Serum amyloid A, but not C-reactive protein, stimulates vascular proteoglycan synthesis in a pro-atherogenic manner

Establishment of a transgenic mouse model specifically expressing human serum amyloid A in adipose tissue

Obesity and obesity co-morbidities are associated with a low grade inflammation and elevated serum levels of acute phase proteins, including serum amyloid A (SAA). In the non-acute phase in humans, adipocytes are major producers of SAA but the function of adipocyte-derived SAA is unknown. To clarify the role of adipocyte-derived SAA, a transgenic mouse model expressing human SAA1 (hSAA) in adipocytes was established. hSAA expression was analysed using real-time PCR analysis. Male animals were challenged with a high fat (HF) diet. Plasma samples were subjected to fast protein liquid chromatography (FPLC) separation. hSAA, cholesterol and triglyceride content were measured in plasma and in FPLC fractions. Real-time PCR analysis confirmed an adipose tissue-specific hSAA gene expression. Moreover, the hSAA gene expression was not influenced by HF diet. However, hSAA plasma levels in HF fed animals (37.7±4.0 µg/mL, n = 7) were increased compared to those in normal chow fed animals (4.8±0.5 µg/mL, n = 10; p<0.001), and plasma levels in the two groups were in the same ranges as in obese and lean human subjects, respectively. In FPLC separated plasma samples, the concentration of hSAA peaked in high-density lipoprotein (HDL) containing fractions. In addition, cholesterol distribution over the different lipoprotein subfractions as assessed by FPLC analysis was similar within the two experimental groups. The established transgenic mouse model demonstrates that adipose tissue produced hSAA enters the circulation, resulting in elevated plasma levels of hSAA. This new model will enable further studies of metabolic effects of adipose tissue-derived SAA.

Inflammatory Markers: Serum Amyloid A, Fibrinogen and C-Reactive Protein — A Revisited Study

The acute phase response is the part of the innate defence system of an animal against trauma, inflammation or infection. During this response, there is increased production and release of certain plasma proteins known as acute phase proteins, which include C-reactive protein (CRP), serum amyloid A (SAA) and fibrinogen (Fg). CRP consists of five identical subunits of 206 amino acids with a molecular weight of approximately 23 kDa. There is strong evidence from numerous studies that CRP is a predictor of inflammation. The acute-phase protein serum amyloid A (SAA) is a clinically useful marker of inflammation. SAA plays not only an important role in the development of AA amyloidosis (an important complication of rheumatoid arthritis) but also interacts with events closely involved in the metabolic syndrome as a high- and low-grade inflammatory modulator. Fibrinogen (Fg) is a high molecular weight plasma adhesion protein and is a biomarker of inflammation. It is synthesized and assembled in hepatocytes and fibroblasts and when secreted into the circulation, its plasma half-life ranges from 3 to 4 days. Several cytokines, are involved in the induction of acute phase protein synthesis, but the mutual importance of these cytokines seems to be cell-type specific and to vary in various experimental settings. Here we revisited the classic acute phase proteins SAA, C-Reactive protein and fibrinogen in their role in inflammation and their interrelationship with some cytokines.

Inflammation, a link between obesity and cardiovascular disease

Obesity, the most common nutritional disorder in industrialized countries, is associated with an increased mortality and morbidity of cardiovascular disease (CVD). Obesity is primarily considered to be a disorder of energy balance, and it has recently been suggested that some forms of obesity are associated with chronic low-grade inflammation. The present paper focuses on the current status of our knowledge regarding chronic inflammation, a link between obesity and CVDs, including heart diseases, vascular disease and atherosclerosis. The paper discusses the methods of body fat evaluation in humans, the endocrinology and distribution of adipose tissue in the genders, the pathophysiology of obesity, the relationship among obesity, inflammation, and CVD, and the adipose tissue-derived cytokines known to affect inflammation. Due to space limitations, this paper focuses on C-reactive protein, serum amyloid A, leptin, adiponectin, resistin, visfatin, chemerin, omentin, vaspin, apelin, and retinol binding protein 4 as adipokines.

Currents concepts on the immunopathology of amyloidosis

Amyloidosis is defined as the extracellular accumulation at systemic or organ-specific level of insoluble low molecular weight protein fibrils manifesting a beta pleated sheet configuration and a characteristic staining pattern. Several different types of proteins may lead to this phenomenon, and amyloidosis is defined by the biochemical nature of the protein in the deposits and further classified according to whether the deposits are localized or systemic, acquired or inherited, and by the resulting clinical phenotype. Amyloidosis includes subtypes such as light chain, associated with serum amyloid A protein, heritable and familial forms, dialysis-related disease, and organ-specific conditions. The pathogenesis and clinical features of these clinical and pathological entities will be critically discussed in this review article.

Therapeutic anti-inflammatory potential of formyl-peptide receptor agonists

The need for novel anti-inflammatory drugs justifies the search for innovative targets that could satisfy this goal. For quite some time now, we have proposed the study of endogenous anti-inflammation as a distinctive approach to the discovery of new drugs. This approach requires development of new compounds that activate specific receptor targets to downregulate the cellular and tissue pathways operative in the host during inflammation. Here we dwell on a family of G-protein coupled receptors (GPCR) termed FPRs, acronym for formyl-peptide receptors. With three and seven members in man and mouse, respectively, these receptors harness many biological functions, spanning odour perception and hair growth, to the control of multiple facets (pain; cell migration; oxidative burst; xenobiotic engulfment) of the inflammatory reaction. We focus on FPR biology with particular attention to molecules able to produce pharmacological effects by interacting with these GPCRs, describing endogenous agonists of FPRs and, more relevantly, the current development of synthetic agonists. Besides being potential leads for the development of the anti-inflammatory therapeutics of the future, these compounds could also help clarify the properties and roles that each FPR might play in the complex network of pathways that is inflammation. We conclude that FPR2 agonists could be valid warhorses for defining a novel philosophy for anti-inflammatory drug discovery programmes: mimicking - with new compounds - the way our body disposes of inflammation could be a viable approach to regulate aberrant inflammatory responses as in the case of several chronic rheumatic and cardiovascular pathologies.

A murine model of obesity with accelerated atherosclerosis

The epidemic of obesity sweeping developed nations is accompanied by an increase in atherosclerotic cardiovascular diseases. Dyslipidemia, diabetes, hypertension, and obesity are risk factors for cardiovascular disease. However, delineating the mechanism of obesity-accelerated atherosclerosis has been hampered by a paucity of animal models. Similar to humans, apolipoprotein E-deficient (apoE(-/-)) mice spontaneously develop atherosclerosis over their lifetime. To determine whether apoE(-/-) mice would develop obesity with accelerated atherosclerosis, we fed mice diets containing 10 (low fat (LF)) or 60 (high fat (HF)) kcal % from fat for 17 weeks. Mice fed the HF diet had a marked increase in body weight and atherosclerotic lesion formation compared to mice fed the LF diet. There were no significant differences between groups in serum total cholesterol, triglycerides, or leptin concentrations. Plasma concentrations of the acute-phase reactant serum amyloid A (SAA) are elevated in both obesity and cardiovascular disease. Accordingly, plasma SAA concentrations were increased fourfold (P < 0.01) in mice fed the HF diet. SAA was associated with both pro- and antiatherogenic lipoproteins in mice fed the HF diet compared to those fed the LF diet, in which SAA was primarily associated with the antiatherogenic lipoprotein high-density lipoprotein (HDL). Moreover, SAA was localized with apoB-containing lipoproteins and biglycan in the vascular wall. Taken together, these data suggest male apoE-deficient mice are a model of metabolic syndrome and that chronic low level inflammation associated with increased SAA concentrations may mediate atherosclerotic lesion formation.