Inbred strains of mice have been powerful tools in the analysis of serum amyloid A (SAA) synthesis and catabolism in normal host defense and in dysfunctions such as amyloidosis. Six inbred strains (C57BL, C3H, BALB/c, DBA/2, CBA, and A) constituted about 70% of the strains used in 1600 wide-ranging research studies reviewed by Festing; with the possible exception of DBA/2, these strains are also most frequently employed to study SAA. Taken together, these studies indicate that the generic term SAA is unsuitable for future studies of SAA regulation by cytokines; since SAA is not a single entity, there is a need to specifically identify the isoform being measured. Initiation and termination of the acute phase SAA response is known to involve cytokines; however, the range of stimulatory factors appears to be broader than proinflammatory cytokines, and serum and other elements such as phorbol esters have been implicated.

The ISA Nomenclature Committee met electronically before and directly after the XVII ISA International Symposium on Amyloidosis, which, unfortunately, had to be virtual in September 2020 due to the ongoing COVID-19 pandemic instead of a planned meeting in Tarragona in March. In addition to confirmation of basic nomenclature, several additional concepts were discussed, which are used in scientific amyloid literature. Among such concepts are cytotoxic oligomers, protofibrils, primary and secondary nucleation, seeding and cross-seeding, amyloid signature proteins, and amyloid plaques. Recommendations for their use are given. Definitions of amyloid and amyloidosis are confirmed. Possible novel human amyloid fibril proteins, appearing as 'classical' in vivo amyloid, were discussed. It was decided to include fibulin-like extracellular matrix protein 1 (amyloid protein: AEFEMP1), which appears as localised amyloid in portal veins. There are several possible amyloid proteins under investigation, and these are included in a new Table.

The nomenclature committee of the International Society of Amyloidosis (ISA) meets every second year to discuss and formulate recommendations. The conclusions from the discussion at the XVI International Symposium on Amyloidosis in Kumamoto, Japan, 25-29 March 2018 and afterwards are summarized in this Nomenclature Article. From having recommended the use of the designation amyloid fibril for in vivo material only, ISA's nomenclature committee now accepts its use more broadly following the international scientific literature. However, it is important always to stress the origin of the -fibrils in order to avoid misunderstanding. Given the more broad use of the word amyloid several classes of amyloid fibrils may be distinguished. For the medical in vivo situation, and to be included in the amyloid nomenclature list, amyloid still means mainly extracellular tissue deposits of protein fibrils, recognized by specific properties, such as green-yellow birefringence after staining with Congo red. It should also be underlined that in vivo amyloid fibrils, in addition to the main protein contain associated compounds, particularly serum amyloid P-component (SAP) and proteoglycans, mainly heparan sulfate proteoglycan. With this definition there are presently 36 human amyloid proteins of which 14 appear only associated with systemic amyloidosis and 19 as localized forms. Three proteins can occur both as localized and systemic amyloidosis. Strictly intracellular aggregates are not included in this list.

The Nomenclature Committee of the International Society of Amyloidosis (ISA) met during the XVth Symposium of the Society, 3 July-7 July 2016, Uppsala, Sweden, to assess and formulate recommendations for nomenclature for amyloid fibril proteins and the clinical classification of the amyloidoses. An amyloid fibril must exhibit affinity for Congo red and with green, yellow or orange birefringence when the Congo red-stained deposits are viewed with polarized light. While congophilia and birefringence remain the gold standard for demonstration of amyloid deposits, new staining and imaging techniques are proving useful. To be included in the nomenclature list, in addition to congophilia and birefringence, the chemical identity of the protein must be unambiguously characterized by protein sequence analysis when possible. In general, it is insufficient to identify a mutation in the gene of a candidate amyloid protein without confirming the variant changes in the amyloid fibril protein. Each distinct form of amyloidosis is uniquely characterized by the chemical identity of the amyloid fibril protein that deposits in the extracellular spaces of tissues and organs and gives rise to the disease syndrome. The fibril proteins are designated as protein A followed by a suffix that is an abbreviation of the parent or precursor protein name. To date, there are 36 known extracellular fibril proteins in humans, 2 of which are iatrogenic in nature and 9 of which have also been identified in animals. Two newly recognized fibril proteins, AApoCII derived from apolipoprotein CII and AApoCIII derived from apolipoprotein CIII, have been added. AApoCII amyloidosis and AApoCIII amyloidosis are hereditary systemic amyloidoses. Intracellular protein inclusions displaying some of the properties of amyloid, "intracellular amyloid" have been reported. Two proteins which were previously characterized as intracellular inclusions, tau and α-synuclein, are now recognized to form extracellular deposits upon cell death and thus have been included in Table 1 as ATau and AαSyn.

Objective— Intracellular cholesterol distribution impacts cell function; however, processes influencing endogenous cholesterol trafficking remain largely unknown. Atherosclerosis is associated with vascular inflammation and these studies address the role of inflammatory mediators on smooth muscle cell cholesterol trafficking. Methods and Results— Interestingly, in the absence of an exogenous cholesterol source, serum amyloid A increased [ 14 C] oleic acid incorporation into cholesteryl ester in rat smooth muscle cells, suggesting endogenous cholesterol trafficking to the endoplasmic reticulum. [ 3 H] cholesteryl ester accumulated in cells prelabeled with [ 3 H] cholesterol, confirming that serum amyloid A mediated the movement of endogenous cholesterol. Cholesterol movement was dependent upon functional endolysosomes. The cholesterol oxidase–sensitive pool of cholesterol decreased in serum amyloid A−treated cells. Furthermore, the mechanism whereby serum amyloid A induced cholesterol trafficking was determined to be via activation of expression of secretory phospholipase A 2 , group IIA (sPLA 2 ) and sPLA 2 –dependent activation of sphingomyelinase. Interestingly, although neither tumor necrosis factor-α nor interferon-γ induced cholesterol trafficking, interleukin-1β induced [ 14 C] cholesteryl ester accumulation that was also dependent upon sPLA 2 and sphingomyelinase activities. Serum amyloid A activates smooth muscle cell interleukin-1β expression, and although the interleukin-1–receptor antagonist inhibited the interleukin-1β−induced cholesterol trafficking, it had no effect on the movement of cholesterol mediated by serum amyloid A. Conclusion— These data support a role for inflammation in endogenous smooth muscle cell cholesterol trafficking from the plasma membrane to the endoplasmic reticulum.

Objective-Intracellular cholesterol distribution impacts cell function; however, processes influencing endogenous cholesterol trafficking remain largely unknown. Atherosclerosis is associated with vascular inflammation and these studies address the role of inflammatory mediators on smooth muscle cell cholesterol trafficking.Methods and Results-Interestingly, in the absence of an exogenous cholesterol source, serum amyloid A increased [C-14] oleic acid incorporation into cholesteryl ester in rat smooth muscle cells, suggesting endogenous cholesterol trafficking to the endoplasmic reticulum. [H-3] cholesteryl ester accumulated in cells prelabeled with [H-3] cholesterol, confirming that serum amyloid A mediated the movement of endogenous cholesterol. Cholesterol movement was dependent upon functional endolysosomes. The cholesterol oxidase-sensitive pool of cholesterol decreased in serum amyloid A-treated cells. Furthermore, the mechanism whereby serum amyloid A induced cholesterol trafficking was determined to be via activation of expression of secretory phospholipase A(2), group IIA (sPLA(2)) and sPLA(2)-dependent activation of sphingomyelinase. Interestingly, although neither tumor necrosis factor-alpha nor interferon-gamma induced cholesterol trafficking, interleukin-1 beta induced [C-14] cholesteryl ester accumulation that was also dependent upon sPLA(2) and sphingomyelinase activities. Serum amyloid A activates smooth muscle cell interleukin-1 beta expression, and although the interleukin-1-receptor antagonist inhibited the interleukin-1 beta-induced cholesterol trafficking, it had no effect on the movement of cholesterol mediated by serum amyloid A.Conclusion-These data support a role for inflammation in endogenous smooth muscle cell cholesterol trafficking from the plasma membrane to the endoplasmic reticulum. (Arterioscler Thromb Vasc Biol. 2012;32:2741-2750.)

A system of amyloid fibril nomenclature based on the chemical identity of the amyloid fibril forming protein is recommended. This system has been in use for approximately 40 years, but current literature remains confused with clinical and histochemical designations used when the amyloid disease processes were poorly understood. To be designated an amyloid fibril protein, the protein must occur in tissue deposits and exhibit affinity for Congo red and green birefringence when viewed by polarisation microscopy. Furthermore, the protein must have been unambiguously characterised by protein sequence analysis (DNA sequencing in the case of familial diseases). Current nomenclature lists of 27 human and nine animal fibril proteins are provided together with a list of eight inclusion bodies that exhibit some of the properties of amyloid fibrils.

Lipoprotein metabolism was assessed in hamsters following subcutaneous injection of AgNO3. Apolipoprotein serum amyloid A (apoSAA) peaked at 36 h, followed by elevations in plasma cholesterol at 56 h and triglycerides at 96 h. There was a striking increase in LDL and a decrease in HDL. Migration of all acute phase (AP) lipoproteins was retarded compared to controls and SDS-PAGE electrophoretic analysis was consistent with agarose gel profiles that revealed increased apoB-rich VLDL, IDL and LDL and decreased apoAI-rich HDL(2) fractions. Cholesterol transported by LDL of AgNO3 treated hamsters was double that of controls while the pool of HDL-cholesterol was only two-thirds that of controls. Fasting triglyceride and cholesterol secretion rates were depressed sharply at 24 h. After E. coli lipopolysaccharide (LPS) injection, apoSAA-HDL particles bound avidly to cultured peritoneal macrophages (m phi s) but in vitro exposure of tissue m phi s to LPS did not alter the binding characteristics of either control- or apoSAA-HDL, Finally, I-125- radiolabelled apoSAA-HDL and apoAI-HDL decreased during 2-4 h exposure to m phi s bur only apoAI remained associated with cells. Collectively, these data support the hypothesis that apoSAA may commandeer HDL during the AP response in order to deliver phospholipids and cholesterol to cells involved in tissue repair at sites of inflammation.

The structure of the SAA gene family has been defined primarily in BALB/c mice, a strain which is the prototype for the large group of inbred strains designated haplotype A. Four different SAA genes have been identified: SAA(1), SAA(2), SAA(3), and SAA(4) (originally described as SAA(5)). The gene products differ in isoelectric point, with experimentally determined pr values of 6.45, 6.3, 9.2, and 8.1, respectively. Members of a smaller subset of inbred strains designated haplotype B, including SJL/J; express a gene whose product is identical in pI to the SAA(1) gene product in BALB/c mice and a variant of the BALB/c SAA(2) gene whose product is more acidic (pI 5.9) because of the substitution of aspartic acid for alanine at position 101. Like inbred mice, wild derived Mus caroli mice respond to inflammatory stimulation with an increase in SAA gene expression; isoelectricfocusing analysis of M. caroli acute phase plasma revealed two major apoSAA isoforms, one corresponding to the haplotype A SAA(2) gene product and the other to the haplotype B SAA(2) gene product. The derived amino acid sequences of M. caroli SAA gene products were investigated using reverse transcriptase polymerase chain reaction (RT-PCR) and rapid amplification of complementary DNA ends (3' and 5' RACE) techniques. The theoretical pls of proteins encoded by two distinct M. caroli SAA specific cDNA clones were identical to the theoretical pI of the acidic variant of apoSAA(2) expressed in haplotype B mice (reported as pI 5.9). However the M. caroli SAA cDNAs differ in derived amino acid sequence from that variant and from each other Our results indicate additional diversity within the murine SAA gene family and demonstrate that apoSAA isoforms among various strains of mice cannot be considered identical solely on the basis of isoelectric point. The approach described here may have general applicability in phylogenetic studies of the SAA gene family.

Edgar S. Cathcart, Professor of Medicine at Boston University School of Medicine, died at his home in Beverly, Massachusetts, on 4 April 2008 at the age of 76. Throughout his career, he was passionately committed to amyloid research and to the clinical care and well being of patients afflicted with rheumatologic diseases. Dr. Cathcart was born in Northern Ireland and earned his M.D. and Doctorate of Science degrees from Queens University, Belfast. He emigrated to Massachusetts 52 years ago to complete residency training at the Lahey Clinic and to obtain subspecialty training in rheumatology at the Massachusetts General Hospital. Subsequently, he was closely affiliated with the Arthritis Programmes at Boston City Hospital and University Hospital. He was also President of the New England Rheumatism Society in 1969–1970. Working together with Dr. Alan Cohen and Dr. Tsuranobu Shirahama, Dr. Cathcart’s studies identified the pentraxin amyloid P component or plasma component of amyloid deposits. Now known as serum amyloid P, the pentraxin is common to all of the more than 20 biochemically distinct forms of amyloidosis. Dr. Cathcart used mouse models extensively to explore the pathogenesis of AA amyloidosis; he carried out pioneering studies on amyloid enhancing factor and proposed early on that dietary factors can play a role in the pathogenesis of AA and other systemic amyloidoses. During the 1980s, Dr. Cathcart established the Geriatric Research Centre at the Edith Nourse Rogers Veterans Hospital in Bedford, MA; in 1984, he was appointed as Chief of Staff there. I had the pleasure of collaborating with the Cathcart group in Bedford on studies of the role of serum amyloid A (SAA) structure in the susceptibility of inbred strains of mice to AA amyloidosis. The capacity of macrophages to remove the amyloidogenic amino terminus of the SAA fibril precursor was demonstrated to play a role in resistance to amyloidosis. Edgar Cathcart persuasively recruited junior investigators to the study of mouse models of AA amyloidogenesis. He delighted in reviewing and discussing data and was generous with his time and support. His broad knowledge of scientific and medical literature was internationally recognised and contributed to fascinating and illuminating discussions with colleagues. He is remembered with warmth and appreciation.

The increasing knowledge of the exact biochemical nature of the localized and systemic amyloid disorders has made a logical and easily understood nomenclature absolutely necessary. Such a nomenclature, biochemically based, has been used for several years but the current literature is still mixed up with many clinical and histochemically based designations from the time when amyloid in general was poorly understood. All amyloid types are today preferably named by their major fibril protein. This makes a simple and rational nomenclature for the increasing number of amyloid disorders known in humans and animals.

The XIth International Amyloid Symposium, organized by Martha Skinner, Amyloid Treatment and Research Program, Boston University, together with local and international committees, was held in the S...