Allan R. Brasier

Hungry bone syndrome : clinical and biochemical predictors of its occurrence after parathyroid surgery

The hospital course of 218 consecutive patients with primary hyperparathyroidism admitted over a three-year period for parathyroidectomy at the Massachusetts General Hospital was reviewed to determine the incidence and identify the risk factors for the development of the hungry bone syndrome. Twenty-five patients with the hungry bone syndrome were identified (12.6 percent). Compared to patients with uncomplicated metabolic responses to parathyroid surgery, these patients were older by a mean of 10 years; they had higher preoperative serum levels of calcium, alkaline phosphatase, N-terminal parathyroid hormone, and blood urea nitrogen; and their resected parathyroid adenomata were larger. The mean duration of hospitalization averaged three days longer in the group with hungry bone disease. Stepwise multivariate analysis of preoperative variables enabled the development of a discriminant function for prediction of postoperative hypocalcemia and hypophosphatemia. Identified predictive variables were volume of resected parathyroid adenoma, blood urea nitrogen, alkaline phosphatase, and age. When validated on an independent patient population, these readily obtainable preoperative clinical and laboratory parameters will allow identification of a subgroup of patients who are at greater risk for the development of the hungry bone syndrome following parathyroid surgery.

A family of constitutive C/EBP-like DNA binding proteins attenuate the IL-1 alpha induced, NF kappa B mediated trans-activation of the angiotensinogen gene acute-phase response element.

The gene encoding angiotensinogen, the glycoprotein precursor of the potent vasopressor peptide angiotensin II, is transcriptionally activated in hepatocytes during the acute‐phase response through interactions of mutually cooperative glucocorticoid receptors and proteins that bind to an acute‐phase response element (APRE) 5′‐AGTTGGGATTTCCCAACC‐3′. The APRE binds a family of constitutive proteins (BPcs) and a cytokine inducible protein (BPi) that is indistinguishable from nuclear factor kappa B (NF kappa B). The interactions of purified proteins with the APRE were studied by in vitro binding and in vivo transcriptional trans‐activation assays. BPc is a family of heat‐stable DNA binding proteins, the different sized members of which are capable of forming heterodimers. BPcs are recognized by anti‐C/EBP antiserum and produce a footprint similar to bacterially expressed C/EBP on the APRE. BPi has a 4‐ to 5‐fold greater affinity for the APRE than the BPcs, and contacts guanosine residues distinct from those contacted by the BPcs, demonstrating that these two classes of proteins contain functionally distinct DNA binding domains. Assays of APRE‐luciferase reporter plasmids transfected into HepG2 cells show that a mutated APRE that binds only BPi functions as an IL‐1 alpha inducible enhancer, whereas a mutated APRE that binds only BPc does not. The APRE mutant that binds the C/EBP‐like BPcs to the exclusion of BPi functions as an uninducible basal enhancer both in the native context of the angiotensinogen gene and when multimerized and placed upstream of a minimal angiotensinogen promoter. The wild‐type APRE that binds both BPi and BPc is less inducible by IL‐1 alpha than the mutated APRE that binds only BPi. Gel shift competition assays demonstrate in vitro that the mechanism of transcriptional regulation by the APRE involves a competition between BPc and the inducible BPi for binding to the APRE. IL‐1 alpha stimulation of hepatocytes leads to nuclear translocation of the NF kappa B‐like BPi which competes with the constitutive C/EBP‐like BPcs for overlapping binding sites on the APRE and thereby replaces weak transcriptional activators with a stronger one.

An inducible 50-kilodalton NF kappa B-like protein and a constitutive protein both bind the acute-phase response element of the angiotensinogen gene.

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.

Angiotensinogen gene-inducible enhancer-binding protein 1, a member of a new family of large nuclear proteins that recognize nuclear factor kappa B-binding sites through a zinc finger motif.

Transcriptional activation of the rat angiotensinogen gene during the acute-phase response is dependent on a previously characterized acute-phase response element (APRE) that binds at least two types of nuclear proteins: a cytokine-inducible activity indistinguishable from nuclear factor kappa-B (NF kappa B) and a family of C/EBP-like proteins. We screened a rat liver cDNA expression library with a labeled APRE DNA probe and isolated a single clone that encodes a sequence-specific APRE-binding protein. This new protein, the angiotensinogen gene-inducible enhancer-binding protein 1 (AGIE-BP1), is encoded by a large continuous open reading frame and contains a zinc finger motif virtually identical to the DNA-binding domain of a recently described human protein, MBP-1/PRDII-BF1, and a homologous mouse protein, alpha A-CRYBP1. Outside the binding domain, the sequences diverged considerably. Southern blot analysis indicated that AGIE-BP1 and alpha A-CRYBP1 are encoded by separate genes, thus defining a new family of DNA-binding proteins. Electrophoretic mobility shift assays, methylation interference, and DNase I footprint protection assays with the bacterially expressed DNA-binding domain of AGIE-BP1 demonstrated a binding specificity indistinguishable from that of purified NF kappa B. Antiserum raised against the bacterially expressed DNA-binding domain of AGIE-BP1 detected on immunoblots of cellular proteins a large (greater than 250-kDa) nuclear protein. Northern (RNA) blot analysis of RNAs from different rat tissues and cell lines indicated different levels of expression of the large (greater than 10-kb) AGIE-BP1 transcript in different tissues. The potential role of AGIE-BP1 in the regulation of gene expression is discussed.

The permissive role of glucocorticoids on interleukin-1 stimulation of angiotensinogen gene transcription is mediated by an interaction between inducible enhancers.

The acute-phase activation of the rat angiotensinogen (rAT) gene in liver cells is a transcriptional event mediated through an interleukin-1-inducible, NF kappa B-binding, cis-acting element (the acute-phase response element [APRE]). Using a cell culture model for the acute-phase response, we showed that the increase in angiotensionogen mRNA in H35 rat hepatoma cells requires costimulation with glucocorticoids and cytokines. Stably transfected rAT promoter-luciferase reporter genes were also activated by cytokines only in the presence of glucocorticoids. This permissive role of glucocorticoids is dependent on the expression of functional glucocorticoid receptors, because in HepG2 cells naturally deficient in such receptors, rAT gene-luciferase reporter constructs responded to interleukin-1 only when cotransfected with an expression vector for the glucocorticoid receptor. Point mutations in the two rAT gene glucocorticoid response elements located adjacent to the APRE led to loss of interleukin-1 inducibility. Induction of luciferase activity in transfected cells occurred even in the presence of cycloheximide, demonstrating that this synergistic response did not depend on new protein synthesis. Thus, a direct interaction between the interleukin-1-inducible NF kappa B-binding APRE and glucocorticoid response elements, located in cis, underlies the acute-phase activation of the rAT gene.

Myopericarditis as an initial presentation of meningococcemia: Unusual manifestation of infection with serotype W135

Acute meningococcemia is a dramatic clinical syndrome from infection with the gram-negative diplococcus, Neisseria meningitidis. Although pericarditis may complicate the course of meningococcemia, it is distinctly unusual as a presenting sign. A case of disseminated meningococcemia presenting as acute myopericarditis is reported. The serotype isolated, type W135, was a sporadic cause of N. meningitidis in the Boston area. Although the patient had meningitis, bacteremia, and myopericarditis, his course was uncomplicated with early institution of antibiotic therapy.

Transcriptional regulation of hepatic angiotensinogen gene expression by the acute-phase response

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.

Use of Firefly Luciferase Reporter Gene to Study Angiotensinogen Acute Phase Response Element

Publisher Summary This chapter describes the use of firefly luciferase reporter gene to study angiotensinogen acute phase response element. Analysis of regulatory sequences of DNA has been greatly facilitated with the introduction of reporter genes, namely, genes that encode an easily assayble product that is not normally present in the cell lines under investigation. Firefly luciferase from the firefly lantern produces light by the ATP-dependent oxidation of luciferin. Modification of the plasmid vector, assay conditions, and incorporation of a contrasfected internal control reporter alkaline phosphatase to control for plate–to–plate transfection efficiency allows for sensitive, reproducible determinations of enhancer/promoter activity in living cells. Luciferase reporter plasmids are introduced into cultured cells using conventional techniques with the optimal method of transfection being determined empirically for individual cell lines. The transiently transfected hepatoma cells after 48 h for the reporter assay, a time at which transfected luciferase reporter activity is maximal, are harvested. Luciferase, CAT, and alkaline phosphatase reporter activity accumulate primarily in the cytoplasm of transfected cells. The firefly luciferase reporter assay provides rapid results of cellular transfections. The cytokine-inducible enhancer sequence, acute phase response element, of the rat angiotensinogen gene is identified in native sequences by site-directed mutagenesis between nucleotides.