was decreased in a time-dependent manner and was significantly reduced after a 24-h incubation, as demonstrated by enzyme linked immunosorbent assay (ELISA). SAA uptake into feline peripheral macrophages was demonstrated by immunofluorescence microscopy. Pretreatment to macrophages with LPS did not affect this decrease in the SAA concentration, but this was significantly blocked by Dex pretreatment. In conclusion, SAA was incorporated by feline macrophages and pretreatment with Dex inhibited SAA uptake by macrophages in this study. Further investigation is needed to determine the molecules that influence SAA uptake by macrophages and the effect of clinical glucocorticoid usage on the SAA concentration in cats.

A molecular history of the amyloidoses

The molecular investigation of the amyloidoses began in the mid-19th century with the observation of areas in human tissues obtained at autopsy that were homogeneous and eosinophilic with conventional stains but became blue when exposed to mixtures of iodine and sulfuric acid. The foci corresponded to regions formerly identified as "waxy" or lardaceous. Subsequent identification of the characteristic staining of the same tissues with metachromatic dyes such as crystal violet or with the cotton dye Congo red (particularly under polarized light) and thioflavins allowed the pathological classification of those tissues as belonging to a set of disorders known as the amyloidoses. Not unexpectedly, progress has reflected evolving technology and parallel advances in all fields of biological science. Investigation using contemporary methods has expanded our notions of amyloid proteins from being simply agents or manifestations of systemic, largely extracellular diseases to include "protein-only infection," the concept that "normal" functional amyloids might exist in eukaryotes and prokaryotes and that aggregatability may be an intrinsic structural price to be paid for some functional protein domains. We now distinguish between the amyloidoses, that is, diseases caused by the deposition of amyloid fibrils and amyloid proteins (i.e., purified or recombinant proteins that form amyloid fibrils in vitro), which may or may not be associated with disease in vivo.

Plasma total prekallikrein/kallikrein activity in rheumatoid arthritis with and without amyloidosis. Increased kaolin-stimulated activity in patients with amyloidosis

Following exposure to kaolin, plasma samples were assayed for total prekallikrein/kallikrein activity in 19 patients with rheumatoid arthritis (RA), 39 patients with RA complicated by amyloidosis, 13 patients with nonamyloid nephropathy and 54 healthy subjects. Increased total kallikrein activity was found in RA patients with amyloidosis and in patients with nonamyloid nephropathy. The concentrations of the plasma kallikrein inhibitors C1-inactivator and alpha 2-macroglobulin were normal in RA patients without amyloidosis, whereas they were increased in patients with amyloidosis as well as in patients with nonamyloid nephropathy. The results suggest that the increased activity of plasma kaolin-stimulated kallikrein in RA patients with amyloidosis is due to the nephropathy per se and probably reflects increased levels of prekallikrein.

Identification in milk of a serum amyloid A peptide chemoattractant for B lymphoblasts

Background

Normal mammary gland contains an extravascular population of B lymphoblasts, precursors of the immunoglobulin plasma cells that play a key role in the passive protection of neonates by secreting immunoglobulins to colostrum and milk. We investigated the presence of chemoattractants in the milk by analysing the chemoattractant activity of various fractions of this secretion. Milk chemoattractants are potentially involved in the recruitment of lymphocytes from the maternal bloodstream in lactating mammary glands.

Results

The dilution-related lymphoid cell chemoattraction of whey was associated with a < 10 kDa ultrafiltrate. Active fractions were purified by reverse-phase high performance liquid chromatography. Two peptides of 2.7 kDa (DMREANYKNSDKYFHARGNYDAA) and 1 kDa (RPPGLPDKY) were identified as fragments of the SAA protein family, tentatively identified as SAA2. Only the 2.7 kDa synthetic peptide displayed chemotactic activity, at two different optimal concentrations. At the lower concentration (3.7 nM), it attracted B-cell lymphoblasts, whereas at the higher (3.7 μM), it attracted B lymphocytes. Then, the SAA mRNA expression was analysed and we observed more SAA transcripts during lactation than gestation.

Conclusion

These data are consistent with the SAA_23–45 fragment being involved in preplasma B-cell recruitment to the mammary gland and resultant benefit to the neonate.

Secondary amyloidosis causing nephrotic syndrome in a patient with non-Hodgkin's lymphoma: quite a rare diagnosis

Secondary amyloidosis is usually a complication of chronic inflammation. Amyloidosis cases during the course of non-Hodgkin's lymphoma (NHL) are usually of AL-type, only one NHL patient with secondary amyloidosis has been reported. Our 79-year-old male patient visited us with multiple lymphadenopathies, and he was diagnosed with nodal marginal zone B-cell lymphoma. After four cycles of combined chemotherapy; his urea, creatinine levels started to increase and he developed nephrotic-range proteinuria. His rectal biopsy demonstrated amyloid deposition in submucosal vessel walls. The patient has been under hemodialysis for 10 months and his lymphoma is still in partial remission. We presented this case because it is the second NHL patient who developed secondary amyloidosis during his disease course.

Purification and separation of hydrophobic serum amyloid A precursor isoforms by a one-step preparative method

The levels of two major serum amyloid A precursor isoforms, SAA1 and SAA2, which are associated with high-density lipoproteins (HDL) are increased during inflammation. The hydrophobic character and the small size difference--corresponding to just 0.8 kDa--between these two members of the SAA family hinder their separation and purification on a large scale by conventional methods. In the current work, both mouse SAA proteins were purified from HDL-SAA and acute-phase serum within 10 h in a one-step procedure using the high-resolution, continuous-elution preparative gel electrophoresis Prep-Cell system in combination with Tris/Glycine SDS-PAGE. Moreover, applying the Tris/Tricine system on the Prep-Cell resulted not only in purification of the SAA proteins, but also in their separation within 16 h. The SAA isoforms were freed from SDS using a Centricon concentrator and were identified using monoclonal antibodies. Optical density profile plots of gel protein or Western blot bands in combination with a colorimetric spectrophotometric protein assay showed that the recovery of the isoforms ranged from 38% to 60%. These results show that the preparative gel electrophoresis system Prep-Cell is a suitable device for separating SAA1 and SAA2 proteins in a simplified, convenient, and fast procedure, which can be applied on a small or large scale.

Generation of Amyloid A Protein by the Cell Lines from Amyloid-Susceptible and -Resistant Mice

It has been proposed that impaired degradation is the cause of amyloid A (AA) formation in reactive amyloidosis (Ham et al., Scand J Immunol 1997; 45: 354-60). The current SDS-PAGE of the culture medium showed that the macrophage cell line from the amyloid-susceptible mouse strain (ANA1) degraded amyloid precursor protein serum amyloid A into the AA-like amyloidogenic product of approximately 8.6 kDa but went no further, whereas cells from the resistant strain (A/J10) cleared the AA-like derivates proceeding to approximately 7.7 kDa products within the incubation period. Degradation occurred in the chemically defined medium at a slower rate than in the medium with serum. This may imply that a lack of the serum components as well as impaired degradation could contribute to the development of amyloidosis.

Cellular defense against oxidized low density lipoproteins and fibrillar amyloid beta in murine cells of monocyte origin with possible susceptibility to the oxidative stress induction

Reactive oxygen species (ROS) are associated with aging and the correlation between Alzheimer's disease and atherosclerosis is a subject of the discussion. The aim of this study was to determine whether genetic factors affect cellular defense against cytotoxic beta-amyloid (Abeta) which is considered to be the source of ROS. Low levels of Abeta (1-10 microM) led to a significant suppression of redox potential as measured by MTT assay in bone marrow-derived cell lines. The atherosclerosis-resistant cells (GG2EE) were less affected than the susceptible cells (ANA1) in the time-, dose-, and Abeta species-dependent manner. Cell death in amyloid treated resident susceptible macrophages (C57BL/6J), measured by lactate dehydrogenase release, was induced during prolonged incubation and increased when compared with the resistant macrophages (C3H/HeJ, P = 0.005). SDS-PAGE showed that Abeta persisted intracellularly during this period. The cytotoxicity of oxidized low density lipoproteins (oxLDLs) significantly affected only the susceptible cells which actually lowered this cytotoxicity, thus, implying that the harmful effect of the oxLDLs was diminished when compared to that of Abeta. This fact demonstrates that in vitro the defense by cells of monocyte origin against Abeta may be determined in part genetically whereas the reaction to oxLDLs could be fully underlined by genetic susceptibility.

Impaired degradation of serum amyloid A (SAA) protein by cytokine-stimulated monocytes

Secondary amyloidosis (AA amyloidosis) is a systemic disease characterized by the extracellular tissue deposition of insoluble amyloid A (AA) protein. Aberrant metabolism of serum amyloid A (SAA) by macrophages is only one of many putative mechanisms which may be important in AA amyloidogenesis. In this study, we investigated the effects of cytokines on human monocyte-mediated SAA proteolysis. Human peripheral blood mononuclear cells (PBMC) or CD14(+) monocytes were cultured with SAA, and the culture supernatants were then subjected to anti-SAA immunoblot. CD14(+) monocytes degraded SAA completely. Whereas, when CD14(+) monocytes were pretreated with IL-1 beta or IFN-gamma, increasing amounts of SAA-related derivatives were detected in culture supernatants. These findings suggest that activation of monocytes by IL-1 beta or IFN-gamma hampers the proteolysis of a precursor protein and leads to a partial degradation of SAA. This down-regulated proteolysis of SAA protein by cytokine-stimulated monocytes may play a role in the mechanism of AA amyloid formation as well as its removal.

C-reactive protein and serum amyloid A protein in neonatal infections

In this study, we examine C-reactive protein (CRP) and serum amyloid protein A (SAA). Although the former is the best known and most commonly used indicator of inflammation, certain considerations underline the inadequacy of CRP determination alone for the early diagnosis of infection. In fact symptoms often precede the CRP elevation. SAA protein comprises a family of polymorphic apolipoproteins produced mainly by the liver, and several studies have stressed its importance in the diagnosis and monitoring of various diseases. Pathological SAA values are often detected in association with normal CRP concentrations. SAA rises earlier and more sharply than CRP. Finally, contrary to CRP, SAA presents the same trend in viral as well as bacterial infections. Although the data available on SAA in neonates are currently very limited, it is possible to postulate a role of primary importance for SAA in the management of neonatal infections.

The genetics of the amyloidoses

The amyloidoses are diseases in which abnormalities in the secondary structure of precursor proteins result in decreased solubility under physiologic conditions, with subsequent organ compromise. A total of 18 proteins have been definitively identified as amyloid precursors associated with human disease. Mutations in the genes that encode some of these proteins produce autosomal dominant disease in mid to late adult life. Until recently, the late onset has obscured the familial nature of some of the disorders. This is especially true in the apparently sporadic disease-producing deposits found even later in life. In many instances, these deposits are derived from precursors encoded by wild-type genes (perhaps influenced by alleles that are polymorphic in the normal population); in other cases, they represent autosomal dominant disease with age-dependent penetrance. The genetic aspects of amyloid diseases produced by the deposition of four different proteins have been investigated in detail and provide insights into the particular diseases and amyloidogenesis in general.

Serum amyloid A-derived peptides, present in human rheumatic synovial fluids, induce the secretion of interferon-gamma by human CD(4)(+) T-lymphocytes

Serum amyloid A (SAA) is a major acute-phase protein whose biochemical functions remain largely obscure. Human rheumatic synovial fluids were screened by high performance liquid chromatography mass spectrometry for SAA-derived peptides, specifically the sequence AGLPEKY (SAA(98-104)) which was previously shown to modulate various leukocyte functions. Two such fluids were found to contain a truncated version of SAA(98-104). Synthetic SAA(98-104) and several of its analogs were shown capable of binding isolated human CD(4)(+) T-lymphocytes and stimulating them to produce interferon-gamma. Given the high acute-phase serum level of SAA and its massive proteolysis by inflammatory related enzymes, SAA-derived peptides may be involved in host defense mechanisms.

Diet, amyloid enhancing factor (AEF) and amyloidogenesis: an hypothesis

At least two forms of amyloidosis, amyloid A (AA) and prion protein (PrP), can be transmitted by dietary ingestion of an agent(s) present in crude mammalian tissues. Although the incubation time for PrP or scrapie-induced diseases to develop in experimental animals extends over months or years, AA or secondary amyloidosis in mice is inducible within a week. In response to inflammatory stimuli we hypothesize that dietary factor(s) modulate the rate at which beta-pleated sheet fibrils accumulate in most forms of amyloidosis. The critical importance of precursor protein polymorphism, cell surface proteoglycans (PG), lipids and apolipoprotein metabolism has also been addressed in this hypothesis.

Serum amyloid A (SAA): a concise review of biology, assay methods and clinical usefulness

Serum amyloid A (SAA) is a family of proteins encoded in a multigene complex. Acute phase isotypes SAA1 and SAA2 are synthesized in response to inflammatory cytokines. SAA and C-reactive protein (CRP) are now the most sensitive indicators for assessing inflammatory activity. In viral infection and kidney allograft rejection, SAA proved more useful than CRP. Development of convenient assay methods for SAA will facilitate its use in clinical laboratories.

Serum amyloid A induces chemotaxis of human mast cells by activating a pertussis toxin-sensitive signal transduction pathway

Serum amyloid A (SAA) is an acute-phase protein and its concentration increases in the blood up to 1000 times during an inflammatory response. Mast cells are known to accumulate in various inflammatory processes, some of which are associated with increased levels of acute-phase reactants such as SAA. We report here that SAA can act as a mast cell chemoattractant. Recombinant SAA at concentrations corresponding to those found during the acute phase induced directional migration of human mast cells. No chemokinetic effect was observed. Preincubation of the cells with pertussis toxin inhibited SAA chemotaxis, suggesting that the effect is mediated by G proteins of the Gi class. Furthermore, chemotaxis was diminished after pretreatment with genistein, a tyrosine kinase inhibitor, or bisindolylmaleimide I, a protein kinase C inhibitor. We suggest that SAA may participate in the migration of mast cells to inflamed tissues during an acute-phase response, acting through a pertussis toxin-sensitive signaling pathway.

Catabolism of lipid-free recombinant apolipoprotein serum amyloid A by mouse macrophages in vitro results in removal of the amyloid fibril-forming amino terminus

Serum amyloid A fibrils are formed when the normally rapid catabolism of the acute-phase reactant apolipoprotein serum amyloid A (apoSAA) is incomplete; thus amyloidosis may be viewed as a condition of dysregulated proteolysis. There is evidence that apoSAA is dissociated from plasma high-density lipoprotein (HDL) prior to fibril formation. The objective of this study was to investigate degradation of lipid-free apoSAA by tissue macrophages derived from amyloid-susceptible CBA/J mice in vitro. Peritoneal macrophages derived from untreated (normal) mice converted apoSAA (12 kDa) to a single 4 kDa C-terminal peptide while splenic macrophages converted apoSAA to 10, 7 and 4 kDa C-terminal peptides and a 4 kDa peptide that lacked the C- and N-terminal regions. Similar patterns of proteolysis occurred when peritoneal and splenic macrophages from amyloidotic CBA/J mice were used. Conditioned medium prepared from peritoneal, but not splenic macrophages, degraded apoSAA. Specific sites of cleavage indicated activity of cathepsin G- and elastase-like neutral proteases. The data indicate that lipid-free apoSAA can be degraded by secreted or cell-associated neutral proteases that are generated by macrophages to yield peptides that lack fibrillogenic potential.

Instability of the amyloidogenic cystatin C variant of hereditary cerebral hemorrhage with amyloidosis, Icelandic type

A cystatin C variant with L68Q substitution and a truncation of 10 NH2-terminal residues is the major constituent of the amyloid deposited in the cerebral vasculature of patients with the Icelandic form of hereditary cerebral hemorrhage with amyloidosis (HCHWA-I). Variant and wild type cystatin C production, processing, secretion, and clearance were studied in human cell lines stably overexpressing the cystatin C genes. Immunoblot and mass spectrometry analyses demonstrated monomeric cystatin C in cell homogenates and culture media. While cystatin C formed concentration-dependent dimers, the HCHWA-I variant dimerized at lower concentrations than the wild type protein. Amino-terminal sequence analysis revealed that the variant and normal proteins produced and secreted are the full-length cystatin C. Pulse-chase experiments demonstrated similar levels of normal and variant cystatin C production and secretion. However, the secreted variant cystatin C exhibited an increased susceptibility to a serine protease in conditioned media and in human cerebrospinal fluid, explaining its depletion from the cerebrospinal fluid of HCHWA-I patients. Thus, the amino acid substitution may induce unstable cystatin C with intact inhibitory activity and predisposition to self-aggregation and amyloid fibril formation.

Localized amyloidosis of the parotid gland: a case report and review of the localized amyloidosis of the head and neck

BACKGROUND

Localized amyloidosis in the head and neck is a rare and benign process.

METHODS

We present the first case report in the literature of localized amyloidosis of the parotid glands and also comprehensively review the literature regarding localized amyloidosis of the head and neck.

RESULTS

Amyloidosis affecting the head and neck region is uncommon and is mostly in the form of localized amyloidosis. Larynx is the commonest site of involvement and accounts for 0.2% to 0.5% of benign laryngeal tumors. Laryngeal involvement could be either diffuse subepithelial deposition or discrete tumor nodules. Although localized amyloidosis occurs much more frequently in the oral cavity and pharynx, only seven cases of nasopharyngeal amyloidosis and eight cases of nasal septum amyloidosis have been reported. There is no documentation to suggest that localized amyloidosis can progress to systemic amyloidosis. Local surgical excision is the treatment of choice for laryngeal amyloidosis and laser excision is probably the best.

CONCLUSION

While localized amyloidosis of the head and neck region is rare, it should be recognized, understood, evaluated, and properly treated.

Theoretic opinion and future treatment of amyloidosis

Amyloidosis is still enigmatic. The etiology and mechanism of storage and organ impairment are still unknown. Not all amyloidogen molecules are definitely pathogenic; some precursors of tissue amyloid are structurally analogous to normal substances produced in the organism. This paper reviews the currently accepted categories, aspects of etiology and pathogenesis, and therapeutic trends of amyloidosis with a special emphasis on plasmapheresis.

High prevalence of serum apolipoprotein E4 isoprotein in rheumatoid arthritis patients with amyloidosis

OBJECTIVE

To determine whether serum Apolipoprotein E (Apo E) type 4 isoprotein is a risk factor for the development of amyloidosis in patients with rheumatoid arthritis (RA).

METHODS

Using isoelectric focusing, we studied Apo E phenotype expression and the corresponding allele frequencies (epsilon 2, epsilon 3, and epsilon 4) in 35 patients with RA and amyloidosis, 65 patients with RA and without amyloidosis, and 63 healthy controls.

RESULTS

The Apo E3/4 phenotype was significantly more common in the group with amyloidosis (31.4%) than in the patients without amyloidosis (12.3%; P < 0.05) or in healthy controls (12.7%; P < 0.05). The frequency of the epsilon 4 allele was significantly greater in the group with amyloidosis (0.16) than in the patients without amyloidosis (0.07; P < 0.05) or in healthy controls (0.07; P < 0.05).

CONCLUSION

The presence of Apo E4 isoprotein may be a risk factor for the development of amyloidosis in patients with RA.

Fine chemical modifications at N- and C-termini enhance peptide presentation to T cells by increasing the lifespan of both free and MHC-complexed peptides

We investigated the effect of modifying the N- and/or C-termini of the snake toxin peptide 24-36 on its presentation to T cells. Acetylation at the N-terminus as well as amidation at the C-terminus enhanced the capacity of the peptide to activate T cells. Simultaneous modifications further increased the stimulating activity, the peptide becoming approximately 100-fold more potent than the unmodified peptide. Clearly, the introduced modifications increased the lifetime of the peptide free in solution, by decreasing its proteolytic degradation, during the T cell stimulation assays. Paradoxically, however, at similar concentrations of free peptides, the modified ones, especially those having an acetylated N-terminus, were much more active than the unmodified peptide, irrespective of the experimental conditions. These observations suggested that components other than protection from proteolytic degradation should be associated with the higher stimulating activities of the modified peptides. Accordingly, chasing experiments with APC revealed that acetylation at N-terminus caused a higher persistence of the peptides at APC surface. Together, our data indicate that (i) the T cell stimulating capacity of a peptide is associated with its lifespans in the free and MHC II bound states; and (ii) these lifespans can be greatly enhanced by introducing fine chemical modifications at N- and C-termini. These data may have some implications in designing more potent peptidic immunomodulators.

Cell surface-bound elastase and cathepsin G on human neutrophils: a novel, non-oxidative mechanism by which neutrophils focus and preserve catalytic activity of serine proteinases

Serine proteinases of human polymorphonuclear neutrophils play an important role in neutrophil-mediated proteolytic events; however, the non-oxidative mechanisms by which the cells can degrade extracellular matrix in the presence of proteinase inhibitors have not been elucidated. Herein, we provide the first report that human neutrophils express persistently active cell surface-bound human leukocyte elastase and cathepsin G on their cell surface. Unstimulated neutrophils have minimal cell surface expression of these enzymes; however, phorbol ester induces a 30-fold increase. While exposure of neutrophils to chemoattractants (fMLP and C5a) stimulates modest (two- to threefold) increases in cell surface expression of serine proteinases, priming with concentrations of lipopolysaccharide as low as 100 fg/ml leads to striking (up to 10-fold) increase in chemoattractant-induced cell surface expression, even in the presence of serum proteins. LPS-primed and fMLP-stimulated neutrophils have approximately 100 ng of cell surface human leukocyte elastase activity per 10(6) cells. Cell surface-bound human leukocyte elastase is catalytically active, yet is remarkably resistant to inhibition by naturally occurring proteinase inhibitors. These data indicate that binding of serine proteinases to the cell surface focuses and preserves their catalytic activity, even in the presence of proteinase inhibitors. Upregulated expression of persistently active cell surface-bound serine proteinases on activated neutrophils provides a novel mechanism to facilitate their egress from the vasculature, penetration of tissue barriers, and recruitment into sites of inflammation. Dysregulation of the cell surface expression of these enzymes has the potential to cause tissue destruction during inflammation.

Glomerular injury in chronic myelomonocytic leukemia

Among 825 cases of de novo myelodysplastic syndromes (MDS) diagnosed over a period of 13 years in our center, 4 had clinically significant glomerulopathy. All 4 fulfilled diagnostic criteria of chronic myelomonocytic leukemia (CMML), and could be classified in the low or intermediate risk groups according to two scoring systems. Presenting symptoms of renal involvement were edema in 3 cases and acute renal failure in the remaining patient. Three patients had the nephrotic syndrome. Renal biopsy (performed in 2 cases but considered as contraindicated in the other cases) showed AL amyloidosis on one case and extracapillary glomerulonephritis in the other case. The 4 patients were treated with V16 or hydroxyurea and two had renal improvement. Only one previous case of MDS associated with glomerulopathy has been reported before and also very probably had CMML. This, and the response of renal disease to chemotherapy in 2 of our patients suggests a possible relationship between the two disorders. More systematic investigation of glomerular function, in CMML, could possibly disclose a higher incidence of cases of glomerular injury in this type of MDS.

In vitro degradation of serum amyloid A by cathepsin D and other acid proteases: possible protection against amyloid fibril formation

The effects of acid proteases on degradation of serum amyloid A protein (SAA) were investigated in vitro. Human recombinant SAA1 (rSAA1), when incubated with human spleen extracts at pH 3.2, was degraded in the amino-terminal portion of the molecule. This reaction was inhibited by an acid protease inhibitor, pepstatin. The degraded SAA molecules lacking nine or more amino-terminal residues, when exposed to in vitro fibril-forming conditions, failed to form Congo red positive precipitates and did not show amyloid fibril-like structure by electron microscopy. This suggests that the amino-terminal portion of SAA is essential for fibril formation. Cathepsin D, one of the lysosomal enzymes, also initiated degradation of rSAA1 at the amino-terminus. Cathepsin D immunoreactivity was detected in marginal areas of amyloid deposits in spleens from patients with reactive amyloidosis. These findings suggest that cathepsin D or similar acid proteases may be involved in SAA catabolism and may protect against amyloid formation.

The molecular basis of reactive amyloidosis

Reactive amyloidosis is a disease occurring in patients suffering from chronic infections, inflammation, and certain malignant conditions that are characterized by a considerable elevation of the acute phase reactant serum amyloid A (SAA). It is defined by the presence of extracellular deposits of fibrillar material containing amyloid A (AA) as its main component. AA is an 8.5-kd protein structurally identical to the NH2-terminal of the acute phase reactant SAA. SAA consists of a group of evolutionally conserved amphipathic proteins, encoded by a large number of genes and produced abundantly during inflammation, all suggesting an important role, probably of a neutralizing (anti-inflammatory) nature. An analysis of various aspects of SAA provides no clues to the mechanism of amyloid production, its occurrence in only selected individuals, and its preferential relationship to one isotype of SAA. Until more data is available, the present view on AA amyloidogenesis remains hypothetical.

Direct evidence for SAA deposition in tissues during murine amyloidogenesis

To study the mechanism of amyloid deposition, the nature of amyloid proteins formed in experimental murine amyloidosis, was examined. Spleen specimens, 15-60 mg, were homogenized and extracted using aqueous acidic acetonitrile, in a recently developed procedure, making it possible to obtain amyloid proteins from minute amounts of tissue. The extracted material, 1.5-4 mg, was analysed by Western blotting and ELISA using antibodies recognizing differentially proteins AA and SAA. Two immunoreactive proteins of 8 and 12 KDa were isolated and subjected to amino acid analysis and N-terminal sequence determination. The results of immunochemical and chemical examination showed that the 8 and 12 KDa proteins represented proteins AA and SAA, respectively. The data obtained provide new direct evidence for SAA in tissues during murine amyloidogenesis.

Combined treatment with terbutaline and aminophylline inhibits experimental amyloidosis in mice

OBJECTIVE

To investigate the effects of drugs known to elevate adenosine 3':5'-cyclic monophosphate (cAMP) on experimental amyloidosis.

METHODS

A beta 2-agonist, terbutaline, and a phosphodiesterase inhibitor, aminophylline, were administered in combination in a mouse model of amyloidosis induced by inflammatory stimulation with silver nitrate. Amyloidosis was quantitated by radioimmunoassay for splenic amyloid A (AA) protein.

RESULTS

At the doses selected, aminophylline/terbutaline inhibited splenic amyloid deposition more potently than did colchicine, a known inhibitor of amyloidosis.

CONCLUSION

Drugs known to elevate cAMP inhibit experimental mouse AA amyloidosis.

Serum amyloid A: an acute phase apolipoprotein and precursor of AA amyloid

Serum amyloid A is an acute phase protein complexed to HDL as an apoprotein. The molecular weight is 11.4-12.5 kDa in different species and the protein has from 104 to 112 amino acids, without or with an insertion of eight amino acids at position 72. The protein is very well conserved throughout evolution, indicating an important biological function. The N-terminal part of the molecule is hydrophobic and probably responsible for the lipid binding properties. The most conserved part is from position 38 to 52 and this part is therefore believed to be responsible for the until now unknown biological function. The protein is coded on chromosome 11p in man, and chromosome 7 in mice, and found in all mammals until now investigated, and also in the Peking duck. In the rat a truncated SAA mRNA has been demonstrated, but no equivalent serum protein has been reported. Acute phase SAA is first of all produced in hepatocytes after induction by cytokines, but extrahepatic expression of both acute phase and constitutive SAA proteins have been demonstrated. Several cytokines, first of all IL-1, IL-6 and TNF are involved in the induction of SAA synthesis, but the mutual importance of these cytokines seems to be cell-type specific and to vary in various experimental settings. The role of corticosteroids in SAA induction is somewhat confusing. In most in vitro studies corticosteroids show an enhancing or synergistic effect with cytokines on SAA production in cultured cell. However, in clinical studies and in vivo studies in animals an inhibitory effect of corticosteroids is evident, probably due to the all over anti-inflammatory effect of the drug. Until now no drug has been found that selectively inhibits SAA production by hepatocytes. Effective anti-inflammatory or antibacterial treatment is the only tool for reducing SAA concentration in serum and reducing the risk of developing secondary amyloidosis. The function of SAA is still unclear. Interesting theories, based on current knowledge of the lipid binding properties of the protein and the relation to macrophages, in the transportation of cholesterol from damaged tissues has been advanced. A putative role in cholesterol metabolism is supported by the findings of SAA as an inhibitor of LCAT. The potential that SAA is a modifying protein in inflammation influencing the function of neutrophils and platelets is interesting and more directly related to the inflammatory process itself.(ABSTRACT TRUNCATED AT 400 WORDS)

Serum amyloid A is a chemoattractant: induction of migration, adhesion, and tissue infiltration of monocytes and polymorphonuclear leukocytes

Serum amyloid A (SAA) is an acute phase protein that in the blood is bound to high density lipoproteins; SAA is secreted mainly by hepatocytes, and its concentration increases in the blood up to 1000 times during an inflammatory response. At present, its biological function is unclear. Since some forms of secondary amyloidosis are caused by deposition in tissues of peptides derived from the SAA and leukocytes seem to be involved in this process, we investigated the effect of human SAA on human monocytes and polymorphonuclear cells (PMN). When recombinant human SAA (rSAA) was used at concentrations corresponding to those found during the acute phase (> 0.8 microM), it induced directional migration of monocytes and polymorphonuclear leukocytes. Preincubation of rSAA with high density lipoproteins blocked this chemoattractant activity for both monocytes and PMN. rSAA also regulated the expression of the adhesion proteins CD11b and leukocyte cell adhesion molecule 1 and induced the adhesion of PMN and monocytes to umbilical cord vein endothelial cell monolayers. When subcutaneously injected into mice, rSAA recruited PMN and monocytes at the injection site. On the basis of these data, we suggest that SAA may participate in enhancing the migration of monocytes and PMN to inflamed tissues during an acute phase response.

Serum amyloid A (SAA): an acute phase protein and apolipoprotein

Serum amyloid A (SAA) proteins comprise a family of apolipoproteins coded for by at least three genes with allelic variation and a high degree of homology between species. The synthesis of certain members of the family is greatly increased in inflammation. However, SAA is not often used as an acute-phase marker despite being at least as sensitive as C-reactive protein. SAA proteins can be considered as apolipoproteins since they associate with plasma lipoproteins mainly within the high density range, perhaps through amphipathic alpha-helical structure. It is not known why certain subjects expressing SAA develop secondary systemic amyloidosis. There is still no specific function attributed to SAA; however, a popular hypothesis suggests that SAA may modulate metabolism of high density lipoproteins (HDL). This may impede the protective function of HDL against the development of atherosclerosis. The potential significance of the association between SAA and lipoproteins needs further evaluation.

De novo amyloidosis in a renal allograft: a case report and review of the literature

Recurrent amyloidosis is an uncommon but well-documented event in up to 26% of renal allograft recipients transplanted for amyloid renal disease. Both primary and secondary amyloidoses recur. De novo primary and secondary amyloid have not been previously reported. We report the first occurrence of de novo secondary amyloid in a renal allograft recipient. The cause of the secondary amyloidosis is unproven, but possible etiologies include inflammation secondary to occult hepatitis, rheumatoid arthritis, or chronic rejection. Colchicine therapy has not resulted in decreased proteinuria or improved renal function.

C5 deficiency in A/J mice is not associated with resistance to the development of secondary amyloidosis

The aim of the study was to determine whether C5 deficiency in the mouse is associated with resistance to the development of secondary amyloidosis. Chronic inflammation was induced in the F2 progeny, derived from matings between amyloid-susceptible and amyloid-resistance mice, by daily injections of azocasein for thirty days. Using a restriction fragment length polymorphism generated by digestion of genomic DNA with the restriction enzyme HindIII, C5 sufficient and deficient DNA can be clearly differentiated. Eight mice were found to be C5 sufficient, 32 were heterozygotes and 14 were found to be C5 deficient. Grading of the splenic amyloid load from negative to 4+ was performed after staining tissue squashes with Congo red and viewing them under a polarizing microscope. Seventeen mice were noted to have negative to trace, 18 had moderate (1+ - 2+) and 19 had heavy (3+ - 4+) amyloid deposition. There was no correlation between splenic amyloid load and C5 deficiency. Based on these results it is clear that C5 deficiency and resistance to secondary amyloidosis are not associated.

A T-cell response to the anti-arthritic drug penicillamine in the mouse: requirements for generation of the drug-derived antigen

Mice primed with the anit-arthritic drug D-penicillamine (DP) developed DP-specific T cells in the draining lymph nodes (DLN) which responded to drug-haptenated stimulator cells, but not to untreated control cells nor to free drug, in in vitro proliferation assays. The responder cells were CD4+ and the response was major histocompatibility complex (MHC) class II restricted. The conditions required to generate efficient stimulator cells for in vitro proliferation assays were investigated. Drug-haptenated syngeneic spleen cells, but not thymocytes, were able to stimulate T cells from DP-sensitized mice. However, prolonged incubations of spleen cells with DP were required to generate the drug-derived T-cell antigen. Further experiments revealed that the generation of a DP-derived antigenic determinant for T cells did not require intracellular processing, as stimulator cells pretreated with fixative or lysosomotropic agents before drug haptenation were as effective as untreated DP-haptenated cells in stimulating the responder cells to proliferative in vitro. These findings show that the protein-reactive drug DP can generate a cellular antigen that is capable of stimulating a T-cell response. Furthermore, the generation of this antigen appears to bypass conventional antigen processing, suggesting perhaps a direct chemical modification of cell surface molecules that are involved in immune recognition. This process may underlie adverse reactions to DP that are believed to be mediated by the cellular immune system.

On the role of monocytes/macrophages in the pathogenesis of central nervous system lesions in hereditary cystatin C amyloid angiopathy

The pathogenesis of the deposition of a variant cystatin C as amyloid in hereditary cystatin C amyloid angiopathy (HCCAA) is not known. To address this question the synthesis and secretion of cystatin C in cultured monocytes from 9 carriers of the mutated cystatin C gene (5 symptomatic and 4 asymptomatic) was examined. The quantity of cystatin C in cells and supernatants was determined by the ELISA method, Western blots were done and selected samples immunostained for cystatin C. Monocytes from individuals carrying the gene defect synthesized cystatin C that was apparently not truncated, a form found in the cerebral amyloid deposits in HCCAA, but showed a distinctly lower rate of cystatin C synthesis than monocytes from healthy controls. The main difference was that the quantity of cystatin C was significantly lower in the supernatants in monocyte cultures from carriers of the gene defect than from healthy controls, possibly due to a partial block in its secretion. This abnormal processing of the cystatin C could explain the low cerebrospinal fluid levels of cystatin C in HCCAA and might be a part of the pathogenetic pathway of amyloid deposition. Furthermore it could, through a lower extracellular concentration of this inhibitor of cysteine proteinases, contribute to destruction of the amyloidotic blood vessels, leading to the most serious clinical manifestation in HCCAA, intracerebral hemorrhage.

Peptides homologous to the amyloid protein of Alzheimer's disease containing a glutamine for glutamic acid substitution have accelerated amyloid fibril formation

beta-Amyloid (A beta) deposition in fibril form is the central event in a number of diseases, including Alzheimer's disease (AD) and hereditary cerebral hemorrhage with amyloidosis - Dutch type (HCHWA-D). A beta is produced by degradation of a larger amyloid precursor protein (APP). Recently a mutation in the APP gene has been found in HCHWA-D causing a glutamine for glutamic acid substitution at residue 22 of A beta. The influence of this mutation on fibrillogenesis is not known, although it is clear that affected patients have accelerated cerebrovascular amyloid deposition, with disease symptoms early in life. We report the in vitro demonstration of accelerated fibril formation in a 28 residue synthetic peptide homologous to the Dutch variant A beta. Furthermore, in eight residue peptides homologous to A beta the presence of the mutation is necessary for fibril formation. These findings provide a mechanism for accelerated amyloid formation in the Dutch variant of APP.

Antigenic competition between dengue and Coxsackie viruses for presentation to B cells by macrophages

Macrophages (M phi) pulsed with dengue type 2 (DV) and Coxsackie B4 (CoxB) viruses present antigen to B lymphocytes leading to their clonal expansion as detected by counting antigen-specific IgM antibody plaque-forming cells (PFC). The present study was undertaken to investigate the site for competition in M phi between the two heterologous antigens, DV and CoxB, for their presentation to B cells. It was observed that DV-pulsed M phi presented antigen to B cells in mice depleted of T cells by treatment with anti-Thy 1.2 monoclonal antibodies. The B cells could not be stimulated in absence of M phi in mice treated with silica. The PFC counts for both the antigens were inhibited when M phi were pulsed simultaneously with DV and CoxB. PFC counts were increased by 53-120% by predigesting the antigens by trypsin. Inhibition of DV-specific response by CoxB was abrogated by predigesting CoxB. A marked reduction in DV-specific PFC response was observed when CoxB was superimposed on M phi pulsed with DV 24 h earlier. CoxB-specific PFC counts were not affected by superimposing DV on M phi pulsed with CoxB 24 h earlier. PFC response to the antigen given to M phi before glutaraldehyde fixation was not affected while that for the antigen given to glutaraldehyde-fixed M phi was markedly depressed. It is concluded that the competition between DV and CoxB for antigen presentation to B cells occurs in M phi at the level of antigen processing.

Requirement for accessory cells in suppression of MOPC-315 IgA secretion by staphylococcal enterotoxin B-induced T-suppressor cells

Staphylococcal enterotoxin B (SEB) is a potent polyclonal activator of both human and murine T cells. We previously reported data which show that SEB-induced T cells suppress antibody secretion by various mouse plasmacytoma cell lines. This suppression of antibody secretion was found to be both idiotype and isotype nonspecific, and the suppressor cell bears the CD5-positive CD8-negative cell surface phenotype. The present studies demonstrate that accessory cells are required in the SEB-primed spleen cell (SEB-PSC) population in order for this population to mediate suppression. The suppressive activity of SEB-PSC is abrogated following accessory cell depletion by passage over Sephadex G-10 columns. B cell depletion using nylon-wool also abrogates suppression mediated by SEB-PSC. The addition of nonelicited adherent peritoneal exudate cells (PECs) restores suppressive activity to accessory cell-depleted SEB-PSC. The restoration of suppression by the PECs is not major histocompatibility complex restricted, since both syngeneic and allogeneic PECs can carry out this activity. In addition, it is not necessary for the accessory cells to be metabolically active in order to participate in the suppressive activity. This is based on results demonstrating that glutaraldehyde fixation, at levels reported to eliminate metabolic activity, does not affect the ability of PECs to restore suppression to Sephadex G-10-depleted SEB-PSC. The results are consistent with the well established requirement for accessory cells in the function of antigen-induced suppressor T cells.