angiotensinogen and Acute-Phase-Reaction

The acute-phase response is a protective physiological reaction to tissue injury manifested by the immediate increase in production and secretion of liver proteins the function of which is to re-establish the homeostasis altered by injury. Such proteins include blood coagulation factors, opsonins, protease-inhibitors and angiotensinogen, a precursor of the potent vasopressor peptide angiotensin II. The angiotensinogen gene is typical of genes regulated during the acute-phase response inasmuch as the promoter regulating its transcription rate is acutely responsive to three known mediators of the acute-phase response: glucocorticoids, and the cytokines interleukin-1 and tumor necrosis factor. We present a model, based on experimental evidence, for the mechanism by which angiotensinogen gene transcription is regulated in a graded fashion by the interplay of several hormonally-inducible transcription factors that bind a hormonally-inducible enhancer unit of the angiotensinogen promoter. These factors include the glucocorticoid receptor, nuclear factor kappa B and members of the CAAT/viral enhancer (C/EBP) family of DNA-binding proteins.

Topics: Acute-Phase Reaction; Angiotensinogen; Animals; Enhancer Elements, Genetic; Gene Expression Regulation; Genes; Glucocorticoids; Interleukin-1; Liver; NF-kappa B; Transcription, Genetic

To investigate whether urinary angiotensinogen (UAGT) levels are correlated with renal involvement of Henoch-Schonlein purpura (HSP) in children, and to explore whether UAGT has any relation to the severity of HSP.. The study sample consisted of 107 patients (50 boys and 57 girls, 6.68±2.41 years) with clinical diagnosis of HSP. A 24 h urine sample was collected before treatment. UAGT levels were measured in patients with HSP in the acute and convalescent phases by enzyme linked immunosorbent assay.. Urinary angiotensinogen/urinary concentration of creatinine levels were significantly higher in proteinuric HSP in the acute phase and the convalescent phase (32.02±3.95 and 25.31±4.11 µg/g) compared with those with HSP without renal involvement (17.26±2.60 and 15.14±3.81 µg/g) and those with hematuric HSP (19.70±2.21 and 17.28±3.62 µg/g) (P<0.0001 and P<0.01, respectively). Using matched urine samples from the same patients, UAGT/urinary concentration of creatinine (UCr) levels of proteinuric HSP patients were significantly lower in the convalescent phase (25.31 ± 4.11 µg/g, P<0.01) than in the acute phase (32.02±3.95 µg/g). UAGT/UCr levels showed positive correlation with 24 h urine protein or serum creatinine in both hematuric HSP and proteinuric HSP groups during the acute phase (P<0.05).. Urinary angiotensinogen levels were remarkably high in the acute phase in the patients with proteinuric HSP, suggesting increased UAGT may indicate a series of functional changes in the kidney and it may be used as a potential biomarker of severity of HSP to monitor the progression of HSP with renal involvement.

Topics: Acute-Phase Reaction; Angiotensinogen; Biomarkers; Child; Child, Preschool; Convalescence; Creatinine; Enzyme-Linked Immunosorbent Assay; Female; Hematuria; Humans; IgA Vasculitis; Kidney; Male; Monitoring, Physiologic; Outcome Assessment, Health Care; Proteinuria; Renin-Angiotensin System; Severity of Illness Index

The signal transducers and activators of transcription (STATs) are cytoplasmic transcription factors mediating acute-phase response (APR) of the human angiotensinogen (hAGT) gene in hepatocytes. The mechanisms of how STAT3 activates target genes are unknown. Here we analyzed the biochemistry of STAT3 activation by interleukin (IL)-6 in hepatocellular carcinoma HepG2 and Balb/C mice.. Immunoprecipitation-Western assays and Matrix Assisted Laser Desorption-Time of Flight mass spectrometry determined sites of STAT3 acetylation by the 300-kilodalton target of E1A (p300) co-activator. The subcellular localization of acetylation-deficient STAT3 molecules were studied by microscopic imaging, effects on DNA binding measured by gel shift and chromatin immunoprecipitation (ChIP) assays, and gene transactivation by Northern blot and reporter assays.. Two Lys residues at amino acids 49 and 87 in the STAT3 NH2 terminus are acetylated by p300. Lys-to-Arg point mutations (STAT3 K49R/K87R) had no effect on inducible DNA binding, but blocked p300-mediated acetyl(Ac)-STAT3 formation and abrogated IL-6-induced hAGT activation. Although STAT3 K49R/K87R rapidly translocated into the nucleus, it did not bind p300 and had delayed cytoplasmic redistribution. ChIP assays show IL-6-inducible acetylated STAT3 and p300 binding to the native hAGT promoter. Activation of the APR in mice induces nuclear Tyr phosphorylated and acetylated STAT3 in hepatic nuclei. We also observed that STAT3 interacts with histone deacetylases (HDACs), specifically HDAC 1, that down-regulate IL-6-induced hAGT transactivation.. IL-6-induced target gene activation requires p300-mediated STAT3 acetylation, and HDACs are involved in the termination of STAT3 action. These studies indicate the acetylation-deacetylation reaction as a novel signaling mechanism controlling the IL-6-STAT3 pathway in the hepatic APR.

Topics: Acetylation; Active Transport, Cell Nucleus; Acute-Phase Reaction; Angiotensinogen; Animals; Carcinoma, Hepatocellular; Cell Line, Tumor; Cytoplasm; E1A-Associated p300 Protein; Humans; Interleukin-6; Lipopolysaccharides; Liver Neoplasms; Lysine; Mice; Mice, Inbred BALB C; Mutagenesis; Phosphorylation; Promoter Regions, Genetic; Signal Transduction; STAT3 Transcription Factor; Transcriptional Activation; Tyrosine

The gene encoding angiotensinogen is regulated at the transcriptional level in hepatocytes in response to glucocorticoids and inflammatory cytokines (IL-1 and TNF). These hormones activate transcription of the angiotensinogen gene by changing the abundance of DNA binding proteins that interact with a multihormone-inducible enhancer located between nucleotides -615 to -440 upstream of the major transcription start site. Activation of this enhancer in hepatocytes is effected by glucocorticoid- and cytokine-inducible DNA binding proteins. Cytokine induction is mediated through the interaction of two classes of transcription factors that bind to the acute-phase response element (APRE): nuclear factor-kappa B (NF-kappa B), and CCAAT-Box/Enhancer Binding Protein (C/EBP). NF-kappa B is a multiprotein DNA binding complex sequestered in the cytoplasm that is induced in the nucleus by cytokines, whereas C/EBP is a nuclear transcription factor family implicated in the expression of differentiated hepatic proteins. During the acute-phase response, individual C/EBP family members are discordinately regulated: C/EBP alpha levels fall, whereas another C/EBP family member termed nuclear factor IL6 (NF-IL6), is induced. We investigated the interaction between the two acute-phase induced APRE-binding proteins: NF-kappa B and NF-IL6. Both proteins bind to overlapping nucleotides in a mutually exclusive fashion with similar affinities for the APRE. NF-IL6, a less potent transactivator, attenuates NF-kappa B mediated transcription late in the evolution of the acute-phase response. These observations argue for a temporal model of sequentially-expressed transcription factors occupying the APRE during the evolution of the inflammatory process.

Topics: Acute-Phase Reaction; Angiotensinogen; Animals; Base Sequence; Binding, Competitive; CCAAT-Enhancer-Binding Proteins; DNA; DNA-Binding Proteins; Gene Expression; Liver; Molecular Sequence Data; NF-kappa B; Nuclear Proteins; Rats; Transcription Factor RelA; Transcription Factors; Transcriptional Activation

Topics: Acute-Phase Reaction; Angiotensinogen; Animals; Carcinoma, Hepatocellular; DNA Probes; Gene Expression Regulation; Liver; Liver Neoplasms; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nucleic Acid Hybridization; RNA, Messenger; Sequence Homology, Nucleic Acid; Species Specificity; Transcription, Genetic; Tumor Cells, Cultured

The rat angiotensinogen gene is induced in the course of the hepatic acute-phase response. We demonstrate that monocyte conditioned medium can stimulate transcription of a stably introduced reporter construct driven by 615 base pairs of the angiotensinogen 5'-flanking sequence, as well as the endogenous gene, in Reuber H35 cells. Point mutations of a cis-acting element, located 545 base pairs from the transcription start site and sharing sequence identity with known nuclear factor kappa B (NF kappa B)-binding sites, led to loss of cytokine inducibility. When cloned upstream of a minimal promoter, this cis-acting element imparted transcriptional inducibility by monocyte conditioned medium, interleukin-1, and tumor necrosis factor on a luciferase reporter gene in HepG2 cells. Two distinct proteins bound this element in vitro: a heat-stable, constitutively present, hepatic nuclear protein that gave rise to a DNase I-protected footprint covering the functionally defined element; and a binding protein of different mobility, induced by monocyte conditioned medium, which also recognized the NF kappa B-binding site of the murine kappa light-chain enhancer. UV cross-linking showed this inducible protein to have an apparent molecular mass of 50 kilodaltons, similar to that described for NF kappa B and distinct from the constitutively present protein that was shown by Southwestern (DNA-protein) blot to have a molecular mass of 32 kilodaltons. Methylation interference analysis showed that the induced species made contact points with guanine residues in the NF kappa B consensus sequence typical of NF kappa B. Induction of this binding activity did not require new protein synthesis, and 12-O-tetradecanoylphorbol-13-acetate could mimic the induction by cytokines. We thus provide direct evidence for involvement of NF kappa B or a similar factor in the hepatic acute-phase response and discuss the potential role of the presence of a constitutive nuclear factor binding the same cis element.

Topics: Acute-Phase Reaction; Angiotensinogen; Animals; Base Sequence; Cycloheximide; DNA Mutational Analysis; DNA-Binding Proteins; Gene Expression Regulation, Enzymologic; Genes; In Vitro Techniques; Inflammation; Lipopolysaccharides; Molecular Sequence Data; Molecular Weight; Nuclear Proteins; Rats; Regulatory Sequences, Nucleic Acid; Tetradecanoylphorbol Acetate; Transcription Factors; Transcription, Genetic

The plasma level of angiotensinogen during the chronic phase of inflammation was studied for comparison with those of other acute-phase reactants in rat adjuvant arthritis. In response to a single injection of Freund's complete adjuvant, this level exhibited a transient increase during the first 24 h. By contrast, increased levels of plasma T-kininogen and alpha 2-macroglobulin, typical acute-phase reactions in the rat, were maintained during the 4-week experimental period. These results suggest that the hepatic synthesis of angiotensinogen is stimulated only in the early phase of chronic inflammation, and therefore that the mechanism underlying the acute-phase response of angiotensinogen is distinct from those currently suggested for other acute-phase reactants.

Topics: Acute-Phase Reaction; alpha-Macroglobulins; Angiotensinogen; Animals; Arthritis; Arthritis, Experimental; Chronic Disease; Corticosterone; Inflammation; Kininogens; Male; Rats

Acute phase responses of plasma angiotensinogen and kininogen were studied in rats. Plasma angiotensinogen levels increased about 3-fold during the first 8 hr, and returned to normal at 48 hr, following the induction of acute inflammation by lipopolysaccharide (LPS). Plasma kininogen reached maximum levels at 48 hr following LPS administration. In adrenalectomized rats, plasma angiotensinogen levels decreased significantly, and the administration of LPS did not elevate plasma angiotensinogen levels. In contrast, plasma kininogen levels were increased by adrenalectomy, as well as by sham-operation. Dexamethasone significantly increased plasma angiotensinogen levels in adrenalectomized rats as well as in normal rats, but aldosterone did not. Plasma kininogen levels of normal rats were not changed by the administration of dexamethasone or aldosterone. From these results, it was concluded that the acute phase response of plasma angiotensinogen is mediated by glucocorticoid, but that of plasma kininogen is not.

Topics: Acute-Phase Reaction; Adrenalectomy; Aldosterone; Angiotensinogen; Animals; Dexamethasone; Inflammation; Kinetics; Kininogens; Lipopolysaccharides; Male; Rats; Rats, Inbred Strains