Contribution of acute-phase reaction proteins to the diagnosis and treatment of 2019 novel coronavirus disease (COVID-19).

The emergence of 2019 novel coronavirus disease (COVID-19) is currently a global concern. In this study, our goal was to explore the changing expression levels of acute-phase reaction proteins (APRPs) in the serum of COVID-19 patients and to elucidate the immunological characteristics of COVID-19. In the study design, we recruited 72 COVID-19 patients, including 22 cases of mild degree, 38 cases of moderate degree and 12 cases of severe degree. We also recruited 20 patients with community-acquired pneumonia (CAP) and 20 normal control subjects as a comparison. Fasting venous blood was taken to detect the content of complement 3 (C3), complement 4 (C4), C-reactive protein (CRP), serum amyloid A (SAA) and prealbumin (PA). When compared the COVID-19 group with the CAP and normal control groups, respectively, the mean value of CRP and SAA in the COVID-19 group (including mild, moderate and severe patients) had increased significantly (P < 0.01), whereas the mean values of C3, C4 and PA decreased (P < 0.01). For the asymptomatic or mild symptomatic patients with COVID-19, the actual aggravation of disease may be more advanced than the clinical appearances. Meanwhile, the statistical analyses indicated that the development of COVID-19 brought about a significant increase in the content of CRP and SAA (P < 0.01), and a decline in the content of C3, C4 and PA (P < 0.01). These findings suggested that the changes in the level of APRPs could be used as indicators to identify the degree and progression of COVID-19, and the significant changes might demonstrate the aggravation of disease. This study provided a new approach to improve the clinical management plan and prognosis of COVID-19.

Toll-like receptor signalling induces the expression of serum amyloid A in epidermal keratinocytes and dermal fibroblasts.

BACKGROUND: Toll-like receptors (TLRs) play critical roles in innate immune response by sensing pathogen- or damage-associated molecular patterns. Epidermal keratinocytes and dermal fibroblasts also produce proinflammatory cytokines and chemokines under stimulation with TLR ligands. Serum amyloid A (SAA) is an essential factor in the pathogenesis of secondary amyloidosis, and also has immunomodulatory functions. SAA are produced mainly by hepatocytes but also by a variety of cells, including immune cells, endothelial cells, synoviocytes, and epidermal keratinocytes. However, SAA expression in human dermal fibroblasts has not been shown to date. AIM: To investigate the effect of TLR ligands on SAA expression in epidermal keratinocytes and dermal fibroblasts. METHODS: We investigated whether TLR ligands induce the expression of SAA in normal human epidermal keratinocytes (NHEKs) and normal human dermal fibroblasts (NHDFs) by real-time quantitative PCR and ELISA. The effect of SAA on its own expression in NHDFs was also studied. RESULTS: SAA expression was induced via nuclear factor-κB by TLR1/2, 3, 5 and 2/6 ligands in NHEKs. In NHDFs, TLR1/2 and TLR2/6 ligands increased SAA expression. SAA further induced its own expression via TLR1/2 and NF-κB in NHDFs, as previously reported for NHEKs. CONCLUSIONS: Our results provide new evidence that the skin's innate immune response contributes to the production of SAA, which might lead to an increased risk of systemic complications such as secondary amyloidosis of recessive dystrophic epidermolysis bullosa.

Hepatic serum amyloid A1 aggravates T cell-mediated hepatitis by inducing chemokines via Toll-like receptor 2 in mice.

Serum amyloid A is a proinflammatory molecule that induces leukocyte infiltration and promotes neutrophil adhesion to endothelial cells under inflammatory conditions. The aim of this study was to examine whether Saa1 aggravates T cell-mediated hepatitis by inducing chemokines in a liver-specific, Saa1-overexpressing, transgenic (TG) mouse model. We generated TG mice in which Saa1 was overexpressed specifically in liver tissue. The chemokines monocyte chemotactic protein 1 (MCP1), MIP1α, MIP1ß, interferon γ-induced protein 10 (IP-10), and eotaxin were induced in Saa1 TG mice. After concanavalin A treatment, Saa1 expression was higher in Saa1 TG mice than in WT mice. More severe liver injury, increased hepatocyte apoptosis, and higher levels of hepatic enzymes were observed in Saa1 TG mice than in WT mice. Liver infiltration of CD4(+) T cells and macrophages increased after inducing hepatitis. Activation of T cells was higher in Saa1 TG mice than in WT mice, and the populations of Th17 cells and regulatory T cells were altered by overexpressing Saa1 in TG mice. Secretion of various cytokines, such as interferon γ, tumor necrosis factor α, and interleukin 6, increased in Saa1 TG mice. Injecting a Toll-like receptor 2 (TLR2) antagonist in vivo inhibited chemokine expression and IκBα phosphorylation and showed that the induction of chemokines by Saa1 was dependent on TLR2. Hepatic Saa1 accelerated T cell-mediated hepatitis by inducing chemokine production and activating T cells by TLR2. Therefore, Saa1 might be a novel inflammatory factor that acts as a chemokine modulator in hepatitis.

Serum amyloid A immunohistochemical staining patterns in hepatitis.

AIMS: Serum amyloid A is an acute phase reactant that is produced by hepatocytes in response to either inflammatory or neoplastic conditions. Because inflammatory adenomas produce this protein, serum amyloid A immunohistochemistry has been used in the evaluation of hepatocellular neoplasms. However, studies evaluating the expression of this protein in hepatitis are lacking. The aim of this study was to perform serum amyloid A immunostains on medical liver biopsy specimens of patients with common chronic liver diseases and correlate them with disease activity and stage. METHODS AND RESULTS: We performed serum amyloid A immunostains on 160 medical liver biopsies, including 100 cases of hepatitis C virus infection at different stages (20 cases of each) and 20 cases each of hepatitis B viral infection, steatohepatitis and autoimmune hepatitis. The extent and location of staining was recorded and correlated with grade, stage and laboratory values (transaminases, bilirubin and viral load). Data were analysed using the Cochran-Mantel-Haenszel χ2 test for trend. Serum amyloid A staining was present in 130 (81%) cases and was limited to zone 3 perivenular hepatocytes in 66 (41%). Biopsy specimens with less fibrosis and/or mild portal inflammation showed significantly more staining than those with cirrhosis (P < 0.001), or at least moderate inflammatory activity (P < 0.001). There was no significant association between lobular inflammation (P = 0.06), bilirubin levels or viral load and immunohistochemical staining for serum amyloid A. CONCLUSIONS: Our results show that liver biopsy specimens with mildly active chronic hepatitis, early fibrosis and normal serum transaminases show more serum amyloid A immunopositivity compared with cases with more inflammatory activity, fibrosis or transaminitis. These findings indicate that serum amyloid A is expressed primarily in the early phases of disease and might influence progression and/or response to treatment.

N-terminal hydrophobic amino acids of activating transcription factor 5 (ATF5) protein confer interleukin 1ß (IL-1ß)-induced stabilization.

Activating transcription factor 5 (ATF5) is a stress-response transcription factor that responds to amino acid limitation and exposure to cadmium chloride (CdCl2) and sodium arsenite (NaAsO2). The N-terminal amino acids contribute to the destabilization of the ATF5 protein in steady-state conditions and serve as a stabilization domain in the stress response after CdCl2 or NaAsO2 exposure. In this study, we show that interleukin 1ß (IL-1ß), a proinflammatory cytokine, increases the expression of ATF5 protein in HepG2 hepatoma cells in part by stabilizing the ATF5 protein. The N-terminal domain rich in hydrophobic amino acids that is predicted to form a hydrophobic network was responsible for destabilization in steady-state conditions and served as an IL-1ß response domain. Furthermore, IL-1ß increased the translational efficiency of ATF5 mRNA via the 5' UTRα and phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α). ATF5 knockdown in HepG2 cells up-regulated the IL-1ß-induced expression of the serum amyloid A 1 (SAA1) and SAA2 genes. Our results show that the N-terminal hydrophobic amino acids play an important role in the regulation of ATF5 protein expression in IL-1ß-mediated immune response and that ATF5 is a negative regulator for IL-1ß-induced expression of SAA1 and SAA2 in HepG2 cells.

Emerging treatments for amyloidosis.

Amyloidosis results from protein misfolding, and ongoing amyloid deposition can ultimately lead to organ failure and death. Historically, this is a group of diseases with limited treatment options and frequently poor prognosis. However, there are now 'targeted' therapeutics emerging in the form of stabilizers of the precursor protein, inhibitors of fibrillogenesis, fibril disruptors, and blockers of protein translation, transcription, and immunotherapy. We review many of these approaches that are currently being assessed in clinical trials.

Clinicopathological characteristics of serum amyloid A-positive hepatocellular neoplasms/nodules arising in alcoholic cirrhosis.

AIMS: To characterize serum amyloid A (SAA)-positive hepatocellular neoplasms/nodules arising in alcoholic cirrhosis, which are detected as hypervascular hepatocellular nodules resembling hepatocellular carcinoma on imaging. METHODS AND RESULTS: Fifty-three hepatocellular nodules were examined with immunostaining for SAA, glutamine synthetase and glypican-3 in 23 patients (four women and 19 men) with alcoholic cirrhosis. Sixteen nodules were examined with magnetic resonance imaging with gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid enhancement (EOB-MRI). Somatic mutations in IL6ST, GNAS and STAT3 were examined in 19 nodules. Thirty-six nodules in 18 patients were diagnosed as SAA-positive hepatocellular neoplasms/nodules, and the remaining 17 nodules in eight patients were SAA-negative focal nodular hyperplasia (FNH)-like nodules. SAA-positive hepatocellular neoplasms/nodules showed significantly more extensive sinusoidal dilatation, inflammatory reaction, abnormally thick arteries and cellular atypia than FNH-like nodules (P < 0.05). Eight SAA-positive hepatocellular neoplasms/nodules (67%) showed slight hypointensity in the hepatobiliary phase on EOB-MRI, whereas all four FNH-like nodules showed iso-intensity (P < 0.05). STAT3 mutations were detected in two of 17 SAA-positive hepatocellular neoplasms/nodules. CONCLUSIONS: This study showed that approximately two-thirds of hypervascular hepatocellular nodules arising in alcoholic cirrhosis were SAA-positive hepatocellular neoplasms/nodules, which show different findings on the EOB-MRI. STAT3 mutations were detected in 11.8% of SAA-positive hepatocellular neoplasms/nodules, supporting a neoplastic nature.

Prediction and experimental validation of a putative non-consensus binding site for transcription factor STAT3 in serum amyloid A gene promoter.

We previously demonstrated that though the human SAA1 gene shows no typical STAT3 response element (STAT3-RE) in its promoter region, STAT3 and the nuclear factor (NF-κB) p65 first form a complex following interleukin IL-1 and IL-6 (IL-1+6) stimulation, after which STAT3 interacts with a region downstream of the NF-κB RE in the SAA1 promoter. In this study, we employed a computational approach based on indirect read outs of protein-DNA contacts to identify a set of candidates for non-consensus STAT3 transcription factor binding sites (TFBSs). The binding of STAT3 to one of the predicted non-consensus TFBSs was experimentally confirmed through a dual luciferase assay and DNA affinity chromatography. The present study defines a novel STAT3 non-consensus TFBS at nt -75/-66 downstream of the NF-κB RE in the SAA1 promoter region that is required for NF-κB p65 and STAT3 to activate SAA1 transcription in human HepG2 liver cells. Our analysis builds upon the current understanding of STAT3 function, suggesting a wider array of mechanisms of STAT3 function in inflammatory response, and provides a useful framework for investigating novel TF-target associations with potential therapeutic implications.

Homocysteine induces serum amyloid A3 in osteoblasts via unlocking RGD-motifs in collagen.

Hyperhomocysteinemia is a risk factor for osteoporotic fractures. Homocysteine (Hcys) inhibits collagen cross-linking and consequently decreases bone extracellular matrix (ECM) quality. Serum amyloid A (A-SAA), an acute-phase protein family, plays an important role in chronic and inflammatory diseases and up-regulates MMP13, which plays an important role in bone development and remodeling. Here, we investigate the effect of Hcys on expression of SAA3, a member of the A-SAA gene family, in osteoblasts characterizing underlying mechanisms and possible consequences on bone metabolism. MC3T3-E1 osteoblast-like cells were cultured up to 21 d with Hcys (low millimolar range) or reseeded onto ECM resulting from untreated or Hcys-treated MC3T3-E1 cells. Fourier-transformed infrared spectroscopy and a discriminative antibody were used to characterize the resulting ECM. Gene expression and signaling pathways were analyzed by gene chip, quantitative RT-PCR, and immunoblotting. Transcriptional regulation of Saa3 was studied by promoter transfection assays, chromatin immunoprecipitation, and immunofluorescence microscopy. Hcys treatment resulted in reduced collagen cross-linking, uncovering of RGD-motifs, and activation of the PTK2-PXN-CTNNB1 pathway followed by RELA activation. These signaling events led to increased SAA3 expression followed by the production of MMP13 and several chemokines, including Ccl5, Ccl2, Cxcl10, and Il6. Our data suggest Saa3 as link between hyperhomocysteinemia and development of osteoporosis.

Control of AA amyloidosis complicating Crohn's disease: a clinico-pathological study.

BACKGROUND: Immunosuppressive drugs may prevent or partially reverse progression of renal AA-amyloidosis, a rare complication of Crohn's disease, often fatal due to renal failure. MATERIALS AND METHODS: The clinical, biological and pathological data of 16 patients treated since 1976 were reviewed. Serum amyloid A was determined in surviving patients. RESULTS: The median age of the 16 patients (13 men) was 23·5 years (range 16-69). At Crohn's disease onset, Montreal phenotypes were similar to reported data. Out of 15 patients with renal insufficiency, 8 developed a nephrotic syndrome and 7 a low grade proteinuria. The single patient without renal insufficiency had nephrotic syndrome. A significant correlation (P < 0·05) between the extension of renal amyloid A and sclerosis was found in 12 patients. One patient had a 10 year remission of nephrotic syndrome with immunosuppressive drugs. In 6 patients treated with anti-TNF-α (Tumor-Necrosis-Factor-α) agents, anaphylactic reaction (1/6), death from septic shock (1/6), 5-year remission (1/6) or reduction of nephrotic syndrome (1/6) and stabilization of renal insufficiency (2/6) were observed. Surgery was performed in 10 patients. Kidney transplantation was performed in 5 of the 8 patients dialysed for end-stage renal failure. Among 6/16 patients (37%) still alive, 3 belong to the 5 transplanted patients (survival: 3-20 years) and 3 to the anti-TNF-α drugs treated patients; all but one exhibited a low serum amyloid A level. CONCLUSIONS: Suppression of Crohn's disease inflammation potentially leads to the control of amyloid A production, assessed by a decrease of serum amyloid A. Kidney transplantation provides a long survival.

Calcitonin gene-related peptide upregulates serum amyloid A synthesis through activation of interleukin-6.

We found that calcitonin gene-related peptide (CGRP) enhanced the expression of levels of serum amyloid A (SAA) and interleukin-6 (IL-6) in HepG2. In addition, CGRP-induced SAA1/2 mRNA expression was blocked by an anti-IL-6 neutralizing antibody in HepG2. These results suggest that CGRP promotes SAA synthesis through activation of IL-6 in human hepatocytes.

Soluble amyloid precursor protein induces rapid neural differentiation of human embryonic stem cells.

Human embryonic stem cells (hESCs) offer tremendous potential for not only treating neurological disorders but also for their ability to serve as vital reagents to model and investigate human disease. To further our understanding of a key protein involved in Alzheimer disease pathogenesis, we stably overexpressed amyloid precursor protein (APP) in hESCs. Remarkably, we found that APP overexpression in hESCs caused a rapid and robust differentiation of pluripotent stem cells toward a neural fate. Despite maintenance in standard hESC media, up to 80% of cells expressed the neural stem cell marker nestin, and 65% exhibited the more mature neural marker ß-3 tubulin within just 5 days of passaging. To elucidate the mechanism underlying the effects of APP on neural differentiation, we examined the proteolysis of APP and performed both gain of function and loss of function experiments. Taken together, our results demonstrate that the N-terminal secreted soluble forms of APP (in particular sAPPß) robustly drive neural differentiation of hESCs. Our findings not only reveal a novel and intriguing role for APP in neural lineage commitment but also identify a straightforward and rapid approach to generate large numbers of neurons from human embryonic stem cells. These novel APP-hESC lines represent a valuable tool to investigate the potential role of APP in development and neurodegeneration and allow for insights into physiological functions of this protein.

Intestine may be a major site of action for the apoA-I mimetic peptide 4F whether administered subcutaneously or orally.

To determine if the dose of peptide administered or the plasma level was more important, doses of 0.15, 0.45, 4.5, or 45 mg/kg/day of the peptide D-4F were administered orally or subcutaneously (SQ) to apoliptotein (apo)E null mice. Plasma levels of peptide were ∼1,000-fold higher when administered SQ compared with orally. Regardless of the route of administration, doses of 4.5 and 45 mg/kg significantly reduced plasma serum amyloid A (SAA) levels and the HDL inflammatory index (P < 0.0001); doses of 0.15 or 0.45 mg/kg did not. A dose of 45 mg/kg/day administered to apoE null mice on a Western diet reduced aortic atherosclerosis by ∼50% (P < 0.0009) whether administered orally or SQ and also significantly reduced plasma levels of SAA (P < 0.002) and lysophosphatidic acid (P < 0.0009). Remarkably, for each dose administered, the concentration and amount of peptide in the feces was similar regardless of whether the peptide was administered orally or SQ. We conclude: i) the dose of 4F administered and not the plasma level achieved determines efficacy; ii) the intestine may be a major site of action for the peptide regardless of the route of administration.

Involvement of STAT3-regulated hepatic soluble factors in attenuation of stellate cell activity and liver fibrogenesis in mice.

Glycoprotein 130 (gp130)/signal transducer and activator of transcription 3 (STAT3) signaling in hepatocytes controls a variety of physiological and pathological processes including liver regeneration, apoptosis resistance and metabolism. Recent research has shed light on the importance of acute phase proteins (APPs) regulated by hepatic gp130/STAT3 in host defense through suppression of innate immune responses during systemic inflammation. To examine whether these STAT3-regulated soluble factors directly affect liver fibrogenic responses during liver injury, hepatocyte-specific STAT3 knockout (L-STAT3 KO) mice and control littermates were subjected to bile duct ligation (BDL) and examined 10 days later. In contrast to controls, L-STAT3 KO mice failed to produce APPs, such as serum amyloid A and haptoglobin, after BDL. Whereas L-STAT3 KO mice displayed similar levels of cholestasis, inflammatory cell infiltration and regeneration in the liver, they developed exacerbated liver injury and fibrosis with significant increases in expression of alpha-smooth muscle actin and type I collagen genes. In vitro experiments revealed that attenuated expression of APPs in primary hepatocytes isolated from L-STAT3 KO mice with IL-6 exposure, compared to wild-type hepatocytes. The cultured supernatant from IL-6-treated wild-type hepatocytes inhibited expression of alpha-smooth muscle actin and type I collagen genes in activated hepatic stellate cells (HSCs), whereas this did not occur with the supernatant from IL-6-treated knockout hepatocytes or with control medium. In conclusion, the absence of STAT3 in hepatocytes leads to exacerbation of liver fibrosis during cholestasis. Soluble factors released from hepatocytes, dependent on STAT3, collectively play a protective role in liver fibrogenesis through an inhibitory effect on activated HSCs.

Expanding the adipokine network in cartilage: identification and regulation of novel factors in human and murine chondrocytes.

BACKGROUND: Obesity is a major risk factor for a plethora of diseases including joint disorders associated with cartilage destruction. Recently, it has been demonstrated that adipose tissue might contribute to degenerative joint diseases via the secretion of potent bioactive molecules termed adipokines. OBJECTIVE: To study expression of the novel adipokines chemerin, lipocalin 2 (LCN2) and serum amyloid A3 (SAA3) in murine and human chondrocytes, under basal conditions, in response to a range of biological and pharmacological treatments, and during chondrocyte differentiation. METHODS: Chemerin, LCN2 and SAA3 mRNA and protein expression were evaluated by quantitative real-time reverse transcription PCR and western blot analysis, respectively, in the ATDC-5 murine chondrocyte cell line, a human immortalised chondrocyte cell line (T/C-28a2) and primary cultured human chondrocytes. RESULTS: Human and murine chondrocytes expressed chemerin, LCN2 and SAA3 mRNA; interleukin (IL)-1ß was a potent inducer of these novel adipokines. Moreover, dexamethasone, lipopolysaccharides (LPS) and other relevant adipokines such as leptin and adiponectin were able to modulate chemerin, LCN2 and SAA3 mRNA expression alone and when coadministered. Intracellular signal transducers involved in the IL-1ß-mediated upregulation of LCN2 and SAA3 included Janus kinase (JAK) 2, phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein (MAP) kinases. Finally, expression of chemerin, LCN2 and SAA3 mRNA expression were modulated throughout chondrocyte differentiation. CONCLUSION: Chemerin, LCN2 and SAA3 are implicated in chondrocyte pathophysiology, and regulated by other relevant factors that drive inflammatory process such as IL-1ß, LPS and adipokines including leptin and adiponectin. It seems likely that JAK2, PI3K and MAP kinases are involved in mediating these responses.

A role for the high-density lipoprotein receptor SR-B1 in synovial inflammation via serum amyloid-A.

Acute phase apoprotein Serum Amyloid A (A-SAA), which is strongly expressed in rheumatoid arthritis synovial membrane (RA SM), induces angiogenesis, adhesion molecule expression, and matrix metalloproteinase production through the G-coupled receptor FPRL-1. Here we report alternative signaling through the high-density lipoprotein receptor scavenger receptor-class B type 1 (SR-B1). Quantitative expression/localization of SR-B1 in RA SM, RA fibroblast-like cells (FLCs), and microvascular endothelial cells (ECs) was assessed by Western blotting and immunohistology/fluorescence. A-SAA-mediated effects were examined using a specific antibody against SR-B1 or amphipathic alpha-Helical Peptides (the SR-B1 antagonists L-37pA and D-37pA), in RA FLCs and ECs. Adhesion molecule expression and cytokine production were quantified using flow cytometry and ELISA. SR-B1 was strongly expressed in the RA SM lining layer and endothelial/perivascular regions compared with osteoarthritis SM or normal control synovium. Differential SR-B1 expression in RA FLC lines (n = 5) and ECs correlated closely with A-SAA, but not tumor necrosis factor alpha-induced intercellular adhesion molecule-1 upregulation. A-SAA-induced interleukin-6 and -8 production was inhibited in the presence of anti-SR-B1 in human microvascular endothelial cells and RA FLCs. Moreover, D-37pA and L-37pA inhibited A-SAA-induced vascular cell adhesion molecule-1 and intercellular adhesion molecule expression from ECs in a dose-dependent manner. As SR-B1 is expressed in RA synovial tissue and mediates A-SAA-induced pro-inflammatory pathways, a better understanding of A-SAA-mediated inflammatory pathways may lead to novel treatment strategies for RA.

Detection of AA-type amyloid protein in labial salivary glands.

OBJECTIVES: Among the diverse forms of amyloidosis, secondary type is the most frequent one. Diagnosis of amyloid deposition is based on the identification of the fibrillary protein amyloid by means of Congo Red (CR) or crystal violet (CV) stains, but these techniques do not differentiate between the different types of amyloid fibrils. The aim of this study was to identify by immunofluorescence (IF) AA amyloid a pathological fibrillar low-molecular-weight protein formed by cleavage of serum amyloid A (SAA) protein in labial salivary gland (LSG) biopsies from patients with secondary amyloidosis. STUDY DESIGN: 98 LSG were studied, 65 were from patients with secondary amyloidosis and 33 from subjects with chronic inflammatory diseases without evidence of this anomaly. All sections were stained with hematoxylin and eosin (H &E), CV, CR and IF using anti-AA antibodies. Positive and negative controls were used for all techniques. RESULTS: CV and CR demonstrated that the amyloid substance was found mainly distributed periductally (93.8%), followed by periacinar and perivascular locations (p <0.001); however, the IF demonstrated that amyloid AA substance predominates in the periacinar area (73.8%), followed by periductal and perivascular locations (p <0.001). IF has a sensitivity of 83%, 100% of specificity, 100% of predictive positive value and 75% of predictive negative value. CONCLUSIONS: The results of this study confirm the efficacy of the LSG biopsy as a highly reliable method for diagnosis of secondary amyloidosis.

Deletion of the alpha 7 nicotinic acetylcholine receptor gene improves cognitive deficits and synaptic pathology in a mouse model of Alzheimer's disease.

It has been recently shown that the Alzheimer's disease (AD) pathogenic peptide amyloid beta(1-42) (Abeta(1-42)) binds to the alpha7 nicotinic acetylcholine receptor (alpha7nAChR) with high affinity and the alpha7nAChR and Abeta(1-42) are both found colocalized in neuritic plaques of human brains with AD. Moreover, the intraneuronal accumulation of Abeta(1-42) was shown to be facilitated by its high-affinity binding to the alpha7nAChR, and alpha7nAChR activation mediates Abeta-induced tau protein phosphorylation. To test the hypothesis that alpha7nAChRs are involved in AD pathogenesis, we used a transgenic mouse model of AD overexpressing a mutated form of the human amyloid precursor protein (APP) and lacking the alpha7nAChR gene (APPalpha7KO). We have shown that, despite the presence of high amounts of APP and amyloid deposits, deleting the alpha7nAChR subunit in the mouse model of AD leads to a protection from the dysfunction in synaptic integrity (pathology and plasticity) and learning and memory behavior. Specifically, APPalpha7KO mice express APP and Abeta at levels similar to APP mice, and yet they were able to solve a cognitive challenge such as the Morris water maze test significantly better than APP, with performances comparable to control groups. Moreover, deleting the alpha7nAChR subunit protected the brain from loss of the synaptic markers synaptophysin and MAP2, reduced the gliosis, and preserved the capacity to elicit long-term potentiation otherwise deficient in APP mice. These results are consistent with the hypothesis that the alpha7nAChR plays a role in AD and suggest that interrupting alpha7nAChR function could be beneficial in the treatment of AD.

Docosahexaenoic acid enhances hepatic serum amyloid A expression via protein kinase A-dependent mechanism.

Serum amyloid A (SAA) reduces fat deposition in adipocytes and hepatoma cells. Human SAA1 mRNA is increased by docosahexaenoic acid (DHA) treatment in human cells. These studies asked whether DHA decreases fat deposition through SAA1 and explored the mechanisms involved. We demonstrated that DHA increased human SAA1 and C/EBPbeta mRNA expression in human hepatoma cells, SK-HEP-1. Utilizing a promoter deletion assay, we found that a CCAAT/enhancer-binding protein beta (C/EBPbeta)-binding site in the SAA1 promoter region between -242 and -102 bp was critical for DHA-mediated SAA1 expression. Mutation of the putative C/EBPbeta-binding site suppressed the DHA-induced SAA1 promoter activity. The addition of the protein kinase A inhibitor H89 negated the DHA-induced increase in C/EBPbeta protein expression. The up-regulation of SAA1 mRNA and protein by DHA was also inhibited by H89. We also demonstrated that DHA increased protein kinase A (PKA) activities. These data suggest that C/EBPbeta is involved in the DHA-regulated increase in SAA1 expression via PKA-dependent mechanisms. Furthermore, the suppressive effect of DHA on triacylglycerol accumulation was abolished by H89 in SK-HEP-1 cells and adipocytes, indicating that DHA also reduces lipid accumulation via PKA. The observation of increased SAA1 expression coupled with reduced fat accumulation mediated by DHA via PKA suggests that SAA1 is involved in DHA-induced triacylglycerol breakdown. These findings provide new insights into the complicated regulatory network in DHA-mediated lipid metabolism and are useful in developing new approaches to reduce body fat deposition and fatty liver.

Intravenous cell therapy for acute renal failure with serum amyloid A protein-reprogrammed cells.

Serum amyloid A protein (SAA), a prominent component of the acute-phase response, is strongly expressed in developing and repairing kidneys and promotes tubulogenesis. Accordingly, we reprogrammed relatively undifferentiated NRK52E cells with the mouse SAA1.1 gene and transplanted SAA-positive and -negative cells into rats with acute renal failure. We found that SAA-positive cells accelerated renal recovery in three models of acute renal failure: gentamicin nephrotoxicity, cisplatin-mediated renal injury, and ischemia-reperfusion renal injury. The dramatic improvement of renal failure was demonstrable within 2 days, consistent with an early paracrine effect. However, abundant donor cells were also found integrated in the healing tubular architecture after 7 days. We conclude that infusions of SAA-positive cells promote renal recovery after acute renal failure and offer a potentially powerful and novel therapy of renal failure.