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Yashiro M, Furukawa H, Asano T, Sato S, Kobayashi H, Watanabe H, Suzuki E, Nakamura T, Koga T, Shimizu T, Umeda M, Nonaka F, Ueki Y, Eguchi K, Kawakami A, Migita K. Serum amyloid A1 (SAA1) gene polymorphisms in Japanese patients with adult-onset Still's disease. Medicine (Baltimore) 2018; 97:e13394. [PMID: 30544414 PMCID: PMC6310518 DOI: 10.1097/md.0000000000013394] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder in which inflammasome activation plays a pathophysiological role. In view of the inflammatory nature of AOSD, we investigated whether serum amyloid A (SAA) gene polymorphisms affect the susceptibility of patients with AOSD.Eighty-seven Japanese patients with AOSD and 200 healthy Japanese subjects were recruited in this study. The genotypes of the -13C/T SNP in the 5'-flanking region of the SAA1 gene (rs12218) and two SNPs within exon 3 of SAA1 (2995C/T and 3010C/T polymorphisms) were determined using polymerase chain reaction fragment length polymorphism (PCR-RFLP) assay in all subjects. In AOSD patients, exons 1, 2, 3, and 10 of the MEFV gene were also genotyped by direct sequencing.The frequency of the SAA1.3 allele was increased in AOSD patients compared with that in healthy subjects (43.1% versus 37.5%), but the difference was not significant. The -13T allele was more frequently observed in AOSD patients than in healthy subjects (50.6% versus 41.0%, P = .0336). AOSD patients with the -13T allele had been treated with immunosuppressants more frequently than those without this allele. MEFV mutations were detected in 49 patients with AOSD (49/87, 57.3%). AOSD patients with MEFV variants frequently exhibit macrophage activation syndrome, but the difference was not significant (34.7% versus 18.4%, P = .081). Also, there was no significant difference in SAA1 -13C/T allele frequency between AOSD patients with and without MEFV mutations.Our data shows a significant association between T allele of rs12218 and AOSD in Japanese population.
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Fujii R, Komatsu R, Sato T, Seki I, Konomi K, Aono H, Niki H, Yudoh K, Nishioka K, Nakajima T. SPACIA1/SAAL1 Deletion Results in a Moderate Delay in Collagen-Induced Arthritis Activity, along with mRNA Decay of Cyclin-dependent Kinase 6 Gene. Int J Mol Sci 2018; 19:ijms19123828. [PMID: 30513680 PMCID: PMC6320788 DOI: 10.3390/ijms19123828] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 11/27/2018] [Accepted: 11/29/2018] [Indexed: 11/18/2022] Open
Abstract
This study was performed to elucidate the molecular function of the synoviocyte proliferation-associated in collagen-induced arthritis (CIA) 1/serum amyloid A-like 1 (SPACIA1/SAAL1) in mice CIA, an animal model of rheumatoid arthritis (RA), and human RA-synovial fibroblasts (RASFs). SPACIA1/SAAL1-deficient mice were generated and used to create mouse models of CIA in mild or severe disease conditions. Cell cycle-related genes, whose expression levels were affected by SPACIA1/SAAL1 small interfering RNA (siRNA), were screened. Transcriptional and post-transcriptional effects of SPACIA1/SAAL1 siRNA on cyclin-dependent kinase (cdk) 6 gene expression were investigated in human RASFs. SPACIA1/SAAL1-deficient mice showed later onset and slower progression of CIA than wild-type mice in severe disease conditions, but not in mild conditions. Expression levels of cdk6, but not cdk4, which are D-type cyclin partners, were downregulated by SPACIA1/SAAL1 siRNA at the post-transcriptional level. The exacerbation of CIA depends on SPACIA1/SAAL1 expression, although CIA also progresses slowly in the absence of SPACIA1/SAAL1. The CDK6, expression of which is up-regulated by the SPACIA1/SAAL1 expression, might be a critical factor in the exacerbation of CIA.
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Ather JL, Dienz O, Boyson JE, Anathy V, Amiel E, Poynter ME. Serum Amyloid A3 is required for normal lung development and survival following influenza infection. Sci Rep 2018; 8:16571. [PMID: 30410021 PMCID: PMC6224415 DOI: 10.1038/s41598-018-34901-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 10/24/2018] [Indexed: 02/06/2023] Open
Abstract
Serum amyloid A (SAA) proteins are a family of acute phase apolipoproteins implicated to directly modulate innate and adaptive immune responses. However, new studies comparing endogenous SAAs and recombinant forms of these proteins have questioned the function of SAA in inflammation and immunity. We generated SAA3 knockout mice to evaluate the contribution of SAA3 to lung development and immune-mediated lung disease. While SAA3 deficiency does not affect the generation of house dust mite-induced allergic asthma, mice lacking SAA3 develop adult-onset obesity, intrinsic airway hyperresponsiveness, increased inflammatory and fibrotic gene expression in the lung, and elevated levels of lung citrullinated proteins. Polyclonally stimulated CD4+ T cells from SAA3-/- mice exhibit impaired glycolytic activity, decreased TH2 and TH1 cytokine secretion, and elevated IL-17A production compared to wild type cells. Polyclonally stimulated CD8+ T cells from SAA3-/- mice also exhibit impaired glycolytic activity as well as a diminished capacity to produce IL-2 and IFNγ. Finally, SAA3-/- mice demonstrate increased mortality in response to H1N1 influenza infection, along with higher copy number of viral RNAs in the lung, a lack of CD8+ T cell IFNγ secretion, and decreased flu-specific antibodies. Our findings indicate that endogenous SAA3 regulates lung development and homeostasis, and is required for protection against H1N1 influenza infection.
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Burgess EJ, Hoyt LR, Randall MJ, Mank MM, Bivona JJ, Eisenhauer PL, Botten JW, Ballif BA, Lam YW, Wargo MJ, Boyson JE, Ather JL, Poynter ME. Bacterial Lipoproteins Constitute the TLR2-Stimulating Activity of Serum Amyloid A. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2018; 201:2377-2384. [PMID: 30158125 PMCID: PMC6179936 DOI: 10.4049/jimmunol.1800503] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 08/04/2018] [Indexed: 12/21/2022]
Abstract
Studies comparing endogenous and recombinant serum amyloid A (SAA) have generated conflicting data on the proinflammatory function of these proteins. In exploring this discrepancy, we found that in contrast to commercially sourced recombinant human SAA1 (hSAA1) proteins produced in Escherichia coli, hSAA1 produced from eukaryotic cells did not promote proinflammatory cytokine production from human or mouse cells, induce Th17 differentiation, or stimulate TLR2. Proteomic analysis of E. coli-derived hSAA1 revealed the presence of numerous bacterial proteins, with several being reported or probable lipoproteins. Treatment of hSAA1 with lipoprotein lipase or addition of a lipopeptide to eukaryotic cell-derived hSAA1 inhibited or induced the production of TNF-α from macrophages, respectively. Our results suggest that a function of SAA is in the binding of TLR2-stimulating bacterial proteins, including lipoproteins, and demand that future studies of SAA employ a recombinant protein derived from eukaryotic cells.
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Wilson PG, Thompson JC, Shridas P, McNamara PJ, de Beer MC, de Beer FC, Webb NR, Tannock LR. Serum Amyloid A Is an Exchangeable Apolipoprotein. Arterioscler Thromb Vasc Biol 2018; 38:1890-1900. [PMID: 29976766 PMCID: PMC6202200 DOI: 10.1161/atvbaha.118.310979] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Objective- SAA (serum amyloid A) is a family of acute-phase reactants that have proinflammatory and proatherogenic activities. SAA is more lipophilic than apoA-I (apolipoprotein A-I), and during an acute-phase response, <10% of plasma SAA is found lipid-free. In most reports, SAA is found exclusively associated with high-density lipoprotein; however, we and others have reported SAA on apoB (apolipoprotein B)-containing lipoproteins in both mice and humans. The goal of this study was to determine whether SAA is an exchangeable apolipoprotein. Approach and Results- Delipidated human SAA was incubated with SAA-free human lipoproteins; then, samples were reisolated by fast protein liquid chromatography, and SAA analyzed by ELISA and immunoblot. Both in vitro and in vivo, we show that SAA associates with any lipoprotein and does not remain in a lipid-free form. Although SAA is preferentially found on high-density lipoprotein, it can exchange between lipoproteins. In the presence of CETP (cholesterol ester transfer protein), there is greater exchange of SAA between lipoproteins. Subjects with diabetes mellitus, but not those with metabolic syndrome, showed altered SAA lipoprotein distribution postprandially. Proteoglycan-mediated lipoprotein retention is thought to be an underlying mechanism for atherosclerosis development. SAA has a proteoglycan-binding domain. Lipoproteins containing SAA had increased proteoglycan binding compared with SAA-free lipoproteins. Conclusions- Thus, SAA is an exchangeable apolipoprotein and increases apoB-containing lipoproteins' proteoglycan binding. We and others have previously reported the presence of SAA on low-density lipoprotein in individuals with obesity, diabetes mellitus, and metabolic syndrome. We propose that the presence of SAA on apoB-containing lipoproteins may contribute to cardiovascular disease development in these populations.
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Törőcsik D, Kovács D, Póliska S, Szentkereszty-Kovács Z, Lovászi M, Hegyi K, Szegedi A, Zouboulis CC, Ståhle M. Genome wide analysis of TLR1/2- and TLR4-activated SZ95 sebocytes reveals a complex immune-competence and identifies serum amyloid A as a marker for activated sebaceous glands. PLoS One 2018; 13:e0198323. [PMID: 29927962 PMCID: PMC6013244 DOI: 10.1371/journal.pone.0198323] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 05/17/2018] [Indexed: 11/18/2022] Open
Abstract
Toll-like receptors (TLR) 2 and 4 are active in sebaceous glands and play a central role in the development of acne. Still, there is only limited knowledge on their effect on sebocytes. In this work we performed global gene expression profile analysis with functional clustering of the differentially regulated genes of TLR1/2 (PAM3CSK4)- and TLR4 (lipopolysaccharide [LPS])-activated SZ95 sebocytes. Both TLR1/2- and 4-activation promoted inflammation in a similar manner already at an early time-point (6 hours), regulating genes involved in inflammation, wound healing and chemotaxis reflecting a more complex cytokine and chemokine regulation than previously known. Importantly, lipid metabolism, the primary feature of sebocytes, was affected at the level of gene expression only at a later time point (24 hours) indicating that sebocytes prioritize to exert a pro-inflammatory phenotype when confronted with a danger signal. Supporting the biological relevance of our results, a meta-analysis revealed that the genes showing the strongest up-regulation were also found up-regulated in acne. Of these genes, serum amyloid A 1/2 (SAA1/2) was confirmed to be a suitable protein marker for in vivo activated sebocytes, underlining their immune-competence, which is structurally defined within sebaceous glands of acne and rosacea skin samples. Altogether our findings demonstrate that sebocytes are not only positioned at the end point of inflammation but are actively involved in shaping the inflammatory response with putative diagnostic and therapeutic relevance.
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Lee-Thacker S, Choi Y, Taniuchi I, Takarada T, Yoneda Y, Ko C, Jo M. Core Binding Factor β Expression in Ovarian Granulosa Cells Is Essential for Female Fertility. Endocrinology 2018; 159:2094-2109. [PMID: 29554271 PMCID: PMC5905395 DOI: 10.1210/en.2018-00011] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 03/11/2018] [Indexed: 02/06/2023]
Abstract
Core binding factor β (CBFβ) is a non-DNA-binding partner of all RUNX proteins and critical for transcription activity of CBF transcription factors (RUNXs/CBFβ). In the ovary, the expression of Runx1 and Runx2 is highly induced by the luteinizing hormone (LH) surge in ovulatory follicles, whereas Cbfb is constitutively expressed. To investigate the physiological significance of CBFs in the ovary, the current study generated two different conditional mutant mouse models in which granulosa cell expression of Cbfb and Runx2 was reduced by Cre recombinase driven by an Esr2 promoter. Cbfbgc-/- and Cbfbgc-/- × Runx2gc+/- mice exhibited severe subfertility and infertility, respectively. In the ovaries of both mutant mice, follicles develop normally, but the majority of preovulatory follicles failed to ovulate either in response to human chorionic gonadotropin administration in pregnant mare serum gonadotropin-primed immature animals or after the LH surge at 5 months of age. Morphological and physiological changes in the corpus luteum of these mutant mice revealed the reduced size, progesterone production, and vascularization, as well as excessive lipid accumulation. In granulosa cells of periovulatory follicles and corpora lutea of these mice, the expression of Edn2, Ptgs1, Lhcgr, Sfrp4, Wnt4, Ccrl2, Lipg, Saa3, and Ptgfr was also drastically reduced. In conclusion, the current study provided in vivo evidence that CBFβ plays an essential role in female fertility by acting as a critical cofactor of CBF transcription factor complexes, which regulate the expression of specific key ovulatory and luteal genes, thus coordinating the ovulatory process and luteal development/function in mice.
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Ghasemi S, Sardari K, Mirshokraei P, Hassanpour H. In vitro study of matrix metalloproteinases 1, 2, 9, 13 and serum amyloid A mRNAs expression in equine fibroblast-like synoviocytes treated with doxycycline. CANADIAN JOURNAL OF VETERINARY RESEARCH = REVUE CANADIENNE DE RECHERCHE VETERINAIRE 2018; 82:82-88. [PMID: 29755186 PMCID: PMC5914083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/25/2017] [Indexed: 06/08/2023]
Abstract
Application of synthetic matrix metalloproteinases (MMPs) inhibitors, such as doxycycline is one of the possible therapeutic options for osteoarthritis. However, little is known about the protective mechanism of doxycycline in equine models on MMPs inhibitors as well as on serum amyloid A (SAA) gene expression. This study investigated the effects of doxycycline on mRNA expression of MMP-1, MMP-2, MMP-9, MMP-13, and SAA of equine fibroblast-like synoviocytes (FLSs). The FLSs were established from synovial fluids of clinically normal metacarpophalangeal joints of 6 skeletally mature horses. The cells were treated with either 10 or 100 μg/mL of doxycycline for 48 h. The mRNA expression of MMP-1, MMP-2, MMP-9, MMP-13, and SAA were assessed using real-time polymerase chain reaction (PCR). Treatment with doxycycline resulted in significantly decreased mRNA expression of MMP-1 in FLSs at both concentrations (P = 0.001). No significant differences were detected among groups for MMP-2, MMP-9, and MMP-13 (P > 0.05). Only a tendency towards a decrease in mRNA expression level of SAA in the presence of doxycycline could be detected. Doxycycline inhibits MMP-1 gene expression at the transcript level. These findings indicate that doxycycline can protect the articular environment through inhibition of MMP-1 at transcript level.
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Ather JL, Poynter ME. Serum amyloid A3 is required for normal weight and immunometabolic function in mice. PLoS One 2018; 13:e0192352. [PMID: 29390039 PMCID: PMC5794179 DOI: 10.1371/journal.pone.0192352] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 01/22/2018] [Indexed: 02/06/2023] Open
Abstract
Serum amyloid A (SAA) is an apolipoprotein that is robustly upregulated in numerous inflammatory diseases and has been implicated as a candidate pro-inflammatory mediator. However, studies comparing endogenous SAAs and recombinant forms of the acute phase protein have generated conflicting data on the function of SAA in immunity. We generated SAA3 knockout mice to evaluate the contribution of SAA3 to immune-mediated disease, and found that mice lacking SAA3 develop adult-onset obesity and metabolic dysfunction along with defects in innate immune development. Mice that lack SAA3 gain more weight, exhibit increased visceral adipose deposition, and develop hepatic steatosis compared to wild-type littermates. Leukocytes from the adipose tissue of SAA3-/- mice express a pro-inflammatory phenotype, and bone marrow derived dendritic cells from mice lacking SAA3 secrete increased levels of IL-1β, IL-6, IL-23, and TNFα in response to LPS compared to cells from wild-type mice. Finally, BMDC lacking SAA3 demonstrate an impaired endotoxin tolerance response and inhibited responses to retinoic acid. Our findings indicate that endogenous SAA3 modulates metabolic and immune homeostasis.
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Huan B, Liu K, Li Y, Wei J, Shao D, Shi Y, Qiu Y, Li B, Ma Z. Porcine serum amyloid A3 is expressed in extrahepatic tissues and facilitates viral replication during porcine respiratory and reproductive syndrome virus infection. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2018; 79:51-58. [PMID: 29056547 DOI: 10.1016/j.dci.2017.10.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/17/2017] [Accepted: 10/17/2017] [Indexed: 06/07/2023]
Abstract
Serum amyloid A (SAA) is an acute phase protein that is expressed rapidly in response to infection and inflammation in vertebrates. Here, we detected the expression of porcine SAA3, an isoform of porcine SAA, during porcine respiratory and reproductive syndrome virus (PRRSV) infection, which is a major threat to the pig industry. In response to PRRSV infection, porcine SAA3 expression was upregulated significantly in porcine pulmonary alveolar macrophages and in extrahepatic tissues, including the lungs and inguinal, mandibular, and hilar lymph nodes, which were affected mainly by PRRSV infection, demonstrating that porcine SAA3 is a tissue-derived isoform that is induced in extrahepatic tissues during the acute phase response. Overexpression of porcine SAA3 increased PRRSV titers in cultured cells, and the exogenous administration of porcine SAA3 facilitated PRRSV adsorption to cells, suggesting that porcine SAA3 assists PRRSV replication. Our data provide insights into the role of porcine SAA3 during PRRSV infection.
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Thompson JC, Wilson PG, Shridas P, Ji A, de Beer M, de Beer FC, Webb NR, Tannock LR. Serum amyloid A3 is pro-atherogenic. Atherosclerosis 2018; 268:32-35. [PMID: 29175652 PMCID: PMC5839639 DOI: 10.1016/j.atherosclerosis.2017.11.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/24/2017] [Accepted: 11/15/2017] [Indexed: 11/26/2022]
Abstract
BACKGROUND AND AIMS Serum amyloid A (SAA) predicts cardiovascular events. Overexpression of SAA increases atherosclerosis development; however, deficiency of two of the murine acute phase isoforms, SAA1.1 and SAA2.1, has no effect on atherosclerosis. SAA3 is a pseudogene in humans, but is an expressed acute phase isoform in mice. The goal of this study was to determine if SAA3 affects atherosclerosis in mice. METHODS ApoE-/- mice were used as the model for all studies. SAA3 was overexpressed by an adeno-associated virus or suppressed using an anti-sense oligonucleotide approach. RESULTS Over-expression of SAA3 led to a 4-fold increase in atherosclerosis lesion area compared to control mice (p = 0.01). Suppression of SAA3 decreased atherosclerosis in mice genetically deficient in SAA1.1 and SAA2.1 (p < 0.0001). CONCLUSIONS SAA3 augments atherosclerosis in mice. Our results resolve a previous paradox in the literature and support extensive epidemiological data that SAA is pro-atherogenic.
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Tashiro M, Iwata A, Yamauchi M, Shimizu K, Okada A, Ishiguro N, Inoshima Y. The N-terminal region of serum amyloid A3 protein activates NF-κB and up-regulates MUC2 mucin mRNA expression in mouse colonic epithelial cells. PLoS One 2017; 12:e0181796. [PMID: 28738073 PMCID: PMC5524290 DOI: 10.1371/journal.pone.0181796] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 07/09/2017] [Indexed: 01/01/2023] Open
Abstract
Serum amyloid A (SAA) is the major acute-phase protein and a precursor of amyloid A (AA) in AA amyloidosis in humans and animals. SAA isoforms have been identified in a wide variety of animals, such as SAA1, SAA2, SAA3, and SAA4 in mouse. Although the biological functions of SAA isoforms are not completely understood, recent studies have suggested that SAA3 plays a role in host defense. Expression of SAA3 is increased on the mouse colon surface in the presence of microbiota in vivo, and it increases mRNA expression of mucin 2 (MUC2) in murine colonic epithelial cells in vitro, which constitutes a protective mucus barrier in the intestinal tract. In this study, to identify responsible regions in SAA3 for MUC2 expression, recombinant murine SAA1 (rSAA1), rSAA3, and rSAA1/3, a chimera protein constructed with mature SAA1 (amino acids 1–36) and SAA3 (amino acids 37–103), and vice versa for rSAA3/1, were added to murine colonic epithelial CMT-93 cells, and the mRNA expressions of MUC2 and cytokines were measured. Inhibition assays with NF-κB inhibitor or TLR4/MD2 inhibitor were also performed. Up-regulation of MUC2 mRNA expression was strongly stimulated by rSAA3 and rSAA3/1, but not by rSAA1 or rSAA1/3. Moreover, NF-κB and TLR4/MD2 inhibitors suppressed the increase of MUC2 mRNA expression. These results suggest that the major responsible region for MUC2 expression exists in amino acids 1–36 of SAA3, and that up-regulations of MUC2 expression by SAA3 and SAA3/1 are involved with activation of NF-κB via the TLR4/MD2 complex.
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Couderc E, Morel F, Levillain P, Buffière-Morgado A, Camus M, Paquier C, Bodet C, Jégou JF, Pohin M, Favot L, Garcia M, Huguier V, Mcheik J, Lacombe C, Yssel H, Guillet G, Bernard FX, Lecron JC. Interleukin-17A-induced production of acute serum amyloid A by keratinocytes contributes to psoriasis pathogenesis. PLoS One 2017; 12:e0181486. [PMID: 28708859 PMCID: PMC5510841 DOI: 10.1371/journal.pone.0181486] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 06/30/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Acute-serum Amyloid A (A-SAA), one of the major acute-phase proteins, is mainly produced in the liver but extra-hepatic synthesis involving the skin has been reported. Its expression is regulated by the transcription factors NF-κB, C/EBPβ, STAT3 activated by proinflammatory cytokines. OBJECTIVES We investigated A-SAA synthesis by resting and cytokine-activated Normal Human Epidermal Keratinocytes (NHEK), and their inflammatory response to A-SAA stimulation. A-SAA expression was also studied in mouse skin and liver in a model mimicking psoriasis and in the skin and sera of psoriatic and atopic dermatitis (AD) patients. METHODS NHEK were stimulated by A-SAA or the cytokines IL-1α, IL-17A, IL-22, OSM, TNF-α alone or in combination, previously reported to reproduce features of psoriasis. Murine skins were treated by imiquimod cream. Human skins and sera were obtained from patients with psoriasis and AD. A-SAA mRNA was quantified by RT qPCR. A-SAA proteins were dosed by ELISA or immunonephelemetry assay. RESULTS IL-1α, TNF-α and mainly IL-17A induced A-SAA expression by NHEK. A-SAA induced its own production and the synthesis of hBD2 and CCL20, both ligands for CCR6, a chemokine receptor involved in the trafficking of Th17 lymphocytes. A-SAA expression was increased in skins and livers from imiquimod-treated mice and in patient skins with psoriasis, but not significantly in those with AD. Correlations between A-SAA and psoriasis severity and duration were observed. CONCLUSION Keratinocytes could contribute to psoriasis pathogenesis via A-SAA production, maintaining a cutaneous inflammatory environment, activating innate immunity and Th17 lymphocyte recruitment.
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Yu J, Tang Y, Li J, Li H, Yu F, Yu W, He F, Fu C, Mao S. Cloning, expression analysis, and antibacterial propertiesof three serum amyloid A in common carp (Cyprinus carpio). FISH & SHELLFISH IMMUNOLOGY 2017; 65:267-277. [PMID: 28442417 DOI: 10.1016/j.fsi.2017.04.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 04/21/2017] [Accepted: 04/21/2017] [Indexed: 06/07/2023]
Abstract
Three serum amyloid A (SAA) genes were identified from the common carp (Cyprinus carpio) by PCR and RT-PCR. Considering both direction and sequence similarity with mammal's orthologs, they were named CcSAA3a, CcSAA3b and CcSAA1. CcSAA3b and CcSAA1 are adjacent on contig LHQP01017858, suggesting that the prototype of or the simplest SAA multigene family have occurred in common carp. A phylogenetic analysis of the SAAs indicated that the fish SAAs were closer to those of invertebrates and Ornithorhynchus anatinus, a primitive mammal, than to mammalian SAAs. Quantitative real-time RT-PCR results displayed different expression profiles of three CcSAAs. The CcSAA3a was detected in all tested tissues, and was most abundant in the muscle; CcSAA3b was predominately expressed in the intestine and liver, and CcSAA1 in the skin. The expression level of CcSAA3a was higher than that of CcSAA3b and CcSAA1 in most tissues. Stimulation with Aeromonas hydrophila dramatically induced the expression of the three CcSAAs in all examined tissues, especially in the liver. Like Epinephelus coioides SAA, all of three rCcSAA fusion proteins could bind to both Gram-negative bacteria (A. hydrophila and E. coli) and Gram-positive bacterium (S. aureus), playing a role in the identification of bacteria. However, only rCcSAA3a showed significantly anti-A. hydrophila and anti-E. coli in vitro antibacterial activity assays. These results suggested that the three CcSAAs were in functional differentiation and play significant roles in the innate immunity of common carp.
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Oller Moreno S, Cominetti O, Núñez Galindo A, Irincheeva I, Corthésy J, Astrup A, Saris WHM, Hager J, Kussmann M, Dayon L. The differential plasma proteome of obese and overweight individuals undergoing a nutritional weight loss and maintenance intervention. Proteomics Clin Appl 2017; 12. [PMID: 28371297 DOI: 10.1002/prca.201600150] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 03/01/2017] [Accepted: 03/27/2017] [Indexed: 01/24/2023]
Abstract
PURPOSE The nutritional intervention program "DiOGenes" focuses on how obesity can be prevented and treated from a dietary perspective. We generated differential plasma proteome profiles in the DiOGenes cohort to identify proteins associated with weight loss and maintenance and explore their relation to body mass index, fat mass, insulin resistance, and sensitivity. EXPERIMENTAL DESIGN Relative protein quantification was obtained at baseline and after combined weight loss/maintenance phases using isobaric tagging and MS/MS. A Welch t-test determined proteins differentially present after intervention. Protein relationships with clinical variables were explored using univariate linear models, considering collection center, gender and age as confounding factors. RESULTS Four hundred and seventy three subjects were measured at baseline and end of the intervention; 39 proteins were longitudinally differential. Proteins with largest changes were sex hormone-binding globulin, adiponectin, C-reactive protein, calprotectin, serum amyloid A, and proteoglycan 4 (PRG4), whose association with obesity and weight loss is known. We identified new putative biomarkers for weight loss/maintenance. Correlation between PRG4 and proline-rich acidic protein 1 variation and Matsuda insulin sensitivity increment was showed. CONCLUSION AND CLINICAL RELEVANCE MS-based proteomic analysis of a large cohort of non-diabetic overweight and obese individuals concomitantly identified known and novel proteins associated with weight loss and maintenance.
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Su BC, Lin WC, Huang HN, Chen JY. Recombinant expression of Epinephelus lanceolatus serum amyloid A (ElSAA) and analysis of its macrophage modulatory activities. FISH & SHELLFISH IMMUNOLOGY 2017; 64:276-286. [PMID: 28323212 DOI: 10.1016/j.fsi.2017.03.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 03/10/2017] [Accepted: 03/16/2017] [Indexed: 06/06/2023]
Abstract
Serum amyloid A (SAA) is an acute-phase protein that plays a crucial role in the inflammatory response. In this study, we identified an SAA homolog from Epinephelus lanceolatus (ElSAA). Molecular characterization revealed that ElSAA contains a fibronectin-like motif that is typical of SAAs. Recombinant ElSAA protein (rElSAA) was produced in E. coli BL21 (DE3) cells and purified as a soluble protein. To analyze its biological activity, mouse Raw264.7 macrophage cells were treated with various concentrations of rElSAA. Expression of several inflammation-related cytokines, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, and IL-10, was induced by rElSAA. This protein also triggered macrophage differentiation, as evidenced by increases in cell size and complexity. To determine whether rElSAA regulates macrophage polarization, we assessed gene expression of M1 and M2 markers. The results demonstrated that rElSAA induced the expression of both M1 and M2 markers, suggesting that it promotes the differentiation of macrophages into a mixed M1/M2 phenotype. To evaluate whether rElSAA enhances phagocytosis via an opsonization-dependent mechanism, GFP-labeled E. coli cells were pretreated with rElSAA, followed by incubation with Raw264.7 cells. Flow cytometry was used to monitor the phagocytic uptake of GFP-labeled E. coli by macrophages. Surprisingly, incubating E. coli with rElSAA did not enhance bacterial uptake by macrophages. However, preincubating Raw264.7 cells with various concentrations of rElSAA, followed by infection with E. coli (multiplicity of infection = 20 or 40), resulted in a clear enhancement of macrophage phagocytic capacity. In conclusion, we have identified SAA from E. lanceolatus and have demonstrated that rElSAA promotes inflammatory cytokine production and macrophage differentiation. In addition, rElSAA enhances phagocytosis of bacteria by macrophages via an opsonization-independent mechanism.
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Baranova IN, Souza ACP, Bocharov AV, Vishnyakova TG, Hu X, Vaisman BL, Amar MJ, Chen Z, Remaley AT, Patterson AP, Yuen PST, Star RA, Eggerman TL. Human SR-BII mediates SAA uptake and contributes to SAA pro-inflammatory signaling in vitro and in vivo. PLoS One 2017; 12:e0175824. [PMID: 28423002 PMCID: PMC5396919 DOI: 10.1371/journal.pone.0175824] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 04/01/2017] [Indexed: 12/13/2022] Open
Abstract
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.
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de Oliveira EM, Visniauskas B, Tufik S, Andersen ML, Chagas JR, Campa A. Serum Amyloid A Production Is Triggered by Sleep Deprivation in Mice and Humans: Is That the Link between Sleep Loss and Associated Comorbidities? Nutrients 2017; 9:nu9030311. [PMID: 28335560 PMCID: PMC5372974 DOI: 10.3390/nu9030311] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 03/07/2017] [Accepted: 03/16/2017] [Indexed: 01/26/2023] Open
Abstract
Serum amyloid A (SAA) was recently associated with metabolic endotoxemia, obesity and insulin resistance. Concurrently, insufficient sleep adversely affects metabolic health and is an independent predisposing factor for obesity and insulin resistance. In this study we investigated whether sleep loss modulates SAA production. The serum SAA concentration increased in C57BL/6 mice subjected to sleep restriction (SR) for 15 days or to paradoxical sleep deprivation (PSD) for 72 h. Sleep restriction also induced the upregulation of Saa1.1/Saa2.1 mRNA levels in the liver and Saa3 mRNA levels in adipose tissue. SAA levels returned to the basal range after 24 h in paradoxical sleep rebound (PSR). Metabolic endotoxemia was also a finding in SR. Increased plasma levels of SAA were also observed in healthy human volunteers subjected to two nights of total sleep deprivation (Total SD), returning to basal levels after one night of recovery. The observed increase in SAA levels may be part of the initial biochemical alterations caused by sleep deprivation, with potential to drive deleterious conditions such as metabolic endotoxemia and weight gain.
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Yang S, Gao Y, Zhang S, Zhang Q, Sun D. Identification of Genetic Associations and Functional Polymorphisms of SAA1 Gene Affecting Milk Production Traits in Dairy Cattle. PLoS One 2016; 11:e0162195. [PMID: 27610623 PMCID: PMC5017741 DOI: 10.1371/journal.pone.0162195] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 08/18/2016] [Indexed: 11/19/2022] Open
Abstract
Our initial RNA sequencing (RNA-seq) revealed that the Serum amyloid A1 (SAA1) gene was differentially expressed in the mammary glands of lactating Holstein cows with extremely high versus low phenotypic values of milk protein and fat percentage. To further validate the genetic effect and potential molecular mechanisms of SAA1 gene involved in regulating milk production traits in dairy cattle, we herein performed a study through genotype-phenotype associations. Six identified SNPs were significantly associated with one or more milk production traits (0.00002< P < 0.0025), providing additional evidence for the potential role of SAA1 variants in milk production traits in dairy cows. Subsequently, both luciferase assay and electrophoretic mobility shift assay (EMSA) clearly demonstrated that the allele A of g.-963C>A increased the promoter activity by binding the PARP factor while allele C did not. Bioinformatics analysis indicated that the secondary structure of SAA protein changed by the substitution A/G in the locus c. +2510A>G. Our findings were the first to reveal the significant associations of the SAA1 gene with milk production traits, providing basis for further biological function validation, and two identified SNPs, g.-963C>A and c. +2510A>G, may be considered as genetic markers for breeding in dairy cattle.
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Atoyan S, Hayrapetyan H, Sarkisian T, Ben-Chetrit E. MEFV and SAA1 genotype associations with clinical features of familial Mediterranean fever and amyloidosis in Armenia. Clin Exp Rheumatol 2016; 34:72-76. [PMID: 27791951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 05/26/2016] [Indexed: 06/06/2023]
Abstract
OBJECTIVES Familial Mediterranean fever (FMF) is a hereditary periodic disease characterised by recurrent attacks of fever and serositis. The most devastating complication of FMF is amyloidosis (AA) affecting mainly the kidneys. Aim of the study is to search for correlations between the MEFV genotype and the SAA polymorphisms with the clinical manifestations of FMF and the occurrence of amyloidosis in a large cohort of Armenian patients. METHODS Information about the MEFV mutations, SAA polymorphisms and FMF clinical features, were obtained for 1017 FMF patients, from the database of the Center of Medical Genetics in Yerevan. For identifying probable correlation between the MEFV and SAA genotype and clinical features of FMF, regression logistic analyses were conducted between the genotype and phenotype of the patients. RESULTS Patients homozygous for M694V were highly associated with all the clinical features of FMF and its complications - proteinuria and amyloidosis. None of the SAA1 polymorphisms had any correlation with FMF clinical features. However, homozygosis for SAA1 α/α polymorphism was associated with proteinuria and amyloidosis whereas carrying the β/β polymorphism was found to be protective for amyloidosis. CONCLUSIONS The SAA1 α allele is strongly associated with amyloidosis in FMF patients. This observation is valid in inflammatory diseases other than FMF too. SAA1 polymorphism has no effect on the clinical features of FMF. M694V homozygosis is highly associated withal typical features of FMF and with amyloidosis. FMF course in Armenia is similar to that in Middle Eastern countries where FMF disease is common.
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de Oliveira EM, Ascar TP, Silva JC, Sandri S, Migliorini S, Fock RA, Campa A. Serum amyloid A links endotoxaemia to weight gain and insulin resistance in mice. Diabetologia 2016; 59:1760-8. [PMID: 27126803 DOI: 10.1007/s00125-016-3970-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 04/06/2016] [Indexed: 01/21/2023]
Abstract
AIMS/HYPOTHESIS Pre-adipocytes and adipocytes are responsive to the acute phase protein serum amyloid A (SAA). The combined effects triggered by SAA encompass an increase in pre-adipocyte proliferation, an induction of TNF-α and IL-6 release and a decrease in glucose uptake in mature adipocytes, strongly supporting a role for SAA in obesity and related comorbidities. This study addressed whether SAA depletion modulates weight gain and insulin resistance induced by a high-fat diet (HFD). METHODS Male Swiss Webster mice were fed an HFD for 10 weeks under an SAA-targeted antisense oligonucleotide (ASOSAA) treatment in order to evaluate the role of SAA in weight gain. RESULTS With ASOSAA treatment, mice receiving an HFD did not differ in energy intake when compared with their controls, but were prevented from gaining weight and developing insulin resistance. The phenotype was characterised by a lack of adipose tissue expansion, with low accumulation of epididymal, retroperitoneal and subcutaneous fat content and decreased inflammatory markers, such as SAA3 and toll-like receptor (TLR)-4 expression, as well as macrophage infiltration into the adipose tissue. Furthermore, a metabolic status similar to chow-fed mice counterparts could be observed, with equivalent levels of leptin, adiponectin, IGF-I, SAA, fasting glucose and insulin, and remarkable improvement in glucose and insulin tolerance test profiles. Surprisingly, the expected HFD-induced metabolic endotoxaemia was also prevented by the ASOSAA treatment. CONCLUSIONS/INTERPRETATION This study provides further evidence of the role of SAA in weight gain and insulin resistance. Moreover, we also suggest that beyond its proliferative and inflammatory effects, SAA is part of the lipopolysaccharide signalling pathway that links inflammation to obesity and insulin resistance.
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Han S, Oh JH, Shin CY, Yoon HS, Lee DH, Chung JH. Serum amyloid A1 is induced by UV irradiation and detected by toll-like receptor 4 to causes skin inflammation. J Dermatol Sci 2016; 84:107-110. [PMID: 27502577 DOI: 10.1016/j.jdermsci.2016.07.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 07/07/2016] [Accepted: 07/21/2016] [Indexed: 11/19/2022]
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Hillreiner M, Flinspach C, Pfaffl MW, Kliem H. Effect of the Ketone Body Beta-Hydroxybutyrate on the Innate Defense Capability of Primary Bovine Mammary Epithelial Cells. PLoS One 2016; 11:e0157774. [PMID: 27310007 PMCID: PMC4910980 DOI: 10.1371/journal.pone.0157774] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 06/03/2016] [Indexed: 11/18/2022] Open
Abstract
Negative energy balance and ketosis are thought to cause impaired immune function and to increase the risk of clinical mastitis in dairy cows. The present in vitro study aimed to investigate the effect of elevated levels of the predominant ketone body β-hydroxybutyrate on the innate defense capability of primary bovine mammary epithelial cells (pbMEC) challenged with the mastitis pathogen Escherichia coli (E. coli). Therefore, pbMEC of healthy dairy cows in mid- lactation were isolated from milk and challenged in culture with 3 mM BHBA and E. coli. pbMEC stimulated with E. coli for 6 h or 30 h showed an up-regulation of several innate immune genes, whereas co-stimulation of pbMEC with 3 mM BHBA and E. coli resulted in the down-regulation of CCL2, SAA3, LF and C3 gene expression compared to the challenge with solely the bacterial stimulus. These results indicated that increased BHBA concentrations may be partially responsible for the higher mastitis susceptibility of dairy cows in early lactation. Elevated levels of BHBA in blood and milk during negative energy balance and ketosis are likely to impair innate immune function in the bovine mammary gland by attenuating the expression of a broad range of innate immune genes.
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Jang WY, Jeong J, Kim S, Kang MC, Sung YH, Choi M, Park SJ, Kim MO, Kim SH, Ryoo ZY. Serum amyloid A1 levels and amyloid deposition following a high-fat diet challenge in transgenic mice overexpressing hepatic serum amyloid A1. Appl Physiol Nutr Metab 2016; 41:640-648. [PMID: 27218680 DOI: 10.1139/apnm-2015-0369] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2023]
Abstract
Serum amyloid A (SAA) is an acute-phase response protein in the liver, and SAA1 is the major precursor protein involved in amyloid A amyloidosis. This amyloidosis has been reported as a complication in chronic inflammatory conditions such as arthritis, lupus, and Crohn's disease. Obesity is also associated with chronic, low-grade inflammation and sustained, elevated levels of SAA1. However, the contribution of elevated circulating SAA1 to metabolic disturbances and their complications is unclear. Furthermore, in several recent studies of transgenic (TG) mice overexpressing SAA1 that were fed a high-fat diet (HFD) for a relatively short period, no relationship was found between SAA1 up-regulation and metabolic disturbances. Therefore, we generated TG mice overexpressing SAA1 in the liver, challenged these mice with an HFD, and investigated the influence of elevated SAA1 levels. Sustained, elevated levels of SAA1 were correlated with metabolic parameters and local cytokine expression in the liver following 16 weeks on the HFD. Moreover, prolonged consumption (52 weeks) of the HFD was associated with impaired glucose tolerance and elevated SAA1 levels and resulted in systemic SAA1-derived amyloid deposition in the kidney, liver, and spleen of TG mice. Thus, we concluded that elevated SAA1 levels under long-term HFD exposure result in extensive SAA1-derived amyloid deposits, which may contribute to the complications associated with HFD-induced obesity and metabolic disorders.
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Rosani U, Domeneghetti S, Gerdol M, Franzoi M, Pallavicini A, Venier P. Serum amyloid A in marine bivalves: An acute phase and innate immunity protein. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2016; 59:136-144. [PMID: 26828389 DOI: 10.1016/j.dci.2016.01.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 01/26/2016] [Accepted: 01/27/2016] [Indexed: 06/05/2023]
Abstract
Serum amyloid A (SAA) is among the most potent acute phase proteins (APP) in vertebrates. After injury, its early expression can dramatically increase to promote the recruitment of immuno-competent cells, expression of pro-inflammatory proteins and the activation of the innate immune defences. Although APP have been studied in many vertebrates, only recently their search was extended to invertebrates and the finding of SAA-like molecules has opened new questions on the immune-regulatory functions of these soluble proteins in the animal kingdom. Taking advantage of the considerable amount of genomic and transcriptomic data currently available, we retrieved 51 SAA-like proteins in several protostome taxa comprising 21 marine bivalve species and basal metazoans. In addition to vertebrate-like SAAs, we identified a second protein type with peculiar features. In the bivalves Crassostrea gigas and Mytilus galloprovincialis, both digital expression analysis and qPCR data indicated an induction of the classical SAA after bacterial challenge.
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